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Associations of GABAA receptor gene variations with alcohol use disorder and conduct disorder phenotypes in Korean-, Chinese-, and European-American college students

Daria Orlowska

Department of Psychiatry, University of California, San Diego, USA

Mimy Y. Eng

Veterans Medical Research Foundation, San Diego, USA

E. Luczak

Department of Psychology, University of Southern California, Los Angeles, USA

Howard J. Edenberg

Departments of Biochemistry and Molecular Biology, Indiana University, School of Medicine, Indianapolis, USA

Tamara L. Wall

Department of Psychiatry, University of California, San Diego, USA

Veterans Medical Research Foundation, San Diego, USA

VA San Diego Healthcare System, San Diego, USA

E-mail : twall@ucsd.edu

DOI: 10.15761/BGG.1000111

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Abstract

Aims: This study aimed to determine whether gamma-aminobutyric acid (GABAA) receptor gene variations differed across individuals of Korean, Chinese, and European ancestry and to test for genes associations with four phenotypes: alcohol dependence diagnosis, alcohol use disorder (AUD; alcohol abuse and dependence) symptom count, conduct disorder diagnosis, and conduct disorder symptom count.

Methods: Male and female college students (n=1,310) were genotyped for ALDH2, ADH1B, and 21 SNPs spanning four GABAA receptor genes, GABRA2, GABRA4, GABRA1, and GABRG3. Phenotypes were assessed using DSM-IV criteria. Complete genotypic and phenotypic data were available for 1,154 participants.

Results: There were significant differences in the allele frequencies of ALDH2, ADH1B, and all 21 GABAA receptor gene SNPs across individuals of Korean, Chinese, and European ancestry. Four GABRA2 SNPs were significantly associated with lifetime AUD symptoms in Korean-American men. Three GABRG3 SNPs were significantly associated with conduct disorder diagnosis in Korean-American men.

Conclusion: Results suggest significant variation across ancestry in GABAA receptor genes and that there may be varied associations with phenotypes in different ancestral groups. These findings highlight the need for replication and increased understanding of the mechanism underlying putative associations of GABAA receptor gene variation with AUD and conduct disorder phenotypes.

Introduction

The etiology of alcohol use disorders (AUDs; alcohol abuse and dependence) includes genetic and environmental influences. Twin studies using samples of primarily European ancestry indicate 50-60% of the variability in alcohol dependence is explained by the combined effects of multiple genes [1,2]. However, rates of AUDs differ substantially by sex and in different populations [3]. In particular, Asians in the U.S. have lower rates of AUDs than Whites, Blacks, Native Americans, and Hispanics [3,4]. Two genetic variants, ALDH2*2 (rs671) and ADH1B*2 (rs1229984), are found predominantly in Asian populations and associated with lower rates of alcohol dependence [5-7]. The hypothesized mechanism underlying the associations of ALDH2*2 and ADH1B*2 with alcohol dependence is that the isoenzymes encoded by these alleles lead to increased acetaldhyde and enhanced reactions to alcohol, which then reduces heavy drinking and AUDs [8].

As an aggregated group, Asians in the U.S. have lower rates of AUDs [3], but there are substantial differences across subgroups [9,10]. In a large cross-national study, the lifetime rate of alcohol abuse and dependence was 23% for South Koreans (43% of men, 3% of women) and 7% for Taiwanese (13% of men, 0.7% for women) compared with 17% for Americans (29% of men, 4% of women) [9]. This large difference in lifetime AUD rates between South Koreans and Taiwanese is similar, but more pronounced, to rates found in more recent epidemiologic studies in Asia and the U.S. [10-12]. Consistent with epidemiologic data, a study from our laboratory found Chinese-American college students had lower rates of alcohol dependence (8% of men, 2% of women) than Korean-American (18% of men, 8% of women) and European-American (22% of men, 12% of women) college students [13].

In most cultures, men have higher rates of AUDs than women, but the sex discrepancy is particularly pronounced in many Asian groups [3,9] and may be due, in part, to societal, familial, and peer pressures on women not to drink. In support of this hypothesis, the male-to-female AUD ratio in South Korea and China has decreased as Westernization has occurred [14,15]. These findings suggest the possibility that the relative influence of genetics on AUDs in Asian men and women may differ from that found in studies of predominantly European men and women [2] and could vary over time.

In our prior study of Korean-, Chinese-, and European-American college students, analyses indicated that the relationship of ancestry with alcohol dependence was mediated by ALDH2 gene status and conduct disorder, although Chinese ancestry remained significant [13]. ADH1B gene status was not related to alcohol dependence with ALDH2 included in the analyses and no interactions were significant. These results suggest that different rates of risk (e.g., conduct disorder) and protective (e.g., ALDH2 status) factors account for some the variability in rates of alcohol dependence between Korean, Chinese, and European Americans.

One set of genes that might contribute to differences in rates of AUDs and conduct disorder observed between Koreans, Chinese, and Europeans are the gamma-aminobutyric acid (GABAA) receptor genes. Multiple reports have identified associations between single nucleotide polymorphisms (SNPs) of the GABAA receptor genes with AUD and/or conduct disorder phenotypes. For the current study, we selected 21 SNPs spanning four GABAA receptor genes, GABRA2 (chromosome 4), GABRA4 (chromosome 4), GABRA1 (chromosome 5), and GABRG3 (chromosome 15) based on prior significant associations with either AUD phenotypes [16-36] or conduct disorder phenotypes [20,34,36-38]. It is important to note that the majority of these reports were case-control studies, which have greater power to detect significant associations than general population studies. In addition, few, if any, participants of Asian descent were included in these prior investigations and not all studies examining the same SNPs have reported consistent associations [23,27,29,31,34,39,40].

