Genetic polymorphism of human liver alcohol and aldehyde dehydrogenases, and their relationship to alcohol metabolism and alcoholism

Alcohol Intake and Breast Cancer Risk: Weighing the Overall Evidence

Moderate alcohol consumption has been linked to an approximate 30-50% increased risk in breast cancer. Case-control and cohort studies have consistently observed this modest increase. We highlight recent evidence from molecular epidemiologic studies and studies of intermediate markers like mammographic density that provide additional evidence that this association is real and not solely explained by factors/correlates of the exposure and outcome present in non-randomized studies. We also review evidence from studies of higher risk women including BRCA1 and BRCA2 mutation carriers. Given the incidence of heart disease is higher than breast cancer and modest alcohol consumption is associated with reduced risk of heart disease, we examine the latest evidence to evaluate if alcohol reduction should be targeted to women at high risk for breast cancer. We also review the most recent evidence on the effect of alcohol use on tumor recurrence and survival for those diagnosed with breast cancer.

Alcohol-metabolizing genes and alcohol phenotypes in an Israeli household sample

BACKGROUND

Alcohol dehydrogenase 1B and 1C (ADH1B and ADH1C) variants have been robustly associated with alcohol phenotypes in East Asian populations, but less so in non-Asian populations where prevalence of the most protective ADH1B allele is low (generally <5%). Further, the joint effects of ADH1B and ADH1C on alcohol phenotypes have been unclear. Therefore, we tested the independent and joint effects of ADH1B and ADH1C on alcohol phenotypes in an Israeli sample, with higher prevalence of the most protective ADH1B allele than other non-Asian populations.

METHODS

A structured interview assessed lifetime drinking and alcohol use disorders (AUDs) in adult Israeli household residents. Four single nucleotide polymorphisms (SNPs) were genotyped: ADH1B (rs1229984, rs1229982, and rs1159918) and ADH1C (rs698). Regression analysis examined the association between alcohol phenotypes and each SNP (absence vs. presence of the protective allele) as well as rs698/rs1229984 diplotypes (also indicating absence or presence of protective alleles) in lifetime drinkers (n = 1,129).

RESULTS

Lack of the ADH1B rs1229984 protective allele was significantly associated with consumption- and AUD-related phenotypes (OR = 1.77 for AUD; OR = 1.83 for risk drinking), while lack of the ADH1C rs698 protective allele was significantly associated with AUD-related phenotypes (OR = 2.32 for AUD). Diplotype analysis indicated that jointly ADH1B and ADH1C significantly influenced AUD-related phenotypes. For example, among those without protective alleles for ADH1B or ADH1C, OR for AUD was 1.87 as compared to those without the protective allele for ADH1B only and was 3.16 as compared to those with protective alleles for both ADH1B and ADH1C.

CONCLUSIONS

This study adds support for the relationship of ADH1B and ADH1C and alcohol phenotypes in non-Asians. Further, these findings help clarify the mixed results from previous studies by showing that ADH1B and ADH1C jointly effect AUDs, but not consumption. Studies of the association between alcohol phenotypes and either ADH1B or ADH1C alone may employ an oversimplified model, masking relevant information.

The ADH1B and DRD2 gene polymorphism may modify the protective effect of the ALDH2 gene against heroin dependence

Understanding the influences of genes involved in dopamine and serotonin metabolism, such as the aldehyde dehydrogenase 2 (ALDH2) and alcohol dehydrogenase 1B (ADH1B) genes, is critical for understanding addictive behavior. In addition, dopamine D2 receptor (DRD2) gene may also interact with the dopamine metabolizing genes and link to addiction. Therefore, we investigated the association between the ALDH2, ADH1B and DRD2 polymorphisms and heroin dependence. Heroin-dependent Han Chinese patients (n=304) and healthy controls (n=335) were recruited. Genotypes of ALDH2, ADH1B and DRD2 polymorphisms were analyzed using a polymerase chain reaction with restriction fragment length polymorphism. The frequency of the ALDH2*1/*1 genotype was significantly lower in heroin-dependent patients than in controls, but the frequency of ADH1B and DRD2 genotypes was not significantly different. Further stratification of the ALDH2 gene with the ADH1B gene showed that the protective effect of ALDH2*1/*1 existed only in patients who also carried the ADH1B*1/*1 and ADH1B*1/*2 genotype. Logistic regression analysis showed a significant interaction between ALDH2 and ADH1B (P=0.022) and DRD2, ALDH2 and ADH1B in patients (P=0.037). The ALDH2*1/*1, ADH1B*1/*1, and ADH1B*1/*2 genotypes may interact and protect their carriers against heroin dependence and the protective effect may be varied by the DRD2 gene polymorphism. We conclude that the protective effect of the ALDH2 polymorphism against heroin dependence may be modified by the ADH1B and DRD2 polymorphism.

Alpha-lipoic acid ameliorates oxidative stress by increasing aldehyde dehydrogenase-2 activity in patients with acute coronary syndrome

Aldehyde dehydrogenase-2 (ALDH2) is the main enzyme responsible for acetaldehyde oxidation in ethanol metabolism and also provides protection against oxidative stress. Alpha-lipoic acid (α-LA), a natural dithiol compound with antioxidant properties, has been reported to increase ALDH2 activity in cultured cells. We analyzed the therapeutic efficacy of α-LA in 63 patients with confirmed acute coronary syndrome (ACS). These patients (52 men and 11 women, with age range 49-72 years) were randomized into two groups: untreated group (n = 30) and α-LA group (n = 33). Patients in the α-LA group were given an intravenous injection of 600 mg α-LA every day for 5 days while the patients in the untreated group were given saline. An isoprostane, 8-iso-prostaglandin F2α (8-iso-PGF2α), one product of arachidonic acid metabolism, was measured as a marker for oxidative stress. The serum levels of 8-iso-PGF2α and ALDH2 activity were determined at admission to the hospital (time 0), and at 24 hours and 1 week after treatment. At 24 hours and 1 week after treatment, ALDH2 activity was significantly higher in the α-LA group than in the untreated group (P < 0.05), whereas the levels of 8-iso-PGF2α were significantly lower in the α-LA group than in the untreated group (all P < 0.05). Importantly, the decrease of 8-iso-PGF2α levels correlated with the increased ALDH2 activity at both 24 hours (r = 0.6234, P < 0.001) and 1 week after treatment (r = -0.3941, P = 0.0014). α-LA may ameliorate oxidative stress through up-regulating ALDH2 activity in patients with ACS.

Ethanol metabolism and its effects on the intestinal epithelial barrier

Ethanol is widely consumed and is associated with an increasing global health burden. Several reviews have addressed the effects of ethanol and its oxidative metabolite, acetaldehyde, on the gastrointestinal (GI) tract, focusing on carcinogenic effects or alcoholic liver disease. However, both the oxidative and the nonoxidative metabolites of ethanol can affect the epithelial barrier of the small and large intestines, thereby contributing to GI and liver diseases. This review outlines the possible mechanisms of ethanol metabolism as well as the effects of ethanol and its metabolites on the intestinal barrier. Limited studies in humans and supporting in vitro data have indicated that ethanol as well as mainly acetaldehyde can increase small intestinal permeability. Limited evidence also points to increased colon permeability following exposure to ethanol or acetaldehyde. In vitro studies have provided several mechanisms for disruption of the epithelial barrier, including activation of different cell-signaling pathways, oxidative stress, and remodeling of the cytoskeleton. Modulation via intestinal microbiota, however, should also be considered. In conclusion, ethanol and its metabolites may act additively or even synergistically in vivo. Therefore, in vivo studies investigating the effects of ethanol and its byproducts on permeability of the small and large intestines are warranted.

