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Akkermansia muciniphila Exerts Strain-Specific Effects on DSS-Induced Ulcerative Colitis in Mice.

ABSTRACT: Akkermansia muciniphila is a commensal bacterium of the gut mucus layer. Although both in vitro and in vivo data have shown that A. muciniphila strains exhibit strain-specific modulation of gut functions, its ability to moderate immunity to ulcerative colitis have not been verified. We selected three isolated human A. muciniphila strains (FSDLZ39M14, FSDLZ36M5 and FSDLZ20M4) and the A. muciniphila type strain ATCC BAA-835 to examine the effects of different A. muciniphila strains on dextran sulfate sodium-induced colitis. All of the A. muciniphila strains were cultured anaerobically in brain heart infusion medium supplemented with 0.25% type II mucin from porcine stomach. To create animal models, colitis was established in C57BL/6 mice which randomly divided into six groups with 10 mice in each group by adding 3% dextran sulfate sodium to drinking water for 7 days. A. muciniphila strains were orally administered to the mice at a dose of 1 × 10⁹ CFU. Only A. muciniphila FSDLZ36M5 exerted significant protection against ulcerative colitis (UC) by increasing the colon length, restoring body weight, decreasing gut permeability and promoting anti-inflammatory cytokine expression. However, the other strains (FSDLZ39M14, ATCC BAA-835 and FSDLZ20M4) failed to provide these effects. Notably, A. muciniphila FSDLZ20M4 showed a tendency to exacerbate inflammation according to several indicators. Gut microbiota sequencing showed that A. muciniphila FSDLZ36M5 supplementation recovered the gut microbiota of mice to a similar state to that of the control group. A comparative genomic analysis demonstrated that the positive effects of A. muciniphila FSDLZ36M5 compared with the FSDLZ20M4 strain may be associated with specific functional genes that are involved in immune defense mechanisms and protein synthesis. Our results verify the efficacy of A. muciniphila in improving UC and provide gene targets for the efficient and rapid screening of A. muciniphila strains with UC-alleviating effects.

SUBMITTER: Liu Q

PROVIDER: S-EPMC8371549 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The present study aimed to determine if metformin exerts anti-inflammatory and mucus-protective effects via the gut microbiota. Metformin has extensive benefits including anti-inflammatory effects. Previous studies showed that metformin changed the gut microbiota composition and increases the number of goblet cells. Intestinal dysbiosis and goblet cell depletion are important features of ulcerative colitis (UC). The underlying mechanism and whether metformin can improve the mucus barrier in UC remain unclear. Metformin (400 mg/kg/day) was administered to mice with dextran sulfate sodium (DSS)-induced UC for 2 wk to investigate the effects of metformin on the intestinal mucus barrier. The gut microbiota was depleted, using antibiotics, to explore its role in the mucus-protecting effects of metformin. Akkermansia muciniphila (A. muciniphila), which was enriched in metformin-treated mice, was administered to mice to investigate the effects of the bacteria on UC and the mucus barrier. Metformin attenuated DSS-induced UC in mice, as evidenced by the alleviation of diarrhea, hematochezia, and the decrease in body weight. The expression of mucin2, a prominent mucus barrier protein, was increased in the metformin-treated group compared to the DSS-treated group. Furthermore, fecal 16S rRNA analysis showed that metformin treatment changed the gut microbiota composition by increasing the relative abundance of Lactobacillus and Akkermansia species while decreasing Erysipelatoclostridium at the genus level. Antibiotic treatment partly abolished the anti-inflammatory and mucus-protecting effects of metformin. Administration of A. muciniphila alleviated the colonic inflammation and mucus barrier disruption. Metformin alleviated DSS-induced UC in mice and protected against cell damage via affecting the gut microbiota, thereby providing a new mechanism for the therapeutic effect of metformin in patients with UC. This study also provides evidence that A. muciniphila as a probiotic has potential benefits for UC.

Project description:Akkermansia muciniphila has been proved to play a crucial role in the progression of colitis, but its underlying mechanism remains inconclusive. In this study, we aim to investigate the effect of A. muciniphila on the development of acute colitis and explore the underlying mechanism. We found that the fecal level of A. muciniphila was decreased in ulcerative colitis (UC) patients compared to the healthy people in the GMrepo database. Oral administration of A. muciniphila strain BAA-835 significantly ameliorated the symptoms in dextran sulfate sodium (DSS)-induced acute colitis, evidenced by decreased body weight loss, colon length shortening, and colon histological inflammatory score. In addition, the number of goblet cells and the mucin family were enhanced after A. muciniphila treatment. Furthermore, proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and monocyte chemoattractant protein 1 (MCP-1) had a downward trend. Mechanistically, the expression of NLRP3, caspase-1 p20, and IL-1β p17 were upregulated in A. muciniphila-treated mice. Additionally, the colon tissues from high-A. muciniphila UC patients had a higher NLRP3 expression than that from low-A. muciniphila UC patients. Moreover, the upregulation of NLRP3 was observed in mouse macrophage Raw264.7 cells and bone marrow-derived macrophage (BMDM) cells after incubation with A. muciniphila. To clarify whether the protective effect of A. muciniphila in colitis depends on NLRP3, we performed the NLRP3-deficient assay in NLRP3-/- mice in vivo. The evidence showed that NLRP3 deficiency eliminated the protective effects of A. muciniphila in acute colitis. In conclusion, A. muciniphila alleviates DSS-induced acute colitis by NLRP3 activation, which enriches the mechanism and provides a new prospect for the probiotic-based treatment of colitis. IMPORTANCE The gut microbiota and host immune response interaction influences the progression of intestinal inflammatory disease. As a well-recognized next-generation probiotic, Akkermansia muciniphila has been proved to play a crucial role in the progression of colitis, but its underlying mechanism remains inconclusive. We found that oral administration of A. muciniphila strain BAA-835 significantly ameliorated the symptoms of acute colitis. Mechanistically, the expression of NLRP3 was upregulated in the A. muciniphila group, and the protective effect of A. muciniphila in colitis depends on NLRP3 activation. This enriches the mechanism and provides a new prospect for the probiotic-based treatment of colitis, which would promote a deeper understanding of the complex characteristics of A. muciniphila and provide guidance for the treatment of human colitis in the future.

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Akkermansia muciniphila Exerts Strain-Specific Effects on DSS-Induced Ulcerative Colitis in Mice.

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