Estudo de polimorfismos da região controle (D-loop) do DNA mitocondrial em pacientes com diabetes tipo 1: relação com a cor autodeclarada em pais e avós

Abstract

Brazilian population results from the of miscegenation between three different ethnic groups: Amerindians, Africans and Europeans. Over the centuries of colonization, these populations mixed asymmetrically, generating the genetic pool of Brazilians. Each Brazilian demographic region will present a particularity in its population, due to the different patterns of miscegenation. Type I diabetes mellitus (DM1) is the most common endocrine pathology in childhood and adolescence, with a higher incidence in individuals who declare themselves white. The self-declaration system in mixed populations, such as Brazil, is flawed. Since phenotypic characteristics such as skin color do not reliably express the genotypic ancestry of the individual. The mitochondrial genome in humans contains 16,569 base pairs has a high genetic variability. Thus, the inference of mtDNA data allows us to characterize the matrilineal ancestry of individuals, being an important genetic marker for population studies. Therefore, the objective of this study was to compare the matrilineal ancestry of individuals with DM1 in Brazil with general data from the Brazilian population regarding their self-declared color and region of birth. For this, the sequencing of the mtDNA control region was performed for 204 diabetic patients from the North regions (7); Northeast (103); Southeast (81) and South (13). The results showed a high molecular diversity, with the presence of 190 unique haplotypes within the universe of 204 possible. Haplogroups of Amerindian origin were the most common, with clade C being the most common (38%). Data stratified by region show that in the Northeast Region, 38.8% had matrilineal ancestry of African origin, 15.5% of European origin and 46.6% of Amerindian origin. In the Southeast region, 43.2% were of African origin, 17.2% of European origin and 39.5% of Amerindian origin. Patients from the North Region had a matrilineal origin represented by 28.5% African and 71.4% Native American origin. And the individuals from the South Region presented their maternal origin of 7% African; 61.5% European and 30.7% Native American. Regarding the self-declaration data, in the studied population, 42.6% declared themselves white, 5.4% black, 50.9% brown and 0.9 yellow. These data are similar to the self-declaration data of the Brazilian population (47.7% white, 7.6% black, 43.1% brown, 1.1% yellow and 0.4 Amerindian). When comparing the data from this work with other populations from different Brazilian regions, we found a similarity between them. This reinforces the pattern of colonization within these regions. Thus, this work brings to light unpublished information about the matrilineal ancestry of diabetic individuals in Brazil. These data may be useful for updating population databases in Brazil, reinforcing historical data on human migration, in addition to their clinical applications.