Serum neurofilament light chain and postural instability/gait difficulty (PIGD) subtypes of Parkinson’s disease in the MARK-PD study

Biomarkers in Parkinson's Disease

Parkinson's disease (PD) is a leading cause of disability worldwide, and there is a pressing need to develop therapeutics to slow or halt disease progression. The identification of reliable biomarkers of PD at all stages of disease will be a critical step toward optimizing diagnosis and therapeutic development. For PD, biomarkers could serve multiple important functions. There have been significant advances in biomarker development in PD in recent years, and in this review, the authors summarize the current state of the PD biomarker field covering major advances in fluid, tissue, and neuroimaging biomarkers.

Amplification parameters of the alpha-synuclein seed amplification assay on CSF predict the clinical subtype of Parkinson's Disease at 10-year follow-up

Importance

Data-driven approaches identified Mild Motor Predominant (MMP), Intermediate (IM) and Diffuse Malignant (DM) as subtypes of Parkinson's Disease (PD) with a different degree of motor and non-motor impairment at time of diagnosis. It is not clear whether subtypes remain stable over time nor whether they represent distinct biological substrates. The recent introduction of alpha-synuclein seed amplification assay on CSF (CSF-αSyn-SAA) might provide further insights.

Objective

To assess the association between the parameters of CSF-αSyn-SAA collected at baseline and the clinical evolution of PD subtypes for 10 years.

Design

Retrospective, longitudinal, cohort study.

Setting

Data were collected from the Parkinson's Progression Marker Initiative (PPMI) cohort.

Participants

Subjects with a sporadic form of PD and positivity on CSF-αSyn-SAA (n=323) were included.

Exposure

clinical and biochemical data available in the PPMI dataset.

Main Outcome and Measure

PD participants were classified as MMP, IM and DM at baseline (n=323) and 10-year follow-up (n=146), based on previously published motor summary score and three non-motor features (cognitive impairment, RBD and dysautonomia). CSF-αSyn-SAA parameters were collected at baseline, including Fmax (maximum fluorescence), T50 (time to reach 50% of Fmax), TTT (time to threshold), Slope, and AUC (area under the curve). CSF Aβ1-42, tTau, pTau181, CSF and serum NfL were also collected at baseline.

Results

Times of reaction (T50 and TTT) and AUC respectively were shorter and larger in DM subtype compared to IM/MMP subtype. The difference in amplification parameters at baseline was more evident when comparing subtypes based on the 10-year clinical features (T50, η2=0.036; TTT, η2=0.031; AUC, η2=0.033; all p values < 0.05) than when comparing subtypes based on the baseline clinical features (T50, η2=0.012; TTT, η2=0.012; AUC, η2=0.013; all p<0.05). Shorter T50 and TTT assessed at baseline were associated with a greater risk of DM subtype versus MMP at 10-year follow-up (T50, OR=3.286, p=0.010; TTT, OR=4.586, p=0.001). CSF Aβ1-42, tTau, pTau181, CSF and Serum NfL did not differ between groups.

Conclusions and Relevance

CSF-αSyn-SAA parameters collected at baseline predicted the long-term progression of PD. In detail, faster reactions were associated with a severer 10-year phenotype of PD considering motor, cognitive, sleep and dysautonomia features.

Serum Neurofilament Light-Chain Levels in Essential Tremor: A Replication Study

INTRODUCTION

Essential tremor (ET) is a highly prevalent neurological disease. At present, there are no clinical biomarkers. Neurofilament light (NfL) has been studied as a measure of neuronal damage in a considerable number of neurological disorders. There have been three studies of ET, and results are inconsistent.

METHODS

Forty ET cases were enrolled in a research study between February and November 2023 and compared to two control groups from study 1 (n = 41) and study 2 (n = 185). Total tremor score was a measure of the severity of action tremor. Blood samples were analyzed for serum NfL level on the Simoa® platform using an NF-Light™ kit as a marker of axonal injury.

RESULTS

Serum log NfL levels were higher in ET cases than controls in study 1 (p < 0.001) and study 2 (p < 0.001). In a multivariate linear regression model, ET cases (p = 0.03) and individuals of older age (p < 0.001) had higher serum log NfL levels than controls (combined in studies 1 and 2). There was no association in ET cases between serum log NfL level and total tremor score (Pearson's r = 0.08, p = 0.63).

CONCLUSION

This new study further validates the elevation in serum NfL levels in ET, now representing the third study to do so. In combination, the converging data suggest that there is an overall increase in serum NfL levels in ET. The demonstration of elevated serum levels of NfL in ET adds an additional piece of evidence that there is neuronal damage in ET.

