Regulatory mechanism of glycyrrhiza polysaccharide on intestinal damage and in-testinal flora in enterotoxigenic Escherichia coli-induced weaning diarrhea piglets
The aim of this study was to investigate the regulation and mechanism of glycyrrhiza pol-ysaccharides in enterotoxigenic Escherichia coli(ETEC)-induced diarrhea in weaned piglets.Twen-ty-four piglets weaned at 21 days of age were randomly divided into the control group(Con),the model group(Mod),and the glycyrrhiza polysaccharide group(GP).The GP group was given gly-cyrrhiza polysaccharide aqueous solution(1 mL/kg,10 g/L)for 14 days,and the other groups were given the same amount of sterile water.On day 15,piglets in the Mod and GP groups were given 1011 CFU/mL of ETEC bacterial solution at 1 mL/kg for 3 consecutive days,while the GP group continued to receive an aqueous glycyrrhiza polysaccharide solution.The diarrhea score of the pig-lets in each group was recorded.The intestinal histopathological changes were detected by HE stai-ning.By real-time quantitative PCR,mRNA levels of IL-1,IL-6,and IL-8 in intestinal tissues were detected.The intestinal flora changes were analyzed by microbial metagenomics.The levels of NF-κB/MAPK signaling pathway-related proteins in intestinal tissues were measured by Western blot.The results showed that,after ETEC infection,the diarrhea score in the Mod group was sig-nificantly increased(P＜0.01)compared to the Con group.The intestinal tissue structure was de-stroyed in the Mod group.The V/C value was significantly decreased(P＜0.01),and the mRNA levels of inflammatory factors IL-1β,IL-6,and IL-8 were significantly increased(P＜0.01)in the Mod group compared with the Con group.Proteobacteria were significantly increased(P＜0.01),and firmicutes were significantly decreased(P＜0.01)in the Mod group compared to the Con group.Lactobacillus was decreased,Fusobacterium was increased,and the ratio of p-JNK/JNK,p-ERK/ERK,p-p38/p38,p-p65/p65,and p-IKBα/IKBα in intestinal tissue was significantly increased(P＜0.01)in the Mod group compared to the Con group.Compared with the Mod group,the diar-rhea score of piglets in the GP group was significantly decreased(P＜0.01).Only a small amount of intestinal villi shed in the GP group,and the intestinal structure was intact.The V/C value was significantly increased(P＜0.01),and mRNA levels of inflammatory cytokines IL-6 and IL-8 were significantly decreased(P＜0.05 or P＜0.01)in the GP group compared to the Mod group.Pro-teobacteria were significantly decreased(P＜0.01),and firmicutes were significantly increased(P＜0.01)in the GP group compared with the Mod group.Lactobacillus was increased,Fusobacte-rium was decreased,and the ratios of p-JNK/JNK,p-ERK/ERK,p-p38/p38,p-p65/p65,and p-IKBα/IκBα in intestinal tissues were significantly decreased(P＜0.05 or P＜0.01)in the GP group compared to the Mod group.The possible tagged species in each group were Lactobacillus in the Con group,Fusobacterium in the Mod group,and Rothia and Eubacterium in the GP group.In con-clusion,glycyrrhiza polysaccharides can effectively relieve ETEC-induced diarrhea in weaned pig-lets.Treatment with glycyrrhiza polysaccharides improves intestinal flora disorders caused by ETEC infection,increases the abundance of beneficial bacteria,and reduces the abundance of harm-ful bacteria.Moreover,glycyrrhiza polysaccharides inhibit the activation of the NF-κB/MAPK sig-naling pathway to alleviate intestinal inflammatory damage induced by ETEC.
enterotoxigenic Escherichia colidiarrhea in weaned pigletsgut microbiotaNF-κB/MAPK signaling pathway
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