Researchers from Johns Hopkins University found new evidence that Parkinson's disease originates among cells in the gut and travels up the body's neurons to the brain.
The study published on Wednesday in the journal Neuron showed that a misfolded protein, associated with the neuro-degenerative disease, could travel along the nerve bundle called vagus nerve that links the stomach and small intestine into the base of the brain.
A growing body of evidence has implicated the gut-brain connection in initiating Parkinson's disease, but it remains unclear how it happens until now.
The researchers injected 25 micrograms of misfolded protein called alpha-synuclein created in the lab into the guts of dozens of healthy mice, and analyzed the mouse brain tissue at one, three, seven and 10 months after injections.
They found that, over the course, the protein began building where the vagus nerve connected to the gut and continued to spread through all parts of the brain.
Then, the researchers cut the vagus nerve in one group of mice before injecting proteins, and they found that those mice with severed nerve bundle showed no sign of cell death found in mice with intact vagus nerves seven months after the injection.
Also, those mice with intact nerve bundle and receiving the misfolded protein injections showed lower motor dexterity and higher anxiety level, according to the study.
The study demonstrated that misfolded alpha-synuclein can be transmitted from the gut to the brain in mice along the vagus nerve, and blocking the transmission route could be key to preventing the physical and cognitive manifestations of Parkinson's disease.
"This is an exciting discovery for the field and presents a target for early intervention in the disease," said Ted Dawson, professor of neurology at the Johns Hopkins University School of Medicine, who led the study.