Correlates of cerebrospinal fluid levels of oligomeric- and total-α-synuclein in premotor, motor and dementia stages of Parkinson’s disease

Cardiovascular dysautonomia and cognitive impairment in Parkinson's disease (Review)

Cognitive impairment is a prevalent non-motor symptom of Parkinson's disease (PD), which can result in significant disability and distress for patients and caregivers. There is a marked variation in the timing, characteristics and rate at which cognitive decline occurs in patients with PD. This decline can vary from normal cognition to mild cognitive impairment and dementia. Cognitive impairment is associated with several pathophysiological mechanisms, including the accumulation of β-amyloid and tau in the brain, oxidative stress and neuroinflammation. Cardiovascular autonomic dysfunctions are commonly observed in patients with PD. These dysfunctions play a role in the progression of cognitive impairment, the incidents of falls and even in mortality. The majority of symptoms of dysautonomia arise from changes in the peripheral autonomic nervous system, including both the sympathetic and parasympathetic nervous systems. Cardiovascular changes, including orthostatic hypotension, supine hypertension and abnormal nocturnal blood pressure (BP), can occur in both the early and advanced stages of PD. These changes tend to increase as the disease advances. The present review aimed to describe the cognitive changes in the setting of cardiovascular dysautonomia and to discuss strategies through which these changes can be modified and managed. It is a multifactorial process usually involving decreased blood flow to the brain, resulting in the development of cerebral ischemic lesions, an increased presence of abnormal white matter signals in the brain, and a potential influence on the process of neurodegeneration in PD. Another possible explanation is this association being independent observations of PD progression. Patients with clinical symptoms of dysautonomia should undergo 24-h ambulatory BP monitoring, as they are frequently subtle and underdiagnosed.

Cerebrospinal Fluid Total, Phosphorylated and Oligomeric A-Synuclein in Parkinson's Disease: A Systematic Review, Meta-Analysis and Meta-Regression Study

Background: The diagnostic accuracy for Parkinson's disease (PD), a synucleinopathy, based on diagnostic criteria is suboptimal. A biomarker for synucleinopathies is pivotal both from a clinical and from a research point of view. CSF a-synuclein has been extensively studied over the past two decades as a candidate biomarker of synucleinopathies. Herein, we present data on studies focusing on total, phosphorylated and oligomeric CSF a-synuclein in PD. Methods: Pubmed, Scopus and Web of Science were searched for studies with >10 PD patients and control subjects, with data (mean, SD) on total, phosphorylated or oligomeric a-synuclein. Cohen's d, as a measure of effect size, was calculated for all a-synuclein forms. Subgroup analysis and meta-regression were performed in an effort to explain between-study heterogeneity. Results: Thirty studies on total, six studies on oligomeric and one study on phosphorylated a-synuclein were included. Total a-synuclein was decreased and oligomeric a-synuclein increased in PD patients vs. controls. The effect size was medium for total and high for oligomeric a-synuclein. A-syn forms provided suboptimal combined sensitivity/specificity for the differentiation of PD from controls. There was significant between-study heterogeneity. The PD cohort characteristics (sex, age, disease duration, UPDRS, H & Y) and study characteristics (study design, healthy vs. neurological controls, control for CSF blood contamination, method of a-syn measurement) could not account for between-study heterogeneity. Publication bias was limited. Conclusions: CSF a-synuclein levels lack sufficient accuracy to be used as biomarkers for PD. The standardization of (pre)analytical variables may improve the discriminatory power of a-synuclein forms in the future.

Plasma level of alpha-synuclein oligomers as a biomarker for isolated rapid eye movement sleep behavior disorder diagnosis and progression: a prospective cohort study

Background

Alpha-synuclein oligomers (o-α-syn) are pivotal in the pathogenesis of α-synucleinopathy. Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) serves as an early indicator of the disease, offering insights into disease mechanisms and early intervention. Nevertheless, the diagnostic and predictive potential of o-α-syn in iRBD remains largely unexplored. This study aimed to evaluate the plasma levels of o-α-syn in patients and investigate their utility as biomarkers for diagnosis of and predicting phenoconversion in iRBD.

Methods

A total of 143 participants, including 77 polysomnography-confirmed iRBD patients and 66 normal controls (NC), were recruited for this longitudinal observational study. Baseline clinical assessments and plasma collection were conducted for all iRBD patients, with 72 of them undergoing regularly prospective follow-up assessments for parkinsonism or dementia. Plasma levels of o-α-syn were quantified using enzyme-linked immunosorbent assay, and were compared between groups using a general linear model adjusted for age and sex. The diagnostic performance of plasma o-α-syn in iRBD was evaluated by area under the receiver operating characteristic curve (AUC) with 95% CI. Cox regression analysis and Kaplan-Meier survival curves were employed to assess the predictive value of plasma o-α-syn for phenoconversion in iRBD.

Results

Plasma o-α-syn levels did not exhibit statistically significant differences among iRBD converter patients, iRBD nonconverter patients, and NC. The AUC for distinguishing NC from iRBD was 0.52 (95% CI: 0.42-0.62, p = 0.682). Spearman correlation analysis revealed a significant positive correlation between plasma o-α-syn levels and MOCA scores in the iRBD group (p < 0.001). Subgroup analyses indicated that iRBD patients with cognitive decline (p = 0.058) and depressive symptoms (p = 0.017) had notably lower o-α-syn levels compared to those without such symptoms. Over a median follow-up period of 5.83 years, 26 iRBD patients developed neurodegenerative synucleinopathies. Cox regression and Kaplan-Meier survival curve analyses indicated that plasma level of o-α-syn lacked a predictive value for disease conversion in iRBD patients.

Conclusion

Despite a potential role in the pathophysiology of iRBD, o-α-syn are not appropriate biomarkers for diagnosing or predicting disease progression. While this study offers insights into the pathogenesis of iRBD and neurodegenerative synucleinopathies, further large-scale longitudinal studies are warranted to validate these findings.

Serum Oligomeric α-Synuclein and p-tau181 in Progressive Supranuclear Palsy and Parkinson's Disease

Clinical differentiation of progressive supranuclear palsy (PSP) from Parkinson's disease (PD) is challenging due to overlapping phenotypes and the late onset of specific atypical signs. Therefore, easily assessable diagnostic biomarkers are highly needed. Since PD is a synucleopathy while PSP is a tauopathy, here, we investigated the clinical usefulness of serum oligomeric-α-synuclein (o-α-synuclein) and 181Thr-phosphorylated tau (p-tau181), which are considered as the most important pathological protein forms in distinguishing between these two parkinsonisms. We assessed serum o-α-synuclein and p-tau181 by ELISA and SIMOA, respectively, in 27 PSP patients, 43 PD patients, and 39 healthy controls (HC). Moreover, we evaluated the correlation between serum biomarkers and biological and clinical features of these subjects. We did not find any difference in serum concentrations of p-tau181 and o-α-synuclein nor in the o-α-synuclein/p-tau181 ratio between groups. However, we observed that serum p-tau181 positively correlated with age in HC and PD, while serum o-α-synuclein correlated positively with disease severity in PD and negatively with age in PSP. Finally, the o-α-synuclein/p-tau181 ratio showed a negative correlation with age in PD.

Evaluating the Diagnostic Potential of Combined Salivary and Skin Biomarkers in Parkinson's Disease

Oligomeric alpha-synuclein (α-syn) in saliva and phosphorylated α-syn deposits in the skin have emerged as promising diagnostic biomarkers for Parkinson's disease (PD). This study aimed to assess and compare the diagnostic value of these biomarkers in discriminating between 38 PD patients and 24 healthy subjects (HSs) using easily accessible biological samples. Additionally, the study sought to determine the diagnostic potential of combining these biomarkers and to explore their correlations with clinical features. Salivary oligomeric α-syn levels were quantified using competitive ELISA, while skin biopsies were analyzed through immunofluorescence to detect phosphorylated α-syn at Ser129 (p-S129). Both biomarkers individually were accurate in discriminating PD patients from HSs, with a modest agreement between them. The combined positivity of salivary α-syn oligomers and skin p-S129 aggregates differentiated PD patients from HSs with an excellent discriminative ability with an AUC of 0.9095. The modest agreement observed between salivary and skin biomarkers individually suggests that they may reflect different aspects of PD pathology, thus providing complementary information when combined. This study's results highlight the potential of utilizing a multimodal biomarker approach to enhance diagnostic accuracy in PD.

Fluid and tissue biomarkers in Parkinson's disease: Immunodetection or seed amplification? Central or peripheral?

Over the last two decades there have been meaningful developments on biomarkers of neurodegenerative diseases, extensively (but not solely) focusing on their proteinopathic nature. Accordingly, in Alzheimer's disease determination of levels of total and phosphorylated tau (τ and p-τ, usually p-τ181) along with amyloid-beta1-42 (Aβ1-42) by immunodetection in cerebrospinal fluid (CSF) and currently even in peripheral blood, have been widely accepted and introduced to routine diagnosis. In the case of Parkinson's disease, α-synuclein as a potential biomarker (both for diagnosis and progression tracking) has proved more elusive under the immunodetection approach. In recent years, the emergence of the so-called seed amplification assays is proving to be a game-changer, with mounting evidence under different technical approaches and using a variety of biofluids or tissues, yielding promising diagnostic accuracies. Currently the least invasive but at once more reliable source of biosamples and techniques are being sought. Here we overview these advances.

