Carbon Monoxide Improves Cardiac Function and Mitochondrial Population Quality in a Mouse Model of Metabolic Syndrome Steve Lancel1*, David Montaigne1, Xavier Marechal1, Camille Marciniak1, Sidi Mohamed Hassoun 1 , Brigitte Decoster1, Caroline Ballot1, Caroline Blazejewski1, Delphine Corseaux2, Bernadette Lescure3, Roberto Motterlini4, Remi Neviere1 1 EA4484, Physiology Department, Lille 2 University, Lille, France, 2 EA2693, Lille 2 University, Lille, France, 3 INSERM IFR65, Institut de Recherche en Sante Saint Antoine (Irssa), Faculty of Medicine, Paris, France, 4 INSERM U955, Faculty of Medicine, Paris-Est University, Cre´teil, France Abstract Aims: Metabolic syndrome induces cardiac dysfunction associated with mitochondria abnormalities. As low levels of carbon monoxide (CO) may improve myocardial and mitochondrial activities, we tested whether a CO-releasing molecule (CORM-3) reverses metabolic syndrome-induced cardiac alteration through changes in mitochondrial biogenesis, dynamics and autophagy. Methods and Results: Mice were fed with normal diet (ND) or high-fat diet (HFD) for twelve weeks. Then, mice received two intraperitoneal injections of CORM-3 (10 mg.kg21), with the second one given 16 hours after the first. Contractile function in isolated hearts and mitochondrial parameters were evaluated 24 hours after the last injection. Mitochondrial population was explored by electron microscopy. Changes in mitochondrial dynamics, biogenesis and autophagy were assessed by western-blot and RT-qPCR. Left ventricular developed pressure was reduced in HFD hearts. Mitochondria from HFD hearts presented reduced membrane potential and diminished ADP-coupled respiration. CORM-3 restored both cardiac and mitochondrial functions. Size and number of mitochondria increased in the HFD hearts but not in the CORM-3–treated HFD group. CORM-3 modulated HFD-activated mitochondrial fusion and biogenesis signalling. While autophagy was not activated in the HFD group, CORM-3 increased the autophagy marker LC3-II. Finally, ex vivo experiments demonstrated that autophagy inhibition by 3-methyladenine abolished the cardioprotective effects of CORM-3. Conclusion: CORM-3 may modulate pathways controlling mitochondrial quality, thus leading to improvements of mitochondrial efficiency and HFD-induced cardiac dysfunction. Citation: Lancel S, Montaigne D, Marechal X, Marciniak C, Hassoun SM, et al. (2012) Carbon Monoxide Improves Cardiac Function and Mitochondrial Population Quality in a Mouse Model of Metabolic Syndrome. PLoS ONE 7(8): e41836. doi:10.1371/journal.pone.0041836 Editor: Krisztian Stadler, Pennington Biomedical Research Center, United States of America Received March 2, 2012; Accepted June 26, 2012; Published August 1, 2012 Copyright: 2012 Lancel et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by EA4484– Universite´ Lille 2– Ministe`re de l’Enseignement Supe´rieur et de la Recherche; CPER ‘‘cardiodiabe`te 2008’’ - FEDER Re´gion Nord Pas-de-Calais 08480265; Fondation de France 2009002501 and Fondation Coeur et Arte`res FCA09T6. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: steve.lancel@univ-lille2.fr Introduction Metabolic syndrome predisposes to cardiovascular diseases. Altered substrate utilization, i.e. reduced glucose utilization and enhanced fatty acid metabolism, and functional and structural alterations of the mitochondrial population are among the important mechanisms involved in this form of myocardial dysfunction [1]. Mitochondrial network dynamics as well as a balance between biogenesis of new mitochondria and autophagy of damaged organelles control quality of the mitochondrial population. Dysregulations of these three pathways may have direct conse- quences on cardiac function. First, pharmacological inhibition of cardiac mitochondrial fission [2] increased cardiac resistance to ischemia/reperfusion injury. Second, peroxisome proliferator- activated receptor c coactivator-1a (Pgc-1a) cardiac overexpression triggers uncontrolled and excessive biogenesis that may disrupt sarcomeres and may lead to dilated cardiomyopathy [3]. Third, regarding the autophagy process, cardiac specific Atg5-deficient mice display disorganized sarcomeres and mitochondrial accumu- lation along with myocardial dysfunction [4]. Although cardiac mitochondria biogenesis is stimulated in the context of diabetes and appears to be maladaptive as cardiac energy production remains insufficient [5], these three signalling pathways regulating mitochondria quality are not well characterized in cardiac dysfunction that occurs during metabolic syndrome. Carbon monoxide (CO) is a well-known poison that binds to haemoglobin with a high affinity. If inhaled at high doses and for prolonged periods of time, CO alters oxygen transport leading to severe tissue hypoxia. In contrast, controlled amounts of CO appear to be beneficial to tissues, as this gas is emerging as an interesting therapeutic agent in a variety of pathophysiological PLoS ONE | www.plosone.org 1 August 2012 | Volume 7 | Issue 8 | e41836