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Xiong K, Li G, Zhang Y, Bao T, Li P, Yang X, Chen J. Effects of glutamine on plasma protein and inflammation in postoperative patients with colorectal cancer: a meta-analysis of randomized controlled trials. Int J Colorectal Dis 2023; 38:212. [PMID: 37566134 PMCID: PMC10421765 DOI: 10.1007/s00384-023-04504-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/29/2023] [Indexed: 08/12/2023]
Abstract
OBJECTIVE To evaluate the effects of glutamine on the plasma protein and inflammatory responses in colorectal cancer (CRC) patients following radical surgery. METHODS We thoroughly retrieved online databases (EMBASE, MEDLINE, PubMed, and others) and selected the randomized controlled trials (RCTs) with glutamine vs. conventional nutrition or blank treatment up until March 2023. The plasma protein associated markers indicators (consisting of albumin (ALB), prealbumin (PA), nitrogen balance (NB), total protein (TP)), inflammatory indicators (including TNF-α, CRP, infectious complications (ICs)), and matching 95% confidence intervals (CIs) were evaluated utilizing the pooled analysis. Subsequently, meta-regression analysis, contour-enhanced funnel plot, Egger's test, and sensitivity analysis were carried out. RESULTS We discovered 26 RCTs, included an aggregate of 1678 patients, out of which 844 were classified into the glutamine group whereas 834 were classified into the control group. The findings recorded from pooled analysis illustrated that glutamine substantially enhanced the plasma protein markers (ALB [SMD[random-effect] = 0.79, 95% CI: 0.55 to 1.03, I2 = 79.4%], PA [SMD[random-effect] = 0.94, 95% CI: 0.69 to 1.20, I2 = 75.1%], NB [SMD[random-effect] = 1.11, 95% CI: 0.46 to 1.75, I2 = 86.9%). However, the content of TP was subjected to comparison across the 2 groups, and no statistical significance was found (SMD[random-effect] = - 0.02, 95% CI: - 0.60 to 0.57, P = 0.959, I2 = 89.7%). Meanwhile, the inflammatory indicators (including TNF-α [SMD[random-effect] = - 1.86, 95% CI: - 2.21 to - 1.59, I2 = 56.7%], CRP [SMD[random-effect] = - 1.94, 95% CI: - 2.41 to - 1.48, I2 = 79.9%], ICs [RR[fixed-effect] = 0.31, 95% CI: 0.21 to 0.46, I2 = 0.00%]) were decreased significantly followed by the treatment of glutamine. CONCLUSIONS The current study's findings illustrated that glutamine was an effective pharmaco-nutrient agent in treating CRC patients following a radical surgical operation. PROSPERO registration number: CRD42021243327.
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Affiliation(s)
- Kai Xiong
- College of Clinical Medicine, Guizhou University of Traditional Chinese Medicine, Guiyang, No. 50 Shi East Road, Nanming District Guiyang, 550002 China
| | - Guangsong Li
- Department of Pharmacy, the First Affiliated Hospital of Guizhou University of Traditional Chinese Medicine, Guiyang, 550002 China
| | - Yu Zhang
- Colorectal and Anal Surgery, Chengdu Anorectal Hospital, Chengdu, 610015 China
| | - Tiantian Bao
- Colorectal and Anal Surgery, the First Affiliated Hospital of Guizhou University of Traditional Chinese Medicine, Guiyang, 550002 China
| | - Ping Li
- Colorectal and Anal Surgery, the First Affiliated Hospital of Guizhou University of Traditional Chinese Medicine, Guiyang, 550002 China
| | - Xiangdong Yang
- Colorectal and Anal Surgery, Chengdu Anorectal Hospital, Chengdu, 610015 China
| | - Jiang Chen
- Colorectal and Anal Surgery, the First Affiliated Hospital of Guizhou University of Traditional Chinese Medicine, Guiyang, 550002 China
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Bonus M, Häussinger D, Gohlke H. Liver cell hydration and integrin signaling. Biol Chem 2021; 402:1033-1045. [PMID: 33915604 DOI: 10.1515/hsz-2021-0193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 04/12/2021] [Indexed: 12/21/2022]
Abstract
Liver cell hydration (cell volume) is dynamic and can change within minutes under the influence of hormones, nutrients, and oxidative stress. Such volume changes were identified as a novel and important modulator of cell function. It provides an early example for the interaction between a physical parameter (cell volume) on the one hand and metabolism, transport, and gene expression on the other. Such events involve mechanotransduction (osmosensing) which triggers signaling cascades towards liver function (osmosignaling). This article reviews our own work on this topic with emphasis on the role of β1 integrins as (osmo-)mechanosensors in the liver, but also on their role in bile acid signaling.
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Affiliation(s)
- Michele Bonus
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany
| | - Dieter Häussinger
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany
- John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Wilhelm-Johnen-Str., D-52428 Jülich, Germany
- Institute of Biological Information Processing (IBI-7: Structural Biochemistry), and Institute of Bio- and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., D-52428 Jülich, Germany
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3
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Muyinda IJ, Park JG, Jang EJ, Yoo BC. KRAS, A Prime Mediator in Pancreatic Lipid Synthesis through Extra Mitochondrial Glutamine and Citrate Metabolism. Int J Mol Sci 2021; 22:5070. [PMID: 34064761 PMCID: PMC8150642 DOI: 10.3390/ijms22105070] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/28/2021] [Accepted: 05/03/2021] [Indexed: 12/12/2022] Open
Abstract
Kirsten rat sarcoma viral oncogene homolog (KRAS)-driven pancreatic cancer is very lethal, with a five-year survival rate of <9%, irrespective of therapeutic advances. Different treatment modalities including chemotherapy, radiotherapy, and immunotherapy demonstrated only marginal efficacies because of pancreatic tumor specificities. Surgery at the early stage of the disease remains the only curative option, although only in 20% of patients with early stage disease. Clinical trials targeting the main oncogenic driver, KRAS, have largely been unsuccessful. Recently, global metabolic reprogramming has been identified in patients with pancreatic cancer and oncogenic KRAS mouse models. The newly reprogrammed metabolic pathways and oncometabolites affect the tumorigenic environment. The development of methods modulating metabolic reprogramming in pancreatic cancer cells might constitute a new approach to its therapy. In this review, we describe the major metabolic pathways providing acetyl-CoA and NADPH essential to sustain lipid synthesis and cell proliferation in pancreatic cancer cells.
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Affiliation(s)
- Isaac James Muyinda
- Department of Translational Science, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang-si 10408, Korea; (I.J.M.); (E.-J.J.)
