Editor's Note: Acute-on-chronic liver failure (ACLF) is a complex syndrome characterized by acute deterioration of liver function in patients with chronic liver disease, accompanied by high mortality rates due to liver and extrahepatic organ failure. The short-term mortality rate of medical comprehensive treatment for ACLF can reach 50% to 90%. Given the high mortality and complex pathogenesis, research and treatment strategies for ACLF are particularly important. At the 2024 European Association for the Study of the Liver (EASL) Annual Meeting, Professor Hai Li from Renji Hospital, affiliated with Shanghai Jiao Tong University, provided insightful commentary on three significant research findings in the ACLF field. These studies delve into the roles and effects of immunosuppression and microbiome variations in acute decompensation (AD) of cirrhosis and ACLF, offering new perspectives for understanding the complex mechanisms of liver disease progression and potential targets for developing new ACLF treatment strategies.OS-011: The Immunosuppressive Role of Leukotoxin 9,10-DiHOME Derived from Linoleic Acid in Patients with Acute-on-Chronic Liver Failure
Research Background and Purpose: Acute decompensation (AD) of cirrhosis is characterized by persistent systemic inflammation, which promotes the development of organ failure, linked to the high short-term mortality rate of acute-on-chronic liver failure (ACLF). In this context, inflammation-associated immunosuppression is a key factor leading to secondary infections and multiple organ dysfunction. This study explores the characteristics of immune-regulatory lipid mediators in AD cirrhosis patients (with or without ACLF) and their impact on leukocyte function.
Research Methods: Using liquid chromatography-tandem mass spectrometry analysis, the study characterized 101 lipid mediators in the plasma of 84 AD cirrhosis patients without ACLF (divided into stable decompensated cirrhosis, unstable decompensated cirrhosis, and high-risk patients prone to ACLF) and 9 AD cirrhosis patients with ACLF. The study included 31 healthy donors for comparison. Changes in polymorphonuclear leukocyte function, including degranulation, respiratory burst capability, and phagocytosis, were assessed via bioassays. Cytokine secretion, autophagic response, and mitochondrial dynamics in mononuclear leukocytes were determined using high-throughput multiplex MILLIPLEX assays and Western blot analysis.
Research Results: Exploratory analysis of baseline lipid mediator characteristics revealed higher levels of linoleic acid (LA)-derived lipid mediators in the plasma of AD cirrhosis patients compared to healthy controls. Multiple tests identified 9,10-dihydroxy-12-octadecenoic acid (9,10-DiHOME), an LA-derived lipid mediator, as the only one capable of distinguishing between AD patients who developed ACLF and those who did not. Plasma levels of 9,10-DiHOME increased with disease severity, significantly elevated during active infection in AD patients, and peaked at ACLF onset. Additionally, soluble epoxide hydrolase (sEH), responsible for the biosynthesis of 9,10-DiHOME, was significantly upregulated in the mononuclear leukocytes of AD patients. In polymorphonuclear leukocyte bioassays, 9,10-DiHOME impaired degranulation, phagocytosis, and respiratory burst capability. In mononuclear leukocyte bioassays, 9,10-DiHOME significantly inhibited cytokine secretion and altered autophagic response and mitochondrial dynamics.
Research Conclusion: Leukotoxin 9,10-DiHOME impairs immune cell responses, suggesting that elevated levels of this lipid mediator in AD cirrhosis patients may increase susceptibility to bacterial infections and induce ACLF. The findings indicate that sEH could be a potential therapeutic target for treating AD.
Expert Commentary: The study elucidates potential mechanisms of immunosuppression in ACLF patients from the perspective of lipid metabolism. Targeted metabolomic analysis of 101 lipid metabolites in 19 pre-ACLF and ACLF patients with underlying cirrhosis revealed significantly elevated levels of leukotoxin, including 9,10-DiHOME, in ACLF patients compared to 53 non-ACLF cirrhosis patients. 9,10-DiHOME inhibits cytokine release from mononuclear cells, reduces cell phagocytic function, and affects mitochondrial functionality. The study further found that soluble epoxide hydrolase (sEH), the rate-limiting enzyme for 9,10-DiHOME synthesis, is significantly elevated in ACLF patients. Therefore, the study suggests that inhibiting sEH could reduce 9,10-DiHOME production, mitigate immunosuppression, enhance infection resistance, and reduce inflammation in ACLF patients.
OS-071-YI: Microbiome Variations and Temporal Dynamics in Multiple Body Sites of Patients with Decompensated Cirrhosis
Research Background and Purpose: Bacterial infections and translocation are major triggers for acute decompensation (AD) of cirrhosis and the development of acute-on-chronic liver failure (ACLF). This study explores microbiome variations across different body sites in cirrhosis patients and their association with the progression of cirrhosis to ACLF.
Research Methods: The study included 93 decompensated cirrhosis patients from the PREDICT study, divided into four groups based on disease course: stable decompensated cirrhosis (SDC), unstable decompensated cirrhosis (UDC), pre-ACLF, and ACLF at admission. Using optimized 16S metabarcoding for low biomass and complex microbiomes, the researchers analyzed microbiome variations in 11 anatomical sites, including blood smears, saliva, upper GI mucosal biopsies, lower GI mucosal biopsies, and feces. The relationships between microbiomes and clinical parameters and disease outcomes were analyzed using PLS-DA, ANCOM II, and SECOM frameworks and tools.
