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Biomedical subjects

C S Lieber

Publications and source records attributed to C S Lieber.

At least 199 records · Page 11Linked to original sources
PubMed1989

Age of alcoholism onset. II. Relationship to susceptibility to serotonin precursor availability.

Alcoholics who start abusing alcohol early in life have been found to exhibit problems with mood and aggression control more frequently than patients with a later onset of alcoholism. Because alcohol preference and consumption, as well as mood and aggression regulation, are believed to be influenced by serotonin, relationships between tryptophan availability and mood and aggression regulation were explored in alcoholics. When studied in the entire population, the ratio of tryptophan over other amino acids competing for brain entry (which influences brain serotonin) was found to be lowest one day after cessation of drinking and to increase progressively over the following two to three weeks. When the population was divided into two groups of patients according to whether subjects started abusing alcohol before or after 20 years of age, associations between a low tryptophan ratio and depressive and aggressive tendencies were significant only in the subgroup of patients with an early onset of alcoholism. They were not significant in the rest of the population. Our data are compatible with the interpretation that patients with an early onset of alcoholism have a preexisting serotonin deficit that could manifest itself by an increased alcohol intake early in life and by an increased vulnerability to fluctuations in precursor availability.

Adult↗
PubMed1989

The intralobular distribution of ethanol-inducible P450IIE1 in rat and human liver.

Perivenular hepatocytes are the first cells within the liver lobule to display signs of toxicity following long-term alcohol use. In an attempt to explain this phenomenon, we have examined the hepatic intralobular distribution in rats and man of P450IIE1, a P-450 isozyme that not only oxidizes ethanol but is also inducible by this agent. Frozen liver sections and microsomes were prepared from male Sprague-Dawley rats pair-fed liquid diets containing 36% of total calories as either ethanol or carbohydrate (control) for 10 to 21 days. Frozen sections or microsomes were also prepared from liver biopsy samples obtained from 17 male patients with diverse drinking histories. Immunohistochemical staining was performed using the peroxidase-antiperoxidase method after liver sections were reacted with monospecific antibody (IgG) directed against human P450IIE1. Immunoreaction intensity was blindly rated in order to provide a semiquantitative assessment of P450IIE1 levels in perivenular, midzonal and periportal hepatocytes. At low applied anti-P450IIE1 IgG concentrations (2.5 micrograms per ml), P450IIE1 immunostaining was observed exclusively within the perivenular area in sections from all ethanol-treated rats, whereas no visible immunoreaction was found in sections from their pair-fed controls. At higher applied antibody concentrations (15 micrograms per ml), panlobular antigen immunostaining was observed in five of the six ethanol-treated animals, and P450IIE1 could now also be detected in perivenular hepatocytes from the control rats. In accordance with these immunohistochemical findings, protein blotting with anti-P450IIE1 IgG revealed a 7.5-fold increase in liver microsomal P450IIE1 content in ethanol-treated animals when compared to their pair-fed controls. With human liver, perivenular P450IIE1 immunostaining was observed only in biopsy sections obtained from recently drinking alcoholics (abstinence period of 1 day) when limiting concentrations (5 micrograms per ml) of the primary antibody were used. Increasing the applied anti-P450IIE1 IgG concentration to 15 micrograms per ml resulted in perivenular staining of the immunogen in liver sections from abstinent alcoholics (abstinence period of 4 to 8 days) and nondrinkers as well. Immunoblot analysis of human liver microsomes disclosed that the hepatic microsomal P450IIE1 content in recently drinking alcoholics was 4-fold higher than that found in nondrinkers. Our results show that, in both rats and in man, P450IIE1 is normally localized within the perivenular region, or zone 3, of the liver lobule, and that induction of P450IIE1 by prolonged alcohol consumption occurs primarily within the same acinar regi

Adult↗
PubMed1989

Experimental methods of ethanol administration.

