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Lees HJ, Swann JR, Poucher S, Holmes E, Wilson ID, Nicholson JK. Obesity and Cage Environment Modulate Metabolism in the Zucker Rat: A Multiple Biological Matrix Approach to Characterizing Metabolic Phenomena. J Proteome Res 2019; 18:2160-2174. [PMID: 30939873 DOI: 10.1021/acs.jproteome.9b00040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Obesity and its comorbidities are increasing worldwide imposing a heavy socioeconomic burden. The effects of obesity on the metabolic profiles of tissues (liver, kidney, pancreas), urine, and the systemic circulation were investigated in the Zucker rat model using 1H NMR spectroscopy coupled to multivariate statistical analysis. The metabolic profiles of the obese ( fa/ fa) animals were clearly differentiated from the two phenotypically lean phenotypes, ((+/+) and ( fa/+)) within each biological compartment studied, and across all matrices combined. No significant differences were observed between the metabolic profiles of the genotypically distinct lean strains. Obese Zucker rats were characterized by higher relative concentrations of blood lipid species, cross-compartmental amino acids (particularly BCAAs), urinary and liver metabolites relating to the TCA cycle and glucose metabolism; and lower amounts of urinary gut microbial-host cometabolites, and intermatrix metabolites associated with creatine metabolism. Further to this, the obese Zucker rat metabotype was defined by significant metabolic alterations relating to disruptions in the metabolism of choline across all compartments analyzed. The cage environment was found to have a significant effect on urinary metabolites related to gut-microbial metabolism, with additional cage-microenvironment trends also observed in liver, kidney, and pancreas. This study emphasizes the value in metabotyping multiple biological matrices simultaneously to gain a better understanding of systemic perturbations in metabolism, and also underscores the need for control or evaluation of cage environment when designing and interpreting data from metabonomic studies in animal models.
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Affiliation(s)
- Hannah J Lees
- Division of Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine , Imperial College London , London , SW7 2AZ , United Kingdom
| | - Jonathan R Swann
- Division of Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine , Imperial College London , London , SW7 2AZ , United Kingdom
| | - Simon Poucher
- AstraZeneca Pharmaceuticals , Mereside , Alderley Park , Macclesfield , SK10 4TG , United Kingdom
| | - Elaine Holmes
- Division of Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine , Imperial College London , London , SW7 2AZ , United Kingdom
| | - Ian D Wilson
- Division of Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine , Imperial College London , London , SW7 2AZ , United Kingdom
| | - Jeremy K Nicholson
- Division of Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine , Imperial College London , London , SW7 2AZ , United Kingdom
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López-Soldado I, Fuentes-Romero R, Duran J, Guinovart JJ. Effects of hepatic glycogen on food intake and glucose homeostasis are mediated by the vagus nerve in mice. Diabetologia 2017; 60:1076-1083. [PMID: 28299379 DOI: 10.1007/s00125-017-4240-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 02/14/2017] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS Liver glycogen plays a key role in regulating food intake and blood glucose. Mice that accumulate large amounts of this polysaccharide in the liver are protected from high-fat diet (HFD)-induced obesity by reduced food intake. Furthermore, these animals show reversal of the glucose intolerance and hyperinsulinaemia caused by the HFD. The aim of this study was to examine the involvement of the hepatic branch of the vagus nerve in regulating food intake and glucose homeostasis in this model. METHODS We performed hepatic branch vagotomy (HBV) or a sham operation on mice overexpressing protein targeting to glycogen (Ptg OE). Starting 1 week after surgery, mice were fed an HFD for 10 weeks. RESULTS HBV did not alter liver glycogen or ATP levels, thereby indicating that this procedure does not interfere with hepatic energy balance. However, HBV reversed the effect of glycogen accumulation on food intake. In wild-type mice, HBV led to a significant reduction in body weight without a change in food intake. Consistent with their body weight reduction, these animals had decreased fat deposition, adipocyte size, and insulin and leptin levels, together with increased energy expenditure. Ptg OE mice showed an increase in energy expenditure and glucose oxidation, and these differences were abolished by HBV. Moreover, Ptg OE mice showed an improvement in HFD-induced glucose intolerance, which was suppressed by HBV. CONCLUSIONS/INTERPRETATION Our results demonstrate that the regulation of food intake and glucose homeostasis by liver glycogen is dependent on the hepatic branch of the vagus nerve.
