- Email: [email protected]
Metabolic regulation of heart failure caused by imbalanced mitochondrial dynamics
242 Conclusion We highlighted a novel role for IH in the development of cardiac insulin resistance, which was associated with a blunted cardiac response to -adrenergic stimulation. Further studies are now needed to better understand the relationship between these two mechanisms. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.130 356
Cardiac manifestations of inherited metabolic disease linked to cellular vitamin B12 (cobalamin) uptake: Study in murine model of invalidation of Mtr gene in the heart V.J. Kosgei 1,∗ , C. Arnold 1 , F. Elkhafifi 1 , P. Lacolley 2 , S. Hergalant 1 , L. Monassier 3 , M. Fatiha 4 , J.L. Guéant 1 , R.M. Guéant-Rodriguez 1 1 Nutrition Génetique et exposition aux risques environmentaux, Nutrition CHU Nancy UMR Inserm 1256, France 2 Défaillance cardiovasculaire aiguë et chronique, UMR Inserm 1116, Vandoeuvre-Les-Nancy 3 Mouse clinical institute MCI, Strasbourg 4 Nancyclotep-GIE Ingénieur d’études imagerie préclinique, Vandoeuvre-Les-Nancy, France ∗ Corresponding author. E-mail address: [email protected] (V.J. Kosgei) Introduction Heart failure is one of the most common cause of death in Western societies. Deficiency in folates and vitamin B12 during gestation and lactation causes foetal programming effect with metabolic cardiomyopathy related to decreased synthesis of methionine by methionine synthase encoded by MTR Gene. Methionine is the precursor for S-adenosyl methionine (SAM) the universal methyl donor. Mutations in MTR gene causes cardiac decompensation in new-borns by unknown mechanisms. Purpose To investigate cardiac metabolic and functional consequences of inhibition of methionine synthesis in conditional knock out of Mtr gene in the heart of C57BL/6 mice. Methods Systolic Blood Pressure in conscious mice was measured using tail-cuff plethysmography. Left ventricular (LV) functions were assessed by Mini-PET and Echocardiography. Transcriptomics analysis was achieved by RNA deep sequencing and proteomic study by LC-MS/MS. Results Systolic hypertension, decreased LV ejection fraction, increased LV mass and heart/body weight ratio were observed in Mtr KO compared to control. RT-qPCR confirmed upregulated expression of natriuretic peptides (ANP and BNP) and decreased alpha MHC/beta MHC ratio in Mtr KO. Biochemical studies revealed decreased SAM/SAH ratio, elevated plasma acylcarnitine and cardiac fibrosis in Mtr KO. The whole heart transcriptome consisted of 16540 expressed genes which were clustered by K-means into three signatures, these signatures were correlated to proteomic results. Dysregulated genes and proteins in Mtr KO were implicated in cardiac contraction, cell growth and energy metabolism. Conclusion Our results suggest that silencing of Methionine synthase in the heart induces hypertension, hypertrophic cardiomyopathy with LV systolic dysfunction. The related mechanisms were dysregulation of energy metabolism and fibrosis. This data provides a novel insight on physiopathological mechanisms of cardiomyopathies of inherited disorders of cobalamin metabolism. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.131
Topic 18 — Heart failure/cardiomyopathy — G 296
Role of mitochondrial fusion in cardiac energy metabolism E. Silva Ramos 1 , N.G. Larsson 1,2 , A. Mourier 3,∗ Mitochondrial Biology, Max-Planck Institute for Biology of Ageing, Cologne, Allemagne 2 Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Suède 3 CNRS, Bordeaux, France ∗ Corresponding author. E-mail address: [email protected] (A. Mourier)
1
