title: Responsiveness of FGF-23 and mineral metabolism to altered dietary phosphate intake in chronic kidney disease (CKD): results of a randomized trial.
abstract: BACKGROUND
  High fibroblast growth factor-23 (FGF-23) levels are associated with adverse outcomes. We studied the responsiveness of FGF-23 and mineral metabolism to altered dietary phosphate intake in chronic kidney disease (CKD) and healthy control patients.
  
  
  METHODS
  Thirty patients were enrolled: 18 normophosphatemic CKD subjects and 12 healthy controls. The study duration was 21 days with three 7-day dietary interventions; a high phosphate (HP, 2000 mg/day), low phosphate (750 mg/day) and low phosphate plus phosphate binder (aluminum hydroxide, 500 mg thrice daily with meals), with comparable macronutrient content, administered in random sequence. Baseline and weekly fasting morning measurements of FGF-23, serum phosphate (sPO(4)), 1,25-hydroxyvitamin D (1,25 D) and 24-h urinary calcium (uCa) and phosphate (uPO(4)) were collected.
  
  
  RESULTS
  FGF-23 levels were higher in subjects versus controls (72 pg/mL versus 30 pg/mL) at baseline, while sPO(4) remained in the normal range throughout the study. The absolute changes of uPO(4) and uCa for CKD and controls vary according to diet. The absolute changes of FGF-23 and sPO(4) suggest that the effect of the diets might also depend on the CKD status (P-values interaction effect = 0.08 and 0.07, respectively); nonetheless, these changes are evident as a function of dietary interventions, irrespective of CKD status (P-values diet effect = 0.006 and <0.001, respectively).
  
  
  CONCLUSIONS
  FGF-23 levels appear to be responsive to changes in diet in both CKD patients and controls. Further studies are required to determine whether lowering dietary phosphate and thus FGF-23 levels are of long-term benefit in CKD patients, irrespective of sPO(4) levels.
authors.affiliation: Division of Nephrology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Mhairi
authors.initials: M
authors.lastname: Sigrist
authors.forename: Mila
authors.initials: M
authors.lastname: Tang
authors.forename: Monica
authors.initials: M
authors.lastname: Beaulieu
authors.forename: Gabriella
authors.initials: G
authors.lastname: Espino-Hernandez
authors.forename: Lee
authors.initials: L
authors.lastname: Er
authors.forename: Ognjenka
authors.initials: O
authors.lastname: Djurdjev
authors.forename: Adeera
authors.initials: A
authors.lastname: Levin
mesh_terms: D000328:Adult; D000368:Aged; D002118:Calcium / Q000097:blood*; D018592:Cross-Over Studies; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D006887:Hydroxycholecalciferols / Q000652:urine*; D008297:Male; D008875:Middle Aged; D008903:Minerals; D010710:Phosphates / Q000008:administration & dosage* / Q000097:blood / Q000652:urine; D016226:Phosphorus, Dietary / Q000494:pharmacology*; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000652:urine
chemical_list: C000717427:FGF23 protein, human; D006887:Hydroxycholecalciferols; D008903:Minerals; D010710:Phosphates; D016226:Phosphorus, Dietary; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002118:Calcium