Aberrant Citric Acid Cycle Metabolites Temporally Coincide With Myocardial Dysfunction in a Rat Model of Stress Cardiomyopathy

Introduction: Stress cardiomyopathy is characterized by transient contractile dysfunction with a poorly understood mechanism. Targeting metabolic derangements has proven efficacious in chronic heart failure, but the role of metabolism in acute cardiac dysfunction is ill-defined. Hypothesis: Characterizing any metabolic alterations in stress cardiomyopathy may help identify potential therapeutic targets. Methods: Sprague-Dawley rats (350 ± 57 g) were given a single intraperitoneal injection of 75 mg/kg isoprenaline. Animals were allocated into groups (N=30 each) based on designated time-points for assessment after injection: control (no injection), day 1, 3, and 7. Rats underwent left ventricular PV loop catheterization followed by harvesting of apical ventricular tissue. Targeted metabolomic analyses were performed via LC-MS and supplemented with enzyme activity assays, qPCR, and Western blotting. Results: Stroke work, cardiac output, and ejection fraction were all significantly reduced by day 1 with recovery by day 7 (Figure A, all p<0.05). Targeted tissue metabolomics revealed peaks in nearly all citric acid cycle metabolites, pyruvate, and lactate that similarly correlated with illness (Figure B). In tandem, anaplerotic amino acids rose with injury while tissue triglycerides decreased. Pyruvate dehydrogenase phosphorylation decreased with decreased expression of pyruvate dehydrogenase kinase (Figure C). However, no differences were noted in tissue acylcarnitine levels despite increased serum fatty acids (all p>0.05). Conclusions: Profound rises in citric acid metabolites with accompanying increases in anaplerotic amino acids are suggestive of metabolic reprogramming in the setting of energetic deficits. Notably, these trends differ from those found in chronic heart failure, and represent a novel phenotypic characterization of stress cardiomyopathy with potential therapeutic implications.