bims-camemi Biomed news
on Mitochondrial metabolism in cancer
Issue of 2018‒11‒25
fifty-five papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit


  1. Cell Metab. 2018 Nov 09. pii: S1550-4131(18)30646-6. [Epub ahead of print]
    Bajzikova M, Kovarova J, Coelho AR, Boukalova S, Oh S, Rohlenova K, Svec D, Hubackova S, Endaya B, Judasova K, Bezawork-Geleta A, Kluckova K, Chatre L, Zobalova R, Novakova A, Vanova K, Ezrova Z, Maghzal GJ, Magalhaes Novais S, Olsinova M, Krobova L, An YJ, Davidova E, Nahacka Z, Sobol M, Cunha-Oliveira T, Sandoval-Acuña C, Strnad H, Zhang T, Huynh T, Serafim TL, Hozak P, Sardao VA, Koopman WJH, Ricchetti M, Oliveira PJ, Kolar F, Kubista M, Truksa J, Dvorakova-Hortova K, Pacak K, Gurlich R, Stocker R, Zhou Y, Berridge MV, Park S, Dong L, Rohlena J, Neuzil J.
      Cancer cells without mitochondrial DNA (mtDNA) do not form tumors unless they reconstitute oxidative phosphorylation (OXPHOS) by mitochondria acquired from host stroma. To understand why functional respiration is crucial for tumorigenesis, we used time-resolved analysis of tumor formation by mtDNA-depleted cells and genetic manipulations of OXPHOS. We show that pyrimidine biosynthesis dependent on respiration-linked dihydroorotate dehydrogenase (DHODH) is required to overcome cell-cycle arrest, while mitochondrial ATP generation is dispensable for tumorigenesis. Latent DHODH in mtDNA-deficient cells is fully activated with restoration of complex III/IV activity and coenzyme Q redox-cycling after mitochondrial transfer, or by introduction of an alternative oxidase. Further, deletion of DHODH interferes with tumor formation in cells with fully functional OXPHOS, while disruption of mitochondrial ATP synthase has little effect. Our results show that DHODH-driven pyrimidine biosynthesis is an essential pathway linking respiration to tumorigenesis, pointing to inhibitors of DHODH as potential anti-cancer agents.
    Keywords:  OXPHOS; cancer; coenzyme Q; dihydroorotate dehydrogenase; mitochondria; pyrimidine biosynthesis; respiration
    DOI:  https://doi.org/10.1016/j.cmet.2018.10.014
  2. Cancer Metastasis Rev. 2018 Nov 17.
    Herst PM, Grasso C, Berridge MV.
      Tumor initiation, progression, and metastasis are tissue context-dependent processes. Cellular and non-cellular factors provide the selective microenvironment that determines the fate of the evolving tumor through mechanisms that include metabolic reprogramming. Genetic and epigenetic changes contribute to this reprogramming process, which is orchestrated through ongoing communication between the mitochondrial and nuclear genomes. Metabolic flexibility, in particular the ability to rapidly adjust the balance between glycolytic and mitochondrial energy production, is a hallmark of aggressive, invasive, and metastatic cancers. Tumor cells sustain damage to both nuclear and mitochondrial DNA during tumorigenesis and as a consequence of anticancer treatments. Nuclear and mitochondrial DNA mutations and polymorphisms are increasingly recognized as factors that influence metabolic reprogramming, tumorigenesis, and tumor progression. Severe mitochondrial DNA damage compromises mitochondrial respiration. When mitochondrial respiration drops below a cell-specific threshold, metabolic reprogramming and plasticity fail to compensate and tumor formation is compromised. In these scenarios, tumorigenesis can be restored by acquisition of respiring mitochondria from surrounding stromal cells. Thus, intercellular mitochondrial transfer has the potential to confer treatment resistance and to promote tumor progression and metastasis. Understanding the constraints of metabolic, and in particular bioenergetic reprogramming, and the role of intercellular mitochondrial transfer in tumorigenesis provides new insights into addressing tumor progression and treatment resistance in highly aggressive cancers.
    Keywords:  Glycolysis; Intercellular mitochondrial transfer; Metabolic reprogramming; Mitochondrial DNA; Respiration
    DOI:  https://doi.org/10.1007/s10555-018-9769-2
  3. Nature. 2018 Nov 21.
    Gonzalez PS, O'Prey J, Cardaci S, Barthet VJA, Sakamaki JI, Beaumatin F, Roseweir A, Gay DM, Mackay G, Malviya G, Kania E, Ritchie S, Baudot AD, Zunino B, Mrowinska A, Nixon C, Ennis D, Hoyle A, Millan D, McNeish IA, Sansom OJ, Edwards J, Ryan KM.
      It is now well established that tumours undergo changes in cellular metabolism1. As this can reveal tumour cell vulnerabilities and because many tumours exhibit enhanced glucose uptake2, we have been interested in how tumour cells respond to different forms of sugar. Here we report that the monosaccharide mannose causes growth retardation in several tumour types in vitro, and enhances cell death in response to major forms of chemotherapy. We then show that these effects also occur in vivo in mice following the oral administration of mannose, without significantly affecting the weight and health of the animals. Mechanistically, mannose is taken up by the same transporter(s) as glucose3 but accumulates as mannose-6-phosphate in cells, and this impairs the further metabolism of glucose in glycolysis, the tricarboxylic acid cycle, the pentose phosphate pathway and glycan synthesis. As a result, the administration of mannose in combination with conventional chemotherapy affects levels of anti-apoptotic proteins of the Bcl-2 family, leading to sensitization to cell death. Finally we show that susceptibility to mannose is dependent on the levels of phosphomannose isomerase (PMI). Cells with low levels of PMI are sensitive to mannose, whereas cells with high levels are resistant, but can be made sensitive by RNA-interference-mediated depletion of the enzyme. In addition, we use tissue microarrays to show that PMI levels also vary greatly between different patients and different tumour types, indicating that PMI levels could be used as a biomarker to direct the successful administration of mannose. We consider that the administration of mannose could be a simple, safe and selective therapy in the treatment of cancer, and could be applicable to multiple tumour types.
    DOI:  https://doi.org/10.1038/s41586-018-0729-3
  4. Nat Commun. 2018 Nov 23. 9(1): 4945
    Santana-Codina N, Roeth AA, Zhang Y, Yang A, Mashadova O, Asara JM, Wang X, Bronson RT, Lyssiotis CA, Ying H, Kimmelman AC.
      Oncogenic KRAS is the key driver of pancreatic ductal adenocarcinoma (PDAC). We previously described a role for KRAS in PDAC tumor maintenance through rewiring of cellular metabolism to support proliferation. Understanding the details of this metabolic reprogramming in human PDAC may provide novel therapeutic opportunities. Here we show that the dependence on oncogenic KRAS correlates with specific metabolic profiles that involve maintenance of nucleotide pools as key mediators of KRAS-dependence. KRAS promotes these effects by activating a MAPK-dependent signaling pathway leading to MYC upregulation and transcription of the non-oxidative pentose phosphate pathway (PPP) gene RPIA, which results in nucleotide biosynthesis. The use of MEK inhibitors recapitulates the KRAS-dependence pattern and the expected metabolic changes. Antagonizing the PPP or pyrimidine biosynthesis inhibits the growth of KRAS-resistant cells. Together, these data reveal differential metabolic rewiring between KRAS-resistant and sensitive cells, and demonstrate that targeting nucleotide metabolism can overcome resistance to KRAS/MEK inhibition.
    DOI:  https://doi.org/10.1038/s41467-018-07472-8
  5. Aging (Albany NY). 2018 Nov 18.
    Crupi AN, Nunnelee JS, Taylor DJ, Thomas A, Vit JP, Riera CE, Gottlieb RA, Goodridge HS.
      Preservation of mitochondrial function, which is dependent on mitochondrial homeostasis (biogenesis, dynamics, disposal/recycling), is critical for maintenance of skeletal muscle function. Skeletal muscle performance declines upon aging (sarcopenia) and is accompanied by decreased mitochondrial function in fast-glycolytic muscles. Oxidative metabolism promotes mitochondrial homeostasis, so we investigated whether mitochondrial function is preserved in oxidative muscles. We compared tibialis anterior (predominantly glycolytic) and soleus (oxidative) muscles from young (3 mo) and old (28-29 mo) C57BL/6J mice. Throughout life, the soleus remained more oxidative than the tibialis anterior and expressed higher levels of markers of mitochondrial biogenesis, fission/fusion and autophagy. The respiratory capacity of mitochondria isolated from the tibialis anterior, but not the soleus, declined upon aging. The soleus and tibialis anterior exhibited similar aging-associated changes in mitochondrial biogenesis, fission/fusion, disposal and autophagy marker expression, but opposite changes in fiber composition: the most oxidative fibers declined in the tibialis anterior, while the more glycolytic fibers declined in the soleus. In conclusion, oxidative muscles are protected from mitochondrial aging, probably due to better mitochondrial homeostasis ab initio and aging-associated changes in fiber composition. Exercise training aimed at enriching oxidative fibers may be valuable in preventing mitochondria-related aging and its contribution to sarcopenia.
    Keywords:  aging; glycolytic; mitochondria; oxidative; sarcopenia; skeletal muscle
    DOI:  https://doi.org/10.18632/aging.101643
  6. Pharmacol Res. 2018 Nov 16. pii: S1043-6618(18)31604-9. [Epub ahead of print]
    Skoda J, Borankova K, Jansson PJ, Huang ML, Veselska R, Richardson DR.
      Mitochondria play vital roles in various cellular processes, ranging from cellular metabolism to signal transduction and cell death regulation. As these properties are critical for cancer growth, the mitochondrion has recently become an attractive target for anti-cancer therapies. In addition, it has come to light that mitochondria are crucially involved in the regulation of stem cell identity, differentiation and fate. A similar role for mitochondria has been also demonstrated in malignant stem-like cells termed cancer stem cells (CSCs), which are implicated in progression and resistance of many tumors. In this review, we summarize different mitochondrial functions reported to promote acquisition and maintenance of CSC phenotype and discuss the rationale for their therapeutic targeting. Particular emphasis is given to therapeutics that act directly through modulation of these mitochondrial functions and have recently emerged as promising anti-CSC drugs in pre-clinical studies. This review highlights the intriguing aspects of mitochondrial biology that may have a crucial role in cancer initiation, progression, and resistance and which might facilitate pharmacological targeting. Indeed, understanding of mitochondrial function in the regulation of CSCs will promote the development of novel CSC-targeted therapeutic strategies, which could significantly improve the long-term survival of cancer patients.
    Keywords:  ( CID: 5388906); ( CID: 9; ( CID: 9840324); 24978538); 843897); ABT-263 ( CID; ABT-737 ( CID: 11228183); Anti-cancer therapeutics; Bedaquiline; Breast cancer; Cancer stem cells; Celecoxib ( CID: 2662); Doxycycline ( CID: 54671203); Etomoxir; Glioblastoma; Mdivi-1 ( CID: 3825829); Metformin ( CID: 4091); Mitochondria; Mitophagy; Teglicar; XCT790 ( CID: 6918788)
    DOI:  https://doi.org/10.1016/j.phrs.2018.11.020
  7. Animal Cells Syst (Seoul). 2018 ;22(5): 289-298
    Jung Kim M.
