Post-Meal Responses of Elongation Factor 2 eEF2 and Adenosine Monophosphate-Activated Protein Kinase AMPK to Leucine and Carbohydrate Supplements for Regulating Protein Synthesis Duration and Energy Homeostasis in Rat Skeletal MusReport as inadecuate




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1

Department of Nutritional Sciences, Rutgers University, The State University of New Jersey, New Brunswick, NJ 08901, USA

2

Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

3

Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA





*

Author to whom correspondence should be addressed.



Abstract Previous research demonstrates that the anabolic response of muscle protein synthesis MPS to a meal is regulated at the level of translation initiation with signals derived from leucine Leu and insulin to activate mTORC1 signaling. Recent evidence suggests that the duration of the meal response is limited by energy status of the cell and inhibition of translation elongation factor 2 eEF2. This study evaluates the potential to extend the anabolic meal response with post-meal supplements of Leu or carbohydrates. Adult ~256 g male Sprague-Dawley rats were food deprived for 12 h, then either euthanized before a standard meal time 0 or at 90 or 180 min post-meal. At 135 min post-meal, rats received one of five oral supplements: 270 mg leucine Leu270, 80:40:40 mg leucine, isoleucine, and valine Leu80, 2.63 g carbohydrates CHO2.6, 1 g carbohydrates CHO1.0, or water Sham control. Following the standard meal, MPS increased at 90 min then declined to pre-meal baseline at 180 min. Rats administered Leu270, Leu80, CHO2.6, or CHO1.0 maintained elevated rates of MPS at 180 min, while Sham controls declined from peak values. Leu80 and CHO1.0 treatments maintained MPS, but with values intermediate between Sham controls and Leu270 and CHO2.6 supplements. Consistent with MPS findings, the supplements maintained elongation activity and cellular energy status by preventing increases in AMP-ATP and phosphorylation of adenosine monophosphate-activated protein kinase AMPK, acetyl-CoA carboxylase ACC and eEF2. The impact of the supplements on MPS and cellular energy status was in proportion to the energy content within the individual treatments i.e., Leu270 > Leu80; CHO2.6 > CHO1.0, but the Leu supplements produced a disproportionate anabolic stimulation of MPS, eEF2 and energy status with significantly lower energy content. In summary, the incongruity between MPS and translation initiation at 180 min reflects a block in translation elongation due to reduced cellular energy, and the extent to which Leu or carbohydrate supplements are able to enhance energy status and prolong the period of muscle anabolism are dose and time-dependent. View Full-Text

Keywords: translation initiation; translation elongation; branched-chain amino acids; whey protein; mTORC1 translation initiation; translation elongation; branched-chain amino acids; whey protein; mTORC1





Author: Gabriel J. Wilson 1, Christopher J. Moulton 2, Peter J. Garlick 3, Tracy G. Anthony 1 and Donald K. Layman 2,*

Source: http://mdpi.com/



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