Metabolic Profile of Obeticholic Acid and Endogenous Bile Acids in Rats with Decompensated Liver Cirrhosis

Metabolomics in cirrhosis: Recent advances and opportunities

Liver cirrhosis (LC) represents a significant hepatic disorder that persistently commands the attention of the scientific community, especially concerning its pathogenesis and therapeutic approaches. Metabolomics, the comprehensive profiling of an organism's metabolome, has been increasingly applied in the research of cirrhosis over the past decade. This review summarizes the recent advancements and applications of metabolomics within the context of LC research, in recent five years. It highlights the role of metabolomics in the diagnosis of LC, the assessment of prognostic markers, and the evaluation of therapeutic outcomes. The discussion focuses on the potential and challenges of metabolomics in LC research, including the evolution of analytical technologies, advancements in bioinformatics, and the challenges impeding clinical implementation. Additionally, the review anticipates the forthcoming developments in metabolomics related to LC research, with the objective of facilitating innovative approaches for early detection and intervention in LC.

Safety, pharmacokinetics and pharmacodynamics of obeticholic acid in subjects with fibrosis or cirrhosis from NASH

BACKGROUND & AIMS

Fibrosis stage is a strong predictor of nonalcoholic steatohepatitis (NASH) outcomes. Two blinded studies evaluated the pharmacokinetics, pharmacodynamics and safety of obeticholic acid (OCA) in subjects with staged NASH fibrosis or cirrhosis.

METHODS

Study 747-117 randomized 51 subjects with NASH (fibrosis stages F1-F4) to daily placebo, OCA 10 or OCA 25 mg (1:2:2) for 85 days. Study 747-118 randomized 24 subjects with NASH cirrhosis (F4; Child-Pugh [CP]-A) and normal liver control subjects matched for similar body weight to daily OCA 10 or OCA 25 mg (1:1) for 28 days. Individual and combined study data were analysed.

RESULTS

No severe or serious adverse events (AEs) or AEs leading to discontinuation or death occurred. Pruritus was the most frequent AE. Plasma OCA exposure (dose-normalized area under the curve) increased with fibrosis stage but was a relatively poor predictor of hepatic OCA exposure (primary site of action), which remained constant across fibrosis stages F1-F3 and increased 1.8-fold compared with F1 in subjects with cirrhosis due to NASH. Both cohorts showed robust changes in farnesoid X receptor activation markers with OCA treatment and marked decreases in alanine transaminase, aspartate transaminase and gamma-glutamyltransferase.

CONCLUSIONS

Despite higher drug exposures in subjects with NASH cirrhosis, short-term daily treatment with OCA 10 or 25 mg was generally safe and well tolerated in subjects with NASH fibrosis or NASH CP-A cirrhosis. Both cohorts experienced improvements in nonhistologic pharmacodynamic markers consistent with previously conducted OCA phase 2 and phase 3 studies in NASH fibrosis.

Novel preclinical developments of the primary sclerosing cholangitis treatment landscape

INTRODUCTION

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease associated with inflammation, fibrosis, and destruction of intra- and extrahepatic bile ducts. Despite substantial recent advances in our understanding of PSC, the only proven treatment of PSC is liver transplantation. There is an urgent unmet need to find medical therapies for this disorder.

AREAS COVERED

Multiple drugs are currently under evaluation as therapeutic options for this disease. This article summarizes the literature on the various novel therapeutic options that have been investigated and are currently under development for the treatment of PSC.

EXPERT OPINION

In the next decade, more than one drug will likely be approved for the treatment of the disease, and we will be looking at combination therapies for the optimal management of the disease.

