title: Free insulin-like growth factor 1 in the vitreous fluid of diabetic patients with proliferative diabetic retinopathy: a case-control study.
abstract: The aim of the study was to evaluate the vitreous levels of free insulin-like growth factor 1 (IGF-1) in patients with proliferative diabetic retinopathy (PDR). For this, a total of 36 diabetic patients with PDR (group A) and 28 non-diabetic patients (group B) in whom a vitrectomy was performed were compared. Both groups were matched by age, sex and serum-free IGF-1. In a subgroup of diabetic patients (n =21) and non-diabetic patients (n =13), vitreous and serum total IGF-1, IGF-binding protein 1 (IGFBP-1) and IGFBP-3 were also determined. Serum and vitreous levels of free IGF-1, total IGF-1, IGFBP-1 and IGFBP-3 were measured by immunological methods. Vitreal proteins were assessed by a turbidimetric method and adjusted for vitreous haemoglobin. Vitreous levels of free IGF-1 were elevated in group A (median, 0.16 ng/ml; range 0.06-0.57 ng/ml) in comparison with group B (median, 0.12 ng/ml; range 0.06-0.22 ng/ml; P <0.001); however, after adjusting for vitreal proteins, free IGF-1 levels were significantly lower in group A in comparison with group B [0.05 ng/mg (0.01-0.45 ng/mg) versus 0.15 ng/mg (0.07-0.66 ng/mg); P <0.001]. The relatively lower free IGF-1 level observed in group A could not be attributed to differences in the distribution of intravitreous IGFBP-1 and IGFBP-3 in relation to total IGF-1. Notably, the contribution of free IGF-1 to total IGF-1 in vitreous fluid was 10% in group A and 42% in group B; these percentages largely exceed that obtained in serum (<1%). Our results suggest that although there is an enhancement of intravitreous free IGF-1 in diabetic patients due to serum diffusion, a deficit in its intraocular production also exists. In addition, these findings support the concept that intraocular-produced free IGF-1 plays a relevant role in retinal homoeostasis.
authors.affiliation: Division of Endocrinology, Hospital General Vall d'Hebron, Barcelona 08035, Spain. rsimo@hg.vhebron.es
authors.forename: Rafael
authors.initials: R
authors.lastname: Simó
authors.forename: Cristina
authors.initials: C
authors.lastname: Hernández
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Segura
authors.forename: José
authors.initials: J
authors.lastname: García-Arumí
authors.forename: Laura
authors.initials: L
authors.lastname: Sararols
authors.forename: Rosa
authors.initials: R
authors.lastname: Burgos
authors.forename: Ana
authors.initials: A
authors.lastname: Cantón
authors.forename: Jordi
authors.initials: J
authors.lastname: Mesa
mesh_terms: D016022:Case-Control Studies; D003930:Diabetic Retinopathy / Q000378:metabolism*; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000032:analysis; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000032:analysis; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D012107:Research Design; 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