title: Plasma myostatin-immunoreactive protein is increased after prolonged bed rest with low-dose T3 administration.
abstract: It has been hypothesized that myostatin, a newly identified member of the transforming growth factor-beta (TGF-beta) family of proteins, acts as a negative regulator of skeletal muscle growth. Because bed rest induced muscle atrophy results from a decreased rate of muscle protein synthesis, we hypothesized that circulating levels of myostatin would be increased following prolonged bed rest. Twelve men (age, 35.8 +/- 4.6 yr; height, 175.7 +/- 2.3 cm; weight, 74.8 +/- 3.5 kg; mean +/- SE) were confined to bed for 25 days at 6 degrees head-down tilt while receiving triiodothyronine (T3; 50 micrograms/day) to accelerate protein loss. Total lean body and appendicular skeletal muscle mass were determined by dual energy x-ray absorptiometry (DEXA) before and after the bed rest period. Plasma myostatin-immunoreactive protein was measured in blood samples obtained after an overnight fast 5 days prior to, and on the 25th day of bed rest. Lean body mass decreased an average 2.2 kg (p < 0.0001). Appendicular skeletal muscle accounted for a majority of the lean body mass loss. On day 25 of bed rest, plasma myostatin-immunoreactive protein was 12% higher (p = 0.01) than measured at baseline. These data support the idea that myostatin regulates muscle growth in humans and that it may be a novel target for interventions aiming to reduce space flight induced muscle atrophy.
authors.affiliation: Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA. zachwijj@mhs.pbrc.edu
authors.forename: J J
authors.initials: JJ
authors.lastname: Zachwieja
authors.forename: S R
authors.initials: SR
authors.lastname: Smith
authors.forename: I
authors.initials: I
authors.lastname: Sinha-Hikim
authors.forename: N
authors.initials: N
authors.lastname: Gonzalez-Cadavid
authors.forename: S
authors.initials: S
authors.lastname: Bhasin
mesh_terms: D000328:Adult; D001510:Bed Rest / Q000009:adverse effects*; D001823:Body Composition; D018475:Head-Down Tilt / Q000009:adverse effects; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects; D009133:Muscular Atrophy / Q000209:etiology / Q000378:metabolism*; D055435:Myostatin; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D016212:Transforming Growth Factor beta / Q000097:blood / Q000378:metabolism*; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology*; D018474:Weightlessness Simulation / Q000009:adverse effects / Q000379:methods
chemical_list: C525911:MSTN protein, human; D055435:Myostatin; D016212:Transforming Growth Factor beta; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine