Alcohol-metabolising genes and alcoholism among Taiwanese Han men: independent effect of ADH2, ADH3 and ALDH2

Harm from others' drinking among young adults in Taiwan: Predictors and deteriorating quality of life

INTRODUCTION

This study aimed to investigate the prevalence of different forms of harm from others' drinking (HFOD), predictors and the relationship with multi-dimensional quality of life among young adults in an emerging alcohol market in Asia-Taiwan.

METHODS

Data were extracted from a 2018 household survey with national representativeness on substance use experiences. The analytic sample comprised 4901 participants aged 18-34. Eight items were used to measure HFOD experiences. Five-dimensional quality of life was assessed by the EQ-5D-5L. Multivariable regressions with complex survey analyses were performed to estimate the prevalence and risk association.

RESULTS

Almost 4.2% of young adults experienced any form of HFOD; psychological harm occurred more prevalently than physical harm (3.7% and 1.5%, respectively). Those aged 25-29 and 30-34 had a two- to three-fold risk of HFOD compared with those aged 18-24. Both non-drunk drinking and drunk drinking were associated with an increased risk of psychological HFOD (adjusted odds ratio 2.36 and 5.89, respectively), whereas the risk of physical HFOD was related only to drunk drinking (adjusted odds ratio 7.8). Psychological HFOD victimisation emerged as the strongest predictor for deteriorated quality of life (adjusted b -0.14; 95% confidence interval -0.24, -0.04), especially in the dimensions of pain/discomfort and anxiety/depression. Among HFOD victims, only 33% sought help.

DISCUSSION AND CONCLUSIONS

The HFOD among young adults, commonly exhibited in psychological form, was linked with deteriorated quality of life; nonetheless, young HFOD victims are under-recognised. When devising interventions for alcohol harm, developmental perspectives should be integrated into policies implemented in healthcare and community settings.

Alcohol Metabolizing Enzymes, Microsomal Ethanol Oxidizing System, Cytochrome P450 2E1, Catalase, and Aldehyde Dehydrogenase in Alcohol-Associated Liver Disease

Once ingested, most of the alcohol is metabolized in the liver by alcohol dehydrogenase to acetaldehyde. Two additional pathways of acetaldehyde generation are by microsomal ethanol oxidizing system (cytochrome P450 2E1) and catalase. Acetaldehyde can form adducts which can interfere with cellular function, leading to alcohol-induced liver injury. The variants of alcohol metabolizing genes encode enzymes with varied kinetic properties and result in the different rate of alcohol elimination and acetaldehyde generation. Allelic variants of these genes with higher enzymatic activity are believed to be able to modify susceptibility to alcohol-induced liver injury; however, the human studies on the association of these variants and alcohol-associated liver disease are inconclusive. In addition to acetaldehyde, the shift in the redox state during alcohol elimination may also link to other pathways resulting in activation of downstream signaling leading to liver injury.

An association study revealed substantial effects of dominance, epistasis and substance dependence co-morbidity on alcohol dependence symptom count

Alcohol dependence is a complex disease involving polygenes, environment and their interactions. Inadequate consideration of these interactions may have hampered the progress on genome-wide association studies of alcohol dependence. By using the dataset of the Study of Addiction: Genetics and Environment with 3838 subjects, we conducted a genome-wide association studies of alcohol dependence symptom count (ADSC) with a full genetic model considering additive, dominance, epistasis and their interactions with ethnicity, as well as conditions of co-morbid substance dependence. Twenty quantitative trait single nucleotide polymorphisms (QTSs) showed highly significant associations with ADSC, including four previously reported genes (ADH1C, PKNOX2, CPE and KCNB2) and the reported intergenic rs1363605, supporting the overall validity of the analysis. Two QTSs within or near ADH1C showed very strong association in a dominance inheritance mode and increased the phenotype value of ADSC when the effect of co-morbid opiate or marijuana dependence was controlled. Highly significant association was also identified in variants within four novel genes (RGS6, FMN1, NRM and BPTF), two non-coding RNA and two epistasis loci. QTS rs7616413, located near PTPRG encoding a protein tyrosine phosphatase receptor, interacted with rs10090742 within ANGPT1 encoding a protein tyrosine phosphatase in an additive × additive or dominance × additive manner. The detected QTSs contributed to about 20 percent of total heritability, in which dominance and epistasis effects accounted for over 50 percent. These results demonstrated that perturbations arising from gene-gene interaction and conditions of co-morbidity substantially influence the genetic architecture of complex trait.

Alcohol consumption induces global gene expression changes in VTA dopaminergic neurons

Alcoholism is associated with dysregulation in the neural circuitry that mediates motivated and goal-directed behaviors. The dopaminergic (DA) connection between the ventral tegmental area (VTA) and the nucleus accumbens is viewed as a critical component of the neurocircuitry mediating alcohol's rewarding and behavioral effects. We sought to determine the effects of binge alcohol drinking on global gene expression in VTA DA neurons. Alcohol-preferring C57BL/6J × FVB/NJ F1 hybrid female mice were exposed to a modified drinking in the dark (DID) procedure for 3 weeks, while control animals had access to water only. Global gene expression of laser-captured tyrosine hydroxylase (TH)-positive VTA DA neurons was measured using microarrays. A total of 644 transcripts were differentially expressed between the drinking and nondrinking mice, and 930 transcripts correlated with alcohol intake during the last 2 days of drinking in the alcohol group. Bioinformatics analysis of alcohol-responsive genes identified molecular pathways and networks perturbed in DA neurons by alcohol consumption, which included neuroimmune and epigenetic functions, alcohol metabolism and brain disorders. The majority of genes with high and specific expression in DA neurons were downregulated by or negatively correlated with alcohol consumption, suggesting a decreased activity of DA neurons in high drinking animals. These changes in the DA transcriptome provide a foundation for alcohol-induced neuroadaptations that may play a crucial role in the transition to addiction.

Comorbid alcohol dependence disorder may be related to aldehyde dehydrogenase 2 (ALDH2) and alcohol dehydrogenase 1B (ADH1B) in bipolar II disorder, but only to ALDH2 in bipolar I disorder, in Han Chinese

OBJECTIVES

A high prevalence rate of bipolar disorder (BP) comorbid with alcohol dependence (AD) (BP+AD) in Western patients with BP has been reported, but whether this is true for Han Chinese with BP is uncertain. We explored the prevalence of BP+AD in a Han Chinese population with BP, and investigated the effect of alcohol-metabolizing genotypes on bipolar I disorder (BP-I) + AD and bipolar II disorder (BP-II) + AD.

METHODS

Healthy controls (HCs) (n = 672) and 18- to 65-year-old patients with BP (BP-I: n = 530; BP-II: n = 788) were recruited. Patients with any other major or minor mental illnesses, neurological disorders, or organic mental disorders were excluded. A polymerase chain reaction and restriction fragment length polymorphism analysis was used to determine genotypes for alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2), two alcohol-metabolizing enzymes.

RESULTS

AD comorbidity rates were 11.7% with BP-I and 17.1% with BP-II. Significantly fewer patients with BP not comorbid with AD (BP-AD) carried the AHD1B*1 allele than did the HCs. Logistic regression analysis showed a main effect of ALDH2*1/*1 only in the BP-I-AD group. In BP+AD patients, logistic regression analysis showed main effects of ALDH2*1/*1 and ADH1B*1/*1 only in the BP-II+AD group.

