GPX1 and renal fibrosis: Compared with untreated Bmi-1-/- mice, the PQQ-treated Bmi-1-/- mice increased the sizes of the body and kidney (Fig. S3A,B), increased renal thickness ratios for cortex/total and cortex/medulla (Fig. S3C,D), decreased the renal fibrosis related parameters (Fig. S3E–J and L–O), and inhibited renal tubule atrophy (Fig. S3K,P), decreased inflammatory cell infiltration and related inflammatory factors (Fig. S4A–F), and decreased the levels of intracellular ROS, whereas the mRNA levels of Gpx1, Gpx4, and GSR were up-regulated significantly (Fig. S4G–I).