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Oeckl J, Janovska P, Adamcova K, Bardova K, Brunner S, Dieckmann S, Ecker J, Fromme T, Funda J, Gantert T, Giansanti P, Hidrobo MS, Kuda O, Kuster B, Li Y, Pohl R, Schmitt S, Schweizer S, Zischka H, Zouhar P, Kopecky J, Klingenspor M. Loss of UCP1 function augments recruitment of futile lipid cycling for thermogenesis in murine brown fat. Mol Metab 2022; 61:101499. [PMID: 35470094 PMCID: PMC9097615 DOI: 10.1016/j.molmet.2022.101499] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/12/2022] [Accepted: 04/12/2022] [Indexed: 11/30/2022] Open
Affiliation(s)
- Josef Oeckl
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Petra Janovska
- Laboratory of Adipose Tissue Biology, Institute of Physiology of the Czech Academy of Sciences, Czech Republic
| | - Katerina Adamcova
- Laboratory of Adipose Tissue Biology, Institute of Physiology of the Czech Academy of Sciences, Czech Republic
| | - Kristina Bardova
- Laboratory of Adipose Tissue Biology, Institute of Physiology of the Czech Academy of Sciences, Czech Republic
| | - Sarah Brunner
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Sebastian Dieckmann
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Josef Ecker
- ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Tobias Fromme
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Jiri Funda
- Laboratory of Adipose Tissue Biology, Institute of Physiology of the Czech Academy of Sciences, Czech Republic
| | - Thomas Gantert
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Piero Giansanti
- Chair of Proteomics and Bioanalytics, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; Bavarian Center for Biomolecular Mass Spectrometry, Technical University of Munich, Freising, Germany
| | - Maria Soledad Hidrobo
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Ondrej Kuda
- Laboratory of Metabolism of Bioactive Lipids, Institute of Physiology of the Czech Academy of Sciences, Czech Republic
| | - Bernhard Kuster
- Chair of Proteomics and Bioanalytics, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; Bavarian Center for Biomolecular Mass Spectrometry, Technical University of Munich, Freising, Germany
| | - Yongguo Li
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Radek Pohl
- NMR spectroscopy, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Czech Republic
| | - Sabine Schmitt
- Institute of Toxicology and Environmental Hygiene, School of Medicine, Technical University of Munich, Munich, Germany
| | - Sabine Schweizer
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Hans Zischka
- Institute of Toxicology and Environmental Hygiene, School of Medicine, Technical University of Munich, Munich, Germany; Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, Munich, Germany
| | - Petr Zouhar
- Laboratory of Adipose Tissue Biology, Institute of Physiology of the Czech Academy of Sciences, Czech Republic
| | - Jan Kopecky
- Laboratory of Adipose Tissue Biology, Institute of Physiology of the Czech Academy of Sciences, Czech Republic.
| | - Martin Klingenspor
- Chair for Molecular Nutritional Medicine, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; EKFZ - Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany; ZIEL Institute for Food & Health, Technical University of Munich, Freising, Germany.
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Fraga A, Ribeiro L, Lobato M, Santos V, Silva JR, Gomes H, da Cunha Moraes JL, de Souza Menezes J, de Oliveira CJL, Campos E, da Fonseca RN. Glycogen and glucose metabolism are essential for early embryonic development of the red flour beetle Tribolium castaneum. PLoS One 2013; 8:e65125. [PMID: 23750237 PMCID: PMC3672164 DOI: 10.1371/journal.pone.0065125] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 04/22/2013] [Indexed: 01/07/2023] Open
Abstract
Control of energy metabolism is an essential process for life. In insects, egg formation (oogenesis) and embryogenesis is dependent on stored molecules deposited by the mother or transcribed later by the zygote. In oviparous insects the egg becomes an isolated system after egg laying with all energy conversion taking place during embryogenesis. Previous studies in a few vector species showed a strong correlation of key morphogenetic events and changes in glucose metabolism. Here, we investigate glycogen and glucose metabolism in the red flour beetle Tribolium castaneum, an insect amenable to functional genomic studies. To examine the role of the key enzymes on glycogen and glucose regulation we cloned and analyzed the function of glycogen synthase kinase 3 (GSK-3) and hexokinase (HexA) genes during T. castaneum embryogenesis. Expression analysis via in situ hybridization shows that both genes are expressed only in the embryonic tissue, suggesting that embryonic and extra-embryonic cells display different metabolic activities. dsRNA adult female injection (parental RNAi) of both genes lead a reduction in egg laying and to embryonic lethality. Morphological analysis via DAPI stainings indicates that early development is impaired in Tc-GSK-3 and Tc-HexA1 RNAi embryos. Importantly, glycogen levels are upregulated after Tc-GSK-3 RNAi and glucose levels are upregulated after Tc-HexA1 RNAi, indicating that both genes control metabolism during embryogenesis and oogenesis, respectively. Altogether our results show that T. castaneum embryogenesis depends on the proper control of glucose and glycogen.
