Mitochondrial aldehyde dehydrogenase polymorphism in Asian and American Indian populations: detection of new ALDH2 alleles

Validation of Alcohol Flushing Questionnaires in Determining Inactive Aldehyde Dehydrogenase-2 and Its Clinical Implication in Alcohol-Related Diseases

BACKGROUND

Our aim was to validate alcohol flushing questionnaires in detecting inactive ALDH2 (ALDH2*1/*2 or ALDH2*2/*2).

METHODS

Two study sets were established; in study set 1, 210 healthy male subjects (age 22 to 59 years) were enrolled; in study set 2, 756 subjects were enrolled who received esophagogastroduodenoscopy to evaluate their dyspeptic symptoms or as part of a gastric cancer screening program. Subjects in study sets 1 and 2 completed the modified alcohol flushing questionnaires of Yokoyama and colleagues (, ). Polymerase chain reaction-restriction fragment length polymorphism method was used to determine ALDH2 genotype.

RESULTS

In study set 1, 29.0% (61 of 210) had inactive ALDH2. The sensitivity and specificity of the modified alcohol flushing questionnaire for detecting inactive ALDH2 were 95.1 and 76.5%, respectively. Drinking problems negatively correlated with positive alcohol flushing response and inactive ALDH2 (all p-values < 0.05). In study set 2, the sensitivity and specificity of the alcohol flushing questionnaire for detecting inactive ALDH2 were 78.9 and 82.1%, respectively. Interestingly, drinking ≥7 units/wk in men or ≥3.5 units/wk in women significantly increased the risk of benign gastric ulcer (BGU) among positive alcohol flushers (odds ratio, 8.97; 95% confidence interval, 1.38 to 58.30), but not among negative alcohol flushers.

CONCLUSIONS

Simple flushing questionnaires may be administered to the Korean population as a screening tool in detecting individuals who carry inactive ALDH2. Alcohol flushing response negatively correlates with drinking problems and can modify the risk for BGU by alcohol intake.

Acetaldehyde production capacity of salivary microflora in alcoholics during early recovery

This study investigated whether a relationship exists between the acetaldehyde production capacity of salivary microflora (sAPC) in recovering alcoholics, and craving, and/or resumption of drinking within 12 weeks after embarking on an abstinence-based treatment program. Serial sAPC measurements were determined by gas chromatography on spontaneous saliva samples of 30 male alcoholics on days 2, 4, 11, and 18 during a 21-day in-patient treatment program. Craving was measured simultaneously with the Penn Alcohol Craving Scale. Outcome over 12 weeks was assessed by telephone interviews. There was no significant change in sAPC values from day 2 to day 18, while craving scores decreased markedly between day 2 to day 4. Sixteen participants remained abstinent for the full 12 weeks. Statistically significant differences were found between the sAPC values of the group that remained abstinent and the group that resumed drinking within 12 weeks. The highest sAPC value measured on day 2 had a strong predictive value for maintained abstinence at 12 weeks for beer-only drinkers or drinkers consuming less than 320 g of alcohol per week. The study is the first investigation into a potential relationship between the acetaldehyde production capacity of salivary microflora and early resumption of drinking in recovering alcoholics. The findings suggest that such a relationship indeed exists for beer-only drinkers, possibly linked to lower alcohol intake, and that it is unrelated to withdrawal craving. sAPC is proposed as a candidate biomarker with diagnostic and/or prognostic potential.

ADH and ALDH polymorphisms and alcohol dependence in Mexican and Native Americans

BACKGROUND

Ethanol is primarily metabolized in the liver by two rate-limiting reactions: conversion of ethanol to acetaldehyde by alcohol dehydrogenase (ADH) and subsequent conversion of acetaldehyde to acetate by aldehyde dehydrogenase (ALDH). ADH and ALDH exist in multiple isozymes that differ in their kinetic properties. Notably, polymorphisms within the genes that encode for these isozymes vary in their allele frequencies between ethnic groups, and thus, they have been considered as candidate genes that may differentially influence risk for the development of alcohol dependence across ethnic groups.

OBJECTIVES AND METHODS

Associations between alcohol dependence and polymorphisms in ADH1B, ADH1C, and ALDH2 were compared in a community sample of Native Americans (n 791) living on reservations and Mexican Americans (n 391) living within the same county.

RESULTS

Two Mexican Americans and no Native Americans possessed one ALDH2*2 allele. Presence of at least one ADH1B*2 allele was found in 7% of the Native Americans and 13% of the Mexican Americans, but was only associated with protection against alcohol dependence in the Mexican Americans. Presence of at least one ADH1B*3 allele was found in 4% of the Native Americans and 2% of the Mexican Americans, but was associated with protection against alcohol dependence only in the Native Americans. No associations between alcohol dependence and polymorphisms in ADH1C were found.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

Polymorphisms in ADH1B are protective against alcoholism in these two populations; however, these findings do not explain the high prevalence of alcoholism in these populations.

Cloning and molecular evolution of the aldehyde dehydrogenase 2 gene (Aldh2) in bats (Chiroptera)

Old World fruit bats (Pteropodidae) and New World fruit bats (Phyllostomidae) ingest significant quantities of ethanol while foraging. Mitochondrial aldehyde dehydrogenase (ALDH2, encoded by the Aldh2 gene) plays an important role in ethanol metabolism. To test whether the Aldh2 gene has undergone adaptive evolution in frugivorous and nectarivorous bats in relation to ethanol elimination, we sequenced part of the coding region of the gene (1,143 bp, ~73 % coverage) in 14 bat species, including three Old World fruit bats and two New World fruit bats. Our results showed that the Aldh2 coding sequences are highly conserved across all bat species we examined, and no evidence of positive selection was detected in the ancestral branches leading to Old World fruit bats and New World fruit bats. Further research is needed to determine whether other genes involved in ethanol metabolism have been the targets of positive selection in frugivorous and nectarivorous bats.

The impact of genetic variability on liver disease in the Hispanic/Latin-American population

Liver cirrhosis is within the top 10 causes of death in Latin-American countries and recent evidence suggests that Hispanics in the USA have a more aggressive course of many types of liver disease and show lower response to treatment of hepatitis C compared with other ethnic groups. Although environmental factors are very important, they do not appear to fully account for the observed ethnic differences in the incidence of cirrhosis and progression rates. Genome-wide association studies have been a powerful tool to identify genetic variants that directly confer susceptibility to liver disease. Here, we review the current knowledge on genetic variants associated with the most common types of liver disease that may contribute to ancestry-related differences in disease progression and mortality.

Association of the aldehyde dehydrogenase 2 promoter polymorphism with alcohol consumption and reactions in an American Jewish population

BACKGROUND

Reduction in activity of the mitochondrial aldehyde dehydrogenase 2 (ALDH2) enzyme due to genetic deficiency causes reactions related to alcohol consumption and lowers the risk of alcoholism. ALDH2*2 is the only functionally significant polymorphism of the ALDH2 gene. An additional polymorphic locus in the promoter (G to A substitution approximately 360 bp from the translation start site) may influence ALDH2 activity through effects on transcriptional activity. The A allele is predicted to be less active transcriptionally than the G allele. Therefore, we hypothesized that individuals with 1 or 2 A alleles would have exaggerated reactions to alcohol.

METHODS

Fifty-three Jewish college students from a Midwestern University and 76 Jewish individuals living in a large Midwestern city (all of Ashkenazi descent) were tested for associations between ALDH2*G and ALDH2*A alleles and self-reported alcohol consumption and responses to alcohol. Genotype determination was performed using PCR and slot-blot hybridization. As alcohol drinking behavior differed substantially between the college students and the general population, as well as between males and females, the analyses were performed separately in each group.

RESULTS

The frequency of the ALDH2*A allele was 0.87 in the 129 Jewish individuals tested. Among the general Jewish population, those who were homozygous for ALDH2*A drank fewer drinks per occasion than individuals who were not homozygous for the ALDH2*A allele, but did not drink significantly less frequently. When the other covariates (ADH1B genotype, gender, and population) were controlled for, there was a marginal association between ALDH2A genotype and quantity of alcohol consumed and the number of drinks consumed before feeling drowsy.