      Betaine is a key metabolite of the methionine cycle and known for attenuating alcoholic steatosis in the liver. Recent studies have focused on the protection effect of betaine in mitochondrial regulation through the enhanced oxidative phosphorylation system. However, the mechanisms of its beneficial effects have not been clearly identified yet. Mitochondrial dynamics is important for the maintenance of functional mitochondria and cell homeostasis. A defective mitochondrial dynamics and oxidative phosphorylation system have been closely linked to several pathologies, raising the possibility that novel drugs targeting mitochondrial dynamics may present a therapeutic potential to restore the cellular homeostasis. In this study, we investigated betaine's effect on mitochondrial morphology and physiology and demonstrated that betaine enhances mitochondrial function by increasing mitochondrial fusion and improves cell survival. Furthermore, it rescued the unbalance of the mitochondrial dynamics from mitochondrial oxidative phosphorylation dysfunction induced by oligomycin and rotenone. The elongation properties by betaine were accompanied by lowering DRP1 and increasing MFN2 expression. These data suggest that betaine could play an important role in remodeling mitochondrial dynamics to enhance mitochondrial function and cell viability.
    Keywords:  Betaine; fission; fusion; mitochondrial dynamics
    DOI:  https://doi.org/10.1080/19768354.2018.1512523
  8. Cell Metab. 2018 Nov 12. pii: S1550-4131(18)30647-8. [Epub ahead of print]
    Puchalska P, Martin SE, Huang X, Lengfeld JE, Daniel B, Graham MJ, Han X, Nagy L, Patti GJ, Crawford PA.
      Metabolic plasticity has been linked to polarized macrophage function, but mechanisms connecting specific fuels to tissue macrophage function remain unresolved. Here we apply a stable isotope tracing, mass spectrometry-based untargeted metabolomics approach to reveal the metabolome penetrated by hepatocyte-derived glucose and ketone bodies. In both classically and alternatively polarized macrophages, [13C]acetoacetate (AcAc) labeled ∼200 chemical features, but its reduced form D-[13C]β-hydroxybutyrate (D-βOHB) labeled almost none. [13C]glucose labeled ∼500 features, and while unlabeled AcAc competed with only ∼15% of them, the vast majority required the mitochondrial enzyme succinyl-coenzyme A-oxoacid transferase (SCOT). AcAc carbon labeled metabolites within the cytoplasmic glycosaminoglycan pathway, which regulates tissue fibrogenesis. Accordingly, livers of mice lacking SCOT in macrophages were predisposed to accelerated fibrogenesis. Exogenous AcAc, but not D-βOHB, ameliorated diet-induced hepatic fibrosis. These data support a hepatocyte-macrophage ketone shuttle that segregates AcAc from D-βOHB, coordinating the fibrogenic response to hepatic injury via mitochondrial metabolism in tissue macrophages.
    Keywords:  acetoacetate; beta-hydroxybutyrate; fibrosis; immunometabolism; ketone bodies; macrophages; nonalcoholic fatty liver disease; stable isotope tracing untargeted metabolomics
    DOI:  https://doi.org/10.1016/j.cmet.2018.10.015
  9. Front Aging Neurosci. 2018 ;10 336
    Zhu T, Chen JL, Wang Q, Shao W, Qi B.
      Mitochondrial dysfunction is a common and prominent feature of prion diseases and other neurodegenerative disorders. Mitochondria are dynamic organelles that constantly fuse with one another and subsequently break apart. Defective or superfluous mitochondria are usually eliminated by a form of autophagy, referred to as mitophagy, to maintain mitochondrial homeostasis. Mitochondrial dynamics are tightly regulated by processes including fusion and fission. Dysfunction of mitochondrial dynamics can lead to the accumulation of abnormal mitochondria and contribute to cellular damage. Neurons are among the cell types that consume the most energy, have a highly complex morphology, and are particularly dependent on mitochondrial functions and dynamics. In this review article, we summarize the molecular mechanisms underlying the mitochondrial dynamics and the regulation of mitophagy and discuss the dysfunction of these processes in the progression of prion diseases and other neurodegenerative disorders. We have also provided an overview of mitochondrial dynamics as a therapeutic target for neurodegenerative diseases.
    Keywords:  mitochondrial dynamics; mitochondrial dysfunction; mitophagy; neurodegenerative diseases; prion diseases; therapeutic target
    DOI:  https://doi.org/10.3389/fnagi.2018.00336
  10. Biochim Biophys Acta Gen Subj. 2018 Nov 15. pii: S0304-4165(18)30358-1. [Epub ahead of print]
    Nadeau L, Patten DA, Caron A, Garneau L, Pinault-Masson E, Foretz M, Haddad P, Anderson BG, Quinn LS, Jardine K, McBurney MW, Pistilli EE, Harper ME, Aguer C.
      BACKGROUND: IL-15 is believed to play a role in the beneficial impact of exercise on muscle energy metabolism. However, previous studies have generally used supraphysiological levels of IL-15 that do not represent contraction-induced IL-15 secretion.METHODS: L6 myotubes were treated acutely (3 h) and chronically (48 h) with concentrations of IL-15 mimicking circulating (1-10 pg/ml) and muscle interstitial (100 pg/ml -20 ng/ml) IL-15 levels with the aim to better understand its autocrine/paracrine role on muscle glucose uptake and mitochondrial function.
    RESULTS: Acute exposure to IL-15 levels representing muscle interstitial IL-15 increased basal glucose uptake without affecting insulin sensitivity. This was accompanied by increased mitochondrial oxidative functions in association with increased AMPK pathway and formation of complex III-containing supercomplexes. Conversely, chronic IL-15 exposure resulted in a biphasic effect on mitochondrial oxidative functions and ETC supercomplex formation was increased with low IL-15 levels but decreased with higher IL-15 concentrations. The AMPK pathway was activated only by high levels of chronic IL-15 treatment. Similar results were obtained in skeletal muscle from muscle-specific IL-15 overexpressing mice that show very high circulating IL-15 levels.
    CONCLUSIONS: Acute IL-15 treatment that mimics local IL-15 concentrations enhances muscle glucose uptake and mitochondrial oxidative functions. That mitochondria respond differently to different levels of IL-15 during chronic treatments indicates that IL-15 might activate two different pathways in muscle depending on IL-15 concentrations.
    GENERAL SIGNIFICANCE: Our results suggest that IL-15 may act in an autocrine/paracrine fashion and be, at least in part, involved in the positive effect of exercise on muscle energy metabolism.
    Keywords:  Insulin sensitivity; Interleukin-15; Mitochondrial supercomplexes; Myokine; Myotubes; Oxidative phosphorylation
    DOI:  https://doi.org/10.1016/j.bbagen.2018.10.021
  11. Front Immunol. 2018 ;9 2489
    Basit F, Mathan T, Sancho D, de Vries IJM.
      Toll-like receptor (TLR) agonists induce metabolic reprogramming, which is required for immune activation. We have investigated mechanisms that regulate metabolic adaptation upon TLR-stimulation in human blood DC subsets, CD1c+ myeloid DCs (mDCs) and plasmacytoid DCs (pDCs). We show that TLR-stimulation changes expression of genes regulating oxidative phosphorylation (OXPHOS) and glutamine metabolism in pDC. TLR-stimulation increases mitochondrial content and intracellular glutamine in an autophagy-dependent manner in pDC. TLR-induced glutaminolysis fuels OXPHOS in pDCs. Notably, inhibition of glutaminolysis and OXPHOS prevents pDC activation. Conversely, TLR-stimulation reduces mitochondrial content, OXPHOS activity and induces glycolysis in CD1c+ mDC. Inhibition of mitochondrial fragmentation or promotion of mitochondrial fusion impairs TLR-stimulation induced glycolysis and activation of CD1c+ mDCs. TLR-stimulation triggers BNIP3-dependent mitophagy, which regulates transcriptional activity of AMPKα1. BNIP3-dependent mitophagy is required for induction of glycolysis and activation of CD1c+ mDCs. Our findings reveal that TLR stimulation differentially regulates mitochondrial dynamics in distinct human DC subsets, which contributes to their activation.
    Keywords:  CD1c+ mDC; OXPHOS; glutaminolysis; glycolysis; mitochondrial dynamics; mitophagy; pDC
    DOI:  https://doi.org/10.3389/fimmu.2018.02489
  12. Front Neurosci. 2018 ;12 799
    Marcus JM, Andrabi SA.
      Sirtuin 3 (SIRT3) is an NAD+ dependent deacetylase that resides primarily in mitochondria and functions to maintain mitochondrial homeostasis under stress. SIRT3 expression has been observed to change under a number of different stresses in multiple tissues and model systems. Inconsistencies in the literature with regards to how and when SIRT3 protein levels change indicates that the mechanism of SIRT3 regulation is multi-faceted. Alterations in SIRT3 have been observed in experimental models of cellular stress, however, the effect these changes have on mitochondrial health remain unknown. Neurons are highly dependent on proper mitochondrial function for their survival. SIRT3 dynamics and function have been studied using models of genotoxic, metabolic, and oxidative stresses, although it remains unclear how SIRT3 is being regulated under these conditions. A closer look into SIRT3 regulation under stress conditions in various model systems will help incorporate the many SIRT3 regulatory mechanisms at play in disease states. In this review, we describe the observations that have been made about SIRT3 protein modulation under basic stress conditions. We then point out consistencies and contradictions in these observations and what they mean. Lastly, we present the observations made in the complicated neuronal stress of stroke. We hope that this review will help consolidate the ambiguous SIRT3 literature and provide a framework for investigation of SIRT3 regulation during stress response.
    Keywords:  NAD+; PARP; SIRT3; bioenergetics; mitochondria; stroke
    DOI:  https://doi.org/10.3389/fnins.2018.00799
  13. PLoS Genet. 2018 Nov;14(11): e1007743
    Sokol AM, Uszczynska-Ratajczak B, Collins MM, Bazala M, Topf U, Lundegaard PR, Sugunan S, Guenther S, Kuenne C, Graumann J, Chan SSL, Stainier DYR, Chacinska A.
      Development and function of tissues and organs are powered by the activity of mitochondria. In humans, inherited genetic mutations that lead to progressive mitochondrial pathology often manifest during infancy and can lead to death, reflecting the indispensable nature of mitochondrial biogenesis and function. Here, we describe a zebrafish mutant for the gene mia40a (chchd4a), the life-essential homologue of the evolutionarily conserved Mia40 oxidoreductase which drives the biogenesis of cysteine-rich mitochondrial proteins. We report that mia40a mutant animals undergo progressive cellular respiration defects and develop enlarged mitochondria in skeletal muscles before their ultimate death at the larval stage. We generated a deep transcriptomic and proteomic resource that allowed us to identify abnormalities in the development and physiology of endodermal organs, in particular the liver and pancreas. We identify the acinar cells of the exocrine pancreas to be severely affected by mutations in the MIA pathway. Our data contribute to a better understanding of the molecular, cellular and organismal effects of mitochondrial deficiency, important for the accurate diagnosis and future treatment strategies of mitochondrial diseases.
    DOI:  https://doi.org/10.1371/journal.pgen.1007743
  14. Free Radic Res. 2018 Nov 20. 1-221
    Wu J, Zeng Z, Zhang W, Deng Z, Wan Y, Zhang Y, An S, Huang Q, Chen Z.
