Measures of adiposity predict interleukin-6 responses to repeated psychosocial stress.

OBJECTIVE Overweight and obese individuals, who comprise approximately two-thirds of the U.S. population, are at increased risk for developing a range of diseases. This increased risk may be due in part to maladaptive stress responses within this group, including heightened low-grade inflammation and HPA axis non-habituation. In this study we tested the relationship between adiposity, plasma interleukin-6 (IL-6) and HPA axis responses to repeated stress. METHODS Sixty-seven healthy participants were exposed to the Trier Social Stress Test (TSST) on two consecutive days. We collected saliva for cortisol measurements at baseline and at 1, 10, 30, 60 and 120min post-TSST, and blood for plasma IL-6 measurements at baseline and 30 and 120min post-TSST. RESULTS Stress exposure induced significant increases of cortisol and IL-6 on both days (cortisol: F=38, p<0.001; IL-6: F=90.8; p<0.001), and repeated exposure was related with cortisol habituation (F=8.2; p<0.001) and IL-6 sensitization (F=5.2; p=0.022). BMI and body fat were related with higher cortisol responses to repeated stress (BMI: beta=0.34; p=0.014; body fat: beta=0.29; p=0.045), and with higher IL-6 responses to repeated stress (BMI: beta=0.27, p=0.044; body fat: beta=0.37; p=0.006). CONCLUSIONS Taken together, individuals with higher measures of adiposity showed less efficient HPA axis habituation as well as sensitization of IL-6 responses to repeated acute stress. These findings point to maladaptive stress response patterns in overweight humans, which, through exposure to higher levels of inflammatory mediators, might partially explain diseases related with overweight and/or obesity.