Do alcohol-metabolizing enzyme gene polymorphisms increase the risk of alcoholism and alcoholic liver disease?

Prenatal alcohol exposure and offspring cognition and school performance. A 'Mendelian randomization' natural experiment

BACKGROUND

There is substantial debate as to whether moderate alcohol use during pregnancy could have subtle but important effects on offspring, by impairing later cognitive function and thus school performance. The authors aimed to investigate the unconfounded effect of moderately increased prenatal alcohol exposure on cognitive/educational performance.

METHODS

We used mother-offspring pairs participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) and performed both conventional observational analyses and Mendelian randomization using an ADH1B variant (rs1229984) associated with reduced alcohol consumption. Women of White European origin with genotype and self-reported prenatal alcohol consumption, whose offspring's IQ score had been assessed in clinic (N=4061 pairs) or Key Stage 2 (KS2) academic achievement score was available through linkage to the National Pupil Database (N=6268), contributed to the analyses.

RESULTS

Women reporting moderate drinking before and during early pregnancy were relatively affluent compared with women reporting lighter drinking, and their children had higher KS2 and IQ scores. In contrast, children whose mothers' genotype predisposes to lower consumption or abstinence during early pregnancy had higher KS2 scores (mean difference +1.7, 95% confidence interval +0.4, +3.0) than children of mothers whose genotype predisposed to heavier drinking, after adjustment for population stratification.

CONCLUSIONS

Better offspring cognitive/educational outcomes observed in association with prenatal alcohol exposure presumably reflected residual confounding by factors associated with social position and maternal education. The unconfounded Mendelian randomization estimates suggest a small but potentially important detrimental effect of small increases in prenatal alcohol exposure, at least on educational outcomes.

Alcoholic liver disease and pancreatitis: global health problems being addressed by the US National Institute on Alcohol Abuse and Alcoholism

The review article summarizes the mission of the National Institute on Alcohol Abuse and Alcoholism (NIAAA) with focus on the NIAAA's current and future research version for alcoholic liver disease and alcoholic pancreatitis.

The role of sociodemographic factors in the risk of transition from alcohol use to disorders and remission in singapore

AIMS

The aim of the study was to define predictors of transition from alcohol use to disorders, and their remission, among adults residing in Singapore.

METHODS

The Singapore Mental Health Study was a cross-sectional survey conducted from December 2009 to December 2010. Information on alcohol use, regular use, DSM-IV criteria for abuse and dependence, and remission among 6616 respondents was obtained with the Composite International Diagnostic Interview.

RESULTS

The prevalence of lifetime alcohol use (drinking at least once in the lifetime) and regular use (ever drinking at least 12 drinks in a 12-month period) was 66.6 and 32%, respectively. Of the regular drinkers, 10.1% progressed into alcohol abuse; 6.9% of abusers turned to alcohol dependence and 16.6 and 7.1% of those with history of alcohol abuse and/or dependence subsequently reported remission defined as cessation of alcohol use and the absence of any symptoms for at least 2 years before interview. Transitions to regular use and to dependence were associated with younger age, Indian ethnicity and an early age of onset of drinking, and women had a higher risk than men of transition from abuse to dependence. Remissions were associated with older age, Malay ethnicity and late age of onset.

CONCLUSION

The rates of alcohol use and transition to disorders were lower than in other developing countries that have been studied. Sociodemographic predictors include younger age of onset of drinking, something that intervention programs and preventive strategies in Singapore should note.

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.

Gene specific modifications unravel ethanol and acetaldehyde actions

Ethanol is metabolized into acetaldehyde mainly by the action of alcohol dehydrogenase in the liver, while mainly by the action of catalase in the brain. Aldehyde dehydrogenase-2 metabolizes acetaldehyde into acetate in both organs. Gene specific modifications reviewed here show that an increased liver generation of acetaldehyde (by transduction of a gene coding for a high-activity liver alcohol dehydrogenase ADH1^*B2) leads to increased blood acetaldehyde levels and aversion to ethanol in animals. Similarly aversive is an increased acetaldehyde level resulting from the inhibition of liver aldehyde dehydrogenase-2 (ALDH2) synthesis (by an antisense coding gene against aldh2 mRNA). The situation is diametrically different when acetaldehyde is generated in the brain. When the brain ventral tegmental area (VTA) is endowed with an increased ability to generate acetaldehyde (by transfection of liver rADH) the reinforcing effects of ethanol are increased, while a highly specific inhibition of catalase synthesis (by transduction of a shRNA anti catalase mRNA) virtually abolishes the reinforcing effects of ethanol as seen by a complete abolition of ethanol intake in rats bred for generations as high ethanol drinkers. Data shows two divergent effects of increases in acetaldehyde generation: aversive in the periphery but reinforcing in the brain.

Genetic polymorphisms of alcohol dehydrogenase-1B and aldehyde dehydrogenase-2 and liver cirrhosis, chronic calcific pancreatitis, diabetes mellitus, and hypertension among Japanese alcoholic men

BACKGROUND

The presence of the less-active form of alcohol dehydrogenase-1B encoded by ADH1B*1/*1 (vs. *2 allele) and active form of aldehyde dehydrogenase-2 (ALDH2) encoded by ALDH2*1/*1 (vs. *2 allele) increases the risk of alcoholism in East Asians.

METHODS

The subjects in this cross-sectional survey were 1,902 Japanese alcoholic men (≥40 years) who underwent ADH1B/ALDH2 genotyping.

RESULTS

Age-adjusted daily alcohol consumption did not differ according to the ADH1B/ALDH2 genotypes. The age-adjusted odds ratios (AORs; 95% confidence interval) for liver cirrhosis (LC; n = 359, 1.58 [1.19 to 2.09]), chronic calcific pancreatitis (CP; n = 80, 2.24 [1.20 to 4.20]), and diabetes mellitus (DM; n = 383, 1.51 [1.15 to 1.99]) were higher in the ADH1B*2 allele carriers than in the ADH1B*1/*1 carriers. The AORs for LC (1.43 [1.01 to 2.02]), CP (1.68 [0.80 to 3.53]), DM (1.63 [1.15 to 2.30]), and hypertension (HT; n = 495, 1.52 [1.11 to 2.07]) were higher in the ALDH2*1/*1 carriers than in the ALDH2*1/*2 carriers. The ADH1B*2-associated AOR for LC was 2.08 (1.46 to 2.94) among those aged 40 to 59 years, but 0.89 (0.56 to 1.43) among those aged 60 years or over, and the interaction between ADH1B genotype and age on the LC risk was significant (p = 0.009). When the group with non-LC and no/mild fibrosis was used as controls, the ADH1B*2-associated AORs increased according to the severity of their liver disease: 1.67 (1.32 to 2.11) for the group with non-LC and serum type IV collagen values ≥200 ng/ml, 1.81 (1.24 to 2.63) for the group of Child-Pugh class A LC, and 3.17 (1.98 to 5.07) for the group with Child-Pugh class B/C LC. Anti-hepatitis C virus (HCV) antibody was positive in 103 patients, and the groups with a high anti-HCV antibody titer and either the ADH1B*2/*2 genotype or the ALDH2*1/*1 genotype had the highest AORs (8.83 and 4.90, respectively). The population attributable fraction (PAF) due to the ADH1B*2 allele was 29% for LC, 47% for CP, and 27% for DM, and the PAF due to the ALDH2*1/*1 genotype was 26% for LC, 34% for DM, and 30% for HT.