FXR agonists for MASH therapy: Lessons and perspectives from obeticholic acid

Nonalcoholic fatty liver disease, also called metabolic dysfunction-associated steatotic liver disease, is the most common liver disease worldwide and has no approved pharmacotherapy. Due to its beneficial effects on metabolic regulation, inflammation suppression, cell death prevention, and fibrogenesis inhibition, farnesoid X receptor (FXR) is widely accepted as a promising therapeutic target for nonalcoholic steatosis (NASH) or called metabolic dysfunction-associated steatohepatitis (MASH). Many FXR agonists have been developed for NASH/MASH therapy. Obeticholic acid (OCA) is the pioneering frontrunner FXR agonist and the first demonstrating success in clinical trials. Unfortunately, OCA did not receive regulatory approval as a NASH pharmacotherapy because its moderate benefits did not outweigh its safety risks, which may cast a shadow over FXR-based drug development for NASH/MASH. This review summarizes the milestones in the development of OCA for NASH/MASH and discuss its limitations, including moderate hepatoprotection and the undesirable side effects of dyslipidemia, pruritus, cholelithiasis, and liver toxicity risk, in depth. More importantly, we provide perspectives on FXR-based therapy for NASH/MASH, hoping to support a successful bench-to-clinic transition.

Obeticholic acid inhibits hepatic fatty acid uptake independent of FXR in mouse

OBJECTIVE

Obeticholic acid (OCA), a farnesoid X receptor (FXR) agonist, is believed to alleviate nonalcoholic fatty liver disease (NAFLD) by decreasing hepatic lipogenesis in an FXR-dependent manner. Here, we revealed a novel mechanism by which OCA improves NAFLD by affecting hepatic long-chain fatty acids (LCFAs) uptake.

METHODS

Stably transfected HEK-293 cells expressing fatty acid transport protein 5 (FATP5) were established to examine fatty acid uptake; FXR^-/-, human (h) FATP5, and FXR^-/-/hFATP5 mouse models were incorporated to explore the effects of OCA on FATP5 ex vivo and in vivo.

RESULTS

OCA inhibited hFATP5 (IC₅₀ =0.07 μM) more than murine (m) FATP5 (IC₅₀ =1.04 μM) as measured by LCFAs uptake in FATP5 expressing HEK-293. OCA also inhibited LCFA uptake in primary hepatocytes from hFATP5 mice, FXR^-/-/hFATP5 mice more than that from FXR^-/- mice, ex vivo. Moreover, OCA inhibited LCFAs uptake by livers in hFATP5 mice and FXR^-/-/hFATP5 mice, but not in FXR^-/- mice, in vivo. Long-term administration of 0.04% OCA markedly reduced hepatic triglyceride (TG) accumulation in hFATP5 mice and FXR^-/-/hFATP5 mice by 63% and 53%, respectively, but not in FXR^-/- mice.

CONCLUSIONS

OCA ameliorated high-fat diet-induced NAFLD independent of FXR by inhibiting hepatic hFATP5-mediated LCFAs uptake. This suggests that the therapeutic effects of OCA on NAFLD in vivo are mediated by a novel, hFATP5 dependent mechanism.

A novel LC-MS/MS method for simultaneous estimation of obeticholic acid, glyco-obeticholic acid, tauro-obeticholic acid in human plasma and its application to a pharmacokinetic study

A rapid, robust, simple, selective, and sensitive liquid chromatography-tandem mass spectrometry method was developed for the simultaneous estimation of obeticholic acid and its two pharmacologically active metabolites, glyco-obeticholic acid, and tauro-obeticholic acid in human plasma. The analytes and their heavy stable isotope-labeled internal standards were extracted from 250 μL human plasma by a solid-phase extraction technique. The method linearity was established over a concentration range of 0.410 to 120.466 ng/mL for obeticholic acid, 0.414 to 121.708 ng/mL for glyco-obeticholic acid, and 0.255 to 75.101 ng/mL for tauro-obeticholic acid. The method was fully validated as per current guidelines on bioanalytical method validation of "United States of Food and Drug Administration" and "European Medicines Agency." The method was successfully applied to study the pharmacokinetics of obeticholic acid, glyco-obeticholic acid, and tauro-obeticholic acid following oral administration of obeticholic acid tablets to healthy male volunteers. All the measured concentrations were within calibration curve ranges.

