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Monnerie H, Romer M, Roth LM, Long C, Millar JS, Jordan-Sciutto KL, Grinspan JB. Inhibition of lipid synthesis by the HIV integrase strand transfer inhibitor elvitegravir in primary rat oligodendrocyte cultures. Front Mol Neurosci 2023; 16:1323431. [PMID: 38146334 PMCID: PMC10749327 DOI: 10.3389/fnmol.2023.1323431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 11/22/2023] [Indexed: 12/27/2023] Open
Abstract
Combined antiretroviral therapy (cART) has greatly decreased mortality and morbidity among persons with HIV; however, neurologic impairments remain prevalent, in particular HIV-associated neurocognitive disorders (HANDs). White matter damage persists in cART-treated persons with HIV and may contribute to neurocognitive dysfunction as the lipid-rich myelin membrane of oligodendrocytes is essential for efficient nerve conduction. Because of the importance of lipids to proper myelination, we examined the regulation of lipid synthesis in oligodendrocyte cultures exposed to the integrase strand transfer inhibitor elvitegravir (EVG), which is administered to persons with HIV as part of their initial regimen. We show that protein levels of genes involved in the fatty acid pathway were reduced, which correlated with greatly diminished de novo levels of fatty acid synthesis. In addition, major regulators of cellular lipid metabolism, the sterol regulatory element-binding proteins (SREBP) 1 and 2, were strikingly altered following exposure to EVG. Impaired oligodendrocyte differentiation manifested as a marked reduction in mature oligodendrocytes. Interestingly, most of these deleterious effects could be prevented by adding serum albumin, a clinically approved neuroprotectant. These new findings, together with our previous study, strengthen the possibility that antiretroviral therapy, at least partially through lipid dysregulation, may contribute to the persistence of white matter changes observed in persons with HIV and that some antiretrovirals may be preferable as life-long therapy.
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Affiliation(s)
- Hubert Monnerie
- Department of Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Micah Romer
- Department of Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Lindsay M. Roth
- Department of Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Caela Long
- Department of Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - John S. Millar
- Institute of Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA, United States
| | - Kelly L. Jordan-Sciutto
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Judith B. Grinspan
- Department of Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
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Dutt V, Srivastava S. Novel quantitative insights into carbon sources for synthesis of poly hydroxybutyrate in Synechocystis PCC 6803. PHOTOSYNTHESIS RESEARCH 2018; 136:303-314. [PMID: 29124651 DOI: 10.1007/s11120-017-0464-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 11/01/2017] [Indexed: 05/11/2023]
Abstract
Many freshwater cyanobacteria accumulate polyhydroxybutyrate (PHB) under nitrogen or phosphorus deprivation. While prior literature has shed lights on transcriptomic and metabolomic changes in the model cyanobacterium Synechocystis PCC 6803 cells, the quantitative contributions of the newly fixed carbon following nitrogen deprivation or the externally added acetate to PHB synthesis are not clear. Similarly, it is not clear how photomixotrophy affects precursor contributions. In this study, we show that (i) the pre-growth mode (photoautotrophic or photomixotrophic), while significantly impacting glycogen levels, does not have any significant effect on PHB levels, (ii) the carbon fixed following nitrogen deprivation contributes 26% of C for PHB synthesis in photoautotrophically pre-grown cells and its contribution to the PHB synthesis goes down with the addition of acetate at the resuspension phase or with photomixotrophic pre-growth, (iii) the acetate added at the start of nitrogen deprivation, doubles the intracellular PHB levels and contributes 44-48% to PHB synthesis and this value is not greatly affected by how the cells were pre-grown. Indirectly, the labeling studies also show that the intracellular C recycling is the most important source of precursors for PHB synthesis, contributing about 74-87% of the C for PHB synthesis in the absence of acetate. The addition of acetate significantly reduces its contribution. In photoautotrophic pre-growth followed by acetate addition under nitrogen starvation, the contribution of intracellular C reduces to about 34%. Thus, our study provides several novel quantitative insights on how prior nutritional status affects the precursor contributions for PHB synthesis.
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Affiliation(s)
- Vaishali Dutt
- Systems Biology for Biofuels Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, 110067, India
| | - Shireesh Srivastava
- Systems Biology for Biofuels Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, 110067, India.
- DBT-ICGEB Center for Advanced Bioenergy Research, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.
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Egnatchik RA, DeBerardinis RJ. Liposuction: Extracellular Fat Removal Promotes Proliferation. Cell Chem Biol 2017; 23:431-2. [PMID: 27105278 DOI: 10.1016/j.chembiol.2016.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In this issue of Cell Chemical Biology, Yao et al. (2016) investigate the makeup of lipid membranes of both cancer and non-transformed cells to reveal that doubling cells preferentially use exogenous fatty acids over de novo synthesis to proliferate.
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Affiliation(s)
- Robert A Egnatchik
- Children's Medical Center Research Institute at the University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA.
| | - Ralph J DeBerardinis
- Children's Medical Center Research Institute at the University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA.
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Ray U, Roy SS. Aberrant lipid metabolism in cancer cells - the role of oncolipid-activated signaling. FEBS J 2017; 285:432-443. [PMID: 28971574 DOI: 10.1111/febs.14281] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/25/2017] [Accepted: 09/26/2017] [Indexed: 12/27/2022]
Abstract
Metabolic activity of malignant cells is very different from that of their nontransformed equivalents, which establishes metabolic reprogramming as an important hallmark of every transformed cell. In particular, the current arena of research in this field aims to understand the regulatory effect of oncogenic signaling on metabolic rewiring in transformed cells in order to exploit this for therapeutic benefit. Alterations in lipid metabolism are one of the main aspects of metabolic rewiring of transformed cells. Up-regulation of several lipogenic enzymes has been reported to be a characteristic of various cancer types. Lysophosphatidic acid (LPA), a simple byproduct of the lipid biosynthesis pathway, has gained immense importance due to its elevated level in several cancers and associated growth-promoting activity. Importantly, a current study revealed its role in increased de novo lipid synthesis through up-regulation of sterol regulatory element-binding protein 1, a master regulator of lipid metabolism. This review summarizes the recent insights in the field of oncolipid LPA-mediated signaling in regard to lipid metabolism in cancers. Future work in this domain is required to understand the up-regulation of the de novo synthesis pathway and the role of its end products in malignant cells. This will open a new arena of research toward the development of specific metabolic inhibitors that can add to the pre-existing chemotherapeutics in order to increase the efficacy of clinical output in cancer patients.