To date, no functional variants have been identified that account for the associations of the GABAA receptor genes with AUDs and/or conduct disorder, and the mechanism of action of these gene associations is unknown. Some investigators have hypothesized that GABRA2 SNPs may exert their effect on alcohol dependence via differences in levels of response to alcohol [32,33]. Roh and colleagues [33] assessed a Japanese sample and stratified by ALDH2 genotype. Individuals heterozygous and homozygous for several GABRA2 variants were more sensitive to the effects of alcohol irrespective of their ALDH2 genotype. This finding suggests that GABRA2 variation, similar to ALDH2 variation, may contribute to individual variability in response to alcohol. Other investigators have hypothesized GABRA2 variants might relate to alcohol dependence and conduct disorder via general externalizing pathways given associations of several SNPs not only with alcohol phenotypes, but also with conduct disorder, antisocial personality disorder, and other (non-alcohol) drug dependencies [20,31,37,39].

To extend our prior research [13], we genotyped for ALDH2, ADH1B, and 21 SNPs spanning four GABAA receptor genes, GABRA2, GABRA4, GABRA1 and GABRG3 and tested for associations with both AUD and conduct disorder phenotypes in a larger sample of Korean-, Chinese-, and European-American college students. We hypothesized that there would be differences in the allele frequencies of GABAA receptor genes across ancestry but not across sex. Given that genetic and environmental influences may differ across groups and across phenotypes, we conducted analyses separately by ancestry and sex and analyzed both dichotomous (i.e., diagnosis) and continuous (i.e., symptom count) outcomes [41]. Based on prior investigations, we hypothesized that there would be significant associations between GABAA receptor gene SNPs and two AUD phenotypes (alcohol dependence diagnosis, AUD symptom count) controlling for variation in the ALDH2 and ADH1B genes. We also hypothesized that there would be significant associations between GABAA receptor gene SNPs and two conduct disorder phenotypes (diagnosis and symptom count).

Methods

Participants were 21 to 26 year old college students recruited from the University of California, San Diego (UCSD). All individuals reported that they were of entirely Korean (nnnSD=1.34) years. A prior report included a subsample of these participants, n=604 (50% female) [13].

Potential participants were recruited based on self-reported ancestry via advertisements on campus for a paid research project. Respondents were initially screened by telephone and then rescreened in person to assure they met inclusion criteria. Europeans who reported any known African, Hispanic, Native American, Asian, or Jewish ancestry were excluded from participation. Asians who reported all grandparents were entirely of Chinese/Taiwanese or entirely Korean ancestry was included in the study. The research protocol was approved by the human research protection program at UCSD. All study participants provided written informed consent for clinical and genetic studies.

Each participant completed an individual assessment with a trained research interviewer. To increase the likelihood of accurate reporting, we explained our procedures for protecting confidentiality. The Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) was used to assess lifetime symptoms and diagnoses of alcohol abuse, alcohol dependence, and conduct disorder (prior to age 18 years) based on the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders [42]. The SSAGA has shown good reliability and validity for these disorders [43,44] and was designed to assess psychiatric symptomatology independent of substance abuse. Thus, no symptom of conduct disorder was the result of substance use.

A blood sample was collected from each participant via fingertip puncture. Genotyping for ALDH2, ADH1B, and 21 SNPs spanning GABRA2, GABRA4, GABRA1 and GABRG3 was conducted using methods described previously [23,45,46]. Complete genotype data were not available for 156 participants.

Genotype distributions in each ancestry group were examined for significant deviation (p < .05) from Hardy-Weinberg equilibrium. Chi-square tests of association were conducted to determine if allele frequencies differed significantly across ancestry and sex. For comparisons of allele frequencies as well as rates of diagnoses and levels of symptoms among the three ancestry groups, we used planned, pair-wise tests, controlling the Type I error-rate by considering significant a p-value less than .0167 (.05/3).

Phenotypic analyses were conducted separately by ancestry and sex. Each SNP was coded 0, 1, or 2 for the major allele and treated as an ordinal relationship when examining relationships between genotypes and phenotypes. Chi-square tests of association were used to examine associations with dichotomous phenotypes. Regression analyses were used to examine associations with continuous phenotypes. For AUD phenotypes, multiple regression analyses also were conducted to control for the effects of ALDH2 and ADH1B as they are related to alcohol dependence and other alcohol phenotypes.

We expected that the four phenotypes would be related. Alcohol dependence and AUD symptoms, as well as conduct disorder and conduct disorder symptoms were expected to be highly correlated; AUD and conduct disorder phenotypes also were expected to be correlated [47]. Due to their close proximity, we expected some SNPs within the same gene to be correlated. We did not make corrections for multiple phenotypic comparisons because it would increase the likelihood of a Type II error due to low phenotype rates in the sample and because predictions were expected to be similar across the set of correlated outcome measures. Multiple comparisons are less critical when tests are correlated [48], i.e., comparisons for related outcome measures and for alleles in linkage disequilibrium do not each provide an independent opportunity for a Type I error.

