Binge ethanol exposure increases liver injury in obese rats

Obesity Induces DNA Damage in Mammary Epithelial Cells Exacerbated by Acrylamide Treatment through CYP2E1-Mediated Oxidative Stress

Obesity and environmental toxins are risk factors for breast cancer; however, there is limited knowledge on how these risk factors interact to promote breast cancer. Acrylamide, a probable carcinogen and obesogen, is a by-product in foods prevalent in the obesity-inducing Western diet. Acrylamide is metabolized by cytochrome P450 2E1 (CYP2E1) to the genotoxic epoxide, glycidamide, and is associated with an increased risk for breast cancer. To investigate how acrylamide and obesity interact to increase breast cancer risk, female mice were fed a low-fat (LFD) or high-fat diet (HFD) and control water or water supplemented with acrylamide at levels similar to the average daily exposure in humans. While HFD significantly enhanced weight gain in mice, the addition of acrylamide did not significantly alter body weights compared to respective controls. Mammary epithelial cells from obese, acrylamide-treated mice had increased DNA strand breaks and oxidative DNA damage compared to all other groups. In vitro, glycidamide-treated COMMA-D cells showed significantly increased DNA strand breaks, while acrylamide-treated cells demonstrated significantly higher levels of intracellular reactive oxygen species. The knockdown of CYP2E1 rescued the acrylamide-induced oxidative stress. These studies suggest that long-term acrylamide exposure through foods common in the Western diet may enhance DNA damage and the CYP2E1-induced generation of oxidative stress in mammary epithelial cells, potentially enhancing obesity-induced breast cancer risk.

Interaction between fatty acid oxidation and ethanol metabolism in liver

Fatty acid oxidation (FAO) releases the energy stored in fat to maintain basic biological processes. Dehydrogenation is a major way to oxidize fatty acids, which needs NAD+ to accept the released H+ from fatty acids and form NADH, which increases the ratio of NADH/NAD+ and consequently inhibits FAO leading to the deposition of fat in the liver, which is termed fatty liver or steatosis. Consumption of alcohol (ethanol) initiates simple steatosis that progresses to alcoholic steatohepatitis, which constitutes a spectrum of liver disorders called alcohol-associated liver disease (ALD). ALD is linked to ethanol metabolism. Ethanol is metabolized by alcohol dehydrogenase (ADH), microsomal ethanol oxidation system (MEOS), mainly cytochrome P450 2E1 (CYP2E1), and catalase. ADH also requires NAD+ to accept the released H+ from ethanol. Thus, ethanol metabolism by ADH leads to increased ratio of NADH/NAD+, which inhibits FAO and induces steatosis. CYP2E1 directly consumes reducing equivalent NADPH to oxidize ethanol, which generates reactive oxygen species (ROS) that lead to cellular injury. Catalase is mainly present in peroxisomes, where very long-chain fatty acids and branched-chain fatty acids are oxidized, and the resultant short-chain fatty acids will be further oxidized in mitochondria. Peroxisomal FAO generates hydrogen peroxide (H2O2), which is locally decomposed by catalase. When ethanol is present, catalase uses H2O2 to oxidize ethanol. In this review, we introduce FAO (including α-, β-, and ω-oxidation) and ethanol metabolism (by ADH, CYP2E1, and catalase) followed by the interaction between FAO and ethanol metabolism in the liver and its pathophysiological significance.

Research progress on rodent models and its mechanisms of liver injury

The liver is the most important organ for biological transformation in the body and is crucial for maintaining the body's vital activities. Liver injury is a serious pathological condition that is commonly found in many liver diseases. It has a high incidence rate, is difficult to cure, and is prone to recurrence. Liver injury can cause serious harm to the body, ranging from mild to severe fatty liver disease. If the condition continues to worsen, it can lead to liver fibrosis and cirrhosis, ultimately resulting in liver failure or liver cancer, which can seriously endanger human life and health. Therefore, establishing an rodent model that mimics the pathogenesis and severity of clinical liver injury is of great significance for better understanding the pathogenesis of liver injury patients and developing more effective clinical treatment methods. The author of this article summarizes common chemical liver injury models, immune liver injury models, alcoholic liver injury models, drug-induced liver injury models, and systematically elaborates on the modeling methods, mechanisms of action, pathways of action, and advantages or disadvantages of each type of model. The aim of this study is to establish reliable rodent models for researchers to use in exploring anti-liver injury and hepatoprotective drugs. By creating more accurate theoretical frameworks, we hope to provide new insights into the treatment of clinical liver injury diseases.

Independent and additive effects of binge drinking and obesity on liver enzymes: a cross-sectional analysis using the Korean National Health Insurance Service data

Background

Binge drinking (BD) has been associated with elevated liver enzymes, but the joint association of BD and adiposity with liver enzymes is understudied. We aimed to examine the combined association of BD and obesity with elevated liver enzymes.

Methods

Data were obtained from 285,600 patients in the Korean National Health check-up program during 2009-2015. Level I BD (BD I) was defined as alcohol consumption of >60 g (men) or >40 g (women) on one occasion in the previous year. High-intensity BD (HIBD) corresponded to at least two times the BD I levels. General and abdominal obesity were defined by body mass index and waist circumference. Logistic regression was used to examine the independent and joint associations of BD and obesity with elevated alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT) levels. Relative excess risk (RERI), attributable proportion (AP), and synergy index (SI) were calculated to estimate the additive interaction effects.

Results

The mean age was 42.1 ± 0.03 years and 50.2% were women. Elevated ALT [odds ratio (OR) 1.09, 95% confidence interval (CI) 1.02-1.16], AST (OR 1.16, 95% CI 1.11-1.23), and GGT (OR 1.84, 95% CI 1.05-1.94) were associated with HIBD. Higher odds of elevated ALT (OR 3.57, 95% CI 3.43-3.71), AST (OR 3.47, 95% CI 3.37-3.58), and GGT (OR 2.10, 95% CI 1.98-2.12) were observed in individuals with general obesity. A similar trend was observed for abdominal obesity. The RERI, AP, and SI for the interaction effect of BD and general obesity were 23%, 7%, and 13% for elevated AST levels, and 67%, 24%, and 58% for elevated GGT levels, respectively. Similar effects were observed for the interaction between BD and abdominal obesity.

Conclusions

Obesity aggravated the odds of elevated liver AST and GGT levels in HIBD.

Sympathetic overdrive and unrestrained adipose lipolysis drive alcohol-induced hepatic steatosis in rodents

OBJECTIVE

Hepatic steatosis is a key initiating event in the pathogenesis of alcohol-associated liver disease (ALD), the most detrimental organ damage resulting from alcohol use disorder. However, the mechanisms by which alcohol induces steatosis remain incompletely understood. We have previously found that alcohol binging impairs brain insulin action, resulting in increased adipose tissue lipolysis by unrestraining sympathetic nervous system (SNS) outflow. Here, we examined whether an impaired brain-SNS-adipose tissue axis drives hepatic steatosis through unrestrained adipose tissue lipolysis and increased lipid flux to the liver.

METHODS

We examined the role of lipolysis, and the brain-SNS-adipose tissue axis and stress in alcohol induced hepatic triglyceride accumulation in a series of rodent models: pharmacological inhibition of the negative regulator of insulin signaling protein-tyrosine phosphatase 1β (PTP1b) in the rat brain, tyrosine hydroxylase (TH) knockout mice as a pharmacogenetic model of sympathectomy, adipocyte specific adipose triglyceride lipase (ATGL) knockout mice, wildtype (WT) mice treated with β3 adrenergic agonist or undergoing restraint stress.

RESULTS

Intracerebral administration of a PTP1b inhibitor, inhibition of adipose tissue lipolysis and reduction of sympathetic outflow ameliorated alcohol induced steatosis. Conversely, induction of adipose tissue lipolysis through β3 adrenergic agonism or by restraint stress worsened alcohol induced steatosis.

CONCLUSIONS

Brain insulin resistance through upregulation of PTP1b, increased sympathetic activity, and unrestrained adipose tissue lipolysis are key drivers of alcoholic steatosis. Targeting these drivers of steatosis may provide effective therapeutic strategies to ameliorate ALD.

