Project description:The human gut microbiota is crucial for degrading dietary fibres from the diet. However, some of these bacteria can also degrade host glycans, such as mucins, the main component of the protective gut mucus layer. Specific microbiota species and mucin degradation patterns are associated with inflammatory processes in the colon. Yet, it remains unclear how the utilization of mucin glycans affects the degradation of dietary fibres by the human microbiota. Here, we used three dietary fibres (apple pectin, β-glucan and xylan) to study in vitro the dynamics of colon mucin and dietary fibre degradation by the human faecal microbiota. The dietary fibres showed clearly distinguishing modulatory effects on faecal microbiota composition. The utilization of colon mucin in cultures led to alterations in microbiota composition and metabolites. Metaproteome analysis showed the central role of the Bacteroides in degradation of complex fibres while Akkermansia muciniphila was the main degrader of colonic mucin. This work demonstrates the intricacy of complex glycan metabolism by the gut microbiota and how the utilization of host glycans leads to alterations in the metabolism of dietary fibres. Metaproteomics analysis of this data reveals the functional activities of the bacteria in consortia, by this contributing to a better understanding of the complex metabolic pathways within the human microbiota that can be manipulated to maximise beneficial microbiota-host interactions. In this study two different mucin samples were used: commercial porcine gastric mucin and in house prepared porcine colonic mucin. This dataset analyses the proteome of: A) autoclaved porcine colonic mucin; B) not autoclaved porcine colonic mucin; C) porcine gastric mucin.
Project description:Increasing the consumption of dietary fibre has been proposed to alleviate the progression of non-communicable diseases such as obesity, type 2 diabetes and cardiovascular disease, yet the effect of dietary fibre on host physiology remains unclear. In this study, we performed a multiple diet feeding study in C57BL/6J mice to compare high fat and high fat modified with dietary fibre diets on host physiology and gut homeostasis by combining proteomic, metagenomic, metabolomic and glycomic techniques with correlation network analysis. We observed significant changes in physiology, liver proteome, gut microbiota and SCFA production in response to high fat diet. Dietary fibre modification did not reverse these changes but was associated with specific changes in the gut microbiota, liver proteome, SCFA production and colonic mucin glycosylation. Furthermore, correlation network analysis identified gut bacterial-glycan associations.
Project description:The human gut microbiota is crucial for degrading dietary fibres from the diet. However, some of these bacteria can also degrade host glycans, such as mucins, the main component of the protective gut mucus layer. Specific microbiota species and mucin degradation patterns are associated with inflammatory processes in the colon. Yet, it remains unclear how the utilization of mucin glycans affects the degradation of dietary fibres by the human microbiota. Here, we used three dietary fibres (apple pectin, β-glucan and xylan) to study in vitro the dynamics of colon mucin and dietary fibre degradation by the human faecal microbiota. The dietary fibres showed clearly distinguishing modulatory effects on faecal microbiota composition. The utilization of colon mucin in cultures led to alterations in microbiota composition and metabolites. Metaproteome analysis showed the central role of the Bacteroides in degradation of complex fibres while Akkermansia muciniphila was the main degrader of colonic mucin. This work demonstrates the intricacy of complex glycan metabolism by the gut microbiota and how the utilization of host glycans leads to alterations in the metabolism of dietary fibres. Metaproteomics analysis of this data reveals the functional activities of the bacteria in consortia, by this contributing to a better understanding of the complex metabolic pathways within the human microbiota that can be manipulated to maximise beneficial microbiota-host interactions.
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.
Project description:The gut microbiota is essential for several aspects of host physiology such as metabolism, epithelial barrier function and immunity. Previous studies have revealed that host immune system as well as diet and other environmental factors have a strong impact on the composition and activity of gut microbiota, but the molecular requirements for such functional regulation remain unknown. We show that the bacteria belonging to phylum Bacteroidetes acquire their symbiotic activity in the colonic mucus, depending on a newly characterized molecular family encoded within the polysaccharide utilization loci (PUL), which we have named Mucus-Associated Functional Factor (MAFF). We used microarray analysis of colonic epithlial cells to determin the impact of MAFF genes on colonic homeostasis.
Project description:Despite accepted health benefits of dietary fiber, little is known about the mechanisms by which fiber deprivation impacts the gut microbiota and alters disease risk. Using a gnotobiotic model, in which mice were colonized with a synthetic human gut microbiota, we elucidated the functional interactions between dietary fiber, the gut microbiota and the colonic mucus barrier, which serves as a primary defence against pathogens. We show that during chronic or intermittent dietary fiber deficiency, the gut microbiota resorts to host-secreted mucus glycoproteins as a nutrient source, leading to erosion of the colonic mucus barrier. Dietary fiber deprivation promoted greater epithelial access and lethal colitis by the mucosal pathogen, Citrobacter rodentium, but only in the presence of a fiber-deprived microbiota that is pushed to degrade the mucus layer. Our work reveals intricate pathways linking diet, gut microbiome and intestinal barrier dysfunction, which could be exploited to improve health using dietary therapeutics. Germ-free mice (Swiss Webster) were colonized with synthetic human gut microbiota comprising of 14 species belonging to five different phyla (names of bacterial species: Bacteroides thetaiotaomicron, Bacteroides ovatus, Bacteroides caccae, Bacteroides uniformis, Barnesiella intestinihominis, Eubacterium rectale, Marvinbryantia formatexigens, Collinsella aerofaciens, Escherichia coli HS, Clostridium symbiosum, Desulfovibrio piger, Akkermansia muciniphila, Faecalibacterium prausnitzii and Roseburia intestinalis). These mice were fed either a fiber-rich diet or a fiber-free diet for about 6 weeks. The mice were then sacrificed and their cecal tissues were immediately flash frozen for RNA extraction. The extracted RNA was subjected to microarray analysis based on Mouse Gene ST 2.1 strips using the Affy Plus kit. Expression values for each gene were calculated using robust multi-array average (RMA) method.
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.
Project description:Dietary fats have been shown to affect gut microbiota composition and aging gene transcription of middle-aged rats at a normal dose, but little is known about such an effect on gut barrier. In colon, the main component of mucus layer is Muc2, produced by the goblet cells. This study investigated the changes in Muc2 expression, goblet cells proliferation, TLRs and inflammatory cytokines in the colon of middle-aged rats. Proteome technology was applied to explore the possible molecular mechanisms. The results indicated that intake of fish oil at a normal dose downregulated colonic Muc2 expression, and this negative effect of fish oil probably involved the suppression of mucin glycosylation process.
Project description:High protein diet alter gut microbiota composition and activity. The objective of this study is to determine the consequences of a high protein diet for the colonic epithelium in rats.