title: Alterations in proton leak, oxidative status and uncoupling protein 3 content in skeletal muscle subsarcolemmal and intermyofibrillar mitochondria in old rats.
abstract: BACKGROUND
  We considered of interest to evaluate how aging affects mitochondrial function in skeletal muscle.
  
  
  METHODS
  We measured mitochondrial oxidative capacity and proton leak, together with lipid oxidative damage, superoxide dismutase specific activity and uncoupling protein 3 content, in subsarcolemmal and intermyofibrillar mitochondria from adult (six months) and old (two years) rats. Body composition, resting metabolic rate and plasma non esterified fatty acid levels were also assessed.
  
  
  RESULTS
  Old rats displayed significantly higher body energy and lipids, while body proteins were significantly lower, compared to adult rats. In addition, plasma non esterified fatty acid levels were significantly higher, while resting metabolic rates were found to be significantly lower, in old rats compared to adult ones. Significantly lower oxidative capacities in whole tissue homogenates and in intermyofibrillar and subsarcolemmal mitochondria were found in old rats compared to adult ones. Subsarcolemmal and intermyofibrillar mitochondria from old rats exhibited a significantly lower proton leak rate, while oxidative damage was found to be significantly higher only in subsarcolemmal mitochondria. Mitochondrial superoxide dismutase specific activity was not significantly affected in old rats, while significantly higher content of uncoupling protein 3 was found in both mitochondrial populations from old rats compared to adult ones, although the magnitude of the increase was lower in subsarcolemmal than in intermyofibrillar mitochondria.
  
  
  CONCLUSIONS
  The decrease in oxidative capacity and proton leak in intermyofibrillar and subsarcolemmal mitochondria could induce a decline in energy expenditure and thus contribute to the reduced resting metabolic rate found in old rats, while oxidative damage is present only in subsarcolemmal mitochondria.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Crescenzo
authors.forename: Francesca
authors.initials: F
authors.lastname: Bianco
authors.forename: Arianna
authors.initials: A
authors.lastname: Mazzoli
authors.forename: Antonia
authors.initials: A
authors.lastname: Giacco
authors.forename: Giovanna
authors.initials: G
authors.lastname: Liverini
authors.affiliation: Department of Biology, Complesso Universitario di Monte Sant'Angelo, Edificio 7, Via Cinthia, I-80126 Napoli, Italy. susiossa@unina.it.
authors.forename: Susanna
authors.initials: S
authors.lastname: Iossa
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D015536:Down-Regulation / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D008931:Mitochondria, Muscle / Q000737:chemistry / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism*; D009210:Myofibrils / Q000737:chemistry / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology*; D011522:Protons; D051381:Rats; D017208:Rats, Wistar; D012508:Sarcolemma / Q000737:chemistry / Q000378:metabolism; D000071247:Uncoupling Protein 3
chemical_list: D007473:Ion Channels; D024101:Mitochondrial Proteins; D011522:Protons; C000604394:Ucp3 protein, rat; D000071247:Uncoupling Protein 3