SMAD4 and renal fibrosis: However, a large number of studies have shown that autophagy can participate in the occurrence and development of renal fibrosis through multiple pathways, including TGF-β/Smad4 signaling pathway, PI3K/Akt/mTOR signaling pathway, MEK/ERK/NRF-1 signaling pathway, and silencing regulatory protein 1(SIRT1)-mediated autophagy [30–33].