Nutritional regulation of insulin-like growth factor-I.
Several lines of evidence indicate that in the human, insulin-like growth factor-I (IGF-I) is nutritionally regulated. Both energy and protein availability are required for maintenance of IGF-I. Measurements of serum IGF-I constitute a sensitive means for monitoring the response of acutely ill patients to nutritional intervention. Serum IGF-I may also serve as a marker for evaluation of nutritional status. Our findings and those of others in animal models suggest that nutrients influence synthesis and action of IGF-I and its binding proteins (IGFBPs) at multiple levels. In fasting, liver growth hormone (GH) binding is decreased, providing one explanation for decreased IGF-I. In protein restriction, GH receptors are maintained, but there is evidence for a postreceptor defects. The latter results from pretranslational and translational defects. Amino acid availability to the hepatocytes is essential for IGF-I gene expression. Protein malnutrition not only decreases IGF-I production rate, but also enhances its serum clearance and degradation. Finally, there is evidence for selective organ resistance to the growth-promoting effects of IGF-I in protein-restricted rats.
D000818:Animals; D004044:Dietary Proteins / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009748:Nutrition Disorders / Q000378:metabolism; D009747:Nutritional Physiological Phenomena / Q000502:physiology*; D011986:Receptors, Somatotropin / Q000378:metabolism
D004044:Dietary Proteins; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone