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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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van Vliet S, Fappi A, Reeds DN, Mittendorfer B. No independent or combined effects of vitamin D and conjugated linoleic acids on muscle protein synthesis in older adults: a randomized, double-blind, placebo-controlled clinical trial. Am J Clin Nutr 2020; 112:1382-1389. [PMID: 32860399 PMCID: PMC7657331 DOI: 10.1093/ajcn/nqaa240] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 07/30/2020] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Aging is associated with skeletal muscle anabolic resistance (i.e., reduced muscle protein synthesis during anabolic conditions such as hyperaminoacidemia). The results from studies conducted in cell culture systems and animals suggest that both vitamin D and conjugated linoleic acids (CLAs) stimulate muscle protein synthesis. OBJECTIVES To conduct a randomized, double-blind, placebo-controlled clinical trial to determine the independent and combined effects of dietary vitamin D and CLA supplementation on myofibrillar protein synthesis rates in sedentary older adults. METHODS Thirty-two sedentary, older adults were randomized to receive either: 1) 2000 IU vitamin D-3 (Vit D) per day; 2) 4000 mg CLA per day; 3) both Vit D (2000 IU/d) and CLA (4000 mg/d); or 4) placebo for 8 wk. Myofibrillar protein synthesis rates were evaluated by using intravenous [ring-2H5]phenylalanine infusion in conjunction with muscle biopsies during basal, postabsorptive conditions and during combined amino acid and insulin infusion before and after the supplementation period. RESULTS Before the intervention, basal myofibrillar protein synthesis rates were not different among groups (Placebo: 0.033 ± 0.003; Vit D: 0.034 ± 0.002; CLA: 0.029 ± 0.005; Vit D + CLA: 0.038 ± 0.005 %·h-1), and hyperinsulinemia-hyperaminoacidemia increased myofibrillar protein synthesis rates by ∼35%. Compared with placebo, neither Vit D nor CLA nor combined Vit D + CLA supplementation affected the basal myofibrillar protein synthesis rates (placebo: 0.040 ± 0.004%/h; Vit D: 0.044 ± 0.006%/h; CLA: 0.039 ± 0.006%/h; Vit D + CLA: 0.040 ± 0.007%/h) or the hyperinsulinemia-hyperaminoacidemia-induced increase in myofibrillar protein synthesis (percentage increase from basal before and after the interventions: placebo, 30 ± 11 and 36 ± 11; Vit D, 38 ± 8 and 34 ± 10; CLA, 50 ± 14 and 51 ± 16; Vit D + CLA, 29 ± 15 and 35 ± 8). CONCLUSIONS Vitamin D and/or CLA supplementation, at the doses provided in our study, does not have muscle anabolic effects in sedentary older adults.The study was registered at clinicaltrials.gov (NCT03115775).
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Affiliation(s)
- Stephan van Vliet
- Center for Human Nutrition, Washington University School of Medicine, St Louis, MO, USA
| | - Alan Fappi
- Center for Human Nutrition, Washington University School of Medicine, St Louis, MO, USA
| | - Dominic N Reeds
- Center for Human Nutrition, Washington University School of Medicine, St Louis, MO, USA
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Brook MS, Wilkinson DJ. Contemporary stable isotope tracer approaches: Insights into skeletal muscle metabolism in health and disease. Exp Physiol 2020; 105:1081-1089. [PMID: 32362047 DOI: 10.1113/ep087492] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 04/27/2020] [Indexed: 12/18/2022]
Abstract
NEW FINDINGS What is the topic of this review? This review discusses the application of new stable isotope tracer techniques in understanding the control of skeletal muscle mass. What advances does it highlight? This review highlights current advances in stable isotope tracer techniques through their combination with high-throughput proteomics technologies. ABSTRACT Beyond its primary locomotory and key structural functions, skeletal muscle provides additional vital roles for maintenance of metabolic health, acting as a storage point for glucose and intramuscular lipids for energy production, alongside being the largest reservoir for amino acids in the body. Therefore, maintenance of muscle mass is key to the promotion of health and well-being across the lifespan and in several disease states. As such, when skeletal muscle is lost, in either clinical (cancer, organ failure etc.) or non-clinical (ageing, inactivity) situations, there are potentially devastating consequences attached, with robust links existing between muscle mass loss and mortality. Great efforts are being made to reverse or slow muscle mass declines in health and disease, through combinations of lifestyle changes and nutritional and/or pharmaceutical intervention. However, despite this comprehensive research effort, the underlying metabolic and molecular mechanisms have yet to be defined properly. However, with the rapid acceleration of analytical developments over recent years, the application of stable isotope tracers to the study of human muscle metabolism is providing unique insights into the mechanisms controlling skeletal muscle loss and allowing more targeted therapeutic strategies to be developed. The aim of this review is to highlight the technical breakthroughs in our understanding of muscle wasting in health and disease and how future directions and developments incorporating 'omics' with stable isotope tracers will allow for a more personalized and stratified therapeutic approach.
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Affiliation(s)
- Matthew S Brook
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK.,School of Life Science, Queen's Medical Centre, Nottingham, UK
| | - Daniel J Wilkinson
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK.,Division of Health Sciences and Graduate Entry Medicine, School of Medicine, Royal Derby Hospital Centre, Derby, UK
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Aerobic Plus Resistance Exercise in Obese Older Adults Improves Muscle Protein Synthesis and Preserves Myocellular Quality Despite Weight Loss. Cell Metab 2019; 30:261-273.e6. [PMID: 31279675 PMCID: PMC6685749 DOI: 10.1016/j.cmet.2019.06.008] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 04/06/2019] [Accepted: 06/07/2019] [Indexed: 12/18/2022]
Abstract
Anabolic resistance and impaired myocellular quality contribute to age-related sarcopenia, which exacerbates with obesity. Diet-induced muscle mass loss is attenuated by resistance or aerobic plus resistance exercise compared to aerobic exercise in obese elderly. We assessed chronic effects of weight loss plus different exercise modalities on muscle protein synthesis response to feeding and myocellular quality. Obese older adults were randomized to a weight-management program plus aerobic, resistance, or combined aerobic and resistance exercise or to control. Participants underwent vastus lateralis biopsies at baseline and 6 months. Muscle protein synthesis rate increased more in resistance and combined than in control. Autophagy mediators' expression decreased more in combined than in aerobic, which experienced a higher increase in inflammation and mitochondrial regulators' expression. In obese elderly, combined aerobic and resistance exercise is superior to either mode independently for improving muscle protein synthesis and myocellular quality, thereby maintaining muscle mass during weight-loss therapy.
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Wilkinson DJ, Hossain T, Limb MC, Phillips BE, Lund J, Williams JP, Brook MS, Cegielski J, Philp A, Ashcroft S, Rathmacher JA, Szewczyk NJ, Smith K, Atherton PJ. Impact of the calcium form of β-hydroxy-β-methylbutyrate upon human skeletal muscle protein metabolism. Clin Nutr 2018; 37:2068-2075. [PMID: 29097038 PMCID: PMC6295980 DOI: 10.1016/j.clnu.2017.09.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 09/24/2017] [Accepted: 09/29/2017] [Indexed: 12/20/2022]
Abstract
BACKGROUND & AIMS β-hydroxy-β-methylbutyrate (HMB) is purported as a key nutritional supplement for the preservation of muscle mass in health, disease and as an ergogenic aid in exercise. Of the two available forms of HMB (calcium (Ca-HMB) salt or free acid (FA-HMB)) - differences in plasma bioavailability have been reported. We previously reported that ∼3 g oral FA-HMB increased muscle protein synthesis (MPS) and reduced muscle protein breakdown (MPB). The objective of the present study was to quantify muscle protein metabolism responses to oral Ca-HMB. METHODS Eight healthy young males received a primed constant infusion of 1,2 13C2 leucine and 2H5 phenylalanine to assess MPS (by tracer incorporation in myofibrils) and MPB (via arterio-venous (A-V) dilution) at baseline and following provision of ∼3 g of Ca-HMB; muscle anabolic (MPS) and catabolic (MPB) signalling was assessed via immunoblotting. RESULTS Ca-HMB led a significant and rapid (<60 min) peak in plasma HMB concentrations (483.6 ± 14.2 μM, p < 0.0001). This rise in plasma HMB was accompanied by increases in MPS (PA: 0.046 ± 0.004%/h, CaHMB: 0.072 ± 0.004%/h, p < 0001) and suppressions in MPB (PA: 7.6 ± 1.2 μmol Phe per leg min-1, Ca-HMB: 5.2 ± 0.8 μmol Phe per leg min-1, p < 0.01). Increases in the phosphorylation of mTORc1 substrates i.e. p70S6K1 and RPS6 were also observed, with no changes detected in the MPB targets measured. CONCLUSIONS These findings support the pro-anabolic properties of HMB via mTORc1, and show that despite proposed differences in bioavailability, Ca-HMB provides a comparable stimulation to MPS and suppression of MPB, to FA-HMB, further supporting its use as a pharmaconutrient in the modulation of muscle mass.
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Affiliation(s)
- D J Wilkinson
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - T Hossain
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - M C Limb
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - B E Phillips
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - J Lund
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - J P Williams
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - M S Brook
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - J Cegielski
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - A Philp
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - S Ashcroft
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - J A Rathmacher
- Metabolic Technologies, Inc, Iowa State University Research Park, 2711 S. Loop Drive, Ste 4400, Ames, IA 50010, USA
| | - N J Szewczyk
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - K Smith
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - P J Atherton
- MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, UK.
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Mazzulla M, Parel JT, Beals JW, VAN Vliet S, Abou Sawan S, West DWD, Paluska SA, Ulanov AV, Moore DR, Burd NA. Endurance Exercise Attenuates Postprandial Whole-Body Leucine Balance in Trained Men. Med Sci Sports Exerc 2018; 49:2585-2592. [PMID: 28767524 DOI: 10.1249/mss.0000000000001394] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE Endurance exercise increases indices of small intestinal damage and leucine oxidation, which may attenuate dietary amino acid appearance and postprandial leucine balance during postexercise recovery. Therefore, the purpose of this study was to examine the effect of an acute bout of endurance exercise on postprandial leucine kinetics and net leucine balance. METHODS In a crossover design, seven trained young men (age = 25.6 ± 2.3 yr; V˙O2peak = 61.4 ± 2.9 mL·kg·min; mean ± SEM) received a primed constant infusion of L-[1-C]leucine before and after ingesting a mixed macronutrient meal containing 18 g whole egg protein intrinsically labeled with L-[5,5,5-H3]leucine, 17 g fat, and 60 g carbohydrate at rest and after 60 min of treadmill running at 70% V˙O2peak. RESULTS Plasma intestinal fatty acid binding protein concentrations and leucine oxidation both increased (P < 0.01) to peaks that were ~2.5-fold above baseline values during exercise with a concomitant decrease (P < 0.01) in nonoxidative leucine disposal. Meal ingestion attenuated (P < 0.01) endogenous leucine rates of appearance at rest and after exercise. There were no differences (both, P > 0.05) in dietary leucine appearance rates or in the amount of dietary protein-derived leucine that appeared into circulation over the 5-h postprandial period at rest and after exercise (62% ± 2% and 63% ± 2%, respectively). Leucine balance over the 5-h postprandial period was positive (P < 0.01) in both conditions but was negative (P < 0.01) during the exercise trial after accounting for exercise-induced leucine oxidation. CONCLUSIONS We demonstrate that endurance exercise does not modulate dietary leucine availability from a mixed meal but attenuates postprandial whole-body leucine balance in trained young men.
