GBA-associated PD: chances and obstacles for targeted treatment strategies

The Molecular Impact of Glucosylceramidase Beta 1 (Gba1) in Parkinson's Disease: a New Genetic State of the Art

Parkinson's disease (PD) is a neurodegenerative disorder affecting 2-3% of those aged over 65, characterized by motor symptoms like slow movement, tremors, and muscle rigidity, along with non-motor symptoms such as anxiety and dementia. Lewy bodies, clumps of misfolded proteins, contribute to neuron loss in PD. Mutations in the GBA1 gene are considered the primary genetic risk factor of PD. GBA1 mutations result in decreased activity of the lysosomal enzyme glucocerebrosidase (GCase) resulting in α-synuclein accumulation. We know that α-synuclein aggregation, lysosomal dysfunction, and endoplasmic reticulum disturbance are recognized factors to PD susceptibility; however, the molecular mechanisms connecting GBA1 gene mutations to increased PD risk remain partly unknown. Thus, in this narrative review conducted according to a systematic review method, we aimed to present the main contributions arising from the molecular impact of the GBA1 gene to the pathogenesis of PD providing new insights into potential impacts for advances in the clinical care of people with PD, a neurological disorder that has contributed to the substantial increase in the global burden of disease accentuated by the aging population. In summary, this narrative review highlights the multifaceted impact of GBA1 mutations in PD, exploring their role in clinical manifestations, genetic predispositions, and molecular mechanisms. The review emphasizes the importance of GBA1 mutations in both motor and non-motor symptoms of PD, suggesting broader therapeutic and management strategies. It also discusses the potential of CRISPR/Cas9 technology in advancing PD treatment and the need for future research to integrate these diverse aspects for improved diagnostics and therapies.

Structural and dynamics insights into the GBA variants associated with Parkinson's disease

The GBA1 gene encodes for the lysosomal enzyme glucocerebrosidase (GCase), which maintains glycosphingolipid homeostasis and regulates the autophagy process. Genomic variants of GBA1 are associated with Goucher disease; however, several heterozygous variants of GBA (E326K, T369M, N370S, L444P) are frequent high-risk factors for Parkinson's disease (PD). The underlying mechanism of these variants has been revealed through functional and patient-centered research, but the structural and dynamical aspects of these variants have not yet been thoroughly investigated. In the current study, we used a thorough computational method to pinpoint the structural changes that GBA underwent because of genomic variants and drug binding mechanisms. According to our findings, PD-linked nsSNP variants of GBA showed structural variation and abnormal dynamics when compared to wild-typ. The docking analysis demonstrated that the mutants E326K, N370S, and L444P have higher binding affinities for Ambroxol. Root means square deviation (RMSD), Root mean square fluctuation analysis (RMSF), and MM-GBSA analysis confirmed that the Ambroxol are more stable in the binding site of N370S and L444P, and that their binding affinities are stronger as compared to the wild-type and T369M variants of GBA. The evaluation of hydrogen bonds and the calculation of the free binding energy provided additional evidence in favor of this conclusion. When docked with Ambroxol, GBA demonstrated an increase in binding affinity and catalytic activity. Understanding the therapeutic efficacy and potential against the aforementioned changes in the GBA will be beneficial in order to use more efficient methods for developing novel drugs.

Parkinson's Disease Gene Screening in Familial Cases from Central and South America

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease following Alzheimer's disease. Nearly 30 causative genes have been identified for PD and related disorders. However, most of these genes were identified in European-derived families, and little is known about their role in Latin American populations.

OBJECTIVES

Our goal was to assess the spectrum and frequency of pathogenic variants in known PD genes in familial PD patients from Latin America.

METHODS

We selected 335 PD patients with a family history of PD from the Latin American Research Consortium on the Genetics of PD. We capture-sequenced the coding regions of 26 genes related to neurodegenerative parkinsonism. Of the 335 PD patients, 324 had sufficient sequencing coverage to be analyzed.

