The Insulin-Like Growth Factor System and Neurological Complications in Diabetes

The IGF system plays vital roles in neuronal development,metabolism, regeneration and survival. It consists ofIGF-I, IGF-II, insulin, IGF-I-receptor, and those of IGF-IIand insulin as well as IGF-binding proteins. In the lastdecades it has become clear that perturbations of the IGFsystem play important roles in the pathogenesis of diabeticneurological complications. In the peripheral nervous systemIGF-I, insulin, and C-peptide particularly in type 1 diabetesparticipate in the development of axonal degenerativechanges and contributes to impaired regenerative capacities.These abnormalities of the IGF system appear to beless pronounced in type 2 diabetes, which may in part accountfor the relatively milder neurological complicationsin this type of diabetes. The members of the IGF systemalso provide anti-apoptotic effects on both peripheral andcentral nervous system neurons. Furthermore, both insulinand C-peptide and probably IGF-I possess gene regulatorycapacities on myelin constituents and axonal cytoskeletalproteins. Therefore, replenishment of various members ofthe IGF system provides a reasonable rational for preventionand treatment of diabetic neurological complications.