CSF α-synuclein levels in dementia with Lewy bodies and Alzheimer's disease

The role of 123-I-MIBG cardiac scintigraphy in the differential diagnosis between dementia with Lewy bodies and Alzheimer's disease

Although detailed diagnostic guidelines are available, differentiating dementia with Lewy bodies from Alzheimer's disease is often difficult. 123-I-MIBG cardiac scintigraphy is one of the tools which have been proposed for the diagnostic procedure. The present review is aimed at evaluating the available literature about this topic. Studies assessing the use of this technique to differentiate between the two diseases have been examined and reported. Overall, despite a certain study-to-study variability, the available literature suggests that 123-I-MIBG cardiac scintigraphy is an effective tool in differentiating between the two diseases, with high sensitivity and specificity values. Although the large-scale application of this technique is limited by possible interactions with specific medications and comorbidities, the reported studies are supportive for the usefulness of this technique in clinical practice.

Cerebrospinal Fluid Alpha-Synuclein Improves the Differentiation between Dementia with Lewy Bodies and Alzheimer's Disease in Clinical Practice

Background: Alpha-synuclein, abnormally aggregated in Dementia with Lewy Bodies (DLB), could represent a potential biomarker to improve the differentiation between DLB and Alzheimer’s disease (AD). Our main objective was to compare Cerebrospinal Fluid (CSF) alpha-synuclein levels between patients with DLB, AD and Neurological Control (NC) individuals. Methods: In a monocentric retrospective study, we assessed CSF alpha-synuclein concentration with a validated ELISA kit (ADx EUROIMMUN) in patients with DLB, AD and NC from a tertiary memory clinic. Between-group comparisons were performed, and Receiver Operating Characteristic analysis was used to identify the best CSF alpha-synuclein threshold. We examined the associations between CSF alpha-synuclein, other core AD CSF biomarkers and brain MRI characteristics. Results: We included 127 participants (mean age: 69.3 ± 8.1, Men: 41.7%). CSF alpha-synuclein levels were significantly lower in DLB than in AD (1.28 ± 0.52 ng/mL vs. 2.26 ± 0.91 ng/mL, respectively, p < 0.001) without differences due to the stage of cognitive impairment. The best alpha-synuclein threshold was characterized by an Area Under the Curve = 0.85, Sensitivity = 82.0% and Specificity = 76.0%. CSF alpha-synuclein was associated with CSF AT(N) biomarkers positivity (p < 0.01) but not with hippocampal atrophy or white matter lesions. Conclusion: CSF Alpha-synuclein evaluation could help to early differentiate patients with DLB and AD in association with existing biomarkers.

Comparative Analysis of Total Alpha-Synuclein (αSYN) Immunoassays Reveals That They Do Not Capture the Diversity of Modified αSYN Proteoforms

Background:

The development of therapeutics for Parkinson’s disease (PD) requires the establishment of biomarker assays to enable stratifying patients, monitoring disease progression, and assessing target engagement. Attempts to develop diagnostic assays based on detecting levels of the α-synuclein (αSYN) protein, a central player in the pathogenesis of PD, have yielded inconsistent results.

Objective:

To determine whether the three commercial kits that have been extensively used for total αSYN quantification in human biological fluids (from Euroimmun, MSD, and Biolegend) are capable of capturing the diversity and complexity of relevant αSYN proteoforms.

Methods:

We investigated and compared the ability of the different assays to detect the diversity of αSYN proteoforms using a library of αSYN proteins that comprise the majority of disease-relevant αSYN variants and post-translational modifications (PTMs).

Results:

Our findings showed that none of the three tested immunoassays accurately capture the totality of relevant αSYN species, and that these assays are unable to recognize most disease-associated C-terminally truncated variants of αSYN. Moreover, several N-terminal truncations and phosphorylation/nitration PTMs differentially modify the level of αSYN detection and recovery by different immunoassays, and a CSF matrix effect was observed for most of the αSYN proteoforms analyzed by the three immunoassays.

Conclusion:

Our results show that the tested immunoassays do not capture the totality of the relevant αSYN species and therefore may not be appropriate tools to provide an accurate measure of total αSYN levels in samples containing modified forms of the protein. This highlights the need for next generation αSYN immunoassays that capture the diversity of αSYN proteoforms.

Synuclein Motor Dysfunction Composite Scale for the Discrimination of Dementia With Lewy Bodies From Alzheimer’s Disease

Background

An abnormal increase of α-synuclein in the brain is the hallmark of dementia with Lewy bodies (DLB). However, the diagnostic power of plasma α-synuclein in DLB is not yet confirmed. Parkinsonism is highly associated with and is one of the core clinical features of DLB. We studied plasma α-synuclein and developed a novel tool that combined plasma α-synuclein level and Motor Dysfunction Questionnaire (MDQ), namely Synuclein Motor Dysfunction Composite Scale (SMDCS), for the clinical discrimination of DLB from Alzheimer’s disease (AD).

Methods

This cross-sectional study analyzed participants’ demographical data, plasma α-synuclein level, MDQ, structured clinical history questionnaire, neuropsychological and motor function tests, and neuroimaging studies. The power of plasma α-synuclein level, MDQ, and SMDCS for discriminating DLB from non-demented controls (NC) or AD were compared.

Results

Overall, 121 participants diagnosed as 58 DLB, 31 AD, and 31 NC were enrolled. Patients with DLB had significantly higher mean plasma α-synuclein level (0.24 ± 0.32 pg/ml) compared to the NC group (0.08 ± 0.05 pg/ml) and the AD group (0.08 ± 0.05 pg/ml). The DLB group demonstrated higher MDQ (2.95 ± 1.60) compared to the NC (0.42 ± 0.98) or AD (0.44 ± 0.99) groups. The sensitivity/specificity of plasma α-synuclein level, MDQ, and SMDCS for differentiating DLB from non-DLB were 0.80/0.64, 0.83/0.89, and 0.88/0.93, respectively.

Conclusion

Both plasma α-synuclein and MDQ were significantly higher in patients with DLB compared to the NC or AD groups. The novel SMDCS, significantly improved accuracy for the clinical differentiation of DLB from AD or NC.

Biomarkers and diagnosis of dementia with Lewy bodies including prodromal: Practical aspects

Dementia with Lewy Bodies (DLB) is a common form of cognitive neurodegenerative disease. More than half of the patients affected are not or misdiagnosed because of the clinical similarity with Alzheimer's disease (AD), Parkinson's disease but also psychiatric diseases such as depression or psychosis. In this review, we evaluate the interest of different biomarkers in the diagnostic process: cerebrospinal fluid (CSF), brain MRI, FP-CIT SPECT, MIBG SPECT, perfusion SPECT, FDG-PET by focusing more specifically on differential diagnosis between DLB and AD. FP-CIT SPECT is of high interest to discriminate DLB and AD, but not at the prodromal stage. Brain MRI has shown differences in group study with lower grey matter concentration of the Insula in prodromal DLB, but its interest in clinical routine is not demonstrated. Among the AD biomarkers (t-Tau, phospho-Tau₁₈₁, Aβ42 and Aβ40) used routinely, t-Tau and phospho-Tau₁₈₁ have shown excellent discrimination whatever the clinical stages severity. CSF Alpha-synuclein assay in the CSF has also an interest in the discrimination between DLB and AD but not in segregation between DLB and healthy elderly subjects. CSF synuclein RT-QuIC seems to be an excellent biomarker but its application in clinical routine remains to be demonstrated, given the non-automation of the process.