Serum Neurofilament Light-Chain Concentrations in Essential Tremor: a Case-Control Study

Essential tremor (ET) is a common neurological disorder, with clinical and pathophysiological links to the cerebellum. Inquiries into the etiology, pathophysiology, and nosology of ET stand to benefit from the identification of disease biomarkers. Serum neurofilament light chain (NfL) has emerged as a novel signature of conditions in which neuronal injury reflects an outcome of the ongoing disease process. We sought to investigate the concentrations of NfL in ET patients and healthy controls. In this case-control study, our powered study population of 41 ET patients and 40 age-matched healthy controls underwent clinical assessments and measurement of serum NfL concentration using Simoa technology. Serum NfL was elevated in ET patients - mean log-transformed serum NfL concentration = 1.23 ± 0.19 (95% confidence interval [CI] = 1.17-1.29) vs. 1.08 ± 0.15 (95% CI = 1.03-1.13), p = 0.0002. This difference persisted after accounting for age, sex and Montreal Cognitive Assessment score in a multiple linear regression model (p = 0.002) and in an age-matched sample subset of 35 ET cases and 35 controls (p = 0.006). There was no association between tremor severity and serum NfL levels (p = 0.73). In this sample of ET patients and controls, serum NfL concentrations were significantly higher in ET. Studies in additional cohorts of ET cases would be of value in attempting to replicate these results and assessing diagnostic utility.

Evaluation of ATNPD Framework and Biofluid Markers to Predict Cognitive Decline in Early Parkinson Disease

BACKGROUND AND OBJECTIVES

In Parkinson disease (PD), Alzheimer disease (AD) copathology is common and clinically relevant. However, the longitudinal progression of AD CSF biomarkers-β-amyloid 1-42 (Aβ42), phosphorylated tau 181 (p-tau181), and total tau (t-tau)-in PD is poorly understood and may be distinct from clinical AD. Moreover, it is unclear whether CSF p-tau181 and serum neurofilament light (NfL) have added prognostic utility in PD, when combined with CSF Aβ42. First, we describe longitudinal trajectories of biofluid markers in PD. Second, we modified the AD β-amyloid/tau/neurodegeneration (ATN) framework for application in PD (ATNPD) using CSF Aβ42 (A), p-tau181 (T), and serum NfL (N) and tested ATNPD prediction of longitudinal cognitive decline in PD.

METHODS

Participants were selected from the Parkinson's Progression Markers Initiative cohort, clinically diagnosed with sporadic PD or as controls, and followed up annually for 5 years. Linear mixed-effects models (LMEMs) tested the interaction of diagnosis with longitudinal trajectories of analytes (log transformed, false discovery rate [FDR] corrected). In patients with PD, LMEMs tested how baseline ATNPD status (AD [A+T+N±] vs not) predicted clinical outcomes, including Montreal Cognitive Assessment (MoCA; rank transformed, FDR corrected).

RESULTS

Participants were 364 patients with PD and 168 controls, with comparable baseline mean (±SD) age (patients with PD = 62 ± 10 years; controls = 61 ± 11 years]; Mann-Whitney Wilcoxon: p = 0.4) and sex distribution (patients with PD = 231 male individuals [63%]; controls = 107 male individuals [64%]; χ2: p = 1). Patients with PD had overall lower CSF p-tau181 (β = -0.16, 95% CI -0.23 to -0.092, p = 2.2e-05) and t-tau than controls (β = -0.13, 95% CI -0.19 to -0.065, p = 4e-04), but not Aβ42 (p = 0.061) or NfL (p = 0.32). Over time, patients with PD had greater increases in serum NfL than controls (β = 0.035, 95% CI 0.022 to 0.048, p = 9.8e-07); slopes of patients with PD did not differ from those of controls for CSF Aβ42 (p = 0.18), p-tau181 (p = 1), or t-tau (p = 0.96). Using ATNPD, PD classified as A+T+N± (n = 32; 9%) had worse cognitive decline on global MoCA (β = -73, 95% CI -110 to -37, p = 0.00077) than all other ATNPD statuses including A+ alone (A+T-N-; n = 75; 21%).

DISCUSSION

In patients with early PD, CSF p-tau181 and t-tau were low compared with those in controls and did not increase over 5 years of follow-up. Our study shows that classification using modified ATNPD (incorporating CSF Aβ42, CSF p-tau181, and serum NfL) can identify biologically relevant subgroups of PD to improve prediction of cognitive decline in early PD.

