Inhibition of intestinal bile acid absorption improves cholestatic liver and bile duct injury in a mouse model of sclerosing cholangitis

Neonatal Cholestasis: Updates on Diagnostics, Therapeutics, and Prevention

Cholestatic jaundice is a common presenting feature of hepatobiliary and/or metabolic dysfunction in the newborn and young infant. Timely detection of cholestasis, followed by rapid step-wise evaluation to determine the etiology, is crucial to identify those causes that are amenable to medical or surgical intervention and to optimize outcomes for all infants. In the past 2 decades, genetic etiologies have been elucidated for many cholestatic diseases, and next-generation sequencing, whole-exome sequencing, and whole-genome sequencing now allow for relatively rapid and cost-effective diagnosis of conditions not previously identifiable via standard blood tests and/or liver biopsy. Advances have also been made in our understanding of risk factors for parenteral nutrition-associated cholestasis/liver disease. New lipid emulsion formulations, coupled with preventive measures to decrease central line-associated bloodstream infections, have resulted in lower rates of cholestasis and liver disease in infants and children receiving long-term parental nutrition. Unfortunately, little progress has been made in determining the exact cause of biliary atresia. The median age at the time of the hepatoportoenterostomy procedure is still greater than 60 days; consequently, biliary atresia remains the primary indication for pediatric liver transplantation. Several emerging therapies may reduce the bile acid load to the liver and improve outcomes in some neonatal cholestatic disorders. The goal of this article is to review the etiologies, diagnostic algorithms, and current and future management strategies for infants with cholestasis.

Treatment of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by progressive fibro-stenotic strictures and destruction of the biliary tree. Currently, there is no effective treatment which can delay its progression or ameliorate the transplant-free survival. Moreover, a major chontroversy in PSC is whether to use UDCA. More recently, novel pharmacological agents emerged aiming at: i) modulation of bile composition; ii) immunomodulation; iii) targeting the gut microbiome; iv) targeting fibrosis. Successful PSC therapy, however, will be most likely a personalized combination of different drugs plus endoscopic treatment. This review aims at offering an overview on the experimental pharmacological strategies currently exploited for PSC treatment.

Review article: therapeutic aspects of bile acid signalling in the gut-liver axis

BACKGROUND

Bile acids are important endocrine modulators of intestinal and hepatic signalling cascades orchestrating critical pathophysiological processes in various liver diseases. Increasing knowledge on bile acid signalling has stimulated the development of synthetic ligands of nuclear bile acid receptors and other bile acid analogues.

AIM

This review summarises important aspects of bile acid-mediated crosstalk between the gut and the liver ("gut-liver axis") as well as recent findings from experimental and clinical studies.

METHODS

We performed a literature review on bile acid signalling, and therapeutic applications in chronic liver disease.

RESULTS

Intestinal and hepatic bile acid signalling pathways maintain bile acid homeostasis. Perturbations of bile acid-mediated gut-liver crosstalk dysregulate transcriptional networks involved in inflammation, fibrosis and endothelial dysfunction. Bile acids induce enterohepatic feedback signalling by the release of intestinal hormones, and regulate enterohepatic circulation. Importantly, bile acid signalling plays a central role in maintaining intestinal barrier integrity and antibacterial defense, which is particularly relevant in cirrhosis, where bacterial translocation has a profound impact on disease progression. The nuclear bile acid farnesoid X receptor (FXR) is a central intersection in bile acid signalling and has emerged as a relevant therapeutic target.

CONCLUSIONS

Experimental evidence suggests that bile acid signalling improves the intestinal barrier and protects against bacterial translocation in cirrhosis. FXR agonists have displayed efficacy for the treatment of cholestatic and metabolic liver disease in randomised controlled clinical trials. However, similar effects remain to be shown in advanced liver disease, particularly in patients with decompensated cirrhosis.

Mechanistic insights into the pathophysiology of cirrhotic cardiomyopathy

Myocardial dysfunction in end stage cirrhotic liver disease, termed cirrhotic cardiomyopathy, is a long known, but little understood comorbidity seen in ∼50% of adults and children who present for liver transplantation. Structural, functional, hemodynamic and electrocardiographic aberrations that occur in the heart as a direct consequence of a damaged liver, is associated with multi-organ failure and increased mortality and morbidity in patients undergoing surgical procedures such as porto-systemic shunt placement and liver transplantation. Despite its clinical significance and rapid advances in science and pharmacotherapy, there is yet no specific treatment for this disease. This may be due to a lack of understanding of the pathogenesis and mechanisms behind how a cirrhotic liver causes cardiac pathology. This review will focus specifically on insights into the molecular mechanisms that drive this liver-heart interaction. Deeper understanding of the etio-pathogenesis of cirrhotic cardiomyopathy will allow us to design and test treatments that can be targeted to prevent and/or reverse this co-morbid consequence of liver failure and improve health care delivery and outcomes in patients with cirrhosis.

Odevixibat: First Approval

Odevixibat (Bylvay™) is a small molecule inhibitor of the ileal bile acid transporter being developed by Albireo Pharma, Inc. for the treatment of various cholestatic diseases, including progressive familial intrahepatic cholestasis (PFIC). In July 2021, odevixibat received its first approval in the EU for the treatment of PFIC in patients aged ≥ 6 months, followed shortly by its approval in the USA for the treatment of pruritus in patients aged ≥ 3 months with PFIC. Odevixibat is also in clinical development for the treatment of other cholestatic diseases, including Alagille syndrome and biliary atresia, in various countries. This article summarizes the milestones in the development of odevixibat leading to this first approval for PFIC.

Effects of blocking chemokine receptor CCR1 with BX471 in two models of fibrosis prevention and rescue in mice

Background

The induction, progression and resolution of liver fibrosis are influenced by multiple chemokines. The inhibition of CCR1 signalling by a specific non-peptide inhibitor (BX471) reduces kidney fibrosis after unilateral ureteral obstruction via suppression of leukocyte recruitment in mice. However, it remains unclear whether selective CCR1 inhibition also affects hepatic fibrogenesis. Therefore we aimed to study the effect of this intervention on liver fibrosis in prevention (CCl₄ administration) and rescue (ABCB4-deficient mice) mouse models.

Methods

In the prevention model, hepatic fibrosis was induced by repeated injections of CCl₄. Additionally, the verum group was treated with subcutaneous injections of BX471, while controls received vehicle only. ABCB4 deficient mice (on the BALB/c-background) with sclerosing cholangitis and biliary fibrosis received BX471 or vehicle, respectively (rescue model). Liver histopathology was assessed after Sirius red staining of collagen, and hepatic collagen contents were measured. In addition, we performed gene expression analyses of fibrosis-related genes.

Results

BX471 injections were tolerated moderately well by all mice, and all mice developed hepatic fibrosis. Significant differences were neither observed in serum aminotransferase activities after 6 weeks of treatment between the two groups in the prevention nor in the rescue model. Interestingly, hepatic collagen contents were significantly higher in mice treated with BX471 in the prevention model as compared to controls but histological stages of liver sections did not differ. Of note, we observed only moderate effects on liver fibrosis in the ABCB4 knock-out model.

Conclusions

Our data indicate that BX471 treatment did neither affect serum and tissue markers of liver injury and fibrosis in the CCl₄ model and only moderately in the Abcb4 ^-/- model of biliary fibrosis. The animal models indicate that treatment with BX471 alone is unlikely to exert major beneficial effects in chronic liver disease.

Staging Liver Fibrosis: Comparison of Native T1 Mapping, T2 Mapping, and T1ρ: An Experimental Study in Rats With Bile Duct Ligation and Carbon Tetrachloride at 11.7 T MRI

BACKGROUND

T1, T2, and T1ρ might be potential biomarkers for assessing liver fibrosis. However, few studies reported the value of them in different animal models.

PURPOSE

To investigate and compare the performances of T1, T2, and T1ρ for noninvasively staging liver fibrosis in bile duct ligation (BDL) or carbon tetrachloride (CCl₄ ) model.

STUDY TYPE

Prospective animal model.

SUBJECTS

Liver fibrosis was induced by BDL or injection of CCl₄ in 120 rats.

