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Hasenour CM, Banerjee DR, Young JD. Metabolic Fluxes in the Renal Cortex Are Dysregulated In Vivo in Response to High-Fat Diet. Diabetes 2024; 73:903-908. [PMID: 38502790 PMCID: PMC11109784 DOI: 10.2337/db23-0710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 03/13/2024] [Indexed: 03/21/2024]
Abstract
Diabetes and obesity are risk factors for kidney disease. Whereas renal glucose production increases in diabetes, recent data suggest that gluconeogenic and oxidative capacity decline in kidney disease. Thus, metabolic dysregulation caused by diet-induced insulin resistance may sensitize the kidney for a loss in function. Here, we examined how diet-induced insulin resistance disrupts mitochondrial metabolic fluxes in the renal cortex in vivo. C57BL/6J mice were rendered insulin resistant through high-fat (HF) feeding; anaplerotic, cataplerotic, and oxidative metabolic fluxes in the cortex were quantified through 13C-isotope tracing during a hyperinsulinemic-euglycemic clamp. As expected, HF-fed mice exhibited increased body weight, gluconeogenesis, and systemic insulin resistance compared with chow-fed mice. Relative to the citric acid cycle, HF feeding increased metabolic flux through pyruvate carboxylation (anaplerosis) and phosphoenolpyruvate carboxykinase (cataplerosis) and decreased flux through the pyruvate dehydrogenase complex in the cortex. Furthermore, the relative flux from nonpyruvate sources of acetyl-CoA profoundly increased in the cortex of HF-fed mice, correlating with a marker of oxidative stress. The data demonstrate that HF feeding spares pyruvate from dehydrogenation at the expense of increasing cataplerosis, which may underpin renal gluconeogenesis during insulin resistance; the results also support the hypothesis that dysregulated oxidative metabolism in the kidney contributes to metabolic disease. ARTICLE HIGHLIGHTS
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Affiliation(s)
- Clinton M. Hasenour
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN
| | - Deveena R. Banerjee
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
| | - Jamey D. Young
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
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2
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Patel NA, Lui A, Trujillo AN, Motawe ZY, Bader D, Schuster J, Burgess A, Alves NG, Jo M, Breslin JW. Female and male obese Zucker rats display differential inflammatory mediator and long non-coding RNA profiles. Life Sci 2023; 335:122285. [PMID: 37995934 PMCID: PMC10760426 DOI: 10.1016/j.lfs.2023.122285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 11/08/2023] [Accepted: 11/20/2023] [Indexed: 11/25/2023]
Abstract
AIMS The goal of this study was to identify mediators in peri-lymphatic adipose tissue (PLAT) that are altered in obese versus lean Zucker rats, with focus on potential sex differences MAIN METHODS: Mesenteric PLAT was analyzed with protein and lncRNA arrays. Additional RT-PCR confirmation was performed with epididymal/ovarian fat. KEY FINDINGS MCP-1, TCK-1, Galectin-1, Galectin-3, and neuropilin-1 were elevated in PLAT from obese rats of both sexes. However, 11 additional proteins were elevated only in obese males while 24 different proteins were elevated in obese females. Profiling of lncRNAs revealed lean males have elevated levels of NEAT1, MALAT1 and GAS5 compared to lean females. NEAT1, MALAT1, and GAS5 were significantly reduced with obesity in males but not in females. Another lncRNA, HOTAIR, was higher in lean females compared to males, and its levels in females were reduced with obesity. Obese rats of both sexes had similar histologic findings of mesenteric macrophage crown-like structures and hepatocyte fat accumulation. SIGNIFICANCE While obese male and female Zucker rats both have increased inflammation, they have distinct signals. Future studies of the proteome and lncRNA landscape of obese males vs. females in various animal models and in human subjects are warranted to better guide development of therapeutics for obesity-induced inflammation.
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Affiliation(s)
- Niketa A Patel
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, United States of America; James A. Haley Veteran's Hospital, United States of America
| | - Ashley Lui
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, United States of America; James A. Haley Veteran's Hospital, United States of America
| | - Andrea N Trujillo
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, United States of America
| | - Zeinab Y Motawe
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, United States of America
| | - Deena Bader
- James A. Haley Veteran's Hospital, United States of America
| | - Jane Schuster
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, United States of America
| | - Andrea Burgess
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, United States of America
| | - Natascha G Alves
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, United States of America
| | - Michiko Jo
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, United States of America; Division of Presymptomatic Disease, Institute of Natural Medicine, University of Toyama, Japan
| | - Jerome W Breslin
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, United States of America.
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3
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Ahmad M, Abramovich I, Agranovich B, Nemirovski A, Gottlieb E, Hinden L, Tam J. Kidney Proximal Tubule GLUT2-More than Meets the Eye. Cells 2022; 12:cells12010094. [PMID: 36611887 PMCID: PMC9818791 DOI: 10.3390/cells12010094] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/06/2022] [Accepted: 12/23/2022] [Indexed: 12/28/2022] Open
Abstract
Tubulopathy plays a central role in the pathophysiology of diabetic kidney disease (DKD). Under diabetic conditions, the kidney proximal tubule cells (KPTCs) are exposed to an extensive amount of nutrients, most notably glucose; these nutrients deteriorate KPTCs function and promote the development and progression of DKD. Recently, the facilitative glucose transporter 2 (GLUT2) in KPTCs has emerged as a central regulator in the pathogenesis of DKD. This has been demonstrated by identifying its specific role in enhancing glucose reabsorption and glucotoxicity, and by deciphering its effect in regulating the expression of the sodium-glucose transporter 2 (SGLT2) in KPTCs. Moreover, reduction/deletion of KPTC-GLUT2 has been recently found to ameliorate DKD, raising the plausible idea of considering it as a therapeutic target against DKD. However, the underlying molecular mechanisms by which GLUT2 exerts its deleterious effects in KPTCs remain vague. Herein, we review the current findings on the proximal tubule GLUT2 biology and function under physiologic conditions, and its involvement in the pathophysiology of DKD. Furthermore, we shed new light on its cellular regulation during diabetic conditions.
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Affiliation(s)
- Majdoleen Ahmad
- Obesity and Metabolism Laboratory, Faculty of Medicine, The Institute for Drug Research, School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem 9112001, Israel
| | - Ifat Abramovich
- Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 3525422, Israel
| | - Bella Agranovich
- Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 3525422, Israel
| | - Alina Nemirovski
- Obesity and Metabolism Laboratory, Faculty of Medicine, The Institute for Drug Research, School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem 9112001, Israel
| | - Eyal Gottlieb
- Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 3525422, Israel
| | - Liad Hinden
- Obesity and Metabolism Laboratory, Faculty of Medicine, The Institute for Drug Research, School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem 9112001, Israel
- Correspondence: (L.H.); (J.T.); Tel.: +972-2-675-7650 (L.H.); +972-2-675-7645 (J.T.)
| | - Joseph Tam
- Obesity and Metabolism Laboratory, Faculty of Medicine, The Institute for Drug Research, School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem 9112001, Israel
- Correspondence: (L.H.); (J.T.); Tel.: +972-2-675-7650 (L.H.); +972-2-675-7645 (J.T.)
