The Contribution of Tau, Amyloid-Beta and Alpha-Synuclein Pathology to Dementia in Lewy Body Disorders

Association of Plasma Amyloid, P-Tau, GFAP, and NfL With CSF, Clinical, and Cognitive Features in Patients With Dementia With Lewy Bodies

BACKGROUND AND OBJECTIVES

Plasma β-amyloid-1-42/1-40 (Aβ42/40), phosphorylated-tau (P-tau), glial fibrillary acidic protein (GFAP), and neurofilament light (NfL) have been widely examined in Alzheimer disease (AD), but little is known about their reflection of copathologies, clinical importance, and predictive value in dementia with Lewy bodies (DLB). We aimed to evaluate associations of these biomarkers with CSF amyloid, cognition, and core features in DLB.

METHODS

This cross-sectional multicenter cohort study with prospective component included individuals with DLB, AD, and healthy controls (HCs), recruited from 2002 to 2020 with an annual follow-up of up to 5 years, from the European-Dementia With Lewy Bodies consortium. Plasma biomarkers were measured by single-molecule array (Neurology 4-Plex E kit). Amyloid status was determined by CSF Aβ42 concentrations, and cognition was assessed by Mini-Mental State Examination (MMSE). Biomarker differences across groups, associations with amyloid status, and clinical core features were assessed by analysis of covariance. Associations with cognitive impairment and decline were assessed by linear regression and linear mixed-effects models.

RESULTS

In our cohort consisting of 562 individuals (HC n = 89, DLB n = 342, AD n = 131; 250 women [44.5%], mean [SD] age of 71 [8] years), sex distribution did not differ between groups. Patients with DLB were significantly older, and had less years of education and worse baseline cognition than HC, but not AD. DLB participants stratified for amyloid status differed significantly in plasma Aβ42/40 ratio (decreased in amyloid abnormal: β = -0.008, 95% CI -0.016 to -0.0003, p = 0.01) and P-tau (increased in amyloid abnormal, P-tau181: β = 0.246, 95% CI 0.011-0.481; P-tau231: β = 0.227, 95% CI 0.035-0.419, both p < 0.05), but not in GFAP (β = 0.068, 95% CI -0.018 to 0.153, p = 0.119), and NfL (β = 0.004, 95% CI -0.087 to 0.096, p = 0.923) concentrations. Higher baseline GFAP, NfL, and P-tau concentrations were associated with lower MMSE scores in DLB, and GFAP and NfL were associated with a faster cognitive decline (GFAP: annual change of -2.11 MMSE points, 95% CI -2.88 to -1.35 MMSE points, p < 0.001; NfL: annual change of -2.13 MMSE points, 95% CI -2.97 to -1.29 MMSE points, p < 0.001). DLB participants with parkinsonism had higher concentrations of NfL (β = 0.08, 95% CI 0.02-0.14, p = 0.006) than those without.

DISCUSSION

Our study suggests a possible utility of plasma Aβ42/40, P-tau181, and P-tau231 as a noninvasive biomarkers to assess amyloid copathology in DLB, and plasma GFAP and NfL as monitoring biomarkers for cognitive symptoms in DLB.

Neuropsychiatric symptoms profile and markers of Alzheimer disease-type pathology in patients with Lewy body dementias

BACKGROUND

To determine whether Lewy body dementia (LBD) patients with likely copathology of Alzheimer's disease (AD) exhibit greater neuropsychiatric symptom (NPS) compared to those without likely AD-type copathology.

METHODS

We enrolled 69 individuals diagnosed with Lewy body dementia (LBD), comprising both dementia with Lewy bodies (DLB) (n = 36) and Parkinson's disease dementia (PDD) (n = 33). These participants had accessible cerebrospinal fluid (CSF) markers related to Alzheimer's disease (AD) and cognitive data. We assessed CSF levels of β-amyloid 42 (Aβ42), phosphorylated tau (p-tau), and total tau (t-tau). Employing autopsy-validated CSF thresholds (t-tau/Aβ42 ratio > 0.3, n = 69), we categorized individuals into LBD with AD pathology (LBD + AD, n = 31) and LBD without apparent AD co-pathology (LBD - AD, n = 38). Moreover, the Hamilton Depression Scale (HAMD24), Hamilton Anxiety Scale (HAMA14), and Neuropsychiatric Inventory Questionnaire (NPI-Q) was used to assess the NPS. Spearman correlations were utilized to explore links between NPS and CSF marker profiles.

RESULTS

In terms of neuropsychiatric symptoms, LBD + AD patients demonstrated notably elevated levels of depressive symptoms (HAMD24) in comparison to LBD - AD patients (P < 0.001). However, based on PDD and DLB groups, no significant variations were noted in the neuropsychiatric symptoms(P＞0.05). Moreover, CSF-derived biomarkers of Aβ42, and t-tau/Aβ42 were also associated with HAMD24 total scores in the LBD + AD subsample (P < 0.05).

CONCLUSION

There is an association between AD pathological markers and the NPS of LBD. The biologically based classification of LBD may be more advantageous in elucidating clinical heterogeneity than clinically defined syndromes.

Neuroinflammation is associated with Alzheimer's disease co-pathology in dementia with Lewy bodies

BACKGROUND

Neuroinflammation and Alzheimer's disease (AD) co-pathology may contribute to disease progression and severity in dementia with Lewy bodies (DLB). This study aims to clarify whether a different pattern of neuroinflammation, such as alteration in microglial and astroglial morphology and distribution, is present in DLB cases with and without AD co-pathology.

METHODS

The morphology and load (% area of immunopositivity) of total (Iba1) and reactive microglia (CD68 and HLA-DR), reactive astrocytes (GFAP) and proteinopathies of alpha-synuclein (KM51/pser129), amyloid-beta (6 F/3D) and p-tau (AT8) were assessed in a cohort of mixed DLB + AD (n = 35), pure DLB (n = 15), pure AD (n = 16) and control (n = 11) donors in limbic and neocortical brain regions using immunostaining, quantitative image analysis and confocal microscopy. Regional and group differences were estimated using a linear mixed model analysis.

RESULTS

Morphologically, reactive and amoeboid microglia were common in mixed DLB + AD, while homeostatic microglia with a small soma and thin processes were observed in pure DLB cases. A higher density of swollen astrocytes was observed in pure AD cases, but not in mixed DLB + AD or pure DLB cases. Mixed DLB + AD had higher CD68-loads in the amygdala and parahippocampal gyrus than pure DLB cases, but did not differ in astrocytic loads. Pure AD showed higher Iba1-loads in the CA1 and CA2, higher CD68-loads in the CA2 and subiculum, and a higher astrocytic load in the CA1-4 and subiculum than mixed DLB + AD cases. In mixed DLB + AD cases, microglial load associated strongly with amyloid-beta (Iba1, CD68 and HLA-DR), and p-tau (CD68 and HLA-DR), and minimally with alpha-synuclein load (CD68). In addition, the highest microglial activity was found in the amygdala and CA2, and astroglial load in the CA4. Confocal microscopy demonstrated co-localization of large amoeboid microglia with neuritic and classic-cored plaques of amyloid-beta and p-tau in mixed DLB + AD cases.

CONCLUSIONS

In conclusion, microglial activation in DLB was largely associated with AD co-pathology, while astrocytic response in DLB was not. In addition, microglial activity was high in limbic regions, with prevalent AD pathology. Our study provides novel insights into the molecular neuropathology of DLB, highlighting the importance of microglial activation in mixed DLB + AD.

Basal forebrain integrity, cholinergic innervation and cognition in idiopathic Parkinson's disease

Most individuals with Parkinson's disease experience cognitive decline. Mounting evidence suggests this is partially caused by cholinergic denervation due to α-synuclein pathology in the cholinergic basal forebrain. Alpha-synuclein deposition causes inflammation, which can be measured with free water fraction, a diffusion MRI-derived metric of extracellular water. Prior studies have shown an association between basal forebrain integrity and cognition, cholinergic levels and cognition, and basal forebrain volume and acetylcholine, but no study has directly investigated whether basal forebrain physiology mediates the relationship between acetylcholine and cognition in Parkinson's disease. We investigated the relationship between these variables in a cross-sectional analysis of 101 individuals with Parkinson's disease. Cholinergic levels were measured using fluorine-18 fluoroethoxybenzovesamicol (18F-FEOBV) PET imaging. Cholinergic innervation regions of interest included the medial, lateral capsular and lateral perisylvian regions and the hippocampus. Brain volume and free water fraction were quantified using T1 and diffusion MRI, respectively. Cognitive measures included composites of attention/working memory, executive function, immediate memory and delayed memory. Data were entered into parallel mediation analyses with the cholinergic projection areas as predictors, cholinergic basal forebrain volume and free water fraction as mediators and each cognitive domain as outcomes. All mediation analyses controlled for age, years of education, levodopa equivalency dose and systolic blood pressure. The basal forebrain integrity metrics fully mediated the relationship between lateral capsular and lateral perisylvian acetylcholine and attention/working memory, and partially mediated the relationship between medial acetylcholine and attention/working memory. Basal forebrain integrity metrics fully mediated the relationship between medial, lateral capsular and lateral perisylvian acetylcholine and free water fraction. For all mediations in attention/working memory and executive function, the free water mediation was significant, while the volume mediation was not. The basal forebrain integrity metrics fully mediated the relationship between hippocampal acetylcholine and delayed memory and partially mediated the relationship between lateral capsular and lateral perisylvian acetylcholine and delayed memory. The volume mediation was significant for the hippocampal and lateral perisylvian models, while free water fraction was not. Free water fraction in the cholinergic basal forebrain mediated the relationship between acetylcholine and attention/working memory and executive function, while cholinergic basal forebrain volume mediated the relationship between acetylcholine in temporal regions in memory. These findings suggest that these two metrics reflect different stages of neurodegenerative processes and add additional evidence for a relationship between pathology in the basal forebrain, acetylcholine denervation and cognitive decline in Parkinson's disease.

