A frequent variant in the human bile salt export pump gene ABCB11 is associated with hepatitis C virus infection, but not liver stiffness in a German population

Influence of the Bile Acid Transporter Genes ABCB4, ABCB8, and ABCB11 and the Farnesoid X Receptor on the Response to Ursodeoxycholic Acid in Patients with Nonalcoholic Steatohepatitis

The prevalence of NAFLD and NASH is increasing worldwide, and there is no approved medical treatment until now. Evidence has emerged that interfering with bile acid metabolism may lead to improvement in NASH. In this study, 28 patients with elevated cholestatic liver function tests (especially GGT) were screened for bile acid gene polymorphisms and treated with UDCA. All patients had a bile acid gene polymorphism in ABCB4 or ABCB11. Treatment with UDCA for 12 months significantly reduced GGT in all patients and ALT in homozygous patients. No difference in fibrosis was observed using FIb-4, NFS, and transient elastography (TE). PNPLA3 and TM6SF2 were the most common NASH-associated polymorphisms, and patients with TM6SF2 showed a significant reduction in GGT and ALT with the administration of UDCA. In conclusion, NASH patients with elevated GGT should be screened for bile acid gene polymorphisms, as UDCA therapy may improve liver function tests. However, no difference in clinical outcomes, such as progression to cirrhosis, has been observed using non-invasive tests (NITs).

The Role of the Sodium-taurocholate Co-transporting Polypeptide (NTCP) and Bile Salt Export Pump (BSEP) in Related Liver Disease

BACKGROUND

Sodium Taurocholate Co-transporting Polypeptide (NTCP) and Bile Salt Export Pump (BSEP) play significant roles as membrane transporters because of their presence in the enterohepatic circulation of bile salts. They have emerged as promising drug targets in related liver disease.

METHODS

We reviewed the literature published over the last 20 years with a focus on NTCP and BSEP.

RESULTS

This review summarizes the current perception about structure, function, genetic variation, and regulation of NTCP and BSEP, highlights the effects of their defects in some hepatic disorders, and discusses the application prospect of new transcriptional activators in liver diseases.

CONCLUSION

NTCP and BSEP are important proteins for transportation and homeostasis maintenance of bile acids. Further research is needed to develop new models for determining the structure-function relationship of bile acid transporters and screening for substrates and inhibitors, as well as to gain more information about the regulatory genetic mechanisms involved in the processes of liver injury.

Dubin-Johnson syndrome and intrahepatic cholestasis of pregnancy in a Sri Lankan family: a case report

Background

Dubin–Johnson syndrome and intrahepatic cholestasis of pregnancy are rare chronic liver disorders. Dubin–Johnson syndrome may manifest as conjugated hyperbilirubinemia, darkly pigmented liver, presence of abnormal pigment in the parenchyma of hepatocytes and abnormal distribution of the coproporphyrin isomers I and III in the urine. Intrahepatic cholestatic jaundice of pregnancy presents as pruritus, abnormal liver biochemistry and increased serum bile acids.

Case presentation

A Sri Lankan girl presented with recurrent episodes of jaundice. She had conjugated hyperbilirubinaemia with diffuse, coarse brown pigments in the hepatocytes. Urine coproporphyrin examination suggested Dubin–Johnson syndrome. Genetic studies confirmed missense homozygous variant p.Trp709Arg in the ATP-binding cassette sub-family C member 2 gene ABCC2 that encodes the Multidrug resistance-associated protein 2 that causes Dubin–Johnson syndrome. The gene study of the mother revealed the same missense variant in ABCC2/MRP2 but with a heterozygous status, and in addition a homozygous missense variant p.Val444Ala in the ATP-binding cassette, sub-family B member 11 gene ABCB11 that encodes the bile salt export pump.

Conclusion

Dubin–Johnson syndrome should be considered when the common causes for conjugated hyperbilirubinaemia have been excluded, and patient has an increased percentage of direct bilirubin relative to total bilirubin concentration. Its early diagnosis prevents repeated hospital admissions and investigations. Knowledge of a well known homozygous variant in ABCB11 gene could help in the management of pregnancy.

