Could a Common Gum Disease Bacteria Kickstart Alzheimer’s?

Could taking care of your gums and teeth lower your risk for Alzheimer’s later in life? Maybe, according to a new study that found a link between gum disease and dementia.

The study, published in the journal Science Advances, found that an enzyme given off by Porphyromonas gingivalis (P. gingivalis) bacteria—the same bacteria associated with gum disease—could be driving Alzheimer’s disease.

“We now have strong evidence connecting P. gingivalis and Alzheimer’s pathogenesis, but more research needs to be done before P. gingivalis is explicitly implicated in the causation or morbidity of AD,” said University of Louisville researcher Jan Potempa, Ph.D., a member of the team led by Cortexyme Inc., a privately held, clinical-stage pharmaceutical company that sponsored the study.

This isn’t the first time oral care has been linked to mental decline. But in the past, it’s been unclear if poor oral habits were the chicken or the egg in kickstarting Alzheimer’s: Did the gum disease trigger Alzheimer’s, or do patients with cognitive problems just have a hard time taking care of their teeth?

When researchers introduced the bacteria in the mouths of mice, it resulted in an increase in beta-amyloid plaques, the toxic protein many researchers point to as the culprit behind Alzheimer’s.

The team also found the enzyme the bacteria gives off, called gingipains, in the neurons of people with Alzheimer’s disease. In 53 subjects, 96 percent of the brains had a form of the enzyme. Scientists also found evidence of the bacteria in the spinal fluid and saliva of ten patients with Alzheimer’s.

However, they also found the bacteria in six healthy brains they tested, suggesting that the presence of bacteria is not an indicator that Alzheimer’s will follow. It could be that certain strains of the bacteria are more destructive than others if it is gum disease that drives Alzheimer’s.

The researchers also developed a drug that targets the bacteria, which helped to reduce beta-amyloid in the mice that were infected with P. gingivalis.

But not everyone is entirely convinced that a bacteria associated with gum disease alone causes Alzheimer’s.

“In research we’ve supported to uncover the key risk factors for Alzheimer’s disease, gum disease hasn’t emerged as a major cause for concern,” said James Pickett, Ph.D., head of research at Alzheimer’s Society.

“This latest study found evidence of gum disease bacteria in the brains of people who died with Alzheimer’s, but also found that people who didn’t have Alzheimer’s showed some of these same signs. The laboratory work does suggest that this infection could cause damage to cells of the brain but there isn’t yet clear evidence that it can cause this damage in people or result in Alzheimer’s,” said Pickett.

Past studies have theorized that the herpes virus might cause Alzheimer’s. It is possible that a viral infection could somehow trigger the events that lead to Alzheimer’s, according to experts.

“Success of this new drug depends on whether the infection really does play an important role in Alzheimer’s disease – it’s important to pursue that as there hasn’t been a new drug for dementia in 15 years. The upcoming clinical trial will be a crucial test to see if this can be a potential treatment for Alzheimer’s.”