A new discovery offers hope for the potential diagnosis of Alzheimer's disease years before symptoms appear, which could make medications or lifestyle changes more effective in preventing complications of the disease. A definitive diagnosis of Alzheimer's disease has only been possible after a person has died, but recent biomarker studies have led to the development of imaging and cerebrospinal fluid tests for those who are still alive. However, these tests can only monitor severe disease and differentiate advanced Alzheimer’s from similar disorders.
According to the American Chemical Society, researchers have identified a biomarker that can help doctors diagnose Alzheimer's disease early, as patients transition to mild cognitive impairment (MCI), an early sign of the disease. In searching for biomarkers for Alzheimer’s, some researchers turned to studying subtle changes in a protein called tau. These changes, or modifications, can make tau protein more prone to accumulation, leading to neurodegeneration and memory impairment. Two of these modifications involve the phosphorylation of tau at specific amino acids, resulting in variants known as p-tau181 and p-tau217.
These biomarkers effectively distinguish Alzheimer’s tissues from those of individuals suffering from other neurodegenerative diseases. Considering the usefulness of having multiple biomarkers available to doctors, Ben Shaw, Jerry Wang, and their colleagues sought additional p-tau biomarkers that could be effective in diagnosing Alzheimer's or possibly detect it in its early stages.
Using post-mortem brain tissues from Alzheimer's patients and non-Alzheimer's patients, researchers identified several p-tau biomarkers selectively associated with tau protein aggregation. Similar to p-tau181 and p-tau217, many of these biomarkers distinguished Alzheimer’s tissues from healthy controls. p-tau198 distinguished Alzheimer's from two other neurodegenerative diseases known for tau deposition. Other experiments showed that p-tau198 was as effective as p-tau181 and p-tau217 in these tests.
Importantly, both p-tau198 and p-tau217 could also differentiate the brain tissues of patients suffering from mild cognitive impairment, an early sign of Alzheimer’s, from older individuals without impairment. According to the researchers, there are currently no established biomarkers that can diagnose mild cognitive impairment. Thus, p-tau198 and p-tau217 may help doctors intervene early, with new treatments available, before significant neurodegeneration occurs. Additionally, researchers say this approach could be used to find tau biomarkers with other modifications beyond phosphorylation.