CONCLUSION

This study suggests that the ALDH2*A allele status may correlate with variations in alcohol consumption patterns among Jews, independent of the effect of ADH1B genotype.

Distribution of alcohol-metabolizing enzyme genotypes in trauma patients with excessive alcohol consumption in the emergency department

OBJECTIVES

The objective of this study was to investigate the distribution of genetic polymorphisms of alcohol-metabolizing enzymes in trauma patients with excessive alcohol consumption in the emergency department (ED).

DESIGN AND METHODS

A total of 100 trauma patients and age-matched control subjects composed of 98 participants were enrolled in this study. The activities of liver enzymes and genotypes of alcohol-metabolizing enzymes, including ADH2, ALDH2, and CYP2E1, were analyzed with the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

There was a significant difference in the allele frequencies of ALDH2 between the two groups. For the genotypes, there were significant differences in the genotype frequencies of ADH2 and ALDH2. There was also a significantly lower frequency in patients with the ALDH2*2 phenotype than those of the controls. For the activities of liver enzymes, there were significant differences between the two groups. For ADH2 and ALDH2, there were significantly higher ORs (odds ratios) in trauma patients with normal activity than those with weak or intermediate activity but there were no significant difference in CYP2E1 genotype between two groups. To investigate the interaction of alcohol-metabolizing enzyme genotypes, we have estimated the odds ratios in two alcohol-metabolizing pathways. The ORs of the combined genotypes of ADH2 (*1/*1+*1/*2) and ALDH2 (*1/*1) and the combined genotypes of either CYP2E1 (*c1/*c1) or CYP2E1 (*c1/*c2+*c2/*c2) and ALDH2 (*1/*1) were significantly higher than that of the reference group in the major and the minor pathway, respectively.

CONCLUSIONS

Genetic variation of alcohol-metabolizing enzymes, especially ALDH2, may play an important role on the occasions of alcohol problems in the emergency department.

Association of alcohol-metabolizing genes with alcoholism in a Mexican Indian (Otomi) population

Association studies provide a powerful approach to link DNA variants and genetic predisposition to complex diseases. In this study, we determined the genotype and allelic frequencies of genes encoding enzymes involved in alcohol metabolism in alcoholic and nonalcoholic subjects of related ethnicity. A total of 118 individuals of Otomi Mexican Indian ancestry were included. Fifty-nine were chronic alcoholics according to WHO criteria and alcohol dependents according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM IV) criteria. They were compared to 59 teetotalers or alcohol consumers of <10 g per day. The restriction fragment length polymorphisms analyzed were ADH1B/MaeIII, ALDH2/MboII, CYP2E1/DraI, CYP2E1/RsaI, and CYP2E1/TaqI. Of the studied polymorphisms, a significant difference between alcoholic and nonalcoholic Otomies was observed only in the CYP2E1/TaqI. The common genotype in alcoholics was A1/A2 (54%), and in nonalcoholics the homozygous A2/A2 (63%) (odds ratio [OR]: 0.28; 95% confidence interval [CI]: 0.13-0.60; P=.002). The frequency of the mutant allele A1 was significantly higher in alcoholics than in nonalcoholics (41 vs. 21%; OR: 2.4; 95% CI: 1.3-4.3; P=.003). This documents the presence of a polymorphism of CYP2E1 that is overexpressed in alcoholic Otomies, in which the variant allele (A1 of CYP2E1/TaqI) is associated with increased susceptibility to alcoholism. The appreciation that this finding may be an additional factor contributing to the high frequency of liver cirrhosis in Otomies requires further investigation.

Alcohol and cancer

A causal association has been established between alcohol consumption and cancers of the oral cavity, pharynx, larynx, oesophagus, liver, colon, rectum, and, in women, breast; an association is suspected for cancers of the pancreas and lung. Evidence suggests that the effect of alcohol is modulated by polymorphisms in genes encoding enzymes for ethanol metabolism (eg, alcohol dehydrogenases, aldehyde dehydrogenases, and cytochrome P450 2E1), folate metabolism, and DNA repair. The mechanisms by which alcohol consumption exerts its carcinogenic effect have not been defined fully, although plausible events include: a genotoxic effect of acetaldehyde, the main metabolite of ethanol; increased oestrogen concentration, which is important for breast carcinogenesis; a role as solvent for tobacco carcinogens; production of reactive oxygen species and nitrogen species; and changes in folate metabolism. Alcohol consumption is increasing in many countries and is an important cause of cancer worldwide.

