title: Serum insulin-like growth factor binding protein-1 (IGFBP-1) phosphorylation status in subjects with and without ischaemic heart disease.
abstract: BACKGROUND
  Insulin-like growth factor binding protein-1 (IGFBP-1) modulates the activity of IGF-I. It exists in serum as phosphorylated and less phosphorylated forms. We wished to measure serum levels of both these forms of IGFBP-1, using a novel assay, in subjects with, or without ischaemic heart disease (IHD).
  
  
  METHODS
  We measured serum concentrations of the phosphorylated and less phosphorylated forms of IGFBP-1 in 75 subjects (36 with and 39 without IHD). Two immunoassays were used, one which detects non-, and less-phosphorylated forms (LpIGFBP-1), and another which specifically detects the serine phosphorylated form of IGFBP-1 (pIGFBP-1).
  
  
  RESULTS
  LpIGFBP-1 concentrations were significantly higher in subjects without IHD than in those with IHD (5.3+/-0.5 microg/L vs. 2.7+/-0.4 microg/L, p<0.001). pIGFBP-1 levels were also significantly higher in subjects without IHD compared to those with IHD (33.3+/-2.0 microg/L vs. 25.3+/-2.2 microg/L, p<0.01). The correlation between LpIGFBP-1 and pIGFBP-1 for all subjects was (r=0.71, p<0.001). This association was stronger in subjects without IHD (r=0.76, p<0.001) than for those with IHD (r=0.60, p<0.001). A significant negative association was observed between IGF-I and the ratio between the two forms (r=-0.45, p<0.0001). Receiver-Operating Characteristic (ROC) curve showed the highest area under the curve for LpIGFBP-1 (0.75) [95% CI: 0.63-0.86] and optimum cut-off value of 2.83 microg/L with 75% sensitivity and 74% specificity.
  
  
  CONCLUSIONS
  We propose that low serum concentrations of IGFBP-1 forms could be a marker of coronary risk, and the LpIGFBP-1:pIGFBP-1 ratio may be an index of biologically active IGF-I.
authors.affiliation: University of Surrey, Guildford GU1 1SU, UK.
authors.forename: Anwar
authors.initials: A
authors.lastname: Borai
authors.forename: Callum
authors.initials: C
authors.lastname: Livingstone
authors.forename: Majid
authors.initials: M
authors.lastname: Ghayour-Mobarhan
authors.forename: Ahmed
authors.initials: A
authors.lastname: Abuosa
authors.forename: Shahida
authors.initials: S
authors.lastname: Shafi
authors.forename: Shweta
authors.initials: S
authors.lastname: Mehta
authors.forename: Alireza
authors.initials: A
authors.lastname: Heidari
authors.forename: Ali
authors.initials: A
authors.lastname: Emadzadeh
authors.forename: Gwen
authors.initials: G
authors.lastname: Wark
authors.forename: Gordon
authors.initials: G
authors.lastname: Ferns
mesh_terms: D000328:Adult; D002318:Cardiovascular Diseases / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007118:Immunoassay / Q000379:methods; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000097:blood / Q000378:metabolism*; D010766:Phosphorylation; D012372:ROC Curve; D012307:Risk Factors; D012694:Serine / Q000737:chemistry
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D012694:Serine