DRD3 gene rs6280 polymorphism may be associated with alcohol dependence overall and with Lesch type I alcohol dependence in Koreans

Functional single nucleotide polymorphisms in dopaminergic receptors D2 predict clinical response to Cariprazine

Cariprazine (CAR) is an antipsychotic drug for the treatment of schizophrenia (SCZ) and bipolar disorder (BD), and it acts as a partial agonist on the dopamine receptors (DR), D2, and D3. Although many single nucleotide polymorphisms (SNPs) in genes coding for these receptors are known to influence response to antipsychotics, to date, no study on CAR pharmacogenetics exists. In this pilot study, we investigated the relationship between SNPs in DRD2 (rs1800497 and rs6277) and DRD3 (rs6280), and response to CAR treatment, evaluated by the psychometric Brief Psychiatric Rating Scale (BPRS), in a cohort of Caucasian patients. We found a significant association between DRD2 rs1800497 and rs6277 and response to CAR treatment. When genotypes were combined into an arbitrary score, the receiver operating characteristic curve analysis showed that using a cut-off value of -2.5 the response to CAR treatment could be predicted with a positive likelihood ratio of 8.0. Our study report, for the first time, a correlation between SNPs in DRD2 and response to CAR treatment. After confirmation in a larger cohort of patients, our results could open the way for the identification of new tools for the provision of response to CAR treatment.

Influence of dopamine-related genes on craving, impulsivity, and aggressiveness in Korean males with alcohol use disorder

Dopamine is a major neuromodulator that is acutely involved in various cognitive processes, reward-motivated behaviors, and impulsivity. Abnormality in dopaminergic neurotransmission is implicated in the pathophysiology of alcohol use disorder (AUD). The present study examined the genetic influence of dopamine system on problematic drinking, impulsivity, and aggressiveness in a Korean male population with AUD. Five single nucleotide polymorphisms (SNPs) (rs4532 in DRD1, rs2283265 in DRD2, rs6280 in DRD3, rs1800497 in ANKK1, and rs4680 in COMT) and a variable number of tandem repeats (VNTRs) in DAT1 in 295 male patients with AUD were genotyped. For AUD-related clinical characteristics, the Alcohol Use Disorders Identification Test and the Obsessive-Compulsive Drinking Scale (OCDS) were used to assess the severity of hazardous drinking and craving symptoms, respectively. Participants also completed the UPPS-P Impulsive Behavior Scale (UPPS-P) and Buss-Perry Aggression Questionnaire (BPAQ). Analyses were performed using R package SNPassoc; statistical significance was set as p < 0.0083 after Bonferroni correction. A significant association was detected between DRD3 SNP rs6280 and OCDS scores. In regard to impulsivity and aggressiveness, rs4532 of DRD1 was significantly associated with UPPS-P score. Also, rs4532 demonstrated a nominally significant association with BPAQ score, although it did not reach statistical significance after correction for multiple comparisons. Results of this study support the idea that genetic variations in the dopamine system may contribute to alcohol cravings and impulsivity in patients with AUD.

Genetic variants in dopamine pathways affect personality dimensions displayed by patients with eating disorders

PURPOSE

We aimed to analyze the association between common polymorphisms in dopamine pathways with personality dimensions frequently present in patients with eating disorders (ED).

METHODS

A total of 324 patients [210 with anorexia nervosa (AN), 80 with bulimia nervosa (BN) and 34 with binge-eating disorder (BED)] were diagnosed according to DSM-5 criteria and interviewed using the EDI 2 and SCL-90R questionnaires at the eating disorders unit. Blood samples were drawn and the DNA screened for polymorphisms in dopamine receptor genes (DRD2 A2/A1 and DRD3 Ser9Gly) and in the dopamine transporter DAT1 10R/9R.

RESULTS

AN patients who carried the DRD3 Gly9Gly genotype displayed significantly higher EDI-2 total scores than patients with the Ser9 allele (118.09 ± 8.75 vs. 97.23 ± 2.73, p = 0.010). In these patients, Gly9Gly carriers also showed higher scores in all the individuals' EDI-2 scales. Differences were especially relevant for bulimia (p = 0.004), ineffectiveness (p = 0.044), interpersonal distrust (p = 0.037), interoceptive awareness (p = 0.006) and maturity fears (p = 0.038). Epistasis analyses showed a strong effect of the interaction between DRD3 Ser9Gly and DRD2 A2A1 on the bulimia (p < 0.05), ineffectiveness (p < 0.05) and asceticism (p < 0.01) scales, as well as on the EDI-2 total score (p < 0.05). The scores of the SCL-90R inventory were largely unaffected by the presence of the polymorphisms.

