DAO and major depressive disorder: In the metabolomics analysis, glycine, serine, and threonine metabolism; alanine, aspartate, and glutamate metabolism; glyoxylate and dicarboxylate metabolism; and starch and sucrose metabolism were the most significant pathways for ASH treating MDD, and a total of 130 targets were involved with the four metabolic pathways, including DAO, MAOA, MAOB, GAA, HK1, and PYGM.