Genes and Extreme Longevity

Catalina Santiago,1,* Nuria Garatachea,2,* Thomas Yvert,1 Gabriel Rodr´ıguez-Romo,3 Alejandro Santos-Lozano,2 Carmen Fiuza-Luces,1 and Alejandro Lucia1

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Abstract

Genes of the proliferator-activated receptor delta (PPARD)-peroxisome proliferator-activated receptor c coactivator 1a (PPARGC1A, also termed PGC1-a)-nuclear respiratory factor (NRF)-mitochondrial transcrip- tion Factor A (TFAM) mitochondriogenesis pathway can influence health/disease phenotypes, yet their as- sociation with extreme longevity is not known. We studied the association of five common polymorphisms in genes of this pathway (rs2267668, rs8192678, rs6949152, rs12594956, rs1937) and extreme longevity using a case (107 centenarians)–control (284 young adults) design. We found no between-group differences in allele/ genotype frequencies, except for CC genotype in rs1937 ( p = 0.003), with no representation in controls (0%), versus 2.8% in centenarians (2 men, 1 woman). In summary, the studied genetic variants of the PPARD- PPARGC1A-NRF-TFAM pathway were not associated with extreme longevity, yet a marginal association could exist for rs1937.

Introduction

coactivator 1a (PPARGC1A, also termed PGC1-a)-nuclear respiratory factor (NRF)-mitochondrial transcription Factor A (TFAM) pathway. Briefly, PPARD induces promotion of PPARGC1A,15 which is the first stimulator of mitochon- driogenesis. NRF1 and 2 (the latter being also known as GA- binding protein alpha chain [GABPA]) are intermediate transcription factors that stimulate the synthesis of TFAM, which is the final effector activating the duplication of mi- tochondrial DNA molecules.16–18

ganelles for understanding the aging process.1 They are both the main source and target of reactive oxygen spe- cies, and accumulation of somatic mutations in mitochon- drial DNA (mtDNA) is one of the main features that accompany the age-related loss of mitochondrial function.2 Because mtDNA haplotypes or haplogroups (i.e., non- pathogenic mtDNA populations that form a series of popu- lation-specific lineages) might influence individual suscepti- bility to mtDNA damage, they could theoretically influence human aging. Yet their association with extreme longevity, i.e., reaching ‡100 years of age, is controversial.3–8 Because extreme longevity is partly influenced by genetic factors,9 other genetic variants related to mitochondrial function might be involved in the heritability of this rare phenotype.

Several genetic variants could affect the PPARD-PPARGC1A- NRF-TFAM pathway and thus influence several important health/disease phenotypes related to mitochondrial func- tion. For instance, a common missense variation (Gly482Ser, rs8192678) at exon 8 of PPARGC1A gene has been repeatedly associated with type 2 diabetes19–22 and with related traits, including insulin resistance,23 obesity,24,25 hypertension,26–28 dyslipidemia,29 or aerobic fitness.30 The aforementioned poly- morphism and the A/G (rs2267668) variation in PPARD are independently implicated in the modulation of insulin sen- sitivity or aerobic fitness,31 and rs2267668 has also been as- sociated with muscle mass.32 Common variants in NRF genes (NRF1 A/G [rs6949152] and NRF2 A/C [rs12594956]) influence aerobic fitness phenotypes,33–35 whereas the TFAM Ser12Thr (rs1937) variation has been associated with late- onset36–38 or sporadic Alzheimer disease.39 Yet, no candi- date gene association study has analyzed whether genetic

taining their normal function as well as for ensuring the functional and structural integrity of post-mitotic tissues.10 Yet the capacity for mitochondrial biogenesis (or mitochon- driogenesis) diminishes with age,11,12 and is responsible for many of the deleterious effects of aging, including loss of muscle mass and function, i.e., sarcopenia.13,14 Mitochondrial synthesis is stimulated by the proliferator-activated receptor delta (PPARD)-peroxisome proliferator-activated receptor c

1Universidad Europea de Madrid, Madrid, Spain. 2Facultad de Ciencias de la Salud y del Deporte, Universidad de Zaragoza, Huesca, Spain. 3INEF, Universidad Polite´cnica, Madrid, Spain.

During years 2008–2010, we extracted genomic DNA from saliva samples in 284 individuals (150 women, 134 men).

variants of the PPARD-PPARGC1A-NRF-TFAM mitochon- driogenesis pathway can influence extreme longevity. Here, we have studied the association of five common polymor- phisms in the aforementioned pathway (rs8192678, rs2267668, rs2267668, rs6949152, and rs12594956) and ex- treme longevity in a Spanish (Caucasian) cohort using a case–control design.

Genotype assessment

Genotyping was performed specifically for research pur- poses. The researchers in charge of genotyping were totally blinded to the participants’ identities, i.e., saliva samples were tracked solely with barcoding and personal identities were only made available to the main study researcher who was not involved in actual genotyping. We used the classical phenol-chloroform DNA extraction protocol with alcoholic precipitation. Genomic DNA was resuspended in 50lL of milli-Q H O and stored at -20(cid:2)C. 2

Methods

The study was designed and carried out in accor- dance with the recommendations for the human genotype– phenotype association studies recently published by the National Cancer Institute–National Human Genome Re- search Institute (NCI-NHGRI) Working Group on Replica- tion in Association Studies.40 These recommendations include among others, the following items: Indicating time period and location of subject recruitment, success rate for DNA acquisition, and sample tracking methods.