Investigation of the genetic interaction between BDNF and DRD3 genes in suicidical behaviour in psychiatric disorders

DRD3 Ser9Gly polymorphism and treatment response to antipsychotics in schizophrenia: A meta-analysis

The association between dopamine D3 receptor (DRD3) Ser9Gly polymorphism and treatment response to antipsychotic drugs (APDs) in schizophrenia (SCZ) has been widely reported with inconsistent results, thus we performed an updated meta-analysis to derive a more precise estimation of the relationship. PubMed, Cochrane Library, Medline, Embase, CNKI, Weipu and Wanfang databases were searched for eligible studies published until March 2022. Odds ratios (ORs) with 95 % confidence intervals (CIs) were used to assess the strength of the associations in four genetic models. A total of 13 studies with 1769 patients were included in this meta-analysis. Our findings suggested that Ser9Gly polymorphism was significantly associated with treatment response to APDs in SCZ in allele model (Ser vs Gly, OR = 0.72, 95 % CI = 0.58-0.89, P = 0.002), recessive model (Ser/Ser vs Ser/Gly + Gly/Gly, OR = 0.55, 95 % CI = 0.36-0.86, P = 0.008) and co-dominant model (Ser/Ser vs Gly/Gly, OR = 0.57, 95 % CI = 0.33-0.99, P = 0.045) in Caucasians, but not in Asians. meta-regression revealed that the associations were not confounded by mean age, male ratio and treatment duration (P > 0.05). In summary, our results indicated the DRD3 Ser9Gly may influence the efficacy of APDs in specific genetic models, of which Ser allele and Ser/Ser genotype contributed to poor treatment response in Caucasians.

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).

The rs6265 Polymorphism of the BDNF Gene Is Related to Higher-Lethality Suicide Attempts in the Korean Population

OBJECTIVE

Since the risk of suicide cannot be predicted by clinical symptoms alone, and suicide is known to have a genetic component, the discovery of genetic markers that can predict the lethality of suicide attempts is a clinically important topic. There have been many studies aiming to determine whether the rs6265 polymorphism of the BDNF gene is associated with suicidality; however, the results have been mixed, and there have been few studies investigating the relationship between this polymorphism and suicide attempt lethality.

METHODS

We assessed suicide lethality in 258 individuals who had attempted suicide using the relative risk ratio (RRR) scale and by genotyping the rs6265 polymorphism of the BDNF gene.

RESULTS

The RRR score for suicide attempts was higher in subjects with Met/Val and Val/Val genotypes than in that with a Met/Met genotype (p=0.015). The RRR score for suicide attempts was also higher in Val allele carriers (Met/Val+Val/Val) than in Met/Met homozygotes (p=0.006).

CONCLUSION

This study demonstrates the possibility that the rs6265 polymorphism of the BDNF gene could be used as a genetic marker to predict the lethality of suicide attempts, but more replication studies are needed for the application of this result in clinical practice.

No association between the Ser9Gly polymorphism of the dopamine receptor D3 gene and schizophrenia: a meta-analysis of family-based association studies

BACKGROUND

Previous studies found that Ser9Gly (rs6280) might be involved in the occurrence of schizophrenia. However, no consist conclusion has yet been achieved. Compared to the case-control study, the family-based study took into account stratification bias. Thus, we conducted a meta-analysis of family-based studies to measure a pooled effect size of the association between Ser9Gly and the risk of schizophrenia.

METHODS

The relevant family-based studies were screened using the electronic databases by the inclusion criteria. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to measure the correction between Ser9Gly polymorphism and schizophrenia susceptibility. Subgroup analysis was performed by stratification of ethnicity (i.e., East Asian, Caucasian, and other populations). Additionally, publication bias was evaluated by the funnel plot.

RESULTS

After literature searching, a total of 13 family-based association studies were included, which contained 11 transmission disequilibrium test (TDT) studies with 1219 informative meiosis and 5 haplotype-based haplotype relative risk (HRR) studies. No statistical significance of the heterogeneity was detected in TDT and HRR studies. Thus, the pooled effect size was calculated under the fixed effect model. The results found that the association was significantly protective in East Asian in TDT studies (204 informative meiosis, OR = 0.744, 95% CI = 0.564-0.980, Z-value = - 2.104, p = 0.035).

CONCLUSIONS

The meta-analysis based on the family study found a protective association of Ser9Gly in East Asian. In future, large sample molecular epidemiology studies are needed to validate our findings.

Brain derived neurotrophic factor (BDNF) and suicidal behavior: A review of studies from Asian countries

The biological basis of suicide and suicidal behavior is actively researched. Recently, the role of Brain Derived Neurotropic Factor (BDNF) in suicidal behavior has gained attention and significant results are observed. In this review, we aimed to focus on the studies from Asian countries that have explored the role of BDNF and suicidal behavior. The review highlights the findings from these studies and discusses the possible avenues that should be explored in future studies from Asian countries to understand more on suicidal behavior and possible prevention.

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.