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Affiliation(s)
- Amanda Fraga
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Programa de Pósgraduação em Produtos Bioativos e Biociências (PPGPRODBIO), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
| | - Lupis Ribeiro
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Programa de Pósgraduação em Produtos Bioativos e Biociências (PPGPRODBIO), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
| | - Mariana Lobato
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
| | - Vitória Santos
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
| | - José Roberto Silva
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Programa de Pósgraduação em Produtos Bioativos e Biociências (PPGPRODBIO), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, Brazil
| | - Helga Gomes
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
| | - Jorge Luiz da Cunha Moraes
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Programa de Pósgraduação em Produtos Bioativos e Biociências (PPGPRODBIO), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, Brazil
| | - Jackson de Souza Menezes
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Programa de Pósgraduação em Produtos Bioativos e Biociências (PPGPRODBIO), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, Brazil
| | - Carlos Jorge Logullo de Oliveira
- Programa de Pósgraduação em Produtos Bioativos e Biociências (PPGPRODBIO), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Laboratório de Química e Função de Proteínas e Peptídeos and Unidade de Experimentação Animal, Universidade Estadual Norte Fluminense Darcy Ribeiro (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, Brazil
| | - Eldo Campos
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Programa de Pósgraduação em Produtos Bioativos e Biociências (PPGPRODBIO), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, Brazil
| | - Rodrigo Nunes da Fonseca
- Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), Núcleo de Pesquisas Ecológicas e Sócioambientais de Macaé (NUPEM), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Programa de Pósgraduação em Produtos Bioativos e Biociências (PPGPRODBIO), Universidade Federal do Rio de Janeiro (UFRJCampus Macaé), Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, Brazil
- * E-mail:
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Scaraffia PY, Gerez de Burgos NM. Effects of temperature and pH on hexokinase from the flight muscles of Dipetalogaster maximus (Hemiptera: Reduviidae). JOURNAL OF MEDICAL ENTOMOLOGY 2000; 37:689-694. [PMID: 11004779 DOI: 10.1603/0022-2585-37.5.689] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Effects of temperature and pH on the catalytic properties of hexokinase (HK, EC 2.7.1.1) from the flight muscles of Dipetalogaster maximus (Uhler) were studied. The enzyme showed a hyperbolic behavior with its two substrates (glucose and ATP). There was no inhibition by glucose. Apparent Km and Vmax increased as pH increased from 7.0 to 8.5. Catalytic efficiency was lowest at pH 7.0. Km, Vmax, and catalytic efficiency were higher at 37 degrees C than at 30 and 20 degrees C. There was marked inhibition by ATP, which was dependent on pH and temperature. Km values for ATP were reduced and catalytic efficiency increased as pH increased. Lowest Vmax was observed at pH 7.0. At this pH there was 87.3% inhibition by ATP, whereas it was only 5.7% at pH 8.5 (at 30 degrees C). Km, Vmax, and catalytic efficiency were higher at 37 degrees C than at 30 and 20 degrees C. The strong inhibition by ATP detected at 20 degrees C (pH 7.6) almost disappeared at 37 degrees C. Therefore, temperature could regulate hexokinase activity by modulating the inhibition produced by ATP. Glucose utilization and ATP production would be promoted when temperature rises from 30 to 37 degrees C. Because insect thoracic muscles increase their temperature over 30 degrees C during flight, this phenomenon elucidates a mechanism enhancing energy supply for muscle activity.
