On top of its physical benefits, exercise has a huge range of psychological benefits — but until now it was not known how or why exercise is so beneficial. Now, a new study has uncovered how exercise protects the brain from stress-related depression.
Researchers at Sweden’s Karolinska Institutet have found that exercise causes important changes in skeletal muscles. These changes help to purge the blood of substances harmful to the brain which build up during stress.
The researchers studied mice which were bred with high levels of a particular protein which is elevated by exercise, called PGC-1a1. These mice, together with another batch of normal mice, were exposed to high levels of stress, equivalent of five really bad weeks at the office.
While the normal mice showed signs of depression, the gym mice behaved absolutely normally, as though nothing had happened.
These results reveal that well-trained muscle produces an enzyme that purges the body of harmful substances. In this context the muscle’s function is reminiscent of that of the kidney or the liver.
The mice with higher levels of the protein PGC-1a1 also had higher levels of enzymes called KAT. KAT converts the substance formed during stress (kynurenine) into an acid, which cannot pass the blood-brain barrier. Even injecting these batch of mice with kynurenine couldn’t make them depressed, as their KAT enzymes produced by their muscles quickly converted it to a more harmless substance.
This work opens up a new pharmacological principle in the treatment of depression, where attempts could be made to influence skeletal muscle function instead of targeting the brain directly.
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Source material from PSY Blog