The relationship between plasma leptin levels and insulin resistance was studied in 66 obese subjects (23 men, 43 women) aged 42.3±13.8 yrs (mean±SD) with a body mass inde×(BMI) of 33.0 ×5.4kg/m².
The subj ects were divided into the following three groups according to WHO criteria for 75-g OGTT: normal glucose tolerance (NGT, n=27); impaired glucose tolerance (IGT, n=16); and diabetic (DM, n=23). Plasma leptin levels were measured with a human leptin RIA kit, insulin resistance (IR) and fl-cell function (β-CF) were calculated by using the HOMA model of Matthews et al. The results were as follows 1. Plasma leptin concentrations in obese subjects were higher in women than in men. 2. The plasma leptin levels in the three obese groups were similar, with no significant differences. 3. There were significant correlations between plasma leptin concentrations and BMI, % body fat, fasting insulin levels and insulin resistance. 4. The plasma leptin level is significantly related to insulin resistance, independently of adiposity. Therefore we conclude that elevated plasma leptin concentrations in the presence of obesity might contribute to insulin resistance but do not influence glucose metabolism.