Practical use of DAT SPECT imaging in diagnosing dementia with Lewy bodies: a US perspective of current guidelines and future directions

Background

Diagnosing Dementia with Lewy Bodies (DLB) remains a challenge in clinical practice. The use of 123I-ioflupane (DaTscan™) SPECT imaging, which detects reduced dopamine transporter (DAT) uptake-a key biomarker in DLB diagnosis-could improve diagnostic accuracy. However, DAT imaging is underutilized despite its potential, contributing to delays and suboptimal patient management.

Methods

This review evaluates DLB diagnostic practices and challenges faced within the U.S. by synthesizing information from current literature, consensus guidelines, expert opinions, and recent updates on DaTscan FDA filings. It contrasts DAT SPECT with alternative biomarkers, provides recommendations for when DAT SPECT imaging may be indicated and discusses the potential of emerging biomarkers in enhancing diagnostic approaches.

Results

The radiopharmaceutical 123I-ioflupane for SPECT imaging was initially approved in Europe (2000) and later in the US (2011) for Parkinsonism/Essential Tremor. Its application was extended in 2022 to include the diagnosis of DLB. DaTscan's diagnostic efficacy for DLB, with its sensitivity, specificity, and predictive values, confirms its clinical utility. However, US implementation faces challenges such as insurance barriers, costs, access issues, and regional availability disparities.

Conclusion

123I-ioflupane SPECT Imaging is indicated for DLB diagnosis and differential diagnosis of Alzheimer's Disease, particularly in uncertain cases. Addressing diagnostic obstacles and enhancing physician-patient education could improve and expedite DLB diagnosis. Collaborative efforts among neurologists, geriatric psychiatrists, psychologists, and memory clinic staff are key to increasing diagnostic accuracy and care in DLB management.

Exploring the potential of amyloids in biomedical applications: A review

Amyloid is defined as a fibrous quaternary structure formed by assembling protein or peptide monomers into intermolecularly hydrogen linked β-sheets. There is a prevalent issue with protein aggregation and the buildup of amyloid molecules, which results in human neurological illnesses including Alzheimer's and Parkinson's. But it is now evident that many organisms, like bacteria, fungi as well as humans, use the same fibrillar structure to carry out a variety of biological functions, such as structure and protection supporting interface transitions and cell-cell recognition, protein control and storage, epigenetic inheritance, and memory. Recent discoveries of self-assembling amyloidogenic peptides and proteins, based on the amyloid core structure, give rise to interesting biomaterials with potential uses in numerous industries. These functions dramatically diverge from the initial conception of amyloid fibrils as intrinsically diseased entities. Apart from the natural ability of amyloids to spontaneously arrange themselves and their exceptional material characteristics, this aspect has prompted extensive research into engineering artificial amyloids for generating various nanostructures, molecular substances, and combined materials. Here, we discuss significant developments in the artificial design of useful amyloids as well as how amyloid materials serve as examples of how function emerges from protein self-assembly at various length scales.

Parkinson's Disease and Dementia with Lewy Bodies: One and the Same

The question whether Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) are expressions of the same underlying disease has been vigorously debated for decades. The recently proposed biological definitions of Lewy body disease, which do not assign any particular importance to the dopamine system over other degenerating neurotransmitter systems, has once more brought the discussion about different types of Lewy body disease to the forefront. Here, we briefly compare PDD and DLB in terms of their symptoms, imaging findings, and neuropathology, ultimately finding them to be indistinguishable. We then present a conceptual framework to demonstrate how one can view different clinical syndromes as manifestations of a shared underlying Lewy body disease. Early Parkinson's disease, isolated RBD, pure autonomic failure and other autonomic symptoms, and perhaps even psychiatric symptoms, represent diverse manifestations of the initial clinical stages of Lewy body disease. They are characterized by heterogeneous and comparatively limited neuronal dysfunction and damage. In contrast, Lewy body dementia, an encompassing term for both PDD and DLB, represents a more uniform and advanced stage of the disease. Patients in this category display extensive and severe Lewy pathology, frequently accompanied by co-existing pathologies, as well as multi-system neuronal dysfunction and degeneration. Thus, we propose that Lewy body disease should be viewed as a single encompassing disease entity. Phenotypic variance is caused by the presence of individual risk factors, disease mechanisms, and co-pathologies. Distinct subtypes of Lewy body disease can therefore be defined by subtype-specific disease mechanisms or biomarkers.

Association of cardiovascular disease management drugs with Lewy body dementia: a case-control study

Lewy body dementia is the second most common neurodegenerative dementia after Alzheimer's disease. Disease-modifying therapies for this disabling neuropsychiatric condition are critically needed. To identify drugs associated with the risk of developing Lewy body dementia, we performed a population-based case-control study of 148 170 US Medicare participants diagnosed with Lewy body dementia between 1 January 2008 and 31 December 2014 and of 1 253 043 frequency-matched controls. We estimated odds ratios and 95% confidence intervals for the association of Lewy body dementia risk with 1017 prescription drugs overall and separately for the three major racial groups (Black, Hispanic and White Americans). We identified significantly reduced Lewy body dementia risk associated with drugs used to treat cardiovascular diseases (anti-hypertensives: odds ratio = 0.72, 95% confidence interval = 0.70-0.74, P-value = 0; cholesterol-lowering agents: odds ratio = 0.85, 95% confidence interval = 0.83-0.87, P-value = 0; anti-diabetics: odds ratio = 0.83, 95% confidence interval = 0.62-0.72, P-value = 0). Notably, anti-diabetic medications were associated with a larger risk reduction among Black Lewy body dementia patients compared with other racial groups (Black: odds ratio = 0.67, 95% confidence interval = 0.62-0.72, P-value = 0; Hispanic: odds ratio = 0.86, 95% = 0.80-0.92, P-value = 5.16 × 10-5; White: odds ratio = 0.85, 95% confidence interval = 0.82-0.88, P-value = 0). To independently confirm the epidemiological findings, we looked for evidence of genetic overlap between Lewy body dementia and cardiovascular traits using whole-genome sequence data generated for 2591 Lewy body dementia patients and 4027 controls. Bivariate mixed modelling identified shared genetic risk between Lewy body dementia and low-density lipoprotein cholesterol levels, Type 2 diabetes and hypertension. By combining epidemiological and genomic data, we demonstrated that drugs treating cardiovascular diseases are associated with reduced Lewy body dementia risk, and these associations varied across racial groups. Future randomized clinical trials need to confirm our findings, but our data suggest that assiduous management of cardiovascular diseases may be beneficial in this understudied form of dementia.

Genetic risk factor clustering within and across neurodegenerative diseases

Overlapping symptoms and co-pathologies are common in closely related neurodegenerative diseases (NDDs). Investigating genetic risk variants across these NDDs can give further insight into disease manifestations. In this study we have leveraged genome-wide single nucleotide polymorphisms and genome-wide association study summary statistics to cluster patients based on their genetic status across identified risk variants for five NDDs (Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Lewy body dementia and frontotemporal dementia). The multi-disease and disease-specific clustering results presented here provide evidence that NDDs have more overlapping genetic aetiology than previously expected and how neurodegeneration should be viewed as a spectrum of symptomology. These clustering analyses also show potential subsets of patients with these diseases that are significantly depleted for any known common genetic risk factors suggesting environmental or other factors at work. Establishing that NDDs with overlapping pathologies share genetic risk loci, future research into how these variants might have different effects on downstream protein expression, pathology and NDD manifestation in general is important for refining and treating NDDs.

Neuropsychological Comparison of Patients With Alzheimer's Disease and Dementia With Lewy Bodies

BACKGROUND AND PURPOSE

This study aimed to determine the neuropsychological differences between patients with early-stage Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) with a Clinical Dementia Rating (CDR) score of ≤1.

METHODS

We examined 168 patients with AD (126 with CDR score=0.5, 42 with CDR score=1) and 169 patients with DLB (104 with CDR score=0.5, 65 with CDR score=1) whose diagnoses were supported by 18F-flobetaben positron-emission tomography (PET) and 18F-N-(3-fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) nortropane PET. Neuropsychological test scores were compared after controlling for age, sex, and education duration. Using a cutoff motor score on the Unified Parkinson's Disease Rating Scale of 20, patients with AD were further divided into AD with parkinsonism (ADP+, n=86) and AD without parkinsonism (ADP-, n=82).

RESULTS

At CDR scores of both 0.5 and 1, the DLB group had lower scores on the attention (digit-span forward at CDR score=0.5 and backward at CDR score=1), visuospatial, and executive (color reading Stroop test at CDR score=0.5 and phonemic fluency test, Stroop tests, and digit symbol coding at CDR score=1) tests than the AD group, but higher scores on the memory tests. The ADP- and ADP+ subgroups had comparable scores on most neuropsychological tests, but the ADP+ subgroup had lower scores on the color reading Stroop test.

CONCLUSIONS

Patients with DLB had worse attention, visuospatial, and executive functions but better memory function than patients with AD. Parkinsonism was not uncommon in the patients with AD and could be related to attention and executive dysfunction.

Is the clinical phenotype impact the prognosis in dementia with Lewy bodies?

INTRODUCTION

The first predominant clinical symptoms of dementia with Lewy bodies (DLB) are highly variable; however, the prognosis based on initial predominant symptoms remains poorly understood.

METHODS

Multicenter retrospective study in 4 French expert neurological centers. Patients were categorized in 3 groups according to their first more predominant symptoms: cognitive, psychiatric, or motor.

RESULTS

Analysis of 310 DLB patients. The mean age was 73.5 years old (SD 7.5) including 32.3% of women. The mean follow-up was 7.25 years (SD 3.6). We observed that the full clinical picture was more frequent in the motor group than in the cognitive group (p = 0.01); male gender and age at onset were associated with a significant excess risk of instantaneous mortality (p = 0.01).

CONCLUSION

Initial symptoms may affect the clinical course of patients, but no significant difference in mortality was observed.

