M2/M1 macrophage polarization modulation (112) increased the ability of quercetin to reduce kidney damage and fibrosis, and treatment with quercetin improved kidney function, reduced oxidation stress factors, serum fibroblast growth factor 23 (FGF23) levels, and renal inflammation in a rat model of adenine-induced chronic kidney disease (113). This evidence concerns the gene FGF23 and chronic kidney disease.