bims-mitdis Biomed News
on Mitochondrial disorders
Issue of 2023–07–02
forty papers selected by
Catalina Vasilescu, Helmholz Munich
  1. Acarbose suppresses symptoms of mitochondrial disease in a mouse model of Leigh syndrome.
  2. Translation termination in human mitochondria - substrate specificity of mitochondrial release factors.
  3. The unfolded protein response of the endoplasmic reticulum supports mitochondrial biogenesis by buffering non-imported proteins.
  4. Structural analysis of mitochondrial rRNA gene variants identified in patients with deafness.
  5. Single-cell multi-omics of mitochondrial DNA disorders reveals dynamics of purifying selection across human immune cells.
  6. Fulminant Neonatal Liver Failure in MPV 17-Related Mitochondrial DNA Depletion Syndrome.
  7. Neural stem cell metabolism revisited: a critical role for mitochondria.
  8. 35 Years of TFAM Research: Old Protein, New Puzzles.
  9. Mitochondrial fitness sustains healthy muscle aging.
  10. Clinical and bi-genomic DNA findings of patients suspected to have mitochondrial diseases.
  11. Insulin-Degrading Enzyme Interacts with Mitochondrial Ribosomes and Respiratory Chain Proteins.
  12. Sensory Ataxic Neuropathy with Dysarthria and Ophthalmoplegia (SANDO): A Multisystem Mitochondrial Disorder.
  13. Syntaphilin mediates axonal growth and synaptic changes through regulation of mitochondrial transport: a potential pharmacological target for neurodegenerative diseases.
  14. Effects of Parkin on the Mitochondrial Genome in the Heart and Brain of Mitochondrial Mutator Mice.
  15. Extracellular Vesicles and Cx43-Gap Junction Channels Are the Main Routes for Mitochondrial Transfer from Ultra-Purified Mesenchymal Stem Cells, RECs.
  16. Implications of MCU complex in metabolic diseases.
  17. Fifty years of the mitochondrial pyruvate carrier: New insights into its structure, function, and inhibition.
  18. Highly Specialized Mechanisms for Mitochondrial Transport in Neurons: From Intracellular Mobility to Intercellular Transfer of Mitochondria.
  19. Single-cell multiomic analyses sheds light on mitochondrial mutational selection.
  20. mTORC2-NDRG1-CDC42 axis couples fasting to mitochondrial fission.
  21. Targeted cross-linker delivery for the in situ mapping of protein conformations and interactions in mitochondria.
  22. Commentary: Aldehyde dehydrogenase, redox balance and exercise physiology: What is missing?
  23. Genomic newborn screening for rare diseases.
  24. Improving Mitochondrial Function in Skeletal Muscle Contributes to the Amelioration of Insulin Resistance by Nicotinamide Riboside.
  25. Sengers syndrome and AGK-related disorders - Minireview of phenotypic variability and clinical outcomes in molecularly confirmed cases.
  26. Molecular Regulations of FUNDC1 at ER-Mitochondria Contacts Under Hypoxic Stress.
  27. Mitochondrial dysfunction and mitophagy defects in LRRK2-R1441C Parkinson's disease models.
  28. Human peroxisomal NAD+/NADH homeostasis is regulated by two independent NAD(H) shuttle systems.
  29. Insights into energy balance dysregulation from a mouse model of methylmalonic aciduria.
  30. Targeting Mitochondrial DNA Transcription by POLRMT Inhibition or Depletion as a Potential Strategy for Cancer Treatment.
  31. Loss of function variants in L2HGDH gene causing L-2-hydroxyglutaric aciduria.
  32. Daytime-restricted feeding enhances running endurance without prior exercise in mice.
  33. Serum factors mediate changes in mitochondrial bioenergetics associated with diet and exercise interventions.
  34. Fast fragmenting mitochondria by TORC2.
  35. Nicotinamide Adenine Dinucleotide in Aging Biology: Potential Applications and Many Unknowns.
  36. Spatially resolved single-cell translatomics at molecular resolution.
  37. Targeting shared molecular etiologies to accelerate drug development for rare diseases.
  38. Mitochondrial Fission as a Therapeutic Target for Metabolic Diseases: Insights into Antioxidant Strategies.
  39. GDF15 promotes weight loss by enhancing energy expenditure in muscle.
  40. Time-restricted feeding makes the mouse run like a pro.
  1. Nat Metab. 2023 06;5(6): 955-967
    Acarbose suppresses symptoms of mitochondrial disease in a mouse model of Leigh syndrome.
    Alessandro Bitto, Anthony S Grillo, Takashi K Ito, Ian B Stanaway, Bao M G Nguyen, Kejun Ying, Herman Tung, Kaleb Smith, Ngoc Tran, Gunnar Velikanje, Silvan R Urfer, Jessica M Snyder, Jacob Barton, Ayush Sharma, Ernst-Bernhard Kayser, Lu Wang, Daniel L Smith, J Will Thompson, Laura DuBois, William DePaolo, Matt Kaeberlein.
      Mitochondrial diseases represent a spectrum of disorders caused by impaired mitochondrial function, ranging in severity from mortality during infancy to progressive adult-onset disease. Mitochondrial dysfunction is also recognized as a molecular hallmark of the biological ageing process. Rapamycin, a drug that increases lifespan and health during normative ageing, also increases survival and reduces neurological symptoms in a mouse model of the severe mitochondrial disease Leigh syndrome. The Ndufs4 knockout (Ndufs4-/-) mouse lacks the complex I subunit NDUFS4 and shows rapid onset and progression of neurodegeneration mimicking patients with Leigh syndrome. Here we show that another drug that extends lifespan and delays normative ageing in mice, acarbose, also suppresses symptoms of disease and improves survival of Ndufs4-/- mice. Unlike rapamycin, acarbose rescues disease phenotypes independently of inhibition of the mechanistic target of rapamycin. Furthermore, rapamycin and acarbose have additive effects in delaying neurological symptoms and increasing maximum lifespan in Ndufs4-/- mice. We find that acarbose remodels the intestinal microbiome and alters the production of short-chain fatty acids. Supplementation with tributyrin, a source of butyric acid, recapitulates some effects of acarbose on lifespan and disease progression, while depletion of the endogenous microbiome in Ndufs4-/- mice appears to fully recapitulate the effects of acarbose on healthspan and lifespan in these animals. To our knowledge, this study provides the first evidence that alteration of the gut microbiome plays a significant role in severe mitochondrial disease and provides further support for the model that biological ageing and severe mitochondrial disorders share underlying common mechanisms.
    DOI:  https://doi.org/10.1038/s42255-023-00815-w
  2. Biol Chem. 2023 Jun 29.
    Translation termination in human mitochondria - substrate specificity of mitochondrial release factors.
    Franziska Nadler, Ricarda Richter-Dennerlein.
      Mitochondria are the essential players in eukaryotic ATP production by oxidative phosphorylation, which relies on the maintenance and accurate expression of the mitochondrial genome. Even though the basic principles of translation are conserved due to the descendance from a bacterial ancestor, some deviations regarding translation factors as well as mRNA characteristics and the applied genetic code are present in human mitochondria. Together, these features are certain challenges during translation the mitochondrion has to handle. Here, we discuss the current knowledge regarding mitochondrial translation focusing on the termination process and the associated quality control mechanisms. We describe how mtRF1a resembles bacterial RF1 mechanistically and summarize in vitro and recent in vivo data leading to the conclusion of mtRF1a being the major mitochondrial release factor. On the other hand, we discuss the ongoing debate about the function of the second codon-dependent mitochondrial release factor mtRF1 regarding its role as a specialized termination factor. Finally, we link defects in mitochondrial translation termination to the activation of mitochondrial rescue mechanisms highlighting the importance of ribosome-associated quality control for sufficient respiratory function and therefore for human health.
    Keywords:  COX1 translation; mitoribosome rescue; mitoribosome-associated quality control; mtRF1; mtRF1a; non-canonical stop codons
    DOI:  https://doi.org/10.1515/hsz-2023-0127
  3. Mol Biol Cell. 2023 Jun 28. mbcE23050205
    The unfolded protein response of the endoplasmic reticulum supports mitochondrial biogenesis by buffering non-imported proteins.
