Population-based case-control study of DRD2 gene polymorphisms and alcoholism

Evaluation of the Relationship Between Dopamine Receptor D2 Gene TaqIA1 Polymorphism and Alcohol Dependence Risk

Several studies are published, that investigated dopamine receptor 2 (DRD2) gene TaqIA polymorphism as a risk factor for alcohol dependence (AD) with positive and negative associations. To derive a more precise estimation of the relationship, a meta-analysis of case-control studies that examined the association between DRD2 gene Taq1A polymorphism and alcohol dependence was performed. Eligible articles were identified through a search of databases including PubMed, Science Direct, Springer link, and Google Scholar. The association between the DRD2 TaqIA polymorphism and AD susceptibility was conducted using odds ratios (ORs) and 95% confidence intervals (95% CIs) as association measures. A total of 69 studies with 9125 cases and 9123 healthy controls were included in the current meta-analysis. Results of the present analysis showed significant association between DRD2 TaqIA polymorphism and AD risk using five genetic modes (allele contrast model-OR 1.22, 95% CI 1.13-1.32, p < 0.0001; homozygote model-OR 1.35, 95%CI 1.18-1.55; p ≤ 0.0001; dominant model-OR 1.29; 95% CI 1.20-1.39; p < 0.0001; recessive model-OR 1.21; 95% CI 1.08-1.36; p = 0.0006). There was no significant association found in subgroup analysis, TaqIA polymorphism was not significantly associated with AD risk in the Asian population under all genetic models, but in the Caucasian population, TaqIA polymorphism was significantly associated with AD risk. Overall, results support the hypothesis that DRD2 Taq1A polymorphism plays a role in alcohol dependence.

Alcohol use disorder research in India: An update

Background

Despite alcohol use being a risk factor for numerous health-related conditions and alcohol use disorder (AUD) recognized as a disease, there was limited research in India until 2010. This narrative review aims to evaluate AUD-related research in India from 2010 to July 2023.

Methods

A PubMed search used key terms for AUD in India after 2010. Indian and international journals with regional significance that publish alcohol-related research were searched by each author individually. These were then collated, and duplicates were removed. In addition, we also conducted a gray literature search on focused areas related to AUD.

Results

The alcohol-related research in India after 2010 focused on diverse areas associated with alcohol use. Some areas of research have received more attention than others. Two major epidemiological surveys conducted in the past decade reveal that around 5% have a problematic alcohol use pattern. Factors associated with alcohol use, like genetic, neurobiological, psychological, and sociocultural, were studied. The studies focused on the clinical profile of AUD, including their correlates, such as craving, withdrawal, alcohol-related harm, and comorbid psychiatric and medical illnesses. During this period, minimal research was conducted to understand AUD's laboratory biomarkers, course, and prognosis. While there was a focus on generating evidence for different psychological interventions for alcohol dependence in management-related research, pharmacological studies centered on anticraving agents like baclofen. Research on noninvasive brain stimulation, such as rTMS, has shown preliminary usefulness in treating alcohol dependence. Very little research has been conducted regarding alcohol policy.

Conclusion

In the past decade, Indian research on alcohol has focused on diverse areas. Epidemiological and psychological management-related research received maximum attention. Considering the magnitude of the alcohol-related burden, it is essential to prioritize research to other less studied areas like pharmacological management of alcohol dependence and alcohol policy.

Meta-Analysis on the Association of Neuropeptide Y rs16139 Variant With the Risk of Alcoholism

Introduction: The neuropeptide-Y (NPY) is involved in the development of alcoholism through NPY receptors. A T>C mutation causes substitution of leucine to proline at codon 7 (L7P; rs16139) in the signal peptide of neuropeptide Y is known to cause a 42% increase in plasma NPY levels. Studies that analyzed the association between NPY rs16139 and alcoholism risk did not demonstrate conclusive evidence for this relationship. The present study aims to evaluate the association between NPY gene rs16139 variant and alcohol dependence. Method: An electronic search of databases including PubMed and Google Scholar was performed to retrieve studies investigating the association between NPY rs16139 and alcoholism. The pooled odds ratio (OR) with 95% confidence interval (CI) was calculated in allelic and dominant genetic models. Sensitivity analyses and publication bias were assessed in our meta-analysis. The meta-analysis was conducted using the MetaGenyo web tool. Result: Significant heterogeneity was observed across studies (p < 0.001). Our results have shown that there is no significant association between NPY rs16139 variant and the risk of alcoholism in allelic (OR = 0.98, 95% CI 0.70-1.38, p = 0.921) and dominant models (OR = 0.98, 95% CI 0.69-1.40, p = 0.919). Begg's funnel plot and Egger's test have not shown publication bias (p = 0.332). Conclusion: To the best of our knowledge, this is the first meta-analysis that evaluates the relationship between the NPY rs16139 polymorphism and the risk of alcoholism. Our large-scale meta-analysis suggests that NPY rs16139 polymorphism is not associated with alcoholism. However, further studies are needed to increase our understanding of the relationship between NPY variants in alcoholism.

