Project description:Gut microbiome research is rapidly moving towards the functional characterization of the microbiota by means of shotgun meta-omics. Here, we selected a cohort of healthy subjects from an indigenous and monitored Sardinian population to analyze their gut microbiota using both shotgun metagenomics and shotgun metaproteomics. We found a considerable divergence between genetic potential and functional activity of the human healthy gut microbiota, in spite of a quite comparable taxonomic structure revealed by the two approaches. Investigation of inter-individual variability of taxonomic features revealed Bacteroides and Akkermansia as remarkably conserved and variable in abundance within the population, respectively. Firmicutes-driven butyrogenesis (mainly due to Faecalibacterium spp.) was shown to be the functional activity with the higher expression rate and the lower inter-individual variability in the study cohort, highlighting the key importance of the biosynthesis of this microbial by-product for the gut homeostasis. The taxon-specific contribution to functional activities and metabolic tasks was also examined, giving insights into the peculiar role of several gut microbiota members in carbohydrate metabolism (including polysaccharide degradation, glycan transport, glycolysis and short-chain fatty acid production). In conclusion, our results provide useful indications regarding the main functions actively exerted by the gut microbiota members of a healthy human cohort, and support metaproteomics as a valuable approach to investigate the functional role of the gut microbiota in health and disease.
Project description:Intracerebral hemorrhage (ICH) induces alterations in the gut microbiota composition, significantly impacting neuroinflammation post-ICH. However, the impact of gut microbiota absence on neuroinflammation following ICH-induced brain injury remain unexplored. Here, we observed that the gut microbiota absence was associated with reduced neuroinflammation, alleviated neurological dysfunction, and mitigated gut barrier dysfunction post-ICH. In contrast, recolonization of microbiota from ICH-induced SPF mice by transplantation of fecal microbiota (FMT) exacerbated brain injury and gut impairment post-ICH. Additionally, microglia with transcriptional changes mediated the protective effects of gut microbiota absence on brain injury, with Apoe emerging as a hub gene. Subsequently, Apoe deficiency in peri-hematomal microglia was associated with improved brain injury. Finally, we revealed that gut microbiota influence brain injury and gut impairment via gut-derived short-chain fatty acids (SCFA).
Project description:BACKGROUND & AIMS: There is mounting evidence that microbes resident in the human intestine contribute to diverse alcohol-associated liver diseases (ALD) including the most deadly form known as alcoholic hepatitis (AH). However, mechanisms by which gut microbiota synergize with excessive alcohol intake to promote liver injury are poorly understood. Furthermore, whether drugs that selectively target gut microbial metabolism can improve ALD has never been tested. METHODS: We used liquid chromatography tandem mass spectrometry to quantify the levels of microbe and host choline co-metabolites in healthy controls and AH patients, and identified the metabolite trimethylamine (TMA) as a gut microbe-derived biomarker of AH. In subsequent studies, we treated mice with non-lethal mechanism-based bacterial choline TMA lyase inhibitors to blunt gut microbe-dependent production of TMA in the context of chronic ethanol administration. Indices of liver injury were quantified by complementary RNA sequencing, biochemical, and histological approaches. In addition, we examined the impact of ethanol consumption and TMA lyase inhibition on gut microbiome structure via 16S rRNA sequencing. RESULTS: We show the gut microbial choline metabolite trimethylamine (TMA) is elevated in AH patients, which is correlated with reduced hepatic expression of the TMA oxygenase flavin-containing monooxygenase 3 (FMO3). Provocatively, we find that small molecule inhibition of gut microbial choline TMA lyase activity protects mice from ethanol-induced liver injury. TMA lyase inhibitor-driven improvement in ethanol-induced liver injury is associated with distinct reorganization of the gut microbiome community and host liver transcriptome. CONCLUSIONS: The microbial metabolite TMA is a biomarker of AH, and blocking TMA production from gut microbes can blunt ALD in mice.
Project description:The gut microbiota-intestine-liver relationship is emerging as an important factor in multiple hepatic pathologies, but the hepatic sensors and effectors of microbial signals are not well defined. By comparing publicly available liver transcriptomics data from conventional vs. germ-free mice, we identified pregnane X receptor (PXR, NR1I2) transcriptional activity as strongly affected by the absence of gut microbes. Microbiota depletion in Pxr+/+ vs Pxr-/- C57Bl6/J mice revealed that most microbiota-sensitive genes were PXR-dependent in the liver in males, but not in females. Pathway enrichment analysis revealed that microbiota-PXR interaction controlled fatty-acid and xenobiotic metabolism. Antibiotic treatment reduced liver triglyceride content and hampered xenobiotic metabolism in livers from Pxr+/+ but not Pxr-/- male mice. These findings identify PXR as a hepatic effector of sexually dimorphic responses to microbiota-derived signals and reveal a potential new mechanism for unexpected drug-drug or food-drug interactions.
Project description:Alcohol consumption leads to disruptions to the gut microbiota including a depletion of tryptophan-derived indole metabolites. Disrupted tryptophan metabolism is clearly associated with alcohol-associated liver disease, yet our understanding of the specific role of gut microbe-driven tryptophan metabolism has been hampered due to lack of mouse models. To address this, we created a defined synthetic microbial community with either intact or genetically deleted tryptophanase activity for in vivo studies. Gnotobiotic mice lacking bacterial tryptophanase activity are more susceptible to ethanol-induced liver injury. Interestingly, mice with intact microbial tryptophanase activity have a robust induction of IL-6 and acute phase proteins when challenged with ethanol. Furthermore, bacterial tryptophanase activity promoted a spatial reorganization of the gut microbiome and colonization of Akkermansia muciniphila within the ileum. Collectively, this study highlights the functional importance of bacterial tryptophan metabolites in shaping ethanol-driven reorganization of the gut microbiome and host immune response to promote liver injury.
