Actions of Peroxisome Proliferator–Activated Receptors–γ Agonists Explaining a Possible Blood Pressure–Lowering Effect

The metabolic syndrome is a cluster of disturbances such as type 2 diabetes mellitus, hypertension, central obesity, dyslipidemia, and others for which insulin resistance and compensatory hyperinsulinemia have been proposed to be the underlying disorders. Several possible mechanisms linking insulin resistance and compensatory hyperinsulinemia with hypertension have been described, such as renal sodium reabsorption enhancement, sympathetic nervous system activation, and blunted insulin-mediated vasodilation caused by endothelial dysfunction. Peroxisome proliferator-activated receptors-gamma agonists or thiazolidinediones (TZD) are a class of agents for the treatment of type 2 diabetes mellitus that act through improvement of insulin sensitivity. In parallel to their antihyperglycemic action, these drugs were found to exert beneficial effects on other components of the metabolic syndrome. For example all TZD have been shown to reduce blood pressure (BP) levels in both animal and human studies. In addition a considerable number of in vitro and in vivo studies report actions of TZD on the cardiovascular system that could explain this blood pressure-lowering effect of TZD, such as restoration of blunted endothelium-mediated vasodilation, attenuation of sympathetic overactivity, inhibition of intracellular Ca(2+) increase, and proliferation of vascular smooth muscle cells and others. This review summarizes the current evidence about these actions of TZD that could positively influence BP, representing possible mechanisms of BP amelioration.