FIELD STRENGTH/SEQUENCE

11.7 T, T1 mapping with 10 repetition times, T2 mapping with 32 echo times, and T1ρ with 10 spin-lock times.

ASSESSMENT

T1, T2, and T1ρ were measured and correlated with liver fibrosis stages, as well as the degree of inflammation, steatosis, iron deposition, and the expression of cytokeratin 19. The discriminative performance of T1, T2, and T1ρ for staging liver fibrosis was compared.

STATISTICAL TESTS

One-way analysis of variance (ANOVA), Spearman's correlation analysis, factorial design ANOVA, and receiver operating characteristic curves (P < 0.05 was considered statistically significant).

RESULTS

T1, T2, and T1ρ (BDL: rho = 0.73, 0.85, 0.68; CCl₄ : rho = 0.80, 0.29, 0.61) were significantly correlated with liver fibrosis stages, while there was no significant difference in T2 among stage F0-F4 in the CCl₄ model (P = 0.204). The area under the curves (AUCs) range of T1, T2, and T1ρ for predicting ≥F1, ≥F2, ≥F3, and F4 were 0.76-0.95, 0.89-0.98, and 0.80-0.94 in the CCl₄ model. For the CCl₄ model, the AUCs range of T1, T2, and T1ρ for predicting ≥F1, ≥F2, ≥F3, and F4 were 0.83-0.95, 0.61-0.74, and 0.73-0.89, respectively. T2 had significantly higher AUC in the BDL model than CCl₄ model for diagnosing liver fibrosis.

DATA CONCLUSION

The most sensitive and accurate method for staging liver fibrosis appeared to be T1 in our animal models followed by T1ρ. T2 may not be suitable for evaluating liver fibrosis.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 2.

Role of FGF15 in Hepatic Surgery in the Presence of Tumorigenesis: Dr. Jekyll or Mr. Hyde?

The pro-tumorigenic activity of fibroblast growth factor (FGF) 19 (FGF15 in its rodent orthologue) in hepatocellular carcinoma (HCC), as well as the unsolved problem that ischemia-reperfusion (IR) injury supposes in liver surgeries, are well known. However, it has been shown that FGF15 administration protects against liver damage and regenerative failure in liver transplantation (LT) from brain-dead donors without tumor signals, providing a benefit in avoiding IR injury. The protection provided by FGF15/19 is due to its anti-apoptotic and pro-regenerative properties, which make this molecule a potentially beneficial or harmful factor, depending on the disease. In the present review, we describe the preclinical models currently available to understand the signaling pathways responsible for the apparent controversial effects of FGF15/19 in the liver (to repair a damaged liver or to promote tumorigenesis). As well, we study the potential pharmacological use that has the activation or inhibition of FGF15/19 pathways depending on the disease to be treated. We also discuss whether FGF15/19 non-pro-tumorigenic variants, which have been developed for the treatment of liver diseases, might be promising approaches in the surgery of hepatic resections and LT using healthy livers and livers from extended-criteria donors.

Gut-restricted apical sodium-dependent bile acid transporter inhibitor attenuates alcohol-induced liver steatosis and injury in mice

BACKGROUND

Recent studies have shown that human and experimental alcohol-related liver disease (ALD) is robustly associated with dysregulation of bile acid homeostasis, which may in turn modulate disease severity. Pharmacological agents targeting bile acid metabolism and signaling may be potential therapeutics for ALD.

METHODS

The potential beneficial effects of a gut-restricted apical sodium-dependent bile acid transporter (ASBT) inhibitor were studied in a chronic-plus-binge ALD mouse model.

RESULTS

Blocking intestinal bile acid reabsorption by the gut-restricted ASBT inhibitor GSK2330672 attenuated hepatic steatosis and liver injury in a chronic-plus-binge ALD mouse model. Alcohol feeding is associated with intestinal bile acid accumulation but paradoxically impaired ileal farnesoid × receptor (FXR) function, and repressed hepatic cholesterol 7α-hydrolase (CYP7A1) expression despite decreased hepatic small heterodimer partner (SHP) and ileal fibroblast growth factor 15 (FGF15) expression. ASBT inhibitor treatment decreased intestinal bile acid accumulation and increased hepatic CYP7A1 expression, but further decreased ileal FXR activity. Alcohol feeding induces serum bile acid concentration that strongly correlates with a liver injury marker. However, alcohol-induced serum bile acid elevation is not due to intrahepatic bile acid accumulation but is strongly and positively associated with hepatic multidrug resistance-associated protein 3 (MRP4) and MRP4 induction but poorly associated with sodium-taurocholate cotransporting peptide (NTCP) expression. ASBT inhibitor treatment decreases serum bile acid concentration without affecting hepatocyte basolateral bile acid uptake and efflux transporters.

CONCLUSION

ASBT inhibitor treatment corrects alcohol-induced bile acid dysregulation and attenuates liver injury in experimental ALD.

Targeting the Four Pillars of Enterohepatic Bile Salt Cycling; Lessons From Genetics and Pharmacology

Bile salts play a pivotal role in lipid homeostasis, are sensed by specialized receptors, and have been implicated in various disorders affecting the gut or liver. They may play a role either as culprit or as potential panacea. Four very efficient transporters mediate most of the hepatic and intestinal bile salt uptake and efflux, and are each essential for the efficient enterohepatic circulation of bile salts. Starting from the intestinal lumen, conjugated bile salts cross the otherwise impermeable lipid bilayer of (primarily terminal ileal) enterocytes through the apical sodium-dependent bile acid transporter (gene SLC10A2) and leave the enterocyte through the basolateral heteromeric organic solute transporter, which consists of an alpha and beta subunit (encoded by SLC51A and SLC51B). The Na+ -taurocholate cotransporting polypeptide (gene SLC10A1) efficiently clears the portal circulation of bile salts, and the apical bile salt export pump (gene ABCB11) pumps the bile salts out of the hepatocyte into primary bile, against a very steep concentration gradient. Recently, individuals lacking either functional Na+ -taurocholate cotransporting polypeptide or organic solute transporter have been described, completing the quartet of bile acid transport deficiencies, as apical sodium-dependent bile acid transporter and bile salt export pump deficiencies were already known for years. Novel pathophysiological insights have been obtained from knockout mice lacking functional expression of these genes and from pharmacological transporter inhibition in mice or humans. Conclusion: We provide a concise overview of the four main bile salt transport pathways and of their status as possible targets of interventions in cholestatic or metabolic disorders.

Network pharmacology-based mechanism prediction and pharmacological validation of Xiaoyan Lidan formula on attenuating alpha-naphthylisothiocyanate induced cholestatic hepatic injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

The well-known Chinese prescription, Xiaoyan Lidan Formula (XYLDF), possesses efficiency of heat-clearing, dampness-eliminating and jaundice-removing. It has long been used clinically for the treatment of hepatobiliary diseases due to intrahepatic cholestasis (IHC). However, the mechanism of XYLDF for its therapeutic effects remains elusive.

AIM OF THE STUDY

The study aimed to explore the potential targets for liver protective mechanism of XYLDF based on network pharmacology and experimental assays in ANIT-induced cholestatic hepatic injury (CHI) in rats.

MATERIALS AND METHODS

On the basis of the 29 serum migrant compounds of XYLDF elucidated by UPLC-TOF-MS/MS, a network pharmacology approach was applied for the mechanism prediction. Systematic networks were constructed to identify potential molecular targets, biological processes, and signaling pathways. And the interactions between significantly potential targets and active compounds were simulated by molecular docking. For the mechanism validation, an ANIT-induced rat model was used to evaluate the effects of XYLDF on CHI according to serum biochemistry, bile flow rates, histopathological examination, and the gene and protein expression including enzymes related to synthesis, export, and import of bile acid in liver and ileum, and those of inflammatory cytokines, analyzed by RT-qPCR and WB.