D-ribose-L-cysteine exhibits neuroprotective activity through inhibition of oxido-behavioral dysfunctions and modulated activities of neurotransmitters in the cerebellum of Juvenile mice exposed to ethanol

Alcohol exposure to the cerebellum has been known to trigger cerebellar dysfunctions through several mechanisms. This present study was designed to evaluate the repealing effect of D-ribose-L-cysteine (DRLC) on alcohol-induced cerebellar dysfunctions in juvenile BALB/c mice. The animals were randomly divided into 4 groups (n = 10 per group). Mice were given oral administration of normal saline (control), DRLC (100 mg/kg, p.o), ethanol (0.2 mL of 10% w/v), or DRLC (100 mg/kg, p.o) + ethanol (0.2 mL of 10% w/v). On day 29 of the study (i.e., 24 h after the administration of the last respective doses), neurochemical quantification of the respective levels of serotonin and dopamine, lipid peroxidation, total antioxidant, superoxide dismutase, and glutathione peroxidase in the cerebellar tissues of the mice were analyzed. Compared with the saline-treated group, the studied neurochemical indices were modulated across the various experimental groups. The administration of ethanol significantly modulates the levels of monoamine neurotransmitters (serotonin and dopamine) as well as contents of total antioxidants, activities of superoxide dismutase, and glutathione peroxidase, with a concurrently increased level of lipid peroxidase in the cerebellar tissue of the mice. DRLC significantly reverses these effects in the DRLC + ethanol co-treated group. Combined exposure to DRLC + ethanol counteracts the deleterious effect of ethanol in the cerebellum of juvenile BALB/c mice via monoamine neurotransmitter, lipid peroxidation, total antioxidant status, superoxide dismutase, and glutathione peroxidase action pathways. Therefore, DRLC could be a pharmacologic or therapeutic agent in attenuating the deleterious effects of alcohol on the cerebellum.

New murine model of alcoholic hepatitis in obesity-induced metabolic-associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) and alcoholic hepatitis (AH) are among the most prevalent liver diseases worldwide, and their coexistence is common in clinical practice. However, currently established models of MAFLD-AH coexistence do not fully replicate their pathological characteristics and require sophisticated experimental techniques. Therefore, we aimed to develop an easily replicable model that mimics obesity-induced MAFLD-AH in patients. Our goal was to establish a murine model that replicates MAFLD and AH coexistence, resulting in significant liver injury and inflammation. To this end, we administered a single ethanol gavage dose to ob/ob mice on a chow diet. The administration of a single dose of ethanol led to elevated serum transaminase levels, increased liver steatosis, and apoptosis in ob/ob mice. Furthermore, ethanol binge caused a significant increase in oxidative stress in ob/ob mice, as measured via 4-hydroxynonenal. Importantly, the single dose of ethanol also markedly exacerbated liver neutrophil infiltration and upregulated the hepatic mRNA expression of several chemokines and neutrophil-related proteins, including Cxcl1, Cxcl2, and Lcn2. Whole-liver transcriptomic analysis revealed that ethanol-induced changes in gene expression profile shared similar features with AH and MAFLD. In ob/ob mice, a single dose of ethanol binge caused significant liver injury and neutrophil infiltration. This easy-to-replicate murine model successfully mimics the pathological and clinical features of patients with coexisting MAFLD and AH and closely resembles the transcriptional regulation seen in human disease.

Experimental models of fatty liver diseases: Status and appraisal

Fatty liver diseases, including alcohol-associated liver disease (ALD) and nonalcoholic fatty liver disease nonalcoholic fatty liver disease (NAFLD), affect a large number of people worldwide and become one of the major causes of end-stage liver disease, such as liver cirrhosis and hepatocellular carcinoma (HCC). Unfortunately, there are currently no approved pharmacological treatments for ALD or NAFLD. This situation highlights the urgent need to explore new intervention targets and discover effective therapeutics for ALD and NAFLD. The lack of properly validated preclinical disease models is a major obstacle to the development of clinical therapies. ALD and NAFLD models have been in the development for decades, but there are still no models that recapitulate the full spectrum of ALD and NAFLD. Throughout this review, we summarize the current in vitro and in vivo models used for research on fatty liver diseases and discuss the advantages and limitations of these models.

Concomitant western diet and chronic-binge alcohol dysregulate hepatic metabolism

BACKGROUND AND AIMS

There is significant overlap between non-alcoholic fatty liver disease (NAFLD) and alcohol-associated liver disease (ALD) with regards to risk factors and disease progression. However, the mechanism by which fatty liver disease arises from concomitant obesity and overconsumption of alcohol (syndrome of metabolic and alcohol-associated fatty liver disease; SMAFLD), is not fully understood.

METHODS

Male C57BL6/J mice were fed chow diet (Chow) or high-fructose, high-fat, high-cholesterol diet (FFC) for 4 weeks, then administered either saline or ethanol (EtOH, 5% in drinking water) for another 12 weeks. The EtOH treatment also consisted of a weekly 2.5 g EtOH/kg body weight gavage. Markers for lipid regulation, oxidative stress, inflammation, and fibrosis were measured by RT-qPCR, RNA-seq, Western blot, and metabolomics.

RESULTS

Combined FFC-EtOH induced more body weight gain, glucose intolerance, steatosis, and hepatomegaly compared to Chow, EtOH, or FFC. Glucose intolerance by FFC-EtOH was associated with decreased hepatic protein kinase B (AKT) protein expression and increased gluconeogenic gene expression. FFC-EtOH increased hepatic triglyceride and ceramide levels, plasma leptin levels, hepatic Perilipin 2 protein expression, and decreased lipolytic gene expression. FFC and FFC-EtOH also increased AMP-activated protein kinase (AMPK) activation. Finally, FFC-EtOH enriched the hepatic transcriptome for genes involved in immune response and lipid metabolism.

CONCLUSIONS

In our model of early SMAFLD, we observed that the combination of an obesogenic diet and alcohol caused more weight gain, promoted glucose intolerance, and contributed to steatosis by dysregulating leptin/AMPK signaling. Our model demonstrates that the combination of an obesogenic diet with a chronic-binge pattern alcohol intake is worse than either insult alone.

Acetaminophen-Induced Hepatotoxicity in Obesity and Nonalcoholic Fatty Liver Disease: A Critical Review

The epidemic of obesity, type 2 diabetes and nonalcoholic liver disease (NAFLD) favors drug consumption, which augments the risk of adverse events including liver injury. For more than 30 years, a series of experimental and clinical investigations reported or suggested that the common pain reliever acetaminophen (APAP) could be more hepatotoxic in obesity and related metabolic diseases, at least after an overdose. Nonetheless, several investigations did not reproduce these data. This discrepancy might come from the extent of obesity and steatosis, accumulation of specific lipid species, mitochondrial dysfunction and diabetes-related parameters such as ketonemia and hyperglycemia. Among these factors, some of them seem pivotal for the induction of cytochrome P450 2E1 (CYP2E1), which favors the conversion of APAP to the toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI). In contrast, other factors might explain why obesity and NAFLD are not always associated with more frequent or more severe APAP-induced acute hepatotoxicity, such as increased volume of distribution in the body, higher hepatic glucuronidation and reduced CYP3A4 activity. Accordingly, the occurrence and outcome of APAP-induced liver injury in an obese individual with NAFLD would depend on a delicate balance between metabolic factors that augment the generation of NAPQI and others that can mitigate hepatotoxicity.

mTORC1 inhibition uncouples lipolysis and thermogenesis in white adipose tissue to contribute to alcoholic liver disease

BACKGROUND

Adipose tissue thermogenic activities use fatty acids from lipolysis for heat generation. Therefore, a tight coupling between lipolysis and thermogenesis is physiologically imperative in maintaining not only body temperature but also lipids homeostasis. Adipose tissue dysfunction contributes to alcoholic liver disease (ALD). Here, studies were conducted to examine how alcohol intake affects adipose tissue thermogenic activities and whether altered adipose tissue thermogenesis contributes to ALD.

METHODS

Both the Lieber-DeCarli and the NIAAA mouse models of ALD were used. Denervation surgery in epididymal fat pads was performed. CL316,243, a selective β3-adrenoceptor agonist, SR59230A, a selective β3 adrenoceptor (ADRB3) antagonist, and rapamycin, a selective mechanistic target of rapamycin complex 1 (mTORC1) inhibitor, were administrated through i.p. injection. Adipocyte-specific Prdm16 knockout mice were subjected to alcohol-containing diet chronically.

RESULTS

Chronic alcohol consumption, which enhances adipose tissue lipolysis, inhibits thermogenic activities of beige adipocytes in inguinal white adipose tissue (WAT), leading to an uncoupling status between lipolysis and thermogenesis in WAT at both basal and ADRB3 stimulation states. CL316,243 administration exacerbates liver pathologies of ALD. Alcohol intake inhibits mTORC1 activities in WAT. In mice, mTORC1 inhibition by rapamycin inhibits the thermogenesis of iWAT, whereas enhancing WAT lipolysis. Further investigations using adipocyte-specific Prdm16 knockout mice revealed that functional deficiency of beige adipocytes aggravates liver pathologies of ALD, suggesting that the inhibitory effect of alcohol on WAT browning/thermogenesis contributes to ALD pathogenesis.

