CIRCULATING INSULIN CONCENTRATIONS, SMOKING, AND ALCOHOL INTAKE ARE IMPORTANT INDEPENDENT PREDICTORS OF LEPTIN IN YOUNG HEALTHY-MEN

Objective: Leptin, an adipocyte-secreted hormone, has been shown to si gnal the status of energy stores to the brain, regulate energy homeost asis, and mediate the neuroendocrine response to food deprivation. Obe sity is associated with increased leptin levels, and several hormones, including insulin and glucocorticoids, have been associated with lept in levels and expression in rodents. Although obesity has been strongl y associated with increased leptin in humans, a significant percentage of leptin's variability remains unexplained. The role of endogenous h ormones, demographic factors, or certain life-style factors in explain ing the residual variability of leptin levels has not yet been clarifi ed. We performed this cross-sectional study to document the relative i mportance of obesity, lifestyle factor, and endogenous hormones in det ermining serum leptin levels. Research Methods and Procedures: We meas ured serum concentrations of insulin, cortisol, testosterone, growth h ormone, and dehydroepiandrosterone sulfate; ascertained anthropometric , demographic, and lifestyle characteristics; and studied these variab les in relationship to serum leptin concentrations in a sample of youn g healthy men. Results: Obesity and alcohol intake were independently and positively associated with circulating leptin concentrations. Addi tionally, cigarette smoking was negatively and independently associate d with leptin concentrations. Finally, se rum insulin concentration wa s an independent hormonal determinant of circulating leptin concentrat ions, whereas serum testosterone was negatively associated with leptin only by bivariate analysis. Discussion: We conclude that, in addition to obesity, cigarette smoking, alcohol intake, and serum insulin leve ls are associated with leptin levels in a population of healthy young men.