MAO-B and COMT Genetic Variations Associated With Levodopa Treatment Response in Patients With Parkinson's Disease

Sex Differences in the Speech of Persons With and Without Parkinson's Disease

BACKGROUND

Sex differences are apparent in the prevalence and the clinical presentation of Parkinson's disease (PD), but their effects on speech have been less studied.

METHOD

Speech acoustics of persons with (34 females and 34 males) and without (age- and sex-matched) PD were examined, assessing the effects of PD diagnosis and sex on ratings of dysarthria severity and acoustic measures of phonation (fundamental frequency standard deviation, smoothed cepstral peak prominence), speech rate (net syllables per second, percent pause ratio), and articulation (articulatory-acoustic vowel space, release burst precision).

RESULTS

Most measures were affected by PD (dysarthria severity, fundamental frequency standard deviation) and sex (smoothed cepstral peak prominence, net syllables per second, percent pause ratio, articulatory-acoustic vowel space), but without interactions between them. Release burst precision was differentially affected by sex in PD. Relative to those without PD, persons with PD produced fewer plosives with a single burst: females more frequently produced multiple bursts, whereas males more frequently produced no burst at all.

CONCLUSIONS

Most metrics did not indicate that speech production is differentially affected by sex in PD. Sex was, however, associated with disparate effects on release burst precision in PD, which deserves further study.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.24388666.

Gene Signals and SNPs Associated with Parkinson's Disease: A Nutrigenomics and Computational Prospective Insights

Parkinson's disease is the most prevalent chronic neurodegenerative disease. Neurological conditions for PD were influenced by a variety of epigenetic factors and SNPs in some of the coexisting genes that were expressed. This article focused on nutrigenomics of PD and the prospective highlighting of how these genes are regulated in terms of nutritive factors and the genetic basis of PD risk, onset, and progression. Multigenetic associations of the following genetic alterations in the genes of SNCA, LRRK2, UCHL1, PARK2,PINK1, DJ-1, and ATP13A2 have been reported with the familial and de novo genetic origins of PD. Over the past two decades, significant attempts have been made to understand the biological mechanisms that are potential causes for this disease, as well as to identify therapeutic substances for the prevention and management of PD. Nutrigenomics has sparked considerable interest due to its nutritional, safe, and therapeutic effects on a variety of chronic diseases. In this study, we summarise some of the nutritive supplements that have an impact on PD.

Sex differences in alpha-synucleinopathies: a systematic review

Background

Past research indicates a higher prevalence, incidence, and severe clinical manifestations of alpha-synucleinopathies in men, leading to a suggestion of neuroprotective properties of female sex hormones (especially estrogen). The potential pathomechanisms of any such effect on alpha-synucleinopathies, however, are far from understood. With that aim, we undertook to systematically review, and to critically assess, contemporary evidence on sex and gender differences in alpha-synucleinopathies using a bench-to-bedside approach.

Methods

In this systematic review, studies investigating sex and gender differences in alpha-synucleinopathies (Rapid Eye Movement (REM) Behavior Disorder (RBD), Parkinson's Disease (PD), Dementia with Lewy Bodies (DLB), Multiple System Atrophy (MSA)) from 2012 to 2022 were identified using electronic database searches of PubMed, Embase and Ovid.

Results

One hundred sixty-two studies were included; 5 RBD, 6 MSA, 20 DLB and 131 PD studies. Overall, there is conclusive evidence to suggest sex-and gender-specific manifestation in demographics, biomarkers, genetics, clinical features, interventions, and quality of life in alpha-synucleinopathies. Only limited data exists on the effects of distinct sex hormones, with majority of studies concentrating on estrogen and its speculated neuroprotective effects.

Conclusion

Future studies disentangling the underlying sex-specific mechanisms of alpha-synucleinopathies are urgently needed in order to enable novel sex-specific therapeutics.

An update on the pharmacogenetic considerations when prescribing dopamine receptor agonists for Parkinson's disease

INTRODUCTION

Parkinson's disease is a chronic neurodegenerative multisystemic disorder that affects approximately 2% of the population over 65 years old. This disorder is characterized by motor symptoms which are frequently accompanied by non-motor symptoms such as cognitive disorders. Current drug therapies aim to reduce the symptoms and increase the patient's life expectancy. Nevertheless, there is heterogeneity in therapy response in terms of efficacy and adverse effects. This wide range in response may be linked to genetic variability. Thus, it has been suggested that pharmacogenomics may help to tailor and personalize drug therapy for Parkinson's disease.

AREAS COVERED

This review describes and updates the clinical impact of genetic factors associated with the efficacy and adverse drug reactions related to common medications used to treat Parkinson's disease. Additionally, we highlight current informative recommendations for the drug treatment of Parkinson's disease.

EXPERT OPINION

The pharmacokinetic, pharmacodynamic, and safety profiles of Parkinson's disease drugs do not favor the development of pharmacogenetic tests with a high probability of success. The chances of obtaining ground-breaking pharmacogenetics biomarkers for Parkinson's disease therapy are limited. Nevertheless, additional information on the metabolism of certain drugs, and an analysis of the potential of pharmacogenetics in novel drugs could be of interest.

Sex and gender differences in Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis: a narrative review

Neurodegenerative diseases (NDs), including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), exhibit high phenotypic variability and they are very common in the general population. These diseases are associated with poor prognosis and a significant burden on patients and their caregivers. Although increasing evidence suggests that biological sex is an important factor for the development and phenotypical expression of some NDs, the role of sex and gender in the diagnosis and prognosis of NDs has been poorly explored. Current knowledge relating to sex- and gender-related differences in the epidemiology, clinical features, biomarkers, and treatment of AD, PD, and ALS will be summarized in this narrative review. The cumulative evidence hitherto collected suggests that sex and gender are factors to be considered in explaining the heterogeneity of these NDs. Clarifying the role of sex and gender in AD, PD, and ALS is a key topic in precision medicine, which will facilitate sex-specific prevention and treatment strategies to be implemented in the near future.

