Molecular mechanisms of alcoholic fatty liver

The biphasic dose effect of lychee (Litchi chinensis Sonn.) pulp phenolic extract on alcoholic liver disease in mice

Lychee pulp phenolic extract (LPPE) has a biphasic dose response in ethanol-induced liver injury in mice.

Resveratrol Ameliorates Alcoholic Fatty Liver by Inducing Autophagy

Alcoholic fatty liver (AFL) is early stage of alcoholic liver disease, which can progress to steatohepatitis, fibrosis, and cirrhosis if alcohol consumption is continued. The pathogenesis of AFL is associated with excessive lipid accumulation in hepatocytes. Resveratrol (RES), a dietary polyphenol found in red wines and grapes, has been shown to have a hepatoprotective effect. Autophagy is a crucial physiological process in cellular catabolism that involves the regulation of lipid droplets. Autophagy maintains a balance between protein synthesis, degradation and self-recycling. In the present study, we evaluated the protective effects of RES (10[Formula: see text]mg/kg, 30[Formula: see text]mg/kg, 100[Formula: see text]mg/kg) on AFL mice fed with an ethanol Lieber-DeCarli liquid diet, and HepG2 cells in the presence of oleic acid and alcohol to investigate whether resveratrol could induce autophagy to attenuate lipid accumulation. The results showed that RES (30[Formula: see text]mg/kg and 100[Formula: see text]mg/kg) treatment significantly attenuated hepatic steatosis and lowered the activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), low density lipoprotein cholesterol (LDL-C). H&E staining showed that RES reduced hepatic lipid accumulation. Transmission electron microscopy (TEM) images showed that RES treatment increased the number of autophagosomes and promoted the formation of autophagy. Western blot analysis showed that RES treatment increased the levels of microtubule-associated protein light chain3- II (LC3-II) and Beclin1, decreased expression of p62 protein. In addition, in vitro studies also demonstrated that RES led to the formation of acidic vesicular organelles (AVOs), however, 3-Methyladenine (3-MA), a specific inhibitor of autophagy, obviously inhibited the above effects of RES. In conclusion, RES has protective effects on alcoholic hepatic steatosis, and the potential mechanism might be involved in inducing autophagy.

Diet Supplementation with Allicin Protects against Alcoholic Fatty Liver Disease in Mice by Improving Anti-inflammation and Antioxidative Functions

This study investigated the liver-protective effects of allicin, an active compound in fresh garlic, against alcoholic fatty liver disease (AFLD) and liver inflammation. Its effects were investigated in an AFLD model in male C57BL/6 mice, which were fed Lieber-DeCarli liquid diet containing ethanol. Allicin (5 and 20 mg/kg bw/day) was orally administered daily in the AFLD mice for 4 weeks. The results indicate that allicin promotes hepatoprotection by significantly reducing aspartate transaminase (AST) and alanine transaminase (ALT) levels (p < 0.05) in the plasma, which are key indicators of liver damage. Allicin reduced fat accumulation, increased glutathione and catalase levels, and decreased microsomal protein cytochrome P450 2E1 (CYP2E1) expression (p < 0.05) in the livers of the AFLD mice. Furthermore, allicin supplementation significantly decreased the levels of proinflammatory tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 and suppressed the expression of sterol regulatory element-binding protein-1 (SREBP-1) (p < 0.05). Additionally, it improved the hepatic alcohol dehydrogenase (ADH) activity (p < 0.05). Collectively, these findings demonstrate that allicin attenuates liver oxidative stress and inflammation.

REV-ERBα Activates C/EBP Homologous Protein to Control Small Heterodimer Partner-Mediated Oscillation of Alcoholic Fatty Liver

The small heterodimer partner (SHP) nuclear receptor is an important regulator of nonalcoholic fatty liver disease. However, little is known about the role of SHP in alcoholic fatty liver. In this study, we used a modified chronic ethanol-binge model to examine cyclic alterations of lipid metabolism in wild-type (WT) and Shp^-/- mice over a 24-hour period after binge. The serum and hepatic lipid profiles, as well as the expression of lipid synthesis genes and markers of endoplasmic reticulum stress, exhibited distinct variations in WT and Shp^-/- mice in response to ethanol diet plus ethanol binge (ED+E) and control diet plus maltose binge. ED+E induced steatosis in WT mice, which correlated with a marked up-regulation of activating transcription factor 4 protein (ATF4) but down-regulation of C/EBP homologous protein (CHOP) and sterol regulatory element-binding transcription factor 1c protein (SREBP-1c). On the contrary, the control diet plus maltose binge caused lipid accumulation in Shp^-/- mice, which was accompanied by a sharp elevation of CHOP, SREBP-1c, and REV-ERBα proteins but a diminished ATF4. REV-ERBα activated CHOP promoter activity and gene transcription, which were inhibited by SHP. Knockdown Rev-Erbα in Shp^-/- mice prevented steatosis induced by ED+E. Our study revealed a critical role of SHP and REV-ERBα in controlling rhythmic CHOP expression in alcoholic fatty liver.

Dietary Fisetin Supplementation Protects Against Alcohol-Induced Liver Injury in Mice

BACKGROUND

Overproduction of reactive oxygen species is associated with the development of alcoholic liver disease (ALD). Plant polyphenols have been used as dietary interventions for multiple diseases including ALD. The objective of this study was to determine whether dietary supplementation with fisetin, a novel flavonoid, exerts beneficial effect on alcohol-induced liver injury.

METHODS

C57BL/6J mice were pair-fed with the Lieber-DeCarli control or ethanol (EtOH) diet for 4 weeks with or without fisetin supplementation at 10 mg/kg/d.

RESULTS

Alcohol feeding induced lipid accumulation in the liver and increased plasma alanine aminotransferase and aspartate aminotransferase activities, which were attenuated by fisetin supplementation. The EtOH concentrations in the plasma and liver were significantly elevated by alcohol exposure but were reduced by fisetin supplementation. Although fisetin did not affect the protein expression of alcohol metabolism enzymes, the aldehyde dehydrogenase activities were significantly increased by fisetin compared to the alcohol alone group. In addition, fisetin supplementation remarkably reduced hepatic NADPH oxidase 4 levels along with decreased plasma hydrogen peroxide and hepatic superoxide and 4-hydroxynonenal levels after alcohol exposure. Alcohol-induced apoptosis and up-regulation of Fas and cleaved caspase-3 in the liver were prevented by fisetin. Moreover, fisetin supplementation attenuated alcohol-induced hepatic steatosis through increasing plasma adiponectin levels and hepatic protein levels of p-AMPK, ACOX1, CYP4A, and MTTP.

CONCLUSIONS

This study demonstrated that the protective effect of fisetin on ALD is achieved by accelerating EtOH clearance and inhibition of oxidative stress. The data suggest that fisetin has a therapeutical potential for treating ALD.

Purple potato (Solanum tuberosum L.) anthocyanins attenuate alcohol-induced hepatic injury by enhancing antioxidant defense

Alcoholic liver disease (ALD) is a serious and challenging health issue. In the past decade, natural components possessing hepatoprotective properties have gained more attention for ALD intervention. In this study, the phytochemical components of anthocyanins from purple potato were assessed using UPLC-MS/MS, and the hepatoprotective effects of purple potato anthocyanins (PPAs) were investigated in the ALD mouse model. Serum and liver biochemical parameters were determined, along with histopathological changes in liver tissue. In addition, the major contributors to alcohol-induced oxidative stress were assessed. The results indicated that the levels of aspartate transaminase and alanine transaminase were lower in the serum of the PPA-treated group than the alcohol-treated group. PPAs significantly inhibited the reduction of total cholesterol and triglycerides. Higher levels of superoxide dismutase and reduced glutathione enzymes as well as a reduction in the formation of malondialdehyde occurred in mice fed with PPAs. In addition, PPAs protected against increased alcohol-induced levels and activity of cytochrome P450 2E1 (CYP2E1), which demonstrates the effects of PPAs against alcohol-induced oxidative stress and liver injury. This study suggests that PPAs could be an effective therapeutic agent in alcohol-induced liver injuries by inhibiting CYP2E1 expression and thereby strengthening antioxidant defenses.

