0393: Impact of miR-378* and its target desmin intermediate filament on mitochondria distribution in cardiomyocytes

BackgroundMiR-378 and miR-378* microRNAs are derived from an intron of the PGC-1β gene, a regulator of mitochondrial biogenesis. Their expression is either repressed or increased during heart failure depending on the model. Through proteomics approaches, we previously identified new targets of these miRs in H9c2 fetal cardiomyoblasts, among which lactate dehydrogenase for miR-378 and key cytoskeletal proteins for miR-378*.AimsTo better assess its role in energy metabolism and differentiation; we overexpressed miR-378 and miR-378* in primary neonate rat cardiomyocytes (NRC) that are more differentiated and less proliferative than H9c2 cardiomyoblasts.ResultsWe identified desmin as a new target of miR-378* in NRC. Desmin network plays a key role as a structural integrator of myofibrils and mitochondria positioning. MiR-378* overexpression reduced desmin levels and disrupted its organization. Confocal microscopy analysis of NRC stained with the mitochondrial dye MitoTracker revealed that miR-378* overexpression alters mitochondria distribution in the cell. AAV-mediated rescue of desmin expression in presence of miR-378* preserved mitochondria distribution. Mir-378 overexpression had a milder impact on cell organization than miR-378* and did not directly targetted desmin.Conclusion and perspectivesThese results suggest that changes in miR-378* expression level could play an important role in the coupled alteration of cytoskeletal and mitochondrial networks observed in failing myocardium.Abstract 0393 – Figure: Biological functions regulated by miR-378/378

Aged Nicotinamide Riboside Kinase 2 Deficient Mice Present an Altered Response to Endurance Exercise Training

Background: Skeletal muscle aging is marked by the development of a sarcopenic phenotype, a global decline of muscle energetic capacities, and an intolerance to exercise. Among the metabolic disorders involved in this syndrome, NAD metabolism was shown to be altered in skeletalmuscle, with an important role for the NAMPT enzyme recycling the nicotinamide precursor. An alternative pathway for NAD biosynthesis has been described for the nicotinamide riboside vitamin B3 precursor used by the NMRK kinases, including the striated muscle-specific NMRK2.Aim: With this study, our goal is to explore the ability of 16-month-old Nmrk2−/− mice to perform endurance exercise and study the consequences on muscle adaptation to exercise.Methods: 10 control and 6 Nmrk2−/− mice were used and randomly assigned to sedentary and treadmill endurance training groups. After 9 weeks of training, heart and skeletal muscle samples were harvested and used for gene expression analysis, NAD levels measurements and immunohistochemistry staining.Results: Endurance training triggered a reduction in the expression of Cpt1b and AcadL genes involved in fatty acid catabolism in the heart of Nmrk2−/− mice, not in control mice. NAD levels were not altered in heart or skeletal muscle, nor at baseline neither after exercise training in any group. Myh7 gene encoding for the slow MHC-I was more strongly induced by exercise in Nmrk2−/− mice than in controls. Moreover, IL-15 expression levels is higher in Nmrk2−/− mice skeletal muscle at baseline compared to controls. No fiber type switch was observed in plantaris after exercise, but fast fibers diameter was reduced in aged control mice, not in Nmrk2−/− mice. No fiber type switch or diameter modification was observed in soleus muscle.Conclusion: In this study, we demonstrated for the first time a phenotype in old Nmrk2−/− mice in response to endurance exercise training. Although NMRK2 seems to be predominantly dispensable to maintain global NAD levels in heart and skeletal muscle, we demonstrated a maladaptive metabolic response to exercise in cardiac and skeletal muscle, showing that NMRK2 has a specific and restricted role in NAD signaling compared to the NAMPT pathway