    Katharina Knöringer, Carina Groh, Lena Krämer, Kevin C Stein, Katja G Hansen, Jannik Zimmermann, Bruce Morgan, Johannes M Herrmann, Judith Frydman, Felix Boos.
      Almost all mitochondrial proteins are synthesized in the cytosol and subsequently targeted to mitochondria. The accumulation of non-imported precursor proteins occurring upon mitochondrial dysfunction can challenge cellular protein homeostasis. Here we show that blocking protein translocation into mitochondria results in the accumulation of mitochondrial membrane proteins at the endoplasmic reticulum, thereby triggering the unfolded protein response (UPRER). Moreover, we find that mitochondrial membrane proteins are also routed to the ER under physiological conditions. The level of ER-resident mitochondrial precursors is enhanced by import defects as well as metabolic stimuli that increase the expression of mitochondrial proteins. Under such conditions, the UPRER is crucial to maintain protein homeostasis and cellular fitness. We propose the ER serves as a physiological buffer zone for those mitochondrial precursors that cannot be immediately imported into mitochondria while engaging the UPRER to adjust the ER proteostasis capacity to the extent of precursor accumulation.
    DOI:  https://doi.org/10.1091/mbc.E23-05-0205
  4. Front Physiol. 2023 ;14 1163496
    Structural analysis of mitochondrial rRNA gene variants identified in patients with deafness.
    Antón Vila-Sanjurjo, Natalia Mallo, Joanna L Elson, Paul M Smith, Emma L Blakely, Robert W Taylor.
      The last few years have witnessed dramatic advances in our understanding of the structure and function of the mammalian mito-ribosome. At the same time, the first attempts to elucidate the effects of mito-ribosomal fidelity (decoding accuracy) in disease have been made. Hence, the time is right to push an important frontier in our understanding of mitochondrial genetics, that is, the elucidation of the phenotypic effects of mtDNA variants affecting the functioning of the mito-ribosome. Here, we have assessed the structural and functional role of 93 mitochondrial (mt-) rRNA variants thought to be associated with deafness, including those located at non-conserved positions. Our analysis has used the structural description of the human mito-ribosome of the highest quality currently available, together with a new understanding of the phenotypic manifestation of mito-ribosomal-associated variants. Basically, any base change capable of inducing a fidelity phenotype may be considered non-silent. Under this light, out of 92 previously reported mt-rRNA variants thought to be associated with deafness, we found that 49 were potentially non-silent. We also dismissed a large number of reportedly pathogenic mtDNA variants, 41, as polymorphisms. These results drastically update our view on the implication of the primary sequence of mt-rRNA in the etiology of deafness and mitochondrial disease in general. Our data sheds much-needed light on the question of how mt-rRNA variants located at non-conserved positions may lead to mitochondrial disease and, most notably, provide evidence of the effect of haplotype context in the manifestation of some mt-rRNA variants.
    Keywords:  deafness (hearing loss); haplotype; mito-ribosomal fidelity; mito-ribosome; mitochondrial rRNA mutations; mtDNA; mtDNA diseases
    DOI:  https://doi.org/10.3389/fphys.2023.1163496
  5. Nat Genet. 2023 Jun 29.
    Single-cell multi-omics of mitochondrial DNA disorders reveals dynamics of purifying selection across human immune cells.
    Caleb A Lareau, Sonia M Dubois, Frank A Buquicchio, Yu-Hsin Hsieh, Kopal Garg, Pauline Kautz, Lena Nitsch, Samantha D Praktiknjo, Patrick Maschmeyer, Jeffrey M Verboon, Jacob C Gutierrez, Yajie Yin, Evgenij Fiskin, Wendy Luo, Eleni P Mimitou, Christoph Muus, Rhea Malhotra, Sumit Parikh, Mark D Fleming, Lena Oevermann, Johannes Schulte, Cornelia Eckert, Anshul Kundaje, Peter Smibert, Santosha A Vardhana, Ansuman T Satpathy, Aviv Regev, Vijay G Sankaran, Suneet Agarwal, Leif S Ludwig.
      Pathogenic mutations in mitochondrial DNA (mtDNA) compromise cellular metabolism, contributing to cellular heterogeneity and disease. Diverse mutations are associated with diverse clinical phenotypes, suggesting distinct organ- and cell-type-specific metabolic vulnerabilities. Here we establish a multi-omics approach to quantify deletions in mtDNA alongside cell state features in single cells derived from six patients across the phenotypic spectrum of single large-scale mtDNA deletions (SLSMDs). By profiling 206,663 cells, we reveal the dynamics of pathogenic mtDNA deletion heteroplasmy consistent with purifying selection and distinct metabolic vulnerabilities across T-cell states in vivo and validate these observations in vitro. By extending analyses to hematopoietic and erythroid progenitors, we reveal mtDNA dynamics and cell-type-specific gene regulatory adaptations, demonstrating the context-dependence of perturbing mitochondrial genomic integrity. Collectively, we report pathogenic mtDNA heteroplasmy dynamics of individual blood and immune cells across lineages, demonstrating the power of single-cell multi-omics for revealing fundamental properties of mitochondrial genetics.
    DOI:  https://doi.org/10.1038/s41588-023-01433-8
  6. Case Reports Hepatol. 2023 ;2023 4514552
    Fulminant Neonatal Liver Failure in MPV 17-Related Mitochondrial DNA Depletion Syndrome.
    Razan Abduljalil, Hadhami Ben Turkia, Aysha Fakhroo, Cristina Skrypnyk.
      Mitochondrial depletion syndromes are well established causes of liver failure in infants. Hepatocerebral variant related to MPV17 gene defect is characterized by infantile onset of progressive liver failure, developmental delay, neurological manifestations, lactic acidosis, hypoglycemia, and mtDNA depletion in liver tissue. We report a hepatocerebral variant of mitochondrial DNA depletion syndrome in a neonate who presented with septic shock picture, hypoglycemia, jaundice, hypotonia, and rotatory nystagmus. Family history was significant for consanguinity and a brother who died at the age of 4 months. Investigations showed mild liver function derangement contrasting with severe coagulopathy, hyperlactatemia, and generalized aminoaciduria. The brain MRI was normal. Next generation sequencing (NGS) panel identified a MPV17 gene missense homozygous pathogenic variant. The infant expired at the age of 2 weeks with refractory ascites. This case illustrates a challenging diagnosis causing liver failure and death in neonatal period. Genetic testing of mitochondrial DNA depletion syndromes should be a part of liver failure workup in addition to other treatable disorders presenting with encephalo-hepatopathy in infancy.
    DOI:  https://doi.org/10.1155/2023/4514552
  7. Trends Endocrinol Metab. 2023 Jun 26. pii: S1043-2760(23)00110-8. [Epub ahead of print]
    Neural stem cell metabolism revisited: a critical role for mitochondria.
    Valentina Scandella, Francesco Petrelli, Darcie L Moore, Simon M G Braun, Marlen Knobloch.
      Metabolism has emerged as a key regulator of stem cell behavior. Mitochondria are crucial metabolic organelles that are important for differentiated cells, yet considered less so for stem cells. However, recent studies have shown that mitochondria influence stem cell maintenance and fate decisions, inviting a revised look at this topic. In this review, we cover the current literature addressing the role of mitochondrial metabolism in mouse and human neural stem cells (NSCs) in the embryonic and adult brain. We summarize how mitochondria are implicated in fate regulation and how substrate oxidation affects NSC quiescence. We further explore single-cell RNA sequencing (scRNA-seq) data for metabolic signatures of adult NSCs, highlight emerging technologies reporting on metabolic signatures, and discuss mitochondrial metabolism in other stem cells.
    Keywords:  metabolism; mitochondria; neural stem cells; quiescence
    DOI:  https://doi.org/10.1016/j.tem.2023.05.008
  8. Biology (Basel). 2023 Jun 06. pii: 823. [Epub ahead of print]12(6):
    35 Years of TFAM Research: Old Protein, New Puzzles.
    Natalya Kozhukhar, Mikhail F Alexeyev.