Neuropsychological Changes in Isolated REM Sleep Behavior Disorder: A Systematic Review and Meta-analysis of Cross-sectional and Longitudinal Studies

The aim of this meta-analysis is twofold: (a) to assess cognitive impairments in isolated rapid eye movement (REM) sleep behavior disorder (iRBD) patients compared to healthy controls (HC); (b) to quantitatively estimate the risk of developing a neurodegenerative disease in iRBD patients according to baseline cognitive assessment. To address the first aim, cross-sectional studies including polysomnography-confirmed iRBD patients, HC, and reporting neuropsychological testing were included. To address the second aim, longitudinal studies including polysomnography-confirmed iRBD patients, reporting baseline neuropsychological testing for converted and still isolated patients separately were included. The literature search was conducted based on PRISMA guidelines and the protocol was registered at PROSPERO (CRD42021253427). Cross-sectional and longitudinal studies were searched from PubMed, Web of Science, Scopus, and Embase databases. Publication bias and statistical heterogeneity were assessed respectively by funnel plot asymmetry and using I2. Finally, a random-effect model was performed to pool the included studies. 75 cross-sectional (2,398 HC and 2,460 iRBD patients) and 11 longitudinal (495 iRBD patients) studies were selected. Cross-sectional studies showed that iRBD patients performed significantly worse in cognitive screening scores (random-effects (RE) model = -0.69), memory (RE model = -0.64), and executive function (RE model = -0.50) domains compared to HC. The survival analyses conducted for longitudinal studies revealed that lower executive function and language performance, as well as the presence of mild cognitive impairment (MCI), at baseline were associated with an increased risk of conversion at follow-up. Our study underlines the importance of a comprehensive neuropsychological assessment in the context of iRBD.

Cerebrospinal-fluid biomarkers for predicting phenoconversion in patients with isolated rapid-eye movement sleep behavior disorder

STUDY OBJECTIVES

Patients with isolated rapid-eye-movement sleep behavior disorder (iRBD) have an increased risk of developing neurodegenerative diseases. This study assessed cerebrospinal-fluid (CSF) biomarkers of neurodegeneration and blood-brain barrier (BBB) alteration in patients with iRBD compared to controls and ascertain whether these biomarkers may predict phenoconversion to alpha-synucleinopathies (Parkinson's Disease (PD), Dementia with Lewy bodies (DLB), Multiple System Atrophy (MSA)).

METHODS

Patients and controls underwent between 2012 and 2016 a neurological assessment, a lumbar puncture for CSF biomarker analysis (β-amyloid42 - Aβ42; total-tau, and phosphorylated tau), and BBB alteration (CSF/serum albumin ratio). All patients with iRBD were followed until 2021 and then classified into patients who converted to alpha-synucleinopathies (iRBD converters, cRBD) or not (iRBD non-converters, ncRBD).

RESULTS

Thirty-four patients with iRBD (mean age 67.12 ± 8.14) and 33 controls (mean age 64.97 ± 8.91) were included. At follow-up (7.63 ± 3.40 years), eight patients were ncRBD and 33 patients were cRBD: eleven converted to PD, 10 to DLB, and two to MSA. Patients with iRBD showed lower CSF Aβ42 levels and higher CSF/serum albumin ratio than controls. Cox regression analysis showed that the phenoconversion rate increases with higher motor impairment (hazard ratio [HR] = 1.23, p = 0.032). CSF Aβ42 levels predicted phenoconversion to DLB (HR = 0.67, p = 0.038) and BBB alteration predicted phenoconversion to PD (HR = 1.20, p = 0.038).

DISCUSSION

This study showed that low CSF Aβ42 levels and high BBB alteration may predict the phenoconversion to DLB and PD in patients with iRBD, respectively. These findings highlight the possibility to discriminate phenoconversion in iRBD patients through CSF biomarkers; however, further studies are needed.

Midbrain and pons MRI shape analysis and its clinical and CSF correlates in degenerative parkinsonisms: a pilot study

OBJECTIVES

To conduct brainstem MRI shape analysis across neurodegenerative parkinsonisms and control subjects (CS), along with its association with clinical and cerebrospinal fluid (CSF) correlates.

METHODOLOGY

We collected demographic and clinical variables, performed planimetric and shape MRI analyses, and determined CSF neurofilament-light chain (NfL) levels in 84 participants: 11 CS, 12 with Parkinson's disease (PD), 26 with multiple system atrophy (MSA), 21 with progressive supranuclear palsy (PSP), and 14 with corticobasal degeneration (CBD).

RESULTS

MSA featured the most extensive and significant brainstem shape narrowing (that is, atrophy), mostly in the pons. CBD presented local atrophy in several small areas in the pons and midbrain compared to PD and CS. PSP presented local atrophy in small areas in the posterior and upper midbrain as well as the rostral pons compared to MSA. Our findings of planimetric MRI measurements and CSF NfL levels replicated those from previous literature. Brainstem shape atrophy correlated with worse motor state in all parkinsonisms and with higher NfL levels in MSA, PSP, and PD.

CONCLUSION

Atypical parkinsonisms present different brainstem shape patterns which correlate with clinical severity and neuronal degeneration. In MSA, shape analysis could be further explored as a potential diagnostic biomarker. By contrast, shape analysis appears to have a rather limited discriminant value in PSP.

KEY POINTS

• Atypical parkinsonisms present different brainstem shape patterns. • Shape patterns correlate with clinical severity and neuronal degeneration. • In MSA, shape analysis could be further explored as a potential diagnostic biomarker.

Fluid and Biopsy Based Biomarkers in Parkinson's Disease

Several advances in fluid and tissue-based biomarkers for use in Parkinson's disease (PD) and other synucleinopathies have been made in the last several years. While work continues on species of alpha-synuclein (aSyn) and other proteins which can be measured from spinal fluid and plasma samples, immunohistochemistry and immunofluorescence from peripheral tissue biopsies and alpha-synuclein seeding amplification assays (aSyn-SAA: including real-time quaking induced conversion (RT-QuIC) and protein misfolding cyclic amplification (PMCA)) now offer a crucial advancement in their ability to identify aSyn species in PD patients in a categorical fashion (i.e., of aSyn + vs aSyn -); to augment clinical diagnosis however, aSyn-specific assays that have quantitative relevance to pathological burden remain an unmet need. Alzheimer's disease (AD) co-pathology is commonly found postmortem in PD, especially in those who develop dementia, and dementia with Lewy bodies (DLB). Biofluid biomarkers for tau and amyloid beta species can detect AD co-pathology in PD and DLB, which does have relevance for prognosis, but further work is needed to understand the interplay of aSyn tau, amyloid beta, and other pathological changes to generate comprehensive biomarker profiles for patients in a manner translatable to clinical trial design and individualized therapies.

The Mechanisms of the Roles of α-Synuclein, Amyloid-β, and Tau Protein in the Lewy Body Diseases: Pathogenesis, Early Detection, and Therapeutics

Lewy body diseases (LBD) are pathologically defined as the accumulation of Lewy bodies composed of an aggregation of α-synuclein (αSyn). In LBD, not only the sole aggregation of αSyn but also the co-aggregation of amyloidogenic proteins, such as amyloid-β (Aβ) and tau, has been reported. In this review, the pathophysiology of co-aggregation of αSyn, Aβ, and tau protein and the advancement in imaging and fluid biomarkers that can detect αSyn and co-occurring Aβ and/or tau pathologies are discussed. Additionally, the αSyn-targeted disease-modifying therapies in clinical trials are summarized.

Parkinson's disease therapy: what lies ahead?

The worldwide prevalence of Parkinson's disease (PD) has been constantly increasing in the last decades. With rising life expectancy, a longer disease duration in PD patients is observed, further increasing the need and socioeconomic importance of adequate PD treatment. Today, PD is exclusively treated symptomatically, mainly by dopaminergic stimulation, while efforts to modify disease progression could not yet be translated to the clinics. New formulations of approved drugs and treatment options of motor fluctuations in advanced stages accompanied by telehealth monitoring have improved PD patients care. In addition, continuous improvement in the understanding of PD disease mechanisms resulted in the identification of new pharmacological targets. Applying novel trial designs, targeting of pre-symptomatic disease stages, and the acknowledgment of PD heterogeneity raise hopes to overcome past failures in the development of drugs for disease modification. In this review, we address these recent developments and venture a glimpse into the future of PD therapy in the years to come.

