bims-mibica 2021-11-07 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2021–11–07
thirty papers selected by
Kelsey Fisher-Wellman, East Carolina University

ND3 Cys39 in complex I is exposed during mitochondrial respiration.
NADPH-to-NADH conversion by mitochondrial transhydrogenase is indispensable for sustaining anaerobic metabolism in Euglena gracilis.
Analysis of Leukemia Cell Metabolism through Stable Isotope Tracing in Mice.
Distinct Mitochondrial Remodeling During Mesoderm Differentiation in a Human-Based Stem Cell Model.
Caseinolytic protease P (CLPP) activated by ONC201 inhibits proliferation and promotes apoptosis in human epithelial ovarian cancer cells by inducing mitochondrial dysfunction.
The mitospecific domain of Mrp7 (bL27) supports mitochondrial translation during fermentation and is required for effective adaptation to respiration.
High ATP Production Fuels Cancer Drug Resistance and Metastasis: Implications for Mitochondrial ATP Depletion Therapy.
Regulatory T cell differentiation is controlled by αKG-induced alterations in mitochondrial metabolism and lipid homeostasis.
A novel protoapigenone analog RY10-4 induces apoptosis of breast cancer cells by exacerbating mitochondrial Ca2+ influx through mitochondrial calcium uniporter.
Subcellular Specialization of Mitochondrial Form and Function in Skeletal Muscle Cells.
Microeconomics of Metabolism: The Warburg Effect as Giffen Behaviour.
Anoxia-reoxygenation modulates cadmium-induced liver mitochondrial reactive oxygen species emission during oxidation of glycerol 3-phosphate.
The existence of a nonclassical TCA cycle in the nucleus that wires the metabolic-epigenetic circuitry.
Role of GM-CSF in regulating metabolism and mitochondrial functions critical to macrophage proliferation.
Remdesivir; molecular and functional measures of mitochondrial safety.
Production of IL-6 and Phagocytosis Are the Most Resilient Immune Functions in Metabolically Compromised Human Monocytes.
Mitochondrial respiration contributes to the interferon gamma response in antigen presenting cells.
Hormetic effect of low doses of rapamycin triggers anti-aging cascades in WRL-68 cells by modulating an mTOR-mitochondria cross-talk.
Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis.
Implications of mitochondrial DNA mutations in human induced pluripotent stem cells.
Mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force.
Metabolic profiling of attached and detached metformin and 2-deoxy-D-glucose treated breast cancer cells reveals adaptive changes in metabolome of detached cells.
The integrity and assay performance of tissue mitochondrial DNA is considerably affected by choice of isolation method.
Biguanide drugs enhance cytotoxic effects of cisplatin by depleting aspartate and NAD+ in sensitive cancer cells.
Macrophages as Emerging Key Players in Mitochondrial Transfers.
Discovery of DS68702229 as a Potent, Orally Available NAMPT (Nicotinamide Phosphoribosyltransferase) Activator.
Constitutive activation of the PI3K-Akt-mTORC1 pathway sustains the m.3243 A > G mtDNA mutation.
Convergence of oncogenic cooperation at single-cell and single-gene levels drives leukemic transformation.
First mitochondrial genome wide association study with metabolomics.
Pan-Cancer Analysis Reveals FH as a Potential Prognostic and Immunological Biomarker in Lung Adenocarcinoma.

Cell Chem Biol. 2021 Nov 02. pii: S2451-9456(21)00444-X. [Epub ahead of print]

ND3 Cys39 in complex I is exposed during mitochondrial respiration.

Nils Burger, Andrew M James, John F Mulvey, Kurt Hoogewijs, Shujing Ding, Ian M Fearnley, Marta Loureiro-López, Abigail A I Norman, Sabine Arndt, Amin Mottahedin, Olga Sauchanka, Richard C Hartley, Thomas Krieg, Michael P Murphy.

  Mammalian complex I can adopt catalytically active (A-) or deactive (D-) states. A defining feature of the reversible transition between these two defined states is thought to be exposure of the ND3 subunit Cys39 residue in the D-state and its occlusion in the A-state. As the catalytic A/D transition is important in health and disease, we set out to quantify it by measuring Cys39 exposure using isotopic labeling and mass spectrometry, in parallel with complex I NADH/CoQ oxidoreductase activity. To our surprise, we found significant Cys39 exposure during NADH/CoQ oxidoreductase activity. Furthermore, this activity was unaffected if Cys39 alkylation occurred during complex I-linked respiration. In contrast, alkylation of catalytically inactive complex I irreversibly blocked the reactivation of NADH/CoQ oxidoreductase activity by NADH. Thus, Cys39 of ND3 is exposed in complex I during mitochondrial respiration, with significant implications for our understanding of the A/D transition and the mechanism of complex I.

Keywords:  Cys39; NADH:ubiquinone oxidoreductase; active/deactive transition; complex I; ischemia-reperfusion (IR) injury; mitochondria; redox regulation; reverse electron transport (RET)

DOI:  https://doi.org/10.1016/j.chembiol.2021.10.010
FEBS Lett. 2021 Nov 05.

NADPH-to-NADH conversion by mitochondrial transhydrogenase is indispensable for sustaining anaerobic metabolism in Euglena gracilis.

Masami Nakazawa, Mutsuki Takahashi, Ryuta Hayashi, Yuki Matsubara, Yuichiro Kashiyama, Mitsuhiro Ueda, Hiroshi Inui, Tatsuji Sakamoto.

  Euglena gracilis produces ATP in the anaerobic mitochondria with concomitant wax ester formation, and NADH is essential for ATP formation and fatty acid synthesis in the mitochondria. This study demonstrated that mitochondrial cofactor conversion by nicotinamide nucleotide transhydrogenase (NNT), converting NADPH/NAD+ to NADP+ /NADH, is indispensable for sustaining anaerobic metabolism. Silencing of NNT genes significantly decreased wax ester production and cellular viability during anaerobiosis but had no such marked effects under aerobic conditions. An analogous phenotype was observed in the silencing of the gene encoding a mitochondrial NADP+ -dependent malic enzyme. These results suggest that the reducing equivalents produced in glycolysis are shuttled to the mitochondria as malate, where cytosolic NAD+ regeneration is coupled with mitochondrial NADPH generation.

Keywords:   Euglena gracilis ; Transhydrogenase; anaerobic respiration; malic enzyme; wax ester fermentation

DOI:  https://doi.org/10.1002/1873-3468.14221
Bio Protoc. 2021 Oct 05. 11(19): e4171

Analysis of Leukemia Cell Metabolism through Stable Isotope Tracing in Mice.

Nick van Gastel, Jessica B Spinelli, Marcia C Haigis, David T Scadden.

