title: Differential effects of IGF-I, IGF-II and insulin in human preadipocytes and adipocytes--role of insulin and IGF-I receptors.
abstract: We compared insulin and IGF effects in adipocytes expressing IR (insulin receptors), and preadipocytes expressing IR and IGF-IR (IGF-I receptors). Treatment of adipocytes with insulin, IGF-II or IGF-I resulted in phosphorylation of IR. Order of potency was insulin>IGF-II>IGF-I. In preadipocytes IR, IGF-IR and insulin/IGF-I hybrid receptors (HR) were detected. Treatment of preadipocytes with IGF-I and IGF-II 10(-8)M resulted in activation of IGF-IR and IR whereas insulin was more potent in activating IR, with no effect on IGF-IR. In adipocytes glucose transport was 100-fold more sensitive to insulin than to IGFs and the maximal effect was higher with insulin. In preadipocytes glucose accumulation and DNA synthesis was equally sensitive to insulin and IGFs but the maximal effect was higher with IGF-I. In conclusion, insulin and IGF-I activate their cognate receptors and IGF-I also HR. IGF-II activates IR, IGF-IR and HR. Insulin and IGF-I are partial agonists to each other's receptors.
authors.affiliation: Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology and Linköping Diabetes Research Centre, Linköping, Sweden. karolina.back@liu.se
authors.forename: Karolina
authors.initials: K
authors.lastname: Bäck
authors.forename: Cecilia
authors.initials: C
authors.lastname: Brännmark
authors.forename: Peter
authors.initials: P
authors.lastname: Strålfors
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Arnqvist
mesh_terms: D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D004261:DNA Replication; D005947:Glucose / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D007328:Insulin / Q000494:pharmacology* / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D010766:Phosphorylation; D011485:Protein Binding; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism
chemical_list: D007328:Insulin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin; D005947:Glucose; D013936:Thymidine