TY - JOUR A1 - Janz, Anna A1 - Walz, Katharina A1 - Cirnu, Alexandra A1 - Surjanto, Jessica A1 - Urlaub, Daniela A1 - Leskien, Miriam A1 - Kohlhaas, Michael A1 - Nickel, Alexander A1 - Brand, Theresa A1 - Nose, Naoko A1 - Wörsdörfer, Philipp A1 - Wagner, Nicole A1 - Higuchi, Takahiro A1 - Maack, Christoph A1 - Dudek, Jan A1 - Lorenz, Kristina A1 - Klopocki, Eva A1 - Ergün, Süleyman A1 - Duff, Henry J. A1 - Gerull, Brenda T1 - Mutations in DNAJC19 cause altered mitochondrial structure and increased mitochondrial respiration in human iPSC-derived cardiomyocytes JF - Molecular Metabolism N2 - Highlights • Loss of DNAJC19's DnaJ domain disrupts cardiac mitochondrial structure, leading to abnormal cristae formation in iPSC-CMs. • Impaired mitochondrial structures lead to an increased mitochondrial respiration, ROS and an elevated membrane potential. • Mutant iPSC-CMs show sarcomere dysfunction and a trend to more arrhythmias, resembling DCMA-associated cardiomyopathy. Background Dilated cardiomyopathy with ataxia (DCMA) is an autosomal recessive disorder arising from truncating mutations in DNAJC19, which encodes an inner mitochondrial membrane protein. Clinical features include an early onset, often life-threatening, cardiomyopathy associated with other metabolic features. Here, we aim to understand the metabolic and pathophysiological mechanisms of mutant DNAJC19 for the development of cardiomyopathy. Methods We generated induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) of two affected siblings with DCMA and a gene-edited truncation variant (tv) of DNAJC19 which all lack the conserved DnaJ interaction domain. The mutant iPSC-CMs and their respective control cells were subjected to various analyses, including assessments of morphology, metabolic function, and physiological consequences such as Ca\(^{2+}\) kinetics, contractility, and arrhythmic potential. Validation of respiration analysis was done in a gene-edited HeLa cell line (DNAJC19tv\(_{HeLa}\)). Results Structural analyses revealed mitochondrial fragmentation and abnormal cristae formation associated with an overall reduced mitochondrial protein expression in mutant iPSC-CMs. Morphological alterations were associated with higher oxygen consumption rates (OCRs) in all three mutant iPSC-CMs, indicating higher electron transport chain activity to meet cellular ATP demands. Additionally, increased extracellular acidification rates suggested an increase in overall metabolic flux, while radioactive tracer uptake studies revealed decreased fatty acid uptake and utilization of glucose. Mutant iPSC-CMs also showed increased reactive oxygen species (ROS) and an elevated mitochondrial membrane potential. Increased mitochondrial respiration with pyruvate and malate as substrates was observed in mutant DNAJC19tv HeLa cells in addition to an upregulation of respiratory chain complexes, while cellular ATP-levels remain the same. Moreover, mitochondrial alterations were associated with increased beating frequencies, elevated diastolic Ca\(^{2+}\) concentrations, reduced sarcomere shortening and an increased beat-to-beat rate variability in mutant cell lines in response to β-adrenergic stimulation. Conclusions Loss of the DnaJ domain disturbs cardiac mitochondrial structure with abnormal cristae formation and leads to mitochondrial dysfunction, suggesting that DNAJC19 plays an essential role in mitochondrial morphogenesis and biogenesis. Moreover, increased mitochondrial respiration, altered substrate utilization, increased ROS production and abnormal Ca\(^{2+}\) kinetics provide insights into the pathogenesis of DCMA-related cardiomyopathy. KW - cell biology KW - molecular biology KW - dilated cardiomyopathy with ataxia KW - genetics KW - metabolism KW - mitochondria KW - OXPHOS KW - ROS KW - contractility Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-350393 SN - 2212-8778 VL - 79 ER - TY - JOUR A1 - Kayvanpour, Elham A1 - Wisdom, Michael A1 - Lackner, Maximilian K. A1 - Sedaghat-Hamedani, Farbod A1 - Boeckel, Jes-Niels A1 - Müller, Marion A1 - Eghbalian, Rose A1 - Dudek, Jan A1 - Doroudgar, Shirin A1 - Maack, Christoph A1 - Frey, Norbert A1 - Meder, Benjamin T1 - VARS2 depletion leads to activation of the integrated stress response and