Association of ALDH2 polymorphism with sensitivity to acetaldehyde-induced micronuclei and facial flushing after alcohol intake

The impact of alcohol consumption on hearing loss in male workers with a focus on alcohol flushing reaction: the Kangbuk Samsung Cohort Study

Background

Despite hearing loss being a prevalent chronic condition, estimated to nearly 20% of the global population by the World Health Organization, the specific association with individual lifestyle factors, particularly alcohol consumption, remains unclear. In South Korea, approximately 80% of the population engages in alcohol consumption, with a notably high prevalence among males, indicating a high-risk drinking pattern. Therefore, this study aimed to assess the correlation between alcohol consumption and hearing loss in male workers, as well as to analyze additional variables such as alcohol flushing reaction, with the intention of improving worker health.

Methods

The study was conducted from January 2012 to December 2019, targeting 114,114 participants who visited Kangbuk Samsung Hospital Total Healthcare Centers. Data were collected through pure-tone audiometry tests and alcohol-related questionnaire, and statistical analysis was performed using Cox regression analysis. Based on previous studies indicating a potential protective effect of light drinking on hearing loss, this group was designated as the reference. Additionally, stratified analyses were conducted based on the presence of alcohol flushing reaction and different working hours.

Results

The hazard ratio (95% confidence interval) for hearing loss was higher in the heavy drinking group (1.23 [1.11-1.37]) compared to the moderate drinking group (1.09 [0.98-1.20]). Stratified analyses revealed a significantly elevated the hazard ratio of hearing loss in groups with alcohol flushing reaction compared to those without this factor.

Conclusions

Our study demonstrated that moderate or heavy alcohol consumption in male workers can increase the risk of hearing loss, particularly in those with alcohol flushing reaction. These findings underscore the importance of addressing alcohol-related factors concerning hearing health among male workers.

Asian flush is a potential protective factor against COVID-19: a web-based retrospective survey in Japan

BACKGROUND

Coronavirus disease 2019 (COVID-19), first reported in December 2019, spread worldwide in a short period, resulting in numerous cases and associated deaths; however, the toll was relatively low in East Asia. A genetic polymorphism unique to East Asians, Aldehyde dehydrogenase 2 rs671, has been reported to confer protection against infections.

METHOD

We retrospectively investigated the association between the surrogate marker of the rs671 variant, the skin flushing phenomenon after alcohol consumption, and the timing of COVID-19 incidence using a web-based survey tool to test any protective effects of rs671 against COVID-19.

RESULTS

A total of 807 valid responses were received from 362 non-flushers and 445 flushers. During the 42 months, from 12/1/2019 to 5/31/2023, 40.6% of non-flushers and 35.7% of flushers experienced COVID-19. Flushers tended to have a later onset (Spearman's partial rank correlation test, p = 0.057, adjusted for sex and age). Similarly, 2.5% of non-flushers and 0.5% of flushers were hospitalized because of COVID-19. Survival analysis estimated lower risks of COVID-19 and associated hospitalization among flushers (p = 0.03 and <0.01, respectively; generalized Wilcoxon test). With the Cox proportional hazards model covering 21 months till 8/31/2021, when approximately half of the Japanese population had received two doses of COVID-19 vaccine, the hazard ratio (95% confidence interval) of COVID-19 incidence was estimated to be 0.21 (0.10-0.46) for flusher versus non-flusher, with adjustment for sex, age, steroid use, and area of residence.

CONCLUSIONS

Our study suggests an association between the flushing phenomenon after drinking and a decreased risk of COVID-19 morbidity and hospitalization, suggesting that the rs671 variant is a protective factor. This study provides valuable information for infection control and helps understand the unique constitutional diversity of East Asians.

Alcohol flushing syndrome is significantly associated with intracranial aneurysm rupture in the Chinese Han population

Objective

Although alcohol flushing syndrome (AFS) has been associated with various diseases, its association with intracranial aneurysm rupture (IAR) is unclear. We aimed to examine this association in the Chinese Han population.

Methods

We retrospectively reviewed Chinese Han patients with intracranial aneurysms who were evaluated and treated at our institution between January 2020 and December 2021. AFS was determined using a semi-structured telephone interview. Clinical data and aneurysm characteristics were assessed. Univariate and multivariate logistic regression were conducted to determine independent factors associated with aneurysmal rupture.

