Genetic association between the dopamine D3 receptor gene polymorphism (Ser9Gly) and tardive dyskinesia in patients with schizophrenia: A reevaluation in East Asian populations

Association of dopamine receptor D3 polymorphism with Levodopa-induced Dyskinesia: A study on Parkinson's disease patients from India

INTRODUCTION

Levodopa-induced dyskinesia (LID) is a debilitating motor feature in a subset of patients with Parkinson's disease (PD) after prolonged therapeutic administration of levodopa. Preliminary animal and human studies are suggestive of a key role of dopamine type 3 (D3) receptor polymorphism (Ser9Gly; rs6280) in LID. Its contribution to development of LID among Indian PD patients has remained relatively unexplored and merits further investigation.

METHODS AND MATERIALS

200 well-characterised PD patients (100 without LID and 100 with LID) and 100 age-matched healthy controls were recruited from the outpatient department of Institute of Neurosciences Kolkata. MDS-UPDRS (Unified Parkinson's Disease Rating Scale from International Movement Disorder Society) Part III and AIMS (abnormal involuntary movement scale) were performed for estimation of severity of motor features and LID respectively in the ON state of the disease. Participants were analysed for the presence of Ser9Gly single nucleotide variant (SNV) (rs6280) by polymerase chain reaction followed by restriction fragment length polymorphism techniques.

RESULTS

The frequency of AA genotype (serine type) was more frequently present in PD patients with LID compared to PD patients without LID (50 % vs 28 %; P = 0.002; OR = 2.57, 95 % CI: 1.43 - 4.62). The abnormal involuntary movement scale score was significantly higher in PD patients with AA genotype compared to carriers of glycine allele (AG + GG) (4.08 ± 3.35; P = 0.002).

CONCLUSION

We observed a significant association of serine type SNV (rs6280) in D3 receptor gene in a cohort of PD patients with LID from India. More severe motor severity was found in patients with glycine substitution of the same SNV. The current study emphasised the role of D3 receptor in the pathogenesis of LID.

Epistasis in neurotransmitter receptors linked to posttraumatic stress disorder and major depressive disorder comorbidity in traumatized Chinese

Background

Posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) comorbidity occurs through exposure to trauma with genetic susceptibility. Neuropeptide-Y (NPY) and dopamine are neurotransmitters associated with anxiety and stress-related psychiatry through receptors. We attempted to explore the genetic association between two neurotransmitter receptor systems and the PTSD-MDD comorbidity.

Methods

Four groups were identified using latent profile analysis (LPA) to examine the patterns of PTSD and MDD comorbidity among survivors exposed to earthquake-related trauma: low symptoms, predominantly depression, predominantly PTSD, and PTSD-MDD comorbidity. NPY2R (rs4425326), NPY5R (rs11724320), DRD2 (rs1079597), and DRD3 (rs6280) were genotyped from 1,140 Chinese participants exposed to earthquake-related trauma. Main, gene-environment interaction (G × E), and gene-gene interaction (G × G) effects for low symptoms, predominantly depression, and predominantly PTSD were tested using a multinomial logistic model with PTSD-MDD comorbidity as a reference.

Results

The results demonstrated that compared to PTSD-MDD comorbidity, epistasis (G × G) NPY2R-DRD2 (rs4425326 × rs1079597) affects low symptoms (β = -0.66, OR = 0.52 [95% CI: 0.32-0.84], p = 0.008, pperm = 0.008) and predominantly PTSD (β = -0.56, OR = 0.57 [95% CI: 0.34-0.97], p = 0.037, pperm = 0.039), while NPY2R-DRD3 (rs4425326 × rs6280) impacts low symptoms (β = 0.82, OR = 2.27 [95% CI: 1.26-4.10], p = 0.006, pperm = 0.005) and predominantly depression (β = 1.08, R = 2.95 [95% CI: 1.55-5.62], p = 0.001, pperm = 0.001). The two G × G effects are independent.

Conclusion

NPY and dopamine receptor genes are related to the genetic etiology of PTSD-MDD comorbidity, whose specific mechanisms can be studied at multiple levels.

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.

New Insight into the human genetic diversity in North African populations by genotyping of SNPs in DRD3, CSMD1 and NRG1 genes

BACKGROUND

The single nucleotide polymorphisms (SNPs) of the dopamine D3 receptor (DRD3), the CUB and sushi multiple domains 1 (CSMD1) and the neuregulin 1 (NRG1) genes were used to study the genetic diversity and affinity among North African populations and to examine their genetic relationships in worldwide populations.

