Development of Alcohol-Associated Hepatitis Is Associated With Specific Changes in Gut-Modified Bile Acids

Gut-liver axis: Recent concepts in pathophysiology in alcohol-associated liver disease

The growing recognition of the role of the gut microbiome's impact on alcohol-associated diseases, especially in alcohol-associated liver disease, emphasizes the need to understand molecular mechanisms involved in governing organ-organ communication to identify novel avenues to combat alcohol-associated diseases. The gut-liver axis refers to the bidirectional communication and interaction between the gut and the liver. Intestinal microbiota plays a pivotal role in maintaining homeostasis within the gut-liver axis, and this axis plays a significant role in alcohol-associated liver disease. The intricate communication between intestine and liver involves communication between multiple cellular components in each organ that enable them to carry out their physiological functions. In this review, we focus on novel approaches to understanding how chronic alcohol exposure impacts the microbiome and individual cells within the liver and intestine, as well as the impact of ethanol on the molecular machinery required for intraorgan and interorgan communication.

Regulation Mechanism and Potential Value of Active Substances in Spices in Alcohol-Liver-Intestine Axis Health

Excessive alcohol intake will aggravate the health risk between the liver and intestine and affect the multi-directional information exchange of metabolites between host cells and microbial communities. Because of the side effects of clinical drugs, people tend to explore the intervention value of natural drugs on diseases. As a flavor substance, spices have been proven to have medicinal value, but they are still rare in treating hepatointestinal diseases caused by alcohol. This paper summarized the metabolic transformation of alcohol in the liver and intestine and summarized the potential value of various perfume active substances in improving liver and intestine diseases caused by alcohol. It is also found that bioactive substances in spices can exert antioxidant activity in the liver and intestine environment and reduce the oxidative stress caused by diseases. These substances can interfere with fatty acid synthesis, promote sugar and lipid metabolism, and reduce liver injury caused by steatosis. They can effectively regulate the balance of intestinal flora, promote the production of SCFAs, and restore the intestinal microenvironment.

Cyanidin-3-O-Glucoside Alleviates Alcoholic Liver Injury via Modulating Gut Microbiota and Metabolites in Mice

Alcoholic liver disease (ALD) is primarily caused by long-term excessive alcohol consumption. Cyanidin-3-O-glucoside (C3G) is a widely occurring natural anthocyanin with multiple biological activities. This study aims to investigate the effects of C3G isolated from black rice on ALD and explore the potential mechanism. C57BL/6J mice (male) were fed with standard diet (CON) and Lieber-DeCarli liquid-fed (Eth) or supplemented with a 100 mg/kg/d C3G Diet (Eth-C3G), respectively. Our results showed that C3G could effectively ameliorate the pathological structure and liver function, and also inhibited the accumulation of liver lipids. C3G supplementation could partially alleviate the injury of intestinal barrier in the alcohol-induced mice. C3G supplementation could increase the abundance of Norank_f_Muribaculaceae, meanwhile, the abundances of Bacteroides, Blautia, Collinsella, Escherichia-Shigella, Enterococcus, Prevotella, [Ruminococcus]_gnavus_group, Methylobacterium-Methylorubrum, Romboutsia, Streptococcus, Bilophila, were decreased. Spearman's correlation analysis showed that 12 distinct genera were correlated with blood lipid levels. Non-targeted metabolic analyses of cecal contents showed that C3G supplementation could affect the composition of intestinal metabolites, particularly bile acids. In conclusion, C3G can attenuate alcohol-induced liver injury by modulating the gut microbiota and metabolites, suggesting its potential as a functional food ingredient against alcoholic liver disease.

Fibroblast Growth Factor 19 Alters Bile Acids to Induce Dysbiosis in Mice With Alcohol-Induced Liver Disease

BACKGROUND & AIMS

Excessive alcohol consumption can lead to alcohol-associated liver disease, a spectrum of conditions ranging from steatosis to fibrosis and cirrhosis. Bile acids regulate metabolic pathways by binding to cellular and nuclear receptors, and they also interact with the gut microbiome to control microbial overgrowth. Fibroblast growth factor 19 (FGF-19) is an ileum-derived hormone induced and released in response to bile acid activation of the nuclear receptor farnesoid X receptor. FGF-19 signaling is dysregulated with ethanol consumption and is increased in patients with alcoholic hepatitis. Here, we examined the effects of FGF-19 in a mouse model of chronic + binge ethanol feeding.

