We’ve all heard of the runner’s high as that addictive “second wind” that hits exercisers whose brains start to release brain-made opioids. But it seems there are other ways exercise can change the chemistry of your brain. A new study out this week has found that muscles may be producing chemicals that can play a direct role in how well the brain clears out old chemicals and, as a result, how likely you are to develop depression.
The researchers initially set out to see if muscles were producing a chemical that was influencing the brain. Prior research had shown that muscles that have undergone exercise produce an enzyme called PGC-1α1 that is especially important in endurance exercise. Mice that are genetically engineered to have a lot of this enzyme show endurance abilities when tested with exercise without prior training. Curious as to how this enzyme might affect depression, the researchers took some of these enzyme-rich mice along with some of their normal counterparts and exposed them to prolonged stress. The regimen would wear on most people. Mice were exposed to multiple stressful events a day at unpredictable times for five weeks. The researchers then tested for depression by putting the mice in a pool of water they couldn’t escape from. Giving up faster has been found to indicate that a mouse is more likely to be depressed. They found that mice with high levels of the PGC-1α1 enzyme were less likely to stop swimming earlier. On further investigation, the researchers found that these mice were also high in an enzyme called KAT. This enzyme converts a byproduct of the amino acid tryptophan, which can normally enter the brain, into one that can’t enter the brain. This chemical is normally present in high levels during stress.
The researchers think that when this chemical enters the brain at times of stress, it may be inducing depression or making it easier for a person to become depressed. It may be that the muscles of people who exercise regularly are producing more KAT, which means they can convert this potentially harmful chemical into a form that never reaches the brain. As a result, they’re less prone to depression. While more studies are clearly needed, the findings could signify a completely new cause of depression, which could be targeted with drugs that may help those struggling with the disease. It also indicates that there are many good reasons to get up and get active when you’re starting to feel down.