Conjugated Bile Acids Research Articles

Lactobacillus rhamnosus GG ameliorates triptolide-induced liver injury through modulation of the bile acid-FXR axis

Triptolide (TP) is the principal bioactive compound of Tripterygium wilfordii with significant anti-tumor, anti-inflammatory and immunosuppressive activities. However, its severe hepatotoxicity greatly limits its clinical use. The underlying mechanism of TP-induced liver damage is still poorly understood. Here, we estimate the role of the gut microbiota in TP hepatotoxicity and investigate the bile acid metabolism mechanisms involved. The results of the antibiotic cocktail (ABX) and fecal microbiota transplantation (FMT) experiment demonstrate the involvement of intestinal flora in TP hepatotoxicity. Moreover, TP treatment significantly perturbed gut microbial composition and reduced the relative abundances of Lactobacillus rhamnosus GG (LGG). Supplementation with LGG reversed TP-induced hepatotoxicity by increasing bile salt hydrolase (BSH) activity and reducing the increased conjugated bile acids (BA). LGG supplementation upregulates hepatic FXR expression and inhibits NLRP3 inflammasome activation in TP-treated mice. In summary, this study found that gut microbiota is involved in TP hepatotoxicity. LGG supplementation protects mice against TP-induced liver damage. The underlying mechanism was associated with the gut microbiota-BA-FXR axis. Therefore, LGG holds the potential to prevent and treat TP hepatotoxicity in the clinic.

Metabolic outcomes in obese mice undergoing one-anastomosis gastric bypass (OAGB) with a long or a short biliopancreatic limb.

One-anastomosis gastric bypass (OAGB) has gained importance as a simple, safe, and effective operation to treat morbid obesity. We previously found that Roux-en-Y gastric bypass surgery with a long compared with a short biliopancreatic limb (BPL) leads to improved weight loss and glucose tolerance in obese mice. However, it is not known whether a long BPL in OAGB surgery also results in beneficial metabolic outcomes. Five-week-old male C57BL/6J mice fed a high-fat diet (HFD) for 8 weeks underwent OAGB surgery with defined BPL lengths (5.5 cm distally of the duodenojejunal junction for short and 9.5 cm for long BPL), or sham surgery combined with caloric restriction. Weight loss, glucose tolerance, obesity-related comorbidities, endocrine effects, gut microbiota, and bile acids were assessed. Total weight loss was independent of the length of the BPL after OAGB surgery. However, a long BPL was associated with lower glucose-stimulated insulin on day 14, and an improved glucose tolerance on day 35 after surgery. Moreover, a long BPL resulted in reduced total cholesterol, while there were no differences in the resolution of metabolic dysfunction-associated steatotic liver disease (MASLD) and adipose tissue inflammation. Tendencies of an attenuated hypothalamic-pituitary-adrenal (HPA) axis and aldosterone were present in the long BPL group. With both the short and long BPL, we found an increase in primary conjugated bile acids (pronounced in long BPL) along with a loss in bacterial Desulfovibrionaceae and Erysipelotrichaceae and simultaneous increase in Akkermansiaceae, Sutterellaceae, and Enterobacteriaceae. In summary, OAGB surgery with a long compared with a short BPL led to similar weight loss, but improved glucose metabolism, lipid, and endocrine outcomes in obese mice, potentially mediated through changes in gut microbiota and related bile acids. Tailoring the BPL length in humans might help to optimize metabolic outcomes after bariatric surgery.NEW & NOTEWORTHY Weight loss following OAGB surgery in obese mice was not influenced by BPL length, but a longer BPL was associated with improved metabolic outcomes, including glucose and lipid homeostasis. These changes could be mediated by bile acids upon altered gut microbiota. Further validation of these findings is required through a randomized human study.