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Affiliation(s)
- P Y Scaraffia
- Cátedra de Química Biológica, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Argentina
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Suarez RK, Staples JF, Lighton JR, West TG. Relationships between enzymatic flux capacities and metabolic flux rates: nonequilibrium reactions in muscle glycolysis. Proc Natl Acad Sci U S A 1997; 94:7065-9. [PMID: 9192692 PMCID: PMC21285 DOI: 10.1073/pnas.94.13.7065] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The rules that govern the relationships between enzymatic flux capacities (Vmax) and maximum physiological flux rates (v) at enzyme-catalyzed steps in pathways are poorly understood. We relate in vitro Vmax values with in vivo flux rates for glycogen phosphorylase, hexokinase, and phosphofructokinase, enzymes catalyzing nonequilibrium reactions, from a variety of muscle types in fishes, insects, birds, and mammals. Flux capacities are in large excess over physiological flux rates in low-flux muscles, resulting in low fractional velocities (%Vmax = v/Vmax x 100) in vivo. In high-flux muscles, close matches between flux capacities and flux rates (resulting in fractional velocities approaching 100% in vivo) are observed. These empirical observations are reconciled with current concepts concerning enzyme function and regulation. We suggest that in high-flux muscles, close matches between enzymatic flux capacities and metabolic flux rates (i.e., the lack of excess capacities) may result from space constraints in the sarcoplasm.
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Affiliation(s)
- R K Suarez
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106-9610, USA.
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Newsholme EA, Parry-Billings M. Some evidence for the existence of substrate cycles and their utility in vivo. Biochem J 1992; 285 ( Pt 1):340-1. [PMID: 1637319 PMCID: PMC1132787 DOI: 10.1042/bj2850340] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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6
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Warm-up and substrate cycling in flight muscles of male bumblebees, Bombus terrestris. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0300-9629(91)90536-l] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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7
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Surholt B, Greive H, Hommel C, Bertsch A. Fuel uptake, storage and use in male bumble beesBombus terrestris L. J Comp Physiol B 1988. [DOI: 10.1007/bf01075840] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Hirose K, Watanabe J, Kanamura S, Tokunaga H, Ogawa R. Significance of the increase in glucose 6-phosphatase activity in skeletal muscle cells of the mouse by starvation. Anat Rec (Hoboken) 1986; 216:133-8. [PMID: 3022618 DOI: 10.1002/ar.1092160204] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effects of starvation on glucose 6-phosphatase (G6Pase; EC 3.1.3.9., D-glucose 6-phosphate phosphohydrolase) and glycogen phosphorylase (EC 2.4.1.1.) activities, and on glycogen content, were studied in skeletal muscles (m. rectus femoris) of mice. In the muscle cells from fed animals, the cytochemical reaction product for G6Pase activity was observed in moderate amounts in the terminal cisternae of sarcoplasmic reticulum and in small amounts in the nuclear envelope, and was rare or absent in the intermyofibrillar sarcoplasmic reticulum. After 4 days of starvation, however, the reaction product became abundant in all of the terminal cisternae, intermyofibrillar sarcoplasmic reticulum, and nuclear envelope. Biochemical G6Pase and glycogen phosphorylase a (active form) activities were higher in the muscles of starved mice than in those of fed animals. The glycogen content decreased markedly in the muscles of starved mice. The results suggest that the role of the increased G6Pase in skeletal muscle cells of starved mice is to release glucose into the blood by hydrolyzing glucose 6-phosphate produced through the increased phosphorylase activity.
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Wegener G, Schmidt H, Leech AR, Newsholme EA. Antagonistic effects of hexose 1,6-bisphosphates and fructose 2,6-bisphosphate on the activity of 6-phosphofructokinase purified from honey-bee flight muscle. Biochem J 1986; 236:925-8. [PMID: 2947573 PMCID: PMC1146929 DOI: 10.1042/bj2360925] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
6-Phosphofructokinase purified from honey-bee flight muscle is inhibited by ATP and, unusually, by glucose 1,6-bisphosphate and fructose 1,6-bisphosphate. The inhibition by either of the bisphosphates is not relieved by AMP, but is relieved by fructose 6-phosphate and especially by fructose 2,6-bisphosphate. Lack of effect by AMP is consistent with a low activity of adenylate kinase in this muscle.