Aldehyde dehydrogenase 2 activity affects symptoms produced by an intraperitoneal acetaldehyde injection, but not acetaldehyde lethality

Aldehyde dehydrogenase 2 (ALDH2) is an important enzyme that oxidizes acetaldehyde. Approximately 45% of Chinese and Japanese individuals are inactive ALDH2 phenotype; acute acetaldehyde toxicity has not been evaluated in these populations. We compared the acute acetaldehyde toxicity between wild-type (Aldh2+/+) and Aldh2-inactive transgenic (Aldh2-/-) mice who were administered an intraperitoneal (ip) injection of a single dose of acetaldehyde. This comparison was made based on the LD(50) values of acetaldehyde and the symptoms following the ip injection. Blood acetaldehyde level was measured in the 400 mg/kg dose group. Immediately after administration of acetaldehyde, the mice exhibited hypoactivity and staggering gait. Subsequently, symptoms such as pale skin, prone position, coma, and abnormal deep respiration were observed. In cases of death, dyspnea, wheezing, and hypothermia were observed from 15 to 30 min after the administration. In cases of survival, crouching, bradypnea, flushing and piloerection were observed. Significant latency of symptom recovery was found in the Aldh2+/- mice as compared with the Aldh2+/+ mice; however, no statistical difference was observed in the acetaldehyde LD(50) values. This might be attributable to the absence of a significant difference in the blood acetaldehyde concentrations in both mice during the first 0-15 min following administration; however, acetaldehyde elimination delay was observed in the Aldh2-/- mice as compared with the Aldh2+/+ mice. Acetaldehyde toxicity difference was observed between the Aldh2+/+ and Aldh2-/- mice; however, no difference in acetaldehyde lethality was observed by administration of a single dose of an ip acetaldehyde injection.

Paired acute inhalation test reveals that acetaldehyde toxicity is higher in aldehyde dehydrogenase 2 knockout mice than in wild-type mice

Aldehyde dehydrogenase 2 (ALDH2) is an important enzyme that oxidizes acetaldehyde. Approximately 45% of Chinese and Japanese individuals have the inactive ALDH2 genotypes (ALDH2*2/*2 and ALDH2*1/*2); acute inhalation toxicity of acetaldehyde has not been evaluated in these populations. We compared the toxicity between wild-type (Aldh2+/+) and Aldh2-inactive transgenic (Aldh2-/-) mice by using the paired acute inhalation test modified from the acute toxic class method (OECD TG433). Blood acetaldehyde level was measured 4 hr after the inhalation. A pair of Aldh2+/+ and Aldh2-/- mice was put into a chamber and was exposed to 5000 ppm of acetaldehyde. At the start of the inhalation, the mice exhibited hypoactivity and closing of the eyes. Subsequently, symptoms such as crouching, bradypnea, and piloerection were observed. Flushing was observed only in the Aldh2+/+ mice. Symptoms such as tears, straggling gait, prone position, pale skin, abnormal deep respiration, dyspnea, and one case of death were observed only in the Aldh2-/- mice. The symptoms did not change 1 hr after inhalation in the Aldh2+/+ mice. In contrast, in the Aldh2-/- mice, the symptoms became more severe until the end of the inhalation. The blood acetaldehyde level in the Aldh2-/- mice was approximately twice that in the Aldh2+/+ mice 4 hr after inhalation. The Aldh2-/- mice evidently showed more severe toxicity as compared with the Aldh2+/+ mice due to acute inhalation of acetaldehyde at a concentration of 5000 ppm. Acetaldehyde toxicity in Aldh2+/+ and Aldh2-/- mice was estimated and classified one class different. Based on this study, acetaldehyde inhalations were inferred to pose a higher risk to ALDH2-inactive human individuals.

