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Yu Y, Clippinger AJ, Pierciey FJ, Alwine JC. Viruses and metabolism: alterations of glucose and glutamine metabolism mediated by human cytomegalovirus. Adv Virus Res 2011; 80:49-67. [PMID: 21762821 DOI: 10.1016/b978-0-12-385987-7.00003-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Recent studies of human cytomegalovirus (HCMV) infection have demonstrated that the virus significantly alters cellular metabolism, especially the utilization of glucose and glutamine. Glucose is not broken down by the tricarboxylic acid (TCA) cycle in infected cells; instead, it is used biosynthetically for fatty acid synthesis for membranes needed during the infection. In this chapter, we discuss the possibility that HCMV integrates its mechanisms for manipulating cellular signaling and stress responses to induce novel adipocyte-like differentiation in order to alter metabolism so that glucose can be used synthetically, that is, for fatty acids and lipids. This process diverts glucose from the TCA cycle and requires induction of enzymes that can convert glutamine to α-ketoglutarate to maintain the TCA cycle (anaplerosis). We discuss data proposing that the anaplerotic utilization of glutamine may be mediated, in part, by c-Myc activation, and the induction of adipocyte-like differentiation may result from the activation of the endoplasmic reticulum resident kinase PKR-like ER kinase. These alterations in metabolism during HCMV infection are comparable to those seen in many tumor cells. Indeed, the alterations in cellular signaling, stress responses, and metabolism that have been characterized could result in unexpected pathogenesis, potentially implicating HCMV as an agent or subtle cofactor in many maladies. Better understanding of HCMV's effects on cell signaling and metabolism will show how HCMV-mediated modifications of cellular processes relate to pathogenesis and will suggest novel avenues for antiviral therapy.
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Affiliation(s)
- Yongjun Yu
- Department of Cancer Biology, Abramson Family Cancer Research Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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152
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Sheena A, Mohan SS, Haridas NPA, Anilkumar G. Elucidation of the glucose transport pathway in glucose transporter 4 via steered molecular dynamics simulations. PLoS One 2011; 6:e25747. [PMID: 22022441 PMCID: PMC3192114 DOI: 10.1371/journal.pone.0025747] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 09/11/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND GLUT4 is a predominant insulin regulated glucose transporter expressed in major glucose disposal tissues such as adipocytes and muscles. Under the unstimulated state, GLUT4 resides within intracellular vesicles. Various stimuli such as insulin translocate this protein to the plasma membrane for glucose transport. In the absence of a crystal structure for GLUT4, very little is known about the mechanism of glucose transport by this protein. Earlier we proposed a homology model for GLUT4 and performed a conventional molecular dynamics study revealing the conformational rearrangements during glucose and ATP binding. However, this study could not explain the transport of glucose through the permeation tunnel. METHODOLOGY/PRINCIPAL FINDINGS To elucidate the molecular mechanism of glucose transport and its energetic, a steered molecular dynamics study (SMD) was used. Glucose was pulled from the extracellular end of GLUT4 to the cytoplasm along the pathway using constant velocity pulling method. We identified several key residues within the tunnel that interact directly with either the backbone ring or the hydroxyl groups of glucose. A rotation of glucose molecule was seen near the sugar binding site facilitating the sugar recognition process at the QLS binding site. CONCLUSIONS/SIGNIFICANCE This study proposes a possible glucose transport pathway and aids the identification of several residues that make direct interactions with glucose during glucose transport. Mutational studies are required to further validate the observation made in this study.
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Affiliation(s)
- Aswathy Sheena
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, India
| | - Suma S. Mohan
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, India
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153
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Kipmen-Korgun D, Ozmen A, Unek G, Simsek M, Demir R, Korgun ET. Triamcinolone up-regulates GLUT 1 and GLUT 3 expression in cultured human placental endothelial cells. Cell Biochem Funct 2011; 30:47-53. [DOI: 10.1002/cbf.1817] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 08/02/2011] [Accepted: 09/20/2011] [Indexed: 11/07/2022]
Affiliation(s)
- Dijle Kipmen-Korgun
- Department of Biochemistry, Medical Faculty; Akdeniz University; Antalya; Turkey
| | - Asli Ozmen
- Department of Histology and Embryology, Medical Faculty; Akdeniz University; Antalya; Turkey
| | - Gozde Unek
- Department of Histology and Embryology, Medical Faculty; Akdeniz University; Antalya; Turkey
| | - Mehmet Simsek
- Department of Obstetrics and Gynecology, Medical Faculty; Akdeniz University; Antalya; Turkey
| | - Ramazan Demir
- Department of Histology and Embryology, Medical Faculty; Akdeniz University; Antalya; Turkey
| | - Emin Turkay Korgun
- Department of Histology and Embryology, Medical Faculty; Akdeniz University; Antalya; Turkey
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154
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S-d-lactoylglutathione as a potential state marker for hemolysis. Med Hypotheses 2011; 77:479-80. [DOI: 10.1016/j.mehy.2011.06.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 06/04/2011] [Indexed: 11/18/2022]
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155
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Pérez A, Ojeda P, Ojeda L, Salas M, Rivas CI, Vera JC, Reyes AM. Hexose transporter GLUT1 harbors several distinct regulatory binding sites for flavones and tyrphostins. Biochemistry 2011; 50:8834-45. [PMID: 21899256 DOI: 10.1021/bi200748b] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The facilitative hexose transporter GLUT1 activity is blocked by tyrosine kinase inhibitors that include natural products such as flavones and isoflavones and synthetic compounds such as tyrphostins, molecules that are structurally unrelated to the transported substrates [Vera, et al. (2001) Biochemistry, 40, 777-790]. Here we analyzed the interaction of GLUT1 with quercetin (a flavone), genistein (an isoflavone), and tyrphostin A47 and B46 to evaluate if they share one common or have several binding sites on the protein. Kinetic assays showed that genistein, quercetin, and tyrphostin B46 behave as competitive inhibitors of equilibrium exchange and zero-trans uptake transport and noncompetitive inhibitors of net sugar exit out of human red cells, suggesting that they interact with the external surface of the GLUT1 molecule. In contrast, tyrphostin A47 was a competitive inhibitor of equilibrium exchange and zero-trans exit transport and a noncompetitive inhibitor of net sugar entry into red cells, suggesting that it interacts with the cytoplasmic surface of the transporter. Genistein protected GLUT1 against iodide-elicited fluorescence quenching and also decreased the affinity of d-glucose for its external binding site, while quercetin and tyrphostins B46 and A47 promoted fluorescence quenching and did not affect the external d-glucose binding site. These findings are explained by a carrier that presents at least three binding sites for tyrosine kinase inhibitors, in which (i) genistein interacts with the transporter in a conformation that binds glucose on the external surface (outward-facing conformation), in a site which overlaps with the external binding site for d-glucose, (ii) quercetin and tyrphostin B46 interact with the GLUT1 conformation which binds glucose by the internal side of the membrane (inward-facing conformation), but to a site accessible from the external surface of the protein, and (iii) the binding site for tyrphostin A47 is accessible from the inner surface of GLUT1 by binding to the inward-facing conformation of the transporter. These data provide groundwork for a molecular understanding of how the tyrosine kinase inhibitors directly affect glucose transport in animal cells.
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Affiliation(s)
- Alejandra Pérez
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Campus Isla Teja s/n, Universidad Austral de Chile, Casilla 567, Valdivia, Chile
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156
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Gandhi GR, Ignacimuthu S, Paulraj MG, Sasikumar P. Antihyperglycemic activity and antidiabetic effect of methyl caffeate isolated from Solanum torvum Swartz. fruit in streptozotocin induced diabetic rats. Eur J Pharmacol 2011; 670:623-31. [PMID: 21963451 DOI: 10.1016/j.ejphar.2011.09.159] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 09/05/2011] [Accepted: 09/11/2011] [Indexed: 10/17/2022]
Abstract
Natural remedies from medicinal plants are considered to be effective and safe alternatives to treat diabetes mellitus. Solanum torvum Swartz. fruit is widely used in the traditional system of medicine to treat diabetes. In the present study methyl caffeate, isolated from S. torvum fruit, was screened for its efficacy in controlling diabetes in animal models. Antihyperglycemic effect of methyl caffeate was studied in normal glucose-fed rats. The effects of oral administration of methyl caffeate (10, 20 and 40 mg/kg) for 28 days on body weight, fasting blood glucose, plasma insulin, hemoglobin, glycated hemoglobin, total protein, hepatic glycogen and carbohydrate metabolism enzymes in streptozotocin induced diabetic rats were investigated. Histological observations in the pancreas and GLUT4 expression in skeletal muscles were also studied. Methyl caffeate at 40 mg/kg significantly prevented the increase in blood glucose level after glucose administration at 60 min in comparison to the hyperglycemic control group. In streptozotocin induced diabetic rats, methyl caffeate produced significant reduction in blood glucose and increased body weight. The levels and/or activities of other biochemical parameters were near normal due to treatment with methyl caffeate. Methyl caffeate treated diabetic rats showed upregulation of GLUT4 and regeneration of β-cells in the pancreas. These results substantiated that methyl caffeate possessed hypoglycemic effect, and it could be developed into a potent oral antidiabetic drug.
