The Integrated "Multiomics" Landscape at Peak Injury and Resolution From Alcohol-Associated Liver Disease

Alcohol-induced epigenetic changes prevent fibrosis resolution after alcohol cessation in miceresolution

BACKGROUND AND AIMS

Alcohol-associated liver disease is a major cause of alcohol-associated mortality. Recently, we identified hepatic demethylases lysine demethylase (KDM)5B and KDM5C as important epigenetic regulators of alcohol response in the liver. In this study, we aimed to investigate the role of KDM5 demethylases in alcohol-associated liver disease resolution.

APPROACH AND RESULTS

We showed that alcohol-induced liver steatosis rapidly resolved after alcohol cessation. In contrast, fibrosis persisted in the liver for up to 8 weeks after the end of alcohol exposure. Defects in fibrosis resolution were in part due to alcohol-induced KDM5B and KDM5C-dependent epigenetic changes in hepatocytes. Using cell-type-specific knockout mice, we found that adeno-associated virus-mediated knockout of KDM5B and KDM5C demethylases in hepatocytes at the time of alcohol withdrawal promoted fibrosis resolution. Single-cell ATAC sequencing analysis showed that during alcohol-associated liver disease resolution epigenetic cell states largely reverted to control conditions. In addition, we found unique epigenetic cell states distinct from both control and alcohol states and identified associated transcriptional regulators, including liver X receptor (LXR) alpha (α). In vitro and in vivo analysis confirmed that knockout of KDM5B and KDM5C demethylases promoted LXRα activity, likely through regulation of oxysterol biosynthesis, and this activity was critical for the fibrosis resolution process. Reduced LXR activity by small molecule inhibitors prevented fibrosis resolution in KDM5-deficient mice.

CONCLUSIONS

In summary, KDM5B and KDM5C demethylases prevent liver fibrosis resolution after alcohol cessation in part through suppression of LXR activity.

Direct effects of alcohol on gut-epithelial barrier: Unraveling the disruption of physical and chemical barrier of the gut-epithelial barrier that compromises the host-microbiota interface upon alcohol exposure

The development of alcohol-associated diseases is multifactorial, mechanism of which involves metabolic alteration, dysregulated immune response, and a perturbed intestinal host-environment interface. Emerging evidence has pinpointed the critical role of the intestinal host-microbiota interaction in alcohol-induced injuries, suggesting its contribution to disease initiation and development. To maintain homeostasis in the gut, the intestinal mucosa serves as the first-line defense against exogenous factors in the gastrointestinal tract, including dietary contents and the commensal microbiota. The gut-epithelial barrier comprises a physical barrier lined with a single layer of intestinal epithelial cells and a chemical barrier with mucus trapping host regulatory factors and gut commensal bacteria. In this article, we review recent studies pertaining to the disrupted gut-epithelial barrier upon alcohol exposure and examine how alcohol and its metabolism can affect the regulatory ability of intestinal epithelium.

Ablation of secreted phosphoprotein-1 in hepatocytes increases fatty acid oxidation and ameliorates alcohol-associated liver disease

BACKGROUND

Previously, we demonstrated that Spp1-/- mice exhibit a greater susceptibility to alcohol-induced liver injury than wild-type (WT) mice. Notably, alcohol triggers the expression of osteopontin (encoded by SPP1) in hepatocytes. However, the specific role of hepatocyte-derived SPP1 in either mitigating or exacerbating alcohol-associated liver disease (AALD) has yet to be elucidated. We hypothesized that hepatocyte-derived SPP1 plays a role in AALD by modulating the regulation of steatosis.

METHODS

We analyzed hepatic SPP1 expression using four publicly available datasets from patients with alcoholic hepatitis (AH). Additionally, we examined SPP1 expression in the livers of WT mice subjected to either a control or ethanol Lieber-DeCarli (LDC) diet for 6 weeks. We compared the relationship between SPP1 expression and significantly dysregulated genes in AH with controls using correlation and enrichment analyses. To investigate the specific impact of hepatocyte-derived SPP1, we generated hepatocyte-specific Spp1 knock-out (Spp1ΔHep) mice and subjected them to either a control or ethanol Lieber-DeCarli diet for 6 weeks.

RESULTS

Alcohol induced hepatic SPP1 expression in both humans and mice. Our analysis, focusing on genes correlated with SPP1, revealed an enrichment of fatty acid oxidation (FAO) in three datasets, and peroxisome proliferator-activated receptor signaling in one dataset. Notably, FAO genes correlating with SPP1 were downregulated in patients with AH. Ethanol-fed WT mice exhibited higher serum-free fatty acids (FFAs), adipose tissue lipolysis, and hepatic fatty acid (FA) transporters. In contrast, ethanol-fed Spp1ΔHep mice displayed lower liver triglycerides, FFAs, and serum alanine transaminase and greater FAO gene expression than WT mice, indicating a protective effect against AALD. Primary hepatocytes from Spp1∆Hep mice exhibited heightened expression of genes encoding proteins involved in FAO.

CONCLUSIONS

Alcohol induces the expression of SPP1 in hepatocytes, leading to impaired FAO and contributing to the development of AALD.

