Macrophage ATP citrate lyase deficiency stabilizes atherosclerotic plaques Jeroen Baardman1,#, Sanne G.S. Verberk2,#, Saskia van der Velden1, Marion J.J. Gijbels1,3, Cindy P.P.A. van Roomen1, Judith C. Sluimer3,4, Jelle Y. Broos5,6, Guillermo R. Griffith1, Koen H.M. Prange1, Michel van Weeghel7,8, Soufyan Lakbir2,9, Douwe Molenaar9, Elisa Meinster2, Annette E. Neele1, Gijs Kooij5, Helga E. de Vries5, Esther Lutgens1,10, Kathryn E. Wellen11, Menno P.J. de Winther1,10,# & Jan Van den Bossche1,2,# 1Department of Medical Biochemistry, Experimental Vascular Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands 2Department of Molecular Cell Biology and Immunology, Amsterdam Cardiovascular Sciences, Cancer Center Amsterdam, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands 3Department of Pathology and Molecular Genetics, CARIM, Maastricht University, Maastricht, Netherlands 4 BHF Centre for Cardiovascular Sciences (CVS), University of Edinburgh, Edinburgh, UK 5Department of Molecular Cell Biology and Immunology, Amsterdam Neuroscience, MS Center Amsterdam, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands 6 Leiden University Medical Center, Center for Proteomics & Metabolomics, Leiden, Netherlands 7Laboratory Genetic Metabolic Diseases, Amsterdam Cardiovascular sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands 8Core Facility Metabolomics, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands 9Systems Bioinformatics, Vrije Universiteit Amsterdam, Amsterdam, Netherlands 10Institute for Cardiovascular Prevention (IPEK), Ludwig Maximilians University, Munich, Germany 11Department of Cancer Biology, Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA #These authors contributed equally. Macrophages represent a major immune cell population in atherosclerotic plaques and play central role in the progression of this lipid-driven chronic inflammatory disease. Targeting immunometabolism is proposed as a strategy to revert aberrant macrophage activation to improve disease outcome. Here, we show ATP citrate lyase (Acly) to be activated in inflammatory macrophages and human atherosclerotic plaques. We demonstrate that myeloid Acly deficiency induces a stable plaque phenotype characterized by increased collagen deposition and fibrous cap thickness, along with a smaller necrotic core. In-depth functional, lipidomic, and transcriptional characterization indicate deregulated fatty acid and cholesterol biosynthesis and reduced liver X receptor activation within the macrophages in vitro. This results in macrophages that are more prone to undergo apoptosis, whilst maintaining their capacity to phagocytose apoptotic cells. Together, our results indicate that targeting macrophage metabolism improves atherosclerosis outcome and we reveal Acly as a promising therapeutic target to stabilize atherosclerotic plaques.