RESULTS

The results of network pharmacology research indicated TNF (TNF-α), RELA (NF-κB), NR1H4 (FXR), and ICAM1 (ICAM-1) to be the important potential targets of XYLDF for cholestatic liver injury, which are related to bile metabolism and NF-κB-mediated inflammatory signaling. And the molecular docking had pre-validated the prediction of network pharmacology, as the core active compounds of XYLDF had shown strong simulation binding affinity with FXR, followed by NF-κB, TNF-α, and ICAM-1. Meanwhile, the effects of XYLDF after oral administration on ANIT-induced CHI in rats exhibited the decreased levels of transaminases (ALT and AST), TBA, and TBIL in serum, raised bile flow rates, and markedly improved hepatic histopathology. Furthermore, consistent to the above targets prediction and molecular docking, XYLDF significantly up-regulated the expression of FXR, SHP, BSEP, and MRP2, and down-regulated CYP7A1 and NTCP in liver, and promoted expression of IBABP and OSTα/β in ileum, suggesting the activation of FXR-mediated pathway referring to bile acid synthesis, transportation, and reabsorption. Moreover, the lower levels of TNF-α in plasma and liver, as well as the reduced hepatic gene and protein expression of NF-κB, TNF-α, and ICAM-1 after XYLDF treatment revealed the suppression of NF-κB-mediated inflammatory signaling pathway, as evidenced by the inhibition of nuclear translocation of NF-κB.

CONCLUSIONS

XYLDF exhibited an ameliorative liver protective effect on ANIT-induced cholestatic hepatic injury. The present study has confirmed its mechanism as activating the FXR-regulated bile acid pathway and inhibiting inflammation via the NF-κB signaling pathway.

Geniposide suppresses liver injury in a mouse model of DDC-induced sclerosing cholangitis

Sclerosing cholangitis, characterized by biliary inflammation, fibrosis, and stricturing, remains one of the most challenging conditions of clinical hepatology. Geniposide (GE) has anti-inflammatory, hepatoprotective, and cholagogic effects. Whether GE provides inhibition on the development of sclerosing cholangitis is unknown. Here, we investigated the role of GE in a mouse model in which mice were fed with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) for 4 weeks to induce sclerosing cholangitis. The results demonstrated that the increased hepatic gene expressions of pro-inflammatory (IL-6, VCAM-1, MCP-1, and F4/80) and profibrogenic markers (Col1α1, Col1α2, TGF-β, and α-SMA) in DDC feeding mice were reversed after treatment with GE. GE also suppressed expressions of CK19 and Ki67 in DDC-fed mice, suggesting that GE could ameliorate DDC-induced hepatocytes and cholangiocytes proliferation. In addition, GE significantly increased bile acids (BAs) secretion in bile, which correlated with induced expressions of hepatic FXR, BAs secretion transporters (BSEP, MRP2, MDR1, and MDR2), and reduced CYP7A1 mRNA expression. Furthermore, higher expressions of ileal FXR-FGF15 signaling and reduced ASBT were also observed after GE treatment. Taken together, these data showed that GE could modulate inflammation, fibrosis, and BAs homeostasis in DDC-fed mice, which lead to efficiently delay the progression of sclerosing cholangitis.

Metabolomics analysis delineates the therapeutic effects of Huangqi decoction and astragalosides on α-naphthylisothiocyanate (ANIT) -induced cholestasis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Cholestasis caused by bile secretion and excretion disorders is a serious manifestation of liver disease. With limited treatment methods, it affects millions of people worldwide. Huangqi decoction (HQD), an effective traditional Chinese medicine, is used to treat chronic cholestatic liver diseases. However, the action mechanisms of it were not fully elucidated.

AIM OF THE STUDY

We aim to investigate the therapeutic effect of HQD, and its active component, astragalosides, against α-naphthylisothiocyanate (ANIT)-induced cholestasis in rats based on targeted metabolomics analysis and revel the potential mechanism.

MATERIALS AND METHODS

The therapeutic effect of HQD and astragalosides on ANIT-induced cholestasis model rats were evaluated by serum biochemical analysis. Liver damage was identified by histopathology. The levels of bile acids (BAs) and free fatty acids (FFAs) in serum and liver tissues were measured by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-TQMS). qRT-PCR and Western blot analysis were used to measure the expression of nuclear hormone receptor, membrane receptor and BA transporter protein in cholestatic rats before and after HQD and astragalosides treatment.

RESULTS

The obtained data showed that the administration of ANIT caused obvious cholestasis with significantly increased intrahepatic retention of hydrophobic BAs and altered FFAs, which were consistent with the liver histopathological and serum biochemical findings. HQD and astragalosides treatment were able to attenuate ANIT-induced BAs and FFAs perturbation, ameliorate the impaired liver function, histopathological ductular reaction, and lipid peroxidation damage by ANIT. Elevated mRNA and protein expression of transporters related to BA metabolism and genes related to lipogenesis and lipid oxidation metabolism in cholestasis were attenuated or normalized by HQD and astragalosides treatment.

CONCLUSIONS

Intervention by ANIT can significantly change the homeostasis of BAs and FFAs. HQD and astragalosides exerted a hepatoprotective effect against cholestatic liver injury by restoring the altered BA and FFA metabolism through the improvement of BA transporter, nucleus hormone receptor, and membrane receptor.

In vitro solubilization of fat-soluble vitamins in structurally defined mixed intestinal assemblies

The structures of fed state intestinal assemblies containing bile components, dietary fat, and fat-soluble vitamins are not well known, although they are involved in lipid transport. In this study, several methods were used to investigate structural transitions upon various dietary lipids or various fat-soluble vitamins incorporation in bile intestinal assemblies. In particular, DLS and turbidimetry were used to study transition points as a function of component concentration, and cryo-TEM and SAXS were used to resolve assembly structures at microscopic and supramolecular scales, respectively. Results showed that increasing the concentration of dietary lipids in bile assembly induced a transition from core-shell micelles to unilamellar vesicles (except with caprylate lipids, always yielding micelles). In these specific assemblies, increasing the concentration of a fat-soluble vitamin either induced a systematic structural transition, defining a solubilization capacity (α-tocopherol or phylloquinone), or induced a structural transition only in micelles (retinol), or did not induce any structural transition up to very high concentrations (cholecalciferol). Using SAXS data, ideal molecular organizations are proposed for assemblies in the absence or presence of α-tocopherol.

A Novel Fluorescence-Based Method to Evaluate Ileal Apical Sodium-Dependent Bile Acid Transporter ASBT

This study aimed to demonstrate usefulness of the fluorophore-labeled bile acid derivative, N-(24-[7-(4-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole)]amino-3α,7α,12α-trihydroxy-27-nor-5β-cholestan-26-oyl)-2'-aminoethane sulfonate (tauro-nor-THCA-24-DBD) as a substrate of apical sodium-dependent bile acid transporter (ASBT, SLC10A2), which is expressed at distal ileum for reabsorption of bile acids and to find a novel fluorescence-based method to evaluate ASBT activity. In HPLC analysis, chromatogram of tauro-nor-THCA-24-DBD showed double peaks: R- and S-isomers of the compound. When ASBT was expressed in Xenopus laevis oocytes, their uptakes were higher than those by control oocytes, demonstrating both are transported by ASBT. Therefore, results were analyzed separately as peak 1, peak 2 and sum of them. Concentration dependent uptake of tauro-nor-THCA-24-DBD in ASBT-expressing oocytes was saturable with Km 122 μM and Vmax 1.49 pmol/oocyte/30 min for peak 1, 30.7 μM and 1.34 pmol/oocyte/30 min for peak 2, and 40.6 μM and 2.36 pmol/oocyte/30 min for sum, respectively. These uptakes were decreased in the presence of taurocholic acid and in the Na⁺ free condition. Furthermore, in Caco-2 cells, tauro-nor-THCA-24-DBD uptake was also Na⁺-dependent and saturable. Additionally, these uptakes were decreased by elobixibat, a selective ASBT inhibitor. Accordingly, it was concluded that tauro-nor-THCA-24-DBD is a substrate of ASBT and useful to evaluate the intestinal ASBT transport activity.

