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González-Hódar L, McDonald JG, Vale G, Thompson BM, Figueroa AM, Tapia PJ, Robledo F, Agarwal AK, Garg A, Horton JD, Cortés V. Decreased caveolae in AGPAT2 lacking adipocytes is independent of changes in cholesterol or sphingolipid levels: A whole cell and plasma membrane lipidomic analysis of adipogenesis. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166167. [PMID: 33989739 DOI: 10.1016/j.bbadis.2021.166167] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 04/19/2021] [Accepted: 05/04/2021] [Indexed: 12/17/2022]
Abstract
BACKGROUND Adipocytes from lipodystrophic Agpat2-/- mice have impaired adipogenesis and fewer caveolae. Herein, we examined whether these defects are associated with changes in lipid composition or abnormal levels of caveolae-associated proteins. Lipidome changes were quantified in differentiated Agpat2-/- adipocytes to identify lipids with potential adipogenic roles. METHODS Agpat2-/- and wild type brown preadipocytes were differentiated in vitro. Plasma membrane was purified by ultracentrifugation. Number of caveolae and caveolae-associated proteins, as well as sterol, sphingolipid, and phospholipid lipidome were determined across differentiation. RESULTS Differentiated Agpat2-/- adipocytes had decreased caveolae number but conserved insulin signaling. Caveolin-1 and cavin-1 levels were equivalent between Agpat2-/- and wild type adipocytes. No differences in PM cholesterol and sphingolipids abundance were detected between genotypes. Levels of phosphatidylserine at day 10 of differentiation were increased in Agpat2-/- adipocytes. Wild type adipocytes had increased whole cell triglyceride, diacylglycerol, phosphatidylglycerol, phosphatidic acid, lysophosphatidylcholine, lysophosphatidylethanolamine, and trihexosyl ceramide, and decreased 24,25-dihydrolanosterol and sitosterol, as a result of adipogenic differentiation. By contrast, adipogenesis did not modify whole cell neutral lipids but increased lysophosphatidylcholine, sphingomyelin, and trihexosyl ceramide levels in Agpat2-/- adipocytes. Unexpectedly, adipogenesis decreased PM levels of main phospholipids in both genotypes. CONCLUSION In Agpat2-/- adipocytes, decreased caveolae is not associated with changes in PM cholesterol nor sphingolipid levels; however, increased PM phosphatidylserine content may be implicated. Abnormal lipid composition is associated with the adipogenic abnormalities of Agpat2 -/- adipocytes but does not prevent insulin signaling.
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Affiliation(s)
- Lila González-Hódar
- Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, 8331150, Chile
| | - Jeffrey G McDonald
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States; Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, United States
| | - Goncalo Vale
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Bonne M Thompson
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
| | - Ana-María Figueroa
- Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, 8331150, Chile
| | - Pablo J Tapia
- Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, 8331150, Chile
| | - Fermín Robledo
- Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, 8331150, Chile
| | - Anil K Agarwal
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, TX 75390, United States
| | - Abhimanyu Garg
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, TX 75390, United States
| | - Jay D Horton
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States; Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, United States; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, United States.
| | - Víctor Cortés
- Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, 8331150, Chile.
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Hesse D, Trost J, Schäfer N, Schwerbel K, Hoeflich A, Schürmann A, Brockmann GA. Effect of adipocyte-derived IGF-I on adipose tissue mass and glucose metabolism in the Berlin Fat Mouse. Growth Factors 2018; 36:78-88. [PMID: 30196772 DOI: 10.1080/08977194.2018.1497621] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Besides liver, IGF-I is expressed in adipose tissue. However, the effects of this local IGF-I on adipose tissue and metabolism are unclear. We generated adipocyte-specific knock-out mice on the background of the Berlin Fat Mouse Inbred (BFMI) line to evaluate the contribution of adipocyte-IGF-I on glucose metabolism and adipose tissue development. BFMI mice are obese, non-diabetic with elevated plasma insulin and IGF-I concentration. The knock-out in adipocytes led to a total white adipose tissue expression of 50-60% due to unaltered Igf-1 expression in stromavascular cells. The lack of IGF-I from adipocytes did not alter plasma IGF-I concentration. BFMIChr3-Igf-I-KOQ-AT mice had reduced adipose tissue mass in most depots. During oral glucose tolerance tests, BFMIChr3-Igf-I-KOQ-AT mice showed an impaired glucose clearance (p = .03). Interestingly, insulin action was enhanced during insulin tolerance tests (p = .05). In conclusion, adipocyte-specific IGF-I ablation in obese BFMI mice results in reduced adipose tissue mass and thereby alters glucose metabolism.
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Affiliation(s)
- Deike Hesse
- a Department of Crop and Animal Sciences, Humboldt-Universität zu Berlin , Berlin , Germany
| | - Jan Trost
- a Department of Crop and Animal Sciences, Humboldt-Universität zu Berlin , Berlin , Germany
| | - Nadine Schäfer
- a Department of Crop and Animal Sciences, Humboldt-Universität zu Berlin , Berlin , Germany
| | - Kristin Schwerbel
- b German Institute of Human Nutrition , Nuthetal , Germany
- c German Center for Diabetes Research , München-Neuherberg , Germany
| | - Andreas Hoeflich
- d Leibniz Institute for Farm Animal Biology , Dummerstorf , Germany
| | - Annette Schürmann
- b German Institute of Human Nutrition , Nuthetal , Germany
- c German Center for Diabetes Research , München-Neuherberg , Germany
| | - Gudrun A Brockmann
- a Department of Crop and Animal Sciences, Humboldt-Universität zu Berlin , Berlin , Germany
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Tando T, Hirayama A, Furukawa M, Sato Y, Kobayashi T, Funayama A, Kanaji A, Hao W, Watanabe R, Morita M, Oike T, Miyamoto K, Soga T, Nomura M, Yoshimura A, Tomita M, Matsumoto M, Nakamura M, Toyama Y, Miyamoto T. Smad2/3 Proteins Are Required for Immobilization-induced Skeletal Muscle Atrophy. J Biol Chem 2016; 291:12184-94. [PMID: 27129272 DOI: 10.1074/jbc.m115.680579] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Indexed: 01/23/2023] Open
Abstract
Skeletal muscle atrophy promotes muscle weakness, limiting activities of daily living. However, mechanisms underlying atrophy remain unclear. Here, we show that skeletal muscle immobilization elevates Smad2/3 protein but not mRNA levels in muscle, promoting atrophy. Furthermore, we demonstrate that myostatin, which negatively regulates muscle hypertrophy, is dispensable for denervation-induced muscle atrophy and Smad2/3 protein accumulation. Moreover, muscle-specific Smad2/3-deficient mice exhibited significant resistance to denervation-induced muscle atrophy. In addition, expression of the atrogenes Atrogin-1 and MuRF1, which underlie muscle atrophy, did not increase in muscles of Smad2/3-deficient mice following denervation. We also demonstrate that serum starvation promotes Smad2/3 protein accumulation in C2C12 myogenic cells, an in vitro muscle atrophy model, an effect inhibited by IGF1 treatment. In vivo, we observed IGF1 receptor deactivation in immobilized muscle, even in the presence of normal levels of circulating IGF1. Denervation-induced muscle atrophy was accompanied by reduced glucose intake and elevated levels of branched-chain amino acids, effects that were Smad2/3-dependent. Thus, muscle immobilization attenuates IGF1 signals at the receptor rather than the ligand level, leading to Smad2/3 protein accumulation, muscle atrophy, and accompanying metabolic changes.
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Affiliation(s)
| | - Akiyoshi Hirayama
- the Institute for Advanced Biosciences, Keio University, 246-2 Mizukami, Kakuganji, Tsuruoka, Yamagata 997-0052, and
| | | | - Yuiko Sato
- From the Departments of Orthopedic Surgery, Musculoskeletal Reconstruction and Regeneration Surgery
| | - Tami Kobayashi
- From the Departments of Orthopedic Surgery, Musculoskeletal Reconstruction and Regeneration Surgery
| | | | | | - Wu Hao
- From the Departments of Orthopedic Surgery
| | | | - Mayu Morita
- Dentistry and Oral Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582
| | | | | | - Tomoyoshi Soga
- the Institute for Advanced Biosciences, Keio University, 246-2 Mizukami, Kakuganji, Tsuruoka, Yamagata 997-0052, and
| | - Masatoshi Nomura
- the Department of Medicine and Bioregulatory Science, Graduate School of Medical Science, Kyushu University, Maidashi 3-1-1, Higashi Ward, Fukuoka 812-8582, Japan
| | | | - Masaru Tomita
- the Institute for Advanced Biosciences, Keio University, 246-2 Mizukami, Kakuganji, Tsuruoka, Yamagata 997-0052, and
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Diamanti-Kandarakis E, Chatzigeorgiou A, Papageorgiou E, Koundouras D, Koutsilieris M. Advanced glycation end-products and insulin signaling in granulosa cells. Exp Biol Med (Maywood) 2015; 241:1438-45. [PMID: 25956684 DOI: 10.1177/1535370215584937] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 04/06/2015] [Indexed: 01/03/2023] Open
Abstract
Advanced glycation end-products (AGEs) may interfere with insulin intracellular signaling and glucose transport in human granulosa cells, potentially affecting ovarian function, follicular growth, linked with diminished fertility. The potential interaction of AGEs with insulin signaling pathways and glucose transport was investigated in human granulosa KGN cells. KGN cells were cultured with variable concentrations of human glycated albumin (HGA, 50-200 µg/mL) or insulin (100 ng/mL). Combined treatments of KGN cells with insulin (100 ng/mL) and HGA (200 µg/mL) were also performed. p-AKT levels and glucose transporter type 4 (Glut-4) translocation analysis were performed by Western blot. Phosphatidylinositol-3-kinase (PI3K)-specific signaling was checked by using the PI3K-inhibitor, LY294002. p-AKT levels were significantly increased following insulin treatment compared to basal levels or HGA exposure. This insulin-mediated AKT-phosphorylation was PI3K-specific and it was inhibited after combined treatment of insulin and HGA. Furthermore, Glut-4 translocation from the cytoplasm to the membrane compartments of KGN cells was remarkably reduced after the combined treatment of insulin and HGA. The present findings support that AGEs interfere with insulin signaling in granulosa cells and prevent Glut-4 membrane translocation suggesting that intra ovarian AGEs accumulation, from endogenous or exogenous sources, may contribute to the pathophysiology of states characterized with anovulation and insulin resistance such as polycystic ovary syndrome.
