Introduction: Low levels of vitamin D are linked to numerous adverse clinical conditions in hemodialysis (HD) patients, including disturbances of mineral and bone metabolism and increased mortality. Klotho, a molecule involved in such processes as phosphate homeostasis and aging, exists in 2 forms: a transmembrane protein acting as a coreceptor for fibroblast growth factor 23 (FGF-23) and soluble form, which is formed by cleavage of the extracellular domain of this molecule.
Objectives: The aim of the study was to evaluate the effect of cholecalciferol supplementation on soluble Klotho levels in HD patients.
Patients and methods: This was a prospective, open-label trial examining the effects of cholecalciferol supplementation on selected laboratory markers in 22 patients on HD. Vitamin D deficiency was assessed by the measurement of 25-hydroxyvitamin D [25(OH)D] levels. Soluble Klotho, intact FGF-23, intact parathormone (iPTH), and markers of bone formation and resorption were measured at baseline and after 12 weeks of cholecalciferol supplementation.
Results: The levels of 25(OH)D increased, while those of iPTH and cross-linked C-telopeptide of type 1 collagen decreased significantly. Cholecalciferol treatment reduced the median concentration of soluble Klotho (from 438.73 pg/ml; interquartile range, 257.99-865.51 pg/ml; to 370.94 pg/ml; 181.72-710.91 pg/ml; P <0.05). FGF‑23 levels were not affected by the treatment.
Conclusions: Supplementation with cholecalciferol in HD patients decreases soluble Klotho levels without affecting the FGF-23 concentration. Replenishment of vitamin D stores results in a decrease in iPTH levels and reduced bone resorption.