Genetic variants in vitamin D pathway in Egyptian asthmatic children: A pilot study

Objectives: Asthma is a genetically heterogeneous disease. Genetic variants in vitamin D pathway have been reported to be involved with asthma risk. The study aimed to test whether vitamin D binding protein (VDBP or GC-group component) and vitamin D receptor (VDR) gene polymorphisms were associated with asthma characteristics as well as vitamin D level in Egyptian children. Design and methods: The study included 51 asthmatic children and 33 healthy controls of matched sex and age. All participants were genotyped for two SNPs; GC (rs2282679) and VDR (rs2228570) using TaqMan allele discrimination assays. Results: Genotype distribution of GC and VDR showed a significant association with asthma (P= 0.02, P= 0.002). Children carrying the risk "G" allele for GC SNP are 2.22. times more prone to develop asthma [OR = 2.22, 95% CI (1.18-4.2)] whereas those carrying the risk "F" allele for VDR SNP are nearly twice and half times susceptible for asthma development [OR = 2.68, 95% CI (1.36-5.28)] than healthy individuals. For the GC SNP, homozygous children "GG" exhibited significant difference in pulmonary functions (FEV1, FEV1/FVC), asthma severity and asthma control, IgE and vitamin D levels compared to pooled cases of GT and TT genotypes. For the VDR SNP, no significant association between VDR variants and the tested characteristics except for the pulmonary functions where the FEV1/FVC in asthmatic children with "FF "genotype differ significantly from those carrying "Ff"genotype. Conclusion: GC and VDR variants may be implicated in asthma susceptibility; hence, further larger studies are still needed to extrapolate our findings to the general population. © 2013 American Society for Histocompatibility and Immunogenetics.