Proteome Analysis in Plasma and Brain Reveals a Novel Plasma Biomarker Linked to Antemortem Cognitive Impairment and Postmortem Neuropathological Traits for Alzheimer Disease

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AbstractBackgroundIdentification of blood‐based biomarkers that are indicative of Alzheimer’s disease (AD) pathology may help with early detection.MethodsWe generated proteome data for ∼7,000 proteins in both antemortem plasma and postmortem brain tissue from 103 participants of the Boston University Alzheimer’s Disease Research Center. All participants completed comprehensive neuropsychological evaluations and dementia severity was measured by global cognitive dementia rating (CDR) scores. A pathological AD diagnosis was established using NIA Reagan criteria. We conducted association tests with dementia (i.e., CDR ≥1 for dementia, CDR <1 for control) and autopsy‐confirmed AD status as binary outcomes. Plasma proteins significantly associated with clinical or pathological AD (P<0.05) were tested for association with quantitative cognitive tests and AD‐related neuropathological traits in which outcomes were rank‐transformed after adjusting for sex and either age at last antemortem exam or death.ResultsOf the 103 brain donors, 43 were diagnosed with dementia and 55 had autopsy‐confirmed AD. Five proteins (ACES, AURKB, CBARP, G45IP, and MMP‐8) measured in plasma were significantly associated with both pathological AD and dementia, while 252 plasma proteins were associated with either diagnosis (P<0.05). MMP‐8 was the only protein that was significantly associated in both plasma and brain with autopsy‐confirmed AD (Pplasma = 0.005, Pbrain = 0.001) and dementia (Pplasma = 0.01, Pbrain = 9×10−5). ACES and AURKB levels in plasma and brain were significantly associated with dementia (P<0.05). Levels of these. Increased MMP‐8 level in plasma was associated with decreased animals (P = 0.03) and scores (P = 0.04), which both assess verbal fluency. Dementia and pathologically confirmed AD were associated with lower AURKB and elevated ACES levels in plasma. Decreased plasma ACES level was associated with executive function (TrailsB: P = 0.01) and language (Boston Naming Test: P = 0.02) impairment, and the reduced plasma AURKB level was associated with memory impairment (Logical Memory Immediate Recall score: P = 0.03).ConclusionMMP‐8, a neutrophil collagenase and member of the matrix metalloproteinase family, is a potential blood‐based biomarker for dementia and underlying AD pathology and is associated predominantly with impaired verbal fluency.