Cardiomyocyte exosomes regulate glycolytic flux in endothelium by direct transfer of GLUT transporters and glycolytic enzymes. 
Cardiomyocytes (CMs) and endothelial cells (ECs) have an intimate anatomical relationship, which is essential for maintaining the metabolic requirements of the heart.  Little is known about the mechanisms that regulate nutrient flow from ECs to associated CMs, especially in situations of acute stress when local active processes are required to regulate endothelial transport.  We examined whether CM-derived exosomes can modulate glucose transport and metabolism in ECs.  In conditions of glucose deprivation, CMs increase the synthesis and secretion of exosomes.  These exosomes are loaded with functional glucose transporters and glycolytic enzymes, which are internalized by ECs, leading to increased glucose uptake, glycolytic activity, and pyruvate production in recipient cells.  These findings establish CM-derived exosomes as key components of the cardio-endothelial communication system which, through intercellular protein complementation, would allow a rapid response from ECs to increase glucose transport and a putative uptake of metabolic fuels from blood to CMs.  This CM-EC protein complementation process might have implications for metabolic regulation in health and disease.