Lack of association between the -759C/T polymorphism of the 5-HT2 _C receptor gene and olanzapine-induced weight gain among Korean schizophrenic patients

Background: Weight gain can be an adverse effect of antipsychotics that significantly affects long-term health and treatment compliance. Many reports have suggested that the 5-HT2C receptor gene (HTR2C) is related to appetite and eating behaviours associated with body weight change. We hypothesized that there was a relationship between the HTR2C -759C/T polymorphism and olanzapine-induced weight gain. Method: Seventy-nine Korean schizophrenic patients were examined. Their weight was measured before starting olanzapine and after long-term treatment for at least 3 months. We controlled the use of drugs other than olanzapine except benzodiazepines and anticholinergics. Genotyping for the HTR2C -759C/T polymorphism was performed on all participants. Result: We found that long-term treatment with olanzapine resulted in mean gains in weight and BMI of 5.2 kg and 1.93 kg/m², respectively. However, body weight changes from baseline to the study endpoint were not significantly associated with genotypes. The frequency of the T allele did not differ significantly between subjects with weight gains below and above a clinically significant cutoff, defined as 7% relative to baseline (χ² = 0.213, P = 0.445), indicating that the T allele had no protective effect against olanzapine-induced weight gain. Discussion and conclusion: The findings from this study do not support the presence of a relationship between the -759C/T polymorphism of the HTR2C gene and weight gain in Korean schizophrenic patients receiving olanzapine treatment.