Vitamin D Deficiency in Uygurs and Kazaks Is Associated with Polymorphisms in CYP2R1 and DHCR7/NADSYN1 Genes.

BACKGROUND: Our study is aimed to 1) clarify the vitamin D status in Uygur and Kazak ethnic populations and 2) elucidate the relationship between 14 SNPs (in 5 vitamin D-related genes) and vitamin D deficiency in these 2 ethnic populations.

MATERIAL AND METHODS: A multistage-cluster sampling survey was carried out for residents with Uygur or Kazak ethnicity in Xinjiang, China. Anthropometric measurements were taken and the concentrations of 25OHD were measured. Fourteen common variants in VDR, GC, CYP2R1, CYP27B1, and DHCR7/NADSYN1 were genotyped by using multiple SNaPshot assay. Logistic regression analysis was performed to identify the possible risk factors for vitamin D deficiency, after adjusting for several environmental and biological factors. The pattern of SNP associations was distinct between Uygurs and Kazaks.

RESULTS: Anthropometric measurements and the concentrations of 25OHD were obtained from 1873 participants (945 Uygur ethnic and 928 Kazak ethnic). The genotypes of 14 SNPs were measured for 300 Uygurs and 300 Kazaks. The median 25OHD concentration was as low as 10.4 ng/ml in Uygurs and 16.2 ng/ml in Kazaks. In Uygurs, the prevalence of vitamin D deficiency, in-sufficiency, and sufficiency was 91.2%, 5.8%, and 3.0%, respectively. CYP2R1-rs10766197 was significantly associated with the presence of vitamin D deficiency in the Uygur ethnic population (P=0.019, OR=6.533, 95%C.I.: 361-31.357), while DHCR7/NADSYN1-rs12785878 was significantly associated with the presence of vitamin D deficiency in the Kazak ethnic population (P=0.011, OR=2.442, 95%C.I.: 1.224-4.873). Of 10 SNPs in VDR and GC genes, none was associated with vitamin D status in these 2 ethnic populations.

CONCLUSIONS: Vitamin D insufficiency is highly prevalent in Uygurs and Kazaks living in Xinjiang, China. Polymorphisms in CYP2R1-rs10766197 and DHCR7/NADSYN1-rs12785878 are associated with vitamin D deficiency in Uygur and Kazak ethnic populations.