Investigating the Convergent Mechanisms between Major Depressive Disorder and Parkinson's Disease

Major depressive disorder (MDD) affects more than cognition, having a temporal relationship with neuroinflammatory pathways of Parkinson's disease (PD). Although this association is supported by epidemiological and clinical studies, the underlying mechanisms are unclear. Microglia and astrocytes play crucial roles in the pathophysiology of both MDD and PD. In PD, these cells can be activated by misfolded forms of the protein α-synuclein to release cytokines that can interact with multiple different physiological processes to produce depressive symptoms, including monoamine transport and availability, the hypothalamus-pituitary axis, and neurogenesis. In MDD, glial cell activation can be induced by peripheral inflammatory agents that cross the blood-brain barrier and/or c-Fos signalling from neurons. The resulting neuroinflammation can cause neurodegeneration due to oxidative stress and glutamate excitotoxicity, contributing to PD pathology. Astrocytes are another major link due to their recognized role in the glymphatic clearance mechanism. Research suggesting that MDD causes astrocytic destruction or structural atrophy highlights the possibility that accumulation of α-synuclein in the brain is facilitated as the brain cannot adequately clear the protein aggregates. This review examines research into the overlapping pathophysiology of MDD and PD with particular focus on the roles of glial cells and neuroinflammation.

Distribution of the Alpha-Synuclein in the Brain and the Primary Organs of the Rhesus Monkey

Previous studies have shown that abnormal aggregation of alpha-synuclein (α-syn) protein is a major trigger of neurodegenerative diseases. The expression level of α-syn in different brain regions and the disease-susceptible regions varies with the development of the disease. The expression pattern of the α-syn protein in mouse brain has been precisely described in the literature. Some studies have also reported the ubiquitous expression of the α-syn protein in the central and peripheral in nonhuman primates (NHPs). However, little is known about the expression pattern of α-syn in the brain or in the primary organs of NHPs. Here, we investigated the expression profile of α-syn in different brain regions and the primary organs of NHPs. The α-syn protein was mainly distributed in layers III and V of the cerebral cortex and the hippocampus. In addition, strong immunofluorescent signals were detected in the striatum and the substantia nigra, especially in the globus pallidus and the substantia nigra pars compacta, where the expression was significantly and particularly strong, compared with that in the cerebellum or the cortex. In the cerebellum, intense α-syn signal was observed in the molecular layer, where it was significantly higher than in the nucleus or the medulla. In the brain, the α-syn was always detected both in the cytoplasm and the synapses. Additionally, the α-syn was widely expressed in primary organs. The α-syn signal was higher in the liver and small intestine than in the spleen. Thus, the regions displaying the highest α-syn expression are also those affected during the progression of neurodegenerative diseases. These results may provide basic reference data for the study of multi-systemic mechanism of neurodegenerative diseases.

Alpha-Synuclein Protofibrils in Cerebrospinal Fluid: A Potential Biomarker for Parkinson's Disease

BACKGROUND

Currently, there is no established biomarker for Parkinson's disease (PD) and easily accessible biomarkers are crucial for developing disease-modifying treatments.

OBJECTIVE

To develop a novel method to quantify cerebrospinal fluid (CSF) levels of α-synuclein protofibrils (α-syn PF) and apply it to clinical cohorts of patients with PD and atypical parkinsonian disorders.

METHODS

A cohort composed of 49 patients with PD, 12 with corticobasal degeneration (CBD), 22 with progressive supranuclear palsy, and 33 controls, that visited the memory clinic but had no biomarker signs of Alzheimer's disease (AD, tau<350 pg/mL, amyloid-beta 42 (Aβ42)>530 pg/mL, and phosphorylated tau (p-tau)<60 pg/mL) was used in this study. The CSF samples were analyzed with the Single molecule array (Simoa) technology. Total α-synuclein (α-syn) levels were analyzed with a commercial ELISA-kit.

RESULTS

The assay is specific to α-syn PF, with no cross-reactivity to monomeric α-syn, or the β- and γ-synuclein variants. CSF α-syn PF levels were increased in PD compared with controls (62.1 and 40.4 pg/mL, respectively, p = 0.03), and CBD (62.1 and 34.2 pg/mL, respectively, p = 0.02). The accuracy of predicting PD using α-syn PF is significantly different from controls (area under the curve 0.68, p = 0.0097) with a sensitivity of 62.8% and specificity of 67.7%. Levels of total α-syn were significantly different between the PD and CBD groups (p = 0.04).

CONCLUSION

The developed method specifically quantifies α-syn PF in human CSF with increased concentrations in PD, but with an overlap with asymptomatic elderly controls.

Genetic Architecture and Molecular, Imaging and Prodromic Markers in Dementia with Lewy Bodies: State of the Art, Opportunities and Challenges

Dementia with Lewy bodies (DLB) is one of the most common causes of dementia and belongs to the group of α-synucleinopathies. Due to its clinical overlap with other neurodegenerative disorders and its high clinical heterogeneity, the clinical differential diagnosis of DLB from other similar disorders is often difficult and it is frequently underdiagnosed. Moreover, its genetic etiology has been studied only recently due to the unavailability of large cohorts with a certain diagnosis and shows genetic heterogeneity with a rare contribution of pathogenic mutations and relatively common risk factors. The rapid increase in the reported cases of DLB highlights the need for an easy, efficient and accurate diagnosis of the disease in its initial stages in order to halt or delay the progression. The currently used diagnostic methods proposed by the International DLB consortium rely on a list of criteria that comprises both clinical observations and the use of biomarkers. Herein, we summarize the up-to-now reported knowledge on the genetic architecture of DLB and discuss the use of prodromal biomarkers as well as recent promising candidates from alternative body fluids and new imaging techniques.

Cerebrospinal Fluid Biomarkers of Alzheimer's Disease: Current Evidence and Future Perspectives

Alzheimer's disease is a progressive, clinically heterogeneous, and particularly complex neurodegenerative disease characterized by a decline in cognition. Over the last two decades, there has been significant growth in the investigation of cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease. This review presents current evidence from many clinical neurochemical studies, with findings that attest to the efficacy of existing core CSF biomarkers such as total tau, phosphorylated tau, and amyloid-β (Aβ42), which diagnose Alzheimer's disease in the early and dementia stages of the disorder. The heterogeneity of the pathophysiology of the late-onset disease warrants the growth of the Alzheimer's disease CSF biomarker toolbox; more biomarkers showing other aspects of the disease mechanism are needed. This review focuses on new biomarkers that track Alzheimer's disease pathology, such as those that assess neuronal injury (VILIP-1 and neurofilament light), neuroinflammation (sTREM2, YKL-40, osteopontin, GFAP, progranulin, and MCP-1), synaptic dysfunction (SNAP-25 and GAP-43), vascular dysregulation (hFABP), as well as CSF α-synuclein levels and TDP-43 pathology. Some of these biomarkers are promising candidates as they are specific and predict future rates of cognitive decline. Findings from the combinations of subclasses of new Alzheimer's disease biomarkers that improve their diagnostic efficacy in detecting associated pathological changes are also presented.

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.

