Bile acids and intestinal microbiota in autoimmune cholestatic liver diseases. Autoimmun Rev. 2017;16:885-896. [PMID: 28698093 DOI: 10.1016/j.autrev.2017.07.002]

Role of bile acids in liver diseases mediated by the gut microbiome

The intensive crosstalk between the liver and the intestine performs many essential functions. This crosstalk is important for natural immune surveillance, adaptive immune response regulation and nutrient metabolism and elimination of toxic bacterial metabolites. The interaction between the gut microbiome and bile acids is bidirectional. The gut microbiome regulates the synthesis of bile acids and their biological signaling activity and circulation via enzymes. Similarly, bile acids also shape the composition of the gut microbiome by modulating the host’s natural antibacterial defense and the intestinal immune system. The interaction between bile acids and the gut microbiome has been implicated in the pathophysiology of many intestinal and extra intestinal diseases, especially liver diseases. As essential mediators of the gut-liver crosstalk, bile acids regulate specific host metabolic pathways and modulate the inflammatory responses through farnesoid X-activated receptor and G protein-coupled bile acid receptor 1. Several clinical trials have demonstrated the signaling effects of bile acids in the context of liver diseases. We hypothesize the existence of a gut microbiome-bile acids-liver triangle and explore the potential therapeutic strategies for liver diseases targeting the triangle.

Clinical Management of Primary Biliary Cholangitis-Strategies and Evolving Trends

PBC is a chronic progressive autoimmune disorder involving the destruction of intrahepatic small bile ducts, cholestasis, fibrosis, and ultimately cirrhosis if left untreated. It is largely driven by the autoimmune response, but bile acids and the intestinal microbiota are implicated in disease progression as well. The only drugs licensed for PBC are UDCA and OCA. UDCA as a first-line and OCA as a second-line therapy are safe and effective, but the lack of response in a significant portion of patients and inadequate control of symptoms such as fatigue and pruritus remain as concerns. Liver transplantation is an end-stage therapy for many patients refractory to UDCA, which gives excellent survival rates but also moderate to high recurrence rates. The limited options for FDA-approved PBC therapies necessitate the development of alternative approaches. Currently, a wide variety of experimental drugs exist targeting immunological and physiological aspects of PBC to suppress inflammation. Immunological therapies include drugs targeting immune molecules in the B cell and T cell response, and specific cytokines and chemokines implicated in inflammation. Drugs targeting bile acids are also noteworthy as bile acids can perpetuate hepatic inflammation and lead to fibrosis over time. These include FXR agonists, ASBT inhibitors, and PPAR agonists such as bezafibrate and fenofibrate. Nonetheless, many of these drugs can only delay disease progression and fail to enhance patients' quality of life. Nanomedicine shows great potential for treatment of autoimmune diseases, as it provides a new approach that focuses on tolerance induction rather than immunosuppression. Tolerogenic nanoparticles carrying immune-modifying agents can be engineered to safely and effectively target the antigen-specific immune response in autoimmune diseases. These may work well with PBC especially, given the anatomical features and immunological specificity of the disease. Nanobiological therapy is thus an area of highly promising research for future treatment of PBC.

Serum Bile Acid Profiles Improve Clinical Prediction of Nonalcoholic Fatty Liver in T2DM patients

Background: The present study aimed to assess the ability of serum bile acid profiles to predict the development of nonalcoholic fatty liver (NAFL) in type 2 diabetes mellitus (T2DM) patients. Methods: Using targeted ultraperformance liquid chromatography (UPLC) coupled with triple quadrupole mass spectrometry (TQ/MS), we compared serum bile acid levels in T2DM patients with NAFL (n = 30) and age- and sex-matched T2DM patients without NAFL (n = 36) at the first time. Second, an independent cohort study of T2DM patients with NAFL (n = 17) and age- and sex-matched T2DM patients without NAFL (n = 20) was used to validate the results. The incremental benefits of serum biomarkers, clinical variables alone, or with biomarkers were then evaluated using receiver operating characteristic (ROC) curves and decision curve analysis. The area under the curve (AUC), integrated discrimination improvement (IDI), and net reclassification improvement (NRI) were used to evaluate the biomarker predictive abilities. Results: The serum bile acid profiles in T2DM patients with NAFL were significantly different from T2DM patients without NAFL, as characterized by the significant elevation of LCA, TLCA, TUDCA, CDCA-24G, and TCDCA, which may be potential biomarkers for the identification of NAFL in T2DM patients. Based on the improvement in AUC, IDI, and NRI, the addition of 5 bile acids to a model with clinical variables statistically improved its predictive value. Similar results were found in the validation cohort. Conclusions: These results highlight that the detected biomarkers may contribute to the progression of NAFL in T2DM patients, and these biomarkers particularly in combination may help in the diagnosis of NAFL and allow earlier intervention in T2DM patients.

Fibrotic Events in the Progression of Cholestatic Liver Disease

Cholestatic liver diseases including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are associated with active hepatic fibrogenesis, which can ultimately lead to the development of cirrhosis. However, the exact relationship between the development of liver fibrosis and the progression of cholestatic liver disease remains elusive. Periductular fibroblasts located around the bile ducts seem biologically different from hepatic stellate cells (HSCs). The fibrotic events in these clinical conditions appear to be related to complex crosstalk between immune/inflammatory mechanisms, cytokine signalling, and perturbed homeostasis between cholangiocytes and mesenchymal cells. Several animal models including bile duct ligation (BDL) and the Mdr2-knockout mice have improved our understanding of mechanisms underlying chronic cholestasis. In the present review, we aim to elucidate the mechanisms of fibrosis in order to help to identify potential diagnostic and therapeutic targets.

Antibody glycosylation in autoimmune diseases

The glycosylation of the fragment crystallizable (Fc) region of immunoglobulins (Ig) is critical for the modulation of antibody effects on inflammation. Moreover, antibody glycosylation may induce pathologic modifications and ultimately contribute to the development of autoimmune diseases. Thanks to progress in the analysis of glycosylation, more data are available on IgG and its subclass structures in the context of autoimmune diseases. In this review, we focused on the impact of Ig glycosylation in autoimmunity, describing how it modulates the immune response and how glycome profiles can be used as biomarkers of disease activity. The analysis of antibody glycosylation demonstrated specific features in human autoimmune and chronic inflammatory conditions, including rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease and autoimmune liver diseases, among others. Within the same disease, different patterns are associated with disease severity and treatment options. Future research may increase the information available on the distinct glycome profiles and expand their potential role as biomarkers and as targets for treatment, ultimately favoring an individualized approach.

Cholestasis-Associated Pruritus and Its Pruritogens

Pruritus is a debilitating symptom of various cholestatic disorders, including primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) and inherited progressive familial intrahepatic cholestasis (PFIC). The molecular mechanisms leading to cholestasis-associated pruritus are still unresolved and the involved pruritogens are indecisive. As a consequence of pruritus, patients suffer from sleep deprivation, loss of daytime concentration, auto-mutilation and sometimes even suicidal ideations. Current guideline-approved therapy of cholestasis-associated pruritus includes stepwise administration of several medications, which may alleviate complaints in some, but not all affected patients. Therefore, also experimental therapeutic approaches are required to improve patients' quality of life. This article reviews the current state of research on pruritogens and their receptors, and shortly discusses the most recent experimental therapies.

Hepatoprotective effects of Huangqi decoction (Astragali Radix and Glycyrrhizae Radix et Rhizoma) on cholestatic liver injury in mice: Involvement of alleviating intestinal microbiota dysbiosis

ETHNOPHARMACOLOGICAL RELEVANCE

Gut microbiome dysbiosis is closely associated with cholestatic liver disease. Huangqi decoction (HQD), a traditional herbal formula, has protection against cholestatic liver injury. However, the effect of HQD on gut microbiome remains unknown.