Results

A total of 1,170 patients with 1,059 unruptured and 236 ruptured aneurysms were included. The incidence of aneurysm rupture was significantly higher in patients without AFS (p &lt; 0.001). Meanwhile, there was a significantly difference between the AFS and non-AFS group in habitual alcohol consumption (10.5 vs. 27.2%, p &lt; 0.001). In the univariate analyses, AFS [odds ratio (OR) 0.49; 95% confidence interval (CI), 0.34–0.72] was significantly associated with IAR. In the multivariate analysis, AFS was an independent predictor of IAR (OR 0.50; 95%, CI, 0.35–0.71). Multivariate analysis revealed that AFS was an independent predictor of IAR in both habitual (OR 0.11; 95% CI, 0.03–0.45) and non-habitual drinkers (OR 0.69; 95% CI, 0.49–0.96).

Conclusion

Alcohol flushing syndrome may be a novel clinical marker to assess the risk of IAR. The association between AFS and IAR exists independently of alcohol consumption. Further single nucleotide polymorphism testing and molecular biology studies are warranted.

Unsupervised Learning for Feature Representation Using Spatial Distribution of Amino Acids in Aldehyde Dehydrogenase (ALDH2) Protein Sequences

Aldehyde dehydrogenase 2 (ALDH2) enzyme is required for alcohol detoxification. ALDH2 belongs to the aldehyde dehydrogenase family, the most important oxidative pathway of alcohol digestion. Two main liver isoforms of aldehyde dehydrogenase are cytosolic and mitochondrial. Approximately 50% of East Asians have ALDH2 deficiency (inactive mitochondrial isozyme), with lysine (K) for glutamate (E) substitution at position 487 (E487K). ALDH2 deficiency is also known as Alcohol Flushing Syndrome or Asian Glow. For people with an ALDH2 deficiency, their face turns red after drinking alcohol, and they are more susceptible to various diseases than ALDH2-normal people. This study performed a machine learning analysis of ALDH2 sequences of thirteen other species by comparing them with the human ALDH2 sequence. Based on the various quantitative metrics (physicochemical properties, secondary structure, Hurst exponent, Shannon entropy, and fractal dimension), these fourteen species were clustered into four clusters using the unsupervised machine learning (K-means clustering) algorithm. We also analyze these species using hierarchical clustering (agglomerative clustering) and draw the phylogenetic trees. The results show that Homo sapiens is more closely related to the Bos taurus and Sus scrofa species. Our experimental results suggest that the testing for discovering medicines may be done on these species before being tested in humans to alleviate the impacts of ALDH2 deficiency.

A Dose–Response Relationship of Alcohol Consumption with Risk of Visual Impairment in Korean Adults: The Kangbuk Samsung Health Study

Visual impairment is a global health problem that leads to poor quality of life. The aim of the study was to examine the dose–response relationship between alcohol consumption and incident visual impairment (VI). This longitudinal cohort study consisted of 287,352 Korean adults who attended health screenings between March 2011 and December 2017 and were followed for up to 8.8 years (median, 4.9 years). Participants were categorized based on their average alcohol consumption. VI was defined as bilateral visual acuity (VA) worse than 0.3 logMAR. We identified 8320 cases of new-onset bilateral VI (incidence rate, 6.0/1000 person-years). Increased alcohol intake was positively and dose-dependently associated with elevated incidence of VI (p_trend < 0.001). With lifetime abstinence (reference), the multivariable-adjusted hazard ratios (HRs) (95% confidence intervals (CIs)) for incident VI with alcohol intake of <10, 10 to <20, 20–39.9, and ≥40 g/day were 1.07 (0.96–1.19), 1.15 (1.03–1.30), 1.15 (1.01–1.30), and 1.23 (1.08–1.40), respectively. Frequent binge drinking (≥once/per week) was associated with elevated risk of VI (HRs, 1.22; 95% CIs: 1.13–1.32). Former drinkers, particularly men, were at a higher risk for incident VI than lifetime abstainers. Similar associations were observed on evaluating changes in alcohol consumption and other confounders as time-varying covariates. Alcohol consumption, both in moderation and excess, was associated with increased VI incidence.

