α-Synuclein genetic variants predict faster motor symptom progression in idiopathic Parkinson disease

Research Priorities on the Role of α-Synuclein in Parkinson's Disease Pathogenesis

Various forms of Parkinson's disease, including its common sporadic form, are characterized by prominent α-synuclein (αSyn) aggregation in affected brain regions. However, the role of αSyn in the pathogenesis and evolution of the disease remains unclear, despite vast research efforts of more than a quarter century. A better understanding of the role of αSyn, either primary or secondary, is critical for developing disease-modifying therapies. Previous attempts to hone this research have been challenged by experimental limitations, but recent technological advances may facilitate progress. The Scientific Issues Committee of the International Parkinson and Movement Disorder Society (MDS) charged a panel of experts in the field to discuss current scientific priorities and identify research strategies with potential for a breakthrough. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Lysosomal genes contribute to Parkinson's disease near agriculture with high intensity pesticide use

Parkinson's disease (PD), the second most common neurodegenerative disorder, develops sporadically, likely through a combination of polygenic and environmental factors. Previous studies associate pesticide exposure and genes involved in lysosomal function with PD risk. We evaluated the frequency of variants in lysosomal function genes among patients from the Parkinson's, Environment, and Genes (PEG) study with ambient pesticide exposure from agricultural sources. 757 PD patients, primarily of White European/non-Hispanic ancestry (75%), were screened for variants in 85 genes using a custom amplicon panel. Variant enrichment was calculated against the Genome Aggregation Database (gnomAD). Enriched exonic variants were prioritized by exposure to a cluster of pesticides used on cotton and severity of disease progression in a subset of 386 patients subdivided by race/ethnicity. Gene enrichment analysis identified 36 variants in 26 genes in PEG PD patients. Twelve of the identified genes (12/26, 46%) had multiple enriched variants and/or a single enriched variant present in multiple individuals, representing 61% (22/36) of the observed variation in the cohort. The majority of enriched variants (26/36, 72%) were found in genes contributing to lysosomal function, particularly autophagy, and were bioinformatically deemed functionally deleterious (31/36, 86%). We conclude that, in this study, variants in genes associated with lysosomal function, notably autophagy, were enriched in PD patients exposed to agricultural pesticides suggesting that altered lysosomal function may generate an underlying susceptibility for developing PD with pesticide exposure. Further study of gene-environment interactions targeting lysosomal function may improve understanding of PD risk in individuals exposed to pesticides.

Seminar: Extracellular Vesicles as Mediators of Environmental Stress in Human Disease

BACKGROUND

Extracellular vesicles (EVs), membrane-bound particles containing a variety of RNA types, DNA, proteins, and other macromolecules, are now appreciated as an important means of communication between cells and tissues, both in normal cellular physiology and as a potential indicator of cellular stress, environmental exposures, and early disease pathogenesis. Extracellular signaling through EVs is a growing field of research for understanding fundamental mechanisms of health and disease and for the potential for biomarker discovery and therapy development. EVs are also known to play important roles in mediating the effects of exposure to environmental stress.

OBJECTIVES

This seminar addresses the application of new tools and approaches for EV research, developed in part through the National Institutes of Health (NIH) Extracellular RNA Communication Program, and reflects presentations and discussions from a workshop held 27-28 September 2021 by the National Institute of Environmental Health Sciences (NIEHS) and the National Center for Advancing Translational Sciences (NCATS) on "Extracellular Vesicles, Exosomes, and Cell-Cell Signaling in Response to Environmental Stress." The panel of experts discussed current research on EVs and environmental exposures, highlighted recent advances in EV isolation and characterization, and considered research gaps and opportunities toward identifying and characterizing the roles for EVs in environmentally related diseases, as well as the current challenges and opportunities in this field.

DISCUSSION

The authors discuss the application of new experimental models, particularly organ-on-chip (OOC) systems and in vitro approaches and how these have the potential to extend findings in population-based studies of EVs in exposure-related diseases. Given the complex challenges of identifying cell-specific EVs related to environmental exposures, as well as the general heterogeneity and variability in EVs in blood and other accessible biological samples, there is a critical need for rigorous reporting of experimental methods and validation studies. The authors note that these efforts, combined with cross-disciplinary approaches, would ensure that future research efforts in environmental health studies on EV biomarkers are rigorous and reproducible. https://doi.org/10.1289/EHP12980.

Ethnicity and Parkinson's Disease: Motor and Nonmotor Features and Disease Progression in Latino Patients Living in Rural California

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disorder among older adults worldwide. Currently, studies of PD progression rely primarily on White non-Latino (WNL) patients. Here, we compare clinical profiles and PD progression in Latino and WNL patients enrolled in a community-based study in rural Central California.

METHOD

PD patients within 5 years of diagnosis were identified from 3 counties between 2001 and 2015. During up to 3 visits, participants were examined by movement disorders specialists and interviewed. We analyzed cross-sectional differences in PD clinical features severity at each study visit and used linear mixed models and Cox proportional hazards models to compare motor, nonmotor, and disability progression longitudinally and to assess time to death in Latinos compared to WNL patients.

RESULTS

Of 775 patients included, 138 (18%) self-identified as Latino and presented with earlier age at diagnosis (63.6 vs 68.9) and death (78.6 vs 81.5) than WNL. Motor (hazard ratio [HR] = 1.17 [0.71, 1.94]) and nonmotor symptoms did not progress faster in Latino versus WNL patients after accounting for differences in baseline symptom severity. However, Latino patients progressed to disability stages according to Hoehn and Yahr faster than WNL (HR = 1.81 [1.11, 2.96]). Motor and nonmotor symptoms in Latino patients were also medically managed less well than in WNL.

CONCLUSIONS

Our PD study with a large proportion of Latino enrollees and progression data reveals disparities in clinical features and progression by ethnicity that may reflect healthcare access and structural socioeconomic disadvantages in Latino patients with PD.

Proximity to residential and workplace pesticides application and the risk of progression of Parkinson's diseases in Central California

BACKGROUND

Pesticide exposure has consistently been associated with Parkinson's disease (PD) onset. Yet, fewer epidemiologic studies have examined whether pesticides influence PD motor and non-motor symptom progression.

OBJECTIVES

Using a geographic information system tool that integrates agricultural pesticide use reports and land use records to derive ambient exposures at residences and workplaces, we assessed associations between specific pesticides previously related to PD onset with PD symptom progression in two PD patient cohorts living in agricultural regions of California.

METHODS

We calculated the pounds of pesticide applied agriculturally near each participant's residential or occupational addresses from 1974 to the year of PD diagnosis, using a geographic information system tool that links the California Pesticide Use Reports database to land use data. We examined 53 pesticides selected a priori as they have previously been associated with PD onset. We longitudinally followed two PD patient cohorts (PEG1 N = 242, PEG2 N = 259) for an average of 5.0 years (SD ± 3.5) and 2.7 years (SD ± 1.6) respectively and assessed PD symptoms using the movement disorder specialist-administered Unified Parkinson's disease Rating Scale part III (UPDRS), Mini-Mental State Examination (MMSE), and Geriatric Depression Scale (GDS). Weighted time-to-event regression models were implemented to estimate effects.

RESULTS

Ten agricultural pesticides, including copper sulfate (pentahydrate), 2-methyl-4-chlorophenoxyacetic acid (MCPA) dimethylamine salt, tribufos, sodium cacodylate, methamidophos, ethephon, propargite, bromoxynil octanoate, monosodium methanearsonate (MSMA), and dicamba, were associated with faster symptom progression. Among these pesticides, residential or workplace proximity to higher amounts of copper sulfate (pentahydrate) and MCPA (dimethylamine salt) was associated with all three progression endpoints (copper sulfate: HRs = 1.22-1.36, 95 % CIs = 1.03-1.73; MCPA: HRs = 1.27-1.35, 95 % CIs = 1.02-1.70).

CONCLUSIONS

Our findings suggest that pesticide exposure may not only be relevant for PD onset but also PD progression phenotypes. We have implicated ten specific pesticide active ingredients in faster PD motor and non-motor decline.

