title: Type 1 collagen marker of bone turnover, insulin-like growth factor, and leptin in dichorionic twins with discordant birth weight.
abstract: OBJECTIVE
  We investigated the relationship between IGF-I-IGF binding protein (IGFBP)-1 and leptin levels with type 1 collagen markers of bone turnover in dichorionic twins with or without discordant birth weight of 20% or greater.
  
  
  METHODS
  Maternal and cord bloods were collected from gestational age-matched dichorionic twins with (n = 16) or without (n = 16) discordant birth weight. The samples were assayed for cross-linked carboxyl terminal telopeptide (ICTP, a marker of bone resorption) and propeptide (PICP, a marker of bone formation) of type I collagen, leptin, IGF-I, and IGFBP-1 by RIA.
  
  
  RESULTS
  The intrauterine growth-restricted (IUGR) twins of the discordant group had higher fetal ICTP (P < 0.001) and IGFBP-1 (P < 0.001) levels, whereas PICP (P < 0.001), IGF-I (P < 0.001), and leptin (P < 0.001) were lower than the cotwins with normal weight (AGA). In contrast, concentrations of IGF-I, IGFBP-1, ICTP, PICP, and leptin were comparable between concordant twin pairs. Leptin levels were positively correlated with PICP (r = 0.61; P < 0.001) and negatively with ICTP (r = -0.57; P < 0.001) in concordant and AGA twins but not in IUGR twins. In IUGR twins, IGF-I had positive association with PICP (r = 0.76; P < 0.001) and negative association with ICTP (r= -0.76; P < 0.001), whereas IGFBP-1 was negatively correlated with PICP levels (r = -0.65; P < 0.01). No such association was found in concordant and AGA twins.
  
  
  CONCLUSIONS
  These data suggest that IUGR twins had high bone turnover, which is independent of maternal factors and perhaps may be due to altered IGF axis.
authors.affiliation: Academic Unit of Obstetrics and Gynecology, St Mary's Hospital for Women and Children, Manchester, United Kingdom.
authors.forename: Rekha
authors.initials: R
authors.lastname: Bajoria
authors.forename: Suren R
authors.initials: SR
authors.lastname: Sooranna
authors.forename: Ratna
authors.initials: R
authors.lastname: Chatterjee
mesh_terms: D015415:Biomarkers; D001724:Birth Weight; D016723:Bone Remodeling; D016022:Case-Control Studies; D024042:Collagen Type I / Q000097:blood*; D005260:Female; D047109:Fetal Development; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D020738:Leptin / Q000097:blood*; D008297:Male; D010446:Peptide Fragments / Q000097:blood; D011247:Pregnancy; D011347:Procollagen / Q000097:blood; D014429:Twins, Dizygotic / Q000097:blood* / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; C032231:IGFBP1 protein, human; D018970:Insulin-Like Growth Factor Binding Protein 1; D020738:Leptin; D010446:Peptide Fragments; D011347:Procollagen; C042813:procollagen type I carboxy terminal peptide; D007334:Insulin-Like Growth Factor I