Bile Acids, Liver Cirrhosis, and Extrahepatic Vascular Dysfunction

Changes in the FXR-cistrome and alterations in bile acid physiology in Wilson disease

BACKGROUND

Wilson disease (WD) is an autosomal recessive disorder that results in excessive hepatic copper, causing hepatic steatosis, inflammation, fibrosis, cirrhosis, and liver failure. Previous studies have revealed dysregulation of many farnesoid X receptor (FXR) metabolic target genes in WD, including the bile salt exporter pump, the major determinant of bile flow.

METHODS

We tested the hypothesis that the FXR-cistrome is decreased in Atp7b-/- mice in accord with dysregulated bile acid homeostasis.

RESULTS

FXR binding within Atp7b-/- mouse livers displayed surprising complexity: FXR binding was increased in distal intergenic regions but decreased in promoter regions in Atp7b-/- versus wild-type mice. Decreased FXR occupancy in Atp7b-/- versus wild-type mice was observed in hepatocyte metabolic and bile acid homeostasis pathways, while enrichment of FXR binding was observed in pathways associated with cellular damage outside of hepatocytes. Indeed, disparate FXR occupancy was identified in parenchymal and non-parenchymal marker genes in a manner that suggests decreased FXR activity in parenchymal cells, as expected, and increased FXR activity in non-parenchymal cells. Consistent with altered FXR function, serum and liver bile acid concentrations were higher in Atp7b-/- mice than in wild-type mice. Comparison of bile acid profiles in the serum of WD patients with "liver," "neurological," or "mixed" disease versus healthy controls also revealed increases in specific bile acids in WD-liver versus healthy controls.

CONCLUSIONS

We identified novel FXR-occupancy across the genome that varied in parenchymal and non-parenchymal cells, demonstrating complex FXR regulation of metabolic and hepatocellular stress pathways in Atp7b-/- mice. Dynamic changes in FXR activity support our novel finding of altered bile acid metabolism in Atp7b-/- mice and WD patients.

Decoding the Liver-Heart Axis in Cardiometabolic Diseases

The liver and heart are closely interconnected organs, and their bidirectional interaction plays a central role in cardiometabolic disease. In this review, we summarize current evidence linking liver dysfunction-particularly metabolic dysfunction-associated steatotic liver disease, alcohol-associated liver disease, and cirrhosis-with an increased risk of heart failure and other cardiovascular diseases. We discuss how these liver conditions contribute to cardiac remodeling, systemic inflammation, and hemodynamic stress and how cardiac dysfunction in turn impairs liver perfusion and promotes hepatic injury. Particular attention is given to the molecular mediators of liver-heart communication, including hepatokines and cardiokines, as well as the emerging role of advanced research methodologies, including omics integration, proximity labeling, and organ-on-chip platforms, that are redefining our understanding of interorgan cross talk. By integrating mechanistic insights with translational tools, this review aims to support the development of multiorgan therapeutic strategies for cardiometabolic disease.

Takeda G protein-coupled receptor 5 (TGR5): an attractive therapeutic target for aging-related cardiovascular diseases

Aging is an independent risk factor for many chronic diseases, including cancer and cardiovascular, pulmonary, and neurodegenerative diseases. In recent years, the mechanisms of aging-related cardiovascular diseases (CVDs) have been studied intensively. Takeda G protein-coupled receptor 5 (TGR5) is a membrane receptor for bile acids that has been found to play an important role in various disease processes, such as inflammation, oxidative stress, and metabolic disorders, all of which contribute to aging-related CVDs. In this review, we summarise the role of TGR5 in aging-related CVDs and propose TGR5 as an attractive therapeutic target based on its mechanism of involvement, which may contribute to future drug target design.

Effect of Daily Fiber Intake Among Cirrhotic Patients With and Without Portosystemic Shunts

Background

A diet rich in fiber, especially soluble fiber, causes cholestatic liver damage and fibrosis in animal models with intestinal dysbiosis, high serum bile acid concentrations, and congenital portosystemic shunts (PSs), but no data on patients with cirrhosis (CIRs) are available.

Objectives

To investigate whether dietary fiber consumption was associated with clinical outcomes of CIRs and whether their effect differed according to the presence of PSs.

Methods

Daily soluble and insoluble fiber intake was extrapolated from 3-d food diaries in 25 patients with chronic hepatitis (CH) and 80 CIRs outpatient liver transplant candidates abstinent from alcohol and nonviremic for ≥6 mo. In CIRs, the presence of PSs was verified by computed tomography, and the model for end-stage liver disease (MELD) score was calculated at enrollment and after 6 mo.

Results

PSs were present in 48 (60%) CIRs. The MELD score after 6 mo, compared with enrollment, had improved in 19 and 10 CIRs with and without PSs, respectively. By adjusting for confounders in logistic regression models we found that improvement in MELD over time was inversely associated with insoluble fiber consumption expressed in milligrams per kilogram (mg/kg) body weight in CIRs without PSs [odds ratio (OR): 0.968; 95% confidence interval (CI): 0.939, 0.997; P = 0.005] but with soluble fiber consumption in CIRs with PSs [OR: 0.946; 95% CI: 0.912, 0.982; P = 0.001]. In CIRs with PSs, soluble fiber consumption was inversely associated with normal serum alkaline phosphatase values at enrollment [OR: 0.964; 95% CI: 0.963, 0.993; P = 0.010]. CHs with normal serum alanine transaminase consumed significantly more soluble fiber (p=0.015) than those with abnormal alanine transaminase.

