Alcohol and the liver: metabolism of ethanol, metabolic effects and pathogenesis of injury

Monascin and Ankaflavin of Monascus purpureus Prevent Alcoholic Liver Disease through Regulating AMPK-Mediated Lipid Metabolism and Enhancing Both Anti-Inflammatory and Anti-Oxidative Systems

Alcohol metabolism causes an excessive accumulation of liver lipids and inflammation, resulting in liver damage. The yellow pigments monascin (MS) and ankaflavin (AK) of Monascus purpureus-fermented rice were proven to regulate ethanol-induced damage in HepG2 cells, but the complete anti-inflammatory and anti-fatty liver mechanisms in the animal model are still unclear. This study explored the roles of MS and AK in improving alcoholic liver injury. MS and AK were simultaneously fed to evaluate their effects and mechanisms in C57BL/6J mice fed the Lieber–DeCarli liquid alcohol diet for 6 weeks. The results indicated that MS and AK significantly reduced the serum aspartate aminotransferase and alanine aminotransferase activity, as well as the total liver cholesterol and triglyceride levels. The histopathological results indicated that MS and AK prevented lipid accumulation in the liver. MS and AK effectively enhanced the activity of antioxidant enzymes and reduced the degree of lipid peroxidation; AK was particularly effective and exhibited a superior preventive effect against alcoholic liver injury and fatty liver. In addition to inhibiting the phosphorylation of the MAPK family, MS and AK directly reduced TNF-α, IL-6, and IL-1β levels, thereby reducing NF-κB and its downstream iNOS and COX-2 expressions, as well as increasing PPAR-γ, Nrf-2, and HO-1 expressions to prevent liver damage. MS and AK also directly reduced TNF-α, IL-6, and IL-1β expression, thereby reducing the production of NF-κB and its downstream iNOS and COX-2, and increasing PPAR-γ, Nrf-2, and HO-1 expressions, preventing alcohol damage to the liver.

Hepatoprotective Effects of the Cichorium intybus Root Extract against Alcohol-Induced Liver Injury in Experimental Rats

The effects of the Cichorium intybus root extract (Cii) on alcohol-induced liver disease were investigated using Chang liver cells and male Sprague Dawley rats. Silymarin, a liver-protective agent, was used as a positive control. In cell experiments, after 24 h of treatment with the extract, no cytotoxicity was noted, and death by alcohol was avoided. Migration of Chang liver cells increased after exposure to the extract at a concentration of 400 μg/mL. In animal experiments, alcohol was injected into 6-week-old rats for 1, 3, and 50 days. Oral administration of the drug was performed 30 min before alcohol administration. The control was treated with distilled water, and the drug groups were administered EtOH (40% EtOH + 2.5 mL/kg), EtOH + Cii L (low concentration, 2 mg/kg), EtOH + Cii H (high concentration, 10 mg/kg), or EtOH + silymarin (100 mg/kg). Increased liver weight was observed in the alcohol group, as were increased blood-alcohol concentration and liver damage indicators (glutamic oxalacetic transaminase (GOT), glutamic pyruvate transaminase (GPT), and triglycerides (TG)), decreased alcoholysis enzymes (ADH and ALDH), and increased CYP2E1. In the Cii treatment group, liver weight, blood-alcohol concentration, liver damage indicators (GOT, GPT, and TG), and CYP2E1 were decreased, while alcoholysis enzymes (ADH and ALDH) were increased. The degree of histopathological liver damage was compared visually and by staining with hematoxylin and eosin and oil red O. These results indicated that ingestion of Cii inhibited alcohol-induced liver damage, indicating Cii as a useful treatment for alcohol-induced liver injury.

Effect of alcohol on blood glucose and antioxidant enzymes in the liver and kidney of diabetic rats

OBJECTIVE

Diabetes mellitus affects every organ in the man including eyes, kidney, heart, and nervous system. Alcohol consumption is a widespread practice. As the effects of chronic alcohol consumption on diabetic state have been little studied, this study was conducted with the objective of evaluating the effect of alcohol in diabetic rats.

MATERIALS AND METHODS

For this study, the rats were divided into five groups (n = 6 in each group): normal control (NC), alcohol treatment (At), diabetic control (DC), diabetic plus alcohol treatment (D + At), diabetic plus glibenclamide treatment (D + Gli). Alcohol treatment was given to the diabetic rats for 30 days. During the period the blood glucose levels, and body weight changes were observed at regular intervals. The antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) levels were assayed in the liver and kidney tissues.

