Peroxisome proliferator-activated receptors and angiogenesis.

The peroxisome proliferator-activated receptors (PPARs) are a group of three nuclear receptor isoforms, PPARalpha, PPARgamma and PPARdelta, encoded by different genes, and they form a subfamily of the nuclear receptor superfamily. The clinical interest in PPARs originates with fibrates and thiazolidinediones, which, respectively, act on PPARalpha and PPARgamma and are used to ameliorate hyperlipidaemia and hyperglycaemia in subjects with type 2 diabetes mellitus (T2DM). PPARs play a central role in these patients due to their ability to regulate the expression of numerous genes involved in glycaemic control, lipid metabolism, vascular tone and inflammation. Abnormal angiogenesis is implicated in several of the long-term complications of diabetes mellitus, characterized by vasculopathy associated with aberrant growth of new blood vessels. This pathological process plays a crucial role in diabetic retinopathy, nephropathy and neuropathy, impaired wound healing and impaired coronary collateral vessel development. In recent years, there has been increasing appreciation of the fact that PPARs might be involved in the molecular mechanisms that regulate angiogenesis through the action of growth factors and cytokines that stimulate migration, proliferation and survival of endothelial cells. During the last few years direct comparative analyses have been performed, using selective PPARs agonists, to clarify the angiogenic properties of the different members of the PPAR family. Lately, the findings provide new information to order to understand the biological, clinical and therapeutic effects of PPARs, and the role of these nuclear receptors in angiogenesis, with potentially important implications for the management of subjects affected by T2DM.