G-protein β3 subunit gene 825C/T polymorphism is not associated with olanzapine-induced weight gain in Korean schizophrenic patients

Objective: Weight gain is a Possible adverse effect of the use of antipsychotics, and is an important factor for long-term health and treatment compliance. Olanzapine, is an atypical antipsychotic known to cause considerable weight gain. A relationship between weight gain and the G protein β3 subunit gene (GNB3) 825C/T polymorphism has been reported. We therefore examined this possible association in a Korean schizophrenic patient group receiving olanzapine treatment. Methods: Weight and height measurements were obtained prior to starting olanzapine and meastapd again after long-term treatment. Genotyping for the 825C/T polymorphism was performed using a PCR-based method. Results: We found that long-term treatment with olanzapine resulted in mean gains in weight and body mass index (BMI) of 5.2 kg and 1.93 kg/ m², respectively. There was a no significant difference in the mean body weight change from baseline to the endpoint after olanzapine treatment between the genotype groups (p=0.796). There were also no significant differences in genotype or allele frequencies between the severe weight-gain (more than 10%) and minimal weight-gain (less than 10%) groups (X²=0.037, VO.98; X²=0.020, p=0.89). Conclusion: The finding from this study thus does not support a relationship between the GNB3 825C/T polymorphism and weight gain in Korean schizophrenic patients receiving olanzapine treatment.