How Exercise May Protect Against Depression

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.