Aldehyde Dehydrogenase 2 Mediates Alcohol-Induced Colorectal Cancer Immune Escape through Stabilizing PD-L1 Expression

Despite the great success of immunotherapy in a small subset of cancer patients, most colorectal cancer (CRC) patients do not respond to programmed cell death receptor 1 (PD-1) blockade immunotherapy. There is an urgent medical need to elucidate how cancer cells evade immune response and to develop novel means to boost the efficacy of immune checkpoint inhibitors. In this study, alcohol induces ligand programmed cell death receptor 1 (PD-L1) expression of CRC cells in vitro and in vivo. Alcohol exposure is shown to induce aldehyde dehydrogenase 2 (ALDH2) expression that is a crucial enzyme involved in alcohol metabolism, and low level of lymphocytes infiltration in the murine CRC model and patients. Intriguingly, ALDH2 and PD-L1 protein expression are positively correlated in tumor tissues from the CRC patients. Mechanistically, ALDH2 stabilizes PD-L1 protein expression by physically interacting with the intracellular segment of PD-L1 and inhibiting its proteasome-dependent degradation mediated by an E3 ubiquitin ligase Speckle Type POZ Protein (SPOP). Importantly, inhibition of ALDH2 reduces PD-L1 protein in CRC cells and promotes tumor-infiltrating T cells (TILs) infiltration, presumably leading to the significant potentiation of anti-PD-1 antibody efficacy in a mouse CT26 CRC model. The findings highlight a crucial role played by ALDH2 to facilitate alcohol-mediated tumor escape from immunity surveillance and promote tumor progression.

Low Levels of Alcohol Consumption and Risk of Intestinal Metaplasia: A Cohort Study

BACKGROUND

The impact of alcohol drinking on gastric precancerous lesions remains unclear. We investigated the relationship of alcohol intake with risk of atrophic gastritis (AG) and intestinal metaplasia (IM).

METHODS

This study included 202,675 Korean adults free from AG and IM on their initial endoscopy who were followed with repeated endoscopic examinations. A parametric proportional hazards model was used to estimate the adjusted HR (aHR) with 95% confidence interval (CI) for incident AG and IM based on endoscopic diagnosis.

RESULTS

During a mean follow-up of 4.7 years, 64,853 incident AG cases and 4,536 IM cases were identified. Alcohol consumption including drinking frequency, quantity, and binge drinking were consistently associated with increased risk of both AG and IM in a dose-response manner. After adjustment for confounders, the multivariable aHRs (95% CIs) for incident IM comparing average alcohol intake of <10, 10-<20, 20-<40, and ≥40 g/day with lifetime abstainers were 1.27 (1.02-1.56), 1.34 (1.07-1.66), 1.50 (1.20-1.86), and 1.54 (1.23-1.93), respectively. Former drinkers were also at a higher risk for AG and IM compared with lifetime abstainers. These associations were consistently observed in never smokers and in time-dependent analyses.

CONCLUSIONS

In a large cohort of Korean individuals, alcohol intake even at low levels was independently associated with increased risk of developing endoscopic AG and IM, supporting a role of alcohol consumption in the pathogenesis of AG and IM, the precursor lesions of stomach cancer.

IMPACT

Alcohol consumption from low-level drinking may contribute to gastric carcinogenesis.

Alcohol and coronary artery calcification: an investigation using alcohol flushing as an instrumental variable

Background

We examined whether alcohol flushing could be used as an instrumental variable (IV) and investigated the effect of alcohol consumption on coronary calcification using alcohol flushing status as an IV.

Methods

We analysed cross-sectional data from 24 681 Korean adults (20 696 men and 3985 women) who had been administered a questionnaire assessing alcohol consumption and alcohol flushing, as well as a coronary artery calcium (CAC) measurement. The associations of alcohol flushing status with potential confounders and alcohol consumption were examined. We employed two-stage predictor substitution methodology for the IV analysis.

Results

The prevalence of alcohol flushing did not differ depending on gender, education, household income, cigarette smoking or physical activity. Balanced levels of confounders were observed between alcohol flushers and non-flushers. Alcohol flushing was closely related to alcohol consumption and levels of liver enzymes. In men, a doubling in alcohol consumption was associated with increased odds of coronary calcification in both the IV analysis [odds ratio (OR) of CAC scores of 1 or over = 1.11; 95% confidence interval (CI) = 1.03-1.20) and the multivariable regression analysis (OR = 1.04; 95% CI = 1.01-1.07). For cardiovascular risk factors, the IV analysis showed a positive association between alcohol consumption and blood pressure and high-density lipoprotein-cholesterol.