METHODS

After injection of adeno-associated virus-green fluorescent protein or AAV-FGF-19, female C57BL/6J mice were pair-fed a Lieber DeCarli liquid diet (5% v/v) or control diet for 10 days and were given a bolus gavage of 5% ethanol or maltose control to represent a binge drinking episode. Tissues were collected for analysis 9 hours after the binge.

RESULTS

Chronic + binge ethanol feeding induced steatosis regardless of FGF-19 expression. Interestingly, FGF-19 and ethanol resulted in significantly increased liver inflammation, as measured by Il6, Tgfβ, and Tnfα, compared with ethanol alone. Both ethanol and FGF-19 decreased bile acid synthesis, and FGF-19 significantly reduced secondary bile acids, leading to overgrowth of specific pathogenic bacteria including Enterococcus faecalis, Escherichia coli, and Clostridium perfringens.

CONCLUSIONS

Dysregulation of FGF-19 and consequent changes in bile acid synthesis and composition during alcohol consumption may be a contributing factor to alcohol-induced liver disease and dysbiosis.

Maternal exposure to 4-vinylcyclohexene diepoxide during pregnancy leads to disorder of gut microbiota and bile acid metabolism in offspring

Our previous study reveals that maternal exposure to 4-vinylcyclohexene diepoxide (VCD) during pregnancy causes insufficient ovarian follicle reserve and decreased fertility in offspring. The present study aims to further explore the reasons for the significant decline of fecundity in mice caused by VCD, and to clarify the changes of gut microbiota and microbial metabolites in F1 mice. The ovarian metabolomics, gut microbiota and microbial metabolites were analyzed. The results of ovarian metabolomics analysis showed that maternal VCD exposure during pregnancy significantly reduced the concentration of carnitine in the ovaries of F1 mice, while supplementation with carnitine (isovalerylcarnitine and valerylcarnitine) significantly increased the number of ovulation. The results of 16 S rDNA-seq and microbial metabolites analysis showed that maternal VCD exposure during pregnancy caused disordered gut microbiota, increased abundance of Parabacteroides and Flexispira bacteria that are involved in secondary bile acid synthesis. The concentrations of NorDCA, LCA-3S, DCA and other secondary bile acids increased significantly. Our results indicate that maternal exposure to VCD during pregnancy leads to disorder in gut microbiota and bile acid metabolism in F1 mice, accompanying with decreased ovarian function, providing further evidence that maternal exposure to VCD during pregnancy has intergenerational deleterious effects on offspring.

Anti-miR-873-5p improves alcohol-related liver disease by enhancing hepatic deacetylation via SIRT1

Background & Aims

Current therapies for the treatment of alcohol-related liver disease (ALD) have proven largely ineffective. Patients relapse and the disease progresses even after liver transplantation. Altered epigenetic mechanisms are characteristic of alcohol metabolism given excessive acetate and NAD depletion and play an important role in liver injury. In this regard, novel therapeutic approaches based on epigenetic modulators are increasingly proposed. MicroRNAs, epigenetic modulators acting at the post-transcriptional level, appear to be promising new targets for the treatment of ALD.

Methods

MiR-873-5p levels were measured in 23 liver tissue from Patients with ALD, and GNMT levels during ALD were confirmed using expression databases (transcriptome n = 62, proteome n = 68). High-resolution proteomics and metabolomics in mice following the Gao-binge model were used to investigate miR-873-5p expression in ALD. Hepatocytes exposed to 50 mM alcohol for 12 h were used to study toxicity. The effect of anti-miR-873-5p in the treatment outcomes of ALD was investigated.

