title: Vitreous levels of IGF-I, IGF binding protein 1, and IGF binding protein 3 in proliferative diabetic retinopathy: a case-control study.
abstract: OBJECTIVE
  To evaluate vitreous levels of IGF-I and its binding proteins IGFBP-1 and IGFBP-3 in patients with proliferative diabetic retinopathy (PDR). Because intravitreal proteins are elevated in patients with PDR due to the disruption of the blood-retinal barrier, we have corrected vitreal IGF-I and IGFBPs by total vitreal proteins to avoid this confounding factor.
  
  
  METHODS
  We compared 21 diabetic patients with proliferative retinopathy (group A) and 13 nondiabetic patients (group B) in whom a vitrectomy was performed. Both groups were matched by age, serum IGF-I, IGFBP-1, and IGFBP-3 levels. Serum and vitreous levels of IGF-I, IGFBP-1, and IGFBP-3 were measured by immunological methods. Vitreal proteins were assessed by turbidimetric method.
  
  
  RESULTS
  Vitreal levels of IGF-I were elevated in group A (median 1.35 ng/ml [range 0.3-8.7]) in comparison with group B (median 0.25 ng/ml [range 0-1.38]), P<0.001. After adjusting by vitreal proteins [ratio IGF-I (ng/ml)/protein (mg/ml)], the differences remain significant (P<0.005). Vitreal levels of IGFBP-1 and IGFBP-3 were also elevated in diabetic patients (IGFBP-1: group A, median 1.6 ng/ml [range 0.6-20.7]; group B, median 0.4 ng/ml [range 0.3-1.9], P<0.001. IGFBP-3: group A, median 102.6 ng/ml [range 53.9-350.8]; group B, median 29.0 ng/ml [range 3.2-87.8], P<0.001). However, when the ratio IGFBP/protein was considered, the differences were not significant.
  
  
  CONCLUSIONS
  Intraocular synthesis contributes to elevated vitreous concentrations of IGF-I found in PDR. By contrast, unspecific increase of intravitreal proteins is the main factor explaining the elevated vitreous levels of IGFBP-1 and IGFBP-3 found in diabetic patients.
authors.affiliation: Diabetes Research Unit, Hospital General Universitari Vall d'Hebron, Barcelona, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Burgos
authors.forename: C
authors.initials: C
authors.lastname: Mateo
authors.forename: A
authors.initials: A
authors.lastname: Cantón
authors.forename: C
authors.initials: C
authors.lastname: Hernández
authors.forename: J
authors.initials: J
authors.lastname: Mesa
authors.forename: R
authors.initials: R
authors.lastname: Simó
mesh_terms: D016022:Case-Control Studies; D003930:Diabetic Retinopathy / Q000097:blood / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000032:analysis* / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008875:Middle Aged; D012016:Reference Values; D012044:Regression Analysis; D014821:Vitrectomy; D014822:Vitreous Body / Q000737:chemistry*
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I