BDNF rs10501087, rs1491850 and rs11030094 polymorphisms associated with delayed progression in early-stage Parkinson's disease

Parkinson's disease (PD) is heterogenous in its presentation, progression and response to therapies. Genetic polymorphisms may account for some of this variability. Several single nucleotide polymorphisms (SNPs) in the brain-derived neurotrophic factor gene BDNF have been associated with differing clinical outcomes from different dopaminergic replacement strategies, and one of these, the rs6265 SNP, has been associated with a milder clinical phenotype in the unmedicated, early-stage of PD. We examined if other BDNF SNPs with potential pharmacogenetic effects also are associated with different rates of disease progression. The Deprenyl And Tocopherol Antioxidative Therapy Of Parkinsonism (DATATOP) study was analyzed retrospectively. DNA samples (n = 217) were genotyped for the BDNF rs908867, rs11030094, rs10501087, rs1157659, and rs1491850 SNPs, and the primary endpoint was time to initiate symptomatic pharmacotherapy. Genotypes were compared using the Cox proportional hazard ratio (HR) with baseline age, sex, site, time since PD diagnosis and rs6265 genotype as covariates. The primary endpoint was associated with a delay with three SNPs: rs10501087 [HR (95% Confidence Interval) = 28.3 (3.6-223.1, p = 0.002) and 7.6 (1.9-29.8, p = 0.004) for T/T and T/C subjects, respectively, vs. C/C subjects], rs1491850 [HR = 3.3 (1.3-8.4, p = 0.04) and 2.8 (1.3-6.4, p = 0.03) for T/T and T/C subjects, respectively, vs. C/C subjects] and rs11030094 [HR = 2.5 (1.1-5.6, p = 0.03) and 2.0 (1.3-6.4, p = 0.03) for A/A and A/G subjects, respectively, vs. G/G subjects]. From the primary endpoint, specific rs10501087, rs1491850, and rs11030094 SNP genotypes are associated with a slower rate of PD progression in the unmedicated state. A prospective clinical trial examining many BDNF SNPs is warranted.

Reproductive Lifespan and Motor Progression of Parkinson’s Disease

Objectives: Estrogen not only plays a key role in the decreased risk of Parkinson’s disease (PD) but also influences its severity. We aimed to explore the effect of the reproductive lifespan on the motor progression of PD female patients in a large prospective cohort study. Methods: A competing risk analysis with a Fine and Gray model on 491 female and 609 male patients with PD was conducted. We regarded the chance of faster motor progression (as measured by the Unified Parkinson’s Disease Rating Scale (UPDRS) III increasing by ≥16 points during follow-up) and the chance of death as competing risks. The reproductive lifespan was regarded as the variable of interest, while faster motor progression was set as the primary outcome. Results: In the multivariable competing risk analysis, the male sex was not significantly associated with faster motor progression (subdistribution hazard ratio (SHR) 0.888, 95% CI 0.652–1.209, p = 0.450), while a shorter reproductive lifespan was associated with faster motor progression in women (SHR 0.964, 95% CI 0.936–0.994, p = 0.019). Sensitivity analysis indicated that a shorter reproductive lifespan was also significantly associated with faster motor progression in the 48 female patients who reported menopause after the onset of PD (SHR 0.156, 95% CI 0.045–0.542, p = 0.003). A linear mixed model also revealed the significant main effects of a short reproductive lifespan on the higher UPDRS III score in PD female patients at the last visit (p = 0.026). Conclusions: Our study indicates that a short reproductive lifespan contributes to faster motor progression in PD female patients, which has important implications for understanding the role of endogenous estrogen exposure in female PD and is beneficial to select appropriate patients in clinical trials.

MAO-B Polymorphism Associated with Progression in a Chinese Parkinson’s Disease Cohort but Not in the PPMI Cohort

Introduction

Genetic factors play an important role in Parkinson's disease (PD) risk. However, the genetic contribution to progression in Chinese PD patients has rarely been studied. This study investigated genetic associations with progression based on 30 PD risk loci common in a longitudinal cohort of Chinese PD patients and the Parkinson's Progression Markers Initiative (PPMI) cohort.

Methods

PD patients from the true world (TW) Chinese PD longitudinal cohort and the PPMI cohort with demographic information and assessment scales were assessed. A panel containing 30 PD risk single nucleotide polymorphisms was tested. Progression rates of each scale were derived from random-effect slope values of mixed-effects regression models. Progression rates of multiple assessments were combined by using principal component analysis (PCA) to derive scores for composite, motor, and nonmotor progression. The association of genetic polymorphism and separate scales or PCA progression was analysed via linear regression.

Results

In the Chinese PD cohort, MAOB rs1799836 was associated with progression based on the Montreal Cognitive Assessment, the top 3 principal components (PCs) of nonmotor PCA and PC1 of the composite PCA. In the PPMI cohort, both MDS-Unified Parkinson's Disease Rating Scale II and motor PC1 progression were associated with RIT2 rs12456492. The PARK16 haplotype was associated with Geriatric Depression Scale and the State-Trait Anxiety Inventory for Adults progression, and the SNCA haplotype was associated with the Hoehn-Yahr staging progression and motor PC1 progression. Ethnicity-stratified analysis showed that the association between MAOB rs1799836 and PD progression may be specific to Asian or Chinese patients.

Conclusion

MAOB rs1799836 was associated with the progression of nonmotor symptoms, especially cognitive impairment, and the composite progression of motor and nonmotor symptoms within our Chinese PD cohort. The RIT2 rs12456492 and SNCA haplotypes were associated with motor function decline, and the PARK16 haplotype was associated with progression in mood in the PPMI cohort.

Air Pollution and the Risk of Parkinson's Disease: A Review

Parkinson's disease, as well as other neurodegenerative disorders, are primarily characterized by pathological accumulation of proteins, inflammation, and neuron loss. Although there are some known genetic risk factors, most cases cannot be explained by genetics alone. Therefore, it is important to determine the environmental factors that confer risk and the mechanisms by which they act. Recent epidemiological studies have found that exposure to air pollution is associated with an increased risk for development of Parkinson's disease, although not all results are uniform. The variability between these studies is likely due to differences in what components of air pollution are measured, timing and methods used to determine exposures, and correction for other variables. There are several potential mechanisms by which air pollution could act to increase the risk for development of Parkinson's disease, including direct neuronal toxicity, induction of systemic inflammation leading to central nervous system inflammation, and alterations in gut physiology and the microbiome. Taken together, air pollution is an emerging risk factor in the development of Parkinson's disease. A number of potential mechanisms have been implicated by which it promotes neuropathology providing biological plausibility, and these mechanisms are likely relevant to the development of other neurodegenerative disorders such as Alzheimer's disease. This field is in its early stages, but a better understanding of how environmental exposures influence the pathogenesis of neurodegeneration is essential for reducing the incidence of disease and finding disease-modifying therapies. © 2022 International Parkinson and Movement Disorder Society.

Stochastic Epigenetic Mutations Influence Parkinson's Disease Risk, Progression, and Mortality

BACKGROUND

Stochastic epigenetic mutations (SEM) reflect a deviation from normal site-specific methylation patterns. Epigenetic mutation load (EML) captures the accumulation of SEMs across an individual's genome and may reflect dysfunction of the epigenetic maintenance system in response to epigenetic challenges.

OBJECTIVE

We investigate whether EML is associated with PD risk and time to events (i.e., death and motor symptom decline).

METHODS

We employed logistic regression and Cox proportional hazards regression to assess the association between EML and several outcomes. Our analyses are based on 568 PD patients and 238 controls from the Parkinson's disease, Environment and Genes (PEG) study, for whom blood-based methylation data was available.

RESULTS

We found an association for PD onset and EML in all genes (OR = 1.90; 95%CI 1.52-2.37) and PD-related genes (OR = 1.87; 95%CI 1.50-2.32). EML was also associated with time to a minimum score of 35 points on the motor UPDRS exam (OR = 1.28; 95%CI 1.06-1.56) and time to death (OR = 1.29, 95%CI 1.11-1.49). An analysis of PD related genes only revealed five intragenic hotspots of high SEM density associated with PD risk.

CONCLUSION

Our findings suggest an enrichment of methylation dysregulation in PD patients in general and specifically in five PD related genes. EML may also be associated with time to death and motor symptom progression in PD patients.

Longitudinal Study of SNCA Rep1 Polymorphism on Executive Function in Early Parkinson's Disease

The alpha-synuclein gene promoter (SNCA-Rep1) is associated with Parkinson's disease (PD), but its relationship with performance across individual cognitive domains in early PD is unknown. This study aims to investigate Rep1 polymorphism and longitudinal change in cognition in early PD. In this longitudinal study, Rep1 allele lengths ("long" and "short") were determined in 204 early PD patients. All participants underwent annual neuropsychological assessments and followed up for 3 years. Linear-mixed model was performed to investigate the association of Rep1 status and longitudinal change in individual cognitive domains. At 3 years, significant decline in executive function was observed in long Rep1 allele carriers vs short allele carriers, controlling for potential confounders. This is the first longitudinal study demonstrating that long Rep1 allele carriers are at higher risk for executive dysfunction in early PD.

