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Sharma AK, Khandelwal R, Wolfrum C. Futile lipid cycling: from biochemistry to physiology. Nat Metab 2024; 6:808-824. [PMID: 38459186 DOI: 10.1038/s42255-024-01003-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 02/02/2024] [Indexed: 03/10/2024]
Abstract
In the healthy state, the fat stored in our body isn't just inert. Rather, it is dynamically mobilized to maintain an adequate concentration of fatty acids (FAs) in our bloodstream. Our body tends to produce excess FAs to ensure that the FA availability is not limiting. The surplus FAs are actively re-esterified into glycerides, initiating a cycle of breakdown and resynthesis of glycerides. This cycle consumes energy without generating a new product and is commonly referred to as the 'futile lipid cycle' or the glyceride/FA cycle. Contrary to the notion that it's a wasteful process, it turns out this cycle is crucial for systemic metabolic homeostasis. It acts as a control point in intra-adipocyte and inter-organ cross-talk, a metabolic rheostat, an energy sensor and a lipid diversifying mechanism. In this Review, we discuss the metabolic regulation and physiological implications of the glyceride/FA cycle and its mechanistic underpinnings.
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Affiliation(s)
- Anand Kumar Sharma
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
| | - Radhika Khandelwal
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland
| | - Christian Wolfrum
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
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2
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Yang H, Su M, Liu M, Sheng Y, Zhu L, Yang L, Mu R, Zou J, Liu X, Liu L. Hepatic retinaldehyde deficiency is involved in diabetes deterioration by enhancing PCK1- and G6PC-mediated gluconeogenesis. Acta Pharm Sin B 2023; 13:3728-3743. [PMID: 37719384 PMCID: PMC10501888 DOI: 10.1016/j.apsb.2023.06.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 03/14/2023] [Accepted: 05/06/2023] [Indexed: 09/19/2023] Open
Abstract
Type 2 diabetes (T2D) is often accompanied with an induction of retinaldehyde dehydrogenase 1 (RALDH1 or ALDH1A1) expression and a consequent decrease in hepatic retinaldehyde (Rald) levels. However, the role of hepatic Rald deficiency in T2D progression remains unclear. In this study, we demonstrated that reversing T2D-mediated hepatic Rald deficiency by Rald or citral treatments, or liver-specific Raldh1 silencing substantially lowered fasting glycemia levels, inhibited hepatic glucogenesis, and downregulated phosphoenolpyruvate carboxykinase 1 (PCK1) and glucose-6-phosphatase (G6PC) expression in diabetic db/db mice. Fasting glycemia and Pck1/G6pc mRNA expression levels were strongly negatively correlated with hepatic Rald levels, indicating the involvement of hepatic Rald depletion in T2D deterioration. A similar result that liver-specific Raldh1 silencing improved glucose metabolism was also observed in high-fat diet-fed mice. In primary human hepatocytes and oleic acid-treated HepG2 cells, Rald or Rald + RALDH1 silencing resulted in decreased glucose production and downregulated PCK1/G6PC mRNA and protein expression. Mechanistically, Rald downregulated direct repeat 1-mediated PCK1 and G6PC expression by antagonizing retinoid X receptor α, as confirmed by luciferase reporter assays and molecular docking. These results highlight the link between hepatic Rald deficiency, glucose dyshomeostasis, and the progression of T2D, whilst also suggesting RALDH1 as a potential therapeutic target for T2D.
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Affiliation(s)
- Hanyu Yang
- State Key Laboratory of Natural Medicines, Key Laboratory of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009, China
- Department of Pharmacology, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Mengxiang Su
- Department of Pharmaceutical Analysis, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Ming Liu
- Department of Pharmacology, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Yun Sheng
- Department of Pharmacology, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Liang Zhu
- Department of Pharmacology, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Lu Yang
- State Key Laboratory of Natural Medicines, Key Laboratory of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009, China
- Department of Pharmacology, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Ruijing Mu
- State Key Laboratory of Natural Medicines, Key Laboratory of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009, China
- Department of Pharmacology, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Jianjun Zou
- Department of Clinical Pharmacology, Nanjing First Hospital, Nanjing Medical University, Nanjing 210006, China
| | - Xiaodong Liu
- State Key Laboratory of Natural Medicines, Key Laboratory of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009, China
- Department of Pharmacology, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Li Liu
- State Key Laboratory of Natural Medicines, Key Laboratory of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009, China
- Department of Pharmacology, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
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Bagheripour F, Jeddi S, Kashfi K, Ghasemi A. Metabolic effects of L-citrulline in type 2 diabetes. Acta Physiol (Oxf) 2023; 237:e13937. [PMID: 36645144 DOI: 10.1111/apha.13937] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 01/01/2023] [Accepted: 01/10/2023] [Indexed: 01/17/2023]
Abstract
The prevalence of type 2 diabetes (T2D) is increasing worldwide. Decreased nitric oxide (NO) bioavailability is involved in the pathophysiology of T2D and its complications. L-citrulline (Cit), a precursor of NO production, has been suggested as a novel therapeutic agent for T2D. Available data from human and animal studies indicate that Cit supplementation in T2D increases circulating levels of Cit and L-arginine while decreasing circulating glucose and free fatty acids and improving dyslipidemia. The underlying mechanisms for these beneficial effects of Cit include increased insulin secretion from the pancreatic β cells, increased glucose uptake by the skeletal muscle, as well as increased lipolysis and β-oxidation, and decreased glyceroneogenesis in the adipose tissue. Thus, Cit has antihyperglycemic, antidyslipidemic, and antioxidant effects and has the potential to be used as a new therapeutic agent in the management of T2D. This review summarizes available literature from human and animal studies to explore the effects of Cit on metabolic parameters in T2D. It also discusses the possible mechanisms underlying Cit-induced improved metabolic parameters in T2D.
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Affiliation(s)
- Fatemeh Bagheripour
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Sajad Jeddi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Khosrow Kashfi
- Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, New York, USA
| | - Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Mal S, Dwivedi AR, Kumar V, Kumar N, Kumar B, Kumar V. Role of Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) in Different Disease States: Recent Updates. Curr Med Chem 2021; 28:3193-3215. [PMID: 32674727 DOI: 10.2174/0929867327666200716113136] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/12/2020] [Accepted: 06/21/2020] [Indexed: 11/22/2022]
Abstract
Peroxisome proliferator-activated receptor (PPAR), a ligand dependant transcription factor, is a member of the nuclear receptor superfamily. PPAR exists in three isoforms i.e. PPAR alpha (PPARα), PPAR beta (PPARβ), and PPAR gamma (PPARγ). These are multi-functional transcription factors and help in regulating inflammation, type 2 diabetes, lipid concentration in the body, metastasis, and tumor growth or angiogenesis. Activation of PPARγ causes inhibition of growth of cultured human breast, gastric, lung, prostate, and other cancer cells. PPARγ is mainly involved in fatty acid storage, glucose metabolism, and homeostasis and adipogenesis regulation. A large number of natural and synthetic ligands bind to PPARγ and modulate its activity. Ligands such as thiazolidinedione, troglitazone, rosiglitazone, pioglitazone effectively bind to PPARγ; however, most of these were found to display severe side effects such as hepatotoxicity, weight gain, cardiovascular complications and bladder tumor. Now the focus is shifted towards the development of dual-acting or pan PPAR ligands. The current review article describes the functions and role of PPARγ in various disease states. In addition, recently reported PPARγ ligands and pan PPAR ligands were discussed in detail. It is envisaged that the present review article may help in the development of potent PPAR ligands with no or minimal side effects.
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Affiliation(s)
- Suvadeep Mal
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Bathinda 151001, Punjab, India
| | - Ashish Ranjan Dwivedi
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Bathinda 151001, Punjab, India
| | - Vijay Kumar
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Bathinda 151001, Punjab, India
| | - Naveen Kumar
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Bathinda 151001, Punjab, India
| | - Bhupinder Kumar
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Bathinda 151001, Punjab, India
| | - Vinod Kumar
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Bathinda 151001, Punjab, India
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Yu S, Meng S, Xiang M, Ma H. Phosphoenolpyruvate carboxykinase in cell metabolism: Roles and mechanisms beyond gluconeogenesis. Mol Metab 2021; 53:101257. [PMID: 34020084 PMCID: PMC8190478 DOI: 10.1016/j.molmet.2021.101257] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 05/12/2021] [Accepted: 05/13/2021] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Phosphoenolpyruvate carboxykinase (PCK) has been almost exclusively recognized as a critical enzyme in gluconeogenesis, especially in the liver and kidney. Accumulating evidence has shown that the enhanced activity of PCK leads to increased glucose output and exacerbation of diabetes, whereas the defects of PCK result in lethal hypoglycemia. Genetic mutations or polymorphisms are reported to be related to the onset and progression of diabetes in humans. SCOPE OF REVIEW Recent studies revealed that the PCK pathway is more complex than just gluconeogenesis, depending on the health or disease condition. Dysregulation of PCK may contribute to the development of obesity, cardiac hypertrophy, stroke, and cancer. Moreover, a regulatory network with multiple layers, from epigenetic regulation, transcription regulation, to posttranscription regulation, precisely tunes the expression of PCK. Deciphering the molecular basis that regulates PCK may pave the way for developing practical strategies to treat metabolic dysfunction. MAJOR CONCLUSIONS In this review, we summarize the metabolic and non-metabolic roles of the PCK enzyme in cells, especially beyond gluconeogenesis. We highlight the distinct functions of PCK isoforms (PCK1 and PCK2), depict a detailed network regulating PCK's expression, and discuss its clinical relevance. We also discuss the therapeutic potential targeting PCK and the future direction that is highly in need to better understand PCK-mediated signaling under diverse conditions.
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Affiliation(s)
- Shuo Yu
- Anesthesiology Department, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China
| | - Simin Meng
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China
| | - Meixiang Xiang
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China.
| | - Hong Ma
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China.
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Chen X, Zhu W, Du Y, Liu X, Geng Z. Genetic Parameters for Yolk Cholesterol and Transcriptional Evidence Indicate a Role of Lipoprotein Lipase in the Cholesterol Metabolism of the Chinese Wenchang Chicken. Front Genet 2019; 10:902. [PMID: 31632438 PMCID: PMC6786094 DOI: 10.3389/fgene.2019.00902] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 08/26/2019] [Indexed: 11/13/2022] Open
Abstract
The yolk cholesterol has been reported to affect egg quality and breeding performance in chickens. However, the genetic parameters and molecular mechanisms regulating yolk cholesterol remain largely unknown. Here, we used the Wenchang chicken, a Chinese indigenous breed with a complete pedigree, as an experimental model, and we examined 24 sire families (24 males and 240 females) and their 362 daughters. First, egg quality and yolk cholesterol content were determined in 40-week-old chickens of two consecutive generations, and the heritability of these parameters was analyzed using the half-sib correlation method. Among first-generation individuals, the egg weight, egg shape index, shell strength, shell thickness, yolk weight, egg white height, Haugh unit, and cholesterol content were 45.36 ± 4.44 g, 0.81 ± 0.12, 3.07 ± 0.92 kg/cm2, 0.340 ± 0.032 mm, 15.57 ± 1.64 g, 3.36 ± 1.15 mm, 58.70 ± 12.33, and 274.3 ± 36.73 mg/egg, respectively. When these indexes were compared to those of the following generation, no statistically significant difference was detected. Although yolk cholesterol content was not associated with egg quality in females, an increase in yolk cholesterol content was correlated with increased yolk weight and albumin height in sire families (p < 0.05). Moreover, the heritability estimates for the yolk cholesterol content were 0.328 and 0.530 in female and sire families, respectively. Therefore, the yolk cholesterol content was more strongly associated with the sire family. Next, chickens with low and high yolk cholesterol contents were selected for follicular membrane collection. Total RNA was extracted from these samples and used as a template for transcriptional sequencing. In total, 375 down- and 578 upregulated genes were identified by comparing the RNA sequencing data of chickens with high and low yolk cholesterol contents. Furthermore, Gene Ontology term and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses indicated the involvement of energy metabolism and immune-related pathways in yolk cholesterol deposition. Several genes participating in the regulation of the yolk cholesterol content were located on the sex chromosome Z, among which lipoprotein lipase (LPL) was associated with the peroxisome proliferator-activated receptor signaling pathway and the Gene Ontology term cellular component. Collectively, our data suggested that the ovarian steroidogenesis pathway and the downregulation of LPL played critical roles in the regulation of yolk cholesterol content.