OPA1 affects lipid metabolism and atherosclerosis progression

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): European Atherosclerosis Society Introduction Mitochondria are involved in cellular metabolism, energy generation, calcium homeostasis, sterol and bile acids (BAs) production. Mitochondria continuously undergo biogenesis, fusion, fission and mitophagy, maintaining a continuous balance between all forms. Purpose On these premises, we test the impact of OPA1, an inner mitochondria membrane fusion protein, on mitochondrial tethering on lipid metabolism in the liver and the atherosclerotic plaque. Methods OPA1HepKO and OPA1 TG on LDLR KO background were fed with a Western-type diet (WTD) respectively for 12 weeks. Inverse calorimetry, GTT, and LipidToleranceTest (LTT) were performed. Paraffin-embedded tissues were used for histological analysis, frozen tissues were used for OMICs analysis. VSMCs were isolated and cultured with VLDL (50 µg/ml). Results While OPA1HepKO mice display altered systemic metabolism with reduced body weight and reduced circulating lipid levels OPA1 overexpression on LDLR KO background showed significantly high cholesterol levels. OPA1 deficiency impair hepatic bile acid conjugation with significant accumulation of primary unconjugated bile acids in the liver. On the contrary OPA1 overexpression leads to a reduction of unconjugated bile acids and higher percentage of conjugated bile acids. OPA1 reduction leads to a reduced atherosclerotic plaque while, on the contrary, its overexpression doesn’t affect atherosclerosis despite an increase in circulating lipid and lipoprotein levels. OPA1 overexpression is therefore promoting plaque stabilization with VSMCs that are less prone to change their metabolism to synthetic. Conclusion Hepatic Opa1 deficiency alters bile acids production and therefore circulating lipid profile with a consequent reduction in atherosclerotic plaque formation. OPA1 overexpression in the aorta affects plaque stability despite the highest levels of circulating lipids.

Offline Two-Dimensional Liquid Chromatography-Mass Spectrometry for Deep Annotation of the Fecal Metabolome Following Fecal Microbiota Transplantation.

Biological interpretation of untargeted LC-MS-based metabolomics data depends on accurate compound identification, but current techniques fall short of identifying most features that can be detected. The human fecal metabolome is complex, variable, incompletely annotated, and serves as an ideal matrix to evaluate novel compound identification methods. We devised an experimental strategy for compound annotation using multidimensional chromatography and semiautomated feature alignment and applied these methods to study the fecal metabolome in the context of fecal microbiota transplantation (FMT) for recurrent C.difficile infection. Pooled fecal samples were fractionated using semipreparative liquid chromatography and analyzed by an orthogonal LC-MS/MS method. The resulting spectra were searched against commercial, public, and local spectral libraries, and annotations were vetted using retention time alignment and prediction. Multidimensional chromatography yielded more than a 2-fold improvement in identified compounds compared to conventional LC-MS/MS and successfully identified several rare and previously unreported compounds, including novel fatty-acid conjugated bile acid species. Using an automated software-based feature alignment strategy, most metabolites identified by the new approach could be matched to features that were detected but not identified in single-dimensional LC-MS/MS data. Overall, our approach represents a powerful strategy to enhance compound identification and biological insight from untargeted metabolomics data.

Metabolic phenotyping reveals an emerging role of ammonia abnormality in Alzheimer’s disease

The metabolic implications in Alzheimer’s disease (AD) remain poorly understood. Here, we conducted a metabolomics study on a moderately aging Chinese Han cohort (n = 1397; mean age 66 years). Conjugated bile acids, branch-chain amino acids (BCAAs), and glutamate-related features exhibited strong correlations with cognitive impairment, clinical stage, and brain amyloid-β deposition (n = 421). These features demonstrated synergistic performances across clinical stages and subpopulations and enhanced the differentiation of AD stages beyond demographics and Apolipoprotein E ε4 allele (APOE-ε4). We validated their performances in eight data sets (total n = 7685) obtained from Alzheimer’s Disease Neuroimaging Initiative (ADNI) and Religious Orders Study and Memory and Aging Project (ROSMAP). Importantly, identified features are linked to blood ammonia homeostasis. We further confirmed the elevated ammonia level through AD development (n = 1060). Our findings highlight AD as a metabolic disease and emphasize the metabolite-mediated ammonia disturbance in AD and its potential as a signature and therapeutic target for AD.

