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Systemic IGF-I treatment inhibits cell death in diabetic rat retina

Authors
Journal
Journal of Diabetes and its Complications
1056-8727
Publisher
Elsevier
Publication Date
Volume
20
Issue
3
Identifiers
DOI: 10.1016/j.jdiacomp.2005.06.007
Keywords
  • Diabetic Retinopathy
  • Insulin-Like Growth Factor
  • Apoptosis
Disciplines
  • Medicine

Abstract

Abstract Diabetic retinopathy can result in apoptotic cell death of retinal neurons, as well as significant visual loss. It is further known that insulin-like growth factor (IGF) levels are reduced in diabetes and that IGF-I can prevent cell death in many cell types. In this study, we tested the hypothesis that systemic treatment with IGF-I could inhibit death of neuroretinal cells in diabetic rats by examining the expression of proapoptotic markers. In diabetic rat retina, the number of TUNEL-immunoreactive cells increased approximately sixfold in the photoreceptor layer ( P<.001) and eightfold in the inner nuclear layer (INL; P<.001); phospho-Akt (p-Akt; Thr 308) immunoreactivity increased eightfold in the ganglion cell layer (GCL; P<.001) and threefold in the INL ( P<.01). Subcutaneous IGF-I treatment significantly reduced the number of TUNEL ( P<.001) and p-Akt immunoreactive retinal cells ( P<.05) in diabetic rats approximately to the level of the nondiabetic group. Qualitative results showed that caspase-3 and BAD immunoreactivities were also elevated in diabetes and reduced in IGF-I-treated animals. Elevated TUNEL and p-Akt immunoreactivities were localized to distinct cell layers in the retina of diabetic rats. Early intervention with systemic IGF-I reduced the presence of proapoptotic markers indicative of neuroretinal cell death, despite ongoing hyperglycemia and weight loss. The eye is a special sensory organ, and these data show that cell loss in the nervous system, even in uncontrolled diabetes, can be prevented by IGF-I administration.

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