Associations between DNA methylation of a glucocorticoid receptor promoter and acute stress responses in a large healthy adult population are largely explained by lifestyle and educational differences

BACKGROUND Glucocorticoids are the key regulators of the biological stress response and act by binding to glucocorticoid receptors (GR). Expression of GR is altered by DNA methylation. Methylation patterns in GR promoters have been shown to be highly variable between individuals, but little is known about the functional consequences of this variation for the acute stress response. The present study investigated associations between methylation status of the GR 1-C promoter and cortisol, cardiovascular and perceived stress responses to a psychosocial stress protocol in a large healthy adult population. METHODS A total of 725 overall healthy men and women, aged 55-60 years, participated in a standardized psychosocial stress protocol consisting of three different stressors. At different stages during the stress protocol, salivary cortisol levels, continuous blood pressure and heart rate (HR) levels as well as perceived stress were measured. Stress reactivity was calculated as the increase between basal and peak measurements. Methylation status of the GR 1-C promoter was assessed in DNA isolated from peripheral blood samples using a methylation sensitive PCR assay for 675 of the 725 participants. RESULTS A decrease in methylation of the GR 1-C promoter was associated with a decrease in stress reactivity as indicated by lower cortisol and lower HR reactivity. A 1% decrease in GR 1-C methylation corresponded with a cortisol decrease by 0.14% (95% CI: 0.03-0.25, p=0.02) and an HR decrease by 0.10 bpm (0.03-0.16, p=0.003). Adjusting for sex, lifestyle and education largely abolished these associations. A decrease in methylation of the GR 1-C promoter was also associated with an increase in stress perception as indicated by higher perceived stress (0.03 points [0.00-0.06, p=0.05]), lower perceived performance (-0.03 points [-0.05 to -0.01], p=0.02), and lower perceived control (-0.03 points [-0.05 to 0.00], p=0.04). After adjusting for sex and educational level the associations were no longer statistically significant. GR 1-C methylation status was not associated with blood pressure responses to the stress protocol. DISCUSSION Although effects were small, variation in methylation status in the GR 1-C promoter was associated with physical and perceived acute stress responses. Interestingly, these associations could largely be explained by differences in lifestyle and education.