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Krishnamurthy KA, Rutten MGS, Hoogerland JA, van Dijk TH, Bos T, Koehorst M, de Vries MP, Kloosterhuis NJ, Havinga H, Schomakers BV, van Weeghel M, Wolters JC, Bakker BM, Oosterveer MH. Hepatic ChREBP orchestrates intrahepatic carbohydrate metabolism to limit hepatic glucose 6-phosphate and glycogen accumulation in a mouse model for acute Glycogen Storage Disease type Ib. Mol Metab 2024; 79:101838. [PMID: 37995884 PMCID: PMC10716006 DOI: 10.1016/j.molmet.2023.101838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 11/13/2023] [Indexed: 11/25/2023] Open
Abstract
OBJECTIVE Carbohydrate Response Element Binding Protein (ChREBP) is a glucose 6-phosphate (G6P)-sensitive transcription factor that acts as a metabolic switch to maintain intracellular glucose and phosphate homeostasis. Hepatic ChREBP is well-known for its regulatory role in glycolysis, the pentose phosphate pathway, and de novo lipogenesis. The physiological role of ChREBP in hepatic glycogen metabolism and blood glucose regulation has not been assessed in detail, and ChREBP's contribution to carbohydrate flux adaptations in hepatic Glycogen Storage Disease type 1 (GSD I) requires further investigation. METHODS The current study aimed to investigate the role of ChREBP as a regulator of glycogen metabolism in response to hepatic G6P accumulation, using a model for acute hepatic GSD type Ib. The immediate biochemical and regulatory responses to hepatic G6P accumulation were evaluated upon G6P transporter inhibition by the chlorogenic acid S4048 in mice that were either treated with a short hairpin RNA (shRNA) directed against ChREBP (shChREBP) or a scrambled shRNA (shSCR). Complementary stable isotope experiments were performed to quantify hepatic carbohydrate fluxes in vivo. RESULTS ShChREBP treatment normalized the S4048-mediated induction of hepatic ChREBP target genes to levels observed in vehicle- and shSCR-treated controls. In parallel, hepatic shChREBP treatment in S4048-infused mice resulted in a more pronounced accumulation of hepatic glycogen and further reduction of blood glucose levels compared to shSCR treatment. Hepatic ChREBP knockdown modestly increased glucokinase (GCK) flux in S4048-treated mice while it enhanced UDP-glucose turnover as well as glycogen synthase and phosphorylase fluxes. Hepatic GCK mRNA and protein levels were induced by shChREBP treatment in both vehicle- and S4048-treated mice, while glycogen synthase 2 (GYS2) and glycogen phosphorylase (PYGL) mRNA and protein levels were reduced. Finally, knockdown of hepatic ChREBP expression reduced starch domain binding protein 1 (STBD1) mRNA and protein levels while it inhibited acid alpha-glucosidase (GAA) activity, suggesting reduced capacity for lysosomal glycogen breakdown. CONCLUSIONS Our data show that ChREBP activation controls hepatic glycogen and blood glucose levels in acute hepatic GSD Ib through concomitant regulation of glucose phosphorylation, glycogenesis, and glycogenolysis. ChREBP-mediated control of GCK enzyme levels aligns with corresponding adaptations in GCK flux. In contrast, ChREBP activation in response to acute hepatic GSD Ib exerts opposite effects on GYS2/PYGL enzyme levels and their corresponding fluxes, indicating that GYS2/PYGL expression levels are not limiting to their respective fluxes under these conditions.
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Affiliation(s)
- K A Krishnamurthy
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands
| | - M G S Rutten
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands
| | - J A Hoogerland
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands
| | - T H van Dijk
- Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, The Netherlands
| | - T Bos
- Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, The Netherlands
| | - M Koehorst
- Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, The Netherlands
| | - M P de Vries
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands; Interfaculty Mass Spectrometry Center, University of Groningen, University Medical Center Groningen, The Netherlands
| | - N J Kloosterhuis
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands
| | - H Havinga
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands
| | - B V Schomakers
- Laboratory Genetic Metabolic Diseases, UMC Amsterdam, The Netherlands; Core Facility Metabolomics, UMC Amsterdam, The Netherlands
| | - M van Weeghel
- Laboratory Genetic Metabolic Diseases, UMC Amsterdam, The Netherlands; Core Facility Metabolomics, UMC Amsterdam, The Netherlands
| | - J C Wolters
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands; Interfaculty Mass Spectrometry Center, University of Groningen, University Medical Center Groningen, The Netherlands
| | - B M Bakker
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands
| | - M H Oosterveer
- Laboratory of Pediatrics, University of Groningen, University Medical Center Groningen, The Netherlands; Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, The Netherlands.
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2
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Uehara K, Santoleri D, Whitlock AEG, Titchenell PM. Insulin Regulation of Hepatic Lipid Homeostasis. Compr Physiol 2023; 13:4785-4809. [PMID: 37358513 PMCID: PMC10760932 DOI: 10.1002/cphy.c220015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
Abstract
The incidence of obesity, insulin resistance, and type II diabetes (T2DM) continues to rise worldwide. The liver is a central insulin-responsive metabolic organ that governs whole-body metabolic homeostasis. Therefore, defining the mechanisms underlying insulin action in the liver is essential to our understanding of the pathogenesis of insulin resistance. During periods of fasting, the liver catabolizes fatty acids and stored glycogen to meet the metabolic demands of the body. In postprandial conditions, insulin signals to the liver to store excess nutrients into triglycerides, cholesterol, and glycogen. In insulin-resistant states, such as T2DM, hepatic insulin signaling continues to promote lipid synthesis but fails to suppress glucose production, leading to hypertriglyceridemia and hyperglycemia. Insulin resistance is associated with the development of metabolic disorders such as cardiovascular and kidney disease, atherosclerosis, stroke, and cancer. Of note, nonalcoholic fatty liver disease (NAFLD), a spectrum of diseases encompassing fatty liver, inflammation, fibrosis, and cirrhosis, is linked to abnormalities in insulin-mediated lipid metabolism. Therefore, understanding the role of insulin signaling under normal and pathologic states may provide insights into preventative and therapeutic opportunities for the treatment of metabolic diseases. Here, we provide a review of the field of hepatic insulin signaling and lipid regulation, including providing historical context, detailed molecular mechanisms, and address gaps in our understanding of hepatic lipid regulation and the derangements under insulin-resistant conditions. © 2023 American Physiological Society. Compr Physiol 13:4785-4809, 2023.
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Affiliation(s)
- Kahealani Uehara
- Institute of Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Dominic Santoleri
- Institute of Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Anna E. Garcia Whitlock
- Institute of Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Paul M. Titchenell
- Institute of Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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3
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Régnier M, Carbinatti T, Parlati L, Benhamed F, Postic C. The role of ChREBP in carbohydrate sensing and NAFLD development. Nat Rev Endocrinol 2023; 19:336-349. [PMID: 37055547 DOI: 10.1038/s41574-023-00809-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/31/2023] [Indexed: 04/15/2023]
Abstract
Excessive sugar consumption and defective glucose sensing by hepatocytes contribute to the development of metabolic diseases including type 2 diabetes mellitus (T2DM) and nonalcoholic fatty liver disease (NAFLD). Hepatic metabolism of carbohydrates into lipids is largely dependent on the carbohydrate-responsive element binding protein (ChREBP), a transcription factor that senses intracellular carbohydrates and activates many different target genes, through the activation of de novo lipogenesis (DNL). This process is crucial for the storage of energy as triglycerides in hepatocytes. Furthermore, ChREBP and its downstream targets represent promising targets for the development of therapies for the treatment of NAFLD and T2DM. Although lipogenic inhibitors (for example, inhibitors of fatty acid synthase, acetyl-CoA carboxylase or ATP citrate lyase) are currently under investigation, targeting lipogenesis remains a topic of discussion for NAFLD treatment. In this Review, we discuss mechanisms that regulate ChREBP activity in a tissue-specific manner and their respective roles in controlling DNL and beyond. We also provide in-depth discussion of the roles of ChREBP in the onset and progression of NAFLD and consider emerging targets for NAFLD therapeutics.
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Affiliation(s)
- Marion Régnier
- Université Paris Cité, Institut Cochin, CNRS, INSERM, Paris, France.
| | - Thaïs Carbinatti
- Université Paris Cité, Institut Cochin, CNRS, INSERM, Paris, France
| | - Lucia Parlati
- Université Paris Cité, Institut Cochin, CNRS, INSERM, Paris, France
| | - Fadila Benhamed
- Université Paris Cité, Institut Cochin, CNRS, INSERM, Paris, France
| | - Catherine Postic
- Université Paris Cité, Institut Cochin, CNRS, INSERM, Paris, France.
