bims-mibica 2020-06-21 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2020–06–21
forty-one papers selected by
Kelsey Fisher-Wellman, East Carolina University

Targeting DGAT1 Ameliorates Glioblastoma by Increasing Fat Catabolism and Oxidative Stress.
Mitochondria in cancer.
Beyond the Warburg Effect: N-Myc Contributes to Metabolic Reprogramming in Cancer Cells.
Mitochondrial protein interaction landscape of SS-31.
Acute insulin deprivation results in altered mitochondrial substrate sensitivity conducive to greater fatty acid transport.
Mitochondria, mitophagy, and metabolic disease: towards assembling the puzzle.
Using flow cytometry for mitochondrial assays.
Statins reduce intratumor cholesterol affecting adrenocortical cancer growth.
Integrated Proteomic and N-Glycoproteomic Analyses of Human Breast Cancer.
Mitochondrial superoxide contributes to oxidative stress exacerbated by DNA damage response in RAD51-depleted ovarian cancer cells.
Thinking outside the nucleus: mitochondrial DNA copy number in health and disease.
Metabolic Syndrome Impairs 3D Mitochondrial Structure, Dynamics, and Function in Swine Mesenchymal Stem Cells.
A single session of physical activity restores the mitochondrial organization disrupted by obesity in skeletal muscle fibers.
Neutralizing mitochondrial ROS does not rescue muscle atrophy induced by hindlimb unloading in female mice.
New imidazoles cause cellular toxicity by impairing redox balance, mitochondrial membrane potential, and modulation of HIF-1α expression.
Mitochondria-adaptor TRAK1 promotes kinesin-1 driven transport in crowded environments.
Long-term high-fat feeding exacerbates short-term increases in adipose mitochondrial reactive oxygen species, without impairing mitochondrial respiration.
Low-intensity exercise stimulates bioenergetics and increases fat oxidation in mitochondria of blood mononuclear cells from sedentary adults.
Mitochondrial respiratory chain composition and organization in response to changing oxygen levels.
Plasma acylcarnitine levels increase with healthy aging.
The proteome landscape of the kingdoms of life.
KLF5 inhibits STAT3 activity and tumor metastasis in prostate cancer by suppressing IGF1 transcription cooperatively with HDAC1.
Clinical significance and biological mechanisms of glutathione S-transferase mu gene family in colon adenocarcinoma.
Differential effects of high fat diet-induced obesity on oocyte mitochondrial functions in inbred and outbred mice.
SLC25A11 serves as a novel prognostic biomarker in liver cancer.
How DNA methylation affects the Warburg effect.
Altered RNA Splicing by Mutant p53 Activates Oncogenic RAS Signaling in Pancreatic Cancer.
Quantitative proteomics reveals specific metabolic features of Acute Myeloid Leukemia stem cells.
Multi-omics analysis delineates the distinct functions of sub-cellular acetyl-CoA pools in Toxoplasma gondii.
Metabolic Fingerprinting Links Oncogenic PIK3CA with Enhanced Arachidonic Acid-Derived Eicosanoids.
Patient-Derived Ovarian Cancer Organoids Mimic Clinical Response and Exhibit Heterogeneous Inter- and Intrapatient Drug Responses.
The Role of Diet in Cancer Prevention and Chemotherapy Efficacy.
Homogeneous Oligomers of Pro-apoptotic BAX Reveal Structural Determinants of Mitochondrial Membrane Permeabilization.
Targeting Metabolism to Improve the Tumor Microenvironment for Cancer Immunotherapy.
MicroRNA-513a-3p regulates colorectal cancer cell metabolism via targeting hexokinase 2.
Down-Regulation of ZEB1 by miR-199a-3p Overexpression Restrains Tumor Stem-Like Properties and Mitochondrial Function of Non-Small Cell Lung Cancer.
Anticancer effect of physical activity is mediated by modulation of extracellular microRNA in blood.
Reclaiming Warburg: using developmental biology to gain insight into human metabolic diseases.
Ca2+ Fluxes and Cancer.
Generation of Hematopoietic-Like Stem Cells from Adult Human Peripheral Blood Following Treatment with Platelet-Derived Mitochondria.
PHGDH supports liver ceramide synthesis and sustains lipid homeostasis.

Cell Metab. 2020 Jun 09. pii: S1550-4131(20)30303-X. [Epub ahead of print]

Targeting DGAT1 Ameliorates Glioblastoma by Increasing Fat Catabolism and Oxidative Stress.

Xiang Cheng, Feng Geng, Meixia Pan, Xiaoning Wu, Yaogang Zhong, Chunyan Wang, Zhihua Tian, Chunming Cheng, Rui Zhang, Vinay Puduvalli, Craig Horbinski, Xiaokui Mo, Xianlin Han, Arnab Chakravarti, Deliang Guo.

  Glioblastoma (GBM), a mostly lethal brain tumor, acquires large amounts of free fatty acids (FAs) to promote cell growth. But how the cancer avoids lipotoxicity is unknown. Here, we identify that GBM upregulates diacylglycerol-acyltransferase 1 (DGAT1) to store excess FAs into triglycerides and lipid droplets. Inhibiting DGAT1 disrupted lipid homeostasis and resulted in excessive FAs moving into mitochondria for oxidation, leading to the generation of high levels of reactive oxygen species (ROS), mitochondrial damage, cytochrome c release, and apoptosis. Adding N-acetyl-cysteine or inhibiting FA shuttling into mitochondria decreased ROS and cell death induced by DGAT1 inhibition. We show in xenograft models that targeting DGAT1 blocked lipid droplet formation, induced tumor cell apoptosis, and markedly suppressed GBM growth. Together, our study demonstrates that DGAT1 upregulation protects GBM from oxidative damage and maintains lipid homeostasis by facilitating storage of excess FAs. Targeting DGAT1 could be a promising therapeutic approach for GBM.

Keywords:  DGAT1; ROS; acylcarnitine; fatty acids; glioblastoma; lipid droplets; lipotoxicity; mitochondria; oxidative stress; triglycerides

DOI:  https://doi.org/10.1016/j.cmet.2020.06.002
Cell Stress. 2020 May 11. 4(6): 114-146

Mitochondria in cancer.

Debora Grasso, Luca X Zampieri, Tânia Capelôa, Justine A Van de Velde, Pierre Sonveaux.

  The rediscovery and reinterpretation of the Warburg effect in the year 2000 occulted for almost a decade the key functions exerted by mitochondria in cancer cells. Until recent times, the scientific community indeed focused on constitutive glycolysis as a hallmark of cancer cells, which it is not, largely ignoring the contribution of mitochondria to the malignancy of oxidative and glycolytic cancer cells, being Warburgian or merely adapted to hypoxia. In this review, we highlight that mitochondria are not only powerhouses in some cancer cells, but also dynamic regulators of life, death, proliferation, motion and stemness in other types of cancer cells. Similar to the cells that host them, mitochondria are capable to adapt to tumoral conditions, and probably to evolve to 'oncogenic mitochondria' capable of transferring malignant capacities to recipient cells. In the wider quest of metabolic modulators of cancer, treatments have already been identified targeting mitochondria in cancer cells, but the field is still in infancy.

Keywords:  apoptosis; mitochondrial biogenesis; mitophagy; oxidative phosphorylation (OXPHOS); reactive oxygen species (ROS); tricarboxylic acid (TCA) cycle; tumor metabolism

DOI:  https://doi.org/10.15698/cst2020.06.221
Front Oncol. 2020 ;10 791

Beyond the Warburg Effect: N-Myc Contributes to Metabolic Reprogramming in Cancer Cells.

Go J Yoshida.

  Cancer cells generate large amounts of lactate derived from glucose regardless of the available oxygen level. Cancer cells finely control ATP synthesis by modulating the uptake of substrates and the activity of enzymes involved in aerobic glycolysis (Warburg effect), which enables them to adapt to the tumor microenvironment. However, increasing evidence suggests that mitochondrial metabolism, including the tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS), and glutaminolysis, is paradoxically activated in MYCN-amplified malignancies. Unlike non-amplified cells, MYCN-amplified cancer cells significantly promote OXPHOS-dependent ATP synthesis. Furthermore, tumor cells are differentially dependent on fatty acid β-oxidation (FAO) according to N-Myc status. Therefore, upregulation of FAO-associated enzymes is positively correlated with both N-Myc expression level and poor clinical outcome. This review explores therapeutic strategies targeting cancer stem-like cells for the treatment of tumors associated with MYCN amplification.

Keywords:  N-Myc; TCA cycle; acyclic retinoid; amino acid transporter; cancer stem-like cells; fatty acid β-oxidation; glutaminolysis; mitochondria

DOI:  https://doi.org/10.3389/fonc.2020.00791
Proc Natl Acad Sci U S A. 2020 Jun 17. pii: 202002250. [Epub ahead of print]

Mitochondrial protein interaction landscape of SS-31.

Juan D Chavez, Xiaoting Tang, Matthew D Campbell, Gustavo Reyes, Philip A Kramer, Rudy Stuppard, Andrew Keller, Huiliang Zhang, Peter S Rabinovitch, David J Marcinek, James E Bruce.

  Mitochondrial dysfunction underlies the etiology of a broad spectrum of diseases including heart disease, cancer, neurodegenerative diseases, and the general aging process. Therapeutics that restore healthy mitochondrial function hold promise for treatment of these conditions. The synthetic tetrapeptide, elamipretide (SS-31), improves mitochondrial function, but mechanistic details of its pharmacological effects are unknown. Reportedly, SS-31 primarily interacts with the phospholipid cardiolipin in the inner mitochondrial membrane. Here we utilize chemical cross-linking with mass spectrometry to identify protein interactors of SS-31 in mitochondria. The SS-31-interacting proteins, all known cardiolipin binders, fall into two groups, those involved in ATP production through the oxidative phosphorylation pathway and those involved in 2-oxoglutarate metabolic processes. Residues cross-linked with SS-31 reveal binding regions that in many cases, are proximal to cardiolipin-protein interacting regions. These results offer a glimpse of the protein interaction landscape of SS-31 and provide mechanistic insight relevant to SS-31 mitochondrial therapy.