Techniques are reviewed for the experimental feeding of alcohol, including a liquid diet procedure invented 25 years ago. This technique results in much higher ethanol intake than with other approaches. As a consequence, various complications observed in alcoholics can be reproduced in animal models. These include fatty liver, hyperlipemia, various metabolic and endocrine disorders, tolerance to ethanol and other drugs, physical dependence and withdrawal and, in the baboon, liver fibrosis and cirrhosis. Variations of the liquid diet formulation are compared, and adequacy of nutrition in terms of minerals, vitamins, lipotropes, carbohydrates and proteins is discussed. The importance of selecting proper controls is emphasized. The respective advantages of three standardized basic rat formulas are reviewed: (i) an all-purpose (35% fat) diet, comparable to the diet previously referred to as the "Lieber-DeCarli formula" and suitable for most experimental applications, particularly those intended to mimic the clinical situation in which the various effects of alcohol occur in the setting of hepatic changes characterized by a fatty liver; (ii) a low-fat diet comparable in all respects to the preceding diet but with a lower fat content, intended to minimize the hepatic changes, and (iii) a high-protein formula particularly useful in those circumstances in which an oversupply of dietary protein might be recommended (i.e. pregnancy). Variations of this technique, including continuous intragastric infusion, are also discussed. It is concluded that, for most experimental studies of chronic alcohol consumption, the liquid diet technique provides one of the most efficient tools to study the effects of ethanol under controlled nutritional conditions because it allows for alcohol consumption of clinical relevance and offers flexibility to adjust to special experimental or physiologic needs by allowing for various substitutions required for a particular experimental design, including changes in lipids, proteins or other dietary constituents. The technique also facilitates the comparison with controls by simplifying the pair feeding and is the best procedure available for the study of the toxic effects of alcohol and their interactions with deficiency or excess of various nutrients.

Administration, Inhalation↗
PubMed1989

Lipid peroxidation and antioxidant defense systems in rat liver after chronic ethanol feeding.

The effects of chronic ethanol feeding on hepatic lipid peroxidation, ascorbic acid, glutathione and vitamin E levels were investigated in rats fed low or adequate amounts of dietary vitamin E. Hepatic lipid peroxidation was significantly increased after chronic ethanol feeding in rats receiving a low-vitamin E diet, indicating that dietary vitamin E is an important determinant of hepatic lipid peroxidation induced by chronic ethanol feeding. No significant change was observed in hepatic non-heme iron content, but hepatic content of ascorbic acid and glutathione was increased by ethanol feeding. Both low dietary vitamin E and ethanol feeding significantly reduced hepatic alpha-tocopherol content, and the lowest hepatic alpha-tocopherol was found in rats receiving a combination of low vitamin E and ethanol. Plasma alpha-tocopherol was elevated after ethanol feeding, probably because of the associated hyperlipemia. Both the ratio of plasma alpha-tocopherol/plasma lipid and the red blood cell alpha-tocopherol were reduced by ethanol feeding. Furthermore, ethanol feeding caused a marked increase of hepatic alpha-tocopheryl quinone, a metabolite of alpha-tocopherol by free radical reactions. Ethanol feeding caused little changes of alpha-tocopherol and alpha-tocopheryl quinone content in mitochondria, whereas a striking increase in alpha-tocopheryl quinone was observed in microsomes. These data suggest that ethanol feeding causes a marked alteration of vitamin E metabolism in the liver and that the combination of ethanol with a low-vitamin E intake results in a decrease of hepatic alpha-tocopherol content which renders the liver more susceptible to free radical attack.

Animals↗
PubMed1989

High levels of acetaldehyde in nonalcoholic liver injury after threonine or ethanol administration.

