Growing muscle weakness Why the power decreases in old age

Limited quality of life: When the power is lacking in old age

At thirty, you are not considered "old" for a long time, but even at this age, muscle breakdown and the associated loss of strength slowly sets in. From about 50 years, this process accelerates. Researchers have now identified a trigger for these changes.

People are getting older all over the world

The World Health Organization (WHO) has reported global rising life expectancy in the past. According to experts, it could soon exceed 90 years in Western industrialized countries. In Germany, average life expectancy had reached a new record level. But with increasing age, muscle weakness also increases. German researchers have now identified a trigger of this change.

With increasing age usually the muscle weakness increases. German researchers have now identified a trigger for this change. (Image: Peter Maszlen / fotolia.com)

Increasing muscle weakness

The increase in average life expectancy is also associated with an increase in age-related diseases affecting 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 of excruciating and agonizing pain in the extremities.

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

Causes not yet systematically investigated

Although the consequences of age-related peripheral nerve degeneration are of major importance for quality of life in old age and the national economy, their causes have not been systematically investigated.

This has now changed: In a new project, scientists at the Neurological Clinic of the Würzburg University Hospital have examined an important and possibly treatable part of age-related nerve degeneration in more detail.

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

Macrophages in the sights

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

In their samples, the scientists encountered an increased number of macrophages. Macrophages are cells that are part of the body's defense and disposal system. For example, they take up pathogens, foreign particles and aging body cells and digest and dispose of them.

They initiate inflammatory processes, help heal wounds, and cleanse the tissues. Unfortunately, they also cause damage to some diseases.

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

"We looked closely at the nerves of 24-month-old mice, which is quite old for mice," explains Martini.

It showed that the age-related changes in the peripheral nerves of the mice strongly resembled those in the nerves of humans. As in humans, the number of macrophages was also increased in the mice.

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

Successful therapy in animal experiments

In a second step, Martini and his team investigated whether macrophages were actually the trigger for these changes.

For this, they gave mice in their advanced age of 18 months a special substance in the feed, which caused a death of the macrophages.

"After six months of treatment, we found that degenerative age changes were much less pronounced in the treated mice," says Martini.

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

For the research team, it is clear: "Our study shows not only a causal relationship of inflammatory reactions in aging nerves with degenerative aging processes, but also a potential therapeutics."

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

Significant for infections and diabetes

However, the interpretation of the findings now allows even more in-depth conclusions: Because inflammatory reactions often occur in infections or old age, such as diabetes mellitus in the body, they also pose an additional risk for aging nerves.

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

Martini and his team want to investigate in further experiments, as it comes to the age-related inflammatory response in the nerve.

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