Protein and amino acid supplementation does not alter proteolytic gene expression following immobilization

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- and nf-b. 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. © 2011 jennifer a. bunn et al.