The gut-brain link in Parkinson’s disease reveals a key role for early sleep disorders

Recent research shows that the first signs of Parkinson’s disease may appear long before motor disorders, particularly in the digestive system. By injecting aggregates of alpha-synuclein—a protein involved in neuronal degeneration—into the intestines of mice, scientists observed a progressive spread of these aggregates to the brain. This spread follows a specific path, traveling via the vagus nerve, which connects the gut to the brain.

The results indicate that these aggregates first accumulate in brain regions controlling non-motor functions, such as sleep and digestion. Among the most striking early symptoms are rapid eye movement (REM) sleep behavior disorders, similar to those observed in humans with REM sleep behavior disorder. These disorders, characterized by a loss of normal muscle atonia during sleep, are often associated with an increased risk of developing Parkinson’s disease.

The study also reveals that the degeneration of dopaminergic neurons, located in a region called the substantia nigra, plays a central role in the onset of these sleep disorders. Indeed, impaired dopamine release in the brain disrupts sleep architecture, particularly by promoting episodes of REM sleep without atonia. These observations suggest that changes in the brain circuits controlling sleep could be an early warning sign of the disease.

Furthermore, researchers noted that motor disorders, such as difficulties with coordination and movement planning, only appear later, when alpha-synuclein aggregates have reached more extensive areas of the brain. This confirms the idea that Parkinson’s disease develops gradually, beginning with non-motor symptoms before affecting motor abilities.

Finally, this study highlights the importance of monitoring sleep and digestive disorders, as they could signal the early stages of broader neurological degeneration. Understanding these mechanisms paves the way for early interventions aimed at slowing or preventing the progression of the disease.

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Official Study Source

DOI: https://doi.org/10.1186/s40035-026-00536-6

Title: Gut-initiated alpha synuclein fibrils drive parkinsonism phenotypes: temporal mapping of REM sleep behavior disorder-like and other non-motor symptoms

Journal: Translational Neurodegeneration

Publisher: Springer Science and Business Media LLC

Authors: Daniel Dautan; Wojciech Paslawski; Sergio G. Montejo; Daniel C. Doyon; Valentina I. Brioschi; Roberta Marongiu; Michael G. Kaplitt; Rong Chen; Valina L. Dawson; Xiaoqun Zhang; Ted M. Dawson; Per Svenningsson