1
|
Perturbed Brain Glucose Metabolism Caused by Absent SIRT3 Activity. Cells 2021; 10:cells10092348. [PMID: 34571997 PMCID: PMC8469836 DOI: 10.3390/cells10092348] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 08/20/2021] [Accepted: 08/24/2021] [Indexed: 12/15/2022] Open
Abstract
Acetylation is a post-translational modification that regulates the activity of enzymes fundamentally involved in cellular and mitochondrial bioenergetic metabolism. NAD+ dependent deacetylase sirtuin 3 (SIRT3) is localized to mitochondria where it plays a key role in regulating acetylation of TCA cycle enzymes and the mitochondrial respiratory complexes. Although the SIRT3 target proteins in mitochondria have been identified, the effect of SIRT3 activity on mitochondrial glucose metabolism in the brain remains elusive. The impact of abolished SIRT3 activity on glucose metabolism was determined in SIRT3 knockout (KO) and wild type (WT) mice injected with [1,6-13C]glucose using ex vivo 13C-NMR spectroscopy. The 1H-NMR spectra and amino acid analysis showed no differences in the concentration of lactate, glutamate, alanine, succinate, or aspartate between SIRT3 KO and WT mice. However, glutamine, total creatine (Cr), and GABA were lower in SIRT3 KO brain. Incorporation of label from [1,6-13C]glucose metabolism into lactate or alanine was not affected in SIRT3 KO brain. However, the incorporation of the label into all isotopomers of glutamate, glutamine, GABA and aspartate was lower in SIRT3 KO brain, reflecting decreased activity of mitochondrial and TCA cycle metabolism in both neurons and astrocytes. This is most likely due to hyperacetylation of mitochondrial enzymes due to suppressed SIRT3 activity in the brain of SIRT3 KO mice. Thus, the absence of Sirt3 results in impaired mitochondrial oxidative energy metabolism and neurotransmitter synthesis in the brain. Since the SIRT3 activity is NAD+ dependent, these results might parallel changes in glucose metabolism under pathologic reduction in mitochondrial NAD+ pools.
Collapse
|
2
|
Ferreira GC, Karimi AJ, Waddell J, McKenna MC. Metabolism of [1,6- 13 C]glucose in the cerebellum of 18-day-old rats: Comparison with cerebral metabolism. J Neurochem 2021; 157:1946-1962. [PMID: 33619759 PMCID: PMC9733799 DOI: 10.1111/jnc.15326] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 02/15/2021] [Accepted: 02/17/2021] [Indexed: 02/06/2023]
Abstract
There is little information on metabolism in developing cerebellum despite the known importance of this region in cognition and motor tasks. Ex vivo 1 H- and 13 C-NMR spectroscopy were used to determine metabolism during late postnatal development in cerebellum and cerebrum from 18-day-old rat pups after intraperitoneal (i.p.) injection of [1,6-13 C]glucose. The concentration of several metabolites in cerebellum was distinctly different than cerebrum; alanine, glutamine, creatine and myo-inositol were higher in cerebellum than cerebrum, the concentrations of lactate, GABA, aspartate and N-acetylaspartate (NAA) were lower in cerebellum than in cerebrum, and levels of glutamate, succinate, choline and taurine were similar in both brain regions. The incorporation of label from the metabolism of [1,6-13 C]glucose into most isotopomers of glutamate (GLU), glutamine (GLN), GABA and aspartate was lower in cerebellum than in cerebrum. Incorporation of label into the C2 position of lactate via the pyruvate recycling pathway was found in both brain regions. The ratio of newly synthesized GLN/GLU was significantly higher in cerebellum than in cerebrum indicating relatively active metabolism via glutamine synthetase in cerebellar astrocytes at postnatal day 18. This is the first study to determine metabolism in the cerebellum and cerebrum of male and female rat brain.