  Once thought to be a mere consequence of the state of a cell, intermediary metabolism is now recognized as a key regulator of mammalian cell fate and function. In addition, cell metabolism is often disturbed in malignancies such as cancer, and targeting metabolic pathways can provide new therapeutic options. Cell metabolism is mostly studied in cell cultures in vitro, using techniques such as metabolomics, stable isotope tracing, and biochemical assays. Increasing evidence however shows that the metabolic profile of cells is highly dependent on the microenvironment, and metabolic vulnerabilities identified in vitro do not always translate to in vivo settings. Here, we provide a detailed protocol on how to perform in vivo stable isotope tracing in leukemia cells in mice, focusing on glutamine metabolism in acute myeloid leukemia (AML) cells. This method allows studying the metabolic profile of leukemia cells in their native bone marrow niche.

Keywords:  Cancer biology; Cell metabolism; Glutamine; Leukemia; Metabolic tracing; Mouse models

DOI:  https://doi.org/10.21769/BioProtoc.4171
Front Cell Dev Biol. 2021 ;9 744777

Distinct Mitochondrial Remodeling During Mesoderm Differentiation in a Human-Based Stem Cell Model.

Sepideh Mostafavi, Novin Balafkan, Ina Katrine Nitschke Pettersen, Gonzalo S Nido, Richard Siller, Charalampos Tzoulis, Gareth J Sullivan, Laurence A Bindoff.

  Given the considerable interest in using stem cells for modeling and treating disease, it is essential to understand what regulates self-renewal and differentiation. Remodeling of mitochondria and metabolism, with the shift from glycolysis to oxidative phosphorylation (OXPHOS), plays a fundamental role in maintaining pluripotency and stem cell fate. It has been suggested that the metabolic "switch" from glycolysis to OXPHOS is germ layer-specific as glycolysis remains active during early ectoderm commitment but is downregulated during the transition to mesoderm and endoderm lineages. How mitochondria adapt during these metabolic changes and whether mitochondria remodeling is tissue specific remain unclear. Here, we address the question of mitochondrial adaptation by examining the differentiation of human pluripotent stem cells to cardiac progenitors and further to differentiated mesodermal derivatives, including functional cardiomyocytes. In contrast to recent findings in neuronal differentiation, we found that mitochondrial content decreases continuously during mesoderm differentiation, despite increased mitochondrial activity and higher levels of ATP-linked respiration. Thus, our work highlights similarities in mitochondrial remodeling during the transition from pluripotent to multipotent state in ectodermal and mesodermal lineages, while at the same time demonstrating cell-lineage-specific adaptations upon further differentiation. Our results improve the understanding of how mitochondrial remodeling and the metabolism interact during mesoderm differentiation and show that it is erroneous to assume that increased OXPHOS activity during differentiation requires a simultaneous expansion of mitochondrial content.

Keywords:  OXPHOS; cardiomyocyte; development; metabolism; mitochondria; stem cells

DOI:  https://doi.org/10.3389/fcell.2021.744777
Ann Transl Med. 2021 Sep;9(18): 1463

Caseinolytic protease P (CLPP) activated by ONC201 inhibits proliferation and promotes apoptosis in human epithelial ovarian cancer cells by inducing mitochondrial dysfunction.

Xinxin Kou, Hui Ding, Lei Li, Hongtu Chao.

   Background: Caseinolytic protease P (CLPP) is a mitochondrial specific protein which has been reported to be related to tumor cell apoptosis. This study aims to explore the roles of CLPP in human epithelial ovarian cancer (EOC).
Methods: We determined CLPP expression in paracancerous tissues and cancer tissues obtained from 20 EOC patients, and also in 4 EOC cell lines, and one normal ovarian cell line (IOSE-80). We knocked CLPP expression down in SK-OV-3 and A2780 cells and overexpressed it in SW626 and OVcar3 cells. The effect of CLPP expression on cell proliferation, mitochondrial membrane potential, and apoptosis was then assessed by flow cytometry assay. Furthermore, the effect of ONC201 (agonist of CLPP) on the EOC cell lines was also investigated.
Results: The CLPP expression was markedly down-regulated in EOC cancer tissues, and the Kaplan-Meier Plotter database revealed its low expression was linked to poor prognosis in EOC patients. Low expression of CLPP up-regulated the expression of NADH: ubiquinone oxidoreductase subunit A12 (NDUFA12), succinate dehydrogenase complex flavoprotein subunit A (SDHA), and succinate dehydrogenase complex iron sulfur subunit B (SDHB), which are key members of the mitochondrial respiratory chain, and these up-regulated proteins further led to the increase of mitochondrial membrane potential, cell proliferation promotion and neoplasm metastasis. Conversely, while overexpression of CLPP led to the opposite results, including inducing the decrease of mitochondrial membrane potential and apoptosis. In addition, stimulation with ONC201 enhanced the function of CLPP in SW626 and OVcar3 cells, and silencing of CLPP could neutralize the effect of ONC201.
Conclusions: Our findings suggest that CLPP mediated mitochondrial dysfunction inhibits the proliferation and migration of EOC cells.

Keywords:  Epithelial ovarian cancer (EOC); caseinolytic protease P (CLPP); cell apoptosis; mitochondria

DOI:  https://doi.org/10.21037/atm-21-4321
Mol Biol Cell. 2021 Nov 03. mbcE21070370

The mitospecific domain of Mrp7 (bL27) supports mitochondrial translation during fermentation and is required for effective adaptation to respiration.

Jessica M Anderson, Jodie M Box, Rosemary A Stuart.

We demonstrate here that mitoribosomal protein synthesis, responsible for the synthesis of oxidative phosphorylation (OXPHOS) subunits encoded by mitochondrial genome, occurs at high levels during glycolysis fermentation and in a manner uncoupled from OXPHOS complex assembly regulation. Furthermore, we provide evidence that the mitospecific domain of Mrp7 (bL27), a mitoribosomal component, is required to maintain mitochondrial protein synthesis during fermentation, but is not required under respiration growth conditions. Maintaining mitotranslation under high glucose fermentation conditions also involves Mam33 (p32/gC1qR homolog), a binding partner of Mrp7's mitospecific domain, and together they confer a competitive advantage for a cell's ability to adapt to respiration-based metabolism when glucose becomes limiting. Furthermore, our findings support that the mitoribosome, and specifically the central protuberance (CP) region, may be differentially regulated and/or assembled, under the different metabolic conditions of fermentation and respiration. Based on our findings, we propose the purpose of mitotranslation is not limited to the assembly of OXPHOS complexes, but also plays a role in mitochondrial signaling critical for switching cellular metabolism from a glycolysis- to a respiratory-based state.