CONCLUSIONS

The ADH1B*2 allele increased the AORs for LC, CP, and DM of the alcoholics, and the ALDH2*1/*1 genotype increased their AORs for LC, DM, and HT. HCV infection and genetic susceptibility had a synergistic effect on the AOR for LC.

Alcohol dehydrogenase-1B genotype (rs1229984) is a strong determinant of the relationship between body weight and alcohol intake in Japanese alcoholic men

BACKGROUND

The calories in alcoholic beverages consumed by alcoholics are a major energy source and a strong modifier of their body weight. Genetic polymorphisms of alcohol dehydrogenase-1B (ADH1B) and aldehyde dehydrogenase-2 (ALDH2) affect susceptibility to alcoholism and may affect body weight via gene-associated differences in fuel utilization in alcoholics.

METHODS

We evaluated associations between ADH1B/ALDH2 genotypes and the body weight and body mass index (BMI) of 1,301 Japanese alcoholic men at the time of their first visit to an addiction center.

RESULTS

Median (25th to 75th) caloric intake in the form of alcoholic beverages was 864 (588 to 1,176) kcal/d. Age-adjusted caloric intake did not differ according to ADH1B/ALDH2 genotypes. The body weight and BMI values showed that the ADH1B*2/*2 and *1/*2 carriers (n = 939) were significantly leaner than the ADH1B*1/*1 carriers (n = 362) irrespective of age, drinking, smoking, and dietary habits. The age-adjusted body weight values of the ADH1B*2/*2, ADH1B*1/*2, and ADH1B*1/*1 carriers were 58.4 ± 0.4, 58.7 ± 0.5, and 63.6 ± 0.5 kg, respectively (ADH1B*2 vs. ADH1B*1/*1 carriers, p < 0.0001), and the corresponding BMI values were 21.0 ± 0.1, 21.0 ± 0.1, and 22.9 ± 0.2 kg/m(2) , respectively (ADH1B*2 vs. ADH1B*1/*1 carriers, p < 0.0001). No effects of inactive ALDH2 on body weight or BMI were observed. A multivariate analysis showed that BMI decreased by 0.35 per 10-year increase in age, by 1.73 in the presence of the ADH1B*2 allele, by 1.55 when the preferred beverage was whiskey, and by 0.19 per +10 cigarettes/d and that it increased by 0.10 per +22 g ethanol (EtOH)/d and by 0.41 per increase in category of frequency of milk intake (every day, occasionally, rarely, and never). The increase in BMI as alcohol consumption increased was significantly smaller in the ADH1B*2 group than in the ADH1B*1/*1 group (p = 0.002).

CONCLUSIONS

ADH1B genotype was a strong determinant of body weight in the alcoholics. The more rapid EtOH elimination associated with the ADH1B*2 allele may result in less efficient utilization of EtOH as an energy source in alcoholics.

Roles of cytochrome P4502E1 gene polymorphisms and the risks of alcoholic liver disease: a meta-analysis

Background

Previous studies investigating the association between cytochrome P4502E1 (CYP2E1) polymorphisms and the risk of alcoholic liver diseases (ALD) have yielded conflicting results. Thus, a meta-analysis was performed to clarify the association between CYP2E1 polymorphisms and the risks of ALD.

Methods

A comprehensive literature search was conducted to identify the relevant studies. The fixed or random effect model was selected based on the heterogeneity test among studies. Publication bias was estimated using Begg’s funnel plots and Egger’s regression test.

Results

A total of 27 and 9 studies were finally included for the association between the CYP2E1 Pst I/Rsa I or Dra I polymorphisms and the risks of ALD, respectively. Overall, the combined results showed that homozygous genotype c2c2 was significantly associated with increase risk of ALD in worldwide populations (c2c2 vs. c1c1: OR = 3.12, 95%CI 1.91–5.11) when ALD patients were compared with alcoholics without ALD. Significant associations between CYP2E1 Pst I/Rsa I polymorphism and ALD risk were also observed in Asians (c2c2 vs. c1c1: OR = 4.11, 95%CI 2.32–7.29) and in Caucasians (c2c2/c1c2 vs. c1c1: OR = 1.58, 95%CI 1.04–2.42) when ALD patients were compared with alcoholics without ALD. However, subgroup analysis stratified by ALD types showed that CYP2E1 Pst I/Rsa I polymorphism was not significantly associated with the risks of alcoholic cirrhosis (ALC). No significant association was observed between CYP2E1 Dra I polymorphism and ALD risks.

Conclusion

This meta-analysis suggested that CYP2E1 Pst I/Rsa I polymorphism might be not significantly associated with advanced form of ALD (ALC), but might be significantly associated with other form of ALD such as steatosis, hepatisis, fibrosis. Furthermore, CYP2E1 Dra I polymorphism might be not significantly associated with the ALD risks. Since potential confounders could not be ruled out completely, further studies were needed to confirm these results.

Trends in gastrectomy and ADH1B and ALDH2 genotypes in Japanese alcoholic men and their gene-gastrectomy, gene-gene and gene-age interactions for risk of alcoholism

AIMS

The life-time drinking profiles of Japanese alcoholics have shown that gastrectomy increases susceptibility to alcoholism. We investigated the trends in gastrectomy and alcohol dehydrogenase-1B (ADH1B) and aldehyde dehydrogenase-2 (ALDH2) genotypes and their interactions in alcoholics.

METHODS

This survey was conducted on 4879 Japanese alcoholic men 40 years of age or older who underwent routine gastrointestinal endoscopic screening during the period 1996-2010. ADH1B/ALDH2 genotyping was performed in 3702 patients.

RESULTS

A history of gastrectomy was found in 508 (10.4%) patients. The reason for the gastrectomy was peptic ulcer in 317 patients and gastric cancer in 187 patients. The frequency of gastrectomy had gradually decreased from 13.3% in 1996-2000 to 10.5% in 2001-2005 and to 7.8% in 2006-2010 (P < 0.0001). ADH1B*1/*1 was less frequent in the gastrectomy group than in the non-gastrectomy group (age-adjusted prevalence: 20.4 vs. 27.6%, P = 0.006). ALDH2 genotype distribution did not differ between the two groups. The frequency of inactive ALDH2*1/*2 heterozygotes increased slightly from 13.0% in 1996-2000 to 14.0% in 2001-2005 and to 15.4% in 2006-2010 (P < 0.08). Two alcoholism-susceptibility genotypes, ADH1B*1/*1 and ALDH2*1/*1, modestly but significantly tended not to occur in the same individual (P = 0.026). The frequency of ADH1B*1/*1 decreased with ascending age groups.

