The kidneys are importantly affected by age-related tissue damage (i.e., renal atrophy, glomerulosclerosis, and tubulointerstitial fibrosis), increasing the risk of CKD and thus decreasing soluble α-Klotho expression [25], which may be explained by the loss of functionality of the nephron cells involved in its expression. The gene discussed is KL; the disease is Renal atrophy.