In recent years, a growing number of scientific studies have supported an alarming hypothesis: Alzheimer’s disease is not just a disease, it’s an infection. While the exact mechanisms of this infection are something that researchers are still trying to isolate, many articles argue that the spread of Alzheimer’s goes further than we used to think.
Now scientists say they have one of the most definitive clues yet for a bacterial culprit behind Alzheimer’s disease: gum disease.
In a paper led by lead author Jan Potempa, a microbiologist at the University of Louisville, the researchers report the discovery of Porphyromonas gingivalisthe pathogen behind chronic periodontitis (also known as gum disease), in the brains of deceased Alzheimer’s patients.
This is not the first time the two factors have been linked, but the researchers went further.
In separate experiments with mice, oral infection with the pathogen led to brain colonization by the bacteria, along with increased production of amyloid beta (Aβ), sticky proteins commonly associated with Alzheimer’s. The research team, coordinated by the pharmaceutical company Cortexyme, does not claim to have discovered definitive evidence of the cause of Alzheimer’s, yet.
But clearly there is a solid line of inquiry here. “Infectious agents have been implicated in the development and progression of Alzheimer’s disease before, but the evidence for causality has not been convincing,” says Dominy.
There is now strong evidence connecting the gram-negative intracellular pathogen, P. gingivalis and Alzheimer’s disease. In addition, the team identified toxic enzymes called gingipains secreted by bacteria in the brains of Alzheimer’s patients, which correlated with two separate markers of the disease: Tau protein and ubiquitin.
But even more compelling, the team identified these toxic gingipains in the brains of deceased people who were never diagnosed with Alzheimer’s. This is important, because although P. gingivalis and disease have been linked before, it has never been known whether gum disease causes Alzheimer’s or whether dementia leads to poor oral care.
The fact that low levels of gingipains were evident even in people never diagnosed with Alzheimer’s suggests that they might have developed the disease if they had lived longer.
Until now, drugs directed at the toxic proteins of bacteria only show benefits in mice, but it is not ruled out that in the future results will be seen in advanced experimental phases in humans, according to a statement from David Reynolds, scientific director from The Alzheimer’s Research UK.
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