Progressive familial intrahepatic cholestasis

Liver pathology in pregnancy

Liver dysfunction occurs in up to 3% of pregnancies and can be due to pregnancy-associated liver injury, exacerbation of pre-existing liver disease, or co-incident with pregnancy. The most common form of pregnancy-associated liver injury is intrahepatic cholestasis of pregnancy (ICP). This condition is typically benign and self-limited, but is associated with fetal morbidity and mortality with high levels of serum bile acids. Acute fatty liver of pregnancy (AFLP) and the hypertensive disorders of pregnancy (including pre-eclampsia, eclampsia, and hemolysis, elevated liver enzymes, and low platelets [HELLP] syndrome) are more commonly associated with maternal and fetal complications and may necessitate expedient delivery. Histologically, ICP shows nonspecific features of cholestasis, while AFLP and the hypertensive disorders have more characteristic histologic findings. While not a true liver disease, hyperemesis gravidarum can cause elevated liver enzymes. Pregnant patients are at increased risk of developing severe hepatitis E and herpesvirus infections, Budd-Chiari syndrome, and gallstones, and they may also experience worsening of known chronic liver disease. Mass lesions in pregnancy including hemangiomas, focal nodular hyperplasia, and hepatocellular adenomas and carcinomas can present unique challenges for diagnosis and management. This review will explore the pathophysiology, presentation, histologic features, and management of these conditions.

Reversal of portal gastropathy with partial internal biliary diversion in a case of progressive familial intrahepatic cholestasis

Progressive intrahepatic cholestasis is a rare, genetic disorder causing bile acid secretion or transport defects. It can result in intrahepatic cholestasis that can progress to end-stage liver disease. Diagnosis is made using a combination of clinical and biochemical approaches. Genetic testing is currently the gold standard for investigation.

We report a case of an 18-month-old male child with cholestatic pattern of jaundice from 16 months of life, which was associated with features suggestive of portal gastropathy. Detailed workup led to the diagnosis of progressive intrahepatic cholestasis (type 2). Early diagnosis prevented the need for liver transplant, and the child underwent surgical treatment with partial internal biliary diversion. Portal gastropathy and disease progression dramatically changed with corrective surgery. The patient was symptom-free at 10-week follow-up.

Detecting this rare genetic disorder early has very good therapeutic implications from the patient's perspective and their morbidity and mortality profile; if untreated, it has a high propensity to progress to end-stage liver disease. The requirement of surgical interventions and liver transplantation is individualized on a case-to-case basis. An early diagnosis and initiation of treatment can prevent the need for a liver transplant as shown in the present case.

Niemann-Pick Disease Type C Diagnosed Using Neonatal Cholestasis Gene Panel

Niemann-Pick disease type C (NPC) is a neurovisceral lysosomal storage disorder caused by mutations in the NPC1 and NPC2 genes. These mutations cause the accumulation of unesterified cholesterol and other lipids in the lysosomes. NPC has a broad spectrum of clinical manifestations, depending on the age of onset. A 15-day-old infant presented at the Seoul National University Children's Hospital with neonatal cholestasis and hepatosplenomegaly, with the onset of jaundice at 5 days of age. Despite supportive treatment, the patient was considered for a liver transplant because of progressive liver failure. Unfortunately, the patient died from gastrointestinal bleeding before undergoing the transplant. The neonatal cholestasis gene panel revealed two novel likely pathogenic variants in the NPC1 gene (c.1145C>G [p.Ser382*] and c.2231_2233del [p.Val744del]). The patient was diagnosed with NPC, and both parents were found to be carriers of each variant. In infants presenting with neonatal cholestasis, a gene panel can help diagnose NPC.

Liver Transplantation in Progressive Familial Intrahepatic Cholestasis with Normal Gamma-Glutamyl Transferase: Evaluation of Post-transplant Steatosis and Steatohepatitis

Background: Progressive familial intrahepatic cholestasis is a disease presenting with severe cholestasis and progressing to the end-stage liver disease later. Liver transplantation is a treatment modality available for progressive familial intrahepatic cholestasis, especially in patients with end-stage liver disease or those who are unsuitable for or have failed biliary diversion. Objectives: To evaluate clinical and pathological characteristics of progressive familial intrahepatic cholestasis patients who had undergone liver transplantation and to determine post-transplant steatosis and steatohepatitis. Methods: We evaluated 111 progressive familial intrahepatic cholestasis patients with normal gamma-glutamyl transferase that performed liver transplantation in Shiraz Transplant Center in Iran between March 2000 and March 2017. Results: The most common clinical manifestations were jaundice and pruritus. Growth retardation and diarrhea were detected in 76.6% and 42.5% of the patients. After transplantation, growth retardation was seen in 31.5% of the patients, and diarrhea in 36.9% of them. Besides, 29.1% of the patients died post-transplant. Post-transplant liver biopsies were taken from 50 patients, and 15 (30%) patients had steatosis or steatohepatitis, five of whom (10%) had macrovesicular steatosis alone, and 10 (20%) had steatohepatitis. Only one patient showed moderate bridging fibrosis (stage III), and none of them showed severe fibrosis. Conclusions: Liver transplantation is the final treatment option for these patients, and it can relieve most clinical manifestations. However, post-transplant mortality rate was relatively high in our center. Diarrhea, growth retardation, and steatosis are unique post-transplant complications in these patients. The rate of post-transplant steatosis and steatohepatitis in patients with liver biopsy in our study was 30%, with a significant difference from previous studies.

ATP-binding cassette transporters mediate differential biosynthesis of glycosphingolipid species

The cytosolic-oriented glucosylceramide (GlcCer) synthase is enigmatic, requiring nascent GlcCer translocation to the luminal Golgi membrane to access glycosphingolipid (GSL) anabolic glycosyltransferases. The mechanism by which GlcCer is flipped remains unclear. To investigate the role of GlcCer-binding partners in this process, we previously made cleavable, biotinylated, photoreactive GlcCer analogs in which the reactive nitrene was closely apposed to the GlcCer head group, while maintaining a C16-acyl chain. GlcCer-binding protein specificity was validated for both photoprobes. Using one probe, XLB, here we identified ATP-binding cassette (ABC) transporters ABCA3, ABCB4, and ABCB10 as unfractionated microsomal GlcCer-binding proteins in DU-145 prostate tumor cells. siRNA knockdown (KD) of these transporters differentially blocked GSL synthesis assessed in toto and via metabolic labeling. KD of ABCA3 reduced acid/neutral GSL levels, but increased those of LacCer, while KD of ABCB4 preferentially reduced neutral GSL levels, and KD of ABCB10 reduced levels of both neutral and acidic GSLs. Depletion of ABCA12, implicated in GlcCer transport, preferentially decreased neutral GSL levels, while ABCB1 KD preferentially reduced gangliosides, but increased neutral GSL Gb3. These results imply that multiple ABC transporters may provide distinct but overlapping GlcCer and LacCer pools within the Golgi lumen for anabolism of different GSL series by metabolic channeling. Differential ABC family member usage may fine-tune GSL biosynthesis depending on cell/tissue type. We conclude that ABC transporters provide a new tool for the regulation of GSL biosynthesis and serve as potential targets to reduce selected GSL species/subsets in diseases in which GSLs are dysregulated.

Case Report: A Novel Homozygous Variant Identified in a Chinese Patient With Benign Recurrent Intrahepatic Cholestasis-Type 1

Benign recurrent intrahepatic cholestasis (BRIC) is a rare hereditary cholestatic liver disorder. Accurate diagnosis and timely interventions are important in determining outcomes. Besides clinical and pathologic diagnosis, genetic study of BRIC remains limited. Here, we report a young man enduring recurrent jaundice and severe pruritus for 15 years. The increased level of direct bilirubin was the main biochemical abnormality, and the work-up for common causes of jaundice were unremarkable. Liver biopsy showed extensive cholestasis of hepatocytes in zone 3. The novel homozygous variant including c.1817T > C and p.I606T was detected on his ATP8B1gene. The patient was finally diagnosed with BRIC-1. His symptoms were relieved, and liver function tests returned to normal after taking ursodeoxycholic acid. This case provides a different perspective to the methodology employed when dealing with cases of jaundice and helping diagnose rare diseases.