CONCLUSIONS

Having BP-II+AD may be related to ALDH2 and ADH1B, but having BP-I+AD may be related only to ALDH2. We conclude that ALDH2 and ADH1B have different effects in Han Chinese patients with BP-I+AD and BP-II+AD.

Effects of genetic variants of ADH1B and ALDH2 and social network on continued alcohol drinking among young adolescents in Taiwan

BACKGROUND

This study aimed (i) to evaluate the effects of genetic variants of ADH1B and ALDH2 and social network position on continued alcohol use in early adolescence, and (ii) to explore possible moderating role of pubertal development on genetic effects.

METHODS

The sample comprised 496 children who ever drank alcohol before the ages of 10-12. Information pertaining to sociodemographic background, pubertal development, parental drinking, alcohol and tobacco use, alcohol-metabolizing genes, and nominated best friends was collected in four waves of assessment. Polymorphisms of ADH1B (rs1229984) and ALDH2 (rs671) were genotyped. The latent class analysis was first used to characterize longitudinal alcohol use pattern, followed by the multinomial logistic regression analyses to assess its association with genes, pubertal development, and social network.

RESULTS

Three distinct classes of alcohol users (i.e. ex-drinkers, sporadic drinkers, and continued drinkers) were derived from alcohol-experienced children. Both alcohol-metabolizing genes appear to have protective effects, yet such relationships were only significant for youngsters in pre-to-early pubertal stage: the adjusted odds ratio (aOR) of ADH1B fast-genotype for sporadic drinkers was 0.46 and that of ALDH2 slow-genotype for both sporadic and continued drinkers was 0.47 and 0.42, respectively. Children having the bridge position in their peer network were more likely to be sporadic drinkers (aOR=4.15) and continued drinkers (aOR=3.16).

CONCLUSIONS

Our results illustrate a potential moderating effect of pubertal development on the protective influence of alcohol-metabolizing genes on subsequent alcohol use among alcohol-experienced children as well as the independent contribution of early life's social network to their alcohol involvement.

"A cool little buzz": alcohol intoxication in the dance club scene

In recent years, there has been increasing concern about youthful "binge" drinking and intoxication. Yet the meaning of intoxication remains under-theorized. This paper examines intoxication in a young adult nightlife scene, using data from a 2005-2008 National Institute on Drug Abuse-funded project on Asian American youth and nightlife. Analyzing in-depth qualitative interview data with 250 Asian American young adults in the San Francisco area, we examine their narratives about alcohol intoxication with respect to sociability, stress, and fun, and their navigation of the fine line between being "buzzed" and being "wasted." Finally, limitations of the study and directions for future research are noted.

Hepatitis C treatment outcome in relation to alcohol consumption and racial differences in southeastern Taiwan

BACKGROUND/PURPOSE

Alcohol use may have negative impacts on hepatitis C virus (HCV) treatment due to low adherence, and racial differences can influence HCV sustained virological response (SVR) rate between East Asian and European ancestry. The objective of this study is to confirm the influence of alcohol consumption and racial differences on HCV treatment outcome in aboriginal and nonaboriginal people of southeastern Taiwan.

METHODS

In this retrospective cohort study, a total of 195 patients were treated with peginterferon-alpha once weekly plus ribavirin for 24 weeks. The efficacy analysis was performed based on the SVR rate for patients who received at least one dose of the study medication or who completed treatment. The endpoints were denoted by virological response rate including the influences of alcohol use, HCV genotype, serum level of HCV virological load, and racial differences.

RESULTS

No differences were observed in the baseline clinical characteristics between drinkers and nondrinkers, but a significant difference was noted in the body mass index between aboriginal and nonaboriginal populations (28.3 vs. 25.8; p < 0.01). With respect to the SVR rate, no difference was found between drinkers and nondrinkers, and between aboriginal and nonaboriginal people. The treatment efficacy of SVR in the whole group was significantly different between patients with HCV genotype 1 and nongenotype 1 (73.5% vs. 91.2%; p < 0.01). An analysis of the SVR rate in the aboriginal group showed no significant difference between patients with genotype 1 and nongenotype 1 (80.0% vs. 91.3%; p = 0.31).

CONCLUSION

In southeastern Taiwan, alcohol consumption did not influence the HCV treatment outcome, and the SVR rates were similar between patients with HCV genotype 1 and nongenotype 1 infections in the aboriginal group.

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.

ADH1C Ile350Val polymorphism and cancer risk: evidence from 35 case-control studies

BACKGROUND

Alcohol dehydrogenase 1C (ADH1C) is the key enzyme catalyze oxidation of alcohol to acetaldehyde, which plays vital roles in the etiology of various cancer. To date, studies investigated the association between a functional polymorphism in ADH1C, Ile350Val (rs698), and risk of cancer have shown inclusive results.

METHODS

A meta-analysis based on 35 case-control studies was performed to address this issue. Odds ratios (OR) with 95% confidence intervals (CIs) were used to assess the association. The statistical heterogeneity across studies was examined with χ2-based Q-test.

RESULTS

Overall, no significant associations between ADH1C Ile350Val polymorphism and cancer risk were observed in any genetic models (P>0.05). In the stratified analyses, there was a significantly increased cancer risk among African (Val/Val vs. Ile/Ile OR  =  2.19, 95% CI  =  1.29-3.73, P(heterogeneity)  =  0.989; Ile/Val + Val/Val vs. Ile/Ile: OR  =  1.79, 95%CI  =  1.18-2.71, P(heterogeneity)  =  0.761; Val/Val vs. Ile/Val + Ile/Ile: OR  =  1.92, 95% CI  =  1.16-3.17, P(heterogeneity)  =  0.981) and Asian (Ile/Val vs. Ile/Ile: OR  =  1.58, 95% CI  =  1.32-1.90, P(heterogeneity)  =  0.375; Val/Val vs. Ile/Ile: OR  =  3.84, 95% CI  =  1.74-8.49, P(heterogeneity)  =  0.160; Ile/Val + Val/Val vs. Ile/Ile: OR  =  1.65, 95% CI  =  1.38-1.96, P(heterogeneity)  =  0.330; Val/Val vs. Ile/Val + Ile/Ile: OR  =  3.54, 95% CI  =  1.62-7.75, P(heterogeneity)  =  0.154) studies.

CONCLUSIONS

The results indicate that ADH1C Ile350Val polymorphism may contribute to cancer risk among Africans and Asians. Additional comprehensive system analyses are required to validate this association combined with other related polymorphisms.

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.

Levels of explanation in psychiatric and substance use disorders: implications for the development of an etiologically based nosology

The soft medical model for psychiatric illness, which was operationalized in DSM-III, defines psychiatric disorders as syndromes with shared symptoms, signs, course of illness and response to treatment. Many in our field want to move to a hard medical model based on etiological mechanisms. This essay explores the feasibility of this move and asks whether psychiatric disorders have the needed single clear level of explanation for an etiologically based nosology. I propose seven criteria for a good explanation: (i) strength, (ii) causal confidence, (iii) generalizability, (iv) specificity, (v) manipulability, (vi) proximity and (vii) generativity. Applying them to cystic fibrosis, a gene-level approach to etiology performs well across the board. By contrast, a detailed review of alcohol dependence and a briefer review of major depression suggests that psychiatric disorders have multiple explanatory perspectives no one of which can be privileged over others using scientific data alone. Therefore, a move toward an etiologically based diagnostic system cannot assume that one level of explanation will stand out as the obvious candidate on which to base the nosology. This leaves two options. Either a hard medical model will be implemented that will require a consensus about a preferred level of explanation which must reflect value judgments as well as science. To take this approach, we need to agree on what we most want from our explanations. Alternatively, we will need to move away from the traditional hard medical model that requires that we ground our diagnoses in single biological essences, and focus instead on fuzzy, cross-level mechanisms, which may more realistically capture the true nature of psychiatric disorders.