Keywords:  aging; cross-linking; interactome; mitochondria

DOI:  https://doi.org/10.1073/pnas.2002250117
Am J Physiol Endocrinol Metab. 2020 Jun 16.

Acute insulin deprivation results in altered mitochondrial substrate sensitivity conducive to greater fatty acid transport.

Paula M Miotto, Heather L Petrick, Graham P Holloway.

  Type 1 and type 2 diabetes are both tightly associated with impaired glucose control. While both pathologies stem from different mechanisms, a reduction in insulin action coincides with drastic metabolic dysfunction in skeletal muscle and metabolic inflexibility. However, the underlying explanation for this response remains poorly understood, particularly since it is difficult to distinguish the role of attenuated insulin action from the detrimental effects of reactive lipid accumulation which impair mitochondrial function and promote reactive oxygen species (ROS) emission. We therefore utilized streptozotocin to examine the effects of acute insulin deprivation, in the absence of a high lipid / nutrient excess environment, on the regulation of mitochondrial substrate sensitivity and ROS emission. The ablation of insulin resulted in reductions in absolute mitochondrial oxidative capacity, ADP-supported respiration, and reduced the ability for malonyl-CoA to inhibit carnitine palmitoyl-transferase I (CPT-I) and suppress fatty acid-supported respiration. These bioenergetic responses coincided with increased mitochondrial derived H2O2 emission and lipid transporter content, independent of major mitochondrial substrate transporter proteins and enzymes involved in fatty acid oxidation. Together, these data suggest that attenuated/ablated insulin signalling does not affect mitochondrial ADP sensitivity, while the increased reliance on fatty acid oxidation in situations where insulin action is reduced may occur as a result of altered regulation of mitochondrial fatty acid transport through CPT-I.

Keywords:  ADP sensitivity; insulin; lipid metabolism; mitochondria; streptozotocin

DOI:  https://doi.org/10.1152/ajpendo.00495.2019
Cell Stress. 2020 May 14. 4(6): 147-150

Mitochondria, mitophagy, and metabolic disease: towards assembling the puzzle.

Zhiyong Chen, Marine Berquez, Alessandro Luciani.

  Dysregulation of the mitochondrial network in terminally differentiated cells contributes to a broad spectrum of disorders. Methylmalonic acidemia (MMA) is an autosomal recessive inborn error of intermediary metabolism caused by the deficiency of methylmalonyl-CoA mutase (MMUT) - a mitochondrial enzyme that mediates the degradation of certain amino acids and lipids. The loss of MMUT activity triggers an accumulation of toxic endogenous metabolites causing severe organ dysfunctions and life-threatening complications. How MMUT deficiency instigates mitochondrial distress and tissue damage remains poorly understood. Using cell and animal-based models, we recently discovered that MMUT deficiency disables the PINK1-induced translocation of PRKN/Parkin to MMA-damaged mitochondria, impeding their delivery and subsequent dismantling by macroautophagy/autophagy-lysosome degradation systems (Luciani et al. Nat Commun. 11(1):970). This promotes an accumulation of damaged and/or dysfunctional mitochondria that spark epithelial distress and tissue damage. Using a systems biology approach based on drug-disease network perturbation modeling, we predicted targetable pathways, whose modulation repairs mitochondrial dysfunctions in patient-derived kidney cells and ameliorates disease-relevant phenotypes in mmut-deficient zebrafish. These results unveil a link between primary MMUT deficiency, defective mitophagy, and cell distress, offering promising therapeutic avenues for MMA and other mitochondria-related diseases.

Keywords:  cell damage; inherited metabolic disorders; kidney tubule; metabolism; mitochondria; mitophagy; organelle quality control; oxidative stress

DOI:  https://doi.org/10.15698/cst2020.06.222
MethodsX. 2020 ;7 100938

Using flow cytometry for mitochondrial assays.

Lauar de Brito Monteiro, Gustavo Gastão Davanzo, Cristhiane Favero de Aguiar, Pedro M M Moraes-Vieira.

  The understanding of how different cell types adapt their metabolism in the face of challenges has been attracting the attention of researchers for many years. Recently, immunologists also started to focus on how the metabolism of immune cells can impact the way that immunity drives its responses. The presence of a pathogen or damage in a tissue changes severely the way that the immune cells need to respond. When activated, immune cells usually shift their metabolism from a high energy demanding status using mitochondria respiration to a glycolytic based rapid ATP production. The diminished amount of respiration leads to changes in the mitochondrial membrane potential and, consequently, generation of reactive oxygen species. Here, we show how flow cytometry can be used to track changes in mitochondrial mass, membrane potential and superoxide (ROS) production in live immune cells. ● This protocol suggests a quick way of evaluating mitochondrial fitness using flow cytometry. We propose using the probes MitoTraker Green and MitoTracker Red/ MitoSOX at the same time. This way, it is possible to evaluate different parameters of mitochondrial biology in living cells. ● Flow cytometry is a highly used tool by immunologists. With the advances of studies focusing on the metabolism of immune cells, a simplified application of flow cytometry for mitochondrial studies and screenings is a helpful clarifying method for immunology.

Keywords:  Immunometabolism; Metabolic reprogramming; Mitochondrial function; Mitochondrial membrane potential

DOI:  https://doi.org/10.1016/j.mex.2020.100938
Mol Cancer Ther. 2020 Jun 16. pii: molcanther.1063.2019. [Epub ahead of print]

Statins reduce intratumor cholesterol affecting adrenocortical cancer growth.

Francesca Trotta, Paola Avena, Adele Chimento, Vittoria Rago, Arianna De Luca, Sara Sculco, Marta Claudia Nocito, Rocco Malivindi, Francesco Fallo, Catia Pilon, Raffaele Pezzani, Francesco Massimo Lasorsa, Simona Nicole Barile, Luigi Palmieri, Antonio Marcondes Lerario, Vincenzo Pezzi, Ivan Casaburi, Rosa Sirianni.

Mitotane causes hypercholesterolemia in ACC patients. We suppose that cholesterol increases within the tumor and can be used to activate proliferative pathways. In this study, we used statins to decrease intratumor cholesterol and investigated the effects on ACC growth related to ERα action at the nuclear and mitochondrial levels. We first used microarray to investigate mitotane effect on genes involved in cholesterol homeostasis and evaluated their relationship with patients' survival in ACC TCGA. We then blocked cholesterol synthesis with simvastatin and determined the effects on H295R cell proliferation, estradiol production and ERα activity in vitro and in xenograft tumors. We found that mitotane increases intratumor cholesterol content and expression of genes involved in cholesterol homeostasis, among them INSIG, whose expression affects patients' survival. Treatment of H295R cells with simvastatin to block cholesterol synthesis decreased cellular cholesterol content and this affected cell viability. Simvastatin reduced estradiol production and decreased nuclear and mitochondrial ERα function. A mitochondrial target of ERα, the respiratory complex IV (COX IV) was reduced after simvastatin treatment, which profoundly affected mitochondrial respiration activating apoptosis. In vivo experiments confirmed the ability of simvastatin to reduce tumor volume and weight of grafted H295R cells, intratumor cholesterol content, Ki-67 and ERα, COX IV expression and activity and increase TUNEL positive cells. Collectively these data demonstrate that a reduction in intratumor cholesterol content prevents estradiol production, inhibits mitochondrial respiratory chain inducing apoptosis in ACC cells. Inhibition of mitochondrial respiration by simvastatin represents a novel strategy to counteract ACC growth.

DOI: https://doi.org/10.1158/1535-7163.MCT-19-1063
J Proteome Res. 2020 Jun 16.

Integrated Proteomic and N-Glycoproteomic Analyses of Human Breast Cancer.

Zhiyuan Wang, Hua Liu, Yu Yan, Xiangyun Yang, Yaoyang Zhang, Linshi Wu.

  Breast cancer is one of the most common cancers in women worldwide. In the past decades, many advances have been made in understanding and treating breast cancer. However, due to the highly heterogeneous nature of this disease, a precise characterization of breast cancer on the molecular level is of great importance but not yet readily available. In the present study, we systematically profiled proteomes and N-glycoproteomes of cancerous, paracancerous, and distal noncancerous tissues from patients with breast cancer. The data revealed distinct proteomic and N-glycoproteomic landscapes between different tissues, showing biological insights obtained from the two data sets were complementary. Specifically, the complement and angiogenesis pathways in the paracancerous tissues were activated. Taken together, the changes that occurred in paracancer tissue and N-glycoproteomics are important complements to the conventional proteomic analysis of cancer tissue. Their combination provides more precise and sensitive molecular correlates of breast cancer. Our data and strategy shed light on precisely defining breast cancer, providing valuable information for individual patient diagnosis and treatment. The MS data of this study have been deposited under the accession number IPX0001924000 at iProX.

Keywords:  N-glycosylation; breast cancer; precision medicine; proteomics

DOI:  https://doi.org/10.1021/acs.jproteome.0c00311
Redox Biol. 2020 Jun 08. pii: S2213-2317(20)30809-0. [Epub ahead of print]36 101604

Mitochondrial superoxide contributes to oxidative stress exacerbated by DNA damage response in RAD51-depleted ovarian cancer cells.