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Affiliation(s)
- Iliana López-Soldado
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona Institute of Science and Technology (BIST), Baldiri i Reixac 10, 08028, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
| | - Rebeca Fuentes-Romero
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona Institute of Science and Technology (BIST), Baldiri i Reixac 10, 08028, Barcelona, Spain
| | - Jordi Duran
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona Institute of Science and Technology (BIST), Baldiri i Reixac 10, 08028, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
| | - Joan J Guinovart
- Institute for Research in Biomedicine (IRB Barcelona), Barcelona Institute of Science and Technology (BIST), Baldiri i Reixac 10, 08028, Barcelona, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain.
- Department of Biochemistry and Molecular Biomedicine, University of Barcelona, Barcelona, Spain.
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McCue MD, Sandoval J, Beltran J, Gerson AR. Dehydration Causes Increased Reliance on Protein Oxidation in Mice: A Test of the Protein-for-Water Hypothesis in a Mammal. Physiol Biochem Zool 2017; 90:359-369. [DOI: 10.1086/690912] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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McCue MD, Welch KC. (13)C-Breath testing in animals: theory, applications, and future directions. J Comp Physiol B 2015; 186:265-85. [PMID: 26660654 DOI: 10.1007/s00360-015-0950-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 11/11/2015] [Accepted: 11/25/2015] [Indexed: 10/22/2022]
Abstract
The carbon isotope values in the exhaled breath of an animal mirror the carbon isotope values of the metabolic fuels being oxidized. The measurement of stable carbon isotopes in carbon dioxide is called (13)C-breath testing and offers a minimally invasive method to study substrate oxidation in vivo. (13)C-breath testing has been broadly used to study human exercise, nutrition, and pathologies since the 1970s. Owing to reduced use of radioactive isotopes and the increased convenience and affordability of (13)C-analyzers, the past decade has witnessed a sharp increase in the use of breath testing throughout comparative physiology--especially to answer questions about how and when animals oxidize particular nutrients. Here, we review the practical aspects of (13)C-breath testing and identify the strengths and weaknesses of different methodological approaches including the use of natural abundance versus artificially-enriched (13)C tracers. We critically compare the information that can be obtained using different experimental protocols such as diet-switching versus fuel-switching. We also discuss several factors that should be considered when designing breath testing experiments including extrinsic versus intrinsic (13)C-labelling and different approaches to model nutrient oxidation. We use case studies to highlight the myriad applications of (13)C-breath testing in basic and clinical human studies as well as comparative studies of fuel use, energetics, and carbon turnover in multiple vertebrate and invertebrate groups. Lastly, we call for increased and rigorous use of (13)C-breath testing to explore a variety of new research areas and potentially answer long standing questions related to thermobiology, locomotion, and nutrition.
