Catechol-O-methyltransferase Val158Met polymorphism: modulation of wearing-off susceptibility in a Chinese cohort of Parkinson's disease

Polymorphisms of the dopamine metabolic and signaling pathways are associated with susceptibility to motor levodopa-induced complications (MLIC) in Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

Dopamine replacement therapy remains the gold standard for symptomatic management of Parkinson's disease worldwide. However, most patients will develop debilitating motor levodopa-induced complications (MLIC) in the form of levodopa-induced dyskinesia (LID) and/or motor fluctuations (MF). This study aimed to conduct a systematic review and meta-analysis on the pharmacogenetic association between LID and MF with common genetic variants of the dopamine metabolic and signaling pathways.

METHODS

A meta-analysis was conducted according to the PRISMA guidelines. Extracted studies include case-control studies evaluating the association between SLC6A3/DAT rs28363170 and rs393795; COMT rs4680 and rs4633; MAO-B rs1799836, BDNF rs6265, DRD1 rs4532, DRD2 rs1800497, DRD3 rs6280, and DRD5 rs6283 polymorphisms; and the overall risk of MLIC and its subtypes LID or MF. Genotypic frequency were tested for deviation from the Hardy-Weinberg equilibrium (HWE), and the genetic association was examined using the allelic (a vs. A), recessive (aa vs. Aa + AA), dominant (aa + Aa vs. AA), overdominant (Aa vs. aa + AA), homozygous (aa vs. AA), and heterozygous (Aa vs. AA and aa vs. aA) models.

RESULTS

Fourteen studies were included in the meta-analysis. A significant association was found between COMT rs46809 polymorphisms with LID but not MF, with the association observable in Asians but not Caucasians. In Asians, the COMT rs4633 was significantly associated with the occurrence of both LID and MF. The MAO-B rs1799836 was associated with both MF and LID. Among all the dopamine receptor genes analyzed, only DRD2 exhibited an association with LID. No association was observed between the SLC6AT/DAT and BDNF genes with either LID or MF.

CONCLUSION

Strong associations were observed between polymorphisms of genes regulating dopamine metabolism with the occurrence of LID and/or MF. The MAO-B rs1799836 may be potential for use as a general pharmacogenetic marker of MLIC, while the COMT rs4680 and rs4633 may be used as markers of LID in Asian ethnicities.

Pharmacogenetic profile and the development of the dyskinesia induced by levodopa-therapy in Parkinson's disease patients: a population-based cohort study

Levodopa-induced dyskinesia (LID) is an adverse effect that negatively impacts the quality of life of patients with Parkinson's disease (PD). Studies report that genetic variations in the genes of the pharmacogenetic pathway of the levodopa (L-DOPA) might be associated with LID development. The goal of the present study was to investigate a possible influence of functional genetic variants in the DRD1 (rs4532), DRD2 (rs1800497), DAT1 (rs28363170), and COMT (rs4680) genes with LID development. A total of 220 patients with idiopathic PD were enrolled. The genotyping for DRD1 (rs4532), DRD2 (rs1800497), DAT1 (rs28363170), and COMT (rs4680) polymorphisms were performed using Restriction Fragment Length Polymorphism (PCR-RFLP). Univariate and multivariate analyses were performed to assess the association of these polymorphisms and risk factors with LID development. Multivariate Cox regression analysis showed increased risk to LID development for both Levodopa Dose Equivalency (LED) (Hazard ratios (HR) = 1.001; 95% CI 1.00-1.01; p = 0.009) and individuals carrying the COMT L/L genotype (HR = 2.974; 95% CI 1.12-7.83; p = 0.010). Furthermore, when performed a Cox regression analysis adjusted for a total LED, we observed that the genotype COMT L/L had a 3.84-fold increased risk for LID development (HR = 3.841; 95% CI 1.29-11.37; p = 0.012). Our results suggest that before treating LID in PD patients, it is important to take into consideration genetic variant in the COMT gene, since COMT LL genotype may increase the risk for LID development.

The role of pharmacogenomics in the personalization of Parkinson's disease treatment

Parkinson's disease (PD)-related phenotypes can vary among patients substantially, including response to dopaminergic treatment in terms of efficacy and occurrence of adverse events. Many pharmacogenetic studies have already been conducted to find genetic markers of response to dopaminergic treatment. Integration of genetic and clinical data has already resulted in construction of clinical pharmacogenetic models for prediction of adverse events. However, the results of pharmacogenetic studies are inconsistent. More comprehensive genome-wide approaches are needed to find genetic biomarkers of PD-related phenotypes to better explain the variability in response to treatment. These genetic markers should be integrated with clinical, environmental, imaging, and other omics data to build clinically useful algorithms for personalization of PD management.