CONCLUSION

Whilst no associations were found for the BN and BED groups, our results suggest that women with AN carrying the homozygous variant Gly9Gly genotype in the dopamine D3 receptor have significantly worse ED-related symptomatology.

LEVEL OF EVIDENCE

Level III (evidence obtained from well-designed cohort or case-control analytic studies).

Understanding the Scientific Basis of Post-traumatic Stress Disorder (PTSD): Precision Behavioral Management Overrides Stigmatization

Post-traumatic stress disorder (PTSD) is a severe polygenic disorder triggered by environmental factors. Many polymorphic genes, particularly the genetic determinants of hypodopaminergia (low dopamine function), associate with a predisposition to PTSD as well as substance use disorder. Support from the National Institutes of Health for neuroimaging research and molecular, genetic applied technologies has improved understanding of brain reward circuitry functions that have inspired the development of new innovative approaches to their early diagnosis and treatment of some PTSD symptomatology and addiction. This review presents psychosocial and genetic evidence that vulnerability or resilience to PTSD can theoretically be impacted by dopamine regulation. From a neuroscience perspective, dopamine is widely accepted as a major neurotransmitter. Questions about how to modulate dopamine clinically in order to treat and prevent PTSD and other types of reward deficiency disorders remain. Identification of genetic variations associated with the relevant genotype-phenotype relationships can be characterized using the Genetic Addiction Risk Score (GARS®) and psychosocial tools. Development of an advanced genetic panel is under study and will be based on a new array of genes linked to PTSD. However, for now, the recommendation is that enlistees for military duty be given the opportunity to voluntarily pre-test for risk of PTSD with GARS, before exposure to environmental triggers or upon return from deployment as part of PTSD management. Dopamine homeostasis may be achieved via customization of neuronutrient supplementation "Precision Behavioral Management" (PBM™) based on GARS test values and other pro-dopamine regulation interventions like exercise, mindfulness, biosensor tracking, and meditation.

Pharmacogenetics and Pharmacotherapy of Military Personnel Suffering from Post-traumatic Stress Disorder

Background:

Posttraumatic stress disorder (PTSD) is a severe problem among soldiers with combating experience difficult to treat. The pathogenesis is still not fully understood at the psychological level. Therefore, genetic research became a focus of interest. The identification of single nucleotide polymorphisms (SNPs) may help to predict, which persons are at high risk to develop PTSD as a starting point to develop novel targeted drugs for treatment.

Methods:

We conducted a systematic review on SNPs in genes related to PTSD pathology and development of targeted pharmacological treatment options based on PubMed database searches. We focused on clinical trials with military personnel.

Results:

SNPs in 22 human genes have been linked to PTSD. These genes encode proteins acting as neurotransmitters and receptors, downstream signal transducers and metabolizing enzymes. Pharmacological inhibitors may serve as drug candidates for PTSD treatment, e.g. β2 adrenoreceptor antagonists, dopamine antagonists, partial dopamine D2 receptor agonists, dopamine β hydroxylase inhibitors, fatty acid amid hydrolase antagonists, glucocorticoid receptor agonists, tropomyosin receptor kinase B agonists, selective serotonin reuptake inhibitors, catechol-O-methyltransferase inhibitors, gamma-amino butyric acid receptor agonists, glutamate receptor inhibitors, monoaminoxidase B inhibitors, N-methyl-d-aspartate receptor antagonists.

Conclusion:

The combination of genetic and pharmacological research may lead to novel target-based drug developments with improved specificity and efficacy to treat PTSD. Specific SNPs may be identified as reliable biomarkers to assess individual disease risk. Focusing on soldiers suffering from PTSD will not only help to improve treatment options for this specific group, but for all PTSD patients and the general population.

