Control of Vascular Cell Proliferation and Migration by PPAR-γ

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Abstract
Compared with nondiabetic subjects, type 2 diabetic individuals are at an increased risk for coronary artery disease and coronary restenosis after angioplasty or stenting. Increased proliferation and migration of vascular smooth muscle cells (VSMCs) contribute importantly to the formation of both atherosclerotic and restenotic lesions. Therefore, pharmaceutical interventions targeting proteins that regulate VSMC growth or movement are a promising new approach to treat diabetes-associated cardiovascular disease. Peroxisome proliferator—activated receptor-γ (PPAR-γ) is a member of the nuclear receptor superfamily that, when activated by thiazolidinedione (TZD) insulin sensitizers, regulates a host of target genes. All of the major cells in the vasculature express PPAR-γ, including endothelial cells, VSMCs, and monocytes/macrophages. PPAR-γ is present in intimal macrophages and VSMCs in early human atheromas. In an animal model of vascular injury, PPAR-γ levels are substantially elevated in the neointima that forms after mechanical injury of the endothelium. Recent experimental studies provide evidence that PPAR-γ may function to protect the vasculature from injury. Cell culture studies have shown that TZD PPAR-γ ligands inhibit both the proliferation and migration of VSMCs. These antiatherogenic activities of PPAR-γ may also occur in vivo,because TZDs inhibit lesion formation in several animal models. PPAR-γligands may also protect the vasculature indirectly by normalizing metabolic abnormalities of the diabetic milieu that increase cardiovascular risk. Activation of PPAR-γ, newly defined in vascular cells, may be a useful approach to protect the vasculature in diabetes.