Metabotropic Glutamate Receptor 5 in Natural Killer Cells Attenuates Liver Fibrosis by Exerting Cytotoxicity to Activated Stellate Cells.

BACKGROUND AND AIMS: The important roles of glutamate and metabotropic glutamate receptor 5 (mGluR5) in HSCs have recently been reported in various liver diseases; however, the mechanism linking the glutamine/glutamate metabolism and mGluR5 in liver fibrosis remains unclear. Here, we report that mGluR5 activation in natural killer (NK) cells attenuates liver fibrosis through increased cytotoxicity and interferon-γ (IFN-γ) production in both mice and humans. APPROACH AND RESULTS: Following 2-week injection of carbon tetrachloride (CCl4 ) or 5-week methionine-deficient and choline-deficient diet, liver fibrosis was more aggravated in mGluR5 knockout mice with significantly decreased frequency of NK cells compared with wild-type mice. Consistently, NK cell-specific mGluR5 knockout mice had aggravated CCl4 -induced liver fibrosis with decreased production of IFN-γ. Conversely, in vitro activation of mGluR5 in NK cells significantly increased the expression of anti-fibrosis-related genes including Ifng, Prf1 (perforin), and Klrk1 (killer cell lectin like receptor K1) and the production of IFN-γ through the mitogen-activated extracellular signal-regulated kinase/extracellular signal-related kinase pathway, contributing to the increased cytotoxicity against activated HSCs. However, we found that the uptake of glutamate was increased in activated HSCs, resulting in shortage of extracellular glutamate and reduced stimulation of mGluR5 in NK cells. Consequently, this could enable HSCs to evade NK cell cytotoxicity in advanced liver fibrosis. In vivo, pharmacologic activation of mGluR5 accelerated CCl4 -induced liver fibrosis regression by restoring NK cell cytotoxicity. In humans, mGluR5 activation enhanced the cytotoxicity of NK cells isolated from healthy donors, but not from patients with cirrhosis with significantly reduced mGluR5 expression in NK cells. CONCLUSIONS: mGluR5 plays important roles in attenuating liver fibrosis by augmenting NK cell cytotoxicity, which could be used as a potential therapeutic target for liver fibrosis.

Mitochondrial Double-Stranded RNA in Exosome Promotes Interleukin-17 Production Through Toll-Like Receptor 3 in Alcohol-associated Liver Injury.

BACKGROUND AND AIMS: Mitochondrial double-stranded RNA (mtdsRNA) and its innate immune responses have been reported previously; however, mtdsRNA generation and its effects on alcohol-associated liver disease (ALD) remain unclear. Here, we report that hepatic mtdsRNA stimulates toll-like receptor 3 (TLR3) in Kupffer cells through the exosome (Exo) to enhance interleukin (IL)-17A (IL-17A) production in ALD. APPROACH AND RESULTS: Following binge ethanol (EtOH) drinking, IL-17A production primarily increased in γδ T cells of wild-type (WT) mice, whereas the production of IL-17A was mainly facilitated by CD4+ T cells in acute-on-chronic EtOH consumption. These were not observed in TLR3 knockout (KO) or Kupffer cell-depleted WT mice. The expression of polynucleotide phosphorylase, an mtdsRNA-restricting enzyme, was significantly decreased in EtOH-exposed livers and hepatocytes of WT mice. Immunostaining revealed that mtdsRNA colocalized with the mitochondria in EtOH-treated hepatocytes from WT mice and healthy humans. Bioanalyzer analysis revealed that small-sized RNAs were enriched in EtOH-treated Exos (EtOH-Exos) rather than EtOH-treated microvesicles in hepatocytes of WT mice and humans. Quantitative real-time PCR and RNA sequencing analyses indicated that mRNA expression of mitochondrial genes encoded by heavy and light strands was robustly increased in EtOH-Exos from mice and humans. After direct treatment with EtOH-Exos, IL-1ß expression was significantly increased in WT Kupffer cells but not in TLR3 KO Kupffer cells, augmenting IL-17A production of γδ T cells in mice and humans. CONCLUSIONS: EtOH-mediated generation of mtdsRNA contributes to TLR3 activation in Kupffer cells through exosomal delivery. Consequently, increased IL-1ß expression in Kupffer cells triggers IL-17A production in γδ T cells at the early stage that may accelerate IL-17A expression in CD4+ T cells in the later stage of ALD. Therefore, mtdsRNA and TLR3 may function as therapeutic targets in ALD.

