Aldehyde dehydrogenases of the rat colon: comparison with other tissues of the alimentary tract and the liver

Intracolonic bacteria have previously been shown to produce substantial amounts of acetaldehyde during ethanol oxidation, and it has been suggested that this acetaldehyde might be associated with alcohol-related colonic disorders, as well as other alcohol-induced organ injuries. The capacity of colonic mucosa to remove this bacterial acetaldehyde by aldehyde dehydrogenase (ALDH) is, however, poorly known. We therefore measured ALDH activities and determined ALDH isoenzyme profiles from different subcellular fractions of rat colonic mucosa. For comparison, hepatic, gastric, and small intestinal samples were studied similarly. Alcohol dehydrogenase (ADH) activities were also measured from all of these tissues. Rat colonic mucosa was found to possess detectable amounts of ALDH activity with both micromolar and millimolar acetaldehyde concentrations and in all subcellular fractions. The ALDH activities of colonic mucosa were, however, generally low when compared with the liver and stomach, and they also tended to be lower than in small intestine. Mitochondrial low K(m) ALDH2 and cytosolic ALDH with low K(m) for acetaldehyde were expressed in the colonic mucosa, whereas some cytosolic high K(m) isoenzymes found in the small intestine and stomach were not detectable in colonic samples. Cytosolic ADH activity corresponded well to ALDH activity in different tissues: in colonic mucosa, it was approximately 6 times lower than in the liver and about one-half of gastric ADH activity. ALDH activity of the colonic mucosa should, thus, be sufficient for the removal of acetaldehyde produced by colonic mucosal ADH during ethanol oxidation. It may, however, be insufficient for the removal of the acetaldehyde produced by intracolonic bacteria. This may lead to the accumulation of acetaldehyde in the colon and colonic mucosa after ingestion of ethanol that might, at least after chronic heavy alcohol consumption, contribute to the development of alcohol-related colonic morbidity, diarrhea, and cancer.     

Genotypes of alcohol dehydrogenase and aldehyde dehydrogenase and their significance for alcohol sensitivity

Genotypes of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) loci were determined, using allele specific oligonucleotides. Gene frequencies of ADH2(1) and ADH2(2) were 0.29 and 0.71, respectively, in the Japanese control group. No significant difference was found in the ADH2 genotype between the patients and the control group. Gene frequency of ALDH2(1) and ALDH2(2) were 0.65 and 0.35 in the control group, while 0.93 and 0.07, respectively in the patient group. Most of the patients, 20 out of 23, were homozygous Caucasian type. All individuals with homozygous atypical ALDH2(2)/ALDH2(2) and most of those with heterozygous atypical ALDH2(1)/ALDH2(1) were alcohol flushers, while all of the usual ALDH2(1)/ALDH2(1) were nonflushers. The results indicate that Japanese with the atypical ALDH2(2) allele are at a much lower risk in developing alcoholic liver disease than those with usual ALDH2(1)/ALDH2(1), presumably due to their sensitivity to alcohol intoxication.     

Acute hepatotoxicity of acetaminophen in rats treated with ethanol plus isopentanol

Acetaminophen (APAP) hepatotoxicity was investigated in rats fed ethanol and isopentanol alone or in combination in a liquid diet for 7 days. Serum levels of aspartate aminotransferase (AST) and histological examination of liver slices were used to assess hepatotoxicity. At 7 hr after intragastric administration of 0.5 or 1.0 g APAP/kg, there was no significant increase in serum levels of AST in rats treated with APAP alone, or in rats pretreated with ethanol or isopentanol alone followed by APAP. There was mild central lobular congestion in the livers of rats pretreated with ethanol alone followed by APAP. In contrast, in rats pretreated with the combination of ethanol and isopentanol, administration of APAP caused a dramatic increase in serum levels of AST, along with marked central lobular necrosis, including steatosis and ischemic changes. Hepatic glutathione levels were decreased to 40-50% of control values in APAP-treated rats that had been pretreated with ethanol either alone or in combination with isopentanol. The serum concentrations of APAP were significantly lower in rats pretreated with the combination of ethanol and isopentanol followed by 1 g APAP/kg than in rats treated with APAP alone, suggesting a greater rate of APAP metabolism. We had reported previously that combined treatment of rats with ethanol and isopentanol resulted in additive to synergistic increases in CYP3A, with no further increases in CYP2E than that caused by ethanol alone. CYP3A may, therefore, be responsible for the increased APAP hepatotoxicity caused by the combined alcohol treatment.     