Conclusions

The clinical impact of dietary fiber changes from beneficial to harmful as the stage of chronic liver disease progresses. In particular, in the advanced cirrhosis stage with PSs, soluble fiber intake appears to significantly influence disease progression and should be kept low.

Total bile acid as a preoperative risk factor for post-hepatectomy liver failure in patients with hepatocellular carcinoma and normal bilirubin

BACKGROUND AND AIMS

Total bile acid (TBA) is associated with portal hypertension, a risk factor for post-hepatectomy liver failure (PHLF). We conducted this study to clarify whether TBA is also associated with PHLF in patients with hepatocellular carcinoma (HCC).

METHODS

We recruited patients with HCC and Child-Pugh class A, who underwent liver resection, and applied multivariate analyses to identify risk factors for PHLF.

RESULTS

We analyzed data from 154 patients. The prevalence of PHLF was 14.3%. The median maximum tumor diameter was 5.1 cm (2.9-6.9 cm). The proportions of patients with elevated TBA levels (P = 0.001), severe albumin-bilirubin (AIBL) grades (P = 0.033), and low platelet counts (P = 0.031) were significantly higher within the subgroup of patients with PHLF than in the subgroup without PHLF. The multivariate analysis results suggest that TBA level (OR, 1.08; 951.03-1.14; P = 0.003) and MRI tumor diameter (OR, 1.17; 95% CI, 1.01-1.35; P = 0.038) are independent preoperative risk factors for PHLF. The TBA levels correlated with the indocyanine green retention rate at 15 minutes (P = 0.001) and the effective hepatic blood flow (P < 0.001), two markers of portal hypertension. However, TBA levels did not correlate with tumor diameter (P = 0.536).

CONCLUSIONS

Compared to ICG R15 and AIBL score, preoperative TBA was risk factor for PHLF in Chinese patients with HCC, and it may impact PHLF through its potential role as a marker of portal hypertension.

Endothelial Dysfunction and Liver Cirrhosis: Unraveling of a Complex Relationship

Endothelial dysfunction (ED) is the in the background of multiple metabolic diseases and a key process in liver disease progression and cirrhosis decompensation. ED affects liver sinusoidal endothelial cells (LSECs) in response to different damaging agents, causing their progressive dedifferentiation, unavoidably associated with an increase in intrahepatic resistance that leads to portal hypertension and hyperdynamic circulation with increased cardiac output and low peripheral artery resistance. These changes are driven by a continuous interplay between different hepatic cell types, invariably leading to increased reactive oxygen species (ROS) formation, increased release of pro-inflammatory cytokines and chemokines, and reduced nitric oxide (NO) bioavailability, with a subsequent loss of proper vascular tone regulation and fibrosis development. ED evaluation is often accomplished by serum markers and the flow-mediated dilation (FMD) measurement of the brachial artery to assess its NO-dependent response to shear stress, which usually decreases in ED. In the context of liver cirrhosis, the ED assessment could help understand the complex hemodynamic changes occurring in the early and late stages of the disease. However, the instauration of a hyperdynamic state and the different NO bioavailability in intrahepatic and systemic circulation-often defined as the NO paradox-must be considered confounding factors during FMD analysis. The primary purpose of this review is to describe the main features of ED and highlight the key findings of the dynamic and intriguing relationship between ED and liver disease. We will also focus on the significance of FMD evaluation in this setting, pointing out its key role as a therapeutic target in the never-ending battle against liver cirrhosis progression.

New insights into potential biomarkers and their roles in biological processes associated with hepatitis C-related liver cirrhosis by hepatic RNA-seq-based transcriptome profiling

Chronic hepatitis C virus infection is a major cause of mortality due to liver cirrhosis globally. Despite the advances in recent therapeutic strategies, there is yet a high burden of HCV-related cirrhosis worldwide concerning low coverage of newly developed antiviral therapies, insufficient validity of the current diagnostic methods for cirrhosis, and incomplete understanding of the pathogenesis in this stage of liver disease. Hence we aimed to clarify the molecular events in HCV-related cirrhosis and identify a liver-specific gene signature to potentially improve diagnosis and prognosis of the disease. Through RNA-seq transcriptome profiling of liver samples of Iranian patients with HCV-related cirrhosis, the differentially expressed genes (DEGs) were identified and subjected to functional annotation including biological process (BP) and molecular function (MF) analysis and also KEGG pathway enrichment analysis. Furthermore, the validation of RNA-seq data was investigated for seven candidate genes using qRT-PCR. Moreover, the diagnostic and prognostic power of validated DEGs were analyzed in both forms of individual DEG and combined biomarkers through receiver operating characteristic (ROC) analysis. Finally, we explored the pair-wise correlation of these six validated DEGs in a new approach. We identified 838 significant DEGs (padj ˂0.05) enriching 375 and 15 significant terms subjected to BP and MF, respectively (false discovery rate ˂ 0.01) and 46 significant pathways (p-value ˂ 0.05). Most of these biological processes and pathways were related to inflammation, immune responses, and cellular processes participating somewhat in the pathogenesis of liver disease. Interestingly, some neurological-associated genes and pathways were involved in HCV cirrhosis-related neuropsychiatric disorders. Out of seven candidate genes, six DEGs, including inflammation-related genes ISLR, LTB, ZAP70, KLRB1, and neuronal-related genes MOXD1 and Slitrk3 were significantly confirmed by qRT-PCR. There was a close agreement in the expression change results between RNA-seq and qRT-PCR for our candidate genes except for SAA2-SAA4 (P= 0.8). High validity and reproducibility of six novel DEGs as diagnostic and prognostic biomarkers were observed. We also found several pair-wise correlations between validated DEGs. Our findings indicate that the six genes LTB, ZAP70, KLRB1, ISLR, MOXD1, and Slitrk3 could stand as promising biomarkers for diagnosing of HCV-related cirrhosis. However, further studies are recommended to validate the diagnostic potential of these biomarkers and evaluate their capability as targets for the prevention and treatment of cirrhosis disease.