Association study of BDNF and DRD3 genes with alcohol use disorder in Schizophrenia

Alcohol use disorder (AUD) is a leading risk factor of disease burden in the world. It is also commonly comorbid with over 20% of schizophrenia patients. The brain-derived neurotrophic factor (BDNF) and dopamine D3 receptor (DRD3) have been implicated in alcohol drinking behaviour. Previous genetic studies of the BDNF and DRD3 genes produced mixed findings; however, only one study investigated two BDNF genetic markers with alcohol dependence in schizophrenia patients. We investigated 15 single-nucleotide polymorphisms (SNPs) in DRD3 and four SNPs in BDNF for possible association with alcohol abuse or dependence in schizophrenia patients of European ancestry (N = 195). The patients were assessed for the occurrence of alcohol abuse or alcohol dependence using the Structured Clinical Interview for DSM-IV Axis I Disorders, Patient Edition (SCID-I/P). We found the BDNF Val66Met to be associated with alcohol dependence (p = 0.004). We also found haplotypes across BDNF to be nominally associated with alcohol dependence. Analyses of DRD3 markers and haplotypes yielded mostly negative findings. Our findings support a role of the BDNF gene in alcohol dependence in schizophrenia patients. Larger samples are required to confirm our findings, particularly those of BDNF haplotypes.

Investigating the Genetic Basis of Social Conformity: The Role of the Dopamine Receptor 3 (DRD3) Gene

BACKGROUND

People often change their opinions or behavior to match the responses of others, a phenomenon known as social conformity. Conforming behavior varies substantially across individuals. However, little is known about the genetic basis underlying individual differences in social conformity. A recent study demonstrated an association between enhanced dopaminergic function and increased conforming behavior. Given the effect of the dopamine receptor 3 gene (DRD3) Ser9Gly polymorphism (rs6280) on dopamine release in the striatum, this study investigated to what extent this polymorphism affects conforming behavior.

METHODS

We categorized Han Chinese individuals according to the polymorphism and tested them with a facial-attractiveness rating task.

RESULTS

We found that individuals with a greater number of the Gly alleles, which are related to an increased dopamine release in the striatum, were more susceptible to social influence and more likely to change their ratings to match those of other people.

CONCLUSIONS

This finding demonstrates the importance of DRD3 Ser9Gly as a genetic basis for social conformity and in predicting individual differences in social learning.

Polymorphisms of Dopamine Receptor Genes and Risk of L-Dopa-Induced Dyskinesia in Parkinson's Disease

L-dopa–induced dyskinesia (LID) is a frequent motor complication of Parkinson’s disease (PD), associated with a negative prognosis. Previous studies showed an association between dopamine receptor (DR) gene (DR) variants and LID, the results of which have not been confirmed. The present study is aimed to determine whether genetic differences of DR are associated with LID in a small but well-characterized cohort of PD patients. To this end we enrolled 100 PD subjects, 50 with and 50 without LID, matched for age, gender, disease duration and dopaminergic medication in a case-control study. We conducted polymerase chain reaction for single nucleotide polymorphisms (SNP) in both D1-like (DRD1A48G; DRD1C62T and DRD5T798C) and D2-like DR (DRD2G2137A, DRD2C957T, DRD3G25A, DRD3G712C, DRD4C616G and DRD4nR VNTR 48bp) analyzed genomic DNA. Our results showed that PD patients carrying allele A at DRD3G3127A had an increased risk of LID (OR 4.9; 95% CI 1.7–13.9; p = 0.004). The present findings may provide valuable information for personalizing pharmacological therapy in PD patients.

Chronic alcohol administration affects purine nucleotide catabolism in vivo

AIMS

To investigate the relationship between chronic alcohol administration and purine nucleotide metabolism in vivo.

MAIN METHODS

Rat models of alcohol dependence and withdrawal were used. The concentrations of uric acid (UAC), urea nitrogen (UREA), creatinine (CREA), and beta-2-microglobulin (β2-M) and creatinine clearance rate (CCR) in plasma were measured. The PLC method was used to detect the absolute content of purine nucleotides in different tissues. Enzymatic activities of adenosine deaminase (ADA), xanthine oxidase (XO), ribose 5-phosphate pyrophosphokinase (RPPPK), glutamine phosphoribosylpyrophosphate amidotransferase (GPRPPAT), hypoxanthine-guanine phosphate ribose transferase (HGPRT), and adenine phosphoribosyltransferase (APRT) in the tissues were analyzed. Real-time PCR was used to determine the relative level of ADA and XO.