METHODS

The rs3773678, rs3732783 and rs6280 SNPs of the DRD3 gene located on chromosome 3, the rs10108270 SNP of the CSMD1 gene and the rs383632, rs385396 and rs1462906 SNPs of the NRG1 gene located on chromosome 8 were analysed in 366 individuals from seven North African populations (Libya, Kairouan, Mehdia, Sousse, Kesra, Smar and Kerkennah).

RESULTS

The low values of FST indicated that only 0.27%-1.65% of the genetic variability was due to the differences between the populations. The Kairouan population has the lowest average heterozygosity among the North African populations. Haplotypes composed of the ancestral alleles ACC and ACAT were more frequent in the Kairouan population than in other North African populations. The PCA and the haplotypic analysis showed that the genetic structure of populations in North Africa was closer to that of Europeans, Admixed Americans, South Asians and East Asians. However, analysis of the rs3732783 and rs6280 SNPs revealed that the CT microhaplotype was specific to the North African population.

CONCLUSIONS

The Kairouan population exhibited a relatively low rate of genetic variability. The North African population has undergone significant gene flow but also evolutionary forces that have made it genetically distinct from other populations.

Genetic Factors Associated With Tardive Dyskinesia: From Pre-clinical Models to Clinical Studies

Tardive dyskinesia is a severe motor adverse event of antipsychotic medication, characterized by involuntary athetoid movements of the trunk, limbs, and/or orofacial areas. It affects two to ten patients under long-term administration of antipsychotics that do not subside for years even after the drug is stopped. Dopamine, serotonin, cannabinoid receptors, oxidative stress, plasticity factors, signaling cascades, as well as CYP isoenzymes and transporters have been associated with tardive dyskinesia (TD) occurrence in terms of genetic variability and metabolic capacity. Besides the factors related to the drug and the dose and patients’ clinical characteristics, a very crucial variable of TD development is individual susceptibility and genetic predisposition. This review summarizes the studies in experimental animal models and clinical studies focusing on the impact of genetic variations on TD occurrence. We identified eight genes emerging from preclinical findings that also reached statistical significance in at least one clinical study. The results of clinical studies are often conflicting and non-conclusive enough to support implementation in clinical practice.

The genetics of drug-related movement disorders, an umbrella review of meta-analyses

This umbrella review investigates which genetic factors are associated with drug-related movement disorders (DRMD), in an attempt to provide a synthesis of published evidence of candidate-gene studies. To identify all relevant meta-analyses, a literature search was performed. Titles and abstracts were screened by two authors and the methodological quality of included meta-analyses was assessed using 'the assessment of multiple systematic reviews' (AMSTAR) critical appraisal checklist. The search yielded 15 meta-analytic studies reporting on genetic variations in 10 genes. DRD3, DRD2, CYP2D6, HTR2A, COMT, HSPG2 and SOD2 genes have variants that may increase the odds of TD. However, these findings do not concur with early genome-wide association studies. Low-power samples are susceptible to 'winner's curse', which was supported by diminishing meta-analytic effects of several genetic variants over time. Furthermore, analyses pertaining to the same genetic variant were difficult to compare due to differences in patient populations, methods used and the choice of studies included in meta-analyses. In conclusion, DRMD is a complex phenotype with multiple genes that impact the probability of onset. More studies with larger samples using other methods than by candidate genes, are essential to developing methods that may predict the probability of DRMD. To achieve this, multiple research groups need to collaborate and a DRMD genetic database needs to be established in order to overcome winner's curse and publication bias, and to allow for stratification by patient characteristics. These endeavours may help the development of a test with clinical value in the prevention and treatment of DRMD.

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.

New findings in pharmacogenetics of schizophrenia

PURPOSE OF REVIEW

This review highlights recent advances in the investigation of genetic factors for antipsychotic response and side effects.

RECENT FINDINGS

Antipsychotics prescribed to treat psychotic symptoms are variable in efficacy and propensity for causing side effects. The major side effects include tardive dyskinesia, antipsychotic-induced weight gain (AIWG), and clozapine-induced agranulocytosis (CIA). Several promising associations of polymorphisms in genes including HSPG2, CNR1, and DPP6 with tardive dyskinesia have been reported. In particular, a functional genetic polymorphism in SLC18A2, which is a target of recently approved tardive dyskinesia medication valbenazine, was associated with tardive dyskinesia. Similarly, several consistent findings primarily from genes modulating energy homeostasis have also been reported (e.g. MC4R, HTR2C). CIA has been consistently associated with polymorphisms in the HLA genes (HLA-DQB1 and HLA-B). The association findings between glutamate system genes and antipsychotic response require additional replications.

