Aims: Atherosclerotic vascular disease has an inflammatory pathogenesis. Heme from intraplaque hemorrhage drives a protective and pro-resolving macrophage M2-like phenotype, Mhem, via AMPK and ATF1. The anti-diabetic drug metformin may also activate AMPK-dependent signalling. Hypothesis: Metformin systematically induces atheroprotective genes in macrophages via AMPK and ATF1, and thereby suppresses atherogenesis. Methods and Results Metformin at a clinically relevant concentration (10μM) evoked AMPK-dependent and ATF1-dependent increases in Hmox1, Nr1h2 (Lxrb), Abca1, Apoe, Igf1 and Pdgf, increases in several M2-markers and decreases in Nos2, in murine bone marrow macrophages. Similar effects were seen in human blood-derived macrophages, in which metformin induced protective genes and M2-like genes, suppressed by si-ATF1-mediated knockdown. Microarray analysis comparing metformin with heme in human macrophages indicated that the transcriptomic effects of metformin were similar to those of heme, but not identical, indicating a different M2-like phenotype. Next, normoglycemic Ldlr-/- hyperlipidemic mice were treated with oral metformin, which profoundly suppressed lesion development (p<5x10-11). Bone marrow transplantation from AMPK-deficient mice demonstrated that metformin-related atheroprotection required myeloid cell AMPK (ANOVA, p<0.03). Metformin induced lesional macrophage expression of p-AMPK, p-ATF1 and downstream M2-like protective effects. Conclusion Metformin activates a conserved AMPK-ATF1-M2-like pathway in mouse and human macrophages, resulting in highly suppressed atherogenesis in hyperlipidemic mice.

03 - METFORMIN DIRECTLY SUPPRESSES ATHEROSCLEROSIS IN NORMOGLYCEMIC MICE VIA HAEMATOPOIETIC ADENOSINE MONOPHOSPHATE-ACTIVATED PROTEIN KINASE (AMPK)