A critical assessment of the potential of pharmacological modulation of aldehyde dehydrogenases to treat the diseases of bone loss.

Chronic alcoholism (CA) decreases bone mass and increases the risk of hip fracture. Alcohol and its main metabolite, acetaldehyde impairs osteoblastogenesis by increasing oxidative stress. Aldehyde dehydrogenase (ALDH) is the rate-limiting enzyme in clearing acetaldehyde from the body. The clinical relevance of ALDH in skeletal function has been established by the discovery of single nucleotide polymorphism, SNP (rs671) in the ALDH2 gene giving rise to an inactive form of the enzyme (ALDH2*2) that causes increased serum acetaldehyde and osteoporosis in the affected individuals. Subsequent mouse genetics studies have replicated human phenotype in mice and confirmed the non-redundant role of ALDH2 in bone homeostasis. The activity of ALDH2 is amenable to pharmacological modulation. ALDH2 inhibition by disulfiram (DSF) and activation by alda-1 cause reduction and induction of bone formation, respectively. DSF also inhibits peak bone mass accrual in growing rats. On the other hand, DSF showed an anti-osteoclastogenic effect and protected mice from alcohol-induced osteopenia by inhibiting ALDH1a1 in bone marrow monocytes. Besides DSF, there are several classes of ALDH inhibitors with disparate skeletal effects. Alda-1, the ALDH2 activator induced osteoblast differentiation by increasing bone morphogenic protein 2 (BMP2) expression via ALDH2 activation. Alda-1 also restored ovariectomy-induced bone loss. The scope of structure-activity based studies with ALDH2 and the alda-1-like molecule could lead to the discovery of novel osteoanabolic molecules. This review will critically discuss the molecular mechanism of the ethanol and its principal metabolite, acetaldehyde in the context of ALDH2 in bone cells, and skeletal homeostasis.

Aldehyde Dehydrogenase 2 and Heart Failure.

Heart failure (HF) is a structural or functional cardiac abnormal syndrome characterized with series of symptoms and signs such as breathlessness, fatigue, pulmonary crackles, and peripheral edema. Being a terminal phase of most myocardial lesions, HF has become a leading cause of mobility and mortality worldwide, associated with heavy clinical burden and economic costs affecting over 23 million people [14]. There is an increase to 5.5% with systolic dysfunction and an increase to 36.0% with diastolic dysfunction in people 60 years or older [85]. The costs accompanied with heart failure stand 2-3% of the total healthcare system expenditure in high-income countries and are expected to increase >2-fold in the next 2 decades [34].

Aldehyde dehydrogenase activity in cryopreserved cord blood cells for quality assessment prior to transplantation.

In umbilical cord blood transplantation (UCBT), the number of cluster of differentiation (CD)34+ cells and colony­forming units (CFUs) in the cord blood (CB) graft positively correlate with patient survival. Therefore, these parameters are currently used for quality assessment of the cryopreserved CB cells in the attached segment that is considered representative of the CB in the main bag prior to UCBT. Since aldehyde dehydrogenase (ALDH) activity is high in hematopoietic stem cells, the number of ALDH­bright (ALDHbr) cells was examined in comparison with the number of CD34+ cells and CFUs for the quality assessment of CB units. In the cryopreserved main bag, the number of ALDHbr cells in the CB unit exhibited positive correlation with the number of CD34+ cells, and with CFU­granulocytes/macrophages and total CFU counts. Furthermore, the concentration of ALDHbr cells in the cryopreserved attached segment was not significantly different compared to that of the main bag, suggesting that the attached segment is representative of the main bag. In conclusion, the present study suggested that ALDHbr cell counts in the cryopreserved attached segments may serve as a quality assessment indicator for CB units prior to UCBT.

Algorithm of Molecular and Biological Assessment of the Mechanisms of Sensitivity to Drug Toxicity by the Example of Cyclophosphamide.