AIM OF THE STUDY

To investigate the effect of HQD on 3, 5-diethoxycarbonyl-1, 4-dihydrocollidine (DDC) induced cholestatic liver injury and its effect on the gut microbiome profiles.

MATERIALS AND METHODS

Mice with DDC-induced cholestatic liver injury were treated with low and high doses of HQD for 8 weeks. Fecal samples were analyzed by 16 S ribosomal DNA sequencing. Barrier function as well as intestinal and hepatic inflammation was analyzed by real-time PCR and western blotting.

RESULTS

HQD treatment ameliorated the DDC-induced liver injury and collagen deposition around hepatic bile ducts. Moreover, decreased diversity, reduced richness, and abnormal composition of intestinal microbiota of cholestatic mice were remarkably attenuated by HQD supplementation. Differences in bacterial abundance, including levels of Prevotellaceae_NK3B31_group, Alistipes, and Gordonibacter, were increased in DDC-induced mice, as compared with control mice, and were decreased after HQD treatment. Moreover, intestinal dysbiosis promoted disruption of the intestinal barrier in cholestatic mice. However, HQD treatment alleviated intestinal barrier dysfunction. Importantly, increased hepatic expression of pro-inflammatory factors and the NLRP3 inflammasome, which have a positive correlation with differential bacteria, were characteristics found in DDC-induced cholestatic mice that were alleviated upon treatment with HQD.

CONCLUSION

HQD treatment alleviated gut microbiota dysbiosis, ameliorated the intestinal barrier dysfunction, inhibited liver inflammation, and protected against DDC-induced cholestatic liver injury.

A novel 7α-hydroxysteroid dehydrogenase: Magnesium ion significantly enhances its activity and thermostability

7α-Hydroxysteroid dehydrogenase (7α-HSDH) plays an important role in the efficient biotransformation of taurochenodeoxycholic acid (TCDCA) to tauroursodeoxycholic acid (TUDCA). In this paper, a novel NADP(H)-dependent 7α-HSDH (named J-1-1) was discovered, heterologously expressed in Escherichia coli and biochemically characterized. J-1-1 exhibited high enzymatic activities. The specific activities of J-1-1 toward TCDCA, glycochenodeoxycholic acid (GCDCA) and ethyl benzoylacetate (EBA) were 188.3 ± 0.2, 217.6 ± 0.4, and 20.0 ± 0.2 U·mg^-1, respectively, in 50 mM Glycine-NaOH, pH 10.5. Simultaneously, J-1-1 showed high thermostability; 73% of its activity maintained after heat treatment at 40 °C for 100 h. Particularly noteworthy is that magnesium ion could stabilize the structure of J-1-1, resulting in the enhancement of its enzymatic activity and thermostability. The enzymatic activity of J-1-1 increased 40-fold in the presence of 50 mM Mg²⁺, and T_0.5 increased by approximately 6 °C. Furthermore, after heat treatment at 40 °C for 20 min, the control group only retained 52% of the residual enzyme activity, while the residual enzyme activity of the experimental group was still 77% of the J-1-1 enzyme activity with Mg²⁺ and without heat treatment. These properties of 7α-HSDH would be expected to contribute to more extensive applications in the biotransformation of related substrates.

NLRP3 inflammasome priming and activation in cholestatic liver injury via the sphingosine 1-phosphate/S1P receptor 2/Gα(12/13)/MAPK signaling pathway

NLRP3 inflammasome-driven inflammation represents a key trigger for hepatic fibrogenesis during cholestatic liver injury. However, whether sphingosine 1-phosphate (S1P) plays a role in NLRP3 inflammasome priming and activation remains unknown. Here, we found that the expression of NLRP3 in macrophages and NLRP3 inflammasome activation were significantly elevated in the liver injured by bile duct ligation (BDL). In vitro, S1P promoted the NLRP3 inflammasome priming and activation via S1P receptor 2 (S1PR2) in bone marrow-derived monocyte/macrophages (BMMs). Focusing on BMMs, the gene silencing of Gα12 or Gα13 by specific siRNA suppressed NLRP3 inflammasome priming and pro-inflammatory cytokine (IL-1β and IL-18) secretion, whereas Gα(i/o) and Gαq were not involved in this process. The MAPK signaling pathways (P38, ERK, and JNK) mediated NLRP3 inflammasome priming and IL-1β and IL-18 secretion, whereas blockage of PI3K, ROCK, and Rho family had no such effect. Moreover, JTE-013 (S1PR2 inhibitor) treatment markedly reduced NLRP3 inflammasome priming and activation in BDL-injured liver. Collectively, S1P promotes NLRP3 inflammasome priming and pro-inflammatory cytokines (IL-1β and IL-18) secretion via the S1PR2/Gα(12/13)/MAPK pathway, which may represent an effective therapeutic strategy for liver disease. KEY MESSAGE: • Hepatic NLRP3 expression was significantly elevated in BMMs of BDL-injured mouse liver. • S1P promoted NLRP3 inflammasome priming and activation in BMMs, depending on the S1PR2/Gα(12/13)/MAPK pathway. • Blockade of S1PR2 by JTE-013 reduced NLRP3 inflammasome priming and activation inflammasome in vivo.

Probiotic Lactobacillus casei Shirota prevents acute liver injury by reshaping the gut microbiota to alleviate excessive inflammation and metabolic disorders

Millions of people die from liver diseases annually, and liver failure is one of the three major outcomes of liver disease. The gut microbiota plays a crucial role in liver diseases. This study aimed to explore the effects of Lactobacillus casei strain Shirota (LcS), a probiotics used widely around the world, on acute liver injury (ALI), as well as the underlying mechanism. Sprague Dawley rats were intragastrically administered LcS suspensions or placebo once daily for 7 days before induction of ALI by intraperitoneal injection of D-galactosamine (D-GalN). Histopathological examination and assessments of liver biochemical markers, inflammatory cytokines, and the gut microbiota, metabolome and transcriptome were conducted. Our results showed that pretreatment with LcS reduced hepatic and intestinal damage and reduced the elevation of serum gamma-glutamyltranspeptidase (GGT), total bile acids, IL-5, IL-10, G-CSF and RANTES. The analysis of the gut microbiota, metabolome and transcriptome showed that LcS lowered the ratio of Firmicutes to Bacteroidetes; reduced the enrichment of metabolites such as chenodeoxycholic acid, deoxycholic acid, lithocholic acid, d-talose and N-acetyl-glucosamine, reduce the depletion of d-glucose and l-methionine; and alleviated the downregulation of retinol metabolism and PPAR signalling and the upregulation of the pyruvate metabolism pathway in the liver. These results indicate the promising prospect of using LcS for the treatment of liver diseases, particularly ALI.

Interaction Mechanisms Between Major Depressive Disorder and Non-alcoholic Fatty Liver Disease

Major depressive disorder (MDD), which is highly associated with non-alcoholic fatty liver disease (NAFLD), has complex pathogenic mechanisms. However, a limited number of studies have evaluated the mutual pathomechanisms involved in MDD and NAFLD development. Chronic stress-mediated elevations in glucocorticoid (GC) levels play an important role in the development of MDD-related NAFLD. Elevated GC levels can induce the release of inflammatory factors and changes in gut permeability. Elevated levels of inflammatory factors activate the hypothalamic-pituitary-adrenal (HPA) axis, which further increases the release of GC. At the same time, changes in gut permeability promote the release of inflammatory factors, which results in a vicious circle among the three, causing disease outbreaks. Even though the specific role of the thyroid hormone (TH) in this pathogenesis has not been fully established, it is highly correlated with MDD and NAFLD. Therefore, changing lifestyles and reducing psychological stress levels are necessary measures for preventing MDD-related NAFLD. Among them, GC inhibitors and receptor antagonists may be key in the alleviation of early and mid-term disease progression. However, combination medications may be important in late-stage diseases, but they are associated with various side effects. Traditional Chinese medicines have been shown to be potential therapeutic alternatives for such complex diseases.

