text:
Prof Toni Vidal-Puig, all publications
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Extracellular Vesicles: Novel Mediators of Cell Communication In Metabolic Disease.
Trends Endocrinol Metab. 2016 Oct 31. pii: S1043-2760(16)30128-X. doi: 10.1016/j.tem.2016.10.003. [Epub ahead of print]
Huang-Doran I1, Zhang CY2, Vidal-Puig A3.
Abstract – show
Metabolic homeostasis emerges from the complex, multidirectional crosstalk between key metabolic tissues including adipose tissue, liver, and skeletal muscle. This crosstalk, traditionally mediated by hormones and metabolites, becomes dysregulated in human diseases such as obesity and diabetes. Extracellular vesicles (EVs; including exosomes) are circulating, cell-derived nanoparticles containing proteins and nucleic acids that interact with and modify local and distant cellular targets. Accumulating evidence, reviewed herein, supports a role for extracellular vesicles in obesity-associated metabolic disturbance, particularly the local and systemic inflammation characteristic of adipose and hepatic stress. As the practical and conceptual challenges facing the field are tackled, this emerging and versatile mode of intercellular communication may afford valuable insights and therapeutic opportunities in combatting these major threats to modern human health.
Copyright © 2016 Elsevier Ltd. All rights reserved.
PMID: 27810172 DOI: 10.1016/j.tem.2016.10.003
Metabolic gene expression profile in circulating mononuclear cells reflects obesity-associated metabolic inflexibility.
Nutr Metab (Lond). 2016 Oct 27;13:74. eCollection 2016.
Baig S1, Parvaresh Rizi E2, Shabeer M1, Chhay V1, Mok SF3, Loh TP4, Magkos F5, Vidal-Puig A6, Tai ES7, Khoo CM7, Toh SA8.
Abstract – show
Obesity is associated with an impaired ability to switch from fatty acid to glucose oxidation during the fasted to fed transition, particularly in skeletal muscle. However, whether such metabolic inflexibility is reflected at the gene transcription level in circulatory mononuclear cells (MNC) is not known.
The whole-body respiratory quotient (RQ) and transcriptional regulation of genes involved in carbohydrate and lipid metabolism in MNC were measured during fasting and in response (up to 6 h) to high-carbohydrate and high-fat meals in nine lean insulin-sensitive and nine obese insulin-resistant men.
Compared to lean subjects, obese subjects had an impaired ability to increase RQ and switch from fatty acid to glucose oxidation following the high-carbohydrate meal (interaction term P < 0.05). This was accompanied by an impaired induction of genes involved in oxidative metabolism of glucose in MNC, such as phosphofructokinase (PFK), pyruvate dehydrogenase kinase 4 (PDK4), peroxisome proliferator-activated receptor alpha (PPARα) and uncoupling protein 3 (UCP3) and increased expression of genes involved in fatty acid metabolism, such as fatty acid translocase (FAT/CD36) and fatty acid synthase (FASN) (P < 0.05). On the contrary, there were no differences in the gene expression profiles between lean and obese subjects following the high-fat meal.
Postprandial expression profiles of genes involved in glucose and fatty acid metabolism in the MNC reflect the differing metabolic flexibility phenotypes of our cohort of lean and obese individuals. These differences in metabolic flexibility between the lean and obese are elicited by an acute meal challenge that is rich in carbohydrate but not fat.
PMID: 27800008 PMCID: PMC5081666 DOI: 10.1186/s12986-016-0135-5
Stearoyl-CoA Desaturase 1 Is a Key Determinant of Membrane Lipid Composition in 3T3-L1 Adipocytes.
PLoS One. 2016 Sep 15;11(9):e0162047. doi: 10.1371/journal.pone.0162047. eCollection 2016.
Rodriguez-Cuenca S1, Whyte L2, Hagen R1, Vidal-Puig A1,3, Fuller M2,4.
Abstract – show
Stearoyl-CoA desaturase 1 (SCD1) is a lipogenic enzyme important for the regulation of membrane lipid homeostasis; dysregulation likely contributes to obesity associated metabolic disturbances. SCD1 catalyses the Δ9 desaturation of 12-19 carbon saturated fatty acids to monounsaturated fatty acids. To understand its influence in cellular lipid composition we investigated the effect of genetic ablation of SCD1 in 3T3-L1 adipocytes on membrane microdomain lipid composition at the species-specific level. Using liquid chromatography/electrospray ionisation-tandem mass spectrometry, we quantified 70 species of ceramide, mono-, di- and trihexosylceramide, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, bis(monoacylglycero)phosphate, phosphatidylinositol and cholesterol in 3T3-L1 adipocytes in which a 90% reduction in scd1 mRNA expression was achieved with siRNA. Cholesterol content was unchanged although decreases in other lipids resulted in cholesterol accounting for a higher proportion of lipid in the membranes. This was associated with decreased membrane lateral diffusion. An increased ratio of 24:0 to 24:1 in ceramide, mono- and dihexosylceramide, and sphingomyelin likely also contributed to this decrease in lateral diffusion. Of particular interest, we observed a decrease in phospholipids containing arachidonic acid. Given the high degree of structural flexibility of this acyl chain this will influence membrane lateral diffusion, and is likely responsible for the transcriptional activation of Lands' cycle enzymes lpcat3 and mboat7. Of relevance these profound changes in the lipidome were not accompanied by dramatic changes in gene expression in mature differentiated adipocytes, suggesting that adaptive homeostatic mechanisms to ensure partial maintenance of the biophysical properties of membranes likely occur at a post-transcriptional level.
PMID: 27632198 PMCID: PMC5025088 DOI: 10.1371/journal.pone.0162047
Assessment of plasma acylcarnitines before and after weight loss in obese subjects.
Arch Biochem Biophys. 2016 Sep 15;606:73-80. doi: 10.1016/j.abb.2016.07.013. Epub 2016 Jul 19.
Schooneman MG1, Napolitano A2, Houten SM3, Ambler GK4, Murgatroyd PR5, Miller SR2, Hollak CE6, Tan CY4, Virtue S4, Vidal-Puig A4, Nunez DJ2, Soeters MR7.
Abstract – show
Acylcarnitines, fatty acid oxidation (FAO) intermediates, have been implicated in diet-induced insulin resistance and type 2 diabetes mellitus, as increased levels are found in obese insulin resistant humans. Moreover plasma acylcarnitines have been associated with clinical parameters related to glucose metabolism, such as fasting glucose levels and HbA1c. We hypothesized that plasma acylcarnitines would correlate with energy expenditure, insulin sensitivity and other clinical parameters before and during a weight loss intervention. We measured plasma acylcarnitines in 60 obese subjects before and after a 12 week weight loss intervention. These samples originated from three different interventions (diet alone (n = 20); diet and exercise (n = 21); diet and drug treatment (n = 19)). Acylcarnitine profiles were analysed in relation to clinical parameters of glucose metabolism, insulin sensitivity and energy expenditure. Conclusions were drawn from all 60 subjects together. Despite amelioration of HOMA-IR, plasma acylcarnitines levels increased during weight loss. HOMA-IR, energy expenditure and respiratory exchange ratio were not related to plasma acylcarnitines. However non-esterified fatty acids correlated strongly with several acylcarnitines at baseline and during the weight loss intervention (p < 0.001). Acylcarnitines did not correlate with clinical parameters of glucose metabolism during weight loss, questioning their role in insulin resistance and type 2 diabetes mellitus.
Copyright © 2016 Elsevier Inc. All rights reserved.
PMID: 27444119 DOI: 10.1016/j.abb.2016.07.013
Genetic identification of thiosulfate sulfurtransferase as an adipocyte-expressed antidiabetic target in mice selected for leanness.
Nat Med. 2016 Jul;22(7):771-9. doi: 10.1038/nm.4115. Epub 2016 Jun 6.
Morton NM1, Beltram J2, Carter RN1, Michailidou Z1, Gorjanc G2, McFadden C1, Barrios-Llerena ME1, Rodriguez-Cuenca S3, Gibbins MT1, Aird RE1, Moreno-Navarrete JM4,5,6, Munger SC7, Svenson KL7, Gastaldello A1, Ramage L1, Naredo G1, Zeyda M8, Wang ZV9, Howie AF10, Saari A11, Sipilä P12, Stulnig TM8, Gudnason V13, Kenyon CJ1, Seckl JR1, Walker BR1, Webster SP1, Dunbar DR1, Churchill GA7, Vidal-Puig A3,14, Fernandez-Real JM4,5,6, Emilsson V13,15, Horvat S2,16.
Abstract – show
The discovery of genetic mechanisms for resistance to obesity and diabetes may illuminate new therapeutic strategies for the treatment of this global health challenge. We used the polygenic 'lean' mouse model, which has been selected for low adiposity over 60 generations, to identify mitochondrial thiosulfate sulfurtransferase (Tst; also known as rhodanese) as a candidate obesity-resistance gene with selectively increased expression in adipocytes. Elevated adipose Tst expression correlated with indices of metabolic health across diverse mouse strains. Transgenic overexpression of Tst in adipocytes protected mice from diet-induced obesity and insulin-resistant diabetes. Tst-deficient mice showed markedly exacerbated diabetes, whereas pharmacological activation of TST ameliorated diabetes in mice. Mechanistically, TST selectively augmented mitochondrial function combined with degradation of reactive oxygen species and sulfide. In humans, TST mRNA expression in adipose tissue correlated positively with insulin sensitivity in adipose tissue and negatively with fat mass. Thus, the genetic identification of Tst as a beneficial regulator of adipocyte mitochondrial function may have therapeutic significance for individuals with type 2 diabetes.
PMID: 27270587 DOI: 10.1038/nm.4115
Mild cold effects on hunger, food intake, satiety and skin temperature in humans.
Endocr Connect. 2016 Mar;5(2):65-73. doi: 10.1530/EC-16-0004. Epub 2016 Feb 10.
Langeveld M1, Tan CY1, Soeters MR2, Virtue S1, Ambler GK3, Watson LP4, Murgatroyd PR4, Chatterjee VK1, Vidal-Puig A1.
Abstract – show
Mild cold exposure increases energy expenditure and can influence energy balance, but at the same time it does not increase appetite and energy intake.
To quantify dermal insulative cold response, we assessed thermal comfort and skin temperatures changes by infrared thermography.
We exposed healthy volunteers to either a single episode of environmental mild cold or thermoneutrality. We measured hunger sensation and actual free food intake. After a thermoneutral overnight stay, five males and five females were exposed to either 18°C (mild cold) or 24°C (thermoneutrality) for 2.5 h. Metabolic rate, vital signs, skin temperature, blood biochemistry, cold and hunger scores were measured at baseline and for every 30 min during the temperature intervention. This was followed by an ad libitum meal to obtain the actual desired energy intake after cold exposure.
We could replicate the cold-induced increase in REE. But no differences were detected in hunger, food intake, or satiety after mild cold exposure compared with thermoneutrality. After long-term cold exposure, high cold sensation scores were reported, which were negatively correlated with thermogenesis. Skin temperature in the sternal area was tightly correlated with the increase in energy expenditure.
It is concluded that short-term mild cold exposure increases energy expenditure without changes in food intake. Mild cold exposure resulted in significant thermal discomfort, which was negatively correlated with the increase in energy expenditure. Moreover, there is a great between-subject variability in cold response. These data provide further insights on cold exposure as an anti-obesity measure.
© 2016 The authors.
Adipose tissue plasticity: how fat depots respond differently to pathophysiological cues.
Diabetologia. 2016 Jun;59(6):1075-88. doi: 10.1007/s00125-016-3933-4. Epub 2016 Apr 4.
Pellegrinelli V1, Carobbio S2,3, Vidal-Puig A4,5.
Abstract – show
White adipose tissue (WAT) has key metabolic and endocrine functions and plays a role in regulating energy homeostasis and insulin sensitivity. WAT is characterised by its capacity to adapt and expand in response to surplus energy through processes of adipocyte hypertrophy and/or recruitment and proliferation of precursor cells in combination with vascular and extracellular matrix remodelling. However, in the context of sustained obesity, WAT undergoes fibro-inflammation, which compromises its functionality, contributing to increased risk of type 2 diabetes and cardiovascular diseases. Conversely, brown adipose tissue (BAT) and browning of WAT represent potential therapeutic approaches, since dysfunctional white adipocyte-induced lipid overspill can be halted by BAT/browning-mediated oxidative anti-lipotoxic effects. Better understanding of the cellular and molecular pathophysiological mechanisms regulating adipocyte size, number and depot-dependent expansion has become a focus of interest over recent decades. Here, we summarise the mechanisms contributing to adipose tissue (AT) plasticity and function including characteristics and cellular complexity of the various adipose depots and we discuss recent insights into AT origins, identification of adipose precursors, pathophysiological regulation of adipogenesis and its relation to WAT/BAT expandability in obesity and its associated comorbidities.
PMID: 27039901 PMCID: PMC4861754 DOI: 10.1007/s00125-016-3933-4
Erratum: Adipose tissue fatty acid chain length and mono-unsaturation increases with obesity and insulin resistance.
Sci Rep. 2016 Mar 30;6:23873. doi: 10.1038/srep23873.
Tan CY, Virtue S, Murfitt S, Roberts LD, Phua YH, Dale M, Griffin JL, Tinahones F, Scherer PE, Vidal-Puig A.
PMID: 27027977 PMCID: PMC4813347 DOI: 10.1038/srep23873
Cdkn1c Boosts the Development of Brown Adipose Tissue in a Murine Model of Silver Russell Syndrome.
PLoS Genet. 2016 Mar 10;12(3):e1005916. doi: 10.1371/journal.pgen.1005916. eCollection 2016.
Van De Pette M1, Tunster SJ1, McNamara GI1, Shelkovnikova T1, Millership S2, Benson L3, Peirson S3, Christian M4, Vidal-Puig A5, John RM1.
Abstract – show
The accurate diagnosis and clinical management of the growth restriction disorder Silver Russell Syndrome (SRS) has confounded researchers and clinicians for many years due to the myriad of genetic and epigenetic alterations reported in these patients and the lack of suitable animal models to test the contribution of specific gene alterations. Some genetic alterations suggest a role for increased dosage of the imprinted CYCLIN DEPENDENT KINASE INHIBITOR 1C (CDKN1C) gene, often mutated in IMAGe Syndrome and Beckwith-Wiedemann Syndrome (BWS). Cdkn1c encodes a potent negative regulator of fetal growth that also regulates placental development, consistent with a proposed role for CDKN1C in these complex childhood growth disorders. Here, we report that a mouse modelling the rare microduplications present in some SRS patients exhibited phenotypes including low birth weight with relative head sparing, neonatal hypoglycemia, absence of catch-up growth and significantly reduced adiposity as adults, all defining features of SRS. Further investigation revealed the presence of substantially more brown adipose tissue in very young mice, of both the classical or canonical type exemplified by interscapular-type brown fat depot in mice (iBAT) and a second type of non-classic BAT that develops postnatally within white adipose tissue (WAT), genetically attributable to a double dose of Cdkn1c in vivo and ex-vivo. Conversely, loss-of-function of Cdkn1c resulted in the complete developmental failure of the brown adipocyte lineage with a loss of markers of both brown adipose fate and function. We further show that Cdkn1c is required for post-transcriptional accumulation of the brown fat determinant PR domain containing 16 (PRDM16) and that CDKN1C and PRDM16 co-localise to the nucleus of rare label-retaining cell within iBAT. This study reveals a key requirement for Cdkn1c in the early development of the brown adipose lineages. Importantly, active BAT consumes high amounts of energy to generate body heat, providing a valid explanation for the persistence of thinness in our model and supporting a major role for elevated CDKN1C in SRS.
PMID: 26963625 PMCID: PMC4786089 DOI: 10.1371/journal.pgen.1005916
Chronic subordination stress selectively downregulates the insulin signaling pathway in liver and skeletal muscle but not in adipose tissue of male mice.
Stress. 2016;19(2):214-24. doi: 10.3109/10253890.2016.1151491. Epub 2016 Mar 7.
Sanghez V1,2, Cubuk C3, Sebastián-Leon P3, Carobbio S4, Dopazo J3, Vidal-Puig A4,5, Bartolomucci A1.
Abstract – show
Chronic stress has been associated with obesity, glucose intolerance, and insulin resistance. We developed a model of chronic psychosocial stress (CPS) in which subordinate mice are vulnerable to obesity and the metabolic-like syndrome while dominant mice exhibit a healthy metabolic phenotype. Here we tested the hypothesis that the metabolic difference between subordinate and dominant mice is associated with changes in functional pathways relevant for insulin sensitivity, glucose and lipid homeostasis. Male mice were exposed to CPS for four weeks and fed either a standard diet or a high-fat diet (HFD). We first measured, by real-time PCR candidate genes, in the liver, skeletal muscle, and the perigonadal white adipose tissue (pWAT). Subsequently, we used a probabilistic analysis approach to analyze different ways in which signals can be transmitted across the pathways in each tissue. Results showed that subordinate mice displayed a drastic downregulation of the insulin pathway in liver and muscle, indicative of insulin resistance, already on standard diet. Conversely, pWAT showed molecular changes suggestive of facilitated fat deposition in an otherwise insulin-sensitive tissue. The molecular changes in subordinate mice fed a standard diet were greater compared to HFD-fed controls. Finally, dominant mice maintained a substantially normal metabolic and molecular phenotype even when fed a HFD. Overall, our data demonstrate that subordination stress is a potent stimulus for the downregulation of the insulin signaling pathway in liver and muscle and a major risk factor for the development of obesity, insulin resistance, and type 2 diabetes mellitus.
Deriving functional beige fat from capillaries.
Nat Med. 2016 Mar;22(3):234-6. doi: 10.1038/nm.4056.
Pellegrinelli V1, Vidal-Puig A1,2.
PMID: 26937616 DOI: 10.1038/nm.4056
Mitochondria are required for pro-ageing features of the senescent phenotype.
EMBO J. 2016 Apr 1;35(7):724-42. doi: 10.15252/embj.201592862. Epub 2016 Feb 4.
Correia-Melo C1, Marques FD2, Anderson R2, Hewitt G2, Hewitt R3, Cole J3, Carroll BM2, Miwa S2, Birch J2, Merz A2, Rushton MD2, Charles M2, Jurk D2, Tait SW3, Czapiewski R2, Greaves L4, Nelson G2, Bohlooly-Y M5, Rodriguez-Cuenca S6, Vidal-Puig A6, Mann D7, Saretzki G2, Quarato G8, Green DR8, Adams PD3, von Zglinicki T2, Korolchuk VI2, Passos JF9.
Abstract – show
Cell senescence is an important tumour suppressor mechanism and driver of ageing. Both functions are dependent on the development of the senescent phenotype, which involves an overproduction of pro-inflammatory and pro-oxidant signals. However, the exact mechanisms regulating these phenotypes remain poorly understood. Here, we show the critical role of mitochondria in cellular senescence. In multiple models of senescence, absence of mitochondria reduced a spectrum of senescence effectors and phenotypes while preserving ATP production via enhanced glycolysis. Global transcriptomic analysis by RNA sequencing revealed that a vast number of senescent-associated changes are dependent on mitochondria, particularly the pro-inflammatory phenotype. Mechanistically, we show that the ATM, Akt and mTORC1 phosphorylation cascade integrates signals from the DNA damage response (DDR) towards PGC-1β-dependent mitochondrial biogenesis, contributing to aROS-mediated activation of the DDR and cell cycle arrest. Finally, we demonstrate that the reduction in mitochondrial content in vivo, by either mTORC1 inhibition or PGC-1β deletion, prevents senescence in the ageing mouse liver. Our results suggest that mitochondria are a candidate target for interventions to reduce the deleterious impact of senescence in ageing tissues.
© 2016 The Authors. Published under the terms of the CC BY 4.0 license.
PMID: 26848154 PMCID: PMC4818766 DOI: 10.15252/embj.201592862
Stress-induced activation of brown adipose tissue prevents obesity in conditions of low adaptive thermogenesis.
Mol Metab. 2015 Nov 11;5(1):19-33. doi: 10.1016/j.molmet.2015.10.005. eCollection 2016.
Razzoli M1, Frontini A2, Gurney A1, Mondini E2, Cubuk C3, Katz LS4, Cero C1, Bolan PJ5, Dopazo J3, Vidal-Puig A6, Cinti S2, Bartolomucci A1.
Abstract – show
Stress-associated conditions such as psychoemotional reactivity and depression have been paradoxically linked to either weight gain or weight loss. This bi-directional effect of stress is not understood at the functional level. Here we tested the hypothesis that pre-stress level of adaptive thermogenesis and brown adipose tissue (BAT) functions explain the vulnerability or resilience to stress-induced obesity.
We used wt and triple β1,β2,β3-Adrenergic Receptors knockout (β-less) mice exposed to a model of chronic subordination stress (CSS) at either room temperature (22 °C) or murine thermoneutrality (30 °C). A combined behavioral, physiological, molecular, and immunohistochemical analysis was conducted to determine stress-induced modulation of energy balance and BAT structure and function. Immortalized brown adipocytes were used for in vitro assays.
Departing from our initial observation that βARs are dispensable for cold-induced BAT browning, we demonstrated that under physiological conditions promoting low adaptive thermogenesis and BAT activity (e.g. thermoneutrality or genetic deletion of the βARs), exposure to CSS acted as a stimulus for BAT activation and thermogenesis, resulting in resistance to diet-induced obesity despite the presence of hyperphagia. Conversely, in wt mice acclimatized to room temperature, and therefore characterized by sustained BAT function, exposure to CSS increased vulnerability to obesity. Exposure to CSS enhanced the sympathetic innervation of BAT in wt acclimatized to thermoneutrality and in β-less mice. Despite increased sympathetic innervation suggesting adrenergic-mediated browning, norepinephrine did not promote browning in βARs knockout brown adipocytes, which led us to identify an alternative sympathetic/brown adipocytes purinergic pathway in the BAT. This pathway is downregulated under conditions of low adaptive thermogenesis requirements, is induced by stress, and elicits activation of UCP1 in wt and β-less brown adipocytes. Importantly, this purinergic pathway is conserved in human BAT.
Our findings demonstrate that thermogenesis and BAT function are determinant of the resilience or vulnerability to stress-induced obesity. Our data support a model in which adrenergic and purinergic pathways exert complementary/synergistic functions in BAT, thus suggesting an alternative to βARs agonists for the activation of human BAT.
PMID: 26844204 PMCID: PMC4703853 DOI: 10.1016/j.molmet.2015.10.005
Adipose tissue fatty acid chain length and mono-unsaturation increases with obesity and insulin resistance.
Sci Rep. 2015 Dec 17;5:18366. doi: 10.1038/srep18366.
Yew Tan C1, Virtue S1, Murfitt S2, Roberts LD, Phua YH2, Dale M1, Griffin JL2,3, Tinahones F4, Scherer PE5, Vidal-Puig A1,6.
Abstract – show
The non-essential fatty acids, C18:1n9, C16:0, C16:1n7, C18:0 and C18:1n7 account for over 75% of fatty acids in white adipose (WAT) triacylglycerol (TAG). The relative composition of these fatty acids (FA) is influenced by the desaturases, SCD1-4 and the elongase, ELOVL6. In knock-out models, loss of SCD1 or ELOVL6 results in reduced Δ9 desaturated and reduced 18-carbon non-essential FA respectively. Both Elovl6 KO and SCD1 KO mice exhibit improved insulin sensitivity. Here we describe the relationship between WAT TAG composition in obese mouse models and obese humans stratified for insulin resistance. In mouse models with increasing obesity and insulin resistance, there was an increase in scWAT Δ9 desaturated FAs (SCD ratio) and FAs with 18-carbons (Elovl6 ratio) in mice. Data from mouse models discordant for obesity and insulin resistance (AKT2 KO, Adiponectin aP2-transgenic), suggested that scWAT TAG Elovl6 ratio was associated with insulin sensitivity, whereas SCD1 ratio was associated with fat mass. In humans, a greater SCD1 and Elovl6 ratio was found in metabolically more harmful visceral adipose tissue when compared to subcutaneous adipose tissue.
PMID: 26679101 PMCID: PMC4683622 DOI: 10.1038/srep18366
Brown Adipose Tissue Thermogenic Capacity Is Regulated by Elovl6.
Cell Rep. 2015 Dec 15;13(10):2039-47. doi: 10.1016/j.celrep.2015.11.004. Epub 2015 Nov 25.
Tan CY1, Virtue S2, Bidault G1, Dale M1, Hagen R1, Griffin JL3, Vidal-Puig A4.
Abstract – show
Although many transcriptional pathways regulating BAT have been identified, the role of lipid biosynthetic enzymes in thermogenesis has been less investigated. Whereas cold exposure causes changes in the fatty acid composition of BAT, the functional consequences of this remains relatively unexplored. In this study, we demonstrate that the enzyme Elongation of Very Long Chain fatty acids 6 (Elovl6) is necessary for the thermogenic action of BAT. Elovl6 is responsible for converting C16 non-essential fatty acids into C18 species. Loss of Elovl6 does not modulate traditional BAT markers; instead, it causes reduced expression of mitochondrial electron transport chain components and lower BAT thermogenic capacity. The reduction in BAT activity appears to be counteracted by increased beiging of scWAT. When beige fat is disabled by thermoneutrality or aging, Elovl6 KO mice gain weight and have increased scWAT mass and impaired carbohydrate metabolism. Overall, our study suggests fatty acid chain length is important for BAT function.
Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
PMID: 26628376 PMCID: PMC4688035 DOI: 10.1016/j.celrep.2015.11.004
Unsuppressed lipolysis in adipocytes is linked with enhanced gluconeogenesis and altered bile acid physiology in Insr(P1195L/+) mice fed high-fat-diet.
Sci Rep. 2015 Nov 30;5:17565. doi: 10.1038/srep17565.
Lee EY1, Sakurai K2, Zhang X1, Toda C3, Tanaka T2, Jiang M4, Shirasawa T5, Tachibana K2, Yokote K2, Vidal-Puig A6, Minokoshi Y3, Miki T1.
Abstract – show
High-fat diet (HFD) triggers insulin resistance and diabetes mellitus, but their link remains unclear. Characterization of overt hyperglycemia in insulin receptor mutant (Insr(P1195L/+)) mice exposed to HFD (Insr(P1195L/+)/HFD mice) revealed increased glucose-6-phosphatase (G6pc) expression in liver and increased gluconeogenesis from glycerol. Lipolysis in white adipose tissues (WAT) and lipolysis-induced blood glucose rise were increased in Insr(P1195L/+)/HFD mice, while wild-type WAT transplantation ameliorated the hyperglycemia and the increased G6pc expression. We found that the expressions of genes involved in bile acid (BA) metabolism were altered in Insr(P1195L/+)/HFD liver. Among these, the expression of Cyp7a1, a BA synthesis enzyme, was insulin-dependent and was markedly decreased in Insr(P1195L/+)/HFD liver. Reduced Cyp7a1 expression in Insr(P1195L/+)/HFD liver was rescued by WAT transplantation, and the expression of Cyp7a1 was suppressed by glycerol administration in wild-type liver. These findings suggest that unsuppressed lipolysis in adipocytes elicited by HFD feeding is linked with enhanced gluconeogenesis from glycerol and with alterations in BA physiology in Insr(P1195L/+)/HFD liver.
PMID: 26615883 PMCID: PMC4663474 DOI: 10.1038/srep17565
Soluble LR11/SorLA represses thermogenesis in adipose tissue and correlates with BMI in humans.
Nat Commun. 2015 Nov 20;6:8951. doi: 10.1038/ncomms9951.
Whittle AJ1, Jiang M2,3, Peirce V1, Relat J4, Virtue S1, Ebinuma H5, Fukamachi I5, Yamaguchi T6, Takahashi M7, Murano T2, Tatsuno I6, Takeuchi M8, Nakaseko C8, Jin W9, Jin Z10, Campbell M1, Schneider WJ11, Vidal-Puig A1,12, Bujo H2,3.
Abstract – show
Thermogenesis in brown adipose tissue (BAT) is an important component of energy expenditure in mammals. Recent studies have confirmed its presence and metabolic role in humans. Defining the physiological regulation of BAT is therefore of great importance for developing strategies to treat metabolic diseases. Here we show that the soluble form of the low-density lipoprotein receptor relative, LR11/SorLA (sLR11), suppresses thermogenesis in adipose tissue in a cell-autonomous manner. Mice lacking LR11 are protected from diet-induced obesity associated with an increased browning of white adipose tissue and hypermetabolism. Treatment of adipocytes with sLR11 inhibits thermogenesis via the bone morphogenetic protein/TGFβ signalling pathway and reduces Smad phosphorylation. In addition, sLR11 levels in humans are shown to positively correlate with body mass index and adiposity. Given the need for tight regulation of a tissue with a high capacity for energy wastage, we propose that LR11 plays an energy conserving role that is exaggerated in states of obesity.
PMID: 26584636 PMCID: PMC4673879 DOI: 10.1038/ncomms9951
Hypophagia and metabolic adaptations in mice with defective ATGL-mediated lipolysis cause resistance to HFD-induced obesity.
Proc Natl Acad Sci U S A. 2015 Nov 10;112(45):13850-5. doi: 10.1073/pnas.1516004112. Epub 2015 Oct 27.
Schreiber R1, Hofer P2, Taschler U2, Voshol PJ3, Rechberger GN2, Kotzbeck P2, Jaeger D2, Preiss-Landl K2, Lord CC4, Brown JM4, Haemmerle G2, Zimmermann R2, Vidal-Puig A3, Zechner R1.
Abstract – show
Adipose triglyceride lipase (ATGL) initiates intracellular triglyceride (TG) catabolism. In humans, ATGL deficiency causes neutral lipid storage disease with myopathy (NLSDM) characterized by a systemic TG accumulation. Mice with a genetic deletion of ATGL (AKO) also accumulate TG in many tissues. However, neither NLSDM patients nor AKO mice are exceedingly obese. This phenotype is unexpected considering the importance of the enzyme for TG catabolism in white adipose tissue (WAT). In this study, we identified the counteracting mechanisms that prevent excessive obesity in the absence of ATGL. We used "healthy" AKO mice expressing ATGL exclusively in cardiomyocytes (AKO/cTg) to circumvent the cardiomyopathy and premature lethality observed in AKO mice. AKO/cTg mice were protected from high-fat diet (HFD)-induced obesity despite complete ATGL deficiency in WAT and normal adipocyte differentiation. AKO/cTg mice were highly insulin sensitive under hyperinsulinemic-euglycemic clamp conditions, eliminating insulin insensitivity as a possible protective mechanism. Instead, reduced food intake and altered signaling by peroxisome proliferator-activated receptor-gamma (PPAR-γ) and sterol regulatory element binding protein-1c in WAT accounted for the phenotype. These adaptations led to reduced lipid synthesis and storage in WAT of HFD-fed AKO/cTg mice. Treatment with the PPAR-γ agonist rosiglitazone reversed the phenotype. These results argue for the existence of an adaptive interdependence between lipolysis and lipid synthesis. Pharmacological inhibition of ATGL may prove useful to prevent HFD-induced obesity and insulin resistance.
PMID: 26508640 PMCID: PMC4653216 DOI: 10.1073/pnas.1516004112
Fatty Acid and Glucose Sensors in Hepatic Lipid Metabolism: Implications in NAFLD.
Semin Liver Dis. 2015 Aug;35(3):250-61. doi: 10.1055/s-0035-1562945. Epub 2015 Sep 17.
Vacca M1, Allison M2, Griffin JL1, Vidal-Puig A3.
Abstract – show
The term nonalcoholic fatty liver disease (NAFLD) covers a pathologic spectrum from lipid accumulation alone (simple steatosis) to steatosis with associated inflammation and fibrosis (nonalcoholic steatohepatitis [NASH]). Nonalcoholic steatohepatitis can progress to cirrhosis and potentially to hepatocellular carcinoma. Although a genetic predisposition has been highlighted, NAFLD is strongly associated with an unhealthy lifestyle and hypercaloric diet in the context of obesity and metabolic disease. The dysregulation of specific pathways (insulin signaling, mitochondrial function, fatty acid, and lipoprotein metabolism) have been linked to steatosis, but elucidating the molecular events determining evolution of the disease still requires further research before it can be translated into specific personalized interventional strategies. In this review, the authors focus on the early events of the pathophysiology of NASH, dissecting the metabolic and nutritional pathways involving fatty acids and glucose sensors that can modulate lipid accumulation in the liver, but also condition the progression to cirrhosis and hepatocellular carcinoma.
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.
PMID: 26378642 DOI: 10.1055/s-0035-1562945
Regulation of mitochondrial morphology and function by stearoylation of TFR1.
Nature. 2015 Sep 3;525(7567):124-8. doi: 10.1038/nature14601. Epub 2015 Jul 27.
Senyilmaz D1, Virtue S2, Xu X1, Tan CY2, Griffin JL3, Miller AK1, Vidal-Puig A2,4, Teleman AA1.
Abstract – show
Mitochondria are involved in a variety of cellular functions, including ATP production, amino acid and lipid biogenesis and breakdown, signalling and apoptosis. Mitochondrial dysfunction has been linked to neurodegenerative diseases, cancer and ageing. Although transcriptional mechanisms that regulate mitochondrial abundance are known, comparatively little is known about how mitochondrial function is regulated. Here we identify the metabolite stearic acid (C18:0) and human transferrin receptor 1 (TFR1; also known as TFRC) as mitochondrial regulators. We elucidate a signalling pathway whereby C18:0 stearoylates TFR1, thereby inhibiting its activation of JNK signalling. This leads to reduced ubiquitination of mitofusin via HUWE1, thereby promoting mitochondrial fusion and function. We find that animal cells are poised to respond to both increases and decreases in C18:0 levels, with increased C18:0 dietary intake boosting mitochondrial fusion in vivo. Intriguingly, dietary C18:0 supplementation can counteract the mitochondrial dysfunction caused by genetic defects such as loss of the Parkinson's disease genes Pink or Parkin in Drosophila. This work identifies the metabolite C18:0 as a signalling molecule regulating mitochondrial function in response to diet.
PMID: 26214738 PMCID: PMC4561519 DOI: 10.1038/nature14601
Lipopolysaccharide binding protein is an adipokine involved in the resilience of the mouse adipocyte to inflammation.
Diabetologia. 2015 Oct;58(10):2424-34. doi: 10.1007/s00125-015-3692-7. Epub 2015 Jul 23.
Moreno-Navarrete JM1,2,3, Escoté X4,5,6, Ortega F1,2,3, Camps M7, Ricart W1,2,3, Zorzano A6,7,8, Vendrell J4,5,6, Vidal-Puig A9, Fernández-Real JM10,11,12.
Abstract – show
Lipopolysaccharide (LPS) binding protein (LBP) is a novel 65 kDa adipokine, linked to adipose tissue (AT) inflammation, obesity and insulin resistance, that inhibits adipocyte differentiation. Here, we investigated the molecular mechanisms behind these detrimental effects on adipogenesis through whole-genome transcriptomics and in vitro experiments.
Permanent and transient knockdown (KD) and co-culture experiments were performed in 3T3-L1 and 3T3-F442A cell lines during adipocyte differentiation. Microarray gene expression was performed using Genechip Affymetrix technology and validated by real-time PCR.
LBP KD of 3T3-L1 cells led to a potentiated adipocyte differentiation with a dose-response relationship; genes involved in mitochondrial biogenesis, fatty acid metabolism and peroxisome proliferator-activated receptor γ (PPAR-γ) action were dramatically upregulated in parallel to increased insulin signalling. Cells with LBP KD became refractory to proinflammatory cytokines and other inflammatory stimuli (LPS and palmitate). This phenotype, mediated through disrupted nuclear factor κB (NFκB) signalling, was reversed by a soluble factor present in a co-culture with native cells and by exogenous LBP. Double-silencing of LBP and toll-like receptor 4 (TLR4) again rendered these cells insensitive to co-culture, LBP and inflammatory factors.
In summary, LBP is a proinflammatory soluble adipokine that acts as a brake for adipogenesis, strengthening the negative effects of palmitate and LPS on adipocyte differentiation.
PMID: 26201685 DOI: 10.1007/s00125-015-3692-7
Ribosomal S6K1 in POMC and AgRP Neurons Regulates Glucose Homeostasis but Not Feeding Behavior in Mice.
Cell Rep. 2015 Apr 21;11(3):335-43. doi: 10.1016/j.celrep.2015.03.029. Epub 2015 Apr 9.
Smith MA1, Katsouri L2, Irvine EE2, Hankir MK2, Pedroni SM2, Voshol PJ3, Gordon MW2, Choudhury AI2, Woods A4, Vidal-Puig A3, Carling D4, Withers DJ5.
Abstract – show
Hypothalamic ribosomal S6K1 has been suggested as a point of convergence for hormonal and nutrient signals in the regulation of feeding behavior, bodyweight, and glucose metabolism. However, the long-term effects of manipulating hypothalamic S6K1 signaling on energy homeostasis and the cellular mechanisms underlying these roles are unclear. We therefore inactivated S6K1 in pro-opiomelanocortin (POMC) and agouti-related protein (AgRP) neurons, key regulators of energy homeostasis, but in contrast to the current view, we found no evidence that S6K1 regulates food intake and bodyweight. In contrast, S6K1 signaling in POMC neurons regulated hepatic glucose production and peripheral lipid metabolism and modulated neuronal excitability. S6K1 signaling in AgRP neurons regulated skeletal muscle insulin sensitivity and was required for glucose sensing by these neurons. Our findings suggest that S6K1 signaling is not a general integrator of energy homeostasis in the mediobasal hypothalamus but has distinct roles in the regulation of glucose homeostasis by POMC and AgRP neurons.
Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
PMID: 25865886 PMCID: PMC4410943 DOI: 10.1016/j.celrep.2015.03.029
Prostaglandin profiling reveals a role for haematopoietic prostaglandin D synthase in adipose tissue macrophage polarisation in mice and humans.
Int J Obes (Lond). 2015 Jul;39(7):1151-60. doi: 10.1038/ijo.2015.34. Epub 2015 Mar 24.
Virtue S1, Masoodi M2, de Weijer BA3, van Eijk M4, Mok CY1, Eiden M5, Dale M1, Pirraco A1, Serlie MJ3, Griffin JL6, Vidal-Puig A1.
Abstract – show
Obesity has been associated with both changes in adipose tissue lipid metabolism and inflammation. A key class of lipid-derived signalling molecules involved in inflammation are the prostaglandins. In this study, we aimed to determine how obesity affects the levels of prostaglandins within white adipose tissue (WAT) and determine which cells within adipose tissue produce them. To avoid the effects of cellular stress on prostaglandin levels, we developed a multivariate statistical approach in which metabolite concentrations and transcriptomic data were integrated, allowing the assignment of metabolites to cell types.
Eicosanoids were measured by liquid chromatography-tandem mass spectrometry and mRNA levels using real-time PCR. Eicosanoid levels and transcriptomic data were combined using principal component analysis and hierarchical clustering in order to associate metabolites with cell types. Samples were obtained from C57Bl/6 mice aged 16 weeks. We studied the ob/ob genetically obese mouse model and diet-induced obesity model. We extended our results in mice to a cohort of morbidly obese humans undergoing bariatric surgery.
Using our modelling approach, we determined that prostglandin D₂ (PGD₂) in adipose tissue was predominantly produced in macrophages by the haematopoietic isoform of prostaglandin D synthase (H-Pgds). Analysis of sub-fractionated WAT confirmed that H-Pgds was expressed in adipose tissue macrophages (ATMs). Furthermore, H-Pgds expression in ATMs isolated from lean and obese mice was consistent with it affecting macrophage polarisation. Functionally, we demonstrated that H-PGDS-produced PGD₂ polarised macrophages toward an M2, anti-inflammatory state. In line with a potential anti-inflammatory role, we found that H-PGDS expression in ATMs was positively correlated with both peripheral insulin and adipose tissue insulin sensitivity in humans.
In this study, we have developed a method to determine the cellular source of metabolites within an organ and used it to identify a new role for PGD₂ in the control of ATM polarisation.
PMID: 25801691 PMCID: PMC4486370 DOI: 10.1038/ijo.2015.34
Human Adipocytes Induce Inflammation and Atrophy in Muscle Cells During Obesity.
Diabetes. 2015 Sep;64(9):3121-34. doi: 10.2337/db14-0796. Epub 2015 Feb 18.
Pellegrinelli V1, Rouault C2, Rodriguez-Cuenca S3, Albert V2, Edom-Vovard F4, Vidal-Puig A3, Clément K2, Butler-Browne GS4, Lacasa D2.
Abstract – show
Inflammation and lipid accumulation are hallmarks of muscular pathologies resulting from metabolic diseases such as obesity and type 2 diabetes. During obesity, the hypertrophy of visceral adipose tissue (VAT) contributes to muscle dysfunction, particularly through the dysregulated production of adipokines. We have investigated the cross talk between human adipocytes and skeletal muscle cells to identify mechanisms linking adiposity and muscular dysfunctions. First, we demonstrated that the secretome of obese adipocytes decreased the expression of contractile proteins in myotubes, consequently inducing atrophy. Using a three-dimensional coculture of human myotubes and VAT adipocytes, we showed the decreased expression of genes corresponding to skeletal muscle contractility complex and myogenesis. We demonstrated an increased secretion by cocultured cells of cytokines and chemokines with interleukin (IL)-6 and IL-1β as key contributors. Moreover, we gathered evidence showing that obese subcutaneous adipocytes were less potent than VAT adipocytes in inducing these myotube dysfunctions. Interestingly, the atrophy induced by visceral adipocytes was corrected by IGF-II/insulin growth factor binding protein-5. Finally, we observed that the skeletal muscle of obese mice displayed decreased expression of muscular markers in correlation with VAT hypertrophy and abnormal distribution of the muscle fiber size. In summary, we show the negative impact of obese adipocytes on muscle phenotype, which could contribute to muscle wasting associated with metabolic disorders.
© 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.
PMID: 25695947 DOI: 10.2337/db14-0796
Hematopoietic IKBKE limits the chronicity of inflammasome priming and metaflammation.
Proc Natl Acad Sci U S A. 2015 Jan 13;112(2):506-11. doi: 10.1073/pnas.1414536112. Epub 2014 Dec 24.
Patel MN1, Bernard WG2, Milev NB1, Cawthorn WP1, Figg N3, Hart D1, Prieur X1, Virtue S1, Hegyi K1, Bonnafous S4, Bailly-Maitre B4, Chu Y5, Griffin JL5, Mallat Z3, Considine RV6, Tran A4, Gual P4, Takeuchi O7, Akira S7, Vidal-Puig A1, Bennett MR3, Sethi JK8.
Abstract – show
Obesity increases the risk of developing life-threatening metabolic diseases including cardiovascular disease, fatty liver disease, diabetes, and cancer. Efforts to curb the global obesity epidemic and its impact have proven unsuccessful in part by a limited understanding of these chronic progressive diseases. It is clear that low-grade chronic inflammation, or metaflammation, underlies the pathogenesis of obesity-associated type 2 diabetes and atherosclerosis. However, the mechanisms that maintain chronicity and prevent inflammatory resolution are poorly understood. Here, we show that inhibitor of κB kinase epsilon (IKBKE) is a novel regulator that limits chronic inflammation during metabolic disease and atherosclerosis. The pathogenic relevance of IKBKE was indicated by the colocalization with macrophages in human and murine tissues and in atherosclerotic plaques. Genetic ablation of IKBKE resulted in enhanced and prolonged priming of the NLRP3 inflammasome in cultured macrophages, in hypertrophic adipose tissue, and in livers of hypercholesterolemic mice. This altered profile associated with enhanced acute phase response, deregulated cholesterol metabolism, and steatoheptatitis. Restoring IKBKE only in hematopoietic cells was sufficient to reverse elevated inflammasome priming and these metabolic features. In advanced atherosclerotic plaques, loss of IKBKE and hematopoietic cell restoration altered plaque composition. These studies reveal a new role for hematopoietic IKBKE: to limit inflammasome priming and metaflammation.
PMID: 25540417 PMCID: PMC4299251 DOI: 10.1073/pnas.1414536112
A Selective Sweep on a Deleterious Mutation in CPT1A in Arctic Populations.
Am J Hum Genet. 2014 Oct 23;95(5):584-589. doi: 10.1016/j.ajhg.2014.09.016. [Epub ahead of print]
Clemente FJ1, Cardona A2, Inchley CE1, Peter BM3, Jacobs G4, Pagani L1, Lawson DJ5, Antão T6, Vicente M1, Mitt M7, DeGiorgio M8, Faltyskova Z1, Xue Y9, Ayub Q9, Szpak M9, Mägi R7, Eriksson A10, Manica A11, Raghavan M12, Rasmussen M12, Rasmussen S13, Willerslev E12, Vidal-Puig A14, Tyler-Smith C9, Villems R15, Nielsen R3, Metspalu M16, Malyarchuk B17, Derenko M17, Kivisild T18.
Abstract – show
Arctic populations live in an environment characterized by extreme cold and the absence of plant foods for much of the year and are likely to have undergone genetic adaptations to these environmental conditions in the time they have been living there. Genome-wide selection scans based on genotype data from native Siberians have previously highlighted a 3 Mb chromosome 11 region containing 79 protein-coding genes as the strongest candidates for positive selection in Northeast Siberians. However, it was not possible to determine which of the genes might be driving the selection signal. Here, using whole-genome high-coverage sequence data, we identified the most likely causative variant as a nonsynonymous G>A transition (rs80356779; c.1436C>T [p.Pro479Leu] on the reverse strand) in CPT1A, a key regulator of mitochondrial long-chain fatty-acid oxidation. Remarkably, the derived allele is associated with hypoketotic hypoglycemia and high infant mortality yet occurs at high frequency in Canadian and Greenland Inuits and was also found at 68% frequency in our Northeast Siberian sample. We provide evidence of one of the strongest selective sweeps reported in humans; this sweep has driven this variant to high frequency in circum-Arctic populations within the last 6-23 ka despite associated deleterious consequences, possibly as a result of the selective advantage it originally provided to either a high-fat diet or a cold environment.