Role of Gut Microbial Metabolites in Cardiovascular Diseases-Current Insights and the Road Ahead

Cardiovascular diseases (CVDs) are the leading cause of premature morbidity and mortality globally. The identification of novel risk factors contributing to CVD onset and progression has enabled an improved understanding of CVD pathophysiology. In addition to the conventional risk factors like high blood pressure, diabetes, obesity and smoking, the role of gut microbiome and intestinal microbe-derived metabolites in maintaining cardiovascular health has gained recent attention in the field of CVD pathophysiology. The human gastrointestinal tract caters to a highly diverse spectrum of microbes recognized as the gut microbiota, which are central to several physiologically significant cascades such as metabolism, nutrient absorption, and energy balance. The manipulation of the gut microbial subtleties potentially contributes to CVD, inflammation, neurodegeneration, obesity, and diabetic onset. The existing paradigm of studies suggests that the disruption of the gut microbial dynamics contributes towards CVD incidence. However, the exact mechanistic understanding of such a correlation from a signaling perspective remains elusive. This review has focused upon an in-depth characterization of gut microbial metabolites and their role in varied pathophysiological conditions, and highlights the potential molecular and signaling mechanisms governing the gut microbial metabolites in CVDs. In addition, it summarizes the existing courses of therapy in modulating the gut microbiome and its metabolites, limitations and scientific gaps in our current understanding, as well as future directions of studies involving the modulation of the gut microbiome and its metabolites, which can be undertaken to develop CVD-associated treatment options. Clarity in the understanding of the molecular interaction(s) and associations governing the gut microbiome and CVD shall potentially enable the development of novel druggable targets to ameliorate CVD in the years to come.

Gut microbiota and metabolites of cirrhotic portal hypertension: a novel target on the therapeutic regulation

BACKGROUND

The regulatory role of gut microbiota and gut-derived metabolites through the gut-liver axis in the development of cirrhotic portal hypertension (PH) has received increasing attention.

METHODS

The review summarized a series of investigations on effects of metabolites derived from microbiota and medicines targeting microbiome including rifaximin, VSL#3, statins, propranolol, FXR agonists as well as drugs derived from bile acids (BAs) on PH progression.

RESULTS

Patients with PH exhibit alterations in gut microbial richness and differential overall microbiota community, and several results clearly displayed the correlation of PH with enrichment of Veillonella dispar or depletion of Clostridiales, Peptostreptococcaceae, Alistipes putredinis, Roseburia faecis and Clostridium cluster IV. The gut-derived metabolites including hydrogen sulfide, tryptophan metabolites, butyric acid, secondary BAs and phenylacetic acid (PAA) participate in a range of pathophysiology process of PH through modulating intrahepatic vascular resistance and portal blood flow associated with the formation and progression of PH. Established and emerging drugs targeting on bacterial translocation and intestinal eubiosis are gradually identified as potential strategies for treatments of liver cirrhosis and PH by modulating intestinal inflammation, splanchnic arterial vasodilation and endothelial dysfunction.

CONCLUSIONS

Future explorations should further characterize the alteration of the fecal microbiome and metabolite profiles in PH and elucidate the regulatory mechanism of the intestinal microbiome, gut-derived metabolites and gut microbiota targeted pharmaceutical treatments involved in PH.

FXR-FGF19 signaling in the gut-liver axis is dysregulated in patients with cirrhosis and correlates with impaired intestinal defence

BACKGROUND AND AIMS

Experimental studies linked dysfunctional Farnesoid X receptor (FXR)-fibroblast growth factor 19 (FGF19) signaling to liver disease. This study investigated key intersections of the FXR-FGF19 pathway along the gut-liver axis and their link to disease severity in patients with cirrhosis.

METHODS

Patients with cirrhosis undergoing hepatic venous pressure gradient measurement (cohort-I n = 107, including n = 53 with concomitant liver biopsy; n = 5 healthy controls) or colonoscopy with ileum biopsy (cohort-II n = 37; n = 6 controls) were included. Hepatic and intestinal gene expression reflecting FXR activation and intestinal barrier integrity was assessed. Systemic bile acid (BA) and FGF19 levels were measured.

