Cognitive Impairment in Parkinson Disease Linked to Mouth and Gut Bacteria
A new study has identified a link between the progression of cognitive impairment in Parkinson disease and the bacteria residing in the mouth and the gut. Findings from the case control study were published in Gut Microbes.
Saeed Shoaie, PhD, MSc, group leader of the Quantitative Systems Biology (QTS) Lab at King’s College London, and study coauthor said in a news release, “The human gut and oral bacterial communities are increasingly linked to neurodegenerative diseases. Disruptions in the gut-brain axis could trigger inflammation and immune responses that contribute to neuronal damage. A common gum disease bacterium like Porphyromonas gingivalis, has been discovered as a potential driver of Alzheimer.”
For the study, researchers collected 228 samples of stool and saliva to analyze gut and mouth bacteria. The samples came from 3 different groups: Parkinson disease patients with mild cognitive decline, Parkinson disease patients with dementia, and healthy controls with no Parkinson disease diagnosis.
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Shotgun metagenomic samples of gut and oral microbiomes that were generated revealed that patients with cognitive impairment had higher levels of more harmful bacteria in the gut, much of which had come from the mouth. Known as “oral-gut translocation,” the oral bacteria move into the gut and then release molecules known as virulence factors, or toxins that can damage gut tissue, influence inflammation, and even affect the brain.
First author Frederick Clasen, PhD, research associate at the QTS lab, said, “We don’t yet know if the bacteria are causing the cognitive decline or if changes in the body due to Parkinson’s allow these bacteria to grow. But our findings suggest they may play an active role in worsening symptoms.”
Authors noted that the study may be limited because it does not account for other host and environmental factors that affect the gut and oral microbiome, like diet, stress, and sleep. Additionally, Parkinson disease patients with more severe motor symptoms may struggle with consistent oral hygiene, which could further impact the microbiome composition.
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