Two Novel Pathogenic Variants of TJP2 Gene and the Underlying Molecular Mechanisms in Progressive Familial Intrahepatic Cholestasis Type 4 Patients

Progressive familial intrahepatic cholestasis (PFIC) is an autosomal recessive inherited disease that accounts for 10%-15% childhood cholestasis and could lead to infant disability or death. There are three well-established types of PFIC (1-3), caused by mutations in the ATP8B1, ABCB11, and ABCB4 genes. Biallelic pathogenic variants in the tight junction protein 2 gene (TJP2) were newly reported as a cause for PFIC type 4; however, only a limited number of patients and undisputable variants have been reported for TJP2, and the underlying mechanism for PFIC 4 remains poorly understood. To explore the diagnostic yield of TJP2 analysis in suspected PFIC patients negative for the PFIC1-3 mutation, we designed a multiplex polymerase chain reaction-based next-generation sequencing method to analyze TJP2 gene variants in 267 PFIC patients and identified biallelic rare variants in three patients, including three known pathogenic variants and two novel variants in three patients. By using CRISPR-cas9 technology, we demonstrated that TJP2 c.1202A > G was pathogenic at least partially by increasing the expression and nuclear localization of TJP2 protein. With the minigene assay, we showed that TJP2 c.2668-11A > G was a new pathogenic variant by inducing abnormal splicing of TJP2 gene and translation of prematurely truncated TJP2 protein. Furthermore, knockdown of TJP2 protein by siRNA technology led to inhibition of cell proliferation, induction of apoptosis, dispersed F-actin, and disordered microfilaments in LO2 and HepG2celles. Global gene expression profiling of TJP2 knockdown LO2 cells and HepG2 cells identified the dysregulated genes involved in the regulation of actin cytoskeleton. Microtubule cytoskeleton genes were significantly downregulated in TJP2 knockdown cells. The results of this study demonstrate that TJP2 c.1202A > G and TJP2 c.2668-11A > G are two novel pathogenic variants and the cytoskeleton-related functions and pathways might be potential molecular pathogenesis for PFIC.

Long-Term Outcome after Liver Transplantation for Progressive Familial Intrahepatic Cholestasis

Background and Objectives: Progressive familial intrahepatic cholestasis (PFIC) is a rare autosomal recessive inherited disease divided into five types (PFIC 1-5). Characteristic for all types is early disease onset, which may result clinically in portal hypertension, fibrosis, cirrhosis, hepatocellular carcinoma (HCC), and extrahepatic manifestations. Liver transplantation (LT) is the only successful treatment approach. Our aim is to present the good long-term outcomes after liver transplantation for PFIC1, focusing on liver function as well as the occurrence of extrahepatic manifestation after liver transplantation. Materials and Methods: A total of seven pediatric patients with PFIC1 underwent liver transplantation between January 1999 and September 2019 at the Department of Surgery, Charité Campus Virchow Klinikum and Charité Campus Mitte of Charité-Universitätsmedizin Berlin. Long-term follow-up data were collected on all patients, specifically considering liver function and extrahepatic manifestations. Results: Seven (3.2%) recipients were found from a cohort of 219 pediatric patients. Two of the seven patients had multilocular HCC in cirrhosis. Disease recurrence or graft loss did not occur in any patient. Two patients (male, siblings) had persistently elevated liver parameters but showed excellent liver function. Patient and graft survival during long-term follow-up was 100%, and no severe extrahepatic manifestations requiring hospitalization or surgery occurred. We noted a low complication rate during long-term follow-up and excellent patient outcome. Conclusions: PFIC1 long-term follow-up after LT shows promising results for this rare disease. In particular, the clinical relevance of extrahepatic manifestations seems acceptable, and graft function seems to be barely affected. Further multicenter studies are needed to analyze the clinically inhomogeneous presentation and to better understand the courses after LT.

Intrahepatic Cholestasis Is a Clinically Significant Feature Associated with Natural History of X-Linked Myotubular Myopathy (XLMTM): A Case Series and Biopsy Report

X-linked myotubular myopathy (XLMTM) is a rare, life-threatening congenital myopathy characterized by profound skeletal muscle weakness, respiratory distress, and motor dysfunction. However, pathology is not limited to muscle and can be associated with life-threatening hepatic peliosis. Hepatobiliary disease has been reported in up to 17% of XLMTM patients but has not been extensively characterized. We report on five XLMTM patients who experienced intrahepatic cholestasis in their disease natural history, illustrating the need to further investigate these manifestations. These patients shared presentations that included pruritus, hypertransaminemia, and hyperbilirubinemia with normal gamma-glutamyl transferase, following infection or vaccination. Three patients who had genetic testing showed no evidence of genetic mutations associated with familial cholestasis. In one patient, progression to cirrhotic, decompensated liver disease occurred. Further investigations into the molecular pathomechanism underpinning these clinical observations in XLMTM patients will be important for informing patient care.

Epidemiology and burden of progressive familial intrahepatic cholestasis: a systematic review

Background

Progressive familial intrahepatic cholestasis is a rare, heterogeneous group of liver disorders of autosomal recessive inheritance, characterised by an early onset of cholestasis with pruritus and malabsorption, which rapidly progresses, eventually culminating in liver failure. For children and their parents, PFIC is an extremely distressing disease. Significant pruritus can lead to severe cutaneous mutilation and may affect many activities of daily living through loss of sleep, irritability, poor attention, and impaired school performance.

Methods

Databases including MEDLINE and Embase were searched for publications on PFIC prevalence, incidence or natural history, and the economic burden or health-related quality of life of patients with PFIC. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed.

Results

Three systematic reviews and twenty-two studies were eligible for inclusion for the epidemiology of PFIC including a total of 2603 patients. Study periods ranged from 3 to 33 years. Local population prevalence of PFIC was reported in three studies, ranging from 9.0 to 12.0% of children admitted with cholestasis, acute liver failure, or splenomegaly. The most detailed data come from the NAPPED study where native liver survival of >15 years is predicted in PFIC2 patients with a serum bile  acid concentration below 102 µmol/L following bile diversion surgery. Burden of disease was mainly reported through health-related quality of life (HRQL), rates of surgery and survival. Rates of biliary diversion and liver transplant varied widely depending on study period, sample size and PFIC type, with many patients have multiple surgeries and progressing to liver transplant. This renders data unsuitable for comparison.

Conclusion

Using robust and transparent methods, this systematic review summarises our current knowledge of PFIC. The epidemiological overview is highly mixed and dependent on presentation and PFIC subtype. Only two studies reported HRQL and mortality results were variable across different subtypes. Lack of data and extensive heterogeneity severely limit understanding across this disease area, particularly variation around and within subtypes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01884-4.

Evaluation of the role of bile acids and serotonin as markers of pruritus in children with chronic cholestatic liver disease

BACKGROUND AND STUDY AIMS

Pruritus is an annoying symptom with an unclear pathogenesis accompanied by chronic cholestasis. This cross-sectional study was conducted to define the relationship between serum levels of presumed pruritogens (bile acids (BAs) and serotonin) and severity of pruritus in pediatric patients with chronic cholestatic liver disease.

PATIENTS AND METHODS

A total of 28 children suffering from pruritus due to chronic cholestatic liver disease and 29 age- and sex-matched healthy control subjects were examined. Scores obtained used the 5-D itch scale were evaluated among patients. Serum levels of BAs and serotonin were determined using enzymatic assays and high-performance liquid chromatography, respectively.

