Project description:Alterations in the gastrointestinal microbiota have been implicated in obesity in mice and humans, but the conserved microbial functions that influence host energy metabolism and adiposity have not been determined. Here we show that bacterial bile salt hydrolase (BSH) controls a microbe-host dialogue which functionally regulates host lipid metabolism and weight gain. Expression of cloned BSH enzymes in the GI tract of gnotobiotic or conventional mice significantly altered plasma bile acid signatures and regulated transcription of key genes involved in lipid metabolism (PPARgamma angptl4), cholesterol metabolism (abcg5/8), gastrointestinal homeostasis (regIIIgamma) and circadian rhythm (dbp, per1/2) in the liver or small intestine. High-level expression of BSH in conventionally raised mice resulted in significant reduction of host weight-gain, plasma cholesterol and liver triglycerides. We demonstrate that bacterial BSH activity significantly impacts systemic metabolic processes and adiposity in the host, and represents a key mechanistic target for the control of obesity and hypercholesterolaemia.
Project description:Alterations in the gastrointestinal microbiota have been implicated in obesity in mice and humans, but the conserved microbial functions that influence host energy metabolism and adiposity have not been determined. Here we show that bacterial bile salt hydrolase (BSH) controls a microbe-host dialogue which functionally regulates host lipid metabolism and weight gain. Expression of cloned BSH enzymes in the GI tract of gnotobiotic or conventional mice significantly altered plasma bile acid signatures and regulated transcription of key genes involved in lipid metabolism (PPARgamma angptl4), cholesterol metabolism (abcg5/8), gastrointestinal homeostasis (regIIIgamma) and circadian rhythm (dbp, per1/2) in the liver or small intestine. High-level expression of BSH in conventionally raised mice resulted in significant reduction of host weight-gain, plasma cholesterol and liver triglycerides. We demonstrate that bacterial BSH activity significantly impacts systemic metabolic processes and adiposity in the host, and represents a key mechanistic target for the control of obesity and hypercholesterolaemia. Germ free Swiss Webster mice were monocolonised with EC containing the bacterial gene, Bile salt hydroalse. The treatment groups and relevant controls were; 1. Germ Free(GF) n=4 , 2. GF and EC n=4, 3. GF and EC +BSH1 n=4, 4. GF and EC+ BSH2 n=4, 5. GF re-conventionalised (CONV-D) n= 5. The Ileum and Liver were removed and the RNA extracted (RNAeasy plus universal kit (Qiagen), quantified and Microarrays were carried out using mouse Exon ST1.0 arrays (Affymetrix) by Almac Group, Craigavon, Northern Ireland. Analysis and pathway mapping was carried out by ALMAC and using Subio Platform software (Subio Inc) and Genesis Software.
Project description:The human gut microbiota impacts host metabolism and has been implicated in the pathophysiology of obesity and metabolic syndromes. However, defining the roles of specific microbial activities and metabolites on host phenotypes has proven challenging due to the complexity of the microbiome-host ecosystem. Here, we identify strains from the abundant gut bacterial phylum Bacteroidetes that display selective bile salt hydrolase (BSH) activity. Using isogenic strains of wild-type and BSH-deleted Bacteroides thetaiotaomicron, we selectively modulated the levels of the bile acid tauro-b-muricholic acid in monocolonized gnotobiotic mice. B. thetaiotaomicron BSH mutant-colonized mice displayed altered metabolism, including reduced weight gain and respiratory exchange ratios, as well as transcriptional changes in metabolic, circadian rhythm, and immune pathways in the gut and liver. Our results demonstrate that metabolites generated by a single microbial gene and enzymatic activity can profoundly alter host metabolism and gene expression at local and organism-level scales.
Project description:Morphine and its pharmacological derivatives are the most prescribed analgesics for moderate to severe pain management. However, chronic use of morphine reduces pathogen clearance and induces bacterial translocation across the gut barrier. The enteric microbiome has been shown to play a critical role in the preservation of the mucosal barrier function and metabolic homeostasis. Here, we show for the first time, using bacterial 16s rDNA sequencing, that chronic morphine treatment significantly alters the gut microbial composition and induces preferential expansion of the gram-positive pathogenic and reduction of bile-deconjugating bacterial strains. A significant reduction in both primary and secondary bile acid levels was seen in the gut, but not in the liver with morphine treatment. Morphine induced microbial dysbiosis and gut barrier disruption was rescued by transplanting placebo-treated microbiota into morphine-treated animals, indicating that microbiome modulation could be exploited as a therapeutic strategy for patients using morphine for pain management. In this study, we establish a link between the two phenomena, namely gut barrier compromise and dysregulated bile acid metabolism. We show for the first time that morphine fosters significant gut microbial dysbiosis and disrupts cholesterol/bile acid metabolism. Changes in the gut microbial composition is strongly correlated to disruption in host inflammatory homeostasis13,14 and in many diseases (e.g. cancer/HIV infection), persistent inflammation is known to aid and promote the progression of the primary morbidity. We show here that chronic morphine, gut microbial dysbiosis, disruption of cholesterol/bile acid metabolism and gut inflammation; have a linear correlation. This opens up the prospect of devising minimally invasive adjunct treatment strategies involving microbiome and bile acid modulation and thus bringing down morphine-mediated inflammation in the host.
