Neither single-marker nor haplotype analyses support an association between the dopamine transporter gene and heroin dependence in Han Chinese

Nerve growth factor gene polymorphisms may be associated with heroin dependence in women but do not mediate specific personality traits

Heroin dependence (HD) is a complex disease with a substantial genetic contribution and is associated with traits of impulsivity and specific personality traits. The neurotrophic factor nerve growth factor (NGF) may mediate the reward processes in HD. This study aims to investigate whether NGF gene polymorphisms are associated with the co-occurrence of HD and impulsivity/specific personality traits in HD patients. To minimize the potential confounding effects of population stratification, we selected a homogeneous Han Chinese population and recruited 1364 participants (831 HD patients and 533 healthy controls). In addition, 163 female HD patients completed the Chinese version of the Barratt Impulsiveness Scale Version 11 (BIS-11), and 440 HD patients completed the Chinese version of the Tridimensional Personality Questionnaire (TPQ) for subsequent analysis. We identified three polymorphisms with altered allele and genotype frequency in HD patients versus controls (p = 0.035 for rs2254527; p = 0.005 for rs6678788; p = 0.006 for rs7523654), especially in the female subgroup. Four associations identified via haplotype analysis were significant in the female subgroup (p = 0.003 for T-T-A haplotype and p = 0.002 for C-C-A haplotype in block 1; p = 0.011 for T-T haplotype and p = 0.009 for C-T haplotypes in block 2), but not in the male subgroup. Male HD patients had higher novelty-seeking (NS) scores, and female HD patients had higher harm avoidance (HA) scores. However, there was no significant association between the selected NGF polymorphisms and BIS or TPQ scores in HD patients. NGF variants may contribute to the risk of HD development in females but do not mediate the relationship between impulsivity and specific personality traits in the female population.

Molecular Imaging of Opioid and Dopamine Systems: Insights Into the Pharmacogenetics of Opioid Use Disorders

Opioid use in the United States has steadily risen since the 1990s, along with staggering increases in addiction and overdose fatalities. With this surge in prescription and illicit opioid abuse, it is paramount to understand the genetic risk factors and neuropsychological effects of opioid use disorder (OUD). Polymorphisms disrupting the opioid and dopamine systems have been associated with increased risk for developing substance use disorders. Molecular imaging studies have revealed how these polymorphisms impact the brain and contribute to cognitive and behavioral differences across individuals. Here, we review the current molecular imaging literature to assess how genetic variations in the opioid and dopamine systems affect function in the brain's reward, cognition, and stress pathways, potentially resulting in vulnerabilities to OUD. Continued research of the functional consequences of genetic variants and corresponding alterations in neural mechanisms will inform prevention and treatment of OUD.

Novelty seeking mediates the effect of DRD3 variation on onset age of amphetamine dependence in Han Chinese population

The dopamine receptor D3 (DRD3) gene, one of the candidate genes for amphetamine dependence (AD), is involved in the mesolimbic dopaminergic system, implicated as the underlying mechanism of addiction. Our case-control study aimed to investigate whether the DRD3 gene is associated with the susceptibility to AD and specific personality traits in AD patients. A total of 1060 unrelated Han Chinese subjects (559 AD patients and 501 controls) were screened using the same assessment tool and genotyped for eight DRD3 polymorphisms. All patients met the DSM-IV-TR criteria for AD, and personality traits of 539 were assessed using a Tridimensional Personality Questionnaire. Furthermore, AD individuals were divided into four clinical subgroups based on gender and psychosis status, to reduce the clinical heterogeneity. We found that the ATA haplotype combination for SNPs rs324029, rs6280, and rs9825563, respectively, was significantly associated with total AD patients (p = 0.0003 after 10,000 permutations). Similar results were observed in the both male and non-psychosis subgroup but not in other subgroups. In addition, DRD3 rs9825563 may influence onset age of drug use, partially mediated by novelty seeking in the non-psychosis AD group. In conclusion, DRD3 is a potential genetic factor in the susceptibility to AD and is associated with onset age of drug use through interaction with novelty seeking in a specific patient group in the Han Chinese population.

The SLC6A3 gene possibly affects susceptibility to late-onset alcohol dependence but not specific personality traits in a Han Chinese population

Dopaminergic dysfunction has an important role in the pathoetiology of alcohol dependence (AD). The purpose of this study was to determine whether the solute carrier family 6 member 3 (SLC6A3) gene (also known as the dopamine transporter DAT gene) was associated with AD, and whether variants in the SLC6A3 locus were associated with specific personality traits in patients with AD. Sixteen polymorphisms in SLC6A3 were analyzed using 637 patients with AD and 523 healthy controls. To reduce clinical heterogeneity, patients were classified into two subgroups: early-onset AD (EOAD) and late-onset AD (LOAD). The Tridimensional Personality Questionnaire was used to assess the personality traits novelty seeking (NS) and harm avoidance (HA) in the patients with AD. Using allele frequency and genotype distribution comparisons and logistic regression analysis, we found evidence of association between rs6350 and AD (P < 0.05). Following subgroup analysis, we confirmed evidence of an association in patients with LOAD (P = 0.003), but not in patients with EOAD. Heterozygous carriers of the A allele have a nearly 3 times greater risk to develop LOAD compared to individuals who do not have an A allele. Although we found that patients with AD had higher NS and HA scores compared to controls (P < 0.001), we did not find evidence of association between SLC6A3 polymorphisms and either NS or HA in patients with AD using linear regression analysis. The findings from our study indicate that the SLC6A3 gene may have a role in susceptibility to late-onset AD in the Han Chinese population.

