Lewy-related pathology exhibits two anatomically and genetically distinct progression patterns: a population-based study of Finns aged 85

In and out: Benchmarking in vitro, in vivo, ex vivo, and xenografting approaches for an integrative brain disease modeling pipeline

Human cellular models and their neuronal derivatives have afforded unprecedented advances in elucidating pathogenic mechanisms of neuropsychiatric diseases. Notwithstanding their indispensable contribution, animal models remain the benchmark in neurobiological research. In an attempt to harness the best of both worlds, researchers have increasingly relied on human/animal chimeras by xenografting human cells into the animal brain. Despite the unparalleled potential of xenografting approaches in the study of the human brain, literature resources that systematically examine their significance and advantages are surprisingly lacking. We fill this gap by providing a comprehensive account of brain diseases that were thus far subjected to all three modeling approaches (transgenic rodents, in vitro human lineages, human-animal xenografting) and provide a critical appraisal of the impact of xenografting approaches for advancing our understanding of those diseases and brain development. Next, we give our perspective on integrating xenografting modeling pipeline with recent cutting-edge technological advancements.

Brain-first vs. body-first Parkinson's disease: An update on recent evidence

We recently proposed a new disease model of Parkinson's disease - the a-Synuclein Origin site and Connectome model. The model posits that the initial pathology starts either in the olfactory bulb or amygdala leading to a brain-first subtype, or in the enteric nervous system leading to a body-first subtype. These subtypes should be distinguishable early in the disease course on a range of imaging, clinical, and neuropathological markers. Here, we review recent original human studies, which tested the predictions of the model. Molecular imaging studies were generally in agreement with the model, whereas structural imaging studies, such as MRI volumetry, showed conflicting findings. Most large-scale clinical studies were supportive, reporting clustering of relevant markers of the body-first subtype, including REM-sleep behavior disorder, constipation, autonomic dysfunction, neuropsychiatric symptoms, and cognitive impairment. Finally, studies of a-synuclein deposition in antemortem and postmortem tissues revealed distribution of pathology, which generally supports the model.

Involvement of ApoE4 in dementia with Lewy bodies in the prodromal and demented stages: evaluation of the Strasbourg cohort

ApoE4 as a risk factor for dementia with Lewy bodies (DLB) is still an issue. We sought to determine the involvement of ApoE4 according to different clinical parameters in our cohort of patients from Strasbourg, France. ApoE genotyping was performed on the AlphaLewyMA cohort. In this cohort, 197 patients were genotyped: 105 DLB patients, 37 Alzheimer's disease (AD) patients, 29 patients with AD/DLB comorbidity, and 26 control subjects (CS). The groups of patients were also classified according to the stage of evolution of the disease: prodromal or demented. We analyzed other parameters in relation to ApoE4 status, such as years of education (YOE) and Alzheimer CSF biomarkers. We observed a higher proportion of ApoE4 carriers in the AD (51.4%) and AD/DLB (72.4%) groups compared to the DLB (25.7%) and CS (11.5%) groups (p < 0.0001). We found a correlation between age at disease onset and YOE in the AD group (p = 0.039) but not in the DLB group (p = 0.056). Interestingly, in the DLB group, the subgroup of patients with high YOE (≥ 11) had significantly more patients with ApoE4 than the subgroup with low YOE (< 11). AD biomarkers did not seem to be impacted by the presence of ApoE4, except for Aβ42: DLB ApoE4-positive demented patients showed a more marked Aβ42 decrease. ApoE4 does not appear to be a risk factor for "pure" DLB patients. These results suggest a strong link between ApoE4 and amyloidopathy and consequently with AD. Trial registration: AlphaLewyMa, Identifier: NCT01876459, date of registration: June 12, 2013.

Age-Related Pathology in Corticobasal Degeneration

Elderly human brains are vulnerable to multiple proteinopathies, although each protein has a different transmission pathway. Tau-immunoreactive astrocytes are well-known in elderly brains. In contrast, astrocytic plaques, a hallmark in corticobasal degeneration (CBD), rarely occur in aging and neurodegenerative disease other than CBD. To elucidate the clinicopathological correlation of aging-related pathology in CBD, we examined 21 pathologically proven CBD cases in our institute (12 males and 9 females, with a mean age of death 70.6 years). All CBD cases showed grains and neurofibrillary tangles (NFTs). Fifteen cases (71.4%) showed beta-amyloid deposition such as senile plaques or cerebral amyloid angiopathy. Three cases (14.3%) had Lewy body pathology. One case was classified as amygdala-predominant Lewy body disease, although no cases met the pathological criteria for Alzheimer's disease. Five cases (23.8%) displayed Limbic-predominant and age-related TDP-43 encephalopathy (LATE). NFTs, grains, and TDP-43-positive neuronal inclusions were widely distributed throughout the limbic system of CBD patients, but their densities were low. CBD might a have similar cell vulnerability and transmission pathway to that of multiple proteinopathy in aging brains.

Hope vs. Hype I: Spreading alpha-synuclein explains cognitive deficits in Parkinson disease

The Parkinson Study Group (PSG) gathered North American experts in Parkinson disease during the 9th Annual Symposium on "Shaping the Management of Parkinson Disease: Debating Current Controversies". Debaters were tasked with agree or disagree positions to a particular prompt. This is the first in three-part series of "Hype vs. Hope" debates involving current trends and advances in Parkinson disease. With the prompt of "Spreading alpha-synuclein explains cognitive deficits in Parkinson disease," Dr. Kelly Mills, MD, MHS was tasked with the "agree" stance and Dr. Abhimanyu Mahajan, MD, MHS was tasked with the "disagree" stance. The following point-of-view article is an adaptation of this debate.

The Body, the Brain, the Environment, and Parkinson's Disease

The brain- and body-first models of Lewy body disorders predict that aggregated alpha-synuclein pathology usually begins in either the olfactory system or the enteric nervous system. In both scenarios the pathology seems to arise in structures that are closely connected to the outside world. Environmental toxicants, including certain pesticides, industrial chemicals, and air pollution are therefore plausible trigger mechanisms for Parkinson's disease and dementia with Lewy bodies. Here, we propose that toxicants inhaled through the nose can lead to pathological changes in alpha-synuclein in the olfactory system that subsequently spread and give rise to a brain-first subtype of Lewy body disease. Similarly, ingested toxicants can pass through the gut and cause alpha-synuclein pathology that then extends via parasympathetic and sympathetic pathways to ultimately produce a body-first subtype. The resulting spread can be tracked by the development of symptoms, clinical assessments, in vivo imaging, and ultimately pathological examination. The integration of environmental exposures into the brain-first and body-first models generates testable hypotheses, including on the prevalence of the clinical conditions, their future incidence, imaging patterns, and pathological signatures. The proposed link, though, has limitations and leaves many questions unanswered, such as the role of the skin, the influence of the microbiome, and the effects of ongoing exposures. Despite these limitations, the interaction of exogenous factors with the nose and the gut may explain many of the mysteries of Parkinson's disease and open the door toward the ultimate goal -prevention.

