title: Effects of leucine supplementation and resistance exercise on dexamethasone-induced muscle atrophy and insulin resistance in rats.
abstract: OBJECTIVE
  We aimed to evaluate the effects of resistance exercise (RE) and leucine (LEU) supplementation on dexamethasone (DEXA)-induced muscle atrophy and insulin resistance.
  
  
  METHODS
  Male Wistar rats were randomly divided into DEXA (DEX), DEXA + RE (DEX-RE), DEXA + LEU (DEX-LEU), and DEXA + RE + LEU (DEX-RE-LEU) groups. Each group received DEXA 5 mg · kg(-1) · d(-1) for 7 d from drinking water and were pair-fed to the DEX group; LEU-supplemented groups received 0.135 g · kg(-1) · d(-1) through gavage for 7 d; the RE protocol was based on three sessions of squat-type exercise composed by three sets of 10 repetitions at 70% of maximal voluntary strength capacity.
  
  
  RESULTS
  The plantaris mass was significantly greater in both trained groups compared with the non-trained groups. Muscle cross-sectional area and fiber areas did not differ between groups. Both trained groups displayed significant increases in the number of intermediated fibers (IIa/IIx), a decreased number of fast-twitch fibers (IIb), an increased ratio of the proteins phospho(Ser2448)/total mammalian target of rapamycin and phospho(Thr389)/total 70-kDa ribosomal protein S6 kinase, and a decreased ratio of phospho(Ser253)/total Forkhead box protein-3a. Plasma glucose was significantly increased in the DEX-LEU group compared with the DEX group and RE significantly decreased hyperglycemia. The DEX-LEU group displayed decreased glucose transporter-4 translocation compared with the DEX group and RE restored this response. LEU supplementation worsened insulin sensitivity and did not attenuate muscle wasting in rats treated with DEXA. Conversely, RE modulated glucose homeostasis and fiber type transition in the plantaris muscle.
  
  
  CONCLUSIONS
  Resistance exercise but not LEU supplementation promoted fiber type transition and improved glucose homeostasis in DEXA-treated rats.
authors.affiliation: Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil. nicastro@usp.br
authors.forename: Humberto
authors.initials: H
authors.lastname: Nicastro
authors.forename: Nelo E
authors.initials: NE
authors.lastname: Zanchi
authors.forename: Claudia R
authors.initials: CR
authors.lastname: da Luz
authors.forename: Wilson M A M
authors.initials: WM
authors.lastname: de Moraes
authors.forename: Pamella
authors.initials: P
authors.lastname: Ramona
authors.forename: Mario A
authors.initials: MA
authors.lastname: de Siqueira Filho
authors.forename: Daniela F S
authors.initials: DF
authors.lastname: Chaves
authors.forename: Alessandra
authors.initials: A
authors.lastname: Medeiros
authors.forename: Patrícia C
authors.initials: PC
authors.lastname: Brum
authors.forename: Dominique
authors.initials: D
authors.lastname: Dardevet
authors.forename: Antonio H
authors.initials: AH
authors.lastname: Lancha
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D003907:Dexamethasone; D019587:Dietary Supplements; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006943:Hyperglycemia / Q000378:metabolism / Q000517:prevention & control; D007333:Insulin Resistance / Q000502:physiology*; D007930:Leucine / Q000494:pharmacology*; D008297:Male; D009068:Movement / Q000502:physiology; D053580:Muscle Strength / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology; D009133:Muscular Atrophy / Q000139:chemically induced / Q000378:metabolism / Q000517:prevention & control*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D055070:Resistance Training; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D051275:Glucose Transporter Type 4; C495694:Slc2a4 protein, rat; D003907:Dexamethasone; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D007930:Leucine