Leucine induces myofibrillar protein accretion in cultured skeletal muscle through mTOR dependent and -independent control of myosin heavy chain mRNA levels

Authors

  • Astrid Haegens,

    Corresponding author
    1. Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
    • Top Institute Food & Nutrition (TIFN), Wageningen, The Netherlands
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  • Annemie M. Schols,

    1. Top Institute Food & Nutrition (TIFN), Wageningen, The Netherlands
    2. Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
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  • Anon L. van Essen,

    1. Top Institute Food & Nutrition (TIFN), Wageningen, The Netherlands
    2. Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
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  • Luc J. van Loon,

    1. Top Institute Food & Nutrition (TIFN), Wageningen, The Netherlands
    2. Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
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  • Ramon C. Langen

    1. Top Institute Food & Nutrition (TIFN), Wageningen, The Netherlands
    2. Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
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Correspondence: Astrid Haegens, Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, PO Box 616, 6200 MD Maastricht, The Netherlands

E-mail: a.haegens@maastrichtuniversity.nl

Fax: +31-43-3875051

Abstract

Scope

Nutritional intervention during muscle wasting aims to attenuate net muscle protein loss. Branched chain amino acids, especially leucine, are able to stimulate the anabolic mammalian target of rapamycin (mTOR) signalling cascade and protein synthesis. It has been suggested that muscle myofibrillar protein expression is more responsive to amino acid supplementation compared to cytoplasmic proteins, although accretion of myofibrillar proteins has not extensively been investigated. We hypothesized that leucine specifically increases myofibrillar protein synthesis in skeletal muscle.

Methods and results

This hypothesis was investigated in C2C12 skeletal muscle cells using physiologically relevant culture conditions. Leucine supplementation specifically increased myofibrillar protein accretion, including myosin heavy chain-slow and -fast and myosin light chain 1 and -3 in C2C12 cells. Neither total protein content, nor de novo protein synthesis was affected, despite leucine-induced increased 4E-BP1 and S6K1 phosphorylation. Leucine supplementation did not affect myogenesis, measured by creatine kinase activity and myoblast fusion, either. Remarkably, leucine-induced increased myofibrillar protein accretion was accompanied by elevated MyHC mRNA levels, which involved mTOR-dependent and -independent regulation of MyHC-4 and MyHC-7 gene-expression, respectively.

Conclusion

This study clearly demonstrates myofibrillar and not generic protein accretion in skeletal muscle following leucine supplementation, and suggests this involves pre-translational control of MyHC expression by leucine.

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