Investigation of the Effect of Akkermansia muciniphila Muc T (ATCC BAA-835) on TLR4/NF-Kappa B/NLRP2 Signaling Pathway and Intestinal Microbiota in Diarrhea-Predominant Irritable Bowel Syndrome in Rats.

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a functional gastrointestinal disorder associated with gut microbiota dysbiosis, intestinal barrier dysfunction, and low-grade inflammation. This study aimed to evaluate the effects of Akkermansia muciniphila Muc T (ATCC BAA-835) on gut microbiota composition, intestinal barrier integrity, and TLR4/NF-κB/NLRP2-mediated inflammatory signaling in a stress-induced rat model of IBS-D. IBS-D was induced in rats using combined chronic and acute stress paradigms. Animals received A. muciniphila supplementation during the experimental period. Serum inflammatory cytokines and tight junction-related proteins were quantified by ELISA. Protein expression levels of TLR4, NF-κB, and NLRP2 were assessed by Western blotting. Gut microbiota composition was analyzed using 16 S rRNA gene sequencing of fecal samples. Histopathological and immunofluorescence analyses were performed to assess tissue inflammation and cellular damage. IBS-D rats exhibited increased inflammatory cytokine levels, impaired tight junction protein expression, activation of the TLR4/NF-κB/NLRP2 pathway, and significant alterations in gut microbiota diversity. A. muciniphila supplementation significantly attenuated inflammatory responses, restored intestinal barrier-associated proteins, and suppressed inflammatory signaling. Microbiota analysis revealed partial correction of dysbiosis, including increased abundance of beneficial taxa such as Faecalibacterium prausnitzii. A. muciniphila alleviates IBS-D-associated intestinal inflammation and barrier dysfunction by modulating gut microbiota composition and inflammatory signaling pathways, supporting its potential as a microbiota-based therapeutic strategy for IBS-D.