KEY FINDINGS

The renal function of rats with alcohol dependence was normal. Further, the content of purine nucleotides (GMP, AMP, GTP, and ATP) in tissues of the rats was decreased, which indicated that the increased uric acid should be derived from the decomposition of nucleotides in vivo. The activity of XO and ADA increased, and their mRNA expression was enhanced in the alcohol dependence group, but there was no significant difference in the activity of RPPPK and GPRPPAT in the liver, small intestine, and muscle; furthermore, no significant difference in the activity of HGPRT and APRT was observed in the brain.

SIGNIFICANCE

These results indicate that chronic alcohol administration might enhance the catabolism of purine nucleotides in tissues by inducing gene expression of ADA and XO, leading to elevation of plasma uric acid levels.

Polymorphisms of dopamine receptor genes and risk of visual hallucinations in Parkinson's patients

BACKGROUND

Visual hallucinations (VHs) are frequent non-motor complication of Parkinson's disease (PD), associated to a negative prognosis. Previous studies showed an association between dopamine receptor (DR) gene (DR) variants and psychosis in Alzheimer's disease, addictions, schizophrenia, and bipolar disorder. However, there are only a few studies on DR variants and VHs in PD, which did not provide conclusive results.

OBJECTIVES

The present study aimed to determine whether genetic differences of DR are associated with visual hallucinations (VHs) in a cohort of Parkinson's disease (PD) patients.

METHODS

A case-control study of 84 PD subjects, 42 with and 42 without VHs,that were matched for age, gender, disease duration, and dopaminergic medication was conducted. Polymerase chain reaction for SNPs in both D1-like (DRD1A-48G [rs4532] and C62T [rs686], DRD5T798C [rs6283]) and D2-like DR (DRD2G2137A [rs1800497] and C957T [rs6277], DRD3G25A [rs6280] and G712C [rs1800828], DRD4C616G [rs747302] and nR VNTR 48bp) analyzed genomic DNA.

RESULTS

Patients carrying allele T at DRD1C62T had an increased risk of VHs, expressed as OR (95 % CI, p value), of 10.7 (2.9-40, p = 0.0001). Moreover, patients with DRD1-48 GG and 62TT genotype displayed shorter time to VHs, whereas a longer time to VHs was found in subjects carrying the DRD4 CG alleles.

CONCLUSIONS

PD patients with VHs display higher frequency of DR SNPs associated with increased D1-like activity and decreased D2-like activity. Our data are in line with associations reported in other neurodegenerative and psychiatric conditions. Results likely provide valuable information for personalizing pharmacological therapy in PD patients.

Dopamine D3 receptor Ser9Gly variant is associated with impulse control disorders in Parkinson's disease patients

INTRODUCTION

Impulse control disorders (ICD) are reported to occur at variable frequencies in different ethnic groups. Genetic vulnerability is suspected to underlie the individual risk for ICD. We investigated whether the allelic variants of dopamine (DRD3), glutamate (GRIN2B) and serotonin (HTR2A) receptors are linked to ICD in Indian Parkinson's disease (PD) patients.

METHODS

We conducted a prospective, case-control study which included PD patients (70 with ICD, 100 without ICD categorized after direct psychiatric interview of patient and caregiver) and 285 healthy controls. Single nucleotide polymorphism (SNP) variants of DRD3 p.S9G (rs6280), GRIN2B c.2664C>T (rs1806201) and HTR2A c.102T>C (rs6313) were genotyped.

RESULTS

Multivariate regression analysis revealed that DRD3 p.Ser9Gly (rs6280) heterozygous variant CT (OR = 2.22, 95% CI: 1.03-4.86, p = 0.041), higher daily Levodopa equivalent doses (LED) of drugs (for 100 mg LED, OR = 1.14, 95% CI: 1.01-1.29, p = 0.041), current dopamine agonist but not Levodopa use (OR = 2.16, 95% CI: 1.03-4.55, p = 0.042) and age of onset of motor symptoms under 50 years (OR 2.09, 95% CI: 1.05-4.18, p = 0.035) were independently associated with ICD.

