1
|
Rodriguez-Lopez C, Santalla A, Valenzuela PL, Real-Martínez A, Villarreal-Salazar M, Rodriguez-Gomez I, Pinós T, Ara I, Lucia A. Muscle glycogen unavailability and fat oxidation rate during exercise: Insights from McArdle disease. J Physiol 2023; 601:551-566. [PMID: 36370371 PMCID: PMC10099855 DOI: 10.1113/jp283743] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 10/31/2022] [Indexed: 11/13/2022] Open
Abstract
Carbohydrate availability affects fat metabolism during exercise; however, the effects of complete muscle glycogen unavailability on maximal fat oxidation (MFO) rate remain unknown. Our purpose was to examine the MFO rate in patients with McArdle disease, comprising an inherited condition caused by complete blockade of muscle glycogen metabolism, compared to healthy controls. Nine patients (three women, aged 36 ± 12 years) and 12 healthy controls (four women, aged 40 ± 13 years) were studied. Several molecular markers of lipid transport/metabolism were also determined in skeletal muscle (gastrocnemius) and white adipose tissue of McArdle (Pygm p.50R*/p.50R*) and wild-type male mice. Peak oxygen uptake ( V ̇ O 2 peak ${\dot V_{{{\rm{O}}_{\rm{2}}}{\rm{peak}}}}$ ), MFO rate, the exercise intensity eliciting MFO rate (FATmax) and the MFO rate-associated workload were determined by indirect calorimetry during an incremental cycle-ergometer test. Despite having a much lower V ̇ O 2 peak ${\dot V_{{{\rm{O}}_{\rm{2}}}{\rm{peak}}}}$ (24.7 ± 4 vs. 42.5 ± 11.4 mL kg-1 min-1 , respectively; P < 0.0001), patients showed considerably higher values for the MFO rate (0.53 ± 0.12 vs. 0.33 ± 0.10 g min-1 , P = 0.001), and for the FATmax (94.4 ± 7.2 vs. 41.3 ± 9.1 % of V ̇ O 2 peak ${\dot V_{{{\rm{O}}_{\rm{2}}}{\rm{peak}}}}$ , P < 0.0001) and MFO rate-associated workload (1.33 ± 0.35 vs. 0.81 ± 0.54 W kg-1 , P = 0.020) than controls. No between-group differences were found overall in molecular markers of lipid transport/metabolism in mice. In summary, patients with McArdle disease show an exceptionally high MFO rate, which they attained at near-maximal exercise capacity. Pending more mechanistic explanations, these findings support the influence of glycogen availability on MFO rate and suggest that these patients develop a unique fat oxidation capacity, possibly as an adaptation to compensate for the inherited blockade in glycogen metabolism, and point to MFO rate as a potential limiting factor of exercise tolerance in this disease. KEY POINTS: Physically active McArdle patients show an exceptional fat oxidation capacity. Maximal fat oxidation rate occurs near-maximal exercise capacity in these patients. McArdle patients' exercise tolerance might rely on maximal fat oxidation rate capacity. Hyperpnoea might cloud substrate oxidation measurements in some patients. An animal model revealed overall no higher molecular markers of lipid transport/metabolism.
