The Effects Of Vitamin D On Inflammatory Bowel Disease

Inflammatory bowel disease(IBD)is a chronic non-specific inflammatory disease of the intestine that is highly prevalent and difficult to cure completely.Studies have indicated that vitamin D(Vit D)supplementation may be effective in relieving IBD,but there is still controversy among different studies.Even with the strong promotion of Vit D fortified foods,Vit D deficiency is still prevalent in IBD patients.Lipids are important carriers for the digestion and absorption of Vit D.Medium and long chain triacylglycerol(MLCT),as novel lipids,have shown beneficial effects on the nutritional treatment of patients with IBD,while differences in the rate,extent and order of hydrolysis among different MLCT structures may affect the degree of digestion and absorbabilty of Vit D.Therefore,in this paper,the correlation between IBD and Vit D was investigated by meta-analysis,and the mechanism of Vit D to alleviate IBD by mice model in the aspects of recovery of epigenetic indicators of enteritis,modulation of inflammatory cytokines,intestinal luminal mucus layer and intestinal barrier protection,etc.Finally,the influence of MLCT structure on the degree of digestion and absorbabilty of Vit D was illustrated from the perspective of lipid digestion and absorption.The main research contents of the paper are as follows.Firstly,this paper uses a systematic evaluation and meta-analysis to integrate data from existing clinical studies to investigate the effects of Vit D supplementation on patients with IBD.The results showed that Vit D supplementation significantly reduced serum levels of C-repector protein(CRP),and the effect was more pronounced in the subgroup with high frequency of vitamin D supplementation.Significant reduction in disease activity index(DAI)levels in IBD patients with Vit D supplementation was shown at higher supplements.In addition,Vit D supplementation significantly increased serum 25 hydroxyvitamin D[25(OH)D]levels,and improved the defiency of Vit D in IBD patients.Secondly,different doses of Vit D were used to intervene in a mice model of ulcerative colitis(UC)to investigate the effects of vitamin D on the apparent indicators of enterocolitis,inflammatory cytokines,intestinal luminal mucus layer,and cell-linked proteins.The results showed that Vit D was effective in alleviating IBD by reducing weight loss,shortening of the colon,and decreasing DAI and tissue damage scores in UC mice compared to the modeling group(P<0.05);decreasing the levels of pro-inflammatory factors tumor necrosis factor-?,interleukin-6 and interleukin-1?(P<0.05)to reduce the inflammation in colon tissue;increasing the levels of mucin(MUC₂),tight junction proteins(ZO-1 and Claudin-3)and adherens juction protein E-cadherin1(P<0.05)to effectively alleviate intestinal barrier damage.The correlation analysis showed that serum 25(OH)D levels is significantly positively correlated with colonic length(R²_adj=0.38,P<0.001);and significantly negatively correlate with DAI(R²_adj=0.18,P<0.05)and tissue damage score(R²_adj=0.40,P<0.001).Spearman correlation analysis showed that inflammatory factors,tight junction protein and adherens junctions protein are correlated with all four of these epistatic indices.The above results showed that Vit D has effective function on UC mice.Finally,the animal models were used to compare the effects of physical mixtures(MCT/LCT)and synthetically structured triacylglycerol(STG)with different MLCT structures on the degree of digestion and absorbability in Vit D,and the reason for the difference from the perspective of lipid digestion and absorption was investigated through in vitro simulated digestion model.The results showed that the delivery of Vit D with STG as a carrier is more bioavailable in animal(18.75 ng/m L,P<0.05).Further,the in vitro simulated digestion results showed that both oil bases had similar results of particle size and Zeta potential during intital stage and stomach digestion stage.The main differences were found in the small intestine stage.The mean particle size of the STG digestion products was larger at earliar stage,while was similar with MCT/LCT for both middle and end stages.The absolute values of the Zeta potential of STG digestion products were larger during small intestine digestion stage,which showed that STG digestion system was more stable.The results for microstructure and particle size potential were consistent.From the results of lipid digestion products,the triacylglycerol structures of MCT/LCT and STG differed,resulting in significant differences in the rate of hydrolysis,the degree of hydrolysis,and the composition of hydrolysis products.The higher maximum FFA release(68.26%,P<0.05),FFA release rate(0.06,P<0.05),lipolysis rate(89.28%,P<0.05)and long-chain fatty acid to short-chain fatty acid ratio(4.85,P<0.05)of STG results in a higher capacity to accommodate Vit D when forming mixed micelles,that is,higher bioaccessibility(61.31%,P<0.05).These factors increases the degree of digestion and absorbability of Vit D.In conclusion,Vit D supplementation has the effect to improve IBD,and the degree of digestion and absorbabilty of Vit D is higher with STG as the delivery carrier.This paper provides theoretical guidance for the search of nutrients with improving IBD effects and effective solutions for the development of products with high Vit D absorption efficiency.