RESULTS

Systemic BA and FGF19 levels correlated significantly (r = 0.461; p < 0.001) and increased with cirrhosis severity. Hepatic SHP expression decreased in patients with cirrhosis (vs. controls; p < 0.001), indicating reduced FXR activation in the liver. Systemic FGF19 (r = -0.512, p < 0.001) and BA (r = -0.487, p < 0.001) levels correlated negatively with hepatic CYP7A1, but not SHP or CYP8B1 expression, suggesting impaired feedback signaling in the liver. In the ileum, expression of FXR, SHP and FGF19 decreased in patients with cirrhosis, and interestingly, intestinal FGF19 expression was not linked to systemic FGF19 levels. Intestinal zonula occludens-1, occludin, and alpha-5-defensin expression in the ileum correlated with SHP and decreased in patients with decompensated cirrhosis as compared to controls.

CONCLUSIONS

FXR-FGF19 signaling is dysregulated at essential molecular intersections along the gut-liver axis in patients with cirrhosis. Decreased FXR activation in the ileum mucosa was linked to reduced expression of intestinal barrier proteins. These human data call for further mechanistic research on interventions targeting the FXR-FGF19 pathway in patients with cirrhosis.

CLINICAL TRIAL NUMBER

NCT03267615.

Vaccine Responses in Patients with Liver Cirrhosis: From the Immune System to the Gut Microbiota

Vaccines prevent a significant number of deaths annually. However, certain populations do not respond adequately to vaccination due to impaired immune systems. Cirrhosis, a condition marked by a profound disruption of immunity, impairs the normal immunization process. Critical vaccines for cirrhotic patients, such as the hepatitis A virus (HAV), hepatitis B virus (HBV), influenza, pneumococcal, and coronavirus disease 19 (COVID-19), often elicit suboptimal responses in these individuals. The humoral response, essential for immunization, is less effective in cirrhosis due to a decline in B memory cells and an increase in plasma blasts, which interfere with the creation of a long-lasting response to antigen vaccination. Additionally, some T cell subtypes exhibit reduced activation in cirrhosis. Nonetheless, the persistence of memory T cell activity, while not preventing infections, may help to attenuate the severity of diseases in these patients. Alongside that, the impairment of innate immunity, particularly in dendritic cells (DCs), prevents the normal priming of adaptive immunity, interrupting the immunization process at its onset. Furthermore, cirrhosis disrupts the gut-liver axis balance, causing dysbiosis, reduced production of short-chain fatty acids (SCFAs), increased intestinal permeability, and bacterial translocation. Undermining the physiological activity of the immune system, these alterations could impact the vaccine response. Enhancing the understanding of the molecular and cellular factors contributing to impaired vaccination responses in cirrhotic patients is crucial for improving vaccine efficacy in this population and developing better prevention strategies.

Understanding the role of ursodeoxycholic acid and gut microbiome in non-alcoholic fatty liver disease: current evidence and perspectives

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, resulting in a huge medical burden worldwide. Accumulating evidence suggests that the gut microbiome and bile acids play pivotal roles during the development of NAFLD. Patients with NAFLD exhibit unique signatures of the intestinal microbiome marked by the priority of Gram-negative bacteria, decreased ratio of Firmicutes/Bacteroidetes (F/B), and increased Prevotella and Lachnospiraceae. The intestinal microbiota is involved in the metabolism of bile acids. Ursodeoxycholic acid (UDCA) is a key determinant in maintaining the dynamic communication between the host and gut microbiota. It generally shows surprising therapeutic potential in NAFLD with several mechanisms, such as improving cellular autophagy, apoptosis, and mitochondrial functions. This action is based on its direct or indirect effect, targeting the farnesoid X receptor (FXR) and various other nuclear receptors. This review aims to discuss the current studies on the involvement of the microbiome-UDCA interface in NAFLD therapy and provide prospective insights into future preventative and therapeutic approaches for NAFLD.

Efficacy and Safety of Elafibranor in Primary Biliary Cholangitis

BACKGROUND

Primary biliary cholangitis is a rare, chronic cholestatic liver disease characterized by the destruction of interlobular bile ducts, leading to cholestasis and liver fibrosis. Whether elafibranor, an oral, dual peroxisome proliferator-activated receptor (PPAR) α and δ agonist, may have benefit as a treatment for primary biliary cholangitis is unknown.

METHODS

In this multinational, phase 3, double-blind, placebo-controlled trial, we randomly assigned (in a 2:1 ratio) patients with primary biliary cholangitis who had had an inadequate response to or unacceptable side effects with ursodeoxycholic acid to receive once-daily elafibranor, at a dose of 80 mg, or placebo. The primary end point was a biochemical response (defined as an alkaline phosphatase level of <1.67 times the upper limit of the normal range, with a reduction of ≥15% from baseline, and normal total bilirubin levels) at week 52. Key secondary end points were normalization of the alkaline phosphatase level at week 52 and a change in pruritus intensity from baseline through week 52 and through week 24, as measured on the Worst Itch Numeric Rating Scale (WI-NRS; scores range from 0 [no itch] to 10 [worst itch imaginable]).

