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LE Fogel, N Alikacem, JJ Alappatt; Elevated IGF-1 and VEGF in Transgenic Diabetic Rat Model . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1307.
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Purpose: To show that levels of serum and retinal insulin growth factor (IGF-1) and vascular endothelial growth factor (VEGF) are higher in insulin-treated transgenic diabetic rats than in normal or untreated transgenic diabetic rats. Methods: Normal rats, untreated diabetic rats and diabetic rats treated with intensive insulin therapy (starting at 8 weeks of age) were sacrificed at specific time points. Blood was collected, enucleation was performed, retinas were harvested and animals were euthanized. ELISA was performed to measure serum and retinal IGF-1 and VEGF. Results: Normal rats produced constant levels of serum and retinal IGF-1 as well as retinal VEGF from 8-24 weeks of age. Untreated diabetic rats showed a continuous decrease in retinal and serum IGF-1 levels starting at 9 weeks of age and continuing to 24 weeks. They showed a gradual increase in retinal VEGF from 10 to 24 weeks of age. Treated diabetic rats showed a continuous increase in serum and retinal IGF-1 as well as retinal VEGF after initiation of intensive insulin therapy. The ELISA kit utilized could not detect serum VEGF in these samples. Although a statistically significant correlation was not found between serum IGF-1 and retinal VEGF (p=0.103), a statistically significant positive correlation was found between retinal IGF-1 and retinal VEGF (p=0.0231). Conclusion: Insulin-treated diabetic rats had serum and retinal IGF-1 as well as retinal VEGF levels higher than those found in normal rats and untreated diabetic rats. Although both treated and untreated diabetic rats showed an increase in retinal VEGF, the levels in treated diabetic rats were 1.5 times greater. A positive correlation between retinal IGF-1 and retinal VEGF exists.
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