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Affiliation(s)
- Michael Mazzulla
- 1Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, CANADA; 2Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Champaign, IL; 3Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Champaign, IL; 4Department of Family Medicine, University of Illinois at Urbana-Champaign, Champaign, IL; and 5Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Champaign, IL
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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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Rundqvist HC, Esbjörnsson M, Rooyackers O, Österlund T, Moberg M, Apro W, Blomstrand E, Jansson E. Influence of nutrient ingestion on amino acid transporters and protein synthesis in human skeletal muscle after sprint exercise. J Appl Physiol (1985) 2017; 123:1501-1515. [DOI: 10.1152/japplphysiol.00244.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Nutrient ingestion is known to increase the exercise-induced stimulation of muscle protein synthesis following resistance exercise. Less is known about the effect of nutrients on muscle protein synthesis following sprint exercise. At two occasions separated by 1 mo, 12 healthy subjects performed three 30-s sprints with 20-min rest between bouts. In randomized order, they consumed a drink with essential amino acids and maltodextrin (nutrient) or flavored water (placebo). Muscle biopsies were obtained 80 and 200 min after the last sprint, and blood samples were taken repeatedly during the experiment. Fractional synthetic rate (FSR) was measured by continuous infusion of l-[2H5]phenylalanine up to 200 min postexercise. The mRNA expression and protein expression of SNAT2 were both 1.4-fold higher ( P < 0.05) after nutrient intake compared with placebo at 200 min postexercise. Phosphorylated Akt, mammalian target of rapamycin (mTOR), and p70S6k were 1.7- to 3.6-fold higher ( P < 0.01) 80 min after the last sprint with nutrient ingestion as compared with placebo. In addition, FSR was higher ( P < 0.05) with nutrients when plasma phenylalanine (FSRplasma) was used as a precursor but not when intracellular phenylalanine (FSRmuscle) was used. Significant correlations were also found between FSRplasma on the one hand and plasma leucine and serum insulin on the other hand in the nutrient condition. The results show that nutrient ingestion induces the expression of the amino acid transporter SNAT2 stimulates Akt/mTOR signaling and most likely the rate of muscle protein synthesis following sprint exercise. NEW & NOTEWORTHY There is limited knowledge regarding the effect of nutrients on muscle protein synthesis following sprint as compared with resistance exercise. The results demonstrate that nutrient ingestion during repeated 30-s bouts of sprint exercise induces expression of the amino acid transporter SNAT2 and stimulates Akt/mTOR signaling and most likely the rate of muscle protein synthesis. Future studies to explore the chronic effects of nutritional ingestion during sprint exercise sessions on muscle mass accretion are warranted.
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Affiliation(s)
- Håkan C. Rundqvist
- Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden
| | - Mona Esbjörnsson
- Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden
| | - Olav Rooyackers
- Division of Anesthesiology and Intensive Care, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Ted Österlund
- Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden
| | - Marcus Moberg
- Åstrand Laboratory, Swedish School of Sport and Health Science, Stockholm, Sweden
| | - William Apro
- Åstrand Laboratory, Swedish School of Sport and Health Science, Stockholm, Sweden
| | - Eva Blomstrand
- Åstrand Laboratory, Swedish School of Sport and Health Science, Stockholm, Sweden
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Eva Jansson
- Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden
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Brook MS, Wilkinson DJ, Mitchell WK, Lund JL, Phillips BE, Szewczyk NJ, Kainulainen H, Lensu S, Koch LG, Britton SL, Greenhaff PL, Smith K, Atherton PJ. A novel D 2O tracer method to quantify RNA turnover as a biomarker of de novo ribosomal biogenesis, in vitro, in animal models, and in human skeletal muscle. Am J Physiol Endocrinol Metab 2017; 313:E681-E689. [PMID: 28811296 PMCID: PMC5814597 DOI: 10.1152/ajpendo.00157.2017] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 08/10/2017] [Accepted: 08/14/2017] [Indexed: 11/22/2022]
Abstract
Current methods to quantify in vivo RNA dynamics are limited. Here, we developed a novel stable isotope (D2O) methodology to quantify RNA synthesis (i.e., ribosomal biogenesis) in cells, animal models, and humans. First, proliferating C2C12 cells were incubated in D2O-enriched media and myotubes ±50 ng/ml IGF-I. Second, rat quadriceps (untrained, n = 9; 7-wk interval-"like" training, n = 13) were collected after ~3-wk D2O (70 atom %) administration, with body-water enrichment monitored via blood sampling. Finally, 10 (23 ± 1 yr) men consumed 150-ml D2O followed by 50 ml/wk and undertook 6-wk resistance exercise (6 × 8 repetitions, 75% 1-repetition maximum 3/wk) with body-water enrichment monitored by saliva sampling and muscle biopsies (for determination of RNA synthesis) at 0, 3, and 6 wk. Ribose mole percent excess (r-MPE) from purine nucleotides was analyzed via GC-MS/MS. Proliferating C2C12 cell r-MPE exhibited a rise to plateau, whereas IGF-I increased myotube RNA from 76 ± 3 to 123 ± 3 ng/μl and r-MPE by 0.39 ± 0.1% (both P < 0.01). After 3 wk, rat quadriceps r-MPE had increased to 0.25 ± 0.01% (P < 0.01) and was greater with running exercise (0.36 ± 0.02%; P < 0.01). Human muscle r-MPE increased to 0.06 ± 0.01 and 0.13 ± 0.02% at 3/6 wk, respectively, equating to synthesis rates of ~0.8%/day, increasing with resistance exercise to 1.7 ± 0.3%/day (P < 0.01) and 1.2 ± 0.1%/day (P < 0.05) at 3/6 wk, respectively. Therefore, we have developed and physiologically validated a novel technique to explore ribosomal biogenesis in a multimodal fashion.
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Affiliation(s)
- M S Brook
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom
| | - D J Wilkinson
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom
| | - W K Mitchell
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom
| | - J L Lund
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom
| | - B E Phillips
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom
| | - N J Szewczyk
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom
| | - H Kainulainen
- Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland; and
| | - S Lensu
- Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland; and
| | - L G Koch
- Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan
| | - S L Britton
- Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan
| | - P L Greenhaff
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom
| | - K Smith
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom
| | - P J Atherton
- Medical Research Council-Arthritis Research UK Centre for Musculoskeletal Ageing Research, Clinical, Metabolic and Molecular Physiology, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom;
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Holwerda AM, Paulussen KJM, Overkamp M, Smeets JSJ, Gijsen AP, Goessens JPB, Verdijk LB, van Loon LJC. Daily resistance-type exercise stimulates muscle protein synthesis in vivo in young men. J Appl Physiol (1985) 2017; 124:66-75. [PMID: 28935828 DOI: 10.1152/japplphysiol.00610.2017] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Resistance-type exercise increases muscle protein synthesis rates during acute postexercise recovery. The impact of resistance-type exercise training on (local) muscle protein synthesis rates under free-living conditions on a day-to-day basis remains unclear. We determined the impact of daily unilateral resistance-type exercise on local myofibrillar protein synthesis rates during a 3-day period. Twelve healthy young men (22 ± 1 yr) were recruited to participate in this study where they performed daily, unilateral resistance-type exercise during a 3-day intervention period. Two days before the exercise training subjects ingested 400 ml deuterated water (2H2O). Additional 50-ml doses of deuterated water were ingested daily during the training period. Saliva and blood samples were collected daily to assess body water and amino acid precursor deuterium enrichments, respectively. Muscle tissue biopsies were collected before and after the 3 days of unilateral resistance-type exercise training from both the exercised and the nonexercised, control leg for the assessment of muscle protein synthesis rates. Deuterated water dosing resulted in a steady-state body water enrichment of 0.70 ± 0.03%. Intramuscular free [2H]alanine enrichment increased up to 1.84 ± 0.06 mole percent excess (MPE) before the exercise training and did not change in both the exercised and control leg during the 3 subsequent exercise training days (2.11 ± 0.11 and 2.19 ± 0.12 MPE, respectively; P > 0.05). Muscle protein synthesis rates averaged 1.984 ± 0.118 and 1.642 ± 0.089%/day in the exercised vs. nonexercised, control leg when assessed over the entire 3-day period ( P < 0.05). Daily resistance-type exercise stimulates (local) muscle protein synthesis in vivo in humans. NEW & NOTEWORTHY This study demonstrates that daily resistance-type exercise stimulates muscle protein synthesis rates in vivo in humans over multiple days. Whereas acute studies have shown that resistance-type exercise increases muscle protein synthesis rates by 50-100%, we observed a lower impact of resistance-type exercise under free-living conditions. We also compared precursor tracer selection for the calculation of muscle protein synthesis rates and observed that saliva deuterium enrichment serves as an appropriate and practical choice of precursor.
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Affiliation(s)
- Andrew M Holwerda
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands
| | - Kevin J M Paulussen
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands
| | - Maarten Overkamp
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands
| | - Joey S J Smeets
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands
| | - Annemie P Gijsen
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands.,Stable Isotope Research Center (SIRC), Maastricht University Medical Center+ (MUMC+) , Maastricht , The Netherlands
| | - Joy P B Goessens
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands.,Stable Isotope Research Center (SIRC), Maastricht University Medical Center+ (MUMC+) , Maastricht , The Netherlands
| | - Lex B Verdijk
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands
| | - Luc J C van Loon
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands
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11
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Millward DJ, Halliday D, Hundal H, Taylor P, Atherton P, Greenhaff P, Smith K. Michael John Rennie, MSc, PhD, FRSE, FHEA, 1946-2017: an appreciation of his work on protein metabolism in human muscle. Am J Clin Nutr 2017; 106:1-9. [PMID: 28566312 DOI: 10.3945/ajcn.117.157818] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 04/25/2017] [Indexed: 11/14/2022] Open
Affiliation(s)
- D Joe Millward
- Department of Nutritional Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom (DJM, e-mail: ); Middlesex, United Kingdom (DH); Division of Cell Signalling and Immunology, School of Life Sciences, University of Dundee, Dundee, United Kingdom (HH and PT); and MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, United Kingdom (PA, PG, and KS)
| | - Dave Halliday
- Department of Nutritional Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom (DJM, e-mail: ); Middlesex, United Kingdom (DH); Division of Cell Signalling and Immunology, School of Life Sciences, University of Dundee, Dundee, United Kingdom (HH and PT); and MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, United Kingdom (PA, PG, and KS)
| | - Hari Hundal
- Department of Nutritional Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom (DJM, e-mail: ); Middlesex, United Kingdom (DH); Division of Cell Signalling and Immunology, School of Life Sciences, University of Dundee, Dundee, United Kingdom (HH and PT); and MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, United Kingdom (PA, PG, and KS)
| | - Peter Taylor
- Department of Nutritional Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom (DJM, e-mail: ); Middlesex, United Kingdom (DH); Division of Cell Signalling and Immunology, School of Life Sciences, University of Dundee, Dundee, United Kingdom (HH and PT); and MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, United Kingdom (PA, PG, and KS)
| | - Philip Atherton
- Department of Nutritional Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom (DJM, e-mail: ); Middlesex, United Kingdom (DH); Division of Cell Signalling and Immunology, School of Life Sciences, University of Dundee, Dundee, United Kingdom (HH and PT); and MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, United Kingdom (PA, PG, and KS)
| | - Paul Greenhaff
- Department of Nutritional Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom (DJM, e-mail: ); Middlesex, United Kingdom (DH); Division of Cell Signalling and Immunology, School of Life Sciences, University of Dundee, Dundee, United Kingdom (HH and PT); and MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, United Kingdom (PA, PG, and KS)
| | - Kenny Smith
- Department of Nutritional Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom (DJM, e-mail: ); Middlesex, United Kingdom (DH); Division of Cell Signalling and Immunology, School of Life Sciences, University of Dundee, Dundee, United Kingdom (HH and PT); and MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, United Kingdom (PA, PG, and KS)
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12
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Jainandunsing S, van Miert JNI, Rietveld T, Darcos Wattimena JL, Sijbrands EJG, de Rooij FWM. A stable isotope method for in vivo assessment of human insulin synthesis and secretion. Acta Diabetol 2016; 53:935-944. [PMID: 27552831 PMCID: PMC5114334 DOI: 10.1007/s00592-016-0896-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 08/06/2016] [Indexed: 01/02/2023]
Abstract
AIMS In vitro, beta cells immediately secrete stored but readily releasable insulin in response to a rise of glucose. During a prolonged insulin response, this is followed by newly synthesized insulin. Our aim was to develop an in vivo test to determine the ratio between readily available and newly synthesized insulin after a stimulus in humans by labelling newly synthesized insulin. METHODS A stable isotope tracer of 1.0 g 13C leucine with C-peptide as target peptide was administered 45 min prior to 75 g glucose load of a frequently blood sampled 210-min oral glucose tolerance test (OGTT). Our OGTT also encompassed collection of urine, which has a high content of C-peptide. Prior, the optimal conditions under which the tracer 13C leucine was administered for enrichment of (pre) proinsulin were established. Also, techniques to obtain urinary C-peptide under highly purified circumstances were set up. Our main outcome measure was the stable isotope enrichment of de novo C-peptide, which we related to early plasma insulin and glucose AUC. Twelve healthy Caucasian individuals (M4F8, age 41.8 ± 2.3, BMI 28.3 ± 1.7) with normal glucose tolerance underwent our OGTT. RESULTS We found that during a 75-g OGTT, newly synthesized insulin contributed approximately 20 % of total insulin secretion. The pattern of isotope enrichment obtained by collecting multiple urine voids was suggestive that the newly synthesized insulin contributes to the late phase of insulin secretion. De novo C-peptide correlated negatively with both early plasma insulin AUC (r = -0.629, P = 0.028) and early plasma glucose AUC (r = -0.605, P = 0.037). CONCLUSIONS With stable isotope technique added to OGTT, we were able to measure newly synthesized insulin in healthy individuals. This new technique holds the promise that it is feasible to develop a direct in vivo beta cell function test.
