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14. Molecular Transducers of Human Skeletal Muscle Remodeling under Different Loading States

Author

Stokes, Tanner, primary, Timmons, James A., additional, Crossland, Hannah, additional, Tripp, Thomas R., additional, Murphy, Kevin, additional, McGlory, Chris, additional, Mitchell, Cameron J., additional, Oikawa, Sara Y., additional, Morton, Robert W., additional, Phillips, Bethan E., additional, Baker, Steven K., additional, Atherton, Phillip J., additional, Wahlestedt, Claes, additional, and Phillips, Stuart M., additional

Published
2020
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23. Validation of a single biopsy approach and bolus protein feeding to determine myofibrillar protein synthesis in stable isotope tracer studies in humans

Author

Baker Steven K, Prior Todd, Rerecich Tracy, West Daniel WD, Burd Nicholas A, and Phillips Stuart M

Subjects
Nutrition. Foods and food supply, TX341-641, Nutritional diseases. Deficiency diseases, RC620-627
Abstract

Abstract Background Minimizing the number of muscle biopsies has important methodological implications and minimizes subject discomfort during a stable isotope amino acid infusion. We aimed to determine the reliability of obtaining a single muscle biopsy for the calculation of muscle protein fractional synthetic rate (FSR) as well as the amount of incorporation time necessary to obtain that biopsy after initiating a stable isotope infusion (Study 1). The calculation of muscle protein FSR requires tracer steady-state during the stable isotope infusion. Therefore, a second aim was to examine if steady-state conditions are compromised in the precursor pools (plasma free or muscle intracellular [IC]) after ingestion of a tracer enriched protein drink and after resistance exercise (Study 2). Methods Sixteen men (23 ± 3 years; BMI = 23.8 ± 2.2 kg/m2, means ± SD) were randomized to perform Study 1 or Study 2 (n = 8, per study). Subjects received a primed, constant infusion of L-[ring-13C6]phenylalanine coupled with muscle biopsies of the vastus lateralis to measure rates of myofibrillar protein synthesis (MPS). Subjects in Study 2 were fed 25 g of whey protein immediately after an acute bout of unilateral resistance exercise. Results There was no difference (P = 0.3) in rates of MPS determined using the steady-state precursor-product equation and determination of tracer incorporation between sequential biopsies 150 min apart or using plasma protein as the baseline enrichment, provided the infusion length was sufficient (230 ± 0.3 min). We also found that adding a modest amount of tracer (4% enriched), calculated based on the measured phenylalanine content of the protein (3.5%) in the drink, did not compromise steady-state conditions (slope of the enrichment curve not different from zero) in the plasma free or, more importantly, the IC pool (both P > 0.05). Conclusions These data demonstrate that the single biopsy approach yields comparable rates of muscle protein synthesis, provided a longer incorporation time is utilized, to that seen with a traditional two biopsy approach. In addition, we demonstrate that enriching protein-containing drinks with tracer does not disturb isotopic steady-state and thus both are reliable techniques to determine rates of MPS in humans.

Published
2011
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29. Altered muscle satellite cell activation following 16 wk of resistance training in young men

Author

Nederveen, Joshua P, Snijders, Tim, Joanisse, Sophie, Wavell, Christopher G, Mitchell, Cameron J, Johnston, Leeann M, Baker, Steven K, Phillips, Stuart M, Parise, Gianni, Nederveen, Joshua P, Snijders, Tim, Joanisse, Sophie, Wavell, Christopher G, Mitchell, Cameron J, Johnston, Leeann M, Baker, Steven K, Phillips, Stuart M, and Parise, Gianni

