title: Anabolic signaling and protein synthesis in human skeletal muscle after dynamic shortening or lengthening exercise.
abstract: We hypothesized a differential activation of the anabolic signaling proteins protein kinase B (PKB) and p70 S6 kinase (p70(S6K)) and subsequent differential stimulation of human muscle protein synthesis (MPS) after dynamic shortening or lengthening exercise. Eight healthy men [25 +/- 5 yr, BMI 26 +/- 3 kg/m(-2) (means +/- SD)] were studied before and after 12 min of repeated stepping up to knee height, and down again, while carrying 25% of their body weight, i.e., shortening exercise with the "up" leg and lengthening exercise with contralateral "down" leg. Quadriceps biopsies were taken before and 3, 6, and 24 h after exercise. After exercise, over 2 h before the biopsies, the subjects ingested 500 ml of water containing 45 g of essential amino acids and 135 g of sucrose. Rates of muscle protein synthesis were determined via incorporation over time of [1-(13)C]leucine (<or=6 h after exercise) or [1-(13)C]valine (21-24 h after exercise) and phosphorylation of signaling proteins by Western analysis. PKB and p70(S6K) phosphorylation increased approximately 3-fold after 3 h and remained elevated at 6 and 24 h. After exercise, rates of myofibrillar and sarcoplasmic protein synthesis were unchanged over the period including exercise and 3 h of recovery but had increased significantly at 6 (approximately 3.0- and 2.4-fold, respectively) and 24 h (approximately 3.2- and 2.0-fold, respectively), independently of the mode of exercise. Short-term dynamic exercise in either shortening or lengthening mode increases MPS at least as much as resistance exercise and is associated with long-term activation of PKB and p70(S6K).
authors.affiliation: Department of Medicine, Ninewells Hospital and Medical School.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Cuthbertson
authors.forename: John
authors.initials: J
authors.lastname: Babraj
authors.forename: Kenneth
authors.initials: K
authors.lastname: Smith
authors.forename: Emilie
authors.initials: E
authors.lastname: Wilkes
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Fedele
authors.forename: Karyn
authors.initials: K
authors.lastname: Esser
authors.forename: Michael
authors.initials: M
authors.lastname: Rennie
mesh_terms: D000328:Adult; D001706:Biopsy; D015153:Blotting, Western; D003094:Collagen / Q000096:biosynthesis; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007930:Leucine / Q000097:blood / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D009210:Myofibrils / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D052097:Quadriceps Muscle / Q000201:enzymology / Q000378:metabolism*; D011897:Random Allocation; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014633:Valine / Q000097:blood / Q000378:metabolism
chemical_list: D009124:Muscle Proteins; D003094:Collagen; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D007930:Leucine; D014633:Valine