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

The Role of Bile Acid in Immune-Mediated Skin Diseases

Immune-mediated skin disorders arise from dysfunctional immune responses, instigating inflammatory dermatoses and a reduced quality of life. The complex pathogenesis likely involves genetic risks, environmental triggers and aberrant immune activation. An emerging body of evidence suggests that bile acid disturbances may critically promote immune pathology in certain skin conditions. Bile acids synthesised from cholesterol regulate nutrient metabolism and immune cell function via nuclear receptors and G protein-coupled receptors (GPCRs). Altered bile acid profiles and receptor expression have been identified in psoriasis, atopic dermatitis (AD) and autoimmune blistering diseases. Disruptions in bile acid signalling affect the inflammatory and metabolic pathways linked to these disorders. Targeting components of the bile acid axis represents a promising therapeutic strategy. This review elucidates the intricate links between bile acid homeostasis and immune dysfunction in inflammatory skin diseases, synthesising evidence that targeting bile acid pathways may unlock innovative therapeutic avenues. This study compiles clinical and experimental data revealing disrupted bile acid signalling and composition in various immune-mediated dermatoses, highlighting the emerging significance of bile acids in cutaneous immune regulation.

Pruritus in Chronic Cholestatic Liver Diseases, Especially in Primary Biliary Cholangitis: A Narrative Review

Patients with chronic cholestatic liver diseases often experience itch and struggle with this symptom. We discuss the mechanism of itch in patients with chronic cholestatic liver diseases, such as primary biliary cholangitis (PBC) and others, and their therapies, including ileal bile acid transporter (IBAT) inhibitors. In patients with PBC, there are high serum/plasma concentrations of multiple factors, including bile salts, bilirubin, endogenous opioids, lysophosphatidic acid (LPA), autotaxin, and histamine. Bile salts, bilirubin, LPA, and autotaxin affect itch mediators in the skin and sensory nerves, while the endogenous opioid balance affects mediators in the spinal cord. Itch is sensitized by both the peripheral and central nervous systems. Both mechanisms are involved in itch in patients with chronic cholestatic liver disease. Although IBAT inhibitors have been approved for use in pediatric cholestatic conditions, such as progressive familial intrahepatic cholestasis and Alagille syndrome, IBAT inhibition seems to be a promising treatment for chronic refractory itch in patients with PBC. A traditional non-systematic review results in this narrative review. Multidisciplinary cooperation, involving hepatologists, dermatologists, and pharmacists, could provide better treatment for PBC patients suffering from refractory itch. In conclusion, we summarized the existing knowledge on itch caused by chronic cholestatic liver diseases, especially in PBC with a focus on the mechanisms and therapies. This narrative review provides the mechanisms and therapeutic options for itch in patients with chronic cholestatic liver diseases.

The bile acid profile

As a large and structurally diverse family of small molecules, bile acids play a crucial role in regulating lipid, glucose, and energy metabolism. In the human body, bile acids share a similar chemical structure with many isomers, exhibit little difference in polarity, and possess various physiological activities. The types and contents of bile acids present in different diseases vary significantly. Therefore, comprehensive and accurate detection of the content of various types of bile acids in different biological samples can not only provide new insights into the pathogenesis of diseases but also facilitate the exploration of novel strategies for disease diagnosis, treatment, and prognosis. The detection of disease-induced changes in bile acid profiles has emerged as a prominent research focus in recent years. Concurrently, targeted metabolomics methods utilizing high-performance liquid chromatography-mass spectrometry (HPLC-MS) have progressively established themselves as the predominant technology for the separation and detection of bile acids. Bile acid profiles will increasingly play an important role in diagnosis and guidance in the future as the relationship between disease and changes in bile acid profiles becomes clearer. This highlights the growing diagnostic value of bile acid profiles and their potential to guide clinical decision-making. This review aims to explore the significance of bile acid profiles in clinical diagnosis from four perspectives: the synthesis and metabolism of bile acids, techniques for detecting bile acid profiles, changes in bile acid profiles associated with diseases, and the challenges and future prospects of applying bile acid profiles in clinical settings.

Serum bile acid change correlates with improvement in pruritus in patients with primary biliary cholangitis receiving linerixibat

BACKGROUND & AIMS

Total serum bile acid (TSBA) levels are elevated in patients with primary biliary cholangitis (PBC) and may mediate cholestatic pruritus. Linerixibat, an ileal bile acid transporter inhibitor, improved pruritus in patients with PBC. We explored the relationship between linerixibat dose, TSBA concentration, and pruritus.