The Oxygen Paradox, the French Paradox, and age-related diseases

open46openDavies, Joanna M. S.; Cillard, Josiane; Friguet, Bertrand; Cadenas, Enrique; Cadet, Jean; Cayce, Rachael; Fishmann, Andrew; Liao, David; Bulteau, Anne-Laure; Derbré, Frédéric; Rébillard, Amélie; Burstein, Steven; Hirsch, Etienne; Kloner, Robert A.; Jakowec, Michael; Petzinger, Giselle; Sauce, Delphine; Sennlaub, Florian; Limon, Isabelle; Ursini, Fulvio; Maiorino, Matilde; Economides, Christina; Pike, Christian J.; Cohen, Pinchas; Salvayre, Anne Negre; Halliday, Matthew R.; Lundquist, Adam J.; Jakowec, Nicolaus A.; Mechta-Grigoriou, Fatima; Mericskay, Mathias; Mariani, Jean; Li, Zhenlin; Huang, David; Grant, Ellsworth; Forman, Henry J.; Finch, Caleb E.; Sun, Patrick Y.; Pomatto, Laura C. D.; Agbulut, Onnik; Warburton, David; Neri, Christian; Rouis, Mustapha; Cillard, Pierre; Capeau, Jacqueline; Rosenbaum, Jean; Davies, Kelvin J. A.Davies, Joanna M. S.; Cillard, Josiane; Friguet, Bertrand; Cadenas, Enrique; Cadet, Jean; Cayce, Rachael; Fishmann, Andrew; Liao, David; Bulteau, Anne-Laure; Derbré, Frédéric; Rébillard, Amélie; Burstein, Steven; Hirsch, Etienne; Kloner, Robert A.; Jakowec, Michael; Petzinger, Giselle; Sauce, Delphine; Sennlaub, Florian; Limon, Isabelle; Ursini, Fulvio; Maiorino, Matilde; Economides, Christina; Pike, Christian J.; Cohen, Pinchas; Salvayre, Anne Negre; Halliday, Matthew R.; Lundquist, Adam J.; Jakowec, Nicolaus A.; Mechta-Grigoriou, Fatima; Mericskay, Mathias; Mariani, Jean; Li, Zhenlin; Huang, David; Grant, Ellsworth; Forman, HENRY J.; Finch, Caleb E.; Sun, Patrick Y.; Pomatto, Laura C. D.; Agbulut, Onnik; Warburton, David; Neri, Christian; Rouis, Mustapha; Cillard, Pierre; Capeau, Jacqueline; Rosenbaum, Jean; Davies, Kelvin J. A

Les microARNs : en quoi intéressent-ils les cardiologues ?

International audienceKey pointsMiRNAs are small 21–22 nucleotides long RNAs transcribed from non coding genes or introns of coding genes that are involved the repression of cellular messenger RNAs by the RISC complex.Close to 2000 miRNAs have been identified in the human genome and the expression of hundreds of them is increased or decreased in pathological condition, modifying on a global scale the expression of cardiac and vascular proteins.MiRNAs regulate most cellular processes involved in the cardiovascular pathophysiology including apoptosis, proliferation and migration, left ventricle hypertrophy, cardiac fibrosis and conduction.MiRNAs form a new class of therapeutic targets that can be introduced in the cells in various forms (synthetic molecules, expression vectors) or inhibited by antisens oligonucleotides called anti-miRs.MiRNAs are actively secreted by specific cells including cardiac fibroblasts and endothelial cells during certain pathophysiological processes, or passively following cell death and can be quantified in all kind of body fluids. They emerge as a new category of cardiovascular disease biomarkers, notably in the context of myocardial infarction.Points essentielsLes miARNs sont des ARN de 21–22 nucléotides issus de gènes non codants ou d’introns de gène codant impliqués dans la répression des ARN messagers cellulaires par le complexe RISC.Près de 2000 miARNs sont identifiés dans le génome humain et des centaines d’entre eux voient leur expression augmentée ou diminuée en situation pathologique, modifiant de manière globale le taux d’expression des protéines cardiaques et vasculaires.Les miARNs affectent la plupart des processus cellulaires impliqués dans la physiopathologie cardiovasculaire : infarctus du myocarde, hypertrophie ventriculaire gauche, la fibrose cardiaque et troubles de la conduction.Les miARNs constituent un nouveau type de cible thérapeutique pouvant être introduits dans les cellules sous différentes formes, synthétique ou vecteur d’expression, ou bien inhibés par des oligonucléotides antisens appelés anti-miRs.Les miARNs sont excrétés activement par certaines cellules dont les fibroblastes cardiaques et les cellules endothéliales au cours de certains processus physiopathologiques, ou passivement lors de la mort cellulaire et peuvent être quantifiés dans tous les fluides corporels. Ils émergent donc comme une nouvelle catégorie de biomarqueurs des pathologies cardiovasculaires, notamment dans le contexte de l’infarctus du myocarde

Regulation of Connective Tissue Growth Factor and Cardiac Fibrosis by an SRF/MicroRNA-133a Axis

International audienceMyocardial fibrosis contributes to the remodeling of heart and the loss of cardiac function leading to heart failure. SRF is a transcription factor implicated in the regulation of a large variety of genes involved in cardiac structure and function. To investigate the impact of an SRF overexpression in heart, we developed a new cardiac-specific and tamoxifen-inducible SRF overexpression mouse model by the Cre/loxP strategy. Here, we report that a high level over-expression of SRF leads to severe modifications of cardiac cytoarchitecture affecting the balance between cardiomyocytes and cardiac fibroblasts and also a profound alteration of cardiac gene expression program. The drastic development of fibrosis was characterized by intense sirius red staining and associated with an increased expression of genes encoding extracellular matrix proteins such as fibronectin, procollagen type 1α1 and type 3α1 and especially connective tissue growth factor (CTGF). Furthermore miR-133a, one of the most predominant cardiac miRNAs, is strongly downregulated when SRF is overexpressed. By comparison a low level overexpression of SRF has minor impact on these different processes. Investigation with miR-133a, antimiR-133a and AdSRF-VP16 experiments in H9c2 cardiac cells demonstrated that: 1)–miR-133a acts as a repressor of SRF and CTGF expression ; 2)–a simultaneous overexpression of SRF by AdSRF-VP16 and inhibition of miR-133a by a specific antimiR increase CTGF expression; 3)–miR-133a overexpression can block the upregulation of CTGF induced by AdSRF-VP16. Taken together, these findings reveal a key role of the SRF/CTGF/miR-133a axis in the regulation of cardiac fibrosis