Metabolomics in Parkinson's disease

Parkinson's disease (PD) is a multifactorial neurodegenerative disorder in which environmental (lifestyle, dietary, infectious disease) factors as well as genetic make-up play a role. Metabolomics, an evolving research field combining biomarker discovery and pathogenetics, is particularly useful in studying complex pathophysiology in general and Parkinson's disease (PD) specifically. PD, the second most frequent neurodegenerative disorder, is characterized by the loss of dopaminergic neurons in the substantia nigra and the presence of intraneural inclusions of α-synuclein aggregates. Although considered a predominantly movement disorder, PD is also associated with number of non-motor features. Metabolomics has provided useful information regarding this neurodegenerative process with the aim of identifying a disease-specific fingerprint. Unfortunately, many disease variables such as clinical presentation, motor system involvement, disease stage and duration substantially affect biomarker relevance. As such, metabolomics provides a unique approach to studying this multifactorial neurodegenerative disorder.

Lack of Association Between GBA Mutations and Motor Complications in European and American Parkinson's Disease Cohorts

Background:

Motor complications are a consequence of the chronic dopaminergic treatment of Parkinson’s disease (PD) and include levodopa-induced dyskinesia (LIDs) and motor fluctuations (MF). Currently, evidence is on lacking whether patients with GBA-associated PD differ in their risk of developing motor complications compared to the general PD population.

Objective:

To evaluate the association of GBA carrier status with the development of LIDS and MFs from early PD.

Methods:

Motor complications were recorded prospectively in 884 patients with PD from four longitudinal cohorts using part IV of the UPDRS or MDS-UPDRS. Subjects were followed for up to 11 years and the associations of GBA mutations with the development of motor complications were assessed using parametric accelerated failure time models.

Results:

In 439 patients from Europe, GBA mutations were detected in 53 (12.1%) patients and a total of 168 cases of LIDs and 258 cases of MF were observed. GBA carrier status was not associated with the time to develop LIDs (HR 0.78, 95%CI 0.47 to 1.26, p = 0.30) or MF (HR 1.19, 95%CI 0.84 to 1.70, p = 0.33). In the American cohorts, GBA mutations were detected in 36 (8.1%) patients and GBA carrier status was also not associated with the progression to LIDs (HR 1.08, 95%CI 0.55 to 2.14, p = 0.82) or MF (HR 1.22, 95%CI 0.74 to 2.04, p = 0.43).

Conclusion:

This study does not provide evidence that GBA-carrier status is associated with a higher risk of developing motor complications. Publication of studies with null results is vital to develop an accurate summary of the clinical features that impact patients with GBA-associated PD.

A systematic review of associations between common SNCA variants and clinical heterogeneity in Parkinson's disease

There is great heterogeneity in both the clinical presentation and rate of disease progression among patients with Parkinson’s disease (PD). This can pose prognostic difficulties in a clinical setting, and a greater understanding of the risk factors that contribute to modify disease course is of clear importance for optimizing patient care and clinical trial design. Genetic variants in SNCA are an established risk factor for PD and are candidates to modify disease presentation and progression. This systematic review aimed to summarize all available primary research reporting the association of SNCA polymorphisms with features of PD. We systematically searched PubMed and Web of Science, from inception to 1 June 2020, for studies evaluating the association of common SNCA variants with age at onset (AAO) or any clinical feature attributed to PD in patients with idiopathic PD. Fifty-eight studies were included in the review that investigated the association between SNCA polymorphisms and a broad range of outcomes, including motor and cognitive impairment, sleep disorders, mental health, hyposmia, or AAO. The most reproducible findings were with the REP1 polymorphism or rs356219 and an earlier AAO, but no clear associations were identified with an SNCA polymorphism and any individual clinical outcome. The results of this comprehensive summary suggest that, while there is evidence that genetic variance in the SNCA region may have a small impact on clinical outcomes in PD, the mechanisms underlying the association of SNCA polymorphisms with PD risk may not be a major factor driving clinical heterogeneity in PD.

Effect of diabetes control status on the progression of Parkinson's disease: A prospective study

OBJECTIVE

To evaluate whether the control status of type 2 diabetes mellitus (DM) influences the progression of Parkinson's disease (PD).

METHODS

We conducted a prospective cohort study from March 2009 to August 2020. Patients at baseline were categorized into DM and non-DM groups, and those with DM were further classified into the well and poorly controlled DM groups based on the 7.0% of glycated hemoglobin (HbA1C) levels. Multivariate Cox proportional hazards regression models were used to explore the predictors for PD-related outcomes by hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Of the 379 patients enrolled, 49 (12.9%) had DM, and 22 of DM (44.9%) were poorly controlled. The adjusted HRs were 2.060 (95% CI 1.165-3.641) for United Rating Scale (UPDRS) III score increased ≥14 in the poorly controlled-DM group, and 1.066 (95% CI 0.572-1.986) in the well-controlled DM group, relative to the non-DM group (p trend = 0.025), after adjusting for sex, age, age of onset, body mass index, and UPDRS III and Montreal Cognitive Assessment (MoCA) scores at baseline. The adjusted HRs were 2.079 (95% CI 1.212-3.566) for reaching Hoehn & Yahr stage ≥3 in the poorly controlled DM group, and 0.879 (95% CI 0.413-1.871) in the well-controlled DM group, compared with the non-DM group (p trend = 0.021). Time to death or time to MoCA 3-point decrease were not significantly different among the three groups.

INTERPRETATION

Poorly controlled DM is an independent risk factor contributing to motor progression in PD. Our study highlights the importance of adequate control of diabetes in PD.

Facial tremor in patients with Parkinson's disease: prevalence, determinants and impacts on disease progression

BACKGROUND

Facial (lip and jaw) tremor (FT) is associated with Parkinson's disease (PD) but few studies have been conducted to explore its clinical profile. We performed this study to investigate the prevalence and clinical correlates of FT in PD, and further to evaluate its effect on disease progression.

METHODS

A retrospective, cross-sectional (n = 2224) and longitudinal (n = 674) study was conducted. The presence of FT was based on a ≥ 1 score in the United PD Rating Scale (UPDRS) item 20A. Group comparisons were conducted, followed by a forward binary logistic regression analysis. Inverse probability of treatment weighting (IPTW) based on the propensity score and weighted or unweighted Cox regression models were used to explore the impact of FT on five clinical milestones including death, UPDRS III 11-point increase, Hoehn and Yahr (H&Y) stage reaching 3, dyskinesia development, and Montreal Cognitive Assessment 3-point decrease.

RESULTS

FT was presented in 403 patients (18.1%), which showed increasing trends with disease duration and H&Y score. Age (P < 0.001), female (P < 0.001), disease duration (P = 0.001), speech (P = 0.011), rigidity (P = 0.026), rest tremor on limbs (P < 0.001), kinetic tremor on hands (P < 0.001), and axial symptoms (P = 0.013) were independent factors associated with FT. Both unweighted and weighted Cox regression models indicated that baseline FT and FT as the initial symptom were not associated with the five outcomes.

CONCLUSIONS

Our study suggested that FT was not uncommon and provided a deeper insight into the characteristics of FT in PD. The predict value of FT on long-term progronis of PD may need future longer follwe-up study.

Genome-Wide Association Studies of Cognitive and Motor Progression in Parkinson's Disease

BACKGROUND

There are currently no treatments that stop or slow the progression of Parkinson's disease (PD). Case-control genome-wide association studies have identified variants associated with disease risk, but not progression. The objective of the current study was to identify genetic variants associated with PD progression.

METHODS

We analyzed 3 large longitudinal cohorts: Tracking Parkinson's, Oxford Discovery, and the Parkinson's Progression Markers Initiative. We included clinical data for 3364 patients with 12,144 observations (mean follow-up 4.2 years). We used a new method in PD, following a similar approach in Huntington's disease, in which we combined multiple assessments using a principal components analysis to derive scores for composite, motor, and cognitive progression. These scores were analyzed in linear regression in genome-wide association studies. We also performed a targeted analysis of the 90 PD risk loci from the latest case-control meta-analysis.

RESULTS

There was no overlap between variants associated with PD risk, from case-control studies, and PD age at onset versus PD progression. The APOE ε4 tagging variant, rs429358, was significantly associated with composite and cognitive progression in PD. Conditional analysis revealed several independent signals in the APOE locus for cognitive progression. No single variants were associated with motor progression. However, in gene-based analysis, ATP8B2, a phospholipid transporter related to vesicle formation, was nominally associated with motor progression (P = 5.3 × 10^-6 ).

