ALDH2 and major depressive disorder: However, it has been demonstrated that the administration of Alda-1, an ALDH2 activator, may improve depressive symptoms in animal models of depression by lowering TNF-α and increasing mRNA levels of peroxisome proliferator-activated receptor-gamma coactivator, PGC-1α, a regulator of mitochondrial biogenesis in the hippocampus and frontal cortex of animals [91].