KL and diabetic kidney disease: The limitations of using α-Klotho as a marker of DKD may be due to the lack of standardization of measurement methods and interactions between Klotho and various signalling pathways, e.g., mammalian target of rapamycin kinase (mTOR), peroxisome proliferator-activated receptor gamma (PPAR-γ), NF-κB that may affect Klotho concentration [179,180].