Nuclear receptors as new perspective for the management of liver diseases

PPARγ signaling in hepatocarcinogenesis: Mechanistic insights for cellular reprogramming and therapeutic implications

Liver cancer or hepatocellular carcinoma (HCC) is leading cause of cancer-related mortalities globally. The therapeutic approaches for chronic liver diseases-associated liver cancers aimed at modulating immune check-points and peroxisome proliferator-activated receptor gamma (PPARγ) signaling pathway during multistep process of hepatocarcinogenesis that played a dispensable role in immunopathogenesis and outcomes of disease. Herein, the review highlights PPARγ-induced effects in balancing inflammatory (tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1) and anti-inflammatory cytokines (IL-10, transforming growth factor beta (TGF-β), and interplay of PPARγ, hepatic stellate cells and fibrogenic niche in cell-intrinsic and -extrinsic crosstalk of hepatocarcinogenesis. PPARγ-mediated effects in pre-malignant microenvironment promote growth arrest, cell senescence and cell clearance in liver cancer pathophysiology. Furthermore, PPARγ-immune cell axis of liver microenvironment exhibits an immunomodulation strategy of resident immune cells of the liver (macrophages, natural killer cells, and dendritic cells) in concomitance with current clinical guidelines of the European Association for Study of Liver Diseases (EASL) for several liver diseases. Thus, mechanistic insights of PPARγ-associated high value targets and canonical signaling suggest PPARγ as a possible therapeutic target in reprogramming of hepatocarcinogenesis to decrease burden of liver cancers, worldwide.

SU5, a new Auraptene analog with improved metabolic stability, ameliorates nonalcoholic fatty liver disease in methionine- and choline-deficient diet-fed db/db mice

Farnesoid X receptor (FXR) has been considered as a promising target for non-alcoholic steatohepatitis (NASH), while existing FXR agonists suffer from serious side effects. Thus, it is very necessary to identify novel FXR agonists with good safety. Auraptene (AUR) is a new FXR agonist with excellent safety and extensive pharmacological activities, while the lactone of AUR is vulnerable to esterolysis. In this study, the lactone of AUR was converted to metabolically stable amide moiety, and the obtained analog SU5 revealed comparable activity and better metabolic stability than that of AUR. In NASH model, SU5 showed stronger efficacy than AUR on fatty liver by up-regulating gene expressions related to FXR in vivo. Moreover, SU5 improved lipid metabolism by down-regulating the gene expressions of lipid synthesis, while up-regulating the gene expressions of fatty acid β-oxidation and triglyceride metabolism. Besides, the inflammation-related genes were significantly decreased in SU5 treated group. These positive results highlighted the pharmacological potential of SU5 for the treatment of NASH.

Predicting Target Genes of San-Huang-Chai-Zhu Formula in Treating ANIT-Induced Acute Intrahepatic Cholestasis Rat Model via Bioinformatics Analysis Combined with Experimental Validation

Background

San-Huang-Chai-Zhu formula (SHCZF) has been used to improve cholestasis for many years. This study aims to predict the possible gene targets of SHCZF in treating acute intrahepatic cholestasis (AIC) in rats.

Materials and Methods

Eighteen SD rats were randomly assigned to the normal group, ANIT group, and ANIT + SHCZF group. Alpha-naphthylisothiocyanate (ANIT) was used to induce AIC. Serum biochemical indexes were detected in each group. After treatment, the livers were collected and used to extract RNA. The library was constructed by TruSeq RNA, sequenced by Illumina, and analyzed by various bioinformatics methods. qRT-PCR was used to verify the target genes related to the efficacy of SHCZF.

Results

Serum ALT, AST, ALP, and TBIL were significantly higher in the ANIT group than in the normal group. Serum ALT and AST levels in the ANIT + SHCZF group were substantially lower than those in the ANIT group. A total of 354 intersected genes were screened by expression level correlation and PCA analysis, GO and KEGG pathway enrichment analysis, and WGCNA and STEM analysis. Then, 4 overlapping genes were found by pathway/BP/gene network construction. SHCZF reversed the downregulation of expression of CYP4A1 and HACL1 and the upregulation of expression of DBI and F11R induced by ANIT. In addition, the qRT-PCR result showed that mRNA expression of CYP4A1, HACL1, and F11R genes in the liver was consistent with the prediction result of bioinformatics analysis.

Conclusion

CYP4A1, HACL1, and F11R are genes related to the occurrence of ANIT-induced AIC in rats and may be considered as targets of SHCZF for the treatment of AIC.

Design, synthesis, and biological evaluation of novel FXR agonists based on auraptene

Farnesoid X receptor (FXR) has been considered as an attractive target for metabolic disorder and liver injury, while many current FXR agonists suffer from undesirable side effects, such as pruritus. Therefore, it is urgent to develop new structure types different from current FXR agonists. In this study, a series of structural optimizations were introduced to displace the unstable coumarin and geraniol scaffolds of auraptene (AUR), a novel and safe FXR agonist. All of these efforts led to the identification of compound 14, a potent FXR agonist with nearly fourfold higher activity than AUR. Molecular modeling study suggested that compound 14 fitted well with binding pocket, and formed the key ionic bond with His291 and Arg328. In acetaminophen-induced acute liver injury model, compound 14 exerts better therapeutic effect than that of AUR, which highlighting its pharmacological potential in the treatment of drug-induced liver injury.

Fxr signaling and microbial metabolism of bile salts in the zebrafish intestine

Bile salt synthesis, secretion into the intestinal lumen, and resorption in the ileum occur in all vertebrate classes. In mammals, bile salt composition is determined by host and microbial enzymes, affecting signaling through the bile salt-binding transcription factor farnesoid X receptor (Fxr). However, these processes in other vertebrate classes remain poorly understood. We show that key components of hepatic bile salt synthesis and ileal transport pathways are conserved and under control of Fxr in zebrafish. Zebrafish bile salts consist primarily of a C27 bile alcohol and a C24 bile acid that undergo multiple microbial modifications including bile acid deconjugation that augments Fxr activity. Using single-cell RNA sequencing, we provide a cellular atlas of the zebrafish intestinal epithelium and uncover roles for Fxr in transcriptional and differentiation programs in ileal and other cell types. These results establish zebrafish as a nonmammalian vertebrate model for studying bile salt metabolism and Fxr signaling.

Predictors of early mortality among patients with acute-on-chronic liver failure

Background and Aim

Acute-on-chronic liver failure (ACLF) is a transpiring entity, which possesses high short-term/early mortality (28 days). Several mortality predictors have been studied, but none were proved reliable. Serum ferritin, an acute phase reactant and marker of hepatic necro-inflammation, is found to predict mortality in multiple liver diseases. We aimed to evaluate the role of serum ferritin and other clinical features, biochemical parameters and conventional scoring systems in predicting early mortality among ACLF.

Methods

A prospective cohort study was done from October 2017 to March 2019 at a tertiary care (non-transplant) center in eastern India. A total of consecutive 50 ACLF patients diagnosed, based on Asia Pacific Association for the Study of liver disease definition, were investigated for ferritin and other laboratory parameters on day-0, day-7, and followed up for 28 days.

