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McColl TJ, Clarke DC. Kinetic modeling of leucine-mediated signaling and protein metabolism in human skeletal muscle. iScience 2024; 27:108634. [PMID: 38188514 PMCID: PMC10767222 DOI: 10.1016/j.isci.2023.108634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 11/15/2023] [Accepted: 12/01/2023] [Indexed: 01/09/2024] Open
Abstract
Skeletal muscle protein levels are governed by the relative rates of muscle protein synthesis (MPS) and breakdown (MPB). The mechanisms controlling these rates are complex, and their integrated behaviors are challenging to study through experiments alone. The purpose of this study was to develop and analyze a kinetic model of leucine-mediated mTOR signaling and protein metabolism in the skeletal muscle of young adults. Our model amalgamates published cellular-level models of the IRS1-PI3K-Akt-mTORC1 signaling system and of skeletal-muscle leucine kinetics with physiological-level models of leucine digestion and transport and insulin dynamics. The model satisfactorily predicts experimental data from diverse leucine feeding protocols. Model analysis revealed that total levels of p70S6K are a primary determinant of MPS, insulin signaling substantially affects muscle net protein balance via its effects on MPB, and p70S6K-mediated feedback of mTORC1 signaling reduces MPS in a dose-dependent manner.
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Affiliation(s)
- Taylor J. McColl
- Department of Biomedical Physiology and KinesiologySimon Fraser University, Burnaby, BC V5A 1S6, Canada
- Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - David C. Clarke
- Department of Biomedical Physiology and KinesiologySimon Fraser University, Burnaby, BC V5A 1S6, Canada
- Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
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Ferrando AA, Wolfe RR, Hirsch KR, Church DD, Kviatkovsky SA, Roberts MD, Stout JR, Gonzalez DE, Sowinski RJ, Kreider RB, Kerksick CM, Burd NA, Pasiakos SM, Ormsbee MJ, Arent SM, Arciero PJ, Campbell BI, VanDusseldorp TA, Jager R, Willoughby DS, Kalman DS, Antonio J. International Society of Sports Nutrition Position Stand: Effects of essential amino acid supplementation on exercise and performance. J Int Soc Sports Nutr 2023; 20:2263409. [PMID: 37800468 PMCID: PMC10561576 DOI: 10.1080/15502783.2023.2263409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 09/21/2023] [Indexed: 10/07/2023] Open
Abstract
Position Statement: The International Society of Sports Nutrition (ISSN) presents this position based on a critical examination of literature surrounding the effects of essential amino acid (EAA) supplementation on skeletal muscle maintenance and performance. This position stand is intended to provide a scientific foundation to athletes, dietitians, trainers, and other practitioners as to the benefits of supplemental EAA in both healthy and resistant (aging/clinical) populations. EAAs are crucial components of protein intake in humans, as the body cannot synthesize them. The daily recommended intake (DRI) for protein was established to prevent deficiencies due to inadequate EAA consumption. The following conclusions represent the official position of the Society: 1. Initial studies on EAAs' effects on skeletal muscle highlight their primary role in stimulating muscle protein synthesis (MPS) and turnover. Protein turnover is critical for replacing degraded or damaged muscle proteins, laying the metabolic foundation for enhanced functional performance. Consequently, research has shifted to examine the effects of EAA supplementation - with and without the benefits of exercise - on skeletal muscle maintenance and performance. 2. Supplementation with free-form EAAs leads to a quick rise in peripheral EAA concentrations, which in turn stimulates MPS. 3. The safe upper limit of EAA intake (amount), without inborn metabolic disease, can easily accommodate additional supplementation. 4. At rest, stimulation of MPS occurs at relatively small dosages (1.5-3.0 g) and seems to plateau at around 15-18 g. 5. The MPS stimulation by EAAs does not require non-essential amino acids. 6. Free-form EAA ingestion stimulates MPS more than an equivalent amount of intact protein. 7. Repeated EAA-induced MPS stimulation throughout the day does not diminish the anabolic effect of meal intake. 8. Although direct comparisons of various formulas have yet to be investigated, aging requires a greater proportion of leucine to overcome the reduced muscle sensitivity known as "anabolic resistance." 9. Without exercise, EAA supplementation can enhance functional outcomes in anabolic-resistant populations. 10. EAA requirements rise in the face of caloric deficits. During caloric deficit, it's essential to meet whole-body EAA requirements to preserve anabolic sensitivity in skeletal muscle.
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Affiliation(s)
- Arny A. Ferrando
- University of Arkansas for Medical Sciences, Center for Translational Research in Aging and Longevity, Department of Geriatrics, Little Rock, AR, USA
| | - Robert R. Wolfe
- University of Arkansas for Medical Sciences, Center for Translational Research in Aging and Longevity, Department of Geriatrics, Little Rock, AR, USA
| | - Katie R. Hirsch
- University of South Carolina, Department of Exercise Science, Arnold School of Public Health, Columbia, SC, USA
| | - David D. Church
- University of Arkansas for Medical Sciences, Center for Translational Research in Aging and Longevity, Department of Geriatrics, Little Rock, AR, USA
| | - Shiloah A. Kviatkovsky
- University of Arkansas for Medical Sciences, Center for Translational Research in Aging and Longevity, Department of Geriatrics, Little Rock, AR, USA
| | | | - Jeffrey R. Stout
- University of Central Florida, School of Kinesiology and Rehabilitation Sciences, Orlando, FL, USA
| | - Drew E. Gonzalez
- Texas A&M University, Exercise & Sport Nutrition Lab, Department of Kinesiology and Sports Management, College Station, TX, USA
| | - Ryan J. Sowinski
- Texas A&M University, Exercise & Sport Nutrition Lab, Department of Kinesiology and Sports Management, College Station, TX, USA
| | - Richard B. Kreider
- Texas A&M University, Exercise & Sport Nutrition Lab, Department of Kinesiology and Sports Management, College Station, TX, USA
| | - Chad M. Kerksick
- Lindenwood University, Exercise and Performance Nutrition Laboratory, College of Science, Technology, and Health, St Charles, MO, USA
| | - Nicholas A. Burd
- University of Illinois Urbana-Champaign, Department of Kinesiology and Community Health, Urbana, IL, USA
| | - Stefan M. Pasiakos
- National Institutes of Health, Office of Dietary Supplements, Bethesda, MD, USA
| | - Michael J. Ormsbee
- Florida State University, Institute of Sports Sciences and Medicine, Nutrition and Integrative Physiology, Tallahassee, FL, USA
| | - Shawn M. Arent
- University of South Carolina, Department of Exercise Science, Arnold School of Public Health, Columbia, SC, USA
| | - Paul J. Arciero
- University of Pittsburgh, Department of Sports Medicine and Nutrition, Pittsburgh, PA, USA
- Skidmore College, Health and Physiological Sciences, Saratoga Springs, NY, USA
| | - Bill I. Campbell
- University of South Florida, Performance & Physique Enhancement Laboratory, Tampa, FL, USA
| | - Trisha A. VanDusseldorp
- Bonafede Health, LLC, JDS Therapeutics, Harrison, NY, USA
- Jacksonville University, Department of Health and Exercise Sciences, Jacksonville, FL, USA
| | | | - Darryn S. Willoughby
- University of Mary Hardin-Baylor, Human Performance Lab, School of Exercise and Sport Science, Belton, TX, USA
| | - Douglas S. Kalman
- Nova Southeastern University, Dr. Kiran C Patel College of Osteopathic Medicine, Department of Nutrition, Davie, FL, USA
| | - Jose Antonio
- Nova Southeastern University, Department of Health and Human Performance, Davie, FL, USA
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3
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Rehou S, de Brito Monteiro L, Auger C, Knuth CM, Abdullahi A, Stanojcic M, Jeschke MG. Propranolol Normalizes Metabolomic Signatures Thereby Improving Outcomes After Burn. Ann Surg 2023; 278:519-529. [PMID: 37389480 DOI: 10.1097/sla.0000000000005973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/01/2023]
Abstract
OBJECTIVE AND BACKGROUND Propranolol, a nonselective beta-receptor blocker, improves outcomes of severely burned patients. While the clinical and physiological benefits of beta-blockade are well characterized, the underlying metabolic mechanisms are less well defined. We hypothesized that propranolol improves outcomes after burn injury by profoundly modulating metabolic pathways. METHODS In this phase II randomized controlled trial, patients with burns ≥20% of total body surface area were randomly assigned to control or propranolol (dose given to decrease heart rate <100 bpm). Outcomes included clinical markers, inflammatory and lipidomic profiles, untargeted metabolomics, and molecular pathways. RESULTS Fifty-two severely burned patients were enrolled in this trial (propranolol, n=23 and controls, n=29). There were no significant differences in demographics or injury severity between groups. Metabolomic pathway analyses of the adipose tissue showed that propranolol substantially alters several essential metabolic pathways involved in energy and nucleotide metabolism, as well as catecholamine degradation ( P <0.05). Lipidomic analysis revealed that propranolol-treated patients had lower levels of proinflammatory palmitic acid ( P <0.05) and saturated fatty acids ( P <0.05) with an increased ratio of polyunsaturated fatty acids ( P <0.05), thus shifting the lipidomic profile towards an anti-inflammatory phenotype after burn ( P <0.05). These metabolic effects were mediated by decreased activation of hormone-sensitive lipase at serine 660 ( P <0.05) and significantly reduced endoplasmic reticulum stress by decreasing phospho-JNK ( P <0.05). CONCLUSION Propranolol's ability to mitigate pathophysiological changes to essential metabolic pathways results in significantly improved stress responses.
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Affiliation(s)
- Sarah Rehou
- Hamilton Health Sciences, Hamilton, ON, Canada
- School of Medicine, St. George's University, True Blue, Grenada
| | | | - Christopher Auger
- Division of Endocrinology, Diabetes and Metabolism, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA
| | - Carly M Knuth
- Division of Endocrinology, Diabetes and Metabolism, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA
- Sunnybrook Research Institute, Toronto, ON, Canada
| | - Abdikarim Abdullahi
- Sunnybrook Research Institute, Toronto, ON, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Mile Stanojcic
- Sunnybrook Research Institute, Toronto, ON, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Marc G Jeschke
- Hamilton Health Sciences, Hamilton, ON, Canada
- Department of Surgery, McMaster University, Hamilton, ON, Canada
- Sunnybrook Research Institute, Toronto, ON, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
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4
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Sadri H, Ghaffari MH, Sauerwein H. Invited review: Muscle protein breakdown and its assessment in periparturient dairy cows. J Dairy Sci 2023; 106:822-842. [PMID: 36460512 DOI: 10.3168/jds.2022-22068] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 08/29/2022] [Indexed: 11/30/2022]
Abstract
Mobilization of body reserves including fat, protein, and glycogen is necessary to overcome phases of negative nutrient balance typical for high-yielding dairy cows during the periparturient period. Skeletal muscle, the largest internal organ in mammals, plays a crucial role in maintaining metabolic homeostasis. However, unlike in liver and adipose tissue, the metabolic and regulatory role of skeletal muscle in the adaptation of dairy cows to the physiological needs of pregnancy and lactation has not been studied extensively. The functional integrity and quality of skeletal muscle are maintained through a constant turnover of protein, resulting from both protein breakdown and protein synthesis. Thus, muscle protein breakdown (MPB) and synthesis are intimately connected and tightly controlled to ensure proper protein homeostasis. Understanding the regulation of MPB, the catabolic component of muscle turnover, and its assessment are therefore important considerations to provide information about the timing and extent of tissue mobilization in periparturient dairy cows. Based on animal models and human studies, it is now evident that MPB occurs via the integration of 3 main systems: autophagy-lysosomal, calpain Ca2+-dependent cysteine proteases, and the ubiquitin-proteasome system. These 3 main systems are interconnected and do not work separately, and the regulation is complex. The ubiquitin-proteasomal system is the most well-known cellular proteolytic system and plays a fundamental role in muscle physiology. Complete degradation of a protein often requires a combination of the systems, depending on the physiological situation. Determination of MPB in dairy cows is technically challenging, resulting in a relative dearth of information. The methods for assessing MPB can be divided into either direct or indirect measurements, both having their strengths and limitations. Available information on the direct measures of MPB primarily comes from stable isotopic tracer methods and those of indirect measurements from assessing expression and activity measures of the components of the 3 MPB systems in muscle biopsy samples. Other indirect approaches (i.e., potential indicators of MPB), including ultrasound imaging and measuring metabolites from muscle degradation (i.e., 3-methylhistidine and creatinine), seem to be applicable methods and can provide useful information about the extent and timing of MPB. This review presents our current understanding, including methodological considerations, of the process of MPB in periparturient dairy cows.