Comparative study of the liver, blood, and spleen of DBA/2JSto and BALB/cJLacSto mice sensitive and resistant to acute toxicity of the cyclophosphamide allowed us to reveal basic toxicity biomarkers of this antitumor and immunosuppressive agent. Obtained results can be used for the development of an algorithm for evaluation of toxic effects of drugs and food components.

Associations between ALDH1A1 polymorphisms, alcohol consumption, and mortality among Hispanic and non-Hispanic white women diagnosed with breast cancer: the Breast Cancer Health Disparities Study.

PURPOSE: ALDH1A1, one of the main isotopes of aldehyde dehydrogenase-1 is involved in the differentiation and protection of normal hematopoietic stem cells and functions in alcohol sensitivity and dependence. We evaluated the associations between ALDH1A1 polymorphisms, alcohol consumption, and mortality among Hispanic and non-Hispanic white (NHW) breast cancer (BC) cases from the Breast Cancer Health Disparities Study. METHODS: Nine SNPs in ALDH1A1 were evaluated in 920 Hispanic and 1372 NHW women diagnosed with incident invasive BC. Adjusted Cox proportional hazard regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Models were stratified by Native American (NA) ancestry and alcohol consumption. RESULTS: A total of 443 deaths occurred over a median follow-up time of 11 years. After adjusting all results for multiple comparisons, rs7027604 was significantly associated with all-cause mortality (HRAA = 1.40; 95% CI 1.13-1.73, P adj = 0.018). The rs1424482 CC genotype (HRCC = 1.69; 95% CI 1.20-2.37, P adj = 0.027) and the rs7027604 AA genotype (HRAA = 1.65; 95% CI 1.21-2.26, P adj = 0.018) were positively associated with non-BC mortality. Among long-term light drinkers, rs1888202 was associated with decreased all-cause mortality (HRCG/GG = 0.36; 95% CI 0.20-0.64), while associations were not significant among non-drinkers or moderate/heavy drinkers (P interation = 0.218). The increased risk of all-cause mortality associated with rs63319 was limited to women with low NA ancestry (HRAA = 1.53; 95% CI 1.19-1.97). CONCLUSIONS: Multiple SNPs in ALDH1A1 were associated with increased risk of mortality after BC. Future BC studies examining the relationship between ALDH1A1 and mortality should consider the modifying effects of alcohol consumption and NA ancestry.

Alcohol Use and Gamma-Glutamyltransferase Using a Mendelian Randomization Design in the Guangzhou Biobank Cohort Study.

BACKGROUND: Observational studies and small intervention studies suggest alcohol raises gamma-glutamyltransferase (GGT). We used Mendelian randomization to assess the causal effect of alcohol use on GGT in older Chinese people. METHODS: An instrumental variable (IV) analysis in 2,321 men and 2,757 women aged 50+ years from phase 3 of the Guangzhou Biobank Cohort Study with ALDH2 (rs671) genotyped, alcohol use and GGT available was used to assess the causal effect of alcohol use on GGT. Rs671 was used as an IV and F-statistics was used to test for weak instrument hypothesis. An F-statistic of ≥10 indicates the IV is not weak. RESULTS: In men, the F-statistic for rs671 on alcohol use was 70. Using IV analysis alcohol use increased GGT by 10.60 U/L per alcohol unit (10 gram ethanol) per day (95% confidence interval (CI) 6.58 to 14.62). The estimate was lower in observational multivariate regression: 3.48 U/L GGT per alcohol unit per day (95% CI 2.84 to 4.11) adjusted for age, education, physical activity and smoking. In women, rs671 was not associated with alcohol or GGT and the F-statistic was 7 precluding IV analysis. CONCLUSION: In Mendelian randomization, we found confirmative evidence that alcohol use increases GGT among Southern Chinese men. Moreover, we found that the ALDH2 variant rs671 was not associated with GGT among Southern Chinese women who generally consume very low levels of alcohol. Taken together our findings strongly suggest that alcohol increases GGT, although we cannot rule out the possibility that other unknown factors may cause a different relation between alcohol and GGT in other populations.