CONCLUSIONS

We provide early evidence that this new method in PD improves measurement of symptom progression. We show that the APOE ε4 allele drives progressive cognitive impairment in PD. Replication of this method and results in independent cohorts are needed. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Association between positive history of essential tremor and disease progression in patients with Parkinson's disease

This study aimed to explore the effect of pre-existing essential tremor (ET) history on the disease progression of Parkinson’s disease (PD). We recruited and followed-up a group of PD patients from March 2009 to July 2020. The ET history of each patient was obtained by retrospective interviews or past medical records. Cox proportional hazards models with inverse probability of treatment weighting (IPTW) were used to estimate the hazard ratio (HR) with 95% confidence intervals (CIs). Of 785 patients who completed the followed-up visits, 61 patients (7.8%) reported a history of pre-existing ET. Cox regression models after IPTW indicated that the positive ET history in patients with PD was protective against time to United PD Rating Scale III 14-point increase (HR = 0.301, 95% CI = 0.134–0.678, P = 0.004), time to akinesia and rigidity 8-point increase (HR = 0.417, 95% CI = 0.218–0.796, P = 0.008), time to conversion to Hoehn and Yahr stage 3 (HR = 0.356, 95% CI = 0.131–0.969, P = 0.043), time to develop dyskinesia (HR = 0.160, 95% CI = 0.037–0.698, P = 0.015), and time to Montreal Cognitive Assessment 3-point decrease (HR = 0.389, 95% CI = 0.160–0.946, P = 0.037), but had no relationship with time to tremor 4-point increase (HR = 1.638, 95% CI = 0.822–3.266, P = 0.161) and time to death (HR = 0.713, 95% CI = 0.219–2.319, P = 0.574). Our study indicated that ET history in patients with PD is associated with a benign prognosis with slower motor and non-motor progression.

Alpha-Synuclein in the Gastrointestinal Tract as a Potential Biomarker for Early Detection of Parkinson's Disease

The primary pathogenesis associated with Parkinson's disease (PD) occurs in peripheral tissues several years before the onset of typical motor symptoms. Early and reliable diagnosis of PD could provide new treatment options for PD patients and improve their quality of life. At present, however, diagnosis relies mainly on clinical symptoms, and definitive diagnosis is still based on postmortem pathological confirmation of dopaminergic neuronal degeneration. In addition, the similarity of the clinical, cognitive, and neuropathological features of PD with other neurodegenerative diseases calls for new biomarkers, suitable for differential diagnosis. Alpha-synuclein (α-Syn) is a potential PD biomarker, due to its close connection with the pathogenesis of the disease. Here we summarize the currently available information on the possible use of α-Syn as a biomarker of early stages of PD in gastrointestinal (GI) tissues, highlight its potential to distinguish PD and other neurodegenerative diseases, and suggest alternative methods (primarily developed for other tissue analysis) that could improve α-Syn detection procedures or diagnostic methods in general.

SNCA Rep1 microsatellite length influences non-motor symptoms in early Parkinson's disease

Long alpha-synuclein gene (SNCA) promoter (Rep1) allele-carriers are linked to higher risk for Parkinson's disease (PD) and faster motor progression. Non-motor symptoms including autonomic, neuropsychiatric, and sleep disorders are common in PD. However, the relationship between SNCA Rep1 microsatellite lengths and non-motor symptoms in early PD remains to be elucidated. 171 consecutive early PD patients were recruited from tertiary clinics and genotyped for Rep1. Multivariable regression analyses were performed to examine associations between Rep1 alleles and non-motor outcome scores. Longer Rep1 alleles significantly associated with higher total Non-Motor Symptom Scale (NMSS) scores (p=.006) and Hospital Anxiety and Depression Scale (HADS) depression subscale scores (p=.002), after adjusting for covariates and Bonferroni correction. We demonstrated that SNCA Rep1 allele length influences overall non-motor symptom burden and depression in early PD patients. Further functional studies to evaluate the role of Rep1 in non-dopaminergic systems may unravel new therapeutic targets for non-motor symptoms in PD.

SNCA-Rep1 polymorphism correlates with susceptibility and iron deficiency in restless legs syndrome

BACKGROUND

Brain iron disequilibrium and dopaminergic dysfunction are key pathophysiological features of Restless Legs Syndrome (RLS). Rep1 polymorphism in the promotor region of SNCA is associated with risk of Parkinson's disease, however its association with RLS and iron status is unclear.

OBJECTIVE

To investigate SNCA-Rep1 polymorphism in RLS and its phenotypes.

METHODS

We recruited RLS patients as well as age and gender matched healthy controls. Demographic information and clinical features of RLS were recorded. Laboratory examinations were performed to exclude possible secondary causes.

RESULTS

215 RLS patients and 369 healthy controls were included. We found that the Rep1 allele 0 homozygosity significantly decreased RLS risk (OR: 0.345; P < 0.0001, and remained significant after the Bonferroni correction). Phenotypic analysis demonstrated that longer Rep1 alleles were associated with increased susceptibility to iron deficiency (53.0% vs 36.1%, P = 0.017), however had no phenotypic significant effects on age, gender, onset age, duration, RLS family history, severity, laterality, extra body involvement and seasonal fluctuation. Multivariate logistic regression analyses confirmed long Rep1 allele was associated with higher risk of iron deficiency in RLS after adjusting for potential confounding factors. In detail, Rep1 allele 2 homozygosity was prone to a higher risk of peripheral iron deficiency in RLS (OR: 4.550, P = 0.006, remained significant after the Bonferroni correction).

CONCLUSION

The SNCA-Rep1 variability modified RLS risk and influenced peripheral iron deficiency in this group of Chinese RLS patients. Rep1 allele 0 homozygosity decreased the risk of RLS, while homozygous allele 2 increased the risk of nonanemic iron deficiency in RLS.

Integrated Analyses of Microbiome and Longitudinal Metabolome Data Reveal Microbial-Host Interactions on Sulfur Metabolism in Parkinson's Disease

Parkinson’s disease (PD) exhibits systemic effects on the human metabolism, with emerging roles for the gut microbiome. Here, we integrate longitudinal metabolome data from 30 drug-naive, de novo PD patients and 30 matched controls with constraint-based modeling of gut microbial communities derived from an independent, drug-naive PD cohort, and prospective data from the general population. Our key results are (1) longitudinal trajectory of metabolites associated with the interconversion of methionine and cysteine via cystathionine differed between PD patients and controls; (2) dopaminergic medication showed strong lipidomic signatures; (3) taurine-conjugated bile acids correlated with the severity of motor symptoms, while low levels of sulfated taurolithocholate were associated with PD incidence in the general population; and (4) computational modeling predicted changes in sulfur metabolism, driven by A. muciniphila and B. wadsworthia, which is consistent with the changed metabolome. The multi-omics integration reveals PD-specific patterns in microbial-host sulfur co-metabolism that may contribute to PD severity.

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Longitudinal metabolomics reveal disturbed transsulfuration in Parkinson’s disease

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Metabolic modeling of gut microbiomes show altered microbial sulfur metabolism

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Changed microbial sulfur metabolism is linked to B. wadsworthia and A. muciniphila

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Taurine-conjugated bile acids are associated with incident Parkinson’s disease

Genetic risk scores and hallucinations in patients with Parkinson disease

Objective

We examine the hypothesized overlap of genetic architecture for Alzheimer disease (AD), schizophrenia (SZ), and Parkinson disease (PD) through the use of polygenic risk scores (PRSs) with the occurrence of hallucinations in PD.

Methods

We used 2 population-based studies (ParkWest, Norway, and Parkinson's Environment and Gene, USA) providing us with 399 patients with PD with European ancestry and a PD diagnosis after age 55 years to assess the associations between 4 PRSs and hallucinations after 5 years of mean disease duration. Based on the existing genome-wide association study of other large consortia, 4 PRSs were created: one each using AD, SZ, and PD cohorts and another PRS for height, which served as a negative control.

Results

A higher prevalence of hallucinations was observed with each SD increase of the AD-PRS (odds ratio [OR]: 1.37, 95% confidence interval [CI]: 1.03-1.83). This effect was mainly driven by APOE (OR: 1.92, 95% CI: 1.14-3.22). In addition, a suggestive decrease and increase, respectively, in hallucination prevalence were observed with the SZ-PRS and the PD-PRS (OR: 0.77, 95% CI: 0.59-1.01; and OR: 1.29, 95% CI: 0.95-1.76, respectively). No association was observed with the height PRS.

