PPARGC1A and depressive symptom measurement: PGC-1α exerts these effects by activating kynurenine acetyltransferases to convert kynurenine (a stress-induced metabolite able to cross the blood-brain barrier and contribute towards depression) into kynurenic acid (which is unable to cross the blood-brain barrier) and thus minimizing the manifestations of depressive symptoms in the brain [57].