Leptin secretion and severity of glycemic disorders in women with body weight excess

Abstract

Aim. To characterize leptin secretion in fasting state and upon intravenous glucose administration in patients with type 2 diabetes mellitus (T2DM), prediabetes and obesity. Materials and methods. 59 female patients took part in this study: 12 had no signs of glycemic disorder, 18 were diagnosed with prediabetes and 30 - with newly diagnosed T2DM. Median age was 54 [48.6-60] years, median BMI - 33.2 [29.0-37.2] kg/m2. All participants were tested for fasting leptin, fasting insulin and blood glucose levels. Prediabetic and diabetic subjects also received a bolus intravenous injection of 40% glucose solution (0.75 g/kg of body mass) with subsequent additional measurement of insulin levels at 2, 70 and 120 min upon injection, and leptin levels - at 120 min. Results. Median fasting leptin in obese and patients with weight excess was 42.0 [22-60] ng/mL, which is about 2 times higher than normal reference maximum (27.6 ng/mL). Subjects with prediabetes and T2DM showed significantly lower median fasting leptin levels of 29.1 ng/mL [13.5-45.7] and 21.3 [14.3-42.2], respectively (p<0.05). After 2 h upon glucose administration we observed a statistically significant reduction in leptin level in both groups as compared to fasting state (p<0.05). In patients with prediabetes the drop reached 23.3% against 15.3% in diabetic subjects (p<0.05). Both groups demonstrated positive correlation between plasma leptin reduction and insulin area under the curve (AUC) during intravenous glucose tolerance test (r=0.4, <0.05). Conclusion. 1) Plasma leptin levels are increased in obese women with normal glucose tolerance (42.0 [22.0-60.0] ng/mL) and significantly decrease upon development of prediabetes or overt T2DM, which is likely associated with progression of insulin deficiency. 2) Leptin drop during intravenous glucose tolerance test was found to be in direct dependence with insulinemia and appeared more prominent in patients with prediabetes than in diabetics (23.1% and 11%, respectively, =0.02).