title: Isobaric Quantification of Cerebrospinal Fluid Amyloid-β Peptides in Alzheimer's Disease: C-Terminal Truncation Relates to Early Measures of Neurodegeneration.
abstract: The amyloid beta (Aβ) peptide is the main constituent of the plaques characteristic of Alzheimer's disease (AD). Measurement of Aβ1-42 in cerebrospinal fluid (CSF) is a valuable marker in AD research, where low levels indicate AD. Although the use of immunoassays measuring Aβ1-38 and Aβ1-40 in addition to Aβ1-42 has increased, quantitative assays of other Aβ peptides remain rarely explored. We recently discovered novel Aβ peptides in CSF using antibodies recognizing the Aβ mid-domain region. Here we have developed a method using both Aβ N-terminal and mid-domain antibodies for immunoprecipitation in combination with isobaric labeling and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for relative quantification of endogenous Aβ peptides in CSF. The developed method was used in a pilot study to produce Aβ peptide profiles from 38 CSF samples. Statistical comparison between CSF samples from 19 AD patients and 19 cognitively healthy controls revealed no significant differences at group level. A significant correlation was found between several larger C-terminally truncated Aβ peptides and protein biomarkers for neuronal damage, particularly prominent in the control group. Comparison of the isobaric quantification with immunoassays measuring Aβ1-38 or Aβ1-40 showed good correlation (r(2) = 0.84 and 0.85, respectively) between the two analysis methods. The developed method could be used to assess disease-modifying therapies directed at Aβ production or degradation.
authors.affiliation: Department of Neurology, Akershus University Hospital , 1478 Lørenskog, Norway.|Department of Clinical Molecular Biology (EpiGen), Division of Medicine, and ∥Department of Neurology, Faculty Division, Akershus University Hospital and University of Oslo , 1478 Lørenskog, Norway.
authors.forename: Magnus
authors.initials: M
authors.lastname: Rogeberg
authors.affiliation: Department of Neurology, Akershus University Hospital , 1478 Lørenskog, Norway.
authors.forename: Ina Selseth
authors.initials: IS
authors.lastname: Almdahl
authors.affiliation: Department of Neurology, Akershus University Hospital , 1478 Lørenskog, Norway.|Department of Clinical Molecular Biology (EpiGen), Division of Medicine, and ∥Department of Neurology, Faculty Division, Akershus University Hospital and University of Oslo , 1478 Lørenskog, Norway.
authors.forename: Marianne
authors.initials: M
authors.lastname: Wettergreen
authors.affiliation: Department of Pharmacology, University of Oslo and Oslo University Hospital , 0372 Oslo, Norway.
authors.forename: Lars N G
authors.initials: LN
authors.lastname: Nilsson
authors.affiliation: Department of Neurology, Akershus University Hospital , 1478 Lørenskog, Norway.
authors.forename: Tormod
authors.initials: T
authors.lastname: Fladby
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000134:cerebrospinal fluid* / Q000175:diagnosis / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000134:cerebrospinal fluid* / Q000737:chemistry / Q000276:immunology; D000906:Antibodies / Q000737:chemistry* / Q000276:immunology; D015415:Biomarkers / Q000134:cerebrospinal fluid; D016022:Case-Control Studies; D002853:Chromatography, Liquid; D003071:Cognition / Q000502:physiology; D005260:Female; D006801:Humans; D007118:Immunoassay; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D010446:Peptide Fragments / Q000134:cerebrospinal fluid* / Q000737:chemistry / Q000276:immunology; D010449:Peptide Mapping; D010865:Pilot Projects; D017434:Protein Structure, Tertiary; D013194:Staining and Labeling / Q000379:methods; D053719:Tandem Mass Spectrometry; D013997:Time Factors
chemical_list: D016229:Amyloid beta-Peptides; D000906:Antibodies; D015415:Biomarkers; D010446:Peptide Fragments; C078639:amyloid beta-protein (1-38); C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)
keywords: Alzheimer’s disease; amyloid beta; cerebrospinal fluid; immunoprecipitation; isobaric labeling; mass spectrometry; proteomics; quantification; tau protein