Clinical and imaging evidence of brain-first and body-first Parkinson's disease

Alpha-synuclein, autophagy-lysosomal pathway, and Lewy bodies: Mutations, propagation, aggregation, and the formation of inclusions

Research into the pathophysiology of Parkinson's disease (PD) is a fast-paced pursuit, with new findings about PD and other synucleinopathies being made each year. The involvement of various lysosomal proteins, such as TFEB, TMEM175, GBA, and LAMP1/2, marks the rising awareness about the importance of lysosomes in PD and other neurodegenerative disorders. This, along with recent developments regarding the involvement of microglia and the immune system in neurodegenerative diseases, has brought about a new era in neurodegeneration: the role of proinflammatory cytokines on the nervous system, and their downstream effects on mitochondria, lysosomal degradation, and autophagy. More effort is needed to understand the interplay between neuroimmunology and disease mechanisms, as many of the mechanisms remain enigmatic. α-synuclein, a key protein in PD and the main component of Lewy bodies, sits at the nexus between lysosomal degradation, autophagy, cellular stress, neuroimmunology, PD pathophysiology, and disease progression. This review revisits some fundamental knowledge about PD while capturing some of the latest trends in PD research, specifically as it relates to α-synuclein.

Inflammation and heterogeneity in synucleinopathies

Neurodegenerative diseases represent a huge healthcare challenge which is predicted to increase with an aging population. Synucleinopathies, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), present complex challenges in understanding their onset and progression. They are characterized by the abnormal aggregation of α-synuclein in the brain leading to neurodegeneration. Accumulating evidence supports the existence of distinct subtypes based on the site of α-synuclein aggregation initiation, genetics, and, more recently, neuroinflammation. Mediated by both central nervous system-resident cells, peripheral immune cells, and gut dysbiosis, neuroinflammation appears as a key process in the onset and progression of neuronal loss. Sex-based differences add another layer of complexity to synucleinopathies, influencing disease prevalence - with a known higher incidence of PD in males compared to females - as well as phenotype and immune responses. Biological sex affects neuroinflammatory pathways and the immune response, suggesting the need for sex-specific therapeutic strategies and biomarker identification. Here, we review the heterogeneity of synucleinopathies, describing the etiology, the mechanisms by which the inflammatory processes contribute to the pathology, and the consideration of sex-based differences to highlight the need for personalized therapeutics.

Difference in gut microbial dysbiotic patterns between body-first and brain-first Parkinson's disease

BACKGROUND

This study aims to identify distinct microbial and functional biomarkers characteristic of body-first or brain-first subtypes of Parkinson's disease (PD). This could illuminate the unique pathogenic mechanisms within these subtypes.

METHODS

In this cross-sectional study, we classified 36 well-characterized PD patients into body-first, brain-first, or undetermined subtypes based on the presence of premotor REM sleep behavior disorder (RBD) and cardiac meta-iodobenzylguanidine (MIBG) uptake. We then conducted an in-depth shotgun metagenomic analysis of the gut microbiome for each subtype and compared the results with those from age- and sex-matched healthy controls.

RESULTS

Significant differences were found in the gut microbiome of body-first PD patients (n = 15) compared to both brain-first PD patients (n = 9) and healthy controls. The gut microbiome in body-first PD showed a distinct profile, characterized by an increased presence of Escherichia coli and Akkermansia muciniphila, and a decreased abundance of short-chain fatty acid-producing commensal bacteria. These shifts were accompanied by a higher abundance of microbial genes associated with curli protein biosynthesis and a lower abundance of genes involved in putrescine and spermidine biosynthesis. Furthermore, the combined use of premotor RBD and MIBG criteria was more strongly correlated with these microbiome differences than the use of each criterion independently.

CONCLUSIONS

Our findings highlight the significant role of dysbiotic and pathogenic gut microbial alterations in body-first PD, supporting the body-first versus brain-first hypothesis. These insights not only reinforce the gut microbiome's potential as a therapeutic target in PD but also suggest the possibility of developing subtype-specific treatment strategies.

MRI subtypes in Parkinson's disease across diverse populations and clustering approaches

Parkinson's disease (PD) is clinically heterogeneous, which suggests the existence of subtypes; however, there has been no consensus regarding their characteristics. This study included 633 PD individuals across distinct cohorts: unmedicated de novo PD, medicated PD, mild-moderate PD, and a cohort based on diagnostic work-up in clinical practice. Additionally, 233 controls were included. Clustering based on cortical and subcortical gray matter measures was conducted with and without adjusting for global atrophy in the entire PD sample and validated within each cohort. Subtypes were characterized using baseline and longitudinal demographic and clinical data. Unadjusted results identified three clusters showing a gradient of neurodegeneration and symptom severity across the entire sample and the individual cohorts. When adjusting for global atrophy eight clusters were identified in the entire sample, lacking consistency in individual cohorts. This study identified atrophy-based subtypes in PD, emphasizing the significant impact of global atrophy on subtype number, patterns, and interpretation in cross-sectional analyses.

Parkinson's disease with hyposmia and dysautonomia: does it represent a distinct subtype?

BACKGROUND AND PURPOSE

Olfactory dysfunction or dysautonomia is one of the earliest prodromal nonmotor symptoms of Parkinson's disease (PD). We aimed to investigate whether PD patients with dysautonomia and hyposmia at the de novo stage present different prognoses regarding PD dementia (PDD) conversion, motor complication development, and change in levodopa-equivalent doses (LED).

METHODS

In this retrograde cohort study, we included 105 patients with newly diagnosed PD patients who underwent cross-cultural smell identification test (CC-SIT), autonomic function tests (AFT), and dopamine transporter (DAT) scan at the de novo stage. PD patients were divided into Hyposmia + /Dysautonomia + (H + /D +) and Hyposmia - /Dysautonomia - (H - /D -) groups depending on the result of AFT and CC-SIT. Baseline clinical, cognitive, imaging characteristics, longitudinal risks of PDD development and motor complication occurrence, and longitudinal LED changes were compared between the two groups.

RESULTS

When compared with the H - /D - group, the H + /D + group showed lower standardized uptake value ratios in all subregions, lower asymmetry index, and steeper ventral - dorsal gradient in the DAT scan. The H + /D + group exhibited poorer performance in frontal/executive function and a higher risk of PDD development. The risk of motor complications including levodopa-induced dyskinesia, wearing off, and freezing of gait, was comparable between the two groups. The analysis of longitudinal changes in LED using a linear mixed model showed that the increase of LED in the H + /D + group was more rapid.

CONCLUSIONS

Our results suggest that PD patients with dysautonomia and hyposmia at the de novo stage show a higher risk of PD dementia conversion and rapid progression of motor symptoms.

Impact of autonomic symptoms on the clinical course of Parkinson's disease

PURPOSE

Patients with Parkinson's disease (PD) exhibit various degrees of autonomic symptoms, which may be associated with Lewy body pathology distributed extensively in the autonomic nervous system. We hypothesized that the severity of autonomic symptoms reflects the severity of PD-related pathology, resulting in poor outcomes. The purpose of this study was to evaluate the impact of autonomic symptoms on PD progression.

METHODS

We conducted a follow-up study among consecutive patients with PD at Dokkyo Medical University Hospital. Patients underwent comprehensive baseline evaluations and were classified into high and low autonomic symptom groups using the Scale for Outcomes in Parkinson's Disease-Autonomic (SCOPA-AUT). The Kaplan‒Meier survival curves were used to analyze the time to discontinuation of their visits because of PD-related endpoints and to evaluate the association with high SCOPA-AUT scores.

RESULTS

Of the 101 patients, 74 (73%) met the inclusion criteria. During the follow-up period (mean 1654 days), 22/74 patients reached PD-related endpoints (death, 4; hospitalization, 9; nursing home institutionalization, 9). PD patients with high SCOPA-AUT scores reached the endpoints faster than those with low SCOPA-AUT scores. A high SCOPA-AUT score, including gastrointestinal, urinary, and thermoregulation domains; high motor symptom scores; and low specific binding ratios (SBRs) on 123I FP-CIT-SPECT (DAT-SPECT) were associated with reaching PD-related endpoints. A high SCOPA-AUT score was associated with reaching the endpoints even after adjustment for covariates.

CONCLUSIONS

Patients with high autonomic symptom scores had a greater risk of reaching PD-related endpoints than patients with low autonomic symptom scores.

