The dreaded condition of Alzheimer's disease (AD) usually strikes people entering their golden years and has no cure. But what if doctors could determine years in advance who would get the disease?
Researchers at the Institute of Psychiatry at King's College London say a simple blood test could soon give Alzheimer's patients ten years advance warning that they will get the disease.
The breakthrough came after researchers found high levels of a protein can be an early sign of the condition.
The study, published in the Archives of General Psychiatry, has found that clusterin levels in blood could be an early biomarker of AD many years before symptoms appear. The international team of scientists also found that higher levels of clusterin were related to more severe and rapid memory loss and greater brain shrinkage.
It is these findings, they say, that could lead to development of a blood test to help identify who would benefit from early treatment of AD and also whether treatments were working to delay or prevent brain damage.
Researchers have been focusing on developing an inexpensive blood test that will accurately reflect the damage detected by brain scans in patients in the early stages of AD, such as shrinkage ("atrophy") in certain regions and abnormal accumulations of a protein called beta amyloid.
In this study, researchers used a novel strategy combining brain scans with proteomics, a method that can detect hundreds of proteins in a single blood sample. They compared blood samples and brain scans of 300 research participants with AD, mild cognitive impairment or normal cognition.
They found that a single protein -- clusterin -- was related to brain shrinkage, severity of memory problems and a risk of faster memory loss. Using the same method in blood samples from volunteers in a continuing study in the United States, they showed that increased amounts of clusterin -- measured a decade earlier to the brain scans -- were linked to higher levels of beta amyloid in the brain.
Finally, in mouse models of AD, researchers discovered increased levels of clusterin in the blood as the mice aged. Under the microscope, they also observed clusterin to be surrounding the amyloid plaques.
They concluded this provides further evidence that clusterin is critically important in Alzheimer's where it probably works to help protect the brain from amyloid protein. This finding from proteomics complements the discovery reported last year by an international team including the KCL group that showed the clusterin gene increased risk of AD -- a finding noted by Time magazine as one of the top ten medical discoveries of 2009.
Easy test
"A primary goal in Alzheimer's research is to develop an inexpensive, easily administered test to accurately detect and track the progression of this devastating disease. Identifying clusterin as a blood biomarker that may be relevant to both the pathology and symptoms of the disease may bring us closer to this goal," said Dr. Madhav Thambisetty, formerly of the IoP KCL UK and now with the National Institute on Aging, National Institutes of Health, US.
The authors say the results of their research add further evidence to the role of clusterin in AD, and though not a test in itself, they hope their work will lead to development of a blood test that can identify future AD victims.
"A simple blood test for detecting Alzheimer's has long been the Holy Grail for dementia researchers and these new findings edge us closer in the search. Early detection of dementia will be crucial to ensuring the treatments of the future can be given swiftly and when most effective," said Rebecca Wood, Chief Executive of the Alzheimer's Research Trust (ART). "Research is the only answer to dementia, yet our scientists remain in desperate need of funds. Investing in research now will bring the treatment breakthroughs we so urgently need in a world where 35 million live with this devastating condition."
