Interaction between the functional polymorphisms of the alcohol-metabolism genes in protection against alcoholism.

The genes that encode the major enzymes of alcohol metabolism, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), exhibit functional polymorphism. The variant alleles ADH2*2 and ADH3*1, which encode high-activity ADH isoforms, and the ALDH2*2 allele, which encodes the low-activity form of ALDH2, protect against alcoholism in East Asians. To investigate possible interactions among these protective genes, we genotyped 340 alcoholic and 545 control Han Chinese living in Taiwan at the ADH2, ADH3, and ALDH2 loci. After the influence of ALDH2*2 was controlled for, multiple logistic regression analysis indicated that allelic variation at ADH3 exerts no significant effect on the risk of alcoholism. This can be accounted for by linkage disequlibrium between ADH3*1 and ADH2*2 ALDH2*2 homozygosity, regardless of the ADH2 genotypes, was fully protective against alcoholism; no individual showing such homozygosity was found among the alcoholics. Logistic regression analyses of the remaining six combinatorial genotypes of the polymorphic ADH2 and ALDH2 loci indicated that individuals carrying one or two copies of ADH2*2 and a single copy of ALDH2*2 had the lowest risk (ORs 0.04-0.05) for alcoholism, as compared with the ADH2*1/*1 and ALDH2*1/*1 genotype. The disease risk associated with the ADH2*2/*2-ALDH2*1/*1 genotype appeared to be about half of that associated with the ADH2*1/*2-ALDH2*1/*1 genotype. The results suggest that protection afforded by the ADH2*2 allele may be independent of that afforded by ALDH2*2.     

Alcohol and aldehyde dehydrogenase genotypes and drinking behavior of Chinese living in Shanghai

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), the principal enzymes responsible for oxidative metabolism of ethanol, exist in multiple, genetically determined molecular forms. Widely different kinetic properties in some of these isozymes account for the individual differences in alcohol sensitivity. In this study we used the polymerase chain reaction/restriction fragment length polymorphism method to determine the genotypes of the ADH2 and ALDH2 loci of alcoholic and nonalcoholic Chinese living in Shanghai. We also investigated the subjects' drinking patterns by means of semistructured interviews. The alcoholics had significantly lower frequencies of the ADH2² and ALDH2² alleles than did the nonalcoholics, suggesting the inhibitory effects of these alleles for the development of alcoholism. In the nonalcoholic subjects, ADH2² had little, if any, effect, despite the significant effect of the ALDH2² allele in decreasing the alcohol consumption of the individual. Taken together, these results fit the proposed hypothesis for the development of alcoholism, i.e., drinking behavior is greatly influenced by the individual's gentoypes of alcohol-metabolizing enzymes, and the risk of becoming alcoholic is proportionate with the ethanol consumption of the individual.     

Genotoxic effects of alcohol in human peripheral lymphocytes modulated by ADH1B and ALDH2 gene polymorphisms

Ethanol is almost totally broken down by oxidative metabolism in vivo. Ethanol per se is considered to be neither carcinogenic, mutagenic nor genotoxic. However, during the metabolic conversion of ethanol to acetaldehyde and acetate, the organism is exposed to both ethanol and acetaldehyde and therefore ethanol is suspected to be co-carcinogenic. The genetic polymorphisms of alcohol dehydrogenase-2 (ADH1B) and acetaldehyde dehydrogenase-2 (ALDH2) influence the metabolism of alcohol. The ADH1B*1/*1 genotype encodes the low-activity form of ADH1B, and ALDH2*1/*2 and ALDH2*2/*2 genotype encode inactive ALDH2. The aim of this study was to test the hypothesis that polymorphisms of the ADH1B and ALDH2 genes are significantly associated with genotoxicity induced by alcohol drinking, measured using the cytokinesis-block micronucleus (CBMN) assay, an established biomarker of genome instability, in peripheral blood lymphocytes of 286 healthy Japanese men. There was a significant trend for the mean micronuclei (MN) frequency in habitual or moderate drinkers without a smoking habit to increase as the numbers of the *1 allele in ADH1B increased (P=0.039 or P=0.029) and the *2 allele in ALDH2 increased (P=0.019 or P=0.037). A logistic regression analysis showed that the number of subjects with MN frequency levels more than median value of MN (3.0) was significantly higher in the subjects with the ADH1B*1 allele as adjusted estimates (OR 2.08, 95% C.I. 1.24-3.48), when the OR for the subjects with the ADH1B*2/*2 genotype was defined as 1.00. The number of subjects with MN frequency levels more than median value of MN was also significantly higher in the subjects with the ALDH2*2 allele as adjusted estimates (OR 1.79, 95% C.I. 1.04-3.11), when the OR for the subjects with the ALDH2*1/*1 genotype was defined as 1.00. The results of this study have identified important novel associations between ADH1B/ALDH2 polymorphisms and genotoxicity in alcohol drinkers.     