Risk of Parkinson's disease in people aged ≥50 years with new-onset anxiety: a retrospective cohort study in UK primary care

BACKGROUND

A history of anxiety is more common in people with Parkinson's disease (PD). The prospective risk of PD in those newly presenting with anxiety and factors that increase the risk of PD in patients with anxiety have not been investigated.

AIM

To investigate the incidence of PD in people with anxiety aged ≥50 years and clinical features associated with later diagnosis of PD in people with anxiety.

DESIGN AND SETTING

A retrospective cohort study using UK primary care data between 2008 and 2018, assessing patients with new-onset anxiety aged ≥50 years.

METHOD

Weibull survival regression models were fitted and hazard ratios (HRs) for modelling time-to-PD was estimated in those with and without anxiety, and when determining the risk of developing PD in those with anxiety. Results were adjusted for sociodemographic and lifestyle factors, and relevant physical and mental health conditions.

RESULTS

The risk of PD increased two-fold compared with the non-anxiety group after adjustment for age, sex, social deprivation, lifestyle factors, severe mental illness, head trauma, and dementia (HR 2.1, 95% confidence interval = 1.9 to 2.4). In those with anxiety, the presence of depression, hypotension, tremor, rigidity, balance impairment, constipation, sleep disturbance, fatigue, and cognitive impairment were associated with an increased risk of developing PD.

CONCLUSION

The risk of developing PD was at least doubled in people with anxiety compared with those without. The clinical features of those who developed PD can help identify patients presenting with anxiety who are in the prodromal phase of PD.

Understanding REM Sleep Behavior Disorder through Functional MRI: A Systematic Review

Neuroimaging studies in rapid eye movement sleep behavior disorder (RBD) can inform fundamental questions about the pathogenesis of Parkinson's disease (PD). Across modalities, functional magnetic resonance imaging (fMRI) may be better suited to identify changes between neural networks in the earliest stages of Lewy body diseases when structural changes may be subtle or absent. This review synthesizes the findings from all fMRI studies of RBD to gain further insight into the pathophysiology and progression of Lewy body diseases. A total of 32 studies were identified using a systematic review conducted according to PRISMA guidelines between January 2000 to February 2024 for original fMRI studies in patients with either isolated RBD (iRBD) or RBD secondary to PD. Common functional alterations were detectable in iRBD patients compared with healthy controls across brainstem nuclei, basal ganglia, frontal and occipital lobes, and whole brain network measures. Patients with established PD and RBD demonstrated decreased functional connectivity across the whole brain and brainstem nuclei, but increased functional connectivity in the cerebellum and frontal lobe compared with those PD patients without RBD. Finally, longitudinal changes in resting state functional connectivity were found to track with disease progression. Currently, fMRI studies in RBD have demonstrated early signatures of neurodegeneration across both motor and non-motor pathways. Although more work is needed, such findings have the potential to inform our understanding of disease, help to distinguish between prodromal PD and prodromal dementia with Lewy bodies, and support the development of fMRI-based outcome measures of phenoconversion and progression in future disease modifying trials. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Interaction between α-Synuclein and Bioactive Lipids: Neurodegeneration, Disease Biomarkers and Emerging Therapies

The present review provides a comprehensive examination of the intricate dynamics between α-synuclein, a protein crucially involved in the pathogenesis of several neurodegenerative diseases, including Parkinson's disease and multiple system atrophy, and endogenously-produced bioactive lipids, which play a pivotal role in neuroinflammation and neurodegeneration. The interaction of α-synuclein with bioactive lipids is emerging as a critical factor in the development and progression of neurodegenerative and neuroinflammatory diseases, offering new insights into disease mechanisms and novel perspectives in the identification of potential biomarkers and therapeutic targets. We delve into the molecular pathways through which α-synuclein interacts with biological membranes and bioactive lipids, influencing the aggregation of α-synuclein and triggering neuroinflammatory responses, highlighting the potential of bioactive lipids as biomarkers for early disease detection and progression monitoring. Moreover, we explore innovative therapeutic strategies aimed at modulating the interaction between α-synuclein and bioactive lipids, including the development of small molecules and nutritional interventions. Finally, the review addresses the significance of the gut-to-brain axis in mediating the effects of bioactive lipids on α-synuclein pathology and discusses the role of altered gut lipid metabolism and microbiota composition in neuroinflammation and neurodegeneration. The present review aims to underscore the potential of targeting α-synuclein-lipid interactions as a multifaceted approach for the detection and treatment of neurodegenerative and neuroinflammatory diseases.

Disease progression modelling reveals heterogeneity in trajectories of Lewy-type α-synuclein pathology

Lewy body (LB) diseases, characterized by the aggregation of misfolded α-synuclein proteins, exhibit notable clinical heterogeneity. This may be due to variations in accumulation patterns of LB neuropathology. Here we apply a data-driven disease progression model to regional neuropathological LB density scores from 814 brain donors with Lewy pathology. We describe three inferred trajectories of LB pathology that are characterized by differing clinicopathological presentation and longitudinal antemortem clinical progression. Most donors (81.9%) show earliest pathology in the olfactory bulb, followed by accumulation in either limbic (60.8%) or brainstem (21.1%) regions. The remaining donors (18.1%) initially exhibit abnormalities in brainstem regions. Early limbic pathology is associated with Alzheimer's disease-associated characteristics while early brainstem pathology is associated with progressive motor impairment and substantial LB pathology outside of the brain. Our data provides evidence for heterogeneity in the temporal spread of LB pathology, possibly explaining some of the clinical disparities observed in Lewy body disease.

Disease progression in proposed brain-first and body-first Parkinson's disease subtypes

A new Parkinson's disease (PD) subtyping model has been recently proposed based on the initial location of α-synuclein inclusions, which divides PD patients into the brain-first subtype and the body-first subtype. Premotor RBD has proven to be a predictive marker of the body-first subtype. We found compared to PD patients without possible RBD (PDpRBD-, representing the brain-first subtype), PD patients with possible premotor RBD (PDpRBD+, representing the body-first subtype) had lower Movement Disorders Society Unified Parkinson's Disease Rating Scale part III (MDS UPDRS-III) score (p = 0.022) at baseline but presented a faster progression rate (p = 0.009) in MDS UPDRS-III score longitudinally. The above finding indicates the body-first subtype exhibited a faster disease progression in motor impairments compared to the brain-first subtype and further validates the proposed subtyping model.

Imaging Procedure and Clinical Studies of [18F]FP-CIT PET

N-3-[18F]fluoropropyl-2β-carbomethoxy-3β-4-iodophenyl nortropane ([18F]FP-CIT) is a radiopharmaceutical for dopamine transporter (DAT) imaging using positron emission tomography (PET) to detect dopaminergic neuronal degeneration in patients with parkinsonian syndrome. [18F]FP-CIT was granted approval by the Ministry of Food and Drug Safety in 2008 as the inaugural radiopharmaceutical for PET imaging, and it has found extensive utilization across numerous institutions in Korea. This review article presents an imaging procedure for [18F]FP-CIT PET to aid nuclear medicine physicians in clinical practice and systematically reviews the clinical studies associated with [18F]FP-CIT PET.

Glutamate Signaling in Patients With Parkinson Disease With REM Sleep Behavior Disorder

BACKGROUND AND OBJECTIVES

Clinical heterogeneity of patients with Parkinson disease (PD) is well recognized. PD with REM sleep behavior disorder (RBD) is a more malignant phenotype with faster motor progression and higher nonmotor symptom burden. However, the neural mechanisms underlying this clinical divergence concerning imbalances in neurotransmitter systems remain elusive.

METHODS

Combining magnetic resonance (MR) spectroscopy and [11C]ABP688 PET on a PET/MR hybrid system, we simultaneously investigated two different mechanisms of glutamate signaling in patients with PD. Patients were grouped according to their RBD status in overnight video-polysomnography and compared with age-matched and sex-matched healthy control (HC) participants. Total volumes of distribution (VT) of [11C]ABP688 were estimated with metabolite-corrected plasma concentrations during steady-state conditions between 45 and 60 minutes of the scan following a bolus-infusion protocol. Glutamate, glutamine, and glutathione levels were investigated with single-voxel stimulated echo acquisition mode MR spectroscopy of the left basal ganglia.

