IGF-I and IGF binding proteins in diabetes-related kidney growth.

The kidney is a site of insulin-like growth factor I (IGF-I) production and IGF-I mediates effects on kidney growth and function. Diabetes is associated with kidney growth in man and the rat and, in the latter, commences within 48 h of induction of diabetes. Levels of kidney IGF-I are increased during the first 2-3 days of diabetes and this is at least partially due to increased production. Additionally, IGF-I binding is increased in diabetic rat kidney, due to increased binding to the IGF-I receptor and induction of proximal tubular binding protein expression. These changes are attenuated in prepubertal rats suggesting hormonal regulation. Further studies suggest that the changes are partly GH-dependent but independent of direct sex steroid effects. As kidney growth has been implicated in the subsequent development of diabetic nephropathy, further exploration of the close association between diabetes-related kidney growth and IGF-I accumulation may lead to an improved understanding of this complication.