      Transcription Factor A Mitochondrial (TFAM), through its contributions to mtDNA maintenance and expression, is essential for cellular bioenergetics and, therefore, for the very survival of cells. Thirty-five years of research on TFAM structure and function generated a considerable body of experimental evidence, some of which remains to be fully reconciled. Recent advancements allowed an unprecedented glimpse into the structure of TFAM complexed with promoter DNA and TFAM within the open promoter complexes. These novel insights, however, raise new questions about the function of this remarkable protein. In our review, we compile the available literature on TFAM structure and function and provide some critical analysis of the available data.
    Keywords:  mitochondria; mitochondrial DNA; mitochondrial DNA repair; mitochondrial DNA replication; mitochondrial DNA transcription; mitochondrial biogenesis; mitochondrial transcription factor A (TFAM)
    DOI:  https://doi.org/10.3390/biology12060823
  9. Aging (Albany NY). 2023 Jun 24. 15
    Mitochondrial fitness sustains healthy muscle aging.
    Andrea Irazoki, Antonio Zorzano, David Sebastián.
      
    Keywords:  aging; mitochondria; mitochondrial dynamics; mitophagy; sarcopenia
    DOI:  https://doi.org/10.18632/aging.204857
  10. Front Genet. 2023 ;14 1191159
    Clinical and bi-genomic DNA findings of patients suspected to have mitochondrial diseases.
    Asuman Gedikbasi, Guven Toksoy, Meryem Karaca, Cagri Gulec, Mehmet Cihan Balci, Dilek Gunes, Seda Gunes, Ayca Dilruba Aslanger, Gokcen Unverengil, Birsen Karaman, Seher Basaran, Mubeccel Demirkol, Gulden Fatma Gokcay, Zehra Oya Uyguner.
      Background: Mitochondrial diseases are the most common group of inherited metabolic disorders, causing difficulties in definite diagnosis due to clinical and genetic heterogeneity. Clinical components are predominantly associated with pathogenic variants shown in nuclear or mitochondrial genomes that affect vital respiratory chain function. The development of high-throughput sequencing technologies has accelerated the elucidation of the genetic etiology of many genetic diseases that previously remained undiagnosed. Methods: Thirty affected patients from 24 unrelated families with clinical, radiological, biochemical, and histopathological evaluations considered for mitochondrial diseases were investigated. DNA isolated from the peripheral blood samples of probands was sequenced for nuclear exome and mitochondrial DNA (mtDNA) analyses. MtDNA sequencing was also performed from the muscle biopsy material in one patient. For segregation, Sanger sequencing is performed for pathogenic alterations in five other affected family members and healthy parents. Results: Exome sequencing revealed 14 different pathogenic variants in nine genes encoding mitochondrial function peptides (AARS2, EARS2, ECHS1, FBXL4, MICOS13, NDUFAF6, OXCT1, POLG, and TK2) in 12 patients from nine families and four variants in genes encoding important for muscle structure (CAPN3, DYSF, and TCAP) in six patients from four families. Three probands carried pathogenic mtDNA variations in two genes (MT-ATP6 and MT-TL1). Nine variants in five genes are reported for the first time with disease association: (AARS2: c.277C>T/p.(R93*), c.845C>G/p.(S282C); EARS2: c.319C>T/p.(R107C), c.1283delC/p.(P428Lfs*); ECHS1: c.161G>A/p.(R54His); c.202G>A/p.(E68Lys); NDUFAF6: c.479delA/p.(N162Ifs*27); and OXCT1: c.1370C>T/p.(T457I), c.1173-139G>T/p.(?). Conclusion: Bi-genomic DNA sequencing clarified genetic etiology in 67% (16/24) of the families. Diagnostic utility by mtDNA sequencing in 13% (3/24) and exome sequencing in 54% (13/24) of the families prioritized searching for nuclear genome pathologies for the first-tier test. Weakness and muscle wasting observed in 17% (4/24) of the families underlined that limb-girdle muscular dystrophy, similar to mitochondrial myopathy, is an essential point for differential diagnosis. The correct diagnosis is crucial for comprehensive genetic counseling of families. Also, it contributes to making treatment-helpful referrals, such as ensuring early access to medication for patients with mutations in the TK2 gene.
    Keywords:  bi-genomic sequencing; differential diagnosis; exome sequencing; mitochondrial diseases; mtDNA
    DOI:  https://doi.org/10.3389/fgene.2023.1191159
  11. Biomolecules. 2023 05 26. pii: 890. [Epub ahead of print]13(6):
    Insulin-Degrading Enzyme Interacts with Mitochondrial Ribosomes and Respiratory Chain Proteins.
    Ayse Yilmaz, Chiara Guerrera, Emmanuelle Waeckel-Énée, Joanna Lipecka, Barbara Bertocci, Peter van Endert.
      Insulin-degrading enzyme (IDE) is a highly conserved metalloprotease that is mainly localized in the cytosol. Although IDE can degrade insulin and some other low molecular weight substrates efficiently, its ubiquitous expression suggests additional functions supported by experimental findings, such as a role in stress responses and cellular protein homeostasis. The translation of a long full-length IDE transcript has been reported to result in targeting to mitochondria, but the role of IDE in this compartment is unknown. To obtain initial leads on the function of IDE in mitochondria, we used a proximity biotinylation approach to identify proteins interacting with wild-type and protease-dead IDE targeted to the mitochondrial matrix. We find that IDE interacts with multiple mitochondrial ribosomal proteins as well as with proteins involved in the synthesis and assembly of mitochondrial complex I and IV. The mitochondrial interactomes of wild type and mutant IDE are highly similar and do not reveal any likely proteolytic IDE substrates. We speculate that IDE could adopt similar additional non-proteolytic functions in mitochondria as in the cytosol, acting as a chaperone and contributing to protein homeostasis and stress responses.
    Keywords:  chaperone; mitochondrial translation; mitochondrion; respiratory chain
    DOI:  https://doi.org/10.3390/biom13060890
  12. J Assoc Physicians India. 2023 Jun;71(6): 11-12
    Sensory Ataxic Neuropathy with Dysarthria and Ophthalmoplegia (SANDO): A Multisystem Mitochondrial Disorder.
    Usharani Budumuru, Padmaja R Sowmini, Malcolm J Krishnaswamy, Sakthi V Saravanan, Kannan Vellaichamy, Viveka S Raju, Mugundhan Krishnan.
      
  13. J Drug Target. 2023 Jun 26. 1-14
    Syntaphilin mediates axonal growth and synaptic changes through regulation of mitochondrial transport: a potential pharmacological target for neurodegenerative diseases.
    Qing-Yun Wu, Hui-Lin Liu, Hai-Yan Wang, Kai-Bin Hu, Ping Liao, Sen Li, Zai-Yun Long, Xiu-Min Lu, Yong-Tang Wang.
      Mitochondria are a crucial energy source for maintaining neuronal growth and synaptic function. Neurons possess unique morphological characteristics, which make the proper regulation of mitochondrial transport essential for meeting their energy demands. Syntaphilin (SNPH) is capable of specifically targeting the outer membrane of axonal mitochondria, anchoring them to microtubules, and thereby preventing their transport. SNPH also interacts with other mitochondrial proteins to regulate mitochondrial transport. The regulation of mitochondrial transport and anchoring mediated by SNPH is indispensable for axonal growth during neuronal development, maintenance of ATP levels during neuronal synaptic activity, and regeneration of mature neurons following damage. Precise blocking of SNPH may be an effective therapeutic strategy for neurodegenerative diseases and related mental disorders.
    Keywords:  Syntaphilin; mitochondrial transport; neurodegenerative diseases; neuronal regeneration; synaptic plasticity
    DOI:  https://doi.org/10.1080/1061186X.2023.2230522
  14. Adv Biol (Weinh). 2023 Jun 27. e2300154
    Effects of Parkin on the Mitochondrial Genome in the Heart and Brain of Mitochondrial Mutator Mice.
    Eliezer Z Lichter, Andrew J Trease, Kathryn Cooper, Kelly L Stauch, Howard S Fox.
