Association of vitamin D receptor gene polymorphisms and serum 25-hydroxyvitamin D levels with Crohn's disease in Chinese patients

Background and Aim:The vitamin D receptor (VDR) regulates immune responses and inflammation through binding with 1,25-dihydroxyvitamin D, the active form of vitamin D. The serum 25-hydroxyvitamin D (25(OH)D) level clinically reflects vitamin D status in the human body. We investigated the association of VDR polymorphisms and 25(OH)D levels in Chinese patients with Crohn's disease (CD). Methods:Vitamin D receptor polymorphisms (FokI, BsmI, ApaI, and TaqI) were genotyped by SNaPshot. Serum 25(OH)D levels were measured by electro-chemiluminescence immunoassay. Results:A total of 297 patients with CD and 446 controls were recruited. Compared with controls, mutant alleles and genotypes of BsmI and TaqI were less prevalent in patients with CD (all P<0.05/4=0.0125). The AAC haplotype formed by BsmI, ApaI, and TaqI was also less prevalent in patients with CD (P=0.004). Furthermore, 124 patients and 188 controls were randomly selected for measurements of 25(OH)D levels. Average 25(OH)D level was lower in patients with CD than in controls (15.468.11 vs 21.64 +/- 9.45ng/mL, P<0.001) and negatively linked to CD activity index (=-0.829, P<0.001), platelet count (=-0.253, P<0.001) and neutrophil percentage (=-0.136, P=0.005) in patients with CD. The ApaI mutant genotype and vitamin D deficiency (<20ng/mL) were independently associated with CD (P=0.009, P<0.001, respectively). In patients with CD, vitamin D deficiency interacted with FokI, ApaI, and TaqI mutant genotypes (P=0.027, P=0.024, and P=0.040, respectively). Conclusions:Vitamin D receptor (BsmI, ApaI, and TaqI) mutations and lower 25(OH)D levels are associated with CD in Chinese patients. Moreover, VDR (FokI, ApaI, and TaqI) mutations and vitamin D deficiency may have a combined impact on CD.