The relation of leptin and insulin with obesity-related cardiovascular risk factors in US adults.

Previous studies of leptin with cardiovascular disease (CVD) risk factors have been limited by clinical samples or lack of representation of the general population. This cross-sectional study, designed to examine whether leptin or insulin may mediate the endogenous relation of obesity with metabolic, inflammatory, and thrombogenic cardiovascular risk factors, included 522 men and 514 women aged >or=40 years who completed a physical examination during the third National Health and Nutrition Examination Survey. Participants were free of existing CVD, cancer (except non-melanoma skin cancer), diabetes, or respiratory disease. In multivariable analyses adjusted for race/ethnicity and lifestyle factors, waist circumference (WC) was positively associated with blood pressure, triglyceride, LDL cholesterol, total cholesterol:HDL ratio, apolipoprotein B, C-reactive protein (CRP), and fibrinogen concentrations, and negatively associated with HDL cholesterol and apolipoprotein A1 levels. The associations of WC with the metabolic CVD risk factors were largely attenuated after adjustment for insulin levels, while the associations of WC with the inflammatory and thrombogenic factors (CRP and fibrinogen, respectively) were largely explained by adjustment for leptin concentrations. However, leptin levels were not independently associated with CRP and fibrinogen in men and CRP in women when adjusted for WC. Positive associations of leptin and insulin with fibrinogen in women, independent of WC, were noted. These results suggest that insulin may be an important mediator of the association of obesity with metabolic but not inflammatory or thrombogenic CVD risk factors, while leptin does not appear to influence cardiovascular risk through a shared association with these risk factors. However, we cannot rule out the possibility that leptin and insulin influence cardiovascular risk in women through independent effects on fibrinogen concentrations.