New research provides insight into how exercise strengthens the brain’s connections

A new study sheds light on how exercise improves brain function by examining the neural component of muscle-brain communication. Study, published in Bulletin of the National Academy of Sciencesreveals that muscles release molecules that support brain cell communication and development, and this release is driven in part by signals from nerves that tell muscles to move. These findings help clarify the complex relationship between exercise, muscle function and brain health.

Previous research has shown that when muscles work during exercise, they release molecules that travel into the bloodstream and positively affect brain cells. These molecules, such as hormones and small vesicles containing RNA, help brain cells to form strong bonds and communicate effectively.

However, the part of the nerves that make the muscles move in this way was not well understood. With age, or due to injury and illness, people tend to lose their nerve connections to their muscles. This reduction in nerve function can lead to muscle breakdown and contribute to major dysfunction of the body’s organs, including the brain.

The researchers aimed to investigate how nerve signals influence the release of molecules that support brain function. They hoped to better understand the mechanisms of this muscle-brain communication and to know ways to maintain or improve this relationship, especially in the elderly or those with neuromuscular diseases. If successful, their findings could provide the basis for developing therapies that target muscle-brain interactions, which could help people maintain cognitive function even when they lose muscle and nerve tissue.

To examine the role of nerve signals in muscle-brain communication, the researchers created two different types of muscle cells: one that included nerve cells, and one that did not. Go for it. This enabled them to compare the two and determine how the presence of nerves affects the muscle’s ability to release brain-boosting molecules.

The muscles were placed in a laboratory dish, where another group of cells received nerve cells, allowing the muscles and nerve cells to form connections similar to what happens in the body. These nerve connections are known as neuromuscular junctions. The second group of muscle cells was left without nerve cells. After creating these two groups, the researchers stimulated the muscles associated with nerves using glutamate, a neurotransmitter that carries signals in the brain and nervous system, to mimic the type of muscle stimulation that can be found during exercise.

The researchers then measured the number and types of molecules released by the muscles into the surrounding fluid. They looked specifically at two types of molecules: hormones, such as irisin, which are known to have beneficial effects on the brain, and extracellular vesicles, small particles that carry RNA and other cargo. of molecules between cells.

In addition to measuring the total number of molecules, the team also analyzed the specific types of RNA found in the vesicles, as these RNA fragments can influence the development of brain cells and communication.

The study revealed several important findings. First, nerve-connected muscle cells released more brain-friendly molecules compared to non-nervous muscle. In particular, the muscles associated with the nerves produced high levels of the hormone irisin, which has been associated with positive effects of good brain exercise. Irisin has been shown to support brain function by crossing the blood-brain barrier and promoting neurogenesis, the process by which new brain cells are formed.

In addition, the muscles connected to the nerves also released many types of extracellular vesicles, which contained RNA particles related to brain development and neuron communication. These vesicles are very important because they can carry molecular signals that help brain cells to form strong bonds and communicate effectively.

When the researchers stimulated the muscles connected to the nerves with glutamate, they saw a greater increase in the release of irisin and extracellular vesicles. The RNA particles found in the vesicles were significantly different in this stimulated group, suggesting that the muscle nerve signals do not increase the amount of molecules released but also improve the the complexity of the molecular properties, making it more useful for brain activity.

These findings highlight the important role that nerve signals play in promoting muscle-brain communication. When muscles lose their nerve connections due to age or injury, their ability to release these brain-supporting molecules decreases, which can contribute to cognitive decline and other related issues. and the brain.

Although this study provided new insight into the role of nerves in muscle-brain communication, it had some limitations. First, the experiments were carried out using muscle tissues grown in the laboratory, which, although they help to isolate certain factors, do not fully reproduce the complex environment of an organism. Future studies will need to examine whether these findings hold true in live animals and humans.

As they continue, the researchers plan to investigate the proper communication mechanisms between nerves and muscle cells. They hope to find out whether nerve impulses directly affect the production of brain neurotransmitters or mainly regulate their release. This knowledge can help inform the development of targeted therapies for people with neuromuscular diseases or age-related muscle loss.

The team also aims to use their laboratory muscle models as a platform to produce molecules that are beneficial to the brain. By simulating exercise at the lab level, they hope to better understand how to improve the release of these molecules, which may pave the way for new treatments that mimic the benefits of exercise for people who don’t. unable to exercise due to injury or illness. .

The study, “Neuronal innervation regulates the secretion of neurotrophic myokines and exosomes from skeletal muscle,” was written by Kai-Yu Huang, Gaurav Upadhyay, Yujin Ahn, Masayoshoi Sakakura, Gelson J. Pagan-Diaz, Younghak Cho, Amanda C. Weiss, Chen Huang, Jennifer W. Mitchell, Jiahui Li, Yanqi Tan, Yu-Heng Deng, Austin Ellis-Mohr, Zhi Dou, Xiaotain Zhang, Sehong Kang, Qian Chen, Jonathan V. Sweedler, Sung Gap Im, Rashid Bashir, Hee Jung Chung, Gabriel Popescu, Martha U. Gillette, Mattia Gazzola, and Hyunjoon Kong.