RESULTS

We identified pathogenic variants in 41 individuals (12.7%) in FBXO7, GCH1, LRRK2, PARK7, PINK1, PLA2G6, PRKN, SNCA, and TARDBP, GBA1 risk variants in 25 individuals (7.7%), and variants of uncertain significance in another 24 individuals (7.4%) in ATP13A2, ATP1A3, DNAJC13, DNAJC6, GBA1, LRKK2, PINK1, VPS13C, and VPS35. Of the 70 unique variants identified, 19 were more frequent in Latin Americans than in any other population.

CONCLUSIONS

This is the first screening of known PD genes in a large cohort of patients with familial PD from Latin America. There were substantial differences in the spectrum of variants observed in comparison to previous findings from PD families of European origin. Our data provide further evidence that differences exist between the genetic architecture of PD in Latinos and European-derived populations. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Activation and Purification of ß-Glucocerebrosidase by Exploiting its Transporter LIMP-2 - Implications for Novel Treatment Strategies in Gaucher's and Parkinson's Disease

Genetic variants of GBA1 can cause the lysosomal storage disorder Gaucher disease and are among the highest genetic risk factors for Parkinson's disease (PD). GBA1 encodes the lysosomal enzyme beta-glucocerebrosidase (GCase), which orchestrates the degradation of glucosylceramide (GluCer) in the lysosome. Recent studies have shown that GluCer accelerates α-synuclein aggregation, exposing GCase deficiency as a major risk factor in PD pathology and as a promising target for treatment. This study investigates the interaction of GCase and three disease-associated variants (p.E326K, p.N370S, p.L444P) with their transporter, the lysosomal integral membrane protein 2 (LIMP-2). Overexpression of LIMP-2 in HEK 293T cells boosts lysosomal abundance of wt, E326K, and N370S GCase and increases/rescues enzymatic activity of the wt and E326K variant. Using a novel purification approach, co-purification of untagged wt, E326K, and N370S GCase in complex with His-tagged LIMP-2 from cell supernatant of HEK 293F cells is achieved, confirming functional binding and trafficking for these variants. Furthermore, a single helix in the LIMP-2 ectodomain is exploited to design a lysosome-targeted peptide that enhances lysosomal GCase activity in PD patient-derived and control fibroblasts. These findings reveal LIMP-2 as an allosteric activator of GCase, suggesting a possible therapeutic potential of targeting this interaction.

Are patients with GBA-Parkinson disease good candidates for deep brain stimulation? A longitudinal multicentric study on a large Italian cohort

BACKGROUND

GBA variants increase the risk of developing Parkinson disease (PD) and influence its outcome. Deep brain stimulation (DBS) is a recognised therapeutic option for advanced PD. Data on DBS long-term outcome in GBA carriers are scarce.

OBJECTIVE

To elucidate the impact of GBA variants on long-term DBS outcome in a large Italian cohort.

METHODS

We retrospectively recruited a multicentric Italian DBS-PD cohort and assessed: (1) GBA prevalence; (2) pre-DBS clinical features; and (3) outcomes of motor, cognitive and other non-motor features up to 5 years post-DBS.

RESULTS

We included 365 patients with PD, of whom 73 (20%) carried GBA variants. 5-year follow-up data were available for 173 PD, including 32 mutated subjects. GBA-PD had an earlier onset and were younger at DBS than non-GBA-PD. They also had shorter disease duration, higher occurrence of dyskinesias and orthostatic hypotension symptoms.At post-DBS, both groups showed marked motor improvement, a significant reduction of fluctuations, dyskinesias and impulsive-compulsive disorders (ICD) and low occurrence of most complications. Only cognitive scores worsened significantly faster in GBA-PD after 3 years. Overt dementia was diagnosed in 11% non-GBA-PD and 25% GBA-PD at 5-year follow-up.

CONCLUSIONS

Evaluation of long-term impact of GBA variants in a large Italian DBS-PD cohort supported the role of DBS surgery as a valid therapeutic strategy in GBA-PD, with long-term benefit on motor performance and ICD. Despite the selective worsening of cognitive scores since 3 years post-DBS, the majority of GBA-PD had not developed dementia at 5-year follow-up.

