Running releases protein associated with improved memory in mice

Running releases protein associated with improved memory in mice”

One month old newly born neurons in the dentate gyrus of the adult mouse hippocampus were labeled by injection of retrovirus expressing green-fluorescent-protein (GFP). The production of newly born neurons is upregulated by voluntary wheel running in mice.

The reason why treadmill training can boost memory recall remains an active area of investigation.

Now researchers at the National Institute on Ageing in the U.S. have discovered that when muscles exercise they produce a protein called cathepsin B which travels to the brain and triggers neuron growth.

The team has also shown that the levels of the protein soars when humans exercise.

"We wanted to cast a wide net".

Over the course of a week, both sets of mice were given a daily swim test in the Morris water maze, in which a mouse is placed in a small pool and must learn to swim to a platform that is hidden just below the surface of the water. 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.

After doing the task for a few days, normal mice eventually learn where to find the platform.

Mice genetically engineered to be unable to produce cathepsin B, on the other hand, didn't benefit from the daily runs. Cathepsin B was considered the most interesting.

To hunt for mucle-produced factors called myokines that might modulate brain function, Henriette van Praag of the National Institute on Aging and colleagues treated rat muscle cells in culture with the drug AICAR-"an exercise mimetic", explained van Praag, meaning it boosts the cells' metabolic activities. "We also have converging evidence from our study that cathepsin B is upregulated in blood by exercise for three species-mice, Rhesus monkeys, and humans".

H.Y. Moon et al., "Running-induced systemic cathepsin B secretion is associated with memory function", Cell Metabolism, doi:10.1016/j.cmet.2016.05.025, 2016.

"Moreover, in humans who exercise consistently for four months, better performance on complex recall tasks, such as drawing from memory, is correlated with increased cathepsin B levels". Their findings highlight a clear difference in the cognition between ordinary control mice and mice that lacked a certain protein known as cathepsin B.

Looking forward, the researchers hope to understand how cathepsin B breaks the blood-brain barrier, the mechanism by which capillaries carry blood to the brain and spinal cord while obstructing the passage of foreign substances, as well as how it activates neuronal signaling, growth, and connections.

"Overall, the message is that a consistently healthy lifestyle pays off", van Praag says. People who exercise regularly tend to have more cells in the memory part of their brain - with a better memory to boot - but exactly how long runs in the park translate to cell growth is a little murky. "The study supports that the more substantial changes occur with the maintenance of a long-term exercise regimen", she said.

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