CONCLUSIONS

The high frequency of history of gastrectomy suggested that gastrectomy is still a risk factor for alcoholism, although the percentage decreased during the period. The alcoholism-susceptibility genotype ADH1B*1/*1 was less frequent in the gastrectomy group, suggesting a competitive gene-gastrectomy interaction for alcoholism. A gene-gene interaction and gene-age interactions regarding the ADH1B genotype were observed.

Genetic instrumental variable studies of effects of prenatal risk factors

Identifying the effects of maternal risk factors during pregnancy on infant and child health is an area of tremendous research interest. However, policymakers are primarily interested in unraveling the causal effects of prenatal risk factors, not their associations with child health, which may be confounded by several unobserved factors. In this article, we evaluate the utility of genetic variants in three genes that have unequivocal evidence of being related to three major risk factors-CHRNA3 for smoking, ADH1B for alcohol use, and FTO for obesity-as instrumental variables for identifying the causal effects of such factors during pregnancy. Using two independent datasets, we find that these variants are overall predictive of the risk factors and are not systematically related to observed confounders, suggesting that they may be useful instruments. We also find some suggestive evidence that genetic effects are stronger during than before pregnancy. We provide an empirical example illustrating the use of these genetic variants as instruments to evaluate the effects of risk factors on birth weight. Finally, we offer suggestions for researchers contemplating the use of these variants as instruments.

Alcohol metabolism

This article describes the pathways and factors that modulate blood alcohol levels and metabolism and describes how the body disposes of alcohol. The various factors that play a role in the distribution of alcohol in the body, influence the absorption of alcohol, and contribute to first-pass metabolism of alcohol are described. Most alcohol is oxidized in the liver, and general principles and overall mechanisms for alcohol oxidation are summarized. The kinetics of alcohol elimination in-vivo and the various genetic and environmental factors that can modify the rate of alcohol metabolism are discussed.

Peter Riederer "70th birthday" neurobiological foundations of modern addiction treatment

Alcohol dependence is caused by complex interactions of multiple susceptibility genes with little effect each and environmental factors. Candidate genes influence metabolism of alcohol, such as alcohol dehydrogenase and aldehyde dehydrogenase, and modulatory transmitter systems, such as the dopaminergic, serotonergic, acetylcholinergic, gamma-aminobutyric acidergic, and various neuropeptidergic systems. Dysfunctional behavioral choices, learning, and memory are involved in the etiology of alcohol dependence. Systematic promotion and maintenance of motivation is a lifetime challenge in the treatment of alcohol use disorders. The second step of treatment management is the discontinuation of alcohol consumption. Withdrawal symptoms can be treated with gamma-aminobutyric acidergic substances such as benzodiazepines. Long-term relapse prevention is another challenge. Multimodal treatment can include naltrexone, a non-selective opioid receptor antagonist, or acamprosate, an N-methyl-D-aspartate receptor modulator, which are first line for pharmacological treatment on the basis of recent Cochrane analyses. Due to the complexity of etiology with both psychological and neurobiological factors, future treatment management of alcoholism may include the combination of individualized disorder-specific psychotherapy and drugs acting on different neuronal pathways, on the basis of individual vulnerability. However, the question remains unsolved whether an individualized approach is feasible and how subgroups should be defined.

Further clarification of the contribution of the ADH1C gene to vulnerability of alcoholism and selected liver diseases

The alcohol dehydrogenase 1C (ADH1C) subunit is an important member of the alcohol dehydrogenase family, a set of genes that plays a major role in the catabolism of ethanol. Numerous association studies have provided compelling evidence that ADH1C gene variation (formerly ADH3) is associated with altered genetic susceptibility to alcoholism and alcohol-related liver disease, cirrhosis, or pancreatitis. However, the results have been inconsistent, partially, because each study involved a limited number of subjects, and some were underpowered. Using cumulative data over the past two decades, this meta-analysis (6,796 cases and 6,938 controls) considered samples of Asian, European, African, and Native American origins to examine whether the aggregate genotype provide statistically significant evidence of association. The results showed strong evidence of association between ADH1C Ile350Val (rs698, formerly ADH1C *1/*2) and alcohol dependence (AD) and abuse in the combined studies. The overall allelic (Val vs. Ile or *2 vs. *1) P value was 1 × 10(-8) and odds ratio (OR) was 1.51 (1.31, 1.73). The Asian populations produced stronger evidence of association with an allelic P value of 4 × 10(-33) [OR 2.14 (1.89, 2.43)] with no evidence of heterogeneity, and the dominant and recessive models revealed even stronger effect sizes. The strong evidence remained when stricter criteria and sub-group analyses were applied, while Asians always showed stronger associations than other populations. Our findings support that ADH1C Ile may lower the risk of AD and alcohol abuse as well as alcohol-related cirrhosis in pooled populations, with the strongest and most consistent effects in Asians.

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.

Strong protective effect of the aldehyde dehydrogenase gene (ALDH2) 504lys (*2) allele against alcoholism and alcohol-induced medical diseases in Asians

Alcohol is oxidized to acetaldehyde, which in turn is oxidized to acetate. The aldehyde dehydrogenase 2 gene (ALDH2) is the most important gene responsible for acetaldehyde metabolism. Individuals heterozygous or homozygous for the lys (A or *2) allele at the single nucleotide polymorphism (SNP) glu504lys (rs671) of ALDH2 have greatly reduced ability to metabolize acetaldehyde, which greatly decreases their risk for alcohol dependence (AD). Case-control studies have shown association between this SNP and alcohol dependence as well as alcohol-induced liver disease. However, some studies have produced insignificant results. Using cumulative data from the past 20 years predominately from Asian populations (from both English and Chinese publications), this meta-analysis sought to examine and update whether the aggregate data provide new evidence of statistical significance for the proposed association. Our results (9,678 cases and 7,331 controls from 53 studies) support a strong association of alcohol abuse and dependence, with allelic P value of 3 × 10(-56) and OR of 0.23 (0.2, 0.28) under the random effects model. The dominant model (lys-lys + lys-glu vs. glu-glu) also showed strong association with P value of 1 × 10(-44) and OR of 0.22 (0.18, 0.27). When stricter criteria and various sub-group analyses were applied, the association remained strong (for example, OR = 0.23 (0.18, 0.3) and P = 2 × 10(-28) for the alcoholic patients with alcoholic liver disease, cirrhosis, or pancreatitis). These findings provide confirmation of the involvement of the human ALDH2 gene in the pathogenesis of AD as well as alcohol-induced medical illnesses in East-Asians.

Reduction of ethanol consumption in alcohol-preferring rats by dual expression gene transfer

AIMS

To mimic, in an animal model of alcoholism, the protective phenotype against alcohol consumption observed in humans carrying a fast alcohol dehydrogenase (ADH1B*2) and an inactive aldehyde dehydrogenase (ALDH2*2).

