Project description:Here we have shown that diet-mediated alterations of the gut microbiota composition cause an erosion of the colonic mucus barrier. A compensatory increase in cellular mucus production by the host is not sufficient to re-establish the barrier, possibly due to a lacking increase in mucus secretion. While microbial transplant from mice fed a fiber-rich diet can prevent the mucus defects, the mechanism seems to be independent of general fiber fermentation and rather depend on distinct bacterial species and/or their metabolites.
Project description:Antibiotic use is a risk factor for development of inflammatory bowel diseases (IBDs). IBDs are characterized by a damaged mucus layer, which does not properly separate the host intestinal epithelium from the microbiota. Here, we hypothesized that antibiotics might affect the integrity of the mucus barrier. By systematically determining the effects of different antibiotics on mucus layer penetrability we found that oral antibiotic treatment led to breakdown of the mucus barrier and penetration of bacteria into the mucus layer. Using fecal microbiota transplant, RNA sequencing followed by machine learning and ex vivo mucus secretion measurements, we determined that antibiotic treatment induces ER stress and inhibits colonic mucus secretion in a microbiota-independent manner. This mucus secretion flaw led to penetration of bacteria into the colonic mucus layer, translocation of microbial antigens into circulation and exacerbation of ulcerations in a mouse model of IBD. Thus, antibiotic use might predispose to development of intestinal inflammation by impeding mucus production.
Project description:Mucus/MUC2 from TGM3-deficient mice is less cross-linked with isopeptide-bond cross-links compared to Mucus/MUC2 from WT mice. This results in protease-labile MUC2-molecules that become degraded in the colonic lumen
Project description:The colonic inner mucus layer protects us from pathogen invasion and commensal-induced inflammation. Mucus abnormalities are common in ulcerative colitis (UC), but their cause and importance are unknown. The aim of this study was to determine the role of compositional mucus barrier alterations in UC. In this single-center case-control study, sigmoid colon biopsies were obtained from UC patients with ongoing inflammation (n=36) and in remission (n=28), and from 47 patients without inflammatory bowel disease. Mucus samples were collected from biopsies ex vivo, and their protein composition analyzed by mass spectrometry. Mucus barrier integrity and goblet cell response to microbial challenge were also assessed for a subset of patients. The core colonic mucus proteome was shown to consist of a small set of 29 secreted proteins. Patients with active UC had reduced levels of major structural components, including the mucin MUC2 (p<0.0001), also in mucus from non-inflamed segments, and their goblet cell secretory response to microbial stimulus was abrogated. Functional mucus barrier failure was observed in a subset of UC patients with and without active inflammation, and accompanied by alterations in proteins associated with mucus secretion and luminal organization. This study represents the first characterization and comparison of the mucus proteomes of the inflamed and non-inflamed colon. Core mucus structural components were reduced in active UC, also in mucus from non-inflamed segments. Thus, weakening of the mucus barrier is likely to occur early in UC pathogenesis, and represents a novel target for intervention.
Project description:The aim of this study was to investigate whether long term intake of pea fiber would improve colonic barrier, bacterial profile and alter colonic gene expression using DNA microarray. Fifty weaned pigs were randomly allocated into 2 groups receiving control and fibrous diet with inclusion of pea fiber from weaning age until d 160. The two diets had similar nutrient levels. Pigs fed pea fiber diet (PF diet) had markedly decreased overall average daily feed intake (ADFI) and Feed:Gain in growing and finishing period (P<0.05). In addition, long term intake of PF diet induced deeper crypt (+50 %, P<0.05), increased protein expression of colonic mucin and sIgA (+13~16 %, P<0.05). Resulting from the increased lactobacillus content (P<0.05), moreover, pigs fed PF diet had significantly higher concentration of colonic total short chain fatty acid (SCFA) and acetic acid. DNA microarray results indicated that feeding PF diet induced alterations in the expression of colonic cancer, immune response and lipid metabolism-related genes, as well as genes involved in signal pathway such as intestinal immune network for IgA production, PPAR signaling pathway and nutrient metabolism-related pathways. Collectively, our results suggested that long term intake of PF diet would improve colonic health via altering colonic bacteria profile, colonic barriers, immune and metabolism related protein or gene expressions. A total of 50 weaned pigs (Duroc×Landrace×Yorkshire, initial body weight: 7.2±0.5 kg) were randomly allocated to 2 groups with 5 pens each group and 5 pig each pen. Pigs were fed control (Control) and fibrous diets (10~20 % inclusion of pea fiber, PF) from weaning at 28 day to 160 day-old-age, which is subjected to phase feeding by weaning diet (weaning to d 30 post-weaning), growing diet (d 30~90 postweaning) and finishing diet (d 90~160 postweaning) according to their physiological stage. At d 160 postweaning, four pigs each group were selected to be slaughtered for collection of colonic tissues and DNA microarray was applied to the colonic tissues for analysis of gene expression.
