This study seeks to understand the prevalence and variability of a gut bacteria gene called csgA in people with Parkinson's Disease. This understanding could inform development of potential new therapies targeting the gut in Parkinson's Disease.

Parkinson's Disease (PD) is a neurodegenerative disorder traditionally associated with motor and non-motor symptoms due to the loss of dopaminergic neurons in the nervous system. Recent research highlights two primary progression patterns: body-first and brain-first PD. In brain-first, PD begins with alpha-synuclein (aSyn) pathology in the brain, particularly in areas like the substantia nigra or olfactory bulb, before potentially involving peripheral systems. Conversely, in the body-first subtype, pathological aSyn aggregates are thought to originate in the enteric nervous system or peripheral autonomic structures, such as the gut and cardiac structures, before spreading to the brain via the vagus nerve. In this subtype of PD, gut dysbiosis and bacterial amyloids could trigger misfolding of aSyn in the enteric nervous system, initiating a cascade of pathology that spreads retrogradely to the brain via the vagus nerve.

The potential influence of the gut microbiome on PD development and progression offers the potential for microbiome targeted therapies to be developed. csgA encodes the major protein subunit of curli, a functional amyloid protein assembly produced by certain gut bacteria like Escherichia coli. Curli proteins help establish extracellular biofilms, and their structural similarity to human amyloids, such as aSyn, suggests they may contribute to pathological processes in PD. CsgA protein could therefore be a potential target for therapies. To develop such interventions, understanding the prevalence and variability of csgA within the microbiomes of individual patients is critical because this information will help guide the development of assays to assess pharmacodynamic effects of a potential therapy. This study therefore focuses on studying the prevalence and inter-individual and week-to-week variability of csgA in the PD population.

Inclusion Criteria:

• Between 18-80 years of age at ICF signing (inclusive)
• A diagnosis of PD within 10 years from the time of ICF signing
• Current or history of gastrointestinal (GI) dysfunction or constipation based on screening assessment
• All participants must understand and provide written informed consent prior to any study specific procedures
• Able to speak, read, and understand study procedures in Dutch sufficiently to allow completion of all study assessments

Exclusion Criteria:

• Any known GI disorder if deemed clinically significant by the investigator. GI disorders may include, but are not limited to: Crohn's disease, ulcerative colitis, celiac disease, irritable bowel syndrome, or lactose intolerance
• Recent GI infection in the past 3 months if deemed clinically significant by the investigator.
• Major GI surgery (excluding appendectomy/cholecystectomy), such as bariatric surgery, gastrectomy, esophagectomy, vagotomy, small intestine surgeries, any type of colectomy, colostomy and anorectal surgeries if deemed clinically significant by the investigator
• Any known current or past eating disorder if deemed clinically significant by the investigator
• Use of systemic antibiotics within 6 months prior to enrollment

Patients with a diagnosis of Parkinson's disease within the last 10 years in the Netherlands