Apolipoprotein E Highly Correlates with AβPP- and Tau-Related Markers in Human Cerebrospinal Fluid

Abstract

We assessed cerebrospinal fluid (CSF) levels of apolipoprotein E (apoE), phospholipid transfer protein (PLTP) activity, cholesterol, secreted amyloid-β protein precursor α and β (sAβPPα, sAβPPβ), amyloid-β peptides 1–40 (Aβ₄₀) and 1–42 (Aβ₄₂), total tau and tau phosphorylated at threonine 181 (pTau) in neurologically healthy, cognitively intact adults. ApoE significantly correlated with sAβPPα (r = 0.679), sAβPPβ (r = 0.634), Aβ₄₀ (r = 0.609), total and pTau (r = 0.589 and r = 0.673, respectively, all p < 0.001), PLTP activity (r = 0.242, p = 0.002) and cholesterol (r = 0.194, p < 0.01). PLTP activity significantly correlated with sAβPPα (r = 0.292), sAβPPβ (r = 0.281), total and pTau (r = 0.265 and 0.258, respectively; all p ⩽ 0.001). Using partial correlations of CSF biomarkers with apoE, PLTP activity, age and gender, apoE remained significantly correlated with sAβPPα, sAβPPβ, Aβ₄₀, total and pTau (p < 0.001). The presence of apoE ε2 was associated with lower levels of apoE, PLTP activity and Aβ₄₂, while APOEε4 had no significant impact on any of the measured variables. Our data suggest that there is a significant physiological link between apoE and AβPP, as well as between apoE and tau in neurologically healthy, cognitively intact individuals.