A biological classification of Parkinson's disease: the SynNeurGe research diagnostic criteria

With the hope that disease-modifying treatments could target the molecular basis of Parkinson's disease, even before the onset of symptoms, we propose a biologically based classification. Our classification acknowledges the complexity and heterogeneity of the disease by use of a three-component system (SynNeurGe): presence or absence of pathological α-synuclein (S) in tissues or CSF; evidence of underlying neurodegeneration (N) defined by neuroimaging procedures; and documentation of pathogenic gene variants (G) that cause or strongly predispose to Parkinson's disease. These three components are linked to a clinical component (C), defined either by a single high-specificity clinical feature or by multiple lower-specificity clinical features. The use of a biological classification will enable advances in both basic and clinical research, and move the field closer to the precision medicine required to develop disease-modifying therapies. We emphasise the initial application of these criteria exclusively for research. We acknowledge its ethical implications, its limitations, and the need for prospective validation in future studies.

Case-Fatality Rate in Parkinson's Disease: A Nationwide Registry Study

BACKGROUND

Patients with Parkinson's disease (PD) may have an increased risk of mortality, but robust estimates are lacking.

OBJECTIVE

To compare mortality rates nationally between patients with PD and controls.

METHODS

The case-fatality rates of Finnish PD patients diagnosed in 2004-2018 (n = 23,688; 57% male, mean age at diagnosis = 71 years) and randomly selected sex- and age-matched control subjects (n = 94,752) were compared using data from national registries. The median follow-up duration was 5.8 years (max 17 years).

RESULTS

The case-fatality rate in patients with PD was higher than that in matched controls (HR 2.29; 95% CI 2.24-2.33; P < 0.0001). Excess fatality among PD patients was already present at 1 year from diagnosis and then plateaued at 29% at 12 years after diagnosis. The long-term relative hazard of death in PD patients vs. matched controls did not differ based on sex. Patients with early-onset PD (age at diagnosis <50 years old) had the highest relative hazard of death (HR 3.36) compared to matched control subjects, and the relative hazard decreased with higher age at diagnosis. The seven-year excess risk of death decreased during the study period, especially in men. In patients with PD, male sex, increasing age, and increasing comorbidity burden were associated with an increased risk of death.

CONCLUSIONS

An increased risk of death among PD patients was evident from early on. The increase in risk was greatest among young-onset patients. The excess risk in early PD declined during the study period, particularly in men. The reasons for this are unknown.

Longitudinal faster anxiety progression of GBA variant carriers in the early Parkinson's disease cohort

Objective

Anxiety symptoms are prevalent neuropsychiatric manifestations in Parkinson's disease (PD) and impact the development of motor complications. Our aim was to evaluate the association of GBA variants with the anxiety development in early PD cohort.

Methods

This cohort study used data from the Parkinson Progression Marker Initiative. The primary outcome anxiety was assessed by State-Trait Anxiety Inventory (STAI). The association between GBA and longitudinal change in the STAI total score was examined using linear mixed-effects model, and the association between GBA and anxiety progression was examined using Cox survival analysis.

Results

A total of 385 patients with PD were included in this study, 39 of them were GBA variant carriers and 346 were idiopathic PD without GBA variants. Patients with GBA variants had faster annual increase in anxiety score (β = 0.44; 95% CI, 0.18 to 0.71; p < 0.001) and were at higher risk of anxiety progression (HR 1.87; 95% CI, 1.03 to 3.41; p = 0.03,). Higher baseline scores for Scales for Outcomes in Parkinson's Disease-Autonomic (SCOPA-AUT), which indicated the autonomic dysfunction, also independently predicted faster increase in anxiety score (β = 0.48; 95%CI, 0.19 to 0.69; p < 0.001) and higher incidence of anxiety development (HR = 1.05; 95% CI, 1.01 to 1.08; p = 0.008).

Interpretation

These findings suggest that longitudinal anxiety symptoms worsening was faster in PD patients who were GBA variant carriers and have dysautonomia, and this association was enhanced if they have both.

