ABCB4 variant is associated with hepatobiliary MR abnormalities in people with low phospholipid associated cholelithiasis syndrome

Primary intrahepatic lithiasis in western countries: role of ultrasound and comparison with MRI with MRCP

OBJECTIVES

To study hepatobiliary expert ultrasound (US) in a cohort of suspected primary intrahepatic lithiasis (IHL) and to compare these findings with MRI/MRCP data.

METHODS

All patients with a diagnosis of primary-IHL based upon biological and, or, clinical symptoms who underwent US between 2008 and 2023 were retrospectively enrolled in two tertiary hepatobiliary centers. Clinical characteristics, available genetic and radiological features (expert US and MRCP) were recorded. Data were compared for the presence of comet-tail images or stones on US, between US and MRCP features and between imaging and patients' genetic status. Statistical analyses were performed with R software environment version 4.2.1, by univariate and multivariate analysis.

RESULTS

A total of 112 primary-IHL patients were included (mean age 43 years old ±14 and 55% women). US identified primary-IHL in 92/112 (82%) patients including intrahepatic biliary comet-tail in 82/112 (73%) and stones in 51/112 (46%). Among these, 66/112 (68%) had both US and MRCP. Lithiasis was identified in 60/76 US (79%) and 44/76 MRCP (58%). MRCP showed only stones in 22/76, 29%. Genetic testing was performed in 66/112 (58%) patients. Thirty-two (49%) of these patients had pathogenic ABCB4/MDR3 gene variants, 14/66 (21%) other pathogenic variants and 5/66 (5%) had unknown significant variants. No genetic abnormalities were found in 19/66 (29%). A multivariate logistic model with the comet-tail sign as an outcome showed that there was a significant negative correlation between other pathogenic genetic variants and the comet-tail phenotype (P-value = 0.049).

CONCLUSION

US, and not MRCP, should be the primary diagnostic tool in suspected primary-IHL patients.

Current approach to diagnosis and management of low-phospholipid associated cholelithiasis syndrome

PURPOSE OF REVIEW

Low phospholipid-associated cholelithiasis (LPAC) syndrome is a rare genetic form of intrahepatic cholesterol lithiasis, affecting mainly young adults. This review describes the recent advances in genetic and clinical characterization, diagnosis and management of LPAC syndrome.

RECENT FINDINGS

Recent publications report data from several retrospective cohorts. These cohorts describe the main clinical features, the most frequent radiological lesions, complications, the results of biliary endoscopic procedures and the prognosis associated with LPAC syndrome.

SUMMARY

LPAC syndrome has been linked to a partial defect in the ATP binding cassette subfamily B member 4 ( ABCB4 ) gene encoding the canalicular phospholipid transporter multidrug resistance protein 3, but this mechanism would explain only half the cases, or even fewer. This syndrome is characterized by the appearance of cholelithiasis at an abnormally early age (before 40) and by the persistence of biliary symptoms after cholecystectomy. The diagnosis is usually confirmed by an ultrasound scan of the liver, which reveals the presence of intrahepatic microlithiasis, as evidenced by comet-tail images or microspots along the intrahepatic bile ducts. Ursodeoxycholic acid, at a daily dose of 5-15 mg/kg, is the reference treatment. If not performed prior to diagnosis, cholecystectomy should be avoided wherever possible. In complicated or refractory forms, endoscopic biliary intervention may be necessary.

Genotypes and different clinical variants between children and adults in progressive familial intrahepatic cholestasis: a state-of-the-art review

INTRODUCTION

Progressive Familial intrahepatic cholestasis (PFIC) are rare disorders of bile acid (BAs) secretion and transport with a genetic background. PFIC are paediatric manifestations, but the same variants causing PFIC can also cause cholestasis with a later paediatric onset or adult-onset cholestatic disease (AOCD). Pruritus is a symptom of cholestasis that can be so devastating that it requires a liver transplant (LT) in children; some PFIC types have been described as at risk of liver cancer development. Commonly prescribed medications for PFIC symptoms can partially relieve pruritus without changing the natural history of the disease. Recently, a therapy reducing the intestinal resorption of BAs has been approved; it is effective on both pruritus and cholestasis in PFIC, potentially being a disease-modifying intervention.

AREAS COVERED

The clinical and genetic characteristics of different PFIC and AOCD are summarized to provide a common background for geneticists and paediatric and adult hepatologists in diagnosis and management.

EXPERT OPINION

Collaboration between paediatric and adult hepatologists and geneticists will become crucial for cholestatic disease research and patient treatment. Therefore, adult hepatologists will need to learn more about FIC. This might enable the implementation of individualized surveillance in FIC patients and the evaluation of patient family histories.

Hepatolithiasis pathogenesis update

Hepatolithiasis is prevalent in East Asian countries and not common in Western countries. In recent years, because of the increased number of immigrants from East Asia in Western countries, hepatolithiasis has gradually become a global problem. Although current surgical interventions for hepatolithiasis boast a high rate of stone clearance, the persistent challenges of the disease's refractory nature and high recurrence rate continue to complicate its treatment. Therefore, understanding its underlying pathogenesis is meaningful for effective treatment. In this review, we discuss the common risk factors: infection, cholangitis, environmental factors and diet habits, abnormal bile components, anatomical abnormalities, and bile stasis, and summarize the relevant mechanisms.

