The spectrum of Progressive Familial Intrahepatic Cholestasis diseases: Update on pathophysiology and emerging treatments

Youngest Living Donor Liver Transplant for End-Stage Liver Disease in a 6-Month-Old With a Novel Aggressive Mutation in KIF12 Gene

BACKGROUND

Kinesin family member 12 (KIF12) mutation-related cholestatic disorder represents a rare subtype of progressive familial intrahepatic cholestasis (PFIC), referred to as PFIC Type 8, with only 21 reported cases globally to date.

METHODS

Here, we present a unique case of a 6-month-old boy diagnosed with homozygous KIF12 gene mutation, who successfully underwent a living donor liver transplant at our center for end-stage liver disease.

RESULTS

This case marks the youngest patient of KIF12-related cholestatic disorder necessitating a liver transplant to date. The child initially presented with neonatal cholestasis and then developed infantile hepatic decompensation. Our report discusses the diagnostic process and management strategies employed. It underscores the importance of prompt diagnosis through clinical suspicion, biochemical parameters, and genetic testing, as well as the adoption of suitable management strategies, including the early contemplation of liver transplant in such exceptional and rare cases of genetic intrahepatic cholestasis.

CONCLUSION

KIF12-related genetic disease should be considered in neonatal cholestasis cases with high gamma glutamyl transpeptidase to differentiate from conditions like biliary atresia. Favorable outcomes post liver transplant stress the importance of early genetic testing and referral to liver transplant centers for unresponsive patients, potentially saving lives.

EASL Clinical Practice Guidelines on genetic cholestatic liver diseases

Genetic cholestatic liver diseases are caused by (often rare) mutations in a multitude of different genes. While these diseases differ in pathobiology, clinical presentation and prognosis, they do have several commonalities due to their cholestatic nature. These Clinical Practice Guidelines (CPGs) offer a general approach to genetic testing and management of cholestatic pruritus, while exploring diagnostic and treatment approaches for a subset of genetic cholestatic liver diseases in depth. An expert panel appointed by the European Association for the Study of the Liver has created recommendations regarding diagnosis and treatment, based on the best evidence currently available in the fields of paediatric and adult hepatology, as well as genetics. The management of these diseases generally takes place in a tertiary referral centre, in order to provide up-to-date approaches and expertise. These CPGs are intended to support hepatologists (for paediatric and adult patients), residents and other healthcare professionals involved in the management of these patients with concrete recommendations based on currently available evidence or, if not available, on expert opinion.

Molecular and computational characterization of ABCB11 and ABCG5 variants in Tunisian patients with neonatal/infantile low-GGT intrahepatic cholestasis: Genetic diagnosis and genotype-phenotype correlation assessment

Many inherited conditions cause hepatocellular cholestasis in infancy, including progressive familial intrahepatic cholestasis (PFIC), a heterogeneous group of diseases with highly overlapping symptoms. In our study, six unrelated Tunisian infants with PFIC suspicion were the subject of a panel-target sequencing followed by an exhaustive bioinformatic and modeling investigations. Results revealed five disease-causative variants including known ones: (the p.Asp482Gly and p.Tyr354 * in the ABCB11 gene and the p.Arg446 * in the ABCC2 gene), a novel p.Ala98Cys variant in the ATP-binding cassette subfamily G member 5 (ABCG5) gene and a first homozygous description of the p.Gln312His in the ABCB11 gene. The p.Gln312His disrupts the interaction pattern of the bile salt export pump as well as the flexibility of the second intracellular loop domain harboring this residue. As for the p.Ala98Cys, it modulates both the interactions within the first nucleotide-binding domain of the bile transporter and its accessibility. Two additional potentially modifier variants in cholestasis-associated genes were retained based on their pathogenicity (p.Gly758Val in the ABCC2 gene) and functionality (p.Asp19His in the ABCG8 gene). Molecular findings allowed a PFIC2 diagnosis in five patients and an unexpected diagnosis of sisterolemia in one case. The absence of genotype/phenotype correlation suggests the implication of environmental and epigenetic factors as well as modifier variants involved directly or indirectly in the bile composition, which could explain the cholestasis phenotypic variability.

