It can be surmised that if kidney injuries, fibrosis occurs and renal function declines, its production would decrease (including membrane α-Klotho and solubleα-Klotho) [15], which has been proved by a prior study that the level of mRNA expression and protein production of α-Klotho both reduced significantly in the kidneys among patients with chronic renal failure [34]. Here, KL is linked to chronic kidney disease.