NFE2L2 and chronic kidney disease: Notably, our clinical data indicated that the level of serum SOD significantly declined from CKD stages 4–5, which was consistent with the downregulation of Nrf2, as reported in a study [24], suggesting that antioxidant capacity was reduced in severe kidney function impairment, especially in patients with CKD stages 4–5, and this could be reflected in decreased Nrf2.