Could Alzheimer?s Stem From Infections? It Makes Sense, Experts Say

[Gert van der Hoek]

See also: Can oral infection (chronic periodontal disease) be a risk factor for Alzheimer?s disease?


May 25, 2016

Could it be that Alzheimer?s disease stems from the toxic remnants of the brain?s attempt to fight off infection?

Provocative new research by a team of investigators at Harvard leads to this startling hypothesis, which could explain the origins of plaque, the mysterious hard little balls that pockmark the brains of people with Alzheimer?s.

It is still early days, but Alzheimer?s experts not associated with the work are captivated by the idea that infections, including ones that are too mild to elicit symptoms, may produce a fierce reaction that leaves debris in the brain, causing Alzheimer?s. The idea is surprising, but it makes sense, and the Harvard group?s data, published Wednesday in the journal Science Translational Medicine, supports it. If it holds up, the hypothesis has major implications for preventing and treating this degenerative brain disease.

The Harvard researchers report a scenario seemingly out of science fiction. A virus, fungus or bacterium gets into the brain, passing through a membrane ? the blood-brain barrier ? that becomes leaky as people age. The brain?s defense system rushes in to stop the invader by making a sticky cage out of proteins, called beta amyloid. The microbe, like a fly in a spider web, becomes trapped in the cage and dies. What is left behind is the cage ? a plaque that is the hallmark of Alzheimer?s.

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[Gert van der Hoek]

Alzheimer?s protein may help brain fight infection

May. 25, 2016

The classic villain in Alzheimer?s disease is ?amyloid, a protein fragment that can misfold and form sticky plaques around neurons in the brain. Now, a new study in mice and worms supports a controversial hypothesis that the plaques may not be all bad. ?amyloid?s tendency to choke neurons could be linked to an ancient evolutionary mission to protect the brain from pathogens, the authors say.


Some say the work could open new avenues for treating and preventing the deadly degenerative disease, but many in the Alzheimer?s field remain skeptical of the research, which used animals genetically modified to make human ?amyloid. Although the new data are "fascinating," they ?remain very contrived in the sense that they don't bear a direct relationship to what we see in the human condition,? says Colin Masters, a neuroscientist at the University of Melbourne in Australia.

If scientists determine that certain microbes do trigger amyloid deposition in human brains, Tanzi suggests it might be possible to develop antibodies that target them and avert that reaction. In addition, if ? amyloid does play an important protective role in the brain, it might make sense to treat it more like cholesterol?which is needed by all cells but dangerous in high levels?than something that needs to be completely eliminated, Tanzi says: ?Slow it down, yes?but don?t wipe it out.?

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