Antiatherogenic effects of liraglutide in hyperglycemic apolipoprotein E-null mice via AMP-activated protein kinase-independent mechanisms

Abstract

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) exert potent glucose-lowering effects without increasing risks for hypoglycemia and weight gain. Preclinical studies have demonstrated direct antiatherogenic effects of GLP-1RAs in normoglycemic animal models; however, the underlying mechanisms in hyperglycemic conditions have not been fully clarified. Here we aimed to elucidate the role of AMP-activated protein kinase (AMPK) in antiatherogenic effects of GLP-1RAs in hyperglycemic mice. Streptozotocin-induced hyperglycemic apolipoprotein E-null mice were treated with vehicle, low-dose liraglutide (17 nmol·kg-1·day-1), or high-dose liraglutide (107 nmol·kg-1·day-1) in experiment 1 and the AMPK inhibitor dorsomorphin, dorsomorphin + low-dose liraglutide, or dorsomorphin + high-dose liraglutide in experiment 2. Four weeks after treatment, aortas were collected to assess atherosclerosis. In experiment 1, metabolic parameters were similar among the groups. Assessment of atherosclerosis revealed that high-dose liraglutide treatments reduced lipid deposition on the aortic surface and plaque volume and intraplaque macrophage accumulation at the aortic sinus. In experiment 2, liraglutide-induced AMPK phosphorylation in the aorta was abolished by dorsomorphin; however, the antiatherogenic effects of high-dose liraglutide were preserved. In cultured human umbilical vein endothelial cells, liraglutide suppressed tumor necrosis factor-induced expression of proatherogenic molecules; these effects were maintained under small interfering RNA-mediated knockdown of AMPKα1 and in the presence of dorsomorphin. Conversely, in human monocytic U937 cells, the anti-inflammatory effects of liraglutide were abolished by dorsomorphin. In conclusion, liraglutide exerted AMPK-independent antiatherogenic effects in hyperlipidemic mice with streptozotocin-induced hyperglycemia, with the possible involvement of AMPK-independent suppression of proatherogenic molecules in vascular endothelial cells.