Liver-specific Gene Inactivation of the Transcription Factor ATF4 Alleviates Alcoholic Liver Steatosis in Mice

Although numerous biological functions of the activating transcription factor 4 (ATF4) have been identified, a direct effect of ATF4 on alcoholic liver steatosis has not been described previously. The aim of our current study is to investigate the role of ATF4 in alcoholic liver steatosis and elucidate the underlying mechanisms. Here, we showed that the expression of ATF4 is induced by ethanol in hepatocytes in vitro and in vivo, and liver-specific ATF4 knock-out mice are resistant to ethanol-induced liver steatosis, associated with stimulated hepatic AMP-activated protein kinase (AMPK) activity. Furthermore, adenovirus-mediated AMPK knockdown significantly reversed the suppressive effects of ATF4 deficiency on ethanol-induced liver steatosis in mice. In addition, ethanol-fed ATF4 knock-out mice exhibit AMPK-dependent inhibition of fatty acid synthase and stimulation of carnitine palmitoyltransferase 1 (CPT1) in the liver. Moreover, hepatic Tribbles homolog 3 (TRB3) expression was stimulated by ethanol in an ATF4-dependent manner, and adenovirus-mediated TRB3 knockdown blocked ATF4-dependent ethanol-induced AMPK inhibition and triglyceride accumulation in AML-12 cells. Finally, TRB3 directly interacted with AMPK to suppress its phosphorylation. Taken together, these results identify the ATF4-TRB3-AMPK axis as a novel pathway responsible for ethanol-induced liver steatosis.

Deletion of Gab2 in mice protects against hepatic steatosis and steatohepatitis: a novel therapeutic target for fatty liver disease

Fatty liver disease is a serious health problem worldwide and is the most common cause for chronic liver disease and metabolic disorders. The major challenge in the prevention and intervention of this disease is the incomplete understanding of the underlying mechanism and thus lack of potent therapeutic targets due to multifaceted and interdependent disease factors. In this study, we investigated the role of a signaling adaptor protein, GRB2-associated-binding protein 2 (Gab2), in fatty liver using an animal disease model. Gab2 expression in hepatocytes responded to various disease factor stimulations, and Gab2 knockout mice exhibited resistance to fat-induced obesity, fat- or alcohol-stimulated hepatic steatosis, as well as methionine and choline deficiency-induced steatohepatitis. Concordantly, the forced expression or knockdown of Gab2 enhanced or diminished oleic acid (OA)- or ethanol-induced lipid production in hepatocytes in vitro, respectively. During lipid accumulation in hepatocytes, both fat and alcohol induced the recruitment of PI3K or Socs3 by Gab2 and the activation of their downstream signaling proteins AKT, ERK, and Stat3. Therefore, Gab2 may be a disease-associated protein that is induced by pathogenic factors to amplify and coordinate multifactor-induced signals to govern disease development in the liver. Our research provides a novel potential target for the prevention and intervention of fatty liver disease.

Ethanolic Extract of Acanthopanax koreanum Nakai Alleviates Alcoholic Liver Damage Combined with a High-Fat Diet in C57BL/6J Mice

Alcoholic and nonalcoholic liver steatosis have an indistinguishable spectrum of histological features and liver enzyme elevations. In this study, we investigated the potential of the ethanolic extract of Acanthopanax koreanum Nakai (AK) to protect against experimental alcoholic liver disease in a mouse model that couples diet and daily ethanol bolus gavage. Fifty-six C57BL/6J mice were randomly divided into seven groups: normal control (NC), alcohol control (AC), alcohol/HFD control (AH), low-dose (1%) AK in alcohol group (ACL), high-dose (3%) AK in alcohol group (ACH), low-dose AK in alcohol/HFD group (AHL), and high-dose AK in alcohol/HFD group (AHH). The AH group showed more severe damage than the AC group in terms of biochemical and molecular data that were observed in this study. The administration of AK exerted remarkable effects in: plasma ALT (p < 0.0001), total lipid (p = 0.014), TG (p = 0.0037) levels; CPT-1α (p = 0.0197), TLR4 (p < 0.0001), CD14 (p = 0.0002), IL-6 (p = 0.0264) and MCP-1 (p = 0.0045) gene expressions; and ALDH (p < 0.0001) and CAT (p = 0.0076) activities. The data suggested that at least the high dose AK might confer protection against alcoholic liver damage combined with an HFD by accelerating lipid oxidation and alcohol metabolism and by suppressing the inflammatory response, including the TLR pathway.

Tobacco Smoke-Induced Hepatic Injury with Steatosis, Inflammation, and Impairments in Insulin and Insulin-Like Growth Factor Signaling

Background

Alcoholic liver disease (ALD) is associated with impairments in hepatic insulin and insulin-like growth factor (IGF) signaling through cell growth, survival, and metabolic pathways. Since not all heavy drinkers develop ALD, co-factors may be important. Epidemiologic data indicate that most heavy drinkers smoke tobacco and experimental data revealed that low-level nitrosamine exposures, including those from tobacco, can cause steatohepatitis with hepatic insulin/IGF resistance and exacerbate ALD. We hypothesize that cigarette smoke (CS) exposures also cause liver injury with impaired hepatic insulin/IGF signaling, and thereby contribute to ALD.

Methods

Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 (CS4) or 8 (CS8) weeks, or CS for 8 weeks with 2 weeks recovery (CS8+R).

Results

CS exposures caused progressive liver injury with disruption of the normal hepatic chord architecture, lobular inflammation, apoptosis or necrosis, micro-steatosis, sinusoidal dilatation, and nuclear pleomorphism. Histopathological liver injury scores increased significantly from A8 to CS4 and then further to CS8 (P<0.0001). The mean histological grade was also higher in CS8+R relative to A8 (P<0.0001) but lower than in CS4, reflecting partial resolution of injury by CS withdrawal. CS exposures impaired insulin and IGF-1 signaling through IRS-1, Akt, GSK-3β, and PRAS40. Livers from CS8+R mice had normalized or elevated levels of insulin receptor, pYpY-Insulin-R, 312S-IRS-1, 473S-Akt, S9-GSK-3β, and pT246-PRAS40 relative to A8, CS4, or CS8, reflecting partial recovery.

Conclusion

CS-mediated liver injury and steatohepatitis with impairments in insulin/IGF signalling are reminiscent of the findings in ALD. Therefore, CS exposures (either first or second-hand) may serve as a co-factor in ALD. The persistence of several abnormalities following CS exposure cessation suggests that some aspects of CS-mediated hepatic metabolic dysfunction are not readily reversible.

Hepatoprotective Effects of Chinese Medicinal Herbs: A Focus on Anti-Inflammatory and Anti-Oxidative Activities

The liver is intimately connected to inflammation, which is the innate defense system of the body for removing harmful stimuli and participates in the hepatic wound-healing response. Sustained inflammation and the corresponding regenerative wound-healing response can induce the development of fibrosis, cirrhosis and eventually hepatocellular carcinoma. Oxidative stress is associated with the activation of inflammatory pathways, while chronic inflammation is found associated with some human cancers. Inflammation and cancer may be connected by the effect of the inflammation-fibrosis-cancer (IFC) axis. Chinese medicinal herbs display abilities in protecting the liver compared to conventional therapies, as many herbal medicines have been shown as effective anti-inflammatory and anti-oxidative agents. We review the relationship between oxidative stress and inflammation, the development of hepatic diseases, and the hepatoprotective effects of Chinese medicinal herbs via anti-inflammatory and anti-oxidative mechanisms. Moreover, several Chinese medicinal herbs and composite formulae, which have been commonly used for preventing and treating hepatic diseases, including Andrographis Herba, Glycyrrhizae Radix et Rhizoma, Ginseng Radix et Rhizoma, Lycii Fructus, Coptidis Rhizoma, curcumin, xiao-cha-hu-tang and shi-quan-da-bu-tang, were selected for reviewing their hepatoprotective effects with focus on their anti-oxidative and ant-inflammatory activities. This review aims to provide new insight into how Chinese medicinal herbs work in therapeutic strategies for liver diseases.

