Biliary physiology and disease: reflections of a physician-scientist

Gallstones: The thing in itself

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Sleep Disturbance Induces Increased Cholesterol Level by NR1D1 Mediated CYP7A1 Inhibition

Disturbed sleep is closely associated with an increased risk of metabolic diseases. However, the underlying mechanisms of circadian clock genes linking sleep and lipid profile abnormalities have not been fully elucidated. This study aimed to explore the important role of the circadian clock in regulating impaired cholesterol metabolism at an early stage of sleep deprivation (SD). Sleep disturbance was conducted using an SD instrument. Our results showed that SD increased the serum cholesterol levels. Concentrations of serum leptin and resistin were much lower after SD, but other metabolic hormone concentrations (adiponectin, glucagon, insulin, thyroxine, norepinephrine, and epinephrine) were unchanged before and after SD. Warning signs of cardiovascular diseases [decreased high density lipoprotein (HDL)-cholesterol and increased corticosterone and 8-hydroxyguanosine levels] and hepatic cholestasis (elevated total bile acids and bilirubin levels) were observed after SD. Cholesterol accumulation was also observed in the liver after SD. The expression levels of HMGCR, the critical enzyme for cholesterol synthesis, remained unchanged in the liver. However, the expression levels of liver CYP7A1, the enzyme responsible for the conversion of cholesterol into bile acids, significantly reduced after SD. Furthermore, expression of NR1D1, a circadian oscillator and transcriptional regulator of CYP7A1, strikingly decreased after SD. Moreover, NR1D1 deficiency decreased liver CYP7A1 levels, and SD could exacerbate the reduction of CYP7A1 expression in NR1D1^-/- mouse livers. Additionally, NR1D1 deficiency could further increase serum cholesterol levels under SD. These results suggest that sleep disturbance can induce increased serum cholesterol levels and liver cholesterol accumulation by NR1D1 mediated CYP7A1 inhibition.

The use of obeticholic acid for the management of non-viral liver disease: current clinical practice and future perspectives

Farnesoid X nuclear receptor is involved in the regulation of lipid and glucose metabolism, though mainly in the homeostasis of bile acids. Indeed, the agonists of farnesoid X nuclear receptor represent promising drugs. Areas covered: Obeticholic acid, a novel semisynthetic analogue of the naturally occurring bile acid, has led to encouraging preliminary results in both cholestatic and metabolic liver disease. In patients with primary biliary cholangitis, obeticholic acid determines a significant biochemical improvement although the effects on liver fibrosis are lacking. Obeticholic acid has been suggested for the treatment of nonalcoholic liver disease with good laboratory results. In cirrhotic animal models, the drug seems to reduce both portal hypertension and gut bacterial translocation. Expert commentary: The use of obeticholic acid for the treatment of primary biliary cholangitis shows satisfying results. However, some open questions remain unresolved. Herein, we provide an overview of the current knowledge about the use of obeticholic acid in the field of nonviral chronic liver diseases. We tried to give a global point of view using a translational approach.

[Neonatal cholestasis]

"Cholestasis" means abnormal synthesis or secretion of bile. The main symptom in a neonate or infant is jaundice. Urine is dark, staining diapers, and stools are variably pale or white. Vitamin K should be injected (to prevent coagulation disorders due to malabsorption). The two diagnoses requiring urgent treatment are urinary tract infection and biliary atresia. If stools are permanently white, biliary atresia is highly probable. A few genetic causes of intrahepatic cholestasis should be screened and corrective surgery organized. The diseases responsible for cholestasis in this age group are described as well as the investigations and treatments, including the management of non-specific complications of cholestasis. A delay in the diagnosis of biliary atresia can have such severe consequences that consultation with a hepatology unit or transfer should be easy and rapid.