Limei Xu, Tingting Wu, Shihua Lu, Xiaohe Hao, Junchao Qin, Jing Wang, Xiyu Zhang, Qiao Liu, Beihua Kong, Yaoqin Gong, Zhaojian Liu, Changshun Shao.

  Ovarian cancer is the most lethal gynecological malignancy. Abnormal homologous recombination repair, high level of reactive oxygen species (ROS) and upregulation of antioxidant genes are characteristic features of ovarian cancer. However, the molecular mechanisms governing the redox homeostasis in ovarian cancer cells remain to be fully elucidated. We here demonstrated a critical role of RAD51, a protein essential for homologous recombination, in the maintenance of redox homeostasis. We found that RAD51 is overexpressed in high grade serous ovarian cancer and is associated with poor prognosis. Depletion or inhibition of RAD51 results in G2/M arrest, increased production of reactive oxygen species and accumulation of oxidative DNA damage. Importantly, antioxidant N-acetylcysteine (NAC) significantly attenuated the induction of DNA damage and the perturbation of proliferation caused by RAD51 depletion. We further demonstrated that RAD51 inhibition or depletion led to elevated production of mitochondrial superoxide and increased accumulation of mitochondria. Moreover, CHK1 activation is required for the G2/M arrest and the generation of mitochondrial stress in response to RAD51 depletion. Together, our results indicate that nuclear DNA damage caused by RAD51 depletion may trigger mitochondria-originated redox dysregulation. Our findings suggest that a vicious cycle of nuclear DNA damage, mitochondrial accumulation and oxidative stress may contribute to the tumor-suppressive effects of RAD51 depletion or inhibition.

Keywords:  CHK1; G2/M arrest; Mitochondria stress; Ovarian cancer; RAD51; Redox homeostasis

DOI:  https://doi.org/10.1016/j.redox.2020.101604
Mitochondrion. 2020 Jun 13. pii: S1567-7249(20)30065-9. [Epub ahead of print]

Thinking outside the nucleus: mitochondrial DNA copy number in health and disease.

Christina A Castellani, Ryan J Longchamps, Jing Sun, Eliseo Guallar, Dan E Arking.

  Mitochondrial DNA copy number (mtDNA-CN) is a biomarker of mitochondrial function and levels of mtDNA-CN have been reproducibly associated with overall mortality and a number of age-related diseases, including cardiovascular disease, chronic kidney disease, and cancer. Recent advancements in techniques for estimating mtDNA-CN, in particular the use of DNA microarrays and next-generation sequencing data, have led to the comprehensive assessment of mtDNA-CN across these and other diseases and traits. The importance of mtDNA-CN measures to disease and these advancing technologies suggest the potential for mtDNA-CN to be a useful biomarker in the clinic. While the exact mechanism(s) underlying the association of mtDNA-CN with disease remain to be elucidated, we review the existing literature which supports roles for inflammatory dynamics, immune function and alterations to cell signaling as consequences of variation in mtDNA-CN. We propose that future studies should focus on characterizing longitudinal, cell-type and cross-tissue profiles of mtDNA-CN as well as improving methods for measuring mtDNA-CN which will expand the potential for its use as a clinical biomarker.

Keywords:  clinical biomarker; complex disease; mitochondrial DNA; mtDNA

DOI:  https://doi.org/10.1016/j.mito.2020.06.004
Stem Cell Rev Rep. 2020 Jun 16.

Metabolic Syndrome Impairs 3D Mitochondrial Structure, Dynamics, and Function in Swine Mesenchymal Stem Cells.

Rahele A Farahani, Mohamed C Farah, Xiang-Yang Zhu, Hui Tang, Ishran M Saadiq, Lilach O Lerman, Alfonso Eirin.

  Transplantation of autologous mesenchymal stem cells (MSCs) is an effective therapy for several diseases. Mitochondria modulate several important aspects of MSC function, but might be damaged by comorbidities and cardiovascular risk factors. We hypothesized that metabolic syndrome (MetS) compromises 3D mitochondrial structure, dynamics, and function in swine adipose tissue-derived MSCs. Domestic pigs were fed a Lean or MetS diet (n = 6 each) for 16 weeks. MSCs were collected from subcutaneous abdominal fat and their mitochondria analyzed using state-of-the-art Serial Block Face Electron Microscopy and 3D reconstruction. Mitochondrial dynamics (fusion/fission) were assessed by mRNA sequencing and Western blotting, and bioenergetics by membrane potential (TMRE), cytochrome-c oxidase (COX)-IV activity, and Seahorse Analyzer. Expression of mitochondria-associated microRNAs (mitomiRs) was measured by quantitative polymerase chain reaction (qPCR). MetS pigs developed obesity, hypertension, insulin resistance, and hyperlipidemia. Mitochondrial density was similar between the groups, but 3D mitochondrial and matrix volumes were lower in MetS-MSCs versus Lean-MSCs. Mitochondrial fission was higher, but fusion lower in MetS-MSCs versus Lean-MSCs, as were membrane potential, COX-IV activity, and ATP production. Contrarily, expression of the mitomiRs miR15a, miR-137, and miR-181c, which target mitochondrial genes that support mitochondrial structure, energy pathways, and dynamics, was higher in MetS-MSCs compared to Lean-MSCs, suggesting a potential to modulate their expression. MetS damages MSC 3D mitochondrial structure, dynamics, and function, and may modulate genes encoding for mitochondrial proteins. These observations support development of mitoprotective strategies to preserve the regenerative potency of MSCs and their suitability for autologous transplantation in patients with MetS.

Keywords:  Mesenchymal stem cells; Metabolic syndrome; Mitochondria; Mitochondrial dynamics; microRNAs

DOI:  https://doi.org/10.1007/s12015-020-09988-3
Life Sci. 2020 Jun 13. pii: S0024-3205(20)30715-3. [Epub ahead of print]256 117965

A single session of physical activity restores the mitochondrial organization disrupted by obesity in skeletal muscle fibers.

Irais Rivera-Alvarez, Perla Pérez-Treviño, Héctor Chapoy-Villanueva, Jorge E Vela-Guajardo, Bianca Nieblas, Salvador Garza-González, Gerardo García-Rivas, Noemí García.

   BACKGROUND: Several studies have proved that physical activity (PA) regulates energetic metabolism associated with mitochondrial dynamics through AMPK activation in healthy subjects. Obesity, a condition that induces oxidative stress, mitochondrial dysfunction, and low AMPK activity leads to mitochondrial fragmentation. However, few studies describe the effect of PA on mitochondrial dynamics regulation in obesity.
AIM: The present study aimed to evaluate the effect of a single session of PA on mitochondrial dynamics regulation as well as its effect on mitochondrial function and organization in skeletal muscles of obese rats (Zucker fa/fa).
MAIN METHODS: Male Zucker lean and Zucker fa/fa rats aged 12 to 13 weeks were divided into sedentary and subjected-to-PA (single session swimming) groups. Gastrocnemius muscle was dissected into isolated fibers, mitochondria, mRNA, and total proteins for their evaluation.
KEY FINDINGS: The results showed that PA increased the Mfn-2 protein level in the lean and obese groups, whereas Drp1 levels decreased in the obese group. OMA1 protease levels increased in the lean group and decreased in the obese group. Additionally, AMPK analysis parameters (expression, protein level, and activity) did not increase in the obese group. These findings correlated with the partial restoration of mitochondrial function in the obese group, increasing the capacity to maintain the membrane potential after adding calcium as a stressor, and increasing the transversal organization level of the mitochondria analyzed in isolated fibers.
SIGNIFICANCE: These results support the notion that obese rats subjected to PA maintain mitochondrial function through mitochondrial fusion activation by an AMPK-independent mechanism.

Keywords:  AMPK; Metabolic syndrome; Mitochondria quality control; Mitochondrial dynamics; Oxidative stress

DOI:  https://doi.org/10.1016/j.lfs.2020.117965
J Appl Physiol (1985). 2020 Jun 18.

Neutralizing mitochondrial ROS does not rescue muscle atrophy induced by hindlimb unloading in female mice.

Hiroaki Eshima, Piyarat Siripoksup, Ziad S Mahmassani, Jordan M Johnson, Patrick J Ferrara, Anthony R P Verkerke, Anahy Salcedo, Micah J Drummond, Katsuhiko Funai.

  Excess reactive oxygen species (ROS) induced by physical inactivity is associated with muscle atrophy and muscle weakness. However, the role of mitochondrial ROS on disuse-induced muscle atrophy is not fully understood. The purpose of this study was to utilize a genetic strategy to examine the effect of neutralizing mitochondrial ROS on disuse-induced skeletal muscle atrophy. This was accomplished by placing wildtype (WT) and mitochondrial-targeted catalase expressing (MCAT) littermate mice on 7-days of hindlimb unloading. After assessment of body weight and composition, muscles were analyzed for individual muscle mass, force generating capacity, fiber-type, cross-sectional area, and mitochondrial phenotyping including H2O2 production. Despite a successful attenuation of mitochondrial ROS, MCAT mice were not protected from muscle atrophy. No differences were observed in body composition, lean mass, individual muscle masses, force-generating capacity, and muscle fiber cross-sectional area. These data suggest that neutralizing mitochondrial ROS is insufficient to suppress disuse-induced loss of skeletal muscle mass and contractile function.

Keywords:  Mitochondria; Oxidative stress; Reactive oxygen species; hindlimb-unloading; muscle atrophy

DOI:  https://doi.org/10.1152/japplphysiol.00456.2019
Biochem Biophys Res Commun. 2020 Aug 13. pii: S0006-291X(20)30967-0. [Epub ahead of print]529(1): 23-27

New imidazoles cause cellular toxicity by impairing redox balance, mitochondrial membrane potential, and modulation of HIF-1α expression.