Collapse
Affiliation(s)
- Gustavo C. Ferreira
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD USA 21201,Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Arman J. Karimi
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD USA 21201
| | - Jaylyn Waddell
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD USA 21201
| | - Mary C. McKenna
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD USA 21201,Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD USA
| |
Collapse
|
3
|
Abstract
Experiments in culture systems where one cell type is provided with abundant nutrients and oxygen have been used to inform much of our understanding of cancer metabolism. However, many differences have been observed between the metabolism of tumors and the metabolism of cancer cells grown in monoculture. These differences reflect, at least in part, the presence of nonmalignant cells in the tumor microenvironment and the interactions between those cells and cancer cells. However, less is known about how the metabolism of various tumor stromal cell types differs from that of cancer cells, and how this difference might inform therapeutic targeting of metabolic pathways. Emerging data have identified both cooperative and competitive relationships between different cell types in a tumor, and this review examines how four abundant stromal cell types in the tumor microenvironment, fibroblasts, T cells, macrophages, and endothelial cells, contribute to the metabolism of tumors.
Collapse
Affiliation(s)
- Allison N. Lau
- Koch Institute for Integrative Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;,
| | - Matthew G. Vander Heiden
- Koch Institute for Integrative Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;,
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA
| |
Collapse
|
4
|
Abstract
Glucose is the long-established, obligatory fuel for brain that fulfills many critical functions, including ATP production, oxidative stress management, and synthesis of neurotransmitters, neuromodulators, and structural components. Neuronal glucose oxidation exceeds that in astrocytes, but both rates increase in direct proportion to excitatory neurotransmission; signaling and metabolism are closely coupled at the local level. Exact details of neuron-astrocyte glutamate-glutamine cycling remain to be established, and the specific roles of glucose and lactate in the cellular energetics of these processes are debated. Glycolysis is preferentially upregulated during brain activation even though oxygen availability is sufficient (aerobic glycolysis). Three major pathways, glycolysis, pentose phosphate shunt, and glycogen turnover, contribute to utilization of glucose in excess of oxygen, and adrenergic regulation of aerobic glycolysis draws attention to astrocytic metabolism, particularly glycogen turnover, which has a high impact on the oxygen-carbohydrate mismatch. Aerobic glycolysis is proposed to be predominant in young children and specific brain regions, but re-evaluation of data is necessary. Shuttling of glucose- and glycogen-derived lactate from astrocytes to neurons during activation, neurotransmission, and memory consolidation are controversial topics for which alternative mechanisms are proposed. Nutritional therapy and vagus nerve stimulation are translational bridges from metabolism to clinical treatment of diverse brain disorders.
Collapse
Affiliation(s)
- Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences , Little Rock, Arkansas ; and Department of Cell Biology and Physiology, University of New Mexico , Albuquerque, New Mexico
| |
Collapse
|
5
|
Bonnet U, Bingmann D, Speckmann EJ, Wiemann M. Small intraneuronal acidification via short-chain monocarboxylates: First evidence of an inhibitory action on over-excited human neocortical neurons. Life Sci 2018; 204:65-70. [PMID: 29730171 DOI: 10.1016/j.lfs.2018.05.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 05/01/2018] [Accepted: 05/02/2018] [Indexed: 10/17/2022]
Abstract
AIMS In cortical mammalian neurons, small fluctuations of intracellular pH (pHi) play a crucial role for inter- and intracellular signaling as well as for cellular and synaptic plasticity. Yet, there have been no respective data about humans. Thus, we investigated the interrelation of pHi and excitability of human cortical neurons. MATERIALS AND METHODS Intracellular electrophysiological and pH-recordings were made in neurons in slices taken from brain tissue resected from the middle temporal gyrus of two male children (26 months and 35 months old) who suffered from pharmacotherapy-resistant temporal lobe epilepsy. To excite the tissue (n = 13), we used the 0-Mg2+/high-K+-in vitro epilepsy model producing robust epileptiform discharges (ED). To evoke an intracellular acidification (n = 12), we used the well-established propionate-model and applied 10 mM propionate to the bath solutions. In addition, we recorded the effects of other strongly related short-chain monocarboxylates (l-lactate (10 mM) and the ketone body DL-β-hydroxybutyrate (10 mM)) on ED and pHi. KEY FINDINGS The ED-frequency was reversibly reduced by propionate (n = 5), l-lactate (n = 5), or DL-β-hydroxybutyrate (n = 3), while the durations of EDs and their after-depolarizations increased. In parallel experiments, all three short-chain monocarboxylates (each n = 4) lowered the pHi of the neurons (n = 12) by 0.05-0.07 pH units which was temporally related to the reported changes in bioelectric activity. SIGNIFICANCE A mild drop of the intraneuronal pH was associated with the control of even over-excited human neocortical tissue. This is identical with prior observations in non-human mammalian cortical neurons. Possible implications for neuroplasticity and the treatment of neuropsychiatric disorders are discussed.