RESULTS

We measured globally elevated VT of [11C]ABP688 in 16 patients with PD and RBD compared with 17 patients without RBD and 15 HC participants (F(2,45) = 5.579, p = 0.007). Conversely, glutamatergic metabolites did not differ between groups and did not correlate with the regional VT of [11C]ABP688. VT of [11C]ABP688 correlated with the amount of REM sleep without atonia (F(1,42) = 5.600, p = 0.023) and with dopaminergic treatment response in patients with PD (F(1,30) = 5.823, p = 0.022).

DISCUSSION

Our results suggest that patients with PD and RBD exhibit altered glutamatergic signaling indicated by higher VT of [11C]ABP688 despite unaffected glutamate levels. The imbalance of glutamate receptors and MR spectroscopy glutamate metabolite levels indicates a novel mechanism contributing to the heterogeneity of PD and warrants further investigation of drugs targeting mGluR5.

Peripheral cutaneous synucleinopathy characteristics in genetic Parkinson's disease

Background

Cutaneous phosphorylated alpha-synuclein (p-α-syn) deposition is an important biomarker of idiopathic Parkinson's disease (iPD). Recent studies have reported synucleinopathies in patients with common genetic forms of PD.

Objective

This study aimed to detect p-α-syn deposition characteristic in rare genetic PD patients with CHCHD2 or RAB39B mutations. Moreover, this study also aimed to describe peripheral alpha-synuclein prion-like activity in genetic PD patients, and acquire whether the cutaneous synucleinopathy characteristics of genetic PD are consistent with central neuropathologies.

Methods

We performed four skin biopsy samples from the distal leg (DL) and proximal neck (C7) of 161 participants, including four patients with CHCHD2 mutations, two patients with RAB39B mutations, 16 patients with PRKN mutations, 14 patients with LRRK2 mutations, five patients with GBA mutations, 100 iPD patients, and 20 healthy controls. We detected cutaneous synucleinopathies using immunofluorescence staining and a seeding amplification assay (SAA). A systematic literature review was also conducted, involving 64 skin biopsies and 205 autopsies of genetic PD patients with synucleinopathy.

Results

P-α-syn was deposited in the peripheral cutaneous nerves of PD patients with CHCHD2, LRRK2, or GBA mutations but not in those with RAB39B or PRKN mutations. There were no significant differences in the location or rate of α-syn-positive deposits between genetic PD and iPD patients. Peripheral cutaneous synucleinopathy appears to well represent brain synucleinopathy of genetic PD, especially autosomal dominant PD (AD-PD). Cutaneous α-synuclein SAA analysis of iPD and LRRK2 and GBA mutation patients revealed prion-like activity.

Conclusion

P-α-syn deposition in peripheral cutaneous nerves, detected using SAA and immunofluorescence staining, may serve as an accurate biomarker for genetic PD and iPD in the future.

Sympathetic dysfunction as an early indicator of autonomic involvement in Parkinson's disease

PURPOSE

The specific characteristics of autonomic involvement in patients with early Parkinson's disease (PD) are unclear. This study aimed to evaluate the characteristics of autonomic dysfunction in drug-naïve patients with early-stage PD without orthostatic hypotension (OH) by analyzing Valsalva maneuver (VM) parameters.

METHODS

We retrospectively analyzed drug-naïve patients without orthostatic hypotension (n = 61) and controls (n = 20). The patients were subcategorized into early PD (n = 35) and mid-PD (n = 26) groups on the basis of the Hoehn and Yahr staging. VM parameters, including changes in systolic blood pressure at late phase 2 (∆SBPVM2), ∆HRVM3, Valsalva ratio (VR), pressure recovery time, adrenergic baroreflex sensitivity, and vagal baroreflex sensitivity, were assessed.

RESULTS

In the early PD group, ∆SBPVM2, a marker of sympathetic function, was significantly lower compared with that in controls (risk ratio = 0.95, P = 0.027). Receiver operating characteristic (ROC) curve analysis showed an optimal cut-off value of -10 mmHg for ∆SBPVM2 [P = 0.002, area under the curve (AUC): 0.737]. VR exhibited an inverse relationship with Unified Parkinson's Disease Rating Scale Part 3 scores in the multivariable regression analysis (VR: P = 0.038, β = -28.61), whereas age showed a positive relationship (age: P = 0.027, β = 0.35).

CONCLUSION

The ∆BPVM2 parameter of the VM may help detect autonomic nervous system involvement in early-PD without OH. Our results suggest that sympathetic dysfunction is an early manifestation of autonomic dysfunction in patients with PD.

Impact of olfactory function on the trajectory of cognition, motor function, and quality of life in Parkinson's disease

Background

Olfactory dysfunction in Parkinson's disease (PD) is associated with more severe phenotypes, but trajectories of cognitive function, disease severity, and subdomains of quality-of-life measurements in patients with distinct olfactory profiles remain underexplored.

Objective

To analyze the influence of olfaction on trajectories of clinical parameters in patients with PD.

Design

Retrospective cohort study.

Subjects

From October 2016 to May 2021, the study tracked 58 participants over 3 years. Participants completed follow-up assessments using tools including the Chinese version of the University of Pennsylvania's Smell Identification Test (UPSIT), Montreal Cognitive Assessment (MoCA), Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale, and the Chinese translation of the 39-item Parkinson's Disease Questionnaire (PDQ-39).

Methods

Participants were divided into anosmia (UPSIT < 19) and non-anosmia (UPSIT ≥ 19) groups based on initial scores. Generalized estimating equations and repeated measures correlations were used to examine longitudinal associations and correlations between olfaction and clinical parameters.

Results

Divergent cognitive trajectories were observed between groups. The anosmia group exhibited a faster cognitive decline (adjusted B [beta coefficient] = -1.8, p = 0.012) according to the interaction effect of olfaction and time on the MoCA score. The anosmia group exhibited no longitudinal correlation between cognition and olfactory function but showed correlations with age (rrm [coefficient of repeated measures correlation] = -0.464, p = 0.004) and disease duration (rrm = -0.457, p = 0.005). The non-anosmia group's UPSIT scores decreased over time (B = -2.3, p = 0.005) alongside a significant correlation with motor function (rrm = -0.479, p = 0.006).

Conclusion

The anosmia group's accelerated cognitive decline correlated with age and disease duration, but not olfactory function, suggesting a poor cognitive outcome in this population despite the lack of longitudinal correlation between cognition and olfaction. The non-anosmia group exhibited progressive olfactory degradation and notable correlations between motor function and UPSIT scores, implying pathological accumulation in the olfactory structure and basal ganglia.

Parkinson's disease motor progression in relation to the timing of REM sleep behavior disorder presentation: an exploratory retrospective study

REM sleep behavior disorder (RBD) is a frequent non-motor symptom of Parkinson's disease (PD), and the timing of its presentation might have a role in the underlying neurodegenerative process. Here, we aimed to define the potential impact of probable RBD (pRBD) on PD motor progression.We conducted a longitudinal retrospective study on 66 PD patients followed up at the University Hospital of Rome Tor Vergata. Patients were divided into three groups: with post-motor pRBD (pRBDpost, n = 25), without pRBD (pRBDwo, n = 20), and with pre-motor pRBD (pRBDpre, n = 21). Hoehn and Yahr (H&Y) scores, Unified PD Rating Scale (UPDRS) motor scores, and levodopa equivalent daily dose were collected at two follow-up visits conducted in a 5-year interval (T0 and T1). pRBDpost patients had a greater rate of motor progression in terms of the H&Y scale compared to pRBDpre and pRBDwo patients, without the influence of anti-parkinsonian treatment.These preliminary findings suggest that the post-motor occurrence of pRBD can be associated with an acceleration in PD motor progression.

Correlation of olfactory function factors with cardiac sympathetic denervation in Parkinson's disease

BACKGROUND

Hyposmia is a common nonmotor symptom of Parkinson's disease (PD) and reportedly associated with dysautonomia in PD. The smell identification test for measuring olfactory function consists of multiple items to discriminate specific scents. In the present study, factor analysis of the smell identification test was performed, and the correlation of extracted factors with cardiac sympathetic denervation (CSD) in patients with PD was investigated.

METHODS

The present study included 183 early PD patients who underwent the Cross-Cultural Smell Identification Test (CC-SIT) and 123I-meta-iodobenzylguanidine (123I-MIBG) myocardial scintigraphy. Factor analysis of 12 items on the CC-SIT was performed using the computed correlation matrix for the binary items, and five smell factors were extracted. Multiple linear regression was performed to determine the correlation of olfactory function with late heart-to-mediastinum (H/M) ratio of 123I-MIBG uptake.

