Association of Misfolded α-Synuclein Derived from Neuronal Exosomes in Blood with Parkinson's Disease Diagnosis and Duration

Background

Misfolded α-synuclein can be detected in blood samples of Parkinson's disease (PD) patients by a seed amplification assay (SAA), but the association with disease duration is not clear, yet.

Objective

In the present study we aimed to elucidate whether seeding activity of misfolded α-synuclein derived from neuronal exosomes in blood is associated with PD diagnosis and disease duration.

Methods

Cross-sectional samples of PD patients were analyzed and compared to samples of age- and gender-matched healthy controls using a blood-based SAA. Presence of α-synuclein seeding activity and differences in seeding parameters, including fluorescence response (in arbitrary units) at the end of the amplification assay (F60) were analyzed. Additionally, available PD samples collected longitudinally over 5-9 years were included.

Results

In the cross-sectional dataset, 79 of 80 PD patients (mean age 69 years, SD = 8; 56% male) and none of the healthy controls (n = 20, mean age 70 years, SD = 10; 55% male) showed seeding activity (sensitivity 98.8%). When comparing subgroups divided by disease duration, longer disease duration was associated with lower α-synuclein seeding activity (F60: p <  0.001). In the longitudinal analysis 10/11 patients showed a gradual decrease of α-synuclein seeding activity over time.

Conclusions

This study confirms the high sensitivity of the blood-based α-synuclein SAA applied here. The negative association of α-synuclein seeding activity in blood with disease duration makes this parameter potentially interesting as biomarker for future studies on the pathophysiology of disease progression in PD, and for biologically oriented trials in this field.

Longitudinal cognitive decline characterizes the profile of non-PD-manifest GBA1 mutation carriers

With disease-modifying treatment for Parkinson's disease (PD) associated with variants in the glucocerebrosidase gene (GBA1) under way, the challenge to design clinical trials with non-PD-manifest GBA mutation carriers (GBA1NMC) comes within close reach. To delineate trajectories of motor and non-motor markers as well as serum neurofilament light (sNfL) levels and to evaluate clinical endpoints as outcomes for clinical trials in GBA1NMC, longitudinal data of 56 GBA1NMC carriers and 112 age- and sex-matched GBA1 wildtype participants (GBA1wildtype) with up to 9 years of follow-up was analyzed using linear mixed-effects models (LMEM) and Kaplan-Meier survival analysis of clinical endpoints for motor and cognitive function. GBA1NMC showed worse performance in Pegboard, 20 m fast walking, global cognition as well as in executive and memory function at baseline. Longitudinally, LMEM revealed a higher annual increase of the MDS-UPDRS III bradykinesia subscore in GBA1NMC compared to GBA1wildtype, but comparable trajectories of all other motor and non-motor markers as well as sNfL. Kaplan-Meier survival analysis showed a significantly earlier progression to clinical endpoints of cognitive decline in GBA1NMC. Incidence of PD was significantly higher in GBA1NMC. In conclusion, our study extends data on GBA1NMC indicating early cognitive decline as a potentially characteristic feature. Comprehensive longitudinal assessments of cognitive function are crucial to delineate the evolution of early changes in GBA1NMC enabling a more accurate stratification and allow for a more precise definition of trial design and sample size.

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

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

Linking the phenotype of SNCA Triplication with PET-MRI imaging pattern and alpha-synuclein CSF seeding

Lewy-body pathology with aggregation of abnormal conformations of the protein alpha-synuclein (α-Syn) represent the histopathological hallmarks of Parkinson’s disease (PD). Genetic prototypes such as PD due to mutations in the alpha-synuclein gene (SNCA) offer the opportunity to evaluate α-Syn-related profiles in patient-derived biomaterial. We identified a family with a SNCA triplication and assessed the index patient for CSF α-Syn seeding capacity and levels of total α-Syn along with other neurodegenerative CSF markers (Aβ_1-42, total-Tau, phospho-Tau, NFL). As no published CSF data in patients with SNCA triplication are available, we descriptively compared his CSF profiles to those of sporadic PD patients and PD patients with GBA mutations as these are also specifically associated with prominent α-Syn pathology. Additionally, skin biopsies with staining for phospho-α-Syn were done. To assess cerebral glucose metabolism and brain atrophy combined positron emission tomography and magnetic resonance imaging ([¹⁸F]FDG-PET/MRI) was performed. Age at onset was 24 years and motor impairment was accompanied by prominent non-motor symptoms with early development of dementia, depression, REM sleep behavior disorder, hyposmia, and dysautonomia. Correspondingly, PET-MRI showed hypometabolism and atrophy in frontal, temporoparietal and occipital regions. CSF levels of total α-Syn were threefold higher and RT-QuIC showed remarkable α-Syn seeding activity in all kinetic categories in the SNCA_Triplication patient compared to patients with GBA mutations. Our results are consistent with findings that not only mutant forms but also overexpression of the wild-type α-Syn protein lead to PD and PD dementia and show a striking CSF α-Syn seeding profile, thus substantiating the role of RT-QuIC as a specific in vivo biomarker of α-Syn brain pathology.

CSF and Serum Levels of Inflammatory Markers in PD: Sparse Correlation, Sex Differences and Association With Neurodegenerative Biomarkers

Background

An involvement of the central-nervous and peripheral, innate and adaptive immune system in the pathogenesis of Parkinson's disease (PD) is nowadays well established.

Objectives

We face several open questions in preparation of clinical trials aiming at disease-modification by targeting the immune system: Do peripheral (blood) inflammatory profiles reflect central (CSF) inflammatory processes? Are blood/CSF inflammatory markers associated with CSF levels of neurodegenerative/PD-specific biomarkers?