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Affiliation(s)
- Sjaam Jainandunsing
- Department of Internal Medicine, Erasmus MC - University Medical Center Rotterdam, Room Na512, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Joram N I van Miert
- Department of Internal Medicine, Erasmus MC - University Medical Center Rotterdam, Room Na512, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Trinet Rietveld
- Department of Internal Medicine, Erasmus MC - University Medical Center Rotterdam, Room Na512, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - J L Darcos Wattimena
- Department of Internal Medicine, Erasmus MC - University Medical Center Rotterdam, Room Na512, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Eric J G Sijbrands
- Department of Internal Medicine, Erasmus MC - University Medical Center Rotterdam, Room Na512, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Felix W M de Rooij
- Department of Internal Medicine, Erasmus MC - University Medical Center Rotterdam, Room Na512, PO Box 2040, 3000 CA, Rotterdam, The Netherlands.
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13
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Wilkinson DJ, Brook MS, Smith K, Atherton PJ. Stable isotope tracers and exercise physiology: past, present and future. J Physiol 2016; 595:2873-2882. [PMID: 27610950 DOI: 10.1113/jp272277] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 08/23/2016] [Indexed: 12/16/2022] Open
Abstract
Stable isotope tracers have been invaluable assets in physiological research for over 80 years. The application of substrate-specific stable isotope tracers has permitted exquisite insight into amino acid, fatty-acid and carbohydrate metabolic regulation (i.e. incorporation, flux, and oxidation, in a tissue-specific and whole-body fashion) in health, disease and response to acute and chronic exercise. Yet, despite many breakthroughs, there are limitations to 'substrate-specific' stable isotope tracers, which limit physiological insight, e.g. the need for intravenous infusions and restriction to short-term studies (hours) in controlled laboratory settings. In recent years significant interest has developed in alternative stable isotope tracer techniques that overcome these limitations, in particular deuterium oxide (D2 O or heavy water). The unique properties of this tracer mean that through oral administration, the turnover and flux through a number of different substrates (muscle proteins, lipids, glucose, DNA (satellite cells)) can be monitored simultaneously and flexibly (hours/weeks/months) without the need for restrictive experimental control. This makes it uniquely suited for the study of 'real world' human exercise physiology (amongst many other applications). Moreover, using D2 O permits evaluation of turnover of plasma and muscle proteins (e.g. dynamic proteomics) in addition to metabolomics (e.g. fluxomics) to seek molecular underpinnings, e.g. of exercise adaptation. Here, we provide insight into the role of stable isotope tracers, from substrate-specific to novel D2 O approaches, in facilitating our understanding of metabolism. Further novel potential applications of stable isotope tracers are also discussed in the context of integration with the snowballing field of 'omic' technologies.
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Affiliation(s)
- Daniel J Wilkinson
- MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - Matthew S Brook
- MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - Kenneth Smith
- MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
| | - Philip J Atherton
- MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, UK
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14
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Kouw IWK, Cermak NM, Burd NA, Churchward-Venne TA, Senden JM, Gijsen AP, van Loon LJC. Sodium nitrate co-ingestion with protein does not augment postprandial muscle protein synthesis rates in older, type 2 diabetes patients. Am J Physiol Endocrinol Metab 2016; 311:E325-34. [PMID: 27221118 DOI: 10.1152/ajpendo.00122.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 05/19/2016] [Indexed: 12/24/2022]
Abstract
The age-related anabolic resistance to protein ingestion is suggested to be associated with impairments in insulin-mediated capillary recruitment and postprandial muscle tissue perfusion. The present study investigated whether dietary nitrate co-ingestion with protein improves muscle protein synthesis in older, type 2 diabetes patients. Twenty-four men with type 2 diabetes (72 ± 1 yr, 26.7 ± 1.4 m/kg(2) body mass index, 7.3 ± 0.4% HbA1C) received a primed continuous infusion of l-[ring-(2)H5]phenylalanine and l-[1-(13)C]leucine and ingested 20 g of intrinsically l-[1-(13)C]phenylalanine- and l-[1-(13)C]leucine-labeled protein with (PRONO3) or without (PRO) sodium nitrate (0.15 mmol/kg). Blood and muscle samples were collected to assess protein digestion and absorption kinetics and postprandial muscle protein synthesis rates. Upon protein ingestion, exogenous phenylalanine appearance rates increased in both groups (P < 0.001), resulting in 55 ± 2% and 53 ± 2% of dietary protein-derived amino acids becoming available in the circulation over the 5h postprandial period in the PRO and PRONO3 groups, respectively. Postprandial myofibrillar protein synthesis rates based on l-[ring-(2)H5]phenylalanine did not differ between groups (0.025 ± 0.004 and 0.021 ± 0.007%/h over 0-2 h and 0.032 ± 0.004 and 0.030 ± 0.003%/h over 2-5 h in PRO and PRONO3, respectively, P = 0.7). No differences in incorporation of dietary protein-derived l-[1-(13)C]phenylalanine into de novo myofibrillar protein were observed at 5 h (0.016 ± 0.002 and 0.014 ± 0.002 mole percent excess in PRO and PRONO3, respectively, P = 0.8). Dietary nitrate co-ingestion with protein does not modulate protein digestion and absorption kinetics, nor does it further increase postprandial muscle protein synthesis rates or the incorporation of dietary protein-derived amino acids into de novo myofibrillar protein in older, type 2 diabetes patients.
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Affiliation(s)
- Imre W K Kouw
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Naomi M Cermak
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Nicholas A Burd
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Tyler A Churchward-Venne
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Joan M Senden
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Annemarie P Gijsen
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Luc J C van Loon
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
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15
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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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16
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Tran L, Masters H, Roust LR, Katsanos CS. A new method to measure muscle protein synthesis in humans by endogenously introduced d9-leucine and using blood for precursor enrichment determination. Physiol Rep 2015; 3:3/8/e12479. [PMID: 26243214 PMCID: PMC4562565 DOI: 10.14814/phy2.12479] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Enrichment from the easily accessible blood amino acid pool is commonly used as precursor enrichment to calculate rates of muscle protein fractional synthesis in relevant human studies in lieu of the less accessible muscle fluid amino acid pool. However, the accuracy of this approach depends largely on the extent to which there is low discrepancy in free amino acid enrichment between blood and muscle. Steady-state gradient (i.e., ratio) of amino acid enrichment between blood and muscle fluid in the basal state and in response to amino acid infusion were determined in five healthy subjects, and in association with two separate tracers: d9-leucine, introduced endogenously by the metabolism of d10-leucine (i.e., l-[2,3,3,4,5,5,5,6,6,6-(2)H10]leucine) infused in blood, and (13)C6-phenylalanine introduced/infused in blood. The blood-to-muscle fluid amino acid enrichment ratio was lower (P < 0.05) for d9-leucine compared to (13)C6-phenylalanine both before (1.5 ± 0.1 vs. 2.5 ± 0.1) and during (1.1 ± 0.1 vs. 1.2 ± 0.1) amino acid infusion. Importantly, the decrease in this ratio in association with the amino acid infusion was considerably less for the d9-leucine than the (13)C6-phenylalanine (-0.38 ± 0.03 vs. -1.29 ± 0.07; P < 0.05). In conclusion, blood d9-leucine enrichment introduced endogenously by intravenous infusion of d10-leucine provides a closer estimate of the muscle fluid amino acid enrichment, and its associated changes, than blood phenylalanine enrichment to calculate rates of muscle protein synthesis in humans.
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Affiliation(s)
- Lee Tran
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, Arizona, USA Mayo Clinic in Arizona, Scottsdale, Arizona, USA
| | - Haley Masters
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, Arizona, USA Mayo Clinic in Arizona, Scottsdale, Arizona, USA
| | - Lori R Roust
- Mayo Clinic in Arizona, Scottsdale, Arizona, USA
| | - Christos S Katsanos
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, Arizona, USA Mayo Clinic in Arizona, Scottsdale, Arizona, USA
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17
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Burd NA, Cermak NM, Kouw IWK, Gorissen SH, Gijsen AP, van Loon LJC. The use of doubly labeled milk protein to measure postprandial muscle protein synthesis rates in vivo in humans. J Appl Physiol (1985) 2014; 117:1363-70. [PMID: 25277738 DOI: 10.1152/japplphysiol.00411.2014] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We aimed to determine the impact of precursor pool dilution on the assessment of postprandial myofibrillar protein synthesis rates (MPS). A Holstein dairy cow was infused with large amounts of L-[1-(13)C]phenylalanine and L-[1-(13)C]leucine, and the milk was collected and fractionated. The enrichment levels in the casein were 38.7 and 9.3 mole percent excess, respectively. In a subsequent human experiment, 11 older men (age: 71 ± 1 y, body mass index: 26 ± 0.1 kg·m(-2)) received a primed constant infusion of L-[ring-(2)H5]phenylalanine and L-[1-(13)C]leucine. Blood and muscle samples were collected before and after the ingestion of 20-g doubly labeled casein to assess postprandial MPS based on the 1) constant tracer infusion of L-[ring-(2)H5]phenylalanine, 2) ingestion of intrinsically L-[1-(13)C]phenylalanine-labeled casein, and 3) constant infusion of L-[1-(13)C]leucine in combination with the ingestion of intrinsically L-[1-(13)C]leucine-labeled casein. Postprandial MPS was increased (P < 0.05) after protein ingestion (∼70% above postabsorptive values) based on the L-[1-(13)C]leucine tracer. There was no significant stimulation of postprandial MPS (∼27% above postabsorptive values) when the calculated fractional synthesis rate was based on the L-[ring-(2)H5]phenylalanine (P = 0.2). Comparisons of postprandial MPS based on the primed continuous infusion of L-[1-(13)C]leucine or the ingestion of intrinsically L-[1-(13)C]phenylalanine-labeled casein protein demonstrated differences compared with the primed continuous infusion of L-[ring-(2)H5]phenylalanine (P > 0.05). Our findings confirm that the postprandial MPS assessed using the primed continuous tracer infusion approach may differ if tracer steady-state conditions in the precursor pools are perturbed. The use of intrinsically doubly labeled protein provides a method to study the metabolic fate of the ingested protein and the subsequent postprandial MPS response.
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Affiliation(s)
- Nicholas A Burd
- NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Naomi M Cermak
- NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Imre W K Kouw
- NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Stefan H Gorissen
- NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Annemie P Gijsen
- NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Luc J C van Loon
- NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
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18
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Phillips BE, Atherton PJ, Varadhan K, Wilkinson DJ, Limb M, Selby AL, Rennie MJ, Smith K, Williams JP. Pharmacological enhancement of leg and muscle microvascular blood flow does not augment anabolic responses in skeletal muscle of young men under fed conditions. Am J Physiol Endocrinol Metab 2014; 306:E168-76. [PMID: 24280127 DOI: 10.1152/ajpendo.00440.2013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Skeletal muscle anabolism associated with postprandial plasma aminoacidemia and insulinemia is contingent upon amino acids (AA) and insulin crossing the microcirculation-myocyte interface. In this study, we hypothesized that increasing muscle microvascular blood volume (flow) would enhance fed-state anabolic responses in muscle protein turnover. We studied 10 young men (23.2 ± 2.1 yr) under postabsorptive and fed [iv Glamin (∼10 g AA), glucose ∼7.5 mmol/l] conditions. Methacholine was infused into the femoral artery of one leg to determine, via bilateral comparison, the effects of feeding alone vs. feeding plus pharmacological vasodilation. We measured leg blood flow (LBF; femoral artery) by Doppler ultrasound, muscle microvascular blood volume (MBV) by contrast-enhanced ultrasound (CEUS), muscle protein synthesis (MPS) and breakdown (MPB; a-v balance modeling), and net protein balance (NPB) using [1,2-(13)C2]leucine and [(2)H5]phenylalanine tracers via gas chromatography-mass spectrometry (GC-MS). Indexes of anabolic signaling/endothelial activation (e.g., Akt/mTORC1/NOS) were assessed using immunoblotting techniques. Under fed conditions, LBF (+12 ± 5%, P < 0.05), MBV (+25 ± 10%, P < 0.05), and MPS (+129 ± 33%, P < 0.05) increased. Infusion of methacholine further enhanced LBF (+126 ± 12%, P < 0.05) and MBV (+79 ± 30%, P < 0.05). Despite these radically different blood flow conditions, neither increases in MPS in response to feeding (0.04 ± 0.004 vs. 0.08 ± 0.01%/h, P < 0.05) nor improvements in NPB (-4.4 ± 2.4 vs. 16.4 ± 5.7 nmol Phe·100 ml leg(-1)·min(-1), P < 0.05) were affected by methacholine infusion (MPS 0.07 ± 0.01%/h; NPB 24.0 ± 7.7 nmol Phe·100 ml leg(-1)·min(-1)), whereas MPB was unaltered by either feeding or infusion of methacholine. Thus, enhancing LBF/MBV above that occurring naturally with feeding alone does not improve muscle anabolism.