CONCLUSION

DRD3 p.Ser9Gly (rs6280) CT genotype is associated with ICD in Indian PD patients and this association is novel. Enhanced D3 receptor affinity due to gain-of-function conferred by the glycine residues could impair reward-risk assessment in the mesolimbic system and contribute to development of impulsive behaviour, in carriers of this genotype.

A pharmacogenetic pilot study reveals MTHFR, DRD3, and MDR1 polymorphisms as biomarker candidates for slow atorvastatin metabolizers

Background

The genetic variation underlying atorvastatin (ATV) pharmacokinetics was evaluated in a Mexican population. Aims of this study were: 1) to reveal the frequency of 87 polymorphisms in 36 genes related to drug metabolism in healthy Mexican volunteers, 2) to evaluate the impact of these polymorphisms on ATV pharmacokinetics, 3) to classify the ATV metabolic phenotypes of healthy volunteers, and 4) to investigate a possible association between genotypes and metabolizer phenotypes.

Methods

A pharmacokinetic study of ATV (single 80-mg dose) was conducted in 60 healthy male volunteers. ATV plasma concentrations were measured by high-performance liquid chromatography mass spectrometry. Pharmacokinetic parameters were calculated by the non-compartmental method. The polymorphisms were determined with the PHARMAchip® microarray and the TaqMan® probes genotyping assay.

Results

Three metabolic phenotypes were found in our population: slow, normal, and rapid. Six gene polymorphisms were found to have a significant effect on ATV pharmacokinetics: MTHFR (rs1801133), DRD3 (rs6280), GSTM3 (rs1799735), TNFα (rs1800629), MDR1 (rs1045642), and SLCO1B1 (rs4149056). The combination of MTHFR, DRD3 and MDR1 polymorphisms associated with a slow ATV metabolizer phenotype.

Conclusion

Further studies using a genetic preselection method and a larger population are needed to confirm these polymorphisms as predictive biomarkers for ATV slow metabolizers.

Trial registration

Australian New Zealand Clinical Trials Registry: ACTRN12614000851662, date registered: August 8, 2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2062-2) contains supplementary material, which is available to authorized users.

Influence of dopamine receptor gene polymorphisms on circulating T lymphocytes: A pilot study in healthy subjects

Dopamine is a key transmitter in the neuroimmune network, acting through five dopaminergic receptors (DR): the D1-like D1 and D5 and the D2-like D2, D3 and D4. Several DR gene variants exist and may affect DR expression and activity. We assessed total lymphocytes, CD3+, CD4+ and CD8+ T lymphocytes in peripheral blood of healthy subjects and their association with selected DR gene variants (DRD1 rs4532 and rs686, DRD5 rs6283, DRD2 rs1800497 and rs6277, DRD3 rs6280 and rs1800828, DRD4 rs747302 and 7 48-base pair VNTR). DRD1 rs4532 and rs686 and DRD5 rs6283 were associated with total lymphocytes, and with CD3+ and CD4+ (but not CD8+) T lymphocytes, while none of the D2-like DR gene variants showed any association with lymphocyte counts. An arbitrary score based on the activity of D1-like vs D2-like DR correlated with total lymphocytes, CD3+ and CD4+ T cells (but not with CD8+ T cells). The association between D1-like DR gene variants and lymphocyte count, and in particular with CD4+ (but not CD8+) T lymphocytes, may imply a functional prevalence of D1-like over D2-like DR in CD4+ T cells. This is the first study showing an influence of DR gene polymorphisms on lymphocyte count, and in particular on CD4+ T cells. Future studies should address the possible association between DR gene variants and the immune function in health and disease. The relevance of these findings for the immune effects of dopaminergic agents should be also carefully examined.

Association of DRD3, COMT, and SLC6A4 Gene Polymorphisms with Type 2 Diabetes in Southern Chinese: A Hospital-Based Case-Control Study

AIM

The aim of this study was to assess the associations of six single nucleotide polymorphisms (SNPs) of three genes (DRD3, COMT, and SCL6A4) with type 2 diabetes mellitus (T2DM) in Southern Chinese.