Methods

Using a multiplex assay we assessed 41 inflammatory markers in CSF/serum pairs in 453 sporadic PD patients. We analyzed CSF/serum correlation as well as associations of inflammatory markers with clinical outcome measures (UPDRS-III, H&amp;Y, MoCA) and with CSF levels of α-synuclein, Aβ1−42, t-Tau, p181-Tau and NFL. All analyses were stratified by sex as the immune system shows relevant sex-specific differences.

Results

Correlations between CSF and serum were sparse and detected in only 25% (9 out of 36) of the analysable inflammatory markers in male PD patients and in only 38% (12 out of 32) of female PD patients. The most important pro-inflammatory mediators associated with motor and cognitive decline as well as with neurodegenerative/PD-specific biomarkers were FABP, ICAM-1, IL-8, MCP-1, MIP-1-beta, and SCF. Results were more robust for CSF than for serum.

Interpretation

Levels of central-nervous and peripheral inflammatory markers might be regulated independently of each other with CSF inflammatory markers reflecting CNS pathology more accurately than peripheral markers. These findings along with sex-specific characteristics have to be considered when designing clinical trials aiming at disease-modification by targeting the immune system.

Association between CSF alpha-synuclein seeding activity and genetic status in Parkinson's disease and dementia with Lewy bodies

The clinicopathological heterogeneity in Lewy-body diseases (LBD) highlights the need for pathology-driven biomarkers in-vivo. Misfolded alpha-synuclein (α-Syn) is a lead candidate based on its crucial role in disease pathophysiology. Real-time quaking-induced conversion (RT-QuIC) analysis of CSF has recently shown high sensitivity and specificity for the detection of misfolded α-Syn in patients with Parkinson's disease (PD) and dementia with Lewy bodies (DLB). In this study we performed the CSF RT-QuIC assay in 236 PD and 49 DLB patients enriched for different genetic forms with mutations in GBA, parkin, PINK1, DJ1, and LRRK2. A subgroup of 100 PD patients was also analysed longitudinally. We correlated kinetic seeding parameters of RT-QuIC with genetic status and CSF protein levels of molecular pathways linked to α-Syn proteostasis. Overall, 85% of PD and 86% of DLB patients showed positive RT-QuIC α-Syn seeding activity. Seeding profiles were significantly associated with mutation status across the spectrum of genetic LBD. In PD patients, we detected positive α-Syn seeding in 93% of patients carrying severe GBA mutations, in 78% with LRRK2 mutations, in 59% carrying heterozygous mutations in recessive genes, and in none of those with bi-allelic mutations in recessive genes. Among PD patients, those with severe GBA mutations showed the highest seeding activity based on RT-QuIC kinetic parameters and the highest proportion of samples with 4 out of 4 positive replicates. In DLB patients, 100% with GBA mutations showed positive α-Syn seeding compared to 79% of wildtype DLB. Moreover, we found an association between α-Syn seeding activity and reduced CSF levels of proteins linked to α-Syn proteostasis, specifically lysosome-associated membrane glycoprotein 2 and neurosecretory protein VGF.

These findings highlight the value of α-Syn seeding activity as an in-vivo marker of Lewy-body pathology and support its use for patient stratification in clinical trials targeting α-Syn.

Gut Microbiome Signatures of Risk and Prodromal Markers of Parkinson Disease

OBJECTIVE

Alterations of the gut microbiome in Parkinson disease (PD) have been repeatedly demonstrated. However, little is known about whether such alterations precede disease onset and how they relate to risk and prodromal markers of PD. We investigated associations of these features with gut microbiome composition.

METHODS

Established risk and prodromal markers of PD as well as factors related to diet/lifestyle, bowel function, and medication were studied in relation to bacterial α-/β-diversity, enterotypes, and differential abundance in stool samples of 666 elderly TREND (Tübingen Evaluation of Risk Factors for Early Detection of Neurodegeneration) study participants.

RESULTS

Among risk and prodromal markers, physical inactivity, occupational solvent exposure, and constipation showed associations with α-diversity. Physical inactivity, sex, constipation, possible rapid eye movement sleep behavior disorder (RBD), and smoking were associated with β-diversity. Subthreshold parkinsonism and physical inactivity showed an interaction effect. Among other factors, age and urate-lowering medication were associated with α- and β-diversity. Constipation was highest in individuals with the Firmicutes-enriched enterotype, and physical inactivity was most frequent in the Bacteroides-enriched enterotype. Constipation was lowest and subthreshold parkinsonism least frequent in individuals with the Prevotella-enriched enterotype. Differentially abundant taxa were linked to constipation, physical inactivity, possible RBD, smoking, and subthreshold parkinsonism. Substantia nigra hyperechogenicity, olfactory loss, depression, orthostatic hypotension, urinary/erectile dysfunction, PD family history, and the prodromal PD probability showed no significant microbiome associations.

INTERPRETATION

Several risk and prodromal markers of PD are associated with gut microbiome composition. However, the impact of the gut microbiome on PD risk and potential microbiome-dependent subtypes in the prodrome of PD need further investigation based on prospective clinical and (multi)omics data in incident PD cases. ANN NEUROL 2021;90:E1-E12.

α-Synuclein in Plasma-Derived Extracellular Vesicles Is a Potential Biomarker of Parkinson's Disease

BACKGROUND

Extracellular vesicles are small vesicles that are released from many cells, including neurons. α-Synuclein has recently been described in extracellular vesicles derived from the central nervous system and may contribute to the spreading of disease pathology in α-synuclein-related neurodegeneration.

OBJECTIVES

We aimed to examine the potential diagnostic value of α-synuclein in plasma extracellular vesicles from patients with Parkinson's disease (PD).

METHODS

Preanalytical variables were studied to establish an optimized assay for preparation of plasma extracellular vesicles and detection of extracellular vesicle-derived α-synuclein. Plasma samples were obtained from 2 independent cohorts. The Tübingen cohort contained 96 patients with PD, 50 patients with dementia with Lewy bodies, 50 patients with progressive supranuclear palsy (PSP), and 42 healthy controls; the Kassel cohort included 47 patients with PD, 43 patients with dementia with Lewy bodies, and 36 controls with secondary parkinsonian syndromes. Extracellular vesicles were prepared from total plasma by size exclusion chromatography and quantified by nanoparticle tracking analysis, α-synuclein content was measured by an electrochemiluminescence assay.