Depression in dementia with Lewy bodies: a critical update

Depression with an estimated prevalence of 35% is a frequent manifestation of dementia with Lewy bodies (DLB), having negative effects on cognitive performance and life expectancy, yet the underlying neurobiology is poorly understood and most likely heterogeneous. Depressive symptoms in DLB can occur during the clinical course and, together with apathy, is a common prodromal neuropsychiatric symptom of this neurocognitive disorder in the group of Lewy body synucleinopathies. There are no essential differences in the frequency of depression in DLB and Parkinson disease-dementia (PDD), while its severity is up to twice as high as in Alzheimer disease (AD). Depression in DLB that is frequently underdiagnosed and undertreated, has been related to a variety of pathogenic mechanisms associated with the basic neurodegenerative process, in particular dysfunctions of neurotransmitter systems (decreased monoaminergic/serotonergic, noradrenergic and dopaminergic metabolism), α-synuclein pathology, synaptic zinc dysregulation, proteasome inhibition, gray matter volume loss in prefrontal and temporal areas as well as dysfunction of neuronal circuits with decreased functional connectivity of specific brain networks. Pharmacotherapy should avoid tricyclic antidepressants (anticholinergic adverse effects), second-generation antidepressants being a better choice, while modified electroconvulsive therapy, transcranial magnetic stimulation therapy and deep brain stimulation may be effective for pharmacotherapy-resistant cases. Since compared to depression in other dementias like Alzheimer disease and other parkinsonian syndromes, our knowledge of its molecular basis is limited, and further studies to elucidate the heterogeneous pathogenesis of depression in DLB are warranted.

The elusive role of herpesviruses in Alzheimer's disease: current evidence and future directions

Alzheimer's disease (AD) is the most common cause of dementia. While pathologic hallmarks, such as extracellular beta-amyloid plaques, are well-characterized in affected individuals, the pathogenesis that causes plaque formation and eventual cognitive decline is not well understood. A recent resurgence of the decades-old "infectious hypothesis" has garnered increased attention on the potential role that microbes may play in AD. In this theory, it is thought that pathogens such as viruses may act as seeds for beta-amyloid aggregation, ultimately leading to plaques. Interest in the infectious hypothesis has also spurred further investigation into additional characteristics of viral infection that may play a role in AD progression, such as neuroinflammation, latency, and viral DNA integration. While a flurry of research in this area has been recently published, with herpesviruses being of particular interest, the role of pathogens in AD remains controversial. In this review, the insights gained thus far into the possible role of herpesviruses in AD are summarized. The challenges and potential future directions of herpesvirus research in AD and dementia are also discussed.

A Precision Medicine Approach to Dementia Care: Syndrome, Etiology, and Copathology

Recognizing multiple neuropathological entities in people with dementia improves understanding of diagnosis, prognosis, and expected outcomes from therapies. Care for the individual with dementia includes the evaluation and management of diseases associated with the aged brain, most commonly neurodegeneration and vascular brain injury (VBI). Terminology has evolved to keep pace with diagnostic, prognostic, and therapeutic advances, and autopsy studies have shown that multiple comorbid neuropathological entities are the rule, not the exception, especially in older individuals. With the advent of disease-modifying therapies, delivering dementia care requires an encompassing framework that allows clinicians to consider all of an individual's underlying diseases and their contributions to symptom burden. A diagnostic approach, common co-occurring pathologies, and implications for current and future clinical care are reviewed.

Clinical update on dementia with Lewy bodies for primary care NPs

ABSTRACT

Dementia with Lewy bodies is the second most common type of neurodegenerative dementia in older adults. NPs in primary care must have a thorough understanding of this complex disease in order to ensure appropriate referrals, provide patient and caregiver education, and comanage this disease with other healthcare professionals.

Mixed pathology as a rule, not exception: Time to reconsider disease nosology

Parkinson's disease is a progressive neurodegenerative disorder that is associated with motor and nonmotor symptoms. Accumulation of misfolded α-synuclein is considered a key pathological feature during disease initiation and progression. While clearly deemed a synucleinopathy, the development of amyloid-β plaques, tau-containing neurofibrillary tangles, and even TDP-43 protein inclusions occur within the nigrostriatal system and in other brain regions. In addition, inflammatory responses, manifested by glial reactivity, T-cell infiltration, and increased expression of inflammatory cytokines, plus other toxic mediators derived from activated glial cells, are currently recognized as prominent drivers of Parkinson's disease pathology. However, copathologies have increasingly been recognized as the rule (>90%) and not the exception, with Parkinson's disease cases on average exhibiting three different copathologies. While microinfarcts, atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy may have an impact on disease progression, α-synuclein, amyloid-β, and TDP-43 pathology do not seem to contribute to progression.

The biological role of prolyl oligopeptidase and the procognitive potential of its peptidic inhibitors from food proteins

Prolyl oligopeptidase (POP) is a conserved serine protease belonging to proline-specific peptidases. It has both enzymatic and non-enzymatic activity and is involved in numerous biological processes in the human body, playing a role in e.g., cellular growth and differentiation, inflammation, as well as the development of some neurodegenerative and neuropsychiatric disorders. This article describes the physiological and pathological aspects of POP activity and the state-of-art of its peptidic inhibitors originating from food proteins, with a particular focus on their potential as cognition-enhancing agents. Although some milk, meat, fish, and plant protein-derived peptides have the potential to be applied as natural, procognitive nutraceuticals, their effectiveness requires further evaluation, especially in clinical trials. We demonstrated that the important features of the most promising POP-inhibiting peptides are very short sequence, high content of hydrophobic amino acids, and usually the presence of proline residue.

Differential Effects of Tau Stage, Lewy Body Pathology, and Substantia Nigra Degeneration on 18F-FDG PET Patterns in Clinical Alzheimer Disease

Comorbid Lewy body (LB) pathology is common in Alzheimer disease (AD). The effect of LB copathology on ¹⁸F-FDG PET patterns in AD is yet to be studied. We analyzed associations of neuropathologically assessed tau pathology, LB pathology, and substantia nigra neuronal loss (SNnl) with antemortem ¹⁸F-FDG PET hypometabolism in patients with a clinical AD presentation. Methods: Twenty-one patients with autopsy-confirmed AD without LB neuropathologic changes (LBNC) (pure-AD), 24 with AD and LBNC copathology (AD-LB), and 7 with LBNC without fulfilling neuropathologic criteria for AD (pure-LB) were studied. Pathologic groups were compared regarding regional and voxelwise ¹⁸F-FDG PET patterns, the cingulate island sign ratio (CISr), and neuropathologic ratings of SNnl. Additional analyses assessed continuous associations of Braak tangle stage and SNnl with ¹⁸F-FDG PET patterns. Results: Pure-AD and AD-LB showed highly similar patterns of AD-typical temporoparietal hypometabolism and did not differ in CISr, regional ¹⁸F-FDG SUVR, or SNnl. By contrast, pure-LB showed the expected pattern of pronounced posterior-occipital hypometabolism typical for dementia with LB (DLB), and both CISr and SNnl were significantly higher compared with the AD groups. In continuous analyses, Braak tangle stage correlated significantly with more AD-like, and SNnl with more DLB-like, ¹⁸F-FDG PET patterns. Conclusion: In autopsy-confirmed AD dementia patients, comorbid LB pathology did not have a notable effect on the regional ¹⁸F-FDG PET pattern. A more DLB-like ¹⁸F-FDG PET pattern was observed in relation to SNnl, but advanced SNnl was mostly limited to relatively pure LB cases. AD pathology may have a dominant effect over LB pathology in determining the regional neurodegeneration phenotype.

Plasma extracellular vesicle tau, β-amyloid, and α-synuclein and the progression of Parkinson's disease: a follow-up study

Background

Plasma extracellular vesicle (EV) contents are promising biomarkers of Parkinson's disease (PD). The pathognomonic proteins of PD, including α-synuclein, tau, and β-amyloid, are altered in people with PD (PwP) and are associated with clinical presentation in previous cross-sectional studies. However, the dynamic changes in these plasma EV proteins in PwP and their correlation with clinical progression remain unclear.

Objective

We investigated the dynamic changes in plasma EV α-synuclein, tau, and β-amyloid and their correlation with/prediction of clinical progression in PwP.

Design

A cohort study.

Methods

In total, 103 PwP and 37 healthy controls (HCs) completed baseline assessment and 1-year follow-up. Clinical assessments included Unified Parkinson's Disease Rating Scale (UPDRS) parts II and III, Mini-Mental State Examination (MMSE), and Montreal Cognitive Assessment (MoCA). Plasma EVs were isolated, and immunomagnetic reduction-based immunoassay was used to assess α-synuclein, tau, and β-amyloid 1-42 (Aβ1-42) levels within the EVs.

Results

Compared with HCs, significant differences were noted in the annual changes in all three EV pathognomonic proteins in PwP. Although the absolute changes in plasma EV pathognomonic proteins did not significantly correlate with clinical changes, PwP with elevated baseline plasma EV tau (upper-half) levels demonstrated significantly greater decline in motor and cognition, and increased plasma EV α-synuclein levels were associated with postural instability and the gait disturbance motor subtype. For PwP with elevated levels of all three biomarkers, clinical deterioration was significant, as indicated by UPDRS-II scores, postural instability and gait disturbance subscores of UPDRS-III, and MMSE score.

Conclusion

The combination of plasma EV α-synuclein, tau, and Aβ1-42 may identify PwP with a high risk of deterioration. Our findings can elucidate the interaction between these pathognomonic proteins, and they may serve as treatment response markers and can be applied in treatment approaches for disease modification.

Effect of Amyloid on Cognitive Performance in Parkinson's Disease and Dementia with Lewy Bodies

BACKGROUND

Concomitant amyloid pathology contributes to the clinical heterogeneity of Lewy body diseases (LBDs).

OBJECTIVE

The objective of this study was to investigate the pattern and effect of amyloid accumulation on cognitive dysfunction in Parkinson's disease (PD) and dementia with Lewy bodies (DLB).