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Iizuka K. Recent Progress on Fructose Metabolism-Chrebp, Fructolysis, and Polyol Pathway. Nutrients 2023; 15:nu15071778. [PMID: 37049617 PMCID: PMC10096667 DOI: 10.3390/nu15071778] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 03/26/2023] [Accepted: 03/29/2023] [Indexed: 04/14/2023] Open
Abstract
Excess fructose intake is associated with obesity, fatty liver, tooth decay, cancer, and cardiovascular diseases. Even after the ingestion of fructose, fructose concentration in the portal blood is never high; fructose is further metabolized in the liver, and the blood fructose concentration is 1/100th of the glucose concentration. It was previously thought that fructose was metabolized in the liver and not in the small intestine, but it has been reported that metabolism in the small intestine also plays an important role in fructose metabolism. Glut5 knockout mice exhibit poor fructose absorption. In addition, endogenous fructose production via the polyol pathway has also received attention; gene deletion of aldose reductase (Ar), ketohexokinase (Khk), and triokinase (Tkfc) has been found to prevent the development of fructose-induced liver lipidosis. Carbohydrate response element-binding protein (Chrebp) regulates the expression of Glut5, Khk, aldolase b, and Tkfc. We review fructose metabolism with a focus on the roles of the glucose-activating transcription factor Chrebp, fructolysis, and the polyol pathway.
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Affiliation(s)
- Katsumi Iizuka
- Department of Clinical Nutrition, Fujita Health University, Toyoake 470-1192, Japan
- Food and Nutrition Service Department, Fujita Health University Hospital, Toyoake 470-1192, Japan
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Molares-Vila A, Corbalán-Rivas A, Carnero-Gregorio M, González-Cespón JL, Rodríguez-Cerdeira C. Biomarkers in Glycogen Storage Diseases: An Update. Int J Mol Sci 2021; 22:4381. [PMID: 33922238 PMCID: PMC8122709 DOI: 10.3390/ijms22094381] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 04/10/2021] [Accepted: 04/19/2021] [Indexed: 01/09/2023] Open
Abstract
Glycogen storage diseases (GSDs) are a group of 19 hereditary diseases caused by a lack of one or more enzymes involved in the synthesis or degradation of glycogen and are characterized by deposits or abnormal types of glycogen in tissues. Their frequency is very low and they are considered rare diseases. Except for X-linked type IX, the different types are inherited in an autosomal recessive pattern. In this study we reviewed the literature from 1977 to 2020 concerning GSDs, biomarkers, and metabolic imbalances in the symptoms of some GSDs. Most of the reported studies were performed with very few patients. Classification of emerging biomarkers between different types of diseases (hepatics GSDs, McArdle and PDs and other possible biomarkers) was done for better understanding. Calprotectin for hepatics GSDs and urinary glucose tetrasaccharide for Pompe disease have been approved for clinical use, and most of the markers mentioned in this review only need clinical validation, as a final step for their routine use. Most of the possible biomarkers are implied in hepatocellular adenomas, cardiomyopathies, in malfunction of skeletal muscle, in growth retardation, neutropenia, osteopenia and bowel inflammation. However, a few markers have lost interest due to a great variability of results, which is the case of biotinidase, actin alpha 2, smooth muscle, aorta and fibroblast growth factor receptor 4. This is the first review published on emerging biomarkers with a potential application to GSDs.
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Affiliation(s)
- Alberto Molares-Vila
- Bioinformatics Platform, Health Research Institute in Santiago de Compostela (IDIS), SERGAS-USC, 15706 Santiago de Compostela, Spain;
| | - Alberte Corbalán-Rivas
- Local Office of Health Inspection, Health Ministry at Galician Autonomous Region, 27880 Burela, Spain;
| | - Miguel Carnero-Gregorio
- Department of Molecular Diagnosis (Arrays Division), Institute of Cellular and Molecular Studies (ICM), 27003 Lugo, Spain;
- Efficiency, Quality, and Costs in Health Services Research Group (EFISALUD), Galicia Sur Health Research Institute (IIS Galicia Sur), SERGAS-UVIGO, 36213 Vigo, Spain;
| | - José Luís González-Cespón
- Efficiency, Quality, and Costs in Health Services Research Group (EFISALUD), Galicia Sur Health Research Institute (IIS Galicia Sur), SERGAS-UVIGO, 36213 Vigo, Spain;
| | - Carmen Rodríguez-Cerdeira
- Efficiency, Quality, and Costs in Health Services Research Group (EFISALUD), Galicia Sur Health Research Institute (IIS Galicia Sur), SERGAS-UVIGO, 36213 Vigo, Spain;
- Dermatology Department, Complexo Hospitalario Universitario de Vigo (CHUVI), Meixoeiro Hospital, SERGAS, 36213 Vigo, Spain
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6
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Adaptive and maladaptive roles for ChREBP in the liver and pancreatic islets. J Biol Chem 2021; 296:100623. [PMID: 33812993 PMCID: PMC8102921 DOI: 10.1016/j.jbc.2021.100623] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 03/29/2021] [Accepted: 03/31/2021] [Indexed: 12/14/2022] Open
Abstract
Excessive sugar consumption is a contributor to the worldwide epidemic of cardiometabolic disease. Understanding mechanisms by which sugar is sensed and regulates metabolic processes may provide new opportunities to prevent and treat these epidemics. Carbohydrate Responsive-Element Binding Protein (ChREBP) is a sugar-sensing transcription factor that mediates genomic responses to changes in carbohydrate abundance in key metabolic tissues. Carbohydrate metabolites activate the canonical form of ChREBP, ChREBP-alpha, which stimulates production of a potent, constitutively active ChREBP isoform called ChREBP-beta. Carbohydrate metabolites and other metabolic signals may also regulate ChREBP activity via posttranslational modifications including phosphorylation, acetylation, and O-GlcNAcylation that can affect ChREBP’s cellular localization, stability, binding to cofactors, and transcriptional activity. In this review, we discuss mechanisms regulating ChREBP activity and highlight phenotypes and controversies in ChREBP gain- and loss-of-function genetic rodent models focused on the liver and pancreatic islets.
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Daniel PV, Mondal P. Causative and Sanative dynamicity of ChREBP in Hepato-Metabolic disorders. Eur J Cell Biol 2020; 99:151128. [PMID: 33232883 DOI: 10.1016/j.ejcb.2020.151128] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 10/22/2020] [Accepted: 10/28/2020] [Indexed: 12/12/2022] Open
Abstract
ChREBP is the master regulator of carbohydrate dependent glycolytic and lipogenic flux within metabolic tissues. It plays a vital role in hyper-calorific milieu by activating glycolysis, lipogenesis along with pentose phosphate shunt and glycogen synthesis, fostering immediate reduction in the systemic glycemic levels. Liver being the primary organ to sense disproportionate dietary intake and linked physiological stress, stimulates ChREBP to perform the aforementioned processes. Activated ChREBP also inhibits lipolysis and encourages proper disposal of excessive triglycerides into adipocytes from the liver ablating hepatic intracellular lipid trafficking. Chronic overeating or onset of positive energy balance, hyper-activates ChREBP and signals development, intensification of hepato-metabolic disorders, and allied discrepancies in the whole-body metabolic functioning. ChREBP thus gets negatively connotated as the primary regulator of hepatic disorders, owing to its inherent features as the primary glycemic sensor and the only transcription factor that can transduce glucose-dependent glycolytic and lipogenic signals. Through this review, we - try to recapitulate and emphasize on the sanative events coordinated by ChREBP in several pathophysiological states. In totality, we aim to uncouple the disease-causing aspects of ChREBP from its positive attributes evoked during a metabolic crisis, in hepato-metabolic diseases.
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Affiliation(s)
- P Vineeth Daniel
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175001, H.P, India.
| | - Prosenjit Mondal
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175001, H.P, India.
