title: Age-related differences in the dose-response relationship of muscle protein synthesis to resistance exercise in young and old men.
abstract: We investigated how myofibrillar protein synthesis (MPS) and muscle anabolic signalling were affected by resistance exercise at 20-90% of 1 repetition maximum (1 RM) in two groups (25 each) of post-absorptive, healthy, young (24 +/- 6 years) and old (70 +/- 5 years) men with identical body mass indices (24 +/- 2 kg m(-2)). We hypothesized that, in response to exercise, anabolic signalling molecule phosphorylation and MPS would be modified in a dose-dependant fashion, but to a lesser extent in older men. Vastus lateralis muscle was sampled before, immediately after, and 1, 2 and 4 h post-exercise. MPS was measured by incorporation of [1,2-(13)C] leucine (gas chromatography-combustion-mass spectrometry using plasma [1,2-(13)C]alpha-ketoisocaparoate as surrogate precursor); the phosphorylation of p70 ribosomal S6 kinase (p70s6K) and eukaryotic initiation factor 4E binding protein 1 (4EBP1) was measured using Western analysis with anti-phosphoantibodies. In each group, there was a sigmoidal dose-response relationship between MPS at 1-2 h post-exercise and exercise intensity, which was blunted (P < 0.05) in the older men. At all intensities, MPS fell in both groups to near-basal values by 2-4 h post-exercise. The phosphorylation of p70s6K and 4EBP1 at 60-90% 1 RM was blunted in older men. At 1 h post-exercise at 60-90% 1 RM, p70s6K phosphorylation predicted the rate of MPS at 1-2 h post-exercise in the young but not in the old. The results suggest that in the post-absorptive state: (i) MPS is dose dependant on intensity rising to a plateau at 60-90% 1 RM; (ii) older men show anabolic resistance of signalling and MPS to resistance exercise.
authors.affiliation: University of Nottingham, School of Graduate Entry Medicine and Health, City Hospital, Uttoxeter Road, Derby, DE22 3DT, UK.
authors.forename: Vinod
authors.initials: V
authors.lastname: Kumar
authors.forename: Anna
authors.initials: A
authors.lastname: Selby
authors.forename: Debbie
authors.initials: D
authors.lastname: Rankin
authors.forename: Rekha
authors.initials: R
authors.lastname: Patel
authors.forename: Philip
authors.initials: P
authors.lastname: Atherton
authors.forename: Wulf
authors.initials: W
authors.lastname: Hildebrandt
authors.forename: John
authors.initials: J
authors.lastname: Williams
authors.forename: Kenneth
authors.initials: K
authors.lastname: Smith
authors.forename: Olivier
authors.initials: O
authors.lastname: Seynnes
authors.forename: Natalie
authors.initials: N
authors.lastname: Hiscock
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rennie
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000328:Adult; D000368:Aged; D000375:Aging / Q000473:pathology / Q000502:physiology*; D018797:Cell Cycle Proteins; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000145:classification / Q000166:cytology / Q000378:metabolism; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000502:physiology; D009210:Myofibrils / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D055070:Resistance Training; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction; D055815:Young Adult
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D009124:Muscle Proteins; D010750:Phosphoproteins; D038762:Ribosomal Protein S6 Kinases, 70-kDa