Adjunct Fenofibrate Up-regulates Bile Acid Glucuronidation and Improves Treatment Response For Patients With Cholestasis

Quantitative comparison of bile acid glucuronides sub-metabolome between intrahepatic cholestasis and healthy pregnant women

Because of the pathological indication and the physiological functions, bile acids (BAs) have occupied the research hotspot in recent decades. Although extensive efforts have been paid onto BAs sub-metabolome characterization, as the subfamily, BA glucuronides (gluA-BAs) profile is seldom concerned. Here, we made efforts to develop a LC-MS/MS program enabling quantitative gluA-BAs sub-metabolome characterization and to explore the differential species in serum between intrahepatic cholestasis of pregnancy (ICP) patients and healthy subjects. To gain as many authentic gluA-BAs as possible, liver microsomes from humans, rats, and mice were deployed to conjugate glucuronyl group to authentic BAs through in vitro incubation. Eighty gluA-BAs were captured and subsequently served as authentic compounds to correlate MS/MS spectral behaviors to structural features using squared energy-resolved MS program. Optimal collision energy (OCE) of [M-H]->[M-H-176.1]- was jointly administrated by [M-H]- mass and glucuronidation site, and identical exciting energies corresponding to 50% survival rate of 1st-generation fragment ion (EE50) were observed merely when the aglycone of a gluA-BA was consistent with the suspected structure. Through integrating high-resolution m/z, OCE, and EE50 information to identify gluA-BAs in a BAs pool, 97 ones were found and identified, and further, quantitative program was built for all annotated gluA-BAs by assigning OCEs to [M-H]->[M-H-176.1]- ion transitions. Quantitative gluA-BAs sub-metabolome of ICP was different from that of the healthy group. More GCDCA-3-G, GDCA-3-G, TCDCA-7-G, TDCA-3-G, and T-β-MCA-3-G were distributed in the ICP group. Above all, this study not only offered a promising analytical tool for in-depth gluA-BAs sub-metabolome characterization, but also clarified gluA-BAs allowing the differentiation of ICP and healthy subjects.

Peroxisome proliferator-activated receptor delta and liver diseases

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors involved in transcriptional regulation and play an important role in many physiological and metabolic processes. Unlike PPAR-alpha and PPAR-gamma, PPAR-delta is ubiquitously expressed, and its activity is key to maintaining proper metabolic homeostasis within the liver. PPAR-delta not only regulates physiologic processes of lipid, glucose, and bile acid metabolism but also attenuates pathologic responses to alcohol metabolism, inflammation, fibrosis, and carcinogenesis, and is considered an important therapeutic target in liver diseases. Promising results have been reported in clinical trials for PPAR-delta agonists in liver disease, and the selective agonist seladelpar was recently conditionally approved in the United States as a new treatment option for primary biliary cholangitis. This review provides an overview of PPAR-delta's function and biology in the liver, examines its kinetics and therapeutic potential across different liver diseases, and discusses the current status of clinical trials involving its agonists.

Primary Biliary Cholangitis and Primary Sclerosing Cholangitis Therapy Landscape

Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are rare, and chronic cholestatic diseases that can progress to liver failure. The goals of treatment are to halt the progression of liver disease to cirrhosis and/or liver failure, and alleviate symptoms associated with these diseases. Ursodeoxycholic acid has historically been the first-line treatment of PBC, with obeticholic acid and fibrates used as second-line or adjunctive therapies. However, the treatment landscape is rapidly expanding. Recently, 2 new second-line agents gained US Food and Drug Administration approval for the treatment of PBC, and several other therapies remain under investigation with promising results. Although significant progress has been made in the development of therapies for PBC, there are no current approved treatments of PSC other than liver transplantation although several emerging therapies have shown encouraging results. This review outlines the current and upcoming treatments of PBC and PSC.

