The effects of wortmannin, a potent inhibitor of phosphatidylinositol 3-kinase, on insulin-stimulated glucose transport, GLUT4 translocation, antilipolysis, and DNA synthesis.
PI 3-kinase, an enzyme that selectively phosphorylates the 3-position of the inositol ring, is acutely activated by insulin and other growth factors. The physiological significance of PI 3-kinase activation and, more specifically, its role in insulin action is an area under intense investigation. In this study, we have examined the role of PI 3-kinase activation in mediating selected metabolic and mitogenic effects of insulin employing the fungal metabolite wortmannin, a potent inhibitor of PI 3-kinase activity. In isolated rat and cultured 3T3-L1 adipocytes, wortmannin inhibited insulin-stimulated glucose transport (IC50 = 9 nM) without a significant effect on basal transport. Insulin-stimulated translocation of GLUT4 in isolated rat adipocytes was markedly inhibited by wortmannin. Wortmannin had no effect on either basal or insulin-stimulated glucose utilization in L6 myocytes, a skeletal muscle cell line in which GLUT1 is the predominant transporter isoform. Wortmannin also partially antagonized the antilipolytic effect of insulin on adenosine deaminase-stimulated lipolysis in isolated rat adipocytes. Furthermore, wortmannin caused a significant reduction in insulin-stimulated DNA synthesis in Fao rat hepatoma cells. We conclude that PI 3-kinase activation is necessary for maximum insulin-stimulated glucose transport, translocation of GLUT4, antilipolysis and DNA synthesis.
Evans
J L
JL
Diabetes Department, Sandoz Research Institute, Sandoz Pharmaceuticals Corporation, East Hanover, NJ 07936, USA.
Honer
C M
CM
Womelsdorf
B E
BE
Kaplan
E L
EL
Bell
P A
PA
D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004261:DNA Replication / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology / Q000502:physiology*; D008066:Lipolysis / Q000187:drug effects; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D009183:Mycotoxins / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014407:Tumor Cells, Cultured; D000077191:Wortmannin
D000730:Androstadienes; D000935:Antifungal Agents; D004791:Enzyme Inhibitors; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009183:Mycotoxins; C495693:Slc2a4 protein, mouse; C495694:Slc2a4 protein, rat; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D005947:Glucose; D000077191:Wortmannin