Prenatal alcohol exposure is associated with changes in placental gene co-expression networks

Alcohol consumption during pregnancy can result in a range of adverse postnatal outcomes among exposed children. However, identifying at-risk children is challenging given the difficulty to confirm prenatal alcohol exposure and the lack of early diagnostic tools. Placental surveys present an important opportunity to uncover early biomarkers to identify those at risk. Here, we report the first transcriptome-wide evaluation to comprehensively evaluate human placental pathways altered by fetal alcohol exposure. In a prospective longitudinal birth cohort in Cape Town, South Africa, we performed bulk tissue RNAseq in placenta samples from 32 women reporting heavy drinking during pregnancy and 30 abstainers/light drinkers. Weighted gene co-expression network analysis (WGCNA) and differential gene expression analysis were performed to assess associations between fetal alcohol exposure and placental gene expression patterns at a network-wide and single gene level, respectively. The results revealed altered expression in genes related to erythropoiesis and angiogenesis, which are implicated in established postnatal phenotypes related to alcohol exposure, including disruptions in iron homeostasis, growth, and neurodevelopment. The reported findings provide insights into the molecular pathways affected by prenatal alcohol exposure and highlight the potential of placental biomarkers for detecting and understanding the effects of alcohol on fetal development.

Anti-miR-96 and Hh pathway inhibitor MDB5 synergistically ameliorate alcohol-associated liver injury in mice

Alcohol-associated liver disease (ALD) and its complications are significant health problems worldwide. Several pathways in ALD are influenced by alcohol that drives inflammation, fatty acid metabolism, and fibrosis. Although miR-96 has become a key regulator in several liver diseases, its function in ALD remains unclear. In contrast, sonic hedgehog (SHH) signaling has a well-defined role in liver disease through influencing the activation of hepatic stellate cells (HSCs) and the inducement of liver fibrosis. In this study, we investigated the expression patterns of miR-96 and Hh molecules in mouse and human liver samples. We showed that miR-96 and Shh were upregulated in ethanol-fed mice. Furthermore, alcoholic hepatitis (AH) patient specimens also showed upregulated FOXO3a, TGF-β1, SHH, and GLI2 proteins. We then examined the effects of Hh inhibitor MDB5 and anti-miR-96 on inflammatory and extracellular matrix (ECM)-related genes. We identified FOXO3 and SMAD7 as direct target genes of miR-96. Inhibition of miR-96 decreased the expression of these genes in vitro in AML12 cells, HSC-T6 cells, and in vivo in ALD mice. Furthermore, MDB5 decreased HSCs activation and the expression of ECM-related genes, such as Gli1, Tgf-β1, and collagen. Lipid nanoparticles (LNPs) loaded with the combination of MDB5, and anti-miR-96 ameliorated ALD in mice. Our study demonstrated that this combination therapy could serve as a new therapeutic target for ALD.

Advancements in the Alcohol-Associated Liver Disease Model

Alcohol-associated liver disease (ALD) is an intricate disease that results in a broad spectrum of liver damage. The presentation of ALD can include simple steatosis, steatohepatitis, liver fibrosis, cirrhosis, and even hepatocellular carcinoma (HCC). Effective prevention and treatment strategies are urgently required for ALD patients. In previous decades, numerous rodent models were established to investigate the mechanisms of alcohol-associated liver disease and explore therapeutic targets. This review provides a summary of the latest developments in rodent models, including those that involve EtOH administration, which will help us to understand the characteristics and causes of ALD at different stages. In addition, we discuss the pathogenesis of ALD and summarize the existing in vitro models. We analyse the pros and cons of these models and their translational relevance and summarize the insights that have been gained regarding the mechanisms of alcoholic liver injury.

Intestinal Osteopontin Protects From Alcohol-induced Liver Injury by Preserving the Gut Microbiome and the Intestinal Barrier Function

BACKGROUND & AIMS

The gut-liver axis plays a key role in the pathogenesis of alcohol-associated liver disease (ALD). We demonstrated that Opn^-/- develop worse ALD than wild-type (WT) mice; however, the role of intestinal osteopontin (OPN) in ALD remains unknown. We hypothesized that overexpression of OPN in intestinal epithelial cells (IECs) could ameliorate ALD by preserving the gut microbiome and the intestinal barrier function.

METHODS

Opn^{KI IEC}, Opn^ΔIEC, and WT mice were fed control or ethanol Lieber-DeCarli diet for 6 weeks.

RESULTS

Opn^{KI IEC} but not Opn^ΔIEC mice showed improved intestinal barrier function and protection from ALD. There were less pathogenic and more beneficial bacteria in ethanol-fed Opn^{KI IEC} than in WT mice. Fecal microbiome transplant (FMT) from Opn^{KI IEC} to WT mice protected from ALD. FMT from ethanol-fed WT to Opn^{KI IEC} mice failed to induce ALD. Antimicrobial peptides, Il33, pSTAT3, aryl hydrocarbon receptor (Ahr), and tight-junction protein expression were higher in IECs from jejunum of ethanol-fed Opn^{KI IEC} than of WT mice. Ethanol-fed Opn^{KI IEC} showed more tryptophan metabolites and short-chain fatty acids in portal serum than WT mice. FMT from Opn^{KI IEC} to WT mice enhanced IECs Ahr and tight-junction protein expression. Oral administration of milk OPN replicated the protective effect of Opn^{KI IEC} mice in ALD.

CONCLUSION

Overexpression of OPN in IECs or administration of milk OPN maintain the intestinal microbiome by intestinal antimicrobial peptides. The increase in tryptophan metabolites and short-chain fatty acids signaling through the Ahr in IECs, preserve the intestinal barrier function and protect from ALD.