A newly developed PET tracer has shown that tau protein clumps within the brain are better indicators of cognitive impairment related to Alzheimer’s disease than beta amyloid proteins, the current standard for evaluating the disease’s progress, according to results of a new study recently published in the journal Science Translational Medicine.
Alzheimer’s disease has been linked to the accumulation of two distinctive proteins produced inside the brain: beta amyloid and tau. Until now, researchers have focused primarily on beta amyloid plaque as a means of assessing declines in cognition among patients.
But advances in imaging tracer sophistication have allowed scientists to take a closer look at tau, which develops as tangled clumps in various regions of the brain, said lead author Matthew Brier and his colleagues at the Washington University School of Medicine in St. Louis.
“Until recently, only [beta amyloids] could be studied in humans using PET imaging owing to a lack of tau PET imaging agents,” they wrote. “Clinical pathological studies have linked tau pathology closely to the onset and progression of cognitive symptoms in patients with Alzheimer’s disease.”
Brier and his team used a recently developed PET tracer known as T807 to image 10 patients with mild Alzheimer’s disease and 36 control participants who were cognitively normal. In addition to brain imaging, subjects were evaluated using the traditional clinical dementia rating scale, cerebrospinal fluid measures and memory tests.
Their results revealed that tau imaging is more effective in establishing the extent of cognitive impairment in Alzheimer’s patients than beta amyloid protein, a discovery that could allow doctors to better track the timeline of Alzheimer’s progression and define which regions of the brain are affected.
“Overall, tau imaging provided a more robust predictor of disease status than did [beta amyloid] imaging,” the researchers concluded. “Thus, whereas [beta amyloid] imaging provides a good marker for early disease state, tau imaging is a more robust predictor of disease progression.”