Association of dopamine-related gene alleles, smoking behavior and decline in FEV1 in subjects with COPD: findings from the lung health study.

Cigarette smoking is the major risk factor for chronic obstructive pulmonary disease (COPD). Specific dopamine related gene alleles have previously been found to be associated with smoking initiation, maintenance and cessation. We investigated the association between specific dopamine related gene alleles and both change in smoking behavior and lung function change over time in individuals with mild-to-moderate COPD. Subjects included a subset of participants in the Lung Health Study (LHS), a smoking intervention study in smokers with mild to moderate COPD. Smoking status was determined and lung function performed at baseline and annually for 5 years. In post-hoc analyses, we assessed the association of the dopamine receptor (DRD2) TaqI A1(+) allele (A1A1, A1A2 genotypes) and A1(-) allele (A2A2 genotype), and the dopamine transporter (DAT) 9R(+) allele (9R9R and 9R10R genotypes) and 9R(-) allele (10R10R genotype) with both changes in smoking status and lung function in a subset of LHS subjects. No significant associations were noted between variants in these genes and success in smoking cessation. However, in exploratory analyses that did not adjust for multiple comparisons, sustained male (but not female) quitters with the DRD2 A1(-) allele and/or the DAT 9R(+) allele showed an accelerated decline in FEV(1) similar to that of continuing smokers over 5 years after quitting smoking. These preliminary findings suggest that dopamine-related genes may play a role in the progression of COPD, at least in the subset of male ex-smokers whose disease continues to progress despite sustained quitting, and warrants additional confirmatory and mechanistic studies.

PTSD and dopaminergic genes, DRD2 and DAT, in multigenerational families exposed to the Spitak earthquake.

The objective of this study was to assess the generality of the association of DRD2 and DAT genes and Post-Traumatic Stress Disorder (PTSD) diagnosis/symptom severity. Two hundred ethnic Armenians from 12 multigenerational families exposed to the catastrophic 1988 Spitak earthquake were studied. Common polymorphisms A1/A2 alleles of the DRD2 and '9' repeat allele of DAT gene were genotyped. Heritability, association and linkage were assessed using variance component genetic analyses. After adjusting for the covariates, the heritabilities of PTSD diagnosis and B and C category symptoms were: 0.37, 0.75 and 0.39 respectively. Category D symptoms were not heritable. Neither the DRD2 nor the DAT polymorphisms explained the variation seen in PTSD diagnosis, total PTSD symptom severity, and categories B and C symptom severities. These findings contradict prior reports of positive associations between both DRD2 and DAT, and PTSD.

Genetic, personality, and environmental predictors of drug use in adolescents.

During adolescence there is a significant increase in risk-taking behavior, including experimenting with alcohol and drugs, which can lead to drug dependence. A new hypothesis regarding the genetic mechanisms that lead to drug use is tested using adolescent Caucasian children of alcoholics (57 males, 54 females; mean age = 14.5 years) data. Variables included in the study were dopaminergic genes (ANKK1 TaqI A, DRD2 C957T, DRD4 7R, COMT Val/Met substitution, and SLC6A3 9R) and a GABAergic gene (GABRB3), all combinations of genes, a count of the number of hypodopaminergic genotypes, personality traits, neurocognitive factors, depressive symptoms, and environmental factors. Separate predictive models were found for males and females. Hypodopaminergic functioning predicted drug use in males; however, in females, a deleterious environment was the salient predictor. This preliminary study suggests that it is possible to identify children at risk for problematic drug use prior to the onset of drug dependence.

D2 dopamine receptor (DRD2) gene, P300, and personality in children of alcoholics.

The D2 dopamine receptor (DRD2) gene has been associated with alcoholism and other drug use disorders. Reduced P300 amplitude has been noted in individuals with psychiatric disorders. Personality variables are also associated with reduced P300 amplitude. The current study was conducted to determine whether variants of the DRD2 would show differential relationships among P300 amplitude and personality traits. The study consisted of 101 adolescent children of alcoholics; 39 carried the A1(+) genotype (A1A1, A1A2) and 62 carried the A1(-) genotype (A2A2). The A1(+) genotype group had higher IQ and Self-Directedness scores than the A1(-) genotype group. As predicted, the negative relationship between Novelty Seeking and Harm Avoidance was present in A1(-) but not A1(+) participants. Additionally, in A1(+) but not in A1(-) participants, there was a negative relationship between Novelty Seeking and Self-Directedness and a positive relationship between P300 amplitude and Cooperativeness. The results suggest that in adolescent children of alcoholics, dopaminergic genetic determinants are critical modifiers of the relationship between neurocognitive and personality endophenotypes proposed as vulnerability markers for substance use disorders.