Effect of methylmercury on the ethanol elimination from the blood and the activity of alcohol dehydrogenase

In an attempt to assess the effects of methylmercury on ethanol metabolism, Sprague-Dawley rats were treated with a daily dose (10 mg/kg i.p.) of methylmercuric chloride for 2 consecutive days and given a test dose (0.4 g/kgi.v.) of ethanol 24 hr after the last treatment. Blood ethanol levels were measured using gaschromatography by the direct introduction of blood samples into the sample vaporizing apparatus attached to the chromatograph. While treatment with methylmercury elicited a slight retardation in the ethanol elimination from the blood during 30 to 90 min, methylmercury did not essentially alter ethanol metabolism. There was no significant change in hepatic alcohol dehydrogenase activity of methylmercury-treated rats. By contrast, the activity of alcohol dehydrogenase purified from liver or yeast was remarkably inhibited by methyl-mercury and the type of inhibition proved to be non-competitive. Moreover, the inhibited activity was reactivated easily by sulfhydryl agents. From these results, it is conceivable that methylmercury has little influence on ethanol metabolism in vivo because of its non-specific binding with sulfhydryl groups in the organism.     

Development and application of a physiologically based pharmacokinetic model for ethanol in the mouse

The purpose of the present study was to develop a physiologically based pharmacokinetic (PBPK) model in the mouse and to utilize it to evaluate the relative contribution, if any, of gastric alcohol dehydrogenase (ADH) to the bioavailability of ethanol. The PBPK model developed in Swiss Webster male mice accurately simulated blood and brain ethanol concentrations following an intraperitoneal administration of 0.82 and 3.2 g of ethanol/kg body weight. Application of the model illustrated that inclusion of gastric ADH into the model provided a less accurate fit to the experimental data, and therefore gastric ADH did not contribute to the overall disposition of an orally administered ethanol dose of 0.75 g/kg. Furthermore, the model also indicated that changes in percentage cardiac output to the liver had a minimal effect on the blood ethanol concentration (BEC) time curve. The results illustrate the validity of the PBPK model developed for ethanol and demonstrate that in the Swiss Webster male mouse the bioavailability of ethanol is minimally affected, if at all, by metabolism by gastric ADH.     

Synergistic increases in rat hepatic cytochrome P450s by ethanol and isopentanol

The purpose of this study was to determine if isopentanol alone or in combination with ethanol increased CYP2B1/2, CYP2E or CYP3A in the livers of rats. Increasing doses of isopentanol (0.5, 1, 2 or 3%) were administered in combination with 5.6% ethanol in the Lieber-DeCarli liquid diet for 7 days. Doses of 0.5 or 3% isopentanol were also administered alone. Isopentanol alone caused small increases in CYP2B1/2 and CYP3A. However, when isopentanol (2 or 3%) was combined with ethanol a synergistic increase in P4502B1/2 was observed. The combined alcohol treatment also resulted in a greater increase in immunoreactive CYP3A than either alcohol alone. Ethanol alone increased CYP2E 5-fold. Inclusion of isopentanol with ethanol resulted in either small or no additional increases in CYP2E. These results confirm our previous findings in cultured hepatocytes that when isopentanol is combined with ethanol, there is a synergistic increase in CYP2B1/2. Increases in CYP2B1/2, CYP2E and CYP3A protein moieties by ethanol, and by ethanol in combination with isopentanol, were associated with increases in their mRNAs. Blood isopentanol levels were 10-fold greater in rats administered 3% isopentanol in combination with ethanol compared to rats administered 3% isopentanol alone. From these results we suggest that isopentanol, a higher chain alcohol in alcoholic beverages, can contribute to increases in hepatic cytochrome P450 observed following consumption of alcoholic beverages.     

