Leptin concentrations during oral glucose tolerance test (OGTT) in obese and normal weight women.

Objective: To examine possible changes of leptin concentrations after the acute administration of glucose orally (OGTT).

Design: Seventy-five grams of glucose were administered per os in one group of obese and normal weight individuals and concentrations of glucose, insulin and leptin were measured at 0, 30, 60, 90 and 120 min. In an age matched control group of individuals with similar BMI water was given and leptin concentrations were measured before and after 30, 60, 90 and 120 min.

Subjects: Twenty-seven obese women aged 34+/-1.57 y with BMI 37.1+/-0.8 kg/m2 and 16 normal weight women, aged 32+/-1.13 y with BMI 23.6+/-0.3 kg/m2 formed the experimental group, while 10 obese and 10 normal weight females with similar age and BMI were used as controls.

Measurements: Weight, height, BMI, body fat, glucose, insulin and leptin at baseline and during OGTT. Variations of the above parameters were calculated from the area under the curve (AUC).

Results: Fasting leptin concentrations and AUC were higher in obese than in normal weight women. In obese women, leptin increased significantly in comparison to its basal concentrations 30 and 60 min after the glucose loading. Insulin was also increased, as expected. No correlation was found between insulin and leptin concentrations after glucose loading. Basal concentrations of leptin did not correlate with those of glucose and insulin. No changes in leptin concentrations were found in normal weight women after OGTT. However, a significant positive correlation was found between insulin and basal leptin. Finally, leptin concentrations did not change in obese and normal weight controls after water administration.

Conclusion: A significant increase in leptin concentrations was found 30 and 60 min after glucose loading in obese individuals. No such increase was found in normal-weight women.