Effect of alcohol and aldehyde dehydrogenase gene polymorphisms on alcohol-associated hypertension: the Guangzhou Biobank Cohort Study

The effects of alcohol dehydrogenase (ADH) 2 and aldehyde dehydrogenase (ALDH) 2 genotypes on the alcohol–blood pressure association are unclear. We examined the association of ADH2 or ALDH2 genotypes with blood pressure in older Chinese men. Based on the Guangzhou Biobank Cohort Study (GBCS), 4792 men with valid ADH2, ALDH2 genotypes were included, and genotyping of rs1229984 ADH2 and rs671 ALDH2 (AA, AG/GA or GG) was performed using a Sequenom Mass-Array platform. Information on socio-demographics and lifestyle factors, including alcohol use, was obtained from a questionnaire, and blood pressure was measured. Among alcohol drinkers, systolic and diastolic blood pressure (SBP and DBP) and mean arterial pressure (MAP) were highest for men with the GG ADH2 genotype (136.6, 77.9 and 97.5 mm Hg, respectively), followed by those with the (AA/AG ADH2+GG ALDH2) genotype (133.4, 77.6 and 96.2 mm Hg, respectively) and then the (AA/AG ADH2+AA/AG ALDH2) genotype (SBP=132.6, DBP=76.6 and MAP=95.2 mm Hg) (P for trend ranged 0.025–0.035). After adjustment for potential confounders, as well as frequency or amount of alcohol use, men with the GG ADH2 genotype were more likely to have hypertension (odds ratio (OR)=1.62, 95% confidence interval 1.15–2.28) as were men with the (AA/AG ADH2+AA/AG ALDH2) genotype (OR=1.40, 95% confidence interval 1.01–1.96) compared with men with the (AA/AG ADH2+GG ALDH2) genotype). ADH2 or ALDH2 genotypes were unrelated to hypertension among those who never drink alcohol. ADH2 genotype influences blood pressure and risk of hypertension among male alcohol drinkers, suggesting that the hypertensive effect of alcohol is due to ethanol rather than acetaldehyde.

Population pharmacokinetics of multiple alcohol intake in humans

The objective of this study was to determine population-based pharmacokinetics parameters for ethanol following multiple intake and to identify the factors influencing the pharmacokinetics. Three different solutions of alcoholic liquor (ethanol 55.39 ± 0.45 g) with different dissolved oxygen concentrations were administered, and blood alcohol concentration was determined in 59 healthy subjects using a breath analyzer. Samples (n = 2955) were collected at various time points. Population pharmacokinetic modeling was performed to describe the pharmacokinetics of ethanol. The influence of individuals' demography and dissolved oxygen concentration was investigated, and Visual Predictive Check and bootstrapping were conducted for internal evaluation. The developed model was used to perform simulations to visualize the effects of covariates on individuals. A one-compartment model with Michaelis-Menten elimination kinetics described the multiple ethanol intake data. Population pharmacokinetic estimates of V(max) and K(m) were 3.256 mmol min(-1) and 0.8183 mmol L(-1), respectively. V(d)/F was estimated to be 77.0 L, and K(a) was 0.0767 min(-1). Body weight, age, and the dissolved oxygen concentration were confirmed to be significant covariates. The mean estimates from the developed population pharmacokinetic model were very similar to those from 500 bootstrap samples, and Visual Predictive Check showed that approximately 94% of the observed data fit well within the 5th-95th percentile. A one-compartment model with nonlinear elimination kinetics for multiple ethanol intake was developed and the significant covariates were determined. The robustness of the developed model was evaluated by bootstrap and Visual Predictive Check. The final model and implanted covariates explained well the variability and underlying mechanism of ethanol PK.

Meta-analysis of the ADH1B and ALDH2 polymorphisms and the risk of colorectal cancer in East Asians

OBJECTIVE

The aldehyde dehydrogenase 2 (ALDH2) and alcohol dehydrogenase 1B (ADH1B) genes have been implicated in the development of colorectal cancer (CRC). However, the results are inconsistent. In this study, a meta-analysis was performed to assess the associations between the ALDH2 and ADH1B polymorphisms and the risk of CRC.

METHODS

Relevant studies were identified using PubMed, Web of Science and CNKI up to February, 2013. The pooled odds ratio (OR) with a 95% confidence interval (CI) was calculated using the fixed- or random-effects model.

RESULTS

A total of 11 case-controlled studies were selected. Of these, 11 studies included 2,893 cases and 3,817 controls concerning the ALDH2 Glu487Lys polymorphism and six studies included 1,864 cases and 3,502 controls concerning the ADH1B polymorphism. The results indicated that there was a statistically significant link between the ALDH2 polymorphism and the risk of CRC (Glu/Lys+Lys/Lys vs. Glu/Glu: OR=0.87, 95%CI: 0.78-0.96, p=0.10; Glu/Lys vs. Glu/Glu: OR=0.87, 95%CI: 0.77-0.97, p=0.38); however, no significant associations were observed between the ADH1B polymorphism and the risk of CRC win any of the genetic models.

CONCLUSION

This meta-analysis demonstrated that the ALDH2 polymorphism, but not the ADH1B polymorphism, significantly increases the risk of CRC in East Asians.

Nur-related receptor 1 gene polymorphisms and alcohol dependence in Mexican Americans

AIM: To investigate the association of polymorphisms of nur-related receptor 1 (Nurr1) and development of alcohol dependence in Mexican Americans.

METHODS: Peripheral blood samples were collected from 374 alcoholic and 346 nonalcoholic Mexican Americans; these two groups were sex- and age-matched. Sample DNA was extracted and genomic DNA was amplified by polymerase chain reaction. The -2922(C) 2-3 polymerase chain reaction products were digested with Sau96I, alleles of 1345(G/C), and -1198(C/G) in the regulatory region as well as Ex+132 (G/T/A/C) and Ex+715(T/-) in exon 3 were studied by sequencing.

RESULTS: The C2/C2, C2/C3, C3/C3 genotype distribution of -2922(C) 2-3 was 34.4%, 38.2% and 27.5% in the nonalcoholic group compared to 23.3%, 51.2% and 25.4% in the alcoholic group (P = 0.001). The C/C, C/G, G/G genotype distribution of -1198(C/G) was 23.5%, 46.1% and 30.3% in the nonalcoholic group compared to 13.9%, 50.9% and 35.3% in the alcoholic group (P = 0.007). However, the -1345 (G/C), Ex3+132(G/T/A/C) and Ex3+715(T/-) alleles were not polymorphic in Mexican Americans, and all those studied had G/G, G/G and T/T genotype for these three alleles, respectively. The -2922(C) 2-3 did not show allele level difference between alcoholic and nonalcoholic individuals, but -1198 (C/G) showed a significant allele frequency difference between alcoholic (39.3%) and nonalcoholic (46.6%) populations (P = 0.005). Excluding obese individuals, significant differences were found at both genotypic and allelic levels for the -2922(C) 2-3 polymorphism (P = 0.000 and P = 0.049) and the -1198 (C/G) polymorphism (P = 0.008 and P = 0.032) between nonobese alcoholics and nonobese controls. Excluding smokers, a significant difference was found only at the genotypic level for the -2922(C) 2-3 polymorphism (P = 0.037) between nonsmoking alcoholics and nonsmoking controls, but only at the allelic level for the -1198(C/G) polymorphism (P = 0.034).

CONCLUSION: Polymorphisms in the regulatory region of Nurr1 are implicated in pathogenesis of alcohol dependence and the Nurr1/dopamine signaling pathway might be important for this dependence development in Mexican Americans.

Single nucleotide polymorphisms of ADH1B, ADH1C and ALDH2 genes and esophageal cancer: a population-based case-control study in China

Alcohol drinking is a major risk factor for esophageal cancer (EC) and the metabolism of ethanol has been suggested to play an important role in esophageal carcinogenesis. Epidemiologic studies, including genomewide association studies (GWAS), have identified single nucleotide polymorphisms (SNPs) in alcohol dehydrogenases (ADHs) and aldehyde dehydrogenases (ALDHs) to be associated with EC. Using a population-based case-control study with 858 EC cases and 1,081 controls conducted in Jiangsu Province, China, we aimed to provide further information on the association of ADH1B (rs1229984), ADH1C (rs698) and ALDH2 (rs671) polymorphisms with EC in a Chinese population. Results showed that ADH1B (rs1229984) was associated with EC with odds ratios (ORs) of 1.34 [95% confidence interval (CI): 1.08-1.66] for G-allele carriers compared to A/A homozygotes. No heterogeneity was detected on this association across different strata of alcohol drinking and tobacco smoking. Statistical interaction between ALDH2 (rs671) and alcohol drinking on EC susceptibility in both additive and multiplicative scales was observed. Compared to G/G homozygotes, A-allele carriers were positively associated with EC among moderate/heavy drinkers (OR = 1.64, 95% CI: 1.12-2.40) and inversely associated with EC among never/light drinks (OR = 0.75, 95% CI: 0.54-1.03). In addition, statistical interaction between ALDH2 and ADH1B polymorphisms on EC susceptibility among never/light drinkers was indicated. We did not observe association of ADH1C polymorphism with EC. In conclusion, our findings indicated that ADH1B (rs1229984) was associated with EC independent of alcohol drinking and tobacco smoking status and alcohol drinking interacted with ALDH2 (rs671) on EC susceptibility in this high-risk Chinese population.

