Dynamic glucose uptake, storage, and release by human microvascular endothelial cells

Mol Biol Cell. 2022 Oct 1;33(12):ar106. doi: 10.1091/mbc.E22-04-0146. Epub 2022 Aug 3.

Abstract

Endothelia determine blood-to-tissue solute delivery, yet glucose transit is poorly understood. To illuminate mechanisms, we tracked [3H]-2-deoxyglucose (2-DG) in human adipose-tissue microvascular endothelial cells. 2-DG uptake was largely facilitated by the glucose transporters GLUT1 and GLUT3. Once in the cytosol, >80% of 2-DG became phosphorylated and ∼20% incorporated into glycogen, suggesting that transported glucose is readily accessible to cytosolic enzymes. Interestingly, a fraction of intracellular 2-DG was released over time (15-20% over 30 min) with slower kinetics than for uptake, involving GLUT3. In contrast to intracellular 2-DG, the released 2-DG was largely unphosphorylated. Glucose release involved endoplasmic reticulum-resident translocases/phosphatases and was stimulated by adrenaline, consistent with participation of glycogenolysis and glucose dephosphorylation. Surprisingly, the fluorescent glucose derivative 2-NBD-glucose (2-NBDG) entered cells largely via fluid phase endocytosis and exited by recycling. 2-NBDG uptake was insensitive to GLUT1/GLUT3 inhibition, suggesting poor influx across membranes. 2-NBDG recycling, but not 2-DG efflux, was sensitive to N-ethyl maleimide. In sum, by utilizing radioactive and fluorescent glucose derivatives, we identified two parallel routes of entry: uptake into the cytosol through dedicated glucose transporters and endocytosis. This reveals the complex glucose handling by endothelial cells that may contribute to glucose delivery to tissues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Deoxyglucose* / pharmacology
  • Endothelial Cells*
  • Epinephrine
  • Glucose / pharmacology
  • Glucose Transporter Type 1
  • Glucose Transporter Type 3
  • Glycogen
  • Humans
  • Maleimides
  • Phosphoric Monoester Hydrolases

Substances

  • Glucose Transporter Type 1
  • Glucose Transporter Type 3
  • Maleimides
  • Glycogen
  • Deoxyglucose
  • Phosphoric Monoester Hydrolases
  • Glucose
  • Epinephrine