Oluyomi Stephen Adeyemi, Abiodun Omokehinde Eseola, Winfried Plass, Chiagoziem A Otuechere, Tobiloba Christiana Elebiyo.

   BACKGROUND: Our previous reports demonstrated the prospects of a new series of imidazoles as a source of alternative anti-parasite treatments, thus warranting further studies that include toxicity profiling.
OBJECTIVE: In this study, we evaluated three imidazoles: bis-imidazole (compound 1), phenyl-substituted 1H-imidazole (compound 2), and thiopene-imidazole (compound 3) for cellular toxicity and possible mechanisms.
METHODS: The three (3) compounds were assessed for in vitro cytotoxic action. Additionally, we probed likely mechanistic actions of these imidazoles. Findings showed dose-dependent cellular toxicity by these imidazoles.
RESULTS: In the presence of antioxidant (Trolox), cytotoxicity was improved for compounds 2 and 3 but not for compound 1. Meantime, compound 7 promoted reactive oxygen species (ROS) production, which was abated in the presence of a standard antioxidant (Trolox). Additionally, the three (3) imidazoles impaired mitochondrial membrane potential (MMP). While MMP was not restored after treatment removal, the addition of antioxidant (Trolox) improved MMP for compounds 2 and 3 treatment. Additionally, compound 1 elevated expression of hypoxia-inducing factor 1-alpha (HIF-1α). This may not be unconnected with the capacity of compound 1 to cause oxidative stress.
CONCLUSION: We show evidence that supports the cytotoxic action of imidazoles involves likely impairment to redox balance and mitochondrial membrane potential. The findings help our understanding of the mechanistic action of these imidazoles in living cells, and altogether may boost their prospects as new and alternative anti-protozoans.

Keywords:  Cellular toxicity; Imidazole derivatives; Mechanism of action; Medicinal biochemistry; Medicinal chemistry

DOI:  https://doi.org/10.1016/j.bbrc.2020.05.059
Nat Commun. 2020 Jun 19. 11(1): 3123

Mitochondria-adaptor TRAK1 promotes kinesin-1 driven transport in crowded environments.

Verena Henrichs, Lenka Grycova, Cyril Barinka, Zuzana Nahacka, Jiri Neuzil, Stefan Diez, Jakub Rohlena, Marcus Braun, Zdenek Lansky.

Intracellular trafficking of organelles, driven by kinesin-1 stepping along microtubules, underpins essential cellular processes. In absence of other proteins on the microtubule surface, kinesin-1 performs micron-long runs. Under crowding conditions, however, kinesin-1 motility is drastically impeded. It is thus unclear how kinesin-1 acts as an efficient transporter in intracellular environments. Here, we demonstrate that TRAK1 (Milton), an adaptor protein essential for mitochondrial trafficking, activates kinesin-1 and increases robustness of kinesin-1 stepping on crowded microtubule surfaces. Interaction with TRAK1 i) facilitates kinesin-1 navigation around obstacles, ii) increases the probability of kinesin-1 passing through cohesive islands of tau and iii) increases the run length of kinesin-1 in cell lysate. We explain the enhanced motility by the observed direct interaction of TRAK1 with microtubules, providing an additional anchor for the kinesin-1-TRAK1 complex. Furthermore, TRAK1 enables mitochondrial transport in vitro. We propose adaptor-mediated tethering as a mechanism regulating kinesin-1 motility in various cellular environments.

DOI: https://doi.org/10.1038/s41467-020-16972-5
Am J Physiol Endocrinol Metab. 2020 Jun 16.

Long-term high-fat feeding exacerbates short-term increases in adipose mitochondrial reactive oxygen species, without impairing mitochondrial respiration.

Valerie Politis-Barber, Henver S Brunetta, Sabina Paglialunga, Heather L Petrick, Graham P Holloway.

  White adipose tissue (WAT) dysfunction in obesity is implicated in the onset of whole-body insulin resistance. Alterations in mitochondrial bioenergetics, namely impaired mitochondrial respiration and increased mitochondrial reactive oxygen species (mtROS) production, have been suggested to contribute to this metabolic dysregulation. However, techniques investigating mitochondrial function are classically normalized to tissue weight, which may be confounding when considering obesity-related adipocyte hypertrophy. Furthermore, the effect of long-term high-fat diet (HFD) on mtROS in WAT has yet to be elucidated. Therefore, we sought to determine the HFD-mediated temporal changes in mitochondrial respiration and mtROS emission in WAT. C57BL/6N mice received low-fat diet or HFD for 1 or 8 weeks and changes in inguinal WAT (iWAT) and epididymal WAT (eWAT) were assessed. While tissue weight-normalized mitochondrial respiration was reduced in iWAT following 8 weeks HFD-feeding, this effect was mitigated when adipocyte cell-size and/or number were considered. These data suggest HFD does not impair mitochondrial respiratory capacity per adipocyte within WAT. In support of this assertion, within eWAT compensatory increases in lipid-supported and maximal succinate-supported respiration occurred at 8-weeks despite cell hypertrophy and increases in WAT inflammation. Although these data suggest impairments in mitochondrial respiration do not contribute to HFD-mediated WAT phenotype, lipid-supported mtROS emission increased following 1-week HFD in eWAT, while both lipid and carbohydrate-supported mtROS were increased at 8 weeks in both depots. Combined, these data establish that while HFD does not impair adipocyte mitochondrial respiratory capacity, increased mtROS is an enduring physiological occurrence within WAT in HFD-induced obesity.

Keywords:  high-fat diet; insulin resistance; mitochondrial function; obesity; white adipose tissue

DOI:  https://doi.org/10.1152/ajpendo.00028.2020
Physiol Rep. 2020 Jun;8(12): e14489

Low-intensity exercise stimulates bioenergetics and increases fat oxidation in mitochondria of blood mononuclear cells from sedentary adults.

Edgars Liepinsh, Elina Makarova, Liga Plakane, Ilze Konrade, Kaspars Liepins, Melita Videja, Eduards Sevostjanovs, Solveiga Grinberga, Marina Makrecka-Kuka, Maija Dambrova.

   AIM: Exercise training induces adaptations in muscle and other tissue mitochondrial metabolism, dynamics, and oxidative phosphorylation capacity. Mitochondrial fatty acid oxidation was shown to be pivotal for the anti-inflammatory status of immune cells. We hypothesize that exercise training can exert effects influence mitochondrial fatty acid metabolism in peripheral blood mononuclear cells (PBMCs). The aim was to investigate the effect of exercise on the fatty acid oxidation-dependent respiration in PBMCs.
DESIGN: Twelve fasted or fed volunteers first performed incremental-load exercise tests to exhaustion on a cycle ergometer to determine the optimal workload ensuring maximal health benefits in volunteers with a sedentary lifestyle. In addition, the same volunteers performed 60 min of low-intensity constant-load exercise.
RESULTS: In the incremental-load exercise, the maximal whole-body fat oxidation rate measured by indirect calorimetry was reached at the fasted state already at a 50 W workload. At the 75-175 W workloads, the contribution of fat oxidation significantly decreased to only 11%, the heart rate increased to 185 BPM, and the study participants reached exhaustion. These results show that low-intensity exercise (50W) is optimal for maximal whole-body fat utilization. After low-intensity exercise, the ROUTINE mitochondrial respiration, as well as fatty acid oxidation-dependent respiration in PBMCs at LEAK and OXPHOS states, were significantly increased by 31%, 65%, and 76%, respectively. In addition, during 60 min of low-intensity (50W) exercise, a 2-fold higher lipolysis rate was observed and 13.5 ± 0.9 g of fat was metabolized, which was 57% more than the amount of fat that was metabolized during the incremental-load exercise.
CONCLUSIONS: In individuals with a sedentary lifestyle participating in a bicycle ergometry exercise program, maximal lipolysis and whole-body fat oxidation rate is reached in a fasted state during low-intensity exercise. For the first time, it was demonstrated that low-intensity exercise improves bioenergetics and increases fatty acid oxidation in PBMCs and may contribute to the anti-inflammatory phenotype.

Keywords:  exercise; fat metabolism; lipolysis; obesity; sedentary adults

DOI:  https://doi.org/10.14814/phy2.14489
J Life Sci (Westlake Village). 2020 Jun;2(2):

Mitochondrial respiratory chain composition and organization in response to changing oxygen levels.

Alba Timón-Gómez, Antoni Barrientos.

  Mitochondria are the major consumer of oxygen in eukaryotic cells, owing to the requirement of oxygen to generate ATP through the mitochondrial respiratory chain (MRC) and the oxidative phosphorylation system (OXPHOS). This aerobic energy transduction is more efficient than anaerobic processes such as glycolysis. Hypoxia, a condition in which environmental or intracellular oxygen levels are below the standard range, triggers an adaptive signaling pathway within the cell. When oxygen concentrations are low, hypoxia-inducible factors (HIFs) become stabilized and activated to mount a transcriptional response that triggers modulation of cellular metabolism to adjust to hypoxic conditions. Mitochondrial aerobic metabolism is one of the main targets of the hypoxic response to regulate its functioning and efficiency in the presence of decreased oxygen levels. During evolution, eukaryotic cells and tissues have increased the plasticity of their mitochondrial OXPHOS system to cope with metabolic needs in different oxygen contexts. In mammalian mitochondria, two factors contribute to this plasticity. First, several subunits of the multimeric MRC complexes I and IV exist in multiple tissue-specific and condition-specific isoforms. Second, the MRC enzymes can coexist organized as individual entities or forming supramolecular structures known as supercomplexes, perhaps in a dynamic manner to respond to environmental conditions and cellular metabolic demands. In this review, we will summarize the information currently available on oxygen-related changes in MRC composition and organization and will discuss gaps of knowledge and research opportunities in the field.