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Affiliation(s)
- Upasana Ray
- Cell Biology and Physiology Division, CSIR-Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, Kolkata, India
| | - Sib Sankar Roy
- Cell Biology and Physiology Division, CSIR-Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, Kolkata, India
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Bai X, Hong W, Cai P, Chen Y, Xu C, Cao D, Yu W, Zhao Z, Huang M, Jin J. Valproate induced hepatic steatosis by enhanced fatty acid uptake and triglyceride synthesis. Toxicol Appl Pharmacol 2017; 324:12-25. [PMID: 28366540 DOI: 10.1016/j.taap.2017.03.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 03/06/2017] [Accepted: 03/28/2017] [Indexed: 02/07/2023]
Abstract
Steatosis is the characteristic type of VPA-induced hepatotoxicity and may result in life-threatening hepatic lesion. Approximately 61% of patients treated with VPA have been diagnosed with hepatic steatosis through ultrasound examination. However, the mechanisms underlying VPA-induced intracellular fat accumulation are not yet fully understood. Here we demonstrated the involvement of fatty acid uptake and lipogenesis in VPA-induced hepatic steatosis in vitro and in vivo by using quantitative real-time PCR (qRT-PCR) analysis, western blotting analysis, fatty acid uptake assays, Nile Red staining assays, and Oil Red O staining assays. Specifically, we found that the expression of cluster of differentiation 36 (CD36), an important fatty acid transport, and diacylglycerol acyltransferase 2 (DGAT2) were significantly up-regulated in HepG2 cells and livers of C57B/6J mice after treatment with VPA. Furthermore, VPA treatment remarkably enhanced the efficiency of fatty acid uptake mediated by CD36, while this effect was abolished by the interference with CD36-specific siRNA. Also, VPA treatment significantly increased DGAT2 expression as a result of the inhibition of mitogen-activated protein kinase kinase (MEK) - extracellular regulated kinase (ERK) pathway; however, DGAT2 knockdown significantly alleviated VPA-induced intracellular lipid accumulation. Additionally, we also found that sterol regulatory element binding protein-1c (SREBP-1c)-mediated fatty acid synthesis may be not involved in VPA-induced hepatic steatosis. Overall, VPA-triggered over-regulation of CD36 and DGAT2 could be helpful for a better understanding of the mechanisms underlying VPA-induced hepatic steatosis and may offer novel therapeutic strategies to combat VPA-induced hepatotoxicity.
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Affiliation(s)
- Xupeng Bai
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Weipeng Hong
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Peiheng Cai
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Yibei Chen
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Chuncao Xu
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Di Cao
- School of Chinese Materia Medica, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Weibang Yu
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Zhongxiang Zhao
- School of Chinese Materia Medica, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Min Huang
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Jing Jin
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China.
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Swierczynski J, Hebanowska A, Sledzinski T. Role of abnormal lipid metabolism in development, progression, diagnosis and therapy of pancreatic cancer. World J Gastroenterol 2014; 20:2279-303. [PMID: 24605027 PMCID: PMC3942833 DOI: 10.3748/wjg.v20.i9.2279] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 12/25/2013] [Accepted: 01/03/2014] [Indexed: 02/07/2023] Open
Abstract
There is growing evidence that metabolic alterations play an important role in cancer development and progression. The metabolism of cancer cells is reprogrammed in order to support their rapid proliferation. Elevated fatty acid synthesis is one of the most important aberrations of cancer cell metabolism. An enhancement of fatty acids synthesis is required both for carcinogenesis and cancer cell survival, as inhibition of key lipogenic enzymes slows down the growth of tumor cells and impairs their survival. Based on the data that serum fatty acid synthase (FASN), also known as oncoantigen 519, is elevated in patients with certain types of cancer, its serum level was proposed as a marker of neoplasia. This review aims to demonstrate the changes in lipid metabolism and other metabolic processes associated with lipid metabolism in pancreatic ductal adenocarcinoma (PDAC), the most common pancreatic neoplasm, characterized by high mortality. We also addressed the influence of some oncogenic factors and tumor suppressors on pancreatic cancer cell metabolism. Additionally the review discusses the potential role of elevated lipid synthesis in diagnosis and treatment of pancreatic cancer. In particular, FASN is a viable candidate for indicator of pathologic state, marker of neoplasia, as well as, pharmacological treatment target in pancreatic cancer. Recent research showed that, in addition to lipogenesis, certain cancer cells can use fatty acids from circulation, derived from diet (chylomicrons), synthesized in liver, or released from adipose tissue for their growth. Thus, the interactions between de novo lipogenesis and uptake of fatty acids from circulation by PDAC cells require further investigation.
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Gu W, Lloyd DJ, Chinookswong N, Komorowski R, Sivits G, Graham M, Winters KA, Yan H, Boros LG, Lindberg RA, Véniant MM. Pharmacological targeting of glucagon and glucagon-like peptide 1 receptors has different effects on energy state and glucose homeostasis in diet-induced obese mice. J Pharmacol Exp Ther 2011; 338:70-81. [PMID: 21471191 DOI: 10.1124/jpet.111.179986] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Pharmacologic contributions of directly agonizing glucagon-like peptide 1 (GLP-1) receptor or antagonizing glucagon receptor (GCGR) on energy state and glucose homeostasis were assessed in diet-induced obese (DIO) mice. Metabolic rate and respiratory quotient (RQ), hyperglycemic clamp, stable isotope-based dynamic metabolic profiling (SiDMAP) studies of (13)C-labeled glucose during glucose tolerance test (GTT) and gene expression were assessed in cohorts of DIO mice after a single administration of GLP-1 analog [GLP-1-(23)] or anti-GCGR antibody (Ab). GLP-1-(23) and GCGR Ab similarly improved GTT. GLP-1-(23) decreased food intake and body weight trended lower. GCGR Ab modestly decreased food intake without significant effect on body weight. GLP-1-(23) and GCGR Ab decreased RQ with GLP-1, causing a greater effect. In a hyperglycemic clamp, GLP-1-(23) reduced hepatic glucose production (HGP), increased glucose infusion rate (GIR), increased glucose uptake in brown adipose tissue, and increased whole-body glucose turnover, glycolysis, and rate of glycogen synthesis. GCGR Ab slightly decreased HGP, increased GIR, and increased glucose uptake in the heart. SiDMAP showed that GLP-1-(23) and GCGR Ab increased (13)C lactate labeling from glucose, indicating that liver, muscle, and other organs were involved in the rapid disposal of glucose from plasma. GCGR Ab and GLP-1-(23) caused different changes in mRNA expression levels of glucose- and lipid metabolism-associated genes. The effect of GLP-1-(23) on energy state and glucose homeostasis was greater than GCGR Ab. Although GCGR antagonism is associated with increased circulating levels of GLP-1, most GLP-1-(23)-associated pharmacologic effects are more pronounced than GCGR Ab.