Prevalence of Concomitant Pathologies in Parkinson's Disease: Implications for Prognosis, Diagnosis, and Insights into Common Pathogenic Mechanisms

Pathologies characteristic of Alzheimer's disease (i.e., hyperphosphorylated tau and amyloid-β (Aβ) plaques), cardiovascular disease, and limbic predominant TDP-43 encephalopathy (LATE) often co-exist in patients with Parkinson's disease (PD), in addition to Lewy body pathology (α-synuclein). Numerous studies point to a putative synergistic relationship between hyperphosphorylation tau, Aβ, cardiovascular lesions, and TDP-43 with α-synuclein, which may alter the stereotypical pattern of pathological progression and accelerate cognitive decline. Here we discuss the prevalence and relationships between common concomitant pathologies observed in PD. In addition, we highlight shared genetic risk factors and developing biomarkers that may provide better diagnostic accuracy for patients with PD that have co-existing pathologies. The tremendous heterogeneity observed across the PD spectrum is most likely caused by the complex interplay between pathogenic, genetic, and environmental factors, and increasing our understanding of how these relate to idiopathic PD will drive research into finding accurate diagnostic tools and disease modifying therapies.

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.

27-Hydroxycholesterol Drives the Spread of α-Synuclein Pathology in Parkinson's Disease

BACKGROUND

The accumulation and aggregation of α-synuclein (α-Syn) are characteristic of Parkinson's disease (PD). Epidemiological evidence indicates that hyperlipidemia is associated with an increased risk of PD. The levels of 27-hydroxycholesterol (27-OHC), a cholesterol oxidation derivative, are increased in the brain and cerebrospinal fluid of patients with PD. However, whether 27-OHC plays a role in α-Syn aggregation and propagation remains elusive.

OBJECTIVE

The aim of this study was to determine whether 27-OHC regulates α-Syn aggregation and propagation.

METHODS

Purified recombinant α-Syn, neuronal cultures, and α-Syn fibril-injected mouse model of PD were treated with 27-OHC. In addition, CYP27A1 knockout mice were used to investigate the effect of lowering 27-OHC on α-Syn pathology in vivo.

RESULTS

27-OHC accelerates the aggregation of α-Syn and enhances the seeding activity of α-Syn fibrils. Furthermore, the 27-OHC-modified α-Syn fibrils localize to the mitochondria and induce mitochondrial dysfunction and neurotoxicity. Injection of 27-OHC-modified α-Syn fibrils induces enhanced spread of α-Syn pathology and dopaminergic neurodegeneration compared with pure α-Syn fibrils. Similarly, subcutaneous administration of 27-OHC facilitates the seeding of α-Syn pathology. Genetic deletion of cytochrome P450 27A1 (CYP27A1), the enzyme that converts cholesterol to 27-OHC, ameliorates the spread of pathologic α-Syn, degeneration of the nigrostriatal dopaminergic pathway, and motor impairments. These results indicate that the cholesterol metabolite 27-OHC plays an important role in the pathogenesis of PD.

CONCLUSIONS

27-OHC promotes the aggregation and spread of α-Syn. Strategies aimed at inhibiting the CYP27A1-27-OHC axis may hold promise as a disease-modifying therapy to halt the progression of α-Syn pathology in PD. © 2023 International Parkinson and Movement Disorder Society.

Two distinct trajectories of clinical and neurodegeneration events in Parkinson's disease

Increasing evidence suggests that Parkinson's disease (PD) exhibits disparate spatial and temporal patterns of progression. Here we used a machine-learning technique-Subtype and Stage Inference (SuStaIn) - to uncover PD subtypes with distinct trajectories of clinical and neurodegeneration events. We enrolled 228 PD patients and 119 healthy controls with comprehensive assessments of olfactory, autonomic, cognitive, sleep, and emotional function. The integrity of substantia nigra (SN), locus coeruleus (LC), amygdala, hippocampus, entorhinal cortex, and basal forebrain were assessed using diffusion and neuromelanin-sensitive MRI. SuStaIn model with above clinical and neuroimaging variables as input was conducted to identify PD subtypes. An independent dataset consisting of 153 PD patients and 67 healthy controls was utilized to validate our findings. We identified two distinct PD subtypes: subtype 1 with rapid eye movement sleep behavior disorder (RBD), autonomic dysfunction, and degeneration of the SN and LC as early manifestations, and cognitive impairment and limbic degeneration as advanced manifestations, while subtype 2 with hyposmia, cognitive impairment, and limbic degeneration as early manifestations, followed later by RBD and degeneration of the LC in advanced disease. Similar subtypes were shown in the validation dataset. Moreover, we found that subtype 1 had weaker levodopa response, more GBA mutations, and poorer prognosis than subtype 2. These findings provide new insights into the underlying disease biology and might be useful for personalized treatment for patients based on their subtype.

Tau seeds occur before earliest Alzheimer's changes and are prevalent across neurodegenerative diseases

Tau neurofibrillary tangles are a hallmark of Alzheimer's disease neuropathological change. However, it remains largely unclear how distinctive Alzheimer's disease tau seeds (i.e. 3R/4R) correlate with histological indicators of tau accumulation. Furthermore, AD tau co-pathology is thought to influence features and progression of other neurodegenerative diseases including Lewy body disease; yet measurements of different types of tau seeds in the setting of such diseases is an unmet need. Here, we use tau real-time quaking-induced conversion (RT-QuIC) assays to selectively quantitate 3R/4R tau seeds in the frontal lobe which accumulates histologically identifiable tau pathology at late disease stages of AD neuropathologic change. Seed quantitation across a spectrum of neurodegenerative disease cases and controls indicated tau seeding activity can be detected well before accompanying histopathological indication of tau deposits, and even prior to the earliest evidence of Alzheimer's-related tau accumulation anywhere in the brain. In later stages of AD, 3R/4R tau RT-QuIC measures correlated with immunohistochemical tau burden. In addition, Alzheimer's tau seeds occur in the vast majority of cases evaluated here inclusive of primary synucleinopathies, frontotemporal lobar degeneration and even controls albeit at multi-log lower levels than Alzheimer's cases. α-synuclein seeding activity confirmed synucleinopathy cases and further indicated the co-occurrence of α-synuclein seeds in some Alzheimer's disease and primary tauopathy cases. Our analysis indicates that 3R/4R tau seeds in the mid-frontal lobe correlate with the overall Braak stage and Alzheimer's disease neuropathologic change, supporting the quantitative predictive value of tau RT-QuIC assays. Our data also indicate 3R/4R tau seeds are elevated in females compared to males at high (≥ IV) Braak stages. This study suggests 3R/4R tau seeds are widespread even prior to the earliest stages of Alzheimer's disease changes, including in normal, and even young individuals, with prevalence across multiple neurodegenerative diseases to further define disease subtypes.

Substantia nigral dopamine transporter uptake in dementia with Lewy bodies

Nigrostriatal dopaminergic degeneration is a pathological hallmark of dementia with Lewy bodies (DLB). To identify the subregional dopamine transporter (DAT) uptake patterns that improve the diagnostic accuracy of DLB, we analyzed N-(3-[18F] fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl)-nortropane (FP-CIT) PET in 51 patients with DLB, in 36 patients with mild cognitive impairment with Lewy body (MCI-LB), and in 40 healthy controls (HCs). In addition to a high affinity for DAT, FP-CIT show a modest affinity to serotonin or norepinephrine transporters. Specific binding ratios (SBRs) of the nigrostriatal subregions were transformed to age-adjusted z-scores (zSBR) based on HCs. The diagnostic accuracy of subregional zSBRs were tested using receiver operating characteristic (ROC) curve analyses separately for MCI-LB and DLB versus HCs. Then, the effect of subregional zSBRs on the presence of clinical features and gray matter (GM) density were evaluated in all patients with MCI-LB or DLB as a group. ROC curve analyses showed that the diagnostic accuracy of DLB based on the zSBR of substantia nigra (area under the curve [AUC], 0.90) or those for MCI-LB (AUC, 0.87) were significantly higher than that based on the zSBR of posterior putamen for DLB (AUC, 0.72) or MCI-LB (AUC, 0.65). Lower zSBRs in nigrostriatal regions were associated with visual hallucination, severe parkinsonism, and cognitive dysfunction, while lower zSBR of substantia nigra was associated with widespread GM atrophy in DLB and MCI-LB patients. Taken together, our results suggest that evaluation of nigral DAT uptake may increase the diagnostic accuracy of DLB and MCI-LB than other striatal regions.

The brain-first vs. body-first model of Parkinson's disease with comparison to alternative models

The ultimate origin of Lewy body disorders, including Parkinson's disease (PD) and Dementia with Lewy bodies (DLB), is still incompletely understood. Although a large number of pathogenic mechanisms have been implicated, accumulating evidence support that aggregation and neuron-to-neuron propagation of alpha-synuclein may be the core feature of these disorders. The synuclein, origin, and connectome (SOC) disease model of Lewy body disorders was recently introduced. This model is based on the hypothesis that in the majority of patients, the first alpha-synuclein pathology arises in single location and spreads from there. The most common origin sites are the enteric nervous system and the olfactory system. The SOC model predicts that gut-first pathology leads to a clinical body-first subtype characterized by prodromal autonomic symptoms and REM sleep behavior disorder. In contrast, olfactory-first pathology leads to a brain-first subtype with fewer non-motor symptoms before diagnosis. The SOC model further predicts that body-first patients are older, more commonly develop symmetric dopaminergic degeneration, and are at increased risk of dementia-compared to brain-first patients. In this review, the SOC model is explained and compared to alternative models of the pathogenesis of Lewy body disorders, including the Braak staging system, and the Unified Staging System for Lewy Body Disorders. Postmortem evidence from brain banks and clinical imaging data of dopaminergic and cardiac sympathetic loss is reviewed. It is concluded that these datasets seem to be more compatible with the SOC model than with those alternative disease models of Lewy body disorders.

The heterogeneity of Parkinson's disease

The heterogeneity of Parkinson's disease (PD), i.e. the various clinical phenotypes, pathological findings, genetic predispositions and probably also the various implicated pathophysiological pathways pose a major challenge for future research projects and therapeutic trail design. We outline several pathophysiological concepts, pathways and mechanisms, including the presumed roles of α-synuclein misfolding and aggregation, Lewy bodies, oxidative stress, iron and melanin, deficient autophagy processes, insulin and incretin signaling, T-cell autoimmunity, the gut-brain axis and the evidence that microbial (viral) agents may induce molecular hallmarks of neurodegeneration. The hypothesis is discussed, whether PD might indeed be triggered by exogenous (infectious) agents in susceptible individuals upon entry via the olfactory bulb (brain first) or the gut (body-first), which would support the idea that disease mechanisms may change over time. The unresolved heterogeneity of PD may have contributed to the failure of past clinical trials, which attempted to slow the course of PD. We thus conclude that PD patients need personalized therapeutic approaches tailored to specific phenomenological and etiologic subtypes of disease.

Proposal for a Biologic Staging System of Parkinson's Disease

The Parkinson's disease (PD) research field has seen the advent of several promising biomarkers and a deeper understanding of the clinical features of the disease from the earliest stages of pathology to manifest disease. Despite progress, a biologically based PD staging system does not exist. Such staging would be a useful framework within which to model the disease, develop and validate biomarkers, guide therapeutic development, and inform clinical trials design. We propose that the presence of aggregated neuronal α-synuclein, dopaminergic neuron dysfunction/degeneration, and clinical signs and symptoms identifies a group of individuals that have Lewy body pathology, which in early stages manifests with what is now referred to as prodromal non-motor features and later stages with the manifestations of PD and related Lewy body diseases as defined by clinical diagnostic criteria. Based on the state of the field, we herein propose a definition and staging of PD based on biology. We present the biologic basis for such a staging system and review key assumptions and evidence that support the proposed approach. We identify gaps in knowledge and delineate crucial research priorities that will inform the ultimate integrated biologic staging system for PD.

A Preliminary Comparison of the Methylome and Transcriptome from the Prefrontal Cortex Across Alzheimer’s Disease and Lewy Body Dementia

Background: Pathological amyloid-β and α-synuclein are associated with a spectrum of related dementias, ranging from Alzheimer’s disease (AD), dementia with Lewy bodies (DLB), to Parkinson disease dementia (PDD). While these diseases share clinical and pathological features, they also have unique patterns of pathology. However, epigenetic factors that contribute to these pathological differences remain unknown. Objective: In this preliminary study, we explore differences in DNA methylation and transcription in five neuropathologically defined groups: cognitively unimpaired controls, AD, pure DLB, DLB with concomitant AD (DLBAD), and PDD. Methods: We employed an Illumina Infinium 850k array and RNA-seq to quantify these differences in DNA methylation and transcription, respectively. We then used Weighted Gene Co-Network Expression Analysis (WGCNA) to determine transcriptional modules and correlated these with DNA methylation. Results: We found that PDD was transcriptionally unique and correlated with an unexpected hypomethylation pattern compared to the other dementias and controls. Surprisingly, differences between PDD and DLB were especially notable with 197 differentially methylated regions. WGCNA yielded numerous modules associated with controls and the four dementias: one module was associated with transcriptional differences between controls and all the dementias as well as having significant overlap with differentially methylated probes. Functional enrichment demonstrated that this module was associated with responses to oxidative stress. Conclusion: Future work that extends these joint DNA methylation and transcription analyses will be critical to better understanding of differences that contribute to varying clinical presentation across dementias.