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Shulman GI, Ladenson PW, Wolfe MH, Ridgway EC, Wolfe RR. Substrate cycling between gluconeogenesis and glycolysis in euthyroid, hypothyroid, and hyperthyroid man. J Clin Invest 1985; 76:757-64. [PMID: 4031071 PMCID: PMC423896 DOI: 10.1172/jci112032] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Substrate, or futile cycles, have been hypothesized to be under hormonal control, and important in metabolic regulation and thermogenesis. To define the role of thyroid hormones in the regulation of substrate cycling in glycolysis and gluconeogenesis, we measured rates of cycling in normal (n = 4), hypothyroid (n = 5), and hyperthyroid (n = 5) subjects employing a stable isotope turnover technique. Glucose labeled with deuterium at different positions (2-D1-, 3-D1-, and 6,6-D2-glucose) was given as a primed-constant infusion in tracer doses, and arterialized plasma samples were obtained and analyzed by gas-chromatography mass-spectrometry for the steady state enrichment of glucose that was labeled at the various positions. The rate of appearance (Ra) was then calculated for each isotopic tracer. The difference between the Ra determined by 2-D1-glucose (Ra2) and the Ra determined by 3-D1-glucose (Ra3) represents the substrate cycling rate (SCR) between glucose and glucose-6-phosphate. The difference between the Ra determined by 3-D1-glucose (Ra3) and the Ra determined by 6,6-D2-glucose (Ra6) represents the SCR between fructose-6-phosphate and fructose-1,6-diphosphate. The difference between Ra2 and Ra6 represents the combined SCR of both cycles. In normal subjects (serum thyroxine [T4] = 8.4 +/- 1.2 microgram/dl (all expressions, mean +/- SD), n = 4), the rates of appearance for Ra2, Ra3, and Ra6 were 3.23 +/- 0.56, 2.64 +/- 0.50, and 2.00 +/- 0.27 mg/kg X min, respectively, whereas those in the hypothyroid subjects (T4 = 1.0 +/- 0.8 microgram/dl; n = 5) were 1.77 +/- 0.56 (P less than 0.01), 1.52, 1.57 +/- 0.31 (P less than 0.05) mg/kg X min, respectively. Conversely, the rates of appearance for Ra2 and Ra6 in the hyperthyroid subjects (T4 = 23.9 +/- 3.6 micrograms/dl) were 3.94 +/- 0.43 (P less than 0.05) and 2.54 +/- 0.22 (P less than 0.02), respectively, compared with the normal subjects. On the basis of these data, we noted that the normal subjects had a combined SCR of 1.23 +/- 0.35 mg/kg X min. In contrast, the hypothyroid patients had a significantly decreased combined SCR, 0.20 +/- 0.54 mg/kg X min (P less than 0.02). The hyperthyroid patients had a combined SCR of 1.39 +/- 0.23 mg/kg X min (P less than NS). To determine whether these cycles responded to thyroid hormone treatment, these same hypothyroid subjects were acutely treated for 1 wk with parenteral 50 micrograms/d sodium L-triiodothyronine and chronically with 100-150 micrograms/d L-thyroxine. After 7 d, their mean oxygen consumption rate and carbon dioxide production rate increased significantly from 102+/-13 micromol/kg.min, to 147+/-34 micromol/kg.min (P<0.05), and from 76+/-13 micromol/kg.min to 111+/-19 micromol/kg.min (P<0.05), respectively. The combined SCR (Ra(2)--Ra(6) remained unchanged at 0.07+/-0.37 mg/kg.min. However, after 6 mo of oral L-thyroxine therapy (T(4)=9.5+/-1.4 microgram/kl) the treated hypothyroid patients had increased their combined SCR (Ra(2)--Ra(6)) to 0.86 +/-0.23 mg/kg.min (P<0.02), a value not significantly different from the combined SCR of normal subjects. We conclude that substrate cycling between glucose and glucose-6-phosphate and between fructose-6-phosphate and fructose-1,6-diphosphate occurs in man and is affected by thyroid hormone. Substrate cycles may represent a mechanism by which thyroid hormone alters the sensitivity of certain reactions to metabolic signals.
