RETRACTED: Ablation of Adenosine Monophosphate-Activated Protein Kinase α1 in Vascular Smooth Muscle Cells Promotes Diet-Induced Atherosclerotic Calcification In Vivo (Retracted article. See vol. 131, 2022)

Rationale: Atherosclerotic calcification is highly linked with plaque rapture. How calcification is regulated is poorly characterized. Objective: We sought to determine the contributions of AMP-activated protein kinase (AMPK) in atherosclerotic calcification. Methods and Results: Aortic calcification was evaluated in aortic roots and brachiocephalic arteries of atherosclerotic prone ApoE-/- mice or in mice with dual deficiencies of ApoE and AMPK alpha isoforms in whole body (ApoE-/-/AMPKa1-/- and ApoE-/-/AMPKa2-/-) or vascular smooth muscle cell (VSMC)-specific or macrophage-specific knockout of AMPK alpha 1 fed with Western diet for 24 weeks. Genetic deficiency of AMPKa1 but not of AMPK alpha 2 promoted atherosclerotic calcification and the expression of Runx2 (Runt-related transcription factor). Conversely, chronic administration of metformin, which activated AMPK, markedly reduced atherosclerotic calcification and Runx2 expression in ApoE-/- mice but had less effects in ApoE-/-/ AMPK alpha 1-/- mice. Furthermore, VSMC-specific but not macrophage-specific ablation of AMPKa1 promoted aortic calcification in vivo. Ablation of AMPKa1 in VSMC prevented Runx2 from proteasome degradation in parallel with aberrant osteoblastic differentiation of VSMC, whereas AMPK activation promoted Runx2 posttranslational modification by small ubiquitin-like modifier (SUMO, SUMOylation), which is associated with its instability. Mechanically, we found that AMPKa1 directly phosphorylated protein inhibitor of activated STAT-1 (PIAS1), the SUMO E3-ligase of Runx2, at serine 510, to promote its SUMO E3-ligase activity. Finally, mutation of protein inhibitor of activated STAT-1 at serine 510 suppressed metformin-induced Runx2 SUMOylation and subsequently prevented metformin's effect on reducing oxidized low-density lipoprotein-triggered Runx2 expression in VSMC. Conclusions: AMPKa1 phosphorylated protein inhibitor of activated STAT-1 to promote Runx2 SUMOylation and subsequently lead to its instability. AMPKa1 deficiency in VSMC increased Runx2 expression and promoted atherosclerotic calcification in vivo.