The evolution and population genetics of the ALDH2 locus: random genetic drift, selection, and low levels of recombination

The catalytic deficiency of human aldehyde dehydrogenase 2 (ALDH2) is caused by a nucleotide substitution (G1510A; Glu487Lys) in exon 12 of the ALDH2 locus. This SNP, and four non-coding SNPs, including one in the promoter, span 40 kb of ALDH2; these and one downstream STRP have been tested in 37 worldwide populations. Only four major SNP-defined haplotypes account for almost all chromosomes in all populations. A fifth haplotype harbours the functional variant and is only found in East Asians. Though the SNPs showed virtually no historic recombination, LD values are quite variable because of varying haplotype frequencies, demonstrating that LD is a statistical abstraction and not a fundamental aspect of the genome, and is not a function solely of recombination. Among populations, different sets of tagging SNPs, sometimes not overlapping, can be required to identify the common haplotypes. Thus, solely because haplotype frequencies vary, there is no common minimum set of tagging SNPs globally applicable. The Fst values of the promoter region SNP and the functional SNP were about two S.D. above the mean for a reference distribution of 117 autosomal biallelic markers. These high Fst values may indicate selection has operated at these or very tightly linked sites.

Genetic polymorphism in ethanol metabolism: acetaldehyde contribution to alcohol abuse and alcoholism

Acetaldehyde, the first product of ethanol metabolism, has been speculated to be involved in many pharmacological and behavioral effects of ethanol. In particular, acetaldehyde has been suggested to contribute to alcohol abuse and alcoholism. In the present paper, we review current data on the role of acetaldehyde and ethanol metabolism in alcohol consumption and abuse. Ethanol metabolism involves several enzymes. Whereas alcohol dehydrogenase metabolizes the bulk of ethanol within the liver, other enzymes, such as cytochrome P4502E1 and catalase, also contributes to the production of acetaldehyde from ethanol oxidation. In turn, acetaldehyde is metabolized by the enzyme aldehyde dehydrogenase. In animal studies, acetaldehyde is mainly reinforcing particularly when injected directly into the brain. In humans, genetic polymorphisms of the enzymes alcohol dehydrogenase and aldehyde dehydrogenase are also associated with alcohol drinking habits and the incidence of alcohol abuse. From these human genetic studies, it has been concluded that blood acetaldehyde accumulation induces unpleasant effects that prevent further alcohol drinking. It is therefore speculated that acetaldehyde exerts opposite hedonic effects depending on the localization of its accumulation. In the periphery, acetaldehyde is primarily aversive, whereas brain acetaldehyde is mainly reinforcing. However, the peripheral effects of acetaldehyde might also be dependent upon its peak blood concentrations and its rate of accumulation, with a narrow range of blood acetaldehyde concentrations being reinforcing.

Allelic variation at alcohol metabolism genes ( ADH1B, ADH1C, ALDH2) 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.

Population distribution of aldehyde dehydrogenase-2 genetic polymorphism: implications for risk assessment

The role of genetic polymorphisms in modulating xenobiotic metabolism and susceptibility to cancer and other health effects has been suggested in numerous studies. However, risk assessments have generally not used this information to characterize population variability or adjust risks for susceptible subgroups. This paper focuses upon the aldehyde dehydrogenase-2 (ALDH2) system because it exemplifies the pivotal role genetic polymorphisms can play in determining enzyme function and susceptibility. Allelic variants in ALDH2 cause decreased ability to clear acetaldehyde and other aldehyde substrates, with homozygous variants (ALDH2*2/2) having no activity and heterozygotes (ALDH2*1/2) having intermediate activity relative to the predominant wild type (ALDH2*1/1). These polymorphisms are associated with increased buildup of acetaldehyde following ethanol ingestion and increased immediate symptoms (flushing syndrome) and long-term cancer risks. We have used Monte Carlo simulation to characterize the population distribution of ALDH2 allelic variants and inter-individual variability in aldehyde internal dose. The nonfunctional allele is rare in most populations, but is common in Asians such that 40% are heterozygotes and 5% are homozygote variants. The ratio of the 95th or 99th percentiles of the Asian population compared to the median of the U.S. population is 14- to 26-fold, a variability factor that is larger than the default pharmacokinetic uncertainty factor (3.2-fold) commonly used in risk assessment. Approaches are described for using ALDH2 population distributions in physiologically based pharmacokinetic-Monte Carlo refinements of risk assessments for xenobiotics which are metabolized to aldehyde intermediates (e.g., ethanol, toluene, ethylene glycol monomethyl ether).