RESULTS

The mean CC-SIT score was 6.1 ± 2.6, and 133 patients (72.7%) had CSD. The CC-SIT score and five smell factors were not associated with dopamine transporter uptake or cognitive functions. However, the CC-SIT score significantly correlated with age (P < 0.001) and late H/M ratio (P < 0.001). Factors 1 and 5 showed an increasing trend with larger H/M ratio, although it was not statistically significant (β = 0.203, P = 0.085 and β = 0.230, P = 0.085, respectively). Factor 5 significantly correlated with the H/M ratio in PD patients with CSD (β = 0.676, P = 0.036).

DISCUSSION

The results showed olfactory dysfunction to be selectively associated with cardiac sympathetic burden in PD. The correlation of certain factors with CSD indicates the possibility of selective hyposmia in PD patients.

Constipation and pain in Parkinson's disease: a clinical analysis

Parkinson's Disease (PD) is a neurodegenerative disorder characterized by both motor and non-motor symptoms (NMS). Among NMS, constipation and pain are both highly prevalent and debilitating affecting up to 80% of PD patients and impairing their quality of life. Here, we investigated the relationship between constipation and pain in PD patients. This is a retrospective study assessing the relationship between pain and constipation in a PD patient population from a clinical database of patients attending the outpatient clinic of the movement disorders division, Neurology Unit of Policlinico Tor Vergata, in Rome. Subjects were assessed with the Unified Parkinson's Disease Rating Scale (UPDRS) part III, Hoehn and Yahr (H&Y) stage, King's Parkinson's Disease Pain Scale (KPPS), Brief Pain Inventory (BPI), Non-Motor Symptoms Scale (NMSS) and Beck Depression Inventory (BDI). Patients were further divided in two groups (Group 1, 32 patients with constipation and Group 2, 35 PD patients without constipation) ANOVA and ANCOVA analysis were used to compare the two groups. PD patients with constipation had significantly higher pain severity and pain interference, as measured by the BPI scale and higher total KPPS score, fluctuation-related pain, nocturnal pain, and radicular pain when compared to PD patients without constipation. This study highlights for the first time a possible interplay between constipation and pain in PD that deserves further investigations.

Comparison of quantitative REM without atonia parameters in isolated REM sleep behavior disorder and early untreated Parkinson's disease

OBJECTIVES

To analyze REM sleep without atonia (RWA) metrics in patients with isolated REM sleep behavior disorder (iRBD), Parkinson's disease (PD) and healthy subjects and compare them in terms of degree of presumed brainstem damage.

METHODS

Forty-nine iRBD patients, 62 PD patients and 38 healthy controls were included into the analysis. Detailed polysomnographic and clinical data including motor, olfactory, autonomic, and cognitive assessment were obtained in all participants and subsequently compared within groups without RBD (i.e., healthy controls, PD-RBD-) and with RBD (i.e., iRBD, PD-RBD+). SINBAR criteria were used to score RWA.

RESULTS

Twenty-one PD patients (33.8 %) had RBD. When comparing PD-RBD-patients and controls, RWA tonic (p = 0.001) and RWA mixed (p = 0.03) were higher in PD-RBD-group. PD-RBD-patients had worse olfactory function than controls (p < 0.001); no significant difference in autonomic or cognitive function was registered. There were no significant differences in RWA parameters when comparing iRBD and PD-RBD + groups. iRBD patients had better olfactory function than PD-RBD+ (p = 0.006); no significant difference in autonomic or cognitive function was registered. PD-RBD + had worse autonomic (p = 0.006) and olfactory (p = 0.001) but not motor and cognitive function compared to PD-RBD-.

CONCLUSIONS

Untreated de-novo PD patients without RBD have increased RWA metrics compared to healthy subjects indicating subclinical degeneration of brainstem nuclei responsible for RWA. iRBD patients do not differ in RWA metrics from untreated de-novo PD patients with premotor RBD suggesting a similar level of brainstem degeneration caudal to substantia nigra in both groups. Groups with RBD are associated with autonomic dysfunction.

The Story behind the Mask: A Narrative Review on Hypomimia in Parkinson's Disease

Facial movements are crucial for social and emotional interaction and well-being. Reduced facial expressions (i.e., hypomimia) is a common feature in patients with Parkinson's disease (PD) and previous studies linked this manifestation to both motor symptoms of the disease and altered emotion recognition and processing. Nevertheless, research on facial motor impairment in PD has been rather scarce and only a limited number of clinical evaluation tools are available, often suffering from poor validation processes and high inter- and intra-rater variability. In recent years, the availability of technology-enhanced quantification methods of facial movements, such as automated video analysis and machine learning application, led to increasing interest in studying hypomimia in PD. In this narrative review, we summarize the current knowledge on pathophysiological hypotheses at the basis of hypomimia in PD, with particular focus on the association between reduced facial expressions and emotional processing and analyze the current evaluation tools and management strategies for this symptom, as well as future research perspectives.

The Potentiality of Natural Products and Herbal Medicine as Novel Medications for Parkinson's Disease: A Promising Therapeutic Approach

As the global population ages, the prevalence of Parkinson's disease (PD) is steadily on the rise. PD demonstrates chronic and progressive characteristics, and many cases can transition into dementia. This increases societal and economic burdens, emphasizing the need to find effective treatments. Among the widely recognized causes of PD is the abnormal accumulation of proteins, and autophagy dysfunction accelerates this accumulation. The resultant Lewy bodies are also commonly found in Alzheimer's disease patients, suggesting an increased potential for the onset of dementia. Additionally, the production of free radicals due to mitochondrial dysfunction contributes to neuronal damage and degeneration. The activation of astrocytes and the M1 phenotype of microglia promote damage to dopamine neurons. The drugs currently used for PD only delay the clinical progression and exacerbation of the disease without targeting its root cause, and come with various side effects. Thus, there is a demand for treatments with fewer side effects, with much potential offered by natural products. In this study, we reviewed a total of 14 articles related to herbal medicines and natural products and investigated their relevance to possible PD treatment. The results showed that the reviewed herbal medicines and natural products are effective against lysosomal disorder, mitochondrial dysfunction, and inflammation, key mechanisms underlying PD. Therefore, natural products and herbal medicines can reduce neurotoxicity and might improve both motor and non-motor symptoms associated with PD. Furthermore, these products, with their multi-target effects, enhance bioavailability, inhibit antibiotic resistance, and might additionally eliminate side effects, making them good alternative therapies for PD treatment.

Advancements in Genetic and Biochemical Insights: Unraveling the Etiopathogenesis of Neurodegeneration in Parkinson's Disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative movement disorder worldwide, which is primarily characterized by motor impairments. Even though multiple hypotheses have been proposed over the decades that explain the pathogenesis of PD, presently, there are no cures or promising preventive therapies for PD. This could be attributed to the intricate pathophysiology of PD and the poorly understood molecular mechanism. To address these challenges comprehensively, a thorough disease model is imperative for a nuanced understanding of PD's underlying pathogenic mechanisms. This review offers a detailed analysis of the current state of knowledge regarding the molecular mechanisms underlying the pathogenesis of PD, with a particular emphasis on the roles played by gene-based factors in the disease's development and progression. This study includes an extensive discussion of the proteins and mutations of primary genes that are linked to PD, including α-synuclein, GBA1, LRRK2, VPS35, PINK1, DJ-1, and Parkin. Further, this review explores plausible mechanisms for DAergic neural loss, non-motor and non-dopaminergic pathologies, and the risk factors associated with PD. The present study will encourage the related research fields to understand better and analyze the current status of the biochemical mechanisms of PD, which might contribute to the design and development of efficacious and safe treatment strategies for PD in future endeavors.

Impact of Non-Motor Symptoms on Quality of Life in Patients with Early-Onset Parkinson's Disease

BACKGROUND

Early-onset Parkinson's disease (EOPD) refers to patients with Parkinson's disease (PD) whose age at disease onset is less than 50 years. Literature on the non-motor symptoms (NMS) in these patients is very limited in the Indian context. We aimed to study the NMS in patients with EOPD and its impact on the quality of life (QoL).