disruptions in mitochondrial fatty acid oxidation JF - International Journal of Molecular Sciences N2 - Mutations in mitochondrial aminoacyl-tRNA synthetases (mtARSs) have been reported in patients with mitochondriopathies: most commonly encephalopathy, but also cardiomyopathy. Through a GWAS, we showed possible associations between mitochondrial valyl-tRNA synthetase (VARS2) dysregulations and non-ischemic cardiomyopathy. We aimed to investigate the possible consequences of VARS2 depletion in zebrafish and cultured HEK293A cells. Transient VARS2 loss-of-function was induced in zebrafish embryos using Morpholinos. The enzymatic activity of VARS2 was measured in VARS2-depleted cells via northern blot. Heterozygous VARS2 knockout was established in HEK293A cells using CRISPR/Cas9 technology. BN-PAGE and SDS-PAGE were used to investigate electron transport chain (ETC) complexes, and the oxygen consumption rate and extracellular acidification rate were measured using a Seahorse XFe96 Analyzer. The activation of the integrated stress response (ISR) and possible disruptions in mitochondrial fatty acid oxidation (FAO) were explored using RT-qPCR and western blot. Zebrafish embryos with transient VARS2 loss-of-function showed features of heart failure as well as indications of CNS and skeletal muscle involvements. The enzymatic activity of VARS2 was significantly reduced in VARS2-depleted cells. Heterozygous VARS2-knockout cells showed a rearrangement of ETC complexes in favor of complexes III\(_2\), III\(_2\) + IV, and supercomplexes without significant respiratory chain deficiencies. These cells also showed the enhanced activation of the ISR, as indicated by increased eIF-2α phosphorylation and a significant increase in the transcript levels of ATF4, ATF5, and DDIT3 (CHOP), as well as disruptions in FAO. The activation of the ISR and disruptions in mitochondrial FAO may underlie the adaptive changes in VARS2-depleted cells. KW - VARS2 KW - heart failure KW - integrated stress response KW - mitochondrial FAO Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284590 SN - 1422-0067 VL - 23 IS - 13 ER - TY - JOUR A1 - Schwemmlein, Julia A1 - Maack, Christoph A1 - Bertero, Edoardo T1 - Mitochondria as therapeutic targets in heart failure JF - Current Heart Failure Reports N2 - Purpose of Review We review therapeutic approaches aimed at restoring function of the failing heart by targeting mitochondrial reactive oxygen species (ROS), ion handling, and substrate utilization for adenosine triphosphate (ATP) production. Recent Findings Mitochondria-targeted therapies have been tested in animal models of and humans with heart failure (HF). Cardiac benefits of sodium/glucose cotransporter 2 inhibitors might be partly explained by their effects on ion handling and metabolism of cardiac myocytes. Summary The large energy requirements of the heart are met by oxidative phosphorylation in mitochondria, which is tightly regulated by the turnover of ATP that fuels cardiac contraction and relaxation. In heart failure (HF), this mechano-energetic coupling is disrupted, leading to bioenergetic mismatch and production of ROS that drive the progression of cardiac dysfunction. Furthermore, HF is accompanied by changes in substrate uptake and oxidation that are considered detrimental for mitochondrial oxidative metabolism and negatively affect cardiac efficiency. Mitochondria lie at the crossroads of metabolic and energetic dysfunction in HF and represent ideal therapeutic targets. KW - mitochondria KW - heart failure KW - reactive oxygen species KW - MitoQ KW - elamipretide KW - SGLT2 inhibitors KW - cardiac metabolism Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324015 VL - 19 IS - 2 ER - TY - JOUR A1 - Dudek, Jan A1 - Maack, Christoph T1 - Mechano-energetic aspects of Barth syndrome JF - Journal of Inherited Metabolic Disease N2 - Energy-demanding organs like the heart are strongly dependent on oxidative phosphorylation in mitochondria. Oxidative phosphorylation is governed by the respiratory chain located in the inner mitochondrial membrane. The inner mitochondrial membrane is the only cellular membrane with significant amounts of the phospholipid cardiolipin, and cardiolipin was found to directly interact with a