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Scientists Reduce Alzheimer's-Linked Brain Plaques in Mice

Team used gene therapy, but there's no guarantee same method will help humans

By Randy Dotinga
HealthDay Reporter

THURSDAY, March 31, 2016 (HealthDay News) -- Scientists working with mice report preliminary progress in efforts to eliminate brain-clogging proteins linked to Alzheimer's disease.

By tweaking genes in the brains of mice, researchers say they reduced levels of a substance called beta amyloid that's closely tied to Alzheimer's.

There's no guarantee the findings will be relevant to people with Alzheimer's disease because results of animal studies often aren't replicated in humans, experts say.

Still, "we can now target amyloids from a different angle," said study co-author Guojun Bu, a neuroscientist and professor of medicine at the Mayo Clinic in Jacksonville, Fla. The approach "can be explored for Alzheimer's disease prevention and therapy," he added.

Clumps of beta-amyloid proteins, known as plaque, are believed to disrupt brain functioning in people with Alzheimer's disease, the most common form of dementia.

The clumps, which appear to kill brain cells, may develop years before someone shows signs of the progressive brain disease. Some research has suggested that the brains of Alzheimer's patients can't easily get rid of the gunk, allowing it to build up and impair their ability to think and move.

In the new study, Bu and colleagues manipulated the genes of mice and removed a gene linked to molecules called heparan sulfates that appear on cell surfaces. The molecules serve a biological purpose, Bu said, but they've also been found within clumps of beta amyloid and related "tangles" in the brains of Alzheimer's patients.

"We found that removing heparan sulfates from the nerve cells vastly reduced amyloids," he said. And according to Bu, this confirms that the molecules play a role in the formation of the amyloid clumps.

The findings suggest that scientists could reduce levels of the brain-clogging material by disrupting the interaction between the molecules and beta amyloid, Bu said. But this would need to happen without "disturbing the normal biological function."

Bu said the next step is to look for a compound that can block the molecules and beta amyloid from interacting without hurting the patient. And, "such preclinical studies can takes years before they can be translated to humans," he explained.

There are other caveats, too. Since it hasn't been proven that beta amyloid actually causes Alzheimer's, stopping amyloid production might not necessarily stop the disease. Also, nothing is known about the cost of the approach or side effects.

Bu said any treatment would need to be given in the early days of Alzheimer's disease before symptoms appear.

Testing could determine whether someone shows signs of early Alzheimer's disease without obvious symptoms, said study co-author Dr. David Holtzman. He is chair of neurology at Washington University School of Medicine in St. Louis.

Scientists could test the treatment, he said, by giving it to people who don't exhibit disrupted thinking but do show signs of amyloid buildup. Then, he said, researchers could follow the participants to see if they develop dementia or if the treatment halted Alzheimer's progression.

Dr. Howard Fillit, executive director and chief science officer at the Alzheimer's Drug Discovery Foundation, praised the study. "In more sophisticated and modern ways, it confirms previous knowledge" about how the molecules interact with beta amyloid, he said.

However, he cautioned that it's very difficult to target the molecules in question with medication. Also, since the heparan sulfate molecules bind with other molecules in the body, getting rid of them "could have many effects we don't know about," Fillit said.

The study was published March 30 in the journal Science Translational Medicine.

More information

For more about beta amyloid's role in Alzheimer's disease, see the Alzheimer's Association.


SOURCES: Guojun Bu, Ph.D., professor, medicine, department of neuroscience, Mayo Clinic, Jacksonville, Fla.; Dave Holtzman, M.D., chair, neurology, Washington University School of Medicine, St. Louis; Howard Fillit, M.D., executive director and chief science officer, Alzheimer's Drug Discovery Foundation, New York City; March 30, 2016, Science Translational Medicine

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