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. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2026.