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Singh P, Banton S, Bosch G, Hendriks WH, Shoveller AK. Beyond the Bowl: Understanding Amino Acid Requirements and Digestibility to Improve Protein Quality Metrics for Dog and Cat Foods. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1446:99-134. [PMID: 38625526 DOI: 10.1007/978-3-031-54192-6_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
The determination of amino acid (AA) requirements for mammals has traditionally been done through nitrogen (N) balance studies, but this technique underestimates AA requirements in adult animals. There has been a shift toward researchers using the indicator amino acid oxidation (IAAO) technique for the determination of AA requirements in humans, and recently in dogs. However, the determination of AA requirements specific to adult dogs and cats at maintenance is lacking and the current requirements outlined by the National Research Council are based on a dearth of data and are likely underreporting the requirements of indispensable AA (IAA) for the population. To ensure the physiological requirements of our cats and dogs are met, we need methods to accurately and precisely measure digestibility. In vivo methods, such as ileal cannulation, are most commonly used, however, due to ethical considerations, we are moving away from animal models and toward in vitro methods. Harmonized static digestion models have the potential to replace in vivo methods but work needs to be done to have these methods more accurately represent the gastrointestinal tract (GIT) of cats and dogs. The Digestible IAA Score (DIAAS) is one metric that can help define protein quality for individual ingredients or mixed diets that uses AA SID estimates and ideally those can be replaced with in vitro AA digestibility estimates. Finally, we need accurate and reliable laboratory AA analyses to measure the AA present in complete diets, especially those used to quantify methionine (Met) and cysteine (Cys), both often limiting AAs in cat and dog diets. Together, this will guide accurate feed formulation for our companion animals to satisfy requirements while avoiding over-supplying protein, which inevitably contributes to excess N excretion, affecting both the environment and feed sustainability.
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Affiliation(s)
- Pawanpreet Singh
- Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - Sydney Banton
- Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - Guido Bosch
- Animal Nutrition Group, Wageningen University, Wageningen, The Netherlands
| | - Wouter H Hendriks
- Animal Nutrition Group, Wageningen University, Wageningen, The Netherlands
| | - Anna K Shoveller
- Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada.
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Tessari P. Stepwise Discovery of Insulin Effects on Amino Acid and Protein Metabolism. Nutrients 2023; 16:119. [PMID: 38201949 PMCID: PMC10780923 DOI: 10.3390/nu16010119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 12/10/2023] [Accepted: 12/22/2023] [Indexed: 01/12/2024] Open
Abstract
A clear effect of insulin deficiency and replacement on body/muscle mass was a landmark observation at the start of the insulin age. Since then, an enormous body of investigations has been produced on the pathophysiology of diabetes mellitus from a hormonal/metabolic point of view. Among them, the study of the effects of insulin on body growth and protein accretion occupies a central place and shows a stepwise, continuous, logical, and creative development. Using a metaphor, insulin may be viewed as a director orchestrating the music (i.e., the metabolic effects) played by the amino acids and proteins. As a hormone, insulin obviously does not provide either energy or substrates by itself. Rather, it tells cells how to produce and utilize them. Although the amino acids can be released and taken up by cells independently of insulin, the latter can powerfully modulate these movements. Insulin regulates (inhibits) protein degradation and, in some instances, stimulates protein synthesis. This review aims to provide a synthetic and historical view of the key steps taken from the discovery of insulin as an "anabolic hormone", to the in-depth analysis of its effects on amino acid metabolism and protein accretions, as well as of its interaction with nutrients.
