Resistance exercise increases leg muscle protein synthesis and mTOR signalling independent of sex.
OBJECTIVE
Sex differences are evident in human skeletal muscle as the cross-sectional area of individual muscle fibres is greater in men than in women. We have recently shown that resistance exercise stimulates mammalian target of rapamycin (mTOR) signalling and muscle protein synthesis in humans during early post-exercise recovery. Therefore, the aim of this study was to determine if sex influences the muscle protein synthesis response during recovery from resistance exercise.


METHODS
Seventeen subjects, nine male and eight female, were studied in the fasted state before, during and for 2 h following a bout of high-intensity leg resistance exercise. Mixed muscle protein fractional synthetic rate was measured using stable isotope techniques and mTOR signalling was assessed by immunoblotting from repeated vastus lateralis muscle biopsy samples.


RESULTS
Post-exercise muscle protein synthesis increased by 52% in the men and by 47% in the women (P < 0.05) and was not different between groups (P > 0.05). Akt phosphorylation increased in both groups at 1 h post-exercise (P < 0.05) and returned to baseline during 2 h post-exercise with no differences between groups (P > 0.05). Phosphorylation of mTOR and its downstream effector S6K1 increased significantly and similarly between groups during post-exercise recovery (P < 0.05). eEF2 phosphorylation decreased at 1- and 2 h post-exercise (P < 0.05) to a similar extent in both groups.


CONCLUSIONS
The contraction-induced increase in early post-exercise mTOR signalling and muscle protein synthesis is independent of sex and appears to not play a role in the sexual dimorphism of leg skeletal muscle in young men and women.
Dreyer
H C
HC
Division of Rehabilitation Sciences, Department of Physical Therapy, University of Texas Medical Branch, Galveston, TX 77555, USA.
Fujita
S
S
Glynn
E L
EL
Drummond
M J
MJ
Volpi
E
E
Rasmussen
B B
BB
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D019344:Lactic Acid / Q000097:blood; D007866:Leg / Q000033:anatomy & histology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*; D010649:Phenylalanine / Q000097:blood; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012039:Regional Blood Flow / Q000502:physiology; D012727:Sex Characteristics; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases; D055815:Young Adult
D001786:Blood Glucose; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D019344:Lactic Acid; D010649:Phenylalanine; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases