IGF1 and pulmonary fibrosis: However other metformin-mediated signaling pathways have been implicated in the reduction of lung fibrosis including suppression of the pro-fibrotic cytokine insulin-like growth factor-1 (IGF-1) [40] and activation of BMP2-PPAR (bone morphogenetic protein-2-peroxisome proliferator-activated receptor) gamma that ultimately results in trans-differentiation of myofibroblasts to lipofibroblasts [39].