Collapse
Affiliation(s)
- Carlos Rodriguez-Lopez
- Department of Geriatrics, Hospital General Universitario Gregorio Marañón. Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain.,GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain.,CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain
| | - Alfredo Santalla
- Department of Sport and Computer Science, Section of Physical Education and Sports, Faculty of Sport, Universidad Pablo de Olavide, Seville, Spain.,EVOPRED Research Group, Universidad Europea de Canarias, Tenerife, Spain
| | - Pedro L Valenzuela
- Instituto de Investigación Sanitaria Hospital '12 de Octubre' ('imas12'), Madrid, Spain
| | - Alberto Real-Martínez
- Mitochondrial and Neuromuscular Disorders Unit, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Spain.,CIBER for rare disease (CIBERER), Madrid, Spain
| | - Mónica Villarreal-Salazar
- Mitochondrial and Neuromuscular Disorders Unit, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Spain.,CIBER for rare disease (CIBERER), Madrid, Spain
| | - Irene Rodriguez-Gomez
- GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain.,CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain
| | - Tomàs Pinós
- Mitochondrial and Neuromuscular Disorders Unit, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Spain.,CIBER for rare disease (CIBERER), Madrid, Spain
| | - Ignacio Ara
- GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain.,CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain
| | - Alejandro Lucia
- CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain.,Instituto de Investigación Sanitaria Hospital '12 de Octubre' ('imas12'), Madrid, Spain.,Faculty of Sport Sciences, Universidad Europea de Madrid, Madrid, Spain
| |
Collapse
|
2
|
Affiliation(s)
- Sean P Langan
- Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT, USA
| | - John S Navarro
- Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT, USA
| |
Collapse
|
3
|
Buch AE, Musumeci O, Wigley R, Stemmerik MPG, Eisum AV, Madsen KL, Preisler N, Hilton‐Jones D, Quinlivan R, Toscano A, Vissing J. Energy metabolism during exercise in patients with β-enolase deficiency (GSDXIII). JIMD Rep 2021; 61:60-66. [PMID: 34485019 PMCID: PMC8411107 DOI: 10.1002/jmd2.12232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 04/28/2021] [Accepted: 05/10/2021] [Indexed: 11/08/2022] Open
Abstract
AIM To investigate the in vivo skeletal muscle metabolism in patients with β-enolase deficiency (GSDXIII) during exercise, and the effect of glucose infusion. METHODS Three patients with GSDXIII and 10 healthy controls performed a nonischemic handgrip test as well as an incremental cycle ergometer test measuring maximal oxidative consumption (VO2max) and a 1-hour submaximal cycle test at an intensity of 65% to 75% of VO2max. The patients repeated the submaximal exercise after 2 days, where they received a 10% iv-glucose supplementation. RESULTS Patients had lower VO2max than healthy controls, and two of three patients had to stop prematurely during the intended 1-hour submaximal exercise test. During nonischemic forearm test, all patients were able to produce lactate in normal amounts. Glucose infusion had no effect on patients' exercise capacity. CONCLUSIONS Patients with GSDXIII experience exercise intolerance and episodes of myoglobinuria, even to the point of needing renal dialysis, but still retain an almost normal anaerobic metabolic response to submaximal intensity exercise. In accordance with this, glucose supplementation did not improve exercise capacity. The findings show that GSDXIII, although causing episodic rhabdomyolysis, is one of the mildest metabolic myopathies affecting glycolysis.
Collapse
Affiliation(s)
- Astrid Emilie Buch
- Copenhagen Neuromuscular Center, Rigshospitalet, University of CopenhagenCopenhagenDenmark
| | - Olimpia Musumeci
- Neurology and Neuromuscular Disorders Unit, Department of Clinical and Experimental MedicineUniversity of MessinaMessinaItaly
| | - Ralph Wigley
- Enzyme Laboratory, Department of Chemical PathologyCameilia Botnar Laboratories, Great Ormond Street Hospital for Sick ChildrenLondonUK
| | | | - Anne‐Sofie Vibæk Eisum
- Copenhagen Neuromuscular Center, Rigshospitalet, University of CopenhagenCopenhagenDenmark
| | - Karen Lindhardt Madsen
- Copenhagen Neuromuscular Center, Rigshospitalet, University of CopenhagenCopenhagenDenmark
| | - Nicolai Preisler
- Copenhagen Neuromuscular Center, Rigshospitalet, University of CopenhagenCopenhagenDenmark
| | - David Hilton‐Jones
- Department of Clinical NeurologyWest Wing, John Radcliffe HospitalOxfordUK
| | - Ros Quinlivan
- Dubowitz Neuromuscular Centre, Great Ormond Street Hospital for Children NHS Foundation TrustLondonUK
| | - Antonio Toscano
- Neurology and Neuromuscular Disorders Unit, Department of Clinical and Experimental MedicineUniversity of MessinaMessinaItaly
| | - John Vissing
- Copenhagen Neuromuscular Center, Rigshospitalet, University of CopenhagenCopenhagenDenmark
| |
Collapse
|
4
|
Scalco RS, Lucia A, Santalla A, Martinuzzi A, Vavla M, Reni G, Toscano A, Musumeci O, Voermans NC, Kouwenberg CV, Laforêt P, San-Millán B, Vieitez I, Siciliano G, Kühnle E, Trost R, Sacconi S, Stemmerik MG, Durmus H, Kierdaszuk B, Wakelin A, Andreu AL, Pinós T, Marti R, Quinlivan R, Vissing J. Data from the European registry for patients with McArdle disease and other muscle glycogenoses (EUROMAC). Orphanet J Rare Dis 2020; 15:330. [PMID: 33234167 PMCID: PMC7687836 DOI: 10.1186/s13023-020-01562-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 09/25/2020] [Indexed: 01/12/2023] Open
Abstract
Background The European registry for patients with McArdle disease and other muscle glycogenoses (EUROMAC) was launched to register rare muscle glycogenoses in Europe, to facilitate recruitment for research trials and to learn about the phenotypes and disseminate knowledge about the diseases through workshops and websites. A network of twenty full and collaborating partners from eight European countries and the US contributed data on rare muscle glycogenosis in the EUROMAC registry. After approximately 3 years of data collection, the data in the registry was analysed.
