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Cardiovascular Research 2007 73(4):841-848; doi:10.1016/j.cardiores.2006.12.006
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Copyright © 2006, European Society of Cardiology

Insulin augments matrix metalloproteinase-9 expression in monocytes

Arne Fischoeder1, Heike Meyborg1, Dietger Stibenz, Eckart Fleck, Kristof Graf and Philipp Stawowy*

Department of Medicine/Cardiology, Deutsches Herzzentrum Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany

* Corresponding author. Tel.: +49 30 4593 2413; fax: +49 30 4593 2415. Email address: stawowy{at}dhzb.de

Objective: Insulin resistance and hyperinsulinemia are major causes of cardiovascular morbidity and mortality. Matrix metalloproteinases (MMPs), highly expressed in activated mononuclear cells in vulnerable atherosclerotic lesions, are the main proteolytic enzymes controlling plaque stability. The aim of this study was to investigate the regulation of monocyte MMP-9 by insulin.

Methods and results: Stimulation of MMP-9 expression by insulin was time- and concentration-dependent in human monocytic THP-1 cells. Inhibition of insulin receptor (IR) maturation via inhibition of its activating convertase furin with the pharmacological furin-inhibitor decanoyl-RVKR-chloromethylketone, as well as blocking of IGF-1R function with a IGF-1R blocking antibody, demonstrated that insulin mediates increases in MMP-9 via IR activation. Inhibition of insulin's "metabolic" phosphatidylinositol 3-kinase signaling with wortmannin (50 nmol/L) or LY294002 (2.5 µmol/L) did not prevent insulin-dependent MMP-9 induction. In contrast inhibition of insulin's "mitogenic" Ras-Raf-mitogen-activated protein kinase–kinase pathways with PD98059 (15 µmol/L) or U0126 (2 µmol/L) inhibited insulin-induced MMP-9 gelatinolytic activity in THP-1 cells. Likewise, PD98059 inhibited insulin augmented MMP-9 levels in primary human monocytes, whereas wortmannin had no effect.

Conclusion: This study demonstrates that insulin can induce MMP-9 via mitogenic signaling pathways in monocytes, whereas phosphatidylinositol 3-kinase-dependent signaling, typically altered in insulin resistance, is not required. Induction of MMP-9 by insulin may potentially contribute to a pro-inflammatory state and the increased cardiovascular morbidity and mortality in type 2 diabetics.

KEYWORDS Matrix metalloproteinases; Inflammation; Type 2 diabetes; Atherosclerosis; Furin; Insulin resistance

1 Equally contributing authors.

Time for primary review 17 days


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