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Affiliation(s)
- Wei Gu
- Department of Metabolic Disorders, Amgen Inc, Thousand Oaks, California 91320, USA
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Xu X, Zur Hausen A, Coy JF, Löchelt M. Transketolase-like protein 1 (TKTL1) is required for rapid cell growth and full viability of human tumor cells. Int J Cancer 2009; 124:1330-7. [PMID: 19065656 DOI: 10.1002/ijc.24078] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cancer cells display high rates of aerobic glycolysis, a phenomenon known as the Warburg effect. Lactate and pyruvate, the end products of glycolysis, are overproduced by cancer cells even in the presence of oxygen. The pentose phosphate pathway (PPP) allows glucose conversion to ribose for nucleic acid synthesis, glucose degradation to lactate, and regeneration of redox equivalents. The nonoxidative part of the PPP is controlled by transketolase (TKT) enzymes. One TKT isoform, the transketolase-like protein 1 (TKTL1) is specifically upregulated in different human cancers and its overexpression predicts a poor patient's survival. This finding implicates that an increased TKTL1 expression may activate the PPP leading to enhanced cancer cell growth and survival. To analyze the functional role of TKTL1 in malignant progression, we inhibited TKTL1 by RNAi technologies in human HCT116 colon carcinoma cells. TKTL1 suppression resulted in a significantly slowed cell growth, glucose consumption and lactate production. In TKTL1 knockdown-cells, the intracellular reactive oxygen species levels were not significantly increased, whereas the sensitivity towards oxidative stress-induced apoptosis was clearly enhanced. These data provide new clues on the importance of TKTL1 dys-regulation in tumor cells and indicate that TKTL1 overexpression may be considered not only as a new tumor marker but also as a good target for anticancer therapy.
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Affiliation(s)
- Xiaojun Xu
- Department of Genome Modifications and Carcinogenesis, Research Program Infection and Cancer, German Cancer Research Centre, Heidelberg, Germany
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9
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Abstract
The metabolic phenotype of tumor cells promote the proliferative state, which indicates that (a) cell transformation is associated with the activation of specific metabolic substrate channels toward nucleic acid synthesis and (b) increased expression phosphorylation, allosteric or transcriptional regulation of intermediary metabolic enzymes and their substrate availability together mediate unlimited growth. It is evident that cell transformation due to various K-ras point mutations is associated with the activation of specific metabolic substrate channels that increase glucose channeling toward nucleic acid synthesis. Therefore, phosphorylation, allosteric and transcriptional regulation of intermediary metabolic enzymes and their substrate availability together mediate cell transformation and growth. In this review, we summarize opposite changes in metabolic phenotypes induced by various cell-transforming agents, and tumor growth-inhibiting drugs or phytochemicals, or novel synthetic antileukemic drugs such as imatinib mesylate (Gleevec). Metabolic enzymes that further incite growth signaling pathways and thus promote malignant cell transformation serve as high-efficacy nongenetic novel targets for cancer therapies.
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Maier K, Hofmann U, Reuss M, Mauch K. Identification of metabolic fluxes in hepatic cells from transient 13C-labeling experiments: Part II. Flux estimation. Biotechnol Bioeng 2008; 100:355-70. [PMID: 18095336 DOI: 10.1002/bit.21746] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
This contribution addresses the identification of metabolic fluxes and metabolite concentrations in mammalian cells from transient (13)C-labeling experiments. Whilst part I describes experimental set-up and acquisition of required metabolite and (13)C-labeling data, part II focuses on setting up network models and the estimation of intracellular fluxes. Metabolic fluxes were determined in glycolysis, pentose-phosphate pathway (PPP), and citric acid cycle (TCA) in a hepatoma cell line grown in aerobic batch cultures. In glycolytic and PPP metabolite pools isotopic stationarity was observed within 30 min, whereas in the TCA cycle the labeling redistribution did not reach isotopic steady state even within 180 min. In silico labeling dynamics were in accordance with in vivo (13)C-labeling data. Split ratio between glycolysis and PPP was 57%:43%; intracellular glucose concentration was estimated at 101.6 nmol per 10(6) cells. In contrast to isotopic stationary (13)C-flux analysis, transient (13)C-flux analysis can also be applied to industrially relevant mammalian cell fed-batch and batch cultures.
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Affiliation(s)
- Klaus Maier
- Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
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Vazquez A, Beg QK, Demenezes MA, Ernst J, Bar-Joseph Z, Barabási AL, Boros LG, Oltvai ZN. Impact of the solvent capacity constraint on E. coli metabolism. BMC SYSTEMS BIOLOGY 2008; 2:7. [PMID: 18215292 PMCID: PMC2270259 DOI: 10.1186/1752-0509-2-7] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2007] [Accepted: 01/23/2008] [Indexed: 11/18/2022]
Abstract
Background Obtaining quantitative predictions for cellular metabolic activities requires the identification and modeling of the physicochemical constraints that are relevant at physiological growth conditions. Molecular crowding in a cell's cytoplasm is one such potential constraint, as it limits the solvent capacity available to metabolic enzymes. Results Using a recently introduced flux balance modeling framework (FBAwMC) here we demonstrate that this constraint determines a metabolic switch in E. coli cells when they are shifted from low to high growth rates. The switch is characterized by a change in effective optimization strategy, the excretion of acetate at high growth rates, and a global reorganization of E. coli metabolic fluxes, the latter being partially confirmed by flux measurements of central metabolic reactions. Conclusion These results implicate the solvent capacity as an important physiological constraint acting on E. coli cells operating at high metabolic rates and for the activation of a metabolic switch when they are shifted from low to high growth rates. The relevance of this constraint in the context of both the aerobic ethanol excretion seen in fast growing yeast cells (Crabtree effect) and the aerobic glycolysis observed in rapidly dividing cancer cells (Warburg effect) should be addressed in the future.
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Affiliation(s)
- Alexei Vazquez
- The Simons Center for Systems Biology, Institute for Advanced Study, Princeton, NJ 08540, USA.
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Huang J, Gabrielsen JS, Cooksey RC, Luo B, Boros LG, Jones DL, Jouihan HA, Soesanto Y, Knecht L, Hazel MW, Kushner JP, McClain DA. Increased glucose disposal and AMP-dependent kinase signaling in a mouse model of hemochromatosis. J Biol Chem 2007; 282:37501-7. [PMID: 17971451 DOI: 10.1074/jbc.m703625200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Hereditary hemochromatosis is an inherited disorder of increased iron absorption that can result in cirrhosis, diabetes, and other morbidities. We have investigated the mechanisms underlying supranormal glucose tolerance despite decreased insulin secretion in a mouse model of hemochromatosis with deletion of the hemochromatosis gene (Hfe(-/-)). Hfe(-/-) mice on 129Sv or C57BL/6J backgrounds have decreased glucose excursions after challenge compared with controls. In the C57BL/6J/ Hfe(-/-), for example, incremental area under the glucose curve is reduced 52% (p < 0.001) despite decreased serum insulin, and homeostasis model assessment insulin resistance is decreased 50% (p < 0.05). When studied by the euglycemic clamp technique 129Sv/Hfe(-/-) mice exhibit a 20% increase in glucose disposal (p < 0.05) at submaximal insulin but no increase at maximal insulin compared with wild types. [1,2-(13)C]D-glucose clearance from plasma is significantly increased in Hfe(-/-) mice (19%, p < 0.05), and lactate derived from glycolysis is elevated 5.1-fold in Hfe(-/-) mice (p < 0.0001). Basal but not insulin-stimulated glucose uptake is elevated in isolated soleus muscle from Hfe(-/-) mice (p < 0.03). Compared with controls Hfe(-/-) mice exhibit no differences in serum lipid, insulin, glucagon, or thyroid hormone levels; adiponectin levels are elevated 41% (p < 0.05), and the adiponectin message in adipocytes is increased 83% (p = 0.04). Insulin action measured by phosphorylation of Akt is not enhanced in muscle, but phosphorylation of AMP-dependent kinase is increased. We conclude that supranormal glucose tolerance in iron overload is characterized by increased glucose disposal that does not result from increased insulin action. Instead, the Hfe(-/-) mice demonstrate increased adiponectin levels and activation of AMP-dependent kinase.