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Affiliation(s)
- H Sadri
- Department of Clinical Science, Faculty of Veterinary Medicine, University of Tabriz, 5166616471 Tabriz, Iran; Institute of Animal Science, Physiology Unit, University of Bonn, 53111 Bonn, Germany.
| | - M H Ghaffari
- Institute of Animal Science, Physiology Unit, University of Bonn, 53111 Bonn, Germany
| | - H Sauerwein
- Institute of Animal Science, Physiology Unit, University of Bonn, 53111 Bonn, Germany
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Lv X, Zhou C, Yan Q, Tan Z, Kang J, Tang S. Elucidating the underlying mechanism of amino acids to regulate muscle protein synthesis: impact on human health. Nutrition 2022; 103-104:111797. [DOI: 10.1016/j.nut.2022.111797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 07/01/2022] [Accepted: 07/04/2022] [Indexed: 10/31/2022]
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Albert BD, Spolidoro GC, Mehta NM. Metabolism and energy prescription in critically III children. Minerva Anestesiol 2021; 87:1025-1033. [PMID: 33853268 DOI: 10.23736/s0375-9393.21.14825-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Optimal nutrition therapy can positively influence clinical outcomes in critically ill children. Accurate assessment of nutritional status, metabolic state, macronutrient requirements and substrate utilization allows accurate prescription of nutrition in this population. In response to stress and injury, the body undergoes adaptive physiologic changes leading to dysregulation of the inflammatory response and hyperactivation of the inflammatory cascade. This results in a global catabolic state with modification in oxygen consumption and macronutrient metabolism. A comprehensive understanding of the metabolic response is essential when prescribing nutritional interventions aimed to offset the burden of this adaptive stress response in the critically ill. In this narrative review we aim to provide a comprehensive review of the physiologic basis, recent literature and some emerging concepts related to energy expenditure and the practical aspects of energy delivery in the critically ill child. Based on the unique metabolic characteristics of the critically ill child, we aim to provide a pragmatic approach to providing nutrition therapy.
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Affiliation(s)
- Ben D Albert
- Department of Anesthesiology, Critical Care and Pain Medicine, Boston Children's Hospital, Boston, MA, USA.,Harvard Medical School, Cambridge, MA, USA
| | - Giulia C Spolidoro
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Nilesh M Mehta
- Department of Anesthesiology, Critical Care and Pain Medicine, Boston Children's Hospital, Boston, MA, USA - .,Harvard Medical School, Cambridge, MA, USA.,Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.,Center for Nutrition, Boston Children's Hospital, Boston, MA, USA
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7
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Wilkinson DJ, Brook MS, Smith K. Principles of stable isotope research - with special reference to protein metabolism. CLINICAL NUTRITION OPEN SCIENCE 2021; 36:111-125. [PMID: 33969338 PMCID: PMC8083121 DOI: 10.1016/j.nutos.2021.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 02/06/2021] [Indexed: 12/13/2022] Open
Abstract
The key to understanding the mechanisms regulating disease stems from the ability to accurately quantify the dynamic nature of the metabolism underlying the physiological and pathological changes occurring as a result of the disease. Stable isotope tracer technologies have been at the forefront of this for almost 80 years now, and through a combination of both intense theoretical and technological development over these decades, it is now possible to utilise stable isotope tracers to investigate the complexities of in vivo human metabolism from a whole body perspective, down to the regulation of sub-nanometer cellular components (i.e organelles, nucleotides and individual proteins). This review therefore aims to highlight; 1) the advances made in these stable isotope tracer approaches - with special reference given to their role in understanding the nutritional regulation of protein metabolism, 2) some considerations required for the appropriate application of these stable isotope techniques to study protein metabolism, 3) and finally how new stable isotopes approaches and instrument/technical developments will help to deliver greater clinical insight in the near future.
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Key Words
- A-V, Arterial Venous
- AA, Amino Acids
- AP(E), Atom percent (excess)
- FBR, Fractional Breakdown Rate
- FSR, Fractional Synthesis Rate
- GC-MS, Gas Chromatography Mass Spectrometry
- LC-MS, Liquid Chromatography Mass Spectrometry
- MPS, Muscle Protein Synthesis
- Muscle
- Protein turnover
- Ra, Rate of Appearance
- Rd, Rate of Disappearance
- Stable isotope tracers
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Affiliation(s)
- Daniel J. Wilkinson
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, UK
- Division of Health Sciences and Graduate Entry Medicine, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - Matthew S. Brook
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, UK
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
| | - Ken Smith
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, UK
- Division of Health Sciences and Graduate Entry Medicine, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
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8
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Kim IY, Park S, Kim Y, Chang Y, Choi CS, Suh SH, Wolfe RR. In Vivo and In Vitro Quantification of Glucose Kinetics: From Bedside to Bench. Endocrinol Metab (Seoul) 2020; 35:733-749. [PMID: 33397035 PMCID: PMC7803595 DOI: 10.3803/enm.2020.406] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 11/19/2020] [Accepted: 11/27/2020] [Indexed: 12/16/2022] Open
Abstract
Like other substrates, plasma glucose is in a dynamic state of constant turnover (i.e., rates of glucose appearance [Ra glucose] into and disappearance [Rd glucose] from the plasma) while staying within a narrow range of normal concentrations, a physiological priority. Persistent imbalance of glucose turnover leads to elevations (i.e., hyperglycemia, Ra>Rd) or falls (i.e., hypoglycemia, Ra
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Affiliation(s)
- Il-Young Kim
- Department of Molecular Medicine, College of Medicine, Gachon University, Incheon, Seoul,
Korea
- Korea Mouse Metabolic Phenotyping Center, Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Incheon, Seoul,
Korea
| | - Sanghee Park
- Department of Molecular Medicine, College of Medicine, Gachon University, Incheon, Seoul,
Korea
- Korea Mouse Metabolic Phenotyping Center, Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Incheon, Seoul,
Korea
| | - Yeongmin Kim
- Department of Health Sciences and Technology, Gachon Advanced Institute for Health Sciences & Technology (GAIHST), Gachon University, Incheon, Seoul,
Korea
| | - Yewon Chang
- Department of Health Sciences and Technology, Gachon Advanced Institute for Health Sciences & Technology (GAIHST), Gachon University, Incheon, Seoul,
Korea
| | - Cheol Soo Choi
- Department of Molecular Medicine, College of Medicine, Gachon University, Incheon, Seoul,
Korea
- Korea Mouse Metabolic Phenotyping Center, Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Incheon, Seoul,
Korea
| | - Sang-Hoon Suh
- Department of Physical Education, Yonsei University, Seoul,
Korea
| | - Robert R. Wolfe
- Department of Geriatrics, the Center for Translational Research in Aging & Longevity, Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, AR,
USA
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Greif DN, Emerson CP, Allegra P, Arizpe A, Mansour KL, Cade WH, Baraga MG. Supplement Use in Patients Undergoing Anterior Cruciate Ligament Reconstruction: A Systematic Review. Arthroscopy 2020; 36:2537-2549. [PMID: 32438028 DOI: 10.1016/j.arthro.2020.04.047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 04/25/2020] [Accepted: 04/25/2020] [Indexed: 02/02/2023]
Abstract
PURPOSE To assess whether a standardized dietary supplementation can help to decrease postoperative muscle atrophy and/or improve rehabilitation outcomes in patients who underwent anterior cruciate ligament reconstruction (ACLR). METHODS A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). MEDLINE, Scopus, and Cochrane Library databases were searched, and articles that examined protein or amino acid, vitamin, or any other type of supplementation in ACLR were reviewed. Two independent reviewers conducted the search using pertinent Boolean operations. RESULTS A total of 1818 articles were found after our database search. Ten studies fulfilled our inclusion criteria and only assessed patients undergoing ACLR. Four studies assessed protein-based supplementation. One study assessed creatine as a supplement. Four studies assessed vitamin-based supplementation. One study assessed testosterone supplementation. Protein and amino acid supplementation showed potential benefits; multiple authors demonstrated a combination of improved achievement of rehabilitation benchmarks, graft maturation, muscular hypertrophic response, and peak dynamic muscle strength. When we examined creatine, vitamin, or hormone-based protocols, none demonstrated results, suggesting these factors may attenuate muscle atrophy after surgery. Vitamin C and E demonstrated potentially increased local inflammation in skeletal muscle, which runs contrary to the belief that antioxidant vitamin-based supplementation may decrease the inflammatory response that plays a role in the post injury/operative period. CONCLUSIONS Protein-based supplementation may play a role in mitigating muscle atrophy associated with ACLR, as multiple authors demonstrated a combination of improved achievement of rehabilitation benchmarks, thigh hypertrophic response, and peak dynamic muscle strength. However, based on current literature, it is not possible to recommend a specific protein-based supplementation protocol at this time for patients undergoing ACLR. Limited evidence suggests no benefit for creatine, vitamin, or hormone-based protocols. LEVEL OF EVIDENCE II, a systematic review of level I-II studies.
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Affiliation(s)
- Dylan N Greif
- University of Miami Sports Medicine Institute, Coral Gables, Florida, U.S.A..
| | | | - Paul Allegra
- Department of Orthopaedic Surgery, University of Miami Miller School of Medicine, Miami, Florida, U.S.A
| | - Azael Arizpe
- Department of Orthopaedic Surgery, University of Miami Miller School of Medicine, Miami, Florida, U.S.A
| | - Kailey L Mansour
- University of Miami Sports Medicine Institute, Coral Gables, Florida, U.S.A
| | - William H Cade
- University of Miami Sports Medicine Institute, Coral Gables, Florida, U.S.A
| | - Michael G Baraga
- University of Miami Sports Medicine Institute, Coral Gables, Florida, U.S.A.; Department of Orthopaedic Surgery, University of Miami Miller School of Medicine, Miami, Florida, U.S.A
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Crossland H, Smith K, Atherton PJ, Wilkinson DJ. A novel stable isotope tracer method to simultaneously quantify skeletal muscle protein synthesis and breakdown. Metabol Open 2020; 5:100022. [PMID: 32494771 PMCID: PMC7259457 DOI: 10.1016/j.metop.2020.100022] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/11/2019] [Accepted: 01/01/2020] [Indexed: 01/08/2023] Open
Abstract
Background/aims Methodological challenges have been associated with the dynamic measurement of muscle protein breakdown (MPB), as have the measurement of both muscle protein synthesis (MPS) and MPB within the same experiment. Our aim was to use the transmethylation properties of methionine as proof-of-concept to measure rates of MPB via its methylation of histidine within skeletal muscle myofibrillar proteins, whilst simultaneously utilising methionine incorporation into bound protein to measure MPS. Results During the synthesis measurement period, incorporation of methyl[D3]-13C-methionine into cellular protein in C2C12 myotubes was observed (representative of MPS), alongside an increase in the appearance of methyl[D3]-methylhistidine into the media following methylation of histidine (representative of MPB). For further validation of this approach, fractional synthetic rates (FSR) of muscle protein were increased following treatment of the cells with the anabolic factors insulin-like growth factor-1 (IGF-1) and insulin, while dexamethasone expectedly reduced MPS. Conversely, rates of MPB were reduced with IGF-1 and insulin treatments, whereas dexamethasone accelerated MPB. Conclusions This is a novel stable isotope tracer approach that permits the dual assessment of muscle cellular protein synthesis and breakdown rates, through the provision of a single methionine amino acid tracer that could be utilised in a wide range of biological settings.
