bims-mitmed 2023-07-23 papers

bims-mitmed

Biomed News

on Mitochondrial medicine

Issue of 2023–07–23
25 papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico

Nanopore long-read next-generation sequencing for detection of mitochondrial DNA large-scale deletions.
Hepatic depletion of nucleolar protein mDEF causes excessive mitochondrial copper accumulation associated with p53 and NRF1 activation.
Small mitochondrial protein NERCLIN regulates cardiolipin homeostasis and mitochondrial ultrastructure.
A biallelic variant in COX18 cause isolated Complex IV deficiency associated with neonatal encephalo-cardio-myopathy and axonal sensory neuropathy.
Clinical, neuroradiological and molecular characterization of mitochondrial threonyl-tRNA-synthetase (TARS2)-related disorder.
Preserving mitochondria to treat hypertrophic cardiomyopathy: From rare mitochondrial DNA mutation to heart failure therapy?
Targeting an allosteric site in dynamin-related protein 1 to inhibit Fis1-mediated mitochondrial dysfunction.
Mitochondria during T cell aging.
Liver mitochondrial cristae organizing protein MIC19 promotes energy expenditure and pedestrian locomotion by altering nucleotide metabolism.
Generation of mouse hippocampal brain organoids from primary embryonic neural stem cells.
Design, Synthesis, and Biological Evaluation of Novel Mitochondria-targeting Exosomes.
Mitochondrial depletion syndrome type 3: the Lebanese variant.
Mitophagy in the retina: Viewing mitochondrial homeostasis through a new lens.
Fatty acid oxidation organizes mitochondrial supercomplexes to sustain astrocytic ROS and cognition.
Parkin regulates amino acid homeostasis at mitochondria-lysosome (M/L) contact sites in Parkinson's disease.
The mitochondrially targeted peptide elamipretide (SS-31) improves ADP sensitivity in aged mitochondria by increasing uptake through the adenine nucleotide translocator (ANT).
Uterus infantilis: a novel phenotype associated with AARS2 new genetic variants. A case report.
Elevation of NAD+ by nicotinamide riboside spares spinal cord tissue from injury and promotes locomotor recovery.
The emerging significance of mitochondrial targeted strategies in NAFLD treatment.
Fetal gene therapy.
Nuclear translocation of mitochondrial dehydrogenases as an adaptive cardioprotective mechanism.
Exploiting inter-tissue stress signaling mechanisms to preserve organismal proteostasis during aging.
Quantification of human mature frataxin protein expression in nonhuman primate hearts after gene therapy.
Gene therapy and other novel treatment approaches for Charcot-Marie-Tooth disease.
Greater Reliance on Glycolysis is Associated with Lower Mitochondrial Substrate Oxidation and Insulin Sensitivity in Infant Myogenic MSCs.

Front Genet. 2023 ;14 1089956

Nanopore long-read next-generation sequencing for detection of mitochondrial DNA large-scale deletions.

Chiara Frascarelli, Nadia Zanetti, Alessia Nasca, Rossella Izzo, Costanza Lamperti, Eleonora Lamantea, Andrea Legati, Daniele Ghezzi.

  Primary mitochondrial diseases are progressive genetic disorders affecting multiple organs and characterized by mitochondrial dysfunction. These disorders can be caused by mutations in nuclear genes coding proteins with mitochondrial localization or by genetic defects in the mitochondrial genome (mtDNA). The latter include point pathogenic variants and large-scale deletions/rearrangements. MtDNA molecules with the wild type or a variant sequence can exist together in a single cell, a condition known as mtDNA heteroplasmy. MtDNA single point mutations are typically detected by means of Next-Generation Sequencing (NGS) based on short reads which, however, are limited for the identification of structural mtDNA alterations. Recently, new NGS technologies based on long reads have been released, allowing to obtain sequences of several kilobases in length; this approach is suitable for detection of structural alterations affecting the mitochondrial genome. In the present work we illustrate the optimization of two sequencing protocols based on long-read Oxford Nanopore Technology to detect mtDNA structural alterations. This approach presents strong advantages in the analysis of mtDNA compared to both short-read NGS and traditional techniques, potentially becoming the method of choice for genetic studies on mtDNA.

Keywords:  MinION; complex-rearrangements; long reads; macrodeletion; mtDNA; multiple deletions; oxford nanopore; structural variants

DOI:  https://doi.org/10.3389/fgene.2023.1089956
iScience. 2023 Jul 21. 26(7): 107220

Hepatic depletion of nucleolar protein mDEF causes excessive mitochondrial copper accumulation associated with p53 and NRF1 activation.

Jinsong Wei, Shuai Wang, Haozhe Zhu, Wei Cui, Jianan Gao, Ce Gao, Bo Yu, Bojing Liu, Jun Chen, Jinrong Peng.

  Copper is an essential component in the mitochondrial respiratory chain complex IV (cytochrome c oxidases). However, whether any nucleolar factor(s) is(are) involved in regulating the mitochondrial copper homeostasis remains unclear. The nucleolar localized Def-Capn3 protein degradation pathway cleaves target proteins, including p53, in both zebrafish and human nucleoli. Here, we report that hepatic depletion of mDEF in mice causes an excessive copper accumulation in the mitochondria. We find that mDEF-depleted hepatocytes show an exclusion of CAPN3 from the nucleoli and accumulate p53 and NRF1 proteins in the nucleoli. Furthermore, we find that NRF1 is a CAPN3 substrate. Elevated p53 and NRF1 enhances the expression of Sco2 and Cox genes, respectively, to allow more copper acquirement in the mDefloxp/loxp, Alb:Cre mitochondria. Our findings reveal that the mDEF-CAPN3 pathway serves as a novel mechanism for regulating the mitochondrial copper homeostasis through targeting its substrates p53 and NRF1.

