WEDNESDAY, March 15 (HealthDay News) -- In a development that could lead to treatments to prevent Alzheimer's disease, scientists say they've discovered a possible cause of memory loss in mice.

The research only applies to rodents so far, and even if it translates to humans, new drugs wouldn't be available for perhaps a decade. Still, the findings are promising.

"We could be on to the ability to diagnose patients who are at risk for Alzheimer's long before they get it, and we could be on to a very effective way of preventing Alzheimer's disease," said study lead author Dr. Karen Hsiao Ashe, professor of neurology and neuroscience at the University of Minnesota.

For years, scientists have thought that Alzheimer's disease was caused by the growth of brain-clogging proteins called "plaques" and "tangles."

Now, Ashe said, there's growing evidence that Alzheimer's takes hold long before plaques and tangles appear. That means early diagnosis is simply not possible at this time.

The disease may actually develop for decades, Ashe said, "but we don't know for sure."

In the new study, published in the March 16 issue of the journal Nature, her team found signs that a particular protein -- a mass of amyloid-b peptides -- accumulates around the brain cells of mice genetically engineered to suffer memory loss. This protein is distinct from the type that makes up the amyloid plaques that form later on.

The researchers also found that they could give healthy rats Alzheimer's symptoms by injecting them with this protein.

That's important, said Dr. Sam Gandy, director of the Farber Institute for Neurosciences at Thomas Jefferson University in Philadelphia. While other researchers have made similar findings, "no one had purified the poison from a sick brain and used it to cause memory loss in an otherwise well animal," said Gandy, who's familiar with the study findings.

What does the memory-sapping protein do? According to Ashe, it appears to act "more like an intoxicant than a poison that kills neurons. It operates by putting them to sleep."

There are caveats to the research, however. While mice brains are considered to be good models of how Alzheimer's disease works in human brains, the two species are hardly alike.

"We won't know for sure how our mouse work relates to humans until we can do an experiment in which we block (the protein) in people who are essentially normal but at risk for Alzheimer's and demonstrate that we can prevent them from getting Alzheimer's," Ashe said.

It may take one to five years to move to human tests, and about a decade before they'd be completed, Ashe said.

Even if a drug treatment is created, it might work better as a means of preventing Alzheimer's rather than stopping it once it develops -- much as lowering cholesterol helps stave off a heart attack.

An estimated 4.5 million Americans have Alzheimers disease, a number that is projected to increase to 14 million in the next 20 years as the population ages.

More information

SOURCES: Karen Hsiao Ashe, Ph.D., M.D., professor, neurology and neuroscience, University of Minnesota, Minneapolis; Sam Gandy, M.D., Ph.D., chairman, Medical and Scientific Advisory Council, Alzheimer's Association, and director, Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia; March 16, 2006, Nature

Last Updated: March 15, 2006

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