Genetic epidemiology of Type 2 diabetes mellitus and complications in the Brazilian population

Type 2 diabetes mellitus (T2DM) is a chronic, complex, multifactorial and polygenic disease, constituting one of the greatest public health challenges worldwide. The genetic background has been shown to strongly influence the disease's susceptibility. We performed genetic screening of risk-variants for T2DM and complications in the Brazilian population. This systematic review is registered in the PROSPERO platform under number CRD42020153032. The searches were conducted in Virtual health library (BVS), EMBASE, Pubmed/NCBI, Scopus, and Web of Science databases, including only case-control studies that related genetic polymorphisms with the risk of developing the disease in the Brazilian population. Among the search results, we also extracted data regarding the susceptibility of developing macro/microvascular complications. Sixteen case-control studies were included, of which 10 addressed T2DM susceptibility and six the disease complications. A total of 4122 individuals were included in the analyses of susceptibility to T2DM, and 1443 in those of susceptibility to complications of the disease. Our findings demonstrate the participation of four main mechanisms in T2DM pathophysiology: glycolytic dysregulation, lipid metabolism, insulin resistance, and inflammatory processes. Among the eight polymorphisms linked to disease susceptibility, we highlight rs7903146 (C/T) in the TCF7L2 gene and rs1800471 (25C/G) in the TGF-beta 1 gene for diabetic retinopathy. In haplotype analysis, two sets were associated with T2DM susceptibility (ADIPOQ and D1O2 genes), and two sets in the UCP2 gene were associated with diabetic retinopathy and nephropathy. Data from this study characterize the genetic profile of the Brazilian population for susceptibility to T2DM and its complications. This is the first genetic epidemiology study to screen risk variants associated with this disease in Brazil. With this mapping, we aimed to contribute to the development of molecular diagnostic technologies and precision medicine, such as a genetic panel for T2DM susceptibility in the Brazilian population.