D2 dopamine receptor Taq1A polymorphism, body weight, and dietary intake in type 2 diabetes.

OBJECTIVE: Certain D2 dopamine receptor Taq 1A genotypes (A1A1, A1A2) have been associated with obesity and substance abuse. We hypothesized that their presence would be associated with reduced efficacy of dietary interventions in individuals with type 2 diabetes. METHODS: In the course of a randomized clinical trial in an outpatient research center in which 93 adults with type 2 diabetes were assigned to a low-fat vegan diet or a diet following 2003 American Diabetes Association guidelines for 74 wk, Taq 1A genotype was determined. Nutrient intake, body weight, and hemoglobin A1c (A1c) were measured over 74 wk. RESULTS: The A1 allele was highly prevalent, occurring in 47% of white participants (n = 49), which was significantly higher than the 29% prevalence previously reported in non-diabetic whites (P = 0.01). The A1 allele was found in 55% of black participants (n = 44). Black participants with A1(+) genotypes had significantly greater mean body weight (11.2 kg heavier, P = 0.05) and greater intake of fat (P = 0.002), saturated fat (P = 0.01), and cholesterol (P = 0.02) compared with A2A2 (A1(-)) individuals; dietary changes during the study did not favor one genotype group. Among whites, baseline anthropometric and nutrient differences between gene groups were small. However, among whites in the vegan group, A1(+) individuals reduced fat intake (P = 0.04) and A1c (P = 0.01) significantly less than did A1(-) individuals. CONCLUSION: The A1 allele appears to be highly prevalent among individuals with type 2 diabetes. Potential influences on diet, weight, and glycemic control merit further exploration.

Heritabilities of symptoms of posttraumatic stress disorder, anxiety, and depression in earthquake exposed Armenian families.

OBJECTIVE: To examine the heritabilities of symptoms of posttraumatic stress disorder (PTSD), anxiety, depression, and the shared genetic component of these symptoms among family members exposed to the 1988 Spitak earthquake in Armenia. METHODS: Two hundred members of 12 multigenerational families exposed to the Spitak earthquake were studied using a battery that assessed earthquake exposure and symptoms of PTSD, anxiety, and depression. Heritabilities of these phenotypes were determined using variance component analyses and shared genetic vulnerabilities between these phenotypes were determined using bivariate analyses. RESULTS: Heritabilities were as follows: PTSD symptoms 41% (P<0.001), anxiety symptoms 61% (P<0.001), and depressive symptoms 66% (P<0.001). The genetic correlation (rhog>0) of PTSD symptoms with anxiety symptoms was 0.75 (P<0.001) and with depressive symptoms it was 0.71 (P<0.001). The genetic correlation of anxiety with depressive symptoms was 0.54 (P<0.001). CONCLUSION: The heritabilities found in this multigenerational family study indicate that the genetic make-up of some individuals renders them substantially more vulnerable than others to develop symptoms of PTSD, anxiety, and depression. A large proportion of the genetic liability for PTSD, anxiety, and depression are shared. The findings offer promise for identifying susceptibility genes for these phenotypes.

The A1 allele of the D2 dopamine receptor gene region, alcohol expectancies and drinking refusal self-efficacy are associated with alcohol dependence severity.

Psychological risk and genetic risk for alcohol dependence are rarely examined in concert. The current study used path analysis (via structural equation modelling) to explore the relationship between the A(1) allele of the D2 dopamine receptor DRD2 gene region, age of problem drinking onset, alcohol expectancy and drinking refusal self-efficacy towards alcohol consumption and dependence severity. One hundred and forty-three (93 male, 50 female) alcohol dependent inpatients provided an extensive clinical history, including age of onset of problem drinking and quantity and frequency of alcohol consumption. The Drinking Expectancy Profile and the Alcohol Dependence Scale were completed, and 10 milliliters of blood were obtained for genetic analysis. The results showed that the posited model fitted the data set well and support the pattern of direct (allele status to drinking) and indirect (allele status influenced by psychosocial variables) relationships hypothesised for the model. A formal test of mediation showed some support for a psychosocial mediational model. The results are discussed in terms of a possible developmental trajectory that involves both genetic risk that influences brain dopamine activity and reinforcement expectancies that both operate via diminished drinking refusal self-efficacy. The prevention and treatment possibilities that arise from understanding this trajectory are examined.