PPARα agonist ameliorates cholestatic liver injury by regulating hepatic macrophage homeostasis

Inflammatory response plays an essential role in the pathogenesis of cholestatic liver injury. PPARα agonists have been shown to regulate bile acid homeostasis and hepatic inflammation. However, the immunoregulatory mechanisms through which PPARα agonists ameliorate cholestatic liver injury remain unclear. In this study, surgical bile duct ligation was performed to establish a mouse model of cholestasis. Our study revealed that PPARα agonist alleviated cholestatic liver injury in mice by suppressing inflammatory response, reducing neutrophil infiltration, and promoting M2-like macrophage polarization. CyTOF analysis showed that PPARα agonist increased the proportion of anti-inflammatory F4/80hiCD44+MHCII- M2-like macrophages while decreasing the proportion of pro-inflammatory CD64+CX3CR1+CCR2hiVISTAhiCD172a+CD44hi M1-like MoMFs. Additionally, scRNA-seq indicated that PPARα agonist regulated the developmental trajectory and homeostasis of hepatic macrophages. Mechanistically, PPARα agonist may influence the expression of immune regulators in heterogeneous macrophages to exert protective effects against cholestasis. In addition, the CCL and MIF signaling pathways may participate in the communication among hepatic immune cells, including macrophages, neutrophils, natural killer cells, and dendritic cells, in response to the PPARα agonist. In conclusions, PPARα agonist alleviated cholestatic liver injury by attenuating the inflammatory response and restoring hepatic macrophage homeostasis. This study might enhance the understanding of the immunoregulatory mechanisms of PPARα agonists, providing promising therapeutic targets for cholestatic liver diseases.

PPAR agonists for the treatment of cholestatic liver diseases: Over a decade of clinical progress

Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are characterized by the destruction of the small bile ducts and the formation of multifocal biliary strictures, respectively, impairing bile flow. This leads to the hepatic accumulation of bile acids, causing liver injury and the risk of progression to cirrhosis and liver failure. First-line therapy for PBC is ursodeoxycholic acid, although up to 40% of treated individuals are incomplete responders, and there is no effective therapy for PSC, highlighting the need for better therapeutic options in these diseases. In addition, pruritus is a common symptom of cholestasis that has severe consequences for quality of life and is often undertreated or untreated. Nuclear receptors are pharmacological targets to treat cholestasis due to their multifactorial regulation of hepatic enzymatic pathways, particularly in bile acid metabolism. The peroxisome proliferator-activated receptor (PPAR) is of significant clinical interest due to its role in regulating bile acid synthesis and detoxification pathways. PPAR agonism by fibrates has traditionally been explored due to PPARα's expression in the liver; however, recent interest has expanded to focus on newer PPAR agonists that activate other PPAR isoforms, for example, δ, γ, alone or in combination. Several PPAR agonists have been investigated as second-line therapy for people living with PBC, including the recent accelerated United States Food and Drug Administration approval of elafibranor and seladelpar. This review evaluates available data on the efficacy and safety of the five PPAR agonists investigated for the treatment of cholestasis and associated pruritus in PBC and PSC, namely fenofibrate, bezafibrate, saroglitazar, elafibranor, and seladelpar.

Management of primary sclerosing cholangitis: Current state-of-the-art

Primary sclerosing cholangitis is a chronic liver disease characterized by progressive inflammation and fibrosis of medium-large bile ducts, most commonly in association with inflammatory bowel disease. Most patients have a progressive disease course, alongside a heightened risk of hepatobiliary and colorectal cancer. Medical therapies are lacking, and this, in part, reflects a poor grasp of disease biology. As a result, current management is largely supportive, with liver transplantation an effective life-prolonging intervention when needed, but not one that cures disease. Emerging therapies targeting disease progression, as well as symptoms such as pruritus, continue to be explored. The trial design is increasingly cognizant of the application of thoughtful inclusion criteria, as well as better endpoints aimed at using surrogates of disease that can identify treatment benefits early. This is hoped to facilitate much-needed advances toward developing safe and effective interventions for patients.