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Lei Y, Hoogerland JA, Bloks VW, Bos T, Bleeker A, Wolters H, Wolters JC, Hijmans BS, van Dijk TH, Thomas R, van Weeghel M, Mithieux G, Houtkooper RH, de Bruin A, Rajas F, Kuipers F, Oosterveer MH. Hepatic Carbohydrate Response Element Binding Protein Activation Limits Nonalcoholic Fatty Liver Disease Development in a Mouse Model for Glycogen Storage Disease Type 1a. Hepatology 2020; 72:1638-1653. [PMID: 32083759 PMCID: PMC7702155 DOI: 10.1002/hep.31198] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 01/29/2020] [Accepted: 02/03/2020] [Indexed: 01/05/2023]
Abstract
BACKGROUND AND AIMS Glycogen storage disease (GSD) type 1a is an inborn error of metabolism caused by defective glucose-6-phosphatase catalytic subunit (G6PC) activity. Patients with GSD 1a exhibit severe hepatomegaly due to glycogen and triglyceride (TG) accumulation in the liver. We have shown that the activity of carbohydrate response element binding protein (ChREBP), a key regulator of glycolysis and de novo lipogenesis, is increased in GSD 1a. In the current study, we assessed the contribution of ChREBP to nonalcoholic fatty liver disease (NAFLD) development in a mouse model for hepatic GSD 1a. APPROACH AND RESULTS Liver-specific G6pc-knockout (L-G6pc-/- ) mice were treated with adeno-associated viruses (AAVs) 2 or 8 directed against short hairpin ChREBP to normalize hepatic ChREBP activity to levels observed in wild-type mice receiving AAV8-scrambled short hairpin RNA (shSCR). Hepatic ChREBP knockdown markedly increased liver weight and hepatocyte size in L-G6pc-/- mice. This was associated with hepatic accumulation of G6P, glycogen, and lipids, whereas the expression of glycolytic and lipogenic genes was reduced. Enzyme activities, flux measurements, hepatic metabolite analysis and very low density lipoprotein (VLDL)-TG secretion assays revealed that hepatic ChREBP knockdown reduced downstream glycolysis and de novo lipogenesis but also strongly suppressed hepatic VLDL lipidation, hence promoting the storage of "old fat." Interestingly, enhanced VLDL-TG secretion in shSCR-treated L-G6pc-/- mice associated with a ChREBP-dependent induction of the VLDL lipidation proteins microsomal TG transfer protein and transmembrane 6 superfamily member 2 (TM6SF2), the latter being confirmed by ChIP-qPCR. CONCLUSIONS Attenuation of hepatic ChREBP induction in GSD 1a liver aggravates hepatomegaly because of further accumulation of glycogen and lipids as a result of reduced glycolysis and suppressed VLDL-TG secretion. TM6SF2, critical for VLDL formation, was identified as a ChREBP target in mouse liver. Altogether, our data show that enhanced ChREBP activity limits NAFLD development in GSD 1a by balancing hepatic TG production and secretion.
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Affiliation(s)
- Yu Lei
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Joanne A. Hoogerland
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Vincent W. Bloks
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Trijnie Bos
- Department of Laboratory MedicineUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Aycha Bleeker
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Henk Wolters
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Justina C. Wolters
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Brenda S. Hijmans
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Theo H. van Dijk
- Department of Laboratory MedicineUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Rachel Thomas
- Dutch Molecular Pathology CenterFaculty of Veterinary MedicineUtrecht UniversityUtrechtthe Netherlands
| | - Michel van Weeghel
- Laboratory Genetic Metabolic DiseasesAmsterdam Gastroenterology and MetabolismAmsterdam Cardiovascular SciencesAmsterdamthe Netherlands,Core Facility of MetabolomicsAmsterdam University Medical CenterUniversity of AmsterdamAmsterdamthe Netherlands
| | - Gilles Mithieux
- National Institute of Health and Medical Research, U1213LyonFrance,University of LyonLyonFrance,University of Lyon 1VilleurbanneFrance
| | - Riekelt H. Houtkooper
- Laboratory Genetic Metabolic DiseasesAmsterdam Gastroenterology and MetabolismAmsterdam Cardiovascular SciencesAmsterdamthe Netherlands
| | - Alain de Bruin
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands,Dutch Molecular Pathology CenterFaculty of Veterinary MedicineUtrecht UniversityUtrechtthe Netherlands
| | - Fabienne Rajas
- National Institute of Health and Medical Research, U1213LyonFrance,University of LyonLyonFrance,University of Lyon 1VilleurbanneFrance
| | - Folkert Kuipers
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands,Department of Laboratory MedicineUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
| | - Maaike H. Oosterveer
- Department of PediatricsUniversity Medical Center GroningenUniversity of GroningenGroningenthe Netherlands
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9
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Saeed A, Hoogerland JA, Wessel H, Heegsma J, Derks TGJ, van der Veer E, Mithieux G, Rajas F, Oosterveer MH, Faber KN. Glycogen storage disease type 1a is associated with disturbed vitamin A metabolism and elevated serum retinol levels. Hum Mol Genet 2020; 29:264-273. [PMID: 31813960 PMCID: PMC7001719 DOI: 10.1093/hmg/ddz283] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 01/02/2023] Open
Abstract
Glycogen storage disease type 1a (GSD Ia) is an inborn error of metabolism caused by mutations in the G6PC gene, encoding the catalytic subunit of glucose-6-phosphatase. Early symptoms include severe fasting intolerance, failure to thrive and hepatomegaly, biochemically associated with nonketotic hypoglycemia, fasting hyperlactidemia, hyperuricemia and hyperlipidemia. Dietary management is the cornerstone of treatment aiming at maintaining euglycemia, prevention of secondary metabolic perturbations and long-term complications, including liver (hepatocellular adenomas and carcinomas), kidney and bone disease (hypovitaminosis D and osteoporosis). As impaired vitamin A homeostasis also associates with similar symptoms and is coordinated by the liver, we here analysed whether vitamin A metabolism is affected in GSD Ia patients and liver-specific G6pc−/− knock-out mice. Serum levels of retinol and retinol binding protein 4 (RBP4) were significantly increased in both GSD Ia patients and L-G6pc−/− mice. In contrast, hepatic retinol levels were significantly reduced in L-G6pc−/− mice, while hepatic retinyl palmitate (vitamin A storage form) and RBP4 levels were not altered. Transcript and protein analyses indicate an enhanced production of retinol and reduced conversion the retinoic acids (unchanged LRAT, Pnpla2/ATGL and Pnpla3 up, Cyp26a1 down) in L-G6pc−/− mice. Aberrant expression of genes involved in vitamin A metabolism was associated with reduced basal messenger RNA levels of markers of inflammation (Cd68, Tnfα, Nos2, Il-6) and fibrosis (Col1a1, Acta2, Tgfβ, Timp1) in livers of L-G6pc−/− mice. In conclusion, GSD Ia is associated with elevated serum retinol and RBP4 levels, which may contribute to disease symptoms, including osteoporosis and hepatic steatosis.
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Affiliation(s)
- Ali Saeed
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.,Institute of Molecular Biology and Biotechnology, Bahauddin Zakariya University Multan, Pakistan
| | - Joanne A Hoogerland
- Department of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Hanna Wessel
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Janette Heegsma
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.,Laboratory Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Terry G J Derks
- Section of Metabolic Diseases, Beatrix Children's Hospital, Center for Liver Digestive, and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Eveline van der Veer
- Laboratory Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Gilles Mithieux
- Institut National de la Santé et de la Recherche Médicale, U1213, Lyon F-69008.,Universite de Lyon, Lyon F-69008, France.,Université Lyon 1, Villeurbanne F-69622, France
| | - Fabienne Rajas
- Institut National de la Santé et de la Recherche Médicale, U1213, Lyon F-69008.,Universite de Lyon, Lyon F-69008, France.,Université Lyon 1, Villeurbanne F-69622, France
| | - Maaike H Oosterveer
- Department of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Klaas Nico Faber
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.,Laboratory Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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10
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Agius L, Ford BE, Chachra SS. The Metformin Mechanism on Gluconeogenesis and AMPK Activation: The Metabolite Perspective. Int J Mol Sci 2020; 21:ijms21093240. [PMID: 32375255 PMCID: PMC7247334 DOI: 10.3390/ijms21093240] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 12/13/2022] Open
Abstract
Metformin therapy lowers blood glucose in type 2 diabetes by targeting various pathways including hepatic gluconeogenesis. Despite widespread clinical use of metformin the molecular mechanisms by which it inhibits gluconeogenesis either acutely through allosteric and covalent mechanisms or chronically through changes in gene expression remain debated. Proposed mechanisms include: inhibition of Complex 1; activation of AMPK; and mechanisms independent of both Complex 1 inhibition and AMPK. The activation of AMPK by metformin could be consequent to Complex 1 inhibition and raised AMP through the canonical adenine nucleotide pathway or alternatively by activation of the lysosomal AMPK pool by other mechanisms involving the aldolase substrate fructose 1,6-bisphosphate or perturbations in the lysosomal membrane. Here we review current interpretations of the effects of metformin on hepatic intermediates of the gluconeogenic and glycolytic pathway and the candidate mechanistic links to regulation of gluconeogenesis. In conditions of either glucose excess or gluconeogenic substrate excess, metformin lowers hexose monophosphates by mechanisms that are independent of AMPK-activation and most likely mediated by allosteric activation of phosphofructokinase-1 and/or inhibition of fructose bisphosphatase-1. The metabolite changes caused by metformin may also have a prominent role in counteracting G6pc gene regulation in conditions of compromised intracellular homeostasis.
