Jesse Cobell, Brigham Young University
Biology
Alzheimer’s disease (AD) is the sixth major cause of death in the U.S. However, at present, no diagnostically useful serum markers for AD have been identified. Hence, we used a novel serum proteomic approach to interrogate the low molecular weight proteome for serum biomarkers. This allowed for survey of around 5000 low MW species. To reduce ion suppression, an acetonitrile precipitation step was used to remove high abundance serum proteins. Protein-depleted sera from 58 cases and 55 controls were analyzed by cLC-ESI-QTOFMS/MS using reverse phase chromatography. Data were reviewed using Applied Biosystem’s Analyst-QS software to compile spectra. Differentially expressed peptides (cases vs. controls) were analyzed statistically using the Student’s t-test. This led to discovery of 36 candidate biomarkers. Additionally, we compared AD subjects with more severe disease (Clinical Dementia Rating (CDR) =3) with non-demented individuals (CDR=0) and found 23 biomarkers. Furthermore, on comparison of mild and moderate stage AD individuals (CDR = 0.5, 1, 2) with those with severe disease (CDR = 3), we found 24 biomarkers. Some of these biomarkers appeared more prominent in one gender. We then fragmented several of these biomarkers on an LTQ-Orbitrap XL hybrid mass spectrometer and cLC-ESI-QTOF-MS/ MS system using collision-induced dissociation to determine amino acid sequence analysis. We have identified 5 biomarkers and are in the process of identifying the remaining biomarker species. This serum proteomics approach found statistically different peptide abundances in subjects with AD. Additional biostatistical evaluations are underway to determine sensitivity and specificity of individual biomarkers and their combinations. Future studies will assess biomarkers according to disease stage and validate current biomarkers in blinded comparisons of other AD sera. This serum proteomics approach appears promising in locating and identifying clinically useful serum biomarkers of AD.