To determine whether FGF21 alone can exert this effect independently of CKD, we administered the AAV8-FGF21 into wild-type normal mice by tail vein injection and raised circulating FGF21 levels to 2915 ± 401 pg/ml (mean ± SEM, N = 8), which was higher than those of wild-type CKD mice and comparable with those of Fgf21−/− control mice injected with AAV8-FGF21 (Fig. 1j). This evidence concerns the gene FGF21 and chronic kidney disease.