Shift of serum osteocalcin components between cord blood and blood at day 5 of life.
Vitamin K deficiency is a relatively common condition in neonates. However, the role of vitamin K in neonatal bone metabolism remains to be determined. Osteocalcin (OC) is the most abundant noncollagenous protein in bone, and is regulated to be gamma-carboxylated by vitamin K. In this study, we measured gamma-carboxylated osteocalcin (Gla-OC) and non- or undercarboxylated osteocalcin (Glu-OC) separately, and examined the effects of vitamin K on osteocalcin metabolism. Eighteen full-term healthy neonates were enrolled in this study. In the cord and d-5 blood samples, the OC levels were determined by three different methods to examine the intact OC by immunoradiometric assay (IRMA), Gla-OC, and Glu-OC. Serum vitamin K fractions, hepaplastin test, and type 1 procollagen carboxyl extension peptide were also determined. Urine samples were also collected from the first voiding and on d 5 to determine urinary pyridinoline, deoxypyridinoline, and gamma-carboxylated glutamic acid. Serum levels of phylloquinone (PK) and menaquinone (MK)-4 increased on d 5 following vitamin K administration and increased intake in breast milk and/or formula. The OC levels determined by IRMA did not change between cord and d-5 blood samples, but the Gla-OC level increased remarkably and Glu-OC reduced to a negligible level. OC in cord blood is mainly Glu-OC, and Glu-OC is replaced with Gla-OC within 5 d of life after vitamin K supplement. The IRMA assay fails to distinguish Gla-OC from Glu-OC and caution is needed to estimate bone turnover with this method in the perinatal period.
Shimizu
Nobuhiko
N
Department of Developmental Medicine (Pediatrics), Osaka University Graduate School of Medicine, Osaka, Japan.
Shima
Masaaki
M
Hirai
Haruhiko
H
Nakajima
Shigeo
S
Nishimura
Kumi
K
Yamaoka
Kanji
K
Okada
Shintaro
S
D000328:Adult; D000596:Amino Acids / Q000652:urine; D001842:Bone and Bones / Q000378:metabolism; D005312:Fetal Blood / Q000737:chemistry*; D006801:Humans; D015592:Immunoradiometric Assay; D007231:Infant, Newborn / Q000097:blood* / Q000652:urine; D015675:Osteocalcin / Q000097:blood*; D011499:Protein Processing, Post-Translational; D014812:Vitamin K / Q000008:administration & dosage / Q000097:blood; D010837:Vitamin K 1 / Q000652:urine; D024482:Vitamin K 2 / Q000652:urine
D000596:Amino Acids; D015675:Osteocalcin; D024482:Vitamin K 2; D014812:Vitamin K; C015484:pyridinoline; D010837:Vitamin K 1; C036020:deoxypyridinoline