Comparison of changes in postprandial serum leptin between healthy and type 2 diabetic individuals

Leptin resistance may be intensified by insulin resistance. This vicious cycle between insulin resistance and leptin resistance may increase feelings of hunger and reduce energy expenditure and ultimately increase obesity. In this study, postprandial changes in leptin, insulin and glucose were compared between healthy subjects and patients with Type 2 diabetes mellitus (DM).

Six men with Type 2 DM and seven healthy men (matched for age and body mass index), after 12 hours of fasting, ate the same Iranian meal (chelo kebab kobibeh) consisting of 46% carbohydrate, 21% protein, 33% fat and 743 kcal energy. Blood samples were obtained before and 1, 2 and 4 hours after the meal, and serum leptin, insulin and glucose levels were measured. The area under incremental curve (AUIC) computed using the Trapezoidal method with fasting values was deducted from each time point, yielding net postprandial changes.

Leptin levels at the first hour were significantly reduced in both groups and then increased at the second and fourth hours after the meal, although not reaching fasting values in the diabetic group at the 4th hour. AUIC for leptin was significantly lower in the diabetic group (p = 0.023). Despite high levels before the meal, the early increase in insulin in the diabetic group was lower and declined more slowly than in the healthy group. The incremental area under the insulin curve was significantly lower in the control group than in the diabetic group (p = 0.006).

It appears that an increased leptin level two hours after the meal is due to increased serum insulin and glucose levels. Leptin AUIC after meals in people with Type 2 DM is lower than in healthy people and may be due to decreased responsiveness to insulin in adipocytes because of insulin resistance.