KL and chronic kidney disease: It has been reported that klotho inhibition increases TGF-β1 expression in mice with renal fibrosis that has been induced by unilateral ureteral obstruction (UUO), and TGF-β1 reduces klotho expression in renal cultured epithelial cells, suggesting that decreased klotho expression enhances TGF-β1 activity and that klotho deficiency is not only a cause but also a result of renal fibrosis in CKD [124].