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Background: The role of blood uric acid as a biomarker in symptomatic motor PD has been increasingly established in the literature., Objective: Our present study assessed the role of serum uric acid as a putative biomarker in a prodromal PD cohort [REM Sleep Behavior disorder (RBD) and Hyposmia] followed longitudinally., Methods: Longitudinal 5-year serum uric acid measurement data of 39 RBD patients and 26 Hyposmia patients with an abnormal DATSCAN imaging were downloaded from the Parkinson's Progression Markers Initiative database. These cohorts were compared with 423 de novo PD patients and 196 healthy controls enrolled in the same study., Results: After adjusting for age, sex, body mass index, and concomitant disorders (hypertension/gout), baseline and longitudinal serum uric acid levels were higher in the RBD subgroup as compared to the established PD cohort (p = 0.004 and p = 0.001). (Baseline RBD 6.07±1.6 vs. Baseline PD 5.35±1.3 mg/dL and Year-5 RBD 5.7±1.3 vs. Year-5 PD 5.26±1.33). This was also true for longitudinal measurements in the Hyposmic subgroup (p = 0.008) (Baseline Hyposmic 5.7±1.6 vs. PD 5.35±1.3 mg/dL and Year-5 Hyposmic 5.58±1.6 vs. PD 5.26±1.33)., Conclusion: Our results indicate that serum uric acid levels are higher in prodromal PD subjects with ongoing dopaminergic degeneration compared to those with manifest PD. These data indicate that the well-established decrease in the levels of serum uric acid occurs with the transition from prodromal to clinical PD. Whether the higher levels of serum uric acid observed in prodromal PD may provide protection against conversion to full-blown clinical PD will require further study.