      As a nicotinamide adenine dinucleotide (NAD)+-dependent protein deacetylase, SIRT3 is highly expressed in tissues with high metabolic turnover and mitochondrial content. It has been demonstrated that SIRT3 plays a critical role in maintaining normal mitochondrial biological function through reversible protein lysine deacetylation. SIRT3 has a variety of substrates that are involved in mitochondrial biological processes such as energy metabolism, reactive oxygen species (ROS) production and clearance, electron transport chain (ETC) flux, mitochondrial membrane potential maintenance and mitochondrial dynamics. In the suppression of SIRT3, functional deficiencies of mitochondria contribute to the development of various cardiovascular disorders. Activation of SIRT3 may represent a promising therapeutic strategy for the improvement of mitochondrial function and the treatment of relevant cardiovascular disorders. In current review, we discuss the emerging roles of SIRT3 in mitochondrial derangements and subsequent cardiovascular malfunctions, including cardiac hypertrophy and heart failure, ischemia-reperfusion (IR) injury, and endothelial dysfunction in hypertension and atherosclerosis.
    Keywords:  Cardiovascular diseases; SIRT3; deacetylation; mitochondrial dysfunction
    DOI:  https://doi.org/10.1080/10715762.2018.1549732
  15. Eur J Pharmacol. 2018 Nov 14. pii: S0014-2999(18)30667-8. [Epub ahead of print]
    Zuo W, Liu Z, Yan F, Mei D, Hu X, Zhang B.
      Exposure to hyperglycemia after cerebral ischemia exacerbates cerebral damage; however, little is known regarding the mechanism. In this study, we focused on the relationship between post-ischemic hyperglycemia and mitochondrial homeostasis at the early stage of ischemia (within the 6h clinical therapeutic window for thrombolysis). Permanent cerebral ischemia was induced by middle cerebral artery occlusion (pMCAO) for 1, 3, and 6h. We first elucidated the role of post-ischemic hyperglycemia on mitochondria-mediated injury by testing reactive oxygen species generation, cyt-c release, and caspase-3 activation. Next, we analyzed mitochondrial homeostasis by testing the protein levels related to fission, fusion, biogenesis and elimination. The results showed that hyperglycemia further augmented the mitochondria-mediated injury induced by pMCAO. No significant differences of Fis1, Opa1 and Mfn2 were observed at each time point. There is no significant influence on these three proteins after hyperglycemia in rats of the experimental group compared to their counterparts in the control group. The translocation of the fission protein Drp1 to the mitochondrial outer-membrane increased at 1h after pMCAO and later steadily decreased over time in normal animals. However, hyperglycemia inhibited both the levels of Drp1 in the cytoplasm and mitochondria. Moreover, hyperglycemia inhibited mitophagy induced by pMCAO at 1h, although the overall autophagy was increased. In conclusion, pMCAO transiently induced the mitochondrial fission and their elimination by mitophagy. However, hyperglycemia abolished this adaptation reaction of the mitochondria and thus resulted in the accumulation of damaged mitochondria and subsequent damage. Our findings help to refine our understanding of the role of post-ischemic hyperglycemia in brain ischemic injury.
    Keywords:  Hyperglycemia; Mitochondrial autophagy; Mitochondrial homeostasis; Permanent cerebral ischemia
    DOI:  https://doi.org/10.1016/j.ejphar.2018.11.011
  16. Mol Genet Metab. 2018 Nov 16. pii: S1096-7192(18)30607-3. [Epub ahead of print]
    Chinopoulos C, Batzios S, van den Heuvel LP, Rodenburg R, Smeets R, Waterham HR, Turkenburg M, Ruiter JP, Wanders RJA, Doczi J, Horvath G, Dobolyi A, Vargiami E, Wevers RA, Zafeiriou D.
      Succinate-CoA ligase (SUCL) is a heterodimer consisting of an alpha subunit encoded by SUCLG1, and a beta subunit encoded by either SUCLA2 or SUCLG2 catalyzing an ATP- or GTP-forming reaction, respectively, in the mitochondrial matrix. The deficiency of this enzyme represents an encephalomyopathic form of mtDNA depletion syndromes. We describe the fatal clinical course of a female patient with a pathogenic mutation in SUCLG1 (c.626C > A, p.Ala209Glu) heterozygous at the genomic DNA level, but homozygous at the transcriptional level. The patient exhibited early-onset neurometabolic abnormality culminating in severe brain atrophy and dystonia leading to death by the age of 3.5 years. Urine and plasma metabolite profiling was consistent with SUCL deficiency which was confirmed by enzyme analysis and lack of mitochondrial substrate-level phosphorylation (mSLP) in skin fibroblasts. Oxygen consumption- but not extracellular acidification rates were altered only when using glutamine as a substrate, and this was associated with mild mtDNA depletion and no changes in ETC activities. Immunoblot analysis revealed no detectable levels of SUCLG1, while SUCLA2 and SUCLG2 protein expressions were largely reduced. Confocal imaging of triple immunocytochemistry of skin fibroblasts showed that SUCLG2 co-localized only partially with the mitochondrial network which otherwise exhibited an increase in fragmentation compared to control cells. Our results outline the catastrophic consequences of the mutated SUCLG1 leading to strongly reduced SUCL activity, mSLP impairment, mislocalization of SUCLG2, morphological alterations in mitochondria and clinically to a severe neurometabolic disease, but in the absence of changes in mtDNA levels or respiratory complex activities.
    DOI:  https://doi.org/10.1016/j.ymgme.2018.11.009
  17. J Physiol. 2018 Nov 21.
    Cortassa S, Caceres V, Tocchetti CG, Bernier M, de Cabo R, Paolocci N, Sollott SJ, Aon MA.
      KEY POINTS: Hearts from type 2 diabetic animals display perturbations in excitation-contraction coupling, impairing myocyte contractility and delaying relaxation, along with altered substrate consumption patterns. Under high glucose and β-adrenergic stimulation conditions, palmitate can, at least in part, offset left ventricle (LV) dysfunction in hearts from diabetic mice improving contractility and relaxation while restoring coronary perfusion pressure. Fluxome calculations of central catabolism in diabetic hearts show that, in presence of palmitate, there is a metabolic remodeling involving tricarboxylic acid cycle, polyol and pentose phosphate pathways, leading to improved redox balance in cytoplasmic and mitochondrial compartments. Under high glucose and increased energy demand, the metabolic/fluxomic re-direction leading to restored redox balance imparted by palmitate helps explain maintained LV function and may contribute to design novel therapeutic approaches to prevent cardiac dysfunction in diabetic patients.ABSTRACT: Type-2 diabetes (T2DM) leads to reduced myocardial performance, and eventually heart failure. Excessive accumulation of lipids and glucose are central to T2DM cardiomyopathy. Previous data showed that palmitate (Palm) or glutathione preserved heart mitochondrial energy/redox balance under excess glucose rescuing β-adrenergic-stimulated cardiac excitation-contraction coupling. However, the mechanisms underlying the accompanying improved contractile performance have been largely ignored. Herein we explore in intact heart under substrate excess the metabolic remodeling associated with cardiac function in diabetic db/db mice subjected to stress given by β-adrenergic stimulation with isoproterenol and high-glucose compared to their nondiabetic controls (+/+, WT) under euglycemic conditions. When perfused with Palm, T2DM hearts exhibit improved contractility/relaxation compared to WT, accompanied by extensive metabolic remodeling as demonstrated by metabolomics-fluxomics combined with bioinformatics and computational modeling. The T2DM heart metabolome showed significant differences in the abundance of metabolites in pathways related to glucose, lipids, and redox metabolism. Using a validated computational model of heart's central catabolism, comprising glucose and fatty acid (FA) oxidation in cytoplasmic and mitochondrial compartments, we estimated that fluxes through glucose degradation pathways are ∼2-fold lower in heart from T2DM vs. WT under all conditions studied. Palm addition elicits improvement of the redox status via enhanced β-oxidation and decreased glucose uptake, leading to flux-redirection away from redox-consuming pathways (e.g., polyol) while maintaining the flux through redox-generating pathways together with glucose-FA "shared fueling" of oxidative phosphorylation. Thus, available FAs such as Palm may help improve function via enhanced redox balance in T2DM hearts during peaks of hyperglycemia and increased workload. Sonia Cortassa has a PhD in Chemical Sciences from the Universidad Nacional de Córdoba, Argentina, country where she held research and teaching positions at Universidad Nacional de Tucumán and Consejo Nacional Investigaciones Científicas y Técnicas (CONICET). In the United States of America, she continued her research at the Johns Hopkins University and, at present, at the Laboratory of Cardiovascular Sciences/National Institute on Aging/NIH. Her field of research is Physiology, Bioenergetics, with expertise in Computational modeling of metabolic networks. She believes that quantitative Systems Biology approaches represent a real opportunity to contribute to the understanding of human body function in health and disease. This article is protected by copyright. All rights reserved.
    DOI:  https://doi.org/10.1113/JP276824
  18. Semin Cancer Biol. 2018 Nov 16. pii: S1044-579X(18)30107-X. [Epub ahead of print]
    Zhu S, Dong Z, Ke X, Hou J, Zhao E, Zhang K, Wang F, Yang L, Xiang Z, Cui H.
      Altering energy metabolism to meet the uncontrolled proliferation and metastasis has emerged as one of the most significant hallmarks in tumors. However, the detailed molecular mechanisms and regulatory actions underlying has not been fully elucidated. As a family of NAD+ dependent protein modifying enzyme, sirtuins (SIRT1-SIRT7) have multiple catalytic functions such as deacetylase, desuccinylase, demalonylase, demyristoylase depalmitoylase, and/or mono-ADP-ribosyltransferase, and play important roles in regulating cell metabolism, especially in glucose and lipid metabolism, thereby exerting complex functions in either increasing or decreasing malignant characteristics in tumors. This review highlights the major function and its mechanisms of sirtuins in cellular metabolic reprogramming, such as glucose metabolism including aerobic glycolysis (the Warburg effect), oxidative phosphorylation (OXPHOS)/ tricarboxylic acid (TCA) cycle, and glutamine metabolism; lipometabolism including fatty acid metabolism, cholesterol metabolism, ketone body metabolism and acetate metabolism; as well as leucine metabolism and urea cycle in tumorigenesis and cancer development.
    Keywords:  Cell metabolism; Glycolysis; Lipometabolism; Sirtuins; Warburg effect
    DOI:  https://doi.org/10.1016/j.semcancer.2018.11.003
  19. Biochim Biophys Acta Bioenerg. 2018 Nov 19. pii: S0005-2728(18)30686-8. [Epub ahead of print]
    Menezes-Filho SL, Amigo I, Luévano-Martínez LA, Kowaltowski AJ.
      Overnight fasting of rodents is commonly adopted in protocols to obtain isolated liver mitochondria, but the effects of fasting itself on mitochondrial function are poorly characterized. In this study we show that overnight fasting (15 h) promotes a shift in the liver mitochondrial bioenergetic profile, with a reduction in ADP-stimulated and maximal respiration, lower membrane potentials and lower resistance to Ca2+-induced mitochondrial permeability transition. Short term fasting (4 h) promoted similar changes, suggesting that this is a physiological shift in mitochondrial function associated with fasting, but not torpor. Our results suggest that the widely adopted liver mitochondrial isolation technique using fasted animals should be reconsidered, and also uncover physiological changes in bioenergetic function associated to nutritional status.
    Keywords:  Coupling; Fasting; Liver; Mitochondria; Permeability transition
    DOI:  https://doi.org/10.1016/j.bbabio.2018.11.017
  20. Redox Biol. 2018 Nov 09. pii: S2213-2317(18)30947-9. [Epub ahead of print]20 458-466
    Madreiter-Sokolowski CT, Waldeck-Weiermair M, Bourguignon MP, Villeneuve N, Gottschalk B, Klec C, Stryeck S, Radulovic S, Parichatikanond W, Frank S, Madl T, Malli R, Graier WF.