Polymorphism in ALDH2-genotype in Japanese men and the alcohol-blood pressure relationship

Aldehyde dehydrogenase with a low Michaelis constant (Km), ALDH2, is a major enzyme involved in the conversion of acetaldehyde, a toxic metabolite of ethanol, into acetic acid in the liver. Inherited deficiency of ALDH2 activity is found in half of Japanese, and is characterized by "Oriental flushing" after alcohol consumption. The aim of the present study is to evaluate the influence of the genetic polymorphism in alcohol metabolism on the sensitivity to the pressor effect of alcohol. Genotypes of ALDH2 were determined in 403 middle-aged Japanese men using genomic DNA extracted from white blood cells. Two hundred and forty-three (60%) of the subjects were shown to be homozygotes for the normal ALDH2 gene, 25 (6%) of the subjects were homozygotes for the mutant ALDH2 gene, and the remaining 135 (33%) were heterozygotes. None of the homozygotes for the mutant gene drank enough to show the pressor effect of alcohol. Elevations of blood pressure associated with increasing alcohol consumption or with elevations of serum gamma-glutamyl transpeptide (GTP) level were not different between the other two ALDH2-genotypes. It can be concluded that polymorphism in the ALDH2-genotype found in Japanese men does not affect the individual sensitivity to the pressor effect of alcohol.     

Interaction between the Adh and Odh loci in response to ethanol in Drosophila melanogaster

Six Drosophila melanogaster strains were constructed from two isofemale lines. The strains had four allele combinations at the alcohol dehydrogenase (Adh) and octanol dehydrogenase (Odh) loci, while all alpha-glycerophosphate dehydrogenase (alpha Gpdh), malate dehydrogenase (Mdh), and aldehyde oxidase (Aldox) alleles were identical. Second-instar and early and late third-instar larvae were exposed to different concentrations of ethanol (0, 5, and 7.5%) and 3 days later fresh weights and the activities of ADH, ODH, alpha GPDH, and MDH were measured. Activity differences were observed between the two Adh genotypes: ADHF allozyme had considerably higher activity than ADHS. Exogenous ethanol resulted in the highest increase in ADH activity in the second- and early third-instar stages. This ADH induction depended on the allele combination at the Adh and Odh loci; e.g., in the strain having the AdhS-OdhS allele combination, increased ADH activity was observed only after exposure to 7.5% ethanol. ODH activities differed according to the Odh genotypes, in that the ODHS allozyme had a higher activity than ODHF. ODH activities did not appreciably respond to different ethanol treatments. All six strains had identical alleles at the Mdh and alpha Gpdh loci, but nevertheless, the responses of these enzymes to ethanol depended on the allele combinations at the Adh and Odh loci. alpha GPDH activity followed that of ADH in all experiments. MDH activities were not influenced by exogenous ethanol in the strains homozygous for the AdhS allele. In AdhF strains, however, exposure to 7.5% ethanol resulted in a considerable decrease in MDH activity in the second-instar larvae. Correlations among the response variables showed that ODH activities were strongly associated with fresh weight and the activities of all other enzymes, except for ADH. ADH activity, however, showed a significant correlation only with alpha GPDH activity throughout the larval life. Both MDH and ODH activities were found to be in strong negative correlation with ADH activity in the second-instar larvae. At this most sensitive life stage, the metabolic response to ethanol is highly correlated.     

Gender differences in ethanol preference and ingestion in rats. The role of the gonadal steroid environment

An ethanol oral self administration paradigm showed the existence of gender differences in alcohol preference in rats: whereas males and females initiated alcohol drinking at similar rates, females maintained their preference for ethanol over a longer duration. Neonatal estrogenization of females, which effectively confers a male phenotype on a genetically female brain, resulted in patterns of drinking that were similar to those displayed by intact male rats, indicating that gender differences in alcohol drinking patterns may be, at least partially, accounted for by sexual differentiation of the brain. To test whether gonadal steroids also exert activational effects on ethanol-seeking behavior, we also examined the effects of gonadectomy alone, or in combination with gonadal steroid replacement therapy. Castration did not significantly alter ethanol consumption in males, although treatment of castrated rats with dihydrotestosterone resulted in a significant inhibition of this parameter. As compared with the situation in intact female rats, ethanol ingestion was significantly reduced in ovariectomized female rats receiving estradiol (E2) and in ovariectomized female rats receiving combined E2 and progesterone replacement therapy. However, neither ovariectomy nor progesterone replacement in ovariectomized rats resulted in ethanol drinking patterns that were different compared to those observed in intact female controls. Thus, dihydrotestosterone and E2, respectively, appear to exert modulatory influences on the male and female rats' preference for ethanol, but further investigations are necessary to determine to what extent these effects result from activational actions on the brain.     