number of essential protein complexes, including respiratory chain complexes I to V. An inherited defect in the biogenesis of cardiolipin causes Barth syndrome, which is associated with cardiomyopathy, skeletal myopathy, neutropenia and growth retardation. Energy conversion is dependent on reducing equivalents, which are replenished by oxidative metabolism in the Krebs cycle. Cardiolipin deficiency in Barth syndrome also affects Krebs cycle activity, metabolite transport and mitochondrial morphology. During excitation-contraction coupling, calcium (Ca\(^{2+}\)) released from the sarcoplasmic reticulum drives sarcomeric contraction. At the same time, Ca\(^{2+}\) influx into mitochondria drives the activation of Krebs cycle dehydrogenases and the regeneration of reducing equivalents. Reducing equivalents are essential not only for energy conversion, but also for maintaining a redox buffer, which is required to detoxify reactive oxygen species (ROS). Defects in CL may also affect Ca\(^{2+}\) uptake into mitochondria and thereby hamper energy supply and demand matching, but also detoxification of ROS. Here, we review the impact of cardiolipin deficiency on mitochondrial function in Barth syndrome and discuss potential therapeutic strategies. KW - Barth syndrome KW - respiratory chain KW - reactive oxygen species KW - cardiolipin KW - mitochondria Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257512 VL - 45 IS - 1 ER - TY - JOUR A1 - Bețiu, Alina M. A1 - Noveanu, Lavinia A1 - Hâncu, Iasmina M. A1 - Lascu, Ana A1 - Petrescu, Lucian A1 - Maack, Christoph A1 - Elmér, Eskil A1 - Muntean, Danina M. T1 - Mitochondrial effects of common cardiovascular medications: the good, the bad and the mixed JF - International Journal of Molecular Sciences N2 - Mitochondria are central organelles in the homeostasis of the cardiovascular system via the integration of several physiological processes, such as ATP generation via oxidative phosphorylation, synthesis/exchange of metabolites, calcium sequestration, reactive oxygen species (ROS) production/buffering and control of cellular survival/death. Mitochondrial impairment has been widely recognized as a central pathomechanism of almost all cardiovascular diseases, rendering these organelles important therapeutic targets. Mitochondrial dysfunction has been reported to occur in the setting of drug-induced toxicity in several tissues and organs, including the heart. Members of the drug classes currently used in the therapeutics of cardiovascular pathologies have been reported to both support and undermine mitochondrial function. For the latter case, mitochondrial toxicity is the consequence of drug interference (direct or off-target effects) with mitochondrial respiration/energy conversion, DNA replication, ROS production and detoxification, cell death signaling and mitochondrial dynamics. The present narrative review aims to summarize the beneficial and deleterious mitochondrial effects of common cardiovascular medications as described in various experimental models and identify those for which evidence for both types of effects is available in the literature. KW - cardiovascular drugs KW - drug toxicity KW - mitochondria function and morphology KW - adverse effects KW - lactic acidosis KW - drug intoxication KW - drug interaction Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-297384 SN - 1422-0067 VL - 23 IS - 21 ER - TY - JOUR A1 - Ljubojević-Holzer, Senka A1 - Kraler, Simon A1 - Djalinac, Nataša A1 - Abdellatif, Mahmoud A1 - Voglhuber, Julia A1 - Schipke, Julia A1 - Schmidt, Marlene A1 - Kling, Katharina-Maria A1 - Franke, Greta Therese A1 - Herbst, Viktoria A1 - Zirlik, Andreas A1 - von Lewinski, Dirk A1 - Scherr, Daniel A1 - Rainer, Peter P A1 - Kohlhaas, Michael A1 - Nickel, Alexander A1 - Mühlfeld, Christian A1 - Maack, Christoph A1 - Sedej, Simon T1 - Loss of autophagy protein ATG5 impairs cardiac capacity in mice and humans through diminishing mitochondrial abundance and disrupting Ca2+ cycling JF - Cardiovascular Research N2 - Aims Autophagy protects against the development of cardiac hypertrophy and failure. While aberrant Ca2+ handling promotes myocardial remodelling and contributes to contractile dysfunction, the role of autophagy in maintaining Ca2+ homeostasis remains elusive. Here, we examined whether Atg5 deficiency-mediated autophagy promotes early changes in subcellular Ca2+ handling in ventricular cardiomyocytes, and whether those alterations associate with compromised cardiac reserve capacity, which commonly precedes the onset of heart failure. Methods and results RT–qPCR and immunoblotting demonstrated reduced Atg5 gene and protein expression and decreased abundancy of autophagy markers in hypertrophied and failing human hearts. The function of ATG5 was examined using cardiomyocyte-specific Atg5-knockout mice (Atg5−/−). Before manifesting cardiac dysfunction, Atg5−/− mice showed compromised cardiac reserve in response to β-adrenergic stimulation. Consequently, effort intolerance and maximal oxygen consumption were reduced during treadmill-based exercise tolerance testing. Mechanistically, cellular imaging revealed that Atg5 deprivation did not alter spatial and functional organization of intracellular Ca2+ stores or affect Ca2+ cycling in response to slow pacing or upon acute isoprenaline administration. However, high-frequency stimulation exposed stunted amplitude of Ca2+ transients, augmented nucleoplasmic Ca2+ load, and increased CaMKII activity, especially in the nuclear region of hypertrophied Atg5−/− cardiomyocytes. These changes in Ca2+ cycling were recapitulated in hypertrophied human cardiomyocytes. Finally, ultrastructural analysis revealed accumulation of mitochondria with reduced volume and size distribution, meanwhile functional measurements showed impaired redox balance in Atg5−/− cardiomyocytes, implying energetic unsustainability due to overcompensation of single mitochondria, particularly under increased workload. Conclusion Loss of cardiac Atg5-dependent autophagy reduces mitochondrial abundance and causes subtle alterations in subcellular Ca2+ cycling upon increased workload in mice. Autophagy-related impairment of Ca2+ handling is progressively worsened by β-adrenergic signalling in ventricular cardiomyocytes, thereby leading to energetic exhaustion and compromised cardiac reserve. KW - cardiomyocytes KW - calcium KW - mitochondria KW - autophagy KW - beta-adrenergic signalling Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-369345 VL - 118 ER - TY - JOUR A1 - Linz, Benedikt A1 - Hohl, Mathias A1 - Lang, Lisa A1 - Wong, Dickson W. L. A1 - Nickel, Alexander G. A1 - De La Torre, Carolina A1 - Sticht, Carsten A1 - Wirth, Klaus A1 - Boor, Peter A1 - Maack, Christoph A1 - Speer, Thimoteus A1 - Jespersen, Thomas A1 - Schotten, Ulrich A1 - Sanders, Prashanthan A1 - Böhm, Michael A1 - Linz, Dominik T1 - Repeated exposure to transient obstructive sleep apnea–related conditions causes an atrial fibrillation substrate in a chronic rat model JF - Heart Rhythm N2 - Background High night-to-night variability in obstructive sleep apnea (OSA) is associated with atrial fibrillation (AF). Obstructive apneas are characterized by intermittent deoxygenation-reoxygenation and intrathoracic pressure swings during ineffective inspiration against occluded upper airways. Objective We elucidated the effect of repeated exposure to transient OSA conditions simulated by intermittent negative upper airway pressure (INAP) on the development of an AF substrate. Methods INAP (48 events/4 h; apnea-hypopnea index 12 events/h) was applied in sedated spontaneously breathing rats (2% isoflurane) to simulate mild-to-moderate OSA. Rats without INAP served as a control group (CTR). In an acute test series (ATS), rats were either killed immediately (n = 9 per group) or after 24 hours of recovery (ATS-REC: n = 5 per group). To simulate high night-to-night variability in OSA, INAP applications (n = 10; 24 events/4 h; apnea-hypopnea index 6/h) were repeated every second day for 3 weeks in a chronic test series (CTS). Results INAP increased atrial oxidative stress acutely, represented in decreases of reduced to oxidized glutathione ratio (ATS: INAP: 0.33 ± 0.05 vs CTR: 1 ± 0.26; P = .016), which was reversible after 24 hours (ATS-REC: INAP vs CTR; P = .274). Although atrial oxidative stress did not accumulate in the CTS, atrial histological analysis revealed increased cardiomyocyte diameters, reduced connexin 43 expression, and increased interstitial