Role of NR3C1 and SLC6A4 methylation in the HPA axis regulation in burnout.

Background: Work-related stress and burnout have become major occupational health concerns. Dysregulation of HPA axis is considered one of the central mechanisms and is potentially moderated through epigenetics. In the present study, we aim to investigate epigenetic regulation of the HPA axis in burnout, by focusing on salivary cortisol and cortisone and DNA methylation of the glucocorticoid receptor gene (NR3C1) and the serotonin transporter gene (SLC6A4).

Methods: We conducted a cross-sectional study with 59 subjects with burnout and 70 healthy controls recruited from the general population. All participants underwent a clinical interview and psychological assessment. Saliva samples were collected at 0, 30 and 60 min after awakening and were used to quantify cortisol and cortisone. Pyrosequencing was performed on whole blood-derived DNA to assess DNA methylation.

Results: There were no between-group differences in cortisol levels, whereas burnout participants had higher levels of cortisone. Job stress was associated with increased cortisol and cortisone. We observed both increased and decreased NR3C1 and SLC6A4 methylation in the burnout group compared to the control group. Some of these methylation changes correlated with burnout symptoms dimensionally. Increased methylation in a specific CpG in the SLC6A4 promoter region moderated the association between job stress and burnout. DNA methylation in this CpG was also associated with increased cortisol. In addition, average methylation of NR3C1 was negatively associated with cortisone levels.

Limitations: This is a cross-sectional study and therefore no conclusions on causality could be made.

Conclusions: We provide first evidence of changes in DNA methylation of NR3C1 and SLC6A4 in burnout, which were further associated with cortisol and cortisone. Further, increased cortisol and cortisone seemed to reflect job stress rather than burnout itself.