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Frasson-Uemura IG, Biazi GR, Miksza DR, Moreira CCL, Cassolla P, Bertolini GL, Bazotte RB, de Souza HM. Infusion of high concentration of lactate in perfused liver, simulating in vivo hyperlactatemia, prevents the reduction of gluconeogenesis in Walker-256 tumor-bearing rats. J Cell Biochem 2019; 120:11068-11080. [PMID: 30719751 DOI: 10.1002/jcb.28384] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 01/10/2019] [Indexed: 01/24/2023]
Abstract
Gluconeogenesis (GN) is increased in patients with cancer cachexia, but is reduced in liver perfusion of Walker-256 tumor-bearing cachectic rats (TB rats). The causes of these differences are unknown. We investigated the influence of circulating concentrations of lactate (NADH generator) and NADH on GN in perfused livers of TB rats. Lactate, at concentrations similar to those found on days 5 (3.0 mM), 8 (5.5 mM), and 12 (8.0 mM) of the tumor, prevented the reduction of GN from 2.0 mM lactate (lactatemia of healthy rat) in TB rats. NADH, 50 or 75 μM, but not 25 μM, increased GN from 2.0 mM lactate in TB rats to higher values than healthy rats. High concentrations of pyruvate (no NADH generator, 5.0 and 8.0 mM) did not prevent the reduction of GN from 2.0 mM pyruvate in TB rats. However, 50 or 75 μM NADH, but not 25 μM, increased GN from 2.0 mM pyruvate in TB rats to similar or higher values than healthy rats. High concentration of glutamine (NADH generator, 2.5 mM) or 50 μM NADH prevented the reduction of GN from 1 mM glutamine in TB rats. Intraperitoneal administration of pyruvate (1.0 mg/kg) or glutamine (0.5 mg/kg) similarly increased the glycemia of healthy and TB rats. In conclusion, high lactate concentration, similar to hyperlactatemia, prevented the reduction of GN in perfused livers of TB rats, an effect probably caused by the increased redox potential (NADH/NAD+ ). Thus, the decreased GN in livers from TB rats is due, at least in part, to the absence of simulation of in vivo hyperlactatemia in liver perfusion studies.
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Affiliation(s)
| | - Giuliana Regina Biazi
- Department of Physiological Sciences, State University of Londrina, Londrina, Paraná, Brazil
| | - Daniele Romani Miksza
- Department of Physiological Sciences, State University of Londrina, Londrina, Paraná, Brazil
| | | | - Priscila Cassolla
- Department of Physiological Sciences, State University of Londrina, Londrina, Paraná, Brazil
| | - Gisele Lopes Bertolini
- Department of Physiological Sciences, State University of Londrina, Londrina, Paraná, Brazil
| | - Roberto Barbosa Bazotte
- Department of Pharmacology and Therapeutics, State University of Maringá, Maringá, Paraná, Brazil
| | - Helenir Medri de Souza
- Department of Physiological Sciences, State University of Londrina, Londrina, Paraná, Brazil
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Cafeteria Diet Feeding in Young Rats Leads to Hepatic Steatosis and Increased Gluconeogenesis under Fatty Acids and Glucagon Influence. Nutrients 2018; 10:nu10111571. [PMID: 30360555 PMCID: PMC6266290 DOI: 10.3390/nu10111571] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 10/15/2018] [Accepted: 10/20/2018] [Indexed: 02/07/2023] Open
Abstract
Gluconeogenesis overstimulation due to hepatic insulin resistance is the best-known mechanism behind elevated glycemia in obese subjects with hepatic steatosis. This suggests that glucose production in fatty livers may differ from that of healthy livers, also in response to other gluconeogenic determinant factors, such as the type of substrate and modulators. Thus, the aim of this study was to investigate the effects of these factors on hepatic gluconeogenesis in cafeteria diet-induced obese adult rats submitted to a cafeteria diet at a young age. The livers of the cafeteria group exhibited higher gluconeogenesis rates when glycerol was the substrate, but lower rates were found when lactate and pyruvate were the substrates. Stearate or glucagon caused higher stimulations in gluconeogenesis in cafeteria group livers, irrespective of the gluconeogenic substrates. An increased mitochondrial NADH/NAD+ ratio and a reduced rate of 14CO2 production from [14C] fatty acids suggested restriction of the citric acid cycle. The higher glycogen and lipid levels were possibly the cause for the reduced cellular and vascular spaces found in cafeteria group livers, likely contributing to oxygen consumption restriction. In conclusion, specific substrates and gluconeogenic modulators contribute to a higher stimulation of gluconeogenesis in livers from the cafeteria group.