- Uganda Cancer Institute, Mulago-Kampala 3935, Uganda
| | - Jae-Gwang Park
- Department of Translational Science, Research Institute, National Cancer Center, Goyang-si 10408, Korea;
| | - Eun-Jung Jang
- Department of Translational Science, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang-si 10408, Korea; (I.J.M.); (E.-J.J.)
| | - Byong-Chul Yoo
- Department of Translational Science, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang-si 10408, Korea; (I.J.M.); (E.-J.J.)
- Department of Translational Science, Research Institute, National Cancer Center, Goyang-si 10408, Korea;
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4
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The synthesis of branched-chain fatty acids is limited by enzymatic decarboxylation of ethyl- and methylmalonyl-CoA. Biochem J 2019; 476:2427-2447. [PMID: 31416829 PMCID: PMC6717113 DOI: 10.1042/bcj20190500] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/12/2019] [Accepted: 08/15/2019] [Indexed: 11/17/2022]
Abstract
Most fatty acids (FAs) are straight chains and are synthesized by fatty acid synthase (FASN) using acetyl-CoA and malonyl-CoA units. Yet, FASN is known to be promiscuous as it may use methylmalonyl-CoA instead of malonyl-CoA and thereby introduce methyl-branches. We have recently found that the cytosolic enzyme ECHDC1 degrades ethylmalonyl-CoA and methylmalonyl-CoA, which presumably result from promiscuous reactions catalyzed by acetyl-CoA carboxylase on butyryl- and propionyl-CoA. Here, we tested the hypothesis that ECHDC1 is a metabolite repair enzyme that serves to prevent the formation of methyl- or ethyl-branched FAs by FASN. Using the purified enzyme, we found that FASN can incorporate not only methylmalonyl-CoA but also ethylmalonyl-CoA, producing methyl- or ethyl-branched FAs. Using a combination of gas-chromatography and liquid chromatography coupled to mass spectrometry, we observed that inactivation of ECHDC1 in adipocytes led to an increase in several methyl-branched FAs (present in different lipid classes), while its overexpression reduced them below wild-type levels. In contrast, the formation of ethyl-branched FAs was observed almost exclusively in ECHDC1 knockout cells, indicating that ECHDC1 and the low activity of FASN toward ethylmalonyl-CoA efficiently prevent their formation. We conclude that ECHDC1 performs a typical metabolite repair function by destroying methyl- and ethylmalonyl-CoA. This reduces the formation of methyl-branched FAs and prevents the formation of ethyl-branched FAs by FASN. The identification of ECHDC1 as a key modulator of the abundance of methyl-branched FAs opens the way to investigate their function.
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Cruzat V, Macedo Rogero M, Noel Keane K, Curi R, Newsholme P. Glutamine: Metabolism and Immune Function, Supplementation and Clinical Translation. Nutrients 2018; 10:nu10111564. [PMID: 30360490 PMCID: PMC6266414 DOI: 10.3390/nu10111564] [Citation(s) in RCA: 558] [Impact Index Per Article: 93.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 10/13/2018] [Accepted: 10/16/2018] [Indexed: 02/07/2023] Open
Abstract
Glutamine is the most abundant and versatile amino acid in the body. In health and disease, the rate of glutamine consumption by immune cells is similar or greater than glucose. For instance, in vitro and in vivo studies have determined that glutamine is an essential nutrient for lymphocyte proliferation and cytokine production, macrophage phagocytic plus secretory activities, and neutrophil bacterial killing. Glutamine release to the circulation and availability is mainly controlled by key metabolic organs, such as the gut, liver, and skeletal muscles. During catabolic/hypercatabolic situations glutamine can become essential for metabolic function, but its availability may be compromised due to the impairment of homeostasis in the inter-tissue metabolism of amino acids. For this reason, glutamine is currently part of clinical nutrition supplementation protocols and/or recommended for immune suppressed individuals. However, in a wide range of catabolic/hypercatabolic situations (e.g., ill/critically ill, post-trauma, sepsis, exhausted athletes), it is currently difficult to determine whether glutamine supplementation (oral/enteral or parenteral) should be recommended based on the amino acid plasma/bloodstream concentration (also known as glutaminemia). Although the beneficial immune-based effects of glutamine supplementation are already established, many questions and evidence for positive in vivo outcomes still remain to be presented. Therefore, this paper provides an integrated review of how glutamine metabolism in key organs is important to cells of the immune system. We also discuss glutamine metabolism and action, and important issues related to the effects of glutamine supplementation in catabolic situations.
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Affiliation(s)
- Vinicius Cruzat
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Biosciences, Curtin University, Perth 6102, Australia.
- Faculty of Health, Torrens University, Melbourne 3065, Australia.
| | - Marcelo Macedo Rogero
- Department of Nutrition, Faculty of Public Health, University of São Paulo, Avenida Doutor Arnaldo 715, São Paulo 01246-904, Brazil.
| | - Kevin Noel Keane
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Biosciences, Curtin University, Perth 6102, Australia.
| | - Rui Curi
- Interdisciplinary Post-Graduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo 01506-000, Brazil.
| | - Philip Newsholme
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Biosciences, Curtin University, Perth 6102, Australia.
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6
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Cruzat V, Macedo Rogero M, Noel Keane K, Curi R, Newsholme P. Glutamine: Metabolism and Immune Function, Supplementation and Clinical Translation. Nutrients 2018. [PMID: 30360490 DOI: 10.20944/preprints201809.0459.v1] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Glutamine is the most abundant and versatile amino acid in the body. In health and disease, the rate of glutamine consumption by immune cells is similar or greater than glucose. For instance, in vitro and in vivo studies have determined that glutamine is an essential nutrient for lymphocyte proliferation and cytokine production, macrophage phagocytic plus secretory activities, and neutrophil bacterial killing. Glutamine release to the circulation and availability is mainly controlled by key metabolic organs, such as the gut, liver, and skeletal muscles. During catabolic/hypercatabolic situations glutamine can become essential for metabolic function, but its availability may be compromised due to the impairment of homeostasis in the inter-tissue metabolism of amino acids. For this reason, glutamine is currently part of clinical nutrition supplementation protocols and/or recommended for immune suppressed individuals. However, in a wide range of catabolic/hypercatabolic situations (e.g., ill/critically ill, post-trauma, sepsis, exhausted athletes), it is currently difficult to determine whether glutamine supplementation (oral/enteral or parenteral) should be recommended based on the amino acid plasma/bloodstream concentration (also known as glutaminemia). Although the beneficial immune-based effects of glutamine supplementation are already established, many questions and evidence for positive in vivo outcomes still remain to be presented. Therefore, this paper provides an integrated review of how glutamine metabolism in key organs is important to cells of the immune system. We also discuss glutamine metabolism and action, and important issues related to the effects of glutamine supplementation in catabolic situations.