DOI: https://doi.org/10.1091/mbc.E21-07-0370
Front Oncol. 2021 ;11 740720

High ATP Production Fuels Cancer Drug Resistance and Metastasis: Implications for Mitochondrial ATP Depletion Therapy.

Marco Fiorillo, Béla Ózsvári, Federica Sotgia, Michael P Lisanti.

  Recently, we presented evidence that high mitochondrial ATP production is a new therapeutic target for cancer treatment. Using ATP as a biomarker, we isolated the "metabolically fittest" cancer cells from the total cell population. Importantly, ATP-high cancer cells were phenotypically the most aggressive, with enhanced stem-like properties, showing multi-drug resistance and an increased capacity for cell migration, invasion and spontaneous metastasis. In support of these observations, ATP-high cells demonstrated the up-regulation of both mitochondrial proteins and other protein biomarkers, specifically associated with stemness and metastasis. Therefore, we propose that the "energetically fittest" cancer cells would be better able to resist the selection pressure provided by i) a hostile micro-environment and/or ii) conventional chemotherapy, allowing them to be naturally-selected for survival, based on their high ATP content, ultimately driving tumor recurrence and distant metastasis. In accordance with this energetic hypothesis, ATP-high MDA-MB-231 breast cancer cells showed a dramatic increase in their ability to metastasize in a pre-clinical model in vivo. Conversely, metastasis was largely prevented by treatment with an FDA-approved drug (Bedaquiline), which binds to and inhibits the mitochondrial ATP-synthase, leading to ATP depletion. Clinically, these new therapeutic approaches could have important implications for preventing treatment failure and avoiding cancer cell dormancy, by employing ATP-depletion therapy, to target even the fittest cancer cells.

Keywords:  ATP; anti-oxidant capacity; bedaquiline; cancer stem cells (CSCs); dormancy; metastasis; mitochondria; multi-drug resistance

DOI:  https://doi.org/10.3389/fonc.2021.740720
Cell Rep. 2021 Nov 02. pii: S2211-1247(21)01384-X. [Epub ahead of print]37(5): 109911

Regulatory T cell differentiation is controlled by αKG-induced alterations in mitochondrial metabolism and lipid homeostasis.

Maria I Matias, Carmen S Yong, Amir Foroushani, Chloe Goldsmith, Cédric Mongellaz, Erdinc Sezgin, Kandice R Levental, Ali Talebi, Julie Perrault, Anais Rivière, Jonas Dehairs, Océane Delos, Justine Bertand-Michel, Jean-Charles Portais, Madeline Wong, Julien C Marie, Ameeta Kelekar, Sandrina Kinet, Valérie S Zimmermann, Ilya Levental, Laurent Yvan-Charvet, Johannes V Swinnen, Stefan A Muljo, Hector Hernandez-Vargas, Saverio Tardito, Naomi Taylor, Valérie Dardalhon.

  Suppressive regulatory T cell (Treg) differentiation is controlled by diverse immunometabolic signaling pathways and intracellular metabolites. Here we show that cell-permeable α-ketoglutarate (αKG) alters the DNA methylation profile of naive CD4 T cells activated under Treg polarizing conditions, markedly attenuating FoxP3+ Treg differentiation and increasing inflammatory cytokines. Adoptive transfer of these T cells into tumor-bearing mice results in enhanced tumor infiltration, decreased FoxP3 expression, and delayed tumor growth. Mechanistically, αKG leads to an energetic state that is reprogrammed toward a mitochondrial metabolism, with increased oxidative phosphorylation and expression of mitochondrial complex enzymes. Furthermore, carbons from ectopic αKG are directly utilized in the generation of fatty acids, associated with lipidome remodeling and increased triacylglyceride stores. Notably, inhibition of either mitochondrial complex II or DGAT2-mediated triacylglyceride synthesis restores Treg differentiation and decreases the αKG-induced inflammatory phenotype. Thus, we identify a crosstalk between αKG, mitochondrial metabolism and triacylglyceride synthesis that controls Treg fate.

Keywords:  CAR T cells; DNA methylation; T cell differentiation; TCA cycle; Th1; Treg; lipidome; mitochondrial metabolism; triacylglyceride synthesis; α-ketoglutarate

DOI:  https://doi.org/10.1016/j.celrep.2021.109911
Toxicol Appl Pharmacol. 2021 Oct 28. pii: S0041-008X(21)00380-X. [Epub ahead of print]433 115776

A novel protoapigenone analog RY10-4 induces apoptosis of breast cancer cells by exacerbating mitochondrial Ca2+ influx through mitochondrial calcium uniporter.

Pingping Xue, Qian Chen, Xiuhua Ren, Dong Liu, Xiaofan Yang.

  RY10-4, a novel protoapigenone analog with a specific nonaromatic B-ring, displayed enhanced cytotoxicity in various tumor cells, especially for breast cancer cells, but the underlying mechanism remains unclear. In the present study, we confirmed the pro-apoptotic effect of RY10-4 on breast cancer cells. Furthermore, mitochondrial calcium uniporter (MCU) was proved to be up-regulated in RY10-4-treated MDA-MB-231 cells, which resulted in the overload of mitochondrial calcium ([Ca2+]m) and subsequently disrupted mitochondrial functions (characterized by mitochondrial reactive oxygen species (mtROS) accumulation, membrane potential (ΔΨm) depolarization and permeability transition pore (mPTP) opening). And finally, the mitochondrial apoptosis was activated by the release of cytochrome C. Interestingly, knockdown of MCU attenuated the overload of [Ca2+]m and blocked the apoptosis of MDA-MB-231 cells induced by RY10-4, which was consistent with the in vivo results. Taken together, this study proved that RY10-4 could induce apoptosis of breast cancer cells by elevating [Ca2+]m through MCU. Our work contributed previously unknown insights into the mechanisms involving in the clinical efficacy of RY10-4 on breast cancer cells, which also advanced calcium homeostasis as a potential target for chemotherapeutic drugs.

Keywords:  Apoptosis; Breast cancer; MCU; Mitochondrial calcium; RY10-4

DOI:  https://doi.org/10.1016/j.taap.2021.115776
Front Cell Dev Biol. 2021 ;9 757305

Subcellular Specialization of Mitochondrial Form and Function in Skeletal Muscle Cells.

T Bradley Willingham, Peter T Ajayi, Brian Glancy.

  Across different cell types and within single cells, mitochondria are heterogeneous in form and function. In skeletal muscle cells, morphologically and functionally distinct subpopulations of mitochondria have been identified, but the mechanisms by which the subcellular specialization of mitochondria contributes to energy homeostasis in working muscles remains unclear. Here, we discuss the current data regarding mitochondrial heterogeneity in skeletal muscle cells and highlight potential new lines of inquiry that have emerged due to advancements in cellular imaging technologies.

