title: Changes in circulating 25-hydroxyvitamin D according to vitamin D binding protein genotypes after vitamin D₃ or D₂supplementation.
abstract: BACKGROUND
  It is not known whether genetic variation in the vitamin D binding protein (DBP) influences 25-hydroxyvitamin D levels [25(OH)D] after vitamin D supplementation. We aimed to investigate the changes of total 25(OH)D, 25(OH)D₃ and 25(OH)D₂ in a Thai cohort, according to type of vitamin D supplement (vitamin D₃ or D₂) and DBP genotype, after receiving vitamin D₃ or D₂ for 3 months.
  
  
  METHODS
  Thirty-nine healthy subjects completed the study. All subjects received 400  IU of either vitamin D₃ or D₂, plus a calcium supplement, every day for 3 months. Total serum 25(OH)D, 25(OH)D₃ and 25(OH)D₂ were measured by LC-MS/MS. Individual genotyping of rs4588 in the DBP gene was performed using real-time PCR.
  
  
  RESULTS
  Vitamin D₃ supplementation of 400  IU/d increased 25(OH)D₃ significantly (+16.2 ± 4.2 nmol/L, p <0.001). Vitamin D₂ (400 IU/d) caused increased 25(OH)D₂ levels (+22.0 ± 2.11 nmol/L, p <0.001), together with a decrease of 25(OH)D₃ (-14.2 ± 2.0 nmol/L, p <0.001). At 3 month, subjects in vitamin D3 group tended to have higher total 25(OH)D levels than those in vitamin D₂ (67.8 ± 3.9 vs. 61.0 ± 3.0 nmol/L; p = 0.08). Subjects were then classified into two subgroups: homozygous for the DBP rs4588 C allele (CC), and the rest (CA or AA). With D₃ supplementation, subjects with CA or AA alleles had significantly less increase in 25(OH)D₃ and total 25(OH)D when compared with those with the CC allele. However, no difference was found when the supplement was vitamin D₂.
  
  
  CONCLUSIONS
  Genetic variation in DBP (rs4588 SNP) influences responsiveness to vitamin D₃ but not vitamin D₂.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Rama 6 Rd, Rajthevi, Bangkok 10400, Thailand. hataikarnn@hotmail.com
authors.forename: Hataikarn
authors.initials: H
authors.lastname: Nimitphong
authors.forename: Sunee
authors.initials: S
authors.lastname: Saetung
authors.forename: Suwannee
authors.initials: S
authors.lastname: Chanprasertyotin
authors.forename: La-Or
authors.initials: LO
authors.lastname: Chailurkit
authors.forename: Boonsong
authors.initials: B
authors.lastname: Ongphiphadhanakul
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000097:blood; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000097:blood; D002853:Chromatography, Liquid; D019587:Dietary Supplements; D004872:Ergocalciferols / Q000008:administration & dosage* / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D053719:Tandem Mass Spectrometry; D014808:Vitamin D Deficiency / Q000097:blood; D014809:Vitamin D-Binding Protein / Q000235:genetics*; D055815:Young Adult
chemical_list: D002136:Calcium, Dietary; D004872:Ergocalciferols; D014809:Vitamin D-Binding Protein; D002762:Cholecalciferol
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