Project Summary Heart failure with reduced ejection fraction is a major public health burden with high morbidity and mortality. Identifying novel approaches towards regenerating heart tissue has significant therapeutic potential for heart failure patients. Similar to lower vertebrates, neonatal mice can regenerate their hearts following injury for a brief window after birth. Remarkably, we recently discovered that inhibition of the mitochondrial enzyme succinate dehydrogenase (SDH) can promote adult cardiac regeneration following myocardial infarction (MI). Our results are distinct from the previous studies demonstrating a cardioprotective role for SDH inhibition against the redox insult during ischemia/reperfusion injury, as we demonstrate that SDH inhibition does not protect the heart against MI-induced infarction. The metabolic switch from glycolysis to fatty acid oxidation in the postnatal heart contributes to cardiomyocyte cell cycle exit and loss of endogenous cardiac regeneration potential. SDH, also known as mitochondrial complex II, plays a central role in regulating cellular metabolism as it is involved in both the tricarboxylic acid (TCA) cycle and the electron transport chain (ETC). Our recently published study demonstrates that inhibition of SDH by malonate treatment of adult mice following myocardial infarction stimulates cardiomyocyte proliferation, revascularization, and results in restoration of cardiac structure and function following infarction. Remarkably, our metabolite analysis following SDH inhibition demonstrates dynamic metabolic changes in the uninjured adult heart. Our overarching hypothesis is that SDH inhibition metabolically reprograms the adult heart to a regenerative state. To define the role of SDH in adult heart regeneration, we will pursue the following aims: 1) Elucidate the metabolic and cellular mechanisms underlying post-MI regeneration following SDH inhibition; 2) Define the molecular mechanisms by which SDH inhibition promotes post-MI regeneration; 3) Determine the role of SDH inhibition by malonate on regenerative potential following myocardial infarction in a porcine model. Our proposed experiments will define the mechanisms by which SDH inhibition promotes cardiac regeneration, as well as establish the therapeutic potential of SDH inhibition in large animal hearts which exhibit distinct physiology from the mouse heart. Collectively, our results reveal a novel role for SDH inhibition in promoting heart regeneration following myocardial infarction, and this proposal will generate important results that will lead to novel therapeutic strategies to regenerate the adult heart following infarction.