The pathophysiology of MASLD: an immunometabolic perspective.

INTRODUCTION: Metabolic-associated liver diseases have emerged pandemically across the globe and are clinically related to metabolic disorders such as obesity and type 2 diabetes. The new nomenclature and definition (i.e. metabolic dysfunction-associated steatotic liver disease - MASLD; metabolic dysfunction-associated steatohepatitis - MASH) reflect the nature of these complex systemic disorders, which are characterized by inflammation, gut dysbiosis and metabolic dysregulation. In this review, we summarize recent advantages in understanding the pathophysiology of MASLD, which we parallel to emerging therapeutic concepts. AREAS COVERED: We summarize the pathophysiologic concepts of MASLD and its transition to MASH and subsequent advanced sequelae of diseases. Furthermore, we highlight how dietary constituents, microbes and associated metabolites, metabolic perturbations, and immune dysregulation fuel lipotoxicity, hepatic inflammation, liver injury, insulin resistance, and systemic inflammation. Deciphering the intricate pathophysiologic processes that contribute to the development and progression of MASLD is essential to develop targeted therapeutic approaches to combat this escalating burden for health-care systems. EXPERT OPINION: The rapidly increasing prevalence of metabolic dysfunction-associated steatotic liver disease challenges health-care systems worldwide. Understanding pathophysiologic traits is crucial to improve the prevention and treatment of this disorder and to slow progression into advanced sequelae such as cirrhosis and hepatocellular carcinoma.

Apelin and the gut microbiome: Potential interaction in human MASLD.

BACKGROUND: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a leading cause of chronic liver disease with increasing numbers worldwide. Adipokines like apelin (APLN) can act as key players in the complex pathophysiology of MASLD. AIMS: Investigating the role of APLN in MASLD. METHODS: Fecal and blood samples were collected in a MASLD cohort and healthy controls (HC). MASLD patients with liver fibrosis and MASLD-associated hepatocellular carcinoma (HCC) were included into the study. Systemic concentration of Apelin, Apelin receptor (APLNR) and circulating cytokines were measured in serum samples. RESULTS: Apelin concentration correlated with the Fib-4 score and was elevated in MASLD patients (mild fibrosis, mF (Fib-4 <3.25) and severe fibrosis, sF (Fib-4 >3.25)) as well as in MASLD-associated HCC patients compared to HC. In accordance APLNR and circulating cytokines were also elevated in mF and sF. In contrast apelin levels were negatively associated with liver survival at three and five years. Changes in taxa composition at phylum level showed an increase of Enterobactericae, Prevotellaceae and Lactobacillaceae in patients with sF compared to mF. We could also observe an association between apelin concentrations and bacterial lineages (phyla). CONCLUSIONS: Circulating apelin is associated with liver fibrosis and HCC. In addition, there might exist an interaction between systemic apelin and the gut microbiome.

24-Norursodeoxycholic acid ameliorates experimental alcohol-related liver disease and activates hepatic PPARγ.

Background & Aims: Alcohol-related liver disease (ALD) is a global healthcare challenge with limited treatment options. 24-Norursodeoxycholic acid (NorUDCA) is a synthetic bile acid with anti-inflammatory properties in experimental and human cholestatic liver diseases. In the present study, we explored the efficacy of norUDCA in experimental ALD. Methods: NorUDCA was tested in a preventive and therapeutic setting in an experimental ALD model (Lieber-DeCarli diet enriched with ethanol). Liver disease was phenotypically evaluated using histology and biochemical methods, and anti-inflammatory properties and peroxisome proliferator-activated receptor gamma activation by norUDCA were evaluated in cellular model systems. Results: NorUDCA administration ameliorated ethanol-induced liver injury, reduced hepatocyte death, and reduced the expression of hepatic pro-inflammatory cytokines including tumour necrosis factor (Tnf), Il-1ß, Il-6, and Il-10. NorUDCA shifted hepatic macrophages towards an anti-inflammatory M2 phenotype. Further, norUDCA administration altered the composition of the intestinal microbiota, specifically increasing the abundance of Roseburia, Enterobacteriaceae, and Clostridum spp. In a therapeutic model, norUDCA also ameliorated ethanol-induced liver injury. Moreover, norUDCA suppressed lipopolysaccharide-induced IL-6 expression in human peripheral blood mononuclear cells and evoked peroxisome proliferator-activated receptor gamma activation. Conclusions: NorUDCA ameliorated experimental ALD, protected against hepatic inflammation, and affected gut microbial commensalism. NorUDCA could serve as a novel therapeutic agent in the future management of patients with ALD. Impact and implications: Alcohol-related liver disease is a global healthcare concern with limited treatment options. 24-Norursodeoxycholic acid (NorUDCA) is a modified bile acid, which was proven to be effective in human cholestatic liver diseases. In the present study, we found a protective effect of norUDCA in experimental alcoholic liver disease. For patients with ALD, norUDCA could be a potential new treatment option.

