title: Skeletal muscle metabolism is impaired during exercise in glycogen storage disease type III.
abstract: OBJECTIVE
  Glycogen storage disease type IIIa (GSDIIIa) is classically regarded as a glycogenosis with fixed weakness, but we hypothesized that exercise intolerance in GSDIIIa is related to muscle energy failure and that oral fructose ingestion could improve exercise tolerance in this metabolic myopathy.
  
  
  METHODS
  We challenged metabolism with cycle-ergometer exercise and measured substrate turnover and oxidation rates using stable isotope methodology and indirect calorimetry in 3 patients and 6 age-matched controls on 1 day, and examined the effect of fructose ingestion on exercise tolerance in the patients on another day.
  
  
  RESULTS
  Total fatty acid oxidation rates during exercise were higher in patients than controls, 32.1 (SE 1.2) vs 20.7 (SE 0.5; range 15.8-29.3) μmol/kg/min (p = 0.048), and oxidation of carbohydrates was lower in patients, 1.0 (SE 5.4) vs 38.4 (SE 8.0; range 23.0-77.1) μmol/kg/min (p = 0.024). Fructose ingestion improved exercise tolerance in the patients.
  
  
  CONCLUSIONS
  Similar to patients with McArdle disease, in whom muscle glycogenolysis is also impaired, GSDIIIa is associated with a reduced skeletal muscle oxidation of carbohydrates and a compensatory increase in fatty acid oxidation, and fructose ingestion improves exercise tolerance. Our results indicate that GSDIIIa should not only be viewed as a glycogenosis with fixed skeletal muscle weakness, but should also be considered among the glycogenoses presenting with exercise-related dynamic symptoms caused by muscular energy deficiency.
  
  
  METHODS
  This study provides Class IV evidence that ingestion of fructose improves exercise tolerance in patients with GSDIIIa.
authors.affiliation: From the Neuromuscular Research Unit, Department of Neurology (N.P., K.L.M., K.P.P., G.H., C.R.V., J.V.), and the Department of Inflammation Research (H.G.), Rigshospitalet, University of Copenhagen, Denmark; and the Centre de Référence de Pathologie Neuromusculaire Paris-Est (P.L.), Institut de Myologie, GH Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, France. npreisler@hotmail.com.
authors.forename: Nicolai
authors.initials: N
authors.lastname: Preisler
authors.affiliation: From the Neuromuscular Research Unit, Department of Neurology (N.P., K.L.M., K.P.P., G.H., C.R.V., J.V.), and the Department of Inflammation Research (H.G.), Rigshospitalet, University of Copenhagen, Denmark; and the Centre de Référence de Pathologie Neuromusculaire Paris-Est (P.L.), Institut de Myologie, GH Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Laforêt
authors.affiliation: From the Neuromuscular Research Unit, Department of Neurology (N.P., K.L.M., K.P.P., G.H., C.R.V., J.V.), and the Department of Inflammation Research (H.G.), Rigshospitalet, University of Copenhagen, Denmark; and the Centre de Référence de Pathologie Neuromusculaire Paris-Est (P.L.), Institut de Myologie, GH Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, France.
authors.forename: Karen Lindhardt
authors.initials: KL
authors.lastname: Madsen
authors.affiliation: From the Neuromuscular Research Unit, Department of Neurology (N.P., K.L.M., K.P.P., G.H., C.R.V., J.V.), and the Department of Inflammation Research (H.G.), Rigshospitalet, University of Copenhagen, Denmark; and the Centre de Référence de Pathologie Neuromusculaire Paris-Est (P.L.), Institut de Myologie, GH Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, France.
authors.forename: Kira Philipsen
authors.initials: KP
authors.lastname: Prahm
authors.affiliation: From the Neuromuscular Research Unit, Department of Neurology (N.P., K.L.M., K.P.P., G.H., C.R.V., J.V.), and the Department of Inflammation Research (H.G.), Rigshospitalet, University of Copenhagen, Denmark; and the Centre de Référence de Pathologie Neuromusculaire Paris-Est (P.L.), Institut de Myologie, GH Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, France.
authors.forename: Gitte
authors.initials: G
authors.lastname: Hedermann
authors.affiliation: From the Neuromuscular Research Unit, Department of Neurology (N.P., K.L.M., K.P.P., G.H., C.R.V., J.V.), and the Department of Inflammation Research (H.G.), Rigshospitalet, University of Copenhagen, Denmark; and the Centre de Référence de Pathologie Neuromusculaire Paris-Est (P.L.), Institut de Myologie, GH Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, France.
authors.forename: Christoffer Rasmus
authors.initials: CR
authors.lastname: Vissing
authors.affiliation: From the Neuromuscular Research Unit, Department of Neurology (N.P., K.L.M., K.P.P., G.H., C.R.V., J.V.), and the Department of Inflammation Research (H.G.), Rigshospitalet, University of Copenhagen, Denmark; and the Centre de Référence de Pathologie Neuromusculaire Paris-Est (P.L.), Institut de Myologie, GH Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, France.
authors.forename: Henrik
authors.initials: H
authors.lastname: Galbo
authors.affiliation: From the Neuromuscular Research Unit, Department of Neurology (N.P., K.L.M., K.P.P., G.H., C.R.V., J.V.), and the Department of Inflammation Research (H.G.), Rigshospitalet, University of Copenhagen, Denmark; and the Centre de Référence de Pathologie Neuromusculaire Paris-Est (P.L.), Institut de Myologie, GH Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, France.
authors.forename: John
authors.initials: J
authors.lastname: Vissing
mesh_terms: D000293:Adolescent; D000328:Adult; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise; D005632:Fructose / Q000008:administration & dosage / Q000494:pharmacology*; D006010:Glycogen Storage Disease Type III / Q000178:diet therapy / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D018908:Muscle Weakness / Q000178:diet therapy / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology; D055815:Young Adult
chemical_list: D005632:Fructose