Circulating IGF-I and its protective role in the pathogenesis of diabetic angiopathy

Poor glycaemic control in type 1 diabetes is associated with elevated serum IGFBP-1 levels and reduced rather than elevated serum IGF-I levels. Increa sing age is accompanied by a further decrease in serum IGF-I levels as well as an increase in IGFBP-1 levels in adult diabetic type 1 and type 2 subje cts. This is especially observed in diabetic type 1 subjects with manifest microvascular complications. IGFBP-I has been proposed as one of the IGF-I inhibitors in the serum of diabetics. Lowered IGF-I and increased IGFBP-1 l evels in the blood may thus result in decreased IGF-I bioavailability at th e tissue level. We hypothesize that the premature and progressive decline in serum IGF-I bi oactivity during ageing in diabetics ultimately results in insufficient pro tective effects by IGF-I in the kidneys, eyes and neurones, and thus the pr ogression of diabetic microvascular complications. If this hypothesis is pr oven to be right, treatment of diabetic patients with IGF-I (eventually com plexed to IGFBPs) as an adjunct to insulin might prevent and not worsen the development of diabetic microvascular complications.