Peroxisome proliferator-activated receptors in vascular biology-molecular mechanisms and clinical implications

Peroxisome proliferator-activated receptors (PPAR)alpha, gamma and beta/delta belong to the nuclear receptor family of ligand-activated transcription factors. PPARs heterodimerize with the retinoid X receptor (RXR) and then act as transcription factors to modulate the function of many target genes. PPAR alpha, gamma and beta/delta subtypes have significant differences in their ligand and gene specificities. PPAR alpha is activated by polyunsaturated fatty acids and by fibrate drugs (fenofibrate and gemfibrozil) and controls expression of genes involved in lipid metabolism. PPAR gamma is activated by fatty acid derivatives, such as hydroxyoctadecadienoic acid (HODEs), prostaglandin derivatives, such as 15-deoxy-Delta(12,14)-prostaglandin J(2), and thiazolidinedione (glitazone) drugs, such as pioglitazone and rosiglitazone. PPAR-gamma is a key regulator of glucose homeostasis and adipogenesis. PPAR beta/delta ligands include polyunsaturated fatty acids, prostaglandins and synthetic compounds and stimulate fatty acid oxidation. All PPARs are expressed in vascular cells where they exert antiatherogenic, anti-inflammatory and vasculoprotective actions. Activators of PPAR alpha (fibrates) and PPAR gamma (thiazolidinediones or glitazones) antagonize angiotensin II effects in vivo and in vitro and have cardiovascular antioxidant and anti-inflammatory actions. PPAR agonists slightly reduce blood pressure are cardio-protective and correct vascular structure and endothelial dysfunction in experimental models of hypertension. Because of these beneficial effects, activators of PPARs may have therapeutic potential in the prevention of cardiovascular disease beyond their actions on carbohydrate and lipid metabolism. The present chapter focuses on the role of PPARs in vascular biology and discusses the clinical implications of using PPAR agonists in the management of vascular disease. (c) 2006 Elsevier Inc. All rights reserved.