Heavy nicotine and alcohol use in alcohol dependence is associated with D2 dopamine receptor (DRD2) polymorphism.

Cigarette smoking in those who are alcohol dependent is associated with higher morbidity and mortality. The A1 allele of the D2 dopamine receptor (DRD2) gene has been independently associated with alcohol and nicotine dependence. Whether this polymorphism is associated with nicotine dependence in those who are also alcohol dependent has not been investigated. Subjects were 84 (61 males; 23 females) Caucasian DSM IV diagnosed nicotine- and alcohol-dependent subjects sampled from consecutive admissions to a hospital alcohol detoxification ward. Data were obtained through standardised measures of nicotine and alcohol consumption and dependence severity. A1+ allelic (A1/A1 or A1/A2 genotype) compared to A1- allelic (A2/A2 genotype only) patients were characterised by higher levels of alcohol and cigarette consumption. A1+ allelic patients reported greater alcohol dependence severity, but not nicotine dependence severity. When the combined nicotine and alcohol dose was examined, A1+ allelic patients consumed significantly more of these drugs than their A1- allelic counterparts.

The D2 dopamine receptor (DRD2) gene is associated with co-morbid depression, anxiety and social dysfunction in untreated veterans with post-traumatic stress disorder.

OBJECTIVE: To identify clusters of patients with post-traumatic stress disorder (PTSD) according to symptom profile and to examine the association of the A1 allele of the D2 dopamine receptor (DRD2) gene with these clusters. METHOD: Fifty-seven untreated Caucasian Vietnam veterans with PTSD were administered the General Health Questionnaire-28 (GHQ) and the Mississippi Scale for combat-related PTSD. DRD2 allelic status was determined by PCR. RESULTS: Subjects with the DRD2 Al allele compared to those without this allele had significantly higher scores on GHQ 2 (anxiety/insomnia), GHQ 3 (social dysfunction) and GHQ 4 (depression). Cluster analysis of the GHQ data identified two primary groups. A high psychopathology cluster (cluster 3), featured by high co-morbid levels of somatic concerns, anxiety/insomnia, social dysfunction and depression, and a low psychopathology cluster (cluster 1), manifested by the reverse pattern. Scores in each of the four GHQ groups were significantly higher in cluster 3 than cluster 1, as was Mississippi Scale PTSD score. DRD2 A1 allele veterans compared to those without this allele were significantly more likely to be found in the high than the low psychopathology cluster group. CONCLUSIONS: DRD2 variants are associated with severe co-morbid psychopathology in PTSD subjects.

P300 development during adolescence: effects of DRD2 genotype.

OBJECTIVE: Young boys at high risk for alcoholism by having a family history of alcoholism (FH+) have lower amplitude of the visual P300 event-related scalp potential. They have also been reported to have a slowing in the rate of P300 amplitude change during adolescence. The present study examined whether the change in P300 amplitude during adolescence in sons of alcoholics and nonalcoholics is affected by D2 dopamine receptor (DRD2) polymorphism. METHODS: P300 was elicited with a visual discrimination task from 71 adolescent sons of alcoholics and social drinkers (Time 1, T1). The task was readministered 2 years later (Time 2, T2). Comparisons were made between boys who had the DRD2 A1 allele (A1+) and boys who did not (A1-), and between boys with one or both parents being alcoholic (FH+) and boys having no alcoholic parents (FH-). RESULTS: Discrimination task accuracy was lowest in the highest risk group (A1+, FH+) at T1, and highest in the lowest risk group (A1-, FH-) at T2, producing a significant interaction of allelic group x family history group x session. Reaction time was faster at T2 than T1, and this effect was larger in FH-boys (125 ms) than FH+boys (40 ms). Overall, the behavioral results suggest mild performance deficits on the discrimination task are associated with higher risk for alcoholism. In both testing sessions, P300 attained larger amplitudes in sons of nonalcoholics than sons of alcoholics. At T2 compared to T1, both the latency and amplitude of the P300 were decreased. However, while the developmental P300 latency effect was equivalent in both the A1+ and A1- allelic groups, the P300 amplitude reduction during adolescence, measured both in response to targets and in target minus non-target subtraction waveforms, was only found in boys with the A1- allele. CONCLUSION: Differences in the developmental course of P300 amplitude over the course of adolescence are dependent on DRD2 polymorphism. SIGNIFICANCE: These results suggest the importance of genetic determinants of the dopaminergic system in understanding the P300 as a risk marker for substance abuse using an integrative developmental perspective.

