Expression of hepatic Fibroblast Growth Factor 19 is enhanced in Primary Biliary Cirrhosis and correlates with severity of the disease

Endocrine fibroblast growth factors in domestic animals

Fibroblast growth factors (FGFs) are a group of structurally homologous yet functionally pleiotropic proteins. Canonical and intracellular FGFs have primarily autocrine or paracrine effects. However, the FGF19 subfamily, composed of FGF15/19, FGF21, and FGF23, act as endocrine hormones that regulate bile acid, metabolic, and phosphorus homeostasis, respectively. Current research in human and rodent models demonstrates the potential of these endocrine FGFs to target various diseases, including disorders of inherited hypophosphatemia, chronic liver disease, obesity, and insulin resistance. Many diseases targeted for therapeutic use in humans have pathophysiological overlaps in domestic animals. Despite the potential clinical and economic impact, little is known about endocrine FGFs and their signaling pathways in major domestic animal species compared with humans and laboratory animals. This review aims to describe the physiology of these endocrine FGFs, discuss their current therapeutic use, and summarize the contemporary literature regarding endocrine FGFs in domestic animals, focusing on potential future directions.

The endocrine FGFs axis: A systemic anti-fibrotic response that could prevent pulmonary fibrogenesis?

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease for which therapeutic options are limited, with an unmet need to identify new therapeutic targets. IPF is thought to be the consequence of repeated microlesions of the alveolar epithelium, leading to aberrant epithelial-mesenchymal communication and the accumulation of extracellular matrix proteins. The reactivation of developmental pathways, such as Fibroblast Growth Factors (FGFs), is a well-described mechanism during lung fibrogenesis. Secreted FGFs with local paracrine effects can either exert an anti-fibrotic or a pro-fibrotic action during this pathological process through their FGF receptors (FGFRs) and heparan sulfate residues as co-receptors. Among FGFs, endocrine FGFs (FGF29, FGF21, and FGF23) play a central role in the control of metabolism and tissue homeostasis. They are characterized by a low affinity for heparan sulfate, present in the cell vicinity, allowing them to have endocrine activity. Nevertheless, their interaction with FGFRs requires the presence of mandatory co-receptors, alpha and beta Klotho proteins (KLA and KLB). Endocrine FGFs are of growing interest for their anti-fibrotic action during liver, kidney, or myocardial fibrosis. Innovative therapies based on FGF19 or FGF21 analogs are currently being studied in humans during liver fibrosis. Recent data report a similar anti-fibrotic action of endocrine FGFs in the lung, suggesting a systemic regulation of the pulmonary fibrotic process. In this review, we summarize the current knowledge on the protective effect of endocrine FGFs during the fibrotic processes, with a focus on pulmonary fibrosis.

FXR-FGF19 signaling in the gut-liver axis is dysregulated in patients with cirrhosis and correlates with impaired intestinal defence

BACKGROUND AND AIMS

Experimental studies linked dysfunctional Farnesoid X receptor (FXR)-fibroblast growth factor 19 (FGF19) signaling to liver disease. This study investigated key intersections of the FXR-FGF19 pathway along the gut-liver axis and their link to disease severity in patients with cirrhosis.

METHODS

Patients with cirrhosis undergoing hepatic venous pressure gradient measurement (cohort-I n = 107, including n = 53 with concomitant liver biopsy; n = 5 healthy controls) or colonoscopy with ileum biopsy (cohort-II n = 37; n = 6 controls) were included. Hepatic and intestinal gene expression reflecting FXR activation and intestinal barrier integrity was assessed. Systemic bile acid (BA) and FGF19 levels were measured.

RESULTS

Systemic BA and FGF19 levels correlated significantly (r = 0.461; p < 0.001) and increased with cirrhosis severity. Hepatic SHP expression decreased in patients with cirrhosis (vs. controls; p < 0.001), indicating reduced FXR activation in the liver. Systemic FGF19 (r = -0.512, p < 0.001) and BA (r = -0.487, p < 0.001) levels correlated negatively with hepatic CYP7A1, but not SHP or CYP8B1 expression, suggesting impaired feedback signaling in the liver. In the ileum, expression of FXR, SHP and FGF19 decreased in patients with cirrhosis, and interestingly, intestinal FGF19 expression was not linked to systemic FGF19 levels. Intestinal zonula occludens-1, occludin, and alpha-5-defensin expression in the ileum correlated with SHP and decreased in patients with decompensated cirrhosis as compared to controls.

CONCLUSIONS

FXR-FGF19 signaling is dysregulated at essential molecular intersections along the gut-liver axis in patients with cirrhosis. Decreased FXR activation in the ileum mucosa was linked to reduced expression of intestinal barrier proteins. These human data call for further mechanistic research on interventions targeting the FXR-FGF19 pathway in patients with cirrhosis.

CLINICAL TRIAL NUMBER

NCT03267615.

Progress in Biomarkers Related to Biliary Atresia

Biliary atresia (BA) is a congenital cholestatic disease that can seriously damage children's liver function. It is one of the main reasons for liver transplantation in children. Early diagnosis of BA is crucial to the prognosis of patients, but there is still a lack of reliable non-invasive diagnostic methods. Additionally, as some children are in urgent need of liver transplantation, evaluating the stage of liver fibrosis and postoperative native liver survival in children with BA using a straightforward, efficient, and less traumatic method is a major focus of doctors. In recent years, an increasing number of BA-related biomarkers have been identified and have shown great potential in the following three aspects of clinical practice: diagnosis, evaluation of the stage of liver fibrosis, and prediction of native liver survival. This review focuses on the pathophysiological function and clinical application of three novel BA-related biomarkers, namely MMP-7, FGF-19, and M2BPGi. Furthermore, progress in well-known biomarkers of BA such as gamma-glutamyltransferase, circulating cytokines, and other potential biomarkers is discussed, aiming to provide a reference for clinical practice.

Targeting the FGF19-FGFR4 pathway for cholestatic, metabolic, and cancerous diseases

Human fibroblast growth factor 19 (FGF19, or FGF15 in rodents) plays a central role in controlling bile acid (BA) synthesis through a negative feedback mechanism. This process involves a postprandial crosstalk between the BA-activated ileal farnesoid X receptor and the hepatic Klotho beta (KLB) coreceptor complexed with fibrobalst growth factor receptor 4 (FGFR4) kinase. Additionally, FGF19 regulates glucose, lipid, and energy metabolism by coordinating responses from functional KLB and FGFR1-3 receptor complexes on the periphery. Pharmacologically, native FGF19 or its analogs decrease elevated BA levels, fat content, and collateral tissue damage. This makes them effective in treating both cholestatic diseases such as primary biliary or sclerosing cholangitis (PBC or PSC) and metabolic abnormalities such as nonalcoholic steatohepatitis (NASH). However, chronic administration of FGF19 drives oncogenesis in mice by activating the FGFR4-dependent mitogenic or hepatic regenerative pathway, which could be a concern in humans. Agents that block FGF19 or FGFR4 signaling have shown great potency in preventing FGF19-responsive hepatocellular carcinoma (HCC) development in animal models. Recent phase 1/2 clinical trials have demonstrated promising results for several FGF19-based agents in selectively treating patients with PBC, PSC, NASH, or HCC. This review aims to provide an update on the clinical development of both analogs and antagonists targeting the FGF19-FGFR4 signaling pathway for patients with cholestatic, metabolic, and cancer diseases. We will also analyze potential safety and mechanistic concerns that should guide future research and advanced trials.