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.

Association of alcohol dehydrogenase genes with alcohol-related phenotypes in a Native American community sample

BACKGROUND

Previous linkage studies, including a study of the Native American population described in the present report, have provided evidence for linkage of alcohol dependence and related traits to chromosome 4q near a cluster of alcohol dehydrogenase (ADH) genes, which encode enzymes of alcohol metabolism.

METHODS

The present study tested for associations between alcohol dependence and related traits and 22 single-nucleotide polymorphisms (SNPs) spanning the 7 ADH genes. Participants included 586 adult men and women recruited from 8 contiguous Native American reservations. A structured interview was used to assess DSM-III-R alcohol dependence criteria as well as a set of severe alcohol misuse symptoms and alcohol withdrawal symptoms.

RESULTS

No evidence for association with the alcohol dependence diagnosis was observed, but an SNP in exon 9 of ADH1B (rs2066702; ADH1B*3) and an SNP at the 5' end of ADH4 (rs3762894) showed significant evidence of association with the presence of withdrawal symptoms (p = 0.0018 and 0.0012, respectively). Further, a haplotype analysis of these 2 SNPs suggested that the haplotypes containing either of the minor alleles were protective against alcohol withdrawal relative to the ancestral haplotype (p = 0.000006).

CONCLUSIONS

These results suggest that variants in the ADH1B and ADH4 genes may be protective against the development of some symptoms associated with alcohol dependence.

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.

The genetic factors affecting drinking behaviors of korean young adults with variant aldehyde dehydrogenase 2 genotype

OBJECTIVE

We determined whether aldehyde dehydrogenase 2 (ALDH2) activity alters the way in which drinking behaviors are affected by gene polymorphisms of other alcohol-metabolizing enzymes and serotonin-related proteins.

METHODS

Through a follow-up survey with a cohort comprising 551 university freshmen over a period of 6 years, we examined the genetic factors affecting drinking behaviors. In 2000, drinking behaviors were assessed and tryptophan hydroxylase (TPH) and ALDH2 gene polymorphisms were determined. Drinking behaviors were repeated in 2006 (n=150), and the gene polymorphisms of ADH1B, ADH1C, CYP2E1, 5-HTR2A 1438A/G, and 5-HTR2A IVS2 were also determined.

RESULTS

In 2000, the variant and wild-type ALDH2 groups exhibited little difference in terms of drinking frequency and problem drinking. Furthermore, some genotypes influenced only the variant group: ADH1B*2/*2 was associated with a lower drinking frequency, and CYP2E1 c2 allele was associated with an increased risk of problem drinking. In 2006, drinking frequency and risk of problem drinking were significantly lower in the variant group than in the wild-type group. However, the TPH AA genotype disturbed that difference, meaning that the subjects in the variant group had developed a similar level of risk of problem drinking to that in the wild-type group.

CONCLUSION

Korean university freshmen who were identified as a variant group drank as frequently as those in the wild-type group. For the subsequent 6 years they drank less frequently, thus decreasing the risk of problem drinking. However, that frequency drop was interrupted in those with gene polymorphisms such as ADH1B*1, CYP2E1 c2, and TPH A.

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.

Neuropsychological functions in patients with bipolar I and bipolar II disorder

The literature reports persistent cognitive impairments in patients with bipolar disorder even after prolonged remission. However, a majority of studies have focused only on bipolar I disorder (BP-I), primarily because bipolar II disorder (BP-II) is often underdiagnosed or misdiagnosed. More attention should be paid to the differences between BP-I and BP-II, especially the aspects of neuropsychological functioning. We examined the different neuropsychological functions in BP-I and BP-II patients and compared them with those of healthy controls.

METHODS

The study included 67 patients with interepisode bipolar disorder (BP-I: n = 30; BP-II: n = 37) and 22 healthy controls compared using a battery of neuropsychological tests that assessed memory, psychomotor speed, and certain aspects of frontal executive function.

RESULTS

The BP-I group performed poorly on verbal memory, psychomotor speed, and executive function compared to the BP-II and control groups. Both bipolar groups performed significantly less well than the control group on measures of working memory and psychomotor speed, while the BP-II group showed an intermediate level of performance in psychomotor speed compared to the BP-I and control groups. There was no difference between the groups on visual memory.

CONCLUSIONS

BP-I was characterized by reduced performance in verbal memory, working memory, psychomotor speed, and executive function, while BP-II patients showed a reduction only in working memory and psychomotor speed. Cognitive impairment existed in both subtypes of bipolar disorder, and was greater in BP-I patients. Rehabilitation interventions should take into account potential cognitive differences between these bipolar subtypes.

Genome-wide association study of alcohol dependence

CONTEXT

Alcohol dependence is a serious and common public health problem. It is well established that genetic factors play a major role in the development of this disorder. Identification of genes that contribute to alcohol dependence will improve our understanding of the mechanisms that underlie this disorder.

OBJECTIVE

To identify susceptibility genes for alcohol dependence through a genome-wide association study (GWAS) and a follow-up study in a population of German male inpatients with an early age at onset.

DESIGN

The GWAS tested 524,396 single-nucleotide polymorphisms (SNPs). All SNPs with P < 10(-4) were subjected to the follow-up study. In addition, nominally significant SNPs from genes that had also shown expression changes in rat brains after long-term alcohol consumption were selected for the follow-up step.

SETTING

Five university hospitals in southern and central Germany.

PARTICIPANTS

The GWAS included 487 male inpatients with alcohol dependence as defined by the DSM-IV and an age at onset younger than 28 years and 1358 population-based control individuals. The follow-up study included 1024 male inpatients and 996 age-matched male controls. All the participants were of German descent.

MAIN OUTCOME MEASURES

Significant association findings in the GWAS and follow-up study with the same alleles.

RESULTS

The GWAS produced 121 SNPs with nominal P < 10(-4). These, together with 19 additional SNPs from homologues of rat genes showing differential expression, were genotyped in the follow-up sample. Fifteen SNPs showed significant association with the same allele as in the GWAS. In the combined analysis, 2 closely linked intergenic SNPs met genome-wide significance (rs7590720, P = 9.72 x 10(-9); rs1344694, P = 1.69 x 10(-8)). They are located on chromosome region 2q35, which has been implicated in linkage studies for alcohol phenotypes. Nine SNPs were located in genes, including the CDH13 and ADH1C genes, that have been reported to be associated with alcohol dependence.

CONCLUSIONS

This is the first GWAS and follow-up study to identify a genome-wide significant association in alcohol dependence. Further independent studies are required to confirm these findings.

Association of ADH1B and ALDH2 gene polymorphisms with alcohol dependence: a pilot study from India

Functional polymorphism in the genes encoding alcohol dehydrogenase (ADH) 1B and aldehyde dehydrogenase (ALDH) 2 are considered most important among several genetic determinants of alcohol dependence, a complex disorder. There is no report on the widely studied Arg47His and Glu487Lys polymorphisms from Indian alcohol-dependent populations. In this paper, we report, for the first time, allelic and genotypic frequencies of Arg47His and Glu487Lys single nucleotide polymorphisms (SNPs) in North Indian alcohol-dependent subjects. A total of 174 alcohol-dependent males, recruited using DSM IV criteria (American Psychiatric Association, 1994), were genotyped using the polymerase chain reaction-restriction fragment length polymorphism method. The results obtained from genetic analysis were correlated with clinical parameters using Student's t-test or Mann Whitney's U test. The highlight of the study findings was the uniquely high frequency of the ALDH2*2/*2 genotype (among alcohol-dependent subjects) being a risk-conferring factor for alcohol dependence.