Keywords:  Biological sciences; Cell biology; Hepatology; Molecular biology; Sequence analysis

DOI:  https://doi.org/10.1016/j.isci.2023.107220
Proc Natl Acad Sci U S A. 2023 07 25. 120(30): e2210599120

Small mitochondrial protein NERCLIN regulates cardiolipin homeostasis and mitochondrial ultrastructure.

Svetlana Konovalova, Rubén Torregrosa-Muñumer, Pooja Manjunath, Xiaonan Liu, Sundar Baral, Kaneez Fatima, Minna Holopainen, Jouni Kvist, Jayasimman Rajendran, Yang Yang, Markku Varjosalo, Reijo Käkelä, Pentti Somerharju, Henna Tyynismaa.

  Cardiolipin (CL) is an essential phospholipid for mitochondrial structure and function. Here, we present a small mitochondrial protein, NERCLIN, as a negative regulator of CL homeostasis and mitochondrial ultrastructure. Primate-specific NERCLIN is expressed ubiquitously from the GRPEL2 locus on a tightly regulated low level. NERCLIN overexpression severely disrupts mitochondrial cristae structure and induces mitochondrial fragmentation. Proximity labeling and immunoprecipitation analysis suggested interactions of NERCLIN with CL synthesis and prohibitin complexes on the matrix side of the inner mitochondrial membrane. Lipid analysis indicated that NERCLIN regulates mitochondrial CL content. Furthermore, NERCLIN is responsive to heat stress ensuring OPA1 processing and cell survival. Thus, we propose that NERCLIN contributes to the stress-induced adaptation of mitochondrial dynamics. Our findings add NERCLIN to the group of recently identified small mitochondrial proteins with important regulatory functions.

Keywords:  NERCLIN; OPA1; cardiolipin; prohibitins; small mitochondrial proteins

DOI:  https://doi.org/10.1073/pnas.2210599120
Eur J Hum Genet. 2023 Jul 19.

A biallelic variant in COX18 cause isolated Complex IV deficiency associated with neonatal encephalo-cardio-myopathy and axonal sensory neuropathy.

Dario Ronchi, Manuela Garbellini, Francesca Magri, Francesca Menni, Megi Meneri, Maria Francesca Bedeschi, Robertino Dilena, Valeria Cecchetti, Irene Picciolli, Francesca Furlan, Valentina Polimeni, Sabrina Salani, Laura Pezzoli, Francesco Fortunato, Matteo Bellini, Daniela Piga, Michela Ripolone, Simona Zanotti, Laura Napoli, Patrizia Ciscato, Monica Sciacco, Giovanna Mangili, Fabio Mosca, Stefania Corti, Maria Iascone, Giacomo Pietro Comi.

Pathogenic variants impacting upon assembly of mitochondrial respiratory chain Complex IV (Cytochrome c Oxidase or COX) predominantly result in early onset mitochondrial disorders often leading to CNS, skeletal and cardiac muscle manifestations. The aim of this study is to describe a molecular defect in the COX assembly factor gene COX18 as the likely cause of a neonatal form of mitochondrial encephalo-cardio-myopathy and axonal sensory neuropathy. The proband is a 19-months old female displaying hypertrophic cardiomyopathy at birth and myopathy with axonal sensory neuropathy and failure to thrive developing in the first months of life. Serum lactate was consistently increased. Whole exome sequencing allowed the prioritization of the unreported homozygous substitution NM_001297732.2:c.667 G > C p.(Asp223His) in COX18. Patient's muscle biopsy revealed severe and diffuse COX deficiency and striking mitochondrial abnormalities. Biochemical and enzymatic studies in patient's myoblasts and in HEK293 cells after COX18 silencing showed a severe impairment of both COX activity and assembly. The biochemical defect was partially rescued by delivery of wild-type COX18 cDNA into patient's myoblasts. Our study identifies a novel defect of COX assembly and expands the number of nuclear genes involved in a mitochondrial disorder due to isolated COX deficiency.

DOI: https://doi.org/10.1038/s41431-023-01433-6
Genet Med. 2023 Jul 13. pii: S1098-3600(23)00951-6. [Epub ahead of print] 100938

Clinical, neuroradiological and molecular characterization of mitochondrial threonyl-tRNA-synthetase (TARS2)-related disorder.

Andrea Accogli, Sheng-Jia Lin, Mariasavina Severino, Sung-Hoon Kim, Kevin Huang, Clarissa Rocca, Megan Landsverk, Maha Zaki, Almundher Al-Maawali, Varunvenkat M Srinivasan, Khalid Al-Thihli, G Bradly Schaefer, Monica Davis, Davide Tonduti, Chiara Doneda, Lara M Marten, Chris Mühlhausen, Maria Gomez, Eleonora Lamantea, Rafael Mena, Mathilde Nizon, Vincent Procaccio, Amber Begtrup, Aida Telegrafi, Hong Cui, Heidi L Schulz, Julia Mohr, Saskia Biskup, Mariana Amina Loos, Hilda Verónica Aráoz, Vincenzo Salpietro, Laura Davis Keppen, Manali Chitre, Cassidy Petree, Lucy Raymond, Julie Vogt, Lindsey B Swayer, Alice A Basinger, Signe Vandal Pedersen, Toni S Pearson, Dorothy K Grange, Lokesh Lingapp, Paige McDunnah, Rita Horvath, Benjamin Cogne, Bertrand Isidor, Andreas Hahn, Karen Gripp, Seyed Mehdi Jafarnejad, Elsebet Ostergaard, Carlos E Prada, Daniele Ghezzi, Vykuntaraju K Gowda, Robert W Taylor, Nahum Sonenberg, Henry Houlden, Marie Sissler, Gaurav K Varshney, Reza Maroofian.

