Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: a double-blind, randomized trial. Issue 2 (27th November 2013)

• Record Type: Journal Article
• Authors: Churchward-Venne, Tyler A; Breen, Leigh; Di Donato, Danielle M; Hector, Amy J; Mitchell, Cameron J; Moore, Daniel R; Stellingwerff, Trent; Breuille, Denis; Offord, Elizabeth A; Baker, Steven K; Phillips, Stuart M
• Is Part Of: American journal of clinical nutrition. Volume 99:Issue 2(2014)
• Page Start: 276
• Page End: 286
• Publication Date: 2013-11-27
• Subjects: Diet therapy -- Periodicals; Nutrition -- Periodicals; Dietetics -- Periodicals; 613.205
• DOI: 10.3945/ajcn.113.068775
• Languages: English
• ISSNs: 0002-9165

Abstract

ABSTRACT: Background: Leucine is a key amino acid involved in the regulation of skeletal muscle protein synthesis. Objective: We assessed the effect of the supplementation of a lower-protein mixed macronutrient beverage with varying doses of leucine or a mixture of branched chain amino acids (BCAAs) on myofibrillar protein synthesis (MPS) at rest and after exercise. Design: In a parallel group design, 40 men (21 ± 1 y) completed unilateral knee-extensor resistance exercise before the ingestion of 25 g whey protein (W25) (3.0 g leucine), 6.25 g whey protein (W6) (0.75g leucine), 6.25 g whey protein supplemented with leucine to 3.0 g total leucine (W6+Low-Leu), 6.25 g whey protein supplemented with leucine to 5.0 g total leucine (W6+High-Leu), or 6.25 g whey protein supplemented with leucine, isoleucine, and valine to 5.0 g total leucine. A primed continuous infusion of l -[ ring - 13 C6 ] phenylalanine with serial muscle biopsies was used to measure MPS under baseline fasted and postprandial conditions in both a rested (response to feeding) and exercised (response to combined feeding and resistance exercise) leg. Results: The area under the blood leucine curve was greatest for the W6+High-Leu group compared with the W6 and W6+Low-Leu groups ( P < 0.001). In the postprandial period, rates of MPS were increased above baseline over 0–1.5 h in all treatments. Over 1.5–4.5 h, MPS remained increased above baseline after all treatments but was greatest after W25 (∼267%) and W6+High-Leu (∼220%) treatments ( P = 0.002). Conclusions: A low-protein (6.25 g) mixed macronutrient beverage can be as effective as a high-protein dose (25 g) at stimulating increased MPS rates when supplemented with a high (5.0 g total leucine) amount of leucine. These results have important implications for formulations of protein beverages designed to enhance muscle anabolism. This trial was registered at clinicaltrials.gov as NCT 1530646.