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Affiliation(s)
- Gopalsamy Rajiv Gandhi
- Division of Ethnopharmacology, Entomology Research Institute, Loyola College, Chennai 600 034, India
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157
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Ware B, Bevier M, Nishijima Y, Rogers S, Carnes CA, Lacombe VA. Chronic heart failure selectively induces regional heterogeneity of insulin-responsive glucose transporters. Am J Physiol Regul Integr Comp Physiol 2011; 301:R1300-6. [PMID: 21849635 DOI: 10.1152/ajpregu.00822.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Glucose uptake across the sarcolemma is regulated by a family of membrane proteins called glucose transporters (GLUTs), which includes GLUT4 (the major cardiac isoform) and GLUT12 (a novel, second insulin-sensitive isoform). Potential regional patterns in glucose transport across the cardiac chambers have not been examined; thus, we hypothesized that insulin-responsive GLUT4 and -12 protein and gene expression would be chamber specific in healthy subjects and during chronic heart failure (HF). Using a canine model of tachypacing-induced, progressive, chronic HF, total GLUT protein and messenger RNA in both ventricles and atria (free wall and appendage) were investigated by immunoblotting and real-time PCR. In controls, GLUT4, but not GLUT12, protein content was significantly higher in the atria compared with the ventricles, with the highest content in the right atrium (RA; P < 0.001). GLUT4 and GLUT12 mRNA levels were similar across the cardiac chambers. During chronic HF, GLUT4 and GLUT12 protein content was highest in the left ventricle (LV; by 2.5- and 4.2-fold, respectively, P < 0.01), with a concomitant increase in GLUT4 and GLUT12 mRNA (P < 0.001). GLUT4, but not GLUT12, protein content was decreased in RA during chronic HF (P = 0.001). In conclusion, GLUT4 protein was differentially expressed across the chambers in the healthy heart, and this regional pattern was reversed during HF. Our data suggest that LV was the primary site dependent on both GLUT4 and GLUT12 during chronic HF. In addition, the paradoxical decrease in GLUT4 content in RA may induce perturbations in atrial energy production during chronic HF.
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Affiliation(s)
- Bruce Ware
- College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, USA
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158
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Stuart CA, Ross IR, Howell MEA, McCurry MP, Wood TG, Ceci JD, Kennel SJ, Wall J. Brain glucose transporter (Glut3) haploinsufficiency does not impair mouse brain glucose uptake. Brain Res 2011; 1384:15-22. [PMID: 21316350 DOI: 10.1016/j.brainres.2011.02.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Revised: 02/01/2011] [Accepted: 02/03/2011] [Indexed: 10/18/2022]
Abstract
Mouse brain expresses three principal glucose transporters. Glut1 is an endothelial marker and is the principal glucose transporter of the blood-brain barrier. Glut3 and Glut6 are expressed in glial cells and neural cells. A mouse line with a null allele for Glut3 has been developed. The Glut3(-/-) genotype is intrauterine lethal by 7days post-coitis, but the heterozygous (Glut3(+/-)) littermate survives, exhibiting rapid post-natal weight gain, but no seizures or other behavioral aberrations. At 12weeks of age, brain uptake of tail vein-injected ((3))H-2-deoxy glucose in Glut3(+/-) mice was not different from Glut3(+/+) littermates, despite 50% less Glut3 protein expression in the brain. The brain uptake of injected ((18))F-2-fluoro-2-deoxy glucose was similarly not different from Glut3(+/-) littermates in the total amount, time course, or brain imaging in the Glut3(+/-) mice. Glut1 and Glut6 protein expressions evaluated by immunoblots were not affected by the diminished Glut3 expression in the Glut3(+/-) mice. We conclude that a 50% decrease in Glut3 is not limiting for the uptake of glucose into the mouse brain, since Glut3 haploinsufficiency does not impair brain glucose uptake or utilization.
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Affiliation(s)
- Charles A Stuart
- East Tennessee State University Quillen College of Medicine, Johnson City, TN, USA.
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159
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Wlodarczyk BJ, Palacios AM, Chapa CJ, Zhu H, George TM, Finnell RH. Genetic basis of susceptibility to teratogen induced birth defects. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2011; 157C:215-26. [PMID: 21766441 DOI: 10.1002/ajmg.c.30314] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Birth defects remain the leading cause of infant death in US. The field of teratology has been focused on the causes and underlying mechanisms of birth defects for decades, yet our understanding of these critical issues remain unacceptably vague. Conclusions from years of animal and human studies made it clear that the vast majority of birth defects have multifactorial origins, with contributions from environmental and genetic factors. The environment comprises not only of the physical, biological, and chemical external environment surrounding the pregnant woman, but it also includes the internal environment of the woman's body that interact with the developing embryo in a complex fashion. The importance of maternal and embryonic genetic factors consisting of countless genetic variants/mutations that exist within every individual contribute to birth defect susceptibility is only now being more fully appreciated. This great complexity of the genome and its diversity within individuals and populations seems to be the principal reason why the same teratogenic exposure can induce severe malformation in one embryo, while fail to do so to other exposed embryos. As the interaction between genetic and environmental factors has long been recognized as the first "Principle of Teratology" by Wilson and Warkany [1965. Teratology: Principles and techniques. Chicago: University of Chicago Press], it is only recently that the appropriate investigative tools have been developed with which to fully investigate this fundamental principle. The introduction of high throughput technologies like whole genome sequencing or genome-wide association studies are promising to deliver an enormous amount of new data that will shed light on the genomic factors that contribute susceptibility to environmental teratogens. In this review, we attempt to summarize the epidemiological and experimental literature concerning birth defects whose phenotypic expression can be clearly related to the interactions between several select environmental factors and those genetic pathways in which they are most likely to have significant modifying effects. © 2011 Wiley-Liss, Inc.
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Affiliation(s)
- Bogdan J Wlodarczyk
- Dell Pediatric Research Institute, 1400 Barbara Jordan Blvd., Austin, TX 78723, USA.
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160
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Zhao FQ, Keating AF. Functional properties and genomics of glucose transporters. Curr Genomics 2011; 8:113-28. [PMID: 18660845 DOI: 10.2174/138920207780368187] [Citation(s) in RCA: 369] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Revised: 12/08/2006] [Accepted: 12/17/2007] [Indexed: 12/17/2022] Open
Abstract
Glucose is the major energy source for mammalian cells as well as an important substrate for protein and lipid synthesis. Mammalian cells take up glucose from extracellular fluid into the cell through two families of structurallyrelated glucose transporters. The facilitative glucose transporter family (solute carriers SLC2A, protein symbol GLUT) mediates a bidirectional and energy-independent process of glucose transport in most tissues and cells, while the NaM(+)/glucose cotransporter family (solute carriers SLC5A, protein symbol SGLT) mediates an active, Na(+)-linked transport process against an electrochemical gradient. The GLUT family consists of thirteen members (GLUT1-12 and HMIT). Phylogenetically, the members of the GLUT family are split into three classes based on protein similarities. Up to now, at least six members of the SGLT family have been cloned (SGLT1-6). In this review, we report both the genomic structure and function of each transporter as well as intra-species comparative genomic analysis of some of these transporters. The affinity for glucose and transport kinetics of each transporter differs and ranges from 0.2 to 17mM. The ability of each protein to transport alternative substrates also differs and includes substrates such as fructose and galactose. In addition, the tissue distribution pattern varies between species. There are different regulation mechanisms of these transporters. Characterization of transcriptional control of some of the gene promoters has been investigated and alternative promoter usage to generate different protein isoforms has been demonstrated. We also introduce some pathophysiological roles of these transporters in human.
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Affiliation(s)
- Feng-Qi Zhao
- Lactation and Mammary Gland Biology Group, Department of Animal Science, University of Vermont, Burlington, VT, USA
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161
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Purcell SH, Moley KH. The impact of obesity on egg quality. J Assist Reprod Genet 2011; 28:517-24. [PMID: 21625966 DOI: 10.1007/s10815-011-9592-y] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 05/23/2011] [Indexed: 11/29/2022] Open
Abstract
Obesity in women is a concern in many countries. This causes numerous health issues; however, this review focuses on the impact of obesity on women's reproduction, and in particular the oocyte. Data from infertility clinics and experimental animal models that address the effects of obesity are presented. Bidirectional communication and metabolic support from the surrounding cumulus cells are critical for oocyte development, and the impact of obesity on these cells is also addressed. Both oocyte maturation and metabolism are impaired due to obesity, negatively impacting further development. In addition to reproductive hormones, obesity induced elevations in insulin, glucose, or free fatty acids, and changes in adipokines appear to impact the developmental competence of the oocyte. The data indicate that any one of these hormones or metabolites can impair oocyte developmental competence in vivo, and the combination of all of these factors and their interactions are the subject of ongoing investigations.
