ABSTRACT
To investigate the potential relationship between HLA alleles and haplotypes and the age at diagnosis of type 1 diabetes (T1DAgeD) in an admixed Brazilian population. This nationwide study was conducted in public clinics across 12 Brazilian cities. We collected demographic and genetic data from 1,600 patients with T1D. DNA samples were utilised to determine genomic ancestry (GA) and perform HLA typings for DRB1, DQA1 and DQB1. We explored allele and haplotype frequencies and GA in patients grouped by T1DAgeD categories (<6 years, ≥6-<11 years, ≥11-<19 years and ≥19 years) through univariate and multivariate analyses and primary component analyses. Additionally, we considered self-reported colour-race and identified a familiar history of T1D in first-degree relatives. The homozygosity index for DRB1~DQA1~DQB1 haplotypes exhibited the highest variation among T1DAgeD groups, and the percentages of Sub-Saharan African and European ancestries showed opposite trends in principal component analysis (PCA) analyses. Regarding the association of alleles and haplotypes with T1DAgeD, risk alleles such as HLA-DQB1*03:02g, -DQA1*03:01g, -02:01g, DRB1*04:05g and -04:02g were more frequently observed in heterozygosity or homozygosity in T1D patients with an early disease onset. Conversely, alleles such as DRB1*07:01g, -13:03g, DQB1*06:02g and DQA1*02:01 were more prevalent in older T1D patients. The combination DR3/DR4.5 was significantly associated with early disease onset. However, gender, GA, familiar history of T1D and self-reported colour-race identity did not exhibit significant associations with the onset of T1D. It is worth noting that the very common risk haplotype DRB1*03:01g~DQA1*05:01g~DQB1*02:01g did not differentiate between T1DAgeD groups. In the admixed Brazilian population, the high-risk haplotype DRB1*04:05~DQA1*03:01~DQB1*03:02 was more prevalent in individuals diagnosed before 6 years of age. In contrast, the protective alleles DQA1*01:02g, DQB1*06:02g, DRB1*07:01g and DRB1*13:03g and haplotypes DRB1*13:03g~DQA1*05:01g~DQB1*03:01g and DRB1*16:02g~DQA1*01:02g~DQB1*05:02g were more frequently observed in patients diagnosed in adulthood. Notably, these associations were independent of factors such as sex, economic status, GA, familiar history of T1D and region of birth in Brazil. These alleles and haplotypes contribute to our understanding of the disease onset heterogeneity and may have implications for early interventions when detected in association with well-known genomic risk or protection factors for T1D.
Subject(s)
Alleles , Diabetes Mellitus, Type 1 , Gene Frequency , Haplotypes , Humans , Brazil/epidemiology , Diabetes Mellitus, Type 1/genetics , Diabetes Mellitus, Type 1/epidemiology , Diabetes Mellitus, Type 1/diagnosis , Male , Female , Child , Adolescent , Adult , Child, Preschool , Young Adult , Genetic Predisposition to Disease , HLA-DRB1 Chains/genetics , HLA-DQ alpha-Chains/genetics , HLA-DQ beta-Chains/genetics , Age of Onset , Infant , Middle AgedABSTRACT
This study aimed to investigate the relationship between genetic ancestry inferred from autosomal and Y chromosome markers and HLA genotypes in patients with Type 1 Diabetes from an admixed Brazilian population. Inference of autosomal ancestry; HLA-DRB1, -DQA1 and -DQB1 typifications; and Y chromosome analysis were performed. European autosomal ancestry was about 50%, followed by approximately 25% of African and Native American. The European Y chromosome was predominant. The HLA-DRB1*03 and DRB1*04 alleles presented risk association with T1D. When the Y chromosome was European, DRB1*03 and DRB1*04 homozygote and DRB1*03/DRB1*04 heterozygote genotypes were the most frequent. The results suggest that individuals from Maranhão have a European origin as their major component; and are patrilineal with greater frequency from the R1b haplogroup. The predominance of the HLA-DRB1*03 and DRB1*04 alleles conferring greater risk in our population and being more frequently related to the ancestry of the European Y chromosome suggests that in our population, the risk of T1D can be transmitted by European ancestors of our process miscegenation. However, the Y sample sizes of Africans and Native Americans were small, and further research should be conducted with large mixed sample sizes to clarify this possible association.
