title: Bed rest reduces metabolic protein content and abolishes exercise-induced mRNA responses in human skeletal muscle.
abstract: The aim was to test the hypothesis that 7 days of bed rest reduces mitochondrial number and expression and activity of oxidative proteins in human skeletal muscle but that exercise-induced intracellular signaling as well as mRNA and microRNA (miR) responses are maintained after bed rest. Twelve young, healthy male subjects completed 7 days of bed rest with vastus lateralis muscle biopsies taken before and after bed rest. In addition, muscle biopsies were obtained from six of the subjects prior to, immediately after, and 3 h after 45 min of one-legged knee extensor exercise performed before and after bed rest. Maximal oxygen uptake decreased by 4%, and exercise endurance decreased nonsignificantly, by 11%, by bed rest. Bed rest reduced skeletal muscle mitochondrial DNA/nuclear DNA content 15%, hexokinase II and sirtuin 1 protein content ∼45%, 3-hydroxyacyl-CoA dehydrogenase and citrate synthase activity ∼8%, and miR-1 and miR-133a content ∼10%. However, cytochrome c and vascular endothelial growth factor (VEGF) protein content as well as capillarization did not change significantly with bed rest. Acute exercise increased AMP-activated protein kinase phosphorylation, peroxisome proliferator activated receptor-γ coactivator-1α, and VEGF mRNA content in skeletal muscle before bed rest, but the responses were abolished after bed rest. The present findings indicate that only 7 days of physical inactivity reduces skeletal muscle metabolic capacity as well as abolishes exercise-induced adaptive gene responses, likely reflecting an interference with the ability of skeletal muscle to adapt to exercise.
authors.affiliation: Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark. srjorgensen@bio.ku.dk
authors.forename: Stine
authors.initials: S
authors.lastname: Ringholm
authors.forename: Rasmus S
authors.initials: RS
authors.lastname: Biensø
authors.forename: Kristian
authors.initials: K
authors.lastname: Kiilerich
authors.forename: Amelia
authors.initials: A
authors.lastname: Guadalupe-Grau
authors.forename: Niels Jacob
authors.initials: NJ
authors.lastname: Aachmann-Andersen
authors.forename: Bengt
authors.initials: B
authors.lastname: Saltin
authors.forename: Peter
authors.initials: P
authors.lastname: Plomgaard
authors.forename: Carsten
authors.initials: C
authors.lastname: Lundby
authors.forename: Jørgen F P
authors.initials: JF
authors.lastname: Wojtaszewski
authors.forename: Jose A
authors.initials: JA
authors.lastname: Calbet
authors.forename: Henriette
authors.initials: H
authors.lastname: Pilegaard
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D000328:Adult; D001510:Bed Rest; D001823:Body Composition / Q000502:physiology; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D004734:Energy Metabolism / Q000235:genetics; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D045304:Cytochromes c; D055372:AMP-Activated Protein Kinases