CSF α-synuclein seed amplification kinetic profiles are associated with cognitive decline in Parkinson's disease

Seed amplification assays have been implemented in Parkinson's disease to reveal disease-specific misfolded alpha-synuclein aggregates in biospecimens. While the assays' qualitative dichotomous seeding response is valuable to stratify and enrich cohorts for alpha-synuclein pathology in general, more quantitative parameters that are associated with clinical dynamics of disease progression and that might potentially serve as exploratory outcome measures in clinical trials targeting alpha-synuclein would add important information. To evaluate whether the seeding kinetic parameters time required to reach the seeding threshold (LAG phase), the peak of fluorescence response (Imax), and the area under the curve (AUC) are associated with clinical trajectories, we analyzed LAG, Imax, and AUC in relation to the development of cognitive decline in a longitudinal cohort of 199 people with Parkinson's disease with positive CSF alpha-synuclein seeding status. Patients were stratified into tertiles based on their individual CSF alpha-synuclein seeding kinetic properties. The effect of the kinetic parameters on longitudinal development of cognitive impairment defined by MoCA ≤25 was analyzed by Cox-Regression. Patients with a higher number of positive seeding replicates and tertile groups of shorter LAG, higher Imax, and higher AUC showed a higher prevalence of and a shorter duration until cognitive impairment longitudinally (3, 6, and 3 years earlier with p ≤ 0.001, respectively). Results remained similar in separate subgroup analyses of patients with and without GBA mutation. We conclude that a more prominent alpha-synuclein seeding kinetic profile translates into a more rapid development of cognitive decline.

Proxy-analysis of the genetics of cognitive decline in Parkinson's disease through polygenic scores

Cognitive decline is common in Parkinson's disease (PD) and its genetic risk factors are not well known to date, besides variants in the GBA and APOE genes. However, variation in complex traits is caused by numerous variants and is usually studied with genome-wide association studies (GWAS), requiring a large sample size, which is difficult to achieve for outcome measures in PD. Taking an alternative approach, we computed 100 polygenic scores (PGS) related to cognitive, dementia, stroke, and brain anatomical phenotypes and investigated their association with cognitive decline in six longitudinal cohorts. The analysis was adjusted for age, sex, genetic ancestry, follow-up duration, GBA and APOE status. Then, we meta-analyzed five of these cohorts, comprising a total of 1702 PD participants with 6156 visits, using the Montreal Cognitive Assessment as a cognitive outcome measure. After correction for multiple comparisons, we found four PGS significantly associated with cognitive decline: intelligence (p = 5.26e-13), cognitive performance (p = 1.46e-12), educational attainment (p = 8.52e-10), and reasoning (p = 3.58e-5). Survival analyses highlighted an offset of several years between the first and last quartiles of PGS, with significant differences for the PGS of cognitive performance (5 years) and educational attainment (7 years). In conclusion, we found four PGS associated with cognitive decline in PD, all associated with general cognitive phenotypes. This study highlights the common genetic factors between cognitive decline in PD and the general population, and the importance of the participant's cognitive reserve for cognitive outcome in PD.

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

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

Cognitive Impairment in Parkinson's Disease: An Updated Overview Focusing on Emerging Pharmaceutical Treatment Approaches

