Age-related selection bias in Parkinson's disease research : are we recruiting the right participants?

Acknowledgements We acknowledge the earlier work of Dr Kate Taylor and Dr Dominique Twelves on the previous systematic review of incidence studies in Parkinson’s disease. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Authors report the following funding received during the conduct of this study: Dr Macleod: fellowship funding from the Chief Scientist Office of the Scottish Government and NHS Education for Scotland; grant funding Parkinson’s UK, the Academy of Medical Sciences, NHS Grampian Endowments, the Wellcome Trust, the University of Aberdeen. Dr Henery: financial support from the University of Aberdeen Dr Nwajiugo: none Dr Scott: none Dr Caslake: grant funding from Parkinson’s UK Dr Counsell: grant funding from the Chief Scientist Office of the Scottish Government, the PSP Association, and NHS Grampian Endowments.Peer reviewedPostprin

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

ACKNOWLEDGMENTS The authors would like to thank all of the patients and controls for participation in each of the studies. Equally, we thank all members of each of the study groups and other personnel for their contributions. Funding sources for the respective studies are as follows: The Norwegian ParkWest study has been funded by the Research Council of Norway (177966), the Western Norway Regional Health Authority (911218), the Norwegian Parkinson’s Research Foundation, and Rebergs Legacy. PINE study was supported by Parkinson’s UK (G0502, G0914, G1302), Scottish Government Chief Scientist Office, BMA Doris Hillier Award, the BUPA Foundation, NHS Grampian Endowments, and RS MacDonald Trust. The NYPUM study has been funded by the Swedish Medical Research Council, the Swedish Parkinson’s disease Association, the Swedish Parkinson’s Foundation, Parkinson Research Foundation, Erling Persson Foundation, Kempe Foundation, the Swedish Brain Foundation (Hjarnfonden), and the Vasterbotten County Council. AAS, JMG and GA are supported by the Research Council of Norway (287842). BLF acknowledges support through donations to the UCLA Clinical Neurogenomics Research Center. CK is supported by the NIH grant F32AG063442. The PEG study was supported by NIH/NIEHS grants R01-ES010544 and U54-ES012078. Publication of this manuscript was supported under the The Michael J. Fox Foundation: 2021 RFA: Accelerating Publication of Parkinson’s Disease Replication Data.Peer reviewedPublisher PD

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.publishedVersio

A systematic review of biomarkers for disease progression in Parkinson's disease

Peer reviewedPublisher PD

A Biodiverse Rich Environment Does Not Contribute to a Better Diet: A Case Study from DR Congo

The potential of biodiversity to increase and sustain nutrition security is increasingly recognized by the international research community. To date however, dietary assessment studies that have assessed how biodiversity actually contributes to human diets are virtually absent. This study measured the contribution of wild edible plants (WEP) to the dietary quality in the high biodiverse context of DR Congo. The habitual dietary intake was estimated from 2 multiple-pass 24 h dietary recalls for 363 urban and 129 rural women. All WEP were collected during previous ethnobotanical investigations and identified and deposited in the National Botanical Garden of Belgium (BR). Results showed that in a high biodiverse region with precarious food security, WEP are insufficiently consumed to increase nutrition security or dietary adequacy. The highest contribution came from Dacryodes edulis in the village sample contributing 4.8% of total energy intake. Considering the nutrient composition of the many WEP available in the region and known by the indigenous populations, the potential to increase nutrition security is vast. Additional research regarding the dietary contribution of agricultural biodiversity and the nutrient composition of WEP would allow to integrate them into appropriate dietary guidelines for the region and pave the way to domesticate the most interesting WEP

Discovery and functional prioritization of Parkinson's disease candidate genes from large-scale whole exome sequencing.