Collapse
Affiliation(s)
- Udo Bonnet
- Department of Psychiatry, Psychotherapy, and Psychosomatic Medicine, Evangelisches Krankenhaus Castrop-Rauxel, Academic Teaching Hospital of the University Duisburg-Essen, Castrop-Rauxel, Germany; Department of Psychiatry and Psychotherapy, Faculty of Medicine, LVR-Hospital Essen, University of Duisburg-Essen, Essen, Germany.
| | - Dieter Bingmann
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany
| | | | - Martin Wiemann
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany; IBE R&D gGmbH, Institute for Lung Health, D-48149 Münster, Germany
| |
Collapse
|
6
|
Fu Y, Liu S, Yin S, Niu W, Xiong W, Tan M, Li G, Zhou M. The reverse Warburg effect is likely to be an Achilles' heel of cancer that can be exploited for cancer therapy. Oncotarget 2017; 8:57813-57825. [PMID: 28915713 PMCID: PMC5593685 DOI: 10.18632/oncotarget.18175] [Citation(s) in RCA: 168] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 04/25/2017] [Indexed: 12/19/2022] Open
Abstract
Although survival outcomes of cancer patients have been improved dramatically via conventional chemotherapy and targeted therapy over the last decades, there are still some tough clinical challenges that badly needs to be overcome, such as anticancer drug resistance, inevitable recurrences, cancer progression and metastasis. Simultaneously, accumulated evidence demonstrates that aberrant glucose metabolism termed ‘the Warburg effect’ in cancer cell is closely associated with malignant phenotypes. In 2009, a novel ‘two-compartment metabolic coupling’ model, also named ‘the reverse Warburg effect’, was proposed and attracted lots of attention. Based on this new model, we consider whether this new viewpoint can be exploited for improving the existent anti-cancer therapeutic strategies. Our review focuses on the paradigm shift from ‘the Warburg effect’ to ‘the reverse Warburg effect’, the features and molecular mechanisms of ‘the reverse Warburg effect’, and then we discuss its significance in fundamental researches and clinical practice.
