Effects And Mechanisms Of Different Bile Acids On Growth Performance And Intestinal Health Of Weaned Piglets

Since the piglets are usually weaned at an early stage,their gastrointestinal digestive systems are not yet mature,and weaning stress often causes changes in intestinal morphology,decreased digestive and absorption capacity,and intestinal barrier damage,which lead to diarrhea,poor growth performance and even death of weaned piglets.Therefore,improving intestinal barrier function and promoting intestinal health is the key to weaning piglets.In the past,the physiological function of bile acids was mainly to promote the digestion and absorption of lipids,and the bile acids were used as feed additives in aquaculture and animal husbandry.Recent studies have found that bile acids can also act as signal molecules of the body,by activating bile acid receptors to participate in the body’s bile acid metabolism,lipid and glucose metabolism,energy metabolism and immune regulation and other processes.However,there are few reports on the regulation of bile acids on the intestinal health of animals,and its mechanism of action remains to be revealed.In order to elucidate the effects and their mechanisms of different bile acids on the growth performance and intestinal health of weaned piglets,chenodeoxycholic acid(CDCA),taurodeoxycholic acid(TUDCA)and hyodeoxycholic acid(HDCA)were selected in this paper.First,the effects of three bile acids on the growth performance and intestinal health of weaned piglets were studied,and then the effect and mechanism of HDCA on intestinal epithelial cell proliferation were studied using the intestinal porcine epithelial(IPEC-J2)cells and weaned piglets.Finally,the effect and mechanism of TUDCA on intestinal epithelial barrier function impairment were investigated by using E.coli-induced IPEC-J2 cell model and lipopolysaccharide(LPS)-induced intestinal epithelial barrier function damage in a mouse model.The specific experimental design and research results are as follows:1.Effects of dietary supplementation with different bile acids on growth performance and intestinal health of weaned pigletsThe results showed that there were differences in the composition of serum and fecal bile acids between healthy and diarrhea weaned piglets,suggesting that bile acids might play an important role in maintaining the intestinal health of weaned piglets.Secondly,we conducted experiments on weaned piglets to study the effects of dietary supplementation with different bile acids on growth performance and intestinal health.144 healthy 28-day-old weaned piglets were randomly divided into 4 groups.The control(CON)group was fed a basal diet,and the CDCA group,TUDCA group and HDCA group were added 200 mg/kg CDCA,200 mg/kg TUDCA and 1000 mg/kg HDCA to the basal diet,respectively.The experiment period was 30 days.The results showed that:(1)Dietary supplementation with CDCA could increase the terminal body weight(BW)and average daily weight gain(ADG)of weaned piglets,and reduce the feed-to-gain ratio(F/G),thereby increasing growth performance;TUDCA did not affect growth performance of weaned piglets,but it reduced the diarrhea rate of weaned piglets;Dietary supplementation of HDCA significantly increased the F/G,thereby reducing the growth performance of weaned piglets.(2)Dietary supplementation with CDCA and TUDCA improved intestinal morphology,increased the number of intestinal goblet cells and the expression of tight junction proteins,reduced intestinal permeability,thereby improving the intestinal barrier function of weaned piglets.In addition,TUDCA could increase the content of Ig G in serum and SIg A in ileum contents,improving intestinal immunity.Dietary supplementation with HDCA significantly reduced the protein expression of proliferating proteins in the jejunum of weaned piglets.(3)Dietary supplementation of CDCA and TUDCA increased the m RNA expression level of pancreatic lipase and had a tendency to increase the activity of jejunum lipase,while dietary supplementation of HDCA significantly reduced the content of TG in serum.2.Effects of dietary supplementation with different bile acids on serum metabolome and gut microbiota of weaned pigletsThe analysis of the serum metabolome and gut microbiota composition showed that:(1)Dietary supplementation of CDCA,TUDCA and HDCA changed the serum metabolome of weaned pigs.KEGG enrichment analysis showed that CDCA,TUDCA and HDCA could affect tryptophan metabolism pathway and microbial metabolism pathway in weaned piglets.(2)CDCA,TUDCA and HDCA showed no significant difference in the Alpha diversity and the composition of gut microbiota at the phylum level.However,at the genus level,CDCA could improve the relative abundance of Prevotella9 and Pevotellaceaetcg-001,and reduce the relative abundance of Dorea;TUDCA could improve the relative abundance of Parabacteroides and Mucispirillum;HDCA could improve the relative abundance of Family XIIITCG-001,Parabacteroides and Prevotellaceaetcc-004.