3β-Isoobeticholic acid efficiently activates the farnesoid X receptor (FXR) due to its epimerization to 3α-epimer by hepatic metabolism

Bile acids (BAs) are important signaling molecules acting via the farnesoid X nuclear receptor (FXR) and the membrane G protein-coupled bile acid receptor 1 (GPBAR1). Besides deconjugation of BAs, the oxidoreductive enzymes of colonic bacteria and hepatocytes enable the conversion of BAs into their epimers or dehydrogenated forms. Obeticholic acid (OCA) is the first-in-class BA-derived FXR agonist approved for the treatment of primary biliary cholangitis. Herein, a library of OCA derivatives, including 7-keto, 6-ethylidene derivatives and 3β-epimers, was synthetized and investigated in terms of interactions with FXR and GPBAR1 in transaction assays and evaluated for FXR target genes expression in human hepatocytes and C57BL/6 mice. The derivatives were further subjected to cell-free analysis employing in silico molecular docking and a TR-FRET assay. The conversion of the 3βhydroxy epimer and its pharmacokinetics in mice were studied using LC-MS. We found that only the 3β-hydroxy epimer of OCA (3β-isoOCA) possesses significant activity to FXR in hepatic cells and mice. However, in a cell-free assay, 3β-isoOCA had about 9-times lower affinity to FXR than did OCA. We observed that 3β-isoOCA readily epimerizes to OCA in hepatocytes and murine liver. This conversion was significantly inhibited by the hydroxy-Δ⁵-steroid dehydrogenase inhibitor trilostane. In addition, we found that 3,7-dehydroobeticholic acid is a potent GPBAR1 agonist. We conclude that 3β-isoOCA significantly activates FXR due to its epimerization to the more active OCA by hepatic metabolism. Other modifications as well as epimerization on the C3/C7 positions and the introduction of 6-ethylidene in the CDCA scaffold abrogate FXR agonism and alleviate GPBAR1 activation.

A novel non-bile acid FXR agonist EDP-305 potently suppresses liver injury and fibrosis without worsening of ductular reaction

BACKGROUND

EDP-305 is a novel and potent farnesoid X receptor (FXR) agonist, with no/minimal cross-reactivity to TGR5 or other nuclear receptors. Herein we report therapeutic efficacy of EDP-305, in direct comparison with the first-in-class FXR agonist obeticholic acid (OCA), in mouse models of liver disease.

METHODS

EDP-305 (10 and 30 mg/kg/day) or OCA (30mg/kg/day) was tested in mouse models of pre-established biliary fibrosis (BALBc.Mdr2-/-, n = 9-12/group) and steatohepatitis induced by methionine/choline-deficient diet (MCD, n = 7-12/group). Effects on biliary epithelium were evaluated in vivo and in primary EpCAM + hepatic progenitor cell (HPC) cultures.

RESULTS

In a BALBc.Mdr2-/- model, EDP-305 reduced serum transaminases by up to 53% and decreased portal pressure, compared to untreated controls. Periportal bridging fibrosis was suppressed by EDP-305 at both doses, with up to a 39% decrease in collagen deposition in high-dose EDP-305. In MCD-fed mice, EDP-305 treatment reduced serum ALT by 62% compared to controls, and profoundly inhibited perisinusoidal 'chicken wire' fibrosis, with over 80% reduction in collagen deposition. In both models, treatment with 30mg/kg OCA reduced serum transaminases up to 30%, but did not improve fibrosis. The limited impact on fibrosis was mediated by cholestasis-independent worsening of ductular reaction by OCA in both disease models; OCA but not EDP-305 at therapeutic doses promoted ductular proliferation in healthy mice and favoured differentiation of primary HPC towards cholangiocyte lineage in vitro.

CONCLUSIONS

EDP-305 potently improved pre-established liver injury and hepatic fibrosis in murine biliary and metabolic models of liver disease, supporting the clinical evaluation of EDP-305 in fibrotic liver diseases including cholangiopathies and non-alcoholic steatohepatitis.

Clinical Updates in Primary Biliary Cholangitis: Trends, Epidemiology, Diagnostics, and New Therapeutic Approaches

Primary biliary cholangitis, formerly known as primary biliary cirrhosis, is a chronic, autoimmune, and cholestatic disease ameliorating the biliary epithelial system causing fibrosis and end-stage liver disease, over time. Patients range from an asymptomatic phase early in the disease course, to symptoms of decompensated cirrhosis later in its course. This review focuses on the current consensus on the epidemiology, diagnosis, and management of patients with primary biliary cholangitis. We also discuss established medical management as well as novel and investigational therapeutics in the pipeline for management of PBC.