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Affiliation(s)
- Xingyong Chen
- College of Animal Science and Technology, Anhui Agricultural University, Hefei, China.,Anhui Province Key Laboratory of Local Livestock and Poultry Genetic Resource Conservation and Bio-breeding, Anhui Agricultural University, Hefei, China
| | - Wenjun Zhu
- College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Yeye Du
- College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Xue Liu
- College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Zhaoyu Geng
- College of Animal Science and Technology, Anhui Agricultural University, Hefei, China.,Anhui Province Key Laboratory of Local Livestock and Poultry Genetic Resource Conservation and Bio-breeding, Anhui Agricultural University, Hefei, China
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Latorre P, Varona L, Burgos C, Carrodeguas JA, López-Buesa P. O-GlcNAcylation mediates the control of cytosolic phosphoenolpyruvate carboxykinase activity via Pgc1α. PLoS One 2017; 12:e0179988. [PMID: 28644880 PMCID: PMC5482481 DOI: 10.1371/journal.pone.0179988] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 06/07/2017] [Indexed: 11/19/2022] Open
Abstract
PGC1α is a coactivator of many transcription factors and cytosolic phosphoenolpyruvate carboxykinase (PCK1) is a key enzyme for gluconeogenesis. PGC1α interacts with the transcription factor PPARγ to stimulate PCK1 expression and thus de novo glucose synthesis. These proteins are not only important for central energy metabolism but also for supplying intermediates for other metabolic pathways, including lipidogenesis and protein synthesis and might therefore be important factors in the ethiopathogenesis of metabolic disorders like diabetes but also in other pathologies like cancer. Since polymorphisms in these proteins have been related to some phenotypic traits in animals like pigs and PGC1α G482S polymorphism increases fat deposition in humans, we have investigated the molecular basis of such effects focusing on a commonly studied polymorphism in pig Pgc1α, which changes a cysteine at position 430 (WT) of the protein to a serine (C430S). Biochemical analyses show that Pgc1α WT stimulates higher expression of human PCK1 in HEK293T and HepG2 cells. Paradoxically, Pgc1α WT is less stable than Pgc1α p.C430S in HEK293T cells. However, the study of different post-translational modifications shows a higher O-GlcNAcylation level of Pgc1α p.C430S. This higher O-GlcNAcylation level significantly decreases the interaction between Pgc1α and PPARγ demonstrating the importance of post-translational glycosylation of PGC1α in the regulation of PCK1 activity. This, furthermore, could explain at least in part the observed epistatic effects between PGC1α and PCK1 in pigs.
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Affiliation(s)
- Pedro Latorre
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain
- Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), BIFIIQFR (CSIC) Joint Unit, Universidad de Zaragoza, Zaragoza, Spain
| | - Luis Varona
- Departamento de Anatomía, Embriología y Genética, Universidad de Zaragoza, Zaragoza, Spain
- Instituto Agroalimentario de Aragón (IA2), Zaragoza, Spain
| | - Carmen Burgos
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain
- Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), BIFIIQFR (CSIC) Joint Unit, Universidad de Zaragoza, Zaragoza, Spain
| | - José A. Carrodeguas
- Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), BIFIIQFR (CSIC) Joint Unit, Universidad de Zaragoza, Zaragoza, Spain
- Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain
- IIS Aragón, Zaragoza, Spain
| | - Pascual López-Buesa
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain
- Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), BIFIIQFR (CSIC) Joint Unit, Universidad de Zaragoza, Zaragoza, Spain
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Forest C, Joffin N, Jaubert AM, Noirez P. What induces watts in WAT? Adipocyte 2016; 5:136-52. [PMID: 27386158 PMCID: PMC4916896 DOI: 10.1080/21623945.2016.1187345] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 04/26/2016] [Accepted: 04/27/2016] [Indexed: 01/05/2023] Open
Abstract
Excess calories stored in white adipose tissue (WAT) could be reduced either through the activation of brown adipose tissue (BAT) or the development of brown-like cells ("beige" or "brite") in WAT, a process named "browning." Calorie dissipation in brown and beige adipocytes might rely on the induction of uncoupling protein 1 (UCP1), which is absent in white fat cells. Any increase in UCP1 is commonly considered as the trademark of energy expenditure. The intracellular events involved in the recruitment process of beige precursors were extensively studied lately, as were the effectors, hormones, cytokines, nutrients and drugs able to modulate the route of browning and theoretically affect fat mass in rodents and in humans. The aim of this review is to update the characterization of the extracellular effectors that induce UCP1 in WAT and potentially provoke calorie dissipation. The potential influence of metabolic cycling in energy expenditure is also questioned.
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Affiliation(s)
- Claude Forest
- Institut National de la Santé et de la Recherche Médicale UMR-S 1124, Faculté des Sciences Fondamentales et Biomédicales, Pharmacologie Toxicologie et Signalisation Cellulaire, Université Paris Descartes, Paris, France
- Institut de Recherche Biomédicale et d'Epidémiologie du Sport, Université Paris Descartes, Paris, France
| | - Nolwenn Joffin
- Institut National de la Santé et de la Recherche Médicale UMR-S 1124, Faculté des Sciences Fondamentales et Biomédicales, Pharmacologie Toxicologie et Signalisation Cellulaire, Université Paris Descartes, Paris, France
- Institut de Recherche Biomédicale et d'Epidémiologie du Sport, Université Paris Descartes, Paris, France
| | - Anne-Marie Jaubert
- Institut National de la Santé et de la Recherche Médicale UMR-S 1124, Faculté des Sciences Fondamentales et Biomédicales, Pharmacologie Toxicologie et Signalisation Cellulaire, Université Paris Descartes, Paris, France
| | - Philippe Noirez
- Institut de Recherche Biomédicale et d'Epidémiologie du Sport, Université Paris Descartes, Paris, France
- Faculté des Sciences et Techniques des Activités Physiques et Sportives, Université Paris Descartes, Paris, France
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Nuotio-Antar AM, Poungvarin N, Li M, Schupp M, Mohammad M, Gerard S, Zou F, Chan L. FABP4-Cre Mediated Expression of Constitutively Active ChREBP Protects Against Obesity, Fatty Liver, and Insulin Resistance. Endocrinology 2015; 156:4020-32. [PMID: 26248218 PMCID: PMC4606753 DOI: 10.1210/en.2015-1210] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Carbohydrate response element binding protein (ChREBP) regulates cellular glucose and lipid homeostasis. Although ChREBP is highly expressed in many key metabolic tissues, the role of ChREBP in most of those tissues and the consequent effects on whole-body glucose and lipid metabolism are not well understood. Therefore, we generated a transgenic mouse that overexpresses a constitutively active ChREBP isoform under the control of the fatty acid binding protein 4-Cre-driven promoter (FaChOX). Weight gain was blunted in male, but not female, FaChOX mice when placed on either a normal chow diet or an obesogenic Western diet. Respiratory exchange ratios were increased in Western diet-fed FaChOX mice, indicating a shift in whole-body substrate use favoring carbohydrate metabolism. Western diet-fed FaChOX mice showed improved insulin sensitivity and glucose tolerance in comparison with controls. Hepatic triglyceride content was reduced in Western diet-fed FaChOX mice in comparison with controls, suggesting protection from fatty liver. Epididymal adipose tissue exhibited differential expression of genes involved in differentiation, browning, metabolism, lipid homeostasis, and inflammation between Western diet-fed FaChOX mice and controls. Our findings support a role for ChREBP in modulating adipocyte differentiation and adipose tissue metabolism and inflammation as well as consequent risks for obesity and insulin resistance.
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Affiliation(s)
- Alli M Nuotio-Antar
- Diabetes and Endocrinology Research Center (A.M.N.-A., N.P., M.L., L.C.), Department of Medicine, and Children's Nutrition Research Center (A.M.N.-A., M.M., S.G., F.Z.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; and Charité University School of Medicine (M.S.), Institute of Pharmacology, Center for Cardiovascular Research, 10115 Berlin, Germany
| | - Naravat Poungvarin
- Diabetes and Endocrinology Research Center (A.M.N.-A., N.P., M.L., L.C.), Department of Medicine, and Children's Nutrition Research Center (A.M.N.-A., M.M., S.G., F.Z.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; and Charité University School of Medicine (M.S.), Institute of Pharmacology, Center for Cardiovascular Research, 10115 Berlin, Germany
| | - Ming Li
- Diabetes and Endocrinology Research Center (A.M.N.-A., N.P., M.L., L.C.), Department of Medicine, and Children's Nutrition Research Center (A.M.N.-A., M.M., S.G., F.Z.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; and Charité University School of Medicine (M.S.), Institute of Pharmacology, Center for Cardiovascular Research, 10115 Berlin, Germany
| | - Michael Schupp
- Diabetes and Endocrinology Research Center (A.M.N.-A., N.P., M.L., L.C.), Department of Medicine, and Children's Nutrition Research Center (A.M.N.-A., M.M., S.G., F.Z.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; and Charité University School of Medicine (M.S.), Institute of Pharmacology, Center for Cardiovascular Research, 10115 Berlin, Germany
| | - Mahmoud Mohammad
- Diabetes and Endocrinology Research Center (A.M.N.-A., N.P., M.L., L.C.), Department of Medicine, and Children's Nutrition Research Center (A.M.N.-A., M.M., S.G., F.Z.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; and Charité University School of Medicine (M.S.), Institute of Pharmacology, Center for Cardiovascular Research, 10115 Berlin, Germany
| | - Sarah Gerard
- Diabetes and Endocrinology Research Center (A.M.N.-A., N.P., M.L., L.C.), Department of Medicine, and Children's Nutrition Research Center (A.M.N.-A., M.M., S.G., F.Z.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; and Charité University School of Medicine (M.S.), Institute of Pharmacology, Center for Cardiovascular Research, 10115 Berlin, Germany
| | - Fang Zou
- Diabetes and Endocrinology Research Center (A.M.N.-A., N.P., M.L., L.C.), Department of Medicine, and Children's Nutrition Research Center (A.M.N.-A., M.M., S.G., F.Z.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; and Charité University School of Medicine (M.S.), Institute of Pharmacology, Center for Cardiovascular Research, 10115 Berlin, Germany
| | - Lawrence Chan
- Diabetes and Endocrinology Research Center (A.M.N.-A., N.P., M.L., L.C.), Department of Medicine, and Children's Nutrition Research Center (A.M.N.-A., M.M., S.G., F.Z.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; and Charité University School of Medicine (M.S.), Institute of Pharmacology, Center for Cardiovascular Research, 10115 Berlin, Germany
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10
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Joffin N, Jaubert AM, Bamba J, Barouki R, Noirez P, Forest C. Acute induction of uncoupling protein 1 by citrulline in cultured explants of white adipose tissue from lean and high-fat-diet-fed rats. Adipocyte 2015; 4:129-34. [PMID: 26167416 PMCID: PMC4497294 DOI: 10.4161/21623945.2014.989748] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 11/13/2014] [Accepted: 11/14/2014] [Indexed: 01/14/2023] Open
Abstract
A diet enriched with citrulline (CIT) reduces white adipose tissue (WAT) mass. We recently showed that CIT stimulated β-oxidation in rat WAT explants from young (2-4 months) but not old (25 months) rats. Here we show that both in old rats and high-fat-diet-fed young rats, uncoupling protein one (UCP1) mRNA and protein expressions were weaker than those in young control rats. Selectively in WAT from young rats, a 24h CIT treatment up-regulated expressions of UCP1, peroxisome proliferator-activated receptor-α (PPARα), PPARγ-coactivator-1-α and mitochondrial-transcription-factor-A whereas it down-regulated PPARγ2 gene expression, whatever the diet. These results suggest that CIT induces a new metabolic status in WAT, with increased β-oxidation and uncoupling of respiratory chain, resulting in energy expenditure that favors fat mass reduction.