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Affiliation(s)
- Scott H Purcell
- Department of Obstetrics and Gynecology, Washington University, St. Louis, MO 63110, USA
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162
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Yu Y, Clippinger AJ, Alwine JC. Viral effects on metabolism: changes in glucose and glutamine utilization during human cytomegalovirus infection. Trends Microbiol 2011; 19:360-7. [PMID: 21570293 DOI: 10.1016/j.tim.2011.04.002] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 04/06/2011] [Accepted: 04/12/2011] [Indexed: 12/21/2022]
Abstract
Human cytomegalovirus (HCMV) infection causes dramatic alterations of intermediary metabolism, similar to those found in tumor cells. In infected cells, glucose carbon is not completely broken down by the tricarboxylic acid (TCA) cycle for energy; instead, it is used biosynthetically. This process requires increased glucose uptake, increased glycolysis and the diversion of glucose carbon, in the form of citrate, from the TCA cycle for use in HCMV-induced fatty acid biosynthesis. The diversion of citrate from the TCA cycle (cataplerosis) requires induction of enzymes to promote glutaminolysis, the conversion of glutamine to α-ketoglutarate to maintain the TCA cycle (anaplerosis) and ATP production. Such changes could result in heretofore uncharacterized pathogenesis, potentially implicating HCMV as a subtle cofactor in many maladies, including oncogenesis. Recognition of the effects of HCMV, and other viruses, on host cell metabolism will provide new understanding of viral pathogenesis and novel avenues for antiviral therapy.
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Affiliation(s)
- Yongjun Yu
- Department of Cancer Biology, Abramson Family Cancer Research Institute, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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163
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Eckert AW, Lautner MHW, Schütze A, Taubert H, Schubert J, Bilkenroth U. Coexpression of hypoxia-inducible factor-1α and glucose transporter-1 is associated with poor prognosis in oral squamous cell carcinoma patients. Histopathology 2011; 58:1136-47. [PMID: 21438910 DOI: 10.1111/j.1365-2559.2011.03806.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
AIMS To study whether coexpression of the two hypoxia-related proteins hypoxia-inducible factor (HIF)-1α and glucose transporter (GLUT)-1 has prognostic relevance in oral squamous cell carcinomas (OSCCs). METHODS AND RESULTS Eighty-two OSCC samples were analysed for expression levels of HIF-1α and GLUT-1 by immunohistochemistry. Protein expression was assessed with an immunoreactive score system, and the correlations between gene expression and both clinical and pathohistological parameters were examined. Overexpression of either GLUT-1 or HIF-1α was associated with poor disease-specific survival in OSCC patients. Multivariate Cox proportional-hazards regression analysis revealed that increased expression of HIF-1α was significantly associated with disease-specific survival (relative risk = 3.24, P = 0.024), as compared with the group with a low level of expression. Coexpression of HIF-1α and GLUT-1 was additively and significantly associated with adverse prognoses in patients with OSCC. Patients whose tumours had increased levels of expression of both HIF-1α and GLUT-1 were found to have a 5.13-fold increased risk of tumour-related death (P = 0.017). CONCLUSIONS Coexpression of high levels of HIF-1α and GLUT-1 is significantly correlated with prognosis in OSCC patients, suggesting that the coexpression of these proteins can be used as both an early diagnostic and independent prognostic marker.
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Affiliation(s)
- Alexander W Eckert
- Department of Oral and Maxillofacial Plastic Surgery, Martin Luther University Halle-Wittenberg, Halle Institute of Pathology, Eisleben, Germany.
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164
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Matschinsky FM, Zelent B, Doliba NM, Kaestner KH, Vanderkooi JM, Grimsby J, Berthel SJ, Sarabu R. Research and development of glucokinase activators for diabetes therapy: theoretical and practical aspects. Handb Exp Pharmacol 2011:357-401. [PMID: 21484579 DOI: 10.1007/978-3-642-17214-4_15] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Glucokinase Glucokinase (GK GK ; EC 2.7.1.1.) phosphorylates and regulates glucose metabolism in insulin-producing pancreatic beta-cells, hepatocytes, and certain cells of the endocrine and nervous systems allowing it to play a central role in glucose homeostasis glucose homeostasis . Most importantly, it serves as glucose sensor glucose sensor in pancreatic beta-cells mediating glucose-stimulated insulin biosynthesis and release and it governs the capacity of the liver to convert glucose to glycogen. Activating and inactivating mutations of the glucokinase gene cause autosomal dominant hyperinsulinemic hypoglycemia and hypoinsulinemic hyperglycemia in humans, respectively, illustrating the preeminent role of glucokinase in the regulation of blood glucose and also identifying the enzyme as a potential target for developing antidiabetic drugs antidiabetic drugs . Small molecules called glucokinase activators (GKAs) glucokinase activators (GKAs) which bind to an allosteric activator allosteric activator site of the enzyme have indeed been discovered and hold great promise as new antidiabetic agents. GKAs increase the enzyme's affinity for glucose and also its maximal catalytic rate. Consequently, they stimulate insulin biosynthesis and secretion, enhance hepatic glucose uptake, and augment glucose metabolism and related processes in other glucokinase-expressing cells. Manifestations of these effects, most prominently a lowering of blood glucose, are observed in normal laboratory animals and man but also in animal models of diabetes and patients with type 2 diabetes mellitus (T2DM T2DM ) type 2 diabetes mellitus (T2DM) . These compelling concepts and results sustain a strong R&D effort by many pharmaceutical companies to generate GKAs with characteristics allowing for a novel drug treatment of T2DM.
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Affiliation(s)
- Franz M Matschinsky
- Department of Biochemistry and Biophysics, University of Pennsylvania, Institute for Diabetes, Obesity and Metabolism, 415 Curie Blvd, 605 CRB, Philadelphia, PA 19104, USA.
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165
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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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166
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Mohan S, Sheena A, Poulose N, Anilkumar G. Molecular dynamics simulation studies of GLUT4: substrate-free and substrate-induced dynamics and ATP-mediated glucose transport inhibition. PLoS One 2010; 5:e14217. [PMID: 21151967 PMCID: PMC2997047 DOI: 10.1371/journal.pone.0014217] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Accepted: 11/15/2010] [Indexed: 02/03/2023] Open
Abstract
Background Glucose transporter 4 (GLUT4) is an insulin facilitated glucose transporter that plays an important role in maintaining blood glucose homeostasis. GLUT4 is sequestered into intracellular vesicles in unstimulated cells and translocated to the plasma membrane by various stimuli. Understanding the structural details of GLUT4 will provide insights into the mechanism of glucose transport and its regulation. To date, a crystal structure for GLUT4 is not available. However, earlier work from our laboratory proposed a well validated homology model for GLUT4 based on the experimental data available on GLUT1 and the crystal structure data obtained from the glycerol 3-phosphate transporter. Methodology/Principal Findings In the present study, the dynamic behavior of GLUT4 in a membrane environment was analyzed using three forms of GLUT4 (apo, substrate and ATP-substrate bound states). Apo form simulation analysis revealed an extracellular open conformation of GLUT4 in the membrane favoring easy exofacial binding of substrate. Simulation studies with the substrate bound form proposed a stable state of GLUT4 with glucose, which can be a substrate-occluded state of the transporter. Principal component analysis suggested a clockwise movement for the domains in the apo form, whereas ATP substrate-bound form induced an anti-clockwise rotation. Simulation studies suggested distinct conformational changes for the GLUT4 domains in the ATP substrate-bound form and favor a constricted behavior for the transport channel. Various inter-domain hydrogen bonds and switching of a salt-bridge network from E345-R350-E409 to E345-R169-E409 contributed to this ATP-mediated channel constriction favoring substrate occlusion and prevention of its release into cytoplasm. These data are consistent with the biochemical studies, suggesting an inhibitory role for ATP in GLUT-mediated glucose transport. Conclusions/Significance In the absence of a crystal structure for any glucose transporter, this study provides mechanistic details of the conformational changes in GLUT4 induced by substrate and its regulator.
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Affiliation(s)
- Suma Mohan
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
| | - Aswathy Sheena
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
| | - Ninu Poulose
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
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167
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Normalizing effects of Costus speciosus rhizome crude extracts and its fractions on diabetic complications in STZ-induced diabetic rats. Med Chem Res 2010. [DOI: 10.1007/s00044-010-9448-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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168
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Augustin R. The protein family of glucose transport facilitators: It's not only about glucose after all. IUBMB Life 2010; 62:315-33. [PMID: 20209635 DOI: 10.1002/iub.315] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The protein family of facilitative glucose transporters comprises 14 isoforms that share common structural features such as 12 transmembrane domains, N- and C-termini facing the cytoplasm of the cell, and a N-glycosylation side either within the first or fifth extracellular loop. Based on their sequence homology, three classes can be distinguished: class I includes GLUT1-4 and GLUT14, class II the "odd transporters" GLUT5, 7, 9, 11, and class III the "even transporters" GLUT6, 8, 10, 12 and the proton driven myoinositol transporter HMIT (or GLUT13). With the cloning and characterization of the more recent class II and III isoforms, it became apparent that despite their structural similarities, the different isoforms not only show a distinct tissue-specific expression pattern but also show distinct characteristics such as alternative splicing, specific (sub)cellular localization, and affinities for a spectrum of substrates. This review summarizes the current understanding of the physiological role for the various transport facilitators based on human genetically inherited disorders or single-nucleotide polymorphisms and knockout mice models. The emphasis of the review will be on the potential functional role of the more recent isoforms.