DRD2 genotypes and substance use in adolescent children of alcoholics.

Research has identified children of alcoholics (COAs) as a population at increased risk for developing substance use problems. Genetic studies support the Al allele of the D2 dopamine receptor gene (DRD2) as a risk marker for alcoholism and substance use disorders. In this study, substance use was assessed in 48 adolescent boys of alcoholics with the DRDR A1(+) allele (A1A1/A1A2 genotypes) or the A1(-) allele (A2A2 genotype). The results revealed that boys with the A1(+) allele tried (p=0.0001) and got intoxicated on alcohol more often (p=0.009) than boys with the A1(-) allele. Boys with the A1(+) allele tried more (p=0.004) and used more substances overall (p=0.008) than boys with the A1(-) allele. Boys with the A1(+) allele developed a tobacco habit more often (p=0.03) and experienced marijuana high at an earlier age (p=0.001) than boys with the A1(-) allele. The best predictors of substance use severity in boys with the A1(+) allele were Psychoticism (p=0.01) and Negative Affect (p=0.04). The results provide support for the DRD2 A1 allele as a marker identifying a subgroup of COAs at high risk for developing substance use problems.

Alcohol-related expectancies are associated with the D2 dopamine receptor and GABAA receptor beta3 subunit genes.

Molecular genetic research has identified promising markers of alcohol dependence, including alleles of the D2 dopamine receptor (DRD2) and the GABAA receptor beta3 subunit (GABRB3) genes. Whether such genetic risk manifests itself in stronger alcohol-related outcome expectancies, or in difficulty resisting alcohol, is unknown. In the present study, A1+ (A1A1 and A1A2 genotypes) and A1- (A2A2 genotype) alleles of the DRD2 and G1+ (G1G1 and G1 non-G1 genotypes) and G1- (non-G1 non-G1 genotype) alleles of the GABRB3 gene were determined in a group of 56 medically ill patients diagnosed with alcohol dependence. Mood-related alcohol expectancy (AE) and drinking refusal self-efficacy (DRSE) were assessed using the Drinking Expectancy Profile (Manual for the Drinking Expectancy Profile, Behaviour Research and Therapy Centre, Brisbane, 1996). Patients with the DRD2 A1+ allele, compared with those with the DRD2 A1- allele, reported significantly lower DRSE in situations of social pressure. Similarly, lower DRSE was reported under social pressure by patients with the GABRB3 G1+ allele when compared to those with the GABRB3 G1- alleles. Patients with the GABRB3 G1+ allele also revealed reduced DRSE in situations characterized by negative affect than those with the GABRB3 G1- alleles. Patients carrying the GABRB3 G1+ allele showed stronger AE relating to negative affective change (for example, increased depression) than their GABRB3 G1- counterparts. Biological influence in the development of some classes of cognitions is hypothesized. The clinical implications, particularly with regard to patient-treatment matching and the development of an integrated psychological and pharmacogenetic approach, are discussed.

Prolactin levels in antipsychotic treatment of patients with schizophrenia carrying the DRD2*A1 allele.

BACKGROUND: Hyperprolactinaemia induced by D(2) dopamine receptor antagonist antipsychotic medication can result in significant health problems. AIMS: To examine the role of DRD2 polymorphism on prolactin levels in patients treated with antipsychotic medication. METHOD: Antipsychotic drugs with different degrees of D(2) receptor binding were given to 144 patients with schizophrenia. Serum prolactin levels were obtained and Taq1A DRD2 alleles were determined. RESULTS: Prolactin levels increased across medication groups reflecting increasingly tight D(2) receptor binding (clozapine, olanzapine, typical antipsychotics and risperidone). In the combined medication group, patients with the DRD2(*)A1allele had 40% higher prolactin levels than patients without this allele. In patients treated with clozapine (the loosest D(2) receptor binding agent), patients with the DRD2(*)A1allele had prolactin levels twice those of patients without this allele. CONCLUSIONS: Patients with the DRD2A1 allele receiving antipsychotic medications had higher prolactin levels and were overrepresented among those with hyperprolactinaemia, suggesting greater functional D(2) receptor binding in this group.