Results

The analysis of human and preclinical ALD samples revealed increased expression of miR-873-5p in the liver. Interestingly, there was an inverse correlation with NNMT, suggesting a novel mechanism for NAD depletion and aberrant acetylation during ALD progression. High-resolution proteomics and metabolomics identified miR-873-5p as a key regulator of NAD metabolism and SIRT1 deacetylase activity. Anti-miR-873-5p reduced NNMT activity, fuelled the NAD salvage pathway, restored the acetylome, and modulated the levels of NF-κB and FXR, two known SIRT1 substrates, thereby protecting the liver from apoptotic and inflammatory processes, and improving bile acid homeostasis.

Conclusions

These data indicate that targeting miR-873-5p, a repressor of GNMT previously associated with NAFLD and acetaminophen-induced liver failure. is a novel and attractive approach to treating alcohol-induced hepatoxicity.

Impact and implications

The role of miR-873-5p has not been explicitly examined in the progression of ALD, a pathology with no therapeutic options. In this study, inhibiting miR-873-5p exerted hepatoprotective effects against ALD through rescued SIRT1 activity and consequently restored bile acid homeostasis and attenuated the inflammatory response. Targeting hepatic miR-873-5p may represent a novel therapeutic approach for the treatment of ALD.

Zhuyu Pill Alleviates Nonalcoholic Fatty Liver Disease by Regulating Bile Acid Metabolism through the Gut-Liver Axis

AIM

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing worldwide, but there are currently limited treatment options available. Therefore, it is necessary to research new treatment strategies. Zhuyu Pill (ZYP) is a well-known herbal recipe consisting of Huanglian (Coptidis rhizoma) and Wuzhuyu (Evodiae Fructus) that has been clinically used to treat NAFLD. This study aimed to investigate the impact of ZYP on NAFLD induced by a high-fat diet (HFD) and to identify its potential mechanism.

METHODS

In this investigation, we used ZYP to treat a mouse model of NAFLD induced by an HFD. We conducted various analyses including assessment of serum biochemical indices, histological evaluation, fecal metabonomics analysis, western blot, and quantitative real-time polymerase chain reaction.

RESULTS

ZYP effectively improved blood lipid levels and reduced inflammatory response in HFD mice, while also alleviating liver cell damage and lipid accumulation. Additionally, ZYP influenced the fecal bile acid (BA) metabolism profiles of HFD mice by inhibiting the signal transduction of ileal farnesoid X receptor (FXR) fibroblast growth factor 15 (FGF15), enhancing the expression of cytochrome P450 family 7 subfamily A member 1(CYP7A1), promoting BA synthesis and increasing the metabolic elimination of cholesterol.

CONCLUSION

ZYP shows promise as a potential treatment for alleviating NAFLD by modulating BA metabolism through the FXR-FGF15-CYP7A1 pathway.

Difference and clinical value of metabolites in plasma and feces of patients with alcohol-related liver cirrhosis

BACKGROUND

Alterations in plasma and intestinal metabolites contribute to the pathogenesis and progression of alcohol-related liver cirrhosis (ALC).

AIM

To explore the common and different metabolites in the plasma and feces of patients with ALC and evaluate their clinical implications.

METHODS

According to the inclusion and exclusion criteria, 27 patients with ALC and 24 healthy controls (HCs) were selected, and plasma and feces samples were collected. Liver function, blood routine, and other indicators were detected with automatic biochemical and blood routine analyzers. Liquid chromatography-mass spectrometry was used to detect the plasma and feces metabolites of the two groups and the metabolomics of plasma and feces. Also, the correlation between metabolites and clinical features was analyzed.

RESULTS

More than 300 common metabolites were identified in the plasma and feces of patients with ALC. Pathway analysis showed that these metabolites are enriched in bile acid and amino acid metabolic pathways. Compared to HCs, patients with ALC had a higher level of glycocholic acid (GCA) and taurocholic acid (TCA) in plasma and a lower level of deoxycholic acid (DCA) in the feces, while L-threonine, L-phenylalanine, and L-tyrosine increased simultaneously in plasma and feces. GCA, TCA, L-methionine, L-phenylalanine, and L-tyrosine in plasma were positively correlated with total bilirubin (TBil), prothrombin time (PT), and maddrey discriminant function score (MDF) and negatively correlated with cholinesterase (CHE) and albumin (ALB). The DCA in feces was negatively correlated with TBil, MDF, and PT and positively correlated with CHE and ALB. Moreover, we established a P/S BA ratio of plasma primary bile acid (GCA and TCA) to fecal secondary bile acid (DCA), which was relevant to TBil, PT, and MDF score.