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Affiliation(s)
- Paolo Tessari
- Department of Medicine, University of Padova, 35128 Padova, Italy
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Huang Y, Xie Y, Zhong C, Zhou F. Finding branched pathways in metabolic network via atom group tracking. PLoS Comput Biol 2021; 17:e1008676. [PMID: 33529200 PMCID: PMC7880430 DOI: 10.1371/journal.pcbi.1008676] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 02/12/2021] [Accepted: 01/05/2021] [Indexed: 12/27/2022] Open
Abstract
Finding non-standard or new metabolic pathways has important applications in metabolic engineering, synthetic biology and the analysis and reconstruction of metabolic networks. Branched metabolic pathways dominate in metabolic networks and depict a more comprehensive picture of metabolism compared to linear pathways. Although progress has been developed to find branched metabolic pathways, few efforts have been made in identifying branched metabolic pathways via atom group tracking. In this paper, we present a pathfinding method called BPFinder for finding branched metabolic pathways by atom group tracking, which aims to guide the synthetic design of metabolic pathways. BPFinder enumerates linear metabolic pathways by tracking the movements of atom groups in metabolic network and merges the linear atom group conserving pathways into branched pathways. Two merging rules based on the structure of conserved atom groups are proposed to accurately merge the branched compounds of linear pathways to identify branched pathways. Furthermore, the integrated information of compound similarity, thermodynamic feasibility and conserved atom groups is also used to rank the pathfinding results for feasible branched pathways. Experimental results show that BPFinder is more capable of recovering known branched metabolic pathways as compared to other existing methods, and is able to return biologically relevant branched pathways and discover alternative branched pathways of biochemical interest. The online server of BPFinder is available at http://114.215.129.245:8080/atomic/. The program, source code and data can be downloaded from https://github.com/hyr0771/BPFinder. Computational search of branched metabolic pathways is a fundamental problem in metabolic engineering and metabolic network analysis, which provides a systematic way of understanding the metabolism and discovering alternative pathways for synthesis of useful biomolecules. We propose BPFinder, a novel computational approach to identify branched metabolic pathways via atom group tracking. Different from other pathfinding methods using atom tracking, BPFinder tracks the movement of atom groups in metabolic network to find linear atom group conserving pathways, and merge the found linear pathways by the selected branched compounds to generate branched pathways. Based on the structure of conserved atom groups in branched compounds, we design two merging rules for branched compounds: overlapping rule and non-overlapping rule. The user can flexibly adopt these rules to accurately find the branched pathways that contain overlapping/non-overlapping conserved atom groups. BPFinder also enables the user to combine the information of compound similarity, Gibbs free energy of reactions, and conserved atom groups to sort resulting pathways. Compared with other existing methods, BPFinder can more accurately recover the known branched pathways. The alternative branched pathways returned by BPFinder reveal that the user can flexibly utilize our proposed merging rules to discover biochemically meaningful pathways of interest.
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Affiliation(s)
- Yiran Huang
- School of Computer and Electronics and Information, Guangxi Key Laboratory of Multimedia Communications and Network Technology, Guangxi University, Nanning, China
- * E-mail:
| | - Yusi Xie
- School of Computer and Electronics and Information, Guangxi Key Laboratory of Multimedia Communications and Network Technology, Guangxi University, Nanning, China
| | - Cheng Zhong
- School of Computer and Electronics and Information, Guangxi Key Laboratory of Multimedia Communications and Network Technology, Guangxi University, Nanning, China
| | - Fengfeng Zhou
- College of Computer Science and Technology, Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, Jilin University, Changchun, China
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Sayda MH, Phillips BE, Williams JP, Greenhaff PL, Wilkinson DJ, Smith K, Atherton PJ. Associations between Plasma Branched Chain Amino Acids and Health Biomarkers in Response to Resistance Exercise Training Across Age. Nutrients 2020; 12:nu12103029. [PMID: 33023275 PMCID: PMC7601782 DOI: 10.3390/nu12103029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/1970] [Revised: 09/24/2020] [Accepted: 09/30/2020] [Indexed: 01/10/2023] Open
Abstract
Leucine, isoleucine and valine (i.e., the branched chain amino acids, BCAA) play a key role in the support and regulation of tissue protein regulation and also as energy substrates. However, positive relationships exist between elevated levels of BCAA and insulin resistance (IR). Thus, we sought to investigate the links between fasting plasma BCAA following a progressive resistance exercise training (RET) programme, an intervention known to improve metabolic health. Fasting plasma BCAA were quantified in adults (young: 18-28 y, n = 8; middle-aged: 45-55 y, n = 9; older: 65-75 y, n = 15; BMI: 23-28 kg/m2, both males and females (~50:50), in a cross-sectional, intervention study. Participants underwent 20-weeks whole-body RET. Measurements of body composition, muscle strength (1-RM) and metabolic health biomarkers (e.g., HOMA-IR) were made pre- and post-RET. BCAA concentrations were determined by gas-chromatography mass spectrometry (GC-MS). No associations were observed across age with BCAA; however, RET elicited (p < 0.05) increases in plasma BCAA (all age-groups), while HOMA-IR scores reduced (p < 0.05) following RET. After RET, positive correlations in lean body mass (p = 0.007) and strength gains (p = 0.001) with fasting BCAA levels were observed. Elevated BCAA are not a robust marker of ageing nor IR in those with a healthy BMI; rather, despite decreasing IR, RET was associated with increased BCAA.
