Researchers investigated the cellular mechanisms behind improved cognition through exercise. They discovered that the contraction of muscle cells releases chemical signals that increase the growth and firing of neurons. They also found that support cells called astrocytes prevent neurons exposed to chemical signals from muscle cells from emitting excessive electrical signals.

Physical exercise is essential for maintaining physical and mental health. Studies show that it has a positive effect on health, even if practiced later in life. Some suggest that exercise improves cognition by inducing long-term changes in the hippocampus, such as increased volume and rate of neuronal formation. However, how exercise changes the hippocampus remains unknown. Better understanding how physical exercise increases the size and function of the hippocampus could help researchers develop treatments for cognitive disorders such as dementia.

Recently, researchers conducted a series of in vitro experiments, in cell cultures, to understand how physical exercise modifies the cells of the hippocampus. They found that chemical signals from muscle cell contraction caused hippocampal cells to grow and emit more electrical signals. They also discovered that supporting cells called astrocytes regulate the growth and activity of neurons for optimal brain function. The implications support findings from other studies that exercise, including muscle-strengthening exercises such as resistance training, can positively impact brain function.
The study was published in the journal Neuroscience.

How muscles can “talk” to the brain

For the study, the researchers isolated small samples of mouse muscle precursor cells and cultured them in Petri dishes. Once mature, they began to contract and release chemical signals into the cell culture. The team then added the chemicals containing the mature muscle cell culture to another dish containing hippocampal neurons and astrocytes. They used immunofluorescence and calcium imaging to track cell growth, as well as multi-electrode arrays to record neuronal activity.

In the end, they found that exposure to chemical signals from muscle cells increased the amounts of neurons and astrocytes in the hippocampus by 1.4 and 4.4 times. The addition of muscle cell cultures also accelerated the creation of mature neuronal networks in the hippocampus, ie cells that send signals in a synchronized fashion. The researchers then sought to explore the influence of astrocytes on mixing. To do this, they observed the effects of removing astrocytes from cell cultures containing hippocampal cells and mature muscle cells.

They then found that the neurons emitted even more electrical signals, suggesting that astrocytes may help moderate and coordinate activation patterns between neurons. Further testing allowed the researchers to find that the muscle contractions were necessary for the changes observed in the hippocampal cultures. When muscle cells are prevented from contracting, hippocampal cells no longer exhibit the same levels of neuronal excitation, although synchronous excitation is not affected. The researchers noted that this means that muscle contractions – or exercise – release factors that stationary cells do not release. They conclude that their findings offer new insights into how exercise can support hippocampal function.

Exercise and dementia risk

This hypothesis has yet to be tested in large clinical trials and further research should also focus on the underlying molecular mechanisms.
Meanwhile, previous research shows that exercise reduces the risk of dementia by:

by increasing blood flow to the brain
by reducing inflammation
by reducing stress
improving sleep
helping to maintain a healthy body weight.

Regular aerobic exercise for 20-30 minutes is a good thing: Regular aerobic exercise for 20-30 minutes a day, which can be done by walking, brisk walking, swimming or using a bicycle apartment. Aim for a heart rate of 70% of your maximum heart rate. To estimate your maximum heart rate for age, subtract your age from 220. This practice has been shown to reduce dementia by 30-35%.

Results that still need to be confirmed in humans This is an in vitro study on rodents, using cell cultures. Further studies are needed to see if these results are applicable to humans.

What could be the future applications?

The results of this study provide further evidence of the importance of physical exercise, at any time of life, in promoting hippocampal plasticity and combating hippocampal atrophy, which is a hallmark of Alzheimer’s disease. In the future, studies like this could play a vital role in helping us optimize exercise regimens to support cognitive health. Moreover, these results could also contribute to the development of new treatments for cognitive disorders.

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