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Planhab*: hypoxia does not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone

Salvadego, D. and Keramidas, M.E. and Kölegard, R. and Brocca, L. and Lazzer, S. and Mavelli, I. and Rittweger, J. and Eiken, O and Mekjavic, I. and Grassi, B. (2018) Planhab*: hypoxia does not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone. Journal of Physiology, 596 (15), pp. 3341-3355. Wiley. DOI: 10.1113/JP275605 ISSN 0022-3751

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Abstract

KEY POINTS: Superposition of hypoxia on 21 day bed rest did not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone. A significant impairment of maximal oxidative performance was identified downstream of cardiovascular O2 delivery, involving both the intramuscular matching between O2 supply and utilization and mitochondrial respiration. These chronic adaptations appear to be relevant in terms of exposure to spaceflights and reduced gravity habitats (Moon or Mars), as characterized by low gravity and hypoxia, in patients with chronic diseases characterized by hypomobility/immobility and hypoxia, as well as in ageing. ABSTRACT: Skeletal muscle oxidative function was evaluated in 11 healthy males (mean ± SD age 27 ± 5 years) prior to (baseline data collection, BDC) and following a 21 day horizontal bed rest (BR), carried out in normoxia ( P IO 2 = 133 mmHg; N-BR) and hypoxia ( P IO 2 = 90 mmHg; H-BR). H-BR was aimed at simulating reduced gravity habitats. The effects of a 21 day hypoxic ambulatory confinement ( P IO 2 = 90 mmHg; H-AMB) were also assessed. Pulmonary O2 uptake ( V ̇ O 2 ), vastus lateralis fractional O2 extraction (changes in deoxygenated haemoglobin + myoglobin concentration, Δ[deoxy(Hb + Mb)]; near-infrared spectroscopy) and femoral artery blood flow (ultrasound Doppler) were evaluated during incremental one-leg knee-extension exercise (reduced constraints to cardiovascular O2 delivery) carried out to voluntary exhaustion in a normoxic environment. Mitochondrial respiration was evaluated ex vivo by high-resolution respirometry in permeabilized vastus lateralis fibres. V ̇ O2 peak decreased (P < 0.05) after N-BR (0.98 ± 0.13 L min-1 ) and H-BR (0.96 ± 0.17 L min-1 ) vs. BDC (1.05 ± 0.14 L min-1 ). In the presence of a decreased (by ∼6-8%) thigh muscle volume, V ̇ O2 peak normalized per unit of muscle mass was not affected by both interventions. Δ[deoxy(Hb + Mb)]peak decreased (P < 0.05) after N-BR (65 ± 13% of limb ischaemia) and H-BR (62 ± 12%) vs. BDC (73 ± 13%). H-AMB did not alter V ̇O2 peak or Δ[deoxy(Hb + Mb)]peak . An overshoot of Δ[deoxy(Hb + Mb)] was evident during the first minute of unloaded exercise after N-BR and H-BR. Arterial blood flow to the lower limb during both unloaded and peak knee extension was not affected by any intervention. Maximal ADP-stimulated mitochondrial respiration decreased (P < 0.05) after all interventions vs. control. In 21 day N-BR, a significant impairment of oxidative metabolism occurred downstream of cardiovascular O2 delivery, affecting both mitochondrial respiration and presumably the intramuscular matching between O2 supply and utilization. Superposition of H on BR did not worsen the impairment induced by BR alone.

Item URL in elib:https://elib.dlr.de/124239/
Document Type:Article
Title:Planhab*: hypoxia does not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Salvadego, D.University of UdineUNSPECIFIED
Keramidas, M.E.Swedish Aerospace Physiology Centre, Royal Institute of Technology, Stockholm, SwedenUNSPECIFIED
Kölegard, R.UNSPECIFIEDUNSPECIFIED
Brocca, L.luca.brocca (at) irpi.cnr.itUNSPECIFIED
Lazzer, S.University of Udine, ItalyUNSPECIFIED
Mavelli, I.University of UdineUNSPECIFIED
Rittweger, J.Joern.Rittweger (at) dlr.dehttps://orcid.org/0000-0002-2223-8963
Eiken, ODepartment of Environmental Physiology, Swedish Aerospace Physiology Centre, Royal Institute of Technology, Stockholm, SwedenUNSPECIFIED
Mekjavic, I.Jozef Stefan InstituteUNSPECIFIED
Grassi, B.University of Udine, ItalyUNSPECIFIED
Date:2018
Journal or Publication Title:Journal of Physiology
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:596
DOI :10.1113/JP275605
Page Range:pp. 3341-3355
Publisher:Wiley
ISSN:0022-3751
Status:Published
Keywords:hypoxia; microgravity; mitochondrial respiration; planetary habitats; skeletal muscle oxidative metabolism
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):R - Vorhaben Systemphysiologie
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Muscle and Bone Metabolism
Deposited By: Becker, Christine
Deposited On:11 Dec 2018 11:42
Last Modified:06 Sep 2019 15:22

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