Fig. 1

The workflow chart based on cell culture substrates with tunable stiffness in vitro. L: low stiffness; M: medium stiffness; H: high stiffness. NC refers to non-metformin intervention; Met refers to metformin intervention. iTRAQ tags 113, 114, 115, 116, 117 and 118 represent NC-L, NC-M, NC-H, Met-L, Met-M and Met-H, respectively