Scientists have uncovered a mechanism in the brain that could account for some of the neural degeneration and memory loss in people with Alzheimer's disease.

The researchers discovered that a common symptom of Alzheimer's disease - the accumulation of amyloid plaques along blood vessels - could be disrupting blood flow in the brain. The results were published in the journal Brain.

Astrocytes serve many support functions, such as shuttling nutrients from blood vessels to nerve cells or removing their waste products," said the author. "They also control the diameter of blood vessels to assure proper nutrient and oxygen delivery to the brain and maintenance of the blood-brain barrier. In response to injury and disease, however, astrocytes become reactive and change many of their supportive properties."

The team discovered that the astrocytes' blood flow regulation is disrupted by plaques formed of misfolded amyloid protein around blood vessels. In a healthy brain, amyloid protein fragments are routinely broken down and eliminated.

We found that amyloid deposits separated astrocytes from the blood vessel wall," said coauthor of the paper. "We also found that these amyloid deposits form an exoskeleton around the blood vessels, a kind of cast that reduces the pliability of the vessels."

The exoskeleton is known as a vascular amyloid. Its inelasticity might result in lower blood flow, which could account for Alzheimer's symptoms, such as memory lapses, impaired decision-making, and personality changes.

While the scientists don't fully understand the role of vascular amyloid in Alzheimer's disease, they now have a possible therapeutic target to study.

http://www.vtnews.vt.edu/articles/2015/11/112415-vtc-alzheimers.html