Genotyping on ALDH2: comparison of four different technologies.

OBJECTIVES: This study aimed to compare the accuracy and performance of four genotyping methods for detecting single nucleotide polymorphisms (SNPs) in aldehyde dehydrogenase-2 (ALDH2), which is the principal enzyme involved in alcohol metabolism. DESIGN AND METHODS: We genotyped rs671 of ALDH2 in 96 coronary heart disease (CHD) patients with four methods including high resolution melting analysis (HRM), TaqMan allelic discrimination assay (TaqMan), allele-specific PCR (AS-PCR) and pyrosequencing. Meanwhile, we compared the accuracy and performance of these methods. RESULTS: All selected patients were successfully genotyped with referred methods. The results of these four assays showed 100% concordant results and had 100% accuracy as verified by Sanger sequencing. CONCLUSIONS: All of the referred methods can be used for genotyping ALDH2 rs671 with the same accuracy compared to Sanger sequencing. In small size of clinical samples, HRM and AS-PCR outperform over others due to their lower cost and less hands-on operation, which are suitable for clinical application.

Simultaneous genotyping of single-nucleotide polymorphisms in alcoholism-related genes using duplex and triplex allele-specific PCR with two-step thermal cycles.

We developed a time- and cost-effective multiplex allele-specific polymerase chain reaction (AS-PCR) method based on the two-step PCR thermal cycles for genotyping single-nucleotide polymorphisms in three alcoholism-related genes: alcohol dehydrogenase 1B, aldehyde dehydrogenase 2 and µ-opioid receptor. Applying MightyAmp(®) DNA polymerase with optimized AS-primers and PCR conditions enabled us to achieve effective and selective amplification of the target alleles from alkaline lysates of a human hair root, and simultaneously to determine the genotypes within less than 1.5 h using minimal lab equipment.

Aldehyde dehydrogenase 2-a potential genetic risk factor for lung function among southern Chinese: evidence from the Guangzhou Biobank Cohort Study.

PURPOSE: In Asia, moderate alcohol users have better lung function. Never users have more inactive aldehyde dehydrogenase 2 (ALDH2) alleles (A) potentially generating confounding because inactive alleles may increase acetaldehyde exposure and reduce lung function. METHODS: We examined the association of ALDH2 genotypes with percentage predicted lung function (forced expiratory volume in 1 second; forced vital capacity) for age, sex, and height among 5641 older Chinese using multivariable linear regression. RESULTS: ALDH2 genotypes were associated with alcohol use and height but not other attributes. Inactive alleles were inversely associated with lung function (percentage predicted forced expiratory volume in 1 second -1.52%, 95% confidence interval [CI], -2.52% to -0.51% for one inactive allele and -2.05%, 95% CI, -3.85% to -0.26% for two inactive alleles compared with two active alleles; and for percentage predicted forced vital capacity -1.25%, 95% CI -2.15% to -0.35% and -1.65%, 95% CI, -3.25% to -0.04%). The association of moderate use with lung function was attenuated after adjusting for ALDH2, in addition to other potential confounders. CONCLUSIONS: Previous findings in Chinese may be confounded by ALDH2. High frequency of inactive ALDH2 alleles in East Asia may exacerbate the effect of environmental acetaldehyde exposure on lung function and potentially on chronic obstructive pulmonary disease.

Assessment of the reproductive toxicity of inhalation exposure to ethyl tertiary butyl ether in male mice with normal, low active and inactive ALDH2.

