Social isolation and depressed mood are associated with elevated serum leptin levels in men but not in women

Background: Leptin, involved in energy homeostasis and a predictor of cardiovascular disease, has recently been recognized as mediator in stress reactions. We aimed to explore the association between leptin levels and two stress-related conditions, social isolation and depressed mood, both associated with increased cardiovascular mortality. Methods: We analysed leptin levels in 1229 subjects (643 men, 586 women), derived from the population-based MONIKA/KORA study. Standardized questionnaires were used to assess depressive mood and social isolation. In a multiple linear regression adjusted for body weight, age and survey, the association between leptin, social isolation and depressed mood and its interaction was explored in men and women separately. Leptin was then dichotomized and four analyses, adjusted for age, BMI, lifestyle factors, psychosomatic complaints and metabolic variables were performed to compare the risk of elevated leptin levels in the risk groups. Results: Increased leptin levels were associated with social isolation (p = 0.04) and the interaction between social isolation and depressed mood ( p = 0.02) in men but not in women. In socially isolated and depressed men, leptin levels (mean: 6.07 ng/ml) were significantly increased compared to neither depressed nor isolated men (mean: 4.51 ng/ml, p = 0.04). In the multivariate adjusted logistic regression model, the combination of depressed state and social isolation was associated with a 4-fold increased risk ( p < 0.001) for elevated leptin levels. Conclusion: The finding of elevated leptin levels in socially isolated and depressed men raises the possibility that increased cardiovascular mortality in socially isolated men is partially mediated by hyperleptinemia. (C) 2010 Elsevier Ltd. All rights reserved.