A new FGF15/19-mediated gut-to-heart axis controls cardiac hypertrophy

FGF15 and its human orthologue, FGF19, are members of the endocrine FGF family and are secreted by ileal enterocytes in response to bile acids. FGF15/19 mainly targets the liver, but recent studies indicate that it also regulates skeletal muscle mass and adipose tissue plasticity. The aim of this study was to determine the role(s) of the enterokine FGF15/19 during the development of cardiac hypertrophy. Studies in a cohort of humans suffering from heart failure showed increased circulating levels of FGF19 compared with control individuals. We found that mice lacking FGF15 did not develop cardiac hypertrophy in response to three different pathophysiological stimuli (high-fat diet, isoproterenol, or cold exposure). The heart weight/tibia length ratio and the cardiomyocyte area (as measures of cardiac hypertrophy development) under hypertrophy-inducing conditions were lower in Fgf15-null mice than in wild-type mice, whereas the levels of the cardiac damage marker atrial natriuretic factor (Nppa) were up-regulated. Echocardiographic measurements showed similar results. Moreover, the genes involved in fatty acid metabolism were down-regulated in Fgf15-null mice. Conversely, experimental increases in FGF15 induced cardiac hypertrophy in vivo, without changes in Nppa and up-regulation of metabolic genes. Finally, in vitro studies using cardiomyocytes showed that FGF19 had a direct effect on these cells promoting hypertrophy. We have identified herein an inter-organ signaling pathway that runs from the gut to the heart, acts through the enterokine FGF15/19, and is involved in cardiac hypertrophy development and regulation of fatty acid metabolism in the myocardium. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Anthocyanin-Rich Butterfly Pea Flower Extract Ameliorating Low-Grade Inflammation in a High-Fat-Diet and Lipopolysaccharide-Induced Mouse Model

This study aimed to explore the enhancive effects of butterfly pea flower (BF) extracts on metabolic and immune homeostasis in a low-grade inflammation mouse model. The BF extract was found to contain mainly anthocyanins among other flavonoids. BF supplementation alleviated metabolic endotoxemia by lowering the plasma glucose, lipopolysaccharide (LPS), and tumor necrosis factor-α (TNF-α) levels and restored lipid metabolism and the balance between Treg and Th17 cells, thereby inhibiting the dysfunctional liver and abdominal white adipose tissues. BF extract increased the tight junction protein expression and reduced the expression of proinflammatory cytokines, therefore sustaining the colonic mucosa structure. Furthermore, BF extracts reshaped the gut microbiota structure characterized by significantly promoted SCFA-producing gut microbiota such as Akkermansia and Butyricicoccaceae. Additionally, BF extracts enhanced fecal primary bile acid (BA) levels and modulated bile acid signaling in the liver and ileum to facilitate BA synthesis for the restoration of lipid metabolism. In summary, anthocyanin-enriched BF extracts alleviated the profound negative dietary alterations and helped maintain the metabolic health by modulating the various aspects of the gut microenvironment and enhancing hepatic bile acid synthesis.

Pharmaceutical Strategies to Improve Druggability of Potential Drug Candidates in Nonalcoholic Fatty Liver Disease Therapy

Nonalcoholic fatty liver disease (NAFLD) has become globally prevalent and is the leading cause of chronic liver disease. Although NAFLD is reversible without medical intervention in the early stage, the condition could be sequentially worsened to nonalcoholic steatohepatitis (NASH) and, eventually, cirrhosis and hepatic cancer. The progression of NAFLD is related to various factors such as genetics, pre-disposed metabolic disorders, and immunologic factors. Thankfully, to date, there have been accumulating research efforts and, as a result, different classes of potent drug candidates have been discovered. In addition, there have also been various attempts to explore pharmaceutical strategies to improve the druggability of drug candidates. In this review, we provided a brief overview of the drug candidates that have undergone clinical trials. In the latter part, strategies for developing better drugs are discussed.

Ductular reaction in non-alcoholic fatty liver disease: When Macbeth is perverted

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction)-associated fatty liver disease is the leading cause of chronic liver diseases defined as a disease spectrum comprising hepatic steatosis, non-alcoholic steatohepatitis (NASH), liver fibrosis, cirrhosis, and hepatic carcinoma. NASH, characterized by hepatocyte injury, steatosis, inflammation, and fibrosis, is associated with NAFLD prognosis. Ductular reaction (DR) is a common compensatory reaction associated with liver injury, which involves the hepatic progenitor cells (HPCs), hepatic stellate cells, myofibroblasts, inflammatory cells (such as macrophages), and their secreted substances. Recently, several studies have shown that the extent of DR parallels the stage of NASH and fibrosis. This review summarizes previous research on the correlation between DR and NASH, the potential interplay mechanism driving HPC differentiation, and NASH progression.

Gut-liver axis: barriers and functional circuits

The gut and the liver are characterized by mutual interactions between both organs, the microbiome, diet and other environmental factors. The sum of these interactions is conceptualized as the gut-liver axis. In this Review we discuss the gut-liver axis, concentrating on the barriers formed by the enterohepatic tissues to restrict gut-derived microorganisms, microbial stimuli and dietary constituents. In addition, we discuss the establishment of barriers in the gut and liver during development and their cooperative function in the adult host. We detail the interplay between microbial and dietary metabolites, the intestinal epithelium, vascular endothelium, the immune system and the various host soluble factors, and how this interplay establishes a homeostatic balance in the healthy gut and liver. Finally, we highlight how this balance is disrupted in diseases of the gut and liver, outline the existing therapeutics and describe the cutting-edge discoveries that could lead to the development of novel treatment approaches.

Serum FGF19 predicts outcomes of Kasai portoenterostomy in biliary atresia

BACKGROUND AND AIMS

Outcomes after Kasai portoenterostomy (KPE) for biliary atresia remain highly variable for unclear reasons. As reliable early biomarkers predicting KPE outcomes are lacking, we studied the prognostic value of FGF19.

APPROACH AND RESULTS

Serum and liver specimens, obtained from biliary atresia patients (N=87) at KPE or age-matched cholestatic controls (N=26) were included. Serum concentration of FGF19 and bile acids, liver mRNA expression of FGF19 , and key regulators of bile acid synthesis were related to KPE outcomes and liver histopathology. Immunohistochemistry and in situ hybridization were used for the localization of liver FGF19 expression. Serum levels (223 vs. 61 pg/mL, p <0.001) and liver mRNA expression of FGF19 were significantly increased in biliary atresia. Patients with unsuccessful KPE (419 vs. 145 pg/mL, p =0.047), and those subsequently underwent liver transplantation (410 vs. 99 pg/mL, p =0.007) had significantly increased serum, but not liver, FGF19, which localized mainly in hepatocytes. In Cox hazard modeling serum FGF19 <109 pg/mL predicted native liver survival (HR: 4.31, p <0.001) also among patients operated <60 days of age (HR: 8.77, p =0.004) or after successful KPE (HR: 6.76, p =0.01). Serum FGF19 correlated positively with increased serum primary bile acids ( R =0.41, p =0.004) and ductular reaction ( R =0.39, p =0.004).

CONCLUSIONS

Increased serum FGF19 at KPE predicted inferior long-term native liver survival in biliary atresia and was associated with unsuccessful KPE, elevated serum primary bile acids, and ductular reaction.

Bile Acids and Biliary Fibrosis

Biliary fibrosis is the driving pathological process in cholangiopathies such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Cholangiopathies are also associated with cholestasis, which is the retention of biliary components, including bile acids, in the liver and blood. Cholestasis may worsen with biliary fibrosis. Furthermore, bile acid levels, composition and homeostasis are dysregulated in PBC and PSC. In fact, mounting data from animal models and human cholangiopathies suggest that bile acids play a crucial role in the pathogenesis and progression of biliary fibrosis. The identification of bile acid receptors has advanced our understanding of various signaling pathways involved in regulating cholangiocyte functions and the potential impact on biliary fibrosis. We will also briefly review recent findings linking these receptors with epigenetic regulatory mechanisms. Further detailed understanding of bile acid signaling in the pathogenesis of biliary fibrosis will uncover additional therapeutic avenues for cholangiopathies.

High prevalence of lower limb atherosclerosis is linked with the gut-liver axis in patients with primary biliary cholangitis

BACKGROUND AND AIMS

Hypercholesterolemia is frequent in people with primary biliary cholangitis (PBC); however, it does not seem to confer an increased risk of cardiovascular disease. We aimed to evaluate the prevalence of peripheral arterial disease in PBC women and its association with the gut-liver axis and systemic inflammation.

METHODS

Thirty patients affected by PBC and hypercholesterolemia were enrolled, with equal-sized groups of women with non-alcoholic fatty liver disease (NAFLD) and healthy controls (CTRL). All patients underwent Doppler ultrasound examination of peripheral arteries, assessment of flow-mediated dilation, quantification of circulating cytokines and vasoactive mediators and characterization of the gut microbiota.

RESULTS

PBC patients had a higher prevalence of lower extremity arterial disease (LEAD) defined as atherosclerotic plaques in any of femoral, popliteal and/or tibial arteries compared with both NAFLD and CTRL women (83.3% vs. 53.3% and 50%, respectively; p = .01). Factors associated with LEAD at univariate analysis were VCAM-1 (p = .002), ICAM-1 (p = .003), and TNF-alpha (p = .04) serum levels, but only VCAM-1 (OR 1.1, 95% CI 1.0-1.1; p = .04) and TNF-alpha (OR 1.12, 95% CI 0.99-1.26; p = .04) were confirmed as independent predictors in the multivariate model. Gut microbiota analysis revealed that Acidaminococcus (FDR = 0.0008), Bifidobacterium (FDR = 0.001) and Oscillospira (FDR = 0.03) were differentially expressed among groups. Acidaminococcus, which was increased in PBC, was positively correlated with TNF-alpha serum levels. Down-regulation of metabolic pathways linked to fatty acid and butyrate metabolism, glyoxylate metabolism and branched-chain amino acids degradation was found in the functional gut metagenome of PBC women.