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4
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Heather LC, Hafstad AD, Halade GV, Harmancey R, Mellor KM, Mishra PK, Mulvihill EE, Nabben M, Nakamura M, Rider OJ, Ruiz M, Wende AR, Ussher JR. Guidelines on Models of Diabetic Heart Disease. Am J Physiol Heart Circ Physiol 2022; 323:H176-H200. [PMID: 35657616 PMCID: PMC9273269 DOI: 10.1152/ajpheart.00058.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Diabetes is a major risk factor for cardiovascular diseases, including diabetic cardiomyopathy, atherosclerosis, myocardial infarction, and heart failure. As cardiovascular disease represents the number one cause of death in people with diabetes, there has been a major emphasis on understanding the mechanisms by which diabetes promotes cardiovascular disease, and how antidiabetic therapies impact diabetic heart disease. With a wide array of models to study diabetes (both type 1 and type 2), the field has made major progress in answering these questions. However, each model has its own inherent limitations. Therefore, the purpose of this guidelines document is to provide the field with information on which aspects of cardiovascular disease in the human diabetic population are most accurately reproduced by the available models. This review aims to emphasize the advantages and disadvantages of each model, and to highlight the practical challenges and technical considerations involved. We will review the preclinical animal models of diabetes (based on their method of induction), appraise models of diabetes-related atherosclerosis and heart failure, and discuss in vitro models of diabetic heart disease. These guidelines will allow researchers to select the appropriate model of diabetic heart disease, depending on the specific research question being addressed.
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Affiliation(s)
- Lisa C Heather
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Anne D Hafstad
- Department of Medical Biology, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Ganesh V Halade
- Department of Medicine, The University of Alabama at Birmingham, Tampa, Florida, United States
| | - Romain Harmancey
- Department of Internal Medicine, Division of Cardiology, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, United States
| | | | - Paras K Mishra
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, United States
| | - Erin E Mulvihill
- University of Ottawa Heart Institute, Ottawa, ON, Canada.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada
| | - Miranda Nabben
- Departments of Genetics and Cell Biology, and Clinical Genetics, Maastricht University Medical Center, CARIM School of Cardiovascular Diseases, Maastricht, the Netherlands
| | - Michinari Nakamura
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, Rutgers New Jersey Medical School, Newark, NJ, United States
| | - Oliver J Rider
- University of Oxford Centre for Clinical Magnetic Resonance Research, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Matthieu Ruiz
- Montreal Heart Institute, Montreal, Quebec, Canada.,Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - Adam R Wende
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - John R Ussher
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada.,Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada
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5
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Li X, Zheng S, Wu G. Amino Acid Metabolism in the Kidneys: Nutritional and Physiological Significance. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1265:71-95. [DOI: 10.1007/978-3-030-45328-2_5] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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6
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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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7
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Alsahli M, Gerich JE. Renal glucose metabolism in normal physiological conditions and in diabetes. Diabetes Res Clin Pract 2017; 133:1-9. [PMID: 28866383 DOI: 10.1016/j.diabres.2017.07.033] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 07/16/2017] [Accepted: 07/26/2017] [Indexed: 01/25/2023]
Abstract
The kidney plays an important role in glucose homeostasis via gluconeogenesis, glucose utilization, and glucose reabsorption from the renal glomerular filtrate. After an overnight fast, 20-25% of glucose released into the circulation originates from the kidneys through gluconeogenesis. In this post-absorptive state, the kidneys utilize about 10% of all glucose utilized by the body. After glucose ingestion, renal gluconeogenesis increases and accounts for approximately 60% of endogenous glucose release in the postprandial period. Each day, the kidneys filter approximately 180g of glucose and virtually all of this is reabsorbed into the circulation. Hormones (most importantly insulin and catecholamines), substrates, enzymes, and glucose transporters are some of the various factors influencing the kidney's role. Patients with type 2 diabetes have an increased renal glucose uptake and release in the fasting and the post-prandial states. Additionally, glucosuria in these patients does not occur at plasma glucose levels that would normally produce glucosuria in healthy individuals. The major abnormality of renal glucose metabolism in type 1 diabetes appears to be impaired renal glucose release during hypoglycemia.
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Affiliation(s)
- Mazen Alsahli
- Southlake Regional Health Center, Newmarket, Ontario, Canada; University of Toronto Faculty of Medicine, Toronto, Ontario, Canada
| | - John E Gerich
- University of Rochester School of Medicine, Rochester, NY, USA.
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8
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London E, Nesterova M, Stratakis CA. Acute vs chronic exposure to high fat diet leads to distinct regulation of PKA. J Mol Endocrinol 2017; 59:1-12. [PMID: 28420713 PMCID: PMC5514540 DOI: 10.1530/jme-16-0188] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 04/18/2017] [Indexed: 01/20/2023]
Abstract
The cAMP-dependent protein kinase (PKA) is an essential regulator of lipid and glucose metabolism that plays a critical role in energy homeostasis. The impact of diet on PKA signaling has not been defined, although perturbations in individual PKA subunits are associated with changes in adiposity, physical activity and energy intake in mice and humans. We hypothesized that a high fat diet (HFD) would elicit peripheral and central alterations in the PKA system that would differ depending on length of exposure to HFD; these differences could protect against or promote diet-induced obesity (DIO). 12-week-old C57Bl/6J mice were randomly assigned to a regular diet or HFD and weighed weekly throughout the feeding studies (4 days, 14 weeks; respectively), and during killing. PKA activity and subunit expression were measured in liver, gonadal adipose tissue (AT) and brain. Acute HFD-feeding suppressed basal hepatic PKA activity. In contrast, hepatic and hypothalamic PKA activities were significantly increased after chronic HFD-feeding. Changes in AT were more subtle, and overall, altered PKA regulation in response to chronic HFD exposure was more profound in female mice. The suppression of hepatic PKA activity after 4 day HFD-feeding was indicative of a protective peripheral effect against obesity in the context of overnutrition. In response to chronic HFD-feeding, and with the development of DIO, dysregulated hepatic and hypothalamic PKA signaling was a signature of obesity that is likely to promote further metabolic dysfunction in mice.