Polymorphisms of alcohol metabolizing enzyme and cytochrome P4502E1 genes in mongolian population

Although the genetic polymorphism of the alcohol-metabolizing enzymes was extensively studied at the molecular level by many investigators, the genetic polymorphism studies for ethanolmetabolizing enzymes in Mongolians are very rare. The present study was therefore performed to determine the genetic distribution of various forms of alcohol-metabolizing enzymes such as alcohol dehydrogenase 2 (ADH2, currently accepted nomenclature ADH1B), ADH3 (ADH1C), aldehyde dehydrogenase 2 (ALDH2) and cytochrome P4502E1 (CYP2E1) in 300 healthy Mongolian males. Genetic polymorphisms were determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) methods. The allele frequencies ofADH2 *1 andADH2 *2 were 0.24 and 0.76;ADH3 *1 andADH3 *2 were 0.92 and 0.08;ALDH2 *1 andALDH2 *2 were 0.96 and 0.04; andCYP2E1 *C andCYP2E1 *D were 0.15 and 0.85, respectively. Compared to the results reported by other investigators, the allele frequencies ofALDH2 *2 andCYP2E1 *C among Mongolian subjects were much lower than among East Asians (Korean, Japanese, and/or Han-Chinese), while those ofADH2 andADH3 were more similar. Interestingly, this study shows that the ineffectiveALDH2 gene (ALDH2*2 allele) among Mongolians is not as common as among East Asians.     

Allelic variation at alcohol metabolism genes (<Emphasis Type="Italic">ADH1B</Emphasis>,<Emphasis Type="Italic"> ADH1C</Emphasis>,<Emphasis Type="Italic"> ALDH2</Emphasis>) and alcohol dependence in an American Indian population

Enzymes encoded by two gene families, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), mediate alcohol metabolism in humans. Allelic variants have been identified that alter metabolic rates and influence risk for alcoholism. Specifically, ADH1B*47His (previously ADH2-2) and ALDH2-2 have been shown to confer protection against alcoholism, presumably through accumulation of acetaldehyde in the blood and a resultant 'flushing response' to alcohol consumption. In the current study, variants at ADH1B (previously ADH2), ADH1C (previously ADH3), and ALDH2 were assayed in DNA extracts from participants belonging to a Southwest American Indian tribe (n=490) with a high prevalence of alcoholism. Each subject underwent a clinical interview for diagnosis of alcohol dependence, as well as evaluation of intermediate phenotypes such as binge drinking and flushing response to alcohol consumption. Detailed haplotypes were constructed and tested against alcohol dependence and related intermediate phenotypes using both association and linkage analysis. ADH and ALDH variants were also assayed in three Asian and one African population (no clinical data) in order to provide an evolutionary context for the haplotype data. Both linkage and association analysis identified several ADH1C alleles and a neighboring microsatellite marker that affected risk of alcohol dependence and were also related to binge drinking. These data strengthen the support for ADH as a candidate locus for alcohol dependence and suggest further productive study.     

