Alcohol and the liver: 1994 update

Is the increase in serum cystathionine levels in patients with liver cirrhosis a consequence of impaired homocysteine transsulfuration at the level of gamma-cystathionase?

BACKGROUND

It has been suggested that the major metabolic block in the methionine catabolic pathway in cirrhotics exists at the level of the enzyme S-adenosylmethionine synthetase because in previous studies using conventional amino-acid analyzers, no intermediates of transmethylation/transsulfuration were found to accumulate in plasma downstream of S-adenosylmethionine synthesis. We therefore measured serum concentration intermediates of methionine transmethylation/transsulfuration using an improved gas chromatography/mass spectrometry technique.

METHODS

Serum concentrations of methionine, homocysteine, cystathionine, N,N-dimethylglycine, N-methylglycine, methylmalonic acid, 2-methylcitric acid and alpha-aminobutyric acid were determined by gas chromatography/mass spectrometry in 108 consecutive patients with liver cirrhosis at Child stages A (mild cirrhosis, n = 27) and B/C (severe cirrhosis, n = 81), 18 outpatients with non-cirrhotic liver disease, and 55 healthy individuals.

RESULTS

Serum levels of methionine, N,N-dimethylglycine, N-methylglycine, cystathionine, and homocysteine were significantly higher in patients at Child stages B/C compared with those of healthy controls (P < 0.01), and they were also significantly higher than in patients with non-cirrhotic liver disease (P < 0.01 and P < 0.05 for homocysteine, respectively). They also correlated with the Child-Pugh score (P < 0.01). Homocysteine, cystathionine, N,N-dimethylglycine, N-methylglycine, methylmalonic acid, and 2-methylcitric acid correlated with serum creatinine. The mean cystathionine concentration was significantly higher in patients with creatinine > or = 1.4 mg/dl than in patients with normal creatinine values (P < 0.01). However, the differences between cirrhotics and healthy controls were still significant after correcting for creatinine.

CONCLUSIONS

Our data provides indirect evidence for two hitherto unrecognized alterations of methionine metabolism in cirrhotics, i.e. impairment of the transsulfuration of homocysteine at the level of cystathionine degradation and a shift in remethylation of homocysteine towards the betaine-homocysteine-methyltransferase reaction.

Risk factors for alcoholic liver disease

Abstract Alcoholic liver disease (ALD) is still a frequent disorder, even though its incidence appears to be decreasing. In spite of intense investigation, the precise mechanisms leading to ALD are still imprecisely known. This is due in part to the lack of a reliable animal model; in part to the difficulty of obtaining clinical data of adequate sample size and derived from unblased populations and finally from the lack of uniformity of the criteria used to define ALD. This paper will review what is known of the various pieces of this puzzle, with particular emphasis not only on the total amount of alcohol consumed, but also on drinking patterns and type of alcoholic beverage ingested. The other potential factors such as age, gender, genetic background, nutritional status, occupational hazards and viral diseases (especially HCV infection) will be touched upon.

Enhanced DNA binding and activation of transcription factors NF-kappa B and AP-1 by acetaldehyde in HEPG2 cells

Because transcription factors NF-kappaB and activator protein-1 (AP-1) are known to regulate gene expression, we have analyzed the role of acetaldehyde in the activation of NF-kappaB and AP-1 in HepG2 cells. Binding activity and transactivation of NF-kappaB and AP-1 were determined by gel retardation assays and transfection of a luciferase reporter construct controlled by kappaB and AP-1 binding sites, respectively. Acetaldehyde enhanced the DNA binding of NF-kappaB and AP-1 by 1 and 4 h, respectively, increasing the kappaB- and AP-1-dependent luciferase expression. Supershift assays revealed the presence of NF-kappaB heterodimers p65/p50 and p50/p52, whereas nuclear c-Jun levels correlated with the DNA binding of AP-1. The enhanced binding of NF-kappaB to DNA by acetaldehyde in intact cells was accompanied by the proteolytic degradation of IkappaB-alpha. However, the addition of acetaldehyde to cytostolic extracts from untreated Hep G2 cells did not affect the DNA binding of AP-1 but activated the NF-kappaB heterodimer p65/p50 in the absence of IkappaB-alpha degradation. Preincubation of HepG2 cells with protein kinase C inhibitors abolished the enhanced DNA binding of NF-kappaB and AP-1 caused by acetaldehyde. Hence, these findings uncover a previously unrecognized role for acetaldehyde in the activation of NF-kappaB and AP-1, which may be of relevance in the alcohol-induced liver disease.

[The impact of alcohol and chronic liver disease of micronutrients metabolism]

Liver disease, alcohol and malnutrition are combinations usually associated with micronutrient impairment. Chronic liver disease courses with lower storage and activation of vitamin-coenzymes related to their malabsorption. Alcohol worsens the picture by reducing food intake, increasing micronutrients utilization and decreasing their absorption secondary to either intestinal or pancreatic injuries. Other concurrent causes would be drug treatments, urinary losses, protein deficiency and oxidative stress. As consequences the clinical signs are anemia, liver steatosis, oxidative stress and immunosuppression.

Superoxide dismutase activity in children with chronic liver diseases

BACKGROUND/AIMS

Liver disease in infancy has multiple etiologies. As reactive oxygen intermediates are involved in several types of tissue damage, we have investigated whether different forms of liver disease in infancy are associated with increased free radical generation, using an indirect approach in which superoxide dismutase (a free radical scavenger) activity is determined in the liver tissue.

METHODS

A total of 48 liver biopsies performed at diagnosis were evaluated retrospectively. Nine infants had biliary atresia, eight Alagille syndrome, seven alantitrypsin deficiency and 12 cryptogenic hepatitis. As controls we studied 12 biopsies with normal histology obtained from seven children with portal vein thrombosis and five children who underwent biopsy for management reason but had no liver disease. Superoxide dismutase activity in liver biopsy specimens was measured using the cytochrome C method by spectrophotometry and expressed as U SOD/mg protein.

RESULTS

Superoxide dismutase activity was significantly increased in biliary atresia (1.25 +/- 0.56 U SOD/mg protein, p<0.0001) and Alagille syndrome (1.31 +/- 0.56 U SOD/mg protein, p<0.0001) as compared with al-antitrypsin deficiency (0.75 +/- 0.3 U SOD/mg protein), neonatal hepatitis (0.72 +/- 0.37 U. SOD/mg protein) and normal controls (0.4 +/- 0.7 U. SOD/mg protein). The highest level of SOD activity was found, however, in control children with portal vein thrombosis (2.09 +/- 0.96 U SOD/mg protein; p<0.0001 as compared to the other groups).

CONCLUSION

Superoxide dismutase, a key enzyme in free radical protection, is increased significantly in the liver tissue of infants with cholestatic liver disease due to bile duct damage and in children with portal vein thrombosis, suggesting that products of free radical reactions are involved in the pathogenesis of these disorders.

The effect of hypermetabolism induced by burn trauma on the ethanol-oxidizing capacity of the liver

OBJECTIVE

To study the rate of elimination of ethanol after a major burn trauma.

DESIGN

Prospective, controlled study.

SETTING

National burns unit in a Swedish university hospital.

PATIENTS AND SUBJECTS

Eight consecutive patients suffering from 18%-72% total burned surface area and nine healthy male control subjects.

INTERVENTIONS

The patients received ethanol, 0.35-0.60 g/kg body weight intravenously, during 1 hr. This was repeated daily during the first week postburn. The control subjects received the same amount of ethanol once.