Opinion paper on the diagnosis and treatment of progressive familial intrahepatic cholestasis

Background & Aims

Progressive familial intrahepatic cholestasis (PFIC) relates to a group of rare, debilitating, liver disorders which typically present in early childhood, but have also been reported in adults. Without early detection and effective treatment, PFIC can result in end-stage liver disease. The aim of the paper was to put forward recommendations that promote standardisation of the management of PFIC in clinical practice.

Methods

A committee of six specialists came together to discuss the challenges faced by physicians in the management of PFIC. The committee agreed on two key areas where expert guidance is required to optimise care: (1) how to diagnose and treat patients with a clinical presentation of PFIC in the absence of clear genetic test results/whilst awaiting results, and (2) how to monitor disease progression and response to treatment. A systematic literature review was undertaken to contextualise and inform the recommendations.

Results

An algorithm was developed for the diagnosis and treatment of children with suspected PFIC. The algorithm recommends the use of licensed inhibitors of ileal bile acid transporters as the first-line treatment for patients with PFIC and suggests that genetic testing be used to confirm genotype whilst treatment is initiated in patients in whom PFIC is suspected. The authors recommend referring patients to an experienced centre, and ensuring that monitoring includes measurements of pruritus, serum bile acid levels, growth, and quality of life following diagnosis and during treatment.

Conclusions

The algorithm presented within this paper offers guidance to optimise the management of paediatric PFIC. The authors hope that these recommendations will help to standardise the management of PFIC in the absence of clear clinical guidelines.

Impact and implications

This opinion paper outlines a consistent approach to the contemporaneous diagnosis, monitoring, referral and management of children with progressive familial intrahepatic cholestasis. This should assist physicians given the recent developments in genetic diagnosis and the availability of effective drug therapy. This manuscript will also help to raise awareness of current developments and educate health planners on the place for new drug therapies in progressive familial intrahepatic cholestasis.

Kaempferol ameliorated alcoholic liver disease through inhibiting hepatic bile acid synthesis by targeting intestinal FXR-FGF15 signaling

BACKGROUND

Alcoholic liver disease (ALD) is characterized by the disturbance of bile acids homeostasis, which further deteriorates ALD. Bile acid metabolism and its related signal molecules have become new therapeutic targets for alcoholic liver disease. This study aimed to investigate the impact of kaempferol (KAE) on ALD and elucidate its underlying mechanisms.

METHODS

C57BL/6 N mice were utilized to establish Binge-on-Chronic alcohol exposure mice model. KAE was administered as an interventional drug to chronic alcohol-fed mice for four weeks to assess its effects on liver damage and bile acid metabolism. And Z-Guggulsterone (Z-Gu), a global FXR inhibitor, was used to investigate the impact of intestinal FXR-FGF15 signal in ALD mice. Additionally, intestinal epithelial cells were exposed to alcohol or specific bile acid to induce the damage of FXR activity in vitro. The dual luciferase activity assay was employed to ascertain the interplay between KAE and FXR activity.

RESULTS

The results indicated that KAE treatment exhibited a significant hepatoprotective effect against chronic alcohol-fed mice. Accompanied by the intestinal FXR activation, the administration of KAE suppressed hepatic bile acid synthesis and promoted intestinal bile acid excretion in chronic ALD mice. And the notable alterations in total bile acid levels and composition were observed in mice after chronic alcohol feeding, which were reversed by KAE supplementation. And more, the protective effects of KAE on ALD mice were deprived by the inhibition of intestinal FXR activation. In vitro experiments demonstrated that KAE effectively activated FXR-FGF15 signaling, mitigated the damage to FXR activity in intestinal epithelial cells caused by alcohol or specific bile acids. Additionally, luciferase activity assays revealed that KAE directly promoted FXR expression, thereby enhancing FXR activity.

