Healthcare (Commonwealth Union) – When we exercise, our muscles release components that help our brain work better. Scientists at the University of Illinois Urbana-Champaign found out that the nerves that make our muscles move also make them release more of this brain-boosting components.
Chemical and biomolecular engineering professor Hyunjoon Kong, who is the lead of the study published in the Proceedings of the National Academy of Sciences indicated that the molecules that muscles let out go into our blood and then to our brain. This creates a kind of conversation between the muscles and the brain. But muscles have a lot of nerves in them. This resulted in the scientists wanting to know how these nerves affect what the muscles do and how they talk to the brain.
Professor Kong explained that as we get older, we lose some of these nerves in our muscles. Some people lose them because of sickness or injury. So, it’s important to understand how these nerves work and how they affect the brain, especially for older folks or people with muscle or nerve problems.
Recent investigations into exercise have revealed a fascinating aspect: muscles not only engage in physical activity but also play a role in hormonal secretion and the transmission of molecular signals via extracellular vesicles. These vesicles, akin to tiny parcels ferrying molecules between cells, contain fragments of RNA that bolster connectivity, signaling, and communication among brain cells. Despite the considerable attention given to muscle-derived factors, the function of the nerves that activate these muscles remains relatively obscure, notes Kai-Yu Huang, the primary author of the study and a graduate student.
Seeking to illuminate this aspect, the researchers embarked on a comparative study of two muscle tissue models—one innervated by neurons and the other not. Their investigation revealed that innervated muscles exhibited heightened production of molecules conducive to brain neuron activity and muscle development regulation, in contrast to their non-innervated counterparts.
Further delving into the intricacies, the researchers subjected the nerves to glutamate, a neurotransmitter. Remarkably, they observed enhanced expression of a crucial gene responsible for secretion regulation in the innervated muscle. This translated into elevated levels of irisin, a hormone associated with the beneficial outcomes of exercise, and an increased release of extracellular vesicles compared to plain muscle tissue.
“We analyzed the cargo carried in the vesicles, and we found that there was a greater diversity of microRNA associated with impact on neurodevelopment,” explained Huang. “These findings highlight the importance of neuron innervation. As we get older, we lose nerve supply to muscle, and our muscles start to break down and lose function. And somehow, this can further result in organ dysfunction. So understanding how to regulate or maintain muscle’s secreting behavior is very important.”
The researchers intend to delve deeper into the mechanisms occurring at the junction where neurons interface with muscle cells. Their aim is to discern how nerve impulses activate muscle stimulation and ascertain whether they impact the production or simply the release of brain-boosting factors. This distinction is vital for potential treatments aimed at individuals who have experienced nerve or muscle loss. Additionally, they aspire to investigate the utility of their tissue model as a platform for efficiently generating these factors. Ultimately, their goal is to achieve a comprehensive understanding of the brain-nerve-muscle loop and develop strategies for its maintenance.
“It’s our individual organs talking to each other: The brain tells the nerves to stimulate the muscle, and the muscle releases back molecules beneficial for brain function,” explained Kong. ”It underscores the importance of exercise. Exercise creates a more robust interface between motor neurons and muscle, and now we know the nerves sending the signal into the muscle releases the molecules and extracellular vesicles that are beneficial to the brain. So we could look at the benefits of exercise focused on fostering that connection more than simply increasing the volume or strength of the muscle.”
This research was backed by the National Science Foundation, the National Institutes of Health, the Alzheimer’s Disease Association, and the Chan Zuckerberg Biohub Chicago. Among the Illinois faculty who contributed to this study are Professor Mattia Gazzola from the Department of Materials Science and Engineering, Professor Martha Gillette from the Department of Cell and Developmental Biology, the late Professor Gabriel Popescu from the Department of Electrical and Computer Engineering (his work was published posthumously), Professor Hee Jung Chung from the Department of Molecular and Integrative Physiology, Professor Rashid Bashir from the Department of Bioengineering and the Dean of The Grainger College of Engineering, Professor Jonathan Sweedler from the Department of Chemistry, and Professor Qian Chen from the Department of Materials Science and Engineering. Additionally, Professor Sung Gap Im from the Korea Advanced Institute of Science and Technology also contributed as a co-author.