CONCLUSION

Chronic alcohol consumption induces an "uncoupling status" between lipolysis and browning/thermogenesis in WAT by inhibiting mTORC1 activation. Diminished WAT browning/thermogenesis, concomitant with enhanced lipolysis, contributes to ALD pathogenesis.

Xenobiotic-Induced Aggravation of Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD), which is often linked to obesity, encompasses a large spectrum of hepatic lesions, including simple fatty liver, steatohepatitis, cirrhosis and hepatocellular carcinoma. Besides nutritional and genetic factors, different xenobiotics such as pharmaceuticals and environmental toxicants are suspected to aggravate MAFLD in obese individuals. More specifically, pre-existing fatty liver or steatohepatitis may worsen, or fatty liver may progress faster to steatohepatitis in treated patients, or exposed individuals. The mechanisms whereby xenobiotics can aggravate MAFLD are still poorly understood and are currently under deep investigations. Nevertheless, previous studies pointed to the role of different metabolic pathways and cellular events such as activation of de novo lipogenesis and mitochondrial dysfunction, mostly associated with reactive oxygen species overproduction. This review presents the available data gathered with some prototypic compounds with a focus on corticosteroids and rosiglitazone for pharmaceuticals as well as bisphenol A and perfluorooctanoic acid for endocrine disruptors. Although not typically considered as a xenobiotic, ethanol is also discussed because its abuse has dire consequences on obese liver.

Deficiency of Cathelicidin Attenuates High-Fat Diet Plus Alcohol-Induced Liver Injury through FGF21/Adiponectin Regulation

Alcohol consumption and obesity are known risk factors of steatohepatitis. Here, we report that the deficiency of CRAMP (cathelicidin-related antimicrobial peptide—gene name: Camp) is protective against a high-fat diet (HFD) plus acute alcohol (HFDE)-induced liver injury. HFDE markedly induced liver injury and steatosis in WT mice, which were attenuated in Camp^–/– mice. Neutrophil infiltration was lessened in the liver of Camp^–/– mice. HFDE feeding dramatically increased epididymal white adipose tissue (eWAT) mass and induced adipocyte hypertrophy in WT mice, whereas these effects were attenuated by the deletion of Camp. Furthermore, Camp^–/– mice had significantly increased eWAT lipolysis, evidenced by up-regulated expression of lipolytic enzymes, adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL). The depletion of Camp also increased uncoupling protein 1 (UCP1)-dependent thermogenesis in the brown adipose tissue (BAT) of mice. HFDE fed Camp^–/– mice had elevated protein levels of fibroblast growth factor 21 (FGF21) in the eWAT, with an increased adiponectin production, which had been shown to alleviate hepatic fat deposition and inflammation. Collectively, we have demonstrated that Camp^–/– mice are protected against HFD plus alcohol-induced liver injury and steatosis through FGF21/adiponectin regulation. Targeting CRAMP could be an effective approach for prevention/treatment of high-fat diet plus alcohol consumption-induced steatohepatitis.

Alcohol and Metabolic-associated Fatty Liver Disease

The diagnosis of metabolic-associated fatty liver disease is based on the detection of liver steatosis together with the presence of metabolic dysfunction. According to this new definition, the diagnosis of metabolic-associated fatty liver disease is independent of the amount of alcohol consumed. Actually, alcohol and its metabolites have various effects on metabolic-associated abnormalities during the process of alcohol metabolism. Studies have shown improved metabolic function in light to moderate alcohol drinkers. There are several studies focusing on the role of light to moderate alcohol intake on metabolic dysfunction. However, the results from studies are diverse, and the conclusions are often controversial. This review systematically discusses the effects of alcohol consumption, focusing on light to moderate alcohol consumption, obesity, lipid and glucose metabolism, and blood pressure.

Experimental models of metabolic and alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a multi-systemic disease that is considered the hepatic manifestation of metabolic syndrome (MetS). Because alcohol consumption in NAFLD patients is common, there is a significant overlap in the pathogenesis of NAFLD and alcoholic liver disease (ALD). Indeed, MetS also significantly contributes to liver injury in ALD patients. This “syndrome of metabolic and alcoholic steatohepatitis” (SMASH) is thus expected to be a more prevalent presentation in liver patients, as the obesity epidemic continues. Several pre-clinical experimental models that couple alcohol consumption with NAFLD-inducing diet or genetic obesity have been developed to better understand the pathogenic mechanisms of SMASH. These models indicate that concomitant MetS and alcohol contribute to lipid dysregulation, oxidative stress, and the induction of innate immune response. There are significant limitations in the applicability of these models to human disease, such as the ability to induce advanced liver injury or replicate patterns in human food/alcohol consumption. Thus, there remains a need to develop models that accurately replicate patterns of obesogenic diet and alcohol consumption in SMASH patients.

Hepatoprotective potential of 7,8-Dihydroxyflavone against alcohol and high-fat diet induced liver toxicity via attenuation of oxido-nitrosative stress and NF-κB activation

BACKGROUND

Fatty liver diseases are the most common and major health concern arises from the modern lifestyle and alcohol (ethanol) abuse. The prevalence of non-alcoholic fatty liver diseases (NAFLD) has been observed prominently in obese and diabetic individuals, while alcoholic liver disease is common in alcoholic persons. Fatty liver disease, such as steatohepatitis, leads to fibrosis, cirrhosis and eventually hepatocellular carcinoma. The present study was designed to investigate the effect of 7,8-Dihydroxyflavone (7,8-DHF) against high-fat diet (HFD) and ethanol (EtOH)-induced hepatotoxicity in rats.

METHODS

Male Wistar rats (150-200 g) were fed HFD (58% calories from fat) and EtOH (3-15% in drinking water) for 12 weeks. 7,8-DHF was administered intraperitoneally at the dose of 5 mg/kg/day for the last four weeks. After 12 weeks, biochemical, ELISA, RT-PCR, and histological studies have been carried out.

RESULTS

Biochemical analyses revealed the involvement of oxidative stress and inflammation in the liver of HFD and EtOH-fed rats. 7,8-DHF treatment significantly reduced HFD and EtOH-induced oxidative stress as evidenced by the reduction of lipid peroxidation and augmentation of reduced glutathione level. Moreover, IL-1β level was found significantly reduced in 7,8-DHF treated EtOH, HFD and EtOH+HFD groups. The semi-quantitative RT-PCR results indicated down-regulation of Nrf-2 and HO-1 and up-regulation of NF-κB and iNOS mRNA expression level in the liver of HFD and EtOH-fed rats, which was ameliorated by 7,8-DHF treatment.

CONCLUSION

The present study suggested that 7,8-DHF could be an effective pharmacological intervention in combating HFD and EtOH-induced hepatotoxicity.

Alcoholic liver disease: A current molecular and clinical perspective

Heavy alcohol use is the cause of alcoholic liver disease (ALD). The ALD spectrum ranges from alcoholic steatosis to steatohepatitis, fibrosis, and cirrhosis. In Western countries, approximately 50% of cirrhosis-related deaths are due to alcohol use. While alcoholic cirrhosis is no longer considered a completely irreversible condition, no effective anti-fibrotic therapies are currently available. Another significant clinical aspect of ALD is alcoholic hepatitis (AH). AH is an acute inflammatory condition that is often comorbid with cirrhosis, and severe AH has a high mortality rate. Therapeutic options for ALD are limited. The established treatment for AH is corticosteroids, which improve short-term survival but do not affect long-term survival. Liver transplantation is a curative treatment option for alcoholic cirrhosis and AH, but patients must abstain from alcohol use for 6 months to qualify. Additional effective therapies are needed. The molecular mechanisms underlying ALD are complex and have not been fully elucidated. Various molecules, signaling pathways, and crosstalk between multiple hepatic and extrahepatic cells contribute to ALD progression. This review highlights established and emerging concepts in ALD clinicopathology, their underlying molecular mechanisms, and current and future ALD treatment options.