Keywords:  bioenergetics; intermyofibrillar mitochondria; mitochondrial connectivity; mitochondrial respiration; organelle interactions; paranuclear mitochondria; paravascular mitochondria; subsarcolemmal mitochondria

DOI:  https://doi.org/10.3389/fcell.2021.757305
Bull Math Biol. 2021 Oct 31. 83(12): 120

Microeconomics of Metabolism: The Warburg Effect as Giffen Behaviour.

Jumpei F Yamagishi, Tetsuhiro S Hatakeyama.

  Metabolic behaviours of proliferating cells are often explained as a consequence of rational optimization of cellular growth rate, whereas microeconomics formulates consumption behaviours as optimization problems. Here, we pushed beyond the analogy to precisely map metabolism onto the theory of consumer choice. We thereby revealed the correspondence between long-standing mysteries in both fields: the Warburg effect, a seemingly wasteful but ubiquitous strategy where cells favour aerobic glycolysis over more energetically efficient oxidative phosphorylation, and Giffen behaviour, the unexpected consumer behaviour where a good is demanded more as its price rises. We identified the minimal, universal requirements for the Warburg effect: a trade-off between oxidative phosphorylation and aerobic glycolysis and complementarity, i.e. impossibility of substitution for different metabolites. Thus, various hypotheses for the Warburg effect are integrated into an identical optimization problem with the same universal structure. Besides, the correspondence between the Warburg effect and Giffen behaviour implies that oxidative phosphorylation is counter-intuitively stimulated when its efficiency is decreased by metabolic perturbations such as drug administration or mitochondrial dysfunction; the concept of Giffen behaviour bridges the Warburg effect and the reverse Warburg effect. This highlights that the application of microeconomics to metabolism can offer new predictions and paradigms for both biology and economics.

Keywords:  Metabolic systems; Overflow metabolism; Reverse Warburg effect; Theory of consumer choice

DOI:  https://doi.org/10.1007/s11538-021-00952-x
Comp Biochem Physiol C Toxicol Pharmacol. 2021 Oct 30. pii: S1532-0456(21)00254-4. [Epub ahead of print] 109227

Anoxia-reoxygenation modulates cadmium-induced liver mitochondrial reactive oxygen species emission during oxidation of glycerol 3-phosphate.

Chidozie N Okoye, Nirmala Chinnappareddy, Don Stevens, Collins Kamunde.

  Aquatic organisms are frequently exposed to multiple stressors including low dissolved oxygen (O2) and metals such as cadmium (Cd). Reduced O2 concentration and Cd exposure alter cellular function in part by impairing energy metabolism and dysregulating reactive oxygen species (ROS) homeostasis. However, little is known about the role of mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH) in ROS homeostasis in fish and its response to environmental stress. In this study, mGPDH activity and the effects of anoxia-reoxygenation (A-RO) and Cd on ROS (as hydrogen peroxide, H2O2) emission in rainbow trout liver mitochondria during oxidation of glycerol 3-phosphate (G3P) were probed. Trout liver mitochondria exhibited low mGPDH activity that supported a low respiratory rate but substantial H2O2 emission rate. Cd evoked a low concentration stimulatory-high concentration inhibitory H2O2 emission pattern that was blunted by A-RO. At specific redox centers, Cd suppressed H2O2 emission from site IQ, but stimulated emission from sites IIIQo and GQ. In contrast, A-RO stimulated H2O2 emission from site IQ following 15 min exposure and augmented Cd-stimulated emission from site IIF after 30 min exposure but did not alter the rate of H2O2 emission from sites IIIQo and GQ. Additionally, Cd neither altered the activities of catalase, glutathione peroxidase, or thioredoxin reductase nor the concentrations of total glutathione, reduced glutathione, or oxidized glutathione. Overall, this study indicates that oxidation of G3P drives ROS production from mGPDH and complexes I, II and III, whereas Cd directly modulates redox sites but not antioxidant defense systems to alter mitochondrial H2O2 emission.

Keywords:  Anoxia-reoxygenation; Antioxidant defense systems; Cadmium; Fish liver mitochondria; Glycerol 3-phosphate; H(2)O(2) emission; mGPDH

DOI:  https://doi.org/10.1016/j.cbpc.2021.109227
Signal Transduct Target Ther. 2021 Nov 03. 6(1): 375

The existence of a nonclassical TCA cycle in the nucleus that wires the metabolic-epigenetic circuitry.

Xujun Liu, Wenzhe Si, Lin He, Jianguo Yang, Yani Peng, Jie Ren, Xiaoping Liu, Tong Jin, Huajing Yu, Zihan Zhang, Xiao Cheng, Wenting Zhang, Lu Xia, Yunchao Huang, Yue Wang, Shumeng Liu, Lin Shan, Yu Zhang, Xiaohan Yang, Haixia Li, Jing Liang, Luyang Sun, Yongfeng Shang.

The scope and variety of the metabolic intermediates from the mitochondrial tricarboxylic acid (TCA) cycle that are engaged in epigenetic regulation of the chromatin function in the nucleus raise an outstanding question about how timely and precise supply/consumption of these metabolites is achieved in the nucleus. We report here the identification of a nonclassical TCA cycle in the nucleus (nTCA cycle). We found that all the TCA cycle-associated enzymes including citrate synthase (CS), aconitase 2 (ACO2), isocitrate dehydrogenase 3 (IDH3), oxoglutarate dehydrogenase (OGDH), succinyl-CoA synthetase (SCS), fumarate hydratase (FH), and malate dehydrogenase 2 (MDH2), except for succinate dehydrogenase (SDH), a component of electron transport chain for generating ATP, exist in the nucleus. We showed that these nuclear enzymes catalyze an incomplete TCA cycle similar to that found in cyanobacteria. We propose that the nTCA cycle is implemented mainly to generate/consume metabolic intermediates, not for energy production. We demonstrated that the nTCA cycle is intrinsically linked to chromatin dynamics and transcription regulation. Together, our study uncovers the existence of a nonclassical TCA cycle in the nucleus that links the metabolic pathway to epigenetic regulation.

DOI: https://doi.org/10.1038/s41392-021-00774-2
Mitochondrion. 2021 Nov 02. pii: S1567-7249(21)00149-5. [Epub ahead of print]

Role of GM-CSF in regulating metabolism and mitochondrial functions critical to macrophage proliferation.

Matthew Wessendarp, Miki Watanabe-Chailland, Serena Liu, Traci Stankiewicz, Yan Ma, Rajesh K Kasam, Kenjiro Shima, Claudia Chalk, Brenna Carey, Lindsey-Romick Rosendale, Marie Dominique Filippi, Paritha Arumugam.