Non-alcoholic fatty liver disease: pathophysiological concepts and treatment options.

The prevalence of non-alcoholic fatty liver disease (NAFLD) is continually increasing due to the global obesity epidemic. NAFLD comprises a systemic metabolic disease accompanied frequently by insulin resistance and hepatic and systemic inflammation. Whereas simple hepatic steatosis is the most common disease manifestation, a more progressive disease course characterized by liver fibrosis and inflammation (i.e. non-alcoholic steatohepatitis) is present in 10-20% of affected individuals. NAFLD furthermore progresses in a substantial number of patients towards liver cirrhosis and hepatocellular carcinoma. Whereas this disease now affects almost 25% of the world's population and is mainly observed in obesity and type 2 diabetes, NAFLD also affects lean individuals. Pathophysiology involves lipotoxicity, hepatic immune disturbances accompanied by hepatic insulin resistance, a gut dysbiosis, and commonly hepatic and systemic insulin resistance defining this disorder a prototypic systemic metabolic disorder. Not surprisingly many affected patients have other disease manifestations, and indeed cardiovascular disease, chronic kidney disease, and extrahepatic malignancies are all contributing substantially to patient outcome. Weight loss and lifestyle change reflect the cornerstone of treatment, and several medical treatment options are currently under investigation. The most promising treatment strategies include glucagon-like peptide 1 receptor antagonists, sodium-glucose transporter 2 inhibitors, Fibroblast Growth Factor analogues, Farnesoid X receptor agonists, and peroxisome proliferator-activated receptor agonists. Here, we review epidemiology, pathophysiology, and therapeutic options for NAFLD.

A gut bacterial signature in blood and liver tissue characterizes cirrhosis and hepatocellular carcinoma.

BACKGROUND: HCC is the leading cause of cancer in chronic liver disease. A growing body of experimental mouse models supports the notion that gut-resident and liver-resident microbes control hepatic immune responses and, thereby, crucially contribute to liver tumorigenesis. However, a comprehensive characterization of the intestinal microbiome in fueling the transition from chronic liver disease to HCC in humans is currently missing. METHODS: Here, we profiled the fecal, blood, and liver tissue microbiome of patients with HCC by 16S rRNA sequencing and compared profiles to nonmalignant cirrhotic and noncirrhotic NAFLD patients. RESULTS: We report a distinct bacterial profile, defined from 16S rRNA gene sequences, with reduced α-and ß-diversity in the feces of patients with HCC and cirrhosis compared to NAFLD. Patients with HCC and cirrhosis exhibited an increased proportion of fecal bacterial gene signatures in the blood and liver compared to NAFLD. Differential analysis of the relative abundance of bacterial genera identified an increased abundance of Ruminococcaceae and Bacteroidaceae in blood and liver tissue from both HCC and cirrhosis patients compared to NAFLD. Fecal samples from cirrhosis and HCC patients both showed a reduced abundance for several taxa, including short-chain fatty acid-producing genera, such as Blautia and Agathobacter. Using paired 16S rRNA and transcriptome sequencing, we identified a direct association between gut bacterial genus abundance and host transcriptome response within the liver tissue. CONCLUSIONS: Our study indicates perturbations of the intestinal and liver-resident microbiome as a critical determinant of patients with cirrhosis and HCC.

Interleukin-11 drives human and mouse alcohol-related liver disease.

