GPLD1 and Parkinson disease: In turn, phospholipase D plays an important role in the synthesis of PA [32]; here, icaritin affected the PA content based on the increased level of glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) in the substantia nigra of rotenone-administered rats, and had a strong affinity for GPI-PLD (Figure 5E,F, Figure S8A, Table S6), further confirming that the beneficial effect of icaritin in the rat model of PD included phospholipid regulation.