Effects of Insulin and Free Fatty Acids on Matrix Metalloproteinases

To investigate if increased activation of matrix metalloproteinases (MMPs) may contribute to the large cardiovascular risk associated with obesity-related insulin resistance, we examined the effects of physiologically elevated levels of insulin and free fatty acid (FFA) on three MMPs and their physiologic inhibitors (tissue inhibitors of MMP [TIMPs]) in aortic tissue of male rats during euglycemic-hyperinsulinemic clamping. Hyper-insulinemia increased the active forms of MMP-2 (similar to sixfold), MMP-9 (similar to 13-fold), and membrane type 1-MMP (MT1-MMP; similar to eightfold) (all Western blots), and the gelatinolytic activity (zymography) of MMP-2 (twofold); it did not affect TIMP-1 and TIMP-2. FFA augmented the insulin-mediated increases in MMP-2 (from similar to six- to similar to 11-fold), MMP-9 (from similar to 13- to similar to 23-fold), MTI-MMP (from similar to eight- to similar to 20-fold), and MMP-2 gelatinolytic activity (from two- to threefold). FFA also increased JNK and p38 mitogen-activated protein kinase activities. The insulin and FFA-induced hyperactivity of three proatherogenic MMPs in vascular tissues may promote degradation of extracellular matrix over time, leading to thinning of atherosclerotic capsules and acute vascular problems.