METHODS

We included 124 patients with EOPD with a mean age at disease onset between 21 and 45 years and 60 healthy controls (HC). NMS were assessed using validated scales, and the QoL domains were evaluated using the PD QoL-39 scale (PDQ-39).

RESULTS

The mean age at disease onset in EOPD patients was 37.33 ± 6.36 years. Majority of the patients were male (66.12%). The average disease duration was 6.62 ± 5.3 years. EOPD patients exhibited a significantly higher number of NMS per patient (7.97 ± 4.69) compared to HC (1.3 ± 1.39; p < 0.001). The most common NMS reported were urinary dysfunction, body pain, poor sleep quality, constipation, anxiety, depression, cognitive impairment, and REM sleep behavior disorder. The total NMS burden correlated with the QoL measures. Distinctive patterns of QoL subdomain involvement were identified, with sleep/fatigue, mood/cognition, and urinary dysfunction independently influencing QoL metrics.

CONCLUSIONS

Our study provides valuable insights into the NMS profile and its impact on QoL in patients with EOPD, addressing an important knowledge gap in the Indian context. By understanding the specific NMS and their influence on QoL, healthcare professionals can develop targeted interventions to address these symptoms and improve the overall QoL.

A multiple hits hypothesis for memory dysfunction in Parkinson disease

Cognitive disorders are increasingly recognized in Parkinson disease (PD), even in early disease stages, and memory is one of the most affected cognitive domains. Classically, hippocampal cholinergic system dysfunction was associated with memory disorders, whereas nigrostriatal dopaminergic system impairment was considered responsible for executive deficits. Evidence from PD studies now supports involvement of the amygdala, which modulates emotional attribution to experiences. Here, we propose a tripartite model including the hippocampus, striatum and amygdala as key structures for cognitive disorders in PD. First, the anatomo-functional relationships of these structures are explored and experimental evidence supporting their role in cognitive dysfunction in PD is summarized. We then discuss the potential role of α-synuclein, a pathological hallmark of PD, in the tripartite memory system as a key mechanism in the pathogenesis of memory disorders in the disease.

Overcoming Methodological Challenges for Advancing Stem Cell Therapies in Parkinson's Disease

The quest for new and improved therapies for Parkinson's disease (PD) remains of paramount importance, despite previous trial failures. There is a current debate regarding the potential of stem cell research as a therapeutic approach for PD. The studies of dopaminergic fetal stem cells for PD treatment, their design, and the results of the initial surgical placebo-controlled trials were reviewed in this study. Some of the fundamental methodological challenges and possible strategies to resolve them were proposed. In this article, we argue that the most important impact lies in the proof-of-principle demonstrated by clinical trials for cell replacement strategies in reconstructing the human brain. While some researchers argue that the considerable technical challenges associated with cell therapies for PD warrant the discontinuation of further development using stem cells, we believe that the opposing viewpoints are instrumental in identifying a series of methodological misunderstandings. Here, we propose to expose key challenges to ensure the advancement of the field and unlock the potential of stem cell therapies in PD treatment. Overall, this review underscores the need for further research and innovation to overcome the hurdles in realizing the potential of stem cell-based therapies for PD.

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.

Disease progression modelling reveals heterogeneity in trajectories of Lewy-type α-synuclein pathology

Lewy body (LB) disorders, characterized by the aggregation of misfolded α-synuclein proteins, exhibit notable clinical heterogeneity. This may be due to variations in accumulation patterns of LB neuropathology. By applying data-driven disease progression modelling to regional neuropathological LB density scores from 814 brain donors, we describe three inferred trajectories of LB pathology that were characterized by differing clinicopathological presentation and longitudinal antemortem clinical progression. Most donors (81.9%) showed earliest pathology in the olfactory bulb, followed by accumulation in either limbic (60.8%) or brainstem (21.1%) regions. The remaining donors (18.1%) exhibited the first abnormalities in brainstem regions. Early limbic pathology was associated with Alzheimer's disease-associated characteristics. Meanwhile, brainstem-first pathology was associated with progressive motor impairment and substantial LB pathology outside of the brain. Our data provides evidence for heterogeneity in the temporal spread of LB pathology, possibly explaining some of the clinical disparities observed in LBDs.

Cardiac 18F-dopamine positron emission tomography predicts the type of phenoconversion of pure autonomic failure

PURPOSE

Pure autonomic failure (PAF) is a rare disease characterized by neurogenic orthostatic hypotension (nOH), no known secondary cause, and lack of a neurodegenerative movement or cognitive disorder. Clinically diagnosed PAF can evolve ("phenoconvert") to a central Lewy body disease [LBD, e.g., Parkinson's disease (PD) or dementia with Lewy bodies (DLB)] or to the non-LBD synucleinopathy multiple system atrophy (MSA). Since cardiac 18F-dopamine-derived radioactivity usually is low in LBDs and usually is normal in MSA, we hypothesized that patients with PAF with low cardiac 18F-dopamine-derived radioactivity would be more likely to phenoconvert to a central LBD than to MSA.

METHODS

We reviewed data from all the patients seen at the National Institutes of Health Clinical Center from 1994 to 2023 with a clinical diagnosis of PAF and data about 18F-dopamine positron emission tomography (PET).

RESULTS

Nineteen patients (15 with low 18F-dopamine-derived radioactivity, 4 with normal radioactivity) met the above criteria and had follow-up data. Nine (47%) phenoconverted to a central synucleinopathy over a mean of 6.6 years (range 1.5-18.8 years). All 6 patients with low cardiac 18F-dopamine-derived radioactivity who phenoconverted during follow-up developed a central LBD, whereas none of 4 patients with consistently normal 18F-dopamine PET phenoconverted to a central LBD (p = 0.0048), 3 evolving to probable MSA and 1 upon autopsy having neither a LBD nor MSA.

CONCLUSION

Cardiac 18F-dopamine PET can predict the type of phenoconversion of PAF. This capability could refine eligibility criteria for entry into disease-modification trials aimed at preventing evolution of PAF to symptomatic central LBDs.

Central and peripheral innate and adaptive immunity in Parkinson's disease

Parkinson's disease (PD) is a multisystem disorder with characteristics of a chronic inflammatory disease. To develop effective immunomodulatory interventions to combat PD, we need to think innovatively about the implications of orchestrated central and peripheral innate and adaptive immune responses that occur as the disease begins and progresses.

Enteric glia as a player of gut-brain interactions during Parkinson's disease

The enteric glia has been shown as a potential component of neuroimmune interactions that signal in the gut-brain axis during Parkinson's disease (PD). Enteric glia are a peripheral glial type found in the enteric nervous system (ENS) that, associated with enteric neurons, command various gastrointestinal (GI) functions. They are a unique cell type, with distinct phenotypes and distribution in the gut layers, which establish relevant neuroimmune modulation and regulate neuronal function. Comprehension of enteric glial roles during prodromal and symptomatic phases of PD should be a priority in neurogastroenterology research, as the reactive enteric glial profile, gastrointestinal dysfunction, and colonic inflammation have been verified during the prodromal phase of PD-a moment that may be interesting for interventions. In this review, we explore the mechanisms that should govern enteric glial signaling through the gut-brain axis to understand pathological events and verify the possible windows and pathways for therapeutic intervention. Enteric glia directly modulate several functional aspects of the intestine, such as motility, visceral sensory signaling, and immune polarization, key GI processes found deregulated in patients with PD. The search for glial biomarkers, the investigation of temporal-spatial events involving glial reactivity/signaling, and the proposal of enteric glia-based therapies are clearly demanded for innovative and intestine-related management of PD.

Motor progression phenotypes in early-stage Parkinson's Disease: A clinical prediction model and the role of glymphatic system imaging biomarkers

BACKGROUND

Substantial heterogeneity of motor symptoms in Parkinson's disease (PD) poses a challenge to disease prediction.

OBJECTIVES

The aim of this study was to construct a nomogram model that can distinguish different longitudinal trajectories of motor symptom changes in early-stage PD patients.

METHODS

Data on 90 patients with 5-years of follow-up were collected from the Parkinson's Progression Marker Initiative (PPMI) cohort. We used a latent class mixed modeling (LCMM) to identify distinct progression patterns of motor symptoms, and backward stepwise logistic regression with baseline information was conducted to identify the potential predictors for motor trajectory and to develop a nomogram. The performance of the nomogram model was then evaluated using the optimism-corrected C-index for internal validation, the area under the curve (AUC) of the receiver operating characteristic (ROC) curve for discrimination, the calibration curve for predictive accuracy, and decision curve analysis (DCA) for its clinical value.