METHODS

Data from Phase 1/2 trials were used to develop a population kinetic-pharmacodynamic model to characterize the linerixibat dose-TSBA relationship. Individual Bayesian parameter estimates for participants in the GLIMMER study were used to derive the area under the TSBA concentration curve over 24 h (AUC0-24). Time-matched post hoc estimates of AUC0-24 were correlated with pruritus reported on a 0-10 numerical rating scale. Baseline TSBA concentration was correlated with change from baseline (ΔBL) in monthly itch score (MIS). ΔBL in model-estimated TSBA AUC0-24 was correlated with time-matched ΔBL in weekly itch score (WIS) or MIS.

RESULTS

Linerixibat dose dependently reduced TSBA AUC0-24, reaching steady state after 5 days. Baseline TSBA levels in GLIMMER did not correlate with ΔBL in MIS. ΔBL in TSBA AUC0-24 correlated with improved WIS over 12 weeks of treatment (r = 0.52, p < 0.0001). Of participants with a ≥30% decrease in TSBA AUC0-24, 60% were pruritus responders (≥2-point improvement in WIS from baseline).

CONCLUSIONS

Linerixibat treatment leads to rapid, dose-dependent TSBA reductions. Baseline TSBA levels do not correlate with on-treatment pruritus change, suggesting they do not predict linerixibat response. Change in TSBA AUC0-24 correlates significantly with, and can be predictive of, pruritus improvement in patients with PBC.

Seladelpar treatment reduces IL-31 and pruritus in patients with primary biliary cholangitis

BACKGROUND AND AIMS

Pruritus is a debilitating symptom for many people living with primary biliary cholangitis (PBC). In studies with seladelpar, a selective peroxisome proliferator-activated receptor-delta agonist, patients with PBC experienced significant improvement in pruritus and reduction of serum bile acids. Interleukin-31 (IL-31) is a cytokine known to mediate pruritus, and blocking IL-31 signaling provides relief in pruritic skin diseases. This study examined the connection between seladelpar's antipruritic effects and IL-31 and bile acid levels in patients with PBC.

APPROACH AND RESULTS

IL-31 levels were quantified in serum samples from the ENHANCE study of patients with PBC receiving daily oral doses of placebo (n = 55), seladelpar 5 mg (n = 53) or 10 mg (n = 53) for 3 months, and for healthy volunteers (n = 55). IL-31 levels were compared with pruritus using a numerical rating scale (NRS, 0-10) and with bile acid levels. Baseline IL-31 levels closely correlated with pruritus NRS ( r = 0.54, p < 0.0001), and total ( r = 0.54, p < 0.0001) and conjugated bile acids (up to 0.64, p < 0.0001). Decreases in IL-31 were observed with seladelpar 5 mg (-30%, p = 0.0003) and 10 mg (-52%, p < 0.0001) versus placebo (+31%). Patients with clinically meaningful improvement in pruritus (NRS ≥ 2 decrease) demonstrated greater dose-dependent reductions in IL-31 compared to those without pruritus improvement (NRS < 2 decrease). Strong correlations were observed for the changes between levels of IL-31 and total bile acids ( r = 0.63, p < 0.0001) in the seladelpar 10 mg group.

CONCLUSIONS

Seladelpar decreased serum IL-31 and bile acids in patients with PBC. The reductions of IL-31 and bile acids correlated closely with each other and pruritus improvement, suggesting a mechanism to explain seladelpar's antipruritic effects.

Pruritus, Fatigue, Osteoporosis and Dyslipoproteinemia in Pbc Patients: A Clinician’s Perspective

In this review article, we summarize the most common clinical manifestations of Primary biliary cholangitis (PBC): pruritus, fatigue, osteoporosis, and dyslipoproteinemia and discuss their impact of the patients’ quality of life. More than half of PBC patients suffer from pruritus or fatigue at the time of diagnosis. We discuss the pathophysiological aspects of the PBC clinical manifestations and treatment options. The pathophysiology of pruritus and fatigue is not adequately elucidated, but IL-31 is associated with the severity of pruritus and could be used to objectify the subjective reporting by questionnaires. Although PBC patients suffer from atherogenic dyslipidemia, they do not seem to have a higher cardiovascular risk; however, this observation needs to be clarified by further clinical studies. The second-line of PBC treatment affects pruritus severity: Obeticholic acid (OCA) worsens pruritus while fibrates improve it. Itching can be alleviated by both non-pharmacological and pharmacological approach, however the are multiple barriers to pharmacological treatment. There is no adequate treatment for fatigue today. Treatment of osteoporosis and dyslipidemia is similar for non-PBC patients; stage of liver disease should be considered in treatment. Further research to clarify the pathophysiology and to eventually discover an effective treatment to improve survival and quality of life (especially pruritus and fatigue) in PBC patients is needed.