Results

Although the majority did not have organ failure (ACLF grade 0) according to European Association for Study of Liver-chronic liver failure sequential organ failure assessment criteria, early mortality was high (56%). On undergoing univariate analysis, multiple variables (ascites, HE, creatinine, total leucocyte count (TLC), bilirubin, albumin) predicted mortality. However, on multivariate analysis, only total bilirubin independently predicted. None of the scores on day-0 were predictive, while model for end-stage liver disease [area under the receiver operating characteristics (AUROC)-0.703, 95% confidence interval [CI]: 0.535-0.859] and Child-Turcotte-Pugh (AUROC-0.697, 95% CI: 0.550-0.855) on day-7 did.

Conclusion

ACLF is a dynamic process; day-7 assessment with above predictors, to be considered a milestone for prognostication and opting treatment modalities. Serum ferritin does not predict early mortality in ACLF.

Atorvastatin Induces FXR and CYP7A1 Activation as a Result of the Sequential Action of PPARγ/PGC-1α/HNF-4α in Hep3B Cells

Backgrounds/Aims

PPARγ, farnesoid X receptor (FXR) and CYP7A1 are associated with solubility of bile. This study was performed to understand a mechanism and interactions of statin-induced PPARγ, PGC-1α and HNF-4α related to the statin-induced activation of FXR and CYP7A1, and verify whether the mevalonate pathway is involved in the mechanism.

Methods

MTT assays were performed using cultured human Hep3B cells to determine the effect of atorvastatin on the cell proliferation. Expression levels of indicated proteins were measured using Western blotting assays by inhibiting the protein expression or not.

Results

Atorvastatin increased expression of PPARγ, PGC-1α, HNF-4α, FXR, and CYP7A1 in Hep3B cells. PPARγ ligand of troglitazone upregulated the expression of PGC-1α, HNF-4α, FXR, and CYP7A1 in Hep3B cells. Silencing of PPARγ, PGC1α, and HNF4α using respective siRNA demonstrated that atorvastatin-induced FXR and CYP7A1 activation required sequential action of PPARγ /PGC-1α/HNF-4α. The silencing of PPARγ completely inhibited atorvastatin-induced PGC-1α expression, and the PGC1α silencing partially inhibited atorvastatin-induced PPARγ expression. The inhibition of HNF4α did not affect atorvastatin-induced PPARγ expression, but partially inhibited atorvastatin-induced PGC-1α expression. Besides, mevalonate completely reversed the effect of atorvastatin on PPARγ, PGC-1α, HNF-4α, FXR, and CYP7A1.

Conclusions

Atorvastatin induces FXR and CYP7A1 activation as a result of sequential action of PPARγ/PGC-1α/HNF-4α in human hepatocytes. We propose that atorvastatin enhances solubility of cholesterol in bile by simultaneously activating of FXR and CYP7A1.

Non-coding RNA crosstalk with nuclear receptors in liver disease

The dysregulation of nuclear receptors (NRs) underlies the pathogenesis of a variety of liver disorders. Non-coding RNAs (ncRNAs) are defined as RNA molecules transcribed from DNA but not translated into proteins. MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are two types of ncRNAs that have been extensively studied for regulating gene expression during diverse cellular processes. NRs as therapeutic targets in liver disease have been exemplified by the successful application of their pharmacological ligands in clinics. MiRNA-based reagents or drugs are emerging as flagship products in clinical trials. Advancing our understanding of the crosstalk between NRs and ncRNAs is critical to the development of diagnostic and therapeutic strategies. This review summarizes recent findings on the reciprocal regulation between NRs and ncRNAs (mainly on miRNAs and lncRNAs) and their implication in liver pathophysiology, which might be informative to the translational medicine of targeting NRs and ncRNAs in liver disease.

Design, synthesis and structure-activity relationship studies of novel partial FXR agonists for the treatment of fatty liver

Nonalcoholic fatty liver disease (NAFLD) is now the most common chronic liver disease, while there is still no medicine available. Farnesoid X receptor (FXR) is considered as a potential target for the treatment of NAFLD, and there are several FXR agonists reached in clinical trials. Based on better safety, industry and academia are pursuing development of the partial FXR agonists. To extend the chemical space of existing partial FXR agonists, we performed a structure-activity relationship study based on previously reported partial agonist 1 by using bioisosteric strategy. All of these efforts resulted in the identification of novel partial FXR agonist 13, which revealed the best agonistic activity in this series. Notably, compound 13 significantly alleviated the hepatic steatosis and hepatic function index in methionine-choline deficient (MCD) induced db/db mice, a classical nonalcoholic steatohepatitis (NASH) model widely used in preclinical evaluation. These results suggested that partial FXR agonist 13 might be a promising lead compound worthy further researches.

A Gilbert syndrome-associated haplotype protects against fatty liver disease in humanized transgenic mice

UDP-glucuronosyltransferases 1 A (UGT1A) enzymes are capable of detoxifying a broad range of endo- and xenobiotic compounds, which contributes to antioxidative effects, modulation of inflammation and cytoprotection. In the presence of low-function genetic UGT1A variants fibrosis development is increased in various diseases. This study aimed to examine the role of common UGT1A polymorphisms in NASH. Therefore, htgUGT1A-WT mice and htgUGT1A-SNP mice (carrying a common human haplotype present in 10% of the white population) were fed a high-fat Paigen diet for 24 weeks. Serum aminotransferase activities, hepatic triglycerides, fibrosis development and UGT1A expression were assessed. Microscopic examination revealed higher hepatic fat deposition and a significant induction of UGT1A gene expression in htgUGT1A-WT mice. In agreement with these observations, lower serum aminotransferase activities and lower expression levels of fibrosis-related genes were measured in htgUGT1A-SNP mice. This was accompanied by reduced PPARα protein levels in htgUGT1A-WT but not in SNP mice. Our data demonstrate a protective effect of a UGT1A SNP haplotype, leading to milder hepatic steatosis and NASH. Higher PPARα protein levels in animals with impaired UGT1A activity are the likely result of reduced glucuronidation of ligands involved in PPARα-mediated fatty acid oxidation and may lead to the observed protection in htgUGT1A-SNP mice.

Impact of farnesoid X receptor single nucleotide polymorphisms on hepatic decompensation and mortality in cirrhotic patients with portal hypertension

BACKGROUND AND AIM

The nuclear farnesoid X receptor (FXR) regulates critical pathways of hepatic metabolism, inflammation, and gut mucosal barrier. Thus, we investigated the association of FXR-single nucleotide polymorphism (SNPs) with hepatic decompensation and liver-related mortality in patients with advanced chronic liver disease.

METHODS

Two FXR-SNPs (rs56163822 G > T and rs35724 G > C) were genotyped in a cohort of 402 prospectively characterized patients with hepatic venous pressure gradient (HVPG) ≥ 6 mmHg.