The role of aldehyde dehydrogenase-1 (ALDH1A1) polymorphisms in harmful alcohol consumption in a Finnish population

Liver cystolic aldehyde dehydrogenase 1 (ALDH1A1) has been previously associated with both alcohol dependence and alcohol consumption behaviour, and has been implicated in alcohol-induced flushing and alcohol sensitivity in Caucasians. The present study tested for association between ALDH1A1 and alcohol consumption behaviour and susceptibility to problem drinking or alcohol dependence in Finnish cohorts of unrelated male subjects recruited from alcoholism clinical treatment facilities (n = 104) and from the general population (n = 201). All participants completed the Alcohol Use Disorder Identification Test (AUDIT) and were genotyped for eight single nucleotide polymorphisms (SNPs) within or flanking ALDH1A1. To test for association between alcohol consumption behaviour and these polymorphisms, we used generalised linear models and haplotypic analysis. Three SNPs were nominally associated (rs348449, p = 0.043; rs610529, p = 0.013; rs348479, p = 0.025) with the quantitative AUDIT score, which evaluates alcohol consumption behaviour. Two-locus (rs6I0529-rs2288087) haplotype analysis increased the strength of association with AUDIT score (p = 0.00I5). Additionally, rs348449 is highly associated with problem drinking (allelic odds ratio [OR] 7.87, 95 per cent confidence interval [CI] 1.67-37.01) but due to the low minor allele frequency (0.01 and 0.07 in controls and problem drinkers, respectively), more samples are required to validate this observation. Conversely, rs348479 (p = 0.019) and rs6I0529 (allelic OR 0.65, 95 per cent CI 0.43-0.98; genotypic OR 0.32, 95 per cent CI 0.12-0.84) are implicated in alcohol dependence status. This study provides further evidence for a role for ALDH1A1 in alcohol consumption behaviour, including problem drinking and possibly alcohol dependence, in our Finnish population.

Associations of ALDH2 and ADH1B genotypes with alcohol-related phenotypes in Asian young adults

BACKGROUND

Associations of ALDH2 and ADH1B genotypes with alcohol use have been evaluated largely using case-control studies, which typically focus on adult samples and dichotomous diagnostic outcomes. Relatively fewer studies have evaluated ALDH2 and ADH1B in relation to continuous drinking outcomes or at different developmental stages. This study examined additive and interactive effects of ALDH2 and ADH1B genotypes on drinking behavior in a mixed-gender sample of Asian young adults, focusing on continuous phenotypes (e.g., heavy episodic and hazardous drinking, alcohol sensitivity, drinking consequences) whose expression is expected to precede the onset of alcohol use disorders.

METHODS

The sample included 182 Chinese- and Korean-American young adults ages 18 years and older (mean age = 20 years). Effects of ALDH2, ADH1B and ethnicity were estimated using generalized linear modeling.

RESULTS

The ALDH2*2 allele predicted lower reported rates of alcohol use and drinking consequences as well as greater reported sensitivity to alcohol. There were significant ethnic group differences in drinking outcomes, such that Korean ethnicity predicted higher drinking rates and lower alcohol sensitivity. ADH1B status was not significantly related to drinking outcomes.

CONCLUSIONS

Ethnicity and ALDH2 status, but not ADH1B status, consistently explained significant variance in alcohol consumption in this relatively young sample. Results extend previous work by showing an association of ALDH2 genotype with drinking consequences. Findings are discussed in the context of possible developmental and population differences in the influence of ALDH2 and ADH1B variations on alcohol-related phenotypes.

ADH single nucleotide polymorphism associations with alcohol metabolism in vivo

We have previously found that variation in alcohol metabolism in Europeans is linked to the chromosome 4q region containing the ADH gene family. We have now typed 103 single nucleotide polymorphisms (SNPs) across this region to test for allelic associations with variation in blood and breath alcohol concentrations after an alcohol challenge. In vivo alcohol metabolism was modelled with three parameters that identified the absorption and rise of alcohol concentration following ingestion, and the rate of elimination. Alleles of ADH7 SNPs were associated with the early stages of alcohol metabolism, with additional effects in the ADH1A, ADH1B and ADH4 regions. Rate of elimination was associated with SNPs in the intragenic region between ADH7 and ADH1C, and across ADH1C and ADH1B. SNPs affecting alcohol metabolism did not correspond to those reported to affect alcohol dependence or alcohol-related disease. The combined SNP associations with early- and late-stage metabolism only account for approximately 20% of the total genetic variance linked to the ADH region, and most of the variance for in vivo alcohol metabolism linked to this region is yet to be explained.

Addiction genetics and pleiotropic effects of common haplotypes that make polygenic contributions to vulnerability to substance dependence

Abundant evidence from family, adoption, and twin studies point to large genetic contributions to individual differences in vulnerability to develop dependence on one or more addictive substances. Twin data suggest that most of this genetic vulnerability is shared by individuals who are dependent on a variety of addictive substances. Molecular genetic studies, especially genomewide and candidate gene association studies, have elucidated common haplotypes in dozens of genes that appear to make polygenic contributions to vulnerability to developing dependence. Most genes that harbor currently identified addiction-associated haplotypes are expressed in the brain. Haplotypes in many of the same genes are identified in genomewide association studies that compare allele frequencies in substance dependent vs. control individuals from European, African, and Asian racial/ethnic backgrounds. Many of these addiction-associated haplotypes display pleiotropic influences on a variety of related brain-based phenotypes that display 1) substantial heritability and 2) clinical cooccurence with substance dependence.

Associations of ADH and ALDH2 gene variation with self report alcohol reactions, consumption and dependence: an integrated analysis

Alcohol dependence (AD) is a complex disorder with environmental and genetic origins. The role of two genetic variants in ALDH2 and ADH1B in AD risk has been extensively investigated. This study tested for associations between nine polymorphisms in ALDH2 and 41 in the seven ADH genes, and alcohol-related flushing, alcohol use and dependence symptom scores in 4597 Australian twins. The vast majority (4296) had consumed alcohol in the previous year, with 547 meeting DSM-IIIR criteria for AD. There were study-wide significant associations (P<2.3 x 10(-4)) between ADH1B-Arg48His (rs1229984) and flushing and consumption, but only nominally significant associations (P<0.01) with dependence. Individuals carrying the rs1229984 G-allele (48Arg) reported a lower prevalence of flushing after alcohol (P=8.2 x 10(-7)), consumed alcohol on more occasions (P=2.7 x 10(-6)), had a higher maximum number of alcoholic drinks in a single day (P=2.7 x 10(-6)) and a higher overall alcohol consumption (P=8.9 x 10(-8)) in the previous year than those with the less common A-allele (48His). After controlling for rs1229984, an independent association was observed between rs1042026 (ADH1B) and alcohol intake (P=4.7 x 10(-5)) and suggestive associations (P<0.001) between alcohol consumption phenotypes and rs1693482 (ADH1C), rs1230165 (ADH5) and rs3762894 (ADH4). ALDH2 variation was not associated with flushing or alcohol consumption, but was weakly associated with AD measures. These results bridge the gap between DNA sequence variation and alcohol-related behavior, confirming that the ADH1B-Arg48His polymorphism affects both alcohol-related flushing in Europeans and alcohol intake. The absence of study-wide significant effects on AD results from the low P-value required when testing multiple single nucleotide polymorphisms and phenotypes.