OBJECTIVE: Alcoholic hepatitis (AH) reflects acute exacerbation of alcoholic liver disease (ALD) and is a growing healthcare burden worldwide. Interleukin-11 (IL-11) is a profibrotic, proinflammatory cytokine with increasingly recognised toxicities in parenchymal and epithelial cells. We explored IL-11 serum levels and their prognostic value in patients suffering from AH and cirrhosis of various aetiology and experimental ALD. DESIGN: IL-11 serum concentration and tissue expression was determined in a cohort comprising 50 patients with AH, 110 patients with cirrhosis and 19 healthy volunteers. Findings were replicated in an independent patient cohort (n=186). Primary human hepatocytes exposed to ethanol were studied in vitro. Ethanol-fed wildtype mice were treated with a neutralising murine IL-11 receptor-antibody (anti-IL11RA) and examined for severity signs and markers of ALD. RESULTS: IL-11 serum concentration and hepatic expression increased with severity of liver disease, mostly pronounced in AH. In a multivariate Cox-regression, a serum level above 6.4 pg/mL was a model of end-stage liver disease independent risk factor for transplant-free survival in patients with compensated and decompensated cirrhosis. In mice, severity of alcohol-induced liver inflammation correlated with enhanced hepatic IL-11 and IL11RA expression. In vitro and in vivo, anti-IL11RA reduced pathogenic signalling pathways (extracellular signal-regulated kinases, c-Jun N-terminal kinase, NADPH oxidase 4) and protected hepatocytes and murine livers from ethanol-induced inflammation and injury. CONCLUSION: Pathogenic IL-11 signalling in hepatocytes plays a crucial role in the pathogenesis of ALD and could serve as an independent prognostic factor for transplant-free survival. Blocking IL-11 signalling might be a therapeutic option in human ALD, particularly AH.

Nonalcoholic Fatty Liver Disease and the Intestinal Microbiome: An Inseparable Link.

Nonalcoholic fatty liver disease (NAFLD) particularly affects patients with type 2 diabetes and obesity. The incidence of NAFLD has increased significantly over the last decades and is now pandemically across the globe. It is a complex systemic disease comprising hepatic lipid accumulation, inflammation, lipotoxicity, gut dysbiosis, and insulin resistance as main features and with the potential to progress to cirrhosis and hepatocellular carcinoma (HCC). In numerous animal and human studies the gut microbiota plays a key role in the pathogenesis of NAFLD, NAFLD-cirrhosis and NAFLD-associated HCC. Lipotoxicity is the driver of inflammation, insulin resistance, and liver injury. Likewise, western diet, obesity, and metabolic disorders may alter the gut microbiota, which activates innate and adaptive immune responses and fuels hereby hepatic and systemic inflammation. Indigestible carbohydrates are fermented by the gut microbiota to produce important metabolites, such as short-chain fatty acids and succinate. Numerous animal and human studies suggested a pivotal role of these metabolites in the progression of NAFLD and its comorbidities. Though, modification of the gut microbiota and/or the metabolites could even be beneficial in patients with NAFLD, NAFLD-cirrhosis, and NAFLD-associated HCC. In this review we collect the evidence that exogenous and endogenous hits drive liver injury in NAFLD and propel liver fibrosis and the progressing to advanced disease stages. NAFLD can be seen as the product of a complex interplay between gut microbiota, the immune response and metabolism. Thus, the challenge will be to understand its pathogenesis and to develop new therapeutic strategies.

MAFLD: what 2 years of the redefinition of fatty liver disease has taught us.

Metabolic dysfunction-associated fatty liver disease (MAFLD) has appeared as the leading liver disease worldwide. Whereas the terminology nonalcoholic fatty liver disease (NAFLD) mainly reflected a negative selection and exclusion of alcohol-related liver disease (ALD), the new definition made its focus on the association of MAFLD with overweight/obesity, type 2 diabetes and metabolic risk factors especially also in normal weight/lean subjects. Several studies from the past 2 years have now used the new definition and have provided substantial information that this new definition might be accurate. Studies from the past 2 years have provided evidence that the new definition might be especially advantageous in the characterization and identification of patients with significant fibrosis. This has also been demonstrated in the well-known Rotterdam study in which the MAFLD-only group showed a higher rate of fibrosis and liver stiffness. MAFLD might also be able to predict all-cause mortality as demonstrated in the Third National Health and Nutrition Examination Survey. Furthermore, MAFLD might improve characterization of the cardiovascular risk of this patient population. As the term MAFLD has not yet been accepted universally, it remains important to coordinate efforts globally to adapt to this new definition and especially involve all specialities dealing with metabolic disorders such as diabetologists to further improve its definition and to prepare the medical community for its future use. The aim of this review is to summarize and critically address evidence emerging over the past 2 years that usage of the term MAFLD could be helpful in daily clinical practice.