Single-molecule studies of amyloid proteins: from biophysical properties to diagnostic perspectives

In neurodegenerative diseases, a wide range of amyloid proteins or peptides such as amyloid-beta and α-synuclein fail to keep native functional conformations, followed by misfolding and self-assembling into a diverse array of aggregates. The aggregates further exert toxicity leading to the dysfunction, degeneration and loss of cells in the affected organs. Due to the disordered structure of the amyloid proteins, endogenous molecules, such as lipids, are prone to interact with amyloid proteins at a low concentration and influence amyloid cytotoxicity. The heterogeneity of amyloid proteinscomplicates the understanding of the amyloid cytotoxicity when relying only on conventional bulk and ensemble techniques. As complementary tools, single-molecule techniques (SMTs) provide novel insights into the different subpopulations of a heterogeneous amyloid mixture as well as the cytotoxicity, in particular as involved in lipid membranes. This review focuses on the recent advances of a series of SMTs, including single-molecule fluorescence imaging, single-molecule force spectroscopy and single-nanopore electrical recording, for the understanding of the amyloid molecular mechanism. The working principles, benefits and limitations of each technique are discussed and compared in amyloid protein related studies.. We also discuss why SMTs show great potential and are worthy of further investigation with feasibility studies as diagnostic tools of neurodegenerative diseases and which limitations are to be addressed.

Cerebrospinal fluid levels of alpha-synuclein, amyloid β, tau, phosphorylated tau, and neuron-specific enolase in patients with Parkinson's disease, dementia with Lewy bodies or other neurological disorders: Their relationships with cognition and nuclear medicine imaging findings

Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are common neurodegenerative disorders, but no established biochemical markers for these diseases have been identified. We enrolled 78 subjects (27 patients with PD/DLB, 34 patients with non-PD/DLB neurodegenerative disorders [non-PD/DLB], and 17 controls). Cerebrospinal fluid (CSF) was collected via the standard lumbar puncture technique. The CSF levels of alpha-synuclein, amyloid β40, amyloid β42, tau, phosphorylated tau (p-tau), neuron-specific enolase (NSE), and hemoglobin were measured with enzyme-linked immunosorbent assays. Dopamine transporter imaging with ¹²³I-ioflupane was also performed. The PD/DLB patients exhibited significantly lower CSF alpha-synuclein levels than non-PD/DLB group. Significantly elevated CSF levels of tau, p-tau, and NSE were detected in the non-PD/DLB group. Multivariate analysis revealed that the mini-mental state examination score was correlated with the CSF amyloid β42 level. The specific binding ratio on ¹²³I-ioflupane imaging was decreased in the PD/DLB group, but it was not correlated with the CSF alpha-synuclein level. These results indicate that (1) the CSF alpha-synuclein level is a useful biomarker of PD/DLB; (2) the CSF levels of tau, p-tau, and NSE can be used to discriminate PD/DLB from non-PD/DLB; and (3) the CSF amyloid β42 level is an independent predictor of cognitive decline in neurological disorders.

Diagnostic accuracy of DAT-SPECT and MIBG scintigraphy for dementia with Lewy bodies: an updated systematic review and Bayesian latent class model meta-analysis

PURPOSE

Imperfect clinical reference standards can preclude accurately estimating the diagnostic accuracy of DAT-SPECT and MIBG myocardial scintigraphy for diagnosing DLB. To investigate the validity of unadjusted accuracy, we updated our previous meta-analysis.

METHODS

Literature search was updated to March 18, 2018. We also examined published systematic review reports. Two investigators extracted data and rated study validity using the QUADAS-2 tool. We performed a Bayesian latent class model meta-analysis accounting for imperfect reference standards.

RESULTS

We evaluated 27 studies including 2236 patients. With the exception of two DAT-SPECT studies that involved postmortem neuropathological verification, studies were susceptible to bias from imperfect reference standards. Compared with the unadjusted accuracy estimates, the adjusted sensitivity values were similar, whereas the adjusted specificity values were generally lower for detecting α-synuclein pathology in the brain. The adjusted summary sensitivity and specificity were 0.86 (95% credible interval [CrI], 0.76-0.95) and 0.81 (CrI, 0.70-0.92), and 0.93 (CrI, 0.74-1.00) and 0.75 (CI, 0.47-0.94) for visual and semi-quantitative assessments of DAT-SPECT, respectively; 0.92 (CrI, 0.81-0.99) and 0.80 (CrI, 0.67-0.93), and 0.87 (CrI, 0.74-0.98) and 0.80 (CrI, 0.69-0.93), for delayed- and early-phase scans of MIBG scintigraphy, respectively. When diagnosing the typical clinical syndrome, the adjusted accuracy values were similar to the unadjusted estimates. The adjusted sensitivity and specificity were 0.89 (CrI, 0.75-0.98) and 0.87 (CrI, 0.72-0.97), and 0.97 (CrI, 0.78-1.0) and 0.70 (CrI, 0.43-0.92) for visual and semi-quantitative assessments of DAT-SPECT, respectively; and 0.93 (CrI, 0.81-0.98) and 0.90 (CrI, 0.73-0.97), and 0.85 (CrI, 0.66-0.96) and 0.96 (95% CI, 0.83-1.0) for delayed- and early-phase scans of MIBG scintigraphy, respectively.

CONCLUSIONS

In our adjusted analyses, both imaging biomarkers had high diagnostic accuracy for detecting the hallmark pathology in the brain and for diagnosing the typical clinical syndrome.

Increased Serum Levels of α-Synuclein in Patients With Major Depressive Disorder

OBJECTIVE

Epidemiologic studies have demonstrated that depression is a risk factor for dementia. In particular, dementia with Lewy bodies (DLB) has been noted to be highly relevant to depression. It has been suggested that α-synuclein (α-syn), a major component of Lewy bodies, is related to the onset and progression of DLB. To investigate the relationship between depression and DLB, we compared serum α-syn levels of patients with depression to those of healthy subjects.

METHODS

The subjects were 103 inpatients with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), or DSM-5 major depressive disorder (MDD) and 132 healthy comparisons. Patients were recruited from Juntendo Koshigaya Hospital, Saitama, Japan, between June 2010 and November 2016. Serum α-syn levels were measured using an enzyme-linked immunosorbent assay kit. Serum α-syn levels were compared using a 2 (age group [<60 years versus ≥60 years]) × 2 (diagnosis [MDD versus comparison]) analysis of variance.

RESULTS

There was no significant main effect of age (F = 1.167, df = 1, 231, p = 0.281). There was a significant main effect of diagnosis (F = 44.657, df = 1, 231, p <0.001), with higher α-syn levels in the MDD group versus the healthy comparison group, regardless of age.

CONCLUSION

The present results suggest that depression may affect the metabolism of α-syn; there is a possibility that depression is not only a prodromal symptom of DLB but also a causal risk factor for DLB.

123I-MIBG scintigraphy utility and cut-off value in a clinically representative dementia cohort

OBJECTIVE

To determine the utility of ¹²³I-metaiodobenzylguanidine cardiac scintigraphy (MIBG), and optimum heart: mediastinum ratio (HMR) for differentiating dementia with Lewy bodies (DLB) from Alzheimer's disease (AD) in a clinically representative population, comparing findings with those of ¹²³I-2β -carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (FP-CIT) SPECT.

METHODS

We recruited subjects with probable DLB (n = 17) and probable AD (n = 16) from clinical services. Each participant underwent clinical examination, cardiac MIBG scintigraphy and FP-CIT SPECT. Diagnosis was made on the basis of clinical symptoms using validated criteria. Cardiac MIBG uptake was measured by the planar HMR, blind to clinical diagnosis, with values below a cut-off taken from a previous study (<2.2 at four hours) defining scans as abnormal. FP-CIT scans were blindly rated according to a visual rating scale.