Preoperative cerebrospinal fluid biomarkers may be associated with postoperative delirium in patients undergoing knee/hip arthroplasty: the PNDABLE study

BACKGROUND

In the global aging population, the incidence of postoperative delirium (POD) is increasing. Therefore, finding its effective predictive tools becomes crucial. We aimed to identify potential Cerebrospinal fluid (CSF)biomarkers for POD.

METHODS

A total of 825 patients undergoing knee/hip arthroplasty under combined spinal-epidural anesthesia were selected. The patients were aged 40 to 90 years with American Society of Anesthesiologists physical status I~II. The Mini-Mental State Examination was completed 1 day before the operation. CSF was extracted after successful spinal-epidural combined puncture, and α-synuclein (α-syn), amyloid beta₄₀ (Aβ₄₀), amyloid beta₄₂ (Aβ₄₂), t-Tau, phosphorylated Tau (p-Tau), progranulin (PGRN) and soluble triggering receptor expressed on myeloid cells 2 (sTREM2) in the CSF were measured by enzyme-linked immunosorbent assays (ELISA). The patient's operation time, anesthesia time, intraoperative blood loss and fluid input were also recorded. After the operation, the occurrence rate and severity of POD were determined by the Confusion Assessment Method and the Memorial Delirium Assessment Scale (MDAS), respectively. Patients were categorized into POD group and non-POD group. Logistic regression analysis was performed on the indicators with statistically significant differences, and the area under the ROC curve (AUC) was used to estimate the predictive accuracy of the biomarkers for POD.

RESULTS

A total of 92 patients developed POD and the incidence of POD was 11.15%. The results of the multivariable logistic regression showed that CSF t-Tau (P = 0.004, OR = 1.006, 95%CI 1.002~1.009) and α-syn (P = 0.004, OR = 1.001, 95%CI 1.000~1.001) were positively associated with the occurrence rate of POD, while Aβ₄₂ (P < 0.001, OR = 0.989, 95%CI 0.986~0.993), CSF PGRN (P = 0.002, OR = 0.999, 95%CI 0.999~1.000), Aβ₄₂/ t-Tau (P < 0.001, OR = 0.181, 95%CI 0.102~0.319) and Aβ₄₂/p-Tau (P < 0.001, OR = 0.617, 95%CI 0.526~0.725) were inversely proportional to the occurrence of POD. ROC curve analysis indicated that Aβ₄₂/t-Tau (AUC = 0.823), CSF Aβ₄₂ (AUC = 0.813), Aβ₄₂/p-Tau (AUC = 0.810), α-syn (AUC = 0.644) and PGRN (AUC = 0.638) could predict the occurrence rate of POD. The combination of all these biomarkers showed a greater AUC(0.896) than using any of them alone.

CONCLUSIONS

CSF Aβ₄₂, PGRN, α-syn, Aβ₄₂/t-Tau and Aβ₄₂/p-Tau might be associated with the occurrence rate of POD in patients undergoing knee/hip arthroplasty.

TRIAL REGISTRATION

Clinical Registration No. ChiCTR2000033439.

Patients with isolated REM-sleep behavior disorder have elevated levels of alpha-synuclein aggregates in stool

Misfolded and aggregated α-synuclein is a neuropathological hallmark of Parkinson's disease (PD). Thus, α-synuclein aggregates are regarded as a biomarker for the development of diagnostic assays. Quantification of α-synuclein aggregates in body fluids is challenging, and requires highly sensitive and specific assays. Recent studies suggest that α-synuclein aggregates may be shed into stool. We used surface-based fluorescence intensity distribution analysis (sFIDA) to detect and quantify single particles of α-synuclein aggregates in stool of 94 PD patients, 72 isolated rapid eye movement sleep behavior disorder (iRBD) patients, and 51 healthy controls. We measured significantly elevated concentrations of α-synuclein aggregates in stool of iRBD patients versus those of controls (p = 0.024) or PD patients (p < 0.001). Our results show that α-synuclein aggregates are excreted in stool and can be measured using the sFIDA assay, which could support the diagnosis of prodromal synucleinopathies.

Combined CSF α-SYN RT-QuIC, CSF NFL and midbrain-pons planimetry in degenerative parkinsonisms: From bedside to bench, and back again

INTRODUCTION

Differential diagnosis between Parkinson's disease (PD) and atypical parkinsonisms (APs: multiple system atrophy[MSA], progressive supranuclear palsy[PSP], corticobasal degeneration[CBD]) remains challenging. Lately, cerebrospinal fluid (CSF) studies of neurofilament light-chain (NFL) and RT-QuIC of alpha-synuclein (α-SYN) have shown promise, but data on their combination with MRI measures is lacking.

OBJECTIVE

(1) to assess the combined diagnostic ability of CSF RT-QuIC α-SYN, CSF NFL and midbrain/pons MRI planimetry in degenerative parkinsonisms; (2) to evaluate if biomarker-signatures relate to clinical diagnoses and whether or not unexpected findings can guide diagnostic revision.

METHODS

We collected demographic and clinical data and set up α-SYN RT-QuIC at our lab in a cross-sectional cohort of 112 participants: 19 control subjects (CSs), 20PD, 37MSA, 23PSP, and 13CBD cases. We also determined CSF NFL by ELISA and, in 74 participants (10CSs, 9PD, 26MSA, 19PSP, 10CBD), automatized planimetric midbrain/pons areas from 3T-MRI.

RESULTS

Sensitivity of α-SYN RT-QuIC for PD was 75% increasing to 81% after revisiting clinical diagnoses with aid of biomarkers. Sensitivity for MSA was 12% but decreased to 9% with diagnostic revision. Specificities were 100% against CSs, and 89% against tauopathies raising to 91% with diagnostic revision. CSF NFL was significantly higher in APs. The combination of biomarkers yielded high diagnostic accuracy (PD vs. non-PD AUC = 0.983; MSA vs. non-MSA AUC = 0.933; tauopathies vs. non-tauopathies AUC = 0.924). Biomarkers-signatures fitted in most cases with clinical classification.

CONCLUSIONS

The combination of CSF NFL, CSF RT-QuIC α-SYN and midbrain/pons MRI measures showed high discriminant ability across all groups. Results opposite to expected can assist diagnostic reclassification.

Plasma and serum alpha-synuclein as a biomarker in Parkinson's disease: A meta-analysis

BACKGROUND

Reliable biomarkers for Parkinson's disease (PD) diagnosis are urgently needed. Alpha-synuclein (α-syn) and its proteoforms play a key role in PD pathology but in vivo measurements have raised conflicting results, and whether α-syn in blood could distinguish PD patients from healthy controls is still controversial.

METHODS

A systematic literature search yielded 35 eligible studies for meta-analysis reporting the concentration of total, oligomeric or phosphorylated α-syn in plasma and/or serum of PD patients and healthy controls. Standardized mean differences (SMD) were pooled using multivariate/multilevel linear mixed-effects models. Meta-regression analyses were conducted to investigate possible modifiers.

RESULTS

A meta-analysis of 32 articles involving 2683 PD patients and 1838 controls showed a significant overall effect of PD on total α-syn levels (SMD = 0.85, p = 0.004). Meta-regression showed that increased SMD of total α-syn in PD was significantly associated with lower age, shorter disease duration, mild motor impairment, and Immunomagnetic Reduction assay for protein quantification. In contrast, no significant differences were observed for oligomeric or phosphorylated α-syn between PD and controls but increased oligomeric α-syn was significantly associated with shorter disease duration. The heterogeneity among studies was high (>98%).

CONCLUSIONS

These findings suggest that increased total plasma/serum α-syn levels in PD primarily occur in early phases of the disease. The evidence obtained from a small number of studies measuring plasma/serum concentrations of oligomeric and phosphorylated species of α-syn shows no difference. The clinical applicability of measuring plasma or serum α-syn species for differentiating PD from healthy control warrants further studies with better clinical profiling of PD patients.

Baseline Cerebrospinal Fluid α-Synuclein in Parkinson's Disease Is Associated with Disease Progression and Cognitive Decline

Biomarkers are increasingly recognized as tools in the diagnosis and prognosis of neurodegenerative diseases. No fluid biomarker for Parkinson’s disease (PD) has been established to date, but α-synuclein, a major component of Lewy bodies in PD and dementia with Lewy bodies (DLB), has become a promising candidate. Here, we investigated CSF α-synuclein in patients with PD (n = 28), PDD (n = 8), and DLB (n = 5), applying an electrochemiluminescence immunoassay. Median values were non-significantly (p = 0.430) higher in patients with PDD and DLB (287 pg/mL) than in PD (236 pg/mL). A group of n = 36 primarily non-demented patients with PD and PDD was clinically followed for up to two years. A higher baseline α-synuclein was associated with increases in Hoehn and Yahr classifications (p = 0.019) and Beck Depression Inventory scores (p < 0.001) as well as worse performance in Trail Making Test A (p = 0.017), Trail Making Test B (p = 0.043), and the Boston Naming Test (p = 0.002) at follow-up. Surprisingly, higher levels were associated with a better performance in semantic verbal fluency tests (p = 0.046). In summary, CSF α-synuclein may be a potential prognostic marker for disease progression, affective symptoms, and executive cognitive function in PD. Larger-scaled studies have to validate these findings and the discordant results for single cognitive tests in this exploratory investigation.

