Transforming growth factor beta-1 upregulates glucose transporter 1 and glycolysis through canonical and noncanonical pathways in hepatic stellate cells

Figure 4 The noncanonical p38 MAPK and PI3K/AKT signaling pathways are also involved in transforming growth factor-β1-mediated glucose transporter 1 expression. A-C: Serum-starved (for 20 h) primary mouse hepatic stellate cells (HSCs) were treated with transforming growth factor-β1 (TGF-β1) (3 ng/mL) and examined at different time points. Western blot analysis using specific antibodies (A). Five independent experiments were performed to quantitatively analyze the levels of phosphorylated p38 (B) MAPK and AKT (C); D and E: HSCs cultured in serum-free medium were pretreated with the p38 MAPK inhibitor SB203580 (10 μm) or the PI3K inhibitor LY294002 (10 μm) for 1 h and then treated with TGF-β1 (3 ng/mL) for 4 h. Western blot analysis using specific antibodies (D). Quantitative analysis of the levels of glucose transporter 1 (GLUT1) and phosphorylated Smad2 and Smad3 proteins (E); F and G: HSCs cultured in serum-free medium were pretreated with the p38 MAPK inhibitor SB203580 (10 μm), the PI3K inhibitor LY294002 (10 μm) and the Smad inhibitor SIS3 (20 μm) for 1 h and then treated with TGF-β1 (3 ng/mL) for 4 h. Western blot analysis using specific antibodies (F). Quantitative analysis of the GLUT1 protein level (G) (the mean ± SE; ^aP < 0.05, ^bP < 0.01 and ^cP < 0.001 compared with the TGF-β1-treated group or the TGF-β1-untreated group, ^dP < 0.05, ^eP < 0.01 and ^fP < 0.001 for the comparison of the group treated with TGF-β1 and the groups treated with TGF-β1 and the corresponding inhibitors; Student’s t test). GLUT1: Glucose transporter 1; TGF-β1: Transforming growth factor-β1.