Gum disease linked to build-up of Alzheimer’s plaque formation

gum disease Alzheimer's plaque formation
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US researchers have shown a link between periodontal (gum) disease and the formation of amyloid plaque, a hallmark of Alzheimer’s disease.

In their paper—published in the Journal of Neuroinflammationscientists at the Forsyth Institute in Cambridge, Massachusetts and their collaborators at Boston University demonstrate that gum disease can lead to changes in brain cells called microglial cells, which are responsible for defending the brain from amyloid plaque. This plaque is a type of protein that is associated with cell death, and cognitive decline in people with Alzheimer’s.

The study provides important insight into how oral bacteria makes its way to the brain, and the role of neuroinflammation in Alzheimer’s disease.

“We knew from one of our previous studies that inflammation associated with gum disease activates an inflammatory response in the brain,” senior author Dr Alpdogan Kantarci said.

“In this study, we were asking the question, can oral bacteria cause a change in the brain cells?”

The microglial cells the researchers studied are a type of white blood cell responsible for digesting amyloid plaque. Forsyth scientists found that when exposed to oral bacteria the microglial cells became overstimulated and ate too much.

“They basically became obese. They no longer could digest plaque formations,” Dr Kantarci said.

The finding is significant for showing the impact of gum disease on systemic health. Gum disease causes lesions to develop between the gums and teeth. The area of this lesion is the size of your palm. 

“It’s an open wound that allows the bacteria in your mouth to enter your bloodstream and circulate to other parts of your body,” Dr Kantarci said.  

These bacteria can pass through the blood/brain barrier and stimulate the microglial cells in your brain.

Using mouse oral bacteria to cause gum disease in lab mice, the scientists were able to track periodontal disease progression in mice and confirm that the bacteria had traveled to the brain.

They then isolated the brain microglial cells and exposed them to the oral bacteria. This exposure stimulated the microglial cells, activated neuroinflammation and changed how microglial cells dealt with amyloid plaques.

“Recognising how oral bacteria causes neuroinflammation will help us to develop much more targeted strategies,” Dr Kantarci said. 

“This study suggests that in order to prevent neuroinflammation and neurodegeneration, it will be critical to control the oral inflammation associated with periodontal disease. The mouth is part of the body and if you don’t take care of oral inflammation and infection, you cannot really prevent systemic diseases, like Alzheimer’s, in a reproducible way.”

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