RESULTS

Patients had higher serum BA levels and lower serotonin levels than control subjects. Serum BA levels were significantly elevated in 61% of patients. The 5-D itch scale scores were significantly higher in cholestatic individuals with normal γ-glutamyl transpeptidase levels. Neither BA nor serotonin levels correlated with the severity of the 5-Ditch scale score.

CONCLUSION

Neither BA nor serotonin levels correlated with the severity of pruritus, indicating that they may not be good laboratory markers for the intensity of itch in children with cholestasis. Our findings suggest that it is necessary to identify another potential pruritogenic mediator, most probably of a biliary origin.

Genetic analysis in European ancestry individuals identifies 517 loci associated with liver enzymes

Serum concentration of hepatic enzymes are linked to liver dysfunction, metabolic and cardiovascular diseases. We perform genetic analysis on serum levels of alanine transaminase (ALT), alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) using data on 437,438 UK Biobank participants. Replication in 315,572 individuals from European descent from the Million Veteran Program, Rotterdam Study and Lifeline study confirms 517 liver enzyme SNPs. Genetic risk score analysis using the identified SNPs is strongly associated with serum activity of liver enzymes in two independent European descent studies (The Airwave Health Monitoring study and the Northern Finland Birth Cohort 1966). Gene-set enrichment analysis using the identified SNPs highlights involvement in liver development and function, lipid metabolism, insulin resistance, and vascular formation. Mendelian randomization analysis shows association of liver enzyme variants with coronary heart disease and ischemic stroke. Genetic risk score for elevated serum activity of liver enzymes is associated with higher fat percentage of body, trunk, and liver and body mass index. Our study highlights the role of molecular pathways regulated by the liver in metabolic disorders and cardiovascular disease.

Use of a Comprehensive 66-Gene Cholestasis Sequencing Panel in 2171 Cholestatic Infants, Children, and Young Adults

OBJECTIVES

Cholestasis is caused by a wide variety of etiologies, often genetic in origin. Broad overlap in clinical presentations, particularly in newborns, renders prioritizing diagnostic investigations challenging. In this setting, a timely, comprehensive assessment using a multigene panel by a clinical diagnostic laboratory would likely prove useful. We summarize initial findings from a testing program designed to discover genetic causes of cholestasis.

METHODS

A neonatal/adult sequencing panel containing 66 genes (originally 57; nine added March 2017) relevant to cholestasis was used. A broad range of eligible patients were enrolled with current/history of cholestasis without an identified cause, or unexplained chronic liver disease. DNA sequencing utilized a custom-designed capture library, and variants were classified and reported as benign, likely benign, variant of unknown significance (VOUS), likely pathogenic (LP), or pathogenic (P), according to the clinical interpretation workflow at EGL Genetics (Tucker, GA).

RESULTS

A total of 2433 samples were submitted between February 2016 and December 2017; 2171 results were reported. Median turnaround time was 21 days. Results from the 2171 subjects (57% <1 year old) included 583 P variants, 79 LP variants, and 3117 VOUS; 166 P/LP variants and 415 VOUS were novel. The panel's overall diagnostic yield was 12% (n = 265/2171) representing 32 genes. The top five genetic diagnoses for the group, in order: JAG1 + NOTCH2 (Alagille syndrome), ABCB11, SERPINA1, ABCB4, and POLG.

CONCLUSIONS

These findings support the utility of comprehensive rapid multigene testing in diagnosing cholestasis and highlight the evolving understanding of genetic variants contributing to the pathogenesis of cholestasis.

Plasma membrane integrity: implications for health and disease

Plasma membrane integrity is essential for cellular homeostasis. In vivo, cells experience plasma membrane damage from a multitude of stressors in the extra- and intra-cellular environment. To avoid lethal consequences, cells are equipped with repair pathways to restore membrane integrity. Here, we assess plasma membrane damage and repair from a whole-body perspective. We highlight the role of tissue-specific stressors in health and disease and examine membrane repair pathways across diverse cell types. Furthermore, we outline the impact of genetic and environmental factors on plasma membrane integrity and how these contribute to disease pathogenesis in different tissues.

Dual β-Catenin and γ-Catenin Loss in Hepatocytes Impacts Their Polarity through Altered Transforming Growth Factor-β and Hepatocyte Nuclear Factor 4α Signaling

Hepatocytes are highly polarized epithelia. Loss of hepatocyte polarity is associated with various liver diseases, including cholestasis. However, the molecular underpinnings of hepatocyte polarization remain poorly understood. Loss of β-catenin at adherens junctions is compensated by γ-catenin and dual loss of both catenins in double knockouts (DKOs) in mice liver leads to progressive intrahepatic cholestasis. However, the clinical relevance of this observation, and further phenotypic characterization of the phenotype, is important. Herein, simultaneous loss of β-catenin and γ-catenin was identified in a subset of liver samples from patients of progressive familial intrahepatic cholestasis and primary sclerosing cholangitis. Hepatocytes in DKO mice exhibited defects in apical-basolateral localization of polarity proteins, impaired bile canaliculi formation, and loss of microvilli. Loss of polarity in DKO livers manifested as epithelial-mesenchymal transition, increased hepatocyte proliferation, and suppression of hepatocyte differentiation, which was associated with up-regulation of transforming growth factor-β signaling and repression of hepatocyte nuclear factor 4α expression and activity. In conclusion, concomitant loss of the two catenins in the liver may play a pathogenic role in subsets of cholangiopathies. The findings also support a previously unknown role of β-catenin and γ-catenin in the maintenance of hepatocyte polarity. Improved understanding of the regulation of hepatocyte polarization processes by β-catenin and γ-catenin may potentially benefit development of new therapies for cholestasis.

Clinical spectrum of chronic liver disease with final outcome in children at a tertiary centre: A single - centre study

Background and Objectives

Chronic liver disease (CLD) in children present a broad spectrum of symptoms. Limited resources in Paediatric Hepatology in developing countries like Pakistan present considerable challenges in investigating and treating children with chronic liver disease in a timely fashion. This study aimed to determine the spectrum and outcomes of CLD other than chronic hep B & C virus (HBV& HCV) liver disease in children.

Methods

This retrospective descriptive study was conducted at the Paediatric Gastroenterology and Hepatology Department, Pakistan Kidney and Liver Institute and Research Centre in Lahore, Pakistan. The duration of the study was from August 2019 to January 2020. A total of 162 children of CLD were seen during this period of time. Of 162 there were 130 children with chronic HBV & HCV who were excluded from this study. 32 children aged 15 years or younger with chronic liver disease were included. The referrals were received from primary and secondary health care centres in different parts of the country. The data were collected from hospital electronic medical records database and then incorporated into a spreadsheet for analysis. The statistical analysis was performed by applying t-test with p value determined.

Results

Of 32 children autoimmune hepatitis (n=11; 34.3%) was the most common cause for chronic liver disease referrals, followed by progressive familial intrahepatic cholestasis type-2, (n=7; 21.8%), post Kasai for biliary atresia, (n=4; 12.5%), glycogen storage disease type-1 (n=5; 15.6%), Wilson disease (n=3; 9.3%) and primary sclerosing cholangitis (n=2; 6.2%). The diagnosis was principally established with the assistance of liver ultrasound, liver biopsy, magnetic resonance cholangiopancreatography and genetic testing.

Conclusion

Autoimmune hepatitis was the most common chronic liver disease. Our systematic approach, in addition to an extensive workup, helped us to diagnose and then initiate an appropriate treatment, which resulted in a more optimal outcome. Prompt referrals to tertiary centres are recommended where resources and expertise are available to reduce patient morbidity and mortality.