RESULTS

We identified two trajectories for motor progression patterns. The first, Class 1 (Motor deteriorated group), was characterized by sustained, continuously worsening motor symptoms, and the second, Class 2 (Motor stable group), had stable motor symptoms throughout the follow-up period. The best combination of 7 baseline variables was identified and assembled into the nomogram: Scopa-AUT [odds ratio (OR), 1.11; p = 0.091], Letter number sequencing (LNS) (OR, 0.76; p = 0.068), the asymmetry index of putamen (OR, 0.95; p = 0.034), mean caudate uptake (OR, 0.14; p = 0.086), CSF pTau/α-synuclein (OR, 0.00; p = 0.011), CSF tTau/Aβ (OR, 25434806; p = 0.025), and the index for diffusion tensor image analysis along the perivascular space (ALPS-index) (OR, 0.02; p = 0.030). The nomogram achieved good discrimination, with an original AUC of 0.901 (95% CI, 0.813-0.989), and the bias-corrected concordance index (C-index) with 1,000 bootstraps was 0.834. The calibration curve and DCA also suggested both the high accuracy and clinical usefulness of the nomogram, respectively.

CONCLUSIONS

This study proposes an effective nomogram to predict different motor progression patterns in early-stage PD. Furthermore, the imaging biomarker indicating glymphatic function could be an independent predictive factor for PD motor progression.

Nanowired delivery of antibodies to tau and neuronal nitric oxide synthase together with cerebrolysin attenuates traumatic brain injury induced exacerbation of brain pathology in Parkinson's disease

Concussive head injury (CHI) is one of the major risk factors for developing Parkinson's disease in later life of military personnel affecting lifetime functional and cognitive disturbances. Till date no suitable therapies are available to attenuate CHI or PD induced brain pathology. Thus, further exploration of novel therapeutic agents are highly warranted using nanomedicine in enhancing the quality of life of veterans or service members of US military. Since PD or CHI induces oxidative stress and perturbs neurotrophic factors regulation associated with phosphorylated tau (p-tau) deposition, a possibility exists that nanodelivery of agents that could enhance neurotrophic factors balance and attenuate oxidative stress could be neuroprotective in nature. In this review, nanowired delivery of cerebrolysin-a balanced composition of several neurotrophic factors and active peptide fragments together with monoclonal antibodies to neuronal nitric oxide synthase (nNOS) with p-tau antibodies was examined in PD following CHI in model experiments. Our results suggest that combined administration of nanowired antibodies to nNOS and p-tau together with cerebrolysin significantly attenuated CHI induced exacerbation of PD brain pathology. This combined treatment also has beneficial effects in CHI or PD alone, not reported earlier.

Shaping the course of early-onset Parkinson's disease: insights from a longitudinal cohort

INTRODUCTION

Early -onset Parkinson's disease (EOPD) labels those cases with onset earlier than fifty. Although peculiarities emerged either in clinical or pathological features, EOPD is managed alike typical, late-onset PD. A customized approach would be, instead, better appropriate. Accordingly, a deeper characterization of the clinical course, with an estimation of the disease progression rate, the therapy flow, and the main motor and non-motor complications occurrence, is needed.

METHODS

A longitudinal cohort of 193 EOPD patients (selected on a single-centre population of 2000 PD cases) was retrospectively analysed, providing descriptive statics on a series of clinical parameters (genetics, phenotype, comorbidities, therapies, motor and non-motor complications, marital and gender issues) and modelling the trajectories from diagnosis to 10 years later of both Hoehn and Yahr (H&Y) stage and levodopa equivalent daily dose (LEDD).

RESULTS

EOPD had a prevalence of 9.7%, including few monogenic cases. It mostly appeared as a motor syndrome, with asymmetric, rigid-akinetic presentation. H&Y linearly progressed with an increment of 0.92 points/10 years; LEDD flow had a non-linear trend, increasing of 526.90 mg/day in 0-5 years, and 166.83 mg/day in 5-10 years. Motor fluctuations started 6.5 ± 3.2 years from onset, affecting up to 80% of the cohort. Neuropsychiatric troubles interested the 50%, sexual complaints the 12%. Gender-specific motor disturbances emerged.

CONCLUSION

We shaped EOPD course, modelling a "brain-first" PD subtype, slowly progressive, with non-linear dopaminergic requirement. Major burden mostly resulted from motor fluctuations, neuropsychiatric complications, sexual and marital complaints, with a considerable gender-effect.

Cardiac 18F-Dopamine Positron Emission Tomography Predicts the Type of Phenoconversion of Pure Autonomic Failure

Background

Pure autonomic failure (PAF) is a rare disease characterized clinically by neurogenic orthostatic hypotension (nOH) and biochemically by peripheral noradrenergic deficiency. Clinically diagnosed PAF can evolve ("phenoconvert") to a central Lewy body disease (LBD, e.g., Parkinson's disease (PD) or dementia with Lewy bodies (DLB)) or to the non-LBD synucleinopathy multiple system atrophy (MSA). We examined whether cardiac 18F-dopamine positron emission tomography (PET) predicts the trajectory of phenoconversion in PAF. Since cardiac 18F-dopamine-derived radioactivity always is decreased in LBDs with nOH and usually is normal in MSA, we hypothesized that PAF patients with low cardiac 18F-dopamine-derived radioactivity may phenoconvert to a central LBD but do not phenoconvert to MSA.

Methods

We reviewed data from all the patients seen at the National Institutes of Health Clinical Center from 1994 to 2023 with a clinical diagnosis of PAF and data about serial 18F-dopamine PET.

Results

Twenty patients met the above criteria. Of 15 with low cardiac 18F-dopamine-derived radioactivity, 6 (40%) phenoconverted to PD or DLB and none to MSA. Of 5 patients with consistently normal 18F-dopamine PET, 4 phenoconverted to MSA, and the other at autopsy had neither a central LBD nor MSA.

Conclusion

In this case series, 40% of patients with nOH and low cardiac 18F-dopamine-derived radioactivity phenoconverted to PD or DLB during follow-up; none phenoconverted to MSA. Cardiac 18F-DA PET therefore can predict the type of phenoconversion in PAF. This capability could refine eligibility criteria for entry into disease-modification trials aiming to prevent evolution of PAF to symptomatic central LBDs.

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.

Effects of different levodopa doses on blood pressure in older patients with early and middle stages of Parkinson's disease

Objective

Levodopa is the first-line treatment for patients with Parkinson's disease (PD). However, only a few studies have focused on the tolerance of this drug in older patients with PD in the early and middle stages. Therefore, this study aimed to explore the effects of different levodopa doses on blood pressure (BP) in this subpopulation.

Methods

This cohort analysis enrolled 83 patients. The levodopa challenge test was used to evaluate drug responsiveness. After at least 12 h following anti-PD drug discontinuation, patients' BPs were measured in a lying position, after 1 min standing, and after 3 min standing, in "off state" and best "on state."

Results

BP in the 250 mg and 375 mg levodopa/benserazide groups decreased significantly in the lying and standing positions. The 3-min standing-position systolic BP was significantly influenced by the dose of levodopa/benserazide. However, no statistical change was observed in the 125 mg group. The postural-mediated systolic BP disparity was significant at 3 min in the upright position. Nineteen (incidence, 22.9%) and Twenty-five patients (incidence, 30.1%) developed complications of orthostatic hypotension (OH) in the "off state" and best "on state," respectively. Mild cognitive impairment was a risk factor for OH occurrence in the "off state." The OH occurrence in the best "on state" was associated with OH in the "off state" and urinary incontinence.

Conclusion

Our findings suggest that 250 mg or more of levodopa/benserazide could significantly reduce BP and orthostatic effect in older patients with PD in the early and middle stages. Therefore, they should routinely monitor their BP.

Trial registration number

ChiCTR2200055707.

