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Leucine partially protects muscle mass and function during bed rest in middle-aged adults.

ABSTRACT: Physical inactivity triggers a rapid loss of muscle mass and function in older adults. Middle-aged adults show few phenotypic signs of aging yet may be more susceptible to inactivity than younger adults.The aim was to determine whether leucine, a stimulator of translation initiation and skeletal muscle protein synthesis (MPS), can protect skeletal muscle health during bed rest.We used a randomized, double-blind, placebo-controlled trial to assess changes in skeletal MPS, cellular signaling, body composition, and skeletal muscle function in middle-aged adults (n = 19; age ± SEM: 52 ± 1 y) in response to leucine supplementation (LEU group: 0.06 g ? kg(-1) ? meal(-1)) or an alanine control (CON group) during 14 d of bed rest.Bed rest decreased postabsorptive MPS by 30% ± 9% (CON group) and by 10% ± 10% (LEU group) (main effect for time, P < 0.05), but no differences between groups with respect to pre-post changes (group × time interactions) were detected for MPS or cell signaling. Leucine protected knee extensor peak torque (CON compared with LEU group: -15% ± 2% and -7% ± 3%; group × time interaction, P < 0.05) and endurance (CON compared with LEU: -14% ± 3% and -2% ± 4%; group × time interaction, P < 0.05), prevented an increase in body fat percentage (group × time interaction, P < 0.05), and reduced whole-body lean mass loss after 7 d (CON compared with LEU: -1.5 ± 0.3 and -0.8 ± 0.3 kg; group × time interaction, P < 0.05) but not 14 d (CON compared with LEU: -1.5 ± 0.3 and -1.0 ± 0.3 kg) of bed rest. Leucine also maintained muscle quality (peak torque/kg leg lean mass) after 14 d of bed-rest inactivity (CON compared with LEU: -9% ± 2% and +1% ± 3%; group × time interaction, P < 0.05).Bed rest has a profoundly negative effect on muscle metabolism, mass, and function in middle-aged adults. Leucine supplementation may partially protect muscle health during relatively brief periods of physical inactivity. This trial was registered at clinicaltrials.gov as NCT00968344.

SUBMITTER: English KL

PROVIDER: S-EPMC4733256 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Leucine partially protects muscle mass and function during bed rest in middle-aged adults.

English Kirk L KL Mettler Joni A JA Ellison Jennifer B JB Mamerow Madonna M MM Arentson-Lantz Emily E Pattarini James M JM Ploutz-Snyder Robert R Sheffield-Moore Melinda M Paddon-Jones Douglas D

The American journal of clinical nutrition 20151230 2

<h4>Background</h4>Physical inactivity triggers a rapid loss of muscle mass and function in older adults. Middle-aged adults show few phenotypic signs of aging yet may be more susceptible to inactivity than younger adults.<h4>Objective</h4>The aim was to determine whether leucine, a stimulator of translation initiation and skeletal muscle protein synthesis (MPS), can protect skeletal muscle health during bed rest.<h4>Design</h4>We used a randomized, double-blind, placebo-controlled trial to asse ...[more]

PMID: 26718415

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Project description:Microgravity has a dramatic impact on human physiology, illustrated in particular with skeletal muscle impairment. A thorough understanding of the mechanisms leading to loss of muscle mass and structural disorders is necessary for the definition of efficient clinical and spaceflight countermeasures. We investigated the effects of long-term bed rest on transcriptome of soleus (SOL) and vastus lateralis (VL) muscles in healthy women (BRC group, n=8), and the potential beneficial impact of protein supplementation (BRN group, n=8) and of a combined resistance and aerobic training (BRE group, n=8). Gene expression profiles were obtained using an in-house made microarray containing 6681 muscles-relevant genes. A two-class statistical analysis was applied on the 2103 genes with consolidated expression. We identified 472 and 207 modified genes, respectively for SOL and VL in BRC group. Further clustering approaches, identifying relevant biological mechanisms or pathways, underlined five main subclusters. Three are composed almost of upregulated genes involved mainly in nucleic acid and protein metabolism, and two composed almost of downregulated genes involved in energy metabolism. Exercise countermeasure demonstrated a drastic compensatory effect, decreasing the number of differentially-expressed genes by 89 and 96% in SOL and VL. In contrast, nutrition countermeasure had a moderate effect and decreased the number of differentially-expressed genes by 40 and 25% in SOL and VL. Our results allowed reporting a systematic, global and comprehensive view of long-term woman muscle atrophy and brought new lights and insights for space environment and for women who undergo a long-term clinical bed rest. Biological samples were collected from Pre- and Post- bed rest (BR) soleus and vastus lateralis biopsies of each subject from the three groups (bed rest only: BRC; Exercise: BRE; Nutrition: BRN). six technical replicate values (2 duplicate hybridizations âa et bâ to chips with triplicate spots âxxxâ) were obtained for each skeletal muscle sample. Thus for each subject, 12 expression measurements (6 before BR and 6 after BR) were obtained for each muscle.

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Leucine partially protects muscle mass and function during bed rest in middle-aged adults.

Publications

Leucine partially protects muscle mass and function during bed rest in middle-aged adults.

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