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Key Words
- ARG, arginine
- ASL, argininosuccinate lyase
- ASS, argininosuccinate synthase
- BSA, bovine serum albumin
- CD, control diet
- CIT, citrulline
- CPT1-b, carnitine palmitoyl transferase 1-b
- EPI, epididymal
- HFD, high-fat-diet
- KREBS, Krebs Ringer Buffer Saline
- NEFA, non-esterified fatty acids
- NO, nitric oxide
- NOS, nitric oxide synthase
- PEPCK-C, cytosolic phosphoenolpyruvate carboxykinase
- PGC-1α, peroxisome proliferator-activated receptor gamma co-activator 1α
- PKA, protein kinase A
- PPAR, peroxisome proliferator-activated receptor
- RET, retroperitoneal
- TFAM, mitochondrial transcription factor A
- UCP1
- VLCAD, very long chain acyl-CoA dehydrogenase
- WAT, white adipose tissue
- adipose tissue
- browning
- citrulline
- fatty acids
- obesity
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Joffin N, Jaubert AM, Durant S, Bastin J, De Bandt JP, Cynober L, Moinard C, Coumoul X, Forest C, Noirez P. Citrulline reduces glyceroneogenesis and induces fatty acid release in visceral adipose tissue from overweight rats. Mol Nutr Food Res 2014; 58:2320-30. [PMID: 25271764 DOI: 10.1002/mnfr.201400507] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/15/2014] [Accepted: 09/21/2014] [Indexed: 12/21/2022]
Abstract
SCOPE High-fat diet (HFD) increases visceral adipose tissue (AT). Our aim was to evaluate whether citrulline (CIT) affected nonesterified fatty acid (NEFA) metabolism in AT from HFD-fed rats. METHODS AND RESULTS Rats were fed for 8 weeks with either a control diet (CD) or HFD. Retroperitoneal AT explants were exposed to 2.5 mmol/L CIT for 24 h. We analyzed lipolysis, beta-oxidation, glyceroneogenesis, and the expression of the key associated enzymes. CIT doubled NEFA release selectively in HFD AT. Phosphorylation of hormone-sensitive lipase was upregulated 50 and 100% by CIT in CD and HFD AT, respectively. Under CIT, beta-oxidation increased similarly whatever the diet, whereas glyceroneogenesis, which permits NEFA re-esterification, was downregulated 50 and 80% in CD and HFD AT, respectively. In the latter, the important decrease in re-esterification probably explains the rise of NEFA release. A pretreatment with the nitric oxide synthase inhibitor N ω-nitro-l-arginine methyl ester abolished CIT effects. CONCLUSION These results demonstrate direct lipolytic and antiglyceroneogenic effects of CIT on CD and HFD AT. The selective CIT-mediated NEFA release from HFD AT was probably the consequence of the drastic decrease in glyceroneogenesis and nitric oxide was a mediator of CIT effects. These results provide evidence for a direct action of CIT on AT to reduce overweight.
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Affiliation(s)
- Nolwenn Joffin
- Université Paris Descartes, Sorbonne Paris Cité, France; Institut National de la Santé et de la Recherche Médicale UMR-S 1124, Faculté des Sciences Fondamentales et Biomédicales, Pharmacologie Toxicologie et Signalisation Cellulaire, Paris, France
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Liu BH, Lin YY, Wang YC, Huang CW, Chen CC, Wu SC, Mersmann HJ, Cheng WTK, Ding ST. Porcine adiponectin receptor 1 transgene resists high-fat/sucrose diet-induced weight gain, hepatosteatosis and insulin resistance in mice. Exp Anim 2014; 62:347-60. [PMID: 24172199 PMCID: PMC4160961 DOI: 10.1538/expanim.62.347] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Adiponectin and its receptors have been demonstrated to play important roles in regulating glucose and lipid metabolism in mice. Obesity, type II diabetes and cardiovascular disease are highly correlated with down-regulated adiponectin signaling. In this study, we generated mice overexpressing the porcine Adipor1 transgene (pAdipor1) to study its beneficial effects in metabolic syndromes as expressed in diet-induced obesity, hepatosteatosis and insulin resistance. Wild-type (WT) and pAdipor1 transgenic mice were fed ad libitum with a standard chow diet (Chow) or a high-fat/sucrose diet (HFSD) for 24 weeks, beginning at 6 to 7 weeks of age. There were 12 mice per genetic/diet/sex group. When challenged with HFSD to induce obesity, the pAdipor1 transgenic mice resisted development of weight gain, hepatosteatosis and insulin resistance. These mice had lowered plasma adiponectin, triglyceride and glycerol concentrations compared to WT mice. Moreover, we found that (indicated by mRNA levels) fatty acid oxidation was enhanced in skeletal muscle and adipose tissue, and liver lipogenesis was inhibited. The pAdipor1 transgene also restored HFSD-reduced phosphoenolpyruvate carboxykinase 1 (Pck1) and glucose transporter 4 mRNA in the adipose tissues, implying that the increased Pck1 may promote glyceroneogenesis to reduce glucose intolerance and thus activate the flux of glyceride-glycerol to resist diet-induced weight gain in the adipose tissues. Taken together, we demonstrated that pAdipor1 can prevent diet-induced weight gain and insulin resistance. Our findings may provide potential therapeutic strategies for treating metabolic syndromes and obesity, such as treatment with an ADIPOR1 agonist or activation of Adipor1 downstream targets.
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Affiliation(s)
- Bing-Hsien Liu
- Department of Animal Science and Technology, National Taiwan University, No. 50, Ln. 155, Sec. 3, Keelung Rd., Da'an Dist., Taipei City 106, Taiwan
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Guan HP, Chen G. Factors affecting insulin-regulated hepatic gene expression. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:165-215. [PMID: 24373238 DOI: 10.1016/b978-0-12-800101-1.00006-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Obesity has become a major concern of public health. A common feature of obesity and related metabolic disorders such as noninsulin-dependent diabetes mellitus is insulin resistance, wherein a given amount of insulin produces less than normal physiological responses. Insulin controls hepatic glucose and fatty acid metabolism, at least in part, via the regulation of gene expression. When the liver is insulin-sensitive, insulin can stimulate the expression of genes for fatty acid synthesis and suppress those for gluconeogenesis. When the liver becomes insulin-resistant, the insulin-mediated suppression of gluconeogenic gene expression is lost, whereas the induction of fatty acid synthetic gene expression remains intact. In the past two decades, the mechanisms of insulin-regulated hepatic gene expression have been studied extensively and many components of insulin signal transduction pathways have been identified. Factors that alter these pathways, and the insulin-regulated hepatic gene expression, have been revealed and the underlying mechanisms have been proposed. This chapter summarizes the recent progresses in our understanding of the effects of dietary factors, drugs, bioactive compounds, hormones, and cytokines on insulin-regulated hepatic gene expression. Given the large amount of information and progresses regarding the roles of insulin, this chapter focuses on findings in the liver and hepatocytes and not those described for other tissues and cells. Typical insulin-regulated hepatic genes, such as insulin-induced glucokinase and sterol regulatory element-binding protein-1c and insulin-suppressed cytosolic phosphoenolpyruvate carboxyl kinase and insulin-like growth factor-binding protein 1, are used as examples to discuss the mechanisms such as insulin regulatory element-mediated transcriptional regulation. We also propose the potential mechanisms by which these factors affect insulin-regulated hepatic gene expression and discuss potential future directions of the area of research.
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Affiliation(s)
- Hong-Ping Guan
- Department of Diabetes, Merck Research Laboratories, Kenilworth, New Jersey, USA
| | - Guoxun Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, Tennessee, USA
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Jung UJ, Park YB, Kim SR, Choi MS. Supplementation of persimmon leaf ameliorates hyperglycemia, dyslipidemia and hepatic fat accumulation in type 2 diabetic mice. PLoS One 2012; 7:e49030. [PMID: 23145054 PMCID: PMC3493507 DOI: 10.1371/journal.pone.0049030] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 10/03/2012] [Indexed: 01/31/2023] Open
Abstract
Persimmon Leaf (PL), commonly consumed as herbal tea and traditional medicines, contains a variety of compounds that exert antioxidant, α-amylase and α-glucosidase inhibitory activity. However, little is known about the in vivo effects and underlying mechanisms of PL on hyperglycemia, hyperlipidemia and hepatic steatosis in type 2 diabetes. Powered PL (5%, w/w) was supplemented with a normal diet to C57BL/KsJ-db/db mice for 5 weeks. PL decreased blood glucose, HOMA-IR, plasma triglyceride and total cholesterol levels, as well as liver weight, hepatic lipid droplets, triglycerides and cholesterol contents, while increasing plasma HDL-cholesterol and adiponectin levels. The anti-hyperglycemic effect was linked to decreased activity of gluconeogenic enzymes as well as increased glycogen content, glucokinase activity and its mRNA level in the liver. PL also led to a decrease in lipogenic transcriptional factor PPARγ as well as gene expression and activity of enzymes involved in lipogenesis, with a simultaneous increase in fecal lipids, which are seemingly attributable to the improved hyperlipidemia and hepatic steatosis and decreased hepatic fatty acid oxidation. Furthermore, PL ameliorated plasma and hepatic oxidative stress. Supplementation with PL may be an effective dietary strategy to improve type 2 diabetes accompanied by dyslipidemia and hepatic steatosis by partly modulating the activity or gene expression of enzymes related to antioxidant, glucose and lipid homeostasis.