Acetaldehyde, a product of ethanol oxidation which forms adducts with proteins, has been incriminated in the pathogenesis of alcoholic liver injury. High serum antibody titers against acetaldehyde-protein adducts have been found not only in alcoholics but also in patients with nonalcoholic liver disease, suggesting a contribution of acetaldehyde derived from sources other than exogenous ethanol. To investigate the effect of liver injury on the removal and the production of acetaldehyde, we produced fibrosis and cirrhosis (by chronic administration of carbon tetrachloride) and fatty liver (with very small doses of dimethylnitrosamine) in rats. Endogenous blood acetaldehyde levels increased by 38% in rats with severe liver injury (p less than 0.005), but not significantly in rats with fatty liver. However, an i.v. load of threonine (a physiological source of acetaldehyde), in amounts equivalent to the daily intake of this amino acid, increased blood and hepatic acetaldehyde levels in the rats with both types of liver injury more than in controls. Threonine dehydrogenase and dehydratase activities, involved in the major pathways for threonine degradation in mitochondria and cytosol, respectively, were markedly decreased in rats with liver injury with a resulting increase in hepatic threonine concentration. Moreover, the threonine aldolase activity, which splits threonine into glycine and acetaldehyde, remained unaffected or even slightly increased. Liver injury was also associated with impaired mitochondrial functions, including a 10 to 23% decrease in acetaldehyde oxidation (depending upon the severity of the lesions). As a consequence, administration of ethanol (an exogenous source of acetaldehyde) resulted in striking elevations in the levels of acetaldehyde in carbon tetrachloride-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1989

Acetaminophen activation by human liver cytochromes P450IIE1 and P450IA2.

Acetaminophen (APAP), a widely used over-the-counter analgesic, is known to cause hepatotoxicity when ingested in large quantities in both animals and man, especially when administered after chronic ethanol consumption. Hepatotoxicity stems from APAP activation by microsomal P450 monooxygenases to a reactive metabolite that binds to tissue macromolecules, thereby initiating cellular necrosis. Alcohol consumption also causes the induction of P450IIE1, a liver microsomal enzyme that in reconstitution studies has proven to be an effective catalyst of APAP oxidation. Thus, elevated microsomal P450IIE1 levels could explain not only the known increase in APAP bioactivating activity of liver microsomes after prolonged ethanol ingestion but also the enhanced susceptibility to APAP toxicity. We therefore examined the role of P450IIE1 in human liver microsomal APAP activation. Liver microsomes from seven non-alcoholic subjects were found to convert 1 mM APAP to a reactive intermediate (detected as an APAP-cysteine conjugate by high-pressure liquid chromatography) at a rate of 0.25 +/- 0.1 nmol conjugate formed/min/nmol microsomal P450 (mean +/- SD), whereas at 10 mM, this rate increased to 0.73 +/- 0.2 nmol product/min/nmol P450. In a reconstituted system, purified human liver P450IIE1 catalyzed APAP activation at rates threefold higher than those obtained with microsomes whereas two other human P450s, P450IIC8 and P450IIC9, exhibited negligible APAP-oxidizing activity. Monospecific antibodies (IgG) directed against human P450IIE1 inhibited APAP activation in each of the human samples, with anti-P450IIE1 IgG-mediated inhibition averaging 52% (range = 30-78%) of the rates determined in the presence of control IgG. The ability of anti-P450IIE1 IgG to inhibit only one-half of the total APAP activation by microsomes suggests, however, that other P450 isozymes besides P450IIE1 contribute to bioactivation of this compound in human liver. Of the other purified P450 isozymes examined, a beta-naphthoflavone (BNF)-inducible hamster liver P450 promoted APAP activation at rates even higher than those obtained with human P450IIE1. The extensive APAP-oxidizing capacity of this hamster P450, designated P450IA2 based upon its similarity to rat P450d and rabbit form 4 in terms of NH2-terminal amino acid sequence, spectral characteristics, immunochemical properties, and inducibility by BNF, agrees with previous reports concerning the APAP substrate specificity of the rat and rabbit P450IA2 proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetaminophen↗
PubMed1989

Effects of cimetidine on gastric alcohol dehydrogenase activity and blood ethanol levels.