Role of the pregnane X receptor in binge ethanol-induced steatosis and hepatotoxicity

The pregnane X receptor (PXR, NR1I2) is a xenobiotic-sensing nuclear receptor that defends against toxic agents. We have shown that PXR promotes chronic ethanol (EtOH)-induced steatosis. Therefore, we examined the role of PXR in binge EtOH-induced hepatotoxicity. Male wild type (WT) and Pxr-null mice were orally administered three binge doses of EtOH (4.5 g/kg, every 12 hours) and euthanized four hours after the final dose. Pxr-null mice displayed higher basal mRNA levels of hepatic lipogenic transcription factor sterol regulatory element binding protein 1c (Srebp-1c) and its target stearoyl-CoA desaturase 1 (Scd1) and the lipid peroxide detoxifying aldo-keto reductase 1b7 (Akr1b7) and higher protein levels of EtOH-metabolizing alcohol dehydrogenase 1 (ADH1). In both genotypes, binge EtOH-induced triglyceride accumulation was associated with inhibition of fatty acid β-oxidation and upregulation of Srebp-1c- regulated lipogenic genes and hepatic CYP2E1 protein. Unexpectedly, gene expression of Cyp2b10, a constitutive androstane receptor target gene, implicated in EtOH hepatotoxicity, was PXR-dependent upregulated by binge EtOH. Also, PXR-dependent was the binge EtOH-induced inhibition of hepatic Akr1b8 mRNA, and protein levels of aldehyde dehydrogenase (ALDH) 1A1 and anti-apoptotic Bcl-2, but increased pro-apoptotic Bax protein expression, leading to increases in residual EtOH concentration and the cellular oxidative stress marker, malondialdehyde. In contrast, Pxr-null mice displayed increased Akr1b7 gene and ADH1 protein expression and hypertriglyceridemia following binge EtOH exposure. Taken together, this study demonstrates that PXR ablation prevents EtOH induced upregulation of Cyp2b10 and that PXR potentiates binge EtOH-induced oxidative stress and inhibition of EtOH catabolism, but protects against alcoholic hyperlipidemia.

The bidirectional impacts of alcohol consumption and the metabolic syndrome: Cofactors for progressive fatty liver disease

Current medical practice artificially dichotomises a diagnosis of fatty liver disease into one of two common forms: alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Together, these account for the majority of chronic liver diseases worldwide. In recent years, there has been a dramatic increase in the prevalence of obesity and metabolic syndrome within the general population. These factors now coexist with alcohol consumption in a substantial proportion of the population. Each exposure sensitises the liver to the injurious effects of the other; an interaction that drives and potentially accelerates the genesis of liver disease. We review the epidemiological evidence and scientific literature that considers how alcohol consumption interacts with components of the metabolic syndrome to exert synergistic or supra-additive effects on the development and progression of liver disease, before discussing how these interactions may be addressed in clinical practice.

Rodent Models of Alcoholic Liver Disease: Role of Binge Ethanol Administration

Both chronic and acute (binge) alcohol drinking are important health and economic concerns worldwide and prominent risk factors for the development of alcoholic liver disease (ALD). There are no FDA-approved medications to prevent or to treat any stage of ALD. Therefore, discovery of novel therapeutic strategies remains a critical need for patients with ALD. Relevant experimental animal models that simulate human drinking patterns and mimic the spectrum and severity of alcohol-induced liver pathology in humans are critical to our ability to identify new mechanisms and therapeutic targets. There are several animal models currently in use, including the most widely utilized chronic ad libitum ethanol (EtOH) feeding (Lieber–DeCarli liquid diet model), chronic intragastric EtOH administration (Tsukamoto–French model), and chronic-plus-binge EtOH challenge (Bin Gao—National Institute on Alcohol Abuse and Alcoholism (NIAAA) model). This review provides an overview of recent advances in rodent models of binge EtOH administration which help to recapitulate different features and etiologies of progressive ALD. These models include EtOH binge alone, and EtOH binge coupled with chronic EtOH intake, a high fat diet, or endotoxin challenge. We analyze the strengths, limitations, and translational relevance of these models, as well as summarize the liver injury outcomes and mechanistic insights. We further discuss the application(s) of binge EtOH models in examining alcohol-induced multi-organ pathology, sex- and age-related differences, as well as circadian rhythm disruption.

Cytochrome P450s and Alcoholic Liver Disease

Alcohol consumption causes liver diseases, designated as Alcoholic Liver Disease (ALD). Because alcohol is detoxified by alcohol dehydrogenase (ADH), a major ethanol metabolism system, the development of ALD was initially believed to be due to malnutrition caused by alcohol metabolism in liver. The discovery of the microsomal ethanol oxidizing system (MEOS) changed this dogma. Cytochrome P450 enzymes (CYP) constitute the major components of MEOS. Cytochrome P450 2E1 (CYP2E1) in MEOS is one of the major ROS generators in liver and is considered to be contributive to ALD. Our labs have been studying the relationship between CYP2E1 and ALD for many years. Recently, we found that human CYP2A6 and its mouse analog CYP2A5 are also induced by alcohol. In mice, the alcohol induction of CYP2A5 is CYP2E1-dependent. Unlike CYP2E1, CYP2A5 protects against the development of ALD. The relationship of CYP2E1, CYP2A5, and ALD is a major focus of this review.

Where should the safe limits of alcohol consumption stand in light of liver enzyme abnormalities in alcohol consumers?

Objectives

To estimate the prevalence and risk factors for abnormal liver enzymes in a large age- and gender stratified population-based sample of apparently healthy individuals with or without alcohol consumption and other health-related risk factors (adiposity, physical inactivity, smoking).

Methods

Data on alcohol use, smoking, diet and physical activity were recorded using structured questionnaires from 13,976 subjects (6513 men, 7463 women, aged 25–74 years) in the national FINRISK studies. Alcohol data was used to categorize the participants into abstainers, light drinkers, moderate drinkers and heavy drinkers. Serum gamma-glutamyltransferase (GGT) and alanine aminotransferase (ALT) activities were measured using standard kinetic methods.

Results

Male light drinkers, moderate drinkers and heavy drinkers showed significantly higher relative risks of abnormal GGT than abstainers: 1.37 (95% confidence interval 1.11 to 1.71, p < 0.01), 2.72 (2.08 to 3.56, p < 0.0005), and 6.10 (4.55 to 7.17, p < 0.0005), respectively. Corresponding values for women were 1.22 (0.99 to 1.51, p = 0.065), 1.90 (1.44 to 2.51, p < 0.0005), and 5.91 (3.80 to 9.17, p < 0.0005). Estimated threshold doses for a significant GGT elevation was 14 standard weekly alcohol doses for men and 7 for women. Excess body weight and age over 40 years modulated the thresholds towards smaller quantities of alcohol. The risk of abnormal GGT was also significantly influenced by physical inactivity and smoking. The relative risks of abnormal ALT activities were increased in male heavy drinkers, especially in those presenting with adiposity and sedentary lifestyle.

Conclusions

Alcohol use markedly increases the risk for abnormal liver enzyme activities in those presenting with age over 40 years, obesity, smoking or sedentary lifestyle. The data should be considered in public health recommendations and in the definitions of safe limits of alcohol use.

Alcohol and Hepatocellular Carcinoma: Adding Fuel to the Flame

Primary tumors of the liver represent the fifth most common type of cancer in the world and the third leading cause of cancer-related death. Case-control studies from different countries report that chronic ethanol consumption is associated with an approximately 2-fold increased odds ratio for hepatocellular carcinoma (HCC). Despite the substantial epidemiologic data in humans demonstrating that chronic alcohol consumption is a major risk factor for HCC development, the pathways causing alcohol-induced liver cancer are poorly understood. In this overview, we summarize the epidemiological evidence for the association between alcohol and liver cancer, review the genetic, oncogenic, and epigenetic factors that drive HCC development synergistically with ethanol intake and discuss the essential molecular and metabolic pathways involved in alcohol-induced liver tumorigenesis.

Identification of cytochrome CYP2E1 as critical mediator of synergistic effects of alcohol and cellular lipid accumulation in hepatocytes in vitro

Clinical studies propose a causative link between the consumption of alcohol and the development and progression of liver disease in obese individuals. However, it is incompletely understood how alcohol and obesity interact and whether the combined effects are additive or synergistic. In this study, we developed an in vitro model to address this question. Lipid accumulation in primary human hepatocytes was induced by incubation with oleic acid. Subsequently, steatotic and control hepatocytes were incubated with up to 50 mM alcohol. This alcohol concentration on its own revealed only minimal effects but significantly enhanced oleate-induced lipogenesis and cellular triglyceride content compared to control cells. Similarly, lipid peroxidation, oxidative stress and pro-inflammatory gene expression as well as CYP2E1 levels and activity were synergistically induced by alcohol and steatosis. CYP2E1 inhibition blunted these synergistic pathological effects. Notably, alcohol and cellular steatosis also induced autophagy in a synergistic manner, and also this was mediated via CYP2E1. Further induction of autophagy ameliorated the joint effects of alcohol and oleic acid on hepatocellular lipid accumulation and inflammatory gene expression while inhibition of autophagy further enhanced the dual pathological effects. Further analyses revealed that the joint synergistic effect of alcohol and steatosis on autophagy was mediated via activation of the JNK-pathway. In summary, our data indicate that alcohol induces not only pathological but also protective mechanisms in steatotic hepatocytes via CYP2E1. These findings may have important implications on the prognosis and treatment of alcoholic liver disease particularly in obese individuals.

