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Last Word on Viewpoint: The curious case of anabolic resistance: old wives' tales or new fables? Nicholas A. Burd, Benjamin T. Wall and Luc J. C. van Loon J Appl Physiol 112:1237, 2012. doi:10.1152/japplphysiol.00109.2012 You might find this additional info useful... This article cites 2 articles, 2 of which can be accessed free at: /content/112/7/1237.full.html#ref-list-1 Updated information and services including high resolution figures, can be found at: /content/112/7/1237.full.html Additional material and information about Journal of Applied Physiology can be found at: http://www.the-aps.org/publications/jappl
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Journal of Applied Physiology publishes original papers that deal with diverse areas of research in applied physiology, especially those papers emphasizing adaptive and integrative mechanisms. It is published 12 times a year (monthly) by the American Physiological Society, 9650 Rockville Pike, Bethesda MD 20814-3991. Copyright © 2012 by the American Physiological Society. ISSN: 0363-6143, ESSN: 1522-1563. Visit our website at http://www.the-aps.org/.
J Appl Physiol 112: 1237, 2012; doi:10.1152/japplphysiol.00109.2012.
Letter To The Editor
Last Word on Viewpoint: The curious case of anabolic resistance: old wives’ tales or new fables? Nicholas A. Burd, Benjamin T. Wall, and Luc J. C. van Loon Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre⫹ (MUMC⫹), Maastricht, The Netherlands SOME PHYSICAL ACTIVITY A DAY KEEPS (MOST OF) THE AGE-RELATED ATROPHY AWAY?
Address for reprint requests and other correspondence: L. J. C. van Loon, Dept. of Human Movement Sciences, Maastricht Univ. Medical Centre⫹, PO Box 616, 6200 MD Maastricht, The Netherlands (e-mail: L.vanLoon @maastrichuniversity.nl).
http://www.jappl.org
DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the authors. AUTHOR CONTRIBUTIONS Author contributions: N.A.B. drafted manuscript; N.A.B., B.T.W., and L.J.v.L. edited and revised manuscript; N.A.B., B.T.W., and L.J.v.L. approved final version of manuscript. REFERENCES 1. Burd NA, Wall BT, van Loon LJ. Viewpoint: The curious case of anabolic resistance: old wives’ tales or new fables? J Appl Physiol; doi:10.1152/ japplphysiol.01343.2011. 2. Burd NA, West DW, Moore DR, Atherton PJ, Staples AW, Prior T, Tang JE, Rennie MJ, Baker SK, Phillips SM. Enhanced amino acid sensitivity of myofibrillar protein synthesis persists for up to 24 h after resistance exercise in young men. J Nutr 141: 568 –573, 2011. 3. Miller BF, Hamilton KL, Cuthbertson DJ, Smith K, Williams J, Mittendorfer B, Greenhaff P, Atherton P. Commentaries on Viewpoint: The curious case of anabolic resistance: old wives’ tales or new fables? J Appl Physiol; doi:10.1152/japplphysiol.00097.2012. 4. Miller BF, Olesen JL, Hansen M, Dossing S, Crameri RM, Welling RJ, Langberg H, Flyvbjerg A, Kjaer M, Babraj JA, Smith K, Rennie MJ. Coordinated collagen and muscle protein synthesis in human patella tendon and quadriceps muscle after exercise. J Physiol 567: 1021–1033, 2005.
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TO THE EDITOR: We would like to thank the scientists for their comments (and agreement) on our Viewpoint article (see Ref. 3). Originally, we put forward the idea that physical inactivity may be a critical factor underpinning age-related differences in postprandial muscle protein synthesis rates (MPS) (1). In our view, this idea remains a strong one. For instance, exercise induces a substantial carryover effect on the feeding-induced stimulation of MPS that can last for days (2, 4). We know very little about whether simply getting out of bed in the morning, walking down/up a flight a stairs, or going for a casual stroll around the neighborhood block will also confer a nutrient sensitizing effect on MPS (an effect observed after higher intensity exercise). However, if the threshold of physical activity that induces a sensitizing effect on MPS is relatively low, than our view may need much more consideration. Specifically, if it is not the aging muscle tissue per se but rather its recruitment in a daily life setting that contributes to the proposed “anabolic resistance” (and its curiosity) then it is not entirely surprising that comparisons between different aging populations from different geographical locations do not seem to line up. For muscle atrophy to occur there must be a net loss of muscle protein brought about by disturbances in muscle protein turnover as the proteins do not simply vanish in aging muscle.
Admittedly, the scientific community is pretty “good” at measuring MPS in vivo in humans. However, stable isotope dilution methods for determining muscle protein breakdown are going to reflect the muscle protein pool that is turning over the quickest and thus we remain relatively in the dark concerning whether specific muscle protein pools are being degraded differently in aging muscle. Ultimately, if the lack of knowledge is the fuel for science then there is still plenty of wood left to be placed on the fire!
