Roles of Gut Microbiota in Alcoholic Liver Disease

Latest Insights in Alcohol-Related Liver Disease and Alcoholic Hepatitis

Alcohol-related liver disease (ALD) is still to this date one of the leading causes of chronic liver disease globally. ALD comprises a wide disease spectrum, from the benign liver steatosis, to the life-threatening inflammatory acute phenotype of alcoholic hepatitis (AH) and ultimately, advanced liver fibrosis and cirrhosis. AH represents an acute inflammatory liver condition caused by prolonged high quantities of alcohol intake. Disease outcome varies from mild to severe, with systemic implication and high mortality. Although the pathogenesis has been extensively studied over the years, little progress has been made regarding therapeutic options. In over 50 years, steroid treatment is still the cornerstone therapeutic option, albeit having multiple limitations and a low success rate. On the other hand, important progress has been made regarding disease management and severity stratification with the implementation of different prognostic score. Although highly prevalent, AH still has many unmet needs, with a growing necessity for novel non-invasive diagnosis, prognosis biomarkers and impactful treatment options.

Therapeutic Role of Probiotics Against Environmental-Induced Hepatotoxicity: Mechanisms, Clinical Perspectives, Limitations, and Future

Hepatotoxicity is one of the biggest health challenges, particularly in the context of liver diseases, often aggravated by gut microbiota dysbiosis. The gut-liver axis has been regarded as a key idea in liver health. It indicates that changes in gut flora caused by various hepatotoxicants, including alcoholism, acetaminophen, carbon tetrachloride, and thioacetamide, can affect the balance of the gut's microflora, which may lead to increased dysbiosis and intestinal permeability. As a result, bacterial endotoxins would eventually enter the bloodstream and liver, causing hepatotoxicity and inducing inflammatory reactions. Many treatments, including liver transplantation and modern drugs, can be used to address these issues. However, because of the many side effects of these approaches, scientists and medical experts are still hoping for a therapeutic approach with fewer side effects and more positive results. Thus, probiotics have become well-known as an adjunctive strategy for managing, preventing, or reducing hepatotoxicity in treating liver injury. By altering the gut microbiota, probiotics offer a secure, non-invasive, and economical way to improve liver health in the treatment of hepatotoxicity. Through various mechanisms such as regulation of gut microbiota, reduction of pathogenic overgrowth, suppression of inflammatory mediators, modification of hepatic lipid metabolism, improvement in the performance of the epithelial barrier of the gut, antioxidative effects, and modulation of mucosal immunity, probiotics play their role in the treatment and prevention of hepatotoxicity. This review highlights the mechanistic effects of probiotics in environmental toxicants-induced hepatotoxicity and current findings on this therapeutic approach's experimental and clinical trials.

NLRP3 and Gut-Liver Axis: New Possibility for the Treatment of Alcohol-Associated Liver Disease

Alcohol-associated liver disease (ALD) is one of the most prevalent chronic diseases worldwide, with persistently high morbidity and mortality rates. Previous studies have identified NLRP3 inflammasome as a class of receptors of intracellular intrinsic immunity. These receptors can be activated by both intrinsic and extracellular danger signals, leading to the release of downstream pro-inflammatory factors, including interleukin IL-1β and IL-18. These vesicles are critical for maintaining host defense. Concurrently, researchers have identified a close relationship between the microbiome, gut-liver axis, and NLRP3 inflammasome with ALD. Consequently, the present study focus on the structure and activation of the NLRP3 inflammasome, the gut-liver axis, and intestinal microecological regulation, as well as the relationship between bile acid metabolism and the gut-liver axis. The objective of this study is to provide a foundation of knowledge and references for the development of targeted therapeutic interventions of ALD that are informed by the dynamic interplay between the NLRP3 inflammasome and the gut-liver axis.

Etiology-Dependent Microbiome Differences in Hepatocellular Carcinoma Development

Chronic liver disease is characterised by persistent inflammation, tissue damage, and regeneration, which leads to steatosis, fibrosis, and, lastly, cirrhosis and hepatocellular carcinoma (HCC). HCC, the most prevalent form of primary liver cancer, is one of the leading causes of cancer-related mortality worldwide. The gut microbiota plays a fundamental role in human physiology, and disturbances in its critical balance are widely recognised as contributors to various pathological conditions, including chronic liver diseases, both infectious and non-infectious in nature. Growing interest in microbiota research has recently shifted the focus towards the study of intratumoural microbiota, referred to as the "oncobiome", which can significantly impact the development and progression of HCC. In this review, we discuss existing research and provide an overview of the microbiota influence on viral hepatitis, particularly in shaping the progression of liver disease caused by the hepatitis B and hepatitis C viruses. We also explore microbial dysbiosis and its contribution to the silent and dangerous progression of non-alcoholic fatty liver disease. Additionally, we address the impact of alcohol on the liver and its interaction with the microbiota, tracing the pathway from inflammation to cirrhosis and cancer. The review emphasises the most common etiologies of hepatocellular carcinoma.