fibrosis formation (CTS: INAP 7.0% ± 0.5% vs CTR 5.1% ± 0.3%; P = .013), which were associated with longer inducible AF episodes (CTS: INAP: 11.65 ± 4.43 seconds vs CTR: 0.7 ± 0.33 seconds; P = .033). Conclusion Acute simulation of OSA was associated with reversible atrial oxidative stress. Cumulative exposure to these transient OSA-related conditions resulted in AF substrates and was associated with increased AF susceptibility. Mild-to-moderate OSA with high night-to-night variability may deserve intensive management to prevent atrial substrate development. KW - atrial fibrillation KW - night-to-night variability KW - obstructive sleep apnea KW - rats KW - substrate Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-369298 VL - 18 ER - TY - JOUR A1 - Wagner, Michael A1 - Bertero, Edoardo A1 - Nickel, Alexander A1 - Kohlhaas, Michael A1 - Gibson, Gary E. A1 - Heggermont, Ward A1 - Heymans, Stephane A1 - Maack, Christoph T1 - Selective NADH communication from α-ketoglutarate dehydrogenase to mitochondrial transhydrogenase prevents reactive oxygen species formation under reducing conditions in the heart JF - Basic Research in Cardiology N2 - In heart failure, a functional block of complex I of the respiratory chain provokes superoxide generation, which is transformed to H\(_2\)O\(_2\) by dismutation. The Krebs cycle produces NADH, which delivers electrons to complex I, and NADPH for H\(_2\)O\(_2\) elimination via isocitrate dehydrogenase and nicotinamide nucleotide transhydrogenase (NNT). At high NADH levels, α-ketoglutarate dehydrogenase (α-KGDH) is a major source of superoxide in skeletal muscle mitochondria with low NNT activity. Here, we analyzed how α-KGDH and NNT control H\(_2\)O\(_2\) emission in cardiac mitochondria. In cardiac mitochondria from NNT-competent BL/6N mice, H\(_2\)O\(_2\) emission is equally low with pyruvate/malate (P/M) or α-ketoglutarate (α-KG) as substrates. Complex I inhibition with rotenone increases H2O2 emission from P/M, but not α-KG respiring mitochondria, which is potentiated by depleting H\(_2\)O\(_2\)-eliminating capacity. Conversely, in NNT-deficient BL/6J mitochondria, H2O2 emission is higher with α-KG than with P/M as substrate, and further potentiated by complex I blockade. Prior depletion of H\(_2\)O\(_2\)-eliminating capacity increases H\(_2\)O\(_2\) emission from P/M, but not α-KG respiring mitochondria. In cardiac myocytes, downregulation of α-KGDH activity impaired dynamic mitochondrial redox adaptation during workload transitions, without increasing H\(_2\)O\(_2\) emission. In conclusion, NADH from α-KGDH selectively shuttles to NNT for NADPH formation rather than to complex I of the respiratory chain for ATP production. Therefore, α-KGDH plays a key role for H\(_2\)O\(_2\) elimination, but is not a relevant source of superoxide in heart. In heart failure, α-KGDH/NNT-dependent NADPH formation ameliorates oxidative stress imposed by complex I blockade. Downregulation of α-KGDH may, therefore, predispose to oxidative stress in heart failure. KW - mitochondria KW - α-Ketoglutarate dehydrogenase KW - reactive oxygen species KW - nicotinamide nucleotide transhydrogenase Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234907 SN - 0300-8428 VL - 115 ER - TY - JOUR A1 - Kolokotronis, Konstantinos A1 - Pluta, Natalie A1 - Klopocki, Eva A1 - Kunstmann, Erdmute A1 - Messroghli, Daniel A1 - Maack, Christoph A1 - Tejman-Yarden, Shai A1 - Arad, Michael A1 - Rost, Simone A1 - Gerull, Brenda T1 - New Insights on Genetic Diagnostics in Cardiomyopathy and Arrhythmia Patients Gained by Stepwise Exome Data Analysis JF - Journal of Clinical Medicine N2 - Inherited cardiomyopathies are characterized by clinical and genetic heterogeneity that challenge genetic diagnostics. In this study, we examined the diagnostic benefit of exome data compared to targeted gene panel analyses, and we propose new candidate genes. We performed exome sequencing in a cohort of 61 consecutive patients with a diagnosis of cardiomyopathy or primary arrhythmia, and we analyzed the data following a stepwise approach. Overall, in 64% of patients, a variant of interest (VOI) was detected. The detection rate in the main sub-cohort consisting of patients with dilated cardiomyopathy (DCM) was much higher