Genetic polymorphism of enzymes of alcohol metabolism and susceptibility to alcoholic liver disease

Differences in the pharmacokinetics of alcohol absorption and elimination are, in part, genetically determined. There are polymorphic variants of the two main enzymes responsible for ethanol oxidation in liver, alcohol dehydrogenase and aldehyde dehydrogenase. The frequency of occurrence of these variants, which have been shown to display strikingly different catalytic properties, differs among different racial populations. Since the activity of alcohol dehydrogenase in liver is a rate-limiting factor for ethanol metabolism in experimental animals, it is likely that the type and content of the polymorphic isoenzyme subunit encoded at ADH2, beta-subunit, and at ADH3, the gamma-subunit, are contributing factors to the genetic variability in ethanol elimination rate. The recent development of methods for genotyping individuals at these loci using white cell DNA will allow us to test this hypothesis as well as any relationship between ADH genotype and the susceptibility to alcoholism or alcohol-related pathology. A polymorphic variant of human liver mitochondrial aldehyde dehydrogenase, ADLH2, which has little or no acetaldehyde oxidizing activity has been identified. Individuals with the deficient ALDH2 phenotype do not have altered ethanol elimination rates but they do exhibit high blood acetaldehyde levels and dysphoric symptoms such as facial flushing, nausea and tachycardia, after drinking alcohol. Because acetaldehyde is so reactive, it binds to free amino groups of proteins including a 37 kilodalton hepatic protein-acetaldehyde adduct and may elicit an antibody response. We would predict that individuals who have low ALDH2 activity because of liver disease or because they have the inactive ALDH2 variant isoenzyme might form more protein-acetaldehyde adducts and elicit a greater immune response. These adducts may represent good biological markers of alcohol abuse and may also play a role in liver injury due to chronic alcohol consumption.     

Polymorphisms of ethanol-oxidizing enzymes in alcoholics with inactive ALDH2

Inactive aldehyde dehydrogenase-2 (ALDH2) is a well-known biological deterrent of heavy drinking among Asians, although some individuals who have inactive ALDH2 do become alcoholics. Unknown biological mechanisms facilitating the development of the disease may operate in such a way that these individuals overcome adverse reactions, or they may lower the intensity of the reactions. To examine our hypothesis that ethanol-oxidizing isoenzymes have lower catalytic properties in some persons, we investigated polymorphisms of ethanol-oxidizing enzymes that may alter their catalytic activities, viz., alcohol dehydrogenase-2 (ADH2) and –3 (ADH3), and cytochrome P450 2E1 (CYTP2E1), among 80 Japanese alcoholics with inactive ALDH2, 575 alcoholics with active ALDH2, and 461 controls. Although higher ADH2*1 and ADH3*2 allele frequencies were observed in alcoholics than in controls, there was no significant difference in ADH2 and ADH3 genotypes between alcoholics with inactive ALDH2 and alcoholics with active ALDH2. The genotype distributions of CYTP2E1 did not differ among the three groups, indicating no allelic association of the c1/c2 polymorphism of CYTP2E1 with alcoholism. These results suggest that genetic variations in ethanol-oxidizing activities are involved in the development of the disease, but that these variations are not specific in alcoholics with inactive ALDH2, a group at genetically low risk for alcoholism.     

