Mouse study helps explain why running improves memory

After a run, levels of the protein, called cathepsin B, increased in the blood of mice, monkeys, and humans, according to the study published this week in the U.S. journal Cell Metabolism, Xinhua reports.

"We wanted to cast a wide net," said senior author Henriette van Praag, a neuroscientist at the U.S. National Institute on Aging.

"Rather than focus on a known factor, we did a screen for proteins that could be secreted by muscle tissue and transported to the brain, and among the most interesting candidates was cathepsin B."

In the study, researchers first exposed muscle cells in a dish to compounds that mimic exercise and observed that the presence of cathepsin B production noticeably increased in the conditioned media of the cultures.

High levels of the protein were also found in the blood and muscle cells of mice that spent time daily for several weeks on their exercise wheels.

Additionally, when cathepsin B was applied to brain cells, it spurred the production of molecules related to the generation of new brain cells.

The researchers then compared memory recall in normal mice with that in mice lacking the ability to produce cathepsin B under both sedentary and running conditions.

Over the course of a week, both sets of mice were given a daily swim test in a water maze, which required them to swim to a platform hidden just below the water surface within a small pool.

The researchers explained mice usually learn where to find the platform after doing this for a few days.

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