Sugar molecule in blood can predict Alzheimer's 10 years early: Study

A sugar molecule in blood can be used to develop a simple screening procedure which is able to predict the onset of Alzheimer's disease 10 years in advance, a study has found.

Researchers at Karolinska Institutet in Sweden found that the sugar molecule called glycan is associated with the level of tau, a protein that plays a critical role in the development of severe dementia.

Glycans are sugar molecules found on the surface of proteins, the building blocks of life, and determine the location and function of these proteins in the body.

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"We demonstrate in our study that blood levels of glycans are altered early during the development of the disease," said Robin Zhou, from Karolinska Institutet.

"This could mean that we’ll be able to predict the risk of Alzheimer's disease with only a blood test and a memory test,” said Zhou, first author of the study published in the journal Alzheimer's & Dementia.

In Alzheimer's disease, the neurons of the brain die, which is thought to be a result of the abnormal accumulation of the proteins amyloid beta and tau.

Clinical trials for Alzheimer’s drugs show that treatment should commence early in the pathological process, before too many neurons have died, to reverse the process before it is too late.

There is both a practical and a financial need for non-invasive screening methods for Alzheimer’s. Markers in blood are preferable, as taking samples of the cerebrospinal fluid is more difficult and brain imaging is expensive.

Researchers found that the level of a certain glycan structure in blood, denoted bisected N-acetylglucosamine, can be used to predict the risk of developing Alzheimer's disease.

By measuring blood glycan levels, the researchers found that individuals with matching levels of glycans and tau were over twice as likely to develop Alzheimer's-type dementia.

"We also show that a simple statistical model that takes into account blood glycan and tau levels, the risk gene APOE4 and a memory test, can be used to predict Alzheimer’s disease to a reliability of 80 per cent almost a decade before symptoms such as memory loss appear," said corresponding author Sophia Schedin Weiss from Karolinska Institutet.

The results are based on 233 participants of the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K).

The samples were collected between 2001 and 2004, and the participants were monitored regularly with respect to factors such as memory loss and the presence of dementia.

The follow-ups were carried out every three to six years and continued for 17 years.

The researchers will now be analysing blood samples from the remaining participants of the SNAC-K study as well as from participants of other aging studies in and outside Sweden.

“We are collaborating with researchers in primary care in Sweden to evaluate different biomarkers for dementia at primary health care centres,” said Weiss.

“We hope that glycans in the blood will prove to be a valuable complement to current methods of screening people for Alzheimer's disease that will enable the disease to be detected early," the researcher added.