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Growing muscle weakness: why the strength decreases with age


Restricted quality of life: when the strength is lacking in old age

At 30, you are generally not considered to be “old”, but muscle degradation and the associated loss of strength begin to occur at this age. This process accelerates from around 50 years of age. Researchers have now identified a trigger for these changes.

Worldwide, people are getting older

The World Health Organization (WHO) has reported increasing life expectancy worldwide. According to experts, it could soon exceed 90 years in western industrialized countries. In Germany, average life expectancy had reached a new record level. With increasing age, however, muscle weakness also increases. German researchers have now identified a trigger for this change.

Increasing muscle weakness

The increase in average life expectancy is also accompanied by an increase in age-related diseases that affect the nervous system. These include Alzheimer's disease and other forms of dementia.

Such pathological changes are not only found in the brain. In the peripheral nervous system, which supplies muscles and the sensory structures of the skin, for example, the risk of degeneration increases with age.

The consequences for those affected are serious: they often suffer from sensations and excruciating pain in the extremities.

The increasing muscle weakness is particularly significant, since it significantly restricts those affected in their mobility and often leads to dangerous falls, which then often lead to the loss of independence.

So far, causes have not been systematically examined

Although the consequences of age-related degeneration of peripheral nerves are of great importance for the quality of life in old age and for the economy, the causes have not been systematically investigated so far.

That has now changed: In a new project, scientists from the Neurological Clinic of the University Hospital in Würzburg have examined an important and potentially treatable sub-aspect of age-related nerve degeneration.

Professor Rudolf Martini, head of the Experimental Developmental Neurobiology section at the Neurological Clinic, was responsible for this. The researchers published the results of their study in the journal “Journal for Neuroscience”.

Target macrophages

"In collaboration with colleagues from the University of Aachen, we first systematically recorded the changes that are found in the peripheral nerves of people between the ages of 65 and 79," Martini explains the approach of his team in a message.

The scientists encountered an increased number of macrophages in their samples. Macrophages are cells that belong to the body's defense and disposal system. For example, they absorb pathogens, foreign particles and aging body cells and digest and dispose of them.

They initiate inflammatory processes, help to heal wounds and clean the tissue. Unfortunately, they also do harm to some diseases.

In an experiment with mice, the scientists studied whether this was also the case with age-related degenerative changes in the nerves.

"To do this, we carefully examined the nerves of 24-month-old mice, which is a fairly old age for mice," explains Martini.

It was found that the age-related changes in the peripheral nerves of the mice were very similar to those in the nerves of humans. As in humans, the number of macrophages was increased in mice.

Similarly, the older animals had less strength than younger specimens, and their motor end plates - the synapses between nerves and muscle fibers - were also less intact.

Successful therapy in animal experiments

In a further step, Martini and his team examined whether macrophages could actually be the cause of these changes.

To do this, they gave mice at an advanced age of 18 months a special substance in the feed that caused the macrophages to die.

"After six months of treatment, we were able to find that the degenerative age changes in the treated mice were much less pronounced," said Martini.

Accordingly, the animals had stronger muscles and their motor end plates were better preserved compared to untreated specimens.

For the research team, one thing is certain: "Our study shows not only a causal connection between inflammatory reactions in aging nerves with degenerative aging processes, but also a potential treatability."

In their view, targeted and, if possible, specific treatment of age-related, macrophage-mediated inflammatory reactions can lead to an improvement in the structure and function of the nerves - and associated with this - to improved mobility and a higher quality of life.

Important for infections and diabetes

However, the interpretation of the knowledge gained now allows further conclusions to be drawn: Because inflammation reactions also occur in the body in the case of infections or chronic diseases that frequently occur in old age, such as diabetes mellitus, these pose an additional risk for aging nerves.

The researchers therefore hope that their findings will help initiate the research and development of active ingredients that specifically target macrophages.

In further experiments, Martini and his team want to investigate how there is an age-related inflammatory reaction in the nerve.

They want to find out which cells in the nerve are responsible for the increased number of macrophages and whether there are other approaches to treating the degenerative changes besides drug therapy - for example, special physiotherapy training programs, as is known from other inflammatory diseases. (ad)

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Video: Muscle StrengthA Medical Perspective, with Tips to Get and Stay Stronger. (August 2020).