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Affiliation(s)
- Edra London
- Section on Endocrinology and GeneticsProgram on Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Maria Nesterova
- Section on Endocrinology and GeneticsProgram on Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Constantine A Stratakis
- Section on Endocrinology and GeneticsProgram on Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
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9
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Reyes-Esparza J, Mendoza-Rivera B, De la Cruz-Cordero R, Rosado JL, Duarte-Vázquez MÁ, Solis MG, Vite-Vallejo O, Rodríguez-Fragoso L. Pharmacological evaluation of a β-hydroxyphosphonate analogue of l-carnitine in obese Zucker fa/fa rats. Basic Clin Pharmacol Toxicol 2012; 112:222-8. [PMID: 23039375 DOI: 10.1111/bcpt.12019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 09/17/2012] [Indexed: 12/14/2022]
Abstract
In this study, we evaluated the effect of an analogue of l-carnitine on parameters involved with Metabolic Syndrome in obese Zucker rats. Twenty-four rats were treated for 5 weeks with l-carnitine (300 mg/kg) and its analogue at two concentrations (100 and 250 mg/kg) to assess their impact on glucose, triglycerides and cholesterol in liver and blood samples, as well as the amount of liver glycogen. Liver slices were also analysed. The analogue reduced the levels of glucose, triglycerides and cholesterol in liver and the level of triglycerides in serum. At 100 mg/kg, the analogue proved more effective than l-carnitine in improving the biochemical alterations present in liver. The amount of liver glycogen content was higher in obese animals treated with both l-carnitine and the analogue. No changes on insulin and leptin were observed in animals treated. l-carnitine and its analogue reduced the microvesicular fatty infiltration in liver. This study demonstrated that the analogue tested is more potent and efficient than l-carnitine and improves the pharmacological profile of l-carnitine.
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Affiliation(s)
- Jorge Reyes-Esparza
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, México
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10
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Abstract
Considerable data have accumulated over the past 20 years, indicating that the human kidney is involved in the regulation of glucose via gluconeogenesis, taking up glucose from the circulation, and by reabsorbing glucose from the glomerular filtrate. In light of the development of glucose-lowering drugs involving inhibition of renal glucose reabsorption, this review summarizes these data. Medline was searched from 1989 to present using the terms 'renal gluconeogenesis', 'renal glucose utilization', 'diabetes mellitus' and 'glucose transporters'. The human liver and kidneys release approximately equal amounts of glucose via gluconeogenesis in the post-absorptive state. In the postprandial state, although overall endogenous glucose release decreases substantially, renal gluconeogenesis increases by approximately twofold. Glucose utilization by the kidneys after an overnight fast accounts for approximately 10% of glucose utilized by the body. Following a meal, glucose utilization by the kidney increases. Normally each day, approximately 180 g of glucose is filtered by the kidneys; almost all of this is reabsorbed by means of sodium-glucose co-transporter 2 (SGLT2), expressed in the proximal tubules. However, the capacity of SGLT2 to reabsorb glucose from the renal tubules is finite and, when plasma glucose concentrations exceed a threshold, glucose appears in the urine. Handling of glucose by the kidney is altered in Type 2 diabetes mellitus (T2DM): renal gluconeogenesis and renal glucose uptake are increased in both the post-absorptive and postprandial states, and renal glucose reabsorption is increased. Specific SGLT2 inhibitors are being developed as a novel means of controlling hyperglycaemia in T2DM.
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Affiliation(s)
- J E Gerich
- University of Rochester School of Medicine, Rochester, NY 14642, USA.
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11
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Doyon C, Denis RG, Baraboi ED, Samson P, Lalonde J, Deshaies Y, Richard D. Effects of rimonabant (SR141716) on fasting-induced hypothalamic-pituitary-adrenal axis and neuronal activation in lean and obese Zucker rats. Diabetes 2006; 55:3403-10. [PMID: 17130486 DOI: 10.2337/db06-0504] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The effects of the cannabinoid-1 receptor (CB(1)) antagonist rimonabant on energy metabolism and fasting-induced hypothalamic-pituitary-adrenal (HPA) axis and neuronal activation were investigated. Lean and obese Zucker rats were treated orally with a daily dose of 10 mg/kg rimonabant for 14 days. A comprehensive energy balance profile based on whole-carcass analyses further demonstrated the potential of CB(1) antagonists for decreasing energy gain through reducing food intake and potentially increasing brown adipose tissue thermogenesis. Rimonabant also reduced plasma glucose, insulin, and homeostasis model assessment of insulin resistance, which further confirms the ability of CB(1) antagonists to improve insulin sensitivity. To test the hypothesis that rimonabant attenuates the effect of fasting on HPA axis activation in the obese Zucker model, rats were either ad libitum-fed or food-deprived for 8 h. Contrary to expectation, rimonabant increased basal circulating corticosterone levels and enhanced the HPA axis response to food deprivation in obese rats. Rimonabant also exacerbated the neuronal activation seen in the arcuate nucleus (ARC) after short-term deprivation. In conclusion, the present study demonstrates that CB(1) blockade does not prevent the hypersensitivity to food deprivation occurring at the level of HPA axis and ARC activation in the obese Zucker rats. This, however, does not prevent CB(1) antagonism from exerting beneficial effects on energy and glucose metabolism.
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Affiliation(s)
- Christian Doyon
- Direction de la recherche, Hôpital Laval, 2725 chemin Sainte-Foy, Québec, Québec, Canada, G1V 4G5
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12
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Ji H, Outterbridge LV, Friedman MI. Phenotype-based treatment of dietary obesity: differential effects of fenofibrate in obesity-prone and obesity-resistant rats. Metabolism 2005; 54:421-9. [PMID: 15798946 DOI: 10.1016/j.metabol.2004.10.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
High-fat diets (HFDs) promote hyperphagia and adiposity in animals and human beings. To test the hypothesis that limitations on fat oxidation underlie this propensity for diet-induced obesity, rats were treated with fenofibrate, which enhances fat oxidation mainly in liver by inducing expression of enzymes and proliferation of organelles involved in fatty acid oxidation. Male Sprague-Dawley rats were fed a HFD (42% fat calorie) for 2 weeks. Rats ranked in the top and bottom thirds for weight gain during this feeding period were designated as obesity prone (OP) and obesity resistant (OR), respectively. Fenofibrate was added to the HFD (0.025% wt/wt) for half of the OP and OR rats. During the next 10 days, fenofibrate treatment significantly (P<.05) reduced food intake, weight gain, feed efficiency, and adiposity in OP rats to levels seen in control OR rats, but had no such effects in OR rats. Fenofibrate treatment increased whole-body fatty acid oxidation, and in liver, the expression of carnitine palmitoyl transferase I only in OP rats, but enhanced expression of acyl-CoA oxidase in both OP and OR rats. Restricting food intake of OP rats to levels seen in rats given fenofibrate similarly reduced weight gain but had little effect on weight of fat pads. Treatment with the daily dosage of fenofibrate given as a bolus did not produce a conditioned flavor aversion. These results suggest that enhancement of mitochondrial fatty acid oxidation in liver may be an effective phenotype-based treatment strategy for dietary obesity.