Epidemiologic study of the association of low-Km mitochondrial acetaldehyde dehydrogenase genotypes with blood pressure level and the prevalence of hypertension in a general population

In Japanese and other Asians, the prevalence of genetically decreased mitochondrial aldehyde dehydrogenase (ALDH2) activity is higher than in Caucasians. The aim of this study was to elucidate the relation between ALDH2 genotypes and blood pressure levels or hypertension in Japanese. After obtaining informed consent for genetic analysis from 917 men and 1,478 women who lived in a mountainous farming region near Kyoto and who were free from cardiovascular disease and liver dysfunction, the authors identified the ALDH2 genotype in all subjects. Differences in blood pressure level among genotypes were then compared by analysis of covariance, and the relation between genotypes and hypertension was also analyzed by logistic regression analysis. The frequencies of genotypes *1/*1, *1/*2, and *2/*2 were 44.7%, 46.9% and 8.4% in men, and 50.1%, 43.2% and 6.8% in women, respectively. In men, systolic and diastolic blood pressures tended to decrease in the order of *1/*1>*1/*2>*2/*2. However, adjustment for confounding factors including alcohol consumption resulted in the disappearance of significance. Logistic regression analysis adjusted for the same confounding factors for men showed that the odds ratios (OR) of being hypertensive in the *2 allele to not having *2 allele were 0.67 (95% confidence interval (CI): 0.47-0.96). However, in the subgroup analyses, this relation was not observed in the group having a below-median level of alcohol consumption (OR = 0.92; 95% CI: 0.53-1.62) or in the group not taking antihypertensive agents (OR = 0.77; 95% CI: 0.52-1.15). Furthermore, we did not observe any relation between the ALDH2/*2 allele and hypertension in women (OR = 1.07; 95% CI: 0.80-1.42). The results suggest that there may be no causal relation between hypertension and the ALDH2 genotype per se, after excluding for some confounding factors, especially for alcohol drinking.

Chaperonin GroESL mediates the protein folding of human liver mitochondrial aldehyde dehydrogenase in Escherichia coli

An efficient bacterial expression system for the human mitochondrial aldehyde dehydrogenase (ALDH2) was developed using co-overexpression of heat shock chaperone gene GroESL. On the basis of the ALDH2 amino acid sequence and cDNA sequences a full-length cDNA encoding wild-type ALDH2 was cloned from a human liver library. A mutant-type ALDH2 (ALDH2(2)) was developed using site-directed mutagenesis of the ALDH2 cDNA and also cloned. Both types of ALDH2 cDNA were subcloned for expression in Escherichia coli (E. coli), recombinant ALDH2 and ALDH2(2) were successfully expressed as soluble active enzymes following co-expression with a second plasmid construct producing GroES and GroEL, E. coli chaperonin proteins. Purified wild-type ALDH2 and mutant ALDH2(2) had a K(m) for acetaldehyde of 0.65 and 25.73 microM, respectively. Co-expression of ALDH2 with ALDH2(2) in the presence of E. coli chaperonins produced a soluble enzyme with a K(m) for acetaldehyde of 8.79 microM, suggesting that the product was a heteromer. Mitochondrial matrix hsp60 and hsp10 chaperonins are then thought to act on imported ALDH2 and are essential for accurate protein folding and multisubunit formation. Protein-protein interactions between ALDH2s and various chaperones were investigated using the yeast two-hybrid system. The wild-type and mutant-type enzymes strongly interacted with each other and GroEL and ALDH2s also interacted but only weakly. Chaperone hsp10 also interacted with hsp60 and ALDH2(1) and ALDH2(2), but again the interactions were weak ones.