Results Of 282 patients with confirmed diagnoses of muscle glycogenosis, 269 had McArdle disease. New phenotypic features of McArdle disease were suggested, including a higher frequency (51.4%) of fixed weakness than reported before, normal CK values in a minority of patients (6.8%), ptosis in 8 patients, body mass index above background population and number of comorbidities with a higher frequency than in the background population (hypothyroidism, coronary heart disease). Conclusions The EUROMAC project and registry have provided insight into new phenotypic features of McArdle disease and the variety of co-comorbidities affecting people with McArdle disease. This should lead to better management of these disorders in the future, including controlling weight, and preventive screening for thyroid and coronary artery diseases, as well as physical examination with attention on occurrence of ptosis and fixed muscle weakness. Normal serum creatine kinase in a minority of patients stresses the need to not discard a diagnosis of McArdle disease even though creatine kinase is normal and episodes of myoglobinuria are absent.
Collapse
Affiliation(s)
- Renata S Scalco
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, National Hospital, London, UK
| | - Alejandro Lucia
- Faculty of Sport Sciences, Universidad Europea de Madrid, Madrid, Spain.,Instituto de Investigación Hospital, 12 de Octubre (imas12), Madrid, Spain
| | - Alfredo Santalla
- Instituto de Investigación Hospital, 12 de Octubre (imas12), Madrid, Spain.,Universidad Pablo de Olavide, Seville, Spain
| | - Andrea Martinuzzi
- Dept. of Conegliano-Pieve Di Soligo, IRCCS Medea Scientific Insitute, Bosisio Parini, Italy
| | - Marinela Vavla
- Dept. of Conegliano-Pieve Di Soligo, IRCCS Medea Scientific Insitute, Bosisio Parini, Italy
| | - Gianluigi Reni
- Dept. of Conegliano-Pieve Di Soligo, IRCCS Medea Scientific Insitute, Bosisio Parini, Italy
| | - Antonio Toscano
- Neurology and Neuromuscular Diseases Unit, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Olimpia Musumeci
- Neurology and Neuromuscular Diseases Unit, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Nicol C Voermans
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Carlyn V Kouwenberg
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Pascal Laforêt
- Nord/Est/Ile de France Neuromuscular Reference Center, Neurology Department, Raymond-Poincaré Teaching Hospital, Garches. AP-HP. INSERM U1179, END-ICAP, Paris Saclay University, Paris, France
| | - Beatriz San-Millán
- Pathology Deparment, Alvaro Cunqueiro Hospital, Vigo, Spain.,Rare Diseases and Pediatric Medicine Research Group, Galicia Sur Health Research Institute (IIS Galicia Sur), SERGAS-UVIGO, Vigo, Spain
| | - Irene Vieitez
- Rare Diseases and Pediatric Medicine Research Group, Galicia Sur Health Research Institute (IIS Galicia Sur), SERGAS-UVIGO, Vigo, Spain
| | - Gabriele Siciliano
- Neurology and Neuromuscular Diseases Unit, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Enrico Kühnle
- Department of Neurology, Heimer Institute for Muscle Research, University Hospital Bochum, Bochum, Germany
| | - Rebeca Trost
- Department of Neurology, Heimer Institute for Muscle Research, University Hospital Bochum, Bochum, Germany
| | - Sabrina Sacconi
- Peripheral Nervous System and Muscle Department, CHU Nice, Université Côte D'Azur, Institute for Research On Cancer and Aging of Nice (IRCAN), INSERM U1081, CNRS UMR 7284, Faculty of Medicine, Université Côte D'Azur (UCA), Nice, France
| | - Mads G Stemmerik
- Copenhagen Neuromuscular Center, Section 6921, Rigshospitalet, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Hacer Durmus
- Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Biruta Kierdaszuk
- Department of Neurology, Medical University of Warsaw, Warsaw, Poland
| | - Andrew Wakelin
- Association for Glycogen Storage Disease (UK), Bristol, UK
| | - Antoni L Andreu
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, and Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Tomàs Pinós
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, and Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Ramon Marti
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, and Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Ros Quinlivan
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, National Hospital, London, UK
| | - John Vissing
- Copenhagen Neuromuscular Center, Section 6921, Rigshospitalet, University of Copenhagen, 2100, Copenhagen, Denmark.