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Affiliation(s)
| | - Antonios Chatzigeorgiou
- Department of Experimental Physiology, University of Athens Medical School, Athens 11527, Greece Department of Clinical Pathobiochemistry, Dresden University of Technology, Dresden, 01307, Germany
| | - Efstathia Papageorgiou
- Department of Experimental Physiology, University of Athens Medical School, Athens 11527, Greece
| | - Dimitrios Koundouras
- Endocrine Unit, Internal Medicine, University of Athens Medical School, Athens 11527, Greece
| | - Michael Koutsilieris
- Department of Experimental Physiology, University of Athens Medical School, Athens 11527, Greece
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Incerpi S, Hsieh MT, Lin HY, Cheng GY, De Vito P, Fiore AM, Ahmed RG, Salvia R, Candelotti E, Leone S, Luly P, Pedersen JZ, Davis FB, Davis PJ. Thyroid hormone inhibition in L6 myoblasts of IGF-I-mediated glucose uptake and proliferation: new roles for integrin αvβ3. Am J Physiol Cell Physiol 2014; 307:C150-61. [PMID: 24808494 DOI: 10.1152/ajpcell.00308.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Thyroid hormones L-thyroxine (T4) and 3,3',5-triiodo-L-thyronine (T3) have been shown to initiate short- and long-term effects via a plasma membrane receptor site located on integrin αvβ3. Also insulin-like growth factor type I (IGF-I) activity is known to be subject to regulation by this integrin. To investigate the possible cross-talk between T4 and IGF-I in rat L6 myoblasts, we have examined integrin αvβ3-mediated modulatory actions of T4 on glucose uptake, measured through carrier-mediated 2-deoxy-[3H]-D-glucose uptake, and on cell proliferation stimulated by IGF-I, assessed by cell counting, [3H]-thymidine incorporation, and fluorescence-activated cell sorting analysis. IGF-I stimulated glucose transport and cell proliferation via the cell surface IGF-I receptor (IGFIR) and, downstream of the receptor, by the phosphatidylinositol 3-kinase signal transduction pathway. Addition of 0.1 nM free T4 caused little or no cell proliferation but prevented both glucose uptake and proliferative actions of IGF-I. These actions of T4 were mediated by an Arg-Gly-Asp (RGD)-sensitive pathway, suggesting the existence of crosstalk between IGFIR and the T4 receptor located near the RGD recognition site on the integrin. An RGD-sequence-containing integrin inhibitor, a monoclonal antibody to αvβ3, and the T4 metabolite tetraiodothyroacetic acid all blocked the inhibition by T4 of IGF-I-stimulated glucose uptake and cell proliferation. Western blotting confirmed roles for activated phosphatidylinositol 3-kinase and extracellular regulated kinase 1/2 (ERK1/2) in the effects of IGF-I and also showed a role for ERK1/2 in the actions of T4 that modified the effects of IGF-I. We conclude that thyroid hormone inhibits IGF-I-stimulated glucose uptake and cell proliferation in L6 myoblasts.
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Affiliation(s)
- Sandra Incerpi
- Department of Sciences, University Roma Tre, Rome, Italy;
| | - Meng-Ti Hsieh
- Taipei Cancer Center, Taipei Medical University, Taipei, Taiwan
| | - Hung-Yun Lin
- Taipei Cancer Center, Taipei Medical University, Taipei, Taiwan; Graduate Institute of Cancer Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Guei-Yun Cheng
- Taipei Cancer Center, Taipei Medical University, Taipei, Taiwan
| | - Paolo De Vito
- Department of Biology, University Tor Vergata, Rome, Italy
| | | | - R G Ahmed
- Department of Zoology, Beni-Suef University, Beni-Suef, Egypt
| | - Rosanna Salvia
- Department of Sciences, University Roma Tre, Rome, Italy
| | | | - Stefano Leone
- Department of Sciences, University Roma Tre, Rome, Italy
| | - Paolo Luly
- Department of Biology, University Tor Vergata, Rome, Italy
| | | | - Faith B Davis
- Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Albany, New York
| | - Paul J Davis
- Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Albany, New York; Department of Medicine, Albany Medical College, Albany, New York
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Neves FA, Cortez E, Bernardo AF, Mattos ABM, Vieira AK, Malafaia TDO, Thole AA, Rodrigues-Cunha ACDS, Garcia-Souza EP, Sichieri R, Moura AS. Heart energy metabolism impairment in Western-diet induced obese mice. J Nutr Biochem 2013; 25:50-7. [PMID: 24314865 DOI: 10.1016/j.jnutbio.2013.08.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 08/20/2013] [Accepted: 08/30/2013] [Indexed: 11/16/2022]
Abstract
Nutritional transition has contributed to growing obesity, mainly by changing eating habits of the population. The mechanisms by which diet-induced obesity leads to cardiac injury are not completely understood, but it is known that obesity is associated to impaired cardiac function and energy metabolism, increasing morbidity and mortality. Therefore, our study aimed to investigate the mechanisms underlying cardiac metabolism impairment related to Western diet-induced obesity. After weaning, male Swiss mice were fed a Western diet for 16 weeks in order to induce obesity. After this period, the content of proteins involved in heart energy metabolism GLUT1, cytosolic lysate and plasma membrane GLUT4, AMPK, pAMPK, IRβ, IRS-1, PGC-1α, CPT1 and UCP2 was evaluated. Also, the oxidative phosphorylation of myocardial fibers was measured by high-resolution respirometry. Mice in the Western diet group (WG) presented altered biometric parameters compared to those in control group, including higher body weight, increased myocardial lipid deposition and glucose intolerance, which demonstrate the obesogenic role of Western diet. WG presented increased CPT1 and UCP2 contents and decreased IRS-1, plasma membrane GLUT4 and PGC-1α contents. In addition, WG presented cardiac mitochondrial dysfunction and reduced biogenesis, demonstrating a lower capacity of carbohydrates and fatty acid oxidation and also decreased coupling between oxidative phosphorylation and adenosine triphosphate synthesis. Cardiac metabolism impairment related to Western diet-induced obesity is probably due to damaged myocardial oxidative capacity, reduced mitochondrial biogenesis and mitochondria uncoupling, which compromise the bioenergetic metabolism of heart.
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Affiliation(s)
- Fabiana A Neves
- Laboratory of Nutrition Physiology and Development, Department of Physiological Sciences, Institute of Biology, State University of Rio de Janeiro, Rio de Janeiro, Brazil
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7
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Russo VC, Higgins S, Werther GA, Cameron FJ. Effects of Fluctuating Glucose Levels on Neuronal Cells In Vitro. Neurochem Res 2012; 37:1768-82. [DOI: 10.1007/s11064-012-0789-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Revised: 04/12/2012] [Accepted: 04/24/2012] [Indexed: 12/29/2022]
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Human cytomegalovirus activates glucose transporter 4 expression to increase glucose uptake during infection. J Virol 2010; 85:1573-80. [PMID: 21147915 DOI: 10.1128/jvi.01967-10] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Glucose transport into mammalian cells is mediated by a group of glucose transporters (GLUTs) on the plasma membrane. Human cytomegalovirus (HCMV)-infected human fibroblasts (HFs) demonstrate significantly increased glucose consumption compared to mock-infected cells, suggesting a possible alteration in glucose transport during infection. Inhibition of GLUTs by using cytochalasin B indicated that infected cells utilize GLUT4, whereas normal HFs use GLUT1. Quantitative reverse transcription-PCR and Western analysis confirmed that GLUT4 levels are greatly increased in infected cells. In contrast, GLUT1 was eliminated by a mechanism involving the HCMV major immediate-early protein IE72. The HCMV-mediated induction of GLUT4 circumvents characterized controls of GLUT4 expression that involve serum stimulation, glucose concentration, and nuclear functions of ATP-citrate lyase (ACL). In infected cells the well-characterized Akt-mediated translocation of GLUT4 to the cell surface is also circumvented; GLUT4 localized on the surface of infected cells that were serum starved and had Akt activity inhibited. The significance of GLUT4 induction for the success of HCMV infection was indicated using indinavir, a drug that specifically inhibits glucose uptake by GLUT4. The addition of the drug inhibited glucose uptake in infected cells as well as viral production. Our data show that HCMV-specific mechanisms are used to replace GLUT1, the normal HF GLUT, with GLUT4, the major glucose transporter in adipose tissue, which has a 3-fold-higher glucose transport capacity.
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Beh JE, Latip J, Abdullah MP, Ismail A, Hamid M. Scoparia dulcis (SDF7) endowed with glucose uptake properties on L6 myotubes compared insulin. JOURNAL OF ETHNOPHARMACOLOGY 2010; 129:23-33. [PMID: 20193753 DOI: 10.1016/j.jep.2010.02.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 12/31/2009] [Accepted: 02/08/2010] [Indexed: 05/28/2023]
Abstract
AIM OF THE STUDY Insulin stimulates glucose uptake and promotes the translocation of glucose transporter 4 (Glut 4) to the plasma membrane on L6 myotubes. The aim of this study is to investigate affect of Scoparia dulcis Linn water extracts on glucose uptake activity and the Glut 4 translocation components (i.e., IRS-1, PI 3-kinase, PKB/Akt2, PKC and TC 10) in L6 myotubes compared to insulin. MATERIALS AND METHODS Extract from TLC fraction-7 (SDF7) was used in this study. The L6 myotubes were treated by various concentrations of SDF7 (1 to 50 microg/ml) and insulin (1 to 100 nM). The glucose uptake activities of L6 myotubes were evaluated using 2-Deoxy-D-glucose uptake assay in with or without fatty acid-induced medium. The Glut 4 translocation components in SDF7-treated L6 myotubes were detected using immunoblotting and quantified by densitometry compared to insulin. Plasma membrane lawn assay and glycogen colorimetry assay were carried out in SDF7- and insulin-treated L6 myotubes in this study. RESULTS Here, our data clearly shows that SDF7 possesses glucose uptake properties on L6 myotubes that are dose-dependent, time-dependent and plasma membrane Glut 4 expression-dependent. SDF7 successfully stimulates glucose uptake activity as potent as insulin at a maximum concentration of 50 microg/ml at 480 min on L6 myotubes. Furthermore, SDF7 stimulates increased Glut 4 expression and translocation to plasma membranes at equivalent times. Even in the insulin resistance stage (free fatty acids-induced), SDF7-treated L6 myotubes were found to be more capable at glucose transport than insulin treatment. CONCLUSIONS Thus, we suggested that Scoparia dulcis has the potential to be categorized as a hypoglycemic medicinal plant based on its good glucose transport properties.
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Affiliation(s)
- Joo Ee Beh
- Department of Microbiology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
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Nam JS, Nam JY, Yoo JS, Cho M, Park JS, Ahn CW, Cha BS, Lee EJ, Lim SK, Kim KR, Lee HC. The effect of mosapride (5HT-4 receptor agonist) on insulin sensitivity and GLUT4 translocation. Diabetes Res Clin Pract 2010; 87:329-34. [PMID: 20060191 DOI: 10.1016/j.diabres.2009.12.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 12/09/2009] [Accepted: 12/15/2009] [Indexed: 01/08/2023]
Abstract
AIMS We investigated the effect of mosapride, 5HT-4 (5-hydroxytryptamine) agonist, on blood glucose level and insulin sensitivity in subjects with impaired glucose tolerance (IGT) and conducted an in vitro study to evaluate the action mechanism. METHODS Thirty IGT patients were randomly assigned to receive either mosapride or placebo for 2 weeks. Biochemical profiles and insulin sensitivity index from euglycemic hyperinsulinemic clamp test were assessed before and after treatment. In cultured myotubes from human skeletal muscle cells, insulin- and mosapride-induced GLUT4 translocation and tyrosine phosphorylation of IRS-1 were determined. RESULTS After 2 weeks of treatment with mosapride, glucose disposal rates were significantly increased up to those of control (mosapride 5.47+/-1.72 vs 7.06+/-2.13, P=0.004, placebo 5.42+/-1.85 vs 5.23+/-1.53mgkg(-1)min(-1)). Fasting plasma glucose (FPG) and insulin levels were decreased. Mosapride increased the contents of GLUT4 in plasma membrane representing the increased recruitment of glucose transporters from intracellular pool. While insulin treatment on human skeletal muscle cell resulted in an increased tyrosine phosphorylation of IRS-1, mosapride did not have any effect. CONCLUSIONS Mosapride is effective in decreasing FPG without stimulating insulin secretion in IGT subjects, possibly by inducing GLUT4 translocation in skeletal muscles.
