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

Concomitant Pathologies and Their Impact on Parkinson Disease: A Narrative Overview of Current Evidence

Many clinico-pathological studies point to the presence of multiple comorbidities/co-pathologies in the course of Parkinson disease (PD). Lewy body pathology, the morphological hallmark of PD, rarely exists in isolation, but is usually associated with other concomitant pathologies, in particular Alzheimer disease-related changes (ADNC), cerebrovascular pathologies (macro- and microinfarcts, cerebral small vessel disease, cerebral amyloid angiopathy), TDP-43 pathology as well as multiple pathological combinations. These include cardiovascular disorders, metabolic syndrome, diabetes mellitus, autoimmune and rheumatic diseases, myasthenia gravis, Sjögren's syndrome, restless leg syndrome or other rare disorders, like Fabry disease. A combination of PD and multiple sclerosis (MS) may be due to the immune function of LRRK2 and its interrelation with α-synuclein. COVID-19 and HIV posed considerable impacts on patients with PD. Epidemiological evidence points to a decreased risk for the majority of neoplasms, except melanoma and other skin cancers, while some tumors (breast, brain) are increased. On the other hand, a lower frequency of malignancies preceding early PD markers may argue for their protective effect on PD risk. Possible pathogenetic factors for the association between PD and cancer are discussed. The tremendous heterogeneity of concomitant pathologies and comorbidities observed across the PD spectrum is most likely caused by the complex interplay between genetic, pathogenic and other risk factors, and further research should provide increasing insight into their relationship with idiopathic PD (and other parkinsonian disorders) in order to find better diagnostic tools and probable disease-modifying therapies.

Gut-first Parkinson's disease is encoded by gut dysbiome

BACKGROUND

In Parkinson's patients, intestinal dysbiosis can occur years before clinical diagnosis, implicating the gut and its microbiota in the disease. Recent evidence suggests the gut microbiota may trigger body-first Parkinson Disease (PD), yet the underlying mechanisms remain unclear. This study aims to elucidate how a dysbiotic microbiome through intestinal immune alterations triggers PD-related neurodegeneration.

METHODS

To determine the impact of gut dysbiosis on the development and progression of PD pathology, wild-type male C57BL/6 mice were transplanted with fecal material from PD patients and age-matched healthy donors to challenge the gut-immune-brain axis.

RESULTS

This study demonstrates that patient-derived intestinal microbiota caused midbrain tyrosine hydroxylase positive (TH +) cell loss and motor dysfunction. Ileum-associated microbiota remodeling correlates with a decrease in Th17 homeostatic cells. This event led to an increase in gut inflammation and intestinal barrier disruption. In this regard, we found a decrease in CD4 + cells and an increase in pro-inflammatory cytokines in the blood of PD transplanted mice that could contribute to an increase in the permeabilization of the blood-brain-barrier, observed by an increase in mesencephalic Ig-G-positive microvascular leaks and by an increase of mesencephalic IL-17 levels, compatible with systemic inflammation. Furthermore, alpha-synuclein aggregates can spread caudo-rostrally, causing fragmentation of neuronal mitochondria. This mitochondrial damage subsequently activates innate immune responses in neurons and triggers microglial activation.

CONCLUSIONS

We propose that the dysbiotic gut microbiome (dysbiome) in PD can disrupt a healthy microbiome and Th17 homeostatic immunity in the ileum mucosa, leading to a cascade effect that propagates to the brain, ultimately contributing to PD pathophysiology. Our landmark study has successfully identified new peripheral biomarkers that could be used to develop highly effective strategies to prevent the progression of PD into the brain.

Effect of host and strain factors on α-synuclein prion pathogenesis

Prion diseases are a group of neurodegenerative disorders caused by misfolding of proteins into pathogenic conformations that self-template to spread disease. Although this mechanism is largely associated with the prion protein (PrP) in classical prion diseases, a growing literature indicates that other proteins, including α-synuclein, rely on a similar disease mechanism. Notably, α-synuclein misfolds into distinct conformations, or strains, that cause discrete clinical disorders including multiple system atrophy (MSA) and Parkinson's disease (PD). Because the recognized similarities between PrP and α-synuclein are increasing, this review article draws from research on PrP to identify the host and strain factors that impact disease pathogenesis, predominantly in rodent models, and focuses on key considerations for future research on α-synuclein prions.

Colonoscopy and Subsequent Risk of Parkinson's Disease

Background

Parkinson's disease (PD) is caused by the misfolding and aggregation of α-synuclein in neurons into toxic oligomers and fibrils that have prion-like properties allowing them to infect healthy neurons and to be transmitted to animal models of PD by injection or oral exposure. Given α-synuclein fibrils' potential transmission on the gut-brain axis, α-synuclein may be transmitted through colonoscopy procedures.

Objective

This study examines a possible association between colonoscopy and PD.

Methods

Longitudinal health insurance data of 250,000 individuals aged 50+ from 2004-2019 was analyzed. Cox proportional hazard and competing risk models with death as a competing event were estimated to calculate the risk of PD. Colonoscopy was categorized as never receiving colonoscopy, colorectal cancer (CRC) screening without or with biopsy, destruction or excision (BDE), and diagnostic colonoscopy without or with BDE.

Results

We identified 6,422 new cases of PD among 221,582 individuals. The Cox model revealed a significantly increased risk of PD for patients who ever had a diagnostic colonoscopy without or with BDE (HR = 1.31; 95% CI: [1.23-1.40]; HR = 1.32 [1.22-1.42]) after adjustment for age and sex. After controlling for covariates and death, persons who ever underwent CRC screening had a 40% reduced risk of PD (CRHR = 0.60 [0.54-0.67]), while persons who underwent diagnostic colonoscopy had a 20% reduced risk of PD (CRHR = 0.81 [0.75-0.88]).

Conclusions

Colonoscopy does not increase the risk of PD, after adjusting for death and covariates. Individuals who underwent only CRC screening had the lowest risk of PD, which may be a result of a more health-conscious lifestyle.

Patients with isolated REM-sleep behavior disorder have elevated levels of alpha-synuclein aggregates in stool

Misfolded and aggregated α-synuclein is a neuropathological hallmark of Parkinson's disease (PD). Thus, α-synuclein aggregates are regarded as a biomarker for the development of diagnostic assays. Quantification of α-synuclein aggregates in body fluids is challenging, and requires highly sensitive and specific assays. Recent studies suggest that α-synuclein aggregates may be shed into stool. We used surface-based fluorescence intensity distribution analysis (sFIDA) to detect and quantify single particles of α-synuclein aggregates in stool of 94 PD patients, 72 isolated rapid eye movement sleep behavior disorder (iRBD) patients, and 51 healthy controls. We measured significantly elevated concentrations of α-synuclein aggregates in stool of iRBD patients versus those of controls (p = 0.024) or PD patients (p < 0.001). Our results show that α-synuclein aggregates are excreted in stool and can be measured using the sFIDA assay, which could support the diagnosis of prodromal synucleinopathies.