Parkinson's Disease: A Narrative Review on Potential Molecular Mechanisms of Sleep Disturbances, REM Behavior Disorder, and Melatonin

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. There is a wide range of sleep disturbances in patients with PD, such as insomnia and rapid eye movement (REM) sleep behavior disorder (or REM behavior disorder (RBD)). RBD is a sleep disorder in which a patient acts out his/her dreams and includes abnormal behaviors during the REM phase of sleep. On the other hand, melatonin is the principal hormone that is secreted by the pineal gland and significantly modulates the circadian clock and mood state. Furthermore, melatonin has a wide range of regulatory effects and is a safe treatment for sleep disturbances such as RBD in PD. However, the molecular mechanisms of melatonin involved in the treatment or control of RBD are unknown. In this study, we reviewed the pathophysiology of PD and sleep disturbances, including RBD. We also discussed the potential molecular mechanisms of melatonin involved in its therapeutic effect. It was concluded that disruption of crucial neurotransmitter systems that mediate sleep, including norepinephrine, serotonin, dopamine, and GABA, and important neurotransmitter systems that mediate the REM phase, including acetylcholine, serotonin, and norepinephrine, are significantly involved in the induction of sleep disturbances, including RBD in PD. It was also concluded that accumulation of α-synuclein in sleep-related brain regions can disrupt sleep processes and the circadian rhythm. We suggested that new treatment strategies for sleep disturbances in PD may focus on the modulation of α-synuclein aggregation or expression.

α-Synuclein seeding activity in duodenum biopsies from Parkinson's disease patients

Abnormal deposition of α-synuclein is a key feature and biomarker of Parkinson's disease. α-Synuclein aggregates can propagate themselves by a prion-like seeding-based mechanism within and between tissues and are hypothesized to move between the intestine and brain. α-Synuclein RT-QuIC seed amplification assays have detected Parkinson's-associated α-synuclein in multiple biospecimens including post-mortem colon samples. Here we show intra vitam detection of seeds in duodenum biopsies from 22/23 Parkinson's patients, but not in 6 healthy controls by RT-QuICR. In contrast, no tau seeding activity was detected in any of the biopsies. Our seed amplifications provide evidence that the upper intestine contains a form(s) of α-synuclein with self-propagating activity. The diagnostic sensitivity and specificity for PD in this biopsy panel were 95.7% and 100% respectively. End-point dilution analysis indicated up to 106 SD50 seeding units per mg of tissue with positivity in two contemporaneous biopsies from individual patients suggesting widespread distribution within the superior and descending parts of duodenum. Our detection of α-synuclein seeding activity in duodenum biopsies of Parkinson's disease patients suggests not only that such analyses may be useful in ante-mortem diagnosis, but also that the duodenum may be a source or a destination for pathological, self-propagating α-synuclein assemblies.

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.

Disruption of locus coeruleus-related functional networks in Parkinson's disease

Locus coeruleus (LC) is severely affected in Parkinson's Disease (PD). However, alterations in LC-related resting-state networks (RSNs) in PD remain unclear. We used resting-state functional MRI to investigate the alterations in functional connectivity (FC) of LC-related RSNs and the associations between RSNs changes and clinical features in idiopathic rapid eye movement sleep behavior disorder (iRBD) and PD patients with (PD^RBD+) and without RBD (PD^RBD-). There was a similarly disrupted FC pattern of LC-related RSNs in iRBD and PD^RBD+ patients, whereas LC-related RSNs were less damaged in PD^RBD- patients than that in patients with iRBD and PD^RBD+. The FC of LC-related RSNs correlated with cognition and duration in iRBD, depression in PD^RBD-, and cognition and severity of RBD in patients with PD^RBD+. Our findings demonstrate that LC-related RSNs are significantly disrupted in the prodromal stage of α-synucleinopathies and proposed body-first PD (PD^RBD+), but are less affected in brain-first PD (PD^RBD-).

Beyond the Microbiota: Understanding the Role of the Enteric Nervous System in Parkinson's Disease from Mice to Human

The enteric nervous system (ENS) is a nerve network composed of neurons and glial cells that regulates the motor and secretory functions of the gastrointestinal (GI) tract. There is abundant evidence of mutual communication between the brain and the GI tract. Dysfunction of these connections appears to be involved in the pathophysiology of Parkinson's disease (PD). Alterations in the ENS have been shown to occur very early in PD, even before central nervous system (CNS) involvement. Post-mortem studies of PD patients have shown aggregation of α-synuclein (αS) in specific subtypes of neurons in the ENS. Subsequently, αS spreads retrogradely in the CNS through preganglionic vagal fibers to this nerve's dorsal motor nucleus (DMV) and other central nervous structures. Here, we highlight the role of the ENS in PD pathogenesis based on evidence observed in animal models and using a translational perspective. While acknowledging the putative role of the microbiome in the gut-brain axis (GBA), this review provides a comprehensive view of the ENS not only as a "second brain", but also as a window into the "first brain", a potentially crucial element in the search for new therapeutic approaches that can delay and even cure the disease.

The role of the microbiota-gut-brain axis and intestinal microbiome dysregulation in Parkinson's disease

Parkinson's disease (PD) is a complex progressive neurodegenerative disease associated with aging. Its main pathological feature is the degeneration and loss of dopaminergic neurons related to the misfolding and aggregation of α-synuclein. The pathogenesis of PD has not yet been fully elucidated, and its occurrence and development process are closely related to the microbiota-gut-brain axis. Dysregulation of intestinal microbiota may promote the damage of the intestinal epithelial barrier, intestinal inflammation, and the upward diffusion of phosphorylated α-synuclein from the enteric nervous system (ENS) to the brain in susceptible individuals and further lead to gastrointestinal dysfunction, neuroinflammation, and neurodegeneration of the central nervous system (CNS) through the disordered microbiota-gut-brain axis. The present review aimed to summarize recent advancements in studies focusing on the role of the microbiota-gut-brain axis in the pathogenesis of PD, especially the mechanism of intestinal microbiome dysregulation, intestinal inflammation, and gastrointestinal dysfunction in PD. Maintaining or restoring homeostasis in the gut microenvironment by targeting the gut microbiome may provide future direction for the development of new biomarkers for early diagnosis of PD and therapeutic strategies to slow disease progression.

Parkinson's Disease, SARS-CoV-2, and Frailty: Is There a Vicious Cycle Related to Hypovitaminosis D?

The literature has long established the association between aging and frailty, with emerging evidence pointing to a relationship between frailty and SARS-CoV-2 contagion. The possible neurological consequences of SARS-CoV-2 infection, associated with physical and cognitive frailty, could lead to a worsening of Parkinson's disease (PD) in infected patients or-more rarely-to an increase in the Parkinsonian symptomatology. A possible link between those clinical pictures could be identified in vitamin D deficiency, while the whole process would appear to be associated with alterations in the microbiota-intestine-brain axis that fall within the α-Synuclein Origin site and Connectome (SOC) model, and allow for the identification of a body-first PD and a brain-first PD. The model of care for this condition must consider intrinsic and extrinsic variables so that care by a multidisciplinary team can be successfully predicted. A multidimensional screening protocol specifically designed to identify people at risk or in the early stages of the disease should begin with the investigation of indices of frailty and microbiota-intestine-brain axis alterations, with a new focus on cases of hypovitaminosis D.

Systemic Metabolic Alteration Dependent on the Thyroid-Liver Axis in Early PD

OBJECTIVE

Parkinson's disease (PD) is a common neurodegenerative disease characterized by initial involvement of the olfactory bulb/amygdala or autonomic nerves followed by nigral degeneration. Although autonomic innervation strictly regulates multiorgan systems, including endocrine functions, circulation, and digestion, how dysautonomia in PD affects systemic metabolism has not been identified. In this study, we tried to estimate the pathogenic linkage of PD by nuclear medicine techniques, trans-omic analysis of blood samples, and cultured cell experiments.

METHODS

Thyroid mediastinum ratio of ¹²³ I-metaiodobenzylguanidine (MIBG) scintigraphy was measured in 1,158 patients with PD. Furthermore, serum exosome miRNA transcriptome analysis and plasma metabolome analysis followed by trans-omic analysis were performed in patients with de novo PD and age-matched healthy control persons. Additionally, thyroid hormone was administered to skeletal muscle and liver derived cells to evaluate the effect of hypothyroidism for these organs.

RESULTS

Sympathetic denervation of thyroid correlating with its cardiac denervation was confirmed in 1,158 patients with PD by MIBG scintigraphy. Among patients with drug-naïve PD, comprehensive metabolome analysis revealed decreased levels of thyroxine and insufficient fatty acid β-oxidation, which positively correlate with one another. Likewise, both plasma metabolome data and transcriptome data of circulating exosomal miRNAs, revealed specific enrichment of the peroxisome proliferator-activated receptor (PPARα) axis. Finally, association of thyroid hormone with PPARα-dependent β-oxidation regulation was confirmed by in vitro experiments.

