Mette Cathrine Ørngreen1, Tina Dysgaard Jeppesen1, Tanja Taivassalo1, Simon Hauerslev1, Nicolai Preisler1, Katja Heinicke1, Ronald G Haller1, John Vissing1, Gerrit van Hall1. 1. Neuromuscular Research Unit, Department of Neurology (M.C.O., T.D.J., S.H., N.P., J.V.), Copenhagen Muscle Research Center (M.C.O., T.D.J., S.H., N.P., J.V., G.H.), and Clinical Metabolomics Core Facility (G.H.), Rigshospitalet, DK-2100 Copenhagen, Denmark; Department of Biomedical Sciences (G.H.), Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark; Neuromuscular Center (T.T., K.H., R.G.H.), Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, and the Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, Texas 75235; and Department of Neurology (R.G.H.), North Texas VA Medical Center, Dallas, Texas 75216.
Abstract
CONTEXT: Patients with blocked muscle glycogen breakdown (McArdle disease) have severely reduced exercise capacity compared to healthy individuals and are not assumed to produce lactate during exercise. OBJECTIVES: The objectives were: 1) to quantify systemic and muscle lactate kinetics and oxidation rates and muscle energy utilization during exercise in patients with McArdle disease; and 2) to elucidate the role of lactate formation in muscle energy production. DESIGN AND SETTING: This was a single trial in a hospital. PARTICIPANTS: Participants were four patients with McArdle disease and seven healthy subjects. INTERVENTION: Patients and healthy controls were studied at rest, which was followed by 40 minutes of cycle-ergometer exercise at 60% of the patients' maximal oxygen uptake (∼35 W). MAIN OUTCOME MEASURES: Main outcome measures were systemic and leg skeletal muscle lactate, alanine, fatty acid, and glucose kinetics. RESULTS: McArdle patients had a marked decrease in plasma lactate concentration at the onset of exercise, and the concentration remained suppressed during exercise. A substantial leg net lactate uptake and subsequent oxidation occurred over the entire exercise period in patients, in contrast to a net lactate release or no exchange in the healthy controls. Despite a net lactate uptake by the active leg, a simultaneous unidirectional lactate release was observed in McArdle patients at rates that were similar to the healthy controls. CONCLUSION: Lactate is an important energy source for contracting skeletal muscle in patients with myophosphorylase deficiency. Although McArdle patients had leg net lactate consumption, a simultaneous release of lactate was observed at rates similar to that found in healthy individuals exercising at the same very low workload, suggesting that lactate formation is mandatory for muscle energy generation during exercise.
CONTEXT: Patients with blocked muscle glycogen breakdown (McArdle disease) have severely reduced exercise capacity compared to healthy individuals and are not assumed to produce lactate during exercise. OBJECTIVES: The objectives were: 1) to quantify systemic and muscle lactate kinetics and oxidation rates and muscle energy utilization during exercise in patients with McArdle disease; and 2) to elucidate the role of lactate formation in muscle energy production. DESIGN AND SETTING: This was a single trial in a hospital. PARTICIPANTS: Participants were four patients with McArdle disease and seven healthy subjects. INTERVENTION: Patients and healthy controls were studied at rest, which was followed by 40 minutes of cycle-ergometer exercise at 60% of the patients' maximal oxygen uptake (∼35 W). MAIN OUTCOME MEASURES: Main outcome measures were systemic and leg skeletal muscle lactate, alanine, fatty acid, and glucose kinetics. RESULTS:McArdlepatients had a marked decrease in plasma lactate concentration at the onset of exercise, and the concentration remained suppressed during exercise. A substantial leg net lactate uptake and subsequent oxidation occurred over the entire exercise period in patients, in contrast to a net lactate release or no exchange in the healthy controls. Despite a net lactate uptake by the active leg, a simultaneous unidirectional lactate release was observed in McArdlepatients at rates that were similar to the healthy controls. CONCLUSION:Lactate is an important energy source for contracting skeletal muscle in patients with myophosphorylase deficiency. Although McArdlepatients had leg net lactate consumption, a simultaneous release of lactate was observed at rates similar to that found in healthy individuals exercising at the same very low workload, suggesting that lactate formation is mandatory for muscle energy generation during exercise.
Authors: María M Adeva-Andany; Manuel González-Lucán; Cristóbal Donapetry-García; Carlos Fernández-Fernández; Eva Ameneiros-Rodríguez Journal: BBA Clin Date: 2016-02-27