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Affiliation(s)
- Hannah Crossland
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Biomedical Research Centre (BRC), Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital, Derby, UK
| | - Kenneth Smith
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Biomedical Research Centre (BRC), Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital, Derby, UK
| | - Philip J Atherton
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Biomedical Research Centre (BRC), Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital, Derby, UK
| | - Daniel J Wilkinson
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Biomedical Research Centre (BRC), Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital, Derby, UK
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11
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Holm L, Dideriksen K, Nielsen RH, Doessing S, Bechshoeft RL, Højfeldt G, Moberg M, Blomstrand E, Reitelseder S, van Hall G. An exploration of the methods to determine the protein-specific synthesis and breakdown rates in vivo in humans. Physiol Rep 2019; 7:e14143. [PMID: 31496135 PMCID: PMC6732504 DOI: 10.14814/phy2.14143] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 05/08/2019] [Accepted: 05/09/2019] [Indexed: 01/02/2023] Open
Abstract
The present study explores the methods to determine human in vivo protein-specific myofibrillar and collagenous connective tissue protein fractional synthesis and breakdown rates. We found that in human myofibrillar proteins, the protein-bound tracer disappearance method to determine the protein fractional breakdown rate (FBR) (via 2 H2 O ingestion, endogenous labeling of 2 H-alanine that is incorporated into proteins, and FBR quantified by its disappearance from these proteins) has a comparable intrasubject reproducibility (range: 0.09-53.5%) as the established direct-essential amino acid, here L-ring-13 C6 -phenylalanine, incorporation method to determine the muscle protein fractional synthesis rate (FSR) (range: 2.8-56.2%). Further, the determination of the protein breakdown in a protein structure with complex post-translational processing and maturation, exemplified by human tendon tissue, was not achieved in this experimentation, but more investigation is encouraged to reveal the possibility. Finally, we found that muscle protein FBR measured with an essential amino acid tracer prelabeling is inappropriate presumably because of significant and prolonged intracellular recycling, which also may become a significant limitation for determination of the myofibrillar FSR when repeated infusion trials are completed in the same participants.
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Affiliation(s)
- Lars Holm
- Institute of Sports Medicine and Department of Orthopedic Surgery MBispebjerg HospitalCopenhagenDenmark
- Department of Biomedical SciencesFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
- School of Sport, Exercise and Rehabilitation SciencesUniversity of BirminghamBirminghamUnited Kingdom
| | - Kasper Dideriksen
- Institute of Sports Medicine and Department of Orthopedic Surgery MBispebjerg HospitalCopenhagenDenmark
| | - Rie H. Nielsen
- Institute of Sports Medicine and Department of Orthopedic Surgery MBispebjerg HospitalCopenhagenDenmark
| | - Simon Doessing
- Institute of Sports Medicine and Department of Orthopedic Surgery MBispebjerg HospitalCopenhagenDenmark
| | - Rasmus L. Bechshoeft
- Institute of Sports Medicine and Department of Orthopedic Surgery MBispebjerg HospitalCopenhagenDenmark
- Department of Biomedical SciencesFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Grith Højfeldt
- Institute of Sports Medicine and Department of Orthopedic Surgery MBispebjerg HospitalCopenhagenDenmark
| | - Marcus Moberg
- Aastrand LaboratorySwedish School of Sport and Health SciencesStockholmSweden
| | - Eva Blomstrand
- Aastrand LaboratorySwedish School of Sport and Health SciencesStockholmSweden
- Department of Physiology and PharmacologyKarolinska InstitutetStockholmSweden
| | - Søren Reitelseder
- Institute of Sports Medicine and Department of Orthopedic Surgery MBispebjerg HospitalCopenhagenDenmark
| | - Gerrit van Hall
- Department of Biomedical SciencesFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
- Clinical Metabolomics Core FacilityDepartment of Clinical Biochemistry, RigshospitaletCopenhagenDenmark
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12
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Church DD, Pasiakos SM, Wolfe RR, Ferrando AA. Acute testosterone administration does not affect muscle anabolism. Nutr Metab (Lond) 2019; 16:56. [PMID: 31440303 PMCID: PMC6704643 DOI: 10.1186/s12986-019-0385-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 08/12/2019] [Indexed: 02/03/2023] Open
Abstract
We previously demonstrated that improved net muscle protein balance, via enhanced protein synthetic efficiency, occurs 5 days after testosterone (T) administration. Whether the effects of T on muscle protein kinetics occur immediately upon exposure is not known. We investigated the effects of acute T exposure on leg muscle protein kinetics and selected amino acid (AA) transport using the arteriovenous balance model, and direct calculations of mixed-muscle protein fractional synthesis (FSR) and breakdown (FBR) rates. Four healthy men were studied over a 5 h period with and without T (infusion rate, 0.25 mg·min- 1). Muscle protein FSR, FBR, and net protein balance (direct measures and model derived) were not affected by T, despite a significant increases in arterial (p = 0.009) and venous (p = 0.064) free T area under the curve during T infusion. T infusion had minimal effects on AA transport kinetics, affecting only the outward transport and total intracellular rate of appearance of leucine. These data indicate that exposing skeletal muscle to T does not confer immediate effects on AA kinetics or muscle anabolism. There remains an uncertainty as to the earliest discernable effects of T on skeletal muscle protein kinetics after initial administration.
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Affiliation(s)
- David D Church
- 1Department of Geriatrics, Donald W. Reynolds Institute on Aging, Center for Translational Research in Aging & Longevity, University of Arkansas for Medical Sciences, Little Rock, AR 72205 USA
| | - Stefan M Pasiakos
- 2Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA USA
| | - Robert R Wolfe
- 1Department of Geriatrics, Donald W. Reynolds Institute on Aging, Center for Translational Research in Aging & Longevity, University of Arkansas for Medical Sciences, Little Rock, AR 72205 USA
| | - Arny A Ferrando
- 1Department of Geriatrics, Donald W. Reynolds Institute on Aging, Center for Translational Research in Aging & Longevity, University of Arkansas for Medical Sciences, Little Rock, AR 72205 USA
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13
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Church DD, Gwin JA, Wolfe RR, Pasiakos SM, Ferrando AA. Mitigation of Muscle Loss in Stressed Physiology: Military Relevance. Nutrients 2019; 11:nu11081703. [PMID: 31344809 PMCID: PMC6724061 DOI: 10.3390/nu11081703] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/15/2019] [Accepted: 07/22/2019] [Indexed: 12/14/2022] Open
Abstract
Military personnel may be exposed to circumstances (e.g., large energy deficits, sleep deprivation, cognitive demands, and environmental extremes) of external stressors during training and combat operations (i.e., operational stressors) that combine to degrade muscle protein. The loss of muscle protein is further exacerbated by frequent periods of severe energy deficit. Exposure to these factors results in a hypogonadal state that may contribute to observed decrements in muscle mass. In this review, lessons learned from studying severe clinical stressed states and the interventions designed to mitigate the loss of muscle protein are discussed in the context of military operational stress. For example, restoration of the anabolic hormonal status (e.g., testosterone, insulin, and growth hormone) in stressed physiological states may be necessary to restore the anabolic influence derived from dietary protein on muscle. Based on our clinical experiences, restoration of the normal testosterone status during sustained periods of operational stress may be advantageous. We demonstrated that in severe burn patients, pharmacologic normalization of the anabolic hormonal status restores the anabolic stimulatory effect of nutrition on muscle by improving the protein synthetic efficiency and limiting amino acid loss from skeletal muscle. Furthermore, an optimal protein intake, and in particular essential amino acid delivery, may be an integral ingredient in a restored anabolic response during the stress state. Interventions which improve the muscle net protein balance may positively impact soldier performance in trying conditions.
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Affiliation(s)
- David D Church
- Department of Geriatrics, Donald W. Reynolds Institute on Aging, Center for Translational Research in Aging & Longevity, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
| | - Jess A Gwin
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
- Oak Ridge Institute for Science and Education Supporting the Military Nutrition Division of the US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
| | - Robert R Wolfe
- Department of Geriatrics, Donald W. Reynolds Institute on Aging, Center for Translational Research in Aging & Longevity, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Stefan M Pasiakos
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
| | - Arny A Ferrando
- Department of Geriatrics, Donald W. Reynolds Institute on Aging, Center for Translational Research in Aging & Longevity, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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14
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Abstract
Muscle protein breakdown (MPB) is an important metabolic component of muscle remodeling, adaptation to training, and increasing muscle mass. Degradation of muscle proteins occurs via the integration of three main systems—autophagy and the calpain and ubiquitin-proteasome systems. These systems do not operate independently, and the regulation is complex. Complete degradation of a protein requires some combination of the systems. Determination of MPB in humans is technically challenging, leading to a relative dearth of information. Available information on the dynamic response of MPB primarily comes from stable isotopic methods with expression and activity measures providing complementary information. It seems clear that resistance exercise increases MPB, but not as much as the increase in muscle protein synthesis. Both hyperaminoacidemia and hyperinsulinemia inhibit the post-exercise response of MPB. Available data do not allow a comprehensive examination of the mechanisms behind these responses. Practical nutrition recommendations for interventions to suppress MPB following exercise are often made. However, it is likely that some degree of increased MPB following exercise is an important component for optimal remodeling. At this time, it is not possible to determine the impact of nutrition on any individual muscle protein. Thus, until we can develop and employ better methods to elucidate the role of MPB following exercise and the response to nutrition, recommendations to optimize post exercise nutrition should focus on the response of muscle protein synthesis. The aim of this review is to provide a comprehensive examination of the state of knowledge, including methodological considerations, of the response of MPB to exercise and nutrition in humans.
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15
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Wilkinson DJ. Historical and contemporary stable isotope tracer approaches to studying mammalian protein metabolism. MASS SPECTROMETRY REVIEWS 2018; 37:57-80. [PMID: 27182900 PMCID: PMC5763415 DOI: 10.1002/mas.21507] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 04/22/2016] [Indexed: 06/05/2023]
Abstract
Over a century ago, Frederick Soddy provided the first evidence for the existence of isotopes; elements that occupy the same position in the periodic table are essentially chemically identical but differ in mass due to a different number of neutrons within the atomic nucleus. Allied to the discovery of isotopes was the development of some of the first forms of mass spectrometers, driven forward by the Nobel laureates JJ Thomson and FW Aston, enabling the accurate separation, identification, and quantification of the relative abundance of these isotopes. As a result, within a few years, the number of known isotopes both stable and radioactive had greatly increased and there are now over 300 stable or radioisotopes presently known. Unknown at the time, however, was the potential utility of these isotopes within biological disciplines, it was soon discovered that these stable isotopes, particularly those of carbon (13 C), nitrogen (15 N), oxygen (18 O), and hydrogen (2 H) could be chemically introduced into organic compounds, such as fatty acids, amino acids, and sugars, and used to "trace" the metabolic fate of these compounds within biological systems. From this important breakthrough, the age of the isotope tracer was born. Over the following 80 yrs, stable isotopes would become a vital tool in not only the biological sciences, but also areas as diverse as forensics, geology, and art. This progress has been almost exclusively driven through the development of new and innovative mass spectrometry equipment from IRMS to GC-MS to LC-MS, which has allowed for the accurate quantitation of isotopic abundance within samples of complex matrices. This historical review details the development of stable isotope tracers as metabolic tools, with particular reference to their use in monitoring protein metabolism, highlighting the unique array of tools that are now available for the investigation of protein metabolism in vivo at a whole body down to a single protein level. Importantly, it will detail how this development has been closely aligned to the technological development within the area of mass spectrometry. Without the dedicated development provided by these mass spectrometrists over the past century, the use of stable isotope tracers within the field of protein metabolism would not be as widely applied as it is today, this relationship will no doubt continue to flourish in the future and stable isotope tracers will maintain their importance as a tool within the biological sciences for many years to come. © 2016 The Authors. Mass Spectrometry Reviews Published by Wiley Periodicals, Inc. Mass Spec Rev.
