title: 25(OH)D2 half-life is shorter than 25(OH)D3 half-life and is influenced by DBP concentration and genotype.
abstract: BACKGROUND
  There is uncertainty over the equivalence of vitamins D2 and D3 to maintain plasma 25-hydroxyvitamin D (25(OH)D).
  
  
  OBJECTIVE
  The objective of the study was to compare the plasma half-lives of 25(OH)D2 and 25(OH)D3 in two distinct populations with different dietary calcium intake and 25(OH)D status.
  
  
  METHODS
  Healthy men (aged 24 and 39 y), resident in The Gambia (n = 18) or the United Kingdom (n = 18) participated in the study.
  
  
  METHODS
  The intervention included an oral tracer dose of deuterated-25(OH)D2 and deuterated-25(OH)D3 (both 40 nmol). Blood samples were collected over 33 days.
  
  
  METHODS
  25(OH)D2 and 25(OH)D3 plasma half-lives, concentrations of 25(OH)D, and vitamin D binding protein (DBP) and DBP genotypes were measured.
  
  
  RESULTS
  25(OH)D2 half-life [mean (SD)] [13.9 (2.6) d] was shorter than 25(OH)D3 half-life [15.1 (3.1) d; P = .001] for countries combined, and in Gambians [12.8 (2.3) d vs 14.7 (3.5) d; P < .001], but not in the United Kingdom [15.1 (2.4) d vs 15.6 (2.5) d; P = .3]. 25(OH)D concentration was 69 (13) and 29 (11) nmol/L (P < .0001), and the DBP concentration was 259 (33) and 269 (23) mg/L (P = .4) in The Gambia and United Kingdom, respectively. Half-lives were positively associated with plasma DBP concentration for countries combined [25(OH)D2 half-life: regression coefficient (SE) 0.03 (0.01) d per 1 mg/L DBP, P = .03; 25(OH)D3 half-life: 0.04 (0.02) d, P = .02] and in Gambians [25(OH)D2 half-life: 0.04 (0.01) d; P = .02; 25(OH)D3 half-life: 0.06 (0.02) d, P = .01] but not in UK participants. The DBP concentration × country interactions were not significant. DBP Gc1f/1f homozygotes had shorter 25(OH)D2 half-lives compared with other combined genotypes (P = .007) after correction for country.
  
  
  CONCLUSIONS
  25(OH)D2 half-life was shorter than 25(OH)D3 half-life, and half-lives were affected by DBP concentration and genotype. The stable isotope 25(OH)D half-life measurements provide a novel tool to investigate vitamin D metabolism and vitamin D expenditure and aid in the assessment of vitamin D requirements.
authors.affiliation: Medical Research Council Human Nutrition Research (K.S.J., S.A., D.H., A.P., I.S.), Cambridge CB1 9NL, United Kingdom; Medical Research Council Keneba (K.S.J., A.P.), The Gambia; Clinic and Laboratory of Experimental Medicine and Endocrinology (R.B.) and Laboratory for Translational Genetics (D.L.), Katholieke Universiteit, B-3000 Leuven, Belgium; and Vesalius Research Center (D.L.), VIB, Katholieke Universiteit, B-3000, Leuven, Belgium.
authors.forename: K S
authors.initials: KS
authors.lastname: Jones
authors.forename: S
authors.initials: S
authors.lastname: Assar
authors.forename: D
authors.initials: D
authors.lastname: Harnpanich
authors.forename: R
authors.initials: R
authors.lastname: Bouillon
authors.forename: D
authors.initials: D
authors.lastname: Lambrechts
authors.forename: A
authors.initials: A
authors.lastname: Prentice
authors.forename: I
authors.initials: I
authors.lastname: Schoenmakers
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3 / Q000097:blood*; D015652:25-Hydroxyvitamin D 2 / Q000097:blood* / Q000493:pharmacokinetics; D000328:Adult; D002112:Calcifediol / Q000097:blood* / Q000493:pharmacokinetics; D002136:Calcium, Dietary / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D000072501:Cytochrome P450 Family 27; D003903:Deuterium; D005714:Gambia; D005838:Genotype; D006801:Humans; D016014:Linear Models; D008297:Male; D008954:Models, Biological; D010281:Parathyroid Hormone / Q000235:genetics / Q000378:metabolism; D006113:United Kingdom; D014809:Vitamin D-Binding Protein / Q000235:genetics* / Q000378:metabolism; D065668:Vitamin D3 24-Hydroxylase / Q000235:genetics / Q000378:metabolism; D014815:Vitamins / Q000097:blood / Q000493:pharmacokinetics; D055815:Young Adult
chemical_list: D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D014809:Vitamin D-Binding Protein; D014815:Vitamins; D015652:25-Hydroxyvitamin D 2; D015650:24,25-Dihydroxyvitamin D 3; D003577:Cytochrome P-450 Enzyme System; D003903:Deuterium; C508522:CYP27C1 protein, human; D000072501:Cytochrome P450 Family 27; C585549:CYP24A1 protein, human; D065668:Vitamin D3 24-Hydroxylase; D002112:Calcifediol