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Tina Dysgaard Jeppesen, MD; Mette Cathrine Ørngreen, MD; Gerrit van Hall, PhD; Ronald G. Haller, MD; John Vissing, MD, DMSci

Arch Neurol. 2009;66(3):365-370.

Objective  To determine whether patients with defects of the respiratory chain have metabolic adaptations that promote a preferential use of fats or carbohydrates, similar to what is observed in metabolic myopathies affecting glycolysis or fat oxidation.

Design  Causation and case-control study. Fat metabolism was determined by means of indirect calorimetry and stable isotope technique in patients and healthy subjects. Patients carried various types and loads (mean [SE], 72% [5%]) of mitochondrial DNA (mtDNA) mutations in skeletal muscle. All subjects exercised at the same absolute workload (mean [SE], 65 [10] W), corresponding to 72% (in patients) and 30% (in healthy subjects) of maximum oxygen consumption.

Setting  Neuromuscular research unit.

Participants  Ten patients with mtDNA mutations and 10 sex-matched healthy subjects.

Main Outcome Measures  Fat turnover, plasma concentrations of palmitate and total free fatty acids, glucose mobilization, and total carbohydrate oxidation.

Results  Fat turnover and plasma concentrations of palmitate and total free fatty acids were similar in patients and healthy subjects at rest and during exercise. In line with the higher relative workload of the patients, glucose mobilization and total carbohydrate oxidation were higher in the patients compared with the healthy subjects.

Conclusion  During moderate-intensity exercise, the balance between fat and carbohydrate use in patients with mtDNA mutations matches that seen in healthy subjects, indicating that manipulating dietary fat and carbohydrate content is not a feasible therapeutic option to improve exercise intolerance in these disorders.

Author Affiliations: Neuromuscular Research Unit, Department of Neurology and Copenhagen Muscle Research Center (Drs Jeppesen, Ørngreen, van Hall, and Vissing), and Department of Biomedical Sciences (Dr Haller), University of Copenhagen, Rigshospitalet, Copenhagen, Denmark; and Institute for Exercise and Environmental Medicine, Neuromuscular Center, Dallas, Texas (Dr Haller).

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