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Affiliation(s)
- Daniel James Wilkinson
- MRC‐ARUK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular PhysiologyUniversity of Nottingham, Royal Derby Hospital CentreDerbyUnited Kingdom
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16
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Rozance PJ, Zastoupil L, Wesolowski SR, Goldstrohm DA, Strahan B, Cree-Green M, Sheffield-Moore M, Meschia G, Hay WW, Wilkening RB, Brown LD. Skeletal muscle protein accretion rates and hindlimb growth are reduced in late gestation intrauterine growth-restricted fetal sheep. J Physiol 2017; 596:67-82. [PMID: 28940557 DOI: 10.1113/jp275230] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 09/12/2017] [Indexed: 12/29/2022] Open
Abstract
KEY POINTS Adults who were affected by intrauterine growth restriction (IUGR) suffer from reductions in muscle mass, which may contribute to insulin resistance and the development of diabetes. We demonstrate slower hindlimb linear growth and muscle protein synthesis rates that match the reduced hindlimb blood flow and oxygen consumption rates in IUGR fetal sheep. These adaptations resulted in hindlimb blood flow rates in IUGR that were similar to control fetuses on a weight-specific basis. Net hindlimb glucose uptake and lactate output rates were similar between groups, whereas amino acid uptake was significantly lower in IUGR fetal sheep. Among all fetuses, blood O2 saturation and plasma glucose, insulin and insulin-like growth factor-1 were positively associated and norepinephrine was negatively associated with hindlimb weight. These results further our understanding of the metabolic and hormonal adaptations to reduced oxygen and nutrient supply with placental insufficiency that develop to slow hindlimb growth and muscle protein accretion. ABSTRACT Reduced skeletal muscle mass in the fetus with intrauterine growth restriction (IUGR) persists into adulthood and may contribute to increased metabolic disease risk. To determine how placental insufficiency with reduced oxygen and nutrient supply to the fetus affects hindlimb blood flow, substrate uptake and protein accretion rates in skeletal muscle, late gestation control (CON) (n = 8) and IUGR (n = 13) fetal sheep were catheterized with aortic and femoral catheters and a flow transducer around the external iliac artery. Muscle protein kinetic rates were measured using isotopic tracers. Hindlimb weight, linear growth rate, muscle protein accretion rate and fractional synthetic rate were lower in IUGR compared to CON (P < 0.05). Absolute hindlimb blood flow was reduced in IUGR (IUGR: 32.9 ± 5.6 ml min-1 ; CON: 60.9 ± 6.5 ml min-1 ; P < 0.005), although flow normalized to hindlimb weight was similar between groups. Hindlimb oxygen consumption rate was lower in IUGR (IUGR: 10.4 ± 1.4 μmol min-1 100 g-1 ; CON: 14.7 ± 1.3 μmol min-1 100 g-1 ; P < 0.05). Hindlimb glucose uptake and lactate output rates were similar between groups, whereas amino acid uptake was lower in IUGR (IUGR: 1.3 ± 0.5 μmol min-1 100 g-1 ; CON: 2.9 ± 0.2 μmol min-1 100 g-1 ; P < 0.05). Blood O2 saturation (r2 = 0.80, P < 0.0001) and plasma glucose (r2 = 0.68, P < 0.0001), insulin (r2 = 0.40, P < 0.005) and insulin-like growth factor (IGF)-1 (r2 = 0.80, P < 0.0001) were positively associated and norepinephrine (r2 = 0.59, P < 0.0001) was negatively associated with hindlimb weight. Slower hindlimb linear growth and muscle protein synthesis rates match reduced hindlimb blood flow and oxygen consumption rates in the IUGR fetus. Metabolic adaptations to slow hindlimb growth are probably hormonally-mediated by mechanisms that include increased fetal norepinephrine and reduced IGF-1 and insulin.
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Affiliation(s)
- Paul J Rozance
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - Laura Zastoupil
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - Stephanie R Wesolowski
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - David A Goldstrohm
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - Brittany Strahan
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - Melanie Cree-Green
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - Melinda Sheffield-Moore
- Department of Internal Medicine, University of Texas Medical Branch, Division of Endocrinology, Galveston, TX, USA
| | - Giacomo Meschia
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - William W Hay
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - Randall B Wilkening
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
| | - Laura D Brown
- Department of Pediatrics, University of Colorado School of Medicine, Perinatal Research Center, Aurora, CO, USA
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17
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Mason A, Engelen MPKJ, Ivanov I, Toffolo GM, Deutz NEP. A four-compartment compartmental model to assess net whole body protein breakdown using a pulse of phenylalanine and tyrosine stable isotopes in humans. Am J Physiol Endocrinol Metab 2017; 313:E63-E74. [PMID: 28270442 PMCID: PMC6109702 DOI: 10.1152/ajpendo.00362.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 02/07/2017] [Accepted: 03/03/2017] [Indexed: 11/22/2022]
Abstract
The stable isotopes of phenylalanine (Phe) and tyrosine (Tyr) are often used to study whole body protein metabolism in humans. Noncompartmental approaches give limited physiological insight in the compartmental characteristics. We therefore developed a compartmental mathematical model of Phe/Tyr metabolism to describe protein fluxes by using stable tracer dynamic data in plasma following intravenous bolus of l-[ring-13C6]Phe and l-[ring-2H4]Tyr in healthy subjects. The model consists of four compartments describing Phe/Tyr kinetics. Because the model is a priori nonidentifiable, it is quantified in terms of two uniquely identifiable submodels representing two limit case scenarios, based on known physiology. The two submodels, identified by using the software SAAM II, fit well the experimental data of all individuals and provide an unbiased overview of the metabolic pathway in terms of intervals of validity of the non-uniquely identifiable variables. The model provides estimates of the flux from Phe to Tyr [4.1 ± 1.0 µmol·kg fat-free mass (FFM)-1·h-1 (mean ± SE)] and intervals of validity of the flux and pool estimates. Our preferred submodel yielded protein breakdown flux (50.5 ± 5.2 µmol·kg FFM-1·h-1), net protein breakdown (4.1 ± 1.0 µmol·kg FFM-1·h-1), Tyr from Phe hydroxylation (~12%), hydroxylated Phe (~8%), and flux ratio of Tyr to Phe arising from protein catabolism (0.68), consistent with available literature. The other submodel suggest that the assumptions made by noncompartmental analysis are consistently underestimated. Our accurate and detailed model for estimating Phe/Tyr metabolic pathways in humans might be essential to applications in a variety of scenarios describing whole body protein synthesis and breakdown in health and disease.
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Affiliation(s)
- Alvise Mason
- Center for Translational Research in Aging & Longevity, Department of Health and Kinesiology, Texas A&M University, College Station, Texas
- Department of Information Engineering, Universita' degli Studi di Padova, Padua, Italy; and
| | - Mariëlle P K J Engelen
- Center for Translational Research in Aging & Longevity, Department of Health and Kinesiology, Texas A&M University, College Station, Texas
| | - Ivan Ivanov
- Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas
| | - Gianna M Toffolo
- Department of Information Engineering, Universita' degli Studi di Padova, Padua, Italy; and
| | - Nicolaas E P Deutz
- Center for Translational Research in Aging & Longevity, Department of Health and Kinesiology, Texas A&M University, College Station, Texas;
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18
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Update on maximal anabolic response to dietary protein. Clin Nutr 2017; 37:411-418. [PMID: 28807333 DOI: 10.1016/j.clnu.2017.05.029] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 05/08/2017] [Accepted: 05/24/2017] [Indexed: 12/15/2022]
Abstract
The anabolic response to dietary protein can be defined as the difference between protein synthesis and breakdown, or the net protein balance, in response to ingestion of protein alone or a mixed meal containing protein. Others have concluded that a maximal anabolic response can be achieved with ingestion of 20-35 g of a high quality protein, leading to the formulation of a popular concept that the maximal anabolic response can be achieved by distributing the total protein intake evenly throughout the day, rather than eating a majority of dietary protein with dinner. However, this concept was based entirely on the measurement of muscle protein synthesis and thus ignored the potential contributions of suppression of protein breakdown to the anabolic response, as well as the possibility that tissues and organs other than muscle may also play a role in the anabolic response. In this review we discuss the factors comprising the total anabolic response, discuss relevant methodological issues, derive a theoretical maximal anabolic response based on current literature values, and interpret recent papers addressing the issue of maximal anabolic response as well as meal distribution of dietary protein. We conclude that it is not likely that there is a practical limit to the maximal anabolic response to a single meal, and the most efficient way in which to maximize the total anabolic response over a 24-h period is to increase dietary protein at breakfast and lunch without reducing protein intake with dinner.
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19
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Mitchell WK, Wilkinson DJ, Phillips BE, Lund JN, Smith K, Atherton PJ. Human Skeletal Muscle Protein Metabolism Responses to Amino Acid Nutrition. Adv Nutr 2016; 7:828S-38S. [PMID: 27422520 PMCID: PMC4942869 DOI: 10.3945/an.115.011650] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Healthy individuals maintain remarkably constant skeletal muscle mass across much of adult life, suggesting the existence of robust homeostatic mechanisms. Muscle exists in dynamic equilibrium whereby the influx of amino acids (AAs) and the resulting increases in muscle protein synthesis (MPS) associated with the intake of dietary proteins cancel out the efflux of AAs from muscle protein breakdown that occurs between meals. Dysregulated proteostasis is evident with aging, especially beyond the sixth decade of life. Women and men aged 75 y lose muscle mass at a rate of ∼0.7% and 1%/y, respectively (sarcopenia), and lose strength 2- to 5-fold faster (dynapenia) as muscle "quality" decreases. Factors contributing to the disruption of an otherwise robust proteostatic system represent targets for potential therapies that promote healthy aging. Understanding age-related impairments in anabolic responses to AAs and identifying strategies to mitigate these factors constitute major areas of interest. Numerous studies have aimed to identify 1) the influence of distinct protein sources on absorption kinetics and muscle anabolism, 2) the latency and time course of MPS responses to protein/AAs, 3) the impacts of protein/AA intake on muscle microvascular recruitment, and 4) the role of certain AAs (e.g., leucine) as signaling molecules, which are able to trigger anabolic pathways in tissues. This review aims to discuss these 4 issues listed, to provide historical and modern perspectives of AAs as modulators of human skeletal muscle protein metabolism, to describe how advances in stable isotope/mass spectrometric approaches and instrumentation have underpinned these advances, and to highlight relevant differences between young adults and older individuals. Whenever possible, observations are based on human studies, with additional consideration of relevant nonhuman studies.
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Affiliation(s)
- W Kyle Mitchell
- Department of Surgery, Royal Derby Hospital, Derby, United Kingdom; and
| | - Daniel J Wilkinson
- Medical Research Council, Arthritis Research United Kingdom, Centre of Excellence for Musculoskeletal Ageing Research, School of Medicine, Royal Derby Hospital, University of Nottingham, Derby, United Kingdom
| | - Bethan E Phillips
- Medical Research Council, Arthritis Research United Kingdom, Centre of Excellence for Musculoskeletal Ageing Research, School of Medicine, Royal Derby Hospital, University of Nottingham, Derby, United Kingdom
| | - Jonathan N Lund
- Department of Surgery, Royal Derby Hospital, Derby, United Kingdom; and,,Medical Research Council, Arthritis Research United Kingdom, Centre of Excellence for Musculoskeletal Ageing Research, School of Medicine, Royal Derby Hospital, University of Nottingham, Derby, United Kingdom
| | - Kenneth Smith
- Medical Research Council, Arthritis Research United Kingdom, Centre of Excellence for Musculoskeletal Ageing Research, School of Medicine, Royal Derby Hospital, University of Nottingham, Derby, United Kingdom
| | - Philip J Atherton
- Medical Research Council, Arthritis Research United Kingdom, Centre of Excellence for Musculoskeletal Ageing Research, School of Medicine, Royal Derby Hospital, University of Nottingham, Derby, United Kingdom
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20
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Applications of stable, nonradioactive isotope tracers in in vivo human metabolic research. Exp Mol Med 2016; 48:e203. [PMID: 26795236 PMCID: PMC4686699 DOI: 10.1038/emm.2015.97] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 10/06/2015] [Indexed: 12/28/2022] Open
Abstract
The human body is in a constant state of turnover, that is, being synthesized, broken down and/or converted to different compounds. The dynamic nature of in vivo kinetics of human metabolism at rest and in stressed conditions such as exercise and pathophysiological conditions such as diabetes and cancer can be quantitatively assessed with stable, nonradioactive isotope tracers in conjunction with gas or liquid chromatography mass spectrometry and modeling. Although measurements of metabolite concentrations have been useful as general indicators of one's health status, critical information on in vivo kinetics of metabolites such as rates of production, appearance or disappearance of metabolites are not provided. Over the past decades, stable, nonradioactive isotope tracers have been used to provide information on dynamics of specific metabolites. Stable isotope tracers can be used in conjunction with molecular and cellular biology tools, thereby providing an in-depth dynamic assessment of metabolic changes, as well as simultaneous investigation of the molecular basis for the observed kinetic responses. In this review, we will introduce basic principles of stable isotope methodology for tracing in vivo kinetics of human or animal metabolism with examples of quantifying certain aspects of in vivo kinetics of carbohydrate, lipid and protein metabolism.