2 Another renaissance for bile acid gastrointestinal microbiology

Abstract The field of bile acid microbiology in the gastrointestinal tract is going through a current rebirth after a peak of activity in the late 1970s and early 1980s. This renewed activity is a result of many factors including the discovery near the turn of the century that bile acids are potent signaling molecules, technological advances in next generation sequencing, computation, culturomics, gnotobiology, and metabolomics. The current state of the field with particular emphasis on questions that have remained unanswered for many decades in both bile acid synthesis by the host, and metabolism by the gut microbiota will be addressed. Current knowledge of established enzymatic pathways including bile salt hydrolase, hydroxysteroid dehydrogenases involved in the oxidation and epimerization of bile acid hydroxy groups, the Hylemon-Bjӧrkhem Pathway (HBP) of bile acid C7-dehydroxylation, and the formation of secondary allo-bile acids are described. Aspects of bile acid conjugation and esterification, and evidence for bile acid C3- and C12-dehydroxylation that are less well understood, but potentially critical for our understanding of bile acid metabolism in the human gut will be covered. The physiological consequences of bile acid metabolism for human health, important caveats and cautionary notes on experimental design and interpretation of bile acid metabolism are also explored.

Bile Acid-Targeted Hyaluronic Acid Nanoparticles for Enhanced Oral Absorption of Deferoxamine.

Patients with β-thalassemia and sickle cell disease often rely on blood transfusions which can lead to hemochromatosis and chronic oxidative stress in cells and tissues. Deferoxamine (DFO) is clinically approved to treat hemochromatosis but is suboptimal to patients due to its poor pharmacokinetics which requires long-term infusion regimens. Although the oral route is preferable, DFO has limited oral bioavailability. Studies have shown that hyaluronic acid (HA) and bile acid (BA) can enhance the oral absorption of poorly absorbed drugs. To improve upon the oral delivery of DFO, we report on the synthesis and characterization of HA (MW 15 kD) conjugated to two types of BA, deoxycholic acid (DOCA) and taurocholic acid (TCA), and DFO. The resulting seven polymeric conjugates all formed self-assembled nanoparticles. The degree of BA and DFO conjugation to the HA polymer was confirmed at each step through nuclear magnetic resonance, Fourier transform infrared spectroscopy, and UV-Vis spectroscopy. The best formulations for further in vitro testing were determined based on physicochemical characterizations and included HA-DFO, TCA9-HA-DFO, and DOCA9-HA-DFO. Results from in vitro assays revealed that TCA9-HA-DFO enhanced the permeation of DFO the most and was also less cytotoxic to cells compared to the free drug DFO. In addition, ferritin reduction studies indicated that the conjugation of DFO to TCA9-HA did not compromise its chelation efficiency at equivalent free DFO concentrations. This research provides supportive data for the idea that TCA conjugated to HA may enhance the oral absorption of DFO, improve its cytocompatibility, and maintain its iron chelation efficiency.

Design and development of novel self-assembled catechol-modified bile acid conjugates as pH-responsive apical sodium-dependent bile acid transporter targeting nanoparticles

Catechol-based biomaterials demonstrate biocompatibility, making them suitable for a wide range of therapeutic applications when integrated into various molecular frameworks. However, the development of orally available catechol-based biomaterials has been hindered by significant pH variations and complex interactions in the gastrointestinal (GI) tract. In this study, we introduce a novel catechol-modified bile acid (CMBA), which is synthesized by anchoring the FDA-approved drug, ursodeoxycholic acid to the neurotransmitter dopamine. This modification could form a new apical sodium-dependent bile acid transporter (ASBT) inhibitor (ASBTi) due to the bile acid moiety. The computational analysis using the TRAnsient Pockets in Proteins (TRAPP) module, coupled with MD simulations, revealed that CMBA exhibits a strong binding affinity at residues 51–55 of ASBT with a low inhibitory constant (Ki) value. Notably, in slightly alkaline biological conditions, CMBA molecules self-assemble into carrier-free nanoparticles with an average size of 240.2 ± 44.2 nm, while maintaining their ability to bind with ASBT. When administered orally, CMBA accumulates in the ileum and liver over 24 h, exhibiting significant therapeutic effects on bile acid (BA) metabolism in a high-fat diet (HFD)-fed mouse model. This study underscores the therapeutic potential of the newly developed catechol-based, pH-responsive ASBT-inhibiting nanoparticles presenting a promising avenue for advancing therapy.