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Plaza-Diaz J, Gomez-Llorente C, Abadia-Molina F, Saez-Lara MJ, Campaña-Martin L, Muñoz-Quezada S, Romero F, Gil A, Fontana L. Effects of Lactobacillus paracasei CNCM I-4034, Bifidobacterium breve CNCM I-4035 and Lactobacillus rhamnosus CNCM I-4036 on hepatic steatosis in Zucker rats. PLoS One 2014; 9:e98401. [PMID: 24852284 PMCID: PMC4031175 DOI: 10.1371/journal.pone.0098401] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 04/16/2014] [Indexed: 12/11/2022] Open
Abstract
We have previously described the safety and immunomodulatory effects of Lactobacillus paracasei CNCM I-4034, Bifidobacterium breve CNCM I-4035 and Lactobacillus rhamnosus CNCM I-4036 in healthy volunteers. The scope of this work was to evaluate the effects of these probiotic strains on the hepatic steatosis of obese rats. We used the Zucker rat as a genetic model of obesity. Zucker-Lepr(fa/fa) rats received one of three probiotic strains, a mixture of L. paracasei CNCM I-4034 and B. breve CNCM I-4035, or a placebo for 30 days. An additional group of Zucker-lean+/fa rats received a placebo for 30 days. No alterations in intestinal histology, in the epithelial, lamina propria, muscular layers of the ileal or colonic mucosa, or the submucosae, were observed in any of the experimental groups. Triacylglycerol content decreased in the liver of Zucker-Lepr(fa/fa) rats that were fed L. rhamnosus, B. breve, or the mixture of B. breve and L. paracasei. Likewise, the area corresponding to neutral lipids was significantly smaller in the liver of all four groups of Zucker-Lepr(fa/fa) rats that received probiotics than in rats fed the placebo. Zucker-Lepr(fa/fa) rats exhibited significantly greater serum LPS levels than Zucker-lean+/fa rats upon administration of placebo for 30 days. In contrast, all four groups of obese Zucker-Lepr(fa/fa) rats that received LAB strains exhibited serum LPS concentrations similar to those of Zucker-lean+/fa rats. Serum TNF-α levels decreased in the Zucker-Lepr(fa/fa) rats that received B. breve, L. rhamnosus, or the mixture, whereas L. paracasei feeding decreased IL-6 levels in the serum of Zucker-Lepr(fa/fa) rats. In conclusion, the probiotic strains reduced hepatic steatosis in part by lowering serum LPS, and had an anti-inflammatory effect in obese Zucker rats.
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Affiliation(s)
- Julio Plaza-Diaz
- Department of Biochemistry & Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- Institute of Nutrition & Food Technology “José Mataix”, Biomedical Research Center, University of Granada, Granada, Spain
| | - Carolina Gomez-Llorente
- Department of Biochemistry & Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- Institute of Nutrition & Food Technology “José Mataix”, Biomedical Research Center, University of Granada, Granada, Spain
| | | | - Maria Jose Saez-Lara
- Department of Biochemistry & Molecular Biology I, School of Sciences, University of Granada, Granada, Spain
| | - Laura Campaña-Martin
- Institute of Nutrition & Food Technology “José Mataix”, Biomedical Research Center, University of Granada, Granada, Spain
| | - Sergio Muñoz-Quezada
- Department of Biochemistry & Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- Institute of Nutrition & Food Technology “José Mataix”, Biomedical Research Center, University of Granada, Granada, Spain
| | - Fernando Romero
- Hero Global Technology Center, Hero Spain, S.A., Alcantarilla, Murcia, Spain
| | - Angel Gil
- Department of Biochemistry & Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- Institute of Nutrition & Food Technology “José Mataix”, Biomedical Research Center, University of Granada, Granada, Spain
| | - Luis Fontana
- Department of Biochemistry & Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
- Institute of Nutrition & Food Technology “José Mataix”, Biomedical Research Center, University of Granada, Granada, Spain
- * E-mail:
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Jarrar SF, Obeid OA. Timing of caffeine ingestion alters postprandial metabolism in rats. Nutrition 2013; 30:107-11. [PMID: 24206825 DOI: 10.1016/j.nut.2013.07.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 06/27/2013] [Accepted: 07/16/2013] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The association between caffeine intake and the risk for chronic diseases, namely type 2 diabetes, has not been consistent, and may be influenced by the timing of caffeine ingestion. The aim of this study was to investigate the acute effect of caffeine administered in different scenarios of meal ingestion on postprandial glycemic and lipidemic status, concomitant with changes in body glycogen stores. METHODS Forty overnight-fasted rats were randomly divided into five groups (meal-ingested, caffeine-administered, post-caffeine meal-ingested, co-caffeine meal-ingested, post-meal caffeine-administered), and tube-fed the appropriate intervention, then sacrificed 2 h later. Livers and gastrocnemius muscles were analyzed for glycogen content; blood samples were analyzed for glucose, insulin, triglycerides, and non-esterified fatty acid concentrations. RESULTS Postprandial plasma glucose concentrations were similar between groups, while significantly higher levels of insulin were witnessed following caffeine administration, irrespective of the timing of meal ingestion. Triglyceride concentrations were significantly lower in the caffeine-administered groups. Regarding glycogen status, although caffeine administration before meal ingestion reduced hepatic glycogen content, co- and post-meal caffeine administration failed to produce such an effect. Muscle glycogen content was not significantly affected by caffeine administration. CONCLUSIONS Caffeine administration seems to decrease insulin sensitivity as indicated by the sustenance of glucose status despite the presence of high insulin levels. The lower triglyceride levels in the presence of caffeine support the theory of retarded postprandial triglyceride absorption. Caffeine seems to play a biphasic role in glucose metabolism, as indicated by its ability to variably influence hepatic glycogen status.