METHODS

We retrospectively assessed 205 patients with LBD (91 with DLB and 114 with PD) who underwent ¹⁸ F-florbetaben positron emission tomography and divided them into amyloid-positive and amyloid-negative groups depending on global standardized uptake value ratios (SUVRs). We investigated the effect of group on the regional and global SUVRs using general linear models (GLMs) after controlling for age, sex, cognitive status, and score on the Korean version of the Mini-Mental State Examination. Moreover, the effect of amyloid on cognitive function, depending on the type of LBD, was evaluated using GLMs with interaction analysis.

RESULTS

In all evaluated regions including the striatum, the DLB group showed a higher SUVR than the PD group. Among amyloid-positive patients, the DLB group had a higher regional SUVR than the PD group in the frontal and parietal cortices. There was a significant interaction effect between amyloid and disease groups in language and memory function. In patients with PD, global amyloid load was negatively associated with language (B = -2.03; P = 0.010) and memory functions (B = -1.96; P < 0.001). However, amyloid load was not significantly associated with cognitive performance in the DLB group.

CONCLUSIONS

Although the burden of amyloid was higher in the DLB group, amyloid accumulation was negatively associated with the memory and language functions in the PD group only. © 2022 International Parkinson and Movement Disorder Society.

Longitudinal striatal dopamine transporter binding and cerebrospinal fluid alpha-synuclein, amyloid beta, total tau, and phosphorylated tau in Parkinson's disease

BACKGROUND

Previous studies investigated CSF levels of α-synuclein (α-syn), amyloid-β (Aβ1-42), total tau (t-tau), and phosphorylated tau (p-tau) with clinical progression of Parkinson's disease (PD). However, there is limited data on the association between CSF biomarkers and dopamine uptake status in PD.

AIM

In the current study, we aim to investigate the longitudinal association between striatal dopaminergic neuronal loss assessed by dopamine active transporter single photon emission computerized tomography (DaTSCAN) imaging with CSF α-syn, t-tau, p-tau, and Aβ1-42.

METHODS

A total of 413 early-stage PD patients and 187 healthy controls (HCs) from the PPMI. Striatal binding ratios (SBRs) of DaTSCAN images in caudate and putamen nuclei were calculated. We investigated the cross-sectional and longitudinal association between CSF biomarkers and dopamine uptake using partial correlation models adjusted for the effect of age, sex, and years of education over 24 months of follow-up.

RESULTS

The level of CSF α-syn, Aβ1-42, t-tau, and p-tau was significantly higher in HCs compared to PD groups at any time point. We found that higher CSF α-syn was associated with a higher SBR score in the left caudate at baseline (P = 0.038) and after 12 months (P = 0.012) in PD patients. Moreover, SBR scores in the left caudate and CSF Aβ1-42 were positively correlated at baseline (P = 0.021), 12 months (P = 0.006), and 24 months (P = 0.014) in patients with PD. Our findings demonstrated that change in CSF Aβ1-42 was positively correlated with change in SBR score in the left caudate after 24 months in the PD group (P = 0.043).

CONCLUSION

We found that cross-sectional levels of α-syn and Aβ1-42 could reflect the degree of dopaminergic neuron loss in the left caudate nucleus. Interestingly, longitudinal changes in CSF Aβ1-42 could predict the severity of left caudal dopaminergic neuron loss throughout the disease. This suggested that Aβ pathology might precede dopaminergic loss in striatal nuclei in this case left caudate and subsequently cognitive impairment in PD patients, although future studies are needed to confirm our results and expand the understanding of the pathophysiology of cognitive dysfunction in PD.

Extracellular vesicle biomarkers for cognitive impairment in Parkinson's disease

Besides motor symptoms, many individuals with Parkinson's disease develop cognitive impairment perhaps due to coexisting α-synuclein and Alzheimer's disease pathologies and impaired brain insulin signalling. Discovering biomarkers for cognitive impairment in Parkinson's disease could help clarify the underlying pathogenic processes and improve Parkinson's disease diagnosis and prognosis. This study used plasma samples from 273 participants: 103 Parkinson's disease individuals with normal cognition, 121 Parkinson's disease individuals with cognitive impairment (81 with mild cognitive impairment, 40 with dementia) and 49 age- and sex-matched controls. Plasma extracellular vesicles enriched for neuronal origin were immunocaptured by targeting the L1 cell adhesion molecule, then biomarkers were quantified using immunoassays. α-Synuclein was lower in Parkinson's disease compared to control individuals (P = 0.004) and in cognitively impaired Parkinson's disease individuals compared to Parkinson's disease with normal cognition (P < 0.001) and control (P < 0.001) individuals. Amyloid-β42 did not differ between groups. Phosphorylated tau (T181) was higher in Parkinson's disease than control individuals (P = 0.003) and in cognitively impaired compared to cognitively normal Parkinson's disease individuals (P < 0.001) and controls (P < 0.001). Total tau was not different between groups. Tyrosine-phosphorylated insulin receptor substrate-1 was lower in Parkinson's disease compared to control individuals (P = 0.03) and in cognitively impaired compared to cognitively normal Parkinson's disease individuals (P = 0.02) and controls (P = 0.01), and also decreased with increasing motor symptom severity (P = 0.005); serine312-phosphorylated insulin receptor substrate-1 was not different between groups. Mechanistic target of rapamycin was not different between groups, whereas phosphorylated mechanistic target of rapamycin trended lower in cognitively impaired compared to cognitively normal Parkinson's disease individuals (P = 0.05). The ratio of α-synuclein to phosphorylated tau181 was lower in Parkinson's disease compared to controls (P = 0.001), in cognitively impaired compared to cognitively normal Parkinson's disease individuals (P < 0.001) and decreased with increasing motor symptom severity (P < 0.001). The ratio of insulin receptor substrate-1 phosphorylated serine312 to insulin receptor substrate-1 phosphorylated tyrosine was higher in Parkinson's disease compared to control individuals (P = 0.01), in cognitively impaired compared to cognitively normal Parkinson's disease individuals (P = 0.02) and increased with increasing motor symptom severity (P = 0.003). α-Synuclein, phosphorylated tau181 and insulin receptor substrate-1 phosphorylated tyrosine contributed in diagnostic classification between groups. These findings suggest that both α-synuclein and tau pathologies and impaired insulin signalling underlie Parkinson's disease with cognitive impairment. Plasma neuronal extracellular vesicles biomarkers may inform cognitive prognosis in Parkinson's disease.

From protein biomarkers to proteomics in dementia with Lewy Bodies

Dementia with Lewy Bodies (DLB) is the second most common neurodegenerative dementia. Despite considerable research progress, there remain gaps in our understanding of the pathophysiology and there is no disease-modifying treatment. Proteomics is a powerful tool to elucidate complex biological pathways across heterogenous conditions. This review summarizes the widely used proteomic methods and presents evidence for protein dysregulation in the brain and peripheral tissues in DLB. Proteomics of post-mortem brain tissue shows that DLB shares common features with other dementias, such as synaptic dysfunction, but retains a unique protein signature. Promising diagnostic biomarkers are being identified in cerebrospinal fluid (CSF), blood, and peripheral tissues, such as serum Heart-type fatty acid binding protein. Research is needed to track these changes from the prodromal stage to established dementia, with standardized workflows to ensure replicability. Identifying novel protein targets in causative biological pathways could lead to the development of new targeted therapeutics or the stratification of participants for clinical trials.

Opportunities and challenges of alpha-synuclein as a potential biomarker for Parkinson's disease and other synucleinopathies

Parkinson’s disease (PD), the second most common progressive neurodegenerative disease, develops and progresses for 10–15 years before the clinical diagnostic symptoms of the disease are manifested. Furthermore, several aspects of PD pathology overlap with other neurodegenerative diseases (NDDs) linked to alpha-synuclein (aSyn) aggregation, also called synucleinopathies. Therefore, there is an urgent need to discover and validate early diagnostic and prognostic markers that reflect disease pathophysiology, progression, severity, and potential differences in disease mechanisms between PD and other NDDs. The close association between aSyn and the development of pathology in synucleinopathies, along with the identification of aSyn species in biological fluids, has led to increasing interest in aSyn species as potential biomarkers for early diagnosis of PD and differentiate it from other synucleinopathies. In this review, we (1) provide an overview of the progress toward mapping the distribution of aSyn species in the brain, peripheral tissues, and biological fluids; (2) present comparative and critical analysis of previous studies that measured total aSyn as well as other species such as modified and aggregated forms of aSyn in different biological fluids; and (3) highlight conceptual and technical gaps and challenges that could hinder the development and validation of reliable aSyn biomarkers; and (4) outline a series of recommendations to address these challenges. Finally, we propose a combined biomarker approach based on integrating biochemical, aggregation and structure features of aSyn, in addition to other biomarkers of neurodegeneration. We believe that capturing the diversity of aSyn species is essential to develop robust assays and diagnostics for early detection, patient stratification, monitoring of disease progression, and differentiation between synucleinopathies. This could transform clinical trial design and implementation, accelerate the development of new therapies, and improve clinical decisions and treatment strategies.

Multi-Omics Interdisciplinary Research Integration to Accelerate Dementia Biomarker Development (MIRIADE)

Proteomics studies have shown differential expression of numerous proteins in dementias but have rarely led to novel biomarker tests for clinical use. The Marie Curie MIRIADE project is designed to experimentally evaluate development strategies to accelerate the validation and ultimate implementation of novel biomarkers in clinical practice, using proteomics-based biomarker development for main dementias as experimental case studies. We address several knowledge gaps that have been identified in the field. First, there is the technology-translation gap of different technologies for the discovery (e.g., mass spectrometry) and the large-scale validation (e.g., immunoassays) of biomarkers. In addition, there is a limited understanding of conformational states of biomarker proteins in different matrices, which affect the selection of reagents for assay development. In this review, we aim to understand the decisions taken in the initial steps of biomarker development, which is done via an interim narrative update of the work of each ESR subproject. The results describe the decision process to shortlist biomarkers from a proteomics to develop immunoassays or mass spectrometry assays for Alzheimer's disease, Lewy body dementia, and frontotemporal dementia. In addition, we explain the approach to prepare the market implementation of novel biomarkers and assays. Moreover, we describe the development of computational protein state and interaction prediction models to support biomarker development, such as the prediction of epitopes. Lastly, we reflect upon activities involved in the biomarker development process to deduce a best-practice roadmap for biomarker development.