Low phospholipid-associated cholelithiasis syndrome, a not uncommon cause of biliary problems and hospital admissions

BACKGROUND AND AIMS

biliary diseases are a major cause of morbidity and mortality for patients and a burden for the healthcare system. The genetic syndrome of low phospholipid-associated cholelithiasis (LPAC) is a little known and rare entity whose treatment with bile salts avoids symptoms, admissions and the need for surgery. The aim of this study was to determine its incidence and characteristics in our center.

METHODS

prospective study performed between February 2021 and September 2022. LPAC was diagnosed if at least two of the following were present: onset of biliary problems < 40 years of age, recurrence of symptoms after cholecystectomy, ultrasound image of hepatolithiasis (multiple echoic foci, comet-tail images, hepatolithiasis with acoustic shadow). Demographic, clinical, genetic (analysis of MDR3 gene mutations) and ultrasound characteristics and their incidence were analyzed in hospital admissions for biliary causes.

RESULTS

thirty-six patients with LPAC were identified. Of these, six were among 237 admissions due to biliary causes in the previous nine months, with an incidence of 2.5 % (95 % CI: 1.17-5.41). By age subgroup, the incidence was 16.7 % in those admitted < 40 years of age and 9.1 % in those < 50. Considering females only, the incidence was 21 % in those admitted < 40 years and 15.8 % in those < 50 years. All patients remained asymptomatic after treatment with ursodeoxycholic acid and there were no new admissions.

CONCLUSIONS

LPAC syndrome is not as uncommon as it may appear, especially in women < 50 years of age admitted with biliary problems. Its correct diagnosis based on simple criteria could avoid a significant number of hospital admissions and unnecessary cholecystectomies.

Genetics of Gallstone Disease and Their Clinical Significance: A Narrative Review

Gallstone (GS) disease is common and arises from a combination of genetic and environmental factors. Although genetic abnormalities specifically leading to cholesterol GSs are rare, there are clinically significant gene variants associated with cholesterol GSs. In contrast, most bilirubin GSs can be attributed to genetic defects. The pathogenesis of cholesterol and bilirubin GSs differs greatly. Cholesterol GSs are notably influenced by genetic variants within the ABC protein superfamily, including ABCG8, ABCG5, ABCB4, and ABCB11, as well as genes from the apolipoprotein family such as ApoB100 and ApoE (especially the E3/E3 and E3/E4 variants), and members of the MUC family. Conversely, bilirubin GSs are associated with genetic variants in highly expressed hepatic genes, notably UGT1A1, ABCC2 (MRP2), ABCC3 (MRP3), CFTR, and MUC, alongside genetic defects linked to hemolytic anemias and conditions impacting erythropoiesis. While genetic cases constitute a small portion of GS disease, recognizing genetic predisposition is essential for proper diagnosis, treatment, and genetic counseling.

Biliary stem cells in health and cholangiopathies and cholangiocarcinoma

PURPOSE OF REVIEW

This review discusses evidence regarding progenitor populations of the biliary tree in the tissue regeneration and homeostasis, and the pathobiology of cholangiopathies and malignancies.

RECENT FINDINGS

In embryogenesis biliary multipotent progenitor subpopulation contributes cells not only to the pancreas and gall bladder but also to the liver. Cells equipped with a constellation of markers suggestive of the primitive endodermal phenotype exist in the peribiliary glands, the bile duct glands, of the intra- and extrahepatic bile ducts. These cells are able to be isolated and cultured easily, which demonstrates the persistence of a stable phenotype during in vitro expansion, the ability to self-renew in vitro, and the ability to differentiate between hepatocyte and biliary and pancreatic islet fates.

SUMMARY

In normal human livers, stem/progenitors cells are mostly restricted in two distinct niches, which are the bile ductules/canals of Hering and the peribiliary glands (PBGs) present inside the wall of large intrahepatic bile ducts. The existence of a network of stem/progenitor cell niches within the liver and along the entire biliary tree inform a patho-biological-based translational approach to biliary diseases and cholangiocarcinoma since it poses the basis to understand biliary regeneration after extensive or chronic injuries and progression to fibrosis and cancer.

A Unique In Vitro Assay to Investigate ABCB4 Transport Function

ABCB4 is almost exclusively expressed in the liver, where it plays an essential role in bile formation by transporting phospholipids into the bile. ABCB4 polymorphisms and deficiencies in humans are associated with a wide spectrum of hepatobiliary disorders, attesting to its crucial physiological function. Inhibition of ABCB4 by drugs may lead to cholestasis and drug-induced liver injury (DILI), although compared with other drug transporters, there are only a few identified substrates and inhibitors of ABCB4. Since ABCB4 shares up to 76% identity and 86% similarity in the amino acid sequence with ABCB1, also known to have common drug substrates and inhibitors, we aimed to develop an ABCB4 expressing Abcb1-knockout MDCKII cell line for transcellular transport assays. This in vitro system allows the screening of ABCB4-specific drug substrates and inhibitors independently of ABCB1 activity. Abcb1KO-MDCKII-ABCB4 cells constitute a reproducible, conclusive, and easy to use assay to study drug interactions with digoxin as a substrate. Screening a set of drugs with different DILI outcomes proved that this assay is applicable to test ABCB4 inhibitory potency. Our results are consistent with prior findings concerning hepatotoxicity causality and provide new insights for identifying drugs as potential ABCB4 inhibitors and substrates.