Detection and assessment of alpha-synuclein in Parkinson disease

PURPOSE

Different studies have reported varying alpha-synuclein values in the cerebrospinal fluid (CSF), serum, and plasma, making determination of the alpha-synuclein cutoff value for Parkinson's disease difficult and rendering identifying the cause of variation essential.

METHOD

We searched PubMed from inception to June 2021 and identified 76 eligible studies. Included studies reported data on total, phosphorylated, and oligomeric alpha-synuclein in the CSF, serum, or plasma from individuals with Parkinson's disease and healthy controls. The mean or median alpha-synuclein values from the included studies were summarized and categorized through laboratory assays to visualize potential trends.

RESULTS

The enzyme-linked immunosorbent assay (ELISA) is the most common assay used to determine alpha-synuclein concentrations. Less common assays include Luminex, single molecule arrays, electrochemiluminescence, and immunomagnetic reduction (IMR). IMR is a single-antibody and wash-free immunoassay designed for determining the extremely low concentration of bio-molecules. For patients with Parkinson's disease, the median or mean testing values ranged from 60.9 to 55,000 pg/mL in the CSF, 0.446 to 1,777,100 pg/mL in plasma, and 0.0292 to 38,200,000 pg/mL in serum. The antibody selection was diverse between studies. The tendency of distribution was more centralized among studies that used the same kit. Studies adopting specific antibodies or in-house assays contribute to the extreme values. Only a few studies on phosphorylated and oligomeric alpha-synuclein were included.

CONCLUSION

The type of assay and antibody selection in the laboratory played major roles in the alpha-synuclein variation. Studies that used the same assay and kit yielded relatively unanimous results. Furthermore, IMR may be a promising assay for plasma and serum alpha-synuclein quantification. A consensus on sample preparation and testing protocol unification is warranted in the future.

Effects of age, amyloid, sex, and APOE ε4 on the CSF proteome in normal cognition

Introduction

It is important to understand which biological processes change with aging, and how such changes are associated with increased Alzheimer's disease (AD) risk. We studied how cerebrospinal fluid (CSF) proteomics changed with age and tested if associations depended on amyloid status, sex, and apolipoprotein E Ɛ4 genotype.

Methods

We included 277 cognitively intact individuals aged 46 to 89 years from Alzheimer's Disease Neuroimaging Initiative, European Medical Information Framework for Alzheimer's Disease Multimodal Biomarker Discovery, and Metabolic Syndrome in Men. In total, 1149 proteins were measured with liquid chromatography mass spectrometry with multiple reaction monitoring/Rules-Based Medicine, tandem mass tag mass spectrometry, and SOMAscan. We tested associations between age and protein levels in linear models and tested enrichment for Reactome pathways.

Results

Levels of 252 proteins increased with age independently of amyloid status. These proteins were associated with immune and signaling processes. Levels of 21 proteins decreased with older age exclusively in amyloid abnormal participants and these were enriched for extracellular matrix organization.

Discussion

We found amyloid-independent and -dependent CSF proteome changes with older age, perhaps representing physiological aging and early AD pathology.

Fibrinogen and Complement Factor H Are Promising CSF Protein Biomarkers for Parkinson's Disease with Cognitive Impairment─A Proteomics-ELISA-Based Study

Parkinson's disease (PD) with cognitive impairment (PDCI) is essentially diagnosed through clinical and neuropsychological examinations. There is a need to identify biomarkers to foresee cognitive decline in them. We performed label-free unbiased nontargeted proteomics (Q-TOF LC/MS-MS) on the CSF of non-neurological control; PDCI; PD; and normal pressure hydrocephalus (NPH) patients, followed by targeted ELISA for validation. Of the 281 proteins identified, 42 were differentially altered in PD, PDCI, and NPH. With a certain overlap, 28 proteins were altered in PDCI and 25 proteins were altered in NPH. Five significantly upregulated proteins in PDCI were fibrinogen, gelsolin, complement factor-H, and apolipoproteins A-I and A-IV, whereas carnosine dipeptidase-1, carboxypeptidase-E, dickkopf-3, and secretogranin-3 precursor proteins were downregulated. Those uniquely altered in NPH were the insulin-like growth factor-binding protein, ceruloplasmin, α-1 antitrypsin, VGF nerve growth factor, and neural cell adhesion molecule L1-like protein. The ELISA-derived protein concentrations correlated with neuropsychological scores of certain cognitive domains. In PDCI, the Wisconsin card sorting percentile correlated negatively with fibrinogen. Intraperitoneal injection of native fibrinogen caused motor deficits in C57BL/6J mice as assessed by the pole test. Thus, a battery of proteins such as fibrinogen-α-chain, CFAH, and APOA-I/APOA-IV alongside neuropsychological assessment could be reliable biomarkers to distinguish PDCI and NPH.

Associations of sleep disorders with cerebrospinal fluid α-synuclein in prodromal and early Parkinson's disease

OBJECTIVES

Our aim is to investigate the associations of sleep disorders with cerebrospinal fluid (CSF) α-synuclein (α-syn) in healthy controls (HCs), and patients with prodromal and early Parkinson's disease (PD).

METHODS

We included a total of 575 individuals, consisting of 360 PD individuals, 46 prodromal PD individuals, and 169 HCs. Multiple linear regression models and linear mixed-effects models were used to investigate the associations of sleep disorders with baseline and longitudinal CSF α-syn. Associations between the change rates of sleep disorders and CSF α-syn were further investigated via multiple linear regression models.

RESULTS

In PD, probable Rapid-eye-movement sleep Behavior Disorder (pRBD) (β = - 0.1199; P = 0.0444) and RBD sub-items, such as aggressive dreams (β = - 0.1652; P = 0.0072) and hurting bed partner (β = - 0.2468; P = 0.0010), contributed to lower CSF α-syn. The association between aggressive dreams and lower CSF α-syn further survived Bonferroni correction (P < 0.0036). In prodromal PD, dream-enacting (a specific RBD behavior) was significantly associated with decreased CSF α-syn during the follow-up (β = - 0.0124; P = 0.0237). HCs with daytime sleepiness when inactive-sitting in public places (β = - 0.0033; P = 0.0135) showed decreased CSF α-syn. Furthermore, increased possibilities of daytime sleepiness when sitting and reading contributed to a greater decrease of CSF α-syn in HCs (β = - 196.8779; P = 0.0433).

CONCLUSIONS

Sleep disorders were associated with decreased CSF α-syn. Sleep management may be important for disease monitoring and preventing the progression of α-syn pathology.

Predictors of Conversion to α-Synucleinopathy Diseases in Idiopathic Rapid Eye Movement Sleep Behavior Disorder

BACKGROUND

Idiopathic rapid eye movement sleep behavior disorder (iRBD) often precedes the development of α-synucleinopathy diseases.

OBJECTIVE

We aimed to assess the predictive value of clinical variables and biomarkers for the early development of α-synucleinopathy diseases in subjects with iRBD.

METHODS

56 patients with RBD Screening Questionnaire (RBDSQ) scores ≥5 at baseline and subsequent visit were enrolled as probable iRBD from the Parkinson's Progression Markers Initiative (PPMI) database. Baseline clinical data and biomarkers were analyzed. The endpoint was defined as disease progression to α-synucleinopathy diseases. Cox proportional hazard and Kaplan-Meier analyses were used to evaluate the predictive values of the indicators.

RESULTS

During a mean follow-up duration of 5.1 years, 15 of 56 patients (26.8%) developed α-synucleinopathy diseases. Baseline clinical variables, including University of Pennsylvania Smell Identification Test (UPSIT, HR = 26.18, p = 0.004), 15-item Geriatric Depression Scale (GDS, HR = 14.26, p = 0.001), Montreal Cognitive Assessment (MoCA, HR = 3.56, p = 0.025), and Hopkins Verbal Learning Test Total recall (HVLT-TR, HR = 3.70, p = 0.014); genotype status of TMEM175 (HR = 3.74, p = 0.017), SCN3A (HR = 5.81, p = 0.022) and NUCKS1 (HR = 0.342, p = 0.049); ratio of phosphorylated tau to total tau (p-tau/t-tau, HR = 8.36, p = 0.001) in cerebrospinal fluid; and gray matter atrophy in inferior frontal gyrus (IFG, HR = 15.49, p = 0.001) were associated with phenoconversion to α-synucleinopathy diseases. A model combined the three independent variables (UPSIT, TMEM175 and gray matter atrophy in IFG) exhibited significantly improved predictive performance.

CONCLUSION

For patients with iRBD, progression to α-synucleinopathy diseases can be predicted with good accuracy using a model combining clinical variables and biomarkers, which could form a basis for future disease prevention.

