Submitted on April 16, 2008
Revised on July 22, 2008
Accepted on July 23, 2008
Effects of Hyperinsulinemia on Hepatic Metalloproteinases and their Tissue Inhibitors
Guenther Boden1*, WeiWei Song2, Karen Kresge2, Maria Mozzoli2, and Peter Cheung2
1 Temple University Hospital
2 Temple University School of Medicine
* To whom correspondence should be addressed. E-mail: bodengh{at}tuhs.temple.edu.
To gain insight into the pathogenesis of hepatic fibrosis/cirrhosis related to obesity/insulin resistance, we have examined the effects of euglycemic-hyperinsulinemia on three matrix metalloproteinases (MMP-2, MMP-9 and MT1-MMP) and on two major tissue inhibitors of MMPs (TIMP-1 and TIMP-2) in rat liver. Four hours of hyperinsulinemia (1.6 nmol/l) decreased hepatic MMP-2 mRNA (by RT-PCR) by ~ 60%, pro-MMP-2 mass by ~ 50%, MMP-2 mass by ~ 75% (by Western blots) and the gelatinolytic activity of MMP-2 (by gelatin zymography) by ~ 60%. MMP-9 and MT1-MMP were similarly reduced by ~ 55% and ~ 65%, respectively. In contrast, TIMP-1 and TIMP-2 concentrations (by ELISA) increased 2.2 and 1.4-fold, respectively. Hyperinsulinemia also increased insulin receptor substrate-1/2 (IRS-1/2) associated phosphoinositide 3 kinase (PI3K) and the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK-1/2) but had no effect on phosphorylation of c-jun NH2 terminal kinase-1 (JNK-1), JNK-2/3 or p38 mitogen-activated kinase (p38 MAPK). We conclude that obesity/insulin resistance related hyperinsulinemia shifts the MMP/TIMP balance towards reduction of extracellular matrix degradation and thus may promote the development of hepatic fibrosis.
