Rat L6 myotubes as an in vitro model system to study GLUT4-dependent glucose uptake stimulated by inositol derivatives.

Some of inositol derivatives have been reported to help the action of insulin stimulating glucose uptake in skeletal muscle cells. Rat L6 myotubes were employed in an attempt to develop an in vitro model system for investigation of the possible insulin-like effect of eight inositol derivatives, namely allo-inositol, D: -chiro-inositol L: -chiro-inositol, epi-inositol, muco-inositol, myo-inositol, scyllo-inositol and D: -pinitol. At a higher concentration of 1 mM seven inositol derivatives other than myo-inositol were able to stimulate glucose uptake, while at 0.1 mM only D: -chiro-inositol, L: -chiro-inositol, epi-inositol and muco-inositol could induce glucose uptake, indicating their significant insulin-mimetic activity. Immunoblot analyses revealed that at least D: -chiro-inositol, L: -chiro-inositol, epi-inositol, muco-inositol and D: -pinitol were able to induce translocation of glucose transporter 4 (GLUT4) to plasma membrane not only in L6 myotubes but also in skeletal muscles of rats ex vivo. These results demonstrated that L6 myotubes appeared efficient as an in vitro system to identify inositol derivatives exerting an insulin-like effect on muscle cells depending on the induced translocation of GLUT4.