CONCLUSIONS

LEAD is common in patients affected by PBC and is associated with inflammatory markers and alterations in the gut-liver axis.

Serum Fibroblast Growth Factor 19 as a Biomarker in Hepatitis B Virus-Related Liver Disease

Background: Past research has found that fibroblast growth factor 19 (FGF19) is associated with several hepatic disorders, such as alcoholic liver disease and primary biliary cirrhosis. However, there is currently a lack of relevant studies on the relationship between FGF19 and hepatitis B virus (HBV)-related liver disease. Objectives: This study aimed to assess the role of serum FGF19 as a new biomarker for HBV-related liver disease and provide scientific data to show the clinical value of this biomarker. Methods: A retrospective study included 37 patients with chronic hepatitis B (CHB), 33 patients with HBV-related cirrhosis (HBV-cirrhosis), and 32 patients with HBV-related hepatocellular carcinoma (HBV-HCC). Furthermore, 33 normal people were randomly selected as healthy controls. The serum levels of FGF19 were measured by ELISA. Results: Serum FGF19 levels were increased sequentially in the CHB group, HBV-cirrhosis group, and HBV-HCC group. Furthermore, serum FGF19 levels positively correlated with alpha-fetoprotein, prothrombin time, international normalized ratio, total bilirubin, direct bilirubin, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl-transferase, alkaline phosphatase, total bile acid, serum markers for liver fibrosis, ascites, cirrhosis, Child-Pugh classification and model for end-stage liver disease sodium (MELD-Na) score, while negatively correlated with platelet count, prothrombin activity, and albumin. The diagnostic threshold of serum FGF19 for HBV-related HCC was 165.32 pg/mL, with a sensitivity of 81.25% and specificity of 58.57%. Conclusions: Serum FGF19 levels are positively associated with cholestasis, hepatocyte damage, and liver fibrosis but negatively correlated with liver synthetic function and liver functional reserve in HBV-related liver disease. Diverse changes in serum FGF19 may be used as a predictive marker for the progression of HBV-related liver disease. In addition, serum FGF19 has a potential role in monitoring carcinogenesis in patients with HBV-related liver disease.

Incomplete response to ursodeoxycholic acid in primary biliary cholangitis: criteria, epidemiology, and possible mechanisms

INTRODUCTION

As a common autoimmune disease with the characteristic of early complication, primary biliary cholangitis (PBC) leads to an increasing number of mortalities among people with end-stage liver disease (ESLD) waiting for liver transplantation. Ursodeoxycholic acid (UDCA) is the only approved first-line medicine for PBC, and a good response to treatment could acquire an ideal prognosis. Patients with poor UDCA response usually have more adverse outcomes and worse survival, therefore, the management of this group become a major consideration.

AREAS COVERED

Due to the complexity of race and environment for PBC, different criteria for UDCA response exhibit various predictive performances. Factors affecting UDCA response conditions include gender, age, ethnicity, serum indicators, auto-antibodies, and autoimmune comorbidities, while no agreement has been reached. In this review, we mainly focus on cellular senescence, immune-mediated damage, and vitamin D deficiency as possible mechanisms for UDCA non-responders.

EXPERT OPINION

The pathogenesis of PBC has yet to be clarified. Immunology-related mechanisms and therapy targets ought to be the main effort made for further study. Irrespective of the response condition, UDCA is recommended for routine administration in all PBC patients without contraindication. Ongoing clinical trials of second-line and additional therapy exhibit promising prospects.

The role of gut microbiota in liver regeneration

The liver has unique regeneration potential, which ensures the continuous dependence of the human body on hepatic functions. As the composition and function of gut microbiota has been gradually elucidated, the vital role of gut microbiota in liver regeneration through gut-liver axis has recently been accepted. In the process of liver regeneration, gut microbiota composition is changed. Moreover, gut microbiota can contribute to the regulation of the liver immune microenvironment, thereby modulating the release of inflammatory factors including IL-6, TNF-α, HGF, IFN-γ and TGF-β, which involve in different phases of liver regeneration. And previous research have demonstrated that through enterohepatic circulation, bile acids (BAs), lipopolysaccharide, short-chain fatty acids and other metabolites of gut microbiota associate with liver and may promote liver regeneration through various pathways. In this perspective, by summarizing gut microbiota-derived signaling pathways that promote liver regeneration, we unveil the role of gut microbiota in liver regeneration and provide feasible strategies to promote liver regeneration by altering gut microbiota composition.

New insights into the bile acid-based regulatory mechanisms and therapeutic perspectives in alcohol-related liver disease

Cholestasis is a key causative factor in alcohol-related liver disease (ALD) and variable degrees of cholestasis occur in all stages of ALD. However, the pathogenetic mechanisms and biomarkers associated with cholestasis are not well characterized. Cholestatic disease is marked by the disruption of bile acids (BA) transport and homeostasis. Consequently, in both human and experimental ALD, the disease shows a direct correlation with an imbalance in BA equilibrium, which in turn may also affect the severity of the disease. Modulation of BA metabolism or signaling pathways is increasingly considered as a potential therapeutic strategy for ALD in humans. In this paper, we highlight the key advances made in the past two decades in characterizing the molecular regulatory mechanisms of BA synthesis, enterohepatic circulation, and BA homeostasis. We summarize recent insights into the nature of the linkage between BA dysregulation and ALD, including the abnormal expression of genes involved in BA metabolism, abnormal changes in receptors that regulate BA metabolism, and disturbance in the gut flora engaged in BA metabolism caused by alcohol consumption. Additionally, we provide novel perspectives on the changes in BAs in various stages of ALD. Finally, we propose potential pharmacological therapies for ALD targeting BA metabolism and signaling.

FGF1 Signaling Modulates Biliary Injury and Liver Fibrosis in the Mdr2-/- Mouse Model of Primary Sclerosing Cholangitis

Fibroblast growth factor 1 (FGF1) belongs to a family of growth factors involved in cellular growth and division. MicroRNA 16 (miR-16) is a regulator of gene expression, which is dysregulated during liver injury and insult. However, the role of FGF1 in the progression of biliary proliferation, senescence, fibrosis, inflammation, angiogenesis, and its potential interaction with miR-16, are unknown. In vivo studies were performed in male bile duct-ligated (BDL, 12-week-old) mice, multidrug resistance 2 knockout (Mdr2-/-) mice (10-week-old), and their corresponding controls, treated with recombinant human FGF1 (rhFGF1), fibroblast growth factor receptor (FGFR) antagonist (AZD4547), or anti-FGF1 monoclonal antibody (mAb). In vitro, the human cholangiocyte cell line (H69) and human hepatic stellate cells (HSCs) were used to determine the expression of proliferation, fibrosis, angiogenesis, and inflammatory genes following rhFGF1 treatment. PSC patient and control livers were used to evaluate FGF1 and miR-16 expression. Intrahepatic bile duct mass (IBDM), along with hepatic fibrosis and inflammation, increased in BDL mice treated with rhFGF1, with a corresponding decrease in miR-16, while treatment with AZD4547 or anti-FGF1 mAb decreased hepatic fibrosis, IBDM, and inflammation in BDL and Mdr2-/- mice. In vitro, H69 and HSCs treated with rhFGF1 had increased expression of proliferation, fibrosis, and inflammatory markers. PSC samples also showed increased FGF1 and FGFRs with corresponding decreases in miR-16 compared with healthy controls. Conclusion: Our study demonstrates that suppression of FGF1 and miR-16 signaling decreases the presence of hepatic fibrosis, biliary proliferation, inflammation, senescence, and angiogenesis. Targeting the FGF1 and miR-16 axis may provide therapeutic options in treating cholangiopathies such as PSC.

Fibroblast growth factor 15/19 expression, regulation, and function: An overview

Since the discovery of fibroblast growth factor (FGF)-19 over 20 years ago, our understanding of the peptide and its role in human biology has moved forward significantly. A member of a superfamily of paracrine growth factors regulating embryonic development, FGF19 is unique in that it is a dietary-responsive endocrine hormone linked with bile acid homeostasis, glucose and lipid metabolism, energy expenditure, and protein synthesis during the fed to fasted state. FGF19 achieves this through targeting multiple tissues and signaling pathways within those tissues. The diverse functional capabilities of FGF19 is due to the unique structural characteristics of the protein and its receptor binding in various cell types. This review will cover the current literature on the protein FGF19, its target receptors, and the biological pathways they target through unique signaling cascades.