A preliminary investigation on single nucleotide polymorphism rs2287622 of bile salt export pump gene in patients with chronic hepatitis C virus infection in Hunan, China

BACKGROUND

European researchers have underscored associations between single nucleotide polymorphism (SNP) rs2287622 of the hepatobiliary bile salt export pump (BSEP) gene and the risk of hepatitis C virus (HCV) infection. The distributions of SNP rs2287622 are racially specific. This study was aimed to preliminarily investigate the distribution of BSEP gene SNP rs2287622 in the Han patients with chronic HCV-infection (CHC) in Hunan, China.

METHODS

BSEP gene SNP rs2287622 of 165 CHC patients, 99 patients with chronic hepatitis B virus infection (CHB) and 99 healthy individuals were analyzed by polymerase chain reaction-restriction fragment length polymorphism analysis and nucleotide sequencing.

RESULTS

The overall frequencies of the C allele of BESP gene SNP rs2287622 in the CHC patients, CHB patients and healthy individuals were 74.2, 72.7 and 74.2%, respectively (P > 0.05). The overall odds ratios (ORs) aiming at predicting CHC risk by comparing the ratios of the frequency distribution of alleles or genotypes in the CHC group with those in the non-CHC group had no statistical significance (P > 0.05). However, the CHC ORs of CC vs TT, TC vs TT and CC + CT vs TT among the individuals aged over 40 years were 2.680, 3.122 and 2.824 respectively (P < 0.05), and the higher risk did not relate to gender, HCV genotypes and presence of HCV-related liver cirrhosis.

CONCLUSIONS

Among the Han individuals aged over 40 years in Hunan, China, genotype CC or CT of BSEP gene SNP rs2287622 may correlate with higher risk of CHC in comparison with genotype TT. Further study with a larger cohort is essential.

Prothrombotic genetic risk factors are associated with an increased risk of liver fibrosis in the general population: The Rotterdam Study

BACKGROUND & AIMS

The coagulation system is known to be involved in fibrogenesis in patients with liver disease. We investigated whether common genetic prothrombotic risk factors are associated with an increased risk of fibrosis in the general population.

METHODS

This investigation was part of the Rotterdam Study, an ongoing, population-based cohort study. Liver stiffness (LS) was measured using transient elastography (Fibroscan) and associated with single nucleotide polymorphisms determining blood group type and presence of the Factor V Leiden (FVL) mutation or prothrombin G20210A gene variant.

RESULTS

Reliable LS measurements and genetic data were obtained from 1055 Caucasian participants. LS ⩾8.0 kPa, suggestive of clinically relevant fibrosis, was observed in 101 subjects (9.6%). Presence of FVL or prothrombin G20210A was independently associated with an increased risk of LS ⩾8.0 kPa (OR 2.09, 95%CI 1.07-4.07, p=0.03). Combination of blood group type non-O and the FVL mutation or prothrombin G20210A variant resulted in an even higher risk of LS ⩾8.0 kPa (OR 3.36, 95%CI 1.50-7.56, p=0.003). Presence of the FVL mutation or prothrombin G20210A variant in participants with blood group non-O was associated with a predicted probability of 14.3% (7.7-23.8) of LS ⩾8.0 kPa.

CONCLUSIONS

Participants carrying the FVL mutation or prothrombin G20210A variant have an increased risk of clinically relevant liver fibrosis, which is even higher in blood group type non-O carriers. The fact that genetic prothrombotic risk factors are associated with an increased risk of liver fibrosis suggests that coagulation plays an important role in fibrogenesis in the general population.

Diagnosis of ABCB11 gene mutations in children with intrahepatic cholestasis using high resolution melting analysis and direct sequencing