Sodium/bile acid co-transporter inhibitors currently in preclinical or early clinical development for the treatment of primary biliary cholangitis

INTRODUCTION

Pruritus is common and often undertreated in patients with primary biliary cholangitis (PBC). Existing treatments largely have an aging and low-quality evidence base, and studies included only small numbers of patients. More recent data that has added to our understanding of pruritus treatments has often come from clinical trials where itching was a secondary outcome measure in a trial designed primarily to assess disease-modifying agents. This area represents an unmet clinical need in the management of PBC.

AREAS COVERED

In this manuscript, we first summarize the proposed mechanisms for PBC-related pruritus and the current treatment paradigm. We then present an appraisal of the existing pre-clinical and clinical evidence for the use of ileal bile acid transporter inhibitors (IBATis) for this indication in PBC patients.

EXPERT OPINION

Evidence for the efficacy of IBATis is promising but limited by the currently available volume of data. Furthermore, larger clinical trials with long-term data on efficacy, safety and tolerability are needed to confirm the role of using IBATis in clinical practice and their place on the itch treatment ladder. Additional focus should also be given to exploring the disease-modifying potential of IBATis in PBC.

Exploring Advanced Therapies for Primary Biliary Cholangitis: Insights from the Gut Microbiota-Bile Acid-Immunity Network

Primary biliary cholangitis (PBC) is a cholestatic liver disease characterized by immune-mediated injury to small bile ducts. Although PBC is an autoimmune disease, the effectiveness of conventional immunosuppressive therapy is disappointing. Nearly 40% of PBC patients do not respond to the first-line drug UDCA. Without appropriate intervention, PBC patients eventually progress to liver cirrhosis and even death. There is an urgent need to develop new therapies. The gut-liver axis emphasizes the interconnection between the gut and the liver, and evidence is increasing that gut microbiota and bile acids play an important role in the pathogenesis of cholestatic diseases. Dysbiosis of gut microbiota, imbalance of bile acids, and immune-mediated bile duct injury constitute the triad of pathophysiology in PBC. Autoimmune cholangitis has the potential to be improved through immune system modulation. Considering the failure of conventional immunotherapies and the involvement of gut microbiota and bile acids in the pathogenesis, targeting immune factors associated with them, such as bile acid receptors, microbial-derived molecules, and related specific immune cells, may offer breakthroughs. Understanding the gut microbiota-bile acid network and related immune dysfunctions in PBC provides a new perspective on therapeutic strategies. Therefore, we summarize the latest advances in research of gut microbiota and bile acids in PBC and, for the first time, explore the possibility of related immune factors as novel immunotherapy targets. This article discusses potential therapeutic approaches focusing on regulating gut microbiota, maintaining bile acid homeostasis, their interactions, and related immune factors.

Paediatric research sets new standards for therapy in paediatric and adult cholestasis

Children with Alagille syndrome and progressive familial intrahepatic cholestasis (PFIC) experience debilitating pruritus, for which there have been few effective treatment options. In the past 2 years, the ileal bile acid transporter (IBAT) inhibitors maralixibat and odevixibat have been approved for the management of cholestatic pruritus in these individuals, representing an important step forward in improving their quality of life. Emerging data suggest these drugs might also improve event-free survival, therefore potentially altering the typical disease course currently seen in these disorders. This Review will discuss how genetic advances have clarified the molecular basis of cholestatic disorders, facilitating the development of new therapeutic options that have only been evaluated in children. We focus specifically on the newly licensed IBAT inhibitors for patients with Alagille syndrome and PFIC and explore the next steps for these drugs in relation to other paediatric and adult cholestatic disorders, recognising that they have the potential to benefit a wider group of patients with gastrointestinal and liver disease.

