Association of a common mineralocorticoid receptor gene polymorphism with salivary cortisol in healthy adults.

A common polymorphism of the mineralocorticoid receptors (MR) gene has been associated with cortisol levels after dexamethasone. However, if and how this MR gene variant affects basal cortisol secretion throughout the day is unknown. The aim of our study was to examine the association between the MR gene polymorphism -2G/C (rs2070951) and salivary cortisol measured at four time points during the day in the Stress, Atherosclerosis, and ECG Study (STRATEGY). We recruited healthy adults from the general population (n=133, distributed equally across four age groups, 30-70 years). Salivary cortisol was assessed at 0800, 1200, 1600 and 2200 h. We found a significant effect of genotype indicating that homozygous G allele carriers had higher overall salivary cortisol levels (F=4.5, p=0.01). Furthermore, we found a significant time × group interaction indicating that the group effect was predominantly driven by higher 0800 h salivary cortisol levels in G/G homozygotes (F=2.9, p=0.02). Participants homozygous for the G allele also had greater area under the curve (AUC) cortisol secretion compared to C allele carriers (F=6.4, p=0.01). Our findings suggest that being homozygous for the G allele of the MR gene polymorphism -2G/G is associated with higher cortisol levels in healthy adults, especially in the morning during peak cortisol secretion. This polymorphism may contribute to the interindividual variability in stress responsiveness and might be involved in stress-related disorders.