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Never heard of kynurenine? Me neither, until I read today's Phys Ed column in The New York Times: How Exercise May Protect Against Depression.
It describes a recent mouse study in the journal Cell that puts forth a new theory for the power of exercise to fight depression. You may be familiar with the longer-standing wisdom that exercise spurs the birth of new neurons in the brain, which also somehow lifts mood. But Phys Ed columnist Gretchen Reynolds writes that the key to the effect may lie in the working muscles, which then affect the brain.
She describes a fascinating experiment in specially bred mice with high levels of PGC-1alpha1, an enzyme thought to guard against depression. The scientists came to focus on kynurenine, a chemical whose levels in the blood rise after stress.
Kynurenine can pass the blood-brain barrier and, in animal studies, has been shown to cause damaging inflammation in the brain, leading, it is thought, to depression.
But in the mice with high levels of PGC-1alpha1, the kynurenine produced by stress was set upon almost immediately by another protein expressed in response to signals from the PGC-1alpha1. This protein changed the kynurenine, breaking it into its component parts, which, interestingly, could not pass the blood-brain barrier. In effect, the extra PGC-1alpha1 had called up guards that defused the threat to the animals’ brains and mood from frequent stress.
Initial studies suggest something similar may happen in humans; more research is under way.