Triomic Approach Reveals the Metabolic, Genomic and Proteomic Influences of the Endogenous Histidyl Dipeptides on Heart

Background: Histidyl dipeptides, such as carnosine (β-alanine-histidine) are synthesized in the heart via enzyme carnosine synthase (CARNS1). These dipeptides are present in the myocardium in micro-millimolar concentration, where they facilitate glycolysis and glucose oxidation by proton buffering and attenuate ischemia reperfusion injury. However, a composite understanding of their roles in myocardium is lacking. Objective: To understand the role of endogenous histidyl dipeptides in regulating the metabolic, genomic and proteomic profiles of heart under basal and ischemic conditions. Methods and Results: We found that mice with cardio specific overexpression of CARNS1, had higher myocardial levels of carnosine, anserine and homocarnosine. Under aerobic conditions, the transgenic hearts had lower levels of short- (dodecanal) and long-chain (propionic) fatty acids and TCA intermediate -succinic acid, and an increase in pyroglutamic acid-an intermediate of glutathione metabolism. When subjected to 5 and 15 min of ischemia, WT hearts showed progressive accumulation of fatty acids and depletion of amino acids, such as aspartate that were significantly attenuated in transgenic hearts. Further, the ischemic transgenic hearts had increased accumulation of citric acid cycle (TCA) intermediate - fumaric acid. Parallel with the increase in β-fatty acid oxidation and TCA cycle, transgenic hearts were enriched in enzymes of β-fatty acid oxidation and TCA cycle. Expression of enzyme glutathione synthetase that regulates pyroglutamic acid synthesis was decreased in the transgenic hearts. Overexpression of CARNS1 also led to a decrease in several micro RNAs, such as miR-6989 and miR-3100 which are paralleled to increased expression of succinate dehydrogenase and 2,3 enoyl-CoA hydratase. Further miR-142 levels in transgenic hearts were decreased that parallels with decreased glutathione synthetase. Conclusion: Our integrated analysis of metabolomics, transcriptomics and proteomics shows histidyl dipeptides are critical regulators of myocardial function and energetics. Importantly these dipeptides promote β-fatty acid oxidation and glycolytic activity under the basal and ischemic conditions.