RESULTS

α-Synuclein concentration in plasma extracellular vesicles provided the best discrimination between PD, dementia with Lewy bodies, PSP, and healthy controls, with an area under the curve of 0.804 (PD vs dementia with Lewy bodies), 0.815 (PD vs. PSP), and 0.769 (PD vs healthy controls) in the Tübingen cohort. Results were validated in the Kassel cohort.

CONCLUSIONS

The concentration of α-synuclein in plasma extracellular vesicles may serve as a potential diagnostic biomarker for PD. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The longevity gene Klotho and its cerebrospinal fluid protein profiles as a modifier for Parkinson´s disease

BACKGROUND

Parkinson´s disease (PD) has a large phenotypic variability, which may, at least partly, be genetically driven including alterations of gene products. Candidates might not only be proteins associated with disease risk but also pathways that play a role in aging.

OBJECTIVE

To evaluate phenotype-modifying effects of genetic variants in Klotho, a longevity gene.

METHODS

We analyzed two longitudinal cohorts: one local cohort comprising 459 PD patients who underwent genotyping for the KL-VS haplotype in Klotho including a subgroup of 125 PD patients and 50 healthy controls who underwent biochemical cerebrospinal fluid (CSF) analyses of Klotho and fibroblast growth factor 23 as well as vitamin D metabolites. The second cohort comprised 297 patients from the Parkinson's Progression Markers Initiative (PPMI) for validation of genetic-clinical findings.

RESULTS

PD patients carrying the KL-VS haplotype demonstrated a shorter interval between PD onset and onset of cognitive impairment (both cohorts) and higher Unified Parkinson´s Disease Rating Scale part III (UPDRS III) scores (PPMI). CSF protein levels of Klotho and fibroblast growth factor 23 were lower in PD patients irrespective of gender compared to controls. Moreover, low CSF levels of Klotho were associated with higher scores in the UPDRS III and Hoehn and Yahr Scale.

CONCLUSIONS

Our results indicate that genetic variants in Klotho together with its corresponding CSF protein profiles are associated with aspects of disease severity in PD. These findings suggest that pathways associated with aging might be targets for future biomarker research in PD.

The Mutation Matters: CSF Profiles of GCase, Sphingolipids, α-Synuclein in PDGBA

BACKGROUND

With pathway-specific trials in PD associated with variants in the glucocerebrosidase gene (PD_GBA ) under way, we need markers that confirm the impact of genetic variants in patient-derived biofluids in order to allow patient stratification merely based on genetics and that might serve as biochemical read-out for target engagement.

OBJECTIVE

To explore GBA-pathway-specific biomarker profiles cross-sectionally (TUEPAC-MIGAP, PPMI) and longitudinally (PPMI).

METHODS

We measured enzyme activity of the lysosomal glucocerebrosidase, CSF levels of glucosylceramides (upstream substrate of glucocerebrosidase), CSF levels of ceramides (downstream product of glucocerebrosidase), lactosylceramides, sphingosines, sphingomyelin (by-products) and CSF levels of total α-synuclein in PD_GBA patients compared to PD_{GBA_wildtype} patients.

RESULTS

Cross-sectionally in both cohorts and longitudinally in PPMI: (1) glucocerebrosidase activity was significantly lower in PD_GBA compared to PD_{GBA_wildtype} . (2) CSF levels of upstream substrates (glucosylceramides species) were higher in PD_GBA compared to PD_{GBA_wildtype} . (3) CSF levels of total α-synuclein were lower in PD_GBA compared to PD_{GBA_wildtype} . All of these findings were most pronounced in PD_GBA with severe mutations (PD_{GBA_severe} ). Cross-sectionally in TUEPAC-MIGAP and longitudinally in PPMI, CSF levels of downstream-products (ceramides) were higher in PD_{GBA_severe} . Cross-sectionally in TUEPAC-MIGAP by-products sphinganine and sphingosine-1-phosphate and longitudinally in PPMI species of by-products lactosylceramides and sphingomyelin were higher in PD_{GBA_severe} .

INTERPRETATION

These findings confirm that GBA mutations have a relevant functional impact on biomarker profiles in patients. Bridging the gap between genetics and biochemical profiles now allows patient stratification for clinical trials merely based on mutation status. Importantly, all findings were most prominent in PD_GBA with severe variants. © 2021 International Parkinson and Movement Disorder Society.

Evaluating the Use of Circulating MicroRNA Profiles for Lung Cancer Detection in Symptomatic Patients

Importance

The overall low survival rate of patients with lung cancer calls for improved detection tools to enable better treatment options and improved patient outcomes. Multivariable molecular signatures, such as blood-borne microRNA (miRNA) signatures, may have high rates of sensitivity and specificity but require additional studies with large cohorts and standardized measurements to confirm the generalizability of miRNA signatures.

Objective

To investigate the use of blood-borne miRNAs as potential circulating markers for detecting lung cancer in an extended cohort of symptomatic patients and control participants.

Design, Setting, and Participants

This multicenter, cohort study included patients from case-control and cohort studies (TREND and COSYCONET) with 3102 patients being enrolled by convenience sampling between March 3, 2009, and March 19, 2018. For the cohort study TREND, population sampling was performed. Clinical diagnoses were obtained for 3046 patients (606 patients with non-small cell and small cell lung cancer, 593 patients with nontumor lung diseases, 883 patients with diseases not affecting the lung, and 964 unaffected control participants). No samples were removed because of experimental issues. The collected data were analyzed between April 2018 and November 2019.

Main Outcomes and Measures

Sensitivity and specificity of liquid biopsy using miRNA signatures for detection of lung cancer.