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Affiliation(s)
- Hong Ji
- Monell Chemical Senses Center, Philadelphia, PA 19104, USA.
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13
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Sun CK, Zhang XY, Zimmermann A, Wheatley AM. The metabolic and microcirculatory impact of orthotopic liver transplantation on the obese Zucker rat. Transplantation 2003; 75:761-9. [PMID: 12660498 DOI: 10.1097/01.tp.0000054680.70476.70] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The purpose of this study was to investigate the metabolic alterations in the recipient and microcirculatory changes to the graft in the first 3 months after orthotopic liver transplantation (OLT) of nonsteatotic liver grafts from lean rats into obese Zucker rats. METHODS Body weight and plasma lipids were measured for 3 months post-OLT. Graft perfusion (hepatic microcirculatory perfusion [HMP]) and vascular structure were measured in vivo at 3 months. Liver biopsy specimens were obtained throughout for morphologic analysis. Sham-operation obese and lean Zucker rats acted as controls. RESULTS Plasma cholesterol levels were elevated from 2 months after OLT, whereas plasma triglyceride levels were reduced (P<0.05). Plasma high-density lipoprotein cholesterol concentrations increased from the first month after OLT (P<0.05). HMP in OLT animals (137+/-3 perfusion units [PU]) (P<0.05) was intermediate between lean (221+/-11 PU) and obese controls (113+/-5 PU). Hepatic cord width in the OLT group was similar to that in lean controls. Mean liver-to-body weight ratios in OLT animals (4.12%+/-0.39%) were significantly higher than in lean controls (3.25%+/-0.1%). The number of viable hepatocytes per high-power field in the OLT animals was lower than in the lean animals but higher than in obese controls (P<0.05). The transplanted livers showed moderate to marked microvesicular fatty change (MIFC) and glycogen deposition at 3 months after OLT. CONCLUSIONS Transplantation of a nonsteatotic liver into an obese Zucker rat initially has a positive effect on lipid metabolism. However, 3 months after OLT, the donor liver became steatotic with MIFC changes and reduced perfusion. The authors' results emphasize the importance of the recipient's metabolic status in the maintenance of liver graft function after OLT.
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Affiliation(s)
- Cheuk-Kwan Sun
- Microcirculatory Research Laboratory, Department of Physiology, School of Medical Sciences, University of Otago, Dunedin, New Zealand
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14
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Trinh KY, O'Doherty RM, Anderson P, Lange AJ, Newgard CB. Perturbation of fuel homeostasis caused by overexpression of the glucose-6-phosphatase catalytic subunit in liver of normal rats. J Biol Chem 1998; 273:31615-20. [PMID: 9813078 DOI: 10.1074/jbc.273.47.31615] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The terminal step in hepatic gluconeogenesis is catalyzed by glucose-6-phosphatase, an enzyme activity residing in the endoplasmic reticulum and consisting of a catalytic subunit (glucose-6-phosphatase (G6Pase)) and putative accessory transport proteins. We show that Zucker diabetic fatty rats (fa/fa), which are known to exhibit impaired suppression of hepatic glucose output, have 2.4-fold more glucose-6-phosphatase activity in liver than lean controls. To define the potential contribution of increased hepatic G6Pase to development of diabetes, we infused recombinant adenoviruses containing the G6Pase cDNA (AdCMV-G6Pase) or the beta-galactosidase gene into normal rats. Animals were studied by one of three protocols as follows: protocol 1, fed ad libitum for 7 days; protocol 2, fed ad libitum for 5 days, fasted overnight, and subjected to an oral glucose tolerance test; protocol 3, fed ad libitum for 4 days, fasted for 48 h, subjected to oral glucose tolerance test, and then allowed to refeed overnight. Hepatic glucose-6-phosphatase enzymatic activity was increased by 1.6-3-fold in microsomes isolated from AdCMV-G6Pase-treated animals in all three protocols, and the resultant metabolic profile was similar in each case. AdCMV-G6Pase-treated animals exhibited several of the abnormalities associated with early stage non-insulin-dependent diabetes mellitus, including glucose intolerance, hyperinsulinemia, decreased hepatic glycogen content, and increased peripheral (muscle) triglyceride stores. These animals also exhibited significant decreases in circulating free fatty acids and triglycerides, changes not normally associated with the disease. Our studies show that overexpression of G6Pase in liver is sufficient to perturb whole animal glucose and lipid homeostasis, possibly contributing to the development of metabolic abnormalities associated with diabetes.
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Affiliation(s)
- K Y Trinh
- Gifford Laboratories for Diabetes Research and Departments of Biochemistry and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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15
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Khandelwal RL, Pugazhenthi S. In vivo effects of vanadate on hepatic glycogen metabolizing and lipogenic enzymes in insulin-dependent and insulin-resistant diabetic animals. Mol Cell Biochem 1995; 153:87-94. [PMID: 8927052 DOI: 10.1007/bf01075922] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The insulin-mimetic action of vanadate is well established but the exact mechanism by which it exerts this effect is still not clearly understood. The role of insulin in the regulation of hepatic glycogen metabolizing and lipogenic enzymes is well known. In our study, we have, therefore, examined the effects of vanadate on these hepatic enzymes using four different models of diabetic and insulin-resistant animals. Vanadate normalized the blood glucose levels in all animal models. In streptozotocin-induced diabetic rats, the amount of liver glycogen and the activities of the active-form of glycogen synthase, both active and inactive-forms of phosphorylase, and lipogenic enzymes like glucose 6-phosphate dehydrogenase and malic enzyme were decreased and vanadate treatment normalized all of these to near normal levels. The other three animal models (db/db mouse, sucrose-fed rats and fa/fa obese Zucker rats) were characterized by hyperinsulinemia, hypertriglyceridemia, increases in activities of lipogenic enzymes, and marginal changes in glycogen metabolizing enzymes. Vanadate treatment brought all of these values towards normal levels. It should be noted that vanadate shows differential effects in the modulation of lipogenic enzymes activities in type I and type II diabetic animals. It increases the activities of lipogenic enzymes in streptozotocin-induced diabetic animals and prevents the evaluation of activities of these enzymes in hyperinsulinemic animals. The insulin-stimulated phosphorylation of insulin receptor beta subunit and its tyrosine kinase activity was increased in streptozotocin-induced diabetic rats after treatment with vanadate. Our results support the view that insulin receptor is one of the sites involved in the insulin-mimetic actions of vanadate.