Gut microbiome, liver immunology, and liver diseases

The gut microbiota is a complex and plastic consortium of microorganisms that are intricately connected with human physiology. The liver is a central immunological organ that is particularly enriched in innate immune cells and constantly exposed to circulating nutrients and endotoxins derived from the gut microbiota. The delicate interaction between the gut and liver prevents accidental immune activation against otherwise harmless antigens. Work on the interplay between the gut microbiota and liver has assisted in understanding the pathophysiology of various liver diseases. Of immense importance is the step from high-throughput sequencing (correlation) to mechanistic studies (causality) and therapeutic intervention. Here, we review the gut microbiota, liver immunology, and the interaction between the gut and liver. In addition, the impairment in the gut-liver axis found in various liver diseases is reviewed here, with an emphasis on alcohol-associated liver disease (ALD), nonalcoholic fatty liver disease (NAFLD), and autoimmune liver disease (AILD). On the basis of growing evidence from these preclinical studies, we propose that the gut-liver axis paves the way for targeted therapeutic modalities for liver diseases.

Response of gut microbiota to serum metabolome changes in intrahepatic cholestasis of pregnant patients

BACKGROUND

Intrahepatic cholestasis in pregnancy (ICP) is the most common liver disease during pregnancy, and its exact etiology and course of progression are still poorly understood.

AIM

To investigate the link between the gut microbiota and serum metabolome in ICP patients.

METHODS

In this study, a total of 30 patients were recruited, including 15 patients with ICP (disease group) and 15 healthy pregnant patients (healthy group). The serum nontarget metabolomes from both groups were determined. Amplification of the 16S rRNA V3-V4 region was performed using fecal samples from the disease and healthy groups. By comparing the differences in the microbiota and metabolite compositions between the two groups, the relationship between the gut microbiota and serum metabolites was also investigated.

RESULTS

The Kyoto Encyclopedia of Genes and Genomes analysis results showed that the primary bile acid biosynthesis, bile secretion and taurine and hypotaurine metabolism pathways were enriched in the ICP patients compared with the healthy controls. In addition, some pathways related to protein metabolism were also enriched in the ICP patients. The principal coordination analysis results showed that there was a distinct difference in the gut microbiota composition (beta diversity) between the ICP patients and healthy controls. At the phylum level, we observed that the relative abundance of Firmicutes was higher in the healthy group, while Bacteroidetes were enriched in the disease group. At the genus level, most of the bacteria depleted in ICP are able to produce short-chain fatty acids (e.g., Faecalibacterium, Blautia and Eubacterium hallii), while the bacteria enriched in ICP are associated with bile acid metabolism (e.g., Parabacteroides and Bilophila). Our results also showed that specific genera were associated with the serum metabolome.

CONCLUSION

Our study showed that the serum metabolome was altered in ICP patients compared to healthy controls, with significant differences in the bile, taurine and hypotaurine metabolite pathways. Alterations in the metabolization of these pathways may lead to disturbances in the gut microbiota, which may further affect the course of progression of ICP.

Current understanding of primary biliary cholangitis

Primary biliary cholangitis (PBC) causes chronic and persistent cholestasis in the liver, eventually resulting in cirrhosis and hepatic failure without appropriate treatment. PBC mainly develops in middle-aged women, but it is also common in young women and men. PBC is considered a model of autoimmune disease because of the presence of disease-specific autoantibodies, that is, antimitochondrial antibodies (AMAs), intense infiltration of mononuclear cells into the bile ducts, and a high prevalence of autoimmune diseases such as comorbidities. Histologically, PBC is characterized by degeneration and necrosis of intrahepatic biliary epithelial cells surrounded by a dense infiltration of mononuclear cells, coined as chronic non-suppurative destructive cholangitis, which leads to destructive changes and the disappearance of small- or medium-sized bile ducts. Since 1990, early diagnosis with the detection of AMAs and introduction of ursodeoxycholic acid as first-line treatment has greatly altered the clinical course of PBC, and liver transplantation-free survival of patients with PBC is now comparable to that of the general population.

Characterization of gut microbiota associated with clinical parameters in intrahepatic cholestasis of pregnancy

Background

Intrahepatic cholestasis of pregnancy (ICP) is a liver disorder that specifically occurs in pregnancy. Elevated levels of liver transaminases aspartate aminotransferase, alanine aminotransferase and serum bilirubin levels are common biochemical characteristics in ICP. The disorder is associated with an increased risk of premature delivery and stillbirth. The characterization of the potential microbiota in ICP could go a long way in the prevention and treatment of this pregnancy disease.

Methods

A total of 58 patients were recruited for our study: 27 ICP patients and 31 healthy pregnant subjects with no ICP. The V3 and V4 regions of the 16S rDNA collected from fecal samples of both diseased and control groups were amplified. 16S rRNA gene amplicon sequencing was then performed on gut microbiota. Sequencing data were analyzed and the correlation between components of microbiota and patient ICP status was found. Related metabolic pathways, relative abundance and significantly different operational taxonomic units (OTUs) between ICP and controls were also identified.

Results

Elevated levels of total bile acid, ALT, AST, Dbil and Tbil were recorded or observed in ICP subjects as compared to the control. Gut microbiota in pregnant women was dominated by four major phyla and 27 core genera. PCoA analysis results indicated that there was no significant clustering in Bray–Curtis distance matrices. Our results showed that there was a correlation between specific OTUs and measured clinical parameters of pregnant women. Comparison at the different taxonomy levels revealed high levels of abundance of Blautia and Citrobacter in ICP patients. At the family level, Enterobacteriaceae and Leuconostocaceae were higher in ICP patients. 638 KEGG Orthologs and 138 pathways significantly differed in the two groups. PLS-DA model with VIP plots indicated a total of eight genera and seven species were key taxa in ICP and control groups.

Conclusions

Our research indicated that although there was no significant clustering by PCoA analysis, patients with ICP have increased rare bacteria at different phylogenetic levels. Our results also illustrated that all 638 KEGG Orthologs and 136 in 138 KEGG pathways were less abundant in ICP patients compared to the controls.

Gut Microbiota-Bile Acid Crosstalk in Diarrhea-Irritable Bowel Syndrome

The occurrence of diarrhea-predominant irritable bowel syndrome (IBS-D) is the result of multiple factors, and its pathogenesis has not yet been clarified. Emerging evidence indicates abnormal changes in gut microbiota and bile acid (BA) metabolism have a close relationship with IBS-D. Gut microbiota is involved in the secondary BA production via deconjugation, 7α-dehydroxylation, oxidation, epimerization, desulfation, and esterification reactions respectively. Changes in the composition and quantity of gut microbiota have an important impact on the metabolism of BAs, which can lead to the occurrence of gastrointestinal diseases. BAs, synthesized in the hepatocytes, play an important role in maintaining the homeostasis of gut microbiota and the balance of glucose and lipid metabolism. In consideration of the complex biological functional connections among gut microbiota, BAs, and IBS-D, it is urgent to review the latest research progress in this field. In this review, we summarized the alterations of gut microbiota in IBS-D and discussed the mechanistic connections between gut microbiota and BA metabolism in IBS-D, which may be involved in activating two important bile acid receptors, G-protein coupled bile acid receptor 1 (TGR5) and farnesoid X receptor (FXR). We also highlight the strategies of prevention and treatment of IBS-D via regulating gut microbiota-bile acid axis, including probiotics, fecal microbiota transplantation (FMT), cholestyramine, and the cutting-edge technology about bacteria genetic engineering.

Comprehensive Analysis of Serum and Fecal Bile Acid Profiles and Interaction with Gut Microbiota in Primary Biliary Cholangitis

Accumulation of bile acids (BAs) contributes significantly to the pathogenesis of primary biliary cholangitis (PBC). Here, we sought to systematically characterize the serum and fecal BA profiles and the linkage between BAs and gut microbiota in PBC. The serum and fecal BAs were compared between 65 UDCA treatment-naive PBC and 109 healthy controls using UPLC-MS in cross-sectional study. In a prospective study, a subgroup of patients was enrolled for BA and microbiota analysis before and after UDCA therapy. BA compositions in serum and feces significantly differed between treatment-naive PBC and controls. Particularly, PBC was associated with decreased conversions of conjugated to unconjugated, and primary to secondary BAs, indicating impaired microbial metabolism of BAs. PBC patients at advanced stage exhibited a more abnormal BA profile compared with early-stage patients. UDCA treatment led to a decreased level of taurine-conjugated BAs, thereby reversing the conjugated/unconjugated ratio in PBC. Moreover, the level of secondary BAs such as DCA and conjugated DCA inversely correlated with PBC-enriched gut microbes (e.g., Veillonella, Klebsiella), while positively correlated with control-enriched microbes (e.g., Faecalibacterium, Oscillospira). Microbiota analysis also revealed a significant increase of taurine-metabolizing bacteria Bilophila spp. in patients after UDCA, which was strongly correlated with decreased taurine-conjugated BAs. In addition, serum FGF19 was remarkably increased in treatment-naïve PBC and decreased after UDCA. Our study established specific alterations of BA compositions in serum and feces of PBC, suggesting the potential for using BAs for diagnosis, and highlighting the possibility of modulating BA profile by altering gut microbiota. Graphical Abstract.

Ten Reasons to Think About Bile Acids in Managing Inflammatory Bowel Disease

There are ten good reasons why it is important to think about abnormalities in bile acid control in inflammatory bowel disease. Before reviewing these reasons, it is relevant to review essential elements in the enterohepatic circulation, synthesis and actions of bile acids.

Fecal Microbiomes Distinguish Patients With Autoimmune Hepatitis From Healthy Individuals

Objective: The intestinal microbiome is associated with various autoimmune diseases. Regional difference is the main influencing factor of intestinal microbial difference. This study aimed to identify the differences in fecal microbiome between autoimmune hepatitis (AIH) patients and healthy controls (HCs) in Central China, and to validate the efficacy of fecal microbiome as a diagnostic tool for AIH. Design: We collected 115 fecal samples from AIH patients (N = 37) and HCs (N = 78) in Central China and performed gene sequencing. Fecal microbiomes were characterized and microbial markers for AIH were identified. Results: Fecal microbial diversity showed a downward trend in AIH compared with HCs. Fecal microbial communities significantly differed between both groups. At the phylum level, Verrucomicrobia abundance was significantly increased, while Lentisphaerae and Synergistetes were significantly decreased in the AIH patients vs. the HCs. Compared to the HCs, 15 genera, including Veillonella, Faecalibacterium, and Akkermansia, were enriched, while 19 genera, such as Pseudobutyrivibrio, Lachnospira, and Ruminococcaceae, were decreased in the AIH patients. Ten genera, including Veillonella, Faecalibacterium, and Akkermansia, predominated in the AIH patients. Five microbial biomarkers were deemed optimal diagnostic tools for AIH. The probability of disease was significantly increased in AIH group vs. HCs, achieving 83.25% value of area under the curve. Conclusion: We present the characteristics of AIH patients in Central China for the first time. Five microbial biomarkers, including Lachnospiraceae, Veillonella, Bacteroides, Roseburia, and Ruminococcaceae, achieved a high potential distinguishing AIH patients from HCs.

Bile acids drive the newborn's gut microbiota maturation

Following birth, the neonatal intestine is exposed to maternal and environmental bacteria that successively form a dense and highly dynamic intestinal microbiota. Whereas the effect of exogenous factors has been extensively investigated, endogenous, host-mediated mechanisms have remained largely unexplored. Concomitantly with microbial colonization, the liver undergoes functional transition from a hematopoietic organ to a central organ of metabolic regulation and immune surveillance. The aim of the present study was to analyze the influence of the developing hepatic function and liver metabolism on the early intestinal microbiota. Here, we report on the characterization of the colonization dynamics and liver metabolism in the murine gastrointestinal tract (n = 6-10 per age group) using metabolomic and microbial profiling in combination with multivariate analysis. We observed major age-dependent microbial and metabolic changes and identified bile acids as potent drivers of the early intestinal microbiota maturation. Consistently, oral administration of tauro-cholic acid or β-tauro-murocholic acid to newborn mice (n = 7-14 per group) accelerated postnatal microbiota maturation.

Galectin-3 in Inflammasome Activation and Primary Biliary Cholangitis Development

Primary biliary cholangitis (PBC) is a chronic inflammatory autoimmune liver disease characterized by inflammation and damage of small bile ducts. The NLRP3 inflammasome is a multimeric complex of proteins that after activation with various stimuli initiates an inflammatory process. Increasing data obtained from animal studies implicate the role of NLRP3 inflammasome in the pathogenesis of various diseases. Galectin-3 is a β-galactoside-binding lectin that plays important roles in various biological processes including cell proliferation, differentiation, transformation and apoptosis, pre-mRNA splicing, inflammation, fibrosis and host defense. The multilineage immune response at various stages of PBC development includes the involvement of Gal-3 in the pathogenesis of this disease. The role of Galectin-3 in the specific binding to NLRP3, and inflammasome activation in models of primary biliary cholangitis has been recently described. This review provides a brief pathogenesis of PBC and discusses the current knowledge about the role of Gal-3 in NLRP3 activation and PBC development.

Bile Acids: Key Regulators and Novel Treatment Targets for Type 2 Diabetes

Type 2 diabetes mellitus (T2DM), characterized by insulin resistance and unclear pathogenesis, is a serious menace to human health. Bile acids are the end products of cholesterol catabolism and play an important role in maintaining cholesterol homeostasis. Furthermore, increasing studies suggest that bile acids may regulate glucose tolerance, insulin sensitivity, and energy metabolism, suggesting that bile acids may represent a potential therapeutic target for T2DM. This study summarizes the metabolism of bile acids and, more importantly, changes in their concentrations, constitution, and receptors in diabetes. Furthermore, we provide an overview of the mechanisms underlying the role of bile acids in glucose and lipid metabolism, as well as the occurrence and development of T2DM. Bile acid-targeted therapy may represent a valid approach for T2DM treatment.

The effects, underlying mechanism and interactions of dexamethasone exposure during pregnancy on maternal bile acid metabolism

As important members in steroids related signal pathways, bile acids are very important in regulating substance metabolism and immune homeostasis. However, bile acids are highly cytotoxic, and the excessive accumulation can induce several abnormalities such as cholestatic liver injury. It is known that the bile acid metabolism alters during pregnancy and mostly will not result in pathologies. However, the effect of dexamethasone exposure during pregnancy on bile acid metabolism is still unknown. In this study, pregnant Wistar rats were subcutaneously administered dexamethasone (0.2 mg/kg.d) or saline from gestation day 9-21, while virgin rats were given the same treatment for 13 days. We found that, physiological pregnancy or dexamethasone exposure during non-pregnancy did not affect maternal serum TBA level and liver function. Nevertheless, dexamethasone exposure during pregnancy increased serum TBA level and accompanied with liver injury. Furthermore, we discovered that the conservation of bile acid homeostasis under pregnancy or dexamethasone exposure was maintained through compensatory pathways. However, dexamethasone exposure during pregnancy tipped the balance of liver bile acid homeostasis by increasing classical synthesis and decreasing efflux and uptake. In addition, dexamethasone exposure during pregnancy also increased serum estrogen level and nuclear receptors mRNA expression levels. Finally, two-way ANOVA analysis showed that dexamethasone exposure during pregnancy could induce or facilitate maternal cholestasis and liver injury by up-regulating ERα and CYP7A1 expression. This study confirmed that dexamethasone exposure during pregnancy was related to maternal intrahepatic cholestasis of pregnancy and should be carefully monitored in clinical settings.

Glycomic analysis of antibody indicates distinctive glycosylation profile in patients with autoimmune cholangitis

Glycosylation of antibodies, particularly in the Fc domain, critically modulate the ability of antibodies to bind to FcRs, maintaining immune quiescence to achieve a finely orchestrated immune response. The removal of sialic acid and galactose residues dramatically alters the physiological function of IgGs, and alterations of Ig glycosylation have been associated with several autoimmune disorders. However, Ig glycosylation has not been extensively studied in autoimmune cholangitis. We applied triple quadruple mass spectroscopy with subsequent multiple reaction monitoring to elucidate the profile, composition and linkage of sugar residues of antibody glycans in patients with primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) and healthy controls (HC). Agalactosylated, HexNAc terminated IgG1 glycoforms were enriched in both PBC and PSC. Levels of IgM glycans at site N439 and fucosylated glycans in J chain, were significantly decreased in PBC compared to PSC and HC. PSC patients had decreased bisecting glycoforms and increased biantennary glycoforms on IgA compared to PBC. Importantly, our data demonstrate the association of distinct branching and composition patterns of Ig glycoforms with disease severity and liver cirrhosis, which highlight the importance of glycan biology as a potential mechanism and/or a disease specific signal of inflammation.

Animal-Origin Prebiotics Based on Chitin: An Alternative for the Future? A Critical Review

The human gut microbiota has been revealed in recent years as a factor that plays a decisive role in the maintenance of human health, as well as in the development of many non-communicable diseases. This microbiota can be modulated by various dietary factors, among which complex carbohydrates have a great influence. Although most complex carbohydrates included in the human diet come from vegetables, there are also options to include complex carbohydrates from non-vegetable sources, such as chitin and its derivatives. Chitin, and its derivatives such as chitosan can be obtained from non-vegetable sources, the best being insects, crustacean exoskeletons and fungi. The present review offers a broad perspective of the current knowledge surrounding the impacts of chitin and its derived polysaccharides on the human gut microbiota and the profound need for more in-depth investigations into this topic. Overall, the effects of whole insects or meal on the gut microbiota have contradictory results, possibly due to their high protein content. Better results are obtained for the case of chitin derivatives, regarding both metabolic effects and effects on the gut microbiota composition.

LC-MS-Based Metabolomic Study of Oleanolic Acid-Induced Hepatotoxicity in Mice

Oleanolic acid (OA), a natural triterpenoid, which has the development prospects in anti-tumor therapy is a widely used hepatoprotective drug in China. It has been reported that OA can cause liver toxicity after higher doses or longer-term use. Therefore, the study aims to explore the possible hepatotoxicity mechanism based on liver metabolic profiles. Liver metabolic profiles were obtained from untargeted ultrahigh performance liquid chromatography (UHPLC)-Q Exactive Orbitrap mass spectrometry (MS) technique. It was found that altered bile acid, amino acid, and energy metabolism might be at least partly responsible for OA-induced hepatotoxicity. Bile acid metabolism, as the most important pathway, was verified by using UHPLC-TSQ-MS, indicating that conjugated bile acids were the main contributors to OA-induced liver toxicity. Our findings confirmed that increased bile acids were the key element of OA hepatotoxicity, which may open new insights for OA hepatotoxicity in-depth investigations, as well as provide a reference basis for more hepatotoxic drug mechanism research.

Alteration in faecal bile acids, gut microbial composition and diversity after laparoscopic sleeve gastrectomy

Background

Laparoscopic sleeve gastrectomy (LSG) is a well established treatment for severe obesity and type 2 diabetes. Although the gut microbiota is linked to the efficacy of LSG, the underlying mechanisms remain elusive. The effect of LSG for morbid obesity on the gut microbiota and bile acids was assessed here.

Methods

Severely obese subjects who were candidates for LSG were included and followed until 6 months after surgery. The composition and abundance of the microbiota and bile acids in faeces were assessed by 16S ribosomal RNA sequencing, quantitative PCR and liquid chromatography–mass spectrometry.

Results

In total, 28 patients with a mean(s.d.) BMI of 44·2(6·6) kg/m2 were enrolled. These patients had achieved excess weight loss of 53·2(19·0) per cent and showed improvement in metabolic diseases by 6 months after LSG, accompanied by an alteration in the faecal microbial community. The increase in α-diversity and abundance of specific taxa, such as Rikenellaceae and Christensenellaceae, was strongly associated with reduced faecal bile acid levels. These changes had a significant positive association with excess weight loss and metabolic alterations. However, the total number of faecal bacteria was lower in patients before (mean(s.d.) 10·26(0·36) log10 cells per g faeces) and after (10·39(0·29) log10 cells per g faeces) operation than in healthy subjects (10·83(0·27) log10 cells per g faeces).

Conclusion

LSG is associated with a reduction in faecal bile acids and greater abundance of specific bacterial taxa and α-diversity that may contribute to the metabolic changes.

Gram-negative Microbiota Blooms in Premature Twins Discordant for Parenteral Nutrition-associated Cholestasis

Parenteral nutrition-associated cholestasis (PNAC) causes serious morbidity in the neonatal intensive care unit. Infection with gut-associated bacteria is associated with cholestasis, but the role of intestinal microbiota in PNAC is poorly understood. We examined the composition of stool microbiota from premature twins discordant for PNAC as a strategy to reduce confounding from variables associated with both microbiota and cholestasis. Eighty-four serial stool samples were included from 4 twin sets discordant for PNAC. Random Forests was utilized to determine genera most discriminatory in classifying samples from infants with and without PNAC. In infants with PNAC, we detected a significant increase in the relative abundance of Klebsiella, Veillonella, Enterobacter, and Enterococcus (P < 0.05). Bray-Curtis dissimilarities in infants with PNAC were significantly different (P < 0.05) from infants without PNAC. Our findings warrant further exploration in larger cohorts and experimental models of PNAC to determine if a microbiota signature predicts PNAC, as a basis for future interventions to mitigate liver injury.

Gut microbiota in non-alcoholic fatty liver disease and alcohol-related liver disease: Current concepts and perspectives

The term, gut-liver axis, is used to highlight the close anatomical and functional relationship between the intestine and the liver. It has been increasingly recognized that the gut-liver axis plays an essential role in the development and progression of liver disease. In particular, in non-alcoholic fatty liver disease and alcohol-related liver disease, the two most common causes of chronic liver disease, a dysbiotic gut microbiota can influence intestinal permeability, allowing some pathogens or bacteria-derived factors from the gut reaching the liver through the enterohepatic circulation contributing to liver injury, steatohepatitis, and fibrosis progression. Pathways involved are multiple, including changes in bile acid metabolism, intestinal ethanol production, generation of short-chain fatty acids, and other by-products. Bile acids act through dedicated bile acid receptors, farnesoid X receptor and TGR5, in both the ileum and the liver, influencing lipid metabolism, inflammation, and fibrogenesis. Currently, both non-alcoholic fatty liver disease and alcohol-related liver disease lack effective therapies, and therapeutic targeting of gut microbiota and bile acids enterohepatic circulation holds promise. In this review, we summarize current knowledge about the role of gut microbiota in the pathogenesis of non-alcoholic fatty liver disease and alcohol-related liver disease, as well as the relevance of microbiota or bile acid-based approaches in the management of those liver diseases.