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Affiliation(s)
- J S Nam
- Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
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Díaz M, Vraskou Y, Gutiérrez J, Planas JV. Expression of rainbow trout glucose transporters GLUT1 and GLUT4 during in vitro muscle cell differentiation and regulation by insulin and IGF-I. Am J Physiol Regul Integr Comp Physiol 2008; 296:R794-800. [PMID: 19118099 DOI: 10.1152/ajpregu.90673.2008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin is an important factor for the maintenance of glucose homeostasis, enhancing glucose uptake in its target tissues in a process that has been conserved between fish and mammals. In fish skeletal muscle cells, like in mammals, insulin promotes GLUT4 translocation to the plasma membrane and, consequently, glucose uptake, but its role regulating the expression of glucose transporters in vitro has not been demonstrated to date. Thus, we investigated the expression of GLUT4 and GLUT1 throughout skeletal muscle cell differentiation and their regulation by insulin and IGF-I using a primary culture of trout muscle cells. GLUT4 expression gradually increased during the muscle cell differentiation process, whereas GLUT1 expression remained fairly constant. Insulin and IGF-I similarly increased the mRNA levels of GLUT4 in myoblasts and myotubes. On the other hand, IGF-I appeared to be more potent than insulin in stimulating GLUT1 expression, particularly at the myoblast stage. Therefore, this work provides the first demonstration in nonmammalian vertebrates that insulin and IGF-I may act directly on trout muscle cells to regulate the expression of GLUT4 and GLUT1.
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Affiliation(s)
- Mònica Díaz
- Departament de Fisiologia, Universitat de Barcelona and Institut de Biomedicina de la Universitat de Barcelona, Spain
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12
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Copland JA, Pardini AW, Wood TG, Yin D, Green A, Bodenburg YH, Urban RJ, Stuart CA. IGF-1 controls GLUT3 expression in muscle via the transcriptional factor Sp1. ACTA ACUST UNITED AC 2007; 1769:631-40. [PMID: 17920708 DOI: 10.1016/j.bbaexp.2007.08.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 06/02/2007] [Accepted: 08/13/2007] [Indexed: 10/22/2022]
Abstract
Glucose transporter 3 (GLUT3), while first found in human fetal muscle, is predominantly expressed in brain and neural tissue. By several independent techniques we have previously shown that GLUT3 is expressed in human skeletal muscle cells. The structure of the human GLUT3 gene has not been previously reported nor has there been any evaluation of the 5'-untranslated region (UTR). To this end, we have cloned and sequenced the human GLUT3 gene. Insulin-like growth factor-1 (IGF-1) increased endogenous Glut3 protein in cultured L6 myotubes, and similarly stimulated luciferase activity in a construct of the human GLUT3 5'-UTR linked to a luciferase reporter gene. Actinomycin D, an inhibitor of mRNA synthesis, prevented IGF-1 stimulation of Glut3 protein. Transfection of L6 cells with Sp1 increased Glut3 and augmented IGF-1 stimulation of Glut3 expression. Knockdown of Glut3 expression in cultured L6 muscle cells using small interference RNA (siRNA) specific for Glut3 significantly reduced myocyte glucose uptake. DNAse footprinting and gel shift assays showed Sp1 specifically bound to the human GLUT3 5'-UTR. Substitution mutants of the human GLUT3 5'-UTR luciferase construct indicated that only one of three Sp1 site clusters was involved in IGF-1 action. These data, using both a human GLUT3 5'-UTR construct and L6 cells' endogenous promoter, suggest that IGF-1 plays a role in maintaining muscle GLUT3 expression and basal glucose uptake via the transcriptional factor Sp1.
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Affiliation(s)
- John A Copland
- The Mayo Clinic Cancer Center, Jacksonville, Florida, USA
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Sferruzzi-Perri AN, Owens JA, Standen P, Taylor RL, Robinson JS, Roberts CT. Early pregnancy maternal endocrine insulin-like growth factor I programs the placenta for increased functional capacity throughout gestation. Endocrinology 2007; 148:4362-70. [PMID: 17525121 DOI: 10.1210/en.2007-0411] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In early pregnancy, the concentrations of IGFs increase in maternal blood. Treatment of pregnant guinea pigs with IGFs in early to midpregnancy enhances placental glucose transport and fetal growth and viability near term. In the current study, we determined whether exogenous IGFs altered placental gene expression, transport, and nutrient partitioning during treatment, which may then persist. Guinea pigs were infused with IGF-I, IGF-II (both 1 mg/kg x d) or vehicle sc from d 20-35 of pregnancy and killed on d 35 (term is 70 d) after administration of [(3)H]methyl-D-glucose (MG) and [(14)C]amino-isobutyric acid (AIB). IGF-I increased placental and fetal weights (+15 and +17%, respectively) and MG and AIB uptake by the placenta (+42 and +68%, respectively) and fetus (+59 and +90%, respectively). IGF-I increased placental mRNA expression of the amino acid transporter gene Slc38a2 (+780%) and reduced that of Igf2 (-51%), without altering the glucose transporter Slc2a1 or Vegf and Igf1 genes. There were modest effects of IGF-I treatment on MG and AIB uptake by individual maternal tissues and no effect on plasma glucose, total amino acids, free fatty acids, triglycerides, and cholesterol concentrations. IGF-II treatment of the mother did not alter any maternal, fetal or placental parameter. In conclusion, exogenous IGF-I, but not IGF-II, in early pregnancy increases placental transport of MG and AIB, enhancing midgestational fetal nutrient uptake and growth. This suggests that early pregnancy rises in maternal circulating IGF-I play a major role in regulating placental growth and functional development and thus fetal growth throughout gestation.
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Affiliation(s)
- Amanda N Sferruzzi-Perri
- Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, South Australia 5005, Australia
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14
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Lin L, Kim SC, Wang Y, Gupta S, Davis B, Simon SI, Torre-Amione G, Knowlton AA. HSP60 in heart failure: abnormal distribution and role in cardiac myocyte apoptosis. Am J Physiol Heart Circ Physiol 2007; 293:H2238-47. [PMID: 17675567 DOI: 10.1152/ajpheart.00740.2007] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Heat shock protein (HSP) 60 is a mitochondrial and cytosolic protein. Previously, we reported that HSP60 doubled in end-stage heart failure, even though levels of the protective HSP72 were unchanged. Furthermore, we observed that acute injury in adult cardiac myocytes resulted in movement of HSP60 to the plasma membrane. We hypothesized that the inflammatory state of heart failure would cause translocation of HSP60 to the plasma membrane and that this would provide a pathway for cardiac injury. Two models were used to test this hypothesis: 1) a rat model of heart failure and 2) human explanted failing hearts. We found that HSP60 localized to the plasma membrane and was also found in the plasma early in heart failure. Plasma membrane HSP60 localized to lipid rafts and was detectable on the cell surface with the use of both flow cytometry and confocal microscopy. Localization of HSP60 to the cell surface correlated with increased apoptosis. In heart failure, HSP60 is in the plasma membrane fraction, on the cell surface, and in the plasma. Membrane HSP60 correlated with increased apoptosis. Release of HSP60 may activate the innate immune system, promoting a proinflammatory state, including an increase in TNF-alpha. Thus abnormal trafficking of HSP60 to the cell surface may be an early trigger for myocyte loss and the progression of heart failure.
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Affiliation(s)
- Li Lin
- Molecular and Cellular Cardiology, Cardiovascular Division, University of California, Davis, California 95616, USA
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15
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Dimopoulos N, Watson M, Sakamoto K, Hundal H. Differential effects of palmitate and palmitoleate on insulin action and glucose utilization in rat L6 skeletal muscle cells. Biochem J 2006; 399:473-81. [PMID: 16822230 PMCID: PMC1615906 DOI: 10.1042/bj20060244] [Citation(s) in RCA: 172] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
An increase in circulating levels of specific NEFAs (non-esterified fatty acids) has been implicated in the pathogenesis of insulin resistance and impaired glucose disposal in skeletal muscle. In particular, elevation of SFAs (saturated fatty acids), such as palmitate, has been correlated with reduced insulin sensitivity, whereas an increase in certain MUFAs and PUFAs (mono- and poly-unsaturated fatty acids respectively) has been suggested to improve glycaemic control, although the underlying mechanisms remain unclear. In the present study, we compare the effects of palmitoleate (a MUFA) and palmitate (a SFA) on insulin action and glucose utilization in rat L6 skeletal muscle cells. Basal glucose uptake was enhanced approx. 2-fold following treatment of cells with palmitoleate. The MUFA-induced increase in glucose transport led to an associated rise in glucose oxidation and glycogen synthesis, which could not be attributed to activation of signalling proteins normally modulated by stimuli such as insulin, nutrients or cell stress. Moreover, although the MUFA-induced increase in glucose uptake was slow in onset, it was not dependent upon protein synthesis, but did, nevertheless, involve an increase in the plasma membrane abundance of GLUT1 and GLUT4. In contrast, palmitate caused a substantial reduction in insulin signalling and insulin-stimulated glucose transport, but was unable to antagonize the increase in transport elicited by palmitoleate. Our findings indicate that SFAs and MUFAs exert distinct effects upon insulin signalling and glucose uptake in L6 muscle cells and suggest that a diet enriched with MUFAs may facilitate uptake and utilization of glucose in normal and insulin-resistant skeletal muscle.
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Affiliation(s)
- Nikolaos Dimopoulos
- *Division of Molecular Physiology, Centre for Interdisciplinary Research, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Maria Watson
- *Division of Molecular Physiology, Centre for Interdisciplinary Research, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Kei Sakamoto
- †MRC Protein Phosphorylation Unit, Centre for Interdisciplinary Research, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Harinder S. Hundal
- *Division of Molecular Physiology, Centre for Interdisciplinary Research, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
- To whom correspondence should be addressed (email )
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16
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Muzumdar RH, Ma X, Fishman S, Yang X, Atzmon G, Vuguin P, Einstein FH, Hwang D, Cohen P, Barzilai N. Central and opposing effects of IGF-I and IGF-binding protein-3 on systemic insulin action. Diabetes 2006; 55:2788-96. [PMID: 17003344 DOI: 10.2337/db06-0318] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
IGF-I is recognized as an insulin sensitizer at the liver and muscle, while recent evidence suggests that IGF-binding protein (IGFBP)-3 acts as an insulin antagonist. As there is a paucity of IGF-I receptors in the liver and as the IGF-IGFBP system in the central nervous system is emerging as physiologically relevant, we examined whether the effects of IGF-I and IGFBP-3 on insulin action are mediated through central mechanisms. Intracerebroventricular (ICV) infusion of IGF-I during the insulin clamp (3 mU x kg(-1) x min(-1)) resulted in significant improvement in hepatic insulin action (50%, P < 0.05). In contrast, ICV infusion of IGFBP-3 significantly impaired insulin action at the liver (45% increase in hepatic glucose production, P < 0.01). While IGF-I marginally increased peripheral glucose uptake, IGFBP-3 significantly decreased peripheral glucose uptake (approximately 30%, P < 0.01). As the nuclear localization signal mutant IGFBP-3, which has a normal affinity to IGFs but binds other IGFBP-3 partners poorly and fails to normally internalize, has reduced central activity on metabolism, we conclude that the effects of IGFBP-3 on the hypothalamus involve activity mediated by interfacing with other molecules in addition to IGFs. Marked, opposing, and independent physiological effects of IGF-I and IGFBP-3 through central mechanisms may have implications on potential strategies in specific modulation of peripheral insulin action.