Patterns of Drinking and Mortality from Different Diseases—An Overview

Alcohol has been linked to a considerable burden of disease worldwide. Recent epidemiological research has shown that dimensions of alcohol exposure other than average volume are causal in the etiology of disease. Based on a systematic, computer-assisted search, this article attempts a qualitative review of this literature. Results show that cardiovascular disease, especially ischaemic heart disease, is linked to patterns of drinking: regular and light to moderate drinking, and drinking with meals are cardioprotective; heavy drinking occasions have been associated with detrimental outcomes and increases in disease risk. For cancers, consumption of spirits is linked to higher risk of cancers of the upper digestive tract. Spirits also may play a particular role in causing liver cirrhosis in addition to heavy drinking occasions. Finally, injuries are especially related to high blood alcohol concentration and to the frequency of heavy drinking occasions. Overall, these findings strongly indicate that alcohol epidemiology should include adequate pattern measures into future research.

Binge ethanol exposure increases the Krüppel-like factor 11-monoamine oxidase (MAO) pathway in rats: Examining the use of MAO inhibitors to prevent ethanol-induced brain injury

Binge drinking induces several neurotoxic consequences including oxidative stress and neurodegeneration. Because of these effects, drugs which prevent ethanol-induced damage to the brain may be clinically beneficial. In this study, we investigated the ethanol-mediated KLF11-MAO cell death cascade in the frontal cortex of Sprague-Dawley rats exposed to a modified Majchowicz 4-day binge ethanol model and control rats. Moreover, MAO inhibitors (MAOIs) were investigated for neuroprotective activity against binge ethanol. Binge ethanol-treated rats demonstrated a significant increase in KLF11, both MAO isoforms, protein oxidation and caspase-3, as well as a reduction in BDNF expression in the frontal cortex compared to control rats. MAOIs prevented these binge ethanol-induced changes, suggesting a neuroprotective benefit. Neither binge ethanol nor MAOI treatment significantly affected protein expression levels of the oxidative stress enzymes, SOD2 or catalase. Furthermore, ethanol-induced antinociception was enhanced following exposure to the 4-day ethanol binge. These results demonstrate that the KLF11-MAO pathway is activated by binge ethanol exposure and MAOIs are neuroprotective by preventing the binge ethanol-induced changes associated with this cell death cascade. This study supports KLF11-MAO as a mechanism of ethanol-induced neurotoxicity and cell death that could be targeted with MAOI drug therapy to alleviate alcohol-related brain injury. Further examination of MAOIs to reduce alcohol use disorder-related brain injury could provide pivotal insight to future pharmacotherapeutic opportunities.

A cellular model to study drug-induced liver injury in nonalcoholic fatty liver disease: Application to acetaminophen

Obesity and nonalcoholic fatty liver disease (NAFLD) can increase susceptibility to hepatotoxicity induced by some xenobiotics including drugs, but the involved mechanisms are poorly understood. For acetaminophen (APAP), a role of hepatic cytochrome P450 2E1 (CYP2E1) is suspected since the activity of this enzyme is consistently enhanced during NAFLD. The first aim of our study was to set up a cellular model of NAFLD characterized not only by triglyceride accumulation but also by higher CYP2E1 activity. To this end, human HepaRG cells were incubated for one week with stearic acid or oleic acid, in the presence of different concentrations of insulin. Although cellular triglycerides and the expression of lipid-responsive genes were similar with both fatty acids, CYP2E1 activity was significantly increased only by stearic acid. CYP2E1 activity was reduced by insulin and this effect was reproduced in cultured primary human hepatocytes. Next, APAP cytotoxicity was assessed in HepaRG cells with or without lipid accretion and CYP2E1 induction. Experiments with a large range of APAP concentrations showed that the loss of ATP and glutathione was almost always greater in the presence of stearic acid. In cells pretreated with the CYP2E1 inhibitor chlormethiazole, recovery of ATP was significantly higher in the presence of stearate with low (2.5mM) or high (20mM) concentrations of APAP. Levels of APAP-glucuronide were significantly enhanced by insulin. Hence, HepaRG cells can be used as a valuable model of NAFLD to unveil important metabolic and hormonal factors which can increase susceptibility to drug-induced hepatotoxicity.

Notch signaling and M1 macrophage activation in obesity-alcohol synergism

Macrophages are a key cell type in the innate immune system, and its proinflammatory (M1) activation in the liver plays a critical role in pathogenesis of alcoholic steatohepatitis. Emerging evidence indicates the involvement of Notch signaling in regulation of innate immune response and cellular metabolism. Metabolic switch to glycolysis characterizes macrophages undergoing M1 activation. It has been proposed that metabolic reprograming in response to extrinsic stimulation, such as bacterial endotoxin, triggers intrinsic signal to dictate cell differentiation. Using an obesity-alcohol synergistic ASH mouse model, we have recently shown that Notch1 pathway promotes M1 activation of hepatic macrophages, through direct upregulation of M1 gene transcription and through reprograming of mitochondrial metabolism to glucose oxidation and subsequent mtROS generation to augment M1 gene expression. Our studies demonstrate a novel mechanism of Notch1 signaling in metabolic reprograming of macrophage for M1 activation in ASH.

Binge alcohol consumption aggravates oxidative stress and promotes pathogenesis of NASH from obesity-induced simple steatosis

The pathogenesis of nonalcoholic steatohepatitis (NASH) is a two-stage process in which steatosis is the "first hit" and an unknown "second hit." We hypothesized that "a binge" could be a "second hit" to develop NASH from obesity-induced simple steatosis. Thirty-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) rats were administered 10 mL of 10% ethanol orally for 5, 3, 2, and 1 d/wk for 3 consecutive weeks. As control, male Otsuka Long-Evans Tokushima (OLET) rats were administered the same amount of alcohol. Various biochemical parameters of obesity, steatosis and NASH were monitored in serum and liver specimens in untreated and ethanol-treated rats. The liver sections were evaluated for histopathological alterations of NASH and stained for cytochrome P-4502E1 (CYP2E1) and 4-hydroxy-nonenal (4-HNE). Simple steatosis, hyperinsulinemia, hyperglycemia, insulin resistance, hypertriglycemia and marked increases in hepatic CYP2E1 and 4-HNE were present in 30-wk-old untreated OLETF rats. Massive steatohepatitis with hepatocyte ballooning was observed in the livers of all OLETF rats treated with ethanol. Serum and hepatic triglyceride levels as well as tumor necrosis factor (TNF)-α mRNA were markedly increased in all ethanol-treated OLETF rats. Staining for CYP2E1 and 4-NHE demonstrated marked increases in the hepatic tissue of all the groups of OLETF rats treated with ethanol compared with OLET rats. Our data demonstrated that "a binge" serves as a "second hit" for development of NASH from obesity-induced simple steatosis through aggravation of oxidative stress. The enhanced levels of CYP2E1 and increased oxidative stress in obesity play a significant role in this process.

Impacts of common factors of life style on serum liver enzymes

AIM: To investigate the impacts of gender, age and factors of life style (alcohol, overweight, coffee and smoking) on serum liver enzymes.

METHODS: Serum alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT) were measured from 6269 apparently healthy individuals (2851 men, 3418 women, mean age 45 ± 12 years, range 25-74 years) in a national cross-sectional health survey. All subjects underwent detailed clinical examinations and interviews including the amount and pattern of alcohol use, coffee consumption and smoking habits.

RESULTS: In this population with a mean ± SD alcohol consumption of 65 ± 105 g/wk and body mass index (BMI) of 26.1 ± 4.3 kg/m², both ALT and GGT were significantly influenced by alcohol use (P < 0.001) and BMI (P < 0.001), whereas smoking increased only GGT (P < 0.001). A significant effect of age on ALT was seen in men (P < 0.001) whereas not in women. Significant two-factor interactions of alcohol use in men were observed with age (ALT: P < 0.01; GGT: P < 0.001) and BMI (GGT: P < 0.05). For ALT, a significant interaction also occurred between BMI and age (P < 0.005). In contrast, women showed significant interactions of alcohol use with BMI (GGT: P < 0.05), smoking (GGT: P < 0.001), and coffee consumption (GGT: P < 0.001).