Chronic use of cimetidine and alcohol are commonly associated, but studies on their interactions are the subject of controversy. To investigate this question, a small ethanol dose (0.15 g/kg body wt) was randomly administered on 2 consecutive days either orally or intravenously to 6 normal volunteers, before and after 1 wk of oral administration of 400 mg of cimetidine twice daily. Although cimetidine did not change the areas under the curve of blood ethanol concentrations after intravenous administration, those after oral alcohol intake were twice as large with cimetidine than without. Similar effects were reproduced in rats after intravenous administration of cimetidine (50 mg/kg body wt). In vitro, cimetidine was a noncompetitive inhibitor of gastric alcohol dehydrogenase activity at concentrations as low as 0.01 mM, 100-fold lower than those needed to inhibit the hepatic dehydrogenase. These results indicate that gastric alcohol dehydrogenase activity governs, in part, the systemic bioavailability of ethanol. Consequently, systemic effects of alcohol may be exacerbated in patients receiving cimetidine.

Adult↗
PubMed1989

Gastric origin of the first-pass metabolism of ethanol in humans: effect of gastrectomy.

The areas under the curve (AUCs) of blood ethanol concentrations are much smaller after oral than after intravenous administration of a small dose of ethanol. To study whether this difference is due to ethanol oxidation in the stomach, in the small intestine, or during first pass through the liver, we compared the AUCs after random administration of the same ethanol dose by the intravenous, oral, and intraduodenal routes to 5 abstaining alcoholics and via the two former routes to 10 subjects with Billroth II subtotal gastrectomy. In the nonoperated subjects, the AUCs after an ethanol dose (0.15 g/kg) given orally were 17% (p less than 0.01) of those achieved intravenously, in spite of the fact that greater than 99% of the dose had disappeared from the stomach at the completion of the AUC. By contrast, the AUCs after intraduodenal administration did not differ from those produced intravenously, indicating that neither the intestine nor the liver make a detectable contribution to this first-pass metabolism. Moreover, gastrectomy completely abolished the first-pass metabolism of ethanol. Gastric metabolism decreases the bioavailability of the ingested alcohol and thus attenuates its systemic toxicity. The abolition of this "protective barrier" in gastrectomized patients may increase their vulnerability to ethanol.

Ethanol↗
PubMed1989

Role of vitamin A degradation in the control of hepatic levels in the rat.

The relationship between excess vitamin A intake and accumulation in various tissues, including the liver, was studied in rats fed for 45 d four levels of vitamin A: 1, 6, 30 and 100 IU/kcal. As vitamin A intake increased, progressively smaller fractions of the administered vitamin A were recovered in tissue. The decrease in fractional recovery in the tissues examined was calculated from the differences between intake, tissue level and excretion, and was found to increase after administration of high vitamin A diets. This could be explained, at least in part, on the basis of an enhanced rate of vitamin A degradation as a function of the increased concentration of retinol in the liver. At high tissue retinol concentrations, calculated rates of retinol metabolism via the hepatic cytosolic retinol dehydrogenase (EC 1.1.1.1) and the recently discovered microsomal retinol dehydrogenase and oxidase vastly exceeded the decrease in fractional recovery of vitamin A accumulation in the tissues. This calculated rise in metabolic rate was verified by a corresponding increase in urinary polar metabolites derived from labeled retinol. Thus, accelerated catabolism as a function of increased hepatic vitamin A concentration may provide a homeostatic mechanism which offsets in part excessive vitamin A accumulation.

Administration, Oral↗
PubMed1989

Effects of mineral and vitamin supplementation on the alcohol-induced fatty liver and microsomal induction.

In rats fed ethanol (36% of total energy) for 1 month as part of a standard liquid diet, significant increases in hepatic lipids, microsomal cytochrome P-450, and in the activity of the microsomal ethanol oxidizing system were observed. Similar effects were noted in another group of animals treated with the same ethanol-containing diet, except that the content of minerals and vitamins was increased by 50%. Body weight gains were also comparable in these groups. It is concluded that these effects of ethanol are not due to vitamin and mineral deficiency secondary to decreased food intake but rather can be attributed to ethanol itself.

