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This Article Full Text Full Text (PDF) All Versions of this Article: 293/3/E843    most recent 00301.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Petersen, A. M. W. Articles by Mittendorfer, B. Search for Related Content PubMed PubMed Citation Articles by Petersen, A. M. W. Articles by Mittendorfer, B.

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

¹Centre of Inflammation and Metabolism, Department of Infectious Diseases and Copenhagen Muscle Research Centre, Copenhagen, Denmark; ²Washington University School of Medicine, St. Louis, Missouri; and ³University of Nottingham Graduate Entry Medical School, Derby, United Kingdom

Submitted 17 May 2007 ; accepted in final form 30 June 2007

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- in muscle, and the concentration of inflammatory markers in plasma (C-reactive protein, TNF-, 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- 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.

muscle growth; stable-isotope-labeled tracers; sarcopenia; protein turnover

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