Gum bacteria implicated in Alzheimer's disease

Researchers have reported how bacteria involved in gum disease can travel throughout the body, exuding toxins connected with Alzheimer’s disease, rheumatoid arthritis and aspiration pneumonia.

The bacterium in question, Porphyromonas gingivalis, is the bad actor involved in periodontitis, the most serious form of gum disease. It commonly begins to infiltrate the gums during the teenage years and, while it is not harmful in most people, if it grows to large numbers the bacteria provoke the body’s immune system to create inflammation, leading to redness, swelling, bleeding and the erosion of gum tissue.

Making matters worse, P. gingivalis even causes benign bacteria in the mouth to change their activities and further increase the immune response. Bacteria can travel from the mouth into the bloodstream through the simple act of chewing or brushing teeth.

While previous researchers have noted the presence of P. gingivalis in brain samples from Alzheimer’s patients, Jan Potempa and his team offer strong evidence that the bacterium may actually contribute to the development of Alzheimer’s disease. Their work was recently presented at the American Association of Anatomists annual meeting, held from 6–9 April as part of Experimental Biology 2019.

Collaborating with biotech company Cortexyme, the researchers compared brain samples from deceased people with and without Alzheimer’s disease who were roughly the same age when they died. They found P. gingivalis was more common in samples from Alzheimer’s patients, evidenced by the bacterium’s DNA fingerprint and the presence of its key toxins, known as gingipains.

In studies using mice, the team showed P. gingivalis can move from the mouth to the brain and that this migration can be blocked by chemicals that interact with gingipains. An experimental drug that blocks gingipains, known as COR388, is currently in phase 1 clinical trials for Alzheimer’s disease. Cortexyme and Potempa’s team are working on other compounds that block enzymes important to P. gingivalis and other gum bacteria in hopes of interrupting their role in advancing Alzheimer’s and other diseases.

“P. gingivalis’s main toxins, the enzymes the bacterium need to exert its devilish tasks, are good targets for potential new medical interventions to counteract a variety of diseases,” said Potempa, who also noted evidence of the bacterium’s role in autoimmune disease rheumatoid arthritis as well as aspiration pneumonia.

“The beauty of such approaches in comparison to antibiotics is that such interventions are aimed only at key pathogens, leaving alone good, commensal bacteria, which we need.”

The findings also underscore the importance of good dental hygiene, with Potempa saying the best way to prevent P. gingivalis from growing out of control is by brushing and flossing regularly and visiting a dental hygienist at least once a year. Smokers and older people are said to be at increased risk for infection.

“Oral hygiene is very important throughout our life, not only for having a beautiful smile but also to decrease the risk of many serious diseases,” said Potempa. “People with genetic risk factors that make them susceptible to rheumatoid arthritis or Alzheimer’s disease should be extremely concerned with preventing gum disease.”

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