What Role Does Beta-Amyloid Play in the Brain?
Beta-amyloid’s role in brain function is unclear, says Dr. Pillai.
“In a healthy brain, it’s broken down and cleared away by enzymes, but in people with Alzheimer’s disease, it builds up and tends to clump together outside the neurons,” he says.
These plaques, along with tau protein (which forms neurofibrillary tangles inside the neurons) are suspected of causing a cascade of events that eventually leads to neuron or brain cell death, causing the symptoms of Alzheimer’s disease, he says.
What Causes It to Clump Together in Some People’s Brains?
The exact mechanisms leading to beta-amyloid clumping are not fully understood.
“In general, the structure of the protein itself is very sticky, which isn’t an issue in a healthy brain where there are normal levels and it’s able to be cleared out,” says Pillai.
But when the clearance mechanisms are compromised or more proteins are generated than necessary, then clumping tends to increase, he says.
What Happens in the Brain as a Result of Amyloid Clumps?
The accumulation of beta-amyloid plaques is associated with damage to brain cells and the disruption of neural communication, which progressively impairs brain functions such as memory, reasoning, and decision-making.
But the key word here is “associated.” Amyloid is certainly part of the Alzheimer’s disease process, but there’s more to the story, says Kyan Younes, MD, a clinical assistant professor and neurologist at Stanford Health Care in Palo Alto, California.
When you look at the brain of someone with Alzheimer’s under a microscope, it requires two proteins — beta-amyloid and tau protein, which is thought to occur after amyloid, says Dr. Younes.
“Amyloid alone is not clearly linked to clinical impairment (or symptoms of Alzheimer’s disease),” he says.
An estimated 40 percent of people in their eighties and older have some amyloid in their brains, but don’t have any Alzheimer’s symptoms, he says.
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