Figure 1

Metformin interacts with TGF-β1 to block its binding with receptors and attenuates downstream signaling (a) Sensorgrams for the binding of metformin and TGF-β1. TGF-β1 was covalently coupled to a CM5 chip and metformin was injected in a two-fold dilution concentration series ranging from 62.5 μM to 1.9 μM. The steady-state values were calculated from the sensorgrams and plotted against the concentration. The data were fit to a single site binding model to calculate the K_D. (b) Metformin inhibited [¹²⁵I]-TGF-β1 receptor binding to 3T3 mouse fibroblasts. The results are expressed as the percentage of specific binding in the absence of metformin (n = 4). (c) Metformin and TGF-β1 (0.5 ng/mL) were premixed for 2 h and then 3T3 cells were treated with the mixture for 30 minutes. Western blot analysis and quantification of phosphorylated-Smad2 (p-Smad2), Smad2, p-Smad3, Smad3 and GAPDH were performed. Data are mean ± SEM from 4 independent experiments. Kruskal–Wallis ANOVA combined with post-hoc Dunn’s multiple comparison test (two tailed) was performed. *P < 0.05 vs. TGF-β1 group.