MEASUREMENTS AND MAIN RESULTS

Blood samples were drawn at 20- to 30-min intervals during 5 hrs after the start of the infusion. Serum ethanol was determined by headspace gas chromatography. The rate of elimination of ethanol was calculated from the concentration time profile. In the control subjects, the median elimination rate was 0.074 g/kg/hr (range, 0.059-0.083 g/kg/hr). In the patients, it was already 0.138 g/kg/hr (range, 0.111-0.201 g/kg/hr) on the first day; this increased even further over the following 6 days, reaching 0.183 g/kg/hr (range, 0.150-0.218 g/kg/hr) on the seventh day.

CONCLUSIONS

Ethanol elimination is augmented postburn. A more effective reoxidation of reduced nicotinamide adenine dinucleotide seems the most likely explanation for the increased rate of ethanol elimination in these hypermetabolic trauma patients. This finding suggests that the oxidative capacity of the liver may be assessed by studying the rate of ethanol elimination in burn victims.

Differential role of ethanol and acetaldehyde in the induction of oxidative stress in HEP G2 cells: effect on transcription factors AP-1 and NF-kappaB

The oxidative metabolism of ethanol by the cytochrome P450 2E1 (CYP2E1) has been recognized to contribute to the ethanol-induced deleterious effects through the induction of oxidative stress. This study compared the effect of ethanol and acetaldehyde in the induction of oxidative stress and activation of transcription factors nuclear factor-kappaB (NF-kappaB) and activating protein 1 (AP-1) in HepG2 cells, which do not express CYP2E1, and HepG2 cells transfected with CYP2E1 (E47 cells). Neither ethanol (80 mmol/L) nor acetaldehyde (25-200 micromol/L) caused oxidative stress in HepG2 cells, an effect that was independent of blocking reduced glutathione (GSH) synthesis with buthionine-L-sulfoximine (BSO). However, BSO preincubation caused an overproduction of peroxides and activation of NF-kappaB and AP-1 in E47 cells even in the absence of ethanol. Furthermore, the incubation of E47 cells with ethanol (80 mmol/L for up to 5 days) depleted cellular GSH stores in both cytosol and mitochondria, reflecting the induction of oxidative stress. Ethanol activated NF-kappaB and AP-1 in E47 cells, an effect that was prevented by 4-methylpyrazole, potentiated by cyanamide, and attenuated by trolox C. Interestingly, however, despite the inability of acetaldehyde to induce oxidative stress in HepG2, acetaldehyde activated NF-kappaB and AP-1; in contrast, ethanol failed to activate these transcription factors in HepG2. Thus, our findings indicate that activation of NF-kappaB and AP-1 by ethanol and acetaldehyde occurs through distinct mechanisms. CYP2E1 is indispensable in the induction of oxidative stress from ethanol, whereas the activation of NF-kappaB and AP-1 by acetaldehyde is independent of oxidative stress.

Inflammation-induced cholestasis

Inflammatory cytokines produced in response to various infectious and non-infectious stimuli are potent inducers of intrahepatic cholestasis (inflammation-induced cholestasis). The cholestatic effect of cytokines results mainly from inhibition of expression and function of hepatocellular transport systems which normally mediate hepatic uptake and biliary excretion of bile salts and various non-bile salt organic anions (e.g. bilirubin). These cytokine effects are reversible and bile secretory function is restored upon disappearance of the inflammatory injury. This review summarizes the clinical, pathophysiological and molecular aspects of inflammation-induced cholestasis.

Activation of nuclear factor kappa B and cytokine imbalance in experimental alcoholic liver disease in the rat

Inflammatory stimuli and lipid peroxidation activate nuclear factor kappa B (NF-kappaB) and upregulate proinflammatory cytokines and chemokines. The present study evaluated the relationship between pathological liver injury, endotoxemia, lipid peroxidation, and NF-kappaB activation and imbalance between pro- and anti-inflammatory cytokines. Rats (5 per group) were fed ethanol and a diet containing saturated fat, palm oil, corn oil, or fish oil by intragastric infusion. Dextrose isocalorically replaced ethanol in control rats. Pathological analysis was performed and measurements of endotoxin were taken, lipid peroxidation, NF-kappaB, and messenger RNA (mRNA) levels of proinflammatory cytokines (tumor necrosis factor-alpha [TNFalpha], interleukin-1 beta [IL-1beta], interferon-gamma, [IFN-gamma], and IL-12), C-C chemokines (regulated upon activation, normal T cell expressed and secreted [RANTES], monocyte chemotactic protein [MCP]-1, macrophage inflammatory protein [MIP]-1alpha), C-X-C chemokines (cytokine induced neutrophil chemoattractant (CINC), MIP-2, IP-10, and epithelial neutrophil activating protein [ENA]-78), and anti-inflammatory cytokines (IL-10, IL-4, and IL-13). Activation of NF-kappaB and increased expression of proinflammatory cytokines C-C and C-X-C chemokines was seen in the rats exhibiting necroinflammatory injury (fish oil-ethanol [FE] and corn oil-ethanol[CE]). These groups also had the highest levels of endotoxin and lipid peroxidation. Levels of IL-10 and IL-4 mRNA were lower in the group exhibiting inflammatory liver injury. Thus, activation of NF-kappaB occurs in the presence of proinflammatory stimuli and results in increased expression of proinflammatory cytokines and chemokines. The Kupffer cell is probably the major cell type showing activation of NF-kappaB although the contribution of endothelial cells and hepatocytes cannot be excluded. Downregulation of anti-inflammatory cytokines may additionally exacerbate liver injury.

Ethanol oxidation and acetaldehyde production in vitro by human intestinal strains of Escherichia coli under aerobic, microaerobic, and anaerobic conditions

BACKGROUND

Many human colonic facultative anaerobic and aerobic bacteria are capable of alcohol dehydrogenase (ADH)-mediated ethanol oxidation. In this bacteriocolonic pathway for ethanol oxidation intracolonic ethanol is first oxidized by bacterial ADHs to acetaldehyde, which is further oxidized by either colonic mucosal or bacterial aldehyde dehydrogenases to acetate. The produced acetaldehyde is a highly toxic and carcinogenic agent. This study was aimed to investigate the ethanol oxidation capability and acetaldehyde formation of Escherichia coli IH 50546 and IH 50817. These intestinal E. coli strains expressed either high (IH 50546) or low (IH 50817) ADH activity.

METHODS

Strains were cultured for 48 h on agar plates supplemented with ethanol under aerobic, microaerobic (6% O2), and anaerobic conditions.

RESULTS

Under aerobic conditions both E. coli strains oxidized ethanol. The ethanol consumption rates (ECR) were 1.046+/-0.025 mM/h and 0.367+/-0.148 mM/h with IH 50546 and IH 50817, respectively. In the case of IH 50546 this was associated with significant acetaldehyde production (418+/-13 microM), suggesting ADH-mediated ethanol oxidation. Under microaerobic conditions only IH 50546 was able to oxidize ethanol (ECR, 0.498+/-0.074 mM/h) and to produce acetaldehyde (up to 440+/-76 microM) to significant extents. Under anaerobic conditions both strains fermented glucose to ethanol.