Elafibranor alleviates alcohol-related liver fibrosis by restoring intestinal barrier function

We discuss the article by Koizumi et al published in the World Journal of Gastroenterology. Our focus is on the therapeutic targets for fibrosis associated with alcohol-related liver disease (ALD) and the mechanism of action of elafibranor (EFN), a dual agonist of peroxisome proliferator-activated receptor α (PPARα) and peroxisome PPAR δ (PPARδ). EFN is currently in phase III clinical trials for the treatment of metabolic dysfunction-associated fatty liver disease and primary biliary cholangitis. ALD progresses from alcoholic fatty liver to alcoholic steatohepatitis (ASH), with chronic ASH eventually leading to fibrosis, cirrhosis, and, in some cases, hepatocellular carcinoma. The pathogenesis of ALD is driven by hepatic steatosis, oxidative stress, and acetaldehyde toxicity. Alcohol consumption disrupts lipid metabolism by inactivating PPARα, exacerbating the progression of ALD. EFN primarily activates PPARα, promoting lipolysis and β-oxidation in ethanol-stimulated HepG2 cells, which significantly reduces hepatic steatosis, apoptosis, and fibrosis in an ALD mouse model. Additionally, alcohol disrupts the gut-liver axis at several interconnected levels, contributing to a proinflammatory environment in the liver. EFN helps alleviate intestinal hyperpermeability by restoring tight junction protein expression and autophagy, inhibiting apoptosis and inflammatory responses, and enhancing intestinal barrier function through PPARδ activation.

Clinical outcomes and associated bacterial and fungal microbiota changes after high dose probiotic therapy for severe alcohol-associated hepatitis: An observational study

Alcohol-associated hepatitis (AH) is a critical condition with high mortality rates and is worsened by infections. Organ failure is strongly associated with intestinal dysbiosis. Emerging research suggests that gut microbiota modulation with probiotics can improve AH outcomes. This study investigated the clinical and microbiome effects of high-dose probiotic infusion (HDPI) compared with corticosteroid therapy (CST) and fecal microbiota transplantation (FMT) in severe AH. Patients with biopsy-proven severe-AH were enrolled from March 2019 to June 2020 and matched for age and disease severity. The patients received HDPI (n = 20), FMT (n = 16), or CST (n = 14). HDPI consists of a potent probiotic mix delivered via a nasoduodenal tube for 6 days. The primary outcome was survival at 90-days. Stool samples were subjected to 16S and 18S rRNA sequencing to assess significant bacterial and fungal taxa and their interactions at baseline and post treatment. At 90-days, survival rates were 55%, 64.3%, and 87.5% (HDPI, CST, respectively). HDPI did not beneficially impact bacterial alpha-diversity but significantly altered beta-diversity. Notably, the number of pathogenic bacteria, such as Bilophila and Roseburia increased. Fungal analysis revealed no significant changes in alpha diversity, but significant dissimilarities in beta diversity post-HDPI. New fungal genera such as Basidiomycota and Phragmoplastophyta have emerged, with significant deleterious expansion in fungal communities and damaging modifications between fungal-bacterial interactions. HDPI failed to outperform CST in improving the clinical outcomes of patients with severe AH. While HDPI influenced both bacterial and fungal microbiomes, it also led to the persistence of pathogenic communities. FMT showed superior survival outcomes, highlighting the urgent need for further controlled trials.

Research on gut microbiota characteristics of PBC patients at different ALBI grades based on machine learning

Background

The Albumin-Bilirubin (ALBI) score and grade are widely used to stratify patients with primary biliary cholangitis (PBC) into different disease statuses and risk levels. Recent studies have increasingly highlighted the role of gut microbiota in autoimmune liver diseases. This study aimed to investigate the differences in gut microbiota among PBC patients with varying ALBI grades.

Methods

Clinical data and stool samples were collected from outpatient and inpatient PBC patients between 2019 and 2022. Gut microbiota profiles were obtained using 16S rDNA sequencing of stool samples. We analyzed alpha diversity, beta diversity, LEfSe analysis and pathway function prediction. Additionally, various machine learning methods-including random forest (RF), lasso, gradient boosting machine (GBM) and support vector machine (SVM)-were employed to identify key features and to build and validate predictive models using bootstrap techniques.

