SMAD1 and Hyperglycemia: In conclusion, we speculated that BMP-7 could upregulate SnoN mRNA level by activating the classical Smad1/5 signaling pathway, and it also could reduce the ubiquitination of SnoN protein, finally restoring the SnoN protein level to inhibit hyperglycemia-mediated renal tubular epithelial fibrosis (Fig. 8d).