Impaired Lipoprotein Receptor-Mediated Peripheral Binding of Plasma Amyloid-β is an Early Biomarker for Mild Cognitive Impairment Preceding Alzheimer's Disease

Article type: Research Article

Authors: Sagare, Abhay P.^a | Deane, Rashid^a | Zetterberg, Henrik^b | Wallin, Anders^b | Blennow, Kaj^b | Zlokovic, Berislav V.^{a; *}

Affiliations: [a] Center for Neurodegenerative and Vascular Brain Disorders, University of Rochester, Rochester, NY, USA | [b] Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at University of Gothenburg, Mölndal, Sweden

Correspondence: [*] Correspondence to: Berislav V. Zlokovic, M.D., Ph.D., Kornberg Medical Research Bldg., Rm. #G-9613, 601 Elmwood Avenue, Box 670, Rochester, New York 14642, USA. Tel.: +1 585 273 3132; Fax: +1 585 273 3133; E-mail: Berislav_zlokovic@urmc.rochester.edu.

Abstract: Soluble circulating low density lipoprotein receptor-related protein-1 (sLRP) provides key plasma binding activity for Alzheimer's disease (AD) amyloid-β peptide (Aβ). sLRP normally binds 70–90% of plasma Aβ preventing free Aβ access to the brain. In AD, Aβ binding to sLRP is compromised by increased levels of oxidized sLRP which does not bind Aβ. Here, we determined plasma oxidized sLRP and Aβ40/42 sLRP-bound, other proteins-bound and free plasma fractions, cerebrospinal fluid (CSF) tau/Aβ42 ratios, and mini-mental state examination (MMSE) scores in patients with mild cognitive impairment (MCI) who progressed to AD (MCI-AD, n = 14), AD (n = 14) and neurologically healthy controls (n = 14) recruited from the Göteborg MCI study. In MCI-AD patients prior to conversion to AD and AD patients, the respective increases in oxidized sLRP and free plasma Aβ40 and Aβ42 levels were 4.9 and 3.7-fold, 1.8, and 1.7-fold and 4.3 and 3.3-fold (p < 0.05, ANOVA with Tuckey post-hoc test). In MCI-AD and AD patients increases in oxidized sLRP and free plasma Aβ40 and Aβ42 correlated with increases in CSF tau/Aβ42 ratios and reductions in MMSE scores (p < 0.05, Pearson analysis). A heterogeneous group of ‘stable’ MCI patients that was followed over 2–4 years (n = 24) had normal CSF tau/Aβ42 ratios but increased oxidized sLRP levels (p < 0.05, Student's t test). Data suggests that a deficient sLRP-Aβ binding might precede and correlate later in disease with an increase in the tau/Aβ42 CSF ratio and global cognitive decline in MCI individuals converting into AD, and therefore is an early biomarker for AD-type dementia.

Keywords: Aging, Alzheimer's disease, biomarker, mild cognitive impairment, soluble low density lipoprotein receptor-related protein (sLRP)

DOI: 10.3233/JAD-2010-101248

Journal: Journal of Alzheimer's Disease, vol. 24, no. 1, pp. 25-34, 2011