Gene polymorphisms and motor levodopa-induced complications in Parkinson's disease

OBJECTIVE

The aim of the study was to evaluate the association of individual and combined single-nucleotide polymorphisms in brain-derived neurotrophic factor (BDNF), dopamine transporter (DAT), and catechol-O-methyltransferase (COMT) genes with the occurrence of motor levodopa-induced complications (MLIC) in Parkinson's disease (PD).

MATERIALS AND METHODS

We studied 76 patients with PD (MLIC occurred in 56.6%) and 60 controls. Allelic discrimination of rs6265 BDNF (Val66Met), rs397595 DAT (SLC6A3), and rs4680 COMT (Val158Met) genes were genotyped. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using multinominal logistic regression. Orthogonal partial least squares (OPLS) analysis and OPLS discriminant analysis (OPLS-DA) were used to analyze qualitative genetic data.

RESULTS

The risk of PD in subjects with the AG BDNF genotype was increased sixfold (OR = 6.12, 95% CI = 2.88-13.02, p < .0001), and AG BDNF and AG DAT genotypes were correlated with PD in OPLS-DA (VIP > 1). There were no differences in distributions of BDNF, DAT and COMT genotypes between PD groups with and without MLIC, while OPLS model showed that genotype combination of AG BDNF, AG DAT, and GG COMT was correlated with MLIC and genotypes combination of GG BDNF, AA DAT, and AA COMT with lack of MLIC in PD patients (VIP > 1).

CONCLUSIONS

Our results confirmed the association of rs6265 BDNF (Val66Met) with the risk of PD and suggest a synergic effect of rs6265 BDNF (Val66Met), rs397595 DAT (SLC6A3), and rs4680 COMT (Val158Met) polymorphisms on the occurrence of MLIC.

Dopaminergic Pathway Genes Influence Adverse Events Related to Dopaminergic Treatment in Parkinson's Disease

Dopaminergic pathway is the most disrupted pathway in the pathogenesis of Parkinson's disease. Several studies reported associations of dopaminergic genes with the occurrence of adverse events of dopaminergic treatment. However, none of these studies adopted a pathway based approach. The aim of this study was to comprehensively evaluate the influence of selected single nucleotide polymorphisms of key dopaminergic pathway genes on the occurrence of motor and non-motor adverse events of dopaminergic treatment in Parkinson's disease. In total, 231 Parkinson's disease patients were enrolled. Demographic and clinical data were collected. Genotyping was performed for 16 single nucleotide polymorphisms from key dopaminergic pathway genes. Logistic and Cox regression analyses were used for evaluation. Results were adjusted for significant clinical data. We observed that carriers of at least one COMT rs165815 C allele had lower odds for developing visual hallucinations (OR = 0.34; 95% CI = 0.16-0.72; p = 0.004), while carriers of at least one DRD3 rs6280 C allele and CC homozygotes had higher odds for this adverse event (OR = 1.88; 95% CI = 1.00-3.54; p = 0.049 and OR = 3.31; 95% CI = 1.37-8.03; p = 0.008, respectively). Carriers of at least one DDC rs921451 C allele and CT heterozygotes had higher odds for orthostatic hypotension (OR = 1.86; 95% CI = 1.07-3.23; p = 0.028 and OR = 2.30; 95% CI = 1.26-4.20; p = 0.007, respectively). Heterozygotes for DDC rs3837091 and SLC22A1 rs628031 AA carriers also had higher odds for orthostatic hypotension (OR = 1.94; 95% CI = 1.07-3.51; p = 0.028 and OR = 2.57; 95% CI = 1.11-5.95; p = 0.028, respectively). Carriers of the SLC22A1 rs628031 AA genotype had higher odds for peripheral edema and impulse control disorders (OR = 4.00; 95% CI = 1.62-9.88; p = 0.003 and OR = 3.16; 95% CI = 1.03-9.72; p = 0.045, respectively). Finally, heterozygotes for SLC22A1 rs628031 and carriers of at least one SLC22A1 rs628031 A allele had lower odds for dyskinesia (OR = 0.48; 95% CI = 0.24-0.98, p = 0.043 and OR = 0.48; 95% CI = 0.25-0.92; p = 0.027, respectively). Gene-gene interactions, more specifically DDC-COMT, SLC18A2-SV2C, and SLC18A2-SLC6A3, also significantly influenced the occurrence of some adverse events. Additionally, haplotypes of COMT and SLC6A3 were associated with the occurrence of visual hallucinations (AT vs. GC: OR = 0.34; 95% CI = 0.16-0.72; p = 0.005) and orthostatic hypotension (ATG vs. ACG: OR = 2.48; 95% CI: 1.01-6.07; p = 0.047), respectively. Pathway based approach allowed us to identify new potential candidates for predictive biomarkers of adverse events of dopaminergic treatment in Parkinson's disease, which could contribute to treatment personalization.

