Elisabeth Krones

Differential effects of norUDCA and UDCA in obstructive cholestasis in mice

Background & Aims The quest for effective drugs to treat cholangiopathies led to the development of norUDCA previously shown to have potent choleretic effects and to heal cholangiopathy in Abcb4 knockout (Abcb4−/−) mice. Its mother compound UDCA had detrimental effects in common bile duct ligated (CBDL) mice, presumably related to its choleretic effects. norUDCA choleretic effects may therefore raise safety concerns when used in cholangiopathies with biliary obstruction. We therefore aimed at comparing the effects of UDCA and norUDCA in clear-cut obstructive cholestasis. Methods 0.5% UDCA- or norUDCA-fed wild type and Abcb4−/− mice were subjected to CBDL or selective bile duct ligation (SBDL) and compared to controls with regard to liver injury. Bile flow, bile composition, and biliary manometry were compared in UDCA-fed, norUDCA-fed and control mice. Toxicity of UDCA and norUDCA was compared in vitro. Results Compared to UDCA, liver injury in CBDL mice was significantly lower in almost all norUDCA groups. In SBDL mice, only UDCA induced bile infarcts in the ligated lobes, whereas norUDCA even ameliorated liver injury. In vitro, UDCA induced cellular ATP depletion and was significantly more toxic than norUDCA in HepG2 cells, mouse bile duct epithelial cells, and primary human hepatocytes. Conclusions Compared to norUDCA, UDCA is significantly more toxic in CBDL mice. norUDCA, in contrast to UDCA, significantly ameliorates liver injury in SBDL mice. Our findings uncover profound differences in metabolism and therapeutic mechanisms of both bile acids with important clinical consequences.

Bile acids trigger cholemic nephropathy in common bile‐duct–ligated mice

Tubular epithelial injury represents an underestimated but important cause of renal dysfunction in patients with cholestasis and advanced liver disease, but the underlying mechanisms are unclear. To address the hypothesis that accumulation and excessive alternative urinary elimination of potentially toxic bile acids (BAs) may contribute to kidney injury in cholestasis, we established a mouse model for detailed in vivo time course as well as treatment studies. Three‐day common bile duct ligation (CBDL) induced renal tubular epithelial injury predominantly at the level of aquaporin 2–positive collecting ducts with tubular epithelial and basement membrane defects. This was followed by progressive interstitial nephritis and tubulointerstitial renal fibrosis in 3‐, 6‐, and 8‐week CBDL mice. Farnesoid X receptor knockout mice (with a hydrophilic BA pool) were completely protected from CBDL‐induced renal fibrosis. Prefeeding of hydrophilic norursodeoxycholic acid inhibited renal tubular epithelial injury in CBDL mice. In addition, we provide evidence for renal tubular injury in cholestatic patients with cholemic nephropathy. Conclusion: We characterized a novel in vivo model for cholemic nephropathy, which offers new perspectives to study the complex pathophysiology of this condition. Our findings suggest that urinary‐excreted toxic BAs represent a pivotal trigger for renal tubular epithelial injury leading to cholemic nephropathy in CBDL mice. (Hepatology 2013; 58:2056–2069)

Inhibition of intestinal bile acid absorption improves cholestatic liver and bile duct injury in a mouse model of sclerosing cholangitis.

