Nutritional regulation of IGF-I and IGFBPs

IGF-I concentrations in serum are decreased in states of chronic undernutrition or when food intake is restricted. A variety of mechanisms including decreased GH receptor binding, post-receptor resistance to GH, and reduced steady-state mRNA for IGF-I contribute to this decrease. In addition, dietary manipulation causes profound alterations in the IGF binding proteins, including reduced IGFBP-3, the principal serum carrier of IGF-I. Under some adverse nutritional conditions IGFBP-1 and IGFBP-2 are increased. Concomitant with changes in IGFBPs, IGF-I volume of distribution is increased and clearance is hastened. It seems likely that nutrition related changes in IGFBPs contribute significantly to alterations in IGF-I concentration and actions.