GBA1 and Parkinson disease: Levels of glucosylceramide (GlcCer), one of the substrates for GBA and GBA2, and lactosylceramide (LacCer), sequential precursors of all more complex GSLs in the biosynthetic pathway, were quantified in substantia nigra from PD patients (n = 18) and age-matched controls (n = 20, provided by HBTRC) by NP-HPLC.