Insulin-like growth factor type 1—friend or foe?

Clinical trials have demonstrated a significant correlation between poor glucose control and a high incidence of diabetic complications.1 Consequently, an intensive insulin treatment regimen is recommended to counteract the deleterious effects of chronic exposure to high levels of glucose. However, insulin is known to positively regulate the production of insulin-like growth factor type 1 (IGF-1) and evidence presented in this issue of theBJO (p 725) demonstrates a clear association between high levels of IGF-1 and the advancement of diabetic retinal disease.

IGF-1 may affect the progression of diabetic retinopathy directly by its mitogenic action2 3 on retinal endothelial cell growth, or indirectly via an increased cell survival because of the antiapoptotic properties of IGF-1.4 The influence of IGF-1 on the induction of other growth factors—for example, vascular endothelial growth factor,5 IGF-1 mediated regulation of glucose metabolism,6 the altered responsiveness of cells to growth factors exposed to high concentrations of glucose,7-9 and the mitogenicity of insulin for REC2 may also be of significance. The concentrations of IGF-1 that are reported in the study presented here are well within the range that are known to promote endothelial cell growth in vitro …