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21
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Atherton PJ, Phillips BE, Wilkinson DJ. Exercise and Regulation of Protein Metabolism. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 135:75-98. [DOI: 10.1016/bs.pmbts.2015.06.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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22
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Sakurai Y. Response to nutritional support and therapeutic approaches of amino acid and protein metabolism in surgical patients. J Gastroenterol Hepatol 2013; 28 Suppl 4:123-30. [PMID: 24251718 DOI: 10.1111/jgh.12405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/17/2013] [Indexed: 01/23/2023]
Abstract
The response to critical illness involves alterations in all aspects of metabolic control, favoring catabolism of body protein. In particular, body protein loss occurring as a result of the alteration of protein metabolism has been reported to be inversely correlated with the survival of critically ill patients. Despite the availability of various therapeutic modalities aiming to prevent loss of the body protein pool, such as total parenteral nutrition, enteral nutrition designed to provide excessive calories as a form of energy substrate, and protein itself, the loss of body protein cannot be prevented by any of these. Loss of the boyd protein store occurs as a consequence of the alteration of the intermediate metabolism that works for the production of energy substrate. This alteration of substrate metabolism may be linked to the alteration of protein metabolism. However, no specific factors regulating amino acid and protein metabolism have been identified. Thus, further investigations evaluating amino acid and protein metabolism are required to obtain better understanding of metabolic regulation in the body, which may lead to the development of novel and more effective therapeutic modalities for nutrition in the future.
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Affiliation(s)
- Yoichi Sakurai
- Department of Surgery, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
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23
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Reitelseder S, Agergaard J, Doessing S, Helmark IC, Schjerling P, van Hall G, Kjaer M, Holm L. Positive muscle protein net balance and differential regulation of atrogene expression after resistance exercise and milk protein supplementation. Eur J Nutr 2013; 53:321-33. [DOI: 10.1007/s00394-013-0530-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 04/21/2013] [Indexed: 11/24/2022]
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24
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Holm L, O'Rourke B, Ebenstein D, Toth MJ, Bechshoeft R, Holstein-Rathlou NH, Kjaer M, Matthews DE. Determination of steady-state protein breakdown rate in vivo by the disappearance of protein-bound tracer-labeled amino acids: a method applicable in humans. Am J Physiol Endocrinol Metab 2013; 304:E895-907. [PMID: 23423170 PMCID: PMC3625778 DOI: 10.1152/ajpendo.00579.2012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A method to determine the rate of protein breakdown in individual proteins was developed and tested in rats and confirmed in humans, using administration of deuterium oxide and incorporation of the deuterium into alanine that was subsequently incorporated into body proteins. Measurement of the fractional breakdown rate of proteins was determined from the rate of disappearance of deuterated alanine from the proteins. The rate of disappearance of deuterated alanine from the proteins was calculated using an exponential decay, giving the fractional breakdown rate (FBR) of the proteins. The applicability of this protein-specific FBR approach is suitable for human in vivo experimentation. The labeling period of deuterium oxide administration is dependent on the turnover rate of the protein of interest.
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Affiliation(s)
- Lars Holm
- Institute of Sports Medicine, Department of Orthopedic Surgery M81, Bispebjerg Hospital, and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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Tuvdendorj D, Chinkes DL, Herndon DN, Zhang XJ, Wolfe RR. A novel stable isotope tracer method to measure muscle protein fractional breakdown rate during a physiological non-steady-state condition. Am J Physiol Endocrinol Metab 2013; 304:E623-30. [PMID: 23321475 PMCID: PMC3602693 DOI: 10.1152/ajpendo.00552.2012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The measurement of the fractional breakdown rate (FBR) of muscle proteins during physiological non-steady state of amino acids (AAs) presents some challenges. Therefore, the goal of the present experiment was to modify the bolus stable isotope tracer injection approach to determine both fractional synthesis rate (FSR) and FBR of leg muscle protein during a physiological non-steady state of AAs. The approach uses the traditional precursor-product principle but is modified with the assumption that inward transport of AAs is proportional to their plasma concentrations. The FBR value calculated from the threonine tracer served as a reference to evaluate the validity of the FBR measurement from the phenylalanine tracer, which was under a non-steady-state condition due to the concomitant injection of unlabeled phenylalanine. Plasma phenylalanine concentration increased more than fourfold after the bolus injection, and thereafter it decreased exponentially, whereas the threonine concentration remained stable. FBR values were similar with the two tracers [0.133 ± 0.003 and 0.148 ± 0.003%/h (means ± SE) for the phenylalanine and threonine tracers, respectively, P > 0.05]. In addition, FSR values for the two tracers were similar (0.069 ± 0.002 and 0.067 ± 0.001%/h for the phenylalanine and threonine tracers, respectively, P > 0.05), indicating that the traditional FSR approach can also be used in the non-steady state. Accordingly, net balance (NB) values were similar (-0.065 ± 0.002 and -0.081 ± 0.002%/h for the phenylalanine and threonine tracers, respectively, P > 0.05). This new method of measuring muscle protein FBR during physiological non-steady state gives reliable results and allows simultaneous measurement of muscle protein FSR and thus a calculation of NB.
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Irving BA, Robinson MM, Nair KS. Age effect on myocellular remodeling: response to exercise and nutrition in humans. Ageing Res Rev 2012; 11:374-89. [PMID: 22085885 DOI: 10.1016/j.arr.2011.11.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 10/27/2011] [Accepted: 11/01/2011] [Indexed: 12/25/2022]
Abstract
Aging is associated with decline in muscle mass and muscle functions. Muscle strength declines disproportionate to the decline in muscle mass indicating that muscle quality or protein quality also declines with age. Human studies have shown a progressive decline in muscle protein synthesis including proteins in the contractile apparatus and mitochondria with age. However, the decline in muscle protein synthesis is disproportionate to the decline in muscle mass that occurs with age prompting to hypothesize that muscle protein degradation also declines with age. A decline in mitochondrial capacity to synthesize ATP is likely a limiting factor of both synthesis and degradation, which are ATP dependent processes. In support of the above hypothesis, several studies have shown a decline in whole body protein turnover (synthesis and degradation). The timely and efficient degradation of irreversibly damaged or modified proteins is critical to maintain the quality of protein. It is proposed that a failure to degrade the damaged proteins and replacing them with newly synthesized proteins contribute to age related decline in muscle mass and quality of muscle proteins. The underlying molecular mechanism of these age related changes in human muscle needs further investigation.
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Tuvdendorj D, Chinkes DL, Zhang XJ, Ferrando AA, Elijah IE, Mlcak RP, Finnerty CC, Wolfe RR, Herndon DN. Adult patients are more catabolic than children during acute phase after burn injury: a retrospective analysis on muscle protein kinetics. Intensive Care Med 2011; 37:1317-22. [PMID: 21647721 PMCID: PMC3280820 DOI: 10.1007/s00134-011-2223-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 03/01/2011] [Indexed: 11/28/2022]
Abstract
PURPOSE This study was performed to determine if there is an age-related specificity in the response of muscle protein metabolism to severe burn injury during acute hospitalization. This is a retrospective analysis of previously published data. METHODS Nineteen adult and 58 pediatric burn-injured patients (age 43.3 ± 14.3 vs. 7.2 ± 5.3 years, adult vs. children) participated in stable isotope [ring-(2)H(5)]phenylalanine (Phe) infusion studies. Femoral arterial and venous blood samples and muscle biopsy samples were collected throughout the study. Data are presented as means ± standard deviation (SD). A p value less than 0.05 was considered statistically significant. RESULTS Muscle net protein balance (NB) was higher in children (adult vs. children, -43 ± 61 vs. 8 ± 68 nmol Phe/min/100 ml leg volume, p < 0.05). Muscle protein fractional synthesis rate (FSR) was higher in children (adult vs. children, 0.11 ± 0.05 vs. 0.16 ± 0.10 %/h, p < 0.05). Leg muscle protein breakdown was not different between the groups (adult vs. children, 179 ± 115 vs. 184 ± 124 nmol Phe/min/100 ml leg volume, p > 0.05); synthesis rate was 134 ± 96 and 192 ± 128 nmol Phe/min/100 ml leg volume in adults and children, respectively (p = 0.07). Age significantly correlated with muscle protein NB (p = 0.01) and FSR (p = 0.02); but not with breakdown (p = 0.67) and synthesis (p = 0.07) rates measured by using a three-pool model. CONCLUSION In burn injury, the muscle protein breakdown may be affected to the same extent in adults and children, whereas synthesis may have age-related specificities, resulting in a better but still low NB in children.
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Affiliation(s)
- Demidmaa Tuvdendorj
- Department of Surgery, Metabolism Unit, Shriners Hospital for Children, University of Texas Medical Branch, 815 Market Street, Galveston, TX 77555-1220, USA
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Bermingham EN, McNabb WC, Sinclair BR, Tavendale MH, Roy NC. Valine partitioning and kinetics between the gastrointestinal tract and hind limbs in lambs with an adult Trichostrongylus colubriformis burden. J Anim Sci 2011; 89:3501-13. [PMID: 21622879 DOI: 10.2527/jas.2010-3145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Intestinal parasitic infection increases the demand for AA because of increased protein synthesis in the intestine and increased luminal losses of AA, and these increased demands may be supported by increased mobilization of AA from the skeletal muscles. Two experiments were conducted to determine the effects of parasitic infection on valine kinetics within the gastrointestinal tract and hind limbs of lambs fed fresh forages. On d 1, lambs were given 6,000 stage-3 Trichostrongylus colubriformis larvae per day for 6 d (n = 6) or kept as parasite-free controls (n = 6) and fed fresh lucerne (Medicago sativa; Exp. 1) or fresh sulla (Hedysarum coronarium; Exp. 2). On d 48, valine kinetics within the mesenteric- (MDV) and portal-drained viscera (PDV) and hind limbs were obtained by carrying out concurrent infusions of para-amminohippuric acid into the mesenteric vein and indocyanin green into the abdominal aorta (for blood flow), and [3,4-(3)H]valine into the jugular vein and [1-(13)C]valine into the abomasum for 8 h (for kinetics). During the infusions, blood was collected from the mesenteric and portal veins and from the mesenteric artery and vena cava, and plasma was harvested. After the 8-h infusion, lambs were euthanized, ileal digesta were collected, and tissues were sampled from the intestine and muscle (biceps femoris). Tissues, digesta, and plasma were analyzed for valine concentration, specific radioactivity, and isotopic enrichment. In both experiments, intestinal worm burdens on d 48 were greater in parasitized lambs (P = 0.0001 and 0.003). In Exp. 1, parasitic infection increased (P = 0.03) the total valine irreversible loss rate (ILR) in the MDV and PDV. In Exp. 2, luminal ILR of valine in the MDV was reduced (P = 0.01); however, ILR of valine in the PDV was unaffected. Despite these changes within the MDV and PDV, parasitic infection did not affect the ILR of valine within the hind limbs, and valine transport rates were largely unchanged. We suggest that the increased mobilization of AA from the hind limbs that might have occurred in the early phase of inflammation was no longer required when the parasitic infection was established. The MDV and PDV data may indicate that the non-MDV parts of the PDV play an important role in this adaptation, which warrants further study.
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Affiliation(s)
- E N Bermingham
- Food, Nutrition Genomics, Food and Bio-Based Products, AgResearch Grasslands, Palmerston North, New Zealand.
