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.

GIP as a Potential Therapeutic Target for Atherosclerotic Cardiovascular Disease–A Systematic Review

“…Both GIP and GLP-1 have been reported to exert direct effects on the cardiovascular system in addition to pancreatic beta cells [12,16]. Indeed, a number of preclinical studies, including ours, have shown the cardiovascular protective effects of native incretins and incretin-based agents partly in a glucose-lowering independent manner [17][18][19][20][21][22][23][24][25][26][27][28], whose observations were consistent with the recent cardiovascular outcome trials demonstrating that GLP-1RAs significantly reduced the cardiovascular and renal events in high-risk type 2 diabetic patients compared with placebo [29][30][31][32][33]. Furthermore, DPP-4 inhibitors have also been shown to improve surrogate markers of atherosclerotic CVD in several clinical trials [34][35][36], although their effects on CV hard events were neutral in various cardiovascular outcome trials [37][38][39][40][41].…”

Liraglutide treatment improves the coronary microcirculation in insulin resistant Zucker obese rats on a high salt diet

“…Multiple experimental studies have demonstrated that GLP-1 agonist treatment has anti-inflammatory effects on endothelial cells and monocytes through inhibition of inflammatory cascades involving vascular cell adhesion molecules and intracellular adhesion molecules [35][36][37]. In addition, a recent clinical study suggest that LIRA treatment decreases endoplasmic reticulum stress in endothelial cells and restores insulin-mediated endothelial NO production in patients with T2DM [38].…”

Anti-inflammatory and atheroprotective properties of glucagon

“…1 Glucagon was continuously infused to mice with osmotic pumps implanted in the dorsal subcutaneous tissue (Alzet minipump 1002; Cupertino, CA, USA). 10 The pumps were replaced every 14 days to avoid glucagon degradation. After 4 weeks of treatment with vehicle or glucagon, mice were euthanized by overdose of isoflurane, and blood and vascular samples were collected for biochemical, histopathological, and reverse-transcription polymerase chain reaction (RT-PCR) analyses.…”

“…Systolic blood pressure and pulse rates were measured using the non-invasive tail-cuff method as previously described. 10…”

“…Atherosclerotic plaques on the aortae were evaluated as previously described. 10 Aortae from the aortic sinus to the bifurcation of common iliac arteries were longitudinally dissected and stained with oil red O to evaluate en face plaque formation (plaque area). Cyrosections of the aortic sinus were stained with oil red O and picro-sirius red (PSR) and immunostained with anti-MOMA-2 antibody (Abcam Japan, Chuo, Tokyo, Japan; Product ID: ab33451; RRID:AB_776518; dilution: 1:60) to assess lipid deposition (plaque volume), intraplaque collagen content, and intraplaque macrophage accumulation levels, respectively.…”