Guidelines on the Diagnosis and Management of Primary Biliary Cholangitis (2021)

In 2015, the Chinese Society of Hepatology and the Chinese Society of Gastroenterology published a consensus on primary biliary cholangitis (PBC). In the past years, numerous clinical studies have been published in the field of PBC. To guide the clinical diagnosis and management of PBC patients, the Chinese Society of Hepatology invited a panel of experts to assess the new clinical evidence and formulate the current guidelines.

GLIMMER: A Randomized Phase 2b Dose-Ranging Trial of Linerixibat in Primary Biliary Cholangitis Patients With Pruritus

BACKGROUND & AIMS

GLIMMER assessed dose-response, efficacy, and safety of linerixibat, an ileal bile acid transporter inhibitor in development for cholestatic pruritus associated with primary biliary cholangitis (PBC).

METHODS

GLIMMER was a Phase 2b, multicenter, randomized, parallel-group study in adults with PBC and moderate-to-severe pruritus (≥4 on 0-10 numerical rating scale [NRS]). After 4 weeks of single-blind placebo, patients with NRS ≥3 were randomized (3:1) to double-blind linerixibat/placebo for 12 weeks (to week 16), followed by single-blind placebo (to week 20). The primary objective was to investigate dose-related changes in mean worst daily itch (MWDI) score.

RESULTS

One hundred forty-seven patients received placebo (n = 36) or linerixibat (once daily: 20 mg, n = 16; 90 mg, n = 23; 180 mg, n = 27; twice daily: 40 mg, n = 23; 90 mg, n = 22). Linerixibat groups exhibited ≥2-point mean reductions in MWDI from baseline at week 16; however, differences from placebo were not significant. Post hoc analysis of change from baseline in monthly itch score over the treatment period (Phase 3 endpoint) showed significant differences between placebo and linerixibat 180 mg once daily (P = .0424), 40 mg twice daily (P = .0105), and 90 mg twice daily (P = .0370). A significant relationship between total daily dose and response was observed post hoc in the per protocol population (P = .0542). Consistent with mechanism of action, diarrhea was the most frequent adverse event, and incidence increased with dose.

CONCLUSIONS

Linerixibat effect on itch was not significantly different versus placebo in the primary intent-to-treat analysis but was associated with a significant dose-dependent reduction in itch in the per protocol population. A well-tolerated dose was identified for Phase 3 investigation for cholestatic pruritus in PBC.

CLINICALTRIALS

gov ID: NCT02966834.

Evaluation and Management of Pruritus in Primary Biliary Cholangitis

Chronic pruritus is a classic symptom in patients with primary biliary cholangitis. It affects up to two-thirds of patients in the course of the disease. Efficient therapy consists of topical treatment combined with systemic options such as anion exchangers, rifampicin, bezafibrate, μ-opioid receptor antagonists, selective-serotonin receptor uptake inhibitors, and gabapentinoids. Future therapeutic approaches may contain the selective blockade of the enterohepatic cycle by inhibiting the ileal bile acid transporter, the agonism at κ-opioid receptors, and antagonism of the mas-related G protein-coupled receptor X4. As nondrug treatment, ultraviolet B therapy, albumin dialysis, and biliary drainage are available at specialized centers.

Immunologic Responses and the Pathophysiology of Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is an autoimmune liver disease with a female predisposition and selective destruction of intrahepatic small bile ducts leading to nonsuppurative destructive cholangitis. It is characterized by seropositivity of antimitochondrial antibodies or PBC-specific antinuclear antibodies, progressive cholestasis, and typical liver histologic manifestations. Destruction of the protective bicarbonate-rich umbrella is attributed to the decreased expression of membrane transporters in biliary epithelial cells (BECs), leading to the accumulation of hydrophobic bile acids and sensitizing BECs to apoptosis. A recent X-wide association study reveals a novel risk locus on the X chromosome, which reiterates the importance of Treg cells.

Cholestatic Itch: Our Current Understanding of Pathophysiology and Treatments

Hepatic pruritus is common in liver conditions, including cholestasis and nonalcoholic fatty liver disease. The pruritus can be severe enough to diminish sleep and decrease quality of life. The pathophysiology likely involves many molecules and receptors, including bile acids, bilirubin, lysophosphatidic acid (LPA), endogenous opioids, and serotonin. Recent advances suggest a significant role of Mas-related G protein-coupled receptor X4 (MRGPRX4) and autotaxin/LPA as key players in cholestatic pruritus. Further research is needed to develop increasingly targeted therapies with greater efficacy, especially given that many patients report itch refractory to various treatments. Cholestyramine was the only US FDA-approved drug for cholestatic pruritus until recent approval of ileal bile acid transporter (IBAT) inhibitors for use in the pediatric cholestatic conditions, progressive familial intrahepatic cholestasis and Alagille syndrome. Both medications decrease the bile acid pool. IBAT inhibitors are under investigation for broader use, and targeting LPA receptors and MRGPR4 are additional attractive options.