Recovery of Bacteroides thetaiotaomicron ameliorates hepatic steatosis in experimental alcohol-related liver disease.

Alcohol-related liver disease (ALD) is a major cause of liver disease and represents a global burden, as treatment options are scarce. Whereas 90% of ethanol abusers develop alcoholic fatty liver disease (AFLD), only a minority evolves to steatohepatitis and cirrhosis. Alcohol increases lipogenesis and suppresses lipid-oxidation implying steatosis, although the key role of intestinal barrier integrity and microbiota in ALD has recently emerged. Bacteroides thetaiotaomicron (Bt) is a prominent member of human and murine intestinal microbiota, and plays important functions in metabolism, gut immunity, and mucosal barrier. We aimed to investigate the role of Bt in the genesis of ethanol-induced liver steatosis. Bt DNA was measured in feces of wild-type mice receiving a Lieber-DeCarli diet supplemented with an increase in alcohol concentration. In a second step, ethanol-fed mice were orally treated with living Bt, followed by analysis of intestinal homeostasis and histological and biochemical alterations in the liver. Alcohol feeding reduced Bt abundance, which was preserved by Bt oral supplementation. Bt-treated mice displayed lower hepatic steatosis and triglyceride content. Bt restored mucosal barrier and reduced LPS translocation by enhancing mucus thickness and production of Mucin2. Furthermore, Bt up-regulated Glucagon-like peptide-1 (GLP-1) expression and restored ethanol-induced Fibroblast growth factor 15 (FGF15) down-regulation. Lipid metabolism was consequently affected as Bt administration reduced fatty acid synthesis (FA) and improved FA oxidation and lipid exportation. Moreover, treatment with Bt preserved the mitochondrial fitness and redox state in alcohol-fed mice. In conclusion, recovery of ethanol-induced Bt depletion by oral supplementation was associated with restored intestinal homeostasis and ameliorated experimental ALD. Bt could serve as a novel probiotic to treat ALD in the future.

PUFA-Induced Metabolic Enteritis as a Fuel for Crohn's Disease.

BACKGROUND & AIMS: Crohn's disease (CD) globally emerges with Westernization of lifestyle and nutritional habits. However, a specific dietary constituent that comprehensively evokes gut inflammation in human inflammatory bowel diseases remains elusive. We aimed to delineate how increased intake of polyunsaturated fatty acids (PUFAs) in a Western diet, known to impart risk for developing CD, affects gut inflammation and disease course. We hypothesized that the unfolded protein response and antioxidative activity of glutathione peroxidase 4 (GPX4), which are compromised in human CD epithelium, compensates for metabolic perturbation evoked by dietary PUFAs. METHODS: We phenotyped and mechanistically dissected enteritis evoked by a PUFA-enriched Western diet in 2 mouse models exhibiting endoplasmic reticulum (ER) stress consequent to intestinal epithelial cell (IEC)-specific deletion of X-box binding protein 1 (Xbp1) or Gpx4. We translated the findings to human CD epithelial organoids and correlated PUFA intake, as estimated by a dietary questionnaire or stool metabolomics, with clinical disease course in 2 independent CD cohorts. RESULTS: PUFA excess in a Western diet potently induced ER stress, driving enteritis in Xbp1-/-IEC and Gpx4+/-IEC mice. ω-3 and ω-6 PUFAs activated the epithelial endoplasmic reticulum sensor inositol-requiring enzyme 1α (IRE1α) by toll-like receptor 2 (TLR2) sensing of oxidation-specific epitopes. TLR2-controlled IRE1α activity governed PUFA-induced chemokine production and enteritis. In active human CD, ω-3 and ω-6 PUFAs instigated epithelial chemokine expression, and patients displayed a compatible inflammatory stress signature in the serum. Estimated PUFA intake correlated with clinical and biochemical disease activity in a cohort of 160 CD patients, which was similarly demonstrable in an independent metabolomic stool analysis from 199 CD patients. CONCLUSIONS: We provide evidence for the concept of PUFA-induced metabolic gut inflammation which may worsen the course of human CD. Our findings provide a basis for targeted nutritional therapy.

