Plasma insulin, leptin, and soluble TNF receptors levels in relation to obesity-related atherogenic and thrombogenic cardiovascular disease risk factors among men.

Obesity is related to cardiovascular disease (CVD) morbidity and mortality, however, the mechanisms for the development of obesity-induced CVD risk remain unclear. Hyperinsulinemia and insulin resistance are considered key components in the metabolic cardiovascular syndrome and as independent risk factors for CVD. Plasma leptin and tumor necrosis factor-alpha (TNF-alpha), two adipocyte products, are also proposed to be associated with the development of CVD risk. The purpose of this study is to evaluate the association of plasma leptin, soluble TNF receptors (sTNF-R), and insulin levels as possible mediators of the effect of obesity on atherogenic and thrombogenic CVD risk factors among men. From the Health Professionals Follow-up Study (HPFS), we selected 268 men, aged 47--83 years, who were free of CVD, diabetes, and cancer (except non-melanoma skin cancer), and who had provided a fasting blood sample in 1994. We measured plasma insulin and leptin levels by radioimmunoassay and sTNF-R levels by ELISA. Men in the highest quintile of body mass index (BMI, mean=30.5 kg/m(2)) were less physically active and had a more adverse cardiovascular lipid and homeostatic profile, as indicated by levels of insulin, triglyceride (TG), tissue plasminogen activator (t-PA) antigen levels, and apolipoprotein A1 (Apo-A1). In a multivariate regression model controlling for age, smoking, alcohol intake, physical activity and diet, BMI was inversely associated with HDL-cholesterol (HDL-C) and Apo-A1 and positively associated with TG, Apo-B and t-PA antigen levels. The associations between BMI and these CVD risk factors were only slightly changed after adjusting for leptin and/or sTNF-R; but were substantially attenuated after controlling for insulin levels. These data suggest that the association between obesity and biological predictors of CVD may be mediated through changes in plasma insulin, rather than leptin or sTNF-R levels. However, plasma leptin may still play a role in CVD through independent effects on lipid metabolism.