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Affiliation(s)
- Jingyu Huang
- Department of Biochemistry, the University of Utah School of Medicine, Salt Lake City, UT 84132, USA
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Abstract
In the post-genomic era, a pressing challenge to biological scientists is to understand the organization of gene functions, the interaction between gene and nutrient environment, and the genesis of phenotypes. Metabolomics, the quantitation of low molecular weight compounds, has been used to provide a phenotypic description of a cell or tissue by a set of metabolites. Gene function is hypothesized from its correlation with the corresponding set of macromolecules by transcriptomics or proteomics. Another approach to genotype-phenotype correlation is by the reconstruction of genome-scale metabolic maps. The utilization of specific pathways as predicted by reaction network analysis provides the phenotypic characterization of a cell, which can be plotted on a phenotypic phase plane. Tracer based metabolomics is the experimental approach to reaction network analysis using stable isotope tracers. The redistribution of the isotope tracer among metabolic intermediates is used to identify a finite number of pathways, the utilization of which is characteristic of the phenotypic behavior of cells. In this paper, we review tracer based metabolomic methods for the construction of phenotypic phase plane plots, and discuss the functional implications of phenotypic phase plane analysis. Examples of phenotypic changes in response to differentiation, inhibition of signaling pathways and perturbation in nutrient environment are provided.
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Affiliation(s)
- Wai Nang P. Lee
- Department of Pediatrics, Harbor-UCLA Medical Center, 1124 W. Carson Street, Torrance, CA 90502 USA
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Boros LG, Lerner MR, Morgan DL, Taylor SL, Smith BJ, Postier RG, Brackett DJ. [1,2-13C2]-D-glucose profiles of the serum, liver, pancreas, and DMBA-induced pancreatic tumors of rats. Pancreas 2005; 31:337-43. [PMID: 16258367 DOI: 10.1097/01.mpa.0000186524.53253.fb] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES In vitro stable isotope glucose tracer studies indicate that undifferentiated cells of the pancreas use glucose primarily through the nonoxidative reactions of the pentose cycle for nucleic acid ribose synthesis, whereas normal or less transformed cells primarily use the oxidative branch of the cycle. METHODS The pancreatic heads of 4 groups (5/group) of male rats were implanted with time-release pellets designed to deliver placebo or 7,12-dimethylbenzanthracene (DMBA) at 11, 33, or 56 mg/d. Four weeks after pancreatic exposure to DMBA, [1,2-C2]-D-glucose tracer (1 g/kg) was injected intraperitoneally followed by sera collection at 1 and 2 hours and harvest of tumors, adjacent pancreatic tissue, and sera at 3 hours. RESULTS Tumors (2-9 mm) were found across DMBA groups, with the largest in the high-dose group (> or =5 mm). Selective monitoring by gas chromatography-mass spectrometry of the doubly-labeled [1,2-C2]-D-ribose of RNA, which requires nonoxidative synthesis in the pentose cycle, showed a 2.8-, 2.9-, and 5.7-fold increase in pancreatic tumors. Liver and adjacent pancreas preferentially produced [1-C1]-D-ribose through the oxidative reactions of the cycle. Tumor-bearing animals also cleared and recycled tracer glucose at a faster rate. CONCLUSIONS Simultaneous selective positional ion monitoring of C-labeled metabolites and their mass isotopomers in tissues and blood opens new avenues for the early detection and response to therapy testing of pancreatic cancer using GC-MS and/or magnetic resonance imaging-based methods. This study emphasizes the benefits of stable isotope-based dynamic metabolic profiling, when applied in vivo, and the several advantages it offers to positron emission tomography.
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Affiliation(s)
- László G Boros
- SIDMAP, LLC, and Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA 90502, USA.
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Cogo PE, Gucciardi A, Traldi U, Hilkert AW, Verlato G, Carnielli V. Measurement of pulmonary surfactant disaturated-phosphatidylcholine synthesis in human infants using deuterium incorporation from body water. JOURNAL OF MASS SPECTROMETRY : JMS 2005; 40:876-81. [PMID: 15892177 DOI: 10.1002/jms.858] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The aim of the study was to determine surfactant palmitate disaturated-phosphatidylcholine (DSPC-PA) synthesis in vivo in humans by the incorporation of deuterium from total body water into DSPC-PA under steady state condition. We studied three newborns and one infant (body weight (BW) 4.6 +/- 2.9 kg, gestational age 37.5 +/- 2 weeks, age 9 +/- 9 days) and four preterm newborns (BW 1.3 +/- 0.6 kg, gestational age 30.3 +/- 2.5 weeks, postnatal age 8.8 +/- 9.2 h). All infants were mechanically ventilated during the study and the four preterm infants received exogenous surfactant at the start of the study. We administered 0.44 g (2)H(2)O/kg BW as a bolus intravenously, followed by 0.0125 g (2)H(2)O/kg BW every 6 h to maintain deuterium enrichment at plateau over 2 days. Urine samples and tracheal aspirates (TA) were obtained prior to dosing and every 6 h thereafter. Isotopic enrichment curves of DSPC-PA from sequential TA and urine deuterium enrichments were analyzed by Gas Chromatography-Isotope Ratio-Mass Spectrometry (GC-IRMS) and normalized for Vienna Standard Mean Ocean Water. Enrichment data were used to measure DSPC-PA fractional synthesis rate (FSR) from the linear portion of the DSPC-PA enrichment rise over time, relative to plateau enrichment of urine deuterium. Secretion time (ST) was defined as the time lag between the start of the study and the appearance of DSPC-PA deuterium enrichment in TA. Data were given as mean +/- SD. All study infants reached deuterium-steady state in urine. DSPC-PA FSR was 6.5 +/- 2.8%/day (range 2.6-10.2). FSR for infants who did not receive exogenous surfactant was 5.7 +/- 3.5%/day (range 2.6-9.9%/day) and 7.3 +/- 2.1%/day (range 5.1-10.2%/day) in the preterms, whereas DSPC-PA ST was 10 +/- 10 h and 31 +/- 10 h respectively. Surfactant DSPC-PA synthesis can be measured in humans by the incorporation of deuterium from body water. This study is a simpler and less invasive method compared to previously published methods on surfactant kinetics by means of stable isotopes.
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Affiliation(s)
- Paola E Cogo
- Department of Pediatrics, University of Padova, Padova, Italy.