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Weber KS, Straßburger K, Fritsch M, Bierwagen A, Koliaki C, Phielix E, Pacini G, Hwang JH, Markgraf DF, Burkart V, Müssig K, Szendroedi J, Roden M. Meal-derived glucagon responses are related to lower hepatic phosphate concentrations in obesity and type 2 diabetes. DIABETES & METABOLISM 2018; 44:444-448. [PMID: 29910091 DOI: 10.1016/j.diabet.2018.05.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 04/30/2018] [Accepted: 05/23/2018] [Indexed: 10/14/2022]
Abstract
AIM Type 2 diabetes (T2D) alters glucagon, glucagon-like peptide (GLP)-1, glucose-dependent insulinotropic polypeptide (GIP) and hepatic energy metabolism, yet the possible relationships remain unclear. METHODS In this observational study, lean insulin-sensitive control subjects (BMI: 23.2±1.5kg/m2), age-matched insulin-resistant obese subjects (BMI: 34.3±1.7kg/m2) and similarly obese elderly T2D patients (BMI: 32.0±2.4kg/m2) underwent mixed-meal tolerance tests (MMTTs), and assessment of hepatic γATP, inorganic phosphate (Pi) and lipids using 31P/1H magnetic resonance spectroscopy. Meal-induced secretion of glucagon and incretins was calculated from incremental areas under the concentration-time curves (iAUCs). Peripheral and adipose tissue insulin sensitivity were assessed from time courses of circulating glucose, insulin and free fatty acids. RESULTS MMTT-derived peripheral insulin sensitivity was lowest in T2D patients (P<0.001), while glucagon concentrations were comparable across all three groups. At 260min, GLP-1 was lower in T2D patients than in controls, whereas GIP was lowest in obese individuals. Fasting glucagon concentrations correlated positively with fasting (r=0.60) and postprandial hepatocellular lipid levels (160min: r=0.51, 240min: r=0.59), and negatively with adipose tissue insulin sensitivity (r=-0.73). Higher meal-induced glucagon release (iAUC0-260min) correlated with lower fasting (r=-0.62) and postprandial Pi levels (160min: r=-0.43, 240min: r=-0.42; all P<0.05). Higher meal-induced release of GIP (iAUC0-260min) correlated positively with fasting (r=0.54) and postprandial serum triglyceride concentrations (iAUC0-260min, r=0.54; all P<0.01). CONCLUSION Correlations between fasting glucagon and hepatic lipids and between meal-induced glucagon and hepatic Pi suggest a role for glucagon in hepatic energy metabolism.
