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51. Failed Recovery of Glycemic Control and Myofibrillar Protein Synthesis With 2 wk of Physical Inactivity in Overweight, Prediabetic Older Adults

Author

McGlory, Chris, primary, von Allmen, Mark T, additional, Stokes, Tanner, additional, Morton, Robert W, additional, Hector, Amy J, additional, Lago, Briony A, additional, Raphenya, Amogelang R, additional, Smith, Brennan K, additional, McArthur, Andrew G, additional, Steinberg, Gregory R, additional, Baker, Steven K, additional, and Phillips, Stuart M, additional

Published
2017
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55. 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

58. Failed Recovery of Glycemic Control and Myofibrillar Protein Synthesis With 2 wk of Physical Inactivity in Overweight, Prediabetic Older Adults.

Author

Smith, Brennan K., McGlory, Chris, von Allmen, Mark T., Stokes, Tanner, Morton, Robert W., Hector, Amy J., Phillips, Stuart M., Lago, Briony A., Raphenya, Amogelang R., McArthur, Andrew G., Steinberg, Gregory R., and Baker, Steven K.

Subjects
SARCOPENIA, DIABETES, METABOLISM, PHYSICAL activity, INSULIN resistance
Abstract

Background: Physical inactivity impairs insulin sensitivity, which is exacerbated with aging. We examined the impact of 2 wk of acute inactivity and recovery on glycemic control, and integrated rates of muscle protein synthesis in older men and women.Methods: Twenty-two overweight, prediabetic older adults (12 men, 10 women, 69 ± 4 y) undertook 7 d of habitual activity (baseline; BL), step reduction (SR; <1,000 steps.d-1 for 14 d), followed by 14 d of recovery (RC). An oral glucose tolerance test was used to assess glycemic control and deuterated water ingestion to measure integrated rates of muscle protein synthesis.Results: Daily step count was reduced (all p < .05) from BL at SR (7362 ± 3294 to 991 ± 97) and returned to BL levels at RC (7117 ± 3819). Homeostasis model assessment-insulin resistance increased from BL to SR and Matsuda insulin sensitivity index decreased and did not return to BL in RC. Glucose and insulin area under the curve were elevated from BL to SR and did not recover in RC. Integrated muscle protein synthesis was reduced during SR and did not return to BL in RC.Conclusions: Our findings demonstrate that 2 wk of SR leads to lowered rates of muscle protein synthesis and a worsening of glycemic control that unlike younger adults is not recovered during return to normal activity in overweight, prediabetic elderly humans.Clinical Trials Registration: ClinicalTrials.gov identifier: NCT03039556. [ABSTRACT FROM AUTHOR]

Published
2018
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60. 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

61. 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

62. 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

74. Reply

Author

Hooper, Davyd R., primary and Baker, Steven K., additional

Published
2012
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79. 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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95. Statin myopathies: pathophysiologic and clinical perspectives.

Author

Baker, Steven K. and Tarnopolsky, Mark A.

Subjects
*STATINS (Cardiovascular agents), *MUSCLE diseases
Abstract

Examines the potential etiologies of statin myopathies in relation to altered cholesterol biosynthesis and muscle physiology. Spectrum of myotoxic reactions to statin drugs; Changes in mammalian skeletal muscle after pharmacologic doses of statins; Effects of statins on membrane function and calcium regulation.

Published
2001

96. Clinical variability in maternally inherited leber hereditary optic neuropathy with the G14459A mutation

Author

Tarnopolsky, Mark A., Baker, Steven K., Myint, Tomoko, Maxner, C.E., Robitaille, J., and Robinson, Brian H.

Abstract

Spasticity and dystonia have been associated with mitochondrial (mt) DNA mutations at A11696G, G14459A, and T14596A. We describe the clinical features and molecular analysis of two Caucasian pedigrees with the 14,459 guanosine (G) → adenine (A) transition. The maternally inherited Leber hereditary optic neuropathy (LHON) phenotypes showed extreme clinical variability and the only screening test that was abnormal in the patient with spasticity/dystonia was a high T2 signal in the putamen bilaterally. The male patient in the second pedigree showed features of optic neuropathy without spasticity/dystonia. These results further support that the 14,459 G → A transition mutation is causally related to LHON and spasticity/dystonia. © 2003 Wiley-Liss, Inc.

Published
2004
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99. Arm Numbness at 45 Degrees Abduction: A Case Report of Thoracic Outlet Syndrome After Brachial Neuritis.

Author

Fleet JL, Harish S, Bain J, and Baker SK

Abstract

Objective: To describe a case of nerve kinking correlating with surgical findings in neurogenic thoracic outlet syndrome in a patient with history of brachial neuritis. Thoracic outlet syndrome and brachial neuritis are briefly reviewed., Case Report: A 32-year-old woman with a history of bilateral brachial neuritis presented with paraesthesias in her hand when abducting her shoulder to 45° or higher. A kink in the superior trunk of the brachial plexus, as well as asymmetrically narrowed costoclavicular space, was found on magnetic resonance imaging with the shoulder abducted. Conservative measures failed, leading to partial anterior scalenectomy and neurolysis, which led to improvement in her symptoms., Conclusion: Anatomical variations in combination with biomechanical changes after brachial neuritis can be associated with neurogenic thoracic outlet syndrome., (Journal Compilation © 2020 Foundation of Rehabilitation Information.)

Published
2020
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100. Failed Recovery of Glycemic Control and Myofibrillar Protein Synthesis With 2 wk of Physical Inactivity in Overweight, Prediabetic Older Adults.

Author

McGlory C, von Allmen MT, Stokes T, Morton RW, Hector AJ, Lago BA, Raphenya AR, Smith BK, McArthur AG, Steinberg GR, Baker SK, and Phillips SM

Subjects
Aged, Exercise physiology, Female, Glucose Tolerance Test, Humans, Male, Overweight blood, Prediabetic State blood, Blood Glucose analysis, Muscle Proteins biosynthesis, Overweight physiopathology, Prediabetic State physiopathology, Sedentary Behavior
Abstract

Background: Physical inactivity impairs insulin sensitivity, which is exacerbated with aging. We examined the impact of 2 wk of acute inactivity and recovery on glycemic control, and integrated rates of muscle protein synthesis in older men and women., Methods: Twenty-two overweight, prediabetic older adults (12 men, 10 women, 69 ± 4 y) undertook 7 d of habitual activity (baseline; BL), step reduction (SR; <1,000 steps.d-1 for 14 d), followed by 14 d of recovery (RC). An oral glucose tolerance test was used to assess glycemic control and deuterated water ingestion to measure integrated rates of muscle protein synthesis., Results: Daily step count was reduced (all p < .05) from BL at SR (7362 ± 3294 to 991 ± 97) and returned to BL levels at RC (7117 ± 3819). Homeostasis model assessment-insulin resistance increased from BL to SR and Matsuda insulin sensitivity index decreased and did not return to BL in RC. Glucose and insulin area under the curve were elevated from BL to SR and did not recover in RC. Integrated muscle protein synthesis was reduced during SR and did not return to BL in RC., Conclusions: Our findings demonstrate that 2 wk of SR leads to lowered rates of muscle protein synthesis and a worsening of glycemic control that unlike younger adults is not recovered during return to normal activity in overweight, prediabetic elderly humans., Clinical Trials Registration: ClinicalTrials.gov identifier: NCT03039556.

Published
2018
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