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16
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Du MX, Sim J, Fang L, Yin Z, Koh S, Stratton J, Pons J, Wang JJX, Carte B. Identification of novel small-molecule inhibitors for human transketolase by high-throughput screening with fluorescent intensity (FLINT) assay. ACTA ACUST UNITED AC 2005; 9:427-33. [PMID: 15296642 DOI: 10.1177/1087057104263913] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The metabolic enzyme transketolase (TK) plays a crucial role in tumor cell nucleic acid synthesis, using glucose through the elevated nonoxidative pentose phosphate pathway (PPP). Identification of inhibitors specifically targeting TK and preventing the nonoxidative PPP from generating the RNA ribose precursor, ribose-5-phosphate, provides a novel approach for developing effective anticancer therapeutic agents. The full-length human transketolase gene was cloned and expressed in Escherichia coli and the recombinant human transketolase protein purified to homogeneity. A fluorescent intensity (FLINT) assay was developed and optimized. Library compounds were screened in a high-throughput screening (HTS) campaign using the FLINT assay. Fifty-four initial hits were identified. Among them, 2 scaffolds with high selectivity, ideal physiochemical properties, and low molecular weight were selected for lead optimization studies. These compounds specifically inhibited in vitro TK enzyme activity and suppressed tumor cell proliferation in at least 3 cancer cell lines: SW620, LS174T, and MIA PaCa-2. Identification of these active scaffolds represents a good starting point for development of drugs specifically targeting TK and the nonoxidative PPP for cancer therapy.
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Schlichtholz B, Turyn J, Goyke E, Biernacki M, Jaskiewicz K, Sledzinski Z, Swierczynski J. Enhanced citrate synthase activity in human pancreatic cancer. Pancreas 2005; 30:99-104. [PMID: 15714131 DOI: 10.1097/01.mpa.0000153326.69816.7d] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVES Assuming that a high flux of carbohydrate is strictly connected with lipid synthesis in neoplastic cells, one can hypothesize that the activity of citrate synthase, which plays an important role in glucose to lipid conversion, is enhanced in pancreatic cancer. The aim of the present study was to verify this hypothesis. METHODS The activity of citrate synthase (as well as lactate and glucose 6-phosphate dehydrogenases) was measured using tissue extract prepared from specimens (pancreatic cancer and control specimens taken from the adjacent pancreatic normal tissue) obtained from 24 patients with ductal carcinoma who underwent pancreatoduodenectomy or total pancreatomy. RESULTS The average of citrate synthase activity in human pancreatic ductal carcinoma is significantly higher comparing with adjacent nonneoplastic tissue: 40.2 +/- 27.2 and 18.3 +/- 13.6 nmole/min/mg protein, respectively (P = 0.001). The lactate dehydrogenase and glucose 6-phosphate dehydrogenase activity in human pancreatic ductal carcinoma were also higher than in adjacent nonneoplastic tissues. CONCLUSION It is likely that enhanced citrate synthase activity contributes to the conversion of glucose to lipids in pancreatic cancer providing substrate for membrane lipids synthesis.
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Affiliation(s)
- Beata Schlichtholz
- Department of Biochemistry, Medical University of Gdansk, Gdansk, Poland
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18
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Lee WNP, Guo P, Lim S, Bassilian S, Lee ST, Boren J, Cascante M, Go VLW, Boros LG. Metabolic sensitivity of pancreatic tumour cell apoptosis to glycogen phosphorylase inhibitor treatment. Br J Cancer 2005; 91:2094-100. [PMID: 15599384 PMCID: PMC2409791 DOI: 10.1038/sj.bjc.6602243] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Inhibitors of glycogen breakdown regulate glucose homeostasis by limiting glucose production in diabetes. Here we demonstrate that restrained glycogen breakdown also inhibits cancer cell proliferation and induces apoptosis through limiting glucose oxidation, as well as nucleic acid and de novo fatty acid synthesis. Increasing doses (50-100 microM) of the glycogen phosphorylase inhibitor CP-320626 inhibited [1,2-(13)C(2)]glucose stable isotope substrate re-distribution among glycolysis, pentose and de novo fatty acid synthesis in MIA pancreatic adenocarcinoma cells. Limited oxidative pentose-phosphate synthesis, glucose contribution to acetyl CoA and de novo fatty acid synthesis closely correlated with decreased cell proliferation. The stable isotope-based dynamic metabolic profile of MIA cells indicated a significant dose-dependent decrease in macromolecule synthesis, which was detected at lower drug doses and before the appearance of apoptosis markers. Normal fibroblasts (CRL-1501) did not show morphological or metabolic signs of apoptosis likely due to their slow rate of growth and metabolic activity. This indicates that limiting carbon re-cycling and rapid substrate mobilisation from glycogen may be an effective and selective target site for new drug development in rapidly dividing cancer cells. In conclusion, pancreatic cancer cell growth arrest and death are closely associated with a characteristic decrease in glycogen breakdown and glucose carbon re-distribution towards RNA/DNA and fatty acids during CP-320626 treatment.
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Affiliation(s)
- W-N P Lee
- Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, RB1, 1124 West Carson Street, Torrance, CA 90502, USA
- SIDMAP, LLC, 10021 Cheviot Drive, Los Angeles, CA 90064, USA
| | - P Guo
- Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, RB1, 1124 West Carson Street, Torrance, CA 90502, USA
| | - S Lim
- Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, RB1, 1124 West Carson Street, Torrance, CA 90502, USA
| | - S Bassilian
- Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, RB1, 1124 West Carson Street, Torrance, CA 90502, USA
| | - S T Lee
- Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, RB1, 1124 West Carson Street, Torrance, CA 90502, USA
| | - J Boren
- Department of Biochemistry and Molecular Biology, University of Barcelona, C/Marti I Franques 1, 08028 Barcelona, Spain
| | - M Cascante
- Department of Biochemistry and Molecular Biology, University of Barcelona, C/Marti I Franques 1, 08028 Barcelona, Spain
| | - V L W Go
- UCLA Center for Human Nutrition, 900 Veteran Avenue, Los Angeles, CA, 90095, USA
| | - L G Boros
- Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, RB1, 1124 West Carson Street, Torrance, CA 90502, USA
- SIDMAP, LLC, 10021 Cheviot Drive, Los Angeles, CA 90064, USA
- SIDMAP, LLC, 10021 Cheviot Drive, Los Angeles, CA 90064, USA. E-mail:
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Abstract
The field of metabolic engineering encompasses a powerful set of tools that can be divided into (a) methods to model complex metabolic pathways and (b) techniques to manipulate these pathways for a desired metabolic outcome. These tools have recently seen increased utility in the medical arena, and this paper aims to review significant accomplishments made using these approaches. The modeling of metabolic pathways has been applied to better understand disease-state physiology in a variety of cellar, subcellular, and organ systems, including the liver, heart, mitochondria, and cancerous cells. Metabolic pathway engineering has been used to generate cells with novel biochemical functions for therapeutic use, and specific examples are provided in the areas of glycosylation engineering and dopamine-replacement therapy. In order to document the potential of applying both metabolic modeling and pathway manipulation, we describe pertinent advances in the field of diabetes research. Undoubtedly, as the field of metabolic engineering matures and is applied to a wider array of problems, new advances and therapeutic strategies will follow.