No data are available regarding aldehyde dehydrogenase 2 (ALDH2) polymorphisms related to the reproductive toxicity possibly caused by ethyl tertiary butyl ether (ETBE). In this study, two inhalation experiments were performed in Aldh2 knockout (KO), heterogeneous (HT) and wild type (WT) C57BL/6 male mice exposed to ETBE, and the data about general toxicity, testicular histopathology, sperm head numbers, sperm motility and sperm DNA damage were collected. The results showed that the 13-week exposure to 0, 500, 1,750 and 5,000 ppm ETBE significantly decreased sperm motility and increased levels of sperm DNA strand breaks and 8-hydroxy-deoxyguanosine in both WT and KO mice, the effects were found in 1,750 and 5,000 ppm groups of WT mice, and all of the three exposed groups of KO mice compared to the corresponding control; furthermore, ETBE also caused decrease in the relative weights of testes and epididymides, the slight atrophy of seminiferous tubules of testis and reduction in sperm numbers of KO mice exposed to ≥500 ppm. In the experiment of exposure to lower concentrations of ETBE (0, 50, 200 and 500 ppm) for 9 weeks, the remarkable effects of ETBE on sperm head numbers, sperm motility and sperm DNA damage were further observed in KO and HT mice exposed to 200 ppm ETBE, but not in WT mice. Our findings suggested that only exposure to high concentrations of ETBE might result in reproductive toxicity in mice with normal active ALDH2, while low active and inactive ALDH2 enzyme significantly enhanced the ETBE-induced reproductive toxicity in mice, even exposed to low concentrations of ETBE, mainly due to the accumulation of acetaldehyde as a primary metabolite of ETBE.

Assessment of the risk of blastomere biopsy during preimplantation genetic diagnosis in a mouse model: reducing female ovary function with an increase in age by proteomics method.

Preimplantation genetic diagnosis (PGD) is important for screening genetic and chromosome mutations in embryos so that the efficiency of assisted reproductive treatment can be increased and birth defects can be decreased; however, some studies have reported a risk from this technology as well as other assisted reproductive technologies. We have developed a blastomere biopsy mouse model to assess the potential effects of blastomere biopsy that was one key procedure in PGD on the fertility of female mice at different ages. We showed that female fertility was decreased in the biopsied mouse model with an increase in age. Moreover, the ovarian weight, serum hormone levels, and the number of primordial, primary, preantral, and antral stage follicles were also decreased in the middle-aged biopsied mouse model. To elucidate the underlying molecular mechanism, we did proteomics analysis on ovarian tissues from puberty biopsied and nonbiopsied mice of the 23 differentially expressed proteins that were screened for in both groups, 3 proteins (PSMB8, ALDH1A1, and HSPA4) were selected and identified by Western blotting and quantitative RT-PCR methods, which showed the 3 proteins to regulate 12 cellular pathways. Furthermore, these three proteins were shown to be located in ovarian tissues, and the dynamic changes of expression profiling in middle-aged biopsied and nonbiopsied mice were demonstrated. The present study showed that blastomere biopsy technology impairs fertility when mice are middle-aged, which possibly resulted in abnormal expression profiling of PSMB8, ALDH1A1, and HSPA4 proteins. Thus, additional studies should be performed to assess the overall risk of blastomere biopsies during PGD procedures.

Is aldehyde dehydrogenase 2 a credible genetic instrument for alcohol use in Mendelian randomization analysis in Southern Chinese men?

BACKGROUND: Mendelian randomization studies provide a means of assessing causal relations without interventions, but require valid genetic instruments. We assessed the credibility of aldehyde dehydrogenase 2 (ALDH2) as a genetic instrument for alcohol use in Southern Chinese men. METHODS: We genotyped the single nucleotide polymorphism rs671 of ALDH2 in 4867 men from the Guangzhou Biobank Cohort Study. We used linear regression to assess the strength of the association of ALDH2 variants with alcohol use, whether ALDH2 variants were independently associated with socio-economic position or other potential confounders and whether associations of ALDH2 variants with cardiovascular risk factors (systolic and diastolic blood pressure, HDL- and LDL-cholesterol, fasting glucose), triglycerides, body mass index, self reported cardiovascular disease, self-reported ischaemic heart disease, cognitive function (delayed 10-word recall and Mini Mental State Examination score) and liver function (alanine transaminase and aspartate transaminase) were fully mediated by alcohol use. RESULTS: The minor allele frequency (A) of ALDH2 was 0.29. The F statistic for ALDH2 variants was 75.0, suggesting that substantial weak instrument bias is unlikely. ALDH2 variants were not associated with socio-economic position, smoking or physical activity. ALDH2 variants were only associated with diastolic blood pressure and HDL-cholesterol, but these genetic associations with blood pressure and HDL-cholesterol were attenuated after adjusting for alcohol use, suggesting the apparent genetic associations were possibly mediated by alcohol use. CONCLUSIONS: ALDH2 variants are a credible genetic instrument for Mendelian randomization studies of alcohol use and many attributes of health in Southern Chinese men.

