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Muc2-dependent microbial colonization of the jejunal mucus layer is diet sensitive and confers resistance to enteric pathogen infection

ABSTRACT: Obesity is associated with an increased risk of mucosal infections; however, the mechanistic basis of this phenomenon remains incompletely defined. Intestinal mucus barrier systems normally prevent infections, but are sensitive to changes in the luminal environment. Here we demonstrate that mice exposed to an obesogenic Western-style diet (WSD) suffer regiospecific failure of the mucus barrier in the small intestinal jejunum caused by diet-induced mucus condensation, which occurs independently of microbiota alterations. Mucus barrier disruption due to either WSD exposure or chromosomal Muc2 deletion results in collapse of the commensal jejunal microbiota, which in turn sensitises mice to atypical jejunal colonization by the enteric pathogen Citrobacter rodentium. We identify the jejunal mucus layer as a microbial habitat, and link the regiospecific mucus dependency of the microbiota to fundamental properties of the jejunal niche. Together, our data identifies a symbiotic mucus-microbiota relationship that normally prevents jejunal pathogen colonization, but is highly sensitive to disruption by exposure to a Western-style diet.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Intestinal Mucosa, Small Intestine

DISEASE(S): Obesity

SUBMITTER: Liisa Arike

LAB HEAD: Liisa Arike

PROVIDER: PXD028613 | Pride | 2023-05-12

REPOSITORIES: Pride

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Project description:Colorectal cancer risk is associated with diets high in red meat. Heme, the pigment of red meat, induces cytotoxicity of colonic contents and elicits epithelial damage and compensatory hyperproliferation, leading to hyperplasia. Here we explore the possible causal role of the gut microbiota in heme-induced hyperproliferation. To this end, mice were fed a purified control or heme diet (0.5 μmol/g heme) with or without broad-spectrum antibiotics for 14 d. Heme-induced hyperproliferation was shown to depend on the presence of the gut microbiota, because hyperproliferation was completely eliminated by antibiotics, although heme-induced luminal cytotoxicity was sustained in these mice. Colon mucosa transcriptomics revealed that antibiotics block heme-induced differential expression of oncogenes, tumor suppressors, and cell turnover genes, implying that antibiotic treatment prevented the heme-dependent cytotoxic micelles to reach the epithelium. Our results indicate that this occurs because antibiotics reinforce the mucus barrier by eliminating sulfide-producing bacteria and mucin-degrading bacteria (e.g., Akkermansia). Sulfide potently reduces disulfide bonds and can drive mucin denaturation and microbial access to the mucus layer. This reduction results in formation of trisulfides that can be detected in vitro and in vivo. Therefore, trisulfides can serve as a novel marker of colonic mucolysis and thus as a proxy for mucus barrier reduction. In feces, antibiotics drastically decreased trisulfides but increased mucin polymers that can be lysed by sulfide. We conclude that the gut microbiota is required for heme-induced epithelial hyperproliferation and hyperplasia because of the capacity to reduce mucus barrier function. Mice were fed a Westernized high fat control diet, or the same diet supplemented with 0.5 µmol heme/g diet. One group of control and one group of heme mice received a mixture of broad spectrum Antibiotics (Abx) (ampicilin, neomycin and metronidazole) in their drinking water. After 14 days of intervention, mice were killed and gene expression was profiled in colon.

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Muc2-dependent microbial colonization of the jejunal mucus layer is diet sensitive and confers resistance to enteric pathogen infection

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