Leucine supplementation enhances integrative myofibrillar protein synthesis in free-living older men consuming lower-and higher-protein diets : A parallel-group crossover study1

Journal article


Murphy, Caoileann H., Saddler, Nelson I., Devries, Michaela C., McGlory, Chris, Baker, Steven K. and Phillips, Stuart M.. (2016) Leucine supplementation enhances integrative myofibrillar protein synthesis in free-living older men consuming lower-and higher-protein diets : A parallel-group crossover study1. American Journal of Clinical Nutrition. 104(6), pp. 1594-1606. https://doi.org/10.3945/ajcn.116.136424
AuthorsMurphy, Caoileann H., Saddler, Nelson I., Devries, Michaela C., McGlory, Chris, Baker, Steven K. and Phillips, Stuart M.
Abstract

Background: Leucine co-ingestion with lower-protein (LP)–containing meals may overcome the blunted muscle protein synthetic response to food intake in the elderly but may be effective only in individuals who consume LP diets.

Objective: We examined the impact of leucine co-ingestion with mixed macronutrient meals on integrated 3-d rates of myofibrillar protein synthesis (MyoPS) in free-living older men who consumed higher protein (HP) (1.2 g · kg–1 · d–1) or LP (0.8 g · kg–1 · d–1) in rested and resistance exercise (REX) conditions.

Design: In a crossover design, 20 healthy older men [aged 65–85 y] were randomly assigned to receive LP or HP diets while ingesting a placebo (days 0–2) and Leu supplement (5 g leucine/meal; days 3–5) with their 3 main daily meals. A bout of unilateral REX was performed during the placebo and Leu treatments. Ingested 2H2O and skeletal muscle biopsies were used to measure the 3-d integrated rate of MyoPS during the placebo and Leu treatments in the rested and REX legs.

Results: Leucinemia was higher with Leu treatment than with placebo treatment (P < 0.001). MyoPS was similar in LP and HP during both treatments (P = 0.39) but was higher with Leu treatment than with placebo treatment in the rested (pooled mean ± SD: Leu, 1.57% ± 0.11%/d; placebo, 1.48% ± 0.08%/d; main effect of treatment: P < 0.001) and REX (pooled mean: Leu, 1.87% ± 0.09%/d; placebo, 1.71 ± 0.10%/d; main effect of treatment: P < 0.001) legs.

Conclusions: Leu co-ingestion with daily meals enhances integrated MyoPS in free-living older men in rested and REX conditions and is equally effective in older men who consume daily protein intakes greater than or equal to the RDA. This trial was registered at clinicaltrials.gov as NCT02371278.

Keywordsaging; deuterated water; dietary protein; leucine; muscle protein synthesis
Year2016
JournalAmerican Journal of Clinical Nutrition
Journal citation104 (6), pp. 1594-1606
PublisherAmerican Society for Nutrition
ISSN0002-9165
Digital Object Identifier (DOI)https://doi.org/10.3945/ajcn.116.136424
Scopus EID2-s2.0-85002441974
Research or scholarlyResearch
Page range1594-1606
Publisher's version
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All rights reserved
File Access Level
Controlled
Output statusPublished
Publication dates
Online09 Nov 2016
Publication process dates
Deposited16 Jul 2021
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