PPAR-Mediated Bile Acid Glucuronidation: Therapeutic Targets for the Treatment of Cholestatic Liver Diseases

Cholestatic liver diseases, including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), result from an impairment of bile flow that leads to the hepatic retention of bile acids, causing liver injury. Until recently, the only approved treatments for PBC were ursodeoxycholic acid (UDCA) and obeticholic acid (OCA). While these therapies slow the progression of PBC in the early stage of the disease, approximately 40% of patients respond incompletely to UDCA, and advanced cases do not respond. UDCA does not improve survival in patients with PSC, and patients often have dose-limiting pruritus reactions to OCA. Left untreated, these diseases can progress to fibrosis and cirrhosis, resulting in liver failure and the need for transplantation. These shortcomings emphasize the urgent need for alternative treatment strategies. Recently, nuclear hormone receptors have been explored as pharmacological targets for adjunct therapy because they regulate enzymes involved in bile acid metabolism and detoxification. In particular, the peroxisome proliferator-activated receptor (PPAR) has emerged as a therapeutic target for patients with PBC or PSC who experience an incomplete response to UDCA. PPARα is predominantly expressed in the liver, and it plays an essential role in the regulation of cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT) enzymes, both of which are critical enzyme families involved in the regulation of bile acid metabolism and glucuronidation, respectively. Importantly, PPARα agonists, e.g., fenofibrate, have shown therapeutic benefits in reducing elevated markers of cholestasis in patients with PBC and PSC, and elafibranor, the first PPAR (dual α, β/δ) agonist, has been FDA-approved for the second-line treatment of PBC. Additionally, newer PPAR agonists that target various PPAR isoforms (β/δ, γ) are under development as an adjunct therapy for PBC or PSC, although their impact on glucuronidation pathways are less characterized. This review will focus on PPAR-mediated bile acid glucuronidation as a therapeutic pathway to improve outcomes for patients with PBC and PSC.

The role of peroxisome proliferator-activated receptors in the regulation of bile acid metabolism

Bile acids are synthesized from cholesterol in the liver. Dysregulation of bile acid homeostasis, characterized by excessive accumulation in the liver, gallbladder and blood, can lead to hepatocellular damage and the development of cholestatic liver disease. Nuclear receptors play a crucial role in the control of bile acid metabolism by efficiently regulating bile acid synthesis and transport in the liver. Among these receptors, peroxisome proliferator-activated receptor (PPAR), a ligand-activated transcription factor belonging to the nuclear hormone receptor superfamily, controls the expression of genes involved in adipogenesis, lipid metabolism, inflammation and glucose homeostasis and has emerged as a potential therapeutic target for the treatment of the metabolic syndrome in the past two decades. Emerging evidence suggests that PPAR activation holds promise as a therapeutic target for cholestatic liver disease, as it affects both bile acid production and transport. This review provides a comprehensive overview of recent advances in elucidating the role of PPAR in the regulation of bile acid metabolism, highlighting the current position of PPAR agonists in the treatment of primary biliary cholangitis. By summarizing the specific regulatory effects of PPAR on bile acids, this review contributes to the exploration of novel therapeutic strategies for cholestatic liver diseases.

Effectiveness of Fenofibrate in Treatment-Naive Patients With Primary Biliary Cholangitis: A Randomized Clinical Trial

INTRODUCTION

Primary biliary cholangitis (PBC) is a progressive autoimmune liver disease, and patients with inadequate response to ursodeoxycholic acid (UDCA) treatment show reduced long-term survival. Recent studies have shown that fenofibrate is an effective off-label therapy for PBC. However, prospective studies on biochemical response including the timing of fenofibrate administration are lacking. This study is aimed to evaluate the efficacy and safety of fenofibrate in UDCA treatment-naive patients with PBC.

METHODS

A total of 117 treatment-naive patients with PBC were recruited from the Xijing Hospital for a 12-month randomized, parallel, and open-label clinical trial. Study participants were assigned to receive either UDCA standard dose (UDCA-only group) or fenofibrate at a daily dose of 200 mg in addition to UDCA (UDCA-Fenofibrate group).

RESULTS

The primary outcome was biochemical response percentage in patients according to the Barcelona criterion at 12 months. In the UDCA-Fenofibrate group, 81.4% (69.9%-92.9%) of patients achieved the primary outcome and 64.3% (51.9%-76.8%) in the UDCA-only group achieved the primary outcome ( P = 0.048). There was no difference between the 2 groups in noninvasive measures of liver fibrosis and biochemical markers other than alkaline phosphatase at 12 months. Creatinine and transaminases levels in the UDCA-Fenofibrate group increased within the first month, then returned to normal, and remained stable thereafter until the end of the study, even in patients with cirrhosis.