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Affiliation(s)
- Vinicius Cruzat
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Biosciences, Curtin University, Perth 6102, Australia. .,Faculty of Health, Torrens University, Melbourne 3065, Australia.
| | - Marcelo Macedo Rogero
- Department of Nutrition, Faculty of Public Health, University of São Paulo, Avenida Doutor Arnaldo 715, São Paulo 01246-904, Brazil.
| | - Kevin Noel Keane
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Biosciences, Curtin University, Perth 6102, Australia.
| | - Rui Curi
- Interdisciplinary Post-Graduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo 01506-000, Brazil.
| | - Philip Newsholme
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Biosciences, Curtin University, Perth 6102, Australia.
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7
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Brose SA, Marquardt AL, Golovko MY. Fatty acid biosynthesis from glutamate and glutamine is specifically induced in neuronal cells under hypoxia. J Neurochem 2013; 129:400-12. [PMID: 24266789 DOI: 10.1111/jnc.12617] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 10/27/2013] [Accepted: 11/14/2013] [Indexed: 12/12/2022]
Abstract
Hypoxia is involved in many neuronal and non-neuronal diseases, and defining the mechanisms for tissue adaptation to hypoxia is critical for the understanding and treatment of these diseases. One mechanism for tissue adaptation to hypoxia is increased glutamine and/or glutamate (Gln/Glu) utilization. To address this mechanism, we determined incorporation of Gln/Glu and other lipogenic substrates into lipids and fatty acids in both primary neurons and a neuronal cell line under normoxic and hypoxic conditions and compared this to non-neuronal primary cells and non-neuronal cell lines. Incorporation of Gln/Glu into total lipids was dramatically and specifically increased under hypoxia in neuronal cells including both primary (2.0- and 3.0-fold for Gln and Glu, respectively) and immortalized cultures (3.5- and 8.0-fold for Gln and Glu, respectively), and 90% to 97% of this increase was accounted for by incorporation into fatty acids (FA) depending upon substrate and cell type. All other non-neuronal cells tested demonstrated decreased or unchanged FA synthesis from Gln/Glu under hypoxia. Consistent with these data, total FA mass was also increased in neuronal cells under hypoxia that was mainly accounted for by the increase in saturated and monounsaturated FA with carbon length from 14 to 24. Incorporation of FA synthesized from Gln/Glu was increased in all major lipid classes including cholesteryl esters, triacylglycerols, diacylglycerols, free FA, and phospholipids, with the highest rate of incorporation into triacylglycerols. These results indicate that increased FA biosynthesis from Gln/Glu followed by esterification may be a neuronal specific pathway for adaptation to hypoxia. We identified a novel neuronal specific pathway for adaptation to hypoxia through increased fatty acid biosynthesis from glutamine and glutamate (Gln/Glu) followed by esterification into lipids. All other non-neuronal cells tested demonstrated decreased or unchanged lipid synthesis from Gln/Glu under hypoxia. Incorporation of other lipogenic substrates into lipids was decreased under hypoxia in neuronal cells. We believe that this finding will provide a novel strategy for treatment of oxygen and energy deficient conditions in the neuronal system.
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Affiliation(s)
- Stephen A Brose
- Department of Pharmacology, Physiology and Therapeutics, University of North Dakota, Grand Forks, ND, USA
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8
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Hua SZ, Pennell T. A microfluidic chip for real-time studies of the volume of single cells. LAB ON A CHIP 2009; 9:251-6. [PMID: 19107281 PMCID: PMC2612590 DOI: 10.1039/b806003g] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We report a microfluidic chip that is capable of measuring volume changes in single cells in real-time. Single eukaryotic cells were immobilized in the sensing area and changes in volume in response to hypotonic challenges and drugs were measured using the electrical impedance method. Experiments on MDCK cells showed that the maximum swelling and the time course of swelling vary between individual cells following hypotonic stimulation. The microfluidic chip allows, rapid and convenient change of solutions, enabling detailed studies of various drugs and chemicals that may play important role in cell physiology at the single cell level.
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Affiliation(s)
- Susan Z Hua
- Bio-MEMS and Biomaterials Laboratory, Department of Mechanical & Aerospace Engineering, SUNY-Buffalo, Buffalo, NY 14260, USA
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9
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Aiken KJ, Bickford JS, Kilberg MS, Nick HS. Metabolic regulation of manganese superoxide dismutase expression via essential amino acid deprivation. J Biol Chem 2008; 283:10252-63. [PMID: 18187411 PMCID: PMC2447627 DOI: 10.1074/jbc.m709944200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2007] [Indexed: 01/13/2023] Open
Abstract
Organisms respond to available nutrient levels by rapidly adjusting metabolic flux, in part through changes in gene expression. A consequence of adaptations in metabolic rate is the production of mitochondria-derived reactive oxygen species. Therefore, we hypothesized that nutrient sensing could regulate the synthesis of the primary defense of the cell against superoxide radicals, manganese superoxide dismutase. Our data establish a novel nutrient-sensing pathway for manganese superoxide dismutase expression mediated through essential amino acid depletion concurrent with an increase in cellular viability. Most relevantly, our results are divergent from current mechanisms governing amino acid-dependent gene regulation. This pathway requires the presence of glutamine, signaling via the tricarboxylic acid cycle/electron transport chain, an intact mitochondrial membrane potential, and the activity of both the MEK/ERK and mammalian target of rapamycin kinases. Our results provide evidence for convergence of metabolic cues with nutrient control of antioxidant gene regulation, revealing a potential signaling strategy that impacts free radical-mediated mutations with implications in cancer and aging.
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Affiliation(s)
- Kimberly J Aiken
- Department of Neuroscience, McKnight Brain Institute, Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610, USA
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Coroadinha AS, Alves PM, Santos SS, Cruz PE, Merten OW, Carrondo MJT. Retrovirus producer cell line metabolism: implications on viral productivity. Appl Microbiol Biotechnol 2006; 72:1125-35. [PMID: 16598449 DOI: 10.1007/s00253-006-0401-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2005] [Revised: 02/09/2006] [Accepted: 03/03/2006] [Indexed: 11/25/2022]
Abstract
The production of retroviral vectors by human cell lines is still hampered by low titers making it relatively difficult to produce very large quantities of this vector of high interest for clinical gene therapy applications. Thus, to improve vector production, we studied the influence of different sugars alone or combinations of sugars on cell growth, vector titers, and metabolism of the producer cell. The use of fructose at 140 mM or a mixed medium (with glucose at 25 mM and fructose at 140 mM) improved the virus titer three- to fourfold, respectively, and the producer cell productivity by fivefold. The increase in the cell productivity was due to a 1.5-fold increase in the vector stability, the remaining increase being due to higher cell specific productivity. The increase in the productivity was associated with lower glucose oxidation and an increase in the lactate and alanine yield. In the mixed medium, an increase in fatty acids derived from the glucose was observed in parallel with a reduction of glutamate and glutamine synthesis via the tricarboxylic acid (TCA) cycle acetyl-CoA and alpha-ketoglutarate, respectively. Although the higher productivities were associated with severe changes in the glycolysis, TCA cycle, and glutaminolysis, the cell energetic status monitored by phosphocreatine and adenosine triphosphate levels was not significantly affected. The synthesis of fatty acids and phospholipids were enhanced in the fructose or mixed media and are possibly key parameters in retroviral vector production.