Alterations of the bile microbiome in primary sclerosing cholangitis

BACKGROUND

Patients with primary sclerosing cholangitis (PSC) display an altered colonic microbiome compared with healthy controls. However, little is known on the bile duct microbiome and its interplay with bile acid metabolism in PSC.

METHODS

Patients with PSC (n=43) and controls without sclerosing cholangitis (n=22) requiring endoscopic retrograde cholangiography were included prospectively. Leading indications in controls were sporadic choledocholithiasis and papillary adenoma. A total of 260 biospecimens were collected from the oral cavity, duodenal fluid and mucosa and ductal bile. Microbiomes of the upper alimentary tract and ductal bile were profiled by sequencing the 16S-rRNA-encoding gene (V1-V2). Bile fluid bile acid composition was measured by high-performance liquid chromatography mass spectrometry and validated in an external cohort (n=20).

RESULTS

The bile fluid harboured a diverse microbiome that was distinct from the oral cavity, the duodenal fluid and duodenal mucosa communities. The upper alimentary tract microbiome differed between PSC patients and controls. However, the strongest differences between PSC patients and controls were observed in the ductal bile fluid, including reduced biodiversity (Shannon entropy, p=0.0127) and increase of pathogen Enterococcus faecalis (FDR=4.18×10^-5) in PSC. Enterococcus abundance in ductal bile was strongly correlated with concentration of the noxious secondary bile acid taurolithocholic acid (r=0.60, p=0.0021).

CONCLUSION

PSC is characterised by an altered microbiome of the upper alimentary tract and bile ducts. Biliary dysbiosis is linked with increased concentrations of the proinflammatory and potentially cancerogenic agent taurolithocholic acid.

Microbiota and metabolites in rheumatic diseases

As a gigantic community in the human body, the microbiota exerts pleiotropic roles in human health and disease ranging from digestion and absorption of nutrients from food, defense against infection of pathogens, to regulation of immune system development and immune homeostasis. Recent advances in "omics" studies and bioinformatics analyses have broadened our insights of the microbiota composition of the inner and other surfaces of the body and their interactions with the host. Apart from the direct contact of microbes at the mucosal barrier, metabolites produced or metabolized by the gut microbes can serve as important immune regulators or initiators in a wide variety of diseases, including gastrointestinal diseases, metabolic disorders and systemic rheumatic diseases. This review focuses on the most recent understanding of how the microbiota and metabolites shape rheumatic diseases. Studies that explore the mechanistic interplay between microbes, metabolites and the host could thereby provide clues for novel methods in the diagnosis, therapy, and prevention of rheumatic diseases.

Li-Dan-He-Ji Improves Infantile Cholestasis Hepatopathy Through Inhibiting Calcium-Sensing Receptor-Mediated Hepatocyte Apoptosis

Infantile cholestatic hepatopathy (ICH) is a clinical syndrome characterized by the accumulation of cytotoxic bile acids in infancy, leading to serious liver cirrhosis or liver failure. The aetiology of ICH is complicated and some of them is unknown. Regardless of the aetiology, the finial pathology of ICH is hepatocyte apoptosis caused by severe and persistent cholestasis. It is already known that activation of calcium-sensing receptor (CaSR) could lead to the apoptosis of cardiomyocytes. However, the mechanism by CaSR-mediated cholestasis-related hepatocyte apoptosis is not fully understood. Li-Dan-He-Ji (LDHJ), a Traditional Chinese Medicine prescription, was developed to treat ICH. Another aim of this study was to investigate the possible mechanisms of LDHJ in cholestasis-related hepatocyte apoptosis. Using the primary hepatocytes, we first investigated the molecular mechanism of CaSR-mediated hepatocyte apoptosis in cholestasis. Then we prepared LDHJ granules and used ultra-high-performance liquid chromatography to identify the predominant drugs; confirmed the stability of the main substances; and for cell experiments screened forsythoside-A, emodin and chlorogenic acid as the three active substances of LDHJ granules. In the young rats with ANIT-induced intrahepatic cholestasis and the primary hepatocytes with TCDC-induced cholestasis-related hepatocyte apoptosis, the levels of liver injury and cholestasis-related biomarkers, calcium-sensing receptor (CaSR), hepatocyte apoptosis, Bax/Bcl-2 ratio, Cytochrome-C, caspase-3, phosphorylated-c-Jun NH₂-terminal kinase (p-JNK)/JNK, and p-P38/P38 were all increased, while the levels of p-extracellular signal-regulated kinase (p-ERK)/ERK were decreased. However, LDHJ granules and its three active substances effectively reversed these changes. Furthermore, the three active substances reduced the increases in the intracellular calcium concentration ([Ca²⁺]_i) and ROS levels and attenuated the dissipation of the mitochondria membrane potential in the TCDC-induced primary hepatocytes. The opposite results were obtained from the TCDC-induced primary hepatocytes treated with an agonist of CaSR (GdCl₃) plus forsythoside-A, emodin or chlorogenic acid. Based on the results from in vivo and in vitro studies, LDHJ functions as an antagonist of CaSR to regulate hepatocyte apoptosis in cholestasis through the mitochondrial pathway and mitogen-activated protein kinase pathway.

Sex-related differences in urinary immune-related metabolic profiling of alopecia areata patients

INTRODUCTION

Alopecia areata is a well-known autoimmune disease affecting humans. Polyamines are closely associated with proliferation and inflammation, and steroid hormones are involved in immune responses. Additionally, bile acids play roles in immune homeostasis by activating various signaling pathways; however, the roles of these substances and their metabolites in alopecia areata remain unclear.

OBJECTIVES

In this study, we aimed to identify differences in metabolite levels in urine samples from patients with alopecia areata and healthy controls.

METHODS

To assess polyamine, androgen, and bile acid concentrations, we performed high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

Our results showed that spermine and dehydroepiandrosterone levels differed significantly between male patients and controls, whereas ursodeoxycholic acid levels were significantly higher in female patients with alopecia areata than in controls.

CONCLUSION

Our findings suggested different urinary polyamine, androgen, and bile acid concentrations between alopecia areata patients and normal controls. Additionally, levels of endogenous substances varied according to sex, and this should be considered when developing appropriate treatments and diagnostic techniques. Our findings improve our understanding of polyamine, androgen, and bile acid profiles in patients with alopecia areata and highlight the need to consider sex-related differences.

Gut Microbiota and Liver Injury (II): Chronic Liver Injury

Chronic liver injury mainly comprises viral hepatitis, fatty liver disease, autoimmune hepatitis, cirrhosis and liver cancer. It is well established that gut microbiota serves as the key upstream modulator for chronic liver injury progression. Indeed, the term "gut-liver axis" was mostly applied for chronic liver injury. In the current chapter, we will summarize the relationship between gut microbiota and chronic liver injury, including the interaction between them based on latest clinic and basic research.