Molecular genetics of addiction and related heritable phenotypes: genome-wide association approaches identify "connectivity constellation" and drug target genes with pleiotropic effects

Genome-wide association (GWA) can elucidate molecular genetic bases for human individual differences in complex phenotypes that include vulnerability to addiction. Here, we review (a) evidence that supports polygenic models with (at least) modest heterogeneity for the genetic architectures of addiction and several related phenotypes; (b) technical and ethical aspects of importance for understanding GWA data, including genotyping in individual samples versus DNA pools, analytic approaches, power estimation, and ethical issues in genotyping individuals with illegal behaviors; (c) the samples and the data that shape our current understanding of the molecular genetics of individual differences in vulnerability to substance dependence and related phenotypes; (d) overlaps between GWA data sets for dependence on different substances; and (e) overlaps between GWA data for addictions versus other heritable, brain-based phenotypes that include bipolar disorder, cognitive ability, frontal lobe brain volume, the ability to successfully quit smoking, neuroticism, and Alzheimer's disease. These convergent results identify potential targets for drugs that might modify addictions and play roles in these other phenotypes. They add to evidence that individual differences in the quality and quantity of brain connections make pleiotropic contributions to individual differences in vulnerability to addictions and to related brain disorders and phenotypes. A "connectivity constellation" of brain phenotypes and disorders appears to receive substantial pathogenic contributions from individual differences in a constellation of genes whose variants provide individual differences in the specification of brain connectivities during development and in adulthood. Heritable brain differences that underlie addiction vulnerability thus lie squarely in the midst of the repertoire of heritable brain differences that underlie vulnerability to other common brain disorders and phenotypes.

Alcohol abuse and related factors in Asia

Alcohol problems are a global issue, and the nature of alcohol abuse is very complicated. The susceptibility to alcohol abuse varies greatly from one individual to another and also from one nation to another, depending on the availability of alcohol, a country's regulation related to alcohol, a country's cultural background, religious tradition and its economics. Alcohol dependence is also a complicated disease process. The prevalence of alcohol dependence also varies greatly from one ethnic group to another. Asia is the world's largest and most populous continent. The natural disasters, religious conflicts as well as political disputes cause people lack of opportunity in many countries. People in this region do not consume more alcohol than the people in the rest of the world. The prevalence of alcohol dependence is not as high as is seen in other regions. In Asia, not only socio-economic factors, but also biological factors influence drinking behaviour. Findings of functional genetic polymorphism of the major alcohol metabolizing enzymes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) have led to the suggestion that this enzyme system may possibly play a diverse but critical role in alcohol dependence and in the alcohol-related disease process in the different ethnic groups. This paper reviews alcohol problems and related factors. Their management and prevention strategy are discussed.

Ethnic related selection for an ADH Class I variant within East Asia

Background

The alcohol dehydrogenases (ADH) are widely studied enzymes and the evolution of the mammalian gene cluster encoding these enzymes is also well studied. Previous studies have shown that the ADH1B*47His allele at one of the seven genes in humans is associated with a decrease in the risk of alcoholism and the core molecular region with this allele has been selected for in some East Asian populations. As the frequency of ADH1B*47His is highest in East Asia, and very low in most of the rest of the world, we have undertaken more detailed investigation in this geographic region.

Methodology/Principal Findings

Here we report new data on 30 SNPs in the ADH7 and Class I ADH region in samples of 24 populations from China and Laos. These populations cover a wide geographic region and diverse ethnicities. Combined with our previously published East Asian data for these SNPs in 8 populations, we have typed populations from all of the 6 major linguistic phyla (Altaic including Korean-Japanese and inland Altaic, Sino-Tibetan, Hmong-Mien, Austro-Asiatic, Daic, and Austronesian). The ADH1B genotyping data are strongly related to ethnicity. Only some eastern ethnic phyla or subphyla (Korean-Japanese, Han Chinese, Hmong-Mien, Daic, and Austronesian) have a high frequency of ADH1B*47His. ADH1B haplotype data clustered the populations into linguistic subphyla, and divided the subphyla into eastern and western parts. In the Hmong-Mien and Altaic populations, the extended haplotype homozygosity (EHH) and relative EHH (REHH) tests for the ADH1B core were consistent with selection for the haplotype with derived SNP alleles. In the other ethnic phyla, the core showed only a weak signal of selection at best.

Conclusions/Significance

The selection distribution is more significantly correlated with the frequency of the derived ADH1B regulatory region polymorphism than the derived amino-acid altering allele ADH1B*47His. Thus, the real focus of selection may be the regulatory region. The obvious ethnicity-related distributions of ADH1B diversities suggest the existence of some culture-related selective forces that have acted on the ADH1B region.

Association of ADH and ALDH genes with alcohol dependence in the Irish Affected Sib Pair Study of alcohol dependence (IASPSAD) sample

BACKGROUND

The genes coding for ethanol metabolism enzymes [alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH)] have been widely studied for their influence on the risk to develop alcohol dependence (AD). However, the relation between polymorphisms of these metabolism genes and AD in Caucasian subjects has not been clearly established. The present study examined evidence for the association of alcohol metabolism genes with AD in the Irish Affected Sib Pair Study of alcohol dependence.

METHODS

We conducted a case-control association study with 575 independent subjects who met Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, AD diagnosis and 530 controls. A total of 77 single nucleotide polymorphisms (SNPs) in the seven ADH (ADH1-7) and two ALDH genes (ALDH1A1 and ALDH2) were genotyped using the Illumina GoldenGate protocols. Several statistical procedures were implemented to control for false discoveries.

RESULTS

All markers with minor allele frequency greater than 0.01 were in Hardy-Weinberg equilibrium. Numerous SNPs in ADH genes showed association with AD, including one marker in the coding region of ADH1C (rs1693482 in exon6, Ile271Gln). Haplotypic association was observed in the ADH5 and ADH1C genes, and in a long haplotype block formed by the ADH1A and ADH1B loci. We detected two significant interactions between pairs of markers in intron 6 of ADH6 and intron 12 of ALDH2 (p = 5 x 10(-5)), and 5' of both ADH4 and ADH1A (p = 2 x 10(-4)).

CONCLUSION

We found evidence for the association of several ADH genes with AD in a sample of Western European origin. The significant interaction effects between markers in ADH and ALDH genes suggest possible epistatic roles between alcohol metabolic enzymes in the risk for AD.

Alcohol-metabolizing enzyme gene polymorphisms and alcohol chronic pancreatitis among Polish individuals

BACKGROUND AND AIMS

Chronic pancreatitis develops in 5-10% of alcohol addicts. In developed societies, alcohol is the cause of chronic pancreatitis in at least 70-80% of cases. The genetic polymorphism of enzymes involved in alcohol metabolism is relevant in the etiopathogenesis of chronic pancreatitis. The aim of the study was to find the ADH, ALDH2 and CYP2E1 alleles and genotypes in the Polish population that are likely to be responsible for higher susceptibility to chronic alcohol pancreatitis.

MATERIAL AND METHODS

We determined the allele and genotype of ADH2, ADH3, ALDH2 and CYP2E1 in 141 subjects: 44 with alcohol chronic pancreatitis (ACP), 43 healthy alcoholics and 54 healthy non-drinkers as the controls. Genotyping was performed using PCR-RELP methods on white cell DNA.