RESULTS

Only 19 patients (4.7%) harbored a rs56163822 T-allele and had less pronounced liver disease as indicated by lower Child-Pugh score (CPS, 6 ± 1 vs 7 ± 2 points, P = 0.034) and higher albumin levels (38.9 ± 4.9 vs 35.9 ± 5.9 g/L, P = 0.026). In contrast, n = 267 (66.4%) patients harbored minor rs35724 allele (G/C or C/C) and had more advanced liver disease, as indicated by a higher model of end-stage liver disease (11 ± 4 vs 10 ± 3, P = 0.016), while other baseline characteristics were similar across FXR-SNP genotypes. In compensated CPS-A patients, the rs35724 minor allele was independently protective for the development of ascites (adjusted hazard ratio [aHR] = 0.411, 95% confidence interval (95% CI): 0.191-0.885; P = 0.023) and tended to reduce the risk of hepatic decompensation (aHR = 0.625, 95% CI: 0.374-1.044, P = 0.072) in multivariate analyses. Of note, transplant-free survival was longer in patients with rs35724 minor allele and HVPG ≥ 10 mmHg (at 5 years: 68.2% vs 55.8%, P = 0.047) and those with HVPG ≥ 16 mmHg (63.3% vs 44.0%, P = 0.021). After adjusting for established risk factors, the rs35724 minor allele was independently associated with reduced liver-related mortality in the overall cohort (aHR = 0.658, 95% CI: 0.434-0.998, P = 0.049), in compensated CPS-A patients (aHR = 0.488, 95% CI: 0.252-0.946, P = 0.034), in patients with HVPG ≥ 10 mmHg (aHR = 0.547, 95% CI: 0.346-0.864, P = 0.010), and in patients with HVPG ≥ 16 mmHg (aHR = 0.519, 95% CI: 0.307-0.878, P = 0.014).

CONCLUSION

The FXR-SNP rs35724 was associated with a reduced risk for development of ascites and liver-related mortality in patients with advanced chronic liver disease.

Adiponectin and PPAR: a setup for intricate crosstalk between obesity and non-alcoholic fatty liver disease

Adiponectin, a soluble adipocytokine, plays an important role in the functioning of adipose tissue and in the regulation of inflammation, particularly hepatic inflammation. The adiponectin subsequently imparts a crucial role in metabolic and hepato-inflammatory diseases. The most recent evidences indicate that lipotoxicity-induced inflammation in the liver is associated with obesity-derived alterations and remolding in adipose tissue that culminates in most prevalent liver pathology named as non-alcoholic fatty liver disease (NAFLD). A comprehensive crosstalk of adiponectin and its cognate receptors, specifically adiponectin receptor-2 in the liver mediates ameliorative effects in obesity-induced NAFLD by interaction with hepatic peroxisome proliferator-activated receptors (PPARs). Recent studies highlight the implication of molecular mediators mainly involved in the pathogenesis of obesity and obesity-driven NAFLD, however, the plausible mechanisms remain elusive. The present review aimed at collating the data regarding mechanistic approaches of adiponectin and adiponectin-activated PPARs as well as PPAR-induced adiponectin levels in attenuation of hepatic lipoinflammation. Understanding the rapidly occurring adiponectin-mediated pathophysiological outcomes might be of importance in the development of new therapies that can potentially resolve obesity and obesity-associated NAFLD.

Docosahexaenoic acid inhibits hepatic stellate cell activation to attenuate liver fibrosis in a PPARγ-dependent manner

Docosahexaenoic acid (DHA) has been found to have a hepatoprotective effect. In this study, we investigated the role of peroxisome proliferator-activated receptor γ (PPARγ) in DHA regulation of liver fibrosis. DHA was found to inhibit hepatic stellate cell (HSC)-LX2 cell viability and downregulate marker proteins of HSC activation. Furthermore, DHA induced cell cycle arrest at G1 phase in HSCs. Antagonism of PPARγ by GW9662 abrogated the effects of DHA on HSCs. Computer-aided molecular docking predicted that DHA bound to PPARγ via hydrogen bonding with residues Ser289, His323, Tyr473, and His499. We overexpressed Ser289 mutant PPARγ in HSC-LX2 cells and investigated fibrotic marker modulation, and found that DHA effects on HSCs were diminished. Thus, bonding with the Ser289 residue might be indispensable for DHA to activate PPARγ to exert its inhibiting effect on activated HSCs. Last, data from a CCl₄-treated mouse model confirmed that PPARγ activation was required for DHA to attenuate liver fibrosis.

The circadian clock and liver function in health and disease

Each day, all organisms are subjected to changes in light intensity because of the Earth's rotation around its own axis. To anticipate this geo-physical variability, and to appropriately respond biochemically, most species, including mammals, have evolved an approximate 24-hour endogenous timing mechanism known as the circadian clock (CC). The 'clock' is self-sustained, cell autonomous and present in every cell type. At the core of the clock resides the CC-oscillator, an exquisitely crafted transcriptional-translational feedback system. Remarkably, components of the CC-oscillator not only maintain daily rhythmicity of their own synthesis, but also generate temporal variability in the expression levels of numerous target genes through transcriptional, post-transcriptional and post-translational mechanisms, thus, ensuring proper chronological coordination in the functioning of cells, tissues and organs, including the liver. Indeed, a variety of physiologically critical hepatic functions and cellular processes are CC-controlled. Thus, it is not surprising that modern lifestyle factors (e.g. travel and jet lag, night and rotating shift work), which force 'circadian misalignment', have emerged as major contributors to global health problems including obesity, non-alcoholic fatty liver disease and steatohepatitis. Herein, we provide an overview of the CC-dependent pathways which play critical roles in mediating several hepatic functions under physiological conditions, and whose deregulation is implicated in chronic liver diseases including non-alcoholic steatohepatitis and alcohol-related liver disease.

Nuclear receptors and liver disease: Summary of the 2017 basic research symposium

The nuclear receptor superfamily contains important transcriptional regulators that play pleiotropic roles in cell differentiation, development, proliferation, and metabolic processes to govern liver physiology and pathology. Many nuclear receptors are ligand-activated transcription factors that regulate the expression of their target genes by modulating transcriptional activities and epigenetic changes. Additionally, the protein complex associated with nuclear receptors consists of a multitude of coregulators, corepressors, and noncoding RNAs. Therefore, acquiring new information on nuclear receptors may provide invaluable insight into novel therapies and shed light on new interventions to reduce the burden and incidence of liver diseases. (Hepatology Communications 2018;2:765-777).

Gadoxetic acid-enhanced magnetic resonance imaging reflects co-activation of β-catenin and hepatocyte nuclear factor 4α in hepatocellular carcinoma

AIM

The aim of this study is to clarify the correlation of the co-activation of β-catenin and hepatocyte nuclear factor (HNF)4α with the findings of gadoxetic acid-enhanced magnetic resonance imaging (MRI), organic anion transporting polypeptide (OATP)1B3 expression, and histological findings in hepatocellular carcinoma (HCC).