      BACKGROUND: Senescence is characterized by a gradual decline in cellular functions, including changes in energy homeostasis and decreased proliferation activity. As cellular power plants, contributors to signal transduction, sources of reactive oxygen species (ROS) and executors of programmed cell death, mitochondria are in a unique position to affect aging-associated processes of cellular decline. Notably, metabolic activation of mitochondria is tightly linked to Ca2+ due to the Ca2+ -dependency of several enzymes in the Krebs cycle, however, overload of mitochondria with Ca2+ triggers cell death pathways. Consequently, a machinery of proteins tightly controls mitochondrial Ca2+ homeostasis as well as the exchange of Ca2+ between the different cellular compartments, including Ca2+ flux between mitochondria and the endoplasmic reticulum (ER).METHODS: In this study, we investigated age-related changes in mitochondrial Ca2+ homeostasis, mitochondrial-ER linkage and the activity of the main ROS production site, the mitochondrial respiration chain, in an in vitro aging model based on porcine aortic endothelial cells (PAECs), using high-resolution live cell imaging, proteomics and various molecular biological methods.
    RESULTS: We describe that in aged endothelial cells, increased ER-mitochondrial Ca2+ crosstalk occurs due to enhanced ER-mitochondrial tethering. The close functional inter-organelle linkage increases mitochondrial Ca2+ uptake and thereby the activity of the mitochondrial respiration, but also makes senescent cells more vulnerable to mitochondrial Ca2+-overload-induced cell death. Moreover, we identified the senolytic properties of the polyphenol resveratrol, triggering cell death via mitochondrial Ca2+ overload exclusively in senescent cells.
    CONCLUSION: By unveiling aging-related changes in the inter-organelle tethering and Ca2+ communications we have advanced the understanding of endothelial aging and highlighted a potential basis to develop drugs specifically targeting senescent cells.
    Keywords:  Calcium signaling; ER-mitochondrial coupling; Endoplasmic reticulum; Mitochondria; Vascular aging
    DOI:  https://doi.org/10.1016/j.redox.2018.11.003
  21. Cell Rep. 2018 Nov 20. pii: S2211-1247(18)31696-6. [Epub ahead of print]25(8): 2044-2052.e5
    Baardman J, Verberk SGS, Prange KHM, van Weeghel M, van der Velden S, Ryan DG, Wüst RCI, Neele AE, Speijer D, Denis SW, Witte ME, Houtkooper RH, O'neill LA, Knatko EV, Dinkova-Kostova AT, Lutgens E, de Winther MPJ, Van den Bossche J.
      Metabolic reprogramming has emerged as a crucial regulator of immune cell activation, but how systemic metabolism influences immune cell metabolism and function remains to be investigated. To investigate the effect of dyslipidemia on immune cell metabolism, we performed in-depth transcriptional, metabolic, and functional characterization of macrophages isolated from hypercholesterolemic mice. Systemic metabolic changes in such mice alter cellular macrophage metabolism and attenuate inflammatory macrophage responses. In addition to diminished maximal mitochondrial respiration, hypercholesterolemia reduces the LPS-mediated induction of the pentose phosphate pathway (PPP) and the Nrf2-mediated oxidative stress response. Our observation that suppression of the PPP diminishes LPS-induced cytokine secretion supports the notion that this pathway contributes to inflammatory macrophage responses. Overall, this study reveals that systemic and cellular metabolism are strongly interconnected, together dictating macrophage phenotype and function.
    Keywords:  Nrf2; atherosclerosis; cardiovascular disease; foam cells; hypercholesterolemia; immunometabolism; inflammation; macrophages; meta-inflammation; metabolic disease; pentose phosphate pathway
    DOI:  https://doi.org/10.1016/j.celrep.2018.10.092
  22. Cell Host Microbe. 2018 Nov 14. pii: S1931-3128(18)30543-2. [Epub ahead of print]24(5): 625-636.e5
    Abuaita BH, Schultz TL, O'Riordan MX.
      Pathogenic bacteria taken up into the macrophage phagosome are the target of many anti-microbial mechanisms. Although mitochondria-derived antimicrobial effectors like reactive oxygen species (mROS) aid in bacterial killing, it is unclear how these effectors reach bacteria within the phagosomal lumen. We show here that endoplasmic reticulum stress triggered upon methicillin-resistant Staphylococcus aureus (MRSA) infection induces mROS that are delivered to bacteria-containing phagosomes via mitochondria-derived vesicles (MDVs). The endoplasmic reticulum stress sensor IRE1α induces mROS, specifically hydrogen peroxide (mH2O2), upon MRSA infection. MRSA infection also stimulates the generation of MDVs, which require the mitochondrial stress response factor Parkin, and contributes to mH2O2 accumulation in bacteria-containing phagosomes. Accumulation of phagosomal H2O2 requires Toll-like receptor signaling and the mitochondrial enzyme superoxide dismutase-2 (Sod2), which is delivered to phagosomes by MDVs. Sod2 depletion compromises mH2O2 production and bacterial killing. Thus, mitochondrial redox capacity enhances macrophage antimicrobial function by delivering mitochondria-derived effector molecules into bacteria-containing phagosomes.
    DOI:  https://doi.org/10.1016/j.chom.2018.10.005
  23. Arch Biochem Biophys. 2018 Nov 16. pii: S0003-9861(18)30779-3. [Epub ahead of print]
    Hyatt H, Deminice R, Yoshihara T, Powers SK.
      Prolonged skeletal muscle inactivity (e.g. limb immobilization, bed rest, mechanical ventilation, spinal cord injury, etc.) results in muscle atrophy that manifests into a decreased quality of life and in select patient populations, a higher risk of morbidity and mortality. Thus, understanding the processes that contribute to muscle atrophy during prolonged periods of muscle disuse is an important area of research. In this regard, mitochondrial dysfunction has been directly linked to the muscle wasting that occurs during extended periods of skeletal muscle inactivity. While the concept that mitochondrial dysfunction contributes to disuse muscle atrophy has been contemplated for nearly 50 years, the mechanisms connecting mitochondrial signaling events to skeletal muscle atrophy remained largely unexplained until recently. Indeed, emerging evidence reveals that mitochondrial dysfunction and the associated mitochondrial signaling events are a requirement for several forms of inactivity-induced skeletal muscle atrophy. Specifically, inactivity-induced alterations in skeletal muscle mitochondria phenotype and increased ROS emission, impaired Ca2+ handling, and release of mitochondria-specific proteolytic activators are established occurrences that promote fiber atrophy during prolonged periods of muscle inactivity. This review highlights the evidence that directly connects mitochondrial dysfunction and aberrant mitochondrial signaling with skeletal muscle atrophy and discusses the mechanisms linking these interconnected phenomena.
    Keywords:  Cell signaling; Disuse muscle atrophy; Mitochondrial dysfunction; Muscle wasting; Proteolysis; Reactive oxygen species
    DOI:  https://doi.org/10.1016/j.abb.2018.11.005
  24. Mol Biol Rep. 2018 Nov 20.
    Reichard A, Asosingh K.
      Angiogenesis extends pre-existing blood vessels to improve oxygen and nutrient delivery to inflamed or otherwise hypoxic tissues. Mitochondria are integral in this process, controlling cellular metabolism to regulate the proliferation, migration, and survival of endothelial cells which comprise the inner lining of blood vessels. Mitochondrial Complex III senses hypoxic conditions and generates mitochondrial reactive oxygen species which stabilize hypoxia-inducible factor (HIF-1α) protein. HIF-1α induces the transcription of the vegfa gene, allowing the translation of vascular endothelial growth factor protein, which interacts with mature and precursor endothelial cells, mobilizing them to form new blood vessels. This cascade can be inhibited at specific points by means of gene knockdown, enzyme treatment, and introduction of naturally occurring small molecules, providing insight into the relationship between mitochondria and angiogenesis. This review focuses on current knowledge of the overall role of mitochondria in controlling angiogenesis and outlines known inhibitors that have been used to elucidate this pathway which may be useful in future research to control angiogenesis in vivo.
    Keywords:  Angiogenesis; Endothelial; HIF-1α; Mitochondria; VEGF; mROS
    DOI:  https://doi.org/10.1007/s11033-018-4488-x
  25. Life Sci Alliance. 2018 May;1(2): e201800036
    Lucas S, Chen G, Aras S, Wang J.
      Breakdown of serine by the enzyme serine hydroxymethyltransferase (SHMT) produces glycine and one-carbon (1C) units. These serine catabolites provide important metabolic intermediates for the synthesis of nucleotides, as well as methyl groups for biosynthetic and regulatory methylation reactions. Recently, it has been shown that serine catabolism is required for efficient cellular respiration. Using CRISPR-Cas9 gene editing, we demonstrate that the mitochondrial SHMT enzyme, SHMT2, is essential to maintain cellular respiration, the main process through which mammalian cells acquire energy. We show that SHMT2 is required for the assembly of Complex I of the respiratory chain. Furthermore, supplementation of formate, a bona fide 1C donor, restores Complex I assembly in the absence of SHMT2. Thus, provision of 1C units by mitochondrial serine catabolism is critical for cellular respiration, at least in part by influencing the assembly of the respiratory apparatus.
    DOI:  https://doi.org/10.26508/lsa.201800036
  26. Am J Physiol Regul Integr Comp Physiol. 2018 Nov 21.
    Kasper JD, Meyer RA, Beard DA, Wiseman RW.
      During aerobic exercise (>65% of VO2max) the primary source of acetyl-CoA to fuel oxidative ATP synthesis in muscle is the pyruvate dehydrogenase (PDH) reaction. This study investigated how regulation of PDH activity affects muscle energetics by determining whether activation of PDH with dichloroacetate (DCA) alters the dynamics of the phosphate potential of rat gastrocnemius muscle during contraction. Twitch contractions were induced in vivo over a broad range of intensities to sample submaximal and maximal aerobic workloads. Muscle phosphorus metabolites were measured in vivo before and after DCA treatment using phosphorus nuclear magnetic resonance spectroscopy. At rest, DCA increased PDH activation compared to control (90±12 vs 23±3%, p<0.05) with parallel decreases in inorganic phosphate (Pi) of 17% (1.4±0.2 vs 1.7±0.1 mM, p<0.05) and an increase in the free energy of ATP hydrolysis (ΔGATP) (-66.2±0.3 vs -65.6±0.2 kJ/mol, p<0.05). During stimulation DCA increased steady state phosphocreatine (PCr) and ΔGATP with concomitant reduction in Pi and ADP concentrations. These effects were not due to kinetic alterations in PCr hydrolysis, resynthesis, or glycolytic ATP production and altered the flow force relationship between mitochondrial ATP synthesis rate (JMITO) and ΔGATP. DCA had no significant effect at 1.0-2.0 Hz stimulation, because physiological mechanisms at these high stimulation levels cause maximal activation of PDH. These data support a role of PDH activation in the regulation of the energetic steady state by altering the thermodynamic set point of the phosphate potential (ΔGATP) at rest and during contraction and do not support kinetic limitations to mitochondria as previously suggested.
    Keywords:  magnetic resonance; mitochondria; phosphate potential; regulation; substrate disposal
    DOI:  https://doi.org/10.1152/ajpregu.00321.2018
  27. Front Biosci (Landmark Ed). 2019 Jan 01. 24 435-450
    Sarkar S, Chakraborty D, Bhowmik A, Ghosh MK.