Physiological and pathophysiological role of endocrine fibroblast growth factors

The endocrine subfamily of fibroblast growth factors (FGF) includes three factors: FGF19, FGF21, FGF23. They act on distal tissues through FGF receptors (FGFRs). The FGFR activation requires two cofactors: α- and β-Klotho, which are structurally related single-pass transmembrane proteins. The endocrine FGFs regulate various metabolic processes involved in the regulation of glucose and lipid metabolism as well as bile acid circulation, vitamin D modulation, and phosphate homeostasis. The FGF-FGFR dysregulation is widely implicated in the pathogenesis of various disorders. Significant alterations in plasma FGF concentration are associated with the most prevalent chronic diseases, including dyslipidemia, type 2 diabetes, cardiovascular diseases, obesity, non-alcoholic fatty liver disease, diseases of the biliary tract, chronic kidney disease, inflammatory bowel disease, osteomalacia, various malignancies, and depression. Therefore, the endocrine FGFs may serve as disease predictors or biomarkers, as well as potential therapeutic targets. Currently, numerous analogues and inhibitors of endocrine FGFs are under development for treatment of various disorders, and recently, a human monoclonal antibody against FGF23 has been approved for treatment of X-linked hypophosphatemia. The aim of this review is to summarize the current data on physiological and pathophysiological actions of the endocrine FGF subfamily and recent research concerning the therapeutic potential of the endocrine FGF pathways.

Assessment of fibroblast growth factor 19 as a non-invasive serum marker for hepatocellular carcinoma

BACKGROUND

Fibroblast growth factor 19 (FGF-19) is one of the founding members of the endocrine FGF subfamily. Recently, it has been the subject of much interest owing to its role in various physiological processes affecting glucose and lipid metabolism and the regulation of bile acid secretion as well as cell proliferation, differentiation, and motility. Additionally, FGF-19 secretion in an autocrine style has reportedly contributed to cancer progression in various types of malignancies including hepatocellular carcinoma (HCC).

AIM

To estimate the serum FGF-19 concentrations in HCC cases and assess its diagnostic performance for the detection of HCC.

METHODS

We recruited 90 adult participants and divided them into three equal groups: Healthy controls, cirrhosis patients, and HCC patients. Serum FGF-19 concentrations were measured using the Human FGF-19 ELISA kit.

RESULTS

We detected a high statistically significant difference in serum FGF-19 levels among the three groups. The highest level was observed in the HCC group, followed by the cirrhosis and control groups (236.44 ± 40.94 vs 125.63 ± 31.54 vs 69.60 ± 20.90 pg/mL, respectively, P ≤ 0.001). FGF-19 was positively correlated with alpha fetoprotein (AFP; r = 0.383, P = 0.003) and international normalised ratio (r = 0.357, P = 0.005), while it was negatively correlated with albumin (r = -0.500, P ≤ 0.001). For the detection of HCC, receiver operating characteristic curve analysis showed that the best cut-off point of AFP was > 8.2 ng/mL with an area under the curve (AUC) of 0.78, sensitivity of 63.33%, specificity of 83.33%, positive predictive value (PPV) of 79.2%, negative predictive value (NPV) of 69.4%, and total accuracy of 78%. However, FGF-19 at a cut-off point > 180 pg/mL had an AUC of 0.98, sensitivity of 100%, specificity of 90.0%, PPV of 90.0%, NPV of 100%, and total accuracy of 98%.

CONCLUSION

FGF-19 represents a possible novel non-invasive marker for HCC. It may improve the prognosis of HCC patients due to its utility in several aspects of HCC detection and management.

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.

Mast Cells Regulate Ductular Reaction and Intestinal Inflammation in Cholestasis Through Farnesoid X Receptor Signaling

BACKGROUND AND AIMS

Cholestasis is characterized by increased total bile acid (TBA) levels, which are regulated by farnesoid X receptor (FXR)/FGF15. Patients with primary sclerosing cholangitis (PSC) typically present with inflammatory bowel disease (IBD). Mast cells (MCs) (i) express FXR and (ii) infiltrate the liver during cholestasis promoting liver fibrosis. In bile-duct-ligated (BDL) MC-deficient mice (B6.Cg-Kit^W-sh /HNihrJaeBsmJ [Kit^W-sh ]), ductular reaction (DR) and liver fibrosis decrease compared with BDL wild type, and MC injection exacerbates liver damage in normal mice.

APPROACH AND RESULTS

In this study, we demonstrated that MC-FXR regulates biliary FXR/FGF15, DR, and hepatic fibrosis and alters intestinal FXR/FGF15. We found increased MC number and biliary FXR expression in patients with liver injury compared with control. Histamine and FGF19 serum levels and small heterodimer partner expression increase in patients PSC and PSC-IBD compared with healthy controls. MC injection increased liver damage, DR, inflammation, biliary senescence/senescence-associated secretory phenotype (SASP), fibrosis, and histamine in Kit^W-sh mice. Inhibition of MC-FXR before injection reduced these parameters. BDL and Kit^W-sh mice injected with MCs displayed increased TBA content, biliary FXR/FGF15, and intestinal inflammation, which decreased in BDL Kit^W-sh and Kit^W-sh mice injected with MC-FXR. MCs increased ileal FXR/FGF15 expression in Kit^W-sh mice that was reduced following FXR inhibition. BDL and multidrug resistance 2/ATP-binding cassette family 2 member 4 knockout (Mdr2^-/- ) mice, models of PSC, displayed increased intestinal MC infiltration and FXR/FGF15 expression. These were reduced following MC stabilization with cromolyn sodium in Mdr2^-/- mice. In vitro, MC-FXR inhibition decreased biliary proliferation/SASP/FGF and hepatic stellate cell activation.

CONCLUSIONS

Our studies demonstrate that MC-FXR plays a key role in liver damage and DR, including TBA regulation through alteration of intestinal and biliary FXR/FGF15 signaling.

Salvianolic acid B blocks hepatic stellate cell activation via FGF19/FGFR4 signaling

INTRODUCTION AND OBJECTIVES

The activation of hepatic stellate cells (HSCs) is the main cause of liver fibrosis. The beneficial effects of fibroblast growth factor (FGF) 19 on liver fibrosis were recently reported. The S. miltiorrhiza as well as S. miltiorrhiza derived bioactive chemical components has shown prominent antifibrotic effects in liver fibrosis but the mechanism is still not fully understood. We aimed to investigate the bioactive compounds derived from S. miltiorrhiza which exerts antifibrotic effects in HSCs via regulating FGF19.

MATERIALS AND METHODS

FGF19 level in culture media was determined by enzyme-linked immunosorbent assay. Cell proliferation was measured by Cell Counting Kit-8 assay. Further, mRNA and protein expressions were assessed by quantitative polymerase chain reaction and western blotting, respectively. Knocking down of FGF receptor 4 (FGFR4) by transfection with siRNA was used to confirm the role of FGF19/FGFR4 signaling.

RESULTS

Using the human HSC cell line LX-2, we screened several natural products and found that bioactive compounds isolated from Salvia miltiorrhiza, particularly salvianolic acid B, strongly upregulated FGF19 secretion by LX-2 cells. We further showed that salvianolic acid B inhibited lipopolysaccharide (LPS)-induced HSC proliferation and activation. LPS treatment may also reduce the mRNA and protein levels of FGF19 and its receptor FGFR4. Salvianolic acid B treatment restored the impaired expressions of FGF19 and FGFR4. Finally, FGFR4 knockdown abolished the antifibrotic effects of salvianolic acid B in the LPS-induced HSC activation model.

CONCLUSIONS

Salvianolic acid B prevented LPS-induced HSC proliferation and activation by enhancing antifibrotic FGF19/FGFR4 signaling.

Gut microbiota depletion exacerbates cholestatic liver injury via loss of FXR signalling

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of unknown aetiology for which there are no approved therapeutic options. Patients with PSC display changes in gut microbiota and in bile acid (BA) composition; however, the contribution of these alterations to disease pathogenesis remains controversial. Here we identify a role for microbiota-dependent changes in BA synthesis that modulates PSC pathophysiology. In a genetic mouse model of PSC, we show that loss of microbiota-mediated negative feedback control of BA synthesis results in increased hepatic BA concentrations, disruption of bile duct barrier function and, consequently, fatal liver injury. We further show that these changes are dependent on decreased BA signalling to the farnesoid X receptor, which modulates the activity of the rate-limiting enzyme in BA synthesis, CYP7A1. Moreover, patients with advanced stages of PSC show suppressed BA synthesis as measured by serum C4 levels, which is associated with poor disease prognosis. Our preclinical data highlight the microbiota-dependent dynamics of BA metabolism in cholestatic liver disease, which could be important for future therapies targeting BA and gut microbiome interactions, and identify C4 as a potential biomarker to functionally stratify patients with PSC and predict disease outcomes.

