Leucine supplementation chronically improves muscle protein synthesis in older adults consuming the RDA for protein

    Authors

    S. L. Casperson; M. Sheffield-Moore; S. J. Hewlings;D. Paddon-Jones

    Comments

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    Abbreviated Journal Title

    Clin. Nutr.

    Keywords

    Aging; Sarcopenia; Nutrition; Protein requirements; ESSENTIAL AMINO-ACIDS; SKELETAL-MUSCLE; TRANSLATIONAL CONTROL; POSTABSORPTIVE RATS; ELDERLY-MEN; INGESTION; ANABOLISM; YOUNG; MEAL; MASS; Nutrition & Dietetics

    Abstract

    Background & aim: Protein-energy supplementation is routinely employed to combat muscle loss. However, success is often compromised by increased satiety, poor palatability, high costs and low compliance. Methods: For 2-weeks we supplemented meals of older individuals with leucine (4 g/meal; 3 meals/day; days 2-14). Metabolic studies were performed prior to (Day 1) and following (Day 15) supplementation. Leucine was not provided on metabolic study days. Venous blood and vastus lateralis muscle biopsies were obtained during a primed constant infusion of L-[ring-C-13(6)] phenylalanine. Mixed muscle fractional synthesis rate (FSR), body composition and markers of nutrient signaling (mTOR, 4E-BP1 and p70S6K1 phosphorylation) were measured before and after a low protein/carbohydrate simulated meal. Results: The meal modestly increased FR on Day 1 (postabsorptive: 0.063 +/- 0.004 vs. postprandial: 0.075 +/- 0.006%/h; p = 0.03), however, two weeks of leucine supplementation increased postabsorptive FSR (p = 0.004) and the response to the meal (p = 0.01) (postabsorptive: 0.074 +/- 0.007 vs. postprandial: 0.10 +/- 0.007%/h). Changes in FSR were mirrored by increased phosphorylation of mTOR, 4E-BP1 and p70S6K1 (p < = 0.1). No change in fat free mass was observed (p > 0.05). Conclusions: In older adults, leucine supplementation may improve muscle protein synthesis in response to lower protein meals. (C) 2012 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

    Journal Title

    Clinical Nutrition

    Volume

    31

    Issue/Number

    4

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    512

    Last Page

    519

    WOS Identifier

    WOS:000307419800011

    ISSN

    0261-5614

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