Extracellular vesicles in fatty liver disease and steatohepatitis: Role as biomarkers and therapeutic targets.

Non-alcoholic fatty liver disease (NAFLD) and alcohol-associated liver disease (ALD) are characterized by lipid deposition in hepatocytes in the absence or presence of excessive alcohol consumption, respectively, ranging from simple steatosis to non-alcoholic steatohepatitis (NASH) or alcoholic hepatitis (AH) and from mild fibrosis to cirrhosis. Fatty liver disease and steatohepatitis similarly occur in individuals who have both metabolic syndrome and excessive alcohol intake; therefore, the single overarching term metabolic associated fatty liver disease (MAFLD) has been proposed to better reflect these risk factors and the continuity of disease progression. Extracellular vesicles (EVs) are membrane-bound endogenous nanoparticles released into the extracellular space by a majority of cell types. Liver disease-related EVs contain a variety of cellular cargo and are internalized into target cells resulting in the transfer of bioinformation reflecting the state of the donor cell to the recipient. Furthermore, EV composition can be used to identify the degree and type of liver disease, suggesting that EV composition may be a useful biomarker. With regard to MAFLD, the presence of metabolic risk factors, such as insulin resistance, will be indicated by adipose tissue-derived EVs and with that comes the potential to use as a clinical monitor of overall metabolic status. However, the inhibition of specific EV composition may be difficult to implement as a real-world therapeutic approach. Current global evidence shows that mesenchymal stem cell (MSCs)-derived EVs (MSC-EVs) play an important role in regulating the immune response, which has spawned a clinical trial to treat liver disease.

Accuracy of carbohydrate-deficient transferrin as a biomarker of chronic alcohol abuse during treatment for alcoholism.

AIM: Clinical evaluations are generally used to verify the effectiveness of detoxification treatments for alcohol dependence, but new objective biomarkers are essential for accurate diagnosis. We aim to assess the accuracy of carbohydrate-deficient transferrin (%CDT) in a cohort of Japanese patients admitted to a psychiatric hospital specializing in alcohol dependence. In addition, we investigated the kinetics of %CDT during alcohol moderation or cessation. METHODS: The study cohort consisted of 126 alcohol-dependent patients. The levels of serum %CDT were assessed by the N Latex CDT direct immunonephelometric assay. RESULTS: Alcohol consumption was significantly correlated with %CDT. The only independent predictive factor of alcohol consumption was %CDT, with glutamyltranspeptidase (GGT) and albumin-bilirubin score proving insufficient. The cut-off value of %CDT was 1.9% with high sensitivity and specificity in detecting alcohol abstinence beyond 30 days (68.6% sensitivity, 91.8% specificity) and excessive alcohol drinking (77.9% sensitivity, 77.1% specificity). The %CDT levels were significantly decreased at 30 days of abstinence when compared with baseline. Notably, %CDT values were significantly changed even in the light alcohol drinking cohort (p = 0.0009), whereas GGT levels were not significantly changed. CONCLUSIONS: Our results indicate that %CDT is an accurate and specific biomarker of alcohol consumption and is useful in detecting alcohol abstinence even in a low alcohol intake patient cohort. These results suggest that %CDT could be a useful objective biomarker of chronic alcohol abuse during clinical treatment for alcoholism.

Hepatocyte pyroptosis and release of inflammasome particles induce stellate cell activation and liver fibrosis.

