ApoE associated with lipid has a reduced capacity to inhibit beta-amyloid fibril formation.

Apolipoprotein E (apoE) and the beta-amyloid peptide are both found in the senile plaques associated with Alzheimer's disease. Several studies have recently determined that apoE can prevent beta-amyloid fibril (Abetaf) formation in vitro. In vivo, apoE is normally associated with a lipid source. We show that both recombinant and purified plasma apoE inhibit Abetaf formation in a dose-dependent manner. The three major apoE isoforms were equipotent at inhibiting Abetaf formation. ApoE associated with either cholesterol-containing liposomes or very low density lipoproteins displayed less potent inhibition of Abetaf formation than their unlipidated counterparts. These results indicate that the presence of associated lipids reduce the ability of apoE to inhibit the formation of Abetaf in vitro.