Research Results: The analysis revealed that microbiome community alpha and beta diversity depended on the sample site. Notably, microbiome load in blood smears of non-ACLF patients (SDC, UDC, and pre-ACLF) increased with the severity of cirrhosis (P=0.023). Longitudinal samples from different body sites of patients who developed ACLF showed increased microbiome dissimilarity, potentially due to bacterial translocation. Significant correlations between different genera in various GI sites suggested bacterial migration. The relative abundance of Lactobacillus in saliva and upper GI positively correlated with ACLF severity. Increased Pseudomonas levels in the upper GI were significantly associated with bacterial infection as an AD trigger. In the lower GI, Enterobacteriaceae abundance correlated with MELD-Na and CLIF-C AD scores. Enterobacteriaceae significantly increased in duodenal biopsies of ACLF patients compared to pre-ACLF patients, even after controlling for confounding factors like medication.
Research Conclusion: The study reveals that unique microbiome characteristics in different body sites increase the risk of ACLF progression. Different genera are associated with clinical events, with microbiomes and bacterial translocation in the small intestine and blood smears appearing to influence ACLF development.
Expert Commentary: The European PREDICT study continuously analyzed microbiomes at multiple time points in various body sites, including peripheral blood mononuclear cell layers, upper and lower GI mucosa, feces, and saliva, in 93 stable cirrhosis, unstable cirrhosis, pre-ACLF, and ACLF patients. The study found that microbiome content in the peripheral blood mononuclear cell layer significantly increased from stable to unstable to pre-ACLF patients. Microbiome dissimilarity in these body sites was significantly higher in ACLF patients. Lactobacillus abundance in the upper GI and saliva correlated with ACLF severity. Pseudomonas levels significantly increased in the upper GI of cirrhotic AD patients with bacterial infections. Enterobacteriaceae abundance in the lower GI correlated with cirrhosis severity (MELD or CLIF-AD scores), and duodenal Enterobacteriaceae levels significantly increased in ACLF patients compared to pre-ACLF patients, even after antibiotic use.
OS-072-YI: Identifying the Severity of Fatty Liver Disease: A Multi-Omics Analysis
Research Background and Purpose: Fatty liver disease (FLD) ranges from simple steatosis to end-stage liver disease. Despite detailed studies on specific aspects of FLD progression, a comprehensive understanding of its driving mechanisms remains lacking. To uncover potential drivers, this study conducted a multi-omics analysis across seven cohorts, exploring the complexity of omics features from healthy to end-stage liver disease of varying severity.
Research Methods: The study integrated seven clinical cohorts from Denmark and Germany, categorizing participants into six disease severity groups: A) healthy individuals without metabolic or alcohol-related risk factors; B) F0-F1 (at least one risk factor); C) F2; D) F3-F4 (including MELD-Na<10); E) MELD-Na 10-15; and F) MELD-Na>15. Linear regression was used to analyze stool metagenomics, targeted stool metabolomics, targeted plasma inflammatory markers, targeted and untargeted plasma metabolomics, and plasma lipidomics. Clustering of omics data revealed dynamic patterns across the disease spectrum, identifying features with linear changes and those stabilizing at later stages.
Research Results: The study included 854 FLD patients, grouped by disease severity (A: 76; B: 171; C: 151; D: 273; E: 81; F: 102). Dynamic clustering identified omics features with linear changes in disease severity, distinguishing between varying FLD stages. Core microbiome, metabolome, and inflammatory markers were affected early in disease progression. Pathobionts, such as Veillonella and Atopobium, and beneficial bacteria, like Blautia, showed differential expression. Mucosal inflammation markers (e.g., plasma TNF-α, MIP-1β, IL-6, IL-1β) and distinct metabolomic and lipidomic changes were observed in early stages. Late-stage disease was characterized by metabolic changes in aromatic amino acid (tryptophan, phenylalanine, tyrosine) metabolism. The multi-omics approach elucidated specific pathways disrupted in FLD, aiding in understanding and guiding future research.
Research Conclusion: The study presents a holistic view of FLD progression, integrating microbiome, metabolomic, inflammatory, and lipidomic data. Identifying stage-specific changes provides insight into FLD mechanisms and potential therapeutic targets, highlighting the importance of a comprehensive approach to understanding liver disease.
Expert Commentary: The multi-omics approach uncovers distinct microbiome, metabolomic, and inflammatory markers associated with various stages of fatty liver disease (FLD), offering potential targets for future therapeutic interventions. This study emphasizes the necessity of a comprehensive understanding of FLD progression to develop effective treatments.
Conclusion: The research findings presented at EASL 2024 provide valuable insights into the complex mechanisms of liver disease progression, focusing on the roles of immunosuppression and microbiome variations. Understanding these factors can inform the development of targeted therapies for acute-on-chronic liver failure and other liver diseases, ultimately improving patient outcomes.
