New clue to Alzheimer's disease found

Posted Jun 23, 2008 by Chris V. Thangham
Harvard scientists have isolated a beta-amyloid molecule from others that is believed to cause Alzheimer’s disease. Only a two-molecule form of soluble beta-amyloid causes Alzheimer's in rats.
Inside Alzheimer s.
Inside Alzheimer's.
Photo by Kaz Ehara
Scientists have known in the past that a plague of beta-amyloid in the brain is one of the primary causes of Alzheimer’s disease. But a new study found that not all forms of beta-amyloid plays a role in the disease.
Dr. Ganesh M. Shankar and Dr. Dennis J. Selkoe of Harvard Medical School analyzed the effect of various forms of beta-amyloids on rats and found only a two-molecule form of beta-amyloid causes the characteristics found in Alzheimer’s, while other forms had no influence.
This also explained how some have beta-amyloids plague in their brains but don’t develop Alzheimer’s.
The two researchers took extracts from the brains of people who died from Alzheimer’s disease and injected the different forms of beta-amyloid in the brains of rats and observed their behaviors.
They found the insoluble plaque or the soluble one-molecule or three molecule forms did not cause any detectable effect on the rats who received the injections.
Only the rats that received two-molecule form of soluble beta-amyloid exhibited signs of Alzheimer's such as impaired memory function, particularly newly learned behaviors.
The two-molecule beta-amyloid form also reduced the density of brain cells by 47 percent according to an AP report. The study is available in Sunday’s online edition of the journal Nature Medicine.
Now the researchers will study why one form of beta-amyloid is harmful, while others are not.
Alzheimer's disease, a major form of dementia, affects an estimated 4.5 million Americans. The disease is believed to begin after age 60. About 5 percent of men and women age 65 to 74 have the disease while of those age 85 or older, half have the disease. There is no cure for Alzheimer’s.
Dr. Marcelle Morrison-Bogorad, director of the division of neuroscience at the National Institute on Aging told AP about this study:
"A lot of work needs to be done…Nature keeps sending us down paths that look straight at the beginning, but there are a lot of curves before we get to the end."
Hopefully they will reach the end soon and find a cure for this dreaded Alzheimer’s disease.