RESULTS

ADH2*1, ADH3*1 alleles and ADH2*1/*1, ADH3*1/*1 genotypes were statistically more frequent among the patients with ACP than among the controls. The ADH3*2/*2 genotype was more frequent among "healthy alcoholics" and in the controls than among those with ACP. In the studied group, only the ALDH2*1 allele was detected, all patients were ALDH2*1/*1 homozygotic. Differences in the CYP2E1 allele and genotype distribution in the examined groups were not significant.

CONCLUSION

In the Polish population examined, ADH3*1 and ADH2*1 alleles may be risk factors for the development of alcoholism. The ADH3*2/*2 genotype may confer protection against ACP. CYP2E1 gene polymorphism is not related to alcoholism and ACP. The Polish population examined is ALDH2*1/*1 homozygotic.

Approach to the genetics of alcoholism: A review based on pathophysiology

Alcohol dependence is a common disorder with a heterogenous etiology. The results of family, twin and adoption studies on alcoholism are reviewed. These studies have revealed a heritability of alcoholism of over 50%. After evaluating the results, it was epidemiologically stated that alcoholism is heterogenous complex disorder with a multiple genetic background. Modern molecular genetic techniques allow examining specific genes involved in the pathophysiology of complex diseases such as alcoholism. Strategies for gene identification are introduced to the reader, including family-based and association studies. The susceptibility genes that are in the focus of this article have been chosen because they are known to encode for underlying mechanisms that are linked to the pathophysiology of alcoholism or that are important for the pharmacotherapeutic approaches in the treatment of alcohol dependence. Postulated candidate genes of the metabolism of alcohol and of the involved neurotransmitter systems are introduced. Genetic studies on alcoholism examining the metabolism of alcohol and the dopaminergic, GABAergic, glutamatergic, opioid, cholinergic and serotonergic neurotransmitter systems as well as the neuropeptide Y are presented. The results are critically discussed followed by a discussion of possible consequences.

Major genetic components underlying alcoholism in Korean population

Alcohol metabolism is one of the biological determinants that could significantly be influenced by genetic polymorphisms in alcohol-metabolism genes. Alcohol dehydrogenase (ADH) converts alcohol to acetaldehyde, and aldehyde dehydrogenase (ALDH) converts acetaldehyde to acetate. The well-known genetic polymorphisms in ADH1B(His47Arg) and ALDH2(Glu487Lys) have dramatic effects on the rate of metabolizing alcohol and acetaldehyde, respectively. The protective allele of ADH1B (ADH1B*47His) encodes for a rapid ethanol-metabolizing enzyme, and the susceptible allele of the ALDH2 (ALDH2*487Lys) is strongly associated with decreased rate of metabolizing acetaldehyde. However, the combined genetic effects of both functional polymorphisms have not been clarified. The combined analysis of two polymorphisms among a Korean population (n = 1,032) revealed dramatic genetic effects on the risk of alcoholism. Individuals bearing susceptible alleles at both loci have 91 times greater risk for alcoholism [odds ratio (OR) = 91.43, P = 1.4 x 10(-32)] and individuals bearing one susceptible and one protective allele at either loci have 11 times greater risk (OR = 11.40, P = 3.5 x 10(-15)) compared with subjects who have both protective alleles. The attributable fraction of those genetic factors, calculated based on population controls, indicates that alcoholism in 86.5% of alcoholic patients can be attributed to the detrimental effect of ADH1B*47Arg and/or ALDH2*487Glu in Korean population.

Alcoholism and alcohol drinking habits predicted from alcohol dehydrogenase genes

Alcohol drinking habits and alcoholism are partly genetically determined. Alcohol is degraded primarily by alcohol dehydrogenase (ADH) wherein genetic variation that affects the rate of alcohol degradation is found in ADH1B and ADH1C. It is biologically plausible that these variations may be associated with alcohol drinking habits and alcoholism. By genotyping 9080 white men and women from the general population, we found that men and women with ADH1B slow vs fast alcohol degradation drank more alcohol and had a higher risk of everyday drinking, heavy drinking, excessive drinking and of alcoholism. For example, the weekly alcohol intake was 9.8 drinks (95% confidence interval (CI): 9.1-11) among men with the ADH1B.1/1 genotype compared to 7.5 drinks (95% CI: 6.4-8.7) among men with the ADH1B.1/2 genotype, and the odds ratio (OR) for heavy drinking was 3.1 (95% CI: 1.7-5.7) among men with the ADH1B.1/1 genotype compared to men with the ADH1B.1/2 genotype. Furthermore, individuals with ADH1C slow vs fast alcohol degradation had a higher risk of heavy and excessive drinking. For example, the OR for heavy drinking was 1.4 (95% CI: 1.1-1.8) among men with the ADH1C.1/2 genotype and 1.4 (95% CI: 1.0-1.9) among men with the ADH1B.2/2 genotype, compared with men with the ADH1C.1/1 genotype. Results for ADH1B and ADH1C genotypes among men and women were similar. Finally, because slow ADH1B alcohol degradation is found in more than 90% of the white population compared to less than 10% of East Asians, the population attributable risk of heavy drinking and alcoholism by ADH1B.1/1 genotype was 67 and 62% among the white population compared with 9 and 24% among the East Asian population.

Association of haplotypic variants in DRD2, ANKK1, TTC12 and NCAM1 to alcohol dependence in independent case–control and family samples

There have been many conflicting reports concerning the association of the DRD2 locus with alcohol dependence (AD). To investigate whether these findings could be reconciled by considering the genomic region of DRD2 in greater detail, we conducted two separate association studies of AD in 1220 European-American subjects using family-based (488 subjects) and case-control (318 cases and 414 controls) designs, and 43 single nucleotide polymorphisms mapped to the gene cluster of NCAM1, TTC12, ANKK1 and DRD2. We used a generalized linear model and haplotype score tests for the case-control sample, and the family-based association test for the family sample. Haplotype associations centered on TTC12 exon 3 [rs1893699-rs723077; optimal individual haplotype simulated P-value (P(oihs)) = 0.00021] in both independent samples (family and case-control). Additional AD-associated haplotypes centered around NCAM1 exon 12 in the family sample (P(oihs) = 0.0032), and at exons 2 and 5 of ANKK1 in the case-control sample (P(oihs) = 0.00058). LD contrasts between cases and controls support selection at TTC12 exon 3 and ANKK1 exon 2. The armadillo repeat domains encoded by TTC12 and dopamine interact in the Wnt pathway and may have effects on dopamine cell development in the ventral midbrain. We conclude that risk for AD is attributable in part to variants in four regions within this cluster: exon 3 of TTC12, exon 12/intron13 of NCAM1 and exons 2 and 5 of ANKK1. The complexity of these relationships, many of which replicate between our independent samples, may explain prior inconsistent results.

"Higher order" addiction molecular genetics: convergent data from genome-wide association in humans and mice

Family, adoption and twin data each support substantial heritability for addictions. Most of this heritable influence is not substance-specific. The overlapping genetic vulnerability for developing dependence on a variety of addictive substances suggests large roles for "higher order" pharamacogenomics in addiction molecular genetics. We and others have now completed genome-wide association (GWA) studies of DNAs from individuals with dependence on a variety of addictive substances versus appropriate controls. Recently reported replicated GWA observations identify a number of genes based on comparisons between controls and European-American and African-American polysubstance abusers. Here we review the convergence between these results and data that compares control samples and (a) alcohol-dependent European-Americans, (b) methamphetamine-dependent Asians and (c) nicotine dependent samples from European backgrounds. We also compare these human data to quantitative trait locus (QTL) results from studies of addiction-related phenotypes in mice that focus on alcohol, methamphetamine and barbiturates. These comparisons support a genetic architecture built from largely polygenic contributions of common allelic variants to dependence on a variety of legal and illegal substances. Many of the gene variants identified in this way are likely to alter specification and maintenance of neuronal connections.

