A Preliminary Study On The Mechanism Of Red Chicory Leaf Dietary Fiber Alleviating Colitis Via The "Intestinal Barrier-gut Microbiota" Pathway

Inflammatory bowel disease(IBD)is a chronic idiopathic inflammation of the gastrointestinal tract.Epidemiological studies have shown that the incidence of IBD is increasing rapidly and has become a global health problem.Red chicory(Cichorium intybus L.)is a biennial or perennial root plant from the Cichorium genus,Asteraceae family,which has significance effect of alleviating inflammation and regulation of gut microbiota.As a common species of chicory,there are few reports on the intervention of red chicory leaf and red chicory leaf dietary fiber in the treatment of colitis.In addition,people pay more attention to the efficacy of soluble dietary fiber rather than the insoluble dietary fiber.Therefore,this study extracted the soluble dietary fiber,insoluble dietary fiber and total dietary fiber from red chicory leaf.Determined the physicochemical properties of red chicory leaf and its different dietary fibers of red chicory leaf.Then,Dextran sodium sulfate-induced colitis mouse model was used to evaluate the protective effects of red chicory leaf and different dietary fibers of red chicory leaf on colitis mice,and from the perspective of intestinal barrier and gut microbiota to explore the potential mechanism.The main research contents and results are as follows:(1)The effect of red chicory leaf and its dietary fibers on disease symptom alleviation in mice with colitis was explored.First,the soluble,insoluble and total dietary fiber of red chicory leaves were extracted by enzymatic hydrolysis,the purity of soluble and insoluble dietary fiber were 86.80±2.05%and 83.85±1.40%,respectively.Red chicory leaf insoluble dietary fiber can significantly alleviate the weight loss,disease activity index(DAI),colon length,spleen distention index and the expression of TNF-α,IL-6 and MPO in the colon in mice with colitis level.In addition,the insoluble dietary fiber of red chicory leaf significantly increased the colon length and the expression level of IL-10 in the colon.Furthermore,red chicory leaf,soluble and total dietary fiber also had alleviation effect,but the effect was subtle in regulating the expression level of colonic inflammatory factors.(2)The effect of red chicory leaf and its dietary fibers on colonic intestinal barrier improvement in colitis mice was studied.The intestinal injury,number of goblet cells,the expression of MUCoprotein 2(MUC2)and tight junction protein were observed by Hematoxylin-eosin(H&E)staining,Alcian blue-Periodic acid Schiff(AB-PAS)staining and immunohistochemistry.The results showed that red chicory leaf insoluble dietary fiber can alleviate inflammation-induced colon inflammatory infiltration and tissue damage.At the same time,it can also increase the number of intestinal goblet cells,promote the expression of mucin MUC2,tight junction proteins ZO-1,Occludin and Claudin-1,and maintain the integrity of the intestinal barrier function.In addition,red chicory leaf and total dietary fiber significantly increased the expressions of MUC2,ZO-1,Occludin and Claudin-1,but did not alleviate the number of goblet cells and colon tissue damage.However,red chicory leaf soluble dietary fiber had limited effect and only significantly increased the expression of ZO-1.(3)The effect of red chicory leaf and its dietary fibers on regulating the gut microbiota in colitis mice was studied.The results of β-diversity showed that the gut microbiota of colitis mice changed after red chicory leaf and its dietary fiber intervention.Among them,the gut microbiota of the red chicory leaf insoluble diet group was most similar to that of the normal group.At the phylum level,the relative abundance of Bacteroidetes increased and the relative abundance of Verrucomicrobia decreased after intervention with soluble,insoluble and total dietary fiber of red chicory leaf.However,no effect was seen with red chicory leaf intervention.Among them,the insoluble dietary fiber has the most significant effect on regulating gut microbiota.Further analysis found that at the genus level,the relative abundances of Akkeriithithmansia,Sutterella,Clostridium,AF12 and Helicobacter were decreased,while the relative abundances of Ruminococcus,Lactococcus and Leuconostoc were increased with insoluble dietary fiber.Correlation analysis showed that t Ruminococcus,Lactococcus and Leuconostoc were positively correlated with the expression of tight junction proteins in the intestinal barrier,and Akkermansia,Sutterella,AF12 and Hellcobacter were negatively correlated with the expression of tight junction proteins in the intestinal barrier.In conclusion,red chicory and its dietary fibers can play a role in relieving colitis in mice by regulating the intestinal barrier and gut microbiota.Among them,insoluble dietary fiber showed the best effects.This study gives technical support for the development and utilization of red chicory and its dietary fiber,and provides a theoretical basis for the mechanism of red chicory and its dietary fiber alleviating colitis.