ABSTRACT
Ethnic admixtures may interfere with the definition of type 1 diabetes (T1D) risk determinants. The role of HLA, PTPN22, INS-VNTR, and CTLA4 in T1D predisposition was analyzed in Brazilian T1D patients (n = 915), with 81.7% self-reporting as white and 789 controls (65.6% white). The results were corrected for population stratification by genotyping 93 ancestry informative markers (AIMs) (BeadXpress platform). Ancestry composition and structural association were characterized using Structure 2.3 and STRAT. Ethnic diversity resulted in T1D determinants that were partially discordant from those reported in Caucasians and Africans. The greatest contributor to T1D was the HLA-DR3/DR4 genotype (OR = 16.5) in 23.9% of the patients, followed by -DR3/DR3 (OR = 8.9) in 8.7%, -DR4/DR4 (OR = 4.7) in 6.0% and -DR3/DR9 (OR = 4.9) in 2.6%. Correction by ancestry also confirmed that the DRB1*09-DQB1*0202 haplotype conferred susceptibility, whereas the DRB1*07-DQB1*0202 and DRB1*11-DQB1*0602 haplotypes were protective, which is similar to reports in African-American patients. By contrast, the DRB1*07-DQB1*0201 haplotype was protective in our population and in Europeans, despite conferring susceptibility to Africans. The DRB1*10-DQB1*0501 haplotype was only protective in the Brazilian population. Predisposition to T1D conferred by PTPN22 and INS-VNTR and protection against T1D conferred by the DRB1*16 allele were confirmed. Correcting for population structure is important to clarify the particular genetic variants that confer susceptibility/protection for T1D in populations with ethnic admixtures.
Subject(s)
Diabetes Mellitus, Type 1/epidemiology , Diabetes Mellitus, Type 1/genetics , Genetic Association Studies , Genetic Markers , Genetic Predisposition to Disease , Adolescent , Adult , Alleles , Case-Control Studies , Child , Diabetes Mellitus, Type 1/diagnosis , Female , Gene Frequency , Genotype , HLA Antigens/genetics , Humans , Male , Odds Ratio , Population Surveillance , Young AdultABSTRACT
There is a scarcity of data of zinc transporter-8 autoantibody (ZnT8A) on mixed populations such as Brazilian. Therefore, we evaluated the relevance of ZnT8A for type 1 diabetes (T1D) diagnosis and the role of ZnT8 coding gene (SLC30A8) in T1D predisposition. Patients with T1D (n = 629; diabetes duration = 11 (6-16) years) and 651 controls were genotyped for SLC30A8 rs16889462 and rs2466295 variants (BeadXpress platform). ZnT8 triple antibody was measured by ELISA; glutamic acid decarboxylase (GAD65A) and protein tyrosine phosphatase (IA-2A) autoantibodies by radioimmunoassay. RESULTS: Znt8A was detected in 68.7% of recent-onset T1D patients and 48.9% of the entire patient cohort, similar to GAD65A (68.3% and 47.2%) and IA-2A (64.8% and 42.4%) positivities respectively. ZnT8A was the only antibody in 8.4% of patients. Znt8A and IA2A frequencies and titers were independent of gender and ethnicity, whereas GAD65A titers were greater in females. The diabetes duration-dependent decline in ZnT8A frequency was similar to GAD65A and IA-2A. The SLC30A8 rs2466293 AG + GG genotypes were associated with T1D risk in non-European descents (56.2% × 42.9%; p = 0.018), and the GG genotype with higher ZnT8A titers in recent-onset T1D: 834.5 IU/mL (711.3-2190.0) × 281 IU/mL (10.7-726.8); p = 0.027. Conclusion ZnT8A detection increases T1D diagnosis rate even in mixed populations. SLC30A8 rs2466293 was associated with T1D predisposition in non-European descents.
