Serum soluble Klotho protein level is associated with residual diuresis in incident peritoneal dialysis patients

Aim: Active vitamin D (1,25-dihydroxyvitamin D3), PTH, fibroblast growth factor-23 (FGF-23) and Klotho protein are key regulators of phosphate metabolism. Hyperphosphatemia and increased FGF-23 level in patients with end-stage renal disease are associated with increased morbidity and mortality. The relationships among key regulators of phosphate metabolism are still being investigated. FGF-23, the humoral factor involved in phosphate metabolism, is strongly associated with serum phosphorus level. Klotho, a transmembrane protein expressed primarily in renal tubules, functions as an obligatory co-receptor for FGF-23. The soluble form of Klotho, produced by the shedding of the transmembrane protein, is detectable in body fluids. The purpose of the study was to assess if serum soluble alpha-Klotho level was related to phosphate metabolism parameters and residual renal function (RRF) in incident peritoneal dialysis (PD) patients. Methods: Thirty-five clinically stable patients 4 to 6 weeks after the onset of PD were included in the study. For each patient, clinical and laboratory data were reviewed. Serum phosphorus concentration, urinary and peritoneal phosphate clearance, serum FGF-23 and soluble Klotho protein concentrations were determined. Results: Serum soluble alpha-Klotho was strongly negatively correlated with 24-hour diuresis (Rs = -0.55, p = 0.004) and renal phosphate clearance (Rs = -0.40, p = 0.049), but not with RRF. Conclusions: Serum soluble Klotho protein concentration is inversely related to residual diuresis and renal phosphate clearance in incident PD patients.