Project Summary Heart failure with preserved ejection fraction (HFpEF) accounts for ≈50% of all patients with heart failure, and is associated with significant morbidity, mortality, and health care expenditures. Yet, no effective treatment for HFpEF has been identified. Commonly coexisting with other metabolic diseases, HFpEF is considered the cardiovascular manifestation of a systemic metabolic disturbance. However, little is known about its underlying mechanisms. Our laboratory recently developed and validated a novel mouse model that faithfully recapitulates most clinical features of human HFpEF. Using this novel mouse model, I discovered significant mitochondrial dysfunction in HFpEF myocardium, which is associated with mitochondrial protein hyperacetylation, a key post- translational modification known to regulate enzymatic activities. This led to our central hypothesis that protein hyperacetylation is a reversible driver of mitochondrial dysfunction and metabolic remodeling in HFpEF and could serve as a meaningful therapeutic target. In this proposal, we aim to (1) Determine the role of Sirtuin 3, the major mitochondrial deacetylase, in regulating mitochondrial function and HFpEF pathogenesis; (2) Identify specific targets through which hyperacetylation impacts mitochondrial function in HFpEF; (3) Determine the therapeutic effect of modulating protein acetylation on HFpEF mitochondrial function and cardiac phenotype. Collectively, these studies will have a meaningful impact on our understanding of HFpEF pathophysiology and potentially unveil novel therapy to effectively treat HFpEF. Furthermore, work proposed here, coupled with a comprehensive training plan, will provide me with the additional knowledge and skills required to launch my career as a successful and fully independent physician-scientist.