Assessment of the Association of D2 Dopamine Receptor Gene and Reported Allele Frequencies With Alcohol Use Disorders: A Systematic Review and Meta-analysis

IMPORTANCE

The association between the D2 dopamine receptor gene (DRD2) Taq1A locus (rs1800497) and alcohol use disorder (AUD) is enduring but the subject of long-standing controversy; meta-analysis of studies across 3 decades shows an association between rs1800497 and AUD, but genome-wide analyses have detected no role for rs1800497 in any phenotype. No evidence has emerged that rs1800497, which is located in ANKK1, perturbs the expression or function of DRD2.

OBJECTIVE

To resolve contradictions in previous studies by identifying hidden confounders and assaying for functional effects of rs1800497 and other loci in the DRD2 region.

DATA SOURCES

PubMed (882 studies), Embase (1056 studies), and Web of Science (501 studies) databases were searched through August 2018. Three clinical populations-Finnish, Native American, and African American participants-were genotyped for 208 to 277 informative single-nucleotide polymorphisms (SNPs) across the DRD2 region to test the associations of SNPs in this region with AUD.

STUDY SELECTION

Eligible studies had diagnosis of AUD made by accepted criteria, reliable genotyping methods, sufficient genotype data to calculate odds ratios and 95% CIs, and availability of control allele frequencies or genotype frequencies.

DATA EXTRACTION AND SYNTHESIS

After meta-analysis of 62 studies, metaregression was performed to detect between-study heterogeneity and to explore the effects of moderators, including deviations of cases and controls from allele frequencies in large population databases (ExAC and 1000 Genomes). Linkage to AUD and the effect on gene expression of rs1800497 were evaluated in the context of other SNPs in the DRD2 region. Data analysis was performed from August 2018 to March 2019. This study follows the Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guideline.

MAIN OUTCOMES AND MEASURES

The effects of rs1800497 and other SNPs in the DRD2 region on gene expression were measured in human postmortem brain samples via differential allelic expression and evaluated in other tissues via publicly available expression quantitative locus data.

RESULTS

A total of 62 studies of DRD2 and AUD with 16 294 participants were meta-analyzed. The rs1800497 SNP was associated with AUD (odds ratio, 1.23; 95% CI, 1.14-1.31; P < .001). However, the association was attributable to spuriously low allele frequencies in controls in positive studies, which also accounted for some between-study heterogeneity (I2 = 43%; 95% CI, 23%-58%; Q61 = 107.20). Differential allelic expression of human postmortem brain and analysis of expression quantitative loci in public data revealed that a cis-acting locus or loci perturb the DRD2 transcript level; however, rs1800497 does not and is not in strong disequilibrium with such a locus. Across the DRD2 region, other SNPs are more strongly associated with AUD than rs1800497, although no DRD2 SNP was significantly associated in these 3 clinical samples.

CONCLUSIONS AND RELEVANCE

In this meta-analysis, the significant association of DRD2 with AUD was reassessed. The DRD2 association was attributable to anomalously low control allele frequencies, not function, in positive studies. For genetic studies, statistical replication is not verification.

Polymorphisms in genes encoding dopamine signalling pathway and risk of alcohol dependence: a systematic review

BACKGROUND

Alcohol dependence (AD) is one of the major elements that significantly influence drinking pattern that provoke the alcohol-induced organ damage. The structural and neurophysiologic abnormalities in the frontal lobes of chronic alcoholics were revealed by magnetic resonance imaging scans. It is well known that candidate genes involved in dopaminergic pathway are of immense interest to the researchers engaged in a wide range of addictive disorders. Dopaminergic pathway gene polymorphisms are being extensively studied with respect to addictive and behavioral disorders.

METHODS

From the broad literature available, the current review summarizes the specific polymorphisms of dopaminergic genes that play a role in alcohol dependence.

RESULTS

No evidence indicating any strong association between AD and polymorphisms of dopamine pathway genes has emerged from the literature.

DISCUSSION

Further studies are warranted, considering a range of alcohol-related traits to determine the genes that influence alcohol dependence.