[The inhibitors of the apical sodium-dependent bile acid transporter (ASBT) as promising drugs]

Inhibition of the apical sodium-dependent bile acid transporter (ASBT, also known as IBAT - ileal bile acid transporter, SLC10A2) leads to disruption of the enterohepatic circulation of bile acids and their excretion with fecal masses. This is accompanied by cholesterol utilization for synthesis of new bile acids. ASBT inhibitors are promising drugs for the treatment of such diseases as non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, type 2 diabetes mellitus, necrotic enterocolitis, chronic constipation, atherosclerosis. To date the most known chemically synthesized inhibitors are: A3309, SHP626, A4250, 264W94, GSK2330672, SC-435. All of them are at different stages of clinical trials, which confirm the high efficacy and good tolerance of these inhibitors. Current trends in this field also include directed chemical synthesis of ASBT inhibitors, as well as their search among substances of plant origin.

ASBT(SLC10A2): A promising target for treatment of diseases and drug discovery

Bile acids has gradually become a new focus in various diseases, and ASBT as a transporter responsible for the reabsorption of ileal bile acids, is a key hinge associated to the bile acids-cholesterol balance and bile acids of enterohepatic circulation. The cumulative studies have also shown that ASBT is a promising target for treatment of liver, gallbladder, intestinal and metabolic diseases. This article briefly reviewed the process of bile acids enterohepatic circulation, as well as the regulations of ASBT expression, covering transcription factors, nuclear receptors and gut microbiota. In addition, the relationship between ASBT and various diseases were discussed in this paper. According to the structural classification of ASBT inhibitors, the research status of ASBT inhibitors and potential ASBT inhibitors of traditional Chinese medicine (such resveratrol, jatrorrhizine in Coptis chinensis) were summarized. This review provides a basis for the development of ASBT inhibitors and the treatment strategy of related diseases.

Glycochenodeoxycholic acid induces stemness and chemoresistance via the STAT3 signaling pathway in hepatocellular carcinoma cells

The poor prognosis of hepatocellular carcinoma (HCC) is primarily attributed to its high frequency of recurrence and resistance to chemotherapy. Epithelial-to-mesenchymal transition (EMT) and the acquisition of cancer stem cells (CSCs) are the fundamental drivers of chemoresistance in HCC. Glycochenodeoxycholic acid (GCDC), a component of bile acid (BA), has been reported to induce necrosis in primary human hepatocytes. In the present work, we investigated the function of GCDC in HCC chemoresistance. We found that GCDC promoted chemoresistance in HCC cells by down-regulating and up-regulating the expression of apoptotic and anti-apoptotic genes, respectively. Furthermore, GCDC induced the EMT phenotype and stemness in HCC cells and activated the STAT3 signaling pathway. These findings reveal that GCDC promotes chemoresistance in HCC by inducing stemness via the STAT3 pathway and could be a potential target in HCC chemotherapy.

Potential of ileal bile acid transporter inhibition as a therapeutic target in Alagille syndrome and progressive familial intrahepatic cholestasis

Alagille syndrome (ALGS) and progressive familial intrahepatic cholestasis (PFIC) are rare, inherited cholestatic liver disorders that manifest in infants and children and are associated with impaired bile flow (ie cholestasis), pruritus and potentially fatal liver disease. There are no effective or approved pharmacologic treatments for these diseases (standard medical treatments are supportive only), and new, noninvasive options would be valuable. Typically, bile acids undergo biliary secretion and intestinal reabsorption (ie enterohepatic circulation). However, in these diseases, disrupted secretion of bile acids leads to their accumulation in the liver, which is thought to underlie pruritus and liver-damaging inflammation. One approach to reducing pathologic bile acid accumulation in the body is surgical biliary diversion, which interrupts the enterohepatic circulation (eg by diverting bile acids to an external stoma). These procedures can normalize serum bile acids, reduce pruritus and liver injury and improve quality of life. A novel, nonsurgical approach to interrupting the enterohepatic circulation is inhibition of the ileal bile acid transporter (IBAT), a key molecule in the enterohepatic circulation that reabsorbs bile acids from the intestine. IBAT inhibition has been shown to reduce serum bile acids and pruritus in trials of paediatric cholestatic liver diseases. This review explores the rationale of inhibition of the IBAT as a therapeutic target, describes IBAT inhibitors in development and summarizes the current data on interrupting the enterohepatic circulation as treatment for cholestatic liver diseases including ALGS and PFIC.

Recent developments in diagnostics and treatment of neonatal cholestasis

Neonatal cholestasis is characterized by conjugated hyperbilirubinemia in the newborn and young infant and is a sign common to over 100 hepatobiliary and/or metabolic disorders. A timely evaluation for its etiology is critical in order to quickly identify treatable causes such as biliary atresia, many of which benefit from early therapy. An expanding group of molecularly defined disorders involving bile formation, canalicular transporters, tight junction proteins and inborn errors of metabolism are being continuously discovered because of advances in genetic testing and bioinformatics. The advent of next generation sequencing has transformed our ability to test for multiple genes and whole exome or whole genome sequencing within days to weeks, enabling rapid and affordable molecular diagnosis for disorders that cannot be directly diagnosed from standard blood tests or liver biopsy. Thus, our diagnostic algorithms for neonatal cholestasis are undergoing transformation, moving genetic sequencing to earlier in the evaluation pathway once biliary atresia, "red flag" disorders and treatable disorders are excluded. Current therapies focus on promoting bile flow, reducing pruritus, ensuring optimal nutrition, and monitoring for complications, without addressing the underlying cause of cholestasis in most instances. Our improved understanding of bile formation and the enterohepatic circulation of bile acids has led to emerging therapies for cholestasis which require appropriate pediatric clinical trials. Despite these advances, the cause and optimal therapy for biliary atresia remain elusive. The goals of this review are to outline the etiologies, diagnostic pathways and current and emerging management strategies for neonatal cholestasis.

Ileal bile acid transporter inhibition as an anticholestatic therapeutic target in biliary atresia and other cholestatic disorders

Biliary atresia is a rare cholestatic liver disease that presents in infants and rapidly advances to death in the absence of intervention. As a result of blockage or destruction of the biliary tract, bile acids accumulate and drive inflammation, fibrosis, and disease progression. The standard of care, Kasai portoenterostomy (KPE), is typically performed shortly after diagnosis (currently at ~ 2 months of age) and aims to restore bile flow and relieve cholestasis. Nevertheless, most patients continue to experience liver injury from accumulation of bile acids after KPE, since there are no known effective therapeutics that may enhance survival after KPE. Improving cholestasis via interruption of the enterohepatic circulation of bile acids may directly attenuate hepatic bile acid retention and reduce the risk of early organ failure. Directly addressing intrahepatic accretion of bile acids to avoid inherent bile acid toxicities provides an attractive and plausible therapeutic target for biliary atresia. This review explores the novel therapeutic concept of inhibiting the sole ileal bile acid transporter (IBAT), also known as ASBT (apical sodium-bile acid transporter, encoded by SLC10A2), as a means to reduce hepatic bile acid concentration after KPE. By reducing return of bile acids to the cholestatic liver, IBAT inhibitors may potentially lessen or delay liver damage associated with the hepatotoxicity and cholangiopathy of bile acid accumulation. The clinical programs of 2 IBAT inhibitors in development for the treatment of pediatric cholestatic liver diseases, maralixibat and odevixibat, are highlighted.

Ileal exclusion for pruritus treatment in children with progressive familial intrahepatic cholestasis and other cholestatic diseases

BACKGROUND

Pruritus is a major health-related quality-of-life burden in progressive familial intrahepatic cholestasis (PFIC) and other childhood cholestatic liver diseases. Several nontransplant surgical techniques were developed in an attempt to ameliorate symptoms and slow disease progression. Very few case-series have been published on a particular intervention, ileal exclusion (IE), which has been considered to be inferior to the other approaches.

METHODS

We conducted a single-center retrospective chart-review case-series of patients submitted to IE as the first-line surgical treatment at our institution from 1995 to 2018. The primary goal was pruritus relief, followed by survival with the native liver and improvement in biochemical parameters.

RESULTS

Eleven patients were submitted to IE, with a mean follow-up of 60 months. Complete resolution or significant reduction of pruritus was obtained in 72.7% (n = 8) of patients. One patient (9.1%) had a major postoperative complication that required surgery. No other morbidities were reported. Two cases progressed to end-stage liver disease (ESLD) within the short-term and one year after surgery.