Adipocyte GPX4 protects against inflammation, hepatic insulin resistance and metabolic dysregulation.

OBJECTIVES: Metabolic inflammation is a hallmark of obesity and related disorders, afflicting substantial morbidity and mortality to individuals worldwide. White visceral and subcutaneous adipose tissue not only serves as energy storage but also controls metabolism. Adipose tissue inflammation, commonly observed in human obesity, is considered a critical driver of metabolic perturbation while molecular hubs are poorly explored. Metabolic stress evoked by e.g. long-chain fatty acids leads to oxidative perturbation of adipocytes and production of inflammatory cytokines, fuelling macrophage infiltration and systemic low-grade inflammation. Glutathione peroxidase 4 (GPX4) protects against lipid peroxidation, accumulation of oxygen-specific epitopes and cell death, collectively referred to as ferroptosis. Here, we explore the function of adipocyte GPX4 in mammalian metabolism. METHODS: We studied the regulation and function of GPX4 in differentiated mouse adipocytes derived from 3T3-L1 fibroblasts. We generated two conditional adipocyte-specific Gpx4 knockout mice by crossing Gpx4fl/fl mice with Adipoq-Cre+ (Gpx4-/-AT) or Fabp4-Cre+ (Gpx4+/-Fabp4) mice. Both models were metabolically characterized by a glucose tolerance test and insulin resistance test, and adipose tissue lipid peroxidation, inflammation and cell death were assessed by quantifying oxygen-specific epitopes, transcriptional analysis of chemokines, quantification of F4/80+ macrophages and TUNEL labelling. RESULTS: GPX4 expression was induced during and required for adipocyte differentiation. In mature adipocytes, impaired GPX4 activity spontaneously evoked lipid peroxidation and expression of inflammatory cytokines such as TNF-α, interleukin 1ß (IL-1ß), IL-6 and the IL-8 homologue CXCL1. Gpx4-/-AT mice spontaneously displayed adipocyte hypertrophy on a chow diet, which was paralleled by the accumulation of oxygen-specific epitopes and macrophage infiltration in adipose tissue. Furthermore, Gpx4-/-AT mice spontaneously developed glucose intolerance, hepatic insulin resistance and systemic low-grade inflammation, when compared to wildtype littermates, which was similarly recapitulated in Gpx4+/-Fabp4 mice. Gpx4-/-AT mice exhibited no signs of adipocyte death. CONCLUSION: Adipocyte GPX4 protects against spontaneous metabolic dysregulation and systemic low-grade inflammation independent from ferroptosis, which could be therapeutically exploited in the future.

Hepatic Meteorin-like and Krüppel-like Factor 3 are Associated with Weight Loss and Liver Injury.

OBJECTIVE: Laparoscopic adjustable gastric banding (LAGB) was found to be effective in reducing body weight and improving insulin resistance in patients with obesity and non-alcoholic fatty liver disease (NAFLD). The adipokine/myokine meteorin-like (METNRL) is an important regulator of whole-body energy expenditure. Krüppel-like factor 3 (KLF3), a regulator of METRNL expression in eosinophils, inhibits the beiging of adipose tissue in mice and therefore regulates adipose tissue development. METHODS: Thirty-three obese patients undergoing LAGB were included in the study. The hepatic and adipose tissue expression of METNRL and KLF3 was determined before (t0) and 6 months after (t6) LABG. The human liver cancer cell line (HepG2) was stimulated with cytokines and fatty acids and METNRL and KLF3 expressions were analyzed. RESULTS: LAGB-associated weight loss was correlated with decreased hepatic METNRL expression. The expression of METNRL and KLF3 in hepatic-and adipose tissues correlated before and after LAGB. Individuals with augmented LAGB-induced weight loss (>20 kg) showed lower hepatic METNRL and KLF3 expression before and after LAGB than patients with <20 kg weight loss. METNRL and KLF3 levels were higher in patients with higher NAFLD activity scores. HepG2 stimulation with interleukin-1ß, tumor necrosis factor-α, palmitic acid but not interleukin-6, oleic acid, or lipopolysaccharide, induced the expression of one or both investigated adipokines. CONCLUSIONS: The novel description of METRNL and KLF3 as hepatokines could pave the way to target their production and/or signaling in obesity, NAFLD, and related disorders. Both proteins may act as possible biomarkers to estimate weight loss after bariatric surgery.

