Effects And Mechanisms Of CDCA On The Intestinal Barrier Dysfunction

Bile acid is the important component of bile.It was thought its physiological role was mainly to promote digestion and absorption of fat and fat-soluble substances.New research shows that bile acid is an important endogenous signal molecule and has a wide range of biological effects such as regulating glucose and lipid metabolism,energy balance,and immune response.Chenodeoxycholic Acid(CDCA)is one of the primary bile acids synthesized by the liver and is secreted from the gallbladder into the intestine after took food.So far,Studies about CDCA regulates lipid metabolism,solubilization and absorption of cholesterol and fat-soluble vitamins,were clearly.But there are few studies investigate the effects of CDCA on intestinal health.To investigate whether CDCA can protect the intestinal barrier,the following experiment were performed in this study.36 4-weeks-old C57/BL male mice were selected and randomly divided in control group,HFD group and HFD+CDCA group.The control group was fed a diet contained 10% energy,the HFD group was fed a diet contained 60% energy,and HFD+CDCA group was contained 0.5% CDCA based on high-fat diets.After 4 weeks of feeding,mice were executed for serum and ileum.The number of goblet cells and expression of tight junction protein in the ileum and the levels of lipopolysaccharides(LPS)in the serum were measured.It was found that high-fat diets can lead to decreasing of the number of goblet cells and the expression of tight junction proteins,whereas the addition of CDCA based on high-fat diets significantly reversed these effects.The level of LPS in serum was increased in the model of intestinal barrier injury induced by HFD.For this reason,LPS was added to drinking water to build another model of intestinal barrier dysfunction to observe its effect on intestinal barrier injury.48 4-weeksold C57/BL male mice were randomly divided into control group,LPS group,CDCA group and LPS+CDCA group while LPS group drank water contained 80 mg/L LPS,and CDCA group fed diet contained 0.5% CDCA,the LPS+CDCA group added CDCA to the diet based on the addition of LPS to the drinking water,and observed whether CDCA had protective effect on LPS-induced intestinal barrier injury in mice.The results showed that the levels of FITC-Dxtran in serum in LPS group mice was increased,and the expression of TJ protein in the intestine of mice was destroyed,and the expression of myosin light chain kinase(MLCK)in the related signaling pathway was significantly increased.The addition of CDCA to the diet significantly alleviated these effects.In order to further reveal the protective mechanism of CDCA on intestinal barrier injury at the cellular and molecular level,intestinal porcine epithelial cells(IPEC-J2)were used in the following experiment,cultured with concentration of 50 ?L of CDCA and 1 ng/ml of LPS to observe changes in trans-epithelium electrical resistance(TEER)and TJ protein expression.The results showed that: LPS significantly increased the number of TEER,and disrupted the expression of tight junction proteins and myosin light chain kinase,CDCA significantly reversed this effect.Based on the above phenotypes,the mechanism of CDCA affecting intestinal mucosal barrier function was further studied: cells cultured with CDCA and LPS while interfered with FXR or TGR5 at the same time,and the number of TEER and expression of tight junction protein were observed.The results showed that effect of CDCA was disappeared after the interference with FXR,but the interference with TGR5 had no similar effect.We further activated the expression of the inflammatory pathway p65,which also reversed the mitigation effect of CDCA on intestinal barrier injury function.The results showed that: CDCA activates FXR to reduce the expression of inflammatory signaling molecule p65,thereby reducing the expression of MLCK and reducing the damage of intestinal mucosal barrier function.