Deletion of tumor progression locus 2 attenuates alcohol-induced hepatic inflammation

BACKGROUND

The pathogenesis of alcoholic liver disease (ALD) involves the interaction of several inflammatory signaling pathways. Tumor progression locus 2 (TPL2), also known as Cancer Osaka Thyroid (COT) and MAP3K8, is a serine-threonine kinase that functions as a critical regulator of inflammatory pathways by up-regulating production of inflammatory cytokines. The present study aims to fill the gap in knowledge regarding the involvement of TPL2 in the mechanism of alcohol-induced hepatic inflammation.

METHODS

Male TPL2(-/-) knockout (TPL2KO) mice and TPL2(+/+) wild-type (WT) mice were group pair-fed with Lieber-DeCarli liquid ethanol diet (EtOH diet, 27% energy from EtOH) or control diet (ctrl diet) for 4 weeks. Both histological and molecular biomarkers involved in the induction of hepatic inflammation by alcohol consumption were examined.

RESULTS

Consumption of the EtOH diet in WT mice lead to a significant induction of TPL2 mRNA expression as compared with WT mice fed ctrl diet. A significant induction in inflammatory foci and steatosis was also observed in WT mice fed EtOH diet. The deletion of TPL2 significantly reduced inflammatory foci in the liver of mice consuming both ctrl and EtOH diets as compared to their respective WT controls. This reduction was associated with suppression of hepatic inflammatory gene expression of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) and macrophage marker F4/80. In addition, histological analysis of livers revealed that TPL2 deletion resulted in reduced steatosis in both ctrl (significant) and EtOH (non-significant) diet-fed mice as compared to their respective WT controls.

CONCLUSIONS

The demonstration that TPL2 deletion attenuates alcohol-induced hepatic inflammation provides evidence of a novel role for TPL2 in the pathogenesis of ALD.

Hepatic non-parenchymal cells: Master regulators of alcoholic liver disease?

Chronic alcohol consumption is one of the most common causes of the progression of alcoholic liver disease (ALD). In the past, alcohol-mediated hepatocyte injury was assumed to be a significantly major cause of ALD. However, a huge number of recent and brilliant studies have demonstrated that hepatic non-parenchymal cells including Kupffer cells, hepatic stellate cells, liver sinusoidal endothelial cells and diverse types of lymphocytes play crucial roles in the pathogenesis of ALD by producing inflammatory mediators such as cytokines, oxidative stress, microRNA, and lipid-originated metabolites (retinoic acid and endocannabinoids) or by directly interacting with parenchymal cells (hepatocytes). Therefore, understanding the comprehensive roles of hepatic non-parenchymal cells during the development of ALD will provide new integrative directions for the treatment of ALD. This review will address the roles of non-parenchymal cells in alcoholic steatosis, inflammation, and liver fibrosis and might help us to discover possible therapeutic targets and treatments involving modulating the non-parenchymal cells in ALD.

Melatonin Upregulates the Activity of AMPK and Attenuates Lipid Accumulation in Alcohol-induced Rats

AIMS

Melatonin is supposed to be an effective hepatoprotective agent. The effects and mechanisms of melatonin on alcoholic fatty liver (AFL) have not been well explored. The aim of this study was to investigate the preventive and therapeutic effects of melatonin on alcohol-induced fatty liver rats.

METHODS

The AFL rats were induced by intragastric infusion of alcohol plus a high-fat diet for 6 weeks, and melatonin (10, 20, 40 mg/kg) was administered by gastric perfusion. We also established fatty acid overload cell model in HepG2 cells to investigate the effect of melatonin on AMP-activated protein kinase (AMPK) activity.

RESULTS

The results showed that melatonin (20 and 40 mg/kg) administration significantly reduced alcohol-induced hepatic steatosis with lowering activities of serum alanine aminotransferase, aspartate aminotransferase and levels of serum and hepatic triglyceride. The activity of superoxide dismutase was increased and the content of malondialdehyde was decreased in liver homogenates of rats treated with melatonin. Melatonin increased the phosphorylation of AMPK in the liver tissues of alcohol-induced rats as well. Additionally, in vitro studies showed that melatonin increased the expression of melatonin1A receptor (MT1R), whereas luzindole, a receptor antagonist of melatonin, had no effect on its expression. In addition, melatonin reduced the levels of adenosine 3',5'-cyclic monophosphate (cAMP) and increased the phosphorylation of AMPK, and melatonin treatment could markedly reverse these effects.

CONCLUSION

In conclusion, melatonin could protect against liver injury caused by alcohol gastric perfusion. The effect may be related to alleviating lipid peroxidation and upregulating the activity of AMPK mediated by MT1R signaling pathway.

Heme oxygenase-1 alleviates alcoholic liver steatosis: histopathological study

Excessive alcohol consumption is one of the most important causes of hepatic steatosis, which involves oxidative stress. In particular, increased oxidative stress has been strongly linked to stimulation of the expression of heme oxygenase-1 (HO-1). This study aimed to investigate whether HO-1 could alleviates alcoholic steatosis in rats. Male Wistar rats were randomly divided into 4 groups: 1) the control group, 2) the EtOH group, 3) the EtOH + ZnPP-IX group and 4) the EtOH + Hemin group. Liver histopathology was investigated in weeks 1 and 4 after the start of the treatment period. Alcohol treatment significantly increased the hepatic malondialdehyde (MDA) levels, an oxidative stress marker. In addition, it increased the triglyceride, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in both weeks. Gross examination demonstrated a yellowish and slightly enlarged liver in the alcohol-treated rats. Hematoxylin and eosin (H&E) and Oil Red O staining indicated hepatic steatosis, which was characterized by diffuse, extensive fatty accumulation and discrete lipid droplets of variable size in hepatocytes of the alcohol-treated rats. Administration of the HO-1 inducer hemin resulted in upregulation of hepatic HO-1 gene expression, reduced the MDA, triglyceride, ALT and AST levels and alleviated alcoholic hepatic steatosis, whereas administration of the HO-1 inhibitor zinc protoporphyrin IX (ZnPP-IX) resulted in downregulation of hepatic HO-1 gene expression and could not alleviate alcoholic hepatic steatosis either week. In conclusion, HO-1 could alleviate alcoholic hepatic steatosis in male Wistar rats and may be useful in development of a new therapeutic approach.

Mitochondrial dysfunction and tissue injury by alcohol, high fat, nonalcoholic substances and pathological conditions through post-translational protein modifications

Mitochondria are critically important in providing cellular energy ATP as well as their involvement in anti-oxidant defense, fat oxidation, intermediary metabolism and cell death processes. It is well-established that mitochondrial functions are suppressed when living cells or organisms are exposed to potentially toxic agents including alcohol, high fat diets, smoking and certain drugs or in many pathophysiological states through increased levels of oxidative/nitrative stress. Under elevated nitroxidative stress, cellular macromolecules proteins, DNA, and lipids can undergo different oxidative modifications, leading to disruption of their normal, sometimes critical, physiological functions. Recent reports also indicated that many mitochondrial proteins are modified via various post-translation modifications (PTMs) and primarily inactivated. Because of the recently-emerging information, in this review, we specifically focus on the mechanisms and roles of five major PTMs (namely oxidation, nitration, phosphorylation, acetylation, and adduct formation with lipid-peroxides, reactive metabolites, or advanced glycation end products) in experimental models of alcoholic and nonalcoholic fatty liver disease as well as acute hepatic injury caused by toxic compounds. We also highlight the role of the ethanol-inducible cytochrome P450-2E1 (CYP2E1) in some of these PTM changes. Finally, we discuss translational research opportunities with natural and/or synthetic anti-oxidants, which can prevent or delay the onset of mitochondrial dysfunction, fat accumulation and tissue injury.

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Hepatotoxic agents including alcohol and high fat elevate nitroxidative stress.

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Increased nitroxidative stress promotes post-translational protein modifications.

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Post-translational protein modifications of many proteins lead to their inactivation.

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Inactivation of mitochondrial proteins contributes to mitochondrial dysfunction.

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Mitochondrial dysfunction contributes to necrotic or apoptotic tissue injury.

