A new investigation of Institute of Psychiatry, Psychology and Neuroscience at King’s College London (United States) has developed a blood test that could be used to predict the risk of Alzheimer’s disease up to 3.5 years before clinical diagnosis.
The study, published in the scientific magazine ‘Brain’supports the idea that human blood components can modulate the formation of new brain cells, a process called neurogenesis. Neurogenesis occurs in an important part of the brain called the hippocampus that is involved in learning and memory.
Alzheimer’s and new brain cells
Although Alzheimer’s disease affects the formation of new brain cells in the hippocampus during the early stages of the disease, previous studies had only been able to study neurogenesis in its most advanced phases through autopsies.
To understand the early changes, the researchers collected blood samples over several years from 56 individuals with mild cognitive impairment (MCI), a disorder in which a person begins to experience worsening of their memory or cognitive ability.
Although not all people with MCI go on to develop Alzheimer’s disease, the percentage of those with it who are diagnosed is much higher than that of the general population. Of the 56 study participants, 36 were diagnosed with Alzheimer’s.
In the study, they treated brain cells with blood taken from people with MCI, exploring how those cells changed in response to blood as Alzheimer’s disease progressed.
Several key discoveries
By studying how blood affected brain cells, researchers made several key discoveries. Blood samples collected over the years from participants who subsequently deteriorated and developed Alzheimer’s disease promoted decreased cell growth and division and increased apoptotic cell death (the process by which cells are programmed to die).
However, the researchers found that these samples also increased the conversion of immature brain cells into hippocampal neurons.
Although the underlying reasons for the increased neurogenesis remain unclear, the researchers theorize that it could be a mechanism of early compensation for the neurodegeneration (loss of brain cells) experienced by those who develop Alzheimer’s disease.
Previous studies have shown that blood from young mice can have a rejuvenating effect on cognition in older mice by enhancing hippocampal neurogenesis. This gave the researchers the idea to model the neurogenesis process in a plate using human brain cells and human blood.
In their study, they set out to use this model to understand the process of neurogenesis and use changes in this process to predict Alzheimer’s disease, and found the first evidence in humans that the body’s circulatory system may have an effect on the ability of the brain to form new cells.
When the researchers used only blood samples collected furthest away from the time the participants were diagnosed with Alzheimer’s disease, they found that changes in neurogenesis occurred 3.5 years before clinical diagnosis.
“Extremely Important” Findings
“Our findings are extremely important, as they could allow us to predict the early onset of Alzheimer’s non-invasively. This could complement other blood biomarkers that reflect classic signs of the disease, such as the accumulation of amyloid and tau (the ‘flagship’ proteins of Alzheimer’s disease),” said Edina Silajdzic, co-author of the study.
The researchers say these findings could present an opportunity to better understand the changes that the brain undergoes in the earliest stages of Alzheimer’s disease.