CONCLUSIONS

This study experimentally shows the potential of certain bacteria representing normal human colonic flora to produce acetaldehyde under various atmospheric conditions that may prevail in different parts of the GI tract. This bacterial adaptation may be an essential feature of the bacteriocolonic pathway to produce toxic and carcinogenic acetaldehyde from either endogenous or exogenous ethanol.

CYP2E1 and CYP3A1/2 gene expression is not associated with the ursodeoxycholate effect on ethanol-induced lipoperoxidation

Ethanol is a well-known hepatotoxicant inducing steatosis and membrane lipoperoxidation. The aim of the present study was to investigate in rats, whether the protective effect of UDC on ethanol-induced lipid peroxidation may be related with CYP2E1 and CYP3A1/2 gene expression. We showed that UDC treatment in ethanol-fed rats induced a significant decrease in liver triglyceride concentration which was closely correlated with a reduction in malondialdehyde and hydroxyalkenal levels. In chronically ethanol-fed rats, CYP2E1 and CYP3A1/2 gene expressions were increased by a post-transcriptional mechanism. These inductions, mainly of CYP2E1, could take part in alcohol-induced hepatic lipoperoxidation. UDC modified neither the specific activity, nor the protein level, nor the mRNA level of CYP2E1 when compared with control. UDC supplementation to alcohol diet did not prevent the increase in CYP2E1 expression of ethanol-fed rats. Furthermore, CYP3A1/2 protein levels were similarly increased by ethanol and ethanol plus UDC treatment. Therefore, UDC protective effect against ethanol-induced lipoperoxidation was not associated with a modification of CYP2E1 and CYP3A1/2 expression.

The influence of anesthetic concentrations of enflurane and ethanol on caffeine metabolism in mice

Enflurane is a fluorinated volatile anesthetic, mostly eliminated unchanged in exhaled air. About 10% of inhaled enflurane undergoes oxidative metabolism in liver via mixed function oxidase. We examined the influence of ethanol and subchronical exposition (6 hours a day, during five consecutive days) to subanesthetic and anesthetic concentrations of enflurane on liver function in BALB/c mice. Specially designed chamber for inhalatory application of anesthetics was constructed for this study. Animals were divided in six groups of twenty. The ethanol treated group was injected with ethanol intraperitoneally (1 g/kg). Two enflurane treated groups were intraperitoneally injected with 0.9% solution of sodium chloride (10 ml/kg) and one of them exposed to subanesthetic (0.5 Vol%) and the other one to anesthetic (2.75 Vol%) concentrations of enflurane. Following two groups received ethanol (1 g/kg) and each of them inhaled enflurane at previously mentioned doses. The control group was intraperitoneally injected with 0.9 % solution of sodium chloride (10 ml/kg) and did not receive any anesthetic. On the day following the last day of exposure half of the animals from each group were sacrificed for determination of glucose levels, erythrocyte glutathion levels, haematocrit, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), liver protein and glutathion levels, and total cytochrome P-450 (CYP P-450). The other half of animals from each group were injected intraperitoneally with caffeine (20 mg/kg). Caffeine and its metabolites in 8 hour urine were analyzed by high performance liquid chromatography (HPLC) method. Excretion of caffeine and its metabolites was different among the groups. We followed two caffeine metabolic ratios - 1,3-dimethyl uric acid and 3,7-xanthine (1,3-U/3,7-X) and 3,7-dimethyl xanthine + 7-xanthine and 1-xanthine + 1,7-dimethyl uric acid (3,7-X + 7-X/1-X + 1,7-U). The difference in caffeine metabolites ratios suggests that enflurane changes oxidative metabolism in liver via certain subtypes of mixed function oxidase, probably via CYP-4502E1. This effect is more expressed when ethanol and enflurane are applied together. Ethanol is well known inductor of CYP-4502E1 and the registrated enzyme induction could be explained by both influences - of ethanol and enflurane.

Measurement of matrix metalloproteinases and tissue inhibitors of metalloproteinases in blood and tissues. Clinical and experimental applications

The balance between production and activation of MMPs and their inhibition by TIMPs is a crucial aspect of cancer invasion and metastasis. On the basis of the concept that MMPs synthesized in tissues seep into the bloodstream, we have examined MMP levels in the plasma of patients with cancer. In colorectal, breast, prostate, and bladder cancer, most patients with aggressive disease have increased plasma levels of gelatinase B. In patients with advanced colorectal cancer, high levels of either gelatinase B or TIMP complex were associated with shortened survival. We propose that these assays may be clinically useful in characterizing metastatic potential in selected kinds of cancer. In rheumatoid arthritis and systemic lupus erythematosus (SLE), serum and plasma levels of stromelysin-1 were approximately 3-5-fold increased. Fluctuating serum stromelysin-1 levels in SLE did not correspond with change in disease activity. In SLE, stromelysin-1 may be a component of the chronic tissue repair process rather than being responsible for inciting tissue damage. On the basis of these observations, we conclude that measurement of plasma/serum MMP and TIMP levels may provide important data for selecting and following patients considered for treatment with drugs that interfere with MMP activity.

Expression of CYP2E1 by human monocyte-derived macrophages

The expression of the ethanol-metabolizing cytochrome P450 (CYP2E1) in human monocyte-derived macrophages was studied at the mRNA and protein levels. The presence of mRNA was investigated by reverse transcriptase-polymerase chain reaction (RT-PCR) and protein by immunocytochemistry. The data show that CYP2E1 is expressed in human monocyte-derived macrophages at a level similar to that demonstrated in other extrahepatic tissues. Although there is circumstantial evidence for the presence of CYP2E1 in human macrophages, it has not previously been demonstrated directly. Its presence in macrophages underlines the potential importance of these cells in initiating alcohol-induced cytotoxicity.

Effect of chronic ethanol ingestion on biochemical circadian rhythms in Wistar rats

Chronic ingestion of ethanol for 60 days was known to alter the characteristics of biochemical circadian rhythms in Wistar rats. Peak times of glucose, potassium and lactic acid rhythms were delayed by 18 h, 3 h, and 3 h respectively, whereas peak times of cholesterol and malondialdehyde rhythms were advanced by 3 h and 9 h respectively during ethanol treatment. Significant changes in range (p < 0.001 expect in calcium) and 24 h mean (p < 0.001) of all the biochemical circadian rhythms studied were observed during ethanol treatment. The alterations in the characteristics of these biochemical circadian rhythms could be principally due to the alterations on the hepatic cellular architecture; other plausible underlying reasons are also discussed.

Ischemia-reperfusion injury in rat fatty liver: role of nutritional status

Fatty livers are more sensitive to the deleterious effects of ischemia-reperfusion than normal livers. Nutritional status greatly modulates this injury in normal livers, but its role in the specific setting of fatty liver is unknown. This study aimed to determine the effect of nutritional status on warm ischemia-reperfusion injury in rat fatty livers. Fed and fasted rats with normal or fatty liver induced by a choline deficient diet underwent 1 hour of lobar ischemia and reperfusion. Rat survival was determined for 7 days. Serum transaminases, liver histology and cell ultrastructure were assessed before and after ischemia, and at 30 minutes, 2 hours, 8 hours, and 24 hours after reperfusion. Survival was also determined in fatty fasted rats supplemented with glucose before surgery. The preischemic hepatic glycogen was measured in all groups. Whereas survival was similar in fasted and fed rats with normal liver (90% vs. 100%), fasting dramatically reduced survival in rats with fatty liver (14% vs. 64%, P <.01). Accordingly, fasting and fatty degeneration had a synergistic effect in exacerbating liver injury. Mitochondrial damage was a predominant feature of ultrastructural hepatocyte injury in fasted fatty livers. Glucose supplementation partially prevented the fasting-induced depletion of glycogen and improved the 7-day rat survival to 45%. These data indicate that rat fatty livers exposed to normothermic ischemia-reperfusion injury are much more sensitive to fasting than histologically normal livers. Because glucose supplementation improves both the hepatic glycogen stores and the rat survival, a nutritional repletion procedure may be part of a treatment strategy aimed to prevent ischemia-reperfusion injury in fatty livers.

