Glucose transport in lung airway epithelial cells

At normal blood glucose concentrations (4.4–6.1 mM), glucose in fluid lining the human airways is < 0.5mM, implying a role for active transport of glucose out of the airway lumen. Glucose transport can occur via the GLUT (facilitative transport) or SGLT (sodium/glucose co‐transport) transporters. The aim of this study was to compare the glucose uptake via GLUT and SGLT both in the human airway epithelial cell line (H441) and primary culture of human bronchial epithelial cells (HBEC) maintained in 5mM glucose by the use of 1mM phloretin (PT)‐GLUT inhibitor or 0.5mM phlorizin (PZ)‐SGLT inhibitor. Uptake was measured by adding 3 H‐glucose for 10 minutes in confluent culture of cells. In non‐polarised cells glucose uptake was 25.8 ± 0.2 nmol/mg protein for H441 and lower in HBEC 1.7 ± 0.4 nmol/mg protein. Uptake in both cell types was inhibited by PT to 3.6 ± 0.3 nmol/g protein in H441 (n = 6; p < 0.05) and 0.7 ± 0.1 nmol/mg protein in HBEC (n = 6; p < 0.05) but not by PZ. Apical and basolateral glucose uptake in polarised H441 cells grown at air interface were inhibited by PT and PZ. Basolateral glucose uptake in HBECs was also reduced by PT and PZ but apical uptake was only inhibited when PT and PZ were applied together. Our results demonstrate that both GLUT and SGLT mediated transport could be responsible for regulating glucose in human airway fluid. Funded by the Wellcome Trust 075049/Z/04/Z