DISCUSSION

In this randomized clinical trial in treatment-naive patients with PBC, the combination of fenofibrate and UDCA resulted in a significantly higher biochemical response rate. Fenofibrate seemed to be well-tolerated in patients.

Recent Advances in the Management of Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by fibroinflammatory damage to the biliary tree, typically in the setting of inflammatory bowel disease, with an increased risk of liver failure and cholangiocarcinoma. A complex pathophysiology, heterogeneity in clinical features, and the rare nature of the disease have contributed to the lack of effective therapy to date. However, recent innovations in the characterization and prognostication of patients with PSC, in addition to new tools for medical management and emerging pharmacologic agents, give rise to the potential for meaningful progress in the next several years. This review summarizes current concepts in PSC and highlights particular areas in need of further study.

New IMB16-4 Hot-Melt Extrusion Preparation Improved Oral Bioavailability and Enhanced Anti-Cholestatic Effect on Rats

Background

Cholestasis is challenging to treat due to lacked effective drugs. N-(3,4,5-trichlorophenyl)-2 (3-nitrobenzenesulfonamido) benzamide, abbreviated as IMB16-4, which may be effective for the treatment of cholestasis. However, its poor solubility and bioavailability seriously obstruct the research programs.

Methods

A hot-melt extrusion (HME) preparation was first applied to increase the bioavailability of IMB16-4, the oral bioavailability, anti-cholestatic effect and vitro cytotoxicity of IMB16-4 and IMB16-4-HME were evaluated. Meanwhile, the molecular docking and qRT-PCR were used to validate the mechanism behind.

Results

The oral bioavailability of IMB16-4-HME improved 65-fold compared with that of pure IMB16-4. Pharmacodynamics results demonstrated that IMB16-4-HME prominently decreased the serum levels of total bile acid (TBA) and alkaline phosphatase (ALP), but elevated the level of total bilirubin (TBIL) and direct bilirubin (DBIL). Histopathology revealed that IMB16-4-HME at lower dose exhibited stronger anti-cholestatic effect compared with pure IMB16-4. In addition, molecular docking demonstrated that IMB16-4 has great affinity with PPARα, and qRT-PCR results revealed that IMB16-4-HME significantly elevated the mRNA expression level of PPARα, but decreased the mRNA level of CYP7A1. Cytotoxicity assays demonstrated that the hepatotoxicity of IMB16-4-HME was absolutely attributed to IMB16-4, and the excipients of IMB16-4-HME may increase the drug load within HepG2 cells.

Conclusion

The HME preparation significantly increased the oral bioavailability and anti-cholestatic effect of pure IMB16-4, but caused liver injury at high dose, which require a dose balance between the curative effect and safety in the future research.

Nigakinone alleviates DSS-induced experimental colitis via regulating bile acid profile and FXR/NLRP3 signaling pathways

The correlation of bile acid (BA) metabolism disorder with the pathogenesis of ulcerative colitis (UC) is realized nowadays. Farnesoid X receptor (FXR), a controller for BA homeostasis and inflammation, is a promising target for UC therapy. Nigakinone has potential therapeutic effects on colitis. Herein, we investigated the anti-UC effects and mechanism of nigakinone in colitic animals induced by dextran sulfate sodium (DSS). The related targets involved in the nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing 3 (NLRP3) signaling pathway were measured. BA-targeted metabolomics was employed to reveal the regulatory effects of nigakinone on BA profile in colitis, while expressions of FXR and its mediated targets referring to BA enterohepatic circulation were determined. The critical role of FXR in the treatment of nigakinone for colitis was studied via molecule-docking, dual-luciferase reporter® (DLR™) assays, FXR silencing cells, and FXR knockout mice. Results showed nigakinone attenuated DSS-induced colitis symptoms, including excessive inflammatory response by NLRP3 activation, and injury of the intestinal mucosal barrier. Nigakinone regulated BA disorders by controlling cholesterol hydroxylase and transporters mediated by FXR, then decreased BA accumulation in colon. Molecular-docking and DLR™ assays indicated FXR might be a target of nigakinone. In vitro, nigakinone restrained BA-induced inflammation and cell damage via FXR activation and inhibition of inflammatory cytokines. However, ameliorating effects of nigakinone on colitis were suppressed by FXR knockout or silencing in vivo or in vitro. Taken together, nigakinone ameliorated experimental colitis via regulating BA profile and FXR/NLRP3 signaling pathway.