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Affiliation(s)
- Martin L Yarmush
- Center for Engineering in Medicine/Surgical Services, Massachusetts General Hospital, Shriners Burns Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
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Boros LG, Steinkamp MP, Fleming JC, Lee WNP, Cascante M, Neufeld EJ. Defective RNA ribose synthesis in fibroblasts from patients with thiamine-responsive megaloblastic anemia (TRMA). Blood 2003; 102:3556-61. [PMID: 12893755 DOI: 10.1182/blood-2003-05-1537] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Fibroblasts from patients with thiamine-responsive megaloblastic anemia (TRMA) syndrome with diabetes and deafness undergo apoptotic cell death in the absence of supplemental thiamine in their cultures. The basis of megaloblastosis in these patients has not been determined. Here we use the stable [1,2-13C2]glucose isotope-based dynamic metabolic profiling technique to demonstrate that defective high-affinity thiamine transport primarily affects the synthesis of nucleic acid ribose via the nonoxidative branch of the pentose cycle. RNA ribose isolated from TRMA fibroblasts in thiamine-depleted cultures shows a time-dependent decrease in the fraction of ribose derived via transketolase, a thiamine-dependent enzyme in the pentose cycle. The fractional rate of de novo ribose synthesis from glucose is decreased several fold 2 to 4 days after removal of thiamine from the culture medium. No such metabolic changes are observed in wild-type fibroblasts or in TRMA mutant cells in thiamine-containing medium. Fluxes through glycolysis are similar in TRMA versus control fibroblasts in the pentose and TCA cycles. We conclude that reduced nucleic acid production through impaired transketolase catalysis is the underlying biochemical disturbance that likely induces cell cycle arrest or apoptosis in bone marrow cells and leads to the TRMA syndrome in patients with defective high-affinity thiamine transport.
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Affiliation(s)
- László G Boros
- Stable Isotope Research Laboratory, Harbor-University of California, Los Angeles Research and Education Institute, UCLA School of Medicine, 1124 West Carson St, RB1, Torrance, CA 90502, USA.
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Boros LG, Torday JS, Paul Lee WN, Rehan VK. Oxygen-induced metabolic changes and transdifferentiation in immature fetal rat lung lipofibroblasts. Mol Genet Metab 2002; 77:230-6. [PMID: 12409271 DOI: 10.1016/s1096-7192(02)00140-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Preterm infants lack adequate surfactant production and often require oxygen support for adequate oxygenation. Prolonged oxygen treatment leads to the development of bronchopulmonary dysplasia (BPD), a disease process characterized by the blunting of alveolarization and proliferation of myofibroblasts. In the present study, we investigated metabolic adaptive changes in cultured fibroblasts isolated from immature (d18) and near-term (d21), fetal rat lungs in response to normoxic (21%) and hyperoxic (95%) exposures. We used the [1,2-13C2]D-glucose tracer and gas chromatography/mass spectrometry to characterize glucose carbon redistribution between the nucleic acid ribose, lactate, and palmitate synthetic pathways, and reverse transcriptase-polymerase chain reaction to assess adipose differentiation related protein (ADRP) mRNA expression in response to hyperoxic exposure. Exposure to hyperoxia at each passage caused decrease (*, p<0.05 vs. 21% O2) in ADRP mRNA expression in the d18 fibroblasts. This passage-dependent transdifferentiation is accompanied by a moderate (9-20%) increase in the synthesis of nucleic acid ribose from glucose through the non-oxidative steps of the pentose cycle. In contrast, d18 fibroblasts showed over an 85% decrease in the de novo synthesis of palmitate from glucose, while d21 fibroblasts showed a less pronounced 32-38% decrease in de novo lipid synthesis in hyperoxia-exposed cultures. It can be concluded from these studies that: (1) there is a maturation dependent sensitivity to hyperoxia; (2) transdifferentiation of flbroblast as demonstrated by changes in ADRP expression is accompanied by metabolic enzymes changes affecting ribose acid synthesis from glucose, and (3) hyperoxia specifically inhibits lipogenesis from glucose. Hyperoxia-induced metabolic changes thus play a key role in the transdifferentiation of lung fibroblasts to myofibroblasts and the pathogenesis of BPD.
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Affiliation(s)
- László G Boros
- Division of Pediatric Endocrinology, Department of Pediatrics, Stable Isotope Research Laboratory, UCLA School of Medicine, Harbor-UCLA Research and Education Institute, 1124 West Carson St., RB1, Torrance, CA 90502, USA
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22
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Mazurek S, Grimm H, Boschek CB, Vaupel P, Eigenbrodt E. Pyruvate kinase type M2: a crossroad in the tumor metabolome. Br J Nutr 2002. [PMID: 11895152 DOI: 10.1079/bjn2001454] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Cell proliferation is a process that consumes large amounts of energy. A reduction in the nutrient supply can lead to cell death by ATP depletion, if cell proliferation is not limited. A key sensor for this regulation is the glycolytic enzyme pyruvate kinase, which determines whether glucose carbons are channelled to synthetic processes or used for glycolytic energy production. In unicellular organisms pyruvate kinase is regulated by ATP, ADP and AMP, by ribose 5-P, the precursor of the nucleic acid synthesis, and by the glycolytic intermediate fructose 1,6-P2 (FBP), thereby adapting cell proliferation to nutrient supply. The mammalian pyruvate kinase isoenzyme type M2 (M2-PK) displays the same kinetic properties as the pyruvate kinase enzyme from unicellular organisms. The mammalian M2-PK isoenzyme can switch between a less active dimeric form and a highly active tetrameric form which regulates the channeling of glucose carbons either to synthetic processes (dimeric form) or to glycolytic energy production (tetrameric form). Tumor cells are usually characterized by a high amount of the dimeric form leading to a strong accumulation of all glycolytic phosphometabolites above pyruvate kinase. The tetramer-dimer ratio is regulated by ATP, FBP and serine and by direct interactions with different oncoproteins (pp60v-src, HPV-16 E7). In solid tumors with sufficient oxygen supply pyruvate is supplied by glutaminolysis. Pyruvate produced in glycolysis and glutaminolysis is used for the synthesis of lactate, glutamate and fatty acids thereby releasing the hydrogen produced in the glycolytic glyceraldehyde 3-phosphate dehydrogenase reaction.
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Affiliation(s)
- S Mazurek
- Institute for Biochemistry & Endocrinology, Veterinary Faculty, University of Giessen, Germany
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23
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Boros LG, Cascante M, Lee WNP. Metabolic profiling of cell growth and death in cancer: applications in drug discovery. Drug Discov Today 2002; 7:364-72. [PMID: 11893545 DOI: 10.1016/s1359-6446(02)02179-7] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Metabolic profiling using stable-isotope tracer technology enables the measurement of substrate redistribution within major metabolic pathways in living cells. This technique has demonstrated that transformed human cells exhibit profound metabolic shifts and that some anti-cancer drugs produce their effects by forcing the reversion of these metabolic changes. By revealing tumor-specific metabolic shifts in tumor cells, metabolic profiling enables drug developers to identify the metabolic steps that control cell proliferation, thus aiding the identification of new anti-cancer targets and screening of lead compounds for anti-proliferative metabolic effects.
