Exenatide exerts direct protective effects on endothelial cells through the AMPK/Akt/eNOS pathway in a GLP-1 receptor-dependent manner

Glucagon-like peptide-1 (GLP-1) may have direct favorable effects on cardiovascular system. The aim of this study was to investigate the effects of the GLP-1 analog exenatide on improving coronary endothelial function in patients with type 2 diabetes and to investigate the underlying mechanisms. The newly diagnosed type 2 diabetic subjects were enrolled and given either lifestyle intervention or lifestyle intervention plus exenatide treatment. After 12-wk treatment, coronary flow velocity reserve (CFVR), an important indicator of coronary endothelial function, was improved significantly, and serum levels of soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) were remarkably decreased in the exenatide treatment group compared with the baseline and the control group. Notably, CFVR was correlated inversely with hemoglobin A(1c) (Hb A(1c)) and positively with high-density lipoprotein cholesterol (HDL-C). In human umbilical vein endothelial cells, exendin-4 (a form of exenatide) significantly increased NO production, endothelial NO synthase (eNOS) phosphorylation, and GTP cyclohydrolase 1 (GTPCH1) level in a dose-dependent manner. The GLP-1 receptor (GLP-1R) antagonist exendin (9-39) or GLP-1R siRNA, adenylyl cyclase inhibitor SQ-22536, AMPK inhibitor compound C, and PI3K inhibitor LY-294002 abolished the effects of exendin-4. Furthermore, exendin-4 reversed homocysteine-induced endothelial dysfunction by decreasing sICAM-1 and reactive oxygen species (ROS) levels and upregulating NO production and eNOS phosphorylation. Likewise, exendin (9 -39) diminished the protective effects of exendin-4 on the homocysteine-induced endothelial dysfunction. In conclusion, exenatide significantly improves coronary endothelial function in patients with newly diagnosed type 2 diabetes. The effect may be mediated through activation of AMPK/PI3K-Akt/eNOS pathway via a GLP-1R/cAMP-dependent mechanism.Chinese National 973 Program [2012CB517502]; National Natural Sciences Foundation of China [81570692, 81400798, 81400767, 81401142, 81270858]; Beijing Natural Sciences Foundation of China [7163233]; Specialized Research Fund for the Doctoral Program of Higher Education [20120001120076, 20120001120069, 20120001120063]SCI(E)PubMedARTICLEtpho66@bjmu.edu.cn11E947-E95731