Researchers at Touro University Nevada have discovered that tiny particles in the blood, called extracellular vesicles (EVs), are a major player in how a group of hormones are shuttled through the body. Physical exercise can stimulate this process. The findings, published in the journal Proceedings of the National Academy of Sciences (PNAS), open the door to deeper understanding of hormone circulation and access to the brain, how exercise may trigger changes in energy balance, mental health, and immune function, and circulation of certain drugs.
Blood and other body fluids are teeming with EVs—tiny particles that exist outside of cells. EVs transmit signals from cell-to-cell within tissues and long distance across organ systems by delivering biological cargo such as proteins, lipids, and nucleic acids into cells. They also remove cell waste.
Scientists have known that EVs play key roles, from the immune response to cancer progression, but much less is known about how they might interact with hormones.
The researchers focused on a hormone precursor called proopiomelanocortin (POMC), which transforms into a range of hormones including endorphins (responsible for the runner's high) and adrenocorticotropic hormone (ACTH), which manages the body's stress response. Because exercise has been previously associated with these hormones, the researchers used exercise to provoke changes to shed light on interactions between POMC and EVs.
The study found that vigorous exercise causes four times more POMC to hitch a ride on the EVs.
"This study doesn't just show an 'exercise effect' but it reveals a new biological mechanism where stress from exercise makes EVs temporarily act as hormone transport shuttles in the bloodstream," explains the study's first author Mark Santos, Ph.D., assistant professor at Touro.
The study also found that in the lab, EV-bound POMC can cross human blood vessel barriers, including the blood-brain barrier, more efficiently than POMC alone.
Since POMC must be processed into so-called "mature" hormones to initiate a response in the notoriously difficult-to-access brain, more work is required to understand how the exercise-induced rise in POMC affects the brain.
"The observation that EVs can carry POMC has so many potential directions, says Aurelio Lorico, MD, PhD, professor of pathology at Touro and co-senior author on the study together with Cheryl Hightower. It may have wide-ranging implications, for pain management, metabolism and obesity, inflammation, and the stress response," he says.