Effect of the CYP2E1 genotype on vinyl chloride monomer-induced liver fibrosis among polyvinyl chloride workers

Although a relationship between vinyl chloride monomer (VCM) and liver cirrhosis has been reported, the underlying mechanisms are not clear. Cytochrome P450 2E1 (CYP2E1), aldehyde dehydrogenase 2 (ALDH2) and glutathione S-transferase theta 1 (GSTT1) enzymes are involved in activation and detoxification of VCM, and thus may be important determinants of interindividual susceptibility to VCM-induced liver damage, including liver cirrhosis. The objective of this study was to evaluate if metabolizing genetic polymorphisms could modify individual susceptibility to liver fibrosis of the VCM exposure. CYP2E1, ALDH2, and GSTT1 polymorphisms were determined by the PCR-RFLP method among 320 workers who were employed in five polyvinyl chloride manufacturing plants. Cumulative VCM exposure levels for study subjects were calculated using a job exposure matrix model. Thirteen workers were diagnosed as having liver fibrosis by using ultrasonography. We observed a dose-response trend between VCM exposure and liver fibrosis. Regarding the results on genetic polymorphisms, CYP2E1 c2c2 genotype showed a significant increase in the risk of liver fibrosis as compared to those with CYP2E1 c1c1 or c1c2 genotypes. No differences were observed between GSTT1 and ALDH2 genotypes and liver fibrosis. In summary, our result suggests that genetic polymorphism in CYP2E1 may be responsible for individual differences in susceptibility to liver fibrosis with regard to chronic VCM exposure. Thus, polymorphism analysis of metabolizing enzymes might be useful in the risk assessment of liver damage in workers with VCM exposure.

5′ UTR polymorphism of dopamine receptor D1 (DRD1) associated with severity and temperament of alcoholism

Multiple dopamine receptors in the dopaminergic system may be prime candidates for genetic influence on alcohol abuse and dependence due to their involvement in reward and reinforcing mechanisms. Genetic polymorphisms in dopamine receptor genes are believed to influence the development and/or severity of alcoholism. To examine the genetic effects of the Dopamine Receptor D1 (DRD) gene family (DRD1-DRD5) in the Korean population, 11 polymorphisms in the DRD gene family were genotyped and analyzed in 535 alcohol-dependent subjects and 273 population controls. Although none of the polymorphisms of DRD1-5 genes were found to be associated with the risk of alcoholism, one 5' UTR polymorphism in the DRD1 (DRD1-48A>G) gene was significantly associated with severity of alcohol-related problem, as measured by the Alcohol Use Disorders Identification Test (AUDIT) in a gene dose-dependent manner, i.e., 24.37 (+/-8.19) among patients with -48A/A genotype, 22.37 (+/-9.49) among those with -48A/G genotype, and 17.38 (+/-8.28) among those with -48G/G genotype (P=0.002). The genetic effects of DRD1-48A>G were further analyzed with other phenotypes among alcohol-dependent subjects. Interestingly, the DRD1-48A>A genotype was also found to be associated with novelty seeking (NC), harm avoidance (HA), and persistence (P) (P =0.01, 0.02, and 0.003, respectively). The information derived from this study could be valuable for understanding the genetic factors involved in alcoholic phenotypes and genetic distribution of the DRD gene family, and could facilitate further investigation in other ethnic groups.

Evidence of positive selection on a class I ADH locus

The alcohol dehydrogenase (ADH) family of enzymes catalyzes the reversible oxidation of alcohol to acetaldehyde. Seven ADH genes exist in a segment of ~370 kb on 4q21. Products of the three class I ADH genes that share 95% sequence identity are believed to play the major role in the first step of ethanol metabolism. Because the common belief that selection has operated at the ADH1B*47His allele in East Asian populations lacks direct biological or statistical evidence, we used genomic data to test the hypothesis. Data consisted of 54 single-nucleotide polymorphisms (SNPs) across the ADH clusters in a global sampling of 42 populations. Both the F(st) statistic and the long-range haplotype (LRH) test provided positive evidence of selection in several East Asian populations. The ADH1B Arg47His functional polymorphism has the highest F(st) of the 54 SNPs in the ADH cluster, and it is significantly above the mean F(st) of 382 presumably neutral sites tested on the same 42 population samples. The LRH test that uses cores including that site and extending on both sides also gives significant evidence of positive selection in some East Asian populations for a specific haplotype carrying the ADH1B*47His allele. Interestingly, this haplotype is present at a high frequency in only some East Asian populations, whereas the specific allele also exists in other East Asian populations and in the Near East and Europe but does not show evidence of selection with use of the LRH test. Although the ADH1B*47His allele conveys a well-confirmed protection against alcoholism, that modern phenotypic manifestation does not easily translate into a positive selective force, and the nature of that selective force, in the past and/or currently, remains speculative.

Interactive effects of lifetime alcohol consumption and alcohol and aldehyde dehydrogenase polymorphisms on esophageal cancer risks

In our previous study, we found that polymorphisms of alcohol and aldehyde dehydrogenase (ADH1B and ALDH2) are important risks for esophageal squamous cell carcinoma in a Taiwanese population. In this study, we increased the sample size to investigate the modifying effect of lifetime alcohol consumption on the association between ADH1B and ALDH2 genotypes and the risks of esophageal cancer. A multicenter hospital-based case-control study was conducted between August 2000 and June 2004. Three hundred and thirty newly-diagnosed esophageal squamous cell carcinoma patients and 592 controls were recruited from National Taiwan University Hospital in Taipei and Kaohsiung Veterans General Hospital and Kaohsiung Medical University Hospital in Kaohsiung, Taiwan. Controls were matched to the case patients by gender and age within 4 years (case:control = 1:1-4). Polymorphisms of ADH1B and ALDH2 were genotyped by the method of PCR-RFLP. Individuals with ADH1B*1/*1 genotype had a 3.99-fold risk (95% CI = 2.13-7.48) of developing esophageal cancer, compared with those with ADH1B*2/*2 genotype, after adjusted for appropriate covariates. Individuals with ALDH2*1/*2 and ALDH2*2/*2 had 4.99-fold risk (95% CI = 3.11-7.99) and 4.24-fold risk (95% CI = 1.52-11.84), respectively, of developing esophageal cancer, compared with those with ALDH2*1/*1, after adjusted for appropriate covariates. We also found a modifying effect of lifetime alcoholic consumption on the association between genotypes of ADH1B and ALDH2 on esophageal cancer risk. These results suggest that ADH1B and ALDH2 polymorphisms play a pivotal role on esophageal cancer and that the effect of these polymorphisms was modified by the amount of alcohol consumed.

Associations of variations in alcohol dehydrogenase genes with the level of response to alcohol in non-Asians

BACKGROUND

Risk and protective factors for alcohol use disorders (AUDs) are complex and reflect both environmental and genetic factors. Genetic components account for about 50% of the variation and influence several phenotypes, including the level of response (LR) to alcohol as well as alcohol-metabolizing enzyme polymorphisms. Variations in the ADH1B and ADH1C genes may influence the LR to alcohol by increasing levels of acetaldehyde during alcohol metabolism, although most data on this question come from Asian populations.