Linkage disequilibrium at the ADH2 and ADH3 loci and risk of alcoholism

Two of the three class I alcohol dehydrogenase (ADH) genes (ADH2 and ADH3) encode known functional variants that act on alcohol with different efficiencies. Variants at both these genes have been implicated in alcoholism in some populations because allele frequencies differ between alcoholics and controls. Specifically, controls have higher frequencies of the variants with higher Vmax (ADH2*2 and ADH3*1). In samples both of alcoholics and of controls from three Taiwanese populations (Chinese, Ami, and Atayal) we found significant pairwise disequilibrium for all comparisons of the two functional polymorphisms and a third, presumably neutral, intronic polymorphism in ADH2. The class I ADH genes all lie within 80 kb on chromosome 4; thus, variants are not inherited independently, and haplotypes must be analyzed when evaluating the risk of alcoholism. In the Taiwanese Chinese we found that, only among those chromosomes containing the ADH3*1 variant (high Vmax), the proportions of chromosomes with ADH2*1 (low Vmax) and those with ADH2*2 (high Vmax) are significantly different between alcoholics and controls (P<10-5). The proportions of chromosomes with ADH3*1 and those with ADH3*2 are not significantly different between alcoholics and controls, on a constant ADH2 background (with ADH2*1, P=.83; with ADH2*2, P=.53). Thus, the observed differences in the frequency of the functional polymorphism at ADH3, between alcoholics and controls, can be accounted for by the disequilibrium with ADH2 in this population.     

Formation of acetaldehyde-derived DNA adducts due to alcohol exposure

Epidemiological studies have identified chronic alcohol consumption as a significant risk factor for cancers of the upper aerodigestive tract, including the oral cavity, pharynx, larynx and esophagus, and for cancer of the liver. Ingested ethanol is mainly oxidized by the enzymes alcohol dehydrogenase (ADH), cytochrome P-450 2E1 (CYP2E1), and catalase to form acetaldehyde, which is subsequently oxidized by aldehyde dehydrogenase 2 (ALDH2) to produce acetate. Polymorphisms of the genes which encode enzymes for ethanol metabolism affect the ethanol/acetaldehyde oxidizing capacity. ADH1B*2 allele (ADH1B, one of the enzyme in ADH family) is commonly observed in Asian population, has much higher enzymatic activity than ADH1B*1 allele. Otherwise, approximately 40% of Japanese have single nucleotide polymorphisms (SNPs) of the ALDH2 gene. The ALDH2 *2 allele encodes a protein with an amino acid change from glutamate to lysine (derived from the ALDH2*1 allele) and devoid of enzymatic activity. Neither the homozygote (ALDH2*2/*2) nor heterozygote (ALDH2*1/*2) is able to metabolize acetaldehyde promptly. Acetaldehyde is a genotoxic compound that reacts with DNA to form primarily a Schiff base N²-ethylidene-2′-deoxyguanosine (N²-ethylidene-dG) adduct, which may be converted by reducing agents to N²-ethyl-2′-deoxyguanosine (N²-ethyl-dG) in vivo, and strongly blocked translesion DNA synthesis. Several studies have demonstrated a relationship between ALDH2 genotypes and the development of certain types of cancer. On the other hand, the drinking of alcohol induces the expression of CYP2E1, resulting in an increase in reactive oxygen species (ROS) and oxidative DNA damage. This review covers the combined effects of alcohol and ALDH2 polymorphisms on cancer risk. Studies show that ALDH2*1/*2 heterozygotes who habitually consume alcohol have higher rates of cancer than ALDH2*1/*1 homozygotes. Moreover, they support that chronic alcohol consumption contributes to formation of various DNA adducts. Although some DNA adducts formation is demonstrated to be an initiation step of carcinogenesis, it is still unclear that whether these alcohol-related DNA adducts are true factors or initiators of cancer. Future studies are needed to better characterize and to validate the roles of these DNA adducts in human study.     

The Activity of Class I, II, III and IV of Alcohol Dehydrogenase (ADH) Isoenzymes and Aldehyde Dehydrogenase (ALDH) in Brain Cancer