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11
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Geelen MJH. The use of digitonin-permeabilized mammalian cells for measuring enzyme activities in the course of studies on lipid metabolism. Anal Biochem 2005; 347:1-9. [PMID: 16291302 DOI: 10.1016/j.ab.2005.03.032] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2005] [Revised: 02/25/2005] [Accepted: 03/17/2005] [Indexed: 10/25/2022]
Affiliation(s)
- Math J H Geelen
- Department of Nutrition, Graduate School of Animal Health, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
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Barber MC, Price NT, Travers MT. Structure and regulation of acetyl-CoA carboxylase genes of metazoa. Biochim Biophys Acta Mol Cell Biol Lipids 2005; 1733:1-28. [PMID: 15749055 DOI: 10.1016/j.bbalip.2004.12.001] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Revised: 11/02/2004] [Accepted: 12/01/2004] [Indexed: 11/16/2022]
Abstract
Acetyl-CoA carboxylase (ACC) plays a fundamental role in fatty acid metabolism. The reaction product, malonyl-CoA, is both an intermediate in the de novo synthesis of long-chain fatty acids and also a substrate for distinct fatty acyl-CoA elongation enzymes. In metazoans, which have evolved energy storage tissues to fuel locomotion and to survive periods of starvation, energy charge sensing at the level of the individual cell plays a role in fuel selection and metabolic orchestration between tissues. In mammals, and probably other metazoans, ACC forms a component of an energy sensor with malonyl-CoA, acting as a signal to reciprocally control the mitochondrial transport step of long-chain fatty acid oxidation through the inhibition of carnitine palmitoyltransferase I (CPT I). To reflect this pivotal role in cell function, ACC is subject to complex regulation. Higher metazoan evolution is associated with the duplication of an ancestral ACC gene, and with organismal complexity, there is an increasing diversity of transcripts from the ACC paraloges with the potential for the existence of several isozymes. This review focuses on the structure of ACC genes and the putative individual roles of their gene products in fatty acid metabolism, taking an evolutionary viewpoint provided by data in genome databases.
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Affiliation(s)
- Michael C Barber
- Hannah Research Institute, Ayr, KA6 5HL, Scotland, United Kingdom.
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Abstract
Amino acids are not only important precursors for the synthesis of proteins and other N-containing compounds, but also participate in the regulation of major metabolic pathways. Glutamate and aspartate, for example, are components of the malate/aspartate shuttle and their concentrations control the rate of mitochondrial oxidation of glycolytic NADH. Glutamate also controls the rate of urea synthesis, not only as the precursor of ammonia and aspartate, but as substrate for synthesis of N-acetylglutamate, the essential activator of carbamoyl-phosphate synthase. This mechanism allows large variations in urea synthesis at relatively constant ammonia concentrations. Increases in intracellular amino acid concentration increase cell volume. Cell swelling per se has anabolic effects on protein, carbohydrate and lipid metabolism: enhanced synthesis of macromolecules compensates for increases in intracellular osmolarity. Mechanisms responsible for cell swelling-induced changes in pathway fluxes include changes in intracellular ion concentrations and in signal transduction. Specific amino acids (e.g., leucine) stimulate protein synthesis and inhibit (autophagic) protein degradation independent of changes in cell volume because they stimulate mTOR (mammalian target of rapamycin), a protein kinase, which is one of the components of a signal transduction pathway used by insulin. When the cellular energy state is low, stimulation of mTOR by amino acids is prevented by activation of AMP-dependent protein kinase. Amino acid-dependent signaling also promotes insulin production by beta-cells. This further adds to the anabolic properties of amino acids. It is concluded that amino acids are important regulators of major metabolic pathways.
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Affiliation(s)
- Alfred J Meijer
- Department of Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands.
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14
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Boone AN, Chan A, Kulpa JE, Brownsey RW. Bimodal activation of acetyl-CoA carboxylase by glutamate. J Biol Chem 2000; 275:10819-25. [PMID: 10753875 DOI: 10.1074/jbc.275.15.10819] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Acetyl-CoA carboxylase (ACC) catalyzes the formation of malonyl-CoA, an essential substrate for fatty acid biosynthesis and a potent inhibitor of fatty acid oxidation. Here, we provide evidence that glutamate may be a physiologically relevant activator of ACC. Glutamate induced the activation of both major isoforms of ACC, prepared from rat liver, heart, or white adipose tissue. In agreement with previous studies, a type 2A protein phosphatase contributed to the effects of glutamate on ACC. However, the protein phosphatase inhibitor microcystin LR did not abolish the effects of glutamate on ACC activity. Moreover, glutamate directly activated purified preparations of ACC when protein phosphatase activity was excluded. Phosphatase-independent ACC activation by glutamate was also reflected by polymerization of the enzyme as judged by size-exclusion chromatography. The sensitivity of ACC to direct activation by glutamate was diminished by treatment in vitro with AMP-activated protein kinase or cAMP-dependent protein kinase or by beta-adrenergic stimulation of intact adipose tissue. We conclude that glutamate, an abundant intracellular amino acid, induces ACC activation through complementary actions as a phosphatase activator and as a direct allosteric ligand for dephosphorylated ACC. This study supports the general hypothesis that amino acids fulfill important roles as signal molecules as well as intermediates in carbon and nitrogen metabolism.