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Affiliation(s)
- László G Boros
- Harbor-UCLA Research and Education Institute, UCLA School of Medicine, 1124 West Carson Street RB1, 90502, Torrance, CA 90502, USA.
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Abstract
INTRODUCTION Tumor cells, just as other living cells, possess the potential for proliferation, differentiation, cell cycle arrest, and apoptosis. There is a specific metabolic phenotype associated with each of these conditions, characterized by the production of both energy and special substrates necessary for the cells to function in that particular state. Unlike that of normal living cells, the metabolic phenotype of tumor cells supports the proliferative state. AIM To present the metabolic hypothesis that (1) cell transformation and tumor growth are associated with the activation of metabolic enzymes that increase glucose carbon utilization for nucleic acid synthesis, while enzymes of the lipid and amino acid synthesis pathways are activated in tumor growth inhibition, and (2) phosphorylation and allosteric and transcriptional regulation of intermediary metabolic enzymes and their substrate availability together mediate and sustain cell transformation from one condition to another. CONCLUSION Evidence is presented that demonstrates opposite changes in metabolic phenotypes induced by TGF-beta, a cell-transforming agent, and tumor growth-inhibiting phytochemicals such as genistein and Avemar, or novel synthetic anti-leukemic drugs such as STI571 (Gleevec). Intermediary metabolic enzymes that mediate the growth signaling pathways and promote malignant cell transformation may serve as high-efficacy nongenetic novel targets for cancer therapies.
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Affiliation(s)
- Laszlo G Boros
- Harbor-University of California Los Angeles Research and Education Institute, UCLA School of Medicine, Torrance, California 90502, USA.
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Lee K, Berthiaume F, Stephanopoulos GN, Yarmush ML. Metabolic flux analysis: a powerful tool for monitoring tissue function. TISSUE ENGINEERING 1999; 5:347-68. [PMID: 10477857 DOI: 10.1089/ten.1999.5.347] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
In recent years, metabolic flux analysis has been widely used in bioprocess engineering to monitor cell viability and improve strain activity. Metabolic flux analysis refers to a methodology for investigating cellular metabolism whereby intracellular fluxes are calculated using a stoichiometric model for the major intracellular reactions and applying mass balances around intracellular metabolites. A powerful feature of this methodology is its ability to consider cellular biochemistry in terms of reaction networks. By considering the stoichiometry of biochemical reactions, it is possible to estimate the degree of engagement of each pathway participating in overall cellular activity, and hence obtain a comprehensive view of a cell s metabolic state. Given the potential impact of cellular energy metabolism on the function of engineered tissues, such comprehensive analysis of metabolic activity can be an extremely useful tool for tissue engineers. Estimates of intracellular fluxes under various environmental conditions could be used to optimize function in vivo as well as culture conditions in vitro. In this review, we provide a brief theoretical background of metabolic flux analysis and summarize the most widely used experimental approaches to obtain flux data. This review is intended as an overview of the field and as a starting point for tissue engineers wishing to learn about and eventually employ this methodology.
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Affiliation(s)
- K Lee
- Center for Engineering in Medicine, Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, Boston, Massachusetts 02114, USA
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26
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Raïs B, Comin B, Puigjaner J, Brandes JL, Creppy E, Saboureau D, Ennamany R, Lee WN, Boros LG, Cascante M. Oxythiamine and dehydroepiandrosterone induce a G1 phase cycle arrest in Ehrlich's tumor cells through inhibition of the pentose cycle. FEBS Lett 1999; 456:113-8. [PMID: 10452541 DOI: 10.1016/s0014-5793(99)00924-2] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Transketolase (TK) reactions play a crucial role in tumor cell nucleic acid ribose synthesis utilizing glucose carbons, yet, current cancer treatments do not target this central pathway. Experimentally, a dramatic decrease in tumor cell proliferation after the administration of the TK inhibitor oxythiamine (OT) was observed in several in vitro and in vivo tumor models. Here, we demonstrate that pentose cycle (PC) inhibitors, OT and dehydroepiandrosterone (DHEA), efficiently regulate the cell cycle and tumor proliferation processes. Increasing doses of OT or DHEA were administered by daily intraperitoneal injections to Ehrlich's ascites tumor hosting mice for 4 days. The tumor cell number and their cycle phase distribution profile were determined by DNA flow histograms. Tumors showed a dose dependent increase in their G0-G1 cell populations after both OT and DHEA treatment and a simultaneous decrease in cells advancing to the S and G2-M cell cycle phases. This effect of PC inhibitors was significant, OT was more effective than DHEA, both drugs acted synergistically in combination and no signs of direct cell or host toxicity were observed. Direct inhibition of PC reactions causes a G1 cell cycle arrest similar to that of 2-deoxyglucose treatment. However, no interference with cell energy production and cell toxicity is observed. PC inhibitors, specifically ones targeting TK, introduce a new target site for the development of future cancer therapies to inhibit glucose utilizing pathways selectively for nucleic acid production.
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Affiliation(s)
- B Raïs
- Department of Biochemistry and Molecular Biology, Institut d'Investigacions Biomèdiques August Pi i Sunyer, University of Barcelona, Spain
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27
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Lee WN, Lim S, Bassilian S, Bergner EA, Edmond J. Fatty acid cycling in human hepatoma cells and the effects of troglitazone. J Biol Chem 1998; 273:20929-34. [PMID: 9694841 DOI: 10.1074/jbc.273.33.20929] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fatty acid cycling by chain shortening/elongation in the peroxisomes is an important source of fatty acids for membrane lipid synthesis. Its role in the homeostasis of nonessential fatty acids is poorly understood. We report here a study on the cycling of saturated fatty acids and the effects of troglitazone in HepG2 cells in culture using [U-13C]stearate or [U-13C]oleate and mass isotopomer analysis. HepG2 cells were grown in the presence of 0.7 mmol/liter [U-13C]stearate or [U-13C]oleate, and in the presence and absence of 50 microM troglitazone for 72 h. Fatty acids extracted from cell pellets after saponification were analyzed by gas chromatography/mass spectrometry. Peroxisomal beta-oxidation of uniformly 13C-labeled stearate (C18:0) and oleate (C18:1) resulted in chain shortening and produced uniformly labeled palmitate (C16:0) and palmitoleate (C16:1). In untreated cells, 16% of C16:0 was derived from C18:0 and 26% of C16:1 from C18:1 by chain shortening. Such contributions were significantly increased by troglitazone to 23.6 and 36.6%, respectively (p < 0.001). Desaturation of stearate contributed 67% of the oleate, while reduction of oleate contributed little to stearate (2%). The desaturation of C18:0 to C18:1 was not affected by troglitazone. Our results demonstrated a high degree of recycling of C18:0 and C18:1 to C16:0 and C16:1 through chain shortening and desaturation. Chain shortening was accompanied by chain elongation in the synthesis of other long chain fatty acids. Troglitazone specifically increased recycling by peroxisomal beta-oxidation of C18 to C16 fatty acids, and the interconversion of long chain fatty acids was associated with reduced de novo lipogenesis.