RESULTS

The blood glucose levels were significantly (P < 0.001) elevated and body weight significantly (P < 0.001) decreased in alcohol-treated diabetic rats. SOD and CAT activities were decreased and the MDA level increased significantly (P < 0.001) in alcohol-treated diabetic rats. Histopathological studies showed that alcohol damages the liver and kidney tissues in diabetic rats.

CONCLUSION

These finddings concluded that the consumption of alcohol in diabetic rats worsens the condition. So the consumption of alcohol by diabetic subjects may be potentially harmful.

Caffeic acid inhibits the formation of 1-hydroxyethyl radical in the reaction mixture of rat liver microsomes with ethanol partly through its metal chelating activity

Effect of caffeic acid on the formation of 1-hydroxyethyl radicals via the microsomal ethanol-oxidizing system pathway was examined. The electron spin resonance spin trapping showed that 1-hydroxyethyl radicals form in the control reaction mixture which contained 0.17 M ethanol, 1 mg protein/ml rat river microsomes, 0.1 M α-(4-pyridyl-1-oxide)-N-tert-butylnitrone, 5 mM nicotinamide adenine dinucleotide phosphate and 30 mM phosphate buffer (pH 7.4). When the electron spin resonance spectra of the control reaction mixtures with caffeic acid were measured, caffeic acid inhibited the formation of 1-hydroxyethyl radicals in a concentration dependent manner. Gallic acid, dopamine, l-dopa, chlorogenic acid and catechin also inhibited the formation of 1-hydroxyethyl radicals. Above results indicated that the catechol moiety is essential to the inhibitory effect. Caffeic acid seems to chelate of iron ion at the catechol moiety. Indeed, the inhibitory effect by caffeic acid was greatly diminished in the presence of desferrioxamine, a potent iron chelator which removes iron ion in the Fe (III)-caffeic acid complex. Since Fe (III)-desferrioxamine complex is active for the 1-hydroxyethyl radicals formation, caffeic acid inhibits the formation of 1-hydroxyethyl radicals in the reaction mixture partly through its metal chelating activity.

Rosiglitazone relieves acute ethanol-induced hangover in Sprague-Dawley rats

AIMS

To assess the efficacy of rosiglitazone in blocking ethanol-induced hangover in rats.

METHODS

Rats injected with ethanol (4 g/kg body weight) were subjected to social interaction tests. Levels of aldehyde dehydrogenase 2 (ALD2), involved in an anti-hangover mechanism, were measured by semi-quantitative RT-PCR and western blot analysis.

RESULTS

Rosiglitazone caused an upregulation of mitochondrial ALD2, thus significantly detoxifying acetaldehyde.

CONCLUSIONS

Rosiglitazone alleviated the symptoms of ethanol-induced hangover by inducing ALD2 expression; this result was reconfirmed by eliminating the effect of rosiglitazone by injecting cyanamide, an ALD2 inhibitor.

H2-antagonists and alcohol. Do they interact?

There are conflicting data on the existence of significant first-pass metabolism of alcohol (ethanol) in the human stomach and its inhibition by histamine H2-receptor antagonists. Alcohol is predominantly metabolised in the liver by the microsomal alcohol oxidising system, alcohol dehydrogenase (ADH) and a catalase enzyme. Histochemical and kinetic studies have revealed several ADH isoenzymes in the gastric mucosa with different kinetic properties. After small oral doses of alcohol first-pass metabolism in the stomach occurs, as shown by reduced area under the plasma concentration-time curve (AUC) compared with intravenous or intraduodenal administration. The activity of gastric ADH is reduced in women, the elderly, Asian individuals, the fasting state, chronic alcoholism and after gastrectomy. The effect is only present with small (< or = 0.3 g/kg) alcohol doses and with a high alcohol concentration. In a number of studies, cimetidine in therapeutic doses over 7 days produced a significant increase in the AUC and in the peak plasma concentration after administration of alcohol 0.15 and 0.30 g/kg. This was related to an inhibition of gastric ADH activity, as shown by in vitro studies. Ranitidine inhibited gastric ADH to a similar extent on a molar basis, but its effect on alcohol levels in vivo was less constant in various studies. Nizatidine also reduced gastric alcohol first-pass metabolism, but famotidine and roxatidine did not show this effect. In other studies, H2-receptor antagonists did not change AUC and peak alcohol concentration. The controversy is not easy to resolve, since a number of the positive studies did not use a placebo-controlled, randomised, crossover design, while some of the negative studies did not exclude habitual alcohol consumers and included Oriental volunteers, although both groups have been shown to lack significant gastric ADH activity. In this case, when first-pass metabolism of alcohol does not exist, this by definition cannot be abolished by H2-antagonists. The inclusion of oral and intravenous dosage data of alcohol is mandatory to positively identify first-pass metabolism in any individuals. The significance of the effect of H2-antagonists on blood alcohol concentrations is minor. It only occurs in young, male, nonalcoholic, non-Asian individuals, and alcohol must be given in a small (social) dose, in a high concentration, and after meals. An increase in alcohol levels in predisposed patients during treatment with some H2-antagonists cannot be excluded, although the likelihood is small. Furthermore, carefully designed studies are needed to clarify fully the significance of this interaction.