Intrahepatic cholestasis represents a heterogeneous group of disorders that begin during childhood, most commonly manifesting as neonatal cholestasis, and lead to ongoing liver dysfunction in children and adults. For children, inherited pathogenic factors of cholestasis have gained increasing attention owing to the rapid development of molecular biology technology. However, these methods have their advantages and disadvantages in terms of simplicity, sensitivity, specificity, time required and expense. In the present study, an effective, sensitive and economical method is recommended, termed high-resolution melting (HRM) analysis and direct sequencing, based on general polymerase chain reaction, to detect mutations in disease-causing genes. As one type of inherited intrahepatic cholestasis, progressive familial intrahepatic cholestasis type 2 (PFIC2) is caused by pathogenic mutations in the ABCB11 gene, HRM was used to detect mutations in the ABCB11 gene in the present study, and the diagnosis for PFIC2 was made by comprehensive analysis of genetic findings and clinical features. Furthermore, the characteristics of mutations and single nucleotide polymorphisms (SNPs) in the ABCB11 gene were elucidated. A total of 14 types of mutations/polymorphisms were identified in 20 patients from mainland China, including six missense mutations (p.Y337H, p.Y472C, p.R696W, p.Q931P, p.D1131V and p.H1198R), one nonsense mutation (p.R928X) and seven SNPs (p.D36D/rs3815675, p.F90F/rs4148777, p.Y269Y/rs2287616, p.I416I/rs183390670, p.V444A/rs2287622, p.A865V/rs118109635 and p.A1028A/rs497692). Five mutations were novel. The majority of the mutations were different from those detected in other population groups. A total of 4/20 patients (1/5) were diagnosed to be PFIC2 by combining genetic findings with the clinical features. Polymorphisms V444A and A1028A, with an allele frequency of 74.5 and 67.2%, respectively, were highly prevalent in the mainland Chinese subjects. No differences were found between the patients with cholestasis and the control subjects. Efficient genetic screening facilitates the clinical diagnosis of genetic disorders. The present study demonstrated that HRM analysis was efficient and effective in detecting mutations and expanded the known spectrum of ABCB11 gene mutations.

Intrahepatic cholestasis in common chronic liver diseases

BACKGROUND AND OBJECTIVE

Cholestasis represents the consequence of impaired bile formation and decrease in bile flow, generally classified as extra- and intrahepatic. Cholestasis is the pivotal hallmark of the so-called primary cholestatic liver diseases but may also emerge in other forms of chronic liver injury. The aim now was to summarise the current state of knowledge on intrahepatic cholestasis related to chronic liver diseases.

METHODS

For this overview on intrahepatic cholestasis in chronic liver disorders other than the 'classic' cholestatic liver diseases, selected references were retrieved by literature search in MEDLINE and textbooks were reviewed. All articles were selected that discussed pathophysiological and clinical aspects of intrahepatic cholestasis in the context of alcoholic liver disease, nonalcoholic fatty liver disease, chronic hepatitis B and C virus infections as well as drug-induced and granulomatous liver diseases. Titles referring to primary biliary cirrhosis and sclerosing cholangitis were excluded.

RESULTS AND CONCLUSIONS

Dependent on the aetiology, intrahepatic cholestasis is present at variable frequencies and in different disease stages in chronic liver diseases. Cholestasis secondary to chronic liver injury may denote a severe disease course and development of end-stage liver disease or specific disease variants. These findings indicate that 'secondary intrahepatic cholestasis' (SIC) can occur in the natural course of chronic liver diseases other than the primary cholestatic diseases, in particular in the setting of advanced disease progression.

Host genetic variants in the pathogenesis of hepatitis C

Direct-acting antiviral drugs (DAAs) are currently replacing antiviral therapy for Hepatitis C infection. Treatment related side effects are even worse and the emergence of resistant viruses must be avoided because of the direct-antiviral action. Altogether it remains a challenge to take treatment decisions in a clinical setting with cost restrictions. Genetic host factors are hereby essential to implement an individualized treatment concept. In recent years results on different genetic variants have been published with a strong association with therapy response, fibrosis and treatment-related side effects. Polymorphisms of the IL28B gene were identified as accurate predictors for therapy response and spontaneous clearance of HCV infection and are already used for diagnostic decisions. For RBV-induced side effects, such as hemolytic anemia, associations to genetic variants of inosine triphosphatase (ITPA) were described and different SLC28 transporters for RBV-uptake have been successfully analyzed. Fibrosis progression has been associated with variants of Vitamin D receptor (VDR) and ABCB11 (bile salt export pump). Cirrhotic patients especially have a high treatment risk and low therapy response, so that personalized antiviral treatment is mandatory. This review focuses on different host genetic variants in the pathogenesis of Hepatitis C at the beginning of a new area of treatment.