Genetic variation in aldehyde dehydrogenase 2 and the effect of alcohol consumption on cholesterol levels

Moderate drinkers with a defective alcohol dehydrogenase type 3 (ADH3) genotype have higher high-density lipoprotein (HDL) levels and a decreased risk of coronary artery disease (CAD). We examined the interaction between the aldehyde dehydrogenase type 2 (ALDH2), alcohol intake, and HDL levels in 826 men and 1295 women in a rural town in Japan. The ALDH2 genotype of each subject was determined by polymerase chain reaction (PCR) analysis. HDL was adjusted for the alcohol intake, age, body mass index, smoking status, total cholesterol, triglycerides and HbA1c levels. None of the subjects had a history or ECG suggestive of CAD. The proportions of ALDH2, *1/*1, *1/*2, and *2/*2 (defective homozygote) were 45.8, 46.0, and 8.2%, respectively, for men. Drinking more than two drinks daily was associated with lower HDL levels in men with the defective genotypes compared with men with a normal genotype (55.6+/-0.9 vs. 51.2+/-0.9 mg/dl, mean+/-S.E., P<0.0001). Also, drinking more than 0.5 drinks daily was not associated with beneficial effects on HDL levels in women with defective ALDH2 genotypes.

CONCLUSIONS

Alcohol intake did not have beneficial effects on HDL levels in the defective ALDH2 genotype and may not protect against CAD in subjects with defective ALDH2 genotypes.

Effects of aldehyde dehydrogenase-2 genetic polymorphisms on metabolism of structurally different aldehydes in human liver

Genotype analysis of the aldehyde dehydrogenase (ALDH)-2 gene was performed using an improved simplified method, and effects of the genotype on the metabolism of a variety of aldehydes in different fractions of human liver cells were investigated. The effects of sex, aging, smoking, drinking alcohol, liver function, and various drugs on ALDH activity were also analyzed. Of the 39 subjects, eight were heterozygotes of the wild (ALDH2*1) and mutant (ALDH2*2) alleles, and the others were homozygotes of the wild allele. ALDH activity toward acetaldehyde in liver mitochondria from subjects with a mutant allele was less than 10% of that with two alleles of wild-type, and the activities toward formaldehyde, propionaldehyde, n-butyraldehyde, capronaldehyde, and heptaldehyde were also significantly lower in the ALDH2*1/*2 rather than ALDH2*1/*1 group. However, the metabolism of octylaldehyde, decylaldehyde, retinaldehyde, benzaldehyde, 3-hydroxybenzaldehyde, and 2,5-dihydroxybenzaldehyde was similar in the two genotypes. Changes in activity in the cytosolic fraction were similar to those in mitochondria. There was no significant difference in ALDH activity in microsomes between the two groups. Total activities of ALDH toward acetaldehyde and other short-chain aliphatic aldehydes in supernatant fractions of homogenized liver were affected in a manner similar to that in mitochondria. Our results suggest that the single nucleotide polymorphisms of the ALDH2 gene only alter the metabolism of aldehydes with a short aliphatic chain. Furthermore, sex, drinking alcohol, and smoking had little effect on ALDH activity, although the activity in elderly individuals tended to be lower albeit statistically insignificant.

Metabolic and ethnic determinants of alcohol drinking habits and vulnerability to alcohol-related disorder

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Shoji Harada and Dharam P. Agarwal. The presentations were (1) Mutations in the exons, exon-intron junctions, and promoter regions of human CYP2E1 gene and alcoholism, by Fumio Nomura; (2) Genetic variability in alcohol metabolism and drinking habits in Japanese, by Shoji Harada; (3) Genetic studies of alcohol dependence using alcoholics with inactive ALDH2, by Susumu Higuchi; and (4) Alcohol consumption, apolipoprotein polymorphisms, and cardiovascular disorders, by Dharam P. Agarwal.