The brain being highly sensitive to the action of alcohol is potentially susceptible to its carcinogenic effects. Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are the main enzymes involved in ethanol metabolism, which leads to the generation of carcinogenic acetaldehyde. Human brain tissue contains various ADH isoenzymes and possess also ALDH activity. The purpose of this study was to compare the capacity for ethanol metabolism measured by ADH isoenzymes and ALDH activity in cancer tissues and healthy brain cells. The samples were taken from 62 brain cancer patients (36 glioblastoma, 26 meningioma). For the measurement of the activity of class I and II ADH isoenzymes and ALDH activity, the fluorometric methods were used. The total ADH activity and activity of class III and IV isoenzymes were measured by the photometric method. The total activity of ADH, and activity of class I ADH were significantly higher in cancer cells than in healthy tissues. The other tested classes of ADH and ALDH did not show statistically significant differences of activity in cancer and in normal cells. Analysis of the enzymes activity did not show significant differences depending on the location of the tumor. The differences in the activity of total alcohol dehydrogenase, and class I isoenzyme between cancer tissues and healthy brain cells might be a factor for metabolic changes and disturbances in low mature cancer cells and additionally might be a reason for higher level of acetaldehyde which can intensify the carcinogenesis.     

The bifunctional Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2) protein is necessary for amebic growth and survival and requires an intact C-terminal domain for both alcohol dahydrogenase and acetaldehyde dehydrogenase activity

The intestinal protozoan pathogen Entamoeba histolytica lacks mitochondria and derives energy from the fermentation of glucose to ethanol with pyruvate, acetyl enzyme Co-A, and acetaldehyde as intermediates. A key enzyme in this pathway may be the 97-kDa bifunctional E. histolytica alcohol dehydrogenase 2 (EhADH2), which possesses both alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase activity (ALDH). EhADH2 appears to be a fusion protein, with separate N-terminal ALDH and C-terminal ADH domains. Here, we demonstrate that EhADH2 expression is required for E. histolytica growth and survival. We find that a mutant EhADH2 enzyme containing the C-terminal 453 amino acids of EhADH2 has ADH activity but lacks ALDH activity. However, a mutant consisting of the N-terminal half of EhADH2 possessed no ADH or ALDH activity. Alteration of a single histidine to arginine in the putative active site of the ADH domain eliminates both ADH and ALDH activity, and this mutant EhADH2 can serve as a dominant negative, eliminating both ADH and ALDH activity when co-expressed with wild-type EhADH2 in Escherichia coli. These data indicate that EhADH2 enzyme is required for E. histolytica growth and survival and that the C-terminal ADH domain of the enzyme functions as a separate entity. However, ALDH activity requires residues in both the N- and C-terminal halves of the molecule.     

Stomach and duodenal alcohol and aldehyde dehydrogenase isozymes in Chinese

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) isozyme phenotypes were determined in surgical and endoscopic biopsies of the stomach and duodenum by agarose isoelectric focusing. gamma-ADH was found to be the predominant form in the mucosal layer whereas beta-ADH was predominant in the muscular layer. Low-Km ALDH1 and ALDH2 were found in the stomach and duodenum. High-Km ALDH3 isozymes occurred only in the stomach but not in the duodenum. The isozyme patterns of gastric mucosal ALDH2 and ALDH3 remained unchanged in the fundus, corpus, and antrum. The stomach ALDH3 isozymes exhibited a Km value for acetaldehyde of 75 mM, and an optimum for acetaldehyde oxidation at pH 8.5. Since the Km value was high, ALDH3 contributed very little, if any, to gastric ethanol metabolism. The activities of ALDH in the gastric mucosa deficient in ALDH2 were 60-70% of that of the ALDH2-active phenotypes. These results indicate that Chinese lacking ALDH2 activity may have a lower acetaldehyde oxidation rate in the stomach during alcohol consumption.     