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Affiliation(s)
- A N Boone
- Department of Biochemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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15
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Bruynseels K, Van Hecke P, Vanstapel F. Further observations on the uptake and effects of phosphonates in perfused rat liver studied by (31)P-NMR. NMR IN BIOMEDICINE 1999; 12:275-285. [PMID: 10484816 DOI: 10.1002/(sici)1099-1492(199908)12:5<275::aid-nbm567>3.0.co;2-s] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We examined the route of uptake of 2-aminoethylphosphonate (NEthPo) and of phenylphosphonate (PhePo; 10 mM each) in perfused liver by (31)P-NMR. Uptake of NEthPo was concentrative. The rate of uptake was reduced to 21 +/- 2% (n = 3; all percentages refer to control rates) by substituting choline for Na(+), and to 21 +/- 4% (n = 3), 32 +/- 6% (n = 5) and 70 +/- 5% (n = 3) by replacing Cl(-) by gluconate, SO(4)(2-) or NO(3)(-), respectively. Taurine (20 mM) reduced NEthPo uptake to 38 +/- 6% (n = 3). The data are consistent with uptake of NEthPo by the Na(+)-coupled Cl(-)-dependent beta-amino acid transporter. A small fraction of NEthPo was incorporated into phospholipid. PhePo uptake evolved over 1 h towards levels of the membrane-permeant volume marker dimethyl methylphosphonate. Uptake depended on H(+), and was inhibited by 4, 4'-diisothiocyanato-stilbene-2,2'-disulphonic acid (100 microM), bumetanide and furosemide (1 mM each) and alpha-cyano-4-OH-cinnamic acid (5 mM) to 31 +/- 4% (n = 4), 28 +/- 4% (n = 4), 27 +/- 5% (n = 6) and 40 +/- 7% (n = 4), respectively. These characteristics of PhePo uptake are reminiscent of H(+)-coupled monocarboxylate transport. The monocarboxylates, lactate and acetate (20 mM), and the substrate analogue, phenylalanine (20 mM), were not inhibitory, while benzoic acid (20 mM) slightly inhibited (to 82 +/- 5%; n = 4) PhePo uptake. The tested phosphonates (10 mM) did not significantly affect hepatic extraction of [(3)H]-cholate or [(3)H]-taurocholate (25 microM each; 1:3 bile salt:albumin). The monocarboxylate analogue, PhePo (10 mM), did not significantly interfere with disposal of lactate (0.3-5 mM).
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Affiliation(s)
- K Bruynseels
- Biomedical NMR Unit, Department of Radiology, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Herestraat 49, B-3000, Leuven, Belgium
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16
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Devin A, Espié P, Guérin B, Rigoulet M. Energetics of swelling in isolated hepatocytes: a comprehensive study. Mol Cell Biochem 1998. [PMID: 9746316 DOI: 10.1023/a:1006847214074] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Cell swelling is now admitted as being a new principle of metabolic control but little is known about the energetics of cell swelling. We have studied the influence of hypo- or hyperosmolarity on both isolated hepatocytes and isolated rat liver mitochondria. Cytosolic hypoosmolarity on isolated hepatocytes induces an increase in matricial volume and does not affect the myxothiazol sensitive respiratory rate while the absolute value of the overall thermodynamic driving force over the electron transport chain increases. This points to an increase in kinetic control upstream the respiratory chain when cytosolic osmolarity is decreased. On isolated rat liver mitochondria incubated in hypoosmotic potassium chloride media, energetic parameters vary as in cells and oxidative phosphorylation efficiency is not affected. Cytosolic hyperosmolarity induced by sodium co-transported amino acids, per se, does not affect either matrix volume or energetic parameters. This is not the case in isolated rat liver mitochondria incubated in sucrose hyperosmotic medium. Indeed, in this medium, adenine nucleotide carrier is inhibited as the external osmolarity increases, which lowers the state 3 respiration close to state 4 level and consequently leads to a decrease in oxidative phosphorylation efficiency. When isolated rat liver mitochondria are incubated in KCl hyperosmotic medium, state 3 respiratory rate, matrix volume and membrane electrical potential vary as a function of time. Indeed, matrix volume is recovered in hyperosmotic KCl medium and this recovery is dependent on Pi-Kentry. State 3 respiratory rate increases and membrane electrical potential difference decreases during the first minutes of mitochondrial incubation until the attainment of the same value as in isoosmotic medium. This shows that matrix volume, flux and force are regulated as a function of time in KCl hyperosmotic medium. Under steady state, neither matrix volume nor energetic parameters are affected. Moreover, NaCl hyperosmotic medium allows matrix volume recovery but induces a decrease in state 3 respiratory flux. This indicates that potassium is necessary for both matrix volume and flux recovery in isolated mitochondria. We conclude that hypoosmotic medium induces an increase in kinetic control both upstream and on the respiratory chain and changes the oxidative phosphorylation response to forces. At steady state, hyperosmolarity, per se, has no effect on oxidative phosphorylation in either isolated hepatocytes or isolated mitochondria incubated in KCl medium. Therefore, potassium plays a key role in matrix volume, flux and force regulation.
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Affiliation(s)
- A Devin
- Institut de Biochimie et Génétique Cellulaires du CNRS, Université de Bordeaux 2, France
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17
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Lankester DL, Brown AM, Zammit VA. Use of cytosolic triacylglycerol hydrolysis products and of exogenous fatty acid for the synthesis of triacylglycerol secreted by cultured rat hepatocytes. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32177-5] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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18
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Häussinger D. Hepatic glutamine transport and metabolism. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 1998; 72:43-86. [PMID: 9559051 DOI: 10.1002/9780470123188.ch3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Although the liver was long known to play a major role in the uptake, synthesis, and disposition of glutamine, metabolite balance studies across the whole liver yielded apparently contradictory findings suggesting that little or no net turnover of glutamine occurred in this organ. Efforts to understand the unique regulatory properties of hepatic glutaminase culminated in the conceptual reformulation of the pathway for glutamine synthesis and turnover, especially as regards the role of sub-acinar distribution of glutamine synthetase and glutaminase. This chapter describes these processes as well as the role of glutamine in hepatocellular hydration, a process that is the consequence of cumulative, osmotically active uptake of glutamine into cells. This topic is also examined in terms of the effects of cell swelling on the selective stimulation or inhibition of other far-ranging cellular processes. The pathophysiology of the intercellular glutamine cycle in cirrhosis is also considered.
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Affiliation(s)
- D Häussinger
- Medizinische Universitätsklinik, Heinrich-Heine-Universität Düsseldorf, Germany
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19
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Lang F, Busch GL, Ritter M, Völkl H, Waldegger S, Gulbins E, Häussinger D. Functional significance of cell volume regulatory mechanisms. Physiol Rev 1998; 78:247-306. [PMID: 9457175 DOI: 10.1152/physrev.1998.78.1.247] [Citation(s) in RCA: 1273] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To survive, cells have to avoid excessive alterations of cell volume that jeopardize structural integrity and constancy of intracellular milieu. The function of cellular proteins seems specifically sensitive to dilution and concentration, determining the extent of macromolecular crowding. Even at constant extracellular osmolarity, volume constancy of any mammalian cell is permanently challenged by transport of osmotically active substances across the cell membrane and formation or disappearance of cellular osmolarity by metabolism. Thus cell volume constancy requires the continued operation of cell volume regulatory mechanisms, including ion transport across the cell membrane as well as accumulation or disposal of organic osmolytes and metabolites. The various cell volume regulatory mechanisms are triggered by a multitude of intracellular signaling events including alterations of cell membrane potential and of intracellular ion composition, various second messenger cascades, phosphorylation of diverse target proteins, and altered gene expression. Hormones and mediators have been shown to exploit the volume regulatory machinery to exert their effects. Thus cell volume may be considered a second message in the transmission of hormonal signals. Accordingly, alterations of cell volume and volume regulatory mechanisms participate in a wide variety of cellular functions including epithelial transport, metabolism, excitation, hormone release, migration, cell proliferation, and cell death.
