Studies of acute effects of insulin-like growth factors I and II in human fat cells.
The acute metabolic effects and receptor binding of insulin-like growth factors (IGFs) I and II were studied in human adipose tissue. The IGFs inhibited fat cell glycerol release and stimulated adipocyte 3-O-methylglucose transport and adipose tissue glucose oxidation as effectively as did insulin, but the biological potencies of the IGFs, on a molar basis, were 600-1000 times less than that of insulin. The insulin dose-response curve for antilipolysis gradually shifted to the left in the presence of submaximally and maximally effective IGF-I concentrations, whereas no additive response was found when fat cells were incubated with maximally effective concentrations of insulin and the IGFs. Adipocyte [125I]IGF-I and -II binding was low and was not inhibited by excess unlabeled IGF. In contrast, IGF-I inhibited [125I]insulin binding with a molar potency 1600 times lower than that of native insulin. In adipose tissue segments obtained from patients with untreated noninsulin-dependent diabetes mellitus, IGF-I and insulin inhibited glycerol release in a normal way. Conversely, neither insulin nor IGF-I increased the rate of glucose oxidation significantly above the nonhormone-stimulated level. We conclude that human fat cells lack specific cell surface IGF-binding sites. However, the IGFs definitely produce acute insulin-like effects in the human adipocyte, which seems to be mediated via the insulin receptor.
D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism; D000328:Adult; D001665:Binding Sites / Q000187:drug effects; D003924:Diabetes Mellitus, Type 2 / Q000473:pathology; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D011972:Receptor, Insulin / Q000378:metabolism; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000494:pharmacology*
D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D011972:Receptor, Insulin; D005947:Glucose