Liraglutide reduces oxidized LDL-induced oxidative stress and fatty degeneration in Raw 264.7 cells involving the AMPK/SREBP1 pathway

BACKGOUND: Recent studies have suggested a potential role for liraglutide in the prevention and stabilization of atherosclerotic vascular disease. However, the molecular mechanisms underlying the effect of liraglutide on atherosclerosis have not been well elucidated. The purpose of this study was to examine whether liraglutide protects against oxidative stress and fatty degeneration via modulation of AMP-activated protein kinase (AMPK)/sterol regulatory element binding transcription factor 1 (SREBP1) signaling pathway in foam cells. METHODS: Mouse macrophages Raw264.7 cells were exposed to oxidized low density lipoprotein (oxLDL) to induce the formation of foam cells. The cells were incubated with oxLDL (50 µg/mL), liraglutide (0.1, 0.5, 1 and 2 nmol/L) or exendin-3 (9-39) (1, 10 and 100 nmol/L) alone, or in combination. Oil Red O staining was used to detect intracellular lipid droplets. The levels of TG and cholesterol were measured using the commercial kits. Oxidative stress was determined by measuring intracellular reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase 1 (SOD). Western blot analysis was used to examine the expression of AMPKα1, SREBP1, phosphorylated AMPKα1, phosphorylated SREBP1, glucagon-like peptide-1 (GLP-1) and GLP-1 receptor (GLP-1R). RESULTS: Oil Red O staining showed that the cytoplasmic lipid droplet accumulation was visibly decreased in foam cells by treatment with liraglutide. The TG and cholesterol content in the liraglutide-treated foam cells was significantly decreased. In addition, foam cells manifested an impaired oxidative stress following liraglutide treatment, as evidenced by increased SOD, and decreased ROS and MDA. However, these effects of liraglutide on foam cells were attenuated by the use of GLP-1R antagonist exendin-3 (9-39). Furthermore, we found that the expression level of AMPKα1 and phosphorylated AMPKα1 was significantly increased while the expression level of SREBP1 and phosphorylated SREBP1 was significantly decreased in foam cells following treatment with liraglutide. CONCLUSIONS: This study for the first time demonstrated that the effect of liraglutide on reducing oxidative stress and fatty degeneration in oxLDL-induced Raw264.7 cells is accompanied by the alteration of AMPK/SREBP1 pathway. This study provided a potential molecular mechanism for the effect of liraglutide on reducing oxidative stress and fatty degeneration.