Gossypol from Cottonseeds Ameliorates Glucose Uptake by Mimicking Insulin Signaling and Improves Glucose Homeostasis in Mice with Streptozotocin-Induced Diabetes

Figure 6

Involvement of the Akt-signaling pathway in gossypol- (GSP-) induced stimulation of glucose uptake. (a) Time course of the effect of GSP on AKT phosphorylation in C2C12 myotubes. Pretreatment of cells with GSP (2 μM) and then incubated with indicated time periods. Cell lysates were prepared, and immunoblotting was performed. Statistical data are represented in the adjacent figure. Values denote means ± SEM of three independent experiments. versus no treatment. (b) C2C12 myotubes were incubated with different concentrations of GSP alone for 2 h, or GSP (2 μM) for 2 h followed by insulin (100 nM) for 30 min. Cell lysates were separated by SDS-PAGE, and immunoblotting was carried out. Statistical data are represented in the adjacent figure. Values denote means ± SEM of three independent experiments. versus no treatment. (c) Effects of Akt inhibitor LY294002 on Akt-signaling pathway. (d) Effects of LY294002 on the translocations of GLUT4 induced by GSP in C2C12 myotubes. Subcellular membrane fractions were extracted and subjected to immunoblot analysis. (e) Effect of GSP on glucose uptake in LY294002-pretreated C2C12 myotubes. Values denote means ± SEM in independent triplicate. versus basal glucose uptake (no stimulation by insulin); versus compound-treated basal glucose uptake; versus compound-treated insulin-induced glucose uptake.

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