Ethanol exposure modulates hepatic S-adenosylmethionine and S-adenosylhomocysteine levels in the isolated perfused rat liver through changes in the redox state of the NADH/NAD(+) system.

Methionine metabolism is disrupted in patients with alcoholic liver disease, resulting in altered hepatic concentrations of S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), and other metabolites. The present study tested the hypothesis that reductive stress mediates the effects of ethanol on liver methionine metabolism. Isolated rat livers were perfused with ethanol or propanol to induce a reductive stress by increasing the NADH/NAD(+) ratio, and the concentrations of SAM and SAH in the liver tissue were determined by high-performance liquid chromatography.

Integrated hepatic transcriptome and proteome analysis of mice with high-fat diet-induced nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver disease in the US and refers to a wide spectrum of liver damage, including simple steatosis, steatohepatitis, fibrosis and cirrhosis. The goal of the present study was to achieve a more detailed understanding of the molecular changes in response to high fat-induced liver steatosis through the identification of a differentially expressed liver transcriptome and proteome. Male C57/BL6 mice fed a high-fat lard diet for 8 weeks developed visceral obesity and hepatic steatosis characterized by significantly increased liver and plasma free fatty acid and triglyceride levels and plasma alanine aminotransferase activities.

Genome-wide transcriptome expression in the liver of a mouse model of high carbohydrate diet-induced liver steatosis and its significance for the disease.

Purpose: To perform a large-scale gene profiling of the liver in a mouse model of fatty liver induced by high carbohydrate (sucrose) diet (HCD) to gain a deeper insight into potential mechanisms of diet-induced hepatic steatosis.

Methods: C57BL/6 male mice were fed either a purified, control diet or a HCD for 16 weeks. HCD feeding led to marked liver steatosis without inflammation or necrosis.

Inhibition of adiponectin production by homocysteine: a potential mechanism for alcoholic liver disease.

Unlabelled: Although recent evidence suggests that down-regulation of production of the adipocyte hormone adiponectin has pathophysiological consequences for the development of alcoholic liver disease (ALD), the underlying mechanisms are elusive. Abnormal hepatic methionine-homocysteine metabolism induced by prolonged alcohol exposure has been reported both in clinical and experimental studies of ALD. Here, we conducted both in vivo and in vitro experiments to examine the effects of prolonged alcohol exposure on homocysteine levels in adipose tissue, its potential involvement in regulating adiponectin production, and the consequences for ALD.

Silymarin prevents palmitate-induced lipotoxicity in HepG2 cells: involvement of maintenance of Akt kinase activation.

Whereas adipocytes have a unique capacity to store excess free fatty acids in the form of triglyceride in lipid droplets, non-adipose tissues, such as liver, have a limited capacity for storage of lipids. Saturated long-chain fatty acids, such as palmitate, are the major contributors to lipotoxicity. Silymarin is a mixture of flavonolignans, extracted from the milk thistle (Silibum marianum).

Involvement of AMP-activated protein kinase in beneficial effects of betaine on high-sucrose diet-induced hepatic steatosis.

Although simple steatosis was originally thought to be a pathologically inert histological change, fat accumulation in the liver may play a critical role not only in disease initiation, but also in the progression to nonalcoholic steatohepatitis and cirrhosis. Therefore, prevention of fat accumulation in the liver may be an effective therapy for multiple stages of nonalcoholic fatty liver disease (NAFLD). Promising beneficial effects of betaine supplementation on human NAFLD have been reported in some pilot clinical studies; however, data related to betaine therapy in NAFLD are limited.

Alcohol-induced S-adenosylhomocysteine accumulation in the liver sensitizes to TNF hepatotoxicity: possible involvement of mitochondrial S-adenosylmethionine transport.

Hepatocytes are resistant to tumor necrosis factor-alpha- (TNF) induced killing/apoptosis under normal circumstances, but primary hepatocytes from rats chronically fed alcohol have increased TNF cytotoxicity. Therefore, there must be mechanism(s) by which alcohol exposure "sensitizes" to TNF hepatotoxicity. Abnormal metabolism of methionine and S-adenosylmethionine (SAM) are well-documented acquired metabolic abnormalities in ALD.