METHODS

This study evaluated associations of ADH1B and ADH1C genotypes in a non-Asian sample. Participants (N = 117, 69.2% female) were 18- to 29-year-old men and women, primarily Caucasian (70.1%) and black (26.5%), recruited in San Diego, California. The Semi-Structured Assessment for the Genetics of Alcoholism Interview was used to assess demographic, substance use, and psychiatric history information, and the Family History Assessment Module was used to determine first-degree family history of alcohol dependence. An alcohol challenge paradigm was used to gather data on the LR to alcohol over 210 minutes.

RESULTS

Participants with the ADH1B*1/*2 genotype had a higher LR to alcohol early in the alcohol challenge (i.e., 30, 60, and 90 minutes after drinking) as measured by both alcohol-related changes in subjective feelings of intoxication and body sway, even when controlling for sex and Russian/Eastern European ancestry. A similar trend was seen for ADH1C*1/*1 genotype, although the results were not significant.

CONCLUSIONS

These findings suggest that studies searching for genes relating to the LR to alcohol as a vulnerability factor for AUDs should consider controlling for ADH1B genotype, as the ADH1B*2 allele could obscure the impact of other genetic polymorphisms.

The genetics of alcoholism: identifying specific genes through family studies

Alcoholism is a complex disorder with both genetic and environmental risk factors. Studies in humans have begun to elucidate the genetic underpinnings of the risk for alcoholism. Here we briefly review strategies for identifying individual genes in which variations affect the risk for alcoholism and related phenotypes, in the context of one large study that has successfully identified such genes. The Collaborative Study on the Genetics of Alcoholism (COGA) is a family-based study that has collected detailed phenotypic data on individuals in families with multiple alcoholic members. A genome-wide linkage approach led to the identification of chromosomal regions containing genes that influenced alcoholism risk and related phenotypes. Subsequently, single nucleotide polymorphisms (SNPs) were genotyped in positional candidate genes located within the linked chromosomal regions, and analyzed for association with these phenotypes. Using this sequential approach, COGA has detected association with GABRA2, CHRM2 and ADH4; these associations have all been replicated by other researchers. COGA has detected association to additional genes including GABRG3, TAS2R16, SNCA, OPRK1 and PDYN, results that are awaiting confirmation. These successes demonstrate that genes contributing to the risk for alcoholism can be reliably identified using human subjects.

Meta-analyses of ALDH2 and ADH1B with alcohol dependence in Asians

Meta-analyses were conducted to determine the magnitude of relationships between polymorphisms in 2 genes, ALDH2 and ADH1B, with alcohol dependence in Asians. For each gene, possession of 1 variant *2 allele was protective against alcohol dependence, and possession of a 2nd *2 allele did not offer significant additional protection. The protective effects of these 2 gene polymorphisms were independent. Diagnostic criteria, recruitment strategy, and Japanese ethnicity moderated the effect of ALDH2*2. Recruitment strategy and gender moderated the effect of ADH1B*2. These findings highlight the importance of methodological issues and potential gene-gene and gene-environment interactions that must be considered when examining relationships between genetic polymorphisms and phenotypes.

ADH1C*2 allele is associated with alcohol dependence and elevated liver enzymes in Trinidad and Tobago

Variants in alcohol dehydrogenase (ADH) genes differ between ethnic groups and have, in some studies, been found to be associated with alcohol dependence and alcoholic liver disease. This study sought to determine whether an association exists between ADH (ADH1C previously ADH3, ADH1B*2 previously ADH2*2) genotypes, alcohol dependence, drinking history, and liver function tests in the two major ethnic groups of Trinidad and Tobago (TT). One hundred and forty-five alcohol-dependent individuals of both East Indian (Indo-TT) and African (Afro-TT) ancestry, and 108 controls matched by age, sex, and education participated in the study. Serum levels of alanine and aspartate aminotransferase (ALT, AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and gamma-glutamyltransferase (GGT) as well as presence of HIV, hepatitis B surface antigen, and anti-hepatitis C virus antibody were determined. There was a significant difference in the distribution of ADH1C allele polymorphisms between the ethnic groups (P<.0001). Forty-three percent of the Indo-TT were found to have one ADH1C*2 allele and 5% were homozygous, whereas, only 23% of Afro-TT had one allele and one was homozygous. Only three individuals had an ADH1B*2 allele (one Indo-TT alcohol dependent, two Indo-TT controls). The ADH1C*2 allele was significantly associated with alcohol dependence overall and within Indo-TT ancestry, however, it was not associated with current or heaviest alcohol consumption levels. Individuals with at least one ADH1C*2 allele also had significantly elevated levels of ALP (P<.02) and GGT (P<.02) as compared to individuals homozygous for ADH1C*. Additionally, GGT levels were also found to be elevated (P<.02) within Indo-TT alcohol dependents with at least one ADH1C*2 allele but not within the Afro-TT alcohol dependents with that allele. A linear regression that included alcohol dependence and levels of alcohol consumption confirmed that levels of serum GGT were significantly associated with the ADH1C*2 genotype. These results suggest that ADH1C polymorphisms are associated with alcohol dependence and alcohol associated elevations of liver enzymes in a population with a low frequency of ADH1B2 alleles.

Diplotype trend regression analysis of the ADH gene cluster and the ALDH2 gene: multiple significant associations with alcohol dependence

The set of alcohol-metabolizing enzymes has considerable genetic and functional complexity. The relationships between some alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) genes and alcohol dependence (AD) have long been studied in many populations, but not comprehensively. In the present study, we genotyped 16 markers within the ADH gene cluster (including the ADH1A, ADH1B, ADH1C, ADH5, ADH6, and ADH7 genes), 4 markers within the ALDH2 gene, and 38 unlinked ancestry-informative markers in a case-control sample of 801 individuals. Associations between markers and disease were analyzed by a Hardy-Weinberg equilibrium (HWE) test, a conventional case-control comparison, a structured association analysis, and a novel diplotype trend regression (DTR) analysis. Finally, the disease alleles were fine mapped by a Hardy-Weinberg disequilibrium (HWD) measure (J). All markers were found to be in HWE in controls, but some markers showed HWD in cases. Genotypes of many markers were associated with AD. DTR analysis showed that ADH5 genotypes and diplotypes of ADH1A, ADH1B, ADH7, and ALDH2 were associated with AD in European Americans and/or African Americans. The risk-influencing alleles were fine mapped from among the markers studied and were found to coincide with some well-known functional variants. We demonstrated that DTR was more powerful than many other conventional association methods. We also found that several ADH genes and the ALDH2 gene were susceptibility loci for AD, and the associations were best explained by several independent risk genes.

Genetics and alcoholism: how close are we to potential clinical applications?

Rapid advancement of genetic knowledge has provided a wealth of data demonstrating a significant contribution of genes to the development of alcoholism but has suggested little in the way of clinical applicability. Twin and adoption studies suggest that 50% to 60% of the development of alcoholism is due to heritable factors, and linkage and association studies have identified chromosomal regions and individual genes that likely contribute to the development of this condition. Most of these genes are related to neurotransmitter systems and to alcohol metabolizing enzymes. We briefly review the evidence for this before discussing intermediate phenotypes of alcoholism under genetic control, pharmacogenetic aspects of alcoholism treatment, and the possibility of future clinical applications based on these areas.