      In cerebral tissues, due to continuous and high metabolic demand, energy is produced exclusively by mitochondrial oxidative phosphorylation (OXPHOS). Obstruction of blood flow leads to cerebral ischemia, hypoxia and decreased cellular ATP production. The reactive oxygen species (ROS) generated as by-product of OXPHOS alter many intracellular signaling pathways and result in damaged cellular components. Under such hypoxic conditions, a key factor known as hypoxia inducible factor 1 (HIF1) is stabilized and activated and such activation induces expression of a defined set of target genes which are required for cell survival and angiogenesis. Reperfusion that follows such ischemia alters signaling pathways which are involved in cellular fate. Here, we will review the role of ROS, HIF-1 alpha and other signaling network in mitochondrial dysfunction and cell fate determination in ischemia-reperfusion models in the brain. We will also address both current and future therapeutic strategies for clinical significance that are being developed for treatment of cerebral ischemia.
  28. Cell Metab. 2018 Nov 12. pii: S1550-4131(18)30645-4. [Epub ahead of print]
    Neinast MD, Jang C, Hui S, Murashige DS, Chu Q, Morscher RJ, Li X, Zhan L, White E, Anthony TG, Rabinowitz JD, Arany Z.
      Elevations in branched-chain amino acids (BCAAs) associate with numerous systemic diseases, including cancer, diabetes, and heart failure. However, an integrated understanding of whole-body BCAA metabolism remains lacking. Here, we employ in vivo isotopic tracing to systemically quantify BCAA oxidation in healthy and insulin-resistant mice. We find that most tissues rapidly oxidize BCAAs into the tricarboxylic acid (TCA) cycle, with the greatest quantity occurring in muscle, brown fat, liver, kidneys, and heart. Notably, pancreas supplies 20% of its TCA carbons from BCAAs. Genetic and pharmacologic suppression of branched-chain alpha-ketoacid dehydrogenase kinase, a clinically targeted regulatory kinase, induces BCAA oxidation primarily in skeletal muscle of healthy mice. While insulin acutely increases BCAA oxidation in cardiac and skeletal muscle, chronically insulin-resistant mice show blunted BCAA oxidation in adipose tissues and liver, shifting BCAA oxidation toward muscle. Together, this work provides a quantitative framework for understanding systemic BCAA oxidation in health and insulin resistance.
    Keywords:  branched chain amino acids; insulin resistance; obesity; stable isotope tracing
    DOI:  https://doi.org/10.1016/j.cmet.2018.10.013
  29. BMC Biol. 2018 Nov 22. 16(1): 141
    Petrů M, Wideman J, Moore K, Alcock F, Palmer T, Doležal P.
      BACKGROUND: Bacteria and mitochondria contain translocases that function to transport proteins across or insert proteins into their inner and outer membranes. Extant mitochondria retain some bacterial-derived translocases but have lost others. While BamA and YidC were integrated into general mitochondrial protein transport pathways (as Sam50 and Oxa1), the inner membrane TAT translocase, which uniquely transports folded proteins across the membrane, was retained sporadically across the eukaryote tree.RESULTS: We have identified mitochondrial TAT machinery in diverse eukaryotic lineages and define three different types of eukaryote-encoded TatABC-derived machineries (TatAC, TatBC and TatC-only). Here, we investigate TatAC and TatC-only machineries, which have not been studied previously. We show that mitochondria-encoded TatAC of the jakobid Andalucia godoyi represent the minimal functional pathway capable of substituting for the Escherichia coli TatABC complex and can transport at least one substrate. However, selected TatC-only machineries, from multiple eukaryotic lineages, were not capable of supporting the translocation of this substrate across the bacterial membrane. Despite the multiple losses of the TatC gene from the mitochondrial genome, the gene was never transferred to the cell nucleus. Although the major constraint preventing nuclear transfer of mitochondrial TatC is likely its high hydrophobicity, we show that in chloroplasts, such transfer of TatC was made possible due to modifications of the first transmembrane domain.
    CONCLUSIONS: At its origin, mitochondria inherited three inner membrane translocases Sec, TAT and Oxa1 (YidC) from its bacterial ancestor. Our work shows for the first time that mitochondrial TAT has likely retained its unique function of transporting folded proteins at least in those few eukaryotes with TatA and TatC subunits encoded in the mitochondrial genome. However, mitochondria, in contrast to chloroplasts, abandoned the machinery multiple times in evolution. The overall lower hydrophobicity of the Oxa1 protein was likely the main reason why this translocase was nearly universally retained in mitochondrial biogenesis pathways.
    Keywords:  Hydrophobicity; Mitochondrial evolution; Protein transport; TAT translocase
    DOI:  https://doi.org/10.1186/s12915-018-0607-3
  30. Adv Anat Embryol Cell Biol. 2018 Nov 23.
    Aw WC, Garvin MR, Ballard JWO.
      In this review, we provide evidence to suggest that the cost of specific mtDNA mutations can be influenced by exogenous factors. We focus on macronutrient-mitochondrial DNA interactions as factors that may differentially influence the consequences of a change as mitochondria must be flexible in its utilization of dietary proteins, carbohydrates, and fats. To understand this fundamental dynamic, we briefly discuss the energy processing pathways in mitochondria. Next, we explore the mitochondrial functions that are initiated during energy deficiency or when cells encounter cellular stress. We consider the anterograde response (nuclear control of mitochondrial function) and the retrograde response (nuclear changes in response to mitochondrial signaling) and how this mito-nuclear crosstalk may be influenced by exogenous factors such as temperature and diet. Finally, we employ Complex I of the mitochondrial electron transport system as a case study and discuss the potential role of the dietary macronutrient ratio as a strong selective force that may shape the frequencies of mitotypes in populations and species. We conclude that this underexplored field likely has implications in the fundamental disciplines of evolutionary biology and quantitative genetics and the more biomedical fields of nutrigenomics and pharmacogenomics.
    Keywords:  Fitness; Functional compensation; Metabolic flexibility
    DOI:  https://doi.org/10.1007/102_2018_2
  31. iScience. 2018 Nov 02. pii: S2589-0042(18)30188-3. [Epub ahead of print]9 298-313
    Puchalska P, Huang X, Martin SE, Han X, Patti GJ, Crawford PA.
      We apply stable isotope tracing, mass-spectrometry-based untargeted metabolomics, to reveal the biochemical space labeled by 13C-substrates in bone-marrow-derived macrophages. At the pathway level, classically (lipopolysaccharide [LPS]-polarized, M1) and alternatively (interleukin [IL]-4-polarized, M2) polarized macrophages were 13C-labeled with surprising concordance. Total pools of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), an intermediate in the hexosamine biosynthetic pathway, were equally abundant in LPS- and IL-4-polarized macrophages. Informatic scrutiny of 13C-isotopologues revealed that LPS-polarized macrophages leverage the pentose phosphate pathway to generate UDP-GlcNAc, whereas IL-4-polarized macrophages rely on intact glucose and mitochondrial metabolism of glucose carbon. Labeling from [13C]glucose is competed by unlabeled fatty acids and acetoacetate, underscoring the broad roles for substrate metabolism beyond energy conversion. Finally, the LPS-polarized macrophage metabolite itaconate is imported into IL-4-polarized macrophages, in which it reprograms [13C]glucose metabolism. Thus, use of fully unsupervised isotope tracing metabolomics in macrophages reveals polarization-state-specific metabolic pathway connectivity, substrate competition, and metabolite allocation among cellular compartments.
    Keywords:  Components of the Immune System; Immunology; Metabolomics
    DOI:  https://doi.org/10.1016/j.isci.2018.10.029
  32. J Cell Physiol. 2018 Nov 19.
    He L, Zhou Q, Huang Z, Xu J, Zhou H, Lv D, Lu L, Huang S, Tang M, Zhong J, Chen J, Luo X, Li L, Chen L.
      Aberrant proliferation of vascular smooth muscle cells (VSMC) is a critical contributor to the pathogenesis of atherosclerosis (AS). Our previous studies have demonstrated that apelin-13/APJ confers a proliferative response in VSMC, however, its underlying mechanism remains elusive. In this study, we aimed to investigate the role of mitophagy in apelin-13-induced VSMC proliferation and atherosclerotic lesions in apolipoprotein E knockout (ApoE-/-) mice. Apelin-13 enhances human aortic VSMC proliferation and proliferative regulator proliferating cell nuclear antigen expression in dose and time-dependent manner, while is abolished by APJ antagonist F13A. We observe the engulfment of damage mitochondria by autophagosomes (mitophagy) of human aortic VSMC in apelin-13 stimulation. Mechanistically, apelin-13 increases p-AMPKα and promotes mitophagic activity such as the LC3I to LC3II ratio, the increase of Beclin-1 level and the decrease of p62 level. Importantly, the expressions of PINK1, Parkin, VDAC1, and Tom20 are induced by apelin-13. Conversely, blockade of APJ by F13A abolishes these stimulatory effects. Human aortic VSMC transfected with AMPKα, PINK1, or Parkin and subjected to apelin-13 impairs mitophagy and prevents proliferation. Additional, apelin-13 not only increases the expression of Drp1 but also reduces the expressions of Mfn1, Mfn2, and OPA1. Remarkably, the mitochondrial division inhibitor-1(Mdivi-1), the pharmacological inhibition of Drp1, attenuates human aortic VSMC proliferation. Treatment of ApoE-/- mice with apelin-13 accelerates atherosclerotic lesions, increases p-AMPKα and mitophagy in aortic wall in vivo. Finally, PINK1-/- mutant mice with apelin-13 attenuates atherosclerotic lesions along with defective in mitophagy. PINK1/Parkin-mediated mitophagy promotes apelin-13-evoked human aortic VSMC proliferation by activating p-AMPKα and exacerbates the progression of atherosclerotic lesions.
    Keywords:  AMPKα; Apelin-13; atherosclerosis (AS); mitophagy; vascular smooth muscle cell proliferation
    DOI:  https://doi.org/10.1002/jcp.27527
  33. Redox Biol. 2018 Nov 08. pii: S2213-2317(18)30853-X. [Epub ahead of print]20 483-488
    Treberg JR, Braun K, Selseleh P.
      Mitochondria are widely recognized as sources of reactive oxygen species in animal cells, with H2O2 being of particular note because it can act not only in oxidative stress but also is important to several signalling pathways. Lesser recognized is that mitochondria can have far greater capacity to consume H2O2 than to produce it; however, the consumption of H2O2 may be kinetically constrained by H2O2 availability especially at the low nanomolar (or lower) concentrations that occur in vivo. The production of H2O2 is a function of many factors, not the least of which are respiratory substrate availability and the protonmotive force (Δp). The Δp, which is predominantly membrane potential (ΔΨ), can be a strong indicator of mitochondrial energy status, particularly if respiratory substrate supply is either not meeting or exceeding demand. The notion that mitochondria may functionally act in regulating H2O2 concentrations may be somewhat implicit but little evidence demonstrating this is available. Here we demonstrate key assumptions that are required for mitochondria to act as regulators of H2O2 by an integrated system of production and concomitant consumption. In particular we show the steady-state level of H2O2 mitochondria approach is a function of both mitochondrial H2O2 consumption and production capacity, the latter of which is strongly influenced by ΔΨ. Our results are consistent with mitochondria being able to manipulate extramitochondrial H2O2 as a means of signalling mitochondrial energetic status, in particular the Δp or ΔΨ. Such a redox-based signal could operate with some independence from other energy sensing mechanisms such as those that transmit information using the cytosolic adenylate pool.
    Keywords:  Antioxidants; Energy sensing; Peroxidase; Peroxiredoxins; Reactive oxygen species (ROS)
    DOI:  https://doi.org/10.1016/j.redox.2018.11.002
  34. Sci Rep. 2018 Nov 20. 8(1): 17081
    Lone A, Harris RA, Singh O, Betts DH, Cumming RC.
      A key pathological feature of Alzheimer's disease (AD) is the accumulation of the neurotoxic amyloid beta (Aβ) peptide within the brains of affected individuals. Previous studies have shown that neuronal cells selected for resistance to Aβ toxicity display a metabolic shift from mitochondrial-dependent oxidative phosphorylation (OXPHOS) to aerobic glycolysis to meet their energy needs. The Src homology/collagen (Shc) adaptor protein p66Shc is a key regulator of mitochondrial function, ROS production and aging. Moreover, increased expression and activation of p66Shc promotes a shift in the cellular metabolic state from aerobic glycolysis to OXPHOS in cancer cells. Here we evaluated the hypothesis that activation of p66Shc in CNS cells promotes both increased OXPHOS and enhanced sensitivity to Aβ toxicity. The effect of altered p66Shc expression on metabolic activity was assessed in rodent HT22 and B12 cell lines of neuronal and glial origin respectively. Overexpression of p66Shc repressed glycolytic enzyme expression and increased both mitochondrial electron transport chain activity and ROS levels in HT22 cells. The opposite effect was observed when endogenous p66Shc expression was knocked down in B12 cells. Moreover, p66Shc activation in both cell lines increased their sensitivity to Aβ toxicity. Our findings indicate that expression and activation of p66Shc renders CNS cells more sensitive to Aβ toxicity by promoting mitochondrial OXPHOS and ROS production while repressing aerobic glycolysis. Thus, p66Shc may represent a potential therapeutically relevant target for the treatment of AD.
    DOI:  https://doi.org/10.1038/s41598-018-35114-y
  35. Front Endocrinol (Lausanne). 2018 ;9 578
    Lambert M, Bastide B, Cieniewski-Bernard C.
      Skeletal muscle represents around 40% of whole body mass. The principal function of skeletal muscle is the conversion of chemical energy toward mechanic energy to ensure the development of force, provide movement and locomotion, and maintain posture. This crucial energy dependence is maintained by the faculty of the skeletal muscle for being a central place as a "reservoir" of amino acids and carbohydrates in the whole body. A fundamental post-translational modification, named O-GlcNAcylation, depends, inter alia, on these nutrients; it consists to the transfer or the removal of a unique monosaccharide (N-acetyl-D-glucosamine) to a serine or threonine hydroxyl group of nucleocytoplasmic and mitochondrial proteins in a dynamic process by the O-GlcNAc Transferase (OGT) and the O-GlcNAcase (OGA), respectively. O-GlcNAcylation has been shown to be strongly involved in crucial intracellular mechanisms through the modulation of signaling pathways, gene expression, or cytoskeletal functions in various organs and tissues, such as the brain, liver, kidney or pancreas, and linked to the etiology of associated diseases. In recent years, several studies were also focused on the role of O-GlcNAcylation in the physiology and the physiopathology of skeletal muscle. These studies were mostly interested in O-GlcNAcylation during muscle exercise or muscle-wasting conditions. Major findings pointed out a different "O-GlcNAc signature" depending on muscle type metabolism at resting, wasting and exercise conditions, as well as depending on acute or long-term exhausting exercise protocol. First insights showed some differential OGT/OGA expression and/or activity associated with some differential stress cellular responses through Reactive Oxygen Species and/or Heat-Shock Proteins. Robust data displayed that these O-GlcNAc changes could lead to (i) a differential modulation of the carbohydrates metabolism, since the majority of enzymes are known to be O-GlcNAcylated, and to (ii) a differential modulation of the protein synthesis/degradation balance since O-GlcNAcylation regulates some key signaling pathways such as Akt/GSK3β, Akt/mTOR, Myogenin/Atrogin-1, Myogenin/Mef2D, Mrf4 and PGC-1α in the skeletal muscle. Finally, such involvement of O-GlcNAcylation in some metabolic processes of the skeletal muscle might be linked to some associated diseases such as type 2 diabetes or neuromuscular diseases showing a critical increase of the global O-GlcNAcylation level.
    Keywords:  O-GlcNAcylation; exercise; fast-twitch muscle; glucose metabolism; skeletal muscle atrophy; slow-twitch muscle
    DOI:  https://doi.org/10.3389/fendo.2018.00578
  36. Trends Pharmacol Sci. 2018 Dec;pii: S0165-6147(18)30182-2. [Epub ahead of print]39(12): 1021-1032
    Limpert AS, Lambert LJ, Bakas NA, Bata N, Brun SN, Shaw RJ, Cosford NDP.
      During times of stress, autophagy is a cellular process that enables cells to reclaim damaged components by a controlled recycling pathway. This mechanism for cellular catabolism is dysregulated in cancer, with evidence indicating that cancer cells rely on autophagy in the hypoxic and nutrient-poor microenvironment of solid tumors. Mounting evidence suggests that autophagy has a role in the resistance of tumors to standard-of-care (SOC) therapies. Therefore, there is significant interest in the discovery of small molecules that can safely modulate autophagy. In this review, we describe recent advances in the identification of new pharmacological compounds that modulate autophagy, with a focus on their mode of action, value as probe compounds, and validation as potential therapeutics.
    Keywords:  autophagosome; autophagy; cancer; kinase; oncology
    DOI:  https://doi.org/10.1016/j.tips.2018.10.004
  37. Hum Mol Genet. 2018 Dec 01. 27(23): 4135-4144
    Pacheu-Grau D, Callegari S, Emperador S, Thompson K, Aich A, Topol SE, Spencer EG, McFarland R, Ruiz-Pesini E, Torkamani A, Taylor RW, Montoya J, Rehling P.
      Protein import into mitochondria is facilitated by translocases within the outer and the inner mitochondrial membranes that are dedicated to a highly specific subset of client proteins. The mitochondrial carrier translocase (TIM22 complex) inserts multispanning proteins, such as mitochondrial metabolite carriers and translocase subunits (TIM23, TIM17A/B and TIM22), into the inner mitochondrial membrane. Both types of substrates are essential for mitochondrial metabolic function and biogenesis. Here, we report on a subject, diagnosed at 1.5 years, with a neuromuscular presentation, comprising hypotonia, gastroesophageal reflux disease and persistently elevated serum and Cerebrospinal fluid lactate (CSF). Patient fibroblasts displayed reduced oxidative capacity and altered mitochondrial morphology. Using trans-mitochondrial cybrid cell lines, we excluded a candidate variant in mitochondrial DNA as causative of these effects. Whole-exome sequencing identified compound heterozygous variants in the TIM22 gene (NM_013337), resulting in premature truncation in one allele (p.Tyr25Ter) and a point mutation in a conserved residue (p.Val33Leu), within the intermembrane space region, of the TIM22 protein in the second allele. Although mRNA transcripts of TIM22 were elevated, biochemical analyses revealed lower levels of TIM22 protein and an even greater deficiency of TIM22 complex formation. In agreement with a defect in carrier translocase function, carrier protein amounts in the inner membrane were found to be reduced. This is the first report of pathogenic variants in the TIM22 pore-forming subunit of the carrier translocase affecting the biogenesis of inner mitochondrial membrane proteins critical for metabolite exchange.
    DOI:  https://doi.org/10.1093/hmg/ddy305
  38. Front Endocrinol (Lausanne). 2018 ;9 599
    Ong Q, Han W, Yang X.
      O-GlcNAcylation is an important posttranslational modification governed by a single pair of enzymes-O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). These two enzymes mediate the dynamic cycling of O-GlcNAcylation on a wide variety of cytosolic, nuclear and mitochondrial proteins in a nutrient- and stress-responsive fashion. While cellular functions of O-GlcNAcylation have been emerging, little is known regarding the precise mechanisms how the enzyme pair senses the environmental cues to elicit molecular and physiological changes. In this review, we discuss how the OGT/OGA pair acts as a metabolic sensor that integrates signaling pathways, given their capability of receiving signaling inputs from various partners, targeting multiple substrates with spatiotemporal specificity and translocating to different parts of the cell. We also discuss how the pair maintains homeostatic signaling within the cell and its physiological relevance. A better understanding of the mechanisms of OGT/OGA action would enable us to derive therapeutic benefits of resetting cellular O-GlcNAc levels within an optimal range.
    Keywords:  O-GlcNAc transferase; O-GlcNAcase; O-GlcNAcylation; homeostasis; metabolic sensor; posttranslational modification; signaling integrator; spatiotemporal dynamics
    DOI:  https://doi.org/10.3389/fendo.2018.00599
  39. Biol Open. 2018 Nov 21. pii: bio.038307. [Epub ahead of print]
    Noree C, Monfort E, Shotelersuk V.
      Cancer cells are characterized by extensive reprogramming of metabolic pathways in order to promote cell division and survival. However, the growth promotion effects of metabolic reprogramming can be due to moonlighting functions of metabolic enzymes as well as the redirection of flux through particular pathways. To identify metabolic enzymes that might have potential moonlighting functions in oncogenesis, we have examined recent screens of the yeast GFP strain collection for metabolic enzymes that have been implicated in cancer metabolism with an unusual subcellular localization. Asparagine synthetase forms filaments in yeast in response to nutrient limitation and is part of a pathway that is a chemotherapy target in acute lymphoblastic leukemia. Interestingly, while yeast asparagine synthetase forms cytoplasmic filaments in response to nutrient stress, human asparagine synthetase is associated with the centrosomes and mitotic spindles. This localization is disrupted by both nocodazole and asparaginase treatments. This failure to localize occurs even though asparagine synthetase is highly up-regulated in response to asparaginase treatment. Together, these results argue that human asparagine synthetase undergoes regulated recruitment to the mitotic spindles and that it may have acquired a second role in mitosis similar to other metabolic enzymes that contribute to metabolic reprogramming in cancer cells.
    Keywords:  Asparagine synthetase; Cell division; Mitosis; Mitotic spindle
    DOI:  https://doi.org/10.1242/bio.038307
  40. Nat Commun. 2018 Nov 19. 9(1): 4859
    Sahu A, Mamiya H, Shinde SN, Cheikhi A, Winter LL, Vo NV, Stolz D, Roginskaya V, Tang WY, St Croix C, Sanders LH, Franti M, Van Houten B, Rando TA, Barchowsky A, Ambrosio F.
      While young muscle is capable of restoring the original architecture of damaged myofibers, aged muscle displays a markedly reduced regeneration. We show that expression of the "anti-aging" protein, α-Klotho, is up-regulated within young injured muscle as a result of transient Klotho promoter demethylation. However, epigenetic control of the Klotho promoter is lost with aging. Genetic inhibition of α-Klotho in vivo disrupted muscle progenitor cell (MPC) lineage progression and impaired myofiber regeneration, revealing a critical role for α-Klotho in the regenerative cascade. Genetic silencing of Klotho in young MPCs drove mitochondrial DNA (mtDNA) damage and decreased cellular bioenergetics. Conversely, supplementation with α-Klotho restored mtDNA integrity and bioenergetics of aged MPCs to youthful levels in vitro and enhanced functional regeneration of aged muscle in vivo in a temporally-dependent manner. These studies identify a role for α-Klotho in the regulation of MPC mitochondrial function and implicate α-Klotho declines as a driver of impaired muscle regeneration with age.
