The profiling of bile acid-inducing proteins in Streptomyces microflavus
Ontology highlight
ABSTRACT:
ORGANISM(S): Streptomyces Microflavus
SUBMITTER: 
Jinlong Wang
PROVIDER: PXD079248 | iProX | Wed Jun 03 00:00:00 BST 2026
REPOSITORIES: iProX
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Project description:Intestinal lipid absorption, the entry point for fats into the body, requires the coordinated actions of bile acids and lipases. Here, we uncover distinct yet cooperative roles of bile acids in driving the differential uptake of dietary fatty acids. We first decreased the bile acid pool size by disrupting the rate-limiting enzyme in bile acid synthesis, Cyp7a1, using liver-directed gene editing in mice. Compared with lipase inhibition, reduced bile acids prevented diet-induced obesity, increased anorectic hormones, suppressed excessive eating, and improved systemic lipid metabolism. Remarkably, decreasing bile acids selectively reduced the absorption of saturated fatty acids but preserved polyunsaturated fatty acids. By targeting additional bile acid enzymes, we identified specific functions of individual bile acid species. Mechanistically, we show that cholic acid preferentially solubilizes polyunsaturated fatty acids into mixed micelles for intestinal uptake. Our studies demonstrate that bile acids can selectively control fatty acid uptake, revealing insights for future interventions in metabolic diseases.
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Project description:Summary Ex vivo liver normothermic machine perfusion (NMP) does not fully recapitulate physiological liver function due to the absence of the enterohepatic circulation as only infusion of the bile acid taurocholate (TCA) is applied in most protocols. In this study we characterized the de novo bile acid synthesis and cholesterol homeostasis during liver NMP. We hypothesized that addition of a more diverse pool of (conjugated)bile acids during liver NMP would decrease the metabolic burden of de novo synthesis and thereby improve liver function during NMP. Method First, human and porcine livers were perfused for 360 min at 37°C and perfusate containing TCA (gene expression at t=0min and t=360min was measured by RNAseq). Next, the infusion of different conjugated bile acid mixes was assessed during porcine and human liver perfusion. Perfusate, bile and tissue samples were obtained to study liver viability, functionality, gene expression (qPCR), cholesterol and bile acid levels. Result During human and porcine perfusions with TCA infusion, composition of bile was comparable to literature however, synthesis rates were above physiological average and a decrease over time in cholesterol perfusate levels was observed. Additionally, over time a decreased expression of bile acid synthesis related genes, increased gene expression of cholesterol metabolism related genes and decreased expression in bile acid-dependent uptake and efflux transporters were detected (RNAseq). Upon infusion of a conjugated bile acid mix lower AST and ALT values and stable cholesterol homeostasis was] observed after 720 min of perfusion. Perfused human livers showed appropriate function and good functioning livers showed rapid bile acid clearance from the perfusate into the bile. Conclusion This study reveals new insights that infusion of (un)conjugated bile acids in NMP alleviated the burden of the de novo bile acid synthesis and improved liver function.
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Project description:Bile acids regulate lipid metabolism through selective actions on fatty acid absorption
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Project description:Background: Previous epidemiological studies have repeatedly found per- and polyfluoroalkyl substances (PFAS) exposure associated with higher circulating cholesterol, one of the greatest risk factors for development of coronary artery disease. The main route of cholesterol catabolism is through its conversion to bile acids, which circulate between the liver and ileum via enterohepatic circulation. Patients with coronary artery disease have decreased bile acid excretion, indicating that PFAS-induced changes of enterohepatic circulation may play a critical role in cardiovascular risk. Objectives: Using a mouse model with high LDL-VLDL cholesterol and aortic lesion development similar to humans, the current study investigates mechanisms linking exposure to a PFAS mixture with increased cholesterol. Methods: Male and female Ldlr-/- mice were fed an atherogenic diet (Clinton/Cybulsky low fat, 0.15% cholesterol) and exposed to a mixture of 5 PFAS representing legacy, replacement, and emerging subtypes (i.e., PFOA, PFOS, PFNA, PFHxS, GenX), each at a concentration of 2 mg/L, for 7 weeks. Blood was collected longitudinally for cholesterol measurements and mass spectrometry was used to measure circulating and fecal bile acids. Transcriptomic analysis of ileal samples was performed via RNA-sequencing. Results: After 7 weeks of PFAS exposure, average circulating PFAS levels were measured at 21.6, 20.1, 31.2, 23.5, and 1.5 µg/mL in PFAS-exposed females and 12.9, 9.7, 23, 14.3, and 1.7 µg/mL in PFAS-exposed males for PFOA, PFOS, PFHxS, PFNA, and GenX, respectively. PFAS exposure led to elevated circulating cholesterol levels after 7 weeks compared to vehicle mice, with females increasing 18% and males increasing 24%. Total circulating bile acid levels were elevated in PFAS-exposed mice by 230% in males and 290% in females compared to vehicle. PFAS decreased fecal bile acid levels by 62% in females and 59% in males. In the ileum, expression levels of the bile acid reuptake transporter ASBT were increased due to PFAS exposure. Discussion: Mice exposed to a PFAS mixture display increased circulating cholesterol and bile acids perhaps due to changes in enterohepatic circulation. This study implicates PFAS-mediated effects at the site of the ileum as a possible critical mediator of increased cardiovascular risk due to PFAS.
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Project description:Dietary nutrients interact with the gene networks to orchestrate adaptive responses during metabolic stress. Tissue metabolic reprogramming is frequently linked to induction of pathways with pathophysiological consequences. Here we identified Baf60a as a diet-sensitive subunit of the SWI/SNF chromatin-remodeling complexes in the liver that links the consumption of fat- and cholesterol-rich diet to elevated plasma cholesterol levels. The expression of Baf60a in the liver was elevated following western diet feeding. Hepatocyte-specific inactivation of Baf60a reduced bile acid production and intestinal cholesterol absorption, and attenuated diet-induced hypercholesterolemia and atherosclerosis in mice. At the mechanistic level, Baf60a stimulates the expression of hepatic genes involved in bile acid synthesis, modification, and transport through a CAR/Baf60a feedforward regulatory loop. Baf60a is required for the recruitment of the SWI/SNF chromatin-remodeling complexes to facilitate an activating epigenetic switch on the CAR target genes. These studies elucidate an unexpected regulatory pathway that mediates the hyperlipidemic and atherogenic effects of western diet consumption. We used microarrays to elucidate the role of hepatic Baf60a in the regulation of lipid metabolism.
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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.
2015-12-22 | E-GEOD-40085 | biostudies-arrayexpress
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.
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