Cognitive impairment in patients with Parkinson's disease (PD) is one of the commonest and most disabling non-motor manifestations during the course of the disease. The clinical spectrum of PD-related cognitive impairment includes subjective cognitive decline (SCD), mild cognitive impairment (MCI) and PD dementia (PDD). As the disease progresses, cognitive decline creates a significant burden for the family members and/or caregivers of patients with PD, and has a great impact on quality of life. Current pharmacological treatments have demonstrated partial efficacy and failed to halt disease progression, and novel, effective, and safe therapeutic strategies are required. Accumulating preclinical and clinical evidence shows that several agents may provide beneficial effects on patients with PD and cognitive impairment, including ceftriaxone, ambroxol, intranasal insulin, nilotinib, atomoxetine, mevidalen, blarcamesine, prasinezumab, SYN120, ENT-01, NYX-458, GRF6021, fosgonimeton, INT-777, Neuropeptide S, silibinin, osmotin, cordycepin, huperzine A, fibroblast growth factor 21, Poloxamer 188, ginsenoside Rb1, thioredoxin-1, tangeretin, istradefylline and Eugenia uniflora. Potential underlying mechanisms include the inhibition of a-synuclein aggregation, the improvement of mitochondrial function, the regulation of synaptic plasticity, an impact on the gut-brain axis, the modulation of neuroinflammation and the upregulation of neurotrophic factors, as well as cholinergic, dopaminergic, serotoninergic and norepinephrine neurotransmission. In this updated overview, we aim to cover the clinical aspects of the spectrum of PD-related cognitive impairment and discuss recent evidence on emerging treatment approaches that are under investigation at a preclinical and clinical level. Finally, we aim to provide additional insights and propose new ideas for investigation that may be feasible and effective for the spectrum of PD-related cognitive impairment.

GBA1 Variants and Parkinson's Disease: Paving the Way for Targeted Therapy

Glucosylceramidase beta 1 (GBA1) variants have attracted enormous attention as the most promising and important genetic candidates for precision medicine in Parkinson's disease (PD). A substantial correlation between GBA1 genotypes and PD phenotypes could inform the prediction of disease progression and promote the development of a preventive intervention for individuals at a higher risk of a worse disease prognosis. Moreover, the GBA1-regulated pathway provides new perspectives on the pathogenesis of PD, such as dysregulated sphingolipid metabolism, impaired protein quality control, and disrupted endoplasmic reticulum-Golgi trafficking. These perspectives have led to the development of novel disease-modifying therapies for PD targeting the GBA1-regulated pathway by repositioning treatment strategies for Gaucher's disease. This review summarizes the current hypotheses on a mechanistic link between GBA1 variants and PD and possible therapeutic options for modulating GBA1-regulated pathways in PD patients.

The Genetic Basis of Probable REM Sleep Behavior Disorder in Parkinson's Disease

Patients with Parkinson's Disease (PD) experience REM sleep behavior disorder (RBD) more frequently than healthy controls. RBD is associated with torpid disease evolution. To test the hypothesis that differential genetic signatures might contribute to the torpid disease evolution in PD patients with RBD we compared the rate of genetic mutations in PD patients with or without probable RBD. Patients with a clinical diagnosis of PD in the Parkinson's Progression Markers Initiative (PPMI) database entered the study. We excluded those with missing data, dementia, psychiatric conditions, or a diagnosis change over the first five years from the initial PD diagnosis. Probable RBD (pRBD) was confirmed by a REM Sleep Behavior Disorder Screening Questionnaire score > 5 points. Logistic regression and Machine Learning (ML) algorithms were used to relate Single Nucleotide Polymorphism (SNPs) in PD-related genes with pRBD. We included 330 PD patients fulfilling all inclusion and exclusion criteria. The final logistic multivariate model revealed that the following SNPs increased the risk of pRBD: GBA_N370S_rs76763715 (OR, 95% CI: 3.38, 1.45-7.93), SNCA_A53T_rs104893877 (8.21, 2.26-36.34), ANK2. CAMK2D_rs78738012 (2.12, 1.08-4.10), and ZNF184_rs9468199 (1.89, 1.08-3.33). Conversely, SNP COQ7. SYT17_rs11343 reduced pRBD risk (0.36, 0.15-0.78). The ML algorithms led to similar results. The predictive models were highly specific (95-99%) but lacked sensitivity (9-39%). We found a distinctive genetic signature for pRBD in PD. The high specificity and low sensitivity of the predictive models suggest that genetic mutations are necessary but not sufficient to develop pRBD in PD. Additional investigations are needed.

