[Insulin secretion in women and insulin sensitivity in men constitute independent determinants of serum leptin concentration].

BACKGROUND: Although its effects in man are still unknown, leptin may play a role in the regulation of insulin sensitivity and insulin secretion. The aim of this study was to determine if these parameters are independent predictors of serum leptin levels. SUBJECTS AND METHODS: Twenty men and 22 women were evaluated through several anthropometric parameters, including percent fat mass (PFM), which was calculated using bioelectric impedance. A standard oral glucose tolerance test (OGTT) was performed in all subjects. Insulin sensitivity (SI) and insulin-secretion (AIRg) were determined through minimal model analysis. RESULTS: Area under the curve for glucose (AUCglu) and insulin (AUCins) levels after OGTT correlated with serum leptin level in men (r = 0.58, p = 0.005 and r = 0.72, p < 0.0001, respectively). Only AUCins was associated with serum leptin levels in women (r = 0.50, p = 0.01), but this correlation disappeared after controlling for PFM. A linear correlation between serum leptin level and SI was observed (r = -0.67, p = 0.001, in men; r = -0.82, p < 0.0001, in women). In a multiple regression analysis, PFM (p = 0.0005), waist-to-hip ratio (p = 0.007) and SI (p = 0.007) independently predicted serum leptin level in men (R2 = 0.82). In women with normal OGTT, only PFM (p = 0.0005) and insulin-secretion (p = 0.02) predicted serum leptin level (R2 = 0.85). CONCLUSIONS: Insulin-sensitivity in men, and insulin-secretion (calculated after intravenous glucose) in women independently predict serum leptin level. Furthermore, insulin response after oral glucose is independently associated with serum leptin level only in men. Leptin is a marker of insulin resistance in man, and, in this sense, might confer cardiovascular risk.