Copyright © 2014 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.
PMID: 25449608 PMCID: PMC4225582 DOI: 10.1016/j.ajhg.2014.09.016
Increased dihydroceramide/ceramide ratio mediated by defective expression of degs1 impairs adipocyte differentiation and function.
Diabetes. 2015 Apr;64(4):1180-92. doi: 10.2337/db14-0359. Epub 2014 Oct 28.
Barbarroja N1, Rodriguez-Cuenca S2, Nygren H3, Camargo A4, Pirraco A5, Relat J6, Cuadrado I7, Pellegrinelli V8, Medina-Gomez G8, Lopez-Pedrera C9, Tinahones FJ10, Symons JD11, Summers SA12, Oresic M13, Vidal-Puig A14.
Abstract – show
Adipose tissue dysfunction is an important determinant of obesity-associated, lipid-induced metabolic complications. Ceramides are well-known mediators of lipid-induced insulin resistance in peripheral organs such as muscle. DEGS1 is the desaturase catalyzing the last step in the main ceramide biosynthetic pathway. Functional suppression of DEGS1 activity results in substantial changes in ceramide species likely to affect fundamental biological functions such as oxidative stress, cell survival, and proliferation. Here, we show that degs1 expression is specifically decreased in the adipose tissue of obese patients and murine models of genetic and nutritional obesity. Moreover, loss-of-function experiments using pharmacological or genetic ablation of DEGS1 in preadipocytes prevented adipogenesis and decreased lipid accumulation. This was associated with elevated oxidative stress, cellular death, and blockage of the cell cycle. These effects were coupled with increased dihydroceramide content. Finally, we validated in vivo that pharmacological inhibition of DEGS1 impairs adipocyte differentiation. These data identify DEGS1 as a new potential target to restore adipose tissue function and prevent obesity-associated metabolic disturbances.
© 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.
PMID: 25352638 DOI: 10.2337/db14-0359
DLK1/PREF1 regulates nutrient metabolism and protects from steatosis.
Proc Natl Acad Sci U S A. 2014 Nov 11;111(45):16088-93. doi: 10.1073/pnas.1406119111. Epub 2014 Oct 27.
Charalambous M1, Da Rocha ST2, Radford EJ2, Medina-Gomez G3, Curran S2, Pinnock SB2, Ferrón SR2, Vidal-Puig A3, Ferguson-Smith AC1.
Abstract – show
Nonalcoholic fatty liver disease (NAFLD) is associated with insulin resistance and obesity, as well as progressive liver dysfunction. Recent animal studies have underscored the importance of hepatic growth hormone (GH) signaling in the development of NAFLD. The imprinted Delta-like homolog 1 (Dlk1)/preadipocyte factor 1 (Pref1) gene encodes a complex protein producing both circulating and membrane-tethered isoforms whose expression dosage is functionally important because even modest elevation during embryogenesis causes lethality. DLK1 is up-regulated during embryogenesis, during suckling, and in the mother during pregnancy. We investigated the normal role for elevated DLK1 dosage by overexpressing Dlk1 from endogenous control elements. This increased DLK1 dosage caused improved glucose tolerance with no primary defect in adipose tissue expansion even under extreme metabolic stress. Rather, Dlk1 overexpression caused reduced fat stores, pituitary insulin-like growth factor 1 (IGF1) resistance, and a defect in feedback regulation of GH. Increased circulatory GH culminated in a switch in whole body fuel metabolism and a reduction in hepatic steatosis. We propose that the function of DLK1 is to shift the metabolic mode of the organism toward peripheral lipid oxidation and away from lipid storage, thus mediating important physiological adaptations associated with early life and with implications for metabolic disease resistance.
PMID: 25349437 PMCID: PMC4234615 DOI: 10.1073/pnas.1406119111
Understanding disease mechanisms with models of signaling pathway activities.
BMC Syst Biol. 2014 Oct 25;8:121. doi: 10.1186/s12918-014-0121-3.
Sebastian-Leon P1, Vidal E2,3,4, Minguez P5,6, Conesa A7, Tarazona S8, Amadoz A9, Armero C10, Salavert F11,12, Vidal-Puig A13, Montaner D14, Dopazo J15,16,17.
Abstract – show
Understanding the aspects of the cell functionality that account for disease or drug action mechanisms is one of the main challenges in the analysis of genomic data and is on the basis of the future implementation of precision medicine.
Here we propose a simple probabilistic model in which signaling pathways are separated into elementary sub-pathways or signal transmission circuits (which ultimately trigger cell functions) and then transforms gene expression measurements into probabilities of activation of such signal transmission circuits. Using this model, differential activation of such circuits between biological conditions can be estimated. Thus, circuit activation statuses can be interpreted as biomarkers that discriminate among the compared conditions. This type of mechanism-based biomarkers accounts for cell functional activities and can easily be associated to disease or drug action mechanisms. The accuracy of the proposed model is demonstrated with simulations and real datasets.
The proposed model provides detailed information that enables the interpretation disease mechanisms as a consequence of the complex combinations of altered gene expression values. Moreover, it offers a framework for suggesting possible ways of therapeutic intervention in a pathologically perturbed system.
PMID: 25344409 PMCID: PMC4213475 DOI: 10.1186/s12918-014-0121-3
Dihydroceramide desaturase 1, the gatekeeper of ceramide induced lipotoxicity.
Biochim Biophys Acta. 2015 Jan;1851(1):40-50. doi: 10.1016/j.bbalip.2014.09.021. Epub 2014 Oct 2.
Rodriguez-Cuenca S1, Barbarroja N2, Vidal-Puig A3.
Abstract – show
The pathogenic relevance of sphingolipid metabolism is increasingly being recognised. Here we elaborate on a new player within the sphingolipid field: the degs1 enzyme, a recently discovered enzyme that catalyses the final step in the de novo biosynthesis of ceramides controlling the step from dihydroceramides to ceramides. Here, we describe its function and dysregulation by factors such as oxidative stress, hypoxia and inflammation and provide evidence indicating that dihydroceramides constitute a biologically active molecule from the sphingolipid family with certain differential characteristics with respect to its delta-4 unsaturated counterparts, the ceramides. Finally we present pathophysiological scenarios characterised by specific increases in dihydroceramide that challenge the concept that "all ceramides species are the same". This article is part of a Special Issue entitled Linking transcription to physiology in lipodomics.
Copyright © 2014 Elsevier B.V. All rights reserved.
PMID: 25283058 DOI: 10.1016/j.bbalip.2014.09.021
Transducin-like enhancer of split 3 (TLE3) in adipose tissue is increased in situations characterized by decreased PPARγ gene expression.
J Mol Med (Berl). 2015 Jan;93(1):83-92. doi: 10.1007/s00109-014-1207-5. Epub 2014 Sep 25.
Ortega FJ1, Serrano M, Rodriguez-Cuenca S, Moreno-Navarrete JM, Gómez-Serrano M, Sabater M, Rodriguez-Hermosa JI, Xifra G, Ricart W, Peral B, Vidal-Puig A, Fernández-Real JM.
Abstract – show
Transgenic overexpression of adipose tissue (AT) transducin-like enhancer of split 3 (TLE3) mimicked peroxisome proliferator-activated receptor gamma (PPARγ) agonists, improving insulin resistance in mice. This study aimed to investigate TLE3 gene expression (qRT-PCR) and protein (Western blot) in subjects with a wide spectrum of obesity and insulin sensitivity and in an independent cohort of obese subjects following surgery-induced weight loss. TLE3 was analyzed in human adipocytes and after treatment with rosiglitazone. Given the findings in humans, TLE3 was also investigated in mice after a high-fat diet (HFD) and in PPARγ knockout mice. Subcutaneous (SC) AT TLE3 was increased in subjects with type 2 diabetes (T2D). In fact, SC TLE3 was associated with increased fasting glucose (r = 0.25, p = 0.015) and S6K1 activity (r = 0.671, p = 0.003), and with decreased Glut4 (r = -0.426, p = 0.006) and IRS-1 expression (-31 %, p = 0.007) and activation (P-IRS-1/IRS-1, -17 %, p = 0.024). TLE3 was preferentially expressed in mature adipocytes and increased during in vitro differentiation in parallel to PPARγ. Weight loss led to improved insulin sensitivity, increased AT PPARγ and decreased TLE3 (-24 %, p = 0.0002), while rosiglitazone administration downregulated TLE3 gene expression in fully differentiated adipocytes (-45 %, p < 0.0001). The concept that TLE3 may act as a homeostatic linchpin in AT was also supported by its increased expression in HFD-fed mice (39 %, p = 0.013) and PPARγ knockout (74 %, p = 0.001). In summary, increased AT TLE3 in subjects with T2D and in AT from HFD-fed and PPARγ knockout mice suggest that TLE3 may play an adaptive regulatory role that improves AT function under decreased PPARγ expression.
TLE3 is expressed in mature adipocytes concomitantly with PPARγ. Subcutaneous adipose TLE3 is increased in T2D patients. Adipose TLE3 is upregulated in genetically ablated PPARγ and HFD-fed mice. TLE3 may be a homeostatic linchpin in insulin resistance and defective PPARγ.
PMID: 25249007 DOI: 10.1007/s00109-014-1207-5
Metabolomic and Lipidomic Analysis of the Heart of Peroxisome Proliferator-Activated Receptor-γ Coactivator 1-β Knock Out Mice on a High Fat Diet.
Metabolites. 2012 Jun 18;2(2):366-81. doi: 10.3390/metabo2020366.
McCombie G1, Medina-Gomez G2, Lelliott CJ3, Vidal-Puig A2, Griffin JL4.
Abstract – show
The peroxisome proliferator-activated receptor-γ coactivators (PGC-1) are transcriptional coactivators with an important role in mitochondrial biogenesis and regulation of genes involved in the electron transport chain and oxidative phosphorylation in oxidative tissues including cardiac tissue. These coactivators are thought to play a key role in the development of obesity, type 2 diabetes and the metabolic syndrome. In this study we have used a combined metabolomic and lipidomic analysis of cardiac tissue from the PGC-1β null mouse to examine the effects of a high fat diet on this organ. Multivariate statistics readily separated tissue from PGC-1β null mice from their wild type controls either in gender specific models or in combined datasets. This was associated with an increase in creatine and a decrease in taurine in the null mouse, and an increase in myristic acid and a reduction in long chain polyunsaturated fatty acids for both genders. The most profound changes were detected by liquid chromatography mass spectrometry analysis of intact lipids with the tissue from the null mouse having a profound increase in a number of triglycerides. The metabolomic and lipodomic changes indicate PGC-1β has a profound influence on cardiac metabolism.
PMID: 24957515 PMCID: PMC3901207 DOI: 10.3390/metabo2020366
The different shades of fat.
Nature. 2014 Jun 5;510(7503):76-83. doi: 10.1038/nature13477.
Peirce V1, Carobbio S2, Vidal-Puig A2.
Abstract – show
Our understanding of adipose tissue biology has progressed rapidly since the turn of the century. White adipose tissue has emerged as a key determinant of healthy metabolism and metabolic dysfunction. This realization is paralleled only by the confirmation that adult humans have heat-dissipating brown adipose tissue, an important contributor to energy balance and a possible therapeutic target for the treatment of metabolic disease. We propose that the development of successful strategies to target brown and white adipose tissues will depend on investigations that elucidate their developmental origins and cell-type-specific functional regulators.
PMID: 24899307 DOI: 10.1038/nature13477
Brown adipose tissue in the treatment of obesity and diabetes: Are we hot enough?
J Diabetes Investig. 2011 Oct 7;2(5):341-50. doi: 10.1111/j.2040-1124.2011.00158.x.
Tan CY1, Ishikawa K1, Virtue S1, Vidal-Puig A1.
Abstract – show
The identification of functional brown adipose tissue in human adults has intensified interest in exploiting thermogenic energy expenditure for the purpose of weight management. However, food intake and energy expenditure are tightly regulated and it is generally accepted that variation in one component results in compensatory changes in the other. In the context of weight loss, additional biological adaptations occur in an attempt to further limit weight loss. In the present review, we discuss the relationship between increasing energy expenditure and body weight in humans, including the effects of cold exposure. The data raise the possibility that some processes, particularly those involved in thermogenesis, induce less compensatory food intake for a given magnitude of additional energy expenditure, a state we term the 'thermogenic disconnect'. Although cold exposure increases thermogenesis and can putatively be exploited to induce weight loss, there are multiple adaptive responses to cold, of which many actually reduce energy expenditure. In order to optimally exploit either cold itself or agents that mimic cold for thermogenic energy expenditure, these non-thermogenic cold responses must be considered. Finally, the relative contribution of brown adipose tissue vs other thermogenic processes in humans remains to be defined. However, overall the data suggest that activation of cold-induced thermogenic processes are promising targets for interventions to treat obesity and its secondary metabolic complications. (J Diabetes Invest, doi:10.1111/j.2040-1124.2011.00158.x, 2011).
PMID: 24843510 PMCID: PMC4019299 DOI: 10.1111/j.2040-1124.2011.00158.x
Response to letter regarding article, "Mitochondrial DNA damage can promote atherosclerosis independently of reactive oxygen species through effects on smooth muscle cells and monocytes and correlates with higher-risk plaques in humans".
Circulation. 2014 Mar 25;129(12):e408. doi: 10.1161/CIRCULATIONAHA.113.008032.
Yu E1, Calvert PA, Mercer JR, Harrison J, Baker L, Figg NL, Kumar S, Wang JJ, Hurst LA, Obaid DR, Logan A, West NE, Clarke MC, Vidal-Puig A, Murphy MP, Bennett MR.
Regulation of glucose homoeostasis by brown adipose tissue.
Lancet Diabetes Endocrinol. 2013 Dec;1(4):353-60. doi: 10.1016/S2213-8587(13)70055-X. Epub 2013 Aug 27.
Peirce V1, Vidal-Puig A2.
Abstract – show
Brown adipose tissue (BAT) has emerged as a therapeutic target for the treatment of obesity. Activation of BAT in human beings could also have beneficial metabolic effects that might resolve common complications of obesity, such as type 2 diabetes, by ameliorating the glucolipotoxic pathological changes that underlie the development of peripheral insulin resistance and impaired insulin secretion due to pancreatic β-cell failure. Evidence from rodent models suggests that BAT activation improves glucose homoeostasis through several mechanisms, which could point to new strategies to optimise stimulation of BAT in human beings and reverse insulin resistance in peripheral tissues.
Copyright © 2013 Elsevier Ltd. All rights reserved.
Methods for performing lipidomics in white adipose tissue.
Methods Enzymol. 2014;538:211-31. doi: 10.1016/B978-0-12-800280-3.00012-8.
Roberts LD1, West JA1, Vidal-Puig A2, Griffin JL3.
Abstract – show
Lipid metabolism is central to the function of white adipose tissue, with the tissue having a central role in storing triacylglycerides following feeding and releasing free fatty acids and monoacylglycerides during periods of fasting. In addition, lipid species have been suggested to play a role in lipotoxicity and as signaling molecules during adipose tissue inflammation. This chapter details how mass spectrometry (MS) can be used to profile a range of lipid species found in adipose tissue. The initial step required in any MS-based approach is to extract the lipid fraction from the tissue. We detail one commonly used method based on the Folch extraction procedure. The total fatty acid composition of the lipid fraction can readily be defined using gas chromatography-MS, and we provide a method routinely used for rodent and human adipose tissue samples. However, such approaches do not provide insight into what lipid classes the various fatty acids are associated with. To better understand the global lipid profile of the tissue, we provide a general-purpose liquid chromatography-MS-based approach useful for processing phospholipids, free fatty acids, and triacylglycerides. In addition, we provide a method for profiling eicosanoids, a class of important lipid-signaling molecules, which have been implicated in white adipose tissue inflammation in rodent models of obesity, insulin resistance, and type 2 diabetes.
© 2014 Elsevier Inc. All rights reserved.
Adipose tissue expandability, lipotoxicity and the metabolic syndrome.
Endocrinol Nutr. 2013;60 Suppl 1:39-43.
Vidal-Puig A.
Central obesity and altered peripheral adipose tissue gene expression characterize the NAFLD patient with insulin resistance: Role of nutrition and insulin challenge.
Nutrition. 2014 Feb;30(2):177-85. doi: 10.1016/j.nut.2013.07.017.
Paniagua JA1, Escandell-Morales JM2, Gil-Contreras D2, Berral de la Rosa FJ3, Romero-Jimenez M2, Gómez-Urbano A2, Sanchez-Lopez A2, Bellido E4, Poyato A5, Calatayud B2, Vidal-Puig AJ6.
Abstract – show
Insulin resistance (IR) and white adipose tissue (WAT) dysfunction frequently are associated with nonalcoholic fatty liver disease (NAFLD); however, the pathogenic mechanisms contributing to their clustering are not well defined. The aim of this study was to define some nutritional, anthropometric, metabolic, and genetic mechanisms contributing to their clustering.
Forty-five (20 men, 25 women) patients (age 45.7 ± 11.1 y) with recent diagnosis of NAFLD were grouped according to IR state. Energy balance was assessed using a food questionnaire and indirect calorimetry, and body composition with anthropometry and dual-energy x-ray absorptiometry. Biochemical and hormonal parameters combined with adipose tissue gene expression were determined. Microarray analysis of gene expression was performed in a subset of WAT samples from IR patients (n = 9), in the fasted state, after specific test meals (monounsaturated fatty acid [MUFA], saturated fat [SAT], and carbohydrate-rich) and after being challenged with insulin.
IR patients exhibited higher trunk fat to leg fat ratio (P < 0.05) and had a higher ratio of SAT/MUFA fat intake (P < 0.05) than insulin-sensitive (IS) individuals. Deposition of fat in the trunk but not in the leg was directly related to liver enzyme levels (P < 0.05). IR patients also had lower adiponectin serum levels and leptin (LEP) mRNA expression in WAT compared with IS patients (P < 0.01 and P < 0.05, respectively). Microarray analysis after insulin challenge confirmed that insulin treatment induces the expression of PPARG gene and LEP and decreases GCGR gene (P < 0.05 for all) in WAT. No changes in these genes were observed in the postprandial state induced after the acute effect of specific diets.
Patients exhibiting NAFLD and IR had preferential central fat deposition directly related to their serum alanine aminotransferase levels. These patients showed peripheral adipose tissue dysfunction and exhibited inappropriately low LEP biosynthesis that could be partially restored after anabolic conditions induced by insulin signaling.
Copyright © 2014 Elsevier Inc. All rights reserved.
PMID: 24377452 DOI: 10.1016/j.nut.2013.07.017
Psychosocial stress induces hyperphagia and exacerbates diet-induced insulin resistance and the manifestations of the Metabolic Syndrome.
Psychoneuroendocrinology. 2013 Dec;38(12):2933-42. doi: 10.1016/j.psyneuen.2013.07.022. Epub 2013 Sep 2.
Sanghez V1, Razzoli M, Carobbio S, Campbell M, McCallum J, Cero C, Ceresini G, Cabassi A, Govoni P, Franceschini P, de Santis V, Gurney A, Ninkovic I, Parmigiani S, Palanza P, Vidal-Puig A, Bartolomucci A.
Abstract – show
Stress and hypercaloric food are recognized risk factors for obesity, Metabolic Syndrome (MetS) and Type 2 Diabetes (T2D). Given the complexity of these metabolic processes and the unavailability of animal models, there is poor understanding of their underlying mechanisms. We established a model of chronic psychosocial stress in which subordinate mice are vulnerable to weight gain while dominant mice are resilient. Subordinate mice fed a standard diet showed marked hyperphagia, high leptin, low adiponectin, and dyslipidemia. Despite these molecular signatures of MetS and T2D, subordinate mice fed a standard diet were still euglycemic. We hypothesized that stress predisposes subordinate mice to develop T2D when synergizing with other risk factors. High fat diet aggravated dyslipidemia and the MetS thus causing a pre-diabetes-like state in subordinate mice. Contrary to subordinates, dominant mice were fully protected from stress-induced metabolic disorders when fed both a standard- and a high fat-diet. Dominant mice showed a hyperphagic response that was similar to subordinate but, unlike subordinates, showed a significant increase in VO2, VCO2, and respiratory exchange ratio when compared to control mice. Overall, we demonstrated a robust stress- and social status-dependent effect on the development of MetS and T2D and provided insights on the physiological mechanisms. Our results are reminiscent of the effect of the individual socioeconomic status on human health and provide an animal model to study the underlying molecular mechanisms.
Copyright © 2013 Elsevier Ltd. All rights reserved.
PMID: 24060458 DOI: 10.1016/j.psyneuen.2013.07.022
Adipogenesis: new insights into brown adipose tissue differentiation.
J Mol Endocrinol. 2013 Nov 26;51(3):T75-85. doi: 10.1530/JME-13-0158. Print 2013 Dec.
Carobbio S1, Rosen B, Vidal-Puig A.
Abstract – show
Confirmation of the presence of functional brown adipose tissue (BAT) in humans has renewed interest in investigating the potential therapeutic use of this tissue. The finding that its activity positively correlates with decreased BMI, decreased fat content, and augmented energy expenditure suggests that increasing BAT mass/activity or browning of white adipose tissue (WAT) could be a strategy to prevent or treat obesity and its associated morbidities. The challenge now is to find a safe and efficient way to develop this idea. Whereas BAT has being widely studied in murine models both in vivo and in vitro, there is an urgent need for human cellular models to investigate BAT physiology and functionality from a molecular point of view. In this review, we focus on the latest insights surrounding BAT development and activation in rodents and humans. Then, we discuss how the availability of murine models has been essential to identify BAT progenitors and trace their lineage. Finally, we address how this information can be exploited to develop human cellular models for BAT differentiation/activation. In this context, human embryonic stem and induced pluripotent stem cells-based cellular models represent a resource of great potential value, as they can provide a virtually inexhaustible supply of starting material for functional genetic studies, -omics based analysis and validation of therapeutic approaches. Moreover, these cells can be readily genetically engineered, opening the possibility of generating patient-specific cellular models, allowing the investigation of the influence of different genetic backgrounds on BAT differentiation in pathological or in physiological states.
A role for adipocyte-derived lipopolysaccharide-binding protein in inflammation- and obesity-associated adipose tissue dysfunction.
Diabetologia. 2013 Nov;56(11):2524-37. doi: 10.1007/s00125-013-3015-9. Epub 2013 Aug 21.
Moreno-Navarrete JM1, Escoté X, Ortega F, Serino M, Campbell M, Michalski MC, Laville M, Xifra G, Luche E, Domingo P, Sabater M, Pardo G, Waget A, Salvador J, Giralt M, Rodriguez-Hermosa JI, Camps M, Kolditz CI, Viguerie N, Galitzky J, Decaunes P, Ricart W, Frühbeck G, Villarroya F, Mingrone G, Langin D, Zorzano A, Vidal H, Vendrell J, Burcelin R, Vidal-Puig A, Fernández-Real JM.
Abstract – show
Circulating lipopolysaccharide-binding protein (LBP) is an acute-phase reactant known to be increased in obesity. We hypothesised that LBP is produced by adipose tissue (AT) in association with obesity.
LBP mRNA and LBP protein levels were analysed in AT from three cross-sectional (n = 210, n = 144 and n = 28) and three longitudinal (n = 8, n = 25, n = 20) human cohorts; in AT from genetically manipulated mice; in isolated adipocytes; and in human and murine cell lines. The effects of a high-fat diet and exposure to lipopolysaccharide (LPS) and peroxisome proliferator-activated receptor (PPAR)γ agonist were explored. Functional in vitro and ex vivo experiments were also performed.
LBP synthesis and release was demonstrated to increase with adipocyte differentiation in human and mouse AT, isolated adipocytes and human and mouse cell lines (Simpson-Golabi-Behmel syndrome [SGBS], human multipotent adipose-derived stem [hMAD] and 3T3-L1 cells). AT LBP expression was robustly associated with inflammatory markers and increased with metabolic deterioration and insulin resistance in two independent cross-sectional human cohorts. AT LBP also increased longitudinally with weight gain and excessive fat accretion in both humans and mice, and decreased with weight loss (in two other independent cohorts), in humans with acquired lipodystrophy, and after ex vivo exposure to PPARγ agonist. Inflammatory agents such as LPS and TNF-α led to increased AT LBP expression in vivo in mice and in vitro, while this effect was prevented in Cd14-knockout mice. Functionally, LBP knockdown using short hairpin (sh)RNA or anti-LBP antibody led to increases in markers of adipogenesis and decreased adipocyte inflammation in human adipocytes.
Collectively, these findings suggest that LBP might have an essential role in inflammation- and obesity-associated AT dysfunction.
PMID: 23963324 DOI: 10.1007/s00125-013-3015-9
Adaptive changes of the Insig1/SREBP1/SCD1 set point help adipose tissue to cope with increased storage demands of obesity.
Diabetes. 2013 Nov;62(11):3697-708. doi: 10.2337/db12-1748. Epub 2013 Aug 6.
Carobbio S1, Hagen RM, Lelliott CJ, Slawik M, Medina-Gomez G, Tan CY, Sicard A, Atherton HJ, Barbarroja N, Bjursell M, Bohlooly-Y M, Virtue S, Tuthill A, Lefai E, Laville M, Wu T, Considine RV, Vidal H, Langin D, Oresic M, Tinahones FJ, Fernandez-Real JM, Griffin JL, Sethi JK, López M, Vidal-Puig A.
Abstract – show
The epidemic of obesity imposes unprecedented challenges on human adipose tissue (WAT) storage capacity that may benefit from adaptive mechanisms to maintain adipocyte functionality. Here, we demonstrate that changes in the regulatory feedback set point control of Insig1/SREBP1 represent an adaptive response that preserves WAT lipid homeostasis in obese and insulin-resistant states. In our experiments, we show that Insig1 mRNA expression decreases in WAT from mice with obesity-associated insulin resistance and from morbidly obese humans and in in vitro models of adipocyte insulin resistance. Insig1 downregulation is part of an adaptive response that promotes the maintenance of SREBP1 maturation and facilitates lipogenesis and availability of appropriate levels of fatty acid unsaturation, partially compensating the antilipogenic effect associated with insulin resistance. We describe for the first time the existence of this adaptive mechanism in WAT, which involves Insig1/SREBP1 and preserves the degree of lipid unsaturation under conditions of obesity-induced insulin resistance. These adaptive mechanisms contribute to maintain lipid desaturation through preferential SCD1 regulation and facilitate fat storage in WAT, despite on-going metabolic stress.
PMID: 23919961 PMCID: PMC3806615 DOI: 10.2337/db12-1748
Mitochondrial DNA damage can promote atherosclerosis independently of reactive oxygen species through effects on smooth muscle cells and monocytes and correlates with higher-risk plaques in humans.
Circulation. 2013 Aug 13;128(7):702-12. doi: 10.1161/CIRCULATIONAHA.113.002271. Epub 2013 Jul 10.
Yu E1, Calvert PA, Mercer JR, Harrison J, Baker L, Figg NL, Kumar S, Wang JC, Hurst LA, Obaid DR, Logan A, West NE, Clarke MC, Vidal-Puig A, Murphy MP, Bennett MR.
Abstract – show
Mitochondrial DNA (mtDNA) damage occurs in both circulating cells and the vessel wall in human atherosclerosis. However, it is unclear whether mtDNA damage directly promotes atherogenesis or is a consequence of tissue damage, which cell types are involved, and whether its effects are mediated only through reactive oxygen species.
mtDNA damage occurred early in the vessel wall in apolipoprotein E-null (ApoE(-/-)) mice, before significant atherosclerosis developed. mtDNA defects were also identified in circulating monocytes and liver and were associated with mitochondrial dysfunction. To determine whether mtDNA damage directly promotes atherosclerosis, we studied ApoE(-/-) mice deficient for mitochondrial polymerase-γ proofreading activity (polG(-/-)/ApoE(-/-)). polG(-/-)/ApoE(-/-) mice showed extensive mtDNA damage and defects in oxidative phosphorylation but no increase in reactive oxygen species. polG(-/-)/ApoE(-/-) mice showed increased atherosclerosis, associated with impaired proliferation and apoptosis of vascular smooth muscle cells, and hyperlipidemia. Transplantation with polG(-/-)/ApoE(-/-) bone marrow increased the features of plaque vulnerability, and polG(-/-)/ApoE(-/-) monocytes showed increased apoptosis and inflammatory cytokine release. To examine mtDNA damage in human atherosclerosis, we assessed mtDNA adducts in plaques and in leukocytes from patients who had undergone virtual histology intravascular ultrasound characterization of coronary plaques. Human atherosclerotic plaques showed increased mtDNA damage compared with normal vessels; in contrast, leukocyte mtDNA damage was associated with higher-risk plaques but not plaque burden.
We show that mtDNA damage in vessel wall and circulating cells is widespread and causative and indicates higher risk in atherosclerosis. Protection against mtDNA damage and improvement of mitochondrial function are potential areas for new therapeutics.
Peroxisome proliferator-activated receptor gamma-coactivator-1 alpha coordinates sphingolipid metabolism, lipid raft composition and myelin protein synthesis.
Eur J Neurosci. 2013 Sep;38(5):2672-83. doi: 10.1111/ejn.12281. Epub 2013 Jun 14.
Camacho A1, Huang JK, Delint-Ramirez I, Yew Tan C, Fuller M, Lelliott CJ, Vidal-Puig A, Franklin RJ.
Abstract – show
Peroxisome proliferator-activated receptor gamma-coactivator-1 alpha (PGC1a) is involved in energy and lipid metabolism, and its loss leads to neurodegenerative changes in the striatum. Here we performed lipidomic analysis on brain extracts from PGC1a mutant and wild-type mice. We found increased phosphatidylcholine and decreased ceramides in the brain of PGC1a-deficient mice. An analysis of lipid raft fractions revealed increased ceramide, glucocylceramides and GM1 ganglioside in the PGC1a mutants. In the cerebellum, we observed a decrease in proteins associated with myelination, but were unable to detect any morphological abnormalities in compact myelin formation in PGC1a mutants compared with wild-type mice. Although PGC1a is involved in lipid biosynthesis, we concluded that altered lipid composition in the PGC1a mutant did not directly affect central nervous system myelin morphology.
© 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.
PMID: 23763823 DOI: 10.1111/ejn.12281
Assessment of brown adipose tissue function.
Front Physiol. 2013 Jun 4;4:128. doi: 10.3389/fphys.2013.00128. eCollection 2013.
Virtue S1, Vidal-Puig A.
Abstract – show
In this review we discuss practical considerations for the assessment of brown adipose tissue in rodent models, focusing on mice. The central aim of the review is to provide a critical appraisal of the utility of specialized techniques for assessing brown adipose tissue function in vivo. We cover several of the most common specialized methods for analysing brown adipose tissue function in vivo, including assessment of maximal thermogenic capacity by indirect calorimetry and the measurement of sympathetic tone to brown adipose tissue. While these techniques are powerful, they are not readily available to all laboratories; therefore we also cover several simple measurements that, particularly in combination, can be used to determine if a mouse model is likely to have alterations in brown adipose tissue function. Such techniques include: pair feeding, analysis of brown adipose tissue lipid content and mRNA and protein markers of brown adipose tissue activation.
PMID: 23760815 PMCID: PMC3671177 DOI: 10.3389/fphys.2013.00128
Harnessing the beneficial properties of adipogenic microbes for improving human health.
Obes Rev. 2013 Sep;14(9):721-35. doi: 10.1111/obr.12045. Epub 2013 May 12.
Dhurandhar NV1, Geurts L, Atkinson RL, Casteilla L, Clement K, Gerard P, Vijay-Kumar M, Nam JH, Nieuwdorp M, Trovato G, Sørensen TI, Vidal-Puig A, Cani PD.
Abstract – show
Obesity is associated with numerous metabolic comorbidities. Weight loss is an effective measure for alleviating many of these metabolic abnormalities. However, considering the limited success of most medical weight-management approaches in producing a sustained weight loss, approaches that improve obesity-related metabolic abnormalities independent of weight loss would be extremely attractive and of practical benefit. Metabolically healthy obesity supports the notion that a better metabolic profile is possible despite obesity. Moreover, adequate expansion of adipose tissue appears to confer protection from obesity-induced metabolic comorbidities. To this end, the 10th Stock conference examined new approaches to improve metabolic comorbidities independent of weight loss. In particular, human adenovirus 36 (Ad36) and specific gut microbes were examined for their potential to influence lipid and glucose homeostasis in animals and humans. While these microbes possess some undesirable properties, research has identified attributes of adenovirus Ad36 and gut microbes that may be selectively harnessed to improve metabolic profile without the obligatory weight loss. Furthermore, identifying the host signalling pathways that these microbes recruit to improve the metabolic profile may offer new templates and targets, which may facilitate the development of novel treatment strategies for obesity-related metabolic conditions.
© 2013 The Authors. obesity reviews © 2013 International Association for the Study of Obesity.
PMID: 23663746 DOI: 10.1111/obr.12045
Pharmacological strategies for targeting BAT thermogenesis.
Trends Pharmacol Sci. 2013 Jun;34(6):347-55. doi: 10.1016/j.tips.2013.04.004. Epub 2013 May 3.
Whittle A1, Relat-Pardo J, Vidal-Puig A.
Abstract – show
Biopsies following positron emission tomography coupled to computer tomography (PET-CT) imaging have confirmed the presence of thermogenically active brown adipose tissue (BAT) in adult humans, leading to suggestions that it could be stimulated to treat obesity and its associated morbidities. The mechanisms regulating thermogenesis in BAT are better understood than ever before, and many new hypotheses for increasing the amount of brown fat or its activity are currently being explored. The challenge now is to identify safe ways to manipulate specific aspects of the physiological regulation of thermogenesis, in a manner that will be bioenergetically effective. This review outlines the nature of these regulatory mechanisms both in terms of their cellular specificity and probable effectiveness given the physiological paradigms in which thermogenesis is activated. Similarly, their potential for being targeted by new or existing drugs is discussed, drawing on the known mechanisms of action of various pharmacological agents and some probable limitations that should be considered.
Copyright © 2013 Elsevier Ltd. All rights reserved.
PMID: 23648356 DOI: 10.1016/j.tips.2013.04.004
When BAT is lacking, WAT steps up.
Cell Res. 2013 Jul;23(7):868-9. doi: 10.1038/cr.2013.58. Epub 2013 Apr 23.
Whittle A1, Vidal-Puig A.
Abstract – show
Brown adipose tissue (BAT) has evolved to generate heat to maintain core body temperature, but it is also of great importance for the regulation of energy balance. In addition to BAT, mammals can induce the formation of "brown adipocyte-like" or "beige" fat cells in white adipose tissue and understanding their regulation could have implications for the treatment of metabolic diseases.
PMID: 23609798 PMCID: PMC3698633 DOI: 10.1038/cr.2013.58
Beyond the sympathetic tone: the new brown fat activators.
Cell Metab. 2013 May 7;17(5):638-43. doi: 10.1016/j.cmet.2013.02.020. Epub 2013 Apr 11.
Villarroya F1, Vidal-Puig A.
Abstract – show
If we could avoid the side effects associated with global sympathetic activation, activating brown adipose tissue to increase thermogenesis would be a safe way to lose weight. The discovery of adrenergic-independent brown fat activators opens the prospect of developing this alternative way to efficiently and safely induce negative energy balance.
Copyright © 2013 Elsevier Inc. All rights reserved.
PMID: 23583169 DOI: 10.1016/j.cmet.2013.02.020
Visceral fat accumulation during lipid overfeeding is related to subcutaneous adipose tissue characteristics in healthy men.
J Clin Endocrinol Metab. 2013 Feb;98(2):802-10. doi: 10.1210/jc.2012-3289. Epub 2013 Jan 2.
Alligier M1, Gabert L, Meugnier E, Lambert-Porcheron S, Chanseaume E, Pilleul F, Debard C, Sauvinet V, Morio B, Vidal-Puig A, Vidal H, Laville M.
Abstract – show
The hypothesis of a limited expansion of sc adipose tissue during weight gain provides an attractive explanation for the reorientation of excess lipids toward ectopic sites, contributing to visceral adipose depots and metabolic syndrome.
Our objective was to define whether the characteristics of sc adipose tissue influence the partition of lipids toward abdominal fat depots during weight gain in healthy men.
Forty-one healthy nonobese volunteers performed a 56-day overfeeding protocol (+760 kcal/d). Insulin sensitivity was estimated by euglycemic hyperinsulinemic clamp. Changes in abdominal visceral and sc adipose tissue depots were measured by magnetic resonance imaging. The fate of ingested lipids before and after overfeeding was investigated using a [d31]palmitate test meal, and gene expression was measured by real-time PCR in sc fat biopsies.
Overfeeding led to a 2.5-kg body weight increase with large interindividual variations in abdominal sc and visceral adipose tissues. There was no relationship between the relative expansions of these 2 depots, but the increase in visceral depot was positively associated with the magnitude of the postprandial exogenous fatty acid release in the circulation during the test meal. The regulation of lipid storage-related genes (DGAT2, SREBP1c, and CIDEA) was defective in the sc fat of the subjects exhibiting the largest accumulation in visceral depot.
Characteristics of sc adipose tissue appear therefore to contribute to the development of visceral fat depot, supporting the adipose tissue expandability theory and extending it to early stages of weight gain in nonobese subjects.
PMID: 23284008 DOI: 10.1210/jc.2012-3289
Identification of novel type 2 diabetes candidate genes involved in the crosstalk between the mitochondrial and the insulin signaling systems.
PLoS Genet. 2012;8(12):e1003046. doi: 10.1371/journal.pgen.1003046. Epub 2012 Dec 6.
Mercader JM1, Puiggros M, Segrè AV, Planet E, Sorianello E, Sebastian D, Rodriguez-Cuenca S, Ribas V, Bonàs-Guarch S, Draghici S, Yang C, Mora S, Vidal-Puig A, Dupuis J; DIAGRAM Consortium, Florez JC; MITIN Consortium, Zorzano A, Torrents D.
Abstract – show
Type 2 Diabetes (T2D) is a highly prevalent chronic metabolic disease with strong co-morbidity with obesity and cardiovascular diseases. There is growing evidence supporting the notion that a crosstalk between mitochondria and the insulin signaling cascade could be involved in the etiology of T2D and insulin resistance. In this study we investigated the molecular basis of this crosstalk by using systems biology approaches. We combined, filtered, and interrogated different types of functional interaction data, such as direct protein-protein interactions, co-expression analyses, and metabolic and signaling dependencies. As a result, we constructed the mitochondria-insulin (MITIN) network, which highlights 286 genes as candidate functional linkers between these two systems. The results of internal gene expression analysis of three independent experimental models of mitochondria and insulin signaling perturbations further support the connecting roles of these genes. In addition, we further assessed whether these genes are involved in the etiology of T2D using the genome-wide association study meta-analysis from the DIAGRAM consortium, involving 8,130 T2D cases and 38,987 controls. We found modest enrichment of genes associated with T2D amongst our linker genes (p = 0.0549), including three already validated T2D SNPs and 15 additional SNPs, which, when combined, were collectively associated to increased fasting glucose levels according to MAGIC genome wide meta-analysis (p = 8.12×10(-5)). This study highlights the potential of combining systems biology, experimental, and genome-wide association data mining for identifying novel genes and related variants that increase vulnerability to complex diseases.
PMID: 23236286 PMCID: PMC3516534 DOI: 10.1371/journal.pgen.1003046
Below thermoneutrality, changes in activity do not drive changes in total daily energy expenditure between groups of mice.
Cell Metab. 2012 Nov 7;16(5):665-71. doi: 10.1016/j.cmet.2012.10.008.
Virtue S1, Even P, Vidal-Puig A.
Abstract – show
In this study we investigated the relationship between activity and energy expenditure (EE) in mice. By determining the relationship between activity and EE over a 24 hr period in an individual mouse, activity was calculated to account for 26.6% ± 1.1% of total EE at 30°C. However, when comparing across multiple mice, only 9.53% ± 1.1% of EE from activity appeared to be independent of other components involved in the thermogenic response, suggesting other metabolic processes may mask the contribution of activity to EE. In line with this concept, below thermoneutrality mice still expended a substantial amount of energy on activity; however, at 24°C, 20°C, or 5°C, no independent effect of EE from activity on total daily EE could be detected. Overall these results suggest that when studying mice at temperatures below thermoneutrality, activity is unlikely to explain differences in EE between groups of animals.
Copyright © 2012 Elsevier Inc. All rights reserved.
PMID: 23140644 PMCID: PMC3556741 DOI: 10.1016/j.cmet.2012.10.008
A new role for lipocalin prostaglandin d synthase in the regulation of brown adipose tissue substrate utilization.
Diabetes. 2012 Dec;61(12):3139-47. doi: 10.2337/db12-0015. Epub 2012 Aug 24.
Virtue S1, Feldmann H, Christian M, Tan CY, Masoodi M, Dale M, Lelliott C, Burling K, Campbell M, Eguchi N, Voshol P, Sethi JK, Parker M, Urade Y, Griffin JL, Cannon B, Vidal-Puig A.
Abstract – show
In this study, we define a new role for lipocalin prostaglandin D synthase (L-PGDS) in the control of metabolic fuel utilization by brown adipose tissue (BAT). We demonstrate that L-PGDS expression in BAT is positively correlated with BAT activity, upregulated by peroxisome proliferator-activated receptor γ coactivator 1α or 1β and repressed by receptor-interacting protein 140. Under cold-acclimated conditions, mice lacking L-PGDS had elevated reliance on carbohydrate to provide fuel for thermogenesis and had increased expression of genes regulating glycolysis and de novo lipogenesis in BAT. These transcriptional differences were associated with increased lipid content in BAT and a BAT lipid composition enriched with de novo synthesized lipids. Consistent with the concept that lack of L-PGDS increases glucose utilization, mice lacking L-PGDS had improved glucose tolerance after high-fat feeding. The improved glucose tolerance appeared to be independent of changes in insulin sensitivity, as insulin levels during the glucose tolerance test and insulin, leptin, and adiponectin levels were unchanged. Moreover, L-PGDS knockout mice exhibited increased expression of genes involved in thermogenesis and increased norepinephrine-stimulated glucose uptake to BAT, suggesting that sympathetically mediated changes in glucose uptake may have improved glucose tolerance. Taken together, these results suggest that L-PGDS plays an important role in the regulation of glucose utilization in vivo.
PMID: 22923471 PMCID: PMC3501861 DOI: 10.2337/db12-0015
The Obese Species: a special issue on obesity and metabolic disorders. Foreword.
Dis Model Mech. 2012 Sep;5(5):563-4. doi: 10.1242/dmm.010611.
Bartolomucci A1, Parmigiani S, Rodgers RJ, Vidal-Puig A, Allan SE, Siegel V.
PMID: 22915014 PMCID: PMC3424436 DOI: 10.1242/dmm.010611
Lipocalin prostaglandin D synthase and PPARγ2 coordinate to regulate carbohydrate and lipid metabolism in vivo.
PLoS One. 2012;7(7):e39512. doi: 10.1371/journal.pone.0039512. Epub 2012 Jul 5.
Virtue S1, Masoodi M, Velagapudi V, Tan CY, Dale M, Suorti T, Slawik M, Blount M, Burling K, Campbell M, Eguchi N, Medina-Gomez G, Sethi JK, Orešič M, Urade Y, Griffin JL, Vidal-Puig A.
Abstract – show
Mice lacking Peroxisome Proliferator-Activated Receptor γ2 (PPARγ2) have unexpectedly normal glucose tolerance and mild insulin resistance. Mice lacking PPARγ2 were found to have elevated levels of Lipocalin prostaglandin D synthase (L-PGDS) expression in BAT and subcutaneous white adipose tissue (WAT). To determine if induction of L-PGDS was compensating for a lack of PPARγ2, we crossed L-PGDS KO mice to PPARγ2 KO mice to generate Double Knock Out mice (DKO). Using DKO mice we demonstrated a requirement of L-PGDS for maintenance of subcutaneous WAT (scWAT) function. In scWAT, DKO mice had reduced expression of thermogenic genes, the de novo lipogenic program and the lipases ATGL and HSL. Despite the reduction in markers of lipolysis in scWAT, DKO mice had a normal metabolic rate and elevated serum FFA levels compared to L-PGDS KO alone. Analysis of intra-abdominal white adipose tissue (epididymal WAT) showed elevated expression of mRNA and protein markers of lipolysis in DKO mice, suggesting that DKO mice may become more reliant on intra-abdominal WAT to supply lipid for oxidation. This switch in depot utilisation from subcutaneous to epididymal white adipose tissue was associated with a worsening of whole organism metabolic function, with DKO mice being glucose intolerant, and having elevated serum triglyceride levels compared to any other genotype. Overall, L-PGDS and PPARγ2 coordinate to regulate carbohydrate and lipid metabolism.
PMID: 22792179 PMCID: PMC3390315 DOI: 10.1371/journal.pone.0039512
Accelerated renal disease is associated with the development of metabolic syndrome in a glucolipotoxic mouse model.