Keywords:  Hypoxia; MRC; Mitochondrial OXPHOS; hypoxia-inducible factors (HIFs)

DOI:  https://doi.org/10.36069/JoLS/20200601
Aging (Albany NY). 2020 Jun 16. 12

Plasma acylcarnitine levels increase with healthy aging.

Zachery R Jarrell, M Ryan Smith, Xin Hu, Michael Orr, Ken H Liu, Arshed A Quyyumi, Dean P Jones, Young-Mi Go.

  Acylcarnitines transport fatty acids into mitochondria and are essential for β-oxidation and energy metabolism. Decreased mitochondrial activity results in increased plasma acylcarnitines, and increased acylcarnitines activate proinflammatory signaling and associate with age-related disease. Changes in acylcarnitines associated with healthy aging, however, are not well characterized. In the present study, we examined the associations of plasma acylcarnitines with age (range: 20-90) in 163 healthy, non-diseased individuals from the predictive medicine research cohort (NCT00336570) and tested for gender-specific differences. The results show that long-chain and very long-chain acylcarnitines increased with age, while many odd-chain acylcarnitines decreased with age. Gender-specific differences were observed for several acylcarnitines, e.g., eicosadienoylcarnitine varied with age in males, and hydroxystearoylcarnitine varied in females. Metabolome-wide association study (MWAS) of age-associated acylcarnitines with all untargeted metabolic features showed little overlap between genders. These results show that plasma concentrations of acylcarnitines vary with age and gender in individuals selected for criteria of health. Whether these variations reflect mitochondrial dysfunction with aging, mitochondrial reprogramming in response to chronic environmental exposures, early pre-disease change, or an adaptive response to healthy aging, is unclear. The results highlight a potential utility for untargeted metabolomics research to elucidate gender-specific mechanisms of aging and age-related disease.

Keywords:  aging; carnitine; lipid metabolism; mitochondria

DOI:  https://doi.org/10.18632/aging.103462
Nature. 2020 Jun 17.

The proteome landscape of the kingdoms of life.

Johannes B Müller, Philipp E Geyer, Ana R Colaço, Peter V Treit, Maximilian T Strauss, Mario Oroshi, Sophia Doll, Sebastian Virreira Winter, Jakob M Bader, Niklas Köhler, Fabian Theis, Alberto Santos, Matthias Mann.

Proteins carry out the vast majority of functions in all biological domains, but for technological reasons their large-scale investigation has lagged behind the study of genomes. Since the first essentially complete eukaryotic proteome was reported1, advances in mass-spectrometry-based proteomics2 have enabled increasingly comprehensive identification and quantification of the human proteome3-6. However, there have been few comparisons across species7,8, in stark contrast with genomics initiatives9. Here we use an advanced proteomics workflow-in which the peptide separation step is performed by a microstructured and extremely reproducible chromatographic system-for the in-depth study of 100 taxonomically diverse organisms. With two million peptide and 340,000 stringent protein identifications obtained in a standardized manner, we double the number of proteins with solid experimental evidence known to the scientific community. The data also provide a large-scale case study for sequence-based machine learning, as we demonstrate by experimentally confirming the predicted properties of peptides from Bacteroides uniformis. Our results offer a comparative view of the functional organization of organisms across the entire evolutionary range. A remarkably high fraction of the total proteome mass in all kingdoms is dedicated to protein homeostasis and folding, highlighting the biological challenge of maintaining protein structure in all branches of life. Likewise, a universally high fraction is involved in supplying energy resources, although these pathways range from photosynthesis through iron sulfur metabolism to carbohydrate metabolism. Generally, however, proteins and proteomes are remarkably diverse between organisms, and they can readily be explored and functionally compared at www.proteomesoflife.org.

DOI: https://doi.org/10.1038/s41586-020-2402-x
Cell Death Dis. 2020 Jun 16. 11(6): 466

KLF5 inhibits STAT3 activity and tumor metastasis in prostate cancer by suppressing IGF1 transcription cooperatively with HDAC1.

Jian-Bin Ma, Ji-Yu Bai, Hai-Bao Zhang, Jing Jia, Qi Shi, Chao Yang, Xinyang Wang, Dalin He, Peng Guo.

KLF5 is frequently deleted and downregulated in prostate cancer, and recently it has been reported that KLF5 loss is enriched in the aggressive branches of prostate cancer evolution. However, why KLF5 loss is associated with prostate cancer aggressiveness is still not clear. Herein, we analyzed KLF5 expression in TCGA and GEO database, as well as prostate cancer tissue microarray, and found that KLF5 expression significantly decreased in prostate cancer accompanying with tumor progression; moreover, KLF5 downregulation was associated with shorter survival of patients. Interestingly, we also found that KLF5 expression was obviously lower in prostate cancer metastases than in localized tissues, indicating that KLF5 downregulation is associated with prostate cancer invasion and metastasis. To assess this effect of KLF5, we knocked down KLF5 in prostate cancer cells and found that KLF5 knockdown promoted invasive ability of prostate cancer cells in vitro and in vivo. Moreover, we found that KLF5 downregulation enhanced the expression of IGF1 and STAT3 phosphorylation, while block of IGF1 with antibody decreased the enhancement of STAT3 activity and prostate cancer cell invasive ability by KLF5 knockdown, indicating that KLF5 inhibits prostate cancer invasion through suppressing IGF1/STAT3 pathway. Mechanistically, we found that KLF5 interacted with deacetylase HDAC1 and KLF5 is necessary for the binding of HDAC1 on IGF1 promoter to suppress IGF1 transcription. Taken together, our results indicate that KLF5 could be an important suppressor of prostate cancer invasion and metastasis, because KLF5 could suppress the transcription of IGF1, a tumor cell autocrine cytokine, and its downstream cell signaling to inhibit cell invasive ability, and reveal a novel mechanism for STAT3 activation in prostate cancer. These findings may provide evidence for the precision medicine in prostate cancer.

DOI: https://doi.org/10.1038/s41419-020-2671-1
BMC Med Genet. 2020 Jun 15. 21(1): 130

Clinical significance and biological mechanisms of glutathione S-transferase mu gene family in colon adenocarcinoma.

Erna Guo, Haotang Wei, Xiwen Liao, Liuyu Wu, Xiaoyun Zeng.

   BACKGROUND: Colon adenocarcinoma (COAD) is the most common form of colon cancer. The glutathione S-transferase Mu (GSTM) gene belongs to the GST gene family, which functions in cell metabolism and detoxification. The relationship between GSTM and COAD and the underlying mechanism remain unknown.
METHODS: Data extracted from The Cancer Genome Atlas included mRNA expression and clinical information such as gender, age, and tumor stage. Prognostic values of GSTM genes were identified by survival analysis. Function and mechanism of prognostic GSTM genes were identified by gene set enrichment analysis. A nomogram was used to predict the contribution of risk factors to the outcome of COAD patients.
RESULTS: Low expression of GSTM1 and GSTM2 was related to favorable OS (adjusted P = 0.006, adjusted HR = 0.559, 95% CI = 0.367-0.849 and adjusted P = 0.002, adjusted HR = 0.519, 95% CI = 0.342-0.790, respectively) after adjusting for tumor stage. Enrichment analysis also showed that genes involved were related to cell cycle, metabolism, and detoxification processes, as well as the Wnt signaling and NF-κB pathways.
CONCLUSIONS: In conclusion, low expression of GSTM1 and GSTM2 were significantly associated with favorable prognosis in COAD. These two genes may serve as potential biomarkers of COAD prognosis.

Keywords:  Colon adenocarcinoma; Expression; GSTM; Prognosis; mRNA

DOI:  https://doi.org/10.1186/s12881-020-01066-2
Sci Rep. 2020 Jun 17. 10(1): 9806

Differential effects of high fat diet-induced obesity on oocyte mitochondrial functions in inbred and outbred mice.

Waleed F A Marei, Anouk Smits, Omnia Mohey-Elsaeed, Isabel Pintelon, Daisy Ginneberge, Peter E J Bols, Katrien Moerloose, Jo L M R Leroy.

Maternal obesity can cause reduced oocyte quality and subfertility. Mitochondrial dysfunction plays a central role here, and most often inbred mouse models are used to study these pathways. We hypothesized that the mouse genetic background can influence the impact of high fat diet (HFD)-induced obesity on oocyte quality. We compared the inbred C57BL/6 (B6) and the outbred Swiss strains after feeding a HFD for 13w. HFD-mice had increased body weight gain, hypercholesterolemia, and increased oocyte lipid droplet (LD) accumulation in both strains. LD distribution was strain-dependent. In Swiss mouse oocytes, HFD significantly increased mitochondrial inner membrane potential (MMP), reactive oxygen species concentrations, mitochondrial ultrastructural abnormalities (by 46.4%), and endoplasmic reticulum (ER) swelling, and decreased mtDNA copy numbers compared with Swiss controls (P < 0.05). Surprisingly, B6-control oocytes exhibited signs of cellular stress compared to the Swiss controls (P < 0.05); upregulated gene expression of ER- and oxidative stress markers, high mitochondrial ultrastructural abnormalities (48.6%) and ER swelling. Consequently, the HFD impact on B6 oocyte quality was less obvious, with 9% higher mitochondrial abnormalities, and no additive effect on MMP and stress marks compared to B6 control (P > 0.1). Interestingly, mtDNA in B6-HFD oocytes was increased suggesting defective mitophagy. In conclusion, we show evidence that the genetic background or inbreeding can affect mitochondrial functions in oocytes and may influence the impact of HFD on oocyte quality. These results should create awareness when choosing and interpreting data obtained from different mouse models before extrapolating to human applications.