BACKGROUND & AIMS: Increased hepatocyte death contributes to the pathology of acute and chronic liver diseases. However, the role of hepatocyte pyroptosis and extracellular inflammasome release in liver disease is unknown. METHODS: We used primary mouse and human hepatocytes, hepatocyte-specific leucine 351 to proline Nlrp3KICreA mice, and GsdmdKO mice to investigate pyroptotic cell death in hepatocytes and its impact on liver inflammation and damage. Extracellular NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasomes were isolated from mutant NLRP3-YFP HEK cells and internalisation was studied in LX2 and primary human hepatic stellate cells. We also examined a cohort of 154 adult patients with biopsy-proven non-alcoholic fatty liver disease (Sir Charles Gairdner Hospital, Nedlands, Western Australia). RESULTS: We demonstrated that primary mouse and human hepatocytes can undergo pyroptosis upon NLRP3 inflammasome activation with subsequent release of NLRP3 inflammasome proteins that amplify and perpetuate inflammasome-driven fibrogenesis. Pyroptosis was inhibited by blocking caspase-1 and gasdermin D activation. The activated form of caspase-1 was detected in the livers and in serum from patients with non-alcoholic steatohepatitis and correlated with disease severity. Nlrp3KICreA mice showed spontaneous liver fibrosis under normal chow diet, and increased sensitivity to liver damage and inflammation after treatment with low dose lipopolysaccharide. Mechanistically, hepatic stellate cells engulfed extracellular NLRP3 inflammasome particles leading to increased IL-1ß secretion and α-smooth muscle actin expression. This effect was abrogated when cells were pre-treated with the endocytosis inhibitor cytochalasin B. CONCLUSIONS: These results identify hepatocyte pyroptosis and release of inflammasome components as a novel mechanism to propagate liver injury and liver fibrosis development. LAY SUMMARY: Our findings identify a novel mechanism of inflammation in the liver. Experiments in cell cultures, mice, and human samples show that a specific form of cell death, called pyroptosis, leads to the release of complex inflammatory particles, the NLRP3 inflammasome, from inside hepatocytes into the extracellular space. From there they are taken up by other cells and thereby mediate inflammatory and pro-fibrogenic stress signals. The discovery of this mechanism may lead to novel treatments for chronic liver diseases in the future.

The Role of Elevated Liver-Type Fatty Acid-Binding Proteins in Liver Diseases.

Liver-type fatty acid-binding protein (L-FABP) is mainly expressed in the liver as well as the proximal tubular epithelial cells in the kidney. In general, the proteins and enzymes existing within the hepatocytes have the potential to become biomarkers, for instance alanine aminotransferase, which reflects hepatocellular damage. However, due to reduced hepatocellular function in late stage of chronic liver diseases (e.g. cirrhosis), proteins and enzymes relating to hepatocellular damage are not always accurate measures of disease progression. Recently, several publications have demonstrated elevated serum L-FABP levels during the progression of human liver diseases, including hepatocellular carcinoma (HCC), and were a prognostic factor for survival in acute and chronic liver disease patients. However, the study regarding serum L-FABP levels and hepatic L-FABP expression in liver diseases is not sufficient to understand the molecular mechanism of L-FABP during the progression of these disease states. In this review, we focus on the use of serum and/or hepatic L-FABP expression as a biomarker in human liver diseases, including mechanistic potential in HCC.

Serum copeptin level is a biomarker associated with ascites retention and the formation of a portosystemic shunt in chronic liver disease.

BACKGROUND AND AIM: Copeptin is a stable cleavage product of the arginine vasopressin precursor and is equimolarly secreted with arginine vasopressin. We aimed to assess whether copeptin is the surrogate marker for complications related chronic liver disease (CLD) such as ascites, hepatic encephalopathy (HE), portosystemic shunts (PSSs), and all causes of mortality in CLD. METHODS: Serum copeptin was measured in 170 CLD patients upon hospital admission. The association of copeptin levels with liver enzymes, liver functional reserve, and clinical parameters was investigated. Cox proportional hazard regression, logistic regression, and Kaplan-Meier analyses were performed to evaluate the associations of copeptin and ascites, HE and PSS formation, and prognostic factors with short-term (1 year) and long-term (4 years) mortality. RESULTS: Serum copeptin levels were significantly correlated with liver and renal function, elevated in parallel with liver disease progression, and also associated with HE. Serum copeptin, albumin-bilirubin score and hepatocellular carcinoma were independent predictors of PSS formation and decreased rate of survival. Serum copeptin and albumin-bilirubin scores were independent predictors of ascites retention. The short-term and long-term cumulative mortality rate was significantly decreased in patients with serum copeptin >5.5 or >4.8 pmol/mL compared with patients in whom serum copeptin levels were <5.5 or <4.8 pmol/mL (P < 0.0001; P < 0.0001). CONCLUSIONS: Serum copeptin level is a predictor for ascites retention and HE and PSS formation associated with portal hypertension. Moreover, serum copeptin level may be useful in predicting the rate of survival in patients with CLD.

