Carnitine palmitoyltransferase-1 up-regulation by PPAR-β/δ prevents lipid-induced endothelial dysfunction

Abstract

Fatty acids cause endothelial dysfunction involving increased ROS (reactive oxygen species) and reduced NO (nitric oxide) bioavailability. We show that in MAECs (mouse aortic endothelial cells), the PPARβ/δ (peroxisome- proliferator-activated receptor β/δ) agonist GW0742 prevented the decreased A23187-stimulated NO production, phosphorylation of eNOS (endothelial nitric oxide synthase) at Ser1177 and increased intracellular ROS levels caused by exposure to palmitate in vitro. The impaired endothelium-dependent relaxation to acetylcholine in mouse aorta induced by palmitate was restored by GW0742. In vivo, GW0742 treatment prevented the reduced aortic relaxation, phosphorylation of eNOS at Ser1177, and increased ROS production and NADPH oxidase in mice fed on a high-fat diet. The PPARβ/δ antagonist GSK0660 abolished all of these protective effects induced by GW0742. This agonist enhanced the expression of CPT (carnitine palmitoyltransferase)-1. The effects of GW0742 on acetylcholine- induced relaxation in aorta and on NO and ROS production in MAECs exposed to palmitate were abolished by the CPT-1 inhibitor etomoxir or by siRNA targeting CPT-1. GW0742 also inhibited the increase in DAG (diacylglycerol), PKCα/βII (protein kinase Cα/βII) activation, and phosphorylation of eNOS at Thr495 induced by palmitate in MAECs, which were abolished by etomoxir. In conclusion, PPARβ/δ activation restored the lipid-induced endothelial dysfunction by up-regulation of CPT-1, thus reducing DAG accumulation and the subsequent PKC-mediated ROS production and eNOS inhibition.