Utility of serum neurofilament light chain and glial fibrillary acidic protein as diagnostic biomarkers of freezing of gait in Parkinson's disease

Freezing of gait (FOG) is one of the most distressing features of Parkinson's disease (PD), increasing the risks of fractures and seriously affecting patients' quality of life. We aimed to examine the potential diagnostic roles of serum neurofilament light chain (NFL) and glial fibrillary acidic protein (GFAP) in PD patients with FOG (PD-FOG). We included 99 patients, comprising 54 PD patients without FOG (PD-NoFOG), 45 PD-FOG and 37 healthy controls (HCs). Our results indicated serum markers were significantly higher in PD-FOG and postural instability and gait difficulty (PIGD) motor subtype patients than in PD-NoFOG and non-PIGD subtype patients (P < 0.05), respectively. Patients with high concentrations of the markers NFL and GFAP had higher PIGD scores and greater FOG severity than those with low concentrations. Moreover, serum levels of both NFL and GFAP were significantly positively associated with age, FOG severity, PD-FOG status, and negatively associated with Mini-Mental State Examination (MMSE) scores. Logistic regression analysis identified serum levels of NFL and GFAP as independent risk factors for PD-FOG. Mediation analysis revealed that MMSE scores fully mediated the relationship between serum GFAP levels and FOG-Q scores, accounting for 33.33% of the total effects (indirect effect = 0.01, 95% CI 0.01-0.02). NFL levels differentiated PD-FOG from PD-NoFOG with reliable diagnostic accuracy (AUC 0.75, 95% CI 0.66-0.84), and the combination of NFL, GFAP, duration and MMSE scores demonstrated high accuracy (AUC 0.84, 95% CI 0.76-0.91). Our findings support the notion that NFL and GFAP may be potential biomarkers for the diagnosis of PD-FOG.

How should we be using biomarkers in trials of disease modification in Parkinson's disease?

The recent validation of the α-synuclein seed amplification assay as a biomarker with high sensitivity and specificity for the diagnosis of Parkinson's disease has formed the backbone for a proposed staging system for incorporation in Parkinson's disease clinical studies and trials. The routine use of this biomarker should greatly aid in the accuracy of diagnosis during recruitment of Parkinson's disease patients into trials (as distinct from patients with non-Parkinson's disease parkinsonism or non-Parkinson's disease tremors). There remain, however, further challenges in the pursuit of biomarkers for clinical trials of disease modifying agents in Parkinson's disease, namely: optimizing the distinction between different α-synucleinopathies; the selection of subgroups most likely to benefit from a candidate disease modifying agent; a sensitive means of confirming target engagement; and the early prediction of longer-term clinical benefit. For example, levels of CSF proteins such as the lysosomal enzyme β-glucocerebrosidase may assist in prognostication or allow enrichment of appropriate patients into disease modifying trials of agents with this enzyme as the target; the presence of coexisting Alzheimer's disease-like pathology (detectable through CSF levels of amyloid-β42 and tau) can predict subsequent cognitive decline; imaging techniques such as free-water or neuromelanin MRI may objectively track decline in Parkinson's disease even in its later stages. The exploitation of additional biomarkers to the α-synuclein seed amplification assay will, therefore, greatly add to our ability to plan trials and assess the disease modifying properties of interventions. The choice of which biomarker(s) to use in the context of disease modifying clinical trials will depend on the intervention, the stage (at risk, premotor, motor, complex) of the population recruited and the aims of the trial. The progress already made lends hope that panels of fluid biomarkers in tandem with structural or functional imaging may provide sensitive and objective methods of confirming that an intervention is modifying a key pathophysiological process of Parkinson's disease. However, correlation with clinical progression does not necessarily equate to causation, and the ongoing validation of quantitative biomarkers will depend on insightful clinical-genetic-pathophysiological comparisons incorporating longitudinal biomarker changes from those at genetic risk with evidence of onset of the pathophysiology and those at each stage of manifest clinical Parkinson's disease.