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Affiliation(s)
- Mariwan H. Sayda
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, University of Nottingham, Nottingham NG7 2RD, UK; (M.H.S.); (B.E.P.); (J.P.W.); (P.L.G.); (D.J.W.); (K.S.)
- The National Centre for Sport and Exercise Medicine—East Midlands, University of Nottingham, Nottingham NG7 2UH, UK
| | - Bethan E. Phillips
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, University of Nottingham, Nottingham NG7 2RD, UK; (M.H.S.); (B.E.P.); (J.P.W.); (P.L.G.); (D.J.W.); (K.S.)
- The National Centre for Sport and Exercise Medicine—East Midlands, University of Nottingham, Nottingham NG7 2UH, UK
- NIHR Biomedical Research Centre, University of Nottingham, Nottingham NG7 2UH, UK
| | - John P. Williams
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, University of Nottingham, Nottingham NG7 2RD, UK; (M.H.S.); (B.E.P.); (J.P.W.); (P.L.G.); (D.J.W.); (K.S.)
| | - Paul L. Greenhaff
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, University of Nottingham, Nottingham NG7 2RD, UK; (M.H.S.); (B.E.P.); (J.P.W.); (P.L.G.); (D.J.W.); (K.S.)
- The National Centre for Sport and Exercise Medicine—East Midlands, University of Nottingham, Nottingham NG7 2UH, UK
- NIHR Biomedical Research Centre, University of Nottingham, Nottingham NG7 2UH, UK
| | - Daniel J. Wilkinson
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, University of Nottingham, Nottingham NG7 2RD, UK; (M.H.S.); (B.E.P.); (J.P.W.); (P.L.G.); (D.J.W.); (K.S.)
- The National Centre for Sport and Exercise Medicine—East Midlands, University of Nottingham, Nottingham NG7 2UH, UK
- NIHR Biomedical Research Centre, University of Nottingham, Nottingham NG7 2UH, UK
| | - Ken Smith
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, University of Nottingham, Nottingham NG7 2RD, UK; (M.H.S.); (B.E.P.); (J.P.W.); (P.L.G.); (D.J.W.); (K.S.)
- The National Centre for Sport and Exercise Medicine—East Midlands, University of Nottingham, Nottingham NG7 2UH, UK
- NIHR Biomedical Research Centre, University of Nottingham, Nottingham NG7 2UH, UK
| | - Philip J. Atherton
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, University of Nottingham, Nottingham NG7 2RD, UK; (M.H.S.); (B.E.P.); (J.P.W.); (P.L.G.); (D.J.W.); (K.S.)
- The National Centre for Sport and Exercise Medicine—East Midlands, University of Nottingham, Nottingham NG7 2UH, UK
- NIHR Biomedical Research Centre, University of Nottingham, Nottingham NG7 2UH, UK
- Correspondence: ; Tel.: +01-332-724-725
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5
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Young VR, Pellett PL. Current Concepts concerning Indispensable Amino Acid Needs in Adults and Their Implications for International Nutrition Planning. Food Nutr Bull 2018. [DOI: 10.1177/156482659001200414] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Merz B, Frommherz L, Rist MJ, Kulling SE, Bub A, Watzl B. Dietary Pattern and Plasma BCAA-Variations in Healthy Men and Women-Results from the KarMeN Study. Nutrients 2018; 10:E623. [PMID: 29762522 PMCID: PMC5985475 DOI: 10.3390/nu10050623] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 05/08/2018] [Accepted: 05/11/2018] [Indexed: 01/04/2023] Open
Abstract
Branched-chain amino acids (BCAA) in plasma are discussed as risk factors for the onset of several diseases. Information about the contribution of the overall diet to plasma BCAA concentrations is controversial. Our objective was to investigate which dietary pattern is associated with plasma BCAA concentrations and whether other additional nutrients besides BCAA further characterize this dietary pattern. Based on the cross-sectional KarMeN study, fasting plasma amino acid (AA) concentrations, as well as current and habitual dietary intake were assessed in 298 healthy individuals. Using reduced rank regression, we derived a habitual dietary pattern that explained 32.5% of plasma BCAA variation. This pattern was high in meat, sausages, sauces, eggs, and ice cream but low in nuts, cereals, mushrooms, and pulses. The age, sex, and energy intake adjusted dietary pattern score was associated with an increase in animal-based protein together with a decrease in plant-based protein, dietary fiber, and an unfavorable fatty acid composition. Besides BCAA, alanine, lysine and the aromatic AA were positively associated with the dietary pattern score as well. All of these factors were reported to be associated with risk of type 2 diabetes and cardiovascular diseases before. Our data suggest that rather than the dietary intake of BCAA, the overall dietary pattern that contributes to high BCAA plasma concentrations may modulate chronic diseases risk.