CONCLUSIONS

This case series study shows that IE provided excellent results in pruritus control and permitted survival with the native liver. We believe IE is a safe procedure, with few associated morbidities, and should be considered more often as primary surgical treatment for PFIC and other cholestasis.

LEVEL OF EVIDENCE

IV.

Genotype correlates with the natural history of severe bile salt export pump deficiency

BACKGROUND & AIMS

Mutations in ABCB11 can cause deficiency of the bile salt export pump (BSEP), leading to cholestasis and end-stage liver disease. Owing to the rarity of the disease, the associations between genotype and natural history, or outcomes following surgical biliary diversion (SBD), remain elusive. We aimed to determine these associations by assembling the largest genetically defined cohort of patients with severe BSEP deficiency to date.

METHODS

This multicentre, retrospective cohort study included 264 patients with homozygous or compound heterozygous pathological ABCB11 mutations. Patients were categorized according to genotypic severity (BSEP1, BSEP2, BSEP3). The predicted residual BSEP transport function decreased with each category.

RESULTS

Genotype severity was strongly associated with native liver survival (NLS, BSEP1 median 20.4 years; BSEP2, 7.0 years; BSEP3, 3.5 years; p <0.001). At 15 years of age, the proportion of patients with hepatocellular carcinoma was 4% in BSEP1, 7% in BSEP2 and 34% in BSEP3 (p = 0.001). SBD was associated with significantly increased NLS (hazard ratio 0.50; 95% CI 0.27-0.94: p = 0.03) in BSEP1 and BSEP2. A serum bile acid concentration below 102 μmol/L or a decrease of at least 75%, each shortly after SBD, reliably predicted NLS of ≥15 years following SBD (each p <0.001).

CONCLUSIONS

The genotype of severe BSEP deficiency strongly predicts long-term NLS, the risk of developing hepatocellular carcinoma, and the chance that SBD will increase NLS. Serum bile acid parameters shortly after SBD can predict long-term NLS.

LAY SUMMARY

This study presents data from the largest genetically defined cohort of patients with severe bile salt export pump deficiency to date. The genotype of patients with severe bile salt export pump deficiency is associated with clinical outcomes and the success of therapeutic interventions. Therefore, genotypic data should be used to guide personalized clinical care throughout childhood and adulthood in patients with this disease.

Pediatric Cholestatic Liver Disease: Review of Bile Acid Metabolism and Discussion of Current and Emerging Therapies

Cholestatic liver diseases are a significant cause of morbidity and mortality and the leading indication for pediatric liver transplant. These include diseases such as biliary atresia, Alagille syndrome, progressive intrahepatic cholestasis entities, ductal plate abnormalities including Caroli syndrome and congenital hepatic fibrosis, primary sclerosing cholangitis, bile acid synthesis defects, and certain metabolic disease. Medical management of these patients typically includes supportive care for complications of chronic cholestasis including malnutrition, pruritus, and portal hypertension. However, there are limited effective interventions to prevent progressive liver damage in these diseases, leaving clinicians to ultimately rely on liver transplantation in many cases. Agents such as ursodeoxycholic acid, bile acid sequestrants, and rifampicin have been mainstays of treatment for years with the understanding that they may decrease or alter the composition of the bile acid pool, though clinical response to these medications is frequently insufficient and their effects on disease progression remain limited. Recently, animal and human studies have identified potential new therapeutic targets which may disrupt the enterohepatic circulation of bile acids, alter the expression of bile acid transporters or decrease the production of bile acids. In this article, we will review bile formation, bile acid signaling, and the relevance for current and newer therapies for pediatric cholestasis. We will also highlight further areas of potential targets for medical intervention for pediatric cholestatic liver diseases.

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.

Survival genes expression analysis following ionizing radiation to LiCl treated KG1a cells

Purpose: Lithium chloride (LiCl) is clinically used for manic disorders. Its role has been shown in improving cell survival by decreasing Bax and p53 expression and increasing Bcl-2 concentration in the cell. This potential of LiCl is responsible for reducing irradiated cell death. In this study, we have explored the role of LiCl as a radioprotectant affecting survival genes.Materials and methods: To find out the cellular response upon LiCl pretreatment to radiation-exposed KG1a cells; viability, clonogenic assay and microarray studies were performed. This was followed by the detection of transcription factor binding motif in coregulated genes. These results were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and chromatin immunoprecipitation (CHIP).Results: LiCl improved irradiated KG1a cell survival and its clonogenicity at 2 mM concentration (clinically used). Microarray data analysis showed differential expression of cell-protecting genes playing an important role in apoptosis, cell cycle, adhesion and inflammation, etc. The coregulation analysis revealed genes involved in bile acid biosynthesis were also affected by LiCl treatment, these genes are likely to be responsible for radiation-induced gastrointestinal (GI) syndrome through bile production.Conclusions: This is the first study with respect to global genetic expression upon LiCl treatment to radiation-exposed cells. Our results suggest considering repurposing of LiCl as a protective agent for radiation injury.

Glycochenodeoxycholate Promotes Liver Fibrosis in Mice with Hepatocellular Cholestasis

Hydrophobic bile salts are considered to promote liver fibrosis in cholestasis. However, evidence for this widely accepted hypothesis remains scarce. In established animal models of cholestasis, e.g., by Mdr2 knockout, cholestasis and fibrosis are both secondary to biliary damage. Therefore, to test the specific contribution of accumulating bile salts to liver fibrosis in cholestatic disease, we applied the unique model of inducible hepatocellular cholestasis in cholate-fed Atp8b1^G308V/G308V mice. Glycochenodeoxycholate (GCDCA) was supplemented to humanize the murine bile salt pool, as confirmed by HPLC. Biomarkers of cholestasis and liver fibrosis were quantified. Hepatic stellate cells (HSC) isolated from wild-type mice were stimulated with bile salts. Proliferation, cell accumulation, and collagen deposition of HSC were determined. In cholestatic Atp8b1^G308V/G308V mice, increased hepatic expression of αSMA and collagen1a mRNA and excess hepatic collagen deposition indicated development of liver fibrosis only upon GCDCA supplementation. In vitro, numbers of myofibroblasts and deposition of collagen were increased after incubation with hydrophobic but not hydrophilic bile salts, and associated with EGFR and MEK1/2 activation. We concluded that chronic hepatocellular cholestasis alone, independently of biliary damage, induces liver fibrosis in mice in presence of the human bile salt GCDCA. Bile salts may have direct pro-fibrotic effects on HSC, putatively involving EGFR and MEK1/2 signaling.

Emerging therapies in primary sclerosing cholangitis: pathophysiological basis and clinical opportunities

Primary sclerosing cholangitis (PSC) is a progressive liver disease, histologically characterized by inflammation and fibrosis of the bile ducts, and clinically leading to multi-focal biliary strictures and with time cirrhosis and liver failure. Patients bear a significant risk of cholangiocarcinoma and colorectal cancer, and frequently have concomitant inflammatory bowel disease and autoimmune disease manifestations. To date, no medical therapy has proven significant impact on clinical outcomes and most patients ultimately need liver transplantation. Several treatment strategies have failed in the past and whilst prescription of ursodeoxycholic acid (UDCA) prevails, controversy regarding benefits remains. Lack of statistical power, slow and variable disease progression, lack of surrogate biomarkers for disease severity and other challenges in trial design serve as critical obstacles in the development of effective therapy. Advances in our understanding of PSC pathogenesis and biliary physiology over recent years has however led to a surge of clinical trials targeting various mechanistic compartments and currently raising hopes for imminent changes in patient management. Here, in light of pathophysiology, we outline and critically evaluate emerging treatment strategies in PSC, as tested in recent or ongoing phase II and III trials, stratified per a triad of targets of nuclear and membrane receptors regulating bile acid metabolism, immune modulators, and effects on the gut microbiome. Furthermore, we revisit the UDCA trials of the past and critically discuss relevant aspects of clinical trial design, including how the choice of endpoints, alkaline phosphatase in particular, may affect the future path to novel, effective PSC therapeutics.