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Affiliation(s)
- Un Ju Jung
- Department of Food Science and Nutrition, Kyungpook National University, Daegu, Republic of Korea
| | - Yong Bok Park
- School of Life Sciences and Biotechnology, Kyungpook National University, Daegu, Republic of Korea
| | - Sang Ryong Kim
- School of Life Sciences and Biotechnology, Kyungpook National University, Daegu, Republic of Korea
- Brain Science and Engineering Institute, Kyungpook National University, Daegu, Republic of Korea
| | - Myung-Sook Choi
- Department of Food Science and Nutrition, Kyungpook National University, Daegu, Republic of Korea
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Niang F, Benelli C, Ribière C, Collinet M, Mehebik-Mojaat N, Penot G, Forest C, Jaubert AM. Leptin induces nitric oxide-mediated inhibition of lipolysis and glyceroneogenesis in rat white adipose tissue. J Nutr 2011; 141:4-9. [PMID: 21068181 DOI: 10.3945/jn.110.125765] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Leptin is secreted by white adipose tissue (WAT) and induces lipolysis and nonesterified fatty acid (NEFA) oxidation. During lipolysis, NEFA efflux is the result of triglyceride breakdown, NEFA oxidation, and re-esterification via glyceroneogenesis. Leptin's effects on glyceroneogenesis remain unexplored. We investigated the effect of a long-term treatment with leptin at a physiological concentration (10 μg/L) on lipolysis and glyceroneogenesis in WAT explants and analyzed the underlying mechanisms. Exposure of rat WAT explants to leptin for 2 h resulted in increased NEFA and glycerol efflux. However, a longer treatment with leptin (18 h) did not affect NEFA release and reduced glycerol output. RT-qPCR showed that leptin significantly downregulated the hormone-sensitive lipase (HSL), cytosolic phosphoenolpyruvate carboxykinase (Pck1), and PPARγ genes. In agreement with its effect on mRNA, leptin also decreased the levels of PEPCK-C and HSL proteins. Glyceroneogenesis, monitored by [1-(14) C] pyruvate incorporation into lipids, was reduced. Because leptin increases nitric oxide (NO) production in adipocytes, we explored the role of NO in the leptin signaling pathway. Pretreatment of explants with the NO synthase inhibitor Nω-nitro-l-arginine methyl ester eliminated the effect of leptin on lipolysis, glyceroneogenesis, and expression of the HSL, Pck1, and PPARγ genes. The NO donor S-nitroso-N-acetyl-DL penicillamine mimicked leptin effects, thus demonstrating the role of NO in these pathways. The inverse time-dependent action of leptin on WAT is consistent with a process that limits NEFA re-esterification and energy storage while reducing glycerol release, thus preventing hypertriglyceridemia.
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Affiliation(s)
- Fatoumata Niang
- Institut National de la Santé et de la Recherche Médicale UMR-S 747, Paris, France
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Nye C, Kim J, Kalhan SC, Hanson RW. Reassessing triglyceride synthesis in adipose tissue. Trends Endocrinol Metab 2008; 19:356-61. [PMID: 18929494 DOI: 10.1016/j.tem.2008.08.003] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Revised: 08/11/2008] [Accepted: 08/12/2008] [Indexed: 10/21/2022]
Abstract
The synthesis and breakdown of triglycerides in adipose tissue and muscle is a crucial element of energy metabolism because it ensures that adequate fuel is available during starvation. Triglyceride turnover determines the availability of fatty acids for utilization by mammalian tissues, and any dysfunction in this process can lead to alterations in glucose metabolism, insulin resistance and type 2 diabetes. Our understanding of the reactions involved in triglyceride synthesis is currently being reassessed, primarily because of the recently identified role that re-esterification of fatty acids plays in triglyceride deposition and, thus, in controlling fatty-acid availability. Here, we review recent information on triglyceride synthesis and introduce the pathway of glyceroneogenesis as an important and highly regulated source of glyceride-glycerol in adipose tissue.
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Affiliation(s)
- Colleen Nye
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106-3549, USA
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Abstract
OBJECTIVES The insulin-sensitizing effects of thiazolidinediones are believed to depend at least in part on reductions in circulating levels of nonesterified fatty acids (NEFA). The mechanisms that mediate the reductions in NEFA are not fully understood and could involve reductions in adipose tissue lipolysis, increases in glyceroneogenesis and NEFA reesterification in triglycerides in adipose tissue and increases in NEFA metabolism by oxidative tissues. METHODS In a congenic strain of spontaneously hypertensive rats that fed a high-sucrose diet to promote features of the metabolic syndrome, we studied the effects of chronic pioglitazone treatment over 4 months on adipose tissue lipolysis and NEFA metabolism. RESULTS We observed significant increases in basal and adrenaline-stimulated NEFA and glycerol release, and near-total suppression of NEFA reesterification in epididymal adipose tissue isolated from rats chronically treated with pioglitazone. However, pioglitazone-treated rats also exhibited significant increases in mitochondrial DNA levels in adipose tissue (3.2-fold increase, P=0.001) and potentially greater sensitivity to the antilipolytic effects of insulin than untreated controls. In addition, chronic pioglitazone treatment was associated with increased palmitate oxidation in soleus muscle, reduced fasting levels of serum NEFA and triglycerides, as well as reduced serum levels of insulin and increased serum levels of adiponectin. CONCLUSIONS Despite suppressing NEFA reesterification and increasing basal and adrenaline-stimulated lipolysis, chronic pioglitazone treatment may decrease circulating NEFA levels in part by increasing adipose tissue sensitivity to the antilipolytic effects of insulin and by enhancing NEFA oxidation in skeletal muscle.
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18
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Cadoudal T, Distel E, Durant S, Fouque F, Blouin JM, Collinet M, Bortoli S, Forest C, Benelli C. Pyruvate dehydrogenase kinase 4: regulation by thiazolidinediones and implication in glyceroneogenesis in adipose tissue. Diabetes 2008; 57:2272-9. [PMID: 18519799 PMCID: PMC2518477 DOI: 10.2337/db08-0477] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Pyruvate dehydrogenase complex (PDC) serves as the metabolic switch between glucose and fatty acid utilization. PDC activity is inhibited by PDC kinase (PDK). PDC shares the same substrate, i.e., pyruvate, as glyceroneogenesis, a pathway controlling fatty acid release from white adipose tissue (WAT). Thiazolidinediones activate glyceroneogenesis. We studied the regulation by rosiglitazone of PDK2 and PDK4 isoforms and tested the hypothesis that glyceroneogenesis could be controlled by PDK. RESEARCH DESIGN AND METHODS Rosiglitazone was administered to Zucker fa/fa rats, and then PDK4 and PDK2 mRNAs were examined in subcutaneous, periepididymal, and retroperitoneal WAT, liver, and muscle by real-time RT-PCR. Cultured WAT explants from humans and rats and 3T3-F442A adipocytes were rosiglitazone-treated before analyses of PDK2 and PDK4 mRNA and protein. Small interfering RNA (siRNA) was transfected by electroporation. Glyceroneogenesis was determined using [1-(14)C]pyruvate incorporation into lipids. RESULTS Rosiglitazone increased PDK4 mRNA in all WAT depots but not in liver and muscle. PDK2 transcript was not affected. This isoform selectivity was also found in ex vivo-treated explants. In 3T3-F442A adipocytes, Pdk4 expression was strongly and selectively induced by rosiglitazone in a direct and transcriptional manner, with a concentration required for half-maximal effect at 1 nmol/l. The use of dichloroacetic acid or leelamine, two PDK inhibitors, or a specific PDK4 siRNA demonstrated that PDK4 participated in glyceroneogenesis, therefore altering nonesterified fatty acid release in both basal and rosiglitazone-activated conditions. CONCLUSIONS These data show that PDK4 upregulation in adipocytes participates in the hypolipidemic effect of thiazolidinediones through modulation of glyceroneogenesis.
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Affiliation(s)
- Thomas Cadoudal
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche-S 747, Université Paris Descartes, Centre Universitaire des Saints-Pères, Paris, France
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Cadoudal T, Fouque F, Benelli C, Forest C. [Glyceroneogenesis and PEPCK-C: pharmacological targets in type 2 diabetes]. Med Sci (Paris) 2008; 24:407-13. [PMID: 18405640 DOI: 10.1051/medsci/2008244407] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Obesity is a major risk factor for insulin resistance and type 2 diabetes. The link between hypertrophied adipose tissue and this pathology is thought to be non-esterified fatty acids (NEFA) arising from adipocyte lipolysis. Sustained increase in plasma NEFA induces insulin resistance. In adipocytes, a significant part of lipolytic NEFA is re-esterified to triacylglycerol. Re-esterification requires glycerol-3-phosphate which, during fasting, is synthesized from lactate, pyruvate or certain amino acids in a metabolic pathway named glyceroneogenesis. The key enzyme in this pathway is the cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C). In this review, we postulate that thiazolidinediones exert their hypolipidemic and antidiabetic effects in adipose tissue at least in part through a rapid and selective induction of PEPCK-C gene transcription leading to increased PEPCK-C and glyceroneogenesis. Subsequent fatty acid re-esterification participates in the reduction in blood NEFA and insulin resistance.
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Affiliation(s)
- Thomas Cadoudal
- Inserm UMR-S 747 ; Université Paris Descartes, Centre universitaire des Saints-Pères, 45, rue des Saints-Pères, 75006 Paris, France
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Cadoudal T, Glorian M, Massias A, Fouque F, Forest C, Benelli C. Retinoids upregulate phosphoenolpyruvate carboxykinase and glyceroneogenesis in human and rodent adipocytes. J Nutr 2008; 138:1004-9. [PMID: 18492826 DOI: 10.1093/jn/138.6.1004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Glyceroneogenesis is an important metabolic pathway for fatty acid reesterification in adipose tissue, thereby reducing fatty acid release. Glyceroneogenesis and cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C), which is the key enzyme in this pathway, are both regulated by a series of hormones and nutrients, among which all-trans retinoic acid (all-trans RA) is a transcriptional inducer of the PEPCK-C gene (Pck1). All-trans RA binds to the retinoic acid receptor (RAR) and activates it, whereas its stereoisomer 9-cis retinoic acid (9-cis RA) is a ligand for the 9-cis RA receptor (RXR). Three RXR-binding elements [retinoic acid response element (RARE)1/PCK1, RARE2, and RARE3/PCK2] were previously located in the promoter of Pck1. Using 3T3-F442A adipocytes, we demonstrated that Pck1 expression was 10-fold more sensitive to 9-cis RA (EC(50): 10 nmol/L) than to all-trans RA. We then analyzed the respective involvement of RARE1/PCK1, RARE2, and RARE3/PCK2 in the response of Pck1 to 9-cis RA and all-trans RA in adipocytes. The response to 9-cis RA mainly involved the RARE1/PCK1 element, whereas RARE2 was mainly responsive to all-trans RA. In contrast, the full response to both RA isomers involved these 2 elements and included RARE3/PCK2 as well. Furthermore, 9-cis RA, but not all-trans RA, selectively induced PCK1 in ex-vivo-treated human adipose tissue explants, with a concomitant induction of glyceroneogenesis monitored by [1-(14)C]-pyruvate incorporation into neutral lipids. The concomitant 9-cis RA-induced reduction in fatty acid output indicates an important role for this RA stereoisomer in lipid homeostasis through stimulation of PEPCK-C and glyceroneogenesis in adipose tissue.
