There is a lot of clinical and research data to suggest the gut is involved in Parkinson's disease (PD). Constipation, a prominent non-motor symptom associated with PD, occurs years prior to diagnosis in many people. Alpha-synuclein, the sticky protein that clumps in the brains of those with PD, is present in the gut. And, research has shown differences in gut bacteria in those with Parkinson's compared to those without.
A new study builds on the theory that PD could start in the gut, rather than the brain. This research, published in the journal Neurology, evaluated the medical records of people who had surgery to cut the vagus nerve, which serves as a direct pathway from the brain to the gut. This procedure, known as a vagotomy, treats ulcers. Researchers found that people who underwent a "truncal vagotomy," which removes all nerve connections from the brain to the abdominal organs and gut, were less likely to have developed PD five years later. When people only had some of the connections severed (i.e., a "selective vagotomy"), the risk of PD did not change.
"These results provide preliminary evidence that Parkinson's disease may start in the gut," study author Bojing Liu, MSc, of the Karolinska Instituet in Stockholm, Sweden told the American Academy of Neurology in a press release. The idea is that the misfolded alpha-synuclein protein could start in the gut and travel through the vagus nerve to the brain, and that cutting the vagus nerve interrupts this spread.
This study adds to the growing research supporting the gut-brain connection in Parkinson's but doesn't suggest that people should get a vagotomy now to prevent or treat PD. As the primary author states, "Much more research is needed to test this theory and to help us understand the role this may play in the development of Parkinson's."