The unique neuropathological vulnerability of the human brain to aging

Alzheimer's disease (AD)-related neurofibrillary tangles (NFT), argyrophilic grain disease (AGD), aging-related tau astrogliopathy (ARTAG), limbic predominant TDP-43 proteinopathy (LATE), and amygdala-predominant Lewy body disease (LBD) are proteinopathies that, together with hippocampal sclerosis, progressively appear in the elderly affecting from 50% to 99% of individuals aged 80 years, depending on the disease. These disorders usually converge on the same subject and associate with additive cognitive impairment. Abnormal Tau, TDP-43, and α-synuclein pathologies progress following a pattern consistent with an active cell-to-cell transmission and abnormal protein processing in the host cell. However, cell vulnerability and transmission pathways are specific for each disorder, albeit abnormal proteins may co-localize in particular neurons. All these alterations are unique or highly prevalent in humans. They all affect, at first, the archicortex and paleocortex to extend at later stages to the neocortex and other regions of the telencephalon. These observations show that the phylogenetically oldest areas of the human cerebral cortex and amygdala are not designed to cope with the lifespan of actual humans. New strategies aimed at reducing the functional overload of the human telencephalon, including optimization of dream repair mechanisms and implementation of artificial circuit devices to surrogate specific brain functions, appear promising.

Genetics and Pathogenesis of Parkinson's Syndrome

Parkinson's disease (PD) is clinically, pathologically, and genetically heterogeneous, resisting distillation to a single, cohesive disorder. Instead, each affected individual develops a virtually unique form of Parkinson's syndrome. Clinical manifestations consist of variable motor and nonmotor features, and myriad overlaps are recognized with other neurodegenerative conditions. Although most commonly characterized by alpha-synuclein protein pathology throughout the central and peripheral nervous systems, the distribution varies and other pathologies commonly modify PD or trigger similar manifestations. Nearly all PD is genetically influenced. More than 100 genes or genetic loci have been identified, and most cases likely arise from interactions among many common and rare genetic variants. Despite its complex architecture, insights from experimental genetic dissection coalesce to reveal unifying biological themes, including synaptic, lysosomal, mitochondrial, andimmune-mediated mechanisms of pathogenesis. This emerging understanding of Parkinson's syndrome, coupled with advances in biomarkers and targeted therapies, presages successful precision medicine strategies.

Age-Related Decline in Gangliosides GM1 and GD1a in Non-CNS Tissues of Normal Mice: Implications for Peripheral Symptoms of Parkinson's Disease

The purpose of this study was to determine whether the age-related decline in a-series gangliosides (especially GM1), shown to be a factor in the brain-related etiology of Parkinson's disease (PD), also pertains to the peripheral nervous system (PNS) and aspects of PD unrelated to the central nervous system (CNS). Following Svennerholm's demonstration of the age-dependent decline in a-series gangliosides (both GM1 and GD1a) in the human brain, we previously demonstrated a similar decline in the normal mouse brain. The present study seeks to determine whether a similar a-series decline occurs in the periphery of normal mice as a possible prelude to the non-CNS symptoms of PD. We used mice of increasing age to measure a-series gangliosides in three peripheral tissues closely associated with PD pathology. Employing high-performance thin-layer chromatography (HPTLC), we found a substantial decrease in both GM1 and GD1a in all three tissues from 191 days of age. Motor and cognitive dysfunction were also shown to worsen, as expected, in synchrony with the decrease in GM1. Based on the previously demonstrated parallel between mice and humans concerning age-related a-series ganglioside decline in the brain, we propose the present findings to suggest a similar a-series decline in human peripheral tissues as the primary contributor to non-CNS pathologies of PD. An onset of sporadic PD would thus be seen as occurring simultaneously throughout the brain and body, albeit at varying rates, in association with the decline in a-series gangliosides. This would obviate the need to postulate the transfer of aggregated α-synuclein between brain and body or to debate brain vs. body as the origin of PD.

Distribution of Lewy-related pathology in the brain, spinal cord, and periphery: the population-based Vantaa 85 + study

Evolving evidence has supported the existence of two anatomically distinct Lewy-related pathology (LRP) types. Investigation of spinal cord and peripheral LRP can elucidate mechanisms of Lewy body disorders and origins of synuclein accumulation. Still, very few unselected studies have focused on LRP in these regions. Here we analysed LRP in spinal cord, dorsal root ganglion, and adrenal gland in the population-based Vantaa 85 + study, including every ≥ 85 years old citizen living in the city of Vantaa in 1991 (n = 601). Samples from spinal cord (C6-7, TH3-4, L3-4, S1-2) were available from 303, lumbar dorsal root ganglion from 219, and adrenal gland from 164 subjects. Semiquantitative scores of LRP were determined from immunohistochemically stained sections (anti-alpha-synuclein antibody 5G4). LRP in the ventral and dorsal horns of spinal cord, thoracic intermediolateral column, dorsal root ganglion and adrenal gland were compared with brain LRP, previously determined according to DLB Consortium criteria and by caudo-rostral versus amygdala-based LRP classification. Spinal LRP was found in 28% of the total population and in 61% of those who had LRP in the brain. Spinal cord LRP was found only in those subjects with LRP in the brain, and the quantity of spinal cord LRP was associated with the severity of brain LRP (p < 0.001). Unsupervised K-means analysis identified two cluster types of spinal and brain LRP corresponding to caudo-rostral and amygdala-based LRP types. The caudo-rostral LRP type exhibited more frequent and severe pathology in spinal cord, dorsal root ganglion and adrenal gland than the amygdala-based LRP type. Analysis of specific spinal cord regions showed that thoracic intermediolateral column and sacral dorsal horn were the most frequently affected regions in both LRP types. This population-based study on brain, spinal and peripheral LRP provides support to the concept of at least two distinct LRP types.

A postmortem study suggests a revision of the dual-hit hypothesis of Parkinson's disease

The dual-hit hypothesis of Parkinson's disease (PD) originally postulated that a neurotropic pathogen leads to formation of α-synuclein pathology in the olfactory bulb (OB) and dorsal motor nucleus of the vagus (DMV) and then invades the brain from these two entry points. Little work has been conducted to validate an important underlying premise for the dual-hit hypothesis, namely that the initial Lewy pathology does arise simultaneously in the OB and the enteric nervous system (ENS) plexuses and DMV at the earliest disease stage. We conducted a focused re-analysis of two postmortem datasets, which included large numbers of mild Lewy body disease (LBD) cases. We found that cases with α-synuclein pathology restricted to the peripheral autonomic nervous system and/or lower brainstem (early body-first LBD cases) very rarely had any OB pathology, suggesting that Lewy pathology commonly arises in the ENS without concomitant involvement of the OB. In contrast, cases with mild amygdala-predominant Lewy pathology (early brain-first LBD cases) nearly always showed OB pathology. This is compatible with the first pathology being triggered in the OB or amygdala followed by secondary spreading to connected structures, but without early involvement of the ENS or lower brainstem. These observations support that the pathologic process starts in either the olfactory bulb or the ENS, but rarely in the olfactory bulb and gut simultaneously. More studies on neuropathological datasets are warranted to reproduce these findings. The agreement between the revised single-hit hypothesis and the recently proposed brain-first vs. body-first model of LBD is discussed.