      Mitochondrial dysfunction has been implicated in neurodegenerative diseases like Parkinson's disease (PD). This study investigates the role of Parkin, a protein involved in mitochondrial quality control, and strongly linked to PD, in the context of mitochondrial DNA (mtDNA) mutations. The authors use mitochondrial mutator mice (PolgD257A/D257A ) (Polg), which are bred with Parkin knockout (PKO) mice or mice with disinhibited Parkin (W402A). In the brain, mtDNA mutations are analyzed in synaptosomes, presynaptic neuronal terminals, which are far from neuronal soma, which likely renders mitochondria there more vulnerable compared with brain homogenate. Surprisingly, PKO results in reduced mtDNA mutations in the brain but increased control region multimer (CRMS) load in synaptosomes. In the heart, both PKO and W402A lead to increased mutations, with W402A showing more mutations in the heart than PKO. Computational analysis reveals many of these mutations are deleterious. These findings suggest that Parkin plays a tissue-dependent role in regulating mtDNA damage response, with differential effects in the brain and heart. Understanding the specific role of Parkin in different tissues may provide insights into the underlying mechanisms of PD and potential therapeutic strategies. Further investigation into these pathways can enhance the understanding of neurodegenerative diseases associated with mitochondrial dysfunction.
    Keywords:  Parkinson's disease; mitochondrial dysfunction; mitochondrial genome; mtDNA; parkin
    DOI:  https://doi.org/10.1002/adbi.202300154
  15. Int J Mol Sci. 2023 Jun 18. pii: 10294. [Epub ahead of print]24(12):
    Extracellular Vesicles and Cx43-Gap Junction Channels Are the Main Routes for Mitochondrial Transfer from Ultra-Purified Mesenchymal Stem Cells, RECs.
    Jiahao Yang, Lu Liu, Yasuaki Oda, Keisuke Wada, Mako Ago, Shinichiro Matsuda, Miho Hattori, Tsukimi Goto, Shuichi Ishibashi, Yuki Kawashima-Sonoyama, Yumi Matsuzaki, Takeshi Taketani.
      Mitochondria are essential organelles for maintaining intracellular homeostasis. Their dysfunction can directly or indirectly affect cell functioning and is linked to multiple diseases. Donation of exogenous mitochondria is potentially a viable therapeutic strategy. For this, selecting appropriate donors of exogenous mitochondria is critical. We previously demonstrated that ultra-purified bone marrow-derived mesenchymal stem cells (RECs) have better stem cell properties and homogeneity than conventionally cultured bone marrow-derived mesenchymal stem cells. Here, we explored the effect of contact and noncontact systems on three possible mitochondrial transfer mechanisms involving tunneling nanotubes, connexin 43 (Cx43)-mediated gap junction channels (GJCs), and extracellular vesicles (Evs). We show that Evs and Cx43-GJCs provide the main mechanism for mitochondrial transfer from RECs. Through these two critical mitochondrial transfer pathways, RECs could transfer a greater number of mitochondria into mitochondria-deficient (ρ0) cells and could significantly restore mitochondrial functional parameters. Furthermore, we analyzed the effect of exosomes (EXO) on the rate of mitochondrial transfer from RECs and recovery of mitochondrial function. REC-derived EXO appeared to promote mitochondrial transfer and slightly improve the recovery of mtDNA content and oxidative phosphorylation in ρ0 cells. Thus, ultrapure, homogenous, and safe stem cell RECs could provide a potential therapeutic tool for diseases associated with mitochondrial dysfunction.
    Keywords:  Cx43-gap junction channels (Cx43-GJCs); extracellular vesicles (Evs); mesenchymal stem cells (MSCs); mitochondrial transfer; rapidly expanding clones (RECs)
    DOI:  https://doi.org/10.3390/ijms241210294
  16. FASEB J. 2023 Aug;37(8): e23046
    Implications of MCU complex in metabolic diseases.
    Chen Li, Jiyu Sun, Xidan Zhang, Min Zhou, Xueqi Gan.
      Metabolic diseases are considered the primary culprit for physical and mental health of individuals. Although the diagnosis of these diseases is relatively easy, more effective and convenient potent drugs are still being explored. Ca2+ across the inner mitochondrial membrane is a vital intracellular messenger that regulates energy metabolism and cellular Ca2+ homeostasis and is involved in cell death. Mitochondria rely on a selective mitochondrial Ca2+ unidirectional transport complex (MCU complex) in their inner membrane for Ca2+ uptake. We found that the channel contains several subunits and undergoes dramatic transformations in various pathological processes, especially in metabolic diseases. In this way, we believe that the MCU complex becomes a target with significant potential for these diseases. However, there is no review linking the two factors, thus hindering the possibility of new drug production. Here, we highlight the connection between MCU complex-related Ca2+ transport and the pathophysiology of metabolic diseases, adding understanding and insight at the molecular level to provide new insights for targeting MCU to reverse metabolism-related diseases.
    Keywords:  MCU complex; homeostasis; metabolic disease; mitochondrial; structure
    DOI:  https://doi.org/10.1096/fj.202300218R
  17. Acta Physiol (Oxf). 2023 Jun 27. e14016
    Fifty years of the mitochondrial pyruvate carrier: New insights into its structure, function, and inhibition.
    Sotiria Tavoulari, Maximilian Sichrovsky, Edmund R S Kunji.
      The mitochondrial pyruvate carrier (MPC) resides in the mitochondrial inner membrane, where it links cytosolic and mitochondrial metabolism by transporting pyruvate produced in glycolysis into the mitochondrial matrix. Due to its central metabolic role, it has been proposed as a potential drug target for diabetes, non-alcoholic fatty liver disease, neurodegeneration, and cancers relying on mitochondrial metabolism. Little is known about the structure and mechanism of MPC, as the proteins involved were only identified a decade ago and technical difficulties concerning their purification and stability have hindered progress in functional and structural analyses. The functional unit of MPC is a hetero-dimer comprising two small homologous membrane proteins, MPC1/MPC2 in humans, with the alternative complex MPC1L/MPC2 forming in the testis, but MPC proteins are found throughout the tree of life. The predicted topology of each protomer consists of an amphipathic helix followed by three transmembrane helices. An increasing number of inhibitors are being identified, expanding MPC pharmacology and providing insights into the inhibitory mechanism. Here, we provide critical insights on the composition, structure, and function of the complex and we summarize the different classes of small molecule inhibitors and their potential in therapeutics.
    Keywords:  metabolism; mitochondria; pyruvate transport; small molecule inhibitors; transport mechanism
    DOI:  https://doi.org/10.1111/apha.14016
  18. Biomolecules. 2023 06 03. pii: 938. [Epub ahead of print]13(6):
    Highly Specialized Mechanisms for Mitochondrial Transport in Neurons: From Intracellular Mobility to Intercellular Transfer of Mitochondria.
    Marta Zaninello, Camilla Bean.
      The highly specialized structure and function of neurons depend on a sophisticated organization of the cytoskeleton, which supports a similarly sophisticated system to traffic organelles and cargo vesicles. Mitochondria sustain crucial functions by providing energy and buffering calcium where it is needed. Accordingly, the distribution of mitochondria is not even in neurons and is regulated by a dynamic balance between active transport and stable docking events. This system is finely tuned to respond to changes in environmental conditions and neuronal activity. In this review, we summarize the mechanisms by which mitochondria are selectively transported in different compartments, taking into account the structure of the cytoskeleton, the molecular motors and the metabolism of neurons. Remarkably, the motor proteins driving the mitochondrial transport in axons have been shown to also mediate their transfer between cells. This so-named intercellular transport of mitochondria is opening new exciting perspectives in the treatment of multiple diseases.
    Keywords:  TNTs; cytoskeleton; microtubules; mitochondria; mitochondrial transplantation; neuron; transport
    DOI:  https://doi.org/10.3390/biom13060938
  19. Nat Genet. 2023 Jun 29.
    Single-cell multiomic analyses sheds light on mitochondrial mutational selection.
    Sarah J Pickett, Gavin Hudson, Laura C Greaves.
      
    DOI:  https://doi.org/10.1038/s41588-023-01436-5
  20. Nat Cell Biol. 2023 Jun 29.
    mTORC2-NDRG1-CDC42 axis couples fasting to mitochondrial fission.
    Nuria Martinez-Lopez, Pamela Mattar, Miriam Toledo, Henrietta Bains, Manu Kalyani, Marie Louise Aoun, Mridul Sharma, Laura Beth J McIntire, Leslie Gunther-Cummins, Frank P Macaluso, Jennifer T Aguilan, Simone Sidoli, Mathieu Bourdenx, Rajat Singh.