Results

A total of 3102 patients with a mean (SD) age of 61.1 (16.2) years were enrolled. Data on the sex of the participants were available for 2856 participants; 1727 (60.5%) were men. Genome-wide miRNA profiles of blood samples from 3046 individuals were evaluated by machine-learning methods. Three classification scenarios were investigated by splitting the samples equally into training and validation sets. First, a 15-miRNA signature from the training set was used to distinguish patients diagnosed with lung cancer from all other individuals in the validation set with an accuracy of 91.4% (95% CI, 91.0%-91.9%), a sensitivity of 82.8% (95% CI, 81.5%-84.1%), and a specificity of 93.5% (95% CI, 93.2%-93.8%). Second, a 14-miRNA signature from the training set was used to distinguish patients with lung cancer from patients with nontumor lung diseases in the validation set with an accuracy of 92.5% (95% CI, 92.1%-92.9%), sensitivity of 96.4% (95% CI, 95.9%-96.9%), and specificity of 88.6% (95% CI, 88.1%-89.2%). Third, a 14-miRNA signature from the training set was used to distinguish patients with early-stage lung cancer from all individuals without lung cancer in the validation set with an accuracy of 95.9% (95% CI, 95.7%-96.2%), sensitivity of 76.3% (95% CI, 74.5%-78.0%), and specificity of 97.5% (95% CI, 97.2%-97.7%).

Conclusions and Relevance

The findings of the study suggest that the identified patterns of miRNAs may be used as a component of a minimally invasive lung cancer test, complementing imaging, sputum cytology, and biopsy tests.

Common diseases alter the physiological age-related blood microRNA profile

Aging is a key risk factor for chronic diseases of the elderly. MicroRNAs regulate post-transcriptional gene silencing through base-pair binding on their target mRNAs. We identified nonlinear changes in age-related microRNAs by analyzing whole blood from 1334 healthy individuals. We observed a larger influence of the age as compared to the sex and provide evidence for a shift to the 5' mature form of miRNAs in healthy aging. The addition of 3059 diseased patients uncovered pan-disease and disease-specific alterations in aging profiles. Disease biomarker sets for all diseases were different between young and old patients. Computational deconvolution of whole-blood miRNAs into blood cell types suggests that cell intrinsic gene expression changes may impart greater significance than cell abundance changes to the whole blood miRNA profile. Altogether, these data provide a foundation for understanding the relationship between healthy aging and disease, and for the development of age-specific disease biomarkers.

Phenylalanine Effects on Brain Function in Adult Phenylketonuria

OBJECTIVE

To evaluate the relationship between circulating phenylalanine and brain function as well as neuropsychiatric symptoms in adults with phenylketonuria.

METHODS

In this prospective cross-sectional study, early-treated patients with phenylketonuria older than 30 years and age- and sex-matched controls were included. Extensive neurologic evaluation, neuropsychological and behavioral testing, sensory and motor evoked potentials, and MRI were performed. CSF concentrations of neurodegenerative markers were evaluated in addition in a subset of 10 patients.

RESULTS

Nineteen patients with phenylketonuria (median age 41 years) with different phenylalanine levels (median 873 μmol/L) entered the study. They showed higher prevalence of neurologic symptoms, cognitive and behavioral abnormalities, autonomic dysfunction, alterations in neurophysiologic measures, and atrophy in putamen and right thalamus compared to controls. In CSF, patients with phenylketonuria exhibited higher β-amyloid 1-42 (p = 0.003), total tau (p < 0.001), and phosphorylated tau (p = 0.032) levels compared to controls. Plasma phenylalanine levels highly correlated with the number of failed neuropsychological tests (r = 0.64, p = 0.003), neuropsychiatric symptoms (r = 0.73, p < 001), motor evoked potential latency (r = 0.48, p = 0.030), and parietal lobe atrophy.

CONCLUSIONS

Our study provides strong evidence for a correlation between phenylalanine levels and clinical, neuropsychological, neurophysiologic, biochemical, and imaging alterations in adult patients with phenylketonuria.

Mitochondrial damage-associated inflammation highlights biomarkers in PRKN/PINK1 parkinsonism

There is increasing evidence for a role of inflammation in Parkinson's disease. Recent research in murine models suggests that parkin and PINK1 deficiency leads to impaired mitophagy, which causes the release of mitochondrial DNA (mtDNA), thereby triggering inflammation. Specifically, the CGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon genes) pathway mitigates activation of the innate immune system, quantifiable as increased interleukin-6 (IL6) levels. However, the role of IL6 and circulating cell-free mtDNA in unaffected and affected individuals harbouring mutations in PRKN/PINK1 and idiopathic Parkinson's disease patients remain elusive. We investigated IL6, C-reactive protein, and circulating cell-free mtDNA in serum of 245 participants in two cohorts from tertiary movement disorder centres. We performed a hypothesis-driven rank-based statistical approach adjusting for multiple testing. We detected (i) elevated IL6 levels in patients with biallelic PRKN/PINK1 mutations compared to healthy control subjects in a German cohort, supporting the concept of a role for inflammation in PRKN/PINK1-linked Parkinson's disease. In addition, the comparison of patients with biallelic and heterozygous mutations in PRKN/PINK1 suggests a gene dosage effect. The differences in IL6 levels were validated in a second independent Italian cohort; (ii) a correlation between IL6 levels and disease duration in carriers of PRKN/PINK1 mutations, while no such association was observed for idiopathic Parkinson's disease patients. These results highlight the potential of IL6 as progression marker in Parkinson's disease due to PRKN/PINK1 mutations; (iii) increased circulating cell-free mtDNA serum levels in both patients with biallelic or with heterozygous PRKN/PINK1 mutations compared to idiopathic Parkinson's disease, which is in line with previous findings in murine models. By contrast, circulating cell-free mtDNA concentrations in unaffected heterozygous carriers of PRKN/PINK1 mutations were comparable to control levels; and (iv) that circulating cell-free mtDNA levels have good predictive potential to discriminate between idiopathic Parkinson's disease and Parkinson's disease linked to heterozygous PRKN/PINK1 mutations, providing functional evidence for a role of heterozygous mutations in PRKN or PINK1 as Parkinson's disease risk factor. Taken together, our study further implicates inflammation due to impaired mitophagy and subsequent mtDNA release in the pathogenesis of PRKN/PINK1-linked Parkinson's disease. In individuals carrying mutations in PRKN/PINK1, IL6 and circulating cell-free mtDNA levels may serve as markers of Parkinson's disease state and progression, respectively. Finally, our study suggests that targeting the immune system with anti-inflammatory medication holds the potential to influence the disease course of Parkinson's disease, at least in this subset of patients.

