Earliest Alzheimer's warning could come from blood-brain barrier

Sept. 25 (UPI) -- Physicians could diagnose Alzheimer's disease sooner by focusing on the brain's circulation system rather than only other biomarkers, according to a study.

Researchers believe this strategy can be a key in stopping or slowing the disease because earlier diagnosis suggests better control of its development. The findings were published Monday in the journal Nature Neuroscience.

"Cognitive impairment, and accumulation in the brain of the abnormal proteins amyloid and tau, are what we currently rely upon to diagnose Alzheimer's disease, but blood-brain barrier breakdown and cerebral blood flow changes can be seen much earlier," Dr. Berislav Zlokovic, a researcher at the Keck School of Medicine of the University of South California, said in a press release. "This shows why healthy blood vessels are so important for normal brain functioning."

The researchers are recommending that the blood-brain barrier, or BBB, be considered an important biomarker and potential drug target for Alzheimer's disease. These tests aren't routinely offered at a doctor's office.

Although Alzheimer's disease affects 5.7 million Americans and is the sixth-leading cause of death in the United States, the disease has not been fully understood.

The USC researchers turned to the blood-brain barrier, the brain's filtration system, which is mainly composed of endothelial cells lining the 400 miles of arteries, veins and capillaries that feed brains.

The system lets in the in good things, such as glucose and amino acids, and keeping out bad things, which include viruses, bacteria and blood.

Leaks in the blood-brain barrier may allow a protein called amyloid into the brain. By sticking to neurons, this triggers the accumulation of more amyloid. It eventually overwhelms and kills brain cells.

"Something is off with the system when that happens," said Dr. Arthur Toga, director of the Laboratory of Neuro Imaging and USC's Neuroimaging and Informatics Institute at the School of Medicine. "Healthy people have amyloid in their bodies. When the system is dysregulated, amyloid can build up and cells die off."

These leaks have been found in other neurodegenerative diseases, including Huntington's disease, Parkinson's disease and multiple sclerosis.

BBB leaks can be detected using an intravenously administered contrast substance with magnetic resonance imaging. In addition, brain microbleeds, another sign of leakage, also can detected with a MRI. Also, a slowdown in the brain's uptake of glucose, which visible via PET scan, can be the result of BBB breakdown.