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Why the risk of Alzheimer's increases with age
It has long been known that the likelihood of developing Alzheimer's increases with age. Researchers have now uncovered a possible cause for this connection: certain proteins involved in Alzheimer's disease - so-called tau proteins - can spread better in the aging brain.
Over a million people in Germany suffer from dementia
In Germany alone, around 1.2 million people suffer from dementia, the majority of them from Alzheimer's. There are around 47 million dementia patients worldwide. Although more and more young people and middle-aged people are now affected, the majority of patients are senior citizens. Researchers have now found evidence of why older people are more susceptible to Alzheimer's.
Illness usually begins with memory disorders
As the German Center for Neurodegenerative Diseases (DZNE) writes in a communication, Alzheimer's disease usually begins with memory disorders and later affects other cognitive abilities.
Two different protein deposits in the patient's brain are involved: “amyloid beta plaques” and “tau neurofibrils”.
The appearance of tau neurofibrils reflects the course of the disease quite precisely: they first appear in the memory centers of the brain and then appear in other areas as the disease progresses.
It is believed that tau proteins or their aggregates migrate along nerve pathways and thus contribute to the disease spreading in the brain.
What role does age play?
But what role does age play in these expansion processes?
If dew spreads more easily in older brains, it could explain why older people are more susceptible to Alzheimer's.
Susanne Wegmann, a scientist at the DZNE, and her colleagues pursued this hypothesis.
Her current study was developed in close collaboration with researchers in the United States at Harvard Medical School and Massachusetts General Hospital. The results were recently published in the science advances.
Spread of dew in aging brains
With the help of a “gene ferry” - a tailor-made virus - the scientists infiltrated the blueprint of the human tau protein into the brains of mice.
As a result, individual cells started producing the protein. Twelve weeks later, the researchers examined how far the tau protein had moved from the production facility.
"The human tau proteins spread about twice as fast in older mice as in younger ones," explains Wegmann.
According to the information, the experimental part of the study took place in Bradley Hyman's group at Harvard Medical School in Boston, USA, where Susanne Wegmann worked for several years.
In 2018, the scientist moved to the Berlin location of the DZNE, where her working group is researching tau-related disease mechanisms. Most of the data analysis and the summary of the results now took place here.
Healthy and sick dew
In addition, the experimental approach allowed scientists to analyze more closely how dew spreads. This protein is found in a healthy, soluble form in all nerve cells in the brain.
In Alzheimer's, however, it can change pathologically by changing its shape and then clumping into so-called fibrils.
"For a long time it was assumed that pathological tau protein was primarily passed on from one nerve cell to the next," explains Wegmann.
“However, our results show that the healthy form of the protein is also carried on in the brain and that this process increases with age. Cells can also be damaged if they receive and accumulate a lot of healthy tau protein, ”said the expert.
The findings from the current study raise a number of new questions, which Wegmann will now investigate with her working group at the DZNE:
What are the processes underlying the increased spread of dew in the aging brain? Is too much tau protein being produced or too little defective protein being broken down? Answering these questions can open up new therapeutic options in the long run. (ad)
More interesting articles on this topic can be found here:
- Alzheimer's - causes, symptoms and therapy
- Dementia: Link between herpes virus and Alzheimer's found
- Alzheimer's in distant relatives also indicates their own risk of developing the disease
Author and source information
This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
- German Center for Neurodegenerative Diseases: Information on why older people are more susceptible to Alzheimer's (accessed: July 9, 2019), German Center for Neurodegenerative Diseases
- Trade magazine "Science Advances": Experimental evidence for the age dependence of tau protein spread in the brain, (accessed: 09.07.2019), Science Advances