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Affiliation(s)
- Sara Farhat Jarrar
- Department of Nutrition and Food Sciences, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon
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Measurements of substrate oxidation using 13CO2-breath testing reveals shifts in fuel mix during starvation. J Comp Physiol B 2013; 183:1039-52. [DOI: 10.1007/s00360-013-0774-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 07/01/2013] [Accepted: 07/19/2013] [Indexed: 10/26/2022]
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McCue MD, Smith A, McKinney R, Rewald B, Pinshow B, McWilliams SR. A Mass Balance Approach to Identify and Compare Differential Routing of 13C-Labeled Carbohydrates, Lipids, and Proteins In Vivo. Physiol Biochem Zool 2011; 84:506-13. [DOI: 10.1086/661638] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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9
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Coope GJ, Atkinson AM, Allott C, McKerrecher D, Johnstone C, Pike KG, Holme PC, Vertigan H, Gill D, Coghlan MP, Leighton B. Predictive blood glucose lowering efficacy by Glucokinase activators in high fat fed female Zucker rats. Br J Pharmacol 2006; 149:328-35. [PMID: 16921397 PMCID: PMC2014270 DOI: 10.1038/sj.bjp.0706848] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Glucokinase (GK) is the rate-limiting enzyme of hepatic glucose metabolism and acts as a sensor for glucose-stimulated insulin release in beta-cells. Here we examine whether the lowering of blood glucose levels in the rat by small molecule glucokinase activators (GKAs) can be predicted from in vitro enzyme potencies and plasma compound exposure. EXPERIMENTAL APPROACH We developed an insulin resistant and hyperinsulinemic animal model, the high fat fed female Zucker (fa/fa) rat (HFFZ), and measured the acute in vivo glucose-lowering efficacy of a number of GKAs in an oral glucose tolerance test. KEY RESULTS Four GKAs (at 1 to 30 mg kg(-1)), with different in vitro enzyme potencies, dose-dependently improved oral glucose tolerance in HFFZ rats (10-40% decrease glucose area under the curve (AUC) from vehicle control). The extent of glucose lowering, or the pharmacodynamic (PD) effect, of a GKA was directly related to the total compound concentration in the plasma; the pharmacokinetic (PK) measurement. This PK-PD relationship was extended across a series of GKAs by accounting for differences in protein binding and in the in vitro potency. CONCLUSIONS AND IMPLICATIONS When the unbound GKA compound level is greater than the in vitro enzyme potency there was significant blood glucose lowering in vivo. This latter relationship was upheld in non-diabetic Wistar rats orally dosed with a GKA. The robust and predictive nature of the PK-PD relationship for GKAs may prove of value in testing these agents in early human clinical studies.