Abstract 7094: Clinical metabolomics reveals baseline biomarkers of hepatic dysfunction correlating with irregular drug-induced ALT and bilirubin elevations

Abstract AZD4573 is a highly potent and selective Cyclin-Dependent Kinase 9 inhibitor. The AZD4573 First-in-Human (FIH) study revealed variable alanine transaminase (ALT) and/or bilirubin elevation and a clear correlation to dose or PK exposure could not be defined. While concurrent ALT elevation ≥3x upper limit of normal (ULN) and bilirubin elevation ≥2x ULN (potential Hy’s law) is a biochemical finding indicating potential drug-induced liver injury, quantitative modeling disconnected ALT and bilirubin elevation demonstrating that the observations were not Hy’s Law cases. Furthermore, we implemented a targeted metabolomics workflow to investigate the ALT and bilirubin elevation mechanism and identify predictive biomarkers to better understand and/or predict any hepatic stress liabilities associated with AZD4573 clinical development. We implemented an established metabolomics methodology to 359 samples from 15 patients yielding 47,000 total data points. Data was separated into 98 different dosing intervals from the 15 patients to identify the ALT and bilirubin-associated metabolic changes conserved across all patients while incorporating metabolic differences in individual patents with ALT and bilirubin elevation in only a fraction of multiple doses. Orthogonal Partial Least Squares modeling identified several metabolites and pathways altered as a function of maximum ALT or bilirubin levels. Post-dose conjugated bile acids were elevated when ALT and bilirubin were elevated. Pre-dose creatine levels were decreased when ALT and bilirubin elevation occurred, and pre-dose glutamate levels were elevated when ALT elevation occurred. Pre-dose decreased total carnitines and kynurenine pathway activation were observed when ALT and bilirubin elevation occurred, but the effect did not reach statistical significance. Elevated bile acids are an established characteristic of cholestasis and suggest cholestasis as a probable mechanism for AZD4573-induced reversible liver stress. Interestingly, decreased creatine, glutamate elevation, decreased total carnitine, and kynurenine pathway activation are all associated with some form of liver stress or disfunction which may explain the irregular ALT and bilirubin elevations observed in patients receiving AZD4573; while ALT itself is a biomarker of liver damage, these pre-dose biochemical changes may illuminate potential preceding liver stress. Dosing patients already experiencing higher liver stress levels may be more susceptible to drug-induced ALT and bilirubin elevation, and patients with increasing in-study liver stress may only present at later doses. This work demonstrates metabolomics utility to elucidate possible mechanisms of liver toxicity as well as to identify potential predictive biomarkers for further investigation to explore individual patient risk in clinical studies. Citation Format: John K. Meissen, Kevin Contrepois, Sophie Regan, Jennifer Tan, Alison J. Foster, Jiaqi Yuan, Shringi Sharma, Dominic Williams, Anton I. Rosenbaum. Clinical metabolomics reveals baseline biomarkers of hepatic dysfunction correlating with irregular drug-induced ALT and bilirubin elevations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7094.

Neuroactive metabolites and bile acids are altered in extremely premature infants with brain injury

The gut microbiome is associated with pathological neurophysiological evolvement in extremely premature infants suffering from brain injury. The exact underlying mechanism and its associated metabolic signatures in infants are not fully understood. To decipher metabolite profiles linked to neonatal brain injury, we investigate the fecal and plasma metabolome of samples obtained from a cohort of 51 extremely premature infants at several time points, using liquid chromatography (LC)-high-resolution mass spectrometry (MS)-based untargeted metabolomics and LC-MS/MS-based targeted analysis for investigating bile acids and amidated bile acid conjugates. The data are integrated with 16S rRNA gene amplicon gut microbiome profiles as well as patient cytokine, growth factor, and Tcell profiles. We find an early onset of differentiation in neuroactive metabolites between infants with and without brain injury. We detect several bacterially derived bile acid amino acid conjugates in plasma and feces. These results provide insights into the early-life metabolome of extremely premature infants.

