VDR polymorphisms influence the immune response in type 1 diabetic children from Santiago, Chile

Abstract

Objective: To evaluate the influence of ApaI, BsmI and TaqI polymorphisms of the VDR gene and HLA-DQB1* alleles in type 1 diabetic children and to assess their possible relationship with circulating levels of 25-hydroxyvitamin D3, auto-antibodies, and INFg/TGFb1 cytokines levels in Chilean cases and controls. Methods: DNA and serum samples from 216 newly diagnosed type 1 diabetic and 203 unrelated control children were evaluated for IA-2 and GAD65 auto-antibodies, 25-hydroxyvitamin D3 levels, HLA-DQB1* alleles, and VDR gene polymorphisms. Results: The frequency of the b allele and the bb genotype in type 1 diabetic patients was significantly lower compared with the control group (0.635 versus 0.749, p < 0.01 and 0.370 versus 0.567, p < 0.04). 25-Hydroxyvitamin D3 levels showed no differences between type 1 diabetic and healthy children. In cases, 25-hydroxyvitamin D3 levels were not associated with a special autoantibodies profile according to the presence or absence of GAD65 + or IA-2+. The haplotype combination BAT was higher in cases (0.062 versus 0.019, p < 0.0022) and bAT was more frequent in controls (0.266 versus 0.180, p < 0.003). In cases, the aaBbTT genotype showed the most significant increase in TGFb1 level across the VDR categories. Finally, when considering the HLA class II risk genotype (DQB1*0302) and the VDR genotypes (AabbTT and aabbTT), higher levels of GAD65, IA-2 and TGFb1 were observed among diabetic children. Conclusion: We found an association between a VDR polymorphism (BsmI) and type 1 diabetes. An association was found of AabbTT and aabbTT genotypes and the HLA-DQB1*0302 allele with high levels of GAD65, IA-2 and TGFb1.