Association of Catechol-O-Methyltransferase Gene Polymorphisms and Haplotypes in the Levodopa-Induced Adverse Events in Subjects with Parkinson's Disease

The presence of dyskinesia is the most common side effect of chronic administration of levodopa in Parkinson's disease (PD) subjects. Genetic polymorphisms in levodopa metabolizing gene, catechol-O-methyl transferase (COMT), is shown to influence the inter-individual variability in drug response and adverse events. In the present study, the association of COMT rs6269, rs4633, rs4818, and rs4680 polymorphisms and haplotypes on pharmacokinetics and adverse events with levodopa was investigated in 150 PD patients. The age of onset of PD was 58.00 ± 10 yrs. The most common side effect faced by 78% of the subjects was dyskinesia. The AUC of levodopa was found to be significantly higher in subjects with dyskinesia (1695 ± 113 ng/ml/hr, p < 0.0001) than those without dyskinesia (1550 ± 122 ng/ml/hr). We found that the frequency of subjects presenting dyskinesia was significantly higher in subjects carrying variant genotype of COMT rs6269, rs4633, and rs4680 than that with wild genotype and these subjects presented higher AUC of levodopa. In addition, in subjects with dyskinesia, the AUC of levodopa was found to be significantly higher with low COMT (ACCG) haplotype. The association of COMT rs6269, COMT rs4633, COMT rs4818, and COMT rs4680 variant genotypes with the risk of dyskinesia due to levodopa therapy showed an ROC AUC of 0.67 indicating the moderate prediction of dyskinesia (p = 0.0021) with these COMT variants. In conclusion, PD subjects carrying the variant genotypes of COMT strongly influence high levodopa-induced dyskinesia. Hence the genotyping of COMT before the levodopa therapy will be useful to reduce the adverse events associated with the chronic levodopa treatment.

Sex and Gender Differences in Neurodegenerative Diseases: Challenges for Therapeutic Opportunities

The term “neurodegenerative diseases” (NDs) identifies a group of heterogeneous diseases characterized by progressive loss of selectively vulnerable populations of neurons, which progressively deteriorates over time, leading to neuronal dysfunction. Protein aggregation and neuronal loss have been considered the most characteristic hallmarks of NDs, but growing evidence confirms that significant dysregulation of innate immune pathways plays a crucial role as well. NDs vary from multiple sclerosis, in which the autoimmune inflammatory component is predominant, to more “classical” NDs, such as Parkinson’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis, and spinal muscular atrophy. Of interest, many of the clinical differences reported in NDs seem to be closely linked to sex, which may be justified by the significant changes in immune mechanisms between affected females and males. In this review, we examined some of the most studied NDs by looking at their pathogenic and phenotypical features to highlight sex-related discrepancies, if any, with particular interest in the individuals’ responses to treatment. We believe that pointing out these differences in clinical practice may help achieve more successful precision and personalized care.

Associations between variants in levodopa metabolic pathway genes and levodopa-induced dyskinesia in Parkinson's disease

INTRODUCTION

Levodopa-induced dyskinesia (LID) is a common motor complication in Parkinson's disease (PD). Several genes in the levodopa metabolic pathway, such as COMT, DRDx and MAO-B, were reported associated with LID. However, there has been no systematic analyses between common variants in levodopa metabolic pathway genes and LID in a large sample of the Chinese population.

METHODS

Through the whole exome sequencing (WES) and target region sequencing, we aimed to explore the potential associations between common single nucleotide polymorphisms (SNPs) in the levodopa metabolic pathway and LID in Chinese PD individuals. Five hundred and two PD individuals were enrolled in our study, among them, 348 individuals underwent WES, and 154 individuals underwent target region sequencing. We acquired the genetic profile of 11 genes including COMT, DDC, DRD1-5, SLC6A3, TH and MAO-A/B. We established a stepwise strategy to filter SNPs, which finally included 34 SNPs in our analyses. And we used a two-stage study, with discovery (348 individuals with WES) and the replication (all 502 individuals) to confirm our findings.

RESULTS

Among the 502 PD individuals, 104 (20.7%) were diagnosed with LID. In the discovery stage, we found that COMT rs6269, DRD2 rs6275 and DRD2 rs1076560 were associated with LID. In the replication stage, associations between the three above-mentioned SNPs and LID were still present in all 502 individuals.

CONCLUSION

We demonstrated that in the Chinese population, COMT rs6269, DRD2 rs6275 and rs1076560 were significantly associated with LID. And rs6275 was reported associated with LID for the first time.

Costunolide and Parthenolide Ameliorate MPP+ Induced Apoptosis in the Cellular Parkinson's Disease Model

Monoamine oxidase B (MAO-B) is an enzyme that metabolizes several chemicals, including dopamine. MAO-B inhibitors are used in the treatment of Parkinson's Disease (PD), and the inhibition of this enzyme reduces dopamine turnover and oxidative stress. The absence of dopamine results in PD pathogenesis originating from decreased Acetylcholinesterase (AChE) activity and elevated oxidative stress. Here, we performed a molecular docking analysis for the potential use of costunolide and parthenolide terpenoids as potential MAO-B inhibitors in the treatment of PD. Neuroprotective properties of plant-originated costunolide and parthenolide terpenoids were investigated in a cellular PD model that was developed by using MPP⁺ toxicity. We investigated neuroprotection mechanisms through the analysis of oxidative stress parameters, acetylcholinesterase activity and apoptotic cell death ratios. Our results showed that 100 µg/mL and 50 µg/mL of costunolide, and 50 µg/mL of parthenolide applied to the cellular disease model ameliorated the cytotoxicity caused by MPP⁺ exposure. We found that acetylcholinesterase activity assays exhibited that terpenoids could ameliorate and restore the enzyme activity as in negative control levels. The oxidative stress parameter analyses revealed that terpenoid application could enhance antioxidant levels and decrease oxidative stress in the cultures. In conclusion, we reported that these two terpenoid molecules could be used in the development of efficient treatment strategies for PD patients.