Conclusions

Alcohol flushing can be used as an IV in studies evaluating the health impact of alcohol consumption, especially in East Asian countries. Through such an analysis, we found that increased alcohol consumption was associated with an increased risk of subclinical coronary atherosclerosis.

Genetic Polymorphisms of the Mitochondrial Aldehyde Dehydrogenase ALDH2 Gene in a Large Ethnic Hakka Population in Southern China

Background

Human mitochondrial aldehyde dehydrogenase 2 (ALDH2) plays a critical role in the detoxification of the ethanol metabolite acetaldehyde. The ALDH2*2 (rs671) gene variant is mainly absent among Europeans but is prevalent in populations in East Asia. The aim of this study was to investigate ALDH2*2 mutant alleles and genotype frequencies in the Hakka population of China.

Material/Methods

Between January 2016 and June 2017, 7,966 unrelated individuals were recruited into the study from the Hakka ethnic population residing in the Meizhou area of Guangdong Province, China, who provided venous blood samples. Genotyping of ALDH2 genotypes were determined using a gene chip platform and confirmed by DNA sequencing.

Results

In the 7,966 individuals from the Hakka population of China in this study, the frequencies of the ALDH2 genotypes *1/*1, *1/*2 and *2/*2 were 52.03%, 39.67%, and 8.30%, respectively; 47.97% of the individuals were found to carry the ALDH2*2 genotype, which was associated with a deficiency in the aldehyde dehydrogenase (ALDH2) enzyme activity. The frequency of the ALDH2*2 allele was lower than that previously reported in the Japanese population but higher than that reported in other Oriental populations.

Conclusions

The findings of this study have provided new information on the ALDH2 gene polymorphisms in the Hakka ethnic population residing in the Meizhou area of Guangdong Province, China, including an understanding of the origin of the atypical ALDH2*2 allele. Also, the study findings may be relevant to the primary care of patients in China.

A standardized extract of the fruit of Hovenia dulcis alleviated alcohol-induced hangover in healthy subjects with heterozygous ALDH2: A randomized, controlled, crossover trial

ETHNOPHARMACOLOGICAL RELEVANCE

Hovenia dulcis, known as the oriental raisin tree, is mainly found in East Asia. It has long been used as traditional folk remedies for alcohol intoxication.

AIM OF THE STUDY

To examine the anti-hangover effect of Hovenia dulcis Thunb. fruit extract (HDE) in a randomized controlled crossover trial.

MATERIALS AND METHODS

Twenty-six eligible male adults with heterozygous ALDH2 (23.7±0.3 years old) consumed 360mL of Korean Soju (50g alcohol) together with HDE (2460mg) or matched placebo with subsequent crossover. The blood samples were taken at baseline and 1, 4, and 12h post-treatment.

RESULTS

Blood alcohol, acetaldehyde, and total hangover scores were highest at 1h post-treatment with no difference between groups, but declines in hangover symptom scores were significant in the HDE group compared to the placebo group. Significant differences between groups were also observed on interleukin (IL)-6, IL-10, IL-10/IL-6 ratio, and aspartate aminotransferase levels, but not on endotoxins. Pearson correlation analysis revealed a positive correlation between total hangover symptom scores and IL-6 and IL-10 level. Further analyses by CYP2E1 polymorphism at rs10776687, rs2031920, rs3813867, and rs4838767 alleles showed a reversed association, suggesting that CYP2E1 polymorphism might be an effect modifier.

CONCLUSIONS

The results suggest that a favorable effect of HDE on alcohol hangovers might be associated with enhancing homeostatic regulation of inflammatory response. The magnitude of impact might be different in the presence of CYP2E1 polymorphism.