Results

Complete genotypic and phenotypic data were available for 1,154 participants. The final sample included 337 Korean- (53% female), 350 Chinese- (49% female), and 467 European-American (49% female) college students. Table 1 displays the allele frequencies across ancestry for ALDH2, ADH1B, and GABAA receptor gene SNPs. All genotype distributions were in Hardy-Weinberg equilibrium (p > .05) except for four correlated GABRA2 SNPs (rs1442059, rs279826, rs279828, rs279836) in Chinese Americans and one GABRA2 SNP (rs1442059) in Korean Americans (Table 1), and likely are due to chance. There were no significant sex differences, but there were significant ancestry differences in allele frequencies of ALDH2, ADH1B, and all 21 GABAA receptor gene SNPs. Planned pair-wise tests (p-values < .0167) revealed significant differences between the Korean-, Chinese-, and European-American groups as shown in Table 1.

Table 1. Allele Frequencies for ALDH2, ADH1B and GABAA Receptor Gene SNPs in Korean, Chinese, and European Americans

Gene SNP NT Korean American(n=337) Chinese American(n=350) European American(n=467) Ancestry differences
ALDH2 rs671 A/G .17/.83 .27/.73 0/1.0 a,b,c
ADH1B rs1229984 A/G .73/.27 .72/.28 .03/.97 b,c
GABRA2 rs1442059 C/T .53/.47 .60/.40 * .42/.58 a,b,c
GABRA2 rs279826 A/G .47/.53 .40/.60 * .56/.45 a,b,c
GABRA2 rs279827 A/G .48/.53 .41/.59 .56/.45 b,c
GABRA2 rs279828 A/C .47/.53 .40/.60 * .56/.45 a,b,c
GABRA2 rs279836 A/T .53/.47 * .60/.40 * .42/.58 a,b,c
GABRA2 rs279845 A/T .53/.47 .59/.41 .45/.56 b,c
GABRA2 rs279858 A/G .51/.49 .47/.53 .57/.43 b,c
GABRA2 rs279871 A/G .51/.49 .47/.53 .57/.43 c
GABRA2 rs490434 A/G .40/.60 .49/.51 .41/.59 c
GABRA2 rs495818 A/G .61/.39 .52/.48 .58/.42 a,c
GABRA2 rs531460 A/G .39/.61 .49/.51 .41/.60 c
GABRA2 rs572227 A/G .39/.61 .48/.52 .42/.58 a
GABRA4 rs2036943 A/T .60/.40 .69/.31 .31/.69 a,b
GABRA1 rs4263535 A/G .51/.49 .55/.45 .82/.18 b,c
GABRA1 rs4478357 A/C .30/.70 .31/.69 .54/.46 b,c
GABRG3 rs3097490 C/T .21/.79 .30/.70 .50/.51 a,b,c
GABRG3 rs3097493 C/G .25/.75 .32/.68 .49/.51 a,b,c
GABRG3 rs3101636 A/G .75/.25 .68/.32 .51/.49 a,b,c
GABRG3 rs3101639 A/G .75/.25 .68/.32 .51/.49 a,b,c
GABRG3 rs140679 C/T .27/.73 .33/.67 .49/.51 a,b,c
GABRG3 rs2303879 A/G .79/.21 .70/.30 .51/.50 a,b,c

Notes.
* Hardy-Weinberg equilibrium violated, p < .05
a – Korean Americans significantly different from Chinese Americans, p <. 0167
b – Korean Americans significantly different from European Americans, p < .0167
c – Chinese Americans significantly different from European Americans, p < .0167

Table 2 presents frequencies for alcohol dependence and conduct disorder diagnoses, and means and SDs for AUD symptoms and conduct disorder symptoms, according to ancestry and sex. For all analyses, square root transformations were used to adjust for the positive skew found for both AUD symptoms and conduct disorder symptoms, but untransformed data are shown to facilitate interpretability.

Table 2. Diagnoses (Percentages) and Symptom Counts (Means and SDs) by Ancestry and Sex

  Korean Americans Chinese American European Americans
  Men
(n=159)
Women
(n=178)
Men
(n=179)
Women
(n=171)
Men
(n=239)
Women
(n=228)
Alcohol dependence 6.3% 2.8% 1.7% 0.6% 11.7% 2.6%
AUD symptoms 1.1 (1.8) 0.6 (1.3) 0.4 (1.0) 0.2 (0.5) 1.4 (2.0) 0.6 (1.2)
Conduct disorder 17.6% 2.8% 5.6% 2.3 % 9.6% 2.6%
Conduct disorder symptoms 1.8 (1.78) 0.4 (0.8) 0.9 (1.3) 0.4 (0.8) 1.2 (1.3) 0.6 (0.9)

In the total sample, 4.6% of participants met criteria for a lifetime diagnosis of alcohol dependence using DSM-IV criteria. Significantly more men (7.1%) than women (2.1%) were alcohol dependent, χ2=16.63, p < .001. Ancestry group differences also were significant, χ2=17.22, p < .001. Chinese Americans (1.1%) were significantly less likely to be diagnosed with alcohol dependence than Korean (4.4%) and European (7.2%) Americans, χ2=16.99, p < .001, but the rate did not significantly differ between Korean and European Americans, χ2=2.74, p=.098. A similar pattern of significance emerged for AUD symptoms (Table 2). Men had significantly more lifetime AUD symptoms than women F (1, 1,153)=12.05, p < .001; Chinese Americans had significantly fewer lifetime AUD symptoms than Korean F (1, 685)=42.19, p < .001) and European F (1, 815)=279.07, p < .001) Americans.