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Affiliation(s)
- Bethan E Phillips
- Division of Medical Science and Graduate Entry Medicine, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom; and
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Smith GI, Yoshino J, Reeds DN, Bradley D, Burrows RE, Heisey HD, Moseley AC, Mittendorfer B. Testosterone and progesterone, but not estradiol, stimulate muscle protein synthesis in postmenopausal women. J Clin Endocrinol Metab 2014; 99:256-65. [PMID: 24203065 PMCID: PMC3879672 DOI: 10.1210/jc.2013-2835] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
CONTEXT The effect of the female sex steroids, estradiol and progesterone, on muscle protein turnover is unclear. Therefore, it is unknown whether the changes in the hormonal milieu throughout the life span in women contribute to the changes in muscle protein turnover and muscle mass (eg, age associated muscle loss). OBJECTIVE The objective of this study was to provide a comprehensive evaluation of the effect of sex hormones on muscle protein synthesis and gene expression of growth-regulatory factors [ie, myogenic differentiation 1 (MYOD1), myostatin (MSTN), follistatin (FST), and forkhead box O3 (FOXO3)]. SUBJECTS AND DESIGN We measured the basal rate of muscle protein synthesis and the expression of muscle growth-regulatory genes in 12 premenopausal women and four groups of postmenopausal women (n=24 total) who were studied before and after treatment with T, estradiol, or progesterone or no intervention (control group). All women were healthy, and pre- and postmenopausal women were carefully matched on body mass, body composition, and insulin sensitivity. RESULTS The muscle protein fractional synthesis rate was approximately 20% faster, and MYOD1, FST, and FOXO3 mRNA expressions were approximately 40%-90% greater (all P<.05) in postmenopausal than premenopausal women. In postmenopausal women, both T and progesterone treatment increased the muscle protein fractional synthesis rate by approximately 50% (both P<.01), whereas it was not affected by estradiol treatment and was unchanged in the control group. Progesterone treatment increased MYOD1 mRNA expression (P<.05) but had no effect on MSTN, FST, and FOXO3 mRNA expression. T and estradiol treatment had no effect on skeletal muscle MYOD1, MSTN, FST, and FOXO3 mRNA expression. CONCLUSION Muscle protein turnover is faster in older, postmenopausal women compared with younger, premenopausal women, but these age-related differences do not appear to be explained by the age- and menopause-related changes in the plasma sex hormone milieu.
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Affiliation(s)
- Gordon I Smith
- Center for Human Nutrition, Division of Geriatrics and Nutritional Science, Department of Internal Medicine, Washington University School of Medicine, St Louis, Missouri 63110
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Albumin synthesis in surgical patients. Nutrition 2013; 29:703-7. [DOI: 10.1016/j.nut.2012.10.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 10/22/2012] [Accepted: 10/23/2012] [Indexed: 11/18/2022]
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Wilkinson DJ, Hossain T, Hill DS, Phillips BE, Crossland H, Williams J, Loughna P, Churchward-Venne TA, Breen L, Phillips SM, Etheridge T, Rathmacher JA, Smith K, Szewczyk NJ, Atherton PJ. Effects of leucine and its metabolite β-hydroxy-β-methylbutyrate on human skeletal muscle protein metabolism. J Physiol 2013; 591:2911-23. [PMID: 23551944 PMCID: PMC3690694 DOI: 10.1113/jphysiol.2013.253203] [Citation(s) in RCA: 335] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Maintenance of skeletal muscle mass is contingent upon the dynamic equilibrium (fasted losses–fed gains) in protein turnover. Of all nutrients, the single amino acid leucine (Leu) possesses the most marked anabolic characteristics in acting as a trigger element for the initiation of protein synthesis. While the mechanisms by which Leu is ‘sensed’ have been the subject of great scrutiny, as a branched-chain amino acid, Leu can be catabolized within muscle, thus posing the possibility that metabolites of Leu could be involved in mediating the anabolic effect(s) of Leu. Our objective was to measure muscle protein anabolism in response to Leu and its metabolite HMB. Using [1,2-13C2]Leu and [2H5]phenylalanine tracers, and GC-MS/GC-C-IRMS we studied the effect of HMB or Leu alone on MPS (by tracer incorporation into myofibrils), and for HMB we also measured muscle proteolysis (by arteriovenous (A–V) dilution). Orally consumed 3.42 g free-acid (FA-HMB) HMB (providing 2.42 g of pure HMB) exhibited rapid bioavailability in plasma and muscle and, similarly to 3.42 g Leu, stimulated muscle protein synthesis (MPS; HMB +70%vs. Leu +110%). While HMB and Leu both increased anabolic signalling (mechanistic target of rapamycin; mTOR), this was more pronounced with Leu (i.e. p70S6K1 signalling ≤90 min vs. ≤30 min for HMB). HMB consumption also attenuated muscle protein breakdown (MPB; −57%) in an insulin-independent manner. We conclude that exogenous HMB induces acute muscle anabolism (increased MPS and reduced MPB) albeit perhaps via distinct, and/or additional mechanism(s) to Leu.
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Affiliation(s)
- D J Wilkinson
- Metabolic and Molecular Physiology Research Group, MRC-ARUK Centre of Excellence for Musculoskeletal Ageing Research, School of Graduate Entry Medicine and Health, Derby DE22 3DT, UK.
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Smith GI, Villareal DT, Sinacore DR, Shah K, Mittendorfer B. Muscle protein synthesis response to exercise training in obese, older men and women. Med Sci Sports Exerc 2012; 44:1259-66. [PMID: 22246218 DOI: 10.1249/mss.0b013e3182496a41] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
INTRODUCTION Physical activity and eating are two major physiological muscle growth stimuli. Although muscle protein turnover rates are not different in young and middle-aged men and women, we recently found that the basal rate of muscle protein synthesis is greater and the anabolic response to mixed-meal intake is blunted in 65- to 80-yr-old women compared with men of the same age. Whether older women are also resistant to the anabolic effect of exercise is not known. METHODS We measured the rate of muscle protein synthesis (both during basal, postabsorptive conditions and during mixed-meal intake) before and after 3 months of exercise training in obese, 65- to 80-yr-old men and women. RESULTS At the beginning of the study (before training) the basal, postabsorptive muscle protein fractional synthesis rate (FSR) was significantly greater in women than in men (0.064 ± 0.006%·h(-1) vs 0.039 ± 0.006%·h(-1), respectively, P < 0.01), whereas the meal-induced increase in the muscle protein FSR was greater in men than in women (P < 0.05). In men, exercise training approximately doubled the basal muscle protein FSR (P = 0.001) but had no effect on the meal-induced increase in muscle protein FSR (P = 0.78). In women, exercise training increased the muscle protein FSR by ~40% (P = 0.03) and also had no effect on the meal-induced increase in muscle protein FSR (P = 0.51). CONCLUSIONS These results suggest that there is significant sexual dimorphism not only in the basal, postabsorptive rate of muscle protein synthesis but also in the anabolic response to feeding and exercise training in obese, older adults.
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Affiliation(s)
- Gordon I Smith
- Center for Human Nutrition, Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO 63110, USA
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Claydon AJ, Beynon R. Proteome dynamics: revisiting turnover with a global perspective. Mol Cell Proteomics 2012; 11:1551-65. [PMID: 23125033 DOI: 10.1074/mcp.o112.022186] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Although bulk protein turnover has been measured with the use of stable isotope labeled tracers for over half a century, it is only recently that the same approach has become applicable to the level of the proteome, permitting analysis of the turnover of many proteins instead of single proteins or an aggregated protein pool. The optimal experimental design for turnover studies is dependent on the nature of the biological system under study, which dictates the choice of precursor label, protein pool sampling strategy, and treatment of data. In this review we discuss different approaches and, in particular, explore how complexity in experimental design and data processing increases as we shift from unicellular to multicellular systems, in particular animals.
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Affiliation(s)
- Amy J Claydon
- Protein Function Group, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom
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Sexually dimorphic effect of aging on skeletal muscle protein synthesis. Biol Sex Differ 2012; 3:11. [PMID: 22620287 PMCID: PMC3467175 DOI: 10.1186/2042-6410-3-11] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 05/06/2012] [Indexed: 12/25/2022] Open
Abstract
Background Although there appear to be no differences in muscle protein turnover in young and middle aged men and women, we have reported significant differences in the rate of muscle protein synthesis between older adult men and women. This suggests that aging may affect muscle protein turnover differently in men and women. Methods We measured the skeletal muscle protein fractional synthesis rate (FSR) by using stable isotope-labeled tracer methods during basal postabsorptive conditions and during a hyperaminoacidemic-hyperinsulinemic-euglycemic clamp in eight young men (25–45 y), ten young women (25–45 y), ten old men (65–85 y) and ten old women (65–85 y). Results The basal muscle protein FSR was not different in young and old men (0.040 ± 0.004 and 0.043 ± 0.005%·h-1, respectively) and combined insulin, glucose and amino acid infusion significantly increased the muscle protein FSR both in young (to 0.063 ± 0.006%·h-1) and old (to 0.051 ± 0.008%·h-1) men but the increase (0.023 ± 0.004 vs. 0.009 ± 0.004%·h-1, respectively) was ~60% less in the old men (P = 0.03). In contrast, the basal muscle protein FSR was ~30% greater in old than young women (0.060 ± 0.003 vs. 0.046 ± 0.004%·h-1, respectively; P < 0.05) and combined insulin, glucose and amino acid infusion significantly increased the muscle protein FSR in young (P < 0.01) but not in old women (P = 0.10) so that the FSR was not different between young and old women during the clamp (0.074 ± 0.006%·h-1 vs. 0.072 ± 0.006%·h-1, respectively). Conclusions There is sexual dimorphism in the age-related changes in muscle protein synthesis and thus the metabolic processes responsible for the age-related decline in muscle mass.
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Wang X, Smith GI, Patterson BW, Reeds DN, Kampelman J, Magkos F, Mittendorfer B. Testosterone increases the muscle protein synthesis rate but does not affect very-low-density lipoprotein metabolism in obese premenopausal women. Am J Physiol Endocrinol Metab 2012; 302:E740-6. [PMID: 22252942 PMCID: PMC3311295 DOI: 10.1152/ajpendo.00533.2011] [Citation(s) in RCA: 23] [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] [Indexed: 11/22/2022]
Abstract
Men and women with hyperandrogenemia have a more proatherogenic plasma lipid profile [e.g., greater triglyceride (TG) and total and low-density lipoprotein-cholesterol and lower high-density lipoprotein-cholesterol concentrations] than healthy premenopausal women. Furthermore, castration of male rats markedly reduces testosterone availability below normal and decreases plasma TG concentration, and testosterone replacement reverses this effect. Testosterone is, therefore, thought to be an important regulator of plasma lipid homeostasis. However, little is known about the effect of testosterone on plasma TG concentration and kinetics. Furthermore, testosterone is a potent skeletal muscle protein anabolic agent in men, but its effect on muscle protein turnover in women is unknown. We measured plasma lipid concentrations, hepatic very low density lipoprotein (VLDL)-TG and VLDL-apolipoprotein B-100 secretion rates, and the muscle protein fractional synthesis rate in 10 obese women before and after trandermal testosterone (1.25 g of 1% AndroGel daily) treatment for 3 wk. Serum total and free testosterone concentrations increased (P < 0.05) by approximately sevenfold in response to testosterone treatment, reaching concentrations that are comparable to those in women with hyperandrogenemia, but lower than the normal range for eugonadal men. Except for a small (∼10%) decrease in plasma high-density lipoprotein particle and cholesterol concentrations (P < 0.04), testosterone therapy had no effect on plasma lipid concentrations, lipoprotein particle sizes, and hepatic VLDL-TG and VLDL-apolipoprotein B-100 secretion rates (all P > 0.05); the muscle protein fractional synthesis rate, however, increased by ∼45% (P < 0.001). We conclude that testosterone is a potent skeletal muscle protein anabolic agent, but not an important regulator of plasma lipid homeostasis in obese women.
