AICAR and compound C negatively modulate HCC-induced primary human hepatic stellate cell activation in vitro.

Tumor stroma and microenvironment have been shown to affect hepatocellular carcinoma (HCC) growth, with activated hepatic stellate cells (HSC) as a major contributor in this process. Recent evidence suggests that the energy sensor adenosine monophosphate-activated kinase (AMPK) may mediate a series of essential processes during carcinogenesis and HCC progression. Here, we investigated the effect of different HCC cell lines with known or mutations on primary human HSC activation, proliferation, and AMPK activation.

Exogenous Liposomal Ceramide-C6 Ameliorates Lipidomic Profile, Energy Homeostasis, and Anti-Oxidant Systems in NASH.

In non-alcoholic steatohepatitis (NASH), many lines of investigation have reported a dysregulation in lipid homeostasis, leading to intrahepatic lipid accumulation. Recently, the role of dysfunctional sphingolipid metabolism has also been proposed. Human and animal models of NASH have been associated with elevated levels of long chain ceramides and pro-apoptotic sphingolipid metabolites, implicated in regulating fatty acid oxidation and inflammation.

TGF-β1-driven reduction of cytoglobin leads to oxidative DNA damage in stellate cells during non-alcoholic steatohepatitis.

Background & Aims: Cytoglobin (CYGB) is a respiratory protein that acts as a scavenger of reactive oxygen species. The molecular role of CYGB in human hepatic stellate cell (HSC) activation and human liver disease remains uncharacterised. The aim of this study was to reveal the mechanism by which the TGF-β1/SMAD2 pathway regulates the human CYGB promoter and the pathophysiological function of CYGB in human non-alcoholic steatohepatitis (NASH).

Cirrhotic Human Liver Extracellular Matrix 3D Scaffolds Promote Smad-Dependent TGF-β1 Epithelial Mesenchymal Transition.

An altered liver microenvironment characterized by a dysregulated extracellular matrix (ECM) supports the development and progression of hepatocellular carcinoma (HCC). The development of experimental platforms able to reproduce these physio-pathological conditions is essential in order to identify and validate new therapeutic targets for HCC. The aim of this work was to validate a new in vitro model based on engineering three-dimensional (3D) healthy and cirrhotic human liver scaffolds with HCC cells recreating the micro-environmental features favoring HCC.

Evaluation of NV556, a Novel Cyclophilin Inhibitor, as a Potential Antifibrotic Compound for Liver Fibrosis.

Hepatic fibrosis can result as a pathological response to nonalcoholic steatohepatitis (NASH). Cirrhosis, the late stage of fibrosis, has been linked to poor survival and an increased risk of developing hepatocellular carcinoma, with limited treatment options available. Therefore, there is an unmet need for novel effective antifibrotic compounds.

The adenosine monophosphate-activated protein kinase-vacuolar adenosine triphosphatase-pH axis: A key regulator of the profibrogenic phenotype of human hepatic stellate cells.

Unlabelled: Liver fibrosis and cirrhosis are characterized by activation of hepatic stellate cells (HSCs), which is associated with higher intracellular pH (pHi). The vacuolar H adenosine-triphosphatase (v-ATPase) multisubunit complex is a key regulator of pHi homeostasis. The present work investigated the functional role of v-ATPase in primary human HSC (hHSC) activation and its modulation by specific adenosine monophosphate-activated protein kinase (AMPK) subunits.

Fibroblast growth factor 2 (FGF2) regulates cytoglobin expression and activation of human hepatic stellate cells via JNK signaling.

Cytoglobin (CYGB) belongs to the mammalian globin family and is exclusively expressed in hepatic stellate cells (HSCs) in the liver. In addition to its gas-binding ability, CYGB is relevant to hepatic inflammation, fibrosis, and cancer because of its anti-oxidative properties; however, the regulation of gene expression remains unknown. Here, we sought to identify factors that induce CYGB expression in HSCs and to clarify the molecular mechanism involved.

Rapid production of human liver scaffolds for functional tissue engineering by high shear stress oscillation-decellularization.

The development of human liver scaffolds retaining their 3-dimensional structure and extra-cellular matrix (ECM) composition is essential for the advancement of liver tissue engineering. We report the design and validation of a new methodology for the rapid and accurate production of human acellular liver tissue cubes (ALTCs) using normal liver tissue unsuitable for transplantation. The application of high shear stress is a key methodological determinant accelerating the process of tissue decellularization while maintaining ECM protein composition, 3D-architecture and physico-chemical properties of the native tissue.