Fenofibrate Downregulates NF-κB Signaling to Inhibit Pro-inflammatory Cytokine Secretion in Human THP-1 Macrophages and During Primary Biliary Cholangitis

Chronic liver diseases, e.g., cholestasis, are negatively impacted by inflammation, which further aggravates liver injury. Pharmacotherapy targeting the peroxisome proliferator-activated receptor alpha (PPARα), e.g., fenofibrate, has recently become an off-label therapeutic option for patients with refractory cholestasis. Clinical studies show that fibrates can reduce some pro-inflammatory cytokines in primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC); however, its anti-inflammatory mechanisms have not been established. Numerous cytokines are regulated by the transcription factor nuclear receptor kappa B (NF-κB), and PPARα has been shown to interfere with NF-κB signaling. This study investigates the anti-inflammatory mechanism of fenofibrate by inhibiting NF-κB signaling in human macrophages and clinical outcomes in patients with PBC. For adult patients with PBC and an incomplete biochemical response to ursodiol (13-15 mg/kg/day), the addition of fenofibrate (145-160 mg/day) reduced serum levels of TNF-α, IL-17A, IL-1β, IL-6, IL-8, and MCP-1 and increased IL-10. In THP-1 cells, pretreatment with fenofibrate (125 μM) reduced LPS-stimulated peak concentrations of IL-1β (- 63%), TNF-α (- 88%), and IL-8 (- 54%), in a PPARα-dependent manner. Treatment with fenofibrate prior to LPS significantly decreased nuclear NF-κB p50 and p65 subunit binding by 49% and 31%, respectively. Additionally, fenofibrate decreased nuclear NF-κB p50 and p65 protein expression by 66% and 55% and increased cytoplasmic levels by 53% and 54% versus LPS alone, respectively. Lastly, fenofibrate increased IκBα levels by 2.7-fold (p < 0.001) vs. LPS. These data demonstrate that fenofibrate reduces pro-inflammatory cytokines section by inhibiting in NF-κB signaling, which likely contribute to its anti-inflammatory effects during chronic liver diseases.

Suppression of Hepatic PPARα in Primary Biliary Cholangitis Is Modulated by miR-155

Background: PPARα is a ligand-activated transcription factor that shows protective effects against metabolic disorders, inflammation and apoptosis. Primary biliary cholangitis and primary sclerosing cholangitis result in the intrahepatic accumulation of bile acids that leads to liver dysfunction and damage. Small, non-coding RNAs such as miR-155 and miR-21 are associated with silencing PPARα. Methods: The expression of miR-155, miR-21 and PPARα were evaluated using real-time PCR on liver tissue, as well as on human hepatocytes (HepG2) or cholangiocytes (NHCs) following exposure to lipopolysaccharide (LPS), glycodeoxycholic acid (GCDCA), lithocholic acid (LCA) and/or ursodeoxycholic acid (UDCA). Results: A reduction of PPARα in primary biliary cholangitis (PBC) livers was associated with miR-21 and miR-155 upregulation. Experimental overexpression of either miR-155 or miR-21 inhibited PPARα in hepatocytes, whereas, in cholangiocytes, only miR-21 suppressed PPARα. Both GCDCA and LCA induced the cell type-specific upregulation of miR-155 or miR-21. In HepG2, LPS-induced miR-155 expression was blocked by a cotreatment with UDCA and was associated with PPARα upregulation. In NHC cells, the expression of miR-21 was induced by LPS but did not affect PPARα expression. Conclusions: Hepatic PPARα expression is reduced in PBC livers as a likely result of miR-155 overexpression. UDCA effectively reduced both baseline and LPS-induced miR-155 expression, thus preventing the suppression of PPARα.