Stratification of risk of death in severe acute alcoholic hepatitis using a panel of adipokines and cytokines

BACKGROUND

Dysregulated adipose tissue metabolism has been implicated in the pathogenesis of alcoholic liver disease in murine models. We aimed to characterize serum markers of adipose tissue metabolism and inflammation in patients with severe acute alcoholic hepatitis (AAH) and determine their utility to predict survival in severe AAH.

METHODS

A prospective, case-control study design was used. Seventy-six patients hospitalized with severe AAH and 25 ambulatory patients with alcoholic cirrhosis as controls were included. Serum samples were collected for biochemical analyses. Patients were followed for 180 days after enrollment to determine the survival.

RESULTS

AAH patients exhibited higher serum glycerol and free fatty acid levels, suggesting enhanced adipose tissue triglyceride hydrolysis. Patients with AAH demonstrated a distinct serum lipidomic profile compared with alcoholic cirrhosis but not in systemic and adipose-specific insulin resistance. AAH patients had higher serum resistin and plasmin activation inhibitor-1 levels, while serum leptin was decreased. Serum levels of the prolipolytic cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-8, and IL-15 were significantly higher in AAH patients. Only 53% of AAH patients survived 180 days after admission, while all cirrhotic patients were alive at the end of the study period. Among patients with severe AAH, white blood cell count, hemoglobin, resistin, IL-6 and TNF-α were associated with 180-day survival, and all 5 markers demonstrated accuracy by area under receiver-operator curve analysis. Serum IL-6 levels ≥38.66 pg/ml most precisely identified deaths in severe AAH. Patients with IL-6 ≥ 38.66 pg/ml had significantly decreased mean survival compared to those with lower levels.

CONCLUSIONS

AAH patients demonstrate evidence of increased adipose tissue lipolysis and altered serum lipidomic profile compared with alcoholic cirrhosis patients. IL-6 may be a useful biomarker to risk stratify severe AAH patients at the highest risk of mortality.

Effect of chronic alcohol consumption on the development and progression of non-alcoholic fatty liver disease (NAFLD)

A number of epidemiologic studies show a protective effect of light to moderate daily alcohol consumption on the development of non-alcoholic fatty liver disease (NAFLD). Although these small amounts of ethanol may prevent fatty liver, they may also be a risk factor for other diseases such as breast and colon cancer. Those individuals who have underlying hepatic steatosis or non-alcoholic steatohepatitis (NASH) should not use ethanol chronically since the data available at present do not support a beneficial effect of alcohol in this situation. Especially overweight and obese individuals may be more susceptible towards alcohol even at moderate doses. Animal experiments show a negative effect of ethanol on liver histology in either dietary or genetic NASH models. In addition, patients with NASH reveal a significant increased risk for hepatocellular cancer (HCC) even with social alcohol consumption. Thus, subjects with underlying NASH should abstain from alcohol at any amounts.

Chronic ethanol consumption induces mitochondrial protein acetylation and oxidative stress in the kidney

In this study, we present the novel findings that chronic ethanol consumption induces mitochondrial protein hyperacetylation in the kidney and correlates with significantly increased renal oxidative stress. A major proteomic footprint of alcoholic liver disease (ALD) is an increase in hepatic mitochondrial protein acetylation. Protein hyperacetylation has been shown to alter enzymatic function of numerous proteins and plays a role in regulating metabolic processes. Renal mitochondrial targets of hyperacetylation include numerous metabolic and antioxidant pathways, such as lipid metabolism, oxidative phosphorylation, and amino acid metabolism, as well as glutathione and thioredoxin pathways. Disruption of protein lysine acetylation has the potential to impair renal function through metabolic dysregulation and decreased antioxidant capacity. Due to a significant elevation in ethanol-mediated renal oxidative stress, we highlight the acetylation of superoxide dismutase, peroxiredoxins, glutathione reductase, and glutathione transferase enzymes. Since oxidative stress is a known factor in ethanol-induced nephrotoxicity, we examined biochemical markers of protein hyperacetylation and oxidative stress. Our results demonstrate increased protein acetylation concurrent with depleted glutathione, altered Cys redox potential, and the presence of 4-HNE protein modifications in our 6-week model of early-stage alcoholic nephrotoxicity. These findings support the hypothesis that ethanol metabolism causes an influx of mitochondrial metabolic substrate, resulting in mitochondrial protein hyperacetylation with the potential to impact mitochondrial metabolic and antioxidant processes.

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Chronic ethanol metabolism induces mitochondrial protein hyperacetylation in the kidney.

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Ethanol-induced hyperacetylation occurs on metabolic and antioxidant proteins.

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The onset of renal oxidative stress correlates with mitochondrial protein hyperacetylation.

Translational Implications of the Alcohol-Metabolizing Enzymes, Including Cytochrome P450-2E1, in Alcoholic and Nonalcoholic Liver Disease

Fat accumulation (hepatic steatosis) in alcoholic and nonalcoholic fatty liver disease is a potentially pathologic condition which can progress to steatohepatitis (inflammation), fibrosis, cirrhosis, and carcinogenesis. Many clinically used drugs or some alternative medicine compounds are also known to cause drug-induced liver injury, which can further lead to fulminant liver failure and acute deaths in extreme cases. During liver disease process, certain cytochromes P450 such as the ethanol-inducible cytochrome P450-2E1 (CYP2E1) and CYP4A isozymes can be induced and/or activated by alcohol and/or high-fat diets and pathophysiological conditions such as fasting, obesity, and diabetes. Activation of these P450 isozymes, involved in the metabolism of ethanol, fatty acids, and various drugs, can produce reactive oxygen/nitrogen species directly and/or indirectly, contributing to oxidative modifications of DNA/RNA, proteins and lipids. In addition, aldehyde dehydrogenases including the mitochondrial low Km aldehyde dehydrogenase-2 (ALDH2), responsible for the metabolism of acetaldehyde and lipid aldehydes, can be inactivated by various hepatotoxic agents. These highly reactive acetaldehyde and lipid peroxides, accumulated due to ALDH2 suppression, can interact with cellular macromolecules DNA/RNA, lipids, and proteins, leading to suppression of their normal function, contributing to DNA mutations, endoplasmic reticulum stress, mitochondrial dysfunction, steatosis, and cell death. In this chapter, we specifically review the roles of the alcohol-metabolizing enzymes including the alcohol dehydrogenase, ALDH2, CYP2E1, and other enzymes in promoting liver disease. We also discuss translational research opportunities with natural and/or synthetic antioxidants, which can prevent or delay the onset of inflammation and liver disease.

Protective Effects of Korean Red Ginseng against Alcohol-Induced Fatty Liver in Rats

The present study tested the hypothesis that Korean red ginseng (KRG) provides a protective effect against alcoholic fatty liver. Male Sprague-Dawley rats were divided into four groups and fed a modified Lieber-DeCarli diet containing 5% (w/v) alcohol or an isocaloric amount of dextrin-maltose for the controls for 6 weeks: normal control (CON), alcohol control (ET), and ET treated with 125 or 250 mg/kg body weight/day of KRG (RGL or RGH, respectively). Compared with the CON group, the ET group exhibited a significant increase in triglycerides, total cholesterol and the presence of lipid droplets in the liver, and a decrease in fat mass, which were all attenuated by KRG supplementation in adose-dependent manner. The mitigation was accompanied by AMP-activated protein kinase (AMPK) signaling pathways in the liver and adipose tissue. In addition, suppression in the alcohol-induced changes of adipose adipokine mRNA expression was also observed in KRG supplementation group. These findings suggest that KRG may have the potential to ameliorate alcoholic fatty liver by suppressing inappropriate lysis of adipose tissue and preventing unnecessary de novo lipogenesis in the liver, which are mediated by AMPK signaling pathways. A mechanism for an interplay between the two organs is still needed to be examined with further assays.

