Hybrid fiber alterations in exercising seniors suggest contribution to fast-to-slow muscle fiber shift.

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License: CC BY-NC 4.0
Serval ID
serval:BIB_747BE57E8C32
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Hybrid fiber alterations in exercising seniors suggest contribution to fast-to-slow muscle fiber shift.
Journal
Journal of cachexia, sarcopenia and muscle
Author(s)
Moreillon M., Conde Alonso S., Broskey N.T., Greggio C., Besson C., Rousson V., Amati F.
ISSN
2190-6009 (Electronic)
ISSN-L
2190-5991
Publication state
Published
Issued date
06/2019
Peer-reviewed
Oui
Volume
10
Number
3
Pages
687-695
Language
english
Notes
Publication types: Journal Article ; Research Support, Non-U.S. Gov't
Publication Status: ppublish
Abstract
Human skeletal muscle is composed of a functional and metabolic continuum of slow (Type I) and fast fibers (IIa and IIx). Hybrid fibers co-expressing different myosin heavy chains are also present and seem to be more prominent in aging muscle. Their role is debated; hybrid fibers were reported either in a transitional state, between slow and fast fibers, or as fixed individual entities. This study examined the fate of hybrid fibers with an endurance exercise intervention in an elderly sedentary population.
Twenty-two sedentary healthy elderly men and women underwent a 16-week supervised endurance exercise intervention. Eighteen endurance-trained age- and gender-matched volunteers served as controls. Fiber type distribution was determined by immunohistochemistry on vastus lateralis muscle biopsies pre-intervention and post-intervention.
A total of 13840 fibers were analyzed. At baseline, a Type II dominant fiber profile was observed compared with the control group, with more Type IIa (P = 0.0301) and Type IIx fibers (P = 0.0328). Hybrid fibers represented almost 5% of total muscle fibers in both groups. There was no significant difference between groups (I-IIa, P = 0.6719 and IIa-IIx, P = 0.0998). Intervention triggered qualitative dynamics towards an increase in Type I, and decrease in Type II fibers, paralleled by an increase in I-IIa hybrids (P = 0.0301).
The present study is, to our knowledge, the first to examine hybrid muscle fiber type adaptations to an endurance exercise intervention in the elderly. Hybrid fiber proportions did not differ between chronic sedentary state and chronic endurance-trained state. Exercise intervention increased Type I-IIa hybrid fibers along with shift dynamics in other fiber types suggesting the contribution of hybrid fiber to a fast-to-slow fiber type transition, eventually serving as intermediate reservoir from one monomorphic myosin heavy chain expressing fiber type to another. This finding favours the transitional theory regarding hybrid muscle fibers and exercise, crucial to understanding reversible mechanisms of sarcopenia and development of prevention measures.
Keywords
Aged, Aging/physiology, Biopsy, Endurance Training, Female, Humans, Male, Middle Aged, Muscle Fibers, Fast-Twitch/physiology, Muscle Fibers, Slow-Twitch/physiology, Myosin Heavy Chains/metabolism, Quadriceps Muscle/physiology, Sarcopenia/physiopathology, Sarcopenia/prevention & control, Sedentary Behavior, Aging, Endurance training, Myosin heavy chain, Skeletal muscle fibre type
Pubmed
Web of science
Open Access
Yes
Funding(s)
Swiss National Science Foundation / Careers / PZ00P3-149398
Swiss National Science Foundation / Careers / PZ00P3-126339
Swiss National Science Foundation / Projects / 320030_170062
Create date
26/03/2019 15:06
Last modification date
07/07/2020 5:20
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