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Affiliation(s)
- R L Khandelwal
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Saskatoon, Canada
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16
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Pugazhenthi S, Khandelwal RL. Regulation of glycogen synthase activation in isolated hepatocytes. Mol Cell Biochem 1995; 149-150:95-101. [PMID: 8569754 DOI: 10.1007/bf01076568] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Glycogen synthase, the regulatory enzyme of glycogen synthesis undergoes multisite phosphorylation leading to its inactivation. The kinases responsible for this covalent modification (ex. cAMP-dependent protein kinase, protein kinase C and glycogen synthase kinase-3) are controlled by the second messengers generated by different hormones. The isolated hepatocytes has been used as one of the experimental models for studying this complex regulatory process. Inactivation of glycogen synthase by glucagon and vasopressin has been shown to be accompanied with incorporation of phosphate into the enzyme protein. Insulin has been shown to activate glycogen synthase by inhibition of kinases and activation of synthase phosphatase. Glycogen synthase is activated by several gluconeogenic substrates, in addition to glucose. Studies in hepatocytes with activators and inhibitors of protein kinase C show that this enzyme negatively controls glycogen synthase. The differential effects of the phosphatase inhibitors, calyculin A and okadaic acid in liver cells provide supporting evidence that protein phosphatase type-1 plays a major role in the regulation of glycogen synthase. Hepatocytes isolated from diabetic rats of both types (insulin-dependent and non-insulin-dependent) mimic the defective glycogen synthase activation seen in vivo.
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Affiliation(s)
- S Pugazhenthi
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Canada
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17
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Doyle P, Rohner-Jeanrenaud F, Jeanrenaud B. Alterations of local cerebral glucose utilization in lean and obese fa/fa rats after acute adrenalectomy. Brain Res 1994; 655:115-20. [PMID: 7812762 DOI: 10.1016/0006-8993(94)91604-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
An animal model often used to investigate the aetiology of obesity is the genetically obese fa/fa rat. It has many abnormalities, including hyperphagia, hyper-insulinemia, insulin resistance, low cerebral glucose utilization and an overactive hypothalamo-pituitary adrenal (HPA) axis with resulting hypercorticism. Due to the latter consideration, the aim of this work was to study the impact of acute adrenalectomy (ADX) on the local cerebral glucose utilization (LCGU) of lean and obese fa/fa rats. ADX resulted in discrete increases in LCGU of regions common to both lean and obese rats. These common regions were found to belong to be related to the limbic system. Within this system, the LCGU of the brain of obese rats was either normalized to lean sham operated values or increased by ADX to a similar degree in both groups on a percentage basis. It was concluded that the LCGU of both lean and obese animals appears to be negatively regulated, albeit to different extents, by glucocorticoids. Such negative regulation is particularly salient within the limbic system of the lean rat and even more so in the fa/fa rat. It is suggested that the long-term hypercorticism of obese fa/fa rats due to abnormal regulation of the HPA axis may result in a decreased LCGU in limbic and related regions of the brain of fa/fa rats and contribute to the expression of the obese phenotype.
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Affiliation(s)
- P Doyle
- Laboratoires de Recherches Métaboliques, Faculty of Medicine, Geneva, Switzerland
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18
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Madar Z, Omursky Z. Inhibition of intestinal α-glucosidase activity and postprandial hyperglycemia by α-glucosidase inhibitors in fa/fa rats. Nutr Res 1991. [DOI: 10.1016/s0271-5317(05)80396-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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19
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Terrettaz J, Jeanrenaud B. Contribution of glycerol and alanine to basal hepatic glucose production in the genetically obese (fa/fa) rat. Biochem J 1990; 270:803-7. [PMID: 2241912 PMCID: PMC1131804 DOI: 10.1042/bj2700803] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Increased hepatic glucose production has been reported to occur in the insulin-resistant genetically obese fa/fa rats. The possible existence of an increased basal gluconeogenesis in obese rats was investigated, upon comparing the metabolic fate of glycerol and alanine in liver of fed anaesthetized lean and genetically obese (fa/fa) rats. Glycerol turnover rate in obese animals was 3 times that of the lean. This increase in glycerol turnover rate was associated with an increase in blood glycerol levels in obese animals. The contribution of glycerol to glucose production was significantly increased in obese animals. In contrast, the contribution of alanine to the hepatic glucose production was similar to lean and obese animals. A higher incorporation of glucose, glycerol and alanine into hepatic lipids was observed in obese animals than in controls. It is concluded that in fed genetically obese (fa/fa) rats the high blood glycerol concentrations is a major driving force for the increased basal hepatic conversion of this substrate into glucose.
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Affiliation(s)
- J Terrettaz
- Laboratories de Recherches Métaboliques, Faculty and Department of Medicine, Genève, Switzerland
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20
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Roesler WJ, Pugazhenthi S, Khandelwal RL. Hepatic glycogen metabolism in the db/db mouse. Mol Cell Biochem 1990; 92:99-106. [PMID: 2407941 DOI: 10.1007/bf00218127] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Knowledge of the metabolic changes that occur in insulin-resistant type 2 diabetes is relatively lacking compared to insulin-deficient type 1 diabetes. This paper summarizes the importance of the C57BL/KsJ-db/db mouse as a model of type 2 diabetes, and illustrates the effects that insulin-deficient and insulin-resistant states have on hepatic glycogen metabolism. A longitudinal study of db/db mice of ages 2-15 weeks revealed that significant changes in certain parameters of hepatic glycogen metabolism occur during this period. The liver glycogen levels were similar between diabetic and control mice. However, glycogen particles from db/db mice were on average smaller in mass and had shorter exterior and interior chain lengths. Total phosphorylase and phosphorylase a activities were elevated in the genetically diabetic mice. This was primarily due to an increase in the amount of enzymic protein apparently the result of a decreased rate of degradation. It was not possible to find a consistent alteration in glycogen activity in the db/db mice. Glycogen synthase and phosphorylase from diabetic liver revealed some changes in kinetic properties in the form of a decrease in Vmax and altered sensitivity to inhibitors like ATP. The altered glycogen structure in db/db mice may have contributed to changes in the activities and properties of glycogen synthase and phosphorylase. The exact role played by hormones (insulin and glucagon) in these changes is not clear but further studies should reveal their contributions. The db/db mouse provides a good model for type 2 diabetes and for fluctuating insulin and glucagon ratios.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- W J Roesler
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
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21
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22
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Abstract
The whole-animal metabolic rates of lean and obese rats cannot be directly compared because obese rats have much greater body mass than lean rats. Expressing the results as metabolic rate per unit of body mass is also not satisfactory because lean and obese rats of the same size have different body compositions. To make possible comparisons between the two types of rats, metabolic rate must be expressed per unit of effective body mass. Effective body mass for lean and obese Zucker rats can be calculated as 1.00 M0.75 and 0.82 M0.75, respectively, where M is the mass of the animal.