In the total sample, 6.6% of participants had a diagnosis of conduct disorder. Rates of conduct disorder differed across sex, χ2=29.8, p < .001, and ancestry, χ2=9.54, p < .001. Significantly more men (10.6%) than women (2.6%) met lifetime criteria for conduct disorder. Korean Americans were significantly more likely to be diagnosed with conduct disorder (9.8%) than European (6.2%) and Chinese (4%) Americans, (χ2=9.04, p < .003), but the rate did not significantly differ between European and Chinese Americans (χ2=1.96, p=.162). A similar pattern of significance emerged for conduct disorder symptoms (Table 2). Men had significantly more lifetime conduct disorder symptoms than women F (1, 1,153)=113.21, p < .001; Chinese Americans had significantly fewer conduct disorder symptoms than Korean F (1, 685)=13.01, p < .001 and European F (1, 815)=11.28, p < .01 Americans.

Four GABRA2 SNPs (rs490434, rs495818, rs531460, rs572227) were significantly associated with AUD symptoms in Korean-American men. These four SNPs were significantly correlated in this sample rs=.57-.94, p-values < .05). In univariate analyses, Korean-American men whose genotype was homozygous for the minor allele: AA for rs490434, GG for rs495818, AA for rs531460, and AA for rs572227 had, on average, a significantly higher number of lifetime AUD symptoms (mean ranged from 1.87–2.08) than Korean-American men whose genotype was heterozygous (mean ranged from 1.15–1.25) or whose genotype was homozygous for the major allele (mean ranged from 0.77–0.78).

Table 3 shows results of multiple regression analyses for each of these four GABRA2 SNPs and ALDH2 and ADH1B on the number of lifetime AUD symptoms in Korean-American men. ALDH2 but not ADH1B was significantly associated with AUD symptoms, and each GABRA2 SNP remained significant. To test for the possibility of a gene x gene interaction, an interaction term of ALDH2 with rs490434, rs495818, rs531460, or rs572227 was added to each respective model. None of the interactions were significant (p-values > .05; data not shown).

Table 3.Summary of Separate Multiple Regression Analyses for Four Adjacent GABRA2 SNPs, ALDH2, and ADH1B, with AUD Symptoms in Korean-American men (n=156)

GABRA2 SNP Variable F-value
df=2, 152
p-value
rs490434 ALDH2*2 5.38 0.006
  ADH1B*2 0.43 0.651
  A allele 6.01 0.003
rs495818 ALDH2*2 5.51 0.005
  ADH1B*2 0.38 0.684
  G allele 4.29 0.015
rs531460 ALDH2*2 5.36 0.006
  ADH1B*2 0.44 0.644
  A allele 6.09 0.003
rs572227 ALDH2*2 5.51 0.005
  ADH1B*2 0.38 0.684
  A allele 4.29 0.015

Three adjacent GABRG3 SNPs (rs3097493, rs3101636, rs3101639) were significantly associated with conduct disorder diagnosis in Korean-American men: rs3097493 χ2 (2, N=159)=7.67, p=.022; rs3101636 χ2 (2, N=159)=7.33, p=.026; rs3101639, χ2 (2, N=159)=7.67, p=.022. These three SNPs were significantly correlated in this sample (rs=.721-.985, p-values < .05). Results indicated Korean-American men whose genotype was homozygous for the major allele: AA for rs3101639, AA for rs3101636, and GG for rs3097493 had a higher frequency of conduct disorder (range 23-24%) than Korean-American men whose genotype was heterozygous (range 8-9%) or whose genotype was homozygous for the minor allele (0%).

Discussion

The aim of this study was to extend prior research and explore associations between GABAA receptor gene SNPs with AUD and conduct disorder phenotypes in samples of Korean-, Chinese-, and European-American college students. Specifically, we determined if there were sex or ancestry differences in the allele frequencies of 21 SNPs spanning four genes, GABRA2, GABRA4, GABRA1 and GABRG3, and tested for associations with alcohol dependence, AUD symptom count, conduct disorder, and conduct disorder symptom count.

The GABAA receptor gene variants were chosen based on prior associations with AUD and/or conduct disorder phenotypes from predominantly case-control studies that included few, if any, participants of Asian descent. As hypothesized, results showed no significant sex differences, but significant ancestry differences for all 21 SNPs, with many (n=10) showing significant differences between all three ancestral groups. Some prior investigations have reported varied associations of GABAA receptor gene variants with AUD or conduct disorder phenotypes in different racial and ethnic groups, primarily African Americans or Hispanics compared with non-Hispanic Caucasians [16,34,38], but have not reported if allele frequencies differed significantly across ancestry. Given the potential for population stratification, it is important to determine if there are ancestry differences in the allele frequencies of candidate genes. Results from the current study suggest there is considerable variation in GABAA receptor gene variants across the Korean-, Chinese- and European-American college students that were sampled in this study.

As expected, there were significant sex differences and significant ancestry differences for the four AUD and conduct disorder phenotypes that were evaluated. Because of phenotypic differences and the potential for population stratification, gene association analyses were conducted stratifying by ancestry and sex. We identified two clusters of GABAA receptor gene SNPs that related significantly to different phenotypes in Korean-American men. One cluster of correlated SNPs (rs490434, rs495818, rs531460, rs572227) located on GABRA2 was significantly associated with AUD symptoms, and the associations remained significant in analyses that included ALDH2 and ADH1B. In previous studies, these four SNPs have been associated with alcohol dependence [16,23,39]. Edenberg and colleagues [23] found multiple GABRA2 SNPs, including rs490434, rs495818, rs531460, and rs572227, were significantly associated with DSM-IV alcohol dependence using data from the Collaborative Study on the Genetics of Alcoholism (COGA) sample, a large study of families in which at least three individuals met diagnostic criteria for alcohol dependence. Agrawal and colleagues [39] replicated the association of these four and other GABRA2 SNPs with alcohol dependence using the COGA sample. However, when individuals with comorbid drug dependence were excluded from analyses, the relationship for many of the SNPs including rs490434, rs495818, rs531460, and rs572227, were no longer significant. Bierut and colleagues [16] examined only one of these four SNPs, rs572227, in a sample of European-American and African-Americans and also replicated a significant association with alcohol dependence. Another study, however, did not corroborate these findings; Philibert and colleagues [31] found that rs495818, rs531460, and rs572227, but not rs490434, were associated with alcohol dependence symptoms. However, the findings were in the opposite direction; they reported that the risk allele for each of these SNPs was A for rs495818, G for rs531460, and G for rs572227.

