The GLP-1 analogue lixisenatide decreases atherosclerosis in insulin-resistant mice by modulating macrophage phenotype.

AIMS/HYPOTHESIS: Recent clinical studies indicate that glucagon-like peptide-1 (GLP-1) analogues prevent acute cardiovascular events in type 2 diabetes mellitus but their mechanisms remain unknown. In the present study, the impact of GLP-1 analogues and their potential underlying molecular mechanisms in insulin resistance and atherosclerosis are investigated. METHODS: Atherosclerosis development was evaluated in Apoe Irs2 mice, a mouse model of insulin resistance, the metabolic syndrome and atherosclerosis, treated with the GLP-1 analogues lixisenatide or liraglutide. In addition, studies in Apoe Irs2 mice and mouse-derived macrophages treated with lixisenatide were performed to investigate the potential inflammatory intracellular pathways. RESULTS: Treatment of Apoe Irs2 mice with either lixisenatide or liraglutide improved glucose metabolism and blood pressure but this was independent of body weight loss. Both drugs significantly decreased atheroma plaque size. Compared with vehicle-treated control mice, lixisenatide treatment generated more stable atheromas, with fewer inflammatory infiltrates, reduced necrotic cores and thicker fibrous caps. Lixisenatide-treated mice also displayed diminished IL-6 levels, proinflammatory Ly6C monocytes and activated T cells. In vitro analysis showed that, in macrophages from Apoe Irs2 mice, lixisenatide reduced the secretion of the proinflammatory cytokine IL-6 accompanied by enhanced activation of signal transducer and activator of transcription (STAT) 3, which is a determinant for M2 macrophage differentiation. STAT1 activation, which is essential for M1 phenotype, was also diminished. Furthermore, atheromas from lixisenatide-treated mice showed higher arginase I content and decreased expression of inducible nitric oxide synthase, indicating the prevalence of the M2 phenotype within plaques. CONCLUSIONS/INTERPRETATION: Lixisenatide decreases atheroma plaque size and instability in Apoe Irs2 mice by reprogramming macrophages towards an M2 phenotype, which leads to reduced inflammation. This study identifies a critical role for this drug in macrophage polarisation inside plaques and provides experimental evidence supporting a novel mechanism of action for GLP-1 analogues in the reduction of cardiovascular risk associated with insulin resistance.