Subject(s)
Autoantibodies/metabolism , Diabetes Mellitus, Type 1/diagnosis , Polymorphism, Single Nucleotide , Zinc Transporter 8/genetics , Zinc Transporter 8/immunology , Adolescent , Adult , Brazil/ethnology , Cohort Studies , Diabetes Mellitus, Type 1/ethnology , Diabetes Mellitus, Type 1/genetics , Diabetes Mellitus, Type 1/immunology , Female , Genetic Association Studies , Genetic Predisposition to Disease , Genotype , Glutamate Decarboxylase/immunology , Humans , Male , Receptor-Like Protein Tyrosine Phosphatases, Class 8/immunology , White People/genetics , Young AdultABSTRACT
A investigação de genes associados a doenças complexas em estudos caso-controle, baseada na frequência de variantes polimórficas, pode não ser adequada na presença de estratificação populacional advinda da mistura étnica, que é uma das características da população brasileira. Torna-se, portanto, difícil utilizar esta metodologia, pelo risco de associações espúrias devido às diferenças no background genético dos indivíduos casos e controles. Marcadores informativos de ancestralidade (AIMs) podem ser aplicados para estimar ancestralidade e corrigir estas distorções. As mesmas variantes genéticas de susceptibilidade para o diabetes tipo 1 autoimune (DM1A) como os alelos HLADR3- DR4 e os polimorfismos do PTPN22, CTLA4 e VNTR-INS presentes em caucasianos não foram sempre encontradas com a mesma frequência na nossa população com DM1A, ou conferiram risco menor quando presentes. Tais diferenças podem advir da nossa miscigenação. Portanto, no presente estudo, objetivou-se: 1) Analisar uma amostra de portadores de DM1A da cidade de São Paulo e controles não diabéticos, utilizando marcadores genéticos autossômicos de ancestralidade, identificando os componentes ancestrais individuais e os da população, permitindo assim, maior compreensão da sua potencial estratificação; 2) Verificar o papel dos alelos do sistema HLA-DR e DQ, dos polimorfismos dos genes PTPN22, CTLA4 e INS-VNTR, na predisposição à doença, corrigindo para o viés introduzido pela estratificação da nossa população. Materiais e métodos: 915 pacientes com DM1A, idade de 24,6±13,0 anos, 81,7% autorreferidos brancos e 789 controles, idade 28,5 ± 11,5 anos, 65,6% autorreferidos brancos participaram do estudo. A genotipagem dos 93 marcadores informativos de ancestralidade foi realizada por meio da plataforma BeadXpress (Illumina, EUA). A composição ancestral dos indivíduos foi caracterizada pelo programa Structure 2.3, e os alelos e variantes dos genes candidatos, testados por...
The investigation of genes associated with complex diseases in case-control studies, based on the frequency of polymorphic variants, may not be appropriate in the presence of population stratification arising from the ethnic admixture, which is characteristic of the Brazilian population. It is therefore difficult to apply this method, due to the risk of spurious associations related to differences in the genetic background of individual cases and controls. Ancestry informative markers (AIMs) can be used to estimate ancestry and correct these distortions. The same genetic variants of susceptibility to type 1 autoimmune diabetes (T1AD) like HLA- DR3 -DR4 alleles and polymorphisms in PTPN22, CTLA4 and VNTR-INS genes usually present in caucasians were not always found at the same frequency in our population with T1AD, or conferred lower risk when present. These discrepancies may result from our miscigenation. Therefore, in this study, we aimed to: 1) analyze a sample of patients with T1AD and health controls, mostly living in São Paulo, using genetic autosomal markers of ancestry, to identify the ancestry of individual components and of the population, that could identify its potential stratification; 2) Evaluate the role of HLA-DR and -DQ alleles and polymorphisms of PTPN22, CTLA4 and INSVNTR genes in the predisposition to disease, correcting for the bias introduced by the stratification of our population. Methods: 915 patients with T1D, aged 24.6±13.0 years, 81.7% self-reported as white and 789 controls, aged 28.5±11.5 years, 65.6% self-reported as white participated of the study. Genotyping of 93 informative markers was performed by BeadXpress platform (Illumina, USA). The ancestry composition of individuals was characterized by Structure 2.3 program, and variants and alleles of candidate genes were tested using structured association analysis with the STRAT program. Results: The european ancestry prevailed in T1AD and control groups (77% and...