The New Cutoff Value of the Hepatic Venous Pressure Gradient on Predicting Long-Term Survival in Cirrhotic Patients.

BACKGROUND: This study aimed to determine the prognostic role of the categorized hemodynamic stage (HS) based on the hepatic venous pressure gradient (HVPG) in patients with portal hypertension. METHODS: Of 1,025 cirrhotic patients who underwent HVPG measurement, data on 572 non-critically-ill patients were collected retrospectively between 2008 and 2013. The following two HS categorizations were used: HS-1 (6-9, 10-12, 13-16, 17-20, and > 20 mmHg; designated as groups 1-5, respectively) and HS-2 (6-12, 13-20, and > 20 mmHg). Clinical characteristics, mortality rates, and prognostic predictors were analyzed according to the categorized HS. RESULTS: During the mean follow-up period of 25 months, 86 (15.0%) patients died. The numbers of deaths in HS-1 groups were 7 (6.3%), 7 (6.9%), 30 (18.0%), 20 (15.6%), and 22 (34.4%), respectively (P < 0.001). However, the traditional HVPG cutoffs of 10 and 16 mmHg did not improve the discrimination of mortality. In contrast, the mortality rates did differ significantly between the three HS-2 groups (P < 0.05). In the multivariate analysis, all models revealed that HS-2 was a common prognostic factor in predicting mortality. The mortality rates increased significantly according to HS-2 in patients with hypoalbuminemia (HVPG, 13-20 mmHg; hazard ratio [HR], 2.54 and HVPG > 20 mmHg; HR, 5.45) and intermediate model for end-stage liver disease (MELD) score (HVPG, 13-20 mmHg; HR, 3.86 and HVPG > 20 mmHg; HR, 8.77; P < 0.05). CONCLUSION: Categorizing HVPG values according to HS-2 is a useful prognostic modality in patients with portal hypertension and can play an independent role in predicting the prognosis in patients with hypoalbuminemia and an intermediate MELD score.

Psyllium fiber improves hangovers and inflammatory liver injury by inhibiting intestinal drinking.

Introduction: Excessive alcohol intake often results in hangovers and inflammatory liver damage, posing a significant health concern. Current treatment options for hangovers are still insufficient, highlighting the urgent need for new therapeutic approaches. Psyllium fiber (PF) is well-known for its gastrointestinal benefits, but its effect on hangovers is less explored. Methods: We utilized a mouse model with a single binge drinking (4 g/kg) to induce hangover and inflammatory liver injury. Intestine and liver injury were serologically and histologically estimated. Hangover symptoms were assessed using cylinder and footprint tests to objectively quantify hangover symptoms in mice. Results: Binge drinking significantly activated alcohol-metabolizing enzymes in the small intestine and liver, leading to inflammatory damage. Concurrently, there was a rise in alcohol metabolites such as acetaldehyde and acetone, which exhibited a positive correlation with hangover symptoms in mice. Interestingly, the oral administration of PF (100 mg/kg) alongside alcohol consumption significantly reduced the activity of these enzymes and lowered the levels of alcohol metabolites. Mice treated with PF exhibited a considerable improvement in hangover symptoms and a reduction in hepatic inflammation, compared to control groups. Furthermore, in vitro experiments using HepG2 cell lines and semipermeable membranes demonstrated that PF effectively inhibits alcohol absorption into the body. Discussion: In conclusion, PF demonstrates a potential protective effect against alcohol-induced hangover and liver injury by inhibiting the absorption of alcohol and lowering hangover-related alcohol metabolites. This study suggests that PF could serve as an effective therapeutic option for mitigating the adverse effects of excessive alcohol consumption.

Reassessing the Impact of Coffee Consumption on Liver Disease: Insights from a Large-Scale Cohort Study with IPTW Adjustment.

Coffee consumption is globally widespread and has become a lifestyle habit. This study investigated coffee consumption and liver-related survival in a large cohort of 455,870 individuals with UK biobank, categorized into without steatosis, metabolic dysfunction-associated steatotic liver disease (MASLD), and MASLD and increased alcohol intake (MetALD). Inverse probability of treatment weighting (IPTW) adjusted for confounding variables was used, followed by Kaplan-Meier analysis. Moderate coffee consumption (1-2 cups per day) was associated with lower all-cause mortality across the entire cohort, without the steatosis, MASLD (p < 0.0001), and MetALD cohorts (p = 0.0047 for pre-IPTW, p = 0.027 for post-IPTW). Before IPTW adjustment, consuming one or more cups of coffee per day appeared to significantly reduce liver-related mortality in the overall (p = 0.015) and MASLD cohorts (p = 0.011). However, post-IPTW application, no significant differences in liver-related mortality were observed between the coffee intake groups (p = 0.778, 0.319, 0.564, 0.238 for each group). While increased coffee consumption initially seemed to reduce liver-related mortality, after IPTW adjustment, only all-cause mortality significantly decreased (p < 0.0001 and p = 0.027). These findings suggest that previous studies might have overestimated the favorable effect of coffee intake on chronic liver disease due to confounding factors.