Nonalcoholic fatty liver disease: predisposing factors and the role of nutrition.

More than 20% of Americans have nonalcoholic fatty liver disease (NAFLD), and this is, by far, the leading cause of abnormal liver enzymes in the United States. Nonalcoholic steatohepatitis (NASH), a more serious form of NAFLD, can proceed to cirrhosis and even hepatocellular carcinoma. These liver diseases represent the hepatic component of the metabolic syndrome, and this spectrum of liver disease represents a major health problem both in the United States and worldwide.

4-Hydroxynonenal-induced apoptosis in rat hepatic stellate cells: mechanistic approach.

Background And Aim: Although lipid peroxidation products act as apoptotic signals for several cell types, including hepatic stellate cells, the underlying mechanisms are not well understood. In this study we determined if: (i) 4-hydroxy-2,3-nonenal (HNE) induces apoptosis in two rat stellate cell lines, HSC-T6 and CFSC-2G; and (ii) if apoptosis is regulated at the transcriptional and/or translational level.

Methods: HSC-T6 and CFSC-2G cells were treated with HNE and total RNA and protein extracted.

Interactions of cytokines, S-Adenosylmethionine, and S-Adenosylhomocysteine in alcohol-induced liver disease and immune suppression.

Alcoholic liver disease (ALD) remains a leading cause of death in the USA. Defining mechanisms for liver cell death in ALD in order to develop potential new agents for therapeutic intervention is a major focus of the authors' work. Abnormal cytokine metabolism is a major feature of ALD, and a thorough understanding of both mechanisms and interactions of cytokine overproduction and sensitization are critical to developing a possible treatment for ALD.

Lessons from large-scale gene profiling of the liver in alcoholic liver disease.

This review examines the studies pertaining to large-scale gene profiling of liver cells and the whole liver as performed with the aid of macro- or microarray gene detection technology under the conditions of alcohol-induced liver injury. The review emphasizes the variability of the data as a function of strain, species, and model of alcohol-induced liver injury employed in different studies. Further, the review highlights the importance of determining if changes in transcriptome expression are parallelled by changes in proteome and metabolome of the liver.

Silymarin protects against acute ethanol-induced hepatotoxicity in mice.

Background: Accumulated evidence has demonstrated that both oxidative stress and abnormal cytokine production, especially tumor necrosis factor-alpha (TNF), play important etiological roles in the pathogenesis of alcoholic liver disease (ALD). Agents that have both antioxidant and anti-inflammation properties, particularly anti-TNF production, represent promising therapeutic interventions for ALD. We investigated the effects and the possible mechanism(s) of silymarin on liver injury induced by acute ethanol (EtOH) administration.

Lipopolysaccharide-induced liver apoptosis is increased in interleukin-10 knockout mice.

Although IL-10 down-regulates pro-inflammatory cytokine secretion by hepatic Kupffer cells, the mechanisms underlying its hepatoprotective effects are not fully clear. This study tested the hypothesis that IL-10 protects the liver against pro-inflammatory cytokines by counteracting their pro-apoptotic effects. Wild type and IL-10 knockout mice were treated with bacterial lipopolysaccharide and sacrificed 1, 4, 8, and 12 h later.

Dysregulated cytokine metabolism, altered hepatic methionine metabolism and proteasome dysfunction in alcoholic liver disease.

Alcoholic liver disease (ALD) remains an important complication and cause of morbidity and mortality from alcohol abuse. Major developments in our understanding of the mechanisms of ALD over the past decade are now being translated into new forms of therapy for this disease process which currently has no FDA approved treatment. Cytokines are low molecular weight mediators of cellular communication, and the pro-inflammatory cytokine tumor necrosis factor (TNF) has been shown to play a pivotal role in the development of experimental ALD.

Clinical implications of oxidative stress and antioxidant therapy.

Oxidative stress occurs when there is an imbalance between generation of reactive oxygen species and inadequate antioxidant defense systems. Oxidative stress can cause cell damage either directly or through altering signaling pathways. Oxidative stress is a unifying mechanism of injury in many types of disease processes, including gastrointestinal diseases.