A possible reason that we found significant associations between these four GABRA2 SNPs and AUD symptoms, but not with alcohol dependence, in our sample of Korean-American men may relate to the characteristics of our sample, which was young (21-26 years of age) and non-treatment seeking. Previous studies that have found significant associations of these SNPs with alcohol dependence have used case-control designs [16,23,39]. Because of the relatively low prevalence of alcohol dependence in our college student sample, we also evaluated AUD symptom count as a phenotype, which includes individuals who are experiencing problems that are below diagnostic thresholds and provides greater power to detect significant associations [40].

We also identified a cluster of correlated SNPs (rs3101639, rs3101636, rs3097493) located on GABRG3 that was significantly associated with conduct disorder in Korean-American men. In the COGA study, these three SNPs were associated with alcohol dependence [18], but they have not been previously tested for an association with conduct disorder. Kramer and colleagues [27] reported that rs3097493 was not associated with problematic alcohol use in a young adult sample (mean age 20.6 years) that was initially ascertained as children in the COGA study, but an association with conduct disorder was not tested. Variation in the GABRG3 gene has been less well studied than the GABRA2, GABRA4, and GABRA1 genes. The current findings suggest that Korean-American men whose genotype is homozygous for the major allele for each of these SNPs have a higher rate of lifetime conduct disorder (23-24%) than Korean-American men whose genotype is heterozygous (8-9%) or homozygous for the minor allele (0%). The major allele for these three SNPs is significantly higher in Korean Americans (.75) than in Chinese (.68) and European (.51) Americans and the Korean-American men in this study have a high rate of conduct disorder (17.6%). These results suggest the possibility that GABRG3 gene variation could contribute to the development of this disorder. Further research is needed to replicate these exploratory findings and to determine the function of the GABRG3 gene to understand the mechanism by which these SNPs might influence the development of conduct disorder and alcohol dependence [18].

Several factors limit the generalizability of these results. Because of the possibility of varied associations, analyses were stratified by ancestry and sex, which limited our sample sizes and power. In addition, the relatively low prevalence of alcohol dependence and conduct disorder in this young adult sample further limited our power to detect associations with diagnostic phenotypes. It is possible that the relationships between these genotypes and phenotypes may change over time as more of the participants develop AUD symptoms and diagnoses. Larger, as well as older, samples of Korean, Chinese, and European participants may reveal additional associations between these GABAA receptor gene SNPs and AUD phenotypes.

Despite these limitations, this study also has several strengths. The total sample is relatively large and diverse in their ancestry. Asian participants are typically underrepresented in U.S. studies and subgroups are often aggregated in analyses. This study included two Asian-American groups, Koreans and Chinese, with significantly different rates of AUDs and conduct disorder. We used a reliable and valid instrument for assessing symptoms and diagnoses, and the current phenotypic results show a similar pattern to our previous findings [13] as well as with extant epidemiologic data [9-12]. Our analyses first determined whether allele frequencies differed across ancestry because of the potential for population stratification. Importantly, we found significant ancestry differences in the allele frequencies of all 21 GABAA receptor gene SNPs that were evaluated. In addition results corroborated findings that GABRA2 SNPs (rs490434, rs495818, rs531460, rs572227) are associated with AUD phenotypes and is the first study to demonstrate an association of GABRG3 SNPs (rs3101639, rs3101636, rs3097493) with conduct disorder in Korean-American men. The results suggest there is significant variation across ancestry in the GABAA receptor genes and that there may be varied associations with phenotypes in different ancestry groups. These findings highlight the need for replication and increased understanding of the mechanism underlying putative associations of GABAA receptor gene variation with AUD and conduct disorder phenotypes.

Acknowledgement

This work was supported by the National Institutes of Health [R01AA11257, T32AA013525, and P50AA07611].

