Extracellular flux analysis in intact cardiac tissue slices—A novel tool to investigate cardiac substrate metabolism in mouse myocardium

Abstract

AbstractAimCardiac pathologies are accompanied by alterations in substrate metabolism, and extracellular flux analysis is a standard tool to investigate metabolic disturbances, especially in immortalized cell lines. However, preparations of primary cells, such as adult cardiomyocytes require enzymatic dissociation and cultivation affecting metabolism. Therefore, we developed a flux analyzer‐based method for the assessment of substrate metabolism in intact vibratome‐sliced mouse heart tissue.MethodsOxygen consumption rates were determined using a Seahorse XFe24‐analyzer and “islet capture plates.” We demonstrate that tissue slices are suitable for extracellular flux analysis and metabolize both free fatty acids (FFA) and glucose/glutamine. Functional integrity of tissue slices was proven by optical mapping‐based assessment of action potentials. In a proof‐of‐principle approach, the sensitivity of the method was tested by analyzing substrate metabolism in the remote myocardium after myocardial infarction (I/R).ResultsHere, I/R increased uncoupled OCR compared with sham animals indicating a stimulated metabolic capacity. This increase was caused by a higher glucose/glutamine metabolism, whereas FFA oxidation was unchanged.ConclusionIn conclusion, we describe a novel method to analyze cardiac substrate metabolism in intact cardiac tissue slices by extracellular flux analysis. The proof‐of‐principle experiment demonstrated that this approach has a sensitivity allowing the investigation of pathophysiologically relevant disturbances in cardiac substrate metabolism.