Direct-to-consumer genetic testing for addiction susceptibility: a premature commercialisation of doubtful validity and value.

Genetic research on addiction liability and pharmacogenetic research on treatments for addiction have identified some genetic variants associated with disease risk and treatment. Genetic testing for addiction liability and treatment response has not been used widely in clinical practice because most of the genes identified only modestly predict addiction risk or treatment response. However, many of these genetic tests have been commercialized prematurely and are available direct to the consumer (DTC). The easy availability of DTC tests for addiction liability and lack of regulation over their use raises a number of ethical concerns. Of paramount concern is the limited predictive power and clinical utility of these tests. Many DTC testing companies do not provide the consumer with the necessary genetic counselling to assist them in interpreting and acting on their test results. They may also engage in misleading marketing to entice consumers to purchase their products. Consumers' genetic information may be vulnerable to misuse by third parties, as there are limited standards to protect the privacy of the genetic information. Non-consensual testing and inappropriate testing of minors may also occur. The United States Food and Drug Administration plans to regulate DTC genetic tests. Based on the ethical concerns we discuss below, we believe there is a strong case for regulation of DTC genetic tests for addiction liability and treatment response. We argue that until this occurs, these tests have more potential to cause harm than to contribute to improved prevention and treatment of addiction.

Genotyping of polymorphisms in alcohol and aldehyde dehydrogenase genes by direct application of PCR-RFLP on dried blood without DNA extraction.

We have developed a simple, labor-saving, inexpensive, and rapid single nucleotide polymorphism (SNP) genotyping method that works directly on whole human blood. This single-tube genotyping method was used to successfully and reliably genotype ADH1B and ALDH2 polymorphisms without DNA isolation using a 1.2-mm disc of dried blood and the KOD FX PCR enzyme kit. SNP genotyping was performed by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. In addition to the labor and expense advantages, the possibility of sample contamination was considerably decreased, since the DNA extraction step was eliminated. In the post-genome era, a simple and inexpensive method for diagnostic analysis is in high demand, and this method will be very useful for genetic diagnoses in biological and medical laboratories.

Application of cryopreserved human hepatocytes in trichloroethylene risk assessment: relative disposition of chloral hydrate to trichloroacetate and trichloroethanol.

BACKGROUND: Trichloroethylene (TCE) is a suspected human carcinogen and a common groundwater contaminant. Chloral hydrate (CH) is the major metabolite of TCE formed in the liver by cytochrome P450 2E1. CH is metabolized to the hepatocarcinogen trichloroacetate (TCA) by aldehyde dehydrogenase (ALDH) and to the noncarcinogenic metabolite trichloroethanol (TCOH) by alcohol dehydrogenase (ADH). ALDH and ADH are polymorphic in humans, and these polymorphisms are known to affect the elimination of ethanol. It is therefore possible that polymorphisms in CH metabolism will yield subpopulations with greater than expected TCA formation with associated enhanced risk of liver tumors after TCE exposure. METHODS: The present studies were undertaken to determine the feasibility of using commercially available, cryogenically preserved human hepatocytes to determine simultaneously the kinetics of CH metabolism and ALDH/ADH genotype. Thirteen human hepatocyte samples were examined. Linear reciprocal plots were obtained for 11 ADH and 12 ALDH determinations. RESULTS: There was large interindividual variation in the Vmax values for both TCOH and TCA formation. Within this limited sample size, no correlation with ADH/ALDH genotype was apparent. Despite the large variation in Vmax values among individuals, disposition of CH into the two competing pathways was relatively constant. CONCLUSIONS: These data support the use of cryopreserved human hepatocytes as an experimental system to generate metabolic and genomic information for incorporation into TCE cancer risk assessment models. The data are discussed with regard to cellular factors, other than genotype, that may contribute to the observed variability in metabolism of CH in human liver.