The role of ALDH2 and ADH1B polymorphism in alcohol consumption and stroke in Han Chinese

The genes encoding the enzymes for metabolising alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2) -- exhibit genetic polymorphism and ethnic variations. Although the ALDH2*2 variant allele has been widely accepted as protecting against the development of alcoholism in Asians, the association of the ADH1B*2 variant allele with drinking behaviour remains inconclusive. The goal of this study was to determine whether the polymorphic ADH1B and ALDH2 genes are associated with stroke in male Han Chinese with high alcohol consumption. Sixty-five stroke patients with a history of heavy drinking (HDS) and 83 stroke patients without such a history (NHDS) were recruited for analysis of the ADH1B and ALDH2 genotypes from the stroke registry in the Tri-Service General Hospital, Taipei, Taiwan, between January 2000 and December 2001. The allelotypes of ADH1B and ALDH2 were determined using the polymerase chain reaction-restriction fragment length polymorphism method. The HDS patients (3 per cent) showed a significantly lower ALDH2*2 allele frequency than NHDS patients (27 per cent) (p < 0.001). After controlling for age, patients with HDS were associated with a significantly higher occurrence of cigarette smoking (p < 0.01) and liver dysfunction (p < 0.01). Multiple logistic regression analyses revealed that the ALDH2*2 variant allele was an independent variable exhibiting strong protection (odds ratio 0.072; 95 per cent confidence interval 0.02-0.26) against HDS after adjustment for hypertension, diabetes mellitus, smoking status and liver dysfunction. By contrast, allelic variations in ADH1B exerted no significant effect on HDS. The present study indicated that, unlike ALDH2*2, ADH1B*2 appears not to be a significant negative risk factor for high alcohol consumption in male Han Chinese with stroke.

Developmental trajectory and environmental moderation of the effect of ALDH2 polymorphism on alcohol use

BACKGROUND

In the aldehyde dehydrogenase 2 (ALDH2) gene, the ALDH2*2 allele, prevalent in East Asian populations, encodes an enzyme with severely reduced activity, thereby disrupting the normal metabolism of alcohol. Possession of the ALDH2*2 allele has been repeatedly shown to be associated with lower risk for alcohol dependence and reduced alcohol use. However, relatively few studies have considered whether the magnitude of the effect of ALDH2 polymorphism upon drinking is related to developmental stage or varies by environmental context.

METHODS

In a longitudinally assessed sample of 356 adopted adolescents and young adults of East Asian descent, we examined the progression over time of the relationship between ALDH2 genotype and multiple measures of drinking behavior. We also sought to determine whether the environmental influences of nonbiological parent and elder sibling alcohol use and misuse, as well as deviant peer behavior, moderated the effect of ALDH2 genotype upon alcohol use.

RESULTS

Across all measures of alcohol use, the association between ALDH2*2 allele possession and reduced drinking went from negligible to moderate between mid-adolescence and early adulthood. A combined index of adoptive parent alcohol use and misuse consistently moderated the protective effect of the ALDH2*2 allele across the measures of quantity and frequency of alcohol use, and symptomology, such that high parental alcohol use and misuse reduced the protective effect of the ALDH2*2 allele, while low parental alcohol use and misuse enhanced the effect of the allele. Neither a combined index of elder sibling alcohol use and misuse, nor deviant peer behavior was consistently related to the effect of ALDH2 genotype.

CONCLUSIONS

The protective effect of the ALDH2*2 allele increases over the course of adolescence and young adulthood and is modified by the environmental influence of parental alcohol use and misuse. As such, ALDH2 provides a model system for exploring the nature of gene-environment interplay across development.

A variant allele of ADH1B and ALDH2, is associated with the risk of esophageal cancer

Alcoholic beverages are causally related to esophageal cancer. The genetic polymorphisms of the alcohol-metabolizing enzymes ADH1B rs1229984 and ALDH2 rs671 may modulate individual differences in alcohol-oxidizing capability. A case-control study was conducted to evaluate the genetic effects of these two functional single nucleotide polymorphisms (SNPs) on the development of esophageal cancer. A total of 380 esophageal squamous cell carcinoma cases and 380 controls were recruited. Genotypes were determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Variant alleles of the functional polymorphism ADH1B rs1229984 SNP were associated with an increased risk of esophageal cancer [adjusted odds ratio (OR)=2.39, 95% confidence interval (CI)=1.42-4.03 for ADH1B rs1229984 GG vs. AA]. There was a borderline-significantly decreased risk between the ALDH2 rs671 genotype and esophageal cancer (adjusted OR=0.47, 95% CI=0.22-1.00 for ALDH2 rs671 AA vs. GG). Stratified analyses indicated that both of these effects were more evident among male, younger subjects and smokers. In conclusion, the functional polymorphisms ADH1B rs1229984 and ALDH2 rs671 may contribute to susceptibility to esophageal cancer, particularly among male, younger subjects and smokers.

Association of a genetic polymorphism of the alcohol-metabolizing enzyme ADH1C with alcohol dependence: results of a case-control study

OBJECTIVE

Alcohol dependence causes serious problems which may be influenced by genetic factors associated with alcohol metabolism. The aim was to investigate the allelic and genotypic difference in distribution of a polymorphism in alcohol dehydrogenase 1C gene (ADH1C) between alcohol-dependent individuals and controls, and to examine if these genotypes were associated with the age at which the patient became alcohol-dependent.

METHODS

We conducted a case-control study including 90 alcohol-dependent cases and 100 historic controls. The genomic DNA was isolated and the alleles were analyzed with an RFLP.

RESULTS

The ADH1C*1 allele frequencies were 0.89 (95% CI 0.84-0.91) in controls and 0.68 (95% CI 0.61-0.74) in alcohol-dependent patients. The frequencies of the ADH1C*2 allele were 0.11 (95% CI 0.07-0.14) and 0.32 (95% CI 0.25-0.38) among controls and alcohol-dependent patients, respectively (p < 0.0001). The ADH1C*1/*1 genotype frequency was significantly higher in the control group (77%) compared to that of the alcohol-dependents (51%, p < 0.0001). The ADH1C*1/*2 genotype frequency was significantly lower in the control group (23%) compared to that of the alcohol-dependents (42%, p < 0.0001). We obtained no statistically significant difference among the ADH1C genotype groups regarding age.

CONCLUSIONS

These findings suggest that a significantly higher presence of ADH1C*2 allele is associated with alcohol dependence in a Turkish population. Studies with other related polymorphisms are needed to more precisely estimate the association of alcohol dependence with ADH1C.

Acyclovir-induced nephrotoxicity: the role of the acyclovir aldehyde metabolite

For decades, acyclovir-induced nephrotoxicity was believed to be secondary to crystalluria. Clinical evidence of nephrotoxicity in the absence of crystalluria suggests that acyclovir induces direct insult to renal tubular cells. We postulated that acyclovir is metabolized by the alcohol dehydrogenase (ADH) enzyme to acyclovir aldehyde, which is metabolized by the aldehyde dehydrognase 2 (ALDH2) enzyme to 9-carboxymethoxymethylguanine (CMMG). We hypothesized that acyclovir aldehyde plays a role in acyclovir-induced nephrotoxicity. Human renal proximal tubular (HK-2) cells were used as our in vitro model. Western blot and enzymes activities assays were performed to determine whether the HK-2 cells express ADH and ALDH2 isozymes, respectively. Cytotoxicity (measured as a function of cell viability) assays were conducted to determine (1) whether the acyclovir aldehyde plays a role in acyclovir-induced nephrotoxicity and (2) whether CMMG induces cell death. A colorimetric assay was performed to determine whether acyclovir was metabolized to an aldehyde in vitro. Our results illustrated that (1) HK-2 cells express ADH and ALDH2 isozymes, (2) 4-methylpyrazole rendered significant protection against cell death, (3) CMMG does not induce cell death, and (4) acyclovir was metabolized to an aldehyde in tubular cells. These data indicate that acyclovir aldehyde is produced in HK-2 cells and that inhibition of its production by 4-methylpyrazole offers significant protection from cell death in vitro, suggesting that acyclovir aldehyde may cause the direct renal tubular insult associated with acyclovir.

The role of alcohol dehydrogenase genes in head and neck cancers: a systematic review and meta-analysis of ADH1B and ADH1C

Alcohol drinking is a major risk factor for head and neck cancer (HNC). This risk may be modified by alcohol dehydrogenase (ADH) genes, particularly ADH1B and ADH1C, that oxidise ethanol to its carcinogenic metabolite, acetaldehyde. A meta-analysis was conducted to assess the association between ADH1B and ADH1C and HNC risk. Twenty-nine studies from 28 articles identified from a literature search were included. Summary odds ratios (meta-ORs) were generated using random effect models. A reduced risk for HNC was associated with carrying the ADH1B*2 and ADH1C*1 alleles that confer faster metabolism of ethanol to acetaldehyde [meta-OR ADH1B, 0.50; 95% confidence interval (CI): 0.37-0.68, 13 studies; meta-OR ADH1C, 0.87; 95% CI: 0.76-0.99, 22 studies]. ADH1B*2 and ADH1C*1 alleles appear to be protective for HNC, possibly due to: (i) decreasing the opportunity for oral microflora to produce acetaldehyde locally from a prolonged systemic circulation of ethanol, (ii) preventing ethanol from acting as a solvent for other carcinogens, and (iii) decreasing the amount of ethanol a person consumes since a consequent peak in systemic acetaldehyde could cause discomfort. These results underscore the importance of ADH1B and ADH1C in the association between alcohol consumption and the risk for HNC.