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Affiliation(s)
- Robert Augustin
- Department of Cardiometabolic Diseases Research, Boehringer-Ingelheim Pharma GmbH&Co KG, Biberach a.d. Riss, Germany.
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169
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Wilson-O'Brien AL, Patron N, Rogers S. Evolutionary ancestry and novel functions of the mammalian glucose transporter (GLUT) family. BMC Evol Biol 2010; 10:152. [PMID: 20487568 PMCID: PMC2890515 DOI: 10.1186/1471-2148-10-152] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Accepted: 05/21/2010] [Indexed: 01/25/2023] Open
Abstract
Background In general, sugar porters function by proton-coupled symport or facilitative transport modes. Symporters, coupled to electrochemical energy, transport nutrients against a substrate gradient. Facilitative carriers transport sugars along a concentration gradient, thus transport is dependent upon extracellular nutrient levels. Across bacteria, fungi, unicellular non-vertebrates and plants, proton-coupled hexose symport is a crucial process supplying energy under conditions of nutrient flux. In mammals it has been assumed that evolution of whole body regulatory mechanisms would eliminate this need. To determine whether any isoforms bearing this function might be conserved in mammals, we investigated the relationship between the transporters of animals and the proton-coupled hexose symporters found in other species. Results We took a comparative genomic approach and have performed the first comprehensive and statistically supported phylogenetic analysis of all mammalian glucose transporter (GLUT) isoforms. Our data reveals the mammalian GLUT proteins segregate into five distinct classes. This evolutionary ancestry gives insight to structure, function and transport mechanisms within the groups. Combined with biological assays, we present novel evidence that, in response to changing nutrient availability and environmental pH, proton-coupled, active glucose symport function is maintained in mammalian cells. Conclusions The analyses show the ancestry, evolutionary conservation and biological importance of the GLUT classes. These findings significantly extend our understanding of the evolution of mammalian glucose transport systems. They also reveal that mammals may have conserved an adaptive response to nutrient demand that would have important physiological implications to cell survival and growth.
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Affiliation(s)
- Amy L Wilson-O'Brien
- Department of Medicine, St, Vincent's, The University of Melbourne, Fitzroy, Victoria 3065, Australia
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170
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Dietvorst J, Karhumaa K, Kielland-Brandt MC, Brandt A. Amino acid residues involved in ligand preference of the Snf3 transporter-like sensor in Saccharomyces cerevisiae. Yeast 2010; 27:131-8. [PMID: 20014043 DOI: 10.1002/yea.1737] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Snf3 is a plasma membrane protein in Saccharomyces cerevisiae able to sense the presence of glucose. Although the Snf3 protein does not transport sugars, it shares sequence similarity with various glucose transporters from other organisms. We investigated the sugar specificity/preferences of Snf3. The ability of cells to sense sugars in vivo was monitored by following the degradation of the Mth1 protein, an early event in the signal pathway. Our study reveals that Snf3, in addition to glucose, also senses fructose and mannose, as well as the glucose analogues 2-deoxyglucose, 3-O-methylglucoside and 6-deoxyglucose. The signalling proficiency of a non-phosphorylatable analogue strongly supports the notion that sensing through Snf3 does not require sugar phosphorylation. Sequence comparisons of Snf3 to glucose transporters indicated amino acid residues possibly involved in sensing of sugars other than glucose. By site-specific mutagenesis of the structural gene, roles of specific residues in Snf3 could be established. Change of isoleucine-374 to valine in transmembrane segment 7 of Snf3 partially abolished sensing of fructose and mannose, while mutagenesis causing a change of phenylalanine-462 to tyrosine in transmembrane segment 10 of Snf3 abolished sensing of fructose. Neither of these amino acid changes affected the ability of Snf3 to sense glucose, nor did they permit Snf3 to sense galactose. These data indicate a similarity between a ligand binding site of the sensor Snf3 and binding sites used for facilitated hexose transport in the GLUT proteins.
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Affiliation(s)
- Judith Dietvorst
- Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Copenhagen Valby, Denmark
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171
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Pathogenesis of insulin resistance in skeletal muscle. J Biomed Biotechnol 2010; 2010:476279. [PMID: 20445742 PMCID: PMC2860140 DOI: 10.1155/2010/476279] [Citation(s) in RCA: 378] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 01/20/2010] [Indexed: 12/16/2022] Open
Abstract
Insulin resistance in skeletal muscle is manifested by decreased insulin-stimulated glucose uptake and results from impaired insulin signaling and multiple post-receptor intracellular defects including impaired glucose transport, glucose phosphorylation, and reduced glucose oxidation and glycogen synthesis. Insulin resistance is a core defect in type 2 diabetes, it is also associated with obesity and the metabolic syndrome. Dysregulation of fatty acid metabolism plays a pivotal role in the pathogenesis of insulin resistance in skeletal muscle. Recent studies have reported a mitochondrial defect in oxidative phosphorylation in skeletal muscle in variety of insulin resistant states. In this review, we summarize the cellular and molecular defects that contribute to the development of insulin resistance in skeletal muscle.
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172
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Naftalin RJ. Reassessment of Models of Facilitated Transport and Cotransport. J Membr Biol 2010; 234:75-112. [DOI: 10.1007/s00232-010-9228-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Accepted: 01/08/2010] [Indexed: 11/29/2022]
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173
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Abstract
The ability to take up and metabolize glucose at the cellular level is a property shared by the vast majority of existing organisms. Most mammalian cells import glucose by a process of facilitative diffusion mediated by members of the Glut (SLC2A) family of membrane transport proteins. Fourteen Glut proteins are expressed in the human and they include transporters for substrates other than glucose, including fructose, myoinositol, and urate. The primary physiological substrates for at least half of the 14 Glut proteins are either uncertain or unknown. The well-established glucose transporter isoforms, Gluts 1-4, are known to have distinct regulatory and/or kinetic properties that reflect their specific roles in cellular and whole body glucose homeostasis. Separate review articles on many of the Glut proteins have recently appeared in this journal. Here, we provide a very brief summary of the known properties of the 14 Glut proteins and suggest some avenues of future investigation in this area.
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Affiliation(s)
- Bernard Thorens
- Department of Physiology and Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
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174
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Kanamori Y, Saito A, Hagiwara-Komoda Y, Tanaka D, Mitsumasu K, Kikuta S, Watanabe M, Cornette R, Kikawada T, Okuda T. The trehalose transporter 1 gene sequence is conserved in insects and encodes proteins with different kinetic properties involved in trehalose import into peripheral tissues. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2010; 40:30-7. [PMID: 20035867 DOI: 10.1016/j.ibmb.2009.12.006] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 11/19/2009] [Accepted: 12/10/2009] [Indexed: 05/09/2023]
Abstract
We recently cloned a trehalose transporter gene (Tret1) that contributes to anhydrobiosis induction in the sleeping chironomid Polypedilum vanderplanki Hinton. Because trehalose is the main haemolymph sugar in most insects, they might possess Tret1 orthologs involved in maintaining haemolymph trehalose levels. We cloned Tret1 orthologs from four species in three insect orders. The similarities of the amino acid sequence to TRET1 in P. vanderplanki were 58.5-80.4%. Phylogenetic analysis suggested the Tret1 sequences were conserved in insects. The Xenopus oocyte expression system showed apparent differences in the K(m) and V(max) values for trehalose transport activity among the six proteins encoded by the corresponding orthologs. The TRET1 orthologs of Anopheles gambiae (K(m): 45.74 +/- 3.58 mM) and Bombyx mori (71.58 +/- 6.45 mM) showed low trehalose affinity, whereas those of Apis mellifera (9.42 +/- 2.37 mM) and Drosophila melanogaster (10.94 +/- 7.70 mM) showed high affinity. This difference in kinetics might be reflected in the haemolymph trehalose:glucose ratio of each species. Tret1 was expressed not only in the fat body but also in muscle and testis. These findings suggest that insect TRET1 is responsible for the release of trehalose from the fat body and the incorporation of trehalose into other tissues that require a carbon source, thereby regulating trehalose levels in the haemolymph.