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Challiss RA, Arch JR, Crabtree B, Newsholme EA. Measurement of the rate of substrate cycling between fructose 6-phosphate and fructose 1,6-bisphosphate in skeletal muscle by using a single-isotope technique. Biochem J 1984; 223:849-53. [PMID: 6391469 PMCID: PMC1144371 DOI: 10.1042/bj2230849] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The effects of several agents on the rates of the fructose 6-phosphate/fructose 1,6-bisphosphate substrate cycle were measured in incubated epitrochlearis muscles of the rat by monitoring the transfer of radiolabel from [6-14C]glucose to the 1-position of glucose residues in glycogen. The cycling rates observed were almost identical with those previously obtained by using the well-established dual-isotope technique. In particular, it was found that the beta-adrenoceptor agonist isoprenaline increased the cycling rate about 12-fold.
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13
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Challiss RA, Arch JR, Newsholme EA. The rate of substrate cycling between fructose 6-phosphate and fructose 1,6-bisphosphate in skeletal muscle. Biochem J 1984; 221:153-61. [PMID: 6380496 PMCID: PMC1144014 DOI: 10.1042/bj2210153] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Substrate cycling of fructose 6-phosphate through reactions catalysed by 6-phosphofructokinase and fructose-1,6-bisphosphatase was measured in skeletal muscles of the rat in vitro. The rate of this cycle was calculated from the steady-state values of the 3H/14C ratio in hexose monophosphates and fructose 1,6-bisphosphate after the metabolism of either [5-3H,6-14C]glucose or [3-3H,2-14C] glucose. Two techniques for the separation of hexose phosphates were studied; t.l.c. chromatography on poly(ethyleneimine)-cellulose sheets or ion-exchange chromatography coupled with enzymic conversion. These two methods gave almost identical results, suggesting that either technique could be used for determination of rates of fructose 6-phosphate/fructose 1,6-bisphosphate cycling. It was found that more than 50% of the 3H was retained in the fructose 1,6-bisphosphate; it is therefore probable that previous measurement of cycling rates, which have assumed complete loss of 3H, have underestimated the rate of this cycle. The effects of insulin, adrenaline and adrenergic agonists and antagonists on rates of fructose 6-phosphate/fructose 1,6-bisphosphate cycling were investigated. In the presence of insulin, adrenaline (1 microM) increased the cycling rate by about 10-fold in epitrochlearis muscle in vitro; the maximum rate under these conditions was about 2.5 mumol/h per g of tissue. The concentration of adrenaline that increased the cycling rate by 50% was about 50 nM. This effect of adrenaline appears to be mediated by the beta-adrenergic receptor, since the rate was increased by beta-adrenergic agonists and blocked by beta-adrenergic antagonists. From the knowledge of the precise rate of this cycle, the possible physiological importance of cycling is discussed.
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14
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Newsholme E, Challiss R, Crabtree B. Substrate cycles: their role in improving sensitivity in metabolic control. Trends Biochem Sci 1984. [DOI: 10.1016/0968-0004(84)90165-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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15
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Lackner R, Challiss RA, West D, Newsholme EA. A problem in the radiochemical assay of glucose-6-phosphatase in muscle. Biochem J 1984; 218:649-51. [PMID: 6324762 PMCID: PMC1153387 DOI: 10.1042/bj2180649] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A radiochemical assay for glucose-6-phosphatase, which depends on the absorption of radiolabelled substrate on to a nascent precipitate of BaSO4 and Zn(OH)2, can give rise to erroneously high activities. Adsorption on to a Fe(OH)3 precipitate does not expose the incubation medium to extreme alkaline conditions and provides a satisfactory and simple assay. This method demonstrates a very low activity of the enzyme in mammalian muscle, in contrast with previous findings.
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