Allium mongolicum Regel flavonoids promote intestinal health in goats by regulating bile acid metabolism and gut microbiota.

UNLABELLED: Bile acids (BAs) are processed and modified by intestinal microorganisms into various secondary BAs, which play a crucial role in maintaining intestinal homeostasis. Recent studies indicate that flavonoids influence the gut microbiota-BAs axis to regulate intestinal immunity and improve metabolic health, though the mechanisms remain to be elucidated. The present findings demonstrate that dietary supplementation with Allium mongolicum Regel flavonoids significantly reduced the serum concentrations of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) and markedly increased the mucosal thickness of the colon in goats. Concomitantly, the expression of tight junction proteins in the colon was upregulated, thereby reinforcing the intestinal physical barrier function. The treatment modulated the balance between T helper 17 cells and T regulatory cells. The concentrations of ursodeoxycholic acid (UDCA), lithocholic acid (LCA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA), and allo-lithocholic acid (alloLCA) increased in the ileum, while in the colon, the levels of UDCA, LCA, DCA, and CDCA were similarly increased. Dietary supplementation with flavonoids significantly reduced the ACE index of colonic bacteria, without significantly affecting β-diversity of the gut microbiota. The stability and complexity of the ileal and colonic microbiota increased. Signaling pathways such as PI3K-Akt, MAPK, and Wnt were associated with the aforementioned changes and may serve as candidate pathways. In summary, dietary supplementation with A. mongolicum Regel flavonoids in goats reduced serum inflammatory cytokines, promoted intestinal health, altered the intestinal bile acid composition (including CDCA, DCA, LCA, UDCA, and alloLCA), and modulated the structure and function of the gut microbiota.

IMPORTANCE: Flavonoids are a class of polyphenolic compounds widely distributed in fruits, vegetables, tea, legumes, and nuts. There exists a complex interplay among bile acids, gut microbiota, and the immune system. Research indicates that flavonoids can ameliorate intestinal health by modulating bile acids metabolism. In this study, dietary supplementation of Allium mongolicum Regel flavonoids significantly reduced serum inflammatory factor levels, improved colonic health of Saanen dairy goats, elevated the concentrations of certain intestinal bile acids, and altered the composition and functions of intestinal microbial communities. These findings provide novel and useful insights into the complex interplay among bile acids, gut microbiota, and intestinal immunity while offering a theoretical basis for the utilization of A. mongolicum Regel flavonoids as a green feed additive.