How are amyloid plaques implicated in Alzheimer’s disease? How does amyloid build-up contribute to cognitive decline?
An abundance of amyloid plaque in a person’s brain is a hallmark of Alzheimer’s, but not all amyloid plagues are created equal. Recent research suggests that some types of amyloid plagues are actually benign and even protective.
Here’s what we know about the role of amyloid plaques in Alzheimer’s disease.
What Are Amyloid Plaques?
Experts have long theorized that the buildup of amyloid plaques in the brain is a leading cause of Alzheimer’s. Amyloid is a protein that helps supply food to brain cells. For unknown reasons, these proteins sometimes become damaged and fold up into a sticky plaque that accumulates outside neurons. When plaques form, they prevent synapses from effectively communicating. If enough synapses are inhibited by amyloid plaques, the brain may lose many of its functions.
Though amyloid plaque has long been connected to cognitive decline, it is still unknown if it is a cause, an effect, or both. Some autopsied brains have been filled with amyloid plaques, yet the patient never showed major signs of cognitive impairment. Also, dementia patients rarely show damage exclusively from amyloid plaques. There are many other ways a brain can be damaged that can lead to dementia.
New Research on Amyloid Plaques
Most Alzheimer’s treatments targeting amyloid plaques have been largely unsuccessful in improving brain function or reducing the effects of the disease. For instance, the most recent FDA-approved drug Aducanumab, which reduces amyloid in the brain, hasn’t been shown to improve cognition. A recent study provides new evidence on why removing amyloid plaques doesn’t alleviate dementia symptoms.
There are many types of amyloid plaques, but the two most prevalent are diffuse plaques and dense-core plaques. Experts believed both plaques caused damage that led to Alzheimer’s, but a 2021 study suggests dense-core plaques may actually be beneficial or benign. The dense-core plaques may play a protective role, which is why treatments that attack both types of amyloid plaques haven’t been successful. This might also explain why some people have a large amount of amyloid plaques but no signs of dementia: The majority of the plaques may have been dense-core plaques.
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