Cognitive Impairment in Parkinson's Disease: Epidemiology, Clinical Profile, Protective and Risk Factors

Cognitive impairment is a common non-motor symptom in Parkinson's Disease (PD) and an important source of patient disability and caregiver burden. The timing, profile and rate of cognitive decline varies widely among individuals with PD and can range from normal cognition to mild cognitive impairment (PD-MCI) and dementia (PDD). Beta-amyloid and tau brain accumulation, oxidative stress and neuroinflammation are reported risk factors for cognitive impairment. Traumatic brain injury and pesticide and tobacco exposure have also been described. Genetic risk factors including genes such as COMT, APOE, MAPT and BDNF may also play a role. Less is known about protective factors, although the Mediterranean diet and exercise may fall in this category. Nonetheless, there is conflicting evidence for most of the factors that have been studied. The use of inconsistent criteria and lack of comprehensive assessment in many studies are important methodological issues. Timing of exposure also plays a crucial role, although identification of the correct time window has been historically difficult in PD. Our understanding of the mechanism behind these factors, as well as the interactions between gene and environment as determinants of disease phenotype and the identification of modifiable risk factors will be paramount, as this will allow for potential interventions even in established PD.

In Vitro Conversion Assays Diagnostic for Neurodegenerative Proteinopathies

BACKGROUND

In vitro conversion assays, including real-time quaking-induced conversion (RT-QuIC) and protein misfolding cyclic amplification (PMCA) techniques, were first developed to study the conversion process of the prion protein to its misfolded, disease-associated conformation. The intrinsic property of prion proteins to propagate their misfolded structure was later exploited to detect subfemtogram quantities of the misfolded protein present in tissues and fluids from humans and animals with transmissible spongiform encephalopathies. Currently, conversion assays are used clinically as sensitive and specific diagnostic tools for antemortem diagnosis of prion disease.

CONTENT

In vitro conversion assays are now being applied to the development of diagnostics for related neurodegenerative diseases, including detection of misfolded α-synuclein in Parkinson disease, misfolded amyloid-β in Alzheimer disease, and misfolded tau in Pick disease. Like the predicate prion protein in vitro conversion diagnostics, these assays exploit the ability of endogenously misfolded proteins to induce misfolding and aggregation of their natively folded counterpart in vitro. This property enables biomarker detection of the underlying protein pathology. Herein, we review RT-QuIC and PMCA for (a) prion-, (b) α-synuclein-, (c) amyloid-β-, and (d) tau-opathies.

SUMMARY

Although already in routine clinical use for the detection of transmissible spongiform encephalopathies, in vitro conversion assays for other neurodegenerative disorders require further development and evaluation of diagnostic performance before consideration for clinical implementation.

Detection of α-synuclein in CSF by RT-QuIC in patients with isolated rapid-eye-movement sleep behaviour disorder: a longitudinal observational study

BACKGROUND

Isolated rapid-eye-movement (REM) sleep behaviour disorder (IRBD) can be part of the prodromal stage of the α-synucleinopathies Parkinson's disease and dementia with Lewy bodies. Real-time quaking-induced conversion (RT-QuIC) analysis of CSF has high sensitivity and specificity for the detection of misfolded α-synuclein in patients with Parkinson's disease and dementia with Lewy bodies. We investigated whether RT-QuIC could detect α-synuclein in the CSF of patients with IRBD and be used as a biomarker of prodromal α-synucleinopathy.

METHODS

In this longitudinal observational study, CSF samples were obtained by lumbar puncture from patients with video polysomnography-confirmed IRBD recruited at a specialised sleep disorders centre in Barcelona, Spain, and from controls free of neurological disease. CSF samples were stored until analysed using RT-QuIC. After lumbar puncture, participants were assessed clinically for neurological status every 3-12 months. Rates of neurological disease-free survival were estimated using the Kaplan-Meier method. Disease-free survival rates were assessed from the date of lumbar puncture to the date of diagnosis of any neurodegenerative disease, or to the last follow-up visit for censored observations.

FINDINGS

52 patients with IRBD and 40 healthy controls matched for age (p=0·20), sex (p=0·15), and duration of follow-up (p=0·27) underwent lumbar puncture between March 23, 2008, and July 16, 2017. The CSF α-synuclein RT-QuIC assay was positive in 47 (90%) patients with IRBD and in four (10%) controls, resulting in a sensitivity of 90·4% (95% CI 79·4-95·8) and a specificity of 90·0% (95% CI 76·9-96·0). Mean follow-up from lumbar puncture until the end of the study (July 31, 2020) was 7·1 years (SD 2·8) in patients with IRBD and 7·7 years (2·9) in controls. During follow-up, 32 (62%) patients were diagnosed with Parkinson's disease or dementia with Lewy bodies a mean 3·4 years (SD 2·6) after lumbar puncture, of whom 31 (97%) were α-synuclein positive at baseline. Kaplan-Meier analysis showed that patients with IRBD who were α-synuclein negative had lower risk for developing Parkinson's disease or dementia with Lewy bodies at 2, 4, 6, 8, and 10 years of follow-up than patients with IRBD who were α-synuclein positive (log-rank test p=0·028; hazard ratio 0·143, 95% CI 0·019-1·063). During follow-up, none of the controls developed an α-synucleinopathy. Kaplan-Meier analysis showed that participants who were α-synuclein negative (ie, five patients with IRBD plus 36 controls) had lower risk of developing Parkinson's disease or dementia with Lewy bodies at 2, 4, 6, 8 and 10 years after lumbar puncture than participants who were α-synuclein positive (ie, 47 patients with IRBD plus four controls; log-rank test p<0·0001; hazard ratio 0·024, 95% CI 0·003-0·177).

INTERPRETATION

In patients with IRBD, RT-QuIC detects misfolded α-synuclein in the CSF with both sensitivity and specificity of 90%, and α-synuclein positivity was associated with increased risk of subsequent diagnosis of Parkinson's disease or dementia with Lewy bodies. Detection of α-synuclein in the CSF represents a potential prodromal marker of Parkinson's disease and dementia with Lewy bodies. If these findings are replicated in additional cohorts, detection of CSF α-synuclein by RT-QuIC could be used to enrich IRBD cohorts in neuroprotective trials, particularly when assessing interventions that target α-synuclein.

FUNDING

Department of Health and Social Care Policy Research Programme, the Scottish Government, and the Weston Brain Institute.

Premotor Parkinson's disease: Overview of clinical symptoms and current diagnostic methods

Parkinson's disease (PD) is characterized by typical motor symptoms. However, recent studies show several non-motor features that may precede the development of the motor symptoms of PD. The best known premotor symptoms include hyposmia, REM sleep behavior disorder (RBD), constipation, and depression; other symptoms are excessive daytime somnolence, orthostatic hypotension and symptomatic hypotension, erectile or urinary dysfunction, musculoskeletal symptoms, pain, and global cognitive deficit. In this review, we summarize currently available diagnostic methods for these symptoms. We also briefly summarize neuroimaging, polyneuropathy, peripheral markers, and cerebrospinal fluid biomarkers that may be used in the early diagnosis of PD.

Neuropathological and Biomarker Findings in Parkinson's Disease and Alzheimer's Disease: From Protein Aggregates to Synaptic Dysfunction

There is mounting evidence that Parkinson’s disease (PD) and Alzheimer’s disease (AD) share neuropathological hallmarks, while similar types of biomarkers are being applied to both. In this review we aimed to explore similarities and differences between PD and AD at both the neuropathology and the biomarker levels, specifically focusing on protein aggregates and synapse dysfunction. Thus, amyloid-β peptide (Aβ) and tau lesions of the Alzheimer-type are common in PD and α-synuclein Lewy-type aggregates are frequent findings in AD. Modern neuropathological techniques adding to routine immunohistochemistry might take further our knowledge of these diseases beyond protein aggregates and down to their presynaptic and postsynaptic terminals, with potential mechanistic and even future therapeutic implications. Translation of neuropathological discoveries to the clinic remains challenging. Cerebrospinal fluid (CSF) and positron emission tomography (PET) markers of Aβ and tau have been shown to be reliable for AD diagnosis. Conversely, CSF markers of α-synuclein have not been that consistent. In terms of PET markers, there is no PET probe available for α-synuclein yet, while the AD PET markers range from consistent evidence of their specificity (amyloid imaging) to greater uncertainty of their reliability due to off-target binding (tau imaging). CSF synaptic markers are attractive, still needing more evidence, which currently suggests those might be non-specific markers of disease progression. It can be summarized that there is neuropathological evidence that protein aggregates of AD and PD are present both at the soma and the synapse. Thus, a number of CSF and PET biomarkers beyond α-synuclein, tau and Aβ might capture these different faces of protein-related neurodegeneration. It remains to be seen what the longitudinal outcomes and the potential value as surrogate markers of these biomarkers are.