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11
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Moonira T, Chachra SS, Ford BE, Marin S, Alshawi A, Adam-Primus NS, Arden C, Al-Oanzi ZH, Foretz M, Viollet B, Cascante M, Agius L. Metformin lowers glucose 6-phosphate in hepatocytes by activation of glycolysis downstream of glucose phosphorylation. J Biol Chem 2020; 295:3330-3346. [PMID: 31974165 PMCID: PMC7062158 DOI: 10.1074/jbc.ra120.012533] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Indexed: 12/31/2022] Open
Abstract
The chronic effects of metformin on liver gluconeogenesis involve repression of the G6pc gene, which is regulated by the carbohydrate-response element-binding protein through raised cellular intermediates of glucose metabolism. In this study we determined the candidate mechanisms by which metformin lowers glucose 6-phosphate (G6P) in mouse and rat hepatocytes challenged with high glucose or gluconeogenic precursors. Cell metformin loads in the therapeutic range lowered cell G6P but not ATP and decreased G6pc mRNA at high glucose. The G6P lowering by metformin was mimicked by a complex 1 inhibitor (rotenone) and an uncoupler (dinitrophenol) and by overexpression of mGPDH, which lowers glycerol 3-phosphate and G6P and also mimics the G6pc repression by metformin. In contrast, direct allosteric activators of AMPK (A-769662, 991, and C-13) had opposite effects from metformin on glycolysis, gluconeogenesis, and cell G6P. The G6P lowering by metformin, which also occurs in hepatocytes from AMPK knockout mice, is best explained by allosteric regulation of phosphofructokinase-1 and/or fructose bisphosphatase-1, as supported by increased metabolism of [3-3H]glucose relative to [2-3H]glucose; by an increase in the lactate m2/m1 isotopolog ratio from [1,2-13C2]glucose; by lowering of glycerol 3-phosphate an allosteric inhibitor of phosphofructokinase-1; and by marked G6P elevation by selective inhibition of phosphofructokinase-1; but not by a more reduced cytoplasmic NADH/NAD redox state. We conclude that therapeutically relevant doses of metformin lower G6P in hepatocytes challenged with high glucose by stimulation of glycolysis by an AMP-activated protein kinase-independent mechanism through changes in allosteric effectors of phosphofructokinase-1 and fructose bisphosphatase-1, including AMP, Pi, and glycerol 3-phosphate.
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Affiliation(s)
- Tabassum Moonira
- Biosciences Institute, Newcastle University, Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Shruti S Chachra
- Biosciences Institute, Newcastle University, Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Brian E Ford
- Biosciences Institute, Newcastle University, Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Silvia Marin
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Universitat de Barcelona, 08007 Barcelona, Spain; CIBEREHD and Metabolomics Node at INB-Bioinformatics Platform, Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Ahmed Alshawi
- Biosciences Institute, Newcastle University, Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Natasha S Adam-Primus
- Biosciences Institute, Newcastle University, Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Catherine Arden
- Biosciences Institute, Newcastle University, Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Ziad H Al-Oanzi
- Biosciences Institute, Newcastle University, Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Marc Foretz
- INSERM, U1016, Institut Cochin, Paris 75014, France; CNRS, UMR8104, Paris 75014, France; Université Paris Descartes, Sorbonne Paris Cité, Paris 75014, France
| | - Benoit Viollet
- INSERM, U1016, Institut Cochin, Paris 75014, France; CNRS, UMR8104, Paris 75014, France; Université Paris Descartes, Sorbonne Paris Cité, Paris 75014, France
| | - Marta Cascante
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Universitat de Barcelona, 08007 Barcelona, Spain; CIBEREHD and Metabolomics Node at INB-Bioinformatics Platform, Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Loranne Agius
- Biosciences Institute, Newcastle University, Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom.
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12
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Agius L, Chachra SS, Ford BE. The Protective Role of the Carbohydrate Response Element Binding Protein in the Liver: The Metabolite Perspective. Front Endocrinol (Lausanne) 2020; 11:594041. [PMID: 33281747 PMCID: PMC7705168 DOI: 10.3389/fendo.2020.594041] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 10/16/2020] [Indexed: 12/15/2022] Open
Abstract
The Carbohydrate response element binding protein, ChREBP encoded by the MLXIPL gene, is a transcription factor that is expressed at high levels in the liver and has a prominent function during consumption of high-carbohydrate diets. ChREBP is activated by raised cellular levels of phosphate ester intermediates of glycolysis, gluconeogenesis and the pentose phosphate pathway. Its target genes include a wide range of enzymes and regulatory proteins, including G6pc, Gckr, Pklr, Prkaa1,2, and enzymes of lipogenesis. ChREBP activation cumulatively promotes increased disposal of phosphate ester intermediates to glucose, via glucose 6-phosphatase or to pyruvate via glycolysis with further metabolism by lipogenesis. Dietary fructose is metabolized in both the intestine and the liver and is more lipogenic than glucose. It also induces greater elevation in phosphate ester intermediates than glucose, and at high concentrations causes transient depletion of inorganic phosphate, compromised ATP homeostasis and degradation of adenine nucleotides to uric acid. ChREBP deficiency predisposes to fructose intolerance and compromised cellular phosphate ester and ATP homeostasis and thereby markedly aggravates the changes in metabolite levels caused by dietary fructose. The recent evidence that high fructose intake causes more severe hepatocyte damage in ChREBP-deficient models confirms the crucial protective role for ChREBP in maintaining intracellular phosphate homeostasis. The improved ATP homeostasis in hepatocytes isolated from mice after chronic activation of ChREBP with a glucokinase activator supports the role of ChREBP in the control of intracellular homeostasis. It is hypothesized that drugs that activate ChREBP confer a protective role in the liver particularly in compromised metabolic states.
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13
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Hoogerland JA, Lei Y, Wolters JC, de Boer JF, Bos T, Bleeker A, Mulder NL, van Dijk TH, Kuivenhoven JA, Rajas F, Mithieux G, Haeusler RA, Verkade HJ, Bloks VW, Kuipers F, Oosterveer MH. Glucose-6-Phosphate Regulates Hepatic Bile Acid Synthesis in Mice. Hepatology 2019; 70:2171-2184. [PMID: 31102537 PMCID: PMC6859192 DOI: 10.1002/hep.30778] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 05/15/2019] [Indexed: 12/22/2022]
Abstract
It is well established that, besides facilitating lipid absorption, bile acids act as signaling molecules that modulate glucose and lipid metabolism. Bile acid metabolism, in turn, is controlled by several nutrient-sensitive transcription factors. Altered intrahepatic glucose signaling in type 2 diabetes associates with perturbed bile acid synthesis. We aimed to characterize the regulatory role of the primary intracellular metabolite of glucose, glucose-6-phosphate (G6P), on bile acid metabolism. Hepatic gene expression patterns and bile acid composition were analyzed in mice that accumulate G6P in the liver, that is, liver-specific glucose-6-phosphatase knockout (L-G6pc-/- ) mice, and mice treated with a pharmacological inhibitor of the G6P transporter. Hepatic G6P accumulation induces sterol 12α-hydroxylase (Cyp8b1) expression, which is mediated by the major glucose-sensitive transcription factor, carbohydrate response element-binding protein (ChREBP). Activation of the G6P-ChREBP-CYP8B1 axis increases the relative abundance of cholic-acid-derived bile acids and induces physiologically relevant shifts in bile composition. The G6P-ChREBP-dependent change in bile acid hydrophobicity associates with elevated plasma campesterol/cholesterol ratio and reduced fecal neutral sterol loss, compatible with enhanced intestinal cholesterol absorption. Conclusion: We report that G6P, the primary intracellular metabolite of glucose, controls hepatic bile acid synthesis. Our work identifies hepatic G6P-ChREBP-CYP8B1 signaling as a regulatory axis in control of bile acid and cholesterol metabolism.