Association of Catechol-O-Methyltransferase Gene rs4680 Polymorphism and Levodopa Induced Dyskinesia in Parkinson's Disease: A Meta-Analysis and Systematic Review

INTRODUCTION

Long-term levodopa therapy for Parkinson's disease (PD) can cause levodopa induced dyskinesia (LID). Genetic predisposition has a significant role to play in inter-individual heterogeneity in the clinical manifestation of LID. Despite accumulating evidence for the role of COMT gene polymorphism (rs4680) as a genetic basis for LID, to date results have been inconsistent. Early assessment of the Catechol-O-Methyltransferase (COMT) genotype might be helpful to stratify PD patients concerning their individual risk for LID.

METHOD

In this meta-analysis, we have used 9 studies, which were selected through online databases. Statistical analysis was performed using R (v-3.6) software. 5 genetic models have been used in the present study: Allele model (A vs. G), Dominant model (AA+AG vs. GG), Homozygote model (AA vs. GG), Co-dominant/heterozygote model (AG vs. GG), and Recessive model (AA vs. AG + GG).

RESULTS

The results indicated a significant association between COMT rs4680 (Val158Met) polymorphism and LID risk. The genotype AA of COMT rs4680 is a risk factor for LID in PD patients under the recessive model (AA vs GG+AG) in the random-effect model. Analysis based on ethnicity showed that COMT rs4680 SNP allele A is a risk factor for LID development in Asian PD patients, while GG genotype is a risk factor for LID development in non-Asian PD patients using different genetic models.

CONCLUSION

The results of the present meta-analysis support that the COMT Val158Met polymorphism is a risk factor for the development of LID in PD patients having ethnic variations.

Pharmacogenomics-a New Frontier for Individualized Treatment of Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease with a significant public health burden. It is characterized by the gradual degeneration of dopamine neurons in the central nervous system. Although symptomatic pharmacological management remains the primary therapeutic method for PD, clinical experience reveals significant inter-individual heterogeneity in treatment effectiveness and adverse medication responses. The mechanisms behind the observed interindividual variability may be elucidated by investigating the role of genetic variation in human-to-human variances in medication responses and adverse effects.

OBJECTIVE

This review aims to explore the impact of gene polymorphism on the efficacy of antiparkinsonian drugs. The identification of factors associated with treatment effectiveness variability might assist the creation of a more tailored pharmacological therapy with higher efficacy, fewer side outcomes, and cheaper costs.

METHODS

In this review, we conducted a thorough search in databases such as PubMed, Web of Science, and Google Scholar, and critically examined current discoveries on Parkinson's disease pharmacogenetics. The ethnicity of the individuals, research methodologies, and potential bias of these studies were thoroughly compared, with the primary focus on consistent conclusions.

RESULTS

This review provides a summary of the existing data on PD pharmacogenetics, identifies its limitations, and offers insights that may be beneficial for future research. Previous studies have investigated the impact of gene polymorphism on the effectiveness and adverse effects of levodopa. The trendiest genes are the COMT gene, DAT gene, and DRD2 gene. However, limited study on other anti-Parkinson's drugs has been conducted.

CONCLUSION

Therefore, In order to develop an individualized precision treatment for PD, it is an inevitable trend to carry out multi-center, prospective, randomized controlled clinical trials of PD pharmacogenomics covering common clinical anti-PD drugs in large, homogeneous cohorts.

Computational Studies Applied to Linalool and Citronellal Derivatives Against Alzheimer's and Parkinson's Disorders: A Review with Experimental Approach

Alzheimer's and Parkinson's are neurodegenerative disorders that affect a great number of people around the world, seriously compromising the quality of life of individuals, due to motor and cognitive damage. In these diseases, pharmacological treatment is used only to alleviate symptoms. This emphasizes the need to discover alternative molecules for use in prevention. Using Molecular Docking, this review aimed to evaluate the anti-Alzheimer's and anti-Parkinson's activity of linalool and citronellal, as well as their derivatives. Before performing Molecular Docking simulations, the compounds' pharmacokinetic characteristics were evaluated. For Molecular Docking, 7 chemical compounds derived from citronellal, and 10 compounds derived from linalool, and molecular targets involved in Alzheimer's and Parkinson's pathophysiology were selected. According to the Lipinski rules, the compounds under study presented good oral absorption and bioavailability. For toxicity, some tissue irritability was observed. For Parkinson-related targets, the citronellal and linalool derived compounds revealed excellent energetic affinity for α-Synuclein, Adenosine Receptors, Monoamine Oxidase (MAO), and Dopamine D1 receptor proteins. For Alzheimer disease targets, only linalool and its derivatives presented promise against BACE enzyme activity. The compounds studied presented high probability of modulatory activity against the disease targets under study, and are potential candidates for future drugs.

Genetic architecture of Parkinson’s disease subtypes – Review of the literature

The heterogeneity of Parkinson’s disease (PD) has been recognized since its description by James Parkinson over 200 years ago. The complexity of motor and non-motor PD manifestations has led to many attempts of PD subtyping with different prognostic outcomes; however, the pathophysiological foundations of PD heterogeneity remain elusive. Genetic contributions to PD may be informative in understanding the underpinnings of PD subtypes. As such, recognizing genotype-phenotype associations may be crucial for successful gene therapy. We review the state of knowledge on the genetic architecture underlying PD subtypes, discussing the monogenic forms, as well as oligo- and polygenic risk factors associated with various PD subtypes. Based on our review, we argue for the unification of PD subtyping classifications, the dichotomy of studies on genetic factors and genetic modifiers of PD, and replication of results from previous studies.