Association between non-alcoholic fatty liver disease and impaired cardiac sympathetic/parasympathetic balance in subjects with and without type 2 diabetes-The Cooperative Health Research in South Tyrol (CHRIS)-NAFLD sub-study.

BACKGROUND AND AIMS: Cardiovascular disease (CVD) is the leading cause of death in patients with non-alcoholic fatty liver disease (NAFLD), both with and without type 2 diabetes mellitus (T2DM). Cardiac autonomic dysfunction is a risk factor for CVD morbidity and mortality. The aim of this pilot study was to assess whether there is an association between NAFLD and impaired cardiac autonomic function. METHODS AND RESULTS: Among the first 4979 participants from the Cooperative Health Research in South Tyrol (CHRIS) study, we randomly recruited 173 individuals with T2DM and 183 age- and sex-matched nondiabetic controls. Participants underwent ultrasonography and vibration-controlled transient elastography (Fibroscan®, Echosens) to assess hepatic steatosis and liver stiffness. The low-to-high-frequency (LF/HF) power ratio and other heart rate variability (HRV) measures were calculated from a 20-min resting electrocardiogram (ECG) to derive a measure of cardiac sympathetic/parasympathetic imbalance. Among the 356 individuals recruited for the study, 117 had NAFLD and T2DM, 56 had T2DM alone, 68 had NAFLD alone, and 115 subjects had neither condition. Individuals with T2DM and NAFLD (adjusted odds ratio [OR] 4.29, 95% confidence intervals [CI] 1.90-10.6) and individuals with NAFLD alone (adjusted OR 3.41, 95% CI 1.59-7.29), but not those with T2DM alone, had a substantially increased risk of having cardiac sympathetic/parasympathetic imbalance, compared with those without NAFLD and T2DM. Logistic regression models were adjusted for age, sex, body mass index (BMI), hypertension, dyslipidemia, insulin resistance, hemoglobin A1c (HbA1c), C-reactive protein (CRP), and Fibroscan®-measured liver stiffness. CONCLUSIONS: NAFLD was associated with cardiac sympathetic/parasympathetic imbalance, regardless of the presence or absence of T2DM, liver stiffness, and other potential confounding factors.

Using Infodemiology Metrics to Assess Public Interest in Liver Transplantation: Google Trends Analysis.

BACKGROUND: Liver transplantation (LT) is the only curative treatment for end-stage liver disease. Less than 10% of global transplantation needs are met worldwide, and the need for LT is still increasing. The death rates on the waiting list remain too high. OBJECTIVE: It is, therefore, critical to raise awareness among the public and health care providers and in turn increasingly acquire donors. METHODS: We performed a Google Trends search using the search terms liver transplantation and liver transplant on October 15, 2020. On the basis of the resulting monthly data, the annual average Google Trends indices were calculated for the years 2004 to 2018. We not only investigated the trend worldwide but also used data from the United Network for Organ Sharing (UNOS), Spain, and Eurotransplant. Using pairwise Spearman correlations, Google Trends indices were examined over time and compared with the total number of liver transplants retrieved from the respective official websites of UNOS, the Organización Nacional de Trasplantes, and Eurotransplant. RESULTS: From 2004 to 2018, there was a significant decrease in the worldwide Google Trends index from 78.2 in 2004 to 20.5 in 2018 (-71.2%). This trend was more evident in UNOS than in the Eurotransplant group. In the same period, the number of transplanted livers increased worldwide. The waiting list mortality rate was 31% for Eurotransplant and 29% for UNOS. However, in Spain, where there are excellent awareness programs, the Google Trends index remained stable over the years with comparable, increasing LT numbers but a significantly lower waiting list mortality (15%). CONCLUSIONS: Public awareness in LT has decreased significantly over the past two decades. Therefore, novel awareness programs should be initialized.

Systemic inflammation as fuel for acute liver injury in COVID-19.