Defining and characterising a toolkit for the development of a successful European registry for rare liver diseases: a model for building a rare disease registry

INTRODUCTION

A rare disease is defined by the European Health Commission as a disorder affecting less than 5/10,000 of the population. There are at least 20 rare liver diseases (RLDs) seen frequently in the adult and paediatric liver clinic, signifying that the hepatology community can be influential in developing such patient databases for registering patients with rare hepatic conditions. The aim of this review was, first, to identify registries for RLDs in Europe, and, second, to design a universal blueprint for the development of a registry for RLD by using lessons learnt from the European registries that have already been established.

METHODS

We searched PubMed, Google Scholar and clinicaltrials.gov using the MESH terms 'registries', 'database management systems', 'database' and the non-MESH terms 'database$', 'registry', 'repository' and 'repositories'. We only included studies in English from countries/consortia of the European Union (EU). Our literature search was performed in 2020.

RESULTS

We identified 37 registries for RLDs in Europe. Using information from the design of these registries we designed a blueprint for the development of a patient registry for an RLD consisting of a theoretical, technical and maintenance phase.

DISCUSSION

It is believed that rare diseases may affect as much as 6-8% of the EU population across its 28 member states. Here we have provided a toolkit for designing a registry for an RLD. Our article will complement the efforts of loco-regional, national and international groups seeking to establish robust systems for data collection and analysis for orphan liver diseases.

Alterations in gut microbiota and elevated serum bilirubin in primary biliary cholangitis patients treated with ursodeoxycholic acid

BACKGROUND

The prognosis of primary bile cholangitis (PBC) is linked to gut microbiota dysbiosis. This study investigated the association between the gut microbiome and elevated total bilirubin (TB) level in PBC patients treated with ursodeoxycholic acid (UCDA).

METHODS

A total of 47 PBC patients with 12 months of UCDA treatment were enrolled. Patients were divided into the TB (+) (TB>1× upper limit of the normal range [ULN]; n = 20) and TB(-) (TB≤1× ULN; n = 27) groups. Stool and serum specimens were collected, and microbiota composition and functional characteristics in the 2 groups were evaluated by 16S RNA gene sequencing and bioinformatic analysis.

RESULTS

Bacterial diversity was lower in the TB(+) group than in the TB(-) group, although there was no significant difference in bacterial community profile. The phylum Saccharibacteria showed differential abundance in the 2 groups. Meanwhile, the TB(-) group had lower abundance of the Gemmiger, Blautia, Anaerostipes and Coprococcus genera than the TB(+) group, whereas Holdemania was absent. The abundance of Gemmiger formicillis and Coprococcus eutactus was positively correlated with that of Faecalibacterium prausnitzii, while Blautia, Anaerostipes and Coprococcus were negatively correlated with total bile acid level.

CONCLUSION

TB level in PBC patients treated for 12 months with UCDA is associated with a distinct gut microbiome profile.

Proof-of-concept study to evaluate the safety and efficacy of saroglitazar in patients with primary biliary cholangitis

BACKGROUND & AIM

Saroglitazar is a novel peroxisome proliferator-activated receptor (PPAR) agonist with dual agonistic properties (α/γ). Due to a strong mechanistic rationale, we aimed to test the safety and efficacy of saroglitazar in patients with primary biliary cholangitis (PBC) who were either ursodeoxycholic acid (UDCA) resistant or intolerant.

METHODS

In this double-blind, phase II proof-of-concept trial, 37 patients with PBC were randomized to saroglitazar 4 mg (n = 13), saroglitazar 2 mg (n = 14), or placebo (n = 10) daily for 16 weeks. The primary efficacy endpoint was the reduction in alkaline phosphatase (ALP) level at Week 16.