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Affiliation(s)
- Thomas Cadoudal
- Institut National de la Recherche Médicale UMR-S 747, Université Paris Descartes, F-75006 Paris, France
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Chang TJ, Lee WJ, Chang HM, Lee KC, Chuang LM. Expression of subcutaneous adipose tissue phosphoenolpyruvate carboxykinase correlates with body mass index in nondiabetic women. Metabolism 2008; 57:367-72. [PMID: 18249209 DOI: 10.1016/j.metabol.2007.10.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Accepted: 10/16/2007] [Indexed: 11/15/2022]
Abstract
Phosphoenolpyruvate carboxykinase (PEPCK) is a key enzyme for glyceroneogenesis in adipose tissues. Dysregulated glyceroneogenesis is associated with abnormal fatty acid homeostasis, obesity, and insulin resistance in both animal and cellular studies. However, the role of PEPCK expression in human adipose tissues on metabolic phenotypes has not been explored. This study aimed to analyze the correlation between PEPCK messenger RNA (mRNA) expressions in the subcutaneous adipose tissues with obesity-related metabolic phenotypes. We obtained the demographic data, biochemical variables, and abdominal subcutaneous adipose tissue from 75 nondiabetic nonmenopausal women. The relative PEPCK mRNA levels were quantified by real-time polymerase chain reaction normalized with beta-actin as a control. The PEPCK mRNA levels of subcutaneous tissue were positively correlated with body mass index (BMI) using either univariate (r = 0.413, P < .001) or multivariate linear regression analysis (beta = .978 +/- .239, P < .001). The mRNA expression of PEPCK was also positively correlated with body fat percentage (r = 0.436, P < .001), plasma triacylglycerol, and total cholesterol levels (both P values < .001). However, the significant correlation between lipid profile and PEPCK expression in subcutaneous tissue was abolished after adjusting for BMI. The relative subcutaneous PEPCK mRNA level was not correlated with fasting plasma glucose and insulin, and with an insulin resistance index measured with homeostasis model assessment. In conclusion, we showed that PEPCK mRNA expression in the subcutaneous adipose tissues was associated with BMI and plasma triacylglycerol and total cholesterol levels, but was not correlated with insulin resistance index.
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Affiliation(s)
- Tien-Jyun Chang
- Division of Endocrinology and Metabolism, Department of Internal Medicine, National Taiwan University Hospital, Taipei 10002, Taiwan
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Balas B, Belfort R, Harrison SA, Darland C, Finch J, Schenker S, Gastaldelli A, Cusi K. Pioglitazone treatment increases whole body fat but not total body water in patients with non-alcoholic steatohepatitis. J Hepatol 2007; 47:565-70. [PMID: 17560678 DOI: 10.1016/j.jhep.2007.04.013] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 04/03/2007] [Accepted: 04/20/2007] [Indexed: 12/31/2022]
Abstract
BACKGROUND/AIMS Non-Alcoholic Steatohepatitis (NASH) is a chronic liver disease frequently associated with insulin resistance and type 2 diabetes mellitus (T2DM). Pioglitazone reverses the metabolic and histological abnormalities of patients with impaired glucose tolerance or T2DM and NASH, but also leads to weight gain. To understand the nature of weight gain associated with pioglitazone treatment in NASH we analyzed 35 patients who completed tests for determination of whole body fat (WBF) and total body water (TBW). METHODS Twenty-one patients received pioglitazone and 14 placebo in a double-blind, randomized fashion for a period of 6 months. WBF and TBW were measured before and after treatment using DXA, a water dilution technique and bioimpedance. RESULTS Pioglitazone increased body weight (from 93.6+/-4.2 to 96.1+/-4.5 kg, p<0.003) and WBF measured with DXA (from 32.9+/-2.1 to 35.4+/-2.5 kg, p<0.002) while no changes were seen with placebo. Total body water was not altered significantly either after pioglitazone (from 45.4+/-2.3 to 45.6+/-2.7 l, p=NS) or placebo. Muscle hydration and extracellular water were unchanged both by pioglitazone and placebo treatments. CONCLUSIONS Six months of pioglitazone treatment in patients with NASH is associated with weight gain that is attributable to an increase in adipose tissue mass and not to water retention.
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Affiliation(s)
- Bogdan Balas
- Diabetes Division, Department of Medicine, University of Texas Health Science Center at San Antonio, Room 3.380S, 7703 Floyd Curl Drive, San Antonio, TX 78284-3900, USA
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Kim HI, Koh YK, Kim TH, Kwon SK, Im SS, Choi HS, Kim KS, Ahn YH. Transcriptional activation of SHP by PPAR-gamma in liver. Biochem Biophys Res Commun 2007; 360:301-6. [PMID: 17601490 DOI: 10.1016/j.bbrc.2007.05.171] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Accepted: 05/18/2007] [Indexed: 10/23/2022]
Abstract
The mechanism of how PPARgamma decrease gluconeogenic gene expressions in liver is still unclear. Since PPARgamma is a transcriptional activator, it requires a mediator to decrease the transcription of gluconeogenic genes. Recently, SHP has been shown to mediate the bile acid-dependent down regulation of gluconeogenic gene expression in liver. This led us to explore the possibility that SHP may mediate the antigluconeogenic effect of PPARgamma. In the present study, we have identified and characterized the presence of functional PPRE in human SHP promoter. We show the binding of PPARgamma/RXRalpha heterodimer to the PPRE and increased SHP expression by rosiglitazone in primary rat hepatocytes. Taken together with the previous reports about the function of SHP on gluconeogenesis, our results indicate that SHP can mediate the acute antigluconeogenic effect of PPARgamma.
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Affiliation(s)
- Ha-il Kim
- Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, 134 Shinchon-dong, Seodaemoon-gu, Seoul 120-752, Republic of Korea
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Tordjman J, Leroyer S, Chauvet G, Quette J, Chauvet C, Tomkiewicz C, Chapron C, Barouki R, Forest C, Aggerbeck M, Antoine B. Cytosolic aspartate aminotransferase, a new partner in adipocyte glyceroneogenesis and an atypical target of thiazolidinedione. J Biol Chem 2007; 282:23591-602. [PMID: 17545671 DOI: 10.1074/jbc.m611111200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We show that cytosolic aspartate aminotransferase (cAspAT) is involved in adipocyte glyceroneogenesis, a regulated pathway that controls fatty acid homeostasis by promoting glycerol 3-phosphate formation for fatty acid re-esterification during fasting. cAspAT activity, as well as the incorporation of [(14)C]aspartate into the neutral lipid fraction of 3T3-F442A adipocytes was stimulated by the thiazolidinedione (TZD) rosiglitazone. Conversely, the ratio of fatty acid to glycerol released into the medium decreased. Regulation of cAspAT gene expression was specific to differentiated adipocytes and did not require any peroxisome proliferator-activated receptor gamma (PPARgamma)/retinoid X receptor-alpha direct binding. Nevertheless, PPARgamma is indirectly necessary for both cAspAT basal expression and TZD responsiveness because they are, respectively, diminished and abolished by ectopic overexpression of a dominant negative PPARgamma. The cAspAT TZD-responsive site was restricted to a single AGGACA hexanucleotide located at -381 to -376 bp whose mutation impaired the specific RORalpha binding. RORalpha ectopic expression activated the cAspAT gene transcription in absence of rosiglitazone, and its protein amount in nuclear extracts is 1.8-fold increased by rosiglitazone treatment of adipocytes. Finally, the amounts of RORalpha and cAspAT mRNAs were similarly increased by TZD treatment of human adipose tissue explants, confirming coordinated regulation. Our data identify cAspAT as a new member of glyceroneogenesis, transcriptionally regulated by TZD via the control of RORalpha expression by PPARgamma in adipocytes.
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Affiliation(s)
- Joan Tordjman
- Inserm U530, Université Paris Descartes, F-75006, Paris, France
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Cadoudal T, Blouin JM, Collinet M, Fouque F, Tan GD, Loizon E, Beale EG, Frayn KN, Karpe F, Vidal H, Benelli C, Forest C. Acute and selective regulation of glyceroneogenesis and cytosolic phosphoenolpyruvate carboxykinase in adipose tissue by thiazolidinediones in type 2 diabetes. Diabetologia 2007; 50:666-75. [PMID: 17242918 DOI: 10.1007/s00125-006-0560-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Accepted: 11/10/2006] [Indexed: 10/23/2022]
Abstract
AIMS/HYPOTHESIS Regulation of glyceroneogenesis and its key enzyme cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) plays a major role in the control of fatty acid release from adipose tissue. Here we investigate the effect of rosiglitazone on the expression of genes involved in fatty acid metabolism and the resulting metabolic consequences. MATERIALS AND METHODS Rosiglitazone was administered to Zucker fa/fa rats for 4 days and to 24 diabetic patients for 12 weeks, then mRNA expression for the genes encoding PEPCK-C, mitochondrial PEPCK, adipocyte lipid-binding protein, glycerol kinase, lipoprotein lipase and glycerol-3-phosphate dehydrogenase was examined in s.c. adipose tissue by real-time RT-PCR. Glyceroneogenesis was determined using [1-(14)C]pyruvate incorporation into lipids. Cultured adipose tissue explants from overweight women undergoing plastic surgery were incubated with rosiglitazone for various times before mRNA determination and analysis of PEPCK-C protein, activity and glyceroneogenesis. RESULTS Rosiglitazone administration to rats induced the expression of the gene encoding PEPCK-C mRNA (PCK1) and PEPCK-C activity in adipose tissue with a resulting 2.5-fold increase in glyceroneogenesis. This was accompanied by an improvement in dyslipidaemia as demonstrated by the decrease in plasma NEFAs and triacylglycerol. In rosiglitazone-treated diabetic patients, PCK1 mRNA was raised 2.5-fold in s.c. adipose tissue. Rosiglitazone treatment of adipose tissue explants from overweight women caused a selective augmentation in PCK1 mRNA which reached a maximum of 9-fold at 14 h, while mRNA for other genes remained unaffected. Experiments with inhibitors showed a direct and transcription-only effect, which was followed by an increase in PEPCK-C protein, enzyme activity and glyceroneogenesis. CONCLUSIONS/INTERPRETATION These results favour adipocyte glyceroneogenesis as the initial thiazolidinedione-responsive pathway leading to improvement in dyslipidaemia.
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Hanson RW, Ballard FJ, Reshef L. Glyceroneogenesis, the pathway that almost wasn't. BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION : A BIMONTHLY PUBLICATION OF THE INTERNATIONAL UNION OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2006; 34:317-323. [PMID: 21638707 DOI: 10.1002/bmb.2006.494034052637] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
"What seest thou else in the dark, backward abysm of time." Prospero in The Tempest As is true in all aspects of human endeavor, a scientific concept can appear before its time and remain unappreciated before events catch up with the concept. Such was the case of the discovery of glyceroneogenesis and the establishment of its biological importance; it took almost 40 years before the significance of this pathway became apparent and the concept of triglyceride recycling was understood by the scientific establishment. Even that may be stretching a point, because today glyceroneogenesis is hardly a household word. In this essay, we will tell the story of the discovery of glyceroneogenesis and the thought processes that led us to propose this pathway. We will also speculate on why the pathway was not more widely embraced by scientists working in lipid metabolism and why that may finally be changing. The reader is warned, however, that this story is a reconstruction of past events and, like all such attempts, suffers from the patina of nostalgia that inevitably covers all things resurrected from memory. Others may view things differently, but this is our story as we remember it.
