TGFB1 and diabetes mellitus: Transforming growth factor β1 (TGF-β1) is an important factor driving tissue fibrosis and can directly activate Smad signal transduction, thus triggering the over-expression of pro-fibrosis genes; the TGF-β1/Smad pathway is closely related to the diabetes-induced renal fibrosis as well as testicular interstitial fibrosis [15,16].