Pinpointing novel risk loci for Lewy body dementia and the shared genetic etiology with Alzheimer's disease and Parkinson's disease: a large-scale multi-trait association analysis

BACKGROUND

The current genome-wide association study (GWAS) of Lewy body dementia (LBD) suffers from low power due to a limited sample size. In addition, the genetic determinants underlying LBD and the shared genetic etiology with Alzheimer's disease (AD) and Parkinson's disease (PD) remain poorly understood.

METHODS

Using the largest GWAS summary statistics of LBD to date (2591 cases and 4027 controls), late-onset AD (86,531 cases and 676,386 controls), and PD (33,674 cases and 449,056 controls), we comprehensively investigated the genetic basis of LBD and shared genetic etiology among LBD, AD, and PD. We first conducted genetic correlation analysis using linkage disequilibrium score regression (LDSC), followed by multi-trait analysis of GWAS (MTAG) and association analysis based on SubSETs (ASSET) to identify the trait-specific SNPs. We then performed SNP-level functional annotation to identify significant genomic risk loci paired with Bayesian fine-mapping and colocalization analysis to identify potential causal variants. Parallel gene-level analysis including GCTA-fastBAT and transcriptome-wide association analysis (TWAS) was implemented to explore novel LBD-associated genes, followed by pathway enrichment analysis to understand underlying biological mechanisms.

RESULTS

Pairwise LDSC analysis found positive genome-wide genetic correlations between LBD and AD (rg = 0.6603, se = 0.2001; P = 0.0010), between LBD and PD (rg = 0.6352, se = 0.1880; P = 0.0007), and between AD and PD (rg = 0.2136, se = 0.0860; P = 0.0130). We identified 13 significant loci for LBD, including 5 previously reported loci (1q22, 2q14.3, 4p16.3, 4q22.1, and 19q13.32) and 8 novel biologically plausible genetic associations (5q12.1, 5q33.3, 6p21.1, 8p23.1, 8p21.1, 16p11.2, 17p12, and 17q21.31), among which APOC1 (19q13.32), SNCA (4q22.1), TMEM175 (4p16.3), CLU (8p21.1), MAPT (17q21.31), and FBXL19 (16p11.2) were also validated by gene-level analysis. Pathway enrichment analysis of 40 common genes identified by GCTA-fastBAT and TWAS implicated significant role of neurofibrillary tangle assembly (GO:1902988, adjusted P = 1.55 × 10^-2).

CONCLUSIONS

Our findings provide novel insights into the genetic determinants of LBD and the shared genetic etiology and biological mechanisms of LBD, AD, and PD, which could benefit the understanding of the co-pathology as well as the potential treatment of these diseases simultaneously.

Recent advances in Lewy body dementia: A comprehensive review

Lewy Body Dementia is the second most frequent neurodegenerative illness proven to cause dementia, after Alzheimer's disease (AD). It is believed to be vastly underdiagnosed, as there is a significant disparity between the number of cases diagnosed clinically and those diagnosed via neuropathology at the time of postmortem autopsy. Strikingly, many of the pharmacologic treatments used to treat behavioral and cognitive symptoms in other forms of dementia exacerbate the symptoms of DLB. Therefore, it is critical to accurately diagnose DLB as these patients require a specific treatment approach. This article focuses on its pathophysiology, risk factors, differentials, and its diverse treatment modalities. In this study, an English language literature search was conducted on Medline, Cochrane, Embase, and Google Scholar till April 2022. The following search strings and Medical Subject Headings (MeSH) terms were used: "Lewy Body Dementia," "Dementia with Lewy bodies," and "Parkinson's Disease Dementia." We explored the literature on Lewy Body Dementia for its epidemiology, pathophysiology, the role of various genes and how they bring about the disease, biomarkers, its differential diagnoses and treatment options.

Alpha synuclein seed amplification assays for diagnosing synucleinopathies: the way forward

Parkinson's disease (PD) is the second most common neurodegenerative disease and the most common synucleinopathy, as alpha-synuclein (α-syn), a prion-like protein, plays an important pathophysiological role in its onset and progression. Although neuropathological changes begin many years before the onset of motor manifestations, diagnosis still relies on the identification of the motor symptoms, which hinders to formulate an early diagnosis. Since α-syn misfolding and aggregation precede clinical manifestations, the possibility to identify these phenomena in PD patients would allow us to recognize the disease at the earliest, premotor phases, as a consequence of the transition from a clinical to a molecular diagnosis.

Seed amplification assays (SAAs) are a group of techniques that currently support the diagnosis of prion subacute encephalopathies, namely Creutzfeldt Jakob disease. These techniques enable the detection of minimal amounts of prions in cerebrospinal fluid (CSF) and other matrices of affected patients. Recently, SAAs have been successfully applied to detect misfolded α-syn in CSF, olfactory mucosa, submandibular gland biopsies, skin and saliva, of patients with PD and other synucleinopathies. In these categories, they can differentiate PD and dementia with Lewy bodies (DLB) from control subjects, even in the prodromal stages of the disease. In terms of differential diagnosis, SAAs satisfactorily differentiated PD, DLB, and multiple system atrophy (MSA) from non-synucleinopathy parkinsonisms. The kinetic analysis of the SAA fluorescence profiles allowed the identification of synucleinopathy-dependent α-syn fibrils conformations, commonly referred to as strains, which have demonstrated diagnostic potential in differentiating among synucleinopathies, especially between Lewy body diseases (PD, DLB) and MSA. In front of these highly promising data, which make the α-syn seeding activity detected by SAAs as the most promising diagnostic biomarker for synucleinopathies, there are still preanalytical and analytical issues, mostly related to the assay standardization, which need to be solved. In this review, we discuss the key findings supporting the clinical application of α-syn SAAs to identify PD and other synucleinopathies, the unmet needs, and future perspectives.

Quantitative detection of α-Synuclein and Tau oligomers and other aggregates by digital single particle counting

The pathological hallmark of neurodegenerative diseases is the formation of toxic oligomers by proteins such as alpha-synuclein (aSyn) or microtubule-associated protein tau (Tau). Consequently, such oligomers are promising biomarker candidates for diagnostics as well as drug development. However, measuring oligomers and other aggregates in human biofluids is still challenging as extreme sensitivity and specificity are required. We previously developed surface-based fluorescence intensity distribution analysis (sFIDA) featuring single-particle sensitivity and absolute specificity for aggregates. In this work, we measured aSyn and Tau aggregate concentrations of 237 cerebrospinal fluid (CSF) samples from five cohorts: Parkinson’s disease (PD), dementia with Lewy bodies (DLB), Alzheimer’s disease (AD), progressive supranuclear palsy (PSP), and a neurologically-normal control group. aSyn aggregate concentration discriminates PD and DLB patients from normal controls (sensitivity 73%, specificity 65%, area under the receiver operating curve (AUC) 0.68). Tau aggregates were significantly elevated in PSP patients compared to all other groups (sensitivity 87%, specificity 70%, AUC 0.76). Further, we found a tight correlation between aSyn and Tau aggregate titers among all patient cohorts (Pearson coefficient of correlation r = 0.81). Our results demonstrate that aSyn and Tau aggregate concentrations measured by sFIDA differentiate neurodegenerative disease diagnostic groups. Moreover, sFIDA-based Tau aggregate measurements might be particularly useful in distinguishing PSP from other parkinsonisms. Finally, our findings suggest that sFIDA can improve pre-clinical and clinical studies by identifying those individuals that will most likely respond to compounds designed to eliminate specific oligomers or to prevent their formation.

Psychosis Management in Lewy Body Dementia: A Comprehensive Clinical Approach

Lewy body dementia (LBD) is asynucleinopathy that results in clinical manifestation of motor and neuropsychiatric symptoms. The disease burden associated with psychosis in LBD patients is significantly higher compared to other types of dementia or even to LBD without psychosis. Effective care management processes should include consideration of de-prescribing any offending agents including anticholinergics and dopaminergic agents, followed by nonpharmacological and low risk pharmacological approach. If addition of pharmacological agents is required, consideration should be given to acetylcholinesterase inhibitors, pimavanserin and atypical antipsychotics such as quetiapine or clozapine. Side effects of these medications should be considered prior to selection and initiation of a medication regimen. Goals of care and functional assessment are a crucial part of the optimized care plan, given overall guarded prognosis, in the context of numerous complications observed in this population. Palliative care consultation could facilitate symptom control and timely enrollment into hospice if consistent with patient's goals.

Clinical Trajectories at the End of Life in Dementia Patients With Alzheimer Disease and Lewy Body Neuropathologic Changes

BACKGROUND AND OBJECTIVES

Evaluating and understanding the heterogeneity in dementia course has important implications for clinical practice, healthcare decision-making, and research. However, inconsistent findings have been reported with regard to the disease courses of the two most common dementias, Alzheimer's disease (AD) and Dementia with Lewy bodies (DLB). Using autopsy-confirmed diagnoses, we aimed to examine the disease trajectories in the years before death among dementia patients with pure AD, pure DLB, or mixed (AD and DLB) pathologies.

METHODS

The current retrospective longitudinal study included 62 participants with autopsy-confirmed diagnoses of pure AD (n=34), mixed AD and DLB (AD+DLB, n = 17), or pure DLB (n=11) from the Predictors 2 Cohort Study, a prospective, clinic-based, cohort of dementia patients. Generalized estimating equation models, with time zero at death, were used to examine the trajectory of cognition (Folstein Mini-Mental State Examination, MMSE), function (Activities of Daily Living, ADL), and dependence scale among patients with different autopsy-confirmed diagnosis (pure AD, AD+DLB, and pure DLB). The models were adjusted for age, sex, education, and baseline features including extrapyramidal signs, MMSE, ADL, and dependence scale.

