The role of circulating IGF-I: lessons from human and animal models.
Insulin-like growth factors (IGF-I and IGF-II) play a crucial role in regulating cell proliferation and differentiation. The IGFs have mitogenic and antiapoptotic effects on normal and transformed cells. These peptide growth factors are produced by virtually all tissues and act in an endocrine, autocrine, and paracrine fashion. The endocrine form of IGF-I originates mostly (75%) from the liver and IGF-binding proteins regulate its bioactivity. Compared to other peptide growth factors, the IGFs are in abundant supply in circulation. The role of this large reservoir of IGFs has been debated for many years. In the last few years substantial progress has been made in understanding the function of the endocrine IGF-I using new animal models. This review will revisit the IGF system with particular attention to the role of circulating IGF-I in growth regulation, metabolism, and cancer.
Yakar
Shoshana
S
Section on Cellular and Molecular Physiology, Clinical Endocrinology Branch, NIDDK, National Institute of Health, Bethesda, MD 20892, USA. shoshanay@intra.niddk.nih.gov
Wu
Yiping
Y
Setser
Jennifer
J
Rosen
Clifford J
CJ
D000818:Animals; D002454:Cell Differentiation; D002455:Cell Division; D003920:Diabetes Mellitus / Q000097:blood; D006130:Growth Disorders / Q000097:blood; D006706:Homeostasis; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D023421:Models, Animal; D009369:Neoplasms / Q000097:blood
D007334:Insulin-Like Growth Factor I