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Affiliation(s)
- Richard W Hanson
- Department of Biochemistry, Case Western Reserve University School of Medicine Cleveland, Ohio 44106-4539.
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Leroyer SN, Tordjman J, Chauvet G, Quette J, Chapron C, Forest C, Antoine B. Rosiglitazone Controls Fatty Acid Cycling in Human Adipose Tissue by Means of Glyceroneogenesis and Glycerol Phosphorylation. J Biol Chem 2006; 281:13141-13149. [PMID: 16524879 DOI: 10.1074/jbc.m512943200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Control of fatty acid homeostasis is crucial to prevent insulin resistance. During fasting, the plasma fatty acid level depends on triglyceride lipolysis and fatty acid re-esterification within fat cells. In rodents, Rosiglitazone controls fatty acid homeostasis by stimulating two pathways in the adipocytes, glyceroneogenesis and glycerol phosphorylation, that provide the glycerol 3-phosphate necessary for fatty acid re-esterification. Here, we analyzed the functionality of both pathways for controlling fatty acid release in subcutaneous adipose tissue samples from lean and overweight women before and after Rosiglitazone ex vivo treatment. In controls, pyruvate, used as a substrate of glyceroneogenesis, could contribute to the re-esterification of up to 65% of the fatty acids released after basal lipolysis, whereas glycerol phosphorylation accounted for only 14 +/- 9%. However, the efficiency of glyceroneogenesis diminished as body mass index (BMI) of women increased. After Rosiglitazone treatment, increase of either pyruvate- or glycerol-dependent fatty acid re-esterification was strictly correlated to that of phosphoenolpyruvate carboxykinase and glycerol kinase, the key enzymes of each pathway, but depended on BMI of the women. Whereas the Rosiglitazone responsiveness of glyceroneogenesis was rather constant according to the BMI of the women, glycerol phosphorylation was mostly enhanced in lean women (BMI < 27). Overall, these data indicate that, whereas glyceroneogenesis is more utilized than glycerol phosphorylation for fatty acid re-esterification in human subcutaneous adipose tissue in the physiological situation, both are solicited in response to Rosiglitazone but with lower efficiency when BMI is increased.
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Affiliation(s)
- Stéphanie N Leroyer
- INSERM-UMR-S 530/747, Université Paris Descartes, 45 Rue des Saints-Pères, 75006 Paris, France
| | - Joan Tordjman
- INSERM-UMR-S 530/747, Université Paris Descartes, 45 Rue des Saints-Pères, 75006 Paris, France
| | - Geneviève Chauvet
- INSERM-UMR-S 530/747, Université Paris Descartes, 45 Rue des Saints-Pères, 75006 Paris, France
| | - Joëlle Quette
- INSERM-UMR-S 530/747, Université Paris Descartes, 45 Rue des Saints-Pères, 75006 Paris, France
| | - Charles Chapron
- Groupe Hospitalier Universitaire Ouest, Centre Hospitalier Universitaire Cochin, Paris, France
| | - Claude Forest
- INSERM-UMR-S 530/747, Université Paris Descartes, 45 Rue des Saints-Pères, 75006 Paris, France
| | - Bénédicte Antoine
- INSERM-UMR-S 530/747, Université Paris Descartes, 45 Rue des Saints-Pères, 75006 Paris, France.
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Abstract
The nuclear receptor family of PPARs was named for the ability of the original member to induce hepatic peroxisome proliferation in mice in response to xenobiotic stimuli. However, studies on the action and structure of the 3 human PPAR isotypes (PPARalpha, PPARdelta, and PPARgamma) suggest that these moieties are intimately involved in nutrient sensing and the regulation of carbohydrate and lipid metabolism. PPARalpha and PPARdelta appear primarily to stimulate oxidative lipid metabolism, while PPARgamma is principally involved in the cellular assimilation of lipids via anabolic pathways. Our understanding of the functions of PPARgamma in humans has been increased by the clinical use of potent agonists and by the discovery of both rare and severely deleterious dominant-negative mutations leading to a stereotyped syndrome of partial lipodystrophy and severe insulin resistance, as well as more common sequence variants with a much smaller impact on receptor function. These may nevertheless have much greater significance for the public health burden of metabolic disease. This Review will focus on the role of PPARgamma in human physiology, with specific reference to clinical pharmacological studies, and analysis of PPARG gene variants in the abnormal lipid and carbohydrate metabolism of the metabolic syndrome.
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Affiliation(s)
- Robert K Semple
- Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
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Gouni-Berthold I, Giannakidou E, Faust M, Berthold HK, Krone W. Association of the promoter polymorphism -232C/G of the phosphoenolpyruvate carboxykinase gene (PCK1) with Type 2 diabetes mellitus. Diabet Med 2006; 23:419-25. [PMID: 16620271 DOI: 10.1111/j.1464-5491.2006.01819.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIMS The phosphoenolpyruvate carboxykinase gene (PCK1) is a potential candidate gene in the pathogenesis of Type 2 diabetes mellitus. A -232C/G promoter polymorphism of PCK1 has been associated with an increased risk of Type 2 diabetes in a Canadian population. The purpose of the present study was to examine this association in a German Caucasian population. METHODS We investigated 397 subjects with Type 2 diabetes [227 men, 170 women, age 63 +/- 11 years, body mass index (BMI) 28.7 +/- 5.1 kg/m2] and 431 control subjects without diabetes (247 men, 184 women, age 64 +/- 7 years, BMI 26.5 +/- 3.7 kg/m2) matched for sex and age. RESULTS In the diabetic and control groups, the CC genotype frequencies were 18.1 and 18.3%, the CG 48.6 and 48.7% and the GG 33.2 and 32.9%, respectively (P = 0.995). The allelic frequencies were 0.51 and 0.57 for the G allele and 0.49 and 0.43 for the C allele, respectively. In a logistic regression model only BMI and family history, but not the polymorphism, were predictors of Type 2 diabetes. In both the control and diabetic subjects, there were no significant differences in BMI or blood pressure between the groups with or without the polymorphism. The variant also had no significant influence on the presence of atherosclerotic disease, while the influence of other known cardiovascular risk factors was confirmed. CONCLUSIONS The present data suggest that, in a German Caucasian population, the -232C/G polymorphism of the PEPCK gene is not associated with Type 2 diabetes.
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Affiliation(s)
- I Gouni-Berthold
- Department of Internal Medicine II, University of Cologne, Cologne, Germany.
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30
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Franckhauser S, Muñoz S, Elias I, Ferre T, Bosch F. Adipose overexpression of phosphoenolpyruvate carboxykinase leads to high susceptibility to diet-induced insulin resistance and obesity. Diabetes 2006; 55:273-80. [PMID: 16443757 DOI: 10.2337/diabetes.55.02.06.db05-0482] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Obesity and insulin resistance are associated with increased serum free fatty acids (FFAs). Thus, a reduction in circulating FFAs may increase insulin sensitivity. This could be achieved by increasing FFA reesterification in adipose tissue. Transgenic mice with increased adipose tissue glyceroneogenesis, caused by overexpression of phosphoenolpyruvate carboxykinase (PEPCK), show increased FFA reesterification and develop obesity but are insulin sensitive. Here, we examined whether these transgenic mice were protected from diet-induced insulin resistance. Surprisingly, when fed a high-fat diet for a short period (6 weeks), transgenic mice developed severe obesity and were more hyperinsulinemic, glucose intolerant, and insulin resistant than controls. The high triglyceride accumulation prevented white adipose tissue from buffering the flux of lipids in circulation and led to increased serum triglyceride levels and fat deposition in liver. Furthermore, circulating leptin and FFA concentrations increased to similar levels in transgenic and control mice, while adiponectin levels decreased in transgenic mice compared with controls. In addition, transgenic mice showed fat accumulation in brown adipose tissue, which decreased uncoupling protein-1 expression, suggesting that these mice had impaired diet-induced thermogenesis. These results indicate that increased PEPCK expression in the presence of high-fat feeding may have deleterious effects and lead to severe insulin resistance and type 2 diabetes.
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Affiliation(s)
- Sylvie Franckhauser
- Center of Animal Biotechnology and Gene Therapy, School of Veterinary Medicine, Universitat Autònoma de Barcelona, Bellaterra, Spain
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31
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Cadoudal T, Leroyer S, Reis AF, Tordjman J, Durant S, Fouque F, Collinet M, Quette J, Chauvet G, Beale E, Velho G, Antoine B, Benelli C, Forest C. Proposed involvement of adipocyte glyceroneogenesis and phosphoenolpyruvate carboxykinase in the metabolic syndrome. Biochimie 2005; 87:27-32. [PMID: 15733733 DOI: 10.1016/j.biochi.2004.12.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Accepted: 12/10/2004] [Indexed: 11/26/2022]
Abstract
Elevated concentration of plasma non-esterified fatty acids (NEFA) is now recognized as a key factor in the onset of insulin-resistance and type 2 diabetes mellitus. During fasting, circulating NEFAs arise from white adipose tissue (WAT) as a consequence of lipolysis from stored triacylglycerols. However, a significant part of these FAs (30-70%) is re-esterified within the adipocyte, so that a recycling occurs and net FA output is much less than << true >> lipolysis. Indeed, a balance between two antagonistic processes, lipolysis and FA re-esterification, controls the rate of net FA release from WAT. During fasting, re-esterification requires glyceroneogenesis defined as the de novo synthesis of glycerol-3-P from pyruvate, lactate or certain amino acids. The key enzyme in this process is the cytosolic isoform of phosphoenolpyruvate carboxykinase (PEPCK-C; EC 4.1.1.32). Recent advance has stressed the role of glyceroneogenesis and of PEPCK-C in FA release from WAT. Results indicate that glyceroneogenesis is indeed important to lipid homeostasis and that a disregulation in this pathway may have profound pathophysiological effects. The present review focuses on the regulation of glyceroneogenesis and of PEPCK-C gene expression and activity by FAs, retinoic acids, glucocorticoids and the hypolipidemic class of drugs, thiazolidinediones.
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Affiliation(s)
- Thomas Cadoudal
- Inserm UMR-S 530; Université Paris5, Centre Universitaire, U.F.R. Biomédicale, 45, rue des Saints-Pères, 75006 Paris, France
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32
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Simon MF, Daviaud D, Pradère JP, Grès S, Guigné C, Wabitsch M, Chun J, Valet P, Saulnier-Blache JS. Lysophosphatidic acid inhibits adipocyte differentiation via lysophosphatidic acid 1 receptor-dependent down-regulation of peroxisome proliferator-activated receptor gamma2. J Biol Chem 2005; 280:14656-62. [PMID: 15710620 DOI: 10.1074/jbc.m412585200] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Lysophosphatidic acid (LPA) is a bioactive phospholipid acting via specific G protein-coupled receptors that is synthesized at the extracellular face of adipocytes by a secreted lysophospholipase D (autotaxin). Preadipocytes mainly express the LPA(1) receptor subtype, and LPA increases their proliferation. In monocytes and CV1 cells LPA was recently reported to bind and activate peroxisome proliferator-activated receptor gamma (PPARgamma), a transcription factor also known to play a pivotal role in adipogenesis. Here we show that, unlike the PPARgamma agonist rosiglitazone, LPA was unable to increase transcription of PPARgamma-sensitive genes (PEPCK and ALBP) in the mouse preadipose cell line 3T3F442A. In contrast, treatment with LPA decreased PPARgamma2 expression, impaired the response of PPARgamma-sensitive genes to rosiglitazone, reduced triglyceride accumulation, and reduced the expression of adipocyte mRNA markers. The anti-adipogenic activity of LPA was also observed in the human SGBS (Simpson-Golabi-Behmel syndrome) preadipocyte cell line, as well as in primary preadipocytes isolated from wild type mice. Conversely, the anti-adipogenic activity of LPA was not observed in primary preadipocytes from LPA(1) receptor knock-out mice, which, in parallel, exhibited a higher adiposity than wild type mice. In conclusion, LPA does not behave as a potent PPARgamma agonist in adipocytes but, conversely, inhibits PPARgamma expression and adipogenesis via LPA(1) receptor activation. The local production of LPA may exert a tonic inhibitory effect on the development of adipose tissue.