SUBJECTS AND METHODS

Five hundred ninety-five cases with T2DM and 725 healthy controls of Han origin were recruited from six hospitals in Guangdong Province, Southern China. Fasting serum concentrations of markers of interest (total cholesterol, triglyceride, plasma glucose, etc.) were measured in hospitals. SNP genotyping was performed using a custom-by-design 2-×48-Plex SNPscan™ kit (Genesky Biotechnologies Inc., Shanghai, China). Single-point SNP analysis, haplotype analysis, and SNP-SNP interactions were carried out.

RESULTS

SNP rs4646312 in COMT achieved statistical significance in both allelic association and genotypic association and even after adjusting covariates (odds ratio [OR]=1.26; 95% confidence interval [CI], 1.04-1.53; P=0.021). Two haplotypes consisting of rs4646312 and rs4680 were also significantly associated with T2DM, of which C-G was a protective haplotype for T2DM (OR=0.83; 95% CI, 0.70-0.98; P=0.029), whereas T-A was a risk one (OR=1.23, 95% CI, 1.03-1.46; P=0.022). Interaction analysis identified a significant epistatic effect between rs4680 in COMT and rs2066713 in SCL6A4 after adjusting for covariates (OR=3.59, 95% CI, 1.72-7.48; P=0.001 for dominant-dominant model). However, only the interaction between rs4680 and rs2066713 was significant, and haplotype T-A showed a marginally increased risk after Bonferroni correction.

CONCLUSIONS

The genetic polymorphisms in COMT and SCL6A4 confer significant effects in joint actions to T2DM in Southern Chinese.

Meta-analysis of six genes (BDNF, DRD1, DRD3, DRD4, GRIN2B and MAOA) involved in neuroplasticity and the risk for alcohol dependence

BACKGROUND

Alcohol-related problems have a large impact on human health, accounting for around 4% of deaths and 4.5% of disability-adjusted life-years around the world. Genetic factors could explain a significant fraction of the risk for alcohol dependence (AD). Recent meta-analyses have found significant pooled odds ratios (ORs) for variants in the ADH1B, ADH1C, DRD2 and HTR2A genes.

METHODS

In the present study, we carried out a meta-analysis of common variants in 6 candidate genes involved in neurotransmission and neuroplasticity: BDNF, DRD1, DRD3, DRD4, GRIN2B and MAOA. We carried out a systematic search for published association studies that analyzed the genes of interest. Relevant articles were retrieved and demographic and genetic data were extracted. Pooled ORs were calculated using a random-effects model using the Meta-Analyst program. Dominant, recessive and allelic models were tested and analyses were also stratified by ethnicity.

RESULTS

Forty two published studies were included in the current meta-analysis: BDNF-rs6265 (nine studies), DRD1-rs4532 (four studies), DRD3-rs6280 (eleven studies), DRD4-VNTR (seven studies), GRIN2B-rs1806201 (three studies) and MAOA-uVNTR (eight studies). We did not find significant pooled ORs for any of the six genes, under different models and stratifying for ethnicity.

CONCLUSIONS

In terms of the number of candidate genes included, this is one of the most comprehensive meta-analyses for genetics of AD. Pooled ORs did not support consistent associations with any of the six candidate genes tested. Future studies of novel genes of functional relevance and meta-analyses of quantitative endophenotypes could identify further susceptibility molecular factors for AD.

Identifying Medication Targets for Psychostimulant Addiction: Unraveling the Dopamine D3 Receptor Hypothesis

The dopamine D3 receptor (D3R) is a target for developing medications to treat substance use disorders. D3R-selective compounds with high affinity and varying efficacies have been discovered, providing critical research tools for cell-based studies that have been translated to in vivo models of drug abuse. D3R antagonists and partial agonists have shown especially promising results in rodent models of relapse-like behavior, including stress-, drug-, and cue-induced reinstatement of drug seeking. However, to date, translation to human studies has been limited. Herein, we present an overview and illustrate some of the pitfalls and challenges of developing novel D3R-selective compounds toward clinical utility, especially for treatment of cocaine abuse. Future research and development of D3R-selective antagonists and partial agonists for substance abuse remains critically important but will also require further evaluation and development of translational animal models to determine the best time in the addiction cycle to target D3Rs for optimal therapeutic efficacy.