Clinimetrics of the 9- and 19-Item Wearing-Off Questionnaire: A Systematic Review

The treatment of Parkinson's disease (PD) with dopaminergic therapy improves functionality and quality of life. However, as the disease progresses, the wearing-off phenomenon develops, which necessitates complex posology adjustment or adjuvant therapy. This phenomenon may not be well recognized, especially if it is mild or involves nonmotor symptoms. Questionnaires were developed to improve the recognition of the wearing-off phenomenon. The questionnaires consist of a list of symptoms that patients must check if they have and if the symptoms improve with medication. A recent review by the Movement Disorder Society suggested the 19-item (WOQ-19) and 9-item (WOQ-9) questionnaires as screening tools for the wearing-off phenomenon. However, there has not been a systematic review to assess the questionnaires' clinimetric properties, such as sensitivity, specificity, test-retest reliability, and responsiveness. We conducted an extensive search for studies using these two tools. We identified 3 studies using WOQ-19 and 5 studies using WOQ-9. Both questionnaires seem to have good sensitivity (0.81–1). WOQ-19 has variable specificity (0.39–0.8), depending on the number of positive items, while WOQ-9 lacks specificity (0.1–0.69). Only one study using WOQ-19 reported test-retest, and only two studies reported responsiveness. Thus, this report describes the first independent systematic review to exam quantitatively the clinimetric properties of these two questionnaires.

From Genomics to Omics Landscapes of Parkinson's Disease: Revealing the Molecular Mechanisms

Molecular mechanisms of Parkinson's disease (PD) have already been investigated in various different omics landscapes. We reviewed the literature about different omics approaches between November 2005 and November 2017 to depict the main pathological pathways for PD development. In total, 107 articles exploring different layers of omics data associated with PD were retrieved. The studies were grouped into 13 omics layers: genomics-DNA level, transcriptomics, epigenomics, proteomics, ncRNomics, interactomics, metabolomics, glycomics, lipidomics, phenomics, environmental omics, pharmacogenomics, and integromics. We discussed characteristics of studies from different landscapes, such as main findings, number of participants, sample type, methodology, and outcome. We also performed curation and preliminary synthesis of multiple omics data, and identified overlapping results, which could lead toward selection of biomarkers for further validation of PD risk loci. Biomarkers could support the development of targeted prognostic/diagnostic panels as a tool for early diagnosis and prediction of progression rate and prognosis. This review presents an example of a comprehensive approach to revealing the underlying processes and risk factors of a complex disease. It urges scientists to structure the already known data and integrate it into a meaningful context.

A systematic review and integrative approach to decode the common molecular link between levodopa response and Parkinson's disease

Background

PD is a progressive neurodegenerative disorder commonly treated by levodopa. The findings from genetic studies on adverse effects (ADRs) and levodopa efficacy are mostly inconclusive. Here, we aim to identify predictive genetic biomarkers for levodopa response (LR) and determine common molecular link with disease susceptibility. A systematic review for LR was conducted for ADR, and drug efficacy, independently. All included articles were assessed for methodological quality on 14 parameters. GWAS of PD were also reviewed. Protein-protein interaction (PPI) analysis using STRING and functional enrichment using WebGestalt was performed to explore the common link between LR and PD.