Mini Review: Correlations of Cognitive Domains With Cerebrospinal Fluid α-Synuclein Levels in Patients With Parkinson's Disease

The level of α-synuclein, a component of Lewy bodies, in cerebrospinal fluid (CSF) in Parkinson's disease (PD) has attracted recent attention. Most meta-analyses conclude that CSF levels of α-synuclein are decreased in PD. Patients with PD present with cognitive impairment, including frontal/executive dysfunction in the early phase and later emergence of visuospatial and mnemonic deficits. To examine whether CSF α-synuclein levels reflect the activities of various cognitive domains, we reviewed reports examining the association of these levels with cognitive performance in each domain in PD. Among 13 cross-sectional studies, five showed that a lower CSF α-synuclein level was associated with worse cognitive function. In four of these five reports, frontal/executive function showed this association, suggesting a link of the pathophysiology with Lewy bodies. In three other reports, a higher CSF α-synuclein level was associated with temporal-parieto-occipital cognitive deterioration such as memory. In the other five reports, the CSF α-synuclein level did not correlate with cognitive performance for any domain. In four longitudinal studies, a higher baseline CSF α-synuclein level was associated with a worse cognitive outcome, including cognitive processing speed, visuospatial function and memory in two, but not with any cognitive outcome in the other two. The different associations may reflect the heterogeneous pathophysiology in PD, including different pathogenic proteins, neurotransmitters. Thus, more studies of the association between cognitive domains and CSF levels of pathogenic proteins are warranted.

Cerebrospinal Fluid α-Synuclein Species in Cognitive and Movements Disorders

Total CSF α-synuclein (t-α-syn), phosphorylated α-syn (pS129-α-syn) and α-syn oligomers (o-α-syn) have been studied as candidate biomarkers for synucleinopathies, with suboptimal specificity and sensitivity in the differentiation from healthy controls. Studies of α-syn species in patients with other underlying pathologies are lacking. The aim of this study was to investigate possible alterations in CSF α-syn species in a cohort of patients with diverse underlying pathologies. A total of 135 patients were included, comprising Parkinson's disease (PD; n = 13), multiple system atrophy (MSA; n = 9), progressive supranuclear palsy (PSP; n = 13), corticobasal degeneration (CBD; n = 9), Alzheimer's disease (AD; n = 51), frontotemporal degeneration (FTD; n = 26) and vascular dementia patients (VD; n = 14). PD patients exhibited higher pS129-α-syn/α-syn ratios compared to FTD (p = 0.045), after exclusion of samples with CSF blood contamination. When comparing movement disorders (i.e., MSA vs. PD vs. PSP vs. CBD), MSA patients had lower α-syn levels compared to CBD (p = 0.024). Patients with a synucleinopathy (PD and MSA) exhibited lower t-α-syn levels (p = 0.002; cut-off value: ≤865 pg/mL; sensitivity: 95%, specificity: 69%) and higher pS129-/t-α-syn ratios (p = 0.020; cut-off value: ≥0.122; sensitivity: 71%, specificity: 77%) compared to patients with tauopathies (PSP and CBD). There are no significant α-syn species alterations in non-synucleinopathies.

Clinically relevant connectivity features define three subtypes of Parkinson's disease patients

Parkinson's disease (PD) is characterized by complex clinical symptoms, including classic motor and nonmotor disturbances. Patients with PD vary in clinical manifestations and prognosis, which point to the existence of subtypes. This study aimed to find the fiber connectivity correlations with several crucial clinical symptoms and identify PD subtypes using unsupervised clustering analysis. One hundred and thirty-four PD patients and 77 normal controls were enrolled. Canonical correlation analysis (CCA) was performed to define the clinically relevant connectivity features, which were then used in the hierarchical clustering analysis to identify the distinct subtypes of PD patients. Multimodal neuroimaging analyses were further used to explore the neurophysiological basis of these subtypes. The methodology was validated in an independent data set. CCA revealed two significant clinically relevant patterns (motor-related pattern and depression-related pattern; r = .94, p < .001 and r = .926, p = .001, respectively) among PD patients, and hierarchical clustering analysis identified three neurophysiological subtypes ("mild" subtype, "severe depression-dominant" subtype and "severe motor-dominant" subtype). Multimodal neuroimaging analyses suggested that the patients in the "severe depression-dominant" subtype exhibited widespread disruptions both in function and structure, while the other two subtypes exhibited relatively mild abnormalities in brain function. In the independent validation, three similar subtypes were identified. In conclusion, we revealed heterogeneous subtypes of PD patients according to their distinct clinically relevant connectivity features. Importantly, depression symptoms have a considerable impact on brain damage in patients with PD.

Cerebrospinal Fluid Cytokines and Neurodegeneration-Associated Proteins in Parkinson's Disease

INTRODUCTION

Immune markers are altered in Parkinson's disease (PD), but relationships between cerebrospinal fluid (CSF) and plasma cytokines and associations with neurodegeneration-associated proteins remain unclear.

METHODS

CSF and plasma samples and demographic/clinical measures were obtained from 35 PD patients. CSF samples were analyzed for cytokines (together with plasma) and for α-synuclein, amyloid β(1-42) peptide, total tau, and phospho(Thr231)-tau.

RESULTS

There were no CSF-plasma cytokine correlations. Interleukin (IL)-8 was higher and interferon-γ, IL-10, and tumor necrosis factor-α were lower in CSF versus plasma. In CSF, total tau correlated positively with IL-8 and IL-1β, whereas α-synuclein correlated positively with amyloid β(1-42) and negatively with semantic fluency (a known marker of PD dementia risk).

DISCUSSION

CSF and peripheral cytokine profiles in PD are not closely related. Associations between CSF IL-8 and IL-1β and tau suggest that CSF inflammatory changes may relate to tau pathology within PD. CSF α-synuclein/amyloid β may reflect the risk of developing PD dementia. © 2020 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Brain atrophy in Parkinson's disease with polysomnography-confirmed REM sleep behavior disorder

We aimed to investigate cortical and subcortical brain alterations in people with Parkinson's disease with polysomnography-confirmed rapid eye movement (REM) sleep behavior disorder (RBD). Thirty people with Parkinson's disease, including 15 people with RBD, were recruited and compared with 41 healthy controls. Surface-based cortical and subcortical analyses were performed on T1-weighted images to investigate thickness and shape abnormalities between groups, and voxel-based and deformation-based morphometry were performed to investigate local volume. Correlations were performed in patients to investigate the structural correlates of motor activity during REM sleep. People with RBD showed cortical thinning in the right perisylvian and inferior temporal cortices and shape contraction in the putamen compared with people without RBD. Compared with controls, people with RBD had extensive cortical thinning and volume loss, brainstem volume was reduced, and shape contraction was found in the basal ganglia and hippocampus. In comparison to controls, people without RBD showed more restricted thinning in the sensorimotor, parietal, and occipital cortices, reduced volume in the brainstem, temporal and more posterior areas, and shape contraction in the pallidum and hippocampus. In Parkinson's disease, higher tonic and phasic REM sleep motor activity was associated with contraction of the thalamic surface, extensive cortical thinning, and subtle volume reduction in the middle temporal gyrus. In Parkinson's disease, the presence of RBD is associated with extensive cortical and subcortical abnormalities, suggesting more severe neurodegeneration in people with RBD. This provides potential neuroanatomical correlates for the more severe clinical phenotype reported in people with Parkinson's disease with RBD.

Molecular profiling in Parkinsonian syndromes: CSF biomarkers

An accurate and early diagnosis of degenerative parkinsonian syndromes is a major need for their correct and timely therapeutic management. The current diagnostic criteria are mostly based on clinical features and molecular imaging. However, diagnostic doubts often persist especially in the early stages of diseases when signs are slight, ambiguous and overlapping among different syndromes. Molecular imaging may not be altered in the early stages of diseases, also failing to discriminate among different syndromes. Cerebrospinal fluid (CSF) represents an ideal source of biomarkers reflecting different pathways of neuropathological changes taking place in the brain and preceding the clinical onset. The aim of this review is to provide un update on CSF biomarkers in parkinsonian disorders, discussing in detail their association with neuropathological correlates. Their potential contribution in differential diagnosis and prognostic assessment of different parkinsonian syndromes is also discussed. Before entering the clinical use both for diagnostic and prognostic purposes, these CSF biomarkers need to be thoroughly assessed in terms of pre-analytical and analytical variability, as well as to clinical validation in independent cohorts.

The Challenge of Disease-Modifying Therapies in Parkinson's Disease: Role of CSF Biomarkers

The development of disease modifying strategies in Parkinson's disease (PD) largely depends on the ability to identify suitable populations after accurate diagnostic work-up. Therefore, patient molecular profiling and disease subtyping are mandatory. Thus far, in clinical trials, PD has been considered to be a "single entity". Conversely, in front of the common feature of nigro-striatal degeneration, PD is pathogenically heterogeneous with a series of several biological and molecular pathways that differently contribute to clinical development and progression. Currently available diagnostic criteria for PD mainly rely on clinical features and imaging biomarkers, thus missing to identify the contribution of pathophysiological pathways, also failing to catch abnormalities occurring in the early stages of disease. Cerebrospinal fluid (CSF) is a promising source of biomarkers, with the high potential for reflecting early changes occurring in PD brain. In this review, we provide an overview on CSF biomarkers in PD, discussing their association with different molecular pathways involved either in pathophysiology or progression in detail. Their potential application in the field of disease modifying treatments is also discussed.

