KL and persistent truncus arteriosus: To test the hypothesis that Fgf23 and Klotho play an essential role in the development of cardiac hypertrophy induced by increased afterload, we induced TAC in wild-type (WT), VDRΔ/Δ, Fgf23−/−/VDRΔ/Δ, and Klotho−/−/VDRΔ/Δ mice.