Burden of illness of progressive familial intrahepatic cholestasis in the US, UK, France, and Germany: study rationale and protocol of the PICTURE study

Background: Progressive familial intrahepatic cholestasis (PFIC) is an ultra-rare disease with a considerable burden on pediatric patients and their caregivers, impacting quality of life (QoL). The mortality rates highlight a significant need for efficacious treatments. Real-world data on associated costs and QoL are needed to gauge the potential impact of new pharmacological treatments.Methods: Clinical and socio-economic burden of PFIC on patients/caregivers, health systems, and society will be assessed. Patient/caregiver- and physician-level retrospective cross-sectional data will be collected from the US, UK, France, and Germany, for PFIC types 1, 2, 3.A representative sample of physicians will provide clinical and resource utilization information using an electronic Case Report Form (eCRF). Patient/caregiver surveys will collect socio-economic and QoL data, enabling assessment of PFIC impact on QoL. Mean costs (direct medical/non-medical, indirect) will be calculated.The study materials were reviewed by medical professionals and patient representatives and received ethical approval from the University of Chester.Discussion: The study aims to reveal the unmet medical need, disease burden, resource utilization, and costs of PFIC, to raise awareness with policymakers and healthcare professionals, and provide support for the patient/caregiver community. As novel PFIC therapies recently emerged, this study will yield quantifiable data for health technology assessments.

Progressive Familial Intrahepatic Cholestasis Type 1 Associated with Cherry-Red Spots in an Infant: A First Case Report

Progressive familial intrahepatic cholestasis type 1 (PFIC1) associated with a cherry-red spot, to our knowledge, has never been reported in the literature. We report the case of a 10‑month‑old girl with prolonged cholestasis. A diagnosis of PFIC1 was made by whole‑exome sequencing. Fundus examination showed a cherry-red spot. Our case provides a new insight toward the first case of ocular manifestation of PFIC1. Further studies are required to elucidate FIC1 gene expression in the macula.

Molecular overview of progressive familial intrahepatic cholestasis

Cholestasis is a clinical condition resulting from the imapairment of bile flow. This condition could be caused by defects of the hepatocytes, which are responsible for the complex process of bile formation and secretion, and/or caused by defects in the secretory machinery of cholangiocytes. Several mutations and pathways that lead to cholestasis have been described. Progressive familial intrahepatic cholestasis (PFIC) is a group of rare diseases caused by autosomal recessive mutations in the genes that encode proteins expressed mainly in the apical membrane of the hepatocytes. PFIC 1, also known as Byler’s disease, is caused by mutations of the ATP8B1 gene, which encodes the familial intrahepatic cholestasis 1 protein. PFIC 2 is characterized by the downregulation or absence of functional bile salt export pump (BSEP) expression via variations in the ABCB11 gene. Mutations of the ABCB4 gene result in lower expression of the multidrug resistance class 3 glycoprotein, leading to the third type of PFIC. Newer variations of this disease have been described. Loss of function of the tight junction protein 2 protein results in PFIC 4, while mutations of the NR1H4 gene, which encodes farnesoid X receptor, an important transcription factor for bile formation, cause PFIC 5. A recently described type of PFIC is associated with a mutation in the MYO5B gene, important for the trafficking of BSEP and hepatocyte membrane polarization. In this review, we provide a brief overview of the molecular mechanisms and clinical features associated with each type of PFIC based on peer reviewed journals published between 1993 and 2020.

Bile Acids and GPBAR-1: Dynamic Interaction Involving Genes, Environment and Gut Microbiome

Bile acids (BA) are amphiphilic molecules synthesized in the liver from cholesterol. BA undergo continuous enterohepatic recycling through intestinal biotransformation by gut microbiome and reabsorption into the portal tract for uptake by hepatocytes. BA are detergent molecules aiding the digestion and absorption of dietary fat and fat-soluble vitamins, but also act as important signaling molecules via the nuclear receptor, farnesoid X receptor (FXR), and the membrane-associated G protein-coupled bile acid receptor 1 (GPBAR-1) in the distal intestine, liver and extra hepatic tissues. The hydrophilic-hydrophobic balance of the BA pool is finely regulated to prevent BA overload and liver injury. By contrast, hydrophilic BA can be hepatoprotective. The ultimate effects of BA-mediated activation of GPBAR-1 is poorly understood, but this receptor may play a role in protecting the remnant liver and in maintaining biliary homeostasis. In addition, GPBAR-1 acts on pathways involved in inflammation, biliary epithelial barrier permeability, BA pool hydrophobicity, and sinusoidal blood flow. Recent evidence suggests that environmental factors influence GPBAR-1 gene expression. Thus, targeting GPBAR-1 might improve liver protection, facilitating beneficial metabolic effects through primary prevention measures. Here, we discuss the complex pathways linked to BA effects, signaling properties of the GPBAR-1, mechanisms of liver damage, gene-environment interactions, and therapeutic aspects.

Phenotypic and Molecular Characteristics of Children with Progressive Familial Intrahepatic Cholestasis in South China

PURPOSE

Progressive familial intrahepatic cholestasis (PFIC) is a rare genetic autosomal recessive disease caused by mutations in ATP8B1, ABCB11 or ABCB4. Mutational analysis of these genes is a reliable approach to identify the disorder.

METHODS

We collected and analyzed relevant data related to clinical diagnosis, biological investigation, and molecular determination in nine children carrying these gene mutations, who were from unrelated families in South China.

RESULTS

Of the nine patients (five males, four females) with PFIC, one case of PFIC1, four cases of PFIC2, and four cases of PFIC3 were diagnosed. Except in patient no. 8, jaundice and severe pruritus were the major clinical signs in all forms. γ-glutamyl transpeptidase was low in patients with PFIC1/PFIC2, and remained mildly elevated in patients with PFIC3. We identified 15 different mutations, including nine novel mutations (p.R470HfsX8, p.Q794X and p.I1170T of ABCB11 gene mutations, p.G319R, p.A1047P, p.G1074R, p.T830NfsX11, p.A1047PfsX8 and p.N1048TfsX of ABCB4 gene mutations) and six known mutations (p.G446R and p.F529del of ATP8B1 gene mutations, p.A588V, p.G1004D and p.R1057X of ABCB11 gene mutations, p.P479L of ABCB4 gene mutations). The results showed that compared with other regions, these three types of PFIC genes had different mutational spectrum in China.

CONCLUSION

The study expands the genotypic spectrum of PFIC. We identified nine novel mutations of PFIC and our findings could help in the diagnosis and treatment of this disease.

Structural basis of tropifexor as a potent and selective agonist of farnesoid X receptor

Farnesoid X receptor (FXR) is considered as a potential target for the treatment of several liver disorders such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Tropifexor is a highly potent and non-steroidal FXR agonist that has progressed into phase II clinical trials in patients with PBC. The clinical trials demonstrate that tropifexor improved serum markers of patients with liver diseases and lower side effect such as pruritus that might be implicated with TGR5 activation. However, the molecular mechanism of the potency and selectivity of tropifexor remains unclear. In this study, the binding affinity of FXR and tropifexor is measured by isothermal titration calorimetry (ITC) assays. The crystal structure of the FXR/tropifexor complex is determined at 2.7 Å resolution to explain the molecular mechanism of tropifexor bound to FXR-LBD. Structural comparison with other FXR/agonists structures reveals the conformational change in the FXR/tropifexor structure. Moreover the structural superposition of TGR5/tropifexor indicates that the steric hindrance between tropifexor and TGR5 might be a possible explanation for the impotency arises of tropifexor to TGR5. Overall, our analyses might provide an insight into the molecular mechanism of tropifexor binding to FXR-LBD and account for the high selectivity of tropifexor for FXR versus TGR5.

Cholestatic Liver Diseases: A Primer for Generalists and Subspecialists

Cholestasis describes impairment in bile formation or flow which can manifest clinically with fatigue, pruritus, and jaundice. The differential diagnosis of cholestatic liver diseases is broad, and the etiologies of cholestasis vary in the anatomical location of the defect and acuity of presentation. Cholestasis may occur in a variety of clinical scenarios. Therefore, it is important for a diverse audience with varied clinical practices to have a basic understanding of manifestations of cholestatic liver diseases.

