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Alzheimer's proteins spread like infections in the brain
More and more people develop Alzheimer's in the course of their lives, and although the causes of the disease have not yet been fully clarified, certain protein deposits in the brain are considered to be a key factor. A research team from the Ludwig Maximilian University of Munich (LMU) has now examined the spread of these proteins in the brain in more detail and found that patterns similar to those of an infection can be seen.
"In the course of Alzheimer's dementia with progressive mental decline, misfolded amyloid and tau proteins accumulate in the brain," the researchers explain in a press release from the LMU on the study results. The current study had shown that the tau proteins apparently spread in connected neuronal networks like an infection. The study results were published in the specialist journal "Nature"
44 million people with Alzheimer's worldwide
"Alzheimer's disease (AD) is one of the most common diseases of the central nervous system and is the main cause of dementia in old age," reports the research team. An estimated 44 million people worldwide are affected. The disease is characterized by memory and orientation disorders, speech disorders, impaired thinking and judgment, and changes in personality. In the advanced stage, those affected are no longer able to cope with their everyday life independently.
Deposit of misfolded proteins
In the course of the disease, the nerve cells and contact points between the neurons, the synapses, are destroyed more and more, the researchers explain. According to the current state of knowledge, Alzheimer's disease begins with the deposition of beta-amyloid proteins in the brain (as so-called plaques), which accumulate outside the nerve cells. Shortly thereafter, a buildup of the tau proteins within the nerve cells in the brain was evident, which is apparently crucial for the progression of dementia.
Distribution of tau proteins examined
"The stronger the tau pathology, the more pronounced the clinical symptoms of the patient are, as a rule," reports Dr. Nicolai Franzmeier from the Institute for Stroke and Dementia Research in the LMU press release. The research team around the head of the working group Professor Michael Ewers and the first author of the study, Dr. Franzmeier has therefore used imaging techniques to investigate the distribution of tau proteins in the brain of people with Alzheimer's.
Examination using special imaging methods
With the sophisticated imaging method of the so-called tau-PET, the distribution of the tau proteins from two samples, each with about 50 Alzheimer's sufferers, was examined. The changes in their brains were tracked over a period of one to two years using a tau-PET examination. In addition, at the start of the study, the brains were examined using functional magnetic resonance imaging (fMRI) to determine the functional linkage of nerve cells or brain regions.
Spread through linked nerve cells
"With these longitudinal data, we analyzed whether the spread of the tau proteins can be predicted using the topology of functional brain networks," reports Dr. Nicolai Franzmeier. In fact, the tau pathology had spread mainly along interconnected brain regions in the course of the disease. The spread takes place via interconnected nerve cells and the tau protein is passed on to other neurons at the synapses. This is reminiscent of an infectious disease or the spread of an infection.
Can individual predictions of the course of the disease be made?
The functional networking of the brain regions is central to mental performance and the prediction of the spread of tau proteins in these networks could also prove important for predicting the future decline in mental performance, adds Professor Ewers. In the long term, the researchers hope that, based on their findings, they will be able to make individual predictions about the spread of tau pathology and thus better predict the course of Alzheimer's disease for the individual concerned. (fp)
Author and source information
This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
Dipl. Geogr. Fabian Peters
- Nicolai Franzmeier, Julia Neitzel, Anna Rubinski, Ruben Smith, Olof Strandberg, Rik Ossenkoppele, Oskar Hansson, Michael Ewers: Functional brain architecture is associated with the rate of tau accumulation in Alzheimer's disease; in: Nature (published 1/17/2020), nature.com
- University of Munich Clinic: Infectious proteins in Alzheimer's disease (January 17, 2020), Klinikum.uni-muenchen.de