Some people with signs of Alzheimer’s disease in their brains may not show any clinical symptoms while alive, according to a new study which may lead to a better understanding of resilience against the debilitating condition.
The findings, according to researchers, may lead to a better understanding of how some people reach the age of 90 or even 100 in good health, without medications or brain disease.
In the study, scientists assessed brain tissue from the Netherlands Brain Bank which contains samples from over 5,000 deceased brain donors with a wide range of diseases.
The brain bank also keeps the documented medical history and detailed disease course with the symptoms of each donor.
Researchers found that a subgroup of people who had Alzheimer’s disease processes in their brains but did not show any clinical symptoms while alive, indicating they were a “resilient” group.
When scientists assessed the gene activity in the brains of members of the group they found that several processes were altered.
A type of star-shaped cells called the astrocytes appeared to produce more of the antioxidant metallothionein.
These cells are known to be garbage collectors in the brain, providing a protective role, but in some cases they may also trigger inflammation via other cells called microglia.
In the resilient group, researchers found that a microglia pathway often linked to Alzheimer’s disease seemed to be less active.
Researchers found a natural reaction that automatically removes a misfolded toxic protein was affected in Alzheimer’s patients, but was relatively normal in resilient individuals.
The study also found that there may be more cell powerhouse mitochondria in the brain cells of resilient individuals, ensuring better energy production in their brains.
“What is happening in these people at a molecular and cellular level was not clear yet. We therefore searched for donors with brain tissue abnormalities who did not show cognitive decline in the Brain Bank,” study co-author Luuk de Vries said.
“Of all the donors we found 12, so it is quite rare. We think that genetics and lifestyle play an important role in resilience, but the exact mechanism is still unknown,” Dr de Vries said.
Recent research has indicated that people who receive a lot of cognitive stimuli, like those working a complex job, can build up more Alzheimer’s pathology before developing symptoms, suggesting they may be building resilience.
Physical exercise and a cognitively active lifestyle with many social contacts has also been shown to delay the onset of Alzheimer’s disease.
“If we can find the molecular basis for resilience, then we have new starting points for the development of medication, which could activate processes related to resilience in Alzheimer’s patients,” Dr de Vries concluded.