RESULTS

MIBG had a sensitivity, specificity and overall accuracy of 71%, 81% and 76% for distinguishing DLB from AD. FP-CIT demonstrated a sensitivity, specificity and accuracy of 82%, 88% and 85%. Using a lower HMR cut-off to distinguish between abnormal and normal MIBG scans improved the accuracy of MIBG, raising specificity (100%) and overall accuracy (85%) without compromising sensitivity (71%). Neither prescription of potentially interfering medications, nor a history of myocardial infarction (MI), had a significant effect on HMR.

CONCLUSION

We found that MIBG did not demonstrate superior sensitivity and overall accuracy to FP-CIT. HMR cut-off influences biomarker utility, and clinical and Caucasian populations may require a lower cut-off than those reported elsewhere. Future MIBG studies should include clinically representative cohorts as neither medications nor previous MI appear to influence HMR.

Brain Atrophy of Secondary REM-Sleep Behavior Disorder in Neurodegenerative Disease

BACKGROUND

Rapid eye movement sleep behavior disorder (RBD) may present as an early manifestation of an evolving neurodegenerative disorder with alpha-synucleinopathy.

OBJECTIVE

We investigated that dementia with RBD might show distinctive cortical atrophic patterns.

METHODS

A total of 31 patients with idiopathic Parkinson's disease (IPD), 23 with clinically probable Alzheimer's disease (AD), and 36 healthy controls participated in this study. Patients with AD and IPD were divided into two groups according to results of polysomnography and rated with a validated Korean version of the RBD screening questionnaire (RBDSQ-K), which covers the clinical features of RBD. Voxel-based morphometry was adapted for detection of regional brain atrophy among groups of subjects.

RESULTS

Scores on RBDSQ-K were higher in the IPD group (3.54 ± 2.8) than in any other group (AD, 2.94 ± 2.4; healthy controls, 2.31 ± 1.9). Atrophic changes according to RBDSQ-K scores were characteristically in the posterior part of the brain and brain stem, including the hypothalamus and posterior temporal region including the hippocampus and bilateral occipital lobe. AD patients with RBD showed more specialized atrophic patterns distributed in the posterior and inferior parts of the brain including the bilateral temporal and occipital cortices compared to groups without RBD. The IPD group with RBD showed right temporal cortical atrophic changes.

CONCLUSION

The group of patients with neurodegenerative diseases and RBD showed distinctive brain atrophy patterns, especially in the posterior and inferior cortices. These results suggest that patients diagnosed with clinically probable AD or IPD might have mixed pathologies including α-synucleinopathy.

A new potential biomarker for dementia with Lewy bodies

Objective:

To investigate whether (1) phosphorylated α-synuclein (p-syn) deposits in skin nerves could be useful in differentiating dementia with Lewy bodies (DLB) from different forms of dementia and (2) small fiber neuropathy (SFN) is associated with DLB.

Methods:

We studied 18 well-characterized patients with DLB (11 with autonomic dysfunction), 23 patients with nonsynucleinopathy dementia (NSD; 13 with young-onset Alzheimer disease dementia, 6 frontotemporal dementia, and 4 vascular dementia), and 25 healthy controls. All participants underwent skin biopsies from proximal (i.e., cervical) and distal (i.e., thigh and distal leg) sites to study small nerve fibers and deposits of p-syn, considered the pathologic form of α-synuclein.

Results:

No p-syn was detected in any skin sample in patients with NSD and controls but was found in all patients with DLB. SFN was found in patients with DLB and the autonomic denervation of skin was more severe in patients with autonomic dysfunctions.

Conclusions:

(1) In autonomic skin nerves, p-syn is a sensitive biomarker for DLB diagnosis, helping to differentiate DLB from other forms of dementia, although this needs to be confirmed in a larger, more representative sample; and (2) skin autonomic neuropathy is part of the DLB pathology and may contribute to autonomic symptoms.

Classification of evidence:

This study provides Class III evidence that p-syn in skin nerve fibers on skin biopsy accurately distinguishes DLB from other forms of dementia.

Single-Molecule Imaging of Individual Amyloid Protein Aggregates in Human Biofluids

The misfolding and aggregation of proteins into amyloid fibrils characterizes many neurodegenerative disorders such as Parkinson’s and Alzheimer’s diseases. We report here a method, termed SAVE (single aggregate visualization by enhancement) imaging, for the ultrasensitive detection of individual amyloid fibrils and oligomers using single-molecule fluorescence microscopy. We demonstrate that this method is able to detect the presence of amyloid aggregates of α-synuclein, tau, and amyloid-β. In addition, we show that aggregates can also be identified in human cerebrospinal fluid (CSF). Significantly, we see a twofold increase in the average aggregate concentration in CSF from Parkinson’s disease patients compared to age-matched controls. Taken together, we conclude that this method provides an opportunity to characterize the structural nature of amyloid aggregates in a key biofluid, and therefore has the potential to study disease progression in both animal models and humans to enhance our understanding of neurodegenerative disorders.

The utility of α-synuclein as biofluid marker in neurodegenerative diseases: a systematic review of the literature

The discovery of α-synuclein (α-syn) as a major component of Lewy bodies, neuropathological hallmark of Parkinson's disease (PD), dementia with Lewy bodies and of glial inclusions in multiple system atrophy initiated the investigation of α-syn as a biomarker in cerebrospinal fluid (CSF). Due to the involvement of the periphery in PD the quantification of α-syn in peripheral fluids such as serum, plasma and saliva has been investigated as well. We review how the development of multiple assays for the quantification of α-syn has yielded novel insights into the variety of α-syn species present in the different fluids; the optimal preanalytical conditions required for robust quantification and the potential clinical value of α-syn as biomarker. We also suggest future approaches to use of CSF α-syn in neurodegenerative diseases.

Induction of α-synuclein aggregate formation by CSF exosomes from patients with Parkinson's disease and dementia with Lewy bodies

Extracellular α-synuclein has been proposed as a crucial mechanism for induction of pathological aggregate formation in previously healthy cells. In vitro, extracellular α-synuclein is partially associated with exosomal vesicles. Recently, we have provided evidence that exosomal α-synuclein is present in the central nervous system in vivo. We hypothesized that exosomal α-synuclein species from patients with α-synuclein related neurodegeneration serve as carriers for interneuronal disease transmission. We isolated exosomes from cerebrospinal fluid from patients with Parkinson's disease, dementia with Lewy bodies, progressive supranuclear palsy as a non-α-synuclein related disorder that clinically overlaps with Parkinson's disease, and neurological controls. Cerebrospinal fluid exosome numbers, α-synuclein protein content of cerebrospinal fluid exosomes and their potential to induce oligomerization of α-synuclein were analysed. The quantification of cerebrospinal fluid exosomal α-synuclein showed distinct differences between patients with Parkinson's disease and dementia with Lewy bodies. In addition, exosomal α-synuclein levels correlated with the severity of cognitive impairment in cross-sectional samples from patients with dementia with Lewy bodies. Importantly, cerebrospinal fluid exosomes derived from Parkinson's disease and dementia with Lewy bodies induce oligomerization of α-synuclein in a reporter cell line in a dose-dependent manner. Our data suggest that cerebrospinal fluid exosomes from patients with Parkinson's disease and dementia with Lewy bodies contain a pathogenic species of α-synuclein, which could initiate oligomerization of soluble α-synuclein in target cells and confer disease pathology.

