(04-10-11) Rapid aminoacidemia enhances myofibrillar protein synthesis

Rapid aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise1,2,3,4
1. Daniel WD West,
2. Nicholas A Burd,
3. Vernon G Coffey,
4. Steven K Baker,
5. Louise M Burke,
6. John A Hawley,
7. Daniel R Moore,
8. Trent Stellingwerff, and
9. Stuart M Phillips
+ Author Affiliations
1. 1From the Exercise Metabolism Research Group, Departments of Kinesiology (DWDW, NAB, and SMP) and Neurology (SKB), McMaster University, Hamilton, Canada; the Health Innovations Research Institute, School of Medical Science, RMIT University, Melbourne, Australia (VGC and JAH); Sports Nutrition, Australian Institute of Sport, Canberra, Australia (LMB); and the Nestl? Research Center, Nestec Ltd, Lausanne, Switzerland (DRM and TS).
+ Author Notes
↵2 DWDW and NAB contributed equally to this study and the writing of the manuscript.
↵3 Supported by the Natural Sciences and Engineering Research Council of Canada, Canadian Institutes of Health Research, and Nestec Ltd, Vevey, Switzerland.
↵4 Address correspondence to SM Phillips, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada. E-mail: [email protected].
Abstract
Background: Ingestion of whey or casein yields divergent patterns of aminoacidemia that influence whole-body and skeletal muscle myofibrillar protein synthesis (MPS) after exercise. Direct comparisons of the effects of contrasting absorption rates exhibited by these proteins are confounded by their differing amino acid contents.
Objective: Our objective was to determine the effect of divergent aminoacidemia by manipulating ingestion patterns of whey protein alone on MPS and anabolic signaling after resistance exercise.
Design: In separate trials, 8 healthy men consumed whey protein either as a single bolus (BOLUS; 25-g dose) or as repeated, small, ?pulsed? drinks (PULSE; ten 2.5-g drinks every 20 min) to mimic a more slowly digested protein. MPS and phosphorylation of signaling proteins involved in protein synthesis were measured at rest and after resistance exercise.
Results: BOLUS increased blood essential amino acid (EAA) concentrations above those of PULSE (162% compared with 53%, P < 0.001) 60 min after exercise, whereas PULSE resulted in a smaller but sustained increase in aminoacidemia that remained elevated above BOLUS amounts later (180?220 min after exercise, P < 0.05). Despite an identical net area under the EAA curve, MPS was elevated to a greater extent after BOLUS than after PULSE early (1?3 h: 95% compared with 42%) and later (3?5 h: 193% compared with 121%) (both P < 0.05). There were greater changes in the phosphorylation of the Akt?mammalian target of rapamycin pathway after BOLUS than after PULSE.
Conclusions: Rapid aminoacidemia in the postexercise period enhances MPS and anabolic signaling to a greater extent than an identical amount of protein fed in small pulses that mimic a more slowly digested protein. A pronounced peak aminoacidemia after exercise enhances protein synthesis. This trial was registered at clinicaltrials.gov as NCT01319513.

Source: Am J Clin Nutr September 2011 vol. 94 no. 3 795-803

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