Differential associations of sex and D2 dopamine receptor (DRD2) genotype with negative affect and other substance abuse risk markers in children of alcoholics.

Children of alcoholics have increased risk for substance abuse problems. Self-medication of negative affect may be one developmental path to future substance abuse. Because the 146 young (adolescent) children of alcoholics in the current sample had not used enough abused substances to study substance use directly, the relation of substance abuse risk markers to negative affect was assessed. Because the D2 dopamine receptor (DRD2) A1 allele has been associated with alcoholism and other substance use disorders, negative affect, measured by the Beck Depression Inventory (BDI), was determined in four groups of children: boys and girls with the A1+ allele (A1A1 and A1A2 genotypes) and with the A1- allele (A2A2 genotype). The other risk markers were stress, low amplitude of the P300 evoked potential, poor visuospatial functioning, novelty seeking (NS), and harm avoidance (HA). Stress was correlated with BDI scores in all groups. In contrast, low P300 was associated with BDI scores only in boys with the A1+ allele (P = .04), NS was associated with BDI scores only in girls with the A1+ allele (P = .02), and HA was associated with BDI scores only in boys with the A1- allele (P = .01). In addition, boys with the A1+ allele had lower BDI (P = .05) and HA (P = .005) scores than the respective scores for boys with the A1- allele. Girls with the A1- allele had lower HA scores compared with scores for boys with the A1- allele (P = .02). Girls with the A1+ allele had lower visuospatial functioning than that of boys with the A1+ allele (P<.001). Results indicate that both sex and DRD2 genotype modify associations between negative affect and other substance abuse risk markers.

D2 dopamine receptor gene polymorphism: paroxetine and social functioning in posttraumatic stress disorder.

This study examined whether allelic status of the D2 dopamine receptor (DRD2) gene was associated with response to a selective serotonin reuptake inhibitor, paroxetine, in the treatment of posttraumatic stress disorder (PTSD). Sixty-three Caucasian war veterans with combat-related PTSD were treated with paroxetine for 8 weeks. Patients were assessed at baseline and at follow-up using the General Health Questionnaire-28 (GHQ). TaqI A DRD2 alleles were determined by PCR. Before paroxetine treatment, patients with the DRD2 A1+ allele (A1A2 genotype) compared to those with the A1- allele (A2A2 genotype) had higher total GHQ psychopathological scores (P=0.040) and higher GHQ subscale scores for anxiety/insomnia (0.046), social dysfunction (P=0.033) and depression (P=0.011). In an intention-to-treat analysis, paroxetine was associated with significant improvement in total GHQ scores (P=0.014) and in the factor scores of social dysfunction (P=0.033), anxiety (P=0.009) and depression (P=0.026). Furthermore, there was a significant allele by time interaction on the social dysfunction scale, with A1+ allelic patients showing significant improvement in social functioning compared to A1- allelic patients (P=0.031), an effect independent of changes in depression or anxiety. This suggests changes in social functioning induced by paroxetine may be, in part, mediated via D2 dopamine receptors. The DRD2 A1 allele may prove to be a useful marker to assist clinicians in predicting which patients with PTSD are likely to obtain improvements in social functioning with paroxetine treatment.

Association of seven polymorphisms of the D2 dopamine receptor gene with brain receptor-binding characteristics.

Association of alleles at the Taq1 A, Taq1 B, intron 6, Taq1 D, exon 7, exon 8, and promoter-141C sites of the D2 dopamine receptor gene with D2 dopamine receptor binding characteristics in the caudate nucleus of Caucasian alcoholic and nonalcoholic subjects was determined. For the Taq1 D, exon 7, exon 8, and promoter- 141C sites there were no significant allelic differences in Bmax (number of binding sites) or Kd (binding affinity) of the D2 dopamine receptors. However, subjects having the minor alleles at the Taq1 A, Taq1 B, and intron 6 sites had significantly lower Bmax than subjects not having them. None of these three polymorphisms had any significant effect on Kd. Highly significant linkage disequilibria were observed among the Taq1 A, Taq1 B, and intron 6 polymorphic sites, but linkage disequilibria between these three sites and each of the Taq1 D, exon 7, exon 8, and promoter-141C sites were of lesser or of no significance. Taken together, these findings suggest that the Taq1 A, Taq1 B, and intron 6 polymorphisms, but not the Taq1 D, exon 7, exon 8, and promoter-141C polymorphisms, are in linkage disequilibrium with a functional allelic variant that affects D2 dopamine receptor expression.