CONCLUSION: Life-style associated changes in liver enzymes may reflect health risks, which should be considered in the definition of normal limits for liver enzymes.

Farnesoid X receptor regulates forkhead Box O3a activation in ethanol-induced autophagy and hepatotoxicity

Alcoholic liver disease encompasses a wide spectrum of pathogenesis including steatosis, fibrosis, cirrhosis, and alcoholic steatohepatitis. Autophagy is a lysosomal degradation process that degrades cellular proteins and damaged/excess organelles, and serves as a protective mechanism in response to various stresses. Acute alcohol treatment induces autophagy via FoxO3a-mediated autophagy gene expression and protects against alcohol-induced steatosis and liver injury in mice. Farnesoid X Receptor (FXR) is a nuclear receptor that regulates cellular bile acid homeostasis. In the present study, wild type and FXR knockout (KO) mice were treated with acute ethanol for 16 h. We found that ethanol treated-FXR KO mice had exacerbated hepatotoxicity and steatosis compared to wild type mice. Furthermore, we found that ethanol treatment had decreased expression of various essential autophagy genes and several other FoxO3 target genes in FXR KO mice compared with wild type mice. Mechanistically, we did not find a direct interaction between FXR and FoxO3. Ethanol-treated FXR KO mice had increased Akt activation, increased phosphorylation of FoxO3 resulting in decreased FoxO3a nuclear retention and DNA binding. Furthermore, ethanol treatment induced hepatic mitochondrial spheroid formation in FXR KO mice but not in wild type mice, which may serve as a compensatory alternative pathway to remove ethanol-induced damaged mitochondria in FXR KO mice. These results suggest that lack of FXR impaired FoxO3a-mediated autophagy and in turn exacerbated alcohol-induced liver injury.

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FXR knockout mice are more susceptible to acute ethanol-induced steatosis and liver injury due to defective hepatic autophagy.

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FXR knockout mice had decreased FoxO3a activation and reduced expression of autophagy related genes in the liver after acute ethanol treatment.

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FXR knockout mice had increased mitochondrial spheroid formation after acute ethanol treatment.

Acetaminophen-induced liver injury in obesity and nonalcoholic fatty liver disease

Although acetaminophen (APAP) is usually considered as a safe drug, this painkiller can lead to acute liver failure after overdoses. Moreover, there is evidence that the maximum recommended dosage can induce hepatic cytolysis in some individuals. Several predisposing factors appear to enhance the risk and severity of APAP-induced liver injury including chronic alcoholic liver disease and nonalcoholic fatty liver disease (NAFLD), which refers to a large spectrum of hepatic lesions linked to obesity. In contrast, obesity by itself does not seem to be associated with a higher risk of APAP-induced liver injury. Since 1987, seven studies dealt with APAP-induced hepatotoxicity in rodent models of NAFLD and five of them found that this liver disease was associated with higher APAP toxicity. Unfortunately, these studies did not unequivocally established the mechanism(s) whereby NAFLD could favour APAP hepatotoxicity, although some investigations suggested that pre-existent induction of hepatic cytochrome P450 2E1 (CYP2E1) could play a significant role by increasing the generation of N-acetyl-p-benzoquinone imine (NAPQI), the toxic metabolite of APAP. Moreover, pre-existent mitochondrial dysfunction associated with NAFLD could also be involved. In contrast, some investigations suggested that factors that could reduce the risk and severity of APAP hepatotoxicity in obesity and NAFLD include higher hepatic APAP glucuronidation, reduced CYP3A4 activity and increased volume of body distribution. Thus, the occurrence and the outcome of APAP-induced liver injury in an obese individual with NAFLD might depend on a delicate balance between metabolic factors that can be protective and others that favour large hepatic levels of NAPQI.

Precision-cut liver slices from diet-induced obese rats exposed to ethanol are susceptible to oxidative stress and increased fatty acid synthesis

Oxidative stress from fat accumulation in the liver has many deleterious effects. Many believe that there is a second hit that causes relatively benign fat accumulation to transform into liver failure. Therefore, we evaluated the effects of ethanol on ex vivo precision-cut liver slice cultures (PCLS) from rats fed a high-fat diet resulting in fatty liver. Age-matched male Sprague-Dawley rats were fed either high-fat (obese) (45% calories from fat, 4.73 kcal/g) or control diet for 13 mo. PCLS were prepared, incubated with 25 mM ethanol for 24, 48, and 72 h, harvested, and evaluated for ethanol metabolism, triglyceride production, oxidative stress, and cytokine expression. Ethanol metabolism and acetaldehyde production decreased in PCLS from obese rats compared with age-matched controls (AMC). Increased triglyceride and smooth muscle actin production was observed in PCLS from obese rats compared with AMC, which further increased following ethanol incubation. Lipid peroxidation, measured by thiobarbituric acid reactive substances assay, increased in response to ethanol, whereas GSH and heme oxygenase I levels were decreased. TNF-α and IL-6 levels were increased in the PCLS from obese rats and increased further with ethanol incubation. Diet-induced fatty liver increases the susceptibility of the liver to toxins such as ethanol, possibly by the increased oxidative stress and cytokine production. These findings support the concept that the development of fatty liver sensitizes the liver to the effects of ethanol and leads to the start of liver failure, necrosis, and eventually cirrhosis.

Effects of binge ethanol on lipid homeostasis and oxidative stress in a rat model of nonalcoholic fatty liver disease

Excess fat accumulation renders the liver more vulnerable to ethanol, but it is still unclear how alcohol enhances lipid dysmetabolism and oxidative stress in a pre-existing steatosis condition. The effects produced by binge ethanol consumption in the liver of male Wistar rats fed a standard (Ctrl) or a high-fat diet HFD were compared. The liver status was checked through tissue histology and standard serum parameters. Alteration of hepatic lipid homeostasis and consequent oxidative unbalance were assessed by quantifying the mRNA expression of the lipid-regulated peroxisome proliferator-activated receptors (PPARs), of the cytochromes CYP2E1 and CYP4A1, and of some antioxidant molecules such as the metallothionein isoforms MT1 and MT2 and the enzymes catalase and superoxide dismutase. The number of adipose differentiation-related protein (ADRP)-positive lipid droplets (LDs) was evaluated by immunohistochemical staining. As a response to the double insult of diet and ethanol the rat liver showed: (1) a larger increase in fat accumulation within ADRP-positive LDs; (2) stimulation of lipid oxidation in the attempt to limit excess fat accumulation; (3) induction of antioxidant proteins (MT2, in particular) to protect the liver from the ethanol-induced overproduction of oxygen radicals. The data indicate an increased susceptibility of fatty liver to ethanol and suggest that the synergistic effect of diet and ethanol on lipid dysmetabolism might be mediated, at least in part, by PPARs and cytochromes CYP4A1 and CYP2E1.

Chronic ethanol consumption decreases serum sulfatide levels by suppressing hepatic cerebroside sulfotransferase expression in mice

Epidemiological studies demonstrate a possible relationship between chronic ethanol drinking and thrombotic diseases, such as myocardial infarction and stroke. However, the precise mechanism for this association remains unclear. Sulfatides are endogenous glycosphingolipids composed of ceramide, galactose, and sulfate, known to have anti-thrombotic properties. Low (0.5 g/kg/day), middle (1.5 g/kg/day), and high (3.0 g/kg/day) doses of ethanol were administered for 21 days intraperitoneally to female wild-type mice, and serum/liver sulfatide levels were measured. No significant changes in cholesterol and triglycerides were seen in serum and liver by ethanol treatment. However, serum/liver sulfatide levels were significantly decreased by middle- and high-dose ethanol treatment, likely due to downregulation of hepatic cerebroside sulfotransferase (CST) levels. Marked decreases in the expression of catalase and superoxide dismutases and ensuing increases in lipid peroxides were also observed in the livers of mice with middle- and high-dose ethanol treatment, suggesting the association between the suppression of hepatic CST expression and enhancement of oxidative stress. Furthermore, serum levels of tissue factor, a typical pro-coagulant molecule, were significantly increased in the mice with middle- and high-dose ethanol treatment showing decreases in serum sulfatide levels. Collectively, these results demonstrate that chronic ethanol consumption reduces serum sulfatide levels by increasing oxidative stress and decreasing the expression of CST in the liver. These findings could provide a mechanism by which chronic ethanol drinking increases thrombotic events.