Introduction: Higher prevalence of motor and non-motor features has been observed in non-manifesting mutation carriers of Parkinson's Disease (PD) compared to Healthy Controls (HC). The aim was to detect the differences between GBA and LRRK2 mutation carriers without PD and HC on neuropsychiatric symptoms., Methods: This is a cross-sectional retrospective study of non-manifesting GBA and LRRK2 mutation carriers and HC enrolled into Parkinson's Progression Markers Initiative (PPMI). Data extracted from the PPMI database contained: demographics and performance in MoCA scale and MDS-UPDRS scale part 1A (neuropsychiatric symptoms). All six features were treated as both continuous (MDS-UPDRS individual scores) and categorical variables (MDS-UPDRS individual score>0 and MDS-UPDRS individual score = 0). Logistic regression analyses were applied to evaluate the association between mutation carrying status and neuropsychiatric symptoms., Results: In this study, the neuropsychiatric evaluation was performed in 285 GBA non-manifesting carriers, 369 LRRK2 non-manifesting carriers and 195 HC. We found that GBA non-manifesting mutation carriers were 2.6 times more likely to present apathy compared to HC, even after adjustment for covariates (adjusted OR = 2.6, 95% CI = 1.1-6.3, p = 0.031). The higher percentage of apathy for LRRK2 carriers compared to HC was marginally non-significant. GBA carriers were 1.5 times more likely to develop features of anxiety compared to LRRK2 carriers (adjusted OR = 1.5, 95% CI = 1.1-2.2, p = 0.015). Other neuropsychiatric symptoms, such as psychotic or depressive manifestations, did not differ between groups., Conclusion: Symptoms of apathy could be present in the prediagnostic period of non-manifesting mutation carriers, especially, GBA. Longitudinal data, including detailed neuropsychiatric evaluation and neuroimaging, would be essential to further investigate the pathophysiological basis of this finding., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Introduction: Blood uric acid represents an important biomarker in sporadic Parkinson's disease (PD). Whether uric acid levels change in genetic forms of PD is beginning to be assessed. The aim of the present study was to evaluate differences in serum uric acid level among PD patients harboring mutations in the glucocerebrosidase (GBA1) gene, sporadic PD, and healthy controls followed longitudinally., Methods: Longitudinal 2-year serum uric acid measurement data of 120 GBA-PD patients have been downloaded from the Parkinson's Progression Markers Initiative (PPMI) database. This cohort was compared with 369 de novo sporadic PD patients and 195 healthy controls enrolled in the same study., Results: Following adjustment for age, sex and BMI the GBA-PD cohort exhibited lower 2-year longitudinal uric acid level as compared to the controls (p = 0.016). Baseline uric acid measurements showed only a marginal difference (p = 0.119), but year 2 uric acid levels were lower in the GBA-PD cohort (p < 0.001). There was no difference in baseline, year 2 and 2-year longitudinal serum uric acid in the GBA-PD cohort as compared to sporadic PD (p = 0.664, p = 0.117 and p = 0.315)., Conclusions: This is the first study to assess serum uric acid in a GBA-PD cohort. Our findings suggest that low serum uric acid might be a progression biomarker in GBA-PD. However, more studies (ideally longitudinal) on the association between low serum uric acid and clinical data in GBA-PD are needed. These results are consistent with data from previous reports assessing uric acid as a biomarker in other genetic forms of PD., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Previous studies have highlighted serum uric acid as a putative idiopathic Parkinson's disease (iPD) biomarker. Only one study, so far, showed higher levels of serum uric acid in leucine-rich repeat kinase 2 (LRRK + 2) carriers compared to those who developed PD, however a longitudinal comparison between LRRK2 + PD and healthy controls (HC) has not been performed., Objective: The aim of this study was to determine whether there are longitudinal differences in serum uric acid between iPD, LRRK2 + PD and HC and their association with motor and non-motor features., Methods: Longitudinal data of uric acid of 282 de novo iPD, 144 LRRK2 + PD patients, and 195 age-matched HC were obtained from the Parkinson's Progression Markers Initiative (PPMI) database. We also used longitudinal Montreal Cognitive Assessment (MoCA), Movement Disorder Society-Unified Parkinson's Disease Rating Scale part III (MDS-UPDRS-III), Geriatric Depression Scale (GDS) scores, and DaTSCAN striatal binding ratios (SBRs)., Results: Longitudinal uric acid measurements were significantly lower in LRRK2 + PD patients compared to HC up to 5 years follow-up. There was no significant impact or correlation of adjusted or unadjusted uric acid levels with MoCA, MDS-UPDRS III, or GDS scores, the presence of RBD or DAT-SCAN SBRs., Conclusion: LRRK2 + PD group had significantly lower uric acid concentrations compared to HC after adjusting for age, sex and baseline BMI up to 5 years follow-up. There were no significant associations between uric acid levels and indices of disease severity. These findings identify serum uric acid as a marker linked to LRRK2 + PD.