SUMMARY

The findings to date are promising and provide us a better understanding of the development of side effects and response to antipsychotics. However, more comprehensive investigations in large, well characterized samples will bring us closer to clinically actionable findings.

Genetics of tardive dyskinesia: Promising leads and ways forward

Tardive dyskinesia (TD) is a potentially irreversible and often debilitating movement disorder secondary to chronic use of dopamine receptor blocking medications. Genetic factors have been implicated in the etiology of TD. We therefore have reviewed the most promising genes associated with TD, including DRD2, DRD3, VMAT2, HSPG2, HTR2A, HTR2C, and SOD2. In addition, we present evidence supporting a role for these genes from preclinical models of TD. The current understanding of the etiogenesis of TD is discussed in the light of the recent approvals of valbenazine and deutetrabenazine, VMAT2 inhibitors, for treating TD.

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.

Pharmacogenetics of tardive dyskinesia: an updated review of the literature

Tardive dyskinesia (TD) is a serious and potentially irreversible side effect of long-term exposure to antipsychotic medication characterized by involuntary trunk, limb and orofacial muscle movements. Various mechanisms have been proposed for the etiopathophysiology of antipsychotic-induced TD in schizophrenia patients with genetic factors playing a prominent role. Earlier association studies have focused on polymorphisms in CYP2D6, dopamine-, serotonin-, GABA- and glutamate genes. This review highlights recent advances in the genetic investigation of TD. Recent promising findings were obtained with the HSPG2, DPP6, MTNR1A, SLC18A2, PIP5K2A and CNR1 genes. More research, including collection of well-characterized samples, enhancement of genome-wide strategies, gene–gene interaction and epigenetic analyses, is needed before genetic tests with clinical utility can be made available for TD.

Clinical significance of pharmacogenomic studies in tardive dyskinesia associated with patients with psychiatric disorders

Pharmacogenomics is the study of the effects of genetic polymorphisms on medication pharmacokinetics and pharmacodynamics. It offers advantages in predicting drug efficacy and/or toxicity and has already changed clinical practice in many fields of medicine. Tardive dyskinesia (TD) is a movement disorder that rarely remits and poses significant social stigma and physical discomfort for the patient. Pharmacokinetic studies show an association between cytochrome P450 enzyme-determined poor metabolizer status and elevated serum antipsychotic and metabolite levels. However, few prospective studies have shown this to correlate with the occurrence of TD. Many retrospective, case-control and cross-sectional studies have examined the association of cytochrome P450 enzyme, dopamine (receptor, metabolizer and transporter), serotonin (receptor and transporter), and oxidative stress enzyme gene polymorphisms with the occurrence and severity of TD. These studies have produced conflicting and confusing results secondary to heterogeneous inclusion criteria and other patient characteristics that also act as confounding factors. This paper aims to review and summarize the pharmacogenetic findings in antipsychotic-associated TD and assess its clinical significance for psychiatry patients. In addition, we hope to provide insight into areas that need further research.

Dopaminergic gene polymorphisms and cognitive function in a north Indian schizophrenia cohort

BACKGROUND

Associations of polymorphisms from dopaminergic neurotransmitter pathway genes have mostly been reported in Caucasian ancestry schizophrenia (SZ) samples. As studies investigating single SNPs with SZ have been inconsistent, more detailed analyses utilizing multiple SNPs with the diagnostic phenotype as well as cognitive function may be more informative. Therefore, these analyses were conducted in a north Indian sample.

METHODS

Indian SZ case-parent trios (n = 601 families); unscreened controls (n = 468) and an independent set of 118 trio families were analyzed. Representative SNPs in the Dopamine D3 receptor (DRD3), dopamine transporter (SLC6A3), vesicular monoamine transporter 2 (SLC18A2), catechol-o-methyltransferase (COMT) and dopamine beta-hydroxylase (DBH) were genotyped using SNaPshot/SNPlex assays (n = 59 SNPs). The Trail Making Test (TMT) was administered to a subset of the sample (n = 260 cases and n = 302 parents).

RESULTS

Eight SNPs were nominally associated with SZ in either case-control or family based analyses (p < 0.05, rs7631540 and rs2046496 in DRD3; rs363399 and rs10082463 in SLC18A2; rs4680, rs4646315 and rs9332377 in COMT). rs6271 at DBH was associated in both analyses. Haplotypes of DRD3 SNPs incorporating rs7631540-rs2134655-rs3773678-rs324030-rs6280-rs905568 showed suggestive associations in both case-parent and trio samples. At SLC18A2, rs10082463 was nominally associated with psychomotor performance and rs363285 with executive functions using the TMT but did not withstand multiple corrections.

