title: Blood amyloid beta levels in healthy, mild cognitive impairment and Alzheimer's disease individuals: replication of diastolic blood pressure correlations and analysis of critical covariates.
abstract: Plasma amyloid beta (Aβ) levels are being investigated as potential biomarkers for Alzheimer's disease. In AB128 cross-sectional study, a number of medical relevant correlates of blood Aβ40 or Aβ42 were analyzed in 140 subjects (51 Alzheimer's disease patients, 53 healthy controls and 36 individuals diagnosed with mild cognitive impairment). We determined the association between multiple variables with Aβ40 and Aβ42 levels measured in three different blood compartments called i) Aβ directly accessible (DA) in the plasma, ii) Aβ recovered from the plasma matrix (RP) after diluting the plasma sample in a formulated buffer, and iii) associated with the remaining cellular pellet (CP). We confirmed that diastolic blood pressure (DBP) is consistently correlated with blood DA Aβ40 levels (r=-0.19, P=0.032). These results were consistent in the three phenotypic groups studied. Importantly, the observation resisted covariation with age, gender or creatinine levels. Observed effect size and direction of Aβ40 levels/DBP correlation are in accordance with previous reports. Of note, DA Aβ40 and the RP Aβ40 were also strongly associated with creatinine levels (r=0.599, P<<0.001) and to a lesser extent to urea, age, hematocrit, uric acid and homocysteine (p<0.001). DBP and the rest of statistical significant correlates identified should be considered as potential confounder factors in studies investigating blood Aβ levels as potential AD biomarker. Remarkably, the factors affecting Aβ levels in plasma (DA, RP) and blood cell compartments (CP) seem completely different.
authors: Alzheimer Research Center and Memory Clinic, Fundació ACE, Institut Català de Neurociències Aplicades, Barcelona, Spain.
authors: Agustín
authors: A
authors: Ruiz
authors: Pedro
authors: P
authors: Pesini
authors: Ana
authors: A
authors: Espinosa
authors: Virginia
authors: V
authors: Pérez-Grijalba
authors: Sergi
authors: S
authors: Valero
authors: Oscar
authors: O
authors: Sotolongo-Grau
authors: Montserrat
authors: M
authors: Alegret
authors: Inmaculada
authors: I
authors: Monleón
authors: Asunción
authors: A
authors: Lafuente
authors: Mar
authors: M
authors: Buendía
authors: Marta
authors: M
authors: Ibarria
authors: Susana
authors: S
authors: Ruiz
authors: Isabel
authors: I
authors: Hernández
authors: Itziar
authors: I
authors: San José
authors: Lluís
authors: L
authors: Tárraga
authors: Mercè
authors: M
authors: Boada
authors: Manuel
authors: M
authors: Sarasa
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000097:blood* / Q000503:physiopathology*; D016229:Amyloid beta-Peptides / Q000097:blood*; D000704:Analysis of Variance; D001774:Blood Chemical Analysis / Q000379:methods*; D001794:Blood Pressure; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000097:blood* / Q000503:physiopathology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood*; D012044:Regression Analysis; D015203:Reproducibility of Results
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40)