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Affiliation(s)
- Radhika H Muzumdar
- Division of Pediatric Endocrinology, Children's Hospital at Montefiore, New York, USA
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17
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Russo VC, Kobayashi K, Najdovska S, Baker NL, Werther GA. Neuronal protection from glucose deprivation via modulation of glucose transport and inhibition of apoptosis: a role for the insulin-like growth factor system. Brain Res 2004; 1009:40-53. [PMID: 15120582 DOI: 10.1016/j.brainres.2004.02.042] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/26/2004] [Indexed: 11/23/2022]
Abstract
Glucose is the brain's major energy source; therefore, loss of neuronal cells is a potential consequence of hypoglycaemia. Since apoptosis is a major mechanism of neuronal loss following a range of insults, we explored potent anti-apoptotic systems (IGF-I and bcl-2) as means of enhancing neuronal survival in the face of glucose deprivation. Human neuroblastoma cells (SH-SY5Y, SHEP and SHEP-bcl-2) were exposed to low glucose as a model of glucopenia-induced neuronal damage. Administration of IGF-I and/or over-expression of the survival gene bcl-2 were exploited to attempt to limit neuronal loss. Neuronal survival mechanisms and interactions between these systems were investigated. Low glucose (0.25-2.5 mM) adversely affected cell growth and survival; however, IGF-I ameliorated these outcomes. Over-expression of bcl-2 blunted low glucose-induced apoptosis and up-regulated IGF-I receptor, with the effect of IGF-I addition being negligible on apoptosis, while significantly enhancing mitochondrial activity. In SH-SY5Y cells, IGF-I significantly changed >two-fold mRNA levels of the apoptosis-related genes gadd45, fas, iNOS, NFkB, TRAIL, without further affecting bcl-2 expression. In low glucose, IGF-I acutely enhanced glucose transport and translocation of GLUT1 protein to the cell membrane. GLUT1 mRNA expression was up-regulated by both IGF-I and bcl-2. The potent anti-apoptotic systems IGF-I and bcl-2 are both thus able to enhance cell survival in a glucose-deprived human neuronal model. Although we clearly show evidence of positive cross-talk via bcl-2 modulation of IGF-I receptor, IGF-I also has enhancing effects on mitochondrial function outside the bcl-2 pathway. The common effect of both systems on enhancement of GLUT-1 expression suggests that this is a key mechanism for enhanced survival. These studies also point to the potential use of IGF-I therapy in prevention or amelioration of hypoglycaemic brain injury.
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Affiliation(s)
- V C Russo
- Centre for Hormone Research, Murdoch Childrens Research Institute, Royal Children's Hospital, Flemington Road, Parkville 3052, Victoria, Australia.
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18
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Biga PR, Schelling GT, Hardy RW, Cain KD, Overturf K, Ott TL. The effects of recombinant bovine somatotropin (rbST) on tissue IGF-I, IGF-I receptor, and GH mRNA levels in rainbow trout, Oncorhynchus mykiss. Gen Comp Endocrinol 2004; 135:324-33. [PMID: 14723884 DOI: 10.1016/j.ygcen.2003.10.014] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Numerous studies demonstrated that rbST increased growth rates in several fish species, and several species exhibit GH production in tissues other than the pituitary. The role of tissue GH and IGF-I in regulating fish growth is poorly understood. Therefore an experiment was conducted to examine the effects of rbST treatment on tissue GH, IGF-I, and IGF-I receptor-A (rA) expression in rainbow trout. Rainbow trout (550 +/- 10 g) received either intra-peritoneal injections of rbST (120 microg/g body weight) or vehicle on days 0 and 21, and tissue samples were collected on days 0, 0.5, 1, 3, 7, and 28 (n = 6/day/trt). Total RNA was isolated and assayed for steady-state levels of IGF-I, IGF-IrA, and GH mRNA using quantitative RT-PCR. Insulin-like growth factor-I mRNA levels increased in liver, gill, gonad, muscle, brain, and intestine in response to rbST treatment (P < 0.10). Liver IGF-I mRNA increased (P < 0.01) 0.5 day after treatment and remained elevated throughout the trial. Intestine IGF-I mRNA increased (P < 0.05) in treated fish from day 1 to day 3, then decreased to day 7 and increased again at day 28, and remained elevated above control levels throughout the trial. Gill IGF-I mRNA levels increased (P < 0.05) 1 day after treatment and remained elevated throughout the trial. Heart IGF-IrA mRNA levels decreased (P < 0.05) while gonad GH mRNA levels increased (P < 0.10) following rbST treatment. These results demonstrate that rbST treatment increased IGF-I mRNA levels in extra-hepatic tissues, and decreased heart IGF-IrA and increased gonad GH mRNA levels. Because the primary source for endocrine IGF-I is liver, the increased IGF-I mRNA reported in extra-hepatic tissues may indicate local paracrine/autocrine actions for IGF-I for local physiological functions.
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Affiliation(s)
- Peggy R Biga
- Department of Animal and Veterinary Science, Center for Reproductive Biology, University of Idaho, Moscow, 83844, USA
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19
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Solini A, Chiozzi P, Morelli A, Passaro A, Fellin R, Di Virgilio F. Defective P2Y purinergic receptor function: A possible novel mechanism for impaired glucose transport. J Cell Physiol 2003; 197:435-44. [PMID: 14566973 DOI: 10.1002/jcp.10379] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Extracellular ATP is an ubiquitous mediator that regulates several cellular functions via specific P2 plasma membrane receptors (P2Rs), for which a role in modulating intracellular glucose metabolism has been recently suggested. We have investigated glucose uptake in response to P2Rs stimulation in fibroblasts from type 2 diabetic (T2D) patients and control subjects. P2Rs expression was evaluated by RT-PCR; intracellular calcium release by fluorometry; glucose transporter (GLUT1) translocation by immunoblotting and chemiluminescence; glucose uptake was measured with 2-deoxy-D-[1-(3)H]glucose (2-DOG) and ATP by luminometry. Cells from T2D patients, in contrast to those from healthy controls, showed no increase in glucose uptake after ATP stimulation; extracellular ATP caused, however, a similar GLUT1 recruitment to the plasma membrane in both groups. P2Rs expression did not differ between fibroblasts from diabetic and healthy subjects, but while plasma membrane depolarization, a P2X-mediated response was similar in both groups, no evident intracellular calcium increase was detectable in the cells from the former group. The calcium response in fibroblasts from diabetics was restored by co-incubation with apyrase or hexokinase, suggesting that P2YRs in those cells were normally expressed but chronically desensitised. In support to this finding, fibroblasts from T2D subjects secreted a two-fold larger amount of ATP compared to controls. Pre-treatment with apyrase or hexokinase also restored ATP stimulated glucose uptake in fibroblasts from diabetic subjects. These results suggest that extracellular ATP plays a role in the modulation of glucose transport via GLUT1, and that the P2Y-dependent GLUT1 activation is deficient in fibroblasts from T2D individuals. Our observations may point to additional therapeutic targets for improving glucose utilization in diabetes.
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Affiliation(s)
- Anna Solini
- Department of Internal Medicine, University of Pisa, Italy
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20
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Hajduch E, Litherland GJ, Turban S, Brot-Laroche E, Hundal HS. Insulin regulates the expression of the GLUT5 transporter in L6 skeletal muscle cells. FEBS Lett 2003; 549:77-82. [PMID: 12914929 DOI: 10.1016/s0014-5793(03)00773-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Skeletal muscle, a primary insulin target tissue, expresses the GLUT5 fructose transporter. Although insulin has no acute effect on GLUT5 expression and function in muscle, we show here that long-term (24 h) insulin treatment of L6 muscle cells induces a dose-dependent increase in GLUT5 protein (by up to two-fold), leading to a concomitant increase in fructose uptake. The increase in GLUT5 expression and function was suppressed by inhibitors of gene transcription and protein synthesis, suggesting that insulin promotes de novo carrier synthesis. Transfection of the GLUT5 gene promoter fused to luciferase into L6 cells revealed that insulin induced a 1.8-fold increase in GLUT5 promoter activity. Our findings indicate that insulin is capable of increasing the abundance and functional activity of GLUT5 in skeletal muscle cells and that this is most likely mediated via activation of the GLUT5 promoter.
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Affiliation(s)
- Eric Hajduch
- Division of Molecular Physiology, School of Life Sciences, MSI/WTB Complex, University of Dundee, Dundee DD1 4HN, UK
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21
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Chaudary N, Shuralyova I, Liron T, Sweeney G, Coe IR. Transport characteristics of HL-1 cells: a new model for the study of adenosine physiology in cardiomyocytes. Biochem Cell Biol 2003; 80:655-65. [PMID: 12440705 DOI: 10.1139/o02-143] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenosine is a physiologically important nucleoside in the cardiovascular system where it can act as a cardioprotectant and modulator of energy usage. Adenosine transporters (ATs) modulate cellular adenosine levels, which, in turn, can affect a number of processes such as receptor activation and glucose uptake, but their role in cardiac physiology is poorly understood. Therefore, we have developed a new cell model by determining various adenosine-related characteristics of HL-1, an immortalized atrial cardiomyocyte murine cell line. Adenosine uptake in HL-1 cells is sodium independent, saturable, and inhibitable by nucleoside transport inhibitors (nitrobenzylthioinosine (NBTI), dipyridamole, dilazep). Reverse transcription--polymerase chain reaction analysis confirmed that HL-1 cells possess mouse equilibrative nucleoside transporters 1 and 2 (mENT1, mENT2) and kinetic analyses indicate moderate-affinity (Km = 51.3 +/- 12.9 microM), NBTI-sensitive adenosine transport. NBTI binds at a high-affinity single site (B(max) = 520 +/- 10 fmol/mg protein, Kd = 0.11 +/- 0.04 nM, 1.6 x 10(5) NBTI-binding sites/cell). HL-1 cells possess adenosine receptor, metabolic enzyme, protein kinase C isoform, and insulin-stimulated glucose transport profiles that match normal mouse heart. Therefore, HL-1 is an excellent model to study ATs within cardiomyocytes and the first model for evaluating in detail the role of the ATs in modulating effects of adenosine.
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Affiliation(s)
- Naz Chaudary
- Department of Biology, York University, Toronto, ON, Canada
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22
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Abstract
BACKGROUND Heat shock protein (HSP)60 is an abundant protein found primarily in the mitochondria, though 15% to 20% is found in the cytosol. Previously we observed that HSP60 complexes with bax in the cytosol. Reduction in HSP60 precipitates translocation of bax to the mitochondria and apoptosis. We hypothesized that HSP60 would decrease with hypoxia/reoxygenation and that this would precipitate bax translocation to the mitochondria and release of cytochrome c. METHODS AND RESULTS Adult rat cardiac myocytes were studied at end-hypoxia and at 10 and 24 hours of reoxygenation. HSP60 levels were unchanged at end-hypoxia and decreased 33% and 40% at 10 and 24 hours of reoxygenation, whereas HSP72 increased 80% and 110%. Bax and bcl-2 decreased during reoxygenation. However, cytochrome c release occurred at end-hypoxia, before reoxygenation. Cell fractionation was done to analyze this further. In normal myocytes, bax and HSP60 were present in the cytosol, and bax coimmunoprecipitated with cytosolic HSP60. At end-hypoxia, mitochondrial HSP60 was unchanged, but cytosolic HSP60 had disappeared and was now in the plasma membrane fraction. Concurrently, bax was no longer in the cytosol but now in the mitochondria. Thus, although total HSP60 remained the same, it no longer complexed with bax, and bax was free to translocate to the mitochondria and precipitate apoptosis. Reduction in ATP had a similar effect. CONCLUSIONS These studies show that hypoxia results in disassociation of the HSP60-bax complex with translocation of cytosolic HSP60 to the plasma membrane and bax to the mitochondria. This is sufficient to trigger apoptosis.