References

  1. Heath AC, Bucholz KK, Madden PA, Dinwiddie SH, Slutske WS, et al. (1997) Genetic and environmental contributions to alcohol dependence risk in a national twin sample: consistency of findings in women and men. Psychol Med 27: 1381-1396. [Crossref]
  2. Prescott CA, Aggen SH, Kendler KS (1999) Sex differences in the sources of genetic liability to alcohol abuse and dependence in a population-based sample of U.S. twins. Alcohol Clin Exp Res 23: 1136-1144. [Crossref]
  3. Grant BF, Stinson FS, Dawson DA, Chou SP, Dufour MC, et al. (2004) Prevalence and co-occurrence of substance use disorders and independent mood and anxiety disorders: results from the National Epidemiologic Survey on Alcohol and Related Conditions. Arch Gen Psychiatry 61: 807-816. [Crossref]
  4. Hasin DS, Stinson FS, Ogburn E, Grant BF (2007) Prevalence, correlates, disability, and comorbidity of DSM-IV alcohol abuse and dependence in the United States: results from the National Epidemiologic Survey on Alcohol and Related Conditions. Arch Gen Psychiatry 64: 830-842. [Crossref]
  5. Eng MY, Luczak SE, 2021 Copyright OAT. All rights reservC genotypes in Asians: a literature review. Alcohol Res Health 30: 22-27. [Crossref]
  6. Luczak SE, Glatt SJ, Wall TL (2006) Meta-analyses of ALDH2 and ADH1B with alcohol dependence in Asians. Psychol Bull 132: 607-621. [Crossref]
  7. Osier MV, Pakstis AJ, Soodyall H, Comas D, Goldman D, et al. (2002) A global perspective on genetic variation at the ADH genes reveals unusual patterns of linkage disequilibrium and diversity. Am J Hum Genet 71: 84-99. [Crossref]
  8. Wall TL, Shea SH, Luczak SE, Cook TA, Carr LG (2005) Genetic associations of alcohol dehydrogenase with alcohol use disorders and endophenotypes in white college students. J Abnorm Psychol 114: 456-465. [Crossref]
  9. Helzer JE, Canino GJ, Yeh EK, Bland RC, Lee CK, et al. (1990) Alcoholism--North America and Asia. A comparison of population surveys with the Diagnostic Interview Schedule. Arch Gen Psychiatry 47: 313-319. [Crossref]
  10. Price RK, Risk NK, Wong MM, Klingle RS (2002) Substance use and abuse by Asian Americans and Pacific Islanders: preliminary results from four national epidemiologic studies. Public Health Rep 117 Suppl 1: S39-50. [Crossref]
  11. Lee HK, Chou SP, Cho MJ, Park JI, Dawson DA, et al. (2010) The prevalence and correlates of alcohol use disorders in the United States and Korea--a cross-national comparative study. Alcohol 44: 297-306. [Crossref]
  12. Sakai JT, Wang C, Price RK (2010) Substance use and dependence among Native Hawaiians, Other Pacific Islanders, and Asian ethnic groups in the United States: contrasting multiple-race and single-race prevalence rates from a national survey. J Ethnicity Sub Abuse 9: 173-185. [Crossref]
  13. Luczak SE, Wall TL, Cook TAR, Shea SH, Carr LG (2004). ALDH2 status and conduct disorder mediate the relationship between ethnicity and alcohol dependence in Chinese, Korean, and White-American American college students. J Abnorm Psychol 113: 271-278. [Crossref]
  14. Cochrane J, Chen H, Conigrave KM, Hao W (2003) Alcohol use in China. Alcohol 38: 537-542. [Crossref]
  15. Hahm HC, Cho MJ (2005) Prevalence of alcohol use disorders in South Korean community: Changes in the pattern of prevalence over the past 15 years. Soc Psychiatry Psychiatric Epidemiology 40: 114-119. [Crossref]
  16. Bierut LJ, Agrawal A, Bucholz KK, Doheny KF, Laurie C, et al. (2010) A genome-wide association study of alcohol dependence. Proc Natl Acad Sci U S A 107: 5082-5087. [Crossref]
  17. Covault J, Gelernter J, Hesselbrock V, Nellissery M, Kranzler HR (2004) Allelic and haplotypic association of GABRA2 with alcohol dependence. Am J Med Genet B Neuropsychiatr Genet 129B: 104-109. [Crossref]
  18. Dick DM, Edenberg HJ, Xuei X, Goate A, Kuperman S, et al. (2004) Association of GABRG3 with alcohol dependence. Alcohol Clin Exp Res 28: 4-9. [Crossref]
  19. Dick DM, Agrawal A, Schuckit MA, Bierut L, Hinrichs A, et al. (2006) Marital status, alcohol dependence, and GABRA2: evidence for gene-environment correlation and interaction. J Stud Alcohol 67: 185-194. [Crossref]
  20. Dick DM, Bierut L, Hinrichs A, Fox L, Bucholz KK, et al. (2006) The role of GABRA2 in risk for conduct disorder and alcohol and drug dependence across developmental stages. Behav Genet 36: 577-590. [Crossref]
  21. Dick DM, Plunkett J, Wetherill LF, Xuei X, Goate A, et al. (2006) Association between GABRA1 and drinking behaviors in the collaborative study on the genetics of alcoholism sample. Alcohol Clin Exp Res 30: 1101-1110. [Crossref]
  22. Drgon T, D’Addario C, Uhl GR (2006) Linkage disequilibrium, haplotype and association studies of a chromosome 4 GABA receptor gene cluster: Candidate gene variants for addictions. Am J Med Genetics Part B Neuropsychiatric Genetics 141: 854-860. [Crossref]
  23. Edenberg HJ, Dick DM, Xuei X, Tian H, Almasy L, et al. (2004) Variations in GABRA2, encoding the alpha 2 subunit of the GABA(A) receptor, are associated with alcohol dependence and with brain oscillations. Am J Hum Genet 74: 705-714. [Crossref]
