15 research outputs found
AltĂ©rations du mĂ©tabolisme cardiaque associĂ©es Ă des dĂ©sordres gĂ©nĂ©tiques de lâoxydation des acides gras Ă chaĂźne longue chez la souris
Bien que le changement dans le choix des substrats Ă©nergĂ©tiques des acides gras (AGs) vers les glucides soit considĂ©rĂ© comme bĂ©nĂ©fique pour le cĆur insuffisant, il nâest pas clair Ă savoir pourquoi les patients atteints de dĂ©sordres de la ÎČ-oxydation (ÎČ-OX) des AGs Ă chaĂźne longue (AGCLs) dĂ©veloppent des troubles du rythme et des cardiomyopathies. De plus, le traitement actuel ne permet pas de prĂ©venir lâapparition du phĂ©notype clinique chez tous les patients, spĂ©cifiquement en condition de jeĂ»ne ou de stress. Ainsi, plusieurs modĂšles de souris dĂ©ficientes pour des enzymes impliquĂ©es dans lâoxydation des acides gras ont Ă©tĂ© dĂ©veloppĂ©s de maniĂšre Ă amĂ©liorer les connaissances de la maladie ainsi que les traitements offerts aux patients.
Ă cet Ă©gard, cette Ă©tude vise Ă Ă©valuer le phĂ©notype mĂ©tabolique et fonctionnel des cĆurs de souris dĂ©ficientes pour le rĂ©cepteur activĂ© de la prolifĂ©ration des peroxysomes-α (PPARα), un facteur de transcription des gĂšnes impliquĂ©s notamment dans la ÎČ-OX des AGs, et pour la dĂ©shydrogĂ©nase des acyl-CoA Ă trĂšs longue chaĂźne (very-long chain acyl-CoA dehydrogenase, VLCAD), le dĂ©ficit de lâoxydation des AGCLs le plus commun chez lâhumain. Lâapproche expĂ©rimentale utilisĂ©e comprend plusieurs techniques dont (i) la perfusion ex vivo de cĆur de souris au travail combinĂ©e Ă lâutilisation de substrats marquĂ©s au carbone 13 (13C) et Ă lâanalyse par chromatographie gazeuse-spectromĂ©trie de masse (GCMS), (ii) lâanalyse de lâexpression gĂ©nique par qPCR et (iii) lâanalyse de lâactivitĂ© Ă©lectrique du cĆur in vivo par tĂ©lĂ©mĂ©trie. De maniĂšre inattendue, les rĂ©sultats de cette Ă©tude menĂ©e chez la souris ont permis de mettre en Ă©vidence que des dĂ©ficits pour des protĂ©ines impliquĂ©es dans lâoxydation des AGCLs sont associĂ©s Ă des altĂ©rations du mĂ©tabolisme (i) des glucides, (ii) des AGs polyinsaturĂ©s (AGPIs), et (iii) mitochondrial, incluant lâanaplĂ©rose, en plus dâĂȘtre liĂ©s Ă des dĂ©sordres de la fonction Ă©lectrique du cĆur, Ă savoir une prolongation du segment QTc. Pris dans leur ensemble, les rĂ©sultats de cette thĂšse pourraient servir Ă lâĂ©laboration de nouvelles interventions mĂ©taboliques destinĂ©es Ă amĂ©liorer les traitements possibles et donc, la qualitĂ© de vie des patients atteints de dĂ©sordres hĂ©rĂ©ditaires de la ÎČ-OX des AGCLs.While a shift from fatty acids to carbohydrate is considered beneficial for the failing heart, it is unclear why patients with fatty acid oxidation disorders present clinical manifestations such as cardiomyopathy, arrhythmia and conduction defects. Unfortunately, the current nutritional treatment for these patients is limited in its ability to prevent these symptoms, especially under fasting and stress conditions. Many mouse models of fatty acid oxidation deficiency have been developed to improve the knowledge of the disease and the treatment of these patients. In this regard, this study aims to characterize the metabolic and functional phenotype of hearts from mice that are deficient for the peroxisome proliferator-activated receptor α, a transcription factor for gene involved in fatty acid oxidation, and very long chain acyl-CoA dehydrogenase, the most common inherited long chain fatty acid oxidation disorder in human, under various conditions.