METHODS

One hundred and ninety-six HCCs surgically resected from 174 patients were enrolled in this study. The HCCs were classified into four groups by immunohistochemical expression of β-catenin, glutamine synthetase (GS), and HNF4α: (i) β-catenin/GS (positive [+]) HNF4α (+); (ii) β-catenin/GS (+) HNF4α (negative [-]); (iii) β-catenin/GS (-) HNF4α (+); and (iv) β-catenin/GS (-) HNF4α (-). We compared the four groups in terms of the enhancement ratio on the hepatobiliary phase of gadoxetic acid-enhanced MRI, immunohistochemical organic anion transporter polypeptide (OATP)1B3 (a main uptake transporter of gadoxetic acid) expression and histological features, overall survival, and no recurrence survival. The Kruskal-Wallis test, Steel-Dwass multiple comparisons test, Fisher's exact test, and log-rank (Mantel-Cox) test were used for statistical analyses.

RESULTS

Enhancement ratio on gadoxetic acid-enhanced MRI in HCC with β-catenin/GS (+) HNF4α (+) was significantly higher than those of the other three groups (P < 0.001). The OATP1B3 grade was also significantly higher in HCC with β-catenin/GS (+) HNF4α (+) (P < 0.001). Hepatocellular carcinoma with β-catenin/GS (+) HNF4α (+) showed the highest differentiation grade as compared to the other groups (P < 0.004). There were no significant differences in portal vein invasion, macroscopic growth pattern, or prognosis analyses between the four groups.

CONCLUSION

Co-activation of β-catenin and HNF4α would promote OATP1B3 expression, and consequently higher enhancement ratio on gadoxetic acid-enhanced MRI and higher differentiation grade in HCC.

Ligand Activation of PPARγ by Ligustrazine Suppresses Pericyte Functions of Hepatic Stellate Cells via SMRT-Mediated Transrepression of HIF-1α

Rationale: Hepatic stellate cells (HSCs) are liver-specific pericytes regulating vascular remodeling during hepatic fibrosis. Here, we investigated how ligustrazine affects HSC pericyte functions.

Methods: Rat HSC-T6 and human HSC-LX2 cells were cultured, and multiple molecular experiments including real-time PCR, Western blot, flow cytometry, immunofluorescence, electrophoretic mobility shift assay and co-immunoprecipitation were used to elucidate the underlying mechanisms. Molecular simulation and site-directed mutagenesis were performed to uncover the target molecule of ligustrazine. Rats were intoxicated with CCl₄ for evaluating ligustrazine's effects in vivo.

Results: Ligustrazine inhibited angiogenic cytokine production, migration, adhesion and contraction in HSCs, and activated PPARγ. Selective PPARγ inhibitor GW9662 potently abrogated ligustrazine suppression of HSC pericyte functions. Additionally, HIF-1α inhibitor PX-478 repressed HSC pericyte functions, and ligustrazine inhibited the transcription of HIF-1α, which was diminished by GW9662. Moreover, ligustrazine downregulation of HIF-1α was rescued by knockdown of SMRT, and ligustrazine increased PPARγ physical interaction with SMRT, which was abolished by GW9662. These findings collectively indicated that activation of PPARγ by ligustrazine led to transrepression of HIF-1α via a SMRT-dependent mechanism. Furthermore, molecular docking evidence revealed that ligustrazine bound to PPARγ in a unique double-molecule manner via hydrogen bonding with the residues Ser289 and Ser342. Site-directed mutation of Ser289 and/or Ser342 resulted in the loss of ligustrazine transrepression of HIF-1α in HSCs, indicating that interactions with both the residues were indispensable for ligustrazine effects. Finally, ligustrazine improved hepatic injury, angiogenesis and vascular remodeling in CCl₄-induced liver fibrosis in rats.

Conclusions: We discovered a novel ligand activation pattern for PPARγ transrepression of the target gene with therapeutic implications in HSC pericyte biology and liver fibrosis.

Pregnane X receptor and constitutive androstane receptor modulate differently CYP3A-mediated metabolism in early- and late-stage cholestasis

AIM

To ascertain whether cholestasis affects the expression of two CYP3A isoforms (CYP3A1 and CYP3A2) and of pregnane X receptor (PXR) and constitutive androstane receptor (CAR).

METHODS

Cholestasis was induced by bile duct ligation in 16 male Wistar rats; whereas 8 sham-operated rats were used as controls. Severity of cholestasis was assessed on histological examination of liver sections, and serum concentrations of albumin, AST, ALT, GGT, ALPK and bilirubin. Gene and protein expressions of PXR, CAR, CYP3A1 and CYP3A2 were assessed by means of qRT-PCR and Western blot, respectively. Alterations in CYP3A activity were measured by calculating the kinetic parameters of 4-OH and 1’-OH-midazolam hydroxylation, marker reactions for CYP3A enzymes.

RESULTS

The mRNA and protein expression of CYP3A1 increased significantly in mild cholestasis (P < 0.01). At variance, mRNA and protein expression of CYP3A2 didn’t change in mild cholestasis, whereas the expression and activity of both CYP3A1 and CYP3A2 decreased dramatically when cholestasis became severe. Consistently with these observations, the nuclear expression of both PXR and CAR, which was measured because they both translocate into the cell nucleus after their activation, virtually disappeared in the late stage of cholestatic injury, after an initial increase. These results indicate that early- and late-stage cholestasis affects CYP3A-mediated drug metabolism differently, probably as consequence of the different activation of PXR and CAR.

CONCLUSION

Early- and late-stage cholestasis affects CYP3A-mediated drug metabolism differently. PXR and CAR might be targeted therapeutically to promote CYP3A-mediated liver detoxification.

Bile acids and intestinal microbiota in autoimmune cholestatic liver diseases

Autoimmune cholestatic liver diseases, including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are manifested as an impairment of normal bile flow and excessive accumulation of potentially toxic bile acids. Endogenous bile acids are involved in the pathogenesis and progression of cholestasis. Consequently, chronic cholestasis affects the expression of bile acid transporters and nuclear receptors, and results in liver injury. Several lines of evidence suggest that intestinal microbiota plays an important role in the etiopathogenesis of cholestatic liver diseases by regulating metabolism and immune responses. However, progression of the disease may also affect the composition of gut microbiota, which in turn exacerbates the progression of cholestasis. In addition, the interaction between intestinal microbiota and bile acids is not unidirectional. Bile acids can shape the gut microbiota community, and in turn, intestinal microbes are able to alter bile acid pool. In general, gut microbiota actively communicates with bile acids, and together play an important role in the pathogenesis of PBC and PSC. Targeting the link between bile acids and intestinal microbiota offers exciting new perspectives for the treatment of those cholestatic liver diseases. This review highlights current understanding of the interactions between bile acids and intestinal microbiota and their roles in autoimmune cholestatic liver diseases. Further, we postulate a bile acids-intestinal microbiota-cholestasis triangle in the pathogenesis of autoimmune cholestatic liver diseases and potential therapeutic strategies by targeting this triangle.