Levodopa responsiveness in Parkinson's disease: harnessing real-life experience with machine-learning analysis

Responsiveness to levodopa varies greatly among patients with Parkinson's disease (PD). The factors that affect it are ill defined. The aim of the study was to identify factors predictive of long-term response to levodopa. The medical records of 296 patients with PD (mean age of onset, 62.2 ± 9.7 years) were screened for demographics, previous treatments, and clinical phenotypes. All patients were assessed with the Unified PD Rating Scale (UPDRS)-III before and 3 months after levodopa initiation. Regression and machine-learning analyses were used to determine factors that are associated with levodopa responsiveness and might identify patients who will benefit from treatment. The UPDRS-III score improved by ≥ 30% (good response) in 128 patients (43%). On regression analysis, female gender, young age at onset, and early use of dopamine agonists predicted a good response. Time to initiation of levodopa treatment had no effect on responsiveness except in patients older than 72 years, who were less responsive. Machine-learning analysis validated these factors and added several others: symptoms of rigidity and bradykinesia, disease onset in the legs and on the left side, and fewer white vascular ischemic changes, comorbidities, and pre-non-motor symptoms. The main determinants of variations in levodopa responsiveness are gender, age, and clinical phenotype. Early use of dopamine agonists does not hamper levodopa responsiveness. In addition to validating the regression analysis results, machine-learning methods helped to determine the specific clinical phenotype of patients who may benefit from levodopa in terms of comorbidities and pre-motor and non-motor symptoms.

Sex and gender differences in movement disorders: Parkinson's disease, essential tremor, dystonia and chorea

Sex and gender-based differences in epidemiology, clinical features and therapeutical responses are emerging in several movement disorders, even though they are still not widely recognized. In this chapter, we summarize the most relevant evidence concerning these differences in Parkinson's disease, essential tremor, dystonia and chorea. Indeed, both sex-related biological (hormonal levels fluctuations) and gender-related variables (socio-cultural and environmental factors) may differently impact symptoms manifestation and severity, phenotype and disease progression of movement disorders on men and women. Moreover, sex differences in treatment responses should be taken into account in any therapeutical planning. Physicians need to be aware of these major differences between men and women that will eventually have a major impact on better tailoring prevention, treatment, or even delaying progression of the most common movement disorders.

Sex Differences in Parkinson’s Disease: From Bench to Bedside

Background: Parkinson’s disease (PD) is the second most common neurodegenerative disorder after Alzheimer’s disease and gender differences have been described on several aspects of PD. In the present commentary, we aimed to collect and discuss the currently available evidence on gender differences in PD regarding biomarkers, genetic factors, motor and non-motor symptoms, therapeutic management (including pharmacological and surgical treatment) as well as preclinical studies. Methods: A systematic literature review was performed by searching the Pubmed and Scopus databases with the search strings “biomarkers”, “deep brain stimulation”, “female”, “gender”, “genetic”, “levodopa”, “men”, “male”, “motor symptoms”, “non-motor symptoms”, “Parkinson disease”, “sex”, “surgery”, and “women”. Results: The present review confirms the existence of differences between men and women in Parkinson Disease, pointing out new information regarding evidence from animal models, genetic factors, biomarkers, clinical features and pharmacological and surgical treatment. Conclusions: The overall goal is to acquire new informations about sex and gender differences in Parkinson Disease, in order to develop tailored intervetions.

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.

Functional MAOB Gene Intron 13 Polymorphism Predicts Dyskinesia in Parkinson’s Disease

Identification of individual risk factors for motor complications in Parkinson's disease (PD) can help to guide personalised medical treatment, particularly since treatment options are still limited. To determine whether common functional gene polymorphisms in the dopamine metabolism predict the onset of motor complications in PD, we performed a retrospective, observer-blinded follow-up study of 30 PD patients who underwent genotyping of dopa-decarboxylase (DDC; rs921451), monoamine oxidase B (MAOB; rs1799836), catechol-O-methyltransferase (COMT; rs4680), and dopamine transporter (DAT; variable number tandem repeat) polymorphisms. Onset of wearing-off and dyskinesias was determined by blinded clinical assessments. Predictive values of genotypes for motor complications were evaluated using Cox proportional hazard models. During a median follow-up time of 11.6 years, 23 (77%) of 30 PD patients developed wearing-off, 16 (53%) dyskinesias, and 23 (77%) any motor complication. The MAOB (rs1799836) polymorphism predicted development of dyskinesias with MAOB^CC/(C)/CT genotypes (resulting in low/intermediate brain enzyme activity) being associated with lower hazard ratios (unadjusted HR [95% CI]: 0.264 [0.089–0.787]; p=0.012; adjusted HR [95% CI]: 0.142 [0.039–0.520]; p=0.003) than MAOB^TT/(T) genotypes (resulting in high brain enzyme activity). DDC (rs921451), COMT (rs4680), and DAT (VNTR) polymorphisms were not predictive of motor complications. Together, the MAOB (rs1799836) polymorphism predicts the development of dyskinesias in PD patients. Our results need confirmation in larger cohorts. If confirmed, individual assessment of this polymorphism might be helpful for early risk stratification and could comprise a step towards patient-tailored therapeutic strategies to prevent or delay motor complications in the course of PD.

The Role of Single Nucleotide Polymorphisms of Monoamine Oxidase B, Dopamine D2 Receptor, and DOPA Decarboxylase Receptors Among Patients Treated for Parkinson's Disease

This study aimed to investigate the association between selected variants of genes related to dopamine metabolism pathways and the risk of and progression of Parkinson’s disease (PD). This prospective cohort study was conducted in one academic teaching hospital. The study was conducted on 126 patients diagnosed with idiopathic Parkinson’s disease. Blood samples were collected to conduct a genotyping of MAOB, DRD1, DRD2, and DDC genes. Genotype and allele frequencies of MAOB (rs1799836) variants were not associated with the course of PD. Genotype and allele frequencies of DRD2 (rs2283265) variants were associated with risk of dementia (p = 0.001) and resulted in parts II and III of the UPDRS scale (p = 0.001). Genotype and allele frequencies of DRD2 (rs1076560) variants were associated with risk of dementia (p = 0.001) and resulted in parts II and III of the UPDRS scale (p = 0.001). Genotype and allele frequencies of DDC (rs921451) variants were not associated with the course of PD.

