[Serum leptin and insulin resistance in obesity and effects of sibutramine on them].

OBJECTIVE

To assess the relationship between serum leptin and insulin resistance (IR) in obesity, and to investigate the effects of sibutramine on obesity, serum leptin and IR.

METHODS

Seventy obese subjects [body mass index (BMI) > or =25 kg/m2] were randomly divided into 2 groups: group B (sibutramine 10 mg/day) and group C (a placebo tablet/day). Both had been treated for 12 weeks. Another 30 healthy adults served as the normal control (group A: BMI < 23 kg/m2). Their height, body weight, waist and hip circumference, fasting plasms glucose (FPG), fasting plasma insulin (FINS), and serum leptin were examined at the baseline and 12 weeks after the therapy. Insulin senstivity index (ISI) was calculated [ISI = 1/(FPG x FINS)]. Multiple linear regression analysis and partial correlation were performed on serum leptin.

RESULTS

The body weight, BMI, waist and hip circumference decreased significantly after the 12 week-treatment with sibutramine in group B (P < 0.01), but those indexes did not change after the treatment with placebo in group C (P > 0.05). The levels of leptin and FINS were higher (P < 0.01), but ISI was lower (P < 0.01) both in group B and C compared with those in group A at the baseline. The levels of serum leptin and FINS decreased (P < 0.01), and ISI increased significantly (P < 0.05) after the treatment with sibutramine in group B, while those indexes did not change after the treatment with placebo in group C. The most important factors to influence serum leptin level were listed as follows: sex > BMI > FINS > ISI (R2 = 0.661, F = 12.662, P < 0.01). The lep- tin was positively correlated with FINS (r = 0.597, P < 0.01) , but negatively correlated with ISI (r = -0.468, P < 0.01 ) after eliminating the effects of sex and BMI. Conclusion Leptin resistance and insulin resistance exist in obesity, and serum leptin is associated with IR. Treatment with sibutramine significantly reduces the body weight and leptin, increases insulin senstivity, and improves IR.