Conclusions

These results suggest that mechanisms for hallucinations in PD may in part be driven by the same genetic architecture that leads to cognitive decline in AD, especially by APOE.

Studying the Pathophysiology of Parkinson's Disease Using Zebrafish

Parkinson's disease is a common neurodegenerative disorder leading to severe disability. The clinical features reflect progressive neuronal loss, especially involving the dopaminergic system. The causes of Parkinson's disease are slowly being uncovered and include both genetic and environmental insults. Zebrafish have been a valuable tool in modeling various aspects of human disease. Here, we review studies utilizing zebrafish to investigate both genetic and toxin causes of Parkinson's disease. They have provided important insights into disease mechanisms and will be of great value in the search for disease-modifying therapies.

When does postural instability appear in monogenic parkinsonisms? An individual-patient meta-analysis

BACKGROUND

Postural instability is a disease milestone signaling advanced disease.

OBJECTIVES

To estimate the onset of postural instability in monogenic parkinsonisms.

METHODS

We systematically reviewed studies (PubMed 1996-2017) in SNCA, PRKN, PINK1, DJ-1, LRRK2, ATP13A2, FBXO7, VPS35, DNAJC6, or SYNJ1-related monogenic parkinsonisms, with documented postural instability. Genes with ≥ 15 patients were included in an individual-patient meta-analysis and compared with a retrospectively collected sporadic Parkinson's disease cohort from our center. The primary outcome measure was the progression-free survival from postural instability using Kaplan-Meier survival curves. Cox proportional hazards analyses were summarized using hazards ratio (HR).

RESULTS

Of 2085 eligible studies, 124 met full criteria (636 patients) for the systematic review, whereas a total of 871 subjects (270 from sporadic cohort, 601 monogenic parkinsonisms) were included in the individual-patient meta-analysis. Postural instability was reported in 80% of DJ-1, 40% of PRKN, 39% of PINK1, 34% of ATP13A2, 31% of LRRK2, and 29% of SNCA patients. Progression-free survival from postural instability at 10 years after disease onset was longest in ATP13A2 (97%) and shortest in SNCA (50%). Halfway between these two extremes were PRKN (88%), PINK1 (87%), and LRRK2 (81%), similar to sporadic Parkinson's disease (72%). Higher risk of postural instability was observed in SNCA (HR = 3.2, p = 0.007) and DJ-1 (HR = 3.96, p = 0.001) compared to sporadic Parkinson's disease. Young age at onset in PINK1 and female sex in LRRK2 were associated with a decreased risk of postural instability.

CONCLUSIONS

Monogenic parkinsonisms exhibit differential timelines to postural instability, informing prognostic counseling and interpretation of future genotype-specific treatment trials.

Longitudinal Epigenome-Wide Methylation Study of Cognitive Decline and Motor Progression in Parkinson's Disease

BACKGROUND

DNA methylation studies in Parkinson's disease (PD) thus far have focused on disease susceptibility but not progression.

OBJECTIVE

In this epigenome-wide association study (EWAS), we aim to identify methylation markers associated with faster cognitive decline or motor progression in PD.

METHODS

We included 232 PD patients from the Parkinson's Environment and Gene follow-up study who provided blood samples at enrolment. Information on cognitive and motor function was collected using the Mini-Mental State Examination (MMSE) and Unified Parkinson's Disease Rating Scale (UPDRS). For EWAS analyses, we used a robust measure of correlation: biweight midcorrelations, t-tests, and Cox proportional hazard models. We also conducted weighted correlation network analysis (WGCNA) to identify CpG modules associated with cognitive decline or motor progression in PD.

RESULTS

Among 197 individuals of European ancestry, with our EWAS approach we identified 7 genome-wide significant CpGs associated with a MMSE 4-point decline and 8 CpGs associated with faster motor progression (i.e., rate of UPDRS increase ≥5-point/year). The most interesting CpGs for cognitive decline include cg17445913 in KCNB1 (cor = 0.36, p = 6.85×10-7) and cg02920897 in DLEU2 (cor = 0.34, p = 3.23×10-6), while for motor progression it was cg01754178 in PTPRN2 (cor = - 0.34, p = 2.07×10-6). In WGCNA, motor progression related modules were enriched for genes related to neuronal synaptic functions, Wnt signaling pathway, and mitochondrial apoptosis.

CONCLUSIONS

Our study provides the first epigenetic evidence that differential methylation in genes previously identified as being associated with cognitive impairment, neuronal synaptic function, Wnt signaling pathway, and mitochondrial apoptosis is associated with cognitive and motor progression in PD.

Plasma ubiquitin C-terminal hydrolase L1 levels reflect disease stage and motor severity in Parkinson's disease

Parkinson’s disease (PD) is characterized by Lewy bodies containing α-synuclein and ubiquitin aggregates, their co-occurrence possibly linked to a failure of the ubiquitin proteasome system. Ubiquitin C-terminal hydrolase L1 (UCHL1) plays an important role in maintenance of nervous system integrity, and overexpression of UCHL1 has been shown to increase ubiquitin levels within neurons. While cerebrospinal fluid ubiquitin levels were reported to be lower in PD vs controls, plasma UCHL1 levels and their relationship with clinical measures in PD has not been reported. We measured plasma UCHL1 levels using single molecule array (Simoa) in 291 subjects (242 PD and 49 healthy controls, HC). We found that UCHL1 levels were significantly higher in PD patients at moderate stages (Hoehn and Yahr, H&Y stage >2) vs milder PD (H&Y ≤2, p<0.001) and HC (p=0.001). There was no significant difference in UCHL1 levels between PD patients at H&Y stages ≤2 vs HC. Across all PD patients, UCHL1 correlated significantly with UPDRS Part III motor scores (β=3.87, 95% CI=0.43-7.31, p=0.028), but not with global cognition. Overall, we found that UCHL1 correlates with motor function in PD, with higher levels seen in later disease stages. These findings will be validated in longitudinal studies.

Cognitive Impairment and Mortality in a Population-Based Parkinson's Disease Cohort

BACKGROUND

Parkinson's disease (PD) is a heterogeneous disorder with variability in phenotype and progression.

OBJECTIVE

We describe characteristics of PD patients in the largest population-based cohort followed for progression to date, and evaluate clinical risk factors for cognitive impairment and mortality.

METHODS

We collected longitudinal data using the Unified Parkinson's Disease Rating Scale (UPDRS), Mini-Mental State Exam (MMSE), and Geriatric Depression Scale (GDS) in 242 new-onset PD patients followed for progression. We compared those who developed cognitive impairment (MMSE≤24) with those who did not, using t-tests, chi-square tests, and Cox proportional hazards regression. Mortality risk factors were assessed in all 360 patients enrolled at baseline.

RESULTS

Thirty-four patients developed cognitive impairment during follow-up. Baseline characteristics predictive of faster time to cognitive impairment were older age at diagnosis, fewer years of education, and longer average sleep duration reported. The 197 patients who died were older at diagnosis, reported longer average sleep duration, had lower baseline MMSE scores, higher UPDRS-III scores, and a higher proportion were of the postural instability gait difficulty (PIGD) subtype. Patients with the tremor dominant (TD) subtype at baseline were less likely to develop cognitive impairment or die during follow-up. Progression of cognitive, depressive, and motor symptoms occurred in parallel.

CONCLUSIONS

Motor symptom severity and subtype influence the incidence of cognitive impairment and mortality in PD, with the TD motor subtype being relatively protective. In addition, we newly found that longer average sleep duration at baseline predicts faster progression to cognitive impairment and mortality.

Association of Polygenic Risk Score With Cognitive Decline and Motor Progression in Parkinson Disease

Importance

Genetic factors have a well-known influence on Parkinson disease (PD) susceptibility. The largest genome-wide association study (GWAS) identified 26 independent single-nucleotide polymorphisms (SNPs) associated with PD risk. Among patients, the course and severity of symptom progression is variable, and little is known about the potential association of genetic factors with phenotypic variance.

Objective

To assess whether GWAS-identified PD risk SNPs also have a cumulative association with the progression of cognitive and motor symptoms in patients with PD.

Design, Setting, and Participants

This longitudinal population-based cohort study of 285 patients of European ancestry with incident PD genotyped 23 GWAS SNPs. One hundred ninety-nine patients were followed up for a mean (SD) of 5.3 (2.1) years for progression (baseline: June 1, 2001, through November 31, 2007; follow-up: June 1, 2007, through August 31, 2013, with mortality surveillance through December 31, 2016); 57 patients had died or were too ill for follow-up, and 29 withdrew or could not be contacted. Movement disorder specialists repeatedly assessed PD symptom progression.