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Abstract
PURPOSE OF REVIEW To outline different approaches of how protein breakdown can be quantified and to present a new approach to determine the fractional breakdown rate of individual slow turnover proteins in vivo. RECENT FINDINGS None of the available methods for determining protein breakdown can be used to determine the breakdown rate of specific proteins and, therefore, do not keep up to the preceding methodological demands in physiological research. A newly developed approach to determine the fractional breakdown rate of single proteins seems promising. Its conceptual advantage is that the proteins of interest are the site of measurement. Hence, the application initially demands the proteins to be labeled with stable isotopically labeled amino acids. Subsequently, the loss of label from the proteins will be dependent on the protein breakdown rate when no labeled amino acids are reincorporated into the protein, the protein mass is steady, and when proteins contained in the measured fraction are stochastically selected for degradation. SUMMARY Although the synthesis rate of specific proteins can be accurately determined, methodological improvements are required to elucidate the physiological role of protein degradation. The novel approach is promising but future studies are needed to address its wider applicability.
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Affiliation(s)
- Lars Holm
- Institute of Sports Medicine and Department of Orthopedic Surgery, Bispebjerg Hospital and Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
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Glynn EL, Fry CS, Drummond MJ, Dreyer HC, Dhanani S, Volpi E, Rasmussen BB. Muscle protein breakdown has a minor role in the protein anabolic response to essential amino acid and carbohydrate intake following resistance exercise. Am J Physiol Regul Integr Comp Physiol 2010; 299:R533-40. [PMID: 20519362 DOI: 10.1152/ajpregu.00077.2010] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Muscle protein breakdown (MPB) is increased following resistance exercise, but ingestion of carbohydrate during postexercise recovery can decrease MPB with no effect on muscle protein synthesis (MPS). We sought to determine whether a combination of essential amino acids (EAA) with low carbohydrate or high carbohydrate could effectively reduce MPB following resistance exercise and improve muscle protein net balance (NB). We hypothesized that higher levels of carbohydrate and resulting increases in circulating insulin would inhibit MPB and associated signaling, resulting in augmented NB. Thirteen male subjects were assigned to one of two groups receiving equivalent amounts of EAA (approximately 20 g) but differing carbohydrate levels (low = 30, high = 90 g). Groups ingested nutrients 1 h after an acute bout of leg resistance exercise. Leg phenylalanine kinetics (e.g., MPB, MPS, NB), signaling proteins, and mRNA expression were assessed on successive muscle biopsies using stable isotopic techniques, immunoblotting, and real-time quantitative PCR, respectively. MPB tended to decrease (P < 0.1) and MPS increased (P < 0.05) similarly in both groups following nutrient ingestion. No group differences were observed, but muscle ring finger 1 (MuRF1) protein content and MuRF1 mRNA expression increased following resistance exercise and remained elevated following nutrient ingestion, while autophagy marker (light-chain 3B-II) decreased after nutrient ingestion (P < 0.05). Forkhead box-O3a phosphorylation, total muscle atrophy F-box (MAFbx) protein, and MAFbx and caspase-3 mRNA expression were unchanged. We conclude that the enhanced muscle protein anabolic response detected when EAA+carbohydrate are ingested postresistance exercise is primarily due to an increase in MPS with minor changes in MPB, regardless of carbohydrate dose or circulating insulin level.
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Affiliation(s)
- Erin L Glynn
- Univ. of Texas Medical Branch, Dept. of Physical Therapy, Galveston, TX 77555-1144, USA
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Protein metabolism in leg muscle following an endotoxin injection in healthy volunteers. Clin Sci (Lond) 2009; 118:421-7. [DOI: 10.1042/cs20090332] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The human endotoxin model has been used to study the early phase of sepsis. The aim of the present study was to assess leg muscle protein kinetics after an endotoxin challenge given to healthy human volunteers. Six healthy male subjects were studied in the post-absorptive state before and during 4 h following an intravenous endotoxin bolus (4 ng/kg of body weight). Primed continuous infusion of [2H5]phenylalanine and [2H3]3-methylhistidine in combination with sampling from the radial artery, femoral vein and muscle tissue were used to assess leg muscle protein kinetics. Both two- and three-compartment models were used to calculate protein kinetics. In addition 26S proteasome activity and protein ubiquitination were assessed. An increase in the net release of phenylalanine from the leg following the endotoxin challenge was observed; however, this phenylalanine originates from the free intracellular pool and not from protein. Net protein balance was unchanged, whereas both protein synthesis and breakdown were decreased. Degradation rates of contractile proteins were not affected by endotoxin, as indicated by an unchanged rate of appearance of 3-methylhistidine from leg muscle. In addition, proteasome activity and protein ubiquitination were unaffected by endotoxaemia. In conclusion, intravenous endotoxin administration to healthy volunteers resulted in an increased release of free phenylalanine from skeletal muscle, whereas protein balance was unaffected. Both protein synthesis and breakdown were decreased to a similar extent.
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Hanigan MD, France J, Mabjeesh SJ, McNabb WC, Bequette BJ. High rates of mammary tissue protein turnover in lactating goats are energetically costly. J Nutr 2009; 139:1118-27. [PMID: 19403714 DOI: 10.3945/jn.108.103002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The high energetic demands and metabolism of amino acids (AA) within the lactating mammary gland have been ascribed to the requirements for milk component synthesis and tissue maintenance. Our objective in this work was to assess rates of protein synthesis from several AA so that the energetic costs of tissue maintenance could be better reflected. Lactating goats (n = 4) were given staggered infusions of 5 labeled forms of phenylalanine (Phe) initiated at 30, 12, 9, 6, and 3 h before goats were killed. [5-(13)CH(3)] Methionine (Met), [1-(13)C] leucine, and [1-(13)C] valine were also infused for 30 h, during which time, the glands were milked hourly and arteriovenous flux measurements were performed the last 6 h. A dynamic, compartmental model capable of simulating fluxes of AA through extracellular and intracellular free, slow and fast turnover tissue-bound, and milk protein pools was developed and fitted to the observed data. The udder removed 81% of the Phe present in plasma using 31% for milk protein synthesis and releasing 66% back into plasma. Transamination accounted for 40% of Phe flux in the mammary and transmethylation accounted for a portion of mammary Met flux. Mammary tissue protein synthesis was >300% the value of milk protein synthesis with fractional protein synthesis rates >130%/d. Assuming 4 mol of ATP/mol of peptide bond formed, we estimate that approximately 50% of ATP generated by the lactating mammary glands is used for synthesis of tissue (nonmilk) protein.
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Affiliation(s)
- Mark D Hanigan
- Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
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Juillet B, Bos C, Gaudichon C, Tomé D, Fouillet H. Parameter estimation for linear compartmental models--a sensitivity analysis approach. Ann Biomed Eng 2009; 37:1028-42. [PMID: 19225890 DOI: 10.1007/s10439-009-9651-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Accepted: 02/06/2009] [Indexed: 11/29/2022]
Abstract
Linear compartmental models are useful, explanatory tools, that have been widely used to represent the dynamic behavior of complex biological systems. This paper addresses the problem of the numerical identification of such models, i.e., the estimation of the parameter values that will generate predictions closest to experimental observations. Traditional local optimization techniques find it difficult to arrive at satisfactory solutions to such a parameter estimation problem, especially when the number of parameters is large and/or few data are available from experiments. We present herewith a method based on a prior sensitivity analysis, which enables division of a large optimization problem into several smaller and simpler subproblems, on which only sensitive parameters are estimated, before the whole optimization problem is tackled from starting points that are already close to the optimum values. This method has been applied successfully to a linear 13-compartment, 21-parameter model describing the postprandial metabolism of dietary nitrogen in humans. The effectiveness of the method has been demonstrated using simulated and real data obtained in the intestine, blood and urine of healthy humans after the ingestion of a [(15)N]-labeled protein meal.
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Affiliation(s)
- Barbara Juillet
- UMR914 Nutrition Physiology and Ingestive Behavior, INRA, AgroParisTech, CRNH-IdF, 16 rue Claude Bernard, F-75005, Paris, France
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Zhang XJ, Chinkes DL, Wolfe RR. The anabolic effect of arginine on proteins in skin wound and muscle is independent of nitric oxide production. Clin Nutr 2008; 27:649-56. [DOI: 10.1016/j.clnu.2008.01.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Revised: 10/21/2007] [Accepted: 01/11/2008] [Indexed: 11/17/2022]
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van Hall G, Steensberg A, Fischer C, Keller C, Møller K, Moseley P, Pedersen BK. Interleukin-6 markedly decreases skeletal muscle protein turnover and increases nonmuscle amino acid utilization in healthy individuals. J Clin Endocrinol Metab 2008; 93:2851-8. [PMID: 18430776 DOI: 10.1210/jc.2007-2223] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
CONTEXT IL-6 is a key modulator of immune function and suggested to be involved in skeletal muscle wasting as seen in sepsis. OBJECTIVE Our objective was to determine the role of IL-6 in human in vivo systemic and skeletal muscle amino acid metabolism and protein turnover. SUBJECTS AND METHODS There were 12 healthy men infused for 3 h with saline (saline, n = 6) or recombinant human IL (rhIL)-6 (n = 6). Systemic and muscle protein turnover was determined with a combination of tracer dilution methodology, primed constant infusion of L-[ring-(2)H(5)]phenylalanine, and femoral arterial-venous blood differences and m. vastus lateralis biopsies after 2-h basal, 3-h infusion, and 3 h after infusion. RESULTS The IL-6 concentration after 30-min infusion was approximately 4 (saline) and 140 pg/ml (rhIL-6). Three-hour rhIL-6 infusion caused an approximate 50% decrease in muscle protein turnover, albeit synthesis was more suppressed than breakdown, causing a small increase in net muscle protein breakdown. Furthermore, rhIL-6 decreased arterial amino acid concentration with 20-40%, despite the increase net release from muscle. CONCLUSIONS We demonstrated that IL-6 profoundly alters amino acid turnover. A substantial decrease in plasma amino acids was observed with a concomitant 50% decrease in muscle protein turnover, however, modest increase in net muscle degradation. We hypothesize that the profound reduction in muscle protein turnover and modest increase in net degradation are primarily caused by the reduced plasma amino acid availability and not directly mediated by IL-6.
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Affiliation(s)
- Gerrit van Hall
- Copenhagen Muscle Research Centre, Rigshospitalet, 9 Blegdamsvej, Copenhagen Ø, Denmark.
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Zhang XJ, Irtun O, Chinkes DL, Wolfe RR. Acute responses of muscle protein metabolism to reduced blood flow reflect metabolic priorities for homeostasis. Am J Physiol Endocrinol Metab 2008; 294:E551-7. [PMID: 18089763 DOI: 10.1152/ajpendo.00467.2007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The present experiment was designed to measure the synthetic and breakdown rates of muscle protein in the hindlimb of rabbits with or without clamping the femoral artery. l-[ring-(13)C(6)]phenylalanine was infused as a tracer for measurement of muscle protein kinetics by means of an arteriovenous model, tracer incorporation, and tracee release methods. The ultrasonic flowmeter, dye dilution, and microsphere methods were used to determine the flow rates in the femoral artery, in the leg, and in muscle capillary, respectively. The femoral artery flow accounted for 65% of leg flow. A 50% reduction in the femoral artery flow reduced leg flow by 28% and nutritive flow by 26%, which did not change protein synthetic or breakdown rate in leg muscle. Full clamp of the femoral artery reduced leg flow by 42% and nutritive flow by 59%, which decreased (P < 0.05) both the fractional synthetic rate from 0.19 +/- 0.05 to 0.14 +/- 0.03%/day and fractional breakdown rate from 0.28 +/- 0.07 to 0.23 +/- 0.09%/day of muscle protein. Neither the partial nor full clamp reduced (P = 0.27-0.39) the intracellular phenylalanine concentration or net protein balance in leg muscle. We conclude that the flow threshold to cause a fall of protein turnover rate in leg muscle was a reduction of 30-40% of the leg flow. The acute responses of muscle protein kinetics to the reductions in blood flow reflected the metabolic priorities to maintain muscle homeostasis. These findings cannot be extrapolated to more chronic conditions without experimental validation.