Identification of actin network proteins, talin-1 and filamin-A, in circulating extracellular vesicles as blood biomarkers for human myalgic encephalomyelitis/chronic fatigue syndrome.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a serious, debilitating disorder with a wide spectrum of symptoms, including pain, depression, and neurocognitive deterioration. Over 17 million people around the world have ME/CFS, predominantly women with peak onset at 30-50 years. Given the wide spectrum of symptoms and unclear etiology, specific biomarkers for diagnosis and stratification of ME/CFS are lacking. Here we show that actin network proteins in circulating extracellular vesicles (EVs) offer specific non-invasive biomarkers for ME/CFS. We found that circulating EVs were significantly increased in ME/CFS patients correlating to C-reactive protein, as well as biological antioxidant potential. Area under the receiver operating characteristic curve for circulating EVs was 0.80, allowing correct diagnosis in 90-94% of ME/CFS cases. From two independent proteomic analyses using circulating EVs from ME/CFS, healthy controls, idiopathic chronic fatigue, and depression, proteins identified from ME/CFS patients are involved in focal adhesion, actin skeletal regulation, PI3K-Akt signaling pathway, and Epstein-Barr virus infection. In particular, talin-1, filamin-A, and 14-3-3 family proteins were the most abundant proteins, representing highly specific ME/CFS biomarkers. Our results identified circulating EV number and EV-specific proteins as novel biomarkers for diagnosing ME/CFS, providing important information on the pathogenic mechanisms of ME/CFS.

Differential Activation of Hepatic Invariant NKT Cell Subsets Plays a Key Role in Progression of Nonalcoholic Steatohepatitis.

Innate immune mechanisms play an important role in inflammatory chronic liver diseases. In this study, we investigated the role of type I or invariant NKT (iNKT) cell subsets in the progression of nonalcoholic steatohepatitis (NASH). We used α-galactosylceramide/CD1d tetramers and clonotypic mAb together with intracytoplasmic cytokine staining to analyze iNKT cells in choline-deficient l-amino acid-defined (CDAA)-induced murine NASH model and in human PBMCs, respectively. Cytokine secretion of hepatic iNKT cells in CDAA-fed C57BL/6 mice altered from predominantly IL-17+ to IFN-γ+ and IL-4+ during NASH progression along with the downmodulation of TCR and NK1.1 expression. Importantly, steatosis, steatohepatitis, and fibrosis were dependent upon the presence of iNKT cells. Hepatic stellate cell activation and infiltration of neutrophils, Kupffer cells, and CD8+ T cells as well as expression of key proinflammatory and fibrogenic genes were significantly blunted in Jα18-/- mice and in C57BL/6 mice treated with an iNKT-inhibitory RAR-γ agonist. Gut microbial diversity was significantly impacted in Jα18-/- and in CDAA diet-fed mice. An increased frequency of CXCR3+IFN-γ+T-bet+ and IL-17A+ iNKT cells was found in PBMC from NASH patients in comparison with nonalcoholic fatty liver patients or healthy controls. Consistent with their in vivo activation, iNKT cells from NASH patients remained hyporesponsive to ex-vivo stimulation with α-galactosylceramide. Accumulation of plasmacytoid dendritic cells in both mice and NASH patients suggest their role in activation of iNKT cells. In summary, our findings indicate that the differential activation of iNKT cells play a key role in mediating diet-induced hepatic steatosis and fibrosis in mice and its potential involvement in NASH progression in humans.