Alcohol Oxidoreductases↗
PubMed1989

Effects of chronic ethanol consumption on carcinogen activating and detoxifying systems in rat upper alimentary tract tissue.

The effect of chronic ethanol consumption on enzyme systems directly involved in carcinogen activation and detoxification were studied in rat upper alimentary tract tissue. Microsomal cytochrome P-450 (P-450) levels and glutathione levels as well as glutathione transferase and UDP-glucuronic acid transferase (UDPGT) activities were measured in mucosa scraped from esophagus, forestomach and glandular stomach of rats which had been pair-fed ethanol or dextrimaltose-containing diets. Esophageal and forestomach P-450 levels were increased in the ethanol-fed rats. The ethanol diet also produced a small but significant increase in esophageal glutathione transferase levels. Glutathione levels and UDPGT activity were unaffected. Since P-450 is directly involved in the activation of many chemical carcinogens, these results are consistent with the hypothesis that the increase in upper alimentary tract cancer risk associated with alcohol abuse is due, at least in part, to ethanol's altering the balance between carcinogen activation and detoxification.

Alcohol Drinking↗
PubMed1989

Characterization of the increased binding of acetaldehyde to red blood cells in alcoholics.

Using equilibrium dialysis, we found that acetaldehyde, at the levels commonly occurring after ethanol ingestion, did not bind detectably to plasma proteins, but there was significant binding to red blood cells, more in alcoholics than in nonalcoholics. The binding to red blood cells was inhibited by pyridoxal phosphate and N-ethylmaleimide, suggesting adduction to amino and thiol groups. Binding kinetics were consistent with at least two sites. The one with the highest affinity for acetaldehyde corresponded to hemoglobin. Its affinity and Bmax were not changed in alcoholics, but these binding sites accounted for only 44% of the sites available in the red blood cells of alcoholics and 80% of those in controls. Moreover, this binding was not inhibited by N-ethylmaleimide. There was no detectable binding to red cell ghosts. Nonprotein binding was then assessed by changes in NADH produced by the addition of protein-free fractions of the cells to an alcohol dehydrogenase system in equilibrium; this revealed a second binder of lower affinity, larger capacity and with sensitivity to both inhibitors. This binding (possibly due to thiazolidine formation with cysteine) was enhanced in alcoholics, whose red blood cell cysteine content was doubled. Levels of red blood cell cysteine and acetaldehyde remained high for 2 weeks after withdrawal. Because of the prolonged persistence after withdrawal, these changes may provide new markers of alcoholism.

Acetaldehyde↗
PubMed1989

Impaired oxygen utilization. A new mechanism for the hepatotoxicity of ethanol in sub-human primates.

The role of oxygenation in the pathogenesis of alcoholic liver injury was investigated in six baboons fed alcohol chronically and in six pair-fed controls. All animals fed alcohol developed fatty liver with, in addition, fibrosis in three. No evidence for hypoxia was found, both in the basal state and after ethanol at moderate (30 mM) or high (55 mM) levels, as shown by unchanged or even increased hepatic venous partial pressure of O2 and O2 saturation of hemoglobin in the tissue. In controls, ethanol administration resulted in enhanced O2 consumption (offset by a commitant increase in splanchnic blood flow), whereas in alcohol fed animals, there was no increase. At the moderate ethanol dose, the flow-independent O2 extraction, measured by reflectance spectroscopy on the liver surface, tended to increase in control animals only, whereas a significant decrease was observed after the high ethanol dose in the alcohol-treated baboons. This was associated with a marked shift in the mitochondrial redox level in the alcohol-fed (but not in control) baboons, with striking rises in splanchnic output of glutamic dehydrogenase and acetaldehyde, reflecting mitochondrial injury. Increased acetaldehyde, in turn, may aggravate the mitochondrial damage and exacerbate defective O2 utilization. Thus impaired O2 consumption rather than lack of O2 supply characterizes liver injury produced by high ethanol levels in baboons fed alcohol chronically.

Acetaldehyde↗
PubMed1989

Liquid diet technique of ethanol administration: 1989 update.

