Family-based association study between the monoamine oxidase A gene and obesity: implications for psychopharmacogenetic studies.

Family studies have reported that obesity has a strong heritable component. It has been suggested that a neurotransmitter dysfunction could be involved in mental disorders and obesity; therefore, candidate genes in psychiatric disorders could be a risk factor for obesity. We investigated the association between the monoamine oxidase A (MAO-A) gene and obesity. Fifty obese subjects and their parents were included in the study. Two polymorphisms designated EcoRV and upstream variable number tandem repeats of the MAO-A gene were analysed using polymerase chain reaction. For analysis of the families, the transmission disequilibrium test (TDT) was applied. The TDT analysis of the EcoRV polymorphism showed in obese subjects with a body mass index (BMI) >/=35 kg/m(2) a preferential transmission of the low activity-related allele (chi(2)(TDT) = 8.0, p = 0.005). Our findings may provide evidence of a candidate gene involved in obese subjects with a BMI >/=35 kg/m(2).