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Affiliation(s)
- R Refinetti
- Institute of Environmental Stress, University of California, Santa Barbara 93106
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23
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Abstract
Insulin secretory response to glucose was investigated in 5- to 6-week-old male Zucker obese (fa/fa) and lean (Fa/Fa) rats using a pancreatic perfusion procedure. Blood glucose response to fasting was studied in lean and obese animals over 24 hours. Plasma glucose was slightly elevated in pentobarbital-anesthetized obese rats. However, plasma insulin was 4.6 times greater than that of leans. A hypoglycemic glucose stimulus (75 mg/dL) caused pancreata from obese animals to release 6 times more insulin than lean animals. Stimuli of 125 mg/dL (normoglycemic) and 600 mg/dL (hyperglycemic) caused hypersecretion of 8 and 5 times, respectively. Hypersecretion was not accounted for solely by the twofold increase in pancreatic insulin content. Obese animals had steeper decreases in plasma glucose than lean controls during seven to 13 hours of fasting. Hypersecretion by pancreata from young obese rats to physiological levels of glucose may result in hyperphagia in order to maintain normoglycemia.
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Affiliation(s)
- A Kuffert
- Department of Nutrition, University of California, Davis 95616
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24
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Margolis RN. Hepatic glycogen synthase phosphatase and phosphorylase phosphatase activities are increased in obese (fa/fa) hyperinsulinemic Zucker rats: effects of glyburide administration. Life Sci 1987; 41:2615-22. [PMID: 2826945 DOI: 10.1016/0024-3205(87)90275-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The chronically hyperinsulinemic Zucker fatty rat, with peripheral insulin resistance and glucose intolerance, represents a model of noninsulin dependent diabetes mellitus (NIDDM). These animals have elevated hepatic glycogen levels. Hepatic levels of synthase phosphatase and phosphorylase phosphatase, which are diminished in the IDDM rat, were markedly increased in the obese rats. Glyburide, a sulfonylurea used in treatment of NIDDM, resulted in reduced levels of glycemia and increased insulin levels in Zucker rats. Hepatic glycogen levels were increased, as was the activation of glycogen synthase, although there were no effects of drug administration on synthase phosphatase or phosphorylase phosphatase activities. G6P levels were increased by glyburide in lean rats but not in obese animals. These effects of glyburide on liver glycogen metabolism are accounted for via potentiation of the glycogenic effects of insulin.
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Affiliation(s)
- R N Margolis
- Department of Anatomy, Howard University Cancer Center, Washington, D.C
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25
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Michaelis OE, Ellwood KC, Tulp OL, Greenwood M. Effect of feeding sucrose or starch diets on parameters of glucose tolerance in the LA/N-corpulent rat. Nutr Res 1986. [DOI: 10.1016/s0271-5317(86)80203-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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26
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Karsenty C, Ulmer M, Chanussot F, Ratanasavanh R, Debry G. Paradoxical effect of ethanol on liver lipogenesis in the genetically-obese Zucker rat. Br J Nutr 1985; 54:15-20. [PMID: 4063299 DOI: 10.1079/bjn19850087] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Sixteen obese (fa/fa) Zucker rats, sixteen lean (Fa/-) Zucker rats and sixteen Wistar rats, all male rats aged 7-8 weeks, were given either a control (C) diet containing no ethanol or an ethanol (E) diet in which 36% of the energy was supplied by ethanol, for a period of 4 weeks. The activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), glucose-6-phosphatase (EC 3.1.3.9) and glycerol kinase (EC 2.7.1.30) and the glycogen content in the livers of obese (fa/fa) rats were lower in animals given diet E than in those given diet C. As a result, hepatic lipogenesis and fatty degeneration of the liver were reduced in obese (fa/fa) rats given diet E.
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27
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Koubi H, Fréminet A. Comparison of glycogen stores in 3- and 7-month-old lean and obese Zucker rats under fed and fasted conditions. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1985; 81:103-10. [PMID: 4017535 DOI: 10.1016/0305-0491(85)90168-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Glycogen content (mg/g) and stores (mg) were determined in 3- and 7-month-old obese and lean Zucker rats, under fed and fasted (48 hr) conditions. Hepatic content was higher in fed obese than in lean rats (3 months: 90 vs 70; 7 months: 107 vs 74); it was exhausted after fasting in lean but decreased by 56% in obese rats. Muscle content in fed obese and lean animals did not differ; it decreased comparably after fasting. Myocardial content was higher in fed obese than lean rats (3 months: 7.2 vs 3.6; 7 months: 7.5 vs 6.3); it was enhanced with fasting (10.0 vs 7.5). Total glycogen stores were higher in obese than in lean animals (3 months: 2500 vs 1400; 7 months: 4000 vs 2000) because of the hepatic store. The discussion includes a comparison with available data, taking into account methodological aspects, lipid stores and the FFA/carbohydrate interrelationship.
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28
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Abstract
The effect of exercise on in vivo insulin sensitivity was examined in lean and obese Zucker rats. Rats (6 to 7 weeks of age) were swum two hours per day or kept sedentary for 8 weeks. Exercise decreased body weight gain as well as percent of fat in both genotypes. Sedentary obese rats had 62% higher gastrocnemius citrate synthase activity per gram of muscle than did lean rats. Exercise increased activity of this oxidative enzyme similarly in both genotypes. Compared to lean rats, obese rats had higher plasma-insulin levels and were less sensitive to insulin during an insulin tolerance test. Although training had no effect on plasma-insulin levels, exercise trained obese rats showed a greater drop in plasma glucose relative to sedentary controls following intravenous injection of three concentrations of insulin. It was concluded that moderate exercise training improved the insulin sensitivity of the obese Zucker rat.
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29
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McCune SA, Durant PJ, Jenkins PA, Harris RA. Comparative studies on fatty acid synthesis, glycogen metabolism, and gluconeogenesis by hepatocytes isolated from lean and obese Zucker rats. Metabolism 1981; 30:1170-8. [PMID: 6273686 DOI: 10.1016/0026-0495(81)90037-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Hepatocytes isolated from genetically obese female Zucker rats and lean female Zucker rats were compared. Hepatocytes from fed obese rats exhibited greater rates of fatty acid synthesis, more extensive accumulation of lactate and pyruvate from their glycogen stores, increased rates of net glucose utilization but produced less ketone bodies from exogenous fatty acids and had lower citrate levels than hepatocytes from lean rats. Lipogenesis was not as sensitive to dibutyryl cyclic AMP (DBcAMP) inhibition in hepatocytes from obese rats but glycogenolysis was stimulated to the same extent by this nucleotide in both preparations. Ketogenesis was less sensitive to stimulation by DBcAMP in hepatocytes from obese rats. A difference in sensitivity of lipogenesis to DBcAMP was not found when lactate plus pyruvate was added to the incubation medium, suggesting that a greater rate of glycolysis by hepatocytes from obese rats accounts for their relative insensitivity to DBcAMP. Citrate levels were elevated by DBcAMP to a greater extent in hepatocytes from obese rats. Hepatocytes prepared from lean rats starved for 48 hr were glycogen depleted and lacked significant capacity for lipogenesis and glycogen synthesis. In contrast, hepatocytes isolated from starved obese rats retained considerable amounts of liver glycogen and exhibited detectable rates of lipogenesis and glycogen synthesis. Hepatocytes prepared from starved lean rats gave faster apparent rates of lactate gluconeogenesis than hepatocytes prepared from starved obese rats. Thus, hepatocytes prepared from obese Zucker rats are more glycogenic, glycolytic, and lipogenic but less ketogenic and glucogenic than hepatocytes prepared from lean rats.