Alcohol abuse, alcoholism, and damage to the immune system--a review

Chronic alcohol abuse exacts a major social and medical toll in the United States and other Western countries. One of the least appreciated medical complications of alcohol abuse is altered immune regulation leading to immunodeficiency and autoimmunity. The consequences of the immunodeficiency include increased susceptibility to bacterial pneumonia, tuberculosis, and other infectious diseases. In addition, the chronic alcoholic often has circulating autoantibodies, and recent investigations indicate that the most destructive complications of alcoholism, such as liver disease and liver failure, may have a component of autoimmunity. Current research on altered cytokine balance produced by alcohol is leading to new insights on the regulation of the immune system in the chronic alcoholic. There is also recent development of exciting new techniques designed to improve or restore immune function by manipulation of cytokine balance. Although much remains to be learned, both in the abnormalities produced by alcohol and in the techniques to reverse those abnormalities, current progress reflects a rapidly improving understanding of the basic immune disorders of the alcoholic.

Acetaldehyde induces histamine release from purified rat peritoneal mast cells

Acetaldehyde is a widely distributed compound in the human environment and it is also formed in the human body from various endogenous and exogenous sources, exogenous ethanol being the most important one. Many alcohol-associated hypersensitivity reactions, e.g. Oriental flushing reaction, appear to be attributable to acetaldehyde rather than to ethanol itself. The pathogenetic mechanism behind such hypersensitivity reactions has been suggested to be histamine release from mast cells or blood basophils. However, the direct effects of acetaldehyde on mast cells, the main source of histamine in a mammalian body, have not been studied. The aim of the present study was, thus, to evaluate whether physiological concentrations of acetaldehyde could release histamine from purified rat peritoneal mast cells. The effects of ethanol were studied similarly. The results show that acetaldehyde, already at a concentration of 50 microM, significantly increases the release of histamine from mast cells. Ethanol has a similar effect but only at molar concentrations. These results indicate that acetaldehyde may contribute to the development of various hypersensitivity reactions by directly increasing histamine release from mast cells.

Ursodeoxycholate alleviates alcoholic fatty liver damage in rats

The hydrophilic bile salt ursodeoxycholate (UDC) improves cholestasis in several liver diseases and is in vitro an efficient membrane stabilizer. However, its action on chronic ethanol-induced liver damage is not established. We thus sought to determine the effect of UDC on chronic ethanol-induced steatosis and on liver plasma membrane fluidity in rats. Male rats were pair-fed liquid diets containing 36% of calories as ethanol (alcohol diet) or an isocaloric maltose-dextrin mixture (control diet). Four groups of 10 animals received, respectively, during 30 days: the control diet, the control diet + UDC (90 mg/kg/day), the alcohol diet, and the alcohol diet + UDC. Bile was collected for assessment of bile flow, biliary lipids, and individual bile salts. Liver lipid contents and lipid peroxidation were determined. Plasma membrane fluidity was assessed by fluorescence polarization of various probes. Alcohol treatment caused a 4-fold increase in liver triacylglycerol and cholesterol ester levels. UDC supplementation significantly reduced these increases by 50% and 40%, respectively. UDC intake was associated with a marked decrease in alcohol-induced lipid peroxidation. Bile flow, bile salt, and phospholipid secretion were slightly increased by alcohol intake. The addition of UDC-enriched bile with tauroursodeoxycholate (38%) without significantly affecting the biliary parameters. Lastly, UDC treatment almost totally prevented the 20% increase in liver plasma membrane fluidity due to chronic alcohol intake. This study shows that UDC intake, concomitant with alcohol diet, exerts a clear-cut membrane protective effect that might alleviate ethanol-induced lipid disorders.

Does steatohepatitis impair liver regeneration? A study in a dietary model of non-alcoholic steatohepatitis in rats

BACKGROUND

Impaired liver regeneration is a feature of alcoholic hepatitis, but the relative importance of alcohol, nutritional imbalance and inflammatory mediators in causing this effect is unclear. Non-alcoholic steatohepatitis (NASH) is a form of liver disease with similar morphology to alcoholic hepatitis, but the effect of this disorder on liver regeneration is unclear. We, therefore, examined the status of liver regeneration in a rat nutritional model of hepatic steatosis with inflammation, which is morphologically identical to NASH in humans.

METHODS

Male Wistar rats received a methionine-choline-deficient diet (MCDD) for 4 weeks before experiments and both isocaloric pair-fed and ad libitum-fed rats were used as controls. Following partial hepatectomy (68%), the extent of hepatic regeneration was determined 24 h later using [3H]-thymidine incorporation and restitution of liver mass.

RESULTS

There was no significant difference of [3H]-thymidine incorporation in MCDD-fed, pair-fed and ad libitum-fed rats (80+/-27, 78+/-11 and 80+/-6.3 d.p.m./microg DNA, respectively). Similarly, restituted liver masses in three groups of rats were not significantly different (17+/-3.8, 18+/-1.8 and 17+/-3.1% initial liver weight, respectively).

CONCLUSIONS

The similarities in hepatic histology and cytochrome P450 2E1 induction between this nutritional model of hepatic steatohepatitis and alcoholic steatohepatitis imply that these two disorders share pathogenetic mechanisms. However, liver regeneration is not altered by NASH in rats, indicating that the nutritional and inflammatory changes that appear similar to those of alcoholic liver disease do not cause impairment of liver regeneration.

Chronic alcohol intake interferes with retinoid metabolism and signaling

Chronic and excessive ethanol consumption is associated with cellular proliferation, fibrosis, cirrhosis, and cancer of the liver. The critical event in early alcohol-induced hepatic injury is an alcohol-induced activation (cell proliferation and increased fibrogenesis) of hepatic stellate cells. However, the mechanisms by which alcohol causes proliferative activation in hepatic stellate cells have not been identified. An important characteristic of alcohol-induced injury is impaired vitamin A nutritional status. The demonstration that retinoic acid is the most physiologically active derivative of vitamin A and the discovery of retinoic acid receptors provide a mechanistic basis for understanding the actions of vitamin A and alcohol on hepatic cell proliferation. Recent studies have demonstrated that chronic alcohol intake can reduce hepatic retinoic acid concentrations, diminish retinoid signaling, and enhance activator protein-1 (AP-1 (c-Jun and c-Fos)) expression in rat liver. These are the possible biochemical and molecular mechanisms whereby ethanol ingestion results in hepatic stellate cell proliferative activation and hepatic fibrogenesis.

