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

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 D(3), auto-antibodies, and INFgamma/TGFbeta1 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 GAD(65) auto-antibodies, 25-hydroxyvitamin D(3) 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 D(3) levels showed no differences between type 1 diabetic and healthy children. In cases, 25-hydroxyvitamin D(3) levels were not associated with a special auto-antibodies profile according to the presence or absence of GAD(65)(+) 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 TGFbeta1 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 GAD(65), IA-2 and TGFbeta1 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 GAD(65), IA-2 and TGFbeta1.