SMPD1 and Alzheimer disease: 7B) Since aSMase [68,69], ceramidase [70] and phospholipase A2 [71–73] are implicated in secretory vesicle formation and membrane restructuring, decreased aSMase that we measured in AD may impact membrane remodeling and the generation of nano- or micro-sized particles, such as those in the NP fraction of CSF.