DOI: https://doi.org/10.1038/s41598-020-66702-6
Sci Rep. 2020 Jun 18. 10(1): 9871

SLC25A11 serves as a novel prognostic biomarker in liver cancer.

Guoqiang Pan, Ruobing Wang, Shengnan Jia, Yanqing Li, Yan Jiao, Nan Liu.

Liver cancer is a disease with high mortality; it is often diagnosed at intermediate and advanced stages and has a high recurrence rate. ROS restriction and adequate energy supply play significant roles in liver cancer. SLC25A11, a member of the malate-aspartate shuttle (MAS), regulates electroneutral exchange between 2-oxoglutarate and other dicarboxylates. It transports glutathione (GSH) from the cytoplasm into mitochondria to maintain GSH levels to limit ROS production. Moreover, SLC25A11 is essential for ATP generation in cancers as it regulates NADH transportation from the cytoplasm to mitochondria. The purpose of this research was to investigate the prognostic value of SLC25A11 in liver cancer. The Cancer Genome Atlas database was used to analyze the levels of SLC25A11 in liver cancer. Fisher's exact and chi-square tests were used to evaluate the relationship between SLC25A11 expression and clinical characteristics. Finally, we explored the value of SLC25A11 in prognosis by Cox analysis and Kaplan-Meier curves. Our results revealed that SLC25A11 was downregulated in liver cancer compared to normal controls. Low expression of SLC25A11 was associated with clinical stage, vital status, histologic grade, overall survival (OS) and relapse-free survival (RFS). Liver cancer patients with low SLC25A11 expression had shorter OS and RFS than patients with high SLC25A11 expression. Multivariate analysis showed that the expression of SLC25A11 was an independent predictor of RFS and OS. In conclusion, this study identified that SLC25A11 serves as a new prognostic marker for liver cancer.

DOI: https://doi.org/10.1038/s41598-020-66837-6
Int J Biol Sci. 2020 ;16(12): 2029-2041

How DNA methylation affects the Warburg effect.

Xingxin Zhu, Zefeng Xuan, Jun Chen, Zequn Li, Shusen Zheng, Penghong Song.

  Significant enhancement of the glycolysis pathway is a major feature of tumor cells, even in the presence of abundant oxygen; this enhancement is known as the Warburg effect, and also called aerobic glycolysis. The Warburg effect was discovered nearly a hundred years ago, but its specific mechanism remains difficult to explain. DNA methylation is considered to be a potential trigger for the Warburg effect, as the two processes have many overlapping links during tumorigenesis. Based on a widely recognized potential mechanism of the Warburg effect, we here summarized the relationship between DNA methylation and the Warburg effect with regard to cellular energy metabolism factors, such as glycolysis related enzymes, mitochondrial function, glycolysis bypass pathways, the tumor oxygen sensing pathway and abnormal methylation conditions. We believe that clarifying the relationship between these different mechanisms may further help us understand how DNA methylation works on tumorigenesis and provide new opportunities for cancer therapy.

Keywords:  DNA methylation; aerobic glycolysis; mitochondria; reactive oxygen species; the Warburg effect

DOI:  https://doi.org/10.7150/ijbs.45420
Cancer Cell. 2020 Jun 02. pii: S1535-6108(20)30260-9. [Epub ahead of print]

Altered RNA Splicing by Mutant p53 Activates Oncogenic RAS Signaling in Pancreatic Cancer.

Luisa F Escobar-Hoyos, Alex Penson, Ram Kannan, Hana Cho, Chun-Hao Pan, Rohit K Singh, Lisa H Apken, G Aaron Hobbs, Renhe Luo, Nicolas Lecomte, Sruthi Babu, Fong Cheng Pan, Direna Alonso-Curbelo, John P Morris, Gokce Askan, Olivera Grbovic-Huezo, Paul Ogrodowski, Jonathan Bermeo, Joseph Saglimbeni, Cristian D Cruz, Yu-Jui Ho, Sharon A Lawrence, Jerry P Melchor, Grant A Goda, Karen Bai, Alessandro Pastore, Simon J Hogg, Srivatsan Raghavan, Peter Bailey, David K Chang, Andrew Biankin, Kenneth R Shroyer, Brian M Wolpin, Andrew J Aguirre, Andrea Ventura, Barry Taylor, Channing J Der, Daniel Dominguez, Daniel Kümmel, Andrea Oeckinghaus, Scott W Lowe, Robert K Bradley, Omar Abdel-Wahab, Steven D Leach.

  Pancreatic ductal adenocarcinoma (PDAC) is driven by co-existing mutations in KRAS and TP53. However, how these mutations collaborate to promote this cancer is unknown. Here, we uncover sequence-specific changes in RNA splicing enforced by mutant p53 which enhance KRAS activity. Mutant p53 increases expression of splicing regulator hnRNPK to promote inclusion of cytosine-rich exons within GTPase-activating proteins (GAPs), negative regulators of RAS family members. Mutant p53-enforced GAP isoforms lose cell membrane association, leading to heightened KRAS activity. Preventing cytosine-rich exon inclusion in mutant KRAS/p53 PDACs decreases tumor growth. Moreover, mutant p53 PDACs are sensitized to inhibition of splicing via spliceosome inhibitors. These data provide insight into co-enrichment of KRAS and p53 mutations and therapeutics targeting this mechanism in PDAC.

Keywords:  GAP17; GTPase signaling; KRAS; RNA splicing; SF3B1; hnRNPK; oncogenes; p53; pancreatic cancer; splicing inhibitors

DOI:  https://doi.org/10.1016/j.ccell.2020.05.010
Blood. 2020 Jun 18. pii: blood.2019003654. [Epub ahead of print]

Quantitative proteomics reveals specific metabolic features of Acute Myeloid Leukemia stem cells.

Simon Raffel, Daniel Klimmeck, Mattia Falcone, Aykut Demir, Alireza Pouya, Petra Zeisberger, Christoph Lutz, Marco Tinelli, Oliver Bischel, Lars Bullinger, Christian Thiede, Anne Flörcken, Jörg Westermann, Gerhard Ehninger, Anthony D Ho, Carsten Müller-Tidow, Zuguang Gu, Carl Herrmann, Jeroen Krijgsveld, Andreas Trumpp, Jenny Hansson.

Acute Myeloid Leukemia (AML) is characterized by the accumulation of clonal myeloid blast cells unable to differentiate into mature leukocytes. Chemotherapy induces remission in the majority of patients, but relapse rates are high and lead to poor clinical outcomes. Since this is primarily caused by chemotherapy-resistant leukemic stem cells (LSCs), it is essential to eradicate LSCs to improve patient survival. LSCs have predominantly been studied at the transcript level, thus lacking information about post-transcriptionally regulated genes and associated networks. Here we extend our previous report on LSC proteomes to healthy age-matched hematopoietic stem and progenitor cells (HSPCs) and correlate the proteomes to the corresponding transcriptomes. By comparing LSCs to leukemic blasts and healthy HSPCs, we validate candidate LSC markers and highlight novel and potentially targetable proteins that are absent or only lowly expressed in HSPCs. In addition, our data provide strong evidence that LSCs harbor a characteristic energy metabolism, adhesion molecule composition, as well as RNA processing properties. Furthermore, correlating proteome and transcript data of the same individual samples highlights the strength of proteome analyses, which are particularly potent in detecting alterations in metabolic pathways. In summary, our study provides a comprehensive proteomic and transcriptomic characterization of functionally validated LSCs, blasts and healthy HSPCs, representing a valuable resource helping to design LSC-directed therapies.

DOI: https://doi.org/10.1182/blood.2019003654
BMC Biol. 2020 Jun 16. 18(1): 67

Multi-omics analysis delineates the distinct functions of sub-cellular acetyl-CoA pools in Toxoplasma gondii.

Joachim Kloehn, Rebecca D Oppenheim, Ghizal Siddiqui, Pieter-Jan De Bock, Sunil Kumar Dogga, Yohann Coute, Mohamed-Ali Hakimi, Darren J Creek, Dominique Soldati-Favre.

   BACKGROUND: Acetyl-CoA is a key molecule in all organisms, implicated in several metabolic pathways as well as in transcriptional regulation and post-translational modification. The human pathogen Toxoplasma gondii possesses at least four enzymes which generate acetyl-CoA in the nucleo-cytosol (acetyl-CoA synthetase (ACS); ATP citrate lyase (ACL)), mitochondrion (branched-chain α-keto acid dehydrogenase-complex (BCKDH)) and apicoplast (pyruvate dehydrogenase complex (PDH)). Given the diverse functions of acetyl-CoA, we know very little about the role of sub-cellular acetyl-CoA pools in parasite physiology.
RESULTS: To assess the importance and functions of sub-cellular acetyl-CoA-pools, we measured the acetylome, transcriptome, proteome and metabolome of parasites lacking ACL/ACS or BCKDH. We demonstrate that ACL/ACS constitute a synthetic lethal pair. Loss of both enzymes causes a halt in fatty acid elongation, hypo-acetylation of nucleo-cytosolic and secretory proteins and broad changes in gene expression. In contrast, loss of BCKDH results in an altered TCA cycle, hypo-acetylation of mitochondrial proteins and few specific changes in gene expression. We provide evidence that changes in the acetylome, transcriptome and proteome of cells lacking BCKDH enable the metabolic adaptations and thus the survival of these parasites.
CONCLUSIONS: Using multi-omics and molecular tools, we obtain a global and integrative picture of the role of distinct acetyl-CoA pools in T. gondii physiology. Cytosolic acetyl-CoA is essential and is required for the synthesis of parasite-specific fatty acids. In contrast, loss of mitochondrial acetyl-CoA can be compensated for through metabolic adaptations implemented at the transcriptional, translational and post-translational level.