NLRP3 inflammasome driven liver injury and fibrosis: Roles of IL-17 and TNF in mice.

The NLRP3 inflammasome, a caspase-1 activation platform, plays a key role in the modulation of liver inflammation and fibrosis. Here, we tested the hypothesis that interleukin 17 (IL-17) and tumor necrosis factor (TNF) are key cytokines involved in amplifying and perpetuating the liver damage and fibrosis resulting from NLRP3 activation. To address this hypothesis, gain-of-function Nlrp3A350V knock-in mice were bred onto il17a and Tnf knockout backgrounds allowing for constitutive Nlrp3 activation in myeloid derived cells in mice deficient in IL-17 or TNF. Livers of Nlrp3A350V knock-in mice exhibited severe liver inflammatory changes characterized by infiltration with neutrophils, increased expression of chemokine (C-X-C motif) ligand (CXCL) 1 and CXCL2 chemokines, activated inflammatory macrophages, and elevated levels of IL-17 and TNF. Mutants with ablation of il17a signal showed fewer neutrophils when compared to intact Nlrp3A350V mutants, but still significant inflammatory changes when compared to the nonmutant il17a knockout littermates. The severe inflammatory changes associated with mutant Nlrp3 were almost completely rescued by Tnf knockout in association with a marked decrease in circulating IL-1ß levels. Intact Nlrp3A350V mutants showed changes in liver fibrosis, as evidenced by morphometric quantitation of Sirius Red staining and increased mRNA levels of profibrotic genes, including connective tissue growth factor and tissue inhibitor of matrix metalloproteinase 1. Il17a lacking mutants exhibited amelioration of the aforementioned fibrosis, whereas Tnf-deficient mutants showed no signs of fibrosis when compared to littermate controls. Conclusion: Our study uncovers key roles for TNF and, to a lesser extent, IL-17 as mediators of liver inflammation and fibrosis induced by constitutive NLRP3 inflammasome activation in myeloid-derived cells. These findings may lead to therapeutic strategies aimed at halting the progression of liver injury and fibrogenesis in various liver pathogeneses driven by NLRP3 activation. (Hepatology 2018;67:736-749).

Ratio between estimated glomerular filtration rates of creatinine and cystatin C predicts overall survival in patients with hepatocellular carcinoma.

AIM: Hepatocellular carcinoma (HCC) patients with sarcopenia have a poor survival, but there are no predictive markers for survival relating to muscle mass and liver function. Therefore, we investigated whether the ratio between estimated glomerular filtration rates of serum creatinine (Scre) and serum cystatin C (Scys) (eGFRcre/eGFRcys) can be used as a predictive marker of survival in HCC patients. METHODS: First, the correlation between Scre/Scys ratio and muscle mass was examined in 50 patients with chronic liver disease. Second, a change in Scre/Scys ratio relating to liver function was investigated in cirrhotic rats. Finally, the relationship between the eGFRcre/eGFRcys ratio and survival was assessed in 86 HCC patients. RESULTS: The Scre/Scys ratio was correlated with skeletal muscle mass index (r = 0.331, P = 0.019) and psoas muscle area index (r = 0.397, P = 0.004) in chronic liver disease patients. In cirrhotic rats, Scre and Scre/Scys ratio were decreased corresponding with liver function. Thirty-five of 86 HCC patients died within the average follow-up period of 35 months. The patients with an eGFRcre/eGFRcys ratio <1.26 had significantly longer rates of survival compared to patients with an eGFRcre/eGFRcys ratio ≥1.26 (28.8 vs. 18.5 months, P = 0.001). Using multivariate Cox regression analyses, the patient-related eGFRcre/eGFRcys ratio (hazard ratio [HR], 4.178; P = 0.007), as well as the tumor-related factors α-fetoprotein (HR, 1.000; P < 0.001) and Barcelona Clinic Liver Cancer stage (HR, 2.589; P < 0.001), were independent predictors of survival. CONCLUSION: The Scre/Scys ratio is associated with muscle mass and liver function. Furthermore, the eGFRcre/eGFRcys ratio could serve as a useful predictive marker for survival of HCC.