Plasticity, genetics, and epigenetics in l-dopa-induced dyskinesias

l-Dopa-induced dyskinesias (LIDs) are a frequent complication in l-dopa-treated patients affected by Parkinson's disease (PD). In the last years, several progresses in the knowledge of LIDs mechanisms have led to the identification of several molecular and electrophysiologic events. A complex cascade of intracellular events underlies the pathophysiology of LIDs, and, among these, aberrant plasticity in the cortico-basal ganglia system, at striatal and cortical level, plays a key role. Furthermore, several recent studies have investigated genetic susceptibility and epigenetic modifications in LIDs pathophysiology that might have future relevance in clinical practice and pharmacologic research. These progresses might lead to the development of specific strategies not only to treat, but also to prevent or delay the development of LIDs in PD.

Association of COMT rs4680 and MAO-B rs1799836 polymorphisms with levodopa-induced dyskinesia in Parkinson's disease-a meta-analysis

BACKGROUND AND PURPOSE

Polymorphisms of the catechol-O-methyl transferase (COMT) or monoamine oxidase B (MAO-B) genes may affect the occurrence of dyskinesia in Parkinson's disease (PD) patients. However, the findings are inconsistent. Thus, we performed a meta-analysis to assess whether COMT and MAO-B genetic variants are associated with an increased incidence of levodopa-induced dyskinesia (LID) in PD patients.

METHODS

A literature search of PubMed, Embase, and Cochrane Library was conducted to identify relevant studies published up to January 2021. The strength of the association between the polymorphisms and LID susceptibility was estimated by odds ratio (OR) and associated 95% confidence interval (CI). The pooled ORs were assessed in different genetic models.

RESULTS

Ten studies involving 2385 PD patients were included in the meta-analysis. Analysis of pooled ORs and 95% CIs suggested that the AA genotype of COMT(rs4680) was associated with LID (OR = 1.39, 95%CI: 1.02-1.89, P = 0.039) in the recessive model, and this correlation was more obvious in Brazilian samples in the analysis stratified by ethnicity. For the AG genotype of MAO-B(rs1799836), the pooled OR was 1.66 (95% CI: 1.04-2.65, P = 0.03) in patients with LID versus those without LID in the heterozygote model.

CONCLUSIONS

Our meta-analysis implicates the AA genotype of the COMT rs4680 polymorphism as potentially increasing the risk of LID in a recessive genetic model for PD patients. Furthermore, the AG genotype of the MAO-B rs1799836 polymorphism may influence the prevalence of LID in PD patients in the heterozygote model. However, further well-designed studies with larger PD patient cohorts are required to validate these results after adjusting for confounding factors.

Biphenylpiperazine Based MAO Inhibitors: Synthesis, Biological Evaluation, Reversibility and Molecular Modeling Studies

In this study, 21 new 1,4-biphenylpiperazine derivatives were designed, synthesized and evaluated as monoamine oxidase (MAO) inhibitors by in vitro fluorometric method. All these compounds exhibited inhibitory activity against hMAO enzymes, 17 analogues of them showed selectivity towards hMAO-B over hMAO-A enzyme. Compound 20 exhibited the best activity and selectivity towards hMAO-B with IC₅₀ value of 53 nM and selectivity index of 1122 folds over MAO-A, compared to the reference drugs rasagiline (IC₅₀ = 66 nM) and selegiline (IC₅₀ = 40 nM). Kinetic study and reversibility test of the most potent compound (20) revealed that it is reversible and mixed competitive inhibitor (K_i value is 17 nM for the inhibition of hMAO-B). Compound 20 was evaluated against normal NIH/3T3 mouse embryonic fibroblast cell lines and it was found that it is non-cytotoxic at its effective concentration against hMAO-B. Moreover, compound 20 and the most potent compounds have acceptable ADME properties and good pharmacokinetics profiles. Molecular docking simulations were performed for explanation and elucidation for the biological activity of compounds 19 and 20. Accordingly, 1,4- biphenylpiperazine derivatives can be considered as a promising lead to produce more potent and safer MAO inhibitors for management of various neurological disorders.

A Systematic Review of Parkinson's Disease Pharmacogenomics: Is There Time for Translation into the Clinics?

BACKGROUND

Parkinson's disease (PD) is the second most frequent neurodegenerative disease, which creates a significant public health burden. There is a challenge for the optimization of therapies since patients not only respond differently to current treatment options but also develop different side effects to the treatment. Genetic variability in the human genome can serve as a biomarker for the metabolism, availability of drugs and stratification of patients for suitable therapies. The goal of this systematic review is to assess the current evidence for the clinical translation of pharmacogenomics in the personalization of treatment for Parkinson's disease.

METHODS

We performed a systematic search of Medline database for publications covering the topic of pharmacogenomics and genotype specific mutations in Parkinson's disease treatment, along with a manual search, and finally included a total of 116 publications in the review.

RESULTS

We analyzed 75 studies and 41 reviews published up to December of 2020. Most research is focused on levodopa pharmacogenomic properties and catechol-O-methyltransferase (COMT) enzymatic pathway polymorphisms, which have potential for clinical implementation due to changes in treatment response and side-effects. Likewise, there is some consistent evidence in the heritability of impulse control disorder via Opioid Receptor Kappa 1 (OPRK1), 5-Hydroxytryptamine Receptor 2A (HTR2a) and Dopa decarboxylase (DDC) genotypes, and hyperhomocysteinemia via the Methylenetetrahydrofolate reductase (MTHFR) gene. On the other hand, many available studies vary in design and methodology and lack in sample size, leading to inconsistent findings.