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Affiliation(s)
- S Gupta
- Baylor College of Medicine and the VA Medical Center, Houston, Tex, USA
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23
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Bertolini M, Beam SW, Shim H, Bertolini LR, Moyer AL, Famula TR, Anderson GB. Growth, development, and gene expression by in vivo- and in vitro-produced day 7 and 16 bovine embryos. Mol Reprod Dev 2002; 63:318-28. [PMID: 12237947 DOI: 10.1002/mrd.90015] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The effects of the embryo production system on growth and transcription rate of day 7 and 16 bovine embryos were investigated. In vivo- (controls) and in vitro-produced (IVP) embryos were transferred to female recipients on day 7 of development, and were allowed to develop in a synchronous uterine environment to day 16. Embryonic transcripts for insulin-like growth factors-1 and -2 (IGF-1 and -2), their receptors (IGF-1r and -2r), facilitative glucose transporters-1 and -3 (Glut-1 and -3), and interferon-tau (IFN-tau) were determined by real-time quantitative PCR (TaqMan); gender diagnosis was performed on day 16 concepti only. On day 7, IVP embryos presented lower mRNA levels than controls (P < 0.05), but these differences were generally reduced on day 16. No IGF-1 transcripts were detected on day 7, but a low IGF-1 mRNA level was observed in day 16 embryos. In the IVP group, IFN-tau mRNA levels were lower on day 7 (P < 0.05), but higher than controls on day 16 (P < 0.05). Control embryos showed a temporal decrease in the relative transcription from day 7 to 16 (P < 0.05), except IGF-1 mRNA. On day 16, IVP concepti were shorter and displayed smaller embryonic discs (P < 0.05). Female concepti were generally smaller than males, and IGF-2r mRNA and growth were negatively correlated. The in vitro production of bovine embryos negatively affected the amount of gene expression on day 7 and the rate of development on day 16. Physical traits and transcriptional activity on day 16 were associated with one another, which appeared to be significant for growth and development.
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Affiliation(s)
- Marcelo Bertolini
- Department of Animal Science, University of California, Davis, California 95616, USA
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Ritter MR, Dorrell MI, Edmonds J, Friedlander SF, Friedlander M. Insulin-like growth factor 2 and potential regulators of hemangioma growth and involution identified by large-scale expression analysis. Proc Natl Acad Sci U S A 2002; 99:7455-60. [PMID: 12032304 PMCID: PMC124252 DOI: 10.1073/pnas.102185799] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Hemangiomas are benign tumors of the vascular endothelium and are the most common tumors of infancy. These tumors are characterized by an initial phase of rapid proliferation, which is followed, in most cases, by spontaneous involution. Although most lesions resolve without complication, there are some cases in which hemangiomas can be life threatening when occurring near a vital structure. Treatment for these aggressive tumors represents an unmet clinical need. In addition, this characteristic progression of hemangiomas through distinct phases provides a unique opportunity for studying endothelial cell biology and angiogenesis. Using DNA microarrays representing approximately 10,000 human genes, we identified insulin-like growth factor 2 (IGF-2) as a potentially important regulator of hemangioma growth. IGF-2 was highly expressed during the proliferative phase and substantially decreased during involution. This finding was confirmed at the message level by quantitative reverse transcription-PCR and at the protein level by immunohistochemistry. IGF-2 protein was localized primarily to tumor vessels or vascular channels. Using a human hemangioma explant model, we show that IGF-2 promotes sprouting from intact hemangioma tissue. In addition, several angiogenesis-related factors, including integrins alpha(v)beta3 and alpha5beta1, are present in proliferating hemangiomas. During the involuting phase, an increase in several IFN-induced genes was observed. These studies identify potential regulators of hemangioma growth and involution and provide a foundation on which to build further mechanistic investigations into angiogenesis, using hemangiomas as a model.
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Affiliation(s)
- Matthew R Ritter
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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25
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Hyde R, Peyrollier K, Hundal HS. Insulin promotes the cell surface recruitment of the SAT2/ATA2 system A amino acid transporter from an endosomal compartment in skeletal muscle cells. J Biol Chem 2002; 277:13628-34. [PMID: 11834730 DOI: 10.1074/jbc.m108609200] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
SAT1-3 comprise members of the recently cloned family of System A transporters that mediate the sodium-coupled uptake of short chain neutral amino acids, and their activity is regulated extensively by stimuli such as insulin, growth factors, and amino acid availability. In skeletal muscle, insulin stimulates System A activity rapidly by a presently ill-defined mechanism. Here we demonstrate that insulin induces an increase in the plasma membrane abundance of SAT2 in a phosphatidylinositol 3-kinase-dependent manner and that this increase is derived from an endosomal compartment that is required for the hormonal activation of System A. Chloroquine, an acidotropic weak base that impairs endosomal recycling of membrane proteins, induced a complete inhibition in the insulin-mediated stimulation of System A, which was associated with a loss in SAT2 recruitment to the plasma membrane. The failure to stimulate System A and recruit SAT2 to the cell surface could not be attributed to a block in insulin signaling, as chloroquine had no effect on the insulin-mediated phosphorylation of protein kinase B or glycogen synthase kinase 3 or upon insulin-stimulated GLUT4 translocation and glucose transport. Our data indicate strongly that insulin increases System A transport in L6 cells by stimulating the exocytosis of SAT2 carriers from a chloroquine-sensitive endosomal compartment.
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Affiliation(s)
- Russell Hyde
- Division of Molecular Physiology, Medical Sciences Institute/Wellcome Trust Biocentre Complex, Dow Street, University of Dundee, Dundee DD1 5EH, United Kingdom
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26
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Klip A, Marette A. Regulation of Glucose Transporters by Insulin and Exercise: Cellular Effects and Implications for Diabetes. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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27
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Méndez E, Smith A, Figueiredo-Garutti ML, Planas JV, Navarro I, Gutiérrez J. Receptors for insulin-like growth factor-I (IGF-I) predominate over insulin receptors in skeletal muscle throughout the life cycle of brown trout, Salmo trutta. Gen Comp Endocrinol 2001; 122:148-57. [PMID: 11316420 DOI: 10.1006/gcen.2001.7621] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin and IGF-I binding has been studied in brown trout (Salmo trutta) wheat germ agglutinin semipurified receptors from embryos (organogenesis), larvae (yolk sac), juveniles (2.98 +/- 0.21 g bw) and adults (111.6 +/- 6.92 and 522 +/- 53 g bw). Embryos and larvae were sampled at 5 and 12 weeks after fertilization (December 1999 and February 2000) and juvenile and adults were taken simultaneously (July 1999) and under the same feeding conditions to minimize potential nutritional and seasonal effects. Insulin receptor number was maximal at 12 weeks (144 fmol/mg glycoprotein) and progressively decreased in subsequent samplings. No alterations in affinity were detected (K(d) range, 0.21-0.32 nM) and changes in number of receptor paralleled changes in total specific binding. IGF-I receptor number was highest at 5 weeks (1044 fmol/mg) and was significantly higher than values for insulin in all samplings. The affinity of IGF-I receptor did not change (K(d) range, 0.11-0.18 nM) but was consistently higher than that for the insulin receptor. A more rapid decrease of IGF-I binding and receptor number was found with age. However, the ratio of insulin/IGF-I binding established in 12-week-old larvae (0.18 +/- 0.01) was thereafter maintained at very similar values in juveniles and adults (0.15-0.17). Tyrosine kinase activity (TKA) for insulin receptors ranged between 136 and 183% and there were no significant changes with age. For the IGF-I receptor, TKA ranged from 174 to 281% and was significantly higher in 5-week-old larvae coincident with the highest levels of receptor number and declined gradually in parallel with binding levels. In conclusion, the greater abundance of IGF-I receptors during embryonic and larval development is maintained throughout juvenile and adult stages. This would suggest a key role for IGF-I in the growth and metabolism of trout muscle.
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Affiliation(s)
- E Méndez
- Departament de Fisiologia, Facultat de Biologia, D. III, Universitat de Barcelona, Avinguda Diagonal 645, Barcelona, 08028, Spain
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Friedlander AL, Butterfield GE, Moynihan S, Grillo J, Pollack M, Holloway L, Friedman L, Yesavage J, Matthias D, Lee S, Marcus R, Hoffman AR. One year of insulin-like growth factor I treatment does not affect bone density, body composition, or psychological measures in postmenopausal women. J Clin Endocrinol Metab 2001; 86:1496-503. [PMID: 11297574 DOI: 10.1210/jcem.86.4.7377] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The activity of the hypothalamic-GH-insulin-like growth factor I (hypothalamic-GH-IGF-I) axis declines with age, and some of the catabolic changes of aging have been attributed to the somatopause. The purpose of this investigation was to determine the impact of 1 yr of IGF-I hormone replacement therapy on body composition, bone density, and psychological parameters in healthy, nonobese, postmenopausal women over 60 yr of age. Subjects (n = 16, 70.6 +/- 2.0 yr, 71.8 +/- 2.8 kg) were randomly assigned to either the self-injection IGF-I (15 microg/kg twice daily) or placebo group and were studied at baseline, at 6 months, and at 1 yr of treatment. There were no significant differences between the IGF-I and placebo groups in any of the measured variables at baseline. Fasting blood IGF-I levels were significantly elevated above baseline values (65.6 +/- 11.9 ng/mL) at 6 months (330.0 +/- 52.8) and 12 months (297.7 +/- 40.8) in the IGF-I treated group but did not change in the placebo subjects. Circulating levels of IGF-binding protein-1 and -3 were unaffected by the IGF-I treatment. Bone mineral density of the forearm, lumbar spine, hip, and whole body [as measured by dual-energy x-ray absorptiometry (DXA)] did not change in either group. Similarly, there was no difference in DXA-measured lean mass, fat mass, or percent body fat throughout the treatment intervention. Muscle strength values (grip, bench press, leg press), blood lipid parameters (cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides), and measures of postmeal glucose disposal were not altered by IGF-I treatment, although postmeal insulin levels were lower in the IGF-I subjects at 12 months. IGF-I did not affect bone turnover markers (osteocalcin and type I collagen N-teleopeptide), but subjects who were taking estrogen had significantly lower turnover markers than subjects who were not on estrogen at baseline, 6 months, and 12 months. Finally, the psychological measures of mood and memory were also not altered by the intervention. Despite the initial intent to recruit additional subjects, the study was discontinued after 16 subjects completed the protocol, because the preliminary analyses above indicated that no changes were occurring in any outcome variables, regardless of treatment regimen. Therefore, we conclude that 1 yr of IGF-I treatment, at a dose sufficient to elevate circulating IGF-I to young normal values, is not an effective means to alter body composition or blood parameters nor improve bone density, strength, mood, or memory in older women.
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Affiliation(s)
- A L Friedlander
- Medical Service, Geriatric Research Education Clinical Center, Palo Alto Veterans Administration Health Care System, California 94304, USA.
