1
|
Chaumontet C, Azzout-Marniche D, Blais A, Chalvon-Dermersay T, Nadkarni NA, Piedcoq J, Fromentin G, Tomé D, Even PC. Rats Prone to Obesity Under a High-Carbohydrate Diet have Increased Post-Meal CCK mRNA Expression and Characteristics of Rats Fed a High-Glycemic Index Diet. Front Nutr 2015. [PMID: 26217667 PMCID: PMC4497311 DOI: 10.3389/fnut.2015.00022] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
We previously reported that rats prone to obesity exhibit an exaggerated increase in glucose oxidation and an exaggerated decline in lipid oxidation under a low-fat high-carbohydrate (LF/HC) diet. The aim of the present study was to investigate the mechanisms involved in these metabolic dysregulations. After a 1-week adaptation to laboratory conditions, 48 male Wistar rats were fed a LF/HC diet for 3 weeks. During weeks 2 and 3, glucose tolerance tests (GTT), insulin tolerance tests (ITT), and meal tolerance tests (MTT) were performed to evaluate blood glucose, plasma, and insulin. Glucose and lipid oxidation were also assayed during the GTT. At the end of the study, body composition was measured in all the rats, and they were classified as carbohydrate resistant (CR) or carbohydrate sensitive (CS) according to their adiposity. Before sacrifice, 24 of the 48 rats received a calibrated LF/HC meal. Liver, muscle, and intestine tissue samples were taken to measure mRNA expression of key genes involved in glucose, lipid, and protein metabolism. ITT, GTT, and MTT showed that CS rats were neither insulin resistant nor glucose intolerant, but mRNA expression of cholecystokinin (CCK) in the duodenum was higher and that of CPT1, PPARα, and PGC1α in liver were lower than in CR rats. From these results, we make the hypothesis that in CS rats, CCK increased pancreatic secretion, which may favor a quicker absorption of carbohydrates and consequently induces an enhanced inhibition of lipid oxidation in the liver, leading to a progressive accumulation of fat preferentially in visceral deposits. Such a mechanism may explain why CS rats share many characteristics observed in rats fed a high-glycemic index diet.
Collapse
Affiliation(s)
- Catherine Chaumontet
- UMR914, CRNH-IdF, INRA, Nutrition Physiology and Ingestive Behavior , Paris , France
| | - Dalila Azzout-Marniche
- UMR914, CRNH-IdF, AgroParisTech, Nutrition Physiology and Ingestive Behavior , Paris , France
| | - Anne Blais
- UMR914, CRNH-IdF, INRA, Nutrition Physiology and Ingestive Behavior , Paris , France
| | | | - Nachiket A Nadkarni
- Chaire Aliment, Nutrition, Comportement Alimentaire (ANCA), AgroParisTech , Paris , France
| | - Julien Piedcoq
- UMR914, CRNH-IdF, INRA, Nutrition Physiology and Ingestive Behavior , Paris , France
| | - Gilles Fromentin
- UMR914, CRNH-IdF, INRA, Nutrition Physiology and Ingestive Behavior , Paris , France
| | - Daniel Tomé
- UMR914, CRNH-IdF, AgroParisTech, Nutrition Physiology and Ingestive Behavior , Paris , France
| | - Patrick C Even
- UMR914, CRNH-IdF, INRA, Nutrition Physiology and Ingestive Behavior , Paris , France
| |
Collapse
|
2
|
Méndez-Lucas A, Duarte J, Sunny NE, Satapati S, He T, Fu X, Bermúdez J, Burgess SC, Perales JC. PEPCK-M expression in mouse liver potentiates, not replaces, PEPCK-C mediated gluconeogenesis. J Hepatol 2013; 59:105-13. [PMID: 23466304 PMCID: PMC3910155 DOI: 10.1016/j.jhep.2013.02.020] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 02/15/2013] [Accepted: 02/23/2013] [Indexed: 12/04/2022]
Abstract
BACKGROUND & AIMS Hepatic gluconeogenesis helps maintain systemic energy homeostasis by compensating for discontinuities in nutrient supply. Liver-specific deletion of cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) abolishes gluconeogenesis from mitochondrial substrates, deregulates lipid metabolism and affects TCA cycle. While the mouse liver almost exclusively expresses PEPCK-C, humans equally present a mitochondrial isozyme (PEPCK-M). Despite clear relevance to human physiology, the role of PEPCK-M and its gluconeogenic potential remain unknown. Here, we test the significance of PEPCK-M in gluconeogenesis and TCA cycle function in liver-specific PEPCK-C knockout and WT mice. METHODS The effects of the overexpression of PEPCK-M were examined by a combination of tracer studies and molecular biology techniques. Partial PEPCK-C re-expression was used as a positive control. Metabolic fluxes were evaluated in isolated livers by NMR using (2)H and (13)C tracers. Gluconeogenic potential, together with metabolic profiling, was investigated in vivo and in primary hepatocytes. RESULTS PEPCK-M expression partially rescued defects in lipid metabolism, gluconeogenesis and TCA cycle function impaired by PEPCK-C deletion, while ∼10% re-expression of PEPCK-C normalized most parameters. When PEPCK-M was expressed in the presence of PEPCK-C, the mitochondrial isozyme amplified total gluconeogenic capacity, suggesting autonomous regulation of oxaloacetate to phosphoenolpyruvate fluxes by the individual isoforms. CONCLUSIONS We conclude that PEPCK-M has gluconeogenic potential per se, and cooperates with PEPCK-C to adjust gluconeogenic/TCA flux to changes in substrate or energy availability, hinting at a role in the regulation of glucose and lipid metabolism in the human liver.
Collapse
Affiliation(s)
- Andrés Méndez-Lucas
- Departament de Ciències Fisiològiques II, Universitat de Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain
| | - João Duarte
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390-8568, USA
| | - Nishanth E. Sunny
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390-8568, USA
| | - Santhosh Satapati
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390-8568, USA
| | - TianTeng He
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390-8568, USA
| | - Xiaorong Fu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390-8568, USA
| | - Jordi Bermúdez
- Departament de Ciències Fisiològiques II, Universitat de Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain
| | - Shawn C. Burgess
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390-8568, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-8568, USA
| | - Jose C. Perales
- Departament de Ciències Fisiològiques II, Universitat de Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain
| |
Collapse
|