Microarray Expression Analysis for the Paradoxical Roles of Acanthopanax senticosus Harms in Treating α-Synucleinopathies

α-Synuclein is a key player in the pathogenesis of neurodegenerative disorders with Lewy bodies. Our previous studies have also showed that Acanthopanax senticosus harms (AS) could significantly suppress α-synuclein overexpression and toxicity. Identifying the RNAs related to α-synucleinopathies may facilitate understanding the pathogenesis of the diseases and the safe application of AS in the clinic. Microarray expression profiling of long non-coding RNAs (lncRNAs) and mRNAs was undertaken in control non-transgenic and human α-synuclein transgenic mice. The effects of AS on central nervous system (CNS) in pathology and physiology were investigated based on the lncRNA/mRNA targets analysis. In total, 341 lncRNAs and 279 mRNAs were differentially expressed by α-synuclein stimulus, among which 29 lncRNAs and 25 mRNAs were involved in the anti-α-synucleinopathies mechanism of AS. However, the levels of 19/29 lncRNAs and 12/25 mRNAs in AS group were similar to those in α-synuclein group, which may cause potential neurotoxicity analogous to α-synuclein. This study demonstrated that some of lncRNAs/mRNAs were involved in α-synuclein related pathophysiology, and AS produced the bidirectional effects on CNS under pathological and physiological conditions.

Cerebrospinal fluid levels of IL-6 are decreased and correlate with cognitive status in DLB patients

Introduction

Inflammatory processes have previously been shown to influence cognition and progression of dementia. An involvement of interleukin (IL)-6 has in particular been suggested as altered levels of IL-6 in cerebrospinal fluid (CSF) have been found in patients with Alzheimer’s disease (AD). Also, an association between cognitive decline and levels of IL-6 in CSF have been reported. The aim of the present study was to investigate whether patients clinically diagnosed with dementia with Lewy bodies (DLB) display altered CSF IL-6 levels in comparison with patients with AD and control subjects without dementia and whether the IL-6 levels are correlated with cognitive status and biomarkers for AD and synucleinopathy.

Methods

To analyse CSF of patients with AD (n = 45), patients with DLB (n = 29) and control subjects without dementia (n = 36), we used immunoassays to measure levels of IL-6 (multiplex electrochemiluminescence); AD markers phosphorylated tau, total tau and amyloid-β_1–42 (enzyme-linked immunosorbent assay [ELISA]); and α-synuclein (ELISA). Cognitive status was evaluated using the Mini Mental State Examination (MMSE).

Results

Our analysis showed significantly lower levels of IL-6 in CSF from patients with DLB than in CSF from patients with AD and control subjects without dementia. The IL-6 levels were also negatively correlated with MMSE and positively correlated with α-synuclein CSF levels.

Conclusions

Our findings support previous studies by demonstrating a link between inflammatory processes and dementia progression and further strengthen the hypothesis that IL-6 is involved in dementia pathology and cognitive decline.

Use of CSF α-synuclein in the differential diagnosis between Alzheimer's disease and other neurodegenerative disorders

BACKGROUND

The etiology and pathogenesis of neurodegenerative disorders has yet to be elucidated, so their differential diagnosis is a challenge. This is especially true in differentiating Alzheimer's disease (AD), dementia with Lewy bodies (DLB), Parkinson disease (PD), and multiple system atrophy (MSA).

METHODS

A total of 11 eligible articles were identified by search of electronic databases including PubMed, Springer Link, Elsevier, and the Cochrane Library, up to June 2014. In meta-analyses, standardized mean differences (SMD), with 95% confidence intervals (CI), comparing cerebrospinal fluid (CSF) measures of α-synuclein between the above conditions were calculated using random-effects models.

RESULTS

CSF α-synuclein concentrations were significantly higher in AD compared to DLB [SMD: 0.32, 95% CI: (0.02, 0.62), z = 2.07, P = 0.038]; PD [SMD: 0.87, 95% CI: (0.15, 1.58), z = 2.38, P = 0.017]; or MSA [SMD: 1.14, 95% CI: (0.15, 2.14), z = 2.25, P = 0.025]. However, no significant difference was found between patients with AD and neurological cognitively normal controls [SMD: 0.02, 95% CI: (-0.21, 0.24), z = 0.13, P = 0.894].

CONCLUSIONS

Results of these meta-analysis suggest that quantification of CSF α-synuclein could help distinguish AD from other neurodegenerative disorders such as DLB, PD, or MSA.

How many biomarkers to discriminate neurodegenerative dementia?

A number of cerebrospinal fluid (CSF) biomarkers are currently used for the diagnosis of dementia. Opposite changes in the level of amyloid-β(1-42) versus total tau and phosphorylated-tau181 in the CSF reflect the specific pathology of Alzheimer's disease (AD) in the brain. This panel of biomarkers has proven to be effective to differentiate AD from controls and from the major types of neurodegenerative dementia, and to evaluate the progression from mild cognitive impairment to AD. In the absence of specific biomarkers reflecting the pathologies of the other most common forms of dementia, such as Lewy Body disease, Frontotemporal lobar degeneration, Creutzfeldt-Jakob disease, etc., the evaluation of biomarkers of AD pathology is used, attempting to exclude rather than to confirm AD. Other biomarkers included in the common clinical practice do not clearly relate to the underlying pathology: progranulin (PGRN) is a selective marker of frontotemporal dementia with mutations in the PGRN gene; the 14-3-3 protein is a highly sensitive and specific marker for Creutzfeldt-Jakob disease, but has to be used carefully in differentiating rapid progressive dementia; and α-synuclein is an emerging candidate biomarker of the different forms of synucleinopathy. This review summarizes several biomarkers of neurodegenerative dementia validated based on the neuropathological processes occurring in brain tissue. Notwithstanding the paucity of pathologically validated biomarkers and their high analytical variability, the combinations of these biomarkers may well represent a key and more precise analytical and diagnostic tool in the complex plethora of degenerative dementia.

Utility of the combination of DAT SPECT and MIBG myocardial scintigraphy in differentiating dementia with Lewy bodies from Alzheimer's disease

Purpose

¹²³I-2β-Carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (¹²³I-FP-CIT) dopamine transporter single photon emission computed tomography (DAT SPECT) and ¹²³I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy can be used to assist in the diagnosis of patients with dementia with Lewy bodies (DLB). We compared the diagnostic value of these two methods in differentiating DLB from Alzheimer’s disease (AD). Furthermore, we evaluated whether a combination of DAT SPECT and MIBG myocardial scintigraphy would provide a more useful means of differentiating between DLB and AD.

Methods

Patients with AD (n = 57) and patients with DLB (n = 76) who underwent both DAT SPECT and MIBG myocardial scintigraphy were enrolled. The sensitivity, specificity, and accuracy of both methods as well as their combination for differentiating DLB from AD were calculated. Moreover, we examined whether symptoms of the patients with DLB were associated with the patterns of the abnormalities displayed on DAT SPECT and MIBG myocardial scintigraphy.

Results

The sensitivity and specificity of differentiating DLB from AD were 72.4 and 94.4 % by the heart to mediastinum ratio of MIBG uptake, 88.2 and 88.9 % by the specific binding ratio on DAT SPECT, and 96.1 and 90.7 % by their combination, respectively. The combined use of DAT SPECT and MIBG myocardial scintigraphy enabled more accurate differentiation between DLB and AD compared with either DAT SPECT or MIBG myocardial scintigraphy alone. There was a significantly higher frequency of parkinsonism in the abnormal DAT SPECT group than the normal DAT SPECT group. On the other hand, there was a higher frequency of the appearance of rapid eye movement (REM) sleep behavior disorder in the abnormal MIBG uptake group than the normal MIBG uptake group.