Reactive gamma-ketoaldehydes as novel activators of hepatic stellate cells in vitro.

Aims: Products of lipid oxidation, such as 4-hydroxynonenal (4-HNE), are key activators of hepatic stellate cells (HSC) to a pro-fibrogenic phenotype. Isolevuglandins (IsoLG) are a family of acyclic γ-ketoaldehydes formed through oxidation of arachidonic acid or as by-products of the cyclooxygenase pathway. IsoLGs are highly reactive aldehydes which are efficient at forming protein adducts and cross-links at concentrations 100-fold lower than 4-hydroxynonenal.

Activation of signal transduction pathways during hepatic oncogenesis.

Background And Aims: Understanding the molecular pathogenesis of hepatocellular carcinoma (HCC) is essential to identify therapeutic targets. A hepatitis B virus (HBV) related double transgenic murine model was developed.

Methods: Liver specific expression of HBV X protein (HBx) and insulin receptor substrate 1 (IRS1) was achieved and transgenic mice were followed from birth to age 21 months.

Decellularized human liver as a natural 3D-scaffold for liver bioengineering and transplantation.

Liver synthetic and metabolic function can only be optimised by the growth of cells within a supportive liver matrix. This can be achieved by the utilisation of decellularised human liver tissue. Here we demonstrate complete decellularization of whole human liver and lobes to form an extracellular matrix scaffold with a preserved architecture.

Therapeutic reversal of chronic alcohol-related steatohepatitis with the ceramide inhibitor myriocin.

Alcohol-related liver disease (ALD) is associated with steatohepatitis and insulin resistance. Insulin resistance impairs growth and disrupts lipid metabolism in hepatocytes. Dysregulated lipid metabolism promotes ceramide accumulation and oxidative stress, leading to lipotoxic states that activate endoplasmic reticulum (ER) stress pathways and worsen inflammation and insulin resistance.

Non-alcoholic fatty liver disease (NAFLD): a tale of fat and sugar?

The global diffusion of the so-called Western diet, which is enriched in fat and carbohydrates, such as fructose, has been proposed to be an underlying cause of the increased prevalence of metabolic conditions, including non-alcoholic fatty liver disease (NAFLD). This Smart Card summarizes the main metabolic and hepatic histological features of rodent models fed with diets combining high fat and fructose.

Ceramide inhibitor myriocin restores insulin/insulin growth factor signaling for liver remodeling in experimental alcohol-related steatohepatitis.

Background And Aim: Alcohol-related liver disease (ALD) is mediated in part by insulin resistance. Attendant dysregulation of lipid metabolism increases accumulation of hepatic ceramides that worsen insulin resistance and compromise the structural and functional integrity of the liver. Insulin and insulin growth factor (IGF) stimulate aspartyl-asparaginyl-β-hydroxylase (AAH), which promotes cell motility needed for structural maintenance and remodeling of the liver.

Insulin resistance, ceramide accumulation and endoplasmic reticulum stress in experimental chronic alcohol-induced steatohepatitis.

Aims: Chronic alcohol abuse causes steatohepatitis with insulin resistance, which impairs hepatocellular growth, survival and metabolism. However, growing evidence supports the concept that progressive alcohol-related liver injury may be mediated by concurrent mal-signaling through other networks that promote insulin resistance, e.g.

Insulin resistance, ceramide accumulation, and endoplasmic reticulum stress in human chronic alcohol-related liver disease.

Background: Chronic alcohol-related liver disease (ALD) is mediated by insulin resistance, mitochondrial dysfunction, inflammation, oxidative stress, and DNA damage. Recent studies suggest that dysregulated lipid metabolism with accumulation of ceramides, together with ER stress potentiate hepatic insulin resistance and may cause steatohepatitis to progress.

Objective: We examined the degree to which hepatic insulin resistance in advanced human ALD is correlated with ER stress, dysregulated lipid metabolism, and ceramide accumulation.

Dysfunctional pro-ceramide, ER stress, and insulin/IGF signaling networks with progression of Alzheimer's disease.

In Alzheimer's disease (AD), brain insulin and insulin-like growth factor (IGF) resistance and deficiency begin early, and worsen with severity of disease. The factors mediating progression of brain insulin/IGF resistance in AD are not well understood. We hypothesize that AD progression is mediated via negative cross-talk that promotes toxic ceramide generation and endoplasmic reticulum (ER) stress.

High fat diet induced hepatic steatosis and insulin resistance: Role of dysregulated ceramide metabolism.

