A protein in cerebrospinal fluid that could possibly indicate Alzheimer’s disease in its earliest stage and predict its progression has been discovered by researchers at Washington University School of Medicine in Saint Louis.

Background: Two proteins that build up in the brain have been linked to Alzheimer’s disease, the most common form of dementia. Amyloid protein plaques form between neurons, and tau tangles form inside neurons. Both of these proteins often begin to develop several years before cognitive impairment. Amyloid plaques or tangles can be found on a PET scan. However, PET scans are expensive and often difficult to obtain.

The researchers looked at a form of tau protein called microtubule binding region (MTBR) tau 243, in the fluid that surrounds the brain and spinal cord, known as cerebrospinal fluid (CSF). CSF can be obtained by doing a spinal tap. Since tau tangles often form before symptoms of cognitive impairment, finding MTBR tau 243 in CSF may diagnose Alzheimer’s at its earliest stage. The research findings are published in the journal Brain.

Study details: The researchers collected CSF from 100 people age 70 or older. MTBR tau 243 was abundant only in people with cognitive impairment or dementia. They followed 28 people from the original group for two to nine years and found that MTBR tau 243 also increased in those who had been diagnosed with Alzheimer’s disease. To test the ability of the MTBR tau 243 to predict the stage of Alzheimer’s, they compared MTBR tau 243 levels with PET-scan imaging in 20 people with Alzheimer’s. The CSF levels of MTBR tau 243 matched the amount of tau tangles found on the scans.

Benefits of early detection: The significance of their discovery, say the researchers, is that diagnosing Alzheimer’s at an early stage could make treatment more effective. Levels of MTBR tau 243 could also be used to study how well an existing or future treatment is working. Finally, an interesting finding was that some MTBR tau 243 were found outside neurons. This raises the possibility that MTBR tau 243 may spread tau tangles from one neuron to another. If that’s the case, it may be a target for new drugs to attack and stop the spread of the tangles that make Alzheimer’s so insidious.

Source: Study titled “CSF Tau Microtubule Binding Region Identifies Tau Tangle and Clinical Stages of Alzheimer’s Disease,” by researchers at Washington University School of Medicine in Saint Louis, published in Brain.