Serum soluble α-Klotho in hemodialysis patients

Background: The extracellular domain of Klotho is cleaved and released into various extracellular fluids, such as blood, urine, and cerebrospinal fluid, as soluble alpha-Klotho (s alpha K1). Methods: We measured s alpha K1 in 53 hemodialysis patients and 20 healthy controls to examine its role in mineral metabolism. Results: The s alpha K1 level of the hemodialysis patients was 430 pg/ml (386 - 540 pg/ml), which was lower than that of healthy controls 740 pg/ml (550 913 pg/ml, p < 0.01). The serum s alpha K1 level showed a positive correlation with serum phosphorus (P) (sigma = 0.33, p = 0.014), while serum corrected Ca tended to be negatively correlated with s alpha K1 (sigma = -0.26, p = 0.06). Both parameters showed the same trends in healthy subjects. However, there was no significant association between serum s alpha K1 and age (sigma = 0.21, p = 0.14), intact PTH (sigma = -0.08, p = 0.55), whole PTH (sigma = -0.08, p = 0.59), or FGF23 (sigma = -0.07, p = 0.62). Multiple regression analysis showed that P was independently associated with the serum s alpha K1 levels (total adjusted R-2 = 0.18, p = 0.02). Conclusions: The s alpha K1 level was lower in hemodialysis patients than in healthy persons. Serum P level was independently associated with the serum s alpha K1 level.