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30
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Bach A, Schirardin H, Bauer M, Schaeffer A, Weryha A. Age-related changes in biological parameters in Zucker rats. Lipids 1981; 16:841-8. [PMID: 7031400 DOI: 10.1007/bf02535040] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Changes in a number of morphological and biochemical parameters were observed in genetically obese Zucker rats and in lean controls between 3 and 58 weeks of age. By 3 weeks, the genetically obese rats had higher proportional (wt/100 g body wt) and absolute amounts of adipose tissue, hyperlipemia affecting all the lipid fractions, and hyperproteinemia compared to lean controls. Obesity, hepatomegaly, high concentrations of hepatic lipids and hyperinsulinemia did not appear until the fifth week. In obese animals, liver lipid concentration reached a maximum at 17 weeks of age and then declined. During this time, the triacylglycerol concentration in the serum remained stable, whereas the cholesterol and phospholipid concentrations continued to increase. The glycogen concentration in obese animals increased, both absolutely and compared to lean controls, between the 12th and 43rd weeks of age. From weaning, the Zucker rats, compared to lean controls, exhibited characteristics of obesity (accumulation of adipose tissue, hyperlipemia and hyperproteinemia), which persisted to the age of 58 weeks.
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31
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Abstract
Fatty acid synthesis and CO2 production were evaluated in hepatocytes from lean and obese Zucker rats in the presence of 3H2O, and several carbon precursors. The incorporation of 3H2O into fatty acids was greater in obese compared to lean rats in both the isolated hepatocyte and in vivo. The rates of incorporation of 3H2O into fatty acids and cholesterol in hepatocytes of both lean and obese rats were linear for 2 hr, in the absence or presence of 16.7 mM glucose. Rates of fatty acid synthesis were higher in the presence of 16.7 mM glucose compared to the absence of glucose in both lean and obese while rates of cholesterol synthesis were similar. The incorporation of 3H2O into fatty acids, but not into cholesterol, was correlated with increasing glucose concentration and was 2 to three-fold higher in hepatocytes of obese compared to lean rats in the presence of several carbon precursors. Differences in CO2 production between lean and obese rats suggested increased pentose phosphate shunt activity, decreased pyruvate dehydrogenase activity, and lower tricarboxylic acid cycle activity in obese rats. Fatty acid synthesis and CO2 production from 3H2O and [U-14C]glucose in hepatocytes of lean and obese rats was similarly elevated by insulin and depressed by glucagon at several concentrations, suggesting that hepatocytes of obese animals respond to these hormones. These data indicate that rates of hepatic fatty acid synthesis although higher in obese rats respond to modulation in a fashion which is similar to the response in lean rats. The present studies suggest that the oxidation of several carbon precursors in the tricarboxylic acid cycle is diminished in obese compared to lean rats, but pentose phosphate shunt activity is greater in the obese Zucker rats.
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32
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McLaughlin CL, Baile CA. Serum insulin, glucose and triglyceride response of Zucker obese and lean rats to cholecystokinin. Physiol Behav 1981; 26:995-9. [PMID: 7025052 DOI: 10.1016/0031-9384(81)90199-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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33
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Levin BE, Comai K, Sullivan AC. Metabolic and sympatho-adrenal abnormalities in the obese Zucker rat: effect of chronic phenoxybenzamine treatment. Pharmacol Biochem Behav 1981; 14:517-25. [PMID: 7015367 DOI: 10.1016/0091-3057(81)90311-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The obese Zucker rat manifests a number of physiologic and metabolic abnormalities which are controlled or modulated by the sympatho-adrenal system. The interrelationship of these was examined by subjecting 3-4 month old male, homozygous lean and obese Zucker rats to various stresses which are known to activate the sympatho-adrenal system, and by chronic (16-19 days) phenoxybenzamine (PBZ) treatment to block alpha-adrenergic receptors. Both obese and lean PBZ treated rats gained only 1% and 10% of the body weight of their respective control rats during the treatment period, while only the lean rats had a significant reduction (20%) in food intake. Control obese rats failed to maintain rectal temperature after 4 hr at 7 degrees C and their relative output of plasma catecholamines (CA) to cold stress, as measured from indwelling atrial cannulae, was decreased. PBZ treatment did not alter this rectal temperature response although it was associated with increased baseline norepinephrine levels (at ambient temperature 21-22 degrees C) and relative output of CA in the obese rats, suggesting tat sympathetic neural activity was increased under these circumstances. No abnormalities of sympatho-adrenal function, as reflected in plasma CA levels, were found in treated or control obese rats immobilization for 1 hr followed by decapitation. Simultaneously obtained baseline plasma glucose levels were similar in untreated lean and obese rats, but insulin and glycerol levels in the obese rat were 1350% and 213% of lean values, respectively. During sequential stresses, the obese rats became markedly hyperglycemic and hyperglycerolemic compared to the lean rats, while insulin levels were decreased more in the obese than lean rats (12-15% versus 34-35% of controls, respectively). PBZ affected insulin levels only in the obese rats, reducing their baseline levels by 4-fold and stressed induced levels to those seen in the lean control rats. These results suggest that some of the metabolic and physiologic abnormalities of the obese Zucker rat which are modulated by the sympatho-adrenal system can be normalized by procedures which increase sympatho-adrenal activity.
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34
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Goldman JK, Bernardis LL, MacKenzie RG, Kodis M, Luboshitzky R. Effects of ventromedial hypothalamic lesions on adipose tissue of weanling male rats. Diabetologia 1981; 20:357-361. [PMID: 27942822 DOI: 10.1007/bf00254503] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In weanling male rats, destruction of the ventromedial hypothalamus causes increased carcass lipid deposition and decreased linear growth without changes in food intake or blood glucose levels. These changes are not dependent on altered pituitary function. Lipogenesis and glucose utilization are increased in vivo and in vitro, while gluconeogenesis is accelerated in vivo. The enhanced lipogenesis occurs before increased gluconeogenesis.