Robust protein nitration contributes to acetaminophen-induced mitochondrial dysfunction and acute liver injury

Acetaminophen (APAP), a widely used analgesic/antipyretic agent, can cause liver injury through increased nitrative stress, leading to protein nitration. However, the identities of nitrated proteins and their roles in hepatotoxicity are poorly understood. Thus, we aimed at studying the mechanism of APAP-induced hepatotoxicity by systematic identification and characterization of nitrated proteins in the absence or presence of an antioxidant, N-acetylcysteine (NAC). The levels of nitrated proteins markedly increased at 2h in mice exposed to a single APAP dose (350mg/kg ip), which caused severe liver necrosis at 24h. Protein nitration and liver necrosis were minimal in mice exposed to nontoxic 3-hydroxyacetanilide or animals co-treated with APAP and NAC. Mass-spectral analysis of the affinity-purified nitrated proteins identified numerous mitochondrial and cytosolic proteins, including mitochondrial aldehyde dehydrogenase, Mn-superoxide dismutase, glutathione peroxidase, ATP synthase, and 3-ketoacyl-CoA thiolase, involved in antioxidant defense, energy supply, or fatty acid metabolism. Immunoprecipitation followed by immunoblot with anti-3-nitrotyrosine antibody confirmed that the aforementioned proteins were nitrated in APAP-exposed mice but not in NAC-cotreated mice. Consistently, NAC cotreatment significantly restored the suppressed activity of these enzymes. Thus, we demonstrate a new mechanism by which many nitrated proteins with concomitantly suppressed activity promotes APAP-induced mitochondrial dysfunction and hepatotoxicity.

Early growth response-1 contributes to steatosis development after acute ethanol administration

BACKGROUND

Previous work demonstrated that the transcription factor, early growth response-1 (Egr-1), participates in the development of steatosis (fatty liver) after chronic ethanol (EtOH) administration. Here, we determined the extent to which Egr-1 is involved in fatty liver development in mice subjected to acute EtOH administration.

METHODS

In acute studies, we treated both wild-type and Egr-1 null mice with either EtOH or phosphate-buffered saline (PBS) by gastric intubation. At various times after treatment, we harvested sera and livers and quantified endotoxin, indices of liver injury, steatosis, and hepatic Egr-1 content. In chronic studies, groups of mice were fed liquid diets containing either EtOH or isocaloric maltose-dextrin for 7 to 8 weeks.

RESULTS

Compared with controls, acute EtOH-treated mice showed a rapid, transient elevation in serum endotoxin beginning 30 minutes after treatment. One hour postgavage, livers from EtOH-treated mice exhibited a robust elevation of both Egr-1 mRNA and protein. By 3 hours postgavage, liver triglyceride increased in EtOH-treated mice as did lipid peroxidation. Acute EtOH treatment of Egr-1-null mice showed no Egr-1 expression, but these animals still developed elevated triglycerides, although significantly lower than EtOH-fed wild-type littermates. Despite showing decreased fatty liver, EtOH-treated Egr-1 null mice exhibited greater liver injury. After chronic EtOH feeding, steatosis and liver enlargement were clearly evident, but there was no indication of elevated endotoxin. Egr-1 levels in EtOH-fed mice were equal to those of pair-fed controls.

CONCLUSIONS

Acute EtOH administration induced the synthesis of Egr-1 in mouse liver. However, despite its robust increase, the transcription factor had a smaller, albeit significant, function in steatosis development after acute EtOH treatment. We propose that the rise in Egr-1 after acute EtOH is an hepatoprotective adaptation to acute liver injury from binge drinking that is triggered by EtOH metabolism and elevated levels of endotoxin.

Structural Correlates of PPAR Agonist Rescue of Experimental Chronic Alcohol-Induced Steatohepatitis

Chronic alcoholic liver disease is associated with hepatic insulin resistance, inflammation, oxidative and ER stress, mitochondrial dysfunction, and DNA damage. Peroxisome-proliferator activated receptor (PPAR) agonists are insulin sensitizers that have anti-inflammatory/anti-oxidant effects. We previously showed that PPAR agonists can restore hepatic insulin responsiveness in chronic ethanol-fed rats with steatohepatitis. Herein, we furthered our investigations by characterizing the histological and ultrastructural changes mediated by PPAR agonist rescue of alcohol-induced steatohepatitis. Adult male Long Evans rats were pair fed with isocaloric liquid diets containing 0% or 37% ethanol (caloric) for 8 weeks. After 3 weeks on the diets, rats were treated with vehicle, or a PPAR-α, PPAR-δ, or PPAR-γ agonist twice weekly by i.p. injection. Ethanol-fed rats developed steatohepatitis with disordered hepatic chord architecture, mega-mitochondria, disruption of the RER, increased apoptosis, and increased 4-hydroxynonenal (HNE) and 3-nitrotyrosine (NTyr) immunoreactivity. PPAR-δ and PPAR-γ agonists reduced the severity of steatohepatitis, and restored the hepatic chord-like architectural, mitochondrial morphology, and RER organization, and the PPAR-δ agonist significantly reduced hepatic HNE. On the other hand, prominent RER tubule dilation, which could reflect ER stress, persisted in ethanol-exposed, PPAR-γ treated but not PPAR-δ treated livers. The PPAR-α agonist exacerbated both steatohepatitis and formation of mega-mitochondria, and it failed to restore RER architecture or lower biochemical indices of oxidative stress. In conclusion, improved hepatic insulin responsiveness and decreased inflammation resulting from PPAR-δ or PPAR-γ agonist treatments of alcohol-induced steatohepatitis are likely mediated by enhanced signaling through metabolic pathways with attendant reductions in ER stress, oxidative stress, and mitochondrial dysfunction.

Increased expression of cytochrome P450 2E1 in nonalcoholic fatty liver disease: mechanisms and pathophysiological role

Due to the worldwide surge in obesity and type 2 diabetes, the increased incidence of nonalcoholic fatty liver disease (NAFLD) is a major concern for the public health. Indeed, NAFLD encompasses a large spectrum of conditions ranging from fatty liver to nonalcoholic steatohepatitis (NASH), which can progress to cirrhosis in some patients. A better understanding of the mechanisms involved in fatty liver and its progression into NASH is important in order to develop efficient drugs able to alleviate these liver diseases. Although numerous investigations pointed to reactive oxygen species (ROS) as key players in the progression of fatty liver to NASH, their exact source is still uncertain. Besides the mitochondrial respiratory chain, cytochrome P450 2E1 (CYP2E1) has recently emerged as another potentially important cause of ROS overproduction. Indeed, higher hepatic CYP2E1 expression and activity have been frequently observed in the context of obesity and NAFLD. It is currently unknown why CYP2E1 is enhanced in these dysmetabolic diseases, although increased hepatic levels of fatty acids and insulin resistance might play a role. Nonetheless, higher hepatic CYP2E1 could play a significant role in the pathophysiology of NASH by inducing lipid peroxidation and oxidative damage of key cellular components. Moreover, CYP2E1-mediated overproduction of ROS could promote hepatic insulin resistance, which can further aggravate fatty liver. Since a significant amount of CYP2E1 can be located within liver mitochondria, higher levels of CYP2E1 in NAFLD could also have detrimental effects on mitochondrial function. Finally, increased CYP2E1 activity during NAFLD could enhance the susceptibility of some patients to the hepatotoxicity of different xenobiotics through the CYP2E1-mediated generation of harmful reactive metabolites.

The amount of alcohol consumption negatively impacts short-term mortality in Mexican patients with alcoholic hepatitis

OBJECTIVES

Mexicans have an increased rate of alcohol abuse and alcoholic liver disease. Factors influencing the severity of alcoholic hepatitis (AH) in Mexicans are unknown. The aims of the present study were to identify the prognostic factors of short-term mortality in Mexican patients with AH and to validate the existing prognostic models.

METHODS

One hundred seventy-five consecutive patients with AH were recruited from four hospital centers in Mexico. Demographic, clinical, and biochemical parameters were obtained at admission. Univariate and multivariate logistic regression analyses were used for the identification of prognostic factors. The accuracy of different models was evaluated by their area under the receiver operating characteristic (AUROC) curve and comparative risk analysis was performed using the Kaplan-Meier method.