   PURPOSE: Biallelic variants in TARS2, encoding the mitochondrial threonyl-tRNA-synthetase, have been reported in a small group of individuals displaying a neurodevelopmental phenotype, but with limited neuroradiological data and insufficient evidence for causality of the variants.
METHODS: Exome or genome sequencing was carried out in 15 families. Clinical and neuroradiological evaluation was performed for all affected individuals, including review of 10 previously reported individuals. The pathogenicity of TARS2 variants was evaluated using in vitro assays, and a zebrafish model.
RESULTS: We report 18 new individuals harboring biallelic TARS2 variants. Phenotypically, these individuals show developmental delay/intellectual disability, regression, cerebellar and cerebral atrophy, basal ganglia signal alterations, hypotonia, cerebellar signs and increased blood lactate. In vitro studies showed that variants within the TARS2301-381 region had decreased binding to Rag GTPases, likely impairing mTORC1 activity. The zebrafish model recapitulated key features of the human phenotype and unraveled dysregulation of downstream targets of mTORC1 signaling. Functional testing of the variants confirmed the pathogenicity in a zebrafish model.
CONCLUSION: We define the clinico-radiological spectrum of TARS2-related mitochondrial disease, unveil the likely involvement of the mTORC1 signaling pathway as a distinct molecular mechanism, and establish a TARS2 zebrafish model as an important tool to study variant pathogenicity.

Keywords:  TARS2; cerebellar atrophy; mTORC1 signaling; mitochondrial dysfunction; mitochondrial threonyl-tRNA-synthetase; white matter

DOI:  https://doi.org/10.1016/j.gim.2023.100938
J Clin Invest. 2023 07 17. pii: e171965. [Epub ahead of print]133(14):

Preserving mitochondria to treat hypertrophic cardiomyopathy: From rare mitochondrial DNA mutation to heart failure therapy?

Abhinav Diwan.

Hypertrophic cardiomyopathy and pathological cardiac hypertrophy are characterized by mitochondrial structural and functional abnormalities. In this issue of the JCI, Zhuang et al. discovered 1-deoxynojirimycin (DNJ) through a screen of mitochondrially targeted compounds. The authors described the effects of DNJ in restoring mitochondria and preventing cardiac myocyte hypertrophy in cellular models carrying a mutant mitochondrial gene, MT-RNR2, which is causally implicated in familial hypertrophic cardiomyopathy. DNJ worked via stabilization of the mitochondrial inner-membrane GTPase OPA1 and other, hitherto unknown, mechanisms to preserve mitochondrial crista and respiratory chain components. The discovery is likely to spur development of a class of therapeutics that restore mitochondrial health to prevent cardiomyopathy and heart failure.

DOI: https://doi.org/10.1172/JCI171965
Nat Commun. 2023 07 19. 14(1): 4356

Targeting an allosteric site in dynamin-related protein 1 to inhibit Fis1-mediated mitochondrial dysfunction.

Luis Rios, Suman Pokhrel, Sin-Jin Li, Gwangbeom Heo, Bereketeab Haileselassie, Daria Mochly-Rosen.

The large cytosolic GTPase, dynamin-related protein 1 (Drp1), mediates both physiological and pathological mitochondrial fission. Cell stress triggers Drp1 binding to mitochondrial Fis1 and subsequently, mitochondrial fragmentation, ROS production, metabolic collapse, and cell death. Because Drp1 also mediates physiological fission by binding to mitochondrial Mff, therapeutics that inhibit pathological fission should spare physiological mitochondrial fission. P110, a peptide inhibitor of Drp1-Fis1 interaction, reduces pathology in numerous models of neurodegeneration, ischemia, and sepsis without blocking the physiological functions of Drp1. Since peptides have pharmacokinetic limitations, we set out to identify small molecules that mimic P110's benefit. We map the P110-binding site to a switch I-adjacent grove (SWAG) on Drp1. Screening for SWAG-binding small molecules identifies SC9, which mimics P110's benefits in cells and a mouse model of endotoxemia. We suggest that the SWAG-binding small molecules discovered in this study may reduce the burden of Drp1-mediated pathologies and potentially pathologies associated with other members of the GTPase family.

DOI: https://doi.org/10.1038/s41467-023-40043-0
Semin Immunol. 2023 Jul 18. pii: S1044-5323(23)00099-4. [Epub ahead of print]69 101808

Mitochondria during T cell aging.

Jose Ignacio Escrig-Larena, Sandra Delgado-Pulido, María Mittelbrunn.

  Mitochondrial dysfunction is a hallmark of aging that contributes to inflammaging. It is characterized by alterations of the mitochondrial DNA, reduced respiratory capacity, decreased mitochondrial membrane potential and increased reactive oxygen species production. These primary alterations disrupt other interconnected and important mitochondrial-related processes such as metabolism, mitochondrial dynamics and biogenesis, mitophagy, calcium homeostasis or apoptosis. In this review, we gather the current knowledge about the different mitochondrial processes which are altered during aging, with special focus on their contribution to age-associated T cell dysfunction and inflammaging.

Keywords:  Aging; Apoptosis; Calcium homeostasis; Inflammaging; Lymphocyte; Mitochondria; Mitochondrial dynamics; Mitokines; Mitophagy; MtDNA; ROS; T cells

DOI:  https://doi.org/10.1016/j.smim.2023.101808
Cell Metab. 2023 Jul 14. pii: S1550-4131(23)00225-5. [Epub ahead of print]

Liver mitochondrial cristae organizing protein MIC19 promotes energy expenditure and pedestrian locomotion by altering nucleotide metabolism.

Jee Hyung Sohn, Beste Mutlu, Pedro Latorre-Muro, Jiaxin Liang, Christopher F Bennett, Kfir Sharabi, Noa Kantorovich, Mark Jedrychowski, Steven P Gygi, Alexander S Banks, Pere Puigserver.