Alcohol and aldehyde dehydrogenase polymorphisms and risk for suicide: a preliminary observation in the Japanese male population

Epidemiological studies have shown that excessive alcohol consumption is a potent risk factor to develop suicidal behavior. Genetic factors for suicidal behavior have been observed in family, twin, and adoption studies. Because alcohol dehydrogenase (ADH1B) His47Arg and mitochondrial aldehyde dehydrogenase (ALDH2) Glu487Lys single nucleotide polymorphisms (SNPs), which affect alcohol metabolism, have been reported to exert significant impacts on alcohol consumption and on the risk for alcoholism in East Asia populations, we explored associations of the two functional SNPs with suicide using a case–control study of 283 completed suicides and 319 control subjects in the Japanese population. We found that the inactive ALDH2 allele (487Lys) was significantly less frequent in the completed suicides (19.3%) than in the controls (29.3%), especially in males, whereas this was not the case in females. The males bearing alcoholism‐susceptible homozygotes at both loci (inactive ADH1B Arg/Arg and active ALDH2 Glu/Glu genotypes) have a 10 times greater risk for suicide compared with the males bearing alcoholism‐protective homozygotes at both loci. Our data show the genetic impact of the two polymorphisms on suicidal behavior in the Japanese population, especially in males. Because we did not verify the daily alcohol consumption, the association of these SNPs with suicide might be due to alcoholism itself. Further studies using case–control subjects, which verifies the details of current and past alcohol consumption and diagnosis for alcoholism, are required to confirm these findings.     

Aldehyde dehydrogenase is essential for both adult and larval ethanol resistance in Drosophila melanogaster

The enzyme aldehyde dehydrogenase (ALDH) is essential for ethanol metabolism in mammals, converting the highly toxic intermediate acetaldehyde to acetate. The role of ALDH in Drosophila has been debated, with some authors arguing that, at least in larvae, acetaldehyde detoxification is carried out mainly by alcohol dehydrogenase (ADH), the enzyme responsible for converting ethanol to acetaldehyde. Here, we report the creation and characterization of four null mutants of Aldh, the putative structural locus for ALDH. Aldh null larvae and adults are poisoned by ethanol concentrations easily tolerated by wild-types; their ethanol sensitivity is in fact comparable to that of Adh nulls. The results refute the view that ALDH plays only a minor role in ethanol detoxification in larvae, and suggest that Aldh and Adh may be equally important players in the evolution of ethanol resistance in fruit-breeding Drosophila.     

Acetaldehyde as an underestimated risk factor for cancer development: role of genetics in ethanol metabolism

Chronic ethanol consumption is a strong risk factor for the development of certain types of cancer including those of the upper aerodigestive tract, the liver, the large intestine and the female breast. Multiple mechanisms are involved in alcohol-mediated carcinogenesis. Among those the action of acetaldehyde (AA), the first metabolite of ethanol oxidation is of particular interest. AA is toxic, mutagenic and carcinogenic in animal experiments. AA binds to DNA and forms carcinogenic adducts. Direct evidence of the role of AA in alcohol-associated carcinogenesis derived from genetic linkage studies in alcoholics. Polymorphisms or mutations of genes coding for AA generation or detoxifying enzymes resulting in elevated AA concentrations are associated with increased cancer risk. Approximately 40% of Japanese, Koreans or Chinese carry the AA dehydrogenase 2*2 (ALDH2*2) allele in its heterozygous form. This allele codes for an ALDH2 enzyme with little activity leading to high AA concentrations after the consumption of even small amounts of alcohol. When individuals with this allele consume ethanol chronically, a significant increased risk for upper alimentary tract and colorectal cancer is noted. In Caucasians, alcohol dehydrogenase 1C*1 (ADH1C*1) allele encodes for an ADH isoenzyme which produces 2.5 times more AA than the corresponding allele ADH1C*2. In studies with moderate to high alcohol intake, ADH1C*1 allele frequency and rate of homozygosity was found to be significantly associated with an increased risk for cancer of the upper aerodigestive tract, the liver, the colon and the female breast. These studies underline the important role of acetaldehyde in ethanol-mediated carcinogenesis.     

