Non-Invasive Stool Test Could Diagnose Early Form of Parkinson’s Disease

Parkinson’s disease (PD) originates in the central nervous system in 70% of cases but also originates in the nervous system of the intestine (enteric nervous system) in about 30% of cases. In the latter form of PD, referred to as body-first PD, the characteristic deposits of aggregates of the body’s own α-synuclein protein are formed in the neurons in the intestine. Now, a research team has shown that a higher concentration of α-synuclein aggregates can be detected in the stool samples of PD patients.

The research team at Heinrich Heine University Düsseldorf (HHU, Düsseldorf, Germany) has shown that it is possible to detect elevated levels of α-synuclein aggregates in the stool samples of PD patients. The team achieved this by using a new surface-based fluorescence intensity distribution analysis (sFIDA) to detect and quantify individual particles of α-synuclein aggregates. In body-first PD, the deposits of fibrils of the body’s own α-synuclein protein, which are a characteristic of PD, first form in the neurons of the enteric nervous system, which serves as the gastrointestinal tract. The aggregates spread to the central nervous system similar to prions, i.e. an existing aggregate combines individual α-synuclein proteins in its vicinity into further aggregates in a nucleation process. These aggregates then spread further throughout the body.

The impact of what happens in the gastrointestinal tract on the brain is termed as the “gut-brain axis”. The gastrointestinal tract is exposed to the environment, creating the possibility of harmful substances like chemicals, bacteria or viruses ingested directly with food or through interaction with the microbiome of the gastrointestinal tract triggering the pathological formation of α-synuclein aggregates.

“We are the first to prove the presence of α-synuclein aggregates in stool samples,” said Professor Erdem Gültekin Tamgüney from the Institute of Physical Biology at HHU who headed the research team. “Our results show a significantly higher level of α-synuclein aggregates in iRBD patients compared with healthy individuals or patients with Parkinson’s. These findings could lead to a non-invasive diagnostic tool for prodromal synucleinopathies – including Parkinson’s – which could in turn enable therapies to be initiated at an early stage before symptoms occur.”

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