Hypozincemia is associated with human hepatocarcinogenesis in hepatitis C virus-related liver cirrhosis.

AIM: Hypozincemia is associated with the progression of chronic liver diseases, but it is unknown whether hypozincemia promotes human hepatocarcinogenesis. Our aim is to evaluate the serum zinc levels in liver cirrhosis (LC) patients and clarify the relationship between the serum zinc levels and the development of hepatocellular carcinoma (HCC). METHODS: Cirrhotic patients without HCC (n = 299) were enrolled from 14 medical institutes in Japan as a multicenter prospective study (No. 2028). Of the 299 patients, 157 were included in the present study based on reliable and consistent serum zinc levels and no history of oral zinc supplementation. Clinical parameters associated with the development of HCC were determined. Furthermore, the cumulative incidence of HCC was analyzed using Kaplan-Meier methods and was calculated using the log-rank test. A Cox regression analysis was utilized for the multivariate analysis to evaluate the predictors of hepatocarcinogenesis. RESULTS: Thirty of 157 patients (19.1%) developed HCC during an observation period of 3 years. Serum zinc levels were significantly decreased in hepatitis C virus-related LC (C-LC) patients with HCC (0.0180). The risk factors for incidence of HCC were hypozincemia (0.0014), high α-fetoprotein (0.0080), low branched chain amino acids-to-tyrosine ratio (0.0128), or female sex (0.0228). Hypozincemia (hazard ratio 1.61, 0.0324) was the only significant predictor of hepatocarcinogenesis by multivariate Cox regression analysis. CONCLUSIONS: Hypozincemia is associated with hepatocarcinogenesis in C-LC patients.

Oxidized linoleic acid metabolites induce liver mitochondrial dysfunction, apoptosis, and NLRP3 activation in mice.

Circulating oxidized linoleic acid (LA) metabolites (OXLAMs) are increased in patients with nonalcoholic steatohepatitis (NASH) and their levels correlate with disease severity. However, the mechanisms by which OXLAMs contribute to NASH development are incompletely understood. We tested the hypothesis that LA or OXLAMs provided directly through the diet are involved in the development of hepatic injury. C57BL/6 mice were fed an isocaloric high-fat diet containing low LA, high LA, or OXLAMs for 8 weeks. The livers of OXLAM-fed mice showed lower triglyceride concentrations, but higher FA oxidation and lipid peroxidation in association with increased oxidative stress. OXLAM-induced mitochondrial dysfunction was associated with reduced Complex I protein and hepatic ATP levels, as well as increased mitochondrial biogenesis and cytoplasmic mitochondrial DNA. Oxidative stress increased thioredoxin-interacting protein (TXNIP) in the liver and stimulated the activation of mitochondrial apoptosis signal-regulating kinase 1 (ASK1) leading to apoptosis. We also found increased levels of NOD-like receptor protein 3 (NLRP3) inflammasome components and Caspase-1 activation in the livers of OXLAM-fed mice. In vitro, OXLAMs induced hepatocyte cell death, which was partly dependent on Caspase-1 activation. This study identified key mechanisms by which dietary OXLAMs contribute to NASH development, including mitochondrial dysfunction, hepatocyte cell death, and NLRP3 inflammasome activation.

Circulating extracellular vesicles are associated with lipid and insulin metabolism.