Project description:The inter-organ cross talk between liver and intestine has been focus of intense research. Key in this cross-talk are bile acids, which are secreted from the liver into the intestine and, via the enterohepatic circulation, reach back to the liver. Important new insights have been gained in the Farnesoid X receptor (Fxr)-mediated communication from intestine-to-liver in health and disease. However, liver-to-intestine communication and the role of bile acids and FXR in this cross talk remain elusive. Here, we analyse Fxr-mediated liver-to-gut communication, and its consequences in the colon. Mice in which Fxr was selectively ablated in intestine (Fxr-intKO), the liver (Fxr-livKO), or in the full body (Fxr-totKO) were engineered. The effects on colonic gene expression (RNA sequencing), on the microbiome (16S rRNA Gene Sequencing) and on mucus barrier were analyzed. Compared to Fxr-intKO and Fxr-totKO mice, more genes were differentially expressed in the colons of Fxr-livKO mice relative to control mice (731, 1824 and 3272 respectively), suggestive of a strong role of hepatic Fxr in liver-to-gut communication. The colons of Fxr-livKO showed increased expression of anti-microbial genes, such as Regenerating islet-derived 3 beta and gamma (Reg3β and Reg3γ), Toll-like receptors (Tlrs), inflammasome related genes and differential expression of genes belonging to the ‘Mucin-type O-glycan biosynthesis’ pathway. Compared to control mice, Fxr-livKO mice have decreased levels of the predicted mucin degrading bacterium Turicibacter and a concomitant increase in the thickness of the inner sterile mucus layer. In conclusion, ablation of Fxr in the liver has a major effect on colonic gene expression, the gut microbiome and on the permeability of the mucus layer. This stresses the importance of the Fxr-mediated liver-to-gut signaling.
Project description:The aim of this study was to investigate whether long term intake of pea fiber would improve colonic barrier, bacterial profile and alter colonic gene expression using DNA microarray. Fifty weaned pigs were randomly allocated into 2 groups receiving control and fibrous diet with inclusion of pea fiber from weaning age until d 160. The two diets had similar nutrient levels. Pigs fed pea fiber diet (PF diet) had markedly decreased overall average daily feed intake (ADFI) and Feed:Gain in growing and finishing period (P<0.05). In addition, long term intake of PF diet induced deeper crypt (+50 %, P<0.05), increased protein expression of colonic mucin and sIgA (+13~16 %, P<0.05). Resulting from the increased lactobacillus content (P<0.05), moreover, pigs fed PF diet had significantly higher concentration of colonic total short chain fatty acid (SCFA) and acetic acid. DNA microarray results indicated that feeding PF diet induced alterations in the expression of colonic cancer, immune response and lipid metabolism-related genes, as well as genes involved in signal pathway such as intestinal immune network for IgA production, PPAR signaling pathway and nutrient metabolism-related pathways. Collectively, our results suggested that long term intake of PF diet would improve colonic health via altering colonic bacteria profile, colonic barriers, immune and metabolism related protein or gene expressions.
Project description:Two C57BL/6 mice colonies maintained in two rooms in the same specific pathogen free (SPF) facility were found to have different gut microbiota and a mucus phenotype specific for each colony. The thickness and growth of the colon mucus was similar in the two colonies, but one colony had mucus not penetrable to bacteria or bacterial-sized beads, similar to what occurs in free-living wild mice. On the other hand, the other colony had an inner mucus layer that was penetrable to bacteria and beads. These different properties of the mucus in the two rooms were dependent on the microbiota, as the phenotypes were transmissible by transfer of ceacal microbiota to germ-free mice. Mice with an impenetrable mucus layer had increased amounts of Erysipelotrichi, while mice with a penetrable mucus layer had higher levels of Proteobacteria and TM7 bacteria in the distal colon mucus. Thus bacteria affect mucus barrier properties in ways that can have implications for health and disease.
Project description:Colonic goblet cells respond to invading enteropathogens by secreting Muc2 mucin and other specific goblet cell proteins that physically entrap and expel microbes away from the epithelium. At present, it is unclear how innate effectors in the gut, including small cationic cathelicidin peptides secreted by the intestinal epithelium and leukocytes, contribute to mucus barrier defense during infections. In this study, we used cathelicidin-deficient (Camp-/-) mice, colonoids, and human colonic LS174T goblet cells to elucidate the mechanisms by which cathelicidin regulates goblet cell secretions in innate host defense against attaching/effacing Citrobacter rodentium. We showed that even though Camp-/- littermates infected with C. rodentium displayed increased fecal shedding and epithelial colonization, Muc2 mucin granules were retained in bloated colonic goblet cells that impaired mucus secretion and expressed less mucus-associated proteins, as quantified by proteomic analysis. C. rodentium infected Camp-/- littermates showed impaired reactive oxygen species (ROS) production and transcriptomic profiling associated with decreased ROS biosynthesis and an increase in ROS negative regulators. Camp-/- bone marrow derived macrophages produced less ROS than their wild-type counterparts. In LS174T goblet cells, human cathelicidin LL-37 promptly induced the secretion of goblet cell-associated TFF3 and RELMβ, which was dependent on ROS production. These findings demonstrate that cathelicidin signaling in colonic goblet cells regulates mucus and mucin-associated protein secretion via an ROS-dependent mechanism to clear bacterial infections and restore gut homeostasis.