Gut microbiota-derived metabolites contribute negatively to hindgut barrier function development at the early weaning goat model

Early weaning induces intestinal injury,leading to a series of long-term symptoms such as inflammation,malabsorption and diarrhea.In this study,we hypothesized that microbes and theirmetabolitesmodulate the host's inflammatory response to early weaning stress in a goatmodel.A total of 18 female Tibetan goat kids(n?9)wereweaned fromtheirmothers at 28 d(D28)and 60 d(D60)postpartum.D60 and D28 groupswere fed the same solid diet ad libitum fromweaning to 75 d of age.The colonic epithelium was subject to RNAsequencing,the caecal digesta metabolomics were assessed by liquid chromatographyetandem mass spectrometry(LC-MS/MS),and the caecal microbiota composition was analysed by 16S ribosomal RNA gene sequencing.We foundthatearlyweaningsubstantially increased the colonic pro-apoptotic gene expressionof B-cell lymphoma associated X(Bax),caspase-9,and caspase-3,and decreased the expression of zonula occludens-1(ZO-1)and claudin-1(P<0.01).In addition,a significant Bacteroides acidifaciens enrichmentwas observed in the hindgut of early-weaned goats(P<0.01),which negatively correlated with lysophosphatidylcholine products.Similarly,the chemokine signaling,IL-17 signaling,and peroxisome proliferatorsactivated receptor(PPAR)signaling pathways were upregulated in the colonic mucosa of the early-weaned goats.By applying caecal microbiota transplantation from goats to defaunated C57/6J mice,we confirmed that caecalmicrobiota of D28 goat kids increased the relative abundance of B.acidifaciens and significantly upregulated the genes of Bax,G proteinecoupled receptor(GPR)109A,GPR 43,fatty acid binding protein 6,nuclear receptor subfamily 1 group H member 3,angiotensin converting enzyme 2,and IL-6 expression(P<0.05),and decreased ZO-1,and claudin-1 protein expression in the mice jejunum and colon(P<0.001).These results proposed that the hindgut microbiota andmetabolites mediate the barrier functionweakening duringearlyweaning,and the relative abundance of B.acidifacienswas negatively correlatedwiththe hindgut barrier gene expression.This studydemonstrateshowweaningstress canaffectkeyhostemicrobe interaction regulators in the hindgut,in a lysophosphatidylcholine dependent and independent manner.Furthermore,based on our mice data,these results are transferable to other mammal species.