(3)After dietary supplementation with CDCA,TUDCA and HDCA,changes in serum metabolome of weaned piglets were significantly related to alterations in gut microbiota.3.Regulation of HDCA on intestinal epithelial cell proliferation and its mechanismThe in vivo results of weaned piglets showed that HDCA could inhibit the proliferation of intestinal epithelial cells.Furthermore,we studied the effect of HDCA on the proliferation of intestinal epithelial cells and its mechanism using IPEC-J2 cells and weaned piglets.The results showed that:(1)HDCA could inhibit the proliferation of intestinal epithelial cells through the FXR-PI3K/AKT pathway.(2)In weaned piglets,HDCA supplementation reduced the serum levels of several conjugated bile acids(GUDCA,GDCA,GCDCA,GCA,TCA,and TDCA)which had a proliferative effect on intestinal epithelial cells,increased fecal HDCA and THDCA+TUDCA levels and reduced the fecal TCA level.(3)The correlation analysis results showed that the changes of bile acid profiles in weaned piglets were significantly related to the alterations of bile acid-metabolizing bacteria in the gut.Therefore,The above results showed that in addition to directly inhibiting the proliferation of intestinal epithelial cells through the FXR-PI3K/AKT signaling pathway,HDCA might indirectly inhibit the proliferation of intestinal epithelial cells by affecting bile acidmetabolizing bacteria in intestinal flora and bile acid profiles in weaned piglets.4.The protective effect of TUDCA on intestinal epithelial barrier function and its mechanismIn the experiment of weaned piglets,TUDCA showed anti-inflammatory effects.Furthermore,we used the E.coli-induced IPEC-J2 model and the LPS-induced intestinal epithelial barrier function damage in a mouse model to study the effect of TUDCA on intestinal epithelial barrier function impairment and its mechanism.The results showed that:(1)100 μM TUDCA could activate TGR5 and reverse the decrease of expression of tight junction proteins ZO-1,Claudin-1 and OCC of IPEC-J2 cells induced by E.coli.After interfering with TGR5,the effect of TUDCA disappeared,indicating that TUDCA protected against E.coli-induced IPEC-J2 cell barrier damage by activating TGR5.(2)In terms of signaling pathways,TUDCA inhibited the activation of MLCK signaling pathway by E.coli,but this effect of TUDCA disappeared when TGR5 was knocked down.In addition,ML-7,a MLCK blocker,also exhibited a similar effect to TUDCA.These results indicated that TUDCA protected against E.coli-induced intestinal epithelial barrier damage through the TGR5-MLCK pathway.(3)In vivo,TUDCA could improve the LPS-induced intestinal morphological damage and reduction of intestinal barrier function of mice,and alleviate the intestinal inflammation induced by LPS,indicating that TUDCA could also repair intestinal epithelial barrier function damage induced by LPS.These above results indicated that TUDCA could protect intestinal epithelial barrier function damage.In summary,the results of this study showed that:(1)Dietary supplementation with CDCA could improve the intestinal barrier function,and improve the growth performance of weaned piglets.This might be related to the fact that CDCA increased the relative abundance of obesity-related bacteria Prevotella9 and prevotellaceae TCG-001 in the intestine,reduced the relative abundance of harmful bacteria Dorea,and increased the content of indole-3-acetic acid in serum.(2)Dietary supplementation with TUDCA could improve intestinal barrier function,enhance intestinal immunity,and reduce intestinal inflammation and diarrhea rate in piglets.This might be related to the fact that TUDCA increasd the relative abundance of Mucispirillum,which was positively correlated with intestinal mucosal immunity,and increased the content of indole-3-acetic acid in serum.In addition,TUDCA could alleviate the impairment of intestinal epithelial barrier function through TGR5-MLCK pathway.(3)Dietary supplementation with HDCA could improve F/G and reduce growth performance of weaned piglets.This might be related to the fact that HDCA increased the relative abundance of Parabacteroides,which was negatively correlated with obesity in the intestines of piglets,and the inhibitory effect of HDCA on intestinal epithelial cell proliferation.On the one hand,HDCA could inhibit the proliferation of intestinal epithelial cells through the FXR-PI3K/AKT pathway.On the other hand,HDCA might indirectly affect the proliferation of intestinal epithelial cells by affecting bile acid-metabolizing bacteria and bile acid profiles.The results of this study revealed the effects and their mechanisms of different bile acids on the growth performance and intestinal health of weaned piglets,which provided a theoretical and experimental basis for the application of bile acids in weaned piglets.