We have reported that hypertrophic adipocytes release extracellular vesicles (EVs) and the number of circulating adipocyte-derived EVs correlated with insulin and homeostasis model assessment-insulin resistance (HOMA-IR) in a pilot study using obese patients. Here, we explored the association between circulating EV level and various metabolic parameters, including obesity and lipid and glucose metabolisms, among 203 subjects (76 men and 127 women; median age, 54 yr) with or without risk factor for metabolic diseases, who received a 75-g oral glucose tolerance test (OGTT). Circulating EV number was significantly higher in men than in women ( P < 0.001). Circulating EV number in individuals with impaired OGTT pattern was significantly higher compared with those with normal OGTT patterns ( P < 0.05). Multiple regression analysis revealed that circulating EV number correlated most strongly and significantly with elevated triglyceride (TG; t = 8.55, P < 0.001). Additionally, circulating EV number correlated significantly with homeostasis model assessment-ß-cell function (HOMA-ß; t = 2.38, P < 0.05). Receiver operating characteristic curve revealed that the cutoff value of EV numbers in individuals with elevated serum TG levels (≧150 mg/dl) was identified (136,738 EVs/µl of plasma, P < 0.001, sensitivity 0.842, false-positive rate of 0.257). Perilipin and asialoglycoprotein receptor 1 were detected on a part of isolated circulating EVs, indicating EV release from adipocytes and hepatocytes, which were related to lipid and glucose metabolism. Circulating EVs represent a promising metabolic biomarker for lipid and glucose metabolism and have potential for monitoring metabolic status in humans, including individuals without metabolic risk factors.

Extracellular vesicles released by hepatocytes from gastric infusion model of alcoholic liver disease contain a MicroRNA barcode that can be detected in blood.

Extracellular vesicles (EVs) released during cell stress, or demise, can contain a barcode of the cell origin, including specific microRNAs (miRNAs). Here, we tested the hypothesis that during early alcoholic steatohepatitis (ASH) development, hepatocytes (HCs) release EVs with an miRNA signature that can be measured in circulation. A time-course experiment showed that after 2 weeks of intragastric infusion, a time point that results in isolated steatosis, there was no increase of blood EVs. After 4 weeks of infusion, mice developed features of early ASH accompanied by a marked increase in the level of EVs in blood (P < 0.05), as well as in culture media of isolated HCs (P < 0.001) and hepatic macrophages (P < 0.001), with HCs being the predominant source of EVs. The transcriptome analysis of HC-EVs from ASH mice detected differentially expressed miRNAs, including nine significantly up-regulated and four significantly down-regulated miRNAs. Target prediction and pathway analyses of the up-regulated miRNAs identified 121 potential target genes involved in inflammatory and cancer pathways, such as nuclear factor kappa B, EGF, Wnt, and B-cell lymphoma 2. Three miRNAs, let7f, miR-29a, and miR-340, were increased in blood EVs from ASH mice (P < 0.05), but not in blood EVs from three other models of chronic liver injury, including bile duct ligation, nonalcoholic steatohepatitis, and obese mice, as well as EVs released from hepatocytes exposed to ethanol. Blood EV level (P < 0.01) and three miRNAs (P < 0.05) were significantly increased in patients with ambulatory mild ALD as compared to nonalcoholics. CONCLUSION: Damaged hepatocytes from ASH mice are a key EV source with a specific miRNA cargo, which are specific for ASH-related liver injury. These findings uncover EVs as a potentially novel diagnostic for ASH. (Hepatology 2017;65:475-490).

Changes in liver function and body composition by direct-acting antiviral therapy for hepatitis C virus infection.

AIM: Management of low skeletal muscle mass (LSM) is a very important topic as LSM affects patient mortality in liver diseases. Changes in body composition are unexplored in chronic hepatitis C virus (HCV) patients, including those with liver cirrhosis, who receive direct-acting antiviral (DAA) therapy. Body composition measurements and liver function tests were carried out before and after DAA therapy. METHODS: Blood examination, visceral fat area (VFA) and extremity skeletal muscle mass were measured using the multifrequency bioelectrical impedance analysis method: (i) at 24 weeks before DAA therapy; (ii) at the start of DAA therapy; (iii) at the end of DAA therapy; (iv) at 24 weeks after DAA therapy; and (v) at 48 weeks after DAA therapy. RESULTS: Serum albumin (Alb) levels were significantly increased at 48 weeks post DAA therapy, especially in patients with LSM. Skeletal muscle mass index (SMI) was significantly increased after DAA therapy (at 24 weeks and 48 weeks post DAA therapy) in patients with LSM (P < 0.05). An increase in SMI was associated with an increase in body weight or a decrease in VFA. CONCLUSIONS: We continuously measured body composition in HCV-infected patients who received DAA therapy and found that skeletal muscle mass was significantly increased, associated with an elevation of serum Alb levels and/or body weight or reduction in VFA, but only in patients who presented with LSM before DAA therapy.

