Amyloid-β can begin building up in the neurons of people only 20 years of age – an age much younger than previously thought, according to a study published in Brain.
The buildup of amyloid-β plaques outside of neurons has long been associated with the development of Alzheimer’s disease, but previously, scientists have only discovered amyloid-β accumulation in older adults.
The researchers studied basal forebrain cholinergic neurons, which are some of the first neurons to be damaged and die in Alzheimer’s disease. Although these neurons are known to be particularly vulnerable to the disease, the mechanisms that make them so susceptible were previously unknown.
The researchers examined neurons from the brains of 50 deceased individuals, divided into three groups: 13 cognitively normal individuals aged 20 to 66 years, 16 older individuals without dementia aged 70 to 99 years, and 21 older individuals with Alzheimer’s disease aged 60 to 95 years.
Using staining techniques on different sections of the brains, the researchers found that amyloid-β oligomers were present even in the neurons of individuals aged 20 and continued to get larger in older individuals and those with Alzheimer’s disease. The same amount of amyloid-β accumulation was not present in nerve cells other than basal forebrain cholinergic neurons, however.
Because the basal forebrain cholinergic neurons experience amyloid-β buildup before other neurons, it may explain why they are often the first to be affected by Alzheimer’s disease and aging.
In the future, the researchers plan to study how the internal amyloid-β damages the neurons as it accumulates.