Nutrition
Volume 28, Issue 4 , Pages 465-471, April 2012

Effects of leucine supplementation and resistance exercise on dexamethasone-induced muscle atrophy and insulin resistance in rats

  • Humberto Nicastro, Ph.D.

      Affiliations

    • Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil
    • Corresponding Author InformationCorresponding author. Tel.: +55-11-3091-3096; fax: +55-11-3091-3136.
    • ,
  • Nelo E. Zanchi, Ph.D.

      Affiliations

    • Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
    • ,
  • Claudia R. da Luz, M.Sc.

      Affiliations

    • Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil
    • ,
  • Wilson M.A.M. de Moraes, M.Sc.

      Affiliations

    • Laboratory of Molecular and Cellular Physiology of Exercise, School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil
    • ,
  • Pamella Ramona, M.Sc.

      Affiliations

    • Laboratory of Experimental Hypertension, School of Medicine, University of São Paulo, São Paulo, Brazil
    • ,
  • Mario A. de Siqueira Filho, Ph.D.

      Affiliations

    • Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
    • ,
  • Daniela F.S. Chaves, Ph.D.

      Affiliations

    • Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil
    • ,
  • Alessandra Medeiros, Ph.D.

      Affiliations

    • Laboratory of Molecular and Cellular Physiology of Exercise, School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil
    • Biosciences Department, Federal University of São Paulo, Santos, São Paulo, Brazil
    • ,
  • Patrícia C. Brum, Ph.D.

      Affiliations

    • Laboratory of Molecular and Cellular Physiology of Exercise, School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil
    • ,
  • Dominique Dardevet, Ph.D.

      Affiliations

    • INRA, UMR 1019 Unité de Nutrition Humaine, Saint Genès Champanelle, France; Clermont Université, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
    • ,
  • Antonio H. Lancha Jr., Ph.D.

      Affiliations

    • Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil

Received 10 March 2011; accepted 17 August 2011. published online 14 November 2011.

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 phosphoSer2448/total mammalian target of rapamycin and phosphoThr389/total 70-kDa ribosomal protein S6 kinase, and a decreased ratio of phosphoSer253/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.

Conclusion

Resistance exercise but not LEU supplementation promoted fiber type transition and improved glucose homeostasis in DEXA-treated rats.

Keywords: Branched-chain amino acids, Glucose transporter-4, Muscle wasting, Mammalian target of rapamycin, Glucocorticoid

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 This study was funded by grant 08/51090-1 from the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP). Humberto Nicastro, Nelo Eidy Zanchi and Claudia Ribeiro da Luz are supported by grants 10/07062-3, 10/10852-6 and 11/04690-6, respectively, from FAPESP.

PII: S0899-9007(11)00305-4

doi:10.1016/j.nut.2011.08.008

Nutrition
Volume 28, Issue 4 , Pages 465-471, April 2012

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