Dis Model Mech. 2012 Sep;5(5):636-48. doi: 10.1242/dmm.009266. Epub 2012 Jul 5.
Martínez-García C1, Izquierdo A, Velagapudi V, Vivas Y, Velasco I, Campbell M, Burling K, Cava F, Ros M, Oresic M, Vidal-Puig A, Medina-Gomez G.
Abstract – show
Individuals with metabolic syndrome are at high risk of developing chronic kidney disease (CKD) through unclear pathogenic mechanisms. Obesity and diabetes are known to induce glucolipotoxic effects in metabolically relevant organs. However, the pathogenic role of glucolipotoxicity in the aetiology of diabetic nephropathy is debated. We generated a murine model, the POKO mouse, obtained by crossing the peroxisome proliferator-activated receptor gamma 2 (PPARγ2) knockout (KO) mouse into a genetically obese ob/ob background. We have previously shown that the POKO mice showed: hyperphagia, insulin resistance, hyperglycaemia and dyslipidaemia as early as 4 weeks of age, and developed a complete loss of normal β-cell function by 16 weeks of age. Metabolic phenotyping of the POKO model has led to investigation of the structural and functional changes in the kidney and changes in blood pressure in these mice. Here we demonstrate that the POKO mouse is a model of renal disease that is accelerated by high levels of glucose and lipid accumulation. Similar to ob/ob mice, at 4 weeks of age these animals exhibited an increased urinary albumin:creatinine ratio and significantly increased blood pressure, but in contrast showed a significant increase in the renal hypertrophy index and an associated increase in p27(Kip1) expression compared with their obese littermates. Moreover, at 4 weeks of age POKO mice showed insulin resistance, an alteration of lipid metabolism and glomeruli damage associated with increased transforming growth factor beta (TGFβ) and parathyroid hormone-related protein (PTHrP) expression. At this age, levels of proinflammatory molecules, such as monocyte chemoattractant protein-1 (MCP-1), and fibrotic factors were also increased at the glomerular level compared with levels in ob/ob mice. At 12 weeks of age, renal damage was fully established. These data suggest an accelerated lesion through glucolipotoxic effects in the renal pathogenesis in POKO mice.
PMID: 22773754 PMCID: PMC3424461 DOI: 10.1242/dmm.009266
Ablation of PGC1 beta prevents mTOR dependent endoplasmic reticulum stress response.
Exp Neurol. 2012 Oct;237(2):396-406. doi: 10.1016/j.expneurol.2012.06.031. Epub 2012 Jul 6.
Camacho A1, Rodriguez-Cuenca S, Blount M, Prieur X, Barbarroja N, Fuller M, Hardingham GE, Vidal-Puig A.
Abstract – show
Mitochondria dysfunction contributes to the pathophysiology of obesity, diabetes, neurodegeneration and ageing. The peroxisome proliferator-activated receptor-gamma coactivator-1β (PGC-1β) coordinates mitochondrial biogenesis and function as well as fatty acid metabolism. It has been suggested that endoplasmic reticulum (ER) stress may be one of the mechanisms linking mitochondrial dysfunction and these pathologies. Here we investigate whether PGC-1β ablation affects the ER stress response induced by specific nutritional and pharmacological challenges in the CNS. By using flow cytometry, western blot, real time PCR and several pharmacological and nutritional interventions in PGC-1β knock out and WT mice, we confirmed that PGC-1β coordinates mitochondria function in brain and reported for the first time that a) ablation of PGC-1β is associated with constitutive activation of mTORC1 pathway associated with increased basal GRP78 protein levels in hypothalamus and cortex of animals fed chow diet; and b) in animals fed chronically with high fat diet (HFD) or high protein diet (HPD), we observed a failure to appropriately induce ER stress response in the absence of PGC-1β, associated with an increase in mTOR pathway phosphorylation. This contrasted with the appropriate upregulation of ER stress response observed in wild type littermates. Additionally, inefficient in vitro induction of ER stress by thapsigargin seems result in apoptotic neuronal cell death in PGC-1β KO. Our data indicate that PGC-1β is required for a neuronal ER response to nutritional stress imposed by HFD and HPD diets and that genetic ablation of PGC-1β might increase the susceptibility to neuronal damage and cell death.
Published by Elsevier Inc.
PMID: 22771762 PMCID: PMC3549498 DOI: 10.1016/j.expneurol.2012.06.031
PGC-1α negatively regulates extrasynaptic NMDAR activity and excitotoxicity.
J Neurosci. 2012 May 16;32(20):6995-7000. doi: 10.1523/JNEUROSCI.6407-11.2012.
Puddifoot C1, Martel MA, Soriano FX, Camacho A, Vidal-Puig A, Wyllie DJ, Hardingham GE.
Abstract – show
Underexpression of the transcriptional coactivator PGC-1α is causally linked to certain neurodegenerative disorders, including Huntington's Disease (HD). HD pathoprogression is also associated with aberrant NMDAR activity, in particular an imbalance between synaptic versus extrasynaptic (NMDAR(EX)) activity. Here we show that PGC-1α controls NMDAR(EX) activity in neurons and that its suppression contributes to mutant Huntingtin (mHtt)-induced increases in NMDAR(EX) activity and vulnerability to excitotoxic insults. We found that knock-down of endogenous PGC-1α increased NMDAR(EX) activity and vulnerability to excitotoxic insults in rat cortical neurons. In contrast, exogenous expression of PGC-1α resulted in a neuroprotective reduction of NMDAR(EX) currents without affecting synaptic NMDAR activity. Since HD models are associated with mHtt-mediated suppression of PGC-1α expression, as well as increased NMDAR(EX) activity, we investigated whether these two events were linked. Expression of mHtt (148Q) resulted in a selective increase in NMDAR(EX) activity, compared with wild-type Htt (18Q), and increased vulnerability to NMDA excitotoxicity. Importantly, we observed that the effects of mHtt and PGC-1α knockdown on NMDAR(EX) activity and vulnerability to excitotoxicity were nonadditive and occluded each other, consistent with a common mechanism. Moreover, exogenous expression of PGC-1α reversed mtHtt-mediated increases in NMDAR(EX) activity and protected neurons against excitotoxic cell death. The link between mHtt, PGC-1α, and NMDAR activity was also confirmed in rat striatal neurons. Thus, targeting levels of PGC-1α expression may help reduce aberrant NMDAR(EX) activity in disorders where PGC-1α is underexpressed.
BMP8B increases brown adipose tissue thermogenesis through both central and peripheral actions.
Cell. 2012 May 11;149(4):871-85. doi: 10.1016/j.cell.2012.02.066.
Whittle AJ1, Carobbio S, Martins L, Slawik M, Hondares E, Vázquez MJ, Morgan D, Csikasz RI, Gallego R, Rodriguez-Cuenca S, Dale M, Virtue S, Villarroya F, Cannon B, Rahmouni K, López M, Vidal-Puig A.
Abstract – show
Thermogenesis in brown adipose tissue (BAT) is fundamental to energy balance and is also relevant for humans. Bone morphogenetic proteins (BMPs) regulate adipogenesis, and, here, we describe a role for BMP8B in the direct regulation of thermogenesis. BMP8B is induced by nutritional and thermogenic factors in mature BAT, increasing the response to noradrenaline through enhanced p38MAPK/CREB signaling and increased lipase activity. Bmp8b(-/-) mice exhibit impaired thermogenesis and reduced metabolic rate, causing weight gain despite hypophagia. BMP8B is also expressed in the hypothalamus, and Bmp8b(-/-) mice display altered neuropeptide levels and reduced phosphorylation of AMP-activated protein kinase (AMPK), indicating an anorexigenic state. Central BMP8B treatment increased sympathetic activation of BAT, dependent on the status of AMPK in key hypothalamic nuclei. Our results indicate that BMP8B is a thermogenic protein that regulates energy balance in partnership with hypothalamic AMPK. BMP8B may offer a mechanism to specifically increase energy dissipation by BAT.
Copyright © 2012 Elsevier Inc. All rights reserved.
PMID: 22579288 PMCID: PMC3383997 DOI: 10.1016/j.cell.2012.02.066
Increasing circulating IGFBP1 levels improves insulin sensitivity, promotes nitric oxide production, lowers blood pressure, and protects against atherosclerosis.
Diabetes. 2012 Apr;61(4):915-24. doi: 10.2337/db11-0963. Epub 2012 Feb 22.
Rajwani A1, Ezzat V, Smith J, Yuldasheva NY, Duncan ER, Gage M, Cubbon RM, Kahn MB, Imrie H, Abbas A, Viswambharan H, Aziz A, Sukumar P, Vidal-Puig A, Sethi JK, Xuan S, Shah AM, Grant PJ, Porter KE, Kearney MT, Wheatcroft SB.
Abstract – show
Low concentrations of insulin-like growth factor (IGF) binding protein-1 (IGFBP1) are associated with insulin resistance, diabetes, and cardiovascular disease. We investigated whether increasing IGFBP1 levels can prevent the development of these disorders. Metabolic and vascular phenotype were examined in response to human IGFBP1 overexpression in mice with diet-induced obesity, mice heterozygous for deletion of insulin receptors (IR(+/-)), and ApoE(-/-) mice. Direct effects of human (h)IGFBP1 on nitric oxide (NO) generation and cellular signaling were studied in isolated vessels and in human endothelial cells. IGFBP1 circulating levels were markedly suppressed in dietary-induced obese mice. Overexpression of hIGFBP1 in obese mice reduced blood pressure, improved insulin sensitivity, and increased insulin-stimulated NO generation. In nonobese IR(+/-) mice, overexpression of hIGFBP1 reduced blood pressure and improved insulin-stimulated NO generation. hIGFBP1 induced vasodilatation independently of IGF and increased endothelial NO synthase (eNOS) activity in arterial segments ex vivo, while in endothelial cells, hIGFBP1 increased eNOS Ser(1177) phosphorylation via phosphatidylinositol 3-kinase signaling. Finally, in ApoE(-/-) mice, overexpression of hIGFBP1 reduced atherosclerosis. These favorable effects of hIGFBP1 on insulin sensitivity, blood pressure, NO production, and atherosclerosis suggest that increasing IGFBP1 concentration may be a novel approach to prevent cardiovascular disease in the setting of insulin resistance and diabetes.
PMID: 22357965 PMCID: PMC3314358 DOI: 10.2337/db11-0963
Prediction of weight loss and regain following dietary, lifestyle, and pharmacologic intervention.
Clin Pharmacol Ther. 2012 Jun;91(6):1027-34. doi: 10.1038/clpt.2011.333. Epub 2012 Feb 15.
Napolitano A1, Miller SR, Murgatroyd PR, Delafont B, Brooke A, Elkhawad M, Tan CY, Virtue S, Vidal-Puig A, Nunez DJ.
Abstract – show
To develop statistical models for predicting weight loss and regain, we analyzed the phenotypic responses in an outpatient study of 60 obese subjects randomized to one of three 12-week interventions, diet (-600 kcal) alone, diet with exercise, and diet with sibutramine. This was followed by 12 weeks of observation. The best of the "baseline covariates" models was one that incorporated intervention group and baseline homeostasis model assessment-estimated insulin resistance (HOMA(IR)). It predicted week 12 weight change with R(2) of 0.38 and root mean square error (√MSE) of 2.92 kg. An alternative model incorporating baseline fat mass plus change in weight and HOMA(IR) at week 4 improved the prediction (R(2), 0.67, √MSE, 2.19 kg). We could not identify a satisfactory model to predict weight regain. We conclude that prediction of weight loss over 12 weeks is significantly improved when short-term weight change is incorporated into the model. This information could be utilized to forecast the success of a weight-loss program and to motivate and contribute to innovative designing of obesity trials.
PMID: 22336590 DOI: 10.1038/clpt.2011.333
Ablation of Pparg2 impairs lipolysis and reveals murine strain differences in lipolytic responses.
FASEB J. 2012 May;26(5):1835-44. doi: 10.1096/fj.11-193631. Epub 2012 Feb 8.
Rodriguez-Cuenca S1, Carobbio S, Vidal-Puig A.
Abstract – show
We investigate the role of PPARg2 as a regulator of lipolysis and its interaction with specific genetic backgrounds as determinants of the severity of the metabolic phenotype. This question was prompted by our previous characterization of Pparg2-knockout (KO) mice that revealed striking genetic background differences in the severity of their adipose tissue development impairment and dysfunction. Analysis is done of pharmacological lipolytic responses combined with protein and mRNA expression analysis in isolated adipocytes from the gonadal pad of Pparg2-KO mice in 2 different backgrounds (129S6/SvEv and C57BL/6). We provide evidence of the prolipolytic role of PPARg2 and how these effects are modulated by genetic background, leading to differential severity of metabolic syndrome. Specifically, ablation of Pparg2 reduced both basal and stimulated lipolysis as a result of impaired β(3)-AR signaling, a general defect at downstream lipases, and increased insulin-mediated antilipolytic action. Of note, the C57BL/6 Pparg2-KO mice exhibited more active lipolytic response to catecholamines than 129S6/SvEv Pparg2-KO mice with respect to their wild-type controls. Pparg2-KO mice exhibit metabolic inflexibility resulting from the combined effects of impaired lipid deposition coupled with impaired lipolytic lipid mobilization. The genetic background-dependent differences in lipolysis may account for Pparg2-KO background-specific differences in the severity of their metabolic disturbances. Our findings identify the isoform Pparg2 as an integrator of the adipose lipid metabolism coordinating both anabolic and catabolic processes.
PMID: 22319009 DOI: 10.1096/fj.11-193631
Nicotine induces negative energy balance through hypothalamic AMP-activated protein kinase.
Diabetes. 2012 Apr;61(4):807-17. doi: 10.2337/db11-1079. Epub 2012 Feb 7.
Martínez de Morentin PB1, Whittle AJ, Fernø J, Nogueiras R, Diéguez C, Vidal-Puig A, López M.
Abstract – show
Smokers around the world commonly report increased body weight after smoking cessation as a major factor that interferes with their attempts to quit. Numerous controlled studies in both humans and rodents have reported that nicotine exerts a marked anorectic action. The effects of nicotine on energy homeostasis have been mostly pinpointed in the central nervous system, but the molecular mechanisms controlling its action are still not fully understood. The aim of this study was to investigate the effect of nicotine on hypothalamic AMP-activated protein kinase (AMPK) and its effect on energy balance. Here we demonstrate that nicotine-induced weight loss is associated with inactivation of hypothalamic AMPK, decreased orexigenic signaling in the hypothalamus, increased energy expenditure as a result of increased locomotor activity, increased thermogenesis in brown adipose tissue (BAT), and alterations in fuel substrate utilization. Conversely, nicotine withdrawal or genetic activation of hypothalamic AMPK in the ventromedial nucleus of the hypothalamus reversed nicotine-induced negative energy balance. Overall these data demonstrate that the effects of nicotine on energy balance involve specific modulation of the hypothalamic AMPK-BAT axis. These targets may be relevant for the development of new therapies for human obesity.
PMID: 22315316 PMCID: PMC3314364 DOI: 10.2337/db11-1079
Peroxisome proliferator-activated receptor γ-dependent regulation of lipolytic nodes and metabolic flexibility.
Mol Cell Biol. 2012 Apr;32(8):1555-65. doi: 10.1128/MCB.06154-11. Epub 2012 Feb 6.
Rodriguez-Cuenca S1, Carobbio S, Velagapudi VR, Barbarroja N, Moreno-Navarrete JM, Tinahones FJ, Fernandez-Real JM, Orešic M, Vidal-Puig A.
Abstract – show
Optimal lipid storage and mobilization are essential for efficient adipose tissue. Nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) regulates adipocyte differentiation and lipid deposition, but its role in lipolysis and dysregulation in obesity is not well defined. This investigation aimed to understand the molecular impact of dysfunctional PPARγ on the lipolytic axis and to explore whether these defects are also confirmed in common forms of human obesity. For this purpose, we used the P465L PPARγ mouse as a model of dysfunctional PPARγ that recapitulates the human pparγ mutation (P467L). We demonstrated that defective PPARγ impairs catecholamine-induced lipolysis. This abnormal lipolytic response is exacerbated by a state of positive energy balance in leptin-deficient ob/ob mice. We identified the protein kinase A (PKA) network as a PPARγ-dependent regulatory node of the lipolytic response. Specifically, defective PPARγ is associated with decreased basal expression of prkaca (PKAcatα) and d-akap1, the lipase genes Pnplaz (ATGL) and Lipe (HSL), and lipid droplet protein genes fsp27 and adrp in vivo and in vitro. Our data indicate that PPARγ is required for activation of the lipolytic regulatory network, dysregulation of which is an important feature of obesity-induced insulin resistance in humans.
NPs — heart hormones that regulate brown fat?
J Clin Invest. 2012 Mar;122(3):804-7. doi: 10.1172/JCI62595. Epub 2012 Feb 6.
Whittle AJ1, Vidal-Puig A.
Abstract – show
Thermogenesis in brown adipose tissue (BAT) is well characterized as being under the control of the sympathetic nervous system. The energy-burning capacity of BAT makes it an attractive target for anti-obesity therapies. However, previous attempts to manipulate BAT's sympathetic activation have lacked specificity. In this issue of the JCI, Bordicchia et al. provide new data indicating that cardiac natriuretic peptides (NPs) are also able to activate thermogenic machinery in adipose tissue. Their findings suggest a novel strategy to increase energy dissipation in adipose tissue, independent of adrenergic receptors.
The mitochondria-targeted antioxidant MitoQ decreases features of the metabolic syndrome in ATM+/-/ApoE-/- mice.
Free Radic Biol Med. 2012 Mar 1;52(5):841-9. doi: 10.1016/j.freeradbiomed.2011.11.026. Epub 2011 Dec 14.
Mercer JR1, Yu E, Figg N, Cheng KK, Prime TA, Griffin JL, Masoodi M, Vidal-Puig A, Murphy MP, Bennett MR.
Abstract – show
A number of recent studies suggest that mitochondrial oxidative damage may be associated with atherosclerosis and the metabolic syndrome. However, much of the evidence linking mitochondrial oxidative damage and excess reactive oxygen species (ROS) with these pathologies is circumstantial. Consequently the importance of mitochondrial ROS in the etiology of these disorders is unclear. Furthermore, the potential of decreasing mitochondrial ROS as a therapy for these indications is not known. We assessed the impact of decreasing mitochondrial oxidative damage and ROS with the mitochondria-targeted antioxidant MitoQ in models of atherosclerosis and the metabolic syndrome (fat-fed ApoE(-/-) mice and ATM(+/-)/ApoE(-/-) mice, which are also haploinsufficient for the protein kinase, ataxia telangiectasia mutated (ATM). MitoQ administered orally for 14weeks prevented the increased adiposity, hypercholesterolemia, and hypertriglyceridemia associated with the metabolic syndrome. MitoQ also corrected hyperglycemia and hepatic steatosis, induced changes in multiple metabolically relevant lipid species, and decreased DNA oxidative damage (8-oxo-G) in multiple organs. Although MitoQ did not affect overall atherosclerotic plaque area in fat-fed ATM(+/+)/ApoE(-/-) and ATM(+/-)/ApoE(-/-) mice, MitoQ reduced the macrophage content and cell proliferation within plaques and 8-oxo-G. MitoQ also significantly reduced mtDNA oxidative damage in the liver. Our data suggest that MitoQ inhibits the development of multiple features of the metabolic syndrome in these mice by affecting redox signaling pathways that depend on mitochondrial ROS such as hydrogen peroxide. These findings strengthen the growing view that elevated mitochondrial ROS contributes to the etiology of the metabolic syndrome and suggest a potential therapeutic role for mitochondria-targeted antioxidants.
Copyright © 2011 Elsevier Inc. All rights reserved.
PMID: 22210379 DOI: 10.1016/j.freeradbiomed.2011.11.026
Early peroxisome proliferator-activated receptor gamma regulated genes involved in expansion of pancreatic beta cell mass.
BMC Med Genomics. 2011 Dec 30;4:86. doi: 10.1186/1755-8794-4-86.
Vivas Y1, Martínez-García C, Izquierdo A, Garcia-Garcia F, Callejas S, Velasco I, Campbell M, Ros M, Dopazo A, Dopazo J, Vidal-Puig A, Medina-Gomez G.
Abstract – show
The progression towards type 2 diabetes depends on the allostatic response of pancreatic beta cells to synthesise and secrete enough insulin to compensate for insulin resistance. The endocrine pancreas is a plastic tissue able to expand or regress in response to the requirements imposed by physiological and pathophysiological states associated to insulin resistance such as pregnancy, obesity or ageing, but the mechanisms mediating beta cell mass expansion in these scenarios are not well defined. We have recently shown that ob/ob mice with genetic ablation of PPARγ2, a mouse model known as the POKO mouse failed to expand its beta cell mass. This phenotype contrasted with the appropriate expansion of the beta cell mass observed in their obese littermate ob/ob mice. Thus, comparison of these models islets particularly at early ages could provide some new insights on early PPARγ dependent transcriptional responses involved in the process of beta cell mass expansion
Here we have investigated PPARγ dependent transcriptional responses occurring during the early stages of beta cell adaptation to insulin resistance in wild type, ob/ob, PPARγ2 KO and POKO mice. We have identified genes known to regulate both the rate of proliferation and the survival signals of beta cells. Moreover we have also identified new pathways induced in ob/ob islets that remained unchanged in POKO islets, suggesting an important role for PPARγ in maintenance/activation of mechanisms essential for the continued function of the beta cell.
Our data suggest that the expansion of beta cell mass observed in ob/ob islets is associated with the activation of an immune response that fails to occur in POKO islets. We have also indentified other PPARγ dependent differentially regulated pathways including cholesterol biosynthesis, apoptosis through TGF-β signaling and decreased oxidative phosphorylation.
Postprandial inflammatory response in adipose tissue of patients with metabolic syndrome after the intake of different dietary models.
Mol Nutr Food Res. 2011 Dec;55(12):1759-70. doi: 10.1002/mnfr.201100200.
Meneses ME1, Camargo A, Perez-Martinez P, Delgado-Lista J, Cruz-Teno C, Jimenez-Gomez Y, Paniagua JA, Gutierrez-Mariscal FM, Tinahones FJ, Vidal-Puig A, Roche HM, Perez-Jimenez F, Malagon MM, Lopez-Miranda J.
Abstract – show
Dysfunctional adipose tissue may be an important trigger of molecular inflammatory pathways that cause cardiovascular diseases. Our aim was to determine whether the specific quality and quantity of dietary fat produce differential postprandial inflammatory responses in adipose tissue from metabolic syndrome (MetS) patients.
A randomized, controlled trial conducted within the LIPGENE study assigned MetS patients to 1 of 4 diets: (i) high-saturated fatty acid (HSFA), (ii) high-monounsaturated fatty acid (HMUFA), (iii) low-fat, high-complex carbohydrate diet supplemented with n-3 polyunsaturated fatty acids (PUFA) (LFHCC n-3), and (iv) low-fat, high-complex carbohydrate diet supplemented with placebo (LFHCC), for 12 wk each. A fat challenge reflecting the fatty acid composition as the original diets was conducted post-intervention. We found that p65 gene expression is induced in adipose tissue (p=0.003) at the postprandial state. In addition, IκBα (p<0.001), MCP-1 (p<0.001) and IL-1β (p<0.001) gene expression was equally induced in the postprandial state, regardless of the quality and quantity of the dietary fat. Notably, IL-6 transcripts were only detected in the postprandial state.
Our results indicate that individuals with MetS typically exhibit exacerbated adipose tissue postprandial inflammatory responses, which seem to be independent of the quality and quantity of dietary fat.
Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
PMID: 22144044 DOI: 10.1002/mnfr.201100200
Physiology: Immune cells fuel the fire.
Nature. 2011 Dec 1;480(7375):46-7. doi: 10.1038/nature10714.
Whittle AJ, Vidal-Puig A.
PMID: 22101432 DOI: 10.1038/nature10714
Carbon-nanoparticle-triggered acute lung inflammation and its resolution are not altered in PPARγ-defective (P465L) mice.
Part Fibre Toxicol. 2011 Sep 20;8:28. doi: 10.1186/1743-8977-8-28.
Götz AA1, Vidal-Puig A, Rödel HG, de Angelis MH, Stoeger T.
Abstract – show
The alveolar macrophage (AM) – first line of innate immune defence against pathogens and environmental irritants – constitutively expresses peroxisome-proliferator activated receptor γ (PPARγ). PPARγ ligand-induced activation keeps the AM quiescent, and thereby contributes to combat invaders and resolve inflammation by augmenting the phagocytosis of apoptotic neutrophils and inhibiting an excessive expression of inflammatory genes. Because of these presumed anti-inflammatory functions of PPARγ we tested the hypothesis, whether reduced functional receptor availability in mutant mice resulted in increased cellular and molecular inflammatory response during acute inflammation and/or in an impairment of its resolution.
To address this hypothesis we examined the effects of a carbon-nanoparticle (CNP) lung challenge, as surrogate for non-infectious environmental irritants, in a murine model carrying a dominant-negative point mutation in the ligand-binding domain of PPARγ (P465L/wt). Animals were instilled intratracheally with Printex 90 CNPs and bronchoalveolar lavage (BAL) was gained 24 h or 72 h after instillation to investigate its cellular and protein composition.
Higher BAL cell numbers – due to higher macrophage counts – were found in mutants irrespective of treatment. Neutrophil numbers in contrast were slightly lower in mutants. Intratracheal CNP instillation resulted in a profound recruitment of inflammatory neutrophils into the alveolus, but genotype related differences at acute inflammation (24 h) and resolution (72 h) were not observed. There were no signs for increased alveolar-capillary membrane damage or necrotic cell death in mutants as determined by BAL protein and lactate-dehydrogenase content. Pro-inflammatory macrophage-derived cytokine osteopontin was higher, but galectin-3 lower in female mutants. CXCL5 and lipocalin-2 markers, attributed to epithelial cell stimulation did not differ.
Despite general genotype-related differences, we had to reject our hypothesis of an increased CNP induced lung inflammation and an impairment of its resolution in PPARγ defective mice. Although earlier studies showed ligand-induced activation of nuclear receptor PPARγ to promote resolution of lung inflammation, its reduced activity did not provide signs of resolution impairment in the settings investigated here.
Olanzapine, but not aripiprazole, weight-independently elevates serum triglycerides and activates lipogenic gene expression in female rats.
Int J Neuropsychopharmacol. 2012 Mar;15(2):163-79. doi: 10.1017/S1461145711001271. Epub 2011 Aug 19.
Skrede S1, Fernø J, Vázquez MJ, Fjær S, Pavlin T, Lunder N, Vidal-Puig A, Diéguez C, Berge RK, López M, Steen VM.
Abstract – show
Metabolic adverse effects such as weight gain and dyslipidaemia represent a major concern in treatment with several antipsychotic drugs, including olanzapine. It remains unclear whether such metabolic side-effects fully depend on appetite-stimulating actions, or whether some dysmetabolic features induced by antipsychotics may arise through direct perturbation of metabolic pathways in relevant peripheral tissues. Recent clinical and preclinical studies indicate that dyslipidaemia could occur independently of weight gain. Using a rat model, we showed that subchronic treatment with olanzapine induces weight gain and increases adipose tissue mass in rats with free access to food. This effect was also observed for aripiprazole, considered metabolically neutral in the clinical setting. In pair-fed rats with limited food access, neither olanzapine nor aripiprazole induced weight gain. Interestingly, olanzapine, but not aripiprazole, induced weight-independent elevation of serum triglycerides, accompanied by up-regulation of several genes involved in lipid biosynthesis, both in liver and in adipose tissues. Our findings support the existence of tissue-specific, weight-independent direct effects of olanzapine on lipid metabolism.
Origins of metabolic complications in obesity: ectopic fat accumulation. The importance of the qualitative aspect of lipotoxicity.
Curr Opin Clin Nutr Metab Care. 2011 Nov;14(6):520-6. doi: 10.1097/MCO.0b013e32834ad966.
Carobbio S1, Rodriguez-Cuenca S, Vidal-Puig A.
Abstract – show
This study highlights two aspects of the concept of lipotoxicity. First, the metabolic consequences following ectopic fat accumulation are not only determined by the amount of lipid accumulated, but also the quality of lipid species. Second, the existence of allostatic mechanisms operating at cellular and tissue levels, which counterbalance the negative effects of lipid overload.
The development of lipidomics has allowed the isolation and identification of a wide range of lipid species. Some are highly reactive and capable of inducing undesirable toxic effects. Here we focus on recent information related to pathways involved in the production of these reactive lipid species, their sites of generation and tropism for specific organelles and the molecular mechanisms through which they exert toxic effects. We describe how cell membranes and the lipid species forming their bilayer constitute the main platform from which reactive lipid species are generated. We propose that strategies aimed at maintaining membrane lipid homeostasis are fundamental to preventing the initiation of metabolically relevant lipotoxicity.
It is essential to understand the qualitative component of lipid species involved in cellular toxicity and the molecular mechanisms mediating these toxic effects to identify new therapeutic targets.
PMID: 21849895 DOI: 10.1097/MCO.0b013e32834ad966
Nothing Iffy about HIF in the Hypothalamus.
PLoS Biol. 2011 Jul;9(7):e1001116. doi: 10.1371/journal.pbio.1001116. Epub 2011 Jul 26.
Virtue S1, Vidal-Puig A.
Abstract – show
Two crucial biological processes are (1) the sensing and coordination of responses to low oxygen levels and (2) the control of food intake and energy expenditure. The hypoxia-inducible factor (HIF) family of proteins is known to regulate responses to low oxygen, whereas neuropeptides derived from proopiomelanocortin (POMC) are implicated in the control of food intake and energy expenditure. It is now becoming apparent that these two apparently disparate processes may be linked, with the exciting discovery that HIF proteins can act in the brain to regulate food intake and energy expenditure as reported in the current issue of PLoS Biology. This primer discusses the traditional role of HIF proteins in terms of responding to oxygen levels in the periphery and also their new role in coordinating responses to nutrients in the brain through regulation of POMC.
PMID: 21814494 PMCID: PMC3144187 DOI: 10.1371/journal.pbio.1001116
PGC-1β deficiency accelerates the transition to heart failure in pressure overload hypertrophy.
Circ Res. 2011 Sep 16;109(7):783-93. doi: 10.1161/CIRCRESAHA.111.243964. Epub 2011 Jul 28.
Riehle C1, Wende AR, Zaha VG, Pires KM, Wayment B, Olsen C, Bugger H, Buchanan J, Wang X, Moreira AB, Doenst T, Medina-Gomez G, Litwin SE, Lelliott CJ, Vidal-Puig A, Abel ED.
Abstract – show
Pressure overload cardiac hypertrophy, a risk factor for heart failure, is associated with reduced mitochondrial fatty acid oxidation (FAO) and oxidative phosphorylation (OXPHOS) proteins that correlate in rodents with reduced PGC-1α expression.
To determine the role of PGC-1β in maintaining mitochondrial energy metabolism and contractile function in pressure overload hypertrophy.
PGC-1β deficient (KO) mice and wildtype (WT) controls were subjected to transverse aortic constriction (TAC). Although LV function was modestly reduced in young KO hearts, there was no further decline with age so that LV function was similar between KO and WT when TAC was performed. WT-TAC mice developed relatively compensated LVH, despite reduced mitochondrial function and repression of OXPHOS and FAO genes. In nonstressed KO hearts, OXPHOS gene expression and palmitoyl-carnitine-supported mitochondrial function were reduced to the same extent as banded WT, but FAO gene expression was normal. Following TAC, KO mice progressed more rapidly to heart failure and developed more severe mitochondrial dysfunction, despite a similar overall pattern of repression of OXPHOS and FAO genes as WT-TAC. However, in relation to WT-TAC, PGC-1β deficient mice exhibited greater degrees of oxidative stress, decreased cardiac efficiency, lower rates of glucose metabolism, and repression of hexokinase II protein.
PGC-1β plays an important role in maintaining baseline mitochondrial function and cardiac contractile function following pressure overload hypertrophy by preserving glucose metabolism and preventing oxidative stress.
Acute effects of orexigenic antipsychotic drugs on lipid and carbohydrate metabolism in rat.
Psychopharmacology (Berl). 2012 Feb;219(3):783-94. doi: 10.1007/s00213-011-2397-y. Epub 2011 Jul 12.
Jassim G1, Skrede S, Vázquez MJ, Wergedal H, Vik-Mo AO, Lunder N, Diéguez C, Vidal-Puig A, Berge RK, López M, Steen VM, Fernø J.
Abstract – show
This study aims to investigate whether orexigenic antipsychotic drugs may induce dyslipidemia and glucose disturbances in female rats through direct perturbation of metabolically active peripheral tissues, independent of prior weight gain.
In the current study, we examined whether a single intraperitoneal injection of clozapine or olanzapine induced metabolic disturbances in adult female outbred Sprague-Dawley rats. Serum glucose and lipid parameters were measured during time-course experiments up to 48 h. Real-time quantitative PCR was used to measure specific transcriptional alterations in lipid and carbohydrate metabolism in adipose tissue depots or in the liver.
Our results demonstrated that acute administration of clozapine or olanzapine induced a rapid, robust elevation of free fatty acids and glucose in serum, followed by hepatic accumulation of lipids evident after 12-24 h. These metabolic disturbances were associated with biphasic patterns of gluconeogenic and lipid-related gene expression in the liver and in white adipose tissue depots.
Our results support that clozapine and olanzapine are associated with primary effects on carbohydrate and lipid metabolism associated with transcriptional changes in metabolically active peripheral tissues prior to the development of drug-induced weight gain.
PMID: 21748251 PMCID: PMC3259403 DOI: 10.1007/s00213-011-2397-y
Genome-wide profiling of microRNAs in adipose mesenchymal stem cell differentiation and mouse models of obesity.
PLoS One. 2011;6(6):e21305. doi: 10.1371/journal.pone.0021305. Epub 2011 Jun 23.
Bengestrate L1, Virtue S, Campbell M, Vidal-Puig A, Hadaschik D, Hahn P, Bielke W.
Abstract – show
In recent years, there has been accumulating evidence that microRNAs are key regulator molecules of gene expression. The cellular processes that are regulated by microRNAs include e.g. cell proliferation, programmed cell death and cell differentiation. Adipocyte differentiation is a highly regulated cellular process for which several important regulating factors have been discovered, but still not all are known to fully understand the underlying mechanisms. In the present study, we analyzed the expression of 597 microRNAs during the differentiation of mouse mesenchymal stem cells into terminally differentiated adipocytes by real-time RT-PCR. In total, 66 miRNAs were differentially expressed in mesenchymal stem cell-derived adipocytes compared to the undifferentiated progenitor cells. To further study the regulation of these 66 miRNAs in white adipose tissue in vivo and their dependence on PPARγ activity, mouse models of genetically or diet induced obesity as well as a mouse line expressing a dominant negative PPARγ mutant were employed.
PMID: 21731698 PMCID: PMC3121761 DOI: 10.1371/journal.pone.0021305
Genetic variation near IRS1 associates with reduced adiposity and an impaired metabolic profile.
Nat Genet. 2011 Jun 26;43(8):753-60. doi: 10.1038/ng.866.
Kilpeläinen TO, Zillikens MC, Stančákova A, Finucane FM, Ried JS, Langenberg C, Zhang W, Beckmann JS, Luan J, Vandenput L, Styrkarsdottir U, Zhou Y, Smith AV, Zhao JH, Amin N, Vedantam S, Shin SY, Haritunians T, Fu M, Feitosa MF, Kumari M, Halldorsson BV, Tikkanen E, Mangino M, Hayward C, Song C, Arnold AM, Aulchenko YS, Oostra BA, Campbell H, Cupples LA, Davis KE, Döring A, Eiriksdottir G, Estrada K, Fernández-Real JM, Garcia M, Gieger C, Glazer NL, Guiducci C, Hofman A, Humphries SE, Isomaa B, Jacobs LC, Jula A, Karasik D, Karlsson MK, Khaw KT, Kim LJ, Kivimäki M, Klopp N, Kühnel B, Kuusisto J, Liu Y, Ljunggren O, Lorentzon M, Luben RN, McKnight B, Mellström D, Mitchell BD, Mooser V, Moreno JM, Männistö S, O'Connell JR, Pascoe L, Peltonen L, Peral B, Perola M, Psaty BM, Salomaa V, Savage DB, Semple RK, Skaric-Juric T, Sigurdsson G, Song KS, Spector TD, Syvänen AC, Talmud PJ, Thorleifsson G, Thorsteinsdottir U, Uitterlinden AG, van Duijn CM, Vidal-Puig A, Wild SH, Wright AF, Clegg DJ, Schadt E, Wilson JF, Rudan I, Ripatti S, Borecki IB, Shuldiner AR, Ingelsson E, Jansson JO, Kaplan RC, Gudnason V, Harris TB, Groop L, Kiel DP, Rivadeneira F, Walker M, Barroso I, Vollenweider P, Waeber G, Chambers JC, Kooner JS, Soranzo N, Hirschhorn JN, Stefansson K, Wichmann HE, Ohlsson C, O'Rahilly S, Wareham NJ, Speliotes EK, Fox CS, Laakso M, Loos RJ.
Abstract – show
Genome-wide association studies have identified 32 loci influencing body mass index, but this measure does not distinguish lean from fat mass. To identify adiposity loci, we meta-analyzed associations between ∼2.5 million SNPs and body fat percentage from 36,626 individuals and followed up the 14 most significant (P < 10(-6)) independent loci in 39,576 individuals. We confirmed a previously established adiposity locus in FTO (P = 3 × 10(-26)) and identified two new loci associated with body fat percentage, one near IRS1 (P = 4 × 10(-11)) and one near SPRY2 (P = 3 × 10(-8)). Both loci contain genes with potential links to adipocyte physiology. Notably, the body-fat-decreasing allele near IRS1 is associated with decreased IRS1 expression and with an impaired metabolic profile, including an increased visceral to subcutaneous fat ratio, insulin resistance, dyslipidemia, risk of diabetes and coronary artery disease and decreased adiponectin levels. Our findings provide new insights into adiposity and insulin resistance.
PMID: 21706003 PMCID: PMC3262230 DOI: 10.1038/ng.866
Olanzapine-induced hyperphagia and weight gain associate with orexigenic hypothalamic neuropeptide signaling without concomitant AMPK phosphorylation.
PLoS One. 2011;6(6):e20571. doi: 10.1371/journal.pone.0020571. Epub 2011 Jun 13.
Fernø J1, Varela L, Skrede S, Vázquez MJ, Nogueiras R, Diéguez C, Vidal-Puig A, Steen VM, López M.
Abstract – show
The success of antipsychotic drug treatment in patients with schizophrenia is limited by the propensity of these drugs to induce hyperphagia, weight gain and other metabolic disturbances, particularly evident for olanzapine and clozapine. However, the molecular mechanisms involved in antipsychotic-induced hyperphagia remain unclear. Here, we investigate the effect of olanzapine administration on the regulation of hypothalamic mechanisms controlling food intake, namely neuropeptide expression and AMP-activated protein kinase (AMPK) phosphorylation in rats. Our results show that subchronic exposure to olanzapine upregulates neuropeptide Y (NPY) and agouti related protein (AgRP) and downregulates proopiomelanocortin (POMC) in the arcuate nucleus of the hypothalamus (ARC). This effect was evident both in rats fed ad libitum and in pair-fed rats. Of note, despite weight gain and increased expression of orexigenic neuropeptides, subchronic administration of olanzapine decreased AMPK phosphorylation levels. This reduction in AMPK was not observed after acute administration of either olanzapine or clozapine. Overall, our data suggest that olanzapine-induced hyperphagia is mediated through appropriate changes in hypothalamic neuropeptides, and that this effect does not require concomitant AMPK activation. Our data shed new light on the hypothalamic mechanism underlying antipsychotic-induced hyperphagia and weight gain, and provide the basis for alternative targets to control energy balance.
PMID: 21695181 PMCID: PMC3113797 DOI: 10.1371/journal.pone.0020571
Association of lipidome remodeling in the adipocyte membrane with acquired obesity in humans.
PLoS Biol. 2011 Jun;9(6):e1000623. doi: 10.1371/journal.pbio.1000623. Epub 2011 Jun 7.
Pietiläinen KH1, Róg T, Seppänen-Laakso T, Virtue S, Gopalacharyulu P, Tang J, Rodriguez-Cuenca S, Maciejewski A, Naukkarinen J, Ruskeepää AL, Niemelä PS, Yetukuri L, Tan CY, Velagapudi V, Castillo S, Nygren H, Hyötyläinen T, Rissanen A, Kaprio J, Yki-Järvinen H, Vattulainen I, Vidal-Puig A, Orešič M.
Abstract – show
Identification of early mechanisms that may lead from obesity towards complications such as metabolic syndrome is of great interest. Here we performed lipidomic analyses of adipose tissue in twin pairs discordant for obesity but still metabolically compensated. In parallel we studied more evolved states of obesity by investigating a separated set of individuals considered to be morbidly obese. Despite lower dietary polyunsaturated fatty acid intake, the obese twin individuals had increased proportions of palmitoleic and arachidonic acids in their adipose tissue, including increased levels of ethanolamine plasmalogens containing arachidonic acid. Information gathered from these experimental groups was used for molecular dynamics simulations of lipid bilayers combined with dependency network analysis of combined clinical, lipidomics, and gene expression data. The simulations suggested that the observed lipid remodeling maintains the biophysical properties of lipid membranes, at the price, however, of increasing their vulnerability to inflammation. Conversely, in morbidly obese subjects, the proportion of plasmalogens containing arachidonic acid in the adipose tissue was markedly decreased. We also show by in vitro Elovl6 knockdown that the lipid network regulating the observed remodeling may be amenable to genetic modulation. Together, our novel approach suggests a physiological mechanism by which adaptation of adipocyte membranes to adipose tissue expansion associates with positive energy balance, potentially leading to higher vulnerability to inflammation in acquired obesity. Further studies will be needed to determine the cause of this effect.
PMID: 21666801 PMCID: PMC3110175 DOI: 10.1371/journal.pbio.1000623
Deletion of the metabolic transcriptional coactivator PGC1β induces cardiac arrhythmia.
Cardiovasc Res. 2011 Oct 1;92(1):29-38. doi: 10.1093/cvr/cvr155. Epub 2011 Jun 1.
Gurung IS1, Medina-Gomez G, Kis A, Baker M, Velagapudi V, Neogi SG, Campbell M, Rodriguez-Cuenca S, Lelliott C, McFarlane I, Oresic M, Grace AA, Vidal-Puig A, Huang CL.
Abstract – show
Peroxisome proliferator-activated receptor-γ coactivators PGC1α and PGC1β modulate mitochondrial biogenesis and energy homeostasis. The function of these transcriptional coactivators is impaired in obesity, insulin resistance, and type 2 diabetes. We searched for transcriptomic, lipidomic, and electrophysiological alterations in PGC1β(-/-) hearts potentially associated with increased arrhythmic risk in metabolic diseases.
Microarray analysis in mouse PGC1β(-/-) hearts confirmed down-regulation of genes related to oxidative phosphorylation and the electron transport chain and up-regulation of hypertrophy- and hypoxia-related genes. Lipidomic analysis showed increased levels of the pro-arrhythmic and pro-inflammatory lipid, lysophosphatidylcholine. PGC1β(-/-) mouse electrocardiograms showed irregular heartbeats and an increased incidence of polymorphic ventricular tachycardia following isoprenaline infusion. Langendorff-perfused PGC1β(-/-) hearts showed action potential alternans, early after-depolarizations, and ventricular tachycardia. PGC1β(-/-) ventricular myocytes showed oscillatory resting potentials, action potentials with early and delayed after-depolarizations, and burst firing during sustained current injection. They showed abnormal diastolic Ca(2+) transients, whose amplitude and frequency were increased by isoprenaline, and Ca(2+) currents with negatively shifted inactivation characteristics, with increased window currents despite unaltered levels of CACNA1C RNA transcripts. Inwardly and outward rectifying K(+) currents were all increased. Quantitiative RT-PCR demonstrated increased SCN5A, KCNA5, RYR2, and Ca(2+)-calmodulin dependent protein kinase II expression.
PGC1β(-/-) hearts showed a lysophospholipid-induced cardiac lipotoxicity and impaired bioenergetics accompanied by an ion channel remodelling and altered Ca(2+) homeostasis, converging to produce a ventricular arrhythmic phenotype particularly during adrenergic stress. This could contribute to the increased cardiac mortality associated with both metabolic and cardiac disease attributable to lysophospholipid accumulation.
PMID: 21632884 PMCID: PMC3172981 DOI: 10.1093/cvr/cvr155
Using brown adipose tissue to treat obesity – the central issue.
Trends Mol Med. 2011 Aug;17(8):405-11. doi: 10.1016/j.molmed.2011.04.001. Epub 2011 May 24.
Whittle AJ1, López M, Vidal-Puig A.
Abstract – show
Current therapeutic strategies are proving inadequate to deal with growing obesity rates because of the inherent resistance of the human body to weight loss. The activation of human brown adipose tissue (BAT) represents an opportunity to increase energy expenditure and weight loss alongside improved lipid and glucose homeostasis. Research into the regulation of BAT has made increasing the thermogenic capacity of an individual to treat metabolic disease a plausible strategy, despite thermogenesis being under tight central nervous system control. Previous therapies targeted at the sympathetic nervous system have had deleterious effects because of a lack of organ specificity, but advances in our understanding of central BAT regulatory systems might open up better strategies to specifically stimulate BAT in obese individuals to aid weight reduction.
