Insulin-secretion in women and insulin sensitivity in men are independent predictors of serum leptin levels

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 pred ictors of serum leptin levels. SUBJECTS AND METHODS: Twenty men and 22 women were evaluated through severa l anthropometric parameters, including percent fat mass (PFM), which was ca lculated using bioelectric impedance. A standard oral glucose tolerance tes t (OGTT) was performed in all subjects. Insulin sensitivity (S-1) and insul in-secretion (AIRg) were determined through minimal model analysis. RESULTS: Area under the curve for glucose (AUCglu) and insulin (AUCins) lev els after OGTT correlated with serum leptin level in men (r = 0.58, p = 0.0 05 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 di sappeared after controlling for PFM. A linear correlation between serum lep tin level and S-1 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), w aist-to-hip ratio (p = 0.007) and S-1 (p = 0.007) independently predicted s erum leptin level in men (R-2 = 0.82). In women with normal OGTT, only PFM (p = 0.0005) and insulin-secretion (p = 0.02) predicted serum leptin level (R-2 = 0.85). CONCLUSIONS: insulin-sensitivity in men, and insulin-secretion (calculated after intravenous glucose) in women independently predict serum leptin leve l. Furthermore, insulin response after oral glucose is independently associ ated with serum leptin level only in men. Leptin is a marker of insulin res istance in man, and, in this sense, might confer cardiovascular risk.