PPARG and major depressive disorder: PPAR-α agonist fenofibrate, PPAR-γ agonist pioglitazone, and PPAR-α/γ dual agonist 2-[4-(5-chlorobenzo [d] thiazol-2-yl) phenoxy]-2-methylpropanoic acid (MHY908) could also protect against DA neuronal loss, motor deficit, depression-like behavior, and the impairment of learning and memory caused by MPTP [59,60,61].