Copyright © 2011 Elsevier Ltd. All rights reserved.
PMID: 21602104 DOI: 10.1016/j.molmed.2011.04.001
Peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC1alpha) is a metabolic regulator of intestinal epithelial cell fate.
Proc Natl Acad Sci U S A. 2011 Apr 19;108(16):6603-8. doi: 10.1073/pnas.1016354108. Epub 2011 Apr 5.
D'Errico I1, Salvatore L, Murzilli S, Lo Sasso G, Latorre D, Martelli N, Egorova AV, Polishuck R, Madeyski-Bengtson K, Lelliott C, Vidal-Puig AJ, Seibel P, Villani G, Moschetta A.
Abstract – show
Peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC1α) is a transcriptional coactivator able to up-regulate mitochondrial biogenesis, respiratory capacity, oxidative phosphorylation, and fatty acid β-oxidation with the final aim of providing a more efficient pathway for aerobic energy production. In the continuously renewed intestinal epithelium, proliferative cells in the crypts migrate along the villus axis and differentiate into mature enterocytes, increasing their respiratory capacity and finally undergoing apoptosis. Here we show that in the intestinal epithelial surface, PGC1α drives mitochondrial biogenesis and respiration in the presence of reduced antioxidant enzyme activities, thus determining the accumulation of reactive oxygen species and fostering the fate of enterocytes toward apoptosis. Combining gain- and loss-of-function genetic approaches in human cells and mouse models of intestinal cancer, we present an intriguing scenario whereby PGC1α regulates enterocyte cell fate and protects against tumorigenesis.
PMID: 21467224 PMCID: PMC3081029 DOI: 10.1073/pnas.1016354108
Hypothalamic AMP-activated protein kinase as a mediator of whole body energy balance.
Rev Endocr Metab Disord. 2011 Sep;12(3):127-40. doi: 10.1007/s11154-011-9165-5.
Blanco Martínez de Morentin P1, González CR, Saha AK, Martins L, Diéguez C, Vidal-Puig A, Tena-Sempere M, López M.
Abstract – show
The AMP-activated protein kinase (AMPK) is the downstream constituent of a kinase cascade that acts as a sensor of cellular energy levels. Current data unequivocally indicate that hypothalamic AMPK plays a key role in the control of the whole body energy balance, by integrating peripheral signals, such as hormones and metabolites, with central signals, such as neuropeptides, and eliciting allostatic changes in energy homeostasis. Although the molecular details of these interactions are not fully understood, recent evidence has suggested that the interaction between AMPK with hypothalamic lipid metabolism and other metabolic sensors, such as the uncoupling protein 2 (UCP-2), the mammalian target of rapamycin (mTOR) and the deacetylase sirtuin 1 (SIRT1), may play a main role in the hypothalamic control of feeding and energy expenditure. Here, we summarize the role of hypothalamic AMPK as whole body energy gauge. Understanding this key molecule and especially its functions at central level may provide new therapeutic targets for the treatment of metabolic alterations and obesity.
PMID: 21347863 DOI: 10.1007/s11154-011-9165-5
Differential lipid partitioning between adipocytes and tissue macrophages modulates macrophage lipotoxicity and M2/M1 polarization in obese mice.
Diabetes. 2011 Mar;60(3):797-809. doi: 10.2337/db10-0705. Epub 2011 Jan 24.
Prieur X1, Mok CY, Velagapudi VR, Núñez V, Fuentes L, Montaner D, Ishikawa K, Camacho A, Barbarroja N, O'Rahilly S, Sethi JK, Dopazo J, Orešič M, Ricote M, Vidal-Puig A.
Abstract – show
Obesity-associated insulin resistance is characterized by a state of chronic, low-grade inflammation that is associated with the accumulation of M1 proinflammatory macrophages in adipose tissue. Although different evidence explains the mechanisms linking the expansion of adipose tissue and adipose tissue macrophage (ATM) polarization, in the current study we investigated the concept of lipid-induced toxicity as the pathogenic link that could explain the trigger of this response.
We addressed this question using isolated ATMs and adipocytes from genetic and diet-induced murine models of obesity. Through transcriptomic and lipidomic analysis, we created a model integrating transcript and lipid species networks simultaneously occurring in adipocytes and ATMs and their reversibility by thiazolidinedione treatment.
We show that polarization of ATMs is associated with lipid accumulation and the consequent formation of foam cell-like cells in adipose tissue. Our study reveals that early stages of adipose tissue expansion are characterized by M2-polarized ATMs and that progressive lipid accumulation within ATMs heralds the M1 polarization, a macrophage phenotype associated with severe obesity and insulin resistance. Furthermore, rosiglitazone treatment, which promotes redistribution of lipids toward adipocytes and extends the M2 ATM polarization state, prevents the lipid alterations associated with M1 ATM polarization.
Our data indicate that the M1 ATM polarization in obesity might be a macrophage-specific manifestation of a more general lipotoxic pathogenic mechanism. This indicates that strategies to optimize fat deposition and repartitioning toward adipocytes might improve insulin sensitivity by preventing ATM lipotoxicity and M1 polarization.
PMID: 21266330 PMCID: PMC3046840 DOI: 10.2337/db10-0705
Could increased time spent in a thermal comfort zone contribute to population increases in obesity?
Obes Rev. 2011 Jul;12(7):543-51. doi: 10.1111/j.1467-789X.2010.00851.x. Epub 2011 Jan 24.
Johnson F1, Mavrogianni A, Ucci M, Vidal-Puig A, Wardle J.
Abstract – show
Domestic winter indoor temperatures in the USA, UK and other developed countries appear to be following an upwards trend. This review examines evidence of a causal link between thermal exposures and increases in obesity prevalence, focusing on acute and longer-term biological effects of time spent in thermal comfort compared with mild cold. Reduced exposure to seasonal cold may have a dual effect on energy expenditure, both minimizing the need for physiological thermogenesis and reducing thermogenic capacity. Experimental studies show a graded association between acute mild cold and human energy expenditure over the range of temperatures relevant to indoor heating trends. Meanwhile, recent studies of the role of brown adipose tissue (BAT) in human thermogenesis suggest that increased time spent in conditions of thermal comfort can lead to a loss of BAT and reduced thermogenic capacity. Pathways linking cold exposure and adiposity have not been directly tested in humans. Research in naturalistic and experimental settings is needed to establish effects of changes in thermal exposures on weight, which may raise possibilities for novel public health strategies to address obesity.
© 2011 The Authors. obesity reviews © 2011 International Association for the Study of Obesity.
PMID: 21261804 DOI: 10.1111/j.1467-789X.2010.00851.x
Ghrelin and lipid metabolism: key partners in energy balance.
J Mol Endocrinol. 2011 Feb 15;46(2):R43-63. doi: 10.1677/JME-10-0068. Print 2011 Apr.
Varela L1, Vázquez MJ, Cordido F, Nogueiras R, Vidal-Puig A, Diéguez C, López M.
Abstract – show
Ghrelin, the endogenous ligand of the GH secretagogue receptor, has a pleiotropic role in the modulation of energy balance. Recent evidence has demonstrated that besides its orexigenic role, ghrelin regulates central and peripheral lipid metabolism through specific control of hypothalamic AMP-activated protein kinase (AMPK), a critical metabolic gauge regulating both cellular and whole-body energy homeostasis. In this review, we summarize the new milestones of ghrelin's actions on energy balance, with particular focus on its molecular interaction with hypothalamic AMPK and fatty acid metabolism. Understanding this new metabolic pathway can provide new therapeutic targets for the treatment of obesity and the metabolic syndrome.
Electrical and optical spectroscopy for quantitative screening of hepatic steatosis in donor livers.
Phys Med Biol. 2010 Nov 21;55(22):6867-79. doi: 10.1088/0031-9155/55/22/017. Epub 2010 Nov 3.
McLaughlin BL, Wells AC, Virtue S, Vidal-Puig A, Wilkinson TD, Watson CJ, Robertson PA.
Abstract – show
Macro-steatosis in deceased donor livers is increasingly prevalent and is associated with poor or non-function of the liver upon reperfusion. Current assessment of the extent of steatosis depends upon the macroscopic assessment of the liver by the surgeon and histological examination, if available. In this paper we demonstrate electrical and optical spectroscopy techniques which quantitatively characterize fatty infiltration in liver tissue. Optical spectroscopy showed a correlation coefficient of 0.85 in humans when referenced to clinical hematoxylin and eosin (H&E) sections in 20 human samples. With further development, an optical probe may provide a comprehensive measure of steatosis across the liver at the time of procurement.
PMID: 21048293 [PubMed – indexed for MEDLINE]
Hypothalamic AMPK and fatty acid metabolism mediate thyroid regulation of energy balance.
Nat Med. 2010 Sep;16(9):1001-8. doi: 10.1038/nm.2207. Epub 2010 Aug 29.
López M, Varela L, Vázquez MJ, Rodríguez-Cuenca S, González CR, Velagapudi VR, Morgan DA, Schoenmakers E, Agassandian K, Lage R, Martínez de Morentin PB, Tovar S, Nogueiras R, Carling D, Lelliott C, Gallego R, Oresic M, Chatterjee K, Saha AK, Rahmouni K, Diéguez C, Vidal-Puig A.
Abstract – show
Thyroid hormones have widespread cellular effects; however it is unclear whether their effects on the central nervous system (CNS) contribute to global energy balance. Here we demonstrate that either whole-body hyperthyroidism or central administration of triiodothyronine (T3) decreases the activity of hypothalamic AMP-activated protein kinase (AMPK), increases sympathetic nervous system (SNS) activity and upregulates thermogenic markers in brown adipose tissue (BAT). Inhibition of the lipogenic pathway in the ventromedial nucleus of the hypothalamus (VMH) prevents CNS-mediated activation of BAT by thyroid hormone and reverses the weight loss associated with hyperthyroidism. Similarly, inhibition of thyroid hormone receptors in the VMH reverses the weight loss associated with hyperthyroidism. This regulatory mechanism depends on AMPK inactivation, as genetic inhibition of this enzyme in the VMH of euthyroid rats induces feeding-independent weight loss and increases expression of thermogenic markers in BAT. These effects are reversed by pharmacological blockade of the SNS. Thus, thyroid hormone-induced modulation of AMPK activity and lipid metabolism in the hypothalamus is a major regulator of whole-body energy homeostasis.
PMID: 20802499 [PubMed – indexed for MEDLINE] PMCID: PMC2935934
LEM-PCR: a method for determining relative transcript isoform proportions using real-time PCR without a standard curve.
Genome. 2010 Aug;53(8):637-42. doi: 10.1139/g10-036.
Virtue S, Dale M, Sethi JK, Vidal-Puig A.
Abstract – show
Many genes express multiple transcript isoforms generated by alternative splicing of mRNA. Using real-time PCR, it is straightforward to determine the relative expression level of each isoform independently. However, it is less trivial to determine the relative proportions of different isoforms in a cDNA sample. The relative proportions of different isoforms can be important, as a small change in a highly abundant transcript may be more relevant than a large change in a minimally expressed transcript. Currently, determining the relative proportions of isoforms requires the construction of a standard curve using recombinant plasmid DNA or genomic DNA. As recombinant or genomic DNA standards often amplify with different efficiencies to cDNA samples, they may give under- or overestimations of isoform abundances. The method described in this article uses a titration curve generated from the same cDNA samples measured in the experiment. By using samples with different levels of separate isoforms, it is possible to derive linear equations which, when solved, allow the determination of the proportion of each isoform within the samples under study.
PMID: 20725151 [PubMed – indexed for MEDLINE]
DNA damage links mitochondrial dysfunction to atherosclerosis and the metabolic syndrome.
Circ Res. 2010 Oct 15;107(8):1021-31. doi: 10.1161/CIRCRESAHA.110.218966. Epub 2010 Aug 12.
Mercer JR, Cheng KK, Figg N, Gorenne I, Mahmoudi M, Griffin J, Vidal-Puig A, Logan A, Murphy MP, Bennett M.
Abstract – show
DNA damage is present in both genomic and mitochondrial DNA in atherosclerosis. However, whether DNA damage itself promotes atherosclerosis, or is simply a byproduct of the risk factors that promote atherosclerosis, is unknown.
To examine the effect of DNA damage on atherosclerosis, we studied apolipoprotein (Apo)E(-/-) mice that were haploinsufficient for the protein kinase ATM (ataxia telangiectasia mutated), which coordinates DNA repair.
ATM(+/-)/ApoE(-/-) mice developed accelerated atherosclerosis and multiple features of the metabolic syndrome, including hypertension, hypercholesterolemia, obesity, steatohepatitis, and glucose intolerance. Transplantation with ATM(+/+) bone marrow attenuated atherosclerosis but not the metabolic syndrome. ATM(+/-) smooth muscle cells and macrophages showed increased nuclear DNA damage and defective DNA repair signaling, growth arrest, and apoptosis. Metabolomic screening of ATM(+/-)/ApoE(-/-) mouse tissues identified metabolic changes compatible with mitochondrial defects, with increased β-hydroxybutyrate but reduced lactate, reduced glucose, and alterations in multiple lipid species. ATM(+/-)/ApoE(-/-) mouse tissues showed an increased frequency of a mouse mitochondrial "common" deletion equivalent and reduced mitochondrial oxidative phosphorylation.
We propose that failure of DNA repair generates defects in cell proliferation, apoptosis, and mitochondrial dysfunction. This in turn leads to ketosis, hyperlipidemia, and increased fat storage, promoting atherosclerosis and the metabolic syndrome. Prevention of mitochondrial dysfunction may represent a novel target in cardiovascular disease.
PMID: 20705925 [PubMed – indexed for MEDLINE] PMCID: PMC2982998
The obese healthy paradox: is inflammation the answer?
Biochem J. 2010 Aug 15;430(1):141-9. doi: 10.1042/BJ20100285.
Barbarroja N, López-Pedrera R, Mayas MD, García-Fuentes E, Garrido-Sánchez L, Macías-González M, El Bekay R, Vidal-Puig A, Tinahones FJ.
Abstract – show
A paradoxical but common finding in the obesity clinic is the identification of individuals who can be considered 'inappropriately' healthy for their degree of obesity. We think that studying these obese but metabolically healthy individuals and comparing them with equally obese but insulin-resistant individuals could provide important insights into the mechanistic link between adipose tissue expansion and associated metabolic alterations. In the present study, we investigated whether there are differences in inflammatory and insulin signalling pathways in VAT (visceral adipose tissue) that could account for the metabolic differences exhibited by morbidly obese individuals who are either insulin-resistant (IR-MO) or paradoxically insulin-sensitive (NIR-MO). Our results indicate that there are pathways common to obesity and unrelated to insulin resistance and others that are discriminative for insulin resistance for a similar degree of obesity. For instance, all morbidly obese patients, irrespective of their insulin resistance, showed increased expression of TNFalpha (tumour necrosis factor alpha) and activation of JNK1/2 (c-Jun N-terminal kinase 1/2). However, the IR-MO group showed significantly elevated expression levels of IL (interleukin)-1beta and IL-6 and increased macrophage infiltrates compared with non-obese individuals and NIR-MO. IkappaBalpha [inhibitor of NF-kappaB (nuclear factor kappaB) alpha], the activation of ERK1/2 (extracellular-signal-regulated kinase 1/2) and NF-kappaB were discriminative of the state of insulin resistance and correlated with differential changes in IRS-1 (insulin receptor substrate 1) expression and Akt activation between IR-MO and NIR-MO individuals. Our results support the concept that NIR-MO individuals lack the inflammatory response that characterizes the IR-MO patient and that IL-6, IL-1beta, ERK and NF-kappaB are important effectors that mediate the inflammation effects promoting insulin resistance.
PMID: 20522023 [PubMed – indexed for MEDLINE]
Secreted frizzled-related protein 1 regulates adipose tissue expansion and is dysregulated in severe obesity.
Int J Obes (Lond). 2010 Dec;34(12):1695-705. doi: 10.1038/ijo.2010.107. Epub 2010 Jun 1.
Lagathu C, Christodoulides C, Tan CY, Virtue S, Laudes M, Campbell M, Ishikawa K, Ortega F, Tinahones FJ, Fernández-Real JM, Orešič M, Sethi JK, Vidal-Puig A.
Abstract – show
The Wnt/β-catenin signaling network offers potential targets to diagnose and uncouple obesity from its metabolic complications. In this study, we investigate the role of the Wnt antagonist, secreted frizzled-related protein 1 (SFRP1), in promoting adipogenesis in vitro and adipose tissue expansion in vivo.
We use a combination of human and murine, in vivo and in vitro models of adipogenesis, adipose tissue expansion and obesity-related metabolic syndrome to profile the involvement of SFRP1.
SFRP1 is expressed in both murine and human mature adipocytes. The expression of SFRP1 is induced during in vitro adipogenesis, and SFRP1 is preferentially expressed in mature adipocytes in human adipose tissue. Constitutive ectopic expression of SFRP1 is proadipogenic and inhibits the Wnt/β-catenin signaling pathway. In vivo endogenous levels of adipose SFRP1 are regulated in line with proadipogenic states. However, in longitudinal studies of high-fat-diet-fed mice, we observed a dynamic temporal but biphasic regulation of endogenous SFRP1. In agreement with this profile, we observed that SFRP1 expression in human tissues peaks in patients with mild obesity and gradually falls in morbidly obese subjects.
Our results suggest that SFRP1 is an endogenous modulator of Wnt/β-catenin signaling and participates in the paracrine regulation of human adipogenesis. The reduced adipose expression of SFRP1 in morbid obesity and its knock-on effect to prevent further adipose tissue expansion may contribute to the development of metabolic complications in these individuals.
PMID: 20514047 [PubMed – indexed for MEDLINE]
No association between polymorphisms in the INSIG1 gene and the risk of type 2 diabetes and related traits.
Am J Clin Nutr. 2010 Jul;92(1):252-7. doi: 10.3945/ajcn.2010.29422. Epub 2010 May 5.
Szopa M, Meirhaeghe A, Luan J, Moreno LA, Gonzalez-Gross M, Vidal-Puig A, Cooper C, Hagen R, Amouyel P, Wareham NJ, Loos RJ.
Abstract – show
The insulin-induced gene 1 (INSIG1) encodes a protein that blocks proteolytic activation of sterol regulatory element binding proteins, which are transcription factors that activate genes that regulate cholesterol, fatty acid, and glucose metabolism.
We tested for associations between 6 INSIG1 tag single nucleotide polymorphisms (SNPs) (and captured all common variations in INSIG1) and the risk of type 2 diabetes (T2D), obesity, and related traits in 10,567 adults and 1155 adolescents from 5 population-based studies, a T2D case-control study, and a T2D case-series.
We genotyped tag SNPs and tested them for associations with the risk of T2D or obesity and with body mass index, waist circumference, systolic and diastolic blood pressure, and concentrations of fasting glucose, 2-h oral-glucose-tolerance test glucose, cholesterol, and triglyceride, with the assumption of an additive effect of the minor allele. Dominant effects were tested for the less-frequent SNPs (minor allele frequency <5%). Summary statistics of each study underwent meta-analysis.
Meta-analyses, which included 1655 T2D cases and 2911 control subjects, showed no association between any of the INSIG1 SNPs and T2D (P > 0.08). Furthermore, none of the SNPs showed an association with obesity in 1666 obese and 5737 nonobese individuals (P > 0.17). In agreement, none of the associations between the SNPs and any of the metabolic traits showed convincing associations in the 7562 adults from 4 population-based studies. Although a few nominally significant associations emerged, none of the associations survived multiple-testing correction. We observed no convincing associations with any of the studied traits in 1155 adolescents.
Although our study was sufficiently powered to identify small effects, the results suggest that common variation in INSIG1 is unlikely to have a major effect on T2D and obesity risk and related traits in white Europeans.
PMID: 20444954 [PubMed – indexed for MEDLINE]
An allostatic control of membrane lipid composition by SREBP1.
FEBS Lett. 2010 Jun 18;584(12):2689-98. doi: 10.1016/j.febslet.2010.04.004. Epub 2010 Apr 10.
Hagen RM, Rodriguez-Cuenca S, Vidal-Puig A.
Abstract – show
The maintenance of membrane lipid composition within strict limits is critical to maintain optimum cellular function. The biophysical properties of the membrane can be influenced among other factors by the saturation/unsaturation of the phospholipid fatty acyl chain. The rate-limiting enzyme in unsaturated fatty acid biosynthesis is the desaturase enzyme which in turn is regulated by the lipid transcription factor sterol regulatory element binding protein (SREBP1). In this review, we collect some evidence suggesting SREBP1 network as an important allostatic regulator necessary to maintain the pool of unsaturated fatty acid lipid species that can be incorporated into biological membranes.
Copyright 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
PMID: 20385130 [PubMed – indexed for MEDLINE]
Ghrelin effects on neuropeptides in the rat hypothalamus depend on fatty acid metabolism actions on BSX but not on gender.
FASEB J. 2010 Aug;24(8):2670-9. doi: 10.1096/fj.09-150672. Epub 2010 Mar 24.
Lage R, Vázquez MJ, Varela L, Saha AK, Vidal-Puig A, Nogueiras R, Diéguez C, López M.
Abstract – show
The orexigenic effect of ghrelin is mediated by neuropeptide Y (NPY) and agouti-related protein (AgRP) in the hypothalamic arcuate nucleus (ARC). Recent evidence also indicates that ghrelin promotes feeding through a mechanism involving activation of hypothalamic AMP-activated protein kinase (AMPK) and inactivation of acetyl-CoA carboxylase and fatty acid synthase (FAS). This results in decreased hypothalamic levels of malonyl-CoA, increased carnitine palmitoyltransferase 1 (CPT1) activity, and mitochondrial production of reactive oxygen species. We evaluated whether these molecular events are part of a unique signaling cascade or whether they represent alternative pathways mediating the orexigenic effect of ghrelin. Moreover, we examined the gender dependency of these mechanisms, because recent evidence has proposed that ghrelin orexigenic effect is reduced in female rats. We studied in both genders the effect of ghrelin on the expression of AgRP and NPY, as well as their transcription factors: cAMP response-element binding protein (CREB and its phosphorylated form, pCREB), forkhead box O1 (FoxO1 and its phosphorylated form, pFoxO1), and brain-specific homeobox transcription factor (BSX). In addition, to establish a mechanistic link between ghrelin, fatty acid metabolism, and neuropeptides, we evaluated the effect of ghrelin after blockage of hypothalamic fatty acid beta oxidation, by using the CPT1 inhibitor etomoxir. Ghrelin-induced changes in the AMPK-CPT1 pathway are associated with increased levels of AgRP and NPY mRNA expression through modulation of BSX, pCREB, and FoxO1, as well as decreased expression of endoplasmic reticulum (ER) stress markers in a gender-independent manner. In addition, blockage of hypothalamic fatty acid beta oxidation prevents the ghrelin-promoting action on AgRP and NPY mRNA expression, also in a gender-independent manner. Notably, this effect is associated with decreased BSX expression and reduced food intake. Overall, our data suggest that BSX integrates changes in neuronal metabolic status with ARC-derived neuropeptides in a gender-independent manner.
PMID: 20335227 [PubMed – indexed for MEDLINE] PMCID: PMC3230529
Extracellular fatty acid synthase: a possible surrogate biomarker of insulin resistance.
Diabetes. 2010 Jun;59(6):1506-11. doi: 10.2337/db09-1756. Epub 2010 Mar 18.
Fernandez-Real JM, Menendez JA, Moreno-Navarrete JM, Blüher M, Vazquez-Martin A, Vázquez MJ, Ortega F, Diéguez C, Frühbeck G, Ricart W, Vidal-Puig A.
Abstract – show
Circulating fatty acid synthase (FASN) is a biomarker of metabolically demanding human diseases. The aim of this study was to determine whether circulating FASN could be a biomarker of overnutrition-induced metabolic stress and insulin resistance in common metabolic disorders.
Circulating FASN was evaluated in two cross-sectional studies in association with insulin sensitivity and in four longitudinal studies investigating the effect of diet- and surgery-induced weight loss, physical training, and adipose tissue expansion using peroxisome proliferator-activated receptor agonist rosiglitazone on circulating FASN.
Age- and BMI-adjusted FASN concentrations were significantly increased in association with obesity-induced insulin resistance in two independent cohorts. Both visceral and subcutaneous FASN expression and protein levels correlated inversely with extracellular circulating FASN (P = -0.63; P < 0.0001), suggesting that circulating FASN is linked to depletion of intracellular FASN. Improved insulin sensitivity induced by therapeutic strategies that decreased fat mass (diet induced, surgery induced, or physical training) all led to decreased FASN levels in blood (P values between 0.02 and 0.04). To discriminate whether this was an effect related to insulin sensitization, we also investigated the effects of rosiglitazone. Rosiglitazone did not lead to significant changes in circulating FASN concentration.
Our results suggest that circulating FASN is a biomarker of overnutrition-induced insulin resistance that could provide diagnostic and prognostic advantages by providing insights on the individualized metabolic stress.
PMID: 20299470 [PubMed – indexed for MEDLINE] PMCID: PMC2874712
Wnt signalling and the control of cellular metabolism.
Biochem J. 2010 Mar 15;427(1):1-17. doi: 10.1042/BJ20091866.
Sethi JK, Vidal-Puig A.
Abstract – show
At the cellular level, the biological processes of cell proliferation, growth arrest, differentiation and apoptosis are all tightly coupled to appropriate alterations in metabolic status. In the case of cell proliferation, this requires redirecting metabolic pathways to provide the fuel and basic components for new cells. Ultimately, the successful co-ordination of cell-specific biology with cellular metabolism underscores multicellular processes as diverse as embryonic development, adult tissue remodelling and cancer cell biology. The Wnt signalling network has been implicated in all of these areas. While each of the Wnt-dependent signalling pathways are being individually delineated in a range of experimental systems, our understanding of how they integrate and regulate cellular metabolism is still in its infancy. In the present review we reassess the roles of Wnt signalling in functionally linking cellular metabolism to tissue development and function.
PMID: 20226003 [PubMed – indexed for MEDLINE]
Abdominal subcutaneous adipose tissue morphology in a patient with a dominant-negative mutation (P467L) in the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARG) gene.
Nutr Metab Cardiovasc Dis. 2010 Mar;20(3):e11-2. doi: 10.1016/j.numecd.2009.10.018. Epub 2010 Feb 12.
Boiani R, Cinti S, Savage DB, Vidal-Puig A, O'Rahilly S.
PMID: 20153617 [PubMed – indexed for MEDLINE]
Adipose tissue expandability, lipotoxicity and the Metabolic Syndrome–an allostatic perspective.
Biochim Biophys Acta. 2010 Mar;1801(3):338-49. doi: 10.1016/j.bbalip.2009.12.006. Epub 2010 Jan 6.
Virtue S, Vidal-Puig A.
Abstract – show
While the link between obesity and type 2 diabetes is clear on an epidemiological level, the underlying mechanism linking these two common disorders is not as clearly understood. One hypothesis linking obesity to type 2 diabetes is the adipose tissue expandability hypothesis. The adipose tissue expandability hypothesis states that a failure in the capacity for adipose tissue expansion, rather than obesity per se is the key factor linking positive energy balance and type 2 diabetes. All individuals possess a maximum capacity for adipose expansion which is determined by both genetic and environmental factors. Once the adipose tissue expansion limit is reached, adipose tissue ceases to store energy efficiently and lipids begin to accumulate in other tissues. Ectopic lipid accumulation in non-adipocyte cells causes lipotoxic insults including insulin resistance, apoptosis and inflammation. This article discusses the links between adipokines, inflammation, adipose tissue expandability and lipotoxicity. Finally, we will discuss how considering the concept of allostasis may enable a better understanding of how diabetes develops and allow the rational design of new anti diabetic treatments.
Copyright (c) 2009 Elsevier B.V. All rights reserved.
PMID: 20056169 [PubMed – indexed for MEDLINE]
Obesity as a clinical and public health problem: is there a need for a new definition based on lipotoxicity effects?
Biochim Biophys Acta. 2010 Mar;1801(3):400-4. doi: 10.1016/j.bbalip.2009.12.011. Epub 2010 Jan 4.
Sørensen TI, Virtue S, Vidal-Puig A.
Abstract – show
The risk functions for obesity (defined as the quantitative relation between degree of obesity throughout its range and the risk of health problems) have been used to define 'obesity' as an excess storage of fat in the body to such an extent that it causes health problems leading to increased mortality. The lipotoxicity theory implies that the fat stored in droplets of triglycerides in the cells are biologically inert and that the metabolic dysfunctions are primarily due to the increased exposure of the cells to fatty acids. If this is true, it has profound implications for the interpretations of the multiple epidemiological studies of the risk functions. It is obvious from all these studies that the sizes of the fat depots are risk indicators of health effects in various ways. Paradoxically, the sizes of the fat stores are also indicators of the preceding implementation of the ability of the body to protect itself against the toxic effects of the free fatty acids. The current risk of metabolic dysfunctions appears to be determined by the balance between the rate of loading of the body with fatty acids and the rate of eliminating the fatty acids by either triglyceride storage or oxidation. The progress in the development of the dysfunction then depends on the persistence of the imbalance leading to future cumulative exposure of the cells to the toxic effects of the fatty acids rather than on the current size of the fat depots. This may be considered as a reason for changing the definition of obesity to one based on better estimates of future risks of health problems derived from later metabolic dysfunctions rather than on the past coping with the exposure to the fatty acids by storage as triglycerides. Implementation of such definition would require a test that measures this residual capacity to avoid excess exposure of the cells to the fatty acids before the metabolic dysfunctions have emerged. In analogy with the glucose tolerance test, a fatty acid tolerance test may be needed to identify individuals who are at a level of risk for developing lipotoxicity induced metabolic dysfunctions such that they require intervention. This test would ideally be a single biomarker that would determine residual capacity for adipose expansion, fatty acid oxidation and safe ectopic lipid deposition.
Copyright (c) 2010 Elsevier B.V. All rights reserved.
PMID: 20045743 [PubMed – indexed for MEDLINE]
Special issue on lipotoxicity.
Biochim Biophys Acta. 2010 Mar;1801(3):207-8. doi: 10.1016/j.bbalip.2009.12.010. Epub 2010 Jan 4.
Vidal-Puig A, Unger RH.
PMID: 20045080 [PubMed – indexed for MEDLINE]
[Adipose tissue as a therapeutic target in obesity].
Endocrinol Nutr. 2009 Oct;56(8):404-11. doi: 10.1016/S1575-0922(09)72710-X.
Medina-Gómez G, Vidal-Puig A.
Abstract – show
Obesity is characterized by an increase of adipose tissue as a result of a positive imbalance between food intake and energy expenditure. Recent studies have indicated that adipocyte function is more complex than expected, since these cells have multiple functions and are integrated in a homeostatic network to optimize energy resources. As metabolic sensors in the body, adipocytes and the surrounding stromal vascular cells produce and secrete autocrine, paracrine and endocrine factors, able to regulate aspects involved in the development of adipocytes, as well as effects in peripheral organs important for metabolism. Regulation of these endocrine factors could lead to new therapeutic approaches targeted at aspects related to adipogenesis, preadipocyte proliferation and differentiation, inflammatory cytokine release and secretion, adipose tissue vascularization, and regulation of lipid metabolism or, alternatively, regulation of energy dissipation in mitochondria. In the study of the mechanisms of adipogenesis and remodulation of adipose tissue with respect to adipocyte size and function, an alternative and unorthodox strategy to improve obesity-associated metabolic complications could consist of increasing the storage capacity of adipose tissue to prevent a toxic response known as lipotoxicity.
PMID: 19959150 [PubMed – indexed for MEDLINE]
Consequences of long-term oral administration of the mitochondria-targeted antioxidant MitoQ to wild-type mice.
Free Radic Biol Med. 2010 Jan 1;48(1):161-72. doi: 10.1016/j.freeradbiomed.2009.10.039. Epub 2009 Oct 23.
Rodriguez-Cuenca S, Cochemé HM, Logan A, Abakumova I, Prime TA, Rose C, Vidal-Puig A, Smith AC, Rubinsztein DC, Fearnley IM, Jones BA, Pope S, Heales SJ, Lam BY, Neogi SG, McFarlane I, James AM, Smith RA, Murphy MP.
Abstract – show
The mitochondria-targeted quinone MitoQ protects mitochondria in animal studies of pathologies in vivo and is being developed as a therapy for humans. However, it is unclear whether the protective action of MitoQ is entirely due to its antioxidant properties, because long-term MitoQ administration may alter whole-body metabolism and gene expression. To address this point, we administered high levels of MitoQ orally to wild-type C57BL/6 mice for up to 28 weeks and investigated the effects on whole-body physiology, metabolism, and gene expression, finding no measurable deleterious effects. In addition, because antioxidants can act as pro-oxidants under certain conditions in vitro, we examined the effects of MitoQ administration on markers of oxidative damage. There were no changes in the expression of mitochondrial or antioxidant genes as assessed by DNA microarray analysis. There were also no increases in oxidative damage to mitochondrial protein, DNA, or cardiolipin, and the activities of mitochondrial enzymes were unchanged. Therefore, MitoQ does not act as a pro-oxidant in vivo. These findings indicate that mitochondria-targeted antioxidants can be safely administered long-term to wild-type mice.
Copyright 2009 Elsevier Inc. All rights reserved.
PMID: 19854266 [PubMed – indexed for MEDLINE]
Adaptation and failure of pancreatic beta cells in murine models with different degrees of metabolic syndrome.
Dis Model Mech. 2009 Nov-Dec;2(11-12):582-92. doi: 10.1242/dmm.003251. Epub 2009 Oct 19.
Medina-Gomez G, Yetukuri L, Velagapudi V, Campbell M, Blount M, Jimenez-Linan M, Ros M, Oresic M, Vidal-Puig A.
Abstract – show
The events that contribute to the expansion of beta-cell mass and enhanced beta-cell function in insulin-resistant states have not been elucidated fully. Recently, we showed that beta-cell adaptation failed dramatically in adult, insulin-resistant POKO mice, which contrasts with the appropriate expansion of beta cells in their ob/ob littermates. Thus, we hypothesised that characterisation of the islets in these mouse models at an early age should provide a unique opportunity to: (1) identify mechanisms involved in sensing insulin resistance at the level of the beta cells, (2) identify molecular effectors that contribute to increasing beta-cell mass and function, and (3) distinguish primary events from secondary events that are more likely to be present at more advanced stages of diabetes. Our results define the POKO mouse as a model of early lipotoxicity. At 4 weeks of age, it manifests with inappropriate beta-cell function and defects in proliferation markers. Other well-recognised pathogenic effectors that were observed previously in 16-week-old mice, such as increased reactive oxygen species (ROS), macrophage infiltration and endoplasmic reticulum (ER) stress, are also present in both young POKO and young ob/ob mice, indicating the lack of predictive power with regards to the severity of beta-cell failure. Of interest, the relatively preserved lipidomic profile in islets from young POKO mice contrasted with the large changes in lipid composition and the differences in the chain length of triacylglycerols in the serum, liver, muscle and adipose tissue in adult POKO mice. Later lipotoxic insults in adult beta cells contribute to the failure of the POKO beta cell. Our results indicate that the rapid development of insulin resistance and beta-cell failure in POKO mice makes this model a useful tool to study early molecular events leading to insulin resistance and beta-cell failure. Furthermore, comparisons with ob/ob mice might reveal important adaptive mechanisms in beta cells with either therapeutic or diagnostic potential.
PMID: 19841237 [PubMed – indexed for MEDLINE] PMCID: PMC2773727
PPARs and adipocyte function.
Mol Cell Endocrinol. 2010 Apr 29;318(1-2):61-8. doi: 10.1016/j.mce.2009.09.014. Epub 2009 Sep 20.
Christodoulides C, Vidal-Puig A.
Abstract – show
For long viewed as passive lipid storage depots, adipocytes are now recognised as key players in the pathogenesis of insulin resistance and metabolic disease. In parallel, the last two decades of research have seen the emergence of transcription factors of the peroxisome proliferator-activated receptor (PPAR) family as central regulators of lipid and glucose homeostasis and molecular targets for drugs to treat hyper-lipidaemia and type 2 diabetes mellitus. In this review we discuss the characteristics of PPARs and the role of the different isotypes in adipocyte biology.
(c) 2009 Elsevier Ireland Ltd. All rights reserved.
PMID: 19772894 [PubMed – indexed for MEDLINE]
Uncoupling protein-1 (UCP1) contributes to the basal proton conductance of brown adipose tissue mitochondria.
J Bioenerg Biomembr. 2009 Aug;41(4):335-42. doi: 10.1007/s10863-009-9232-8. Epub 2009 Aug 25.
Parker N, Crichton PG, Vidal-Puig AJ, Brand MD.
Abstract – show
Proton leak pathways uncouple substrate oxidation from ATP synthesis in mitochondria. These pathways are classified as basal (not regulated) or inducible (activated and inhibited). Previously it was found that over half of the basal proton conductance of muscle mitochondria was catalyzed by the adenine nucleotide translocase (ANT), an abundant mitochondrial anion carrier protein. To determine whether ANT is the unique protein catalyst, or one of many proteins that catalyze basal proton conductance, we measured proton leak kinetics in mitochondria isolated from brown adipose tissue (BAT). BAT can express another mitochondrial anion carrier, UCP1, at concentrations similar to ANT. Basal proton conductance was measured under conditions where UCP1 and ANT were catalytically inactive and was found to be lower in mitochondria from UCP1 knockout mice compared to wild-type. Ablation of another abundant inner membrane protein, nicotinamide nucleotide transhydrogenase, had no effect on proton leak kinetics in mitochondria from liver, kidney or muscle, showing that basal proton conductance is not catalyzed by all membrane proteins. We identify UCP1 as a second protein propagating basal proton leak, lending support to the hypothesis that basal leak pathways are perpetrated by members of the mitochondrial anion carrier family but not by other mitochondrial inner membrane proteins.
PMID: 19705265 [PubMed – indexed for MEDLINE]
Leptin-mediated changes in hepatic mitochondrial metabolism, structure, and protein levels.
Proc Natl Acad Sci U S A. 2009 Aug 4;106(31):13100-5. doi: 10.1073/pnas.0903723106. Epub 2009 Jul 21.
Singh A, Wirtz M, Parker N, Hogan M, Strahler J, Michailidis G, Schmidt S, Vidal-Puig A, Diano S, Andrews P, Brand MD, Friedman J.
Abstract – show
Leptin reduces body weight in ob/ob mice by decreasing food intake and increasing energy expenditure; however, the mechanisms by which it does the latter are not known. Here we report that 30% of the weight loss induced by leptin treatment of ob/ob mice is due to changes in energy expenditure. In assessing leptin's effects on specific tissues, we found that hepatic basal metabolic rate was paradoxically decreased 1.7-fold with leptin treatment, which was the result of a 1.6-fold reduction in mitochondrial volume density and altered substrate oxidation kinetics. The altered kinetics were associated with a decrease in protein levels of 2 mitochondrial respiratory chain components–cytochrome c oxidase subunit VIa and cytochrome c oxidase subunit IV. In addition to reduced hepatic metabolism, there was reduced long chain fatty acid production and a 2.5-fold increase in hepatic lipid export, both of which explain the reduced steatosis in leptin-treated animals. These data help clarify the role of the liver in leptin-mediated weight loss and define the mechanisms by which leptin alters hepatic metabolism and corrects steatosis.
PMID: 19622746 [PubMed – indexed for MEDLINE] PMCID: PMC2713753
Not all mitochondrial carrier proteins support permeability transition pore formation: no involvement of uncoupling protein 1.
Biosci Rep. 2009 Dec 15;30(3):187-92. doi: 10.1042/BSR20090063.
Crichton PG, Parker N, Vidal-Puig AJ, Brand MD.
Abstract – show
The mPTP (mitochondrial permeability transition pore) is a non-specific channel that is formed in the mitochondrial inner membrane in response to several stimuli, including elevated levels of matrix calcium. The pore is proposed to be composed of the ANT (adenine nucleotide translocase), voltage-dependent anion channel and cyclophilin D. Knockout studies, however, have demonstrated that ANT is not essential for permeability transition, which has led to the proposal that other members of the mitochondrial carrier protein family may be able to play a similar function to ANT in pore formation. To investigate this possibility, we have studied the permeability transition properties of BAT (brown adipose tissue) mitochondria in which levels of the mitochondrial carrier protein, UCP1 (uncoupling protein 1), can exceed those of ANT. Using an improved spectroscopic assay, we have quantified mPTP formation in de-energized mitochondria from wild-type and Ucp1KO (Ucp1-knockout) mice and assessed the dependence of pore formation on UCP1. When correctly normalized for differences in mitochondrial morphology, we find that calcium-induced mPTP activity is the same in both types of mitochondria, with similar sensitivity to GDP (approximately 50% inhibited), although the portion sensitive to cyclosporin A is higher in mitochondria lacking UCP1 (approximately 80% inhibited, compared with approximately 60% in mitochondria containing UCP1). We conclude that UCP1 is not a component of the cyclosporin A-sensitive mPTP in BAT and that playing a role in mPTP formation is not a general characteristic of the mitochondrial carrier protein family but is, more likely, restricted to specific members including ANT.
PMID: 19622065 [PubMed – indexed for MEDLINE] PMCID: PMC2805926
Metabolic phenotyping of a model of adipocyte differentiation.
Physiol Genomics. 2009 Oct 7;39(2):109-19. doi: 10.1152/physiolgenomics.90365.2008. Epub 2009 Jul 14.
Roberts LD, Virtue S, Vidal-Puig A, Nicholls AW, Griffin JL.
Abstract – show
The 3T3-L1 murine cell line is a robust and widely used model for the study of adipogenesis and processes occurring in mature adipocytes. The fibroblastic like cells can be induced by hormones to differentiate into mature adipocytes. In this study, the metabolic phenotype associated with differentiation of the 3T3-L1 cell line has been studied using gas chromatography-mass spectrometry, (1)H nuclear magnetic resonance spectroscopy, liquid chromatography-mass spectrometry, direct infusion-mass spectrometry, and 13C substrate labeling in conjunction with multivariate statistics. The changes in metabolite concentrations at distinct periods during differentiation have been defined including alterations in the TCA cycle, glycolysis, the production of odd chain fatty acids by alpha-oxidation, fatty acid synthesis, fatty acid desaturation, polyamine biosynthesis, and trans-esterification to produce complex lipids. The metabolic changes induced during differentiation of the 3T3-L1 cell line were then compared with the metabolic differences between pre- and postdifferentiation primary adipocytes. These metabolic alterations reflect the changing role of the 3T3-L1 cells during differentiation, as well as possibly providing metabolic triggers to stimulate the processes which occur during differentiation.
PMID: 19602617 [PubMed – indexed for MEDLINE] PMCID: PMC2765066
Dysregulation of glucose homeostasis in nicotinamide nucleotide transhydrogenase knockout mice is independent of uncoupling protein 2.
Biochim Biophys Acta. 2009 Dec;1787(12):1451-7. doi: 10.1016/j.bbabio.2009.06.005. Epub 2009 Jun 17.
Parker N, Vidal-Puig AJ, Azzu V, Brand MD.
Abstract – show
Glucose intolerance in C57Bl/6 mice has been associated with mutations in the nicotinamide nucleotide transhydrogenase (Nnt) gene. It has been proposed that the absence of NNT from mitochondria leads to increased mitochondrial reactive oxygen species production and subsequent activation of uncoupling protein 2 (UCP2). Activation of UCP2 has been suggested to uncouple electron transport from ATP synthesis in pancreatic beta cell mitochondria thereby decreasing glucose tolerance due to decreased insulin secretion through lower ATP/ADP ratios. The hypothesis tested in this paper is that UCP2 function is required for the dysregulation of glucose homeostasis observed in NNT ablated mice. Single and double Nnt and Ucp2 knockout mouse lines were used to measure glucose tolerance, whole animal energy balance and biochemical characteristics of mitochondrial uncoupling. As expected, glucose tolerance was diminished in mice lacking NNT. This was independent of UCP2 as it was observed either in the presence or absence of UCP2. The range of metabolic parameters examined in the mice and the proton conductance of isolated mitochondria remained unaltered in this double NNT and UCP2 knockout model. Ablation of UCP2 did not itself affect glucose tolerance and therefore previous observations of increased glucose tolerance of mice lacking UCP2 were not confirmed. We conclude that the decreased glucose tolerance in Nnt knockout mice observed in our experiments does not require UCP2.
PMID: 19539600 [PubMed – indexed for MEDLINE] PMCID: PMC2741566
PGC-1beta: a co-activator that sets the tone for both basal and stress-stimulated mitochondrial activity.
Adv Exp Med Biol. 2009;646:133-9. doi: 10.1007/978-1-4020-9173-5_15.
Lelliott CJ, Vidal-Puig A.
Abstract – show
The peroxisomal proliferator-activated receptor-gamma coactivator (PGC) family of transcriptional coactivators are central regulators of a wide-range of metabolic processes, which combine to control whole-body homeostasis. However, the specific function of each PGC in a tissue and pathway-specific context is only now being elucidated. In order to define the specific roles of PGC-1beta, we generated a mouse lacking this gene and studied its phenotype using a combination of physiological experiments, guided by a systems biology approach. We found that despite the predicted obese phenotype, PGC1betaKO were leaner than wild-type and had elevated energy expenditure in the resting state, probably due to upregulation of a wide-range of oxidative and fuel-handling genes in the brown adipose tissue (BAT), including PGC family member PGC-1alpha. Nonetheless, we identified that PGC-1beta ablation results in a global reduction in oxidative phosphorylation and electron transport chain genes and this translates into mitochondrial dysfunction in selected tissues. PGC1betaKO mice also demonstrate blunted responses to physiological stresses such as cold exposure in BAT, adrenergic stimulation in BAT and heart and acute dietary lipid loads in liver. In summary, while lack of PGC-1beta is not deleterious, it is essential for the normal expression of mitochondrial metabolic genes and for the optimal ability to handle physiological stresses.