  Liver mitochondria undergo architectural remodeling that maintains energy homeostasis in response to feeding and fasting. However, the specific components and molecular mechanisms driving these changes and their impact on energy metabolism remain unclear. Through comparative mouse proteomics, we found that fasting induces strain-specific mitochondrial cristae formation in the liver by upregulating MIC19, a subunit of the MICOS complex. Enforced MIC19 expression in the liver promotes cristae formation, mitochondrial respiration, and fatty acid oxidation while suppressing gluconeogenesis. Mice overexpressing hepatic MIC19 show resistance to diet-induced obesity and improved glucose homeostasis. Interestingly, MIC19 overexpressing mice exhibit elevated energy expenditure and increased pedestrian locomotion. Metabolite profiling revealed that uracil accumulates in the livers of these mice due to increased uridine phosphorylase UPP2 activity. Furthermore, uracil-supplemented diet increases locomotion in wild-type mice. Thus, MIC19-induced mitochondrial cristae formation in the liver increases uracil as a signal to promote locomotion, with protective effects against diet-induced obesity.

Keywords:  brisk walking; diabetes; fatty liver; mitochondrial cristae; obesity; uracil

DOI:  https://doi.org/10.1016/j.cmet.2023.06.015
STAR Protoc. 2023 Jul 14. pii: S2666-1667(23)00380-5. [Epub ahead of print]4(3): 102413

Generation of mouse hippocampal brain organoids from primary embryonic neural stem cells.

Francesca Ciarpella, Raluca Georgiana Zamfir, Alessandra Campanelli, Giulia Pedrotti, Marzia Di Chio, Emanuela Bottani, Ilaria Decimo.

  Here we present a protocol to generate standardized cerebral organoids with hippocampal regional specification using morphogen WNT3a. We describe steps for isolating mouse embryonic (E14.5) neural stem cells from the brain subgranular zone, preparing organoids samples for immunofluorescence, calcium imaging, and metabolic profiling. This protocol can be used to generate mouse brain organoids for developmental studies, modeling disease, and drug screening. Organoids can be obtained in one month, thus providing a rapid tool for high-throughput data validation. For complete details on the use and execution of this protocol, please refer to Ciarpella et al. "Murine cerebral organoids develop network of functional neurons and hippocampal brain region identity".1.

Keywords:  Cell Biology; Cell Differentiation; Model Organisms; Neuroscience; Organoids; Stem Cells

DOI:  https://doi.org/10.1016/j.xpro.2023.102413
bioRxiv. 2023 Jul 04. pii: 2023.07.04.547719. [Epub ahead of print]

Design, Synthesis, and Biological Evaluation of Novel Mitochondria-targeting Exosomes.

Xin Yan, Xinqian Chen, Zhiying Shan, Lanrong Bi.

Mitochondrial dysfunction is implicated in both brain tumors and neurodegenerative diseases, leading to various cellular abnormalities that can promote tumor growth and resistance to thera-pies, as well as impaired energy production and compromised neuronal function. Developing targeted therapies aimed at restoring mitochondrial function and improving overall cellular health could potentially be a promising approach to treating these conditions. Brain-derived exosomes (BR-EVs) have emerged as potential drug delivery vessels for neurological conditions. Herein, we report a new method for creating mitochondria-targeting exosomes and test its application in vitro and in vivo.

DOI: https://doi.org/10.1101/2023.07.04.547719
Front Genet. 2023 ;14 1215083

Mitochondrial depletion syndrome type 3: the Lebanese variant.

Marianne Majdalani, Nadine Yazbeck, Lamis El Harake, Jinane Samaha, Pascale E Karam.

  Introduction: Mitochondrial DNA depletion syndrome type 3 is an emerging disorder linked to variants in the deoxyguanosine kinase gene, which encodes for mitochondrial maintenance. This autosomal recessive disorder is frequent in the Middle East and North Africa. Diagnosis is often delayed due to the non-specificity of clinical presentation with cerebro-hepatic deterioration. The only therapeutic option is liver transplantation, although the value of this remains debatable. Methods: We describe the clinical, biochemical, and molecular profiles of Lebanese patients with this rare disorder. We also present a review of all cases from the Middle East and North Africa. Results: All Lebanese patients share a unique mutation, unreported in other populations. Almost half of patients worldwide originate from the Middle East and North Africa, with cases reported from only 7 of the 21 countries in this region. Clinical presentation is heterogeneous, with early-onset neurological and hepatic signs. Liver failure and lactic acidosis are constants. Several variants can be identified in each population; a unique c.235C>T p. (Gln79*) pathogenic variant is found in Lebanese patients. Outcome is poor, with death before 1 year of age. Conclusion: The pathogenic nonsense variant c.235C>T p. (Gln79*) in the deoxyguanosine kinase gene may be considered a founder mutation in Lebanon. Further genotypic delineation of this devastating disorder in populations with high consanguinity rates is needed.

Keywords:  DGUOK; Lebanon; MENA; lactic acidosis; liver transplantation; mitochondrial depletion; mtDNA maintenance defects; neonatal liver failure

DOI:  https://doi.org/10.3389/fgene.2023.1215083
Prog Retin Eye Res. 2023 Jul 15. pii: S1350-9462(23)00044-7. [Epub ahead of print]96 101205

Mitophagy in the retina: Viewing mitochondrial homeostasis through a new lens.

Juan Ignacio Jiménez-Loygorri, Rocío Benítez-Fernández, Álvaro Viedma-Poyatos, Juan Zapata-Muñoz, Beatriz Villarejo-Zori, Raquel Gómez-Sintes, Patricia Boya.