METHODS

We developed a multiple expression cassette adenoviral vector (AdV-ADH/asALDH2) encoding both a fast rat ADH and an antisense RNA against rat ALDH2. A control adenoviral vector (AdV-C) containing intronic non-coding DNA was also developed. These adenoviral vectors were administered intravenously to rats bred as high alcohol-drinkers (University of Chile bibulous) that were previously rendered alcohol dependent by a 75-day period of voluntary 10% ethanol intake.

RESULTS

Animals administered AdV-ADH/asALDH2 showed a 176% increase in liver ADH activity, whereas liver ALDH2 activity was reduced by 24%, and upon the administration of a dose of ethanol (1 g/kg, i.p.), these showed arterial acetaldehyde levels that were 400% higher than those of animals administered AdV-C. Rats that received the AdV-ADH/asALDH2 vector reduced by 60% their voluntary ethanol intake versus controls.

CONCLUSION

This study provides evidence that the simultaneous increase of liver ADH and a reduction of ALDH activity by gene transfer could constitute a potential therapeutic strategy for the treatment of alcoholism.

Estimating the mode of inheritance in genetic association studies of qualitative traits based on the degree of dominance index

BACKGROUND

The biological justification for the choice of the genetic mode in genetic association studies (GAS) is seldom available. Then, the mode of inheritance is approximated by investigating a number of non-orthogonal genetic contrasts making the interpretation of results difficult.

METHODS

We propose to define the mode of inheritance by the significance of the deviance of the co-dominant contrast and the degree of dominance (h), which is a function of two orthogonal contrasts (the co-dominant and additive). Non-dominance exists when the co-dominant contrast is non-significant and, hence, the risk effect of heterozygotes lies in the middle of the risk of the two homozygotes. Otherwise, dominance (including over- and under-dominance) is present and the direction of dominance depends on the value of h.

RESULTS

Simulations show that h may capture the real mode of inheritance and it is affected by deviations from Hardy-Weinberg equilibrium (HWE). In addition, power for detecting significance of h when the study conforms to HWE rule increases with the degree of dominance and to some extent is related to the mutant allele frequency.

CONCLUSION

The introduction of the degree of dominance provides useful insights into the mode of inheritance in GAS.

Meta-analysis: glutathione-S-transferase allelic variants are associated with alcoholic liver disease

BACKGROUND

Only a minority of alcoholics develop alcoholic liver disease (ALD) and allelic variants within genes encoding glutathione-S-transferases (GST) have been associated with ALD vulnerability with controversial results.

AIM

To assess the effects of GST polymorphisms on ALD by means of a genetic association study and meta-analysis.

METHODS

We retrieved published studies on the relationship between allelic variants within GST genes and ALD by means of electronic database search. A meta-analysis was conducted in a fixed or random effects model. Calculations of odds ratios (OR) and their confidence intervals (CI), tests for heterogeneity of the results and sensitivity analysis, have been performed. A genetic association study comparing GSTM1, GSTT1 and GSTP1 genotype distribution among 279 alcoholics with or without ALD and 144 controls was also performed. Results  Fifteen previous studies were identified analysing the association of ALD with polymorphisms within GST genes. After meta-analysis, we found a significant association between the possession of the GSTM1 null allele and the presence of ALD (OR=1.43; 95% CI: 1.14, 1.78; P=0.002) among alcoholic patients. A significant association was also found for the possession of the GSTP1 Val/Val genotype and the presence of ALD (OR=2.04; 95% CI: 1.09, 3.80; P=0.03).

CONCLUSIONS

Our results suggest that, among alcoholics, carriers of GSTM1 null genetic variant or Val/Val genotype of Ile/Val GSTP1 polymorphism have an increased risk to suffer from alcoholic liver disease. The role of glutathione-S-transferase as a potential therapeutic target in alcoholic liver disease is reinforced.

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.

Strong association of the alcohol dehydrogenase 1B gene (ADH1B) with alcohol dependence and alcohol-induced medical diseases

BACKGROUND

The alcohol dehydrogenase 1B gene (ADH1B) is hypothesized to affect predisposition to alcohol dependence (AD) and abuse. A variant of the ADH1B gene (rs1229984 or Arg48His; previously referred to as Arg [*1] and His [*1]) has been reported to be associated with reduced rates of alcohol and drug dependence. Different studies have produced inconclusive results regarding association between rs1229984 (or rs2066702) and substance dependence.

METHODS

Using the cumulative association study literature from the past 21 years from both English- and Chinese-language publications, this meta-analysis seeks to clarify the contradictory findings and to examine whether the aggregate data provide new evidence of significant association.

RESULTS

The results, based on a large sample size (9638 cases and 9517 controls), suggested strong associations with alcohol dependence and abuse as well as alcohol-induced liver diseases, with an allelic (Arg vs. His) p value being 1 × 10(-36) and odds ratio (OR) (95% confidence intervals [CI]) 2.06 (1.84-2.31) under the random effects model. The dominant and recessive models produced larger ORs of 2.17 and 3.05, respectively. When more stringent criteria and subgroup analyses were imposed, the associations remained consistent and were strongest in various Asian groups (allelic p = 7 × 10(-42) and OR (95% CI) = 2.24 [1.99-2.51] with ORs of 2.16 and 4.11 for dominant and recessive models, respectively).

CONCLUSIONS

Our findings provide further strong evidence for the involvement of the ADH1B gene in the pathogenesis of alcohol dependence and abuse as well as for some alcohol-induced medical diseases in the multiple ethnic populations--in particular, certain Asian populations.

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.

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

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

Alcoholic liver disease: pathogenesis and new targets for therapy

Alcoholic liver disease (ALD) is a major cause of morbidity and mortality worldwide. The spectrum of disease ranges from fatty liver to hepatic inflammation, necrosis, progressive fibrosis and hepatocellular carcinoma. In developed countries, ALD is a major cause of end-stage liver disease that requires transplantation. The most effective therapy for ALD is alcohol abstinence. However, for patients with severe forms of ALD (that is, alcoholic hepatitis) and for those who do not achieve abstinence from alcohol, targeted therapies are urgently needed. The development of new drugs for ALD is hampered by the scarcity of studies and the drawbacks of existing animal models, which do not reflect all the features of the human disease. However, translational research using liver samples from patients with ALD has identified new potential therapeutic targets, such as CXC chemokines, osteopontin and tumor necrosis factor receptor superfamily member 12A. The pathogenetic roles of these targets, however, remain to be confirmed in animal models. This Review summarizes the epidemiology, natural history, risk factors and current knowledge of the pathogenetic mechanisms of ALD. In addition, this article provides a detailed description of the findings of these translational studies and of the animal models used to study ALD.

