Vitamin D receptor rs7975232, rs731236 and rs1544410 single nucleotide polymorphisms, and 25-hydroxyvitamin D levels in Egyptian children with type 1 diabetes mellitus: effect of vitamin D co-therapy

Purpose: We aimed to examine the possible association role of vitamin D and vitamin D receptor (VDR) single nucleotide polymorphisms (SNPs) in type 1 diabetes mellitus (T1DM) development, glycemic control and complications among a cohort of Egyptian children. Subjects and methods: A prospective case-control study has been conducted on 50 Egyptian children with T1DM who were comparable with 50 controls. Vitamin D and HbA1c were measured. VDR-SNPs [ApaI (rs7975232), TaqI (rs731236) and BsmI (rs1544410)] detection was done by polymerase chain reaction through restriction fragment length polymorphism (PCR-RFLP) technique. Vitamin D supplements were given to the included T1DM children with low vitamin D and reassessments of both HbA1c% and 25(OH)D serum levels were performed in those children three months later. Results: Eighty percent of the included diabetic patients have poor glycemic control. Vitamin D was deficient in 68% and insufficient in 16% of diabetic patients. Significant improvements in both vitamin D and glycemic status among T1DM children, who have low vitamin D and received vitamin D supplementations. There were significantly negative correlations between serum levels of vitamin D with both HbA1c % (r= -0.358, P˂0.05) and daily insulin dose (r=-0.473, P˂0.05). Compared with controls, T1DM children presented more commonly with ApaI a allele (OR: 2.87; 95%CI: 1.39-5.91, P˂0.05) and BsmI b allele (OR: 4.38; 95%CI: 2.30-8.33, P˂0.05). TaqI t allele wasn't significantly differing among patients and controls (P˃0.05). Aa+aa and Bb+bb genotypes were significantly higher among T1DM vs the controls (OR: 3.08;, 95%CI: 1.33-7.15, P˂0.05 and OR: 9.33; 95%CI: 3.61-24.17, P˂0.05respectively). Conclusion: ApaI and BsmI were associated with risk of T1DM development among Egyptian children. Low vitamin D status was frequently occurring among T1DM with significant improvement in the glycemic control of such children when adding vitamin D supplements to the standard insulin therapy.