Scientists are seeking ways to detect the earliest stages of
Alzheimer's disease, since harmful changes may be taking place in the brain
years before symptoms appear.
Now, researchers report that a blood test detecting a
specific protein in blood samples from cognitively normal older people may
reflect the levels of beta-amyloid protein in the brain -- a hallmark of the disease.
Findings of the study, supported in part by the National
Institutes of Health (NIH), may eventually lead to a blood
test that helps predict risk for Alzheimer's disease and who may be a good
candidate for participating in clinical trials.
"Recent advances in imaging and biomarkers that help
track the onset and progression of Alzheimer's disease show promise for early
detection of the disease process, and for tracking the effectiveness of early
interventions," said National Institute on Aging (NIA) Director Richard J. Hodes, M.D. "This is critically important in
streamlining and conducting trials more efficiently so that we can find out
about possible therapies that much sooner."
Protein study
Using proteomics technology, a method of studying hundreds
of proteins from a small blood sample, the researchers analyzed blood samples
of 57 older and symptom-free volunteers to determine whether specific proteins
were associated with amyloid burden in the brain.
They measured brain amyloid using PET (positron emission
tomography) scans with Pittsburgh Compound B, a tracer that binds to amyloid
plaques. The volunteers are participating in the NIA's Baltimore Longitudinal
Study of Aging (BLSA), America's longest-running scientific study of human
aging.
The researchers found the amount of a specific protein
called apolipoprotein E, or ApoE, in the blood samples was strongly associated
with the level of beta amyloid in the brain. Those with high blood levels of
the protein had significantly greater deposits of amyloid in the medial
temporal lobe, the region of the brain important to memory function.
'Intriguing' results
"These results are especially intriguing as this
protein is made by the APOE gene, the most robust genetic risk factor for
late-onset Alzheimer's," said Madhav Thambisetty, M.D., Ph.D., of the
Intramural Research Program at NIA, the
lead author on the study. Late-onset Alzheimer's is the most common form of the
disease and occurs around age 65 or later.
He now plans to test these findings in serial blood samples
collected every year in BLSA volunteers to determine how changing blood levels
of ApoE protein may relate to pathological changes in the brain over time.
"If the results are equally positive, we may be able to
develop a blood test that provides a less invasive, inexpensive method that
helps to detect the early pathological changes of Alzheimer's disease," he
said.
The study appears in the Dec. 20, 2010, issue of the Journal
of Alzheimer's Disease.