A Meta-Analysis of Preclinical Studies to Investigate the Effect of Panax ginseng on Alcohol-Associated Liver Disease.

Alcohol-associated liver disease (ALD) has become a major global concern, but the development of effective drugs remains a challenge despite numerous preclinical and clinical pieces of research on the effects of natural compounds. To address this, a meta-analysis was conducted on the efficacy of Panax ginseng for ALD based on preclinical studies. We identified 18 relevant studies from PubMed, Web of Science, and Cochrane Library database and evaluated their methodological quality using the Systematic Review Centre for Laboratory animal Experimentation tool. We analyzed the data using I2, p-values, and fixed effects models to assess overall efficacy and heterogeneity. The results of the meta-analysis suggested that Panax ginseng treatment is effective in reducing the levels of inflammatory markers associated with hepatic injury caused by ALD in animal experiments. Additionally, the administration of Panax ginseng was found to down-regulate inflammatory cytokines and attenuate lipid metabolism in ALD. Moreover, Panax ginseng markedly improved the antioxidant systems in ALD. Therefore, we concluded that Panax ginseng has the potential to be a promising therapeutic agent for ALD. Further research is needed to confirm these findings and to determine the optimal dosage and duration of treatment for patients with ALD.

Defecation alleviates hangover by terminating intestinal drinking.

Introduction: The concept of "intestinal drinking" in this study refers to the continued absorption of alcohol in the gastrointestinal tract until adequate defecation occurs. Methods: A longitudinal observation of hangover symptoms and alcohol metabolites in healthy humans following binge drinking was conducted. Results: The hangover symptoms resulting from binge alcohol consumption were relieved by defecation. Following the defecation process, not only the blood ethanol levels, but also the concentrations of blood acetaldehyde, methanol, and iso-propanol, exhibited significant reductions. Conclusions: This pilot study provides a different perspective for addressing hangovers and potentially mitigating the risks of alcoholic liver diseases.

Comprehensive transcriptomic analysis and meta-analysis identify therapeutic effects of N-acetylcysteine in nonalcoholic fatty liver disease.

Introduction: The continuous rise in the prevalence of nonalcoholic fatty liver disease (NAFLD) is emerging as a global health issue. Although the protective effects of N-acetylcysteine (NAC), an antioxidant, against various diseases have been reported, it is still unclear whether NAC has therapeutic potential in NAFLD. Thus, the present meta-analysis aimed to investigate the efficacy of NAC on NAFLD in preclinical studies. Methods: By searching PubMed, Web of Science, and Cochrane Library, 13 studies were included. The methodological quality was assessed based on the SYstematic Review Centre for Laboratory animal Experimentation guideline, and heterogeneity was evaluated with I 2 and p values. Publication bias was assessed by Egger's test and sensitivity analysis was performed. Results: The results showed that NAC treatment significantly improved systemic and hepatic lipid metabolism (p < 0.01), inflammation-related liver injury (p < 0.01), glucose intolerance (p < 0.05), and hepatic steatosis (p < 0.01) by restoring hepatic glutathione (GSH) (p < 0.05) and GSH reductase (p < 0.05) levels compared to controls in NAFLD-induced animals. Consistently, in bulk, single-cell, and spatial transcriptomics data, the abovementioned target pathways of NAC were strongly associated with NAFLD development in mice and patients. Conclusion: Our study suggests that NAC has therapeutic potential for NAFLD and should be considered for future clinical trials.

Catecholamine induces Kupffer cell apoptosis via growth differentiation factor 15 in alcohol-associated liver disease.