RESULTS

A significant reduction of mean ALP levels was observed at Week 16 relative to baseline in both the saroglitazar 4 mg (least-squares [LS] mean =-163.3 U/L, SE = 25.1, p <0.001) and 2 mg (LS mean =-155.8 U/L, SE = 24.4, p <0.001) groups, compared with placebo (LS mean =-21.1 U/L, SE = 28.9). Treatment with saroglitazar resulted in a rapid reduction of ALP concentration at Week 4 that was sustained through the study duration. At least 1 treatment-emergent adverse event occurred in 11 (84.6%) patients in the saroglitazar 4 mg group, in 12 (85.7%) patients in the 2 mg group and in 8 (80%) patients in the placebo group. Study drug was discontinued in 4 patients (3 patients in the 4 mg group and 1 patient in the 2 mg group) due to aminotransferase increases that promptly returned to baseline values after drug discontinuation.

CONCLUSIONS

Saroglitazar at 2 mg and 4 mg daily was tolerated and resulted in rapid and sustained improvements in ALP. Further studies are underway at a daily dose of 2 mg and 1 mg due to the higher incidence of elevated liver enzymes observed with the 4 mg dose. CLINICALTRIALS.

GOV IDENTIFIER

NCT03112681 LAY SUMMARY: Saroglitazar resulted in a rapid and sustained improvement in alkaline phosphatase levels in patients with primary biliary cholangitis. The mean percentage reductions in alkaline phosphatase levels were 49% and 51% in the saroglitazar 4 mg and 2 mg groups compared to 3% in the placebo group.

Pharmacokinetics and ADME Characterization of Intravenous and Oral [14C]-Linerixibat in Healthy Male Volunteers

Linerixibat, an oral small-molecule ileal bile acid transporter inhibitor under development for cholestatic pruritus in primary biliary cholangitis, was designed for minimal absorption from the intestine (site of pharmacological action). This study characterized the pharmacokinetics, absorption, metabolism, and excretion of [14C]-linerixibat in humans after an intravenous microtracer concomitant with unlabeled oral tablets and [14C]-linerixibat oral solution. Linerixibat exhibited absorption-limited flip-flop kinetics: longer oral versus intravenous half-life (6-7 hours vs. 0.8 hours). The short intravenous half-life was consistent with high systemic clearance (61.9 l/h) and low volume of distribution (16.3 l). In vitro studies predicted rapid hepatic clearance via cytochrome P450 3A4 metabolism, which predicted human hepatic clearance within 1.5-fold. However, linerixibat was minimally metabolized in humans after intravenous administration: ∼80% elimination via biliary/fecal excretion (>90%-97% as unchanged parent) and ∼20% renal elimination by glomerular filtration (>97% as unchanged parent). Absolute oral bioavailability of linerixibat was exceedingly low (0.05%), primarily because of a very low fraction absorbed (0.167%; fraction escaping first-pass gut metabolism (fg) ∼100%), with high hepatic extraction ratio (77.0%) acting as a secondary barrier to systemic exposure. Oral linerixibat was almost entirely excreted (>99% recovered radioactivity) in feces as unchanged and unabsorbed linerixibat. Consistent with the low oral fraction absorbed and ∼20% renal recovery of intravenous [14C]-linerixibat, urinary elimination of orally administered radioactivity was negligible (<0.04% of dose). Linerixibat unequivocally exhibited minimal gastrointestinal absorption and oral systemic exposure. Linerixibat represents a unique example of high CYP3A4 clearance in vitro but nearly complete excretion as unchanged parent drug via the biliary/fecal route. SIGNIFICANCE STATEMENT: This study conclusively established minimal absorption and systemic exposure to orally administered linerixibat in humans. The small amount of linerixibat absorbed was eliminated efficiently as unchanged parent drug via the biliary/fecal route. The hepatic clearance mechanism was mispredicted to be mediated via cytochrome P450 3A4 metabolism in vitro rather than biliary excretion of unchanged linerixibat in vivo.

Association between circulating bile acid alterations and nonalcoholic steatohepatitis independent of obesity and diabetes mellitus

BACKGROUND AND AIMS

Bile acid (BA) dysregulation is related to not only metabolic diseases but also nonalcoholic fatty liver disease (NAFLD). We investigated whether circulating BA levels are altered according to the histological severity of NAFLD independent of metabolic derangements.