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Affiliation(s)
- Xuewen Wang
- Washington Univ. School of Medicine, Division of Geriatrics & Nutritional Science, St. Louis, MO 63110, USA
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Etheridge T, Atherton PJ, Wilkinson D, Selby A, Rankin D, Webborn N, Smith K, Watt PW. Effects of hypoxia on muscle protein synthesis and anabolic signaling at rest and in response to acute resistance exercise. Am J Physiol Endocrinol Metab 2011; 301:E697-702. [PMID: 21750270 PMCID: PMC3191550 DOI: 10.1152/ajpendo.00276.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [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
Chronic reductions in tissue O(2) tension (hypoxia) are associated with muscle atrophy and blunted hypertrophic responses to resistance exercise (RE) training. However, the effect of hypoxia on muscle protein synthesis (MPS) at rest and after RE is unknown. In a crossover study, seven healthy men (21.4 ± 0.7 yr) performed unilateral leg RE (6 × 8 repetitions at 70% 1-repetition maximum) under normoxic (20.9% inspired O(2)) and normobaric hypoxic (12% inspired O(2) for 3.5 h) postabsorptive conditions. Immediately after RE the rested leg was biopsied, and a primed continuous infusion of [1,2-(13)C(2)]leucine was maintained for 2.5 h before final biopsies from both legs to measure tracer incorporation and signaling responses (i.e., ribosomal S6 kinase 1). After 3.5 h of hypoxia, MPS was not different from normoxia in the rested leg (normoxia 0.033 ± 0.016 vs. hypoxia 0.043 ± 0.016%/h). MPS increased significantly from baseline 2.5 h after RE in normoxia (0.033 ± 0.016 vs. 0.104 ± 0.038%/h) but not hypoxia (0.043 ± 0.016 vs. 0.060 ± 0.063%/h). A significant linear relationship existed between MPS 2.5 h after RE in hypoxia and mean arterial blood O(2) saturation during hypoxia (r(2) = 0.49, P = 0.04). Phosphorylation of p70S6K(Thr389) remained unchanged in hypoxia at rest but increased after RE in both normoxia and hypoxia (2.6 ± 1.2-fold and 3.4 ± 1.1-fold, respectively). Concentrations of the hypoxia-responsive mTOR inhibitor regulated in development and DNA damage-1 were unaltered by hypoxia or RE. We conclude that normobaric hypoxia does not reduce MPS over 3.5 h at rest but blunts the increased MPS response to acute RE to a degree dependent on extant SpO(2).
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Affiliation(s)
- Timothy Etheridge
- University of Nottingham, School of Graduate Entry Medicine and Health, Derby, UK.
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Omega-3 polyunsaturated fatty acids augment the muscle protein anabolic response to hyperinsulinaemia-hyperaminoacidaemia in healthy young and middle-aged men and women. Clin Sci (Lond) 2011; 121:267-78. [PMID: 21501117 DOI: 10.1042/cs20100597] [Citation(s) in RCA: 242] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Increased dietary LCn-3PUFA (long-chain n-3 polyunsaturated fatty acid) intake stimulates muscle protein anabolism in individuals who experience muscle loss due to aging or cancer cachexia. However, it is not known whether LCn-3PUFAs elicit similar anabolic effects in healthy individuals. To answer this question, we evaluated the effect of 8 weeks of LCn-3PUFA supplementation (4 g of Lovaza®/day) in nine 25-45-year-old healthy subjects on the rate of muscle protein synthesis (by using stable isotope-labelled tracer techniques) and the activation (phosphorylation) of elements of the mTOR (mammalian target of rapamycin)/p70S6K (p70 S6 kinase) signalling pathway during basal post-absorptive conditions and during a hyperinsulinaemic-hyperaminoacidaemic clamp. We also measured the concentrations of protein, RNA and DNA in muscle to obtain indices of the protein synthetic capacity, translational efficiency and cell size. Neither the basal muscle protein fractional synthesis rate nor basal signalling element phosphorylation changed in response to LCn-3PUFA supplementation, but the anabolic response to insulin and amino acid infusion was greater after LCn-3PUFA [i.e. the muscle protein fractional synthesis rate during insulin and amino acid infusion increased from 0.062±0.004 to 0.083±0.007%/h and the phospho-mTOR (Ser2448) and phospho-p70S6K (Thr389) levels increased by ∼50%; all P<0.05]. In addition, the muscle protein concentration and the protein/DNA ratio (i.e. muscle cell size) were both greater (P<0.05) after LCn-3PUFA supplementation. We conclude that LCn-3PUFAs have anabolic properties in healthy young and middle-aged adults.
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Yarasheski KE, Castaneda-Sceppa C, He J, Kawakubo M, Bhasin S, Binder EF, Schroeder ET, Roubenoff R, Azen SP, Sattler FR. Whole-body and muscle protein metabolism are not affected by acute deviations from habitual protein intake in older men: the Hormonal Regulators of Muscle and Metabolism in Aging (HORMA) Study. Am J Clin Nutr 2011; 94:172-81. [PMID: 21543538 PMCID: PMC3127526 DOI: 10.3945/ajcn.110.010959] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Acute deviations in protein intake before the quantification of protein kinetics in older humans may explain the controversy over the effects of older age on muscle protein synthesis and proteolysis rates. OBJECTIVE We hypothesized that an acute decrease in protein intake from the habitual intake is associated with lower muscle protein synthesis and higher proteolysis rates, whereas an acute increase in protein intake from the habitual intake is associated with higher muscle protein synthesis and lower proteolysis rates. DESIGN In 112 community-dwelling healthy men aged 65-90 y, we quantified resting whole-body [1,2-(13)C(2)]leucine kinetics, muscle mixed protein fractional synthesis rates (FSRs), and muscle proteasome proteolytic enzyme activities after participants consumed for 3 d controlled research meals (0.9-1.1 g protein · kg(-1) · d(-1)) that contained more or less protein than that habitually consumed and that induced alterations in nitrogen balance. RESULTS Protein kinetic parameters were not significantly different between the groups, despite controlled research protein intakes that were lower (-0.2 to -0.3 g · kg(-1) · d(-1)) or higher (+0.2 g · kg(-1) · d(-1)) than habitual intakes and that induced negative (-22 to -25 mg · kg(-1) · d(-1)) or positive (22-25 mg · kg(-1) · d(-1)) nitrogen balance. Within these acutely altered protein intake and nitrogen balance boundaries, a reduction in protein intake from habitual intake and induction of negative nitrogen balance were not associated with higher proteolysis or lower muscle FSR, and an acute increase in protein intake from habitual intake and induction of positive nitrogen balance were not associated with lower proteolysis or higher muscle FSR. A higher quantitative insulin sensitivity check index was associated with lower whole-body proteolysis rates. CONCLUSIONS The practice of acutely controlling protein intake, even at intakes lower than habitual intakes that induce negative nitrogen balance, before quantifying human protein kinetics does not significantly reduce muscle protein synthesis or increase proteolysis. Factors other than protein intake explain lower muscle protein synthesis rates with advanced age. This trial is registered at clinicaltrials.gov as NCT00183040.
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Harber MP, Dickinson JM, Crane JD, Trappe SW, Trappe TA. Influence of tracer selection on protein synthesis rates at rest and postexercise in multiple human muscles. Metabolism 2011; 60:689-97. [PMID: 20822780 PMCID: PMC3079802 DOI: 10.1016/j.metabol.2010.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 06/25/2010] [Accepted: 07/01/2010] [Indexed: 12/29/2022]
Abstract
The goal of this investigation was to assess the influence of tracer selection on mixed muscle fractional synthesis rate (FSR) at rest and postexercise during amino acid infusion in multiple human skeletal muscles. Fractional synthesis rate was measured before and 24 hours after 45 minutes of running using simultaneous infusion of [(2)H(5)]-phenylalanine (Phe) and [(2)H(3)]-leucine (Leu) coupled with muscle biopsies from the vastus lateralis and soleus in aerobically trained men (n = 8; age, 26 ± 2 years). Mixed muscle protein FSR was analyzed by gas chromatography-mass spectrometry combined with a standard curve using the enriched muscle tissue fluid as the precursor pool. To control for potential analytical differences between tracers, all samples and standards for both tracers were matched for m + 0 abundance. Tracer selection did not influence resting FSR for the vastus lateralis or soleus (P > .05). Fractional synthesis rate measured 24 hours postexercise was higher (P < .05) compared with rate at rest and was similar between tracers for the vastus lateralis (Phe, 0.110% ± 0.010%·h(-1); Leu, 0.109% ± 0.005%·h(-1)) and soleus (Phe, 0.123% ± 0.008%·h(-1); Leu, 0.122% ± 0.005%·h(-1)). These data demonstrate that tracer selection does not influence the assessment of resting or postexercise FSR, thereby supporting the use of both [(2)H(5)]-phenylalanine and [(2)H(3)]-leucine for the measurement of FSR in exercise-based studies of human skeletal muscle.
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Affiliation(s)
- Matthew P Harber
- Human Performance Laboratory, Ball State University, Muncie, IN 47306, USA.
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Chen F, Lam R, Shaywitz D, Hendrickson RC, Opiteck GJ, Wishengrad D, Liaw A, Song Q, Stewart AJ, Cummings CE, Beals C, Yarasheski KE, Reicin A, Ruddy M, Hu X, Yates NA, Menetski J, Herman GA. Evaluation of early biomarkers of muscle anabolic response to testosterone. J Cachexia Sarcopenia Muscle 2011; 2:45-56. [PMID: 21475673 PMCID: PMC3063869 DOI: 10.1007/s13539-011-0021-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 01/31/2011] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND: Early biomarkers of skeletal muscle anabolism will facilitate the development of therapies for sarcopenia and frailty. METHODS AND RESULTS: We examined plasma type III collagen N-terminal propeptide (P3NP), skeletal muscle protein fractional synthesis rate, and gene and protein expression profiles to identify testosterone-induced changes in muscle anabolism. Two placebo-controlled studies enrolled community-dwelling men (study 1, 60-75 years; study 2, 18-40 years) with low to normal testosterone levels. Men were randomized to lower dose (study 1, 100 mg; study 2, 200 mg) or higher dose (study 1, 300 mg; study 2, 600 mg) single intramuscular testosterone or saline injection. After 1 week, testosterone acutely increased plasma P3NP levels in a dose-dependent manner and altered the expression of several skeletal muscle transcripts and proteins. Though not statistically significant, mixed muscle protein fractional synthesis rate tended to increase (1.08-fold with 100 mg testosterone, 1.12-fold with 300 mg testosterone). Testosterone exposure also increased skeletal muscle expression of the collagen type III gene that encodes P3NP. CONCLUSION: P3NP is a potentially useful early biomarker for muscle anabolic therapy. Skeletal muscle protein and RNA profiling are useful tools for the discovery of novel muscle anabolic biomarkers.
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Affiliation(s)
- Fabian Chen
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Raymond Lam
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - David Shaywitz
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
- Present Address: Theravance Inc., South San Francisco, CA 94080 USA
| | - Ronald C. Hendrickson
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Gregory J. Opiteck
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Dana Wishengrad
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Andy Liaw
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Qinghua Song
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | | | | | - Chan Beals
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | | | - Alise Reicin
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Marcella Ruddy
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Xuguang Hu
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Nathan A. Yates
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Joseph Menetski
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
| | - Gary A. Herman
- Merck Research Laboratories, Merck & Co. Inc., 126 E. Lincoln Avenue, PO Box 2000, Rahway, NJ 07065 USA
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Villareal DT, Smith GI, Sinacore DR, Shah K, Mittendorfer B. Regular multicomponent exercise increases physical fitness and muscle protein anabolism in frail, obese, older adults. Obesity (Silver Spring) 2011; 19:312-8. [PMID: 20489691 PMCID: PMC3069710 DOI: 10.1038/oby.2010.110] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Aging is associated with a decline in strength, endurance, balance, and mobility. Obesity worsens the age-related impairment in physical function and often leads to frailty. The American College of Sports Medicine recommends a multicomponent (strength, endurance, flexibility, and balance) exercise program to maintain physical fitness. However, the effect of such an exercise program on physical fitness in frail, obese older adults is not known. We therefore determined the effect of a 3-month long multicomponent exercise training program, on endurance (peak aerobic capacity (VO(2) peak)), muscle strength, muscle mass, and the rate of muscle protein synthesis (basal rate and anabolic response to feeding) in nine 65- to 80-year-old, moderately frail, obese older adults. After 3 months of training, fat mass decreased (P < 0.05) whereas fat-free mass (FFM), appendicular lean body mass, strength, and VO(2) peak increased (all P < 0.05). Regular strength and endurance exercise increased the mixed muscle protein fractional synthesis rate (FSR) but had no effect on the feeding-induced increase in muscle protein FSR (~0.02%/h increase from basal values both before and after exercise training; effect of feeding: P = 0.02; effect of training: P = 0.047; no interaction: P = 0.84). We conclude that: (i) a multicomponent exercise training program has beneficial effects on muscle mass and physical function and should therefore be recommended to frail, obese older adults, and (ii) regular multicomponent exercise increases the basal rate of muscle protein synthesis without affecting the magnitude of the muscle protein anabolic response to feeding.