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Navarrete Santos A, Augustin R, Lazzari G, Galli C, Sreenan JM, Fischer B. The insulin-dependent glucose transporter isoform 4 is expressed in bovine blastocysts. Biochem Biophys Res Commun 2000; 271:753-60. [PMID: 10814535 DOI: 10.1006/bbrc.2000.2646] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have investigated the expression of two glucose transporter isoforms, Glut1 and 4, in 14- and 16-day-old bovine blastocysts (d14, d16) using RT-PCR, competitive RT-PCR and in situ hybridization. The blastocysts were grown in vivo or had been produced in vitro. Glut1 mRNA was detected in all blastocysts studied, Glut4 in all d14 blastocysts, but only in a few d16 blastocysts. Glut4 mRNA was localized in trophoblast and endoderm cells. Glut1 mRNA increased from d14 to d16 while Glut4 transcription was down-regulated in d16 blastocysts. The mRNA amounts varied between 0.8 to 23 pg and 3.9 to 65 fg per 100 ng embryonic RNA for Glut1 and Glut4, respectively, displaying a 100- to 1500-fold lower expression of Glut4 compared with Glut1 during blastocyst elongation. This is the first report on the expression of the insulin-sensitive Glut4 isoform in mammalian preimplantation embryos.
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Affiliation(s)
- A Navarrete Santos
- Department of Anatomy and Cell Biology, Martin Luther University Faculty of Medicine, Halle (Saale), Germany.
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30
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Frick F, Oscarsson J, Vikman-Adolfsson K, Ottosson M, Yoshida N, Edén S. Different effects of IGF-I on insulin-stimulated glucose uptake in adipose tissue and skeletal muscle. Am J Physiol Endocrinol Metab 2000; 278:E729-37. [PMID: 10751208 DOI: 10.1152/ajpendo.2000.278.4.e729] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of insulin-like growth factor I (IGF-I) on insulin-stimulated glucose uptake was studied in adipose and muscle tissues of hypophysectomized female rats. IGF-I was given as a subcutaneous infusion via osmotic minipumps for 6 or 20 days. All hypophysectomized rats received L-thyroxine and cortisol replacement therapy. IGF-I treatment increased body weight gain but had no effect on serum glucose or free fatty acid levels. Serum insulin and C-peptide concentrations decreased. Basal and insulin-stimulated glucose incorporation into lipids was reduced in adipose tissue segments and isolated adipocytes from the IGF-I-treated rats. In contrast, insulin treatment of hypophysectomized rats for 7 days increased basal and insulin-stimulated glucose incorporation into lipids in isolated adipocytes. Pretreatment of isolated adipocytes in vitro with IGF-I increased basal and insulin-stimulated glucose incorporation into lipids. These results indicate that the effect of IGF-I on lipogenesis in adipose tissue is not direct but via decreased serum insulin levels, which reduce the capacity of adipocytes to metabolize glucose. Isoproterenol-stimulated lipolysis, but not basal lipolysis, was enhanced in adipocytes from IGF-I-treated animals. In the soleus muscle, the glycogen content and insulin-stimulated glucose incorporation into glycogen were increased in IGF-I-treated rats. In summary, IGF-I has opposite effects on glucose uptake in adipose tissue and skeletal muscle, findings which at least partly explain previous reports of reduced body fat mass, increased body cell mass, and increased insulin responsiveness after IGF-I treatment.
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Affiliation(s)
- F Frick
- Department of Physiology and Pharmacology, Göteborg University, S-405 30 Goteborg, Sweden
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31
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Giorgino F, de Robertis O, Laviola L, Montrone C, Perrini S, McCowen KC, Smith RJ. The sentrin-conjugating enzyme mUbc9 interacts with GLUT4 and GLUT1 glucose transporters and regulates transporter levels in skeletal muscle cells. Proc Natl Acad Sci U S A 2000; 97:1125-30. [PMID: 10655495 PMCID: PMC15543 DOI: 10.1073/pnas.97.3.1125] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Glucose transport in insulin-regulated tissues is mediated by the GLUT4 and GLUT1 transporters. Using the yeast two-hybrid system, we have cloned the sentrin-conjugating enzyme mUbc9 as a protein that interacts with the GLUT4 COOH-terminal intracellular domain. The mUbc9 enzyme was found to bind directly to GLUT4 and GLUT1 through an 11-aa sequence common to the two transporters and to modify both transporters covalently by conjugation with the mUbc9 substrate, sentrin. Overexpression of mUbc9 in L6 skeletal muscle cells decreased GLUT1 transporter abundance 65%, resulting in decreased basal glucose transport. By contrast, mUbc9 overexpression increased GLUT4 abundance 8-fold, leading to enhanced transport stimulation by insulin. A dominant-negative mUbc9 mutant lacking catalytic activity had effects opposite to those of wild-type mUbc9. The regulation of GLUT4 and GLUT1 was specific, as evidenced by an absence of mUbc9 interaction with or regulation of the GLUT3 transporter isoform in L6 skeletal muscle cells. The mUbc9 sentrin-conjugating enzyme represents a novel regulator of GLUT1 and GLUT4 protein levels with potential importance as a determinant of basal and insulin-stimulated glucose uptake in normal and pathophysiological states.
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Affiliation(s)
- F Giorgino
- Istituto di Clinica Medica, Endocrinologia e Malattie Metaboliche, University of Bari School of Medicine, I-70124 Bari, Italy.
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32
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Abstract
A series of metabolic changes within the immature rat uterus begins minutes after the administration of microgram quantities of estradiol (E2). One of the earliest effects that has been measured is an increase in the rate at which the uterus takes up glucose. To characterize the effect of E2 on glucose transport stimulation, whole protein preparations were examined for the presence of mammalian glucose transport proteins Glut1 through Glut5. E2-stimulated changes in the steady state levels of messenger RNA (mRNA) and protein were measured for Glut1 and Glut4 by quantitative competitive RT-PCR and Western blots. Both Glut1 mRNA and protein increased approximately 3- to 4-fold within 4-8 h. This increase in Glut1 mRNA and protein agrees with the maximal stimulation of the glucose transport rate that was observed. No translocation of either Glut1 or Glut4 was observed 2 h after E2 injection, indicating that translocation is not the mechanism responsible for the initial E2-stimulated increase in glucose transport observed in immature rat uterus. These data support the conclusion that the prolonged increase in glucose transport rate is due to either the transcriptional activation of Glut1 and/or the increased Glut1 mRNA half-life.
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Affiliation(s)
- R D Welch
- Department of Biochemistry, University of Wisconsin, Madison 53706-1569, USA
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33
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Hajduch E, Rencurel F, Balendran A, Batty IH, Downes CP, Hundal HS. Serotonin (5-Hydroxytryptamine), a novel regulator of glucose transport in rat skeletal muscle. J Biol Chem 1999; 274:13563-8. [PMID: 10224126 DOI: 10.1074/jbc.274.19.13563] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study we show that serotonin (5-hydroxytryptamine (5-HT)) causes a rapid stimulation in glucose uptake by approximately 50% in both L6 myotubes and isolated rat skeletal muscle. This activation is mediated via the 5-HT2A receptor, which is expressed in L6, rat, and human skeletal muscle. In L6 cells, expression of the 5-HT2A receptor is developmentally regulated based on the finding that receptor abundance increases by over 3-fold during differentiation from myoblasts to myotubes. Stimulation of the 5-HT2A receptor using methylserotonin (m-HT), a selective 5-HT2A agonist, increased muscle glucose uptake in a manner similar to that seen in response to 5-HT. The agonist-mediated stimulation in glucose uptake was attributable to an increase in the plasma membrane content of GLUT1, GLUT3, and GLUT4. The stimulatory effects of 5-HT and m-HT were suppressed in the presence of submicromolar concentrations of ketanserin (a selective 5-HT2A antagonist) providing further evidence that the increase in glucose uptake was specifically mediated via the 5-HT2A receptor. Treatment of L6 cells with insulin resulted in tyrosine phosphorylation of IRS1, increased cellular production of phosphatidylinositol 3,4,5-phosphate and a 41-fold activation in protein kinase B (PKB/Akt) activity. In contrast, m-HT did not modulate IRS1, phosphoinositide 3-kinase, or PKB activity. The present results indicate that rat and human skeletal muscle both express the 5-HT2A receptor and that 5-HT and specific 5-HT2A agonists can rapidly stimulate glucose uptake in skeletal muscle by a mechanism which does not depend upon components that participate in the insulin signaling pathway.
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Affiliation(s)
- E Hajduch
- Departments of Anatomy and Physiology, The University of Dundee, Dundee DD1 4HN, Scotland
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34
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Inoki K, Haneda M, Maeda S, Koya D, Kikkawa R. TGF-beta 1 stimulates glucose uptake by enhancing GLUT1 expression in mesangial cells. Kidney Int 1999; 55:1704-12. [PMID: 10231432 DOI: 10.1046/j.1523-1755.1999.00438.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND An increase in the expression of transforming growth factor-beta 1 (TGF-beta 1) has been proposed to play an important role in the excessive production of extracellular matrix (ECM) proteins seen in diabetes. Because the linkage between glucose metabolism and ECM protein production was found in mesangial cells overexpressed with the brain-type glucose transporter (GLUT1), we hypothesized that TGF-beta 1 could affect glucose metabolism. METHODS To prove this hypothesis, we examined the effect of TGF-beta 1 on glucose uptake, the first step of glucose metabolism, in mesangial cells. 2-Deoxy-D-glucose (2DOG) uptake and the expression of GLUT1 were measured in mesangial cells exposed to various concentrations of TGF-beta 1. The kinetic constants were determined using 2DOG and 3-O-methyl-D-glucose (3OMG). The effect of anti-TGF-beta neutralizing antibody on 2DOG uptake and GLUT1 mRNA was also examined in mesangial cells cultured under high-glucose (22.2 mM) conditions for 72 hours. RESULTS TGF-beta 1 stimulated 2DOG uptake in mesangial cells by approximately 2.5-fold in a dose- (1.25 ng/ml maximum) and time-dependent manner, with a peak stimulation at nine hours. The increase in 2DOG uptake by TGF-beta 1 was completely abolished by the addition of 1 microgram/ml cycloheximide, and kinetic analysis of 2DOG or 3OMG uptake revealed an increase in Vmax by TGF-beta 1. Furthermore, TGF-beta 1 enhanced the expression of GLUT1 mRNA from one hour, followed by an enhancement of the expression of GLUT1 protein at nine hours. Finally, 2DOG uptake was significantly enhanced in cells cultured under high-glucose (22.2 mM) conditions as compared with that in cells under normal glucose (5.6 mM) conditions, and this increase in 2DOG uptake in cells under high-glucose conditions was inhibited by the addition of anti-TGF-beta neutralizing antibody. CONCLUSIONS TGF-beta 1 stimulates glucose uptake by enhancing the expression of GLUT1 in mesangial cells, which leads to the acceleration of intracellular metabolic abnormalities in diabetes.