Peripheral blood lymphocyte micronucleus frequencies in men from areas of Kerala, India, with high vs normal levels of natural background ionizing radiation

We have measured the frequencies of micronuclei (MN) in adult male individuals living in areas of the Kerala coast, southwest India, with either high (HLNRA, >1.5mGy/year) or normal levels of natural ionizing radiation (NLNRA, ≤1.5mGy/year). Blood samples were obtained from 141 individuals, 94 from HLNRA and 47 from NLNRA, aged 18-72, and were subjected to the cytokinesis-block micronucleus (CBMN) assay. An average of 1835 binucleated (BN) cells per individual were scored. The overall frequency of MN (mean±SD) was 11.7±6.7 per 1000 BN cells. The frequencies of MN in the HLNRA (11.7±6.6) and NLNRA (11.6±6.7) were not statistically significantly different (P=0.59). However, a statistically significant (P<0.001) age-dependent increase in MN frequency was observed among individuals from both HLNRA and NLNRA. No natural background radiation dose-dependent increase in MN frequency was seen. MN frequency was not influenced by tobacco smoking or chewing but it was increased among individuals consuming alcohol. Chronic low-dose radiation in the Kerala coast did not have a significant effect on MN frequency among adult men.

Chromosomal DNA damage in APOE ɛ4 carriers and noncarriers does not appear to be different

DNA damage may play a key role in promoting disease-onset and accelerated disease progression in Alzheimer's disease (AD) by increasing the rates of neuronal cell death. The ɛ4 allele of the APOE gene is the best characterised genetic risk factor for AD, however, it is unknown if APOE ɛ4 carriers exhibit increased levels of DNA damage which may contribute to increased AD risk. 175 healthy participants (aged 34-67 years old) from South Australia were recruited into the study and provided a single blood sample for the isolation of peripheral blood lymphocytes, APOE genotyping and lymphocyte chromosomal DNA damage analysis using the Cytokinesis-Block micronucleus cytome (CBMN-Cyt) assay with the micronucleus index being the primary outcome measure. When compared to non-APOE ɛ4 carriers, APOE ɛ4 carriers did not exhibit altered rates of i) cell division, represented by the nuclear division index (NDI, P = 0.372), ii) cell death as represented by apoptotic (P = 0.457) and necrotic (P = 0.393) frequencies and iii) chromosomal DNA damage as indicated by the number of micronuclei (MNi, P = 0.795), nucleoplasmic bridges (NPBs, P = 0.221) or nuclear buds (NBUDs, P = 0.293) scored in binucleated cells. In conclusion, although we and others have previously shown that rates of chromosomal DNA damage measured using the CBMN-Cyt assay are elevated in individuals with cognitive impairment, in this South Australian cohort the frequency of genome instability is not substantially influenced by the presence of the APOE ɛ4 allele.

Nutriomes and personalised nutrition for DNA damage prevention, telomere integrity maintenance and cancer growth control

DNA damage at the base sequence and chromosome level is a fundamental cause of developmental and degenerative diseases. Multiple micronutrients and their interactions with the inherited and/or acquired genome determine DNA damage and genomic instability rates. The challenge is to identify for each individual the combination of micronutrients and their doses (i.e. the nutriome) that optimises genome stability, including telomere integrity and functionality and DNA repair. Using nutrient array systems with high-content analysis diagnostics of DNA damage, cell death and cell growth, it is possible to define, on an individual basis, the optimal nutriome for DNA damage prevention and cancer growth control. This knowledge can also be used to improve culture systems for cells used in therapeutics such as stem cells to ensure that they are not genetically aberrant when returned to the body. Furthermore, this information could be used to design dietary patterns that deliver the micronutrient combinations and concentrations required for preventing DNA damage by micronutrient deficiency or excess. Using this approach, new knowledge could be obtained to identify the dietary restrictions and/or supplementations required to control specific cancers, which is particularly important given that reliable validated advice is not yet available for those diagnosed with cancer.

The acute effects of ethanol and acetaldehyde on physiological responses after ethanol ingestion in young healthy men with different ALDH2 genotypes

BACKGROUND

This study investigated the acute effects of ethanol and acetaldehyde on physiological responses in healthy men according to ALDH2 genotype by measuring them directly in human blood.

METHODS

Twenty-four men, 12 with the ALDH2*1/*1 genotype and 12 with the ALDH2*1/*2 genotype, were selected. In a double-blind placebo-controlled crossover design, each subject was administered one of three doses of ethanol (0.25, 0.5 or 0.75 g/kg) or a placebo on four separate occasions. The blood ethanol concentration (BEC), blood acetaldehyde concentration (BAAC) and physiological responses including facial redness, pulse rate and systolic and diastolic blood pressures were assessed.