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Affiliation(s)
- K S Weber
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany
| | - K Straßburger
- German Centre for Diabetes Research (DZD), München-Neuherberg, Germany; Institute for Biometrics and Epidemiology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany
| | - M Fritsch
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany; Department of Pediatric and Adolescent Medicine, Medical University of Vienna, Vienna, Austria
| | - A Bierwagen
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany
| | - C Koliaki
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany; Division of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; Athens University Medical School, Athens, Greece
| | - E Phielix
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany; Department of Human Biology and Movement Sciences, NUTRIM school for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, Netherlands
| | - G Pacini
- Metabolic Unit, Institute of Neuroscience, National Research Council, Padova, Italy
| | - J-H Hwang
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany
| | - D F Markgraf
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany
| | - V Burkart
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany
| | - K Müssig
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany; Division of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - J Szendroedi
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany; Division of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - M Roden
- Institute for Clinical Diabetology, German Diabetes Centre at Heinrich Heine University, Leibniz Centre for Diabetes Research, Düsseldorf, Germany; German Centre for Diabetes Research (DZD), München-Neuherberg, Germany; Division of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
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de Oliveira AL, de Paula MN, Comar JF, Vilela VR, Peralta RM, Bracht A. Adrenergic metabolic and hemodynamic effects of octopamine in the liver. Int J Mol Sci 2013; 14:21858-72. [PMID: 24196353 PMCID: PMC3856039 DOI: 10.3390/ijms141121858] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Revised: 10/21/2013] [Accepted: 10/22/2013] [Indexed: 11/16/2022] Open
Abstract
The fruit extracts of Citrus aurantium (bitter orange) are traditionally used as weight-loss products and as appetite suppressants. A component of these extracts is octopamine, which is an adrenergic agent. Weight-loss and adrenergic actions are always related to metabolic changes and this work was designed to investigate a possible action of octopamine on liver metabolism. The isolated perfused rat liver was used to measure catabolic and anabolic pathways and hemodynamics. Octopamine increased glycogenolysis, glycolysis, oxygen uptake, gluconeogenesis and the portal perfusion pressure. Octopamine also accelerated the oxidation of exogenous fatty acids (octanoate and oleate), as revealed by the increase in ¹⁴CO₂ production derived from ¹⁴C labeled precursors. The changes in glycogenolysis, oxygen uptake and perfusion pressure were almost completely abolished by α₁-adrenergic antagonists. The same changes were partly sensitive to the β-adrenergic antagonist propranolol. It can be concluded that octopamine accelerates both catabolic and anabolic processes in the liver via adrenergic stimulation. Acceleration of oxygen uptake under substrate-free perfusion conditions also means acceleration of the oxidation of endogenous fatty acids, which are derived from lipolysis. All these effects are compatible with an overall stimulating effect of octopamine on metabolism, which is compatible with its reported weight-loss effects in experimental animals.
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Affiliation(s)
- Andrea Luiza de Oliveira
- Department of Biochemistry, University of Maringá, Avenida Colombo 5790, Maringá 87020900, Brazil.
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Ozcan L, Wong CC, Li G, Xu T, Pajvani U, Park SKR, Wronska A, Chen BX, Marks AR, Fukamizu A, Backs J, Singer HA, Yates JR, Accili D, Tabas I. Calcium signaling through CaMKII regulates hepatic glucose production in fasting and obesity. Cell Metab 2012; 15:739-51. [PMID: 22503562 PMCID: PMC3348356 DOI: 10.1016/j.cmet.2012.03.002] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Revised: 01/20/2012] [Accepted: 03/05/2012] [Indexed: 12/31/2022]
Abstract
Hepatic glucose production (HGP) is crucial for glucose homeostasis, but the underlying mechanisms have not been fully elucidated. Here, we show that a calcium-sensing enzyme, CaMKII, is activated in a calcium- and IP3R-dependent manner by cAMP and glucagon in primary hepatocytes and by glucagon and fasting in vivo. Genetic deficiency or inhibition of CaMKII blocks nuclear translocation of FoxO1 by affecting its phosphorylation, impairs fasting- and glucagon/cAMP-induced glycogenolysis and gluconeogenesis, and lowers blood glucose levels, while constitutively active CaMKII has the opposite effects. Importantly, the suppressive effect of CaMKII deficiency on glucose metabolism is abrogated by transduction with constitutively nuclear FoxO1, indicating that the effect of CaMKII deficiency requires nuclear exclusion of FoxO1. This same pathway is also involved in excessive HGP in the setting of obesity. These results reveal a calcium-mediated signaling pathway involved in FoxO1 nuclear localization and hepatic glucose homeostasis.