Liver Bid suppression for treatment of fibrosis associated with non-alcoholic steatohepatitis.

BACKGROUND & AIMS: Liver fibrosis is the most worrisome feature of non-alcoholic steatohepatitis (NASH). Growing evidence supports a link between hepatocyte apoptosis and liver fibrogenesis. Our aim was to determine the therapeutic efficacy and safety of liver Bid, a key pro-apoptotic molecule, suppression using RNA interference (RNAi) for the treatment of fibrosis. METHODS: First, we optimized the delivery system for Bid siRNA in mice using ten different stealth RNAi siRNAs and two lipid formulations -Invivofectamine2.0 and a newly developed Invivofectamine3.0 - that have been designed for high efficacy accumulation in the liver, assessed via real-time PCR of Bid mRNA. Next, C57BL/6 mice were placed on a choline-deficient L-amino acid defined (CDAA) diet. After 19weeks of the CDAA diet, a time point that results in severe fibrotic NASH, mice were injected with the selected Bid siRNA-Invivofectamine3.0 biweekly for three weeks. Additionally hepatocyte-specific Bid deficient (Bid(Δhep)) mice were placed on CDAA diet for 20weeks. RESULTS: A maximum Bid knockdown was achieved at 1.5mg/kg siRNA with Invivofectamine3.0, whereas it was at 7mg/kg with Invivofectamine2.0. In NASH mice, after 3weeks of treatment, BID protein was reduced to 10% and this was associated with an improvement in liver fibrosis and inflammation associated with a marked reduction in TUNEL positive cells, caspase 3 activation, and a reduction in mitochondrial BAX and BAK. Bid(Δhep) mice showed similar protection from fibrotic changes. CONCLUSION: Our data demonstrate that liver Bid suppression by RNAi technology, as well as hepatocyte-specific Bid deficiency, improves liver fibrosis coupled with a reduction of inflammation in experimental NASH. These findings are consistent with existing evidence that hepatocyte apoptosis triggers hepatic stellate cell activation and liver fibrosis and suggest that Bid inhibition may be useful as an antifibrotic NASH therapy.

Factors contributing to the development of overt encephalopathy in liver cirrhosis patients.

The aim of this study was to clarify the relationships among psychometric testing results, blood ammonia (NH3) levels, electrolyte abnormalities, and degree of inflammation, and their associations with the development of overt hepatic encephalopathy (HE) in liver cirrhosis (LC) patients. The relationships between covert HE and blood NH3, sodium (Na), and C-reactive protein (CRP) were examined in 40 LC patients. The effects of elevated NH3, hyponatremia, and elevated CRP on the development of overt HE were also investigated. The covert HE group had significantly lower serum Na levels and significantly higher serum CRP levels. During the median observation period of 11 months, 10 patients developed overt HE, and the results of multivariate analysis showed that covert HE and elevated blood NH3 were factors contributing to the development of overt HE. Electrolyte abnormalities and mild inflammation are involved in the pathogenesis of HE. Abnormal psychometric testing results and hyperammonemia are linked to subsequent development of overt HE.

GIV/girdin links vascular endothelial growth factor signaling to Akt survival signaling in podocytes independent of nephrin.

