Altered plasma concentrations of glutamate, alanine and citrate in the early phase of acute myocardial infarction in man

Plasma levels of glutamate, alanine, free fatty acids (FFA), citrate, glucose, insulin, lactate, creatine kinase and aspartate aminotransferase were determined frequently during the first 2-48 h after onset of chest pain in 10 patients who developed acute myocardial infarction (AMI) and in 8 who did not (non-AMI). An initial decrease in plasma glutamate and increase in alanine was found in AMI compared to non-AMI patients. The AMI group showed early, moderate rises of plasma FFA and citrate concentrations, positively related to the initial ST-segment elevation and to the enzymatic estimated infarct size. The AMI patients were continuously hyperglycaemic, but their relative insulin response i.e. plasma glucose/insulin ratio was identical to that of non-AMI patients. Lactate values did not differ between the two groups. Via participation in the malate-aspartate shuttle and by shunting pyruvate to alanine instead of lactate, glutamate is of importance for maintaining myocardial glucose utilization. Our finding of initial low plasma glutamate concentrations after onset of myocardial infarction suggests insufficient glutamate supply to the ischaemic myocardium. On basis of this and animal experiments, an external supply of glutamate might be a 'metabolic' treatment of AMI, alternative or additional to glucose-insulin-potassium infusion in order to promote myocardial glucose oxidation.