Role of fibroblast growth factor signalling in hepatic fibrosis

Fibrotic remodelling is a highly conserved protective response to tissue injury and it is essential for the maintenance of structural and functional tissue integrity. Also hepatic fibrosis can be considered as a wound-healing response to liver injury, reflecting a balance between liver repair and scar formation. In contrast, pathological fibrosis corresponds to impaired wound healing. Usually, the liver regenerates after acute injury. However, if the damaging mechanisms persist, the liver reacts with progressive and uncontrolled accumulation of extracellular matrix proteins. Eventually, excessive fibrosis can lead to cirrhosis and hepatic failure. Furthermore, cirrhosis is the major risk factor for the development of hepatocellular cancer (HCC). Therefore, hepatic fibrosis is the most critical pathological factor that determines the morbidity and mortality of patients with chronic liver disease. Still, no effective anti-fibrogenic therapies exist, despite the very high medical need. The regulation of fibroblast growth factor (FGF) signalling is a prerequisite for adequate wound healing, repair and homeostasis in various tissues and organs. The FGF family comprises 22 proteins that can be classified into paracrine, intracrine and endocrine factors. Most FGFs signal through transmembrane tyrosine kinase FGF receptors (FGFRs). Although FGFRs are promising targets for the treatment of HCC, the expression and function of FGFR-ligands in hepatic fibrosis is still poorly understood. This review summarizes the latest advances in our understanding of FGF signalling in hepatic fibrosis. Furthermore, the potential of FGFs as targets for the treatment of hepatic fibrosis and remaining challenges for the field are discussed.

The Role of Fibroblast Growth Factor 19 in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common type of cancer and the third leading cause of cancer-related deaths worldwide. Liver resection or liver transplantation is the most effective therapy for HCC because drugs approved by the US Food and Drug Administration to treat patients with unresectable HCC have an unfavorable overall survival rate. Therefore, the development of biomarkers for early diagnosis and effective therapy strategies are still necessary to improve patient outcomes. Fibroblast growth factor (FGF) 19 was amplified in patients with HCC from various studies, including patients from The Cancer Genome Atlas. FGF19 plays a syngeneic function with other signaling pathways in primary liver cancer development, such as epidermal growth factor receptor, Wnt/β-catenin, the endoplasmic reticulum-related signaling pathway, STAT3/IL-6, RAS, and extracellular signal-regulated protein kinase, among others. The current review presents a comprehensive description of the FGF19 signaling pathway involved in liver cancer development. The use of big data and bioinformatic analysis can provide useful clues for further studies of the FGF19 pathway in HCC, including its application as a biomarker, targeted therapy, and combination therapy strategies.

Post-Translational Modifications of FXR; Implications for Cholestasis and Obesity-Related Disorders

The Farnesoid X receptor (FXR) is a nuclear receptor which is activated by bile acids. Bile acids function in solubilization of dietary fats and vitamins in the intestine. In addition, bile acids have been increasingly recognized to act as signaling molecules involved in energy metabolism pathways, amongst others via activating FXR. Upon activation by bile acids, FXR controls the expression of many genes involved in bile acid, lipid, glucose and amino acid metabolism. An inability to properly use and store energy substrates may predispose to metabolic disorders, such as obesity, diabetes, cholestasis and non-alcoholic fatty liver disease. These diseases arise through a complex interplay between genetics, environment and nutrition. Due to its function in metabolism, FXR is an attractive treatment target for these disorders. The regulation of FXR expression and activity occurs both at the transcriptional and at the post-transcriptional level. It has been shown that FXR can be phosphorylated, SUMOylated and acetylated, amongst other modifications, and that these modifications have functional consequences for DNA and ligand binding, heterodimerization and subcellular localization of FXR. In addition, these post-translational modifications may selectively increase or decrease transcription of certain target genes. In this review, we provide an overview of the posttranslational modifications of FXR and discuss their potential involvement in cholestatic and metabolic disorders.

S-adenosyl-L-methionine (SAMe) halts the autoimmune response in patients with primary biliary cholangitis (PBC) via antioxidant and S-glutathionylation processes in cholangiocytes

S-adenosyl-L-methionine is an endogenous molecule with hepato-protective properties linked to redox regulation and methylation. Here, the potential therapeutic value of SAMe was tested in 17 patients with PBC, a cholestatic disease with autoimmune phenomena targeting small bile ducts. Nine patients responded to SAMe (SAMe responders) with increased serum protein S-glutathionylation. That posttranslational protein modification was associated with reduction of serum anti-mitochondrial autoantibodies (AMA-M2) titers and improvement of liver biochemistry. Clinically, SAMe responders were younger at diagnosis, had longer duration of the disease and lower level of serum S-glutathionylated proteins at entry. SAMe treatment was associated with negative correlation between protein S-glutathionylation and TNFα. Furthermore, AMA-M2 titers correlated positively with INFγ and FGF-19 while negatively with TGFβ. Additionally, cirrhotic PBC livers showed reduced levels of glutathionylated proteins, glutaredoxine-1 (Grx-1) and GSH synthase (GS). The effect of SAMe was also analyzed in vitro. In human cholangiocytes overexpressing miR-506, which induces PBC-like features, SAMe increased total protein S-glutathionylation and the level of γ-glutamylcysteine ligase (GCLC), whereas reduced Grx-1 level. Moreover, SAMe protected primary human cholangiocytes against mitochondrial oxidative stress induced by tBHQ (tert-Butylhydroquinone) via raising the level of Nrf2 and HO-1. Finally, SAMe reduced apoptosis (cleaved-caspase3) and PDC-E2 (antigen responsible of the AMA-M2) induced experimentally by glycochenodeoxycholic acid (GCDC). These data suggest that SAMe may inhibit autoimmune events in patients with PBC via its antioxidant and S-glutathionylation properties. These findings provide new insights into the molecular events promoting progression of PBC and suggest potential therapeutic application of SAMe in PBC.

Comprehensive Analysis of Serum and Fecal Bile Acid Profiles and Interaction with Gut Microbiota in Primary Biliary Cholangitis

Accumulation of bile acids (BAs) contributes significantly to the pathogenesis of primary biliary cholangitis (PBC). Here, we sought to systematically characterize the serum and fecal BA profiles and the linkage between BAs and gut microbiota in PBC. The serum and fecal BAs were compared between 65 UDCA treatment-naive PBC and 109 healthy controls using UPLC-MS in cross-sectional study. In a prospective study, a subgroup of patients was enrolled for BA and microbiota analysis before and after UDCA therapy. BA compositions in serum and feces significantly differed between treatment-naive PBC and controls. Particularly, PBC was associated with decreased conversions of conjugated to unconjugated, and primary to secondary BAs, indicating impaired microbial metabolism of BAs. PBC patients at advanced stage exhibited a more abnormal BA profile compared with early-stage patients. UDCA treatment led to a decreased level of taurine-conjugated BAs, thereby reversing the conjugated/unconjugated ratio in PBC. Moreover, the level of secondary BAs such as DCA and conjugated DCA inversely correlated with PBC-enriched gut microbes (e.g., Veillonella, Klebsiella), while positively correlated with control-enriched microbes (e.g., Faecalibacterium, Oscillospira). Microbiota analysis also revealed a significant increase of taurine-metabolizing bacteria Bilophila spp. in patients after UDCA, which was strongly correlated with decreased taurine-conjugated BAs. In addition, serum FGF19 was remarkably increased in treatment-naïve PBC and decreased after UDCA. Our study established specific alterations of BA compositions in serum and feces of PBC, suggesting the potential for using BAs for diagnosis, and highlighting the possibility of modulating BA profile by altering gut microbiota. Graphical Abstract.

Dysregulation of Circulating FGF19 and Bile Acids in Primary Biliary Cholangitis-Autoimmune Hepatitis Overlap Syndrome

Background

Primary biliary cholangitis-autoimmune hepatitis overlap syndrome (PBC-AIH OS), which exhibits features between autoimmune hepatitis and cholestasis, is a common condition and usually shows a progressive course toward cirrhosis and liver failure without adequate treatment. Synthesis of bile acids (BAs) plays an important role in liver injury in cholestasis, and the process is regulated by fibroblast growth factor 19 (FGF19). The overall role of circulating FGF19 in BA synthesis and PBC-AIH OS requires further investigation.