  Granulocyte-macrophage colony-stimulating factor (GM-CSF) exerts pleiotropic effects on macrophages and is required for self-renewal but the mechanisms responsible are unknown. Using mouse models with disrupted GM-CSF signaling, we show GM-CSF is critical for mitochondrial turnover, functions, and integrity. GM-CSF signaling is essential for fatty acid β-oxidation and markedly increased tricarboxylic acid cycle activity, oxidative phosphorylation, and ATP production. GM-CSF also regulated cytosolic pathways including glycolysis, pentose phosphate pathway, and amino acid synthesis. We conclude that GM-CSF regulates macrophages in part through a critical role in maintaining mitochondria, which are necessary for cellular metabolism as well as proliferation and self-renewal.

Keywords:  GM-CSF; apoptosis; fatty acid oxidation; macrophage metabolism; mitochondrial functions; self-renewal

DOI:  https://doi.org/10.1016/j.mito.2021.10.009
Toxicol Appl Pharmacol. 2021 Nov 02. pii: S0041-008X(21)00387-2. [Epub ahead of print] 115783

Remdesivir; molecular and functional measures of mitochondrial safety.

J A Bjork, K B Wallace.

  Remdesivir is one of a few antiviral drugs approved for treating severe cases of coronavirus 2 (SARS-CoV-2) infection in hospitalized patients. The prodrug is a nucleoside analog that interferes with viral replication by inhibiting viral RNA-dependent RNA polymerase. The drug has also been shown to be a weak inhibitor of human mitochondrial RNA polymerase, leaving open the possibility of mitochondrial off-targets and toxicity. The investigation was designed to explore whether remdesivir causes mitochondrial toxicity, using both genomic and functional parameters in the assessment. Human-derived HepG2 liver cells were exposed for up to 48 h in culture to increasing concentrations of remdesivir. At sub-cytotoxic concentrations (<1 μM), the drug failed to alter either the number of copies or the expression of the mitochondrial genome. mtDNA copy number was unaffected as was the relative rates of expression of mtDNA-encoded and nuclear encoded subunits of complexes I and IV of the mitochondrial respiratory chain. Consistent with this is the observation that remdesivir was without effect on mitochondrial respiration, including basal respiration, proton leak, maximum uncoupled respiration, spare respiratory capacity or coupling efficiency. We conclude that although remdesivir has weak inhibitory activity towards mitochondrial RNA polymerase, mitochondria are not primary off-targets for the mechanism of cytotoxicity of the drug.

Keywords:  COVID; Mitochondria; Off-Target; Remdesivir

DOI:  https://doi.org/10.1016/j.taap.2021.115783
Front Immunol. 2021 ;12 730672

Production of IL-6 and Phagocytosis Are the Most Resilient Immune Functions in Metabolically Compromised Human Monocytes.

Pierre-Louis Krauss, Moritz Pfeiffenberger, Alexandra Damerau, Thomas Buttgereit, Yuling Chen, Timo Gaber, Frank Buttgereit.

  At sites of inflammation, monocytes carry out specific immune functions while facing challenging metabolic restrictions. Here, we investigated the potential of human monocytes to adapt to conditions of gradually inhibited oxidative phosphorylation (OXPHOS) under glucose free conditions. We used myxothiazol, an inhibitor of mitochondrial respiration, to adjust two different levels of decreased mitochondrial ATP production. At these levels, and compared to uninhibited OXPHOS, we assessed phagocytosis, production of reactive oxygen species (ROS) through NADPH oxidase (NOX), expression of surface activation markers CD16, CD80, CD11b, HLA-DR, and production of the inflammatory cytokines IL-1β, IL-6 and TNF-α in human monocytes. We found phagocytosis and the production of IL-6 to be least sensitive to metabolic restrictions while surface expression of CD11b, HLA-DR, production of TNF-α, IL-1β and production of ROS through NOX were most compromised by inhibition of OXPHOS in the absence of glucose. Our data demonstrate a short-term hierarchy of immune functions in human monocytes, which represents novel knowledge potentially leading to the development of new therapeutics in monocyte-mediated inflammatory diseases.

Keywords:  ATP; IL-6; bioenergetics; energy; human monocytes; immunometabolism; lack of glucose availability; phagocytosis

DOI:  https://doi.org/10.3389/fimmu.2021.730672
Elife. 2021 Nov 02. pii: e65109. [Epub ahead of print]10

Mitochondrial respiration contributes to the interferon gamma response in antigen presenting cells.

Michael C Kiritsy, Katelyn McCann, Daniel Mott, Stephen M Holland, Samuel M Behar, Christopher M Sassetti, Andrew J Olive.

  The immunological synapse allows antigen presenting cells (APC) to convey a wide array of functionally distinct signals to T cells, which ultimately shape the immune response. The relative effect of stimulatory and inhibitory signals is influenced by the activation state of the APC, which is determined by an interplay between signal transduction and metabolic pathways. While pathways downstream of toll-like receptors rely on glycolytic metabolism for the proper expression of inflammatory mediators, little is known about the metabolic dependencies of other critical signals such as interferon gamma (IFNg). Using CRISPR-Cas9, we performed a series of genome-wide knockout screens in murine macrophages to identify the regulators of IFNg-inducible T cell stimulatory or inhibitory proteins MHCII, CD40, and PD-L1. Our multi-screen approach enabled us to identify novel pathways that control these functionally distinct markers. Further integration of these screening data implicated complex I of the mitochondrial respiratory chain in the expression of all three markers, and by extension the IFNg signaling pathway. We report that the IFNg response requires mitochondrial respiration, and APCs are unable to activate T cells upon genetic or chemical inhibition of complex I. These findings suggest a dichotomous metabolic dependency between IFNg and toll-like receptor signaling, implicating mitochondrial function as a fulcrum of innate immunity.

Keywords:  human; immunology; inflammation; mouse

DOI:  https://doi.org/10.7554/eLife.65109
Mol Biol Rep. 2021 Nov 05.

Hormetic effect of low doses of rapamycin triggers anti-aging cascades in WRL-68 cells by modulating an mTOR-mitochondria cross-talk.

R Mahalakshmi, J Priyanga, Dipita Bhakta-Guha, Gunjan Guha.