Metabolic Profile of Obeticholic Acid and Endogenous Bile Acids in Rats with Decompensated Liver Cirrhosis

Obeticholic acid (OCA) is a semisynthetic bile acid (BA) analog and potent farnesoid X receptor agonist approved to treat cholestasis. We evaluated the biodistribution and metabolism of OCA administered to carbon tetrachloride-induced cirrhotic rats. This was to ascertain if plasma and hepatic concentrations of OCA are potentially more harmful than those of endogenous BAs. After administration of OCA (30 mg/kg), we used liquid chromatography-mass spectrometry to measure OCA, its metabolites, and BAs at different timepoints in various organs and fluids. Plasma and hepatic concentrations of OCA and BAs were higher in cirrhotic rats than in controls. OCA and endogenous BAs had similar metabolic pathways in cirrhotic rats, although OCA hepatic and intestinal clearance were lower than in controls. BAs' qualitative and quantitative compositions were not modified by a single administration of OCA. In all the matrices studied, OCA concentrations were significantly lower than those of endogenous BAs, potentially much more cytotoxic.

The FXR agonist PX20606 ameliorates portal hypertension by targeting vascular remodelling and sinusoidal dysfunction

BACKGROUND & AIMS

Steroidal farnesoid X receptor (FXR) agonists demonstrated potent anti-fibrotic activities and lowered portal hypertension in experimental models. The impact of the novel non-steroidal and selective FXR agonist PX20606 on portal hypertension and fibrosis was explored in this study.

METHODS

In experimental models of non-cirrhotic (partial portal vein ligation, PPVL, 7days) and cirrhotic (carbon tetrachloride, CCl₄, 14weeks) portal hypertension, PX20606 (PX,10mg/kg) or the steroidal FXR agonist obeticholic acid (OCA,10mg/kg) were gavaged. We then measured portal pressure, intrahepatic vascular resistance, liver fibrosis and bacterial translocation.

RESULTS

PX decreased portal pressure in non-cirrhotic PPVL (12.6±1.7 vs. 10.4±1.1mmHg; p=0.020) and cirrhotic CCl₄ (15.2±0.5 vs. 11.8±0.4mmHg; p=0.001) rats. In PPVL animals, we observed less bacterial translocation (-36%; p=0.041), a decrease in lipopolysaccharide binding protein (-30%; p=0.024) and splanchnic tumour necrosis factor α levels (-39%; p=0.044) after PX treatment. In CCl₄ rats, PX decreased fibrotic Sirius Red area (-43%; p=0.005), hepatic hydroxyproline (-66%; p<0.001), and expression of profibrogenic proteins (Col1a1, α smooth muscle actin, transforming growth factor β). CCl₄-PX rats had significantly lower transaminase levels and reduced hepatic macrophage infiltration. Moreover, PX induced sinusoidal vasodilation (upregulation of cystathionase, dimethylaminohydrolase (DDAH)1, endothelial nitric oxide synthase (eNOS), GTP-cyclohydrolase1) and reduced intrahepatic vasoconstriction (downregulation of endothelin-1, p-Moesin). In cirrhosis, PX improved endothelial dysfunction (decreased von-Willebrand factor) and normalized overexpression of vascular endothelial growth factor, platelet-derived growth factor and angiopoietins. While short-term 3-day PX treatment reduced portal pressure (-14%; p=0.041) by restoring endothelial function, 14week PX therapy additionally inhibited sinusoidal remodelling and decreased portal pressure to a greater extent (-22%; p=0.001). In human liver sinusoidal endothelial cells, PX increased eNOS and DDAH expression.

CONCLUSIONS

The non-steroidal FXR agonist PX20606 ameliorates portal hypertension by reducing liver fibrosis, vascular remodelling and sinusoidal dysfunction.

LAY SUMMARY

The novel drug PX20606 activates the bile acid receptor FXR and shows beneficial effects in experimental liver cirrhosis: In the liver, it reduces scarring and inflammation, and also widens blood vessels. Thus, PX20606 leads to an improved blood flow through the liver and decreases hypertension of the portal vein. Additionally, PX20606 improves the altered intestinal barrier and decreases bacterial migration from the gut.

Nuclear Receptors as Therapeutic Targets in Liver Disease: Are We There Yet?

Nuclear receptors (NR) are ligand-modulated transcription factors that play diverse roles in cell differentiation, development, proliferation, and metabolism and are associated with numerous liver pathologies such as cancer, steatosis, inflammation, fibrosis, cholestasis, and xenobiotic/drug-induced liver injury. The network of target proteins associated with NRs is extremely complex, comprising coregulators, small noncoding microRNAs, and long noncoding RNAs. The importance of NRs as targets of liver disease is exemplified by the number of NR ligands that are currently used in the clinics or in clinical trials with promising results. Understanding the regulation by NR during pathophysiological conditions, and identifying ligands for orphan NR, points to a potential therapeutic approach for patients with liver diseases. An overview of complex NR metabolic networks and their pharmacological implications in liver disease is presented here.

Inflammation-associated upregulation of the sulfated steroid transporter Slc10a6 in mouse liver and macrophage cell lines

AIM

Slc10a6, an incompletely characterized member of the SLC10A bile acid transporter family, was one of the most highly induced RNA transcripts identified in a screen for inflammation-responsive genes in mouse liver. This study aimed to elucidate a role for Slc10a6 in hepatic inflammation.

METHODS

Mice were treated with lipopolysaccharide (LPS; 2 mg/kg) or interleukin (IL)-1β (5 mg/kg) for various time points. Cells were treated with LPS (1 μg/mL) at various time points, with cell signaling inhibitors, nuclear receptor ligands and Slc10a6 substrates. All mRNA levels were determined by quantitative polymerase chain reaction.

RESULTS

Slc10a6 mRNA levels were upregulated in mouse liver at 2 h (7-fold), 4 h (100-fold) and 16 h (50-fold) after LPS treatment, and 35-fold by the cytokine IL-1β (4 h). Both absence of the nuclear receptor Fxr and pretreating mice with the synthetic retinoid X receptor-α ligand LG268 attenuated the LPS upregulation of Slc10a6 mRNA by 60-75%. In vitro, Slc10a6 mRNA was induced 30-fold by LPS in mouse RAW264.7 macrophages in a time-dependent manner (maximum at 8 h). The Slc10a6 substrate dehydroepiandrosterone sulfate (DHEAS) enhanced LPS induction of CCL5 mRNA, a pro-inflammatory chemokine, by 50% in RAW264.7 cells. This effect was abrogated in the presence of anti-inflammatory nuclear receptor ligands 9-cis-retinoic acid and dexamethasone.

CONCLUSION

Dramatic upregulation of Slc10a6 mRNA by LPS combined with enhanced LPS stimulation of CCL5 expression by the Slc10a6 substrate DHEAS in macrophages suggests that Slc10a6 function contributes to the hepatic inflammatory response.