RESULTS

The participants on average received 9.4±4.6 assessments at 6-month intervals during a mean 5.4±2.9 years of follow-up time. The three groups were similar in both cognition and function status at baseline. Cognition and function were highly correlated among AD+DLB patients but not in pure AD or pure DLB patients at baseline. Patients of the three groups all declined in both cognition and function but had different trajectories of decline. More specifically, the pure DLB patients experienced approximately double the rate of both cognitive decline and functional decline than the pure AD patients, and the mixed pathology group showed double the rate of functional decline as compared to pure AD patients.

DISCUSSION

In this longitudinal study, we found that among patients with dementia, those with Lewy body pathology experienced faster cognitive and functional decline than those with pure AD pathology.

Brain Perfusion Single-Photon Emission Computed Tomography Using an Easy Z-Score Imaging System Predicts Progression to Neurodegenerative Dementia in Rapid Eye Movement Sleep Behavior Disorder

INTRODUCTION

Longitudinal studies have reported that patients with idiopathic rapid eye movement sleep behavior disorder (IRBD) have an increased risk of developing synucleinopathies, such as Parkinson's disease and dementia with Lewy bodies (DLB). Clinical trials of disease-modifying therapies for IRBD patients require suitable biomarkers that can predict the short-term onset of neurodegenerative dementia.

METHODS

We retrospectively examined if easy Z-score imaging system-specific volume-of-interest analysis (SVA) using brain perfusion single-photon emission computed tomography (SPECT) imaging or the cingulate island sign score can predict the short-term development of neurodegenerative dementia in 30 patients with IRBD.

RESULTS

Ten patients (33.3%) who exceeded the thresholds for three indicators (severity, extent, and ratio) were included in an SVA-positive group, while 20 (66.7%) were included in an SVA-negative group. Nine (30.0%) IRBD patients had phenoconversion, of which eight had DLB and one had Parkinson's disease with dementia. In Kaplan-Meier analysis, patients in the SVA-positive group converted to neurodegenerative dementia in a significantly shorter period of time compared to patients in the SVA-negative group.

CONCLUSIONS

These data suggest that SVA-positive IRBD patients have an increased short-term risk of developing neurodegenerative dementia.

The Cause of Alzheimer's Disease: The Theory of Multipathology Convergence to Chronic Neuronal Stress

The field of Alzheimer's disease (AD) research critically lacks an all-inclusive etiology theory that would integrate existing hypotheses and explain the heterogeneity of disease trajectory and pathologies observed in each individual patient. Here, we propose a novel comprehensive theory that we named: the multipathology convergence to chronic neuronal stress. Our new theory reconsiders long-standing dogmas advanced by previous incomplete theories. Firstly, while it is undeniable that amyloid beta (Aβ) is involved in AD, in the seminal stage of the disease Aβ is unlikely pathogenic. Instead, we hypothesize that the root cause of AD is neuronal stress in the central nervous system (CNS), and Aβ is expressed as part of the physiological response to protect CNS neurons from stress. If there is no return to homeostasis, then Aβ becomes overexpressed, and this includes the generation of longer forms that are more toxic and prone to oligomerization. Secondly, AD etiology is plausibly not strictly compartmentalized within the CNS but may also result from the dysfunction of other physiological systems in the entire body. This view implies that AD may not have a single cause, but rather needs to be considered as a spectrum of multiple chronic pathological modalities converging to the persistent stressing of CNS neurons. These chronic pathological modalities, which include cardiovascular disease, metabolic disorders, and CNS structural changes, often start individually, and over time combine with other chronic modalities to incrementally escalate the amount of stress applied to CNS neurons. We present the case for considering Aβ as a marker of neuronal stress in response to hypoxic, toxic, and starvation events, rather than solely a marker of AD. We also detail numerous human chronic conditions that can lead to neuronal stress in the CNS, making the link with co-morbidities encountered in daily clinical AD practice. Finally, we explain how our theory could be leveraged to improve clinical care for AD and related dementia in personalized medicine paradigms in the near future.

Therapeutic Potential of Astrocyte Transplantation

Cell transplantation is an attractive treatment strategy for a variety of brain disorders, as it promises to replenish lost functions and rejuvenate the brain. In particular, transplantation of astrocytes has come into light recently as a therapy for amyotrophic lateral sclerosis (ALS); moreover, grafting of astrocytes also showed positive results in models of other conditions ranging from neurodegenerative diseases of older age to traumatic injury and stroke. Despite clear differences in etiology, disorders such as ALS, Parkinson's, Alzheimer's, and Huntington's diseases, as well as traumatic injury and stroke, converge on a number of underlying astrocytic abnormalities, which include inflammatory changes, mitochondrial damage, calcium signaling disturbance, hemichannel opening, and loss of glutamate transporters. In this review, we examine these convergent pathways leading to astrocyte dysfunction, and explore the existing evidence for a therapeutic potential of transplantation of healthy astrocytes in various models. Existing literature presents a wide variety of methods to generate astrocytes, or relevant precursor cells, for subsequent transplantation, while described outcomes of this type of treatment also differ between studies. We take technical differences between methodologies into account to understand the variability of therapeutic benefits, or lack thereof, at a deeper level. We conclude by discussing some key requirements of an astrocyte graft that would be most suitable for clinical applications.

Advances in dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is a clinical diagnosis representing a specific presentation of a pathological α-synucleinopathy (Lewy body disease). DLB is one entity under the broader term Lewy body dementia, which also includes Parkinson’s disease dementia. Recent advances in DLB include publication of updated diagnostic criteria and recognition of prodromal DLB states, including mild cognitive impairment, delirium-onset, and psychiatric-onset forms. Research criteria for the mild cognitive impairment form of DLB were published in 2020. Increasing research shows that concomitant Alzheimer’s disease pathology in individuals with DLB is common in addition to the α-synucleinopathy pathology. This has implications for biomarker use and expected progression. Identifying biomarkers for DLB is an area of active research. Cerebrospinal fluid and skin biopsy tests are now commercially available in the United States, but their role in routine clinical care is not yet established. Additional research and biomarkers are needed. Research suggests that median survival after DLB diagnosis is 3–4 years, but there are rapidly and slowly progressive forms. Most individuals with DLB die of complications of the disease. Clinical trials for individuals with DLB have increased over the last 5 years, targeting both symptoms and underlying pathology. Effective therapies remain an unmet need, however. This review focuses on recent advances with an emphasis on literature that informs clinical care.

Association of Plasma p-tau181 and p-tau231 Concentrations With Cognitive Decline in Patients With Probable Dementia With Lewy Bodies

Importance

Plasma phosphorylated tau (p-tau) has proven to be an accurate biomarker for Alzheimer disease (AD) pathologic characteristics, offering a less expensive and less invasive alternative to cerebrospinal fluid (CSF) and positron emission tomography biomarkers for amyloid-β and tau. Alzheimer disease comorbid pathologic characteristics are common and are associated with more rapid cognitive decline in patients with dementia with Lewy bodies (DLB); therefore, it is anticipated that plasma p-tau concentrations may have utility in assessing cognitive impairment in individuals with this disorder.

Objective

To measure the concentrations of plasma p-tau (p-tau181 and p-tau231) and evaluate their associations with cognitive decline in individuals with probable DLB.

Design, Setting, and Participants

This multicenter longitudinal cohort study included participants from the European-DLB (E-DLB) Consortium cohort enrolled at 10 centers with harmonized diagnostic procedures from January 1, 2002, to December 31, 2020, with up to 5 years of follow-up. A total of 1122 participants with plasma samples were available. Participants with acute delirium or terminal illness and patients with other previous major psychiatric or neurologic disorders were excluded, leaving a cohort of 987 clinically diagnosed participants with probable DLB (n = 371), Parkinson disease (n = 204), AD (n = 207), as well as healthy controls (HCs) (n = 205).

Main Outcomes and Measures

The main outcome was plasma p-tau181 and p-tau231 levels measured with in-house single molecule array assays. The Mini-Mental State Examination (MMSE) was used to measure cognition.

Results

Among this cohort of 987 patients (512 men [51.9%]; mean [SD] age, 70.0 [8.8] years), patients with DLB did not differ significantly regarding age, sex, or years of education from those in the AD group, but the DLB group was older than the HC group and included more men than the AD and HC groups. Baseline concentrations of plasma p-tau181 and p-tau231 in patients with DLB were significantly higher than those in the HC group but lower than in the AD group and similar to the Parkinson disease group. Higher plasma concentrations of both p-tau markers were found in a subgroup of patients with DLB with abnormal CSF amyloid-β42 levels compared with those with normal levels (difference in the groups in p-tau181, -3.61 pg/mL; 95% CI, -5.43 to -1.79 pg/mL; P = .049; difference in the groups in p-tau231, -2.51 pg/mL; 95% CI, -3.63 to -1.39 pg/mL; P = .02). There was no difference between p-tau181 level and p-tau231 level across confirmed AD pathologic characteristcs based on reduced Aβ42 level in CSF in individuals with DLB. In DLB, a significant association was found between higher plasma p-tau181 and p-tau231 levels and lower MMSE scores at baseline (for p-tau181, -0.092 MMSE points; 95% CI, -0.12 to -0.06 MMSE points; P = .001; for p-tau231, -0.16 MMSE points; 95% CI, -0.21 to -0.12 MMSE points; P < .001), as well as more rapid MMSE decline over time. Plasma p-tau181 level was associated with a decrease of -0.094 MMSE points per year (95% CI, -0.144 to -0.052 MMSE points; P = .02), whereas plasma p-tau231 level was associated with an annual decrease of -0.130 MMSE points (95% CI, -0.201 to -0.071 MMSE points; P = .02), after adjusting for sex and age.