Gut Microbiome Signatures of Risk and Prodromal Markers of Parkinson Disease

OBJECTIVE

Alterations of the gut microbiome in Parkinson disease (PD) have been repeatedly demonstrated. However, little is known about whether such alterations precede disease onset and how they relate to risk and prodromal markers of PD. We investigated associations of these features with gut microbiome composition.

METHODS

Established risk and prodromal markers of PD as well as factors related to diet/lifestyle, bowel function, and medication were studied in relation to bacterial α-/β-diversity, enterotypes, and differential abundance in stool samples of 666 elderly TREND (Tübingen Evaluation of Risk Factors for Early Detection of Neurodegeneration) study participants.

RESULTS

Among risk and prodromal markers, physical activity, occupational solvent exposure, and constipation showed associations with α-diversity. Physical activity, sex, constipation, possible rapid eye movement sleep behavior disorder (RBD), and smoking were associated with β-diversity. Subthreshold parkinsonism and physical activity showed an interaction effect. Among other factors, age and urate-lowering medication were associated with α- and β-diversity. Physical inactivity and constipation were highest in individuals with the Firmicutes-enriched enterotype. Constipation was lowest and subthreshold parkinsonism least frequent in individuals with the Prevotella-enriched enterotype. Differentially abundant taxa were linked to constipation, physical activity, possible RBD, smoking, and subthreshold parkinsonism. Substantia nigra hyperechogenicity, olfactory loss, depression, orthostatic hypotension, urinary/erectile dysfunction, PD family history, and the prodromal PD probability showed no significant microbiome associations.

INTERPRETATION

Several risk and prodromal markers of PD are associated with gut microbiome composition. However, the impact of the gut microbiome on PD risk and potential microbiome-dependent subtypes in the prodrome of PD need further investigation based on prospective clinical and (multi)omics data in incident PD cases. ANN NEUROL 2020;88:320-331.

Machine Learning to Detect Alzheimer's Disease from Circulating Non-coding RNAs

Blood-borne small non-coding (sncRNAs) are among the prominent candidates for blood-based diagnostic tests. Often, high-throughput approaches are applied to discover biomarker signatures. These have to be validated in larger cohorts and evaluated by adequate statistical learning approaches. Previously, we published high-throughput sequencing based microRNA (miRNA) signatures in Alzheimer’s disease (AD) patients in the United States (US) and Germany. Here, we determined abundance levels of 21 known circulating miRNAs in 465 individuals encompassing AD patients and controls by RT-qPCR. We computed models to assess the relation between miRNA expression and phenotypes, gender, age, or disease severity (Mini-Mental State Examination; MMSE). Of the 21 miRNAs, expression levels of 20 miRNAs were consistently de-regulated in the US and German cohorts. 18 miRNAs were significantly correlated with neurodegeneration (Benjamini-Hochberg adjusted P < 0.05) with highest significance for miR-532-5p (Benjamini-Hochberg adjusted P = 4.8 × 10⁻³⁰). Machine learning models reached an area under the curve (AUC) value of 87.6% in differentiating AD patients from controls. Further, ten miRNAs were significantly correlated with MMSE, in particular miR-26a/26b-5p (adjusted P = 0.0002). Interestingly, the miRNAs with lower abundance in AD were enriched in monocytes and T-helper cells, while those up-regulated in AD were enriched in serum, exosomes, cytotoxic t-cells, and B-cells. Our study represents the next important step in translational research for a miRNA-based AD test.

A combined miRNA-piRNA signature to detect Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder causing huge emotional and economic burden to our societies. An effective therapy has not been implicated yet, which is in part also due to the fact that pathological changes occur years before clinical symptoms manifest. Thus, there is a great need for the development of a translatable biomarker. Recent evidence highlights microRNAs as candidate biomarkers. In this study, we use next-generation sequencing to study the small noncoding RNAome (sncRNAome) in exosomes derived from human cerebrospinal fluid (CSF). We show that the sncRNAome from CSF-derived exosomes is dominated not only by microRNAs (miRNAs) but also by PIWI-interacting RNAs (piRNAs). We define a combined signature consisting of three miRNAs and three piRNAs that are suitable to detect AD with an AUC of 0.83 in a replication cohort and furthermore predict the conversion of mild-cognitive impaired (MCI) patients to AD dementia with an AUC of 0.86 for the piRNA signature. When combining the smallRNA signature with pTau and Aβ 42/40 ratio the AUC reaches 0.98. Our study reports a novel exosomal small noncoding RNA signature to detect AD pathology and provides the first evidence that in addition to miRNAs, piRNAs should also be considered as a candidate biomarker for AD.

Correlations between serum and CSF pNfH levels in ALS, FTD and controls: a comparison of three analytical approaches

Background

Phosphorylated neurofilament heavy (pNfH), a neuronal cytoskeleton protein, might provide a promising blood biomarker of neuronal damage in neurodegenerative diseases (NDDs). The best analytical approaches to measure pNfH levels and whether serum levels correlate with cerebrospinal fluid (CSF) levels in NDDs remain to be determined.

