ACE and Alzheimer disease: ACE-1 activity can be measured in ante-mortem CSF and is elevated in AD (24) raising the possibility that changes in CSF ACE-1 enzyme activity alongside established CSF biomarkers (Aβ/tau), or changes in vascular markers such as soluble platelet-derived growth factor receptor, will be useful to identify those patients for which early RAS-targeted intervention will be most effective.