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Affiliation(s)
- Xiao-Jun Zhang
- Metabolism Unit, Shriners Hospital for Children, The University of Texas Medical Branch, Galveston, Texas, USA
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Fujita S, Dreyer HC, Drummond MJ, Glynn EL, Cadenas JG, Yoshizawa F, Volpi E, Rasmussen BB. Nutrient signalling in the regulation of human muscle protein synthesis. J Physiol 2007; 582:813-23. [PMID: 17478528 PMCID: PMC2075348 DOI: 10.1113/jphysiol.2007.134593] [Citation(s) in RCA: 224] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) are important nutrient- and energy-sensing and signalling proteins in skeletal muscle. AMPK activation decreases muscle protein synthesis by inhibiting mTOR signalling to regulatory proteins associated with translation initiation and elongation. On the other hand, essential amino acids (leucine in particular) and insulin stimulate mTOR signalling and protein synthesis. We hypothesized that anabolic nutrients would be sensed by both AMPK and mTOR, resulting in an acute and potent stimulation of human skeletal muscle protein synthesis via enhanced translation initiation and elongation. We measured muscle protein synthesis and mTOR-associated upstream and downstream signalling proteins in young male subjects (n=14) using stable isotopic and immunoblotting techniques. Following a first muscle biopsy, subjects in the 'Nutrition' group ingested a leucine-enriched essential amino acid-carbohydrate mixture (EAC). Subjects in the Control group did not consume nutrients. A second biopsy was obtained 1 h later. Ingestion of EAC significantly increased muscle protein synthesis, modestly reduced AMPK phosphorylation, and increased Akt/PKB (protein kinase B) and mTOR phosphorylation (P<0.05). mTOR signalling to its downstream effectors (S6 kinase 1 (S6K1) and 4E-binding protein 1 (4E-BP1) phosphorylation status) was also increased (P<0.05). In addition, eukaryotic elongation factor 2 (eEF2) phosphorylation was significantly reduced (P<0.05). Protein synthesis and cell signalling (phosphorylation status) was unchanged in the control group (P>0.05). We conclude that anabolic nutrients alter the phosphorylation status of both AMPK- and mTOR-associated signalling proteins in human muscle, in association with an increase in protein synthesis not only via enhanced translation initiation but also through signalling promoting translation elongation.
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Affiliation(s)
- Satoshi Fujita
- University of Texas Medical Branch, Department of Internal Medicine, Galveston, TX 77555-1144, USA
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Tipton KD, Sharp CP. The response of intracellular signaling and muscle-protein metabolism to nutrition and exercise. Eur J Sport Sci 2007. [DOI: 10.1080/17461390500233607] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Paddon-Jones D, Sheffield-Moore M, Cree MG, Hewlings SJ, Aarsland A, Wolfe RR, Ferrando AA. Atrophy and impaired muscle protein synthesis during prolonged inactivity and stress. J Clin Endocrinol Metab 2006; 91:4836-41. [PMID: 16984982 DOI: 10.1210/jc.2006-0651] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
CONTEXT We recently demonstrated that 28-d bed rest in healthy volunteers results in a moderate loss of lean leg mass and strength. OBJECTIVE The objective of this study was to quantify changes in muscle protein kinetics, body composition, and strength during a clinical bed rest model reflecting both physical inactivity and the hormonal stress response to injury or illness. DESIGN Muscle protein kinetics were calculated during a primed, continuous infusion (0.08 micromol/kg.min) of 13C6-phenylalanine on d 1 and 28 of bed rest. SETTING The setting for this study was the General Clinical Research Center at the University of Texas Medical Branch. PARTICIPANTS Participants were healthy male volunteers (n = 6, 28 +/- 2 yr, 84 +/- 4 kg, 178 +/- 3 cm). INTERVENTION During bed rest, hydrocortisone sodium succinate was administered iv (d 1 and 28) and orally (d 2-27) to reproduce plasma cortisol concentrations consistent with trauma or illness (approximately 22 microg/dl). MAIN OUTCOME MEASURES We hypothesized that inactivity and hypercortisolemia would reduce lean muscle mass, leg extension strength, and muscle protein synthesis. RESULTS Volunteers experienced a 28.4 +/- 4.4% loss of leg extension strength (P = 0.012) and a 3-fold greater loss of lean leg mass (1.4 +/- 0.1 kg) (P = 0.004) compared with our previous bed rest-only model. Net protein catabolism was primarily due to a reduction in muscle protein synthesis [fractional synthesis rate, 0.081 +/- 0.004 (d 1) vs. 0.054 +/- 0.007%/h (d 28); P = 0.023]. There was no change in muscle protein breakdown. CONCLUSION Prolonged inactivity and hypercortisolemia represents a persistent catabolic stimulus that exacerbates strength and lean muscle loss via a chronic reduction in muscle protein synthesis.
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Affiliation(s)
- Douglas Paddon-Jones
- Department of Surgery, The University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77550, USA.
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Gore DC, Chinkes DL, Wolf SE, Sanford AP, Herndon DN, Wolfe RR. Quantification of protein metabolism in vivo for skin, wound, and muscle in severe burn patients. JPEN J Parenter Enteral Nutr 2006; 30:331-8. [PMID: 16804131 DOI: 10.1177/0148607106030004331] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND In response to injury, muscle catabolism can be extensive, and in theory, the wound consumes amino acids to support healing. The purpose of this study is to assess a technique by which in vivo protein kinetics of muscle, wound, and normal skin can be quantified in burn-injured patients. METHODS Study protocol consisting of infusion of d5 phenylalanine; biopsies of skeletal muscle, skin, and donor-site wound on the leg; quantification of blood flow to total leg, wound, and skin; and sequential blood sampling from the femoral artery and vein. Five-compartment modeling was used to quantify the rates of protein synthesis, breakdown, and phenylalanine transport between muscle, wound, and skin. RESULTS The study results demonstrated a net release of phenylalanine from muscle yet a net consumption of phenylalanine by the wound. Compared with skin, the wound had a substantially increased rate of protein synthesis and a reduced rate of protein breakdown (p < .01). Transport rates into and out of muscle were significantly higher than those for wound (p < .01). CONCLUSIONS This novel methodology enables in vivo quantification of the integrated response of muscle, wound, and skin protein/amino acid metabolism and confirms the long-held theory of a net catabolism of muscle and a net anabolism of wound protein in patients after injury. This methodology can be used to assess the metabolic impact of such measures as nutrition, pharmacologic agents, and surgical procedures.
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Affiliation(s)
- Dennis C Gore
- Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77555-1172, USA.
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Holm L, Esmarck B, Mizuno M, Hansen H, Suetta C, Hölmich P, Krogsgaard M, Kjaer M. The effect of protein and carbohydrate supplementation on strength training outcome of rehabilitation in ACL patients. J Orthop Res 2006; 24:2114-23. [PMID: 16917926 DOI: 10.1002/jor.20147] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Patients with anterior cruciate ligament (ACL) injury experience atrophy and weakening of the extensor as well as the hamstrings muscles at the injured leg. Especially, the weakness of the quadriceps muscle has been ascribed to hamper daily physical tasks. The purpose of the present study was therefore to investigate if nutrient supplementation during 12 weeks of conservative rehabilitation strength training could enhance hypertrophy and strength of the quadriceps muscle in ACL-injured patients. Twenty-six ACL-injured men and women were included and randomly distributed into three supplementation groups: Protein+Carbohydrate (PC), Isocaloric-Carbohydrate (IC), or Placebo (PL), ingesting the supplementation immediately after each of 36 training sessions. Determined from images of thigh cross-sections (magnetic resonance imaging) the hypertrophy of the quadriceps muscle differed significantly between groups at the distal part, with the PC group demonstrating the largest hypertrophy. Peak torque of the quadriceps muscle at constant velocity 60 degrees.s-1 was significantly elevated in the PC group only, and the time to reach peak torque tended to decrease as well only in the PC group. The results from this study demonstrate that restoration of the distal vasti muscle mass and knee extension muscle strength with resistance training is promoted further by protein-containing nutrient supplementation immediately after single exercise sessions. Thus, exercise-related protein supplementation may seem important for surgery-related rehabilitation of skeletal muscle.
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Affiliation(s)
- L Holm
- Institute of Sports Medicine, Copenhagen, Bispebjerg Hospital, Bispebjerg Bakke 23, Bldg. 8, 1st, 2400 København NV, Copenhagen, Denmark.
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Chow LS, Albright RC, Bigelow ML, Toffolo G, Cobelli C, Nair KS. Mechanism of insulin's anabolic effect on muscle: measurements of muscle protein synthesis and breakdown using aminoacyl-tRNA and other surrogate measures. Am J Physiol Endocrinol Metab 2006; 291:E729-36. [PMID: 16705065 DOI: 10.1152/ajpendo.00003.2006] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Despite being an anabolic hormone in skeletal muscle, insulin's anticatabolic mechanism in humans remains controversial, with contradictory reports showing either stimulation of protein synthesis (PS) or inhibition of protein breakdown (PB) by insulin. Earlier measurements of muscle PS and PB in humans have relied on different surrogate measures of aminoacyl-tRNA and intracellular pools. We report that insulin's effect on muscle protein turnover using aminoacyl-tRNA as the precursor of PS and PB is calculated by mass balance of tracee amino acid (AA). We compared the results calculated from various surrogate measures. To determine the physiological role of insulin on muscle protein metabolism, we infused tracers of leucine and phenylalanine into 18 healthy subjects, and after 3 h, 10 subjects received a 4-h femoral arterial infusion of insulin (0.125 mUxkg(-1)xmin(-1)), while eight subjects continued with saline. Tracer-to-tracee ratios of leucine, phenylalanine, and ketoisocaproate were measured in the arterial and venous plasma, muscle tissue fluid, and AA-tRNA to calculate muscle PB and PS. Insulin infusion, unlike saline, significantly reduced the efflux of leucine and phenylalanine from muscle bed, based on various surrogate measures which agreed with those based on leucyl-tRNA (-28%), indicating a reduction in muscle PB (P < 0.02) without any significant effect on muscle PS. In conclusion, using AA-tRNA as the precursor pool, it is demonstrated that, in healthy humans in the postabsorptive state, insulin does not stimulate muscle protein synthesis and confirmed that insulin achieves muscle protein anabolism by inhibition of muscle protein breakdown.
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Affiliation(s)
- Lisa S Chow
- Division of Endocrinology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905, USA
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Gore DC, Wolfe RR. Hemodynamic and metabolic effects of selective beta1 adrenergic blockade during sepsis. Surgery 2006; 139:686-94. [PMID: 16701103 DOI: 10.1016/j.surg.2005.10.010] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Revised: 10/27/2005] [Accepted: 10/29/2005] [Indexed: 11/18/2022]
Abstract
BACKGROUND Selective beta adrenergic antagonists are commonly used to reduce myocardial demise in patients at risk for cardiac-related death. The purpose of this study was to examine the hemodynamic and metabolic effects of cardiac selective beta adrenergic blockade in patients. METHODS Muscle protein kinetics were quantified using isotopic tracer methodology in 6 moderately septic, mechanically ventilated patients with pneumonia before and then at the conclusion of a 3-hour infusion of esmolol of sufficient dose to reduce heart rate by 20% from baseline. A battery of hemodynamic measurements as facilitated by a thermodilution pulmonary artery catheter and indirect calorimetry were also measured before and after the 3-hour selective beta adrenergic blockade. RESULTS Selective beta adrenergic blockade was associated with the 20% reduction in heart rate and a comparable decrease in cardiac output. Esmolol administration failed to affect systemic or pulmonary vascular resistance, oxygen consumption, hepatic or leg blood flow, energy expenditure, or ATP availability/energy charge within muscle. Esmolol infuse did incite a shift in fuel oxidation toward an increase in palmitate oxidation and with a decrease in the oxidation of glucose. There was no demonstrable influence beta1 adrenergic blockade on muscle protein kinetics. CONCLUSIONS Cardiac selective beta adrenergic blockade with esmolol reduces cardiac output in proportion to the percentage decreases in heart rate in moderately severe septic patients without adversely affecting oxygen utilization or hepatic, peripheral blood flow.