Behavioral, Metabolic, and Immune Consequences of Chronic Alcohol or Cannabinoids on HIV/AIDs: Studies in the Non-Human Primate SIV Model

HIV-associated mortality has been significantly reduced with antiretroviral therapy (ART), and HIV infection has become a chronic disease that frequently coexists with many disorders, including substance abuse (Azar et al. Drug Alcohol Depend 112:178-193, 2010; Phillips et al. J Gen Int Med 16:165, 2001). Alcohol and drugs of abuse may modify host-pathogen interactions at various levels including behavioral, metabolic, and immune consequences of HIV infection, as well as the ability of the virus to integrate into the genome and replicate in host cells. Identifying mechanisms responsible for these interactions is complicated by many factors, such as the tissue specific responses to viral infection, multiple cellular mechanisms involved in inflammatory responses, neuroendocrine and localized responses to infection, and kinetics of viral replication. An integrated physiological analysis of the biomedical consequences of chronic alcohol and drug use or abuse on disease progression is possible using rhesus macaques infected with simian immunodeficiency virus (SIV), a relevant model of HIV infection. This review will provide an overview of the data gathered using this model to show that chronic administration of two of the most commonly abused substances, alcohol and cannabinoids (Δ(9)-Tetrahydrocannabinol; THC), affect host-pathogen interactions.

Invariant NKT cells promote alcohol-induced steatohepatitis through interleukin-1β in mice

BACKGROUND & AIMS

It was reported that alcohol consumption activated the NLRP3 inflammasome in Kupffer cells, leading to mature interleukin (IL)-1β release in alcoholic liver injury; however, how IL-1β promotes liver injury remains unclear.

METHODS

We investigated the role of IL-1β in alcoholic steatohepatitis by using a chronic plus single-binge ethanol consumption mouse model.

RESULTS

Here, liver steatosis was accompanied by notably increased invariant natural killer T (iNKT) cell numbers and activation, and iNKT-deficient Jα18(-/-) mice developed less alcohol-induced steatosis, with reduced liver inflammation and neutrophil infiltration. Kupffer cells and IL-1β were required for the hepatic iNKT accumulation, as either blocking IL-1β signaling with a recombinant IL-1 receptor antagonist (IL-1Ra), depleting Kupffer cells by clodronate liposomes, or specifically silencing IL-1β in Kupffer cells by nanoparticle-encapsulated siRNA, resulted in inhibited hepatic iNKT cell accumulation and activation, as well as amelioration of alcoholic fatty liver. In addition, IL-1β overexpression in hepatocytes was sufficient to compensate for Kupffer cell depletion. Increased gene and protein expression of mature IL-1β correlated with elevated expression of the NLRP3 inflammasome components NLRP3, ASC, and cleaved caspase-1 in Kupffer cells from ethanol-exposed wild-type mice. NLRP3 deficiency led to the attenuation of alcoholic steatosis, similarly as Kupffer cell depletion, almost without hepatic NKT cells.

CONCLUSIONS

After alcohol-exposure Kupffer cell-derived IL-1β triggered by NLRP3 activation, recruits and activates hepatic iNKT cells, subsequently promoting liver inflammation and neutrophil infiltration, and inducing alcoholic liver injury.

Alcoholic Steatosis in Different Strains of Rat: A Comparative Study

Background

Different strains of rats have been used to study alcoholic liver disease (ALD) while the reason for selecting a particular rat strain was not apparent.

Purpose

The aim of our study was to compare outbred (Wistar) and inbred (Fischer) strains to evaluate pathological, biochemical changes, and gene expression differences associated with ethanol-induced early hepatic steatosis.

Study Design

Male Wistar and Fischer-344 rats were pair-fed for 6 weeks with or without 5% ethanol in Lieber-DeCarli liquid diet. Livers were analyzed for histological and lipid-related differences.

Results

Hepatic midzonal steatosis was mainly found in Wistar rats while Fischer rats showed mostly pericentral steatosis. Increased hepatic steatosis in ethanol-fed Wistar rats is supported by increases in lipids with related genes and transcription factors involved in fatty acid and triglyceride synthesis.

Conclusion

Our data showed that Fischer rats are relatively less prone to ethanol-mediated steatosis with pericentral lipid deposition pattern in the liver which is similar to humans and show no trace level of lipid accumulation in pair-fed controls as observed in Wistar (outbred) strain. Therefore, Fischer rats are better suited for lipid studies in an early development of ALD.

Herbal SGR Formula Prevents Acute Ethanol-Induced Liver Steatosis via Inhibition of Lipogenesis and Enhancement Fatty Acid Oxidation in Mice

Our previous study indicated that herbal SGR formula partially attenuates ethanol-induced fatty liver, but the underlying mechanisms remain unclear. In the present study, mice were pretreated with SGR (100 and 200 mg/kg/d bw) for 30 d before being exposed to ethanol (4.8 g/kg bw). The biochemical indices and histopathological changes were examined to evaluate the protective effects and to explore potential mechanisms by investigating the adiponectin, tumor necrosis factor-α (TNF-α), peroxisome proliferators-activated receptor-α (PPAR-α), sterol regulatory element binding protein-1c (SREBP-1c), adenosine monophosphate-activated protein kinase (AMPK), and so forth. Results showed that SGR pretreatment markedly inhibited acute ethanol-induced liver steatosis, significantly reduced serum and hepatic triglyceride (TG) level, and improved classic histopathological changes. SGR suppressed the protein expression of hepatic SREBP-1c and TNF-α and increased adiponectin, PPAR-α, and AMPK phosphorylation in the liver. Meanwhile, acute toxicity tests showed that no death or toxic side effects within 14 days were observed upon oral administration of the extracts at a dose of 16 g/kg body wt. These results demonstrate that SGR could protect against acute alcohol-induced liver steatosis without any toxic side effects. Therefore, our studies provide novel molecular insights into the hepatoprotective effect of SGR formula, which may be exploited as a therapeutic agent for ethanol-induced hepatosteatosis.

Moderate alcohol consumption diminishes the development of non-alcoholic fatty liver disease (NAFLD) in ob/ob mice

PURPOSE

Using ob/ob mice as a model of non-alcoholic fatty liver disease (NAFLD), we investigated the effect of moderate alcohol intake on the development of NAFLD and molecular mechanisms involved.

METHODS

Ob/ob mice were fed water or ethanol solution (2.5 g/kg body weight/day) for 6 weeks, and markers of liver injury, insulin signalling and adiponectin in visceral adipose tissue were determined.

RESULTS

Whereas bodyweight and the degree of liver steatosis did not differ among ob/ob mouse groups, those consuming ethanol had markedly less macrovesicular hepatic fat accumulation, inflammatory alterations and significantly lower transaminase levels. Despite similarly elevated protein levels of tumour necrosis factor α, protein concentrations of plasminogen activator inhibitor 1 were significantly lower in livers of ob/ob mice consuming ethanol in comparison with controls. The hepato-protective property of moderate alcohol ingestion in ob/ob mice was associated with an induction of the sirtuin-1/adiponectin-signalling cascade in visceral fat tissue and an activation of Akt in the liver. Similar effects of moderate alcohol exposure were also found in vitro in 3T3-L1 and AML-12 cells.

CONCLUSION

These data suggest that moderate alcohol intake may diminish the development of NAFLD through sirtuin-1/-adiponectin-dependent signalling cascades.

Zinc deficiency mediates alcohol-induced apoptotic cell death in the liver of rats through activating ER and mitochondrial cell death pathways

Hepatic zinc deficiency has been well documented in alcoholic patients, but the mechanisms by which zinc deficiency mediates cell death have not been well defined. The objectives of this study were to determine whether alcohol perturbs subcellular zinc homeostasis and how organelle zinc depletion may link with cell death pathways. Wistar rats were pair-fed with the Lieber-DeCarli control or ethanol diet for 5 mo. Chronic alcohol exposure significantly reduced zinc level in isolated hepatic endoplasmic reticulum (ER) and mitochondria. Among the detected zinc transporters, ER Zrt/Irt-like protein (ZIP)13 and mitochondrial ZIP8, which transport zinc from ER and mitochondria to cytosol, were significantly increased. Mitochondrial zinc transporter (ZnT) 4, which transports zinc from cytosol to mitochondria, was also increased. ER phosphorylated eukaryotic initiation factor 2α, activating transcription factor 4, and C/EBP homologous protein were significantly upregulated, and mitochondrial cytochrome c release and Bax insertion were detected in association with caspase-3 activation and apoptotic cell death. To define the role of zinc deficiency in ER and mitochondrial stress, H4IIEC3 cells were treated with 3 μM N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine for 6 h with or without supplementation with zinc or N-acetylcysteine (NAC). The results demonstrated that zinc deprivation induced caspase-3 activation and apoptosis in association with ER and mitochondria dysfunction, which were inhibited by zinc as low as 10 μM but not by 2 mM NAC. These results suggest that chronic ethanol exposure induced in ER and mitochondrial zinc deficiency might activate intrinsic cell death signaling pathway, which could not be effectively rescued by antioxidant treatment.