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Affiliation(s)
- Joanne A. Hoogerland
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Yu Lei
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Justina C. Wolters
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Jan Freark de Boer
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands,Laboratory MedicineUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands
| | - Trijnie Bos
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Aycha Bleeker
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Niels L. Mulder
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Theo H. van Dijk
- Laboratory MedicineUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands
| | - Jan A. Kuivenhoven
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Fabienne Rajas
- Institut National de la Santé et de la Recherche Médicale, U1213Université Claude Bernard LyonVilleurbanneFrance
| | - Gilles Mithieux
- Institut National de la Santé et de la Recherche Médicale, U1213Université Claude Bernard LyonVilleurbanneFrance
| | - Rebecca A. Haeusler
- Department of Pathology and Cell BiologyColumbia University College of Physicians and SurgeonsNew YorkNY
| | - Henkjan J. Verkade
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Vincent W. Bloks
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
| | - Folkert Kuipers
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands,Laboratory MedicineUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands
| | - Maaike H. Oosterveer
- Department of PediatricsUniversity Medical Center GroningenGroningenThe Netherlands
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14
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Rajas F, Gautier-Stein A, Mithieux G. Glucose-6 Phosphate, A Central Hub for Liver Carbohydrate Metabolism. Metabolites 2019; 9:metabo9120282. [PMID: 31756997 PMCID: PMC6950410 DOI: 10.3390/metabo9120282] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 11/14/2019] [Accepted: 11/18/2019] [Indexed: 12/23/2022] Open
Abstract
Cells efficiently adjust their metabolism according to the abundance of nutrients and energy. The ability to switch cellular metabolism between anabolic and catabolic processes is critical for cell growth. Glucose-6 phosphate is the first intermediate of glucose metabolism and plays a central role in the energy metabolism of the liver. It acts as a hub to metabolically connect glycolysis, the pentose phosphate pathway, glycogen synthesis, de novo lipogenesis, and the hexosamine pathway. In this review, we describe the metabolic fate of glucose-6 phosphate in a healthy liver and the metabolic reprogramming occurring in two pathologies characterized by a deregulation of glucose homeostasis, namely type 2 diabetes, which is characterized by fasting hyperglycemia; and glycogen storage disease type I, where patients develop severe hypoglycemia during short fasting periods. In these two conditions, dysfunction of glucose metabolism results in non-alcoholic fatty liver disease, which may possibly lead to the development of hepatic tumors. Moreover, we also emphasize the role of the transcription factor carbohydrate response element-binding protein (ChREBP), known to link glucose and lipid metabolisms. In this regard, comparing these two metabolic diseases is a fruitful approach to better understand the key role of glucose-6 phosphate in liver metabolism in health and disease.
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Affiliation(s)
- Fabienne Rajas
- Institut National de la Santé et de la Recherche Médicale, U1213, F-69008 Lyon, France; (A.G.-S.); (G.M.)
- Université de Lyon, F-69008 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
- Correspondence:
| | - Amandine Gautier-Stein
- Institut National de la Santé et de la Recherche Médicale, U1213, F-69008 Lyon, France; (A.G.-S.); (G.M.)
- Université de Lyon, F-69008 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
| | - Gilles Mithieux
- Institut National de la Santé et de la Recherche Médicale, U1213, F-69008 Lyon, France; (A.G.-S.); (G.M.)
- Université de Lyon, F-69008 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
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15
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Reijngoud DJ. Flux analysis of inborn errors of metabolism. J Inherit Metab Dis 2018; 41:309-328. [PMID: 29318410 PMCID: PMC5959979 DOI: 10.1007/s10545-017-0124-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 12/04/2017] [Accepted: 12/05/2017] [Indexed: 02/07/2023]
Abstract
Patients with an inborn error of metabolism (IEM) are deficient of an enzyme involved in metabolism, and as a consequence metabolism reprograms itself to reach a new steady state. This new steady state underlies the clinical phenotype associated with the deficiency. Hence, we need to know the flux of metabolites through the different metabolic pathways in this new steady state of the reprogrammed metabolism. Stable isotope technology is best suited to study this. In this review the progress made in characterizing the altered metabolism will be presented. Studies done in patients to estimate the residual flux through the metabolic pathway affected by enzyme deficiencies will be discussed. After this, studies done in model systems will be reviewed. The focus will be on glycogen storage disease type I, medium-chain acyl-CoA dehydrogenase deficiency, propionic and methylmalonic aciduria, urea cycle defects, phenylketonuria, and combined D,L-2-hydroxyglutaric aciduria. Finally, new developments are discussed, which allow the tracing of metabolic reprogramming in IEM on a genome-wide scale. In conclusion, the outlook for flux analysis of metabolic derangement in IEMs looks promising.
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Affiliation(s)
- D-J Reijngoud
- Section of Systems Medicine and Metabolic Signaling, Laboratory of Pediatrics, Department of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
- Center of Liver, Digestive and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
- European Research Institute of the Biology of Ageing, Internal ZIP code EA12, A. Deusinglaan 1, 9713, AV, Groningen, The Netherlands.
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16
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Cappello AR, Curcio R, Lappano R, Maggiolini M, Dolce V. The Physiopathological Role of the Exchangers Belonging to the SLC37 Family. Front Chem 2018; 6:122. [PMID: 29719821 PMCID: PMC5913288 DOI: 10.3389/fchem.2018.00122] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Accepted: 03/30/2018] [Indexed: 12/14/2022] Open
Abstract
The human SLC37 gene family includes four proteins SLC37A1-4, localized in the endoplasmic reticulum (ER) membrane. They have been grouped into the SLC37 family due to their sequence homology to the bacterial organophosphate/phosphate (Pi) antiporter. SLC37A1-3 are the less characterized isoforms. SLC37A1 and SLC37A2 are Pi-linked glucose-6-phosphate (G6P) antiporters, catalyzing both homologous (Pi/Pi) and heterologous (G6P/Pi) exchanges, whereas SLC37A3 transport properties remain to be clarified. Furthermore, SLC37A1 is highly homologous to the bacterial glycerol 3-phosphate permeases, so it is supposed to transport also glycerol-3-phosphate. The physiological role of SLC37A1-3 is yet to be further investigated. SLC37A1 seems to be required for lipid biosynthesis in cancer cell lines, SLC37A2 has been proposed as a vitamin D and a phospho-progesterone receptor target gene, while mutations in the SLC37A3 gene appear to be associated with congenital hyperinsulinism of infancy. SLC37A4, also known as glucose-6-phosphate translocase (G6PT), transports G6P from the cytoplasm into the ER lumen, working in complex with either glucose-6-phosphatase-α (G6Pase-α) or G6Pase-β to hydrolyze intraluminal G6P to Pi and glucose. G6PT and G6Pase-β are ubiquitously expressed, whereas G6Pase-α is specifically expressed in the liver, kidney and intestine. G6PT/G6Pase-α complex activity regulates fasting blood glucose levels, whereas G6PT/G6Pase-β is required for neutrophil functions. G6PT deficiency is responsible for glycogen storage disease type Ib (GSD-Ib), an autosomal recessive disorder associated with both defective metabolic and myeloid phenotypes. Several kinds of mutations have been identified in the SLC37A4 gene, affecting G6PT function. An increased autoimmunity risk for GSD-Ib patients has also been reported, moreover, SLC37A4 seems to be involved in autophagy.
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Affiliation(s)
- Anna Rita Cappello
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
| | - Rosita Curcio
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
| | - Rosamaria Lappano
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
| | - Marcello Maggiolini
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
| | - Vincenza Dolce
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
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17
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Hepatic mitochondrial dysfunction is a feature of Glycogen Storage Disease Type Ia (GSDIa). Sci Rep 2017; 7:44408. [PMID: 28317891 PMCID: PMC5357851 DOI: 10.1038/srep44408] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 02/10/2017] [Indexed: 12/12/2022] Open
Abstract
Glycogen storage disease type Ia (GSDIa, von Gierke disease) is the most common glycogen storage disorder. It is caused by the deficiency of glucose-6-phosphatase, an enzyme which catalyses the final step of gluconeogenesis and glycogenolysis. Clinically, GSDIa is characterized by fasting hypoglycaemia and hepatic glycogen and triglyceride overaccumulation. The latter leads to steatohepatitis, cirrhosis, and the formation of hepatic adenomas and carcinomas. Currently, little is known about the function of various organelles and their impact on metabolism in GSDIa. Accordingly, we investigated mitochondrial function in cell culture and mouse models of GSDIa. We found impairments in oxidative phosphorylation and changes in TCA cycle metabolites, as well as decreased mitochondrial membrane potential and deranged mitochondrial ultra-structure in these model systems. Mitochondrial content also was decreased, likely secondary to decreased mitochondrial biogenesis. These deleterious effects culminated in the activation of the mitochondrial apoptosis pathway. Taken together, our results demonstrate a role for mitochondrial dysfunction in the pathogenesis of GSDIa, and identify a new potential target for the treatment of this disease. They also provide new insight into the role of carbohydrate overload on mitochondrial function in other hepatic diseases, such as non-alcoholic fatty liver disease.