Exercise and Organ Cross Talk

Chronic heart failure, diabetes, depression, and other chronic diseases are associated with high mortality rate and low cure rate. Exercise induces muscle contraction and secretes multiple myokines, which affects the signaling pathways in skeletal muscle tissues and regulate remote organ functions. Exercise is known to be effective in treating a variety of chronic diseases. Here we summarize how exercise influences skeletal muscle, heart, brain, gut, and liver, and prevents heart failure, cognitive dysfunction, obesity, fatty liver, and other diseases. Exercise training may achieve additional benefits as compared to the present medication for these chronic diseases through cross talk among skeletal muscle and other organs.

The challenges of primary biliary cholangitis: What is new and what needs to be done

Primary Biliary Cholangitis (PBC) is an uncommon, chronic, cholangiopathy of autoimmune origin and unknown etiology characterized by positive anti-mitochondrial autoantibodies (AMA), female preponderance and progression to cirrhosis if left untreated. The diagnosis is based on AMA- or PBC-specific anti-nuclear antibody (ANA)-positivity in the presence of a cholestatic biochemical profile, histologic confirmation being mandatory only in seronegative cases. First-line treatment is ursodeoxycholic acid (UDCA), which is effective in preventing disease progression in about two thirds of the patients. The only approved second-line treatment is obeticholic acid. This article summarizes the most relevant conclusions of a meeting held in Lugano, Switzerland, from September 23rd-25th 2018, gathering basic and clinical scientists with various background from around the world to discuss the latest advances in PBC research. The meeting was dedicated to Ian Mackay, pioneer in the field of autoimmune liver diseases. The role of liver histology needs to be reconsidered: liver pathology consistent with PBC in AMA-positive individuals without biochemical cholestasis is increasingly reported, raising the question as to whether biochemical cholestasis is a reliable disease marker for both clinical practice and trials. The urgent need for new biomarkers, including more accurate markers of cholestasis, was also widely discussed during the meeting. Moreover, new insights in interactions of bile acids with biliary epithelia in PBC provide solid evidence of a role for impaired epithelial protection against potentially toxic hydrophobic bile acids, raising the fundamental question as to whether this bile acid-induced epithelial damage is the cause or the consequence of the autoimmune attack to the biliary epithelium. Strategies are needed to identify difficult-to-treat patients at an early disease stage, when new therapeutic approaches targeting immunologic pathways, in addition to bile acid-based therapies, may be effective. In conclusion, using interdisciplinary approaches, groundbreaking advances can be expected before long in respect to our understanding of the etiopathogenesis of PBC, with the ultimate aim of improving its treatment.

Functional Microbiomics in Liver Transplantation: Identifying Novel Targets for Improving Allograft Outcomes

Gut dysbiosis, defined as a maladaptive gut microbial imbalance, has been demonstrated in patients with end-stage liver disease, defined as a contributor to disease progression, and associated clinically with severity of disease and liver-related morbidity and mortality. Despite this well-recognized phenomena in patients with end-stage liver disease, the impact of gut dysbiosis and its rate of recovery following liver transplantation (LT) remains incompletely understood. The mechanisms by which alterations in the gut microbiota impact allograft metabolism and immunity, both directly and indirectly, are multifactorial and reflect the complexity of the gut-liver axis. Importantly, while research has largely focused on quantitative and qualitative changes in gut microbial composition, changes in microbial functionality (in the presence or absence of compositional changes) are of critical importance. Therefore, to translate functional microbiomics into clinical practice, one must understand not only the compositional but also the functional changes associated with gut dysbiosis and its resolution post-LT. In this review, we will summarize critical advances in functional microbiomics in LT recipients as they apply to immune-mediated allograft injury, posttransplant complications, and disease recurrence, while highlighting potential areas for microbial-based therapeutics in LT recipients.

Seeking biomarkers for acute graft-versus-host disease: where we are and where we are heading?

Acute graft-versus-host disease (aGVHD) is one of the most important complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT), which would seriously affect the clinical outcomes of patients. Early diagnosis and early intervention are keys for improving its curative efficacy. Thus, seeking the biomarkers of aGVHD that can accurately identify and diagnose aGVHD is very important to guiding the intervention and treatment of aGVHD. For the past decades, many studies have focused on searching for aGVHD-related biological markers to assist in diagnosis, early warning, and risk stratification. Unfortunately, until now, no reliable aGVHD biomarker is available that is recognized and widely used in clinical practice. With the continuous development of biological technology, as well as our in-depth understanding of the pathophysiologic mechanism of aGVHD, the selection, examination and application of biological markers have changed much. In this review, we summarized the progress of aGVHD biological marker screening, identification, preliminary clinical application, and look forward to a promising development direction in the future.

Ursodeoxycholic acid accelerates bile acid enterohepatic circulation

BACKGROUND AND PURPOSE

Ursodeoxycholic acid (UDCA) is the first-line treatment for primary biliary cholangitis, but its effects on the enterohepatic circulation of bile acid (BA) have been under-investigated. Therefore, we studied the influence of UDCA on BA enterohepatic circulation in vivo and the mechanisms by which UDCA affects the BA kinetics.

EXPERIMENTAL APPROACH

Mice were treated with UDCA and other BAs to observe changes in BA pool and BA transporters involved in enterohepatic circulation. Isotope dilution techniques and biochemical analyses were applied to study BA kinetics after oral administration of UDCA, and the mechanism involved.

KEY RESULTS

Oral administration of UDCA in mice reduced the overall BA pool and produced a unique BA profile with high-abundance conjugated UDCA species, including tauroursodeoxycholic acid (TUDCA) and GUDCA. We found increased expression of several main BA transporters in the ileum and liver. BA kinetic experiment showed that feeding UDCA shortened cycling time of BA and accelerated BA enterohepatic circulation. Additionally, we found evidence that the effect of UDCA administration on accelerating BA enterohepatic circulation was due to the inhibition of farnesoid X receptor (FXR) signalling in the ileum and FGF15/19 in the liver.

CONCLUSION AND IMPLICATIONS

Oral administration of UDCA produced a unique BA profile with high-abundance TUDCA and GUDCA and significantly accelerated BA enterohepatic circulation through the inhibition of intestinal FXR signalling and reduced level of FGF15/19, which in turn, induced the expression of BA transporters in the liver. These findings highlight a critical role for UDCA in maintaining the homeostasis of BA enterohepatic circulation in vivo.

Development of liposome as a novel adsorbent for artificial liver support system in liver failure

Artificial liver support systems (ALSS), represented by albumin dialysis, are designed to replace the liver detoxification function and to serve as supportive therapy until liver transplantation or liver regeneration. We introduce liposome, which is majorly formed by soybean lecithin as the adsorbent nanomaterial in dialysate for the removal of protein-bound and liver failure-related solutes. The binding rate was detected by ultrafiltration column. In vitro and in vivo dialysis was performed in a recirculation system. Unconjugated bilirubin (52.83-99.87%) and bile salts (50.54-94.75%) were bound by liposomes (5-80 g/L) in a dose-response relationship. The in vitro haemodialysis model showed that the concentration of unconjugated bilirubin (45.64 ± 0.90 μmol/L vs. 54.47 ± 3.48 μmol/L, p < 0.05) and bile salts (153.75 ± 7.72 μmol/L vs. 180.72 ± 7.95 μmol/L, p < 0.05) were significantly decreased in the liposome dialysis group than in the phosphate buffer saline group. The in vivo haemodialysis model showed that 40 g/L liposome-containing dialysate led to a significant higher reduction ratio in total bilirubin (6.56 ± 5.72% vs. -1.86 ± 5.99%, p < 0.05) and more total bile acids (7.63 ± 5.27 μmol vs. 2.13 ± 2.32 μmol, p < 0.05) extracted in the dialysate in comparison with the conventional dialysate. In conclusion, the liposome-added dialysate proved to impose good extraction effects on the unconjugated bilirubin and bile salts. These findings indicate that conventional dialysate supported by this nanomaterial can markedly improve the removal of protein-bound and liver failure-related solutes, thus suggesting a novel and promising liver dialysis system.

