Abstract
Little is known about interventions that may prevent predegenerative changes in the diabetic retina. This study tested the hypothesis that immediate, systemic treatment with an insulin-like growth factor (IGF)-1 analog can prevent abnormal accumulations of type 1 IGF receptor, and phospho-Akt (Thr 308) immunoreactivity in predegenerative retinas of streptozotocin (STZ) diabetic rats. Type 1 IGF receptor immunoreactivity increased approximately 3-fold in both inner nuclear layer (INL) and ganglion cell layer (GCL) in retinas from STZ rats versus nondiabetic controls. Phospho-Akt (Thr 308) immunoreactivity increased 5-fold in GCL and 8-fold in INL of STZ rat retinas. In all cases, immunoreactive cells were significantly reduced in STZ des(1-3)IGF-1-treated versus STZ rats. Preliminary results suggested that vascular endothelial growth factor (VEGF) levels may also be reduced. Hyperglycemia/failure of weight gain in diabetic rats continued despite systemic des(1-3)IGF-1. These data show that an IGF-1 analog can prevent early retinal biochemical abnormalities implicated in the progression of diabetic retinopathy, despite ongoing hyperglycemia.