Ethanol increases receptor-dependent cyclic AMP production in cultured hepatocytes by decreasing G(i)-mediated inhibition

Increasing evidence suggests that ethanol-induced changes in cyclic AMP (cAMP) signal transduction play a critical role in the acute and chronic effects of ethanol. Here we have investigated the effects of ethanol on cAMP signal transduction in primary cultures of rat hepatocytes. Acute exposure to ethanol had a biphasic effect on glucagon-receptor-dependent cAMP production in intact cells: 25-50 mM-ethanol decreased cAMP, whereas treatment with 100-200 mM-ethanol increased cAMP. After chronic exposure to 50-200 mM-ethanol for 48 h in culture, glucagon-receptor-dependent cAMP levels were increased, but no change in glucagon receptor number was observed. These effects of ethanol were independent of ethanol oxidation. Chronic ethanol treatment also increased adenosine-receptor- and forskolin-stimulated cAMP production. Increased cAMP production was also observed upon stimulation of adenylate cyclase with glucagon, forskolin and F- in membranes isolated from cells cultured with 100 mM-ethanol for 48 h. However, no differences were observed in basal and MnCl2-stimulated adenylate cyclase activity. The quantity of alpha i protein was decreased by 35% after chronic ethanol treatment, but no change in the quantity of alpha s protein was detected. Decreased alpha i protein was associated with a decrease in G(i) function, as assessed by the ability of 0.1 nM-guanosine 5'-[beta gamma-imido]triphosphate and 1 microM-somatostatin to inhibit forskolin-stimulated adenylate cyclase activity. Taken together, these results suggest that chronic exposure to ethanol increases receptor-dependent cAMP production in hepatocytes by decreasing the quantity of alpha i protein at the plasma membrane and thereby decreasing the inhibitory effects of G(i) on adenylate cyclase activity.

Role of the Golgi apparatus in cellular pathology

The Golgi apparatus response to pathological disorders is predominantly as an intermediary component of membrane biogenesis where it is involved in processing, sorting and secretion of materials via secretory granules, and in the formation of lysosomes. A common initial response of the Golgi apparatus to any stress is an alteration or cessation of secretory activity. In the transformed cell, the Golgi apparatus is altered both morphologically and biochemically, suggesting a shift from a secretory to a membrane-generating mode of functioning. However, since fewer or less well-developed Golgi apparatus are frequently found in transformed cells, analytical methods of membrane isolation developed for normal tissues may not always yield equivalent results when applied to tumors. Cell surface alterations characteristic of malignant cells may result from modifications occurring at the level of the Golgi apparatus. Some lysosomal dysfunctions may result from underglycosylation of acid hydrolases by the Golgi apparatus. The use of cell-free systems between endoplasmic reticulum and Golgi apparatus or within Golgi apparatus cisterane is providing a new approach to the elucidation of the role of the Golgi apparatus in normal as well as pathological states.

Reactive free radical generation in vivo in heart and liver of ethanol-fed rats: correlation with radical formation in vitro

Rats fed a high-fat ethanol-containing diet for 2 weeks were found to generate free radicals in liver and heart in vivo. The radicals are believed to be carbon-centered radicals, were detected by administering spin-trapping agents to the rats, and were characterized by electron paramagnetic resonance spectroscopy. The radicals in the liver were demonstrated to be localized in the endoplasmic reticulum. Rats fed ethanol in a low-fat diet showed significantly less free radical generation. Control animals given isocaloric diets without ethanol showed no evidence of free radicals in liver and heart. When liver microsomes prepared from rats fed the high-fat ethanol diet were incubated in a system containing ethanol, NADPH, and a spin-trapping agent, the generation of 1-hydroxyethyl radicals was observed. The latter was verified by using 13C-substituted ethanol. Microsomes from animals fed the high-fat ethanol-containing diet had higher levels of cytochrome P-450 than microsomes from rats fed the low-fat ethanol-containing diet. The results suggest that the consumption of ethanol results in the production of free radicals in rat liver and heart in vivo that appear to initiate lipid peroxidation.