Ultrasensitive Detection of Aggregated α-Synuclein in Glial Cells, Human Cerebrospinal Fluid, and Brain Tissue Using the RT-QuIC Assay: New High-Throughput Neuroimmune Biomarker Assay for Parkinsonian Disorders

Adult-onset neurodegenerative disorders, like Parkinson's disease (PD) and dementia with Lewy bodies (DLB), that share the accumulation of aggregated α-synuclein (αSynagg) as their hallmark molecular pathology are collectively known as α-synucleinopathies. Diagnosing α-synucleinopathies requires the post-mortem detection of αSynagg in various brain regions. Recent efforts to measure αSynagg in living patients include quantifying αSynagg in different biofluids as a biomarker for PD. We adopted the real-time quaking-induced conversion (RT-QuIC) assay to detect very low levels of αSynagg. We first optimized RT-QuIC for sensitivity, specificity, and reproducibility by using monomeric recombinant human wild-type αSyn as a substrate and αSynagg as the seed. Next, we exposed mouse microglia to αSyn pre-formed fibrils (αSynPFF) for 24 h. RT-QuIC assay revealed that the αSynPFF is taken up rapidly by mouse microglia, within 30 min, and cleared within 24 h. We then evaluated the αSyn RT-QuIC assay for detecting αSynagg in human PD, DLB, and Alzheimer's disease (AD) post-mortem brain homogenates (BH) along with PD and progressive supranuclear palsy (PSP) cerebrospinal fluid (CSF) samples and then determined protein aggregation rate (PAR) for αSynagg. The PD and DLB BH samples not only showed significantly higher αSynagg PAR compared to age-matched healthy controls and AD, but RT-QuIC was also highly reproducible with 94% sensitivity and 100% specificity. Similarly, PD CSF samples demonstrated significantly higher αSynagg PAR compared to age-matched healthy controls, with 100% sensitivity and specificity. Overall, the RT-QuIC assay accurately detects αSynagg seeding activity, offering a potential tool for antemortem diagnosis of α-synucleinopathies and other protein-misfolding disorders. Graphical Abstract A schematic representation of αSyn RT-QuIC assay.

Longitudinal analyses of cerebrospinal fluid α-Synuclein in prodromal and early Parkinson's disease

BACKGROUND

Aggregation of α-synuclein is central to the pathophysiology of PD. Biomarkers related to α-synuclein may be informative for PD diagnosis/progression.

OBJECTIVES

To analyze α-synuclein in CSF in drug-naïve PD, healthy controls, and prodromal PD in the Parkinson's Progression Markers Initiative.

METHODS

Over up to 36-month follow-up, CSF total α-synuclein and its association with MDS-UPDRS motor scores, cognitive assessments, and dopamine transporter imaging were assessed.

RESULTS

The inception cohort included PD (n = 376; age [mean {standard deviation} years]: 61.7 [9.62]), healthy controls (n = 173; age, 60.9 [11.3]), hyposmics (n = 16; age, 68.3 [6.15]), and idiopathic rapid eye movement sleep behavior disorder (n = 32; age, 69.3 [4.83]). Baseline CSF α-synuclein was lower in manifest and prodromal PD versus healthy controls. Longitudinal α-synuclein decreased significantly in PD at 24 and 36 months, did not change in prodromal PD over 12 months, and trended toward an increase in healthy controls. The decrease in PD was not shown when CSF samples with high hemoglobin concentration were removed from the analysis. CSF α-synuclein changes did not correlate with longitudinal MDS-UPDRS motor scores or dopamine transporter scan.

CONCLUSIONS

CSF α-synuclein decreases early in the disease, preceding motor PD. CSF α-synuclein does not correlate with progression and therefore does not reflect ongoing dopaminergic neurodegeneration. Decreased CSF α-synuclein may be an indirect index of changes in the balance between α-synuclein secretion, solubility, or aggregation in the brain, reflecting its overall turnover. Additional biomarkers more directly related to α-synuclein pathophysiology and disease progression and other markers to be identified by, for example, proteomics and metabolomics are needed. © 2019 International Parkinson and Movement Disorder Society.

Progressive brain atrophy in Parkinson's disease patients who convert to mild cognitive impairment

Aims

Cognitive impairment is a common symptom in the trajectory of Parkinson's disease (PD). However, the pathological underpinning is not fully known. We aimed to explore the critical structural alterations in the process of cognitive decline and its relationships with the dopaminergic deficit and the level of related cerebrospinal fluid (CSF) proteins.

Methods

Ninety‐four patients with PD and 32 controls were included in this study. Neuropsychological tests were performed at baseline and after 28 months to identify which patients had normal cognition and which ones developed PD‐MCI after follow‐up (“converters”). Gray matter atrophy was assessed in cross‐sectional and longitudinal analyses, respectively. The associations between altered GMV with dopamine transporter (DAT) results and the level of CSF proteins were assessed.

Results

Among the 94 patients with normal cognition at baseline, 24 (mean age, 63.1 years) developed PD‐MCI after 28 months of follow‐up, and 70 (mean age, 62.3 years) remained nonconverters. The converters showed significant right temporal atrophy at baseline and extensive atrophy in temporal lobe at follow‐up. Progressive bilateral frontal lobe atrophy was found in the converters. Baseline right temporal atrophy was correlated with the striatal dopaminergic degeneration in the converters. No correlation was found between the right temporal atrophy and the alterations of CSF proteins.

Conclusion

Early atrophy in temporal lobes and progressive atrophy in frontal lobes might be a biomarker for developing multidomain impairment of cognition and converting to PD‐MCI. Furthermore, cognition‐related temporal atrophy might be associated with dopaminergic deficit reflected by DAT scan but independent of CSF proteins in patients with PD who convert to PD‐MCI.

CCAAT/enhancer binding protein δ is a transcriptional repressor of α-synuclein

α-Synuclein is the main component of Lewy bodies, the intracellular protein aggregates representing the histological hallmark of Parkinson's disease. Elevated α-synuclein levels and mutations in SNCA gene are associated with increased risk for Parkinson's disease. Despite this, little is known about the molecular mechanisms regulating SNCA transcription. CCAAT/enhancer binding protein (C/EBP) β and δ are b-zip transcription factors that play distinct roles in neurons and glial cells. C/EBPβ overexpression increases SNCA expression in neuroblastoma cells and putative C/EBPβ and δ binding sites are present in the SNCA genomic region suggesting that these proteins could regulate SNCA transcription. Based on these premises, the goal of this study was to determine if C/EBPβ and δ regulate the expression of SNCA. We first observed that α-synuclein CNS expression was not affected by C/EBPβ deficiency but it was markedly increased in C/EBPδ-deficient mice. This prompted us to characterize further the role of C/EBPδ in SNCA transcription. C/EBPδ absence led to the in vivo increase of α-synuclein in all brain regions analyzed, both at mRNA and protein level, and in primary neuronal cultures. In agreement with this, CEBPD overexpression in neuroblastoma cells and in primary neuronal cultures markedly reduced SNCA expression. ChIP experiments demonstrated C/EBPδ binding to the SNCA genomic region of mice and humans and luciferase experiments showed decreased expression of a reporter gene attributable to C/EBPδ binding to the SNCA promoter. Finally, decreased CEBPD expression was observed in the substantia nigra and in iPSC-derived dopaminergic neurons from Parkinson patients resulting in a significant negative correlation between SNCA and CEBPD levels. This study points to C/EBPδ as an important repressor of SNCA transcription and suggests that reduced C/EBPδ neuronal levels could be a pathogenic factor in Parkinson's disease and other synucleinopathies and C/EBPδ activity a potential pharmacological target for these neurological disorders.

Biomarkers for Dementia, Fatigue, and Depression in Parkinson's Disease

Parkinson's disease is a common multisystem neurodegenerative disorder characterized by typical motor and non-motor symptoms. There is an urgent need for biomarkers for assessment of disease severity, complications and prognosis. In addition, biomarkers reporting the underlying pathophysiology assist in understanding the disease and developing neuroprotective therapies. Ultimately, biomarkers could be used to develop a more efficient personalized approach for clinical trials and treatment strategies. With the goal to improve quality of life in Parkinson's disease it is essential to understand and objectively monitor non-motor symptoms. This narrative review provides an overview of recent developments of biomarkers (biofluid samples and imaging) for three common neuropsychological syndromes in Parkinson's disease: dementia, fatigue, and depression.

α-Synuclein species as potential cerebrospinal fluid biomarkers for dementia with lewy bodies

Background: The objective of this study was to investigate the discriminating value of a range of CSF α‐synuclein species for dementia with Lewy bodies compared with Alzheimer's disease, PD, and cognitively normal controls.

