Role of glucagon-like peptide-1 in vascular endothelial dysfunction

Abstract

The present study has been undertaken to investigate the effect of exendin-4 (a glucagon-like peptide-1 agonist) in diabetes mellitus (DM) and hyperhomocysteinemia (HHcy)-induced vascular endothelial dysfunction (VED). Streptozotocin (55 mg kg⁻¹, iv, once) and methionine (1.7% w/w, po, 4 weeks) were administered to rats to produce DM (serum glucose <i>></i>200 mg dl⁻¹) and HHcy (serum homocysteine <i>></i>10 μ<i style="">M</i>) respectively. VED was assessed using isolated aortic ring preparation, microscopy of thoracic aorta, and serum nitrite/nitrate concentration. Serum TBARS concentration was estimated to assess oxidative stress. Atorvastatin has been employed as standard agent. Exendin-4<b> </b>(1 μg kg⁻¹, ip) and atorvastatin (30 mg kg⁻¹, po) treatments significantly attenuated increase in serum glucose and homocysteine but their concentrations remained markedly higher than sham control value. Exendin-4<b> </b>and atorvastatin treatments markedly prevented DM and HHcy-induced (i) attenuation of acetylcholine-induced endothelium-dependent relaxation, (ii) impairment of vascular endothelial lining, (iii) decrease in serum nitrite/nitrate concentration, and (iv) increase in serum TBARS. However, this ameliorative effect of exendin-4 has been prevented by L-NAME (25 mg kg^-1, ip), an inhibitor of NOS. It may be concluded that exendin-4 may activate eNOS due to activation of GLP-1 and consequently reduce oxidative stress to improve vascular endothelial dysfunction.