A Phase 1B Trial in GBA1-Associated Parkinson's Disease of BIA-28-6156, a Glucocerebrosidase Activator

BACKGROUND

Loss-of-function mutations in the GBA1 gene are one of the most common genetic risk factors for onset of Parkinson's disease and subsequent progression (GBA-PD). GBA1 encodes the lysosomal enzyme glucocerebrosidase (GCase), a promising target for a possible first disease-modifying therapy. LTI-291 is an allosteric activator of GCase, which increases the activity of normal and mutant forms of GCase.

OBJECTIVES

This first-in-patient study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of 28 daily doses of LTI-291 in GBA-PD.

METHODS

This was a randomized, double-blind, placebo-controlled trial in 40 GBA-PD participants. Twenty-eight consecutive daily doses of 10, 30, or 60 mg of LTI-291 or placebo were administered (n = 10 per treatment allocation). Glycosphingolipid (glucosylceramide and lactosylceramide) levels were measured in peripheral blood mononuclear cells (PBMCs), plasma, and cerebrospinal fluid (CSF), and a test battery of neurocognitive tasks, the Movement Disorder Society-Unified Parkinson's Disease Rating Scale and the Mini-Mental State Exam, were performed.

RESULTS

LTI-291 was generally well tolerated, no deaths or treatment-related serious adverse events occurred, and no participants withdrew due to adverse events. C_max , and AUC_0-6 of LTI-291 increased in a dose-proportional manner, with free CSF concentrations equal to the free fraction in plasma. A treatment-related transient increase in intracellular glucosylceramide (GluCer) in PBMCs was measured.

CONCLUSION

These first-in-patient studies demonstrated that LTI-291 was well tolerated when administered orally for 28 consecutive days to patients with GBA-PD. Plasma and CSF concentrations that are considered pharmacologically active were reached (ie, sufficient to at least double GCase activity). Intracellular GluCer elevations were detected. Clinical benefit will be assessed in a larger long-term trial in GBA-PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A severe neurodegenerative disease with Lewy bodies and a mutation in the glucocerebrosidase gene

Several heterozygous variants of the glucocerebrosidase gene (GBA1) have been reported to increase the risk of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). GBA1-associated PD has been reported to be more severe than idiopathic PD, and more deleterious variants are associated with more severe clinical phenotypes. We report a family with a heterozygous p.Pro454Leu variant in GBA1. The variant was associated with a severe and rapidly progressive neurodegenerative disease with Lewy bodies that were clinically and pathologically diverse. Pathogenicity prediction algorithms and evolutionary analyses suggested that p.Pro454Leu is deleterious.

The Genetic Testing Experience of Individuals with Parkinson's Disease

Background

The perspective and experiences of individuals with Parkinson's disease (PD) regarding genetic testing is limited.

Objectives

To determine if anticipated benefits and negative consequences of genetic testing noted in prior studies have occurred in a surveyed group of patients with PD and to identify reasons why some individuals with PD have not had testing.

Methods

Individuals were surveyed from 22 support/advocacy groups throughout the US. Information about patient demographics and genetic testing were assessed, along with the consequences experienced after testing or anticipated by those who have not had testing. Descriptive statistics, Pearson correlation coefficient, ANOVA, and independent sample t-test were utilized for data analysis.

Results

Of the genetic testing group (n = 78), most received testing through a research study (44.9%) or a Direct-to-Consumer company (46.2%). Most did not meet with a genetic counselor before (87.2%) or after testing (64.1%). Fewer positive and fewer negative consequences were reported after testing compared to the consequences anticipated by those who have not undergone testing (P < 0.001, all comparisons). Of the non-genetic testing group (n = 166), 49.4% did not undergo testing because they were not aware it was available and 38.0% because their doctor did not offer it.

Conclusions

Findings demonstrate the need for providers to have genetic testing discussions with PD patients, who may otherwise seek testing via Direct-to-Consumer companies or be unaware it is available. Collaborations with genetic counselors trained in providing anticipatory guidance may assist patients in forming more realistic expectations regarding the consequences experienced after genetic testing for PD.