  Mitochondrial function is key to support metabolism and homeostasis in the retina, an organ that has one of the highest metabolic rates body-wide and is constantly exposed to photooxidative damage and external stressors. Mitophagy is the selective autophagic degradation of mitochondria within lysosomes, and can be triggered by distinct stimuli such as mitochondrial damage or hypoxia. Here, we review the importance of mitophagy in retinal physiology and pathology. In the developing retina, mitophagy is essential for metabolic reprogramming and differentiation of retina ganglion cells (RGCs). In basal conditions, mitophagy acts as a quality control mechanism, maintaining a healthy mitochondrial pool to meet cellular demands. We summarize the different autophagy- and mitophagy-deficient mouse models described in the literature, and discuss the potential role of mitophagy dysregulation in retinal diseases such as glaucoma, diabetic retinopathy, retinitis pigmentosa, and age-related macular degeneration. Finally, we provide an overview of methods used to monitor mitophagy in vitro, ex vivo, and in vivo. This review highlights the important role of mitophagy in sustaining visual function, and its potential as a putative therapeutic target for retinal and other diseases.

Keywords:  Age-related macular degeneration; Autophagy; Diabetic retinopathy; Glaucoma; Metabolism; Mitochondria; Mitophagy; Retinal development; Retinal homeostasis; Retinitis pigmentosa

DOI:  https://doi.org/10.1016/j.preteyeres.2023.101205
Nat Metab. 2023 Jul 17.

Fatty acid oxidation organizes mitochondrial supercomplexes to sustain astrocytic ROS and cognition.

Brenda Morant-Ferrando, Daniel Jimenez-Blasco, Paula Alonso-Batan, Jesús Agulla, Rebeca Lapresa, Dario Garcia-Rodriguez, Sara Yunta-Sanchez, Irene Lopez-Fabuel, Emilio Fernandez, Peter Carmeliet, Angeles Almeida, Marina Garcia-Macia, Juan P Bolaños.

Having direct access to brain vasculature, astrocytes can take up available blood nutrients and metabolize them to fulfil their own energy needs and deliver metabolic intermediates to local synapses1,2. These glial cells should be, therefore, metabolically adaptable to swap different substrates. However, in vitro and in vivo studies consistently show that astrocytes are primarily glycolytic3-7, suggesting glucose is their main metabolic precursor. Notably, transcriptomic data8,9 and in vitro10 studies reveal that mouse astrocytes are capable of mitochondrially oxidizing fatty acids and that they can detoxify excess neuronal-derived fatty acids in disease models11,12. Still, the factual metabolic advantage of fatty acid use by astrocytes and its physiological impact on higher-order cerebral functions remain unknown. Here, we show that knockout of carnitine-palmitoyl transferase-1A (CPT1A)-a key enzyme of mitochondrial fatty acid oxidation-in adult mouse astrocytes causes cognitive impairment. Mechanistically, decreased fatty acid oxidation rewired astrocytic pyruvate metabolism to facilitate electron flux through a super-assembled mitochondrial respiratory chain, resulting in attenuation of reactive oxygen species formation. Thus, astrocytes naturally metabolize fatty acids to preserve the mitochondrial respiratory chain in an energetically inefficient disassembled conformation that secures signalling reactive oxygen species and sustains cognitive performance.

DOI: https://doi.org/10.1038/s42255-023-00835-6
Sci Adv. 2023 Jul 21. 9(29): eadh3347

Parkin regulates amino acid homeostasis at mitochondria-lysosome (M/L) contact sites in Parkinson's disease.

Wesley Peng, Leonie F Schröder, Pingping Song, Yvette C Wong, Dimitri Krainc.

Mutations in the E3 ubiquitin ligase parkin are the most common cause of early-onset Parkinson's disease (PD). Although parkin modulates mitochondrial and endolysosomal homeostasis during cellular stress, whether parkin regulates mitochondrial and lysosomal cross-talk under physiologic conditions remains unresolved. Using transcriptomics, metabolomics and super-resolution microscopy, we identify amino acid metabolism as a disrupted pathway in iPSC-derived dopaminergic neurons from patients with parkin PD. Compared to isogenic controls, parkin mutant neurons exhibit decreased mitochondria-lysosome contacts via destabilization of active Rab7. Subcellular metabolomics in parkin mutant neurons reveals amino acid accumulation in lysosomes and their deficiency in mitochondria. Knockdown of the Rab7 GTPase-activating protein TBC1D15 restores mitochondria-lysosome tethering and ameliorates cellular and subcellular amino acid profiles in parkin mutant neurons. Our data thus uncover a function of parkin in promoting mitochondrial and lysosomal amino acid homeostasis through stabilization of mitochondria-lysosome contacts and suggest that modulation of interorganelle contacts may serve as a potential target for ameliorating amino acid dyshomeostasis in disease.

DOI: https://doi.org/10.1126/sciadv.adh3347
Geroscience. 2023 Jul 18.

The mitochondrially targeted peptide elamipretide (SS-31) improves ADP sensitivity in aged mitochondria by increasing uptake through the adenine nucleotide translocator (ANT).

Gavin Pharaoh, Varun Kamat, Sricharan Kannan, Rudolph S Stuppard, Jeremy Whitson, Miguel Martín-Pérez, Wei-Jun Qian, Michael J MacCoss, Judit Villén, Peter Rabinovitch, Matthew D Campbell, Ian R Sweet, David J Marcinek.