BACKGROUND AND AIMS Approximately 95% of bile acids (BAs) excreted into bile are reabsorbed in the gut and circulate back to the liver for further biliary secretion. Therefore, pharmacological inhibition of the ileal apical sodium-dependent BA transporter (ASBT/SLC10A2) may protect against BA-mediated cholestatic liver and bile duct injury. METHODS Eight week old Mdr2(-/-) (Abcb4(-/-)) mice (model of cholestatic liver injury and sclerosing cholangitis) received either a diet supplemented with A4250 (0.01% w/w) - a highly potent and selective ASBT inhibitor - or a chow diet. Liver injury was assessed biochemically and histologically after 4weeks of A4250 treatment. Expression profiles of genes involved in BA homeostasis, inflammation and fibrosis were assessed via RT-PCR from liver and ileum homogenates. Intestinal inflammation was assessed by RNA expression profiling and immunohistochemistry. Bile flow and composition, as well as biliary and fecal BA profiles were analyzed after 1week of ASBT inhibitor feeding. RESULTS A4250 improved sclerosing cholangitis in Mdr2(-/-) mice and significantly reduced serum alanine aminotransferase, alkaline phosphatase and BAs levels, hepatic expression of pro-inflammatory (Tnf-α, Vcam1, Mcp-1) and pro-fibrogenic (Col1a1, Col1a2) genes and bile duct proliferation (mRNA and immunohistochemistry for cytokeratin 19 (CK19)). Furthermore, A4250 significantly reduced bile flow and biliary BA output, which correlated with reduced Bsep transcription, while Ntcp and Cyp7a1 were induced. Importantly A4250 significantly reduced biliary BA secretion but preserved HCO3(-) and biliary phospholipid secretion resulting in an increased HCO3(-)/BA and PL/BA ratio. In addition, A4250 profoundly increased fecal BA excretion without causing diarrhea and altered BA pool composition, resulting in diminished concentrations of primary BAs tauro-β-muricholic acid and taurocholic acid. CONCLUSIONS Pharmacological ASBT inhibition attenuates cholestatic liver and bile duct injury by reducing biliary BA concentrations in mice.

Diarrhea in the Immunocompromised Patient

Diarrhea is a common problem in patients with immunocompromising conditions. The etiologic spectrum differs from patients with diarrhea who have a normal immune system. This article reviews the most important causes of diarrhea in immunocompromised patients, ranging from infectious causes to noninfectious causes of diarrhea in the setting of HIV infection as a model for other conditions of immunosuppression. It also deals with diarrhea in specific situations, eg, after hematopoietic stem cell or solid organ transplantation, diarrhea induced by immunosuppressive drugs, and diarrhea in congenital immunodeficiency syndromes.

Evolving concepts in primary sclerosing cholangitis

Patients suffering from primary sclerosing cholangitis (PSC) show considerable differences regarding clinical manifestations (i.e. large duct versus small‐duct PSC, presence or absence of concomitant inflammatory bowel disease), disease progression, risk for malignancy and response to therapy, raising the question whether PSC may represent a mixed bag of diseases of different aetiologies. The growing list of secondary causes and diseases ‘mimicking’ or even overlapping with PSC (e.g. IgG4‐associated sclerosing cholangitis), which frequently causes problems in clear‐cut discrimination from classic PSC and the emerging knowledge about potential disease modifier genes (e.g. variants of CFTR, TGR5 and MDR3) support such a conceptual view. In addition, PSC in children differs significantly from PSC in adults in several aspects resulting in distinct therapeutic concepts. From a clinical perspective, appropriate categorization and careful differential diagnosis are essential for the management of concerned patients. Therefore, the aim of the current review is to summarize current and evolving pathophysiological concepts and to provide up‐to‐date perspectives including future treatment strategies for PSC.

Bile acid-induced cholemic nephropathy.

Kidney injury in deeply jaundiced patients became known as cholemic nephropathy. This umbrella term covers impaired renal function in cholestatic patients with characteristic histomorphological changes including intratubular cast formation and tubular epithelial cell injury. Cholemic nephropathy represents a widely underestimated but important cause of kidney dysfunction in patients with cholestasis and advanced liver disease. However, the nomenclature is inconsistent since there are numerous synonyms used; the underlying mechanisms of cholemic nephropathy are not entirely clear, and widely accepted diagnostic criteria are still missing. Consequently, the current article aims to summarize the present knowledge on the clinical and morphological characteristics, available preclinical models, derived potential pathomechanisms, and future diagnostic and therapeutic strategies in cholemic nephropathy. Furthermore, we provide a potential research agenda for this evolving field.

Primary sclerosing cholangitis: new approaches to diagnosis, surveillance and treatment.

Primary sclerosing cholangitis (PSC) is a chronic inflammatory bile duct disease of unknown etiology, frequently associated with inflammatory bowel disease and leading to end-stage liver disease requiring liver transplantation. Moreover, PSC is a premalignant condition associated with an increased risk for hepatobiliary and colorectal malignancy. Since effective medical therapy for PSC is still lacking, this disorder represents a potentially fatal disease with poor prognosis. This article is a summary of an overview given at the 5th Falk Gastro Conference in Munich 2012 and reviews the challenges associated with diagnosis, surveillance and therapy of PSC.