UPLC-MS-based urine metabolomics reveals indole-3-lactic acid and phenyllactic acid as conserved biomarkers for alcohol-induced liver disease in the Ppara-null mouse model

Since the development and prognosis of alcohol-induced liver disease (ALD) vary significantly with genetic background, identification of a genetic background-independent noninvasive ALD biomarker would significantly improve screening and diagnosis. This study explored the effect of genetic background on the ALD-associated urinary metabolome using the Ppara-null mouse model on two different backgrounds, C57BL/6 (B6) and 129/SvJ (129S), along with their wild-type counterparts. Reversed-phase gradient UPLC-ESI-QTOF-MS analysis revealed that urinary excretion of a number of metabolites, such as ethylsulfate, 4-hydroxyphenylacetic acid, 4-hydroxyphenylacetic acid sulfate, adipic acid, pimelic acid, xanthurenic acid, and taurine, were background-dependent. Elevation of ethyl-β-d-glucuronide and N-acetylglycine was found to be a common signature of the metabolomic response to alcohol exposure in wild-type as well as in Ppara-null mice of both strains. However, increased excretion of indole-3-lactic acid and phenyllactic acid was found to be a conserved feature exclusively associated with the alcohol-treated Ppara-null mouse on both backgrounds that develop liver pathologies similar to the early stages of human ALD. These markers reflected the biochemical events associated with early stages of ALD pathogenesis. The results suggest that indole-3-lactic acid and phenyllactic acid are potential candidates for conserved and pathology-specific high-throughput noninvasive biomarkers for early stages of ALD.

Pathogenesis of alcohol-induced liver disease: classical concepts and recent advances

Alcoholic liver disease (ALD) is a primary consequence of heavy and prolonged drinking. ALD contributes to the bulk of liver disease burden worldwide. Progression of ALD is a multifactorial and multistep process that includes many genetic and environmental risk factors. The molecular pathogenesis of ALD involves alcohol metabolism and secondary mechanisms such as oxidative stress, endotoxin, cytokines and immune regulators. The histopathological manifestation of ALD occurs as an outcome of complex but controlled interactions between hepatic cell types. Hepatic stellate cells (HSCs) are the key drivers of fibrogenesis, but transformation of hepatocytes to myofibroblastoids also implicate parenchymal cells as playing an active role in hepatic fibrogenesis. Recent discoveries indicate that lipogenesis during the early stages of ALD is a risk for advancement to cirrhosis. Other recently identified novel molecules and physiological/cell signaling pathways include fibrinolysis, osteopontin, transforming growth factor-β-SMAD and hedgehog signaling, and involvement of novel cytokines in hepatic fibrogenesis. The observation that ALD and non-alcoholic steatohepatitis share common pathways and genetic polymorphisms suggests operation of parallel pathogenic mechanisms. Future research involving genomics, epigenomics, deep sequencing and non-coding regulatory elements holds promise to identify novel diagnostic and therapeutic targets for ALD. There is also a need for adequate animal models to study pathogenic mechanisms at the molecular level and targeted therapy.

p53 protein accumulation, iodine-unstained lesions, and alcohol dehydrogenase-1B and aldehyde dehydrogenase-2 genotypes in Japanese alcoholic men with esophageal dysplasia

Inactive heterozygous aldehyde dehydrogenase-2 (ALDH2(*)1/(*)2) and less-active alcohol dehydrogenase-1B (ADH1B(*)1/(*)1) increase the risk of esophageal cancer in East Asian drinkers, and esophageal cancer multiplicity is strongly associated with ALDH2(*)1/(*)2. p53 alterations are key molecular events in multifocal carcinogenesis in the esophagus. We studied 260 esophageal-cancer free Japanese alcoholics with esophageal dysplasia diagnosed by biopsy of distinct iodine-unstained lesions (DIULs) ≥5mm. The degree of p53 protein accumulation was positively associated with the degree of atypia (p<0.0001) and size (p=0.040) of DIULs and with the presence of multiple DIULs (p=0.070), but not with ALDH2(*)1/(*)2 or ADH1B(*)1/(*)1.

Gender-specific interactions between alcohol metabolism genes and severity of quantitative alcohol-related-traits in a Tibetan population

Association between genes influencing alcohol metabolism and alcohol use disorders (AUD) has been extensively studied, but the effect of interactions between these genes and AUD have rarely been tested. Our previous case-control study in a Tibetan population noted that the positive association between c2 allele of cytochrome P4502E1 (CYP2E1) gene and AUD might only exist in males who are homozygotes for 1 alleles of aldehyde dehydrogenase-2 (ALDH2) and alcohol dehydrogenase-1B (ADH1B) genes, but this interaction did not reach statistical significance. Using the same set of data, the present study was aimed at exploring interactions between these genes and quantitative alcohol-related-trait scores (QARTs), and whether these are influenced by gender. The sample included 383 AUD cases with the alcohol use disorders identification test (AUDIT) score ≥10 and 350 normal controls with the AUDIT score ≤5. QARTs were measured using three factors from AUDIT. Possible associations of QARTs with interactions among genotypes of ALDH2 1/ 2, ADH1B1/2 and CYP2E1 c1/c2 and sex were analyzed in AUD cases and normal controls separately. The subjects with 2 alleles of ALDH2 or/and ADH1B had significantly lower scores of alcohol intake among controls but had significantly higher scores of alcohol related problems among cases. The score of alcohol intake in male cases who are homozygous for ALDH2 1 and ADH1B 1 and with CYP2E1 c2 allele was significantly higher than that of other cases. These findings suggest that interactions between genes influencing alcohol metabolism are influenced by gender and might affect QARTs differently between the milder-/non-drinkers and AUD cases.

Genetics of alcohol dependence

Twin, family, and adoption studies have consistently shown that genetic factors play an important role in the pathogenesis of alcohol dependence. Numerous studies have aimed to identify genes that contribute to susceptibility to alcohol dependence. Whole-genome linkage studies have identified several chromosomal regions that are linked with alcohol dependence. Association studies have also identified genes associated with alcohol dependence. Alcohol-metabolizing enzymes, such as alcohol dehydrogenase-1B and aldehyde dehydrogenase-2, are the most well-established genes that have polymorphisms associated with the risk for alcohol dependence. Polymorphisms in gamma-aminobutyric acid receptor genes are also reported to be associated with alcohol dependence. The polymorphism of opioid receptor mu 1 gene is of interest because it alters the treatment effects of naltrexone. Several genes related to neural transmission have been reported to be associated with alcohol dependence, but results are inconsistent among studies. One reason for these inconsistent results is the great heterogeneity of alcohol dependence. Classifying alcohol dependence into homogeneous phenotypes is a good strategy to solve this problem. Recently, several genome-wide association studies have been reported. Genome-wide association studies enable hypothesis-free genome mapping of vulnerability-contributing genes and are expected to add data to identify genes associated with the susceptibility to alcohol dependence. Knowledge of the genetic basis of alcohol dependence is growing and leads to a better understanding of the biological mechanisms of addiction, which can help with strategies to prevent and treat this disease.

Acetaldehyde burst protection of ADH1B*2 against alcoholism: an additional hormesis protection against esophageal cancers following alcohol consumption?

