Bed Rest Decreases Whole-Body Protein Turnover in Post-Absorptive Man

Bettany, G. E. A.; Ang, B. C. N.; Georgiannos, Stavros N; Halliday, D.; Powell-Tuck, J

doi:10.1042/cs0900073

Cited by 12 publications

(3 citation statements)

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“…Results from the current study could be different from existing literature because ingestion of extra dietary PAA may not effectively alter the physiological changes in the body that are induced by muscle unloading. It is suggested that amino acid catabolism and whole body protein turnover is upregulated during unloading and immobilization [2], and in as little as 14 days of bed rest whole body protein turnover decreases by 15%, with 50% of the decrease coming from an attenuation of protein synthesis [29]. Research also indicates that during unloading and disuse conditions, the decrease in protein synthesis appears to drive the loss of muscle mass, while the rate of protein degradation remains fairly constant [28, 29].…”

Section: Discussionmentioning

confidence: 99%

Protein and Amino Acid Supplementation Does Not Alter Proteolytic Gene Expression following Immobilization

Bunn

Buford

Serra

et al. 2011

Journal of Nutrition and Metabolism

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Objective. To determine if supplementation of protein and amino acids (PAA) decreases skeletal muscle expression of atrophy-related genes, muscle mass, and strength during immobilization in humans. Methods. Twenty males wore a lower-limb immobilization boot for 28 days and consumed either a PAA supplement (28 g protein) or carbohydrate placebo (28 g maltodextrose), while consuming their normal daily diet. Testing sessions included dietary analysis, lower-leg girth and body composition measurements, strength testing, and gastrocnemius muscle biopsies. Muscle was analyzed for mRNA expression of markers in the ubiquitin and calpain systems, myostatin, TNF-α, and NF-κB. Results. All genes of interest increased over time (P < .05), but there was no difference between groups. Lower-leg girth decreased over time (P = 0.02); however, there were no significant changes in body composition or strength. Conclusion. Short-term lower-limb disuse, despite the absence of significant muscle atrophy, is associated with increases in skeletal muscle gene expression of several proteolysis-related genes. These changes do not appear to be altered by oral PAA supplementation.

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Section: Discussionmentioning

confidence: 99%

Protein and Amino Acid Supplementation Does Not Alter Proteolytic Gene Expression following Immobilization

Bunn

Buford

Serra

et al. 2011

Journal of Nutrition and Metabolism

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“…With bed rest alone, whole body measurements are largely reflective of skeletal muscle changes [8]. Whole body protein turnover decreases in as little as 9 h of inactivity [17], and integrated measures over 24 h that include nutrient intake confirm net muscle catabolism with acute inactivity [18]. Whole body protein turnover decreases after 7 [19] and 14 days [8,20] of bed rest as a result of a decrease in protein synthesis.…”

Section: Inactivity and Muscle Protein Metabolismmentioning

confidence: 99%

Bed rest and myopathies

Ferrando

Paddon‐Jones

Wolfe

2006

Current Opinion in Clinical Nutrition &Amp; Metabolic Care

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Skeletal muscle loss with trauma or critical illness is due in great part to the interaction of bed rest (muscular inactivity) and stress (hypercortisolemia). Younger individuals respond to nutritional and pharmacological interventions during bed rest alone. Given a lower relative lean mass in the elderly and the importance of skeletal muscle as a metabolic reserve during stress, it is understandable that clinical outcomes are worse in older patients. Countermeasures to the loss of skeletal muscle, especially in the stressed patient, must be developed.

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“…Unfortunately, a degree of muscular inactivity is inevitable in many situations, including convalescence from illness or injury, exposure to microgravity, and the progression of aging. Mechanistically, the loss of lean body mass associated with prolonged bedrest is primarily due to alterations in protein turnover (1), including an increase in protein degradation and/or a decrease in protein synthesis (2)(3)(4). In each instance, the resultant muscle atrophy is most pronounced in the muscles of the lower back and legs (5)(6)(7)(8).…”

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confidence: 98%

Essential Amino Acid and Carbohydrate Supplementation Ameliorates Muscle Protein Loss in Humans during 28 Days Bedrest

Paddon‐Jones¹,

Sheffield‐Moore²,

Urban³

et al. 2004

The Journal of Clinical Endocrinology & Metabolism

288

274

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We determined whether essential amino acid and carbohydrate supplementation could offset the catabolic response to prolonged inactivity. Major outcome measures included mixed muscle fractional synthetic rate (FSR), phenylalanine net balance, lean leg mass, and leg extension strength. On d 1 and 28, vastus lateralis muscle biopsies and femoral arteriovenous blood samples were obtained during a primed constant infusion of L-[ring-2 H 5 ]phenylalanine. Net balance and FSR were calculated over 16 h, during which the control group (CON) received a nutritionally mixed meal every 5 h (0830, 1330, and 1830 h). The experimental group (EXP) also consumed 16.5 g essential amino acids and 30 g carbohydrate (1100, 1600, and 2100 h). The dietary regimen was maintained during bedrest. FSR was higher in the EXP group on d 1 (EXP, 0.099 ؎ 0.008%/h; CON: 0.075 ؎ 0.005%/h) and d 28 (EXP, 0.093 ؎ 0.006%/h; CON, 0.055 ؎ 0.007%/h). Lean leg mass was maintained throughout bedrest in the EXP group (؉0.2 ؎ 0.3 kg), but fell in the CON group (؊0.4 ؎ 0.1 kg). Strength loss was more pronounced in the CON group (EXP, ؊8.8 ؎ 1.4 kg; CON, ؊17.8 ؎ 4.4 kg). Essential amino acid and carbohydrate supplementation may represent a viable intervention for individuals at risk of sarcopenia due to immobility or prolonged bedrest. (J Clin Endocrinol Metab 89: 4351-4358, 2004)

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Bed Rest Decreases Whole-Body Protein Turnover in Post-Absorptive Man

Cited by 12 publications

References 0 publications

Protein and Amino Acid Supplementation Does Not Alter Proteolytic Gene Expression following Immobilization

Protein and Amino Acid Supplementation Does Not Alter Proteolytic Gene Expression following Immobilization

Bed rest and myopathies

Essential Amino Acid and Carbohydrate Supplementation Ameliorates Muscle Protein Loss in Humans during 28 Days Bedrest

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