Conclusions

In summary, our work expands upon prior studies to define how increasing extracellular glutamine reprograms endothelial metabolism across a higher than physiological range, including concentrations commonly used in cell culture media. Using isotope assisted metabolomics, we show that endothelial cells increase glutamine uptake with increased availability, while glutamate secretion and glutaminolysis saturated above 2 mM glutamine. Glutamine increased isotopic enrichment and total abundance of most TCA cycle metabolites, glutathione, proline, aspartate, and UDP-GlcNAc, while reducing total abundance of succinate, citrulline, arginine, PUFAs, folate, and histidine. Together, these findings highlight glutamine as a metabolic regulator that maintains the endothelial TCA cycle and endothelial redox homeostasis.