Introduction Mitochondrial dynamics is an essential physiological process controlling mitochondrial content mixing and mobility to ensure proper function and localization of mitochondria at intracellular sites of high-energy demand. Intriguingly, for yet unknown reasons, severe impairment of mitochondrial fusion drastically affects mtDNA copy number. Objective The goal of our work was to determine the importance of mitochondrial fusion on heart energy homeostasis. Method and results To decipher the link between mitochondrial dynamics and mtDNA maintenance and heart energy metabolism, we studied heart conditional knockout mouse and mouse embryonic fibroblasts (MEFs) with disruption of mitochondrial fusion. Super-resolution microscopy analyses revealed that loss of outer mitochondrial membrane (OMM) fusion, but not inner mitochondrial membrane (IMM) fusion, leads to clustering and loss of nucleoids. Remarkably, fluorescence in situ hybridization (FISH) in MEFs, bromouridine labeling of MEFs and assessment of mitochondrial transcription in tissue homogenates revealed that abolished OMM fusion does not affect transcription. Conclusion The profound mtDNA depletion in hearts lacking OMM fusion is not caused by defective integrity or increased mutagenesis of mtDNA, but, instead, we show that mitochondrial fusion is necessary to maintain the stoichiometry of the protein components of the mtDNA replisome. OMM fusion is necessary for proliferating MEFs to recover from mtDNA depletion and for the marked increase of mtDNA copy number during postnatal heart development. Our findings thus link OMM fusion to replication and distribution of mtDNA. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.132 453
Metabolic regulation of heart failure caused by imbalanced mitochondrial dynamics L.E. De la Rosa Vargas 1,∗ , E. Dale Abel 2 , T. Langer 3,4 , T. Wai 1 Université Paris Descartes-Sorbonne Paris Cité 2 Institut Pasteur, Paris, France 3 Carver College of Medicine, IA, Etats-Unis 4 Max Planck Institut for the Biology of Ageing, Cologne, Allemagne ∗ Corresponding author. E-mail address: [email protected] (L.E. De la Rosa Vargas)
1
Background Dilated Cardiomyopathy (DCM) is characterized by an expansion of the left ventricle having as a consequence inefficient oxygenated blood pumping to the body. DCM can result in heart failure and is the most common cause of heart transplantation. The healthy adult heart relies mainly on free fatty acids as its main fuel source and rather than glucose but in the failing heart, a metabolic switch away from fatty acid oxidation and towards glucose uptake has been observed and has been proposed to represent an adaptive bioenergetic mechanism. We developed a mouse model of DCM caused my mitochondrial fragmentation in cardiomyocytes due to the deletion of the mitochondrial protease YME1L.
Topic 18 — Heart failure/cardiomyopathy — G This mouse model recapitulates all the clinical features of DCM as well as the metabolic features, such as cardiac glucose overload, progressing into chronic heart failure and middle-aged death. Aim Using our DCM mouse model, we will test whether reducing cardiac glucose overload to the heart diminishes or exacerbates cardiac and metabolic dysfunction. To his end, we will ablate the primary glucose transporter GLUT 4 either partially or completely in DCM mice to diminish glucose uptake to the heart. Results We generated cardiac specific deletions of YME1L and GLUT4 by crossing the cardiomyocyte specific Crerecombinase drive Myh6-Cre to conditional YME1LLoxp/LoxP and SLC2A4Loxp/LoxP mice. Cardiac function will be assessed using echocardiography and mitochondrial activity using high resolution oxygraphy (Oroboros) in isolated cardiac mitochondria. Conclusion and perspectives Our studies will allow us to determine the importance of glucose uptake and usage in the failing adult heart. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.133 395
Cardiac myocyte-specific expression of beta3-adrenergic receptors sustains AMPK activation and glucose uptake while reducing hypertrophy following pressure overload L. Michel 1,∗ , E. Dubois-Deruy 1 , R. Gelinas 2 , H. Esfahani 1 , V. Roelants 3 , L. Bertrand 2 , C. Beauloye 2 , J.L. Balligand 1 1 Pole de pharmacologie et therapeutiques, institut de recherche expérimentale et clinique, université catholique de Louvain 2 Pole de recherche cardiovasculaire, institut de recherche expérimentale et clinique, Université catholique de Louvain 3 Service de médecine nucléaire, cliniques universitaires St-Luc, Bruxelles, Belgique ∗ Corresponding author. E-mail address: [email protected] (L. Michel)
