An association of CSF apolipoprotein E glycosylation and amyloid-beta 42 in individuals who carry the APOE4 allele

Carrying the apolipoprotein E (ApoE) sigma 4 allele is associated with an increased risk of cerebral amyloidosis and late-onset Alzheimer's disease, but the degree to which apoE glycosylation affects its development is not clear. In a previous pilot study, we identified distinct total and secondary isoform-specific cerebral spinal fluid (CSF) apoE glycosylation profiles, with the E4 isoform having the lowest glycosylation percentage (E2 > E3 > E4). In this work, we extend the analysis to a larger cohort of individuals (n = 106), utilizing matched plasma and CSF samples with clinical measures of AD biomarkers. The results confirm the isoform-specific glycosylation of apoE in CSF, resulting from secondary CSF apoE glycosylation patterns. CSF apoE glycosylation percentages positively correlated with CSF A beta(42) levels (r = 0.53, p < 0.0001). These correlations were not observed for plasma apoE glycosylation. CSF total and secondary apoE glycosylation percentages also correlated with the concentration of CSF small high-density lipoprotein particles (s-HDL-P), which we have previously shown to be correlated with CSF A beta(42) levels and measures of cognitive function. Desialylation of apoE purified from CSF showed reduced A beta(42) degradation in microglia with E4 > E3 and increased binding affinity to heparin. These results indicate that apoE glycosylation has a new and important role in influencing brain A beta metabolism and can be a potential target of treatment.

Automated summary

Carrying the ApoE sigma 4 allele is associated with an increased risk of cerebral amyloidosis and late-onset Alzheimer's disease. The study found that apoE glycosylation in cerebrospinal fluid (CSF) correlates with CSF A beta(42) levels and small high-density lipoprotein particles (s-HDL-P), indicating a potential role of apoE glycosylation in influencing brain A beta metabolism.