Serum Starvation Accelerates Intracellular Metabolism in Endothelial Cells

Periods of low energy supply are challenging conditions for organisms and cells during fasting or famine. Although changes in nutrient levels in the blood are first sensed by endothelial cells, studies on their metabolic adaptations to diminished energy supply are lacking. We analyzed the dynamic metabolic activity of human umbilical vein endothelial cells (HUVECs) in basal conditions and after serum starvation. Metabolites of glycolysis, the tricarboxylic acid (TCA) cycle, and the glycerol pathway showed lower levels after serum starvation, whereas amino acids had increased levels. A metabolic flux analysis with C-13-glucose or C-13-glutamine labeling for different time points reached a plateau phase of incorporation after 30 h for C-13-glucose and after 8 h for C-13-glutamine under both experimental conditions. Notably, we observed a faster label incorporation for both C-13-glucose and C-13-glutamine after serum starvation. In the linear range of label incorporation after 3 h, we found a significantly faster incorporation of central carbon metabolites after serum starvation compared to the basal state. These findings may indicate that endothelial cells develop increased metabolic activity to cope with energy deficiency. Physiologically, it can be a prerequisite for endothelial cells to form new blood vessels under unfavorable conditions during the process of angiogenesis in vivo.

Automated summary

Periods of low energy supply pose challenges for organisms and cells. In this study, we examined the metabolic changes in human umbilical vein endothelial cells (HUVECs) during serum starvation. The results showed decreased levels of metabolites involved in glycolysis, the TCA cycle, and the glycerol pathway, while amino acid levels increased. Metabolic flux analysis revealed faster incorporation of labeled glucose and glutamine into cellular metabolism after serum starvation, suggesting increased metabolic activity to cope with energy deficiency.