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Introduction: Patients with heart failure and a preserved ejection fraction (HFpEF) present heart function abnormalities that remain poorly understood. Defining proteomic signature of HF that is independent of left ventricular hypertrophy (LVH) should allow for stratification of its subtypes and potential mechanism that contributes to the disease. Hypothesis: We hypothesized that HFpEF proteomic signature would be comprised of the hypertrophy and contractile protein phenotype. Methods: Intraoperative left ventricular (LV) myocardial biopsies were obtained from patients (n=21) recruited to undergo coronary artery bypass grafting (CABG). Patients were categorized to: control non-hypertensive (n=9), LVH (n=5), and HFpEF (n=7). Myocardial tissue was subfractionated: cytoplasmic- (neutral pH), myofilament- (acidic pH), and membrane-enriched extract (SDS-soluble). All fractions were assessed for protein quantity and Lys/Arg modifications using liquid chromatography mass spectrometry (LC-MS). Results: In HFpEF, 13% of the cardiac LV proteome changed compared to control heart, with a substantial proportion (77%) decreasing in quantity across all three cardiac fractions, while with LVH, 61% of the proteomic LV changes were increased. Although glycolysis and gluconeogenesis increased in both cardiopathies with respect to control, in HFpEF more subtly than in LVH. Modified proteome of the HFpEF was dominated by decreases in protein succinylation (e.g. ATP5L, THIM, IDHP, APOB, GSH1, KNTC1) and to a lesser degree in methylation (ROA3, HSP7C) or acetylation compared to control. This general trend of down-regulation of succinylation can be attributed to depletion in the levels of succinyl-CoA, the cofactor of enzymatic Lys succinylation. Importantly, there was a striking discordant activation/inhibition of cell death and proliferation pathways between the HFpEF and LVH. Two major upstream regulator clusters linked the proteome changes in cell growth and proliferation to RICTOR and Myc that showed completely opposite trends in LVH and HFpEF groups. Conclusions: HFpEF has a unique proteome signature compared to LV hypertrophy profile which does not arise from sub-proteome involved in contraction but rather is involved in overall cell death.