   BACKGROUND: Rapamycin is hormetic in nature-it demonstrates contrasting effects at high and low doses. It is toxic at moderate/high doses, while it can restrain aging and extend lifespan at low doses. However, it is not fully understood how rapamycin governs cellular aging. On the other hand, aging is putatively correlated to mitochondrial dysregulation. Although previous studies have suggested that hormetic (low) doses of rapamycin can cause partial/incomplete inhibition of mTOR, the actual modus operandi of how such partial mTOR inhibition might modulate the mTOR-mitochondria cross-talk remained to be deciphered in the context of cellular aging. The present study was designed to understand the hormetic effects of rapamycin on cellular factors that govern aging-associated changes in mitochondrial facets, such as functional and metabolic homeostases, sustenance of membrane potential, biogenesis, mitophagy, and oxidative injury to mitochondrial macromolecules.
METHODS AND RESULTS: WRL-68 cells treated (24 h) with variable doses of rapamycin were studied for estimating their viability, apoptosis, senescence, mitochondrial density and Δψm. Expression levels of key functional proteins were estimated by immunofluorescence/immunoblots. Oxidative damage to mtDNA/mtRNA/proteins was measured in mitochondrial lysates. We demonstrated that hormetic doses (0.1 and 1 nM) of rapamycin can alleviate aging-associated mitochondrial dyshomeostasis in WRL-68 cells, such as oxidative injury to mitochondrial nucleic acids and proteins, as well as disequilibrium of mitochondrial density, membrane potential, biogenesis, mitophagy and overall metabolism.
CONCLUSIONS: We established that low doses of rapamycin can hormetically amend the mTOR-mitochondria cross-talk, and can consequently promote anti-aging outcome in cells.

Keywords:  Anti-aging; Hormesis; Mitochondria; Oxidative stress; Rapamycin; mTOR

DOI:  https://doi.org/10.1007/s11033-021-06898-6
Hum Mol Genet. 2021 Oct 28. pii: ddab314. [Epub ahead of print]

Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis.

Kah Ying Ng, Uwe Richter, Christopher B Jackson, Sara Seneca, Brendan J Battersby.

Pathogenic variants that disrupt human mitochondrial protein synthesis are associated with a clinically heterogenous group of diseases. Despite an impairment in oxidative phosphorylation being a common phenotype, the underlying molecular pathogenesis is more complex than simply a bioenergetic deficiency. Currently, we have limited mechanistic understanding on the scope by which a primary defect in mitochondrial protein synthesis contributes to organelle dysfunction. Since the proteins encoded in the mitochondrial genome are hydrophobic and need co-translational insertion into a lipid bilayer, responsive quality control mechanisms are required to resolve aberrations that arise with the synthesis of truncated and misfolded proteins. Here, we show that defects in the OXA1L-mediated insertion of MT-ATP6 nascent chains into the mitochondrial inner membrane are rapidly resolved by the AFG3L2 protease complex. Using pathogenic MT-ATP6 variants, we then reveal discrete steps in this quality control mechanism and the differential functional consequences to mitochondrial gene expression. The inherent ability of a given cell type to recognize and resolve impairments in mitochondrial protein synthesis may in part contribute at the molecular level to the wide clinical spectrum of these disorders.

DOI: https://doi.org/10.1093/hmg/ddab314
Nat Rev Genet. 2021 Nov 02.

Implications of mitochondrial DNA mutations in human induced pluripotent stem cells.

Valerio Carelli, Michio Hirano, José Antonio Enríquez, Patrick F Chinnery.

DOI: https://doi.org/10.1038/s41576-021-00430-z
FASEB J. 2021 Dec;35(12): e22010

Mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force.

Zhengye Liu, Thomas Chaillou, Estela Santos Alves, Theresa Mader, Baptiste Jude, Duarte M S Ferreira, Heidi Hynynen, Arthur J Cheng, William O Jonsson, Gianluigi Pironti, Daniel C Andersson, Ellinor Kenne, Jorge L Ruas, Pasi Tavi, Johanna T Lanner.

  The hypoxia-inducible nuclear-encoded mitochondrial protein NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4-like 2 (NDUFA4L2) has been demonstrated to decrease oxidative phosphorylation and production of reactive oxygen species in neonatal cardiomyocytes, brain tissue and hypoxic domains of cancer cells. Prolonged local hypoxia can negatively affect skeletal muscle size and tissue oxidative capacity. Although skeletal muscle is a mitochondrial rich, oxygen sensitive tissue, the role of NDUFA4L2 in skeletal muscle has not previously been investigated. Here we ectopically expressed NDUFA4L2 in mouse skeletal muscles using adenovirus-mediated expression and in vivo electroporation. Moreover, femoral artery ligation (FAL) was used as a model of peripheral vascular disease to induce hind limb ischemia and muscle damage. Ectopic NDUFA4L2 expression resulted in reduced mitochondrial respiration and reactive oxygen species followed by lowered AMP, ADP, ATP, and NAD+ levels without affecting the overall protein content of the mitochondrial electron transport chain. Furthermore, ectopically expressed NDUFA4L2 caused a ~20% reduction in muscle mass that resulted in weaker muscles. The loss of muscle mass was associated with increased gene expression of atrogenes MurF1 and Mul1, and apoptotic genes caspase 3 and Bax. Finally, we showed that NDUFA4L2 was induced by FAL and that the Ndufa4l2 mRNA expression correlated with the reduced capacity of the muscle to generate force after the ischemic insult. These results show, for the first time, that mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force. Specifically, induced NDUFA4L2 reduces mitochondrial activity leading to lower levels of important intramuscular metabolites, including adenine nucleotides and NAD+ , which are hallmarks of mitochondrial dysfunction and hence shows that dysfunctional mitochondrial activity may drive muscle wasting.

Keywords:  NDUFA4L2; mitochondria; muscle mass; skeletal muscle

DOI:  https://doi.org/10.1096/fj.202100066R
Sci Rep. 2021 Nov 01. 11(1): 21354

Metabolic profiling of attached and detached metformin and 2-deoxy-D-glucose treated breast cancer cells reveals adaptive changes in metabolome of detached cells.

Jernej Repas, Elmar Zügner, Boris Gole, Maruša Bizjak, Uroš Potočnik, Christoph Magnes, Mojca Pavlin.

Anchorage-independent growth of cancer cells in vitro is correlated to metastasis formation in vivo. Metformin use is associated with decreased breast cancer incidence and currently evaluated in cancer clinical trials. The combined treatment with metformin and 2-deoxy-D-glucose (2DG) in vitro induces detachment of viable MDA-MB-231 breast cancer cells that retain their proliferation capacity. This might be important for cell detachment from primary tumors, but the metabolic changes involved are unknown. We performed LC/MS metabolic profiling on separated attached and detached MDA-MB-231 cells treated with metformin and/or 2DG. High 2DG and metformin plus 2DG altered the metabolic profile similarly to metformin, inferring that metabolic changes are necessary but not sufficient while the specific effects of 2DG are crucial for detachment. Detached cells had higher NADPH levels and lower fatty acids and glutamine levels compared to attached cells, supporting the role of AMPK activation and reductive carboxylation in supporting anchorage-independent survival. Surprisingly, the metabolic profile of detached cells was closer to untreated control cells than attached treated cells, suggesting detachment might help cells adapt to energy stress. Metformin treated cells had higher fatty and amino acid levels with lower purine nucleotide levels, which is relevant for understanding the anticancer mechanisms of metformin.