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Affiliation(s)
- F Lang
- Institute of Physiology, University of Tübingen, Germany
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20
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Espié P, Devin A, Guérin B, Rigoulet M. Energetics of isolated hepatocyte swelling induced by sodium co-transported amino acids. J Bioenerg Biomembr 1997; 29:591-601. [PMID: 9559860 DOI: 10.1023/a:1022487119390] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This study was designed to investigate the energetics of isolated rat hepatocyte swelling due to sodium-cotransported amino acid accumulation in a medium containing either glucose or octanoate as basal substrate. We show that the size of the increase in cytosolic volume is directly correlated with the total amino acid accumulation, which depends on the difference of electrical potential across the plasma membrane. Such a change in cell volume, with either glucose or octanoate, does not modify the mitochondrial volume. Addition of sodium-cotransported amino acids for which the metabolism was avoided showed that the rise in cell volume, per se, did not change the respiratory rate, deltap, or phosphate potential in either mitochondrial or cytosolic compartments. Conversely, the large increase in oxidative phosphorylation flux was due to the metabolism of amino acids as a consequence of a rise in electron supply for the respiratory chain rather than an increase in cellular ATP demand, as indicated by the increase in cytosolic phosphate potential. Moreover, although we confirm that octanoate addition largely increases the respiratory rate by a process different from uncoupling, we observed that the same overall thermodynamic driving force through the respiratory chain and the same mitochondrial or cytosolic phosphate potential were maintained for much higher oxygen consumption when octanoate was present. We propose that these octanoate effects are due to a decrease in the actual protons/2 electrons stoichiometry as a consequence of a shift in electron supply toward a two-coupling site instead of a three-coupling site. The change in the FADH2/NADH formation flux ratio in either fatty acid or carbohydrate oxidation explains such results.
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Affiliation(s)
- P Espié
- Institut de Biochimie et Génétique Cellulaires du CNRS, Bordeaux, France
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21
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Devin A, Guérin B, Rigoulet M. Response of isolated rat liver mitochondria to variation of external osmolarity in KCl medium: regulation of matrix volume and oxidative phosphorylation. J Bioenerg Biomembr 1997; 29:579-90. [PMID: 9559859 DOI: 10.1023/a:1022435102552] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
When isolated rat liver mitochondria are incubated in KCI medium, matrix volume, flux, and forces in both hypo- and hyperosmolarity are time-dependent. In hypoosmotic KCl medium, matrix volume is regulated via the K+/H+ exchanger. In hyperosmotic medium, the volume is regulated in such a manner that at steady state, which is reached within 4 min, it is maintained whatever the hyperosmolarity. This regulation is Pi- and deltamuH+-dependent, indicating Pi-K salt entry into the matrix. Under steady state, hyperosmolarity has no effect on isolated rat liver mitochondria energetic parameters such as respiratory rate, proton electrochemical potential difference, and oxidative phosphorylation yield. Hypoosmolarity decreases the NADH/NAD+ ratio, state 3 respiratory rate, and deltamuH+, while oxidative phosphorylation yield is not significantly modified. This indicates kinetic control upstream the respiratory chain. This study points out the key role of potassium on the regulation of matrix volume, flux, and forces. Indeed, while matrix volume is regulated in NaCl hyperosmotic medium, flux and force restoration in hyperosmotic medium occurs only in the presence of external potassium.
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Affiliation(s)
- A Devin
- Institut de Biochimie et Génétique Cellulaires du CNRS, Université de Bordeaux, France
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22
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Gaussin V, Skarlas P, Ching YP, Hardie DG, Hue L. Distinct type-2A protein phosphatases activate HMGCoA reductase and acetyl-CoA carboxylase in liver. FEBS Lett 1997; 413:115-8. [PMID: 9287127 DOI: 10.1016/s0014-5793(97)00890-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Acetyl-CoA carboxylase and HMGCoA reductase are inactivated by the same AMP-activated protein kinase and are activated by type-2A protein phosphatase. To determine whether the same species of protein phosphatase-2A were involved, we studied the interconversion of acetyl-CoA carboxylase and HMGCoA reductase in isolated rat hepatocytes. We show that (i) these enzymes are differently regulated in hepatocytes and (ii) the species of type-2A protein phosphatase involved in their activation are different and can be separated by anion-exchange chromatography.
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Affiliation(s)
- V Gaussin
- Hormone and Metabolic Research Unit, International Institute of Cellular and Molecular Pathology, Louvain University Medical School, Brussels, Belgium
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23
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Krause U, Rider MH, Hue L. Protein kinase signaling pathway triggered by cell swelling and involved in the activation of glycogen synthase and acetyl-CoA carboxylase in isolated rat hepatocytes. J Biol Chem 1996; 271:16668-73. [PMID: 8663301 DOI: 10.1074/jbc.271.28.16668] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Incubation of isolated hepatocytes with glutamine or proline or in hypotonic media is known to activate glycogen synthase and acetyl-CoA carboxylase as a result of cell swelling. We report here that the same experimental conditions caused an activation of phosphatidylinositol 3-kinase and p70 ribosomal protein S6 kinase (p70 S6 kinase) but did not modify the activity of p42 mitogen-activated protein kinase. In addition, rapamycin, an inhibitor of p70 S6 kinase activation, prevented the amino acid- and hypotonicity-induced activation of p70 S6 kinase but did not block the activation of glycogen synthase and acetyl-CoA carboxylase, thus ruling out p70 S6 kinase as a necessary component in the activation pathway. By contrast, wortmannin or LY294002, inhibitors of phosphatidylinositol 3-kinase, completely blocked the activation of phosphatidylinositol 3-kinase and p70 S6 kinase and partly blocked the activation of glycogen synthase and acetyl-CoA carboxylase. Therefore, phosphatidylinositol 3-kinase might be a component of the signaling pathway that is triggered by cell swelling and is responsible, at least in part, for the activation of glycogen synthase and acetyl-CoA carboxylase. Incubation of hepatocytes with 0.1 microM epidermal growth factor doubled the activity of p42 mitogen-activated protein kinase without activating glycogen synthase.
