Association between GABA receptor delta subunit gene polymorphisms and heroin addiction

Molecular and Environmental Determinants of Addictive Substances

Knowledge about determinants of addiction in people taking addictive substances is poor and needs to be supplemented. The novelty of this paper consists in the analysis of innovative aspects of current research about relationships between determinants of addiction in Polish patients taking addictive substances and rare available data regarding the relationships between these factors from studies from recent years from other environments, mainly in Europe, and on the development of genetic determinants of physiological responses. We try to explain the role of the microelements Mn, Fe, Cu, Co, Zn, Cr, Ni, Tl, Se, Al, B, Mo, V, Sn, Sb, Ag, Sr, and Ba, the toxic metals Cd, Hg, As, and Pb, and the rare earth elements Sc, La, Ce, Pr, Eu, Gd, and Nd as factors that may shape the development of addiction to addictive substances or drugs. The interactions between factors (gene polymorphism, especially ANKK1 (TaqI A), ANKK1 (Taq1 A-CT), DRD2 (TaqI B, DRD2 Taq1 B-GA, DRD2 Taq1 B-AA, DRD2-141C Ins/Del), and OPRM1 (A118G)) in patients addicted to addictive substances and consumption of vegetables, consumption of dairy products, exposure to harmful factors, and their relationships with physiological responses, which confirm the importance of internal factors as determinants of addiction, are analyzed, taking into account gender and region. The innovation of this review is to show that the homozygous TT mutant of the ANKK1 TaqI A polymorphism rs 1800497 may be a factor in increased risk of opioid dependence. We identify a variation in the functioning of the immune system in addicted patients from different environments as a result of the interaction of polymorphisms.

Association of GABA receptor delta subunit gene variations with increased risk of methamphetamine dependence

OBJECTIVE

Evidence reveals that γ-aminobutyric acid (GABA) receptors are involved in the development of methamphetamine (METH) dependence. The GABA receptor delta subunit gene (GABRD) might be a good candidate gene for METH dependence. In a case-control study, we investigated the association between the single nucleotide polymorphisms (SNPs) in GABRD and METH dependence in a Chinese Han population.

METHODS

A total of 300 METH dependent patients and 300 age and sex matched normal control subjects were recruited. Four SNPs (rs13303344, rs4481796, rs2376805, and rs2229110) in GABRD were determined with the TaqMan genotyping assay. The association of the SNPs with METH dependence was assessed.

RESULTS

Only the allele frequency of rs2376805 significantly differed between the patients and controls (P = 0.030). The G allele frequency of rs2376805 was higher in the METH dependent group than in the controls (odds ratio = 1.332, 95 % CI: 1.028-1.724). This association was found in females but not in males. In females, the frequencies of genotype and allele at rs2376805 significantly differed between the patients and controls (P = 0.025, 0.022, respectively); the rs2376805 G allele may also be a risk factor for METH dependence (odds ratio = 1.548, 95 % CI: 1.063-2.257). The haplotype ACGT frequency significantly differed between the patients and controls in total subjects (P = 0.008, odds ratio = 1.815, 95 % CI: 1.183-2.782), as well as in females (P = 0.005, odds ratio = 2.702, 95 % CI: 1.313-5.562). In females only, the METH craving score was significantly lower in patients harboring the G allele at rs2376805 than in those harboring the homozygous AA genotype (P = 0.044).

CONCLUSION

The preliminary results indicate that GABRD rs2376805 is associated with METH dependence, especially in females.

Splice-Site Variants in the Gene Encoding GABA-A Receptor Delta Subunit Are Associated with Amphetamine Use in Patients under Methadone Maintenance Treatment

Chronic opioid use disorder patients often also use other substances such as amphetamines. The gene-based analysis method was applied in the genomic database obtained from our previous study with 343 methadone maintenance treatment (MMT) patients. We found that the gene encoding gamma-aminobutyric acid type A receptors (GABA-A receptor) delta subunit isoforms (GABRD) was associated with amphetamine use in heroin dependent patients under MMT in Taiwan. A total of 15% of the 343 MMT patients tested positive for amphetamine in the urine toxicology test. Two genetic variants in the GABRD, rs2889475 and rs2376805, were found to be associated with the positive urine amphetamine test. They are located in the exon 1 of the splice variant and altered amino acid compositions (T126I, C/T, for rs2889475, and R252Q, G/A, for rs2376805). The CC genotype carriers of rs2889475 showed a four times higher risk of amphetamine use than those with TT genotype. The GG genotype carriers of rs2376805 showed a three times higher risk of amphetamine use than the AA genotype carriers. To our knowledge, this is the first report that demonstrated an association of the delta splice variant isoform in the GABA-A receptor with an increased risk of amphetamine use in MMT patients. Our results suggest that rs2889475 and rs2376805 may be indicators for the functional role and risk of amphetamine use in MMT patients.

Association study of genetic polymorphisms in GABRD with treatment response and dose in methadone maintenance treatment

Aim: This study determined if gene variants in the GABA receptor delta subunit (GABRD) are associated with treatment response and dose in methadone maintenance treatment (MMT) for heroin addiction. Materials & methods: A total of 286 MMT patients were recruited and divided into response and nonresponse groups based on retention time in therapy. A total of 177 responders were classified into low dose and high dose subgroups according to the stabilized methadone dose. Four (single nucleotide polymorphisms) SNPs (rs13303344, rs4481796, rs2376805 and rs2229110) in GABRD were genotyped using the TaqMan SNP assay. Logistic regression was used to assess the genetic effects of the SNPs in MMT. Results: No significant associations were observed between the SNPs and treatment response or dose, except the frequency of haplotype ACGC at the four SNPs significantly differed between responders and nonresponders. Conclusion: The results indicated that GABRD variants may play a small role in modulating methadone treatment response.