Metabolic Lipid Tracing in the Rodent Heart

Abstract

Cardiovascular diseases remain the leading cause of death worldwide and represent enormous medical challenge. Therefore, the search for better treatment strategies and markers for early cardiovascular diseases detection is of a great importance. Changes in lipid metabolism have been observed in many cardiac diseases and are often a target of the drug therapy. <br/> This thesis aims to use alkyne-lipid tracers to deepen the understanding of lipid metabolism in a rodent heart. The goals are (I) to compare the metabolism of different alkyne-fatty acid tracers in various cardiac setups; (II) to study cardiac triglycerides pool; (III) to follow the effect of erucic acid on cardiac lipid accumulation; and (IV) to study influence of hypoxia and oxidative stress on lipid metabolism and remodeling. <br/> (I) Alkyne-fatty acid tracers allowed to follow lipid metabolism in heart lysates, H9c2 cells, viable slices and isolated perfused heart (Langendorff heart). Medium-chain alkyne-fatty acids were catabolized more intensively than long-chain alkyne-fatty acids, whereas long-chain alkyne-fatty acids were the preferred substrate for the cardiac anabolism. The fatty acid length influenced the distribution of the tracer within major lipid classes. Modification of alkyne-palmitic and alkyne-linoleic acid-derived phosphatidylcholines was observed. (II) ATGListatin caused significant accumulation of triglycerides, supporting the existence of cardiac triglycerides pool with a high turnover. ATGListatin slowed down the triglycerides cycling speed and caused lipid droplet accumulation. (III) Erucic acid affected metabolism of common dietary long-chain fatty acids (neutral lipid accumulation, arachidonic acid-containing phosphatidylinositol amount, acyl-carnitines formation), systematically influenced cardiac lipidome (total lipid amount, neutral-to-polar lipids ratio, long-chain species enrichment) and caused lipid droplet accumulation and enlargement. (IV) Hypoxia and oxidative stress resulted into persistent changes in polar-to-neutral lipid ratio, alterations in membrane phospholipid biosynthesis and remodeling. <br/> This study pioneered the application of alkyne-fatty acid tracers in cardiac setup and showed differences in various fatty acid handling by the heart under physiological and pathological conditions. This project confirmed the existence of the cardiac triglycerides pool and showed the effect of erucic acid on cardiac lipid accumulation.