Evaluation of genome-wide loci of iron metabolism in hereditary hemochromatosis identifies PCSK7 as a host risk factor of liver cirrhosis

Genome-wide association studies (GWAS) have revealed genetic determinants of iron metabolism, but correlation of these with clinical phenotypes is pending. Homozygosity for HFE C282Y is the predominant genetic risk factor for hereditary hemochromatosis (HH) and may cause liver cirrhosis. However, this genotype has a low penetrance. Thus, detection of yet unknown genetic markers that identify patients at risk of developing severe liver disease is necessary for better prevention. Genetic loci associated with iron metabolism (TF, TMPRSS6, PCSK7, TFR2 and Chr2p14) in recent GWAS and liver fibrosis (PNPLA3) in recent meta-analysis were analyzed for association with either liver cirrhosis or advanced fibrosis in 148 German HFE C282Y homozygotes. Replication of associations was sought in additional 499 Austrian/Swiss and 112 HFE C282Y homozygotes from Sweden. Only variant rs236918 in the PCSK7 gene (proprotein convertase subtilisin/kexin type 7) was associated with cirrhosis or advanced fibrosis (P = 1.02 × 10(-5)) in the German cohort with genotypic odds ratios of 3.56 (95% CI 1.29-9.77) for CG heterozygotes and 5.38 (95% CI 2.39-12.10) for C allele carriers. Association between rs236918 and cirrhosis was confirmed in Austrian/Swiss HFE C282Y homozygotes (P = 0.014; ORallelic = 1.82 (95% CI 1.12-2.95) but not in Swedish patients. Post hoc combined analyses of German/Swiss/Austrian patients with available liver histology (N = 244, P = 0.00014, ORallelic = 2.84) and of males only (N = 431, P = 2.17 × 10(-5), ORallelic = 2.54) were consistent with the premier finding. Association between rs236918 and cirrhosis was not confirmed in alcoholic cirrhotics, suggesting specificity of this genetic risk factor for HH. PCSK7 variant rs236918 is a risk factor for cirrhosis in HH patients homozygous for the HFE C282Y mutation.

Randomised clinical trial: the effects of a multispecies probiotic vs. placebo on innate immune function, bacterial translocation and gut permeability in patients with cirrhosis

Probiotics may correct intestinal dysbiosis and proinflammatory conditions in patients with liver cirrhosis.

NorUrsodeoxycholic acid ameliorates cholemic nephropathy in bile duct ligated mice

BACKGROUND & AIMS Severe cholestasis may cause cholemic nephropathy that can be modeled in common bile duct ligated (CBDL) mice. We aimed to explore the therapeutic efficacy and mechanisms of norursodeoxycholic acid (norUDCA) in cholemic nephropathy. METHODS In 8-week CBDL mice fed with norUDCA (prior or post CBDL) or chow we evaluated serum urea levels, urine cytology and urinary neutrophil gelatinase associated lipocalin (uNGAL), kidney and liver tissue quantification of fibrosis by hydroxyproline content and gene chip expression looking at key genes of inflammation and fibrosis. Moreover, we comprehensively analysed bile acid profiles in liver, kidney, serum and urine samples. RESULTS NorUDCA-fed CBDL mice had significantly lower serum urea and uNGAL levels and less severe cholemic nephropathy as demonstrated by normal urine cytology, significantly reduced tubulointerstitial nephritis, and renal fibrosis as compared to controls. NorUDCA underwent extensive metabolism to produce even more hydrophilic compounds that were significantly enriched in kidneys. CONCLUSION NorUDCA ameliorates cholemic nephropathy due to the formation of highly hydrophilic metabolites enriched in kidney. Consequently, norUDCA may represent a medical treatment for cholemic nephropathy. LAY SUMMARY The term cholemic nephropathy describes renal dysfunction together with characteristic morphological alterations of the kidney in obstructive cholestasis that can be mimicked by ligation of the common bile duct in mice. Feeding the hydrophilic bile acid norUDCA to bile duct ligated mice leads to a significant amelioration of the renal phenotype due to the formation of highly hydrophilic metabolites enriched in the kidney and may therefore represent a medical treatment for cholemic nephropathy.