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Muscle fibre size and myonuclear positioning in trained and aged humans

Battey, E, Levy, Y, Pollock, RD, Pugh, JN, Close, GL, Kalakoutis, M, Lazarus, NR, Harridge, SDR, Ochala, J and Stroud, MJ (2024) Muscle fibre size and myonuclear positioning in trained and aged humans. Experimental Physiology, 109 (4). pp. 549-561. ISSN 0958-0670

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Changes in myonuclear architecture and positioning are associated with exercise adaptations and ageing. However, data on the positioning and number of myonuclei following exercise are inconsistent. Additionally, whether myonuclear domains (MNDs; i.e., the theoretical volume of cytoplasm within which a myonucleus is responsible for transcribing DNA) and myonuclear positioning are altered with age remains unclear. The aim of this investigation was to investigate relationships between age and activity status and myonuclear domains and positioning. Vastus lateralis muscle biopsies from younger endurance-trained (YT) and older endurance-trained (OT) individuals were compared with age-matched untrained counterparts (YU and OU; OU samples were acquired during surgical operation). Serial, optical z-slices were acquired throughout isolated muscle fibres and analysed to give three-dimensional coordinates for myonuclei and muscle fibre dimensions. The mean cross-sectional area (CSA) of muscle fibres from OU individuals was 33%–53% smaller compared with the other groups. The number of nuclei relative to fibre CSA was 90% greater in OU compared with YU muscle fibres. Additionally, scaling of MND volume with fibre size was altered in older untrained individuals. The myonuclear arrangement, in contrast, was similar across groups. Fibre CSA and most myonuclear parameters were significantly associated with age in untrained individuals, but not in trained individuals. These data indicate that regular endurance exercise throughout the lifespan might better preserve the size of muscle fibres in older age and maintain the relationship between fibre size and MND volumes. Inactivity, however, might result in reduced muscle fibre size and altered myonuclear parameters.

Item Type: Article
Uncontrolled Keywords: ageing; cross-sectional area; exercise; myonuclear domains; nuclei; 0606 Physiology; 1106 Human Movement and Sports Sciences; 1116 Medical Physiology; Physiology
Subjects: Q Science > QP Physiology
R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
Publisher: Wiley
SWORD Depositor: A Symplectic
Date Deposited: 08 Apr 2024 14:46
Last Modified: 08 Apr 2024 14:46
DOI or ID number: 10.1113/EP091567
URI: https://researchonline.ljmu.ac.uk/id/eprint/22979
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