GFAP: Another Promising Blood-Based Biomarker for AD

By Ram Rao, Ph.D., Principal Research Scientist for Apollo Health

Recent advances in Alzheimer’s disease (AD) research include blood-based biomarkers developed for early diagnosis and prognosis of AD and to seek suitable interventions at the prodromal or early stage of the disease. In addition to p-tau 217, another promising blood-based biomarker is glial fibrillary acidic protein (GFAP).

Astrocytes are glial cells-a subtype of non-neuronal cells that make up the majority of cells in the human central nervous system (CNS). They are involved in metabolic, structural, homeostatic, and neuroprotective functions. Astrocytes outnumber neurons in the human brain and play a key role in stabilizing and regulating the blood-brain barrier, supporting, guiding, nurturing, and signaling neuronal architecture and activity, and promoting synapse formation.

One of the primary structural components of astrocytic cells is the intermediate filament (IF), which regulates the shape and diameter of the astrocytes. Glial fibrillary acidic protein (GFAP), a subtype of the IF, is encoded by the GFAP gene and is expressed in astrocytic glial cells. GFAP is involved in many important CNS processes, including cell-cell communication and maintenance of the blood-brain barrier.  Being a brain-specific protein, the blood levels of GFAP are low in healthy individuals; in contrast, it is elevated in subjects with early, mild, and moderate AD.

AD is characterized by an event termed Gliosis-a reactive change of glial cells in response to damage to the brain. In most cases, gliosis involves the proliferation of several different types of glial cells, including astrocytes, microglia, and oligodendrocytes, leading to the formation of a glial scar. This breakdown of astrocytes triggers the release of GFAP from the brain tissue into the blood. Furthermore, the integrity of the blood-brain barrier is compromised in AD, which could also cause the leakage of GFAP into the blood. Thus, GFAP may serve as a sensitive blood biomarker for tracking gliosis and detecting early signs of AD.

There are several advantages to measuring GFAP in the blood for AD diagnosis. First, highly sensitive state-of-the-art assays have made it possible to measure GFAP in the blood. Second, blood levels of GFAP serve as an important marker for the early detection and prediction of the time course of AD and follow the disease progression. Third, several studies have now reported that plasma levels of GFAP are significantly higher in AD individuals than those in normal individuals. Finally, compared to the invasive and expensive lumbar puncture for measuring GFAP in the cerebrospinal fluid, blood GFAP offers the advantage of greater availability and tolerability for both clinicians and patients.

Though the blood GFAP test is not meant to make a definitive diagnosis of AD pathology, the test results serve as an early indicator of brain inflammation and ongoing repair, so it is important to determine what is causing this increase and then begin suitable treatment procedures like AHNP’s ReCODE protocol.

Apollo Health is now working with a specialized clinical laboratory focused on neurological disorders to offer the blood GFAP test and several other promising markers at a discounted price. Sign up here to be among the first to be notified when the pioneering diagnostics to prevent and reverse cognitive decline become available so you can assess your risk.