METHODS

Global metabolic profiling and targeted BA analysis using sera collected from biopsy-proven no-NAFLD (n = 67), nonalcoholic fatty liver (NAFL) (n = 99), and nonalcoholic steatohepatitis (NASH, n = 75) subjects were performed sequentially. Circulating metabolome analysis integrated with the hepatic transcriptome was performed to elucidate the mechanistic basis of altered circulating BA profiles after stratification by obesity (body mass index ≤ 25 kg/m² ). Circulating BA alterations were also validated in an independent validation cohort (29 no-NAFLD, 70 NAFL and 37 NASH).

RESULTS

Global profiling analysis showed that BA was the metabolite significantly altered in NASH compared to NAFL. Targeted BA analysis demonstrated that glyco-/tauro-conjugated primary BAs were commonly increased in nonobese and obese NASH, while unconjugated primary BAs increased only in nonobese NASH. These characteristic primary BA level changes were maintained even after stratification according to diabetes status and were replicated in the independent validation cohort. Compared to nonobese NAFL patients, nonobese NASH patients exhibited upregulated hepatic expression of CYP8B1.

CONCLUSIONS

BA metabolism is dysregulated as the histological severity of NAFLD worsens, independent of obesity and diabetes status; dysregulation is more prominent in nonobese NAFLD patients. Metabolome-driven omics approach provides new insight into our understanding of altered BA metabolism associated with individual phenotypes of NAFLD.

The Gut-Liver Axis in Cholestatic Liver Diseases

The gut-liver axis describes the physiological interplay between the gut and the liver and has important implications for the maintenance of health. Disruptions of this equilibrium are an important factor in the evolution and progression of many liver diseases. The composition of the gut microbiome, the gut barrier, bacterial translocation, and bile acid metabolism are the key features of this cycle. Chronic cholestatic liver diseases include primary sclerosing cholangitis, the generic term secondary sclerosing cholangitis implying the disease secondary sclerosing cholangitis in critically ill patients and primary biliary cirrhosis. Pathophysiology of these diseases is not fully understood but seems to be multifactorial. Knowledge about the alterations of the gut-liver axis influencing the pathogenesis and the outcome of these diseases has considerably increased. Therefore, this review aims to describe the function of the healthy gut-liver axis and to sum up the pathological changes in these cholestatic liver diseases. The review compromises the actual level of knowledge about the gut microbiome (including the mycobiome and the virome), the gut barrier and the consequences of increased gut permeability, the effects of bacterial translocation, and the influence of bile acid composition and pool size in chronic cholestatic liver diseases. Furthermore, therapeutic implications and future scientific objectives are outlined.

Cholestasis-Associated Pruritus and Its Pruritogens

Pruritus is a debilitating symptom of various cholestatic disorders, including primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) and inherited progressive familial intrahepatic cholestasis (PFIC). The molecular mechanisms leading to cholestasis-associated pruritus are still unresolved and the involved pruritogens are indecisive. As a consequence of pruritus, patients suffer from sleep deprivation, loss of daytime concentration, auto-mutilation and sometimes even suicidal ideations. Current guideline-approved therapy of cholestasis-associated pruritus includes stepwise administration of several medications, which may alleviate complaints in some, but not all affected patients. Therefore, also experimental therapeutic approaches are required to improve patients' quality of life. This article reviews the current state of research on pruritogens and their receptors, and shortly discusses the most recent experimental therapies.

Metabolomic Signature of Human Aortic Valve Stenosis

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This study is the first step towards the creation of a metabolomic map of calcified human aortic valves.

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The study highlights an independent association of LysoPA with CAVS severity.

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The study demonstrates that LysoPA levels are associated with faster CAVS progression rate.

This study outlines the first step toward creating the metabolite atlas of human calcified aortic valves by identifying the expression of metabolites and metabolic pathways involved at various stages of calcific aortic valve stenosis progression. Untargeted analysis identified 72 metabolites and lipids that were significantly altered (p < 0.01) across different stages of disease progression. Of these metabolites and lipids, the levels of lysophosphatidic acid were shown to correlate with faster hemodynamic progression and could select patients at risk for faster progression rate.

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.

Relationship between pruritus and autotaxin in intrahepatic cholestasis of pregnancy

OBJECTIVE

Intrahepatic cholestasis of pregnancy is a temporary, pregnancy-specific disease that resolves with delivery, characterized by itching (pruritus), as well as high transaminase and serum bile acid levels in the third trimester of pregnancy. Due to the effects of Autotaxin on the physiology of pregnancy, we aimed to investigate Autotaxin activity in patients with intrahepatic cholestasis of pregnancy.