RESULTS

A total of 161 patients underwent randomization. A biochemical response (the primary end point) was observed in 51% of the patients (55 of 108) who received elafibranor and in 4% (2 of 53) who received placebo, for a difference of 47 percentage points (95% confidence interval [CI], 32 to 57; P<0.001). The alkaline phosphatase level normalized in 15% of the patients in the elafibranor group and in none of the patients in the placebo group at week 52 (difference, 15 percentage points; 95% CI, 6 to 23; P = 0.002). Among patients who had moderate-to-severe pruritus (44 patients in the elafibranor group and 22 in the placebo group), the least-squares mean change from baseline through week 52 on the WI-NRS did not differ significantly between the groups (-1.93 vs. -1.15; difference, -0.78; 95% CI, -1.99 to 0.42; P = 0.20). Adverse events that occurred more frequently with elafibranor than with placebo included abdominal pain, diarrhea, nausea, and vomiting.

CONCLUSIONS

Treatment with elafibranor resulted in significantly greater improvements in relevant biochemical indicators of cholestasis than placebo. (Funded by GENFIT and Ipsen; ELATIVE ClinicalTrials.gov number, NCT04526665.).

Exploring the Relationship between Liver Disease, Bacterial Translocation, and Dysbiosis: Unveiling the Gut-Liver Axis

Background

The global burden of liver disease and cirrhosis has been progressively increasing in the last decade. The interplay between gut microbiota and immune system and the bidirectional relationship with the liver, known as the gut-liver axis, has arisen as a fundamental aspect of liver disease.

Summary

Alterations of the gut microbiome have been described and include both dysbiotic microbial signatures and intestinal bacterial overgrowth. The integrity of the intestinal epithelial barrier is essential for preventing the access of harmful substances and bacterial products into the host. Bacterial translocation due to altered host-microbiota interactions triggers local immune cell activation and facilitates a chronic inflammatory state that can ultimately lead to immune exhaustion, characteristic of cirrhosis. In cirrhosis, breakdown of the gut vascular barrier allows access of bacterial products to portal blood circulation and facilitates their influx into the liver, further contributing to disease progression.

Key Messages

A better understanding of the contributing factors to pathological bacterial translocation and the impact of dysbiosis in liver disease will lead to achieve innovative therapeutic strategies in cirrhosis.

Bile acid profiles in adult patients with biliary atresia who achieve native liver survival after portoenterostomy

Bile acids have received increasing attention as a marker of the long-term prognosis and a potential therapeutic target in patients with biliary atresia, which is a progressive disease of the hepatobiliary system. A detailed analysis of serum and urinary bile acid compositions was conducted to assess the characteristics of bile acid profiles and the correlation between bile acid profiles and liver fibrosis markers in adult patients with biliary atresia who achieved bilirubin normalization. Serum total bile acids and glucuronide-conjugated (glyco- and tauro-) cholic acids (GCA and TCA) and chenodeoxycholic acids (GCDCA and TCDCA) were significantly higher in patients with biliary atresia than in healthy controls, whereas unconjugated CA and CDCA showed no significant difference. There were no significant differences in CA to CDCA ratios and glycine-to-taurine-conjugated ratios. Urinary glycocholic acid 3-sulfate (GCA-3S) was significantly higher in patients with biliary atresia. Serum GCDCA showed a strong positive correlation with Mac-2 binding protein glycosylation isomer (M2BPGi). These results demonstrate that bile acid congestion persists into adulthood in patients with biliary atresia, even after cholestasis has completely improved after Kasai portoenterostomy. These fundamental data on bile acid profiles also suggest the potential value of investigating bile acid profiles in patients with biliary atresia.

Viral Liver Disease and Intestinal Gut–Liver Axis

The intestinal microbiota is closely related to liver diseases via the intestinal barrier and bile secretion to the gut. Impairment of the barrier can translocate microbes or their components to the liver where they can contribute to liver damage and fibrosis. The components of the barrier are discussed in this review along with the other elements of the so-called gut–liver axis. This bidirectional relation has been widely studied in alcoholic and non-alcoholic liver disease. However, the involvement of microbiota in the pathogenesis and treatment of viral liver diseases have not been extensively studied, and controversial data have been published. Therefore, we reviewed data regarding the integrity and function of the intestinal barrier and the changes of the intestinal microbioma that contribute to progression of Hepatitis B (HBV) and Hepatitis C (HCV) infection. Their consequences, such as cirrhosis and hepatic encephalopathy, were also discussed in connection with therapeutic interventions such as the effects of antiviral eradication and the use of probiotics that may influence the outcome of liver disease. Profound alterations of the microbioma with significant reduction in microbial diversity and changes in the abundance of both beneficial and pathogenic bacteria were found.

An integrated analysis of fecal microbiome and metabolomic features distinguish non-cirrhotic NASH from healthy control populations

BACKGROUND AND AIMS

There is great interest in identifying microbiome features as reliable noninvasive diagnostic and/or prognostic biomarkers for non-cirrhotic NASH fibrosis. Several cross-sectional studies have reported gut microbiome features associated with advanced NASH fibrosis and cirrhosis, where the most prominent features are associated with cirrhosis. However, no large, prospectively collected data exist establishing microbiome features that discern non-cirrhotic NASH fibrosis, integrate the fecal metabolome as disease biomarkers, and are unconfounded by BMI and age.