The associations of cerebrospinal fluid biomarkers with cognition, and rapid eye movement sleep behavior disorder in early Parkinson's disease

Background

In Parkinson's disease (PD), levels of cerebrospinal fluid (CSF) biomarkers and progression of non-motor symptoms are associated, but the specifics are not yet clear.

Objective

The aim of this study was to investigate the associations of non-motor symptoms with CSF biomarkers in PD.

Materials and methods

We assessed 487 individuals from the Parkinson's Progression Markers Initiative (PPMI), consisting of 155 healthy controls (HCs) and 332 individuals with PD. Patients with PD were grouped according to non-motor symptoms and compared CSF α-synuclein (α-syn), amyloid-beta 1-42 (Aβ_1-42), and total tau (t-tau) levels. Multiple linear regressions were used in baseline analysis and linear mixed-effects models in longitudinal analysis. Analyses of mediating effects between cognition and CSF biomarkers were also performed.

Results

At baseline, PD patients with cognitive impairment (PDCI) exhibited significantly lower CSF α-syn (β = -0.1244; P = 0.0469), Aβ (β = -0.1302; P = 0.0447), and t-tau (β = -0.1260; P = 0.0131) levels than PD patients without cognitive impairment (PDCU). Moreover, a faster decline of α-syn (β = -0.2152; P = 0.0374) and Aβ (β = -0.3114; P = 0.0023) and a faster rise of t-tau (β = -0.1534; P = 0.0274) have been found in longitudinal analysis. The Aβ positive group showed an earlier decline in cognitive performance (β = -0.5341; P = 0.0180) compared with the negative Aβ group in both analyses. In addition, we found that PD patients with probable rapid eye movement sleep behavior disorder (pRBD) showed decreased CSF α-syn (β = -0.1343; P = 0.0033) levels. Finally, mediation analysis demonstrated that olfactory function partially mediated the relationship between cognition and CSF biomarkers levels.

Conclusion

Our study shows that CSF biomarkers are associated with cognition at baseline and longitudinally. Cognitive impairment is more severe in patients with a heavier Aβ burden. CSF α-syn decreased in PD patients with pRBD. This study suggests that early recognition of the increased risk of non-motor symptoms is important for disease surveillance and may be associated with the pathological progression of CSF markers.

Impact of aging on animal models of Parkinson's disease

Aging is the biggest risk factor for developing Parkinson's disease (PD), the second most common neurodegenerative disorder. Several animal models have been developed to explore the pathophysiology underlying neurodegeneration and the initiation and spread of alpha-synuclein-related PD pathology, and to investigate biomarkers and therapeutic strategies. However, bench-to-bedside translation of preclinical findings remains suboptimal and successful disease-modifying treatments remain to be discovered. Despite aging being the main risk factor for developing idiopathic PD, most studies employ young animals in their experimental set-up, hereby ignoring age-related cellular and molecular mechanisms at play. Consequently, studies in young animals may not be an accurate reflection of human PD, limiting translational outcomes. Recently, it has been shown that aged animals in PD research demonstrate a higher susceptibility to developing pathology and neurodegeneration, and present with a more disseminated and accelerated disease course, compared to young animals. Here we review recent advances in the investigation of the role of aging in preclinical PD research, including challenges related to aged animal models that are limiting widespread use. Overall, current findings indicate that the use of aged animals may be required to account for age-related interactions in PD pathophysiology. Thus, although the use of older animals has disadvantages, a model that better represents clinical disease within the elderly would be more beneficial in the long run, as it will increase translational value and minimize the risk of therapies failing during clinical studies. Furthermore, we provide recommendations to manage the challenges related to aged animal models.

Genetic evaluation of dementia with Lewy bodies implicates distinct disease subgroups

The APOE locus is strongly associated with risk for developing Alzheimer's disease and dementia with Lewy bodies. In particular, the role of the APOE ε4 allele as a putative driver of α-synuclein pathology is a topic of intense debate. Here, we performed a comprehensive evaluation in 2466 dementia with Lewy bodies cases versus 2928 neurologically healthy, aged controls. Using an APOE-stratified genome-wide association study approach, we found that GBA is associated with risk for dementia with Lewy bodies in patients without APOE ε4 (P = 6.58 × 10-9, OR = 3.41, 95% CI = 2.25-5.17), but not with dementia with Lewy bodies with APOE ε4 (P = 0.034, OR = 1.87, 95%, 95% CI = 1.05-3.37). We then divided 495 neuropathologically examined dementia with Lewy bodies cases into three groups based on the extent of concomitant Alzheimer's disease co-pathology: pure dementia with Lewy bodies (n = 88), dementia with Lewy bodies with intermediate Alzheimer's disease co-pathology (n = 66) and dementia with Lewy bodies with high Alzheimer's disease co-pathology (n = 341). In each group, we tested the association of the APOE ε4 against the 2928 neurologically healthy controls. Our examination found that APOE ε4 was associated with dementia with Lewy bodies + Alzheimer's disease (P = 1.29 × 10-32, OR = 4.25, 95% CI = 3.35-5.39) and dementia with Lewy bodies + intermediate Alzheimer's disease (P = 0.0011, OR = 2.31, 95% CI = 1.40-3.83), but not with pure dementia with Lewy bodies (P = 0.31, OR = 0.75, 95% CI = 0.43-1.30). In conclusion, although deep clinical data were not available for these samples, our findings do not support the notion that APOE ε4 is an independent driver of α-synuclein pathology in pure dementia with Lewy bodies, but rather implicate GBA as the main risk gene for the pure dementia with Lewy bodies subgroup.

Gastrointestinal Symptoms and Dopamine Transporter Asymmetry in Early Parkinson's Disease

Background

The neurophysiological correlates of gastrointestinal symptoms (GISs) in Parkinson's disease (PD) are not well understood. It has been proposed that in patients with a gastrointestinal origin of PD dopaminergic neurodegeneration would be more symmetric.

Objectives

The aim is to assess the associations between GISs and asymmetry of nigrostriatal dopaminergic neurodegeneration in PD.

Methods

Ninety PD patients were assessed using motor and GIS scales and ¹²³I‐FP‐CIT SPECT. We calculated the asymmetry index and the predominant side of motor symptoms and dopamine transporter (DAT) imaging defect and assessed their association with GISs.

Results

There were no significant differences in GISs between symmetric and asymmetric dopaminergic defect. Left predominant defect was related to more GIS and higher constipation scores.

Conclusions

GISs were associated with left predominant reduction in putaminal DAT binding but not asymmetry per se. It remains open whether left‐sided DAT deficit is related to more pronounced GI involvement or symptom perception in PD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.