PATIENTS AND METHODS

Sixty-nine patients diagnosed with intrahepatic cholestasis of pregnancy and 20 healthy pregnant women were enrolled in the study. Fasting serum bile acid, pruritus intensity, serum parameters, gestational week of the patients at the time of diagnosis were recorded, and birth week and birth weight were monitored. Autotaxin serum level was measured enzymatically.

RESULTS

The mean serum bile acid level (n=69; 38.74±35.92μmol/L) in patients with intrahepatic cholestasis of pregnancy (n=69) was detected to be higher than healthy pregnant women (n=20; 5.05±1.88μmol/L) (p<0.001). Weak correlation was detected between serum bile acid level and itch intensity (p=0.014, r=0.295), while no relation was detected between Autotaxin and itch intensity (p=0.446, r=0.09). Although mean Autotaxin (intrahepatic cholestasis of pregnancy: 678.10±424.42pg/mL, control: 535.16±256.47pg/mL) levels were high in patients with intrahepatic cholestasis of pregnancy, it was not statistically significant (p=0.157).

CONCLUSION

In our study, we observed that the serum Autotaxin level did not make a significant difference in patients with intrahepatic cholestasis of pregnancy compared to healthy pregnant women. These findings suggest that larger clinical studies are required to reveal the physio-pathological effects of Autotaxin on pregnancy.

Recent advances in understanding the molecular mechanisms of cholestatic pruritus: A review

Cholestasis, a condition characterized by an abnormal decrease in bile flow, is accompanied by various symptoms such as pruritus. Although cholestatic pruritus is a prominent condition, its precise mechanisms have largely been elusive. Recently, advancements have been made for understanding the etiology and pathogenesis of cholestatic pruritus. The current review therefore focuses on summarizing the overall progress made in the elucidation of its molecular mechanisms. We have reviewed the available animal models on cholestasis to compare the differences between them, characterized potential pruritogens involved in cholestatic pruritus, and have summarized the receptor and ion channels implicated in the condition. Finally, we have discussed the available treatment options for alleviation of cholestatic pruritus. As our understanding of the mechanisms of cholestatic pruritus deepens, novel strategies to cure this condition are awaited.

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.

Newer Approaches to the Management of Pruritus in Cholestatic Liver Disease

Purpose of Review

Chronic pruritus represents a burdensome symptom in cholestatic liver disease. This review recommends a stepwise therapeutic approach, alongside with providing information on epidemiology, pathophysiology, and novel drug targets.

Recent Findings

Current epidemiological data emphasize chronic itch as a major symptom in immune-mediated liver diseases such as primary biliary cholangitis affecting up to 70% of patients with a significant number suffering from long-lasting and severe pruritus. κ-opioid receptor (KOR) agonists, PPAR agonists, and ileal bile acid transporter (IBAT) inhibitors are currently investigated for their anti-pruritic efficacy in clinical trials. Future therapies may target the autotaxin-lysophosphatidic acid-axis or the Mas-related GPCR MRGPRX4.

Summary

Cholestatic pruritus still remains a challenging symptom for patients and physicians. Using a stepwise approach including cholestyramine, rifampicin, bezafibrate, naltrexone, and sertraline, pruritus is often adequately manageable. KOR agonists and IBAT inhibitors are currently the most promising anti-pruritic drugs for cholestatic pruritus in development.

Treatment of Pruritus Secondary to Liver Disease

PURPOSE OF REVIEW

Pruritus is a common extrahepatic symptom in various liver disorders, in particularly those with cholestatic features. This review summarizes epidemiology, pathophysiology, evidence-based therapeutic recommendations and currently investigated drugs for pruritus in hepatobiliary disorders.

RECENT FINDINGS

Recent epidemiological data suggest pruritus as a common and relevant symptom in immune-mediated liver diseases, i.e., primary biliary cholangitis (PBC) with over 70% affected patients, up to 56% suffering from chronic pruritus. The better pathophysiological understanding of hepatic pruritus has led to the identification of novel therapeutic targets, addressed in drug trials using KOR agonists, PPAR agonists, and ileal bile acid transporter inhibitors. Hepatic itch remains among the most agonizing symptoms for affected patients and a clinical challenge for physicians. Therapeutic recommendations include a guideline-based stepwise approach starting with cholestyramine, followed by rifampicin, naltrexone, and sertraline. Bezafibrate and ileal bile acid transporter inhibitors represent promising future anti-pruritic treatment options.