Vitamin D plasma concentration and vitamin D receptor genetic variants confer risk of asthma: A comparison study of Taiwanese and Mongolian populations

BACKGROUND: Recent reports have suggested that lower vitamin D serum levels are associated with susceptibility to and severity of asthma in different white populations, which may be due to a lack of sunlight exposure, genetic polymorphism of vitamin D pathway genes, and dietary intake. We investigated the associations between vitamin D concentration, genetic polymorphism of the vitamin D receptor (VDR), and asthma traits in Mongolian and Taiwanese populations that inhabited two different geographical areas. METHODS: In total, 328 Han Taiwanese subjects and 381 Mongolian subjects were enrolled, and their vitamin D serum levels assayed. Genomic DNA of 178 Han Taiwanese subjects and 90 Mongolian subjects was obtained from blood samples. Single-nucleotide polymorphisms (SNPs) of VDR, ApaI (rs7975232), TaqI (rs731236), BsmI (rs1544410) and FokI (rs2228570), were selected for genotyping. Logistic regression analyses were performed to detect an association between allergic asthma status and the interaction of the VDR SNP and serum vitamin D concentration in the case–control samples. RESULTS: We observed a significantly lower vitamin D level in the Mongolian subjects as compared with the Taiwanese population. In particular, in the population under 14 years of age, the serum vitamin D level was significantly higher in the Taiwanese population, in both non-asthmatic and asthmatic subjects, than in the Mongolian non-asthmatic and asthmatic subjects, respectively (P < 0.01). Moreover, the vitamin D level in the asthmatic children was significantly lower than that in the non-asthmatic children in both the Taiwanese and Mongolian populations (P < 0.01, respectively). Furthermore, we found that the rs2228570 genotype (OR, 3.763) of the VDR SNP and the vitamin D concentration (lower than 40 ng/ml, OR: 38.938) both contribute to increased susceptibility to bronchial asthma. CONCLUSION: Our results demonstrated an association between vitamin D concentration and the risk of asthma in two populations of differing ethnicity living in different geographical areas. This information implies a potential role of vitamin D in the prevention and treatment of asthma worldwide.