Podocytes are critically involved in the maintenance of the glomerular filtration barrier and are key targets of injury in many glomerular diseases. Chronic injury leads to progressive loss of podocytes, glomerulosclerosis, and renal failure. Thus, it is essential to maintain podocyte survival and avoid apoptosis after acute glomerular injury. In normal glomeruli, podocyte survival is mediated via nephrin-dependent Akt signaling. In several glomerular diseases, nephrin expression decreases and podocyte survival correlates with increased vascular endothelial growth factor (VEGF) signaling. How VEGF signaling contributes to podocyte survival and prevents apoptosis remains unknown. We show here that Gα-interacting, vesicle-associated protein (GIV)/girdin mediates VEGF receptor 2 (VEGFR2) signaling and compensates for nephrin loss. In puromycin aminonucleoside nephrosis (PAN), GIV expression increased, GIV was phosphorylated by VEGFR2, and p-GIV bound and activated Gαi3 and enhanced downstream Akt2, mammalian target of rapamycin complex 1 (mTORC1), and mammalian target of rapamycin complex-2 (mTORC2) signaling. In GIV-depleted podocytes, VEGF-induced Akt activation was abolished, apoptosis was triggered, and cell migration was impaired. These effects were reversed by introducing GIV but not a GIV mutant that cannot activate Gαi3. Our data indicate that after PAN injury, VEGF promotes podocyte survival by triggering assembly of an activated VEGFR2/GIV/Gαi3 signaling complex and enhancing downstream PI3K/Akt survival signaling. Because of its important role in promoting podocyte survival, GIV may represent a novel target for therapeutic intervention in the nephrotic syndrome and other proteinuric diseases.

Circulating microRNAs: emerging biomarkers of liver disease.

Development of reliable, noninvasive biomarkers that allow for diagnosis, risk stratification, and monitoring of disease changes over time or in response to specific therapies represents a key priority in the field of hepatology. Recent evidence has uncovered the role of microRNAs as potential ideal biomarkers of liver injury in various acute and chronic liver diseases. These small noncoding RNAs are released to the extracellular space in a stress-specific manner and are remarkably stable in most bodily fluids including blood, where they circulate in specific compartments including extracellular vesicles and protein complexes. In this review, the authors provide a concise overview of available information on the emerging role of quantitation of circulating microRNAs in different liver diseases and their use as biomarkers for both diagnosis and prognosis assessment. Additionally, several key issues that still need to be addressed for microRNAs to become useful tools in daily clinical practice are critically reviewed.

Arginase 2 deficiency results in spontaneous steatohepatitis: a novel link between innate immune activation and hepatic de novo lipogenesis.

BACKGROUND & AIMS: Innate immune activation has been postulated as a central mechanism for disease progression from hepatic steatosis to steatohepatitis in obesity-related fatty liver disease. Arginase 2 competes with inducible nitric oxide synthase (iNOS) for its substrate and the balance between these two enzymes plays a crucial role in regulating immune responses and macrophage activation. Our aim was to test the hypothesis that arginase 2 deficiency in mice favours progression from isolated hepatic steatosis, induced by high fat feeding, to steatohepatitis. METHODS: Arginase 2-knockout (Arg2(-/-)) mice were studied for changes in liver histology and metabolic phenotype at baseline and after a short term course (7 week) feeding with a high fat (HFAT) diet. In additional experiments, Arg2(-/-) mice received tail vein injections of liposome-encapsulated clodronate (CLOD) over a three-week period to selectively deplete liver macrophages. RESULTS: Unexpectedly, Arg2(-/-) mice showed profound changes in their livers at baseline, characterized by significant steatosis as demonstrated with histological and biochemical analysis. These changes were independent of systemic metabolic parameters and associated with marked mRNA level increases of genes involved in hepatic de novo lipogenesis. Liver injury and inflammation were present with elevated serum ALT, marked infiltration of F4/80 positive cells, and increased mRNA levels of inflammatory genes. HFAT feeding exacerbated these changes. Macrophage depletion after CLOD injection significantly attenuated lipid deposition and normalized lipogenic mRNA profile of livers from Arg2(-/-) mice. CONCLUSIONS: This study identifies arginase 2 as a novel link between innate immune responses, hepatic lipid deposition, and liver injury.