Conclusions and Relevance

This study suggests that plasma p-tau181 and p-tau231 levels may be used as cost-effective and accessible biomarkers to assess cognitive decline in individuals with DLB.

HIV-Associated Neurocognitive Disorder (HAND): Relative Risk Factors

This chapter will address the issue of risk for HIV-associated neurocognitive disorder (HAND), focusing on HIV-associated dementia (HAD), among persons living with HIV in relationship to the risk for other dementias. Advances in effective antiretroviral therapy (ART) have led to an increase in the prevalence of older persons surviving with HIV - in addition to older persons who become infected by HIV later in life. Hence, HIV is no longer a disease of younger persons, and additional attention has been brought to bear against the plight of older persons living with HIV - not only as it pertains to treatment but also to prevention. The additional risk caused by aging among older persons living with HIV is complex to asses, and HIV infection is a research area that requires a robust approach to multiple other factors causing neurocognitive impairment with older age. The long-term and potentially neurotoxic exposure to ART and the deleterious consequences of chronic infection with HIV and its associated neuro-inflammation have been described for health. This aids in the understanding of dementia risk factors in this patient population, but the comorbidities (HIV- and non-HIV-associated) occurring among older persons living with HIV must also be addressed to properly assess the overall impact on dementia risk in this group. This need also warrants our examination of the risk factors for other dementias (and comorbid dementias) in persons living with HIV versus the general population through the assessment and quantification of modifiable and non-modifiable risk factors identified as major contributors toward dementia.

αS Oligomers Generated from Interactions with a Polyunsaturated Fatty Acid and a Dopamine Metabolite Differentially Interact with Aβ to Enhance Neurotoxicity

It is increasingly becoming clear that neurodegenerative diseases are not as discrete as originally thought to be but display significant overlap in histopathological and clinical presentations. For example, nearly half of the patients with Alzheimer's disease (AD) and synucleinopathies such as Parkinson's disease (PD) show symptoms and pathological features of one another. Yet, the molecular events and features that underlie such comorbidities in neurodegenerative diseases remain poorly understood. Here, inspired to uncover the molecular underpinnings of the overlap between AD and PD, we investigated the interactions between amyloid-β (Aβ) and α-synuclein (αS), aggregates of which form the major components of amyloid plaques and Lewy bodies, respectively. Specifically, we focused on αS oligomers generated from the dopamine metabolite called dihydroxyphenylacetaldehyde (DOPAL) and a polyunsaturated fatty acid docosahexaenoic acid (DHA). The two αS oligomers showed structural and conformational differences as confirmed by the disparity in size, secondary structure, susceptibility to proteinase K digestion, and cytotoxicity. More importantly, the two oligomers differentially modulated Aβ aggregation; while both inhibited Aβ aggregation to varying extents, they also induced structurally different Aβ assemblies. Furthermore, Aβ seeded with DHA-derived αS oligomers showed greater toxicity than DOPAL-derived αS oligomers in SH-SY5Y neuroblastoma cells. These results provide insights into the interactions between two amyloid proteins with empirically distinctive biophysical and cellular manifestations, enunciating a basis for potentially ubiquitous cross-amyloid interactions across many neurodegenerative diseases.

Plasma extracellular vesicles tau and β-amyloid as biomarkers of cognitive dysfunction of Parkinson's disease

The contribution of circulatory tau and β-amyloid in Parkinson's disease (PD), especially the cognitive function, remains inconclusive. Extracellular vesicles (EVs) cargo these proteins throughout the bloodstream after they are directly secreted from many cells, including neurons. The present study aims to investigate the role of the plasma EV-borne tau and β-amyloid as biomarkers for cognitive dysfunction in PD by investigating subjects with mild to moderate stage of PD (n = 116) and non-PD controls (n = 46). Plasma EVs were isolated, and immunomagnetic reduction-based immunoassay was used to assess the levels of α-synuclein, tau, and β-amyloid 1-42 (Aβ1-42) within the EVs. Artificial neural network (ANN) models were then applied to predict cognitive dysfunction. We observed no significant difference in plasma EV tau and Aβ1-42 between PD patients and controls. Plasma EV tau was significantly associated with cognitive function. Moreover, plasma EV tau and Aβ1-42 were significantly elevated in PD patients with cognitive impairment when compared to PD patients with optimal cognition. The ANN model used the plasma EV α-synuclein, tau, and Aβ1-42, as well as the patient's age and gender, as predicting factors. The model achieved an accuracy of 91.3% in identifying cognitive dysfunction in PD patients, and plasma EV tau and Aβ1-42 are the most valuable factors. In conclusion, plasma EV tau and Aβ1-42 are significant markers of cognitive function in PD patients. Combining with the plasma EV α-synuclein, age, and sex, plasma EV tau and Aβ1-42 can identify cognitive dysfunction in PD patients. This study corroborates the prognostic roles of plasma EV tau and Aβ1-42 in PD.

The contribution of beta-amyloid to dementia in Lewy body diseases: a 1-year follow-up study

Dementia in Lewy Body Diseases (Parkinson’s disease and dementia with Lewy Bodies) affects progression of disabilities, quality of life and well-being. Understanding its pathogenetic mechanisms is critical to properly implement disease-modifying strategies. It has been hypothesized that synuclein- and amyloid-pathology act synergistically aggravating cognitive decline in elderly patients but their precise contribution to dementia is debated. In this study, we aimed at exploring if presence of amyloid deposits influences clinical, cognitive and neuroanatomical correlates of mental decline in a cohort of 40 Parkinson’s disease patients with normal cognition (n = 5), mild cognitive impairment (n = 22), and dementia (n = 13) as well as in Dementia with Lewy Bodies (n = 10). Patients underwent simultaneous 3 T PET/MRI with [¹⁸F]-flutemetamol and were assessed with an extensive baseline motor and neuropsychological examination, which allowed level II diagnosis of mild cognitive impairment and dementia. The role of amyloid positivity on each cognitive domain, and on the rate of conversion to dementia at 1-year follow-up was explored. A Kaplan Meier and the Log Rank (Mantel–Cox) test were used to assess the pairwise differences in time-to-develop dementia in Parkinson’s disease patients with and without significant amyloidosis. Furthermore, the presence of an Alzheimer’s dementia-like morphological pattern was evaluated using visual and automated assessment of T₁-weighted and T₂-weighted MRI images. We observed similar percentage of amyloid deposits in Parkinson’s disease dementia and dementia with Lewy Bodies cohorts (50% in each group) with an overall prevalence of 34% of significant amyloid depositions in Lewy Body Diseases. PET amyloid positivity was associated with worse global cognition (Montreal Cognitive Assessment and Mini Mental State Examination), executive and language difficulties. At 12-month follow-up, amyloid positive Parkinson’s disease patients were more likely to have become demented than those without amyloidosis. Moreover, there was no difference in the presence of an Alzheimer’s disease-like atrophy pattern and in vascular load (at Fazekas scale) between Lewy Body Diseases with and without significant amyloid deposits. Our findings suggest that in Lewy Body Diseases, amyloid deposition enhances cognitive deficits, particularly attention-executive and language dysfunctions. However, the large number of patients without significant amyloid deposits among our cognitively impaired patients indicates that synuclein pathology itself plays a critical role in the development of dementia in Lewy Body Diseases.

Comparison of early F-18 Florbetaben PET/CT to Tc-99m ECD SPECT using voxel, regional, and network analysis

This study aimed to validate early-phase F-18 Florbetaben positron emission tomography (eFBB PET) as a brain perfusion test and determine the optimal reference region. A total of 27 patients with early Parkinson's disease with Tc-99m ethyl cysteinate dimer single photon emission tomography (ECD SPECT) and FBB PET were included. Six reference regions, including whole brain (GN), pons, central white matter (CWM), whole cerebellum (WC), WC with brain stem (WC + B), and cerebellar grey matter (CG), were applied to obtain SUVR using cortex volume-of-interest (VOI). Reference regions of WC (r 0.886), WC + B (r 0.897), and CG (r 0.904) had highest correlation values of cortex-VOI SUVR between both perfusion images (all p < 0.001). Early-phase FBB PET had a significant linear correlation of CG-normalized SUVR of the cortex, basal ganglia, thalamus, and midbrain with ECD SPECT in voxel-wise analysis (FDR adjusted-p < 0.05). Early-phase FBB PET extracts more ICNS than ECD SPECT, as 9 ICNS and 4 ICNs, respectively. Both eFBB PET and ECD SPECT well discriminated PD from DLB (Area-under-curve of receiver-operating-characteristics, 0.911 for eFBB PET, 0.922 for ECD SPECT). Our findings suggest that eFBB PET is a reliable perfusion test based on a high correlation with ECD SPECT using cerebellum-based normalization methods.

Brain Atrophy Mediates the Relationship between Misfolded Proteins Deposition and Cognitive Impairment in Parkinson's Disease

Parkinson’s disease is associated with cognitive decline, misfolded protein deposition and brain atrophy. We herein hypothesized that structural abnormalities may be mediators between plasma misfolded proteins and cognitive functions. Neuropsychological assessments including five domains (attention, executive, speech and language, memory and visuospatial functions), ultra-sensitive immunomagnetic reduction-based immunoassay (IMR) measured misfolded protein levels (phosphorylated-Tau, Amyloidβ-42 and 40, α-synuclein and neurofilament light chain) and auto-segmented brain volumetry using FreeSurfur were performed for 54 Parkinson’s disease (PD) patients and 37 normal participants. Our results revealed that PD patients have higher plasma misfolded protein levels. Phosphorylated-Tau (p-Tau) and Amyloidβ-42 (Aβ-42) were correlated with atrophy of bilateral cerebellum, right caudate nucleus, and right accumbens area (RAA). In mediation analysis, RAA atrophy completely mediated the relationship between p-Tau and digit symbol coding (DSC). RAA and bilateral cerebellar cortex atrophy partially mediated the Aβ-42 and executive function (DSC and abstract thinking) relationship. Our study concluded that, in PD, p-Tau deposition adversely impacts DSC by causing RAA atrophy. Aβ-42 deposition adversely impacts executive functions by causing RAA and bilateral cerebellum atrophy.