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Affiliation(s)
- U Krause
- Hormone and Metabolic Research Unit, University of Louvain Medical School, and International Institute of Cellular and Molecular Pathology, B-1200 Brussels, Belgium
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24
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Gaussin V, Hue L, Stalmans W, Bollen M. Activation of hepatic acetyl-CoA carboxylase by glutamate and Mg2+ is mediated by protein phosphatase-2A. Biochem J 1996; 316 ( Pt 1):217-24. [PMID: 8645208 PMCID: PMC1217325 DOI: 10.1042/bj3160217] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The activation of hepatic acetyl-CoA carboxylase by Na(+)-cotransported amino acids such as glutamine has been attributed mainly to the stimulation of its dephosphorylation by accumulating dicarboxylic acids, e.g. glutamate. We report here on a hepatic species of protein phosphatase-2A that activates acetyl-CoA carboxylase in the presence of physiological concentrations of glutamate or Mg2+ and, under these conditions, accounts for virtually all the hepatic acetyl-CoA carboxylase phosphatase activity. Glutamate also stimulated the dephosphorylation of a synthetic pentadecapeptide encompassing the Ser-79 phosphorylation site of rat acetyl-CoA carboxylase, but did not affect the dephosphorylation of other substrates such as phosphorylase. Conversely, protamine, which stimulated the dephosphorylation of phosphorylase, inhibited the activation of acetyl-CoA carboxylase. A comparison with various species of muscle protein phosphatase-2A showed that the stimulatory effects of glutamate and Mg2+ on the acetyl-CoA carboxylase phosphatase activity are largely mediated by the regulatory A subunit. Glutamate and Mg2+ emerge from our study as novel regulators of protein phosphatase-2A when acting on acetyl-CoA carboxylase.
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Affiliation(s)
- V Gaussin
- Hormone and Metabolic Research Unit, University of Louvain Medical School, Brussels, Belgium
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25
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Affiliation(s)
- D Häussinger
- Medizinische Universitätsklinik, Heinrich Heine Universität, Düsseldorf, Germany
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26
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Devin A, Guérin B, Rigoulet M. Dependence of flux size and efficiency of oxidative phosphorylation on external osmolarity in isolated rat liver mitochondria: role of adenine nucleotide carrier. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1273:13-20. [PMID: 8573591 DOI: 10.1016/0005-2728(95)00130-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The aim of this work was a thermodynamic and kinetic study of the influence of varying external osmolarity on overall oxidative phosphorylations in isolated rat liver mitochondria. When external osmolarity is increased from 100 to 400 mosM by using a non-penetrant sugar: (i) matrix volume diminishes, (ii) state 3 respiratory rate decreases when state 4 slightly varies, (iii) states 3 and 4 protonmotive force and NAD(P)H level increase, whereas oxidative phosphorylation efficiency (ATP/O) decreases. Indeed, respiratory flux versus protonmotive force relationships depend on the osmolarity considered: the lower the external osmolarity, the higher the span of overall driving force necessary for the same respiratory rate. To further investigate the mechanism of the decrease in respiratory and ATP synthesis flux leading to a lowering in oxidative phosphorylation efficiency, we determined the adenine nucleotide carrier control coefficient on respiratory and ATP synthesis rates respectively. The main result is that the adenine nucleotide carrier control coefficient on respiratory rate decreases, and conversely that adenine nucleotide carrier control on ATP synthesis rate increases, from iso- to hyperosmolarity. Furthermore, whatever the osmolarity, when state 3 respiratory rate is titrated with carboxyatractyloside, the same relationship is observed between ATP/O ratio and respiratory flux. From many previous studies, it has been shown that an increase in external osmolarity and a consequent decrease in matrix volume inhibits almost all mitochondrial proton pumps (coupling site 1 and 2 of respiratory chain, ATPase) in different ways. In this work, we show that in phosphorylating mitochondria, the adenine nucleotide carrier plays a key role: its inhibition as the external osmolarity increases lowers the state 3 respiration close to state 4 level and consequently leads to a decrease in oxidative phosphorylation efficiency.
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Affiliation(s)
- A Devin
- Institut de Biochimie et Génétique Cellulaires du CNRS, Université de Bordeaux 2, France
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27
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Zammit VA. Effects of hydration state on the synthesis and secretion of triacylglycerol by isolated rat hepatocytes. Implications for the actions of insulin and glucagon on hepatic secretion. Biochem J 1995; 312 ( Pt 1):57-62. [PMID: 7492335 PMCID: PMC1136226 DOI: 10.1042/bj3120057] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effects of hepatocyte volume on the secretion of triacylglycerol were studied in order to test the suggestion that increases in the portal concentrations of osmolyte amino acids and metal ions during the prandial/early-absorptive phase may be involved in mediating the acute changes in glycerolipid metabolism observed in vivo [Zammit (1995) Biochem Soc. Trans. 23, 506-511]. Incubation of isolated rat hepatocytes with hypo-osmotic medium or in the presence of glutamine (in the presence or absence of leucine), conditions which gave an increase in cell water content of between 8 and 27%, resulted in a decrease in the rate of [14C]triacylglycerol (TAG) secretion when [14C]palmitate was used as substrate. The inhibition was proportional to the increase in cell water content. At low exogenous palmitate concentration (0.05 mM), the inhibition of [14C]TAG secretion was accompanied by a marked shift in the incorporation of label from TAG to phospholipid. In the presence of 0.5 mM palmitate this effect was attenuated, and in the presence of 1 mM palmitate it was abolished. Increased cell volume associated with incubation of hepatocytes with glutamine (in the presence or absence of leucine) also resulted in a decrease in the fraction of newly labelled TAG that was secreted into the medium. Decreased cell volume, achieved by incubation of hepatocytes with hyperosmotic medium (sufficient to decrease cell water content by approx. 9%) decreased overall [14C]TAG secretion, but did not affect the amount of label that was incorporated into phospholipid as a fraction of that incorporated into total glycerolipids. Cell shrinkage, however, diminished the fraction of newly labelled [14C]TAG that was secreted. When intracellular TAG was prelabelled with [3H]glycerol, it was found that cell shrinkage markedly inhibited (preformed) [3H]TAG secretion, whereas cell swelling did not affect this route of TAG secretion. The data are discussed in terms of the possible action of changes in cell hydration at the different loci at which hepatocyte TAG secretion is controlled, with reference to previous observations that both insulin and glucagon are able to inhibit TAG secretion in cultured rat hepatocytes and HepG2 cells.
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Affiliation(s)
- V A Zammit
- Hannah Research Institute, Ayr, Scotland, U.K
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28
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Espie P, Guerin B, Rigoulet M. On isolated hepatocytes mitochondrial swelling induced in hypoosmotic medium does not affect the respiration rate. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1230:139-46. [PMID: 7619832 DOI: 10.1016/0005-2728(95)00045-k] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In isolated hepatocytes incubated in hypoosmotic media, a large increase in the mitochondrial volume is not directly involved in the activation of respiration. Moreover, results of the quantification of the various bioenergetic parameters are not in accordance with an activation of the respiratory chain as previously proposed (Halestrap, A.P. (1989) Biochim. Biophys. Acta, 973, 355-382), but point more to an inhibition of respiration. The same respiration rate is obtained in hypoosmolar incubation media in vitro and in situ for a higher overall thermodynamic driving force over the electron transport chain.
