Fat Mass and Obesity-Related Gene Variants rs9939609 and rs7185735 are Associated with Second-Generation Antipsychotic-Induced Weight Gain.

Introduction: Weight gain is a limiting and frequent adverse effect of second-generation antipsychotic therapy. Identifying genetic risk factors would significantly improve pharmacotherapy.

Methods: We focused on rs7185735 and rs9939609, 2 common single nucleotide polymorphisms of the fat mass and obesity-associated (FTO) gene reported to be associated with obesity. Three-hundred fifty Caucasian inpatients were included in a naturalistic study.

Results: After 4 weeks of treatment, we did not observe any significant association of polymorphisms with weight change in the whole study population (p>0.05). In a subpopulation without additional weight-inducing comedication (n=178), G-allele carriers of rs7185735 gained 3.4 times more weight (1.69 kg±3.1 kg, p=0.019) than AA genotypes (0.49 kg±3.1 kg). A-allele carriers of rs9939609 gained 3.1 times more weight (1.65 kg±3.1 kg, p=0.029) than TT genotypes (0.54 kg±3.2 kg).

Discussion: Our findings confirm the role of the FTO gene as a high-potential risk factor for obesity and indicate a value for predicting a weight gain induced by second-generation antipsychotics. Further, we detected an additive effect of FTO rs7185735 and MC4R rs17782313.