Exploring the association between BDNF Val66Met polymorphism and suicidal behavior: Meta-analysis and systematic review

Suicide is a serious worldwide health problem of critical consequences. Nowadays genetic factors are considered to be an important cause of suicide. The association between Val66Met (rs6265) polymorphism of the BDNF gene and suicide behavior has been increasingly studied. The aim of this study was to perform a meta-analysis in order to unravel the possible association between BDNF gene Val66Met polymorphism and suicide behavior. These meta-analysis and systematic review were performed using 23 articles that searched for a genetic association between Val66Met and suicide behavior, including 4532 cases and 5364 control subjects. The association was analyzed following the models: allelic, homozygous, heterozygous, dominant and recessive. Also, analyses by ethnicity (Caucasian and Asian populations) were done following the same four models. When the overall population was evaluated, we found no evidence of association between the polymorphism Val66Met of BDNF (rs6265) and suicide behavior (Met vs. Val: OR: 1.01; 95% CI = 0.92-1.10). However, a significant increased risk was found in the subgroup analysis by ethnicity in Caucasian populations (Met-Met vs. Met-Val + Val-Val: OR: 1.96; 95% CI = 1.58-2.43) and Asian populations (Val-Val vs. Val-Met + Met: OR: 1.36; 95% CI = 1.04-1.78). Our results suggest there is no association between the BDNF gene Val66Met (rs6265) and suicide behavior in the overall population. However, ethnic differences can be observed and the BDNF Val66Met might increase the risk for suicide behavior in Asian and Caucasian populations. Further studies with larger samples are necessary in order to have conclusive outcomes.

Biomarkers of Suicide Attempt Behavior: Towards a Biological Model of Risk

PURPOSE OF REVIEW

The rising suicide rate in the USA will not be reversed without improved risk assessment and prevention practices. To date, the best method for clinicians to assess a patient's risk for suicide is screening for past suicide attempts in the patient and their family. However, neuroimaging, genomic, and biochemical studies have generated a body of findings that allow description of an initial heuristic biological model for suicidal behavior that may have predictive value.

RECENT FINDINGS

We review studies from the past 3 years examining potential biological predictors of suicide attempt behavior. We divide findings into two major categories: (1) structural and functional brain imaging findings and (2) biochemical and genomic findings encompassing several systems, including major neurotransmitters (serotonin, catecholamines, GABA, and glutamate), the hypothalamic pituitary adrenal (HPA) axis, the inflammasome, lipids, and neuroplasticity. The biomarkers that appear promising for assessing suicide risk in clinical settings include indices of serotonergic function, inflammation, neuronal plasticity, and lipids.

The involvement of DARPP-32 in the pathophysiology of schizophrenia

Schizophrenia is one of the most devastating heterogeneous psychiatric disorders. The dopamine hypothesis is the longest standing pathoetiologic theory of schizophrenia based on neurochemical evidences of elevated brain striatal dopamine synthesis capacity and increased dopamine release in response to stress. Dopamine and cyclic AMP-regulated phosphoprotein of relative molecular mass 32,000 (DARPP-32) is a cytosolic protein highly enriched in the medium spiny neurons of the neostriatum, considered as the most important integrator between the cortical input and the basal ganglia, and associated with motor control. Accumulating evidences has indicated the involvement of DARPP-32 in the development of schizophrenia; i. DARPP-32 phosphorylation is regulated by several neurotransmitters, including dopamine and glutamate, neurotransmitters implicated in schizophrenia pathogenesis; ii. decrease of both total and phosphorylated DARPP-32 in the prefrontal cortex are observed in schizophrenic animal models; iii. postmortem brain studies indicated decreased expression of DARPP-32 protein in the superior temporal gyrus and dorsolateral prefrontal cortex in patients with schizophrenia; iv. DARPP-32 phosphorylation is increased upon therapy with antipsychotic drugs, such as haloperidol and risperidone which improve behavioral performance in experimental animal models and patients; v. Genetic analysis of the gene coding for DARPP-32 propose an association with schizophrenia. Cumulatively, these findings implicate DARPP-32 protein in schizophrenia and propose it as a potential therapeutic target. Here, we summarize the possible roles of DARPP-32 during the development of schizophrenia and make some recommendations for future research. We propose that DARPP-32 and its interacting proteins may serve as potential therapeutic targets in the treatment of schizophrenia.

No association between dopamine D3 receptor gene Ser9Gly polymorphism (rs6280) and risk of schizophrenia: an updated meta-analysis

OBJECTIVE

Ser9Gly (rs6280) is a functional single-nucleotide polymorphism (SNP) in the dopamine receptor D3 (DRD3) gene that may be associated with schizophrenia. We performed a meta-analysis to determine whether Ser9Gly influences the risk of schizophrenia and examined the relationship between the Ser9Gly SNP and the etiology of schizophrenia.

METHODS

Case-control studies were retrieved from literature databases in accordance with established inclusion criteria. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the association between Ser9Gly and schizophrenia. Subgroup analysis and sensitivity analysis were also performed.

RESULTS

Seventy-three studies comprising 10,634 patients with schizophrenia (cases) and 11,258 controls were included in this meta-analysis. Summary results indicated no association between Ser9Gly and risk of schizophrenia. In the dominant genetic model, the pooled OR using a random effects model was 0.950 (95% CI, 0.847-1.064; P=0.374).

CONCLUSION

Results of this meta-analysis suggest that the Ser9Gly SNP is not associated with schizophrenia. These data provide possible avenues for future case-control studies related to schizophrenia.