CONCLUSION

The enrichment of GCA, TCA, L-phenylalanine, L-tyrosine, and L-methionine in the plasma of patients with ALC and the reduction of DCA in feces were related to the severity of ALC. These metabolites may be used as indicators to evaluate the progression of alcohol-related liver cirrhosis.

Probiotic-derived nanoparticles inhibit ALD through intestinal miR194 suppression and subsequent FXR activation

BACKGROUND AND AIMS

Intestinal farnesoid X receptor (FXR) plays a critical role in alcohol-associated liver disease (ALD). We aimed to investigate whether alcohol-induced dysbiosis increased intestinal microRNA194 (miR194) that suppressed Fxr transcription and whether Lactobacillus rhamnosus GG-derived exosome-like nanoparticles (LDNPs) protected against ALD through regulation of intestinal miR194-FXR signaling in mice.

APPROACH AND RESULTS

Binge-on-chronic alcohol exposure mouse model was utilized. In addition to the decreased ligand-mediated FXR activation, alcohol feeding repressed intestinal Fxr transcription and increased miR194 expression. This transcriptional suppression of Fxr by miR194 was confirmed in intestinal epithelial Caco-2 cells and mouse enteriods. The alcohol feeding-reduced intestinal FXR activation was further demonstrated by the reduced FXR reporter activity in fecal samples and by the decreased fibroblast growth factor 15 (Fgf15) messenger RNA (mRNA) in intestine and protein levels in the serum, which caused an increased hepatic bile acid synthesis and lipogeneses. We further demonstrated that alcohol feeding increased-miR194 expression was mediated by taurine-upregulated gene 1 (Tug1) through gut microbiota regulation of taurine metabolism. Importantly, 3-day oral administration of LDNPs increased bile salt hydrolase (BSH)-harboring bacteria that decreased conjugated bile acids and increased gut taurine concentration, which upregulated Tug1, leading to a suppression of intestinal miR194 expression and recovery of FXR activation. Activated FXR upregulated FGF15 signaling and subsequently reduced hepatic bile acid synthesis and lipogenesis and attenuated ALD. These protective effects of LDNPs were eliminated in intestinal FxrΔIEC and Fgf15-/- mice. We further showed that miR194 was upregulated, whereas BSH activity and taurine levels were decreased in fecal samples of patients with ALD.

CONCLUSIONS

Our results demonstrated that gut microbiota-mediated miR194 regulation contributes to ALD pathogenesis and to the protective effects of LDNPs through modulating intestinal FXR signaling.

Metabolic reprogramming of the intestinal microbiome with functional bile acid changes underlie the development of NAFLD

BACKGROUND AND AIMS

Bile acids are hepatic metabolites and have many properties considered to be relevant to the pathophysiology of NAFLD. Circulating levels of the intestinal microbiome-modified bile acid deoxycholate are increased in cirrhosis.

APPROACH AND RESULTS

To further elucidate the role of bile acids and intestinal microbiota linked to bile acids in progressively severe NAFLD, a multiomic study of feces including 16S rRNA sequencing, microbial transcriptomics and metabolomics was performed in a cohort with varying phenotypes of NAFLD. Several bile acids of microbial origin derived from deoxycholic acid (DCA) (glycodeoxycholate, 7-ketodeoxycholic acid, dehydrocholic acid) increased with disease activity and fibrosis stage. These were linked to increased expression of microbial bile salt hydrolase, bile acid operon (BaiCD) and hydroxysteroid dehydrogenases (hdhA) required for DCA and downstream metabolite synthesis providing a mechanistic basis for altered bile acid profiles with disease progression. Bacteroidetes and several genera of Lachnospiraceae family containing DCA generating genes increased with increasing disease severity, whereas several potentially beneficial microbes sensitive to antibacterial effects of DCA e.g., Ruminococcaceae were decreased. The clinical relevance of these data was confirmed in an independent cohort enrolled in a clinical trial for NASH where at entry DCA and its conjugates were associated with advanced fibrosis. In patients treated with placebo, DCA declined in those with fibrosis regression and increased in those with fibrosis progression. DCA rose further in those with compensated cirrhosis when they experienced decompensation.