Twelve-hour normothermic liver perfusion in a rat model: characterization of the changes in the ex-situ bio-molecular phenotype and metabolism

The partial understanding of the biological events that occur during normothermic machine perfusion (NMP) and particularly during prolonged perfusion might hinder its deployment in clinical transplantation. The aim of our study was to implement a rat model of prolonged NMP to characterize the bio-molecular phenotype and metabolism of the perfused organs. Livers (n = 5/group) were procured and underwent 4 h (NMP4h) or 12 h (NMP12h) NMP, respectively, using a perfusion fluid supplemented with an acellular oxygen carrier. Organs that were not exposed to any procedure served as controls (Native). All perfused organs met clinically derived viability criteria at the end of NMP. Factors related to stress-response and survival were increased after prolonged perfusion. No signs of oxidative damage were detected in both NMP groups. Evaluation of metabolite profiles showed preserved mitochondrial function, activation of Cori cycle, induction of lipolysis, acetogenesis and ketogenesis in livers exposed to 12 h-NMP. Increased concentrations of metabolites involved in glycogen synthesis, glucuronidation, bile acid conjugation, and antioxidant response were likewise observed. In conclusion, our NMP12h model was able to sustain liver viability and function, thereby deeply changing cell homeostasis to maintain a newly developed equilibrium. Our findings provide valuable information for the implementation of optimized protocols for prolonged NMP.

A Probiotic Targets Bile Acids Metabolism to Alleviate Ulcerative Colitis by Reducing Conjugated Bile Acids.

Gut microbiota (GM) dysbiosis and dysregulated bile acids (BAs) metabolism have been linked to ulcerative colitis (UC) pathogenesis. The possibility of utilizing live probiotics with a defined BAs-metabolizing capability to modify the composition BAs for UC treatment remains unexplored. In this study, Strain GR-4 is sourced from traditional Chinese fermented food, "Jiangshui," and demonstrated the ability to deconjugate two common conjugated BAs by over 69% and 98.47%, respectively. It administers strain GR-4 to dextran sulfate sodium (DSS)-induced UC mice, and observes an overall alleviation of UC symptoms, as evidence by improved colon morphology, reduces inflammation and oxidative stress, and restores intestinal barrier function. Importantly, these effects are reliant on an intact commensal microbiota, as depletion of GM mitigated GR-4s efficacy. Metabolomics analysis unveils a decline in conjugated BAs and an increase in secondary BAs following GR-4 administration. GM analysis indicates that GR-4 selectively enriches bacterial taxa linked to BAs metabolism, enhancing GM's capacity to modify BAs. This research demonstrates the potential for natural fermented foods and probiotics to effectively manipulate BAs composition, including conjugated and secondary BAs, to alleviate UC symptoms, underscoring the benefits of these approaches for gut health.

Exploring Individual Variability in Drug-Induced Liver Injury (DILI) Responses through Metabolomic Analysis.

Drug-induced liver injury (DILI) is a serious adverse hepatic event presenting diagnostic and prognostic challenges. The clinical categorization of DILI into hepatocellular, cholestatic, or mixed phenotype is based on serum alanine aminotransferase (ALT) and alkaline phosphatase (ALP) values; however, this classification may not capture the full spectrum of DILI subtypes. With this aim, we explored the utility of assessing changes in the plasma metabolomic profiles of 79 DILI patients assessed by the RUCAM (Roussel Uclaf Causality Assessment Method) score to better characterize this condition and compare results obtained with the standard clinical characterization. Through the identification of various metabolites in the plasma (including free and conjugated bile acids and glycerophospholipids), and the integration of this information into predictive models, we were able to evaluate the extent of the hepatocellular or cholestatic phenotype and to assign a numeric value with the contribution of each specific DILI sub-phenotype into the patient's general condition. Additionally, our results showed that metabolomic analysis enabled the monitoring of DILI variability responses to the same drug, the transitions between sub-phenotypes during disease progression, and identified a spectrum of residual DILI metabolic features, which can be overlooked using standard clinical diagnosis during patient follow-up.