  Aging muscle experiences functional decline in part mediated by impaired mitochondrial ADP sensitivity. Elamipretide (ELAM) rapidly improves physiological and mitochondrial function in aging and binds directly to the mitochondrial ADP transporter ANT. We hypothesized that ELAM improves ADP sensitivity in aging leading to rescued physiological function. We measured the response to ADP stimulation in young and old muscle mitochondria with ELAM treatment, in vivo heart and muscle function, and compared protein abundance, phosphorylation, and S-glutathionylation of ADP/ATP pathway proteins. ELAM treatment increased ADP sensitivity in old muscle mitochondria by increasing uptake of ADP through the ANT and rescued muscle force and heart systolic function. Protein abundance in the ADP/ATP transport and synthesis pathway was unchanged, but ELAM treatment decreased protein s-glutathionylation incuding of ANT. Mitochondrial ADP sensitivity is rapidly modifiable. This research supports the hypothesis that ELAM improves ANT function in aging and links mitochondrial ADP sensitivity to physiological function. ELAM binds directly to ANT and ATP synthase and ELAM treatment improves ADP sensitivity, increases ATP production, and improves physiological function in old muscles. ADP (adenosine diphosphate), ATP (adenosine triphosphate), VDAC (voltage-dependent anion channel), ANT (adenine nucleotide translocator), H+ (proton), ROS (reactive oxygen species), NADH (nicotinamide adenine dinucleotide), FADH2 (flavin adenine dinucleotide), O2 (oxygen), ELAM (elamipretide), -SH (free thiol), -SSG (glutathionylated protein).

Keywords:  ATP production; Adenine nucleotide translocator (ANT); Adenosine diphosphate (ADP) sensitivity; Elamipretide or SS-31; Mitochondrial dysfunction; Oxygen consumption rate (OCR)

DOI:  https://doi.org/10.1007/s11357-023-00861-y
Front Neurol. 2023 ;14 878446

Uterus infantilis: a novel phenotype associated with AARS2 new genetic variants. A case report.

Ekaterina Kazakova, José Alberto Téllez-Martínez, Leonardo Flores-Lagunes, Ana Luisa Sosa-Ortiz, Karol Carillo-Sánchez, Carolina Molina-Garay, Carlos Alberto González-Domínguez, Marco Jimenez-Olivares, Francisca Fernandez-Valverde, Edwin Steven Vargas-Cañas, Martha Elisa Vázquez-Memije, Ethel Awilda Garcia-Latorre, Iván Martínez-Duncker, Carmen Alaez-Verson.

   Objectives: To report the first Mexican case with two novel AARS2 mutations causing primary ovarian failure, uterus infantilis, and early-onset dementia secondary to leukoencephalopathy.
Methods: Detailed clinical, clinimetric, neuroimaging features, muscle biopsy with biochemical assays of the main oxidative phosphorylation complexes activities, and molecular studies were performed on samples from a Mexican female.
Results: We present a 41-year-old female patient with learning difficulties since childhood and primary amenorrhea who developed severe cognitive, motor, and behavioral impairment in early adulthood. Neuroimaging studies revealed frontal leukoencephalopathy with hypometabolism at the fronto-cerebellar cortex and caudate nucleus. Uterus infantilis was detected on ultrasound study. Clinical exome sequencing identified two novel variants, NM_020745:c.2864G>A (p.W955*) and NM_020745:c.1036C>A (p.P346T, p.P346Wfs*18), in AARS2. Histopathological and biochemical studies on muscle biopsy revealed mitochondrial disorder with cytochrome C oxidase (COX) deficiency.
Conclusions: Several adult-onset cases of leukoencephalopathy and ovarian failure associated with AARS2 variants have been reported. To our best knowledge, none of them showed uterus infantilis. Here we enlarge the genetic and phenotypic spectrum of AARS2-related dementia with leukoencephalopathy and ovarian failure and contribute with detailed clinical, clinometric, neuroimaging, and molecular studies to disease and novel molecular variants characterization.

Keywords:  AARS2; AARS2 leukoencephalopathy; adult-onset leukodystrophy; alanyl-transfer RNA synthetase 2 mutation-related leukodystrophy; early-onset dementia; mitochondrial aminoacyl-tRNA synthetase; progressive leukoencephalopathy with ovarian failure; uterus infantilis

DOI:  https://doi.org/10.3389/fneur.2023.878446
Exp Neurol. 2023 Jul 14. pii: S0014-4886(23)00164-4. [Epub ahead of print] 114479

Elevation of NAD+ by nicotinamide riboside spares spinal cord tissue from injury and promotes locomotor recovery.

Mariajose Metcalfe, Brian T David, Brett C Langley, Caitlin E Hill.

  Spinal cord injury (SCI)-induced tissue damage spreads to neighboring spared cells in the hours, days, and weeks following injury, leading to exacerbation of tissue damage and functional deficits. Among the biochemical changes is the rapid reduction of cellular nicotinamide adenine dinucleotide (NAD+), an essential coenzyme for energy metabolism and an essential cofactor for non-redox NAD+-dependent enzymes with critical functions in sensing and repairing damaged tissue. NAD+ depletion propagates tissue damage. Augmenting NAD+ by exogenous application of NAD+, its synthesizing enzymes, or its cellular precursors mitigates tissue damage. Nicotinamide riboside (NR) is considered to be one of the most promising NAD+ precursors for clinical application due to its ability to safely and effectively boost cellular NAD+ synthesis in rats and humans. Moreover, various preclinical studies have demonstrated that NR can provide tissue protection. Despite these promising findings, little is known about the potential benefits of NR in the context of SCI. In the current study, we tested whether NR administration could effectively increase NAD+ levels in the injured spinal cord and whether this augmentation of NAD+ would promote spinal cord tissue protection and ultimately lead to improvements in locomotor function. Our findings indicate that administering NR (500 mg/kg) via intraperitoneal route, four days before and two weeks after a mid-thoracic contusion-SCI injury, effectively doubles NAD+ levels in the spinal cord of Long-Evans rats. Moreover, NR administration plays a protective role in preserving spinal cord tissue post-injury, particularly in neurons and axons, as evident from the observed gray and white matter sparing. Additionally, it enhances motor function, as evaluated through the BBB subscore and missteps on the horizontal ladderwalk. Collectively, these findings demonstrate that administering NR, a precursor of NAD+ increases NAD+ within the injured spinal cord and effectively mitigates the tissue damage and functional decline that occurs following SCI.