Mechanisms of non-alcoholic steatohepatitis.

In 1980, the term non-alcoholic steatohepatitis was coined to describe a new syndrome occurring in patients who usually were obese (often diabetic) females who had a liver biopsy picture consistent with alcoholic hepatitis, but who denied alcohol use. The causes of this syndrome were unknown, and there was no defined therapy. More than two decades later, this clinical syndrome is only somewhat better understood, and still there is no Food and Drug Administration-approved or even generally accepted drug therapy.

Modulation of endotoxin stimulated interleukin-6 production in monocytes and Kupffer cells by S-adenosylmethionine (SAMe).

Interleukin-6 (IL-6) is a multifunctional cytokine having primarily anti-apoptotic and anti-inflammatory effects. Recent reports have documented that IL-6 plays a key role in liver regeneration. Intracellular deficiency of S-adenosylmethionine (SAMe) is a hallmark of toxin-induced liver injury.

Gene expression in the liver of rats fed alcohol by means of intragastric infusion.

It has become increasingly evident that one of the most fruitful approaches to understanding cellular processes and their relation to disease consists of large-scale gene profiling of cells, tissues, and organs. This also constitutes a first step in exploring the molecular biologic basis of various diseases. In the current study, we used cDNA microarray technology to assess possible changes in the expression of a large number of genes in the liver of rats fed alcohol (ethanol) chronically (4 weeks) by means of intragastric infusion.

Recent advances in alcoholic liver disease. IV. Dysregulated cytokine metabolism in alcoholic liver disease.

Alcoholic liver disease (ALD) remains a leading cause of death from liver disease in the United States for which there is no FDA-approved therapy. Abnormal cytokine metabolism is a major feature of ALD. Elevated serum concentration levels of TNF-alpha and TNF-alpha-inducible cytokines/chemokines, such as IL-6, -8, and -18, have been reported in patients with alcoholic hepatitis and/or cirrhosis, and levels correlated with markers of the acute phase response, liver function, and clinical outcome.

Microarray gene analysis of the liver in a rat model of chronic, voluntary alcohol intake.

The mechanisms underlying alcoholic liver disease are not fully understood. It has been established that alcohol interferes with transcriptional and translational regulatory steps of cell function. To understand such an effect, assessment of alcohol-induced changes in the simultaneous expression of a large number of genes may prove very useful.

Alcohol, but not lipopolysaccharide-induced liver apoptosis involves changes in intracellular compartmentalization of apoptotic regulators.

Background: While alcohol-induced augmentation of liver apoptosis has been demonstrated in humans and laboratory animals, the underlying mechanisms are not fully elucidated. This study addresses the question whether alcohol and bacterial lipopolysaccharide (LPS), a putative mediator of alcohol effects on the liver, induce augmentation of liver apoptosis by intrinsic or extrinsic signaling pathways. This information may prove important for future design of therapies for alcoholic liver disease.

Large-scale gene profiling of the liver in a mouse model of chronic, intragastric ethanol infusion.

Background/aims: The mechanisms underlying alcohol-induced liver injury are not fully elucidated. An approach in this direction would consist of an all-inclusive assessment of gene expression in the liver. The purpose of this study was to perform a comprehensive analysis of gene expression in the livers of mice treated with ethanol by means of intragastric infusion.

Role of apoptosis in alcoholic liver injury.

This article represents the proceedings of a symposium at the 2002 ISBRA/RSA meeting in San Francisco, USA. The organizer and chair was H. Ishii and co-chair was A.

The regulation of Fas (CD95/Apo-1)-mediated liver apoptosis in Kupffer cell-depleted mice.

The purpose of this study was to further characterize Fas-mediated liver apoptosis. We investigated whether Fas-mediated apoptosis in the liver requires induction of apoptosis-related regulators and whether Kupffer cells play a role in this process. Mice were injected with GdCl(3) to deplete/suppress Kupffer cells, followed by treatment with an anti-Fas agonistic antibody, Jo2.