Changes in hepatic enzyme activities related to ethanol metabolism in mice following chronic ethanol administration

Male mice of three strains, C57BL, DBA and C3H/He, were fed on commercial food with 10% (v/v) ethanol solution as drinking liquid ad libitum for eighty days, and the changes in the activities of enzymes in the metabolic pathway of ethanol in the liver were examined. C57BL and C3H/He mice showed a preference for drinking the 10% (v/v) ethanol solution, while DBA mice did not. The ethanol intake g/g of body weight of C3H/He mice showed the highest value among all three strains and that of C57BL mice tended to show higher value than that of DBA mice. The liver weights of C57BL and C3H/He mice increased significantly following chronic ethanol administration, but that of DBA did not. The cytosolic enzyme alcohol dehydrogenase (ADH) showed no changes in any of the strains following chronic ethanol administration. The microsomal ethanol-oxidizing system (MEOS) of C57BL mice exhibited approximately 2-fold higher activity compared to that of DBA and C3H/He mice but did not increase in any strain following chronic ethanol administration. However, the microsomal aniline hydroxylase activity in the liver increased significantly in C57BL and C3H/He mice following chronic administration of ethanol. The microsomal cytochrome P-450 content also tended to slightly increase in the same strains of mice. It seemed that cytochrome P-450IIE1 was induced in the liver microsomes of these strains. Total aldehyde dehydrogenase (ALDH) activities together with high-Km ALDH activity increased markedly in the microsomes of C57BL mice and tended to increase in C3H/He mice, while it did not change in DBA mice following chronic ethanol administration. In the mitochondria of C57BL, total ALDH activities increased slightly and high-Km ALDH activities tended to increase. These mitochondrial ALDH activities of C3H/He and DBA mice tended to increase following chronic ethanol administration. The cytosolic ALDH activity showed no changes in any strain of mice following chronic ethanol administration. It seemed that in the microsomes, the activities of enzymes related to oxidation of ethanol increased in C57BL and C3H/He mice, which tended to consume a large amount of ethanol, and did not in DBA mice which tended to consume a small amount of it. It seemed that the increases in activities of enzymes related to oxidation of acetaldehyde in the microsomes and in the mitochondria were responsible for the strain difference.     

Alcohol metabolism in Asian-American men with genetic polymorphisms of aldehyde dehydrogenase

BACKGROUND: About half of certain Asians have a deficiency of the low-Km aldehyde dehydrogenase (ALDH2) isoenzyme. This deficiency results from inheritance of a mutant ALDH2*2 allele. OBJECTIVE: To determine whether Asian Americans with ALDH2*2 alleles differ from Asian Americans without this mutation in terms of blood levels of alcohol and acetaldehyde after ingestion of a moderate amount of alcohol. DESIGN: Double-blind, crossover study. SETTING: Private research institute. PARTICIPANTS: 35 healthy Asian-American men. Three men who became ill after alcohol ingestion and one who had outlying data were excluded. INTERVENTION: Alcoholic beverage, containing 0.56 g of alcohol per kg of body weight, or placebo beverage, containing 3 mL of alcohol, given orally on separate occasions. MEASUREMENTS: Blood levels of alcohol and acetaldehyde measured before and several times after ingestion of the alcoholic or placebo beverage. RESULTS: Participants with ALDH2*2 alleles had significantly higher blood acetaldehyde levels after ingesting alcoholic and placebo beverages than did participants with ALDH2*1 alleles, despite similar blood alcohol concentrations. CONCLUSIONS: Blood acetaldehyde levels rather than blood alcohol concentration may mediate enhanced alcohol sensitivity among Asians with ALDH2*2 alleles.     