Introduction: It has been reported that early onset Parkinson's Disease (PD) patients have a less profound dopaminergic degeneration. The aim of the current study was to determine whether there are longitudinal differences in dopaminergic denervation [signal reduction in 123I-FP-CIT SPECT] in early versus mid and late onset PD., Methods: DaTSCAN (123I-FP-CIT SPECT) imaging was acquired at Parkinson's Progression Markers Initiative (PPMI) imaging centers and sent to the imaging core for calculation of striatal binding ratios. Data from the PPMI database of 58 early de novo PD patients (age ≤ 50 years) were compared to those of 362 mid and late onset PD patients (age > 50 years)., Results: Although raw striatal binding ratios were higher in early onset versus mid/late onset PD, especially on the ipsilateral side, such differences were not observed, and were in fact reversed in the contralateral putamen, after age correction. The rate of signal decline was similar between the two groups. Interestingly, based on both raw and age-adjusted data, caudate nucleus and putamen asymmetry (contralateral/ipsilateral ratio) was more pronounced in early onset PD. Striatal asymmetry also significantly correlated with age at onset as a continuous variable., Conclusion: Early onset PD patients exhibited similar rates of decline of dopaminergic denervation compared to mid/late onset PD. These results are not supportive of a more benign disease in this subgroup. The more pronounced asymmetry in early onset PD may however signify a qualitatively different pattern of neurodegeneration compared to mid/late onset PD., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Variations of α-synuclein levels have been reported in serum and plasma in Parkinson's Disease (PD) Patients., Methods: Serum and plasma were obtained from PD patients without known mutations (GU-PD, n = 124)), carriers of the A53T/G209A point mutation in the α-synuclein gene (SNCA) (n = 29), and respective age-/sex-matched controls. Levels of total α-synuclein were assessed using an in-house ELISA assay., Results: A statistically significant increase of α-synuclein levels was found in serum, but not plasma, from GU-PD patients compared to healthy controls. A statistically significant decrease of α-synuclein levels was found in serum and plasma from symptomatic A53T mutation carriers compared to healthy controls. Plasma α-synuclein levels were modestly negatively correlated with UPDRS part III score and disease duration in A53T-PD patients., Conclusion: Increased α-synuclein levels in serum of GU-PD patients suggest a systemic deregulation of α-synuclein homeostasis in PD. The opposite results in A53T-PD highlight the complexity of α-synuclein homeostatic regulation in PD, and suggest the possibility of reduced expression of the mutant allele., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Blood uric acid level represents an emerging biomarker in Parkinson's disease (PD). Whether uric acid levels change in genetic forms of PD is just beginning to be explored., Objective: The aim of the present study was to assess differences in serum uric acid level among PD patients harboring the p.A53T mutation in the alpha-synuclein gene, idiopathic PD, and healthy controls., Methods: Longitudinal 5-year serum uric acid measurement data of 369 de novo idiopathic PD patients and 174 age- and gender-matched healthy controls have been downloaded from the Parkinson's Progression Markers Initiative (PPMI) database. Furthermore, we assessed baseline serum uric acid measurements of 24 p.A53T alpha-synuclein PD patients enrolled in PPMI and followed in our site as compared to 24 age-, gender- and disease duration-matched sporadic PD patients and 24 healthy controls., Results: Longitudinal serum uric acid measurements did not differ statistically between idiopathic PD patients and healthy controls (despite a trend for lower uric acid in the PD group) (p = 0.879). This was also true when male and female subgroups were assessed separately. The p.A53T SNCA mutation carrier PD group exhibited lower baseline serum uric acid level as compared to their matched healthy controls (p = 0.025)., Conclusion: In the present study we did not replicate the established lower serum uric acid measurements in PD patients as compared to controls using PPMI data, possibly due to the fact that PD patients in baseline visit were de novo and the average disease duration was shorter than that observed in most epidemiological PD studies. The faster progression rate and increased disease severity in p.A53T PD possibly correlate with the lower serum uric acid observed in this subgroup.

Background: The p.A53T point mutation in the α-synuclein gene (SNCA) is a rare but highly relevant cause of autosomal dominant Parkinson's disease (PD)., Objectives: The objective of this study was to assess striatal dopaminergic denervation in a cohort of symptomatic carriers of the p.A53T SNCA mutation as compared to PD patients., Methods: Data from the Parkinson's Progression Markers Initiative database of 11 symptomatic p.A53T SNCA mutation carriers who underwent 123I-FP-CIT SPECT [(123) I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane single photon emission computed tomography] imaging at our site were compared with those of 33 age-, sex-, and disease duration-matched PD patients., Results: The p.A53T mutation carriers had significantly lower caudate nucleus binding ratio both contralaterally and ipsilaterally to the most affected side (P = .002 and P = .006) and a decreased contralateral caudate/putamen signal ratio (P = .007) as compared to PD. A similar degree of striatal asymmetry was observed in both subgroups. No correlation between scores in neuropsychological tests and caudate nucleus dopaminergic denervation could be demonstrated., Conclusions: PD patients harboring the p.A53T SNCA mutation show evidence of a more severe nigrostriatal denervation, especially evident in the caudate nucleus. The lack of significant differences in the putaminal binding ratios may reflect a floor effect or a true preferential targeting of the caudate terminals in p.A53T SNCA-associated PD. © 2018 International Parkinson and Movement Disorder Society., (© 2018 International Parkinson and Movement Disorder Society.)