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Affiliation(s)
- Dennis T. Villareal
- Center for Human Nutrition, Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Gordon I. Smith
- Center for Human Nutrition, Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - David R. Sinacore
- Center for Human Nutrition, Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO 63110, USA
- Program in Physical Therapy, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Krupa Shah
- Center for Human Nutrition, Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Bettina Mittendorfer
- Center for Human Nutrition, Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO 63110, USA
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Smith GI, Atherton P, Reeds DN, Mohammed BS, Rankin D, Rennie MJ, Mittendorfer B. Dietary omega-3 fatty acid supplementation increases the rate of muscle protein synthesis in older adults: a randomized controlled trial. Am J Clin Nutr 2011; 93:402-12. [PMID: 21159787 PMCID: PMC3021432 DOI: 10.3945/ajcn.110.005611] [Citation(s) in RCA: 418] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Loss of muscle mass with aging is a major public health concern. Omega-3 (n-3) fatty acids stimulate protein anabolism in animals and might therefore be useful for the treatment of sarcopenia. However, the effect of omega-3 fatty acids on human protein metabolism is unknown. OBJECTIVE The objective of this study was to evaluate the effect of omega-3 fatty acid supplementation on the rate of muscle protein synthesis in older adults. DESIGN Sixteen healthy, older adults were randomly assigned to receive either omega-3 fatty acids or corn oil for 8 wk. The rate of muscle protein synthesis and the phosphorylation of key elements of the anabolic signaling pathway were evaluated before and after supplementation during basal, postabsorptive conditions and during a hyperaminoacidemic-hyperinsulinemic clamp. RESULTS Corn oil supplementation had no effect on the muscle protein synthesis rate and the extent of anabolic signaling element phosphorylation in muscle. Omega-3 fatty acid supplementation had no effect on the basal rate of muscle protein synthesis (mean ± SEM: 0.051 ± 0.005%/h compared with 0.053 ± 0.008%/h before and after supplementation, respectively; P = 0.80) but augmented the hyperaminoacidemia-hyperinsulinemia-induced increase in the rate of muscle protein synthesis (from 0.009 ± 0.005%/h above basal values to 0.031 ± 0.003%/h above basal values; P < 0.01), which was accompanied by greater increases in muscle mTOR(Ser2448) (P = 0.08) and p70s6k(Thr389) (P < 0.01) phosphorylation. CONCLUSION Omega-3 fatty acids stimulate muscle protein synthesis in older adults and may be useful for the prevention and treatment of sarcopenia. This trial was registered at clinical trials.gov as NCT00794079.
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Affiliation(s)
- Gordon I Smith
- Washington University School of Medicine, St Louis, MO 63110, USA
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Smith GI, Patterson BW, Mittendorfer B. Human muscle protein turnover--why is it so variable? J Appl Physiol (1985) 2010; 110:480-91. [PMID: 21109595 DOI: 10.1152/japplphysiol.00125.2010] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
We undertook a comprehensive review of the literature to unravel the nature of the variability in the reported rate of human muscle protein synthesis. We analyzed the results from studies that report the protein fractional synthesis rate (FSR) in the vastus lateralis in healthy, nonobese, untrained adults ≤50 yr of age in the postabsorptive state at rest by using the primed, constant tracer amino acid infusion method according to experimental design characteristics. We hypothesized that if the variability is methodological (rather than physiological) in nature, systematic clustering of FSR values would be evident, and outliers would become apparent. Overall, as expected, the mixed muscle protein FSR values were significantly (P < 0.001) greater when the muscle vs. the plasma free amino acid enrichment is used as the surrogate precursor pool enrichment, and the average mixed muscle protein FSR values were significantly greater (P = 0.05) than the myofibrillar/myosin heavy chain FSR values. The within-study variability (i.e., population variance) was somewhat smaller in studies that used plasma amino acid/ketoacid enrichments vs. muscle free amino acid enrichment (∼24 vs. ∼31%), but this was not apparent in all circumstances. Furthermore, the between-study consistency of measured FSR values (i.e., interquartile range) was inversely correlated with the average duration between biopsies. Aside from that, the variation in reported FSR values could not be explained by differences in the experimental design and analytical methods, and none of the most commonly used approaches stood out as clearly superior in terms of consistency of results and/or within-study variability. We conclude that the variability in reported values is in part due to 1) differences in experimental design (e.g., choice of precursor pool) and 2) considerable within-subject variability. The summary of the results from our analysis can be used as guidelines for "normal" average basal FSR values at rest in healthy adults.
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Affiliation(s)
- Gordon I Smith
- Division of Geriatrics and Nutritional Science, Washington Univ. School of Medicine, 660 South Euclid Ave., Campus Box 8031, St. Louis, MO 63110, USA
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Gasier HG, Fluckey JD, Previs SF. The application of 2H2O to measure skeletal muscle protein synthesis. Nutr Metab (Lond) 2010; 7:31. [PMID: 20409307 PMCID: PMC2873296 DOI: 10.1186/1743-7075-7-31] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 04/21/2010] [Indexed: 12/21/2022] Open
Abstract
Skeletal muscle protein synthesis has generally been determined by the precursor:product labeling approach using labeled amino acids (e.g., [13C]leucine or [13C]-, [15N]-, or [2H]phenylalanine) as the tracers. Although reliable for determining rates of protein synthesis, this methodological approach requires experiments to be conducted in a controlled environment, and as a result, has limited our understanding of muscle protein renewal under free-living conditions over extended periods of time (i.e., integrative/cumulative assessments). An alternative tracer, 2H2O, has been successfully used to measure rates of muscle protein synthesis in mice, rats, fish and humans. Moreover, perturbations such as feeding and exercise have been included in these measurements without exclusion of common environmental and biological factors. In this review, we discuss the principle behind using 2H2O to measure muscle protein synthesis and highlight recent investigations that have examined the effects of feeding and exercise. The framework provided in this review should assist muscle biologists in designing experiments that advance our understanding of conditions in which anabolism is altered (e.g., exercise, feeding, growth, debilitating and metabolic pathologies).
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Affiliation(s)
- Heath G Gasier
- Naval Submarine Medical Research Laboratory, Groton, CT, USA.
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Robinson MM, Richards JC, Hickey MS, Moore DR, Phillips SM, Bell C, Miller BF. Acute β-adrenergic stimulation does not alter mitochondrial protein synthesis or markers of mitochondrial biogenesis in adult men. Am J Physiol Regul Integr Comp Physiol 2010; 298:R25-33. [DOI: 10.1152/ajpregu.00524.2009] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exercise-induced expression of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) is dramatically inhibited in mice pretreated with a β-adrenergic receptor (β-AR) antagonist, suggesting that β-ARs play an important role in the regulation of skeletal muscle PGC-1α expression, and potentially, mitochondrial biogenesis. Accordingly, we hypothesized that acute β-AR stimulation would induce transcriptional pathways involved in skeletal muscle mitochondrial biogenesis in humans. Whole body protein turnover (WBPT), myofibrillar protein synthesis (MyPS), skeletal muscle mitochondrial protein synthesis (MiPS), and mitochondrial biogenic signaling were determined in samples of vastus lateralis obtained on two separate occasions in 10 young adult males following 1 h of continuous intravenous administration of saline (CON) or a nonspecific β-AR agonist [isoproterenol (ISO): 12 ng·kg fat free mass−1·min−1], combined with coinfusion of [1,2]13C-leucine. β-AR stimulation induced appreciable increases in heart rate and systolic blood pressure (both P < 0.001) but did not affect mitochondrial biogenic signaling (no change in PGC-1α, TFAM, NRF-1, NRF-2, COX, or NADHox expression via RT-PCR; P > 0.05). Additionally, MiPS [CON: 0.099 ± 0.028, ISO: 0.074 ± 0.046 (mean ± SD); P > 0.05] and MyPS (CON: 0.059 ± 0.008, ISO: 0.055 ± 0.009; P > 0.05), as well as measures of WBPT were unaffected. On the basis of this investigation, we conclude that acute intravenous β-AR stimulation does not increase mitochondrial protein synthesis or biogenesis signals in skeletal muscle.
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Affiliation(s)
- Matthew M. Robinson
- Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; and
| | - Jennifer C. Richards
- Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; and
| | - Matthew S. Hickey
- Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; and
| | - Daniel R. Moore
- Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
| | - Stuart M. Phillips
- Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
| | - Christopher Bell
- Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; and
| | - Benjamin F. Miller
- Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; and
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Smith GI, Villareal DT, Lambert CP, Reeds DN, Mohammed BS, Mittendorfer B. Timing of the initial muscle biopsy does not affect the measured muscle protein fractional synthesis rate during basal, postabsorptive conditions. J Appl Physiol (1985) 2009; 108:363-8. [PMID: 19940095 DOI: 10.1152/japplphysiol.00957.2009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The muscle protein fractional synthesis rate (FSR) is determined by monitoring the incorporation of an amino acid tracer into muscle protein during a constant-rate intravenous tracer infusion. Commonly two sequential muscle biopsies are obtained some time after starting the tracer infusion. However, other protocols, including those with an initial biopsy before starting the tracer infusion to measure the background enrichment and those with only a single biopsy after several hours of tracer infusion have been used. To assess the validity of these approaches, we compared the muscle protein FSR obtained by calculating the difference in [ring-(2)H(5)]phenylalanine and [5,5,5-(2)H(3)]leucine incorporation into muscle protein at approximately 3.5 h after starting the tracer infusion and 1) at 60 min; 2) before starting the tracer infusion (background enrichment); 3) a population average muscle protein background enrichment; and 4) by measuring the tracer incorporation into muscle protein at approximately 3.5 h assuming essentially no background enrichment. Irrespective of the tracer used, the muscle protein FSR calculated from the difference in the muscle protein labeling several hours after starting the tracer infusion and either the labeling at 60 min or the background enrichment were not different (e.g., 0.049 +/- 0.007%/h vs. 0.049 +/- 0.007%/h, respectively, with [(2)H(5)]phenylalanine; P = 0.99). However, omitting the initial biopsy and assuming no background enrichment yielded average FSR values that were approximately 15% (with [(2)H(5)]phenylalanine) to 80% (with [(2)H(3)]leucine) greater (P < or = 0.059); using a population average background enrichment reduced the difference to approximately 3% (P = 0.76) and 22% (P = 0.52) with [(2)H(5)]phenylalanine and [(2)H(3)]leucine, respectively. We conclude that during basal, postabsorptive conditions, valid muscle protein FSR values can be obtained irrespective of the timing of the initial biopsy so long as the protein labeling in two sequential biopsies is measured whereas the single biopsy approach should be avoided.
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Affiliation(s)
- Gordon I Smith
- Washington Univ. School of Medicine, 660 South Euclid Ave., Campus Box 8031, St. Louis, MO 63110, USA
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Wilkes EA, Selby AL, Atherton PJ, Patel R, Rankin D, Smith K, Rennie MJ. Blunting of insulin inhibition of proteolysis in legs of older subjects may contribute to age-related sarcopenia. Am J Clin Nutr 2009; 90:1343-50. [PMID: 19740975 DOI: 10.3945/ajcn.2009.27543] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Reduced postprandial muscle proteolysis is mainly due to increased insulin availability. Whether rates of proteolysis in response to low physiologic doses of insulin are affected by aging is unknown. OBJECTIVES We tested the hypothesis that suppression of leg protein breakdown (LPB) by insulin is blunted in older subjects, together with blunted activation of Akt-protein kinase B (PKB). DESIGN Groups of 8 young [mean (+/-SD) age: 24.5 +/- 1.8 y] and older (65.0 +/- 1.3 y) participants were studied during euglycemic (5 mmol/L), isoaminoacidemic (blood leucine approximately 120 micromol/L) clamp procedures at plasma insulin concentrations of approximately 5 and approximately 15 microIU/mL for 1.5 h. Leg amino acid balance, whole-leg protein turnover (as dilution of amino acid tracers), and muscle protein synthesis were measured with D(5)-phenylalanine and [1,2-(13)C(2)]leucine. The kinase activity of muscle Akt-PKB and the extent of phosphorylation of signaling proteins associated with the mTOR (mammalian target of rapamycin) pathway were measured before and after the clamp procedures. RESULTS Basal LPB rates were not different between groups (66 +/- 11 compared with 51 +/- 10 nmol leucine x 100 mL leg(-1) x min(-1) and 30 +/- 5 compared with 24 +/- 4 nmol phenylalanine x 100 mL leg(-1) x min(-1) in young and older groups, respectively). However, although insulin at approximately 15 microIU/mL lowered LPB by 47% in the young subjects (P < 0.05) and abolished the negative leg amino acid balance, this caused only a 12% fall (P > 0.05) in the older group. Akt-PKB activity mirrored decreases in LPB. No differences were seen in muscle protein synthesis or associated anabolic signaling phosphoproteins. CONCLUSIONS At moderate availability, the effect of insulin on LPB is diminished in older human beings, and this effect may be mediated through blunted Akt-PKB activation.
