Glucose uptake stimulator YM‐138552 activates gene expression and translocation of glucose transporter isotype 4

Abstract

In this study, we examined the effect of YM-138552 on the glucose uptake, gene expression, and transport activities of the insulin-regulatable glucose transporter isotype 4 (Glut4) in skeletal muscle cells. YM-138552 stimulated medium glucose consumption in a dose-dependent manner (EC50 = 0.07 μM) in myoblast muscle C2C12 cells under differentiation conditions with 2% horse serum supplement. The stimulatory effect of glucose consumption was verified by radiolabeled 2-DG uptake assay. The compound showed dose-dependent stimulation of 2-DG uptake in G8 myoblast muscle cells up to a 1 μM concentration (EC50 = 0.19 μM). To investigate the mechanism of glucose uptake stimulation by YM-138552, the mRNA level of Glut4 was determined using real-time quantitative RT-PCR. The Glut4 mRNA level expressed in C2C12 cells treated with YM-138552 increased up to at least 24 h (227% vs. control), after which it gradually decreased to the initial level at 36 h. In addition, we established that C2C12 cells stably expressed the myc-tagged Glut4 protein (C2C12-Glut4myc) and measured the Glut4 translocation activity. The Glut4 translocation activity was stimulated by treatment of YM-138552 without insulin in a dose-dependent manner (EC50 = 0.62 μM), and no insulin effect (100 nM) was observed. This suggests that YM-138552 has an insulin-like effect. These results suggest that the stimulation of glucose uptake by YM-138552 in muscle cells was partly due to upregulation of the Glut4 gene expression and its translocation activation. Our findings on the in vitro effects of YM-138552 glucose uptake stimulation through the Glut4 transporter may suggest a direction for the development of new drugs for the treatment of NIDDM. Drug Dev. Res. 51:43–48, 2000. © 2000 Wiley-Liss, Inc.