Figure 2.

Impaired GLUT4 translocation to plasma membrane caused by simvastatin is restored by geranylgeranyl pyrophosphate (GGPP). (A) C2C12 myotubes were pretreated with 10 μM simvastatin, 10 μM FTI‐277, 10 μM GGTI‐298, 1.5 mM 3‐PEHPC, and 1 mM perillyl alcohol for 24 h. Then cells were incubated with or without 100 nM insulin for 30 min, total protein and plasma membrane protein were harvested, and GLUT4 expression was analysed by western blot, with GAPDH as the loading control (n = 3). (B) C2C12 myotubes were previously transfected with siRNAs targeting GGPS1, PGGT1B, and RABGGTA, respectively, for 48 h. Then cells were incubated with or without 100 nM insulin for 30 min, then total protein and plasma membrane protein were harvested, and GLUT4 expression was analysed by western blot, with GAPDH as the loading control (n = 3). (C) C2C12 myotubes were pretreated with 10 μM GGPP, 10 μM simvastatin, and 10 μM GGPP combined with 10 μM simvastatin for 24 h, and then cells were treated with 100 nM insulin for 30 min. Total protein samples and plasma membrane protein samples were harvested, and GLUT4 expression was analysed by western blot, with GAPDH as the loading control (n = 3). (D, E) Male C57BL/6J mice (20 ± 2 g) were randomly grouped (n = 6). After administration of geranylgeraniol (GGOH) (25 mg/kg/day), simvastatin (40 mg/kg/day), and GGOH combined with simvastatin for 3 weeks, mice were sacrificed and membrane GLUT4 expression in gastrocnemius (D) and tibialis anterior (E) was analysed by western blot, with GAPDH as the loading control (n = 3). Data represented the mean ± SEM. Statistical analysis was performed with one‐way ANOVA. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns denotes no significance.