APPROACH AND RESULTS

Results from shotgun metagenomic sequencing performed on fecal samples prospectively collected from 279 US patients with biopsy-proven NASH (F1-F3 fibrosis) enrolled in the REGENERATE I303 study were compared to those from 3 healthy control cohorts and integrated with the absolute quantification of fecal bile acids. Microbiota beta-diversity was different, and BMI- and age-adjusted logistic regression identified 12 NASH-associated species. Random forest prediction models resulted in an AUC of 0.75-0.81 in a receiver operator characteristic analysis. In addition, specific fecal bile acids were significantly lower in NASH and correlated with plasma C4 levels. Microbial gene abundance analysis revealed 127 genes increased in controls, many involving protein synthesis, whereas 362 genes were increased in NASH many involving bacterial environmental responses (false discovery rate < 0.01). Finally, we provide evidence that fecal bile acid levels may be a better discriminator of non-cirrhotic NASH versus health than either plasma bile acids or gut microbiome features.

CONCLUSIONS

These results may have value as a set of baseline characteristics of non-cirrhotic NASH against which therapeutic interventions to prevent cirrhosis can be compared and microbiome-based diagnostic biomarkers identified.

Deciphering the role of gut metabolites in non-alcoholic fatty liver disease

Perturbations in microbial abundance or diversity in the intestinal lumen leads to intestinal inflammation and disruption of intestinal membrane which eventually facilitates the translocation of microbial metabolites or whole microbes to the liver and other organs through portal vein. This process of translocation finally leads to multitude of health disorders. In this review, we are going to focus on the mechanisms by which gut metabolites like SCFAs, tryptophan (Trp) metabolites, bile acids (BAs), ethanol, and choline can either cause the development/progression of non-alcoholic fatty liver disease (NAFLD) or serves as a therapeutic treatment for the disease. Alterations in some metabolites like SCFAs, Trp metabolites, etc., can serve as biomarker molecules whereas presence of specific metabolites like ethanol definitely leads to disease progression. Thus, proper understanding of these mechanisms will subsequently help in designing of microbiome-based therapeutic approaches. Furthermore, we have also focussed on the role of dysbiosis on the mucosal immune system. In addition, we would also compile up the microbiome-based clinical trials which are currently undergoing for the treatment of NAFLD and non-alcoholic steatohepatitis (NASH). It has been observed that the use of microbiome-based approaches like prebiotics, probiotics, symbiotics, etc., can act as a beneficial treatment option but more research needs to be done to know how to manipulate the composition of gut microbes.

The regulatory role of bile acid microbiota in the progression of liver cirrhosis

Bile acids (BAs) are synthesized in liver tissue from cholesterol and are an important endocrine regulator and signaling molecule in the liver and intestine. It maintains BAs homeostasis, and the integrity of intestinal barrier function, and regulates enterohepatic circulation in vivo by modulating farnesoid X receptors (FXR) and membrane receptors. Cirrhosis and its associated complications can lead to changes in the composition of intestinal micro-ecosystem, resulting in dysbiosis of the intestinal microbiota. These changes may be related to the altered composition of BAs. The BAs transported to the intestinal cavity through the enterohepatic circulation are hydrolyzed and oxidized by intestinal microorganisms, resulting in changes in their physicochemical properties, which can also lead to dysbiosis of intestinal microbiota and overgrowth of pathogenic bacteria, induction of inflammation, and damage to the intestinal barrier, thus aggravating the progression of cirrhosis. In this paper, we review the discussion of BAs synthesis pathway and signal transduction, the bidirectional regulation of bile acids and intestinal microbiota, and further explore the role of reduced total bile acid concentration and dysregulated intestinal microbiota ratio in the development of cirrhosis, in order to provide a new theoretical basis for the clinical treatment of cirrhosis and its complications.

Ursodeoxycholic acid induces sarcopenia associated with decreased protein synthesis and autophagic flux

BACKGROUND

Skeletal muscle generates force and movements and maintains posture. Under pathological conditions, muscle fibers suffer an imbalance in protein synthesis/degradation. This event causes muscle mass loss and decreased strength and muscle function, a syndrome known as sarcopenia. Recently, our laboratory described secondary sarcopenia in a chronic cholestatic liver disease (CCLD) mouse model. Interestingly, the administration of ursodeoxycholic acid (UDCA), a hydrophilic bile acid, is an effective therapy for cholestatic hepatic alterations. However, the effect of UDCA on skeletal muscle mass and functionality has never been evaluated, nor the possible involved mechanisms.

METHODS

We assessed the ability of UDCA to generate sarcopenia in C57BL6 mice and develop a sarcopenic-like phenotype in C₂C₁₂ myotubes and isolated muscle fibers. In mice, we measured muscle strength by a grip strength test, muscle mass by bioimpedance and mass for specific muscles, and physical function by a treadmill test. We also detected the fiber's diameter and content of sarcomeric proteins. In C₂C₁₂ myotubes and/or isolated muscle fibers, we determined the diameter and troponin I level to validate the cellular effect. Moreover, to evaluate possible mechanisms, we detected puromycin incorporation, p70S6K, and 4EBP1 to evaluate protein synthesis and ULK1, LC3 I, and II protein levels to determine autophagic flux. The mitophagosome-like structures were detected by transmission electron microscopy.