Methods

We here compared analytical sensitivity and reliability of three novel analytical approaches (homebrew Simoa, commercial Simoa and ELISA) for quantifying pNfH in both CSF and serum in samples of amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) and control subjects.

Results

While all three assays showed highly correlated CSF measurements, Simoa assays also yielded high between-assay correlations for serum measurements (ϱ = 0.95). Serum levels also correlated strongly with CSF levels for Simoa-based measurements (both ϱ = 0.62). All three assays allowed distinguishing ALS from controls by increased CSF pNfH levels, and Simoa assays also by increased serum pNfH levels. pNfH levels were also increased in FTD.

Conclusions

pNfH concentrations in CSF and, if measured by Simoa assays, in blood might provide a sensitive and reliable biomarker of neuronal damage, with good between-assay correlations. Serum pNfH levels measured by Simoa assays closely reflect CSF levels, rendering serum pNfH an easily accessible blood biomarker of neuronal damage in NDDs.

Parkinson's disease: evolution of cognitive impairment and CSF Aβ1-42 profiles in a prospective longitudinal study

OBJECTIVE

To evaluate the evolution of cognitive impairment in relation to cerebrospinal fluid (CSF) profiles of amyloid-β (Aβ), total-Tau and phosphorylated-Tau in Parkinson's disease (PD).

METHODS

Prospective, longitudinal, observational study up to 10 years with follow-up every 2  years. We assessed CSF profiles in 415 patients with sporadic PD (median age 66; 63% men) and 142 healthy controls (median age 62; 43% men).

RESULTS

Patients with PD with low CSF Aβ_1-42 levels at baseline were more often cognitively impaired than patients with intermediate and high Aβ_1-42 levels. Sixty-seven per cent of the patients with low Aβ_1-42 levels at baseline and normal cognition developed cognitive impairment during follow-up, compared with 41% and 37% of patients having intermediate and high CSF Aβ_1-42 levels. Kaplan-Meier survival curves and Cox regression revealed that patients with low CSF Aβ_1-42 levels at baseline developed cognitive impairment more frequently and earlier during follow-up.

CONCLUSION

We conclude that in patients with sporadic PD, low levels of Aβ_1-42 are associated with a higher risk of developing cognitive impairment earlier in the disease process at least in a subgroup of patients.

Dementia with Lewy bodies: cerebrospinal fluid suppresses neuronal network activity

One of the core clinical criteria of Dementia with Lewy bodies (DLB) are fluctuations of cognition. Underlying processes may be rather functional than neurodegenerative, reflected by, for example, factors present in cerebrospinal fluid (CSF). The aim of this study was to identify in-vitro neuronal network activity (ivNNA) changes of CSF from DLB patients compared with patients with Parkinson's disease (PD) and controls. Primary neuronal mouse cultures were grown on microelectrode arrays to record ivNNA when exposed to respective CSF samples. If exposed to CSF of DLB patients, ivNNA showed a reduced spike rate and burst rate compared with CSF of PD patients and controls. Our data are suggestive of the presence of functional factors in the CSF of DLB patients that differentiate network activity from PD patients and controls. Future studies should evaluate whether this pilot observation might be related to fluctuations of cognition in DLB.

Metabolomic Profiles for Primary Progressive Multiple Sclerosis Stratification and Disease Course Monitoring

Primary progressive multiple sclerosis (PPMS) shows a highly variable disease progression with poor prognosis and a characteristic accumulation of disabilities in patients. These hallmarks of PPMS make it difficult to diagnose and currently impossible to efficiently treat. This study aimed to identify plasma metabolite profiles that allow diagnosis of PPMS and its differentiation from the relapsing-remitting subtype (RRMS), primary neurodegenerative disease (Parkinson’s disease, PD), and healthy controls (HCs) and that significantly change during the disease course and could serve as surrogate markers of multiple sclerosis (MS)-associated neurodegeneration over time. We applied untargeted high-resolution metabolomics to plasma samples to identify PPMS-specific signatures, validated our findings in independent sex- and age-matched PPMS and HC cohorts and built discriminatory models by partial least square discriminant analysis (PLS-DA). This signature was compared to sex- and age-matched RRMS patients, to patients with PD and HC. Finally, we investigated these metabolites in a longitudinal cohort of PPMS patients over a 24-month period. PLS-DA yielded predictive models for classification along with a set of 20 PPMS-specific informative metabolite markers. These metabolites suggest disease-specific alterations in glycerophospholipid and linoleic acid pathways. Notably, the glycerophospholipid LysoPC(20:0) significantly decreased during the observation period. These findings show potential for diagnosis and disease course monitoring, and might serve as biomarkers to assess treatment efficacy in future clinical trials for neuroprotective MS therapies.

Promising Metabolite Profiles in the Plasma and CSF of Early Clinical Parkinson's Disease

Parkinson's disease (PD) shows high heterogeneity with regard to the underlying molecular pathogenesis involving multiple pathways and mechanisms. Diagnosis is still challenging and rests entirely on clinical features. Thus, there is an urgent need for robust diagnostic biofluid markers. Untargeted metabolomics allows establishing low-molecular compound biomarkers in a wide range of complex diseases by the measurement of various molecular classes in biofluids such as blood plasma, serum, and cerebrospinal fluid (CSF). Here, we applied untargeted high-resolution mass spectrometry to determine plasma and CSF metabolite profiles. We semiquantitatively determined small-molecule levels (≤1.5 kDa) in the plasma and CSF from early PD patients (disease duration 0-4 years; n = 80 and 40, respectively), and sex- and age-matched controls (n = 76 and 38, respectively). We performed statistical analyses utilizing partial least square and random forest analysis with a 70/30 training and testing split approach, leading to the identification of 20 promising plasma and 14 CSF metabolites. These metabolites differentiated the test set with an AUC of 0.8 (plasma) and 0.9 (CSF). Characteristics of the metabolites indicate perturbations in the glycerophospholipid, sphingolipid, and amino acid metabolism in PD, which underscores the high power of metabolomic approaches. Further studies will enable to develop a potential metabolite-based biomarker panel specific for PD.