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Affiliation(s)
- K Inoki
- Third Department of Medicine, Shiga University of Medical Science, Japan
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35
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Sweeney G, Somwar R, Ramlal T, Volchuk A, Ueyama A, Klip A. An inhibitor of p38 mitogen-activated protein kinase prevents insulin-stimulated glucose transport but not glucose transporter translocation in 3T3-L1 adipocytes and L6 myotubes. J Biol Chem 1999; 274:10071-8. [PMID: 10187787 DOI: 10.1074/jbc.274.15.10071] [Citation(s) in RCA: 248] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The precise mechanisms underlying insulin-stimulated glucose transport still require investigation. Here we assessed the effect of SB203580, an inhibitor of the p38 MAP kinase family, on insulin-stimulated glucose transport in 3T3-L1 adipocytes and L6 myotubes. We found that SB203580, but not its inactive analogue (SB202474), prevented insulin-stimulated glucose transport in both cell types with an IC50 similar to that for inhibition of p38 MAP kinase (0.6 microM). Basal glucose uptake was not affected. Moreover, SB203580 added only during the transport assay did not inhibit basal or insulin-stimulated transport. SB203580 did not inhibit insulin-stimulated translocation of the glucose transporters GLUT1 or GLUT4 in 3T3-L1 adipocytes as assessed by immunoblotting of subcellular fractions or by immunofluorescence of membrane lawns. L6 muscle cells expressing GLUT4 tagged on an extracellular domain with a Myc epitope (GLUT4myc) were used to assess the functional insertion of GLUT4 into the plasma membrane. SB203580 did not affect the insulin-induced gain in GLUT4myc exposure at the cell surface but largely reduced the stimulation of glucose uptake. SB203580 had no effect on insulin-dependent insulin receptor substrate-1 phosphorylation, association of the p85 subunit of phosphatidylinositol 3-kinase with insulin receptor substrate-1, nor on phosphatidylinositol 3-kinase, Akt1, Akt2, or Akt3 activities in 3T3-L1 adipocytes. In conclusion, in the presence of SB203580, insulin caused normal translocation and cell surface membrane insertion of glucose transporters without stimulating glucose transport. We propose that insulin stimulates two independent signals contributing to stimulation of glucose transport: phosphatidylinositol 3-kinase leads to glucose transporter translocation and a pathway involving p38 MAP kinase leads to activation of the recruited glucose transporter at the membrane.
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Affiliation(s)
- G Sweeney
- Programme in Cell Biology, Hospital for Sick Children, University of Toronto, Toronto, Ontario, M5G 1X8 Canada
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36
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Ahmed N, Berridge MV. Distinct regulation of glucose transport by interleukin-3 and oncogenes in a murine bone marrow-derived cell line. Biochem Pharmacol 1999; 57:387-96. [PMID: 9933027 DOI: 10.1016/s0006-2952(98)00267-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Growth factors and oncogenes promote glucose uptake, but the extent to which increased uptake is regulated at the level of glucose transporter function has not been clearly established. In this paper, we show that interleukin-3 (IL-3), a cytokine growth factor, and the transforming oncogenes ras and abl alter the activation state of glucose transporters by distinct mechanisms. Using bone marrow-derived IL-3-dependent 32Dc13 (32D clone 3) cells and 32D cells transformed with ras and abl oncogenes, we demonstrated that IL-3 enhanced [3H]-2-deoxyglucose (2-DOG) uptake in parental 32Dc13 cells by 40-50% at 0.2 mM 2-DOG, and this was associated with a 2.5-fold increase in transporter affinity for glucose (reduced Km). In comparison, ras and abl oncogenes enhanced 2-DOG uptake by 72-112%, associated with a 2-fold greater transporter affinity for glucose. The tyrosine kinase inhibitor genistein reversed the effects of both IL-3 and oncogenes on glucose uptake and reduced transporter affinity for glucose. Likewise, with exponentially growing 32D cells in the presence of IL-3, a protein kinase C inhibitor, staurosporine, and a phosphatidylinositol 3-kinase (PI-3) kinase inhibitor, wortmannin, inhibited 2-DOG uptake and decreased transporter affinity for glucose. In contrast, in oncogene-transformed cells, staurosporine inhibited 2-DOG uptake but failed to decrease transporter affinity for glucose, whereas wortmannin did not affect 2-DOG uptake. Inhibition of protein tyrosine phosphatases with vanadate enhanced 2-DOG uptake and transporter affinity for glucose in parental cells and in ras-transformed cells but had little effect on abl-transformed cells. Consistently, the serine/threonine phosphatase type 2A inhibitor okadaic acid enhanced 2-DOG uptake and transporter affinity for glucose in parental cells but had little effect on ras- or abl-transformed cells. These results demonstrate differences in the regulation of glucose transport in parental and oncogene-transformed 32D cells. Thus, IL-3 responses are dependent upon tyrosine, serine/threonine, and PI-3 kinases, whereas ras and abl effects on glucose transport depend upon tyrosine phosphorylation but are compromised in their dependence upon serine/threonine and PI-3 kinases.
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Affiliation(s)
- N Ahmed
- Malaghan Institute of Medical Research, Wellington School of Medicine, Wellington South, New Zealand.
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37
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Khayat ZA, McCall AL, Klip A. Unique mechanism of GLUT3 glucose transporter regulation by prolonged energy demand: increased protein half-life. Biochem J 1998; 333 ( Pt 3):713-8. [PMID: 9677332 PMCID: PMC1219636 DOI: 10.1042/bj3330713] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
L6 muscle cells survive long-term (18 h) disruption of oxidative phosphorylation by the mitochondrial uncoupler 2,4-dinitrophenol (DNP) because, in response to this metabolic stress, they increase their rate of glucose transport. This response is associated with an elevation of the protein content of glucose transporter isoforms GLUT3 and GLUT1, but not GLUT4. Previously we have reported that the rise in GLUT1 expression is likely to be a result of de novo biosynthesis of the transporter, since the uncoupler increases GLUT1 mRNA levels. Unlike GLUT1, very little is known about how interfering with mitochondrial ATP production regulates GLUT3 protein expression. Here we examine the mechanisms employed by DNP to increase GLUT3 protein content and glucose uptake in L6 muscle cells. We report that, in contrast with GLUT1, continuous exposure to DNP had no effect on GLUT3 mRNA levels. DNP-stimulated glucose transport was unaffected by the protein-synthesis inhibitor cycloheximide. The increase in GLUT3 protein mediated by DNP was also insensitive to cycloheximide, paralleling the response of glucose uptake, whereas the rise in GLUT1 protein levels was blocked by the inhibitor. The GLUT3 glucose transporter may therefore provide the majority of the glucose transport stimulation by DNP, despite elevated levels of GLUT1 protein. The half-lives of GLUT3 and GLUT1 proteins in L6 myotubes were determined to be about 15 h and 6 h respectively. DNP prolonged the half-life of both proteins. After 24 h of DNP treatment, 88% of GLUT3 protein and 57% of GLUT1 protein had not turned over, compared with 25% in untreated cells. We conclude that the long-term stimulation of glucose transport by DNP arises from an elevation of GLUT3 protein content associated with an increase in GLUT3 protein half-life. These findings suggest that disruption of the oxidative chain of L6 muscle cells leads to an adaptive response of glucose transport that is distinct from the insulin response, involving specific glucose transporter isoforms that are regulated by different mechanisms.
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Affiliation(s)
- Z A Khayat
- Programme in Cell Biology, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, Canada, M5G 1X8, and Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada, M5S 1A8
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38
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Wang Q, Khayat Z, Kishi K, Ebina Y, Klip A. GLUT4 translocation by insulin in intact muscle cells: detection by a fast and quantitative assay. FEBS Lett 1998; 427:193-7. [PMID: 9607310 DOI: 10.1016/s0014-5793(98)00423-2] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We report a rapid and sensitive colorimetric approach to quantitate the amount of glucose transporters exposed at the surface of intact cells, using L6 muscle cells expressing GLUT4 containing an exofacial myc epitope. Unstimulated cells exposed to the surface 5 fmol GLUT4myc per mg protein. This value increased to 10 fmol/mg protein in response to insulin as 2-deoxyglucose (10 microM) uptake doubled. The results are substantiated by immunofluorescent detection of GLUT4myc in unpermeabilized cells and by subcellular fractionation. We further show that wortmannin and the cytoskeleton disruptors cytochalasin D and latrunculin B completely blocked these insulin effects. The rapid quantitative assay described here could be of high value to study insulin signals and to screen for potential anti-diabetic drugs.
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Affiliation(s)
- Q Wang
- Programme in Cell Biology, The Hospital for Sick Children, Toronto, Ont, Canada
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39
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Lamothe B, Baudry A, Christoffersen CT, De Meyts P, Jami J, Bucchini D, Joshi RL. Insulin receptor-deficient cells as a new tool for dissecting complex interplay in insulin and insulin-like growth factors. FEBS Lett 1998; 426:381-5. [PMID: 9600271 DOI: 10.1016/s0014-5793(98)00377-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cell systems derived from knockout mice for the insulin receptor (IR) or the IGF-1 receptor (IGF-1R) represent unique tools for dissecting complex interplay in the actions of insulin and insulin-like growth factors through their cognate versus non-cognate receptor. In this study, we used a fibroblast cell line derived from IR-deficient mice to investigate metabolic and mitogenic effects of IGF-1 and insulin. IGF-1 was able to stimulate glucose uptake, glucose incorporation into glycogen and thymidine incorporation in such cells. Phosphatidylinositol 3-kinase and mitogen-activated protein kinase, two enzymes of major metabolic-mitogenic signaling pathways, were activated upon stimulating these cells with IGF-1. All these effects were also achieved when IR-deficient cells were stimulated with insulin. Thus, IGF-1R can represent an alternative receptor through which insulin might exert some of its effects.
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Affiliation(s)
- B Lamothe
- Institut Cochin de Génétique Moléculaire, INSERM U257, Paris, France
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40
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McCoy KD, Ahmed N, Tan AS, Berridge MV. The hemopoietic growth factor, interleukin-3, promotes glucose transport by increasing the specific activity and maintaining the affinity for glucose of plasma membrane glucose transporters. J Biol Chem 1997; 272:17276-82. [PMID: 9211864 DOI: 10.1074/jbc.272.28.17276] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Most mammalian cells rely on an external supply of glucose for survival, proliferation, and function. Glucose enters cells through specific transporter molecules at the plasma membrane by a facilitative process that does not expend energy. Regulation of glucose transport into cells is thought to occur largely through transporter expression at the cell surface, but the extent to which the intrinsic properties of glucose transporters are regulated is at present controversial. Using a bone marrow-derived cell line that responds to the hemopoietic growth factor, interleukin-3 (IL-3), we investigated IL-3 regulation of glucose transport. IL-3 significantly increased 2-deoxyglucose (2-DOG) uptake within 1 h (26 +/- 8.0%, n = 11) with a maximum 73% increase after 6 h. Withdrawal of IL-3 resulted in decreased uptake within 1 h and this continued to decline to 43% of initial uptake by 16 h. To determine whether these changes in 2-DOG uptake were associated with corresponding changes in glucose transporter expression, subtype-specific antisera against Glut-1 and Glut-3 were used. Little change in membrane expression of these transporters was observed prior to 16 h. Fractionation of cell membranes on Nycodenz gradients showed that the majority of each transporter subtype was associated with the plasma membrane (63-93%) and that transporter distribution did not change markedly in response to addition or withdrawal of IL-3. These results demonstrate that IL-3 regulates glucose uptake by modulating the intrinsic transporting ability of glucose transporters. Decreased transporter affinity for 2-DOG and 3-O-methylglucose was observed following IL-3 withdrawal. Similar affinity changes were observed with 2-DOG following exposure of IL-3-stimulated cells to the protein kinase inhibitors, genistein and staurosporine. In contrast, the tyrosine phosphatase inhibitor, vanadate, acted like IL-3 to increase transporter affinity for glucose. Together these results demonstrate that IL-3 acts to maintain the intrinsic transport properties of glucose transporters without markedly affecting their expression or translocation.