An autopsy case of Alzheimer's disease with amygdala-predominant Lewy pathology presenting with frontotemporal dementia-like psychiatric symptoms

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are progressive neurodegenerative diseases associated with several cognitive and behavioral symptoms. It is sometimes difficult to distinguish AD from FTD in a patient because both of them can exhibit clinical overlap. In the present study, we report a case of a patient who showed sychiatric symptoms mimicking the behavioral variant of FTD (bvFTD) and combined AD amygdala-predominant Lewy pathologies on autopsy. The patient was a Japanese man who developed personality changes in his late 50s, presenting with obsessive-compulsive stereotypical behavior, stereotypy of speech, behavioral disinhibition, inertia, loss of empathy or sympathy, change in eating habits, and stimulus-bound behavior. He also frequently left during medical examinations. Eventually, he was clinically diagnosed as having possible bvFTD, according to the International Consensus Criteria for bvFTD. The patient died of systemic metastasis of gastric cancer at 69 years of age. Postmortem neuropathological examination revealed severe AD pathology (Braak Amyloid stage C, Consortium to Establish a Registry for Alzheimer's Disease [CERAD] stage C, Thal phase 5, and Braak AT8 stage IV) along with Lewy pathology and argyrophilic grains, predominantly in the amygdala. Furthermore, no transactivation response DNA-binding protein of 43 kDa (TDP-43) pathology was observed. Our results suggest that a combination of these pathologies causes bvFTD-like cognitive and behavioral symptoms. This case is very insightful when considering the lesions responsible for the psychiatric symptoms characteristic of bvFTD.

Passive Immunization in Alpha-Synuclein Preclinical Animal Models

Alpha-synucleinopathies include Parkinson’s disease, dementia with Lewy bodies, pure autonomic failure and multiple system atrophy. These are all progressive neurodegenerative diseases that are characterized by pathological misfolding and accumulation of the protein alpha-synuclein (αsyn) in neurons, axons or glial cells in the brain, but also in other organs. The abnormal accumulation and propagation of pathogenic αsyn across the autonomic connectome is associated with progressive loss of neurons in the brain and peripheral organs, resulting in motor and non-motor symptoms. To date, no cure is available for synucleinopathies, and therapy is limited to symptomatic treatment of motor and non-motor symptoms upon diagnosis. Recent advances using passive immunization that target different αsyn structures show great potential to block disease progression in rodent studies of synucleinopathies. However, passive immunotherapy in clinical trials has been proven safe but less effective than in preclinical conditions. Here we review current achievements of passive immunotherapy in animal models of synucleinopathies. Furthermore, we propose new research strategies to increase translational outcome in patient studies, (1) by using antibodies against immature conformations of pathogenic αsyn (monomers, post-translationally modified monomers, oligomers and protofibrils) and (2) by focusing treatment on body-first synucleinopathies where damage in the brain is still limited and effective immunization could potentially stop disease progression by blocking the spread of pathogenic αsyn from peripheral organs to the brain.

Colonic Leucine-Rich Repeat Kinase 2 Expression Is Increased and Associated With Disease Severity in Patients With Parkinson’s Disease

Background

Mutations in leucine-rich repeat kinase 2 (LRRK2) comprise a common genetic risk factor for Parkinson’s disease (PD) and inflammatory bowel disease (IBD). We investigated the expression of LRRK2 in colonic biopsies obtained from a cohort of PD patients and healthy controls.

Methods

A cohort of 51 PD patients and 40 age- and gender-matched controls who have colonic biopsied samples were recruited. Among these participants, 26 individuals (12 PD patients and 14 controls) had a series of colon biopsies. For the patients with PD, the first biopsies were taken before the PD diagnosis. The colonic expression of LRRK2 was assayed by immunohistochemical staining.

Results

The fraction of LRRK2-positive cells among the total cell count in biopsied colonic tissues was significantly higher in PD patients than controls (0.81% ± 0.53% vs. 0.45% ± 0.39%; P = 0.02). Colonic LRRK2 immunoreactivity was higher in those with LRRK2 genetic variants compared to those with wild type LRRK2 (2.44% ± 1.15% vs. 0.21 ± 0.13%, P < 0.01). Age had no effect on LRRK2 expression (P = 0.96). LRRK2 expression correlated with disease severity in regards to motor symptoms measured by the UPDRS part III scores (r = 6335, P < 0.001) and cognitive dysfunction measured by the mini-mental status examination scores (r = -0.5774, P < 0.001). PD patients in the prodromal phase had a steeper increase in colonic LRRK2 expression compared to controls during the serial colon biopsy assessment (P < 0.01).

Conclusion

Colonic LRRK2 expression was increased in PD patients compared to controls, and the expression level correlated with disease severity.

Body-first Parkinson's disease and variant Creutzfeldt-Jakob disease - similar or different?

In several neurodegenerative disorders, proteins that typically exhibit an α-helical structure misfold into an amyloid conformation rich in β-sheet content. Through a self-templating mechanism, these amyloids are able to induce additional protein misfolding, facilitating their propagation throughout the central nervous system. This disease mechanism was originally identified for the prion protein (PrP), which misfolds into PrP^Sc in a number of disorders, including variant Creutzfeldt-Jakob disease (vCJD) and bovine spongiform encephalopathy (BSE). More recently, the prion mechanism of disease was expanded to include other proteins that rely on this self-templating mechanism to cause progressive degeneration, including α-synuclein misfolding in Parkinson's disease (PD). Several studies now suggest that PD patients can be subcategorized based on where in the body misfolded α-synuclein originates, either the brain or the gut, similar to patients developing sporadic CJD or vCJD. In this review, we discuss the human and animal model data indicating that α-synuclein and PrP^Sc misfolding originates in the gut in body-first PD and vCJD, and summarize the data identifying the role of the autonomic nervous system in the gut-brain axis of both diseases.

Primary Age‐Related Tauopathy (PART) in a Finnish Population‐Based Study of the Oldest Old (Vantaa 85+)

Aims

Few studies have investigated primary age‐related tauopathy (PART) in a population‐based setting. Here, we assessed its prevalence, genetic background, comorbidities and features of cognitive decline in an unselected elderly population.

Methods

The population‐based Vantaa 85+ study includes all 601 inhabitants of Vantaa aged ≥ 85 years in 1991. Neuropathological assessment was possible in 301. Dementia (DSM IIIR criteria) and Mini‐Mental State Examination (MMSE) scores were assessed at the baseline of the study and follow‐ups. PART subjects were identified according to the criteria by Crary et al and were compared with subjects with mild and severe Alzheimer's disease (AD) neuropathological changes. The effects of other neuropathologies were taken into account using multivariate and sensitivity assays. Genetic analyses included APOE genotypes and 29 polymorphisms of the MAPT 3′ untranslated region (3′UTR region).

Results

The frequency of PART was 20% (n = 61/301, definite PART 5%). When PART subjects were compared with those with severe AD pathology, dementia was less common, its age at onset was higher and duration shorter. No such differences were seen when compared with those with milder AD pathology. However, both AD groups showed a steeper decline in MMSE scores in follow‐ups compared with PART. APOE ε4 frequency was lower, and APOE ε2 frequency higher in the PART group compared with each AD group. The detected nominally significant associations between PART and two MAPT 3′UTR polymorphisms and haplotypes did not survive Bonferroni correction.