CONCLUSIONS

Suggestive associations with dopaminergic genes were detected in this study, but convincing links between dopaminergic polymorphisms and SZ or cognitive function were not observed.

Do we need to consider ethno-cultural variation in the use of atypical antipsychotics for Asian patients with major depressive disorder?

Asian and western countries differ in the prevalence, symptom manifestation, diagnostic procedures, patient recognition and treatments of major depressive disorder (MDD), according to a number of studies. Ethnic differences in pharmacological profiles are also important in the prescription of certain antipsychotic medications because they may impact treatment outcomes and adverse events. Differential pharmacokinetic and pharmacodynamic properties of antipsychotics may be practically useful in the control of specific depressive symptoms. Furthermore, patient compliance with prescribed medications has been found to be different across races and ethnicities. Therefore, this article explores practical clinical issues for the use of atypical antipsychotics in patients with MDD, focusing on ethno-cultural differences.

The pharmacogenetics of antipsychotic-induced adverse events

PURPOSE OF REVIEW

Antipsychotic drugs are effective in alleviating a variety of symptoms and are medication of first choice in schizophrenia. However, a substantial interindividual variability in side effects often requires a lengthy 'trial-and-error' approach until the right medication is found for the right patient. Genetic factors have long been hypothesized to be involved and identification of related gene variants could be used to predict and tailor drug treatment.

RECENT FINDINGS

This review highlighting the most recent genetic findings was conducted on the two most common and most well-studied side effects: antipsychotic-induced weight gain and tardive dyskinesia.

SUMMARY

Regarding weight gain, most promising and most consistent findings were obtained in the serotonergic system (HTR2C) and with hypothalamic leptin-melanocortin genes, in particular with one variant close to the melanocortin-4-receptor (MC4R) gene. With respect to tardive dyskinesia, most interesting findings were generally obtained in genes related to the dopaminergic system (dopamine receptors D2 and D3), and more recently with glutamatergic system genes. Overall, genetic studies have been successful in identifying strong findings, in particular for antipsychotic-induced weight gain and to some extent for tardive dyskinesia. Apart from the need for replication studies in larger and well-characterized samples, the next challenge will be to create predictive algorithms that can be used for clinical practice.

Treatment of neurolept-induced tardive dyskinesia

Tardive dyskinesia (TDK) includes orobuccolingual movements and "piano-playing" movements of the limbs. It is a movement disorder of delayed onset that can occur in the setting of neuroleptic treatment as well as in other diseases and following treatment with other drugs. The specific pathophysiology resulting in TDK is still not completely understood but possible mechanisms include postsynaptic dopamine receptor hypersensitivity, abnormalities of striatal gamma-aminobutyric acid (GABA) neurons, and degeneration of striatal cholinergic interneurons. More recently, the theory of synaptic plasticity has been proposed. Considering these proposed mechanisms of disease, therapeutic interventions have attempted to manipulate dopamine, GABA, acetylcholine, norepinephrine and serotonin pathways and receptors. The data for the effectiveness of each class of drugs and the side effects were considered in turn.

Melatonin: an overlooked factor in schizophrenia and in the inhibition of anti-psychotic side effects

This paper reviews melatonin as an overlooked factor in the developmental etiology and maintenance of schizophrenia; the neuroimmune and oxidative pathophysiology of schizophrenia; specific symptoms in schizophrenia, including sleep disturbance; circadian rhythms; and side effects of antipsychotics, including tardive dyskinesia and metabolic syndrome. Electronic databases, i.e. PUBMED, Scopus and Google Scholar were used as sources for this review using keywords: schizophrenia, psychosis, tardive dyskinesia, antipsychotics, metabolic syndrome, drug side effects and melatonin. Articles were selected on the basis of relevance to the etiology, course and treatment of schizophrenia. Melatonin levels and melatonin circadian rhythm are significantly decreased in schizophrenic patients. The adjunctive use of melatonin in schizophrenia may augment the efficacy of antipsychotics through its anti-inflammatory and antioxidative effects. Further, melatonin would be expected to improve sleep disorders in schizophrenia and side effects of anti-psychotics, such as tardive dyskinesia, metaboilic syndrome and hypertension. It is proposed that melatonin also impacts on the tryptophan catabolic pathway via its effect on stress response and cortisol secretion, thereby impacting on cortex associated cognition, amygdala associated affect and striatal motivational processing. The secretion of melatonin is decreased in schizophrenia, contributing to its etiology, pathophysiology and management. Melatonin is likely to have impacts on the metabolic side effects of anti-psychotics that contribute to subsequent decreases in life-expectancy.