title: Effects of immobilization and aerobic training on proteins related to intramuscular substrate storage and metabolism in young and older men.
abstract: OBJECTIVE
  Aging and inactivity lead to skeletal muscle metabolic inflexibility, but the underlying molecular mechanisms are not entirely elucidated. Therefore, we investigated how muscle lipid and glycogen stores and major regulatory proteins were affected by short-term immobilization followed by aerobic training in young and older men.
  
  
  METHODS
  17 young (23 ± 1 years, 24 ± 1 kg m(-2), and 20 ± 2% body fat) and 15 older men (68 ± 1 years; 27 ± 1 kg m(-2), and 29 ± 2% body fat) underwent 2 weeks' one leg immobilization followed by 6 weeks' cycle training. Biopsies were obtained from m. vastus lateralis just before immobilization (at inclusion), after immobilization, and the after 6 weeks' training. The biopsies were analyzed for muscle substrates; muscle perilipin protein (PLIN), glycogen synthase (GS), synaptosomal-associated protein of 23 kDa (SNAP23) protein content, and muscle 3-hydroxyacyl-CoA dehydrogenase (HAD) activity
  
  
  RESULTS
  The older men had higher intramuscular triglyceride (IMTG) (73 %) and Glycogen (16%) levels compared to the young men, and IMTG tended to increase with immobilization. PLIN2 and 3 protein content increased with immobilization in the older men only. The young men had higher GS (74%) protein compared to the older men. Immobilization decreased and training restored HAD activity, GS and SNAP23 protein content in young and older men.
  
  
  CONCLUSIONS
  Evidence of age-related metabolic inflexibility is presented, seen as body fat and IMTG accumulation. The question arises as to whether IMTG accumulation in the older men is caused by or leading to the increase in PLIN2 and 3 protein content. Training decreased body fat and IMTG levels in both young and older men; hence, training should be prioritized to reduce the detrimental effect of aging on metabolism.
authors.affiliation: Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, 2200, Copenhagen, Denmark. avhansen@sund.ku.dk.
authors.forename: Andreas
authors.initials: A
authors.lastname: Vigelsø
authors.affiliation: Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
authors.forename: Martin
authors.initials: M
authors.lastname: Gram
authors.affiliation: Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
authors.forename: Caroline
authors.initials: C
authors.lastname: Wiuff
authors.affiliation: Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
authors.forename: Christina Neigaard
authors.initials: CN
authors.lastname: Hansen
authors.affiliation: Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
authors.forename: Clara
authors.initials: C
authors.lastname: Prats
authors.affiliation: Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
authors.forename: Flemming
authors.initials: F
authors.lastname: Dela
authors.affiliation: Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
authors.forename: Jørn Wulff
authors.initials: JW
authors.lastname: Helge
mesh_terms: D063988:3-Hydroxyacyl-CoA Dehydrogenase / Q000378:metabolism; D000368:Aged; D002352:Carrier Proteins / Q000378:metabolism; D015444:Exercise; D006003:Glycogen / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism; D006801:Humans; D007103:Immobilization / Q000009:adverse effects*; D050356:Lipid Metabolism; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism*; D000070778:Perilipin-1; D010750:Phosphoproteins / Q000378:metabolism; D050766:Qb-SNARE Proteins / Q000378:metabolism; D050767:Qc-SNARE Proteins / Q000378:metabolism; D055815:Young Adult
chemical_list: D002352:Carrier Proteins; D009124:Muscle Proteins; D000070778:Perilipin-1; D010750:Phosphoproteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; C100493:SNAP23 protein, human; D006003:Glycogen; D063988:3-Hydroxyacyl-CoA Dehydrogenase; D006006:Glycogen Synthase
keywords: Aerobic training; Aging; Immobilization; Intramuscular triglycerides; Muscle metabolism; Perilipin protein