Abstract

Skeletal muscle satellite cells (SC) play an important role in muscle adaptation. In untrained individuals, SC content and activation status have been observed to increase in response to a single bout of exercise. Muscle fiber characteristics change considerably when resistance exercise is performed chronically, but whether training status affects the activity of SC in response to a single bout of exercise remains unknown. We examined the changes in SC content and activation status following a single bout of resistance exercise, before and following a 16-wk progressive resistance training (RT) program in 14 young (25 ± 3 yr) men. Before and after RT, percutaneous biopsies from the vastus lateralis muscle were taken before a single bout of resistance exercise and after 24 and 72 h of postexercise recovery. Muscle fiber size, capillarization, and SC response were determined by immunohistochemistry. Following RT, there was a greater activation of SC after 24 h in response to a single bout of resistance exercise (Pre, 1.4 ± 0.3; 24 h, 3.1 ± 0.3 Pax7+/MyoD+ cells per 100 fibers) compared with before RT (Pre, 1.4 ± 0.3; 24 h, 2.2 ± 0.3 Pax7+/MyoD+ cells per 100 fibers, P < 0.05); no difference was observed 72 h postexercise. Following 16 wk of RT, MyoD mRNA expression increased from basal to 24 h after the single bout of exercise ( P < 0.05); this change was not observed before training. Individual capillary-to-fiber ratio (C/F i) increased in both type I (1.8 ± 0.3 to 2.0 ± 0.3 C/F i, P < 0.05) and type II (1.7 ± 0.3 to 2.2 ± 0.3 C/F i, P < 0.05) fibers in response to RT. After RT, enhanced activation of SC in response to resistance exercise is accompanied by increases in muscle fiber capillarization.

Published
2017

32. Skeletal muscle satellite cells are located at a closer proximity to capillaries in healthy young compared with older men

Author

Nederveen, Joshua P, Joanisse, Sophie, Snijders, Tim, Ivankovic, Victoria, Baker, Steven K, Phillips, Stuart M, Parise, Gianni, Nederveen, Joshua P, Joanisse, Sophie, Snijders, Tim, Ivankovic, Victoria, Baker, Steven K, Phillips, Stuart M, and Parise, Gianni

Abstract

Background Skeletal muscle satellite cells (SC) are instrumental in maintenance of muscle fibres, the adaptive responses to exercise, and there is an age‐related decline in SC. A spatial relationship exists between SC and muscle fibre capillaries. In the present study, we aimed to investigate whether chronologic age has an impact on the spatial relationship between SC and muscle fibre capillaries. Secondly, we determined whether this spatial relationship changes in response to a single session of resistance exercise. Methods Muscle biopsies were obtained from the vastus lateralis of previously untrained young men (YM, 24 ± 3 years; n = 23) and older men (OM, 67 ± 4 years; n = 22) at rest. A subset of YM (n = 9) performed a single bout of resistance exercise, where additional muscle biopsies taken at 24 and 72 h post‐exercise recovery. Skeletal muscle fibre capillarization, SC content, and activation status were assessed using immunofluorescent microscopy of muscle cross sections. Results Type II muscle fibre SC and capillary content was significantly lower in the YM compared with OM (P < 0.05). Furthermore, type II muscle fibre SC were located at a greater distance from the nearest capillary in OM compared with YM (21.6 ± 1.3 vs. 17.0 ± 0.8 µm, respectively; P < 0.05). In response to a single bout of exercise, we observed a significant increase in SC number and activation status (P < 0.05). In addition, activated vs. quiescent SC were situated closer (P < 0.05) to capillaries. Conclusions We demonstrate that there is a greater distance between capillaries and type II fibre‐associated SC in OM as compared with YM. Furthermore, quiescent SC are located significantly further away from capillaries than active SC after single bout of exercise. Our data have implications for how muscle adapts to exercise and how aging may affect such adaptations.