Collapse
Affiliation(s)
- Yaojie Fu
- The Key Laboratory of Carcinogenesis of The Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410078, P. R. China.,Cancer Research Institute, Central South University, Changsha, Hunan 410078, P. R. China.,Medical School of Xiangya, Central South University, Changsha, Hunan 410013, P. R. China
| | - Shanshan Liu
- The Key Laboratory of Carcinogenesis of The Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410078, P. R. China.,Cancer Research Institute, Central South University, Changsha, Hunan 410078, P. R. China.,Medical School of Xiangya, Central South University, Changsha, Hunan 410013, P. R. China
| | - Shanghelin Yin
- The Key Laboratory of Carcinogenesis of The Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410078, P. R. China.,Cancer Research Institute, Central South University, Changsha, Hunan 410078, P. R. China.,Medical School of Xiangya, Central South University, Changsha, Hunan 410013, P. R. China
| | - Weihong Niu
- The Key Laboratory of Carcinogenesis of The Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410078, P. R. China.,Cancer Research Institute, Central South University, Changsha, Hunan 410078, P. R. China
| | - Wei Xiong
- The Key Laboratory of Carcinogenesis of The Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410078, P. R. China.,Cancer Research Institute, Central South University, Changsha, Hunan 410078, P. R. China
| | - Ming Tan
- Mitchell Cancer Institute, University of South Alabama, Mobile, AL 36604, USA
| | - Guiyuan Li
- The Key Laboratory of Carcinogenesis of The Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410078, P. R. China.,Cancer Research Institute, Central South University, Changsha, Hunan 410078, P. R. China
| | - Ming Zhou
- The Key Laboratory of Carcinogenesis of The Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, Hunan 410078, P. R. China.,Cancer Research Institute, Central South University, Changsha, Hunan 410078, P. R. China
| |
Collapse
|
7
|
McNair LF, Kornfelt R, Walls AB, Andersen JV, Aldana BI, Nissen JD, Schousboe A, Waagepetersen HS. Metabolic Characterization of Acutely Isolated Hippocampal and Cerebral Cortical Slices Using [U-13C]Glucose and [1,2-13C]Acetate as Substrates. Neurochem Res 2016; 42:810-826. [DOI: 10.1007/s11064-016-2116-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 11/11/2016] [Accepted: 11/16/2016] [Indexed: 12/21/2022]
|
8
|
Brekke E, Morken TS, Walls AB, Waagepetersen H, Schousboe A, Sonnewald U. Anaplerosis for Glutamate Synthesis in the Neonate and in Adulthood. ADVANCES IN NEUROBIOLOGY 2016; 13:43-58. [PMID: 27885626 DOI: 10.1007/978-3-319-45096-4_3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A central task of the tricarboxylic acid (TCA, Krebs, citric acid) cycle in brain is to provide precursors for biosynthesis of glutamate, GABA, aspartate and glutamine. Three of these amino acids are the partners in the intricate interaction between astrocytes and neurons and form the so-called glutamine-glutamate (GABA) cycle. The ketoacids α-ketoglutarate and oxaloacetate are removed from the cycle for this process. When something is removed from the TCA cycle it must be replaced to permit the continued function of this essential pathway, a process termed anaplerosis. This anaplerotic process in the brain is mainly carried out by pyruvate carboxylation performed by pyruvate carboxylase. The present book chapter gives an introduction and overview into this carboxylation and additionally anaplerosis mediated by propionyl-CoA carboxylase under physiological conditions in the adult and in the developing rodent brain. Furthermore, examples are given about pathological conditions in which anaplerosis is disturbed.
Collapse
Affiliation(s)
- Eva Brekke
- Department of Pediatrics, Nordland Hospital Trust, Bodo, Norway
| | - Tora Sund Morken
- Department of Ophthalmology, Trondheim University Hospital, Trondheim, 7006, Norway.,Department of Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology (NTNU), Trondheim, 7489, Norway
| | - Anne B Walls
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, 2100, Denmark
| | - Helle Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, 2100, Denmark
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, 2100, Denmark
| | - Ursula Sonnewald
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, 2100, Denmark. .,Department of Neuroscience, Norwegian University of Science and Technology (NTNU), Postboks 8905, Trondheim, 7489, Norway.