Claudin 2 deficiency reduces bile flow and increases susceptibility to cholesterol gallstone disease in mice

BACKGROUND & AIMS

Bile formation and secretion are essential functions of the hepatobiliary system. Bile flow is generated by transepithelial transport of water and ionic/nonionic solutes via transcellular and paracellular pathways that is mainly driven by osmotic pressure. We examined the role of tight junction-based paracellular transport in bile secretion. Claudins are cell-cell adhesion molecules in tight junctions that create the paracellular barrier. The claudin family has 27 reported members, some of which have paracellular ion- and/or water-channel-like functions. Claudin 2 is a paracellular channel-forming protein that is highly expressed in hepatocytes and cholangiocytes; we examined the hepatobiliary system of claudin 2 knockout (Cldn2(-/-)) mice.

METHODS

We collected liver and biliary tissues from Cldn2(-/-) and Cldn2(+/+) mice and performed histologic, biochemical, and electrophysiologic analyses. We measured osmotic movement of water and/or ions in Cldn2(-/-) and Cldn2(+/+) hepatocytes and bile ducts. Mice were placed on lithogenic diets for 4 weeks and development of gallstone disease was assessed.

RESULTS

The rate of bile flow in Cldn2(-/-) mice was half that of Cldn2(+/+) mice, resulting in significantly more concentrated bile in livers of Cldn2(-/-) mice. Consistent with these findings, osmotic gradient-driven water flow was significantly reduced in hepatocyte bile canaliculi and bile ducts isolated from Cldn2(-/-) mice, compared with Cldn2(+/+) mice. After 4 weeks on lithogenic diets, all Cldn2(-/-) mice developed macroscopically visible gallstones; the main component of the gallstones was cholesterol (>98%). In contrast, none of the Cldn2(+/+) mice placed on lithogenic diets developed gallstones.

CONCLUSIONS

Based on studies of Cldn2(-/-) mice, claudin 2 regulates paracellular ion and water flow required for proper regulation of bile composition and flow. Dysregulation of this process increases susceptibility to cholesterol gallstone disease in mice.

Identification of Salmonella enterica serovar Typhimurium genes regulated during biofilm formation on cholesterol gallstone surfaces

Salmonella spp. are able to form biofilms on abiotic and biotic surfaces. In vivo studies in our laboratory have shown that Salmonella can form biofilms on the surfaces of cholesterol gallstones in the gallbladders of mice and human carriers. Biofilm formation on gallstones has been demonstrated to be a mechanism of persistence. The purpose of this work was to identify and evaluate Salmonella sp. cholesterol-dependent biofilm factors. Differential gene expression analysis between biofilms on glass or cholesterol-coated surfaces and subsequent quantitative real-time PCR (qRT-PCR) revealed that type 1 fimbria structural genes and a gene encoding a putative outer membrane protein (ycfR) were specifically upregulated in Salmonella enterica serovar Typhimurium biofilms grown on cholesterol-coated surfaces. Spatiotemporal expression of ycfR and FimA verified their regulation during biofilm development on cholesterol-coated surfaces. Surprisingly, confocal and scanning electron microscopy demonstrated that a mutant of type 1 fimbria structural genes (ΔfimAICDHF) and a ycfR mutant showed increased biofilm formation on cholesterol-coated surfaces. In vivo experiments using Nramp1(+/+) mice harboring gallstones showed that only the ΔycfR mutant formed extensive biofilms on mouse gallstones at 7 and 21 days postinfection; ΔfimAICDHF was not observed on gallstone surfaces after the 7-day-postinfection time point. These data suggest that in Salmonella spp., wild-type type 1 fimbriae are important for attachment to and/or persistence on gallstones at later points of chronic infection, whereas YcfR may represent a specific potential natural inhibitor of initial biofilm formation on gallstones.