243 Introduction Cardiac beta3-adrenergic receptors (B3AR) produce effects antipathetic to those of B1 and B2 receptors. Importantly, B3AR are resistant to desensitization and their expression is upregulated in the diseased myocardium. We previously showed that mice with moderate cardiac-specific expression of the human B3AR (B3TG) are protected from hypertrophy and fibrosis upon hemodynamic or neurohormonal stress. Objective Here we tested the hypothesis that myocardial protection may be mediated by metabolic effects of B3AR in cardiac myocytes, akin to well-known B3AR metabolic effects in adipose tissue. Method We used both B3-TG mice (and WT littermate) and isolated adult cardiac myocytes exposed to hemodynamic overload (TAC) (or sham control). Results We found that 9 week-TAC induced hypertrophy and fibrosis in WT mice, as expected. Notably this was paralleled with decreased activation of AMPK assessed by AMPK phosphorylation at Thr-172 and phosphorylation of its downstream target ACC. However, in B3-TG mice AMPK activation was preserved post TAC. Moreover, siRNA downregulation of alpha1/2 AMPK attenuated the protection from hypertrophy by B3AR expression, confirming AMPK implication in the B3AR control of hypertrophy. As cardiac AMPK controls metabolic substrate use and uptake, we examined glucose uptake in adult cardiac myocytes isolated from B3-TG (and WT) mice after TAC, with/without insulin. Cardiac myocytes from stressed B3TG mice exhibited a significant increase in 2-3H glucose uptake upon insulin treatment, whereas WT myocytes developed insulinoresistance. In vivo B3-TG also exhibited an increased myocardial uptake of the glucose analog 18FDG compared to WT littermates, e.g. at 9 weeks post-TAC. Conclusion We conclude that cardiac myocyte-specific expression of B3AR concurrently prevents the development of insulin resistance and maintains AMPK activation contributing to the protection from hypertrophic remodeling under hemodynamic stress. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.134
Cardiac manifestations of inherited metabolic disease linked to cellular vitamin B12 (cobalamin) uptake: Study in murine model of invalidation of Mtr gene in the heart V.J. Kosgei 1,∗ , C. Arnold 1 , F. Elkhafifi 1 , P. Lacolley 2 , S. Hergalant 1 , L. Monassier 3 , M. Fatiha 4 , J.L. Guéant 1 , R.M. Guéant-Rodriguez 1 1 Nutrition Génetique et exposition aux risques environmentaux, Nutrition CHU Nancy UMR Inserm 1256, France 2 Défaillance cardiovasculaire aiguë et chronique, UMR Inserm 1116, Vandoeuvre-Les-Nancy 3 Mouse clinical institute MCI, Strasbourg 4 Nancyclotep-GIE Ingénieur d’études imagerie préclinique, Vandoeuvre-Les-Nancy, France ∗ Corresponding author. E-mail address: [email protected] (V.J. Kosgei) Introduction Heart failure is one of the most common cause of death in Western societies. Deficiency in folates and vitamin B12 during gestation and lactation causes foetal programming effect with metabolic cardiomyopathy related to decreased synthesis of methionine by methionine synthase encoded by MTR Gene. Methionine is the precursor for S-adenosyl methionine (SAM) the universal methyl donor. Mutations in MTR gene causes cardiac decompensation in new-borns by unknown mechanisms. Purpose To investigate cardiac metabolic and functional consequences of inhibition of methionine synthesis in conditional knock out of Mtr gene in the heart of C57BL/6 mice. Methods Systolic Blood Pressure in conscious mice was measured using tail-cuff plethysmography. Left ventricular (LV) functions were assessed by Mini-PET and Echocardiography. Transcriptomics analysis was achieved by RNA deep sequencing and proteomic study by LC-MS/MS. Results Systolic hypertension, decreased LV ejection fraction, increased LV mass and heart/body weight ratio were observed in Mtr KO compared to control. RT-qPCR confirmed upregulated expression of natriuretic peptides (ANP and BNP) and decreased alpha MHC/beta MHC ratio in Mtr KO. Biochemical