Genetic polymorphisms of genes coding to alcohol-metabolizing enzymes in western Mexicans: association of CYP2E1*c2/CYP2E1*5B allele with cirrhosis and liver function

BACKGROUND

Alcoholic cirrhosis constitutes a major public health problem in the world where ADH1B, ALDH2, and CYP2E1 polymorphisms could be playing an important role. We determined ADH1B*2, ALDH2*2, and CYP2E1*c2 allele frequencies in healthy control individuals (C) and patients with alcoholic cirrhosis (AC) from western Mexico.

METHODS

Ninety C and 41 patients with AC were studied. Genotype and allele frequency were determined through polymerase chain reaction-restriction fragment length polymorphisms.

RESULTS

Polymorphic allele distribution in AC was 1.6%ADH1B*2, 0.0%ALDH2*2, and 19.5%CYP2E1*c2; in C: 6.1%ADH1B*2, 0%ALDH2*2, and 10.6%CYP2E1*c2. CYP2E1*c2 polymorphic allele and c1/c2 genotype frequency were significantly higher (p < 0.05 and p < 0.01, respectively) in patients with AC when compared to C. Patients with AC, carrying the CYP2E1*c2 allele, exhibited more decompensated liver functioning evaluated by total bilirubin and prothrombin time, than c1 allele carrying patients (p < 0.05). Cirrhosis severity, assessed by Child's Pugh score and mortality, was higher in patients carrying the c2 allele, although not statistically significant.

CONCLUSIONS

In this study, CYP2E1*c2 allele was associated with susceptibility to AC; meanwhile, ADH1B*2 and ALDH2*2 alleles were not. CYP2E1*c2 allele was associated with AC severity, which could probably be attributed to the oxidative stress promoted by this polymorphic form. Further studies to clearly establish CYP2E1*c2 clinical relevance in the development of alcohol-induced liver damage and its usefulness as a probable prognostic marker, should be performed. Also, increasing the number of patients and including a control group conformed by alcoholic patients free of liver damage may render more conclusive results. These findings contribute to the understanding of the influence of gene variations in AC development among populations, alcohol metabolism, and pharmacogenetics.

Ethanol metabolism by HeLa cells transduced with human alcohol dehydrogenase isoenzymes: control of the pathway by acetaldehyde concentration

BACKGROUND

Human class I alcohol dehydrogenase 2 isoenzymes (encoded by the ADH1B locus) have large differences in kinetic properties; however, individuals inheriting the alleles for the different isoenzymes exhibit only small differences in alcohol elimination rates. This suggests that other cellular factors must regulate the activity of the isoenzymes.

METHODS

The activity of the isoenzymes expressed from ADH1B*1, ADH1B*2, and ADH1B*3 cDNAs was examined in stably transduced HeLa cell lines, including lines which expressed human low K(m) aldehyde dehydrogenase (ALDH2). The ability of the cells to metabolize ethanol was compared with that of HeLa cells expressing rat class I alcohol dehydrogenase (ADH) (HeLa-rat ADH cells), rat hepatoma (H4IIEC3) cells, and rat hepatocytes.

RESULTS

The isoenzymes had similar protein half-lives in the HeLa cells. Rat hepatocytes, H4IIEC3 cells, and HeLa-rat ADH cells oxidized ethanol much faster than the cells expressing the ADH1B isoenzymes. This was not explained by high cellular NADH levels or endogenous inhibitors; but rather because the activity of the β1 and β2 ADHs was constrained by the accumulation of acetaldehyde, as shown by the increased rate of ethanol oxidation by cell lines expressing β2 ADH plus ALDH2.

CONCLUSION

The activity of the human β2 ADH isoenzyme is sensitive to inhibition by acetaldehyde, which likely limits its activity in vivo. This study emphasizes the importance of maintaining a low steady-state acetaldehyde concentration in hepatocytes during ethanol metabolism.

ADH1B and ALDH2 polymorphisms and their associations with increased risk of squamous cell carcinoma of the head and neck in the Korean population

Alcohol consumption is a major risk factor for squamous cell carcinoma of the head and neck (SCCHN). Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are key enzymes in ethanol metabolism. The objective of this study was to investigate the relationships of ADH and ALDH single nucleotide polymorphisms (SNPs) with the risk of developing SCCHN in a Korean sample. We genotyped ADH1B +3170A>G (rs1229984) and ALDH2 +1951G>A (rs671) SNPs in 225 Korean SCCHN patients and 301 healthy controls by single base extension and TaqMan assay. The frequencies of the ADH1B +3170A>G (*2*2/*2*1/*1*1) genotypes were 48.0%/38.7%/13.3% in SCCHN patients, and 57.8%/37.2%/5.0% in controls, respectively. The odds ratio (OR) and 95% confidence interval of the ADH1B*1*1 genotype was 1.89 (1.23-2.92) relative to the *2*2 genotype. The frequencies of the ALDH2 +1951G>A (*1*1/*1*2/*2*2) genotypes were 67.6%/31.6%/0.9% in SCCHN patients, and 67.8%/29.6%/2.7% in controls, respectively. In subgroup analyses according to smoking and alcohol drinking status, the OR of the ADH1B*1*1 genotype was increased in the heavy drinker group [8.85 (1.095-40.0)] and in the heavy smoker group [4.7 (1.54-14.29)]. We conclude that the ADH1B*1*1 genotype is associated with an increased risk of SCCHN, especially in heavy drinkers and heavy smokers. This genotype could be a useful biomarker for identifying Koreans with a greater risk of SCCHN.

Alcohol consumption, alcohol dehydrogenase 1C (ADH1C) genotype, and risk of colorectal cancer in the Netherlands Cohort Study on diet and cancer

Within the Netherlands Cohort Study (1986), we examined associations between alcohol consumption, the alcohol dehydrogenase 1C (ADH1C) genotype, and risk of colorectal cancer (CRC). After a follow-up period of 7.3 years, 594 CRC cases with information on genotype and baseline alcohol intake were available for analyses. Adjusted incidence rate ratios (RRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models. In subjects who reported to have consumed equal amounts of total alcohol both 5 years before baseline and at baseline, drinkers of ≥30g of alcohol per day with the ADH1C*2/*2 genotype were associated-although not statistically significant-with an increased risk of CRC relative to abstainers with the ADH1C*1/*1 genotype (RR: 1.91, 95% CI: 0.68, 5.34). The risk estimate in this exposure group increased slightly when compared with light drinkers of ≥0.5-<5g/day with the ADH1C*1/*1 genotype (RR: 2.32, 95% CI: 0.80, 6.72). The interaction term however, was not statistically significant (P>.05). In subjects who reported to have consumed equal amounts of total alcohol both 5 years before baseline and at baseline, drinkers of ≥30g of alcohol per day were associated-although not statistically significant-with an increased risk of CRC relative to abstainers (RR: 1.38, 95% CI: 0.80, 2.38). This risk estimate for high-level drinkers became stronger when compared with light drinkers (RR: 1.74, 95% CI: 1.01, 2.99). As main effect of genotype, we observed that the ADH1C*2/*2 genotype was associated with a 42% increase in risk of CRC when compared with the ADH1C*1/*1 genotype. In conclusion, both genotype and alcohol consumption were associated with an increased risk of CRC. Owing to limited statistical power, we found no apparent evidence for the ADH1C genotype as effect modifier of the relationship between alcohol intake and CRC. Nevertheless, the interaction deserves further investigation in larger genetic epidemiologic studies.

Association between alcohol intake and risk for gastric cancer with regard to ALDH2 genotype in the Korean population

BACKGROUND

The relationship between alcohol intake and the risk for gastric cancer is not fully understood. The association between alcohol consumption and the risk for gastric cancer was investigated in the Korean population with the ALDH2 genotype.

METHODS

From 2003 to 2008, 445 patients with gastric cancer and 370 control subjects ≥ 50 years of age were included in the analysis. Logistic regression models including age, gender, education, smoking and drinking status, Helicobacter pylori infection and ALDH2 genotype were evaluated to estimate the adjusted odds ratios (ORs) for the development of gastric cancer.