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Affiliation(s)
- Emilie A Wilkes
- University of Nottingham, School of Graduate Entry Medicine and Health, Derby, United Kingdom
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Smith GI, Atherton P, Reeds DN, Mohammed BS, Jaffery H, Rankin D, Rennie MJ, Mittendorfer B. No major sex differences in muscle protein synthesis rates in the postabsorptive state and during hyperinsulinemia-hyperaminoacidemia in middle-aged adults. J Appl Physiol (1985) 2009; 107:1308-15. [PMID: 19644030 DOI: 10.1152/japplphysiol.00348.2009] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Men have more muscle than women, but most studies evaluating sex differences in muscle protein metabolism have been unable to discern sexual dimorphism in basal muscle protein turnover rates in young and middle-aged adults. We hypothesized that the anabolic response to nutritional stimuli (i.e., amino acids and insulin) would be greater in young/middle-aged men than women. We therefore measured the rates of muscle protein synthesis (MPS) in 16 healthy individuals [8 men and 8 women, matched for age (mean +/- SE: 37.7 +/- 1.5 yr) and body mass index (25.2 +/- 0.7 kg/m2)] after an overnight fast (plasma insulin approximately 5 microU/ml and plasma phenylalanine approximately 60 microM) and during a hyperinsulinemic-hyperaminoacidemic-euglycemic clamp (plasma insulin approximately 28 microU/ml; plasma phenylalanine approximately 110 microM; plasma glucose approximately 5.4 mM). The rates of MPS were not different between men and women (ANOVA main effect for sex; P = 0.49). During the clamp, the rate of MPS increased by approximately 50% (P = 0.003) with no difference in the increases from basal values between men and women (+0.019 +/- 0.004 vs. +0.018 +/- 0.010%/h, respectively; P = 0.93). There were also no differences between men and women in the basal concentrations of muscle phosphorylated Akt(Ser473), Akt(Thr308), mTOR(Ser2448), and p70s6k(Thr389) or in the hyperinsulinemia-hyperaminoacidemia-induced increases in phosphorylation of those signaling elements (P > or = 0.25). We conclude that there are no major differences in the rate of MPS and its intracellular control during basal conditions and during hyperinsulinemia-hyperaminoacidema between young and middle-aged adult men and women.
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Affiliation(s)
- Gordon I Smith
- Division of Geriatrics and Nutritional Science, Washington University School of Medicine, 660 South Euclid Ave, Campus Box 8031, St. Louis, MO 63110, USA
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Moore DR, Robinson MJ, Fry JL, Tang JE, Glover EI, Wilkinson SB, Prior T, Tarnopolsky MA, Phillips SM. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am J Clin Nutr 2009; 89:161-8. [PMID: 19056590 DOI: 10.3945/ajcn.2008.26401] [Citation(s) in RCA: 577] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The anabolic effect of resistance exercise is enhanced by the provision of dietary protein. OBJECTIVES We aimed to determine the ingested protein dose response of muscle (MPS) and albumin protein synthesis (APS) after resistance exercise. In addition, we measured the phosphorylation of candidate signaling proteins thought to regulate acute changes in MPS. DESIGN Six healthy young men reported to the laboratory on 5 separate occasions to perform an intense bout of leg-based resistance exercise. After exercise, participants consumed, in a randomized order, drinks containing 0, 5, 10, 20, or 40 g whole egg protein. Protein synthesis and whole-body leucine oxidation were measured over 4 h after exercise by a primed constant infusion of [1-(13)C]leucine. RESULTS MPS displayed a dose response to dietary protein ingestion and was maximally stimulated at 20 g. The phosphorylation of ribosomal protein S6 kinase (Thr(389)), ribosomal protein S6 (Ser(240/244)), and the epsilon-subunit of eukaryotic initiation factor 2B (Ser(539)) were unaffected by protein ingestion. APS increased in a dose-dependent manner and also reached a plateau at 20 g ingested protein. Leucine oxidation was significantly increased after 20 and 40 g protein were ingested. CONCLUSIONS Ingestion of 20 g intact protein is sufficient to maximally stimulate MPS and APS after resistance exercise. Phosphorylation of candidate signaling proteins was not enhanced with any dose of protein ingested, which suggested that the stimulation of MPS after resistance exercise may be related to amino acid availability. Finally, dietary protein consumed after exercise in excess of the rate at which it can be incorporated into tissue protein stimulates irreversible oxidation.
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Affiliation(s)
- Daniel R Moore
- Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Canada
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Kumar V, Selby A, Rankin D, Patel R, Atherton P, Hildebrandt W, Williams J, Smith K, Seynnes O, Hiscock N, Rennie MJ. Age-related differences in the dose-response relationship of muscle protein synthesis to resistance exercise in young and old men. J Physiol 2008; 587:211-7. [PMID: 19001042 DOI: 10.1113/jphysiol.2008.164483] [Citation(s) in RCA: 498] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We investigated how myofibrillar protein synthesis (MPS) and muscle anabolic signalling were affected by resistance exercise at 20-90% of 1 repetition maximum (1 RM) in two groups (25 each) of post-absorptive, healthy, young (24 +/- 6 years) and old (70 +/- 5 years) men with identical body mass indices (24 +/- 2 kg m(-2)). We hypothesized that, in response to exercise, anabolic signalling molecule phosphorylation and MPS would be modified in a dose-dependant fashion, but to a lesser extent in older men. Vastus lateralis muscle was sampled before, immediately after, and 1, 2 and 4 h post-exercise. MPS was measured by incorporation of [1,2-(13)C] leucine (gas chromatography-combustion-mass spectrometry using plasma [1,2-(13)C]alpha-ketoisocaparoate as surrogate precursor); the phosphorylation of p70 ribosomal S6 kinase (p70s6K) and eukaryotic initiation factor 4E binding protein 1 (4EBP1) was measured using Western analysis with anti-phosphoantibodies. In each group, there was a sigmoidal dose-response relationship between MPS at 1-2 h post-exercise and exercise intensity, which was blunted (P < 0.05) in the older men. At all intensities, MPS fell in both groups to near-basal values by 2-4 h post-exercise. The phosphorylation of p70s6K and 4EBP1 at 60-90% 1 RM was blunted in older men. At 1 h post-exercise at 60-90% 1 RM, p70s6K phosphorylation predicted the rate of MPS at 1-2 h post-exercise in the young but not in the old. The results suggest that in the post-absorptive state: (i) MPS is dose dependant on intensity rising to a plateau at 60-90% 1 RM; (ii) older men show anabolic resistance of signalling and MPS to resistance exercise.
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Affiliation(s)
- Vinod Kumar
- University of Nottingham, School of Graduate Entry Medicine and Health, City Hospital, Uttoxeter Road, Derby, DE22 3DT, UK
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Raj D, Moseley P, Dominic E, Onime A, Tzamaloukas A, Boyd A, Shah V, Glew R, Wolfe R, Ferrando A. Interleukin-6 modulates hepatic and muscle protein synthesis during hemodialysis. Kidney Int 2008; 73:1054-61. [DOI: 10.1038/ki.2008.21] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Smith GI, Atherton P, Villareal DT, Frimel TN, Rankin D, Rennie MJ, Mittendorfer B. Differences in muscle protein synthesis and anabolic signaling in the postabsorptive state and in response to food in 65-80 year old men and women. PLoS One 2008; 3:e1875. [PMID: 18365020 PMCID: PMC2267222 DOI: 10.1371/journal.pone.0001875] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Accepted: 02/21/2008] [Indexed: 12/25/2022] Open
Abstract
Women have less muscle than men but lose it more slowly during aging. To discover potential underlying mechanism(s) for this we evaluated the muscle protein synthesis process in postabsorptive conditions and during feeding in twenty-nine 65-80 year old men (n = 13) and women (n = 16). We discovered that the basal concentration of phosphorylated eEF2(Thr56) was approximately 40% less (P<0.05) and the basal rate of MPS was approximately 30% greater (P = 0.02) in women than in men; the basal concentrations of muscle phosphorylated Akt(Thr308), p70s6k(Thr389), eIF4E(Ser209), and eIF4E-BP1(Thr37/46) were not different between the sexes. Feeding increased (P<0.05) Akt(Thr308) and p70s6k(Thr389) phosphorylation to the same extent in men and women but increased (P<0.05) the phosphorylation of eIF4E(Ser209) and eIF4E-BP1(Thr37/46) in men only. Accordingly, feeding increased MPS in men (P<0.01) but not in women. The postabsorptive muscle mRNA concentrations for myoD and myostatin were not different between sexes; feeding doubled myoD mRNA (P<0.05) and halved that of myostatin (P<0.05) in both sexes. Thus, there is sexual dimorphism in MPS and its control in older adults; a greater basal rate of MPS, operating over most of the day may partially explain the slower loss of muscle in older women.
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Affiliation(s)
- Gordon I. Smith
- School of Medicine, Washington University, St. Louis, Missouri, United States of America
| | - Philip Atherton
- School of Graduate Entry Medicine and Health, University of Nottingham, Derby, United Kingdom
| | - Dennis T. Villareal
- School of Medicine, Washington University, St. Louis, Missouri, United States of America
| | - Tiffany N. Frimel
- School of Medicine, Washington University, St. Louis, Missouri, United States of America
| | - Debbie Rankin
- School of Graduate Entry Medicine and Health, University of Nottingham, Derby, United Kingdom
| | - Michael J. Rennie
- School of Graduate Entry Medicine and Health, University of Nottingham, Derby, United Kingdom
| | - Bettina Mittendorfer
- School of Medicine, Washington University, St. Louis, Missouri, United States of America
- * E-mail:
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Januszkiewicz A, Rooyackers O, Wernerman J. Quantitative in vivo Protein Synthesis as a Measure of Immune Function. Intensive Care Med 2007. [DOI: 10.1007/0-387-35096-9_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Afolabi PR, Jahoor F, Jackson AA, Stubbs J, Johnstone AM, Faber P, Lobley G, Gibney E, Elia M. The effect of total starvation and very low energy diet in lean men on kinetics of whole body protein and five hepatic secretory proteins. Am J Physiol Endocrinol Metab 2007; 293:E1580-9. [PMID: 17878226 DOI: 10.1152/ajpendo.00169.2007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is unclear whether the rate of weight loss, independent of magnitude, affects whole body protein metabolism and the synthesis and plasma concentrations of specific hepatic secretory proteins. We examined 1) whether lean men losing weight rapidly (starvation) show greater changes in whole body protein kinetics, synthesis, and circulating concentrations of selected hepatic secretory proteins than those losing the same amount of weight more slowly [very low energy diet (VLED)]; and 2) whether plasma concentrations and synthetic rates of these proteins are related. Whole body protein kinetics were measured using [1-(13)C]leucine in 11 lean men (6 starvation, 5 VLED). Fractional and absolute synthetic rates of HDL-apolipoprotein A1 (apoA1), retinol binding protein, transthyretin, alpha(1)-antitrypsin (alpha(1)-AT), and transferrin were measured using a prime-constant intravenous infusion of [(13)C(2)]glycine. Compared with VLED group, the starvation group showed greater increases (at a 5% weight loss) in whole body protein oxidation (P < 0.05); fractional synthetic rates of HDL-apoA1 (25.3 vs. -1.52%; P = 0.003) and retinol binding protein (30.6 vs. 7.1%; P = 0.007); absolute synthetic rates of HDL-apoA1 (7.1 vs. -3.8 mg.kg(-1).day(-1); P = 0.003) and alpha(1)-AT (17.8 vs. 3.6 mg.kg(-1).day(-1); P = 0.02); and plasma concentration of alpha(1)-AT (P = 0.025). Relationships between synthetic rates and plasma concentrations varied between the secreted proteins. It is concluded that synthetic rates of hepatic secreted proteins in lean men are more closely related to the rate than the magnitude of weight loss. Changes in concentration of these secreted proteins can occur independently of changes in synthetic rates, and vice versa.