Chronic alcohol consumption often induces hepatic steatosis but rarely causes severe inflammation in Kupffer cells (KCs) despite the increased hepatic influx of lipopolysaccharide (LPS), suggesting the presence of a veiled tolerance mechanism. In addition to LPS, the liver is affected by several gut-derived neurotransmitters through the portal blood, but the effects of catecholamines on KCs have not been clearly explored in alcohol-associated liver disease (ALD). Hence, we investigated the regulatory roles of catecholamine on inflammatory KCs under chronic alcohol exposure. We discovered that catecholamine levels were significantly elevated in the cecum, portal blood, and liver tissues of chronic ethanol-fed mice. Increased catecholamines induced mitochondrial translocation of cytochrome P450 2E1 in perivenous hepatocytes expressing the ß2-adrenergic receptor (ADRB2), leading to the enhanced production of growth differentiation factor 15 (GDF15). Subsequently, GDF15 profoundly increased ADRB2 expression in adjacent inflammatory KCs to facilitate catecholamine/ADRB2-mediated apoptosis. Single-cell RNA sequencing of KCs confirmed the elevated expression of Adrb2 and apoptotic genes after chronic ethanol intake. Genetic ablation of Adrb2 or hepatic Gdf15 robustly decreased the number of apoptotic KCs near perivenous areas, exacerbating alcohol-associated inflammation. Consistently, we found that blood and stool catecholamine levels and perivenous GDF15 expression were increased in patients with early-stage ALD along with an increase in apoptotic KCs. Our findings reveal a novel protective mechanism against ALD, in which the catecholamine/GDF15 axis plays a critical role in KC apoptosis, and identify a unique neuro-metabo-immune axis between the gut and liver that elicits hepatoprotection against alcohol-mediated pathogenic challenges.

xCT-mediated glutamate excretion in white adipocytes stimulates interferon-γ production by natural killer cells in obesity.

Obesity-mediated hypoxic stress underlies inflammation, including interferon (IFN)-γ production by natural killer (NK) cells in white adipose tissue. However, the effects of obesity on NK cell IFN-γ production remain obscure. Here, we show that hypoxia promotes xCT-mediated glutamate excretion and C-X-C motif chemokine ligand 12 (CXCL12) expression in white adipocytes, resulting in CXCR4+ NK cell recruitment. Interestingly, this spatial proximity between adipocytes and NK cells induces IFN-γ production in NK cells by stimulating metabotropic glutamate receptor 5 (mGluR5). IFN-γ then triggers inflammatory activation of macrophages and augments xCT and CXCL12 expression in adipocytes, forming a bidirectional pathway. Genetic or pharmacological inhibition of xCT, mGluR5, or IFN-γ receptor in adipocytes or NK cells alleviates obesity-related metabolic disorders in mice. Consistently, patients with obesity showed elevated levels of glutamate/mGluR5 and CXCL12/CXCR4 axes, suggesting that a bidirectional pathway between adipocytes and NK cells could be a viable therapeutic target in obesity-related metabolic disorders.

Clinical impact of serum exosomal microRNA in liver fibrosis.

BACKGROUND/AIM: We investigated alterations in the expression of serum exosomal miRNAs with the progression of liver fibrosis and evaluated their clinical applicability as biomarkers. METHODS: This study prospectively enrolled 71 patients who underwent liver biopsy at an academic hospital in Korea. Exosomes were extracted from serum samples, followed by next-generation sequencing (NGS) of miRNAs and targeted real-time quantitative polymerase chain reaction. A model was derived to discriminate advanced fibrosis based on miRNA levels and the performance of this model was evaluated. Validation of the effect of miRNA on liver fibrosis in vitro was followed. RESULTS: NGS data revealed that exosomal miR-660-5p, miR-125a-5p, and miR-122 expression were changed significantly with the progression of liver fibrosis, of which miR-122 exhibited high read counts enough to be used as a biomarker. The level of exosomal miR-122 decreased as the pathologic fibrosis grade progressed and patients with biopsy-proven advanced fibrosis had significantly lower levels of exosomal miR-122 (P < 0.001) than those without advanced fibrosis. Exosomal miR-122 exhibited a fair performance in discriminating advanced fibrosis especially in combination with fibrosis-4 score and transient elastography. In a subgroup of patients with a non-viral etiology of liver disease, the performance of exosomal miR-122 as a biomarker was greatly improved. Inhibition of miR-122 expression increased the proliferation of the human hepatic stellate cell line, LX-2, and upregulated the expression of various fibrosis related proteins. CONCLUSION: Exosomal miR-122 may serve as a useful non-invasive biomarker for liver fibrosis, especially in patients with non-viral etiologies of chronic liver disease.

Esophageal Involvement and Determinants of Perception of Esophageal Symptoms Among South Koreans With Systemic Sclerosis.