Background: Variations of α-synuclein levels or species have been reported in Parkinson's Disease (PD). There has been little systematic examination of erythrocytes, a rich source of α-synuclein., Methods: Erythrocyte membranes were obtained from PD patients (mutation carriers in the α-synuclein gene (A53T-PD) and glucocerebrosidase gene (GBA-PD) (n=18 each), and patients without known mutations (GU-PD, n=56)), and age-/sex-matched controls (n=56). Levels of monomeric and dimeric α-synuclein were assessed using Western immunoblotting., Results: A statistically significant increase of α-synuclein dimer and dimer to monomer ratio was found in GBA-PD and GU-PD. In contrast, dimer levels of A53T-PD were not different from controls. No difference was found in α-synuclein monomer levels., Conclusions: The increased α-synuclein dimer in GBA-PD and GU-PD is suggestive of an apparent systemic dysfunction causing the dimerization, and potentially oligomerization, of α-synuclein. These results may have implications for PD pathogenesis and biomarker development., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: To evaluate nonmotor symptoms in early SNCA /p.A53T Parkinson disease (PD) (A53T PD) compared to typical PD (tPD)., Methods: The presence of hyposmia, neuropsychiatric, dysautonomic, and sleep disturbances was assessed by standardized questionnaires and validated scales in 18 patients with A53T PD and 18 patients with tPD, matched for age, sex, and disease duration. All patients were enrolled into the Parkinson's Progression Markers Initiative study., Results: The levodopa equivalent daily dose was higher in the A53T PD ( p = 0.018) group vs the tPD group. Scores on the University of Pennsylvania Smell Identification Test ( p = 0.001), Benton Judgement of Line Orientation test ( p = 0.001), Letter Number Sequencing Test ( p = 0.002), and phonemic verbal fluency ( p = 0.002) were lower in the A53T PD group vs the tPD group. In contrast, overall cognition, verbal memory, and semantic fluency were similar between groups., Conclusion: The observed selective cognitive impairment reflecting frontal-parietal network dysfunction, together with impaired olfaction, define a set of nonmotor dysfunctions related to A53T PD. These results have implications for the prognosis of patients with A53T PD. Moreover, as the archetypal α-synucleinopathy, such results may give insights into tPD., (© 2018 American Academy of Neurology.)

α-Synuclein (αSyn) is the major gene linked to sporadic Parkinson's disease (PD), whereas the G209A (p.A53T) αSyn mutation causes a familial form of PD characterized by early onset and a generally severe phenotype, including nonmotor manifestations. Here we generated de novo induced pluripotent stem cells (iPSCs) from patients harboring the p.A53T mutation and developed a robust model that captures PD pathogenic processes under basal conditions. iPSC-derived mutant neurons displayed novel disease-relevant phenotypes, including protein aggregation, compromised neuritic outgrowth, and contorted or fragmented axons with swollen varicosities containing αSyn and Tau. The identified neuropathological features closely resembled those in brains of p.A53T patients. Small molecules targeting αSyn reverted the degenerative phenotype under both basal and induced stress conditions, indicating a treatment strategy for PD and other synucleinopathies. Furthermore, mutant neurons showed disrupted synaptic connectivity and widespread transcriptional alterations in genes involved in synaptic signaling, a number of which have been previously linked to mental disorders, raising intriguing implications for potentially converging disease mechanisms., Competing Interests: The authors declare no conflict of interest.

Background: G209A SNCA mutation carriers represent an important group of genetic PD. We describe motor and nonmotor features of G209A SNCA mutation carriers., Methods: Longitudinal clinical assessments over 2 years were collected in 22 symptomatic and 8 asymptomatic G209A SNCA mutation carriers. Motor and nonmotor rating scales were administered. Correlations were performed between clinical variables and disease duration or age. Penetrance was calculated using Kaplan-Meier survival curves., Results: Asymptomatic carriers did not manifest clear premotor symptoms, but symptomatic carriers often reported that olfactory dysfunction and rapid eye movement sleep behavior disorder preceded motor symptoms. Prominent motor decline and deterioration of autonomic and cognitive function occurred at follow-up; such nonmotor features correlated with disease duration, but not age. Disease penetrance was estimated at around 90%., Conclusions: This study may help to inform clinical trials and provide the basis for studies of disease modifiers in genetic synucleinopathy cohorts. © 2016 International Parkinson and Movement Disorder Society., (© 2016 International Parkinson and Movement Disorder Society.)