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Affiliation(s)
- Yasushi Kanamori
- Anhydrobiosis Research Unit, National Institute of Agrobiological Sciences, Ohwashi 1-2, Tsukuba, Ibaraki 305-8634, Japan
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175
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Ueda M, Furuyashiki T, Yamada K, Aoki Y, Sakane I, Fukuda I, Yoshida KI, Ashida H. Tea catechins modulate the glucose transport system in 3T3-L1 adipocytes. Food Funct 2010; 1:167-73. [DOI: 10.1039/c0fo00105h] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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176
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Daisy P, Balasubramanian K, Rajalakshmi M, Eliza J, Selvaraj J. Insulin mimetic impact of Catechin isolated from Cassia fistula on the glucose oxidation and molecular mechanisms of glucose uptake on Streptozotocin-induced diabetic Wistar rats. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2010; 17:28-36. [PMID: 19931438 DOI: 10.1016/j.phymed.2009.10.018] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Accepted: 10/15/2009] [Indexed: 05/13/2023]
Abstract
Diabetes mellitus is the most common and serious metabolic disorder among people all over the world. Many plants have successfully been used to overcome this problem. Cassia fistula, an ethnomedicnal plant, is widely used in Indian medicine to treat diabetes. Methanol extract of stem of plant, reduced the blood glucose levels in Streptozotocin-induced diabetic rats. Bioassay guided fractionation was followed to isolate Catechin from methanol extract. Catechin was administered to Streptozotocin (60mg/kg b.w.)-induced diabetic male Wistar rats at different doses (5, 10, 20mg/kg b.w.) for 6 weeks to assess its effect on fasting plasma glucose. The plasma glucose was significantly (p<0.05) reduced when compared to the control. Oral administration of Catechin (20mg/kg b.w.) markedly increased tissue glycogen, and (14)C-glucose oxidation without any change in plasma insulin and C-peptide. Catechin restored the altered Glucokinase, glucose-6 Phosphatase, Glycogen Synthase and Glycogen Phosphorylase levels to near normal. GLUT4 mRNA and protein expression were enhanced after Catechin treatment. The results of this experimental study indicated that Catechin possesses hypo-glycemic, Glucose oxidizing and insulin mimetic activities and hence it could be used as a drug for treating diabetes.
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Affiliation(s)
- P Daisy
- PG & Research Department of Biotechnology & Bioinformatics, Holy Cross College (Autonomous), Trichy 620002, Tamilnadu, India.
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177
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Abstract
Type 2 diabetes mellitus (T2DM) affects a large population worldwide. T2DM is a complex heterogeneous group of metabolic disorders including hyperglycemia and impaired insulin action and/or insulin secretion. T2DM causes dysfunctions in multiple organs or tissues. Current theories of T2DM include a defect in insulin-mediated glucose uptake in muscle, a dysfunction of the pancreatic beta-cells, a disruption of secretory function of adipocytes, and an impaired insulin action in liver. The etiology of human T2DM is multifactorial, with genetic background and physical inactivity as two critical components. The pathogenesis of T2DM is not fully understood. Animal models of T2DM have been proved to be useful to study the pathogenesis of, and to find a new therapy for, the disease. Although different animal models share similar characteristics, each mimics a specific aspect of genetic, endocrine, metabolic, and morphologic changes that occur in human T2DM. The purpose of this review is to provide the recent progress and current theories in T2DM and to summarize animal models for studying the pathogenesis of the disease.
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Affiliation(s)
- Yi Lin
- Department of Physiology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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178
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Evans SA, Doblado M, Chi MM, Corbett JA, Moley KH. Facilitative glucose transporter 9 expression affects glucose sensing in pancreatic beta-cells. Endocrinology 2009; 150:5302-10. [PMID: 19808778 PMCID: PMC2795723 DOI: 10.1210/en.2009-0747] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Accepted: 08/27/2009] [Indexed: 11/19/2022]
Abstract
Facilitative glucose transporters (GLUTs) including GLUT9, accelerate the facilitative diffusion of glucose across the plasma membrane. Studies in GLUT2-deficient mice suggested the existence of another GLUT in the mammalian beta-cell responsible for glucose sensing. The objective of this study was to determine the expression and function of GLUT9 in murine and human beta-cells. mRNA and protein expression levels were determined for both isoforms of GLUT9 in murine and human isolated islets as well as insulinoma cell lines (MIN6). Immunohistochemistry and subcellular localization were performed to localize the protein within the cell. Small interfering RNA knockdown of GLUT9 was used to determine the effect of this transporter, in the presence of GLUT2, on cell metabolism and insulin secretion in MIN6 and INS cells. In this report we demonstrate that GLUT9a and GLUT9b are expressed in pancreatic islets and that this expression localizes to insulin-containing beta-cells. Subcellular localization studies indicate that mGLUT9b is found associated with the plasma membrane as well as in the high-density microsome fraction and low-density microsome fraction, whereas mGLUT9a appears to be located only in the high-density microsome and low-density microsome under basal conditions. Functionally GLUT9 appears to participate in the regulation of glucose-stimulated insulin secretion in addition to GLUT2. small interfering RNA knockdown of GLUT9 results in reduced cellular ATP levels that correlate with reductions in glucose-stimulated insulin secretion in MIN6 and INS cells. These studies confirm the expression of GLUT9a and GLUT9b in murine and human beta-cells and suggest that GLUT9 may participate in glucose-sensing in beta-cells.
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Affiliation(s)
- Sarah A Evans
- Department of Obstetrics and Gynecology, Washington University Schoolof Medicine, St Louis, Missouri 63110, USA
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179
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Purcell SH, Moley KH. Glucose transporters in gametes and preimplantation embryos. Trends Endocrinol Metab 2009; 20:483-9. [PMID: 19811929 PMCID: PMC6175277 DOI: 10.1016/j.tem.2009.06.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 06/17/2009] [Accepted: 06/18/2009] [Indexed: 10/20/2022]
Abstract
The oocyte, sperm and preimplantation embryo have unique metabolic needs that must be met to ensure successful pregnancy. The family of facilitative glucose transporters (GLUTs) plays a major role in providing metabolic substrates to these tissues. The variety of GLUTs expressed in these tissues allows for flexibility to adapt to a changing environment. Alterations in glucose transport and metabolism at the earliest stages of development can impact fetal development. Research into the mechanisms of normal glucose transport into cells is critical for improving outcomes in the increasingly common diabetic maternal environment. Here, we review the current understanding in the distribution and role of glucose transporters in gametes and preimplantation embryos under normal and diabetic conditions.
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Affiliation(s)
- Scott H Purcell
- Department of Obstetrics and Gynecology, Washington University in St. Louis, St. Louis, MO, USA
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180
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Carruthers A, DeZutter J, Ganguly A, Devaskar SU. Will the original glucose transporter isoform please stand up! Am J Physiol Endocrinol Metab 2009; 297:E836-48. [PMID: 19690067 PMCID: PMC2763785 DOI: 10.1152/ajpendo.00496.2009] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Monosaccharides enter cells by slow translipid bilayer diffusion by rapid, protein-mediated, cation-dependent cotransport and by rapid, protein-mediated equilibrative transport. This review addresses protein-mediated, equilibrative glucose transport catalyzed by GLUT1, the first equilibrative glucose transporter to be identified, purified, and cloned. GLUT1 is a polytopic, membrane-spanning protein that is one of 13 members of the human equilibrative glucose transport protein family. We review GLUT1 catalytic and ligand-binding properties and interpret these behaviors in the context of several putative mechanisms for protein-mediated transport. We conclude that no single model satisfactorily explains GLUT1 behavior. We then review GLUT1 topology, subunit architecture, and oligomeric structure and examine a new model for sugar transport that combines structural and kinetic analyses to satisfactorily reproduce GLUT1 behavior in human erythrocytes. We next review GLUT1 cell biology and the transcriptional and posttranscriptional regulation of GLUT1 expression in the context of development and in response to glucose perturbations and hypoxia in blood-tissue barriers. Emphasis is placed on transgenic GLUT1 overexpression and null mutant model systems, the latter serving as surrogates for the human GLUT1 deficiency syndrome. Finally, we review the role of GLUT1 in the absence or deficiency of a related isoform, GLUT3, toward establishing the physiological significance of coordination between these two isoforms.