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Affiliation(s)
- G J Coope
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - A M Atkinson
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - C Allott
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - D McKerrecher
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - C Johnstone
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - K G Pike
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - P C Holme
- Syngenta Central Toxicology Department Macclesfield, Cheshire, UK
| | - H Vertigan
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - D Gill
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - M P Coghlan
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
| | - B Leighton
- Cardiovascular and Gastrointestinal Department AstraZeneca, Macclesfield, Cheshire, UK
- Author for correspondence:
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Obeid OA, Jamal ZM, Hwalla N, Emery PW. The effect of glutamine and dihydroxyacetone supplementation on food intake, weight gain, and postprandial glycogen synthesis in female Zucker rats. Nutrition 2006; 22:794-801. [PMID: 16730949 DOI: 10.1016/j.nut.2006.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Revised: 04/03/2006] [Accepted: 04/03/2006] [Indexed: 11/20/2022]
Abstract
OBJECTIVE We sought to test the hypothesis that increasing postprandial hepatic glycogen synthesis rate would decrease food intake and growth rate in obese Zucker rats. DESIGN Supplements of glutamine, with and without dihydroxyacetone (DHA), which have previously been shown to stimulate hepatic glycogen synthesis, were administered in the diet of obese Zucker rats for periods of 1 and 3 wk. MEASUREMENTS Food intake and body weight were monitored throughout the experiments. At the end of the feeding period the rats were fed a test meal and injected with (3)H(2)O to measure in vivo rates of glycogen and lipid synthesis. Final plasma glucose and triacylglycerol and hepatic glycogen content were also determined. Carcass fat and water contents were also measured in the 3-wk study. RESULTS Dietary glutamine had no effect on food intake, weight gain, or body composition. Addition of DHA caused a reduction in food intake and weight gain and a stimulation of in vivo hepatic glycogen synthesis after 1 wk, but these changes were abolished by the end of 3 wk. Hepatic lipogenesis in vivo was increased by DHA treatment for 1 and 3 wk. CONCLUSIONS Stimulation of hepatic glycogen synthesis by DHA treatment was associated with a reduction in food intake. However, the effect of DHA on glycogen synthesis and food intake disappeared after 3 wk of supplementation.
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Affiliation(s)
- Omar A Obeid
- Department of Food Technology and Nutrition, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon
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Arden C, Green AR, Hampson LJ, Aiston S, Härndahl L, Greenberg CC, Brady MJ, Freeman S, Poucher SM, Agius L. Increased sensitivity of glycogen synthesis to phosphorylase-a and impaired expression of the glycogen-targeting protein R6 in hepatocytes from insulin-resistant Zucker fa/fa rats. FEBS J 2006; 273:1989-99. [PMID: 16640562 DOI: 10.1111/j.1742-4658.2006.05215.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Hepatic insulin resistance in the leptin-receptor defective Zucker fa/fa rat is associated with impaired glycogen synthesis and increased activity of phosphorylase-a. We investigated the coupling between phosphorylase-a and glycogen synthesis in hepatocytes from fa/fa rats by modulating the concentration of phosphorylase-a. Treatment of hepatocytes from fa/fa rats and Fa/? controls with a selective phosphorylase inhibitor caused depletion of phosphorylase-a, activation of glycogen synthase and stimulation of glycogen synthesis. The flux-control coefficient of phosphorylase on glycogen synthesis was glucose dependent and at 10 mm glucose was higher in fa/fa than Fa/? hepatocytes. There was an inverse correlation between the activities of glycogen synthase and phosphorylase-a in both fa/fa and Fa/? hepatocytes. However, fa/fa hepatocytes had a higher activity of phosphorylase-a, for a corresponding activity of glycogen synthase. This defect was, in part, normalized by expression of the glycogen-targeting protein, PTG. Hepatocytes from fa/fa rats had normal expression of the glycogen-targeting proteins G(L) and PTG but markedly reduced expression of R6. Expression of R6 protein was increased in hepatocytes from Wistar rats after incubation with leptin and insulin. Diminished hepatic R6 expression in the leptin-receptor defective fa/fa rat may be a contributing factor to the elevated phosphorylase activity and/or its high control strength on glycogen synthesis.