In this study, numerous approaches have been used, which includes validated experimental paradigms, namely, (i) ex vivo heart perfusion in the working mode with concomitant evaluation of myocardial contractility and metabolic fluxes, employing 13C-labeled substrates combined with mass isotopomer analysis by gas chromatography coupled to mass spectrometry, (ii) gene expression analysis by qPCR and (iii) electrocardiogram monitoring in vivo by telemetry. Unexpectedly, results from the present thesis demonstrate that fatty acid oxidation disorders cause alterations in metabolism of (i) carbohydrates (ii) polyunsaturated fatty acids of the omega-3 type, specifically docosahaexanoic acid, and (iii) mitochondria including anaplerosis, in addition to lead to functional abnormalities, namely a prolongation of the QT interval. Altogether, results from this thesis could contribute to new metabolic therapy development to improve the quality of life of the patients with inherited long chain fatty acid oxidation disorder
TECRL, a new lifeâthreatening inherited arrhythmia gene associated with overlapping clinical features of both LQTS and CPVT
Genetic causes of many familial arrhythmia syndromes remain elusive. In this study, whole-exome sequencing (WES) was carried out on patients from three different families that presented with life-threatening arrhythmias and high risk of sudden cardiac death (SCD). Two French Canadian probands carried identical homozygous rare variant in TECRL gene (p.Arg196Gln), which encodes the trans-2,3-enoyl-CoA reductase-like protein. Both patients had cardiac arrest, stress-induced atrial and ventricular tachycardia, and QT prolongation on adrenergic stimulation. A third patient from a consanguineous Sudanese family diagnosed with catecholaminergic polymorphic ventricular tachycardia (CPVT) had a homozygous splice site mutation (c.331+1G>A) in TECRL Analysis of intracellular calcium ([Ca(2+)]i) dynamics in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) generated from this individual (TECRLHom-hiPSCs), his heterozygous but clinically asymptomatic father (TECRLHet-hiPSCs), and a healthy individual (CTRL-hiPSCs) from the same Sudanese family, revealed smaller [Ca(2+)]i transient amplitudes as well as elevated diastolic [Ca(2+)]i in TECRLHom-hiPSC-CMs compared with CTRL-hiPSC-CMs. The [Ca(2+)]i transient also rose markedly slower and contained lower sarcoplasmic reticulum (SR) calcium stores, evidenced by the decreased magnitude of caffeine-induced [Ca(2+)]i transients. In addition, the decay phase of the [Ca(2+)]i transient was slower in TECRLHom-hiPSC-CMs due to decreased SERCA and NCX activities. Furthermore, TECRLHom-hiPSC-CMs showed prolonged action potentials (APs) compared with CTRL-hiPSC-CMs. TECRL knockdown in control human embryonic stem cell-derived CMs (hESC-CMs) also resulted in significantly longer APs. Moreover, stimulation by noradrenaline (NA) significantly increased the propensity for triggered activity based on delayed afterdepolarizations (DADs) in TECRLHom-hiPSC-CMs and treatment with flecainide, a class Ic antiarrhythmic drug, significantly reduced the triggered activity in these cells. In summary, we report that mutations in TECRL are associated with inherited arrhythmias characterized by clinical features of both LQTS and CPVT Patient-specific hiPSC-CMs recapitulated salient features of the clinical phenotype and provide a platform for drug screening evidenced by initial identification of flecainide as a potential therapeutic. These findings have implications for diagnosis and treatment of inherited cardiac arrhythmias
O-GlcNAcylation, enemy or ally during cardiac hypertrophy development?
