[ExI] Alzheimer's link to gum disease

[Stuart LaForge]

Back when I was in graduate school for microbiology, they had  
discovered that the bacteria in dental plaque was also found in  
arterial plaques of heart disease patients. Now they have found the  
bacteria that causes gingivitis or gum disease (Porphyromonas  
gingivalis) in the brains of deceased Alzheimer's patients. Also when  
the study's authors swabbed the bacteria onto the gums of mice, within  
a matter of weeks, they found the bacteria in the brains of the mice  
as well as abnormal beta-amyloid proteins that are associated with  
Alzheimer's patients.

The take home message is brushing and flossing is good for your brain  
in addition to your heart and teeth.

Summary
https://www.sciencemag.org/news/2019/01/gum-disease-causing-bacteria-could-spur-alzheimer-s

Full paper
http://advances.sciencemag.org/content/5/1/eaau3333

Excerpt:
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"Working with labs in Europe, the United States, New Zealand, and  
Australia, the Cortexyme team confirmed earlier reports that P.  
gingivalis can be found in the brains of deceased people with  
Alzheimer’s, and they detected the microbe’s DNA in living patients’  
spinal fluid. In more than 90% of the more than 50 Alzheimer’s brain  
samples, they also spotted toxic enzymes produced by the bacteria  
called gingipains. Brains with more gingipains had higher quantities  
of the Alzheimer’s-linked proteins tau and ubiquitin. Even the brains  
of roughly 50 deceased, apparently dementia-free elderly people  
selected as controls often had lower levels of both gingipains and the  
proteins indicating Alzheimer’s pathology. That early appearance is  
important, Lynch says, because “you would expect it to be there before  
the onset” of symptoms.

To explore whether the bacteria were causing disease, the team swabbed  
the gums of healthy mice with P. gingivalis every other day for 6  
weeks to establish an infection. They later detected the bacteria in  
the animals’ brains, along with dying neurons and higher than normal  
levels of β-amyloid protein. In a lab dish, the gingipains—whose job  
is to chop up proteins—damaged tau, a regularly occurring brain  
protein that forms tangles in people with Alzheimer’s. In the brain,  
this protein damage may spur the formation of tangles, they say."
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Stuart LaForge