PPARα: A potential therapeutic target of cholestasis

The accumulation of bile acids in the liver leads to the development of cholestasis and hepatocyte injury. Nuclear receptors control the synthesis and transport of bile acids in the liver. Among them, the farnesoid X receptor (FXR) is the most common receptor studied in treating cholestasis. The activation of this receptor can reduce the amount of bile acid synthesis and decrease the bile acid content in the liver, alleviating cholestasis. Ursodeoxycholic acid (UDCA) and obeticholic acid (OCA) have a FXR excitatory effect, but the unresponsiveness of some patients and the side effect of pruritus seriously affect the results of UDCA or OCA treatment. The activator of peroxisome proliferator-activated receptor alpha (PPARα) has emerged as a new target for controlling the synthesis and transport of bile acids during cholestasis. Moreover, the anti-inflammatory effect of PPARα can effectively reduce cholestatic liver injury, thereby improving patients’ physiological status. Here, we will focus on the function of PPARα and its involvement in the regulation of bile acid transport and metabolism. In addition, the anti-inflammatory effects of PPARα will be discussed in some detail. Finally, we will discuss the application of PPARα agonists for cholestatic liver disorders.

Predictive value of serum bile acids as metabolite biomarkers for liver cirrhosis: a systematic review and meta-analysis

INTRODUCTION

A large number of studies have explored the potential biomarkers for detecting liver cirrhosis in an early stage, yet consistent conclusions are still warranted.

OBJECTIVES

To conduct a review and a meta-analysis of the existing studies that test the serum level of bile acids in cirrhosis as the potential biomarkers to predict cirrhosis.

METHODS

Six databases had been searched from inception date to April 12, 2021. Screening and selection of the records were based on the inclusion criteria. The risk of bias was assessed with the Newcastle-Ottawa quality assessment scale (NOS). Mean difference (MD) and confidence intervals 95% (95% CI) were calculated by using the random effect model for the concentrations of bile acids in the meta-analysis, and I² statistic was used to measure studies heterogeneity. This study was registered on PROSPERO.

RESULTS

A total of 1583 records were identified and 31 studies with 2679 participants (1263 in the cirrhosis group, 1416 in the healthy control group) were included. The quality of included studies was generally high, with 25 studies (80.6%) rated over 7 stars. A total of 45 bile acids or their ratios in included studies were extracted. 36 increased in the cirrhosis group compared with those of the healthy controls by a qualitative summary, 5 decreased and 4 presented with mixing results. The result of meta-analysis among 12 studies showed that 13 bile acids increased, among which four primary conjugated bile acids showed the most significant elevation in the cirrhosis group: GCDCA (MD = 11.38 μmol/L, 95% CI 8.21-14.55, P < 0.0001), GCA (MD = 5.72 μmol/L, 95% CI 3.47-7.97, P < 0.0001), TCDCA (MD = 3.57 μmol/L, 95% CI 2.64-4.49, P < 0.0001) and TCA (MD = 2.14 μmol/L, 95% CI 1.56-2.72, P < 0.0001). No significant differences were found between the two groups in terms of DCA (MD = - 0.1 μmol/L, 95% CI - 0.18 to - 0.01, P < 0.0001) and LCA (MD = - 0.01 μmol/L, 95% CI - 0.01 to - 0.02, P < 0.0001), UDCA (MD = - 0.14 μmol/L, 95% CI - 0.04 to - 0.32, P < 0.0001), and TLCA (MD = 0 μmol/L, 95% CI 0-0.01, P < 0.0001). Subgroup analysis in patients with hepatitis B cirrhosis showed similar results.

CONCLUSION

Altered serum bile acids profile seems to be associated with cirrhosis. Some specific bile acids (GCA, GCDCA, TCA, and TCDCA) may increase with the development of cirrhosis, which possibly underlay their potential role as predictive biomarkers for cirrhosis. Yet this predictive value still needs further investigation and validation in larger prospective cohort studies.