SMAD3 and renal fibrosis: In the db/db mouse model, the Smad3 inhibitor SIS3 significantly suppresses TGF-β/Smad3 pathway activation, thereby alleviating renal fibrosis and inflammation while concurrently upregulating Smad7 expression and restoring the balance of the TGF-β/Smad signaling axis (He et al., 2024b).