CONCLUSION

KAE treatment inhibited hepatic bile acids synthesis, maintained bile acids homeostasis in ALD mice by directly activating intestinal FXR-FGF15 signaling, which effectively alleviated liver injury induced by chronic alcohol consumption.

Management and outcomes after liver transplantation for progressive familial intrahepatic cholestasis: A systematic review and meta-analysis

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) is a heterogeneous rare congenital cholestatic liver disease. Disease progression might necessitate liver transplantation (LT). The aim of this study was to describe the outcome of PFIC1-4 patients after LT.

METHODS

Electronic databases were searched to identify studies on PFIC and LT. Patients were categorized according to PFIC type, genotype, graft type, age at LT, time of follow-up, and complications and treatment during follow-up.

RESULTS

Seventy-nine studies with 507 patients met inclusion criteria; most patients were classified as PFIC1-3. The median age at LT was 50 months. The overall 5-year patient survival was 98.5%. PFIC1 patients with diarrhea after LT were at significant risk of developing graft steatosis ( p < 0.0001). Meta-analysis showed an efficacy of 100% [95% CI: 73.9%-100%] for surgical biliary diversion to ameliorate steatosis and 94.9% [95% CI: 53.7%-100%] to improve diarrhea (n = 8). PFIC2 patients with bile salt export pump (BSEP)2 or BSEP3-genotype were at significant risk of developing antibody-induced BSEP deficiency (AIBD) ( p < 0.0001), which was reported in 16.2% of patients at a median of 36.5 months after LT. Meta-analysis showed an efficacy of 81.1% [95% CI: 47.5%-100%] for rituximab-based treatment regimens to improve AIBD (n = 18). HCC was detected in 3.6% of PFIC2 and 13.8% of PFIC4 patients at LT.

CONCLUSIONS

Fifty percent of PFIC1 patients develop diarrhea and steatosis after LT. Biliary diversion can protect the graft from injury. PFIC2 patients with BSEP2 and BSEP3 genotypes are at significant risk of developing AIBD, and rituximab-based treatment regimens effectively improve AIBD. PFIC3 patients have no PFIC-specific complications following LT.

Determination of Optimal Vitamin D Dosage in Children with Cholestasis

BACKGROUND

Vitamin D deficiency in patients with cholestasis is due to impaired intestinal vitamin D absorption, which results from decreased intestinal bile acid concentration. Patients with cholestasis usually do not achieve optimal vitamin D status when a treatment regimen for children without cholestasis is used. However, data on high-dose vitamin D treatment in patients with cholestasis are limited.

METHODS

This study is a prospective study that included pediatric patients with cholestasis (serum direct bilirubin > 1 mg/dL) who had vitamin D deficiency (serum 25-hydroxyvitamin D, 25-OHD, < 20 ng/mL). In Phase 1, single-day oral loading of 300,000 IU (or 600,000 IU if weight ≥ 20 kg) of vitamin D2 was administered, followed by an additional loading if serum 25-OHD < 30 ng/mL, and 4-week continuation of treatment using a vitamin D2 dose calculated based on the increment of 25-OHD after first loading. In Phase 2, oral vitamin D2 (200,000 IU/day) was administered for 12 days, followed by 400,000 IU/day of vitamin D2 orally for another 8 weeks if serum 25-OHD < 30 ng/mL.

RESULTS

Phase 1: Seven patients were enrolled. Three out of seven patients had a moderate increase in serum 25-OHD after loading (up to 20.3-27.2 ng/mL). These patients had conditions with partially preserved bile flow. The remaining four patients, who had biliary atresia with failed or no Kasai operation, had low increments of serum 25-OHD. Phase 2: Eleven patients were enrolled. Eight out of 11 patients had a moderate increase in serum 25-OHD after 200,000 IU/day of vitamin D2 for 12 days. Serum 25-OHD continued increasing after administering 400,000 IU/day of vitamin D2 for another 8 weeks, with maximal serum 25-OHD of 15.7-22.8 ng/mL.