Conclusions

PART is common among very elderly. PART subjects differ from individuals with AD‐type changes in the pattern of cognitive decline, associated genetic and neuropathological features.

Neuropathological evidence of body-first vs. brain-first Lewy body disease

Aggregation of alpha-synuclein into inclusion bodies, termed Lewy pathology, is a defining feature of Parkinson's disease (PD) and Dementia with Lewy bodies (DLB). In the majority of post mortem cases, the distribution of Lewy pathology seems to follow two overarching patterns: a caudo-rostral pattern with relatively more pathology in the brainstem than in the telencephalon, and an amygdala-centered pattern with the most abundant pathology in the "center of the brain", including the amygdala, entorhinal cortex, and substantia nigra, and relatively less pathology in the lower brainstem and spinal autonomic nuclei. The recent body-first versus brain-first model of Lewy Body Disorders proposes that the initial pathogenic alpha-synuclein in some patients originates in the enteric nervous system with secondary spreading to the brain; and in other patients originates inside the CNS with secondary spreading to the lower brainstem and peripheral autonomic nervous system. Here, we use two existing post mortem datasets to explore the possibility that clinical body-first and brain-first subtypes are equivalent to the caudo-rostral and amygdala-centered patterns of Lewy pathology seen at post mortem.

The temporal onset of the core features in dementia with Lewy bodies

Introduction

We examined the temporal sequence of the core features in probable dementia with Lewy bodies (DLB).

Methods

In 488 patients with probable DLB, the onset of each core feature and time to diagnosis was determined for men and women, and a pathologic subgroup (n = 209).

Results

REM sleep behavior disorder (RBD) developed before the other core features in men and women. Men were more likely to have RBD and were diagnosed with probable DLB earlier than women. Visual hallucinations developed after the other core features in men, but in women, they appeared earlier and concurrently with fluctuations and parkinsonism. Women were older and more cognitively impaired at first visit, were less likely to have RBD, more likely to be diagnosed with probable DLB later than men, and more likely to have neocortical tangles.

Discussion

An earlier latency to probable DLB was associated with men, RBD, and Lewy body disease without neocortical tangles.

Braak's Unfinished Hypothesis: A Clinicopathological Case Report of α-Synuclein Peripheral Neuropathy Preceding Parkinsonism by 20 Years

Background

α-synuclein aggregates in the form of Lewy bodies and Lewy neurites are the pathological hallmark of Parkinson disease (PD) and dementia with Lewy bodies (DLB). Autopsy studies suggest that α-synuclein aggregates appear in localized areas of the central nervous system before spreading in a sequential pattern from the brainstem to the cerebral cortex, known as the Braak hypothesis. Increased prevalence of peripheral neuropathy in PD is recognized, with multiple hypothesized mechanisms including α-synuclein deposition.

Method

We describe a patient who developed a peripheral sensory neuropathy at age 60, which progressed insidiously over the following decade.

Results

During the patient's eighth decade, the patient developed a fluctuant cognitive disturbance with hallucinations before becoming overtly parkinsonian at age 78 years leading to a diagnosis of DLB. At this point, histology slides from a sural nerve biopsy taken at age 72 were re-evaluated and immunohistochemistry demonstrated α-synuclein deposition.

Conclusion

This case provides important in vivo clinical correlation for the Braak hypothesis, extending its scope beyond idiopathic PD. A growing body of evidence supports the α-synuclein spreading hypothesis that posits the pathologic process begins in the peripheral nerves and spreads trans-synaptically to the CNS in an ascending pattern.

Alpha-synuclein research: defining strategic moves in the battle against Parkinson's disease

With the advent of the genetic era in Parkinson's disease (PD) research in 1997, α-synuclein was identified as an important player in a complex neurodegenerative disease that affects >10 million people worldwide. PD has been estimated to have an economic impact of $51.9 billion in the US alone. Since the initial association with PD, hundreds of researchers have contributed to elucidating the functions of α-synuclein in normal and pathological states, and these remain critical areas for continued research. With this position paper the authors strive to achieve two goals: first, to succinctly summarize the critical features that define α-synuclein's varied roles, as they are known today; and second, to identify the most pressing knowledge gaps and delineate a multipronged strategy for future research with the goal of enabling therapies to stop or slow disease progression in PD.

Neurodegenerative disorders and gut-brain interactions

Neurodegenerative disorders (NDs) affect essential functions not only in the CNS, but also cause persistent gut dysfunctions, suggesting that they have an impact on both CNS and gut-innervating neurons. Although the CNS biology of NDs continues to be well studied, how gut-innervating neurons, including those that connect the gut to the brain, are affected by or involved in the etiology of these debilitating and progressive disorders has been understudied. Studies in recent years have shown how CNS and gut biology, aided by the gut-brain connecting neurons, modulate each other's functions. These studies underscore the importance of exploring the gut-innervating and gut-brain connecting neurons of the CNS and gut function in health, as well as the etiology and progression of dysfunction in NDs. In this Review, we discuss our current understanding of how the various gut-innervating neurons and gut physiology are involved in the etiology of NDs, including Parkinson's disease, Alzheimer's disease, Huntington's disease, and amyotrophic lateral sclerosis, to cause progressive CNS and persistent gut dysfunction.

Prodromal Parkinson disease subtypes - key to understanding heterogeneity

In Parkinson disease (PD), pathological processes and neurodegeneration begin long before the cardinal motor symptoms develop and enable clinical diagnosis. In this prodromal phase, risk and prodromal markers can be used to identify individuals who are likely to develop PD, as in the recently updated International Parkinson and Movement Disorders Society research criteria for prodromal PD. However, increasing evidence suggests that clinical and prodromal PD are heterogeneous, and can be classified into subtypes with different clinical manifestations, pathomechanisms and patterns of spatial and temporal progression in the CNS and PNS. Genetic, pathological and imaging markers, as well as motor and non-motor symptoms, might define prodromal subtypes of PD. Moreover, concomitant pathology or other factors, including amyloid-β and tau pathology, age and environmental factors, can cause variability in prodromal PD. Patients with REM sleep behaviour disorder (RBD) exhibit distinct patterns of α-synuclein pathology propagation and might indicate a body-first subtype rather than a brain-first subtype. Identification of prodromal PD subtypes and a full understanding of variability at this stage of the disease is crucial for early and accurate diagnosis and for targeting of neuroprotective interventions to ensure efficacy.

