title: Expression of mitochondrial fission and fusion regulatory proteins in skeletal muscle during chronic use and disuse.
abstract: BACKGROUND
  The mitochondrial network within cells is mediated by fission and fusion processes.
  
  
  METHODS
  We investigated the expression of the proteins responsible for these events during conditions of altered oxidative capacity.
  
  
  RESULTS
  With chronic contractile activity, the mitochondrial reticulum increased in size, along with concomitant increases in the fusion proteins Opa1 and Mfn2 (by 36% and 53%; P < 0.05). When we induced muscle disuse through denervation for 7 days, fragmented mitochondria were observed, along with significant decreases in the expression of Mfn2 and Opa1 (by 84% and 70%). To assess the effects of aging on mitochondrial morphology, young (5 month) and aged (35 month) Fisher 344 Brown Norway rats were used. Aged animals also possessed smaller mitochondria and displayed increased levels of fission proteins.
  
  
  CONCLUSIONS
  Chronic muscle use increases the ratio of fusion:fission proteins, leading to reticular mitochondria, whereas muscle disuse and aging result in a decrease in this ratio, culminating in fragmented organelles.
authors.affiliation: School of Kinesiology and Health Science, and the Muscle Health Research Centre, York University, Toronto, Ontario, M3J 1P3, Canada.
authors.forename: Sobia
authors.initials: S
authors.lastname: Iqbal
authors.forename: Olga
authors.initials: O
authors.lastname: Ostojic
authors.forename: Kaustabh
authors.initials: K
authors.lastname: Singh
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Joseph
authors.forename: David A
authors.initials: DA
authors.lastname: Hood
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D004195:Disease Models, Animal; D003576:Electron Transport Complex IV / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008931:Mitochondria, Muscle / Q000378:metabolism / Q000648:ultrastructure; D063154:Mitochondrial Dynamics / Q000502:physiology; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009121:Muscle Denervation / Q000009:adverse effects; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D009135:Muscular Diseases / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley
chemical_list: D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D003576:Electron Transport Complex IV; D020558:GTP Phosphohydrolases; C489710:Mfn2 protein, rat; C498811:Opa1 protein, rat
keywords: aging; denervation; exercise; fiber types; mitochondria