Smoking impairs muscle protein synthesis and increases the expression of myostatin and MAFbx in muscle

Anne Marie Winther Petersen, Faidon Magkos, Philip Atherton, Anna Selby, Kenneth Smith, Michael J. Rennie, Bente Klarlund Pedersen, Bettina Mittendorfer

Research output: Contribution to journalArticle

96 Scopus citations

Abstract

Smoking causes multiple organ dysfunction. The effect of smoking on skeletal muscle protein metabolism is unknown. We hypothesized that the rate of skeletal muscle protein synthesis is depressed in smokers compared with non-smokers. We studied eight smokers (≥20 cigarettes/day for ≥20 years) and eight non-smokers matched for sex (4 men and 4 women per group), age (65 ± 3 and 63 ± 3 yr, respectively; means ± SEM) and body mass index (25.9 ± 0.9 and 25.1 ± 1.2 kg/m2, respectively). Each subject underwent an intravenous infusion of stable isotope-labeled leucine in conjunction with blood and muscle tissue sampling to measure the mixed muscle protein fractional synthesis rate (FSR) and whole body leucine rate of appearance (Ra) in plasma (an index of whole body proteolysis), the expression of genes involved in the regulation of muscle mass (myostatin, a muscle growth inhibitor, and MAFBx and MuRF-1, which encode E3 ubiquitin ligases in the proteasome proteolytic pathway) and that for the inflammatory cytokine TNF-α in muscle, and the concentration of inflammatory markers in plasma (C-reactive protein, TNF-α, interleukin-6) which are associated with muscle wasting in other conditions. There were no differences between nonsmokers and smokers in plasma leucine concentration, leucine rate of appearance, and plasma concentrations of inflammatory markers, or TNF-α mRNA in muscle, but muscle protein FSR was much less (0.037 ± 0.005 vs. 0.059 ± 0.005%/h, respectively, P = 0.004), and myostatin and MAFBx (but not MuRF-1) expression were much greater (by ∼33 and 45%, respectivley, P < 0.05) in the muscle of smokers than of nonsmokers. We conclude that smoking impairs the muscle protein synthesis process and increases the expression of genes associated with impaired muscle maintenance; smoking therefore likely increases the risk of sarcopenia.

Original languageEnglish
Pages (from-to)E843-E848
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume293
Issue number3
DOIs
StatePublished - Sep 1 2007

Keywords

  • Muscle growth
  • Protein turnover
  • Sarcopenia
  • Stable-isotope-labeled tracers

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