Association between DNA methylation of the <i>KITLG</i> gene and cortisol levels under stress: a replication study

<p>A recent study reported for the first time, that DNA methylation of the <i>KITLG</i> gene mediates the association between childhood trauma and cortisol stress reactivity. Our study aimed to provide the first independent replication of these findings. ESPRIT is a prospective study of community-dwelling participants (age ≥ 65), randomly selected from the electoral rolls of the Montpellier district, in France. Clinical depression was assessed using the Mini-International Neuropsychiatric Interview (MINI, French version 5.00), and the Centre for Epidemiological Studies Depression Scale (CES-D). Experiences of childhood adversity were ascertained <i>via</i> a 25-item questionnaire. Morning, evening, and diurnal salivary cortisol was measured under basal and stress conditions and determined using direct radioimmunoassay analysis. DNA methylation of the <i>KITLG</i> gene was quantified in whole blood using the SEQUENOM MassARRAY EpiTYPER platform. A significant negative association was observed between <i>KITLG</i> DNA methylation and both morning cortisol (β = −1.846 ± 0.666, <i>p</i> = .007) and diurnal cortisol (area under curve [AUC]) (β = −19.429 ± 8.868, <i>p</i> = .031) under a stress condition. However, only the former association was significant after correcting for multiple testing. Further, this association remained after adjusting for age, sex, and depression status. No significant association was observed between childhood trauma and <i>KITLG</i> DNA methylation in this older population. This study provides support for an association between <i>KITLG</i> methylation and stress cortisol levels, suggesting that DNA methylation of this gene may play a role in the longer term regulation of the stress system.Lay summary</p><p>  The significant negative association between <i>KITLG</i> DNA methylation and morning cortisol, measured under a stressful condition, suggests that individuals with higher <i>KITLG</i> methylation will secrete lower levels of cortisol whilst under stress.</p><p></p> <p>  The significant negative association between <i>KITLG</i> DNA methylation and morning cortisol, measured under a stressful condition, suggests that individuals with higher <i>KITLG</i> methylation will secrete lower levels of cortisol whilst under stress.</p>