DOI: https://doi.org/10.1038/s41598-021-98642-0
Mitochondrion. 2021 Oct 30. pii: S1567-7249(21)00145-8. [Epub ahead of print]

The integrity and assay performance of tissue mitochondrial DNA is considerably affected by choice of isolation method.

Bruno Marçal Repolês, Choco Michael Gorospe, Phong Tran, Anna Karin Nilsson, Paulina H Wanrooij.

  The integrity of mitochondrial DNA (mtDNA) isolated from solid tissues is critical for analyses such as long-range PCR, but is typically assessed under conditions that fail to provide information on the individual mtDNA strands. Using denaturing gel electrophoresis, we show that commonly-used isolation procedures generate mtDNA containing several single-strand breaks per strand. Through systematic comparison of DNA isolation methods, we identify a procedure yielding the highest integrity of mtDNA that we demonstrate displays improved performance in downstream assays. Our results highlight the importance of isolation method choice, and serve as a resource to researchers requiring high-quality mtDNA from solid tissues.

Keywords:  DNA integrity; long-range PCR; mitochondrial DNA; mtDNA; nuclease activity

DOI:  https://doi.org/10.1016/j.mito.2021.10.005
Cancer Biol Ther. 2021 Oct 31. 1-8

Biguanide drugs enhance cytotoxic effects of cisplatin by depleting aspartate and NAD+ in sensitive cancer cells.

Ellen Tully, Santosh Bharti, Juhyung Woo, Zaver Bhujwalla, Edward Gabrielson.

  Biguanide drugs (metformin and phenformin) have drawn interest for potential cancer treatments, and laboratory studies show that some cancer cells are selectively sensitive to growth-inhibitory effects of biguanides. Examining metabolic pathways affected by biguanide treatments in cancer cells that are highly sensitive to biguanides, we found that biguanide treatment depletes cellular levels of both aspartate and NAD+. Experiments to replenish these metabolites or block steps of the aspartate-malate shuttle suggest that depletion of both metabolites, rather than either aspartate of NAD+ individually, is critical for growth-inhibitory effects of biguanide exposure. Even in sensitive cancer cells, though, biguanide treatment alone over a broad range of doses only inhibits cell replication without significantly affecting cell viability. Noting that clinical observations of biguanide efficacy have used combinations of agents that typically include cisplatin, we found that biguanide treatment at a cytostatic level substantially decreases survival of lung cancer and breast cancer cells when co-treated with cisplatin at doses that alone are also non-cytotoxic. This striking enhancement of cisplatin toxicity by biguanides depends on reductions of levels of NAD+ and aspartate, since addition of either of these metabolites prevented this potentiation of cisplatin cytotoxicity. Thus, biguanide drugs can have cytotoxic effects when used in combination with other cancer drugs, such as cisplatin, and depleting cellular levels of NAD+ and aspartate is critical for enhancing the cytotoxicity of cisplatin by biguanide drugs in sensitive cancer cells.

Keywords:  Biguanides; aspartate; cisplatin; metformin; nad; phenformin

DOI:  https://doi.org/10.1080/15384047.2021.1982599
Front Cell Dev Biol. 2021 ;9 747377

Macrophages as Emerging Key Players in Mitochondrial Transfers.

Yidan Pang, Changqing Zhang, Junjie Gao.

  Macrophages are a group of heterogeneous cells widely present throughout the body. Under the influence of their specific environments, via both contact and noncontact signals, macrophages integrate into host tissues and contribute to their development and the functions of their constituent cells. Mitochondria are essential organelles that perform intercellular transfers to regulate cell homeostasis. Our review focuses on newly discovered roles of mitochondrial transfers between macrophages and surrounding cells and summarizes emerging functions of macrophages in transmitophagy, metabolic regulation, and immune defense. We also discuss the negative influence of mitochondrial transfers on macrophages, as well as current therapies targeting mitochondria in macrophages. Regulation of macrophages through mitochondrial transfers between macrophages and their surrounding cells is a promising therapy for various diseases, including cardiovascular diseases, inflammatory diseases, obesity, and cancer.

Keywords:  adipocyte; cardiomyocyte; macrophage; mitochondrial transfer; mitophagy

DOI:  https://doi.org/10.3389/fcell.2021.747377
Chem Pharm Bull (Tokyo). 2021 ;69(11): 1110-1122

Discovery of DS68702229 as a Potent, Orally Available NAMPT (Nicotinamide Phosphoribosyltransferase) Activator.

Mayuko Akiu, Takashi Tsuji, Kouki Iida, Yoshitaka Sogawa, Koji Terayama, Mika Yokoyama, Jun Tanaka, Daigo Asano, Tomohiro Honda, Ken Sakurai, Anthony B Pinkerton, Tsuyoshi Nakamura.

  Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step of the nicotinamide adenine dinucleotide (NAD+) salvage pathway. Because NAD+ plays a pivotal role in energy metabolism and boosting NAD+ has positive effects on metabolic regulation, activation of NAMPT is an attractive therapeutic approach for the treatment of various diseases, including type 2 diabetes and obesity. Herein we report the discovery of 1-(2-phenyl-1,3-benzoxazol-6-yl)-3-(pyridin-4-ylmethyl)urea 12c (DS68702229), which was identified as a potent NAMPT activator. Compound 12c activated NAMPT, increased cellular NAD+ levels, and exhibited an excellent pharmacokinetic profile in mice after oral administration. Oral administration of compound 12c to high-fat diet-induced obese mice decreased body weight. These observations indicate that compound 12c is a promising anti-obesity drug candidate.

Keywords:  anti-obesity; benzoxazole; body weight reduction; nicotinamide adenine dinucleotide (NAD+); nicotinamide phosphoribosyltransferase activator

DOI:  https://doi.org/10.1248/cpb.c21-00700
Nat Commun. 2021 Nov 04. 12(1): 6409

Constitutive activation of the PI3K-Akt-mTORC1 pathway sustains the m.3243 A > G mtDNA mutation.

Chih-Yao Chung, Kritarth Singh, Vassilios N Kotiadis, Gabriel E Valdebenito, Jee Hwan Ahn, Emilie Topley, Joycelyn Tan, William D Andrews, Benoit Bilanges, Robert D S Pitceathly, Gyorgy Szabadkai, Mariia Yuneva, Michael R Duchen.