| | | |
Collapse
|
5
|
Storgaard JH, Madsen KL, Løkken N, Vissing J, van Hall G, Lund AM, Ørngreen MC. Impaired lipolysis in propionic acidemia: A new metabolic myopathy? JIMD Rep 2020; 53:16-21. [PMID: 32395405 PMCID: PMC7203654 DOI: 10.1002/jmd2.12113] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 02/21/2020] [Accepted: 02/27/2020] [Indexed: 12/14/2022] Open
Abstract
The objective of this study was to investigate the fat and carbohydrate metabolism in a patient with propionic acidemia (PA) during exercise by means of indirect calorimetry and stable isotope technique. A 34-year-old patient with PA performed a 30-minute submaximal cycle ergometer test. Data were compared to results from six gender- and age-matched healthy controls. Main findings are that the patient with PA had impaired lipolysis, blunted fatty acid oxidation, compensatory increase in carbohydrate utilization, and low work capacity. Our findings indicate that PA should be added to the list of metabolic myopathies.
Collapse
Affiliation(s)
- Jesper H. Storgaard
- Department of Neurology, Copenhagen Neuromuscular Center, RigshospitaletCopenhagen University HospitalCopenhagenDenmark
| | - Karen L. Madsen
- Department of Neurology, Copenhagen Neuromuscular Center, RigshospitaletCopenhagen University HospitalCopenhagenDenmark
| | - Nicoline Løkken
- Department of Neurology, Copenhagen Neuromuscular Center, RigshospitaletCopenhagen University HospitalCopenhagenDenmark
| | - John Vissing
- Department of Neurology, Copenhagen Neuromuscular Center, RigshospitaletCopenhagen University HospitalCopenhagenDenmark
| | - Gerrit van Hall
- Department of Biomedical SciencesRigshospitalet, University of CopenhagenCopenhagenDenmark
| | - Allan M. Lund
- Department of Clinical GeneticsCentre for Inherited Metabolic Diseases, Rigshospitalet, Copenhagen University HospitalCopenhagenDenmark
- Department of Pediatrics and Adolescent MedicineCentre for Inherited Metabolic Diseases, Rigshospitalet, Copenhagen University HospitalCopenhagenDenmark
| | - Mette C. Ørngreen
- Department of Neurology, Copenhagen Neuromuscular Center, RigshospitaletCopenhagen University HospitalCopenhagenDenmark
- Department of Clinical GeneticsCentre for Inherited Metabolic Diseases, Rigshospitalet, Copenhagen University HospitalCopenhagenDenmark
- Department of Pediatrics and Adolescent MedicineCentre for Inherited Metabolic Diseases, Rigshospitalet, Copenhagen University HospitalCopenhagenDenmark
| |
Collapse
|
6
|
Semplicini C, Hézode-Arzel M, Laforêt P, Béhin A, Leonard-Louis S, Hogrel JY, Petit F, Eymard B, Stojkovic T, Fournier E. The role of electrodiagnosis with long exercise test in mcardle disease. Muscle Nerve 2018; 58:64-71. [PMID: 29350794 DOI: 10.1002/mus.26074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 01/11/2018] [Accepted: 01/13/2018] [Indexed: 11/07/2022]
Abstract
INTRODUCTION In this study we evaluated the role of an electrodiagnostic provocative test (long exercise test) in McArdle disease. METHODS Twenty-five McArdle patients and 2 control groups underwent an electrodiagnostic protocol with long exercise test (LET), consisting of recording the compound muscle action potential (CMAP) before and after 5 minutes of isometric contraction. RESULTS The LET disclosed a postexercise decrease in CMAP amplitude in 23 of 25 McArdle patients. The immediate and long-lasting decrease differentiated McArdle patients from controls. Patients with a normal LET demonstrated milder symptoms and/or residual myophosphorylase activity. DISCUSSION The LET is a sensitive, safe, and noninvasive provocative test that may guide clinicians toward molecular analysis of the myophosphorylase gene. The abnormalities observed on LET point toward complex biochemical mechanisms determined by the absence of myophosphorylase, beyond simple glycolytic blockade (ionic pump dysfunction, sarcolemmal inexcitability). The normal LET in patients with milder symptoms indicates a relationship of the LET with clinical severity, thus identifying it as a potential outcome measure. Muscle Nerve, 2018.
