Prediction of successful weight reduction under sibutramine therapy through genotyping of the G-protein ??3 subunit gene (GNB3) C825T polymorphism

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Abstract
Sibutramine, a centrally acting noradrenaline and serotonin re-uptake inhibitor, enhances satiety and is frequently used to support weight loss. However, a significant variability exists among individuals concerning the response to sibutramine. We genotyped 111 participants of a randomized placebo-controlled clinical trial for the GNB3 C825T polymorphism and analysed associations of genotypes with treatment outcome. Patients undergoing a structured weight loss programme were treated with either placebo or 15 mg sibutramine daily for 54 weeks. In the placebo group, the non-pharmacological programme alone resulted in a significantly greater weight loss in individuals with the GNB3 TT/TC genotypes as compared to individuals with the CC genotype (-7.1 +/- 1.2 vs. -2.7 +/- 1.5 kg, P = 0.031). Administration of 15 mg sibutramine was more effective in individuals with the CC genotype than in the subjects with the TT/TC genotypes (weight loss: 7.2 +/- 2.2 vs. 4.1 +/- 2.1 kg, P = 0.0013, sibutramine vs. placebo). In the CC genotype carriers, the odds ratio (OR) for a weight loss greater than 5% (sibutramine vs. placebo) was 6.6 (95% CI 1.8-25.6; P = 0.004) and for a weight loss greater than 10% was 9.6 (95% CI 1.7-53.8; P = 0.010). Genotyping for the GNB3 C825T polymorphism is highly predictive for the identification of obese individuals who will benefit from sibutramine treatment.