Catechol-O-methyltransferase and dopamine receptor D4 gene variants: Possible association with substance abuse in Bangladeshi male

Gene Variant Frequencies of IDO1, IDO2, TDO, and KMO in Substance Use Disorder Cohorts

BACKGROUND

Substance use disorder in the United States represents a complex and growing public health crisis, marked by increasing rates of overdose deaths and the misuse of prescription medications. There is a critical need for furthering the understanding of the molecular and genetic mechanisms that can lead to substance use disorder. Identifying significant variants in the kynurenine pathway could help identify therapeutic targets for intervention.

METHODS

The All of Us cohort builder evaluated the frequency of variants of four genes, TDO2, IDO1, IDO2, and KMO, encoding enzymes in the kynurenine pathway. The samples were broken into six cohorts: alcohol, cannabis, cocaine, opioid, other use disorder, and control. Using Chi-square analysis, the frequency of at least one copy of a variant allele was calculated.

RESULTS

Chi-square analysis showed a significant variation in genetic frequency (p-value < 0.005) in 14 of 18 polymorphisms analyzed. The cocaine cohort had the most significant variants (13), cannabis had 11, opioids had 3, other use disorders had 2, and alcohol had 1 significant variant.

CONCLUSIONS

This study found associations of polymorphisms in the TDO2, IDO1, IDO2, and KMO genes of individuals with a substance use disorder. These results provide evidence of potential predictors of increased susceptibility to substance use disorder.

Association of DRD2, DRD4 and COMT genes variants and their gene-gene interactions with antipsychotic treatment response in patients with schizophrenia

Antipsychotic drugs are the first line of treatment in schizophrenia; although antipsychotic responses indicate a wide interindividual variety in patients with schizophrenia. This study aimed to investigate the association between four polymorphisms in DRD2, DRD4 and COMT genes and their gene-gene interactions with antipsychotic treatment response in patients with schizophrenia. A total of 101 patients with schizophrenia were recruited and stratified in treatment responder and treatment resistant groups based on the published criteria of resistant to treatment using PANSS. Clinical and demographic factors were analyzed. Genomic DNA was extracted from whole blood and genotyping for the four polymorphisms were done by ARMS-PCR, PCR-RFLP and gap-PCR. Gene-gene interactions were analyzed by logistic regression. In case of DRD2 A-241G, G allele was significantly associated with resistant to treatment. Regarding DRD4 120-bp duplication, 240/240 genotype was significantly associated with resistant to treatment comparing to other genotypes in a dominant model. The genotype combination of DRD4 240/240 and COMT Val/Val was significantly associated with treatment resistant. Among DRD2 AA genotype, COMT met allele carriers which also had a 120 bp allele of DRD4 had a significantly better response to antipsychotics. Moreover, analysis of clinical and demographic factors demonstrated a significantly longer duration of hospitalization and higher chlorpromazine-equivalent daily dose in resistant to treatment patients. Discovering the polymorphisms which effect treatment response to antipsychotics will provide the possibility of genetic screening before starting an antipsychotic treatment which enhances the chance of responding to antipsychotics and decreases drugs side effects and costs.

A review of pharmacogenetic studies in the Bangladeshi population

Pharmacogenetics (PGx)-guided prescribing is an evidence-based precision medicine strategy. Although the past two decades have reported significant advancements in both the quality and quantity of PGx research studies, they are seldom done in developing countries like Bangladesh. This review identified and summarized PGx studies conducted in the Bangladeshi population by searching PubMed and Google Scholar. Additionally, a quality evaluation of the identified studies was also carried out. Eleven PGx studies were identified that looked at the effects of genetic variants on blood thinners (CYP2C9, VKORC1, and ITGB3), cancer drugs (TPMT, MTHFR, DPYD, ERCC1, GSTP1, XPC, XRCC1, TP53, XPD, and ABCC4), statins (COQ2, CYP2D6, and CYP3A5), and prednisolone (ABCB1, CYP3A5, and NR3C1) in the Bangladeshi population. Most studies were of low to moderate quality. Although the identified studies demonstrated the potential for PGx testing, the limited PGx literature in the Bangladeshi population poses a significant challenge in the widespread implementation of PGx testing in Bangladesh.

Significant Association of the Catechol-O-Methyltransferase Gene Polymorphism (rs4680) and Opioid Use Disorder in Asian Populations, but not Caucasian Populations: A Meta-analysis

Objective: Previous studies have reported on the association between the rs4680 polymorphism in the Catechol-O-methyltransferase (COMT) gene and opioid use disorder (OUD) with inconsistent outcomes. The goal of this study was to examine the correlation of the rs4680 polymorphism and OUD using a meta-analysis approach. Methods: Six electronic databases, including PubMed, Web of Science, Cochrane Library, EMBASE, Wanfang and CNKI, were searched thoroughly for relevant studies on the association of the rs4680 polymorphism and OUD up to September, 2021. Summary odds ratios (ORs) with 95% confidence intervals (CIs) were utilized to test the association. Statistical analyses was performed using RevMan 5.3 software. Results: Eleven studies with 13 independent cohorts encompassing 2538 cases and 2519 controls were included in this study. In the overall analysis, the rs4680 polymorphism was not associated with OUD susceptibility. Subgroup analyses suggested that rs4680 was significantly correlated with OUD in Asian populations: VV vs. MM, OR = 1.46, 95% CI 1.05-2.02, p = 0.02; VM vs. MM, OR = 1.44, 95% CI 1.04-2.00, p = 0.03; VV+VM vs. MM, OR = 1.45, 95% CI 1.07-1.99, p = 0.02. However, the pooled data did not suggest any significant association in the Caucasian population. Conclusion: This meta-analysis supports a significant association between the rs4680 polymorphism and predisposition to OUD in Asians, carriers of VV and VM genotypes appear to have an increased susceptibility to OUD. However, the association does not exist in Caucasians.