Differences among Lactiplantibacillus plantarum strains isolated from different fermented foods in their potential cholesterol-lowering properties

Elevated levels of plasma low-density lipoprotein (LDL) cholesterol have been associated with incident atherosclerotic cardiovascular disease. Animal studies and clinical trials have demonstrated that several Lactiplantibacillus plantarum strains are effective in reducing plasma LDL cholesterol levels. However, it is unclear whether the habitats from which Lactiplantibacillus plantarum strains are isolated have an impact on their potential cholesterol-lowering properties. In this study, 107 Lactiplantibacillus plantarum strains isolated from three habitats (20 isolated from fermented dairy products, 23 from fermented grape must, and 64 from fermented vegetables) were compared for their potential cholesterol-lowering properties on an origin scale. These properties included acid resistance, bile tolerance, surface hydrophobicity, and bile acid deconjugation. The results showed that the fermented dairy products-derived strains were the most bile-tolerant and hydrophobic, the fermented grape must-derived strains were the most effective at hydrolyzing conjugated bile acids, and the fermented vegetables-derived strains were the most acid-resistant. Bile salt hydrolase (BSH) genes were detected in 97.2% of the total strains and 100% of the fermented dairy products-derived strains by standard PCR with agarose gel electrophoresis detection. In the 104 bsh genes-containing strains, 92.3% had detectable BSH activity (n = 96). These BSH-positive strains exhibited a greater substrate preference for glycine-conjugated bile acids than taurine-conjugated bile acids. Overall, the fermented dairy products-derived strains appeared to have greater cholesterol-lowering potential than those isolated from the other two habitats. This study provided valuable information regarding where to obtain Lactiplantibacillus plantarum strains with greater cholesterol-lowering potential.

Ginsenoside Rb1, Compound K and 20(S)-Protopanaxadiol Attenuate High-Fat Diet-Induced Hyperlipidemia in Rats via Modulation of Gut Microbiota and Bile Acid Metabolism.

Hyperlipidemia, characterized by elevated serum lipid concentrations resulting from lipid metabolism dysfunction, represents a prevalent global health concern. Ginsenoside Rb1, compound K (CK), and 20(S)-protopanaxadiol (PPD), bioactive constituents derived from Panax ginseng, have shown promise in mitigating lipid metabolism disorders. However, the comparative efficacy and underlying mechanisms of these compounds in hyperlipidemia prevention remain inadequately explored. This study investigates the impact of ginsenoside Rb1, CK, and PPD supplementation on hyperlipidemia in rats induced by a high-fat diet. Our findings demonstrate that ginsenoside Rb1 significantly decreased body weight and body weight gain, ameliorated hepatic steatosis, and improved dyslipidemia in HFD-fed rats, outperforming CK and PPD. Moreover, ginsenoside Rb1, CK, and PPD distinctly modified gut microbiota composition and function. Ginsenoside Rb1 increased the relative abundance of Blautia and Eubacterium, while PPD elevated Akkermansia levels. Both CK and PPD increased Prevotella and Bacteroides, whereas Clostridium-sensu-stricto and Lactobacillus were reduced following treatment with all three compounds. Notably, only ginsenoside Rb1 enhanced lipid metabolism by modulating the PPARγ/ACC/FAS signaling pathway and promoting fatty acid β-oxidation. Additionally, all three ginsenosides markedly improved bile acid enterohepatic circulation via the FXR/CYP7A1 pathway, reducing hepatic and serum total bile acids and modulating bile acid pool composition by decreasing primary/unconjugated bile acids (CA, CDCA, and β-MCA) and increasing conjugated bile acids (TCDCA, GCDCA, GDCA, and TUDCA), correlated with gut microbiota changes. In conclusion, our results suggest that ginsenoside Rb1, CK, and PPD supplementation offer promising prebiotic interventions for managing HFD-induced hyperlipidemia in rats, with ginsenoside Rb1 demonstrating superior efficacy.

Another renaissance for bile acid gastrointestinal microbiology.

