Absolute and Relative Quantitation of Apolipoprotein E Isoform Levels in Human Cerebrospinal Fluid and Brain

摘要

Absolute quantitation of ApoE in human CSF and brain: 1. Older ApoE33 and ApoE34 individuals (over age 60) exhibited an age-related increase in total ApoE (Figure 3). 2. Increased ApoE4 compared to ApoE3 was observed in nearly every ApoE34 case examined. Student's t-tests showed a highly significant elevated amount of ApoE4 versus ApoE3; t(34) = 12.21, p < 0.0001 in the older cohort and t(13) = 3.517, p < 0.005 in YNCs. The increase was most pronounced in brain samples, which exhibited 30% increased ApoE4 compared to ApoE3; t(31) = 9.677, p < 0.001 (Figure 4a). 3. Total ApoE amount does not differ by genotype in young normal controls (YNC; age 20-55 years) or between ApoE3 and ApoE4 carriers in frontal cortex (Figure 4b,c). 4. Older ApoE44 individuals (who are all amyloid positive) did not demonstrate an age-related increase. Older ApoE44 subjects had 40% reduced total ApoE compared to the other genotypes in this age cohort (Figure 5). 5. Measured against the same standards as CSF, frontal cortex from ApoE33 and ApoE34 carriers contained a 50% higher concentration of ApoE than CSF from the older cohort(Figure 5). 6. Although CSF ApoE amounts (total or isoform specific) and measures of amyloid pathology (including Aβ42:Aβ40 ratio and PiB PET visualization of amyloid-β deposition) were not found to be directly correlated, an age and amyloid interaction is observed with ApoE amounts in CSF. Brain amyloidosis and Brain ApoE were not assessed as AD pathology was excluded from the analyzed brain samples. Relative quantitation of ApoE in human CSF: 1. Isoform-specific and selected common peptides demonstrated similar kinetic profiles within subjects for ApoE labeling studies (Figure 7). 2. ApoE exhibits an age-related slowing in turnover rates (Figure 8).