Cognitive impairment in Glucocerebrosidase (GBA)-associated PD: Not primarily associated with cerebrospinal fluid Abeta and Tau profiles

BACKGROUND

A proportion of idiopathic Parkinson's disease patients (PD_idiopathic ) with dementia show altered CSF profiles of amyloid β (Aβ) and Tau. PD patients with Glucocerebrosidase (GBA) mutations (PD_GBA ) present with even more cognitive decline than seen in PD_idiopathic .

OBJECTIVE

The objective of this study was to evaluate whether CSF profiles of Aβ and tau are associated with the prominent cognitive impairment in PD_GBA .

METHODS

CSF levels of Aβ_1-42 , t-Tau, p-Tau, and total alpha-synuclein were assessed in 479 participants (50 PD_GBA , 308 PD_idiopathic , 121 healthy controls).

RESULTS

Older age was associated with cognitive impairment in PD_GBA and PD_idiopathic . Despite prominent cognitive impairment, PD_GBA showed similar CSF levels of Aβ_1-42 , t-Tau, and p-Tau as seen in healthy controls. In contrast, lower levels of Aβ_1-42 and higher levels of t-Tau and p-Tau were associated with worse cognitive performance in PD_idiopathic .

CONCLUSIONS

The prominent cognitive impairment in PD_GBA seems not primarily associated with Aβ and Tau profiles in CSF. © 2017 International Parkinson and Movement Disorder Society.

Serum Levels of Progranulin Do Not Reflect Cerebrospinal Fluid Levels in Neurodegenerative Disease

Altered progranulin levels play a major role in neurodegenerative diseases, like Alzheimer's dementia (AD), frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), even in the absence of GRN mutations. Increasing progranulin levels could hereby provide a novel treatment strategy. However, knowledge on progranulin regulation in neurodegenerative diseases remains limited. We here demonstrate that cerebrospinal fluid progranulin levels do not correlate with its serum levels in AD, FTD and ALS, indicating a differential regulation of its central and peripheral levels in neurodegeneration. Blood progranulin levels thus do not reliably predict central nervous progranulin levels and their response to future progranulin-increasing therapeutics.

Cerebrospinal Fluid Progranulin, but Not Serum Progranulin, Is Reduced in GRN-Negative Frontotemporal Dementia

BACKGROUND AND OBJECTIVE

Reduced progranulin levels are a hallmark of frontotemporal dementia (FTD) caused by loss-of-function (LoF) mutations in the progranulin gene (GRN). However, alterations of central nervous progranulin expression also occur in neurodegenerative disorders unrelated to GRN mutations, such as Alzheimer's disease. We hypothesised that central nervous progranulin levels are also reduced in GRN-negative FTD.

METHODS

Progranulin levels were determined in both cerebrospinal fluid (CSF) and serum in 75 subjects (37 FTD patients and 38 controls). All FTD patients were assessed by whole-exome sequencing for GRN mutations, yielding a target cohort of 34 patients without pathogenic mutations in GRN (GRN-negative cohort) and 3 GRN mutation carriers (2 LoF variants and 1 novel missense variant).

RESULTS

Not only the GRN mutation carriers but also the GRN-negative patients showed decreased CSF levels of progranulin (serum levels in GRN-negative patients were normal). The decreased CSF progranulin levels were unrelated to patients' increased CSF levels of total tau, possibly indicating different destructive neuronal processes within FTD neurodegeneration. The patient with the novel GRN missense variant (c.1117C>T, p.P373S) showed substantially decreased CSF levels of progranulin, comparable to the 2 patients with GRN LoF mutations, suggesting a pathogenic effect of this missense variant.

CONCLUSIONS

Our results indicate that central nervous progranulin reduction is not restricted to the relatively rare cases of FTD caused by GRN LoF mutations, but also contributes to the more common GRN-negative forms of FTD. Central nervous progranulin reduction might reflect a partially distinct pathogenic mechanism underlying FTD neurodegeneration and is not directly linked to tau alterations.

Insulin-Like Growth Factor 1 (IGF-1) in Parkinson's Disease: Potential as Trait-, Progression- and Prediction Marker and Confounding Factors

INTRODUCTION

Biomarkers indicating trait, progression and prediction of pathology and symptoms in Parkinson's disease (PD) often lack specificity or reliability. Investigating biomarker variance between individuals and over time and the effect of confounding factors is essential for the evaluation of biomarkers in PD, such as insulin-like growth factor 1 (IGF-1).

MATERIALS AND METHODS

IGF-1 serum levels were investigated in up to 8 biannual visits in 37 PD patients and 22 healthy controls (HC) in the longitudinal MODEP study. IGF-1 baseline levels and annual changes in IGF-1 were compared between PD patients and HC while accounting for baseline disease duration (19 early stage: ≤3.5 years; 18 moderate stage: >4 years), age, sex, body mass index (BMI) and common medical factors putatively modulating IGF-1. In addition, associations of baseline IGF-1 with annual changes of motor, cognitive and depressive symptoms and medication dose were investigated.

RESULTS

PD patients in moderate (130±26 ng/mL; p = .004), but not early stages (115±19, p>.1), showed significantly increased baseline IGF-1 levels compared with HC (106±24 ng/mL; p = .017). Age had a significant negative correlation with IGF-1 levels in HC (r = -.47, p = .028) and no correlation in PD patients (r = -.06, p>.1). BMI was negatively correlated in the overall group (r = -.28, p = .034). The annual changes in IGF-1 did not differ significantly between groups and were not correlated with disease duration. Baseline IGF-1 levels were not associated with annual changes of clinical parameters.

