title: FGF-23 and sFRP-4 in chronic kidney disease and post-renal transplantation.
abstract: BACKGROUND
  The phosphatonins fibroblast growth factor-23 (FGF-23) and FRP-4 are inhibitors of tubular phosphate reabsorption that may play a role in the hyperphosphatemia associated with chronic kidney disease (CKD) or in the hypophosphatemia associated with renal transplants.
  
  
  METHODS
  Plasma FGF-23, FRP-4, phosphorus and parathyroid hormone were measured in patients at all stages of CKD. Phosphate regulation of FGF-23 and secreted frizzled related protein-4 (sFRP-4) was examined in end-stage renal disease patients in the presence and absence of therapeutic phosphate binder usage. In renal transplant patients, plasma FGF-23, sFRP-4 and phosphorus concentrations were determined before and 4-5 days after transplantation.
  
  
  RESULTS
  Plasma FGF-23 correlated with creatinine clearance (r2 = -0.584, p < 0.0001) and plasma phosphorus (r2 = 0.347, p < 0.001) in CKD patients and with plasma phosphorus (r2 = 0.448, p < 0.001) in end-stage renal disease patients. Phosphate binder withdrawal increased FGF-23 levels. In kidney transplant patients, dramatic decreases in FGF-23 (-88.8 +/- 5.4%) and phosphorus (-64 +/- 10.2%) were observed by 4-5 days post-transplantation. In patients with post-transplant hypophosphatemia, FGF-23 levels correlated inversely with plasma phosphorus (r2 = 0.661, p < 0.05). sFRP-4 levels did not change with creatinine clearance or hyperphosphatemia in CKD or end-stage renal disease patients, and no relation was noted between post-transplant sFRP-4 levels and hypophosphatemia.
  
  
  CONCLUSIONS
  In CKD, FGF-23 levels rose with decreasing creatinine clearance rates and increasing plasma phosphorus levels, and rapidly decreased post-transplantation suggesting FGF-23 is cleared by the kidney. Residual FGF-23 may contribute to the hypophosphatemia in post-transplant patients.
authors.affiliation: Renal Division, Washington University School of Medicine, St. Louis, Mo. 63110, USA.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Pande
authors.forename: Cynthia S
authors.initials: CS
authors.lastname: Ritter
authors.forename: Marcos
authors.initials: M
authors.lastname: Rothstein
authors.forename: Karen
authors.initials: K
authors.lastname: Wiesen
authors.forename: John
authors.initials: J
authors.lastname: Vassiliadis
authors.forename: Rajiv
authors.initials: R
authors.lastname: Kumar
authors.forename: Susan C
authors.initials: SC
authors.lastname: Schiavi
authors.forename: Eduardo
authors.initials: E
authors.lastname: Slatapolsky
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Brown
mesh_terms: D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D017674:Hypophosphatemia / Q000097:blood / Q000378:metabolism*; D007676:Kidney Failure, Chronic / Q000097:blood / Q000378:metabolism*; D016030:Kidney Transplantation; D007684:Kidney Tubules / Q000378:metabolism; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000097:blood / Q000378:metabolism; D011183:Postoperative Complications / Q000097:blood; D011518:Proto-Oncogene Proteins / Q000097:blood*; D000094742:Secreted Frizzled-Related Proteins
chemical_list: D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors; D010281:Parathyroid Hormone; D010710:Phosphates; D011518:Proto-Oncogene Proteins; C000717427:FGF23 protein, human; C118723:SFRP4 protein, human; D000094742:Secreted Frizzled-Related Proteins