Collapse
Affiliation(s)
- Claudio Semplicini
- Department of Neuroscience, University of Padova, Padova, Italy
- Paris-Est Neuromuscular Center, APHP-GH Pitié-Salpêtrière, Paris, France
| | | | - Pascal Laforêt
- Centre de référence des maladies neuromusculaires Nord/Est/Ile de France Service de Neurologie, Hôpital Raymond-Poincaré, AP-HP, Garches INSERM U1179, END-ICAP, équipe biothérapies des maladies du système neuromusculaire Université Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France
| | - Anthony Béhin
- Paris-Est Neuromuscular Center, APHP-GH Pitié-Salpêtrière, Paris, France
| | | | - Jean-Yves Hogrel
- Neuromuscular Physiology Laboratory, Institut de Myologie, APHP-GH Pitié-Salpêtrière, Paris, France
| | - François Petit
- Molecular Genetics; Metabolic Diseases Lab, Antoine Béclère Hospital, Clamart, France
| | - Bruno Eymard
- Paris-Est Neuromuscular Center, APHP-GH Pitié-Salpêtrière, Paris, France
| | - Tanya Stojkovic
- Paris-Est Neuromuscular Center, APHP-GH Pitié-Salpêtrière, Paris, France
| | - Emmanuel Fournier
- Department of Clinical Neurophysiology, APHP-GH Pitié-Salpêtrière, Paris, France
| |
Collapse
|
7
|
Adeva-Andany MM, González-Lucán M, Donapetry-García C, Fernández-Fernández C, Ameneiros-Rodríguez E. Glycogen metabolism in humans. BBA CLINICAL 2016; 5:85-100. [PMID: 27051594 PMCID: PMC4802397 DOI: 10.1016/j.bbacli.2016.02.001] [Citation(s) in RCA: 253] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/10/2016] [Accepted: 02/16/2016] [Indexed: 12/31/2022]
Abstract
In the human body, glycogen is a branched polymer of glucose stored mainly in the liver and the skeletal muscle that supplies glucose to the blood stream during fasting periods and to the muscle cells during muscle contraction. Glycogen has been identified in other tissues such as brain, heart, kidney, adipose tissue, and erythrocytes, but glycogen function in these tissues is mostly unknown. Glycogen synthesis requires a series of reactions that include glucose entrance into the cell through transporters, phosphorylation of glucose to glucose 6-phosphate, isomerization to glucose 1-phosphate, and formation of uridine 5'-diphosphate-glucose, which is the direct glucose donor for glycogen synthesis. Glycogenin catalyzes the formation of a short glucose polymer that is extended by the action of glycogen synthase. Glycogen branching enzyme introduces branch points in the glycogen particle at even intervals. Laforin and malin are proteins involved in glycogen assembly but their specific function remains elusive in humans. Glycogen is accumulated in the liver primarily during the postprandial period and in the skeletal muscle predominantly after exercise. In the cytosol, glycogen breakdown or glycogenolysis is carried out by two enzymes, glycogen phosphorylase which releases glucose 1-phosphate from the linear chains of glycogen, and glycogen debranching enzyme which untangles the branch points. In the lysosomes, glycogen degradation is catalyzed by α-glucosidase. The glucose 6-phosphatase system catalyzes the dephosphorylation of glucose 6-phosphate to glucose, a necessary step for free glucose to leave the cell. Mutations in the genes encoding the enzymes involved in glycogen metabolism cause glycogen storage diseases.
Collapse
Affiliation(s)
- María M. Adeva-Andany
- Nephrology Division, Hospital General Juan Cardona, c/ Pardo Bazán s/n, 15406 Ferrol, Spain
| | | | | | | | | |
Collapse
|