Inside the Oral Microbiome: How Periodontitis May Increase the Risk for Alzheimers Disease

Abstract: The oral microbiome is the site of the second most abundant microbiota after the gastrointestinal tract. The expanded Human Oral Microbiome Database (eHOMD) that was last updated on November 22, 2017, contains the information of a number of bacterial species, scientists have struggled to categorize and understand every species due to their difficulty of laboratory study. While this much is known, the scientific community still has minimal knowledge of the entire oral microbiome and how it may relate to potential manifestations of various diseases. Periodontitis is one disease that is directly related to the oral microbiome. Periodontitis is the infection of the gums that is associated with poor dental hygiene. This oral malady has been hypothesized to be a potential precursor to neurological Alzheimer’s disease (AD.) Since AD is difficult to study until postmortem, there has been limited availability to study pathways where this may occur. The proposed method by which periodontitis, while primarily hypothesized, includes a shift in the microbiota of the oral cavity to a more pathogenic state. The shift to pathogenicity is mainly believed to be due to an increase in the bacterium Porphyromonas gingivalis. P. gingivalis produces protein plaques on the teeth that can travel through the bloodstream to the brain. The proposed mechanism is hypothesized to weaken the blood-brain barrier and allow for plaque aggregation on the brain seen in AD-infected brains. While more research is necessary to conclude the pathogenesis from periodontitis to Alzheimer’s disease definitively, strides are being made that may help give scientists, and healthcare workers begin preventative measures.