Blocked muscle fat oxidation during exercise in neutral lipid storage disease
Pascal Laforêt1, Mette Ørngreen, Nicolai Preisler
1Centre de Référence de Pathologie Neuromusculaire Paris-Est, Bâtiment Babinski, Groupe Hospitalier Pitié-Salpêtrière, 47-83 Boulevard de l'Hôpital, 75651 Paris CEDEX 13, France. pascal.laforet@psl.aphp.fr
Objective:
To determine whether impaired exercise capacity in neutral lipid storage disease with myopathy is solely caused by muscle weakness or whether a defect in energy metabolism (blocked fat oxidation) may also play a role.
Design:
We studied a 37-year-old woman with neutral lipid storage disease with myopathy, who cycled while lipid oxidation was assessed using U-(13)C palmitate tracer dilution technique. The effect of a glucose infusion during exercise was also studied.
Setting:
Neuromuscular research unit.
Results:
The exercise-induced increase in fat oxidation was virtually abolished in the patient. Treatment with intravenous glucose infusion improved maximal oxygen uptake from 23 to 27 mL × kg(-1) × min(-1), and maximal workload from 75 to 100 W.
Conclusions:
These results demonstrate that in addition to fixed weakness, neutral lipid storage disease with myopathy is also characterized by a profound block in fat oxidation, which limits exercise tolerance.
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