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:The interrelationships between our diets and the structure and operations of our gut microbial communities are poorly understood. A model microbial community of ten sequenced human gut bacteria was introduced into gnotobiotic mice and changes in the abundance of each species were measured in response to randomized perturbations of four defined ingredients in the host diet. From the responses, we developed a statistical model that predicted over 50% of the variation in species abundance in response to the diet perturbations and were able to identify which factors in the diet best explained the changes seen for each community member. The community’s transcriptional response was driven by the absolute abundance of each species, as diet ingredient concentrations were not associated with significant changes in the transcription of individual community members.
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.