title: Time-course analysis of 3-epi-25-hydroxyvitamin D3 shows markedly elevated levels in early life, particularly from vitamin D supplementation in preterm infants.
abstract: BACKGROUND
  An epimeric form of 25-hydroxyvitamin D3 (25(OH)D3) has recently been detected in clinical samples, with relatively high levels in infants. Little is known on 3-epi-25(OH)D3 formation and physiological function. Our objective was to study dynamics of 3-epi-25(OH)D3 formation during infancy.
  
  
  METHODS
  25(OH)D3 and 3-epi-25(OH)D3 levels were measured by liquid chromatography-tandem mass spectrometry in 22 preterm (aged 34-37 wk), 15 early preterm (aged <34 wk), and 118 term infants up to 2 y of age. All infants were prescribed vitamin D 400 IU/day after the first week of life.
  
  
  RESULTS
  At birth, 3-epi-25(OH)D3 levels were 3 (1-7) nmol/l, <10% of total 25(OH)D3. From the second week to 3 mo of age, both 25(OH)D3 and 3-epi-25(OH)D3 increased, with highest 3-epi-25(OH)D3 contribution in early preterm infants (up to 55% of total 25(OH)D3 vs. 36% in term infants, P < 0.0001). After 3 mo of age, 3-epi-25(OH)D3 normalized to <10% in all infants.
  
  
  CONCLUSIONS
  At birth, all infants showed low contribution of 3-epi-25(OH)D3, increasing the week after starting vitamin D supplementation, until 3 mo of age. Highest levels of 3-epi-25(OH)D3 were found in early preterm infants, supporting the hypothesis that hepatic immaturity plays a role in 3-epi-25(OH)D3 formation.
authors.affiliation: Department of Pediatrics, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: Nina
authors.initials: N
authors.lastname: Ooms
authors.affiliation: Department of Clinical Chemistry, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: Henny
authors.initials: H
authors.lastname: van Daal
authors.affiliation: Department of Clinical Chemistry, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: Antonius M
authors.initials: AM
authors.lastname: Beijers
authors.affiliation: Department of Pediatrics, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: G Peter J M
authors.initials: GP
authors.lastname: Gerrits
authors.affiliation: Department of Pediatrics, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: Ben A
authors.initials: BA
authors.lastname: Semmekrot
authors.affiliation: Department of Clinical Chemistry, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: Johannes M W
authors.initials: JM
authors.lastname: van den Ouweland
mesh_terms: D002112:Calcifediol / Q000378:metabolism*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D014807:Vitamin D / Q000008:administration & dosage*
chemical_list: D014807:Vitamin D; D002112:Calcifediol