Circulating leptin and stress-induced cardiovascular activity in humans

Obesity is associated with an elevated risk of hypertension and cardiovascular disease. The adipocyte hormone leptin, which stimulates energy expenditure in animals by activating the sympathetic nervous system (SNS), is believed to play a role in this association. However, evidence in humans remains sparse. We investigated the relationship between circulating leptin and cardiovascular and inflammatory responses to acute psychological stress in humans. Participants were 32 men and 62 women aged 18-25 years. Cardiovascular activity was assessed using impedance cardiography at baseline, during acute laboratory stress, and during a 45-min recovery period. Plasma cytokines were measured in blood drawn at baseline and 45-min poststress. In women only, baseline plasma leptin was significantly associated with stress-induced changes in heart rate (beta = 0.53, P = 0.006), heart rate variability (HRV) (beta = -0.44, P = 0.015), and cardiac preejection period (PEP) (beta = -0.51, P = 0.004), independent of age, adiposity, and smoking. Women's plasma leptin levels also correlated with stress-induced elevations in the proinflammatory cytokine interleukin-6 (IL-6) (beta = 0.35, P = 0.042). Circulating leptin is an independent predictor of sympathetic cardiovascular activity, parasympathetic withdrawal, and inflammatory responses to stress in women. Because cardiovascular and inflammatory stress responses are predictive of future cardiovascular disease, leptin may be a mechanism mediating the adverse effects of stress and obesity on women's cardiovascular health.