This account of recent work presented at the 4th International Symposium on Alcohol Pancreatitis and Cirrhosis reports animal studies aimed at determining the role of the "acetaldehyde burst," generated shortly upon ethanol intake, as the mechanism of protection against alcoholism conferred by the ADH1B*2 polymorphism. Literature studies discussed suggest an additional role of the acetaldehyde burst on the paradoxical (hormesis) protection of the ADH1B*2 polymorphism against esophageal cancers in alcoholics.

Gender differences in ethanol-induced behavioral sensitivity in zebrafish

Gender-related differential sensitivity to ethanol has long been recognized. Our previous studies have demonstrated that the zebrafish, an animal model used currently to study genetics and development related to a variety of human diseases, is also sensitive to pharmacologically relevant concentrations of ethanol. Sensitivity to ethanol in the zebrafish can be easily gauged with a simple nonintrusive behavioral test that measures ethanol-related alterations in schooling by determining the distance between each fish and its nearest neighbor. The purpose of this study was to determine the influence of gender on the strain-specific ethanol sensitivity that we had observed previously. One hundred and sixty zebrafish of the wild-type (WT) and the long fin striped (LFS) strains were equally divided by gender for use in this study. For acute ethanol treatment, the fish were separated by gender and strain and exposed to 0.0, 0.125, 0.25 0.50, or 1.0% (vol/vol) ethanol. In the chronic study, eight fish of each strain and gender were exposed to 0.5% (vol/vol) ethanol for a period of 10 weeks and the swimming behavior tested before treatment and after each week of treatment. Results showed that female WT zebrafish displayed enhanced sensitivity to the effects of chronic ethanol exposure of increased nearest neighbor distances, whereas male and female LFS fish were not significantly affected by chronic ethanol exposure. Results of the acute ethanol study showed a dose-dependent effect in both strains and a gender effect that needs to be further investigated before enhanced female sensitivity to acute ethanol can be verified.

Haplotype-based study of the association of alcohol-metabolizing genes with alcohol dependence in four independent populations

BACKGROUND

Ethanol is metabolized by 2 rate-limiting reactions: alcohol dehydrogenases (ADH) convert ethanol to acetaldehyde that is subsequently metabolized to acetate by aldehyde dehydrogenases (ALDH). Approximately 50% of East Asians have genetic variants that significantly impair this pathway and influence alcohol dependence (AD) vulnerability. We investigated whether variation in alcohol metabolism genes might alter the AD risk in four non-East Asian populations by performing systematic haplotype association analyses to maximize the chances of capturing functional variation.

METHODS

Haplotype-tagging SNPs were genotyped using the Illumina GoldenGate platform. Genotypes were available for 40 SNPs across the ADH genes cluster and 24 SNPs across the two ALDH genes in four diverse samples that included cases (lifetime AD) and controls (no Axis 1 disorders). The case control sample sizes were the following: Finnish Caucasians: 232, 194; African Americans: 267, 422; Plains American Indians: 226, 110; and Southwestern American (SW) Indians: 317, 72.

RESULTS

In all four populations, as well as HapMap populations, 5 haplotype blocks were identified across the ADH gene cluster: (i) ADH5-ADH4; (ii) ADH6-ADH1A-ADH1B; (iii) ADH1C; (iv) intergenic; (v) ADH7. The ALDH1A1 gene was defined by 4 blocks and ALDH2 by 1 block. No haplotype or SNP association results were significant after correction for multiple comparisons; however, several results, particularly for ALDH1A1 and ADH4, replicated earlier findings. There was an ALDH1A1 block 1 and 2 (extending from intron 5 to the 3' UTR) yin yang haplotype (haplotypes that have opposite allelic configuration) association with AD in the Finns driven by SNPs rs3764435 and rs2303317, respectively, and an ALDH1A1 block 3 (including the promoter region) yin yang haplotype association in SW Indians driven by 5 SNPs, all in allelic identity. The ADH4 SNP rs3762894 was associated with AD in Plains Indians.

CONCLUSIONS

The systematic evaluation of alcohol-metabolizing genes in four non-East Asian populations has shown only modest associations with AD, largely for ALDH1A1 and ADH4. A concentration of signals for AD with ALDH1A1 yin yang haplotypes in several populations warrants further study.

Associations between ADH gene variants and alcohol phenotypes in Dutch adults

Recently, Macgregor et al. (2009) demonstrated significant associations of ADH polymorphisms with reactions to alcohol and alcohol consumption measures in an Australian sample. The aim of the present study was to replicate these findings in a Dutch sample. Survey data on alcohol phenotypes came from 1,754 unrelated individuals registered with the Netherlands Twin Register. SNPs in the ADH gene cluster located on chromosome 4q (n = 491) were subdivided in seven gene sets: ADH5, ADH4, ADH6, ADH1A, ADH1B, ADH1C and ADH7. Within these sets associations of SNPs with alcohol consumption measures, age at onset variables, reactions to alcohol and problem drinking liability were examined. Of the original 38 SNPs studied by Macgregor et al. (2009), six SNPs were not available in our dataset, because one of them had a minor allele frequency < .01 (rs1229984) and five could not be imputed. The remaining SNP associations with alcohol phenotypes as identified by Macgregor et al. (2009) were not replicated in the Dutch sample, after correcting for multiple genotype and phenotype testing. Significant associations were found however, for reactions to alcohol with a SNP in ADH5 (rs6827292, p = .001) and a SNP just upstream of ADH5 (rs6819724, p = .0007) that is in strong LD with rs6827292. Furthermore, an association between age at onset of regular alcohol use and a SNP just upstream of ADH7 (rs2654849, p = .003) was observed. No significant associations were found for alcohol consumption and problem drinking liability. Although these findings do not replicate the earlier findings at the SNP level, the results confirm the role of the ADH gene cluster in alcohol phenotypes.

Polymorphisms of alcohol dehydrogenase-1B and aldehyde dehydrogenase-2 and the blood and salivary ethanol and acetaldehyde concentrations of Japanese alcoholic men

BACKGROUND

The effects of genetic polymorphism of aldehyde dehydrogenase-2 (ALDH2) on alcohol metabolism are striking in nonalcoholics, and the effects of genetic polymorphism of alcohol dehydrogenase-1B (ADH1B) are modest at most, whereas genetic polymorphisms of both strongly affect the susceptibility to alcoholism and upper aerodigestive tract (UADT) cancer of drinkers.

METHODS

We evaluated associations between ADH1B/ADH1C/ALDH2 genotypes and the blood and salivary ethanol and acetaldehyde levels of 168 Japanese alcoholic men who came to our hospital for the first time in the morning and had been drinking until the day before.