Recent Insights into the Interplay of Alpha-Synuclein and Sphingolipid Signaling in Parkinson's Disease

Molecular studies have provided increasing evidence that Parkinson’s disease (PD) is a protein conformational disease, where the spread of alpha-synuclein (ASN) pathology along the neuraxis correlates with clinical disease outcome. Pathogenic forms of ASN evoke oxidative stress (OS), neuroinflammation, and protein alterations in neighboring cells, thereby intensifying ASN toxicity, neurodegeneration, and neuronal death. A number of evidence suggest that homeostasis between bioactive sphingolipids with opposing function—e.g., sphingosine-1-phosphate (S1P) and ceramide—is essential in pro-survival signaling and cell defense against OS. In contrast, imbalance of the “sphingolipid biostat” favoring pro-oxidative/pro-apoptotic ceramide-mediated changes have been indicated in PD and other neurodegenerative disorders. Therefore, we focused on the role of sphingolipid alterations in ASN burden, as well as in a vast range of its neurotoxic effects. Sphingolipid homeostasis is principally directed by sphingosine kinases (SphKs), which synthesize S1P—a potent lipid mediator regulating cell fate and inflammatory response—making SphK/S1P signaling an essential pharmacological target. A growing number of studies have shown that S1P receptor modulators, and agonists are promising protectants in several neurological diseases. This review demonstrates the relationship between ASN toxicity and alteration of SphK-dependent S1P signaling in OS, neuroinflammation, and neuronal death. Moreover, we discuss the S1P receptor-mediated pathways as a novel promising therapeutic approach in PD.

Plasma Extracellular Vesicle α-Synuclein Level in Patients with Parkinson's Disease

BACKGROUND

The most established pathognomonic protein of Parkinson's disease (PD), α-synuclein, is extensively investigated for disease diagnosis and prognosis; however, investigations into whether the free form of α-synuclein in the blood functions as a PD biomarker have not been fruitful. Extracellular vesicles (EVs) secreted from cells and present in blood transport molecules are novel platforms for biomarker identification. In blood EVs, α-synuclein originates predominantly from the brain without the interference of the blood-brain barrier. The present study investigated the role of plasma EV-borne α-synuclein as a biomarker of PD.

METHODS

Patients with mild to moderate stages of PD (n = 116) and individuals without PD (n = 46) were recruited to serve as the PD study group and the control group, respectively. Plasma EVs were isolated, and immunomagnetic reduction-based immunoassay was used to assess EV α-synuclein levels. Conventional statistical analysis was performed using SPSS 25.0, and p < 0.05 was considered significant.

RESULTS

Compared with controls, we observed significantly lower plasma EV α-synuclein levels in the patients with PD (PD: 56.0 ± 3.7 fg/mL vs. control: 74.5 ± 4.3 fg/mL, p = 0.009), and the significance remained after adjustment for age and sex. Plasma EV α-synuclein levels in the patients with PD did not correlate with age, disease duration, Part I and II scores of the Unified Parkinson's Disease Rating Scale (UPDRS), or the Mini-Mental State Examination scores. However, such levels were significantly correlated with UPDRS Part III score, which assesses motor dysfunction. Furthermore, the severity of akinetic-rigidity symptoms, but not tremor, was inversely associated with plasma EV α-synuclein level.

CONCLUSION

Plasma EV α-synuclein was significantly different between the control and PD group and was associated with akinetic-rigidity symptom severity in patients with PD. This study corroborates the possible diagnostic and subtyping roles of plasma EV α-synuclein in patients with PD, and it further provides a basis for this protein's clinical relevance and feasibility as a PD biomarker.

Greater Variability in Cognitive Decline in Lewy Body Dementia Compared to Alzheimer's Disease

Studies indicate more rapid cognitive decline in patients with Lewy body dementia (LBD) compared to Alzheimer's disease (AD). However, there has been less focus on any difference in the variability of cognitive decline. We assessed Mini-Mental State Examination (MMSE) test performance at baseline and annually for 5 years in 222 patients with mild dementia in the DemVest study who had either AD (137) or LBD (85). We used linear mixed models (LMMs) with random intercepts (variability in MMSE at baseline) and slopes (variability in MMSE decline), with years in study, age, gender, and diagnosis as independent variables. A non-linear (quadratic) trajectory was selected, interacting with age and diagnosis. To study differences in variance, we compared a regular LMM (i.e., a homoscedastic model), which assumes equal variance across groups, to a heteroscedastic model, assuming unequal intercept and slope variance based on diagnosis. The heteroscedastic model gave a better fit (Likelihood ratio test: χ2 = 30.3, p < 0.001), showing overall more variability in LBD. Further, the differences in intercept and slope variances were tested using a modified Wald test. The MMSE intercept variance (AD: 2.78, LBD: 7.75, difference: 4.97, p = 0.021) and slope variance (AD: 2.62, LBD 7.81, difference: 5.19, p = 0.004) were both higher in LBD. In conclusion, patients with LBD in the DemVest study have a higher variability in MMSE scores at study inclusion, and in MMSE decline compared to AD. Accordingly, clinical trials on LBD may need a larger sample size compared to AD.

Associations of Alzheimer's Disease Neuropathologic Changes with Clinical Presentations of Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) and Alzheimer's disease (AD) are the two most prevalent neurodegenerative diseases associated with age. Pathological studies have shown that these two diseases share a certain degree of neuropathological overlap. AD neuropathologic change contributes to cognitive impairment in PD. However, the impact of AD pathology on other clinical phenotypes in PD remains largely unknown.

OBJECTIVE

Herein we aimed to assess the impact of co-occurring AD neuropathologic change on the clinical phenotypes of PD.

METHODS

We examined 46 autopsy brains of PD patients and available clinical information to retrospectively assess the effects of comorbid AD pathology on dementia, hallucinations, and dyskinesia commonly seen in advanced PD.

RESULTS

AD neuropathology significantly increased the risk of hallucinations and dementia, but not dyskinesia in PD patients. Surprisingly, diffuse Lewy body pathology, but not AD pathology, was associated with the occurrence of dementia and hallucinations. Most importantly, we reported that the severity of neuronal loss in the locus coeruleus (LC), but not the severity of neuronal loss in the substantia nigra (SN), was associated with the occurrence of dyskinesia in advanced PD patients, while neither Lewy body scores in SN nor LC had significant effects.

CONCLUSION

We show for the first time that neuronal loss in LC contributes to dyskinesia. Understanding the relationships between the two distinct pathologies and their relevant clinical phenotypes will be crucial in the development of effective disease-modifying therapies for PD.

Significance of cerebral amyloid angiopathy and other co-morbidities in Lewy body diseases

Lewy body dementia (LBD) and Parkinson's disease-dementia (PDD) are two major neurocognitive disorders with Lewy bodies (LB) of unknown etiology. There is considerable clinical and pathological overlap between these two conditions that are clinically distinguished based on the duration of Parkinsonism prior to development of dementia. Their morphology is characterized by a variable combination of LB and Alzheimer's disease (AD) pathologies. Cerebral amyloid angiopathy (CAA), very common in aged persons and particularly in AD, is increasingly recognized for its association with both pathologies and dementia. To investigate neuropathological differences between LB diseases with and without dementia, 110 PDD and 60 LBD cases were compared with 60 Parkinson's disease (PD) cases without dementia (PDND). The major demographic and neuropathological data were assessed retrospectively. PDD patients were significantly older than PDND ones (83.9 vs 77.8 years; p < 0.05); the age of LB patients was in between both groups (mean 80.2 years), while the duration of disease was LBD < PDD < PDND (mean 6.7 vs 12.5 and 14.3 years). LBD patients had higher neuritic Braak stages (mean 5.1 vs 4.5 and 4.0, respectively), LB scores (mean 5.3 vs 4.2 and 4.0, respectively), and Thal amyloid phases (mean 4.1 vs 3.0 and 2.3, respectively) than the two other groups. CAA was more common in LBD than in the PDD and PDND groups (93 vs 50 and 21.7%, respectively). Its severity was significantly greater in LBD than in PDD and PDND (p < 0.01), involving mainly the occipital lobes. Moreover, striatal Aβ deposition highly differentiated LBD brains from PDD. Braak neurofibrillary tangle (NFT) stages, CAA, and less Thal Aβ phases were positively correlated with LB pathology (p < 0.05), which was significantly higher in LBD than in PDD < PDND. Survival analysis showed worse prognosis in LBD than in PDD (and PDND), which was linked to both increased Braak tau stages and more severe CAA. These and other recent studies imply the association of CAA-and both tau and LB pathologies-with cognitive decline and more rapid disease progression that distinguishes LBD from PDD (and PDND).

Mitochondrial CHCHD2: Disease-Associated Mutations, Physiological Functions, and Current Animal Models

Rare mutations in the mitochondrial protein coiled-coil-helix-coiled-coil-helix domain containing 2 (CHCHD2) are associated with Parkinson's disease (PD) and other Lewy body disorders. CHCHD2 is a bi-organellar mediator of oxidative phosphorylation, playing crucial roles in regulating electron flow in the mitochondrial electron transport chain and acting as a nuclear transcription factor for a cytochrome c oxidase subunit (COX4I2) and itself in response to hypoxic stress. CHCHD2 also regulates cell migration and differentiation, mitochondrial cristae structure, and apoptosis. In this review, we summarize the known disease-associated mutations of CHCHD2 in Asian and Caucasian populations, the physiological functions of CHCHD2, how CHCHD2 mutations contribute to α-synuclein pathology, and current animal models of CHCHD2. Further, we discuss the necessity of continued investigation into the divergent functions of CHCHD2 and CHCHD10 to determine how mutations in these similar mitochondrial proteins contribute to different neurodegenerative diseases.