RESULTS

UDCA induced sarcopenia in healthy mice, evidenced by decreased strength, muscle mass, and physical function, with a decline in the fiber's diameter and the troponin I protein levels. In the C₂C₁₂ myotubes, we observed that UDCA caused a reduction in the diameter and content of MHC, troponin I, puromycin incorporation, and phosphorylated forms of p70S6K and 4EBP1. Further, we detected increased levels of phosphorylated ULK1, the LC3II/LC3I ratio, and the number of mitophagosome-like structures. These data suggest that UDCA induces a sarcopenic-like phenotype with decreased protein synthesis and autophagic flux.

CONCLUSIONS

Our results indicate that UDCA induces sarcopenia in mice and sarcopenic-like features in C₂C₁₂ myotubes and/or isolated muscle fibers concomitantly with decreased protein synthesis and alterations in autophagic flux.

Elevated bile acids are associated with left ventricular structural changes in biliary atresia

BACKGROUND

In children with biliary atresia (BA), pathologic structural changes within the heart, which define cirrhotic cardiomyopathy, are associated with adverse perioperative outcomes. Despite their clinical relevance, little is known about the pathogenesis and triggers of pathologic remodeling. Bile acid excess causes cardiomyopathy in experimental cirrhosis, but its role in BA is poorly understood.

METHODS

Echocardiographic parameters of left ventricular (LV) geometry [LV mass (LVM), LVM indexed to height, left atrial volume indexed to BSA (LAVI), and LV internal diameter (LVID)] were correlated with circulating serum bile acid concentrations in 40 children (52% female) with BA listed for transplantation. A receiver-operating characteristic curve was generated to determine optimal threshold values of bile acids to detect pathologic changes in LV geometry using Youden index. Paraffin-embedded human heart tissue was separately analyzed by immunohistochemistry for the presence of bile acid-sensing Takeda G-protein-coupled membrane receptor type 5.

RESULTS

In the cohort, 52% (21/40) of children had abnormal LV geometry; the optimal bile acid concentration to detect this abnormality with 70% sensitivity and 64% specificity was 152 µmol/L (C-statistics=0.68). Children with bile acid concentrations >152 µmol/L had ∼8-fold increased odds of detecting abnormalities in LVM, LVM index, left atrial volume index, and LV internal diameter. Serum bile acids positively correlated with LVM, LVM index, and LV internal diameter. Separately, Takeda G-protein-coupled membrane receptor type 5 protein was detected in myocardial vasculature and cardiomyocytes on immunohistochemistry.

CONCLUSION

This association highlights the unique role of bile acids as one of the targetable potential triggers for myocardial structural changes in BA.

Beta-blockers in patients with liver cirrhosis: Pragmatism or perfection?

With increasing decompensation, hyperdynamic circulatory disturbance occurs in liver cirrhosis despite activation of vasoconstrictors. Here, the concept of a therapy with non-selective beta-blockers was established decades ago. They lower elevated portal pressure, protect against variceal hemorrhage, and may also have pleiotropic immunomodulatory effects. Recently, the beneficial effect of carvedilol, which blocks alpha and beta receptors, has been highlighted. Carvedilol leads to "biased-signaling" via recruitment of beta-arrestin. This effect and its consequences have not been sufficiently investigated in patients with liver cirrhosis. Also, a number of questions remain open regarding the expression of beta-receptors and its intracellular signaling and the respective consequences in the intra- and extrahepatic tissue compartments. Despite the undisputed role of non-selective beta-blockers in the treatment of liver cirrhosis, we still can improve the knowledge as to when and how beta-blockers should be used in which patients.

Association of lithocholic acid with skeletal muscle hypertrophy through TGR5-IGF-1 and skeletal muscle mass in cultured mouse myotubes, chronic liver disease rats and humans

Background:

Hepatic sarcopenia is one of many complications associated with chronic liver disease (CLD) and has a high mortality rate; however, the liver-muscle axis is not fully understood. Therefore, few effective treatments exist for hepatic sarcopenia, the best of which being branched-chain amino acid (BCAA) supplementation to help increase muscle mass. Our aim was to investigate the molecular mechanism(s) of hepatic sarcopenia focused on bile acid (BA) composition.

Methods:

The correlation between serum BA levels and psoas muscle mass index (PMI) was examined in 73 CLD patients. Gastrocnemius muscle phenotype and serum BA levels were assessed in CLD rats treated with BCAA. Mouse skeletal muscle cells (C2C12) were incubated with lithocholic acid (LCA), G-protein-coupled receptor 5 (TGR5) agonist or TGR5 antagonist to assess skeletal muscle hypertrophy.

Results:

In human CLD, serum LCA levels were the sole factor positively correlated with PMI and were significantly decreased in both the low muscle mass group and the deceased group. Serum LCA levels were also shown to predict patient survival. Gastrocnemius muscle weight significantly increased in CLD rats treated with BCAA via suppression of protein degradation pathways, coupled with a significant increase in serum LCA levels. LCA treated C2C12 hypertrophy occurred in a concentration-dependent manner linked with TGR5-Akt pathways based upon inhibition results via a TGR5 antagonist.