The field of bile acid microbiology in the gastrointestinal tract is going through a current rebirth after a peak of activity in the late 1970s and early 1980s. This renewed activity is a result of many factors, including the discovery near the turn of the century that bile acids are potent signalling molecules and technological advances in next-generation sequencing, computation, culturomics, gnotobiology, and metabolomics. We describe the current state of the field with particular emphasis on questions that have remained unanswered for many decades in both bile acid synthesis by the host and metabolism by the gut microbiota. Current knowledge of established enzymatic pathways, including bile salt hydrolase, hydroxysteroid dehydrogenases involved in the oxidation and epimerization of bile acid hydroxy groups, the Hylemon-Bjӧrkhem pathway of bile acid C7-dehydroxylation, and the formation of secondary allo-bile acids, is described. We cover aspects of bile acid conjugation and esterification as well as evidence for bile acid C3-dehydroxylation and C12-dehydroxylation that are less well understood but potentially critical for our understanding of bile acid metabolism in the human gut. The physiological consequences of bile acid metabolism for human health, important caveats and cautionary notes on experimental design and interpretation of data reflecting bile acid metabolism are also explored.

Ginsenosides retard atherogenesis via remodelling host-microbiome metabolic homeostasis.

Panax ginseng is widely applied in the adjuvant treatment of cardiometabolic diseases in clinical practice without clear mechanisms. This study aims to clearly define the efficacy and underlying mechanism of P.ginseng and its active components in protecting against atherosclerosis. The anti-atherogenic efficacy of total ginseng saponin extract (TGS) and its components was evaluated on Ldlr-/- mice. Gut microbial structure was analysed by 16S rRNA sequencing and PCR. Bile acid profiles were revealed using targeted metabolomics with LC-MS/MS analysis. The contribution of gut microbiota to atherosclerosis was assessed by co-housing experiments. Ginsenoside Rb1, representing protopanaxadiol (PPD)-type saponins, increased intestinal Lactobacillus abundance, resulting in enhanced bile salt hydrolase (BSH) activity to promote intestinal conjugated bile acid hydrolysis and excretion, followed by suppression of enterohepatic farnesoid X receptor (FXR)-fibroblast growth factor 15 (FGF15) signal, and thereby increased cholesterol 7α-hydroxylase (CYP7A1) transcriptional expression and facilitated metabolic elimination of cholesterol. Synergistically, protopanaxatriol (PPT)-type saponins, represented by ginsenoside Rg1, protected against atherogenesis-triggered gut leak and metabolic endotoxaemia. Ginsenoside Rg1 directly induced mucin production to nutritionally maintain Akkermansia muciniphila, which reciprocally inhibited gut permeation. Rb1/Rg1 combination, rather than a single compound, can largely mimic the holistic efficacy of TGS in protecting Ldlr-/- mice from atherogenesis. Our study provides strong evidence supporting TGS and ginsenoside Rb1/Rg1 combinations as effective therapies against atherogenesis, via targeting different signal nodes by different components and may provide some elucidation of the holistic mode of herbal medicines.

Vagal activation alters prandial bile acid composition and glycemia in patients with hypoglycemia after Roux-en-Y gastric bypass surgery.

Altered prandial glycemic response after Roux-en-Y gastric bypass (RYGB) is exaggerated in patients with post-RYGB hypoglycemia. Increased contribution of glucagon-like peptide 1 (GLP-1) to prandial insulin secretion plays a key role in developing hypoglycemia after RYGB, but the role of nonhormonal gut factors remains unknown. Here, the effect of vagal activation on prandial bile acid (BA) composition in relation to glucose, insulin and gut hormone responses was examined in a small size group of nondiabetic subjects after RYGB with intact gallbladder compared to nonoperated controls. Concentrations of blood glucose, hormones, and BAs were measured in two RYGB subjects with documented hypoglycemia (HGB), three asymptomatic RYGB-treated subjects (AGB), and four nonoperated controls with intact gallbladders during a meal-tolerance test with (MTT-Sham) and without (MTT) preceding modified sham feeding (chew and spit). Meal ingestion raised serum total BAs in RYGB-treated subjects without any effect in nonoperated controls. Modified sham feeding similarly increased meal-induced responses of conjugated BAs (CBAs) in all subjects (p < 0.05 compared to MTT alone), whereas unconjugated BAs (UBAs), mainly deoxycholic and chenodeoxycholic acid, were raised only in the HGB group (p < 0.001 for interaction). Prandial UBAs had an inverse correlation with glucose nadir (r = -0.75, p < 0.05) and were directly associated with ISR and GLP-1 during MTT-Sham. In this small cohort, vagal activation by modified sham feeding increases prandial CBAs in both operated and nonoperated subjects but enhances UBAs only in patients with documented post-RYGB hypoglycemia. Our findings highlight a potential role for nonhormonal gut factors, such as BA and gut microbiome, in glucose abnormalities after RYGB.