Background/Aims: Our study aims to characterize esophageal motor function; evaluate the relationships among esophagogastroduodenoscopy (EGD), high-resolution manometry (HRM), and 24-hour esophageal multichannel intraluminal impedance monitoring combined with pH-metry (MII-pH); and elucidate the determinants of esophageal symptom perception in South Koreans with systemic sclerosis (SSc). Methods: We reviewed prospectively collected HRM (n = 46), EGD (n = 41), and MII-pH (n = 37) data from 46 consecutive patients with SSc (42 females; mean age 50.1 years) who underwent esophageal tests between June 2013 and September 2018. Results: The most common HRM diagnosis was normal (39.1%), followed by ineffective esophageal motility (23.9%) and absent contractility (21.7%). Erosive esophagitis was observed in 12.2% of total SSc patients, with a higher frequency in patients with absent contractility than those with normal motility (44.5% vs 0.0%, P = 0.01). Pathologic acid exposure was observed in 6 patients (20.0%) and positive symptom association in 18 patients (60.0%) in MII-pH tests of symptomatic patients. The proportion of SSc patients with esophageal symptoms not explained by reflux or mucosal or motor esophageal abnormalities was 33.0%. Conclusions: Esophageal involvement among South Koreans with SSc was characterized by heterogeneous motility patterns, with a higher prevalence of normal motility and lower prevalence of erosive esophagitis. Reflux hypersensitivity or functional heartburn might be partly attributed to the perception of esophageal symptoms in SSc patients who have neither gastroesophageal reflux disease nor esophageal dysmotility.

Ginsenoside F2 attenuates chronic-binge ethanol-induced liver injury by increasing regulatory T cells and decreasing Th17 cells.

BACKGROUND: Recently, beneficial roles of ginsenoside F2 (GF2), a minor constituent of Panax ginseng, have been demonstrated in diverse inflammatory diseases. However, its roles in alcoholic liver inflammation and injury have not been clearly understood. Here, we investigated the underlying mechanism by which GF2 ameliorated alcoholic liver injury. METHODS: To induce alcoholic liver injury, C57BL/6J wild type (WT) or interleukin (IL)-10 knockout (KO) mice were orally administered with ethanol (3 g/kg) or ethanol-containing GF2 (50 mg/kg) for 2 wk. Liver injury and infiltration of macrophages and neutrophils were evaluated by serum biochemistry and immunohistochemistry, respectively. The changes of hepatic immune cells were assessed by flow cytometry and polymerase chain reaction analysis. In vitro differentiation of naïve T cells was performed. RESULTS: GF2 treatment significantly attenuated alcoholic liver injury, in which infiltrations of inflammatory macrophages and neutrophils were decreased. Moreover, the frequencies of Foxp3+ regulatory T cells (Tregs) increased but IL-17-producing T (Th17) cells decreased in GF2-treated mice compared to controls. Furthermore, the mRNA expression of IL-10 and Foxp3 was significantly increased, whereas IL-17 mRNA expression was suppressed in GF2-treated mice. However, these beneficial roles of GF2 were not observed in GF2-treated IL-10 KO mice, suggesting a critical role of IL-10. Similarly, GF2 treatment suppressed differentiation of naïve T cells into Th17 cells by inhibiting RORγt expression and stimulating Foxp3 expression. CONCLUSION: The present study suggests that GF2 treatment attenuates alcoholic liver injury by increasing IL-10 expression and Tregs and decreasing IL-17 expression and Th17 cells.

Glutamate Signaling in Hepatic Stellate Cells Drives Alcoholic Steatosis.

Activation of hepatocyte cannabinoid receptor-1 (CB1R) by hepatic stellate cell (HSC)-derived 2-arachidonoylglycerol (2-AG) drives de novo lipogenesis in alcoholic liver disease (ALD). How alcohol stimulates 2-AG production in HSCs is unknown. Here, we report that chronic alcohol consumption induced hepatic cysteine deficiency and subsequent glutathione depletion by impaired transsulfuration pathway. A compensatory increase in hepatic cystine-glutamate anti-porter xCT boosted extracellular glutamate levels coupled to cystine uptake both in mice and in patients with ALD. Alcohol also induced the selective expression of metabotropic glutamate receptor-5 (mGluR5) in HSCs where mGluR5 activation stimulated 2-AG production. Consistently, genetic or pharmacologic inhibition of mGluR5 or xCT attenuated alcoholic steatosis in mice via the suppression of 2-AG production and subsequent CB1R-mediated de novo lipogenesis. We conclude that a bidirectional signaling operates at a metabolic synapse between hepatocytes and HSCs through xCT-mediated glutamate-mGluR5 signaling to produce 2-AG, which induces CB1R-mediated alcoholic steatosis.