Vitamin D supplementation partially affects colonic changes in dextran sulfate sodium-induced colitis obese mice but not lean mice.

Inflammatory bowel disease (IBD) often accompanies vitamin D deficiency, and vitamin D supplementation ameliorates IBD symptoms in animal models and humans. Because altered vitamin D metabolism has been reported in obesity, we hypothesized that the effects of vitamin D on the development of IBD would be different between obese and control mice. Five-week-old male C57BL/6N mice were divided into 4 groups and fed a diet differing in fat content (10% or 45%, normal diet [ND] or high-fat diet [HFD]) and vitamin D content (1000 or 10 000 IU/kg of diet, vDC or vDS) for 14 weeks. At week 13, colitis was induced by administration of 2% dextran sodium sulfate for 7 days. Histology score tended to be lower in the HFD-vDS group than HFD-vDC group, but there was no effect of vitamin D on the ND group. Colonic Cldn1 and Cyp27b1 mRNA levels were higher in the HFD-vDS than HFD-vDC group, but these effects of vitamin D were not observed in the ND group. The serum 25-hydroxy vitamin D levels were negatively correlated with the histology score in the HFD group but not in the ND group. Overall, these results suggest that vitamin D supplementation partially prevents the histological damage of the colon in obese mice but not in control mice. This effect might be mediated by increased colonic Cyp27b1 levels, leading to upregulation of local 1,25-dihydroxy vitamin D production.