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 ( Fok I, Bsm I, Apa I, and Taq I) 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 Bsm I and Taq I were less prevalent in patients with CD (all P  < 0.05/4 = 0.0125). The AAC haplotype formed by Bsm I, Apa I, and Taq I 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 (15.46 ± 8.11 vs 21.64 ± 9.45 ng/mL, P  < 0.001) and negatively linked to CD activity index ( β  = −0.829, P  < 0.001), platelet count ( β  = −0.253, P  < 0.001) and neutrophil percentage ( β  = −0.136, P  = 0.005) in patients with CD. The Apa I mutant genotype and vitamin D deficiency (<20 ng/mL) were independently associated with CD ( P  = 0.009, P  < 0.001, respectively). In patients with CD, vitamin D deficiency interacted with Fok I, Apa I, and Taq I mutant genotypes ( P  = 0.027, P  = 0.024, and P  = 0.040, respectively). Conclusions: Vitamin D receptor ( Bsm I, Apa I, and Taq I) mutations and lower 25(OH)D levels are associated with CD in Chinese patients. Moreover, VDR ( Fok I, Apa I, and Taq I) mutations and vitamin D deficiency may have a combined impact on CD.