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Affiliation(s)
- Anthony Carruthers
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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181
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Stuart CA, Howell MEA, Zhang Y, Yin D. Insulin-stimulated translocation of glucose transporter (GLUT) 12 parallels that of GLUT4 in normal muscle. J Clin Endocrinol Metab 2009; 94:3535-42. [PMID: 19549745 PMCID: PMC2741719 DOI: 10.1210/jc.2009-0162] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
CONTEXT GLUT4 is the predominant glucose transporter isoform expressed in fat and muscle. In GLUT4 null mice, insulin-stimulated glucose uptake into muscle was diminished but not eliminated, suggesting that another insulin-sensitive system was present. OBJECTIVE This study was intended to determine whether insulin caused GLUT12 translocation in muscle. DESIGN Six normal volunteers had muscle biopsies before and after euglycemic insulin infusions. SETTING Infusions and biopsies were performed in an outpatient clinic. PARTICIPANTS Subjects were nonobese, young adults with no family history of diabetes. MAIN OUTCOME MEASURES GLUT12, GLUT4, and GLUT1 proteins were quantified in muscle biopsy fractions. Cultured myoblasts were used to determine whether GLUT12 translocation was phosphatidyl inositol-3 kinase (PI3-K)-dependent. INTERVENTION Insulin was infused at 40 mU/m(2) x min for 3 h. RESULTS In human muscle, insulin caused a shift of a portion of GLUT12 from intracellular low-density microsomes to the plasma membrane (PM) fraction (17% in PM at baseline, 38% in PM after insulin). Insulin increased GLUT4 in PM from 13 to 42%. GLUT1 was predominantly in the PM fractions at baseline and did not change significantly after insulin. L6 myoblasts in culture also expressed and translocated GLUT12 in response to insulin, but inhibiting PI3-K prevented the translocation of GLUT12 and GLUT4. CONCLUSIONS Insulin causes GLUT12 to translocate from an intracellular location to the plasma membrane in normal human skeletal muscle. Translocation of GLUT12 in cultured myoblasts was dependent on activation of PI3-K. GLUT12 may have evolutionarily preceded GLUT4 and now provides redundancy to the dominant GLUT4 system in muscle.
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Affiliation(s)
- Charles A Stuart
- Department of Internal Medicine, East Tennessee State University, Quillen College of Medicine, P.O. Box 70622, Johnson City, Tennessee 37614-0622, USA.
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182
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Zhu H, Kartiko S, Finnell RH. Importance of gene-environment interactions in the etiology of selected birth defects. Clin Genet 2009; 75:409-23. [PMID: 19459879 DOI: 10.1111/j.1399-0004.2009.01174.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
It is generally understood that both genetic and environmental factors contribute to the highly complex etiology of structural birth defects, including neural tube defects, oral clefts and congenital heart defects, by disrupting highly regulated embryonic developmental processes. The intrauterine environment of the developing embryo/fetus is determined by maternal factors such as health/disease status, lifestyle, medication, exposure to environmental teratogens, as well as the maternal genotype. Certain genetic characteristics of the embryo/fetus also predispose it to developmental abnormalities. Epidemiologic and animal studies conducted over the last few decades have suggested that the interplay between genes and environmental factors underlies the etiological heterogeneity of these defects. It is now widely believed that the study of gene-environment interactions will lead to better understanding of the biological mechanisms and pathological processes that contribute to the development of complex birth defects. It is only through such an understanding that more efficient measures will be developed to prevent these severe, costly and often deadly defects. In this review, we attempt to summarize the complex clinical and experimental literature on current hypotheses of interactions between several select environmental factors and those genetic pathways in which they are most likely to have significant modifying effects. These include maternal folate nutritional status, maternal diabetes/obesity-related conditions, and maternal exposure to selected medications and environmental contaminants. Our goal is to highlight the potential gene-environment interactions affecting early embryogenesis that deserve comprehensive study.
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Affiliation(s)
- H Zhu
- Center for Environmental and Genetic Medicine, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX 77030, USA.
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183
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Alves-Wagner ABT, De Freitas HS, De Souza PB, Seraphim PM, Mori RCT, Machado UF. β-Adrenergic activity preserves GLUT4 protein in glycolytic fibers in fasting. Muscle Nerve 2009; 40:847-54. [DOI: 10.1002/mus.21359] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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184
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Tonack S, Ramin N, Garimella S, Rao R, Seshagiri PB, Fischer B, Navarrete Santos A. Expression of glucose transporter isoforms and the insulin receptor during hamster preimplantation embryo development. Ann Anat 2009; 191:485-95. [PMID: 19615873 DOI: 10.1016/j.aanat.2009.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 05/06/2009] [Accepted: 06/03/2009] [Indexed: 11/15/2022]
Abstract
During preimplantation development, embryos of many species are known to express up to five isoforms of the facilitative glucose transporter proteins (GLUT). Development of hamster blastocysts is inhibited by glucose. We therefore investigated GLUT isoform and insulin receptor (IR) expression in hamster preimplantation embryos cultured in glucose-free medium from the 8-cell stage onwards. We show that GLUT1, 3 and 8 mRNA are constitutively expressed from the 8-cell to the blastocyst stage. The IR is expressed from the morula stage onwards. Messenger RNA of the insulin-responsive GLUT4 was not detected at any stage. GLUT1 and 3 were localised by immunocytochemistry. GLUT1 was expressed in both embryoblast and trophoblast, in the latter, mainly in basal and lateral membranes directed towards the blastocoel and embryoblast. GLUT3 was exclusively localised in the apical membrane of trophoblast cells. We show that hamster preimplantation embryos express several GLUT isoforms thus closely resembling embryos of other mammalian species. Despite endogenous IR expression, the insulin-sensitive isoform GLUT4 was not expressed, indicating that the insulin-mediated glucose uptake known from classical insulin target cells may not be relevant for hamster blastocysts.
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Affiliation(s)
- Sarah Tonack
- Department of Anatomy and Cell Biology, Martin Luther University Faculty of Medicine, Grosse Steinstrasse 52, 06097 Halle (Saale), Germany
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185
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Mueckler M, Makepeace C. Model of the exofacial substrate-binding site and helical folding of the human Glut1 glucose transporter based on scanning mutagenesis. Biochemistry 2009; 48:5934-42. [PMID: 19449892 DOI: 10.1021/bi900521n] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transmembrane helix 9 of the Glut1 glucose transporter was analyzed by cysteine-scanning mutagenesis and the substituted cysteine accessibility method (SCAM). A cysteine-less (C-less) template transporter containing amino acid substitutions for the six native cysteine residues present in human Glut1 was used to generate a series of 21 mutant transporters by substituting each successive residue in predicted transmembrane segment 9 with a cysteine residue. The mutant proteins were expressed in Xenopus oocytes, and their specific transport activities were directly compared to that of the parental C-less molecule whose function has been shown to be indistinguishable from that of native Glut1. Only a single mutant (G340C) had activity that was reduced (by 75%) relative to that of the C-less parent. These data suggest that none of the amino acid side chains in helix 9 is absolutely required for transport function and that this helix is not likely to be directly involved in substrate binding or translocation. Transport activity of the cysteine mutants was also tested after incubation of oocytes in the presence of the impermeant sulfhydryl-specific reagent, p-chloromercuribenzene sulfonate (pCMBS). Only a single mutant (T352C) exhibited transport inhibition in the presence of pCMBS, and the extent of inhibition was minimal (11%), indicating that only a very small portion of helix 9 is accessible to the external solvent. These results are consistent with the conclusion that helix 9 plays an outer stabilizing role for the inner helical bundle predicted to form the exofacial substrate-binding site. All 12 of the predicted transmembrane segments of Glut1 encompassing 252 amino acid residues and more than 50% of the complete polypeptide sequence have now been analyzed by scanning mutagenesis and SCAM. An updated model is presented for the outward-facing substrate-binding site and relative orientation of the 12 transmembrane helices of Glut1.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA.
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186
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Kipmen‐Korgun D, Bilmen‐Sarikcioglu S, Altunbas H, Demir R, Korgun ET. Type‐2 diabetes down‐regulates glucose transporter proteins and genes of the human blood leukocytes. Scandinavian Journal of Clinical and Laboratory Investigation 2009; 69:350-8. [DOI: 10.1080/00365510802632163] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
| | | | - H. Altunbas
- Department of Internal Medicine, Division of Endocrinology and Metabolism
| | - R. Demir
- Department of Histology and Embryology, Akdeniz University, Medical Faculty, Antalya, Turkey
| | - E. T. Korgun
- Department of Histology and Embryology, Akdeniz University, Medical Faculty, Antalya, Turkey
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187
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Freitas HS, Schaan BD, David-Silva A, Sabino-Silva R, Okamoto MM, Alves-Wagner AB, Mori RC, Machado UF. SLC2A2 gene expression in kidney of diabetic rats is regulated by HNF-1alpha and HNF-3beta. Mol Cell Endocrinol 2009; 305:63-70. [PMID: 19433262 DOI: 10.1016/j.mce.2009.02.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Revised: 02/13/2009] [Accepted: 02/18/2009] [Indexed: 11/26/2022]
Abstract
We hypothesize that, in kidney of diabetic rats, hepatocyte nuclear factors (HNF-1alpha and HNF-3beta) play a critical role in the overexpression of solute carrier 2A2 (SLC2A2) gene. Diabetic rats submitted or not to rapid (up to 12h) and short-term (1, 4 and 6 days) insulin treatment were investigated. Twofold increase in GLUT2 mRNA was observed in diabetic, accompanied by significant increases in HNF-1alpha and HNF-3beta expression and binding activity. Additional 2-fold increase in GLUT2 mRNA and HNF-3beta expression/activity was observed in 12-h insulin-treated rats. Six-day insulin treatment decreased GLUT2 mRNA and HNF-1alpha expression and activity to levels of non-diabetic rats, whereas HNF-3beta decreased to levels of non-insulin-treated diabetic rats. Our results provide evidence for a link between the overexpression of SLC2A2 gene and the transcriptional activity of HNF-1alpha and HNF-3beta in kidney of diabetic rats. Furthermore, recovery of SLC2A2 gene after 6-day insulin treatment also involves HNF-1alpha and HNF-3beta activity.
