Relationship Between Residual Renal Function and Serum Fibroblast Growth Factor 23 in Patients on Peritoneal Dialysis

Abstract

Fibroblast growth factor 23 (FGF23) levels in dialysis patients are influenced by various factors, including phosphorus load. However, the clinical parameters that determine serum FGF23 levels in patients on peritoneal dialysis (PD) remain unclear. The aim of the present study was to examine the effects of clinical factors, on serum FGF23 levels, with an emphasis on residual renal function (RRF). This cross-sectional study included 56 outpatients undergoing PD therapy. Urine volume ≥ 100 mL/day or renal creatinine (Cr) clearance was used as a surrogate marker for RRF. Clinical characteristics were compared between patients with and without RRF. Linear regression analysis was conducted with serum FGF23 level as the dependent variable and renal Cr clearance as the main independent variable. The median and interquartile range of serum FGF23 levels were 5970 (1451-11,688) pg/mL. Patients with RRF showed higher urinary and total phosphate eliminations, and lower serum FGF23 and phosphate levels than patients without RRF. Multivariate linear regression analysis showed that the renal Cr clearance and serum phosphate and dialysis history were negatively associated with serum FGF23 levels, even after adjusting for potential confounders including peritoneal Cr clearance. Further, the predictabilities of serum FGF23 were comparable among renal Cr clearance, Kt/V for urea, and renal phosphate clearance. RRF determined by renal Cr clearance or residual urine volume is an independent negative determinant of serum FGF23 levels in PD patients.

Total Phosphate Elimination is Negatively Associated With Increased Serum Fibroblast Growth Factor 23 Levels in Patients who Undergo Peritoneal Dialysis

“…Theoretically, dietary P intake should increase sFGF23, whereas P elimination and use of P‐binders decrease sFGF23 by reducing P load; and in fact, P‐binders and dietary P restriction are shown to reduce sFGF23 . We recently showed in a cross‐sectional study that sFGF23 was negatively correlated with RKF . In the present study, we showed that at 18‐months, sFGF23 was negatively associated with baseline renal Cr clearance, and total P elimination at baseline was negatively correlated with sFGF23 increase.…”

“…Demographic, clinical, and prescription data at each 6‐month examination were also recorded. Blood, urine, and peritoneal dialysate samples were collected from patients undergoing PD at Kyushu University Hospital every 6 months to evaluate their medical condition, adequacy of dialysis, and peritoneal status . One day before their regular visits, urine and peritoneal dialysate were collected for 24 h at the patients’ homes and the 24 h volumes of urine and peritoneal dialysate were recorded.…”

“…Besides, the effects of clinical interventions, especially those related to PD treatment on sFGF23, have not been fully examined yet. We recently associated several clinical factors with sFGF23 in patients who undergo PD , but were unable to clarify their cause–effect relationships due to the critical drawbacks of cross‐sectional studies.…”

Factors associated with serum soluble inhibitors of Wnt‐β‐catenin signaling (sclerostin and dickkopf‐1) in patients undergoing peritoneal dialysis

“…Blood, 24‐h urine, and peritoneal dialysate samples were collected from patients undergoing PD at Kyushu University Hospital every 6 months to evaluate their medical condition, adequacy of dialysis, and peritoneal status . Demographic, clinical, and prescription data at each 6 month examination were also recorded based on the guidelines .…”

Positive association of residual kidney function with hemoglobin level in patients on peritoneal dialysis independent of endogenous erythropoietin concentration

“…Blood, 24-h urine, and peritoneal dialysate samples were collected from PD patients at least every 6 months to evaluate their dialysis and peritoneal status as well as medical condition [11]. Demographic, clinical, and prescription data at each 6-monthly examination were also recorded based on the guidelines [12].…”