RESULTS

The ethanol levels in their blood and saliva were similar, but the acetaldehyde levels in their saliva were much higher than in their blood, probably because of acetaldehyde production by oral bacteria. Blood and salivary ethanol and acetaldehyde levels were both significantly higher in the subjects with the less active ADH1B*1/*1 genotype than in the ADH1B*2 carriers, but none of the levels differed according to ALDH2 genotype. Significant linkage disequilibrium was detected between the ADH1B and ADH1C genotypes, but ADH1C genotype did not affect the blood or salivary ethanol or acetaldehyde levels. High blood acetaldehyde levels were found even in the active ALDH2*1/*1 alcoholics, which were comparable with the levels of the inactive heterozygous ALDH2*1/*2 alcoholics with less active ADH1B*1/*1. The slope of the increase in blood acetaldehyde level as the blood ethanol level increased was significantly steeper in alcoholics with inactive heterozygous ALDH2*1/*2 plus ADH1B*2 allele than with any other genotype combinations, but the slopes of the increase in salivary acetaldehyde level as the salivary ethanol level increased did not differ between the groups of subjects with any combinations of ALDH2 and ADH1B genotypes.

CONCLUSIONS

The ADH1B/ALDH2 genotype affected the blood and salivary ethanol and acetaldehyde levels of nonabstinent alcoholics in a different manner from nonalcoholics, and clear effects of ADH1B genotype and less clear effects of ALDH2 were observed in the alcoholics. Alterations in alcohol metabolism as a result of alcoholism may modify the gene effects, and these findings provide some clues in regard to associations between the genotypes and the risks of alcoholism and UADT cancer.

Polymorphisms in the interleukin-10 gene promoter and the risk of alcoholism and alcoholic liver disease in Caucasian Spaniard men

Controversy surrounds the possible influence of the single nucleotide polymorphisms (SNPs) of the interleukin-10 (IL-10) gene promoter on the risk for alcoholic liver disease. Our aim was to determine whether the SNP of the IL-10 gene promoter are associated with an increased risk for alcoholism and for alcoholic liver disease in male Spaniards. The -627 C>A SNP of the IL-10 gene promoter was assessed in a cohort of 344 Caucasian Spanish men, 168 alcoholics, and 176 nonalcoholics. The alcoholic group comprised 79 individuals without liver histopathologic abnormalities and 89 patients with chronic alcoholic liver disease. The nonalcoholic group was made of 62 healthy controls and 114 patients with chronic nonalcoholic liver disease. Genotyping was performed using PCR and automatic sequencing analysis methods on white cell DNA. Genotype and allele frequencies were compared by using the chi(2) test. Overall, no differences in either genotype and allele distribution was observed when comparing the four patient categories defined (P=0.62 and P=0.33, respectively). Subset analyses showed no differences in the genotype and allele distributions between all alcoholic and all nonalcoholic subjects (P=0.55 and P=0.29, respectively). This study failed to detect significant associations of the IL-10 -627C>A SNP and alcoholism or alcoholic liver disease in a cohort of Caucasian male Spaniards.

ADH1B*2 allele is protective against alcoholism but not chronic liver disease in the Hungarian population

BACKGROUND

Standardized death rates from chronic liver diseases (CLDs) in Hungary are much higher than the European Union average. Carrying the alcohol dehydrogenase 1B 48His allele (rs1229984 or ADH1B*2) could decrease the risk of alcoholism, but with persistent drinking may confer a greater risk of CLDs. The aim of this study was to assess the prevalence of this polymorphism in the Hungarian population and its association with alcohol consumption and with CLDs.

METHODS AND RESULTS

A total of 278 cases with diagnosed CLDs and 752 controls without any alterations in liver function, all males aged 45-64, were screened for ADH1B Arg48His polymorphism. ADH1B*2 allele frequencies in controls and cases were 8.31% and 4.50%, respectively (chi(2) = 9.2; P = 0.01). Carrying the ADH1B*2 allele was associated with significantly lower odds ratio (OR) for drinking frequency (OR = 0.63; P = 0.003), the number of positive answers on CAGE (Cut-down, Annoyed, Guilt, Eye-opener) assessment (OR = 0.58; P = 0.005) and a positive CAGE status (OR = 0.55; P = 0.007). There was a significant association between ADH1B*2 and CLDs (OR = 0.50; P = 0.003), but it disappeared after adjusting for CAGE status and scores (OR = 0.67 P = 0.134; OR = 0.67 P = 0.148, respectively) and weakened after adjusting for drinking frequency (OR = 0.61; P = 0.045). Among heavy drinkers the presence of ADH1B*2 did not increase the risk of cirrhosis but there was a significant interaction between genotype and CAGE status (P = 0.003, P = 0.042), with ADH1B*2 conferring reduced risk of CLDs in CAGE negatives.

CONCLUSION

In Hungarians, the ADH1B 48His allele reduces the risk of alcoholism, but not the risk of chronic liver disease among heavy drinkers.

ADH1A variation predisposes to personality traits and substance dependence

Human personality traits are strong predictors or characteristics of many psychiatric disorders including substance dependence (SD). Recently, significant associations between alcohol dehydrogenase type 1A gene (ADH1A) and SD have been reported, which led us to investigate the impact of ADH1A variation on personality traits and risk of SD. Five hundred fifty-eight subjects with SD [398 European-Americans (EAs) and 160 African-Americans (AAs)], 517 college students (384 EAs and 133 European-origin Hispanics), and 448 healthy subjects (385 EAs, 48 AAs, and 15 European-origin Hispanics) participated. Personality traits were assessed in 247 subjects with SD (179 EAs and 68 AAs), all 517 college students, and 332 healthy subjects (285 EAs, 40 AAs, and 7 European-origin Hispanics). The relationships between ADH1A and personality traits were comprehensively examined using stepwise multivariate analysis of covariance (MANCOVA), and then decomposed by stepwise analysis of covariance (ANCOVA). The relationship between ADH1A and SD was examined using stepwise logistic regression analysis. Admixture effects on analyses were considered. Overall, Agreeableness and Conscientiousness were associated with the diplotypes, haplotypes, genotypes, and/or alleles of ADH1A in three of four phenotype groups including EA SD subjects, healthy subjects, and AA SD subjects (1.7 x 10(-4) <or= P <or= 0.055), but not college students. Neuroticism was associated with diplotype, haplotypes and genotypes in AA SD subjects (0.001 <or= P <or= 0.031). In addition, SD was associated with diplotypes, haplotypes, genotypes, and/or alleles of ADH1A (0.008 <or= P <or= 0.060). The present study demonstrates that the ADH1A variation may contribute to the genetic component of variation in personality traits and SD.

