title: Urinary and dialysate losses of vitamin D-binding protein in children on chronic peritoneal dialysis.
abstract: BACKGROUND
  Vitamin D deficiency is widely prevalent in chronic kidney disease [CKD] patients. The aim of our study was to determine whether losses of vitamin D binding protein [VDBP] in urine and dialysate contribute to circulating 25-hydroxyvitamin D [25OHD] levels in chronic peritoneal dialysis [PD] patients.
  
  
  METHODS
  Dialysate, serum, and urine VDBP levels were measured in 16 children on PD and compared with serum and urine VDBP in ten CKD4-5 patients. Serum VDBP levels were correlated with total circulating 25OHD and peritoneal VDBP losses.
  
  
  RESULTS
  The mean age of the study population was 9.4 ± 3.8 years and the median time on dialysis 7.5 (1-18) months. In CKD4-5 patients, urinary VDBP losses were >300-fold higher than seen in age-matched healthy children and correlated with urinary albumin loss (p = 0.0008). There was a significant correlation between serum VDBP and total dialysate and urine losses of VDBP (p = 0.03, r = -0.53). Dialysate VDBP losses correlate with dialysate albumin loss (p = 0.01). VDBP losses in the long daytime dwell were higher than in the overnight drain (p = 0.04). Serum VDBP levels were lower in children with a longer dialysis vintage (p = 0.0004, r = -0.77). In PD patients, the mean total loss of VDBP in dialysate and urine was 1.91 ± 1.6 μmol/day, equivalent to ~7% of the total circulating level of VDBP in healthy controls. There was no correlation between 25(OH)D and VDBP.
  
  
  CONCLUSIONS
  Peritoneal VDBP losses mirror both dialysate and urinary albumin losses, and are associated with a longer dialysis vintage but do not contribute to vitamin D deficiency in children on PD.
authors.affiliation: Renal Unit, Great Ormond Street Hospital for Children NHS, Trust and Institute of Child Health, London, United Kingdom.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Prytuła
authors.forename: David
authors.initials: D
authors.lastname: Wells
authors.forename: Timothy
authors.initials: T
authors.lastname: McLean
authors.forename: Filipa
authors.initials: F
authors.lastname: Balona
authors.forename: Ambrose
authors.initials: A
authors.lastname: Gullett
authors.forename: Craig
authors.initials: C
authors.lastname: Knott
authors.forename: Michelle
authors.initials: M
authors.lastname: Cantwell
authors.forename: Kimberly
authors.initials: K
authors.lastname: Hassen
authors.forename: Sarah
authors.initials: S
authors.lastname: Ledermann
authors.forename: Lesley
authors.initials: L
authors.lastname: Rees
authors.forename: Rukshana
authors.initials: R
authors.lastname: Shroff
mesh_terms: D002648:Child; D015314:Dialysis Solutions / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D010530:Peritoneal Dialysis / Q000009:adverse effects*; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000628:therapy*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014809:Vitamin D-Binding Protein / Q000032:analysis*
chemical_list: D015314:Dialysis Solutions; D014809:Vitamin D-Binding Protein; D014807:Vitamin D; C104450:25-hydroxyvitamin D
references.citation: Pediatr Nephrol. 1995 Dec;9(6):791-2
references.pmid: 8747131
references.citation: J Clin Invest. 1999 Jan;103(2):239-51
references.pmid: 9916136
references.citation: Clin Chim Acta. 2006 Oct;372(1-2):33-42
references.pmid: 16697362
references.citation: Kidney Int. 1992 Jan;41(1):161-5
references.pmid: 1593853
references.citation: Pediatrics. 2009 Mar;123(3):791-6
references.pmid: 19255004
references.citation: J Clin Endocrinol Metab. 1985 Nov;61(5):969-75
references.pmid: 3840175
references.citation: N Engl J Med. 2000 May 18;342(20):1478-83
references.pmid: 10816185
references.citation: J Clin Endocrinol Metab. 2009 Jan;94(1):26-34
references.pmid: 18854395
references.citation: Pediatr Nephrol. 1995 Jun;9(3):278-81
references.pmid: 7632510
references.citation: Am J Physiol Renal Physiol. 2005 Jul;289(1):F8-28
references.pmid: 15951480
references.citation: Miner Electrolyte Metab. 1983 Mar-Apr;9(2):82-6
references.pmid: 6601753
references.citation: J Clin Invest. 1985 Dec;76(6):2420-4
references.pmid: 2416779
references.citation: J Am Soc Nephrol. 2008 Jun;19(6):1239-46
references.pmid: 18337484
references.citation: Circulation. 2008 Oct 21;118(17):1748-57
references.pmid: 18838561
references.citation: Perit Dial Int. 1989;9(4):281-4
references.pmid: 2488382
references.citation: J Clin Invest. 1976 Nov;58(5):1217-22
references.pmid: 1086857
references.citation: Circulation. 2002 Jul 2;106(1):100-5
references.pmid: 12093777
references.citation: N Engl J Med. 2007 Jul 19;357(3):266-81
references.pmid: 17634462
references.citation: Nephron. 1984;36(2):111-3
references.pmid: 6607420
references.citation: Bone Miner. 1992 Jun;17(3):389-98
references.pmid: 1623332
references.citation: Pediatr Nephrol. 2007 Jul;22(7):1014-20
references.pmid: 17380351
references.citation: Cell. 1999 Feb 19;96(4):507-15
references.pmid: 10052453
references.citation: J Clin Invest. 1984 Dec;74(6):1966-71
references.pmid: 6549014
references.citation: Lancet. 1977 Sep 24;2(8039):629-32
references.pmid: 71448
references.citation: J Am Soc Nephrol. 2005 May;16(5):1494-500
references.pmid: 15772249
references.citation: Kidney Int. 2007 Jan;71(1):31-8
references.pmid: 17091124
references.citation: Clin Nephrol. 1988;30 Suppl 1:S59-63
references.pmid: 3141094
references.citation: Pediatr Nephrol. 2010 Sep;25(9):1607-20
references.pmid: 20393752
references.citation: Am J Clin Nutr. 2008 Aug;88(2):582S-586S
references.pmid: 18689406
references.citation: Nephrol Dial Transplant. 2008 Aug;23(8):2552-7
references.pmid: 18344239