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:Lactobacillus salivarius is a member of the indigenous microbiota of the human gastrointestinal tract (GIT). Tolerance to bile stress is crucial for intestinal lactobacilli to survive in the GIT and to exert their beneficial actions. In this work, the Next-Generation Sequencing platform Illumina HiSeq 2000 was used to investigate the global response to bile in L. salivarius Ren, a potential probiotic strain isolated from a healthy centenarian. In the presence of 0.75 g liter-1 oxgall, the transcription of nearly 200 genes was detected to be associated with bile stress, including genes involved in carbohydrate and amino acid metabolism, cell envelope and fatty acid biogenesis, transcription and translation. This study improves our understanding on bile stress response in L. salivarius Ren.
Project description:Cholestasis of pregnancy endangers fetal and neonatal survival, however, the underlying mechanisms are largely undetermined. By RNA-sequencing analysis of developing placentas, we identified "bile acids secretion" and "complement and coagulation system" as the most affected KEGG pathway during late pregnancy. In "bile acids secretion" pathway, the downregulated placental carbonic anhydrase II (CA2) expression may in part account for the impaired placental bile acids transport in response to maternal cholestasis. In "complement and coagulation system", the activated placental C5a receptor 1(C5aR1) might provide further evidence for the potential correlation of serum C5a concentration and fetal death as previously observed in humans. Collectively, these results provide new explanation for impaired placental bile acids transport as pregnancy advances, and imply the potential role of "complement and coagulation system" activation in causing adverse fetal outcomes.
Project description:Bile acids act as ligands for several nuclear receptors expressed in the small intestine, especially the terminal ileum. Bile acid pool composition can be influenced by health and disease states. Here, we used RNA-seq to investigate the effects of altering bile acid pool composition on gene expression in ileal organoids.
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:To investigate the role of bile acids in regulating intestinal epithelium differentiation, mouse small intestinal organoids cultured for 2 days were incubated with a series of bile acids at 50 mmol/L for 96 hours and lysed for RNA extraction.
Project description:In this study, we aimed at the characterization of C. difficile’s stress response to the main four human bile acids. Although, a phenotypically description of growth differences upon challenge with different bile acids has been described (Lewis 2016, Thanissery 2017), there is no information on the adaptation of gene expression available. We employed a comprehensive proteomics approach to record stress signatures of the unconjugated bile acids CA, CDCA, DCA and LCA during long-term-stress conditions and could depict a general stress response concerning all four bile acids, but also specific responses to only a single or a few of the different bile acids. Our results are a starting point for the understanding of how the individual bile acids cocktail of a patient can decide on the outcome of a C. difficile infection
Project description:In addition to their role as a digestive detergent, bile acids have the ability to modulate the expression of genes. The intestinal content of cholic acids (CA) fluctuated in response to the daily feeding-fasting cycle; therefore, we hypothesized that the temporal accumulation of CA may affect the expression of genes in intestinal epithelial cells. To screen bile acid-regulated genes, we performed oligonucleotide microarray analyses using RNA isolated from the CA-treated intestinal cells of mice. Several types of genes were screened as candidates for bile acid-regulated genes. They included genes that encoded lipid metabolism-related proteins, receptors, transcriptional factors, and plasma-membrane transporters.
Project description:In this study, we aimed at the characterization of C. difficile’s stress response to the main four human bile acids. Although, a phenotypically description of growth differences upon challenge with different bile acids has been described (Lewis 2016, Thanissery 2017), there is no information on the adaptation of gene expression available. We employed a comprehensive proteomics approach to record stress signatures of the unconjugated bile acids CA, CDCA, DCA and LCA in shock experiments as well as during long-term-stress conditions and could depict a general stress response concerning all four bile acids, but also specific responses to only a single or a few of the different bile acids. Our results are a starting point for the understanding of how the individual bile acids cocktail of a patient can decide on the outcome of a C. difficile infection.
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.