TGFB1 and diabetic kidney disease: TGF-β1 is directly involved in the epithelial-to-mesenchymal transition process of DKD, leading to renal interstitial fibrosis (Zheng et al., 2016; Yang Y. et al., 2020), and it can activate the downstream Smad signaling pathway, thereby mediating fibrogenesis (Hathaway et al., 2015).