The Association Between Vitamin D Receptor Polymorphisms and Serum 25-hydroxyvitamin D Levels with Ulcerative Colitis in Chinese Han Population

There is now growing evidence suggesting that Vitamin D is playing a critical role in modulating the innate and adaptive immune responses. Several polymorphisms have been identified in the vitamin D receptor (VDR) gene but their association with ulcerative colitis (UC) susceptibility remained controversy. In the current study, we examined the association between VDR polymorphisms and serum level of 25-hydroxyvitamin D [25(OH)D] with UC in Chinese Han population. Polymorphisms of FokI (rs2228570)/BsmI (rs1544410)/ApaI (rs7975232)/TaqI (rs731236) in the VDR gene were assessed in a case-control study comprising 404 UC patients and 612 controls. Moreover, 25(OH)D levels were measured by electro-chemiluminescence immunoassay in 75 UC patients and 120 controls. Our results suggested that BsmI polymorphism frequency was significantly lower in UC patients (P=0.028), and the frequency of AAC haplotype formed by BsmI, ApaI and TaqI was also significantly lower in UC patients (P=0.012). Moreover, FokI polymorphism was more frequently observed in patients with mild and moderate UC as compared to those with severe UC (P=0.001, P<0.001, respectively). Average 25(OH)D level was lower in UC patients than in controls (19.3±6.8 vs. 21.8±7.3ng/mL, P=0.017), and was significantly correlated with hemoglobin (β=0.49, P<0.001), C-reactive protein (β=-0.36, P<0.001), severity of UC (β=-0.21, P=0.025) and FokI polymorphism (β=-0.20, P=0.031) in UC patients. Interestingly, there was a significant correlation between FokI polymorphism and vitamin D deficiency (<20ng/mL) in UC patients (P=0.006). Together, these results supported that VDR polymorphisms and 25(OH)D level were significantly correlated with UC risk and severity in Chinese Han population.