GLUT4 translocation induction by putative insulin mimetic herbal compounds quantitated by TIRF microscopy.

(A) Schematic illustration of insulin or herbal compound induced GLUT4 translocation. Putative insulin mimetic substances stimulating the insulin receptor (IR), other plasma membrane or cytosolic effector proteins (1) induce signal transduction events (2) that lead to the translocation of GLUT4 containing vesicles (3) and their subsequent fusion with the PM (4). This transfer is linked to an increase of the GFP-signal intensity in the evanescent field. (B) GLUT4-GFP signal in CHO-K1 hIR/GLUT4-myc-GFP cells before and after stimulation with indicated substances. Cells were seeded in 96-well plates (35,000 cells/well) and grown over night followed by 3 hours of starvation in HBSS buffer. Cells were then stimulated by the indicated substances for 10 min and the GFP-signal was recorded. Scale bar = 20 μm. (C) The GLUT4-GFP signal intensity increase in the evanescent field was quantitated after 10 and 60 minutes. Error bars are based on the standard error of the mean. At least 60 cells were analyzed for each substance. Data were collected from the same cells before and after substance application. ***P < 0.001 and ****P < 0.0001, significant increase with respect to KRPH (Ins, PP60, PUR) or 0.25% DMSO in KRPH (TIN, GIN, BIL, JIA, MT) treated cells, respectively.