Farnesoid X Receptor Agonists and Other Bile Acid Signaling Strategies for Treatment of Liver Disease

The intracellular nuclear receptor farnesoid X receptor (FXR) and the transmembrane G protein-coupled receptor 5 (TGR5) respond to bile acids (BAs) by activating transcriptional networks and/or signaling cascades. These cascades affect the expression of a great number of target genes relevant for BA, cholesterol, lipid and carbohydrate metabolism, as well as genes involved in inflammation, fibrosis and carcinogenesis. FXR activation in the liver tissue and beyond, such as the gut-liver axis, kidney and adipose tissue, plays a role in metabolic diseases. These BA receptors activators hold promise to become a new class of drugs to be used in the treatment of chronic liver disease, hepatocellular cancer and extrahepatic inflammatory and metabolic diseases. This review discusses the relevant BA receptors, the new drugs that target BA transport and signaling and their possible applications.

Pathophysiology and Mechanisms of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver disorders characterized by abnormal hepatic fat accumulation, inflammation, and hepatocyte dysfunction. Importantly, it is also closely linked to obesity and the metabolic syndrome. NAFLD predisposes susceptible individuals to cirrhosis, hepatocellular carcinoma, and cardiovascular disease. Although the precise signals remain poorly understood, NAFLD pathogenesis likely involves actions of the different hepatic cell types and multiple extrahepatic signals. The complexity of this disease has been a major impediment to the development of appropriate metrics of its progression and effective therapies. Recent clinical data place increasing importance on identifying fibrosis, as it is a strong indicator of hepatic disease-related mortality. Preclinical modeling of the fibrotic process remains challenging, particularly in the contexts of obesity and the metabolic syndrome. Future studies are needed to define the molecular pathways determining the natural progression of NAFLD, including key determinants of fibrosis and disease-related outcomes. This review covers the evolving concepts of NAFLD from both human and animal studies. We discuss recent clinical and diagnostic methods assessing NAFLD diagnosis, progression, and outcomes; compare the features of genetic and dietary animal models of NAFLD; and highlight pharmacological approaches for disease treatment.

Fragmentation of GW4064 led to a highly potent partial farnesoid X receptor agonist with improved drug-like properties

The ligand activated transcription factor farnesoid X receptor (FXR) is a crucial regulator of several metabolic and inflammatory pathways and its activation by agonistic ligands seems a valuable therapeutic approach for many disorders. Most known non-steroidal FXR agonists however, have limitations that hinder their clinical development and novel FXR ligands are required. Evaluation of the co-crystal structures of the widely used FXR agonist GW4064 and related compounds in complex with the FXR ligand binding domain indicated that their disubstituted isoxazole moiety is especially relevant for FXR activation. By investigation of GW4064-fragments missing the aromatic tail, we discovered a highly potent and soluble partial FXR agonist (14, ST-1892) as well as a fluorescent FXR ligand (15) as potential pharmacological tool.

Bile acid signaling in metabolic disease and drug therapy

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates hepatobiliary secretion of lipids, lipophilic metabolites, and xenobiotics. In the intestine, bile acids are essential for the absorption, transport, and metabolism of dietary fats and lipid-soluble vitamins. Extensive research in the last 2 decades has unveiled new functions of bile acids as signaling molecules and metabolic integrators. The bile acid-activated nuclear receptors farnesoid X receptor, pregnane X receptor, constitutive androstane receptor, vitamin D receptor, and G protein-coupled bile acid receptor play critical roles in the regulation of lipid, glucose, and energy metabolism, inflammation, and drug metabolism and detoxification. Bile acid synthesis exhibits a strong diurnal rhythm, which is entrained by fasting and refeeding as well as nutrient status and plays an important role for maintaining metabolic homeostasis. Recent research revealed an interaction of liver bile acids and gut microbiota in the regulation of liver metabolism. Circadian disturbance and altered gut microbiota contribute to the pathogenesis of liver diseases, inflammatory bowel diseases, nonalcoholic fatty liver disease, diabetes, and obesity. Bile acids and their derivatives are potential therapeutic agents for treating metabolic diseases of the liver.

Biological functions of thyroid hormone in placenta

The thyroid hormone, 3,3,5-triiodo-l-thyronine (T₃), modulates several physiological processes, including cellular growth, differentiation, metabolism, inflammation and proliferation, via interactions with thyroid hormone response elements (TREs) in the regulatory regions of target genes. Infection and inflammation are critical processes in placental development and pregnancy-related diseases. In particular, infection is the leading cause of neonatal mortality and morbidity worldwide. However, to date, no successful approach has been developed for the effective diagnosis of infection in preterm infants. Pre-eclampsia (PE) is a serious disorder that adversely affects ~5% of human pregnancies. Recent studies identified a multiprotein complex, the inflammasome, including the Nod-like receptor (NLR) family of cytosolic pattern recognition receptors, the adaptor protein apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and caspase-1, which plays a vital role in the placenta. The thyroid hormone modulates inflammation processes and is additionally implicated in placental development and disease. Therefore, elucidation of thyroid hormone receptor-regulated inflammation-related molecules, and their underlying mechanisms in placenta, should facilitate the identification of novel predictive and therapeutic targets for placental disorders. This review provides a detailed summary of current knowledge with respect to identification of useful biomarkers and their physiological significance in placenta.

Bile acid signaling through farnesoid X and TGR5 receptors in hepatobiliary and intestinal diseases

BACKGROUND

The well-known functions of bile acids (BAs) are the emulsification and absorption of lipophilic xenobiotics. However, the emerging evidences in the past decade showed that BAs act as signaling molecules that not only autoregulate their own metabolism and enterohepatic recirculation, but also as important regulators of integrative metabolism by activating nuclear and membrane-bound G protein-coupled receptors. The present review was to get insight into the role of maintenance of BA homeostasis and BA signaling pathways in development and management of hepatobiliary and intestinal diseases.

DATA SOURCES

Detailed and comprehensive search of PubMed and Scopus databases was carried out for original and review articles.

RESULTS

Disturbances in BA homeostasis contribute to the development of several hepatobiliary and intestinal disorders, such as non-alcoholic fatty liver disease, liver cirrhosis, cholesterol gallstone disease, intestinal diseases and both hepatocellular and colorectal carcinoma.

CONCLUSION

Further efforts made in order to advance the understanding of sophisticated BA signaling network may be promising in developing novel therapeutic strategies related not only to hepatobiliary and gastrointestinal but also systemic diseases.

Nuclear receptor gene alteration in human induced pluripotent stem cells with hepatic differentiation propensity

AIM

Human induced pluripotent stem (hiPS) cells are an alternative cell source of regenerative medicine for liver disease. Because variations in hepatic differentiation efficacy among hiPS cells exist, it is important to select a hiPS cell line with hepatic differentiation propensity. In addition, nuclear receptors (NR) regulate essential biological processes including differentiation and development. In this study, we identified the hiPS cell line with hepatic differentiation propensity and examined expression levels of 48 NR during this process.

METHODS

We screened 28 hiPS cell lines, which are established from various tissues of healthy persons with various reprogramming methods, using a three-step differentiation method, and examined expression levels of 48 NR by quantitative real-time polymerase chain reaction during the differentiation process in the selected cells.