A technique of feeding alcohol as part of a liquid diet is reviewed that achieves an alcohol consumption of clinical relevance, while maintaining dietary control and providing adequate nutrition. With this procedure, blood alcohol levels are obtained which mimic clinical conditions and allow experimental duplications of many pathological complications caused by alcohol. In the rat, the liquid diet technique provides a model for the alcoholic fatty liver, various alcohol-induced metabolic, endocrine and central nervous system abnormalities (including tolerance and dependence) and the interaction of ethanol with industrial solvents, many commonly used drugs, analgesics, carcinogens and nutrients. This technique also resulted in the discovery of a new pathway of ethanol metabolism in the microsomes involving an ethanol-specific cytochrome P-450 (P450IIE1), which has now been confirmed in man. P450IIE1 contributes not only to the metabolic tolerance to ethanol, but also explains the enhanced susceptibility of the alcoholic to many ubiquitous xenobiotic agents. The liquid diet technique provides the flexibility to adjust to special experimental or physiological needs by allowing for various substitutions including changes in lipids, proteins or other dietary constituents. This procedure is thereby ideally suited for the study of the interactions of alcohol with deficiency or excess of various nutrients. The technique also facilitates the comparison with controls by simplifying pair feeding procedures. Although the flexibility of the liquid diet technique is one of its key advantages, a standard 'all purpose' liquid diet is described which is appropriate for most experimental applications. In addition, two other general formulae are given, namely a low fat diet (that allows the study of the effects of ethanol in the presence of minimal hepatic lipid accumulation) and a high protein diet (to meet increased needs, e.g. during pregnancy and lactation). The optimal amount of ethanol for the rat liquid diet was found to be 5 g/dl or 36% of total energy. With lesser amounts of alcohol, intake falls below a critical threshold; blood levels of alcohol then become negligible and the model becomes irrelevant to clinical conditions. In the rat, amounts of ethanol above 5 g/dl were not found to be associated with any further gain in alcohol ingestion. By contrast, in the baboon, the ethanol content could be raised profitably to 7 g/dl or 50% of total energy and resulted in the development of cirrhosis. This higher alcohol intake, together with species difference, may explain the greater severity of liver lesions produced by alcohol in the baboon.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohol Drinking↗
PubMed1988

Acetaldehyde production and transfer by the perfused human placental cotyledon.

Fetal injury associated with maternal ethanol ingestion is a major cause of congenital anomalies and mental retardation. Studies with animals suggest that acetaldehyde, the primary hepatic oxidative metabolite of ethanol, may contribute to fetal damage. It is not known, however, whether acetaldehyde reaches the human fetus, either by placental production or transfer. Studies utilizing the perfused human placental cotyledon show that the human placenta oxidizes ethanol to acetaldehyde, releasing it into the fetal perfusate. Moreover, when acetaldehyde is present in the maternal perfusate, it is transferred to the fetal side, reaching approximately 50 percent of the maternal level. These findings suggest that the human placenta may play a pivotal role in the pathophysiology of ethanol-associated fetal injury.

Acetaldehyde↗
PubMed1988

Formation of acetaldehyde adducts with ethanol-inducible P450IIE1 in vivo.

Hepatic microsomes, obtained from rats pair-fed liquid diets supplemented with either ethanol or an isocaloric amount of carbohydrates (for 4 weeks), were subjected to crossed immunoelectrophoresis. Anti-acetaldehyde adduct-specific immunoglobulin reacted on the protein blots with a single major 52,000 dalton polypeptide. This same protein was recognized by antibodies specific for P450IIE1, an ethanol-inducible P450 isozyme. Furthermore, a single protein, also reactive with anti-P450IIE1 IgG, was isolated from liver microsomes of ethanol-fed rats by immunoaffinity chromatography on Sepharose-conjugated anti-acetaldehyde adduct IgG. These results indicate that P450IIE1 is a target protein for acetaldehyde binding in liver microsomes in vivo.

Acetaldehyde↗