Blood biomarkers could reveal Alzheimer’s disease up to ten years before the onset of any symptoms, a new study has revealed.
Research on inherited forms of the dementia shows that the GFAP protein is a possible biomarker for very early stages of the disease, and can reflect changes much earlier than current known measures.
The study, by Karolinska Institutet, could one day lead to earlier detection of Alzheimer’s, the researchers say.
“The first change we observed was an increase in GFAP approximately ten years before the first disease symptoms,” says the study’s last author Professor Caroline Graff, of the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet.
“This was followed by increased concentrations of P-tau181 and, later, NfL (neurofilament light protein), which we already know is directly associated with the extent of neuronal damage in the Alzheimer brain. This finding about GFAP improves the chances of early diagnosis.”
In Alzheimer’s disease, nerve cells in the brain degenerate as a result of the abnormal accumulation of the proteins beta-amyloid and tau. As more brain neurons become damaged, this manifests in dysfunction of cognitive functions such as memory and speech.
The disease progresses insidiously and biological changes in the brain begin as early as 20 to 25 years before memory loss and other cognitive symptoms become evident. The earlier a patient is correctly diagnosed, the sooner they can be offered the right treatment.
Alzheimer’s is the most common form of dementia, accounting for 60 to 80 per cent of all cases. Globally, dementia cases are predicted to triple by 2050.
This inspired the latest research by which Karolinska Institutet, along with colleagues at Landspitali University Hospital in Iceland, Gothenburg University and University College London, has been studying biomarkers in blood for very early pathological changes in a rare and inherited form of Alzheimer disease that accounts for less than one percent of all cases.
Individuals with a parent with Alzheimer disease caused by a mutation have a 50 percent risk of developing the disease themselves.
For this study, the researchers analysed 164 blood plasma samples from 33 mutation carriers and 42 relatives without the inherited pathogenic predisposition. The data were collected between 1994 and 2018.
Their results reveal clear changes of several blood protein concentrations in the mutation-carriers.
“Our results suggest that GFAP, a presumed biomarker for activated immune cells in the brain, reflects changes in the brain due to Alzheimer’s disease that occur before the accumulation of tau protein and measurable neuronal damage,” says the study’s first author Charlotte Johansson, doctoral student at the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet.
“In the future it could be used as a non-invasive biomarker for the early activation of immune cells such as astrocytes in the central nervous system, which can be valuable to the development of new drugs and to the diagnostics of cognitive diseases.”
