Difference in body fat percentage does not explain the gender dimorphism in leptin in Asian Indians

Leptin is a hormone probably having regulatory function on energy intake and metabolic activities in humans. The study was done: (a) To determine the relation of leptin with the body fat% in Indians, (b) To see whether the differences in body fat accounted for the gender differences in the concentration of leptin and (c) to look for the effect of diabetes on the levels of leptin.

Glucose tolerance was determined by oral glucose tolerance test (GTT) in 87 subjects with no known history of diabetes. Leptin was estimated by radio immuno assay. Age, height, weight, waist and hip circumferences were noted. Body mass index (BMI, weight kg/height m2) and waist:hip ratio (WHR) were calculated. The body fat % was estimated by bioelectrical impedance analysis.

Leptin correlated with log fat % and BMI, body weight and waist circumference in different categories of glucose tolerance (Pearson's correlation test). Leptin values were higher in women than in men even after correcting for the body fat % indicating that the gender dimorphism was not explained by the higher fat % in women. The geometric mean of leptin concentration in men was 3.6 ng/ml and in women 10.9 ng/ml (P < 0.0001). Leptin level were not influenced by the status of glucose tolerance. Gender showed a significant effect on leptin concentration (F = 11.0, df = 1.39, P = 0.002) after adjusting for the effect of covariates i.e. percentage of fat (log), BMI, age, WHR and 2 h plasma glucose by ANCOVA. None of the covariates except BMI (P < 0.0001) showed significant correlation with leptin. The total variance explained was 68.4%.

We conclude that (1) Plasma leptin is strongly correlated to the body fat content (2) the gender dimorphism of leptin is not explained by the differences in fat percentage and (3) hyperglycemia does not influence plasma leptin levels.