BACKGROUND: A cytokine storm conceivably contributes to manifestations of corona virus disease (COVID-19). Inflammatory cytokines such as interleukin-6 (IL-6) cause acute liver injury while serum detectability indicates systemic inflammation. AIMS: We explored a link between systemic IL-6, related acute phase proteins and liver injury in hospitalized COVID-19 patients. METHODS: 655 patients with suspected COVID-19 were screened in the emergency department at the University Hospital of Innsbruck, Austria, between February and April 2020. 96 patients (∼15%) were hospitalized with COVID-19. 15 patients required intensive-care treatment (ICT). Plasma aminotransferases, alkaline phosphatase, bilirubin, and gamma glutamyl transferase, as well as IL-6, C-reactive protein (CRP), ferritin and lactate dehydrogenase (LDH) were determined by standard clinical assays. RESULTS: Of all hospitalized COVID-19 patients, 41 (42%) showed elevated aspartate aminotransferase (AST) concentration. COVID-19 patients with elevated AST exhibited significantly higher IL-6 (p < 0.001), ferritin (p < 0.001), LDH (p < 0.001) and CRP (p < 0.05) serum concentrations compared to patients with normal AST. Liver injury correlated with systemic IL-6 (p < 0.001), CRP (p < 0.001), ferritin (p < 0.001) and LDH (p < 0.001) concentration. In COVID-19 patients requiring ICT, correlations were more pronounced. CONCLUSION: Systemic inflammation could be a fuel for hepatic injury in COVID-19.

Alpha-1 antitrypsin governs alcohol-related liver disease in mice and humans.

OBJECTIVE: Alcohol-related liver disease (ALD) is a global healthcare problem with limited treatment options. Alpha-1 antitrypsin (AAT, encoded by SERPINA1) shows potent anti-inflammatory activities in many preclinical and clinical trials. In our study, we aimed to explore the role of AAT in ALD. DESIGN: An unselected cohort of 512 patients with cirrhosis was clinically characterised. Survival, clinical and biochemical parameters including AAT serum concentration were compared between patients with ALD and other aetiologies of liver disease. The role of AAT was evaluated in experimental ALD models. RESULTS: Cirrhotic ALD patients with AAT serum concentrations less than 120 mg/dL had a significantly higher risk for death/liver transplantation as compared with patients with AAT serum concentrations higher than 120 mg/dL. Multivariate Cox regression analysis showed that low AAT serum concentration was a NaMELD-independent predictor of survival/transplantation. Ethanol-fed wild-type (wt) mice displayed a significant decline in hepatic AAT compared with pair-fed mice. Therefore, hAAT-Tg mice were ethanol-fed, and these mice displayed protection from liver injury associated with decreased steatosis, hepatic neutrophil infiltration and abated expression of proinflammatory cytokines. To test the therapeutic capability of AAT, ethanol-fed wt mice were treated with human AAT. Administration of AAT ameliorated hepatic injury, neutrophil infiltration and steatosis. CONCLUSION: Cirrhotic ALD patients with AAT concentrations less than 120 mg/dL displayed an increased risk for death/liver transplantation. Both hAAT-Tg mice and AAT-treated wt animals showed protection from ethanol-induced liver injury. AAT could reflect a treatment option for human ALD, especially for alcoholic hepatitis.

The role of gut vascular barrier in experimental alcoholic liver disease and A. muciniphila supplementation.

The translocation of bacterial components from the intestinal lumen into the portal circulation is crucial in the pathogenesis of alcoholic liver disease (ALD). Recently the important role of the gut vascular barrier (GVB) was elucidated in alcoholic liver disease. Here we report about the influence of A. muciniphila supplementation in experimental ALD on the GVB. Ethanol feeding was associated with increased Pv-1, indicating altered endothelial barrier function, whereas A. muciniphila administration tended to restore GVB. To further investigate GVB in experimental ALD, ß-catenin gain-of-function mice, which display an enhanced GVB, were ethanol-fed. ß-catenin gain-of-function mice were not protected from ethanol-induced liver injury, suggest an alternative mechanism of ethanol-induced GVB disruption. The description of the GVB in ALD could pave the way for new therapeutic options in the future.

Liver stiffness by transient elastography accompanies illness severity in COVID-19.