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Affiliation(s)
- H S Freitas
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Av. Prof. Lineu Prestes 1524, 05505-900 Sao Paulo (SP), Brazil.
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188
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Castro MA, Beltrán FA, Brauchi S, Concha II. A metabolic switch in brain: glucose and lactate metabolism modulation by ascorbic acid. J Neurochem 2009; 110:423-40. [PMID: 19457103 DOI: 10.1111/j.1471-4159.2009.06151.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In this review, we discuss a novel function of ascorbic acid in brain energetics. It has been proposed that during glutamatergic synaptic activity neurons preferably consume lactate released from glia. The key to this energetic coupling is the metabolic activation that occurs in astrocytes by glutamate and an increase in extracellular [K(+)]. Neurons are cells well equipped to consume glucose because they express glucose transporters and glycolytic and tricarboxylic acid cycle enzymes. Moreover, neuronal cells express monocarboxylate transporters and lactate dehydrogenase isoenzyme 1, which is inhibited by pyruvate. As glycolysis produces an increase in pyruvate concentration and a decrease in NAD(+)/NADH, lactate and glucose consumption are not viable at the same time. In this context, we discuss ascorbic acid participation as a metabolic switch modulating neuronal metabolism between rest and activation periods. Ascorbic acid is highly concentrated in CNS. Glutamate stimulates ascorbic acid release from astrocytes. Ascorbic acid entry into neurons and within the cell can inhibit glucose consumption and stimulate lactate transport. For this switch to occur, an ascorbic acid flow is necessary between astrocytes and neurons, which is driven by neural activity and is part of vitamin C recycling. Here, we review the role of glucose and lactate as metabolic substrates and the modulation of neuronal metabolism by ascorbic acid.
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Affiliation(s)
- Maite A Castro
- Instituto de Bioquímica, Universidad Austral de Chile, Valdivia, Chile.
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189
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Terova G, Rimoldi S, Brambilla F, Gornati R, Bernardini G, Saroglia M. In vivo regulation of GLUT2 mRNA in sea bass (Dicentrarchus labrax) in response to acute and chronic hypoxia. Comp Biochem Physiol B Biochem Mol Biol 2009; 152:306-16. [DOI: 10.1016/j.cbpb.2008.12.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2008] [Revised: 12/15/2008] [Accepted: 12/16/2008] [Indexed: 02/03/2023]
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190
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Kim ST, Moley KH. Regulation of facilitative glucose transporters and AKT/MAPK/PRKAA signaling via estradiol and progesterone in the mouse uterine epithelium. Biol Reprod 2009; 81:188-98. [PMID: 19208550 DOI: 10.1095/biolreprod.108.072629] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Adequate uterine glucose metabolism is an essential part of embryo implantation and the development of an adequate utero-fetal environment. However, expression of facilitative glucose transporters (GLUTs [solute transporter family SLC2A]) and AKT/MAPK/PRKAA (PRKAA) signaling has not been described in the mouse uterine cells, to our knowledge. The objective of this study was to determine the hormonal regulation of SLC2A protein expression and AKT/MAPK/PRKAA signaling in the mouse uterine epithelial cells during estrous cycles and peri-implantation periods. SLC2As 1, 4, 8, and 9B were highly expressed in the luminal and glandular epithelia of estrous stage. In metestrous and diestrous stages, expression of SLC2As 1, 4, 8, and 9B was lower than that in proestrous stage. Levels of activated phospho-AKT (p-AKT), p-MAPK3, and p-MAPK1 also varied during the estrous cycle. Estrogen and progesterone injection in an ovariectomized mouse (delayed implantation model) resulted in a decrease and an increase, respectively, in expression of GLUTs in the luminal epithelial cells of the uterus. The expression of SLC2A1, SLC2A8, SLC2A9B, p-AKT, p-MAPK3/1, and p-PRKAA was increased in the decidual region of the implantation sites and was significantly increased in the uterus of activated implantation. Using an artificial decidualization mouse model, it was also demonstrated that expression of the same GLUTs, p-MAPK3/1, and p-PRKAA was dramatically higher in the decidualized uteri than that in the control uteri. These results suggest that steroid hormones regulate expression of uterine epithelial GLUTs possibly through AKT/MAPK/PRKAA signaling pathways and that glucose utilization may have an important role in decidualization and possibly in the maintenance of pregnancy.
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Affiliation(s)
- Sung Tae Kim
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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191
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Vishnu Prasad C, Suma Mohan S, Banerji A, Gopalakrishnapillai A. Kaempferitrin inhibits GLUT4 translocation and glucose uptake in 3T3-L1 adipocytes. Biochem Biophys Res Commun 2009; 380:39-43. [DOI: 10.1016/j.bbrc.2009.01.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2008] [Accepted: 01/04/2009] [Indexed: 01/01/2023]
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192
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193
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Rivas CI, Zúñiga FA, Salas-Burgos A, Mardones L, Ormazabal V, Vera JC. Vitamin C transporters. J Physiol Biochem 2008; 64:357-75. [DOI: 10.1007/bf03174092] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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194
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Blodgett DM, Graybill C, Carruthers A. Analysis of glucose transporter topology and structural dynamics. J Biol Chem 2008; 283:36416-24. [PMID: 18981181 DOI: 10.1074/jbc.m804802200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homology modeling and scanning cysteine mutagenesis studies suggest that the human glucose transport protein GLUT1 and its distant bacterial homologs LacY and GlpT share similar structures. We tested this hypothesis by mapping the accessibility of purified, reconstituted human erythrocyte GLUT1 to aqueous probes. GLUT1 contains 35 potential tryptic cleavage sites. Fourteen of 16 lysine residues and 18 of 19 arginine residues were accessible to trypsin. GLUT1 lysine residues were modified by isothiocyanates and N-hydroxysuccinimide (NHS) esters in a substrate-dependent manner. Twelve lysine residues were accessible to sulfo-NHS-LC-biotin. GLUT1 trypsinization released full-length transmembrane helix 1, cytoplasmic loop 6-7, and the long cytoplasmic C terminus from membranes. Trypsin-digested GLUT1 retained cytochalasin B and d-glucose binding capacity and released full-length transmembrane helix 8 upon cytochalasin B (but not D-glucose) binding. Transmembrane helix 8 release did not abrogate cytochalasin B binding. GLUT1 was extensively proteolyzed by alpha-chymotrypsin, which cuts putative pore-forming amphipathic alpha-helices 1, 2, 4, 7, 8, 10, and 11 at multiple sites to release transmembrane peptide fragments into the aqueous solvent. Putative scaffolding membrane helices 3, 6, 9, and 12 are strongly hydrophobic, resistant to alpha-chymotrypsin, and retained by the membrane bilayer. These observations provide experimental support for the proposed GLUT1 architecture; indicate that the proposed topology of membrane helices 5, 6, and 12 requires adjustment; and suggest that the metastable conformations of transmembrane helices 1 and 8 within the GLUT1 scaffold destabilize a sugar translocation intermediate.
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Affiliation(s)
- David M Blodgett
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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195
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Tseng YC, Hwang PP. Some insights into energy metabolism for osmoregulation in fish. Comp Biochem Physiol C Toxicol Pharmacol 2008; 148:419-29. [PMID: 18539088 DOI: 10.1016/j.cbpc.2008.04.009] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Revised: 04/22/2008] [Accepted: 04/23/2008] [Indexed: 01/01/2023]
Abstract
A sufficient and timely energy supply is a prerequisite for the operation of iono- and osmoregulatory mechanisms in fish. Measurements of whole-fish or isolated-gill (or other organs) oxygen consumption have demonstrated regulation of the energy supply during acclimation to different osmotic environments, and such regulation is dependent on species, the situation of acclimation or acclimatization, and life habits. Carbohydrate metabolism appears to play a major role in the energy supply for iono- and osmoregulation, and the liver is the major source supplying carbohydrate metabolites to osmoregulatory organs. Compared with carbohydrates, the roles of lipids and proteins remain largely unclear. Energy metabolite translocation was recently found to occur between fish gill ionocytes and neighboring glycogen-rich (GR) cells, indicating the physiological significance of a local energy supply for gill ion regulatory mechanisms. Spatial and temporal relationships between the liver and other osmoregulatory and non-osmoregulatory organs in partitioning the energy supply for ion regulatory mechanisms during salinity challenges were also proposed. A novel glucose transporter was found to specifically be expressed and function in gill ionocytes, providing the first cue for investigating energy translocation among gill cells. Advanced molecular physiological approaches can be used to examine energy metabolism relevant to a particular cell type (e.g., gill ionocytes), and functional genomics may also provide another powerful approach to explore new metabolic pathways related to fish ion regulation.