than previously reported (25/36; 69%). The majority of VOIs were found in disease-specific panels, while a further analysis of an extended panel and exome data led to an additional diagnostic yield of 13% and 5%, respectively. Exome data analysis also detected variants in candidate genes whose functional profile suggested a probable pathogenetic role, the strongest candidate being a truncating variant in STK38. In conclusion, although the diagnostic yield of gene panels is acceptable for routine diagnostics, the genetic heterogeneity of cardiomyopathies and the presence of still-unknown causes favor exome sequencing, which enables the detection of interesting phenotype–genotype correlations, as well as the identification of novel candidate genes. KW - cardiomyopathy KW - cardiogenetics KW - whole exome sequencing KW - targeted gene panel KW - candidate genes Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-236094 VL - 9 IS - 7 ER - TY - JOUR A1 - Seidlmayer, Lea K. A1 - Mages, Christine A1 - Berbner, Annette A1 - Eder-Negrin, Petra A1 - Arias-Loza, Paula Anahi A1 - Kaspar, Mathias A1 - Song, Moshi A1 - Dorn, Gerald W. A1 - Kohlhaas, Michael A1 - Frantz, Stefan A1 - Maack, Christoph A1 - Gerull, Brenda A1 - Dedkova, Elena N. T1 - Mitofusin 2 is essential for IP3-mediated SR/Mitochondria metabolic feedback in ventricular myocytes JF - Frontiers in Physiology N2 - Aim: Endothelin-1 (ET-1) and angiotensin II (Ang II) are multifunctional peptide hormones that regulate the function of the cardiovascular and renal systems. Both hormones increase the intracellular production of inositol-1,4,5-trisphosphate (IP\(_3\)) by activating their membrane-bound receptors. We have previously demonstrated that IP\(_3\)-mediated sarcoplasmic reticulum (SR) Ca\(^{2+}\) release results in mitochondrial Ca\(^{2+}\) uptake and activation of ATP production. In this study, we tested the hypothesis that intact SR/mitochondria microdomains are required for metabolic IP\(_3\)-mediated SR/mitochondrial feedback in ventricular myocytes. Methods: As a model for disrupted mitochondrial/SR microdomains, cardio-specific tamoxifen-inducible mitofusin 2 (Mfn2) knock out (KO) mice were used. Mitochondrial Ca\(^{2+}\) uptake, membrane potential, redox state, and ATP generation were monitored in freshly isolated ventricular myocytes from Mfn2 KO mice and their control wild-type (WT) littermates. Results: Stimulation of ET-1 receptors in healthy control myocytes increases mitochondrial Ca\(^{2+}\) uptake, maintains mitochondrial membrane potential and redox balance leading to the enhanced ATP generation. Mitochondrial Ca\(^{2+}\) uptake upon ET-1 stimulation was significantly higher in interfibrillar (IFM) and perinuclear (PNM) mitochondria compared to subsarcolemmal mitochondria (SSM) in WT myocytes. Mfn2 KO completely abolished mitochondrial Ca\(^{2+}\) uptake in IFM and PNM mitochondria but not in SSM. However, mitochondrial Ca2+ uptake induced by beta-adrenergic receptors activation with isoproterenol (ISO) was highest in SSM, intermediate in IFM, and smallest in PNM regions. Furthermore, Mfn2 KO did not affect ISO-induced mitochondrial Ca\(^{2+}\) uptake in SSM and IFM mitochondria; however, enhanced mitochondrial Ca\(^{2+}\) uptake in PNM. In contrast to ET-1, ISO induced a decrease in ATP levels in WT myocytes. Mfn2 KO abolished ATP generation upon ET-1 stimulation but increased ATP levels upon ISO application with highest levels observed in PNM regions. Conclusion: When the physical link between SR and mitochondria by Mfn2 was disrupted, the SR/mitochondrial metabolic feedback mechanism was impaired resulting in the inability of the IP\(_3\)-mediated SR Ca\(^{2+}\) release to induce ATP production in ventricular myocytes from Mfn2 KO mice. Furthermore, we revealed the difference in Mfn2-mediated SR-mitochondrial communication depending on mitochondrial location and type of communication (IP\(_3\)R-mRyR1 vs. ryanodine receptor type 2-mitochondrial calcium uniporter). KW - mitofusin 2 KW - IP3 KW - SR/mitochondria metabolic feedback KW - mitochondrial mRyR1 KW - ATP generation KW - endothelin-1 KW - Mfn2 KO mice Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-199141 SN - 1664-042X VL - 10 IS - 733 ER - TY - JOUR A1 - Sacchetto, Claudia A1 - Sequeira, Vasco A1 - Bertero, Edoardo A1 - Dudek, Jan A1 - Maack, Christoph A1 - Calore, Martina T1 - Metabolic Alterations in Inherited Cardiomyopathies JF - Journal of Clinical Medicine N2 - The normal function of the heart relies on a series of complex metabolic processes orchestrating the proper generation and use of energy. In this context, mitochondria serve a crucial role as a platform for energy transduction by supplying ATP to the varying demand of cardiomyocytes, involving an intricate network of pathways regulating the metabolic flux of substrates. The failure of these processes results in structural and functional deficiencies of the cardiac muscle, including inherited cardiomyopathies. These genetic diseases are characterized by cardiac structural and functional anomalies in the absence of abnormal conditions that can explain the observed myocardial abnormality, and are frequently associated with heart failure. Since their original description, major advances have been achieved in the genetic and phenotype knowledge, highlighting the involvement of metabolic abnormalities in their pathogenesis. This review provides a brief overview of the role of mitochondria in the energy metabolism in the heart and focuses on metabolic abnormalities, mitochondrial dysfunction, and storage diseases associated with inherited cardiomyopathies. KW - inherited cardiomyopathies KW - mitochondria KW - cardiac metabolism Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193806 SN - 2077-0383 VL - 8 IS - 12 ER - TY - JOUR A1 - de Boer, Rudolf A. A1 - De Keulenaer, Gilles A1 - Bauersachs, Johann A1 - Brutsaert, Dirk A1 - Cleland, John G. A1 - Diez, Javier A1 - Du, Xiao-Jun A1 - Ford, Paul A1 - Heinzel, Frank R. A1 - Lipson, Kenneth E. A1 - McDonagh, Theresa A1 - Lopez-Andres, Natalia A1 - Lunde, Ida G. A1 - Lyon, Alexander R. A1 - Pollesello, Piero A1 - Prasad, Sanjay K. A1 - Tocchetti, Carlo G. A1 - Mayr, Manuel A1 - Sluijter, Joost P. G. A1 - Thum, Thomas A1 - Tschöpe, Carsten A1 - Zannad, Faiez A1 - Zimmermann, Wolfram-Hubertus A1 - Ruschitzka, Frank A1 - Filippatos, Gerasimos A1 - Lindsey, Merry L. A1 - Maack, Christoph A1 - Heymans, Stephane T1 - Towards better definition, quantification and treatment of fibrosis in heart failure. A scientific roadmap by the Committee of Translational Research of the Heart Failure Association (HFA) of the European Society of Cardiology JF - European Journal of Heart Failure N2 - Fibrosis is a pivotal player in heart failure development and progression. Measurements of (markers of) fibrosis in tissue and blood may help to diagnose and risk stratify patients with heart failure, and its treatment may be effective in preventing heart failure and its progression. A lack of pathophysiological insights and uniform definitions has hampered the research in fibrosis and heart failure. The Translational Research Committee of the Heart Failure Association discussed several aspects of fibrosis in their workshop. Early insidious perturbations such as subclinical hypertension or inflammation may trigger first fibrotic events, while more dramatic triggers such as myocardial infarction and myocarditis give rise to full blown scar formation and ongoing fibrosis in diseased hearts. Aging itself is also associated with a cardiac phenotype that includes fibrosis. Fibrosis is an extremely heterogeneous phenomenon, as several stages of the fibrotic process exist, each with different fibrosis subtypes and a different composition of various cells and proteins — resulting in a very complex pathophysiology. As a result, detection of fibrosis, e.g. using current cardiac imaging modalities or plasma biomarkers, will detect only specific subforms of fibrosis, but cannot capture all aspects of the complex fibrotic process. Furthermore, several anti-fibrotic therapies are under investigation, but such therapies generally target aspecific aspects of the fibrotic process and suffer from a lack of precision. This review discusses the mechanisms and the caveats and proposes a roadmap for future research. KW - fibrosis KW - heart failure KW - biomarkers KW - fibroblast KW - matrix KW - prognosis KW - imaging Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-223613 VL - 21 ER -