Aim:   Non-alcoholic fatty liver disease (NAFLD) is an insulin resistance disease that can progress to cirrhosis and liver failure. We hypothesized that in NAFLD, insulin resistance dysregulates lipid metabolism, increasing production of cytotoxic lipids including ceramides, which exacerbate hepatic insulin resistance and injury.

Methods:   Long Evans rats were pair-fed low (LFD) or high (HFD) fat diets for 8 weeks.

Weight loss amelioration of non-alcoholic steatohepatitis linked to shifts in hepatic ceramide expression and serum ceramide levels.

Aim:   Non-alcoholic steatohepatitis (NASH) is associated with increased hepatic insulin resistance. Ceramides and other toxic sphingolipids promote inflammation, lipotoxicity and insulin resistance; however, the role of ceramides in the pathogenesis of NASH has not been determined. This study characterizes expression of ceramide-related genes in human livers with NASH and examines the effects of weight loss on NASH and pro-ceramide gene expression in liver.

Limited therapeutic effect of N-acetylcysteine on hepatic insulin resistance in an experimental model of alcohol-induced steatohepatitis.

Background: Alcohol-related steatohepatitis is associated with increased oxidative stress, DNA damage, lipotoxicity, and insulin resistance in liver. As inflammation and oxidative stress can promote insulin resistance, effective treatment with antioxidants, for example, N-acetylcysteine (NAC), may restore ethanol-impaired insulin signaling in the liver.

Methods: Adult male Sprague-Dawley rats were fed for 130 days with liquid diets containing 0 or 37% ethanol by caloric content, and simultaneously treated with vehicle or NAC.

Peroxisome proliferator-activated receptor agonist treatment of alcohol-induced hepatic insulin resistance.

Aim:   Chronic ethanol exposure impairs insulin signaling in the liver. Peroxisome-proliferator activated receptor (PPAR) agonists function as insulin sensitizers and are used to treat type 2 diabetes mellitus. We examined the therapeutic effectiveness of PPAR agonists in reducing alcoholic hepatitis and hepatic insulin resistance in a model of chronic ethanol feeding.

Rat strain differences in susceptibility to alcohol-induced chronic liver injury and hepatic insulin resistance.

The finding of more severe steatohepatitis in alcohol fed Long Evans (LE) compared with Sprague Dawley (SD) and Fisher 344 (FS) rats prompted us to determine whether host factors related to alcohol metabolism, inflammation, and insulin/IGF signaling predict proneness to alcohol-mediated liver injury. Adult FS, SD, and LE rats were fed liquid diets containing 0% or 37% (calories) ethanol for 8 weeks. Among controls, LE rats had significantly higher ALT and reduced GAPDH relative to SD and FS rats.

Ceramide-mediated insulin resistance and impairment of cognitive-motor functions.

Obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic steatohepatitis (NASH) are associated with cognitive impairment, brain insulin resistance, and neurodegeneration. Recent studies linked these effects to increased pro-ceramide gene expression in liver and increased ceramide levels in serum. Since ceramides are neurotoxic and cause insulin resistance, we directly examined the role of ceramides as mediators of impaired signaling and central nervous system function using an in vivo model.

Early limited nitrosamine exposures exacerbate high fat diet-mediated type 2 diabetes and neurodegeneration.

Background: Type 2 diabetes mellitus (T2DM) and several types of neurodegeneration, including Alzheimer's, are linked to insulin-resistance, and chronic high dietary fat intake causes T2DM with mild neurodegeneration. Intra-cerebral Streptozotocin, a nitrosamine-related compound, causes neurodegeneration, whereas peripheral treatment causes DM.

Hypothesis: Limited early exposures to nitrosamines that are widely present in the environment, enhance the deleterious effects of high fat intake in promoting T2DM and neurodegeneration.

Nitrosamine exposure exacerbates high fat diet-mediated type 2 diabetes mellitus, non-alcoholic steatohepatitis, and neurodegeneration with cognitive impairment.

Background: The current epidemics of type 2 diabetes mellitus (T2DM), non-alcoholic steatohepatitis (NASH), and Alzheimer's disease (AD) all represent insulin-resistance diseases. Previous studies linked insulin resistance diseases to high fat diets or exposure to streptozotocin, a nitrosamine-related compound that causes T2DM, NASH, and AD-type neurodegeneration. We hypothesize that low-level exposure to nitrosamines that are widely present in processed foods, amplifies the deleterious effects of high fat intake in promoting T2DM, NASH, and neurodegeneration.