Identification of Novel Insulin Mimetic Drugs by Quantitative TIRF Microscopy

BACKGROUND AND PURPOSE. Insulin stimulates the transport of glucose into target tissues by triggering the translocation of glucose transporter 4 (GLUT4) to the plasma membrane. Resistance to insulin, the major abnormality in type 2 diabetes, results in a decreased GLUT4 translocation efficiency. Thus, special attention is drawn on the search for compounds, which are able to enhance this translocation process in the absence of insulin. EXPERIMENTAL APPROACH. In the present work Total Internal Reflection Fluorescence (TIRF) microcopy was applied to quantitate GLUT4 translocation in highly insulin sensitive CHO-K1 cells expressing a GLUT4-myc-GFP fusion protein. KEY RESULTS. Using our approach we proved the GLUT4 translocation modulatory properties of selected substances and identified novel potential insulin mimetics. The increase in the TIRF-signal was found to correlate with an elevated glucose uptake. Variation in the expression level of the human insulin receptor (hIR) proved that identified insulin mimetics stimulate GLUT4 translocation independent of the presence of the hIR. CONCLUSIONS AND IMPLICATIONS. Taken together, TIRF microscopy proved to be a superior tool for the quantitation of GLUT4 translocation and the search for insulin mimetic drugs.