Plasminogen activator inhibitor-1 synthesis in the human hepatoma cell line Hep G2. Metformin inhibits the stimulating effect of insulin.
High plasma plasminogen activator inhibitor-1 (PAI-1) activity is associated with insulin resistance and is correlated with hyperinsulinemia. The cellular origin of plasma PAI-1 in insulin resistance is not known. The hepatoma cell line Hep G2 has been shown to synthesize PAI-1 in response to insulin. The aim of this study was to analyze the insulin-mediated response of PAI-1 and lipid synthesis in Hep G2 cells after producing an insulin-resistant state by decreasing insulin receptor numbers. The effect of metformin, a dimethyl-substituted biguanide, known to lower plasma insulin and PAI-1 levels in vivo was concomitantly evaluated. Preincubation by an 18-h exposure of Hep G2 cells to 10(-7) M insulin aimed at reducing the number of insulin receptors, was followed by a subsequent 24-h stimulation with 10(-9) M insulin. The decrease in insulin receptors was accompanied as expected, by a reduction in [14C]acetate incorporation, an index of lipid synthesis, whereas PAI-1 secretion and PAI-1 mRNA expression were enhanced. The addition of metformin did not modify the effect of insulin on insulin receptors or [14C]acetate incorporation. In contrast, the drug (10(-4) M) inhibited insulin-mediated PAI-1 synthesis. The results indicate that PAI-1 synthesis in presence of insulin is markedly increased in down-regulated cells, and that metformin inhibits this effect by acting at the cellular level. These in vitro data are relevant with those found in vivo in insulin-resistant patients. Hep G2 cells may be a suitable model to study PAI-1 regulation in response to hyperinsulinemia.
Laboratory of Hematology, Centre Hospitalier Universitaire Timone, Marseille, France.
F
F
Anfosso
N
N
Chomiki
M C
MC
Alessi
P
P
Vague
I
I
Juhan-Vague
D000085:Acetates / Q000378:metabolism; D002250:Carbon Radioisotopes; D006528:Carcinoma, Hepatocellular; D002478:Cells, Cultured; D015342:DNA Probes; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D007329:Insulin Antagonists / Q000494:pharmacology*; D016753:Interleukin-10 / Q000494:pharmacology; D007700:Kinetics; D008113:Liver Neoplasms; D008687:Metformin / Q000494:pharmacology*; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis* / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D011972:Receptor, Insulin / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014471:Umbilical Veins
D000085:Acetates; D002250:Carbon Radioisotopes; D015342:DNA Probes; D007328:Insulin; D007329:Insulin Antagonists; D017395:Plasminogen Activator Inhibitor 1; D012334:RNA, Neoplasm; D011994:Recombinant Proteins; C008147:insulin, iodo-; D016753:Interleukin-10; D008687:Metformin; D011972:Receptor, Insulin; D013755:Tetradecanoylphorbol Acetate