title: Plasma apolipoprotein E and Alzheimer disease risk: the AIBL study of aging.
abstract: OBJECTIVE
  There is mounting evidence for the contribution of apoE to the pathophysiology of Alzheimer disease (AD). Studies also indicate that plasma apoE levels may reflect disease status, suggesting that apoE is a potential AD biomarker. However, while some studies of apoE levels in plasma have presented correlations with AD pathology, others have not. Thus, there is a lack of consensus as to the suitability of plasma apoE as an AD biomarker. The major objective of this cross-sectional study was to investigate total plasma apoE as well as levels of the apoE4 form in a large, highly characterized cohort which included both healthy controls and participants with early-stage AD.
  
  
  METHODS
  Total apoE and apoE4 were measured in 1,079 individuals drawn from the highly characterized Australian Imaging, Biomarkers and Lifestyle (AIBL) study. Total and isoform-specific plasma apoE levels were then compared with cerebral Aβ load, as assessed by PET using Pittsburgh compound B (PiB).
  
  
  RESULTS
  Total apoE and apoE4 levels were found to be significantly lower in patients with AD in the entire cohort, and decrease with Aβ load in the PiB-PET subset. ApoE levels were significantly lower among ε4 homozygous individuals. In APOE ε3/ε4 heterozygote carriers, apoE4 levels decrease, indicating that apoE3 levels increase with disease.
  
  
  CONCLUSIONS
  Analysis of cross-sectional data from the AIBL study indicates that plasma apoE levels are altered in AD and correlate with AD pathology level. The significance of these findings will be determined in the AIBL longitudinal study of aging.
authors.affiliation: Centre of Excellence for Alzheimer’s Disease Research & Care, School of Exercise Biomedical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.
authors.forename: V B
authors.initials: VB
authors.lastname: Gupta
authors.forename: S M
authors.initials: SM
authors.lastname: Laws
authors.forename: V L
authors.initials: VL
authors.lastname: Villemagne
authors.forename: D
authors.initials: D
authors.lastname: Ames
authors.forename: A I
authors.initials: AI
authors.lastname: Bush
authors.forename: K A
authors.initials: KA
authors.lastname: Ellis
authors.forename: J K
authors.initials: JK
authors.lastname: Lui
authors.forename: C
authors.initials: C
authors.lastname: Masters
authors.forename: C C
authors.initials: CC
authors.lastname: Rowe
authors.forename: C
authors.initials: C
authors.lastname: Szoeke
authors.forename: K
authors.initials: K
authors.lastname: Taddei
authors.forename: R N
authors.initials: RN
authors.lastname: Martins
mesh_terms: D000368:Aged; D000375:Aging / Q000097:blood / Q000378:metabolism* / Q000523:psychology; D000544:Alzheimer Disease / Q000097:blood / Q000150:complications / Q000175:diagnosis* / Q000000981:diagnostic imaging; D016229:Amyloid beta-Peptides / Q000378:metabolism; D000814:Aniline Compounds; D053327:Apolipoprotein E4 / Q000097:blood*; D001057:Apolipoproteins E / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D002250:Carbon Radioisotopes; D003072:Cognition Disorders / Q000097:blood / Q000150:complications / Q000175:diagnosis* / Q000000981:diagnostic imaging; D003430:Cross-Sectional Studies; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D049268:Positron-Emission Tomography / Q000379:methods*; D012307:Risk Factors; D013844:Thiazoles
chemical_list: C475519:2-(4'-(methylamino)phenyl)-6-hydroxybenzothiazole; D016229:Amyloid beta-Peptides; D000814:Aniline Compounds; D053327:Apolipoprotein E4; D001057:Apolipoproteins E; D015415:Biomarkers; D002250:Carbon Radioisotopes; D013844:Thiazoles