Aryl hydrocarbon receptor-dependent stanniocalcin 2 induction by cinnabarinic acid provides cytoprotection against endoplasmic reticulum and oxidative stress

The aryl hydrocarbon receptor (AhR) is a cytosolic ligand-activated transcription factor historically known for its role in xenobiotic metabolism. Although AhR activity has previously been shown to play a cytoprotective role against intrinsic apoptotic stimuli, the underlying mechanism by which AhR confers cytoprotection against apoptosis is largely unknown. Here, we demonstrate that activation of AhR by the tryptophan catabolite cinnabarinic acid (CA) directly upregulates expression of stanniocalcin 2 (Stc2) to elicit cytoprotection against apoptosis induced by endoplasmic reticulum stress and oxidative stress. Chromatin immunoprecipitation studies demonstrated that CA treatment induces direct AhR binding to a region of the Stc2 promoter containing multiple xenobiotic response elements. Using isolated primary hepatocytes from AhR wild-type (AhR floxed) and liver-specific AhR conditional knockout mice, we showed that pretreatment with CA conferred cytoprotection against hydrogen peroxide (H(2)O(2))-, thapsigargin-, and ethanol-induced apoptosis in an AhR-dependent manner. Furthermore, suppressing Stc2 expression using RNA interference confirmed that the cytoprotective properties of CA against H(2)O(2), thapsigargin, and ethanol injury were absolutely dependent on Stc2. Immunochemistry revealed the presence of Stc2 in the endoplasmic reticulum and on the cell surface, consistent with Stc2 secretion and autocrine and/or paracrine signaling. Finally, in vivo data using a mouse model of acute alcohol hepatotoxicity demonstrated that CA provided cytoprotection against ethanol-induced apoptosis, hepatic microvesicular steatosis, and liver injury. Collectively, our data uncovered a novel mechanism for AhR-mediated cytoprotection in the liver that is dependent on CA-induced Stc2 activity.

Protective effect of oligomeric proanthocyanidins against alcohol-induced liver steatosis and injury in mice

The long-term consumption of alcohol has been associated with multiple pathologies at all levels, such as alcoholism, chronic pancreatitis, malnutrition, alcoholic liver disease (ALD) and cancer. In the current study, we investigated the protective effect of oligomeric proanthocyanidins (OPC) against alcohol-induced liver steatosis and injury and the possible mechanisms using ethanol-induced chronic liver damage mouse models. The results showed that OPC significantly improved alcohol-induced dyslipidemia and alleviated liver steatosis by reducing levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total triglyceride (TG), total cholesterol (TC), low-density cholesterol (LDL-c) and liver malondialdehyde (MDA), and increasing levels of serum high-density lipoprotein (HDL-c), liver superoxide dismutase (SOD). Further investigation indicated that OPC markedly decreased the expressions of lipid synthesis genes and inflammation genes such as sterol regulatory element-binding protein-1c (Srebp-1c), protein-2 (Srebp2), interleukin IL-1β, IL-6 and TNF-α. Furthermore, AML-12 cells line was used to investigate the possible mechanisms which indicated that OPC might alleviate liver steatosis and damage through AMP-activated protein kinase (AMPK) activation involving oxidative stress. In conclusion, our study demonstrated excellent protective effect of OPC against alcohol-induced liver steatosis and injury, which could a potential drug for the treatment of alcohol-induced liver injury in the future.

L-serine supplementation attenuates alcoholic fatty liver by enhancing homocysteine metabolism in mice and rats

BACKGROUND

Hyperhomocysteinemia plays an important role in the development of hepatic steatosis, and studies indicate that homocysteine-lowering treatment inhibits the development of fatty liver.

OBJECTIVE

We evaluated the effects of L-serine on alcoholic fatty liver and homocysteine metabolism.

METHODS

In a binge ethanol study, male C57BL/6 mice were divided into 4 groups: control, ethanol + vehicle, and ethanol + 20 or 200 mg/kg L-serine. Mice were gavaged with ethanol (5 g/kg body weight) 3 times every 12 h with or without L-serine which was given twice 30 min before the last 2 ethanol doses. Control mice were fed isocaloric dextran-maltose. In a chronic ethanol study, male Wistar rats were divided into 3 groups: control, ethanol, and ethanol + L-serine. Rats were fed a standard Lieber-DeCarli ethanol diet (36% ethanol-derived calories) for 4 wk with or without dietary L-serine supplementation (1%; wt:vol) for the last 2 wk. In control rats, the ethanol-derived calories were replaced with dextran-maltose. The effects of L-serine were also tested in AML12 cells manipulated to have high homocysteine concentrations by silencing the genes involved in homocysteine metabolism.

RESULTS

Binge ethanol treatment increased serum homocysteine and hepatic triglyceride (TG) concentrations by >5-fold vs. controls, which were attenuated in the 200-mg/kg L-serine treatment group by 60.0% and 47.5%, respectively, compared with the ethanol group. In the chronic ethanol study, L-serine also decreased hepatic neutral lipid accumulation by 63.3% compared with the ethanol group. L-serine increased glutathione and S-adenosylmethionine by 94.0% and 30.6%, respectively, compared with the ethanol group. Silencing betaine homocysteine methyltransferase, cystathionine β-synthase, or methionine increased intracellular homocysteine and TG concentrations by >2-fold, which was reversed by L-serine when L-serine-independent betaine homocysteine methyltransferase was knocked down.

CONCLUSION

These results demonstrate that L-serine ameliorates alcoholic fatty liver by accelerating L-serine-dependent homocysteine metabolism.

Potential contributions of the tobacco nicotine-derived nitrosamine ketone (NNK) in the pathogenesis of steatohepatitis in a chronic plus binge rat model of alcoholic liver disease

AIMS

Alcoholic liver disease (ALD) is linked to binge drinking and cigarette smoking. Heavy chronic ± binge alcohol, or low-level exposures to dietary nitrosamines cause steatohepatitis with insulin resistance and oxidative stress in animal models. This study examines hepatotoxic effects of sub-mutagenic exposures to tobacco-specific nitrosamine (NNK) in relation to ALD.

METHODS

Long Evans rats were fed liquid diets containing 0 or 26% (caloric) ethanol (EtOH) for 8 weeks. In Weeks 3 through 8, rats were treated with NNK (2 mg/kg) or saline by i.p. injection, 3×/week, and in Weeks 7 and 8, EtOH-fed rats were binge-administered 2 g/kg EtOH 3×/week; controls were given saline.

RESULTS

EtOH ± NNK caused steatohepatitis with necrosis, disruption of the hepatic cord architecture, ballooning degeneration, early fibrosis, mitochondrial cytopathy and ER disruption. Severity of lesions was highest in the EtOH+NNK group. EtOH and NNK inhibited insulin/IGF signaling through Akt and activated pro-inflammatory cytokines, while EtOH promoted lipid peroxidation, and NNK increased apoptosis. O(6)-methyl-Guanine adducts were only detected in NNK-exposed livers.

CONCLUSION

Both alcohol and NNK exposures contribute to ALD pathogenesis, including insulin/IGF resistance and inflammation. The differential effects of EtOH and NNK on adduct formation are critical to ALD progression among alcoholics who smoke.

