title: Protein and Amino Acid Supplementation Does Not Alter Proteolytic Gene Expression following Immobilization.
abstract: 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.
authors.affiliation: Exercise and Biochemical Nutritional Laboratory, Department of Health, Human Performance, and Recreation, Baylor University, Waco, TX 76798, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Bunn
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Buford
authors.forename: Monica C
authors.initials: MC
authors.lastname: Serra
authors.forename: Richard B
authors.initials: RB
authors.lastname: Kreider
authors.forename: Darryn S
authors.initials: DS
authors.lastname: Willoughby