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Affiliation(s)
- J K Goldman
- Buffalo Veterans Administration Medical Center, State University of New York, Buffalo, New York, USA
| | - L L Bernardis
- Buffalo Veterans Administration Medical Center, State University of New York, Buffalo, New York, USA
| | - R G MacKenzie
- Buffalo Veterans Administration Medical Center, State University of New York, Buffalo, New York, USA
| | - M Kodis
- Buffalo Veterans Administration Medical Center, State University of New York, Buffalo, New York, USA
| | - R Luboshitzky
- Buffalo Veterans Administration Medical Center, State University of New York, Buffalo, New York, USA
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35
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Orosco M, Jacquot C, Wepierre J, Cohen Y. GABA levels and synthesis index in different brain areas of two obese rat models. GENERAL PHARMACOLOGY 1981; 12:369-71. [PMID: 7286606 DOI: 10.1016/0306-3623(81)90093-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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36
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Levin BE, Triscari J, Sullivan AC. Abnormal sympatho- adrenal function and plasma catecholamines in obese Zucker rats. Pharmacol Biochem Behav 1980; 13:107-13. [PMID: 7403213 DOI: 10.1016/0091-3057(80)90128-8] [Citation(s) in RCA: 78] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The functional integrity of the peripheral sympathetic nervous system and adrenal medulla was assessed in homozygous, lean and obese, 7--8 month old male Zucker rats by the changes in plasma catecholamines during cold and immobilization stresses. Five of eight obese, but no lean rats died during a 24 hr cold stress (4--7 degrees C) from hypothermia. While both lean and obese rats had decreased rectal temperatures after 4 hr of cold stress, the obese had lower temperatures, relatively less of an increase of plasma norepinephrine (NE) and epinephrine (E) than the lean rats, and were unable to consistently maintain their temperatures even during intravenous NE infusions. Obese rats had lower rectal temperatures and higher plasma NE and dopamine levels at 21--22 degrees C ambient temperature, a relative failure to increase plasma NE and E levels after 1 hr of immobilization, but normal or supranormal plasma catecholamine levels after decapitation compared to the lean rats. These results suggest that the obese Zucker rat has abnormalities of both peripheral sympatho-adrenal function and thermoregulation, which may play roles in the development and/or maintenance of many of the physiological and metabolic defects in this animal model of genetic obesity.
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37
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Nosadini R, Ursini F, Tessari P, Garotti MC, de Biasi F, Tiengo A. Hormonal and metabolic characteristics of genetically obese Zucker and dietary obese Sprague-Dawley rats. Eur J Clin Invest 1980; 10:113-8. [PMID: 6780357 DOI: 10.1111/j.1365-2362.1980.tb02069.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The endocrine-metabolic plasma pattern and the capacity of isolated perfused livers to produce triglycerides and ketone bodies have been studied in genetically and diet-acquired obese rats (Zucker and Sprague-Dawley obese rats), and in control groups of the same strains. An increased plasma insulin/glucagon molar ratio with hyperinsulinaemia and hypoglucagonaemia was associated with hypertriglyceridaemia, normal ketonaemia, elevated free fatty acids and normal or slight hyperglycaemia in obese rats. During oleate perfusion, the livers of Zucker and Sprague-Dawley obese rats showed an increase in triglyceride output and liver triglyceride content. The ketone body output as well as the mitocondrial carnitine palmitoyl transferase activity were normal or slightly decreased. In our rat population, a positive correlation between the insulin/glucagon molar ratio and triglyceride output has been found.
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Abstract
The effects of fasting on lipid and carbohydrate metabolism and plasma insulin and glucagon levels were compared in lean and obese Zucker rats. Sixteen-month-old female and male rats were fasted for periods of 2, 4, 6 and 12 days. Fasting produced significant decreases in hepatic rates of lipid, cholesterol, and glycogen synthesis, as well as circulating levels of triglycerides, cholesterol, phospholipids, and insulin. Significant increases in hepatic lipid levels and serum free fatty acids were noted. When compared to lean rats, obese rats had elevated rates of hepatic lipid and glycogen synthesis, hepatic lipid and glycogen stores, serum triglycerides, cholesterol, phospholipids, and plasma insulin. Lean rats had higher plasma glucagon levels. Sex differences in several parameters were observed. Females demonstrated higher levels of lipid and cholesterol synthesis and serum free fatty acids, whereas serum cholesterol levels and hepatic glycogen stores were higher in males. Following a 12-day fast, carcass fat and protein content were decreased in both lean and obese rats, but the obese animals maintained an obese body composition. It is concluded that fasting results in qualitatively similar metabolic and hormonal changes in both lean and obese rats, but that abnormalities in carbohydrate and lipid metabolism persist in obese rats even after a 12-day fast.
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Abstract
The effects of short-term (7 days) administration of dichloroacetate (DCA) on carbohydrate and lipid metabolism in the Zucker obese and lean rat were investigated. Metabolic effects of the drug were more pronounced in the obese than in the lean rat. DCA decreased fasting blood glucose concentrations in both lean and obese rats, but more so in the fat animals, probably because of higher initial levels. The hypoglycemic action of DCA is likely attributable to a direct effect on liver and peripheral tissues and not to an indirect action caused by a decrease in the glucagon-to-insulin ratio because the drug induced just the opposite effect. DCA decreased plasma triglycerides (TG) and free fatty acids (FFA) in the hyperlipemic rats but not in lean rats. Intrahepatic triglyceride content diminished after drug treatment in fat rats, suggesting decreased hepatic TG synthesis. Hyperketonemia, induced in both lean and fat rats by DCA treatment, was also greater in the obese animal. This response was probably caused by accelerated hepatic ketone body production due to increased beta-oxidation, and not to enhance FFA substrate supply. These data demonstrate that DCA is capable of correcting many of the underlying abnormalities in carbohydrate and fat metabolism in the obese Zucker rat.
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Wade AJ. Glucose metabolism and recycling of radioactively labelled glucose in the Zucker genetically obese rat (fa/fa). Biochem J 1980; 186:161-8. [PMID: 7370005 PMCID: PMC1161515 DOI: 10.1042/bj1860161] [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: 01/24/2023]
Abstract
1. The glucose metabolism of conscious lean and obese rats of the Zucker strain was studied by using doubly labelled glucose ([6-3H,U-14C]glucose) given by intravenous injection as a single dose. Fed animals were used, allowing the study to be made in conditions favouring active lipogenesis. 2. At any given prior food intake (consumption during preceding 24 h), the irreversible glucose replacement rate, R0, was considerably higher in the growing obese rat (4-6 months old) when both of these variables were scaled in terms of the total body water of the animals. 3. When scaled in a similar way, the minimal mass of glucose (Mmin.) was also larger in the obese rats. The mean transit time, t, through the pool did not differ significantly between the two groups, but there was a tendency for this to be shorter in obese rats. 4. There was no difference in the proportion of 14C (derived from metabolized labelled glucose) that recycled as [14C]-glucose after passing through the pyruvate pool in the two groups of rats if the rate of recycling of radioactivity (Rc) was expressed as a percentage of R0.
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