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Affiliation(s)
- Yung-Che Tseng
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, 11529, Taiwan, ROC
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196
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Ueda M, Nishiumi S, Nagayasu H, Fukuda I, Yoshida KI, Ashida H. Epigallocatechin gallate promotes GLUT4 translocation in skeletal muscle. Biochem Biophys Res Commun 2008; 377:286-90. [PMID: 18845128 DOI: 10.1016/j.bbrc.2008.09.128] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Accepted: 09/29/2008] [Indexed: 11/29/2022]
Abstract
In this study, we investigated whether epigallocatechin gallate (EGCg) affects glucose uptake activity and the translocation of insulin-sensitive glucose transporter (GLUT) 4 in skeletal muscle. A single oral administration of EGCg at 75 mg/kg body weight promoted GLUT4 translocation in skeletal muscle of rats. EGCg significantly increased glucose uptake accompanying GLUT4 translocation in L6 myotubes at 1 nM. The translocation of GLUT4 was also observed both in skeletal muscle of mice and rats ex vivo and in insulin-resistant L6 myotubes. Wortmannin, an inhibitor of phosphatidylinositol 3'-kinase, inhibited both EGCg- and insulin-increased glucose uptakes, while genistein, an inhibitor of tyrosine kinase, failed to inhibit the EGCg-increased uptake. Therefore, EGCg may improve hyperglycemia by promoting GLUT4 translocation in skeletal muscle with partially different mechanism from insulin.
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Affiliation(s)
- Manabu Ueda
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe, Japan
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197
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Ciampi R, Vivaldi A, Romei C, Del Guerra A, Salvadori P, Cosci B, Pinchera A, Elisei R. Expression analysis of facilitative glucose transporters (GLUTs) in human thyroid carcinoma cell lines and primary tumors. Mol Cell Endocrinol 2008; 291:57-62. [PMID: 18571834 DOI: 10.1016/j.mce.2008.05.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 04/03/2008] [Accepted: 05/07/2008] [Indexed: 10/22/2022]
Abstract
Fluorine-18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) is based on cell capability to take-up glucose. While a significantly higher expression of the glucose transporter GLUT1 has been reported in thyroid tumors only few data are available on the expression of other GLUT isoforms. We studied several GLUT isoforms expression in thyroid tumor cell lines deriving from anaplastic (ARO, FRO), papillary (NPA), follicular (WRO) and medullary (TT) human thyroid carcinoma. GLUT1 and GLUT3 were also studied in 157 human thyroid malignant and benign tissues. Quantitative Real-time RT-PCR analysis revealed that GLUT1 mRNA levels were higher in less-differentiated cells (ARO, FRO) while GLUT3 mRNA levels were prevalent in well-differentiated cells (NPA, WRO). Accordingly, Western blot showed high expression and correct membrane targeting of GLUT1 protein in ARO and FRO and of GLUT3 protein in NPA and WRO. All cell lines were able to take-up different rates of (3)H-deoxy-glucose. The analysis of GLUT1 and GLUT3 mRNA expression in human thyroid tissues showed the prevalence of GLUT1, but not of GLUT3, in malignant with respect to normal tissues. Finally, both GLUT1 and GLUT3 showed a slightly higher expression in anaplastic than in well-differentiated tumors. In conclusion, we showed that GLUT1 and GLUT3 were the most important glucose transporters in the thyroid tumoral cells. In particular GLUT1 was the most prevalent in less-differentiated cells (ARO and FRO) while GLUT3 was the most prevalent in well-differentiated cells (NPA and WRO). A similar pattern of expression was found for GLUT1 but not for GLUT3 in human thyroid tumors.
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Affiliation(s)
- Raffaele Ciampi
- Department of Endocrinology and Metabolism, University of Pisa, Via Paradisa 2, 56124 Pisa, Italy
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198
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Kim ST, Moley KH. Paternal effect on embryo quality in diabetic mice is related to poor sperm quality and associated with decreased glucose transporter expression. Reproduction 2008; 136:313-22. [DOI: 10.1530/rep-08-0167] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The objective of this study was to determine whether sperm quality, fertilization capacity, and subsequent embryo development are altered in diabetic male mice and whether differences in facilitative glucose transporter (GLUT; now known as solute carrier family 2, SLC2A) expression in the testis and sperm exist. Using two type 1 diabetic mouse models, SLC2A expression in the testis and sperm was determined by western immunoblotting and immunofluorescence staining. To address sperm quality and fertilization capacity, computer-assisted sperm analysis andin vitrofertilization were performed. SLC2A1, SLC2A3, and SLC2A5 did not change in expression in the testes or sperm between diabetic and non-diabetic mice. SLC2A8 and SLC2A9b were less expressed in the testes of both diabetic models versus controls. SLC2A9a was not expressed in the Akita testis or sperm when compared with strain-matched controls. 3β-hydroxysteroid dehydrogenase (HSD3B) expression was significantly decreased in the Leydig cells from the diabetic mice. Sperm concentration and motility were significantly lower in both the diabetics when compared with the control. These parameters normalized in Akita diabetic males treated with insulin. In addition, fertilization rates were significantly lower in the Akita group (17.9%) and the streptozotocin (STZ)-injected male group (43.6%) when compared with the normal group (88.8%). Interestingly, of the fertilized zygotes, embryo developmental rates to the blastocyst stage were lower in both diabetic models (7.1% Akita and 50.0% STZ) when compared with controls (71.7%). Male diabetes may cause male subfertility by altering steroidogenesis, sperm motility, and SLC2A expression. This is the first study to link a paternal metabolic abnormality to a sperm effect on cell division and subsequent embryonic development.
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199
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Buller CL, Loberg RD, Fan MH, Zhu Q, Park JL, Vesely E, Inoki K, Guan KL, Brosius FC. A GSK-3/TSC2/mTOR pathway regulates glucose uptake and GLUT1 glucose transporter expression. Am J Physiol Cell Physiol 2008; 295:C836-43. [PMID: 18650261 PMCID: PMC2544442 DOI: 10.1152/ajpcell.00554.2007] [Citation(s) in RCA: 182] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Glucose transport is a highly regulated process and is dependent on a variety of signaling events. Glycogen synthase kinase-3 (GSK-3) has been implicated in various aspects of the regulation of glucose transport, but the mechanisms by which GSK-3 activity affects glucose uptake have not been well defined. We report that basal glycogen synthase kinase-3 (GSK-3) activity regulates glucose transport in several cell types. Chronic inhibition of basal GSK-3 activity (8-24 h) in several cell types, including vascular smooth muscle cells, resulted in an approximately twofold increase in glucose uptake due to a similar increase in protein expression of the facilitative glucose transporter 1 (GLUT1). Conversely, expression of a constitutively active form of GSK-3beta resulted in at least a twofold decrease in GLUT1 expression and glucose uptake. Since GSK-3 can inhibit mammalian target of rapamycin (mTOR) signaling via phosphorylation of the tuberous sclerosis complex subunit 2 (TSC2) tumor suppressor, we investigated whether chronic GSK-3 effects on glucose uptake and GLUT1 expression depended on TSC2 phosphorylation and TSC inhibition of mTOR. We found that absence of functional TSC2 resulted in a 1.5-to 3-fold increase in glucose uptake and GLUT1 expression in multiple cell types. These increases in glucose uptake and GLUT1 levels were prevented by inhibition of mTOR with rapamycin. GSK-3 inhibition had no effect on glucose uptake or GLUT1 expression in TSC2 mutant cells, indicating that GSK-3 effects on GLUT1 and glucose uptake were mediated by a TSC2/mTOR-dependent pathway. The effect of GSK-3 inhibition on GLUT1 expression and glucose uptake was restored in TSC2 mutant cells by transfection of a wild-type TSC2 vector, but not by a TSC2 construct with mutated GSK-3 phosphorylation sites. Thus, TSC2 and rapamycin-sensitive mTOR function downstream of GSK-3 to modulate effects of GSK-3 on glucose uptake and GLUT1 expression. GSK-3 therefore suppresses glucose uptake via TSC2 and mTOR and may serve to match energy substrate utilization to cellular growth.
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Affiliation(s)
- Carolyn L. Buller
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
| | - Robert D. Loberg
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
| | - Ming-Hui Fan
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
| | - Qihong Zhu
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
| | - James L. Park
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
| | - Eileen Vesely
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
| | - Ken Inoki
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
| | - Kun-Liang Guan
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
| | - Frank C. Brosius
- Departments of Internal Medicine, Physiology, and Biochemistry; and Life Sciences Institute, University of Michigan Medical School, Ann Arbor, Michigan
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200
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Immunodetection of hexose transporters in mammalian spermatozoa. Vet Res Commun 2008; 32 Suppl 1:S119-21. [PMID: 18696246 DOI: 10.1007/s11259-008-9102-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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