studies revealed decreased SAM/SAH ratio, elevated plasma acylcarnitine and cardiac fibrosis in Mtr KO. The whole heart transcriptome consisted of 16540 expressed genes which were clustered by K-means into three signatures, these signatures were correlated to proteomic results. Dysregulated genes and proteins in Mtr KO were implicated in cardiac contraction, cell growth and energy metabolism. Conclusion Our results suggest that silencing of Methionine synthase in the heart induces hypertension, hypertrophic cardiomyopathy with LV systolic dysfunction. The related mechanisms were dysregulation of energy metabolism and fibrosis. This data provides a novel insight on physiopathological mechanisms of cardiomyopathies of inherited disorders of cobalamin metabolism. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.131
Topic 18 — Heart failure/cardiomyopathy — G 296
Role of mitochondrial fusion in cardiac energy metabolism E. Silva Ramos 1 , N.G. Larsson 1,2 , A. Mourier 3,∗ Mitochondrial Biology, Max-Planck Institute for Biology of Ageing, Cologne, Allemagne 2 Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Suède 3 CNRS, Bordeaux, France ∗ Corresponding author. E-mail address: [email protected] (A. Mourier)
1
Introduction Mitochondrial dynamics is an essential physiological process controlling mitochondrial content mixing and mobility to ensure proper function and localization of mitochondria at intracellular sites of high-energy demand. Intriguingly, for yet unknown reasons, severe impairment of mitochondrial fusion drastically affects mtDNA copy number. Objective The goal of our work was to determine the importance of mitochondrial fusion on heart energy homeostasis. Method and results To decipher the link between mitochondrial dynamics and mtDNA maintenance and heart energy metabolism, we studied heart conditional knockout mouse and mouse embryonic fibroblasts (MEFs) with disruption of mitochondrial fusion. Super-resolution microscopy analyses revealed that loss of outer mitochondrial membrane (OMM) fusion, but not inner mitochondrial membrane (IMM) fusion, leads to clustering and loss of nucleoids. Remarkably, fluorescence in situ hybridization (FISH) in MEFs, bromouridine labeling of MEFs and assessment of mitochondrial transcription in tissue homogenates revealed that abolished OMM fusion does not affect transcription. Conclusion The profound mtDNA depletion in hearts lacking OMM fusion is not caused by defective integrity or increased mutagenesis of mtDNA, but, instead, we show that mitochondrial fusion is necessary to maintain the stoichiometry of the protein components of the mtDNA replisome. OMM fusion is necessary for proliferating MEFs to recover from mtDNA depletion and for the marked increase of mtDNA copy number during postnatal heart development. Our findings thus link OMM fusion to replication and distribution of mtDNA. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.132 453
Metabolic regulation of heart failure caused by imbalanced mitochondrial dynamics L.E. De la Rosa Vargas 1,∗ , E. Dale Abel 2 , T. Langer 3,4 , T. Wai 1 Université Paris Descartes-Sorbonne Paris Cité 2 Institut Pasteur, Paris, France 3 Carver College of Medicine, IA, Etats-Unis 4 Max Planck Institut for the Biology of Ageing, Cologne, Allemagne ∗ Corresponding author. E-mail address: [email protected] (L.E. De la Rosa Vargas)
1
Background Dilated Cardiomyopathy (DCM) is characterized by an expansion of the left ventricle having as a consequence inefficient oxygenated blood pumping to the body. DCM can result in heart failure and is the most common cause of heart transplantation. The healthy adult heart relies mainly on free fatty acids as its main fuel source and rather than glucose but in the failing heart, a metabolic switch away from fatty acid oxidation and towards glucose uptake has been observed and has been proposed to represent an adaptive bioenergetic mechanism. We developed a mouse model of DCM caused my mitochondrial fragmentation in cardiomyocytes due to the deletion of the mitochondrial protease YME1L.