Blood neurofilament light chain in Parkinson's disease

Blood neurofilament light chain (NfL) is an easily accessible, highly sensitive and reliable biomarker for neuroaxonal damage. Currently, its role in Parkinson's disease (PD) remains unclear. Here, we demonstrate that blood NfL can distinguish idiopathic PD from atypical parkinsonian syndromes (APS) with high sensitivity and specificity. In cross-sectional studies, some found significant correlations between blood NfL with motor and cognitive function, whereas others did not. In contrast, prospective studies reported very consistent associations between baseline blood NfL with motor progression and cognitive worsening. Amongst PD subtypes, especially postural instability and gait disorder (PIGD) subtype, symptoms and scores are reliably linked with blood NfL. Different non-motor PD comorbidities have also been associated with high blood NfL levels suggesting that the neuroaxonal damage of the autonomic nervous system as well as serotonergic, cholinergic and noradrenergic neurons is quantifiable. Numerous absolute NfL cutoff levels have been suggested in different cohort studies; however, validation across cohorts remains weak. However, age-adjusted percentiles and intra-individual blood NfL changes might represent more valid and consistent parameters compared with absolute NfL concentrations. In summary, blood NfL has the potential as biomarker in PD patients to be used in clinical practice for prediction of disease severity and especially progression.

Traditional Chinese medicine Pingchan granule for motor symptoms and functions in Parkinson's disease: A multicenter, randomized, double-blind, placebo-controlled study

BACKGROUND

Pingchan granule (PCG) is a traditional Chinese medicine for Parkinson's disease (PD).

HYPOTHESIS/PURPOSE

This was the first study aiming to evaluate the efficacy and safety of PCG for motor symptoms, gait impairments and quality of life in PD.

STUDY DESIGN AND METHODS

In this multicenter, randomized, double-blind, placebo-controlled trial, 292 participants were included and followed for 9 months, randomly assigned at a 1:1 ratio to receive PCG or placebo. The primary outcome was the severity of motor symptoms assessed by Movement Disorder Society Unified Parkinson's Rating Scale III (MDS-UPDRS-III) motor score. Secondary outcomes included timed up and go test (TUG), functional gait assessment (FGA), freezing of gait (FOG), and quality of life assessed by Parkinson's disease questionnaire (PDQ-39). Assessments were done at baseline (T0), 3 months (T1), 6 months (T2) and 9 months (T3).

TRIAL REGISTRATION

Chinese Clinical Trial Register, ChiCTR-INR-1,701,194.

RESULTS

Generalized estimating equation analyses revealed that PCG group had significantly better improvement in MDS-UPDRS-III motor score than placebo group, as well as its domain scores of axial symptoms, bradykinesia, rigidity, and tremor. Improvements of TUG time, FGA, FOG questionnaire (FOGQ), and PDQ39 scores were also observed.

CONCLUSION

PCG had a long-lasting efficacy for motor symptoms and function in PD with good tolerance, supporting that PCG might be a viable alternative in the management of PD.

Blood-based biomarker in Parkinson's disease: potential for future applications in clinical research and practice

The clinical presentation of Parkinson's disease (PD) is both complex and heterogeneous, and its precise classification often requires an intensive work-up. The differential diagnosis, assessment of disease progression, evaluation of therapeutic responses, or identification of PD subtypes frequently remains uncertain from a clinical point of view. Various tissue- and fluid-based biomarkers are currently being investigated to improve the description of PD. From a clinician's perspective, signatures from blood that are relatively easy to obtain would have great potential for use in clinical practice if they fulfill the necessary requirements as PD biomarker. In this review article, we summarize the knowledge on blood-based PD biomarkers and present both a researcher's and a clinician's perspective on recent developments and potential future applications.

Disease modification in Parkinsonism: obstacles and ways forward

To date, the diagnoses of Parkinson syndromes are based on clinical examination. Therefore, these specific diagnoses are made, when the neuropathological process is already advanced. However, disease modification or neuroprotection, is considered to be most effective before marked neurodegeneration has occurred. In recent years, early clinical or prodromal stages of Parkinson syndromes came into focus. Moreover, subtypes of distinct diseases will allow predictions of the individual course of the diseases more precisely. Thereby, patients will be enrolled into clinical trials with more specific disease entities and endpoints. Furthermore, novel fluid and imaging biomarkers that allow biochemical diagnoses are under development. These will lead to earlier diagnoses and earlier therapy in the future as consequence. Furthermore, therapeutic approaches will take the underlying neuropathological process of neurodegenerative Parkinson syndromes more specific into account. Specifically, future therapies will target the aggregation of aggregation-prone proteins such as alpha-synuclein and tau, the degradation of pathological aggregates, and the spreading of pathological protein aggregates throughout the brain. Many of these approaches are already in (pre)clinical development. In addition, anti-inflammatory approaches are in development. Furthermore, drug-repurposing is a feasible approach to shorten the developmental process of new drugs.