Main Outcomes Measures

The combined association of PD risk loci, after creating a weighted polygenic risk score (PRS), with cognitive decline, motor progression, and survival, relying on Cox proportional hazards regression models and inverse probability weights to account for censoring.

Results

Of the 285 patients undergoing genotyping, 160 were men (56.1%) and 125 were women (43.9%); the mean (SD) age at diagnosis was 69.1 (10.4) years. The weighted PRS was associated with significantly faster cognitive decline, measured by change in the Mini-Mental State Examination (hazard ratio [HR] per 1 SD, 1.44; 95% CI, 1.00-2.07). The PRS was also associated with faster motor decline, measured by time to Hoehn & Yahr Scale stage 3 (HR, 1.34; 95% CI, 1.00-1.79) and change in Unified Parkinson's Disease Rating Scale part III score (HR, 1.42; 95% CI, 1.00-2.01).

Conclusions and Relevance

Susceptibility SNPs for PD combined with a cumulative PRS were associated with faster motor and cognitive decline in patients. Thus, these genetic markers may be associated with not only PD susceptibility but also disease progression in multiple domains.

Translational Informatics for Parkinson's Disease: from Big Biomedical Data to Small Actionable Alterations

Parkinson's disease (PD) is a common neurological disease in elderly people, and its morbidity and mortality are increasing with the advent of global ageing. The traditional paradigm of moving from small data to big data in biomedical research is shifting toward big data-based identification of small actionable alterations. To highlight the use of big data for precision PD medicine, we review PD big data and informatics for the translation of basic PD research to clinical applications. We emphasize some key findings in clinically actionable changes, such as susceptibility genetic variations for PD risk population screening, biomarkers for the diagnosis and stratification of PD patients, risk factors for PD, and lifestyles for the prevention of PD. The challenges associated with the collection, storage, and modelling of diverse big data for PD precision medicine and healthcare are also summarized. Future perspectives on systems modelling and intelligent medicine for PD monitoring, diagnosis, treatment, and healthcare are discussed in the end.

Effect of polygenic load on striatal dopaminergic deterioration in Parkinson disease

OBJECTIVE

To investigate the effect of polygenic load on the progression of striatal dopaminergic dysfunction in patients with Parkinson disease (PD).

METHODS

Using data from 335 patients with PD in the Parkinson's Progression Markers Initiative (PPMI) database, we investigated the longitudinal association of PD-associated polygenic load with changes in striatal dopaminergic activity as measured by ¹²³I-N-3-fluoropropyl-2-β-carboxymethoxy-3β-(4-iodophenyl) nortropane (¹²³I-FP-CIT) SPECT over 4 years. PD-associated polygenic load was estimated by calculating weighted genetic risk scores (GRS) using 1) all available 27 PD-risk single nucleotide polymorphisms (SNPs) in the PPMI database (GRS1) and 2) 23 SNPs with minor allele frequency >0.05 (GRS2).

RESULTS

GRS1 and GRS2 were correlated with younger age at onset in patients with PD (GRS1, Spearman ρ = -0.128, p = 0.019; GRS2, Spearman ρ = -0.109, p = 0.047). Although GRS1 did not show an association with changes in striatal ¹²³I-FP-CIT availability, GRS2 was associated with a slower decline of striatal dopaminergic activity (interactions with disease duration in linear mixed model; caudate nucleus, estimate = 0.399, SE = 0.165, p = 0.028; putamen, estimate = 0.396, SE = 0.137, p = 0.016).

CONCLUSIONS

Our results suggest that genetic factors for PD risk may have heterogeneous effects on striatal dopaminergic degeneration, and some factors may be associated with a slower decline of dopaminergic activity. Composition of PD progression-specific GRS may be useful in predicting disease progression in patients.

Antibodies against alpha-synuclein: tools and therapies

Synucleinopathies including Parkinson's disease, dementia with Lewy bodies and multiple system atrophy are characterized by the abnormal accumulation and propagation of α-synuclein (α-syn) pathology in the central and peripheral nervous system as Lewy bodies or glial cytoplasmic inclusions. Several antibodies against α-syn have been developed since it was first detected as the major component of Lewy bodies and glial cytoplasmic inclusions. Over the years, researchers have generated specific antibodies that alleviate the accumulation of intracellular aggregated α-syn and associated pathology in cellular and preclinical models of synucleinopathies. So far, antibodies have been the first choice as tools for research and diagnosis and currently, a wide variety of antibody fragments have been developed as an alternative to full-length antibodies for increasing its therapeutic usefulness. Recently, conformation specific antibody-based approaches have been found to be promising as therapeutic strategies, both to block α-syn aggregation and ameliorate the resultant cytotoxicity, and as diagnostic tools. In this review, we summarize different α-syn specific antibodies and provide their usefulness in tackling synucleinopathies. This article is part of the Special Issue "Synuclein".

SNCA Rep1 promoter variability influences cognition in Parkinson's disease

BACKGROUND

While the association between alpha-synuclein gene promoter (Rep1) variability and risk of PD is well established, its association with cognition is unclear.

OBJECTIVES

To investigate the association between Rep1 and motor and cognitive outcomes in PD.

METHODS

Rep1 allele lengths were determined in 172 PD patients who were grouped into "long" and "short" carriers according to previous methods. Multivariable regression analysis was performed to investigate the effect of Rep1 length on cognitive and motor scores.

RESULTS

Long Rep1 allele carriers had significantly lower MMSE (P = 0.010) and higher UPDRS Part III (P = 0.026) and H & Y (P = 0.008) scores compared to short allele carriers (controlled for age, sex, and disease duration). Interaction analyses of Rep1 with apolipoprotein 4 revealed no significant effect on clinical outcomes.

CONCLUSIONS

PD patients carrying long Rep1 alleles are more impaired on cognitive and motor function independent of apolipoprotein 4 genotype. © 2019 International Parkinson and Movement Disorder Society.

The association between lifestyle factors and Parkinson's disease progression and mortality

BACKGROUND

Lifestyle factors may contribute to the development of Parkinson's disease, but little is known about factors that influence progression. The objective of the current study was to examine whether caffeine or alcohol consumption, physical activity, or cigarette smoking is associated with progression and survival among PD patients.

METHODS

We assessed lifelong coffee, tea, and alcohol consumption, smoking, and physical activity in a prospective community-based cohort (n = 360). All patients were passively followed for mortality (2001-2016); 244 were actively followed on average ± SD 5.3 ± 2.1 years (2007-2014). Movement disorder specialists repeatedly assessed motor function (Hoehn & Yahr) and cognition (Mini-Mental State Exam). We used Cox proportional hazards models and inverse probability weights to account for censoring.

RESULTS

Coffee, caffeinated tea, moderate alcohol consumption, and physical activity were protective against at least 1 outcome. Smoking and heavy alcohol consumption were associated with increased risks. Coffee was protective against time to Hoehn & Yahr stage 3 (hazard ratio, 0.52; 95% confidence interval, 0.28-1.01), cognitive decline (hazard ratio, 0.23; 95% confidence interval, 0.11, 0.48), and mortality (hazard ratio, 0.47; 95% confidence interval, 0.32-0.69). Relative to moderate drinkers, those who never drank liquor and those who drank more heavily were at an increased risk of Hoehn & Yahr 3 (hazard ratio, 3.48; 95% confidence interval, 1.90-6.38; and hazard ratio, 2.16; 95% confidence interval, 1.03, 4.54, respectively). A history of competitive sports was protective against cognitive decline (hazard ratio, 0.46; 95% confidence interval, 0.22-0.96) and Hoehn & Yahr 3 (hazard ratio, 0.42; 95% confidence interval, 0.23-0.79), as was physical activity measured by metabolic-equivalent hours. Current cigarette smoking was associated with faster cognitive decline (hazard ratio, 3.20; 95% confidence interval, 1.02-10.01).

CONCLUSIONS

This population-based study suggests that lifestyle factors influence PD progression and mortality. © 2019 International Parkinson and Movement Disorder Society.

Parkinson's Disease: Basic Pathomechanisms and a Clinical Overview

PD is a common and a debilitating degenerative movement disorder. The number of patients is increasing worldwide and as yet there is no cure for the disease. The majority of existing treatments target motor symptom control. Over the last two decades the impact of the genetic contribution to PD has been appreciated. Significant discoveries have been made, which have advanced our understanding of the pathophysiological and molecular basis of PD. In this chapter we outline current knowledge of the clinical aspects of PD and the basic mechanistic understanding.

