A new study published in Cell Metabolism has found that running releases a protein that is associated with improved memory in mice in laboratory conditions. This protein, called cathepsin B (CTSB), was known to help sore muscles recover and is secreted by muscle during exercise. The researchers found that adding CTSB to neurons in petri dishes led to brain cell production in mice. Furthermore, they showed a positive correlation between running and increased levels of the CTSB protein in mouse, monkey, and human subjects.

The researchers found increased levels of CTSB in the bloodstream of humans, along with mice and monkeys, who ran regularly. CTSB plasma levels in the exercise group differed significantly from the control group after 4 months of treadmill exercise. People and mice also showed improved memory function in tests like complex recall tasks. The research team also bred mice who were not able to naturally produce CTSB. These mice then showed no increase in learning or skill development after running. Interestingly, the researchers note that high levels of CTSB are present in some cancers, and play a role in cancer cell migration. In the future, senior author Henriette van Praag and her team hope to figure out how the CTSB protein crosses the blood-brain barrier and to better understand its mechanisms. “Overall, the message is that a consistently healthy lifestyle pays off,” van Praag says.