    DOI:  https://doi.org/10.1038/s41467-018-07253-3
  41. Cell Rep. 2018 Nov 20. pii: S2211-1247(18)31687-5. [Epub ahead of print]25(8): 2036-2043.e5
    Opaliński Ł, Song J, Priesnitz C, Wenz LS, Oeljeklaus S, Warscheid B, Pfanner N, Becker T.
      Mitochondria possess elaborate machineries for the import of proteins from the cytosol. Cytosolic factors like Hsp70 chaperones and their co-chaperones, the J-proteins, guide proteins to the mitochondrial surface. The translocase of the mitochondrial outer membrane (TOM) forms the entry gate for preproteins. How the proteins are delivered to mitochondrial preprotein receptors is poorly understood. We identify the cytosolic J-protein Xdj1 as a specific interaction partner of the central receptor Tom22. Tom22 recruits Xdj1 to the mitochondrial surface to promote import of preproteins and assembly of the TOM complex. Additionally, we find that the receptor Tom70 binds a different cytosolic J-protein, Djp1. Our findings suggest that cytosolic J-proteins target distinct TOM receptors and promote the biogenesis of mitochondrial proteins.
    Keywords:  J-proteins; TOM complex; cytosolic chaperones; mitochondria; protein targeting
    DOI:  https://doi.org/10.1016/j.celrep.2018.10.083
  42. Nat Commun. 2018 Nov 19. 9(1): 4862
    Boulter E, Estrach S, Tissot FS, Hennrich ML, Tosello L, Cailleteau L, de la Ballina LR, Pisano S, Gavin AC, Féral CC.
      Mechanical and metabolic cues independently contribute to the regulation of cell and tissue homeostasis. However, how they cross-regulate each other during this process remains largely unknown. Here, we show that cellular metabolism can regulate integrin rigidity-sensing via the sphingolipid metabolic pathway controlled by the amino acid transporter and integrin coreceptor CD98hc (SLC3A2). Genetic invalidation of CD98hc in dermal cells and tissue impairs rigidity sensing and mechanical signaling downstream of integrins, including RhoA activation, resulting in aberrant tissue mechanical homeostasis. Unexpectedly, we found that this regulation does not occur directly through regulation of integrins by CD98hc but indirectly, via the regulation of sphingolipid synthesis and the delta-4-desaturase DES2. Loss of CD98hc decreases sphingolipid availability preventing proper membrane recruitment, shuttling and activation of upstream regulators of RhoA including Src kinases and GEF-H1. Altogether, our results unravel a novel cross-talk regulation between integrin mechanosensing and cellular metabolism which may constitute an important new regulatory framework contributing to mechanical homeostasis.
    DOI:  https://doi.org/10.1038/s41467-018-07268-w
  43. Curr Pharm Des. 2018 Nov 20.
    Pittas K, Vrachatis DA, Angelidis C, Tsoucala S, Giannopoulos G, Defteros S.
      Cardiovascular diseases, such as stroke and myocardial infarction (MI) remain the major cause of death and disability worldwide. However, the mortality of MI has declined dramatically over the past several decades because of advances in medicines (thrombolytic agents, antiplatelet drugs, beta blockers, and angiotensin converting enzyme inhibitors) and approaches to restore tissue perfusion(percutaneous coronary intervention and cardiopulmonary bypass). Animals studies have been shown that these treatments have been effective in reducing acute myocardial ischemic injury and limiting MI size. The paradox is that the process of reperfusion can itself amplify cell injury and death, known as myocardial ischemia-reperfusion injury (I/R). Intensive research has uncovered several complex mechanisms of cardiomyocyte damage after reperfusion,and potential therapeutic targets for preventing I/R. Importantly, it is now recognized that excessive elevation of intracellular and mitochondrial Ca2+during reperfusion predisposes the cells to hypercontracture, proteolysis and mitochondrial failure and eventually to necrotic or apoptotic death. These enormous alterations in cytosolic Ca2+ levels are induced by the Ca2+ channels of the sarcolemma(L-Type Ca2+channels, sodium/calcium exchanger), the endoplasmic/sarcoplasmic reticulum (SERCA ATPase) and ryanodine receptors, SOCE(store-operated calcium entry), lysosomals and others, which are modified by I/R injury. The overall goal of this review is to describe the different pathways that lead to I/R injury via Ca2+ overload, focus on recent discoveries and highlight prospects for therapeutic strategies for clinical benefit.
    Keywords:  calcium; myocardium ; reperfusion
    DOI:  https://doi.org/10.2174/1381612825666181120155953
  44. Trends Cancer. 2018 Dec;pii: S2405-8033(18)30219-X. [Epub ahead of print]4(12): 849-860
    Schmidt SF, Rohm M, Herzig S, Berriel Diaz M.
      Cancer cachexia is a multifactorial condition characterized by body weight loss that negatively affects quality of life and survival of patients with cancer. Despite the clinical relevance, there is currently no defined standard of care to effectively counteract cancer-associated progressive tissue wasting. Skeletal muscle atrophy represents the main manifestation of cancer cachexia. However, cancer cachexia is increasingly seen as a systemic phenomenon affecting and/or influenced by various organs. Here, we describe recent developments elucidating the roles of different tissues as well as tissue crosstalk in this wasting syndrome, including potential links to other cancer-associated morbidities. A more comprehensive understanding of cancer cachexia etiology and heterogeneity may enable the development of intervention strategies to prevent or reverse this devastating condition.
    DOI:  https://doi.org/10.1016/j.trecan.2018.10.001
  45. Mol Cell. 2018 Nov 15. pii: S1097-2765(18)30755-X. [Epub ahead of print]72(4): 778-785.e3
    Paillard M, Csordás G, Huang KT, Várnai P, Joseph SK, Hajnóczky G.
      Proper control of the mitochondrial Ca2+ uniporter's pore (MCU) is required to allow Ca2+-dependent activation of oxidative metabolism and to avoid mitochondrial Ca2+ overload and cell death. The MCU's gatekeeping and cooperative activation is mediated by the Ca2+-sensing MICU1 protein, which has been proposed to form dimeric complexes anchored to the EMRE scaffold of MCU. We unexpectedly find that MICU1 suppresses inhibition of MCU by ruthenium red/Ru360, which bind to MCU's DIME motif, the selectivity filter. This led us to recognize in MICU1's sequence a putative DIME interacting domain (DID), which is required for both gatekeeping and cooperative activation of MCU and for cell survival. Thus, we propose that MICU1 has to interact with the D-ring formed by the DIME domains in MCU to control the uniporter.
    Keywords:  Ca(2+) uptake; calcium signaling; cooperativity; mitochondria; oxidative stress; threshold
    DOI:  https://doi.org/10.1016/j.molcel.2018.09.008
  46. J Virol. 2018 Nov 21. pii: JVI.01599-18. [Epub ahead of print]
    Li T, Zhu Y, Cheng F, Lu C, Jung JU, Gao SJ.
      Cancer cells are required to rewire existing metabolic pathways to support their abnormal proliferation. We have previously shown that, unlike glucose-addicted cancers, Kaposi's sarcoma-associated herpesvirus (KSHV)-transformed cells depend on glutamine rather than glucose for energy production, and amino acid and nucleotide syntheses. High-level consumption of glutamine is tightly regulated and often coupled with the citrulline-nitric oxide (NO) cycle. We have found that KSHV infection accelerates the nitrogen efflux by upregulating the expression of argininosuccinate synthase 1 (ASS1), a key enzyme in the citrulline-NO cycle. KSHV utilizes multiple microRNAs to upregulate ASS1 expression. Depletion of either ASS1 or inducible nitric oxide synthase (iNOS) in KSHV-transformed cells suppresses growth proliferation, abolishes colony formation in soft agar, and decreases NO generation. Furthermore, by maintaining intracellular NO level, ASS1 expression facilitates KSHV-mediated activation of the STAT3 pathway, which is critical for virus-induced transformation. These results illustrate a novel mechanism by which an oncogenic virus hijacks a key metabolic pathway to promote growth transformation and reveal a potential novel therapeutic target for KSHV-induced malignancies.IMPORTANCE We have previously shown that Kaposi's sarcoma-associated herpesvirus (KSHV)-transformed cells depend on glutamine rather than glucose for energy production, and amino acid and nucleotide syntheses. In this study, we have further examined how the KSHV-reprogramed metabolic pathways are regulated and discovered that KSHV hijacks the citrulline-nitric oxide (NO) cycle to promote growth proliferation and transformation. Multiple KSHV-encoded microRNAs upregulate argininosuccinate synthase 1 (ASS1), a key enzyme in the citrulline-NO cycle. ASS1 is required for KSHV-induced proliferation, colony formation in soft agar, and NO generation of KSHV-transformed cells, which also depends on inducible nitric oxide synthase. By maintaining intracellular NO level, ASS1 mediates KSHV activation of the STAT3 pathway, which is essential for KSHV-induced abnormal cell proliferation and transformation. These results illustrate a novel mechanism by which an oncogenic virus hijacks a key metabolic pathway to promote growth transformation and reveal a potential novel therapeutic target for KSHV-induced malignancies.
    DOI:  https://doi.org/10.1128/JVI.01599-18
  47. Front Oncol. 2018 ;8 500
    Zaal EA, Berkers CR.
      Resistance to therapeutic agents, either intrinsic or acquired, is currently a major problem in the treatment of cancers and occurs in virtually every type of anti-cancer therapy. Therefore, understanding how resistance can be prevented, targeted and predicted becomes increasingly important to improve cancer therapy. In the last decade, it has become apparent that alterations in cellular metabolism are a hallmark of cancer cells and that a rewired metabolism is essential for rapid tumor growth and proliferation. Recently, metabolic alterations have been shown to play a role in the sensitivity of cancer cells to widely-used first-line chemotherapeutics. This suggests that metabolic pathways are important mediators of resistance toward anticancer agents. In this review, we highlight the metabolic alterations associated with resistance toward different anticancer agents and discuss how metabolism may be exploited to overcome drug resistance to classical chemotherapy.
    Keywords:  BRAF inhibitors; bortezomib; breast cancer; cancer metabolism; cisplatin; drug resistance; melanoma; multiple myeloma
    DOI:  https://doi.org/10.3389/fonc.2018.00500
  48. Cell Rep. 2018 Nov 20. pii: S2211-1247(18)31714-5. [Epub ahead of print]25(8): 2285-2298.e4
    Zhu D, Zhao Z, Cui G, Chang S, Hu L, See YX, Lim MGL, Guo D, Chen X, Robson P, Luo Y, Cheung E.
      Estrogen drives breast cancer (BCa) progression by directly activating estrogen receptor α (ERα). However, because of the stochastic nature of gene transcription, it is important to study the estrogen signaling pathway at the single-cell level to fully understand how ERα regulates transcription. Here, we performed single-cell transcriptome analysis on ERα-positive BCa cells following 17β-estradiol stimulation and reconstructed the dynamic estrogen-responsive transcriptional network from discrete time points into a pseudotemporal continuum. Notably, differentially expressed genes show an estrogen-stimulated metabolic switch that favors biosynthesis but reduces estrogen degradation. Moreover, folate-mediated one-carbon metabolism is reprogrammed through the mitochondrial folate pathway and polyamine and purine synthesis are upregulated coordinately. Finally, we show AZIN1 and PPAT are direct ERα targets that are essential for BCa cell survival and growth. In summary, our study highlights the dynamic transcriptional heterogeneity in ERα-positive BCa cells upon estrogen stimulation and uncovers a mechanism of estrogen-mediated metabolic switch.
