KL and chronic kidney disease: Because CKD is characterized by Klotho deficiency [43] and Nfx mice have lower Klotho levels than Sham mice (1.2 ng/mL ± 0.2 vs. 11.9 ng/mL ± 5.5, respectively, P < 0.001), we chose to treat Nfx mice chronically during 6 weeks with recombinant murine Klotho (rKL).