Intestinal Absorption of Bile Acids in Health and Disease

The intestinal reclamation of bile acids is crucial for the maintenance of their enterohepatic circulation. The majority of bile acids are actively absorbed via specific transport proteins that are highly expressed in the distal ileum. The uptake of bile acids by intestinal epithelial cells modulates the activation of cytosolic and membrane receptors such as the farnesoid X receptor (FXR) and G protein-coupled bile acid receptor 1 (GPBAR1), which has a profound effect on hepatic synthesis of bile acids as well as glucose and lipid metabolism. Extensive research has focused on delineating the processes of bile acid absorption and determining the contribution of dysregulated ileal signaling in the development of intestinal and hepatic disorders. For example, a decrease in the levels of the bile acid-induced ileal hormone FGF15/19 is implicated in bile acid-induced diarrhea (BAD). Conversely, the increase in bile acid absorption with subsequent overload of bile acids could be involved in the pathophysiology of liver and metabolic disorders such as fatty liver diseases and type 2 diabetes mellitus. This review article will attempt to provide a comprehensive overview of the mechanisms involved in the intestinal handling of bile acids, the pathological implications of disrupted intestinal bile acid homeostasis, and the potential therapeutic targets for the treatment of bile acid-related disorders. Published 2020. Compr Physiol 10:21-56, 2020.

Expression Analysis of ATP-Binding Cassette Transporters ABCB11 and ABCB4 in Primary Sclerosing Cholangitis and Variety of Pediatric and Adult Cholestatic and Noncholestatic Liver Diseases

ATP-binding cassette (ABC) transporters are the members of the efflux pumps that are responsible for the removal of cytotoxic substances by active transport. ABCB11, the bile salt efflux pump of hepatocytes, coordinates cellular excretion of numerous conjugated bile salts into the bile canaliculi, whereas ABCB4 acts as an ATP-dependent floppase translocating phosphatidylcholine from the inner to the outer leaflet of the bile canalicular membrane. Loss of functional ABCB11 and ABCB4 proteins causes early-onset refractory cholestasis or cholangiopathy. In this study, we investigated the expression and localization pattern of ABCB11 and ABCB4 using immunohistochemistry and RNA profiling in liver samples from patients with different types and stages of chronic cholestatic liver disease, with emphasis on primary sclerosing cholangitis (PSC), compared to a variety of cholestatic and noncholestatic hepatopathies. Therefore, ABCB11 and ABCB4 expressions were investigated on formalin-fixed and paraffin-embedded (FFPE) material in a patient cohort of total 43 patients with or without cholestatic liver diseases, on protein level using immunohistochemistry and on RNA level using nanoString technology. Intriguingly, our results demonstrated increased expression of ABCB11 and ABCB4 on protein as well as RNA level in PSC, and the expression pattern correlated with disease progression. We concluded from our study that patients with PSC demonstrate altered expression levels and pattern of ABCB11 and ABCB4 which correlated with disease progression; thereby, ABCB11 and ABCB4 analysis may be a useful tool for assessment of disease stages in PSC.

Cholestatic liver disease results increased production of reactive aldehydes and an atypical periportal hepatic antioxidant response

Cholangiopathies such as primary sclerosing cholangitis (PSC) are chronic liver diseases characterized by increased cholestasis, biliary inflammation and oxidative stress. The objective of this study was to elucidate the impact of cholestatic injury on oxidative stress-related factors. Using hepatic tissue and whole cell liver extracts (LE) isolated from 11-week old C57BL/6J (WT) and Mdr2^KO mice, inflammation and oxidative stress was assessed. Concurrently, specific targets of carbonylation were assessed in LE prepared from murine groups as well as from normal and human patients with end-stage PSC. Identified carbonylated proteins were further evaluated using bioinformatics analyses. Picrosirius red staining revealed extensive fibrosis in Mdr2^KO liver, and fibrosis colocalized with increased periportal inflammatory cells and both acrolein and 4-HNE staining. Western blot analysis revealed elevated periportal expression of antioxidant proteins Cbr3, GSTμ, Prdx5, TrxR1 and HO-1 but not GCLC, GSTπ or catalase in the Mdr2^KO group when compared to WT. From immunohistochemical analysis, increased periportal reactive aldehyde production colocalized with elevated staining of Cbr3, GSTμ and TrxR1 but surprisingly not with Nrf2. Mass spectrometric analysis revealed an increase in carbonylated proteins in the Mdr2^KO and PSC groups compared to respective controls. Gene ontology and KEGG pathway analysis of carbonylated proteins revealed a propensity for increased carbonylation of proteins broadly involved in metabolic processes as well more specifically in Rab-mediated signal transduction, lysosomes and the large ribosomal subunit in human PSC. Western blot analysis of Rab-GTPase expression revealed no significant differences in Mdr2^KO mice when compared to WT livers. In contrast, PSC tissue exhibited decreased levels of Rabs 4, 5 and increased abundance of Rabs 6 and 9a protein. Results herein reveal that cholestasis induces stage-dependent increases in periportal oxidative stress responses and protein carbonylation, potentially contributing to pathogenesis in Mdr2^KO. Furthermore, during early stage cholestasis, there is cell-specific upregulation of some but not all, antioxidant proteins.

Activated hepatic stellate cells and portal fibroblasts contribute to cholestatic liver fibrosis in MDR2 knockout mice

BACKGROUND & AIMS

Chronic liver injury often results in the activation of hepatic myofibroblasts and the development of liver fibrosis. Hepatic myofibroblasts may originate from 3 major sources: hepatic stellate cells (HSCs), portal fibroblasts (PFs), and fibrocytes, with varying contributions depending on the etiology of liver injury. Here, we assessed the composition of hepatic myofibroblasts in multidrug resistance gene 2 knockout (Mdr2-/-) mice, a genetic model that resembles primary sclerosing cholangitis in patients.

METHODS

Mdr2-/- mice expressing a collagen-GFP reporter were analyzed at different ages. Hepatic non-parenchymal cells isolated from collagen-GFP Mdr2-/- mice were sorted based on collagen-GFP and vitamin A. An NADPH oxidase (NOX) 1/4 inhibitor was administrated to Mdr2-/- mice aged 12-16 weeks old to assess the therapeutic approach of targeting oxidative stress in cholestatic injury.

RESULTS

Thy1+ activated PFs accounted for 26%, 51%, and 54% of collagen-GFP+ myofibroblasts in Mdr2-/- mice at 4, 8, and 16 weeks of age, respectively. The remaining collagen-GFP+ myofibroblasts were composed of activated HSCs, suggesting that PFs and HSCs are both activated in Mdr2-/- mice. Bone-marrow-derived fibrocytes minimally contributed to liver fibrosis in Mdr2-/- mice. The development of cholestatic liver fibrosis in Mdr2-/- mice was associated with early recruitment of Gr1+ myeloid cells and upregulation of pro-inflammatory cytokines (4 weeks). Administration of a NOX inhibitor to 12-week-old Mdr2-/- mice suppressed the activation of myofibroblasts and attenuated the development of cholestatic fibrosis.

CONCLUSIONS

Activated PFs and activated HSCs contribute to cholestatic fibrosis in Mdr2-/- mice, and serve as targets for antifibrotic therapy.

LAY SUMMARY

Activated portal fibroblasts and hepatic stellate cells, but not fibrocytes, contributed to the production of the fibrous scar in livers of Mdr2-/- mice, and these cells can serve as targets for antifibrotic therapy in cholestatic injury. Therapeutic inhibition of the enzyme NADPH oxidase (NOX) in Mdr2-/- mice reversed cholestatic fibrosis, suggesting that targeting NOXs may be an effective strategy for the treatment of cholestatic fibrosis.

Cholestatic liver diseases: An era of emerging therapies

Recently the field of cholestasis has expanded enormously reflecting an improved understanding of the molecular mechanisms underlying bile secretion and its perturbation in chronic cholestatic disease. Novel anti-cholestatic therapeutic options have been developed for patients not favorably responding to ursodeoxycholic acid (UDCA), the current standard treatment for cholestatic liver disease. Important novel treatment targets now also include nuclear receptors involved in bile acid (BA) homoeostasis like farnesoid X receptor and G protein-coupled receptors e.g., the G-protein-coupled BA receptor "transmembrane G coupled receptor 5". Fibroblast growth factor-19 and enterohepatic BA transporters also deserve attention as additional drug targets as does the potential treatment agent norUDCA. In this review, we discuss recent and future promising therapeutic agents and their potential molecular mechanisms in cholestatic liver disorders.

