Extracellular Vesicles Research: What Happens Inside the Body When We Exercise?

We are all familiar with the sensations inside our bodies during exercise: increased body temperature and heart rate, sweating, etc. At the molecular level, we know we are burning calories and perhaps even building muscle. Although biologists have been focusing on these processes for many years, the actual pathways that the body takes to initiate a coordinated response to exercise remain mysterious as of yet.

A study from the Garvan Institute of Medical Research in Sydney, Australia, has shed new light on the changes that occur at the cellular level when we exercise. We now know that it's all about the extracellular vesicles (EVs), the microscopic parts of cells that transport molecules from one place to another within the cell.

According to this study published in Cell Metabolism, EVs are responsible for much more than we have realized. They are likely to also be responsible for much of the body's internal communication, especially during exercise. The researchers found that EVs contain not only discarded genetic material, but also thousands of different proteins that we never knew existed, including hundreds that appear to have specific functions during exercise.

In this study, the team drew blood from the femoral arteries of 11 healthy men, who exercised on a kinetic bike for one hour, before, during and after exercise. With the new sampling technique, the researchers were able to isolate and quantify EVs and proteins in the blood, and the results they found were very surprising.

There were 300 more proteins in the EVs of the men tested during exercise compared with that before exercise or after four hours of rest, many of which have been identified as having a role in metabolism and energy regulation, but the scientists never realized that such large amounts of these proteins present in the blood during exercise.

However, knowing the presence of these proteins, researchers wanted to figure out what role they play during exercise. In the mouse study, the team placed fluorescent markers into the EVs of mice, half of which were sedentary and half of which were exercising. In the exercising mice, their EVs went directly to the liver, which is responsible for producing energy during exercise. In short, exercise loads the EVs with more proteins and transports them directly to the body's energy producers.

Martin Whitham, a biologist at the Garvan Institute for Medical Research, thought that this study shows that blood flow during exercise is very complex, and we have underestimated its complexity in the past.

Whitman and his research team also thought that this study unveiling EV functions in exercise is only the tip of the iceberg when it comes to understanding the body's internal communications during exercise, but with this new finding, they hope to unlock more mysteries about the body's biochemistry. For example, the team is performing further research, which will track the pathways of excercise-induced EVs to other organs in the body, particularly the brain. Perhaps after that, researchers will be able to better understand the mechanisms behind runner's high, which can give exercisers a mental boost when they exercise.

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