Peripheral inflammatory immune response differs among sporadic and familial Parkinson's disease

Peripheral inflammatory immune responses are thought to play a major role in the pathogenesis of Parkinson's disease (PD). The neutrophil-to-lymphocyte ratio (NLR), a biomarker of systemic inflammation, has been reported to be higher in patients with PD than in healthy controls (HCs). The present study was aimed at determining if the peripheral inflammatory immune response could be influenced by the genetic background of patients with PD. We included a discovery cohort with 222 patients with PD (132 sporadic PD, 44 LRRK2-associated PD (with p.G2019S and p.R1441G variants), and 46 GBA-associated PD), as well as 299 HCs. Demographic and clinical data were recorded. Leukocytes and their subpopulations, and the NLR were measured in peripheral blood. Multivariate lineal regression and post-hoc tests were applied to determine the differences among the groups. Subsequently, a replication study using the Parkinson's Progression Markers Initiative cohort was performed which included 401 patients with PD (281 sPD patients, 66 LRRK2-PD patients, 54 GBA-PD patients) and a group of 174 HCs. Patients with sporadic PD and GBA-associated PD showed a significantly lower lymphocyte count, a non-significantly higher neutrophil count and a significantly higher NLR than HCs. The peripheral inflammatory immune response of patients with LRRK2-associated PD did not differ from HCs. Our study supports the involvement of a peripheral inflammatory immune response in the pathophysiology of sPD and GBA-associated PD. However, this inflammatory response was not found in LRRK2-associated PD, probably reflecting different pathogenic inflammatory mechanisms.

The Consequences of GBA Deficiency in the Autophagy-Lysosome System in Parkinson's Disease Associated with GBA

GBA gene variants were the first genetic risk factor for Parkinson's disease. GBA encodes the lysosomal enzyme glucocerebrosidase (GBA), which is involved in sphingolipid metabolism. GBA exhibits a complex physiological function that includes not only the degradation of its substrate glucosylceramide but also the metabolism of other sphingolipids and additional lipids such as cholesterol, particularly when glucocerebrosidase activity is deficient. In the context of Parkinson's disease associated with GBA, the loss of GBA activity has been associated with the accumulation of α-synuclein species. In recent years, several hypotheses have proposed alternative and complementary pathological mechanisms to explain why lysosomal enzyme mutations lead to α-synuclein accumulation and become important risk factors in Parkinson's disease etiology. Classically, loss of GBA activity has been linked to a dysfunctional autophagy-lysosome system and to a subsequent decrease in autophagy-dependent α-synuclein turnover; however, several other pathological mechanisms underlying GBA-associated parkinsonism have been proposed. This review summarizes and discusses the different hypotheses with a special focus on autophagy-dependent mechanisms, as well as autophagy-independent mechanisms, where the role of other players such as sphingolipids, cholesterol and other GBA-related proteins make important contributions to Parkinson's disease pathogenesis.

Genetic stratification of motor and QoL outcomes in Parkinson's disease in the EARLYSTIM study

PURPOSE

The decision for subthalamic deep brain stimulation (STN-DBS) in Parkinson's disease (PD) relies on clinical predictors. Whether genetic variables could predict favourable or unfavourable decisions is under investigation.

OBJECTIVE

First, we aimed to reproduce the previous observation that SNCA rs356220 was associated with favourable STN-DBS motor response. In additional exploratory analyses, we studied if other PD risk and progression variants from the latest GWAS are associated with therapeutic outcome. Further, we evaluated the predictive value of polygenic risk scores.

METHODS

We comprehensively genotyped patients from the EarlyStim cohort using NeuroChip, and assessed the clinico-genetic associations with longitudinal outcome parameters.

RESULTS

The SNCA rs356220 variant did not predict UPDRS III outcomes. However, it was associated with quality of life improvement in secondary analyses. Several polymorphisms from previously identified GWAS hits predicted motor or quality of life outcomes in DBS patients. Polygenic risk scores did not predict any outcome parameter.

CONCLUSIONS

Our findings support the hypothesis that different common genetic markers are associated with favourable quality of life outcomes of STN-DBS in PD. These findings can be the basis for further validation in larger and independent cohorts.