Variants in ABCB4 (MDR3) across the spectrum of cholestatic liver diseases in adults

The ATP binding cassette subfamily B member 4 (ABCB4) gene on chromosome 7 encodes the ABCB4 protein (alias multidrug resistance protein 3 [MDR3]), a P-glycoprotein in the canalicular membrane of the hepatocytes that acts as a translocator of phospholipids into bile. Several variants in ABCB4 have been shown to cause ABCB4 deficiency, accounting for a disease spectrum ranging from progressive familial cholestasis type 3 to less severe conditions like low phospholipid-associated cholelithiasis, intrahepatic cholestasis of pregnancy or drug-induced liver injury. Furthermore, whole genome sequencing has shown that ABCB4 variants are associated with an increased incidence of gallstone disease, gallbladder and bile duct carcinoma, liver cirrhosis or elevated liver function tests. Diagnosis of ABCB4 deficiency-related diseases is based on clinical presentation, serum biomarkers, imaging techniques, liver histology and genetic testing. Nevertheless, the clinical presentation can vary widely and clear genotype-phenotype correlations are currently lacking. Ursodeoxycholic acid is the most commonly used medical treatment, but its efficacy has yet to be proven in large controlled clinical studies. Future pharmacological options may include stimulation/restoration of residual function by chaperones (e.g. 4-phenyl butyric acid, curcumin) or induction of ABCB4 transcription by FXR (farnesoid X receptor) agonists or PPARα (peroxisome proliferator-activated receptor-α)-ligands/fibrates. Orthotopic liver transplantation remains the last and often only therapeutic option in cirrhotic patients with end-stage liver disease or patients with intractable pruritus.

Surgical diversion of enterohepatic circulation in pediatric cholestasis

Progressive familial intrahepatic cholestasis (PFIC) and Alagille syndrome (AS) are conditions caused by either an autosomal recessive or an autosomal dominant genetic defect, and they are both characterized by cholestasis, jaundice, and severe debilitating pruritus refractory to medical management. Before the advent of liver transplantation, most PFIC patients would die from end-stage liver disease in the first decade of life. Although liver transplantation has led to patients' survival, disease recurrence (PFIC-2) and severe extra-hepatic manifestations of the disease (PFIC-1) occurred post transplant. In the late 1980s, Whitington described the use of partial external biliary diversion in PFIC and AS patients as a successful way to improve symptoms and decrease circulating bile acid serum concentrations. Since then, other diversion techniques have been described (ileal exclusion and partial internal biliary diversion). These techniques have the benefit of avoiding a stoma, but equivalent results have not been demonstrated (recurrence of cholestasis after ileal exclusion, limited follow up after internal biliary diversion). Overall, studies have showed that biliary diversions in children with cholestasis are safe procedures with low morbidity and mortality, and that they can reduce inflammation and ongoing liver injury, therefore delaying or avoiding the need for liver transplantation in some patients.

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

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

Biopsy Validated Study of Biomarkers for Liver Fibrosis and Transplant Prediction in Inherited Cholestasis

Alagille syndrome (ALGS) and progressive familial intrahepatic cholestasis (PFIC) are inherited cholestatic disorders with risk of developing end‐stage liver disease requiring liver transplantation (LT). We investigated aspartate aminotransferase‐to‐platelet ratio index (APRI), Fibrosis‐4 score (FIB‐4), and conjugated bilirubin as biomarkers to assess fibrosis severity and risk for LT among children with ALGS and PFIC. This multicenter, cross‐sectional study included 64 children with ALGS or PFIC (per genetics or strict clinical criteria) with APRI, FIB‐4, and conjugated bilirubin levels collected within ±90 days of their most recent liver biopsy. A single, blinded pathologist staged all biopsies (metavir; F0‐F2: nonsevere, F3‐F4: severe). Logistic regression and area under the receiver operating characteristic curve analysis (AUC) were used to assess biomarker associations with fibrosis severity and risk for LT. In ALGS, only APRI distinguished F3‐F4 (AUC 0.72, P = 0.012), with a cutoff greater than 2.97 demonstrating a sensitivity of 61.5% (95% confidence interval 0.32, 0.86) and specificity of 81.5% (0.62, 0.94). In ALGS, a 50% increase of APRI increased the odds of F3‐F4 by 1.31‐fold (1.04, 1.65; P = 0.023). In ALGS, APRI (AUC 0.87; P < 0.001) and FIB‐4 (AUC 0.84; P < 0.001) were able to predict risk for LT. In PFIC, only APRI distinguished F3‐4 (AUC 0.74, P = 0.039), with a cutoff greater than 0.99 demonstrating a sensitivity of 80% (0.44, 0.98) and specificity of 64.3% (0.35, 0.87). In PFIC, only FIB‐4 was able predict risk for LT (AUC 0.80; P = 0.002). In ALGS or PFIC, conjugated bilirubin could not distinguish F3‐F4 or predict risk for LT. Conclusion: This liver biopsy–validated study suggests that APRI is able to distinguish F3‐F4 from F0‐F2 in ALGS and PFIC. APRI and FIB‐4 may also serve as predictors of risk for LT in ALGS (APRI and FIB‐4) and PFIC (FIB‐4).

Progressive familial intrahepatic cholestasis type 4 in an Indian child: presentation, initial course and novel compound heterozygous mutation

A 15-year-old boy who had a history of on and off pruritus and jaundice since many years found to have a novel mutation in TJP2 gene. On examination, he had clubbing, splenomegaly, grade 3 oesophageal varices and short stature. Investigation revealed direct hyperbirubinemia with elevated liver enzymes with normal gamma-glutamyl transferase (GGT). Antinuclear antibody (ANA), smooth muscle antibody (SMA) anti-liver kidney microsomal (anti-LKM) and viral markers for hepatitis were negative. However, IgG was elevated and anti-smooth muscle antibody (ASMA) was weekly positive (1:20). He was also given a trial of steroid and azathioprine for 1 year on the basis of liver biopsy findings, raised IgG and positive ASMA but finding no improvement stopped. Genetic testing by next-generation sequencing found a novel compound heterozygous missense variation in exon 17 of the TJP2 gene confirming progressive familial intrahepatic cholestasis type 4 as the aetiology of cholestatic liver disease.

Transcriptomic analysis across liver diseases reveals disease-modulating activation of constitutive androstane receptor in cholestasis

Background & Aims

Liver diseases are caused by many factors, such as genetics, nutrition, and viruses. Therefore, it is important to delineate transcriptomic changes that occur in various liver diseases.

Methods

We performed high-throughput sequencing of mouse livers with diverse types of injuries, including cholestasis, diet-induced steatosis, and partial hepatectomy. Comparative analysis of liver transcriptome from mice and human samples of viral infections (HBV and HCV), alcoholic hepatitis (AH), non-alcoholic steatohepatitis (NASH), and biliary atresia revealed distinct and overlapping gene profiles associated with liver diseases. We hypothesised that discrete molecular signatures could be utilised to assess therapeutic outcomes. We focused on cholestasis to test and validate the hypothesis using pharmacological approaches.

Results

Here, we report significant overlap in the expression of inflammatory and proliferation-related genes across liver diseases. However, cholestatic livers were unique and displayed robust induction of genes involved in drug metabolism. Consistently, we found that constitutive androstane receptor (CAR) activation is crucial for the induction of the drug metabolic gene programme in cholestasis. When challenged, cholestatic mice were protected against zoxazolamine-induced paralysis and acetaminophen-induced hepatotoxicity. These protective effects were diminished upon inhibition of CAR activity. Further, drug metabolic genes were also induced in the livers from a subset of biliary atresia patients, but not in HBV and HCV infections, AH, or NASH. We also found a higher expression of CYP2B6, a CAR target, in the livers of biliary atresia patients, underscoring the clinical importance of our findings.

