Liraglutide Lowers Endothelial Vascular Cell Adhesion Molecule-1 in Murine Atherosclerosis Independent of Glucose Levels

Abstract

The authors determined the effect of the GLP-1 receptor agonist liraglutide on endothelial surface expression of vascular cell adhesion molecule (VCAM)-1 in murine apolipoprotein E knockout atherosclerosis. Contrast-enhanced ultrasound molecular imaging using microbubbles targeted to VCAM-1 and control microbubbles showed a 3-fold increase in endothelial surface VCAM-1 signal in vehicle-treated animals, whereas in the liraglutide-treated animals the signal ratio remained around 1 throughout the study. Liraglutide had no influence on low-density lipoprotein cholesterol or glycated hemoglobin, but reduced TNF-α, IL-1β, MCP-1, and OPN. Aortic plaque lesion area and luminal VCAM-1 expression on immunohistology were reduced under liraglutide treatment.

Keywords: ApoE, apolipoprotein E; CEUMI, contrast-enhanced ultrasound molecular imaging; CVD, cardiovascular disease; GLP, glucagon-like peptide; GLP-1R, glucagon-like peptide-1 receptor; GLP-1RA, glucagon-like peptide-1 receptor agonist; HDL-C, high-density lipoprotein cholesterol; HbA1c, glycated hemoglobin; ICAM, intercellular cell adhesion molecule; IL, interleukin; LDL-C, low-density lipoprotein cholesterol; MB, microbubble; MBCtr, control microbubbles; MBVCAM-1, microbubbles targeted to VCAM; MCP, monocyte chemoattractant protein; OPN, osteopontin; TG, triglycerides; TGRL, triglyceride-rich lipoproteins; TNF, tumor necrosis factor; VCAM, vascular cell adhesion molecule; VLDL-C, very low-density lipoprotein cholesterol; atherosclerosis; liraglutide; molecular imaging; ultrasound.

Graphical abstract

Figure 1

Effect of Liraglutide Treatment on Body Weight Percentage change from baseline in body weight of apolipoprotein E^−/− mice after high-fat diet and daily subcutaneous liraglutide or vehicle treatment up to 84 days. Data are mean ± SEM.

Figure 2

Effect of Liraglutide Treatment on Plasma Lipids Plasma triglyceride and cholesterol levels of apolipoprotein E^−/− mice after high-fat diet and daily subcutaneous liraglutide or vehicle treatment for (A) 8 weeks (triglycerides, n = 19-21; cholesterol, n = 14) and (B) 12 weeks (triglycerides, n = 16-19; cholesterol, n = 15) (∗P < 0.05; ∗∗P < 0.01). Data are median (horizontal line), 25% to 75% percentiles (box), and range of values (whiskers). HDL-C = high-density lipoprotein cholesterol; LDL-C = low-density lipoprotein cholesterol; VLDL-C = very low-density lipoprotein cholesterol.

Figure 3

Effect of Liraglutide Treatment on Plasma HbA_1c and Glucose Plasma glycated hemoglobin (HbA_1c) and glucose levels of apolipoprotein E^−/− mice after high-fat diet and daily subcutaneous liraglutide or vehicle treatment for (A) 8 weeks (n = 16-20) and (B) 12 weeks (n = 17-20). Data are mean ± SD. Blood HbA_1c percentage (%) levels shown in (C), and data are median (horizontal line), 25% to 75% percentiles (box), and range of values (whiskers).

Figure 4

Molecular Imaging of the Aortic Arch (A) Fold change of background-subtracted contrast-enhanced ultrasound molecular imaging signal intensity from the aortic arch after injection of MB_Vcam-1 (microbubbles targeted to vascular cell adhesion molecule [VCAM]-1) and MB_Ctr (control) microbubbles (MB) in apolipoprotein E^−/− mice at baseline (no treatment) and after high-fat diet and daily subcutaneous liraglutide or vehicle treatment for 4 weeks (n = 18-20), 8 weeks (n = 17-20), and 12 weeks (n = 15-17) (∗P < 0.05; ∗∗∗P < 0.001). Data are median (horizontal line), 25% to 75% percentiles (box), and range of values (whiskers). (B) Examples of color-coded CEUMI overlaid on anatomic images of the aortic arch illustrating low signal after injection of MB_Ctr in vehicle and liraglutide treated animals (top row), high signal after injection of MB_Vcam-1 in a vehicle treated animal (bottom row left) and low signal after injection of MB_Vcam-1 in a liraglutied treated animal (bottom row right).

Figure 5

Effect of Liraglutide Treatment on Aortic Root Atherosclerotic Plaque Burden Percent of total luminal plaque area at the aortic root of apolipoprotein E^−/− mice after high-fat diet and daily subcutaneous liraglutide or vehicle treatment for (A) 9 weeks (n = 6) and (B) 12 weeks (n = 6) (∗P < 0.05; ∗∗P < 0.005). Data are mean ± SD. Representative image of Masson's trichrome stain of aortic root after (C and D) 8 weeks and (E and F) 12 weeks of high-fat diet and liraglutide or vehicle treatment.

Figure 6

Effect of Liraglutide Treatment on Ascending Aortic Atherosclerotic Plaque Burden Percent of total luminal plaque area in the ascending aorta of apolipoprotein E^−/− mice after high-fat diet and daily subcutaneous liraglutide or vehicle treatment for (A) 8 weeks (n = 6) and (B) 12 weeks (n = 6) (∗P < 0.05; ∗∗P < 0.005). Data are mean ± SD. Representative image of Masson's trichrome stain of aortic root after (C and D) 8 weeks and (E and F) 12 weeks of high-fat diet and liraglutide or vehicle treatment.

Figure 7

Effect of Liraglutide Treatment on Aortic Luminal Interface Expression of VCAM-1 Percentage of endothelial vascular cell adhesion molecule 1 (VCAM-1) immunofluorescent staining of the aortic root and ascending aorta of apolipoprotein E^−/− mice after high-fat diet and daily subcutaneous liraglutide or vehicle treatment for (A) 8 weeks (n = 8-9) and (B) 12 weeks (n = 14-16) (∗P < 0.05; ∗∗P < 0.005; ∗∗∗P < 0.001). Data are mean ± SD. Representative image of endothelial VCAM-1 immunofluorescent staining shown for vehicle (C) and liraglutide (D) treatment.

Figure 8

Effect of Liraglutide Treatment on Plasma Cytokine Levels Plasma cytokine levels of apolipoprotein E^−/− mice after high-fat diet and daily subcutaneous liraglutide or vehicle treatment for (A) 8 weeks (TNF-α, IL-1β, and MCP-1, n = 18-19; OPN, n = 10) and (B) 12 weeks (TNF-α, IL-1β, and MCP-1, n = 13-14; OPN, n = 10) (∗P < 0.05; ∗∗P < 0.01). Data are median (horizontal line), 25% to 75% percentiles (box), and range of values (whiskers). TNF = tumor necrosis factor; IL = interleukin; MCP = monocyte chemoattractant protein.