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Affiliation(s)
- Marie Françoise Simon
- INSERM U586, Institut Louis Bugnard, Rangueil Hospital, BP84225, 31432 Toulouse, Cedex 4, France
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Jenkins CM, Mancuso DJ, Yan W, Sims HF, Gibson B, Gross RW. Identification, cloning, expression, and purification of three novel human calcium-independent phospholipase A2 family members possessing triacylglycerol lipase and acylglycerol transacylase activities. J Biol Chem 2004; 279:48968-75. [PMID: 15364929 DOI: 10.1074/jbc.m407841200] [Citation(s) in RCA: 658] [Impact Index Per Article: 32.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Genetic knockout of hormone-sensitive lipase in mice has implicated the presence of other intracellular triacylglycerol (TAG) lipases mediating TAG hydrolysis in adipocytes. Despite intense interest in these TAG lipases, their molecular identities thus far are largely unknown. Sequence data base searches for proteins containing calcium-independent phospholipase A2 (iPLA2) dual signature nucleotide ((G/A)XGXXG) and lipase (GXSXG) consensus sequence motifs identified a novel subfamily of three putative iPLA2/lipase family members designated iPLA2epsilon, iPLA2zeta, and iPLA2eta (previously named adiponutrin, TTS-2.2, and GS2, respectively) of previously unknown catalytic function. Herein we describe the cloning, heterologous expression, and affinity purification of the three human isoforms of this iPLA2 subfamily in Sf9 cells, and we demonstrate that each possesses abundant TAG lipase activity. Moreover, iPLA2epsilon, iPLA2zeta, and iPLA2eta also possess acylglycerol transacylase activity utilizing mono-olein as an acyl donor which, in the presence of mono-olein or diolein acceptors, results in the synthesis of diolein and triolein, respectively. (E)-6-(Bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one, a mechanism-based suicide substrate inhibitor of all known iPLA2s, inhibits the triglyceride lipase activity of each of the three isoforms similarly (IC50=0.1-0.5 microm). Quantitative PCR revealed dramatically increased expression of iPLA2epsilon and iPLA2zeta transcripts during the hormone-induced differentiation of 3T3-L1 cells into adipocytes and identified the presence of all three iPLA2 isoforms in human SW872 liposarcoma cells. Collectively, these results identify three novel TAG lipases/acylglycerol transacylases that likely participate in TAG hydrolysis and the acyl-CoA independent transacylation of acylglycerols, thereby facilitating energy mobilization and storage in adipocytes.
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Affiliation(s)
- Christopher M Jenkins
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Tsai YS, Kim HJ, Takahashi N, Kim HS, Hagaman JR, Kim JK, Maeda N. Hypertension and abnormal fat distribution but not insulin resistance in mice with P465L PPARgamma. J Clin Invest 2004; 114:240-9. [PMID: 15254591 PMCID: PMC449746 DOI: 10.1172/jci20964] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 05/20/2004] [Indexed: 12/16/2022] Open
Abstract
Peroxisome proliferator-activated receptor gamma (PPARgamma), the molecular target of a class of insulin sensitizers, regulates adipocyte differentiation and lipid metabolism. A dominant negative P467L mutation in the ligand-binding domain of PPARgamma in humans is associated with severe insulin resistance and hypertension. Homozygous mice with the equivalent P465L mutation die in utero. Heterozygous mice grow normally and have normal total adipose tissue weight. However, they have reduced interscapular brown adipose tissue and intra-abdominal fat mass, and increased extra-abdominal subcutaneous fat, compared with wild-type mice. They have normal plasma glucose levels and insulin sensitivity, and increased glucose tolerance. However, during high-fat feeding, their plasma insulin levels are mildly elevated in association with a significant increase in pancreatic islet mass. They are hypertensive, and expression of the angiotensinogen gene is increased in their subcutaneous adipose tissues. The effects of P465L on blood pressure, fat distribution, and insulin sensitivity are the same in both male and female mice regardless of diet and age. Thus the P465L mutation alone is sufficient to cause abnormal fat distribution and hypertension but not insulin resistance in mice. These results provide genetic evidence for a critical role for PPARgamma in blood pressure regulation that is not dependent on altered insulin sensitivity.
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Affiliation(s)
- Yau-Sheng Tsai
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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Tsai YS, Kim HJ, Takahashi N, Kim HS, Hagaman JR, Kim JK, Maeda N. Hypertension and abnormal fat distribution but not insulin resistance in mice with P465L PPARγ. J Clin Invest 2004. [DOI: 10.1172/jci200420964] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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Bogacka I, Xie H, Bray GA, Smith SR. The effect of pioglitazone on peroxisome proliferator-activated receptor-gamma target genes related to lipid storage in vivo. Diabetes Care 2004; 27:1660-7. [PMID: 15220243 DOI: 10.2337/diacare.27.7.1660] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Pioglitazone is a member of the thiazolidinediones (TZDs), insulin-sensitizing agents used to treat type 2 diabetes. The aim of this study was to define the effect of pioglitazone on the expression of genes related to carbohydrate and lipid metabolism in subcutaneous fat obtained from type 2 diabetic patients. RESEARCH DESIGN AND METHODS Forty-eight volunteers with type 2 diabetes were divided into two groups treated for 12 weeks with placebo or pioglitazone (30 mg/day). The expression of several genes was quantified by real-time RT-PCR. RESULTS Pioglitazone treatment increased the expression of genes involved in glycerol-3-phosphate synthesis. The mRNA expression of PEPCK-C and glycerol-3-phosphate dehydrogenase (GPDH) increased (P < 0.01) in patients treated with pioglitazone. There was no difference in glycerol kinase (GyK) mRNA levels. The expression of genes that regulate fatty acid availability in adipocytes, including lipoprotein lipase (LPL) and acetyl-CoA synthetase (ACS), was higher (P < 0.01) in pioglitazone-treated patients. Pioglitazone stimulated (P < 0.0001) expression of c-Cbl-associated protein (CAP), whereas tumor necrosis factor-alpha, leptin, resistin, angiopoietin like-4, and 11-beta-hydroxysteroid dehydrogenase type 1 (11beta HSD 1) were not affected by pioglitazone. The baseline peroxisome proliferator-activated receptor (PPAR)-gamma1 mRNA was significantly correlated with mRNA for LPL, CAP, ACS, 11beta HSD 1, GyK, fatty acid synthase, leptin, and GPDH, whereas PPAR-gamma2 mRNA was correlated with CAP, PEPCK-C, leptin, and GPDH. CONCLUSIONS Treatment with pioglitazone increased body weight, and this is associated with upregulation of some, but not all, genes previously demonstrated as "TZD responsive" in subcutaneous fat. The results suggest that TZDs might increase body weight through the upregulation of genes facilitating adipocyte lipid storage in vivo.
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Affiliation(s)
- Iwona Bogacka
- Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA.
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Tiraby C, Tavernier G, Lefort C, Larrouy D, Bouillaud F, Ricquier D, Langin D. Acquirement of brown fat cell features by human white adipocytes. J Biol Chem 2003; 278:33370-6. [PMID: 12807871 DOI: 10.1074/jbc.m305235200] [Citation(s) in RCA: 336] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Obesity, i.e. an excess of white adipose tissue (WAT), predisposes to the development of type 2 diabetes and cardiovascular disease. Brown adipose tissue is present in rodents but not in adult humans. It expresses uncoupling protein 1 (UCP1) that allows dissipation of energy as heat. Peroxisome proliferator-activated receptor gamma (PPAR gamma) and PPAR gamma coactivator 1 alpha (PGC-1 alpha) activate mouse UCP1 gene transcription. We show here that human PGC-1 alpha induced the activation of the human UCP1 promoter by PPAR gamma. Adenovirus-mediated expression of human PGC-1 alpha increased the expression of UCP1, respiratory chain proteins, and fatty acid oxidation enzymes in human subcutaneous white adipocytes. Changes in the expression of other genes were also consistent with brown adipocyte mRNA expression profile. PGC-1 alpha increased the palmitate oxidation rate by fat cells. Human white adipocytes can therefore acquire typical features of brown fat cells. The PPAR gamma agonist rosiglitazone potentiated the effect of PGC-1 alpha on UCP1 expression and fatty acid oxidation. Hence, PGC-1 alpha is able to direct human WAT PPAR gamma toward a transcriptional program linked to energy dissipation. However, the response of typical white adipocyte targets to rosiglitazone treatment was not altered by PGC-1 alpha. UCP1 mRNA induction was shown in vivo by injection of the PGC-1 alpha adenovirus in mouse white fat. Alteration of energy balance through an increased utilization of fat in WAT may be a conceivable strategy for the treatment of obesity.
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Affiliation(s)
- Claire Tiraby
- Unité de Recherches sur les Obésités, Institut National de la Santé et de la Recherche Médicale Unité 586, Institut Louis Bugnard, Centre Hospitalier Universitaire de Toulouse, Université Paul Sabatier, 31403 Toulouse, France
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Reshef L, Olswang Y, Cassuto H, Blum B, Croniger CM, Kalhan SC, Tilghman SM, Hanson RW. Glyceroneogenesis and the triglyceride/fatty acid cycle. J Biol Chem 2003; 278:30413-6. [PMID: 12788931 DOI: 10.1074/jbc.r300017200] [Citation(s) in RCA: 334] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Lea Reshef
- Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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Ruan H, Pownall HJ, Lodish HF. Troglitazone antagonizes tumor necrosis factor-alpha-induced reprogramming of adipocyte gene expression by inhibiting the transcriptional regulatory functions of NF-kappaB. J Biol Chem 2003; 278:28181-92. [PMID: 12732648 DOI: 10.1074/jbc.m303141200] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Troglitazone (TGZ), a member of the thiazolidinedione class of anti-diabetic compounds and a peroxisome proliferator activator receptor-gamma (PPAR-gamma) agonist, restores systemic insulin sensitivity and improves the full insulin resistance syndrome in vivo. The mechanisms underlying its in vivo function are not understood. Here we investigated the potential functional interaction between PPAR-gamma and NF-kappaB in adipocytes. We show that TGZ selectively blocked tumor necrosis factor-alpha-induced and NF-kappaB-dependent repression of multiple adipocyte-specific genes and induction of growth phase and other genes. This occurs without interfering with NF-kappaB expression, activation, nuclear translocation, or DNA binding and without suppressing NF-kappaB-dependent survival signals. Notably, the expressions of some tumor necrosis factor-alpha-induced genes in adipocytes were unaffected by PPAR-gamma activation. In reporter gene assays in HeLa cells, ectopic expression of PPAR-gamma abolished induction of a NF-kappaB-responsive reporter gene by the p65 subunit (RelA) of NF-kappaB, and the inhibition was further enhanced in the presence of TGZ. Conversely, overexpression of p65 inhibited induction of a PPAR-gamma-responsive reporter gene by activated PPAR-gamma in a dose-dependent manner. The inhibitory effect was independent of the presence of NF-kappaB-binding sites in the promoter region. Other NF-kappaB family members, p50 and c-Rel as well as the S276A mutant of p65, blocked PPAR-gamma-mediated gene transcription less effectively. Thus, p65 antagonizes the transcriptional regulatory activity of PPAR-gamma in adipocytes, and PPAR-gamma activation can at least partially override the inhibitory effects of p65 on the expression of key adipocyte genes. Our data suggest that inhibition of NF-kappaB activity is a mechanism by which PPAR-gamma agonists improve insulin sensitivity in vivo and that adipocyte NF-kappaB is a potential therapeutic target for obesity-linked type 2 diabetes.