Interaction among genes influencing ethanol metabolism and sex is association with alcohol use disorders in a Tibet population

Associations between alcohol use disorders and polymorphisms of genes influencing ethanol metabolism have been widely reported, but gene-gene and gene-sex interaction studies have rarely been examined. Using a set of samples collected during an epidemiological study of alcohol use disorders AUDs in a Tibetan population in China, we performed a case-control study to investigate the relationship between the functional polymorphisms of genes influencing ethanol metabolism and AUDs. The sample included 383 individuals with an AUDIT score >or=10 and 350 control subjects with the AUDIT score <or=5. All participants were genotyped for ALDH2*1/*2, ADH1B*1/*2, and CYP2E1*c1/c2*. Data were analyzed employing an integrated strategy using MDR, SPSS, and UNPHASED software. The MDR analysis showed that the four-factor model including ADH1B*1/*2, ALDH2*1/*2, and CYP2E1*c1/*c2 polymorphisms, and sex was the most accurate model associated with AUDs with the highest OR 3.299. It also revealed that CYP2E1 *c1/*c2 polymorphism interacted significantly with sex. Independent analysis confirmed that both ADH2*2 and ALDH2*2 allele were significantly associated with AUDs (OR: 0.441 for ADH2*2 and 0.137 for ALDH2*2). CYP2E1*c2 was positively associated with AUDs only in males homozygotic for ALDH2*1 and ADH1B*1 (OR: 2.585). Cumulative association analysis showed the number of protective alleles and genotypes were negatively associated with AUDs. In conclusion, ALDH2*2 and ADH1B*2 alleles were not only independently associated with AUDs but also demonstrated cumulative dosage effects. However the positive association between CYP2E1*c2 allele and AUDs might only exist in males homozygotic for ALDH2*1 and ADH1B*1.

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.

Tumor necrosis factor polymorphisms and alcoholic liver disease: a HuGE review and meta-analysis

The association between alcoholic liver disease (ALD) and tumor necrosis factor-alpha gene (TNFA) polymorphisms has been analyzed in several studies, but results have been conflicting. The main purpose of this study was to integrate previous findings and explore whether these polymorphisms are associated with susceptibility to ALD. The authors surveyed studies on the relation between TNFA gene polymorphisms and ALD by means of an electronic database search. A meta-analysis was conducted in a random-effects model. The association between ALD and the -238G>A or -308G>A polymorphism of the TNFA gene has been analyzed in 11 studies. Concerning the -238G>A polymorphism, the authors found a significant association between possession of the A allele and risk of alcoholic liver cirrhosis (odds ratio = 1.47, 95% confidence interval: 1.05, 2.07). Meta-analysis of the relation between the -308G>A polymorphism and ALD did not show any significant association. Given the limited number of studies and the potential biases, more data are needed to confirm the association described for the -238A allele.

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.

Mechanism of protection against alcoholism by an alcohol dehydrogenase polymorphism: development of an animal model

Humans who carry a point mutation in the gene coding for alcohol dehydrogenase-1B (ADH1B*2; Arg47His) are markedly protected against alcoholism. Although this mutation results in a 100-fold increase in enzyme activity, it has not been reported to cause higher levels of acetaldehyde, a metabolite of ethanol known to deter alcohol intake. Hence, the mechanism by which this mutation confers protection against alcoholism is unknown. To study this protective effect, the wild-type rat cDNA encoding rADH-47Arg was mutated to encode rADH-47His, mimicking the human mutation. The mutated cDNA was incorporated into an adenoviral vector and administered to genetically selected alcohol-preferring rats. The V(max) of rADH-47His was 6-fold higher (P<0.001) than that of the wild-type rADH-47Arg. Animals transduced with rAdh-47His showed a 90% (P<0.01) increase in liver ADH activity and a 50% reduction (P<0.001) in voluntary ethanol intake. In animals transduced with rAdh-47His, administration of ethanol (1g/kg) produced a short-lived increase of arterial blood acetaldehyde concentration to levels that were 3.5- to 5-fold greater than those in animals transduced with the wild-type rAdh-47Arg vector or with a noncoding vector. This brief increase (burst) in arterial acetaldehyde concentration after ethanol ingestion may constitute the mechanism by which humans carrying the ADH1B*2 allele are protected against alcoholism.

A non-synonymous variant in ADH1B is strongly associated with prenatal alcohol use in a European sample of pregnant women

Pregnant women are advised to abstain from alcohol despite insufficient evidence on the fetal consequences of moderate prenatal alcohol use. Mendelian randomization could help distinguish causal effects from artifacts due to residual confounding and measurement errors; however, polymorphisms reliably associated with alcohol phenotypes are needed. We aimed to test whether alcohol dehydrogenase (ADH) gene variants were associated with alcohol use before and during pregnancy. Ten variants in four ADH genes were genotyped in women from South-West England. Phenotypes of interest were quantity and patterns of alcohol consumption before and during pregnancy, including quitting alcohol following pregnancy recognition. We tested single-locus associations between genotypes and phenotypes with regression models. We used Bayesian models (multi-locus) to take account of linkage disequilibrium and reanalyzed the data with further exclusions following two conservative definitions of ‘white ethnicity’ based on the woman's reported parental ethnicity or a set of ancestry-informative genetic markers. Single-locus analyses on 7410 women of white/European background showed strong associations for rs1229984 (ADH1B). Rare allele carriers consumed less alcohol before pregnancy [odds ratio (OR) = 0.69; 95% confidence interval (CI): 0.56–0.86, P = 0.001], were less likely to have ‘binged’ during pregnancy (OR = 0.55, 95% CI: 0.38–0.78, P = 0.0009), and more likely to have abstained in the first trimester of gestation (adjusted OR = 1.42, 95% CI: 1.12–1.80, P = 0.004). Multi-locus models confirmed these results. Sensitivity analyses did not suggest the presence of residual population stratification. We confirmed the established association of rs1229984 with reduced alcohol consumption over the life-course, contributing new evidence of an effect before and during pregnancy.

Associations of cohort and socio-demographic correlates with transitions from alcohol use to disorders and remission in metropolitan China

AIMS

To examine socio-demographic associations of transitions from alcohol use to disorders and of remission from disorders in metropolitan China.

DESIGN AND SETTING

Face-to-face interviewing by trained lay-interviewers on a multi-staged, clustered sample from the general population of Beijing and Shanghai, China.

PARTICIPANTS

A total of 5201 adults aged 18-70 years and with household registration.

MEASUREMENTS

World Mental Health version of Composite International Diagnostic Interview.

FINDINGS

Lifetime prevalence estimates for alcohol use, regular use (at least 12 drinks in a year), DSM-IV abuse and dependence with abuse were 65.4%, 39.5% (60.4% of ever-drinkers), 4.6% (11.6% of regular users) and 0.9% (20.4% of lifetime alcohol abusers), respectively. These estimates were higher among respondents from the recent cohort; 64.3% and 36.9% respondents with a history of lifetime abuse and dependence respectively had remitted. The number of socio-demographic associations for the onset of each transitional stage decreased from alcohol use to alcohol dependence. Onset of ever-use was more common in respondents who were male, 18-50 years of age, with middle education level and never married, but less common among the previously married and students. First onset of regular use among those with ever-use was more common in respondents who were male, less than 50 years of age and never married, but less common in students. Being male and less than 50 years of age was associated with more alcohol abusers among regular users.

CONCLUSION

This study was the first to reveal in a Chinese population that qualitatively different risk factors might operate during the different stages of progression from alcohol use to disorders. Further research is needed to clarify the mechanisms underlying these differences in order to guide prevention programmes.