DISCUSSION

Elevated IGF-1 in serum might differentiate between patients in moderate PD stages and HC. However, the value of serum IGF-1 as a trait-, progression- and prediction marker in PD is limited as IGF-1 showed large inter- and intraindividual variability and may be modulated by several confounders.

GDF15/MIC1 and MMP9 Cerebrospinal Fluid Levels in Parkinson's Disease and Lewy Body Dementia

Based on animal and ex-vivo experiments, Growth/Differentiation Factor-15 (GDF15, also called Macrophage Inhibitory Cytokine-1, MIC1), a member of the transforming growth factor-beta family, and Matrix Metalloproteinase-9 (MMP9), a member of the matrix metalloprotease family may be potential markers for Lewy body disorders, i.e. Parkinson’s disease with (PDD) and without dementia (PDND) and Lewy body dementia (DLB). GDF15 has a prominent role in development, cell proliferation, differentiation, and repair, whereas MMP9 degrades, as a proteolytic enzyme, components of the extracellular matrix. In this study, cerebrospinal fluid GDF15 and MMP9 levels of 59 PDND, 17 PDD and 23 DLB patients, as well as of 95 controls were determined, and associated with demographic, clinical and biochemical parameters. Our analysis confirmed the already described association of GDF15 levels with age and gender. Corrected GDF15 levels were significantly higher in PDD than in PDND patients, and intermediate in DLB patients. Within Lewy body disorders, GDF15 levels correlated positively with age at onset of Parkinsonism and dementia, Hoehn & Yahr stage and cerebrospinal fluid t-Tau and p-Tau levels, and negatively with the Mini Mental State Examination. Remarkably, it does not relevantly correlate with disease duration. MMP9 was not relevantly associated with any of these parameters. Cerebrospinal GDF15, but not MMP9, may be a potential marker of and in Lewy body disorders.

Comparable autoantibody serum levels against amyloid- and inflammation-associated proteins in Parkinson's disease patients and controls

Naturally occurring autoantibodies (NAbs) against a number of potentially disease-associated cellular proteins, including Amyloid-beta_1–42 (Abeta_1–42), Alpha-synuclein (Asyn), myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), and S100 calcium binding protein B (S100B) have been suggested to be associated with neurodegenerative disorders, in particular Alzheimer’s (AD) and Parkinson’s disease (PD). Whereas the (reduced) occurrence of specific NAbs in AD is widely accepted, previous literature examining the relation of these NAb titres between PD patients and controls, as well as comparing these levels with demographic and clinical parameters in PD patients have produced inconsistent findings. We therefore aimed, in a cross-sectional approach, to determine serum titres of the above NAbs in a cohort of 93 PD patients (31 of them demented) and 194 controls. Levels were correlated with demographic and clinical variables, cerebrospinal fluid Abeta_1–42, total tau and phospho-tau levels, as well as with single nucleotide polymorphisms (SNPs) of genes which either have been reported to influence the immune system, the amyloid cascade or the occurrence of PD (ApoE, GSK3B, HLA-DRA, HSPA5, SNCA, and STK39). The investigated NAb titres were neither significantly associated with the occurrence of PD, nor with demographic and clinical parameters, neurodegenerative markers or genetic variables. These results argue against a major potential of blood-borne parameters of the adaptive immune system to serve as trait or state markers in PD.

Plasma ceramide and glucosylceramide metabolism is altered in sporadic Parkinson's disease and associated with cognitive impairment: a pilot study

Background

Mutations in the gene coding for glucocerebrosidase (GBA), which metabolizes glucosylceramide (a monohexosylceramide) into glucose and ceramide, is the most common genetic risk factor for sporadic Parkinson's disease (PD). GBA mutation carriers are more likely to have an earlier age of onset and to develop cognitive impairment and dementia. We hypothesized that plasma levels of lipids involved in ceramide metabolism would also be altered in PD non-GBA mutation carriers and associated with worse cognition.

Methods

Plasma ceramide, monohexosylceramide, and lactosylceramide levels in 26 cognitively normal PD patients, 26 PD patients with cognitive impairment or dementia, and 5 cognitively normal non-PD controls were determined by LC/ESI/MS/MS.

Results

Levels of all lipid species were higher in PD patients versus controls. Among PD patients, levels of ceramide C16:0, C18:0, C20:0, C22:0, and C24:1 and monohexosylceramide C16:0, C20:0 and C24:0 species were higher (all P<0.05) in those with versus without cognitive impairment.

Conclusion

These results suggest that plasma ceramide and monohexosylceramide metabolism is altered in PD non-GBA mutation carriers and that higher levels are associated with worse cognition. Additional studies with larger sample sizes, including cognitively normal controls, are needed to confirm these findings.

Cerebrospinal fluid fatty acids in glucocerebrosidase-associated Parkinson's disease

BACKGROUND

Heterozygous mutations in the glucocerebrosidase gene lead to an increased risk for and to more severe alpha-synuclein-associated pathology in Parkinson's disease. As both glucocerebrosidase and alpha-synuclein interact with fatty acids, we hypothesized that cerebrospinal fluid fatty acid levels are altered in these Parkinson's disease patients.

METHODS

Cerebrospinal fluid levels of 13 fatty acids in 8 Parkinson's disease patients with a heterozygous glucocerebrosidase mutation were compared with those of 41 idiopathic Parkinson's disease patients and 30 controls using gas chromatography.

RESULTS

Parkinson's disease patients with a heterozygous glucocerebrosidase mutation had lower levels of palmitoleic (P ≤ .007), oleic (P ≤ .016), linoleic (P ≤ .005), arachidonic (P ≤ .003), eicosapentaenoic (P ≤ .003) and decosahexaenoic (P ≤ .03) acids and lower levels of total fatty acids (P < .005) compared with both idiopathic Parkinson's disease patients and control subjects.

CONCLUSIONS

These results suggest that abnormalities of fatty acid metabolism are specifically involved in the pathogenesis of Parkinson's disease associated with a heterozygous glucocerebrosidase mutation.