Percentage of Free to Total Leptin in Diabetic Patients and its Correlation to Blood Insulin, Glucose and Lipids

INTRODUCTION: Leptin is a hormone resulting from the obesity gene which could be important in the pathogenesis of the insulin. Only limited data concerning the interaction of insulin, glucose tolerance and free leptin are available and no data exist on the potential influence of free vs. bound circulating leptin. We, therefore, studied percentage of free to total leptin in diabetic patients. MATERIAL AND METHODS: Thirty non-insulin dependent diabetic obese patients (age: 50±20 years, BMI >30 kg/m²) and 30 non-insulin dependent diabetic non-obese patients (age: 50±20 years, BMI <25 kg/m²) were studied. Free leptin was purified by Gel filtration chroma-tography and the fractions were collected and then their free leptin was measured by a high sensitive ELISA method. Circulation total leptin and insulin was measured by ELISA. RESULTS: Circulation total leptin was significantly correlated to insulin (P < 0.005). Percen-tage of free leptin to total in obese subjects was more than non-obese subjects (27% ± %1 vs. %3 ± %4, [P < 0.001]). Percentage of free to total leptin showed a positive correlation with insulin (r = 0.58 [P < 0.001]), insulin resistance (r = 31 [P < 0.015]) and BMI (r = 0.86 [P < 0.001]). CONCLUSION: The majority of leptin which circulates in obese individuals was free form. Presumably it is bioactive protein of hormone and thus obese subjects are resistant to free leptin.