Conclusions:

Our results indicate LCA-mediated skeletal muscle hypertrophy via activation of TGR5-IGF1-Akt signaling pathways. In addition, serum LCA levels were associated with skeletal muscle mass in cirrhotic rats, as well as CLD patients, and predicted overall patient survival.

Funding:

This research was supported by JSPS KAKENHI Grant Number 22K08011 and 21H02892, and AMED under Grant Number JP21fk0210090 and JP22fk0210115. Maintaining cirrhotic rats were partially supported by Otsuka Pharmaceutical Company.

Systematic Characterization of the Disruption of Intestine during Liver Tumor Progression in the xmrk Oncogene Transgenic Zebrafish Model

The crosstalk between tumors and their local microenvironment has been well studied, whereas the effect of tumors on distant tissues remains understudied. Studying how tumors affect other tissues is important for understanding the systemic effect of tumors and for improving the overall health of cancer patients. In this study, we focused on the changes in the intestine during liver tumor progression, using a previously established liver tumor model through inducible expression of the oncogene xmrk in zebrafish. Progressive disruption of intestinal structure was found in the tumor fish, displaying villus damage, thinning of bowel wall, increase in goblet cell number, decrease in goblet cell size and infiltration of eosinophils, most of which were observed phenotypes of an inflammatory intestine. Intestinal epithelial cell renewal was also disrupted, with decreased cell proliferation and increased cell death. Analysis of intestinal gene expression through RNA-seq suggested deregulation of genes related to intestinal function, epithelial barrier and homeostasis and activation of pathways in inflammation, epithelial mesenchymal transition, extracellular matrix organization, as well as hemostasis. Gene set enrichment analysis showed common gene signatures between the intestine of liver tumor fish and human inflammatory bowel disease, the association of which with cancer has been recently noticed. Overall, this study represented the first systematic characterization of the disruption of intestine under the liver tumor condition and suggested targeting intestinal inflammation as a potential approach for managing cancer cachexia.

Hepatorenal Syndrome: Pathophysiology

Hepatorenal syndrome (HRS) is defined as a functional renal failure without major histologic changes in individuals with severe liver disease and it is associated with a high mortality rate. Renal hypoperfusion due to marked vasoconstriction as a result of complex circulatory dysfunction has been suggested to be the cornerstone of HRS. Splanchnic and peripheral arterial vasodilation and cirrhotic cardiomyopathy result in effective arterial hypovolemia and compensatory activation of vasoconstrictor mechanisms. The efficacy of current therapeutic strategies targeting this circulatory dysfunction is limited. Increasing evidence suggests a substantial role of systemic inflammation in HRS via either vascular or direct renal effects. Here we summarize the current understanding of HRS pathophysiology.

Anti-Liver Fibrosis Activity and the Potential Mode of Action of Ruangan Granules: Integrated Network Pharmacology and Metabolomics

Ruangan granules (RGGs) have been used to treat liver fibrosis with good clinical efficacy for many years. However, the potential mechanism of action of RGGs against liver fibrosis is still unclear. In this study, we evaluated the quality and safety of this preparation and aimed to explore the anti-liver fibrosis activity and potential mode of action of RGGs using network pharmacology and metabolomics. The results showed that RGGs contained abundant ferulic acid, salvianolic acid B and paeoniflorin, and at the given contents and doses, RGGs were safe and presented anti-liver fibrosis activity. They presented anti-liver fibrosis activity by improving liver function (ALT and AST, p < 0.01) and pathology and decreasing fibrosis markers in the serum of rats caused by CCl₄, including HA, LN, PC III, HYP, CoII-V, and α-SMA, and the oxidant stress and inflammatory response were also alleviated in a dose-dependent manner, especially for high-dose RGGs (p < 0.01). Further studies showed that RGGs inhibited the activation of the PI3K-Akt signaling pathway in rats induced by CCl₄, regulated pyrimidine metabolism, improved oxidative stress and the inflammatory response by regulating mitochondrial morphology, and alleviated liver fibrosis. Luteolin, quercetin, morin and kaempferol were active compounds and presented the cytotoxicity toward to LX-02 cells. This study provides an overall view of the mechanism underlying the action of RGGs protecting against liver fibrosis.

Intestinal Barrier in Human Health and Disease

The intestinal mucosa provides a selective permeable barrier for nutrient absorption and protection from external factors. It consists of epithelial cells, immune cells and their secretions. The gut microbiota participates in regulating the integrity and function of the intestinal barrier in a homeostatic balance. Pathogens, xenobiotics and food can disrupt the intestinal barrier, promoting systemic inflammation and tissue damage. Genetic and immune factors predispose individuals to gut barrier dysfunction, and changes in the composition and function of the gut microbiota are central to this process. The progressive identification of these changes has led to the development of the concept of ‘leaky gut syndrome’ and ‘gut dysbiosis’, which underlie the relationship between intestinal barrier impairment, metabolic diseases and autoimmunity. Understanding the mechanisms underlying this process is an intriguing subject of research for the diagnosis and treatment of various intestinal and extraintestinal diseases.