Methods: We applied our recently published enzyme‐linked immunosorbent assays to measure the CSF levels of total α‐synuclein, oligomeric α‐synuclein, and phosphorylated α‐synuclein in dementia with Lewy bodies (n = 42), Alzheimer's disease (n = 39), PD (n = 46), and controls (n = 78). General linear models corrected for age and sex were performed to assess differences in α‐synuclein levels between groups. We used backward‐elimination logistic regression analysis to investigate the combined discriminating value of the different CSF α‐synuclein species and Alzheimer's disease biomarkers.

Results: CSF levels of total α‐synuclein were lower in dementia with Lewy bodies and PD compared with Alzheimer's disease as well as controls (P < 0.001). In contrast, CSF levels of oligomeric α‐synuclein were higher in dementia with Lewy bodies and PD compared with Alzheimer's disease (P < 0.05) and controls (P < 0.001). No group differences were found for phosphorylated α‐synuclein. In dementia with Lewy bodies and PD, CSF total α‐synuclein levels positively correlated with tau and phosphorylated tau (both r > 0.40, P < 0.01), but not with amyloid‐β_1‐42. The optimal combination to differentiate dementia with Lewy bodies from controls consisted of amyloid‐β_1‐42, tau, total α‐synuclein, oligomeric α‐synuclein, age, and sex (AUC, 0.90). To differentiate dementia with Lewy bodies from Alzheimer's disease, the combination of tau and oligomeric α‐synuclein resulted in an AUC of 0.83. CSF α‐synuclein species do not contribute to the differentiation of dementia with Lewy bodies from PD.

Conclusions: CSF α‐synuclein species could be useful as part of a biomarker panel for dementia with Lewy bodies. Evaluating both oligomeric α‐synuclein and total α‐synuclein in CSF helps in the diagnosis of dementia with Lewy bodies. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Baseline concentration of misfolded α-synuclein aggregates in cerebrospinal fluid predicts risk of cognitive decline in Parkinson's disease

BACKGROUND

The prognostic significance of misfolded α-synuclein (α-Syn) aggregates in Parkinson's disease (PD) has not been well investigated. The aim of this study was to reveal the relationship between misfolded α-Syn aggregate concentration in cerebrospinal fluid (CSF) and cognitive decline risk in PD.

METHODS

A total of 278 patients with PD were retrospectively included. They were diagnosed between 2011 and 2013. The end-point was 2016, and the follow-up period was 54.3 ± 10.0 months. Cognitive decline was defined as a 4-point decrease in the Mini-Mental State Examination score during follow-up. Misfolded α-Syn aggregate concentration in baseline CSF was measured using the protein misfolding cyclic amplification (PMCA) technique. Time to reach 50% of the maximum fluorescence value was recorded.

RESULTS

The PMCA technique successfully detected the level of misfolded α-Syn aggregates in CSF with a sensitivity of 85.3% and a specificity of 91.4%. The time to reach 50% of the maximum fluorescence value was shorter in the patients with cognitive decline than in the patients without cognitive decline (190.7 ± 40.1 h vs. 240.8 ± 45.6 h, P < 0.001). Multifactorial Cox regression analysis revealed that reaching 50% of the maximum fluorescence value in ≤219 h at baseline was associated with increased risk of cognitive decline during the follow-up (HR: 4.90, 95% CI: 2.75-8.74, P < 0.001).

CONCLUSION

Baseline concentration of misfolded α-Syn aggregates in CSF measured by the PMCA technique predicts risk of cognitive decline in PD.

Diagnostic biomarkers for Parkinson's disease: focus on α-synuclein in cerebrospinal fluid

Diagnostic biomarkers are measures that detect or confirm the presence of a disease or identify individuals with a subtype of the disease. For Parkinson's disease, unlike other neurodegenerative diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease, diagnostic biomarkers remain elusive as none are yet available or approved for clinical use. A biomarker to diagnose early or prodromal Parkinson's disease with high accuracy would significantly enhance clinical practice as well as advance clinical therapeutic trials. Multiple lines of evidence support a role of α-synuclein in the pathophysiology of Parkinson's disease and hence major ongoing efforts to identify biomarkers for Parkinson's disease are aimed at measuring α-synuclein in peripheral tissues and biofluids, including cerebrospinal fluid. This work is still in the early stages of biomarker development and has been accompanied by both losses and victories. Here, α-synuclein in cerebrospinal fluid as a diagnostic marker for Parkinson's disease is reviewed, including measures of total α-synuclein, oligomeric and phosphorylated α-synuclein, and seeding activity of α-synuclein.

Ratios of proteins in cerebrospinal fluid in Parkinson's disease cognitive decline: prospective study

BACKGROUND

There is a need for biomarkers of dementia in PD.

OBJECTIVES

To determine if the levels of the main CSF proteins and their ratios are associated with deterioration in cognition and progression to dementia in the short to mid term.

METHODS

The Parkinson's Progression Markers Initiative database was used as an exploratory cohort, and a center-based cohort was used as a replication cohort. Amyloid ß1-42, total tau, threonine-181 phosphorylated tau, and α-synuclein in the CSF and the ratios of these proteins were assessed.

RESULTS

In the Parkinson's Progression Markers Initiative cohort (n = 281), the total tau/amyloid ß1-42, total tau/α-synuclein, total tau/amyloid ß1-42+α-synuclein, and amyloid ß1-42/total tau ratios were associated with a risk of progression to dementia over a 3-year follow-up. In the replication cohort (n = 40), the total tau/α-synuclein and total tau/amyloid ß1-42+α-synuclein ratios were associated with progression to dementia over a 41-month follow-up.

CONCLUSION

Ratios of the main proteins found in PD patient brain inclusions that can be measured in the CSF appear to have value as short- to mid-term predictors of dementia. © 2018 International Parkinson and Movement Disorder Society.

CSF Aβ1-42 level is associated with cognitive decline in early Parkinson's disease with rapid eye movement sleep behavior disorder

Background

Rapid eye movement sleep behavior disorder (RBD) is associated with cognitive decline in early Parkinson's disease (PD). However, the underlyling basis for this association remains unclear.

Methods

Parkinson's Progression Marker's Initiative (PPMI) subjects underwent baseline RBD testing with RBD sleep questionnaire (RBDSQ). Serial assessments included measures of motor symptoms, non-motor symptoms (NMS), neuropsychological assessment, blood and cerebrospinal fluid (CSF) biomarkers. Up to three years follow-up data were included. We stratified early PD subjects into PD with RBD (RBDSQ score > 5) and PD without RBD groups. Then, we evaluated baseline biomarkers in each group as a predictor of cognitive decline using Montreal Cognitive Assessment (MoCA) score changes over three years in regression models.

Results

Four hundred twenty-three PD subjects were enrolled at baseline, and a total of 350 PD subjects had completed 3 years of study follow-up with completely serial assessments. We found that at baseline, only CSF β-amyloid 1-42 (Aβ_1-42) was significantly lower in PD subjects with RBD. On three years follow-up analysis, PD subjects with RBD were more likely to develop incident mild cognitive impairment (MCI) and presented greater cognitive decline in MoCA score. Lower baseline CSF Aβ_1-42 predicted cognitive decline over 3 years only in PD subjects with RBD (β = - 0.03, P = 0.003). A significant interaction between Aβ_1-42 and the 2 groups confirmed that this effect was indeed higher in PD with RBD than the other individual (β = - 2.85, P = 0.014).

Conclusion

These findings indicate that CSF Aβ_1-42 level is associated with global cognitive decline in early PD with RBD. The addition of CSF Aβ_1-42 to RBD testing increase the likelihood of identifying those at high risk for cognitive decline in early PD.

Are We Ready for Detecting α-Synuclein Prone to Aggregation in Patients? The Case of "Protein-Misfolding Cyclic Amplification" and "Real-Time Quaking-Induced Conversion" as Diagnostic Tools

The accumulation and deposition of α-synuclein aggregates in brain tissue is the main event in the pathogenesis of different neurodegenerative disorders grouped under the term of synucleinopathies. They include Parkinson's disease, dementia with Lewy bodies and multiple system atrophy. To date, the diagnosis of any of these disorders mainly relies on the recognition of clinical symptoms, when the neurodegeneration is already in an advanced phase. In the last years, several efforts have been carried out to develop new diagnostic tools for early diagnosis of synucleinopathies, with special interest to Parkinson's disease. The Protein-Misfolding Cyclic Amplification (PMCA) and the Real-Time Quaking-Induced Conversion (RT-QuIC) are ultrasensitive protein amplification assays for the detection of misfolded protein aggregates. Starting from the successful application in the diagnosis of human prion diseases, these techniques were recently tested for the detection of misfolded α-synuclein in brain homogenates and cerebrospinal fluid samples of patients affected by synucleinopathies. So far, only a few studies on a limited number of samples have been performed to test PMCA and RT-QuIC diagnostic reliability. Neverthless, these assays have shown very high sensitivity and specificity in detecting synucleinopathies even at the pre-clinical stage. Despite the application of PMCA and RT-QuIC for α-synuclein detection in biological fluids is very recent, these techniques seem to have the potential for identifying subjects that will be likely to develop synucleinopathies.