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MESH Headings
- Animals
- Carrier Proteins/antagonists & inhibitors
- Carrier Proteins/biosynthesis
- Carrier Proteins/physiology
- Cells, Cultured
- Diabetes Mellitus, Type 2/enzymology
- Diabetes Mellitus, Type 2/genetics
- Disease Models, Animal
- Female
- Glycogen/biosynthesis
- Glycogen/metabolism
- Glycogen/physiology
- Hepatocytes/enzymology
- Insulin/chemistry
- Insulin Resistance/genetics
- Intracellular Signaling Peptides and Proteins
- Leptin/chemistry
- Male
- Obesity/enzymology
- Obesity/genetics
- Phosphoprotein Phosphatases/antagonists & inhibitors
- Phosphoprotein Phosphatases/biosynthesis
- Phosphoprotein Phosphatases/metabolism
- Phosphorylase a/chemistry
- Phosphorylase a/physiology
- Protein Subunits/antagonists & inhibitors
- Protein Subunits/biosynthesis
- Protein Subunits/metabolism
- Rats
- Rats, Wistar
- Rats, Zucker
- Receptors, Cell Surface/deficiency
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/physiology
- Receptors, Leptin
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Affiliation(s)
- Catherine Arden
- School of Clinical Medical Sciences--Diabetes, University of Newcastle upon Tyne, UK
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Obeid OA, Boukarim LK, Al Awar RM, Hwalla N. Postprandial glycogen and lipid synthesis in prednisolone-treated rats maintained on high-protein diets with varied carbohydrate levels. Nutrition 2006; 22:288-94. [PMID: 16412611 DOI: 10.1016/j.nut.2005.07.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2005] [Accepted: 07/25/2005] [Indexed: 11/28/2022]
Abstract
OBJECTIVE The present experiment was designed to study the effect of a high-protein, high-carbohydrate diet versus a high-protein, low-carbohydrate diet on in vivo postprandial glycogen and lipid synthesis of rats treated with prednisolone. METHODS Thirty-two 6-wk-old male Sprague-Dawley rats were randomly assigned to one of four equal groups: high-protein, high-carbohydrate; high-protein, high-carbohydrate with prednisolone; high-protein, low-carbohydrate; and high-protein, low-carbohydrate with prednisolone. Rats were sham operated or subcutaneously implanted with prednisolone pellets while being maintained on their respective diets (39% of energy from protein) for 6 wk. Food intake and body weight were monitored throughout the experiment. At the end of the feeding period, overnight-fasted rats were fed a test meal and injected with 3H2O to measure in vivo rates of glycogen and lipid synthesis. Final plasma glucose, insulin, and triacylglycerol concentrations and hepatic glycogen content were also measured. RESULTS Results showed that hepatic glycogen content (milligrams per gram of liver) was similar across all four experimental groups. Total hepatic glycogen synthesis and its percentage synthesis via pyruvate (indirect pathway) were higher in rats maintained on the high-protein, high-carbohydrate diet compared with those on the high-protein, low-carbohydrate diet and this was not substantially affected by prednisolone administration. Hepatic and epididymal fat pad lipid syntheses were not altered by diet or prednisolone treatments. CONCLUSION Under long-term high-protein conditions, prednisolone administration does not seem to affect hepatic glycogen synthesis, which was increased with the increased carbohydrate content of the diet.
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Affiliation(s)
- Omar A Obeid
- Department of Nutrition and Food Sciences, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon.
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Obeid OA, Bittar ST, Hwalla N, Emery PW. Effect of diet supplementation with glutamine, dihydroxyacetone, and leucine on food intake, weight gain, and postprandial glycogen metabolism of rats. Nutrition 2005; 21:224-9. [PMID: 15723752 DOI: 10.1016/j.nut.2004.03.026] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2003] [Revised: 11/17/2003] [Accepted: 03/18/2004] [Indexed: 11/21/2022]
Abstract
OBJECTIVE We tested the hypothesis that increasing the rate of postprandial hepatic glycogen synthesis would decrease food intake and growth rate in normal rats. METHODS Diets supplemented with glutamine, glutamine plus dihydroxyacetone, and glutamine plus dihydroxyacetone plus leucine were administered to male Sprague-Dawley rats for 1 wk. These are combinations that have been shown to stimulate hepatic glycogen synthesis in vitro. Food intake and body weight were monitored throughout the experiment. At the end of the feeding period, rats were fed a test meal and injected with 3H2O to measure in vivo rates of glycogen and lipid synthesis. Positional analysis of the 3H incorporated into glycogen was used to determine the proportion of glycogen synthesized via pyruvate. Final levels of plasma glucose and triacylglycerol and hepatic glycogen were also measured. RESULTS Dietary glutamine increased hepatic glycogen synthesis. Addition of dihydroxyacetone, with or without additional leucine, caused an additional increase in hepatic glycogen synthesis and increased the proportion of glycogen synthesized via pyruvate. Lipogenesis was not altered in the liver or adipose tissue. None of the dietary treatments had any effect on food intake, but the diets that contained dihydroxyacetone decreased the rate of weight gain. CONCLUSIONS Increasing glycogen synthesis had no effect on food intake. Increasing the proportion of glycogen synthesized by the indirect pathway through pyruvate was associated with a decrease in weight gain.