RESULTS

For all subjects, the risk for gastric cancer was increased in ex-drinkers [OR 1.68, 95% confidence interval (CI) 1.07-2.64], but not in current drinkers. Subjects with inactive ALDH2 *2 allele(s) showed a lower level of alcohol consumption than ALDH2 *1/*1 homozygotes (P < 0.001). Among the ALDH2 *1/*2 carriers (n = 243), current/ex-drinkers had a significantly increased risk for gastric cancer compared with never/rare drinkers (OR 2.80, 95% CI 1.51-5.19). Among heavy drinkers (n = 115), ALDH2 *1/*2 heterozygotes had a 4-fold increased risk for gastric cancer compared with *1/*1 homozygotes (OR 4.26, 95% CI 1.10-16.47); however, no risk increase was seen among never/rare drinkers.

CONCLUSIONS

A dose-response association between alcohol intake and the risk for gastric cancer was not observed. However, ALDH2 polymorphisms were found to modify the susceptibility to the development of gastric cancer associated with alcohol intake, especially in case of ALDH2 *1/*2 genotype. The findings suggest an alcohol-ALDH2 genotype interaction in gastric carcinogenesis.

ALDH2 and ADH1B interactions in retrospective reports of low-dose reactions and initial sensitivity to alcohol in Asian American college students

BACKGROUND

A mechanistic model has been proposed for how alcohol-metabolizing gene variants protect individuals from the development of alcohol use disorders, with heightened sensitivity to alcohol being an early step (endophenotype) in this model. This study was designed to determine whether possession of 2 alcohol-metabolizing genes variations, the aldehyde dehydrogenase ALDH2*2 allele and the alcohol dehydrogenase ADH1B*2 allele, was associated with self-reported sensitivity to alcohol at low doses and at initial use.

METHODS

Asian-American college students (N=784) of Chinese and Korean descent were genotyped at the ALDH2 and ADH1B loci and assessed for lifetime alcohol symptoms following 1 or 2 drinks and level of response to alcohol during the first 5 lifetime drinking episodes.

RESULTS

Participants who had an ALDH2*2 allele were more likely to report experiencing all 6 low-dose symptoms and having heightened initial response to alcohol. An interaction was found between ALDH2*2 and ADH1B*2, with ADH1B*2 being associated with heightened self-reported sensitivity to alcohol only in individuals who also possessed 1 ALDH2*2 allele.

CONCLUSIONS

These findings suggest the effects of ADH1B*2 may be felt more strongly in Asians who already have some heightened sensitivity to alcohol from possessing 1 ALDH2*2 allele, but who are not too sensitized to alcohol from possessing 2 ALDH2*2 alleles. These results offer additional insight into the discrepant findings that have been reported in the literature for the role of ADH1B*2 in response to alcohol and the development of alcohol-related problems.

Meta-analysis of ADH1B and ALDH2 polymorphisms and esophageal cancer risk in China

AIM: To evaluate whether alcohol dehydrogenase-1B (ADH1B) His47Arg and aldehyde dehydrogenase-2 (ALDH2) Glu487Lys polymorphism is involved in the esophageal squamous cell carcinoma (ESCC) risk in Chinese Han population.

METHODS: Seven studies of ADH1B and ALDH2 genotypes in Chinese Han population in 1450 cases and 2459 controls were included for meta-analysis. Stratified analyses were carried out to determine the gene-alcohol and gene-gene interaction with ESCC risk. Potential sources of heterogeneity between studies were explored, and publication bias was also evaluated.

RESULTS: Individuals with ADH1B arginine (Arg)/Arg genotype showed 3.95-fold increased ESCC risk in the recessive genetic model [Arg/Arg vs Arg/histidine (His) + His/His: odds ratio (OR) = 3.95, 95% confidence interval (CI): 2.76-5.67]. Significant association was found in the dominant model for ALDH2 lysine (Lys) allele [glutamate (Glu)/Lys + Lys/Lys vs Glu/Glu: OR = 2.00, 95% CI: 1.54-2.61]. Compared with the non-alcoholics, Arg/Arg (OR = 25.20, 95% CI: 10.87-53.44) and Glu/Lys + Lys/Lys (OR = 21.47, 95% CI: 6.44-71.59) were found to interact with alcohol drinking to increase the ESCC risk. ADH1B Arg+ and ALDH2 Lys+ had a higher risk for ESCC (OR = 7.09, 95% CI: 2.16-23.33).

CONCLUSION: The genetic variations of ADH1B His47Arg and ALDH2 Glu487Lys are susceptible loci for ESCC in Chinese Han population and interact substantially with alcohol consumption. The individuals carrying both risky genotypes have a higher baseline risk of ESCC.

Deficient aldehyde dehydrogenase 2 is associated with increased risk for esophageal squamous cell carcinoma in the presence of gastric hypochlorhydria

OBJECTIVE

In Orientals, deficient aldehyde dehydrogenase 2 (ALDH2) is associated with an increased risk for esophageal squamous cell carcinoma (ESCC). The local metabolism of carcinogenic acetaldehyde in the upper gastrointestinal tract could be involved in the association, but the underlying mechanism has not been fully elucidated. Since an anacidic stomach can promote bacteria-catalyzed local acetaldehyde production, the gastric acid level could also affect acetaldehyde metabolism. This study investigated whether ALDH2-related susceptibility to ESCC differs depending on the gastric secretion level.

MATERIAL AND METHODS

Sixty-two patients with ESCC and sex- and age-matched normal controls were enrolled in this study. ALDH2 polymorphism was analyzed by polymerase chain-restriction fragment length polymorphism, and those with an inactive allele (ALDH2-1/2-2 or ALDH2-2/2-2) were defined as ALDH2 deficient. Gastrin-stimulated acid output was assessed by endoscopic gastrin test and hypochlorhydria was defined as 0.6 mEq/10 min or lower. Multiple logistic regression analyses were used to adjust for other potential confounders.

RESULTS

ALDH2 deficiency or hypochlorhydria was more prevalent in ESCC compared with controls and both showed increased independent associations with ESCC in multivariate analysis. Stratified analysis by the gastric acid secretion level revealed that the associations between the ALDH2 genotype and ESCC differed according to the individual gastric acid secretion levels and that ALDH2 deficiency was a significant risk factor for ESCC exclusively in individuals with hypochlorhydria with an odds ratio (95% confidence interval): 5.0 (1.2-21.2).

CONCLUSION

Microbial production of carcinogen acetaldehyde in the presence of gastric hypochlorhydria is most probably involved in the mechanism of ALDH2-related susceptibility to ESCC.

ADH1B Arg47His polymorphism is associated with esophageal cancer risk in high-incidence Asian population: evidence from a meta-analysis

BACKGROUND AND OBJECTIVES

Incidence of Esophageal squamous cell carcinoma (ESCC) is prevalent in Asian populations, especially in the ones from the "Asian esophageal cancer belt" along the Silk Road and the ones from East Asia (including Japan). Silk Road and Eastern Asia population genetics are relevant to the ancient population migration from central China. The Arg47His (rs1229984) polymorphism of ADH1B is the highest in East Asians, and ancient migrations along the Silk Road were thought to be contributive to a frequent ADH1B*47His allele in Central Asians. This polymorphism was identified as responsible for susceptibility in the first large-scale genome-wide association study of ESCC and that's explained by its modulation of alcohol oxidization capability. To investigate the association of ADH1B Arg47His with ESCC in Asian populations under a common ancestry scenario of the susceptibility loci, we combined all available studies into a meta-analysis.

METHODS

A dataset composed of 4,220 cases and 8,946 controls from twelve studies of Asian populations was analyzed for ADH1B Arg47His association with ESCC and its interactions with alcohol drinking and ALDH2 Glu504Lys. Heterogeneity among studies and their publication bias were also tested.

RESULTS

The ADH1B*47Arg allele was found to be associated to increased risk of ESCC, with the odds ratios (OR) being 1.62 (95% CI: 1.49-1.76) and 3.86 (2.96-5.03) for the His/Arg and the Arg/Arg genotypes, respectively. When compared with the His/His genotype of non-drinkers, the Arg/Arg genotype can interact with alcohol drinking and greatly increase the risk of ESCC (OR = 20.69, 95%CI: 5.09-84.13). Statistical tests also showed gene-gene interaction of ADH1B Arg+ with ALDH2 Lys+ can bring more risk to ESCC (OR  = 13.46, 95% CI: 2.32-78.07).

CONCLUSION

Revealed by this meta-analysis, ADH1B*47Arg as a common ancestral allele can significantly increase the risk of ESCC in Asians, especially when coupled with alcohol drinking or the ALDH2*504Lys allele.

