Prodromal Parkinson's Disease

The purpose of this research study is to identify the role that the gut-brain axis, the group of nerves that connect the brain and gut, plays in Parkinson's disease (PD). The National Institute of Diabetes and Digestive and Kidney Diseases is sponsoring this research study. During this study, specific groups of participants, also known as "cohorts", will be identified based on the severity of their PD. There will also be a cohort enrolling participants who do not have Parkinson's and a cohort enrolling participants that are at risk for developing PD. Each of these cohorts will be compared to the others to assess the differences in the gut-brain connection. Participants in this study will: * meet with a medical provider * answer questionnaires * give samples of blood, stool, and saliva * have X-rays taken while swallowing different foods (swallowing study) * have X-rays taken to see how long it takes markers to move through their colon (colon transit study) * have a flexible sigmoidoscopy, where a doctor looks inside the lower part of the colon and takes small tissue samples (biopsies) from the mucosa (lining) * have samples taken of their skin * have an anorectal manometry and a balloon expulsion test, where a small tube and balloon are placed in the rectum to measure muscle function. Participation in the study will last up to 24 months (2 years).

The study is a longitudinal, multi-center study to assess progression of \[18F\] AV-133 imaging in Prodromal PD participants. Participants will be followed for up to 24 months. Approximately 100 Prodromal participants will be recruited from up to 10 sites. Participants will be comprehensively assessed at baseline and follow up. Participants will undergo imaging assessments with \[18F\] AV-133 and clinical (motor, neuropsychiatric, cognitive and imaging and biomarker) assessments (conducted under the PPMI Clinical protocol).

Early diagnosis of Neurodegenerative diseases (NDDs) and accurate patient profiling are key goals needed to tailor prompt personalized therapeutic strategies that can significantly impact disease progression and patients' quality of life. The project will validate a novel, cost-effective and quick biophotonic-based method for early and differential diagnosis of NDDs (Parkinson's disease, atypical parkinsonisms, Alzheimer's disease) and for routine clinical monitoring of NDD progression (longitudinal study). Raman spectroscopy (RS) will be applied to biochemically profile saliva and salivaderived Extracellular Vesicles (sEVs) and to identify a spectroscopic biomarker for NDDs. Optimized protocols for RS will be used to concomitantly evaluate saliva and sEVs from people with NDDs and to detect salivary changes in the biochemical profile, with special focus on EV-associated components. The accuracy of the method in discriminating NDDs at different disease stages and during disease progression will be verified. A nanotechnology-based biomolecular characterization of saliva and sEV will clarify the involvement of specific pathological molecules in NDDs progression.