Mayo Clinic Study of Thousands of Brains Reveals Tau as Driver of Alzheimer’s Disease

April 23, 2015

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Originally published on the In the Loop blog on April 7, 2015.

For the past 25 years, much of the energy in Alzheimer’s research has been focused on amyloid protein as the primary driver of cognitive decline in patients. But recently, researchers from Mayo Clinic have stepped up to say, “Wait a minute … take a look at the tau protein.” The researchers, led by Melissa Murray, Ph.D., a Mayo neuroscientist, recently shared their findings in the journal Brain, adding fuel to the ongoing debate about whether amyloid or tau contributes most to Alzheimer’s progression.

The collaborative research started in Florida, where scientists examined more than 3,600 postmortem brains from the Mayo Clinic Brain Bank and found varying stages of Alzheimer’s in about half. Dr. Murray describes examining what they found as being like looking at the rings of a tree. “You can identify patterns, like the changing seasons and the aging of the tree, when viewing the tree’s cross-section,” Dr. Murray says. “Studying brains at different stages of Alzheimer’s gives us a perspective of the cognitive impact of a wide range of both amyloid and tau severity.”

Researchers in Rochester then examined amyloid brain scans taken of patients prior to death and compared them to the measure of tau and amyloid brain pathology. The results led them to conclude that it was the severity of tau, and not amyloid, that best predicts the age of onset, cognitive deterioration, and the duration of the disease. The research doesn’t exclude consideration of amyloid but instead suggests that researchers take a fresh look at tau. David Knopman, M.D., a Mayo neurologist, tells WCCO News, “We like to think of A causes B causes C. Well, it may be here that A causes C and B causes C. What this study does is to validate that the scans we are doing in life, in fact, reflect what the brain looks like in the traditional way under the microscope, after they die.”

Although more than 5.3 million American have been diagnosed with Alzheimer’s, and millions more likely will be diagnosed in the future, Alzheimer’s research receives only a fraction of the funding of diseases like cancer and heart disease. Last month, Ronald Petersen, M.D., Ph.D., director of Mayo Clinic’s Alzheimer’s Disease Research Center, testified before the Senate Special Committee on Aging to try and change that. He told legislators that scientific investigators will need at least $2 billion a year (comparable to annual spending on heart research) if effective treatments for the disease are to be found in the next 10 years.