Binding of fatty acid ethyl esters to albumin for transport to cells in culture

Fatty acid ethyl esters (FAEE) are non-oxidative products of ethanol metabolism that have been proposed to mediate pathological changes in various organs and tissues resulting from excessive ethanol consumption. Evidence supporting this proposal is scant, however, mainly because of the lack of adequate methods with which to solubilize the highly hydrophobic FAEE in aqueous medium for testing under physiological conditions. In this report we describe a simple and practical method for solubilizing FAEE in aqueous medium by binding them to albumin. We also report that the albumin-bound FAEE are readily taken up by rat alveolar macrophages in culture. The availability of FAEE bound to albumin, their main physiological carrier in vivo, will facilitate the investigation of the role that these metabolites may have in mediating pathological changes associated with excess ethanol consumption.

Acetaldehyde inhibits NF-kappaB activation through IkappaBalpha preservation in rat Kupffer cells

BACKGROUND AND AIMS

Treatment with acetaldehyde dehydrogenase inhibitors leads to increased liver acetaldehyde levels and prevents hepatic inflammation and necrosis in ethanol-fed rats. This is accompanied by IkappaBa preservation and decreased activation of nuclear factor (NF)-kappaB. The present in vitro study was aimed to clarify whether acetaldehyde has an effect on degradation of IkappaBalpha and activation of NF-kappaB in LPS-stimulated rat Kupffer cells.

METHODS

Kupffer cells were isolated from male Sprague-Dawley rats and preincubated with various concentrations of acetaldehyde (25-100 microM). Thereafter the cells were stimulated with LPS, and cytosolic and nuclear fractions were prepared. IkappaBalpha and p65 proteins and activation of NF-kappaB were evaluated.

RESULTS

In LPS-stimulated rat Kupffer cells, acetaldehyde diminished proteolytic degradation of IkappaBalpha, inhibited nuclear translocation of cytosolic p65 protein, and, accordingly, markedly decreased NF-kappaB activation.

CONCLUSIONS

Acetaldehyde is clearly involved in the stabilization of IkappaBalpha protein and suppression of NF-kappaB activation in rat Kupffer cells. Acetaldehyde may form an adduct with IkappaBalpha, thus making the protein less susceptible to degradation.

Incorporation of exogenous precursors into neutral lipids and phospholipids in rat hepatocytes: effect of ethanol in vitro

We studied the incorporation of different radioactively labeled exogenous substrates into the lipids of rat hepatocytes previously incubated with ethanol. Glycerol, oleate, and serine were all incorporated into neutral lipids to a significantly greater degree in the presence of ethanol, the increase in radioactivity in the triacylglycerol fraction being quite substantial. A similar ethanol-induced increase was found in the incorporation of these substrates into the various phospholipids. This lipogenic activity did not occur when the metabolism of ethanol was blocked by 4-methylpyrazole, an inhibitor of hepatic ADH (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) activity, thus demonstrating that one of the initial effects of ethanol on lipid biosynthesis was mediated by some products of its metabolism in the liver. The only alteration that persisted in the presence of 4-methylpyrazole was an inhibitory effect on the esterification of free cholesterol from oleate, suggesting that ethanol specifically inhibits hepatic ACAT (acyl CoA:cholesterol O-acyltransferase, EC 2.3.1.26) activity.

Chlorzoxazone pharmacokinetics as a marker of hepatic cytochrome P4502E1 in humans

OBJECTIVE

Previous in vitro studies have demonstrated that hepatic P4502E1 metabolizes chlorzoxazone (CZX, a commonly used muscle relaxant) to 6-hydroxychlorzoxazone (6-OH-CZX). We thus assessed whether measurement of the plasma 6-OH-CZX/CZX ratio after a CZX challenge could serve as a marker of hepatic P4502E1 content.

METHODS

Three subject groups were included: recently drinking alcoholics (N = 6), abstinent alcoholics (N = 5), and nonalcoholic subjects with liver disease (N = 5) undergoing liver biopsy. Excess tissue was procured for immunochemical determination of hepatic P4502E1 content. Within an hour of the biopsy, 750 mg CZX was administered orally and serial plasma samples were collected for 6 h.

RESULTS

Recently drinking alcoholic subjects had a higher area under the curve for plasma 6-OH-CZX (1.354 +/- 0.258 microg x min x ml(-1)) then abstinent alcoholic subjects (0.296 +/- 0.080 microg x min x ml(-1), p < 0.005) and subjects with nonalcoholic liver disease (0.428 +/- 0.061 microg x min x ml(-1), p < 0.005). The use of the plasma 6-OH-CZX/CZX ratio at 90, 120, and 180 min discriminated between recently drinking alcoholic and nondrinking subjects. Hepatic P4502E1 content significantly correlated with the maximal 6-OH-CZX concentration (r = 0.76, p = 0.001) and other pharmacokinetic parameters. In the recently drinking group, the area under the curve for plasma 6-OH-CZX significantly decreased after 8 days of abstinence.

CONCLUSIONS

Measurement of plasma 6-OH-CZX after administration of a CZX challenge can serve as a marker of hepatic P4502E1 activity and thus help avoid adverse drug reactions secondary to P4502E1 induction, particularly in heavy drinkers.

Alcohol consumption enhances liver metastasis in colorectal carcinoma patients

BACKGROUND

It is important to identify risk factors for liver metastasis in patients with colorectal carcinoma because the liver is the most common site of recurrence. Alcohol consumption reportedly is associated with hematogenous metastasis in certain animal models. Furthermore, some studies have shown that carmofur, a derivative of 5-fluorouracil, is particularly effective as adjuvant chemotherapy for colorectal carcinoma, and may even suppress liver metastasis, although the mechanism by which this occurs remains unknown. In addition, carmofur is known to inhibit alcohol metabolism. To the authors' knowledge, the relation between liver metastasis in colorectal carcinoma and alcohol consumption has not been examined previously. Therefore, the authors studied the relations between liver metastasis in colorectal carcinoma and various clinicopathologic factors including alcohol consumption status.

METHODS

This study was comprised of 133 colorectal carcinoma patients with invasion beyond the submucosal layer who had undergone surgical resection. The subjects were examined and divided into two groups according to the occurrence or absence of liver metastasis. The relations between liver metastasis and other clinicopathologic factors were analyzed by univariate and multivariate statistical methods.

RESULTS

Univariate analysis showed alcohol consumption (P=0.0021) and blood vessel invasion (P=0.0045) were correlated with liver metastasis. Multivariate analysis showed both to be independent risk factors for liver metastasis.

CONCLUSIONS

Alcohol consumption is an independent risk factor for liver metastasis in colorectal carcinoma patients. Therefore, patients with colorectal carcinoma who drink alcohol require intensive examination and follow-up with respect to liver metastasis. Further study is necessary to confirm the effect of adjuvant chemotherapy using carmofur in colorectal carcinoma patients.

Ethanol metabolism by macrophages: possible role in organ damage

Macrophages and hepatocytes oxidize ethanol to acetate in vitro at comparable rates but by different biochemical pathways. Ethanol metabolism by macrophages is largely ADH-independent and mainly based on cytochrome P450 and on the extracellular release of superoxide anion radicals. There is also evidence that during ethanol metabolism, macrophages release more acetaldehyde extracellularly than hepatocytes; the high concentrations of acetaldehyde around macrophages may damage surrounding tissue cells. Some of this acetaldehyde forms unstable cytotoxic complexes with serum albumin and with erythrocytes. The superoxide anion radicals released by macrophages may not only oxidize ethanol to acetaldehyde but also react with and damage cells in their immediate vicinity. After exposure to ethanol, macrophage-depleted rodents show markedly reduced levels of cytotoxic acetaldehyde-albumin complexes in the blood and reduced levels of hydroxyethyl radicals in the bile compared to control animals, indicating that the generation of such potentially pathogenic molecules is, to a large extent, dependent on macrophage activity. Macrophage-depleted animals also show less early liver damage than control animals. The reduction in ethanol-induced liver damage in macrophage-depleted mice and rats may be due to a reduction or elimination of the generation of various Kupffer-cell-derived hepatotoxic substances, including acetaldehyde and reactive oxygen radicals, in such animals. These data suggest that ethanol metabolism by tissue macrophages may play an important role in mediating ethanol-related tissue damage.

