BackgroundSeveral studies have demonstrated a fundamental role for the HLA in the susceptibility of, or protection to, type 1 diabetes mellitus (T1DM). However, this has not been adequately studied in Asian Indian populations. To assess the frequency of HLA class II (DPA1, DPB1, DQA1, DQB1 and DRB1) associated to susceptibility or protection toT1DM in a Bengali population of India with diabetes.ResultsSingle nucleotide polymorphism study. The HLA genotyping was performed by a polymerase chain reaction followed by their HLA-DP, DQ, and DRB1 genotypes and haplotypes by sequencing method. The results are studied by Plink software. The χ2 tests were used for the inferential statistics. To our knowledge, this study is the first of a kind which has attempted to check the HLA association with T1DM by SNPs analysis. The study recruited 151 patients with T1DM and same number of ethno-linguistic, sex matched non-diabetic controls. The present study found a significant SNP rs7990 of HLA-DQA1 (p = 0.009) negative correlation, again indicating that risk from HLA is considerably more with T1DM.ConclusionsThis study demonstrates that the HLA class-II alleles play a major role in genetic basis of T1DM.

Type 1 diabetes is a multifactorial disease with an early age of onset, in which the insulin producing β cell of the pancreas are destroyed because of autoimmunity. It is the second most common chronic disease in children and account for 5% to 10% of all diagnosed cases of diabetes. India is having an incidence of 10.6 cases/year/100,000, and recent studies indicate that the prevalence of type 1 diabetes in India is increasing. However in view of poor health care network, there is no monitoring system in the country. Of the 18 genomic intervals implicated for the risk to develop type 1 diabetes, the major histocompatibility complex (MHC) region on chromosome 6p21.31 has been the major contributor estimated to account for 40-50%, followed by 10% frequency of INS-VNTR at 5’ flanking region of the insulin gene on chromosome 11p15.5. However, population studies suggest that > 95% of type 1 diabetes have HLA-DR3 or DR4, or both, and in family studies, sibling pairs affected with type 1 diabetes have a non-random distribution of shared HLA haplotypes. As predisposing genetic factors such as HLA alleles are known, immunological interventions to prevent type 1 diabetes are of great interest. In the present study we have reviewed the status of molecular genetics of the disease and the approaches that need to be adopted in terms of developing patient and suitable control cohorts in the country.

Our study displays that age at menarche is delayed in young women with T1DM compared to the concurrent overall mean age at menarche in the West Bengal population.

To assess the contribution of the HLA class II region for susceptibility to type 1 diabetes mellitus (T1DM), we investigated the association of HLA class II alleles-DP, DQ, and DRB1. Here, we present an extensive molecular typing for HLA class II alleles and their haplotypes in a Bengali-speaking Indian population of T1DM patients (n=151) and controls (n=151) from West Bengal. HLA typing was done by DNA sequencing using a 3730 DNA Analyzer. The individual analysis of each gene gave the following alleles to be higher in cases than in controls, thus making them susceptible alleles-DPA1*020103, DPB1*020102, DQA1*050101, DQA1*0201, and DQB1*020101G. Similarly, the following alleles are protective alleles in our study-DPA1*010602, DPB1*040101, DQA1*010201, DQA1*0103, and DRB1*15. Our result confidently establishes that HLA-DP allelic, and its haplotypic, diversity contributes significantly to the risk for T1DM. The DQA1*0103 allele is a novel allele with a significant association with the protection from T1DM. Among the various haplotypes tested, the DQA1*0201:DQB1*020101G, DQA1*050101:DQB1*020101G, and DQA1*0201:DQB1*030101G were the most frequently found in T1DM patients. In India, very few investigations have been undertaken to study the impact of the genetic background on the risk to develop T1DM in its population, where the annual average incidence is 10.5/100,000/year. In conclusion, the present study highlights the genetic effect of HLA haplotypes that contributes to the susceptibility to T1DM.