Project description:The gut microbiota exerts a profound influence on host physiology, but its systemic impact on gene expression across diverse tissues remains poorly characterized. This study investigated the transcriptional effects of gut microbiota depletion and restoration in mice across six tissues (colon, jejunum, liver, heart, lung, and kidney) using whole-transcriptome sequencing. We found that the presence of gut microbiota significantly altered the transcriptome, with the most pronounced effects in the colon. Using a linear mixed-effects model, we identified 7,365 effector genes. Tissue-specific analysis revealed that these genes were associated with distinct functional pathways, such as immunity in the gut and lung, and metabolism in the liver. Further refinement with LASSO regression pinpointed gut microbiota-mediated key effector genes, whose expression levels were significantly associated with patient survival in corresponding human cancers (e.g., LIHC, LUAD, KIRC). Furthermore, we observed a widespread remodeling of competing endogenous RNA (ceRNA) networks by the gut microbiota. Single-cell data analysis highlighted a potential gut-liver axis interaction, primarily mediated by colonic enterocytes and hepatic cholangiocytes, meanwhile gut microbiota repressed the transcription initiation of Noct in colonic enterocytes, whose expression level was significantly negatively correlated to gut-liver axis interaction. Our findings provide a comprehensive map of the multi-tissue transcriptional landscape shaped by the gut microbiota, revealing tissue-specific regulatory mechanisms and identifying key genes with potential clinical relevance in cancer.
Project description:The increased consumption of various beverages has been paralleled by an epidemic of several intestinal diseases around the world, such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and colorectal cancer. Mounting evidence have shown that excessive consumption of beverages increases the risk of IBD and IBS. In addition, sugar-sweeter, food additives and food ingredients were identified to play important roles in these conditions. Consuming cold beverage is common among some people, especially in the youngsters. However, whether the cold stress contribute directly to host metabolism, gut barrier and gut-brain axis is unclear. In an intestinal function disorder model induced by cold water in mice, we investigated changes in gut transit, anxiety and depression like behavior. To evaluate the effect of cold water on gut barrier, we investigate the tight junctions in the colon. In addition, we employed RNA sequencing transcriptomic analysis to identify genes potentially driving the gut injury, and in parallel, examine the gut microbiota and metabolites in the feces.In an intestinal function disorder model induced by cold water in mice, we investigated changes in gut transit, anxiety and depression like behavior. To evaluate the effect of cold water on gut barrier, we investigate the tight junctions in the colon. In addition, we employed RNA sequencing transcriptomic analysis to identify genes potentially driving the gut injury, and in parallel, examine the gut microbiota and metabolites in the feces.
Project description:Abstract. Background: The cause of ulcerative colitis (UC) is not yet fully understood. Previous research has pointed towards a potential role for mutations in NOD2 in promoting the onset and progression of inflammatory bowel disease (IBD) by altering the microbiota of the gut. However, the relationship between toll-like receptor 4 (TLR4) and gut microbiota in IBD is not well understood. To shed light on this, the interaction between TLR4 and gut microbiota was studied using a mouse model of IBD. Methods: To examine the function of TLR4 signaling in intestinal injury repair, researchers developed Dextran Sulfate Sodium Salt (DSS)-induced colitis and injury models in both wild-type (WT) mice and TLR4 knockout (TLR4-KO) mice. To assess changes in the gut microbiota, 16S rRNA sequencing was conducted on fecal samples from both the TLR4-KO and WT enteritis mouse models. Results: The data obtained depicted a protective function of TLR4 against DSS-induced colitis. The gut microbiota composition was found to vary considerably between the WT and TLR4-KO mice groups as indicated by β-diversity analysis and operational taxonomic units (OTUs) cluster. Statistical analysis of microbial multivariate variables depicted an elevated abundance of Escherichia coli/Shigella, Gammaproteobacteria, Tenerlcutes, Deferribacteres, Enterobacteria, Rikenellaceae, and Proteobacteria in the gut microbiota of TLR4-KO mice, whereas there was a considerable reduction in Bacteroidetes at five different levels of the phylogenetic hierarchy including phylum, class, order, family, and genus in comparison with the WT control. Conclusion: TLR4 may protect intestinal epithelial cells from damage in response to DSS-induced injury by controlling the microbiota in the gut.
Project description:Using diet-induced pre-obese and obese mouse models, we found that SXB reduced hepatic steatosis and inflammation in both conditions, together with increased expression of genes linked to mitochondrial respiratory function. In obese mice, SXB further improved insulin resistance and attenuated body weight gain by limiting fat mass expansion. These metabolic improvements were accompanied by enhanced adipose tissue function, reflected by reduced adipocyte hypertrophy and inflammation in white adipose tissue and by reduced lipid content and increased uncoupling protein 1 (UCP-1) abundance in brown adipose tissue. Mechanistically, SXB reshaped the gut microbiota in a manner that contributed toassociates with improved liver metabolic function. Consistent with a causal role for microbiota, fecal microbiota transplantation (FMT) from SXB-treated obese donors recapitulated these benefits in untreated obese recipients, rescuing diet-induced weight gain, hyperglycemia, and hepatic steatosis. These findings identify suggest the gut microbiota as a key potential mediator of the metabolic effects of SXB, support further investigation of gut microbiota alterations in narcolepsy, and underscore the broader translational relevance of drug-microbiota interactions in metabolic dysfunction.