OBJECTIVE: Severe liver damage is associated with worse outcome in COVID-19. Our aim was to explore the degree of liver damage, liver stiffness (LS) and severity of illness in patients with COVID-19. DESIGN: We investigated 32 patients with COVID-19 admitted to the University Hospital of Innsbruck in a prospective cross-sectional study. We performed laboratory testing, liver and spleen sonography and elastography to measure organ stiffness. RESULTS: 12 patients (38%) showed elevated aminotransferases and gamma-glutamyltransferase levels. LS was positively correlated with elevated aminotransferase levels in patients with COVID-19 compared with those without elevated enzymes. Even mild liver damage raised LS significantly in COVID-19 as it was in patients with gastrointestinal symptoms. Furthermore, higher LS measurements were significantly associated with illness severity like pneumonia, need for mechanical ventilation, and even death. CONCLUSION: Transient elastography is a useful and non-invasive tool to assess onset and severity of acute liver injury in patients with COVID-19 patients. Increased LS seems to be predictive for a more severe and complicated course of disease.

Gastric banding-associated weight loss diminishes hepatic Tsukushi expression.

Obesity has emerged as a substantial global healthcare issue that is frequently associated with insulin resistance and non-alcoholic fatty liver disease (NAFLD). Tsukushi (TSK), a liver-derived molecule, was recently identified as a major driver of NAFLD. Laparoscopic adjustable gastric banding (LAGB) has proven effective in reducing body weight and improving NAFLD. We therefore aimed to investigate the relation between LAGB-induced weight loss and TSK expression. Twenty-six obese patients undergoing LAGB were included in the study and metabolic parameters were assessed before (t0) and six months after LAGB (t6). The expression of TSK in liver and subcutaneous adipose tissue (AT) specimens was determined at both time points. To unravel regulatory mechanisms of TSK expression, human peripheral blood mononuclear cells (PBMCs) were stimulated with pro-inflammatory cytokines and TSK mRNA levels were analyzed by quantitative polymerase chain reaction. LAGB induced pronounced weight loss which was paralleled by amelioration of metabolic disturbances and histologically defined NAFLD. While hepatic TSK expression was markedly decreased after LAGB, adipose tissue TSK expression remained comparable to baseline. The decline in hepatic TSK expression after LAGB positively correlated with weight loss and the reduction in BMI, and negatively correlated with NAFLD activity score (NAS). In human PBMCs, pro-inflammatory cytokines such as IL-1ß and TNFα induced the expression of TSK. In conclusion, LAGB-induced weight loss reduces hepatic TSK expression. Inhibiting TSK might represent a promising target for treating NAFLD in the future.

Dimethyl fumarate ameliorates hepatic inflammation in alcohol related liver disease.

BACKGROUND & AIMS: Alcohol-related liver disease (ALD) comprises different liver disorders which impose a health care issue. ALD and particularly alcoholic steatohepatitis, an acute inflammatory condition, cause a substantial morbidity and mortality as effective treatment options remain elusive. Inflammation in ALD is fuelled by macrophages (Kupffer cells [KCs]) which are activated by intestinal pathogen associated molecular patterns, eg lipopolysaccharide (LPS), disseminated beyond a defective intestinal barrier. We hypothesized that the immunomodulator dimethyl-fumarate (DMF), which is approved for the treatment of human inflammatory conditions such as multiple sclerosis or psoriasis, ameliorates the course of experimental ALD. METHODS: Dimethyl-fumarate or vehicle was orally administered to wild-type mice receiving a Lieber-DeCarli diet containing 5% ethanol for 15 days. Liver injury, steatosis and inflammation were evaluated by histology, biochemical- and immunoassays. Moreover, we investigated a direct immunosuppressive effect of DMF on KCs and explored a potential impact on ethanol-induced intestinal barrier disruption. RESULTS: Dimethyl-fumarate protected against ethanol-induced hepatic injury, steatosis and inflammation in mice. Specifically, we observed reduced hepatic triglyceride and ALT accumulation, reduced hepatic expression of inflammatory cytokines (Tnf-α, Il-1ß, Cxcl1) and reduced abundance of neutrophils and macrophages in ethanol-fed and DMF-treated mice when compared to vehicle. DMF protected against ethanol-induced barrier disruption and abrogated systemic LPS concentration. In addition, DMF abolished LPS-induced cytokine responses of KCs. CONCLUSIONS: Dimethyl-fumarate counteracts ethanol-induced barrier dysfunction, suppresses inflammatory responses of KCs and ameliorates hepatic inflammation and steatosis, hallmarks of experimental ALD. Our data indicates that DMF treatment might be beneficial in human ALD and respective clinical trials are eagerly awaited.