CONCLUSIONS

These findings demonstrate a role for bile acids and the bile acid dependent microbiome in the development and progression of NAFLD and set the stage to leverage these findings for NASH biomarker development and for therapeutics.

New insights into the bile acid-based regulatory mechanisms and therapeutic perspectives in alcohol-related liver disease

Cholestasis is a key causative factor in alcohol-related liver disease (ALD) and variable degrees of cholestasis occur in all stages of ALD. However, the pathogenetic mechanisms and biomarkers associated with cholestasis are not well characterized. Cholestatic disease is marked by the disruption of bile acids (BA) transport and homeostasis. Consequently, in both human and experimental ALD, the disease shows a direct correlation with an imbalance in BA equilibrium, which in turn may also affect the severity of the disease. Modulation of BA metabolism or signaling pathways is increasingly considered as a potential therapeutic strategy for ALD in humans. In this paper, we highlight the key advances made in the past two decades in characterizing the molecular regulatory mechanisms of BA synthesis, enterohepatic circulation, and BA homeostasis. We summarize recent insights into the nature of the linkage between BA dysregulation and ALD, including the abnormal expression of genes involved in BA metabolism, abnormal changes in receptors that regulate BA metabolism, and disturbance in the gut flora engaged in BA metabolism caused by alcohol consumption. Additionally, we provide novel perspectives on the changes in BAs in various stages of ALD. Finally, we propose potential pharmacological therapies for ALD targeting BA metabolism and signaling.

Key Signaling in Alcohol-Associated Liver Disease: The Role of Bile Acids

Alcohol-associated liver disease (ALD) is a spectrum of diseases, the onset and progression of which are due to chronic alcohol use. ALD ranges, by increasing severity, from hepatic steatosis to alcoholic hepatitis (AH) and alcohol-associated cirrhosis (AC), and in some cases, can lead to the development of hepatocellular carcinoma (HCC). ALD continues to be a significant health burden and is now the main cause of liver transplantations in the United States. ALD leads to biological, microbial, physical, metabolic, and inflammatory changes in patients that vary depending on disease severity. ALD deaths have been increasing in recent years and are projected to continue to increase. Current treatment centers focus on abstinence and symptom management, with little in the way of resolving disease progression. Due to the metabolic disruption and gut dysbiosis in ALD, bile acid (BA) signaling and metabolism are also notably affected and play a prominent role in disease progression in ALD, as well as other liver disease states, such as non-alcoholic fatty liver disease (NAFLD). In this review, we summarize the recent advances in the understanding of the mechanisms by which alcohol consumption induces hepatic injury and the role of BA-mediated signaling in the pathogenesis of ALD.

Modulation of the Bile Acid Enterohepatic Cycle by Intestinal Microbiota Alleviates Alcohol Liver Disease

Reshaping the intestinal microbiota by the ingestion of fiber, such as pectin, improves alcohol-induced liver lesions in mice by modulating bacterial metabolites, including indoles, as well as bile acids (BAs). In this context, we aimed to elucidate how oral supplementation of pectin affects BA metabolism in alcohol-challenged mice receiving feces from patients with alcoholic hepatitis. Pectin reduced alcohol liver disease. This beneficial effect correlated with lower BA levels in the plasma and liver but higher levels in the caecum, suggesting that pectin stimulated BA excretion. Pectin modified the overall BA composition, favoring an augmentation in the proportion of hydrophilic forms in the liver, plasma, and gut. This effect was linked to an imbalance between hydrophobic and hydrophilic (less toxic) BAs in the gut. Pectin induced the enrichment of intestinal bacteria harboring genes that encode BA-metabolizing enzymes. The modulation of BA content by pectin inhibited farnesoid X receptor signaling in the ileum and the subsequent upregulation of Cyp7a1 in the liver. Despite an increase in BA synthesis, pectin reduced BA serum levels by promoting their intestinal excretion. In conclusion, pectin alleviates alcohol liver disease by modifying the BA cycle through effects on the intestinal microbiota and enhanced BA excretion.