Alcohol and cancer

A great number of epidemiological data have identified chronic alcohol consumption as a significant risk factor for upper alimentary tract cancer, including cancer of the oropharynx, larynx, and the esophagus, and for the liver. In contrast to those organs, the risk by which alcohol consumption increases cancer in the large intestine and in the breast is much smaller. However, although the risk is lower, carcinogenesis can be enhanced with relatively low daily doses of ethanol. Considering the high prevalence of these tumors, even a small increase in cancer risk is of great importance, especially in those individuals who exhibit a higher risk for other reasons. The epidemiological data on alcohol and other organ cancers are controversial and there is at present not enough evidence for a significant association. Although the exact mechanisms by which chronic alcohol ingestion stimulates carcinogenesis are not known, experimental studies in animals support the concept that ethanol is not a carcinogen, but under certain experimental conditions is a cocarcinogen and/or (especially in the liver) a tumor promoter. The metabolism of ethanol leads to the generation of acetaldehyde and free radicals. These highly reactive compounds bind rapidly to cell constituents and possibly to DNA. Acetaldehyde decreases DNA repair mechanisms and the methylation of cytosine in DNA. It also traps glutathione, an important peptide in detoxification. Furthermore, it leads to chromosomal aberrations and seems to be associated with tissue damage and secondary compensatory hyperregeneration. More recently, the finding of considerable production of acetaldehyde by gastrointestinal bacteria was reported. Other mechanisms by which alcohol stimulates carcinogenesis include the induction of cytochrome P4502E1, associated with an enhanced activation of various procarcinogens present in alcoholic beverages, in association with tobacco smoke and in diets, a change in the metabolism and distribution of carcinogens, alterations in cell cycle behavior such as cell cycle duration leading to hyperregeneration, nutritional deficiencies such as methyl, vitamin A, folate, pyrridoxalphosphate, zinc and selenium deficiency, and alterations of the immune system, eventually resulting in an increased susceptibility to certain viral infections such as hepatitis B virus and hepatitis C virus. In addition, local mechanisms in the upper gastrointestinal tract and in the rectum may be of particular importance. Such mechanisms lead to tissue injury such as cirrhosis of the liver, a major prerequisite for hepatocellular carcinoma. Thus, all these mechanisms, functioning in concert, actively modulate carcinogenesis, leading to its stimulation.

Effects of ethanol on mitogen-activated protein kinase and stress-activated protein kinase cascades in normal and regenerating liver

To understand the mechanisms by which ethanol inhibits hepatocyte proliferation, we studied the effects of ethanol on p42/44 mitogen-activated protein kinase (MAPK), p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK) in normal and regenerating rat liver. Treatment of rat hepatocytes with 100 mM ethanol in vitro for 16 h prolonged the activation of p42/44 MAPK and p38 MAPK induced by various agonists. Such treatment also increased basal JNK activity, but did not potentiate or prolong agonist-induced JNK activation. Ethanol potentiation of the activation of p42/44 MAPK was abolished by pertussis toxin. In contrast, chronic ethanol consumption in vivo inhibited the activation of p42/44 MAPK, p38 MAPK and JNK induced either by partial hepatectomy or by various agonists. However, both acute and chronic ethanol inhibited hepatocyte proliferation induced by insulin and epidermal growth factor. A selective inhibitor of p42/44 MAPK partially prevented the inhibition of hepatocyte proliferation caused by acute, but not by chronic, ethanol exposure, whereas a selective inhibitor of p38 MAPK further inhibited hepatocyte proliferation under both conditions. These data suggest that acute and chronic ethanol inhibit hepatocyte proliferation by different mechanisms. The effect of acute ethanol may be related to the prolongation of p42/44 MAPK activation, whereas inhibition of hepatocyte proliferation by chronic ethanol may be due to inhibition of p38 MAPK activation.

Chronic alcohol intake reduces retinoic acid concentration and enhances AP-1 (c-Jun and c-Fos) expression in rat liver

Chronic ethanol intake may interfere with retinoid signal transduction by inhibiting retinoic acid synthesis and by enhancing activator protein-1 (AP-1) (c-Jun and c-Fos) expression, thereby contributing to malignant transformation. To determine the effect of ethanol on hepatic retinoid levels, retinoic acid receptors (RARs) and AP-1 (c-Jun and c-Fos) gene expression, chronic ethanol (36% of total calorie intake) pair-feeding was conducted on rats for a 1-month period. Retinoic acid, retinol, and retinyl ester concentrations in both liver and plasma were examined by using high-performance liquid chromatography (HPLC). Both retinoic acid receptor (alpha, beta, gamma) and AP-1 (c-Jun and c-Fos) expression in the rat liver were examined by using Western blot analysis. Treatment with high-dose ethanol led to a significant reduction of retinoic acid concentration in both the liver and the plasma (11- and 8.5-fold reduction, respectively), as compared with animals pair-fed an isocaloric control diet containing the same amount of vitamin A. Similar to the retinoic acid reductions, both retinol and retinyl palmitate levels in the livers of the alcohol-fed group decreased significantly, but in smaller fold reduction (6.5- and 2.6-fold reduction, respectively). Ethanol did not modulate the expression of RARalpha, -beta, and -gamma genes in the liver. However, chronic alcohol feeding enhanced AP-1 (c-Jun and c-Fos) expression by 7- to 8-fold, as compared with the control group. These data suggest that functional downregulation of RARs by inhibiting biosynthesis of retinoic acid and up-regulation of AP-1 gene expression may be important mechanisms for causing malignant transformation by ethanol.

Distinct patterns of chemokine expression are associated with leukocyte recruitment in alcoholic hepatitis and alcoholic cirrhosis

Alcoholic liver disease is associated with three histologically distinct processes: steatosis (parenchymal fat accumulation), alcoholic hepatitis (characterized by parenchymal infiltration by neutrophil polymorphs), and alcoholic cirrhosis (in which chronic inflammation and fibrosis dominate). Chemokines are cytokines that promote subset-specific leukoycte recruitment to tissues and could therefore play a crucial role in determining which leukocyte subsets are recruited to the liver in alcoholic liver disease. This paper reports that chemokine expression is increased in the liver of patients with alcoholic liver disease and, moreover, that distinct patterns of chemokine expression are associated with the different inflammatory responses to alcohol. Interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1 alpha (MIP-1 alpha), and MIP-1 beta were all detected in the parenchyma at sites of inflammation in alcoholic hepatitis, whereas in alcoholic cirrhosis, chemokines were restricted to inflammatory cells and endothelium in the fibrous septa and portal tracts. In alcoholic hepatitis, chemokine transcription was localized to sinusoidal cells, leukocytes, and fibroblasts in areas of parenchymal inflammation, but hepatocytes, despite staining strongly for chemokine protein, were negative. In alcoholic cirrhosis, chemokine mRNA was detected in portal tract endothelium, leukocytes, and fibroblasts. Thus, alcoholic hepatitis and alcoholic cirrhosis are associated with distinct patterns of chemokine expression that are likely to be important factors in determining whether a patient develops acute parenchymal inflammation and alcoholic hepatitis, or chronic septal inflammation and alcoholic cirrhosis.