RESULTS

hiPS-RIKEN-2B and hiPS-RIKEN-2F cells have hepatic differentiation propensity. Differentiation propensity towards endoderm was affected by donor origin but not by reprogramming methods or cell type of origins. Expression levels of NR were closely associated with those of hepatic differentiation markers. Furthermore, expression patterns of NR were categorized as five patterns. In particular, seven NR such as chicken ovalbumin upstream promoter transcription factor 1, retinoic acid receptor α, peroxisome proliferator-activated receptor-γ, progesterone receptor, photoreceptor cell-specific nuclear receptor, tailless homolog orphan receptor and glucocorticoid receptor were identified as the genes of which expression gradually goes up with differentiation.

CONCLUSION

These findings will be useful for not only elucidating mechanisms of hepatic differentiation of hiPS cells but also cell-based therapy for liver diseases.

Gd-EOB-DTPA-enhanced magnetic resonance imaging and alpha-fetoprotein predict prognosis of early-stage hepatocellular carcinoma

The survival of patients with hepatocellular carcinoma (HCC) is often individually different even after surgery for early-stage tumors. Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) has been introduced recently to evaluate hepatic lesions with regard to vascularity and the activity of the organic anion transporter OATP1B3. Here we report that Gd-EOB-DTPA-enhanced MRI (EOB-MRI) in combination with serum alpha-fetoprotein (AFP) status reflects the stem/maturational status of HCC with distinct biology and prognostic information. Gd-EOB-DTPA uptake in the hepatobiliary phase was observed in ∼15% of HCCs. This uptake correlated with low serum AFP levels, maintenance of hepatocyte function with the up-regulation of OATP1B3 and HNF4A expression, and good prognosis. By contrast, HCC showing reduced Gd-EOB-DTPA uptake with high serum AFP levels was associated with poor prognosis and the activation of the oncogene FOXM1. Knockdown of HNF4A in HCC cells showing Gd-EOB-DTPA uptake resulted in the increased expression of AFP and FOXM1 and the loss of OATP1B3 expression accompanied by morphological changes, enhanced tumorigenesis, and loss of Gd-EOB-DTPA uptake in vivo. HCC classification based on EOB-MRI and serum AFP levels predicted overall survival in a single-institution cohort (n=70), and its prognostic utility was validated independently in a multi-institution cohort of early-stage HCCs (n=109).

CONCLUSION

This noninvasive classification system is molecularly based on the stem/maturation status of HCCs and can be incorporated into current staging practices to improve management algorithms, especially in the early stage of disease.

Pregnane X receptor activation and silencing promote steatosis of human hepatic cells by distinct lipogenic mechanisms

In addition to its well-characterized role in the regulation of drug metabolism and transport by xenobiotics, pregnane X receptor (PXR) critically impacts on lipid homeostasis. In mice, both ligand-dependent activation and knockout of PXR were previously shown to promote hepatic steatosis. To elucidate the respective pathways in human liver, we generated clones of human hepatoma HepG2 cells exhibiting different PXR protein levels, and analyzed effects of PXR activation and knockdown on steatosis and expression of lipogenic genes. Ligand-dependent activation as well as knockdown of PXR resulted in increased steatosis in HepG2 cells. Activation of PXR induced the sterol regulatory element-binding protein (SREBP) 1-dependent lipogenic pathway via PXR-dependent induction of SREBP1a, which was confirmed in primary human hepatocytes. Inhibiting SREBP1 activity by blocking the cleavage-dependent maturation of SREBP1 protein impaired the induction of lipogenic SREBP1 target genes and triglyceride accumulation by PXR activation. On the other hand, PXR knockdown resulted in up-regulation of aldo-keto reductase (AKR) 1B10, which enhanced the acetyl-CoA carboxylase (ACC)-catalyzed reaction step of de novo lipogenesis. In a cohort of human liver samples histologically classified for non-alcoholic fatty liver disease, AKR1B10, SREBP1a and SREBP1 lipogenic target genes proved to be up-regulated in steatohepatitis, while PXR protein was reduced. In summary, our data suggest that activation and knockdown of PXR in human hepatic cells promote de novo lipogenesis and steatosis by induction of the SREBP1 pathway and AKR1B10-mediated increase of ACC activity, respectively, thus providing mechanistic explanations for a putative dual role of PXR in the pathogenesis of steatohepatitis.

Clustering nuclear receptors in liver regeneration identifies candidate modulators of hepatocyte proliferation and hepatocarcinoma

Background & Aims

Liver regeneration (LR) is a valuable model for studying mechanisms modulating hepatocyte proliferation. Nuclear receptors (NRs) are key players in the control of cellular functions, being ideal modulators of hepatic proliferation and carcinogenesis.

Methods & Results

We used a previously validated RT-qPCR platform to profile modifications in the expression of all 49 members of the NR superfamily in mouse liver during LR. Twenty-nine NR transcripts were significantly modified in their expression during LR, including fatty acid (peroxisome proliferator-activated receptors, PPARs) and oxysterol (liver X receptors, Lxrs) sensors, circadian masters RevErbα and RevErbβ, glucocorticoid receptor (Gr) and constitutive androxane receptor (Car). In order to detect the NRs that better characterize proliferative status vs. proliferating liver, we used the novel Random Forest (RF) analysis to selected a trio of down-regulated NRs (thyroid receptor alpha, Trα; farsenoid X receptor beta, Fxrβ; Pparδ) as best discriminators of the proliferating status. To validate our approach, we further studied PPARδ role in modulating hepatic proliferation. We first confirmed the suppression of PPARδ both in LR and human hepatocellular carcinoma at protein level, and then demonstrated that PPARδ agonist GW501516 reduces the proliferative potential of hepatoma cells.

Conclusions

Our data suggest that NR transcriptome is modulated in proliferating liver and is a source of biomarkers and bona fide pharmacological targets for the management of liver disease affecting hepatocyte proliferation.

Cystic fibrosis related liver disease--another black box in hepatology

Due to improved medical care, life expectancy in patients with cystic fibrosis (CF) has veritably improved over the last decades. Importantly, cystic fibrosis related liver disease (CFLD) has become one of the leading causes of morbidity and mortality in CF patients. However, CFLD might be largely underdiagnosed and diagnostic criteria need to be refined. The underlying pathomechanisms are largely unknown, and treatment strategies with proven efficacy are lacking. This review focuses on current invasive and non-invasive diagnostic standards, the current knowledge on the pathophysiology of CFLD, treatment strategies, and possible future developments.

