Project description:Host-microbiome communication is frequently perturbed in gut pathologies due to microbiome dysbiosis, leading to altered production of bacterial metabolites. Among these, 7a-dehydroxylated bile acids are notably diminished in inflammatory bowel disease patients. Herein, we investigated whether restoration of 7a-dehydroxylated bile acids levels by Clostridium scindens, a human-derived 7a-dehydroxylating bacterium, can reestablish intestinal epithelium homeostasis following colon injury. Gnotobiotic and conventional mice were subjected to chemically-induced experimental colitis following administration of Clostridium scindens. Colonization enhanced the production of 7a-dehydroxylated bile acids and conferred prophylactic and therapeutic protection against colon injury through epithelial regeneration and specification. Computational analysis of human datasets confirmed defects in intestinal cell renewal and differentiation in ulcerative colitis patients while expression of genes involved in those pathways showed a robust positive correlation with 7a-dehydroxylated bile acid levels. Clostridium scindens administration could therefore be a promising biotherapeutic strategy to foster mucosal healing following colon injury by restoring bile acid homeostasis.
Project description:Background & Aims: Wilson disease (WD) is an autosomal recessive disorder that results in excessive hepatic copper causing hepatic steatosis, inflammation, fibrosis, cirrhosis, and liver failure. Previous studies have revealed dysregulation of many FXR metabolic target genes in animal models of WD, including Bsep, the major determinant of bile flow. Approach & Results: We tested the hypothesis that the FXR-cistrome is decreased in Atp7b-/- mice in accord with dysregulated bile acid homeostasis. RNA-Seq and ChIP-Seq analyses of Atp7b-/- and wild-type (WT) mouse livers confirmed that significantly altered transcripts and FXR-binding events overlapped. Decreased FXR occupancy in Atp7b-/- versus WT mice was observed genes of metabolic pathways and bile acid homeostasis, while enrichment of FXR binding was observed pathways associated with cellular damage, such as the focal adhesion pathway. Consistent with decreased FXR function, serum and liver bile acid concentrations were higher in Atp7b-/- mice than in WT mice. Comparison of bile acid profiles in the serum of WD patients with “liver,” “neurological,” or “mixed” disease vs. healthy controls also revealed increases in specific bile acids in WD-liver vs. healthy controls. Conclusions: Atp7b-/- mice and WD patients exhibited changes in serum bile acid speciation, likely due to FXR dysfunction. These findings provide new insights into possible aberrant bile acid homeostasis in patients with WD.
Project description:Intrahepatic cholestasis of pregnancy (ICP) is estimated to impact between 0.4% and 5% of pregnancies worldwide. This disease is associated with elevated maternal bile acids and frequently untoward neonatal outcomes such as respiratory distress and asphyxia. Multiple candidate genes have been implicated, but none have provided insight into the mechanisms of neonatal respiratory distress and death. Herein our studies demonstrate that maternal cholestasis (due to Abcb11 deficiency) produces 100% neonatal death within 24h due to atelectasis producing pulmonary hypoxia, which recapitulates the respiratory distress and asphyxia of human ICP. We show that these neonates have elevated pulmonary bile acids that are associated with disrupted structure of pulmonary surfactant. Maternal absence of Nr1i2 superimposed upon Abcb11 deficiency strongly increased neonatal survival and is directly related to reduced maternal bile acid concentrations. The mechanism accounting for reduced serum bile acids in the mothers deficient in both Nr1i2 and Abcb11 appears related to disrupted reabsorption of intestinal bile acids due to changes in transporter expression. These findings provide novel insights into pulmonary failure by revealing bile acids capability to disrupt the structure of surfactant producing collapsed alveoli, pulmonary failure and ultimately death. These findings have important implications for neonatal health especially when maternal bile acids are elevated during pregnancy and highlight a potential pathway and targets amenable to therapeutic intervention to ameliorate this condition.
