Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. J Pysiol

Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
The Journal of Physiology (Impact Factor: 5.04). 03/2012; 590(Pt 11):2751-65. DOI: 10.1113/jphysiol.2012.228833
Source: PubMed


Leucine is a nutrient regulator of muscle protein synthesis by activating mTOR and possibly other proteins in this pathway. The purpose of this study was to examine the role of leucine in the regulation of human myofibrillar protein synthesis (MPS). Twenty-four males completed an acute bout of unilateral resistance exercise prior to consuming either: a dose (25 g) of whey protein (WHEY); 6.25 g whey protein with total leucine equivalent to WHEY (LEU); or 6.25 g whey protein with total essential amino acids (EAAs) equivalent to WHEY for all EAAs except leucine (EAA-LEU). Measures of MPS, signalling through mTOR, and amino acid transporter (AAT) mRNA abundance were made while fasted (FAST), and following feeding under rested (FED) and post-exercise (EX-FED) conditions. Leucinaemia was equivalent between WHEY and LEU and elevated compared to EAA-LEU (P=0.001). MPS was increased above FAST at 1–3 h post-exercise in both FED (P <0.001) and EX-FED (P <0.001) conditions with no treatment effect.At 3–5 h, only WHEY remained significantly elevated above FAST in EX-FED(WHEY 184% vs. LEU 55% and EAA-LEU 35%; P =0.036). AAT mRNA abundance was increased above FAST after feeding and exercise with no effect of leucinaemia. In summary, a low dose of whey protein supplemented with leucine or all other essential amino acids was as effective as a complete protein (WHEY) in stimulating postprandial MPS; however only WHEY was able to sustain increased rates of MPS post-exercise and may therefore be most suited to increase exercise-induced muscle protein accretion.

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Available from: Stuart M Phillips
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    • "Leucine alone can activate protein synthesis in humans to the same extent as whey protein and mixed essential amino acids plus leucine when administered 1–3 h postresistance exercise (Churchward-Venne et al., 2012). However , the requirement for whey protein for optimal protein synthesis 3– 5 h postexercise is acknowledged (Churchward-Venne et al., 2012; Phillips, 2014). Previously, Mourier and colleagues observed that DR in human males (wrestlers) when combined with supplementation of mixed BCAAs led to a reduction in total body mass and fat mass (À17.3%), "
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    • "The branched-chain amino acid leucine has been well studied for its ability to promote positive nitrogen balance as both a protein precursor and a signaling molecule in muscle of rats (Crozier et al. 2004), piglets (Boutry et al. 2013; Yin et al. 2010) and humans (Burd et al. 2012; Churchward-Venne et al. 2012; Li et al. 2011). Leucine has also been shown to decrease muscle protein breakdown in humans (Louard et al. 1990). "
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    • "However, whey protein contains a greater amount of the BCAAs leucine, isoleucine, and valine than does casein. Of the BCAAs, leucine is thought to be the most potent activator of protein synthesis (Katsanos et al., 2006; van Loon, 2012), although a recent study has shown that high levels of nonleucine BCAAs can induce equivalent protein synthesis when given with a whey protein supplement (Churchward-Venne et al., 2012). Casein in turn contains several essential amino acids (EAAs), including histine, methionine, and phenylalanine in a greater amount than whey protein, and also contains a greater amount of the non-EAAs arginine, glutamic acid, proline, serine, and tyrosine (Hall et al., 2003). "
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