Probing the Role of Mitochondrial Short-chain Carbon Homeostasis in the Hypertrophied and Failing Heart

Sanford Burnham Prebys Medical Discovery Institute, La Jolla CA

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Abstract

? DESCRIPTION (provided by applicant): Significant evidence indicates that during the development of heart failure (HF) the heart undergoes dramatic alterations in mitochondrial fuel metabolism and bioenergetics. Specifically, the capacity for oxidizing the chief fuels, fatty acids and glucose, becomes constrained during the development of cardiac hypertrophy, and in the failing heart. Studies in animal models and in humans have shown that a reduction in myocardial high-energy phosphate stores occurs in early stages of HF, setting the stage for a vicious cycle of energy-starvation, contractile dysfunction, and progression of disease. To date, most studies aimed at delineating mechanisms driving the energy metabolic derangements of HF have been conducted in late stage disease, and have focused on gene regulatory mechanisms. The results of such studies have pointed to altered mitochondrial function, cardiac myocyte death, and widespread downregulation of genes involved in mitochondrial energy transduction. However, it is likely that many of these abnormalities reflect end-stage irreversible processes. Over the past several years, we have embarked on studies to elucidate energy metabolic remodeling events that occur in early stages of pathologic remodeling in route to HF in well-defined mouse models. For these studies, we employed a systems biology approach supported by an NHLBI-supported team-based funding initiative (RFA-HL-10-002). Integrated transcriptomic and metabolomics profiling was conducted on heart samples representing pathologic (pressure overload) and adaptive (exercise training) forms of cardiac hypertrophy, and in the early stages of HF. Comparative analysis of the datasets led to several surprising findings that have led to the hypothesis that during the early stages of pathologic cardiac remodeling caused by pressure overload, a myocardial substrate shift from reliance on fatty acids to ketone utilization sets the stage for expansion of the mitochondrial acetyl-CoA pool resulting in hyperacetylation of mitochondrial proteins, further reducing capacity for fuel oxidation and contributing to the pathogenesis of HF. We have assembled a multi-PI team to address this hypothesis. In Aim 1, we will employ a novel approach to define the stoichiometry of mitochondrial protein acetylation, and determine its functional consequences, in the early stage failing mouse heart. In Aim 2, we will determine the impact of modulating mitochondrial short-chain carbon export on protein acetylation, substrate metabolism, and remodeling in the normal, hypertrophied, and failing heart. Aim 3 is designed to explore the impact of chronic shifts in myocardial fuel utilization on cardiac mitochondrial protein acetylatio, substrate metabolism, and remodeling in the normal and failing mouse heart. The long-term goal of this project is to identify new mechanisms and therapeutic targets relevant to the development of innovative metabolic modulatory strategies for the prevention and early-stage treatment of heart failure.