Keywords:  ATP citrate lyase (ACL); Acetyl-CoA; Acetyl-CoA synthetase (ACS); Acetylome; Branched-chain α-keto acid dehydrogenase-complex (BCKDH); Formate/nitrite transporter (FNT); Metabolism; Multi-omics; Phosphoenolpyruvate carboxykinase (PEPCK); Toxoplasma gondii

DOI:  https://doi.org/10.1186/s12915-020-00791-7
Cell. 2020 Jun 18. pii: S0092-8674(20)30686-3. [Epub ahead of print]

Metabolic Fingerprinting Links Oncogenic PIK3CA with Enhanced Arachidonic Acid-Derived Eicosanoids.

Nikos Koundouros, Evdoxia Karali, Aurelien Tripp, Adamo Valle, Paolo Inglese, Nicholas J S Perry, David J Magee, Sara Anjomani Virmouni, George A Elder, Adam L Tyson, Maria Luisa Dória, Antoinette van Weverwijk, Renata F Soares, Clare M Isacke, Jeremy K Nicholson, Robert C Glen, Zoltan Takats, George Poulogiannis.

  Oncogenic transformation is associated with profound changes in cellular metabolism, but whether tracking these can improve disease stratification or influence therapy decision-making is largely unknown. Using the iKnife to sample the aerosol of cauterized specimens, we demonstrate a new mode of real-time diagnosis, coupling metabolic phenotype to mutant PIK3CA genotype. Oncogenic PIK3CA results in an increase in arachidonic acid and a concomitant overproduction of eicosanoids, acting to promote cell proliferation beyond a cell-autonomous manner. Mechanistically, mutant PIK3CA drives a multimodal signaling network involving mTORC2-PKCζ-mediated activation of the calcium-dependent phospholipase A2 (cPLA2). Notably, inhibiting cPLA2 synergizes with fatty acid-free diet to restore immunogenicity and selectively reduce mutant PIK3CA-induced tumorigenicity. Besides highlighting the potential for metabolic phenotyping in stratified medicine, this study reveals an important role for activated PI3K signaling in regulating arachidonic acid metabolism, uncovering a targetable metabolic vulnerability that largely depends on dietary fat restriction.

Keywords:  PIK3CA; PKCζ; arachidonic acid; cPLA2; cancer metabolism; diet; eicosanoids; fat restriction; iKnife; mTORC2

DOI:  https://doi.org/10.1016/j.cell.2020.05.053
Cell Rep. 2020 Jun 16. pii: S2211-1247(20)30742-7. [Epub ahead of print]31(11): 107762

Patient-Derived Ovarian Cancer Organoids Mimic Clinical Response and Exhibit Heterogeneous Inter- and Intrapatient Drug Responses.

Chris Jenske de Witte, Jose Espejo Valle-Inclan, Nizar Hami, Kadi Lõhmussaar, Oded Kopper, Celien Philomena Henrieke Vreuls, Geertruida Nellie Jonges, Paul van Diest, Luan Nguyen, Hans Clevers, Wigard Pieter Kloosterman, Edwin Cuppen, Hugo Johannes Gerhardus Snippert, Ronald Peter Zweemer, Petronella Oda Witteveen, Ellen Stelloo.

  There remains an unmet need for preclinical models to enable personalized therapy for ovarian cancer (OC) patients. Here we evaluate the capacity of patient-derived organoids (PDOs) to predict clinical drug response and functional consequences of tumor heterogeneity. We included 36 whole-genome-characterized PDOs from 23 OC patients with known clinical histories. OC PDOs maintain the genomic features of the original tumor lesion and recapitulate patient response to neoadjuvant carboplatin/paclitaxel combination treatment. PDOs display inter- and intrapatient drug response heterogeneity to chemotherapy and targeted drugs, which can be partially explained by genetic aberrations. PDO drug screening identifies high responsiveness to at least one drug for 88% of patients. PDOs are valuable preclinical models that can provide insights into drug response for individual patients with OC, complementary to genetic testing. Generating PDOs of multiple tumor locations can improve clinical decision making and increase our knowledge of genetic and drug response heterogeneity.

Keywords:  WGS; chemotherapy; clinical response; drug screening; heterogeneity; organoids; ovarian cancer

DOI:  https://doi.org/10.1016/j.celrep.2020.107762
Annu Rev Nutr. 2020 Jun 16.

The Role of Diet in Cancer Prevention and Chemotherapy Efficacy.

Steven D Mittelman.

Despite great advances in treatment, cancer remains a leading cause of death worldwide. Diet can greatly impact health, while caloric restriction and fasting have putative benefits for disease prevention and longevity. Strong epidemiological associations exist between obesity and cancer, whereas healthy diets can reduce cancer risk. However, less is known about how diet might impact cancer once it has been diagnosed and particularly how diet can impact cancer treatment. In the present review, we discuss the links between obesity, diet, and cancer. We explore potential mechanisms by which diet can improve cancer outcomes, including through hormonal, metabolic, and immune/inflammatory effects, and present the limited clinical research that has been published in this arena. Though data are sparse, diet intervention may reduce toxicity, improve chemotherapy efficacy, and lower the risk of long-term complications in cancer patients. Thus, it is important that we understand and expand the science of this important but complex adjunctive cancer treatment strategy. Please see http://www.annualreviews.org/page/journal/pubdates for expected final online publication date for the Annual Review of Nutrition, Volume 40. 2020.

DOI: https://doi.org/10.1146/annurev-nutr-013120-041149
Mol Cell. 2020 Jun 09. pii: S1097-2765(20)30349-X. [Epub ahead of print]

Homogeneous Oligomers of Pro-apoptotic BAX Reveal Structural Determinants of Mitochondrial Membrane Permeabilization.

Zachary J Hauseman, Edward P Harvey, Catherine E Newman, Thomas E Wales, Joel C Bucci, Julian Mintseris, Devin K Schweppe, Liron David, Lixin Fan, Daniel T Cohen, Henry D Herce, Rida Mourtada, Yael Ben-Nun, Noah B Bloch, Scott B Hansen, Hao Wu, Steven P Gygi, John R Engen, Loren D Walensky.

  BAX is a pro-apoptotic protein that transforms from a cytosolic monomer into a toxic oligomer that permeabilizes the mitochondrial outer membrane. How BAX monomers assemble into a higher-order conformation, and the structural determinants essential to membrane permeabilization, remain a mechanistic mystery. A key hurdle has been the inability to generate a homogeneous BAX oligomer (BAXO) for analysis. Here, we report the production and characterization of a full-length BAXO that recapitulates physiologic BAX activation. Multidisciplinary studies revealed striking conformational consequences of oligomerization and insight into the macromolecular structure of oligomeric BAX. Importantly, BAXO enabled the assignment of specific roles to particular residues and α helices that mediate individual steps of the BAX activation pathway, including unexpected functionalities of BAX α6 and α9 in driving membrane disruption. Our results provide the first glimpse of a full-length and functional BAXO, revealing structural requirements for the elusive execution phase of mitochondrial apoptosis.

Keywords:  BAX; BCL-2 family; activation; alpha-helix; apoptosis; membrane permeabilization; mitochondria; monomer; oligomer; structure

DOI:  https://doi.org/10.1016/j.molcel.2020.05.029
Mol Cell. 2020 Jun 18. pii: S1097-2765(20)30355-5. [Epub ahead of print]78(6): 1019-1033

Targeting Metabolism to Improve the Tumor Microenvironment for Cancer Immunotherapy.

Jackie E Bader, Kelsey Voss, Jeffrey C Rathmell.

The growing field of immune metabolism has revealed promising indications for metabolic targets to modulate anti-cancer immunity. Combination therapies involving metabolic inhibitors with immune checkpoint blockade (ICB), chemotherapy, radiation, and/or diet now offer new approaches for cancer therapy. However, it remains uncertain how to best utilize these strategies in the context of the complex tumor microenvironment (TME). Oncogene-driven changes in tumor cell metabolism can impact the TME to limit immune responses and present barriers to cancer therapy. These changes also reveal opportunities to reshape the TME by targeting metabolic pathways to favor immunity. Here we explore current strategies that shift immune cell metabolism to pro-inflammatory states in the TME and highlight a need to better replicate physiologic conditions to select targets, clarify mechanisms, and optimize metabolic inhibitors. Unifying our understanding of these pathways and interactions within the heterogenous TME will be instrumental to advance this promising field and enhance immunotherapy.

DOI: https://doi.org/10.1016/j.molcel.2020.05.034
Exp Ther Med. 2020 Jul;20(1): 572-580

MicroRNA-513a-3p regulates colorectal cancer cell metabolism via targeting hexokinase 2.

Chen Li, Zhijin Yu, Jinpeng Ye.

  Disruption of cell metabolism is a hallmark of cancer cells. Accumulating evidence suggests that microRNAs (miRNAs/miRs) are involved in almost all physiological and pathological processes. The aberrant expression of miRNAs induces metabolic reprogramming in cancer cells and thus, promotes proliferation. In the current study, miR-513a-3p was identified as a significantly downregulated miRNA in colorectal cancer cells and tumors. Overexpression of miR-513a-3p in colorectal cancer cells inhibited proliferation and glycolysis. A well-documented metabolic regulator, hexokinase 2 (HK2), was predicted and validated HK2to be a target gene of miR-513a-3p in colorectal cancer cells. In addition, overexpression of HK2 reversed the miR-513a-3p mimic-induced inhibition of proliferation. The association between HK2 and miR-513a-3p was further observed in tumors collected from patients with colorectal cancer. The findings suggest that miR-513a-5p may inhibit glycolysis in colorectal cancer cells via repressing HK2 expression, indicating that miR-513a-5p may be a tumor suppressor in colorectal cancer.