Sex differences, alcohol dehydrogenase, acetaldehyde burst, and aversion to ethanol in the rat: a systems perspective

Individuals who carry the most active alcohol dehydrogenase (ADH) isoforms are protected against alcoholism. This work addresses the mechanism by which a high ADH activity leads to low ethanol intake in animals. Male and female ethanol drinker rats (UChB) were allowed access to 10% ethanol for 1 h. Females showed 70% higher hepatic ADH activity and displayed 60% lower voluntary ethanol intake than males. Following ethanol administration (1 g/kg ip), females generated a transient blood acetaldehyde increase ("burst") with levels that were 2.5-fold greater than in males (P < 0.02). Castration of males led to 1) an increased ADH activity (+50%, P < 0.001), 2) the appearance of an acetaldehyde burst (3- to 4-fold vs. sham), and 3) a reduction of voluntary ethanol intake comparable with that of na?ve females. The ADH inhibitor 4-methylpyrazole blocked the appearance of arterial acetaldehyde and increased ethanol intake. Since the release of NADH from the ADH.NADH complex constitutes the rate-limiting step of ADH (but not of ALDH2) activity, endogenous NADH oxidizing substrates present at the time of ethanol intake may contribute to the acetaldehyde burst. Sodium pyruvate given at the time of ethanol administration led to an abrupt acetaldehyde burst and a greatly reduced voluntary ethanol intake. Overall, a transient surge of arterial acetaldehyde occurs upon ethanol administration due to 1) high ADH levels and 2) available metabolites that can oxidize hepatic NADH. The acetaldehyde burst is strongly associated with a marked reduction in ethanol intake.     

Alcohol Dehydrogenase-1B (rs1229984) and Aldehyde Dehydrogenase-2 (rs671) Genotypes Are Strong Determinants of the Serum Triglyceride and Cholesterol Levels of Japanese Alcoholic Men

Background

Elevated serum triglyceride (TG) and high-density-lipoprotein cholesterol (HDL-C) levels are common in drinkers. The fast-metabolizing alcohol dehydrogenase-1B encoded by the ADH1B*2 allele (vs. ADH1B*1/*1 genotype) and inactive aldehyde dehydrogenase-2 encoded by the ALDH2*2 allele (vs. ALDH2*1/*1 genotype) modify ethanol metabolism and are prevalent (≈90% and ≈40%, respectively) in East Asians. We attempted to evaluate the associations between the ADH1B and ALDH2 genotypes and lipid levels in alcoholics.

Methods

The population consisted of 1806 Japanese alcoholic men (≥40 years) who had undergone ADH1B and ALDH2 genotyping and whose serum TG, total cholesterol, and HDL-C levels in the fasting state had been measured within 3 days after admission.

Results

High serum levels of TG (≥150 mg/dl), HDL-C (>80 mg/dl), and low-density-lipoprotein cholesterol (LDL-C calculated by the Friedewald formula ≥140 mg/dl) were observed in 24.3%, 16.8%, and 15.6%, respectively, of the subjects. Diabetes, cirrhosis, smoking, and body mass index (BMI) affected the serum lipid levels. Multivariate analysis revealed that the presence of the ADH1B*2 allele and the active ALDH2*1/*1 genotype increased the odds ratio (OR; 95% confidence interval) for a high TG level (2.22 [1.67–2.94] and 1.39 [0.99–1.96], respectively), and decreased the OR for a high HDL-C level (0.37 [0.28–0.49] and 0.51 [0.37–0.69], respectively). The presence of the ADH1B*2 allele decreased the OR for a high LDL-C level (0.60 [0.45–0.80]). The ADH1B*2 plus ALDH2*1/*1 combination yielded the highest ORs for high TG levels and lowest OR for a high HDL-C level. The genotype effects were more prominent in relation to the higher levels of TG (≥220 mg/dl) and HDL-C (≥100 mg/dl).

Conclusions

The fast-metabolizing ADH1B and active ALDH2, and especially a combination of the two were strongly associated with higher serum TG levels and lower serum HDL-C levels of alcoholics. The fast-metabolizing ADH1B was associated with lower serum LDL-C levels.     