  24. Enoch MA, Schwartz L, Albaugh B, Virkkunen M, Goldman D (2006) Dimensional anxiety mediates linkage of GABRA2 haplotypes with alcoholism. Am J Med Genet B Neuropsychiatr Genet 141B: 599-607. [Crossref]
  25. Enoch MA, Hodgkinson CA, Yuan Q, Albaugh B, Virkkunen M, et al. (2009) GABRG1 and GABRA2 as independent predictors for alcoholism in two populations. Neuropsychopharmacology 34: 1245-1254. [Crossref]
  26. Fehr C, Sander T, Tadic A, Lenzen KP, Anghelescu I, et al. (2006) Confirmation of association of the GABRA2 gene with alcohol dependence by subtype-specific analysis. Psychiatric Genetics 16: 9-17. [Crossref]
  27. Kramer JR, Chan G, Dick DM, Kuperman S, Bucholz KK, et al. (2008) Multiple-domain predictors of problematic alcohol use in young adulthood. J Stud Alcohol Drugs 69: 649-659. [Crossref]
  28. Lappalainen J, Krupitsky E, Remizov M, Pchelina S, Taraskina A, et al. (2005) Association between alcoholism and gamma- amino butyric acid alpha2 receptor subtype in Russian population. Alcohol Clin Exp Res 4: 493-498. [Crossref]
  29. Lind PA, Macgregor S, Agrawal A, Montgomery GW, Heath AC, et al. (2008) Effects of GABRA2 variation on physiological, psychomotor and subjective responses in the alcohol challenge twin study. Twin Res Hum Genet 11: 174-182. [Crossref]
  30. Matthews AG, Hoffman EK, Zezza N, Stiffler S, Hill SY (2007) The role of the GABRA2 polymorphism in multiplex alcohol dependence families with minimal comorbidity: Within-family association and linkage analyses. J Stud Alcohol Drugs 68: 625-633. [Crossref]
  31. Philibert RA, Gunter TD, Beach SR, Brody GH, Hollenbeck N, et al. (2009) Role of GABRA2 on risk for alcohol, nicotine, and cannabis dependence in the Iowa Adoption Studies. Psychiatr Genet 19: 91-98. [Crossref]
  32. Pierucci-Lagha A, Covault J, Feinn R, Nellissery M, Hernandez-Avila C, et al. (2005) GABRA2 alleles moderate the subjective effects of alcohol, which are attenuated by finasteride. Neuropsychopharmacology 30: 1193-1203. [Crossref]
  33. Roh S, Matsushita S, Hara S, Maesato H, Matsui T, et al. (2011) Role of GABRA2 in moderating subjective responses to alcohol. Alcohol Clin Exp Res 35: 400-407. [Crossref]
  34. Sakai JT, Stallings MC, Crowley TJ, Gelhorn HL, McQueen MB, et al. (2010) Test of association between GABRA2 (SNP rs279871) and adolescent conduct/alcohol use disorders utilizing a sample of clinic referred youth with serious substance and conduct problems, controls and available first degree relatives. Drug Alcohol Depend 106: 199-203. [Crossref]
  35. Soyka M, Preuss UW, Hesselbrock V, Zill P, Koller G, et al. (2008) GABA-A2 receptor subunit gene (GABRA2) polymorphisms and risk for alcohol dependence. J Psychiatr Res 42: 184-191. [Crossref]
  36. Villafuerte S, Heitzeg MM, Foley S, Yau WY, Majczenko K, et al. (2011). Impulsiveness and insula activation during reward anticipation are associated with genetic variants in GABRA2 in a family sample enriched for alcoholism. Mol Psychiatry 4: 1-9. [Crossref]
  37. Dick DM, Latendresse SJ, Lansford JE, Budde JP, Goate A, et al. (2009) Role of GABRA2 in trajectories of externalizing behavior across development and evidence of moderation by parental monitoring. Arch Gen Psychiatry66: 649-657. [Crossref]
  38. Dick DM, Aliev F, Krueger RF, Edwards A, Agrawal A, et al. (2011) Genome-wide association study of conduct disorder symptomatology. Mol Psychiatry 16: 800-808. [Crossref]
  39. Agrawal A, Edenberg HJ, Foroud T, Bierut LJ, Dunne G, et al. (2006) Association of GABRA2 with drug dependence in the collaborative study of the genetics of alcoholism sample. Behav Genet 36: 640-650. [Crossref]
  40. Enoch MA, Hodgkinson CA, Yuan Q, Shen PH, Goldman D, et al. (2010) The influence of GABRA2, childhood trauma, and their interaction on alcohol, heroin, and cocaine dependence. Biol Psychiatry 67: 20-27. [Crossref]
  41. Hasin DS, Liu X, Alderson D, Grant BF (2006) DSM-IV alcohol dependence: a categorical or dimensional phenotype? Psychol Med 36: 1695-1705. [Crossref]
  42. American Psychiatric Association (1994) Diagnostic and Statistical Manual of Mental Disorde. (4th edn). Washington, DC.
  43. Bucholz KK, Cadoret R, Cloninger CR, Dinwiddie SH, Hesselbrock VM, et al. (1994) A new semi-structured psychiatric interview for use in genetic linkage studies: A report on the reliability of the SSAGA. J Stud Alcohol 55: 149-158. [Crossref]
  44. Hesselbrock M, Easton C, Bucholz KK, Schuckit M, Hesselbrock V (1999) A validity study of the SSAGA--a comparison with the SCAN. Addiction 94: 1361-1370. [Crossref]
  45. Crabb DW, Edenberg HJ, Bosron WF, Li TK (1989) Genotypes for aldehyde dehydrogenase deficiency and alcohol sensitivity. The inactive ALDH2(2) allele is dominant. J Clin Invest 83: 314-316. [Crossref]
  46. Xu YL, Carr LG, Bosron WF, Li TK, Edenberg HJ (1988) Genotyping of human alcohol dehydrogenases at the ADH2 and ADH3 loci following DNA sequence amplification. Genomics 2: 209-214. [Crossref]
  47. Slutske WS, Heath AC, Madden PAF, Bucholz KK, Dunne MP, et al. (1998). Common genetic risk factors for conduct disorder and alcohol dependence. J Abnorm Psychol 107: 363-374. [Crossref]
  48. Nyholt DR (2001) Genetic case-control association studies--correcting for multiple testing. Hum Genet 109: 564-567. [Crossref]

