Exercise Improves Memory by Promoting Nerve Cell Growth

• A healthy lifestyle may be the key to better memory and brain health, according to a recent study.
• Muscles release a protein, cathepsin B in response to aerobic exercise.
• Cathepsin B crosses over to the brain and stimulates growth in the area of the brain responsible for memory.

Scientists have long believed and emphasized on the benefits of regular aerobic exercise for memory improvement. It has been believed that there exists a strong association between bodily movements and cognition but the mechanism was not clear. A recent study published the journal Cell Metabolism provides evidence that a protein released by the muscles while exercising may be the reason why exercise boosts memory and learning.

The Three-step Study Links Cathepsin B and Memory

This study was conducted at the National Institute on Ageing in the U.S. by Professor Emrah Duzel and his team of researchers using a three-step approach. First of all, the researchers took muscle fibers in Petri dishes and stimulated them. They examined all the proteins that were released during this process and studied them for the ones with a size that could enable them to cross the blood-brain membrane. This resulted in the discovery of a protein known as cathepsin B.

In the next step, the effects of exercise on cathepsin B levels and memory were studied in mice. It was observed that the level of the protein in the blood rose in mice after running on wheels. The mice even scored better on a memory test, which involved swimming to a platform under water.

Mice were then divided into two groups - normal ones and ‘knockout’ mice, engineered in a way that rendered them unable to respond to cathepsin B. The two groups were again subjected to exercise by making them run on wheels. It was observed that both the groups of mice showed an elevated level of cathepsin B in their blood but the normal mice fared better on the memory test than before while the ‘knockout’ mice showed no improvement in memory. The normal group even demonstrated an increase in the growth of nerve cells in the hippocampus, the area of the brain which controls memory. This clearly showed that rendering the ‘knockout’ mice incapable of responding to the protein left them devoid of the benefits of the same.

Scientists now wanted to observe the effects in another species and chose to conduct the same experiment with Rhesus monkeys. Even in the monkeys, blood levels of cathepsin B were found elevated after exercise.

In the third and final step of the study, researchers took to studying humans. They selected 43 university students with a sedentary lifestyle and divided them into two groups. While one group was left as such, the second group was subjected to regular exercise on treadmills for four months. At the end of four months, this group was fitter and showed elevated blood levels of cathepsin B and even fared better on a memory test involving drawing a geometric shape they were shown some time prior.

The study therefore clearly linked cathepsin B with memory improvement. The lead author Professor Duzel, however, emphasized that the association between exercise and memory was probably due to several other factors as well and cathepsin B could not be held solely responsible.

Concern Regarding Cathepsin B

Evidently, from the study, cathepsin B is a very beneficial protein but actually, it has a downside to it as well. It is reported to be produced by tumor cells. Some studies on Alzheimer’s disease report association of the protein with cell death and plaque formation while others point towards a neuroprotective effect of clearing amyloid plaques of the same. There seems to be an uncertainty regarding cathepsin B. Therefore, it still remains to be studied whether using supplements to artificially increase cathepsin B in the body would be a wise thing to do or not.

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Dr. Hanriett van Praag, another author of the study, feels that the protein may demonstrate different effects in different blood levels and under different physiological conditions.

However, the researchers of this study themselves believe in the beneficial effects of naturally enhancing their cathepsin B levels and admitted to increasing their physical activity and exercise after the study.

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“Overall, the message is that consistently healthy lifestyle pays off. People often ask us, how long do you have to exercise, how many hours? The study supports that the more substantial changes occur with the maintenance of a long-term exercise regimen”, said Dr. Praag.

The study and its findings may even have an impact on the treatment modalities of various memory-associated neurological conditions like dementia.

Dr. Olivier Piguet, of Neuroscience Research, Australia, feels that increasing the levels of cathepsin B in the brain and the resultant enhancement in brain cell growth and regeneration may result in an intervention technique against dementia in future.

References:

1. Moon et al. Running-Induced Systemic Cathepsin B Secretion Is Associated with Memory Function. Cell Metabolism, 2016
2. A Protein That Moves From Muscle To Brain May Tie Exercise To Memory - (http://www.npr.org/sections/health-shots/2016/06/23/483245084/a-protein-that-moves-from-muscle-to-brain-may-tie-exercise-to-memory)

Source-Medindia