Results

Clinical characteristics of ALBI grade 1 patients were comparatively better than those of ALBI grade 2 and 3 patients, including multiple laboratory indices. Gut microbiota analysis revealed that species richness and balance were higher in ALBI grade 1 patients. Both the comparison of the most abundant genera and the linear discriminant analysis (LDA) in LEfSe demonstrated that Lachnospira had a higher abundance and better discriminative ability in ALBI grade 1. Pathway function prediction indicated that sulfur metabolism was upregulated in higher ALBI grades. Furthermore, RF identified 10 specific genera, which were then used to build and validate models for discriminating PBC patients according to their ALBI grades. All three models, developed using different machine learning methods, demonstrated good discrimination ability (mean AUC 0.75-0.80).

Conclusion

This study highlights significant differences in gut microbiota profiles among PBC patients with different ALBI grades. The increased abundance of Lachnospira and upregulation of sulfur metabolism pathways are notable in patients with lower ALBI grades. The machine learning models developed based on gut microbiota features offer promising tools for discriminating between PBC patients with varying disease severities, which could enhance the precision of treatment strategies.

Nutritional and microbiota-based therapeutic interventions for alcohol-associated liver disease: From pathogenesis to therapeutic insights

Alcohol-associated liver disease (ALD) manifests as a consequence of prolonged and excessive alcohol consumption. This disease is closely associated with the interplay between gut health and liver function, which can lead to complex pathophysiological changes in the body. This review offers a comprehensive exploration of ALD's multifaceted nature, with a keen focus on its pathogenesis and the potential of nutritional and microbiota-based therapies. Insights derived from diverse case studies are utilized to shed light on how interventions can rebalance the gut microbiome and enhance liver function in ALD patients. Furthermore, the feasibility of liver transplantation and stem cell therapy as ultimate measures for ALD has been discussed, with acknowledgment of the inherent risks and challenges accompanying them. ALD's complexity underscores the necessity for a thorough understanding of its etiology and progression to devise effective treatments that mitigate its profound impact on an individual's health.

Potential mechanisms of traditional Chinese medicine in the treatment of liver cirrhosis: a focus on gut microbiota

Cirrhosis, a pathological stage that develops from various chronic liver diseases, is characterized by liver fibrosis, pseudolobular formation, and chronic inflammation. When it progresses to the decompensated phase, the mortality rate of cirrhosis can reach 80%. The role of gut microbiota in the progression of liver diseases has received significant attention. Numerous studies have shown that regulating gut microbiota has significant therapeutic effects on preventing and reversing liver cirrhosis. This article reviewed the mechanisms by which gut microbiota influence liver cirrhosis, explaining the effective therapeutic effects of traditional Chinese medicine. Through multi-directional regulation involving signaling pathways, gut microbiota diversity, and restoration of intestinal barrier function, traditional Chinese medicine has been promising in ameliorating liver cirrhosis, providing treatment options and pharmacological guidance for the occurrence and development of liver cirrhosis.

The potential role of Akkermansia muciniphila in liver health

Akkermansia muciniphila (A. muciniphila) is a 'star strain' that has attracted much attention in recent years. A. muciniphila can effectively regulate host metabolism, significantly affect host immune function, and play an important role in balancing host health and disease. As one of the organs most closely related to the gut (the two can communicate through the hepatic portal vein and bile duct system), liver is widely affected by intestinal microorganisms. A growing body of evidence suggests that A. muciniphila may alleviate liver-related diseases by improving the intestinal barrier, energy metabolism and regulating inflammation through its protein components and metabolites. This paper systematically reviews the key roles of A. muciniphila and its derivatives in maintaining liver health and improving liver disease.

Alcoholic Liver Disease in China: A Disease Influenced by Complex Social Factors That Should Not Be Neglected

Alcoholic liver disease (ALD) encompasses liver damage caused by chronic, excessive alcohol consumption. It manifests initially as marked hepatocellular steatosis and can progress to steatohepatitis, liver fibrosis, and cirrhosis. With China's rapid economic growth, coupled with a complex social background and the influence of a deleterious wine culture, the number of patients with ALD in China has increased significantly; the disease has become a social and health problem that cannot be ignored. In this review, we briefly described the social factors affecting ALD in China and elaborated on differences between alcoholic and other liver diseases in terms of complications (e.g., cirrhosis, upper gastrointestinal bleeding, hepatic encephalopathy, hepatocellular carcinoma, addiction, and other extrahepatic diseases). We also emphasized that ALD was more dangerous and difficult to treat than other liver diseases due to its complications, and that precise and effective treatment measures were lacking. In addition, we considered new ideas and treatment methods that may be generated in the future.