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Affiliation(s)
- P Espie
- Institut de Biochimie et Génétique Cellulaires (C.N.R.S.), Bordeaux, France
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29
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Moir AM, Zammit VA. Insulin-independent and extremely rapid switch in the partitioning of hepatic fatty acids from oxidation to esterification in starved-refed diabetic rats. Possible roles for changes in cell pH and volume. Biochem J 1995; 305 ( Pt 3):953-8. [PMID: 7848296 PMCID: PMC1136350 DOI: 10.1042/bj3050953] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The requirement for a normal insulin response in mediating the starved-to-refed transition, with respect to the partitioning of hepatic fatty acids between beta-oxidation and esterification to glycerol, was studied. Diabetic rats were starved for 24 h and refed ad libitum for various periods of time. There was no increase in plasma insulin in response to the meal. However, the fatty acid oxidation:esterification ratio was very rapidly decreased from the starved to the fed value, most of the transition being achieved within the first hour of refeeding. There was a 2 h lag in the response of hepatic malonyl-CoA concentration, such that this rapid switch from oxidation to esterification could not be explained on the basis of changes in the absolute concentration of this inhibitor of carnitine palmitoyltransferase I (CPT I). Hepatic pyruvate and lactate concentrations both increased by several-fold upon refeeding and peaked after 1 h and 3 h, respectively. The hepatic lactate:pyruvate ratio increased 3.2-fold during the first 3 h of refeeding, suggesting that the cytosolic NAD(+)-NADH couple became much more highly reduced during the lag-period between the onset of inhibition of flux of fatty acids towards oxidation and the rise in malonyl-CoA concentration. This may be indicative of a lowering of intracellular pH, which would amplify greatly the sensitivity of CPT I to the inhibitor. In view of the very rapid and high food intake by these diabetic rats, the possibility is also considered that portal concentrations of amino acids and other metabolites could give rise to an increase in liver cell-volume that would inhibit CPT I acutely by an as yet unknown mechanism [M. Guzman, G. Velasco, J. Castro and V. A. Zammit (1994) FEBS Lett. 344, 239-241].
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Affiliation(s)
- A M Moir
- Hannah Research Institute, Ayr, U.K
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30
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Newsome WP, Warskulat U, Noe B, Wettstein M, Stoll B, Gerok W, Häussinger D. Modulation of phosphoenolpyruvate carboxykinase mRNA levels by the hepatocellular hydration state. Biochem J 1994; 304 ( Pt 2):555-60. [PMID: 7998992 PMCID: PMC1137528 DOI: 10.1042/bj3040555] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Exposure of isolated perfused rat livers to hypo-osmotic (225 mosmol/l) perfusion media for 3 h led to a decrease of about 60% in mRNA levels for phosphoenolpyruvate carboxy-kinase (PEPCK) compared with normo-osmotic (305 mosmol/l) perfusions. Conversely, PEPCK mRNA levels increased about 3-fold during hyperosmotic (385 mosmol/l) perfusions. The anisotonicity effects were not explained by changes in the intracellular cyclic AMP (cAMP) concentration or by changes of the extracellular Na+ or Cl- activity. Similar effects of aniso-osmolarity on PEPCK mRNA levels were found in cultured rat hepatoma H4IIE.C3 cells, the experimental system used for further characterization of the effect. Whereas during the first hour of anisotonic exposure no effects on PEPCK mRNA levels were detectable, near-maximal aniso-osmolarity effects were observed within the next 2-3 h. PEPCK mRNA levels increased sigmoidally with the osmolarity of the medium, and the anisotonicity effects were most pronounced upon modulation of osmolarity between 250 and 350 mosmol/l. The aniso-osmolarity effects on PEPCK mRNA were not affected in presence of Gö 6850, protein kinase C inhibitor. cAMP increased the PEPCK mRNA levels about 2.3-fold in normo-osmotic media, whereas insulin lowered the PEPCK mRNA levels to about 8%. The effects of cAMP and insulin were also observed during hypo-osmotic and hyperosmotic exposure, respectively, but the anisotonicity effects were not abolished in presence of the hormones. The data suggest that hepatocellular hydration affects hepatic carbohydrate metabolism also over a longer term by modulating PEPCK mRNA levels. This is apparently unrelated to protein kinase C or alterations of cAMP levels. The data strengthen the view that cellular hydration is an important determinant for cell metabolic function by extending its regulatory role in carbohydrate metabolism to the level of mRNA.
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Affiliation(s)
- W P Newsome
- Medizinische Universitätsklinik Freiburg, Federal Republic of Germany
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31
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Häussinger D, Lang F, Gerok W. Regulation of cell function by the cellular hydration state. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 267:E343-55. [PMID: 7943214 DOI: 10.1152/ajpendo.1994.267.3.e343] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cellular hydration can change within minutes under the influence of hormones, nutrients, and oxidative stress. Such short-term modulation of cell volume within a narrow range acts per se as a potent signal which modifies cellular metabolism and gene expression. It appears that cell swelling and cell shrinkage lead to certain opposite patterns of cellular metabolic function. Apparently, hormones and amino acids can trigger those patterns simply by altering cell volume. Thus alterations of cellular hydration may represent another important mechanism for metabolic control and act as another second or third messenger linking cell function to hormonal and environmental alterations.
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Affiliation(s)
- D Häussinger
- Medizinische Universitätsklinik Freiburg, Germany
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32
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Guzmán M, Velasco G, Castro J, Zammit VA. Inhibition of carnitine palmitoyltransferase I by hepatocyte swelling. FEBS Lett 1994; 344:239-41. [PMID: 7910567 DOI: 10.1016/0014-5793(94)00405-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Incubation of hepatocytes under conditions known to increase their volume, i.e. with amino acids (glutamine, proline) or in hypo-osmotic medium, decreased carnitine palmitoyl-transferase I (CPT-I) activity. This effect of hepatocyte swelling was antagonized by okadaic acid and dibutyryl-cAMP. Physiological concentrations of glutamate inhibited CPT-I activity in digitonin-permeabilized hepatocytes but not in isolated mitochondria. Results suggest that the amino acid-induced inhibition of CPT-I shares a common mechanism with the amino acid-induced stimulation of acetyl-CoA carboxylase and glycogen synthase [(1993) Eur. J. Biochem. 217, 1083-1089].
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Affiliation(s)
- M Guzmán
- Department of Biochemistry and Molecular Biology I, Faculty of Chemistry, Complutense University, Madrid, Spain
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