PMID: 19536672 [PubMed – indexed for MEDLINE]
Defective peroxisomal proliferators activated receptor gamma activity due to dominant-negative mutation synergizes with hypertension to accelerate cardiac fibrosis in mice.
Eur J Heart Fail. 2009 Jun;11(6):533-41. doi: 10.1093/eurjhf/hfp048. Epub 2009 Apr 24.
Kis A, Murdoch C, Zhang M, Siva A, Rodriguez-Cuenca S, Carobbio S, Lukasik A, Blount M, O'Rahilly S, Gray SL, Shah AM, Vidal-Puig A.
Abstract – show
Humans with inactivating mutations in peroxisomal proliferators activated receptor gamma (PPARgamma) typically develop a complex metabolic syndrome characterized by insulin resistance, diabetes, lipodystrophy, hypertension, and dyslipidaemia which is likely to increase their cardiovascular risk. Despite evidence that the activation of PPARgamma may prevent cardiac fibrosis and hypertrophy, recent evidence has suggested that pharmacological activation of PPARgamma causes increased cardiovascular mortality. In this study, we investigated the effects of defective PPARgamma function on the development of cardiac fibrosis and hypertrophy in a murine model carrying a human dominant-negative mutation in PPARgamma.
Mice with a dominant-negative point mutation in PPARgamma (P465L) and their wild-type (WT) littermates were treated with either subcutaneous angiotensin II (AngII) infusion or saline for 2 weeks. Heterozygous P465L and WT mice developed a similar increase in systolic blood pressure, but the mutant mice developed significantly more severe cardiac fibrosis to AngII that correlated with increased expression of profibrotic genes. Both groups similarly increased the heart weight to body weight ratio compared with saline-treated controls. There were no differences in fibrosis between saline-treated WT and P465L mice.
These results show synergistic pathogenic effects between the presence of defective PPARgamma and AngII-induced hypertension and suggest that patients with PPARgamma mutation and hypertension may need more aggressive therapeutic measures to reduce the risk of accelerated cardiac fibrosis.
PMID: 19395708 [PubMed – indexed for MEDLINE] PMCID: PMC2686026
CXC ligand 5 is an adipose-tissue derived factor that links obesity to insulin resistance.
Cell Metab. 2009 Apr;9(4):339-49. doi: 10.1016/j.cmet.2009.03.002.
Chavey C, Lazennec G, Lagarrigue S, Clapé C, Iankova I, Teyssier J, Annicotte JS, Schmidt J, Mataki C, Yamamoto H, Sanches R, Guma A, Stich V, Vitkova M, Jardin-Watelet B, Renard E, Strieter R, Tuthill A, Hotamisligil GS, Vidal-Puig A, Zorzano A, Langin D, Fajas L.
Abstract – show
We show here high levels of expression and secretion of the chemokine CXC ligand 5 (CXCL5) in the macrophage fraction of white adipose tissue (WAT). Moreover, we find that CXCL5 is dramatically increased in serum of human obese compared to lean subjects. Conversely, CXCL5 concentration is decreased in obese subjects after a weight reduction program, or in obese non-insulin-resistant, compared to insulin-resistant, subjects. Most importantly we demonstrate that treatment with recombinant CXCL5 blocks insulin-stimulated glucose uptake in muscle in mice. CXCL5 blocks insulin signaling by activating the Jak2/STAT5/SOCS2 pathway. Finally, by treating obese, insulin-resistant mice with either anti-CXCL5 neutralizing antibodies or antagonists of CXCR2, which is the CXCL5 receptor, we demonstrate that CXCL5 mediates insulin resistance. Furthermore CXCR2-/- mice are protected against obesity-induced insulin resistance. Taken together, these results show that secretion of CXCL5 by WAT resident macrophages represents a link between obesity, inflammation, and insulin resistance.
PMID: 19356715 [PubMed – indexed for MEDLINE] PMCID: PMC2804846
Integrating post-genomic approaches as a strategy to advance our understanding of health and disease.
Genome Med. 2009 Mar 30;1(3):35. doi: 10.1186/gm35.
Tang J, Tan CY, Oresic M, Vidal-Puig A.
Abstract – show
Following the publication of the complete human genomic sequence, the post-genomic era is driven by the need to extract useful information from genomic data. Genomics, transcriptomics, proteomics, metabolomics, epidemiological data and microbial data provide different angles to our understanding of gene-environment interactions and the determinants of disease and health. Our goal and our challenge are to integrate these very different types of data and perspectives of disease into a global model suitable for dissecting the mechanisms of disease and for predicting novel therapeutic strategies. This review aims to highlight the need for and problems with complex data integration, and proposes a framework for data integration. While there are many obstacles to overcome, biological models based upon multiple datasets will probably become the basis that drives future biomedical research.
PMID: 19341506 [PubMed] PMCID: PMC2664946
Coordination of PGC-1beta and iron uptake in mitochondrial biogenesis and osteoclast activation.
Nat Med. 2009 Mar;15(3):259-66. doi: 10.1038/nm.1910. Epub 2009 Mar 1.
Ishii KA, Fumoto T, Iwai K, Takeshita S, Ito M, Shimohata N, Aburatani H, Taketani S, Lelliott CJ, Vidal-Puig A, Ikeda K.
Abstract – show
Osteoclasts are acid-secreting polykaryons that have high energy demands and contain abundant mitochondria. How mitochondrial biogenesis is integrated with osteoclast differentiation is unknown. We found that the transcription of Ppargc1b, which encodes peroxisome proliferator-activated receptor-gamma coactivator 1beta (PGC-1beta), was induced during osteoclast differentiation by cAMP response element-binding protein (CREB) as a result of reactive oxygen species. Knockdown of Ppargc1b in vitro inhibited osteoclast differentiation and mitochondria biogenesis, whereas deletion of the Ppargc1b gene in mice resulted in increased bone mass due to impaired osteoclast function. We also observed defects in PGC-1beta-deficient osteoblasts. Owing to the heightened iron demand in osteoclast development, transferrin receptor 1 (TfR1) expression was induced post-transcriptionally via iron regulatory protein 2. TfR1-mediated iron uptake promoted osteoclast differentiation and bone-resorbing activity, associated with the induction of mitochondrial respiration, production of reactive oxygen species and accelerated Ppargc1b transcription. Iron chelation inhibited osteoclastic bone resorption and protected against bone loss following estrogen deficiency resulting from ovariectomy. These data establish mitochondrial biogenesis orchestrated by PGC-1beta, coupled with iron uptake through TfR1 and iron supply to mitochondrial respiratory proteins, as a fundamental pathway linked to osteoclast activation and bone metabolism.
PMID: 19252502 [PubMed – indexed for MEDLINE]
Dact1, a nutritionally regulated preadipocyte gene, controls adipogenesis by coordinating the Wnt/beta-catenin signaling network.
Diabetes. 2009 Mar;58(3):609-19. doi: 10.2337/db08-1180. Epub 2008 Dec 10.
Lagathu C, Christodoulides C, Virtue S, Cawthorn WP, Franzin C, Kimber WA, Nora ED, Campbell M, Medina-Gomez G, Cheyette BN, Vidal-Puig AJ, Sethi JK.
Abstract – show
Wnt signaling inhibits adipogenesis, but its regulation, physiological relevance, and molecular effectors are poorly understood. Here, we identify the Wnt modulator Dapper1/Frodo1 (Dact1) as a new preadipocyte gene involved in the regulation of murine and human adipogenesis.
Changes in Dact1 expression were investigated in three in vitro models of adipogenesis. In vitro gain- and loss-of-function studies were used to investigate the mechanism of Dact1 action during adipogenesis. The in vivo regulation of Dact1 and Wnt/beta-catenin signaling were investigated in murine models of altered nutritional status, of pharmacological stimulation of in vivo adipogenesis, and during the development of dietary and genetic obesity.
Dact1 is a preadipocyte gene that decreases during adipogenesis. However, Dact1 knockdown impairs adipogenesis through activation of the Wnt/beta-catenin signaling pathway, and this is reversed by treatment with the secreted Wnt antagonist, secreted Frizzled-related protein 1 (Sfrp1). In contrast, constitutive Dact1 overexpression promotes adipogenesis and confers resistance to Wnt ligand-induced antiadipogenesis through increased expression of endogenous Sfrps and reduced expression of Wnts. In vivo, in white adipose tissue, Dact1 and Wnt/beta-catenin signaling also exhibit coordinated expression profiles in response to altered nutritional status, in response to pharmacological stimulation of in vivo adipogenesis, and during the development of dietary and genetic obesity.
Dact1 regulates adipogenesis through coordinated effects on gene expression that selectively alter intracellular and paracrine/autocrine components of the Wnt/beta-catenin signaling pathway. These novel insights into the molecular mechanisms controlling adipose tissue plasticity provide a functional network with therapeutic potential against diseases, such as obesity and associated metabolic disorders.
PMID: 19073771 [PubMed – indexed for MEDLINE] PMCID: PMC2646059
Adipogenesis and WNT signalling.
Trends Endocrinol Metab. 2009 Jan;20(1):16-24. doi: 10.1016/j.tem.2008.09.002. Epub 2008 Nov 13.
Christodoulides C, Lagathu C, Sethi JK, Vidal-Puig A.
Abstract – show
An inability of adipose tissue to expand consequent to exhausted capacity to recruit new adipocytes might underlie the association between obesity and insulin resistance. Adipocytes arise from mesenchymal precursors whose commitment and differentiation along the adipocytic lineage is tightly regulated. These regulatory factors mediate cross-talk between adipose cells, ensuring that adipocyte growth and differentiation are coupled to energy storage demands. The WNT family of autocrine and paracrine growth factors regulates adult tissue maintenance and remodelling and, consequently, is well suited to mediate adipose cell communication. Indeed, several recent reports, summarized in this review, implicate WNT signalling in regulating adipogenesis. Manipulating the WNT pathway to alter adipose cellular makeup, therefore, constitutes an attractive drug-development target to combat obesity-associated metabolic complications.
PMID: 19008118 [PubMed – indexed for MEDLINE]
Wnt signalling at the crossroads of nutritional regulation.
Biochem J. 2008 Dec 1;416(2):e11-3. doi: 10.1042/BJ20082074.
Sethi JK, Vidal-Puig AJ.
Abstract – show
The ability to sense and respond to nutritional cues is among the most fundamental processes that support life in living organisms. At the cellular level, a number of biochemical mechanisms have been proposed to mediate cellular glucose sensing. These include ATP-sensitive potassium channels, AMP-activated protein kinase, activation of PKC (protein kinase C), and flux through the hexosamine pathway. Less well known is how cellularly heterogenous organs couple nutrient availability to prioritization of cell autonomous functions and appropriate growth of the entire organ. Yet what is clear is that when such mechanisms fail or become inappropriately active they can lead to dire consequences such as diabetes, metabolic syndromes, cardiovascular diseases and cancer. In this issue of the Biochemical Journal, Anagnostou and Shepherd report the identification of an important link between cellular glucose sensing and the Wnt/beta-catenin signalling pathway in macrophages. Their data strongly indicate that the Wnt/beta-catenin pathway of Wnt signalling is responsive to physiological concentrations of nutrients but also suggests that that this system could be inappropriately activated in the diabetic (hyperglycaemic) or other metabolically compromised pathological states. This opens the exciting possibility that organ-selective modulation of Wnt signalling may become an attractive therapeutic target to treat these diseases.
PMID: 18990086 [PubMed – indexed for MEDLINE]
UCPs–unlikely calcium porters.
Nat Cell Biol. 2008 Nov;10(11):1235-7; author reply 1237-40. doi: 10.1038/ncb1108-1235.
Brookes PS, Parker N, Buckingham JA, Vidal-Puig A, Halestrap AP, Gunter TE, Nicholls DG, Bernardi P, Lemasters JJ, Brand MD.
PMID: 18978830 [PubMed – indexed for MEDLINE] PMCID: PMC2691551
AMPK: a metabolic gauge regulating whole-body energy homeostasis.
Trends Mol Med. 2008 Dec;14(12):539-49. doi: 10.1016/j.molmed.2008.09.007. Epub 2008 Nov 1.
Lage R, Diéguez C, Vidal-Puig A, López M.
Abstract – show
AMP-activated protein kinase (AMPK) is the downstream component of a kinase cascade that acts as a gauge of cellular energy levels. Over the last few years, accumulating evidence has demonstrated that AMPK is also involved in the regulation of energy balance at the whole-body level by responding to hormones and nutrient signals, which leads to changes in energy homeostasis. The physiological relevance of this new role of AMPK is demonstrated by the fact that impairment of AMPK function is associated with metabolic alterations, insulin resistance, obesity, hormonal disorders and cardiovascular disease. Here, we summarize the role of AMPK in the regulation of energy homeostasis. Understanding this key enzyme and its tissue-specific regulation will provide new targets for the treatment of metabolic disorders.
PMID: 18977694 [PubMed – indexed for MEDLINE]
Mitochondrial fusion is increased by the nuclear coactivator PGC-1beta.
PLoS One. 2008;3(10):e3613. doi: 10.1371/journal.pone.0003613. Epub 2008 Oct 31.
Liesa M, Borda-d'Agua B, Medina-Gómez G, Lelliott CJ, Paz JC, Rojo M, Palacín M, Vidal-Puig A, Zorzano A.
Abstract – show
There is no evidence to date on whether transcriptional regulators are able to shift the balance between mitochondrial fusion and fission events through selective control of gene expression.
Here, we demonstrate that reduced mitochondrial size observed in knock-out mice for the transcriptional regulator PGC-1beta is associated with a selective reduction in Mitofusin 2 (Mfn2) expression, a mitochondrial fusion protein. This decrease in Mfn2 is specific since expression of the remaining components of mitochondrial fusion and fission machinery were not affected. Furthermore, PGC-1beta increases mitochondrial fusion and elongates mitochondrial tubules. This PGC-1beta-induced elongation specifically requires Mfn2 as this process is absent in Mfn2-ablated cells. Finally, we show that PGC-1beta increases Mfn2 promoter activity and transcription by coactivating the nuclear receptor Estrogen Related Receptor alpha (ERRalpha).
Taken together, our data reveal a novel mechanism by which mammalian cells control mitochondrial fusion. In addition, we describe a novel role of PGC-1beta in mitochondrial physiology, namely the control of mitochondrial fusion mainly through Mfn2.
PMID: 18974884 [PubMed – indexed for MEDLINE] PMCID: PMC2570954
Lipidomics: a new window to biomedical frontiers.
Trends Biotechnol. 2008 Dec;26(12):647-52. doi: 10.1016/j.tibtech.2008.09.001. Epub 2008 Oct 23.
Oresic M, Hänninen VA, Vidal-Puig A.
Abstract – show
Lipids are a highly diverse class of molecules with crucial roles in cellular energy storage, structure and signaling. Lipid homeostasis is fundamental to maintain health, and lipid defects are central to the pathogenesis of important and devastating diseases. Newly emerging advances have facilitated the development of so-called lipidomics technologies and offer an opportunity to elucidate the mechanisms leading to disease. Furthermore, these advances also provide the tools to unravel the complexity of the 'allostatic forces' that allow maintenance of normal cellular/tissue phenotypes through the application of bioenergetically inefficient adaptive mechanisms. An alternative strategy is to focus on tissues with limited allostatic capacity, such as the eye, that could be used as readouts of metabolic stress over time. Identification of these allostatic mechanisms and pathological 'scares' might provide a window to unknown pathogenic mechanisms, as well as facilitate identification of early biomarkers of disease.
PMID: 18951641 [PubMed – indexed for MEDLINE]
Adipose tissue expandability and the metabolic syndrome.
Genes Nutr. 2007 Oct;2(1):41-5. doi: 10.1007/s12263-007-0014-9.
Slawik M, Vidal-Puig AJ.
PMID: 18850138 [PubMed] PMCID: PMC2474894
It's not how fat you are, it's what you do with it that counts.
PLoS Biol. 2008 Sep 23;6(9):e237. doi: 10.1371/journal.pbio.0060237.
Virtue S, Vidal-Puig A.
PMID: 18816166 [PubMed – indexed for MEDLINE] PMCID: PMC2553843
Adipose tissue expandability: the metabolic problems of obesity may arise from the inability to become more obese.
Biochem Soc Trans. 2008 Oct;36(Pt 5):935-40. doi: 10.1042/BST0360935.
Tan CY, Vidal-Puig A.
Abstract – show
The prevalence of obesity is increasing and with it the prevalence of associated metabolic complications. Precisely how obesity results in metabolic disturbances remains unclear. In the face of persistent positive caloric balance, it has been postulated that the capacity of adipose tissue to safely store fat may be vital. This paper explores some of the evidence suggesting that the risk of developing metabolic disturbances is not related to how much fat an individual has, but how well their fat can expand to accommodate the caloric excess. If this is true, the metabolic consequences of obesity may arise from the inability to become more obese.
PMID: 18793164 [PubMed – indexed for MEDLINE]
Brain lipogenesis and regulation of energy metabolism.
Curr Opin Clin Nutr Metab Care. 2008 Jul;11(4):483-90. doi: 10.1097/MCO.0b013e328302f3d8.
López M, Vidal-Puig A.
Abstract – show
To revise current available information related to the role of brain lipogenic pathways in the regulation of energy homeostasis.
The 'classical' hypothalamic neuropeptide view of feeding regulation has been extensively reviewed and revised during the past few years. Accumulating evidence indicates that the modulation of lipogenesis de novo in the hypothalamus, through selective pharmacologic and genetic manipulation of acetyl-CoA carboxylase, AMP-activated protein kinase, carnitine palmitoyltransferase 1, fatty acid synthase and malonyl-CoA decarboxylase enzymes, has a severe impact on food intake and body weight homeostasis. Furthermore, as these manipulations alter the hypothalamic pool of lipids, such as malonyl-CoA or long chain fatty acyl-CoA or both, the concept of lipids as signals of nutrient abundance able to modulate feeding in the hypothalamus has recently re-emerged.
In this review, we summarize what is known about brain lipogenesis and energy balance and propose further avenues of research. Defining these novel mechanisms could offer new targets for the treatment of obesity and metabolic syndrome.
PMID: 18542011 [PubMed – indexed for MEDLINE]
Central resistin regulates hypothalamic and peripheral lipid metabolism in a nutritional-dependent fashion.
Endocrinology. 2008 Sep;149(9):4534-43. doi: 10.1210/en.2007-1708. Epub 2008 May 22.
Vázquez MJ, González CR, Varela L, Lage R, Tovar S, Sangiao-Alvarellos S, Williams LM, Vidal-Puig A, Nogueiras R, López M, Diéguez C.
Abstract – show
Evidence suggests that the adipocyte-derived hormone resistin (RSTN) directly regulates both feeding and peripheral metabolism through, so far, undefined hypothalamic-mediated mechanisms. Here, we demonstrate that the anorectic effect of RSTN is associated with inappropriately decreased mRNA expression of orexigenic (agouti-related protein and neuropeptide Y) and increased mRNA expression of anorexigenic (cocaine and amphetamine-regulated transcript) neuropeptides in the arcuate nucleus of the hypothalamus. Of interest, RSTN also exerts a profound nutrition-dependent inhibitory effect on hypothalamic fatty acid metabolism, as indicated by increased phosphorylation levels of both AMP-activated protein kinase and its downstream target acetyl-coenzyme A carboxylase, associated with decreased expression of fatty acid synthase in the ventromedial nucleus of the hypothalamus. In addition, we also demonstrate that chronic central RSTN infusion results in decreased body weight and major changes in peripheral expression of lipogenic enzymes, in a tissue-specific and nutrition-dependent manner. Thus, in the fed state central RSTN is associated with induced expression of fatty acid synthesis enzymes and proinflammatory cytokines in liver, whereas its administration in the fasted state does so in white adipose tissue. Overall, our results indicate that RSTN controls feeding and peripheral lipid metabolism and suggest that hepatic RSTN-induced insulin resistance may be mediated by central activation of de novo lipogenesis in liver.
PMID: 18499762 [PubMed – indexed for MEDLINE]
Hypothalamic fatty acid metabolism mediates the orexigenic action of ghrelin.
Cell Metab. 2008 May;7(5):389-99. doi: 10.1016/j.cmet.2008.03.006.
López M, Lage R, Saha AK, Pérez-Tilve D, Vázquez MJ, Varela L, Sangiao-Alvarellos S, Tovar S, Raghay K, Rodríguez-Cuenca S, Deoliveira RM, Castañeda T, Datta R, Dong JZ, Culler M, Sleeman MW, Alvarez CV, Gallego R, Lelliott CJ, Carling D, Tschöp MH, Diéguez C, Vidal-Puig A.
Abstract – show
Current evidence suggests that hypothalamic fatty acid metabolism may play a role in regulating food intake; however, confirmation that it is a physiologically relevant regulatory system of feeding is still incomplete. Here, we use pharmacological and genetic approaches to demonstrate that the physiological orexigenic response to ghrelin involves specific inhibition of fatty acid biosynthesis induced by AMP-activated protein kinase (AMPK) resulting in decreased hypothalamic levels of malonyl-CoA and increased carnitine palmitoyltransferase 1 (CPT1) activity. In addition, we also demonstrate that fasting downregulates fatty acid synthase (FAS) in a region-specific manner and that this effect is mediated by an AMPK and ghrelin-dependent mechanisms. Thus, decreasing AMPK activity in the ventromedial nucleus of the hypothalamus (VMH) is sufficient to inhibit ghrelin's effects on FAS expression and feeding. Overall, our results indicate that modulation of hypothalamic fatty acid metabolism specifically in the VMH in response to ghrelin is a physiological mechanism that controls feeding.
PMID: 18460330 [PubMed – indexed for MEDLINE]
Serum levels of retinol-binding protein 4 and adiponectin in women with polycystic ovary syndrome: associations with visceral fat but no evidence for fat mass-independent effects on pathogenesis in this condition.
J Clin Endocrinol Metab. 2008 Jul;93(7):2859-65. doi: 10.1210/jc.2007-2759. Epub 2008 Apr 29.
Barber TM, Hazell M, Christodoulides C, Golding SJ, Alvey C, Burling K, Vidal-Puig A, Groome NP, Wass JA, Franks S, McCarthy MI.
Abstract – show
Insulin resistance, which associates with levels of retinol-binding protein 4 (RBP4) and adiponectin, is implicated in the development of polycystic ovary syndrome (PCOS).
The objective of the study was to explore the potential contribution of RBP4 and adiponectin in the etiology of PCOS and their relationships with specific fat depot measurements.
This was a cross-sectional study.
Serum RBP4 and adiponectin levels were compared between 50 PCOS cases and 28 female controls (including 22 body mass index/fat mass-matched pairs) and correlated with specific fat depot (including visceral) axial magnetic resonance imaging cross-sectional area measurements. All subjects were of U.K. British/Irish origin.
Serum levels of RBP4 (automated immunonephelometric assay) and adiponectin [immunoassay: total and high molecular weight (HMW)]. Data are reported as geometric mean (sd, range) and optionally adjusted for fat mass and age.
Between the 50 PCOS cases and 28 controls, serum RBP4 levels were indistinguishable [39.0 microg/ml (31.0, 49.0) vs. 41.6 microg/ml (32.7, 52.9), respectively, unadjusted P = 0.24; adjusted P = 0.55]. Total (and HMW) adiponectin levels were lower in PCOS cases [total adiponectin 19.9 microg/ml (14.2, 27.8) vs. 25.8 microg/ml (17.7, 37.7), respectively, unadjusted P = 2.4 x 10(-3); adjusted P = 0.10]. For the paired-sample analyzes, there were no differences in RBP4 (P = 0.09), total adiponectin (P = 0.06), HMW adiponectin (P =0.19), or HMW to total adiponectin ratio (P = 0.98). In PCOS cases, L4-visceral fat area was associated positively with RBP4 (r(2) = 0.34, P = 0.01) and negatively with HMW to total adiponectin ratio (r(2) = -0.44, P = 1.3 x 10(-3)). Controls showed similar relationships.
Although associated with visceral fat, serum RBP4 and adiponectin levels do not play important, fat-mass-independent primary roles in the development of PCOS.
PMID: 18445670 [PubMed – indexed for MEDLINE]
Current challenges in metabolomics for diabetes research: a vital functional genomic tool or just a ploy for gaining funding?
Physiol Genomics. 2008 Jun 12;34(1):1-5. doi: 10.1152/physiolgenomics.00009.2008. Epub 2008 Apr 15.
Griffin JL, Vidal-Puig A.
Abstract – show
Metabolomics aims to profile all the small molecule metabolites found within a cell, tissue, organ, or organism and use this information to understand a biological manipulation such as a drug intervention or a gene knockout. While neither mass spectrometry or NMR spectroscopy, the two most commonly used analytical tools in metabolomics, can provide a complete coverage of the metabolome, compared with other functional genomic tools for profiling biological moieties the approach is cheap and high throughput. In diabetes and obesity research this has provided the opportunity to assess large human populations or investigate a range of different tissues in animal studies both rapidly and cheaply. However, the approach has a number of major challenges, particularly with the interpretation of the data obtained. For example, some key pathways are better represented by high concentration metabolites inside the cell, and thus, the coverage of the metabolome may become biased towards these pathways (e.g., the TCA cycle, amino acid metabolism). There is also the challenge of statistically modeling datasets with large numbers of variables but relatively small sample sizes. This perspective discusses our own experience of some of the benefits and pitfalls with using metabolomics to understand diseases associated with type 2 diabetes.
PMID: 18413782 [PubMed – indexed for MEDLINE]
Stimulation of mitochondrial proton conductance by hydroxynonenal requires a high membrane potential.
Biosci Rep. 2008 Apr;28(2):83-8. doi: 10.1042/BSR20080002.
Parker N, Vidal-Puig A, Brand MD.
Abstract – show
Mild uncoupling of oxidative phosphorylation, caused by a leak of protons back into the matrix, limits mitochondrial production of ROS (reactive oxygen species). This proton leak can be induced by the lipid peroxidation products of ROS, such as HNE (4-hydroxynonenal). HNE activates uncoupling proteins (UCP1, UCP2 and UCP3) and ANT (adenine nucleotide translocase), thereby providing a negative feedback loop. The mechanism of activation and the conditions necessary to induce uncoupling by HNE are unclear. We have found that activation of proton leak by HNE in rat and mouse skeletal muscle mitochondria is dependent on incubation with respiratory substrate. In the presence of HNE, mitochondria energized with succinate became progressively more leaky to protons over time compared with mitochondria in the absence of either HNE or succinate. Energized mitochondria must attain a high membrane potential to allow HNE to activate uncoupling: a drop of 10-20 mV from the resting value is sufficient to blunt induction of proton leak by HNE. Uncoupling occurs through UCP3 (11%), ANT (64%) and other pathways (25%). Our findings have shown that exogenous HNE only activates uncoupling at high membrane potential. These results suggest that both endogenous HNE production and high membrane potential are required before mild uncoupling will be triggered to attenuate mitochondrial ROS production.
PMID: 18384278 [PubMed – indexed for MEDLINE] PMCID: PMC2518262
Bsx, a novel hypothalamic factor linking feeding with locomotor activity, is regulated by energy availability.
Endocrinology. 2008 Jun;149(6):3009-15. doi: 10.1210/en.2007-1684. Epub 2008 Feb 28.
Nogueiras R, López M, Lage R, Perez-Tilve D, Pfluger P, Mendieta-Zerón H, Sakkou M, Wiedmer P, Benoit SC, Datta R, Dong JZ, Culler M, Sleeman M, Vidal-Puig A, Horvath T, Treier M, Diéguez C, Tschöp MH.
Abstract – show
We recently reported that the hypothalamic homeobox domain transcription factor Bsx plays an essential role in the central nervous system control of spontaneous physical activity and the generation of hyperphagic responses. Moreover, we found Bsx to be a master regulator for the hypothalamic expression of key orexigenic neuropeptide Y and agouti gene-related protein. We now hypothesized that Bsx, which is expressed in the dorsomedial and arcuate nucleus (ARC) of the hypothalamus, is regulated by afferent signals in response to peripheral energy balance. Bsx expression was analyzed using in situ hybridization in fed vs. fasted (24 h) and ghrelin vs. leptin-treated rats, as well as in mice deficient for leptin or the ghrelin signaling. Ghrelin administration increased, whereas ghrelin receptor antagonist decreased ARC Bsx expression. Leptin injection attenuated the fasting-induced increase in ARC Bsx levels but had no effect in fed rats. Dorsomedial hypothalamic nucleus Bsx expression was unaffected by pharmacological modifications of leptin or ghrelin signaling. Obese leptin-deficient (ob/ob) mice, but not obese melanocortin 4 receptor-knockout mice, showed higher expression of Bsx, consistent with dependency from afferent leptin rather than increased adiposity per se. Interestingly, exposure to a high-fat diet triggered Bsx expression, consistent with the concept that decreased leptin signaling due to a high-fat diet induced leptin resistance. Our data indicate that ARC Bsx expression is specifically regulated by afferent energy balance signals, including input from leptin and ghrelin. Future studies will be necessary to test if Bsx may be involved in the pathogenesis of leptin resistance.
PMID: 18308842 [PubMed – indexed for MEDLINE] PMCID: PMC2408820
The metabolic profile of early Huntington's disease–a combined human and transgenic mouse study.
Exp Neurol. 2008 Apr;210(2):691-8. doi: 10.1016/j.expneurol.2007.12.026. Epub 2008 Jan 19.
Goodman AO, Murgatroyd PR, Medina-Gomez G, Wood NI, Finer N, Vidal-Puig AJ, Morton AJ, Barker RA.
Abstract – show
Huntington's disease (HD) is a debilitating autosomal dominant, neurodegenerative disease with a fatal prognosis. Classical symptoms include motor disturbances, subcortical dementia and psychiatric symptoms but are not restricted to this triad. Patients often experience other problems such as weight loss, although why and when this occurs in the disease course is not known. We studied metabolism using whole body indirect calorimetry in both early stage HD patients and in the R6/2 transgenic mouse model of HD, at times before and after they displayed signs of disease. Using this combined approach we found that patients with early HD tended to be in negative energy balance for reasons not related to their movement disorder, which was paralleled in the transgenic R6/2 mice. These mice had significantly elevated total energy expenditure as they developed overt disease with weight loss due primarily to a loss of muscle bulk. This study has shown for the first time that in HD there is the development of early negative energy balance, which in turn may cause weight loss with loss of muscle bulk in particular. The reason for this is not known but may reflect a catabolic state secondary to hypothalamic pathology, as abnormalities have been reported in the hypothalamus early in the disease course.
PMID: 18284928 [PubMed – indexed for MEDLINE]
Energization-dependent endogenous activation of proton conductance in skeletal muscle mitochondria.
Biochem J. 2008 May 15;412(1):131-9. doi: 10.1042/BJ20080006.
Parker N, Affourtit C, Vidal-Puig A, Brand MD.
Abstract – show
Leak of protons into the mitochondrial matrix during substrate oxidation partially uncouples electron transport from phosphorylation of ADP, but the functions and source of basal and inducible proton leak in vivo remain controversial. In the present study we describe an endogenous activation of proton conductance in mitochondria isolated from rat and mouse skeletal muscle following addition of respiratory substrate. This endogenous activation increased with time, required a high membrane potential and was diminished by high concentrations of serum albumin. Inhibition of this endogenous activation by GDP [classically considered specific for UCPs (uncoupling proteins)], carboxyatractylate and bongkrekate (considered specific for the adenine nucleotide translocase) was examined in skeletal muscle mitochondria from wild-type and Ucp3-knockout mice. Proton conductance through endogenously activated UCP3 was calculated as the difference in leak between mitochondria from wild-type and Ucp3-knockout mice, and was found to be inhibited by carboxyatractylate and bongkrekate, but not GDP. Proton conductance in mitochondria from Ucp3-knockout mice was strongly inhibited by carboxyatractylate, bongkrekate and partially by GDP. We conclude the following: (i) at high protonmotive force, an endogenously generated activator stimulates proton conductance catalysed partly by UCP3 and partly by the adenine nucleotide translocase; (ii) GDP is not a specific inhibitor of UCP3, but also inhibits proton translocation by the adenine nucleotide translocase; and (iii) the inhibition of UCP3 by carboxyatractylate and bongkrekate is likely to be indirect, acting through the adenine nucleotide translocase.
PMID: 18251717 [PubMed – indexed for MEDLINE] PMCID: PMC2474556
A prevalent variant in PPP1R3A impairs glycogen synthesis and reduces muscle glycogen content in humans and mice.
PLoS Med. 2008 Jan 29;5(1):e27. doi: 10.1371/journal.pmed.0050027.
Savage DB, Zhai L, Ravikumar B, Choi CS, Snaar JE, McGuire AC, Wou SE, Medina-Gomez G, Kim S, Bock CB, Segvich DM, Solanky B, Deelchand D, Vidal-Puig A, Wareham NJ, Shulman GI, Karpe F, Taylor R, Pederson BA, Roach PJ, O'Rahilly S, DePaoli-Roach AA.
Abstract – show
Stored glycogen is an important source of energy for skeletal muscle. Human genetic disorders primarily affecting skeletal muscle glycogen turnover are well-recognised, but rare. We previously reported that a frameshift/premature stop mutation in PPP1R3A, the gene encoding RGL, a key regulator of muscle glycogen metabolism, was present in 1.36% of participants from a population of white individuals in the UK. However, the functional implications of the mutation were not known. The objective of this study was to characterise the molecular and physiological consequences of this genetic variant.
In this study we found a similar prevalence of the variant in an independent UK white population of 744 participants (1.46%) and, using in vivo (13)C magnetic resonance spectroscopy studies, demonstrate that human carriers (n = 6) of the variant have low basal (65% lower, p = 0.002) and postprandial muscle glycogen levels. Mice engineered to express the equivalent mutation had similarly decreased muscle glycogen levels (40% lower in heterozygous knock-in mice, p < 0.05). In muscle tissue from these mice, failure of the truncated mutant to bind glycogen and colocalize with glycogen synthase (GS) decreased GS and increased glycogen phosphorylase activity states, which account for the decreased glycogen content.
Thus, PPP1R3A C1984DeltaAG (stop codon 668) is, to our knowledge, the first prevalent mutation described that directly impairs glycogen synthesis and decreases glycogen levels in human skeletal muscle. The fact that it is present in approximately 1 in 70 UK whites increases the potential biomedical relevance of these observations.
PMID: 18232732 [PubMed – indexed for MEDLINE] PMCID: PMC2214798
Informatics and computational strategies for the study of lipids.
Mol Biosyst. 2008 Feb;4(2):121-7. doi: 10.1039/b715468b. Epub 2007 Dec 18.
Yetukuri L, Ekroos K, Vidal-Puig A, Oresic M.
Abstract – show
Recent advances in mass spectrometry (MS)-based techniques for lipidomic analysis have empowered us with the tools that afford studies of lipidomes at the systems level. However, these techniques pose a number of challenges for lipidomic raw data processing, lipid informatics, and the interpretation of lipidomic data in the context of lipid function and structure. Integration of lipidomic data with other systemic levels, such as genomic or proteomic, in the context of molecular pathways and biophysical processes provides a basis for the understanding of lipid function at the systems level. The present report, based on the limited literature, is an update on a young but rapidly emerging field of lipid informatics and related pathway reconstruction strategies.
PMID: 18213405 [PubMed – indexed for MEDLINE]
Feeding and metabolism in mice lacking pituitary adenylate cyclase-activating polypeptide.
Endocrinology. 2008 Apr;149(4):1571-80. Epub 2007 Dec 27.
Adams BA, Gray SL, Isaac ER, Bianco AC, Vidal-Puig AJ, Sherwood NM.
Abstract – show
Disruption of the pituitary adenylate cyclase-activating polypeptide (PACAP) gene in mice has demonstrated a role for this highly conserved neuropeptide in the regulation of metabolism and temperature control. Localization of PACAP neurons within hypothalamic nuclei that regulate appetite suggest PACAP may affect feeding and thus energy balance. We used PACAP-null mice to address this question, examining both food intake and energy expenditure. PACAP-null mice were leaner than wild-type littermates due to decreased adiposity and displayed increased insulin sensitivity. The lean phenotype in the PACAP-null mice was completely eliminated if animals were fed a high-fat diet or housed near thermoneutrality (28 C). Further metabolic analyses of PACAP-null mice housed at 21 C indicated that the reduced body weight could not be explained by decreased food intake, increased metabolic rate, or increased locomotor activity. The thyroid hormone axis of PACAP-null mice was affected, because mRNA levels of hypothalamic TRH and brown adipose tissue type 2 deiodinase were reduced in PACAP-null mice housed at room temperature, and brain deiodinase activity was lower in PACAP-null mice after an acute cold challenge compared with wild-type controls. These results demonstrate that PACAP is not required for the regulation of food intake yet is necessary to maintain normal energy homeostasis, likely playing a role in central cold-sensing mechanisms.
PMID: 18162530 [PubMed – indexed for MEDLINE] PMCID: PMC2276722
Critical assessment of the current guidelines for the management and treatment of morbidly obese patients.
J Endocrinol Invest. 2007 Nov;30(10):844-52.
Burguera B, Agusti A, Arner P, Baltasar A, Barbe F, Barcelo A, Breton I, Cabanes T, Casanueva FF, Couce ME, Dieguez C, Fiol M, Fernandez Real JM, Formiguera X, Fruhbeck G, Garcia Romero M, Garcia Sanz M, Ghigo E, Gomis R, Higa K, Ibarra O, Lacy A, Larrad A, Masmiquel L, Moizé V, Moreno B, Moreiro J, Ricart W, Riesco M, Salinas R, Salvador J, Pi-Sunyer FX, Scopinaro N, Sjostrom L, Pagan A, Pereg V, Sánchez Pernaute A, Torres A, Urgeles JR, Vidal-Puig A, Vidal J, Vila M.
Abstract – show
An interdisciplinary panel of specialists met in Mallorca in the first European Symposium on Morbid Obesity entitled; "Morbid Obesity, an Interdisciplinary Approach". During the two and half days of the meeting, the participants discussed several aspects related to pathogenesis, evaluation, and treatment of morbid obesity. The expert panel included basic research scientists, dietitians and nutritionists, exercise physiologists, endocrinologists, psychiatrists, cardiologists, pneumonologists, anesthesiologists, and bariatric surgeons with expertise in the different weight loss surgeries. The symposium was sponsored by the Balearic Islands Health Department; however, this statement is an independent report of the panel and is not a policy statement of any of the sponsors or endorsers of the Symposium. The prevalence of morbid obesity, the most severe state of the disease, has become epidemic. The current recommendations for the therapy of the morbidly obese comes as a result of a National Institutes of Health (NIH) Consensus Conference held in 1991 and subsequently reviewed in 2004 by the American Society for Bariatric Surgery. This document reviews the work-up evaluation of the morbidly obese patient, the current status of the indications for bariatric surgery and which type of procedure should be recommended; it also brings up for discussion some important real-life clinical practice issues, which should be taken into consideration when evaluating and treating morbidly obese patients. Finally, it also goes through current scientific evidence supporting the potential effectiveness of medical therapy as treatment of patients with morbid obesity.
PMID: 18075287 [PubMed – indexed for MEDLINE]
Adipogenesis and lipotoxicity: role of peroxisome proliferator-activated receptor gamma (PPARgamma) and PPARgammacoactivator-1 (PGC1).
Public Health Nutr. 2007 Oct;10(10A):1132-7.
Medina-Gomez G, Gray S, Vidal-Puig A.
Abstract – show
Obesity is characterised by an increase in the adipose deposits, resulting from an imbalance between food intake and energy expenditure. When expansion of the adipose tissue reaches its maximum limit, as in obesity, fat accumulates in non-adipose tissues such as liver, heart, muscle and pancreas, developing a toxic response known as lipotoxicity, a condition that promotes the development of insulin resistance and other metabolic complications. Thus, the lipotoxic state may contribute to the increased risk of insulin resistance, diabetes, fatty liver and cardiovascular complications associated with obesity. We are interested in studying adipose tissue, specifically how mechanisms of adipogenesis and remodelling of adipose tissue, in terms of size and function of the adipocytes, could be considered a strategy to increase the capacity for lipid storage and prevent lipotoxicity. The peroxisome proliferator-activated receptors (PPARs) are a family of transcription factors that regulate energy balance by promoting either energy deposition or energy dissipation. Under normal physiological conditions, PPARgamma is mainly expressed in adipose tissue and regulates diverse functions such as the development of fat cells and their capacity to store lipids. The generation of PPARgamma knockout mice, either tissue specific or isoform specific, has provided new models to study PPARgamma's role in adipose tissue differentiation and function and have highlighted the essential role of PPARgamma in adipogenesis and lipogenesis.A second strategy to prevent lipotoxicity is to increase the capacity of tissues to oxidise fatty acids. PPARgammacoactivator-1alpha is a coactivator of PPARgamma that induces the expression of genes that promote the differentiation of preadipocytes to brown adipocytes. Recently, it has been implicated in increasing the oxidation of fatty acids via increasing mitochondrial capacity and function, making this co-factor a key candidate for the treatment of lipotoxicity.
PMID: 17903321 [PubMed – indexed for MEDLINE]
Regulation of insulin secretion, glucokinase gene transcription and beta cell proliferation by adipocyte-derived Wnt signalling molecules.
Diabetologia. 2008 Jan;51(1):147-54. Epub 2007 Nov 10.
Schinner S, Ulgen F, Papewalis C, Schott M, Woelk A, Vidal-Puig A, Scherbaum WA.
Abstract – show
Adipocytes secrete signalling molecules that elicit responses from target cells, including pancreatic beta cells. Wnt signalling molecules have recently been identified as novel adipocyte-derived factors. They also regulate insulin secretion in pancreatic beta cells and the cell cycle. The aim of this study was to investigate the effect of adipocyte-derived Wnt signalling molecules on insulin secretion and beta cell proliferation.
Human adipocytes were isolated to generate fat cell-conditioned medium (FCCM). Ins-1 cells were stimulated with FCCM and transiently transfected with reporter genes. Proliferation assays using [3H]thymidine incorporation were carried out in Ins-1 cells and primary islet cells. Insulin secretion from primary islets was assessed by radioimmunoassay. Gene expression in primary islets was assessed by Taqman PCR.
Treatment with human FCCM increased the transcription of a T cell-specific transcription factor reporter gene (TOPFLASH) in Ins-1 cells (241%, p < 0.05). FCCM induced the proliferation of Ins-1 cells (1.8 fold, p < 0.05) and primary mouse islet cells (1.6 fold, p < 0.05). Antagonizing Wnt signalling with secreted Frizzled-related protein 1 (FRP-1) inhibited the proliferative effect induced by Wnt3a and FCCM on Ins-1 cells by 49 and 41%, respectively. In addition, FCCM led to a twofold (p < 0.05) induction of cyclin D1 promoter activity in Ins-1 cells. Furthermore, FCCM stimulated insulin secretion (204% of controls, p > 0.05) in primary mouse islets, and this stimulation was inhibited by sFRP-1. At a molecular level, canonical Wnt signalling induced glucokinase gene transcription in a peroxisome proliferator-activated receptor gamma-dependent fashion, thereby defining the glucokinase gene as a novel Wnt target gene.
Taken together, these data show that adipocyte-derived Wnt signalling molecules induce beta cell proliferation and insulin secretion in vitro, suggesting a novel mechanism linking obesity to hyperinsulinaemia.
PMID: 17994217 [PubMed – indexed for MEDLINE]
A MUFA-rich diet improves posprandial glucose, lipid and GLP-1 responses in insulin-resistant subjects.
J Am Coll Nutr. 2007 Oct;26(5):434-44.
Paniagua JA, de la Sacristana AG, Sánchez E, Romero I, Vidal-Puig A, Berral FJ, Escribano A, Moyano MJ, Peréz-Martinez P, López-Miranda J, Pérez-Jiménez F.
Abstract – show
To study the effects of three weight-maintenance diets with different macronutrient composition on carbohydrate, lipid metabolism, insulin and incretin levels in insulin-resistant subjects.
A prospective study was performed in eleven (7 W, 4 M) offspring of obese and type 2 diabetes patients. Subjects had a BMI > 25 Kg/m2, waist circumference (men/women) > 102/88, HBA1c < 6.5% and were regarded as insulin-resistant after an OGTT (Matsuda ISIm <4). They were randomly divided into three groups and underwent three dietary periods each of 28 days in a crossover design: a) diet high in saturated fat (SAT), b) diet rich in monounsaturated fat (MUFA; Mediterranean diet) and c) diet rich in carbohydrate (CHO).