| |
Collapse
|
9
|
Rowlands BD, Lau CL, Ryall JG, Thomas DS, Klugmann M, Beart PM, Rae CD. Silent information regulator 1 modulator resveratrol increases brain lactate production and inhibits mitochondrial metabolism, whereas SRT1720 increases oxidative metabolism. J Neurosci Res 2015; 93:1147-56. [PMID: 25677687 DOI: 10.1002/jnr.23570] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 01/16/2015] [Accepted: 01/16/2015] [Indexed: 12/26/2022]
Abstract
Silent information regulators (SIRTs) have been shown to deacetylate a range of metabolic enzymes, including those in glycolysis and the Krebs cycle, and thus alter their activity. SIRTs require NAD(+) for their activity, linking cellular energy status to enzyme activity. To examine the impact of SIRT1 modulation on oxidative metabolism, this study tests the effect of ligands that are either SIRT-activating compounds (resveratrol and SRT1720) or SIRT inhibitors (EX527) on the metabolism of (13)C-enriched substrates by guinea pig brain cortical tissue slices with (13)C and (1)H nuclear magnetic resonance spectroscopy. Resveratrol increased lactate labeling but decreased incorporation of (13)C into Krebs cycle intermediates, consistent with effects on AMPK and inhibition of the F0/F1-ATPase. By testing with resveratrol that was directly applied to astrocytes with a Seahorse analyzer, increased glycolytic shift and increased mitochondrial proton leak resulting from interactions of resveratrol with the mitochondrial electron transport chain were revealed. SRT1720, by contrast, stimulated incorporation of (13)C into Krebs cycle intermediates and reduced incorporation into lactate, although the inhibitor EX527 paradoxically also increased Krebs cycle (13)C incorporation. In summary, the various SIRT1 modulators show distinct acute effects on oxidative metabolism. The strong effects of resveratrol on the mitochondrial respiratory chain and on glycolysis suggest that caution should be used in attempts to increase bioavailability of this compound in the CNS.
Collapse
Affiliation(s)
- Benjamin D Rowlands
- Neuroscience Research Australia, Randwick, New South Wales, Australia.,Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Randwick, New South Wales, Australia
| | - Chew Ling Lau
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia
| | - James G Ryall
- Stem Cell Metabolism and Regenerative Medicine Group, Basic and Clinical Myology Laboratory, Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia
| | - Donald S Thomas
- Mark Wainwright Analytical Centre, The University of New South Wales, Randwick, New South Wales, Australia
| | - Matthias Klugmann
- Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Randwick, New South Wales, Australia
| | - Philip M Beart
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Randwick, New South Wales, Australia.,Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Randwick, New South Wales, Australia
| |
Collapse
|
10
|
El-Gebali S, Bentz S, Hediger MA, Anderle P. Solute carriers (SLCs) in cancer. Mol Aspects Med 2013; 34:719-34. [PMID: 23506905 DOI: 10.1016/j.mam.2012.12.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 12/13/2012] [Indexed: 12/26/2022]
Abstract
During tumor progression cells acquire an altered metabolism, either as a cause or as a consequence of an increased need of energy and nutrients. All four major classes of macromolecules are affected: carbohydrates, proteins, lipids and nucleic acids. As a result of the changed needs, solute carriers (SLCs) which are the major transporters of these molecules are differently expressed. This renders them important targets in the treatment of cancer. Blocking or activating SLCs is one possible therapeutic strategy. For example, some SLCs are upregulated in tumor cells due to the increased demand for energy and nutritional needs. Thus, blocking them and turning off the delivery of fuel or nutrients could be one way to interfere with tumor progression. Specific drug delivery to cancer cells via transporters is another approach. Some SLCs are also interesting as chemosensitizing targets because blocking or activating them may result in an altered response to chemotherapy. In this review we summarize the roles of SLCs in cancer therapy and specifically their potential as direct or indirect targets, as drug carriers or as chemosensitizing targets.
