Detection Of Plasma Biomarker Candidates Of Alzheimer’s Disease And Amnestic Mild Cognitive Impairment

Objective This study is to detect candidate biomarkers in peripheral plasma of AD and its early stage of amnestic mild cognitive impairment that facilitate to early detection of AD and monitor the progression of disease.Methods In the study,the subjects of amnestic mild cognitive impairment(aMCI)and the normal controls(NC)with the age above 55 years old were selected from the elderly people enrolled in cohort study of aging in Shanghai in China.The AD patients were recruited in the geriatric clinic in Shanghai Mental Health Center from August 2015 to September 2017.A strict entry and exclusion criteria was taken to exclude confounding physical conditions to control bias.Finally 30 cases of AD,29 cases of aMCI and 21 cases of NC were included in the study.A non-targeted method of digital independent acquisition(DIA)of mass spectrometry was taken firstly to detect the protein expression between 8 cases of AD,6 cases of aMCI and 6 cases of NC,which was randomly selected in this sample.Candidate biomarkers selected from proteins differently expressed between groups with the P value<0.05 and the fold change≥1.5 which also should be related to neurological diseases by Ingenuity Pathway Analysis(IPA),and the proteins with trend of expression were consistent within three groups were also included in the following detection of quantify.Parallel reaction monitoring(PRM)of mass spectrometry was taken to accurately quantify in the rest samples and Receiver Operating Characteristic was used to differentiate samples in different groups finally.Results According to the results of DIA detection,179 differently expressed proteins between groups were obtained and among them 68 protein were found related to neurological diseases according to IPA analysis.61 proteins with consistent trend in three groups were also enrolled in the list for quantitative detection by PRM-MS.After feasibility analysis,56 candidate proteins were detected to be the potential biomarker of AD.The results of ROC analysis were:(1)to early detection of aMCI: Insulin-like growth factor-binding protein 3 can distinguish within aMCI and NC with the susceptibility 74% and specificity 93%(AUC=0.803,P=0.002<0.05).(2)to distinguish between aMCI and AD:Cholinesterase can distinguish between aMCI and AD with the susceptibility 83% and specificity 95%(AUC=0.90,P=0.000 < 0.05).Syntaxin-binding protein 5 can distinguish between aMCI and AD with the susceptibility 83% and specificity 95%(AUC=0.89,P=0.000<0.05).Fetuin-A can distinguish between aMCI and AD with the susceptibility 87% and specificity 82%(AUC=0.87,P=0.000<0.05);Complement C3 can distinguish between aMCI and AD with the susceptibility 78% and specificity 86%(AUC=0.87,P=0.000<0.05);Alpha-1-antitrypsin can distinguish between aMCI and AD with the susceptibility 83% and specificity 82%(AUC=0.86,P=0.000<0.05).(3)to distinguish between AD and non-AD : Mesothelin can distinguish between AD and non-AD with the susceptibility 95% and specificity 92%(AUC=0.96,P=0.000<0.05);Fetuin-A can distinguish between AD and non-AD with the susceptibility 82% and specificity 82%(AUC=0.87,P=0.000<0.05);Transthyretin can distinguish between AD and non-AD with the susceptibility 82% and specificity 82%(AUC=0.85,P=0.000<0.05);Alpha-1-antitrypsin can distinguish between AD and non-AD with the susceptibility 79% and specificity 82%(AUC=0.85,P=0.000 < 0.05);Complement C3 can distinguish between AD and non-AD with the susceptibility 79% and specificity 82%(AUC=0.85,P=0.000<0.05).Conclusions Insulin-like growth factor-binding protein 3 is expected to be a blood biomarker for early screening of AD.Fetuin A,Alpha-1-antitrypsin,Complement C3,Transthyretin,Mesothelin are expected to be blood biomarkers for diagnosis of AD.Fetuin A,Alpha-1-antitrypsin,Complement C3,Cholinesterase,Syntaxin-binding protein 5 can effectively distinguish between aMCI and AD,may be the potential biomarkers to monitor the progression of Alzheimer’s disease.