Results

From 37 candidate studies on levodopa toxicity, 18 genes were found associated, of which, CA_n STR 13, 14 (DRD2) was most significantly associated with dyskinesia, followed by rs1801133 (MTHFR) with hyper-homocysteinemia, and rs474559 (HOMER1) with hallucination. Similarly, 8 studies on efficacy resulted in 4 genes in which rs28363170, rs3836790 (SLC6A3) and rs4680 (COMT), were significant. To establish the molecular connection between LR with PD, we identified 35 genes significantly associated with PD. With 19 proteins associated with LR and 35 with PD, two independent PPI networks were constructed. Among the 67 nodes (263 edges) in LR, and 62 nodes (190 edges) in PD pathophysiology, UBC, SNCA, FYN, SRC, CAMK2A, and SLC6A3 were identified as common potential candidates.

Conclusion

Our study revealed the genetically significant polymorphism concerning the ADRs and levodopa efficacy. The six common genes may be used as predictive markers for therapy optimization and as putative drug target candidates.

Electronic supplementary material

The online version of this article (10.1186/s12920-017-0291-0) contains supplementary material, which is available to authorized users.

Roles of functional catechol-O-methyltransferase genotypes in Chinese patients with Parkinson's disease

Background

Recent studies have found that the functional catechol-O-methyltransferase (COMT) gene may be associated with the susceptibility to and pharmacotherapy of Parkinson’s disease (PD). In this case–control study, we investigated the most common functional COMT gene haplotypes that had been shown to influence COMT enzymatic activity and the association of the single and combined COMT haplotypes with clinical symptoms and pharmacotherapy in Chinese patients with PD.

Methods

One hundred forty-three patients with idiopathic PD and 157 healthy individuals were enrolled in this study. Four single nucleotide polymorphisms (SNPs) in the COMT gene (formed by SNPs) were genotyped in each participant: rs6269 A > G; rs4633 C > T; rs4818 C > G; and rs4680 G > A.

Results

The frequencies of rs4633 T carriers, rs4680 A carriers and the two linked rs4633-rs4680 T/A carriers were significantly higher in the early onset PD group than in the healthy controls (all P < 0.05). Homozygosity for rs4633 (TT), rs4680 (AA) and of the two linked rs4633-rs4680 (TT/AA) was significantly more frequent in patients who exhibited the “wearing-off” phenomenon, longer disease duration, higher levodopa equivalent doses (LED) and higher Unified Parkinson’s Disease Rating Scale (UPDRS) scores (P < 0.05). No significant differences were observed in the clinical features of patients who carried individual rs6269 and rs4818, the two linked rs6269-rs4818 and the four combined COMT SNPs.

Conclusions

The results showed a possible association of combined functional COMT SNPs with PD risk, disease duration, the “wearing-off” phenomenon, daily LEDs and higher UPDRS scores, which may be useful in instituting individualized therapy for patients with PD.

Electronic supplementary material

The online version of this article (doi:10.1186/s40035-017-0081-9) contains supplementary material, which is available to authorized users.

Pharmacogenetics of Parkinson's Disease in Clinical Practice

Background

Pharmacogenetics aims to identify the genetic factors participating in the heterogeneity of drug response. The ultimate goal is to provide personalized treatment by identifying responders and non-responders, individuals at risk of developing drug adverse effects, and by adjusting dosage. Several studies have been performed in Parkinson's disease (PD), to investigate drug response variability according to genetic factors for dopamine replacement therapies.

Methods

We performed a systematic literature search of articles related to pharmacogenetic studies in PD, and found 47 studies.

Findings

Motor response and adverse reactions to dopaminergic drugs were associated with genes encoding enzymes of their metabolism as well as their receptors or targets. Despite some interesting results, considerable work remains to be done to replicate and validate their clinical relevance before translation into clinical practice.

Conclusions

There are currently no guidelines published for pharmacogenetic factors related to PD drugs. More research is need in this field in order to improve our knowledge in drug response variability in PD. Algorithms taking into account clinical, pharmacological, and genetic factors are probably the most promising way to help for a personalized medicine in PD.

How close are we to individualized medicine for Parkinson's disease?

INTRODUCTION

There is a considerable inter-individual heterogeneity in clinical features, disease course, and treatment response in Parkinson's disease (PD), which can be explained not only by disease process and clinical variables, but also by an impact from genetic factors. Evidence-based medicine relies on large randomized control trials and meta-analysis-average medicine, which ignores individual differences. However, we are now in the early phases of a paradigm shift in medicine relating to individuality and variability. The purpose of individualized medicine is to predict patients' responses to targeted therapy using diagnostic tests based on genetics or other molecular mechanisms, thus providing the right drug at the right dose at the right time.