Collapse
Affiliation(s)
- Sara El-Gebali
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | | | | | | |
Collapse
|
11
|
Metabolism, Compartmentation, Transport and Production of Acetate in the Cortical Brain Tissue Slice. Neurochem Res 2012; 37:2541-53. [DOI: 10.1007/s11064-012-0847-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 07/12/2012] [Accepted: 07/13/2012] [Indexed: 10/28/2022]
|
12
|
Metabolic targeting of lactate efflux by malignant glioma inhibits invasiveness and induces necrosis: an in vivo study. Neoplasia 2011; 13:620-32. [PMID: 21750656 DOI: 10.1593/neo.11134] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Revised: 05/06/2011] [Accepted: 05/12/2011] [Indexed: 11/18/2022] Open
Abstract
Glioblastoma multiforme (GBM) are the most malignant among brain tumors. They are frequently refractory to chemotherapy and radiotherapy with mean patient survival of approximately 6 months, despite surgical intervention. The highly glycolytic nature of glioblastomas describes their propensity to metabolize glucose to lactic acid at an elevated rate. To survive, GBMs efflux lactic acid to the tumor microenvironment through transmembrane transporters denoted monocarboxylate transporters (MCTs). We hypothesized that inhibition of MCT function would impair the glycolytic metabolism and affect both glioma invasiveness and survival. We examined the effect on invasiveness with α-cyano-4-hydroxy-cinnamic acid (ACCA, 4CIN, CHCA), a small-molecule inhibitor of lactate transport, through Matrigel-based and organotypic (brain) slice culture invasive assays using U87-MG and U251-MG glioma cells. We then conducted studies in immunodeficient rats by stereotaxic intracranial implantation of the glioma cells followed by programmed orthotopic application of ACCA through osmotic pumps. Effect on the implanted tumor was monitored by small-animal magnetic resonance imaging. Our assays indicated that glioma invasion was markedly impaired when lactate efflux was inhibited. Convection-enhanced delivery of inhibitor to the tumor bed caused tumor necrosis, with 50% of the animals surviving beyond the experimental end points (3 months after inhibitor exhaustion). Most importantly, control animals did not display any adverse neurologic effects during orthotopic administration of ACCA to brain through programmed delivery. These results indicate the clinical potential of targeting lactate efflux in glioma through delivery of small-molecule inhibitors of MCTs either to the tumor bed or to the postsurgical resection cavity.
Collapse
|
13
|
Rat brain slices oxidize glucose at high rates: a (13)C NMR study. Neurochem Int 2011; 59:1145-54. [PMID: 22067134 DOI: 10.1016/j.neuint.2011.10.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 10/11/2011] [Accepted: 10/21/2011] [Indexed: 11/24/2022]
Abstract
Since glucose is the main cerebral substrate, we have characterized the metabolism of various (13)C glucose isotopomers in rat brain slices. For this, we have used our cellular metabolomic approach that combines enzymatic and carbon 13 NMR techniques with mathematical models of metabolic pathways. We identified the fate and the pathways of the conversion of glucose carbons into various products (pyruvate, lactate, alanine, aspartate, glutamate, GABA, glutamine and CO(2)) and determined absolute fluxes through pathways of glucose metabolism. After 60 min of incubation, lactate and CO(2) were the main end-products of the metabolism of glucose which was avidly metabolized by the slices. Lactate was also used at high rates by the slices and mainly converted into CO(2). High values of flux through pyruvate carboxylase, which were similar with glucose and lactate as substrate, were observed. The addition of glutamine, but not of acetate, stimulated pyruvate carboxylation, the conversion of glutamate into succinate and fluxes through succinate dehydrogenase, malic enzyme, glutamine synthetase and aspartate aminotransferase. It is concluded that, unlike brain cells in culture, and consistent with high fluxes through PDH and enzymes of the tricarboxylic acid cycle, rat brain slices oxidized both glucose and lactate at high rates.
Collapse
|
14
|
The inhibition of monocarboxylate transporter 2 (MCT2) by AR-C155858 is modulated by the associated ancillary protein. Biochem J 2010; 431:217-25. [PMID: 20695846 PMCID: PMC2947196 DOI: 10.1042/bj20100890] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In mammalian cells, MCTs (monocarboxylate transporters) require association with an ancillary protein to enable plasma membrane expression of the active transporter. Basigin is the preferred binding partner for MCT1, MCT3 and MCT4, and embigin for MCT2. In rat and rabbit erythrocytes, MCT1 is associated with embigin and basigin respectively, but its sensitivity to inhibition by AR-C155858 was found to be identical. Using RT (reverse transcription)–PCR, we have shown that Xenopus laevis oocytes contain endogenous basigin, but not embigin. Co-expression of exogenous embigin was without effect on either the expression of MCT1 or its inhibition by AR-C155858. In contrast, expression of active MCT2 at the plasma membrane of oocytes was significantly enhanced by co-expression of exogenous embigin. This additional transport activity was insensitive to inhibition by AR-C155858 unlike that by MCT2 expressed with endogenous basigin that was potently inhibited by AR-C155858. Chimaeras and C-terminal truncations of MCT1 and MCT2 were also expressed in oocytes in the presence and absence of exogenous embigin. L-Lactate Km values for these constructs were determined and revealed that the TM (transmembrane) domains of an MCT, most probably TM7–TM12, but not the C-terminus, are the major determinants of L-lactate affinity, whereas the associated ancillary protein has little or no effect. Inhibitor titrations of lactate transport by these constructs indicated that embigin modulates MCT2 sensitivity to AR-C155858 through interactions with both the intracellular C-terminus and TMs 3 and 6 of MCT2. The C-terminus of MCT2 was found to be essential for its expression with endogenous basigin.