MK-329 blocks the inhibition of alcohol intake by CCK-8

Peripheral administration of sulfated cholecystokinin octapeptide (CCK-8) potently reduces alcohol intake, preference, and blood levels in rats. MK-329 (L-364,718 or Devazepide) acts at peripheral cholecystokinin (CCKA) receptors to antagonize CCK-8's physiological and behavioral effects, such as pancreatic stimulation and inhibition of feeding. We determined whether CCKA receptor blockade would also prevent CCK-8's alcohol satiety effect. Water-deprived female and male rats (n = 7 for each) received randomized combinations of intraperitoneal injections of MK-329 (0, 100, 200, or 400 micrograms/kg) followed by CCK-8 (0 or 4 micrograms/kg). Rats were then given access to 5% w/v ethanol for 30 min, followed by 30-min access to water, with food ad lib. MK-329 at all doses significantly (p < 0.05) reduced the suppression of alcohol intake and food intake by CCK-8. MK-329 alone increased alcohol intake at 400 micrograms/kg, and increased food intake, in females and males at 100 and 200 micrograms/kg, respectively. We concluded that CCK-8's alcohol and food satiation effects depend on specific, peripheral CCKA receptors, and satiation of alcohol consumption and drinking-associated feeding reflect an endogenous functional interaction of CCK-8 with CCKA receptors.     

ALDH2, ADH1B and alcohol expectancies: Integrating genetic and learning perspectives.

The present study evaluated associations of ALDH2 and ADH1B genotypes with alcohol expectancies and drinking behavior in a sample of Asian American young adults. In addition to assessing global alcohol expectancies, the authors developed a measure of physiological expectancies to evaluate an expectancy phenotype specific to the mechanism by which ALDH2 and ADH1B variations presumably influence drinking behavior. Compared with individuals with the ALDH2*1/*1 genotype, those with the ALDH2*2 allele reported greater negative alcohol expectancies, greater expectancies for physiological effects of alcohol and lower rates of alcohol use. ADH1B was not associated with alcohol expectancies or drinking behavior. Hierarchical models showed that demographic factors, ALDH2 genotype, and expectancy variables explained unique variance in drinking outcomes. Mediation tests showed significant indirect effects of ALDH2 on drinking frequency and peak lifetime consumption through expectancies. These results provide support for influences of genetic factors and alcohol sensitivity on alcohol-related learning and suggest the importance of developing biopsychosocial models of drinking behavior in Asian Americans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ethanol consumption by rats is inversely related to hepatic alcohol dehydrogenase activity

Under normal circumstances the rate of hepatic ethanol oxidation and the rate at which ethanol is removed from the blood are dependent on the hepatic activity of alcohol dehydrogenase. It is possible that ethanol metabolism, and thus hepatic alcohol dehydrogenase, could influence ethanol consumption. In this study 11 adult female Wistar rats were provided with 20% ethanol as their sole drinking fluid and ethanol consumption was measured. After a further period of drinking tap water, the hepatic alcohol dehydrogenase activity was determined. A significant inverse relationship was found between the ethanol consumption by the rats and the hepatic activity of alcohol dehydrogenase (P < 0.05). This enzyme could therefore play a role in determining the amount of alcohol an animal will consume.     

Meta-analyses of ALDH2 and ADH1B with alcohol dependence in Asians.

Meta-analyses were conducted to determine the magnitude of relationships between polymorphisms in 2 genes, ALDH2 and ADH1B, with alcohol dependence in Asians. For each gene, possession of 1 variant *2 allele was protective against alcohol dependence, and possession of a 2nd *2 allele did not offer significant additional protection. The protective effects of these 2 gene polymorphisms were independent. Diagnostic criteria, recruitment strategy, and Japanese ethnicity moderated the effect of ALDH2*2. Recruitment strategy and gender moderated the effect of ADH1B*2. These findings highlight the importance of methodological issues and potential gene-gene and gene-environment interactions that must be considered when examining relationships between genetic polymorphisms and phenotypes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ALDH2 Status and Conduct Disorder Mediate the Relationship Between Ethnicity and Alcohol Dependence in Chinese, Korean, and White American College Students.