Therapeutic role of bile acids and nuclear receptor agonists in fibrosing cholangiopathies

Chronic inflammatory bile duct diseases such as primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) result in progressive fibrosis of the biliary tract and ultimately cirrhosis of the liver. Since the etiology and pathogenesis of these fibrosing cholangiopathies are still poorly understood, therapeutic options are rather limited at present. Ursodeoxycholic acid (UDCA) is the paradigm therapeutic bile acid and established standard treatment for PBC, but its role for medical therapy of PSC is still under debate. Promising novel bile acid-based therapeutic options include 24-norursodeoxycholic acid, a side chain-shortened C23 homologue of UDCA, and bile acid receptor/farnesoid X receptor agonists (e.g., obeticholic acid) which currently undergo clinical development for fibrosing cholangiopathies such as PBC and PSC. Other nuclear receptors such as vitamin D receptor and fatty acid-activated peroxisome proliferator-activated receptors are also of considerable interest. This review article is a summary of an overview talk given at Falk Symposium 191 on Advances in Pathogenesis and Treatment of Liver Diseases held in London, October 3-4, 2013, and summarizes the recent progress with novel therapeutic bile acids and bile acid derivatives as novel therapies for fibrosing cholangiopathies such as PBC and PSC.

Hepatobiliary manifestations of ulcerative colitis: an example of gut-liver crosstalk

The interaction between inflammatory bowel disease (IBD) and hepatobiliary manifestations represents a classic example of liver-gut crosstalk. The importance of liver-gut crosstalk in IBD is demonstrated in the pathogenesis and outcome of primary sclerosing cholangitis (PSC) in IBD patients. Immunoglobulin G4-associated cholangitis (IAC), which has recently been described in UC patients, may also illustrate the significance of gut-liver interaction in these patients. Presence of these hepatobiliary manifestations influences the outcome of associated IBD, in particular ulcerative colitis (UC), and vice versa. The pathogenesis of PSC is postulated to be related to gut inflammation in IBD that results in inflammation in the portal tracts (the 'leaky gut'). Enterohepatic circulation of lymphocytes from the gut to the liver is also of potential relevance to PSC pathogenesis and outcomes. The presence of PSC and gut inflammation in IBD influences the course and outcomes of both diseases. Further research is required, to understand the mutual effect of liver-gut crosstalk in the outcomes of UC patients, and highlights the importance of an interdisciplinary approach-involving gastroenterologists, hepatologists, advanced endoscopists and liver transplant surgeons-in the management of these patients.

Hypolipidemic effect of dietary water-soluble protein extract from chicken: impact on genes regulating hepatic lipid and bile acid metabolism

BACKGROUND

Amount and type of dietary protein have been shown to influence blood lipids. The present study aimed to evaluate the effects of a water-soluble fraction of chicken protein (CP) on plasma and hepatic lipid metabolism in normolipidemic rats.

METHODS

Male Wistar rats were fed either a control diet with 20 % w/w casein as the protein source, or an experimental diet where casein was replaced with CP at 6, 14, or 20 % w/w for 4 weeks.

RESULTS

Rats fed CP had markedly reduced levels of triacylglycerols (TAG) and cholesterol in both plasma and liver, accompanied by stimulated hepatic mitochondrial fatty acid oxidation and carnitine palmitoyltransferase 2 activity in the 20 % CP group compared to the control group. In addition, reduced activities and gene expression of hepatic enzymes involved in lipogenesis were observed. The gene expression of sterol regulatory element-binding transcription factor 1 was reduced in the 20 % CP-fed rats, whereas gene expression of peroxisome proliferator-activated receptor alpha was increased. Moreover, 6, 14, and 20 % CP-fed rats had significantly increased free carnitine and acylcarnitine plasma levels compared to control rats. The plasma methionine/glycine and lysine/arginine ratios were reduced in 20 % CP-treated rats. The mRNA level of ATP-binding cassette 4 was increased in the 20 % CP group, accompanied by the increased level of plasma bile acids.

CONCLUSIONS

The present data suggest that the hypotriglyceridemic property of a water-soluble fraction of CP is primarily due to effects on TAG synthesis and mitochondrial fatty acid oxidation. The cholesterol-lowering effect by CP may be linked to increased bile acid formation.

Pravastatin activates the expression of farnesoid X receptor and liver X receptor alpha in Hep3B cells

BACKGROUND

Statins are suggested to preserve gallbladder function by suppressing pro-inflammatory cytokines and preventing cholesterol accumulation in gallbladder epithelial cells. They also affect cross-talk among the nuclear hormone receptors that regulate cholesterol-bile acid metabolism in the nuclei of hepatocytes. However, there is controversy over whether or how statins change the expression of peroxisome proliferator-activated receptor (PPAR)alpha, PPARgamma, liver X receptor alpha (LXRalpha), farnesoid X receptor (FXR), ABCG5, ABCG8, and 7alpha-hydroxylase (CYP7A1) which are directly involved in the cholesterol saturation index in bile.

METHODS

Human Hep3B cells were cultured on dishes. MTT assays were performed to determine the appropriate concentrations of reagents to be used. The protein expression of PPARalpha and PPARgamma was measured by Western blotting analysis, and the mRNA expression of LXRalpha, FXR, ABCG5, ABCG8 and CYP7A1 was estimated by RT-PCR.

RESULTS

In cultured Hep3B cells, pravastatin activated PPARalpha and PPARgamma protein expression, induced stronger expression of PPARgamma than that of PPARalpha, increased LXRalpha mRNA expression, activated ABCG5 and ABCG8 mRNA expression mediated by FXR as well as LXRalpha, enhanced FXR mRNA expression, and increased CYP7A1 mRNA expression mediated by the PPARgamma and LXRalpha pathways, together or independently.

CONCLUSION

Our data suggested that pravastatin prevents cholesterol gallstone diseases via the increase of FXR, LXRalpha and CYP7A1 in human hepatocytes.

Clostridium butyricum MIYAIRI 588 improves high-fat diet-induced non-alcoholic fatty liver disease in rats

BACKGROUND/AIMS

Non-alcoholic fatty liver disease (NAFLD) has become a common liver disease, as its prevalence has increased markedly in recent decades. The aim of the present study was to examine the improving effect of Clostridium butyricum MIYAIRI 588 (CBM588), a probiotic in clinical use for antibiotic-associated diarrhea, against high-fat diet (HFD)-induced fatty liver in rats.

METHODS

After feeding HFD or HFD coated with CBM588 (HFD-CBM) for 12 weeks, we evaluated the hepatic mRNA levels related to lipid metabolism, and then assessed the hepatic protein levels of several transcription factors regulating these lipogenic gene expressions.

RESULTS

The HFD-CBM group had decreased accumulation of lipid droplets in the liver compared with the HFD group. The HFD-CBM group had significantly decreased diacylglycerol acyltransferase (DGAT) 2 mRNA in the liver compared with the HFD group, whereas DGAT1 mRNA did not change between the HFD group and the HFD-CBM group. Moreover, the HFD-CBM group had significantly increased hepatic mRNA regulating cholesterol catabolism enzymes and excretion transporters. Correspondingly, the HFD-CBM588 groups had increased hepatic protein levels of peroxisome proliferator-activated receptor α/γ and liver X receptor α compared with the HFD group. The HFD-CBM group had accelerated excretion of total bile acid and non-esterified fatty acid in the feces.

CONCLUSIONS

CBM588 intake may have novel potential for improving NAFLD.