Published
2016

35. Muscle time under tension during resistance exercise stimulates differential muscle protein sub-fractional synthetic responses in men

Author

Burd, Nicholas A, Andrews, Richard J, West, Daniel WD, Little, Jonathan P, Cochran, Andrew JR, Hector, Amy J, Cashaback, Joshua GA, Gibala, Martin J, Potvin, James R, Baker, Steven K, and Phillips, Stuart M

Subjects
Blood Glucose, Male, Time Factors, Electromyography, Biopsy, Muscle Proteins, Resistance Training, Young Adult, Humans, Insulin, Amino Acids, Muscle, Skeletal, Exercise, Skeletal Muscle and Exercise, Muscle Contraction
Abstract

We aimed to determine if the time that muscle is under loaded tension during low intensity resistance exercise affects the synthesis of specific muscle protein fractions or phosphorylation of anabolic signalling proteins. Eight men (24 ± 1 years (sem), BMI = 26.5 ± 1.0 kg m(-2)) performed three sets of unilateral knee extension exercise at 30% of one-repetition maximum strength involving concentric and eccentric actions that were 6 s in duration to failure (SLOW) or a work-matched bout that consisted of concentric and eccentric actions that were 1 s in duration (CTL). Participants ingested 20 g of whey protein immediately after exercise and again at 24 h recovery. Needle biopsies (vastus lateralis) were obtained while fasted at rest and after 6, 24 and 30 h post-exercise in the fed-state following a primed, constant infusion of l-[ring-(13)C(6)]phenylalanine. Myofibrillar protein synthetic rate was higher in the SLOW condition versus CTL after 24-30 h recovery (P 0.001) and correlated to p70S6K phosphorylation (r = 0.42, P = 0.02). Exercise-induced rates of mitochondrial and sarcoplasmic protein synthesis were elevated by 114% and 77%, respectively, above rest at 0-6 h post-exercise only in the SLOW condition (both P 0.05). Mitochondrial protein synthesis rates were elevated above rest during 24-30 h recovery in the SLOW (175%) and CTL (126%) conditions (both P 0.05). Lastly, muscle PGC-1α expression was increased at 6 h post-exercise compared to rest with no difference between conditions (main effect for time, P 0.001). These data show that greater muscle time under tension increased the acute amplitude of mitochondrial and sarcoplasmic protein synthesis and also resulted in a robust, but delayed stimulation of myofibrillar protein synthesis 24-30 h after resistance exercise.

Published
2011

36. Resistance exercise volume affects myofibrillar protein synthesis and anabolic signalling molecule phosphorylation in young men

Author

Burd, Nicholas A, Holwerda, Andrew M, Selby, Keegan C, West, Daniel W D, Staples, Aaron W, Cain, Nathan E, Cashaback, Joshua G A, Potvin, James R, Baker, Steven K, and Phillips, Stuart M

Subjects
Adult, Blood Glucose, Male, Time Factors, Biopsy, Phenylalanine, Blotting, Western, Muscle Proteins, Ribosomal Protein S6 Kinases, 90-kDa, Quadriceps Muscle, Young Adult, Myofibrils, Humans, Insulin, Phosphorylation, Infusions, Intravenous, Ribosomal Protein S6, Electromyography, Intracellular Signaling Peptides and Proteins, Ribosomal Protein S6 Kinases, 70-kDa, Resistance Training, Fasting, Postprandial Period, Eukaryotic Initiation Factor-2B, Muscle Fatigue, Skeletal Muscle and Exercise, Signal Transduction
Abstract