This study examined aldehyde dehydrogense (ALDH2) gene status, alcohol dehydrogense (ADH2) gene status, conduct disorder, and alcohol dependence in Chinese, Korean, and White American college students. Chinese had a lower rate of alcohol dependence (5%) than Koreans (13%) and Whites (17%). Koreans had a higher rate of conduct disorder (15%) than Whites (9%) and Chinese (6%). The relationship of ethnicity to alcohol dependence was mediated by ALDH2 status and conduct disorder, although Chinese ethnicity remained significant. ADH2 status was not related to alcohol dependence with ALDH2 included, and no interactions were significant. Results suggest that different rates of risk (e.g., conduct disorder) and protective (e.g., ALDH2 status) factors partially account for ethnic differences in rates of alcohol dependence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of phenobarbital and diazepam on imipramine-induced changes in blood pressure, heart rate and rectal temperature of rats

To investigate the safety of anticonvulsants in doses found equipotent in suppressing imipramine induced convulsions, the effects of diazepam (1.8 mg/kg) or phenobarbital (40 mg/kg) following a toxic dose of imipramine (50 mg/kg) on heart rate, blood pressure and body temperature were examined in male Wistar rats. Administration of imipramine alone resulted in significant decreases in blood pressure, heart rate and rectal temperature. Phenobarbital or diazepam alone failed to significantly affect any of these parameters apart from a slight reduction in rectal temperature seen with phenobarbital. Diazepam given after imipramine antagonized the imipramine-induced decrease in heart rate but increased the hypotensive and hypothermic effects. Phenobarbital failed to significantly affect the imipramine-induced changes in any of the physiological parameters studied. The present data suggests that phenobarbital may be preferable to diazepam in treatment of imipramine-induced convulsions.     

Effect of aniline on ethanol oxidation and carbohydrate metabolism in isolated hepatocytes

The addition of aniline to isolated hepatocytes derived from fasted rats and incubated with ethanol, caused a 30-60% decrease in the rate of ethanol oxidation. The degree of inhibition was dependent on aniline concentration, 5 mM causing near-maximal inhibition. Aniline reduced the activity of alcohol dehydrogenase in a noncompetitive manner, but had no effect on aldehyde dehydrogenase activity nor on reducing-equivalent transfer between the cytoplasm and mitochondria. The inhibition of alcohol dehydrogenase by aniline was associated with a decrease in the inhibitory effects of ethanol on glycolysis. Aniline, added to hepatocytes in the presence or absence of ethanol, inhibited gluconeogenesis from lactate and pyruvate, but not from sorbitol or fructose.     

Modulation of glycerol and ethanol yields during alcoholic fermentation in Saccharomyces cerevisiae strains overexpressed or disrupted for GPD1 encoding glycerol 3-phosphate dehydrogenase

The possibility of the diversion of carbon flux from ethanol towards glycerol in Saccharomyces cerevisiae during alcoholic fermentation was investigated. Variations in the glycerol 3-phosphate dehydrogenase (GPDH) level and similar trends for alcohol dehydrogenase (ADH), pyruvate decarboxylase and glycerol-3-phosphatase were found when low and high glycerol-forming wine yeast strains were compared. GPDH is thus a limiting enzyme for glycerol production. Wine yeast strains with modulated GPD1 (encoding one of the two GPDH isoenzymes) expression were constructed and characterized during fermentation on glucose-rich medium. Engineered strains fermented glucose with a strongly modified [glycerol] : [ethanol] ratio. gpd1delta mutants exhibited a 50% decrease in glycerol production and increased ethanol yield. Overexpression of GPD1 on synthetic must (200 g/l glucose) resulted in a substantial increase in glycerol production ( x 4) at the expense of ethanol. Acetaldehyde accumulated through the competitive regeneration of NADH via GPDH. Accumulation of by-products such as pyruvate, acetate, acetoin, 2,3 butane-diol and succinate was observed, with a marked increase in acetoin production.     

Ureteropyelostomy for obstructed duplicated ureter an easy and reliable operation in infants]

Combined effects of moxonidine and ethanol on ultrastructure of selected Wistar-Kyoto rat organs (kidney, liver, heart) were investigated. In cells of the animals, which received moxonidine alone, no morphological changes were found. In the group of rats which received alcohol, several typical submicroscopical changes were found, especially related to the mitochondria. After the combined administration of ethanol and moxonidine the pathological changes were bigger than those found in animals which received alcohol alone. Those changes were particularly significant in kidney and liver. The results might indicate that moxonidine increased cytotoxic activity of ethanol on several organs in rats.