@article{JanzWalzCirnuetal.2024,
  author    = {Janz, Anna and Walz, Katharina and Cirnu, Alexandra and Surjanto, Jessica and Urlaub, Daniela and Leskien, Miriam and Kohlhaas, Michael and Nickel, Alexander and Brand, Theresa and Nose, Naoko and W{\"o}rsd{\"o}rfer, Philipp and Wagner, Nicole and Higuchi, Takahiro and Maack, Christoph and Dudek, Jan and Lorenz, Kristina and Klopocki, Eva and Erg{\"u}n, S{\"u}leyman and Duff, Henry J. and Gerull, Brenda},
  title     = {Mutations in DNAJC19 cause altered mitochondrial structure and increased mitochondrial respiration in human iPSC-derived cardiomyocytes},
  series = {Molecular Metabolism},
  volume    = {79},
  journal   = {Molecular Metabolism},
  issn      = {2212-8778},
  doi       = {10.1016/j.molmet.2023.101859},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-350393},
  year      = {2024},
  abstract  = {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.},
  language  = {en}
}
@article{SchwemmleinMaackBertero2022,
  author    = {Schwemmlein, Julia and Maack, Christoph and Bertero, Edoardo},
  title     = {Mitochondria as therapeutic targets in heart failure},
  series = {Current Heart Failure Reports},
  volume    = {19},
  journal   = {Current Heart Failure Reports},
  number    = {2},
  doi       = {10.1007/s11897-022-00539-0},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324015},
  pages     = {27-37},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{BețiuNoveanuHancuetal.2022,
  author    = {Bețiu, Alina M. and Noveanu, Lavinia and H{\^a}ncu, Iasmina M. and Lascu, Ana and Petrescu, Lucian and Maack, Christoph and Elm{\´e}r, Eskil and Muntean, Danina M.},
  title     = {Mitochondrial effects of common cardiovascular medications: the good, the bad and the mixed},
  series = {International Journal of Molecular Sciences},
  volume    = {23},
  journal   = {International Journal of Molecular Sciences},
  number    = {21},
  issn      = {1422-0067},
  doi       = {10.3390/ijms232113653},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-297384},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{KayvanpourWisdomLackneretal.2022,
  author    = {Kayvanpour, Elham and Wisdom, Michael and Lackner, Maximilian K. and Sedaghat-Hamedani, Farbod and Boeckel, Jes-Niels and M{\"u}ller, Marion and Eghbalian, Rose and Dudek, Jan and Doroudgar, Shirin and Maack, Christoph and Frey, Norbert and Meder, Benjamin},
  title     = {VARS2 depletion leads to activation of the integrated stress response and disruptions in mitochondrial fatty acid oxidation},
  series = {International Journal of Molecular Sciences},
  volume    = {23},
  journal   = {International Journal of Molecular Sciences},
  number    = {13},
  issn      = {1422-0067},
  doi       = {10.3390/ijms23137327},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-284590},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{DudekMaack2022,
  author    = {Dudek, Jan and Maack, Christoph},
  title     = {Mechano-energetic aspects of Barth syndrome},
  series = {Journal of Inherited Metabolic Disease},
  volume    = {45},
  journal   = {Journal of Inherited Metabolic Disease},
  number    = {1},
  doi       = {10.1002/jimd.12427},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257512},
  pages     = {82-98},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{WagnerBerteroNickeletal.2020,
  author    = {Wagner, Michael and Bertero, Edoardo and Nickel, Alexander and Kohlhaas, Michael and Gibson, Gary E. and Heggermont, Ward and Heymans, Stephane and Maack, Christoph},
  title     = {Selective NADH communication from α-ketoglutarate dehydrogenase to mitochondrial transhydrogenase prevents reactive oxygen species formation under reducing conditions in the heart},
  series = {Basic Research in Cardiology},
  volume    = {115},
  journal   = {Basic Research in Cardiology},
  issn      = {0300-8428},
  doi       = {10.1007/s00395-020-0815-1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234907},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{KolokotronisPlutaKlopockietal.2020,
  author    = {Kolokotronis, Konstantinos and Pluta, Natalie and Klopocki, Eva and Kunstmann, Erdmute and Messroghli, Daniel and Maack, Christoph and Tejman-Yarden, Shai and Arad, Michael and Rost, Simone and Gerull, Brenda},
  title     = {New Insights on Genetic Diagnostics in Cardiomyopathy and Arrhythmia Patients Gained by Stepwise Exome Data Analysis},
  series = {Journal of Clinical Medicine},
  volume    = {9},
  journal   = {Journal of Clinical Medicine},
  number    = {7},
  doi       = {10.3390/jcm9072168},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236094},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{SacchettoSequeiraBerteroetal.2019,
  author    = {Sacchetto, Claudia and Sequeira, Vasco and Bertero, Edoardo and Dudek, Jan and Maack, Christoph and Calore, Martina},
  title     = {Metabolic Alterations in Inherited Cardiomyopathies},
  series = {Journal of Clinical Medicine},
  volume    = {8},
  journal   = {Journal of Clinical Medicine},
  number    = {12},
  issn      = {2077-0383},
  doi       = {10.3390/jcm8122195},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-193806},
  year      = {2019},
  abstract  = {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.},
  language  = {en}
}
@article{SeidlmayerMagesBerbneretal.2019,
  author    = {Seidlmayer, Lea K. and Mages, Christine and Berbner, Annette and Eder-Negrin, Petra and Arias-Loza, Paula Anahi and Kaspar, Mathias and Song, Moshi and Dorn, Gerald W. and Kohlhaas, Michael and Frantz, Stefan and Maack, Christoph and Gerull, Brenda and Dedkova, Elena N.},
  title     = {Mitofusin 2 is essential for IP3-mediated SR/Mitochondria metabolic feedback in ventricular myocytes},
  series = {Frontiers in Physiology},
  volume    = {10},
  journal   = {Frontiers in Physiology},
  number    = {733},
  issn      = {1664-042X},
  doi       = {10.3389/fphys.2019.00733},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-199141},
  year      = {2019},
  abstract  = {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).},
  language  = {en}
}