Mutations of the mitochondrial genome (mtDNA) cause a range of profoundly debilitating clinical conditions for which treatment options are very limited. Most mtDNA diseases show heteroplasmy - tissues express both wild-type and mutant mtDNA. While the level of heteroplasmy broadly correlates with disease severity, the relationships between specific mtDNA mutations, heteroplasmy, disease phenotype and severity are poorly understood. We have carried out extensive bioenergetic, metabolomic and RNAseq studies on heteroplasmic patient-derived cells carrying the most prevalent disease related mtDNA mutation, the m.3243 A > G. These studies reveal that the mutation promotes changes in metabolites which are associated with the upregulation of the PI3K-Akt-mTORC1 axis in patient-derived cells and tissues. Remarkably, pharmacological inhibition of PI3K, Akt, or mTORC1 reduced mtDNA mutant load and partially rescued cellular bioenergetic function. The PI3K-Akt-mTORC1 axis thus represents a potential therapeutic target that may benefit people suffering from the consequences of the m.3243 A > G mutation.

DOI: https://doi.org/10.1038/s41467-021-26746-2
Nat Commun. 2021 Nov 03. 12(1): 6323

Convergence of oncogenic cooperation at single-cell and single-gene levels drives leukemic transformation.

Yuxuan Liu, Zhimin Gu, Hui Cao, Pranita Kaphle, Junhua Lyu, Yuannyu Zhang, Wenhuo Hu, Stephen S Chung, Kathryn E Dickerson, Jian Xu.

Cancers develop from the accumulation of somatic mutations, yet it remains unclear how oncogenic lesions cooperate to drive cancer progression. Using a mouse model harboring NRasG12D and EZH2 mutations that recapitulates leukemic progression, we employ single-cell transcriptomic profiling to map cellular composition and gene expression alterations in healthy or diseased bone marrows during leukemogenesis. At cellular level, NRasG12D induces myeloid lineage-biased differentiation and EZH2-deficiency impairs myeloid cell maturation, whereas they cooperate to promote myeloid neoplasms with dysregulated transcriptional programs. At gene level, NRasG12D and EZH2-deficiency independently and synergistically deregulate gene expression. We integrate results from histopathology, leukemia repopulation, and leukemia-initiating cell assays to validate transcriptome-based cellular profiles. We use this resource to relate developmental hierarchies to leukemia phenotypes, evaluate oncogenic cooperation at single-cell and single-gene levels, and identify GEM as a regulator of leukemia-initiating cells. Our studies establish an integrative approach to deconvolute cancer evolution at single-cell resolution in vivo.

DOI: https://doi.org/10.1038/s41467-021-26582-4
Hum Mol Genet. 2021 Oct 27. pii: ddab312. [Epub ahead of print]

First mitochondrial genome wide association study with metabolomics.

Brahim Aboulmaouahib, Gabi Kastenmüller, Karsten Suhre, Sebastian Zöllner, Hansi Weissensteiner, Christian Gieger, Rui Wang-Sattler, Peter Lichtner, Konstantin Strauch, Antònia Flaquer.

INTRODUCTION: In the era of personalized medicine with more and more patient specific targeted therapies being used, we need reliable, dynamic, faster, and sensitive biomarkers both to track the causes of disease and to develop and evolve therapies during the course of treatment. Metabolomics recently has shown substantial evidence to support its emerging role in disease diagnosis and prognosis. Aside from biomarkers and development of therapies, it is also an important goal to understand the involvement of mitochondrial DNA mtDNA in metabolic regulation, aging, and disease development. Somatic mutations of the mitochondrial genome are also heavily implicated in age-related disease and aging. The general hypothesis is that an alteration in the concentration of metabolite profiles (possibly conveyed by lifestyle and environmental factors) influences the increase of mutation rate in the mtDNA, and thereby contributes to a range of pathophysiological alterations observed in complex diseases.
METHODS: We performed an inverted mitochondrial genome wide association analysis between mitochondrial nucleotide variants (mtSNVs) and concentration of metabolites. We used 151 metabolites and the whole sequenced mitochondrial genome from 2718 individuals to identify genetic variants associated with metabolite profiles. Because of the high coverage, next generation sequencing-based analysis of the mitochondrial genome allows for an accurate detection of mitochondrial heteroplasmy and for identification of variants associated with the metabolome.
RESULTS: The strongest association was found for mt715G > A located in the MT-12SrRNA with the metabolite ratio C2/C10:1 (p-value = 6.82*10-09, β = 0.909). The second most significant mtSNV was found for mt3714A > G located in the MT-ND1 with the metabolite ratio PC ae C42:5/PC ae C44:5 (p-value = 1.02*10-08, β = 3.631). A large number of significant metabolite ratios were observed involving PC aa C36:6 and the variant mt10689G > A, located in the MT-ND4L gene.
CONCLUSION: These results show an important interconnection between mitochondria and metabolite concentrations. Considering that some of the significant metabolites found in this study have been previously related to complex diseases such as neurological disorders and metabolic conditions, these associations found here might play a crucial role for further investigations of such complex diseases. Understanding the mechanisms that control human health and disease, in particular the role of genetic predispositions and their interaction with environmental factors is a prerequisite for the development of safe and efficient therapies for complex disorders.

DOI: https://doi.org/10.1093/hmg/ddab312
Dis Markers. 2021 ;2021 8554844

Pan-Cancer Analysis Reveals FH as a Potential Prognostic and Immunological Biomarker in Lung Adenocarcinoma.

Heng Zhang, Qiang Ju, Jing Ji, Yanjie Zhao.

Fumarate hydratase (FH) is an important enzymatic component in the tricarboxylic acid cycle. Studies have reported that FH plays an important role in hereditary leiomyomatosis and renal cell cancer (HLRCC). However, the role of FH in human different cancers remains unknown. This study is aimed at analyzing the prognostic value of FH and demonstrating the correlation between FH expression and tumor immunity. Results showed that FH was mutated or copy number varied in 27 types of cancer. FH mRNA was abnormally upregulated across various cancers. Survival analysis suggested high expression of FH was associated with poor prognosis in many cancer types, including lung adenocarcinoma (LUAD). Additionally, FH expression was associated with immune infiltration, including B cells, CD4+ T cells, CD8+ T cells, neutrophils, macrophages, and dendritic cells, especially in liver hepatocellular carcinoma (LIHC), LUAD, and lung squamous cell carcinoma (LUSC). Moreover, FH expression showed a strong correlation with immune checkpoint markers in LUAD and testicular germ cell tumors (TGCT). These results indicate that FH is an immunotherapeutic target and a potential prognostic biomarker in LUAD.

DOI: https://doi.org/10.1155/2021/8554844