Assessment of association between mitochondrial aldehyde dehydrogenase polymorphism and Alzheimer's disease in an older Korean population.

BACKGROUND: The mutant allele of mitochondrial aldehyde dehydrogenase (ALDH2(*)2) was found to be associated with Alzheimer's disease (AD) in a Japanese sample, interacting with the apolipoprotein E epsilon 4 allele (Apo E4). OBJECTIVE: In a community Korean population we sought to investigate associations between ALDH2 genotypes and the following outcomes: cognitive impairment, previous cognitive decline, dementia and AD. METHODS: Six hundred ninety community residents aged 65 or over were assessed for demographic characteristics, drinking behaviour, cognitive function, clinical diagnoses of dementia and AD, physical health status, and genotype (ALDH2 and Apo E). RESULTS: There were no significant associations between the ALDH2(*)2 and any cognitive outcome, before or after adjustment for alcohol-related characteristics. These findings were consistent both in the non-drinkers and drinkers. Interaction between ALDH2 and Apo E was only found for one outcome (previous cognitive decline) at borderline levels of significance (P=0.058). CONCLUSIONS: Overall, these findings in a community population did not support a substantial role for ALDH2 genotype in the aetiology of dementia.

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).

Assessment of a difference in ALDH2 heterozygotes and alcoholic liver injury.

We have speculated that the degree of liver dysfunction in alcoholic liver disease with ALDH2*1/2*2 may be less pronounced than that with ALDH2*1/2*1. In the present study, outpatients with alcoholic liver injury were examined for ALDH2 genotype and biochemical data. The number of patients was 29 cases of nonspecific changes, 16 cases of fatty liver, 5 cases of liver fibrosis, and 44 cases of liver cirrhosis. Biochemical data were evaluated with ALDH2 heterozygotes data obtained by PCR-SSCP. The ALDH2*1/2*1 and ALDH2*1/2*1 genotypes accounted for 90% and 10%, respectively. As for ALDH2*1/2*2, there were three patients with nonspecific changes, three with fatty liver, one with liver fibrosis, and two with liver cirrhosis. In alcoholic liver disease patients, when the ALDH2*1/2*2 genotype was compared with the ALDH2*1/2*1 genotype with biochemical data, the gamma-GTP value in patients with ALDH2*1/2*2 was significantly higher than with ALDH2*1/2*1 ( < 0.005). When the frequency of ALDH2 genotype was determined in patients with alcoholic liver injury, ALDH2 heterozygotes accounted for 15% for the non-cirrhosis group, and 5% for the cirrhotic group. When a relationship between the amount of ethanol intake and biochemical data were determined in patients with alcoholic liver injury who have ALDH2 heterozygotes, the glutamic oxaloacetic transaminase (GOT) and gamma-GTP values were significantly higher at an ethanol intake amount of ethanol more than 100 g per day than intake less than 100 g per day ( < 0.05). The alcoholic patients with ALDH2*1/2*2 drink a slight amount of ethanol, the liver injury is found to be stronger than those with ALDH2*1/2*1 when they drink more than 100 g ethanol per day.

[Classification of alcohol metabolizing enzymes and polymorphisms--specificity in Japanese].