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Affiliation(s)
- W N Lee
- Harbor-UCLA Medical Center, Torrance, California 90502, USA.
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Aarsland A, Wolfe RR. Hepatic secretion of VLDL fatty acids during stimulated lipogenesis in men. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32553-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Lee WN, Boros LG, Puigjaner J, Bassilian S, Lim S, Cascante M. Mass isotopomer study of the nonoxidative pathways of the pentose cycle with [1,2-13C2]glucose. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:E843-51. [PMID: 9612242 DOI: 10.1152/ajpendo.1998.274.5.e843] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We present a single-tracer method for the study of the pentose phosphate pathway (PPP) using [1,2-13C2]glucose and mass isotopomer analysis. The metabolism of [1,2-13C2]glucose by the glucose-6-phosphate dehydrogenase, transketolase (TK), and transaldolase (TA) reactions results in unique pentose and lactate isotopomers with either one or two 13C substitutions. The distribution of these isotopomers was used to estimate parameters of the PPP using the model of Katz and Rognstad (J. Katz and R. Rognstad. Biochemistry 6: 2227-2247, 1967). Mass and position isotopomers of ribose, and lactate and palmitate (products from triose phosphate) from human hepatoma cells (Hep G2) incubated with 30% enriched [1,2-13C2]glucose were determined using gas chromatography-mass spectrometry. After 24-72 h incubation, 1.9% of lactate molecules in the medium contained one 13C substitution (m1) and 10% contained two 13C substitutions (m2). A similar m1-to-m2 ratio was found in palmitate as expected. Pentose cycle (PC) activity determined from incubation with [1,2-13C2]glucose was 5.73 +/- 0.52% of the glucose flux, which was identical to the value of PC (5.55 +/- 0.73%) determined by separate incubations with [1-13C] and [6-13C]glucose, 13C was found to be distributed in four ribose isotopomers ([1-13C]-, [5-13C]-, [1,2-13C2]-, and [4,5-13C2]ribose). The observed ribose isotopomer distribution was best matched with that provided from simulation by substituting 0.032 for TK and 0.85 for TA activity relative to glucose uptake into the model of Katz and Rognstad. The use of [1,2-13C2]glucose not only permits the determination of PC but also allows estimation of relative rates through the TK and TA reactions.
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Affiliation(s)
- W N Lee
- Department of Pediatrics, Harbor-University of California Los Angeles Medical Center, Torrance 90502, USA
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Boros LG, Lee PW, Brandes JL, Cascante M, Muscarella P, Schirmer WJ, Melvin WS, Ellison EC. Nonoxidative pentose phosphate pathways and their direct role in ribose synthesis in tumors: is cancer a disease of cellular glucose metabolism? Med Hypotheses 1998; 50:55-9. [PMID: 9488183 DOI: 10.1016/s0306-9877(98)90178-5] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Pentose phosphate pathways (PPP) are considered important in tumor proliferation processes because of their role in supplying tumor cells with reduced NADP and carbons for intracellular anabolic processes. Direct involvement of PPP in tumor DNA/RNA synthesis is not considered as significant as in lipid and protein syntheses. Currently, PPP activity in tumor cells is measured by lactate production, which shows a moderate activity: about 4% to 7% compared with glycolysis. Recent data generated in our laboratory indicate that PPP are directly involved in ribose synthesis in pancreatic adenocarcinoma cells, through oxidative steps (< 31%) and transketolase reactions (69%). These findings raise serious questions about the adequacy of lactate in measuring PPP activity in tumors. We hypothesize that ribose, not lactate, is the major product of PPP in tumor cells. Control of both oxidative and nonoxidative PPP may be critical in the treatment of cancer. PPP are substantially involved in the proliferation of human tumors, which raises the prospect of new treatment strategies targeting specific biochemical reactions of PPP by hormones related to glucose metabolism, controlling thiamine intake, the cofactor of the nonoxidative transketolase PPP reaction, or treating cancer patients with antithiamine analogues.
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Affiliation(s)
- L G Boros
- Department of Surgery, The Ohio State University College of Medicine, Columbus 43210, USA.
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Brunengraber H, Kelleher JK, Des Rosiers C. Applications of mass isotopomer analysis to nutrition research. Annu Rev Nutr 1997; 17:559-96. [PMID: 9240940 DOI: 10.1146/annurev.nutr.17.1.559] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Investigations into regulating metabolic pathways with stable isotopes have, over the past decade, undergone major development with the use of nuclear magnetic resonance and mass spectrometry in studying labeling patterns of newly synthesized biomolecules. In this review, we concentrate on investigations of mass isotopomer distribution (MID) measured by mass spectrometry. We review the applications of MID to analytical problems, in particular the possibility of amplifying the measurement of low isotopic enrichments by incorporating multiple molecules or atoms of a primary analyte into the molecule of a secondary analyte, the MID of which is assayed. We also review new information on the regulation of intermediary metabolism gathered from the analysis of MID patterns of synthesized compounds. Lastly, we review the applications of MID to the synthesis of polymeric molecules, with emphasis on the validity of these techniques. A number of these techniques are applicable to investigations of nutrient metabolism in health and disease.
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Affiliation(s)
- H Brunengraber
- Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Diraison F, Pachiaudi C, Beylot M. In vivo measurement of plasma cholesterol and fatty acid synthesis with deuterated water: determination of the average number of deuterium atoms incorporated. Metabolism 1996; 45:817-21. [PMID: 8692014 DOI: 10.1016/s0026-0495(96)90152-3] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Fractional lipid synthesis can be measured using the incorporation of deuterium from deuterated water. The calculations require knowledge of the maximum incorporation number (N) of deuterium atoms in the molecules synthesized. For both tissue palmitate and cholesterol, N values have been found to be higher during in vivo versus in vitro experiments. We determined the N values to be used for measuring the fractional synthesis of plasma cholesterol and of palmitate triglycerides (TG). Rats were given drinking water enriched (7% to 10%) with deuterated water, and N was determined from the mass isotopomer distributions of plasma cholesterol and plasma TG palmitate and the deuterium enrichment of plasma water. We found N to be 21 for palmitate and 27 for cholesterol. These values agree with those reported for tissue palmitate and cholesterol in vivo, and are higher than values found in vitro. We also found large deuterium enrichments in plasma glucose and in liver lactate and pyruvate. We suggest that, compared with in vitro studies, in vivo metabolism of these compounds leads to an additional pathway of incorporation of deuterium into lipids through deuterium-labeled acetyl coenzyme A (CoA). This could explain why N values are higher in vivo than in vitro.
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Affiliation(s)
- F Diraison
- INSERM U. 197, Faculté de Médecine Alexis Carrel, Lyon, France
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Lee WN. Stable isotopes and mass isotopomer study of fatty acid and cholesterol synthesis. A review of the MIDA approach. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1996; 399:95-114. [PMID: 8937551 DOI: 10.1007/978-1-4613-1151-5_8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- W N Lee
- Research and Education Institute, Harbor-UCLA Medical Center, Torrance 90502, USA
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