title: The phosphorylation status of insulin-like growth factor-binding protein-1 in prepubertal obese children.
abstract: OBJECTIVE
  We measured the total and nonphosphorylated insulin-like growth factor-binding protein (IGFBP)-1 concentrations in obese children to determine the effect of obesity on the status of IGFBP-1 phosphorylation. We also measured the serum levels of insulin, total and free IGF-I, and IGFBP-3 to investigate their relationships to the IGFBP-1 phosphorylation status in obese subjects.
  
  
  METHODS
  Nineteen prepubertal obese and 15 age-matched control children were included in the study. The serum levels of total and nonphosphorylated IGFBP-1 were determined by noncompetitive RIAs.
  
  
  RESULTS
  The serum levels of total and nonphosphorylated IGFBP-1 were significantly lower in the obese group (48.7+/-5.6 microgram/l, P<0.001 and 11.1+/-1.9 microgram/l, P<0.01 respectively) than in the controls (86.7+/-9.0 microgram/l and 28.8+/-6.2 microgram/l respectively). However, the ratio of nonphosphorylated IGFBP-1 to total IGFBP-1 did not differ significantly between the obese and control groups. The circulating free IGF-I level was significantly higher in the obese children than in the controls (P<0.05), while the serum levels of insulin, total IGF-I and IGFBP-3 were not significantly different between the two groups. A stepwise regression analysis of the combined group revealed that only the total IGFBP-1 level was an independent predictor of the free IGF-I concentration (P<0.001).
  
  
  CONCLUSIONS
  The present study shows that both total and nonphosphorylated IGFBP-1 concentrations are decreased in obese children and the increased free IGF-I level in obese children is related to the reduced total IGFBP-1 level, but unrelated to the change in the IGFBP-1 phosphorylation status.
authors.affiliation: Department of Pediatrics, University of Tsukuba, Tsukuba, Japan. tkamoda@md.tsukuba.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Kamoda
authors.forename: H
authors.initials: H
authors.lastname: Saitoh
authors.forename: S
authors.initials: S
authors.lastname: Nakahara
authors.forename: M
authors.initials: M
authors.lastname: Inudoh
authors.forename: T
authors.initials: T
authors.lastname: Hirano
authors.forename: A
authors.initials: A
authors.lastname: Matsui
mesh_terms: D002648:Child; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D009765:Obesity / Q000097:blood*; D010766:Phosphorylation; D011627:Puberty; D012044:Regression Analysis
chemical_list: D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I