Genetic determinants of cholestasis

Cholestasis is an overarching term applied for conditions whereby biliary constituents are found in the circulation because of impairment to bile flow. A variety of processes can lead to cholestasis, be they acute or chronic injuries to hepatocytes, cholangiocytes, or the broader biliary tree itself. Such injuries may be driven by rare but highly informative primary genetic abnormalities, or may be seen in individuals with a prior genetic predisposition when confronted by specific environmental challenges such as drug exposure. This review provides a broad outline of some fundamental primary genetic cholestatic syndromes and an update on varying genetic predisposition underlying several acquired cholestatic processes.

The effects of serum cholesterol, LDL, and HDL levels on gallstone cholesterol concentration

OBJECTIVE

Gallbladder stones are common in the Western world, and 70% to 80% of gallstones are cholesterol stones. This study investigates the effects of serum cholesterol, LDL, and HDL levels on gallstone cholesterol concentration.

METHODOLOGY

The gallstones of 75 patients with cholelithiasis were examined using spectrophotometry.

RESULTS

High serum cholesterol and LDL levels were associated with high cholesterol stone rates (86.7% vs. 40.0%, P < 0.001; 75.0% vs. 48.9%, P < 0.05, respectively). Similarly, high serum cholesterol and LDL levels were correlated with high gallbladder stone cholesterol concentrations (63.6% vs. 44.4%, P < 0.001; 62.3% vs. 46.0%, P < 0.001, respectively). In contrast, low serum HDL levels do not seem to affect the occurrence of gallbladder cholesterol stones (60.0% vs. 58.3%, respectively, P > 0.05) or gallbladder stone cholesterol concentrations (50.8% vs. 52.4%, respectively, P > 0.05).

CONCLUSION

The relationship between cholesterol, LDL, and HDL levels and cholesterol gallstone formation is multifactorial and complex and is also dependent on other individual properties.

Primary sclerosing cholangitis and bile acids

Primary sclerosing cholangitis (PSC) is a rare and complex chronic cholestatic liver disease, and its management is hindered by a very poor understanding of its pathogenesis. Endogenous bile acids are likely to play a role either directly or indirectly in the pathogenesis and/or progression of PSC ('toxic-bile'hypothesis). At present, no medical therapies have been proven to delay disease progression. Ursodeoxycholic acid (UDCA) is the agent that has received the most attention. Based on large randomized studies, it appears that UDCA at doses from 13 to 23 mg/kg/d has no proven benefit on survival, but is well tolerated and improves serum liver tests and surrogate markers of prognosis whereas, at higher doses (28-30 mg/kg/d), it is associated with a worsened outcome. However, except at very high doses and despite the controversies, many hepatologists still consider UDCA a reasonable treatment choice. Indeed, its use at dosages of 15-20 mg/kg/d has recently been approved for the treatment of PSC by the French National Health Authority. In addition, 24-nor-ursodeoxycholic acid, a side-chain-modified UDCA derivative, has shown promising results in animal models of PSC and is currently under investigation in humans.

Metabolomic study of serum from rabbits with acute acalculous cholecystitis

OBJECTIVES

(1)H-NMR is a powerful approach of metabolomics. This study aimed to apply it to detect the serum metabolites in rabbits with acute acalculous cholecystitis (AAC), and to analyze their potential roles in AAC.

METHODS

Fourteen rabbits were randomly divided into two groups, the AAC group and the CON group. In the AAC rabbit model, Escherichia coli solution was injected into the gallbladder, while same volume of saline, instead of E. coli solution, was injected into the gallbladder of the CON rabbit. General morphological, light microscopic and transmission electron microscopic observations were used to evaluate the model. Metabolic profiles of serum from rabbits with AAC were investigated through (1)H-NMR spectroscopy coupled with multivariate statistical analysis, such as principal components analysis and orthogonal partial least-squares discriminant analysis.

RESULTS

The pathohistology of gallbladders showed a significant difference between the two groups, proving the successful induction of inflammation in the gallbladders of the AAC group. The serum concentration of lipids (LDL and VLDL) increased during AAC, while the concentrations of phospholipids, lactic acid, 3-hydroxybutyric acid, lysine, citric acid, asparagine, histidine, glucose and some other small molecular metabolites decreased.