The gut microbial influence on cholestatic liver disease

Patients with cholestatic liver diseases like primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC) have a different gut microbiome composition than healthy controls. In contrast with PBC, PSC has a strong association with inflammatory bowel disease and is the prototypical disease of the gut-liver axis. Still, there are some distinct overlapping microbial features in the microbiome of patients with PSC and PBC suggesting similarities in cholestatic diseases, although the possible pathogenetic involvement of these shared microbial changes is unknown. Herein, we present an overview of the available data and discuss the relevance for potential disease relevant host-microbiota interactions. In general, the microbiome interacts with the host via the immunobiome (interactions between the host immune system and the gut microbiome), the endobiome (where the gut microbiome contributes to host physiology by producing or metabolizing endogenous molecules) and the xenobiome (gut microbial transformation of exogenous compounds, including nutrients and drugs). Experimental and human observational evidence suggest that the presence and functions of gut microbes are relevant for the severity and progression of cholestatic liver disease. Interestingly, the majority of new drugs that are currently being tested in PBC and PSC in clinical trials act on bile acid homeostasis, where the endobiome is important. In the future, it will be paramount to perform longitudinal studies, through which we can identify new intervention targets, biomarkers or treatment-stratifiers. In this way, gut microbiome-based clinical care and therapy may become relevant in cholestatic liver disease within the foreseeable future.

Role of the intestinal microbiome in liver fibrosis development and new treatment strategies

Liver cirrhosis is a major cause of morbidity and mortality worldwide. The most common chronic liver diseases in western countries are alcohol-associated liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Although these diseases have different causes, liver fibrosis develops via shared mechanisms. The liver and intestinal microbiome are linked by the portal vein and have bidirectional interactions. Changes in the intestinal microbiome contribute to the pathogenesis and progression of liver diseases including ALD, NAFLD, viral hepatitis and cholestatic disorders, based on studies in patients and animal models. Intestinal microbial dysbiosis has been associated with liver cirrhosis and its complications. We review the mechanisms by which alterations in the microbiome contribute to liver fibrosis and discuss microbiome-based treatment approaches.

Common functional alterations identified in blood transcriptome of autoimmune cholestatic liver and inflammatory bowel diseases

Primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis (UC), are heterogeneous chronic autoimmune diseases that may share underlying pathogenic mechanisms. Herein, we compared simultaneously analyzed blood transcriptomes from patients with PBC, PSC, and IBD. Microarray-based measurements were conducted using RNA isolated from whole blood samples from 90, 45, 95 and 93 patients with PBC, PSC, CD, and UC, respectively, and 47 healthy controls. Expression levels of selected transcripts were analyzed by quantitative reverse-transcribed PCR using an independent cohort of 292, 71 and 727 patients with PBC, PSC, and IBD, respectively. Of 4026, 2650 and 4967 probe sets differentially expressed (adjusted p-value < 0.05) in samples from patients with PBC, PSC, and IBD, respectively, compared with healthy controls, 1946 were common to all three comparisons. Functional analyses indicated that most terms enriched for genes differentially expressed in PBC, PSC, and IBD patients compared with healthy controls were related to mitochondrial function, the vesicle endomembrane system, and GTPase-mediated processes. This study indicates that microarray-based profiling of blood gene expression supports research into the molecular mechanisms underlying disease, rather than being useful for selection of diagnostic biomarkers for use in clinical practice.

Pathophysiology of Cystic Fibrosis Liver Disease: A Channelopathy Leading to Alterations in Innate Immunity and in Microbiota

Cystic fibrosis (CF) is a monogenic disease caused by mutation of Cftr. CF-associated liver disease (CFLD) is a common nonpulmonary cause of mortality in CF and accounts for approximately 2.5%-5% of overall CF mortality. The peak of the disease is in the pediatric population, but a second wave of liver disease in CF adults has been reported in the past decade in association with an increase in the life expectancy of these patients. New drugs are available to correct the basic defect in CF but their efficacy in CFLD is not known. The cystic fibrosis transmembrane conductance regulator, expressed in the apical membrane of cholangiocytes, is a major determinant for bile secretion and CFLD classically has been considered a channelopathy. However, the recent findings of the cystic fibrosis transmembrane conductance regulator as a regulator of epithelial innate immunity and the possible influence of the intestinal disease with an altered microbiota on the liver complication have opened new mechanistic insights on the pathogenesis of CFLD. This review provides an overview of the current understanding of the pathophysiology of the disease and discusses a potential target for intervention.

Autotaxin, bile acid profile and effect of ileal bile acid transporter inhibition in primary biliary cholangitis patients with pruritus

BACKGROUND AND AIMS

Pruritus is a common symptom in patients with primary biliary cholangitis (PBC) for which ileal bile acid transporter (IBAT) inhibition is emerging as a potential therapy. We explored the serum metabonome and gut microbiota profile in PBC patients with pruritus and investigated the effect of GSK2330672, an IBAT inhibitor.

METHODS

We studied fasting serum bile acids (BAs), autotaxin and faecal microbiota in 22 PBC patients with pruritus at baseline and after 2 weeks of GSK2330672 treatment. Control group included 31 asymptomatic PBC patients and 18 healthy volunteers. BA profiling was done by ultra performance liquid chromatography coupled to a mass spectrometry (UPLC-MS). Faecal microbiomes were analysed by 16S ribosomal RNA gene sequencing.

RESULTS

In PBC patients with pruritus, serum levels of total and glyco-conjugated primary BAs and autotaxin were significantly elevated. Autotaxin activity correlated significantly with tauro- and glyco-conjugated cholic acid (CA) and chenodeoxycholic acid (CDCA), both at baseline and after GSK2330672. GSK2330672 significantly reduced autotaxin and all tauro- and glyco- conjugated BAs and increased faecal levels of CA (P = 0.048) and CDCA (P = 0.027). Gut microbiota of PBC patients with pruritus was similar to control groups. GSK2330672 increased the relative abundance of Firmicutes (P = 0.033) and Clostridia (P = 0.04) and decreased Bacteroidetes (P = 0.033) and Bacteroidia (P = 0.04).

CONCLUSIONS

Pruritus in PBC does not show a distinct gut bacterial profile but is associated with elevated serum bile acid and autotaxin levels which decrease after IBAT inhibition. In cholestatic pruritus, a complex interplay between BAs and autotaxin is likely and may be modified by IBAT inhibition.

Anti-inflammatory, anti-oxidative stress and novel therapeutic targets for cholestatic liver injury

Cholestasis is a pathological process in which bile drainage is poor for a variety of reasons. Many studies have shown that cholestatic liver injury is a neutrophil-mediated inflammatory response, and oxidative stress induced by neutrophils is the main mechanism of liver cell death. The literature summarizes the bile acid signaling pathway, the neutrophil chemotaxis recruitment process during cholestasis, and the oxidative stress damage produced by neutrophil activation, summarizes the latest research progress. Sphingosine-1-phosphate receptor (S1PR) is a potential therapeutic target for cholestasis that reduces neutrophil aggregation without inhibiting systemic immune status. Early growth response factor 1 (Egr-1) may play a central role in the inflammation induced by cholestasis, and it is also a potential therapeutic target to inhibit the inflammation induced by cholestasis. Strengthening the antioxidant system of hepatocytes to cope with oxidative stress of neutrophils is a feasible treatment for cholestatic liver injury.