Maternal alcohol consumption, alcohol metabolism genes, and the risk of oral clefts: a population-based case-control study in Norway, 1996-2001

Heavy maternal alcohol consumption during early pregnancy increases the risk of oral clefts, but little is known about how genetic variation in alcohol metabolism affects this association. Variants in the alcohol dehydrogenase 1C (ADH1C) gene may modify the association between alcohol and clefts. In a population-based case-control study carried out in Norway (1996-2001), the authors examined the association between maternal alcohol consumption and risk of oral clefts according to mother and infant ADH1C haplotypes encoding fast or slow alcohol-metabolizing phenotypes. Subjects were 483 infants with oral cleft malformations and 503 control infants and their mothers, randomly selected from all other livebirths taking place during the same period. Mothers who consumed 5 or more alcoholic drinks per sitting during the first trimester of pregnancy had an elevated risk of oral cleft in their offspring (odds ratio (OR) = 2.6, 95% confidence interval (CI): 1.4, 4.7). This increased risk was evident only in mothers or children who carried the ADH1C haplotype associated with reduced alcohol metabolism (OR= 3.0, 95% CI: 1.4, 6.8). There was no evidence of alcohol-related risk when both mother and infant carried only the rapid-metabolism ADH1C variant (OR = 0.9, 95% CI: 0.2, 4.1). The teratogenic effect of alcohol may depend on the genetic capacity of the mother and fetus to metabolize alcohol.

Inhibition of aldehyde dehydrogenase 2 by oxidative stress is associated with cardiac dysfunction in diabetic rats

Left ventricular (LV) dysfunction is a common comorbidity in diabetic patients, although the molecular mechanisms underlying this cardiomyopathic feature are not completely understood. Aldehyde dehydrogenase 2 (ALDH2) has been considered a key cardioprotective enzyme susceptible to oxidative inactivation. We hypothesized that hyperglycemia-induced oxidative stress would influence ALDH2 activity, and ALDH2 inhibition would lead to cardiac functional alterations in diabetic rats. Diabetes was induced by intraperitoneal (i.p.) injection of 60 mg/kg streptozotocin. Rats were divided randomly into four groups: control, untreated diabetic, diabetic treated with N-acetylcysteine (NAC) and diabetic treated with α-lipoic acid (α-LA). Cardiac contractile function, oxidative stress markers and reactive oxygen species (ROS) levels were assessed. ALDH2 activity and expression also were determined. The role of ALDH2 activity in change in hyperglycemia-induced mitochondrial membrane potential (Δψ) was tested in cultured neonatal cardiomyocytes. Myocardial MDA content and ROS were significantly higher in diabetic rats than in controls, whereas GSH content and Mn-SOD activity were decreased in diabetic rats. Compared with controls, diabetic rats exhibited significant reduction in LV ejection fraction and fractional shortening, accompanied by decreases in ALDH2 activity and expression. NAC and α-LA attenuated these changes. Mitochondrial Δψ was decreased greatly with hyperglycemia treatment, and high glucose combined with ALDH2 inhibition with daidzin further decreased Δψ. The ALDH2 activity can be regulated by oxidative stress in the diabetic rat heart. ALDH2 inhibition may be associated with LV reduced contractility, and mitochondrial impairment aggravated by ALDH2 inhibition might reflect an underlying mechanism which causes cardiac dysfunction in diabetic rats.

Comparison between self-reported facial flushing after alcohol consumption and ALDH2 Glu504Lys polymorphism for risk of upper aerodigestive tract cancer in a Japanese population

Some Japanese exhibit facial flushing after drinking alcohol. Facial flushing was considered to be caused by acetaldehydemia. The concentration of blood acetaldehyde was concerned with the catalytic activity of acetaldehyde dehydrogenase (ALDH). Acetaldehyde dehydrogenase (ALDH)-2 polymorphism (rs671, Glu504Lys) was known to be associated with upper aerodigestive tract (UAT) cancer due to modulation of ALDH2 enzyme activity. It remains controversial whether facial flushing is useful in predicting UAT cancer risk as a surrogate marker of ALDH2 polymorphism. We conducted a case-control study to assess the risk of UAT cancer and facial flushing and ALDH2 polymorphism. Cases and controls were 585 UAT cancer patients and matched 1170 noncancer outpatients of Aichi Cancer Center Hospital. Information on facial flushing and other lifestyle factors was collected via a self-administered questionnaire. Association between facial flushing, polymorphism, and UAT cancer was assessed by odds ratios and 95% confidence intervals by using conditional logistic regression models. The facial flushing had no significant association with UAT cancer, although ALDH2 Lys allele was significantly associated with UAT cancer. No significant interaction between facial flushing and alcohol consumption was observed in this study, whereas ALDH2 Lys allele had significant association with UAT cancer. The misclassification between facial flushing and ALDH2 genotype was observed in 18% of controls with ALDH2 Glu/Glu genotype and in 16% of controls with ALDH2 Glu/Lys genotype. Facial flushing was less useful to predict UAT cancer risk than genotyping ALDH2 polymorphism.

Alcohol drinking habits, alcohol dehydrogenase genotypes and risk of acute coronary syndrome

Aims: The risk of myocardial infarction is lower among light-to-moderate drinkers compared with abstainers. Results from some previous studies, but not all, suggest that this association is modified by variations in genes coding for alcohol dehydrogenase (ADH). We aimed to test this hypothesis, including alcohol as both the amount of alcohol and the frequency of drinking. Methods: we conducted a nested case-cohort study within the Danish Diet, Cancer and Health study, including 1,645 men (770 incident cases of acute coronary syndrome from 1993—1997 through 2004 and 875 randomly selected controls). Results: Higher alcohol intake (measured as amount or drinking frequency) was associated with lower risk of acute coronary syndrome; however, there was no evidence that these finding were modified by ADH1B or ADH1C genotypes. Conclusions: The importance of functional variation in alcohol dehydrogenase for the association between alcohol drinking habits and the risk of developing acute coronary syndrome, if any, is very limited.

DNA polymorphism and risk of esophageal squamous cell carcinoma in a population of North Xinjiang, China

AIM: To investigate the role of metabolic enzyme and DNA repair genes in susceptibility of esophageal squamous cell carcinoma (ESCC).

METHODS: A case-control study was designed with 454 samples from 128 ESCC patients and 326 gender, age and ethnicity-matched control subjects. Genotypes of 69 single nucleotide polymorphisms (SNPs) of metabolic enzyme (aldehyde dehydrogenase-2, ALDH2; alcohol dehydrogenase-1 B, ADHB1; Cytochrome P450 2A6, CYP2A6) and DNA repair capacity genes (excision repair cross complementing group 1, ERCC1; O⁶-methylguanine DNA methyltransferase, MGMT; xeroderma pigmentosum group A, XPA; xeroderma pigmentosum group A, XPD) were determined by the Sequenom MassARRAY system, and results were analyzed using unconditional logistic regression adjusted for age, gender.

RESULTS: There was no association between the variation in the ERCC1, XPA, ADHB1 genes and ESCC risk. Increased risk of ESCC was suggested in ALDH2 for frequency of presence C allele of SNP [Rs886205: 1.626 (1.158-2.284)], XPD for C allele [Rs50872: 1.482 (1.058-2.074)], and MGMT for A allele [Rs11016897: 1.666 (1.245-2.228)]. Five variants of MGMT were associated with a protective effect on ESCC carcinogenesis, including C allele [Rs7069143: 0.698 (0.518-0.939)], C allele [Rs3793909: 0.653 (0.429-0.995)], A allele [Rs12771882: 0.719 (0.524-0.986)], C allele [Rs551491: 0.707 (0.529-0.945)], and A allele [Rs7071825: 0.618 (0.506-0.910)]. At the genotype level, increased risk of ESCC carcinogenesis was found in homozygous carriers of the ALDH2 Rs886205 [CC vs TT, odds ratios (OR): 3.116, 95% CI: 1.179-8.234], MGMT Rs11016879 (AA vs GG, OR: 3.112, 95% CI: 1.565-6.181), Rs12771882 (AA vs GG, OR: 2.442, 95% CI: 1.204-4.595), and heterozygotes carriers of the ALDH2 Rs886205 (CT vs TT, OR: 3.930, 95% CI: 1.470-10.504), MGMT Rs11016879 (AG vs GG, OR: 3.933, 95% CI: 2.216-6.982) and Rs7075748 (CT vs CC, OR: 1.949, 95% CI: 1.134-3.350), respectively. Three variants were associated with a protective effect on ESCC carcinogenesis, carriers of the MGMT Rs11016878 (AG vs AA, OR: 0.388, 95% CI: 0.180-0.836), Rs7069143(CT vs CC, OR: 0.478, 95% CI: 0.303-0.754) and Rs7071825 (GG vs AA, OR: 0.493, 95% CI: 0.266-0.915). Increased risk of ESCC metastasis was indicated in MGMT for frequency of presence C allele [Rs7068306: 2.204 (1.244-3.906)], A allele [Rs10734088: 1.968 (1.111-3.484)] and C allele [Rs4751115: 2.178 (1.251-3.791)]. Two variants in frequency of presence C allele of CYP2A6 [Rs8192720: 0.290 (0.099-0.855)] and A allele of MGMT [Rs2053139: 0.511 (0.289-0.903)] were associated with a protective effect on ESCC progression. Increased risk of ESCC metastasis was found in heterozygote carriers of the MGMT Rs7068306 (CG vs CC, OR: 4.706, 95% CI: 1.872-11.833).