Dietary Ethanol Mediates Selection on Aldehyde Dehydrogenase Activity in Drosophila melanogaster

Ethanol is an important environmental variable for fruit-breedingDrosophila species, serving as a resource at low levels anda toxin at high levels. The first step of ethanol metabolism,the conversion of ethanol to acetaldehyde, is catalyzed primarilyby the enzyme alcohol dehydrogenase (ADH). The second step,the oxidation of acetaldehyde to acetate, has been a sourceof controversy, with some authors arguing that it is carriedout primarily by ADH itself, rather than a separate aldehydedehydrogenase (ALDH) as in mammals. We review recent evidencethat ALDH plays an important role in ethanol metabolism in Drosophila.In support of this view, we report that D. melanogaster populationsmaintained on ethanol-supplemented media evolved higher activityof ALDH, as well as of ADH. We have also tentatively identifiedthe structural gene responsible for the majority of ALDH activityin D. melanogaster. We hypothesize that variation in ALDH activitymay make an important contribution to the observed wide variationin ethanol tolerance within and among Drosophila species.     

Expression and localization of human alcohol and aldehyde dehydrogenase enzymes in skin.

Alcohol dehydrogenase (ADH; EC 1.1.1.1) and aldehyde dehydrogenase (ALDH; EC 1.2.1.3.) are important enzymes involved in the biotransformation of both alcohols and aldehydes. Today, six classes of ADH and twelve classes of ALDH have been defined in mammals. Here we report the detection and localisation of three classes of ADH and two classes of ALDH in human skin, using Western blot analysis and immunohistochemistry with class-specific antisera. Western blot analysis of human skin cytosol revealed that class I-III ADH and class 1 and class 3 ALDH enzymes are expressed, constitutively, in three different anatomical regions of human skin (foreskin, breast, abdomen). Densitometric analysis of the immunoreactive bands revealed differential constitutive expression of these enzymes in foreskin, breast, and abdomen skin. Immunohistochemistry showed the presence of class I ADH and class III ADH enzymes, predominantly in the epidermis with some localised expression in the dermal appendages of human skin. In comparison, staining for class II ADH was more faint in the epidermis with very little dermal expression. Class 1 ALDH and class 3 ALDH were predominantly localised to the epidermis with minimal, highly localised dermal appendageal expression. These cutaneous ADH and ALDH enzymes may play significant roles in the metabolism of endogenous or xenobiotic alcohols and aldehydes.     

Gene-environmental interactions between alcohol-drinking behavior and ALDH2 and CYP2E1 polymorphisms and their impact on micronuclei frequency in human lymphocytes

Ethanol is converted to acetaldehyde by alcohol dehydrogenase (ADH), cytochrome p4502E1 (CYP2E1) and catalase. This metabolite is then detoxified by aldehyde dehydrogenase 2 (ALDH2), a key enzyme in the elimination of acetaldehyde, via further oxidation to acetic acid. The toxic effects of acetaldehyde are well documented and may be partially mediated by genotoxic damage. In the present study, we investigated the effects of alcohol-drinking behavior and genetic polymorphisms in two different genes (ALDH2 and CYP2E1) on the micronuclei (MN) frequency in 248 healthy Japanese men. Genotyping was performed by PCR-RFLP analysis. The ALDH2 variant (deficient type) was significantly associated with an increased MN frequency in subjects drinking more than three times/wk, while habitual drinkers with wild-type CYP2E1 also had a significantly increased MN frequency. Furthermore, when the subjects were divided into eight groups according to their drinking frequency and genotypes of ALDH2 and CYP2E1, we found that habitual drinkers with homozygous CYP2E1*1/*1 and heterozygous ALDH2*1/*2 or homozygous ALDH2*2/*2 showed the highest mean MN frequency. In the present study, we found clear associations among ALDH2 and CYP2E1 gene polymorphisms, alcohol-drinking behavior and genotoxic effects in a healthy Japanese population. Therefore, analysis of the polymorphisms of alcohol-metabolizing enzymes may lead to elucidation of the mechanism(s) for individual susceptibilities to the toxicity of ethanol metabolites.