J Physiol. 2018 Nov 21.
KEY POINTS: Hearts from type 2 diabetic animals display perturbations in excitation-contraction coupling, impairing myocyte contractility and delaying relaxation, along with altered substrate consumption patterns. Under high glucose and β-adrenergic stimulation conditions, palmitate can, at least in part, offset left ventricle (LV) dysfunction in hearts from diabetic mice improving contractility and relaxation while restoring coronary perfusion pressure. Fluxome calculations of central catabolism in diabetic hearts show that, in presence of palmitate, there is a metabolic remodeling involving tricarboxylic acid cycle, polyol and pentose phosphate pathways, leading to improved redox balance in cytoplasmic and mitochondrial compartments. Under high glucose and increased energy demand, the metabolic/fluxomic re-direction leading to restored redox balance imparted by palmitate helps explain maintained LV function and may contribute to design novel therapeutic approaches to prevent cardiac dysfunction in diabetic patients.ABSTRACT: Type-2 diabetes (T2DM) leads to reduced myocardial performance, and eventually heart failure. Excessive accumulation of lipids and glucose are central to T2DM cardiomyopathy. Previous data showed that palmitate (Palm) or glutathione preserved heart mitochondrial energy/redox balance under excess glucose rescuing β-adrenergic-stimulated cardiac excitation-contraction coupling. However, the mechanisms underlying the accompanying improved contractile performance have been largely ignored. Herein we explore in intact heart under substrate excess the metabolic remodeling associated with cardiac function in diabetic db/db mice subjected to stress given by β-adrenergic stimulation with isoproterenol and high-glucose compared to their nondiabetic controls (+/+, WT) under euglycemic conditions. When perfused with Palm, T2DM hearts exhibit improved contractility/relaxation compared to WT, accompanied by extensive metabolic remodeling as demonstrated by metabolomics-fluxomics combined with bioinformatics and computational modeling. The T2DM heart metabolome showed significant differences in the abundance of metabolites in pathways related to glucose, lipids, and redox metabolism. Using a validated computational model of heart's central catabolism, comprising glucose and fatty acid (FA) oxidation in cytoplasmic and mitochondrial compartments, we estimated that fluxes through glucose degradation pathways are ∼2-fold lower in heart from T2DM vs. WT under all conditions studied. Palm addition elicits improvement of the redox status via enhanced β-oxidation and decreased glucose uptake, leading to flux-redirection away from redox-consuming pathways (e.g., polyol) while maintaining the flux through redox-generating pathways together with glucose-FA "shared fueling" of oxidative phosphorylation. Thus, available FAs such as Palm may help improve function via enhanced redox balance in T2DM hearts during peaks of hyperglycemia and increased workload. Sonia Cortassa has a PhD in Chemical Sciences from the Universidad Nacional de Córdoba, Argentina, country where she held research and teaching positions at Universidad Nacional de Tucumán and Consejo Nacional Investigaciones Científicas y Técnicas (CONICET). In the United States of America, she continued her research at the Johns Hopkins University and, at present, at the Laboratory of Cardiovascular Sciences/National Institute on Aging/NIH. Her field of research is Physiology, Bioenergetics, with expertise in Computational modeling of metabolic networks. She believes that quantitative Systems Biology approaches represent a real opportunity to contribute to the understanding of human body function in health and disease. This article is protected by copyright. All rights reserved.