O-linked attachment of the monosaccharide ÎČ-N-acetyl-glucosamine (O-GlcNAcylation) is a post-translational modification occurring on serine and threonine residues, which is evolving as an important mechanism for the regulation of various cellular processes. The present review will, first, provide a general background on the molecular regulation of protein O-GlcNAcylation and will summarize the role of this post-translational modification in various acute cardiac pathologies including ischemia-reperfusion. Then, we will focus on research studies examining protein O-GlcNAcylation in the context of cardiac hypertrophy. A particular emphasis will be laid on the convergent but also divergent actions of O-GlcNAcylation according to the type of hypertrophy investigated, including physiological, pressure overload-induced and diabetes-linked cardiac hypertrophy. In an attempt to distinguish whether O-GlcNAcylation is detrimental or beneficial, this review will present the different O-GlcNAcylated targets involved in hypertrophy development. We will finally argue on potential interest to target O-GlcNAc processes to treat cardiac hypertrophy. This article is part of a Special Issue entitled: The role of post-translational protein modifications on heart and vascular metabolism edited by Jason R.B. Dyck & Jan F.C. Glatz
AMP-Activated Protein Kinase and O-GlcNAcylation, Two Partners Tightly Connected to Regulate Key Cellular Processes.
The AMP-activated protein kinase (AMPK) is an important cellular energy sensor. Its activation under energetic stress is known to activate energy-producing pathways and to inactivate energy-consuming pathways, promoting ATP preservation and cell survival. AMPK has been shown to play protective role in many pathophysiological processes including cardiovascular diseases, diabetes, and cancer. Its action is multi-faceted and comprises short-term regulation of enzymes by direct phosphorylation as well as long-term adaptation via control of transcription factors and cellular events such as autophagy. During the last decade, several studies underline the particular importance of the interaction between AMPK and the post-translational modification called O-GlcNAcylation. O-GlcNAcylation means the O-linked attachment of a single N-acetylglucosamine moiety on serine or threonine residues. O-GlcNAcylation plays a role in multiple physiological cellular processes but is also associated with the development of various diseases. The first goal of the present review is to present the tight molecular relationship between AMPK and enzymes regulating O-GlcNAcylation. We then draw the attention of the reader on the putative importance of this interaction in different pathophysiological events
Ivabradine reduces heart rate while preserving metabolic fluxes and energy status of healthy normoxic working hearts
Metabolism and acetylation contribute to leucine-mediated inhibition of cardiac glucose uptake.
High plasma leucine levels strongly correlate with type 2 diabetes. Studies of muscle cells suggest that leucine alters the insulin response for glucose transport by activating an insulin-negative feedback loop driven by the mammalian target of rapamycin/p70 ribosomal S6 kinase (mTOR/p70S6K) pathway. Here, we examined the molecular mechanism involved in leucine's action on cardiac glucose uptake. Leucine was indeed able to curb glucose uptake after insulin stimulation in both cultured cardiomyocytes and perfused hearts. Although leucine activated mTOR/p70S6K, the mTOR inhibitor rapamycin did not prevent leucine's inhibitory action on glucose uptake, ruling out the contribution of the insulin-negative feedback loop. α-Ketoisocaproate, the first metabolite of leucine catabolism, mimicked leucine's effect on glucose uptake. Incubation of cardiomyocytes with (13)C-labeled leucine ascertained its metabolism to ketone bodies (KBs), which had similar negative impact on insulin-stimulated glucose transport. Both leucine and KBs reduced glucose uptake by affecting translocation of the glucose transporter 4 (GLUT4) to the plasma membrane. Finally, we found that leucine elevated global protein acetylation level. Pharmacological inhibition of lysine acetyltransferases counteracted this increase in protein acetylation and prevented leucine's inhibitory action on both glucose uptake and GLUT4 translocation. Taken together, these results indicate that leucine metabolism into KBs contributes to inhibition of cardiac glucose uptake by hampering the translocation of GLUT4-containing vesicles via acetylation. They offer new insight into the establishment of insulin resistance in the heart
A-769662 potentiates the effect of other AMP-activated protein kinase activators on cardiac glucose uptake.