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Affiliation(s)
- Dennis C Gore
- Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
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Børsheim E, Kobayashi H, Traber DL, Wolfe RR. Compartmental distribution of amino acids during hemodialysis-induced hypoaminoacidemia. Am J Physiol Endocrinol Metab 2006; 290:E643-52. [PMID: 16278248 DOI: 10.1152/ajpendo.00267.2005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The intracellular concentrations of essential amino acids (EAA) in muscle are maintained relatively constant under a variety of conditions. However, the effect of a decrease in blood amino acid concentrations on intracellular concentrations is not clear. Similarly, the relation between intracellular and interstitial concentrations has not been determined in this circumstance. Thus the aim of this study was to determine the effect of hypoaminoacidemia on intracellular, interstitial, and plasma concentrations of EAA and the mechanisms responsible for the respective changes. Twelve normal pigs were investigated before and during 120 min of hemodialysis by use of stable-isotope tracer methodology, microdialysis technique, and muscle biopsies. During hemodialysis, there was a decrease in the interstitial fluid concentrations of phenylalanine, leucine, alanine, and lysine that corresponded to their decrease in plasma concentration. Nonetheless, the intracellular concentrations of these amino acids were maintained at the basal levels throughout the entire period due principally to a reduction in the rate of incorporation of amino acids into protein that was approximately equivalent to the decrease in uptake from the plasma. In conclusion, intracellular concentrations of amino acids are regulated to maintain relatively constant values, even when plasma and interstitial concentrations fall as a consequence of hemodialysis.
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Affiliation(s)
- Elisabet Børsheim
- Metabolism Unit, Department of Surgery, Shriners Hospitals for Children/Galveston, and University of Texas Medical Branch, Galveston, Texas 77550, USA.
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Barrow RE, Wolfe RR, Dasu MR, Barrow LN, Herndon DN. The use of beta-adrenergic blockade in preventing trauma-induced hepatomegaly. Ann Surg 2006; 243:115-20. [PMID: 16371745 PMCID: PMC1449976 DOI: 10.1097/01.sla.0000193834.07413.91] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The objective of this study was to test the hypothesis that hepatomegaly in burned children can be attenuated or reversed by blocking lipolysis and reducing free fatty acids delivered to the liver. SUMMARY BACKGROUND DATA Accelerated lipolysis in severely burned children has been shown to play an important role in the accumulation of hepatic TGs. Severely burned children who survive 10 days or more after injury commonly have enlarged livers often twice or more normal size for their sex, age, and weight. METHODS Ninety-eight children, 2 to 18 years of age, with burns covering more than 40% of their body surface and who received either propranolol (beta-adrenergic blockade) or placebo were studied. Liver weights were measured by ultrasonic scanning. Body composition changes were identified by dual-image x-ray absorptiometry and validated by whole-body potassium-40 scintillation counting. Discarded abdominal cutaneous adipose tissue was collected before and after propranolol or placebo for microarray analysis. RESULTS In 80% of severely burned children studied not receiving propranolol, liver sizes increased by 100% or more while 86% of burned children receiving propranolol showed a decrease or no change in liver size over the same period of time after injury. Gene expression patterns of adipose tissue after propranolol treatment showed that all of the identified genes related to lipid metabolism were down-regulated. CONCLUSIONS Data reported here support the hypothesis that beta-adrenergic blockade can reduce delivery of fatty acids to the liver and hepatic congestion commonly found in severely burned children by inhibiting lipolysis and reducing hepatic blood flow.
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Affiliation(s)
- Robert E Barrow
- Department of Surgery, University of Texas Medical Branch, and Shriners Hospitals for Children, Galveston, TX 77550, USA.
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Kobayashi H, Kato H, Hirabayashi Y, Murakami H, Suzuki H. Modulations of muscle protein metabolism by branched-chain amino acids in normal and muscle-atrophying rats. J Nutr 2006; 136:234S-6S. [PMID: 16365089 DOI: 10.1093/jn/136.1.234s] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
It has been shown that BCAAs, especially leucine, regulate skeletal muscle protein metabolism. However, it remains unclear how BCAAs regulate muscle protein metabolism and lead to anabolism in vivo. We examined muscle protein synthesis rate and breakdown rate simultaneously during BCAA infusion in muscle atrophy models as well as in normal healthy rats. Corticosterone-treated rats and hindlimb-immobilized rats were used as muscle atrophy models. Muscle protein synthesis rate and breakdown rate were measured as phenylalanine kinetics across the hindlimb. In anesthetized normal rats, BCAAs stimulated muscle protein synthesis despite low insulin concentration and did not suppress muscle protein breakdown. In corticosterone-treated rats, BCAAs failed to restore inhibited muscle protein synthesis, but reduced muscle protein breakdown. Immobilization of hindlimb increased muscle protein breakdown within a day. BCAAs did not change muscle protein metabolism, although essential amino acids (EAAs) suppressed muscle protein breakdown in hindlimb-immobilized rats. We also evaluated changes of fractional synthesis rate (FSR) of skeletal muscle protein during infusion of leucine alone or EAAs for 4 h in anesthetized normal rats. FSR showed a transient increase at 15-30 min of leucine infusion and then declined, whereas FSR stayed elevated throughout EAA infusion. We concluded that 1) BCAAs primarily stimulate muscle protein synthesis in normal rats independently of insulin; 2) EAAs are required to maintain the BCAA stimulation of muscle protein synthesis; and 3) The effects of BCAAs on muscle protein metabolism differ between atrophy models.
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Affiliation(s)
- Hisamine Kobayashi
- Applied Research Department, AminoScience Laboratories, Ajinomoto Co., Kawasaki, Japan.
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Gore DC, Herndon DN, Wolfe RR. Comparison of peripheral metabolic effects of insulin and metformin following severe burn injury. ACTA ACUST UNITED AC 2005; 59:316-22; discussion 322-3. [PMID: 16294070 DOI: 10.1097/01.ta.0000180387.34057.5a] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE Both insulin and metformin have been shown to attenuate hyperglycemia and reduce net muscle protein catabolism following burn injury. The purpose of this study was to compare the peripheral metabolic effects of insulin and metformin in severe burn patients. METHODS Six adult patients with burns greater than 40% of their body surface underwent metabolic evaluation utilizing isotopic dilution of phenylalanine, femoral arterial and venous blood sampling, and sequential biopsies of leg muscle. Following baseline measurements, insulin was infused into the femoral artery at 0.45 mIU/min 100 mL leg volume. Patients were then given metformin (850 mg every 8 hours) for seven days with repeat metabolic evaluation before and during intra-arterial infusion of insulin. RESULTS Intra-arterial administration of insulin significantly increased insulin concentrations within the femoral vein, creating hyperinsulinemia localized to the extremity. Metformin had no significant effect on either peripheral glucose clearance or the rate of glucose oxidation. Furthermore, the availability of ATP and energy charge within muscle was not overtly affected by either insulin or metformin. Metformin did significantly increase the fractional synthetic rate of muscle protein which increased even further with insulin administration. Both metformin and insulin separately increased the rate of muscle protein synthesis as calculated using three compartment modeling. CONCLUSION This study demonstrates a significant anabolic effect on muscle protein with metformin and a modest response with insulin. Findings also suggest that metformin and insulin may work synergistically to further improve muscle protein kinetics.
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Affiliation(s)
- Dennis C Gore
- Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
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Katsanos CS, Chinkes DL, Sheffield-Moore M, Aarsland A, Kobayashi H, Wolfe RR. Method for the determination of the arteriovenous muscle protein balance during non-steady-state blood and muscle amino acid concentrations. Am J Physiol Endocrinol Metab 2005; 289:E1064-70. [PMID: 16091388 DOI: 10.1152/ajpendo.00141.2005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We describe a method based on the traditional arteriovenous balance technique in conjunction with muscle biopsies for the determination of leg muscle protein balance during the nonsteady state in blood amino acid concentrations. Six young, healthy individuals were studied in the postabsorptive state (pre-Phe) and after a bolus ingestion of approximately 0.5 g phenylalanine (post-Phe). Post-Phe free phenylalanine concentrations in blood and muscle increased (P < 0.05), but the respective concentrations of the amino acid threonine did not change. The average post-Phe leg net balance (NB) for threonine decreased from basal (P < 0.05), but that for phenylalanine did not change. A volume of distribution for free phenylalanine in the leg was calculated based on the leg lean mass and the relative muscle water content and used to estimate the rate of accumulation of free phenylalanine in the leg. When the post-Phe NB for phenylalanine was corrected for the rate of accumulation of free phenylalanine in the leg, the post-Phe NB for phenylalanine decreased from basal (P < 0.05). This corrected value was not different (P > 0.05) from the value predicted for the phenylalanine NB based on the pre- and post-Phe NB responses for threonine. We conclude that the protein NB in non-steady-state blood phenylalanine concentrations can be determined from the arteriovenous phenylalanine NB by accounting for changes in free phenylalanine within its volume of distribution.
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Affiliation(s)
- Christos S Katsanos
- Department of Surgery, Shriners Hospitals for Children-Galveston, and University of Texas Medical Branch, Galveston, TX 77550, USA
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Abstract
PURPOSE OF REVIEW To describe the latest innovations in measuring protein breakdown in vivo, particularly in muscle. RECENT FINDINGS The traditional method of using 3-methylhistidine excretion to measure muscle protein breakdown has been updated to include arteriovenous or microdialysis measurements, which address the concern that there are alternative sources of 3-methylhistidine in the body other than muscle. Several variations of a precursor-product method to measure fractional breakdown rate of tissues have been developed that are analogous to fractional synthesis rate of tissues. These methods are more generally applicable than the 3-methylhistidine methods and are less invasive than arteriovenous methods. The various precursor-product methods are distinguished by whether they require an isotopic steady state or multiple tracers and by how many biopsies are required. SUMMARY The new precursor-product methods have enabled assessment in clinical trials of protein breakdown for proteins other than myofibrillar proteins and in circumstances in which arteriovenous sampling is not feasible.
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Affiliation(s)
- David L Chinkes
- Department of Surgery, University of Texas Medical Branch and Shriners Hospitals for Children, Galveston, Texas 77550, USA.
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Phillips SM, Hartman JW, Wilkinson SB. Dietary protein to support anabolism with resistance exercise in young men. J Am Coll Nutr 2005; 24:134S-139S. [PMID: 15798080 DOI: 10.1080/07315724.2005.10719454] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Resistance exercise is fundamentally anabolic and as such stimulates the process of skeletal muscle protein synthesis (MPS) in an absolute sense and relative to skeletal muscle protein breakdown (MPB). However, the net effect of resistance exercise is to shift net protein balance (NPB = MPS - MPB) to a more positive value; however, in the absence of feeding NPB remains negative. Feeding stimulates MPS to an extent where NPB becomes positive, for a transient time. When combined, resistance exercise and feeding synergistically interact to result in NPB being greater than with feeding alone. This feeding- and exercise-induced stimulation of NPB is what, albeit slowly, results in muscle hypertrophy. With this rudimentary knowledge we are now at the point where we can manipulate variables within the system to see what impact these interventions have on the processes of MPS, MPB, and NPB and ultimately and perhaps most importantly, muscle hypertrophy and strength. We used established models of skeletal muscle amino acid turnover to examine how protein source (milk versus soy) acutely affects the processes of MPS and MPB after resistance exercise. Our findings revealed that even when balanced quantities of total protein and energy are consumed that milk proteins are more effective in stimulating amino acid uptake and net protein deposition in skeletal muscle after resistance exercise than are hydrolyzed soy proteins. Importantly, the finding of increased amino acid uptake would be independent of the differences in amino acid composition of the two proteins. We propose that the improved net protein deposition with milk protein consumption is also not due to differences in amino acid composition, but is due to a different pattern of amino acid delivery associated with milk versus hydrolyzed soy proteins. If our acute findings are accurate then we hypothesized that chronically the greater net protein deposition associated with milk protein consumption post-resistance exercise would eventually lead to greater net protein accretion (i.e., muscle fiber hypertrophy), over a longer time period. In young men completing 12 weeks of resistance training (5d/wk) we observed a tendency (P = 0.11) for greater gains in whole body lean mass and whole as greater muscle fiber hypertrophy with consumption of milk. While strength gains were not different between the soy and milk-supplemented groups we would argue that the true significance of a greater increase in lean mass that we observed with milk consumption may be more important in groups of persons with lower initial lean mass and strength such as the elderly.
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Affiliation(s)
- Stuart M Phillips
- Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1 CANADA.
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