CONCLUSIONS

This systematic review demonstrated that the evidence for implementation of pharmacogenomics in clinical practice is still lacking and that further research needs to be done to enable a more personalized approach to therapy for each patient.

Should we start integrating genetic data in decision-making on device-aided therapies in Parkinson disease? A point of view

Parkinson disease (PD) is a complex heterogeneous neurodegenerative disorder. Association studies have revealed numerous genetic risk loci and variants, and about 5-10% suffer from a monogenic form. Because the presentation and course of PD is unique to each patient, personalized symptomatic treatment should ideally be offered to treat the most disabling motor and non-motor symptoms. Indeed, clinical milestones and treatment complications that appear during disease progression are influenced by the genetic imprint. With recent advances in PD, more patients live longer to become eligible for device-aided therapies, such as apomorphine continuous subcutaneous infusion, levodopa duodenal gel infusion, and deep brain stimulation surgery, each with its own inclusion and exclusion criteria, advantages and disadvantages. Because genetic variants influence the expression of particular clinical profiles, factors for better or worse outcomes for device-aided therapies may then be proactively identified. For example, mutations in PRKN, LRRK2 and GBA express phenotypes that favor suitability for different device therapies, although with marked differences in the therapeutic window; whereas multiplications of SNCA express phenotypes that make them less desirable for device therapies.

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.

Polymorphism of the Dopa-Decarboxylase Gene Modifies the Motor Response to Levodopa in Chinese Patients With Parkinson's Disease

Levodopa (L-DOPA) is the most effective drug for Parkinson's disease (PD). However, the response to L-DOPA remains individually variable, which hampers the practical value of L-DOPA in the clinic. Genetic factors play a role in L-DOPA efficacy. This study explored the associations between polymorphisms and motor response to L-DOPA in Chinese patients with PD. A total of 51 Chinese PD patients were enrolled in this study. Patients underwent an acute L-DOPA challenge and were evaluated by the Unified Parkinson Disease Rating Scale (UPDRS) part III at baseline and after L-DOPA administration. Subjects were genotyped for polymorphisms: rs921451 and rs3837091 in the DDC loci, rs3836790 in the SLC6A3 locus, rs4680 in the COMT locus, and rs1799836 in the MAOB locus. We found that patients carrying the DDC CT or TT genotype exhibited a better motor response to L-DOPA than patients with the DDC CC genotype, and there was still a significant difference after adjustment for the L-DOPA dose in the acute challenge. Improvement in the UPDRS III subscores, including bradykinesia and axial symptoms, was significantly lower in patients with the DDC CC genotype than in patients with the CT or TT genotype. There were no significant associations between the motor response to L-DOPA and the rs3837091, rs3836790, rs4680, and rs1799836 variants. The DDC single nucleotide polymorphism rs921451 modulated the motor response to L-DOPA in Chinese PD patients. Our results suggested that DDC may be a modifier gene for the L-DOPA treatment response in PD.

Contribution of Five Functional Loci of Dopamine Metabolism-Related Genes to Parkinson's Disease and Multiple System Atrophy in a Chinese Population

Background: Impaired dopamine metabolism is associated with Parkinson’s disease (PD). Considering the overlap in the clinical and pathological characteristics between PD and multiple system atrophy (MSA), we investigated the effect of five potential functional polymorphisms in dopamine metabolism-related genes on disease susceptibility, phenotypes, and responses to dopamine in a large sample of PD and MSA patients.

Methods: A total of 1506 PD patients, 496 MSA patients, and 894 healthy controls were included in this study. Five variants (rs6356 in TH, rs921451 in DDC, rs4680 in COMT, rs1799836 in MAOB, and rs1611115 in DBH) were genotyped in all cases using Sequenom iPLEX Assay technology.

Results: After adjusting for gender and age at onset, except for DDC rs921451, which was associated with an increased risk of MSA (p = 0.001, OR = 1.21), no significant differences were found in genotype distribution or minor allele frequencies for the other four variants between PD and MSA patients and healthy controls. In the subgroup analysis, DDC rs921451 was associated with an increased risk for late-onset PD as well as for PD onset in males (p = 0.002 [OR = 1.13] p = 0.003 [OR = 1.15], respectively). In addition, patients harboring the risk allele DDC rs921451 required lower levodopa equivalent daily doses of dopaminergic medication than those without the risk allele (52.00 ± 21.31 mg/day, p = 0.015).

Conclusion: None of the five candidate functional variants is a major determinant of the risk for PD or MSA. The modified PD phenotypes associated with these variants requires further confirmation.

High levodopa plasma concentration after oral administration predicts levodopa-induced dyskinesia in Parkinson's disease

INTRODUCTION

In patients with Parkinson's disease (PD), pulsatile dopaminergic stimulation may be a primary cause of levodopa-induced dyskinesia (LID). We aimed to investigate the correlation between levodopa pharmacokinetics (PK) and LID in PD.

METHODS

We retrospectively reviewed the consecutive series of 255 PD patients without LID who underwent PK assessments with 100 mg levodopa. The type of peripheral decarboxylase inhibitor used in the PK assessments was determined by the usual prescription of the formulations of levodopa (10 mg carbidopa [n = 185] and 25 mg benserazide [n = 70]).

RESULTS

During a median follow-up of 32 months (IQR, 16-49 months), 73 patients (29%) developed LID. Compared with patients who did not develop LID (PD-LID-), those who developed LID (PD-LID+) were younger (p = 0.003) and had significantly higher maximum levodopa concentration (Cmax) (p = 0.002) and area under the curve (p < 0.001), LEDD (p < 0.001), and improvement of motor symptoms (p = 0.009). In the multivariate Cox proportional hazards models, Cmax and AUC were associated with incident LID (Hazard Ratio [HR] 1.11, 95% confidence interval [CI] 1.03-1.19 and HR 1.13, 95% CI 1.03-1.24, respectively). In addition, younger age, benserazide use, LEDD, and MAOBI use were associated with incident LID.