Relationship between serum levels of anti-low-density lipoprotein-acetaldehyde-adduct antibody and aldehyde dehydrogenase 2 heterozygotes in patients with alcoholic liver injury

We prepared low-density lipoprotein (LDL)-acetaldehyde-adduct (hereafter abbreviated as LDL-adduct) and anti-LDL-adduct antibody by using Watanabe hyperlipidemic rabbits, and determined values of serum anti-LDL-adduct antibody levels by the ELISA method in healthy adults and patients with alcoholic liver injury. In the nondrinking group in healthy adults, values of anti-LDL-adduct antibody levels were 25 +/- 13 microg/ml, and there was no significant difference between moderate drinkers without diseases and the nondrinking group in healthy adults. Values of anti-LDL-adduct antibody in alcoholic disease groups, 17 +/- 9 microg/ml for the patients with the fatty liver group, 21 +/- 14 microg/ml for the hepatic fibrosis group, 70 +/- 21 microg/ml for the alcoholic hepatitis group, 41 +/- 50 microg/ml for the alcoholic cirrhosis group, and 19 +/- 18 microg/ml for the alcoholic pancreatitis group. Examinations of aldehyde dehydrogenase 2 (ALDH2) genetic variations by the polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) method in the healthy group and the liver injury group revealed a tendency for patients with ALDH2(1)/2(2) in the liver injury group to have relatively mild liver lesions. When comparing anti-LDL-adduct antibody levels between ALDH2 genetic variations, those for the patients with ALDH2(1)/2(2) (36 +/- 40 microg/ml) were significantly higher than those for patients with ALDH2(1)/2(2) (11 +/- 5 microg/ml). Results of the present study suggest that genetic variation may influence the progression of liver injury.

The role of non-P450 enzymes in drug oxidation

In addition to cytochrome P450, oxidation of drugs and other xenobiotics can also be mediated by non-P450 enzymes, the most significant of which are flavin monooxygenase, monoamine oxidase, alcohol dehydrogenase, aldehyde dehydrogenase, aldehyde oxidase and xanthine oxidase. This article highlights the importance of these non-P450 enzymes in drug metabolism. A brief introduction to each of the non-P450 oxidizing enzymes is given in this review and the oxidative reactions have been illustrated with clinical examples. Drug oxidation catalyzed by enzymes such as flavin monooxygenase and monoamine oxidase may often produce the same metablolites as those generated by P450 adn thus drug interactions may be difficult to predict without a clear knowledge of the underlying enzymology. In contrast, oxidation via aldehyde oxidase and xanthine oxidase gives different metabolites to those resulting from P450 hydroxylation. Although oxidation catalyzed by non-P450 enzymes can lead to drug inactivation, oxidation may be essential for the generation of active metabolite(s). The activation of a number of prodrugs by non-P450 enzymes is thus described. It is concluded that there is still much to learn about factors affecting the non-P450 enzymes in the clinical situation.

Acute reactions to alcohol

Where the experience of alcohol is unpleasant because of adverse reactions to small amounts, alcohol consumption is likely to be low and alcohol dependence rare. This is shown by many studies of Asian subjects who experience the alcohol flush reaction (AFR) due to inherited aldehyde dehydrogenase (ALDH) deficiency. Alcohol reactions are less common and on average less severe in non-Asian subjects, but they do occur and can affect alcohol consumption. Information about alcohol reactions and their consequences in Europeans is reviewed, and such reactions are compared with those caused by mitochondrial ALDH deficiency in Asians.

Simple and rapid determination of the acetaldehyde dehydrogenase (ALDH2) genotypes by nonradioactive single-strand conformation polymorphism analysis

The genotyping of mitochondrial acetaldehyde dehydrogenase (ALDH2) is very important in alcohol studies. We describe an ALDH2 genotyping method based on nonradioactive single-strand conformation polymorphism (SSCP) analysis on mini-gels following amplification with a mutated primer set. The three ALDH2 genotypes were clearly and unambiguously distinguished. This method was applied to the ALDH2 genotyping of 129 unrelated Japanese. The allele frequency of ALDH2*2 was calculated to be 0.271, which was consistent with the previous data. The method proved to be simple, rapid and reliable, and dispensed with isotopic reagent and expensive restriction enzymes and equipment. The SSCP method described here is valuable in routine ALDH2 genotyping.