APOE4 carriers display loss of anticipatory cerebral vascular regulation over AD progression

INTRODUCTIONMaintenance of cerebral blood flow during orthostasis is impaired with aging and associated with cognitive decline, but the effect of Apolipoprotein L4-allele (APOE4) is unknown. METHODSOlder adults (n=108) (APOE4 carriers, n=47; noncarriers, n=61) diagnosed as cognitively-normal (NC), MCI, or AD participated. Middle cerebral artery blood velocity (MCAv), assessed using Transcranial Doppler ultrasound, and beat-to-beat mean arterial blood pressure (MAP) were continuously recorded during a sit-to-stand transition. Anticipatory and orthostatic-induced MCAv and MAP responses were compared between genotypes and across disease progression. RESULTSCognitively-normal APOE4 carriers showed greater anticipatory MCAv increase, greater MCAv decrease with orthostasis, and shorter latency of peripheral MAP responses to orthostasis compared to noncarriers. MCAv and MAP responses were delayed and attenuated across the APOE4 disease progression, with no differences between genotypes in MCI and AD. DISCUSSIONAPOE4 carriers and noncarriers present with distinct phenotypes of cerebral vascular dysfunction during hemodynamic orthostatic challenge. Unique cerebral and peripheral vascular compensation observed in APOE4 carriers may be lost as AD progresses.