CONCLUSION

High levodopa plasma concentration after oral administration was associated with incident LID in patients with PD.

Parkinson's Disease in Women and Men: What's the Difference?

Increasing evidence points to biological sex as an important factor in the development and phenotypical expression of Parkinson’s disease (PD). Risk of developing PD is twice as high in men than women, but women have a higher mortality rate and faster progression of the disease. Moreover, motor and nonmotor symptoms, response to treatments and disease risk factors differ between women and men. Altogether, sex-related differences in PD support the idea that disease development might involve distinct pathogenic mechanisms (or the same mechanism but in a different way) in male and female patients. This review summarizes the most recent knowledge concerning differences between women and men in PD clinical features, risk factors, response to treatments and mechanisms underlying the disease pathophysiology. Unraveling how the pathology differently affect the two sexes might allow the development of tailored interventions and the design of innovative programs that meet the distinct needs of men and women, improving patient care.

Role of Genetic Variations in the Hepatic Handling of Drugs

The liver plays a pivotal role in drug handling due to its contribution to the processes of detoxification (phases 0 to 3). In addition, the liver is also an essential organ for the mechanism of action of many families of drugs, such as cholesterol-lowering, antidiabetic, antiviral, anticoagulant, and anticancer agents. Accordingly, the presence of genetic variants affecting a high number of genes expressed in hepatocytes has a critical clinical impact. The present review is not an exhaustive list but a general overview of the most relevant variants of genes involved in detoxification phases. The available information highlights the importance of defining the genomic profile responsible for the hepatic handling of drugs in many ways, such as (i) impaired uptake, (ii) enhanced export, (iii) altered metabolism due to decreased activation of prodrugs or enhanced inactivation of active compounds, and (iv) altered molecular targets located in the liver due to genetic changes or activation/downregulation of alternative/compensatory pathways. In conclusion, the advance in this field of modern pharmacology, which allows one to predict the outcome of the treatments and to develop more effective and selective agents able to overcome the lack of effect associated with the existence of some genetic variants, is required to step forward toward a more personalized medicine.

Monoamine oxidase B rs1799836 G allele polymorphism is a risk factor for early development of levodopa-induced dyskinesia in Parkinson's disease

Background

Dopamine replacement therapy is an established treatment for motor symptoms of Parkinson's disease, but its long-term use is often limited by the eventual development of motor complications, including levodopa-induced dyskinesia. Genetic background, particularly polymorphisms of dopamine metabolism genes, may affect the occurrence of dyskinesia in Parkinson's disease patients.

Methods

We investigated polymorphisms of dopamine metabolism genes, including catechol-O-methyltransferase, monoamine oxidase B, dopamine beta-hydroxylasedopamine, dopamine receptors D1, D2, and D3, and dopamine transporter, in 110 patients with Parkinson's disease. Cox proportional hazards regression was used to detect associations between genotypes and levodopa-induced dyskinesia.

Results

Monoamine oxidase B rs1799836 was the only polymorphism correlated with risk of dyskinesia. Patients with an AG or GG genotype were more likely to have dyskinesia than those with an AA genotype (adjusted hazard ratio, 3.41; 95% confidence interval, 1.28-9.10). Also, Kaplan-Meier curves demonstrated that patients with an AG or GG genotype developed dyskinesia earlier than those with an AA genotype (log-rank test, p = .004).

Conclusions

In Parkinson's disease patients, the monoamine oxidase B rs1799836 G allele is associated with a greater likelihood of developing dyskinesia than the A allele, possibly due to its association with lower monoamine oxidase B activity in the brain. Thus, detection of monoamine oxidase B polymorphisms may be useful for determining the optimal dosing of antiparkinson medications.

Initiation of pharmacological therapy in Parkinson's disease: when, why, and how

Debate is ongoing regarding when, why, and how to initiate pharmacotherapy for Parkinson's disease. Early initiation of dopaminergic therapies does not convey disease-modifying effects but does reduce disability. Concerns about the development of motor complications arising from the early initiation of levodopa, which led to misconceived levodopa-sparing strategies, have been largely mitigated by the outcomes of the PD MED and Levodopa in Early Parkinson's Disease (LEAP) studies. The LEAP study also showed the potential for early improvement in quality of life, even when disability is negligible. Until more effective methods of providing stable dopamine concentrations are developed, current evidence supports the use of levodopa as initial symptomatic treatment in most patients with Parkinson's disease, starting with low doses and titrating to therapeutic threshold. Monoamine oxidase-B inhibitors and dopamine agonists can be reserved as potential adjunct treatments later in the disease course. Future research will need to establish effective disease-modifying treatments, address whether patients' quality of life is substantially improved with early initiation of treatment rather than a wait and watch strategy, and establish whether new levodopa formulations will delay onset of dyskinesia.

Sex differences in movement disorders

In a range of neurological conditions, including movement disorders, sex-related differences are emerging not only in brain anatomy and function, but also in pathogenesis, clinical features and response to treatment. In Parkinson disease (PD), for example, oestrogens can influence the severity of motor symptoms, whereas elevation of androgens can exacerbate tic disorders. Nevertheless, the real impact of sex differences in movement disorders remains under-recognized. In this article, we provide an up-to-date review of sex-related differences in PD and the most common hyperkinetic movement disorders, namely, essential tremor, dystonia, Huntington disease and other chorea syndromes, and Tourette syndrome and other chronic tic disorders. We highlight the most relevant clinical aspects of movement disorders that differ between men and women. Increased recognition of these differences and their impact on patient care could aid the development of tailored approaches to the management of movement disorders and enable the optimization of preclinical research and clinical studies.