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Affiliation(s)
- Paul R Afolabi
- Institute of Human Nutrition, Univ. of Southampton, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD United Kingdom
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Wolfe RR, Song J, Sun J, Zhang XJ. Total aminoacyl-transfer RNA pool is greater in liver than muscle in rabbits. J Nutr 2007; 137:2333-8. [PMID: 17951466 DOI: 10.1093/jn/137.11.2333] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Transfer RNA (tRNA)-charged amino acids are direct precursors of protein synthesis. Therefore, the amount and profile of amino acids in the aminoacyl-tRNA pool may be closely related to the rate of protein synthesis in the tissue. This study was designed to compare the aminoacyl-tRNA pools in liver and muscle, 2 distinct tissues with different rates of protein synthesis. Liver and muscle samples were taken from 6 rabbits and aminoacyl-tRNA was isolated with sequential acid-phenol:chloroform extraction, followed by total RNA and tRNA purification. Amino acids in the aminoacyl-tRNA pool were measured by HPLC after deacylation. Liver contained 3.4 times more tRNA than muscle (585 +/- 120 vs. 132 +/- 11 microg of tRNA/g of tissue; P < 0.001). Overall tRNA charging was also greater in liver (14.22 +/- 4.42 nmol of amino acids/mg of tRNA) than in muscle (7.00 +/- 1.76 nmol of amino acids/mg of tRNA) (P < 0.05). The greater availability and charging efficiency of tRNA in liver as compared with muscle may influence the extent to which amino acid precursor availability regulates protein synthesis in these 2 tissues.
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Affiliation(s)
- Robert R Wolfe
- Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
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Petersen AMW, Magkos F, Atherton P, Selby A, Smith K, Rennie MJ, Pedersen BK, Mittendorfer B. Smoking impairs muscle protein synthesis and increases the expression of myostatin and MAFbx in muscle. Am J Physiol Endocrinol Metab 2007; 293:E843-8. [PMID: 17609255 DOI: 10.1152/ajpendo.00301.2007] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Smoking causes multiple organ dysfunction. The effect of smoking on skeletal muscle protein metabolism is unknown. We hypothesized that the rate of skeletal muscle protein synthesis is depressed in smokers compared with non-smokers. We studied eight smokers (> or =20 cigarettes/day for > or =20 years) and eight non-smokers matched for sex (4 men and 4 women per group), age (65 +/- 3 and 63 +/- 3 yr, respectively; means +/- SEM) and body mass index (25.9 +/- 0.9 and 25.1 +/- 1.2 kg/m(2), respectively). Each subject underwent an intravenous infusion of stable isotope-labeled leucine in conjunction with blood and muscle tissue sampling to measure the mixed muscle protein fractional synthesis rate (FSR) and whole body leucine rate of appearance (Ra) in plasma (an index of whole body proteolysis), the expression of genes involved in the regulation of muscle mass (myostatin, a muscle growth inhibitor, and MAFBx and MuRF-1, which encode E3 ubiquitin ligases in the proteasome proteolytic pathway) and that for the inflammatory cytokine TNF-alpha in muscle, and the concentration of inflammatory markers in plasma (C-reactive protein, TNF-alpha, interleukin-6) which are associated with muscle wasting in other conditions. There were no differences between nonsmokers and smokers in plasma leucine concentration, leucine rate of appearance, and plasma concentrations of inflammatory markers, or TNF-alpha mRNA in muscle, but muscle protein FSR was much less (0.037 +/- 0.005 vs. 0.059 +/- 0.005%/h, respectively, P = 0.004), and myostatin and MAFBx (but not MuRF-1) expression were much greater (by approximately 33 and 45%, respectivley, P < 0.05) in the muscle of smokers than of nonsmokers. We conclude that smoking impairs the muscle protein synthesis process and increases the expression of genes associated with impaired muscle maintenance; smoking therefore likely increases the risk of sarcopenia.
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Affiliation(s)
- Anne Marie Winther Petersen
- Centre of Inflammation and Metabolism, Department of Infectious Diseases and Copenhagen Muscle Research Centre, Copenhagen, Denmark
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Smith GI, Villareal DT, Mittendorfer B. Measurement of human mixed muscle protein fractional synthesis rate depends on the choice of amino acid tracer. Am J Physiol Endocrinol Metab 2007; 293:E666-71. [PMID: 17535855 DOI: 10.1152/ajpendo.00185.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The goal of this study was to discover whether using different tracers affects the measured rate of muscle protein synthesis in human muscle. We therefore measured the mixed muscle protein fractional synthesis rate (FSR) in the quadriceps of older adults during basal, postabsorptive conditions and mixed meal feeding (70 mg protein x kg fat-free mass(-1) x h(-1) x 2.5 h) by simultaneous intravenous infusions of [5,5,5-(2)H(3)]leucine and either [ring-(13)C(6)]phenylalanine or [ring-(2)H(5)]phenylalanine and analysis of muscle tissue samples by gas chromatography-mass spectrometry. Both the basal FSR and the FSR during feeding were approximately 20% greater (P < 0.001) when calculated from the leucine labeling in muscle tissue fluid and proteins (fasted: 0.063 +/- 0.005%/h; fed: 0.080 +/- 0.007%/h) than when calculated from the phenylalanine enrichment data (0.051 +/- 0.004 and 0.066 +/- 0.005%/h, respectively). The feeding-induced increase in the FSR ( approximately 20%; P = 0.011) was not different with leucine and phenylalanine tracers (P = 0.69). Furthermore, the difference between the leucine- and phenylalanine-derived FSRs was independent of the phenylalanine isotopomer used (P = 0.92). We conclude that when using stable isotope-labeled tracers and the classic precursor product model to measure the rate of muscle protein synthesis, absolute rates of muscle protein FSR differ significantly depending on the tracer amino acid used; however, the anabolic response to feeding is independent of the tracer used. Thus different precursor amino acid tracers cannot be used interchangeably for the evaluation of muscle protein synthesis, and data from studies using different tracer amino acids can be compared qualitatively but not quantitatively.
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Affiliation(s)
- Gordon I Smith
- Washington University School of Medicine, St. Louis, MO 63110, USA
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Winter TA, O'Keefe SJ, Callanan M, Marks T. Effect of severe undernutrition and subsequent refeeding on gut mucosal protein fractional synthesis in human subjects. Nutrition 2007; 23:29-35. [PMID: 17189088 DOI: 10.1016/j.nut.2006.10.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Revised: 10/12/2006] [Accepted: 10/16/2006] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Undernutrition has been associated with gut mucosal atrophy, impaired absorption, and increased permeability. This study investigated the effect of severe undernutrition and subsequent refeeding on gastric and duodenal mucosal protein fractional syntheses (MPFS). METHODS MPFS was investigated in the gastric body, antrum, and duodenum of 23 severely undernourished patients by means of (14)C-leucine incorporation into tissue protein and repeated after a period of refeeding. Results were evaluated in comparison with a group of 22 healthy controls and presented as mean +/- standard error of the mean. RESULTS The mean body index of the undernourished patients was 13.29 +/- 0.33 kg/m(2) versus 22.67 +/- 0.63 kg/m(2) in the controls (P < 0.001). MPFS in the controls and undernourished patients were similar (gastric body, 36.49 +/- 2.88 versus 33.41 +/- 3.08%/d; gastric antrum, 25.51 +/- 2.20 versus 24.95 +/- 2.32%/d; duodenum, 25.90 +/- 2.58 versus 25.49 +/- 1.99%/d). After refeeding, the body mass index of the undernourished patients increased to 15.87 +/- 0.44 kg/m(2) (P < 0.001). The MPFS increased significantly (gastric body, 51.80 +/- 8.12%/d, P < 0.05; gastric antrum, 33.44 +/- 3.66%/d, P < 0.05; duodenum, 46.27 +/- 8.02%/d, P < 0.01), with the MPFS of the duodenum significantly greater than the control values (P = 0.01). CONCLUSION Despite severe undernutrition, MPFS of the gastric body, antrum, and duodenum remained similar to control values. Enteral feeding resulted in a significant increase in MPFS, indicating a trophic response.
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Affiliation(s)
- Trevor A Winter
- Division of Digestive Disease and Nutrition, University of Kentucky, Lexington, Kentucky, USA.
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Caso G, Garlick PJ, Ballou LM, Vosswinkel JA, Gelato MC, McNurlan MA. The increase in human muscle protein synthesis induced by food intake is similar when assessed with the constant infusion and flooding techniques. J Nutr 2006; 136:1504-10. [PMID: 16702312 DOI: 10.1093/jn/136.6.1504] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Food intake is accompanied by a stimulation of muscle protein synthesis. However, the reported magnitude of the response differs with different methods of measurement. The aim of this study was to assess whether the response to feeding is dependent on the technique used for measurement when length and amount of feeding are controlled. Muscle protein fractional synthesis rates (FSRs) were measured both in the fasting and feeding states in 2 groups of healthy volunteers (n = 8). Two techniques were used to measure FSR: in one group, FSRs were assessed with a primed constant infusion of L-[2H5]phenylalanine, whereas in the other, a flooding amount of the same label was employed. The fasting FSRs assessed with the constant infusion method and estimated using the free amino acid in the tissue fluid to represent the precursor pool for protein synthesis were comparable to those obtained with the flooding method (1.94 +/- 0.15 vs. 1.86 +/- 0.13%/d). The degree of stimulation due to feeding (P < 0.02) did not differ between the constant infusion (+15%) and flooding (+22%) techniques. The stimulatory effect of feeding on muscle FSR was associated with enhanced phosphorylation of the Mr = 70,000 ribosomal protein S6 kinase, suggesting that it may involve activation of translation. This study demonstrates that human muscle FSRs obtained with the constant infusion technique are comparable to those obtained with the flooding method and that, in response to feeding, the 2 techniques give comparable estimates of stimulation.
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Affiliation(s)
- Giuseppe Caso
- Department of Surgery, Stony Brook University, Stony Brook, NY 11794, USA.
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Prod'homme M, Rochon C, Balage M, Laurichesse H, Tauveron I, Champredon C, Thieblot P, Beytout J, Grizard J. Whole body leucine flux in HIV-infected patients treated with or without protease inhibitors. Am J Physiol Endocrinol Metab 2006; 290:E685-93. [PMID: 16249256 DOI: 10.1152/ajpendo.00067.2005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study was carried out to assess the effects of protease inhibitor (PI) therapy on basal whole body protein metabolism and its response to acute amino acid-glucose infusion in 14 human immunodeficiency virus (HIV)-infected patients. Patients treated with PIs (PI+, 7 patients) or without PIs (PI-, 7 patients) were studied after an overnight fast during a 180-min basal period followed by a 140-min period of amino acid-glucose infusion. Protein metabolism was investigated by a primed constant infusion of l-[1-(13)C]leucine. Dual-energy X-ray absorptiometry for determination of fat-free mass (FFM) and body fat mass measured body composition. In the postabsorptive state, whole body leucine balance was 2.5 times (P < 0.05) less negative in the PI+ than in the PI- group. In HIV-infected patients treated with PIs, the oxidative leucine disposal during an acute amino acid-glucose infusion was lower (0.58 +/- 0.09 vs. 0.81 +/- 0.07 micromol x kg FFM(-1) x min(-1) using plasma [(13)C]leucine enrichment, P = 0.06; or 0.70 +/- 0.10 vs. 0.99 +/- 0.08 micromol x kg FFM(-1) x min(-1) using plasma [(13)C]ketoisocaproic acid enrichment, P = 0.04 in PI+ and PI- groups, respectively) than in patients treated without PIs. Consequently, whole body nonoxidative leucine disposal (an index of protein synthesis) and leucine balance (0.50 +/- 0.10 vs. 0.18 +/- 0.06 micromol x kg FFM x (-1) x min(-1) in PI+ and PI- groups respectively, P < 0.05) were significantly improved during amino acid-glucose infusion in patients treated with PIs. However, whereas the response of whole body protein anabolism to an amino acid-glucose infusion was increased in HIV-infected patients treated with PIs, any improvement in lean body mass was detected.
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Affiliation(s)
- Magali Prod'homme
- Unité de Nutrition et Métabolisme Protéique, Institut National de la Recherche Agronomique, Clermont-Ferrand/Theix, Saint-Genès-Champanelle, France
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