Keywords:  Nicotinamide adenine dinucleotide; Nicotinamide riboside; Spinal cord injury

DOI:  https://doi.org/10.1016/j.expneurol.2023.114479
Life Sci. 2023 Jul 15. pii: S0024-3205(23)00578-7. [Epub ahead of print]329 121943

The emerging significance of mitochondrial targeted strategies in NAFLD treatment.

Tao Zhang, Yingli Nie, Jiliang Wang.

  Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide, ranging from liver steatosis to nonalcoholic steatohepatitis, which ultimately progresses to fibrosis, cirrhosis, and hepatocellular carcinoma. Individuals with NAFLD have a higher risk of developing cardiovascular and extrahepatic cancers. Despite the great progress being made in understanding the pathogenesis and the introduction of new pharmacological targets for NAFLD, no drug or intervention has been accepted for its management. Recent evidence suggests that NAFLD may be a mitochondrial disease, as mitochondrial dysfunction is involved in the pathological processes that lead to NAFLD. In this review, we describe the recent advances in our understanding of the mechanisms associated with mitochondrial dysfunction in NAFLD progression. Moreover, we discuss recent advances in the efficacy of mitochondria-targeted compounds (e.g., Mito-Q, MitoVit-E, MitoTEMPO, SS-31, mitochondrial uncouplers, and mitochondrial pyruvate carrier inhibitors) for treating NAFLD. Furthermore, we present some medications currently being tested in clinical trials for NAFLD treatment, such as exercise, mesenchymal stem cells, bile acids and their analogs, and antidiabetic drugs, with a focus on their efficacy in improving mitochondrial function. Based on this evidence, further investigations into the development of mitochondria-based agents may provide new and promising alternatives for NAFLD management.

Keywords:  Mitochondrial dysfunction; Mitochondrial quality control; Nonalcoholic fatty liver disease; Nonalcoholic steatohepatitis; Reactive oxygen species; Therapeutics

DOI:  https://doi.org/10.1016/j.lfs.2023.121943
J Inherit Metab Dis. 2023 Jul 20.

Fetal gene therapy.

Simon N Waddington, William H Peranteau, Ahad A Rahim, Ashley K Boyle, Manju A Kurian, Paul Gissen, Jerry K Y Chan, Anna L David.

Fetal gene therapy was first proposed towards the end of the 1990s when the field of gene therapy was, to quote the Gartner hype cycle, at its "peak of inflated expectations". Gene therapy was still an immature field but over the ensuing decade it matured and is now a clinical and market reality. The trajectory of treatment for several genetic diseases is towards earlier intervention. The ability, capacity, and the will to diagnose genetic disease early - in utero improves day by day. A confluence of clinical trials now signposts a trajectory towards fetal gene therapy. In this review we recount the history of fetal gene therapy in the context of the broader field, discuss advances in fetal surgery and diagnosis, and explore the full ambit of preclinical gene therapy for inherited metabolic disease. This article is protected by copyright. All rights reserved.

DOI: https://doi.org/10.1002/jimd.12659
Nat Commun. 2023 07 19. 14(1): 4360

Nuclear translocation of mitochondrial dehydrogenases as an adaptive cardioprotective mechanism.

Shubhi Srivastava, Priyanka Gajwani, Jordan Jousma, Hiroe Miyamoto, Youjeong Kwon, Arundhati Jana, Peter T Toth, Gege Yan, Sang-Ging Ong, Jalees Rehman.

Chemotherapy-induced cardiac damage remains a leading cause of death amongst cancer survivors. Anthracycline-induced cardiotoxicity is mediated by severe mitochondrial injury, but little is known about the mechanisms by which cardiomyocytes adaptively respond to the injury. We observed the translocation of selected mitochondrial tricarboxylic acid (TCA) cycle dehydrogenases to the nucleus as an adaptive stress response to anthracycline-cardiotoxicity in human induced pluripotent stem cell-derived cardiomyocytes and in vivo. The expression of nuclear-targeted mitochondrial dehydrogenases shifts the nuclear metabolic milieu to maintain their function both in vitro and in vivo. This protective effect is mediated by two parallel pathways: metabolite-induced chromatin accessibility and AMP-kinase (AMPK) signaling. The extent of chemotherapy-induced cardiac damage thus reflects a balance between mitochondrial injury and the protective response initiated by the nuclear pool of mitochondrial dehydrogenases. Our study identifies nuclear translocation of mitochondrial dehydrogenases as an endogenous adaptive mechanism that can be leveraged to attenuate cardiomyocyte injury.

DOI: https://doi.org/10.1038/s41467-023-40084-5
Front Physiol. 2023 ;14 1228490

Exploiting inter-tissue stress signaling mechanisms to preserve organismal proteostasis during aging.

Patricija van Oosten-Hawle.

  Aging results in a decline of cellular proteostasis capacity which culminates in the accumulation of phototoxic material, causing the onset of age-related maladies and ultimately cell death. Mechanisms that regulate proteostasis such as cellular stress response pathways sense disturbances in the proteome. They are activated to increase the expression of protein quality control components that counteract cellular damage. Utilizing invertebrate model organisms such as Caenorhabditis elegans, it has become increasingly evident that the regulation of proteostasis and the activation of cellular stress responses is not a cell autonomous process. In animals, stress responses are orchestrated by signals coming from other tissues, including the nervous system, the intestine and the germline that have a profound impact on determining the aging process. Genetic pathways discovered in C. elegans that facilitate cell nonautonomous regulation of stress responses are providing an exciting feeding ground for new interventions. In this review I will discuss cell nonautonomous proteostasis mechanisms and their impact on aging as well as ongoing research and clinical trials that can increase organismal proteostasis to lengthen health- and lifespan.

