Myocardial Injury Is Distinguished from Stable Angina by a Set of Candidate Plasma Biomarkers Identified Using iTRAQ/MRM-Based Approach

The lack of precise biomarkers that
identify patients at risk for
myocardial injury and stable angina delays administration of optimal
therapy. Hence, the search for noninvasive biomarkers that could accurately
stratify patients with impending heart attack, from patients with
stable coronary artery disease (CAD), is urgently needed in the clinic.
Herein, we performed comparative quantitative proteomics on whole
plasma sampled from patients with stable angina (NMI), acute myocardial
infarction (MI), and healthy control subjects (Ctrl). We detected
a total of 371 proteins with high confidence (FDR < 1%, p < 0.05) including 53 preliminary biomarkers that displayed
≥2-fold modulated expression in patients with CAD (27 associated
with atherosclerotic stable angina, 26 with myocardial injury). In
the verification phase, we used label-free LC–MRM-MS-based
targeted method to verify the preliminary biomarkers in pooled plasma,
excluded peptides that were poorly distinguished from background,
and performed further validation of the remaining candidates in 49
individual plasma samples. Using this approach, we identified a final
panel of eight novel candidate biomarkers that were significantly
modulated in CAD (p < 0.05) including proteins
associated with atherosclerotic stable angina that were implicated
in endothelial dysfunction (F10 and MST1), proteins associated with
myocardial injury reportedly involved in plaque destabilization (SERPINA3,
CPN2, LUM), and in tissue protection/repair mechanisms (ORM2, ACTG1,
NAGLU). Taken together, our data showed that candidate biomarkers
with potential diagnostic values can be successfully detected in nondepleted
human plasma using an iTRAQ/MRM-based discovery-validation approach
and demonstrated the plausible clinical utility of the proposed panel
in discriminating atherosclerotic stable angina from myocardial injury
in the studied cohort.