Assuming the hypothesis is right, it's still not quite clear when and how the bacteria migrate from the gums to the brain and start doing damage, since far more people have gum disease than Alzheimer's.
University of Louisville researcher Jan Potempa, Ph.D., Department of Oral Immunology and Infectious Diseases in the School of Dentistry, was part of the team of global scientists led by Cortexyme Inc., a privately held, clinical-stage pharmaceutical company.
New Scientist reports that elsewhere, Australian researchers are working on a vaccine for P. gingivalis - if this vaccine prevents gum disease and Alzheimer's at the same time, millions of people could be saved. They also demonstrate the presence of P. gingivalis DNA in post-mortem Alzheimer's brain samples (both hippocampus and cerebral cortex) and in the CSF of living patients who are believed to have the disease as well. The new drug is now being tested on people in clinical trials.
"Success of this new drug depends on whether the infection really does play an important role in Alzheimer's disease".
The new study found that toxic enzymes from the bacteria Pg, called gingipains, were also found in the brains of Alzheimer's disease patients and that their levels correlated with levels of tau.
Researchers found that, in mice, tau levels were about twice as high during times when they were awake and active.
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Even in healthy individuals tau is found in the brain, under certain conditions tau can clump together into tangles that injure nearby tissues and presage cognitive decline. Cortexyme's gingipain blockers have passed initial safety tests and the company plans on launching a clinical trial soon that will investigate the drug's effects on cognition. What's more, autopsies have shown that protein plaques can appear in people who had no Alzheimer's disease. And this 2015 paper reported that gum disease was associated with higher amyloid levels in the normal elderly as well.
Those concerned that poor dental health could increase their risk of Alzheimer's disease are advised to practice good oral hygiene to preclude the prevalence of P. gingivalis in the mouth, said Dominy.
The findings, which were published in the January 14 issue of Nature Medicine, can potentially help with early Alzheimer's diagnoses and new drug development.
The researchers hope this will provide the basis for developing a new therapy that could one day treat humans in a similar way.
Spires-Jones added that Alzheimer's disease patients also have disruption of their blood-brain barriers, "making them more susceptible to getting infections in their brains, so while these data are interesting, it is possible that the infection is a by-product instead of a cause of disease".
Statistics record that as many as one in 14 over the age of 65 will be affected by one form or another of dementia. "We even have people who don't know anyone or have anyone in their families with Alzheimer's that come to the presentations, but it is a great way for them sitting in on this program to spread awareness what we do".
Infecting tau-expressing cell cultures with P. gingivalis led to breakdown of the tau protein, apparently through the actions of those gingipain proteases.