Project description:<p>Accurate tests for microbiologic diagnosis of lower respiratory tract infections (LRTI) are needed. Gene expression profiling of whole blood represents a powerful new approach for analysis of the host response during respiratory infection that can be used to supplement pathogen detection testing. Using qPCR, we prospectively validated the differential expression of 10 genes previously shown to discriminate bacterial and non-bacterial LRTI confirming the utility of this approach. In addition, a novel approach using RNAseq analysis identified 141 genes differentially expressed in LRTI subjects with bacterial infection. Using "pathway-informed" dimension reduction, we identified a novel 11 gene set (selected from lymphocyte, α-linoleic acid metabolism, and IGF regulation pathways) and demonstrated a predictive accuracy for bacterial LRTI (nested CV-AUC=0.87). RNAseq represents a new and an unbiased tool to evaluate host gene expression for the diagnosis of LRTI.</p>
Project description:Specific bile acids are potent signaling molecules that modulate metabolic pathways affecting lipid, glucose and bile acid homeostasis, and the microbiota. Bile acids are synthesized from cholesterol in the liver, and the key enzymes involved in bile acid synthesis (Cyp7a1, Cyp8b1) are regulated transcriptionally by the nuclear receptor FXR. We have identified an FXR-regulated pathway upstream of a transcriptional repressor that controls multiple bile acid metabolism genes. We identify MafG as an FXR target gene and show that hepatic MAFG overexpression represses genes of the bile acid synthetic pathway and modifies the biliary bile acid composition. In contrast, loss-of-function studies using MafG(+/-) mice causes de-repression of the same genes with concordant changes in biliary bile acid levels. Finally, we identify functional MafG response elements in bile acid metabolism genes using ChIP-seq analysis. Our studies identify a molecular mechanism for the complex feedback regulation of bile acid synthesis controlled by FXR
Project description:Specific bile acids are potent signaling molecules that modulate metabolic pathways affecting lipid, glucose and bile acid homeostasis, and the microbiota. Bile acids are synthesized from cholesterol in the liver, and the key enzymes involved in bile acid synthesis (Cyp7a1, Cyp8b1) are regulated transcriptionally by the nuclear receptor FXR. We have identified an FXR-regulated pathway upstream of a transcriptional repressor that controls multiple bile acid metabolism genes. We identify MafG as an FXR target gene and show that hepatic MAFG overexpression represses genes of the bile acid synthetic pathway and modifies the biliary bile acid composition. In contrast, loss-of-function studies using MafG(+/-) mice causes de-repression of the same genes with concordant changes in biliary bile acid levels. Finally, we identify functional MafG response elements in bile acid metabolism genes using ChIP-seq analysis. Our studies identify a molecular mechanism for the complex feedback regulation of bile acid synthesis controlled by FXR.
Project description:Cytokine signaling has been connected to regulation of metabolism and energy balance. Numerous cytokine gene expression changes are stimulated by accumulation of bile acids in livers of young Foxa2 liver-conditional null mice. We hypothesized that bile acid-induced inflammation in young Foxa2 mutants, once chronic, affects metabolic homeostasis. We found that loss of Foxa2 in the liver results in a premature aging phenotype, including significant weight gain, reduced food intake, and decreased energy expenditure. We show that Foxa2 antagonizes the mammalian target of rapamycin (mTOR) pathway, resulting in increased hepatic lipogenesis and adiposity. While much prior work has focused on adipose tissue in obesity, we discovered a novel age-onset obesity phenotype in a model where genetic deletion occurs only in the liver, underscoring the importance of the role hepatic lipogenesis plays in the development of obesity.
Project description:Bile acids play multiple roles in vertebrate metabolism by facilitating lipid absorption in the intestine and acting as a signaling molecule in lipid and carbohydrate metabolism. Bile acids are also the main route to excrete excess cholesterol out of the body. Alpha-methyl-Coa racemase (Amacr) is one of the enzymes needed to produce bile acids from cholesterol. The mouse model lacking Amacr can produce only minor (less than 10%) amounts of bile acids, but still they are symptomless in normal laboratory conditions. Bile acid synthesis occurs in liver. In this experiment, liver samples from Amacr-/- and wild-type mice were collected and their gene expression levels were compared. 4 biological replicates per genotype.