Impaired dopamine metabolism in Parkinson's disease pathogenesis

A full understanding of Parkinson's Disease etiopathogenesis and of the causes of the preferential vulnerability of nigrostriatal dopaminergic neurons is still an unsolved puzzle. A multiple-hit hypothesis has been proposed, which may explain the convergence of familial, environmental and idiopathic forms of the disease. Among the various determinants of the degeneration of the neurons in Substantia Nigra pars compacta, in this review we will focus on the endotoxicity associated to dopamine dyshomeostasis. In particular, we will discuss the relevance of the reactive dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) in the catechol-induced neurotoxicity. Indeed, the synergy between the catechol and the aldehyde moieties of DOPAL exacerbates its reactivity, resulting in modification of functional protein residues, protein aggregation, oxidative stress and cell death. Interestingly, αSynuclein, whose altered proteostasis is a recurrent element in Parkinson's Disease pathology, is considered a preferential target of DOPAL modification. DOPAL triggers αSynuclein oligomerization leading to synapse physiology impairment. Several factors can be responsible for DOPAL accumulation at the pre-synaptic terminals, i.e. dopamine leakage from synaptic vesicles, increased rate of dopamine conversion to DOPAL by upregulated monoamine oxidase and decreased DOPAL degradation by aldehyde dehydrogenases. Various studies report the decreased expression and activity of aldehyde dehydrogenases in parkinsonian brains, as well as genetic variants associated to increased risk in developing the pathology. Thus, we discuss how the deregulation of these enzymes might be considered a contributing element in the pathogenesis of Parkinson's Disease or a down-stream effect. Finally, we propose that a better understanding of the impaired dopamine metabolism in Parkinson's Disease would allow a more refined patients stratification and the design of more targeted and successful therapeutic strategies.

Sleep Pharmacogenetics: The Promise of Precision Medicine

Pharmacogenetics is the branch of personalized medicine concerned with the variability in drug response occurring because of heredity. Advances in genetics research, and decreasing costs of gene sequencing, are promoting tremendous growth in pharmacogenetics in all areas of medicine, including sleep medicine. This article reviews the body of research indicating that there are genetic variations that affect the therapeutic actions and adverse effects of agents used for the treatment of sleep disorders to show the potential of pharmacogenetics to improve the clinical practice of sleep medicine.

Pharmacogenetic Profile and the Occurrence of Visual Hallucinations in Patients With Sporadic Parkinson's Disease

Visual hallucinations are significant nonmotor symptoms in the course of treatment of Parkinson's disease. Previous studies have shown that the interindividual variability and pharmacogenetic profile of Parkinson's disease patients seem to influence the occurrence of visual hallucinations. In our study, we investigated a possible relationship of sequence variants in DRD1, DRD2, DRD3, DAT1, and COMT genes with the presence of visual hallucinations in Parkinson's disease patients. A total of 224 Brazilian patients from the Pro-Parkinson service at the Clinical Hospital of the University of Pernambuco, diagnosed with sporadic Parkinson's disease, were enrolled. Parkinson's disease patients were divided into 2 groups based on the presence or absence of visual hallucinations. The sequence variants for DRD1, DRD2, DRD3, DAT1, and COMT were determined through the polymerase chain reaction-restriction fragment length polymorphism technique. Multiple Poisson regression analyses showed that individuals carrying the DRD3 Ser/Ser and Ser/Gly genotypes presented increased prevalence ratios of visual hallucinations (9.7-fold and 4.4-fold, respectively; P < .001). Regarding DAT1 rs28363170, there was a 9.82-fold increase in the prevalence ratio in patients with the 10/11 genotype, 8.78-fold for the 10/8 genotype, and 2.44-fold for the 9/8 genotypes (P < .001, for all). In addition, visual hallucinations were also associated with use of transdermal patches with rotigotine (PR, 3.7; 95%CI, 1.2-10.9; P = .017) and rasagiline (PR, 2.8; 95%CI, 1.3-6.0; P = .006). Our results suggest that the genetic variants DRD3 and DAT1, along with other therapeutic confounders, may influence the prevalence ratio of visual hallucinations.

Viewpoint: Developing drugs for levodopa-induced dyskinesia in PD: Lessons learnt, what does the future hold?

The drive to develop drugs to treat PD starts and ends with the patient. Herein, we discuss how the experience with drug development for LID has led the field in translational studies in PD with advancing ground-breaking science via rigorous clinical trial design, to deliver clinical proof-of-concepts across multiple therapeutic targets. However, issues remain in advancing drugs efficacious preclinically to the clinic, and future studies need to learn from past successes and failures. Such lessons include implementing better early indicators of tolerability, for instance evaluating non-motor symptoms in preclinical models; improving patient-related outcome measures in clinical trials, as well as considering the unique nature of dyskinesia in an individual patient. The field of translational studies needs to become more patient focused to improve successful outcomes.

L-DOPA for Parkinson's disease-a bittersweet pill

3,4-dihydroxy-L-phenylalanine (L-DOPA) is the gold standard treatment for Parkinson's disease. It has earned that title through its highly effective treatment of some of the motor symptoms in the early stages of the disease but it is a far from perfect drug. The inevitable long-term treatment that comes with this chronic neurodegenerative condition raises the risk significantly of the development of motor fluctuations including disabling L-DOPA-induced dyskinesia. Being unsurpassed as a therapy means that understanding the mechanisms of dyskinesia priming and induction is vital to the search for therapies to treat these side effects and allow optimal use of L-DOPA. However, L-DOPA use may also have consequences (positive or negative) for the development of other interventions, such as cell transplantation, which are designed to treat or repair the ailing brain. This review looks at the issues around the use of L-DOPA with a focus on its potential impact on advanced reparative interventions.