Maltol, a food flavoring agent, attenuates acute alcohol-induced oxidative damage in mice

The purpose of this study was to evaluate the hepatoprotective effect of maltol, a food-flavoring agent, on alcohol-induced acute oxidative damage in mice. Maltol used in this study was isolated from red ginseng (Panax ginseng C.A Meyer) and analyzed by high performance liquid chromatography (HPLC) and mass spectrometry. For hepatoprotective activity in vivo, pretreatment with maltol (12.5, 25 and 50 mg/kg; 15 days) drastically prevented the elevated activities of aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and triglyceride (TG) in serum and the levels of malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) in liver tissue (p < 0.05). Meanwhile, the levels of hepatic antioxidant, such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) were elevated by maltol pretreatment, compared to the alcohol group (p < 0.05). Histopathological examination revealed that maltol pretreatment significantly inhibited alcohol-induced hepatocyte apoptosis and fatty degeneration. Interestingly, pretreatment of maltol effectively relieved alcohol-induced oxidative damage in a dose-dependent manner. Maltol appeared to possess promising anti-oxidative and anti-inflammatory capacities. It was suggested that the hepatoprotective effect exhibited by maltol on alcohol-induced liver oxidative injury may be due to its potent antioxidant properties.

Wild bitter gourd protects against alcoholic fatty liver in mice by attenuating oxidative stress and inflammatory responses

Bitter gourd (Momordica charantia L.) is a common vegetable grown widely in Asia that is used as a traditional medicine. The objective of this study was to investigate whether wild bitter gourd possessed protective effects against chronic alcohol-induced liver injury in mice. C57BL/6 mice were fed an alcohol-containing liquid diet for 4 weeks to induce alcoholic fatty liver. Meanwhile, mice were treated with ethanol extracts from four different wild bitter gourd cultivars: Hualien No. 1', Hualien No. 2', Hualien No. 3' and Hualien No. 4'. The results indicated that the daily administration of 500 mg kg body weight(-1) of a Hualien No. 3' extract (H3E) or a Hualien No. 4' extract (H4E) markedly reduced the steatotic alternation of liver histopathology. In addition, the activation of serum aminotransferases (AST and ALT) and the accumulation of hepatic TG content caused by alcohol were ameliorated. The hepatoprotective effects of H3E and H4E involved the enhancement of the antioxidant defence system (GSH, GPx, GRd, CAT and SOD), inhibition of lipid peroxidation (MDA) and reduction of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) in the liver. Moreover, H3E and H4E supplementation suppressed the alcohol-induced elevation of CYP2E1, SREBP-1, FAS and ACC protein expression. These results demonstrated that ethanol extracts of Hualien No. 3' and Hualien No. 4' have beneficial effects against alcoholic fatty liver, in which they attenuate oxidative stress and inflammatory responses.

Sorghum-based alcoholic beverage, Burukutu, perturbs the redox status of the liver of male rats

The redox status of male rat liver following 28 days consumption of Burukutu was investigated. Twenty rats were randomized into four groups with five rats each. Burukutu consumption at 0.78 g/kg alcohol produced no significant change in the activities of alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). However, 3.71 and 7.43 g/kg dosages resulted in significant decrease in the activities of ALP, ALT and AST with corresponding increase in serum. The activity of cytochrome P₄₅₀(CYP 2E1) increased significantly in the liver of rats following consumption of Burukutu at all doses investigated. The activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose 6-phosphate dehydrogenase decreased significantly (P < 0.05) in rats treat with 0.78 g/kg, 3.41 and 7.43 g/kg Burukutu. There was a significant increase in the level of glutathione disulfide (GSSG) with reduction in the levels of glutathione reduced (GSH) and GSH:GSSG. The levels of oxidative stress biomarkers, malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl and percentage DNA fragmentation, increased significantly (P < 0.05). It is evident from the alterations in the activities of the hepatocellular enzymes, antioxidant enzymes and oxidative stress biomarkers that Burukutu mediated its toxicity through the depletion of the antioxidant enzymes.

FGF21 treatment ameliorates alcoholic fatty liver through activation of AMPK-SIRT1 pathway

Fibroblast growth factor 21 (FGF21), a recently identified member of the FGF superfamily, is mainly secreted from the liver and adipose tissues and plays an important role in improving metabolic syndrome and homeostasis. The aim of this study is to evaluate the role of FGF21 in alcoholic fatty liver disease (AFLD) and to determine if it has a therapeutic effect on AFLD. In this paper, we tested the effect of FGF21 on alcohol-induced liver injury in a murine model of chronic ethanol gavage and alcohol-treated HepG2 cells. Male KM mice received single dose of 5 g/kg ethanol gavage every day for 6 weeks, which induced significant fatty liver and liver injury. The alcohol-induced fatty liver cell model was achieved by adding ethanol into the medium of HepG2 cell cultures at a final concentration of 75 mM for 9 days. Results showed that treatment with recombinant FGF21 ameliorated alcoholic fatty liver and liver injury both in a murine model of chronic ethanol gavage and alcohol-treated HepG2 cells. In addition, FGF21 treatment down-regulated the hepatic expression of fatty acid synthetic key enzyme, activated hepatic AMPK-SIRT1 pathway and significantly down-regulated hepatic oxidative stress protein. Taken together, FGF21 corrects multiple metabolic parameters of AFLD in vitro and in vivo by activation of the AMPK-SIRT1 pathway.

Toll-like receptor-mediated signaling cascade as a regulator of the inflammation network during alcoholic liver disease

Chronic abuse of alcohol leads to various histological abnormalities in the liver. These are conditions collectively known as alcoholic liver disease (ALD). Currently, ALD is considered to be one of the major causes of death worldwide. An impaired intestinal barrier with related endotoxemia is among the various pathogenetic factors. This is mainly characterized by circulating levels of lipopolysaccharide (LPS), considered critical for the onset of intra-hepatic inflammation. This in turn promotes hepatocellular damage and fibrosis in ALD. Elevated levels of LPS exert their effects by binding to Toll-like receptors (TLRs) which are expressed by all liver-resident cells. The activation of TLR signaling triggers an overproduction and release of some cytokines, which promote an autocatalytic cascade of other pro-inflammatory signals. In this review, we provide an overview of the mechanisms that sustain LPS-mediated activation of TLR signaling, reporting current experimental and clinical evidence of its role during inflammation in ALD.

Hypoxia and fatty liver

The liver is a central organ that metabolizes excessive nutrients for storage in the form of glycogen and lipids and supplies energy-producing substrates to the peripheral tissues to maintain their function, even under starved conditions. These processes require a considerable amount of oxygen, which causes a steep oxygen gradient throughout the hepatic lobules. Alcohol consumption and/or excessive food intake can alter the hepatic metabolic balance drastically, which can precipitate fatty liver disease, a major cause of chronic liver diseases worldwide, ranging from simple steatosis, through steatohepatitis and hepatic fibrosis, to liver cirrhosis. Altered hepatic metabolism and tissue remodeling in fatty liver disease further disrupt hepatic oxygen homeostasis, resulting in severe liver hypoxia. As master regulators of adaptive responses to hypoxic stress, hypoxia-inducible factors (HIFs) modulate various cellular and organ functions, including erythropoiesis, angiogenesis, metabolic demand, and cell survival, by activating their target genes during fetal development and also in many disease conditions such as cancer, heart failure, and diabetes. In the past decade, it has become clear that HIFs serve as key factors in the regulation of lipid metabolism and fatty liver formation. This review discusses the molecular mechanisms by which hypoxia and HIFs regulate lipid metabolism in the development and progression of fatty liver disease.

Dietary umbelliferone attenuates alcohol-induced fatty liver via regulation of PPARα and SREBP-1c in rats

This study investigated the effects of umbelliferone (UF) on alcoholic fatty liver and its underlying mechanism. Rats were fed a Lieber-DeCarli liquid diet with 36% of calories as alcohol with or without UF (0.05 g/L) for 8 weeks. Pair-fed rats received an isocaloric carbohydrate liquid diet. UF significantly reduced the severity of alcohol-induced body weight loss, hepatic lipid accumulation and droplet formation, and dyslipidemia. UF decreased plasma AST, ALT, and γGTP activity. UF significantly reduced hepatic cytochrome P450 2E1 activities and increased alcohol dehydrogenase and aldehyde dehydrogenase 2 activities compared to the alcohol control group, which resulted in a lower plasma acetaldehyde level in the rats that received UF. Chronic alcohol exposure inhibited hepatic AMPK activation compared to the pair-fed rats, which was reversed by UF supplementation. UF also significantly suppressed the lipogenic gene expression (SREBP-1c, SREBP-2, FAS, CIDEA, and PPARγ) and elevated the fatty acid oxidation gene expression (PPARα, Acsl1, CPT, Acox, and Acaa1a) compared to the alcohol control group, which could lead to inhibition of FAS activity and stimulation of CPT and fatty acid β-oxidation activities in the liver of chronic alcohol-fed rats. These results indicated that UF attenuated alcoholic steatosis through down-regulation of SREBP-1c-mediated lipogenesis and up-regulation of PPARα-mediated fatty acid oxidation. Therefore, UF may provide a promising natural therapeutic strategy against alcoholic fatty liver.

