Short-term step reduction reduces citrate synthase activity without altering skeletal muscle markers of oxidative metabolism or insulin-mediated signaling in young males

Sophie J Edwards, Brandon J Shad, Ryan N Marshall, Paul T Morgan, Gareth Anthony Wallis, Leigh Breen

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Abstract

Mitochondria are critical to skeletal muscle contractile function and metabolic health. Short-term periods of step reduction (SR) are associated with alterations in muscle protein turnover and mass. However, the effects of SR on mitochondrial metabolism/muscle oxidative metabolism and insulin-mediated signaling are unclear. We tested the hypothesis that the total and/or phosphorylated protein content of key skeletal muscle markers of mitochondrial/oxidative metabolism, and insulin-mediated signaling would be altered over 7 days of SR in young healthy males. Eleven, healthy, recreationally active males (means ± SE, age: 22 ± 1 yr, BMI: 23.4 ± 0.7 kg·m 2) underwent a 7-day period of SR. Immediately before and following SR, fasted-state muscle biopsy samples were acquired and analyzed for the assessment of total and phosphorylated protein content of key markers of mitochondrial/oxidative metabolism and insulin-mediated signaling. Daily step count was significantly reduced during the SR intervention (13,054 ± 833 to 1,192 ± 99 steps·day -1, P < 0.001). Following SR, there was a significant decline in maximal citrate synthase activity (fold change: 0.94 ± 0.08, P < 0.05) and a significant increase in the protein content of p-glycogen synthase (P-GS S641; fold change: 1.47 ± 0.14, P < 0.05). No significant differences were observed in the total or phosphorylated protein content of other key markers of insulin-mediated signaling, oxidative metabolism, mitochondrial function, or mitochondrial dynamics (all P > 0.05). These results suggest that short-term SR reduces the maximal activity of citrate synthase, a marker of mitochondrial content, without altering the total or phosphorylated protein content of key markers of skeletal muscle mitochondrial metabolism and insulin signaling in young healthy males.

Original languageEnglish
Pages (from-to)1653-1662
Number of pages10
JournalJournal of Applied Physiology
Volume131
Issue number6
Early online date4 Nov 2021
DOIs
Publication statusPublished - 1 Dec 2021

Bibliographical note

Funding Information:
This work was supported by a studentship (to S.J.E) from the BBSRC Midlands Integrative Biosciences Training Partnership and a Exercise as Medicine studentship (to B.J.S) from the College of Life and Environmental Sciences, University of Birmingham.

Publisher Copyright:
Copyright © 2021 The Authors. Licensed under Creative Commons Attribution CC-BY 4.0.

Keywords

  • Insulin sensitivity
  • Mitochondria
  • Physical inactivity
  • Skeletal muscle
  • Step reduction

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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