title: Vitamin D Binding Protein Is Not Involved in Vitamin D Deficiency in Patients with Chronic Kidney Disease.
abstract: OBJECTIVE
  This study was designed to evaluate vitamin D status with separate determination of 25-OH D2 and 25-OH D3 and its relationship to vitamin D binding protein (VDBP) in patients with chronic kidney disease (CKD) and long-term haemodialysis patients (HD).
  
  
  METHODS
  45 CKD patients, 103 HD patients, and 25 controls (C) were included. Plasma vitamin D concentrations were determined using chromatography and VDBP in serum and urine in CKD using enzyme immunoassay.
  
  
  RESULTS
  Plasma vitamin D levels were lower in CKD (30.16 ± 16.74 ng/mL) and HD (18.85 ± 15.85 ng/mL) versus C (48.72 ± 18.35 ng/mL), P < 0.0001. 25-OH D3 was the dominant form of vitamin D. Serum VDBP was higher in CKD (273.2 ± 93.8 ug/mL) versus C (222 ± 87.6 ug/mL) and HD (213.8 ± 70.9 ug/mL), P = 0.0003. Vitamin D/VDBP ratio was the highest in C and the lowest in HD; however, there was no correlation between vitamin D and VDBP. Urinary concentration of VDBP in CKD (0.25 ± 0.13 ug/mL) correlated with proteinuria (r = 0.43, P = 0.003).
  
  
  CONCLUSIONS
  Plasma levels of vitamin D are decreased in CKD patients and especially in HD patients. 25-OH D3 was the major form of vitamin D. Despite urinary losses of VDBP, CKD patients had higher serum VDBP concentrations, indicating compensatory enhanced production. Vitamin D binding protein is not involved in vitamin D deficiency.
authors.affiliation: Institute of Medical Biochemistry and Laboratory Diagnostics, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, U Nemocnice 499/2, 128 01 Prague, Czech Republic.
authors.forename: Marta
authors.initials: M
authors.lastname: Kalousova
authors.affiliation: Haemodialysis Centre, University Hospital Hradec Kralove, Sokolská 581, 500 05 Hradec Kralove, Czech Republic.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Dusilova-Sulkova
authors.affiliation: Department of Nephrology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, U Nemocnice 499/2, 128 08 Prague, Czech Republic.
authors.forename: Oskar
authors.initials: O
authors.lastname: Zakiyanov
authors.affiliation: Institute of Medical Biochemistry and Laboratory Diagnostics, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, U Nemocnice 499/2, 128 01 Prague, Czech Republic.
authors.forename: Milada
authors.initials: M
authors.lastname: Kostirova
authors.affiliation: Haemodialysis Centre, University Hospital Hradec Kralove, Sokolská 581, 500 05 Hradec Kralove, Czech Republic.
authors.forename: Roman
authors.initials: R
authors.lastname: Safranek
authors.affiliation: Department of Nephrology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, U Nemocnice 499/2, 128 08 Prague, Czech Republic.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Tesar
authors.affiliation: Institute of Medical Biochemistry and Laboratory Diagnostics, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, U Nemocnice 499/2, 128 01 Prague, Czech Republic.
authors.forename: Tomas
authors.initials: T
authors.lastname: Zima
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood; D000328:Adult; D000368:Aged; D002112:Calcifediol / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000150:complications / Q000473:pathology; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000150:complications / Q000473:pathology; D014809:Vitamin D-Binding Protein / Q000097:blood*
chemical_list: D014809:Vitamin D-Binding Protein; D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2; D002112:Calcifediol