We aimed to determine if any mechanistic differences exist between a single set (1SET) and multiple sets (i.e. 3 sets; 3SET) of resistance exercise by utilizing a primed constant infusion of [ring-13C6]phenylalanine to determine myofibrillar protein synthesis (MPS) and Western blot analysis to examine anabolic signalling molecule phosphorylation following an acute bout of resistance exercise. Eight resistance-trained men (24 ± 5 years, BMI = 25 ± 4 kg m−2) were randomly assigned to perform unilateral leg extension exercise at 70% concentric one repetition maximum (1RM) until volitional fatigue for 1SET or 3SET. Biopsies from the vastus lateralis were taken in the fasted state (Fast) and fed state (Fed; 20 g of whey protein isolate) at rest, 5 h Fed, 24 h Fast and 29 h Fed post-exercise. Fed-state MPS was transiently elevated above rest at 5 h for 1SET (2.3-fold) and returned to resting levels by 29 h post-exercise. However, the exercise induced increase in MPS following 3SET was superior in amplitude and duration as compared to 1SET at both 5 h (3.1-fold above rest) and 29 h post-exercise (2.3-fold above rest). Phosphorylation of 70 kDa S6 protein kinase (p70S6K) demonstrated a coordinated increase with MPS at 5 h and 29 h post-exercise such that the extent of p70S6K phosphorylation was related to the MPS response (r = 0.338, P = 0.033). Phosphorylation of 90 kDa ribosomal S6 protein kinase (p90RSK) and ribosomal protein S6 (rps6) was similar for 1SET and 3SET at 24 h Fast and 29 h Fed, respectively. However, 3SET induced a greater activation of eukaryotic translation initiation factor 2Bɛ (eIF2Bɛ) and rpS6 at 5 h Fed. These data suggest that 3SET of resistance exercise is more anabolic than 1SET and may lead to greater increases in myofibrillar protein accretion over time.

Published
2010

37. Resistance exercise-induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men

Author

West, Daniel W D, Kujbida, Gregory W, Moore, Daniel R, Atherton, Philip, Burd, Nicholas A, Padzik, Jan P, De Lisio, Michael, Tang, Jason E, Parise, Gianni, Rennie, Michael J, Baker, Steven K, and Phillips, Stuart M

Subjects
Male, Young Adult, Anabolic Agents, Growth Hormone, Humans, Muscle Proteins, Resistance Training, Testosterone, Insulin-Like Growth Factor I, Muscle, Skeletal, Skeletal Muscle and Exercise, Signal Transduction
Abstract

We aimed to determine whether exercise-induced elevations in systemic concentration of testosterone, growth hormone (GH) and insulin-like growth factor-1 (IGF-1) enhanced post-exercise myofibrillar protein synthesis (MPS) and phosphorylation of signalling proteins important in regulating mRNA translation. Eight young men (20 +/- 1.1 years, BMI = 26 +/- 3.5 kg m(-2)) completed two exercise protocols designed to maintain basal hormone concentrations (low hormone, LH) or elicit increases in endogenous hormones (high hormone, HH). In the LH protocol, participants performed a bout of unilateral resistance exercise with the elbow flexors. The HH protocol consisted of the same elbow flexor exercise with the contralateral arm followed immediately by high-volume leg resistance exercise. Participants consumed 25 g of protein after arm exercise to maximize MPS. Muscle biopsies and blood samples were taken as appropriate. There were no changes in serum testosterone, GH or IGF-1 after the LH protocol, whereas there were marked elevations after HH (testosterone, P0.001; GH, P0.001; IGF-1, P0.05). Exercise stimulated a rise in MPS in the biceps brachii (rest = 0.040 +/- 0.007, LH = 0.071 +/- 0.008, HH = 0.064 +/- 0.014% h(-1); P0.05) with no effect of elevated hormones (P = 0.72). Phosphorylation of the 70 kDa S6 protein kinase (p70S6K) also increased post-exercise (P0.05) with no differences between conditions. We conclude that the transient increases in endogenous purportedly anabolic hormones do not enhance fed-state anabolic signalling or MPS following resistance exercise. Local mechanisms are likely to be of predominant importance for the post-exercise increase in MPS.

Published
2009

47. Low-Load High Volume Resistance Exercise Stimulates Muscle Protein Synthesis More Than High-Load Low Volume Resistance Exercise in Young Men

Author

Burd, Nicholas A., primary, West, Daniel W. D., additional, Staples, Aaron W., additional, Atherton, Philip J., additional, Baker, Jeff M., additional, Moore, Daniel R., additional, Holwerda, Andrew M., additional, Parise, Gianni, additional, Rennie, Michael J., additional, Baker, Steven K., additional, and Phillips, Stuart M., additional

Published
2010
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