Body weight and resting energy expenditure did not changed during the three dietary periods. Fasting serum glucose concentrations fell during MUFA-rich and CHO-rich diets compared with high-SAT diets (5.02 +/- 0.1, 5.03 +/- 0.1, 5.50 +/- 0.2 mmol/L, respectively. Anova < 0.05). The MUFA-rich diet improved insulin sensitivity, as indicated by lower homeostasis model analysis-insulin resistance (HOMA-ir), compared with CHO-rich and high-SAT diets (2.32 +/- 0.3, 2.52 +/- 0.4, 2.72 +/- 0.4, respectively, Anova < 0.01). After a MUFA-rich and high-SAT breakfasts (443 kcal) the postprandial integrated area under curve (AUC) of glucose and insulin were lowered compared with isocaloric CHO-rich breakfast (7.8 +/- 1.3, 5.84 +/- 1.2, 11.9 +/- 2.7 mmol . 180 min/L, Anova < 0.05; and 1004 +/- 147, 1253 +/- 140, 2667 +/- 329 pmol . 180 min/L, Anova <0.01, respectively); while the integrated glucagon-like peptide-1 response increased with MUFA and SAT breakfasts compared with isocaloric CHO-rich meals (4.22 +/- 0.7, 4.34 +/- 1.1, 1.85 +/- 1.1, respectively, Anova < 0.05). Fasting and postprandial HDL cholesterol concentrations rose with MUFA-rich diets, and the AUCs of triacylglycerol fell with the CHO-rich diet. Similarly fasting proinsulin (PI) concentration fell, while stimulated ratio PI/I was not changed by MUFA-rich diet.
Weight maintenance with a MUFA-rich diet improves HOMA-ir and fasting proinsulin levels in insulin-resistant subjects. Ingestion of a virgin olive oil-based breakfast decreased postprandial glucose and insulin concentrations, and increased HDL-C and GLP-1 concentrations as compared with CHO-rich diet.
PMID: 17914131 [PubMed – indexed for MEDLINE]
Brain fatty acid synthase activates PPARalpha to maintain energy homeostasis.
J Clin Invest. 2007 Sep;117(9):2539-52.
Chakravarthy MV, Zhu Y, López M, Yin L, Wozniak DF, Coleman T, Hu Z, Wolfgang M, Vidal-Puig A, Lane MD, Semenkovich CF.
Abstract – show
Central nervous system control of energy balance affects susceptibility to obesity and diabetes, but how fatty acids, malonyl-CoA, and other metabolites act at this site to alter metabolism is poorly understood. Pharmacological inhibition of fatty acid synthase (FAS), rate limiting for de novo lipogenesis, decreases appetite independently of leptin but also promotes weight loss through activities unrelated to FAS inhibition. Here we report that the conditional genetic inactivation of FAS in pancreatic beta cells and hypothalamus produced lean, hypophagic mice with increased physical activity and impaired hypothalamic PPARalpha signaling. Administration of a PPARalpha agonist into the hypothalamus increased PPARalpha target genes and normalized food intake. Inactivation of beta cell FAS enzyme activity had no effect on islet function in culture or in vivo. These results suggest a critical role for brain FAS in the regulation of not only feeding, but also physical activity, effects that appear to be mediated through the provision of ligands generated by FAS to PPARalpha. Thus, 2 diametrically opposed proteins, FAS (induced by feeding) and PPARalpha (induced by starvation), unexpectedly form an integrative sensory module in the central nervous system to orchestrate energy balance.
PMID: 17694178 [PubMed – indexed for MEDLINE] PMCID: PMC1937501
Orexin expression is regulated by alpha-melanocyte-stimulating hormone.
J Neuroendocrinol. 2007 Sep;19(9):703-7.
López M, Lage R, Tung YC, Challis BG, Varela L, Virtue S, O'Rahilly S, Vidal-Puig A, Diéguez C, Coll AP.
Abstract – show
The hypothalamic melanocortin system plays a fundamental role in the regulation of energy homeostasis. Orexins (hypocretins) are also involved in a diverse range of physiological processes, including food intake. Previous evidence has suggested that hypothalamic orexin expression may be influenced by the central melanocortin system. Here, we studied orexin mRNA levels in pro-opiomelanocortin-deficient (Pomc(-/-)) mice, a mouse model lacking all endogenously produced melanocortin peptides. Orexin expression in the lateral hypothalamus was significantly increased in corticosterone deficient Pomc(-/-) mice. Furthermore, when circulating glucocorticoids were restored to levels within the physiological range, orexin expression remained elevated. However, i.c.v. administration of the melanocortin alpha-melanocyte-stimulating hormone (MSH) to Pomc(-/-) mice reduced orexin expression back down to wild-type levels. This was independent of the effects of alpha-MSH on food intake because elevated orexin expression persisted in Pomc(-/-) mice pairfed to alpha-MSH-treated animals. These data indicate that alpha-MSH may play a role in the regulation of orexin expression in Pomc(-/-), with an elevation in orexin levels contributing to the hyperphagia seen in these animals.
PMID: 17680885 [PubMed – indexed for MEDLINE] PMCID: PMC2637479
Adipose tissue expandability in the maintenance of metabolic homeostasis.
Nutr Rev. 2007 Jun;65(6 Pt 2):S7-12.
Gray SL, Vidal-Puig AJ.
Abstract – show
Adipose tissue expands to accommodate increased lipid through hypertrophy of existing adipocytes and by initiating differentiation of preadipocytes. The capacity of adipose tissue to expand is critical for accommodating changes in energy availability, but this capacity is not an unlimited process and likely varies between individuals. We suggest that it is not the absolute amount of adipose tissue but rather the capacity of adipose tissue to expand that affects metabolic homeostasis. Here we highlight examples of disease states and transgenic animal models with altered adipose tissue function that support this hypothesis and discuss possible mechanisms by which altered adipose tissue expandability impairs metabolic homeostasis.
PMID: 17605308 [PubMed – indexed for MEDLINE]
Targeting fat to prevent diabetes.
Cell Metab. 2007 May;5(5):323-5.
Sethi JK, Vidal-Puig AJ.
Abstract – show
An emerging view is that obesity causes metabolic problems when adipose tissue fails to meet the increased demands for fat storage. A study in this issue of Cell Metabolism (Waki et al., 2007) has identified harmine as a proadipogenic small molecule that promotes energy expenditure in white adipose tissue and delays the onset of obesity-associated diabetes.
PMID: 17488634 [PubMed – indexed for MEDLINE]
PPAR gamma 2 prevents lipotoxicity by controlling adipose tissue expandability and peripheral lipid metabolism.
PLoS Genet. 2007 Apr 27;3(4):e64.
Medina-Gomez G, Gray SL, Yetukuri L, Shimomura K, Virtue S, Campbell M, Curtis RK, Jimenez-Linan M, Blount M, Yeo GS, Lopez M, Seppänen-Laakso T, Ashcroft FM, Oresic M, Vidal-Puig A.
Abstract – show
Peroxisome proliferator activated receptor gamma 2 (PPARg2) is the nutritionally regulated isoform of PPARg. Ablation of PPARg2 in the ob/ob background, PPARg2(-/-) Lep(ob)/Lep(ob) (POKO mouse), resulted in decreased fat mass, severe insulin resistance, beta-cell failure, and dyslipidaemia. Our results indicate that the PPARg2 isoform plays an important role, mediating adipose tissue expansion in response to positive energy balance. Lipidomic analyses suggest that PPARg2 plays an important antilipotoxic role when induced ectopically in liver and muscle by facilitating deposition of fat as relatively harmless triacylglycerol species and thus preventing accumulation of reactive lipid species. Our data also indicate that PPARg2 may be required for the beta-cell hypertrophic adaptive response to insulin resistance. In summary, the PPARg2 isoform prevents lipotoxicity by (a) promoting adipose tissue expansion, (b) increasing the lipid-buffering capacity of peripheral organs, and (c) facilitating the adaptive proliferative response of beta-cells to insulin resistance.
PMID: 17465682 [PubMed – indexed for MEDLINE] PMCID: PMC1857730
Bioinformatics strategies for lipidomics analysis: characterization of obesity related hepatic steatosis.
BMC Syst Biol. 2007 Feb 15;1:12.
Yetukuri L, Katajamaa M, Medina-Gomez G, Seppänen-Laakso T, Vidal-Puig A, Oresic M.
Abstract – show
Lipids are an important and highly diverse class of molecules having structural, energy storage and signaling roles. Modern analytical technologies afford screening of many lipid molecular species in parallel. One of the biggest challenges of lipidomics is elucidation of important pathobiological phenomena from the integration of the large amounts of new data becoming available.
We present computational and informatics approaches to study lipid molecular profiles in the context of known metabolic pathways and established pathophysiological responses, utilizing information obtained from modern analytical technologies. In order to facilitate identification of lipids, we compute the scaffold of theoretically possible lipids based on known lipid building blocks such as polar head groups and fatty acids. Each compound entry is linked to the available information on lipid pathways and contains the information that can be utilized for its automated identification from high-throughput UPLC/MS-based lipidomics experiments. The utility of our approach is demonstrated by its application to the lipidomic characterization of the fatty liver of the genetically obese insulin resistant ob/ob mouse model. We investigate the changes of correlation structure of the lipidome using multivariate analysis, as well as reconstruct the pathways for specific molecular species of interest using available lipidomic and gene expression data.
The methodology presented herein facilitates identification and interpretation of high-throughput lipidomics data. In the context of the ob/ob mouse liver profiling, we have identified the parallel associations between the elevated triacylglycerol levels and the ceramides, as well as the putative activated ceramide-synthesis pathways.
PMID: 17408502 [PubMed – indexed for MEDLINE] PMCID: PMC1839890
Monounsaturated fat-rich diet prevents central body fat distribution and decreases postprandial adiponectin expression induced by a carbohydrate-rich diet in insulin-resistant subjects.
Diabetes Care. 2007 Jul;30(7):1717-23. Epub 2007 Mar 23.
Paniagua JA, Gallego de la Sacristana A, Romero I, Vidal-Puig A, Latre JM, Sanchez E, Perez-Martinez P, Lopez-Miranda J, Perez-Jimenez F.
Abstract – show
Central obesity is associated with insulin resistance through factors that are not fully understood. We studied the effects of three different isocaloric diets on body fat distribution, insulin sensitivity, and peripheral adiponectin gene expression.
Eleven volunteers, offspring of obese type 2 diabetic patients with abdominal fat deposition, were studied. These subjects were considered insulin resistant as indicated by Matsuda index values <4 after an oral glucose tolerance test, and they maintained A1C <6.5% without therapeutic intervention. All subjects underwent three dietary periods of 28 days each in a crossover design: 1) diet enriched in saturated fat (SAT), 2) diet rich in monounsaturated fat (MUFA) (Mediterranean diet), and 3) diet rich in carbohydrates (CHOs).
Weight, body composition, and resting energy expenditure remained unchanged during the three sequential dietary periods. Using dual-energy X-ray absorptiometry we observed that when patients were fed a CHO-enriched diet, their fat mass was redistributed toward the abdominal depot, whereas periphery fat accumulation decreased compared with isocaloric MUFA-rich and high-SAT diets (ANOVA P < 0.05). Changes in fat deposition were associated with decreased postprandial mRNA adiponectin levels in peripheral adipose tissue and lower insulin sensitivity index values from a frequently sampled insulin-assisted intravenous glucose tolerance test in patients fed a CHO-rich diet compared with a MUFA-rich diet (ANOVA P < 0.05).
An isocaloric MUFA-rich diet prevents central fat redistribution and the postprandial decrease in peripheral adiponectin gene expression and insulin resistance induced by a CHO-rich diet in insulin-resistant subjects.
PMID: 17384344 [PubMed – indexed for MEDLINE]
Thematic review series: adipocyte biology. Adipose tissue function and plasticity orchestrate nutritional adaptation.
J Lipid Res. 2007 Jun;48(6):1253-62. Epub 2007 Mar 20.
Sethi JK, Vidal-Puig AJ.
Abstract – show
This review focuses on adipose tissue biology and introduces the concept of adipose tissue plasticity and expandability as key determinants of obesity-associated metabolic dysregulation. This concept is fundamental to our understanding of adipose tissue as a dynamic organ at the center of nutritional adaptation. Here, we summarize the current knowledge of the mechanisms by which adipose tissue can affect peripheral energy homeostasis, particularly in the context of overnutrition. Two mechanisms emerge that provide a molecular understanding for obesity-associated insulin resistance. These are a) the dysregulation of adipose tissue expandability and b) the abnormal production of adipokines. This knowledge has the potential to pave the way for novel therapeutic concepts and strategies for managing and/or correcting complications associated with obesity and the metabolic syndrome.
PMID: 17374880 [PubMed – indexed for MEDLINE]
Hypothalamic fatty acid metabolism: a housekeeping pathway that regulates food intake.
Bioessays. 2007 Mar;29(3):248-61.
López M, Lelliott CJ, Vidal-Puig A.
Abstract – show
The hypothalamus is a specialized area in the brain that integrates the control of energy homeostasis. More than 70 years ago, it was proposed that the central nervous system sensed circulating levels of metabolites such as glucose, lipids and amino acids and modified feeding according to the levels of those molecules. This led to the formulation of the Glucostatic, Lipostatic and Aminostatic Hypotheses. It has taken almost that much time to demonstrate that circulating long-chain fatty acids act as signals of nutrient surplus in the hypothalamus. Moreover, pharmacological and/or genetic inhibition of fatty acid synthase, AMP-activated protein kinase and carnitine palmitoyltransferase 1 results in profound decrease in feeding and body weight in rodents. The molecular mechanism behind these actions depends on changes in the cellular pool of malonyl-CoA and fatty acyl-CoAs. Current evidence also suggests that this pathway may play a major role in the physiological regulation of feeding, by integrating hormonal and nutrient-derived signals in the hypothalamus. Here, we summarize what is known about hypothalamic fatty acid metabolism and feeding control and provide future directions for research. Understanding these molecular mechanisms could provide new targets for the treatment of obesity and related disorders.
PMID: 17295284 [PubMed – indexed for MEDLINE]
IGF-binding protein-2 protects against the development of obesity and insulin resistance.
Diabetes. 2007 Feb;56(2):285-94.
Wheatcroft SB, Kearney MT, Shah AM, Ezzat VA, Miell JR, Modo M, Williams SC, Cawthorn WP, Medina-Gomez G, Vidal-Puig A, Sethi JK, Crossey PA.
Abstract – show
Proliferation of adipocyte precursors and their differentiation into mature adipocytes contributes to the development of obesity in mammals. IGF-I is a potent mitogen and important stimulus for adipocyte differentiation. The biological actions of IGFs are closely regulated by a family of IGF-binding proteins (IGFBPs), which exert predominantly inhibitory effects. IGFBP-2 is the principal binding protein secreted by differentiating white preadipocytes, suggesting a potential role in the development of obesity. We have generated transgenic mice overexpressing human IGFBP-2 under the control of its native promoter, and we show that overexpression of IGFBP-2 is associated with reduced susceptibility to obesity and improved insulin sensitivity. Whereas wild-type littermates developed glucose intolerance and increased blood pressure with aging, mice overexpressing IGFBP-2 were protected. Furthermore, when fed a high-fat/high-energy diet, IGFBP-2-overexpressing mice were resistant to the development of obesity and insulin resistance. This lean phenotype was associated with decreased leptin levels, increased glucose sensitivity, and lower blood pressure compared with wild-type animals consuming similar amounts of high-fat diet. Our in vitro data suggest a direct effect of IGFBP-2 preventing adipogenesis as indicated by the ability of recombinant IGFBP-2 to impair 3T3-L1 differentiation. These findings suggest an important, novel role for IGFBP-2 in obesity prevention.
PMID: 17259371 [PubMed – indexed for MEDLINE]
Ablation of PGC-1beta results in defective mitochondrial activity, thermogenesis, hepatic function, and cardiac performance.
PLoS Biol. 2006 Nov;4(11):e369.
Lelliott CJ, Medina-Gomez G, Petrovic N, Kis A, Feldmann HM, Bjursell M, Parker N, Curtis K, Campbell M, Hu P, Zhang D, Litwin SE, Zaha VG, Fountain KT, Boudina S, Jimenez-Linan M, Blount M, Lopez M, Meirhaeghe A, Bohlooly-Y M, Storlien L, Strömstedt M, Snaith M, Oresic M, Abel ED, Cannon B, Vidal-Puig A.
Abstract – show
The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator-1beta (PGC-1beta) has been implicated in important metabolic processes. A mouse lacking PGC-1beta (PGC1betaKO) was generated and phenotyped using physiological, molecular, and bioinformatic approaches. PGC1betaKO mice are generally viable and metabolically healthy. Using systems biology, we identified a general defect in the expression of genes involved in mitochondrial function and, specifically, the electron transport chain. This defect correlated with reduced mitochondrial volume fraction in soleus muscle and heart, but not brown adipose tissue (BAT). Under ambient temperature conditions, PGC-1beta ablation was partially compensated by up-regulation of PGC-1alpha in BAT and white adipose tissue (WAT) that lead to increased thermogenesis, reduced body weight, and reduced fat mass. Despite their decreased fat mass, PGC1betaKO mice had hypertrophic adipocytes in WAT. The thermogenic role of PGC-1beta was identified in thermoneutral and cold-adapted conditions by inadequate responses to norepinephrine injection. Furthermore, PGC1betaKO hearts showed a blunted chronotropic response to dobutamine stimulation, and isolated soleus muscle fibres from PGC1betaKO mice have impaired mitochondrial function. Lack of PGC-1beta also impaired hepatic lipid metabolism in response to acute high fat dietary loads, resulting in hepatic steatosis and reduced lipoprotein-associated triglyceride and cholesterol content. Altogether, our data suggest that PGC-1beta plays a general role in controlling basal mitochondrial function and also participates in tissue-specific adaptive responses during metabolic stress.
PMID: 17090215 [PubMed – indexed for MEDLINE] PMCID: PMC1634886
Leptin deficiency unmasks the deleterious effects of impaired peroxisome proliferator-activated receptor gamma function (P465L PPARgamma) in mice.
Diabetes. 2006 Oct;55(10):2669-77.
Gray SL, Nora ED, Grosse J, Manieri M, Stoeger T, Medina-Gomez G, Burling K, Wattler S, Russ A, Yeo GS, Chatterjee VK, O'Rahilly S, Voshol PJ, Cinti S, Vidal-Puig A.
Abstract – show
Peroxisome proliferator-activated receptor (PPAR)gamma is a key transcription factor facilitating fat deposition in adipose tissue through its proadipogenic and lipogenic actions. Human patients with dominant-negative mutations in PPARgamma display lipodystrophy and extreme insulin resistance. For this reason it was completely unexpected that mice harboring an equivalent mutation (P465L) in PPARgamma developed normal amounts of adipose tissue and were insulin sensitive. This finding raised important doubts about the interspecies translatability of PPARgamma-related findings, bringing into question the relevance of other PPARgamma murine models. Here, we demonstrate that when expressed on a hyperphagic ob/ob background, the P465L PPARgamma mutant grossly exacerbates the insulin resistance and metabolic disturbances associated with leptin deficiency, yet reduces whole-body adiposity and adipocyte size. In mouse, coexistence of the P465L PPARgamma mutation and the leptin-deficient state creates a mismatch between insufficient adipose tissue expandability and excessive energy availability, unmasking the deleterious effects of PPARgamma mutations on carbohydrate metabolism and replicating the characteristic clinical symptoms observed in human patients with dominant-negative PPARgamma mutations. Thus, adipose tissue expandability is identified as an important factor for the development of insulin resistance in the context of positive energy balance.
PMID: 17003330 [PubMed – indexed for MEDLINE]
Decreased brown adipocyte recruitment and thermogenic capacity in mice with impaired peroxisome proliferator-activated receptor (P465L PPARgamma) function.
Endocrinology. 2006 Dec;147(12):5708-14. Epub 2006 Sep 15.
Gray SL, Dalla Nora E, Backlund EC, Manieri M, Virtue S, Noland RC, O'Rahilly S, Cortright RN, Cinti S, Cannon B, Vidal-Puig A.
Abstract – show
Mice with a dominant-negative peroxisome proliferator-activated receptor gamma (PPARgamma) mutation (P465L) unexpectedly had normal amounts of adipose tissue. Here, we investigate the adipose tissue of the PPARgamma P465L mouse in detail. Microscopic analysis of interscapular adipose tissue of P465L PPARgamma mice revealed brown adipocytes with larger unilocular lipid droplets, indicative of reduced thermogenic capacity. Under conditions of cold exposure, the brown adipose tissue of the PPARgamma P465L mice was less active, a fact reflected in decreased uncoupling protein 1 levels. Analysis of the white adipocytes confirmed their normal cytoarchitecture and development, yet classical white adipose depots of the P465L PPARgamma mice had a striking reduction in brown adipocyte recruitment, a finding supported by reduced expression of UCP1 in the perigonadal adipose depot. Taken together, these data suggest that whole animal impairment of PPARgamma alters the cellular composition of the adipose organ to a more "white" adipose phenotype. Physiologically, this impairment in brown adipocyte recruitment is associated with decreased nonshivering thermogenic capacity after cold acclimation as revealed by norepinephrine responsiveness. Our results indicate that maintenance of oxidative brown-like adipose tissue is more dependent on PPARgamma function for development than white adipose tissue, an observation that may be relevant when considering PPARgamma-dependent strategies for the treatment of obesity.
PMID: 16980437 [PubMed – indexed for MEDLINE]
Metabolomic approaches to phenotype characterization and applications to complex diseases.
Expert Rev Mol Diagn. 2006 Jul;6(4):575-85.
Oresic M, Vidal-Puig A, Hänninen V.
Abstract – show
Metabolites are the key regulators of systems homeostasis. As such, concentration changes of specific groups of metabolites may reflect systemic responses to environmental, therapeutic or genetic interventions. Thus, the study of metabolites is a powerful tool for the characterization of complex phenotypes as well as for the development of biomarkers for specific physiological responses. Therefore, metabolomics is a valuable platform for studies of complex diseases and the development of new therapies, both in nonclinical disease model characterization and clinical settings.
PMID: 16824031 [PubMed – indexed for MEDLINE]
The Wnt antagonist Dickkopf-1 and its receptors are coordinately regulated during early human adipogenesis.
J Cell Sci. 2006 Jun 15;119(Pt 12):2613-20.
Christodoulides C, Laudes M, Cawthorn WP, Schinner S, Soos M, O'Rahilly S, Sethi JK, Vidal-Puig A.
Abstract – show
Secretion of Wnts by adipose cells has an important role in the control of murine adipogenesis. We present the first evidence that a Wnt antagonist, Dickkopf 1 (Dkk1), is secreted by human preadipocytes and promotes adipogenesis. DKK1 mRNA increases six hours after onset of human adipogenesis and this is followed by an increase in Dkk1 protein. With further differentiation, the mRNA and protein levels progressively decline such that they are undetectable in mature adipocytes. The transient induction in DKK1 correlates with downregulation of cytoplasmic and nuclear beta-catenin levels, this being a surrogate marker of canonical Wnt signalling, and Wnt/beta-catenin transcriptional activity. In addition, constitutive expression of Dkk1 in 3T3-L1 preadipocytes promotes their differentiation, further supporting the functional significance of increased Dkk1 levels during human adipogenesis. Concomitant downregulation of the Dkk1 receptors LRP5 and LRP6 is likely to potentiate the ability of Dkk1 to inhibit Wnt signalling and promote differentiation. Notably, Dkk1 is not expressed in primary murine preadipocytes or cell lines. The involvement of Dkk1 in human but not murine adipogenesis indicates that inter-species differences exist in the molecular control of this process. Given the public health importance of disorders of adipose mass, further knowledge of the pathways involved specifically in human adipocyte differentiation might ultimately be of clinical relevance.
PMID: 16763196 [PubMed – indexed for MEDLINE]
[Obesity, MODY and juvenile diabetes: a new diagnostic challenge].
Med Clin (Barc). 2006 May 6;126(17):656-7.
Vidal-Puig A.
PMID: 16759566 [PubMed – indexed for MEDLINE]
Tamoxifen-induced anorexia is associated with fatty acid synthase inhibition in the ventromedial nucleus of the hypothalamus and accumulation of malonyl-CoA.
Diabetes. 2006 May;55(5):1327-36.
López M, Lelliott CJ, Tovar S, Kimber W, Gallego R, Virtue S, Blount M, Vázquez MJ, Finer N, Powles TJ, O'Rahilly S, Saha AK, Diéguez C, Vidal-Puig AJ.
Abstract – show
Fatty acid metabolism in the hypothalamus has recently been shown to regulate feeding. The selective estrogen receptor modulator tamoxifen (TMX) exerts a potent anorectic effect. Here, we show that the anorectic effect of TMX is associated with the accumulation of malonyl-CoA in the hypothalamus and inhibition of fatty acid synthase (FAS) expression specifically in the ventromedial nucleus of the hypothalamus (VMN). Furthermore, we demonstrate that FAS mRNA expression is physiologically regulated by fasting and refeeding in the VMN but not in other hypothalamic nuclei. Thus, the VMN appears to be the hypothalamic site where regulation of FAS and feeding converge. Supporting the potential clinical relevance of these observations, reanalysis of a primary breast cancer prevention study showed that obese women treated with TMX gained significantly less body weight over a 6-year period than obese women given placebo. The finding that TMX can modulate appetite through alterations in FAS expression and malonyl-CoA levels suggests a link between hypothalamic sex steroid receptors, fatty acid metabolism, and feeding behavior.
PMID: 16644689 [PubMed – indexed for MEDLINE]
Lipotoxicity, overnutrition and energy metabolism in aging.
Ageing Res Rev. 2006 May;5(2):144-64. Epub 2006 Apr 21.
Slawik M, Vidal-Puig AJ.
Abstract – show
The safest place to store lipids is the white adipose tissue, but its storage capacity may become saturated resulting in excess of fat "overspilled" to non-adipose tissues. This overspill of fat occurs in apparently opposite pathological states such as lipodistrophy or obesity. When the excess of energy is redirected towards peripheral organs, their initial response is to facilitate the storage of the surplus in the form of triacylglycerol, but the limited triacylglycerol buffer capacity becomes saturated soon. Under these conditions excess of lipids enter alternative non-oxidative pathways that result in production of toxic reactive lipid species that induce organ-specific toxic responses leading to apoptosis. Reactive lipids can accumulate in non-adipose tissues of metabolically relevant organs such as pancreatic beta-cells, liver, heart and skeletal muscle leading to lipotoxicity, a process that contributes substantially to the pathophysiology of insulin resistance, type 2 diabetes, steatotic liver disease and heart failure. The effects of this lipotoxic insult can be minimised by several strategies: (a) decreased incorporation of energy, (b) a less orthodox approach such as increased adipose tissue expandability and/or (c) increased oxidation of fat in peripheral organs. Aging should be considered as physiological degenerative process potentially accelerated by concomitant lipotoxic insults. Conversely, the process of aging can sensitise cells to effects of lipid toxicity.
PMID: 16630750 [PubMed – indexed for MEDLINE]
An update on visfatin/pre-B cell colony-enhancing factor, an ubiquitously expressed, illusive cytokine that is regulated in obesity.
Curr Opin Lipidol. 2006 Apr;17(2):128-31.
Stephens JM, Vidal-Puig AJ.
Abstract – show
The aim of this article is to summarize all of the recent studies on pre-B cell colony-enhancing factor visfatin, a ubiquitously expressed secreted protein that has been implicated in obesity and insulin resistance. Although pre-B-cell colony-enhancing factor was discovered over 10 years ago, there are many remaining questions about the regulation and function of this protein.
Studies in the last decade have revealed the endocrine properties of fat cells. One of the most recent proteins shown to be highly expressed in adipose tissue is visfatin, originally identified as pre-B-cell colony-enhancing factor. Visfatin/pre-B-cell colony-enhancing factor appears to be preferentially produced by the visceral adipose tissue and has insulin mimetic actions. Studies by many groups indicate that obesity-related diabetes and accompanying metabolic disorders in humans have been specifically linked to increased visceral adipose tissue mass. The different roles of various adipocyte depots, however, are still poorly understood. It has been hypothesized that understanding the differences in the biology of visceral and subcutaneous human adipose tissue may hold the key to therapeutic strategies aimed at reducing obesity-induced insulin resistance and alleviating symptoms of the metabolic syndrome. Interestingly, some observed actions of visfatin indicate that this secreted protein may be an interesting therapeutic target. Several recent studies, however, indicate that our understanding of visfatin is still speculative.
This review summarizes all of the papers in the last year on the expression and function of visfatin/pre-B-cell colony-enhancing factor and highlights inconsistent observations from various investigators studying this protein. It also highlights previous observations on the role of pre-B-cell colony-enhancing factor. We suggest that the pathophysiologic role of visfatin/pre-B-cell colony-enhancing factor in humans remains largely unknown.
PMID: 16531748 [PubMed – indexed for MEDLINE]
Anaplerotic roles of pyruvate carboxylase in mammalian tissues.
Cell Mol Life Sci. 2006 Apr;63(7-8):843-54.
Jitrapakdee S, Vidal-Puig A, Wallace JC.
Abstract – show
Pyruvate carboxylase (PC) catalyzes the ATP-dependent carboxylation of pyruvate to oxaloacetate. PC serves an anaplerotic role for the tricarboxylic acid cycle, when intermediates are removed for different biosynthetic purposes. In liver and kidney, PC provides oxaloacetate for gluconeogenesis. In adipocytes PC is involved in de novo fatty acid synthesis and glyceroneogenesis, and is regulated by the peroxisome proliferator-activated receptor-gamma, suggesting that PC is involved in the metabolic switch controlling fuel partitioning toward lipogenesis. In islets, PC is necessary for glucose-induced insulin secretion by providing oxaloacetate to form malate that participates in the 'pyruvate/malate cycle' to shuttle 3C or 4C between mitochondria and cytoplasm. Hyperglycemia and hyperlipidemia impair this cycle and affect glucose-stimulated insulin release. In astrocytes, PC is important for de novo synthesis of glutamate, an important excitatory neurotransmitter supplied to neurons. Transcriptional studies of the PC gene pinpoint some transcription factors that determine tissue-specific expression.
PMID: 16505973 [PubMed – indexed for MEDLINE]
WNT10B mutations in human obesity.
Diabetologia. 2006 Apr;49(4):678-84. Epub 2006 Feb 14.
Christodoulides C, Scarda A, Granzotto M, Milan G, Dalla Nora E, Keogh J, De Pergola G, Stirling H, Pannacciulli N, Sethi JK, Federspil G, Vidal-Puig A, Farooqi IS, O'Rahilly S, Vettor R.
Abstract – show
Recent studies suggest that wingless-type MMTV integration site family, member 10B (WNT10B) may play a role in the negative regulation of adipocyte differentiation in vitro and in vivo. In order to determine whether mutations in WNT10B contribute to human obesity, we screened two independent populations of obese subjects for mutations in this gene.
We studied 96 subjects with severe obesity of early onset (less than 10 years of age) from the UK Genetics of Obesity Study and 115 obese Italian subjects of European origin.
One proband with early-onset obesity was found to be heterozygous for a C256Y mutation, which abrogated the ability of WNT10B to activate canonical WNT signalling and block adipogenesis and was not found in 600 control alleles. All relatives of the proband who carried this allele were either overweight or obese. Three other rare missense variants were found in obese probands, but these did not clearly cosegregate with obesity in family studies and one (P301S), which was found in three unrelated subjects with early-onset obesity, had normal functional properties.
These mutations represent the first naturally occurring missense variants of WNT10B. While the pedigree analysis in the case of C256Y WNT10B does not provide definitive proof of a causal link of this variant with obesity, the finding of a non-functioning WNT10B allele in a human family affected by obesity should encourage further study of this gene in other obese populations.
PMID: 16477437 [PubMed – indexed for MEDLINE]
Liver-specific deletion of insulin receptor substrate 2 does not impair hepatic glucose and lipid metabolism in mice.
Diabetologia. 2006 Mar;49(3):552-61. Epub 2006 Jan 11.
Simmgen M, Knauf C, Lopez M, Choudhury AI, Charalambous M, Cantley J, Bedford DC, Claret M, Iglesias MA, Heffron H, Cani PD, Vidal-Puig A, Burcelin R, Withers DJ.
Abstract – show
Hepatic insulin resistance is thought to be a critical component in the pathogenesis of type 2 diabetes but the role of intrinsic insulin signalling pathways in the regulation of hepatic metabolism remains controversial. Global gene targeting in mice and in vitro studies have suggested that IRS2 mediates the physiological effects of insulin in the liver. Reduced hepatic production of IRS2 is found in many cases of insulin resistance. To investigate the role of IRS2 in regulating liver function in vivo, we generated mice that specifically lack Irs2 in the liver (LivIrs2KO).
Hepatic insulin signalling events were examined in LivIrs2KO mice by western blotting. Glucose homeostasis and insulin sensitivity were assessed by glucose tolerance tests and hyperinsulinaemic-euglycaemic clamp studies. The effects of high-fat feeding upon glucose homeostasis were also determined. Liver function tests were performed and expression of key metabolic genes in the liver was determined by RT-PCR.
Proximal insulin signalling events and forkhead box O1 and A2 function were normal in the liver of LivIrs2KO mice, which displayed minimal abnormalities in glucose and lipid homeostasis, hepatic gene expression and liver function. In addition, hepatic lipid homeostasis and the metabolic response to a high-fat diet did not differ between LivIrs2KO and control mice.
Our findings suggest that liver IRS2 signalling, surprisingly, is not required for the long-term maintenance of glucose and lipid homeostasis, and that extra-hepatic IRS2-dependent mechanisms are involved in the regulation of these processes.
PMID: 16404553 [PubMed – indexed for MEDLINE]
Mouse models of PPAR-gamma deficiency: dissecting PPAR-gamma's role in metabolic homoeostasis.
Biochem Soc Trans. 2005 Nov;33(Pt 5):1053-8.
Gray SL, Dalla Nora E, Vidal-Puig AJ.
Abstract – show
The identification of humans with mutations in PPAR-gamma (peroxisome-proliferator-activated receptor-gamma) has underlined its importance in the pathogenesis of the metabolic syndrome. Genetically modified mice provide powerful tools to dissect the mechanisms by which PPAR-gamma regulates metabolic processes. Ablation of PPAR-gamma in vivo is lethal and thus dissection of PPAR-gamma function using mouse models has relied on the development of tissue and isoform-specific ablation and mouse models of human mutations. These models exhibit phenotypes of partial PPAR-gamma impairment and are useful to elucidate how PPAR-gamma regulates specific metabolic processes. These murine models have confirmed the involvement of PPAR-gamma in adipose tissue development, maintenance and distribution. The mechanism involved in PPAR-gamma regulation of glucose homoeostasis is obscure as both agonism and partial impairment of PPAR-gamma increase insulin sensitivity. While adipose tissue is likely to be the primary target for the insulin-sensitizing effects of PPAR-gamma, some murine models suggest PPAR-gamma expressed outside adipose tissue may also contribute actively to maintain glucose homoeostasis. Interestingly, mutations in PPAR-gamma that cause severe insulin resistance in humans when expressed in mice do not result in insulin insensitivity. However, these murine models can recapitulate the effects in fuel partitioning, post-prandial lipid handling and vasculature dysfunction observed in humans. In summary, these murine models of PPAR-gamma have provided useful in vivo systems to dissect the function of PPAR-gamma, but additionally have revealed a picture of complexity. These models have confirmed a key role for PPAR-gamma in the metabolic syndrome; however, they challenge the concept that insulin resistance is the main factor linking the clinical manifestations of the metabolic syndrome.
PMID: 16246044 [PubMed – indexed for MEDLINE]
Visfatin: the missing link between intra-abdominal obesity and diabetes?
Trends Mol Med. 2005 Aug;11(8):344-7.
Sethi JK, Vidal-Puig A.
Abstract – show
Human obesity-related diabetes and the accompanying metabolic disorders have been specifically linked to increased visceral adipose tissue mass. Understanding the differences in biology of the two human fat depots (visceral and subcutaneous) might hold the key to therapeutic strategies aimed at reducing obesity-induced insulin resistance and alleviating symptoms of the metabolic syndrome. Visfatin (pre-B-cell colony-enhancing factor, PBEF) is a novel adipokine that appears to be preferentially produced by visceral adipose tissue and has insulin-mimetic actions. Could this molecule hold the key to future treatments for type 1 and 2 diabetes? This article discusses the pros and cons of visfatin action and how it might affect future therapeutic strategies.
PMID: 16005682 [PubMed – indexed for MEDLINE]
Transcript and metabolite analysis of the effects of tamoxifen in rat liver reveals inhibition of fatty acid synthesis in the presence of hepatic steatosis.
FASEB J. 2005 Jul;19(9):1108-19.
Lelliott CJ, López M, Curtis RK, Parker N, Laudes M, Yeo G, Jimenez-Liñan M, Grosse J, Saha AK, Wiggins D, Hauton D, Brand MD, O'Rahilly S, Griffin JL, Gibbons GF, Vidal-Puig A.
Abstract – show
Nonalcoholic steatohepatitis (NASH) is a common feature of the metabolic syndrome and toxic reactions to pharmacological drugs. Tamoxifen, (TMX) a widely used anti-breast cancer drug, can induce NASH and changes in plasma cholesterol levels through mechanisms that are unclear. We studied primary actions of TMX using a short-term treatment (5 days) that induces microvesicular hepatic steatosis and marked hypercholesterolemia in male rats. Using a combined approach of gene expression profiling and NMR-based metabolite analysis, we found that TMX-treated livers have increased saturated fatty acid content despite changes in gene expression, indicating decreased de novo lipogenesis and increased fatty acid oxidation. Our results show that TMX predominantly down-regulates FAS expression and activity as indicated by the accumulation of malonyl-CoA, a known inhibitor of mitochondrial beta-oxidation. In the face of a continued supply of exogenous free fatty acids, the blockade of fatty acid oxidation produced by elevated malonyl-CoA is likely to be the major factor leading to steatosis. Use of a combination of metabolomic and transcriptomic analysis has allowed us to identify mechanisms underlying important metabolic side effects of a widely prescribed drug. Given the broader importance of hepatic steatosis, the novel molecular mechanism revealed in this study should be examined in other forms of steatosis and nonalcoholic steatohepatitis.
PMID: 15985534 [PubMed – indexed for MEDLINE]
Pathways to the analysis of microarray data.
Trends Biotechnol. 2005 Aug;23(8):429-35.
Curtis RK, Oresic M, Vidal-Puig A.
Abstract – show
The development of microarray technology allows the simultaneous measurement of the expression of many thousands of genes. The information gained offers an unprecedented opportunity to fully characterize biological processes. However, this challenge will only be successful if new tools for the efficient integration and interpretation of large datasets are available. One of these tools, pathway analysis, involves looking for consistent but subtle changes in gene expression by incorporating either pathway or functional annotations. We review several methods of pathway analysis and compare the performance of three, the binomial distribution, z scores, and gene set enrichment analysis, on two microarray datasets. Pathway analysis is a promising tool to identify the mechanisms that underlie diseases, adaptive physiological compensatory responses and new avenues for investigation.
PMID: 15950303 [PubMed – indexed for MEDLINE]
Gateway to the metabolic syndrome.
Nat Med. 2005 Jun;11(6):602-3.
Medina-Gomez G, Vidal-Puig A.
PMID: 15937471 [PubMed – indexed for MEDLINE]
The link between nutritional status and insulin sensitivity is dependent on the adipocyte-specific peroxisome proliferator-activated receptor-gamma2 isoform.
Diabetes. 2005 Jun;54(6):1706-16.
Medina-Gomez G, Virtue S, Lelliott C, Boiani R, Campbell M, Christodoulides C, Perrin C, Jimenez-Linan M, Blount M, Dixon J, Zahn D, Thresher RR, Aparicio S, Carlton M, Colledge WH, Kettunen MI, Seppänen-Laakso T, Sethi JK, O'Rahilly S, Brindle K, Cinti S, Oresic M, Burcelin R, Vidal-Puig A.
Abstract – show
The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) is critically required for adipogenesis. PPARgamma exists as two isoforms, gamma1 and gamma2. PPARgamma2 is the more potent adipogenic isoform in vitro and is normally restricted to adipose tissues, where it is regulated more by nutritional state than PPARgamma1. To elucidate the relevance of the PPARgamma2 in vivo, we generated a mouse model in which the PPARgamma2 isoform was specifically disrupted. Despite similar weight, body composition, food intake, energy expenditure, and adipose tissue morphology, male mice lacking the gamma2 isoform were more insulin resistant than wild-type animals when fed a regular diet. These results indicate that insulin resistance associated with ablation of PPARgamma2 is not the result of lipodystrophy and suggests a specific role for PPARgamma2 in maintaining insulin sensitivity independently of its effects on adipogenesis. Furthermore, PPARgamma2 knockout mice fed a high-fat diet did not become more insulin resistant than those on a normal diet, despite a marked increase in their mean adipocyte cell size. These findings suggest that PPARgamma2 is required for the maintenance of normal insulin sensitivity in mice but also raises the intriguing notion that PPARgamma2 may be necessary for the adverse effects of a high-fat diet on carbohydrate metabolism.
PMID: 15919792 [PubMed – indexed for MEDLINE]
The peroxisome proliferator-activated receptor-gamma regulates murine pyruvate carboxylase gene expression in vivo and in vitro.
J Biol Chem. 2005 Jul 22;280(29):27466-76. Epub 2005 May 25.
Jitrapakdee S, Slawik M, Medina-Gomez G, Campbell M, Wallace JC, Sethi JK, O'rahilly S, Vidal-Puig AJ.
Abstract – show
Pyruvate carboxylase (PC) plays a crucial role in various metabolic pathways, including gluconeogenesis, lipogenesis, and glucose-induced insulin secretion. Here we showed for the first time that the PC gene is transcriptionally regulated by peroxisome proliferator-activated receptor-gamma (PPARgamma) in vitro and in vivo in white and brown adipose tissue. PC mRNA and protein are markedly increased during differentiation of 3T3-L1 cells and HIB-1B, in parallel with the expression of the adipogenic transcription factors, CCAAT-enhancer binding protein alpha, PPARgamma1, and PPARgamma2. Tumor necrosis factor-alpha, a cytokine that blocks differentiation of 3T3-L1 cells, suppressed PC expression. Co-transfection studies in 3T3-L1 preadipocytes or HEK293T cells with a 2.3-kb promoter fragment of mouse PC gene linked to a luciferase reporter construct and with plasmids overexpressing retinoid X receptor alpha/PPARgamma1 or retinoid X receptor alpha/PPARgamma2 showed a 6-8-fold increase above the basal promoter activity. Furthermore, treatment of these transfected cells with the PPARgamma agonist doubled the promoter activity. Mutation of the putative PPAR-response element-(-386/-374) of this 2.3-kb PC promoter fragment abolished the PPARgamma response. Gel shift and chromatin immunoprecipitation assays demonstrated that endogenous PPARgamma binds to this functional PPAR-response element of the PC promoter. Mice with targeted disruption of the PPARgamma2 gene displayed approximately 50-60% reduction of PC mRNA and protein in white adipose tissue. Similarly, in brown adipose tissue of PPARgamma2-deficient mice subjected to cold exposure, PC mRNA was 40% lower than that of wild type mice. Impaired in vitro differentiation of white adipocytes of PPARgamma2 knock-out mice was also associated with a marked reduction of PC mRNA. Our findings identified PC as a PPARgamma-regulated gene and suggested a role for PPARgamma regulating intermediary metabolism.
PMID: 15917242 [PubMed – indexed for MEDLINE]
Regulation of adiponectin expression in human adipocytes: effects of adiposity, glucocorticoids, and tumor necrosis factor alpha.
Obes Res. 2005 Apr;13(4):662-9.
Degawa-Yamauchi M, Moss KA, Bovenkerk JE, Shankar SS, Morrison CL, Lelliott CJ, Vidal-Puig A, Jones R, Considine RV.
Abstract – show
Adiponectin mRNA expression in isolated subcutaneous and omental adipocytes was examined across a wide range of adiposity to determine whether adiponectin synthesis is impaired in these adipose tissue depots in obese humans. Tumor necrosis factor (TNF)alpha and dexamethasone were tested for inhibitory effects on adiponectin release from human adipocytes in vitro.
Adipocytes were isolated by collagenase digestion of abdominal adipose tissue obtained from subjects undergoing surgical procedures or outpatient needle biopsy. Adiponectin and leptin mRNA were quantitated by real-time reverse transcriptase-polymerase chain reaction. Adiponectin and leptin secretion from isolated adipocytes treated with dexamethasone or TNFalpha were determined by radioimmunoassay.
There was a significant negative correlation between adiponectin gene expression and BMI in subcutaneous adipocytes from 32 women (r = 0.420; p = 0.02). Adiponectin mRNA was also significantly correlated with serum adiponectin (r = 0.44; p = 0.03; n = 25). There was no correlation between adiponectin mRNA expression and BMI in omental adipocytes from 29 women. Leptin mRNA was significantly and positively correlated (r = 0.484; p = 0.01) with BMI in the same omental adipocyte mRNA preparations. In subcutaneous adipocytes from lean subjects, TNFalpha inhibited adiponectin release by 7.4 +/- 1.2% (n = 9, p < 0.05) but had no effect on adiponectin release from subcutaneous or omental adipocytes from obese subjects. Dexamethasone significantly inhibited adiponectin release with 24 hours of treatment.
The data suggest that reduced adiponectin synthesis in subcutaneous adipocytes contributes to lower serum adiponectin levels in obesity and that glucocorticoids regulate adiponectin gene expression in human adipocytes. TNFalpha does not seem to directly inhibit adiponectin synthesis in human adipocytes.