RESULTS

Significant differences were observed in the physiological responses between the ALDH2*1/*2 and ALDH2*1/*1 groups. Significant gene effects were observed for pulse rate and facial flushing (F-values =62.344; p values <0.001 and F-values =7.062; p values =0.010, respectively, by repeated-measures analysis of variance), which were significantly greater in subjects with the ALDH2*1/*2 genotype. In a linear regression analysis, BAAC significantly predicted increased facial redness at 30 minutes (adjusted R( 2 ): 0.209; p values <0.001) and pulse rate at 30, 60, 90 and 120 minutes (adjusted R( 2 ): 0.454, 0.490, 0.428 and 0.193, respectively; all p values <0.001), whereas BEC was not associated with any physiological response measure at any time.

CONCLUSIONS

Facial redness and pulse rate after ethanol ingestion were significantly higher in the ALDH2*1/*2 genotype, and were significantly associated with blood acetaldehyde concentrations. The acute effects of ethanol on the physiological responses were mediated mainly by acetaldehyde, the active metabolite of ethanol, rather than by ethanol itself.

Genetic and environmental influences on spontaneous micronuclei frequencies in children and adults: a twin study

The primary aim of this study was to quantify genetic and environmental influences on the frequency of spontaneously occurring micronuclei in children and adults. To meet this aim, a total of 63 male and female twin pairs and 19 singletons (145 individuals) were evaluated, ranging in age from 7 to 85 years. Micronuclei frequencies significantly increased with age for both genders (r = 0.49, P < 0.001), with the lowest and highest rates being seen in the 7- to 9 (mean = 0.56%, SD = .28) and 60- to 69-year-olds (mean = 2.12%, SD = 1.0), respectively. This age effect was significantly more pronounced in females than males (P = 0.017). In addition to the main effect of age, the completion of puberty in either gender (P = 0.036) and menopause in females (P = 0.024) was associated with a significant increase in micronuclei frequencies. Genetic model fitting indicated that influences from both additive genetic (65.2% of variance) and unique environmental (34.8% of variance) sources best explained the observed micronuclei frequencies in monozygotic and dizygotic twin pairs. Self-reported health conditions associated with an increased frequency of micronuclei included a history of allergies (P < 0.007) and migraines (P = 0.026). Multivitamin use was also associated with increased micronuclei frequencies (P = 0.004). In contrast, significantly lower micronuclei frequencies were associated with arthritis (P = 0.002), as well as consuming fruit (P = 0.014), green, leafy vegetables (P < 0.001) and/or folate-enriched bread (P = 0.035). A sex-specific effect, resulting in a significantly increased frequency of micronuclei with tobacco usage, was observed for females (but not males). Gender differences also moderated the impact of vitamin D and calcium consumption. In conclusion, the frequency of spontaneously arising micronuclei in humans is a complex trait, being influenced by both heritable genetic and environmental components. Recognition of factors contributing to baseline levels of micronuclei should provide guidance to researchers in designing studies to evaluate agents hypothesised to influence chromosomal instability.

Nutriomes and nutrient arrays - the key to personalised nutrition for DNA damage prevention and cancer growth control

DNA damage at the base-sequence, epigenome and chromosome level is a fundamental cause of developmental and degenerative diseases. Multiple micronutrients and their interactions with the inherited and/or acquired genome determine DNA damage and genomic instability rates. The challenge is to identify for each individual the combination of micronutrients and their doses (i.e. the nutriome) that optimises genome stability and DNA repair. In this paper I describe and propose the use of high-throughput nutrient array systems with high content analysis diagnostics of DNA damage, cell death and cell growth for defining, on an individual basis, the optimal nutriome for DNA damage prevention and cancer growth control.

The influence of genetic polymorphisms on population variability in six xenobiotic-metabolizing enzymes