Posttranslational modifications of desmin and their implication in biological processes and pathologies

International audienceDesmin, the muscle-specific intermediate filament, is involved in myofibrillar myopathies, dilated cardiomyopathy and muscle wasting. Desmin is the target of posttranslational modifications (PTMs) such as phosphorylation, ADP-ribosylation and ubiquitylation as well as nonenzymatic modifications such as glycation, oxidation and nitration. Several PTM target residues and their corresponding modifying enzymes have been discovered in human and nonhuman desmin. The major effect of phosphorylation and ADP-ribosylation is the disassembly of desmin filaments, while ubiquitylation of desmin leads to its degradation. The regulation of the desmin filament network by phosphorylation and ADP-ribosylation was found to be implicated in several major biological processes such as myogenesis, myoblast fusion, muscle contraction, muscle atrophy, cell division and possibly desmin interactions with its binding partners. Phosphorylation of desmin is also implicated in many forms of desmin-related myopathies (desminopathies). In this review, we summarize the findings on desmin PTMs and their implication in biological processes and pathologies, and discuss the current knowledge on the regulation of the desmin network by PTMs. We conclude that the desmin filament network can be seen as an intricate scaffold for muscle cell structure and biological processes and that its dynamics can be affected by PTMs. There are now precise tools to investigate PTMs and visualize cellular structures that have been underexploited in the study of desminopathies. Future studies should focus on these aspects

Metabolic Therapy of Heart Failure: Is There a Future for B Vitamins?

International audienceHeart failure (HF) is a plague of the aging population in industrialized countries that continues to cause many deaths despite intensive research into more effective treatments. Although the therapeutic arsenal to face heart failure has been expanding, the relatively short life expectancy of HF patients is pushing towards novel therapeutic strategies. Heart failure is associated with drastic metabolic disorders, including severe myocardial mitochondrial dysfunction and systemic nutrient deprivation secondary to severe cardiac dysfunction. To date, no effective therapy has been developed to restore the cardiac energy metabolism of the failing myocardium, mainly due to the metabolic complexity and intertwining of the involved processes. Recent years have witnessed a growing scientific interest in natural molecules that play a pivotal role in energy metabolism with promising therapeutic effects against heart failure. Among these molecules, B vitamins are a class of water soluble vitamins that are directly involved in energy metabolism and are of particular interest since they are intimately linked to energy metabolism and HF patients are often B vitamin deficient. This review aims at assessing the value of B vitamin supplementation in the treatment of heart failure

Aged Nicotinamide Riboside Kinase 2 Deficient Mice Present an Altered Response to Endurance Exercise Training

International audienceBackground: Skeletal muscle aging is marked by the development of a sarcopenic phenotype, a global decline of muscle energetic capacities, and an intolerance to exercise. Among the metabolic disorders involved in this syndrome, NAD metabolism was shown to be altered in skeletalmuscle, with an important role for the NAMPT enzyme recycling the nicotinamide precursor. An alternative pathway for NAD biosynthesis has been described for the nicotinamide riboside vitamin B3 precursor used by the NMRK kinases, including the striated muscle-specific NMRK2.Aim: With this study, our goal is to explore the ability of 16-month-old Nmrk2−/− mice to perform endurance exercise and study the consequences on muscle adaptation to exercise.Methods: 10 control and 6 Nmrk2−/− mice were used and randomly assigned to sedentary and treadmill endurance training groups. After 9 weeks of training, heart and skeletal muscle samples were harvested and used for gene expression analysis, NAD levels measurements and immunohistochemistry staining.Results: Endurance training triggered a reduction in the expression of Cpt1b and AcadL genes involved in fatty acid catabolism in the heart of Nmrk2−/− mice, not in control mice. NAD levels were not altered in heart or skeletal muscle, nor at baseline neither after exercise training in any group. Myh7 gene encoding for the slow MHC-I was more strongly induced by exercise in Nmrk2−/− mice than in controls. Moreover, IL-15 expression levels is higher in Nmrk2−/− mice skeletal muscle at baseline compared to controls. No fiber type switch was observed in plantaris after exercise, but fast fibers diameter was reduced in aged control mice, not in Nmrk2−/− mice. No fiber type switch or diameter modification was observed in soleus muscle.Conclusion: In this study, we demonstrated for the first time a phenotype in old Nmrk2−/− mice in response to endurance exercise training. Although NMRK2 seems to be predominantly dispensable to maintain global NAD levels in heart and skeletal muscle, we demonstrated a maladaptive metabolic response to exercise in cardiac and skeletal muscle, showing that NMRK2 has a specific and restricted role in NAD signaling compared to the NAMPT pathway