Methods

We analyzed BA synthesis and correlated clinical parameters with serum BAs and FGF19 in 35 patients with PBC-AIH OS. Serum concentrations of 7alpha-hydroxycholest-4-en-3-one (C4) were used to quantify the synthesis of BA directly.

Results

Serum FGF19 levels were higher, while C4 levels were substantially lower in PBC-AIH OS patients than those in healthy controls. Circulating FGF19 levels strongly correlated with C4 (r = −0.695, p < 0.0001), direct bilirubin (r = 0.598, p = 0.0001), and total bile acids (r = 0.595, p = 0.002). Moreover, circulating FGF19 levels strongly correlated with the model for end-stage liver disease score (r = 0.574, p = 0.0005) and Mayo risk score (r = 0.578, p = 0.001).

Conclusions

Serum FGF19 is significantly increased in patients with PBC-AIH OS, while BA synthesis is suppressed. Circulating FGF19 primarily controls the regulation of BA synthesis in response to cholestasis and under cholestatic conditions. Therefore, modulation of circulating FGF19 could provide a promising targeted therapy for patients with PBC-AIH OS.

MicroRNA-210 Promotes Bile Acid-Induced Cholestatic Liver Injury by Targeting Mixed-Lineage Leukemia-4 Methyltransferase in Mice

BACKGROUND AND AIMS

Bile acids (BAs) are important regulators of metabolism and energy balance, but excess BAs cause cholestatic liver injury. The histone methyltransferase mixed-lineage leukemia-4 (MLL4) is a transcriptional coactivator of the BA-sensing nuclear receptor farnesoid X receptor (FXR) and epigenetically up-regulates FXR targets important for the regulation of BA levels, small heterodimer partner (SHP), and bile salt export pump (BSEP). MLL4 expression is aberrantly down-regulated and BA homeostasis is disrupted in cholestatic mice, but the underlying mechanisms are unclear.

APPROACH AND RESULTS

We examined whether elevated microRNA-210 (miR-210) in cholestatic liver promotes BA-induced pathology by inhibiting MLL4 expression. miR-210 was the most highly elevated miR in hepatic SHP-down-regulated mice with elevated hepatic BA levels. MLL4 was identified as a direct target of miR-210, and overexpression of miR-210 inhibited MLL4 and, subsequently, BSEP and SHP expression, resulting in defective BA metabolism and hepatotoxicity with inflammation. miR-210 levels were elevated in cholestatic mouse models, and in vivo silencing of miR-210 ameliorated BA-induced liver pathology and decreased hydrophobic BA levels in an MLL4-dependent manner. In gene expression studies, SHP inhibited miR-210 expression by repressing a transcriptional activator, Kruppel-like factor-4 (KLF4). In patients with primary biliary cholangitis/cirrhosis (PBC), hepatic levels of miR-210 and KLF4 were highly elevated, whereas nuclear levels of SHP and MLL4 were reduced.

CONCLUSIONS

Hepatic miR-210 is physiologically regulated by SHP but elevated in cholestatic mice and patients with PBC, promoting BA-induced liver injury in part by targeting MLL4. The miR-210-MLL4 axis is a potential target for the treatment of BA-associated hepatobiliary disease.

Emerging drugs for the treatment of primary biliary cholangitis

INTRODUCTION

Primary biliary cholangitis (PBC) is a progressive inflammatory autoimmune cholestatic liver disease. Without treatment, it may result in fibrosis and eventually end stage liver disease. In addition to the disease burden, the symptom impact on the quality of life for PBC patients is significant. Ursodeoxycholic acid, and the second-line therapy, Obeticholic acid, are the only available licensed treatments. Although there has been rapid development of novel therapies in recent years for the treatment of PBC, there are very few symptoms directed therapies.

AREA COVERED

This literature review aims to review the current treatment landscape in PBC and to explore how the next few years may unfold in the field. The current guidelines and emerging therapies in phase 2, 3 and 4 clinical trials have been included.

EXPERT OPINION

The currently available therapies are effective, but their use has limitations and challenges and there is still significant unmet need. Although there have been promising therapeutic interventions in recent years, further research into personalizing therapeutic strategies with available treatments and new agents is needed.

Regulation of bile acid metabolism in biliary atresia: reduction of FGF19 by Kasai portoenterostomy and possible relation to early outcome

BACKGROUND

Fibroblast growth factor 19 (FGF19) is produced in the small intestine and is involved in suppression of hepatic bile acid (BA) synthesis. FGF19 is also expressed in the liver and serum levels are elevated in adults with cholestatic liver disease. This may reflect a rescue mechanism to dampen liver injury caused by increased intrahepatic BAs.

OBJECTIVES

To examine circulating FGF19 at early stages of biliary atresia and at short-term follow-up post-Kasai portoenterostomy (KPE) in relation to noncholestatic infants. The relationship between FGF19, BAs and markers for BA synthesis and hepatic gene expression of factors involved in BA metabolism were also evaluated.

METHODS

Liver tissue, portal and peripheral blood samples were obtained from fifteen patients at KPE; additional blood was collected 4-6 months after surgery. Two control groups were included; to examine possible changes related to surgery and to compare FGF19 in biliary atresia to noncholestatic infants.

RESULTS

Circulating FGF19 levels correlated to its hepatic gene expression at time of KPE in biliary atresia and levels were elevated compared to noncholestatic infants. At follow-up, FGF19 levels were markedly reduced, and the decline coincided with reductions in bilirubin and conjugated chenodeoxycholic acid and with increased levels of the BA synthesis marker C4.

CONCLUSION

Elevated circulating FGF19 in biliary atresia is of hepatic origin and reduced following KPE. Changes in serum FGF19 may reflect the level of restoration of the enterohepatic circulation, and this warrants further long-term studies on the role of FGF19 in the cholestatic liver.

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.

Enhanced expression of miR-21 and miR-150 is a feature of anti-mitochondrial antibody-negative primary biliary cholangitis

Background & Aims

Anti-mitochondrial-autoantibodies (AMA) remain a hallmark of Primary Biliary Cholangitis (PBC) however approximately 10% of patients test negative for these antibodies. They do not differ in terms of biochemistry or clinical presentation from AMA positive ones. Epigenetics play a key role in immune signalling. Two microRNAs (miRs), namely, miR-21 and miR-150 are known to be involved in liver inflammation and fibrosis. The expression of those two microRNAs and their downstream targets were analyze in the context of AMA-status and the stage of liver fibrosis.

Methods

The relative levels of miR-21 and miR-150 and their target genes: cMyb, RAS-guanyl-releasing protein-1(RASGRP1), and DNA-methyltransferase-1(DNMT1) were determined by Real-Time PCR in serum, liver tissue and peripheral blood mononuclear cells (PBMCs) of patients with PBC.

Results

Serum expressions of miR-21 and miR-150 were significantly enhanced in AMA-negative patients, and they inversely correlated with disease-specific AMA titers in PBS patients. In PBMCs, an increased expression of miR-21 correlated with decreased levels of RASGRP1 and DNMT1 mRNAs whereas, the level of miR-150 remained comparable to controls; and cMyb mRNA was downregulated. In cirrhotic livers, the level of miR-21 was unchanged while miR-150 expression was increased.

Conclusion

This study convincingly report, that AMA-negative PBC is characterized by notable alternations of miR-21 and miR-150 and their downstream targets compared to AMA-positive patients underlining their possible importance in the induction of the disease and its progression to fibrosis.

Chenodeoxycholic Acid Modulates Bile Acid Synthesis Independent of Fibroblast Growth Factor 19 in Primary Human Hepatocytes

Bile acids (BAs) are detergents essential for intestinal absorption of lipids. Disruption of BA homeostasis can lead to severe liver damage. BA metabolism is therefore under strict regulation by sophisticated feedback mechanisms. The hormone-like protein Fibroblast growth factor 19 (FGF19) is essential for maintaining BA homeostasis by down regulating BA synthesis. Here, the impact of both FGF19 and chenodeoxycholic acid (CDCA) on primary human hepatocytes was investigated and a possible autocrine/paracrine function of FGF19 in regulation of BA synthesis evaluated. Primary human hepatocytes were treated with CDCA, recombinant FGF19 or conditioned medium containing endogenously produced FGF19. RNA sequencing revealed that treatment with CDCA causes deregulation of transcripts involved in BA metabolism, whereas treatment with FGF19 had minor effects. CDCA increased FGF19 mRNA expression within 1 h. We detected secretion of the resulting FGF19 protein into medium, mimicking in vivo observations. Furthermore, medium enriched with endogenously produced FGF19 reduced BA synthesis by down regulating CYP7A1 gene expression. However, following knockdown of FGF19, CDCA still independently decreased BA synthesis, presumably through the regulatory protein small heterodimer partner (SHP). In summary, we show that in primary human hepatocytes CDCA regulates BA synthesis in an FGF19-independent manner.

