It has been well-known that exercise protects against depression but researchers did not fully understand how. However, a new study investigates the mechanisms behind the protection exercise offers from depression. A systematic review, done last year, analyzed 35 randomized controlled trials involving 1,356 participants diagnosed with depression. It was found that exercising was beneficial for people with depression but researchers cautioned that further research was needed to be done.
In the new study, researchers from the Karolinska Institute in Sweden investigated if the protein called PGC-1a1 is responsible for the protective benefits of exercise. Researchers exposed genetically modified mice with high levels of PGC-1a1 in skeletal muscle and normal mice to a high-stress environment for 5 weeks. After the 5 weeks, the normal mice developed depression, where the genetically modified mice did not.
“Our initial research hypothesis was that trained muscle would produce a substance with beneficial effects on the brain,” says Jorge Ruas, principal investigator at the Department of Physiology and Pharmacology, Karolinska Institutet. “We actually found the opposite: well-trained muscle produces an enzyme that purges the body of harmful substances. So in this context the muscle’s function is reminiscent of that of the kidney or the liver.”
In addition, researchers found the mice with elevated levels of PGC-1a1 also had higher levels of KAT enzymes, enzymes that convert kynurenine – a substance formed during stress – into kynurenic acid. “Our study represents another piece in the puzzle, since we provide an explanation for the protective biochemical changes induced by physical exercise that prevent the brain from being damaged during stress,” said researcher Mia Lindskog.