Project description:Intrahepatic cholestasis of pregnancy (ICP) is estimated to impact between 0.4% and 5% of pregnancies worldwide. This disease is associated with elevated maternal bile acids and frequently untoward neonatal outcomes such as respiratory distress and asphyxia. Multiple candidate genes have been implicated, but none have provided insight into the mechanisms of neonatal respiratory distress and death. Herein our studies demonstrate that maternal cholestasis (due to Abcb11 deficiency) produces 100% neonatal death within 24h due to atelectasis producing pulmonary hypoxia, which recapitulates the respiratory distress and asphyxia of human ICP. We show that these neonates have elevated pulmonary bile acids that are associated with disrupted structure of pulmonary surfactant. Maternal absence of Nr1i2 superimposed upon Abcb11 deficiency strongly increased neonatal survival and is directly related to reduced maternal bile acid concentrations. The mechanism accounting for reduced serum bile acids in the mothers deficient in both Nr1i2 and Abcb11 appears related to disrupted reabsorption of intestinal bile acids due to changes in transporter expression. These findings provide novel insights into pulmonary failure by revealing bile acids capability to disrupt the structure of surfactant producing collapsed alveoli, pulmonary failure and ultimately death. These findings have important implications for neonatal health especially when maternal bile acids are elevated during pregnancy and highlight a potential pathway and targets amenable to therapeutic intervention to ameliorate this condition. We used microarrays to measure changes in gene expression profiles in lung tissues from Abcb11+/- lungs after interbreeding C57BL/6 wild-type female or C57BL/6 Abcb11-/- female mice against either C57BL/6 wild-type male mice or C57BL/6 Abcb11-/- male mice to create only heterozygote offspring. We also measured profiles in liver tissues from age-matched C57BL/6 wild-type and C57BL/6 Abcb11-/- mice. Lung tissues were collected from day E17.5, E18.5 and neonatal (N0) mice. Liver tissues were collected from 1.5-month-old C57BL/6 wildtype and Abcb11-/- mice.
Project description:Background & Aims: Wilson disease (WD) is an autosomal recessive disorder that results in excessive hepatic copper causing hepatic steatosis, inflammation, fibrosis, cirrhosis, and liver failure. Previous studies have revealed dysregulation of many FXR metabolic target genes in animal models of WD, including Bsep, the major determinant of bile flow. Approach & Results: We tested the hypothesis that the FXR-cistrome is decreased in Atp7b-/- mice in accord with dysregulated bile acid homeostasis. RNA-Seq and ChIP-Seq analyses of Atp7b-/- and wild-type (WT) mouse livers confirmed that significantly altered transcripts and FXR-binding events overlapped. Decreased FXR occupancy in Atp7b-/- versus WT mice was observed genes of metabolic pathways and bile acid homeostasis, while enrichment of FXR binding was observed pathways associated with cellular damage, such as the focal adhesion pathway. Consistent with decreased FXR function, serum and liver bile acid concentrations were higher in Atp7b-/- mice than in WT mice. Comparison of bile acid profiles in the serum of WD patients with “liver,” “neurological,” or “mixed” disease vs. healthy controls also revealed increases in specific bile acids in WD-liver vs. healthy controls. Conclusions: Atp7b-/- mice and WD patients exhibited changes in serum bile acid speciation, likely due to FXR dysfunction. These findings provide new insights into possible aberrant bile acid homeostasis in patients with WD.
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:Liver sinusoidal endothelial cells (LSEC) are unique endothelial cell typelining the sinusoids of the liver and we have shown that these cells respond in a unique matter when exposed to saturated and unsaturated free fatty acids (FFA) and bile acids. We used microarray to analyze the transcriptional differences between the LSEC exposed to free fatty acids and bile acid receptor agonists to further shed light on their role in non-alcoholic fatty liver disease. The Murine Liver Sinusoidal Endothelial Cell Line (TSEC) was treated with palmitic and oleic acid or the bile acid receptor agonist INT-767 for 8 hours. Total RNA was then harvested to determine transcriptional differences.
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.