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Affiliation(s)
- Omar A Obeid
- Department of Nutrition and Food Sciences, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon
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Lindén D, William-Olsson L, Rhedin M, Asztély AK, Clapham JC, Schreyer S. Overexpression of mitochondrial GPAT in rat hepatocytes leads to decreased fatty acid oxidation and increased glycerolipid biosynthesis. J Lipid Res 2004; 45:1279-88. [PMID: 15102885 DOI: 10.1194/jlr.m400010-jlr200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glycerol-3-phosphate acyltransferase (GPAT) catalyses the first committed step in glycerolipid biosynthesis. The mitochondrial isoform (mtGPAT) is mainly expressed in liver, where it is highly regulated, indicating that mtGPAT may have a unique role in hepatic fatty acid metabolism. Because both mtGPAT and carnitine palmitoyl transferase-1 are located on the outer mitochondrial membrane, we hypothesized that mtGPAT directs fatty acyl-CoA away from beta-oxidation and toward glycerolipid synthesis. Adenoviral-mediated overexpression of murine mtGPAT in primary cultures of rat hepatocytes increased mtGPAT activity 2.7-fold with no compensatory effect on microsomal GPAT activity. MtGPAT overexpression resulted in a dramatic 80% reduction in fatty acid oxidation and a significant increase in hepatic diacylglycerol and phospholipid biosynthesis. Following lipid loading of the cells, intracellular triacylglycerol biosynthesis was also induced by mtGPAT overexpression. Changing an invariant aspartic acid residue to a glycine [D235G] in mtGPAT resulted in an inactive enzyme, which helps define the active site required for mammalian mtGPAT function. To determine if obesity increases hepatic mtGPAT activity, two models of rodent obesity were examined and shown to have >2-fold increased enzyme activity. Overall, these results support the concept that increased hepatic mtGPAT activity associated with obesity positively contributes to lipid disorders by reducing oxidative processes and promoting de novo glycerolipid synthesis.
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Kurosaki E, Momose K, Nakano R, Shimaya A, Suzuki T, Shibasaki M, Shikama H. Hypoglycemic agent YM440 ameliorates the impaired hepatic glycogenesis after glucose loading by increasing glycogen synthase activity in obese Zucker rats. JAPANESE JOURNAL OF PHARMACOLOGY 2002; 89:274-81. [PMID: 12184733 DOI: 10.1254/jjp.89.274] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We studied the role of hepatic glycogenesis in glucose intolerance after glucose loading in obese Zucker rats and the effects of YM440 ((Z)-1,4-bis[4-[(3,5-dioxo-1,2,4-oxadiazolidin-2-yl)methyl]phenoxy]but-2-ene) on it. Lean and obese Zucker rats were treated with YM440 (300 mg/kg) for 14 days and then fasted for 20 h. Thirty percent glucose (0.6 g/kg) or saline was administered intravenously followed by NaH14CO3. Gluconeogenesis was evaluated based on the incorporation of 14C-bicarbonate into blood glucose and hepatic glycogen. Obese rats showed an increase in the incorporation of 14C into blood glucose of 2.5-fold compared to lean rats. The glucose loading decreased the 14C-blood glucose release by 18% in obese rats and 43% in lean rats at 45 min. Glucose loading increased the hepatic glycogen content and 14C incorporation into glycogen in lean but not obese rats. YM440 decreased levels of fasting plasma insulin and blood glucose and the hepatic glycogen content by 50% compared with values for untreated obese rats. After glucose loading, YM440 promoted the incorporation of 14C into glycogen and glycogen synthase activity, leading to an improvement in glucose tolerance. These results indicate that glucose intolerance in obese rats was associated with decreased hepatic glycogenesis and YM440 improved the intolerance by normalizing glycogen metabolism.
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Affiliation(s)
- Eiji Kurosaki
- Pharmacology Laboratories, Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Ltd., Tsukuba, Ibaraki, Japan
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