Topic 18 — Heart failure/cardiomyopathy — G This mouse model recapitulates all the clinical features of DCM as well as the metabolic features, such as cardiac glucose overload, progressing into chronic heart failure and middle-aged death. Aim Using our DCM mouse model, we will test whether reducing cardiac glucose overload to the heart diminishes or exacerbates cardiac and metabolic dysfunction. To his end, we will ablate the primary glucose transporter GLUT 4 either partially or completely in DCM mice to diminish glucose uptake to the heart. Results We generated cardiac specific deletions of YME1L and GLUT4 by crossing the cardiomyocyte specific Crerecombinase drive Myh6-Cre to conditional YME1LLoxp/LoxP and SLC2A4Loxp/LoxP mice. Cardiac function will be assessed using echocardiography and mitochondrial activity using high resolution oxygraphy (Oroboros) in isolated cardiac mitochondria. Conclusion and perspectives Our studies will allow us to determine the importance of glucose uptake and usage in the failing adult heart. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.133 395
Cardiac myocyte-specific expression of beta3-adrenergic receptors sustains AMPK activation and glucose uptake while reducing hypertrophy following pressure overload L. Michel 1,∗ , E. Dubois-Deruy 1 , R. Gelinas 2 , H. Esfahani 1 , V. Roelants 3 , L. Bertrand 2 , C. Beauloye 2 , J.L. Balligand 1 1 Pole de pharmacologie et therapeutiques, institut de recherche expérimentale et clinique, université catholique de Louvain 2 Pole de recherche cardiovasculaire, institut de recherche expérimentale et clinique, Université catholique de Louvain 3 Service de médecine nucléaire, cliniques universitaires St-Luc, Bruxelles, Belgique ∗ Corresponding author. E-mail address: [email protected] (L. Michel)
243 Introduction Cardiac beta3-adrenergic receptors (B3AR) produce effects antipathetic to those of B1 and B2 receptors. Importantly, B3AR are resistant to desensitization and their expression is upregulated in the diseased myocardium. We previously showed that mice with moderate cardiac-specific expression of the human B3AR (B3TG) are protected from hypertrophy and fibrosis upon hemodynamic or neurohormonal stress. Objective Here we tested the hypothesis that myocardial protection may be mediated by metabolic effects of B3AR in cardiac myocytes, akin to well-known B3AR metabolic effects in adipose tissue. Method We used both B3-TG mice (and WT littermate) and isolated adult cardiac myocytes exposed to hemodynamic overload (TAC) (or sham control). Results We found that 9 week-TAC induced hypertrophy and fibrosis in WT mice, as expected. Notably this was paralleled with decreased activation of AMPK assessed by AMPK phosphorylation at Thr-172 and phosphorylation of its downstream target ACC. However, in B3-TG mice AMPK activation was preserved post TAC. Moreover, siRNA downregulation of alpha1/2 AMPK attenuated the protection from hypertrophy by B3AR expression, confirming AMPK implication in the B3AR control of hypertrophy. As cardiac AMPK controls metabolic substrate use and uptake, we examined glucose uptake in adult cardiac myocytes isolated from B3-TG (and WT) mice after TAC, with/without insulin. Cardiac myocytes from stressed B3TG mice exhibited a significant increase in 2-3H glucose uptake upon insulin treatment, whereas WT myocytes developed insulinoresistance. In vivo B3-TG also exhibited an increased myocardial uptake of the glucose analog 18FDG compared to WT littermates, e.g. at 9 weeks post-TAC. Conclusion We conclude that cardiac myocyte-specific expression of B3AR concurrently prevents the development of insulin resistance and maintains AMPK activation contributing to the protection from hypertrophic remodeling under hemodynamic stress. Disclosure of interest The authors declare that they have no competing interest. https://doi.org/10.1016/j.acvdsp.2019.02.134