This review provides variability statistics for polymorphic enzymes that are involved in the metabolism of xenobiotics. Six enzymes were evaluated: cytochrome P-450 (CYP) 2D6, CYP2E1, aldehyde dehydrogenase-2 (ALDH2), paraoxonase (PON1), glutathione transferases (GSTM1, GSTT1, and GSTP1), and N-acetyltransferases (NAT1 and NAT2). The polymorphisms were characterized with respect to (1) number and type of variants, (2) effects of polymorphisms on enzyme function, and (3) frequency of genotypes within specified human populations. This information was incorporated into Monte Carlo simulations to predict the population distribution and describe interindividual variability in enzyme activity. The results were assessed in terms of (1) role of these enzymes in toxicant activation and clearance, (2) molecular epidemiology evidence of health risk, and (3) comparing enzyme variability to that commonly assumed for pharmacokinetics. Overall, the Monte Carlo simulations indicated a large degree of interindividual variability in enzyme function, in some cases characterized by multimodal distributions. This study illustrates that polymorphic metabolizing systems are potentially important sources of pharmacokinetic variability, but there are a number of other factors including blood flow to liver and compensating pathways for clearance that affect how a specific polymorphism will alter internal dose and toxicity. This is best evaluated with the aid of physiologically based pharmacokinetic (PBPK) modeling. The population distribution of enzyme activity presented in this series of articles serves as inputs to such PBPK modeling analyses.

Genetic polymorphisms and micronucleus formation: a review of the literature

The formation of micronuclei (MN) is extensively used in molecular epidemiology as a biomarker of chromosomal damage, genome instability, and eventually of cancer risk. The occurrence of MN represents an integrated response to chromosome-instability phenotypes and altered cellular viabilities caused by genetic defects and/or exogenous exposures to genotoxic agents. The present article reviews human population studies addressing the relationship between genetic polymorphisms and MN formation, and provides insight into how genetic variants could modulate the effect of environmental exposures to genotoxic agents, host factors (gender, age), lifestyle characteristics (smoking, alcohol, folate), and diseases (coronary artery disease, cancer). Seventy-two studies measuring MN frequency either in peripheral blood lymphocytes or exfoliated cells were retrieved after an extensive search of the MedLine/PubMed database. The effect of genetic polymorphisms on MN formation is complex, influenced to a different extent by several polymorphisms of proteins or enzymes involved in xenobiotic metabolism, DNA repair proteins, and folate-metabolism enzymes. This heterogeneity reflects the presence of multiple external and internal exposures, and the large number of chromosomal alterations eventually resulting in MN formation. Polymorphisms of EPHX, GSTT1, and GSTM1 are of special importance in modulating the frequency of chromosomal damage in individuals exposed to genotoxic agents and in unexposed populations. Variants of ALDH2 genes are consistently associated with MN formation induced by alcohol drinking. Carriers of BRCA1 and BRCA2 mutations (with or without breast cancer) show enhanced sensitivity to clastogens. Some evidence further suggests that DNA repair (XRCC1 and XRCC3) and folate-metabolism genes (MTHFR) also influence MN formation. As some of the findings are based on relatively small numbers of subjects, larger scale studies are required that include scoring of additional endpoints (e.g., MN in combination with fluorescent in situ hybridization, analysis of nucleoplasmic bridges and nuclear buds), and address gene-gene interactions.

Candidate genes, pathways and mechanisms for alcoholism: an expanded convergent functional genomics approach

We describe a comprehensive translational approach for identifying candidate genes for alcoholism. The approach relies on the cross-matching of animal model brain gene expression data with human genetic linkage data, as well as human tissue data and biological roles data, an approach termed convergent functional genomics. An analysis of three animal model paradigms, based on inbred alcohol-preferring (iP) and alcohol-non-preferring (iNP) rats, and their response to treatments with alcohol, was used. A comprehensive analysis of microarray gene expression data from five key brain regions (frontal cortex, amygdala, caudate-putamen, nucleus accumbens and hippocampus) was carried out. The Bayesian-like integration of multiple independent lines of evidence, each by itself lacking sufficient discriminatory power, led to the identification of high probability candidate genes, pathways and mechanisms for alcoholism. These data reveal that alcohol has pleiotropic effects on multiple systems, which may explain the diverse neuropsychiatric and medical pathology in alcoholism. Some of the pathways identified suggest avenues for pharmacotherapy of alcoholism with existing agents, such as angiotensin-converting enzyme (ACE) inhibitors. Experiments we carried out in alcohol-preferring rats with an ACE inhibitor show a marked modulation of alcohol intake. Other pathways are new potential targets for drug development. The emergent overall picture is that physical and physiological robustness may permit alcohol-preferring individuals to withstand the aversive effects of alcohol. In conjunction with a higher reactivity to its rewarding effects, they may able to ingest enough of this nonspecific drug for a strong hedonic and addictive effect to occur.

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

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