Our body tissues crosstalk during exercise.

Gretchen Reynolds points to fascinating work showing that exercise causes cells to release tiny lipid coated hollow spheres (vesicles) containing protein molecules that carry signals between muscle cells, fat cells, and the liver cells that generate energy during exercise - regulating coordination between organs during exercise. 

Highlights

•Exosomes and small vesicles are released into circulation with exercise 

•Proteins without a signal peptide sequence circulate in vesicles during exercise 

•Exercise-liberated vesicles have a propensity to localize in the liver 

•Femoral arteriovenous difference analysis identifies 35 novel candidate myokines

Summary

Exercise stimulates the release of molecules into the circulation, supporting the concept that inter-tissue signaling proteins are important mediators of adaptations to exercise. Recognizing that many circulating proteins are packaged in extracellular vesicles (EVs), we employed quantitative proteomic techniques to characterize the exercise-induced secretion of EV-contained proteins. Following a 1-hr bout of cycling exercise in healthy humans, we observed an increase in the circulation of over 300 proteins, with a notable enrichment of several classes of proteins that compose exosomes and small vesicles. Pulse-chase and intravital imaging experiments suggested EVs liberated by exercise have a propensity to localize in the liver and can transfer their protein cargo. Moreover, by employing arteriovenous balance studies across the contracting human limb, we identified several novel candidate myokines, released into circulation independently of classical secretion. These data identify a new paradigm by which tissue crosstalk during exercise can exert systemic biological effects.