Exercise has long been known to improve both physical and mental health. Now, a team of researchers from the Beckman Institute for Advanced Science and Technology has provided evidence that exercise may also impact brain health more directly, through chemical signals released by muscle contractions that promote neuronal development.
When muscles contract during exercise, they release different compounds into the bloodstream which can travel to various parts of the body, including the brain. In this study, the experts examined how exercise could benefit a part of the brain called the hippocampus, which plays a major role in learning and memory, and thus in cognitive health. Better understanding how physical activity benefits this brain region may lead to exercise-based treatments for various conditions, including Alzheimer’s disease.
To isolate the chemicals released by contracting muscles and test their effect on hippocampal neurons, the scientists collected muscle cell samples from mice and grew them in cell cultures in the lab. When they matured, the muscles started to contract on their own, releasing chemical signals into the cell culture. Then, the researchers added this culture to another one containing hippocampal neurons and other support cells called astrocytes. By using immunofluorescent and calcium imaging to track cell growth, as well as multi-electrode arrays to record neuronal electrical activity, they investigated how exposure to the chemical signals released by contracting muscles affected the hippocampal cells.
The analysis revealed that exposure to these chemical signals led to significant growth and development of hippocampal neurons. Moreover, removing astrocytes from the cell cultures caused the neurons to fire even more electrical signals, suggesting that without the astrocytes, the neurons may grow to a point where they may become unmanageable.
“Astrocytes play a critical role in mediating the effects of exercise,” explained study lead author Ki Yun Lee, a PhD student in Mechanical Science and Engineering at the University of Illinois Urbana-Champaign. “By regulating neuronal activity and preventing hyperexcitability of neurons, astrocytes contribute to the balance necessary for optimal brain function.”
Clarifying the relationship between muscle contraction and the growth and regulation of hippocampal neurons is an important step in understanding how exercise improves brain health. “Ultimately, our research may contribute to the development of more effective exercise regimens for cognitive disorders such as Alzheimer’s disease,” Lee concluded.
The study is published in the journal Neuroscience.