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Affiliation(s)
- Lale Ozcan
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Catherine C.L. Wong
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Gang Li
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Tao Xu
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Utpal Pajvani
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Sung Kyu Robin Park
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Anetta Wronska
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Bi-Xing Chen
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Andrew R. Marks
- Department of Medicine, Columbia University, New York, NY 10032, USA
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Akiyoshi Fukamizu
- Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Japan
| | - Johannes Backs
- Department of Internal Medicine III, University of Heidelberg, Heidelberg, Germany
| | - Harold A. Singer
- Center for Cardiovascular Sciences, Albany Medical College, Albany, NY 12208 USA
| | - John R. Yates
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Domenico Accili
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Ira Tabas
- Department of Medicine, Columbia University, New York, NY 10032, USA
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
- Department of Pathology & Cell Biology, Columbia University, New York, NY 10032, USA
- Correspondence:
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Martins AG, Constantin J, Bracht F, Kelmer-Bracht AM, Bracht A. The action of extracellular NAD+ on gluconeogenesis in the perfused rat liver. Mol Cell Biochem 2006; 286:115-24. [PMID: 16652226 DOI: 10.1007/s11010-005-9101-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Accepted: 12/01/2005] [Indexed: 02/02/2023]
Abstract
In the rat liver NAD+ infusion produces increases in portal perfusion pressure and glycogenolysis and transient inhibition of oxygen consumption. The aim of the present work was to investigate the possible action of this agent on gluconeogenesis using lactate as a gluconeogenic precursor. Hemoglobin-free rat liver perfusion in antegrade and retrograde modes was used with enzymatic determination of glucose production and polarographic assay of oxygen uptake. NAD+ infusion into the portal vein (antegrade perfusion) produced a concentration-dependent (25-100 microM) transient inhibition of oxygen uptake and gluconeogenesis. For both parameters inhibition was followed by stimulation. NAD+ infusion into the hepatic vein (retrograde perfusion) produced only transient stimulations. During Ca2+-free perfusion the action of NAD+ was restricted to small transient stimulations. Inhibitors of eicosanoid synthesis with different specificities (indo-methacin, nordihydroguaiaretic acid, bromophenacyl bromide) either inhibited or changed the action of NAD+. The action of NAD+ on gluconeogenesis is probably mediated by eicosanoids synthesized in non-parenchymal cells. As in the fed state, in the fasted condition extracellular NAD+ is also able to exert two opposite effects, inhibition and stimulation. Since inhibition did not manifest significantly in retrograde perfusion it is likely that the generating signal is located in pre-sinusoidal regions.
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Affiliation(s)
- Adriana G Martins
- Laboratory of Liver Metabolism, University of Maringá, 87020900 Maringá, Brazil
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Martinovich GG, Cherenkevich SN, Sauer H. Intracellular redox state: towards quantitative description. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2005; 34:937-42. [PMID: 16215752 DOI: 10.1007/s00249-005-0470-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Accepted: 01/28/2005] [Indexed: 02/04/2023]
Abstract
Redox state is a widely used term for the description of redox phenomena in biological systems. The regulating mechanisms responsible for maintaining the redox state are not yet fully known. But it was shown that changes in the redox state might lead to a cascade of intracellular events, beneficial or deleterious to the cell. There are several methods for the description of the intracellular redox state. These methods are based on using measured intracellular concentrations of reduced and oxidized glutathione in the Nernst equation. However, glutathione is not always a basic redox component in biological fluids, organelles, cells or tissues. As a result, changes in the intracellular redox state are not always accompanied by considerable changes of glutathione concentration. In this work it was proposed to use the concept of effective reduction potential for the quantitative characteristic of the intracellular redox state. The effective reduction potential was substantiated on the basis of a thermodynamic description. A new equation for the calculation of the effective reduction potential was derived. This equation summarizes the contribution of different oxidizing and reducing agents in the formation of an effective redox potential. The theoretical estimation of the effective reduction potential values for the different biological fluids and cells was carried out with the use of a method developed.