Conclusion

These results suggested that using a combination of these scintigraphic methods is a useful and practical approach to differentiate DLB from AD.

Validation of a quantitative cerebrospinal fluid alpha-synuclein assay in a European-wide interlaboratory study

Decreased levels of alpha-synuclein (aSyn) in cerebrospinal fluid (CSF) in Parkinson's disease and related synucleinopathies have been reported, however, not consistently in all cross-sectional studies. To test the performance of one recently released human-specific enzyme-linked immunosorbent assay (ELISA) for the quantification of aSyn in CSF, we carried out a round robin trial with 18 participating laboratories trained in CSF ELISA analyses within the BIOMARKAPD project in the EU Joint Program - Neurodegenerative Disease Research. CSF samples (homogeneous aliquots from pools) and ELISA kits (one lot) were provided centrally and data reported back to one laboratory for data analysis. Our study showed that although factors such as preanalytical sample handling and lot-to-lot variability were minimized by our study design, we identified high variation in absolute values of CSF aSyn even when the same samples and same lots of assays were applied. We further demonstrate that although absolute concentrations differ between laboratories the quantitative results are comparable. With further standardization this assay may become an attractive tool for comparing aSyn measurements in diverse settings. Recommendations for further validation experiments and improvement of the interlaboratory results obtained are given.

Delirium and dementia with Lewy bodies: distinct diagnoses or part of the same spectrum?

Dementia with Lewy bodies (DLB) is recognised as the second most common form of dementia in older people. Delirium is a condition of acute brain dysfunction for which a pre-existing diagnosis of dementia is a risk factor. Conversely delirium is associated with an increased risk of developing dementia. The reasons for this bidirectional relationship are not well understood. Our aim was to review possible similarities in the clinical presentation and pathophysiology between delirium and DLB, and explore possible links between these diagnoses. A systematic search using Medline, Embase and Psychinfo was performed. References were scanned for relevant articles, supplemented by articles identified from reference lists and those known to the authors. 94 articles were selected for inclusion in the review. Delirium and DLB share a number of clinical similarities, including global impairment of cognition, fluctuations in attention and perceptual abnormalities. Delirium is a frequent presenting feature of DLB. In terms of pathophysiological mechanisms, cholinergic dysfunction and genetics may provide a common link. Neuroimaging studies suggest a brain vulnerability in delirium which may also occur in dementia. The basal ganglia, which play a key role in DLB, have also been implicated in delirium. The role of Cerebrospinal fluid (CSF) and serum biomarkers for both diagnoses is an interesting area although some results are conflicting and further work in this area is needed. Delirium and DLB share a number of features and we hypothesise that delirium may, in some cases, represent early or 'prodromal' DLB. Further research is needed to test the novel hypothesis that delirium may be an early marker for future DLB, which would aid early diagnosis of DLB and identify those at high risk.

Cerebrospinal fluid biomarkers in trials for Alzheimer and Parkinson diseases

Alzheimer disease (AD) and Parkinson disease (PD) are the most common neurodegenerative disorders. For both diseases, early intervention is thought to be essential to the success of disease-modifying treatments. Cerebrospinal fluid (CSF) can reflect some of the pathophysiological changes that occur in the brain, and the number of CSF biomarkers under investigation in neurodegenerative conditions has grown rapidly in the past 20 years. In AD, CSF biomarkers are increasingly being used in clinical practice, and have been incorporated into the majority of clinical trials to demonstrate target engagement, to enrich or stratify patient groups, and to find evidence of disease modification. In PD, CSF biomarkers have not yet reached the clinic, but are being studied in patients with parkinsonism, and are being used in clinical trials either to monitor progression or to demonstrate target engagement and downstream effects of drugs. CSF biomarkers might also serve as surrogate markers of clinical benefit after a specific therapeutic intervention, although additional data are required. It is anticipated that CSF biomarkers will have an important role in trials aimed at disease modification in the near future. In this Review, we provide an overview of CSF biomarkers in AD and PD, and discuss their role in clinical trials.

Detection of disease-associated α-synuclein in the cerebrospinal fluid: a feasibility study

With the aim to evaluate the significance and reliability of detecting disease-specific α-synuclein in the cerebrospinal fluid (CSF) we developed an ELISA and bead-assay. We used a commercial antibody (5G4) that does not bind to the physiological monomeric form of α-synuclein, but is highly specific for the disease-associated forms, including high molecular weight fraction of β-sheet rich oligomers. We applied both tests in CSF from a series of neuropathologically confirmed α-synucleinopathy cases, including Parkinson’s disease dementia (PDD) and dementia with Lewy bodies (DLB) (n = 7), as well as Alzheimer’s disease (n = 6), and control patients without neurodegenerative pathologies (n = 9). Disease-specific α-synuclein was detectable in the CSF in a subset of patients with α-synuclein pathology in the brain. When combined with the analysis of total α-synuclein, the bead-assay for disease-specific α-synuclein was highly specific for PDD/DLB. Detection of disease-associated α-synuclein combined with the total levels of α-synuclein is a promising tool for the in-vivo diagnosis of α-synucleinopathies, including PDD and LBD.

Cerebrospinal fluid biomarkers in parkinsonian conditions: an update and future directions

Parkinsonian diseases comprise a heterogeneous group of neurodegenerative disorders, which show significant clinical and pathological overlap. Accurate diagnosis still largely relies on clinical acumen; pathological diagnosis remains the gold standard. There is an urgent need for biomarkers to diagnose parkinsonian disorders, particularly in the early stages when diagnosis is most difficult. In this review, several of the most promising cerebrospinal fluid candidate markers will be discussed. Their strengths and limitations will be considered together with future developments in the field.

Assessment of CSF Aβ42 as an aid to discriminating Alzheimer's disease from other dementias and mild cognitive impairment: a meta-analysis of 50 studies

Mild Alzheimer's disease (AD) is usually difficult to differentiate from other dementias or mild cognitive impairment (MCI). The aim of our study is to evaluate the clinical importance of cerebrospinal fluid (CSF) β-amyloid 42 (Aβ42) in MCI, AD and other dementias, more specifically: frontotemporal dementia (FTD), dementia with Lewy bodies (DLB), Parkinson's disease (PD) with dementia (PDD) and vascular dementia (VaD). Fifty eligible articles were identified by search of databases including PubMed, EMBASE, Elsevier, Springer Link and the Cochrane Library, from January 1990 to May 2014. The random effects model was used to calculate the standardized mean difference (SMD) with corresponding 95% CI by STATA 9.0 software. The subgroup analyses were made on the method (ELISA, xMAP). We found that CSF Aβ42 concentrations were significantly lower in AD compared to MCI (SMD: -0.68, 95% CI: [-0.80, -0.56], z=11.34, P<0.001), FTD (SMD: -1.09, 95% CI: [-1.41, -0.76], z=6.62, P<0.001), PDD (SMD: -0.75, 95% CI: [-1.39, -0.10], z=2.27, P=0.023), VaD (SMD: -0.95, 95% CI: [-1.30, -0.61], z=5.43, P<0.001). In addition, compared to DLB, Aβ42 concentrations are moderately lower in AD (SMD: -0.27, 95% CI: [-0.51, -0.03], z=2.20, P=0.028). Results from this meta-analysis hinted that CSF Aβ42 is a good biomarker for discriminating Alzheimer's disease from other dementias and MCI.