Liver nuclear ethanol metabolizing systems (NEMS) producing acetaldehyde and 1-hydroxyethyl free radicals

Biotransformation of ethanol by liver nuclei was studied. The formation of acetaldehyde was determined by GC/FID. The 1-hydroxyethyl (1HEt) formation was established by spin trapping of the radical with N-t-butyl-alpha-phenylnitrone (PBN) followed by GC/MS. Liver nuclei, free of endoplasmic reticulum, cytosol or mitochondria, were able to biotransform ethanol to acetaldehyde in the presence of NADPH under air. Only 22% activity was observed in the absence of the cofactor. Twenty-six percent of the NADPH-dependent activity and 47% of the NADPH-independent activity were observable under nitrogen. Aerobic biotransformation was inhibited by CO, SKF 525A, 4-methylpyrazole and by diethyldithiocarbamate. This suggests that CYP2E1 is involved in the process. However, the formation of acetaldehyde was able to proceed under a pure CO atmosphere. The lack of inhibitory effects of 2-mercapto-1-methylimidazol and thiobenzamide excludes the potential participation of the NADPH flavin monooxigenase system. The formation of hydroxyl radicals in the process is suggested by the partial inhibitory effect of 5 mM mannitol and 5 mM sodium benzoate and by the fact that the 1HEt was detected. The NADPH-dependent anaerobic ethanol biotransformation pathway was stimulated by FAD and inhibited to some extent by iron chelators. The relevance of a liver nuclear ethanol biotransformation, generating reactive metabolites, such as acetaldehyde and free radicals, nearby DNA, nuclear proteins and lipids is discussed.

Role of cytokines in ethanol-induced cytotoxicity in vitro in Hep G2 cells

BACKGROUND & AIMS

As shown previously by us, ethanol (EtOH) causes time- and concentration-dependent reduction in cytoviability. Tauroursodeoxycholic acid (TUDCA) and ursodeoxycholic acid (UDCA) were shown to reduce cytotoxicity. Long-term EtOH exposure leads to immunoregulatory and detoxification impairment. This study aimed to determine the relationship between cytokine (interleukin [IL]-1 alpha and IL-6 and tumor necrosis factor [TNF]-alpha) production and expression, glutathione (GSH) status, and EtOH-induced cytotoxicity on Hep G2 cells.

METHODS

Cells were incubated with 80 mmol/L EtOH or alpha-minimal essential medium (control) in the presence or absence of 50 mumol/L TUDCA or UDCA. Cytokine release was quantitated by enzyme-linked immunosorbent assay. Cytokine expression was measured by reverse-transcription polymerase chain reaction. GSH content was determined in both the cytosolic and mitochondrial fractions.

RESULTS

After 24 hours of EtOH exposure, the release of IL-1 alpha doubled, that of IL-6 increased 10 times, and that of TNF-alpha increased 3.5 times. Cytokine expression was up-regulated compared with control for IL-1 alpha (42%), IL-6 (26%), and TNF-alpha (52%). Addition of 50 mumol/L TUDCA or UDCA reduced cytokine release and expression. TNF-alpha increased cytotoxicity by 18%. Anti-TNF-alpha antibody almost abolished it. EtOH depleted mGSH levels by 55% (P < 0.001). TUDCA replenished them by 88%.

CONCLUSIONS

EtOH up-regulated expression of cytokines in Hep G2 cells is down-regulated by bile acids. Increased amounts of TNF-alpha and depletion in both cytosolic and mitochondrial GSH contribute to EtOH cytotoxicity. Bile acids prevent toxicity.

Ethanol enhances cholesterol synthesis and secretion in human hepatomal cells

Excessive consumption of alcohol leads to severe alterations of lipid metabolism, including hyperlipemia and hypercholesterolemia. Following these epidemiological observations, we investigated the effects of ethanol at the cellular level by employing a human hepatomal cell line (HepG2) and by evaluating the biosyntheses of lipid classes from different labeled precursors. Incubation of cells with 2% ethanol resulted in a decreased labeling of phospholipids and in an increase in cholesterol synthesis and secretion. Triglyceride synthesis was increased by ethanol but their secretion in the medium was reduced, suggesting that these alterations may be related to their accumulation in the liver. The alcohol-induced alterations of lipid metabolism are not due to its metabolite acetaldehyde and data suggest that alcohol enhances cholesterol synthesis by affecting the initial steps without increasing HMGCoA expression. The observed modifications of lipid metabolism in HepG2 may partially explain the enhanced incidence of cardiovascular disorders that has been associated with alcoholism.

Alcoholic liver disease. Treatment strategies for the potentially reversible stages

Even modest alcohol ingestion can increase the risk of steatosis, and long-term, excessive consumption can lead to alcoholic hepatitis and eventually cirrhosis. Most patients with clinically significant alcoholic liver disease have histologic findings typical of all three conditions. The only clearly beneficial treatment is abstinence from alcohol. Abstinence in combination with proper nutrition and general supportive care is state of the art. Steatosis is reversible upon withdrawal of alcohol, but alcoholic hepatitis can persist even with abstinence and may progress to cirrhosis. Corticosteroid therapy may reduce short-term mortality rates in patients with moderate or severe alcoholic hepatitis who have hepatic encephalopathy but no evidence of infection or gastrointestinal bleeding. Treatment with colchicine may decrease the risk of cirrhosis; however, once cirrhosis has developed, the liver damage is irreversible. The prognosis is improved with abstinence, but complications (e.g., ascites, gastrointestinal bleeding) often occur. Liver transplantation may be considered in patients with severe complications.

Chronic ethanol consumption affects glutathione status in rat liver

There is no consensus yet on the role of oxidative stress in the nutritional outcome of chronic ethanol feeding and the status of cellular antioxidative defense systems against ethanol toxicity. In this study, chronic alcohol consumption in humans was reproduced in Sprague-Dawley rats to investigate the effect of ethanol ingestion on the regulation of oxidative stress in liver with a special focus on glutathione. Adult male rats were given 36% of total energy as alcohol in the Lieber-DeCarli liquid diet for 6 wk. The control group was pair-fed the diet containing isocaloric dextrin-maltose instead of ethanol. Chronic ethanol ingestion enhanced expression of cytochrome P450 II E1 in the liver, but did not significantly alter either the level of hepatic thiobarbituric acid reactive substances or the carbonyl group content of proteins. The hepatic concentrations of total and reduced glutathione and the activities of catalase, glutathione reductase and glutathione S-transferase were significantly higher in the ethanol group than in the control group. The activities of glutathione peroxidase and glucose-6-phosphate dehydrogenase were significantly lower in the ethanol group than in controls. Chronic ethanol consumption by well-nourished rats for 6 wk increased enzyme activities related to the recycling and utilization of glutathione in the liver. Such an enhancement in the activities of the hepatic antioxidative defense system may be one of the protective mechanisms of the body against oxidative tissue damage caused by ethanol-induced free radicals.

