Estudo de associação entre obesidade na infância e os SNPs TaqIA C32806T do gene DRD2 e G308A do gene TNF-a

Abstract

The worldwide prevalence of obesity has increased at an alarming rate in all age groups. Although it has been described some rare obesity syndromes caused by mutations in single genes, the highest proportion of obesity results from an interaction between variants in multiple genes (susceptible genotype) and a favorable environment (plenty of calories and lack of physical activity). Classically, it has been studied genes involved in the control of intake, energy expenditure and the metabolism of glucose and lipids. In the last decade the discovery of numerous substances secreted by adipocytes among them hormones and inflammatory cytokines opened a new research front. The “Reward Deficient Syndrome” (RDS) is characterized as a hypodopaminegic state that predisposes to obsessive-compulsive behavior and impulsivity. Obesity is part of the RDS, as the individual overeats as a manner to compensate de dopamine defect. In this context, this study was designed to investigate the relationship between childhood onset obesity and polymorphisms of the tumor necrosis factor alpha (TNF alpha) and the Dopamine D2 Receptor (DRD2). Our research is a case control study that included 105 children, being 55 obese and 50 normal weight (control group). Peripheral blood samples were collected for the determination of lipid profile, glucose and insulin levels, and for the evaluation of the genetic polymorphisms of TNF- gene (G308A) and DRD2 (Taq1 - C32806T), by ARMS-PCR and RFLP-PCR, respectively. Genetic variants of the SNP G308A TNF- failed to confirm a participation in weight gain in children. The A1 allele (T) of the Taq1 polymorphism in the DRD2 gene was associated with an increase in childhood obesity and higher BMI of the parents, corroborating some data of the literature. Our results showed for the first time that the A1 allele is associated with Total Cholesterol 70 mg/dl, minor levels of triglycerides and a relative risk of 1.5 for HOMA ß secretion. Understanding how genetic variations affect the tendency to become or remain obese is an important step in understanding the mechanisms that lead to obesity.