New Delhi: Bacteria from the mouth that colonize the gut may influence brain health and increase the risk of Parkinson’s disease, researchers from South Korea have found.
A team at the Pohang University of Science and Technology uncovered how metabolites produced by oral bacteria in the gut can affect neurons in the brain, potentially triggering Parkinson’s, a neurological disorder marked by tremors, stiffness and slowed movement.
“Our study provides a mechanistic understanding of how oral microbes in the gut can influence the brain and contribute to the development of Parkinson's disease,” said Professor Ara Koh. “It highlights the potential of targeting the gut microbiota as a therapeutic strategy, offering a new direction for Parkinson's treatment.”
The research, published in Nature Communications, showed higher levels of Streptococcus mutans, a common oral bacterium that causes tooth decay, in the gut microbiome of Parkinson’s patients.
The study revealed that S. mutans produces an enzyme, urocanate reductase (UrdA), and a metabolite, imidazole propionate (ImP). Both were found at elevated levels in the gut and blood of patients. ImP appeared capable of entering circulation, reaching the brain, and contributing to the death of dopaminergic neurons.
Using mouse models, the scientists introduced S. mutans into the gut or engineered E. coli to express UrdA. The animals developed high levels of ImP in blood and brain tissue, along with Parkinson’s-like symptoms such as neuronal loss, neuroinflammation, impaired movement, and greater aggregation of alpha-synuclein, a protein central to the disease.
Further tests showed that these effects depended on activation of the signaling protein complex mTORC1. Treating the mice with an mTORC1 inhibitor reduced neuroinflammation, neuronal loss, alpha-synuclein aggregation, and motor dysfunction.
The findings suggest that targeting the oral-gut microbiome and its metabolites could open new avenues for Parkinson’s treatment.