Background: Reduced expression of lysosomal-associated membrane protein 2a and heatshock-cognate 70 proteins, involved in chaperone-mediated autophagy and of glucocerebrosidase, is reported in PD brains. The aim of this study was to identify systemic alterations in lysosomal-associated membrane protein 2a, heatshock cognate-70, and glucocerebrosidase levels/activity in peripheral blood mononuclear cells from PD patients., Methods: Protein/mRNA levels were assessed in PD patients from genetically undetermined background, alpha-synuclein (G209A/A53T), or glucocerebrosidase mutation carriers and age-/sex-matched controls., Results: Heatshock cognate 70 protein levels were reduced in all PD groups, whereas its mRNA levels were decreased only in the genetically undetermined group. Glucocerebrosidase protein levels were decreased only in the genetic PD groups, whereas increased mRNA levels and decreased activity were detected only in the glucocerebrosidase mutation group., Conclusions: Reduced heatshock cognate-70 levels are suggestive of an apparent systemic chaperone-mediated autophagy dysfunction irrespective of genetic background. Glucocerebrosidase activity may serve as a screening tool to identify glucocerebrosidase mutation carriers with PD., (© 2015 International Parkinson and Movement Disorder Society.)

Background and Purpose: Although the first mutation associated with Parkinson's disease (PD) was identified several years ago in the alpha-synuclein (SNCA) gene in families of Greek and Italian ancestry, a more systematic study of this and other known PD mutations has not been performed in the Greek population., Methods: A genetic analysis in 111 familial or sporadic with early-onset (≤50 years, EO) PD patients was performed for the presence of the A53T SNCA mutation. In separate subgroups of these patients, further mutations in the SNCA, LRRK2, Parkin, PINK1 and DJ-1 genes were searched for. Additionally, a subgroup of familial cases was analysed for mutations in the glucocerebrosidase (GBA) gene., Results: In total, five patients (4.5% of our whole population) were identified with the A53T SNCA mutation, two with a heterozygote dosage mutation and one with a heterozygote point mutation in the Parkin gene, and seven patients (10.3% of our familial cohort) with GBA gene mutations., Conclusions: The A53T mutation in the SNCA gene, although uncommon, does represent a cause of PD in the Greek population, especially of familial EOPD with autosomal dominant inheritance. GBA mutations in the familial cohort tested here were as common as in a cohort of sporadic cases previously examined from the same centres. For the remainder of the genes, genetic defects that could definitively account for the disease were not identified. These results suggest that further Mendelian traits that lead to PD in the Greek population remain to be identified., (© 2013 The Author(s) European Journal of Neurology © 2013 EAN.)

Lysosomal protein 2 (LIMP2), the product of the scavenger receptor class B member 2 (SCARB2) gene, is a ubiquitously expressed transmembrane protein that is the mannose-6-phosphate-independent receptor for glucocerebrosidase (β-GCase); a deficiency in this protein causes Gaucher disease. Several studies have shown a link between mutations in the β-GCase gene and diseases characterized clinically by Parkinsonism and by the presence of Lewy body-related pathology. We hypothesized that genetic variants in the SCARB2 gene could be risk factors for Parkinson's disease (PD). A candidate-gene study of 347 Greek patients with sporadic PD and 329 healthy controls was conducted to investigate the association between 5 polymorphisms in the SCARB2 gene (rs6824953, rs6825004, rs4241591, rs9991821, and rs17234715) and the development of PD. The single-locus analysis for the 5 polymorphisms revealed an association only for the rs6825004 polymorphism: the generalized odds ratio (OR(G) ) was 0.68 (95% confidence interval [CI], 0.51-0.90), and the OR for the allelic test was OR = 0.71 (95% CI, 0.56-0.90). Haplotype analysis showed an association for the GCGGT haplotype (P < .01). Our study supports a genetic contribution of the SCARB2 locus to PD; future studies in larger cohorts are necessary to verify this finding., (Copyright © 2012 Movement Disorder Society.)