Free methionine supplementation limits alcohol-induced liver damage in rats

Alcohol feeding to rats that were submitted to a jejunoileal bypass operation has been shown to result in liver damage being comparable with alcohol-induced liver disease in man. In the present study, a striking effect of free methionine consumption on histological liver injury, triglyceride accumulation, and energy-rich nucleoside content in the liver of rats with a jejunoileal bypass is demonstrated. The animals obtained 0, 30, and 120 mg of methionine in the control group and 0, 30, 120, and 240 mg in the alcohol-fed group per day and per kilogram of body weight for 12 weeks. Methionine was found to strongly improve the alcohol-induced histological changes in the liver. Triglyceride content of the liver was found to decrease in a dose-dependent manner with increasing methionine ingestion (from 255 +/- 20.7 to 49.7 +/- 6.1 micromol/g of protein in the control group and from 233 +/- 17.3 to 42.1 +/- 7.2 micromol/g of protein in the alcohol group). Hepatic adenosine triphosphate content increased significantly with higher methionine consumption (13.5 +/- 0.8 vs. 26.9 +/- 2.8 micromol/g of protein in the control group and 11.9 +/- 1.4 vs. 20.5 +/- 2.5 micromol/g of protein in the alcohol group), whereas no differences were found in the protein and DNA content of the liver. These results underscore the impairment of the transmethylation/transsulfuration pathway in the development of alcohol-induced liver diseases.

Association of polymorphism in the alcohol dehydrogenase 2 gene with alcohol-related organ injuries, especially liver cirrhosis

The class I hepatic alcohol dehydrogenases (ADHs) are primarily responsible for ethanol metabolism in humans. Genetic polymorphism at the ADH2 locus results in the inheritance of isozymes of strikingly different catalytic properties. In European and Caucasian American populations, β1, which is encoded by ADH2(1) , is the most common form of the enzyme, while β2, encoded by the ADH2(2) allele, is found primarily in Orientals. The β2β2 enzyme encoded by ADH2(2) /ADH2(2) is approximately 20 times more active in ethanol oxidation than the β1β1 enzyme. In vivo the kinetic differences of ADH2 isozymes may influence individual risk for the effects of ethanol. This article will review the role of polymorphisms at the ADH2 loci in genetic predisposition to alcoholism and alcohol-related organ injury, especially alcoholic cirrhosis.

Cytochrome P4502E1 inducibility and hydroxyethyl radical formation among alcoholics

BACKGROUND/AIMS

Animal studies have shown that the induction of cytochrome P4502E1 (CYP2E1) modulates oxidative damage induced by ethanol. Since CYP2E1 activity varies substantially in humans, we have investigated whether differences in CYP2E1 activity might influence the formation of hydroxyethyl free radicals and the stimulation of lipid peroxidation among alcohol abusers.

METHODS

Chlorzoxazone oxidation, an index of CYP2E1 activity, and the levels of antibodies reacting with hydroxyethyl radical and malonyldialdehyde protein adducts were investigated in 51 alcoholic patients.

RESULTS

We observed that in 40 out of 51 (78%) alcoholics, chlorzoxazone oxidation was increased over the control levels, consistently with CYP2E1 induction by ethanol. However, in the remaining 22% of the patients, in spite of a similar alcohol intake, chlorzoxazone oxidation was within the control range, indicating a lack of CYP2E1 inducibility. IgG reacting with hydroxyethyl free radical-protein adducts were absent in subjects without CYP2E1 induction, while they were significantly increased in alcoholics with induced CYP2E1 activity. IgG against malonyldialdehyde protein-adducts were increased in all patients, irrespective of CYP2E1 inducibility. Moreover, chlorzoxazone oxidation was significantly lower in alcoholics without clinical and biochemical signs of liver disease as compared to patients with alcoholic liver disease.

CONCLUSIONS

These results indicate that CYP2E1 activity greatly influences the formation of hydroxyethyl radicals in humans, and suggest a possible role of CYP2E1 in the development of alcoholic liver disease.

Gastrointestinal alcohol dehydrogenase

Alcohol dehydrogenase (ADH) consists of a family of isozymes that convert alcohols to their corresponding aldehydes using NAD+ as a cofactor. The metabolism of ethanol by gastrointestinal ADH isozymes results in the production of acetaldehyde, a highly toxic compound that binds to cellular protein and DNA if not further metabolized to acetate by acetaldehyde dehydrogenase isozymes. Acetaldehyde seems to be involved in ethanol-associated cocarcinogenesis. The metabolism of retinol and the generation of retinoic acid is a function of class I and class IV ADH, and its inhibition by alcohol may lead to an alteration of epithelial cell differentiation and cell growth and may also be involved in ethanol-associated gastrointestinal cocarcinogenesis.

Metabolism of ethanol and some associated adverse effects on the liver and the stomach

Current knowledge of alcohol oxidation and its effects on hepatic metabolism and its toxicity are summarized. This includes an evaluation of the relationship of the level of consumption to its interaction with nutrients (especially retinoids, carotenoids, and folate) and the development of various stages of liver disease. Ethanol metabolism in the stomach and its link to pathology and Helicobacter pylori is reviewed. Promising therapeutic approaches evolving from newly gained insight in the pathogenesis of medical complications of alcoholism are outlined. At present, the established approach for the prevention and treatment of alcoholism are outlined. At present, the established approach for the prevention and treatment of alcoholic liver injury is to control alcohol abuse, with the judicial application of selective antioxidant therapy, instituted at early stages, prior to the social or medical disintegration of the patient, and associated with antiinflammatory agents at the acute phase of alcoholic hepatitis. In addition, effective antifibrotic therapy may soon become available.

Metadoxine accelerates fatty liver recovery in alcoholic patients: results of a randomized double-blind, placebo-control trial. Spanish Group for the Study of Alcoholic Fatty Liver

BACKGROUND/AIMS

Our aim was to investigate the effectiveness of metadoxine (pyridoxol L, 2 pyrrolidone-5-carboxylate) in the treatment of alcoholic fatty liver.

METHODS

A double-blind randomized multicenter trial involving 136 chronic active alcoholic patients diagnosed with fatty liver by clinical, biochemical and ultrasonographic criteria was performed. Patients were treated with 1500 mg/day of metadoxine (n = 69) or placebo (n = 67) for 3 months. Patients were clinically and biochemically evaluated every month. Ultrasonography was performed before and after treatment.

RESULTS

At the end of the study there was a significant improvement in the liver function tests in both groups. However, the changes were more rapid and greater in patients treated with metadoxine, in whom significant changes in serum levels of bilirubin, aminotransferases and gammaglutamyl transpeptidase were already observed after 1 month of treatment, and normalization of these parameters was observed at the end. After treatment, the percentage of patients with ultrasonographic signs of steatosis was significantly lower in the metadoxine group (28% vs 70%, p < 0.01) and the degree of steatosis was also lower in this group. Sixteen patients treated with metadoxine and 15 with placebo continued drinking. Alcohol intake was lower than initially, and similar in both groups. In the metadoxine group, the biochemical changes were similar in both the abstinent and the nonabstinent patients. In contrast, in the placebo group the improvement in the liver function tests was significantly higher in abstinents. Among patients who continued drinking, the prevalence (45% vs 92%, p < 0.05) and the degree of steatosis were also significantly lower in patients treated with metadoxine.

CONCLUSIONS

In patients with alcoholic fatty liver, metadoxine accelerates the normalization of liver function tests and the ultrasonographic changes, even in those who do not completely abstain from alcohol intake. Thus, metadoxine could be useful in the treatment of the early stages of alcoholic liver disease.