AMP-activated protein kinase (AMPK), a key cellular sensor of energy, regulates metabolic homeostasis and plays a protective role in the ischemic or diabetic heart. Stimulation of cardiac glucose uptake contributes to this AMPK-mediated protection. The small-molecule AMPK activator A-769662, which binds and directly activates AMPK, has recently been characterized. A-769662-dependent AMPK activation protects the heart against an ischemia-reperfusion episode but is unable to stimulate skeletal muscle glucose uptake. Here, we tried to reconcile these conflicting findings by investigating the impact of A-769662 on cardiac AMPK signaling and glucose uptake. We showed that A-769662 promoted AMPK activation, resulting in the phosphorylation of several downstream targets, but was incapable of stimulating glucose uptake in cultured cardiomyocytes and the perfused heart. The lack of glucose uptake stimulation can be explained by A-769662's narrow specificity, since it selectively activates cardiac AMPK heterotrimeric complexes containing α2/ÎČ1-subunits, the others being presumably required for this metabolic outcome. However, when combined with classical AMPK activators, such as metformin, phenformin, oligomycin, or hypoxia, which impact AMPK heterotrimers more broadly via elevation of cellular AMP levels, A-769662 induced more profound AMPK phosphorylation and subsequent glucose uptake stimulation. The synergistic effect of A-769662 under such ischemia-mimetic conditions protected cardiomyocytes against ROS production and cell death. In conclusion, despite the fact that A-769662 activates AMPK, it alone does not significantly stimulate glucose uptake. However, strikingly, its ability of potentiating the action on other AMPK activators makes it a potentially useful participant in the protective role of AMPK in the heart
Remodeling of lipid landscape in high fat fed very-long chain acyl-CoA dehydrogenase null mice favors pro-arrhythmic polyunsaturated fatty acids and their downstream metabolites
International audienceVery-long chain acyl-CoA dehydrogenase (VLCAD) catalyzes the initial step of mitochondrial long chain (LC) fatty acid ÎČ-oxidation (FAO). Inherited VLCAD deficiency (VLCADD) predisposes to neonatal arrhythmias whose pathophysiology is still not understood. We hypothesized that VLCADD results in global disruption of cardiac complex lipid homeostasis, which may set conditions predisposing to arrhythmia. To test this, we assessed the cardiac lipidome and related molecular markers in seven-month-old VLCAD-/- mice, which mimic to some extent the human cardiac phenotype. Mice were sacrificed in the fed or fasted state after receiving for two weeks a chow or a high-fat diet (HFD), the latter condition being known to worsen symptoms in human VLCADD. Compared to their littermate counterparts, HFD/fasted VLCAD-/- mouse hearts displayed the following lipid alterations: (1) Lower LC, but higher VLC-acylcarnitines accumulation, (2) higher levels of arachidonic acid (AA) and lower docosahexaenoic acid (DHA) contents in glycerophospholipids (GPLs), as well as (3) corresponding changes in pro-arrhythmogenic AA-derived isoprostanes and thromboxane B2 (higher), and anti-arrythmogenic DHA-derived neuroprostanes (lower). These changes were associated with remodeling in the expression of gene or protein markers of (1) GPLs remodeling: higher calcium-dependent phospholipase A2 and lysophosphatidylcholine-acyltransferase 2, (2) calcium handling perturbations, and (3) endoplasmic reticulum stress. Altogether, these results highlight global lipid dyshomeostasis beyond FAO in VLCAD-/- mouse hearts, which may set conditions predisposing the hearts to calcium mishandling and endoplasmic reticulum stress and thereby may contribute to the pathogenesis of arrhythmias in VLCADD in mice as well as in humans