BACKGROUND: Whole-exome sequencing (WES) has been successful in identifying genes that cause familial Parkinson's disease (PD). However, until now this approach has not been deployed to study large cohorts of unrelated participants. To discover rare PD susceptibility variants, we performed WES in 1148 unrelated cases and 503 control participants. Candidate genes were subsequently validated for functions relevant to PD based on parallel RNA-interference (RNAi) screens in human cell culture and Drosophila and C. elegans models. RESULTS: Assuming autosomal recessive inheritance, we identify 27 genes that have homozygous or compound heterozygous loss-of-function variants in PD cases. Definitive replication and confirmation of these findings were hindered by potential heterogeneity and by the rarity of the implicated alleles. We therefore looked for potential genetic interactions with established PD mechanisms. Following RNAi-mediated knockdown, 15 of the genes modulated mitochondrial dynamics in human neuronal cultures and four candidates enhanced α-synuclein-induced neurodegeneration in Drosophila. Based on complementary analyses in independent human datasets, five functionally validated genes-GPATCH2L, UHRF1BP1L, PTPRH, ARSB, and VPS13C-also showed evidence consistent with genetic replication. CONCLUSIONS: By integrating human genetic and functional evidence, we identify several PD susceptibility gene candidates for further investigation. Our approach highlights a powerful experimental strategy with broad applicability for future studies of disorders with complex genetic etiologies

Association of SNCA Parkinson's Disease Risk Polymorphisms With Disease Progression in Newly Diagnosed Patients

Objectives: To evaluate the impact of SNCA polymorphisms originally identified as risk factors for Parkinson's disease (PD) on the clinical presentation and progression of the disease in a large cohort of population-based patients with incident PD. Methods: Four hundred thirty-three patients and 417 controls from three longitudinal cohorts were included in the study. Disease progression was recorded annually for up to 9 years using the Unified Parkinson's Disease Rating Scale (UPDRS) or Mini-Mental State Examination. Genotypes for five variants within the SNCA locus (rs2870004, rs356182, rs5019538, rs356219, and rs763443) were determined. We studied the association between each variant and disease progression using linear mixed-effects regression models. Results: The clinical profile of the patients with PD at the point of diagnosis was highly uniform between genotype groups. The rs356219-GG genotype was associated with a higher UPDRS II score than A-allele carriers (β = 1.52; 95% confidence interval 0.10–2.95; p = 0.036), but no differences were observed in the rate of progression of the UPDRS II scores. rs356219-GG was also associated with a faster annual change in Mini-Mental State Examination score compared with A-carriers (β = 0.03; 95% confidence interval 0.00–0.06; p = 0.043). Conclusions: We show that the known PD-risk variant rs356219 has a minor effect on modifying disease progression, whereas no differences were associated with rs2870004, rs356182, rs5019538, and rs763443. These findings suggest that SNCA variants associated with PD risk may not be major driving factors to the clinical heterogeneity observed for PD.publishedVersio

Association of SNCA Parkinson's Disease Risk Polymorphisms With Disease Progression in Newly Diagnosed Patients

Objectives: To evaluate the impact of SNCA polymorphisms originally identified as risk factors for Parkinson's disease (PD) on the clinical presentation and progression of the disease in a large cohort of population-based patients with incident PD. Methods: Four hundred thirty-three patients and 417 controls from three longitudinal cohorts were included in the study. Disease progression was recorded annually for up to 9 years using the Unified Parkinson's Disease Rating Scale (UPDRS) or Mini-Mental State Examination. Genotypes for five variants within the SNCA locus (rs2870004, rs356182, rs5019538, rs356219, and rs763443) were determined. We studied the association between each variant and disease progression using linear mixed-effects regression models. Results: The clinical profile of the patients with PD at the point of diagnosis was highly uniform between genotype groups. The rs356219-GG genotype was associated with a higher UPDRS II score than A-allele carriers (β = 1.52; 95% confidence interval 0.10–2.95; p = 0.036), but no differences were observed in the rate of progression of the UPDRS II scores. rs356219-GG was also associated with a faster annual change in Mini-Mental State Examination score compared with A-carriers (β = 0.03; 95% confidence interval 0.00–0.06; p = 0.043). Conclusions: We show that the known PD-risk variant rs356219 has a minor effect on modifying disease progression, whereas no differences were associated with rs2870004, rs356182, rs5019538, and rs763443. These findings suggest that SNCA variants associated with PD risk may not be major driving factors to the clinical heterogeneity observed for PD