Effect of gene polymorphisms in transmembrane protein 18 (TMEM18) and neuronal growth regulator 1 (NEGR1) on body mass index in obese subjects

Obesity is a complex disorder with nearly epidemic proportions in many parts of the world. Genome-wide association studies have demonstrated high heritability for obesity and body mass, with associations of certain candidate genes and their variations with respect to race, geographical location/country of origin. However, the functional mechanisms and different ethnic data of these loci are still poorly understood. In this case-control study, we investigated two single nucleotide polymorphisms, rs2815752 in the neuronal growth regulator 1 (NEGR1) gene and rs6548238 in the transmembrane protein 18 (TMEM18) gene, for association in a group of obese residents of Afyonkarahisar province (Turkey). Polymorphisms were genotyped in 172 obese subjects and 77 healthy controls. The results showed no significant differences between the obese subjects and the controls in terms of the allele and genotype frequencies of the NEGR1 gene rs2815752 and the TMEM18 gene rs6548238 polymorphisms. There were no significant associations of the rs2815752 polymorphism in obese subjects and controls with regard to anthropometric measurements and body composition parameters. However, several significant associations were found for the rs6548238 polymorphism with regard to anthropometric measurements and body composition. Consequently, there were no significant differences between the genotype and allele frequencies of NEGR1 gene rs2815752 and TMEM18 gene rs6548238 polymorphisms in the obese group and the controls. There were significant associations for the rs6548238 polymorphism, but not the rs2815752 polymorphism, with the anthropometric measurements and body composition parameters in the group of obese subjects.