PMID: 15897474 [PubMed – indexed for MEDLINE]
A dominant negative human peroxisome proliferator-activated receptor (PPAR){alpha} is a constitutive transcriptional corepressor and inhibits signaling through all PPAR isoforms.
Endocrinology. 2005 Apr;146(4):1871-82. Epub 2005 Jan 20.
Semple RK, Meirhaeghe A, Vidal-Puig AJ, Schwabe JW, Wiggins D, Gibbons GF, Gurnell M, Chatterjee VK, O'Rahilly S.
Abstract – show
Several missense mutations in the ligand-binding domain of human peroxisome proliferator-activated receptor (PPAR)gamma have been described in subjects with dominantly inherited severe insulin resistance associated with partial lipodystrophy, hypertension, and dyslipidemia. These mutant receptors behave as dominant-negative inhibitors of PPARgamma signaling when studied in transfected cells. The extent to which such dominant-negative effects extend to signaling through other coexpressed PPAR isoforms has not been evaluated. To examine these issues further, we have created a PPARalpha mutant harboring twin substitutions, Leu459Ala and Glu462Ala, within the ligand binding domain (PPARalpha(mut)), examined its signaling properties, and compared the effects of dominant-negative PPARalpha and PPARgamma mutants on basal and ligand-induced gene transcription in adipocytes and hepatocytes. PPARalpha(mut) was transcriptionally inactive, repressed basal activity from a PPAR response element-containing promoter, inhibited the coactivator function of cotransfected PPAR-gamma coactivator 1alpha, and strongly inhibited the transcriptional response to cotransfected wild-type receptor. In contrast to PPARgamma, wild-type PPARalpha failed to recruit the transcriptional corepressors NCoR and SMRT. However, PPARalpha(mut) avidly recruited these corepressors in a ligand-dissociable manner. In hepatocytes and adipocytes, both PPARalpha(mut) and the corresponding PPARgamma mutant were capable of inhibiting the expression of genes primarily regulated by PPARalpha, -gamma, or -delta ligands, albeit with some differences in potency. Thus, dominant-negative forms of PPARalpha and PPARgamma are capable of interfering with PPAR signaling in a manner that is not wholly restricted to their cognate target genes. These findings may have implications for the pathogenesis of human syndromes resulting from mutations in this family of transcription factors.
PMID: 15661858 [PubMed – indexed for MEDLINE]
Lipotoxicity, an imbalance between lipogenesis de novo and fatty acid oxidation.
Int J Obes Relat Metab Disord. 2004 Dec;28 Suppl 4:S22-8.
Lelliott C, Vidal-Puig AJ.
Abstract – show
Obesity and type 2 diabetes mellitus are the major noncommunicable public health problem of the 21st century. The best strategy to tackle this problem is to develop strategies to prevent/treat obesity. However, it is becoming clear that despite successful research identifying weight regulatory pathways, the development of the obesity epidemic is outpacing scientific progress. The lack of success controlling the obesity epidemic in an aging population will result in another subsequent uncontrolled epidemic of complications. Our research focuses on the mechanisms causing lipotoxicity aiming to identify suitable strategies to prevent or at least retard the development of the metabolic syndrome. Previous work using transgenic and knockout mouse models has shown an interplay between white adipose tissue and skeletal muscle linking fatty acid (FA) synthesis with reciprocal effects on FA oxidation. Work from our lab and others suggests that defective adipose tissue is a key link between obesity, insulin resistance and type 2 diabetes mellitus by promoting the development of lipotoxicity in peripheral tissues. We propose a series of models to describe the process by which the adipose tissue could react to an energy-rich environment and responds depending on genetic and physiological factors, impacting on the functions of other peripheral tissues. We suggest that by examining hypotheses that encompass multiple organs and the partitioning of energy between these organs, a suitable strategy can be devised for the treatment of chronic obesity.
PMID: 15592482 [PubMed – indexed for MEDLINE]
ETO/MTG8 is an inhibitor of C/EBPbeta activity and a regulator of early adipogenesis.
Mol Cell Biol. 2004 Nov;24(22):9863-72.
Rochford JJ, Semple RK, Laudes M, Boyle KB, Christodoulides C, Mulligan C, Lelliott CJ, Schinner S, Hadaschik D, Mahadevan M, Sethi JK, Vidal-Puig A, O'Rahilly S.
Abstract – show
The putative transcriptional corepressor ETO/MTG8 has been extensively studied due to its involvement in a chromosomal translocation causing the t(8;21) form of acute myeloid leukemia. Despite this, the role of ETO in normal physiology has remained obscure. Here we show that ETO is highly expressed in preadipocytes and acts as an inhibitor of C/EBPbeta during early adipogenesis, contributing to its characteristically delayed activation. ETO prevents both the transcriptional activation of the C/EBPalpha promoter by C/EBPbeta and its concurrent accumulation in centromeric sites during early adipogenesis. ETO expression rapidly reduces after the initiation of adipogenesis, and this is essential to the normal induction of adipogenic gene expression. These findings define, for the first time, a molecular role for ETO in normal physiology as an inhibitor of C/EBPbeta and a novel regulator of early adipogenesis.
PMID: 15509789 [PubMed – indexed for MEDLINE] PMCID: PMC525461
Thyroid hormones directly activate the expression of the human and mouse uncoupling protein-3 genes through a thyroid response element in the proximal promoter region.
Biochem J. 2005 Mar 15;386(Pt 3):505-13.
Solanes G, Pedraza N, Calvo V, Vidal-Puig A, Lowell BB, Villarroya F.
Abstract – show
The transcription of the human UCP3 (uncoupling protein-3) gene in skeletal muscle is tightly regulated by metabolic signals related to fatty acid availability. However, changes in thyroid status also modulate UCP3 gene expression, albeit by unknown mechanisms. We created transgenic mice bearing the entire human UCP3 gene to investigate the effect of thyroid hormones on human UCP3 gene expression. Treatment of human UCP3 transgenic mice with thyroid hormones induced the expression of the human gene in skeletal muscle. In addition, transient transfection experiments demonstrate that thyroid hormones activate the transcription of the human UCP3 gene promoter when MyoD and the TR (thyroid hormone receptor) were co-transfected. The action of thyroid hormones on UCP3 gene transcription is mediated by the binding of the TR to a proximal region in the UCP3 gene promoter that contains a direct repeat structure. An intact DNA sequence of this site is required for thyroid hormone responsiveness and TR binding. Chromatin immunoprecipitation assays revealed that the TR binds this element in vivo. The murine Ucp3 gene promoter was also dependent on MyoD and responsive to thyroid hormone in transient transfection assays. However, it was much less sensitive to thyroid hormone than the human UCP3 promoter. In summary, UCP3 gene transcription is activated by thyroid hormone treatment in vivo, and this activation is mediated by a TRE (thyroid hormone response element) in the proximal promoter region. Such regulation suggests a link between UCP3 gene expression and the effects of thyroid hormone on mitochondrial function in skeletal muscle.
PMID: 15496137 [PubMed – indexed for MEDLINE] PMCID: PMC1134869
Nuclear receptor corepressor RIP140 regulates fat accumulation.
Proc Natl Acad Sci U S A. 2004 Jun 1;101(22):8437-42. Epub 2004 May 20.
Leonardsson G, Steel JH, Christian M, Pocock V, Milligan S, Bell J, So PW, Medina-Gomez G, Vidal-Puig A, White R, Parker MG.
Abstract – show
Nuclear receptors and their coactivators have been shown to function as key regulators of adipose tissue biology. Here we show that a ligand-dependent transcriptional repressor for nuclear receptors plays a crucial role in regulating the balance between energy storage and energy expenditure. Mice devoid of the corepressor protein RIP140 are lean, show resistance to high-fat diet-induced obesity and hepatic steatosis, and have increased oxygen consumption. Although the process of adipogenesis is unaffected, expression of certain lipogenic enzymes is reduced. In contrast, genes involved in energy dissipation and mitochondrial uncoupling, including uncoupling protein 1, are markedly increased. Therefore, the maintenance of energy homeostasis requires the action of a transcriptional repressor in white adipose tissue, and ligand-dependent recruitment of RIP140 to nuclear receptors may provide a therapeutic target in the treatment of obesity and related disorders.
PMID: 15155905 [PubMed – indexed for MEDLINE] PMCID: PMC420412
Genetic variants in human sterol regulatory element binding protein-1c in syndromes of severe insulin resistance and type 2 diabetes.
Diabetes. 2004 Mar;53(3):842-6.
Laudes M, Barroso I, Luan J, Soos MA, Yeo G, Meirhaeghe A, Logie L, Vidal-Puig A, Schafer AJ, Wareham NJ, O'Rahilly S.
Abstract – show
The transcription factor sterol regulatory element binding protein (SREBP)-1c is intimately involved in the regulation of lipid and glucose metabolism. To investigate whether mutations in this gene might contribute to insulin resistance, we screened the exons encoding the aminoterminal transcriptional activation domain in a cohort of 85 unrelated human subjects with severe insulin resistance. Two missense mutations (P87L and P416A) were found in single affected patients but not in 47 control subjects. However, these variants were indistinguishable from the wild-type in their ability to bind DNA or to transactivate an SREBP-1 responsive promoter construct. We also identified a common intronic single nucleotide polymorphism (C/T) located between exon 18c and 19c. In a case-control study of 517 U.K. Caucasian case subjects and 517 age- and sex-matched control subjects, the T-allele at this locus was significantly associated with type 2 diabetes in men (odds ratio = 1.42 [1.11-1.82], P = 0.005) but not women. In a separate population-based study of 1,100 Caucasians, carriers of the T-allele showed significantly higher levels of total and LDL cholesterol (P < 0.05) compared with wild-type individuals. In summary, we have conducted the first study of the SREBP-1c gene as a candidate for human insulin resistance. Although the rare mutations identified were functionally silent in the assays used, we obtained some evidence, which requires conformation in other populations, that a common variant in the SREBP-1c gene might influence diabetes risk and plasma cholesterol level.
PMID: 14988272 [PubMed – indexed for MEDLINE]
Signalling activity of beta-catenin targeted to different subcellular compartments.
Biochem J. 2004 Apr 15;379(Pt 2):471-7.
Hagen T, Sethi JK, Foxwell N, Vidal-Puig A.
Abstract – show
Beta-catenin plays a dual role as an adhesion molecule in adherens junctions at the plasma membrane and as a key intermediate in the canonical Wnt signalling pathway. The cytosolic soluble pool of beta-catenin, involved in the transmission of the Wnt signal, is normally subjected to rapid protein degradation. On activation of the Wnt cascade, beta-catenin becomes stabilized and then translocates into the nucleus where it co-activates transcription factors of the TCF (T-cell factor)/LEF (lymphoid enhancer factor) family. The expression of plasma membrane-targeted forms of beta-catenin has been shown to also activate TCF/LEF-dependent transcription and different mechanisms have been put forward. In the present study, we have undertaken a systematic analysis of the signalling capability of non-degradable forms of beta-catenin targeted to different cellular compartments. beta-Catenin targeted to the plasma membrane activated transcription to a greater extent compared with non-targeted beta-catenin, and led to a marked stabilization of cytosolic soluble beta-catenin. These effects were independent of the competition with endogenous beta-catenin for binding to E-cadherin at the plasma membrane, since targeting non-degradable beta-catenin to other cellular compartments, i.e. the outer mitochondrial membrane and the endoplasmic reticulum membrane, also resulted in the accumulation of cytosolic wild-type beta-catenin and activation of beta-catenin-dependent signalling. In contrast, nuclear-targeted beta-catenin was without significant effect on cytosolic wild-type beta-catenin and did not activate transcription. Our results suggest that cytosolic accumulation of beta-catenin is a prerequisite for the activation of TCF/LEF-dependent transcription in the nucleus.
PMID: 14733614 [PubMed – indexed for MEDLINE] PMCID: PMC1224088
Role of the POZ zinc finger transcription factor FBI-1 in human and murine adipogenesis.
J Biol Chem. 2004 Mar 19;279(12):11711-8. Epub 2003 Dec 30.
Laudes M, Christodoulides C, Sewter C, Rochford JJ, Considine RV, Sethi JK, Vidal-Puig A, O'Rahilly S.
Abstract – show
Poxvirus zinc finger (POZ) zinc finger domain transcription factors have been shown to play a role in the control of growth arrest and differentiation in several types of mesenchymal cells but not, as yet, adipocytes. We found that a POZ domain protein, factor that binds to inducer of short transcripts-1 (FBI-1), was induced during both murine and human preadipocyte differentiation with maximal expression levels seen at days 2-4. FBI-1 mRNA was expressed in human adipose tissue with the highest levels found in samples from morbidly obese subjects. Murine cell lines constitutively expressing FBI-1 showed evidence for accelerated adipogenesis with earlier induction of markers of differentiation and enhanced lipid accumulation, suggesting that FBI-1 may be an active participant in the differentiation process. Consistent with the properties of this family of proteins in other cell systems, 3T3L1 cells stably overexpressing FBI-1 showed reduced DNA synthesis and reduced expression of cyclin A, cyclin-dependent kinase 2, and p107, proteins known to be involved in the regulation of mitotic clonal expansion. In addition, FBI-1 reduced the transcriptional activity of the cyclin A promoter. Thus, FBI-1, a POZ zinc finger transcription factor, is induced during the early phases of human and murine preadipocyte differentiation where it may contribute to adipogenesis through influencing the switch from cellular proliferation to terminal differentiation.
PMID: 14701838 [PubMed – indexed for MEDLINE]
Expression of the thermogenic nuclear hormone receptor coactivator PGC-1alpha is reduced in the adipose tissue of morbidly obese subjects.
Int J Obes Relat Metab Disord. 2004 Jan;28(1):176-9.
Semple RK, Crowley VC, Sewter CP, Laudes M, Christodoulides C, Considine RV, Vidal-Puig A, O'Rahilly S.
Abstract – show
Peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC1alpha) is an accessory protein which can potentiate the transcriptional activation function of many nuclear hormone receptors. Its tissue distribution and physiological studies suggest that its principal in vivo roles are to promote cold-induced thermogenesis, mitochondrial biogenesis, hepatic gluconeogenesis, and fatty acid beta-oxidation. It is expressed in the white adipose tissue of both humans and rodents, and in rodents it has been suggested to mediate in part the leptin-induced conversion of white adipocytes from fat storing to fat oxidising cells. In this study, quantitative real-time PCR has been used in human tissue to demonstrate that (1) PGC1alpha mRNA levels in subcutaneous fat are three-fold lower in morbidly obese than in slim subjects; (2) there are no differences in PGC1alpha mRNA between omental and subcutaneous mature adipocytes; (3) there is a robust induction of PGC1alpha expression during subcutaneous human preadipocyte differentiation ex vivo. Whether low PGC1alpha expression is a prelude to the development of obesity, or a consequence of that obesity, attempts to upregulate endogenous white adipose tissue expression may prove a valuable new avenue to explore in obesity therapy.
PMID: 14557831 [PubMed – indexed for MEDLINE]
A signalling role for 4-hydroxy-2-nonenal in regulation of mitochondrial uncoupling.
EMBO J. 2003 Aug 15;22(16):4103-10.
Echtay KS, Esteves TC, Pakay JL, Jekabsons MB, Lambert AJ, Portero-Otín M, Pamplona R, Vidal-Puig AJ, Wang S, Roebuck SJ, Brand MD.
Abstract – show
Oxidative stress and mitochondrial dysfunction are associated with disease and aging. Oxidative stress results from overproduction of reactive oxygen species (ROS), often leading to peroxidation of membrane phospholipids and production of reactive aldehydes, particularly 4-hydroxy-2-nonenal. Mild uncoupling of oxidative phosphorylation protects by decreasing mitochondrial ROS production. We find that hydroxynonenal and structurally related compounds (such as trans-retinoic acid, trans-retinal and other 2-alkenals) specifically induce uncoupling of mitochondria through the uncoupling proteins UCP1, UCP2 and UCP3 and the adenine nucleotide translocase (ANT). Hydroxynonenal-induced uncoupling was inhibited by potent inhibitors of ANT (carboxyatractylate and bongkrekate) and UCP (GDP). The GDP-sensitive proton conductance induced by hydroxynonenal correlated with tissue expression of UCPs, appeared in yeast mitochondria expressing UCP1 and was absent in skeletal muscle mitochondria from UCP3 knockout mice. The carboxyatractylate-sensitive hydroxynonenal stimulation correlated with ANT content in mitochondria from Drosophila melanogaster expressing different amounts of ANT. Our findings indicate that hydroxynonenal is not merely toxic, but may be a biological signal to induce uncoupling through UCPs and ANT and thus decrease mitochondrial ROS production.
PMID: 12912909 [PubMed – indexed for MEDLINE] PMCID: PMC175801
Characterization of the human, mouse and rat PGC1 beta (peroxisome-proliferator-activated receptor-gamma co-activator 1 beta) gene in vitro and in vivo.
Biochem J. 2003 Jul 1;373(Pt 1):155-65.
Meirhaeghe A, Crowley V, Lenaghan C, Lelliott C, Green K, Stewart A, Hart K, Schinner S, Sethi JK, Yeo G, Brand MD, Cortright RN, O'Rahilly S, Montague C, Vidal-Puig AJ.
Abstract – show
PGC1 alpha is a co-activator involved in adaptive thermogenesis, fatty-acid oxidation and gluconeogenesis. We describe the identification of several isoforms of a new human PGC1 alpha homologue, cloned independently and named PGC1 beta. The human PGC1 beta gene is localized to chromosome 5, has 13 exons and spans more than 78 kb. Two different 5′ and 3′ ends due to differential splicing were identified by rapid amplification of cDNA ends PCR and screening of human cDNA libraries. We show that PGC1 beta variants in humans, mice and rats are expressed predominantly in heart, brown adipose tissue, brain and skeletal muscle. PGC1 beta expression, unlike PGC1 alpha, is not up-regulated in brown adipose tissue in response to cold or obesity. Fasting experiments showed that PGC1 alpha, but not PGC1 beta, is induced in liver and this suggests that only PGC1 alpha is involved in the hepatic gluconeogenesis. No changes in PGC1 beta gene expression were observed associated with exercise. Human PGC1 beta-1a and -2a isoforms localized to the cell nucleus and, specifically, the isoform PGC1 beta-1a co-activated peroxisome-proliferator-activated receptor-gamma, -alpha and the thyroid hormone receptor beta1. Finally, we show that ectopic expression PGC1 beta leads to increased mitochondrial number and basal oxygen consumption. These results suggest that PGC1 beta may play a role in constitutive adrenergic-independent mitochondrial biogenesis.
PMID: 12678921 [PubMed – indexed for MEDLINE] PMCID: PMC1223480
Human metabolic syndrome resulting from dominant-negative mutations in the nuclear receptor peroxisome proliferator-activated receptor-gamma.
Diabetes. 2003 Apr;52(4):910-7.
Savage DB, Tan GD, Acerini CL, Jebb SA, Agostini M, Gurnell M, Williams RL, Umpleby AM, Thomas EL, Bell JD, Dixon AK, Dunne F, Boiani R, Cinti S, Vidal-Puig A, Karpe F, Chatterjee VK, O'Rahilly S.
Abstract – show
We previously reported a syndrome of severe hyperinsulinemia and early-onset hypertension in three patients with dominant-negative mutations in the nuclear hormone receptor peroxisome proliferator-activated receptor (PPAR)-gamma. We now report the results of further detailed pathophysiological evaluation of these subjects, the identification of affected prepubertal children within one of the original families, and the effects of thiazolidinedione therapy in two subjects. These studies 1) definitively demonstrate the presence of severe peripheral and hepatic insulin resistance in the affected subjects; 2) describe a stereotyped pattern of partial lipodystrophy associated with all the features of the metabolic syndrome and nonalcoholic steatohepatitis; 3) document abnormalities in the in vivo function of remaining adipose tissue, including the inability of subcutaneous abdominal adipose tissue to trap and store free fatty acids postprandially and the presence of very low circulating levels of adiponectin; 4) document the presence of severe hyperinsulinemia in prepubertal carriers of the proline-467-leucine (P467L) PPAR-gamma mutation; 5) provide the first direct evidence of cellular resistance to PPAR-gamma agonists in mononuclear cells derived from the patients; and 6) report on the metabolic response to thiazolidinedione therapy in two affected subjects. Although the condition is rare, the study of humans with dominant-negative mutations in PPAR-gamma can provide important insight into the roles of this nuclear receptor in human metabolism.
PMID: 12663460 [PubMed – indexed for MEDLINE]
Acute endurance exercise increases skeletal muscle uncoupling protein-3 gene expression in untrained but not trained humans.
Metabolism. 2003 Feb;52(2):152-8.
Noland RC, Hickner RC, Jimenez-Linan M, Vidal-Puig A, Zheng D, Dohm GL, Cortright RN.
Abstract – show
In rodents, acute exercise increases skeletal muscle uncoupling protein (UCP) gene expression and is associated with elevations in serum nonesterified fatty acids (NEFA). To test whether contractions increase UCP mRNA levels in humans, vastus lateralis biopsies were obtained 1 hour postexercise from untrained and trained subjects and analyzed for UCP-2 and UCP-3 long (UCP-3(L)) and short (UCP-3(S)) isoforms. The acute exercise bout (graded cycling protocol; 65% to 85% relative VO(2)max) induced significant (P <.01) elevations in serum NEFA in both untrained and trained subjects, but the increase in untrained subjects was significantly (P <.05) greater (60% v 30%). Ribonuclease protection assay demonstrated that basal levels of all UCP isoforms measured were similar between the 2 groups. However, acute exercise induced a significant increase (P <.02) in both UCP-3(L) and UCP-3(S), but not UCP-2 mRNA levels in untrained, but not trained subjects. Correlation analysis did not show a significant relationship between exercise-induced changes in NEFA and UCP-3 levels. These results demonstrate that acute endurance exercise increases UCP-3 gene expression only in untrained skeletal muscle, but this effect does not seem to be tightly linked to the exercise-induced fluctuations in serum NEFA levels.
Copyright 2003, Elsevier Science (USA). All rights reserved.
PMID: 12601624 [PubMed – indexed for MEDLINE]
Differential effects of adiposity on peroxisomal proliferator-activated receptor gamma1 and gamma2 messenger ribonucleic acid expression in human adipocytes.
J Clin Endocrinol Metab. 2002 Sep;87(9):4203-7.
Sewter C, Blows F, Considine R, Vidal-Puig A, O'Rahilly S.
Abstract – show
Both genetic and pharmacological studies raise the possibility that a primary increase in the amount or activity of peroxisomal proliferator-activated receptor gamma (PPARgamma) in adipocytes could play a role in common types of human obesity. Using real-time RT-PCR assays we examined the relationship between body mass index (BMI) and PPARgamma isoform expression in freshly isolated human adipocytes. There were no consistent differences in the expression of either PPARgamma1 mRNA or PPARgamma2 mRNA between omental and sc adipocytes. In a group of 17 subjects (BMI range, 17-34 kg/m(2)) there was a strong and highly significant inverse correlation (r = -0.68; P < 0.005) between PPARgamma1 mRNA expression in adipocytes and BMI, whereas no significant relationship was apparent for PPARgamma2. In an independent study PPARgamma1 mRNA levels were decreased (1.1 +/- 0.1 vs. 3.7 +/- 0.8 arbitrary units; P < 0.01) in adipocytes from morbidly obese (BMI, 50.6 +/- 14.1 kg/m(2)) vs. lean (BMI, 21.1 +/- 1.0 kg/m(2)) subjects. In contrast, there was a significant increase in the expression of PPARgamma2 mRNA levels between the morbidly obese and lean groups (1.7 +/- 0.2 vs. 1.1 +/- 0.2 arbitrary units; P < 0.05). Treatment of isolated human adipocytes with TNFalpha resulted in a significant decrease in both PPARgamma1 and PPARgamma2 mRNA levels [40.6 +/- 5.5% relative to control (P = 0.01) and 60.9 +/- 24.8% (P = 0.02) respectively]. The strong inverse relationship between BMI and PPARgamma1 expression in human adipocytes is striking and may represent part of an autoregulatory mechanism restraining the expansion of individual adipocytes in states of positive energy balance. On the other hand, the increase in PPARgamma2 observed in adipocytes of morbidly obese individuals suggests a potential pathogenic effect of this isoform in promoting fat acquisition. Although an autocrine effect of the enhanced TNFalpha secretion seen with increasing obesity might play a role in the changes in PPARgamma1, this would not provide an explanation for the different relationship of PPARgamma2 to adiposity. The significance of the divergent effect of human adiposity on the two isoforms will require a greater understanding of the differential properties of the two isoforms and of the differences in the functions of their respective regulatory elements.
PMID: 12213872 [PubMed – indexed for MEDLINE]
Digenic inheritance of severe insulin resistance in a human pedigree.
Nat Genet. 2002 Aug;31(4):379-84. Epub 2002 Jul 15.
Savage DB, Agostini M, Barroso I, Gurnell M, Luan J, Meirhaeghe A, Harding AH, Ihrke G, Rajanayagam O, Soos MA, George S, Berger D, Thomas EL, Bell JD, Meeran K, Ross RJ, Vidal-Puig A, Wareham NJ, O'Rahilly S, Chatterjee VK, Schafer AJ.
Abstract – show
Impaired insulin action is a key feature of type 2 diabetes and is also found, to a more extreme degree, in familial syndromes of insulin resistance. Although inherited susceptibility to insulin resistance may involve the interplay of several genetic loci, no clear examples of interactions among genes have yet been reported. Here we describe a family in which five individuals with severe insulin resistance, but no unaffected family members, were doubly [corrected] heterozygous with respect to frameshift/premature stop mutations in two unlinked genes, PPARG and PPP1R3A these encode peroxisome proliferator activated receptor gamma, which is highly expressed in adipocytes, and protein phosphatase 1, regulatory subunit 3, the muscle-specific regulatory subunit of protein phosphatase 1, which are centrally involved in the regulation of carbohydrate and lipid metabolism, respectively. That mutant molecules primarily involved in either carbohydrate or lipid metabolism can combine to produce a phenotype of extreme insulin resistance provides a model of interactions among genes that may underlie common human metabolic disorders such as type 2 diabetes.
PMID: 12118251 [PubMed – indexed for MEDLINE]
PPARgamma and the thiazolidinediones: molecular basis for a treatment of 'Syndrome X'?
Diabetes Obes Metab. 2002 Jul;4(4):239-48.
Sewter C, Vidal-Puig A.
PMID: 12099972 [PubMed – indexed for MEDLINE]
Isomer-dependent metabolic effects of conjugated linoleic acid: insights from molecular markers sterol regulatory element-binding protein-1c and LXRalpha.
Diabetes. 2002 Jul;51(7):2037-44.
Roche HM, Noone E, Sewter C, Mc Bennett S, Savage D, Gibney MJ, O'Rahilly S, Vidal-Puig AJ.
Abstract – show
Conjugated linoleic acid (CLA) is a heterogeneous group of positional and geometric isomers of linoleic acid. This study demonstrates the divergent effects of the cis-9 trans-11 (c9,t11-CLA) and trans-10 cis-12 (t10,c12-CLA) isomers of CLA on lipid metabolism and nutrient regulation of gene expression in ob/ob mice. The c9, t11-CLA diet decreased serum triacylglycerol (P = 0.01) and nonesterified fatty acid (NEFA) (P = 0.05) concentrations, and this was associated with reduced hepatic sterol regulatory element-binding protein-1c (SREBP-1c; P = 0.0045) mRNA expression, coupled with reduced levels of both the membrane-bound precursor and the nuclear forms of the SREBP-1 protein. C9,t11-CLA significantly reduced hepatic LXRalpha (P = 0.019) mRNA expression, a novel regulator of SREBP-1c. In contrast, c9,t11-CLA increased adipose tissue SREBP-1c mRNA expression (P = 0.0162) proportionally to the degree of reduction of tumor necrosis factor alpha (TNF-alpha) mRNA (P = 0.012). Recombinant TNF-alpha almost completely abolished adipose tissue SREBP-1c mRNA expression in vivo. The t10,c12-CLA diet promoted insulin resistance and increased serum glucose (P = 0.025) and insulin (P = 0.01) concentrations. T10, c12-CLA induced profound weight loss (P = 0.0001) and increased brown and white adipose tissue UCP-2 (P = 0.001) and skeletal muscle UCP-3 (P = 0.008) mRNA expression. This study highlights the contrasting molecular and metabolic effect of two isomers of the same fatty acids. The ameliorative effect of c9,t11-CLA on lipid metabolism may be ascribed to reduced synthesis and cleavage of hepatic SREBP-1, which in turn may be regulated by hepatic LXRalpha expression.
PMID: 12086931 [PubMed – indexed for MEDLINE]
Characterisation of the phosphorylation of beta-catenin at the GSK-3 priming site Ser45.
Biochem Biophys Res Commun. 2002 Jun 7;294(2):324-8.
Hagen T, Vidal-Puig A.
Abstract – show
Activation of the canonical Wnt signalling pathway results in stabilisation and nuclear translocation of beta-catenin. In the absence of a Wnt signal, beta-catenin is phosphorylated at four conserved serine and threonine residues at the N-terminus of the protein, which results in beta-catenin ubiquitination and proteasome-dependent degradation. The phosphorylation of three of these residues, Thr41, Ser37, and Ser33, is mediated by glycogen synthase kinase-3 (GSK-3) in a sequential manner, beginning from the C-terminal Thr41. It has recently been shown that the GSK-3 dependent phosphorylation of beta-catenin requires prior priming through phosphorylation of Ser45. However, it is not known whether phosphorylation of Ser45 is carried out by GSK-3 itself or by an alternative kinase. In this study, the phosphorylation of beta-catenin at Ser45 was characterised using a phospho-specific antibody. GSK-3beta was found to be unable to phosphorylate beta-catenin at Ser45 in vitro and in intact cells. However, inhibition of GSK-3 in intact cells reduced Ser45 phosphorylation, suggesting that GSK-3 kinase activity is required for the phosphorylation event. In vitro, CK1, but not CK2, phosphorylates Ser45. Ser45 phosphorylation in intact cells is not mediated by CK1varepsilon, a known positive regulator of Wnt signalling, as overexpression of this kinase leads to decreased phosphorylation levels. In conclusion, phosphorylation of beta-catenin at the GSK-3 priming site Ser45 is not mediated by GSK-3 itself, but by an alternative kinase, indicating that beta-catenin is not an unprimed substrate for GSK-3 in vivo. Priming of GSK-3 dependent phosphorylation of beta-catenin by a different kinase could have important implications for the regulation of Wnt signalling.
(c) 2002 Elsevier Science (USA).
PMID: 12051714 [PubMed – indexed for MEDLINE]
Human obesity and type 2 diabetes are associated with alterations in SREBP1 isoform expression that are reproduced ex vivo by tumor necrosis factor-alpha.
Diabetes. 2002 Apr;51(4):1035-41.
Sewter C, Berger D, Considine RV, Medina G, Rochford J, Ciaraldi T, Henry R, Dohm L, Flier JS, O'Rahilly S, Vidal-Puig AJ.
Abstract – show
Sterol regulatory element binding protein (SREBP)-1 is a transcription factor with important roles in the control of fatty acid metabolism and adipogenesis. Little information is available regarding the expression of this molecule in human health or disease. Exposure of isolated human adipocytes to insulin enhanced SREBP1 gene expression and promoted its proteolytic cleavage to the active form. Furthermore, 3 h of in vivo hyperinsulinemia also significantly increased SREBP1 gene expression in human skeletal muscle. Transcript levels of SREBP1c, the most abundant isoform in adipose tissue, were significantly decreased in the subcutaneous adipose tissue of obese normoglycemic and type 2 diabetic subjects compared with that of nonobese normoglycemic control subjects. In skeletal muscle, SREBP1 expression was significantly reduced in type 2 diabetic subjects but not in obese subjects. Within the diabetic group, the extent of SREBP1 suppression was inversely related to metabolic control and was normalized by 3 h of in vivo hyperinsulinemia. Exposure of isolated human adipocytes to tumor necrosis factor-alpha (TNF-alpha) produced a marked and specific decrease in the mRNA encoding the SREBP1c isoform and completely blocked the insulin-induced cleavage of SREBP1 protein. Thus, both the expression and proteolytic maturation of human SREBP1 are positively modulated by insulin. The specific reduction in the SREBP1c isoform seen in the adipose tissue of obese and type 2 diabetic subjects can be recapitulated ex vivo by TNF-alpha, suggesting a possible mechanism for this association.
PMID: 11916923 [PubMed – indexed for MEDLINE]
Regional differences in the response of human pre-adipocytes to PPARgamma and RXRalpha agonists.
Diabetes. 2002 Mar;51(3):718-23.
Sewter CP, Blows F, Vidal-Puig A, O'Rahilly S.
Abstract – show
We have previously reported that omental (OM) preadipocytes respond less well to the prodifferentiating effects of thiazolidinediones than do preadipocytes from subcutaneous (SC) depots. This finding is consistent with in vivo alterations in fat distribution that occur in humans treated with thiazolidinediones. To explore these site-related differences further, we used real-time RT-PCR to quantify the specific mRNAs encoding peroxisome proliferator-activated receptor (PPAR) gamma1 and gamma2 and found that both isoforms were more highly expressed in SC than in OM preadipocytes. After 10 days of thiazolidinedione treatment, preadipocytes from both depots showed a small and comparable increase in expression of PPARgamma1 mRNA (1.7 +/- 0.2-fold [P = 0.007]) and 1.3 +/- 0.1-fold [P = 0.008] increase for SC and OM, respectively). There was a much larger increase in PPARgamma2 expression, which was significantly greater in SC compared with OM preadipocytes (11.1 +/- 2.8-fold [P = 0.0003] and 5.5 +/- 1.7-fold [P = 0.0003], respectively; P = 0.014 for SC versus OM). To establish whether the refractoriness of OM preadipocytes to differentiation was unique to activators of the PPARgamma pathway, we examined the effects of the retinoid X receptor (RXR) ligand LG100268. As assessed by glycerol-3-phosphate dehydrogenase activity, LG100268 had a greater effect on the differentiation of SC compared with OM preadipocytes when examined alone (SC = 5.7 +/- 1.7-fold vs. OM = 1.9 +/- 0.6-fold; P < 0.05) or in combination with rosiglitazone (SC = 27.0 +/- 7.5 vs. OM = 10.6 +/- 3.6-fold; P < 0.05). Consistent with this, RXRalpha mRNA levels were also higher in SC than in OM preadipocytes. In summary, the previously reported insensitivity of OM preadipocytes to the differentiating effects of thiazolidinediones may relate to their lower basal levels of PPARgamma1 and gamma2 mRNA and their diminished capacity to upregulate PPARgamma2 expression in response to ligand. That omentally derived cells also show reduced responsiveness to the prodifferentiating actions of an RXR ligand and a lower expression of RXRalpha in the undifferentiated state suggests that they may have a more generalized resistance to differentiation.
PMID: 11872672 [PubMed – indexed for MEDLINE]
Mitochondrial uncoupling proteins in human physiology and disease.
Minerva Med. 2002 Feb;93(1):41-57.
Hagen T, Vidal-Puig A.
Abstract – show
Uncoupling proteins are mitochondrial carrier proteins that catalyse a regulated proton leak across the inner mitochondrial membrane, diverting free energy from ATP synthesis by the mitochondrial F0F1-ATP synthase to the production of heat. Uncoupling protein 1 (UCP1), which is exclusively expressed in brown adipose tissue, is the mediator of thermogenesis in response to beta-adrenergic stimulation. Using gene a knockout mouse model, UCP1 has been shown to be required for cold acclimation. Two homologues of UCP1, UCP2 and UCP3, have been identified recently and show a much wider tissue distribution. UCP2 and UCP3 have been postulated to play a role in the regulation of cold acclimation, energy expenditure and diet-induced thermogenesis in humans, who, in contrast to rodents, have very little brown fat in adult life. However, evidence is accumulating that thermogenesis and regulation of body weight may not be the physiological functions of UCP2 and UCP3. For instance, mice deficient for UCP2 or UCP3 are not cold-intolerant and do not develop obesity. Alternative functions were suggested, primarily based on findings in UCP2 and UCP3 gene knockout mice. Both UCP2- and UCP3-deficient mice were found to overproduce reactive oxygen species and UCP2-deficient mice to hypersecrete insulin. Thus, the UCP1 homologues may play a role in regulating mitochondrial production of reactive oxygen species and b-cell function. In this review, we discuss the role of UCP1, UCP2 and UCP3 in human physiology and disease, primarily based on findings from the various animal models that have been generated.
PMID: 11850613 [PubMed – indexed for MEDLINE]
Lamin expression in human adipose cells in relation to anatomical site and differentiation state.
J Clin Endocrinol Metab. 2002 Feb;87(2):728-34.
Lelliott CJ, Logie L, Sewter CP, Berger D, Jani P, Blows F, O'Rahilly S, Vidal-Puig A.
Abstract – show
Familial partial lipodystrophy-Dunnigan variety (FPLD) is an autosomal dominant form of lipodystrophy resulting in a loss of sc fat from the trunk and limbs with retention of fat in the visceral depots, face, and neck. Specific point mutations in the gene encoding the nuclear lamina proteins, lamins A and C, have been established to cause this syndrome. We undertook studies to determine which members of the lamin family were expressed in human fat cells, to examine the effect of differentiation state on lamin A and C expression in human preadipocytes, and to test the hypothesis that regional variation in lamin A/C expression might underlie the stereotyped anatomical pattern of FPLD. Lamins A, C, and B1, but not B2, were expressed in sc mature human adipocytes. Subcutaneous preadipocytes expressed all four lamins, with lamin A and C expression increasing with ex vivo differentiation. Consistent with previously reported resistance to ex vivo differentiation, omental preadipocytes did not show an increase in lamin A or C mRNA under these conditions. Lamin A/C mRNA levels were similar in isolated mature adipocytes and preadipocytes from omental, sc, and neck sites. However, lamin C was consistently lower, and the ratio of lamin A/C mRNA was higher in sc mature adipocytes compared with omental mature adipocytes. We conclude that the depot-specific pattern of lamin A/C expression does not provide clues to the mechanism of FPLD. Nonetheless, these studies provide new information regarding the expression of lamin isoforms in normal human adipose cells, which will inform future studies of the molecular pathogenesis of FPLD.
PMID: 11836312 [PubMed – indexed for MEDLINE]
Resistin: a new link between obesity and insulin resistance?
Clin Endocrinol (Oxf). 2001 Oct;55(4):437-8.
Vidal-Puig A, O'Rahilly S.
PMID: 11678824 [PubMed – indexed for MEDLINE]
Resistin / Fizz3 expression in relation to obesity and peroxisome proliferator-activated receptor-gamma action in humans.
Diabetes. 2001 Oct;50(10):2199-202.
Savage DB, Sewter CP, Klenk ES, Segal DG, Vidal-Puig A, Considine RV, O'Rahilly S.
Abstract – show
Recent studies in murine models suggest that resistin (also called Fizz3 [1]), a novel cysteine-rich protein secreted by adipocytes, may represent the long-sought link between obesity and insulin resistance (2). Furthermore, peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists appear to inhibit resistin expression in murine adipocytes, providing a possible explanation for the mode of action of this class of insulin sensitizers (2). Using a fluorescent real-time reverse transcriptase-polymerase chain reaction-based assay, we found that resistin mRNA levels in whole adipose tissue samples were increased in morbidly obese humans compared with lean control subjects. However, in freshly isolated human adipocytes, resistin mRNA levels were very low and showed no correlation with BMI. Resistin mRNA was undetectable in preadipocytes, endothelial cells, and vascular smooth muscle cells, but it was readily detectable in circulating mononuclear cells. Although exposure of human mononuclear cells to PPAR-gamma agonists markedly upregulated fatty acid-binding protein-4 expression, these agents had no effect on mononuclear cell resistin expression. Finally, resistin mRNA was undetectable in adipocytes from a severely insulin-resistant subject with a dominant-negative mutation in PPAR-gamma (3). We conclude that the recently described relationships of murine resistin/Fizz3 expression with obesity, insulin resistance, and PPAR-gamma action may not readily translate to humans. Further studies of this novel class of proteins are needed to clarify their roles in human metabolism.
PMID: 11574398 [PubMed – indexed for MEDLINE]
Metabolism. Controlling the glucose factory.
Nature. 2001 Sep 13;413(6852):125-6.
Vidal-Puig A, O'Rahilly S.
PMID: 11557965 [PubMed – indexed for MEDLINE]
Uncoupling protein-2 negatively regulates insulin secretion and is a major link between obesity, beta cell dysfunction, and type 2 diabetes.
Cell. 2001 Jun 15;105(6):745-55.
Zhang CY, Baffy G, Perret P, Krauss S, Peroni O, Grujic D, Hagen T, Vidal-Puig AJ, Boss O, Kim YB, Zheng XX, Wheeler MB, Shulman GI, Chan CB, Lowell BB.
Abstract – show
beta cells sense glucose through its metabolism and the resulting increase in ATP, which subsequently stimulates insulin secretion. Uncoupling protein-2 (UCP2) mediates mitochondrial proton leak, decreasing ATP production. In the present study, we assessed UCP2's role in regulating insulin secretion. UCP2-deficient mice had higher islet ATP levels and increased glucose-stimulated insulin secretion, establishing that UCP2 negatively regulates insulin secretion. Of pathophysiologic significance, UCP2 was markedly upregulated in islets of ob/ob mice, a model of obesity-induced diabetes. Importantly, ob/ob mice lacking UCP2 had restored first-phase insulin secretion, increased serum insulin levels, and greatly decreased levels of glycemia. These results establish UCP2 as a key component of beta cell glucose sensing, and as a critical link between obesity, beta cell dysfunction, and type 2 diabetes.
PMID: 11440717 [PubMed – indexed for MEDLINE]
Mitochondrial uncoupling proteins (UCPs) and obesity.
Nutr Metab Cardiovasc Dis. 2001 Feb;11(1):70-5.
Crowley V, Vidal-Puig AJ.
Abstract – show
Obesity is now regarded as major public health problem worldwide. Research into this condition has been increasingly focussed on elucidating the cellular and molecular mechanisms regulating mammalian energy intake and expenditure. It is widely acknowledged that the brown adipose tissue (BAT) mitochondrial uncoupling protein (UCP1) plays a pivotal role in adaptive thermogenic responses. Two homologues of UCP1 (UCP2 and UCP3) have recently been identified and population-based genetic studies have linked them with basal metabolic rate, while in vitro studies report that both have proton transport activity and may thus be involved in regulation of energy homeostasis and hence obesity. However, evidence from genetically modified animal models indicates that UCP2 and UCP3 have no specific physiological thermogenic function in vivo, though they may still be useful therapeutic targets for obesity. Furthermore, their role in modulating levels of reactive oxygen species and glucose homeostasis is also being investigated.
PMID: 11383327 [PubMed – indexed for MEDLINE]
Uncoupling protein 3 (UCP3) stimulates glucose uptake in muscle cells through a phosphoinositide 3-kinase-dependent mechanism.
J Biol Chem. 2001 Apr 20;276(16):12520-9. Epub 2001 Jan 12.
Huppertz C, Fischer BM, Kim YB, Kotani K, Vidal-Puig A, Slieker LJ, Sloop KW, Lowell BB, Kahn BB.
Abstract – show
UCP3 is a mitochondrial membrane protein expressed in humans selectively in skeletal muscle. To determine the mechanisms by which UCP3 plays a role in regulating glucose metabolism, we expressed human UCP3 in L6 myotubes by adenovirus-mediated gene transfer and in H(9)C(2) cardiomyoblasts by stable transfection with a tetracycline-repressible UCP3 construct. Expression of UCP3 in L6 myotubes increased 2-deoxyglucose uptake 2-fold and cell surface GLUT4 2.3-fold, thereby reaching maximally insulin-stimulated levels in control myotubes. Wortmannin, LY 294002, or the tyrosine kinase inhibitor genistein abolished the effect of UCP3 on glucose uptake, and wortmannin inhibited UCP3-induced GLUT4 cell surface recruitment. UCP3 overexpression increased phosphotyrosine-associated phosphoinositide 3-kinase (PI3K) activity 2.2-fold compared with control cells (p < 0.05). UCP3 overexpression increased lactate release 1.5- to 2-fold above control cells, indicating increased glucose metabolism. In H(9)C(2) cardiomyoblasts stably transfected with UCP3 under control of a tetracycline-repressible promotor, removal of doxycycline resulted in detectable levels of UCP3 at 12 h and 2.2-fold induction at 7 days compared with 12 h. In parallel, glucose transport increased 1.3- and 2-fold at 12 h and 7 days, respectively, and the stimulation was inhibited by wortmannin or genistein. p85 association with membranes was increased 5.5-fold and phosphotyrosine-associated PI3K activity 3.8-fold. In contrast, overexpression of UCP3 in 3T3-L1 adipocytes did not alter glucose uptake, suggesting tissue-specific effects of human UCP3. Thus, UCP3 stimulates glucose transport and GLUT4 translocation to the cell surface in cardiac and skeletal muscle cells by activating a PI3K dependent pathway.
PMID: 11278970 [PubMed – indexed for MEDLINE]
In vivo effects of uncoupling protein-3 gene disruption on mitochondrial energy metabolism.
J Biol Chem. 2001 Jun 8;276(23):20240-4. Epub 2001 Mar 27.
Cline GW, Vidal-Puig AJ, Dufour S, Cadman KS, Lowell BB, Shulman GI.
