APOE and Alzheimer disease: This is consistent with the previous findings that APOE4 carriers have less full-length ApoE but more ApoE fragments in brain parenchyma and plasma than APOE2 carriers (Riddell et al., 2008; Gupta et al., 2011); with decreased ApoE levels in APOE4 carriers considered an important factor for AD onset/development (Verghese et al., 2011; Holtzman et al., 2012).