A team at the University of Leeds, part-funded by Alzheimer's Research UK and the Medical Research Council (MRC), studied an enzyme called alkaline phosphatase. It's thought the enzyme could be linked to the build-up of tau, a hallmark toxic protein in Alzheimer’s disease.
The researchers, led by Prof Nigel Hooper, studied blood plasma samples and post-mortem brain tissue, provided by the MRC London Neurodegenerative Diseases Brain Bank, from people with Alzheimer’s and from healthy people. They found that people with the disease had more of the enzyme in the hippocampus – one of the first regions of the brain to be damaged in Alzheimer's – than healthy people when they died.
People with the disease also had greater levels of the enzyme in their blood. Further analysis showed that higher levels of alkaline phosphatase were associated with a greater loss of cognitive function.
Although levels of the enzyme in blood samples were higher in Alzheimer's, the measurements were still within the normal range, meaning they would not be useful for diagnosing the disease. However, the findings could give researchers a new tool for clinical trials, helping them to monitor how people are responding to treatments.
The findings are published today in the journal Neurodegenerative Diseases.
Prof Hooper, a Scientific Adviser to Alzheimer's Research UK, said:
“We were surprised to find that levels of this enzyme in people's blood correlated with cognitive decline, and we think this could be significant for helping to monitor people with Alzheimer's over a period of time. We hope that with more research, our results could be useful to people who are testing new drugs, giving us a better chance of finding an effective treatment to fight Alzheimer's.
“Dementia is not a normal part of ageing, and with research it can be beaten, but we need to know much more about its causes in order to develop effective treatments. I hope our research can help bring us a step closer to that goal.”
Dr Simon Ridley, Head of Research at Alzheimer's Research UK, said:
“These important findings could give researchers a vital tool to aid the development of new drugs for Alzheimer's disease. It will also be important to find out what causes alkaline phosphatase to increase as the disease develops.
“Alzheimer's is the most common form of dementia, which currently affects 820,000 people in the UK and more than 7,500 people in Leeds alone. If we are to find new treatments that could really benefit people in the future, it's crucial that we invest in research now.”
Professor James Ironside, Director of the MRC-led UK Brain Banks Network, said:
“What's so fascinating about this study is that the researchers were able to directly compare healthy tissue with samples from Alzheimer's sufferers to demonstrate the importance of alkaline phosphatase levels in the brain.
“This cutting-edge research would not be possible without access to a reliable supply of high-quality brain tissue samples, which is why the UK Brain Banks network is so important as a national resource to support neuroscience research.”
The study received funding from Alzheimer's Research UK, the Health Foundation and the Medical Research Council.