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18
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The transcription factor carbohydrate-response element-binding protein (ChREBP): A possible link between metabolic disease and cancer. Biochim Biophys Acta Mol Basis Dis 2016; 1863:474-485. [PMID: 27919710 DOI: 10.1016/j.bbadis.2016.11.029] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 11/24/2016] [Accepted: 11/29/2016] [Indexed: 12/19/2022]
Abstract
Carbohydrate-response element-binding protein (ChREBP) has been identified as a transcription factor that binds to carbohydrate response element in the promoter of pyruvate kinase, liver and red blood cells. ChREBP is activated by metabolites derived from glucose and suppressed by adenosine monophosphate (AMP), ketone bodies and cyclic cAMP. ChREBP regulates gene transcription related to glucose and lipid metabolism. Findings from knockout mice and human subjects suggest that ChREBP helps to induce hepatic steatosis, dyslipidemia, and glucose intolerance. Moreover, in tumor cells, ChREBP promotes aerobic glycolysis through p53 inhibition, resulting in tumor cell proliferation. Anti-diabetic and anti-lipidemic drugs such as atorvastatin, metformin, bile acid sequestrants, docosahexaenoic acid and eicosapentaenoic acid may affect ChREBP transactivity. Secretory proteins such as fibroblast growth factor 21 and ANGPTL8 (Betatrophin) may be promising candidates for biologic markers reflecting ChREBP transactivity. Thus, ChREBP is associated with metabolic diseases and cancers, and may be a link between them.
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19
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Gjorgjieva M, Oosterveer MH, Mithieux G, Rajas F. Mechanisms by Which Metabolic Reprogramming in GSD1 Liver Generates a Favorable Tumorigenic Environment. JOURNAL OF INBORN ERRORS OF METABOLISM AND SCREENING 2016. [DOI: 10.1177/2326409816679429] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Affiliation(s)
- Monika Gjorgjieva
- Institut National de la Santé et de la Recherche Médicale, U1213 “Nutrition, Diabetes and the Brain”, Lyon, France
- Université de Lyon, Lyon, France
- Université Lyon 1, Villeurbanne, France
| | - Maaike H. Oosterveer
- Department of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Gilles Mithieux
- Institut National de la Santé et de la Recherche Médicale, U1213 “Nutrition, Diabetes and the Brain”, Lyon, France
- Université de Lyon, Lyon, France
- Université Lyon 1, Villeurbanne, France
| | - Fabienne Rajas
- Institut National de la Santé et de la Recherche Médicale, U1213 “Nutrition, Diabetes and the Brain”, Lyon, France
- Université de Lyon, Lyon, France
- Université Lyon 1, Villeurbanne, France
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20
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Affiliation(s)
- Loranne Agius
- Institutes of Cellular Medicine and Ageing and Health, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH United Kingdom;
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21
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Derks TGJ, van Rijn M. Lipids in hepatic glycogen storage diseases: pathophysiology, monitoring of dietary management and future directions. J Inherit Metab Dis 2015; 38:537-43. [PMID: 25633903 PMCID: PMC4432100 DOI: 10.1007/s10545-015-9811-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 12/30/2014] [Accepted: 01/06/2015] [Indexed: 11/05/2022]
Abstract
Hepatic glycogen storage diseases (GSD) underscore the intimate relationship between carbohydrate and lipid metabolism. The hyperlipidemias in hepatic GSD reflect perturbed intracellular metabolism, providing biomarkers in blood to monitor dietary management. In different types of GSD, hyperlipidemias are of a different origin. Hypertriglyceridemia is most prominent in GSD type Ia and associated with long-term outcome morbidity, like pancreatitis and hepatic adenomas. In the ketotic subtypes of GSD, hypertriglyceridemia reflects the age-dependent fasting intolerance, secondary lipolysis and increased mitochondrial fatty acid oxidation. The role of high protein diets is established for ketotic types of GSD, but non-traditional dietary interventions (like medium-chain triglycerides and the ketogenic diet) in hepatic GSD are still controversial and necessitate further studies. Patients with these rare inherited disorders of carbohydrate metabolism meet several criteria of the metabolic syndrome, therefore close monitoring for cardiovascular diseases in ageing GSD patients may be justified.
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Affiliation(s)
- Terry G J Derks
- Section of Metabolic Diseases, Beatrix Children's Hospital, University of Groningen, University Medical Center Groningen, PO Box 30 001, 9700 RB, Groningen, The Netherlands,
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22
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Abdul-Wahed A, Gautier-Stein A, Casteras S, Soty M, Roussel D, Romestaing C, Guillou H, Tourette JA, Pleche N, Zitoun C, Gri B, Sardella A, Rajas F, Mithieux G. A link between hepatic glucose production and peripheral energy metabolism via hepatokines. Mol Metab 2014; 3:531-43. [PMID: 25061558 PMCID: PMC4099510 DOI: 10.1016/j.molmet.2014.05.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 05/16/2014] [Accepted: 05/20/2014] [Indexed: 12/25/2022] Open
Abstract
Type 2 diabetes is characterized by a deterioration of glucose tolerance, which associates insulin resistance of glucose uptake by peripheral tissues and increased endogenous glucose production. Here we report that the specific suppression of hepatic glucose production positively modulates whole-body glucose and energy metabolism. We used mice deficient in liver glucose-6 phosphatase that is mandatory for endogenous glucose production. When they were fed a high fat/high sucrose diet, they resisted the development of diabetes and obesity due to the activation of peripheral glucose metabolism and thermogenesis. This was linked to the secretion of hepatic hormones like fibroblast growth factor 21 and angiopoietin-like factor 6. Interestingly, the deletion of hepatic glucose-6 phosphatase in previously obese and insulin-resistant mice resulted in the rapid restoration of glucose and body weight controls. Therefore, hepatic glucose production is an essential lever for the control of whole-body energy metabolism during the development of obesity and diabetes.
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Affiliation(s)
- Aya Abdul-Wahed
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France ; University of Aleppo, Aleppo, Syria
| | - Amandine Gautier-Stein
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Sylvie Casteras
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Maud Soty
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Damien Roussel
- Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France ; Centre National de la Recherche Scientifique, UMR5023, Villeurbanne, F-69622, France
| | - Caroline Romestaing
- Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France ; Centre National de la Recherche Scientifique, UMR5023, Villeurbanne, F-69622, France
| | | | - Jean-André Tourette
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Nicolas Pleche
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Carine Zitoun
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Blandine Gri
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Anne Sardella
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Fabienne Rajas
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
| | - Gilles Mithieux
- Institut National de la Santé et de la Recherche Médicale, U855, Lyon, F-69008, France ; Université de Lyon, Lyon, F-69008, France ; Université Lyon 1, Villeurbanne, F-69622, France
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23
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Oosterveer MH, Schoonjans K. Hepatic glucose sensing and integrative pathways in the liver. Cell Mol Life Sci 2014; 71:1453-67. [PMID: 24196749 PMCID: PMC11114046 DOI: 10.1007/s00018-013-1505-z] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 10/17/2013] [Accepted: 10/18/2013] [Indexed: 12/21/2022]
Abstract
The hepatic glucose-sensing system is a functional network of enzymes and transcription factors that is critical for the maintenance of energy homeostasis and systemic glycemia. Here we review the recent literature on its components and metabolic actions. Glucokinase (GCK) is generally considered as the initial postprandial glucose-sensing component, which acts as the gatekeeper for hepatic glucose metabolism and provides metabolites that activate the transcription factor carbohydrate response element binding protein (ChREBP). Recently, liver receptor homolog 1 (LRH-1) has emerged as an upstream regulator of the central GCK-ChREBP axis, with a critical role in the integration of hepatic intermediary metabolism in response to glucose. Evidence is also accumulating that O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) and acetylation can act as glucose-sensitive modifications that may contribute to hepatic glucose sensing by targeting regulatory proteins and the epigenome. Further elucidation of the components and functional roles of the hepatic glucose-sensing system may contribute to the future treatment of liver diseases associated with deregulated glucose sensors.