FGF19 and FGF21 for the Treatment of NASH-Two Sides of the Same Coin? Differential and Overlapping Effects of FGF19 and FGF21 From Mice to Human

FGF19 and FGF21 analogues are currently in clinical development for the potential treatment of NASH. In Phase 2 clinical trials analogues of FGF19 and FGF21 decrease hepatic steatosis with up to 70% (MRI-PDFF) after 12 weeks and as early as 12-16 weeks of treatment an improvement in NASH resolution and fibrosis has been observed. Therefore, this class of compounds is currently of great interest in the field of NASH. FGF19 and FGF21 belong to the endocrine FGF19 subfamily and both require the co-receptor beta-klotho for binding and signalling through the FGF receptors. FGF19 is expressed in the ileal enterocytes and is released into the enterohepatic circulation in response to bile acids stimuli and in the liver FGF19 inhibits hepatic bile acids synthesis by transcriptional regulation of Cyp7A1, which is the rate limiting enzyme. FGF21 is, on the other hand, highly expressed in the liver and is released in response to high glucose, high free-fatty acids and low amino-acid supply and regulates energy, glucose and lipid homeostasis by actions in the CNS and in the adipose tissue. FGF19 and FGF21 are differentially expressed, have distinct target tissues and separate physiological functions. It is therefore of peculiar interest to understand why treatment with both FGF19 and FGF21 analogues have strong beneficial effects on NASH parameters in mice and human and whether the mode of action is overlapping This review will highlight the physiological and pharmacological effects of FGF19 and FGF21. The potential mode of action behind the anti-steatotic, anti-inflammatory and anti-fibrotic effects of FGF19 and FGF21 will be discussed. Finally, development of drugs is always a risk benefit analysis and the human relevance of adverse effects observed in pre-clinical species as well as findings in humans will be discussed. The aim is to provide a comprehensive overview of the current understanding of this drug class for the potential treatment of NASH.

Paracrine Fibroblast Growth Factor 1 Functions as Potent Therapeutic Agent for Intrahepatic Cholestasis by Downregulating Synthesis of Bile Acid

Endocrine fibroblast growth factor (FGF) 19 has been shown to be capable of maintaining bile acid (BA) homeostasis and thus hold promise to be a potential therapeutic agent for cholestasis liver disease. However, whether paracrine FGFs possess this BA regulatory activity remains to be determined. In our study, we identified that paracrine fibroblast growth factor 1 (FGF1) was selectively downregulated in the liver of alpha naphthylisothiocyanate (ANIT)-induced intrahepatic cholestasis mice, suggesting a pathological relevance of this paracrine FGF with abnormal BA metabolism. Therefore, we evaluated the effects of engineered FGF1 mutant - FGF1^ΔHBS on the metabolism of hepatic BA and found that this protein showed a more potent inhibitory effect of BA biosynthesis than FGF19 without any hepatic mitogenic activity. Moreover, the chronic administration of FGF1^ΔHBS protected liver against ANIT-induced injury by reducing hepatic BA accumulation. Taken together, these data suggest that FGF1^ΔHBS may function as a potent therapeutic agent for intrahepatic cholestasis liver disease.

The Effect of Fibroblast Growth Factor 15 Signaling in Non-Steatotic and Steatotic Liver Transplantation from Cardiocirculatory Death

We elucidate the relevance of fibroblast growth factor 15 (FGF15) in liver transplantation (LT) using rats with both steatotic and non-steatotic organs from donors after cardiocirculatory death (DCD). Compared to LT from non-DCDs, the induction of cardiocirculatory death (CD) increases hepatic damage, proliferation, and intestinal and circulatory FGF15. This is associated with high levels of FGF15, bilirubin and bile acids (BAs), and overexpression of the enzyme involved in the alternative BA synthesis pathway, CYP27A1, in non-steatotic livers. Furthermore, CD activates the proliferative pathway, Hippo/YAP, in these types of liver. Blocking FGF15 action in LT from DCDs does not affect CYP27A1 but causes an overexpression of CYP7A, an enzyme from the classic BA synthesis pathway, and this is related to further accumulation of BAs and exacerbated damage. FGF15 inhibition also impairs proliferation without changing Hippo/YAP. In spite of worse damage, steatosis prevents a proliferative response in livers from DCDs. In steatotic grafts, CD does not modify CYP7A1, CYP27A1, BA, or the Hippo/YAP pathway, and FGF15 is not involved in damage or proliferation. Thus, endogenous FGF15 protects against BA accumulation and damage and promotes regeneration independently of the Hippo/YAP pathway, in non-steatotic LT from DCDs. Herein we show a minor role of FGF15 in steatotic LT from DCDs.

Gut-liver axis signaling in portal hypertension

Portal hypertension (PHT) in advanced chronic liver disease (ACLD) results from increased intrahepatic resistance caused by pathologic changes of liver tissue composition (structural component) and intrahepatic vasoconstriction (functional component). PHT is an important driver of hepatic decompensation such as development of ascites or variceal bleeding. Dysbiosis and an impaired intestinal barrier in ACLD facilitate translocation of bacteria and pathogen-associated molecular patterns (PAMPs) that promote disease progression via immune system activation with subsequent induction of proinflammatory and profibrogenic pathways. Congestive portal venous blood flow represents a critical pathophysiological mechanism linking PHT to increased intestinal permeability: The intestinal barrier function is affected by impaired microcirculation, neoangiogenesis, and abnormal vascular and mucosal permeability. The close bidirectional relationship between the gut and the liver has been termed “gut-liver axis”. Treatment strategies targeting the gut-liver axis by modulation of microbiota composition and function, intestinal barrier integrity, as well as amelioration of liver fibrosis and PHT are supposed to exert beneficial effects. The activation of the farnesoid X receptor in the liver and the gut was associated with beneficial effects in animal experiments, however, further studies regarding efficacy and safety of pharmacological FXR modulation in patients with ACLD are needed. In this review, we summarize the clinical impact of PHT on the course of liver disease, discuss the underlying pathophysiological link of PHT to gut-liver axis signaling, and provide insight into molecular mechanisms that may represent novel therapeutic targets.

Pharmacologic Modulation of Bile Acid-FXR-FGF15/FGF19 Pathway for the Treatment of Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is within the spectrum of nonalcoholic fatty liver disease (NAFLD) and can progress to fibrosis, cirrhosis, and even hepatocellular carcinoma (HCC). The prevalence of NASH is rising and has become a large burden to the medical system worldwide. Unfortunately, despite its high prevalence and severe health consequences, there is currently no therapeutic agent approved to treat NASH. Therefore, the development of efficacious therapies is of utmost urgency and importance. Many molecular targets are currently under investigation for their ability to halt NASH progression. One of the most promising and well-studied targets is the bile acid (BA)-activated nuclear receptor, farnesoid X receptor (FXR). In this chapter, the characteristics, etiology, and prevalence of NASH will be discussed. A brief introduction to FXR regulation of BA homeostasis will be described. However, for more details regarding FXR in BA homeostasis, please refer to previous chapters. In this chapter, the mechanisms by which tissue and cell type-specific FXR regulates NASH development will be discussed in detail. Several FXR agonists have reached later phase clinical trials for treatment of NASH. The progress of these compounds and summary of released data will be provided. Lastly, this chapter will address safety liabilities specific to the development of FXR agonists.

Bile Modulates Secretion of Incretins and Insulin: A Study of Human Extrahepatic Cholestasis

OBJECTIVE

Changes in bile flow after bariatric surgery may beneficially modulate secretion of insulin and incretins, leading to diabetes remission. However, the exact mechanism(s) involved is still unclear. Here, we propose an alternative method to investigate the relationship between alterations in physiological bile flow and insulin and incretin secretion by studying changes in gut-pancreatic function in extrahepatic cholestasis in nondiabetic humans.

METHODS

To pursue this aim, 58 nondiabetic patients with recent diagnosis of periampullary tumors underwent an oral glucose tolerance test (OGTT), and a subgroup of 16 patients also underwent 4-hour mixed meal tests and hyperinsulinemic-euglycemic clamps.