Conclusions

Comparative transcriptome analysis of different liver disorders revealed specific induction of phase I and II metabolic genes in cholestasis. Our results demonstrate that CAR activation may lead to variations in drug metabolism and clinical outcomes in biliary atresia.

Lay summary

Transcriptomic analysis of diverse liver diseases revealed alterations in common and distinct pathways. Specifically, in cholestasis, we found that detoxification genes and their activity are increased. Thus, cholestatic patients may have an unintended consequence on drug metabolism and not only have a beneficial effect against liver toxicity, but also may require adjustments to their therapeutic dosage.

•

Cell cycle, inflammation, and glucose homeostasis are some of the common pathways altered in a variety of liver disorders.

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Phase I and II metabolic genes are induced in Fxr^−/−Shp^−/− double knockouts (DKOs) and bile-acid-fed control mice.

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Activation of xeno-sensor, constitutive androstane receptor (CAR), is observed in cholestasis.

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Inhibiting CAR activity in DKO mice exacerbates zoxazolamine-induced paralysis and acetaminophen-induced hepatotoxicity.

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A subset of patients with biliary atresia display increased expression of CAR target protein CYP2B6.

Machine learning guided association of adverse drug reactions with in vitro target-based pharmacology

BACKGROUND

Adverse drug reactions (ADRs) are one of the leading causes of morbidity and mortality in health care. Understanding which drug targets are linked to ADRs can lead to the development of safer medicines.

METHODS

Here, we analyse in vitro secondary pharmacology of common (off) targets for 2134 marketed drugs. To associate these drugs with human ADRs, we utilized FDA Adverse Event Reports and developed random forest models that predict ADR occurrences from in vitro pharmacological profiles.

FINDINGS

By evaluating Gini importance scores of model features, we identify 221 target-ADR associations, which co-occur in PubMed abstracts to a greater extent than expected by chance. Amongst these are established relations, such as the association of in vitro hERG binding with cardiac arrhythmias, which further validate our machine learning approach. Evidence on bile acid metabolism supports our identification of associations between the Bile Salt Export Pump and renal, thyroid, lipid metabolism, respiratory tract and central nervous system disorders. Unexpectedly, our model suggests PDE3 is associated with 40 ADRs.

INTERPRETATION

These associations provide a comprehensive resource to support drug development and human biology studies.

FUNDING

This study was not supported by any formal funding bodies.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

IV.

Odevixibat and partial external biliary diversion showed equal improvement of cholestasis in a patient with progressive familial intrahepatic cholestasis

Untreated progressive familial intrahepatic cholestasis (PFIC) type 2, or bile salt exporter protein deficiency, frequently leads to severe pruritus, impaired growth and progressive liver fibrosis with risk of organ failure. We describe a 15-month-old male patient with severe pruritus diagnosed with PFIC type 2 enrolled in an open-label phase 2 study who received 4 weeks of treatment with odevixibat, an ileal bile acid transporter inhibitor under development for cholestatic liver disease treatment. The patient experienced reductions in serum bile acids and improvement in itching and sleep scores, and odevixibat was well tolerated. After the odevixibat study, symptoms returned and the patient underwent partial external biliary diversion (PEBD). Odevixibat treatment and PEBD produced similar normalisation of serum bile acid levels and improvements in pruritus and sleep disruptions. Thus, odevixibat appeared to be as effective as invasive PEBD in treating serum bile acids and cholestatic pruritus in this patient.

Treatment of rickets and dyslipidemia in twins with progressive familial intrahepatic cholestasis type 2

Background

Progressive Familial Intrahepatic Cholestasis Type 2 (PFIC2) is a rare congenital cholestatic liver disease that progresses to end stage liver disease. It is associated with fat soluble vitamin D deficiency rickets and severe dyslipidemia; however, treatment of these secondary effects remains a challenge.

Case presentation

One year old twin males born to a mother with intrahepatic cholestasis during pregnancy presented with jaundice, pruritus and failure to thrive. Lab evaluation revealed significant transaminitis, direct hyperbilirubinemia and normal gamma glutamyl transferase (GGT). Genetic studies confirmed PFIC2. Further evaluation for fat soluble vitamin deficiencies revealed severe vitamin D deficiency rickets. High dose vitamin D replacement therapy using Ergocalciferol (Vitamin D₂) 50,000 IU three times a week over 10 weeks led to the improvement of Vitamin D, 25-Hydroxy (25-OH) serum levels and resolution of rickets. Dyslipidemia with very low high density lipoprotein-cholesterol (HDL-C) and high triglycerides was more profound in our patients compared to what has been described in the literature thus far. The dyslipidemia improved 2 months after internal biliary diversion.

Conclusions

Higher doses of Vitamin D therapy are needed for treatment of rickets secondary to cholestasis. Extremely low HDL-C levels are characteristic of PFIC and improve with treatment of underlying cholestasis. Maternal intrahepatic cholestasis during pregnancy can be an early warning sign.

Effects of partial internal biliary diversion on long-term outcomes in patients with progressive familial intrahepatic cholestasis: experience in 44 patients

PURPOSE

Progressive familial intrahepatic cholestasis (PFIC) is a hereditary disease characterized by cholestasis, which may cause jaundice, severe pruritus, and cirrhosis in the later stages. By the invention of biliary diversion methods, these patients were prevented from undergoing liver transplant. Using biliary diversion techniques, the entero-hepatic cycle was interrupted. This lowers the bile acid pool and resolves the pruritus. Herein, we report 44 cases of PFIC who underwent partial internal biliary diversion (PIBD) and long-term follow-up of these children. This comprises the largest case series of PIBD.

METHODS

All patients were diagnosed by liver biopsy as PFIC before the operation. All underwent cholecysto colic bypass by jejunal interposition due to severe pruritus unresponsive to medication. Laboratory blood tests, sonography, and physical exam were done before and after the operation once every 3 months. Besides, a questionnaire was designed to ask the patients about the symptoms after the operation, and a pruritus score was measured using the 5D-itch scale.

RESULTS

44 children (25 boys, 19 girls), between 1.75 and 27.5 years (at the time of this study) were followed for a median period of 54 months. Age at operation ranged from 2 months to 18 years, with a median of 29 months. Of these children, 14 were lost to follow up. Results showed a significant decrease in pruritus and sleep disturbance after the surgery (p < 0.001). Also, jaundice decreased from 82.1 before to 7.1% following the surgery. 50% of the patients became medication-free at follow-up.

CONCLUSION

PIBD is a safe procedure which helps non-cirrhotic children preserve their liver function. Therefore, PIBD prevents them from undergoing liver transplant. Effective results were achieved in terms of severe pruritus and jaundice, and children were able to regain their sleep patterns. It also avoided external stoma, which is more convenient from the patient's point of view.

Novel ABCB4 mutation in a Chinese female patient with progressive familial intrahepatic cholestasis type 3: a case report

Background

Progressive familial intrahepatic cholestasis (PFIC) is a rare group of autosomal recessive hereditary hepatic diseases. There are three types of PFIC, classified according to the mutated gene. For example, PFIC type 3 (PFIC3) is due to mutations in the ABCB4 gene (encoding multidrug-resistant protein 3 [MDR3]).

Case presentation

We present a 19-year-old Chinese female patient who had a 2-year history of recurrent liver dysfunction, with mainly elevated alkaline phosphatase and γ-glutamyl transpeptidase(γ-GT) levels. After excluding other causes of abnormal liver function and cholestasis, the final diagnosis of PFIC3 was confirmed by histopathological examination and gene detection. The immunohistochemical results showed no MDR3 protein expression in the bile duct membrane. Genetic sequencing analysis revealed a novel heterozygous 2137G > A; p. V713M mutation (Exon 17) and a synonymous 504C > T; p. N168N mutation (Exon 6) in ABCB4.