Relationship among methadone dose, polymorphisms of dopamine D2 receptor and tri-dimensional personality questionnaire in heroin-addicted patients

BACKGROUND

We investigated whether variation in the dopamine D2 receptor gene (DRD2) and tri-dimensional personality questionnaire (TPQ) scores could be used to aid adjustment of daily methadone requirements of heroin addicts. DRD2 TaqI B polymorphisms and TPQ scores were determined in 138 male Taiwanese heroin addicts who were receiving methadone treatment. Borderline index (harm avoidance + novelty seeking-reward dependence) was calculated for each subject, and three groups were defined: high (mean from all subjects plus 1 standard deviation, or greater), low (half of the calculated high score, or lower) and medium (all values between the high and low scores).

RESULTS

No significant differences in age (p = 0.60), mean methadone dose (p = 0.75) or borderline index group (p = 0.25) were observed between subjects bearing the B1/B1, B1/B2 and B2/B2 DRD2 TaqI genotypes. Among the individuals with low (≤10), medium (11-20) and high (≥21) borderline index scores, there was a significant difference in mean methadone dose (p = 0.04), but not age (p = 0.90). Further analysis showed that mean methadone dose was significantly higher in subjects with low borderline index scores than in those with high scores (62.5 vs. 47.0 mg/day, p = 0.03). The odds ratio for a daily methadone requirement ≥60 mg (median dose across the 138 subjects) was 2.64-fold greater in the low borderline index group than in the high group (p = 0.04).

CONCLUSIONS

Although the DRD2 TaqI B genotype was not associated with methadone use requirements, borderline index was revealed as a potential predictive marker for the adjustment of methadone dosage requirements in heroin addicts.

Advances in genetic studies of substance abuse in China

Summary

The importance of genetic factors in substance addiction has long been established. The rationale for this work is that understanding of the function of addiction genes and delineation of the key molecular pathways of these genes would enhance the development of novel therapeutic targets and biomarkers that could be used in the prevention and management of substance abuse. Over the past few years, there has been a substantial increase in the number of genetic studies conducted on addiction in China; these studies have primarily focused on heroin, alcohol, and nicotine dependence. Most studies of candidate genes have concentrated on the dopamine, opioid, and serotonin systems. A number of genes associated with substance abuse in Caucasians are also risk factors in Chinese, but several novel genes and genetic risk factors associated with substance abuse in Chinese subjects have also been identified. This paper reviews the genetic studies of substance abuse performed by Chinese researchers. Genotypes and alleles related to addictive behavior in Chinese individuals are discussed and the contributions of Chinese researchers to the international corpus of knowledge about the genetic understanding of substance abuse are described.

Association of dopamine receptor gene polymorphism and psychological personality traits in liability for opioid addiction

There is a clear evidence that same psychoactive substance may cause various individual physiological reactions in same environmental conditions. Although there is a general attitude on equal liability to opioid addiction, latest genetic analysis findings imply there are certain quantifiable factors that could lead to elevated individual liability towards development of opioid addiction. The goal of this study was to investigate association of certain personality traits and genetic factors (separately and in combination) with heroin addiction. Total of 200 individuals participated in the study: 100 patients on Metadone Maintenance Treatment (MMT) and 100 age and sex matched healthy volunteers. All were medically examined, interviewed and psychologically evaluated using Eysenck personality questionnaire (EPQ) and genotyped for DRD2 (rs1800497) using PCR-RFLP method. Overrepresentation of certain personality traits (neuroticism, psychoticism and extraversion/ intraversion), together with environemental risk factors such as: upbringing within incomplete families and familial history of psychotropic substances abuse, are associated with high-risk development of opioid addiction.

Association of catechol-O-methyltransferase gene polymorphisms with schizophrenia and negative symptoms in a Chinese population

The gene encoding Catechol-O-methyltransferase (COMT), a dopamine catabolic enzyme, has been associated inconsistently with schizophrenia in spite of consistent evidence for dopaminergic dysfunction in the prefrontal cortex (PFC) of schizophrenia. Since one contribution to this inconsistency might be genetic heterogeneity, this study investigated whether the COMT gene was associated with the development and symptoms of schizophrenia in relatively genetically homogeneous Chinese schizophrenic patients. We analyzed two polymorphisms (rs740603 and rs4818) of the COMT gene in a case-control study of 604 Han Chinese (284 patients and 320 controls). The patients' psychopathology was assessed using the Positive and Negative Syndrome Scale (PANSS). We found no significant differences in the rs740603 and rs4818 genotype and allele distributions between the patient and control groups. Quantitative trait analysis by the UNPHASED program showed that the rs740603 and rs740603(G)-rs4818(G) haplotypes were associated with negative symptoms in the schizophrenic patients, particularly among female patients. Thus, the COMT gene polymorphisms may not contribute to the susceptibility to schizophrenia, but may contribute to the negative symptoms of schizophrenia among Han Chinese.