GLP-1(7-36) inhibits atherosclerosis progression in ApoE-/- mouse aorta by lowering expressions of CD36 and ACAT1 in foam cells

Abstract

Objective To investigate whether glucagon-like peptide-1 (GLP-1) (7-36) inhibits the progression of aortic atherosclerotic plaque in ApoE knockout (ApoE-/-) mice fed with high-fat diet and the effect of GLP-1 (7-36) on the expressions of CD36 and acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT1) in macrophage-derived foam cells. Methods Forty male ApoE-/- mice (6-8 weeks old, weighing 18-20 g) were randomized equally into normal diet group, high-fat diet (model) group, GLP-1 (7-36) group, and GLP-1 (7-36)+Exendin (9-39) group. The area of the atherosclerotic plaque in the aortic root of the mice was determined using HE staining, oil red O staining, and immunohistochemical staining with CD36 and ACAT1 antibodies. In the cell experiment, the macrophages (RAW264.7 cells) were induced with oxidized low-density lipoprotein (ox-LDL) and treated with different concentrations of GLP-1 (7-36), alone or in combination with Exendin (9-39). The expressions of CD36 and ACAT1 mRNAs and proteins in the cells was detected using RT-PCR and Western blotting, respectively. The levels of total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) in the cells were detected using high-performance liquid chromatography, and immunofluorescence analysis was performed to detect the expressions of CD36 and ACAT1 receptor proteins. Results Compared with the control mice, ApoE-/- mice on high-fat diet showed significantly higher expression levels of CD36 and ACAT1 at both the mRNA and protein levels in the aortic atherosclerotic plaques (P < 0.05). CD36 and ACAT1 expressions in the plaques were significantly lowered by treatment of the mice with GLP-1 (7-36) (P < 0.05); the expression levels of CD36 and ACAT1 were significantly higher in GLP-1+Exendin group than in GLP-1 group (P < 0.05). HE and oil red O staining showed that in the model group, the mean proportion of the plaque area in the aortic intimal area was (30.3±3.8)%, which was significantly lowered to (15.1±4.3)% in GLP-1 group (P < 0.05); the ratio of the plaque area was (25.7±3.4)% in GLP-1+Exendin group, where significantly more numerous atherosclerotic plaques were observed below the intima as compared with GLP-1 group (P < 0.05). GLP-1 (7-36) significantly decreased the percentage of CD36- and ACAT1-positive cells in the aorta of the mice (P < 0.05). Conclusion GLP-1 can reduce the accumulation of intracellular cholesterol by inhibiting the expression of CD36 and ACAT1 to suppress the foaming of macrophages, and thus inhibits the formation of atherosclerotic plaques.

Keywords

• glucagon-like peptide-1
• atherosclerosis
• acat1
• cd36