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Updated: Apr 15, 2026

Quantification of Subcellular Glycogen Distribution in Skeletal Muscle Fibers using Transmission Electron Microscopy
Published on: February 7, 2022
Skeletal muscle metabolism is impaired during exercise in glycogen storage disease type III
Nicolai Preisler1, Pascal Laforêt2, Karen Lindhardt Madsen2
1From 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.
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.
Conclusion:
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.
Classification Of Evidence:
This study provides Class IV evidence that ingestion of fructose improves exercise tolerance in patients with GSDIIIa.
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