Human iPS Cell-Derived Patient Tissues and 3D Cell Culture Part 1: Target Identification and Lead Optimization

Human-induced pluripotent stem cells (HiPSCs), and new technologies to culture them into functional cell types and tissues, are now aiding drug discovery. Patient-derived HiPSCs can provide disease models that are more clinically relevant and so more predictive than the currently available animal-derived or tumor cell-derived cells. These cells, consequently, exhibit disease phenotypes close to the human pathology, particularly when cultured under conditions that allow them to recapitulate the tissue architecture in three-dimensional (3D) systems. A key feature of HiPSCs is that they can be cultured under conditions that favor formation of multicellular spheroids or organoids. By culturing and differentiating in systems mimicking the human tissue in vivo, the HiPSC microenvironment further reflects patient in vivo physiology, pathophysiology, and ultimately pharmacological responsiveness. We assess the rationale for using HiPSCs in several phases of preclinical drug discovery, specifically in disease modeling, target identification, and lead optimization. We also discuss the growing use of HiPSCs in compound lead optimization, particularly in profiling compounds for their potential metabolic liability and off-target toxicities. Collectively, we contend that both approaches, HiPSCs and 3D cell culture, when used in concert, have exciting potential for the development of novel medicines.

SNCA REP1 and Parkinson's disease

REP1 is a polymorphic dinucleotide repeat sequence located in the promoter region of the SNCA gene (OMIM 163890). Opinions regarding the interaction between the various REP1 alleles and Parkinson's disease (PD) or its phenotypes have been inconsistent and have thus far not been comprehensively analyzed. In this study, we searched Medline, Embase and Cochrane databases as well as the Chinese-language Wanfang and CNKI databases using strict inclusion and exclusion criteria and conducted our analysis using Revman 5.3 software. Our search produced 28 articles describing REP1 alleles and their associated PD risks and 8 articles which discussed the relationship between REP1 variation and PD phenotypes. We found that the 265-, 269-, and 271-bp alleles of REP1 (using the nomenclature established by Xia et al.) increased the risk of PD (OR: 1.81, 1.05, 1.17; p: 0.0002, 0.003, 0.002) while the 267-bp allele decreased PD risk (OR: 0.86, p: <0.00001) when taking all populations into account. By ethnicity, we observed an obvious population heterogeneity in the effects of various alleles, where the 269-, 271-, and 273-bp alleles increased PD risk (OR: 1.06, 1.22, 1.89; p: 0.001, 0.003, 0.001) and the 267-bp allele decreased PD risk (OR: 0.85; p: <0.00001) in Caucasian populations, and the 263- and 265-bp alleles increased the risk of PD (OR: 2.22, 2.03; p: 0.03, 0.0002) and the 267- and 273-bp alleles decreased PD risk (OR: 0.90, 0.78; p: 0.02, 0.03) in Asian populations. We also determined that the 267-, 269-, and 271-bp alleles occurred the most frequently, although the frequency distribution varied among different ethnicities. Phenotypic analysis demonstrated that PD patients carrying the 271-bp allele were prone to early onset PD (OR: 1.75, p: 0.02) while the 267-bp had the opposite effect (OR: 0.81; p: 0.01).

NFE2L2, PPARGC1α, and pesticides and Parkinson's disease risk and progression

OBJECTIVE

To investigate three expression-altering NFE2L2 SNPs and four PPARGC1α previously implicated SNPs and pesticides on Parkinson's disease (PD) risk and symptom progression.

METHODS

In 472 PD patients and 532 population-based controls, we examined variants and their interactions with maneb and paraquat (MB/PQ) pesticide exposure on PD onset (logistic regression) and progression of motor symptoms and cognitive decline (n = 192; linear repeated measures).

RESULTS

NFE2L2 rs6721961 T allele was associated with a reduced risk of PD (OR = 0.70, 95% CI = 0.53, 0.94) and slower cognitive decline (β = 0.095; p = 0.0004). None of the PPARGC1α SNPs were marginally associated with PD risk. We estimate statistical interactions between MB/PQ and PPARGC1α rs6821591 (interaction p = 0.009) and rs8192678 (interaction p = 0.05), such that those with high exposure and the variant allele were at an increased risk of PD (OR ≥ 1.30, p ≤ 0.05). PPARGC1α rs6821591 was also associated with faster motor symptom progression as measured with the UPDRS-III (β = 0.234; p = 0.001).

CONCLUSION

Our study provides support for the involvement of both NFE2L2 and PPARGC1α in PD susceptibility and progression, marginally and through pathways involving MB/PQ exposure.

The Length of SNCA Rep1 Microsatellite May Influence Cognitive Evolution in Parkinson's Disease

Background

Alpha-synuclein is a constituent of Lewy bodies and mutations of its gene cause familial Parkinson's disease (PD). A previous study showed that a variant of the alpha-synuclein gene (SNCA), namely the 263 bp allele of Rep1 was associated with faster motor progression in PD. On the contrary, a recent report failed to detect a detrimental effect of Rep1 263 on both motor and cognitive outcomes in PD. Aim of this study was to evaluate the influence of the Rep1 variants on disease progression in PD patients.

Methods

We recruited and genotyped for SNCA Rep1 426 PD patients with age at onset ≥40 years and disease duration ≥4 years. We then analyzed frequency and time of occurrence of wearing-off, dyskinesia, freezing of gait, visual hallucinations, and dementia using a multivariate Cox's proportional hazards regression model.

Results

SNCA Rep1 263 carriers showed significantly increased risk of both dementia (HR = 3.03) and visual hallucinations (HR = 2.69) compared to 263 non-carriers. Risk of motor complications did not differ in the two groups.

Conclusion

SNCA Rep1 263 allele is associated with a worse cognitive outcome in PD.

Risk variants of the α-synuclein locus and REM sleep behavior disorder in Parkinson's disease: a genetic association study

BACKGROUND

Parkinson's disease is a heterogeneous disorder where genetic factors may underlie clinical variability. Rapid eye movement sleep behavior disorder (RBD) is a parasomnia strongly linked to synucleinopathies, including Parkinson's disease. We hypothesized that SNCA variants conferring risk of Parkinson's disease would also predispose to an RBD phenotype.

METHODS

We assessed possible RBD (pRBD) status using the RBD screening questionnaire and investigated known susceptibility variants for Parkinson's disease located in the α-synuclein (SNCA) and tau (MAPT) gene loci in 325 Parkinson's disease patients. Associations between genetic risk variants and RBD were investigated by logistic regression, and an independent dataset of 382 patients from the Parkinson's Progression Marker Initiative (PPMI) study was used for replication.

RESULTS

pRBD was associated with rs3756063 located in the 5' region of SNCA (two-sided p = 0.018, odds ratio 1.44). We replicated this finding in the PPMI dataset (one-sided p = 0.036, odds ratio 1.35) and meta-analyzed the results (two-sided p = 0.0032, odds ratio 1.40). The Parkinson's disease risk variant in the 3' region of SNCA and the MAPT variant showed no association with pRBD.

CONCLUSIONS

Our findings provide proof of principle that a largely stable, dichotomous clinical feature of Parkinson's disease can be linked to a specific genetic susceptibility profile. Indirectly, it also supports the hypothesis of RBD as relevant marker for a distinct subtype of the disorder.

Genetics of Parkinson disease

An understanding of the genetic etiology of Parkinson disease (PD) has become imperative for the modern-day neurologist. Although genetic forms cause only a minority of PD, the disease mechanisms they elucidate advance the understanding of idiopathic cases. Moreover, recently identified susceptibility variants contribute to complex-etiology PD and broaden the contribution of genetics beyond familial and early-onset cases. Dominantly inherited monogenic forms mimic idiopathic PD and are caused by mutations or copy number variations of SNCA, LRRK2, and VPS35. On the other hand, early-onset forms are associated with PARKIN, PINK1, and DJ1 mutations, nominating mitochondrial dysfunction and oxidative stress as another important molecular pathway in the causation of the disease, in addition to alpha-synuclein accumulation. Common variants in GBA are consistently identified by association studies and may be considered to be a major risk gene for PD, with markedly reduced penetrance. Other genes have been proposed to be associated with PD; however, these only cause very rare forms, if at all. Current guidelines recommend testing for LRRK2 variants in familial PD or in specific populations (ancestry), and for the recessive genes in early-onset PD. However, gene panels have made testing for multiple forms of genetic PD a viable approach.