FXR modulates the gut-vascular barrier by regulating the entry sites for bacterial translocation in experimental cirrhosis

BACKGROUND & AIMS

Pathological bacterial translocation (PBT) in cirrhosis is the hallmark of spontaneous bacterial infections, increasing mortality several-fold. Increased intestinal permeability is known to contribute to PBT in cirrhosis, although the role of the mucus layer has not been addressed in detail. A clear route of translocation for luminal intestinal bacteria is yet to be defined, but we hypothesize that the recently described gut-vascular barrier (GVB) is impaired in experimental portal hypertension, leading to increased accessibility of the vascular compartment for translocating bacteria.

MATERIALS

Cirrhosis was induced in mouse models using bile-duct ligation (BDL) and CCl₄. Pre-hepatic portal-hypertension was induced by partial portal vein ligation (PPVL). Intestinal permeability was compared in these mice after GFP-Escherichia coli or different sized FITC-dextrans were injected into the intestine.

RESULTS

Healthy and pre-hepatic portal-hypertensive (PPVL) mice lack translocation of FITC-dextran and GFP-E. coli from the small intestine to the liver, whereas BDL and CCl₄-induced cirrhotic mice demonstrate pathological translocation, which is not altered by prior thoracic-duct ligation. The mucus layer is reduced in thickness, with loss of goblet cells and Muc2-staining and expression in cirrhotic but not PPVL mice. These changes are associated with bacterial overgrowth in the inner mucus layer and pathological translocation of GFP-E. coli through the ileal epithelium. GVB is profoundly altered in BDL and CCl₄-mice with Ileal extravasation of large-sized 150 kDa-FITC-dextran, but only slightly altered in PPVL mice. This pathological endothelial permeability and accessibility in cirrhotic mice is associated with augmented expression of PV1 in intestinal vessels. OCA but not fexaramine stabilizes the GVB, whereas both FXR-agonists ameliorate gut to liver translocation of GFP-E. coli.

CONCLUSIONS

Cirrhosis, but not portal hypertension per se, grossly impairs the endothelial and muco-epithelial barriers, promoting PBT to the portal-venous circulation. Both barriers appear to be FXR-modulated, with FXR-agonists reducing PBT via the portal-venous route.

LAY SUMMARY

For intestinal bacteria to enter the systemic circulation, they must cross the mucus and epithelial layer, as well as the gut-vascular barrier. Cirrhosis disrupts all 3 of these barriers, giving bacteria access to the portal-venous circulation and thus, the gut-liver axis. Diminished luminal bile acid availability, cirrhosis and the associated reduction in farnesoid x receptor (FXR) signaling seem, at least partly, to mediate these changes, as FXR-agonists reduce bacterial translocation via the portal-venous route to the liver in cirrhosis.

