Project description:Bile acids are multifunctional signaling molecules that play significant roles in maintaining microbial homeostasis. N6-methyladenine (m6A), the most abundant epitranscriptomic modification, mediates various biological processes by modulating RNA metabolism. However, the precise regulatory mechanisms of m6A methylation in bile acid metabolism, and its downstream effects on microbiota remain unclear. In this study, liver-specific Mettl14 knockout (Mettl14-LKO) reshaped bile acid profile and expression levels of protein related to bile acid metabolism, namely CYP7A1, FXR, and BSEP. M6A-seq data revealed m6A methylated peaks on CYP7A1. Mettl14-LKO significantly elevated expression of m6A “reader” IGF2BP3. Knockdown of IGF2BP3 inhibited CYP7A1 expression by decreasing mRNA stability. Mechanistically, Mettl14-LKO promoted bile acid synthesis by upregulating CYP7A1 expression in an m6A-IGF2BP3-dependent manner. Interestingly, Mettl14-LKO reduced bile acid content in ileum due to decreased BSEP level in liver. Noteworthy, we discovered for the first time that Mettl14 knockout in the liver altered fecal microbiota composition. Specifically, it changed the abundance of Cyanobacteria and Patescibacteria at phylum level, and Lachnochostridium, Candidatus-Saccharimonas, and Roseburia at genera level. Remarkably, Roseburia was negatively correlated with the bile acid levels and CYP7A1 expression. Our findings provide new insights into the role of METTL14 in regulating bile acid homeostasis and its impact on fecal microbiota. Roseburia emerges as a potential target for addressing metabolic diseases linked to disrupted METTL14 signaling.
Project description:UPLC-MS/MS data used to confirm the retention times of bile acid conjugates to GABA and tyramine that were detected in microbial culture and human fecal samples. Synthesized conjugates included here are GABA-deoxycholic acid, tyramine-deoxycholic acid, GABA-cholic acid, tyramine-cholic acid, GABA-chenodeoxycholic acid, and tyramine-chenodeoxycholic acid. Data of biological samples (B. fragilis P207 spiked with DCA, healthy human donor 11 feces, patient 207 v12 feces) from the same UPLCMS/MS sequence is included for comparison and validation. All using positive ionization.
Project description:Bacteria that colonize the human gut must withstand a variety of stressors, including detergent-like compounds known as bile acids. Here, we investigated how bile acids found in the human cecum and colon impact the behavior of the probiotic strain Escherichia coli Nissle 1917 (EcN). We found that lithocholic acid (LCA), which is a microbiota-derived secondary bile acid, promotes the formation of a distinctive surface-coating biofilm by EcN, including on an organoid-derived model of the human colonic epithelium. Mechanistic investigations, including RNA-sequencing, revealed that LCA upregulates the production of several components of flagella, which are essential for LCA-induced biofilm formation and form part of the biofilm extracellular matrix.
Project description:Bile acids are not only crucial for the uptake of lipids, but also have widespread systematic ef-fects and shape the gut-microbiome composition. Bile acids can directly shape the gut-microbiome and can be modified by bacteria such as Eggerthella lenta which in turn plays a crucial role in host metabolism and immune response. We cultivated eight strains that represent a simplified human intestinal microbiome and inves-tigated the molecular response to bile acids, co-culturing with Eggerthella lenta and the combina-tion. We observed growth inhibition of particularly gram-positive strains during bile acid stress, which could be alleviated through co-culturing with Eggerthella lenta. The inhibition of growth was related to a decrease in membrane integrity and genotoxic effects of bile acids, which we investigated using zeta potential measurements in combination with proteomic and metabolomic analyses. Co-culturing with Eggerthella lenta alleviated stress through formation of oxidized and epimer-ized bile acids and the molecular response to co-culturing was seen to be strain specific. We also note that we could detect the recently described Microbial Bile Salt Conjugates in our cultures. This study highlights the significance of a potent bile acid modifier and how in-depth molecular analyses are required to decipher cross-communication between gut and host.
Project description:The disruption of cholesterol homeostasis leads to an increase in cholesterol levels which results in the development of cardiovascular disease. Mitogen Inducible Gene 6 (Mig-6) is an immediate early response gene that can be induced by various mitogens, stresses, and hormones. To identify the metabolic role of Mig-6 in the liver, we conditionally ablated Mig-6 in the liver using the Albumin-Cre mouse model (Albcre/+Mig-6f/f; Mig-6d/d). Mig-6d/d mice exhibit hepatomegaly and fatty liver. Serum levels of total, LDL, and HDL cholesterol and hepatic lipid were significantly increased in the Mig-6d/d mice. The daily excretion of fecal bile acids was significantly decreased in the Mig-6d/d mice. DNA microarray analysis of mRNA isolated from the livers of these mice showed alterations in genes that regulate lipid metabolism, bile acid, and cholesterol synthesis, while the expression of genes that regulate biliary excretion of bile acid and triglyceride synthesis showed no difference in the Mig-6d/d mice compared to Mig-6f/f controls. These results indicate that Mig-6 plays an important role in cholesterol homeostasis and bile acid synthesis. Mice with liver specific conditional ablation of Mig-6 develop hepatomegaly and increased intrahepatic lipid and provide a novel model system to investigate the genetic and molecular events involved in the regulation of cholesterol homeostasis and bile acid synthesis. Defining the molecular mechanisms by which Mig-6 regulates cholesterol homeostasis will provide new insights into the development of more effective ways for the treatment and prevention of cardiovascular disease. Eight week old Mig-6f/f vs Mig-6d/d male mice after undergoing a 24 hour fast
Project description:Data acquired for conjugated bile acids with amino acids analysis of human fecal samples by targeted LC-MS. These samples are a part of a study investigating a new BSH function as an amine N-acyl transferase that conjugates amines to form bacterial bile acid amidates (BBAAs).
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.