AREAS COVERED

In this article, we outline current state of individualized medicine for PD. Expert Commentary: Pharmacogenomics, an important element of individualized medicine, is just beginning to be considered in PD. To advance the clinical use of pharmacogenomics, big data cohort for genomic research and multidisciplinary team approaches are necessary.

Advances in understanding genomic markers and pharmacogenetics of Parkinson's disease

INTRODUCTION

The inheritance pattern of Parkinson's disease (PD) is likely multifactorial (owing to the interplay of genetic predisposition and environmental factors). Many pharmacogenetic studies have tried to establish a possible role of candidate genes in PD risk. Several studies have focused on the influence of genes in the response to antiparkinsonian drugs and in the risk of developing side-effects of these drugs.

AREAS COVERED

This review presents an overview of current knowledge, with particular emphasis on the most recent advances, both in case-control association studies on the role of candidate genes in the risk for PD as well as pharmacogenetic studies on the role of genes in the development of side effects of antiparkinsonian drugs. The most reliable results should be derived from meta-analyses of case-control association studies on candidate genes involving large series of PD patients and controls, and from genome-wide association studies (GWAS).

EXPERT OPINION

Prospective studies of large samples involving several genes with a detailed history of exposure to environmental factors in the same cohort of subjects, should be useful to clarify the role of genes in the risk for PD. The results of studies on the role of genes in the development of side-effects of antiparkinsonian drugs should, at this stage, only be considered preliminary.

Clinical implications of neuropharmacogenetics

INTRODUCTION

Pharmacogenetics aims to identify the underlying genetic factors participating in the variability of drug response. Indeed, genetic variability at the DNA or RNA levels can directly or indirectly modify the pharmacokinetic or the pharmacodynamic parameters of a drug. The ultimate aim of pharmacogenetics is to move towards a personalised medicine by predicting responders and non-responders, adjusting the dose of the treatment, and identifying individuals at risk of adverse drug effects.

METHODS

A literature research was performed in which we reviewed all pharmacogenetic studies in neurological disorders including neurodegenerative diseases, multiple sclerosis, stroke and epilepsy.

RESULTS

Several pharmacogenetic studies have been performed in neurology, bringing insights into the inter-individual drug response variability and in the pathophysiology of neurological diseases. The principal implications of these studies for the management of patients in clinical practice are discussed.

CONCLUSION/DISCUSSION

Although several genetic factors have been identified in the modification of drug response in neurological disorders, most of them have a marginal predictive effect at the single gene level, suggesting mutagenic interactions as well as other factors related to drug interaction and disease subtypes. Most pharmacogenetic studies deserve further replication in independent populations and, ideally, in pharmacogenetic clinical trials to demonstrate their relevance in clinical practice.

Risk factors and safe dosage of levodopa for wearing-off phenomenon in Chinese patients with Parkinson's disease

The objective of this study was to investigate the risk factors of wearing-off phenomenon in Parkinson's disease (PD) and propose safe dosage of levodopa to reduce wearing-off development based on Chinese cohort. Patients with PD who had taken levodopa (L-dopa) for at least 1 month were recruited. Wearing-off was diagnosed based on validated Chinese version of a patient self-rated 9-question Wearing-Off Questionnaire (WOQ-9) and clinical definition. Eleven variables (gender, disease duration at L-dopa initiation, disease duration at assessment, age at onset, age at assessment, H-Y stage, UPDRS III, L-dopa daily total dosage and dosage adjusted to weight, duration of L-dopa treatment, initial drug recipe) were included in our analysis. Univariate analysis, multivariate logistic regression analysis and decision tree classification model(DTC) were used to detect risk factors of wearing-off. Receiver operating characteristic (ROC) curve and DTC were used to investigate cut-off value of L-dopa to best predict wearing-off. Two hundred and thirty-four patients were investigated in our study, among whom 111 developed wearing-off. Patients with wearing-off tended to receive higher L-dopa dosage and endure longer duration of L-dopa treatment. L-Dopa dosage as 281 mg/day and 4.2 mg/kg/day by ROC, as well as 269 mg/day and 3.2 mg/kg/day by DTC were cut-off values for wearing-off. L-Dopa dosage and duration of L-dopa treatment were related to increased wearing-off development. Cumulative L-dopa dosage and L-dopa daily dosage were better predictive of wearing-off. Inadequate evidence was present for delayed L-dopa initiation. L-Dopa daily dosage no more than 275 mg or 4.2 mg/kg was regarded as safe.