Bile salt hydrolase acyltransferase activity expands bile acid diversity.

Bile acids (BAs) are steroid detergents in bile that contribute to the absorption of fats and fat-soluble vitamins while shaping the gut microbiome because of their antimicrobial properties1-4. Here we identify the enzyme responsible for a mechanism of BA metabolism by the gut microbiota involving amino acid conjugation to the acyl-site of BAs, thus producing a diverse suite of microbially conjugated bile acids (MCBAs). We show that this transformation is mediated by acyltransferase activity of bile salt hydrolase (bile salt hydrolase/transferase,BSH/T). Clostridium perfringens BSH/T rapidly performed acyl transfer when provided various amino acids and taurocholate, glycocholate or cholate, with an optimum at pH 5.3. Amino acid conjugation by C. perfringens BSH/T was diverse, including all proteinaceous amino acids except proline and aspartate. MCBA production was widespread among gut bacteria, with strain-specific amino acid use. Species with similar BSH/T amino acid sequences had similar conjugation profiles and several bsh/t alleles correlated with increased conjugation diversity. Tertiary structure mapping of BSH/T followed by mutagenesis experiments showed that active site structure affects amino acid selectivity. These MCBA products had antimicrobial properties, where greater amino acid hydrophobicity showed greater antimicrobial activity. Inhibitory concentrations of MCBAs reached those measured natively in the mammalian gut. MCBAs fed to mice entered enterohepatic circulation, in which liver and gallbladder concentrations varied depending on the conjugated amino acid. Quantifying MCBAs in human faecal samples showed that they reach concentrations equal to or greater than secondary and primary BAs and were reduced after bariatric surgery, thus supporting MCBAs as a significant component of the BA pool that can be altered by changes in gastrointestinal physiology. In conclusion, the inherent acyltransferase activity of BSH/T greatly diversifies BA chemistry, creating a set of previously underappreciated metabolites with the potential to affect the microbiome and human health.

Reversal of cholestatic liver disease by the inhibition of sphingosine 1-phosphate receptor 2 signaling.

The objective of this study is to examine the impact of inhibiting Sphingosine 1-phosphate receptor 2 (S1PR2) on liver inflammation, fibrogenesis, and changes of gut microbiome in the context of cholestasis-induced conditions. The cholestatic liver injury model was developed by common bile duct ligation (CBDL). Sprague-Dawley rats were randomly allocated to three groups, sham operation, CBDL group and JTE-013 treated CBDL group. Biochemical and histological assessments were conducted to investigate the influence of S1PR2 on the modulation of fibrogenic factors and inflammatory infiltration. We conducted an analysis of the fecal microbiome by using 16S rRNA sequencing. Serum bile acid composition was evaluated through the utilization of liquid chromatography-mass spectrometry techniques. In the BDL rat model, the study findings revealed a significant increase in serum levels of conjugated bile acids, accompanied by an overexpression of S1PR2. Treatment with the specific inhibitor of S1PR2, known as JTE-013, resulted in a range of specific effects on the BDL rats. These effects included the improvement of liver function, reduction of liver inflammation, inhibition of hepatocyte apoptosis, and suppression of NETosis. These effects are likely mediated through the TCA/S1PR2/NOX2/NLRP3 pathway. Furthermore, the administration of JTE-013 resulted in an augmentation of the diversity of the bacterial community's diversity, facilitating the proliferation of advantageous species while concurrently inhibiting the prevalence of detrimental bacteria. The results of our study suggest that the administration of JTE-013 may have a beneficial effect in alleviating cholestatic liver disease and restoring the balance of intestinal flora.