MAM secreted by Faecalibacterium prausnitzii ameliorates colitis through activation of autophagy and modulation of gut microbiota

Objective: Faecalibacterium prausnitzii is a major commensal bacterium that contributes to intestinal homeostasis. Its secreted microbial anti-inflammatory molecule (MAM) has been identified as a potential therapeutic agent for inflammatory bowel disease (IBD). However, the underlying molecular mechanisms through which MAM exerts its beneficial effects remain incompletely understood. This study aimed to investigate whether MAM modulates autophagy and to evaluate its therapeutic potential in a murine model of colitis. Methods: A genetically engineered Lactococcus lactis strain expressing MAM was administered to mice with dextran sulfate sodium (DSS)-induced colitis. The therapeutic effects of MAM were evaluated by clinical scoring, histopathological analysis, and measurement of inflammatory cytokines. Intestinal barrier function was assessed by measuring tight junction protein expression. Autophagy-related signaling pathways were analyzed using Western blotting and immunohistochemistry. Gut microbiota composition was profiled via 16S rRNA sequencing. To assess the role of autophagy in MAM-mediated protection, an autophagy inhibitor was administered to a subset of DSS-treated mice. Results: MAM treatment significantly alleviated DSS-induced colitis, as indicated by reduced disease activity index (DAI), improved histopathological scores, and decreased levels of pro-inflammatory cytokines such as TNF-α and IL-6. MAM enhanced intestinal barrier integrity by upregulating ZO-1 and occludin. Mechanistically, MAM modulated key autophagy-related proteins, including P62 and Beclin-1. Notably, even under conditions of autophagy inhibition, MAM retained partial anti-inflammatory effects, suggesting that its therapeutic action is not solely dependent on autophagy. Furthermore, 16S rRNA sequencing revealed that MAM treatment enriched beneficial taxa such as Lactobacillus and Lachnospiraceae_NK4A136_group , indicating a potential role in microbiota remodeling. Conclusion: This study identifies MAM as a multifunctional microbial effector with potent anti-inflammatory properties. Through dual mechanisms involving modulation of autophagy and gut microbiota composition, MAM improves intestinal barrier function and attenuates experimental colitis. These findings highlight the translational potential of MAM and support further investigation into its use as a novel therapeutic strategy for IBD.