Investigação de associação entre ancestralidade genética, polimorfismos genéticos relacionados à obesidade e marcadores de adiposidade: estudo Pró-Saúde

Abstract

Obesity susceptibility is related to environmental, social, cultural, and genetic factors. Among genetic factors, the ancestry and genes which act within the central nervous system are highlighted. Ancestry estimates have been used in different ways to understand the role of the genetic contribution on the individual variation in obesity parameters and body composition, mainly in miscegenated groups known to differ in susceptibility to obesity. Ancestry informative markers (AIMs) genotyping allow the genetic ancestry determination of individuals within a sample. This study aimed to investigate for the first time, in a population sample of the State of Rio de Janeiro, the association between ancestry, markers in genes described as associated with obesity and adiposity, in order to contribute to knowledge about the health of this population fraction. To investigate the association between genetic factors and adiposity, it was analysed a total of 501 unrelated individuals from the State of Rio de Janeiro, all participants of the Pro-Saúde Study (EPS). Forty-six insertion/deletion (InDels) polymorphisms were evaluated as AIMs and four single nucleotide polymorphisms (SNPs), rs17782313, rs9939609, rs7138803, and rs4074134, located in the genes MC4R, FTO, FAIM2 and BDNF, respectively, described as associated with obesity. The results were interpreted considering the information available in previous publications on different populations. The adiposity markers used in the association analyses were BMI, waist circumference, waist-to-hip ratio and body fat percentage. Through an analysis of population substructure, it was observed that the studied population presents Hardy-Weinberg disequilibrium. The use of AIMs as a correction factor in the analyses of association between SNPs associated with obesity and markers of adiposity is vital so that these substructuring effects do not bias the association and lead to spurious interpretations. From the genotyping of the AIMs and SNPs, the ancestry and genotypic profile of the population sample were identified, respectively. The sample showed a major European ancestry (57.2 %), followed by African (28.8 %) and, lastly, Amerindian (14 %). In this Brazilian population sample, no statistically significant associations were observed between the studied genetic factors and the markers of adiposity related to obesity. It is observed in the literature that the role of genetic factors in the increase in adiposity and manifestation of obesity is controversial. Some authors point out genetic responsibility, while others do not observe it. One explanation is that the increase in adiposity and consequent obesity are multifactorial conditions and have other variables that may have a greater effect on its development, such as environmental, social and cultural factors.