Ethanol-induced impairment in the biosynthesis of N-linked glycosylation

Deficiency in N-linked protein glycosylation is a long-known characteristic of alcoholic liver disease and congenital disorders of glycosylation. Previous investigations of ethanol-induced glycosylation deficiency demonstrated perturbations in the early steps of substrate synthesis and in the final steps of capping N-linked glycans in the Golgi. The significance of the biosynthesis of N-glycan precursors in the endoplasmic reticulum, however, has not yet been addressed in alcoholic liver disease. Ethanol-metabolizing hepatoma cells were treated with increasing concentrations of ethanol. Transcript analysis of genes involved in the biosynthesis of N-glycans, activity assays of related enzymes, dolichol-phosphate quantification, and analysis of dolichol-linked oligosaccharides were performed. Upon treatment of cells with ethanol, we found a decrease in the final N-glycan precursor Dol-PP-GlcNAc(2) Man(9) Glc(3) and in C95- and C100-dolichol-phosphate levels. Transcript analysis of genes involved in N-glycosylation showed a 17% decrease in expression levels of DPM1, a subunit of the dolichol-phosphate-mannose synthase, and an 8% increase in RPN2, a subunit of the oligosaccharyl transferase. Ethanol treatment decreases the biosynthesis of dolichol-phosphate. Consequently, the formation of N-glycan precursors is affected, resulting in an aberrant precursor assembly. Messenger RNA levels of genes involved in N-glycan biosynthesis are slightly affected by ethanol treatment, indicating that the assembly of N-glycan precursors is not regulated at the transcriptional level. This study confirms that ethanol impairs N-linked glycosylation by affecting dolichol biosynthesis leading to impaired dolichol-linked oligosaccharide assembly. Together our data help to explain the underglycosylation phenotype observed in alcoholic liver disease and congenital disorders of glycosylation.

Korean Red Ginseng attenuates ethanol-induced steatosis and oxidative stress via AMPK/Sirt1 activation

Background

Alcoholic steatosis is the earliest and most common liver disease, and may precede the onset of more severe forms of liver injury.

Methods

The effect of Korean Red Ginseng extract (RGE) was tested in two murine models of ethanol (EtOH)-feeding and EtOH-treated hepatocytes.

Results

Blood biochemistry analysis demonstrated that RGE treatment improved liver function. Histopathology and measurement of hepatic triglyceride content verified the ability of RGE to inhibit fat accumulation. Consistent with this, RGE administration downregulated hepatic lipogenic gene induction and restored hepatic lipolytic gene repression by EtOH. The role of oxidative stress in the pathogenesis of alcoholic liver diseases is well established. Treatment with RGE attenuated EtOH-induced cytochrome P450 2E1, 4-hydroxynonenal, and nitrotyrosine levels. Alcohol consumption also decreased phosphorylation of adenosine monophosphate-activated protein kinase, which was restored by RGE. Moreover, RGE markedly inhibited fat accumulation in EtOH-treated hepatocytes, which correlated with a decrease in sterol regulatory element-binding protein-1 and a commensurate increase in sirtuin 1 and peroxisome proliferator-activated receptor-α expression. Interestingly, the ginsenosides Rb2 and Rd, but not Rb1, significantly inhibited fat accumulation in hepatocytes.

Conclusion

These results demonstrate that RGE and its ginsenoside components inhibit alcoholic steatosis and liver injury by adenosine monophosphate-activated protein kinase/sirtuin 1 activation both in vivo and in vitro, suggesting that RGE may have a potential to treat alcoholic liver disease.

Schisandra chinensis prevents alcohol-induced fatty liver disease in rats

Schisandra chinensis (SC), a traditional herbal medicine, has been prescribed for patients suffering from various liver diseases, including hepatic cancer, hypercholesterolemia, and CCl₄-induced liver injury. We investigated whether SC extract has a protective effect on alcohol-induced fatty liver and studied its underlying mechanisms. Rats were fed with ethanol by intragastric administration every day for 5 weeks to induce alcoholic fatty liver. Ethanol treatment resulted in a significant increase in alanine aminotransferase, aspartate aminotransferase, and hepatic triglyceride (TG) levels and caused fatty degeneration of liver. Ethanol administration also elevated serum TG and total cholesterol (TC) and decreased high-density lipoprotein (HDL) cholesterol levels. However, after administration of ethanol plus SC extracts, the ethanol-induced elevation in liver TC and TG levels was reversed. Elevation in serum TG was not observed after treatment with SC. Moreover, compared with the ethanol-fed group, the rats administered ethanol along with SC extracts for 5 weeks showed attenuated fatty degeneration and an altered lipid profile with decreased serum TC and TG, and increased HDL cholesterol levels. Chronic ethanol consumption did not affect peroxisome proliferator-activated receptor γ (PPARγ) levels, but it decreased PPARα and phospho-AMP-activated protein kinase (AMPK) levels in the liver. However, SC prevented the ethanol-induced decrease in PPARα expression and induced a significant decrease in sterol regulatory element-binding protein-1 expression and increase in phospho-AMPK expression in rats with alcoholic fatty liver. SC administration resulted in a significant decrease in intracellular lipid accumulation in hepatocytes along with a decrease in serum TG levels, and it reversed fatty liver to normal conditions, as measured by biochemical and histological analyses. Our results indicate that the protective effect of SC is accompanied by a significant increase in phospho-AMPK and PPARα expression in hepatic tissue of alcoholic rats, thereby suggesting that SC has the ability to prevent ethanol-induced fatty liver, possibly through activation of AMPK and PPARα signaling.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

CMZ reversed chronic ethanol-induced disturbance of PPAR-α possibly by suppressing oxidative stress and PGC-1α acetylation, and activating the MAPK and GSK3β pathway

Background

Cytochrome P4502E1 (CYP2E1) has been suggested to play critical roles in the pathogenesis of alcoholic fatty liver (AFL), but the underlying mechanisms remains unclear. The current study was designed to evaluate whether CYP2E1 suppression by chlormethiazole (CMZ) could suppress AFL in mice, and to explore the underlying mechanisms.

Methods

Mice were treated with or without CMZ (50 mg/kg bw, i.p.) and subjected to liquid diet with or without ethanol (5%, w/v) for 4 weeks. Biochemical parameters were measured using commercial kits. The protein and mRNA levels were detected by western blot and qPCR, respectively. Histopathology and immunohistochemical assay were performed with routine methods.

Results

CYP2E1 inhibition by CMZ completely blocked AFL in mice, shown as the decline of the hepatic and serum triglyceride levels, and the fewer fat droplets in the liver sections. Chronic ethanol exposure led to significant decrease of the mRNA and protein levels of peroxisome proliferator-activated receptor α (PPAR-α), which was blocked by CMZ co-treatment. CMZ co-treatment suppressed ethanol-induced oxidative stress, overproduction of tumor necrosis α (TNF-α), and decrease of protein levels of the PPAR-α co-activators including p300 and deacetylated PGC1-α. Furthermore, CMZ co-treatment led to the activation of AMP-activated protein kinase (AMPK), mitogen-activated protein kinase (MAPK), and PI3K/Akt/GSK3β pathway. However, chronic ethanol-induced decline of acyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) protein levels was partially restored by CMZ, while the activation of autophagy appeared to be suppressed by CMZ.

Conclusion

These results suggested that CMZ suppressed chronic ethanol-induced oxidative stress, TNF-α overproduction, decline of p300 protein level and deacetylation of PGC1-α, and activated AMPK, MAPK, and PI3K/Akt/GSK3β pathway, which might contribute to the activation of PPAR-α and account for the protection of CMZ against AFL.