RESULTS

Age, serum creatinine, serum bilirubin, leukocyte count, and alcohol consumption >120 g/day were independently associated with short-term mortality. The impact of alcohol consumption was significant among patients with severe AH (48 vs. 72% risk of death, P=0.03). The AUROC (95% confidence interval) curves for the different scores were Maddrey's discriminant function 0.79 (0.72-0.86); model for end-stage liver disease (MELD) 0.83 (0.75-0.89); Glasgow AH score 0.77 (0.70-0.84); and age-bilirubin-international normalized ratio-creatinine (ABIC) score 0.82 (0.75-0.88). The ABIC score allowed an accurate stratification into three different risk subgroups with 13%, 50%, and 81% mortality rate at 90 days (P<0.001).

CONCLUSIONS

The amount of alcohol consumption has a negative impact on short-term mortality among Mexicans with AH. The ABIC score is useful and comparable with MELD score for the prognostic stratification of these patients.

Post-translational modifications of mitochondrial aldehyde dehydrogenase and biomedical implications

Aldehyde dehydrogenases (ALDHs) represent large family members of NAD(P)+-dependent dehydrogenases responsible for the irreversible metabolism of many endogenous and exogenous aldehydes to the corresponding acids. Among 19 ALDH isozymes, mitochondrial ALDH2 is a low Km enzyme responsible for the metabolism of acetaldehyde and lipid peroxides such as malondialdehyde and 4-hydroxynonenal, both of which are highly reactive and toxic. Consequently, inhibition of ALDH2 would lead to elevated levels of acetaldehyde and other reactive lipid peroxides following ethanol intake and/or exposure to toxic chemicals. In addition, many East Asian people with a dominant negative mutation in ALDH2 gene possess a decreased ALDH2 activity with increased risks for various types of cancer, myocardial infarct, alcoholic liver disease, and other pathological conditions. The aim of this review is to briefly describe the multiple post-translational modifications of mitochondrial ALDH2, as an example, after exposure to toxic chemicals or under different disease states and their pathophysiological roles in promoting alcohol/drug-mediated tissue damage. We also briefly mention exciting preclinical translational research opportunities to identify small molecule activators of ALDH2 and its isozymes as potentially therapeutic/preventive agents against various disease states where the expression or activity of ALDH enzymes is altered or inactivated.

Drug-induced toxicity on mitochondria and lipid metabolism: mechanistic diversity and deleterious consequences for the liver

Numerous investigations have shown that mitochondrial dysfunction is a major mechanism of drug-induced liver injury, which involves the parent drug or a reactive metabolite generated through cytochromes P450. Depending of their nature and their severity, the mitochondrial alterations are able to induce mild to fulminant hepatic cytolysis and steatosis (lipid accumulation), which can have different clinical and pathological features. Microvesicular steatosis, a potentially severe liver lesion usually associated with liver failure and profound hypoglycemia, is due to a major inhibition of mitochondrial fatty acid oxidation (FAO). Macrovacuolar steatosis, a relatively benign liver lesion in the short term, can be induced not only by a moderate reduction of mitochondrial FAO but also by an increased hepatic de novo lipid synthesis and a decreased secretion of VLDL-associated triglycerides. Moreover, recent investigations suggest that some drugs could favor lipid deposition in the liver through primary alterations of white adipose tissue (WAT) homeostasis. If the treatment is not interrupted, steatosis can evolve toward steatohepatitis, which is characterized not only by lipid accumulation but also by necroinflammation and fibrosis. Although the mechanisms involved in this aggravation are not fully characterized, it appears that overproduction of reactive oxygen species by the damaged mitochondria could play a salient role. Numerous factors could favor drug-induced mitochondrial and metabolic toxicity, such as the structure of the parent molecule, genetic predispositions (in particular those involving mitochondrial enzymes), alcohol intoxication, hepatitis virus C infection, and obesity. In obese and diabetic patients, some drugs may induce acute liver injury more frequently while others may worsen the pre-existent steatosis (or steatohepatitis).

Autophagy reduces acute ethanol-induced hepatotoxicity and steatosis in mice

BACKGROUND & AIMS

Alcohol abuse is a major cause of liver injury. The pathologic features of alcoholic liver disease develop over prolonged periods, yet the cellular defense mechanisms against the detrimental effects of alcohol are not well understood. We investigated whether macroautophagy, an evolutionarily conserved cellular mechanism that is commonly activated in response to stress, could protect liver cells from ethanol toxicity.

METHODS

Mice were acutely given ethanol by gavage. The effects of ethanol on primary hepatocytes and hepatic cell lines were also studied in vitro.

RESULTS

Ethanol-induced macroautophagy in the livers of mice and cultured cells required ethanol metabolism, generation of reactive oxygen species, and inhibition of mammalian target of rapamycin signaling. Suppression of macroautophagy with pharmacologic agents or small interfering RNAs significantly increased hepatocyte apoptosis and liver injury; macroautophagy therefore protected cells from the toxic effects of ethanol. Macroautophagy induced by ethanol seemed to be selective for damaged mitochondria and accumulated lipid droplets, but not long-lived proteins, which could account for its protective effects. Increasing macroautophagy pharmacologically reduced hepatotoxicity and steatosis associated with acute ethanol exposure.

CONCLUSIONS

Macroautophagy protects against ethanol-induced toxicity in livers of mice. Reagents that modify macroautophagy might be developed as therapeutics for patients with alcoholic liver disease.

Laboratory models available to study alcohol-induced organ damage and immune variations: choosing the appropriate model

The morbidity and mortality resulting from alcohol-related diseases globally impose a substantive cost to society. To minimize the financial burden on society and improve the quality of life for individuals suffering from the ill effects of alcohol abuse, substantial research in the alcohol field is focused on understanding the mechanisms by which alcohol-related diseases develop and progress. Since ethical concerns and inherent difficulties limit the amount of alcohol abuse research that can be performed in humans, most studies are performed in laboratory animals. This article summarizes the various laboratory models of alcohol abuse that are currently available and are used to study the mechanisms by which alcohol abuse induces organ damage and immune defects. The strengths and weaknesses of each of the models are discussed. Integrated into the review are the presentations that were made in the symposium "Methods of Ethanol Application in Alcohol Model-How Long is Long Enough" at the joint 2008 Research Society on Alcoholism (RSA) and International Society for Biomedical Research on Alcoholism (ISBRA) meeting, Washington, DC, emphasizing the importance not only of selecting the most appropriate laboratory alcohol model to address the specific goals of a project but also of ensuring that the findings can be extrapolated to alcohol-induced diseases in humans.

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. Among ethanol-fed rats, despite similar blood alcohol levels, LE rats had more pronounced steatohepatitis and fibrosis, higher levels of ALT, DNA damage, pro-inflammatory cytokines, ADH, ALDH, catalase, GFAP, desmin, and collagen expression, and reduced insulin receptor binding relative to FS rats. Ethanol-exposed SD rats had intermediate degrees of steatohepatitis, increased ALT, ADH and profibrogenesis gene expression, and suppressed insulin receptor binding and GAPDH expression, while pro-inflammatory cytokines were similarly increased as in LE rats. Ethanol feeding in FS rats only reduced IL-6, ALDH1-3, CYP2E1, and GAPDH expression in liver. In conclusion, susceptibility to chronic steatohepatitis may be driven by factors related to efficiency of ethanol metabolism and degree to which ethanol exposure causes hepatic insulin resistance and cytokine activation.

Evaluation of reference intervals for biomarkers sensitive to alcohol consumption, excess body weight and oxidative stress

BACKGROUND

Unexplained liver enzyme activities are often found in health screening programs and constitute an increasingly common cause for referral to specialized clinics. Recent studies have indicated that both excess body weight and alcohol consumption may lead to metabolic aberrations which are readily reflected in the activities of liver enzymes in circulation.

MATERIALS AND METHODS

We compared various laboratory markers and their upper normal limits in relation to information on alcohol consumption and BMI in a large population of apparently healthy individuals collected from Nordic countries.

RESULTS

Based on the data obtained from normal weight abstainers (BMI 19-25 kg/m(2)) the upper normal limits in men should be 50 U/L for ALT, and 45 U/L (<40 years) and 70 U/L (>or=40 years) for GGT, while the current recommendations are 70 U/L, 80 U/L, and 115 U/L, respectively. Already in comparisons between normal weight abstainers and corresponding moderate drinkers notable impacts (+14% - +74%) on upper limits for these analytes were seen, which further grew when adiposity occurred together with alcohol drinking (+75% - +186%, BMI >or=27 kg/m(2)). In addition to liver enzymes, similar changes were also found for uric acid.

CONCLUSIONS

Alcohol consumption and excess body weight even in apparently healthy individuals have a significant influence on liver enzyme activities, which may be due to a cumulative oxidative stress burden. The metabolic changes induced by adiposity or ethanol intake should be considered in the definition of normal ranges for all laboratory parameters sensitive to oxidative stress.