Keywords:  aging; healthspan; proteostasis; stress responses; transcellular

DOI:  https://doi.org/10.3389/fphys.2023.1228490
Res Sq. 2023 Jun 29. pii: rs.3.rs-3121549. [Epub ahead of print]

Quantification of human mature frataxin protein expression in nonhuman primate hearts after gene therapy.

Ian Blair, Teerapat Rojsajjakul, Juliette Hordeaux, Gourav Chaudhary, Christian Hinderer, Clementina Mesaros, James Wilson.

Deficiency in human mature frataxin (hFXN-M) protein is responsible for the devastating neurodegenerative and cardiodegenerative disease of Friedreich's ataxia (FRDA). It results primarily by epigenetic silencing the FXN gene due to up to 1400 GAA triplet repeats in intron 1 of both alleles of the gene; a subset of approximately 3% of FRDA patients have a mutation on one allele. FRDA patients die most commonly in their 30s from heart disease. Therefore, increasing expression of heart hFXN-M using gene therapy offers a way to prevent early mortality in FRDA. We used rhesus macaque monkeys to test the pharmacology of an adeno-associated virus (AAV)hu68.CB7.hFXN therapy. The advantage of using non-human primates for hFXN-M gene therapy studies is that hFXN-M and monkey FXN-M (mFXN-M) are 98.5% identical, which limits potential immunologic side-effects. However, this presented a formidable bioanalytical challenge in quantification of proteins with almost identical sequences. This was overcome by development of a species-specific quantitative mass spectrometry-based method, which revealed for the first time, robust transgene-specific human protein expression in monkey heart tissue. The dose response was non-linear resulting in a ten-fold increase in monkey heart hFXN-M protein expression with only a three-fold increase in dose of the vector.

DOI: https://doi.org/10.21203/rs.3.rs-3121549/v1
Neuromuscul Disord. 2023 Jul 04. pii: S0960-8966(23)00169-4. [Epub ahead of print]

Gene therapy and other novel treatment approaches for Charcot-Marie-Tooth disease.

Chiara Pisciotta, Davide Pareyson.

  There is still no effective drug treatment available for Charcot-Marie-Tooth disease (CMT). Current management relies on rehabilitation therapy, surgery for skeletal deformities, and symptomatic treatment. The challenge is to find disease-modifying therapies. Several approaches, including gene silencing (by means of ASO, siRNA, shRNA, miRNA, CRISPR-Cas9 editing), to counteract the PMP22 gene overexpression in the most frequent CMT1A type are under investigation. PXT3003 is the compound in the most advanced phase for CMT1A, as a second phase-III trial is ongoing. Gene therapy to substitute defective genes (particularly in recessive forms associated with loss-of-function mutations) or insert novel ones (e.g., NT3 gene) are being developed and tested in animal models and in still exceptional cases have reached the clinical trial phase in humans. Novel treatment approaches are also aimed at developing compounds acting on pathways important for different CMT types. Modulation of the neuregulin pathway determining myelin thickness is promising for both hypo-demyelinating and hypermyelinating neuropathies; intervention on Unfolded Protein Response seems effective for rescuing misfolded myelin proteins such as MPZ in CMT1B. HDAC6 inhibitors improved axonal transport and ameliorated phenotypes in different CMT models. Other potential therapeutic strategies include targeting macrophages, lipid metabolism, and Nav1.8 sodium channel in demyelinating CMT and the P2×7 receptor, which regulates calcium influx into Schwann cells, in CMT1A. Further approaches are aimed at correcting metabolic abnormalities, including the accumulation of sorbitol caused by biallelic mutations in the sorbitol dehydrogenase (SORD) gene and of neurotoxic glycosphingolipids in HSN1.

Keywords:  Charcot-Marie-Tooth; Clinical trial; Disease-modifying therapy; Gene therapy; Inherited neuropathies; Novel treatment

DOI:  https://doi.org/10.1016/j.nmd.2023.07.001
Am J Physiol Endocrinol Metab. 2023 Jul 19.

Greater Reliance on Glycolysis is Associated with Lower Mitochondrial Substrate Oxidation and Insulin Sensitivity in Infant Myogenic MSCs.

Filip Jevtovic, Donghai Zheng, Christian A Lopez, Kara Kern, Charles J Tanner, Terry E Jones, Walter J Pories, G Lynis Dohm, Joseph A Houmard, Linda E May, Nicholas T Broskey.

  Individuals with insulin resistance and obesity display higher skeletal muscle production of non-oxidized glycolytic products (i.e., lactate), and lower complete mitochondrial substrate oxidation to CO2. These findings have also been observed in individuals without obesity and are associated with an increased risk for metabolic disease. The purpose of this study was to determine if substrate preference is evident at the earliest stage of life (birth) and to provide a clinical blood marker (lactate) that could be indicative of a predisposition for metabolic disease later. We used radiolabeled tracers to assess substrate oxidation and insulin sensitivity of myogenically differentiated mesenchymal stem cells (MSCs), a proxy of infant skeletal muscle tissue, derived from umbilical cords of full-term infants. We found that greater production of non-oxidized glycolytic products (lactate, pyruvate, alanine) is directly proportional to lower substrate oxidation and insulin sensitivity in MSCs. Additionally, we found an inverse relationship between the ration of complete glucose oxidation to CO2 and infant blood lactate at 1 month of age. Collectively, considering that higher lactate was associated with lower MSC glucose oxidation and has been shown to be implicated with metabolic disease, it may be an early indicator of infant skeletal muscle phenotype.

Keywords:  glycolysis; infant; insulin sensitivity; metabolism; stem cells

DOI:  https://doi.org/10.1152/ajpendo.00159.2023