Genetic variants in the glucocorticoid receptor gene (NR3C1) and cardiovascular disease risk: The Leiden 85-plus Study
Maris Kuningas, Simon P. Mooijaart, P. Eline Slagboom, Rudi G. J. Westendorp, and Diana van Heemst

Received: 23 December 2005 / Accepted: 30 January 2006 / Published online: 5 May 2006
Springer Science+Business Media, Inc. 2006

Abstract:
Recently, the ER22/23EK, N363S, and BclI polymorphisms in the glucocorticoid receptor (GR) gene have been linked to altered cortisol sensitivity and cortisol-associated disorders. This study aims to investigate the effect of these genetic variants in the GR gene on cardiovascular disease and mortality in elderly individuals aged 85 years and over. In the population-based Leiden 85-plus Study, 552 participants were genotyped for the ER22/23EK, N363S, and BclI polymorphisms. The effects of the polymorphisms on metabolic profile, body composition, and the prevalence of cardiovascular pathologies at baseline were assessed. All-cause and cardiovascular disease mortality risks dependent on the SNPs were calculated after a 4.2-year follow-up.

The analyses of metabolic profile revealed that carriers of the ER22/23EK polymorphism have higher HbA1C levels (P < 0.001), and carriers of the N363S SNP have higher LDL cholesterol (P < 0.001) and triglyceride concentrations (P=0.03) compared to non-carriers. The only significant association between genotype and body composition analyses was for height and the ER22/23EK polymorphism. Men carrying the ER22/23EK polymorphism were taller (P=0.02) compared to non-carriers. No associations with cardiovascular pathologies, all-cause, and cardiovascular mortality were observed for any of the polymorphisms. We conclude that, despite the effect of the ER22/23EK and N363S SNPs on metabolism, these polymorphisms together with the BclI SNP do not affect the risks of cardiovascular disease and survival at old age.

Keywords:
Ageing, Cardiovascular disease, Glucocorticoid receptor, Metabolism, Survival

M. Kuningas, S. P. Mooijaart, R. G. J. Westendorp, D. van Heemst (&) 
Department of Gerontology and Geriatrics C-R, Leiden University Medical Center (LUMC), PO box, RC Leiden, The Netherlands
e-mail: D.van_Heemst@lumc.nl 

Introduction:
In response to various stimuli, including stress, cortisol coordinates metabolic, endocrine, immune, and nervous system responses (Chrousos 1995, 1998; Munck et al. 1984; de Kloet et al. 1998; McEwen 1998). Cortisol exerts the majority of its functions through glucocorticoid receptors (GRs). Disturbances in cortisol signaling resulting from either altered hormone availability or decreased/increased receptor-mediated signal transduction have been associated with a variety of phenotypes including cardiovascular disease which is a major cause of death at old age.

It is known that sensitivity to cortisol varies considerably between individuals as demonstrated by the dexamethasone suppression test (Huizenga et al. 1998b). Therefore, the underlying susceptibility to cortisol-associated disorders may vary. A degree of inter-individual variation in responsiveness to cortisol is attributable to three polymorphisms in the GR gene (NR3C1). Recently an ER22/23EK variation in the GR gene was associated with resistance to cortisol, and shown to result in a better metabolic and cardiovascular health profile, leading to an increased survival rate (van Rossum et al. 2002, 2004a, b). On the other hand, increased sensitivity to cortisol related to the N363S (Huizenga et al. 1998a) and BclI (van Rossum et al. 2003) polymorphisms has been shown to cause opposite effects. In middle-aged subjects, the N363S and BclI polymorphisms were associated with an increased body mass index (BMI) and with several risk factors for atherosclerosis and coronary artery disease (Lin et al. 2003; van Rossum et al. 2003; Di Blasio et al. 2003). Together these results suggest that the GR gene plays an important role in modulating susceptibility to cardiovascular disease. However, there are disparities in the published literature. For instance, in some studies associations between these three polymorphisms and metabolic parameters or body composition have been found (van Rossum et alThis text seems to be formatted properly and there are no spelling mistakes. However, there are some minor grammatical errors and awkward phrasing in some sentences. Here is the processed text:

The study involved a practitioner or nursing home physician. Electrocardiograms were recorded on a Siemens Sic-card 440 and transmitted by telephone to the ECG Core Lab in Glasgow for automated Minnesota coding (Macfarlane and Latif 1996). Cardiovascular pathologies were classified as myocardial infarction, myocardial ischemia, intermittent claudication, or stroke (van Exel et al. 2002).

DNA was available for 563 participants, of which 11 were excluded due to the use of corticosteroids. The baseline characteristics of the remaining 552 participants are presented in Table 1. All study subjects were genotyped for the ER22/23EK, N363S, and BclI polymorphisms with a genotyping error of lower than 5%. Therefore, the total number of analyzed participants was 540 for ER22/23EK, 548 for N363S, and 526 for the BclI polymorphisms. The minor allele frequencies were 0.03, 0.05, and 0.34 for the ER22/23EK, N363S, and BclI polymorphisms, respectively. The overall genotype distributions and resulting allelic frequencies of the SNPs were in agreement with the distribution predicted by the Hardy-Weinberg equilibrium.

In this study, the calculated allele and genotype frequencies did not differ between elderly and young subjects (n=370, median age 32 years) (data not shown).