title: McArdle disease does not affect skeletal muscle fibre type profiles in humans.
abstract: Patients suffering from glycogen storage disease V (McArdle disease) were shown to have higher surface electrical activity in their skeletal muscles when exercising at the same intensity as their healthy counterparts, indicating more muscle fibre recruitment. To explain this phenomenon, this study investigated whether muscle fibre type is shifted towards a predominance in type I fibres as a consequence of the disease. Muscle biopsies from the Biceps brachii (BB) (n = 9) or Vastus lateralis (VL) (n = 8) were collected over a 13-year period from male and female patients diagnosed with McArdle disease, analysed for myosin heavy chain (MHC) isoform content using SDS-PAGE, and compared to healthy controls (BB: n = 3; VL: n = 10). All three isoforms were expressed and no difference in isoform expression in VL was found between the McArdle patients and healthy controls (MHC I: 33±19% vs. 43±7%; MHC IIa: 52±9% vs. 40±7%; MHC IIx: 15±18% vs. 17±9%). Similarly, the BB isoform content was also not different between the two groups (MHC I: 33±14% vs. 30±11%; MHC IIa: 46±17% vs. 39±5%; MHC IIx: 21±13% vs. 31±14%). In conclusion, fibre type distribution does not seem to explain the higher surface EMG in McArdle patients. Future studies need to investigate muscle fibre size and contractility of McArdle patients.
authors.affiliation: UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, PO Box 115, Newlands 7725, South Africa ta.kohn@uct.ac.za.
authors.forename: Tertius Abraham
authors.initials: TA
authors.lastname: Kohn
authors.affiliation: UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, PO Box 115, Newlands 7725, South Africa.
authors.forename: Timothy David
authors.initials: TD
authors.lastname: Noakes
authors.affiliation: UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, PO Box 115, Newlands 7725, South Africa.
authors.forename: Dale Elizabeth
authors.initials: DE
authors.lastname: Rae
authors.affiliation: Mitochondrial and Neuromuscular Diseases Laboratory, i+12 Research Institute, Hospital 12 de Octubre, 28041 Madrid, Spain.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Rubio
authors.affiliation: Department of Sport Science, Universidad Pablo de Olavide, 41013 Seville, Spain.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Santalla
authors.affiliation: Neuromuscular Diseases Unit, Institut de Recerca del Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, 08193 Barcelona, Spain.
authors.forename: Gisela
authors.initials: G
authors.lastname: Nogales-Gadea
authors.affiliation: Departament de Patologia Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron, Institut de Recerca (VHIR), Universitat Autónoma de Barcelona, 08193 Barcelona, Spain.
authors.forename: Tomas
authors.initials: T
authors.lastname: Pinós
authors.affiliation: Mitochondrial and Neuromuscular Diseases Laboratory, i+12 Research Institute, Hospital 12 de Octubre, 28041 Madrid, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Martín
authors.affiliation: Mitochondrial and Neuromuscular Diseases Laboratory, i+12 Research Institute, Hospital 12 de Octubre, 28041 Madrid, Spain.
authors.forename: Joaquin
authors.initials: J
authors.lastname: Arenas
authors.affiliation: Mitochondrial and Neuromuscular Diseases Laboratory, i+12 Research Institute, Hospital 12 de Octubre, 28041 Madrid, Spain European University of Madrid, 28670 Madrid, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Lucia
keywords: Glycogen storage disease V; Myosin heavy chain; Phosphorylase deficiency