RESULTS

The analysis of the entire cohort revealed a strong inverse correlation between total bilirubin levels and insulinogenic index. When subjects were divided on the basis of bilirubin levels, used as a marker of altered bile flow, subjects with high bilirubin levels displayed inferior glucose control and decreased insulin secretion during the OGTT. Altered bile flow elicited a markedly greater increase in glucagon and glucagon-like peptide 1 (GLP-1) secretion at fasting state, and following the meal, both glucagon and GLP-1 levels remained increased over time. Conversely, Glucose-dependent insulinotropic polypeptide (GIP) levels were comparable at the fasting state, whereas the increase following meal ingestion was significantly blunted with high bilirubin levels. We reveal strong correlations between total bilirubin and glucagon and GLP-1 levels.

CONCLUSIONS

Our findings suggest that acute extrahepatic cholestasis determines major impairment in enteroendocrine gut-pancreatic secretory function. The altered bile flow may determine a direct deleterious effect on β-cell function, perhaps mediated by the impairment of incretin hormone function.

Fibroblast growth factors in control of lipid metabolism: from biological function to clinical application

PURPOSE OF REVIEW

Several members of the fibroblast growth factor (FGF) family have been identified as key regulators of energy metabolism in rodents and nonhuman primates. Translational studies show that their metabolic actions are largely conserved in humans, which led to the development of various FGF-based drugs, including FGF21-mimetics LY2405319, PF-05231023, and pegbelfermin, and the FGF19-mimetic NGM282. Recently, a number of clinical trials have been published that examined the safety and efficacy of these novel therapeutic proteins in the treatment of obesity, type 2 diabetes (T2D), nonalcoholic steatohepatitis (NASH), and cholestatic liver disease. In this review, we discuss the current understanding of FGFs in metabolic regulation and their clinical potential.

RECENT FINDINGS

FGF21-based drugs induce weight loss and improve dyslipidemia in patients with obesity and T2D, and reduce steatosis in patients with NASH. FGF19-based drugs reduce steatosis in patients with NASH, and ameliorate bile acid-induced liver damage in patients with cholestasis. In contrast to their potent antidiabetic effects in rodents and nonhuman primates, FGF-based drugs do not appear to improve glycemia in humans. In addition, various safety concerns, including elevation of low-density lipoprotein cholesterol, modulation of bone homeostasis, and increased blood pressure, have been reported as well.

SUMMARY

Clinical trials with FGF-based drugs report beneficial effects in lipid and bile acid metabolism, with clinical improvements in dyslipidemia, steatosis, weight loss, and liver damage. In contrast, glucose-lowering effects, as observed in preclinical models, are currently lacking.

Metabolic Messengers: fibroblast growth factor 15/19

Fibroblast growth factor (FGF) 15 in mice and its human orthologue FGF19 (together denoted FGF15/19) are gut hormones that control homeostasis of bile acids and glucose during the transition from the fed to the fasted state. Apart from its central role in the regulation of bile acid homeostasis, FGF15/19 is now recognized as a transversal metabolic coordinator at the crossroads of the gut, liver, brain and white adipose tissue. Dysregulation of FGF15/19 signalling may contribute to the pathogenesis of several diseases affecting the gut-liver axis and to metabolic diseases. Here, we provide an overview of current knowledge of the physiological roles of the enterokine FGF15/19 and highlight commonalities and differences between the two orthologues. We also discuss the putative therapeutic potential in areas of unmet medical need-such has cholestatic liver diseases and non-alcoholic steatohepatitis, for which FGF19 is being tested in ongoing clinical trials-as well as the possibility of using FGF19 for the treatment of obesity and type II diabetes.

Bile acid receptor agonists in primary biliary cholangitis: Regulation of the cholangiocyte secretome and downstream T cell differentiation

Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease. Approximately 30% of patients do not respond to therapy with ursodeoxycholic acid (UDCA). Previous studies have implicated increased senescence of cholangiocytes in patients who do not respond to UDCA. This may increase the release of cytokines which drive pathogenic T cell polarization. As FXR agonists are beneficial in treating UDCA non-responsive patients, the current study was designed to model the interactions between cholangiocytes and CD4+ T cells to investigate potential immunomodulatory mechanisms of bile acid receptor agonists. Human cholangiocytes were co-cultured with CD4+ T cells to model the biliary stress response. Senescent cholangiocytes were able to polarize T cells toward a Th17 phenotype and suppressed expression of FoxP3 (P = 0.0043). Whilst FXR and TGR5 receptor agonists were unable directly to alter cholangiocyte cytokine expression, FGF19 was capable of significantly reducing IL-6 release (P = 0.044). Bile acid receptor expression was assessed in PBC patients with well-characterized responsiveness to UDCA therapy. A reduction in FXR staining was observed in both cholangiocytes and hepatocytes in PBC patients without adequate response to UDCA. Increased IL-6 expression by senescent cholangiocytes represents a potential mechanism by which biliary damage in PBC could contribute to excessive inflammation.

CYP7A1 expression in hepatocytes is retained with upregulated fibroblast growth factor 19 in pediatric biliary atresia

AIM

Bile acid biosynthesis is strictly regulated under physiological conditions. The expression of fibroblast growth factor (FGF) 19 is induced when bile acids bind to the farnesoid X receptor in the intestinal epithelium. Fibroblast growth factor 19 is then transported by the portal flow, causing transcriptional inhibition of cytochrome P450, family 7, subfamily A, polypeptide 1 (CYP7A1), a key enzyme in bile acid biosynthesis, through the extracellular signal-regulated kinase (ERK) pathway. However, the regulatory mechanisms of these signaling pathways in hepatocytes under chronic cholestasis remain unclear. We investigated the regulation of these signaling pathways in patients with biliary atresia (BA).

METHODS

We analyzed the regulation of molecules in these signaling pathways using liver and serum samples from eight BA children and four non-cholestatic disease controls.

RESULTS

CYP7A1 mRNA expression was not inhibited in BA microdissected hepatocyte-enriched tissue (HET) despite high serum bile acid concentrations. The FGF19 protein was synthesized in BA HET, and its serum concentration was elevated. Fibroblast growth factor receptor 4 was phosphorylated in BA livers. However, ERK phosphorylation was significantly reduced. We examined SPRY2 expression to determine how the ERK pathway was inactivated downstream of the FGF receptor; the expression was significantly increased in BA HET.

CONCLUSIONS

This is the first study to measure the CYP7A1 mRNA levels in human BA HET. Fibroblast growth factor 19 was increased in BA hepatocytes. By focusing on its regulation in hepatocytes, we showed that the FGF19 pathway did not suppress bile acid synthesis, probably due to an altered mechanism involving upregulated SPRY2 in BA patients.

Characterization of Hepatocellular Carcinoma Patients with FGF19 Amplification Assessed by Fluorescence in situ Hybridization: A Large Cohort Study

BACKGROUND

FGF19 amplification is a relatively novel type of genetic aberration that has been proposed to be a driver of hepatocarcinogenesis. Selective inhibitors of FGFR4, a receptor of FGF19, have been developed as targeted therapies for hepatocellular carcinoma (HCC). Despite the role of FGF19 in mediating HCC progression, the clinicopathological characterization of patients exhibiting FGF19 amplification remains unclear. Immunohistochemical staining is the simplest and most widely used method of identifying aberrations in the FGF19 gene, although its specificity is very low.

METHODS

This study investigated the prognostic significance of FGF19 amplification in a large cohort of 989 HCC patients using fluorescence in situ hybridization (FISH), which has a high degree of specificity. In addition, FISH data from formalin-fixed, paraffin-embedded sections were compared with copy number variation (CNV) data obtained from fresh frozen sections to validate the use of FISH as a diagnostic tool.

RESULTS

FGF19 amplifications were detected by FISH in 51 (5.15%) of the 989 patients, and were independently associated with poor survival and a higher risk of tumor recurrence, as well as with poor prognostic factors such as a high α-fetoprotein level, hepatitis B or C virus infection, a large tumor size, microvascular invasion, and necrosis. In addition, FGF19 amplification was associated with TP53 mutation, and was mutually exclusive with CTNNB1 mutation. The results of the FISH and CNV analyses exhibited a significant concordance rate of 96% (κ = 0.618, p < 0.001).

CONCLUSIONS

These data indicate that FGF19 amplification represents a unique molecular subtype associated with poor prognostic characteristics, which supports the hypothesis that the FGF19-FGFR4 signaling pathway plays an important role in hepatocarcinogenesis. We have also demonstrated that FISH is a viable alternative to CNV analysis, offering a number of advantages in the clinical setting.