Does Vitamin D Protect the Gut Mucosal Barrier? Mechanistic Insights from Experimental Colitis

Excerpt

There is growing interest in how vitamin D and the vitamin D receptor (VDR) regulate immune responses in inflammatory bowel disease (IBD), a topic addressed by Golan et al. [1] in this issue of Digestive Diseases and Sciences. Vitamin D deficiency, measured by low circulating serum 25-hydroxyvitamin D concentration, is common in IBD and may correlate with higher disease risk, severity, and relapse rates, suggesting that targeting vitamin D pathways may provide the basis for novel therapeutic strategies [2, 3]. This hypothesis is supported by data obtained from animal models, in which vitamin D deficiency accelerates the development of experimental colitis, whereas vitamin D treatment protects against colitis and attenuates inflammation [4, 5]. The VDR is expressed in multiple cell types including T cells, macrophages, and intestinal epithelial cells. There is a considerable body of evidence from murine models of colitis indicating that the immune modulatory effects of vitamin D on T cells are mediated through the VDR [6]. Vitamin D may also regulate intestinal barrier function [7‐9], although the mechanism by which vitamin D alters the intestinal barrier in IBD is unclear. In line with this, Golan et al. [1] report their data on vitamin D/VDR-mediated mechanisms in maintaining gut barrier function in experimental colitis. …