CONCLUSION: Polymorphic variation in ALDH2, XPD and MGMT genes may be of importance for ESCC susceptibility. Polymorphic variation in CYP2A6 and MGMT are associated with ESCC metastasis.

Effect of gene polymorphisms and ethanol consumption on micronucleus frequency in human reticulocytes: a preliminary study

OBJECTIVE

Results from previous studies suggest that alcohol consumption can be genotoxic on peripheral lymphocytes. The aim of our study was to examine the association of alcohol consumption and its genotoxic effect on hematopoietic stem cells in vivo.

METHODS

We investigated 156 healthy Japanese males in a cross-sectional study. Lifestyles, including alcohol drinking behavior and cigarette smoking status, were investigated by means of a self-completed questionnaire. Polymorphisms of ADH1B and ALDH2 were identified by PCR-restriction fragment length polymorphism (RFLP) analysis. The presence of micronuclei in transferrin-positive reticulocytes (MN-RET) was detected with a single-laser flow cytometer. Associations between the genetic polymorphisms, lifestyle factors, and MN-RET frequency were statistically analyzed.

RESULTS

We found a significant difference in the mean frequencies of MN-RET between habitual drinkers and non-habitual drinkers (P = 0.043), and between the ALDH2*1/*1 and ALDH2*2/*2 genotype (P = 0.015). The ADH1B*2 and ALDH2*2 haplotype was estimated to have a significantly higher influence on MN-RET frequency than the ADH1B*2 and ALDH2*1 haplotype (P = 0.00035), and the frequency of alcohol consumption played a significant role in MN-RET frequency on the background of the ADH1B*2 and ALDH2*1 haplotype (P = 0.012).

CONCLUSION

The results of our study suggest a possible association between the ADH1B and ALDH2 polymorphism and the genotoxic effects of alcohol drinking on hematopoietic stem cells.

Association of alcohol intake with the risk of malignant lymphoma and plasma cell myeloma in Japanese: a population-based cohort study (Japan Public Health Center-based Prospective Study)

Few studies have evaluated the association between alcohol intake and the risk of the lymphoid neoplasms malignant lymphoma (ML) and plasma cell myeloma (PCM) among Asian populations. We conducted a large-scale population-based cohort study of 95,520 Japanese subjects (45,453 men and 50,067 women; age 40-69 years at baseline) with an average 13 years of follow-up, during which a total of 257 cases of ML and 89 of PCM were identified. Hazard ratios and 95% confidence intervals were estimated using a Cox regression model adjusted for potential confounders. Alcohol intake of > or = 300 g/week was associated with a significantly lower risk of lymphoid neoplasms (hazard ratio, 0.60; 95% confidence interval, 0.37-0.98) than occasional drinking at a frequency of <1 day/month, and the trend for alcohol consumption was significant (P = 0.028). A similar trend was observed for the subcategories of ML, PCM, and non-Hodgkin lymphoma (NHL), albeit that the results were significant only for alcohol consumption at > or = 300 g/week in NHL patients, probably due to the small number of subjects in each category. In conclusion, we found that alcohol had an inverse association with the risk of lymphoid neoplasms, particularly the risk of NHL, among a Japanese population.

Oral cancer and polymorphism of ethanol metabolising genes

Oral cancer is the sixth most common cancer worldwide and a major health problem in some parts of the world. Epidemiological studies have shown that habitual alcohol consumption could be a risk factor in oral carcinogenesis, although the true involvement of alcohol is unknown. Via alcohol dehydrogenase (ADH) and cytochrome P450 oxidase (CYP) alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Subsequently, and during the metabolizing process, acetaldehyde becomes acetate by acetaldehyde dehydrogenase (ALDH). Therefore, acetaldehyde levels are determined mainly by the action of ADH, CYP and ALDH. Recently, several studies have found that certain polymorphisms of genes encoding these enzymes confer a higher or lower metabolic activity and therefore different risk for certain malignancies such as oral cancer. In this review, we analyze the polymorphisms of alcohol metabolising enzymes in relation susceptibility to an oral cancer.

Functional variants in ADH1B and ALDH2 coupled with alcohol and smoking synergistically enhance esophageal cancer risk

BACKGROUND & AIMS

Esophageal squamous cell carcinoma (ESCC) is prevalent among Asian populations, with marked regional variations in incidence and mortality. Patients with ESCC have a very poor prognosis, but detection of ESCC at earlier stages could improve clinical outcome. Therefore, identification of epidemiologic factors that influence the development of ESCC would facilitate prevention and/or early detection of the disease.

METHODS

We performed a 2-step genome-wide association study with subsequent replication analysis using a total of 1070 Japanese ESCC cases and 2836 controls. We also used logistic regression analysis to estimate the effect of gene-gene and gene-environmental interactions.

RESULTS

We identified the significant associations of ESCC with 4q21-23 and 12q24 regions, which include nonsynonymous single nucleotide polymorphisms (SNP) in ADH1B (rs1229984, P = 6.76 x 10(-35)) and ALDH2 (rs671, P = 3.68 x 10(-68)) that were previously shown to be associated with ESCC susceptibility. Multiple logistic regression analysis revealed SNP rs671, rs1229984, alcohol drinking, and smoking as the independent risk factors for ESCC (odds ratios of 1.66, 1.85, 1.92, and 1.79, respectively). Moreover, individuals who had both genetic and lifestyle-related risk factors had a nearly 190 times higher risk of ESCC than those who had neither of these.

CONCLUSIONS

We found 2 known functional variants involved in the metabolism of alcohol and tobacco by-products as the most significant risk factors for the development of ESCC in a Japanese population. The individuals carrying both risk genotypes have a higher baseline risk of ESCC that is substantially increased by 2 lifestyle risk factors.

Polymorphisms of alcohol metabolizing enzymes in indigenous Mexican population: unusual high frequency of CYP2E1*c2 allele

BACKGROUND

Alcohol abuse represents the major identified etiological factor of cirrhosis in México. ADH1B, ALDH2, and CYP2E1 have been considered candidate genes in alcohol-related diseases. Controversial results probably due to ethnic differences, among other factors, have been reported. Mexican Mestizos (MES) derive from the combination of indigenous, Spaniard, and African genes. Huichols (HUI) constitute an indigenous group from western Mexico with no racial admixture. We determined ADH1B*2, ALDH2*2, and CYP2E1*c2 allele frequencies in healthy HUI and MES from western Mexico. Lipid and hepatic profile were also carried out.

METHODS

One hundred and one HUI and 331 MES subjects were studied. Genotype and allele frequency were assessed through polymerase chain reaction-restriction fragment length polymorphism after DNA isolation from peripheral leukocytes. Commercial kits for lipid and hepatic determinations were used.

RESULTS

Polymorphic allele distribution in HUI was: 0%ADH1B*2, 0.5%ALDH2*2, 51.5%CYP2E1*c2; in MES: 3.4%ADH1B*2, 0%ALDH2*2, 16.1%CYP2E1*c2. Frequency of ADH1B*2 was statistically (p < 0.001) lower in HUI than MES. CYP2E1*c2 polymorphic allele was significantly higher (p < 0.0001) in HUI than MES. Hepatic profile was normal in both groups. HUI showed a better lipid profile than MES independently of genotype.

CONCLUSIONS

Huichols exhibited the highest CYP2E1*c2 allele frequency of the world documented up to this date; meanwhile, ADH1B*2 and ALDH2*2 were practically absent. This feature could be useful in the understanding of Mexican population gene composition, alcohol metabolism, and alcoholic liver disease development. However, further association studies are necessary. The heterogeneity of Mexican population was evidenced by the significantly different distribution of CYP2E1*c2 allele observed among different regions of the country. Lipid and hepatic values were not associated to genotype. This report constitutes the first study dealing with gene polymorphisms of alcohol metabolizing enzymes conducted in HUI.

