Investigations of cellular glucose transport and its regulation under the influence of insulin in human peripheral blood lymphocytes.

INTRODUCTION: We investigated the effects of insulin on glucose transport in human peripheral lymphocytes using flow cytometry. We hypothesized that lymphocytes could be used as tools to study insulin action at the cellular level and facilitate the investigation of mechanisms that lead to insulin resistance.
MATERIAL AND METHODS: Blood was withdrawn from 25 healthy subjects. The expression of glucose transporter (GLUT) isoforms in plasma membrane and the rates of glucose transport were determined with and without insulin (10 to 100 mU/L). Anti-CD3 phycoerythrin monoclonal antibody was used for lymphocyte gating. GLUT1, GLUT3, and GLUT4 isoforms were determined after staining cells with specific monoclonal antibodies to GLUT1, 3, and 4. Glucose transport was monitored with deoxy-D-glucose, 2-[3H(G)] - 185-370 GBq.
RESULTS: Insulin increased the uptake of deoxy-D-glucose and the expression of GLUT1, GLUT3, and GLUT4 isoforms in the plasma membrane. The optimal effects were always reached at 50 mU/L of insulin with the increase in GLUT1, 3, and 4 expression of 12%, 44%, and 38%, respectively. Mean baseline values of deoxy-D-glucose uptake were 3409 ccpm at 15 min., 6587 ccpm at 30 min., and 12525 ccpm at 60 min. of investigation. The maximal uptake in insulin-stimulated conditions was reached with 50 mU/L of insulin and went up to 12450 ccpm at 15 min., 37482 ccpm at 30 min., and 37916 ccpm at 60 min. of investigation (p < 0.01).
CONCLUSIONS: Peripheral blood lymphocytes may become an interesting model system to study the effects of insulin on cellular glucose transport. Flow cytometry is suitable for this investigation and may be used as a method to estimate the influence of insulin on GLUTprotein translocation and the dynamics of glucose uptake by lymphocytes.