Abstract – show
To clarify the role of uncoupling protein-3 (UCP3) in skeletal muscle, we used NMR and isotopic labeling experiments to evaluate the effect of UCP3 knockout (UCP3KO) in mice on the regulation of energy metabolism in vivo. Whole body energy expenditure was determined from the turnover of doubly labeled body water. Coupling of mitochondrial oxidative phosphorylation in skeletal muscle was evaluated from measurements of rates of ATP synthesis (using (31)P NMR magnetization transfer experiments) and tricarboxylic acid (TCA) cycle flux (calculated from the time course of (13)C enrichment in C-4 and C-2 of glutamate during an infusion of [2-(13)C]acetate). At the whole body level, we observed no change in energy expenditure. However, at the cellular level, skeletal muscle UCP3KO increased the rate of ATP synthesis from P(i) more than 4-fold under fasting conditions (wild type, 2.2 +/- 0.6 versus knockout, 9.1 +/- 1.4 micromol/g of muscle/min, p < 0.001) with no change in TCA cycle flux rate (wild type, 0.74 +/- 0.04 versus knockout, 0.71 +/- 0.03 micromol/g of muscle/min). The increased efficiency of ATP production may account for the significant (p < 0.05) increase in the ratio of ATP to ADP in the muscle of UCP3KO mice (5.9 +/- 0.3) compared with controls (4.5 +/- 0.4). The data presented here provide the first evidence of uncoupling activity by UCP3 in skeletal muscle in vivo.
PMID: 11274222 [PubMed – indexed for MEDLINE]
Uncoupling expectations.
Nat Genet. 2000 Dec;26(4):387-8.
Vidal-Puig AJ.
PMID: 11101825 [PubMed – indexed for MEDLINE]
Obesity and diabetes: an avalanche of new information.
Mol Med Today. 2000 Jun;6(6):221-3.
Vidal-Puig A, O'Rahilly S.
PMID: 10939842 [PubMed – indexed for MEDLINE]
Energy metabolism in uncoupling protein 3 gene knockout mice.
J Biol Chem. 2000 May 26;275(21):16258-66.
Vidal-Puig AJ, Grujic D, Zhang CY, Hagen T, Boss O, Ido Y, Szczepanik A, Wade J, Mootha V, Cortright R, Muoio DM, Lowell BB.
Abstract – show
Uncoupling protein 3 (UCP3) is a member of the mitochondrial anion carrier superfamily. Based upon its high homology with UCP1 and its restricted tissue distribution to skeletal muscle and brown adipose tissue, UCP3 has been suggested to play important roles in regulating energy expenditure, body weight, and thermoregulation. Other postulated roles for UCP3 include regulation of fatty acid metabolism, adaptive responses to acute exercise and starvation, and prevention of reactive oxygen species (ROS) formation. To address these questions, we have generated mice lacking UCP3 (UCP3 knockout (KO) mice). Here, we provide evidence that skeletal muscle mitochondria lacking UCP3 are more coupled (i.e. increased state 3/state 4 ratio), indicating that UCP3 has uncoupling activity. In addition, production of ROS is increased in mitochondria lacking UCP3. This study demonstrates that UCP3 has uncoupling activity and that its absence may lead to increased production of ROS. Despite these effects on mitochondrial function, UCP3 does not seem to be required for body weight regulation, exercise tolerance, fatty acid oxidation, or cold-induced thermogenesis. The absence of such phenotypes in UCP3 KO mice could not be attributed to up-regulation of other UCP mRNAs. However, alternative compensatory mechanisms cannot be excluded. The consequence of increased mitochondrial coupling in UCP3 KO mice on metabolism and the possible role of yet unidentified compensatory mechanisms, remains to be determined.
PMID: 10748196 [PubMed – indexed for MEDLINE]
Genetic and physiologic analysis of the role of uncoupling protein 3 in human energy homeostasis.
Diabetes. 1999 Sep;48(9):1890-5.
Chung WK, Luke A, Cooper RS, Rotini C, Vidal-Puig A, Rosenbaum M, Chua M, Solanes G, Zheng M, Zhao L, LeDuc C, Eisberg A, Chu F, Murphy E, Schreier M, Aronne L, Caprio S, Kahle B, Gordon D, Leal SM, Goldsmith R, Andreu AL, Bruno C, DiMauro S, Leibel RL, et al.
Abstract – show
By virtue of its potential effects on rates of energy expenditure, uncoupling protein 3 (UCP3) is an obesity candidate gene. We identified nine sequence variants in UCP3, including Val9Met, Val102Ile, Arg282Cys, and a splice site mutation in the intron between exons 6 and 7. The splice mutation results in an inability to synthesize mRNA for the long isoform (UCP3L) of UCP3. Linkage (sib pair), association, and transmission disequilibrium testing studies on 942 African-Americans did not suggest a significant effect of UCP3 on body composition in this group. In vastus lateralis skeletal muscle of individuals homozygous for the splice mutation, no UCP3L mRNA was detectable; the short isoform (UCP3S) was present in an increased amount. In this muscle, we detected no alterations of in vitro mitochondrial coupling activity, mitochondrial respiratory enzyme activity, or systemic oxygen consumption or respiratory quotient at rest or during exercise. These genetic and physiologic data suggest the following possibilities: UCP3S has uncoupling capabilities equivalent to UCP3L; other UCPs may compensate for a deficiency of bioactive UCP3L; UCP3L does not function primarily as a mitochondrial uncoupling protein.
PMID: 10480626 [PubMed – indexed for MEDLINE]
The long isoform uncoupling protein-3 (UCP3L) in human energy homeostasis.
Int J Obes Relat Metab Disord. 1999 Jun;23 Suppl 6:S49-50.
Chung WK, Luke A, Cooper RS, Rotini C, Vidal-Puig A, Rosenbaum M, Gordon D, Leal SM, Caprio S, Goldsmith R, Andreu AL, Bruno C, DiMauro S, Heo M, Lowe WL Jr, Lowell BB, Allison DB, Leibel RL.
Abstract – show
The biological role(s) proposed for UCP3 in energy homeostasis have been based primarily upon amino acid sequence homology to UCP1. Spontaneous mutations of UCP3> have been described in humans, but not in rodents. The functional consequences-or lack thereof-of these mutations in humans will be of great importance in elucidating the biology of this protein. The results of two such studies are summarized here.
PMID: 10454123 [PubMed – indexed for MEDLINE]
Role of the beta(3)-adrenergic receptor and/or a putative beta(4)-adrenergic receptor on the expression of uncoupling proteins and peroxisome proliferator-activated receptor-gamma coactivator-1.
Biochem Biophys Res Commun. 1999 Aug 11;261(3):870-6.
Boss O, Bachman E, Vidal-Puig A, Zhang CY, Peroni O, Lowell BB.
Abstract – show
Administration of beta-adrenergic receptor (beta-AR) agonists, especially beta(3)-AR agonists, is well known to increase thermogenesis in rodents and humans. In this work we studied the role of the beta(3)-AR in regulating mRNA expression of genes involved in thermogenesis, i.e., mitochondrial uncoupling proteins UCP2 and UCP3, and peroxisome proliferator-activated receptor-gamma coactivator-1 (PGC-1), in mouse skeletal muscle. For this purpose, different beta(3)-AR agonists were administered acutely to both wild type mice and mice whose beta(3)-AR gene has been disrupted (beta(3)-AR KO mice). CL 316243 increased the expression of UCP2, UCP3 and PGC-1 in wild type mice only. By contrast, BRL 37344 and CGP 12177 increased the expression of UCP2 and UCP3 in both wild type and beta(3)-AR KO mice, whereas they increased the expression of PGC-1 in wild type mice only. Finally, acute (3 h) cold exposure increased the expression of UCP2 and UCP3, but not PGC-1, in skeletal muscle of both wild type and beta(3)-AR KO mice. These results show that selective stimulation of the beta(3)-AR affects the expression of UCP2, UCP3 and PGC-1 in skeletal muscle. This effect is probably indirect, as muscle does not seem to express beta(3)-AR. In addition, our data suggest that BRL 37344 and CGP 12177 act, in part, through an as yet unidentified receptor, possibly a beta(4)-AR.
Copyright 1999 Academic Press.
PMID: 10441518 [PubMed – indexed for MEDLINE]
Effects of obesity and stable weight reduction on UCP2 and UCP3 gene expression in humans.
Obes Res. 1999 Mar;7(2):133-40.
Vidal-Puig A, Rosenbaum M, Considine RC, Leibel RL, Dohm GL, Lowell BB.
Abstract – show
The molecular determinants of energy expenditure are presently unknown. Recently, two uncoupling protein homologues, UCP2 and UCP3, have been identified. UCP2 is expressed widely, and UCP3 is expressed abundantly in skeletal muscle. Both could be important regulators of energy balance. In this paper, we investigated whether altered UCP2 and UCP3 mRNA levels are associated with obesity or weight reduction.
UCP2, UCP3 long and short mRNA levels were examined in skeletal muscle and in white adipose tissue of lean, obese, and weight-reduced individuals by RNase protection assay.
Expression of UCP2, UCP3S, and UCP3L mRNA in skeletal muscle was similar in lean individuals and in individuals with obesity at stable weight. In contrast, UCP3L and UCP3S mRNAs were decreased by 38% (p<0.0059) and 48% (p<0.0047), respectively, in 20% weight-reduced patients with obesity at stable weight. In contrast, UCP2 mRNA levels were increased by 30% in skeletal muscle of 20% weight-reduced subjects with obesity. In a different set of patients, mostly lean, UCP3L mRNA in skeletal muscle was decreased by 28% (p = 0.0425) after 10% weight reduction at stable weight. Expression of UCP2 mRNA in subcutaneous adipose tissue was similar in lean individuals and in individuals with obesity, and was increased by 58% during active weight loss.
Stabilization at reduced body weight in humans is associated with a decrease in UCP3 mRNA in muscle. It is possible that reduced UCP3 expression could contribute to decreased energy expenditure in weight-stable, weight-reduced individuals.
PMID: 10102249 [PubMed – indexed for MEDLINE]
Leptin in relation to resumption of menses in women with anorexia nervosa.
Mol Psychiatry. 1998 Nov;3(6):544-7.
Audi L, Mantzoros CS, Vidal-Puig A, Vargas D, Gussinye M, Carrascosa A.
Abstract – show
Serum levels of leptin are decreased in underweight AN patients and increase with weight restoration. To assess the relationship of decreased leptin levels with other hormonal abnormalities in AN and to evaluate the possible role of increasing leptin levels, alone or in combination with other hormones, in the resumption of menses that accompanies weight gain, we studied cross-sectionally sixty-five consecutively enrolled AN patients. Subjects were divided in three groups: (I) underweight and amenorrheic; (II) weight-recovered but still amenorrheic; and (III) weight-recovered and eumenorrheic women. Patients in group I had decreased BMI, serum leptin, estradiol (E2), insulin-like growth factor 1 (IGF-1) and urinary growth hormone (GH) levels and increased sex hormone-binding globulin (SHBG) levels, compared to AN patients in groups II and III. Moreover, although no differences in leptin levels or BMI were observed between amenorrheic and eumenorrheic weight-recovered patients (groups II and III), free E2 and GH levels were higher (P<0.02) in weight-recovered, eumenorrheic women. Thus, it appears that leptin is a necessary, but not a sufficient, factor for the resumption of menses in AN patients.
PMID: 9857982 [PubMed – indexed for MEDLINE]
Mice expressing human but not murine beta3-adrenergic receptors under the control of human gene regulatory elements.
Diabetes. 1998 Sep;47(9):1464-71.
Ito M, Grujic D, Abel ED, Vidal-Puig A, Susulic VS, Lawitts J, Harper ME, Himms-Hagen J, Strosberg AD, Lowell BB.
Abstract – show
Beta-adrenergic receptors (ARs) are expressed predominantly in adipose tissue, and beta3-selective agonists are effective anti-obesity drugs in rodents. Rodent and human beta3-ARs differ with respect to expression in white versus brown adipocytes as well as their ability to be stimulated by beta3-AR-selective agonists. Humans express beta3-AR mRNA abundantly in brown but not white adipocytes, while rodents express beta3-AR mRNA abundantly in both sites. To determine the basis for this difference, we have transgenically introduced 74 kilobases (kb) of human beta3-AR genomic sequence into gene knockout mice lacking beta3-ARs. Importantly, human beta3-AR mRNA was expressed only in brown adipose tissue (BAT) of transgenic mice, with little or no expression being detected in white adipose tissue (WAT), liver, stomach, small intestine, skeletal muscle, and heart. This pattern of expression differed from that observed in mice bearing a murine beta3-AR genomic transgene in which beta3-AR mRNA was expressed in both WAT and BAT, but not in other sites. Furthermore, we have transgenically introduced smaller human constructs containing -14.5 and -0.6 kb of upstream sequence into beta3-AR gene knockout mice. Both -14.5 and -0.6 kb constructs were expressed in BAT but not WAT. Thus, human but not murine cis-regulatory elements direct beta3-AR gene expression preferentially to brown adipocytes. Identification of responsible cis-regulatory element(s) and relevant trans-acting factor(s) should provide insight into mechanisms controlling human beta3-AR gene expression. In addition, the beta3-AR agonist, CGP-12177, stimulated oxygen consumption in mice expressing human but not murine beta3-ARs by 91% compared with only 49% in control beta3-AR gene knockout mice, demonstrating that the human beta3-AR can functionally couple with energy expenditure. These "humanized" mice should assist us in the development of drugs that may become effective anti-obesity agents in humans.
PMID: 9726236 [PubMed – indexed for MEDLINE]
Troglitazone effects on gene expression in human skeletal muscle of type II diabetes involve up-regulation of peroxisome proliferator-activated receptor-gamma.
J Clin Endocrinol Metab. 1998 Aug;83(8):2830-5.
Park KS, Ciaraldi TP, Lindgren K, Abrams-Carter L, Mudaliar S, Nikoulina SE, Tufari SR, Veerkamp JH, Vidal-Puig A, Henry RR.
Abstract – show
Troglitazone, besides improving insulin action in insulin-resistant subjects, is also a specific ligand for the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma). To determine whether troglitazone might enhance insulin action by stimulation of PPARgamma gene expression in muscle, total PPARgamma messenger RNA (mRNA), and protein were determined in skeletal muscle cultures from nondiabetic control and type II diabetic subjects before and after treatment of cultures with troglitazone (4 days +/- troglitazone, 11.5 microM). Troglitazone treatment increased PPARgamma mRNA levels up to 3-fold in muscle cultures from type II diabetics (277 +/- 63 to 630 +/- 100 x 10(3) copies/microg total RNA, P = 0.003) and in nondiabetic control subjects (200 +/- 42 to 490 +/- 81, P = 0.003). PPARgamma protein levels in both diabetic (4.7 +/- 1.6 to 13.6 +/- 3.0 AU/10 microg protein, P < 0.02) and nondiabetic cells (7.4 +/- 1.0 to 12.7 +/- 1.8, P < 0.05) were also upregulated by troglitazone treatment. Increased PPARgamma was associated with stimulation of human adipocyte lipid binding protein (ALBP) and muscle fatty acid binding protein (mFABP) mRNA, without change in the mRNA for glycerol-3-phosphate dehydrogenase, PPARdelta, myogenin, uncoupling protein-2, or sarcomeric alpha-actin protein. In summary, we showed that troglitazone markedly induces PPARgamma, ALBP, and mFABP mRNA abundance in muscle cultures from both nondiabetic and type II diabetic subjects. Increased expression of PPARgamma protein and other genes involved in glucose and lipid metabolism in skeletal muscle may account, in part, for the insulin sensitizing effects of troglitazone in type II diabetes.
PMID: 9709955 [PubMed – indexed for MEDLINE]
The human uncoupling protein-3 gene. Genomic structure, chromosomal localization, and genetic basis for short and long form transcripts.
J Biol Chem. 1997 Oct 10;272(41):25433-6.
Solanes G, Vidal-Puig A, Grujic D, Flier JS, Lowell BB.
Abstract – show
Uncoupling protein-3 (UCP3) is a recently identified candidate mediator of adaptive thermogenesis in humans. Unlike UCP1 and UCP2, UCP3 is expressed preferentially and at high levels in human skeletal muscle and exists as short and long form transcripts, UCP3S and UCP3L. UCP3S is predicted to encode a protein which lacks the last 37 C-terminal residues of UCP3L. In the present study, we have defined the intron-exon structure for the human UCP3 gene and determined that UCP3S is generated when a cleavage and polyadenylation signal (AATAAA) located in the last intron prematurely terminates message elongation. In addition we have mapped UCP3 to the distal segment of human chromosome 11q13 (between framework markers D11S916 and D11S911), adjacent to UCP2. Of note, UCP2 and UCP3 in both mice and humans colocalize in P1 and BAC genomic clones indicating that these two UCPs are located within 75-150 kilobases of each other and most likely resulted from a gene duplication event. Previous studies have noted that mouse UCP2 maps to a region of chromosome 7 which is coincident with three independently mapped quantitative trait loci for obesity. Our study shows that UCP3 is also coincident with these quantitative trait loci raising the possibility that abnormalities in UCP3 are responsible for obesity in these models.
PMID: 9325252 [PubMed – indexed for MEDLINE]
Ligand-independent activation domain in the N terminus of peroxisome proliferator-activated receptor gamma (PPARgamma). Differential activity of PPARgamma1 and -2 isoforms and influence of insulin.
J Biol Chem. 1997 Aug 8;272(32):20230-5.
Werman A, Hollenberg A, Solanes G, Bjorbaek C, Vidal-Puig AJ, Flier JS.
Abstract – show
Peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the nuclear hormone receptor superfamily, and is an important regulator of adipogenesis and adipocyte gene expression. PPARgamma exists as two isoforms, PPARgamma1 and PPARgamma2, that differ only in their N termini. Both isoforms are activated by ligands that include the antidiabetic thiazoladinedione drugs and 15-deoxy-Delta12, 14-prostaglandin J2, and potential differences in their function have yet to be described. We report that, in addition to a ligand-activated transcriptional activity, when studied under conditions of ligand depletion, intact PPARgamma has a ligand-independent activation domain. To identify the basis for this ligand-independent activation, we used GAL4-PPARgamma chimeric expression constructs and UAS-TK-LUC in CV1 cells and isolated rat adipocytes. In both cell systems, isolated PPARgamma1 and PPARgamma2 N termini have activation domains, and the activation function of PPARgamma2 is 5-6-fold greater than that of PPARgamma1. Insulin enhances the transcriptional effect mediated by both PPARgamma1 and PPARgamma2 N-terminal domains. These data demonstrate that 1) PPARgamma has an N-terminal (ligand-independent) activation domain; 2) PPARgamma1 and PPARgamma2 N termini have distinct activation capacities; and 3) insulin can potentiate the activity of the N-terminal domain of PPARgamma.
PMID: 9242701 [PubMed – indexed for MEDLINE]
The organization, promoter analysis, and expression of the human PPARgamma gene.
J Biol Chem. 1997 Jul 25;272(30):18779-89.
Fajas L, Auboeuf D, Raspé E, Schoonjans K, Lefebvre AM, Saladin R, Najib J, Laville M, Fruchart JC, Deeb S, Vidal-Puig A, Flier J, Briggs MR, Staels B, Vidal H, Auwerx J.
Abstract – show
PPARgamma is a member of the PPAR subfamily of nuclear receptors. In this work, the structure of the human PPARgamma cDNA and gene was determined, and its promoters and tissue-specific expression were functionally characterized. Similar to the mouse, two PPAR isoforms, PPARgamma1 and PPARgamma2, were detected in man. The relative expression of human PPARgamma was studied by a newly developed and sensitive reverse transcriptase-competitive polymerase chain reaction method, which allowed us to distinguish between PPARgamma1 and gamma2 mRNA. In all tissues analyzed, PPARgamma2 was much less abundant than PPARgamma1. Adipose tissue and large intestine have the highest levels of PPARgamma mRNA; kidney, liver, and small intestine have intermediate levels; whereas PPARgamma is barely detectable in muscle. This high level expression of PPARgamma in colon warrants further study in view of the well established role of fatty acid and arachidonic acid derivatives in colonic disease. Similarly as mouse PPARgammas, the human PPARgammas are activated by thiazolidinediones and prostaglandin J and bind with high affinity to a PPRE. The human PPARgamma gene has nine exons and extends over more than 100 kilobases of genomic DNA. Alternate transcription start sites and alternate splicing generate the PPARgamma1 and PPARgamma2 mRNAs, which differ at their 5′-ends. PPARgamma1 is encoded by eight exons, and PPARgamma2 is encoded by seven exons. The 5′-untranslated sequence of PPARgamma1 is comprised of exons A1 and A2, whereas that of PPARgamma2 plus the additional PPARgamma2-specific N-terminal amino acids are encoded by exon B, located between exons A2 and A1. The remaining six exons, termed 1 to 6, are common to the PPARgamma1 and gamma2. Knowledge of the gene structure will allow screening for PPARgamma mutations in humans with metabolic disorders, whereas knowledge of its expression pattern and factors regulating its expression could be of major importance in understanding its biology.
PMID: 9228052 [PubMed – indexed for MEDLINE]
[Molecular genetics of non insulin dependent diabetes mellitus].
Med Clin (Barc). 1997 Jun 14;109(3):107-14.
Vidal-Puig A, Bjørbaek C.
PMID: 9289511 [PubMed – indexed for MEDLINE]
UCP3: an uncoupling protein homologue expressed preferentially and abundantly in skeletal muscle and brown adipose tissue.
Biochem Biophys Res Commun. 1997 Jun 9;235(1):79-82.
Vidal-Puig A, Solanes G, Grujic D, Flier JS, Lowell BB.
Abstract – show
Uncoupling proteins (UCPs) are inner mitochondrial membrane transporters which dissipate the proton gradient, releasing stored energy as heat. UCP1 is expressed exclusively in brown adipocytes while UCP2 is expressed widely. We now report the molecular cloning of a third uncoupling protein homologue, designated UCP3. At the amino acid level, hUCP3 is 71% identical to hUCP2 and 57% identical to hUCP1. UCP3 is distinguished from UCP1 and UCP2 by its abundant and preferential expression in skeletal muscle in humans, and brown adipose tissue and skeletal muscle in rodents. Since skeletal muscle and brown adipose tissue are believed to be important sites for regulated energy expenditure in humans and rodents, respectively, UCP3 may be an important mediator of adaptive thermogenesis. Since UCP3 is minimally expressed in human heart and other critical organs, it is a promising target for anti-obesity drug development aimed at increasing thermogenesis.
PMID: 9196039 [PubMed – indexed for MEDLINE]
Peroxisome proliferator-activated receptor gene expression in human tissues. Effects of obesity, weight loss, and regulation by insulin and glucocorticoids.
J Clin Invest. 1997 May 15;99(10):2416-22.
Vidal-Puig AJ, Considine RV, Jimenez-Liñan M, Werman A, Pories WJ, Caro JF, Flier JS.
Abstract – show
The peroxisome proliferator activated receptor (PPAR gamma) plays a key role in adipogenesis and adipocyte gene expression and is the receptor for the thiazolidinedione class of insulin-sensitizing drugs. The tissue expression and potential for regulation of human PPAR gamma gene expression in vivo are unknown. We have cloned a partial human PPAR gamma cDNA, and established an RNase protection assay that permits simultaneous measurements of both PPAR gamma1 and PPAR gamma2 splice variants. Both gamma1 and gamma2 mRNAs were abundantly expressed in adipose tissue. PPAR gamma1 was detected at lower levels in liver and heart, whereas both gamma1 and gamma2 mRNAs were expressed at low levels in skeletal muscle. To examine the hypothesis that obesity is associated with abnormal adipose tissue expression of PPAR gamma, we quantitated PPARgamma mRNA splice variants in subcutaneous adipose tissue of 14 lean and 24 obese subjects. Adipose expression of PPARgamma 2 mRNA was increased in human obesity (14.25 attomol PPAR gamma2/18S in obese females vs 9.9 in lean, P = 0.003). This increase was observed in both male and females. In contrast, no differences were observed in PPAR gamma1/18S mRNA expression. There was a strong positive correlation (r = 0.70, P < 0.001) between the ratio of PPAR gamma2/gamma1 and the body mass index of these patients. We also observed sexually dimorphic expression with increased expression of both PPAR gamma1 and PPAR gamma2 mRNAs in the subcutaneous adipose tissue of women compared with men. To determine the effect of weight loss on PPAR gamma mRNA expression, seven additional obese subjects were fed a low calorie diet (800 Kcal) until 10% weight loss was achieved. Mean expression of adipose PPAR gamma2 mRNA fell 25% (P = 0.0250 after a 10% reduction in body weight), but then increased to pretreatment levels after 4 wk of weight maintenance. Nutritional regulation of PPAR gamma1 was not seen. In vitro experiments revealed a synergistic effect of insulin and corticosteroids to induce PPAR gamma expression in isolated human adipocytes in culture. We conclude that: (a) human PPAR gamma mRNA expression is most abundant in adipose tissue, but lower level expression of both splice variants is seen in skeletal muscle; to an extent that is unlikely to be due to adipose contamination. (b) RNA derived from adipose tissue of obese humans has increased expression of PPAR gamma 2 mRNA, as well as an increased ratio of PPAR gamma2/gamma1 splice variants that is proportional to the BMI; (c) a low calorie diet specifically down-regulates the expression of PPAR gamma2 mRNA in adipose tissue of obese humans; (d) insulin and corticosteroids synergistically induce PPAR gamma mRNA after in vitro exposure to isolated human adipocytes; and (e) the in vivo modulation of PPAR gamma2 mRNA levels is an additional level of regulation for the control of adipocyte development and function, and could provide a molecular mechanism for alterations in adipocyte number and function in obesity.
PMID: 9153284 [PubMed – indexed for MEDLINE] PMCID: PMC508081
Regulation of PPAR gamma gene expression by nutrition and obesity in rodents.
J Clin Invest. 1996 Jun 1;97(11):2553-61.
Vidal-Puig A, Jimenez-Liñan M, Lowell BB, Hamann A, Hu E, Spiegelman B, Flier JS, Moller DE.
Abstract – show
The orphan nuclear receptor, peroxisome proliferator-activated receptor (PPAR) gamma, is implicated in mediating expression of fat-specific genes and in activating the program of adipocyte differentiation. The potential for regulation of PPAR gamma gene expression in vivo is unknown. We cloned a partial mouse PPAR gamma cDNA and developed an RNase protection assay that permits simultaneous quantitation of mRNAs for both gamma l and gamma 2 isoforms encoded by the PPAR gamma gene. Probes for detection of adipocyte P2, the obese gene product, leptin, and 18S mRNAs were also employed. Both gamma l and gamma 2 mRNAs were abundantly expressed in adipose tissue. PPAR gamma 1 expression was also detected at lower levels in liver, spleen, and heart; whereas, gamma l and gamma 2 mRNA were expressed at low levels in skeletal muscle. Adipose tissue levels of gamma l and gamma 2 were not altered in two murine models of obesity (gold thioglucose and ob/ob), but were modestly increased in mice with toxigene-induced brown fat ablation uncoupling protein diphtheria toxin A mice. Fasting (12-48 h) was associated with an 80% fall in PPAR gamma 2 and a 50% fall in PPAR gamma mRNA levels in adipose tissue. Western blot analysis demonstrated a marked effect of fasting to reduce PPAR gamma protein levels in adipose tissue. Similar effects of fasting on PPAR gamma mRNAs were noted in all three models of obesity. Insulin-deficient (streptozotocin) diabetes suppressed adipose tissue gamma l and gamma 2 expression by 75% in normal mice with partial restoration during insulin treatment. Levels of adipose tissue PPAR gamma 2 mRNA were increased by 50% in normal mice exposed to a high fat diet. In obese uncoupling protein diphtheria toxin A mice, high fat feeding resulted in de novo induction of PPAR gamma 2 expression in liver. We conclude (a) PPAR gamma 2 mRNA expression is most abundant in adipocytes in normal mice, but lower level expression is seen in skeletal muscle; (b) expression of adipose tissue gamma1 or gamma2 mRNAs is increased in only one of the three models of obesity; (c) PPAR gamma 1 and gamma 2 expression is downregulated by fasting and insulin-deficient diabetes; and (d) exposure of mice to a high fat diet increases adipose tissue expression of PPAR gamma (in normal mice) and induces PPAR gamma 2 mRNA expression in liver (in obese mice). These findings demonstrate in vivo modulation of PPAR gamma mRNA levels over a fourfold range and provide an additional level of regulation for the control of adipocyte development and function.
PMID: 8647948 [PubMed – indexed for MEDLINE] PMCID: PMC507341
Candidate genes for insulin resistance.
Diabetes Care. 1996 Apr;19(4):396-400.
Moller DE, Bjørbaek C, Vidal-Puig A.
Abstract – show
Insulin resistance confers increased susceptibility to NIDDM, atherosclerotic cardiovascular disease, ovarian hyperandrogenism, and possibly hypertension. Insulin resistance is largely inherited, in rare cases as a monogenic disorder or more commonly as a complex trait. The search for insulin resistance genes relies mainly on two complementary approaches: 1) positional cloning using random DNA markers present throughout the genome; and 2) the analysis of specific candidate genes. This report briefly summarizes the candidate gene approach to insulin resistance. Progress related to the analysis of genes encoding molecules that participate in insulin action is reviewed. In addition, the spectrum of potential genetic defects that might contribute to insulin resistance, both at the level of the target cell and secondarily (e.g., obesity genes), is discussed.
PMID: 8729172 [PubMed – indexed for MEDLINE]
Examination of the phosphoenolpyruvate carboxykinase gene promoter in patients with noninsulin-dependent diabetes mellitus.
J Clin Endocrinol Metab. 1996 Feb;81(2):503-6.
Ludwig DS, Vidal-Puig A, O'Brien RM, Printz RL, Granner DK, Moller DE, Flier JS.
Abstract – show
Expression of phosphoenolpyruvate carboxykinase (PEPCK), a rate-limiting enzyme in gluconeogenesis, is under dominant negative regulation by insulin. In this study, we sought to test the hypothesis that mutations in the PEPCK gene promoter may impair the ability of insulin to suppress hepatic glucose production, thereby contributing to both the insulin resistance and increased rate of gluconeogenesis characteristic of NIDDM. The proximal PEPCK promoter region in 117 patients with noninsulin-dependent diabetes mellitus and 20 obese Pima Indians was amplified by PCR and analyzed with single strand conformation polymorphism techniques. In addition, limited direct DNA sequencing was performed on the insulin response sequence and flanking regions. No DNA sequence polymorphisms were found in any patient. This result suggests that mutations in cis-acting PEPCK gene regulatory elements do not constitute a common cause of noninsulin-dependent diabetes mellitus. The significance of genetic variation in promoter regions to human disease is discussed.
PMID: 8636258 [PubMed – indexed for MEDLINE]
Genetic variability in the TNF-alpha promoter is not associated with type II diabetes mellitus (NIDDM).
Biochem Biophys Res Commun. 1995 Jun 26;211(3):833-9.
Hamann A, Mantzoros C, Vidal-Puig A, Flier JS.
Abstract – show
Recent evidence suggests that expression of tumor necrosis factor-alpha (TNF-alpha) by adipocytes is a molecular mediator of insulin resistance in obesity. We have therefore tested the hypothesis that variations within the regulatory region of the TNF-alpha gene, which might cause increased adipocyte or generalized TNF-alpha synthesis, are associated with NIDDM, a state in which insulin resistance is routinely observed. Neither the previously known variants within the TNF-alpha promoter at position -308 and -238, nor two newly identified polymorphisms at position -376 and -163, were found at a significantly higher frequency in Caucasian NIDDM patients compared to non-diabetic controls. No genetic variants were found in Pima Indians. These data make it unlikely that mutations within regulatory elements of the TNF-alpha gene are associated with an increase in the prevalence of NIDDM.
PMID: 7598712 [PubMed – indexed for MEDLINE]
Analysis of the hexokinase II gene in subjects with insulin resistance and NIDDM and detection of a Gln142–>His substitution.
Diabetes. 1995 Mar;44(3):340-6.
Vidal-Puig A, Printz RL, Stratton IM, Granner DK, Moller DE.
Abstract – show
Hexokinase II (HKII) is the predominant hexokinase isozyme expressed in insulin-responsive tissues. Since defects involving glucose transport and/or its phosphorylation to glucose-6-phosphate are present in muscle of insulin-resistant humans, HKII should be viewed as a candidate gene for inherited insulin resistance and susceptibility to non-insulin-dependent diabetes mellitus (NIDDM). To investigate the prevalence of potential mutations in the gene encoding HKII, we used the polymerase chain reaction (PCR) to amplify each of the 18 exons of the HKII gene from genomic DNA derived from 59 subjects: 25 insulin-resistant probands with clinical features of the type A syndrome and 34 NIDDM subjects enrolled in the United Kingdom Prospective Study of Therapies of NIDDM (UKPDS) who represented the highest percentile of fasting hyperinsulinemia in the UKPDS population of 5,098 subjects. PCR products corresponding to individual HKII exons derived from each subject were screened for the presence of nucleotide variation using a sensitive nonradioactive single-strand conformation polymorphism (SSCP) protocol. Variant SSCP patterns indicative of genetic variation were detected only in PCR amplimers containing exons 4-7, 10, 15, and 17. Direct sequencing of amplified DNA from individuals affected with variant SSCP patterns revealed the presence of the following silent polymorphisms: Asp251 (GAT/C) in exon 7 and Asn692 (AAT/C) in exon 15. SSCP variants detected in PCR products containing exons 5, 10, and 17 were due to single base substitutions in flanking intronic sequences. A polymorphic GGA repeat was identified within intron 5.(ABSTRACT TRUNCATED AT 250 WORDS)
PMID: 7883122 [PubMed – indexed for MEDLINE]
Tolerance to peripheral tissue is transient and maintained by tissue-specific class I expression.
Transplant Proc. 1994 Dec;26(6):3314-6.
Vidal-Puig A, Faustman DL.
PMID: 7998151 [PubMed – indexed for MEDLINE]
Hyperinsulinemia in polycystic ovary syndrome: relationship to clinical and hormonal factors.
Clin Investig. 1994 Nov;72(11):853-7.
Vidal-Puig A, Muñoz-Torres M, Jodar-Gimeno E, García-Calvente C, Lardelli P, Ruiz-Requena ME, Escobar-Jiménez F.
Abstract – show
We analyzed the association between hyperandrogenism and hyperinsulinemia, and their relationship to body mass index, in a large series of patients with polycystic ovary syndrome (PCOS). A characteristic hormonal profile was sought in women with marked hyperinsulinemia. The patient group consisted of 73 women with PCOS, ranging in age from 16 to 29 years. The control group consisted of 34 healthy women with no evidence of hyperandrogenism, aged 19-30 years. None of the patients or control women had a body mass index above 27 kg/m2. Follicle-stimulating hormone, luteinizing hormone, prolactin, testosterone, estradiol, androstenedione, dehydroepiandrosterone sulfate, sex hormone binding globulin, 17-hydroxyprogesterone, and free cortisol were determined by radioimmunoassay. The free testosterone index was calculated. The oral glucose tolerance test was used to analyze basal insulinemia, maximum insulin peak, and the insulinemia/glycemia index. In the group with PCOS body mass index was greater, free testosterone index was higher, and levels of dehydroepiandrosterone sulfate, testosterone, 17-hydroxyprogesterone (P < 0.001) and androstenedione (P < 0.05) were higher than in the control group. Of the insulin parameters, basal insulinemia, maximum insulin peak, and insulinemia/glycemia index were higher in the patient group (P < 0.001). In patients with marked insulinemia, free testosterone index was more markedly elevated, and gonadotrophin levels were normal. Our data confirm that a characteristic pattern of hyperinsulinemia is associated with PCOS. We found no causal relationship between hyperinsulinemia and androgen levels. A characteristic hormonal pattern was found in patients with marked hyperinsulinemia.
PMID: 7894211 [PubMed – indexed for MEDLINE]
Reduction of endogenous, ovarian and adrenal androgens with ketoconazole does not alter insulin response in the polycystic ovary syndrome.
J Endocrinol Invest. 1994 Sep;17(8):647-52.
Vidal-Puig A, Muñoz-Torres M, Garcia-Calvente C, Jodar-Gimeno E, Lardelli P, Ruiz-Requena ME, Escobar-Jiménez F.
Abstract – show
Several different strategies were used to investigate the relationship between hyperandrogenism and hyperinsulinemia associated with polycystic ovary syndrome. Ketoconazole was given orally (400 mg/day) for 9 months to evaluate the effect of reduction in ovarian and adrenal androgens on insulin response (oral glucose tolerance test) in 35 women with polycystic ovary syndrome. Androgenic steroids (testosterone, androstenedione, dehydroepiandrosterone sulphate, and free testosterone index) decreased (p < 0.01), but basal insulinemia, maximum peak insulin, and insulin/glucose ratio showed no significant changes. One month after treatment was stopped, free testosterone index, and serum concentrations of androstenedione and testosterone, increased (p < 0.05), but no alterations were noted in insulin parameters. Body mass index was stable throughout the ten-month study period. Our findings suggest that endogenous androgens, no matter whether they are of ovarian or adrenal origin, do not play a major role in the modulation of hyperinsulinemia in patients with polycystic ovary syndrome.
PMID: 7868804 [PubMed – indexed for MEDLINE]
Comparative sensitivity of alternative single-strand conformation polymorphism (SSCP) methods.
Biotechniques. 1994 Sep;17(3):490-2, 494, 496.
Vidal-Puig A, Moller DE.
Abstract – show
Single-strand conformation polymorphism (SSCP) analysis is a genetic screening technique that allows for the rapid detection of single nucleotide substitutions in fragments of PCR-amplified genomic DNA or cDNA. Several alternative protocols are now being commonly used to resolve differences in electrophoretic mobility of single-stranded DNA fragments. The aim of this study was to directly compare the sensitivity of three popular SSCP methods using a panel of 19 known human mutations/polymorphisms present in genomic DNA samples. Using a single electrophoresis protocol, 95% of the mutations were detected using small-format PhastGel and the PhastSystem. Large-format gels (5% polyacrylamide and Hydrolink-MDE) were tested both with and without the addition of 10% glycerol. The sensitivity for polyacrylamide and Hydrolink-MDE gels without glycerol was 89% and 79%, respectively, and 68% or 63%, respectively, for glycerol-containing gels. However, all mutations were detected with either polyacrylamide or Hydrolink-MDE when both glycerol and non-glycerol gels were examined. We conclude that comparable very high detection efficiency can be achieved using the PhastSystem or by using a combination of two large-gel conditions with either polyacrylamide or Hydrolink-MDE.
PMID: 7818902 [PubMed – indexed for MEDLINE]
Ketoconazole therapy: hormonal and clinical effects in non-tumoral hyperandrogenism.
Eur J Endocrinol. 1994 Apr;130(4):333-8.
Vidal-Puig AJ, Muñoz-Torres M, Jódar-Gimeno E, García-Calvente CJ, Lardelli P, Ruiz-Requena ME, Escobar-Jiménez F.
Abstract – show
The aim of this study was to assess the usefulness of ketoconazole as a therapeutic alternative to polycystic ovary syndrome. The study group comprised 37 women with signs of hyperandrogenism (hirsutism, acne) and oligomenorrhea. A low dose (400 mg/day) of ketoconazole was tested in a 9-month prospective clinical study. Clinical response (Ferriman & Gallway score, acne) and modifications in hormone pattern (luteinizing hormone, follicle-stimulating hormone, estradiol, testosterone, prolactin, 17-hydroxy-progesterone, androstenedione, steroid hormone-binding globulin, dehydroepiandrosterone sulfate, cortisol, adrenocorticotropin (ACTH) and free testesterone index) were measured, and ACTH stimulation tests were performed. Tolerance and side-effect also were assessed. After 9 months of ketoconazole treatment, the patients' Ferriman & Gallway scores (18.26 +/- 4.6 vs 12.4 +/- 4.1; p < 0.001) and acne had improved markedly. Hormone patterns also became more favorable, with decreases in androgenic steroids (testosterone, androstenedione, free testosterone index and dehydroepiandrosterone sulfate; p < 0.01) and increases in estradiol (p < 0.01). Basal cortisol levels and cortisol after ACTH stimulation were not changed significantly, remaining within the reference range. Increases in ACTH were observed only in the 3rd month (p < 0.01). Initial levels of androgenic steroids were correlated inversely with their percentage decrease in successive samplings. Decreases in adrenal androgenic steroids were associated with an increase in steroid hormone-binding globulin. The side-effects of treatment, although not severe, caused some discomfort and led to a high drop-out rate (30%).(ABSTRACT TRUNCATED AT 250 WORDS)
PMID: 8162160 [PubMed – indexed for MEDLINE]
[Lipid profile of hyperandrogenic women undergoing treatment with ketoconazole and its relationship with the evolution of the hormone pattern].
Med Clin (Barc). 1993 Dec 11;101(20):766-8.
Vidal-Puig A, Muñoz-Torres M, García Calvente C, Lardelli P, Jódar Gimeno E, Cano M, Ruiz Requena ME, Escobar-Jiménez FE.
Abstract – show
Previous studies have demonstrated changes in the lipidic profile following treatment with ketoconazole. However, the possible influence in patients with hyperandrogenism treated with this drug and its possible relation with the evolution of the hormonal pattern is unknown.
Thirty-seven women with no tumoral hyperandrogenism treated with ketoconazole for 9 months (400 mg/day) were studied during treatment and one month after suppression of the medication. The study included the evaluation of total cholesterol, HDL cholesterol, triglycerides, LDL cholesterol and hormonal determinations of estradiol, androstenedione, testosterone, dehydroepiandrosterone, sulphate and sex hormone binding globulin.
A rapid and significant decrease of LDL cholesterol and total cholesterol was observed (p < 0.01) which was reversible upon discontinuation of treatment. The HDL cholesterol levels and triglycerides did not modify. The final hormonal profile was more favorable with a significant reduction of testosterone and dehydroepiandrosterone sulphate (p < 0.01) and an increase in estradiol (p < 0.01). No statistical correlation was observed between the changes of sexual steroids and the changes in the lipidic pattern.
In patients with non tumoral hyperandrogenism treated with ketoconazole the modifications of the steroid hormone profile do not appear to be related with changes in lipidic metabolism.
PMID: 8114536 [PubMed – indexed for MEDLINE]
[Adrenal androgens: traditionally forgotten hormones. Today, of current importance].
An Med Interna. 1993 Nov;10(11):559-64.
Vidal-Puig A, García-Calvente C, Muñoz Torres M.
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Androgens have been some traditionally forgotten hormones because, apparently, they do not play a main role in any pathology. However, the conviction that hormones circulating at such a high plasmatic concentration must have a biologic function, have promote an active research in this field, resulting in a better understanding of the regulation mechanisms of the synthesis of these hormones, as well as demonstrating its potential relationship with the etiopathogenicity of such important pathologies as obesity, arteriosclerosis or diabetes. In the present review, we approach the specific regulation mechanisms of synthesis of adrenal androgens, as well as their implications in severe physiological and pathological conditions.
PMID: 8117874 [PubMed – indexed for MEDLINE]
[New trends in the definition and diagnostic criteria of polycystic ovary syndrome].
Med Clin (Barc). 1993 Mar 13;100(10):389-93.
Vidal-Puig A, Muñoz-Torres M, Escobar-Jiménez F.
PMID: 8474284 [PubMed – indexed for MEDLINE]
Dehydroepiandrosterone sulfate and other possible influencing factors that modulate sex hormone-binding globulin levels in the hirsute patient.
J Steroid Biochem Mol Biol. 1992 Jul;42(6):607-11.
Vidal-Puig A, Muñoz-Torres M, Escobar-Jiménez F, Ruiz Requena ME, Garcia-Calvente C, Torres-Vela E.
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This study was designed to investigate the most important factors affecting serum concentrations of sex hormone-binding globulin (SHBG) in women with hirsutism. We compared endocrine profiles based on biochemical measurements of LH, FSH, oestradiol, testosterone (T), prolactin, 17-hydroxy-progesterone, dehydroepiandrosterone sulphate (DHEAS), SHBG, cortisol and insulin in the follicular phase in 32 healthy women and 52 patients. The study group was subdivided according to SHBG levels into Group A (low level) and Group B (high level). Significant differences between Groups A and B were found in DHEAS and T levels, but not in body mass index or insulinaemia. There was a relationship between DHEAS and SHBG levels (r = 0.51) and between T and SHBG (r = 0.31). We conclude that DHEAS may be a significant modulator of SHBG in the female hirsute patient, an observation seldom mentioned in previous reports.
PMID: 1386249 [PubMed – indexed for MEDLINE]
[Primary hypothyroidism associated with changes in the sella turcica and the hypophyseal function. Description of 5 cases].
Rev Clin Esp. 1990 Apr;186(6):274-6.
Muñoz Torres M, Céspedes Mas S, Díaz de Madrid J, Vidal Puig A, Alvarez Cienfuegos E, Escobar Jiménez F.
Abstract – show
We report 5 clinical cases of primary hypothyroidism or premixedema with associated pituitary lesion. Before treatment was started with L-thyroixine (L-T4) pituitary hormones were examined and an X-ray of the silla turca as well as a CT scan of the hypophysis (CTH) was done. Once supplementation treatment was started hormone levels normalized. In three out of the 5 cases, CT scan done after establishing therapy, showed empty silla turca. Therefore, me stress the importance of closely examining the pituitary gland in patients with untreated primary hypothyroidism.
PMID: 2392582 [PubMed – indexed for MEDLINE]