Does CSF p-tau181 help to discriminate Alzheimer's disease from other dementias and mild cognitive impairment? A meta-analysis of the literature

To evaluate the clinical importance of cerebrospinal fluid (CSF) phosphorylated tau 181 (p-tau181) in mild cognitive impairment (MCI), Alzheimer's disease (AD) and other dementias, more specifically: frontotemporal degeneration (FTD), dementia with Lewy bodies (DLB), vascular dementia (VaD) and Parkinson's disease (PD) with dementia (PDD). Fifty eligible articles were identified by search of databases including PubMed, EMBASE, Elsevier, Springer Link and the Cochrane Library, up to December 2013. The random effects model was used to calculate the standardized mean difference (SMD) with corresponding 95% CI by STATA 9.0 software. The subgroup analyses were made on the methods or PD with dementia. We found that CSF p-tau181 concentrations were significantly higher in AD compared to MCI [SMD: 0.61, 95% CI: (0.46, 0.76), z = 8.07, P < 0.001], FTD [SMD: 1.23, 95% CI: (0.89, 1.56), z = 7.19, P < 0.001], DLB [SMD: 1.08, 95% CI: (0.80, 1.37), z = 7.41, P < 0.001], PDD [SMD: 1.05, 95% CI: (0.02, 2.07), z = 2.00, P = 0.045] and VaD [SMD: 1.28, 95% CI: (0.68, 1.88), z = 4.19, P < 0.001]. Results from this meta-analysis implied that CSF p-tau181 is a good biomarker for discriminating Alzheimer's disease from other dementias and mild cognitive impairment.

Levels of cerebrospinal fluid α-synuclein oligomers are increased in Parkinson's disease with dementia and dementia with Lewy bodies compared to Alzheimer's disease

Introduction

The objective was to study whether α-synuclein oligomers are altered in the cerebrospinal fluid (CSF) of patients with dementia, including Parkinson disease with dementia (PDD), dementia with Lewy bodies (DLB), and Alzheimer disease (AD), compared with age-matched controls.

Methods

In total, 247 CSF samples were assessed in this study, including 71 patients with DLB, 30 patients with PDD, 48 patients with AD, and 98 healthy age-matched controls. Both total and oligomeric α-synuclein levels were evaluated by using well-established immunoassays.

Results

The levels of α-synuclein oligomers in the CSF were increased in patients with PDD compared with the controls (P < 0.05), but not in patients with DLB compared with controls. Interestingly, the levels of α-synuclein oligomers in the CSF were also significantly higher in patients with PDD (P < 0.01) and DLB (P < 0.05) compared with patients with AD. The levels of CSF α-synuclein oligomers and the ratio of oligomeric/total-α-synuclein could distinguish DLB or PDD patients from AD patients, with areas under the curves (AUCs) of 0.64 and 0.75, respectively. In addition, total-α-synuclein alone could distinguish DLB or PDD patients from AD patients, with an AUC of 0.80.

Conclusions

The levels of α-synuclein oligomers were increased in the CSF from α-synucleinopathy patients with dementia compared with AD cases.

Differential role of CSF alpha-synuclein species, tau, and Aβ42 in Parkinson's Disease

There is a great interest in developing cerebrospinal fluid (CSF) biomarkers for diagnosis and prognosis of Parkinson's disease (PD). CSF alpha synuclein (α-syn) species, namely total and oligomeric α-syn (t-α-syn and o-α-syn), have shown to be of help for PD diagnosis. Preliminary evidences show that the combination of CSF t-α-syn and classical Alzheimer's disease (AD) biomarkers—β-amyloid 1–42 (Aβ₄₂), total tau (t-tau), phosphorylated tau (p-tau)—differentiate PD patients from controls, and that reduced levels of Aβ₄₂ represent a predictive factor for development of cognitive deterioration in PD. In this prospective study carried out in 44 PD patients and 25 neurological controls we wanted to verify whether the combination of CSF α-synuclein species—t-α-syn and o-α-syn—and classical AD biomarkers may help in differentiating PD from neurological controls, and if these biomarkers may predict cognitive decline. The median of follow-up duration was 3 years (range: 2–6 years). Mini Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were used for monitoring cognitive changes along time, being administered once a year. Oligo/total α-syn ratio (o/t-α-syn ratio) confirmed its diagnostic value, significantly contributing to the discrimination of PD from neurological controls. A greater diagnostic accuracy was reached when combining o/t-α-syn and Aβ₄₂/tau ratios (Sens = 0.70, Spec = 0.84, AUC = 0.82; PPV = 0.89, NPV = 0.62, LR+ = 4.40, DOR = 12.52). Low CSF Aβ₄₂ level was associated with a higher rate of MMSE and MoCA decline, confirming its role as independent predictive factor for cognitive decline in PD. None of the other biomarkers assessed (t-tau, p-tau, t-α-syn and o-α-syn) showed to have prognostic value. We conclude that combination of CSF o/t-α-syn and Aβ₄₂/tau ratios improve the diagnostic accuracy of PD. PD patients showing low CSF Aβ₄₂ levels at baseline are more prone to develop cognitive decline.

Increased CSF α-synuclein levels in Alzheimer's disease: correlation with tau levels

BACKGROUND

Given the difficult clinical differential diagnosis between Alzheimer's disease (AD) and dementia with Lewy bodies (DLB), growing interest resulted in research on α-synuclein as a potential cerebrospinal fluid biomarker (CSF) for synucleinopathies.

METHODS

CSF α-synuclein-140 concentrations were determined by a prototype xMAP™ bead-based assay (Innogenetics NV, Belgium). In addition, CSF amyloid β1-42 (Aβ1-42), total tau (T-tau), and phosphorylated tau (P-tau181P) levels were determined.

RESULTS

CSF α-synuclein levels were higher in AD patients as compared with cognitively healthy controls (P=.019) and patients with synucleinopathies (P<.001). CSF α-synuclein levels were correlated with T-tau (P<.001) and P-tau181P (P<.001) levels in autopsy-confirmed AD patients. A diagnostic algorithm using α-synuclein and P-tau181P discriminated neuropathologically confirmed AD from DLB patients, resulting in sensitivity and specificity values of 85% and 81%, respectively.

CONCLUSION

Because CSF α-synuclein levels were significantly higher in AD as compared with synucleinopathies, α-synuclein might have a value as a biomarker for differential dementia diagnosis.

The diagnostic value of CSF α-synuclein in the differential diagnosis of dementia with Lewy bodies vs. normal subjects and patients with Alzheimer's disease

The detection of α-synuclein (α-syn) in the cerebrospinal fluid (CSF) of patients with synucleinopathy has yielded promising but inconclusive results. The aim of the present study was to determine the diagnostic value of α-syn as a biological marker for Dementia with Lewy bodies (DLB) vs. normal subjects and patients with Alzheimer’s disease (AD), after strict control of several recognized confounders. Sixteen patients with DLB, 18 patients with AD and 22 age- and sex-matched normal controls (CTRL) were recruited. The levels of total α-syn in CSF were measured using a novel enzyme-linked immunosorbent assay. There was a significant increase of CSF α-syn levels in DLB patients as compared to the CTRL and AD groups (P= 0.049 and 0.01 respectively). ROC analysis revealed that increased α-syn was 81.8% specific for the discrimination of DLB vs. CTRL and 90% vs. AD. However, sensitivity was lower (56.2 % and 50% respectively). These findings provide evidence for a possible diagnostic role of α-syn as a surrogate biomarker for DLB.

