2024-11-12 23:07:00
Sport is good for the brain, wise men have supported it since time immemorial (the motto ‘mens sana in corpore sano’ teaches) and new evidence comes from science to support the mental benefits of an active lifestyle and a possible ‘therapeutic’ outcome. One study demonstrated these benefits at the individual neuron level. A team of researchers and engineers from MIT (Massachusetts Institute of Technology) conducted the experiments. What emerged was that when muscles train, they help neurons grow. As? Experts have observed that when muscles contract during exercise, they release a ‘soup’ of biochemical signals called myokines. In the presence of these signals generated by the muscles, neurons grow 4 times more than those not exposed to myokines. These experiments at the cellular level suggest that exercise can have a significant biochemical effect on nerve growth.
Muscles, neurons and myokines
But not only that: the researchers also discovered that neurons respond to the biochemical signals of exercise, but also to its physical impacts. The team observed that when neurons are repeatedly pulled back and forth – similar to how muscles contract and expand during exercise – they grow as much as they do when they are exposed to a muscle’s myokines. While previous studies have indicated a potential biochemical link between muscle activity and nerve growth, this work is the first to demonstrate that physical effects may be equally important, the researchers say. The results of the experiments conducted, which will be published in the journal ‘Advanced Healthcare Materials’, shed light on the connection between muscles and nerves during exercise and could guide exercise-related therapies to repair damaged and deteriorated nerves.
“Now that we know this cross-communication exists between muscle and nerve, it may be useful for treating problems such as nerve injury, where communication between nerve and muscle is disrupted,” highlights study lead author Ritu Raman, associate professor of engineering mechanics at MIT. “Perhaps if we stimulate the muscle, we could encourage the nerve to heal and restore mobility in those who have lost it due to traumatic injury or neurodegenerative disease.”
In 2023, Raman and colleagues reported that they were able to restore mobility in mice that had suffered a traumatic muscle injury by first implanting muscle tissue at the site of the injury, and then exercising the new tissue by repeatedly stimulating it with light. Over time, they found that the trained graft helped the mice regain motor function, reaching activity levels comparable to those of healthy mice. When the researchers analyzed the graft itself, it was found that regular exercise stimulated the grafted muscle to produce certain biochemical signals that are known to promote the growth of nerves and blood vessels. “We always think that nerves control muscles, but we never think that muscles respond to nerves,” Raman reflects. “So, we started thinking that stimulating muscles encouraged nerve growth.”
The biochemical ’soup’
In the new study, the team set out to determine whether exercising muscles has a direct effect on just that, the way nerves grow, by focusing solely on muscle and nerve tissue. The researchers grew mouse muscle cells into long fibers that fused to form a small sheet of mature muscle tissue about the size of a quarter. They then genetically modified the muscle to contract in response to light, to mimic the act of exercise. Raman had previously developed a gel mat on which to grow and exercise muscle tissue. The team then collected samples of the surrounding solution in which the muscle tissue had been trained, thinking it must contain myokines, including growth factors, RNA and a mix of other proteins. In other words, “a biochemical soup of things that muscles secrete, some of which might be good for nerves“, says Raman. “Muscles practically always secrete myokines, but when you train them they produce more.”
The team transferred the myokine solution into a separate capsule containing motor neurons, nerves in the spinal cord that control muscles involved in voluntary movement. As with muscle tissue, the neurons were grown on a similar gel mat. After the neurons were exposed to the myokine mixture, the team observed that they began to grow rapidly, 4 times faster than neurons that did not receive the biochemical solution. “They grow much further and faster, and the effect is pretty immediate,” Raman notes. From the genetic analysis “we saw that many of the genes upregulated in exercise-stimulated neurons were not only related to the growth of the neurons, but also to their maturation, how well they communicate with muscles and other nerves, and how mature the axons are. Exercise therefore appears to have an impact not only on the growth of neurons, but also on how mature and well functioning they are.”
