Researchers in the US have found that measuring proteins in blood may be able to identify people in the early stages of Alzheimer’s disease, before symptoms develop. The study is published on Wednesday 10 June in the journal Neurology online.
Studies have shown that Alzheimer’s disease, the most common cause of dementia, begins to develop in the brain years before symptoms such as memory loss appear. A team led by researchers at the University of California, San Francisco, investigated whether proteins contained in exosomes – tiny particles that are released by cells into the blood and other bodily fluids – may act as a marker for these early brain changes.
The team first compared blood samples from 26 cognitively healthy people, and 26 people with either Alzheimer’s disease or amnestic mild cognitive impairment (aMCI) – a condition that causes problems with memory not severe enough to be classed as Alzheimer’s. They also compared blood samples from 16 people with frontotemporal dementia (FTD), and 16 people without the disease. In particular, they looked at exosomes released by brain cells, and measured the amount of four different proteins called cathepsin D, LAMP-1, ubiquitin and HSP70.
They found that people with Alzheimer’s or aMCI had higher levels of cathepsin D, LAMP-1 and ubiquitin compared to healthy people, while levels of HPS70 were lower than those in healthy people. In people with FTD, levels of cathepsin D were raised compared to people without the disease, while levels of HPS70 were lower, with levels dropping below those in people with Alzheimer’s.
The researchers also analysed blood samples from 20 people with Alzheimer’s or aMCI, each of whom had given a sample before their symptoms began, and again up to 10 years later when they were diagnosed. These samples were compared with 20 people without memory problems. The results showed that people with Alzheimer’s and aMCI had similar differences in protein levels compared to healthy people, even before their symptoms had developed.
Dr Eric Karran, Director of Research at Alzheimer’s Research UK, the UK’s leading dementia research charity, said:
“This small study is one of an emerging research area that might hold real promise for early diagnosis of some neurodegenerative diseases. It needs to be confirmed in much larger groups of patients to ensure the findings reported are robust. The ability to accurately identify Alzheimer’s at the earliest stages would be a crucial step forward for research, as it’s likely that new treatments will have the best chance of success if given early. If confirmed in larger studies, these findings could enable the right people to be recruited for clinical trials, but this test is not designed for use in the doctor’s clinic.
“Research like this can also provide valuable clues about changes inside brain cells during Alzheimer’s, helping to guide efforts to develop new and effective treatments. Over half a million people are affected by Alzheimer’s in the UK today, and only through research will we be able to successfully fight the disease.”