Neonatal cholestasis: emerging molecular diagnostics and potential novel therapeutics

Neonatal cholestasis is a group of rare disorders of impaired bile flow characterized by conjugated hyperbilirubinaemia in the newborn and young infant. Neonatal cholestasis is never physiological but rather is a sign of hepatobiliary and/or metabolic disorders, some of which might be fatal if not identified and treated rapidly. A step-wise timely evaluation is essential to quickly identify those causes amenable to treatment and to offer accurate prognosis. The aetiology of neonatal cholestasis now includes an expanding group of molecularly defined entities with overlapping clinical presentations. In the past two decades, our understanding of the molecular basis of many of these cholestatic diseases has improved markedly. Simultaneous next-generation sequencing for multiple genes and whole-exome or whole-genome sequencing now enable rapid and affordable molecular diagnosis for many of these disorders that cannot be directly diagnosed from standard blood tests or liver biopsy. Unfortunately, despite these advances, the aetiology and optimal therapeutic approach of the most common of these disorders, biliary atresia, remain unclear. The goals of this Review are to discuss the aetiologies, algorithms for evaluation and current and emerging therapeutic options for neonatal cholestasis.

Autotaxin, bile acid profile and effect of ileal bile acid transporter inhibition in primary biliary cholangitis patients with pruritus

BACKGROUND AND AIMS

Pruritus is a common symptom in patients with primary biliary cholangitis (PBC) for which ileal bile acid transporter (IBAT) inhibition is emerging as a potential therapy. We explored the serum metabonome and gut microbiota profile in PBC patients with pruritus and investigated the effect of GSK2330672, an IBAT inhibitor.

METHODS

We studied fasting serum bile acids (BAs), autotaxin and faecal microbiota in 22 PBC patients with pruritus at baseline and after 2 weeks of GSK2330672 treatment. Control group included 31 asymptomatic PBC patients and 18 healthy volunteers. BA profiling was done by ultra performance liquid chromatography coupled to a mass spectrometry (UPLC-MS). Faecal microbiomes were analysed by 16S ribosomal RNA gene sequencing.

RESULTS

In PBC patients with pruritus, serum levels of total and glyco-conjugated primary BAs and autotaxin were significantly elevated. Autotaxin activity correlated significantly with tauro- and glyco-conjugated cholic acid (CA) and chenodeoxycholic acid (CDCA), both at baseline and after GSK2330672. GSK2330672 significantly reduced autotaxin and all tauro- and glyco- conjugated BAs and increased faecal levels of CA (P = 0.048) and CDCA (P = 0.027). Gut microbiota of PBC patients with pruritus was similar to control groups. GSK2330672 increased the relative abundance of Firmicutes (P = 0.033) and Clostridia (P = 0.04) and decreased Bacteroidetes (P = 0.033) and Bacteroidia (P = 0.04).

CONCLUSIONS

Pruritus in PBC does not show a distinct gut bacterial profile but is associated with elevated serum bile acid and autotaxin levels which decrease after IBAT inhibition. In cholestatic pruritus, a complex interplay between BAs and autotaxin is likely and may be modified by IBAT inhibition.

Preclinical insights into cholangiopathies: disease modeling and emerging therapeutic targets

INTRODUCTION

The common predominant clinical features of cholangiopathies such as primary sclerosing cholangitis (PSC), primary biliary cholangitis (PBC), and biliary atresia (BA) are biliary damage/senescence and liver fibrosis. Curative therapies are lacking, and liver transplantation is the only option. An understanding of the mechanisms and pathogenesis is needed to develop novel therapies. Previous studies have developed various disease-based research models and have identified candidate therapeutic targets. Areas covered: This review summarizes recent studies performed in preclinical models of cholangiopathies and the current understanding of the pathophysiology representing potential targets for novel therapies. A literature search was conducted in PubMed using the combination of the searched term 'cholangiopathies' with one or two keywords including 'model', 'cholangiocyte', 'animal', or 'fibrosis'. Papers published within five years were obtained. Expert opinion: Access to appropriate research models is a key challenge in cholangiopathy research; establishing more appropriate models for PBC is an important goal. Several preclinical studies have demonstrated promising results and have led to novel therapeutic approaches, especially for PSC. Further studies on the pathophysiology of PBC and BA are necessary to identify candidate targets. Innovative therapeutic approaches such as stem cell transplantation have been introduced, and those therapies could be applied to PSC, PBC, and BA.

Therapeutic Roles of Bile Acid Signaling in Chronic Liver Diseases

Bile acids (BAs) are the major metabolic product of cholesterol, having detergent-like activities and being responsible for absorption of lipid and lipid-soluble vitamins. In addition, it has been increasingly recognized that BAs are important signaling molecules, regulating energy metabolism and immunity. Under physiological circumstances, synthesis and transport of BAs are precisely regulated to maintain bile acid homeostasis. Disruption of bile acid homeostasis results in pathological cholestasis and metabolic liver diseases. During the last decades, BAs have been gradually recognized as an important therapeutic target for novel treatment in chronic liver diseases. This review will provide an update on the current understanding of synthesis, transport and regulation of BAs, with a focus on the therapeutic roles of bile acid signaling in chronic liver diseases.

Developments in bile salt based therapies: A critical overview

Bile acids, amphipathic molecules known for their facilitating role in fat absorption, are also recognized as signalling molecules acting via nuclear and membrane receptors. Of the bile acid-activated receptors, the Farnesoid X Receptor (FXR) and the G protein-coupled bile acid receptor-1 (Gpbar1 or TGR5) have been studied most extensively. Bile acid signaling is critical in the regulation of bile acid metabolism itself, but it also plays a significant role in glucose, lipid and energy metabolism. Activation of FXR and TGR5 leads to reduced hepatic bile salt load, improved insulin sensitivity and glucose regulation, increased energy expenditure, and anti-inflammatory effects. These beneficial effects render bile acid signaling an interesting therapeutic target for the treatment of diseases such as cholestasis, non-alcoholic fatty liver disease, and diabetes. Here, we summarize recent findings on bile acid signaling and discuss potential and current limitations of bile acid receptor agonist and modulators of bile acid transport as future therapeutics for a wide-spectrum of diseases.

Dysregulated bile acid signaling contributes to the neurological impairment in murine models of acute and chronic liver failure

BACKGROUND

Hepatic encephalopathy (HE), a severe neuropsychiatric complication, is associated with increased blood levels of ammonia and bile acids (BAs). We sought to determine (1) whether abnormally increased blood BAs in liver cirrhotic patients with HE is caused by elevation of apical sodium-dependent BA transporter (ASBT)-mediated BA reabsorption; and (2) whether increased BA reabsorption would exacerbate ammonia-induced brain injuries.

METHODS

We quantitatively measured blood BA and ammonia levels in liver cirrhosis patients with or without HE and healthy controls. We characterized ASBT expression, BA profiles, and ammonia concentrations in a chronic liver disease (CLD) mouse model induced by streptozotocin-high fat diet (STZ-HFD) and an azoxymethane (AOM) - induced acute liver failure (ALF) mouse model. These two mouse models were treated with SC-435 (ASBT inhibitor) and budesonide (ASBT activator), respectively.

FINDINGS

Blood concentrations of ammonia and conjugated BAs were substantially increased in cirrhotic patients with HE (n = 75) compared to cirrhotic patients without HE (n = 126). Pharmacological inhibition of the enterohepatic BA circulation using a luminal- restricted ASBT inhibitor, SC-435, in mice with AOM-induced ALF and STZ-HFD -induced CLD effectively reduced BA and ammonia concentrations in the blood and brain, and alleviated liver and brain damages. Budesonide treatment induced liver and brain damages in normal mice, and exacerbated these damages in AOM-treated mice.