Collapse
|
15
|
Sonnewald U, Rae C. Pyruvate carboxylation in different model systems studied by (13)C MRS. Neurochem Res 2010; 35:1916-21. [PMID: 20842423 PMCID: PMC3002159 DOI: 10.1007/s11064-010-0257-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2010] [Indexed: 11/17/2022]
Abstract
Pyruvate carboxylation is of great importance in the brain since it is responsible for adding net carbons to the tricarboxylic acid cycle following removal of carbon backbone for synthesis of the two most abundant neurotransmitters, glutamate and GABA. Despite having such a pivotal role, there is still much uncertainty in the exact metabolic details about where and how this carbon is returned. Pyruvate carboxylation has been studied in various model systems of the brain and 13C magnetic resonance spectroscopy is an excellent tool for doing this. This review will focus on results dealing with the extent and cellular location of pyruvate carboxylation and its role in pathophysiology and concludes that pyruvate carboxylation is an extraordinarily important predominantly astrocytic pathway which plays a pivotal part in a number of diseases.
Collapse
Affiliation(s)
- Ursula Sonnewald
- Department of Neuroscience, Norwegian University of Science and Technology, 7489 Trondheim, Norway.
| | | |
Collapse
|
16
|
AR-C155858 is a potent inhibitor of monocarboxylate transporters MCT1 and MCT2 that binds to an intracellular site involving transmembrane helices 7-10. Biochem J 2010; 425:523-30. [PMID: 19929853 PMCID: PMC2811425 DOI: 10.1042/bj20091515] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In the present study we characterize the properties of the potent MCT1 (monocarboxylate transporter 1) inhibitor AR-C155858. Inhibitor titrations of L-lactate transport by MCT1 in rat erythrocytes were used to determine the Ki value and number of AR-C155858-binding sites (Et) on MCT1 and the turnover number of the transporter (kcat). Derived values were 2.3±1.4 nM, 1.29±0.09 nmol per ml of packed cells and 12.2±1.1 s−1 respectively. When expressed in Xenopus laevis oocytes, MCT1 and MCT2 were potently inhibited by AR-C155858, whereas MCT4 was not. Inhibition of MCT1 was shown to be time-dependent, and the compound was also active when microinjected, suggesting that AR-C155858 probably enters the cell before binding to an intracellular site on MCT1. Measurement of the inhibitor sensitivity of several chimaeric transporters combining different domains of MCT1 and MCT4 revealed that the binding site for AR-C155858 is contained within the C-terminal half of MCT1, and involves TM (transmembrane) domains 7–10. This is consistent with previous data identifying Phe360 (in TM10) and Asp302 plus Arg306 (TM8) as key residues in substrate binding and translocation by MCT1. Measurement of the Km values of the chimaeras for L-lactate and pyruvate demonstrate that both the C- and N-terminal halves of the molecule influence transport kinetics consistent with our proposed molecular model of MCT1 and its translocation mechanism that requires Lys38 in TM1 in addition to Asp302 and Arg306 in TM8 [Wilson, Meredith, Bunnun, Sessions and Halestrap (2009) J. Biol. Chem. 284, 20011–20021].
Collapse
|