Document Detail

Sex-based comparisons of myofibrillar protein synthesis after resistance exercise in the fed state.
MedLine Citation:
PMID:  22383503     Owner:  NLM     Status:  MEDLINE    
We made sex-based comparisons of rates of myofibrillar protein synthesis (MPS) and anabolic signaling after a single bout of high-intensity resistance exercise. Eight men (20 ± 10 yr, BMI = 24.3 ± 2.4) and eight women (22 ± 1.8 yr, BMI = 23.0 ± 1.9) underwent primed constant infusions of l-[ring-(13)C(6)]phenylalanine on consecutive days with serial muscle biopsies. Biopsies were taken from the vastus lateralis at rest and 1, 3, 5, 24, 26, and 28 h after exercise. Twenty-five grams of whey protein was ingested immediately and 26 h after exercise. We also measured exercise-induced serum testosterone because it is purported to contribute to increases in myofibrillar protein synthesis (MPS) postexercise and its absence has been hypothesized to attenuate adaptative responses to resistance exercise in women. The exercise-induced area under the testosterone curve was 45-fold greater in men than women in the early (1 h) recovery period following exercise (P < 0.001). MPS was elevated similarly in men and women (2.3- and 2.7-fold, respectively) 1-5 h postexercise and after protein ingestion following 24 h recovery. Phosphorylation of mTOR(Ser2448) was elevated to a greater extent in men than women acutely after exercise (P = 0.003), whereas increased phosphorylation of p70S6K1(Thr389) was not different between sexes. Androgen receptor content was greater in men (main effect for sex, P = 0.049). Atrogin-1 mRNA abundance was decreased after 5 h recovery in both men and women (P < 0.001), and MuRF-1 expression was elevated in men after protein ingestion following 24 h recovery (P = 0.003). These results demonstrate minor sex-based differences in signaling responses and no difference in the MPS response to resistance exercise in the fed state. Interestingly, our data demonstrate that exercise-induced increases in MPS are dissociated from postexercise testosteronemia and that stimulation of MPS occurs effectively with low systemic testosterone concentrations in women.
Daniel W D West; Nicholas A Burd; Tyler A Churchward-Venne; Donny M Camera; Cameron J Mitchell; Steven K Baker; John A Hawley; Vernon G Coffey; Stuart M Phillips
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-03-01
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  112     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2012 Jun 
Date Detail:
Created Date:  2012-06-04     Completed Date:  2013-04-01     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1805-13     Citation Subset:  IM    
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
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MeSH Terms
Dietary Proteins / administration & dosage*
Fasting / metabolism
Milk Proteins / administration & dosage
Muscle Proteins / biosynthesis*
Myofibrils / drug effects,  metabolism*
Postprandial Period / drug effects,  physiology*
Resistance Training* / methods
Sex Characteristics*
Young Adult
Grant Support
//Canadian Institutes of Health Research
Reg. No./Substance:
0/Dietary Proteins; 0/Milk Proteins; 0/Muscle Proteins; 0/whey protein
Comment In:
J Appl Physiol (1985). 2012 Jun;112(11):1803-4   [PMID:  22442029 ]

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