      Fasting triggers diverse physiological adaptations including increases in circulating fatty acids and mitochondrial respiration to facilitate organismal survival. The mechanisms driving mitochondrial adaptations and respiratory sufficiency during fasting remain incompletely understood. Here we show that fasting or lipid availability stimulates mTORC2 activity. Activation of mTORC2 and phosphorylation of its downstream target NDRG1 at serine 336 sustains mitochondrial fission and respiratory sufficiency. Time-lapse imaging shows that NDRG1, but not the phosphorylation-deficient NDRG1Ser336Ala mutant, engages with mitochondria to facilitate fission in control cells, as well as in those lacking DRP1. Using proteomics, a small interfering RNA screen, and epistasis experiments, we show that mTORC2-phosphorylated NDRG1 cooperates with small GTPase CDC42 and effectors and regulators of CDC42 to orchestrate fission. Accordingly, RictorKO, NDRG1Ser336Ala mutants and Cdc42-deficient cells each display mitochondrial phenotypes reminiscent of fission failure. During nutrient surplus, mTOR complexes perform anabolic functions; however, paradoxical reactivation of mTORC2 during fasting unexpectedly drives mitochondrial fission and respiration.
    DOI:  https://doi.org/10.1038/s41556-023-01163-3
  21. Nat Commun. 2023 Jun 30. 14(1): 3882
    Targeted cross-linker delivery for the in situ mapping of protein conformations and interactions in mitochondria.
    Yuwan Chen, Wen Zhou, Yufei Xia, Weijie Zhang, Qun Zhao, Xinwei Li, Hang Gao, Zhen Liang, Guanghui Ma, Kaiguang Yang, Lihua Zhang, Yukui Zhang.
      Current methods for intracellular protein analysis mostly require the separation of specific organelles or changes to the intracellular environment. However, the functions of proteins are determined by their native microenvironment as they usually form complexes with ions, nucleic acids, and other proteins. Here, we show a method for in situ cross-linking and analysis of mitochondrial proteins in living cells. By using the poly(lactic-co-glycolic acid) (PLGA) nanoparticles functionalized with dimethyldioctadecylammonium bromide (DDAB) to deliver protein cross-linkers into mitochondria, we subsequently analyze the cross-linked proteins using mass spectrometry. With this method, we identify a total of 74 pairs of protein-protein interactions that do not exist in the STRING database. Interestingly, our data on mitochondrial respiratory chain proteins ( ~ 94%) are also consistent with the experimental or predicted structural analysis of these proteins. Thus, we provide a promising technology platform for in situ defining protein analysis in cellular organelles under their native microenvironment.
    DOI:  https://doi.org/10.1038/s41467-023-39485-3
  22. Comp Biochem Physiol A Mol Integr Physiol. 2023 Jun 25. pii: S1095-6433(23)00103-4. [Epub ahead of print]283 111470
    Commentary: Aldehyde dehydrogenase, redox balance and exercise physiology: What is missing?
    Wagner Ribeiro Pereira, Julio Cesar Batista Ferreira, Guilherme Giannini Artioli.
      Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme involved in reactive aldehyde detoxification. Approximately 560 million people (about 8% of the world's population) carry a point mutation in the aldehyde dehydrogenase 2 gene (ALDH2), identified as ALDH2*2, which leads to decreased ALDH2 catalytic activity. ALDH2*2 variant is associated with an accumulation of toxic reactive aldehydes and consequent disruption of cellular metabolism, which contributes to the establishment and progression of several degenerative diseases. Consequences of aldehyde accumulation include impaired mitochondrial functional, hindered anabolic signaling in the skeletal muscle, impaired cardiovascular and pulmonary function, and reduced osteoblastogenesis. Considering that aldehydes are endogenously produced through redox processes, it is expected that conditions that have a high energy demand, such as exercise, might be affected by impaired aldehyde clearance in ALDH2*2 individuals. Despite the large body of evidence supporting the importance of ALDH2 to ethanol metabolism, redox homeostasis and overall health, specific research investigating the impact of ALDH2*2 on phenotypes relevant to exercise performance are notoriously scarce. In this commentary, we highlight the consolidated knowledge on the impact of ALDH2*2 on physiological processes that are relevant to exercise.
    Keywords:  Aldehyde dehydrogenase 2 enzyme; Bone health, cardiovascular function; Reactive aldehydes; Skeletal muscle
    DOI:  https://doi.org/10.1016/j.cbpa.2023.111470
  23. Nat Rev Genet. 2023 Jun 29.
    Genomic newborn screening for rare diseases.
    Zornitza Stark, Richard H Scott.
      Rare diseases are a leading cause of infant mortality and lifelong disability. To improve outcomes, timely diagnosis and effective treatments are needed. Genomic sequencing has transformed the traditional diagnostic process, providing rapid, accurate and cost-effective genetic diagnoses to many. Incorporating genomic sequencing into newborn screening programmes at the population scale holds the promise of substantially expanding the early detection of treatable rare diseases, with stored genomic data potentially benefitting health over a lifetime and supporting further research. As several large-scale newborn genomic screening projects launch internationally, we review the challenges and opportunities presented, particularly the need to generate evidence of benefit and to address the ethical, legal and psychosocial issues that genomic newborn screening raises.
    DOI:  https://doi.org/10.1038/s41576-023-00621-w
  24. Int J Mol Sci. 2023 Jun 12. pii: 10015. [Epub ahead of print]24(12):
    Improving Mitochondrial Function in Skeletal Muscle Contributes to the Amelioration of Insulin Resistance by Nicotinamide Riboside.
    Qiuyan Li, Xuye Jiang, Yujia Zhou, Yingying Gu, Yijie Ding, Jing Luo, Nengzhi Pang, Yan Sun, Lei Pei, Jie Pan, Mengqi Gao, Sixi Ma, Ying Xiao, De Hu, Feilong Wu, Lili Yang.
      High-fat diet (HFD)-induced insulin resistance (IR) in skeletal muscle is often accompanied by mitochondrial dysfunction and oxidative stress. Boosting nicotinamide adenine dinucleotide (NAD) using nicotinamide riboside (NR) can effectively decrease oxidative stress and increase mitochondrial function. However, whether NR can ameliorate IR in skeletal muscle is still inconclusive. We fed male C57BL/6J mice with an HFD (60% fat) ± 400 mg/kg·bw NR for 24 weeks. C2C12 myotube cells were treated with 0.25 mM palmitic acid (PA) ± 0.5 mM NR for 24 h. Indicators for IR and mitochondrial dysfunction were analyzed. NR treatment alleviated IR in HFD-fed mice with regard to improved glucose tolerance and a remarkable decrease in the levels of fasting blood glucose, fasting insulin and HOMA-IR index. NR-treated HFD-fed mice also showed improved metabolic status regarding a significant reduction in body weight and lipid contents in serum and the liver. NR activated AMPK in the skeletal muscle of HFD-fed mice and PA-treated C2C12 myotube cells and upregulated the expression of mitochondria-related transcriptional factors and coactivators, thereby improving mitochondrial function and alleviating oxidative stress. Upon inhibiting AMPK using Compound C, NR lost its ability in enhancing mitochondrial function and protection against IR induced by PA. In summary, improving mitochondrial function through the activation of AMPK pathway in skeletal muscle may play an important role in the amelioration of IR using NR.
    Keywords:  AMPK activation; NAD; insulin resistance; mitochondrial dysfunction; nicotinamide riboside (NR); oxidative stress
    DOI:  https://doi.org/10.3390/ijms241210015
  25. Mol Genet Metab. 2023 Jul;pii: S1096-7192(23)00256-1. [Epub ahead of print]139(3): 107626
    Sengers syndrome and AGK-related disorders - Minireview of phenotypic variability and clinical outcomes in molecularly confirmed cases.
    Chen-Han Wilfred Wu, Martin Caha, Leslie Smoot, David J Harris, Amy E Roberts, Stephanie Sacharow, Olaf Bodamer.