Medial Temporal Lobe Involvement in Human Prion Diseases: Implications for the Study of Focal Non Prion Neurodegenerative Pathology

Human prion and non-prion neurodegenerative diseases share pathogenic mechanisms and neuropathological features. The lesion profile of a particular entity results from specific involvement of vulnerable neuron populations and connectivity circuits by a pathogenic protein isoform with strain-like properties. The lesion profile of the medial temporal lobe (MTL) was studied in postmortem tissue of 143 patients with human prion disease (HPD) including sporadic, genetic, and acquired forms. Most cases (90%) were classified according to PrP^res type and/or PRNP codon 129 status, in addition to a full neuropathological profile. Mixed histotypes represented 29.4% of total sporadic Creutzfeldt-Jakob disease (sCJD) cases. An intensity score of involvement including spongiosis and astrogliosis was determined for the amygdala, presubiculum, subiculum, entorhinal cortex, CA1 to CA4 sectors of the hippocampal cortex, and dentate gyrus. Connectivity hubs within the MTL presented the highest scores. Diverse lesion profiles were obtained for different types and subtypes of HPD. Impact of mixed PrP^res types on the MTL lesion profile was higher for sCJDMV2K cases than in other histotypes. Differences between MTL profiles was globally consistent with current evidence on specific strains in HPD. These results may be relevant for the analysis of possible strain effects in focal non-prion neurodegenerative conditions limited to the MTL.

Lewy pathology of the esophagus correlates with the progression of Lewy body disease: a Japanese cohort study of autopsy cases

Lewy body disease (LBD) is a spectrum of progressive neurodegenerative disorders characterized by the wide distribution of Lewy bodies and neurites in the central and peripheral nervous system (CNS, PNS). Clinical diagnoses include Parkinson's disease (PD), dementia with Lewy bodies, or pure autonomic failure. All types of LBD are accompanied by non-motor symptoms (NMSs) including gastrointestinal dysfunctions such as constipation. Its relationship to Lewy body-related α-synucleinopathy (Lewy pathology) of the enteric nervous system (ENS) is attracting attention because it can precede the motor symptoms. To clarify the role of ENS Lewy pathology in disease progression, we performed a clinicopathological study using the Brain Bank for Aging Research in Japan. Five-hundred and eighteen cases were enrolled in the study. Lewy pathology of the CNS and PNS, including the lower esophagus as a representative of the ENS, was examined via autopsy findings. Results showed that one-third of older people (178 cases, 34%) exhibited Lewy pathology, of which 78 cases (43.8%) exhibited the pathology in the esophagus. In the esophageal wall, Auerbach's plexus (41.6%) was most susceptible to the pathology, followed by the adventitia (33.1%) and Meissner's plexus (14.6%). Lewy pathology of the esophagus was significantly associated with autonomic failures such as constipation (p < 0.0001) and among PNS regions, correlated the most with LBD progression (r = 0.95, p < 0.05). These findings suggest that the propagation of esophageal Lewy pathology is a predictive factor of LBD.

The α-Synuclein Origin and Connectome Model (SOC Model) of Parkinson's Disease: Explaining Motor Asymmetry, Non-Motor Phenotypes, and Cognitive Decline

A new model of Parkinson's disease (PD) pathogenesis is proposed, the α-Synuclein Origin site and Connectome (SOC) model, incorporating two aspects of α-synuclein pathobiology that impact the disease course for each patient: the anatomical location of the initial α-synuclein inclusion, and α-synuclein propagation dependent on the ipsilateral connections that dominate connectivity of the human brain. In some patients, initial α-synuclein pathology occurs within the CNS, leading to a brain-first subtype of PD. In others, pathology begins in the peripheral autonomic nervous system, leading to a body-first subtype. In brain-first cases, it is proposed that the first pathology appears unilaterally, often in the amygdala. If α-synuclein propagation depends on connection strength, a unilateral focus of pathology will disseminate more to the ipsilateral hemisphere. Thus, α-synuclein spreads mainly to ipsilateral structures including the substantia nigra. The asymmetric distribution of pathology leads to asymmetric dopaminergic degeneration and motor asymmetry. In body-first cases, the α-synuclein pathology ascends via the vagus to both the left and right dorsal motor nuclei of the vagus owing to the overlapping parasympathetic innervation of the gut. Consequently, the initial α-synuclein pathology inside the CNS is more symmetric, which promotes more symmetric propagation in the brainstem, leading to more symmetric dopaminergic degeneration and less motor asymmetry. At diagnosis, body-first patients already have a larger, more symmetric burden of α-synuclein pathology, which in turn promotes faster disease progression and accelerated cognitive decline. The SOC model is supported by a considerable body of existing evidence and may have improved explanatory power.

Brain-first versus body-first Parkinson’s disease: a multimodal imaging case-control study

Parkinson’s disease is characterized by the presence of abnormal, intraneuronal α-synuclein aggregates, which may propagate from cell-to-cell in a prion-like manner. However, it remains uncertain where the initial α-synuclein aggregates originate. We have hypothesized that Parkinson’s disease comprises two subtypes. A brain-first (top-down) type, where α-synuclein pathology initially arises in the brain with secondary spreading to the peripheral autonomic nervous system; and a body-first (bottom-up) type, where the pathology originates in the enteric or peripheral autonomic nervous system and then spreads to the brain. We also hypothesized that isolated REM sleep behaviour disorder (iRBD) is a prodromal phenotype for the body-first type. Using multimodal imaging, we tested the hypothesis by quantifying neuronal dysfunction in structures corresponding to Braak stages I, II and III involvement in three distinct patient groups. We included 37 consecutive de novo patients with Parkinson’s disease into this case-control PET study. Patients with Parkinson’s disease were divided into 24 RBD-negative (PDRBD−) and 13 RBD-positive cases (PDRBD+) and a comparator group of 22 iRBD patients. We used 11C-donepezil PET/CT to assess cholinergic (parasympathetic) innervation, 123I-metaiodobenzylguanidine (MIBG) scintigraphy to measure cardiac sympathetic innervation, neuromelanin-sensitive MRI to measure the integrity of locus coeruleus pigmented neurons, and 18F-dihydroxyphenylalanine (FDOPA) PET to assess putaminal dopamine storage capacity. Colon volume and transit times were assessed with CT scans and radiopaque markers. Imaging data from the three groups were interrogated with ANOVA and Kruskal-Wallis tests corrected for multiple comparisons. The PDRBD− and PDRBD+ groups showed similar marked reductions in putaminal FDOPA-specific uptake, whereas two-thirds of iRBD patients had normal scans (P &lt; 10−13, ANOVA). When compared to the PDRBD− patients, the PDRBD+ and iRBD patients showed reduced mean MIBG heart:mediastinum ratios (P &lt; 10−5, ANOVA) and colon 11C-donepezil standard uptake values (P = 0.008, ANOVA). The PDRBD+ group trended towards a reduced mean MRI locus coeruleus: pons ratio compared to PDRBD− (P = 0.07, t-test). In comparison to the other groups, the PDRBD+ group also had enlarged colon volumes (P &lt; 0.001, ANOVA) and delayed colonic transit times (P = 0.01, Kruskal-Wallis). The combined iRBD and PDRBD+ patient data were compatible with a body-first trajectory, characterized by initial loss of cardiac MIBG signal and 11C-colonic donepezil signal followed by loss of putaminal FDOPA uptake. In contrast, the PDRBD− data were compatible with a brain-first trajectory, characterized by primary loss of putaminal FDOPA uptake followed by a secondary loss of cardiac MIBG signal and 11C-donepezil signal. These findings support the existence of brain-first and body-first subtypes of Parkinson’s disease.