CONCLUSION

Very high doses of vitamin D2 (200,000 and 400,000 IU/day) partly overcame poor intestinal vitamin D absorption and resulted in moderate increases in serum 25-OHD in pediatric patients with cholestasis, particularly when cholestasis was caused by uncorrectable bile duct obstruction.

An approach to recognising and identifying metabolic presentations in the paediatric Irish Traveller population

The Irish Traveller population are an endogamous, traditionally nomadic, Irish population. Irish Travellers practice consanguinity in the majority of marriages, thus resulting in a higher rate of rare autosomal recessive conditions within the population due to homozygous variants. Herein, we outline the clinical phenotypes associated with metabolic conditions seen in this population presenting in the neonatal period, infancy and childhood. Although Irish Travellers are traditionally based in Ireland and the UK, there are populations also living in mainland Europe and the USA. While there is generally an understanding amongst Irish paediatricians of the recessive conditions seen with this population in Ireland, they may be less commonly encountered abroad. It is important to consider a non-genetic aetiology alongside any consideration for a metabolic disorder.

CONCLUSION

This paper acts as a comprehensive review of the metabolic conditions seen and provides a guide for the investigation of an Irish Traveller child with a suspected metabolic condition.

WHAT IS KNOWN

• The Irish Traveller population are an endogenous population. • There are higher rates of inherited metabolic conditions in this population compared to the general population in Ireland.

WHAT IS NEW

• This paper is a comprehensive review of all known inherited metabolic conditions encountered in the Irish Traveller population.

Bile Acid and Gut Microbiota in Irritable Bowel Syndrome

Gut microbiota and their metabolites like bile acid (BA) have been investigated as causes of irritable bowel syndrome (IBS) symptoms. Primary BAs are synthesized and conjugated in the liver and released into the duodenum. BA biotransformation by gut microbiota begins in the intestine and results in production of a broad range of secondary BAs. Deconjugation is considered the gateway reaction for further modification and is mediated by bile salt hydrolase, which is widely expressed by the gut microbiota. However, gut bacteria that convert primary BAs to secondary BAs belong to a limited number of species, mainly Clostridiales. Like gut microbiota modify BA profile, BAs can shape gut microbiota via direct and indirect actions. BAs have prosecretory effects and regulates gut motility. BAs can also affect gut sensitivity. Because of the vital role of the gut microbiota and BAs in gut function, their bidirectional relationship may contribute to the pathophysiology of IBS. Individuals with IBS have been reported to have altered microbial profiles and modified BA profiles. A significant increase in fecal primary BA and a corresponding decrease in secondary BA have been observed in IBS with predominant diarrhea. In addition, primary BA was positively correlated with IBS symptoms. In IBS with predominant diarrhea, bacteria with reduced abundance mainly belonged to the genera in Ruminococcaceae and exhibited a negative correlation with primary BAs. Integrating the analysis of the gut microbiota and BAs could better understanding of IBS pathophysiology. The gap in this field needs to be further filled in the future.

Role and Regulation of Hepatobiliary ATP-Binding Cassette Transporters during Chemical-Induced Liver Injury

Severity of drug-induced liver injury (DILI) ranges from mild, asymptomatic, and transient elevations in liver function tests to irreversible liver damage, often needing transplantation. Traditionally, DILI is classified mechanistically as high-frequency intrinsic DILI, commonly dose dependent or DILI that rarely occurs and is idiosyncratic in nature. This latter form is not dose dependent and has a pattern of histopathological manifestation that is not always uniform. Currently, a third type of DILI called indirect hepatotoxicity has been described that is associated with the pharmacological action of the drug. Historically, DILI was primarily linked to drug metabolism events; however, the impact of transporter-mediated rates of drug uptake and excretion has gained greater prominence in DILI research. This review provides a comprehensive view of the major findings from studies examining the contribution of hepatic ATP-binding cassette transporters as key contributors to DILI and how changes in their expression and function influence the development, severity, and overall toxicity outcome. SIGNIFICANCE STATEMENT: Drug-induced liver injury (DILI) continues to be a focal point in drug development research. ATP-binding cassette (ABC) transporters have emerged as important determinants of drug detoxification, disposition, and safety. This review article provides a comprehensive analysis of the literature addressing: (a) the role of hepatic ABC transporters in DILI, (b) the influence of genetic mutations in ABC transporters on DILI, and (c) new areas of research emphasis, such as the influence of the gut microbiota and epigenetic regulation, on ABC transporters.