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Affiliation(s)
- Hong Ruan
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA
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Tordjman J, Chauvet G, Quette J, Beale EG, Forest C, Antoine B. Thiazolidinediones block fatty acid release by inducing glyceroneogenesis in fat cells. J Biol Chem 2003; 278:18785-90. [PMID: 12644461 DOI: 10.1074/jbc.m206999200] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thiazolidinediones are used to treat type 2 diabetes mellitus because they decrease plasma glucose, insulin, triglyceride, and fatty acid levels. Thiazolidinediones are agonists for peroxisome proliferator-activated receptor gamma, a nuclear receptor that is highly expressed in fat tissue. We identify glyceroneogenesis as a target of thiazolidinediones in cultured adipocytes and fat tissues of Wistar rats. The activation of glyceroneogenesis by thiazolidinediones occurs mainly in visceral fat, the same fat depot that is specifically implicated in the progression of obesity to type 2 diabetes. The increase in glyceroneogenesis is a result of the induction of its key enzyme, phosphoenolpyruvate carboxykinase, whose gene expression is peroxisome proliferator-activated receptor gamma-dependent in adipocytes. The main role of this metabolic pathway is to allow the re-esterification of fatty acids via a futile cycle in adipocytes, thus lowering fatty acid release into the plasma. The importance of such a fatty acid re-esterification process in the control of lipid homeostasis is highlighted by the existence of a second thiazolidinedione-induced pathway involving glycerol kinase. We show that glyceroneogenesis accounts for at least 75% of the whole thiazolidinedione effect. Because elevated plasma fatty acids promote insulin resistance, these results suggest that the glyceroneogenesis-dependent fatty acid-lowering effect of thiazolidinediones could be an essential aspect of the antidiabetic action of these drugs.
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Affiliation(s)
- Joan Tordjman
- UMR-S 530 INSERM, Université Paris 5, Centre Universitaire, 45 rue des Saints-Pères, 75006 Paris, France
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Duplus E, Glorian M, Tordjman J, Berge R, Forest C. Evidence for selective induction of phosphoenolpyruvate carboxykinase gene expression by unsaturated and nonmetabolized fatty acids in adipocytes. J Cell Biochem 2002; 85:651-61. [PMID: 11968005 DOI: 10.1002/jcb.10175] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Polyunsaturated fatty acids (PUFAs) and 3-thia fatty acids are hypolipidemic and decrease insulin resistance in Type II diabetic animals. To exert such an action, these FAs could decrease adipose tissue lipolysis or increase esterification. Glyceroneogenesis is an important metabolic pathway in adipocytes for re-esterification of FAs originating from lipolysis and in hepatocytes for triacylglycerol synthesis during fasting. Cytosolic phosphoenolpyruvate carboxykinase (PEPCK) plays a key role in this pathway. Here we show that the PUFA docosahexaenoic acid (DHA) stimulates PEPCK mRNA in glucose-deprived adipose tissue explants from fed rats and in 3T3-F442A differentiated adipocytes. This effect is maximum at 3 h, stable up to at least 11 h of treatment, and affects the transcription of the gene. PEPCK mRNA half-life is not affected. Among a series of adipocyte transcripts, only the adipocyte lipid binding protein mRNA is also increased by DHA, although later than the PEPCK mRNA and at a much lower extent. DHA has no effect on PEPCK gene expression in the H4IIE hepatoma cells in which this gene is responsive to other inducers like cAMP. This lack of effect is not due to a failure of DHA to act in H4IIE cells since it induces the carnitine palmitoyltransferase 1 (CPT-1) mRNA. Therefore, the DHA effect appears to be cell-selective. Results of experiments using either tetradecylthio acetic acid and alpha-bromopalmitate, two nonmetabolized Fas, or a series of inhibitors of FA metabolism show that the FA effect on PEPCK mRNA is not due to a product of its metabolism. Hence, polyunsaturated and nonmetabolized FAs stimulate adipose PEPCK, therefore potentially enhancing glyceroneogenesis and reducing FA output. This mechanism could participate in the hypolipidemic action of PUFAs.
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MESH Headings
- Adipocytes/drug effects
- Adipocytes/metabolism
- Adipose Tissue/drug effects
- Adipose Tissue/metabolism
- Animals
- Carcinoma, Hepatocellular/genetics
- Carcinoma, Hepatocellular/metabolism
- Cells, Cultured
- Docosahexaenoic Acids/metabolism
- Docosahexaenoic Acids/pharmacology
- Dose-Response Relationship, Drug
- Fatty Acids, Unsaturated/metabolism
- Fatty Acids, Unsaturated/pharmacology
- Gene Expression Regulation/drug effects
- Half-Life
- Liver Neoplasms/genetics
- Liver Neoplasms/metabolism
- Male
- Nutritional Status
- Phosphoenolpyruvate Carboxykinase (GTP)/drug effects
- Phosphoenolpyruvate Carboxykinase (GTP)/genetics
- Phosphoenolpyruvate Carboxykinase (GTP)/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Transcription, Genetic
- Tumor Cells, Cultured
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Affiliation(s)
- Eric Duplus
- INSERM Unit 530, Centre Universitaire des Saints-Pères, 45 rue des Saints-Pères, 75006, Paris, France
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Abstract
Glyceroneogenesis is a generally ignored metabolic pathway that occurs in adipose tissues and liver of mammalian species. This short review highlights a series of recent discoveries showing that glyceroneogenesis is important in lipid homeostasis.
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Affiliation(s)
- Elmus G Beale
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA.
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Abstract
Besides their role as energetic molecules, fatty acids (FAs) also act as signals involved in regulating gene expression. This review focuses on a few examples of FA regulation. The hepatic lipogenic enzyme, fatty acid synthase (FAS) is negatively regulated by polyunsaturated FAs (PUFAs) which suppress sterol regulatory element-binding protein 1 (SREBP 1) gene expression and nuclear content in hepatocytes, thereby reducing FAS gene transcription. It was proposed recently that this reduction in SREBP 1 was the result of a PUFA-induced antagonism of ligand-dependent activation of the liver X nuclear receptor (LXR), known to be an inducer of the SREBP 1 gene. In contrast, several genes are turned on by long-chain (LCFAs) and nonmetabolized FAs in a physiologically relevant manner. These include the acyl-CoA oxidase (AOX), the liver carnitine palmitoyltransferase 1 (L-CPT 1) and the liver fatty acid binding protein (L-FABP). While induction of AOX gene transcription appears to be PPARalpha-dependent, that of the L-CPT 1 gene seems disconnected from PPAR activation. Results obtained in preadipocytes and in intestine cells are in support of a key role played by the beta/delta isoform of PPAR in LCFA induction of the FABP gene. Transcription of the phosphoenolpyruvate carboxykinase (PEPCK) gene is stimulated by unsaturated and nonmetabolized LCFAs specifically in adipocytes. Our results reported here support the notion that the mechanisms by which PPARgamma activators and FAs induce transcription of the PEPCK gene are distinct. Altogether these data argue that several FA effects are PPAR-independent. Evidences suggesting that other transcription factors might be involved are debated. It seems now clear that depending upon the cell-specific context and the target gene, FAs can take very different routes to alter transcription.
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Affiliation(s)
- Eric Duplus
- Inserm U530-Université Paris 5, Centre Universitaire U.F.R. Biomédicale, 45 rue des Saints-Pères, 75006 Paris, France
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Martens FMAC, Visseren FLJ, Lemay J, de Koning EJP, Rabelink TJ. Metabolic and additional vascular effects of thiazolidinediones. Drugs 2002; 62:1463-80. [PMID: 12093315 DOI: 10.2165/00003495-200262100-00004] [Citation(s) in RCA: 209] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Several cardiovascular risk factors (dyslipidaemia, hypertension, glucose intolerance, hypercoagulability, obesity, hyperinsulinaemia and low-grade inflammation) cluster in the insulin resistance syndrome. Treatment of these individual risk factors reduces cardiovascular complications. However, targeting the underlying pathophysiological mechanisms of the insulin resistance syndrome is a more rational treatment strategy to further improve cardiovascular outcome. Our understanding of the so-called cardiovascular dysmetabolic syndrome has been improved by the discovery of nuclear peroxisome proliferator-activated receptors (PPARs). PPARs are ligand-activated transcription factors belonging to the nuclear receptor superfamily. As transcription factors, PPARs regulate the expression of numerous genes and affect glycaemic control, lipid metabolism, vascular tone and inflammation. Activation of the subtype PPAR-gamma improves insulin sensitivity. Expression of PPAR-gamma is present in several cell types involved in the process of atherosclerosis. Thus, modulation of PPAR-gamma activity is an interesting therapeutic approach to reduce cardiovascular events. Thiazolidinediones are PPAR-gamma agonists and constitute a new class of pharmacological agents for the treatment of type 2 (non-insulin-dependent) diabetes mellitus. Two such compounds are currently available for clinical use: rosiglitazone and pioglitazone. Thiazolidinediones improve insulin sensitivity and glycaemic control in patients with type 2 diabetes. In addition, improvement in endothelial function, a decrease in inflammatory conditions, a decrease in plasma levels of free fatty acids and lower blood pressure have been observed, which may have important beneficial effects on the vasculature. Several questions remain to be answered about PPAR-gamma agonists, particularly with respect to the role of PPAR-gamma in vascular pathophysiology. More needs to be known about the adverse effects of thiazolidinediones, such as hepatotoxicity, increased low-density lipoprotein cholesterol levels and increased oedema. The paradox of adipocyte differentiation with weight gain concurring with the insulin-sensitising effect of thiazolidinediones is not completely understood. The decrease in blood pressure induced by thiazolidinedione treatment seems incompatible with an increase in the plasma volume, and the discrepancy between the stimulation of the expression of CD36 and the antiatherogenic effects of the thiazolidinediones also needs further explanation. Long-term clinical trials of thiazolidinediones with cardiovascular endpoints are currently in progress. In conclusion, studying the effects of thiazolidinediones may shed more light on the mechanisms involved in the insulin resistance syndrome. Furthermore, thiazolidinediones could have specific, direct effects on processes involved in the development of vascular abnormalities.
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Affiliation(s)
- Fabrice M A C Martens
- Department of Internal Medicine, Section of Vascular Medicine and Diabetology, University Medical Center Utrecht, Room F.02.126, Heidelberglaan 100, PO Box 85500, 3508 GA Utrecht, The Netherlands.
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