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Affiliation(s)
- K D McCoy
- Malaghan Institute of Medical Research, Wellington School of Medicine, P. O. Box 7060, Wellington South 6002, New Zealand
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41
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McDowell HE, Walker T, Hajduch E, Christie G, Batty IH, Downes CP, Hundal HS. Inositol phospholipid 3-kinase is activated by cellular stress but is not required for the stress-induced activation of glucose transport in L6 rat skeletal muscle cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 247:306-13. [PMID: 9249041 DOI: 10.1111/j.1432-1033.1997.00306.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A characteristic response of cells subjected to a stress stimulus is a rapid activation of cellular glucose transport. The mechanisms governing this increase in glucose transport are poorly understood, but it has been suggested that the response may involve the intracellular-signaling components that also participate in the hormonal activation of glucose transport. In skeletal muscle and fat tissue, inositol phospholipid 3-kinase plays an integral role in the regulation of both basal and insulin-stimulated glucose transport. In this study, we have investigated whether inositol phospholipid 3-kinase is activated by chemical stress and, if so, whether it has a role to play in the stress-induced increase in glucose transport in L6 muscle cells. Furthermore, we have attempted to assess the basis by which inositol phospholipid 3-kinase may participate in the regulation of basal glucose transport. Acute exposure (30 min) of L6 muscle cells to 0.5 mM arsenite induced an 80% stimulation in glucose transport. This activation was due to a rise in the number of cell-surface glucose transporters, based on an increase in the Vmax of glucose transport and the observation that arsenite increases the plasma membrane content of GLUT1 and GLUT4 glucose transporters by 95% and 60%, respectively, from an intracellular compartment. Arsenite induced rapid activation (< 2 min) of inositol phospholipid 3-kinase with an approximately fourfold increase in phosphatidylinositol 3,4,5-trisphosphate (PtdIns3,4,5P3). In contrast, phosphatidylinositol 3-phosphate (PtdIns3P) levels were unaffected. Prior treatment of L6 cells with 100 nM wortmannin suppressed the arsenite-induced increase in PtdIns3,4,5P3 and reduced the cellular content of PtdIns3P by 50%. Under these conditions however, wortmannin failed to prevent the stress-induced activation of glucose transport, but suppressed basal glucose transport by 60% with an IC50 of about 10 nM. In the absence of arsenite, wortmannin caused a dose-dependent inhibition in the cellular levels of PtdIns3P and PtdIns3,4,5P3 with IC50 values of about 10 nM and 100 nM, respectively. In summary, the present results demonstrate that chemical stress activates inositol phospholipid 3-kinase and glucose transport in L6 muscle cells, but unlike the hormonal responses of these cells the activation of inositol phospholipid 3-kinase is not responsible for the stress-induced increase in glucose transport. This implies that stress-induced and hormonal stimulated increases in PtdIns3,4,5P3 levels are functionally distinct. By contrast, the maintenance of PtdIns3P levels, presumably involving a PtdIns-specific, wortmannin-sensitive inositol phospholipid 3-kinase may be required to support basal glucose transport.
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Affiliation(s)
- H E McDowell
- Department of Anatomy and Physiology, The University of Dundee, UK
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Hokama JY, Streeper RS, Henriksen EJ. Voluntary exercise training enhances glucose transport in muscle stimulated by insulin-like growth factor I. J Appl Physiol (1985) 1997; 82:508-12. [PMID: 9049730 DOI: 10.1152/jappl.1997.82.2.508] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Skeletal muscle glucose transport can be regulated by hormonal factors such as insulin and insulin-like growth factor I (IGF-I). Although it is well established that exercise training increases insulin action on muscle glucose transport, it is currently unknown whether exercise training leads to an enhancement of IGF-I-stimulated glucose transport in skeletal muscle. Therefore, we measured glucose transport activity [by using 2-deoxy-D-glucose glucose (2-DG) uptake] in the isolated rat epitrochlearis muscle stimulated by submaximally and maximally effective concentrations of insulin (0.2 and 13.3 nM) or IGF-I (5 and 50 nM) after 1, 2, and 3 wk of voluntary wheel running (WR). After 1 wk of WR, both submaximal and maximal insulin-stimulated 2-DG uptake rates were significantly (P < 0.05) enhanced (43 and 31%) compared with those of sedentary controls, and these variables were further increased after 2 (86 and 57%) and 3 wk (71 and 70%) of WR. Submaximal and maximal IGF-I-stimulated 2-DG uptake rates were significantly enhanced after 1 wk of WR (82 and 61%, and these increases did not expand substantially after 2 (71 and 58%) and 3 wk (96 and 70%) of WR. This enhancement of hormone-stimulated 2-DG uptake in WR muscles preceded any alteration in glucose transporter (GLUT-4) protein level, which increased only after 2 (24%) and 3 wk (54%) of WR. Increases in GLUT-4 protein were significantly correlated (r = 0.844) with increases in citrate synthase. These results indicate that exercise training can enhance both insulin-stimulated and IGF-I-stimulated muscle glucose transport activity and that these improvements can develop without an increase in GLUT-4 protein.
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Affiliation(s)
- J Y Hokama
- Department of Physiology, University of Arizona College of Medicine, Tucson 85721-0093, USA
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Wilson CM, Mitsumoto Y, Maher F, Klip A. Regulation of cell surface GLUT1, GLUT3, and GLUT4 by insulin and IGF-I in L6 myotubes. FEBS Lett 1995; 368:19-22. [PMID: 7615080 DOI: 10.1016/0014-5793(95)00589-2] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effects of insulin and IGF-I on the cell surface quantities of GLUT1, GLUT3 and GLUT4 glucose transporters in L6 myotubes were determined with the exofacial bis-mannose phololabel (ATB-BMPA). In basal cells, an equal molar quantity of each transporter isoform was found at the cell surface. Insulin stimulated the translocation of all three glucose transporter isoforms to the plasma membrane fraction from the light microsome fraction, resulting in equal molar quantities on the cell surface. IGF-I stimulated a similar translocation of all isoforms, augmented by an increase in surface GLUT3 as assessed by ATB-BMPA.
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Affiliation(s)
- C M Wilson
- Experimental Diabetes, Metabolism and Nutrition Section, NIDDK National Institutes of Health, Bethesda, MD 20892-1420, USA
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Hauguel-de Mouzon S, Leturque A, Alsat E, Loizeau M, Evain-Brion D, Girard J. Developmental expression of Glut1 glucose transporter and c-fos genes in human placental cells. Placenta 1994; 15:35-46. [PMID: 8208668 DOI: 10.1016/s0143-4004(05)80234-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Glut1, the brain/erythrocyte glucose transporter is one major isoform of the human placenta and displays an age-specific pattern of expression with mRNA levels five-fold higher in first trimester than in term placenta. By contrast, the mRNA level of the insulin-regulatable glucose transporter Glut4 remains at the limit of detection throughout pregnancy indicating a very low expression of this isoform in the placenta. The nuclear proto-oncogenes c-fos and c-myc were also detectable in the human placenta, but c-fos only exhibited an age-specific pattern of expression with levels higher in third trimester than in term placenta. Primary cultures of human trophoblast cells from term placenta were used to further study the expression and regulation of Glut1 and c-fos genes. Fetal calf serum rapidly and transiently (15 to 60 min) stimulated c-fos and Glut1 gene expression suggesting that both genes share similar growth factor-controlled pathways. Glucose inhibited Glut1, but not c-fos expression. An eight-fold decrease in Glut1 mRNA was observed when glucose concentration in the medium was increased from 0 to 25 mM, whereas c-fos mRNA levels remained very low. These results suggest that in the human placenta, the expression of Glut1 is specifically regulated by glucose concentration. These data demonstrate that (1) Glut1 and c-fos mRNA transcripts are expressed in the human placenta exhibiting an age-specific pattern of expression, (2) In cultured trophoblast cells, both genes are stimulatable by fetal calf serum and in contrast to c-fos, Glut1 is negatively regulated by glucose. This differential regulation of Glut1 and c-fos genes could be relevant to specific metabolic and mitogenic pathways implicated in placental growth and differentiation.
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Affiliation(s)
- S Hauguel-de Mouzon
- Centre de Recherche sur l'Endocrinologie Moléculaire et le Développement, CNRS, Meudon-Belleuve, France
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Klip A, Ramlal T, Bilan PJ, Marette A, Liu Z, Mitsumoto Y. What signals are involved in the stimulation of glucose transport by insulin in muscle cells? Cell Signal 1993; 5:519-29. [PMID: 8312129 DOI: 10.1016/0898-6568(93)90047-p] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- A Klip
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
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46
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Sargeant R, Mitsumoto Y, Sarabia V, Shillabeer G, Klip A. Hormonal regulation of glucose transporters in muscle cells in culture. J Endocrinol Invest 1993; 16:147-62. [PMID: 8463552 DOI: 10.1007/bf03347669] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- R Sargeant
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
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Bach LA, Rechler MM. Insulin-like growth factors and diabetes. DIABETES/METABOLISM REVIEWS 1992; 8:229-57. [PMID: 1292913 DOI: 10.1002/dmr.5610080304] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- L A Bach
- Growth and Development Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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Hundal HS, Ahmed A, Gumà A, Mitsumoto Y, Marette A, Rennie MJ, Klip A. Biochemical and immunocytochemical localization of the 'GLUT5 glucose transporter' in human skeletal muscle. Biochem J 1992; 286 ( Pt 2):339-43. [PMID: 1530566 PMCID: PMC1132902 DOI: 10.1042/bj2860339] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Using biochemical and immunocytochemical techniques, we have assessed both the protein expression and the cellular localization of the GLUT5 transporter in human skeletal muscle. Human muscle membranes, prepared by subcellular fractionation, were subjected to SDS/PAGE and Western-blot analyses using antiserum raised against a specific C-terminal amino acid sequence of the human GLUT5 transporter. GLUT5 was detected as a discrete 49 kDa protein band in a plasma-membrane-enriched fraction prepared from either soleus or gracilis muscle. In contrast, GLUT5 protein was not detectable to any significant extent in fractions which were devoid of muscle plasma membranes (mean GLUT5 abundance in intracellular fractions from three muscle preparations amounted to approximately 10% of that in the plasma-membrane-enriched fraction). Immunofluorescence studies using cryostat sections of human triceps muscle supported the biochemical observations and revealed that GLUT5 antibody selectivity labelled the plasma membrane of muscle cells. This immuno-labelling was significantly suppressed after tissue incubation with antiserum in the presence of a 14-amino-acid synthetic peptide corresponding to a specific C-terminus sequence of human GLUT5. These results indicate that human skeletal muscle expresses the GLUT5 transporter and that it is specifically localized to the plasma membrane, where it may participate in regulating hexose transfer across the sarcolemma.
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Affiliation(s)
- H S Hundal
- Division of Cell Biology, Hospital For Sick Children, Toronto, Ontario, Canada
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Bilan PJ, Mitsumoto Y, Maher F, Simpson IA, Klip A. Detection of the GLUT3 facilitative glucose transporter in rat L6 muscle cells: regulation by cellular differentiation, insulin and insulin-like growth factor-I. Biochem Biophys Res Commun 1992; 186:1129-37. [PMID: 1497646 DOI: 10.1016/0006-291x(92)90864-h] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The GLUT3 facilitative glucose transporter protein was found to be expressed in rat L6 muscle cells. It was detected at both the myoblast and myotube stage. GLUT3 protein content per mg of total membrane protein increased significantly during L6 cell differentiation. Subcellular fractionation demonstrated that the GLUT3 protein was predominantly localized in plasma membrane-enriched fractions of either myoblasts or myotubes. Short-term exposure of L6 myotubes to IGF-I or insulin caused a redistribution of GLUT3 protein from an intracellular membrane fraction to the plasma membrane, without affecting total membrane GLUT3 protein content. Long-term exposure of L6 myotubes to IGF-I produced an increase of GLUT3 protein in total membranes and all subcellular membrane fractions, especially the plasma membrane. We propose that the GLUT3 glucose transporter may play an important role in glucose metabolism in developing muscle.
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Affiliation(s)
- P J Bilan
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
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