      Sengers syndrome (OMIM# 212350) is a rare autosomal recessive mitochondrial disease caused by biallelic pathogenic variants in the AGK gene, which encodes the acylglycerol kinase enzyme. The syndrome was originally defined as a "triad" of hypertrophic cardiomyopathy, cataracts, and lactic acidosis, with or without skeletal myopathy. The clinical manifestation of Sengers Syndrome exhibits substantial heterogeneity, with mild and severe/infantile forms reported. Further, biallelic AGK pathogenic variants have also been identified in a familial case of non-syndromic isolated cataract (OMIM# 614691), expanding our understanding of the gene's influence beyond the originally defined syndrome. In this study, we provide a systematic review of molecularly confirmed cases with biallelic AGK pathogenic variants (Supplementary Table 1). Our analysis demonstrates the variable expressivity and penetrance of the central features of Sengers syndrome, as follows: cataracts (98%), cardiomyopathy (88%), lactic acidosis (adjusted 88%), and skeletal myopathy (adjusted 74%) (Table 1). Furthermore, we investigate the associations between genotype, biochemical profiles, and clinical outcomes, with a particular focus on infantile mortality. Our findings reveal that patients carrying homozygous nonsense variants have a higher incidence of infant mortality and a lower median age of death (p = 0.005 and p = 0.02, Table 2a). However, the location of pathogenic variants within the AGK domains was not significantly associated with infantile death (p = 0.62, Table 2b). Additionally, we observe a borderline association between the absence of lactic acidosis and longer survival (p = 0.053, Table 2c). Overall, our systematic review sheds light on the diverse clinical manifestations of AGK-related disorders and highlights potential factors that influence its prognosis. These provide important implications for the diagnosis, treatment, and counseling of affected individuals and families.
    Keywords:  Biochemical genetics; Metabolism
    DOI:  https://doi.org/10.1016/j.ymgme.2023.107626
  26. Contact (Thousand Oaks). 2022 Jan-Dec;5:5 25152564221092487
    Molecular Regulations of FUNDC1 at ER-Mitochondria Contacts Under Hypoxic Stress.
    Yi Zhang, Haixia Zhuang, Hao Liu, Du Feng.
      A recent research paper published in Journal of Cell Biology by Chen and colleagues describes a novel mechanism by which the MAM (Mitochondrial-associated endoplasmic reticulum membrane) protein FUNDC1 (FUN14 domain-containing protein 1) regulates mitochondrial division through altered protein post-translational modifications under hypoxic stress. The authors found that in a hypoxic environment, the endoplasmic reticulum-localized deubiquitinating enzyme USP19 accumulates at the MAM and interacts with the enriched mitochondrial outer membrane protein FUNDC1, which subsequently induces its deubiquitination and promotes the oligomerization and activity of DRP1, and mitochondria eventually divide in the presence of DRP1. This article provides new insights into the regulation of mitochondrial dynamics by FUNDC1 under hypoxic condition.
    Keywords:  DRP1; FUNDC1; MAM; Mitochondria; USP19
    DOI:  https://doi.org/10.1177/25152564221092487
  27. Hum Mol Genet. 2023 Jun 29. pii: ddad102. [Epub ahead of print]
    Mitochondrial dysfunction and mitophagy defects in LRRK2-R1441C Parkinson's disease models.
    Matthew G Williamson, Marta Madureira, William McGuinness, Rachel Heon-Roberts, Elliot D Mock, Kalina Naidoo, Kaitlyn M L Cramb, Maria-Claudia Caiazza, Ana Belen Malpartida, Martha Lavelle, Katrina Savory, Stewart W Humble, Ryan Patterson, John B Davis, Natalie Connor-Robson, Brent J Ryan, Richard Wade-Martins.
      Mutations in the Leucine-Rich Repeat Kinase 2 (LRRK2) gene have been identified as one of the most common genetic causes of Parkinson's disease (PD). The LRRK2 PD-associated mutations LRRK2G2019S and LRRK2R1441C, located in the kinase domain and in the ROC-COR domain, respectively, have been demonstrated to impair mitochondrial function. Here, we sought to further our understanding of mitochondrial health and mitophagy by integrating data from LRRK2R1441C rat primary cortical and human induced pluripotent stem cell-derived dopamine (iPSC-DA) neuronal cultures as models of PD. We found LRRK2R1441C neurons exhibit decreased mitochondrial membrane potential, impaired mitochondrial function and decreased basal mitophagy levels. Mitochondrial morphology was altered in LRRK2R1441C iPSC-DA but not in cortical neuronal cultures or aged striatal tissue, indicating a cell type-specific phenotype. Additionally, LRRK2R1441C but not LRRK2G2019S neurons demonstrated decreased levels of the mitophagy marker pS65Ub in response to mitochondrial damage, which could disrupt degradation of damaged mitochondria. This impaired mitophagy activation and mitochondrial function were not corrected by the LRRK2 inhibitor MLi-2 in LRRK2R1441C iPSC-DA neuronal cultures. Furthermore, we demonstrate LRRK2 interaction with MIRO1, a protein necessary to stabilise and to anchor mitochondria for transport, occurs at mitochondria, in a genotype-independent manner. Despite this, we found that degradation of MIRO1 was impaired in LRRK2R1441C cultures upon induced mitochondrial damage, suggesting a divergent mechanism from the LRRK2G2019S mutation.
    DOI:  https://doi.org/10.1093/hmg/ddad102
  28. Free Radic Biol Med. 2023 Jun 22. pii: S0891-5849(23)00507-5. [Epub ahead of print]
    Human peroxisomal NAD+/NADH homeostasis is regulated by two independent NAD(H) shuttle systems.
    Serhii Chornyi, Cláudio F Costa, Lodewijk IJlst, Marc Fransen, Ronald J A Wanders, Carlo W T van Roermund, Hans R Waterham.
      Reduced (NADH) and oxidized (NAD+) nicotinamide adenine dinucleotides are ubiquitous hydride-donating/accepting cofactors that are essential for cellular bioenergetics. Peroxisomes are single-membrane-bounded organelles that are involved in multiple lipid metabolism pathways, including beta-oxidation of fatty acids, and which contain several NAD(H)-dependent enzymes. Although maintenance of NAD(H) homeostasis in peroxisomes is considered essential for peroxisomal beta-oxidation, little is known about the regulation thereof. To resolve this issue, we have developed methods to specifically measure intraperoxisomal NADH levels in human cells using peroxisome-targeted NADH biosensors. By targeted CRISPR-Cas9-mediated genome editing of human cells, we showed with these sensors that the NAD+/NADH ratio in cytosol and peroxisomes are closely connected and that this crosstalk is mediated by intraperoxisomal lactate and malate dehydrogenases, generated via translational stop codon readthrough of the LDHB and MDH1 mRNAs. Our study provides evidence for the existence of two independent redox shuttle systems in human peroxisomes that regulate peroxisomal NAD+/NADH homeostasis. This is the first study that shows a specific metabolic function of protein isoforms generated by translational stop codon readthrough in humans.
    Keywords:  Beta-oxidation; Bioenergetics; Cofactor; Dehydrogenase; Metabolism; Redox balance
    DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.06.020
  29. Hum Mol Genet. 2023 Jun 27. pii: ddad100. [Epub ahead of print]
    Insights into energy balance dysregulation from a mouse model of methylmalonic aciduria.
    Marie Lucienne, Raffaele Gerlini, Birgit Rathkolb, Julia Calzada-Wack, Patrick Forny, Stephan Wueest, Andres Kaech, Florian Traversi, Merima Forny, Céline Bürer, Antonio Aguilar-Pimentel, Martin Irmler, Johannes Beckers, Sven Sauer, Stefan Kölker, Joseph P Dewulf, Guido T Bommer, Daniel Hoces, Valerie Gailus-Durner, Helmut Fuchs, Jan Rozman, D Sean Froese, Matthias R Baumgartner, Martin Hrabě de Angelis.