Severe Alcoholic Hepatitis-optimizing Medical Management: Whether we need a Liver Transplant

Severe alcoholic hepatitis is an ethical and clinical conundrum, wherein a liver transplant is often recommended. The adequacy of medical treatment versus the risk of recidivism after transplant is often debated. Complete recovery in 26 of 27 patients with severe alcoholic hepatitis was observed, and hence the data was retrospectively analysed. Methods: 27 patients, with severe alcoholic hepatitis, with Maddrey's discriminant function between 59.7 to 165.2 (mean 107.53), from June 2017 to May 2022, were followed up for between 11 months to 6 years. INR ranged from 1.99 to 3.7 (mean 2.709), and bilirubin was between 7.6 to 37.01, (mean 20.859). 8 patients had pre-existing liver cirrhosis. All patients received probiotics, nutritional support, physical rehabilitation, saturated fat (clarified butter/ desi ghee) supplementation, and anti-oxidant support. At 90 days, total bilirubin improved to between 1.0 to 6.8 (mean 2.625). ALT (Alanine Transaminase/ SGPT) ranged from 65 to 550 (mean ALT – 197); and AST (Aspartate Transaminase / SGOT) ranged from 58 to 810 (mean AST – 271.51). Both the AST and ALT were near normal after 90 days. One patient died due to bacterial pneumonia and sepsis; the remaining 26 patients made a complete recovery. All patients including those with diagnosed liver cirrhosis, had complete resolution of their ascites, and near-normal liver function. At the last outpatient visit, none had ascites, edema, or encephalopathy, and had normal albumin levels and INR values. Conclusion: Probiotics, nutrition, a saturated fat diet, and exercise; all have shown benefits in patients with severe alcoholic hepatitis when tested individually. Concomitant use of all the above has not been reported in the treatment of alcoholic hepatitis. The role of nutrition alone versus the contribution of nutritional deficiencies and the role of gut-derived endotoxemia need to be studied in detail. How to identify patients who need a transplant, if it is needed at all, remains a challenge.

Microbiota Therapy in Inflammatory Bowel Disease

Background

In both Crohn's disease (CD) and ulcerative colitis (UC), the two major forms of inflammatory bowel disease (IBD) the immune reaction is - at least partially - directed against components of the luminal microbiota of the gut. These immune responses as well as other factors contribute to a phenomenon frequently described as "dysbiosis" meaning an alteration of the composition of the colonic microbiota. To improve the dysbiosis and to restore the normal composition of the colonic microbiota, fecal microbiota transplantation (FMT) has been tested as a therapeutic option to induce and maintain remission in IBD patients.

Summary

This review will first discuss changes in the composition of the intestinal microbiota found in IBD patients and second the therapeutic potential of microbiological interventions for the treatment of these patients. FMT has been studied in several clinical trials in both, CD and UC. Reported results and subsequent meta-analyses indicate that FMT may be effective to induce remission in UC. However, the optimal route of FMT, the necessary number of administrations and the question whether life bacteria of freshly prepared stool is more effective than frozen are still unclear. Concepts associated with an optimization of FMT such as the "super donor concept" or the "consortia-approach" will be discussed to illustrate open questions and difficulties associated with microbiota therapy in IBD.

Key Messages

The microbiota composition in IBD patients shows significant alterations compared to healthy individuals termed as "dysbiosis". FMT and other therapeutic approaches to modify the microbiota composition have been studied in clinical trials in recent years. Efficacy has been shown in UC; however, many questions with respect to the optimization of microbiota therapy remain to be answered.

The Role of Cytokines in the Pathogenesis and Treatment of Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a major cause of chronic liver disease. This term covers a broad spectrum of liver lesions, from simple steatosis to alcoholic hepatitis and cirrhosis. The pathogenesis of ALD is multifactorial and not fully elucidated due to complex mechanisms related to direct ethanol toxicity with subsequent hepatic and systemic inflammation. The accumulation of pro-inflammatory cytokines and the reduction of anti-inflammatory cytokines promote the development and progression of ALD. To date, there are no targeted therapies to counter the progression of chronic alcohol-related liver disease and prevent acute liver failure. Corticosteroids reduce mortality by acting on the hepatic-systemic inflammation. On the other hand, several studies analyzed the effect of inhibiting pro-inflammatory cytokines and stimulating anti-inflammatory cytokines as potential therapeutic targets in ALD. This narrative review aims to clarify the role of the main cytokines involved in the pathogenesis and treatment of ALD.