Korean scientists have found strong evidence that bacteria from the mouth can settle in the gut, affect the brain, and possibly trigger Parkinson’s disease.
The research team included Professor Ara Koh and doctoral student Hyunji Park from POSTECH, Professor Yunjong Lee and doctoral student Jiwon Cheon from Sungkyunkwan University, and Professor Han-Joon Kim from Seoul National University. Their work was published in Nature Communications.
Parkinson’s disease is a brain disorder that causes shaking, stiffness, and slower movements. It affects about 1–2% of people over age 65. Scientists already knew gut bacteria were different in people with Parkinson’s, but didn’t know which bacteria or chemicals were to blame.
This study found that people with Parkinson’s had higher levels of a common mouth bacterium—Streptococcus mutans—in their gut. This bacterium normally causes tooth decay, but it can also make a chemical called imidazole propionate (ImP) using an enzyme called UrdA.
The researchers found more of this chemical, ImP, in both the gut and blood of Parkinson’s patients. ImP can travel in the blood, reach the brain, and damage nerve cells that make dopamine—an important brain chemical for movement.
In mouse experiments, the scientists added S. mutans to the gut or used lab bacteria to produce UrdA. These mice showed Parkinson-like signs: less dopamine, more brain inflammation, movement problems, and buildup of a sticky brain protein called alpha-synuclein.
They discovered that these effects depend on a brain pathway called mTORC1. When they gave mice a drug to block mTORC1, the brain damage and movement problems were much better.
This study shows how bacteria from the mouth, once inside the gut, can affect the brain. It also suggests that changing gut bacteria or blocking their harmful chemicals might help treat or prevent Parkinson’s.
“Our research shows how oral bacteria in the gut might help cause Parkinson’s disease,” said Professor Koh. “It opens the door to new ways of treating the disease by targeting gut microbes.”
If you care about Parkinson’s disease, please read studies about how to improve walking in people with Parkinson’s disease and Scientists find causes of Parkinson’s and Lewy body dementia.
For more about Parkinson’s disease, please read studies These common drugs may increase risk of Parkinson’s disease and Researchers find an important cause of Parkinson’s disease.
The study is published in Nature Communications.
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