A popular science piece on a new association in the biochemistry of Alzheimer's disease:
It is one of the big scientific mysteries of Alzheimer's disease: Why do some people whose brains accumulate the plaques and tangles so strongly associated with Alzheimer's not develop the disease? The memory and thinking problems of Alzheimer's disease and other dementias, which affect an estimated seven million Americans, may be related to a failure in the brain's stress response system, the new research suggests. If this system is working well, it can protect the brain from abnormal Alzheimer's proteins; if it gets derailed, critical areas of the brain start degenerating.
The research focuses on a protein previously thought to act mostly in the brains of developing fetuses. The scientists found that the protein also appears to protect neurons in healthy older people from aging-related stresses. But in people with Alzheimer's and other dementias, the protein is sharply depleted in key brain regions.
"Why should a fetal gene be coming on in an aging brain?" [Researchers] hypothesized that it was because in aging, as in birth, brains encounter great stress, threatening neurons that cannot regenerate if harmed. [Researchers] discovered that REST appears to switch off genes that promote cell death, protecting neurons from normal aging processes like energy decrease, inflammation and oxidative stress.
In people with Alzheimer's, mild cognitive impairment, frontotemporal dementia and Lewy body dementia, the brain areas affected by these diseases contained much less REST than healthy brains.This was true only in people who actually had memory and thinking problems. People who remained cognitively healthy, but whose brains had the same accumulation of amyloid plaques and tau tangles as people with Alzheimer's, had three times more REST than those suffering Alzheimer's symptoms. About a third of people who have such plaques will not develop Alzheimer's symptoms, studies show.