Differential toll-like receptor 2 activation by Akkermansia muciniphila and Bacteroides thetaiotaomicron mediates the beneficial effects of Fu brick tea polysaccharide against colitis.

Fu Brick Tea Polysaccharide (FBTP) ameliorates dextran sulfate sodium (DSS)-induced colitis in mice. However, the key intestinal bacterial strains and downstream molecular mechanisms mediating these protective effects remain unclear. In this study, FBTP ameliorated colitis and concurrent liver injury in a microbiota-dependent manner, primarily by enriching Akkermansia muciniphila (A. muciniphila) and depleting Bacteroides thetaiotaomicron (B. thetaiotaomicron). The essential role of the microbiota was confirmed through fecal microbiota transplantation. Mechanistically, A. muciniphila synergistically employed both its microbe-associated molecular patterns (MAMPs) and metabolic activity to activate the toll-like receptor 2 (TLR2)-Akt anti-inflammatory signaling pathway, favorably modulating Treg/Th17 immune homeostasis. However, challenging its established status as a beneficial commensal, B. thetaiotaomicron was found to activate the TLR2-NF-κB pro-inflammatory pathway driven primarily by its MAMPs, significantly exacerbating colitis, bacterial translocation, and liver injury. The pivotal role of TLR2 in mediating these divergent bacterial outcomes was confirmed through gene knockdown experiments. In conclusion, this study reveals that FBTP restores immune homeostasis by orchestrating a complex, TLR2-dependent interplay between beneficial (A. muciniphila) and pathobiontic (B. thetaiotaomicron) bacteria. This discovery not only clarifies the therapeutic mechanism of FBTP but also highlights the context-dependent risk of key commensals, offering critical insights for developing more precise microbiota-targeted interventions.