The Effect of Sex and Obesity on the Gene Expression of Lipid Flippases in Adipose Tissue

Molecular mechanisms behind obesity and sex-related effects in adipose tissue remain elusive. During adipocyte expansion, adipocytes undergo drastic remodelling of lipid membrane compositions. Lipid flippases catalyse phospholipid translocation from exoplasmic to the cytoplasmic leaflet of membranes. The present study aimed to analyse the effect of sex, obesity, and their interactions on the gene expression of two lipid flippases—ATP8A1 and ATP8B1—and their possible microRNA (miR) modulators in visceral adipose tissue (VAT). In total, 12 normal-weight subjects (5 premenopausal women and 7 men) and 13 morbidly obese patients (7 premenopausal women and 6 men) were submitted to surgery, and VAT samples were obtained. Gene expression levels of ATP8A1, ATP8B1, miR-548b-5p, and miR-4643 were measured in VAT. Our results showed a marked influence of obesity on VAT ATP8A1 and ATP8B1, although the effects of obesity were stronger in men for ATP8A1. Both genes positively correlated with obesity and metabolic markers. Furthermore, ATP8B1 was positively associated with miR-548b-5p and negatively associated with miR-4643. Both miRs were also affected by sex. Thus, lipid flippases are altered by obesity in VAT in a sex-specific manner. Our study provides a better understanding of the sex-specific molecular mechanisms underlying obesity, which may contribute to the development of sex-based precision medicine.

Bile acids and their receptors: modulators and therapeutic targets in liver inflammation

Bile acids participate in the intestinal emulsion, digestion, and absorption of lipids and fat-soluble vitamins. When present in high concentrations, as in cholestatic liver diseases, bile acids can damage cells and cause inflammation. After the discovery of bile acids receptors about two decades ago, bile acids are considered signaling molecules. Besides regulating bile acid, xenobiotic, and nutrient metabolism, bile acids and their receptors have shown immunomodulatory properties and have been proposed as therapeutic targets for inflammatory diseases of the liver. This review focuses on bile acid-related signaling pathways that affect inflammation in the liver and provides an overview of the preclinical and clinical applications of modulators of these pathways for the treatment of cholestatic and autoimmune liver diseases.

Case Report: A Rare Heterozygous ATP8B1 Mutation in a BRIC1 Patient: Haploinsufficiency?

Benign recurrent intrahepatic cholestasis (BRIC) is an autosomal recessive disorder characterized by recurrent cholestasis. ATPase class I, type 8B, member 1 (ATP8B1) encodes familial intrahepatic cholestasis 1 (FIC1), which acts as a phosphatidylserine reversing enzyme in the tubule membrane of hepatocytes to mediate the inward translocation of phosphatidylserine (PS). At present, dozens of ATP8B1 pathogenic mutations have been identified that mainly cause BRIC1 and progressive familial intrahepatic cholestasis 1 (PFIC1). The diagnosis of BRIC1 is based on symptoms, laboratory tests, imaging, liver histology, and genetic testing. BRIC1 treatment seeks to prevent recurrence and reduce disease severity. At present, the main treatment methods include ursodeoxycholic acid (UDCA), rifampin, cholestyramine and haemofiltration, and endoscopic nasobiliary drainage (ENBD). Here, we report a 17-year-old patient with cholestasis who has a rare heterozygous ATP8B1 gene mutation (p.T888K). The patient was treated with UDCA, glucocorticoids and haemofiltration, after which bilirubin levels gradually returned to normal. This case was thought to be caused by an ATP8B1 heterozygous mutation, which may be related to haploinsufficiency (HI).