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Affiliation(s)
- Grigory G Martinovich
- Department of Biophysics, Belarus State University, Fr. Skorina Ave. 4, 220050 Minsk, Belarus.
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Corbello Pereira SR, Darronqui E, Constantin J, da Silva MHDRA, Yamamoto NS, Bracht A. The urea cycle and related pathways in the liver of Walker-256 tumor-bearing rats. Biochim Biophys Acta Mol Basis Dis 2004; 1688:187-96. [PMID: 15062868 DOI: 10.1016/j.bbadis.2003.12.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2003] [Revised: 12/02/2003] [Accepted: 12/03/2003] [Indexed: 11/28/2022]
Abstract
The urea cycle was evaluated in perfused livers isolated from cachectic tumor-bearing rats (Walker-256 tumor). Urea production in livers of tumor-bearing rats was decreased in the presence of the following substrates: alanine, alanine + ornithine, alanine + aspartate, ammonia, ammonia + lactate, ammonia + pyruvate and glutamine. Urea production from arginine was higher in livers of tumor-bearing rats. No difference was found with aspartate, aspartate + ammonia, citrulline, citrulline + aspartate and glutamine + aspartate. Ammonia consumption was smaller in livers from cachectic rats when the substance was infused together with lactate and pyruvate. Glucose production was smaller in the cachectic condition only when alanine was the gluconeogenic substrate. Blood urea was higher in tumor-bearing rats, suggesting higher rates of urea production. The availability of aspartate seems to be critical for urea synthesis in the liver of tumor-bearing rats, which is possibly unable to produce this amino acid in sufficient amounts from endogenous sources. The liver of tumor-bearing rats may have a different exogenous substrate supply of nitrogenous compounds. Arginine could be one of these compounds in addition to aspartate which seems to be essential for an efficient ureogenesis in tumor-bearing rats.
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Begum L, Jalil MA, Kobayashi K, Iijima M, Li MX, Yasuda T, Horiuchi M, del Arco A, Satrústegui J, Saheki T. Expression of three mitochondrial solute carriers, citrin, aralar1 and ornithine transporter, in relation to urea cycle in mice. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1574:283-92. [PMID: 11997094 DOI: 10.1016/s0167-4781(01)00376-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The present report describes the expression profiles of different tissues and developmental changes of mouse aspartate/glutamate carrier (AGC) genes, Slc25a13 and Slc25a12, and an ornithine transporter gene, Ornt1, in relation to urea cycle enzyme genes, carbamoylphosphate synthetase I (CPS) and argininosuccinate synthetase (ASS). Slc25a13 encodes citrin, recently found to be deficient in adult-onset type II citrullinemia and to function as AGC together with its isoform and product of Slc25a12, aralar1. Citrin was broadly distributed, but mainly in the liver, kidney and heart. Aralar1 was expressed in diaphragm, skeletal muscle, heart, brain and kidney, but not in the liver. These distribution profiles are different from the restricted of Ornt1, ASS and CPS. Citrin, ASS, CPS and Ornt1 showed similar patterns of developmental changes in the liver and small intestine, where they play a role in urea and arginine synthesis. Dietary, hormonal and physical manipulations caused varied changes of CPS, ASS and Ornt1 in the liver, but the change of citrin was not so marked as that of the others. Analysis using RT-PCR and restriction enzyme digestion revealed that the ornithine transporter most expressed is Ornt1, although Ornt2 is detectable at a minute level. All these results suggest that citrin as AGC plays a role in urea synthesis as well as many fundamental metabolic pathways in the liver, and shares metabolic functions with aralar1 in other tissues, and that Ornt1 is an important component in urea synthesis in the liver and in arginine synthesis in the small intestine during the neonatal period.
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Affiliation(s)
- Laila Begum
- Department of Biochemistry, Faculty of Medicine, Kagoshima University, 8-35-1 Sakuragaoka, 890-8520, Kagoshima, Japan
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