C-peptide induces human renal mesangial cell proliferation in vitro, activating Src-kinase, PI-3 kinase and ERK1/2

► C-peptide induces human renal mesangial cell proliferation. ► Activation of PI-3 kinase and MAP kinase signaling pathway are involved in this process. ► C-peptide induces cyclin D1 expression and phosphorylation of retinoblastoma protein.