Blood Biomarkers in Alzheimer's Disease.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that affects millions of people worldwide. The characteristic pathological manifestation of AD includes the deposition of extracellular insoluble β amyloid plaques and intracellular neurofibrillary tangles formed from hyperphosphorylated tau protein. Cost effective and minimally invasive peripheral blood-based biomarkers are critical for early AD diagnosis. Currently, the plasma based two fraction of β amyloid peptide ratio (Aβ42/40) and phosphorylated tau (p-tau) are considered as blood-based biomarkers for AD diagnosis. Recent research indicates that oxidative stress (OS) occurs prior to amyloid plaque (Aβ) formation and abnormal tau phosphorylation in AD. The imbalance of the master antioxidant, glutathione (GSH), and prooxidants (iron, zinc, and copper)─plays a crucial role in AD neurodegeneration. We present peripheral blood-based OS related biomarkers that are mechanistically involved in the disease process and may serve as a novel screening tool for early detection of AD onset. This OS based approach may also provide a quick and cost efficient method to monitor the effects of disease-modifying therapies in AD clinical trials.