This is a proposal from a multidisciplinary team with expertise in cardiac physiology, mitochondrial biology, advanced proteomics technologies, biostatistics and bioinformatics to work together to improve understanding of the role of cardiomyocyte mitochondrial dysfunction and adaptation in cardiac aging and failure. This proposal builds upon our novel observations that overexpression of mitochondrial catalase (mCAT) can delay cardiac aging and prevent cardiac hypertrophy and failure and that mitochondrial targeted peptide antioxidants can be cardioprotective. We will study the mechanisms responsible for cardioprotection conferred by mCAT and we will test the translational potential of newly developed mitochondrially targeted antioxidant and protective peptide drugs. Aim 1 (Mechanism) will determine the mechanism(s) of this protection and will elucidate how the changes in the mitochondrial proteome contribute to the functional and biochemical causes of cardiac hypertrophy and failure. To do this we will combine state-of-the art quantitative label-free differential proteomics to measure differences in abundance of the cardiac mitochondrial proteome with in vivo heavy labeling to measure proteome-wide differences in cardiac mitochondrial protein syntheses and turnover rates. The proposed proteomic approach will provide a unique insight into the relationship between mitochondrial function, biology and protein turnover, and abundance. Aim 2 (Translation) will test whether and how newly developed mitochondrially targeted antioxidant and protective drugs have the potential to translate mitochondrial protection into a clinical intervention. This comprehensive approach will provide an integrated assessment of the role of mitochondria in cardiac health, disease and disease-resistance. (End of Abstract)