Keywords:  colorectal cancer; hexokinase 2; microRNA-513a-3p

DOI:  https://doi.org/10.3892/etm.2020.8727
Onco Targets Ther. 2020 ;13 4607-4616

Down-Regulation of ZEB1 by miR-199a-3p Overexpression Restrains Tumor Stem-Like Properties and Mitochondrial Function of Non-Small Cell Lung Cancer.

Juan Bai, Wen-Yu Jiao.

   Objective: MicroRNA-199a-3p (miR-199a-3p or miR-199b-3p) targeting of 3'-UTR of ZEB1 was characterized as an important way to inhibit invasion and metastases in non-small cell lung cancer (NSCLC), one of the most common cancers around the world. Here we aimed to investigate the tumor-suppressive role of miR-199a-3p targeted ZEB1.
Materials and Methods: A549 cells were transfected with ZEB1 and/or miR-199a-3p. Then, tumor growth was investigated in xenograft mice. Stem-like property, proliferation and mitochondria injury were further validated in vitro.
Results: Overexpression of miR-199a-3p with premiRNAs significantly reduced tumor growth inhibited CD44 and Ki67 and increased Caspase-3 in A549 xenograft mice. Sphere formation and protein expression of stem-like markers showed that miR-199a-3p inhibited stemness of A549 cell. miR-199a-3p reduced proliferation of A549 cells, as showed with EdU staining and reduced expression of Ki67. Transfection of miR-199a-3p also promoted apoptosis, as indicated with increased apoptotic cells with flow cytometry, and increased cleaved Caspase-3/Caspase3 and Bcl-2/Bax. Apoptosis was further validated to be induced with mitochondria dysfunction, which indicated with JC-1 labeled loss of mitochondrial membrane potential, reduced activity of SOD, and increased MDA and LDH. All these effects were inverted with overexpression of ZEB1.
Conclusion: Altogether, the findings suggested that the up-regulation of miR-199a-3p significantly inhibited NSCLC growth in vivo, and reduced A549 cell proliferation and promoted mitochondrial-mediated apoptosis, through down-regulation of ZEB1. The findings supported ZEB1 down-expression with miR-199a-3p as a novel therapeutic target for NSCLC treatment.

Keywords:  ZEB1; lung cancer; miR-199a-3p; miR-199b-3p

DOI:  https://doi.org/10.2147/OTT.S244525
Oncotarget. 2020 Jun 02. 11(22): 2106-2119

Anticancer effect of physical activity is mediated by modulation of extracellular microRNA in blood.

Pulliero Alessandra, You Ming, Chaluvally-Raghavan Pradeep, Marengo Barbara, Domenicotti Cinzia, Banelli Barbara, Degan Paolo, Molfetta Luigi, Gianiorio Fabio, Izzotti Alberto.

  Epidemiological studies provide evidence that physical activity reduces the risk of cancer, particularly of breast cancer. However, little is known about the underlying molecular mechanisms as related to microRNAs. The goal of the herein presented study is to explore the involvement of miRNAs in beneficial effects exerted by physical activity in breast cancer prevention. Thirty subjects (mean age: 57.1 ± 14.7 years) underwent 45 minutes of treadmill walking under standardized conditions. The levels of extracellular miRNAs were evaluated in blood plasma before and after structured exercise by means of microarray analysis of 1,900 miRNAs identifying mostly modulated miRNAs. Structured exercise has been found to modulate the expression of 14 miRNAs involved in pathways relevant to cancer. The different expression of two miRNAs involved in breast cancer progression, i. e. up-regulation of miR-206 and down-regulation of anti-miR-30c, were the most striking effects induced by exercise. The biological effects of these miRNAs were investigated in MCF-7 human breast cancer cells. miR-206 transfection and anti-miR-30c silencing, inhibited cell growth and increased apoptosis of MCF-7 cells. Moreover, the combined use of the two miRNAs further enhanced apoptosis and induced growth arrest in the G1/S phase of cell cycle. Our results support that physical activity effectively change the expression of extracellular miRNAs. Specifically, miR-206 up-regulation and anti-miR-30c down-regulation act as suppressors in breast cancer cells. The evaluation of these miRNAs in blood can be used as non-invasive biomarkers for breast cancer prevention.

Keywords:  cancer prevention; carcinogenesis; circulating microRNAs; microRNA transfection; sports and exercise

DOI:  https://doi.org/10.18632/oncotarget.27609
Development. 2020 Jun 14. pii: dev189340. [Epub ahead of print]147(11):

Reclaiming Warburg: using developmental biology to gain insight into human metabolic diseases.

Daniela Drummond-Barbosa, Jason M Tennessen.

  Developmental biologists have frequently pushed the frontiers of modern biomedical research. From the discovery and characterization of novel signal transduction pathways to exploring the molecular underpinnings of genetic inheritance, transcription, the cell cycle, cell death and stem cell biology, studies of metazoan development have historically opened new fields of study and consistently revealed previously unforeseen avenues of clinical therapies. From this perspective, it is not surprising that our community is now an integral part of the current renaissance in metabolic research. Amidst the global rise in metabolic syndrome, the discovery of novel signaling roles for metabolites, and the increasing links between altered metabolism and many human diseases, we as developmental biologists can contribute skills and expertise that are uniquely suited for investigating the mechanisms underpinning human metabolic health and disease. Here, we summarize the opportunities and challenges that our community faces, and discuss how developmental biologists can make unique and valuable contributions to the field of metabolism and physiology.

Keywords:  Drosophila; Human disease; Inter-organ communication; Metabolism; Oogenesis; Warburg effect

DOI:  https://doi.org/10.1242/dev.189340
Mol Cell. 2020 Jun 18. pii: S1097-2765(20)30259-8. [Epub ahead of print]78(6): 1055-1069

Ca2+ Fluxes and Cancer.

Saverio Marchi, Carlotta Giorgi, Lorenzo Galluzzi, Paolo Pinton.

  Ca2+ ions are key second messengers in both excitable and non-excitable cells. Owing to the rather pleiotropic nature of Ca2+ transporters and other Ca2+-binding proteins, however, Ca2+ signaling has attracted limited attention as a potential target of anticancer therapy. Here, we discuss cancer-associated alterations of Ca2+ fluxes at specific organelles as we identify novel candidates for the development of drugs that selectively target Ca2+ signaling in malignant cells.

Keywords:  IP(3)R; MCU complex; ORAI; TRP channels; mitochondrial permeability transition; store-operated calcium entry

DOI:  https://doi.org/10.1016/j.molcel.2020.04.017
Int J Mol Sci. 2020 Jun 15. pii: E4249. [Epub ahead of print]21(12):

Generation of Hematopoietic-Like Stem Cells from Adult Human Peripheral Blood Following Treatment with Platelet-Derived Mitochondria.

Haibo Yu, Wei Hu, Xiang Song, Dante Descalzi-Montoya, Zheng Yang, Robert Korngold, Yong Zhao.

  Adult stem cells represent a potential source for cellular therapy to treat serious human diseases. We characterized the insulin-producing cells from adult peripheral blood (designated PB-IPC), which displayed a unique phenotype. Mitochondria are normally located in the cellular cytoplasm, where they generate ATP to power the cell's functions. Ex vivo and in vivo functional studies established that treatment with platelet-derived mitochondria can reprogram the transformation of adult PB-IPC into functional CD34+ hematopoietic stem cells (HSC)-like cells, leading to the production of blood cells such as T cells, B cells, monocytes/macrophages, granulocytes, red blood cells, and megakaryocytes (MKs)/platelets. These findings revealed a novel function of mitochondria in directly contributing to cellular reprogramming, thus overcoming the limitations and safety concerns of using conventional technologies to reprogram embryonic stem (ES) and induced pluripotent stem (iPS) cells in regenerative medicine.

Keywords:  PB-IPC; blood; differentiation; hematopoietic stem cells; mitochondria

DOI:  https://doi.org/10.3390/ijms21124249
Cancer Metab. 2020 ;8 6

PHGDH supports liver ceramide synthesis and sustains lipid homeostasis.

Yun Pyo Kang, Aimee Falzone, Min Liu, Paloma González-Sánchez, Bo-Hyun Choi, Jonathan L Coloff, James J Saller, Florian A Karreth, Gina M DeNicola.

   Background: d-3-phosphoglycerate dehydrogenase (PHGDH), which encodes the first enzyme in serine biosynthesis, is overexpressed in human cancers and has been proposed as a drug target. However, whether PHGDH is critical for the proliferation or homeostasis of tissues following the postnatal period is unknown.
Methods: To study PHGDH inhibition in adult animals, we developed a knock-in mouse model harboring a PHGDH shRNA under the control of a doxycycline-inducible promoter. With this model, PHGDH depletion can be globally induced in adult animals, while sparing the brain due to poor doxycycline delivery.
Results: We found that PHGDH depletion is well tolerated, and no overt phenotypes were observed in multiple highly proliferative cell compartments. Further, despite detectable knockdown and impaired serine synthesis, liver and pancreatic functions were normal. Interestingly, diminished PHGDH expression reduced liver serine and ceramide levels without increasing the levels of deoxysphingolipids. Further, liver triacylglycerol profiles were altered, with an accumulation of longer chain, polyunsaturated tails upon PHGDH knockdown.
Conclusions: These results suggest that dietary serine is adequate to support the function of healthy, adult murine tissues, but PHGDH-derived serine supports liver ceramide synthesis and sustains general lipid homeostasis.

Keywords:  Ceramide; Mouse model; PHGDH; Serine; Triacylglycerol

DOI:  https://doi.org/10.1186/s40170-020-00212-x