Emerging biomarkers in cognition

Knowledge of aging and dementia is rapidly evolving with the aim of identifying individuals in the earliest stages of disease processes. Biomarkers allow clinicians to show the presence of a pathologic process and resultant synapse dysfunction and neurodegeneration, even in the earliest stages. This article focuses on biomarkers for mild cognitive impairment caused by Alzheimer disease, structural magnetic resonance imaging, fluorodeoxyglucose positron emission tomography (PET) or single-photon emission computed tomography, and PET with dopamine ligands. Although these biomarkers are useful, several limitations exist. Several new biomarkers are emerging and a more biological characterization of underlying pathophysiologic spectra may become possible.

Alpha-synuclein post-translational modifications as potential biomarkers for Parkinson disease and other synucleinopathies

The development of novel therapies against neurodegenerative disorders requires the ability to detect their early, presymptomatic manifestations in order to enable treatment before irreversible cellular damage occurs. Precocious signs indicative of neurodegeneration include characteristic changes in certain protein levels, which can be used as diagnostic biomarkers when they can be detected in fluids such as blood plasma or cerebrospinal fluid. In the case of synucleinopathies, cerebrospinal alpha-synuclein (α-syn) has attracted great interest as a potential biomarker; however, there is ongoing debate regarding the association between cerebrospinal α-syn levels and neurodegeneration in Parkinson disease and synucleinopathies. Post-translational modifications (PTMs) have emerged as important determinants of α-syn's physiological and pathological functions. Several PTMs are enriched within Lewy bodies and exist at higher levels in α-synucleinopathy brains, suggesting that certain modified forms of α-syn might be more relevant biomarkers than the total α-syn levels. However, the quantification of PTMs in bodily fluids poses several challenges. This review describes the limitations of current immunoassay-based α-syn quantification methods and highlights how these limitations can be overcome using novel mass-spectrometry-based assays. In addition, we describe how advances in chemical synthesis, which have enabled the preparation of α-syn proteins that are site-specifically modified at single or multiple residues, can facilitate the development of more accurate assays for detecting and quantifying α-syn PTMs in health and disease.

The diagnostic utility of cerebrospinal fluid alpha-synuclein analysis in dementia with Lewy bodies - a systematic review and meta-analysis

BACKGROUND

Dementia with Lewy Bodies (DLB) can be difficult to distinguish clinically from other dementias.

OBJECTIVE

To investigate the diagnostic utility of CSF alpha-synuclein in differentiating between DLB and other dementias.

METHODS

Electronic databases were systematically searched for studies investigating reproducible alpha synuclein quantification methods. Random effects model was used to calculate weighted mean difference (WMD) and 95% confidence intervals between DLB and other groups.

RESULTS

A total of 13 studies, comprising 2728 patients were included. Mean CSF alpha-synuclein concentration was significantly lower in DLB patients compared to those with Alzheimers disease (AD) [WMD -0.24; 95% CI, -0.45, -0.03; p = 0.02]. No significant difference was found between patients with DLB compared to Parkinsons disease [WMD 0.05; 95% CI, -0.17, 0.28; p = 0.65] or other neurodegenerative conditions.

CONCLUSION

CSF alpha synuclein may be of diagnostic use in differentiating between DLB and AD. We propose several recommendations to guide better design of future studies.

Evaluation of annexin A5 as a biomarker for Alzheimer's disease and dementia with lewy bodies

Background: Alzheimer's disease (AD) differs from other forms of dementia in its relation to amyloid beta peptide (Aβ₄₂). Using a cell culture model we previously identified annexin A5, a Ca²⁺, and phospholipid binding protein, as an AD biomarker. Plasma level of annexin A5 was significantly higher in AD patients compared to that in a control group. On the other hand, AD has been identified to share a number of clinical and pathological features with Dementia with Lewy bodies (DLB). The present study was done to examine whether or not plasma annexin A5 is a specific marker for AD, when being compared with the levels of DLB patients. As Apolipoprotein E (ApoE) gene subtype ε4 (ApoE-ε4) has been noticed as the probable genetic factor for AD, we also examined and compared ApoE genotype in both AD and DLB.

Methods: Blood samples were obtained from 150 patients with AD (aged 77.6 ± 6.5 years), 50 patients of DLB (79.4 ± 5.0) and 279 community-dwelling healthy elderly individuals of comparable age and sex (75.6 ± 8.1). All AD patients met NINCDS-ADRDA criteria and all DLB patients were diagnosed as probable DLB according to the latest consensus diagnostic criteria. Quantification was done using the Chemiluminescent Enzyme Immunoassay (CLEIA) Technique (SphereLight assay) using the monoclonal antibodies against annexin A5. DNA genotyping of ApoE was performed by distinguishing unique combinations of Hha1 fragments of PCR-amplified genomic DNA products.

Results: The plasma level of annexin A5 was significantly higher in AD patients than in the healthy individuals (control) (P < 0.0001). The plasma annexin A5 level was also significantly higher in DLB patients than in the control group (P < 0.0001). From the ROC curves with plasma annexin A5 concentrations, the mean areas under the curve were 0.863 and 0.838 for the AD/control and DLB/control, respectively. The rate of ApoE4 carrier status and the frequency of the ε4 allele were significantly higher in AD or DLB than in control and there was no significant difference between AD and DLB.

Conclusions: These results suggest that both annexin A5 and ApoE4 are common markers for AD and DLB.

Cerebrospinal fluid biomarkers in Parkinson disease

Clinical diagnosis of Parkinson disease (PD) is difficult in early stages of disease, with high risk of misdiagnosis. The long preclinical phase of PD provides the possibility for early therapeutic intervention once disease-modifying therapies have been developed, but lack of biomarkers for early diagnosis and monitoring of disease progression represents a major obstacle to achievement of this goal. Accordingly, research efforts aimed at identification of novel biomarkers have been increasing in the past 5 years. Cerebrospinal fluid (CSF) is an accessible source of brain-derived proteins, which mirror molecular changes that take place in the CNS. In this Review, we discuss evidence from numerous studies that have focused on identification of candidate CSF biomarkers for PD. Notably, molecular pathways related to α-synuclein, tau and β-amyloid peptides have received considerable attention. CSF levels of the protein DJ-1 are also of interest, although further investigation of this candidate marker is required. These studies support the usefulness of a combination of various CSF biomarkers of PD to increase diagnostic accuracy during early phases of the disease, and to differentiate PD from other neurodegenerative disorders.

[Α-synuclein as a biomarker for early diagnosis of Parkinsonism]

Although α-synuclein protein (αS) aggregates from a monomer to assemblies such as oligomer, protofibril and mature fibril, the early intermediate aggregate, that is, oligomer has been considered to be most toxic species in recent reports. While it was reported that αS concentration in cerebrospinal fluid was decreased significantly in the patients with Parkinson's disease (PD) and dementia with Lewy bodies, there were reports that αS oligomer concentration was elevated in cerebrospinal fluid of PD patients. Moreover, it was supposed that αS oligomer concentration was also elevated in blood of PD patients. Further studies of αS in cerebrospinal fluid and blood would lead to establishment of the significance of αS as a biomarker for α-synucleinopathies including PD.