      Inherited disorders of mitochondrial metabolism, including isolated methylmalonic aciduria, present unique challenges to energetic homeostasis by disrupting energy producing pathways. To better understand global responses to energy shortage, we investigated a hemizygous mouse model of methylmalonyl-CoA mutase (Mmut) type methylmalonic aciduria. We found Mmut mutant mice to have reduced appetite, energy expenditure and body mass compared to littermate controls, along with a relative reduction in lean mass but increase in fat mass. Brown adipose tissue showed a process of whitening, in line with lower body surface temperature and lesser ability to cope with cold challenge. Mutant mice had dysregulated plasma glucose, delayed glucose clearance and a lesser ability to regulate energy sources when switching from the fed to fasted state, while liver investigations indicated metabolite accumulation and altered expression of peroxisome proliferator-activated receptor and Fgf21-controlled pathways. Together, these shed light on the mechanisms and adaptations behind energy imbalance in methylmalonic aciduria and provide insight into metabolic responses to chronic energy shortage, which may have important implications for disease understanding and patient management.
    DOI:  https://doi.org/10.1093/hmg/ddad100
  30. Biomedicines. 2023 May 31. pii: 1598. [Epub ahead of print]11(6):
    Targeting Mitochondrial DNA Transcription by POLRMT Inhibition or Depletion as a Potential Strategy for Cancer Treatment.
    Sabrina C D Daglish, Emily M J Fennell, Lee M Graves.
      Transcription of the mitochondrial genome is essential for the maintenance of oxidative phosphorylation (OXPHOS) and other functions directly related to this unique genome. Considerable evidence suggests that mitochondrial transcription is dysregulated in cancer and cancer metastasis and contributes significantly to cancer cell metabolism. Recently, inhibitors of the mitochondrial DNA-dependent RNA polymerase (POLRMT) were identified as potentially attractive new anti-cancer compounds. These molecules (IMT1, IMT1B) inactivate cancer cell metabolism through reduced transcription of mitochondrially-encoded OXPHOS subunits such as ND1-5 (Complex I) and COI-IV (Complex IV). Studies from our lab have discovered small molecule regulators of the mitochondrial matrix caseinolytic protease (ClpP) as probable inhibitors of mitochondrial transcription. These compounds activate ClpP proteolysis and lead to the rapid depletion of POLRMT and other matrix proteins, resulting in inhibition of mitochondrial transcription and growth arrest. Herein we present a comparison of POLRMT inhibition and ClpP activation, both conceptually and experimentally, and evaluate the results of these treatments on mitochondrial transcription, inhibition of OXPHOS, and ultimately cancer cell growth. We discuss the potential for targeting mitochondrial transcription as a cancer cell vulnerability.
    Keywords:  ClpP; POLRMT; mechanism of action; mitochondria; mitochondrial DNA; mitochondrial transcription; oxidative phosphorylation
    DOI:  https://doi.org/10.3390/biomedicines11061598
  31. Acta Neurol Belg. 2023 Jun 28.
    Loss of function variants in L2HGDH gene causing L-2-hydroxyglutaric aciduria.
    Anikha Bellad, Vikram V Holla, Riyanka Kumari, Nitish Kamble, Ravi Yadav, Akhilesh Pandey, Pramod Kumar Pal, Babylakshmi Muthusamy.
       BACKGROUND: L-2-Hydroxyglutaric aciduria (L2HGA) is a rare progressive neurometabolic disorder with variable clinical presentation including cerebellar ataxia, psychomotor retardation, seizures, macrocephaly and speech problems. In this study, we aimed at identifying the genetic cause in two unrelated families suspected with L2HGA.
    METHODS: Exome sequencing was performed on two patients from family 1 with suspected L2HGA. MLPA analysis was carried out on the index patient of family 2 to detect deletions/duplications in the L2HGDH gene. Sanger sequencing was carried out to validate the identified variants and to confirm segregation of the variants in the family members.
    RESULTS: In family 1, a novel homozygous variant c.1156C > T resulting in a nonsense mutation p.Gln386Ter was identified in the L2HGDH gene. The variant segregated with autosomal recessive inheritance in the family. In family 2, a homozygous deletion of exon 10 in the L2HGDH gene was identified in the index patient using MLPA analysis. PCR validation confirmed the presence of the deletion variant in the patient which is not present in the unaffected mother or an unrelated control.
    CONCLUSION: This study identified novel pathogenic variants in the L2HGDH gene in patients with L2HGA. These findings contribute to the understanding of the genetic basis of L2HGA and highlight the importance of genetic testing for diagnosis and genetic counseling of affected families.
    Keywords:  Intellectual disability; L-2-Hydroxyglutaric aciduria; Metabolic disorders; Mitochondrial enzymes
    DOI:  https://doi.org/10.1007/s13760-023-02318-7
  32. Nat Metab. 2023 Jun 26.
    Daytime-restricted feeding enhances running endurance without prior exercise in mice.
    Haoran Xin, Rongfeng Huang, Meiyu Zhou, Jianghui Chen, Jianxin Zhang, Tingting Zhou, Shushen Ji, Xiao Liu, He Tian, Sin Man Lam, Xinyu Bao, Lihua Li, Shifei Tong, Fang Deng, Guanghou Shui, Zhihui Zhang, Catherine C L Wong, Min-Dian Li.
      Physical endurance and energy conservation are essential for survival in the wild. However, it remains unknown whether and how meal timing regulates physical endurance and muscle diurnal rhythms. Here, we show that day/sleep time-restricted feeding (DRF) enhances running endurance by 100% throughout the circadian cycle in both male and female mice, compared to either ad libitum feeding or night/wake time-restricted feeding. Ablation of the circadian clock in the whole body or the muscle abolished the exercise regulatory effect of DRF. Multi-omics analysis revealed that DRF robustly entrains diurnal rhythms of a mitochondrial oxidative metabolism-centric network, compared to night/wake time-restricted feeding. Remarkably, muscle-specific knockdown of the myocyte lipid droplet protein perilipin-5 completely mimics DRF in enhancing endurance, enhancing oxidative bioenergetics and outputting rhythmicity to circulating energy substrates, including acylcarnitine. Together, our work identifies a potent dietary regimen to enhance running endurance without prior exercise, as well as providing a multi-omics atlas of muscle circadian biology regulated by meal timing.
    DOI:  https://doi.org/10.1038/s42255-023-00826-7
  33. Geroscience. 2023 Jun 27.
    Serum factors mediate changes in mitochondrial bioenergetics associated with diet and exercise interventions.
    Jenny L Gonzalez-Armenta, Jaclyn Bergstrom, Jingyun Lee, Cristina M Furdui, Barbara J Nicklas, Anthony J A Molina.
      Mitochondrial improvements resulting from behavioral interventions, such as diet and exercise, are systemic and apparent across multiple tissues. Here, we test the hypothesis that factors present in serum, and therefore circulating throughout the body, can mediate changes in mitochondrial function in response to intervention. To investigate this, we used stored serum from a clinical trial comparing resistance training (RT) and RT plus caloric restriction (RT + CR) to examine effects of blood borne circulating factors on myoblasts in vitro. We report that exposure to dilute serum is sufficient to mediate bioenergetic benefits of these interventions. Additionally, serum-mediated bioenergetic changes can differentiate between interventions, recapitulate sex differences in bioenergetic responses, and is linked to improvements in physical function and inflammation. Using metabolomics, we identified circulating factors associated with changes in mitochondrial bioenergetics and the effects of interventions. This study provides new evidence that circulating factors play a role in the beneficial effects of interventions that improve healthspan among older adults. Understanding the factors that drive improvements in mitochondrial function is a key step towards predicting intervention outcomes and developing strategies to countermand systemic age-related bioenergetic decline.
    Keywords:  Bioenergetics; Caloric restriction; Metabolomics; Mitochondria; Older adults; Resistance training
    DOI:  https://doi.org/10.1007/s11357-023-00855-w
  34. Nat Cell Biol. 2023 Jun 29.
    Fast fragmenting mitochondria by TORC2.
    Miriam Valera-Alberni, William B Mair.
      
    DOI:  https://doi.org/10.1038/s41556-023-01173-1
  35. Endocr Rev. 2023 Jun 26. pii: bnad019. [Epub ahead of print]
    Nicotinamide Adenine Dinucleotide in Aging Biology: Potential Applications and Many Unknowns.
    Shalender Bhasin, Douglas Seals, Marie Migaud, Nicolas Musi, Joseph A Baur.