Editorial Information

Editor-in-Chief

Hieronim Jakubowski

Rutgers University-New Jersey Medical School

Article Type

Research Article

Publication history

Received: June 12 2016
Accepted: July 28, 2016
Published:Aug 01, 2016

Copyright

©2016 Orlowska D. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Citation

Orlowska D, Eng MY, Luczak SE, Edenberg HJ, Wall TL (2016) Associations of GABAA Receptor Gene Variations with Alcohol Use Disorder and Conduct Disorder Phenotypes in Korean-, Chinese-, and European-American College Students. Biomed Genet Genomics 1: DOI: 10.15761/BGG.1000111

Corresponding author

Tamara L. Wall, Ph.D.

VA San Diego Healthcare System, Psychology Service (116B), 3350 La Jolla Village Drive, San Diego, CA 92161. Tel.: 858-552-8585.

E-mail : twall@ucsd.edu

Table 1. Allele Frequencies for ALDH2, ADH1B and GABAA Receptor Gene SNPs in Korean, Chinese, and European Americans

Gene SNP NT Korean American(n=337) Chinese American(n=350) European American(n=467) Ancestry differences
ALDH2 rs671 A/G .17/.83 .27/.73 0/1.0 a,b,c
ADH1B rs1229984 A/G .73/.27 .72/.28 .03/.97 b,c
GABRA2 rs1442059 C/T .53/.47 .60/.40 * .42/.58 a,b,c
GABRA2 rs279826 A/G .47/.53 .40/.60 * .56/.45 a,b,c
GABRA2 rs279827 A/G .48/.53 .41/.59 .56/.45 b,c
GABRA2 rs279828 A/C .47/.53 .40/.60 * .56/.45 a,b,c
GABRA2 rs279836 A/T .53/.47 * .60/.40 * .42/.58 a,b,c
GABRA2 rs279845 A/T .53/.47 .59/.41 .45/.56 b,c
GABRA2 rs279858 A/G .51/.49 .47/.53 .57/.43 b,c
GABRA2 rs279871 A/G .51/.49 .47/.53 .57/.43 c
GABRA2 rs490434 A/G .40/.60 .49/.51 .41/.59 c
GABRA2 rs495818 A/G .61/.39 .52/.48 .58/.42 a,c
GABRA2 rs531460 A/G .39/.61 .49/.51 .41/.60 c
GABRA2 rs572227 A/G .39/.61 .48/.52 .42/.58 a
GABRA4 rs2036943 A/T .60/.40 .69/.31 .31/.69 a,b
GABRA1 rs4263535 A/G .51/.49 .55/.45 .82/.18 b,c
GABRA1 rs4478357 A/C .30/.70 .31/.69 .54/.46 b,c
GABRG3 rs3097490 C/T .21/.79 .30/.70 .50/.51 a,b,c
GABRG3 rs3097493 C/G .25/.75 .32/.68 .49/.51 a,b,c
GABRG3 rs3101636 A/G .75/.25 .68/.32 .51/.49 a,b,c
GABRG3 rs3101639 A/G .75/.25 .68/.32 .51/.49 a,b,c
GABRG3 rs140679 C/T .27/.73 .33/.67 .49/.51 a,b,c
GABRG3 rs2303879 A/G .79/.21 .70/.30 .51/.50 a,b,c

Notes.
* Hardy-Weinberg equilibrium violated, p < .05
a – Korean Americans significantly different from Chinese Americans, p <. 0167
b – Korean Americans significantly different from European Americans, p < .0167
c – Chinese Americans significantly different from European Americans, p < .0167

Table 2. Diagnoses (Percentages) and Symptom Counts (Means and SDs) by Ancestry and Sex

  Korean Americans Chinese American European Americans
  Men
(n=159)
Women
(n=178)
Men
(n=179)
Women
(n=171)
Men
(n=239)
Women
(n=228)
Alcohol dependence 6.3% 2.8% 1.7% 0.6% 11.7% 2.6%
AUD symptoms 1.1 (1.8) 0.6 (1.3) 0.4 (1.0) 0.2 (0.5) 1.4 (2.0) 0.6 (1.2)
Conduct disorder 17.6% 2.8% 5.6% 2.3 % 9.6% 2.6%
Conduct disorder symptoms 1.8 (1.78) 0.4 (0.8) 0.9 (1.3) 0.4 (0.8) 1.2 (1.3) 0.6 (0.9)

Table 3.Summary of Separate Multiple Regression Analyses for Four Adjacent GABRA2 SNPs, ALDH2, and ADH1B, with AUD Symptoms in Korean-American men (n=156)

GABRA2 SNP Variable F-value
df=2, 152
p-value
rs490434 ALDH2*2 5.38 0.006
  ADH1B*2 0.43 0.651
  A allele 6.01 0.003
rs495818 ALDH2*2 5.51 0.005
  ADH1B*2 0.38 0.684
  G allele 4.29 0.015
rs531460 ALDH2*2 5.36 0.006
  ADH1B*2 0.44 0.644
  A allele 6.09 0.003
rs572227 ALDH2*2 5.51 0.005
  ADH1B*2 0.38 0.684
  A allele 4.29 0.015