CONCLUSION

The profiling of serum metabolites in rabbits with acute acalculous cholecystitis changed significantly. These changes referred to the metabolic disturbance of carbohydrate, amino acids and lipids, inhibition of immunological functions and inflammation reaction.

A review of indocyanine green fluorescent imaging in surgery

The purpose of this paper is to give an overview of the recent surgical intraoperational applications of indocyanine green fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.

Scoparone potentiates transactivation of the bile salt export pump gene and this effect is enhanced by cytochrome P450 metabolism but abolished by a PKC inhibitor

BACKGROUND AND PURPOSE

Hyperbilirubinaemia and cholestasis are two major forms of liver abnormality. The Chinese herb Yin Chin has been used for thousands of years to treat liver dysfunctions. In mice, this herb and its principal ingredient scoparone were found to accelerate the clearance of bilirubin accompanied by the induction of uridine diphosphate-5'-glucuronosyltransferase-1A1 (UGT1A1), a bilirubin processing enzyme. The aim of this study was to determine whether scoparone induces the expression of human UGT1A1. In addition, the expression of the bile salt export pump (BSEP), a transporter of bile acids, was determined.

EXPERIMENTAL APPROACH

Primary human hepatocytes and hepatoma line Huh7 were treated with scoparone, chenodeoxycholic acid (CDCA) or both. The expression of UGT1A1 and BSEP mRNA was determined. The activation of the human BSEP promoter reporter by scoparone was determined in Huh7 cells by transient transfection and in mice by bioluminescent imaging. The metabolism of scoparone was investigated by recombinant CYP enzymes and pooled human liver microsomes.

KEY RESULTS

Scoparone did not enhance the expression of either human BSEP or, surprisingly, UGT1A1. However, scoparone significantly potentiated the expression of BSEP induced by CDCA. Consistent with this, scoparone potentiated the stimulant effect of CDCA on the human BSEP promoter. This potentiation was enhanced by co-transfection of cytochrome P4501A2 but abolished by the PKC inhibitor GF109203X.

CONCLUSIONS AND IMPLICATIONS

Scoparone and Yin Chin normalize liver function primarily by enhancing the secretion of bile acids, and this effect probably varies depending on the metabolic rate of scoparone.

Current consensus on the management of primary sclerosing cholangitis

Guidelines for the management of primary sclerosing cholangitis (PSC) have recently been published by both the European Association for the Study of the Liver (EASL) and the American Association for the Study of Liver Diseases (AASLD). The current review focuses on the management of PSC, based on these guidelines. There is no established medical therapy for PSC. The role for UDCA in slowing the disease progression and improving survival is as yet unclear, and there are no specific recommendations for the general use of UDCA in this condition. Guidelines recommend that dominant bile duct strictures with significant cholestasis should be treated with biliary dilatation, with or without stenting. Prospective studies to define type, duration, optimal frequency and long-term effects of endoscopic therapy are needed. Liver transplantation is recommended for end stage disease and has excellent results. PSC patients with dysplasia in biliary brush cytology specimens should also be considered for transplantation. There is no evidence-based algorithm for the follow-up of PSC patients, but some regular investigations are recommended (surveillance colonoscopies in patients with IBD and ultrasound to detect gallbladder mass lesions).

Chronic and acute infection of the gall bladder by Salmonella Typhi: understanding the carrier state

Despite major treatment and prevention efforts, millions of new typhoid infections occur worldwide each year. For a subset of infected individuals, Salmonella enterica subsp. enterica serovar Typhi colonizes the gall bladder and remains there long after symptoms subside, serving as a reservoir for the further spread of the disease. In this Progress article, we explore recent advances in our understanding of the mechanisms by which Salmonella spp.--predominantly S. Typhi--colonize and persist in the human gall bladder.