Multiple forms and gene loci of human alcohol dehydrogenase (ADH EC: 1.2.1.3) and aldehyde dehydrogenase (ALDH, EC: 1.2.1.3) in the major pathway of alcohol metabolism have been found and characterized in the last two decades. With the coenzyme NAD, these enzymes catalyze the reversible conversion of organic alcohols to ketones or aldehydes, and aldehyde to acetic acid. The ADH genes are mapped to chromosome 4p21-25, but the ALDH genes are localized at different chromosomes. The cytochrome P450 2E1 (CYP2E1) gene, which is mapped to chromosome 10q24.3-qter contributes also the conversion of ethanol to acetaldehyde. Genetic polymorphisms have been reported in these alcohol metabolizing enzymes. The metabolisms of alcohol and acetaldehyde in liver and blood after drinking alcohol are thought to be influenced by the interactive action of these enzymes. Amongst the five major classes of the ADH subunits (alpha, beta, gamma, pi, chi, sigma), beta and gamma subunits show genetic polymorphisms. Recently a new nomenclature for ALDH genes has been recommend based on divergent evolution and chromosomal mapping. Two major isoforms designated as cytosolic ALDH1 and mitochondrial ALDH2 can be distinguished by their electrophoretic and kinetic properties as well as by their subcellular localization. Mitochondrial ALDH2 is a major enzyme in the oxidation of acetaldehyde derived from ethanol metabolism. The catalytic deficiency of ALDH2 isozyme is responsible for flushing and other vasomotor symptoms caused by higher acetaldehyde levels after alcohol intake. So far, frequencies of the two alleles of ALDH2 in Mongoloid have been reported in the different population groups. The catalytic deficiency of ALDH2 is caused by a structural point mutation at amino acid position 487, where a substitution of Glu to Lys resulting from a transition of G (C) to A (T) at 1510 nucleotide from the initiation codon has occurred. Individuals deficient in ALDH2 activity refrain from excessive drinking of alcohol due to the aversive reactions, leading to protection against alcoholism. Prevalence of the ALDH2*1 allele is associated with alcoholism, and subsequent studies have confirmed the allelic association with alcoholism in different ethnic groups. The effects of polymorphisms of ADH2 and CYP2E1 remained controversial, even in the same ethnic group. Investigation of mutations for the transacting cis-element in promoter region of the ALDH2 gene will provide important information with respect to regulation of this gene. Transfection assays using the first 600 bp of the upstream nucleotide sequences indicated that a region from -75 to -120 was necessary for the ALDH2 gene expression, and especially NF-Y/CP1 binding site from -92 to -96 (CCAAT box) is important in the expression of the gene. A novel polymorphism due to the nucleotide replacement at -357 G to A was found in all the population groups. Alcoholism is thought to be a multifactorial disease with complex mode of inheritance in addition to psychological and social factors, and many studies of family, adoption and twins concerning alcoholism have revealed that hereditary factor is an important determinant for developing alcoholism. Genetic association studies have contributed to the identification of a number of genetic risk factors for the chronic diseases influenced by genetic disorders and environmental factors.

[Association among genotypes of aldehyde dehydrogenase 2 and alcohol consumption].

A large population survey was made for the determination of aldehyde dehydrogenase 2 (ALDH2) genotypes among 630 unrelated Japanese adults by PCR using allele specific primers. The frequencies of three genotypes were 60% ALDH2*1/ALDH2*1 (NN) type, 35% ALDH2*1/ALDH2*2 (ND) type and 5% ALDH2*2/ALDH2*2 (dd) type. Average amounts of alcohol consumption per month for three genotypes were 965.8 g/month for NN type, 629.5 g/month for ND type and 179 g/month for DD type. The differences in average alcohol consumption were significant (p < 0.01) among the three genetic different groups. When male and female date were analyzed separately for these three groups, significant differences among three groups were found in both genders. These results indicated that ALDH2 mutant is an important genetic factor for limiting the alcohol consumption. The frequencies of ALDH2 genotypes were not significantly different between male and female population groups, however, their average alcohol consumption were significantly different between the two groups. Therefore, various social factors and life styles, in addition to genetic factors, might concern in the difference of alcohol consumption.