    Keywords:  breast cancer; estrogen receptor α; metabolic switch; single-cell RNA sequencing
    DOI:  https://doi.org/10.1016/j.celrep.2018.10.093
  49. Nat Commun. 2018 Nov 19. 9(1): 4874
    Wang F, Meng M, Mo B, Yang Y, Ji Y, Huang P, Lai W, Pan X, You T, Luo H, Guan X, Deng Y, Yuan S, Chu J, Namaka M, Hughes T, Ye L, Yu J, Li X, Deng Y.
      The metabolic checkpoint kinase mechanistic/mammalian target of rapamycin (mTOR) regulates natural killer (NK) cell development and function, but the exact underlying mechanisms remain unclear. Here, we show, via conditional deletion of Raptor (mTORC1) or Rictor (mTORC2), that mTORC1 and mTORC2 promote NK cell maturation in a cooperative and non-redundant manner, mainly by controlling the expression of Tbx21 and Eomes. Intriguingly, mTORC1 and mTORC2 regulate cytolytic function in an opposing way, exhibiting promoting and inhibitory effects on the anti-tumor ability and metabolism, respectively. mTORC1 sustains mTORC2 activity by maintaining CD122-mediated IL-15 signaling, whereas mTORC2 represses mTORC1-modulated NK cell effector functions by restraining STAT5-mediated SLC7A5 expression. These positive and negative crosstalks between mTORC1 and mTORC2 signaling thus variegate the magnitudes and kinetics of NK cell activation, and help define a paradigm for the modulation of NK maturation and effector functions.
    DOI:  https://doi.org/10.1038/s41467-018-07277-9
  50. Cell Death Discov. 2018 ;4 104
    Tamari K, Konno M, Asai A, Koseki J, Hayashi K, Kawamoto K, Murai N, Matsufuji S, Isohashi F, Satoh T, Goto N, Tanaka S, Doki Y, Mori M, Ogawa K, Ishii H.
      Cancer stem cells (CSCs) exhibit tumorigenic potential and can generate resistance to chemotherapy and radiotherapy. A labeled ornithine decarboxylase (ODC, a rate-limiting enzyme involved in polyamine [PA] biosynthesis) degradation motif (degron) system allows visualization of a fraction of CSC-like cells in heterogeneous tumor populations. A labeled ODC degradation motif system allowed visualization of a fraction of CSC-like cells in heterogeneous tumor populations. Using this system, analysis of polyamine flux indicated that polyamine metabolism is active in CSCs. The results showed that intracellular polyamines inhibited the activity of histone lysine 4 demethylase enzymes, including lysine-specific demethylase-1 (LSD1). Chromatin immunoprecipitation with Pol II antibody followed by massively parallel DNA sequencing, revealed the global enrichment of Pol II in transcription start sites in CSCs. Increase of polyamines within cells resulted in an enhancement of ID1 gene expression. The results of this study reveal details of metabolic pathways that drive epigenetic control of cancer cell stemness and determine effective therapeutic targets in CSCs.
    DOI:  https://doi.org/10.1038/s41420-018-0117-7
  51. Cancer Sci. 2018 Nov 20.
    Hong SM, Hwang SW, Wang T, Park CW, Ryu YM, Jung JH, Shin JH, Kim SY, Lee JL, Kim CW, Yoon G, Kim KH, Myung SJ, Choi KY.
      Nicotinamide adenine dinucleotide (NAD) exists in a reduced form (NADH) and an oxidized form (NAD+). NAD+ plays crucial roles in cancer metabolism, including in cellular signaling, energy production and redox regulation. However, it remains unclear whether NAD(H) pool size (NAD+ and NADH) could be used as biomarker for colon cancer progression. Here, we showed that the NAD(H) pool size and NAD+ /NADH ratio both increased during colorectal cancer (CRC) progression due to activation of the NAD+ salvage pathway mediated by nicotinamide phosphoribosyltransferase (NAMPT). The NAMPT expression was upregulated in adenoma and adenocarcinoma tissues from CRC patients. The NADH fluorescence intensity measured by two-photon excitation fluorescence (TPEF) microscopy was consistently increased in CRC cell lines, azoxymethane/dextran sodium sulfate (AOM/DSS)-induced CRC tissues and tumor tissues from CRC patients. The increases in the NAD(H) pool inhibited the accumulation of excessive ROS levels and FK866, a specific inhibitor of NAMPT, treatment decreased the CRC nodule size by increasing ROS levels in AOM/DSS mice. Collectively, our results suggest that NAMPT-mediated upregulation of the NAD(H) pool protects cancer cells against detrimental oxidative stress and that detecting NADH fluorescence by TPEF microscopy could be a potential method for monitoring CRC progression. This article is protected by copyright. All rights reserved.
    Keywords:   NAMPT ; Colon cancer; Inflammation; NAD(H) pool; Two-photon excitation fluorescence microscopy
    DOI:  https://doi.org/10.1111/cas.13886
  52. Surg Pathol Clin. 2018 Dec;pii: S1875-9181(18)30060-6. [Epub ahead of print]11(4): 725-737
    Peng YC, Chen YB.
      A heightened understanding of hereditary renal cancer syndromes and their molecular basis has led to an increased awareness and recognition of these renal neoplasms by pathologists. Because a diagnosis of hereditary renal cell carcinoma has a profound impact on the patient and family members, when and how to raise such a suspicion via pathologic assessment has become an important yet very challenging task. This review discusses key clinicopathologic, immunohistochemical, and genetic characteristics of hereditary renal cancer syndromes, and important differential diagnostic challenges, emphasizing recent pathologic and molecular advances.
    Keywords:  Birt-Hogg-Dubé; Familial; Hereditary leiomyomatosis renal cell carcinoma; Hereditary papillary; Kidney cancer; Succinate dehydrogenase; Tuberous sclerosis; von Hippel-Lindau
    DOI:  https://doi.org/10.1016/j.path.2018.07.010
  53. Int J Mol Sci. 2018 Nov 17. pii: E3631. [Epub ahead of print]19(11):
    Dioguardi FS, Flati V, Corsetti G, Pasini E, Romano C.
      Energy production is the main task of the cancer cell metabolism because the costs of duplicating are enormous. Although energy is derived in cells by dismantling the carbon-to-carbon bonds of any macronutrient, cancer nutritional needs for energetic purposes have been studied primarily as being dependent on glycolysis. Since the end of the last century, the awareness of the dependence of cancer metabolism on amino acids not only for protein synthesis but also to match energy needs has grown. The roles of specific amino acids such as glutamine, glycine and serine have been explored in different experimental conditions and reviewed. Moreover, epidemiological evidence has revealed that some amino acids used as a supplement for therapeutic reasons, particularly the branched-chain ones, may reduce the incidence of liver cancer and a specific molecular mechanism has been proposed as functional to their protective action. By contrast and puzzling clinicians, the metabolomic signature of some pathologies connected to an increased risk of cancer, such as prolonged hyperinsulinemia in insulin-resistant patients, is identified by elevated plasma levels of the same branched-chain amino acids. Most recently, certain formulations of amino acids, deeply different from the amino acid compositions normally present in foods, have shown the power to master cancer cells epigenetically, slowing growth or driving cancer cells to apoptotic death, while being both beneficial for normal cell function and the animal's health and lifespan. In this review, we will analyze and try to disentangle some of the many knots dealing with the complexities of amino acid biology and links to cancer metabolism.
    Keywords:  amino acids; apoptosis; autophagy; cancer; diabetes type 2; energy metabolism; glutamine
    DOI:  https://doi.org/10.3390/ijms19113631
  54. NMR Biomed. 2018 Nov 20. e4032
    Jagannathan NR.
      In the last two decades, various in vivo MR methodologies have been evaluated for their potential in the study of cancer metabolism. During malignant transformation, metabolic alterations occur, leading to morphological and functional changes. Among various MR methods, in vivo MRS has been extensively used in breast cancer to study the metabolism of cells, tissues or whole organs. It provides biochemical information at the metabolite level. Altered choline, phospholipid and energy metabolism has been documented using proton (1 H), phosphorus (31 P) and carbon (13 C) isotopes. Increased levels of choline-containing compounds, phosphomonoesters and phosphodiesters in breast cancer, which are indicative of altered choline and phospholipid metabolism, have been reported using in vivo, in vitro and ex vivo NMR studies. These changes are reversed on successful therapy, which depends on the treatment regimen given. Monitoring the various tumor intermediary metabolic pathways using nuclear spin hyperpolarization of 13 C-labeled substrates by dynamic nuclear polarization has also been recently reported. Furthermore, the utility of various methods such as diffusion, dynamic contrast and perfusion MRI have also been evaluated to study breast tumor metabolism. Parameters such as tumor volume, apparent diffusion coefficient, volume transfer coefficient and extracellular volume ratio are estimated. These parameters provide information on the changes in tumor microstructure, microenvironment, abnormal vasculature, permeability and grade of the tumor. Such changes seen during cancer progression are due to alterations in the tumor metabolism, leading to changes in cell architecture. Due to architectural changes, the tissue mechanical properties are altered; this can be studied using magnetic resonance elastography, which measures the elastic properties of tissues. Moreover, these structural MRI methods can be used to investigate the effect of therapy-induced changes in tumor characteristics. This review discusses the potential of various in vivo MR methodologies in the study of breast cancer metabolism.
    Keywords:  MR elastography; MRI; MRS; breast cancer; diffusion MRI; dynamic contrast MRI; metabolism
    DOI:  https://doi.org/10.1002/nbm.4032
  55. Cell Physiol Biochem. 2018 Nov 22. 51(2): 854-870
    Riess C, Shokraie F, Classen CF, Kreikemeyer B, Fiedler T, Junghanss C, Maletzki C.
      Arginine auxotrophy occurs in certain tumor types and is usually caused by the silencing of argininosuccinate synthetase 1 or arginine lyase genes. Such tumors are often associated with an intrinsic chemoresistance and thus a poor prognosis. Arginine auxotrophy however renders these tumors vulnerable to treatment with arginine-degrading enzymes. Among the most frequently applied arginine-degrading agents are bacterial arginine deiminases (ADI). The anti-cancerous effects of ADI derived from different bacteria were extensively studied in numerous preclinical cell culture and xenograft models. Mycoplasma-derived ADI-PEG20 is most commonly used and is currently under clinical investigation as a single agent therapeutic as well as in combination with different antineoplastic compounds. Mechanistically, ADI is capable of reducing metabolic activity in tumor cells, contributing to autophagy, senescence and apoptosis in arginine auxotrophic cells. Although clinical trials are promising, the resistance development upon initial treatment response is an increasing challenge. Furthermore, interference of ADI with the tumor microenvironment is poorly understood. In the present review, we outline recent experimental ADI-based treatment approaches and their translation into the clinic. Furthermore, we summarize new insights into the molecular mechanisms underlying the anti-cancer effects of ADI that might facilitate the refinement of ADI-based combination therapy approaches.
    Keywords:  Arginine deiminase; Arginine-auxotrophy; Combination therapy; Therapy resistance; Tumor microenvironment
    DOI:  https://doi.org/10.1159/000495382