      Recent research has unveiled an expansive role of NAD+ in cellular energy generation, redox reactions, and as a substrate or co-substrate in signaling pathways that regulate health-span and aging. This review provides a critical appraisal of the clinical pharmacology and the pre-clinical and clinical evidence for therapeutic effects of NAD+ precursors for age-related conditions, with a particular focus on cardiometabolic disorders, and discusses gaps in current knowledge. NAD+ levels decrease throughout life; age-related decline in NAD+ bioavailability has been postulated to be a contributor to many age-related diseases. Raising NAD+ levels in model organisms by administration of NAD+ precursors improves glucose and lipid metabolism; attenuates diet-induced weight-gain, diabetes, diabetic kidney disease, and hepatic steatosis; reduces endothelial dysfunction; protects heart from ischemic injury; improves left ventricular function in models of heart failure; attenuates cerebrovascular and neurodegenerative disorders; and increases health-span. Early human studies show that NAD+ levels can be raised safely in blood and some tissues by oral NAD+ precursors and suggest benefit in preventing nonmelanotic skin cancer, modestly reducing blood pressure and improving lipid profile in older adults with obesity or overweight; preventing kidney injury in at-risk patients; and suppressing inflammation in Parkinson's disease and SARS-CoV-2 infection. Clinical pharmacology, metabolism, and therapeutic mechanisms of NAD+ precursors remain incompletely understood. We suggest that these early findings provide the rationale for adequately-powered randomized trials to evaluate the efficacy of NAD+ augmentation as a therapeutic strategy to prevent and treat metabolic disorders and age-related conditions.
    DOI:  https://doi.org/10.1210/endrev/bnad019
  36. Science. 2023 Jun 30. 380(6652): eadd3067
    Spatially resolved single-cell translatomics at molecular resolution.
    Hu Zeng, Jiahao Huang, Jingyi Ren, Connie Kangni Wang, Zefang Tang, Haowen Zhou, Yiming Zhou, Hailing Shi, Abhishek Aditham, Xin Sui, Hongyu Chen, Jennifer A Lo, Xiao Wang.
      The precise control of messenger RNA (mRNA) translation is a crucial step in posttranscriptional gene regulation of cellular physiology. However, it remains a challenge to systematically study mRNA translation at the transcriptomic scale with spatial and single-cell resolution. Here, we report the development of ribosome-bound mRNA mapping (RIBOmap), a highly multiplexed three-dimensional in situ profiling method to detect cellular translatome. RIBOmap profiling of 981 genes in HeLa cells revealed cell cycle-dependent translational control and colocalized translation of functional gene modules. We mapped 5413 genes in mouse brain tissues, yielding spatially resolved single-cell translatomic profiles for 119,173 cells and revealing cell type-specific and brain region-specific translational regulation, including translation remodeling during oligodendrocyte maturation. Our method detected widespread patterns of localized translation in neuronal and glial cells in intact brain tissue networks.
    DOI:  https://doi.org/10.1126/science.add3067
  37. EMBO Mol Med. 2023 Jun 27. e17159
    Targeting shared molecular etiologies to accelerate drug development for rare diseases.
    Galliano Zanello, Macarena Garrido-Estepa, Ana Crespo, Daniel O'Connor, Rima Nabbout, Christina Waters, Anthony Hall, Maurizio Taglialatela, Chun-Hung Chan, David A Pearce, Marc Dooms, Philip John Brooks.
      Rare diseases affect over 400 million people worldwide and less than 5% of rare diseases have an approved treatment. Fortunately, the number of underlying disease etiologies is far less than the number of diseases, because many rare diseases share a common molecular etiology. Moreover, many of these shared molecular etiologies are therapeutically actionable. Grouping rare disease patients for clinical trials based on the underlying molecular etiology, rather than the traditional, symptom-based definition of disease, has the potential to greatly increase the number of patients gaining access to clinical trials. Basket clinical trials based on a shared molecular drug target have become common in the field of oncology and have been accepted by regulatory agencies as a basis for drug approvals. Implementation of basket clinical trials in the field of rare diseases is seen by multiple stakeholders-patients, researchers, clinicians, industry, regulators, and funders-as a solution to accelerate the identification of new therapies and address patient's unmet needs.
    Keywords:  IRDiRC; basket clinical trials; rare diseases; shared molecular etiologies; therapeutic development
    DOI:  https://doi.org/10.15252/emmm.202217159
  38. Antioxidants (Basel). 2023 May 27. pii: 1163. [Epub ahead of print]12(6):
    Mitochondrial Fission as a Therapeutic Target for Metabolic Diseases: Insights into Antioxidant Strategies.
    Tianzheng Yu, Li Wang, Lei Zhang, Patricia A Deuster.
      Mitochondrial fission is a crucial process in maintaining metabolic homeostasis in normal physiology and under conditions of stress. Its dysregulation has been associated with several metabolic diseases, including, but not limited to, obesity, type 2 diabetes (T2DM), and cardiovascular diseases. Reactive oxygen species (ROS) serve a vital role in the genesis of these conditions, and mitochondria are both the main sites of ROS production and the primary targets of ROS. In this review, we explore the physiological and pathological roles of mitochondrial fission, its regulation by dynamin-related protein 1 (Drp1), and the interplay between ROS and mitochondria in health and metabolic diseases. We also discuss the potential therapeutic strategies of targeting mitochondrial fission through antioxidant treatments for ROS-induced conditions, including the effects of lifestyle interventions, dietary supplements, and chemicals, such as mitochondrial division inhibitor-1 (Mdivi-1) and other mitochondrial fission inhibitors, as well as certain commonly used drugs for metabolic diseases. This review highlights the importance of understanding the role of mitochondrial fission in health and metabolic diseases, and the potential of targeting mitochondrial fission as a therapeutic approach to protecting against these conditions.
    Keywords:  Coenzyme Q10; Drp1; L-citrulline; astaxanthin; curcumin; exercise; lifestyle interventions; mitochondrial integrity; pharmacological management; reactive oxygen species; resveratrol
    DOI:  https://doi.org/10.3390/antiox12061163
  39. Nature. 2023 Jun 28.
    GDF15 promotes weight loss by enhancing energy expenditure in muscle.
    Dongdong Wang, Logan K Townsend, Geneviève J DesOrmeaux, Sara M Frangos, Battsetseg Batchuluun, Lauralyne Dumont, Rune Ehrenreich Kuhre, Elham Ahmadi, Sumei Hu, Irena A Rebalka, Jaya Gautam, Maria Joy Therese Jabile, Chantal A Pileggi, Sonia Rehal, Eric M Desjardins, Evangelia E Tsakiridis, James S V Lally, Emma Sara Juracic, A Russell Tupling, Hertzel C Gerstein, Guillaume Paré, Theodoros Tsakiridis, Mary-Ellen Harper, Thomas J Hawke, John R Speakman, Denis P Blondin, Graham P Holloway, Sebastian Beck Jørgensen, Gregory R Steinberg.
      Caloric restriction that promotes weight loss is an effective strategy for treating non-alcoholic fatty liver disease and improving insulin sensitivity in people with type 2 diabetes1. Despite its effectiveness, in most individuals, weight loss is usually not maintained partly due to physiological adaptations that suppress energy expenditure, a process known as adaptive thermogenesis, the mechanistic underpinnings of which are unclear2,3. Treatment of rodents fed a high-fat diet with recombinant growth differentiating factor 15 (GDF15) reduces obesity and improves glycaemic control through glial-cell-derived neurotrophic factor family receptor α-like (GFRAL)-dependent suppression of food intake4-7. Here we find that, in addition to suppressing appetite, GDF15 counteracts compensatory reductions in energy expenditure, eliciting greater weight loss and reductions in non-alcoholic fatty liver disease (NAFLD) compared to caloric restriction alone. This effect of GDF15 to maintain energy expenditure during calorie restriction requires a GFRAL-β-adrenergic-dependent signalling axis that increases fatty acid oxidation and calcium futile cycling in the skeletal muscle of mice. These data indicate that therapeutic targeting of the GDF15-GFRAL pathway may be useful for maintaining energy expenditure in skeletal muscle during caloric restriction.
    DOI:  https://doi.org/10.1038/s41586-023-06249-4
  40. Nat Metab. 2023 Jun 26.
    Time-restricted feeding makes the mouse run like a pro.
    Mayer M Chalom, Chih-Hao Lee.
      
    DOI:  https://doi.org/10.1038/s42255-023-00833-8
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