Study Shows Loss of Key Enzymes Occurs Later Than Previously Thought

April 21, 1999

A new finding that may help unravel the Alzheimer's disease (AD) puzzle shows that loss of enzymes associated with the production of acetylcholine, a brain chemical implicated in memory function, may occur much later in Alzheimer's disease than formerly believed.

Dr. Kenneth Davis and colleagues at the Mount Sinai Alzheimer's Disease Research Center in New York studied the brains after death of people with early and late AD and people with no memory problems. The study appears in the April 21, 1999, issue of the Journal of the American Medical Association (JAMA).

The findings indicate that patients in early stages of the disease, while exhibiting memory deficits and classic pathological signs, such as plaques and tangles, have relatively normal levels of the enzymes regulating acetylcholine levels. Only in patients with severe Alzheimer's disease did they see much diminished levels of these enzymes. These findings suggest that overall deficits of these enzymes may not be an early pathological feature of the disease, although they do not exclude the possibility that more subtle losses might have occurred in specific neuron populations. Positive effects of currently approved drugs on early-stage AD patients might not be due to maintaining falling levels of acetylcholine but to boosting normal levels of this important chemical.

The National Institute on Aging (NIA) currently funds Alzheimer's disease Centers at medical institutions around the nation. The NIA network of centers has played a major role in advancing research on Alzheimer's disease. The NIA is the lead federal agency supporting and conducting Alzheimer's disease research, including studies of the basic, clinical, and epidemiological aspects of this and other related dementias of aging.