The FXR agonist obeticholic acid inhibits the cancerogenic potential of human cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive cancer with high resistance to chemotherapeutics. CCA is enriched in cancer stem cells, which correlate with aggressiveness and prognosis. FXR, a member of the metabolic nuclear receptor family, is markedly down-regulated in human CCA. Our aim was to evaluate, in primary cultures of human intrahepatic CCA (iCCA), the effects of the FXR agonist obeticholic acid (OCA), a semisynthetic bile acid derivative, on their cancerogenic potential. Primary human iCCA cell cultures were prepared from surgical specimens of mucinous or mixed iCCA subtypes. Increasing concentrations (0-2.5 μM) of OCA were added to culture media and, after 3-10 days, effects on proliferation (MTS assay, cell population doubling time), apoptosis (annexin V-FITC/propidium iodide), cell migration and invasion (wound healing response and Matrigel invasion assay), and cancerogenic potential (spheroid formation, clonogenic assay, colony formation capacity) were evaluated. Results: FXR gene expression was downregulated (RT-qPCR) in iCCA cells vs normal human biliary tree stem cells (p < 0.05) and in mucinous iCCA vs mixed iCCA cells (p < 0.05) but was upregulated by addition of OCA. OCA significantly (p < 0.05) inhibited proliferation of both mucinous and mixed iCCA cells, starting at a concentration as low as 0.05 μM. Also, CDCA (but not UDCA) inhibited cell proliferation, although to a much lower extent than OCA, consistent with its different affinity for FXR. OCA significantly induced apoptosis of both iCCA subtypes and decreased their in vitro cancerogenic potential, as evaluated by impairment of colony and spheroid formation capacity and delayed wound healing and Matrigel invasion. In general, these effects were more evident in mixed than mucinous iCCA cells. When tested together with Gemcitabine and Cisplatin, OCA potentiated the anti-proliferative and pro-apoptotic effects of these chemotherapeutics, but mainly in mixed iCCA cells. OCA abolished the capacity of both mucinous and mixed iCCA cells to form colonies when administered together with Gemcitabine and Cisplatin. In subcutaneous xenografts of mixed iCCA cells, OCA alone or combined with Gemcitabine or Cisplatin markedly reduced the tumor size after 5 weeks of treatment by inducing necrosis of tumor mass and inhibiting cell proliferation. In conclusion, FXR is down-regulated in iCCA cells, and its activation by OCA results in anti-cancerogenic effects against mucinous and mixed iCCA cells, both in vitro and in vivo. The effects of OCA predominated in mixed iCCA cells, consistent with the lower aggressiveness and the higher FXR expression in this CCA subtype. These results, showing the FXR-mediated capacity of OCA to inhibit cholangiocarcinogenesis, represent the basis for testing OCA in clinical trials of CCA patients.

A nonalcoholic fatty liver disease model in human induced pluripotent stem cell-derived hepatocytes, created by endoplasmic reticulum stress-induced steatosis

Hepatic steatosis, a reversible state of metabolic dysregulation, can promote the onset of nonalcoholic steatohepatitis (NASH), and its transition is thought to be critical in disease evolution. The association between endoplasmic reticulum (ER) stress response and hepatocyte metabolism disorders prompted us to characterize ER stress-induced hepatic metabolic dysfunction in human induced pluripotent stem cell-derived hepatocytes (hiPSC-Hep), to explore regulatory pathways and validate a phenotypic in vitro model for progression of liver steatosis. We treated hiPSC-Hep with a ratio of unsaturated and saturated fatty acids in the presence of an inducer of ER stress to synergistically promote triglyceride accumulation and dysregulate lipid metabolism. We monitored lipid accumulation by high-content imaging and measured gene regulation by RNA sequencing and reverse transcription quantitative PCR analyses. Our results show that ER stress potentiated intracellular lipid accumulation by 5-fold in hiPSC-Hep in the absence of apoptosis. Transcriptome pathway analysis identified ER stress pathways as the most significantly dysregulated of all pathways affected. Obeticholic acid dose dependently inhibited lipid accumulation and modulated gene expression downstream of the farnesoid X receptor. We were able to identify modulation of hepatic markers and gene pathways known to be involved in steatosis and nonalcoholic fatty liver disease (NAFLD), in support of a hiPSC-Hep disease model that is relevant to clinical data for human NASH. Our results show that the model can serve as a translational discovery platform for the understanding of molecular pathways involved in NAFLD, and can facilitate the identification of novel therapeutic molecules based on high-throughput screening strategies.

Summary: Our study demonstrates expanded use of human induced pluripotent stem cell-derived hepatocytes for molecular studies and drug screening, to evaluate new therapeutics with an antisteatotic mechanism of action for nonalcoholic fatty liver disease.

Role of bile acids in inflammatory bowel disease

Bile acids (BAs) are the end product of cholesterol catabolism. Their synthesis is regulated by the nuclear receptor farnesoid X receptor, also involved in the control of their enterohepatic circulation. Inflammatory bowel diseases (IBD), which include Crohn's disease (CD) and ulcerative colitis (UC), are multifactorial diseases characterized by diarrhea. The pathogenesis of diarrhea in IBD is still debated. The most important factor is the inflammatory process of the intestinal wall, causing alterations of solute and water absorption/secretion, deterioration of epithelial cell integrity, disruption of the intestinal microflora homeostasis, and impairment of specific transport mechanisms within the gut (including that of BAs). In this review, we summarize the current state of the art in this area and we critically evaluate the alterations of BA metabolism in patients with CD and UC.