This happens on a biochemical level. But the physical impact of exercise on nerves? “Neurons are physically attached to muscles, so they stretch and move with the muscle,” Raman says. “We wanted to see, even in the absence of biochemical signals from the muscle, whether we could stretch the neurons back and forth, mimicking the mechanical forces (of exercise), and whether this could also impact growth.” So the researchers grew a different set of motor neurons on a gel mat embedded with tiny magnets. With an external magnet they made the mat (and the neurons) move back and forth. In this way, they ‘exercised’ the neurons for 30 minutes a day. Surprisingly, they found that this mechanical exercise stimulated the neurons to grow as much as the myokines. “This is a good sign, because it tells us that both the biochemical and physical effects of exercise are equally important,” concludes Raman. Next challenge? Understand how targeted muscle stimulation can be used to grow and heal damaged nerves and restore mobility in people suffering from a neurodegenerative disease such as ALS. “This is just our first step towards understanding and controlling exercise as medicine,” says the scientist.
Interview: Unpacking the Connection Between Muscles and Nerves in Exercise
Editor (Time.news): Welcome to Time.news, where we dive into the fascinating intersection of science and our daily lives. Today, we’re speaking with Dr. Ritu Raman, an associate professor of engineering mechanics at MIT and lead author of a groundbreaking study that explores how exercise impacts not just our muscles, but our neurons too. Dr. Raman, thank you for joining us!
Dr. Ritu Raman: Thank you for having me. I’m excited to discuss this research and its implications!
Editor: Let’s start with the big picture. Your study revealed that exercising not only benefits muscles but also has significant effects on neuronal growth. How did you first come to investigate this connection?
Dr. Raman: Traditionally, we viewed the relationship as one-directional—nerves controlling muscles. But in our research, we started to appreciate that muscles might also have a say in nerve growth and repair. It led us to think: if we can stimulate muscle activity, could it encourage nerve regeneration?
Editor: Fascinating! So, you’re suggesting that the biochemical signals released by muscles during exercise—these so-called myokines—play a crucial role in neuronal health. How exactly do these myokines influence nerve growth?
Dr. Raman: Yes, myokines are essentially a ”soup” of biochemical signals released during muscle contraction. When we stimulated muscle tissue in our experiments, we found that the surrounding environment became rich in these signals, prompting neurons to grow four times faster than those not exposed to them. This shows that exercise creates a supportive biochemical environment for nerves.
Editor: And this isn’t just theoretical. You’ve shown in your previous work that stimulating muscles can actually restore mobility in injured mice. Can you tell us more about that groundbreaking finding?
Dr. Raman: In that study, we implanted muscle tissue at the site of an injury and then exercised the new tissue using light stimulation. Over time, we observed that this not only restored motor function but also stimulated nerve and blood vessel growth in the grafted muscle. It was a remarkable demonstration of the muscle-neuron relationship.
Editor: That sounds revolutionary! What implications do you see this research having for therapy, particularly for conditions like neurodegenerative diseases or traumatic nerve injuries?
Dr. Raman: I believe we could develop innovative therapies that harness this muscle-neuron communication. For instance, patients with nerve injuries often struggle with recovery because the connection between nerve and muscle is disrupted. By stimulating the muscle, we might provide the necessary biochemical cues for nerve repair, potentially restoring mobility and function.
Editor: This certainly reshapes our understanding of rehabilitation strategies. Moving forward, what do you hope to explore further in your research?
Dr. Raman: I want to delve deeper into the specific myokines involved and their mechanisms. Additionally, studying how different types of exercise affect nerve growth could guide tailored therapeutic approaches. Understanding these nuances will help us exploit this muscle-neuron communication more effectively.
Editor: It’s clear that your research opens a whole new frontier in both sports science and rehabilitation. Before we wrap up, what would you say to our readers about the importance of staying active based on your findings?
Dr. Raman: Exercise has long been known to have physical benefits, but our research underscores its mental and neurological advantages too. Staying active supports not only your body but also your brain. It’s a simple yet powerful way to enhance overall health and well-being.
Editor: Thank you, Dr. Raman, for sharing your insights with us today. Your work is genuinely inspiring, and we look forward to seeing future advancements in this exciting field.
Dr. Raman: Thank you! I appreciate the opportunity to share this research with a wider audience, and I’m eager to see how this knowledge will impact health and recovery.
Editor: This has been enlightening. For our readers, remember that each workout is more than just a physical endeavor—it’s a step towards better brain health too. Until next time, stay active and curious!