Evaluation of vitamin D receptor gene polymorphisms (Fok-I and Bsm-I) in T1DM Saudi children

Vitamin D deficiency conferred strongest susceptibility to pathogenesis of type 1 diabetes mellitus (T1DM). Altered gene expression and function have strong effect on VDR gene polymorphism.

We aimed to check for the association of two single nucleotide polymorphisms (SNPs) in VDR gene (Fok-I and Bsm-I) with T1DM in Saudi children.

Cross-sectional study included 100 T1DM Saudi children, plus 102 unrelated healthy subjects. PCR technique was used for detection of Fok-I and Bsm-I SNPs in VDR gene.

Regarding the Fok-I polymorphisms, T1DM cases showed a significant increased frequency of the heterozygous genotype (Ff) than controls (33% vs 21%, OR = 1.9, 95% CI = 1.006-3.587, P = .04). In the meantime, they showed significantly lower frequency of the homozygous (ff) genotype (64% vs 79%, OR = 0.51, 95% CI = 0.28-0.96, P = .03). Cases showed also a significantly lower frequency of the (f) allele than controls (80.5% vs 87.7%, OR = 0.57, 95% CI = 0.33-0.995, P = .04). On the other hand, cases showed significantly higher frequency of the Bsm-I homozygous (bb) and heterozygous (Bb) genotypes (25% vs 11.8%, P = .01, OR = 2.5, 95% CI = 1.18-5.31) & (45% vs 27.5%, P = .0, OR = 2.1, 95 % CI = 1.20-3.89, respectively). Cases showed also significantly higher frequency of (b) allele compared to control (47.5% vs 25.5%, P = .0, OR = 2.6, 95% CI = 1.74-4.02). Haplotype analysis showed an increased risk with the fB and fb haplotypes.

This study emphasizes a positive association between SNPs (Fok-I and Bsm-I) and T1DM among Saudi children with increased risk with the Fok-I F and Bsm-I b alleles.