Galacto-Oligosaccharides Alleviate LPS-Induced Immune Imbalance in Small Intestine through Regulating Gut Microbe Composition and Bile Acid Pool

Recent evidence suggests that the protective effect of gut microbiota on intestinal inflammation can be achieved through a microbe-bile acids (BAs) mechanism. Galacto-oligosaccharides (GOS) are a kind of prebiotic that alter gut microbiota composition. To verify whether GOS has a protective effect on intestinal inflammation through a microbe-BAs mechanism, this research was performed in a lipopolysaccharide (LPS) porcine model with the presence or absence of GOS. GOS prevented LPS-induced production of pro-inflammatory cytokines, the decrease of bacterial bile salt hydrolase-containing bacteria abundance, and the decrease of chendoxycholic acid (CDCA) level in piglets. Additionally, CDCA decreased LPS-induced production of pro-inflammatory cytokines, induced the expression of the takeda G-protein receptor 5 (TGR5), and its downstream cyclic adenosine monophosphate (cAMP) production in lamina propria-derived CD11b⁺ cells. The cAMP inhibitor eliminated the protective effect of CDCA on lamina propria-derived CD11b⁺ cells. These results suggested that GOS reduced the production of pro-inflammatory cytokines and inhibited NF-κB activation via microbe-BA-dependent TGR5-cAMP signaling in LPS-challenged piglets.