Conclusions

Our patient with long-term liver dysfunction demonstrated that elevated alkaline phosphatase and γ-GT levels should be associated with the diagnosis of PFIC3, and gene detection is the key to diagnosis. From our in silico analysis, the novel mutation p. V713M in Exon 17 was predicted to affect protein function, with a SIFT (Sorting Intolerant from Tolerant) score of 0.02, indicating a deleterious effect. Further studies are necessary to investigate the impact of the novel heterozygous 2137G > A; p. V713M mutation (Exon 17) on functional defects of MDR3 and PFIC3.

Phenotype-Genotype Correlation of North Indian Progressive Familial Intrahepatic Cholestasis type2 Children Shows p.Val444Ala and p.Asn591Ser Variants and Retained BSEP Expression

Backgrounds and Aims: Progressive familial intrahepatic cholestasis type 2 (PFIC2) is caused by a defect or deficiency of bile salt export protein (BSEP) due to mutation in the ABCB11 gene. We intend to evaluate the phenotype-genotype correlation in 10 diagnosed cases of PFIC2 in a single tertiary care center in North India. Methods: The clinical, biochemical, histopathological, immunohistochemical, ultrastructural and genetic data of the 10 diagnosed cases of PFIC2 were recorded. Results: Icterus, pruritus and bleeding manifestations were the commonest clinical symptoms. Giant cell transformation was seen in 50% of the patients. Two predominant genetic variants were ABCB11 missense p.Val444Ala (c. 1331 T > C) and ABCB11 missense p.Asn591Ser (c. 1772 A > G) in their homozygous or compound heterozygous states and were associated with retained BSEP immunopositivity and reduced but retained BSEP immunopositivity respectively. Conclusion: Retention of BSEP is common in North Indian children of PFIC2 with no phenotype-genotype correlation.

Mechanism-based integrated assay systems for the prediction of drug-induced liver injury

Drug-induced liver injury (DILI) can cause hepatic failure and result in drug withdrawal from the market. It has host-related and compound-dependent mechanisms. Preclinical prediction of DILI risk is very challenging and safety assessments based on animals inadequately forecast human DILI risk. In contrast, human-derived in vitro cell culture-based models could improve DILI risk prediction accuracy. Here, we developed and validated an innovative method to assess DILI risk associated with various compounds. Fifty-four marketed and withdrawn drugs classified as DILI risks of "most concern", "less concern", and "no concern" were tested using a combination of four assays addressing mitochondrial injury, intrahepatic lipid accumulation, inhibition of bile canalicular network formation, and bile acid accumulation. Using the inhibitory potencies of the drugs evaluated in these in vitro tests, an algorithm with the highest available DILI risk prediction power was built by artificial neural network (ANN) analysis. It had an overall forecasting accuracy of 73%. We excluded the intrahepatic lipid accumulation assay to avoid overfitting. The accuracy of the algorithm in terms of predicting DILI risks was 62% when it was constructed by ANN but only 49% when it was built by the point-added scoring method. The final algorithm based on three assays made no DILI risk prediction errors such as "most concern " instead of "no concern" and vice-versa. Our mechanistic approach may accurately predict DILI risks associated with numerous candidate drugs.

Combination of Novel c.3484G> T/p.Glu162Ter Variant in ABCB11 and c.208G> A/p.Asp70Asn Variant in ATP8B1 Are Associated with Severe Symptoms in Progressive Family Intrahepatic Cholestasis

Progressive family intrahepatic cholestasis (PFIC) is an autosomal recessive disease that causes chronic cholestasis. It is associated with pathogenic variants in genes that encode proteins involved in bile secretion to canaliculus from hepatocytes. In this study, we present a 16-year-old boy who presented with severe pruritus and cholestatic jaundice. All possible infectious etiologies were negative. A liver biopsy was consistent with intrahepatic cholestasis and portal fibrosis. DNA was isolated from a peripheral blood sample, and whole exome sequencing was performed. A novel c.3484G > T/p.Glu162Ter variant in the ABCB11 gene and a c.208G> A/p.Asp70Asn variant in the ATP8B1 gene were detected. Despite traditional treatment, the patient's recurrent severe symptoms did not improve. The patient was referred for a liver transplantation. This novel c.3484G > T/p.Glu162Ter variant is associated with a severe and recurrent presentation, and the two compound variants could explain the severity of PFIC.

Intestinal Absorption of Bile Acids in Health and Disease

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

Comorbidity between progressive familial intrahepatic cholestasis and atopic dermatitis in a 19-month-old child

Atopic dermatitis (AD) is the most common chronic skin disease in children, with an increasing prevalence in the past three decades. Adequate treatment is prescribed for individual patient based on symptoms and disease severity. However, further underlying diagnosis should be researched when therapeutic strategies for symptoms fail and skin lesions and pruritus persist. We reported herein the case of a 19-month-old infant with a history of AD unresponsive to treatment due to the type 2 progressive familial intrahepatic cholestasis (PFIC). A new homozygous mutation of the ABCB11 gene was found. The severe pruritus, the early onset jaundice, poor growth and raised transaminase levels with normal gamma glutamyl transpeptidase have led to the suspicion of PFIC. The presence of severe AD and intrahepatic chronic cholestasis, both pruritus associated, could delay a proper diagnosis. To our knowledge, for the first time, a case of comorbidity between type 2 PFIC and AD-like disease had been described.

A Physiology-Based Model of Human Bile Acid Metabolism for Predicting Bile Acid Tissue Levels After Drug Administration in Healthy Subjects and BRIC Type 2 Patients

Drug-induced liver injury (DILI) is a matter of concern in the course of drug development and patient safety, often leading to discontinuation of drug-development programs or early withdrawal of drugs from market. Hepatocellular toxicity or impairment of bile acid (BA) metabolism, known as cholestasis, are the two clinical forms of DILI. Whole-body physiology-based modelling allows a mechanistic investigation of the physiological processes leading to cholestasis in man. Objectives of the present study were: (1) the development of a physiology-based model of the human BA metabolism, (2) population-based model validation and characterisation, and (3) the prediction and quantification of altered BA levels in special genotype subgroups and after drug administration. The developed physiology-based bile acid (PBBA) model describes the systemic BA circulation in humans and includes mechanistically relevant active and passive processes such as the hepatic synthesis, gallbladder emptying, transition through the gastrointestinal tract, reabsorption into the liver, distribution within the whole body, and excretion via urine and faeces. The kinetics of active processes were determined for the exemplary BA glycochenodeoxycholic acid (GCDCA) based on blood plasma concentration-time profiles. The robustness of our PBBA model was verified with population simulations of healthy individuals. In addition to plasma levels, the possibility to estimate BA concentrations in relevant tissues like the intracellular space of the liver enhance the mechanistic understanding of cholestasis. We analysed BA levels in various tissues of Benign Recurrent Intrahepatic Cholestasis type 2 (BRIC2) patients and our simulations suggest a higher susceptibility of BRIC2 patients toward cholestatic DILI due to BA accumulation in the liver. The effect of drugs on systemic BA levels were simulated for cyclosporine A (CsA). Our results confirmed the higher risk of DILI after CsA administration in healthy and BRIC2 patients. The presented PBBA model enhances our mechanistic understanding underlying cholestasis and drug-induced alterations of BA levels in blood and organs. The developed PBBA model might be applied in the future to anticipate potential risk of cholestasis in patients.

Novel ATP8B1 Gene Mutations in a Child with Progressive Familial Intrahepatic Cholestasis Type 1

Progressive familial intrahepatic cholestasis (PFIC) is a group of severe genetic disorders, inherited in an autosomal recessive manner, causing cholestasis of hepatocellular origin, later progressing to biliary cirrhosis and liver failure. This is the first report of PFIC type 1 with novel compound heterozygous mutations in Korea. The patient was presented with intrahepatic cholestasis, a normal level of serum γ-glutamyl transferase, steatorrhea, and growth failure. Genetic testing of this patient revealed novel compound heterozygous mutations (p.Glu585Ter and p.Leu749Pro) in the ATP8B1 gene. After a liver transplantation at age 19 months, the patient developed severe post-transplant steatohepatitis.

