Scientists believe that Alzheimer's disease develops over decades, but it is usually not diagnosed until well after patients have started to experience serious symptoms of dementia. While researchers have recently been able to develop better diagnostic tests for Alzheimer's that rely on blood samples, those tests are generally only useful when a person is already having memory problems. So investigators are still searching for better ways to identify dementia and Alzheimer's before cognitive symptoms get arise.
In a new study reported in eBioMedicine, researchers analyzed plasma biomarkers in a diverse collection of patients who had received treatment for various issues involving memory problems.
This work revealed that other than NfL, all of the plasma biomarkers that were assessed (pTau181, pTau217, and pTau231) were linked to the abnormal buildup of a misfolded protein called amyloid, which is a hallmark of Alzheimer's disease. But the only biomarker with levels that could be fully explained by patient symptoms was pTau217, while more than 70 percent of the variability in other plasma biomarker levels was unexplained.
"These findings are in line with the other recent reports on this topic, and add to the emerging body of evidence that plasma pTau217 is a dual marker of amyloid and tau pathology," noted first study author Dr. Marina Bluma, postdoctoral fellow at the Department of Neurobiology. "Unlike these biomarkers, increased NfL levels were more indicative of brain atrophy and older age."
Studies have also indicated that dysfunction in the cells that line the brain's blood vessels can promote the development of cerebral small vessel disease (CSVD), which can play a major role in dementia and cognitive decline. It's thought that as these blood vessel cells become dysfunctional, inflammatory molecules and fluids are able to seep into brain tissue and cause problems.
Usually, CSVD has to be diagnosed with an MRI, which highlights the brain lesions as white spots on MRI scans. These are known as white matter hyperintensities (WMH). A recent study has shown that WMH can indicate dementia. But it may soon be possible to detect these problems with a blood test, instead of a costly and challenging MRI.
Reporting in Alzheimer's & Dementia, scientists have found a protein in blood that seems to be related to the permeability that can arise in brain blood vessels, and which is linked to cognitive decline.
"Evaluating data from a large group of patients with a range of vascular risk profiles and cognition ranging from unimpaired to mild dementia, we found that plasma levels of this protein, placental growth factor (PlGF), could potentially be used as a biomarker to screen for and monitor cognitive impairment and dementia," said senior study author Jason Hinman, MD, PhD, a vascular neurologist at UCLA Health, among other appointments.
Sources: University of California, Los Angeles; Karolinska Institute; Alzheimer's & Dementia, eBioMedicine