INTERPRETATION

Our findings suggest that interorgan communications between the thyroid and liver are disorganized in the early stage of PD, which would be a sensitive diagnostic biomarker for PD. ANN NEUROL 2023;93:303-316.

Factors contributing to sleep disturbances and excessive daytime sleepiness in patients with Parkinson's disease

Background

Sleep disturbances and excessive daytime sleepiness (EDS) are common non-motor symptoms in patients with Parkinson's disease (PD). The purpose of this study was to identify the contributors to sleep disturbances, including insomnia, restless legs syndrome, rapid eye movement sleep behavior disorder (RBD), sleep-disordered breathing, nocturnal akinesia and EDS, in patients with PD.

Methods

We conducted a cross-sectional study including 128 consecutive Japanese patients with PD. Sleep disturbances and EDS were defined as a PD Sleep Scale-2 (PDSS-2) total score ≥15 and an Epworth Sleepiness Scale (ESS) score >10, respectively. The patients were divided into four groups according to the presence or absence of sleep disturbances and EDS. We evaluated the disease severity, motor symptoms, cognition, olfactory test, the Scales for Outcomes in PD-Autonomic dysfunction (SCOPA-AUT), the Beck Depression Inventory-II (BDI-II), and the RBD Screening Questionnaire Japanese version (RBDSQ-J).

Results

Of 128 patients, 64 had neither EDS nor sleep disturbances, 29 had sleep disturbances without EDS, 14 had EDS without sleep disturbances, and 21 had both EDS and sleep disturbances. Patients with sleep disturbances had higher BDI-II scores than those without sleep disturbances. Probable RBD was more frequent in patients with both sleep disturbances and EDS than in those with neither EDS nor sleep disturbances. The SCOPA-AUT score was lower in patients with neither EDS nor sleep disturbances than in patients in the other three groups. Using multivariable logistic regression analysis with neither sleep disturbances nor EDS as a reference group, that the SCOPA-AUT score was an independent contributor to sleep disturbances (adjusted OR, 1.192; 95% CI, 1.065-1.333; P = 0.002) or EDS (OR, 1.245; 95% CI, 1.087-1.424; P = 0.001) and that the BDI-II (OR, 1.121; 95% CI, 1.021-1.230; P = 0.016) and RBDSQ-J scores (OR, 1.235; 95% CI, 1.007-1.516; P = 0.043) as well as the SCOPA-AUT score (OR, 1.137; 95% CI, 1.006-1.285; P = 0.040) were independent contributors to both sleep disturbances and EDS.

Conclusions

Autonomic symptoms were associated with patients with sleep disturbances or EDS, and depressive and RBD symptoms in addition to autonomic symptoms were associated with patients with both sleep disturbances and EDS.

Pesticides and the Microbiome-Gut-Brain Axis: Convergent Pathways in the Pathogenesis of Parkinson's Disease

The increasing global burden of Parkinson's disease (PD), termed the PD pandemic, is exceeding expectations related purely to population aging and is likely driven in part by lifestyle changes and environmental factors. Pesticides are well recognized risk factors for PD, supported by both epidemiological and experimental evidence, with multiple detrimental effects beyond dopaminergic neuron damage alone. The microbiome-gut-brain axis has gained much attention in recent years and is considered to be a significant contributor and driver of PD pathogenesis. In this narrative review, we first focus on how both pesticides and the microbiome may influence PD initiation and progression independently, describing pesticide-related central and peripheral neurotoxicity and microbiome-related local and systemic effects due to dysbiosis and microbial metabolites. We then depict the bidirectional interplay between pesticides and the microbiome in the context of PD, synthesizing current knowledge about pesticide-induced dysbiosis, microbiome-mediated alterations in pesticide availability, metabolism and toxicity, and complex systemic pesticide-microbiome-host interactions related to inflammatory and metabolic pathways, insulin resistance and other mechanisms. An overview of the unknowns follows, and the role of pesticide-microbiome interactions in the proposed body-/brain-first phenotypes of PD, the complexity of environmental exposures and gene-environment interactions is discussed. The final part deals with possible further steps for translation, consisting of recommendations on future pesticide use and research as well as an outline of promising preventive/therapeutic approaches targeted on strengthening or restoring a healthy gut microbiome, closing with a summary of current gaps and future perspectives in the field.

Assessment of Multivariate Information Transmission in Space-Time-Frequency Domain: A Case Study for EEG Signals

OBJECTIVE

Multivariate signal (MS) analysis, especially the assessment of its information transmission (for example, from the perspective of network science), is the key to our understanding of various phenomena in biology, physics and economics. Although there is a large amount of literature demonstrating that MS can be decomposed into space-time-frequency domain information, there seems to be no research confirming that multivariate information transmission (MIT) in these three domains can be quantified. Therefore, in this study, we attempted to combine dynamic mode decomposition (DMD) and parallel communication model (PCM) together to realize it.

METHODS

We first regarded MS as a large-scale system and then used DMD to decompose it into specific subsystems with their own intrinsic oscillatory frequencies. At the same time, the transition probability matrix (TPM) of information transmission within and between MS at two consecutive moments in each subsystem can also be calculated. Then, communication parameters (CPs) derived from each TPM were calculated in order to quantify the MIT in the space-time-frequency domain. In this study, multidimensional electroencephalogram (EEG) signals were used to illustrate our method.

RESULTS

Compared with traditional EEG brain networks, this method shows greater potential in EEG analysis to distinguish between patients and healthy controls.

CONCLUSION

This study demonstrates the feasibility of measuring MIT in the space-time-frequency domain simultaneously.

SIGNIFICANCE

This study shows that MIT analysis in the space-time-frequency domain is not only completely different from the MS decomposition in these three domains, but also can reveal many new phenomena behind MS that have not yet been discovered.

Selecting the Best Animal Model of Parkinson's Disease for Your Research Purpose: Insight from in vivo PET Imaging Studies

Parkinson's disease (PD) is a debilitating neurodegenerative multisystem disorder leading to motor and non-motor symptoms in millions of individuals. Despite intense research, there is still no cure, and early disease biomarkers are lacking. Animal models of PD have been inspired by basic elements of its pathogenesis, such as dopamine dysfunction, alpha-synuclein accumulation, neuroinflammation and disruption of protein degradation, and these have been crucial for a deeper understanding of the mechanisms of pathology, the identification of biomarkers, and evaluation of novel therapies. Imaging biomarkers are non-invasive tools to assess disease progression and response to therapies; their discovery and validation have been an active field of translational research. Here, we highlight different considerations of animal models of PD that can be applied to future research, in terms of their suitability to answer different research questions. We provide the reader with important considerations of the best choice of model to use based on the disease features of each model, including issues related to different species. In addition, positron emission tomography studies conducted in PD animal models in the last 5 years are presented. With a variety of different species, interventions and genetic information, the choice of the most appropriate model to answer research questions can be daunting, especially since no single model recapitulates all aspects of this complex disorder. Appropriate animal models in conjunction with in vivo molecular imaging tools, if selected properly, can be a powerful combination for the assessment of novel therapies and developing tools for early diagnosis.

Disruption of Sleep Microarchitecture Is a Sensitive and Early Marker of Parkinson's Disease

BACKGROUND

Although sleep disturbances are highly prevalent in patients with Parkinson's disease, sleep macroarchitecture metrics show only minor changes.

OBJECTIVE

To assess alterations of the cyclic alternating pattern (CAP) as a critical feature of sleep microarchitecture in patients with prodromal, recent, and established Parkinson's disease.

METHODS

We evaluated overnight polysomnography for classic sleep macroarchitecture and CAP metrics in 68 patients at various disease stages and compared results to 22 age- and sex-matched controls.

RESULTS

Already at the prodromal stage, patients showed a significantly reduced CAP rate as a central characteristic of sleep microarchitecture. Temporal characteristics of CAP showed a gradual change over disease stages and correlated with motor performance. In contrast, the sleep macroarchitecture metrics did not differ between groups.

CONCLUSION

Data suggest that alterations of sleep microarchitecture are an early and more sensitive characteristic of Parkinson's disease than changes in sleep macroarchitecture.