Alzheimer’s disease: study reveals cause of disease progression in brain

The mystery surrounding Alzheimer’s disease is dispelled. According to a recent study published in Science Advances, on Friday, October 29, the progression of the disease is due to clusters of toxic proteins, responsible for the cognitive decline associated with Alzheimer’s disease, which reach different areas of the brain and accumulate there over decades.

The study is the first to use human data to quantify the rate of molecular processes leading to this neurodegenerative disease. This discovery could influence the development of treatments.

The theory, found in mice that clusters form in one place and trigger a chain reaction in other areas of the brain, does not fully apply to humans. According to the researchers, this propagation phenomenon can occur but it is not the main driver.

According to Georg Meisl, a chemist at Cambridge University and author of the article, “two elements made this work possible”. First, “studying very detailed data from PET scans and various data sets collected”, as well as “mathematical models which have been developed over the past ten years”.

To reach this conclusion, the researchers used 400 brain samples taken after the death of people with Alzheimer’s and 100 PET scans performed on patients to monitor tau protein aggregation. It is the build-up of this and another protein called beta-amyloid that causes brain cell death and brain shrinkage.

It is therefore this phenomenon that causes memory loss and an inability to perform daily tasks.

In their research, scientists also found that it took five years for aggregates to double in number. For Georg Meisl, it is a number “encouraging” since this indicates that neurons are already able to fight aggregates. “Maybe if we manage to improve them a bit, we can significantly delay the onset of critical illness.”, adds the researcher.

Alzheimer’s disease is classified by the “Braak stages”. Scientists say it would take about 35 years to go from stage 3, where mild symptoms appear, to stage 6, the most advanced. Aggregates grow rapidly, which explains, according to Georg Meisl, “why the disease takes so long to develop, and why the condition of people tends to worsen rapidly”.

Alzheimer’s, one of the main public health problems, currently affects 40 million people worldwide. This discovery is therefore a hope for all people with the disease. Sara Imarisio, from Alzheimer’s Research UK, hopes this study and others will help “to guide the development of future treatments targeting the tau protein, so that they have a better chance of slowing the disease and helping people with dementia.”