Analysis of the relationship between fasting serum leptin levels and estimates of beta-cell function and insulin sensitivity in a population sample of 380 healthy young Caucasians.

OBJECTIVE Circulating leptin levels correlate positively with the degree of obesity and prolonged hyperinsulinaemia increases serum leptin levels. Moreover, insulin secreting beta-cells express functional leptin receptors indicating a functional relationship between leptin and insulin. The aim of this study was to examine the relationship between fasting serum leptin levels and measures of insulin sensitivity and beta-cell function in a population-based sample of 380 young healthy Caucasians. DESIGN AND METHODS Multiple regression analysis was employed to analyse the relationship between fasting serum leptin levels and levels of fasting serum insulin, insulin sensitivity index and acute insulin response (AIR) in a population-based study of 380 young healthy Caucasians who underwent a combined intravenous glucose and tolbutamide tolerance test. RESULTS AND CONCLUSION Serum leptin levels were positively correlated to measures of adiposity and were 3.2 times higher in women than in men (P<0.00001). In multiple regression analyses adjusting for age, percentage body fat, waist circumference and maximal aerobic capacity, a significant positive correlation was observed between the fasting serum leptin concentrations and both fasting serum insulin levels (P<0.0001) and AIR (P = 0.014) for women. No significant interrelation of these variables was found in men. However, for both genders a significant negative correlation was observed between fasting serum leptin levels and measures of insulin sensitivity index (P = 0.007).