Inventory of real world data sources in Parkinson's disease

Background

Real world data have an important role to play in the evaluation of epidemiology and burden of disease; and in assisting health-care decision-makers, especially related to coverage and payment decisions. However, there is currently no overview of the existing longitudinal real world data sources in Parkinson’s disease (PD) in the USA. Such an assessment can be very helpful, to support a future effort to harmonize real world data collection and use the available resources in an optimal way.

Methods

The objective of this comprehensive literature review is to systematically identify and describe the longitudinal, real world data sources in PD in the USA, and to provide a summary of their measurements (categorized into 8 main dimensions: motor and neurological functions, cognition, psychiatry, activities of daily living, sleep, quality of life, autonomic symptoms and other). The literature search was performed using MEDLINE, EMBASE and internet key word search.

Results

Of the 53 data sources identified between May and August 2016, 16 were still ongoing. Current medications (81%) and comorbidities (79%) were frequently collected, in comparison to medical imaging (36%), genetic information (30%), caregiver burden (11%) and healthcare costs (2%). Many different measurements (n = 108) were performed and an interesting variability among used measurements was revealed.

Conclusions

Many longitudinal real world data sources on PD exist. Different types of measurements have been performed over time. To allow comparison and pooling of these multiple data sources, it will be essential to harmonize practices in terms of types of measurements.

Dopamine receptors and BDNF-haplotypes predict dyskinesia in Parkinson's disease

OBJECTIVE

Dyskinesia is a known side-effect of the treatment of Parkinson's Disease (PD). We examined the influence of haplotypes in three dopamine receptors (DRD1, DRD2 and DRD3) and the Brain Derived Neurotrophic Factor (BDNF) on dyskinesia.

METHODS

Patient data were drawn from a population-based case-control study. We included 418 patients with confirmed diagnoses by movement disorder specialists, using levodopa and a minimum three years disease duration at the time of assessment. Applying Haploview and Phase, we created haploblocks for DRD1-3 and BDNF. Risk scores for DRD2 and DRD3 were generated. We calculated risk ratios using Poisson regression with robust error variance.

RESULTS

There was no difference in dyskinesia prevalence among carriers of various haplotypes in DRD1. However, one haplotype in each DRD2 haploblocks was associated with a 29 to 50% increase in dyskinesia risk. For each unit increase in risk score, we observed a 16% increase in dyskinesia risk for DRD2 (95%CI: 1.05-1.29) and a 17% (95%CI: 0.99-1.40) increase for DRD3. The BDNF haploblock was not associated, but the minor allele of the rs6265 SNP was associated with dyskinesia (adjusted RR 1.31 (95%CI: 1.01-1.70)).

CONCLUSION

Carriers of DRD2 risk haplotypes and possibly the BDNF variants rs6265 and DRD3 haplotypes, were at increased risk of dyskinesia, suggesting that these genes may be involved in dyskinesia related pathomechanisms. PD patients with these genetic variants might be prime candidates for treatments aiming to prevent or delay the onset of dyskinesia.

Organophosphate pesticides and PON1 L55M in Parkinson's disease progression

BACKGROUND

Parkinson's disease (PD) has motor and non-motor features that contribute to its phenotype and functional decline. Organophosphate (OP) pesticides and PON1 L55M, which influences OP metabolism, have been implicated in multiple mechanisms related to neuronal cell death and may influence PD symptom progression.

OBJECTIVE

To investigate whether ambient agricultural OP exposure and PON1 L55M influence the rate of motor, cognitive, and mood-related symptom progression in PD.

METHODS

We followed a longitudinal cohort of 246 incident PD patients on average over 5years (7.5years after diagnosis), repeatedly measuring symptom progression with the Mini-Mental State Exam (MMSE), Unified Parkinson's Disease Rating Scale (UPDRS), and Geriatric Depressive Scale (GDS). OP exposures were generated with a geographic information system (GIS) based exposure assessment tool. We employed repeated-measures regression to assess associations between OP exposure and/or PON1 L55M genotype and progression.

RESULTS

High OP exposures were associated with faster progression of motor (UPDRS β=0.24, 95% CI=-0.01, 0.49) and cognitive scores (MMSE β=-0.06, 95% CI=-0.11, -0.01). PON1 55MM was associated with faster progression of motor (UPDRS β=0.28, 95% CI=0.08, 0.48) and depressive symptoms (GDS β=0.07; 95% CI=0.01, 0.13). We also found the PON1 L55M variant to interact with OP exposures in influencing MMSE cognitive scores (β=-1.26, 95% CI=-2.43, -0.09).

CONCLUSION

Our study provides preliminary support for the involvement of OP pesticides and PON1 in PD-related motor, cognitive, or depressive symptom progression. Future studies are needed to replicate findings and examine whether elderly populations generally are similarly impacted by pesticides or PON1 55M genotypes.

Regional analysis and genetic association of nigrostriatal degeneration in Lewy body disease

BACKGROUND

A number of genetic loci are associated with risk for Parkinson's disease (PD) based on genome-wide association studies; however, the relationship between genetic variants and nigrostriatal degeneration, which is the structural correlate of parkinsonism, has not been reported.

OBJECTIVES

We quantified nigrostriatal dopaminergic integrity with image analysis of putaminal tyrosine hydroxylase immunoreactivity in 492 brains with Lewy body disease and used this pathologic endophenotype to explore possible association with PD genetic variants.

METHODS

The study cases had Lewy-related pathology and variable degrees of nigrostriatal degeneration. They were assigned to one of the following clinical subgroups according to their predominant clinical syndrome: parkinsonism-predominant, parkinsonism+dementia, and dementia-predominant. In addition to putaminal tyrosine hydroxylase immunoreactivity, semiquantitative scoring was used to assess substantia nigra neuronal loss. A total of 29 PD genetic risk variants were genotyped on each case.

RESULTS

When compared with controls, tyrosine hydroxylase immunoreactivity was reduced in Lewy body cases in the dorsolateral (79%) and ventromedial (57%) putamen. The dorsolateral region was better preserved in dementia-predominant cases than in cases with parkinsonism. Dorsolateral putaminal tyrosine hydroxylase immunoreactivity correlated with neuronal loss in the ventrolateral substantia nigra. Genetic analyses showed no significant association of PD risk variants with putaminal tyrosine hydroxylase immunoreactivity.

CONCLUSIONS

The results confirm regional differences in putaminal dopaminergic degeneration and vulnerability of nigrostriatal pathway in Lewy body disorders with parkinsonism. The lack of association with PD genetic risk variants suggests that they may not be associated with quantitative endophenotypes of nigrostriatal degeneration, but more likely related to the risk of disease per se. © 2017 International Parkinson and Movement Disorder Society.

Genetic Variants in SNCA and the Risk of Sporadic Parkinson's Disease and Clinical Outcomes: A Review

There is increasing evidence of the contribution of genetic susceptibility to the etiology of Parkinson's disease (PD). Genetic variations in the SNCA gene are well established by linkage and genome-wide association studies. Positive associations of single nucleotide polymorphisms (SNPs) in SNCA and increased risk for PD were found. However, the role of SNCA variants in individual traits or phenotypes of PD is unknown. Here, we reviewed the current literature and identified 57 studies, performed in fourteen different countries, that investigated SNCA variants and susceptibility to PD. We discussed the findings based on environmental factors, history of PD, clinical outcomes, and ethnicity. In conclusion, SNPs within the SNCA gene can modify the susceptibility to PD, leading to increased or decreased risk. The risk associations of some SNPs varied among samples. Of notice, no studies in South American or African populations were found. There is little information about the effects of these variants on particular clinical aspects of PD, such as motor and nonmotor symptoms. Similarly, evidence of possible interactions between SNCA SNPs and environmental factors or disease progression is scarce. There is a need to expand the clinical applicability of these data as well as to investigate the role of SNCA SNPs in populations with different ethnic backgrounds.

[Genetic risk variants in Parkinson's disease and other movement disorders]

Movement disorders are often genetically complex with genetic risk factors playing a major role. For example, monogenic causes of Parkinson's disease (PD) can be found in only 2-5% of patients who often have an early onset (<40 years). In the majority of patients, common genetic variants seem to contribute to the disease risk. To date, 24 genetic risk factors have been identified. For restless legs syndrome (RLS), six different risk variants have been reported but no monogenic cause is known yet. For the genetic risk factors of essential tremor and dystonia, which are less well studied, only five and two candidate variants, respectively, have been described but their roles still require independent confirmation. In this review, we provide an overview on the involved genes, their function, and discuss possible, disease mechanism-driven therapies.