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.

Alcohol Intake, Myocardial Infarction, Biochemical Risk Factors, and Alcohol Dehydrogenase Genotypes

Background— The risk of myocardial infarction is lower among light-to-moderate alcohol drinkers compared with abstainers. We tested associations between alcohol intake and risk of myocardial infarction and risk factors and whether these associations are modified by variations in alcohol dehydrogenases.

Methods and Results— We used information on 9584 men and women from the Danish general population in the Copenhagen City Heart Study. During follow-up, from 1991 to 2007, 663 incident cases of myocardial infarction occurred. We observed that increasing alcohol intake was associated with decreasing risk of myocardial infarction, decreasing low-density lipoprotein cholesterol and fibrinogen, increasing diastolic and systolic blood pressure and high-density lipoprotein cholesterol, and with U-shaped nonfasting triglycerides. In contrast, ADH1B and ADH1C genotypes were not associated with risk of myocardial infarction or with any of the cardiovascular biochemical risk factors, and there was no indication that associations between alcohol intake and myocardial infarction and between alcohol intake and risk factors were modified by genotypes.

Conclusions— Increasing alcohol intake is associated with decreasing risk of myocardial infarction, decreasing low-density lipoprotein cholesterol and fibrinogen, increasing diastolic and systolic blood pressure and high-density lipoprotein cholesterol, and U-shaped nonfasting triglycerides. These associations were not modified by ADH1B and ADH1C are genotypes.

Alcohol intake, alcohol dehydrogenase genotypes, and liver damage and disease in the Danish general population

OBJECTIVES

We tested the hypothesis that alcohol, alone and in combination with alcohol dehydrogenase (ADH) 1B and ADH1C genotypes, affects liver damage and disease in the general population.

METHODS

Information on alcohol intake and on liver disease was obtained from 9,080 men and women from the Copenhagen City Heart Study. Biochemical tests for the detection of liver damage were specific for alanine aminotransferase (ALT), aspartate aminotransferase (AST)-to-ALT ratio (AST/ALT), gamma-glutamyl transpeptidase (gamma-GT), albumin, bilirubin, alkaline phosphatase, coagulation factors, and erythrocyte volume.

RESULTS

Increasing alcohol intake was associated with increasing erythrocyte volume, AST/ALT, and levels of ALT, gamma-GT, albumin, bilirubin, coagulation factors, and with decreasing levels of alkaline phosphatase. Multifactorially adjusted hazard ratios for alcoholic liver disease overall were 0.9 (95% confidence interval (CI), 0.6-1.4), 1.4 (0.8-2.5), 1.8 (0.9-3.5), and 4.1 (2.5-7.0) for an alcohol intake of 1-13, 14-20, 21-27, and > or = 28 drinks per week, respectively, compared with drinking <1 drink per week (P for trend<0.0001); the corresponding hazard ratios for alcoholic liver cirrhosis were 1.7 (0.6-4.7), 2.0 (0.8-7.1), 6.5 (2.0-21), and 13 (4.6-37) (P for trend<0.0001). ADH1B and ADH1C genotypes were not associated with and did not modify the effect of alcohol on biochemical tests or risk of liver disease.

CONCLUSIONS

Increasing alcohol intake from none to low (1-6 drinks per week) through to moderate (7-20 drinks per week) and excessive intake (> or = 21 drinks per week) leads to stepwise increases in signs of liver damage with no threshold effect, and to an increased risk of liver disease. The minor changes in biochemical tests for low alcohol intake may not account for subclinical liver disease.

Genetic modulation of ADH1B and ALDH2 polymorphisms with regard to alcohol and tobacco consumption for younger aged esophageal squamous cell carcinoma diagnosis

Genetic variants in alcohol dehydrogenase-1B (ADH1B) and aldehyde dehydrogenase-2 (ALDH2) genes modulate acetaldehyde removal upon alcohol ingestion. Although these genetic vulnerabilities have been linked to higher esophageal squamous cell carcinoma (ESCC) risks, it is unclear whether they also determine the time of malignancy presentation. The purpose of this investigation was to unravel genotoxic effects of the two alcohol-metabolizing genes with regard to alcohol and tobacco consumption on the age at ESCC diagnosis and tumor dissemination. ADH1B/ALDH2 genotyping was performed on lymphocyte DNA specimens taken from 406 consecutively registered incident patients with pathology-proven ESCC. To fully utilize individual genetic and survival information, survival analyses and gene-longevity applied approaches were introduced. Among heavy drinkers, the ADH1B Arg/Arg (55 years) and ALDH2 Glu/Lys genotypes (54 years) were found to confer a 15 and 16 years earlier carcinoma diagnosed age than His/His and Glu/Glu nondrinkers (both 70 years), respectively. For drinkers, 1-year age advancement was, separately, associated with a 0.977 and 0.953-fold stepwise reduced likelihood of being ADH1B Arg homozygote and ALDH2 Lys variant. Noticeably elevated hazard-ratio (HR) for drinkers of ADH1B slow-form genotype and ALDH2 inactive-form allele were identified in smokers (HR = 2.3-2.6), but no in nonsmokers. In smokers, appreciably higher cumulative cancer onset risks were correspondingly recognized from the age of 45 and 49 upward among any + Lys allele and Arg/Arg + Glu/Glu combined-ADH1B/ALDH2-genotype drinkers than nondrinkers. In conclusion, consumption of tobacco and alcohol, coupled with genetic susceptibilities associated with acetaldehyde elimination, as modulated by ADH1B and ALDH2 genotypes, determines a substantial magnitude of tumorigenetic effect on earlier age ESCC diagnosis.

Interaction of the effects of alcohol drinking and polymorphisms in alcohol-metabolizing enzymes on the risk of female breast cancer in Japan

BACKGROUND

Epidemiological studies consistently indicate that alcoholic beverages are an independent risk factor for female breast cancer. Although the mechanism underlying this effect remains unknown, the predominant hypothesis implicates mutagenesis via the ethanol metabolite acetaldehyde, whose impact on the carcinogenesis of several types of cancer has been shown in both experimental models and molecular epidemiological studies. Many of the epidemiological studies have investigated genetic polymorphisms of alcohol dehydrogenase-1B (ADH1B) His48Arg and aldehyde dehydrogenase-2 (ALDH2) Glu504Lys, because of the strong impact these polymorphisms have on exposure to and accumulation of acetaldehyde. With regard to breast cancer, however, evidence is scarce.

METHODS

To clarify the impact on female breast cancer risk of the interaction of the effects of alcohol consumption and polymorphisms in the alcohol-metabolizing enzymes ADH1B and ALDH2, we conducted a case-control study of 456 newly and histologically diagnosed breast cancer cases and 912 age- and menopausal status-matched noncancer controls. Gene-gene and gene-environment interactions between individual and combined ADH1B and ALDH2 gene polymorphisms and alcohol consumption were evaluated.

RESULTS

Despite sufficient statistical power, there was no significant impact of ADH1B and ALDH2 on the risk of breast cancer. Neither was there any significant gene-environment interactions between alcohol drinking and polymorphisms in ADH1B and ALDH2.

CONCLUSIONS

Our findings do not support the hypothesis that acetaldehyde is the main contributor to the carcinogenesis of alcohol-induced breast cancer.

Alcohol dehydrogenases: gene multiplicity and differential functions of five classes of isozymes

Mammalian alcohol dehydrogenases (ADHs) constitute an enzyme family of multiple forms (isozymes) which are differentially distributed throughout the body. Subunit types alpha, beta and gamma in dimeric combinations constitute the isozymes of human liver class I ADH, and are >94% homologous in structure. Human pi and chi subunits form homodimeric Class II and III ADH isozymes. pi-ADH is liver specific whereas chi-ADH is widely distributed throughout the body. A sixth human ADH subunit (designated mu or sigma), forming a new dimeric human stomach ADH, has been recently reported as Class IV ADH. Evidence for a seventh human ADH subunit has also been described, designated as Class V, the transcripts having been reported in the stomach and liver. All five classes of ADH represent isozymes which are homologous but exhibit at least 30% sequence differences in primary srtructure. Kinetic analyses of four of these classes of ADH indicated differential functions, serving either in the oxidative or reductive mode. Studies from various laboratories indicate the following respective functions: oxidation of aliphatic and aromatic alcohols-liver Class I and Class II, and stomach Class IV ADHs; reduction of peroxidic aldehydes-Classes I, II and IV; 'biogenic' alcohol oxidation-Classes I and II; and glutathione-dependent formaldehyde dehydrogenase-Class III.