The association between DRD2/ANKK1 and genetically informed measures of alcohol use and problems

In 1990, Blum and colleagues first reported an association between DRD2 and alcoholism. While there have been subsequent replications of this genetic association, there have also been numerous studies that failed to detect an association between DRD2 and alcohol dependence. We propose that one aspect contributing to this inconsistency is the variation in alcohol phenotype used across studies. Within the population-based Finnish twin sample, FinnTwin16, we previously performed multivariate twin analyses to extract latent genetic factors, which account for the variation across seven measures of alcohol consumption (frequency of drinking, frequency × quantity, frequency of heavy drinking, frequency of intoxication and maximum drinks in a 24-hour period) and problems (the Rutgers Alcohol Problem Index-RAPI and the Mälmö-modified Michigan Alcohol Screen Test-MmMAST) in 3065 twins. In the present study, we examined the association between 31 DRD2/ANKK1 single-nucleotide polymorphisms (SNPs) and the genetic factor scores generated by twin analyses in a subset of FinnTwin16 (n = 602). We focus on two of the genetic factors: a general alcohol consumption and problems factor score, which represents shared genetic variance across alcohol measures, and a alcohol problems genetic factor score, which loads onto the two indices of problematic drinking (MAST and RAPI). After correction for multiple testing across SNPs and phenotypes, of the 31 SNPs genotyped across DRD2/ANKK1, one SNP (rs10891549) showed significant association with the general alcohol consumption and problems factor score (P = 0.004), and four SNPs (rs10891549, rs1554929, rs6275, rs6279), representing two independent signals after accounting for linkage disequilibrium, showed significant association with the alcohol problems genetic factor score (P = 0.005, P = 0.005, P = 0.003, P = 0.003). In this study, we provide additional positive evidence for the association between DRD2/ANKK1 and alcohol outcomes, including frequency of drinking and drinking problems. Additionally, post hoc analyses indicate stronger association signals using genetic factor scores than individual measures, which suggest that accounting for the genetic architecture of the alcohol measures reduces genetic heterogeneity in alcohol dependence outcomes in this sample and enhances the ability to detect association.

DRD2 and ANKK1 gene polymorphisms and alcohol dependence: a case-control study among a Mendelian population of East Asian ancestry

AIMS

Dopamine receptors are extensively studied in association with alcohol dependence (AD), since they are thought to be the key neural substrate for alcohol and other drug-related reinforcement and reward behaviours. The present study aims to understand the role of dopamine receptors in susceptibility to AD with respect to three sites of DRD2 gene (-141C Ins/Del, TaqIB and TaqID) and TaqIA site of ANKK1 gene among Meiteis of Manipur, a Mendelian population of India.

METHODS

A total of 129 individuals who all met the DSM-IV criteria for AD and 286 controls were screened for four single-nucleotide polymorphisms (SNPs) -141C Ins/Del, TaqIB TaqID and TaqIA. Both AD cases and controls were unrelated up to first cousin.

RESULTS

Early age of onset of alcohol consumption and smoking status were significantly associated with AD. Improvement in education and occupation statuses showed decreased risk of AD. The heterozygous and mutant homozygous conditions of ANKK1 TaqIA polymorphism were found to be significantly associated with AD (odds ratio = 2.13, 95% confidential interval 1.04-4.39, P < 0.05), whereas a borderline significance of the -141C Del allele was observed (P = 0.059). Such a trend was not observed between AD and the other polymorphism, i.e., TaqIB and TaqID.

CONCLUSIONS

Individuals carrying the A1 allele of ANKK1 TaqIA polymorphism may be relatively more susceptible to AD. Interaction of both ANKK1 TaqIA and -141C Ins/Del polymorphism is likely to increase risk of AD phenotypes among Meiteis of Manipur, India.

A large-scale meta-analysis of the association between the ANKK1/DRD2 Taq1A polymorphism and alcohol dependence

Alcohol dependence (AD) is a common neuropsychiatric disorder with high heritability. A number of studies have analyzed the association between the Taq1A polymorphism (located in the gene cluster ANKK1/DRD2) and AD. In the present study, we conducted a large-scale meta-analysis to confirm the association between the Taq1A polymorphism and the risk for AD in over 18,000 subjects included in 61 case-control studies that were published up to August 2012. Our meta-analysis demonstrated both allelic and genotypic association between the Taq1A polymorphism and AD susceptibility [allelic: P(Z) = 1.1 × 10(-5), OR = 1.19; genotypic: P(Z) = 3.2 × 10(-5), OR = 1.24]. The association remained significant after adjustment for publication bias using the trim and fill method. Sensitivity analysis showed that the effect size of the Taq1A polymorphism on AD risk was moderate and not influenced by any individual study. The pooled odds ratio from published studies decreased with the year of publication, but stabilized after the year 2001. Subgroup analysis indicated that publication bias could be influenced by racial ancestry. In summary, this large-scale meta-analysis confirmed the association between the Taq1A polymorphism and AD. Future studies are required to investigate the functional significance of the ANKK1/DRD2 Taq1A polymorphism in AD.