THURSDAY, Sept. 12 (HealthDay News) -- Differences in
plaque-forming structures in the brains of Alzheimer's patients may
offer clues to why the disease can progress more rapidly or be less
severe in some people, a new study suggests.
The research could spur the development of new imaging agents
that highlight specific structures in the brain -- called
beta-amyloid fibrils -- improving the reliability and specificity
of diagnosis, according to Robert Tycko, lead author of the paper
published Sept. 12 in the journal
"Variations in disease may have a structural basis and be due to differences in the molecular structure of the fibrils," said Tycko, a senior investigator with the intramural research program of the U.S. National Institutes of Health.
The study represents an important advance in Alzheimer's
research, an expert not involved with the study noted.
Beta-amyloid fibrils are responsible for the amyloid plaques
seen in Alzheimer's disease, the most common form of dementia.
Alzheimer's is the sixth leading cause of death in the United
States and more than 5 million Americans have the disease,
according to the Alzheimer's Association.
For the research, the scientists took tissue from the brains of
two deceased female Alzheimer's patients with different signs and
symptoms of the disease. They extracted beta-amyloid from the
tissue and used it as "seeds" to grow beta-amyloid fibrils. The
investigators found that the same "seeds" -- the amino acid
sequence -- could assemble into different molecular structures.
Using nuclear magnetic resonance and electron microscopy to
visualize the beta-amyloid fibrils in the patients' brain tissue,
the scientists discovered correlations between variations in the
disease and differences in molecular structure.
"There are at least two different varieties [of amyloid structure] in Alzheimer's disease," Tycko said. "And certain fibril structures may be more likely than others to cause the disease."
Tycko explained that while the research team was able to
determine that there are at least two structural varieties of
Alzheimer's disease, they were unable to prove that there are
correlations between variations in disease and molecular
He said he hopes that the research will eventually lead to the
ability to tell someone with memory loss whether or not the problem
is likely to lead to a serious or fast-moving form of
One expert not involved with the research called the discovery a
"technical tour de force."
"The research is a huge step forward," said Terrence Town, a professor of physiology and biophysics at the Keck School of Medicine at the University of Southern California. "They have accomplished something we have been trying to do for a decade."
For years, researchers have been focusing on something smaller
than a fibril, called an oligomer, considered to be especially
toxic to the brain, Town explained. "Now this paper is drawing
attention to something different: fibrils."
The findings will help researchers focus on the fibrils, ideally
working toward developing ways to identify and diagnose people in
the earliest stages of the disease, Town said.
Learn more about Alzheimer's disease from the
Centers for Disease Control and Prevention.
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