Pathobiology of inherited biliary diseases: a roadmap to understand acquired liver diseases

Bile duct epithelial cells, also known as cholangiocytes, regulate the composition of bile and its flow. Acquired, congenital and genetic dysfunctions in these cells give rise to a set of diverse and complex diseases, often of unknown aetiology, called cholangiopathies. New knowledge has been steadily acquired about genetic and congenital cholangiopathies, and this has led to a better understanding of the mechanisms of acquired cholangiopathies. This Review focuses on findings from studies on Alagille syndrome, polycystic liver diseases, fibropolycystic liver diseases (Caroli disease and congenital hepatic fibrosis) and cystic fibrosis-related liver disease. In particular, knowledge on the role of Notch signalling in biliary repair and tubulogenesis has been advanced by work on Alagille syndrome, and investigations in polycystic liver diseases have highlighted the role of primary cilia in biliary pathophysiology and the concept of biliary angiogenic signalling and its role in cyst growth and biliary repair. In fibropolycystic liver disease, research has shown that loss of fibrocystin generates a signalling cascade that increases β-catenin signalling, activates the NOD-, LRR- and pyrin domain-containing 3 inflammasome, and promotes production of IL-1β and other chemokines that attract macrophages and orchestrate the process of pericystic and portal fibrosis, which are the main mechanisms of progression in cholangiopathies. In cystic fibrosis-related liver disease, lack of cystic fibrosis transmembrane conductance regulator increases the sensitivity of epithelial Toll-like receptor 4 that sustains the secretion of nuclear factor-κB-dependent cytokines and peribiliary inflammation in response to gut-derived products, providing a model for primary sclerosing cholangitis. These signalling mechanisms may be targeted therapeutically and they offer a possibility for the development of novel treatments for acquired cholangiopathies.

Familial intrahepatic cholestasis: New and wide perspectives

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) includes autosomal recessive cholestatic rare diseases of childhood.

AIMS

To update the panel of single genes mutations involved in familial cholestasis.

METHODS

PubMed search for "familial intrahepatic cholestasis" alone as well as in combination with other key words was performed considering primarily original studies and meta-analyses.

RESULTS

PFIC1 involves ATP8B1 gene encoding for aminophospholipid flippase FIC1. PFIC2 includes ABCB11 gene, encoding for protein functioning as bile salt export pump. PFIC3 is due to mutations of ABCB4 gene responsible for the synthesis of class III multidrug resistance P-glycoprotein flippase. PFIC4 and PFIC5 involve tight junction protein-2 gene and NR1H4 gene encoding for farnesoid X receptor. Benign Intrahepatic Cholestasis, Intrahepatic Cholestasis of Pregnancy and Low-phospholipid-associated cholelithiasis involve the same genes and are characterized by intermittent attacks of cholestasis, no progression to cirrhosis, reversible pregnancy-specific cholestasis and cholelithiasis in young people. Blood and liver tissue levels of bile-excreted drugs can be influenced by the presence of mutations in PFIC genes, causing drug-induced cholestasis. Mutations in PFIC genes might increase the risk of liver cancer.

CONCLUSION

There is a high proportion of unexplained cholestasis potentially caused by specific genetic pathophysiologic pathways. The use of next generation sequencing and whole-exome sequencing could improve the diagnostic process in this setting.

Severe Hepatotoxicity of Mithramycin Therapy Caused by Altered Expression of Hepatocellular Bile Transporters

Mithramycin demonstrates preclinical anticancer activity, but its therapeutic dose is limited by the development of hepatotoxicity that remains poorly characterized. A pharmacogenomics characterization of mithramycin-induced transaminitis revealed that hepatotoxicity is associated with germline variants in genes involved in bile disposition: ABCB4 (multidrug resistance 3) rs2302387 and ABCB11 [bile salt export pump (BSEP)] rs4668115 reduce transporter expression (P < 0.05) and were associated with ≥grade 3 transaminitis developing 24 hours after the third infusion of mithramycin (25 mcg/kg, 6 hours/infusion, every day ×7, every 28 days; P < 0.0040). A similar relationship was observed in a pediatric cohort. We therefore undertook to characterize the mechanism of mithramycin-induced acute transaminitis. As mithramycin affects cellular response to bile acid treatment by altering the expression of multiple bile transporters (e.g., ABCB4, ABCB11, sodium/taurocholate cotransporting polypeptide, organic solute transporter α/β) in several cell lines [Huh7, HepaRG, HepaRG BSEP (-/-)] and primary human hepatocytes, we hypothesized that mithramycin inhibited bile-mediated activation of the farnesoid X receptor (FXR). FXR was downregulated in all hepatocyte cell lines and primary human hepatocytes (P < 0.0001), and mithramycin inhibited chenodeoxycholic acid- and GW4046-induced FXR-galactose-induced gene 4 luciferase reporter activity (P < 0.001). Mithramycin promoted glycochenodeoxycholic acid-induced cytotoxicity in ABCB11 (-/-) cells and increased the overall intracellular concentration of bile acids in primary human hepatocytes grown in sandwich culture (P < 0.01). Mithramycin is a FXR expression and FXR transactivation inhibitor that inhibits bile flow and potentiates bile-induced cellular toxicity, particularly in cells with low ABCB11 function. These results suggest that mithramycin causes hepatotoxicity through derangement of bile acid disposition; results also suggest that pharmacogenomic markers may be useful to identify patients who may tolerate higher mithramycin doses. SIGNIFICANCE STATEMENT: The present study characterizes a novel mechanism of drug-induced hepatotoxicity in which mithramycin not only alters farnesoid X receptor (FXR) and small heterodimer partner gene expression but also inhibits bile acid binding to FXR, resulting in deregulation of cellular bile homeostasis. Two novel single-nucleotide polymorphisms in bile flow transporters are associated with mithramycin-induced liver function test elevations, and the present results are the rationale for a genotype-directed clinical trial using mithramycin in patients with thoracic malignancies.

Expanding etiology of progressive familial intrahepatic cholestasis

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) refers to a disparate group of autosomal recessive disorders that are linked by the inability to appropriately form and excrete bile from hepatocytes, resulting in a hepatocellular form of cholestasis. While the diagnosis of such disorders had historically been based on pattern recognition of unremitting cholestasis without other identified molecular or anatomic cause, recent scientific advancements have uncovered multiple specific responsible proteins. The variety of identified defects has resulted in an ever-broadening phenotypic spectrum, ranging from traditional benign recurrent jaundice to progressive cholestasis and end-stage liver disease.

AIM

To review current data on defects in bile acid homeostasis, explore the expanding knowledge base of genetic based diseases in this field, and report disease characteristics and management.

METHODS

We conducted a systemic review according to PRISMA guidelines. We performed a Medline/PubMed search in February-March 2019 for relevant articles relating to the understanding, diagnosis, and management of bile acid homeostasis with a focus on the family of diseases collectively known as PFIC. English only articles were accessed in full. The manual search included references of retrieved articles. We extracted data on disease characteristics, associations with other diseases, and treatment. Data was summarized and presented in text, figure, and table format.

RESULTS

Genetic-based liver disease resulting in the inability to properly form and secrete bile constitute an important cause of morbidity and mortality in children and increasingly in adults. A growing number of PFIC have been described based on an expanded understanding of biliary transport mechanism defects and the development of a common phenotype.

CONCLUSION

We present a summary of current advances made in a number of areas relevant to both the classically described FIC1 (ATP8B1), BSEP (ABCB11), and MDR3 (ABCB4) transporter deficiencies, as well as more recently described gene mutations -- TJP2 (TJP2), FXR (NR1H4), MYO5B (MYO5B), and others which expand the etiology and understanding of PFIC-related cholestatic diseases and bile transport.