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Affiliation(s)
- Maaike H. Oosterveer
- Department of Pediatrics and Laboratory Medicine, University of Groningen, University Medical Center Groningen, 9713 GZ Groningen, The Netherlands
| | - Kristina Schoonjans
- Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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24
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Abstract
The SLC37 family members are endoplasmic reticulum (ER)-associated sugar-phosphate/phosphate (P(i)) exchangers. Three of the four members, SLC37A1, SLC37A2, and SLC37A4, function as Pi-linked glucose-6-phosphate (G6P) antiporters catalyzing G6P:P(i) and P(i):P(i) exchanges. The activity of SLC37A3 is unknown. SLC37A4, better known as the G6P transporter (G6PT), has been extensively characterized, functionally and structurally, and is the best characterized family member. G6PT contains 10 transmembrane helices with both N and C termini facing the cytoplasm. The primary in vivo function of the G6PT protein is to translocate G6P from the cytoplasm into the ER lumen where it couples with either the liver/kidney/intestine-restricted glucose-6-phosphatase-α (G6Pase-α or G6PC) or the ubiquitously expressed G6Pase-β (or G6PC3) to hydrolyze G6P to glucose and P(i). The G6PT/G6Pase-α complex maintains interprandial glucose homeostasis, and the G6PT/G6Pase-β complex maintains neutrophil energy homeostasis and functionality. G6PT is highly selective for G6P and is competitively inhibited by cholorogenic acid and its derivatives. Neither SLC37A1 nor SLC37A2 can couple functionally with G6Pase-α or G6Pase-β, and the antiporter activities of SLC37A1 or SLC37A2 are not inhibited by cholorogenic acid. Deficiencies in G6PT cause glycogen storage disease type Ib (GSD-Ib), a metabolic and immune disorder. To date, 91 separate SLC37A4 mutations, including 39 missense mutations, have been identified in GSD-Ib patients. Characterization of missense mutations has yielded valuable information on functionally important residues in the G6PT protein. The biological roles of the other SLC37 proteins remain to be determined and deficiencies have not yet been correlated to diseases.
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Affiliation(s)
- Janice Y Chou
- Section on Cellular Differentiation, Program on Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA.
| | - Brian C Mansfield
- Section on Cellular Differentiation, Program on Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA; Foundation Fighting Blindness, Columbia, Maryland, USA
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25
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Cortés VA, Cautivo KM, Rong S, Garg A, Horton JD, Agarwal AK. Leptin ameliorates insulin resistance and hepatic steatosis in Agpat2-/- lipodystrophic mice independent of hepatocyte leptin receptors. J Lipid Res 2013; 55:276-88. [PMID: 24293639 DOI: 10.1194/jlr.m045799] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Leptin is essential for energy homeostasis and regulation of food intake. Patients with congenital generalized lipodystrophy (CGL) due to mutations in 1-acylglycerol-3-phosphate-O-acyltransferase 2 (AGPAT2) and the CGL murine model (Agpat2(-/-) mice) both have severe insulin resistance, diabetes mellitus, hepatic steatosis, and low plasma leptin levels. In this study, we show that continuous leptin treatment of Agpat2(-/-) mice for 28 days reduced plasma insulin and glucose levels and normalized hepatic steatosis and hypertriglyceridemia. Leptin also partially, but significantly, reversed the low plasma thyroxine and high corticosterone levels found in Agpat2(-/-) mice. Levels of carbohydrate response element binding protein (ChREBP) were reduced, whereas lipogenic gene expression were increased in the livers of Agpat2(-/-) mice, suggesting that deregulated ChREBP contributed to the development of fatty livers in these mice and that this transcription factor is a target of leptin's beneficial metabolic action. Leptin administration did not change hepatic fatty acid oxidation enzymes mRNA levels in Agpat2(-/-) mice. The selective deletion of leptin receptors only in hepatocytes did not prevent the positive metabolic actions of leptin in Agpat2(-/-) mice, supporting the notion that the majority of metabolic actions of leptin are dependent on its action in nonhepatocyte cells and/or the central nervous system.
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Affiliation(s)
- Víctor A Cortés
- Department of Molecular Genetics, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
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26
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Glycogen storage disease type 1 and diabetes: Learning by comparing and contrasting the two disorders. DIABETES & METABOLISM 2013; 39:377-87. [DOI: 10.1016/j.diabet.2013.03.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 02/25/2013] [Accepted: 03/11/2013] [Indexed: 12/18/2022]
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27
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Glucose induces protein targeting to glycogen in hepatocytes by fructose 2,6-bisphosphate-mediated recruitment of MondoA to the promoter. Mol Cell Biol 2012. [PMID: 23207906 DOI: 10.1128/mcb.01576-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the liver, a high glucose concentration activates transcription of genes encoding glucose 6-phosphatase and enzymes for glycolysis and lipogenesis by elevation in phosphorylated intermediates and recruitment of the transcription factor ChREBP (carbohydrate response element binding protein) and its partner, Mlx, to gene promoters. A proposed function for this mechanism is intracellular phosphate homeostasis. In extrahepatic tissues, MondoA, the paralog of ChREBP, partners with Mlx in transcriptional induction by glucose. We tested for glucose induction of regulatory proteins of the glycogenic pathway in hepatocytes and identified the glycogen-targeting proteins, G(L) and PTG (protein targeting to glycogen), as being encoded by Mlx-dependent glucose-inducible genes. PTG induction by glucose was MondoA dependent but ChREBP independent and was enhanced by forced elevation of fructose 2,6-bisphosphate and by additional xylitol-derived metabolites. It was counteracted by selective depletion of fructose 2,6-bisphosphate with a bisphosphatase-active kinase-deficient variant of phosphofructokinase 2/fructosebisphosphatase 2, which prevented translocation of MondoA to the nucleus and recruitment to the PTG promoter. We identify a novel role for MondoA in the liver and demonstrate that elevated fructose 2,6-bisphosphate is essential for recruitment of MondoA to the PTG promoter. Phosphometabolite activation of MondoA and ChREBP and their recruitment to target genes is consistent with a mechanism for gene regulation to maintain intracellular phosphate homeostasis.
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28
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Agius L. High-carbohydrate diets induce hepatic insulin resistance to protect the liver from substrate overload. Biochem Pharmacol 2012; 85:306-12. [PMID: 23022226 DOI: 10.1016/j.bcp.2012.09.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 09/17/2012] [Accepted: 09/18/2012] [Indexed: 12/14/2022]
Abstract
In population studies hepatic steatosis in subjects with Non-alcoholic fatty liver disease (NAFLD) is strongly associated with insulin resistance. This association has encouraged debate whether hepatic steatosis is the cause or the consequence of hepatic insulin resistance? Although genome-wide studies have identified several gene variants associated with either hepatic steatosis or type 2 diabetes, no variants have been identified associated with both hepatic steatosis and insulin resistance. Here, the hypothesis is proposed that high-carbohydrate diets contribute to the association between hepatic steatosis and insulin resistance through activation of the transcription factor ChREBP (Carbohydrate response element binding protein). Postprandial hyperglycaemia raises the hepatic concentrations of phosphorylated intermediates causing activation of ChREBP and induction of its target genes. These include not only enzymes of glycolysis and lipogenesis that predispose to hepatic steatosis but also glucose 6-phosphatase (G6PC) that catalyses the final reaction in glucose production and GCKR, the inhibitor of hepatic glucokinase that curtails hepatic glucose uptake. Induction of G6PC and GCKR manifests as hepatic glucose intolerance or insulin resistance. Induction of these two genes by high glucose serves to safeguard intrahepatic homeostasis of phosphorylated intermediates. The importance of GCKR in this protective mechanism is supported by "less-active" GCKR variants in association not only with hepatic steatosis and hyperuricaemia but also with lower fasting plasma glucose and decreased insulin resistance. This supports a role for GCKR in restricting hepatic glucose phosphorylation to maintain intrahepatic homeostasis. Pharmacological targeting of the glucokinase-GCKR interaction can favour either glucose clearance by the liver or intrahepatic metabolite homeostasis.