INTERPRETATION

ASBT mediated BA reabsorption increases intestinal luminal pH and facilitates conversion of intestinal ammonium to ammonia, leading to abnormally high levels of neurotoxic ammonia and cytotoxic BAs in the blood and brain. Inhibition of intestinal ASBT with SC-435 can effectively remove neurotoxic BAs and ammonia from the bloodstream and thus, mitigate liver and brain injuries resulting from liver failure.

Progressive familial intrahepatic cholestasis: diagnosis, management, and treatment

Progressive familial intrahepatic cholestasis (PFIC) is a group of autosomal recessive cholestatic liver diseases which are subgrouped according to the genetic defect, clinical presentation, laboratory findings and liver histology. Progressive liver fibrosis, cirrhosis, and end stage liver disease (ESLD) may eventually develop. PFIC was first described in Amish descendants of Jacob Byler, therefore it was originally called Byler disease. But it can be seen anywhere on the globe. This review summarizes the main features of the subtypes of the disease and discusses the current available diagnosis, conservative and surgical therapeutic options.

Colesevelam attenuates cholestatic liver and bile duct injury in Mdr2-/- mice by modulating composition, signalling and excretion of faecal bile acids

BACKGROUND AND AIMS

Interruption of the enterohepatic circulation of bile acids (BAs) may protect against BA-mediated cholestatic liver and bile duct injury. BA sequestrants are established to treat cholestatic pruritus, but their impact on the underlying cholestasis is still unclear. We aimed to explore the therapeutic effects and mechanisms of the BA sequestrant colesevelam in a mouse model of sclerosing cholangitis.

METHODS

Mdr2^-/- mice received colesevelam for 8 weeks. Gene expression profiles of BA homeostasis, inflammation and fibrosis were explored in liver, intestine and colon. Hepatic and faecal BA profiles and gut microbiome were analysed. Glucagon-like peptide 1 (GLP-1) levels in portal blood were measured by ELISA. Furthermore, Mdr2^-/- mice as well as wild-type 3,5-diethoxy-carbonyl-1,4-dihydrocollidine-fed mice were treated with GLP-1-receptor agonist exendin-4 for 2 weeks prior to analysis.

RESULTS

Colesevelam reduced serum liver enzymes, BAs and expression of proinflammatory and profibrogenic markers. Faecal BA profiling revealed increased levels of secondary BAs after resin treatment, while hepatic and biliary BA composition showed a shift towards more hydrophilic BAs. Colonic GLP-1 secretion, portal venous GLP-1 levels and intestinal messenger RNA expression of gut hormone Proglucagon were increased, while ileal Fgf15 expression was abolished by colesevelam. Exendin-4 treatment increased bile duct mass without promoting a reactive cholangiocyte phenotype in mouse models of sclerosing cholangitis. Microbiota analysis showed an increase of the phylum δ-Proteobacteria after colesevelam treatment and a shift within the phyla Firmicutes from Clostridiales to Lactobacillus.

CONCLUSION

Colesevelam increases faecal BA excretion and enhances BA conversion towards secondary BAs, thereby stimulating secretion of GLP-1 from enteroendocrine L-cells and attenuates liver and bile duct injury in Mdr2^-/- mice.

Biliary Atresia: Clinical and Research Challenges for the Twenty-First Century

Biliary atresia (BA) is a fibroinflammatory disease of the intrahepatic and extrahepatic biliary tree. Surgical hepatic portoenterostomy (HPE) may restore bile drainage, but progression of the intrahepatic disease results in complications of portal hypertension and advanced cirrhosis in most children. Recognizing that further progress in the field is unlikely without a better understanding of the underlying cause(s) and pathogenesis of the disease, the National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK) sponsored a research workshop focused on innovative and promising approaches and on identifying future areas of research. Investigators discussed recent advances using gestational ultrasound and results of newborn BA screening with serum direct (conjugated) bilirubin that support a prenatal onset of biliary injury. Experimental and human studies implicate the toxic properties of environmental toxins (e.g., biliatresone) and of viruses (e.g., cytomegalovirus) to the biliary system. Among host factors, sequence variants in genes related to biliary development and ciliopathies, a notable lack of a cholangiocyte glycocalyx and of submucosal collagen bundles in the neonatal extrahepatic bile ducts, and an innate proinflammatory bias of the neonatal immune system contribute to an increased susceptibility to damage and obstruction following epithelial injury. These advances form the foundation for a future research agenda focused on identifying the environmental and host factor(s) that cause BA, the potential use of population screening, studies of the mechanisms of prominent fibrosis in young infants, determinations of clinical surrogates of disease progression, and the design of clinical trials that target subgroups of patients with initial drainage following HPE. (Hepatology 2018; 00:000-000).

Na+ -taurocholate cotransporting polypeptide inhibition has hepatoprotective effects in cholestasis in mice

Accumulation of bile salts (BSs) during cholestasis leads to hepatic and biliary injury, driving inflammatory and fibrotic processes. The Na⁺ -Taurocholate Cotransporting Polypeptide (NTCP) is the major hepatic uptake transporter of BSs, and can be specifically inhibited by myrcludex B. We hypothesized that inhibition of NTCP dampens cholestatic liver injury. Acute cholestasis was induced in mice by a 3.5-diethoxycarbonyl-1.4-dihydrocollidine (DDC) diet or by bile duct ligation (BDL). Chronic cholestasis was investigated in Atp8b1-G308V and Abcb4/Mdr2 deficient mice. Mice were injected daily with myrcludex B or vehicle. Myrcludex B reduced plasma alkaline phosphatase (ALP) levels in DDC-fed, Atp8b1-G308V and BDL mice by 39%, 27% and 48% respectively. Expression of genes involved in fibrosis, proliferation and inflammation was reduced by myrcludex B treatment in DDC-fed and Atp8b1-G308V mice. NTCP-inhibition increased plasma BS levels from 604±277 to 1746±719 μm in DDC-fed mice, 432±280 to 762±288 μm in Atp8b1-G308V mice and from 522±130 to 3625±378 μm in BDL mice. NTCP-inhibition strongly aggravated weight loss in BDL mice, but not in other cholestatic models studied. NTCP-inhibition reduced biliary BS output in DDC-fed and Atp8b1-G308V mice by ∼50% while phospholipid (PL) output was maintained, resulting in a higher PL/BS ratio. Conversely, liver injury in Abcb4 deficient mice, lacking biliary phospholipid output, was aggravated after myrcludex B treatment. Conclusion: NTCP-inhibition by myrcludex B has hepatoprotective effects, by reducing BS load in hepatocytes and increasing the biliary PL/BS ratio. High micromolar plasma BS levels after NTCP-inhibition were well tolerated. NTCP-inhibition may be beneficial in selected forms of cholestasis. (Hepatology 2018).

Ileal Bile Acid Transporter Inhibition for the Treatment of Chronic Constipation, Cholestatic Pruritus, and NASH

Bile acids are synthesized from cholesterol in the liver, excreted with bile into the duodenum, almost completely taken up again in the distal ileum and finally returned to the liver with portal blood in a process termed enterohepatic circulation. Bile acid synthesis, excretion, and reuptake are tightly regulated. The apical sodium-dependent bile acid transporter [ASBT; also known as ileal bile acid transporter (IBAT) and SLC10A2] is pivotal for the almost complete reabsorption of conjugated bile acids in the ileum. Dysfunctional IBAT may be the cause of bile acid diarrhea. Pharmacological IBAT inhibition results in an increased bile acid load in the colon and subsequently a lower bile acid pool, which is associated with improved liver histology in animal models of cholestatic liver disease and non-alcoholic steatohepatitis (NASH). In humans, IBAT inhibitors have been tested in clinical trials with widely different indications: in patients with idiopathic chronic constipation, an increased number of bowel movements was observed. In adult and pediatric cholestatic liver diseases with pruritus, various IBAT inhibitors showed potential to improve itching. Adverse events of IBAT inhibitors, based on their mode of action, are abdominal pain and diarrhea which might patients to withdraw from study medications. So far, no data are available of a study of IBAT inhibitors in patients with NASH. In this review we summarize the preclinical and most recent clinical studies with various IBAT inhibitors and discuss the difficulties that should be addressed in future studies.