A healthy salivary microbiota is now recognized as vital not only to teeth and gums but also to remote organ sites including the brain. Not surprisingly, the oral cavity hosts a varied menu of microbes.
In prior research, bacteria in the oral cavity had been linked to Alzheimer’s disease (AD). Lipopolysaccharide, a component of P. gingivalis (key pathogen in periodontal disease inflammation) was found in four out of 10 AD brain samples. In brains of people without AD, none was evident.
The researchers postulated that the bacteria found in the brain triggered immune responses setting up an environment for diseases such as Alzheimer’s.
Gingipains as neurotoxins
Recent research in 2019 takes it a step further. P. gingivalis makes toxic proteases called gingipains, also seen in the brain of Alzheimer’s patients. Gingipains are neurotoxic, affecting the tau protein needed for normal neuronal function. Indeed, gingipain inhibition in one study showed positive results, suggesting a valuable new treatment model in fighting neurodegeneration in Alzheimer’s disease.
The salivary microbiota of Alzheimer’s patients
An interesting addition to this avenue of investigation comes from China. Researchers there looked at the composition of oral bacteria in 78 participants, half with Alzheimer’s and the other half healthy controls. They also explored whether the bacteria were associated somehow to the severity of the dementia and whether the risk factor APOEɛ4 polymorphism showed differences in flora.
Saliva was collected from each subject. Analysis was completed via 16S ribosomal RNA sequencing. Results:
- AD patients showed lower richness and diversity than healthy controls.
- AD patients had more abundance of Moraxella, Leptotrichia, and Sphaerochaeta whereas Rothia was reduced.
- Patients carrying the APOEɛ4 had reduced Actinobacillus and Actinomyces but more abundant Abiotrophia and Desulfomicrobium than negative carriers.
- No bacteria were found to be associated with the severity of AD.
Analysis of Salivary Microbiome in Patients with Alzheimer’s Disease appeared in the Journal of Alzheimer’s Disease in October of 2019.
As is evident, a distinct role for the oral microbiota is emerging in Alzheimer’s disease. Taking care of your teeth and gums may be another way of protecting your brain.