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Affiliation(s)
- Loranne Agius
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
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29
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Arden C, Tudhope SJ, Petrie JL, Al-Oanzi ZH, Cullen KS, Lange AJ, Towle HC, Agius L. Fructose 2,6-bisphosphate is essential for glucose-regulated gene transcription of glucose-6-phosphatase and other ChREBP target genes in hepatocytes. Biochem J 2012; 443:111-23. [PMID: 22214556 DOI: 10.1042/bj20111280] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/01/2024]
Abstract
Glucose metabolism in the liver activates the transcription of various genes encoding enzymes of glycolysis and lipogenesis and also G6pc (glucose-6-phosphatase). Allosteric mechanisms involving glucose 6-phosphate or xylulose 5-phosphate and covalent modification of ChREBP (carbohydrate-response element-binding protein) have been implicated in this mechanism. However, evidence supporting an essential role for a specific metabolite or pathway in hepatocytes remains equivocal. By using diverse substrates and inhibitors and a kinase-deficient bisphosphatase-active variant of the bifunctional enzyme PFK2/FBP2 (6-phosphofructo-2-kinase-fructose-2,6-bisphosphatase), we demonstrate an essential role for fructose 2,6-bisphosphate in the induction of G6pc and other ChREBP target genes by glucose. Selective depletion of fructose 2,6-bisphosphate inhibits glucose-induced recruitment of ChREBP to the G6pc promoter and also induction of G6pc by xylitol and gluconeogenic precursors. The requirement for fructose 2,6-bisphosphate for ChREBP recruitment to the promoter does not exclude the involvement of additional metabolites acting either co-ordinately or at downstream sites. Glucose raises fructose 2,6-bisphosphate levels in hepatocytes by reversing the phosphorylation of PFK2/FBP2 at Ser32, but also independently of Ser32 dephosphorylation. This supports a role for the bifunctional enzyme as the phosphometabolite sensor and for its product, fructose 2,6-bisphosphate, as the metabolic signal for substrate-regulated ChREBP-mediated expression of G6pc and other ChREBP target genes.
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Affiliation(s)
- Catherine Arden
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
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30
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Dentin R, Tomas-Cobos L, Foufelle F, Leopold J, Girard J, Postic C, Ferré P. Glucose 6-phosphate, rather than xylulose 5-phosphate, is required for the activation of ChREBP in response to glucose in the liver. J Hepatol 2012; 56:199-209. [PMID: 21835137 DOI: 10.1016/j.jhep.2011.07.019] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 07/07/2011] [Accepted: 07/11/2011] [Indexed: 12/04/2022]
Abstract
BACKGROUND & AIMS In liver, the glucose-responsive transcription factor ChREBP plays a critical role in converting excess carbohydrates into triglycerides through de novo lipogenesis. Although the importance of ChREBP in glucose sensing and hepatic energy utilization is strongly supported, the mechanism driving its activation in response to glucose in the liver is not fully understood. Indeed, the current model of ChREBP activation, which depends on Serine 196 and Threonine 666 dephosphorylation, phosphatase 2A (PP2A) activity, and xylulose 5-phosphate (X5P) as a signaling metabolite, has been challenged. METHODS We inhibited PP2A activity in HepG2 cells through the overexpression of SV40 small t antigen and addressed the importance of ChREBP dephosphorylation on Ser-196 using a phospho-specific antibody. To identify the exact nature of the metabolite signal required for ChREBP activity in liver, we focused on the importance of G6P synthesis in liver cells, through the modulation of glucose 6-phosphate dehydrogenase (G6PDH) activity, the rate-limiting enzyme of the pentose phosphate pathway in hepatocytes, and in HepG2 cells using both adenoviral and siRNA approaches. RESULTS In contrast to the current proposed model, our study reports that PP2A activity is dispensable for ChREBP activation in response to glucose and that dephosphorylation on Ser-196 is not sufficient to promote ChREBP nuclear translocation in the absence of a rise in glucose metabolism. By deciphering the respective roles of G6P and X5P as signaling metabolites, our study reveals that G6P produced by GK, but not X5P, is essential for both ChREBP nuclear translocation and transcriptional activity in response to glucose in liver cells. CONCLUSIONS Altogether, our study, by reporting that G6P is the glucose-signaling metabolite, challenges the PP2A/X5P-dependent model currently described for ChREBP activation in response to glucose in liver.
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Arden C, Petrie JL, Tudhope SJ, Al-Oanzi Z, Claydon AJ, Beynon RJ, Towle HC, Agius L. Elevated glucose represses liver glucokinase and induces its regulatory protein to safeguard hepatic phosphate homeostasis. Diabetes 2011; 60:3110-20. [PMID: 22013014 PMCID: PMC3219956 DOI: 10.2337/db11-0061] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
OBJECTIVE The induction of hepatic glucose 6-phosphatase (G6pc) by glucose presents a paradox of glucose-induced glucose intolerance. We tested whether glucose regulation of liver gene expression is geared toward intracellular homeostasis. RESEARCH DESIGN AND METHODS The effect of glucose-induced accumulation of phosphorylated intermediates on expression of glucokinase (Gck) and its regulator Gckr was determined in hepatocytes. Cell ATP and uric acid production were measured as indices of cell phosphate homeostasis. RESULTS Accumulation of phosphorylated intermediates in hepatocytes incubated at elevated glucose induced rapid and inverse changes in Gck (repression) and Gckr (induction) mRNA concomitantly with induction of G6pc, but had slower effects on the Gckr-to-Gck protein ratio. Dynamic metabolic labeling in mice and liver proteome analysis confirmed that Gckr and Gck are low-turnover proteins. Involvement of Max-like protein X in glucose-mediated Gck-repression was confirmed by chromatin immunoprecipitation analysis. Elevation of the Gck-to-Gckr ratio in hepatocytes was associated with glucose-dependent ATP depletion and elevated urate production confirming compromised phosphate homeostasis. CONCLUSIONS The lowering by glucose of the Gck-to-Gckr ratio provides a potential explanation for the impaired hepatic glucose uptake in diabetes. Elevated uric acid production at an elevated Gck-to-Gckr ratio supports a role for glucose regulation of gene expression in hepatic phosphate homeostasis.
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Affiliation(s)
- Catherine Arden
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
| | - John L. Petrie
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
| | - Susan J. Tudhope
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
| | - Ziad Al-Oanzi
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
- Department of Laboratory Medicine, Al-Jouf University, Sakaka, Saudi Arabia
| | - Amy J. Claydon
- Protein Function Group, Institute of Integrative Biology, University of Liverpool, Liverpool, U.K
| | - Robert J. Beynon
- Protein Function Group, Institute of Integrative Biology, University of Liverpool, Liverpool, U.K
| | - Howard C. Towle
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Loranne Agius
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
- Corresponding author: Loranne Agius,
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32
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Poupeau A, Postic C. Cross-regulation of hepatic glucose metabolism via ChREBP and nuclear receptors. Biochim Biophys Acta Mol Basis Dis 2011; 1812:995-1006. [PMID: 21453770 DOI: 10.1016/j.bbadis.2011.03.015] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 03/21/2011] [Accepted: 03/22/2011] [Indexed: 01/17/2023]
Abstract
There is a worldwide epidemic of obesity and type 2 diabetes, two major public health concerns associated with alterations in both insulin and glucose signaling pathways. Glucose is not only an energy source but also controls the expression of key genes involved in energetic metabolism, through the glucose-signaling transcription factor, Carbohydrate Responsive Element Binding Protein (ChREBP). ChREBP has emerged as a central regulator of de novo fatty acid synthesis (lipogenesis) in response to glucose under both physiological and physiopathological conditions. Glucose activates ChREBP by regulating its entry from the cytosol to the nucleus, thereby promoting its binding to carbohydrate responsive element (ChoRE) in the promoter regions of glycolytic (L-PK) and lipogenic genes (ACC and FAS). We have previously reported that the inhibition of ChREBP in liver of obese ob/ob mice improves the metabolic alterations linked to obesity, fatty liver and insulin-resistance. Therefore, regulating ChREBP activity could be an attractive target for lipid-lowering therapies in obesity and diabetes. However, before this is possible, a better understanding of the mechanism(s) regulating its activity is needed. In this review, we summarize recent findings on the role and regulation of ChREBP and particularly emphasize on the cross-regulations that may exist between key nuclear receptors (LXR, TR, HNF4α) and ChREBP for the control of hepatic glucose metabolism. These novel molecular cross-talks may open the way to new pharmacological opportunities. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.
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