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Affiliation(s)
- Benedikt Merz
- Department of Physiology and Biochemistry of Nutrition, Max Rubner-Institut, 76131 Karlsruhe, Germany.
| | - Lara Frommherz
- Department of Safety and Quality of Fruit and Vegetables, Max Rubner-Institut, 76131 Karlsruhe, Germany.
| | - Manuela J Rist
- Department of Physiology and Biochemistry of Nutrition, Max Rubner-Institut, 76131 Karlsruhe, Germany.
| | - Sabine E Kulling
- Department of Safety and Quality of Fruit and Vegetables, Max Rubner-Institut, 76131 Karlsruhe, Germany.
| | - Achim Bub
- Department of Physiology and Biochemistry of Nutrition, Max Rubner-Institut, 76131 Karlsruhe, Germany.
| | - Bernhard Watzl
- Department of Physiology and Biochemistry of Nutrition, Max Rubner-Institut, 76131 Karlsruhe, Germany.
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Abstract
Nearly 50 years ago, I set out to investigate the clinical problem of hypoglycemia in children with illnesses that limited their food intake. My goal was to gather accurate and precise measurable data. At the time, I wasn't interested in nutrition as a discipline defined in its more general or popular sense. To address the specific problem that interested me required development of entirely new methods based on stable, nonradioactive tracers that satisfied the conditions of accuracy and precision. At the time, I had no inclination of the various theoretical and practical problems that would have to be solved to achieve this goal. Some are briefly described here. Nor did I have the slightest idea that developing the field would result in a fundamental change in how human clinical investigation was conducted, with the eventual replacement of radiotracers with stable isotopically labeled ones, even for adult clinical investigation. Additionally, I had no inclination that the original questions would open avenues to much broader questions of practical nutritional relevance. Moreover, only much later as the editor of The American Journal of Clinical Nutrition did I appreciate the policy implications of how nutritional data are presented in the scientific literature. At least in part, less accurate and precise measurements and less than full transparency in reporting nutritional data have resulted in widespread debate about the public policy recommendations and guidelines that are the intended result of collecting the data in the first place. This article provides a personal recollection (with all the known faults of self-reporting and retrospective memory) of the journey that starts with measurement certainty and ends with policy uncertainty.
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Affiliation(s)
- Dennis M Bier
- USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030;
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Pencharz PB, Elango R, Ball RO. An approach to defining the upper safe limits of amino acid intake. J Nutr 2008; 138:1996S-2002S. [PMID: 18806114 DOI: 10.1093/jn/138.10.1996s] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The existing data on the safe upper limits of amino acid intake in humans is essentially observational; how much do individuals ingest and what side effects do they have? There are numerous studies in humans comparing the effects of high doses of amino acids given as protein bound vs. as free amino acids. These studies have shown that protein-bound amino acids have much less effect on plasma levels of the test amino acid, because protein intake stimulates protein synthesis as another sink for the increased amino acid intake. In practice, the highest amino acid intakes occur with free amino acid supplements that may be ingested by athletes who believe that the amino acids will benefit them in training and/or performance. Previously, in a piglet study, we were able to define the point at which maximal phenylalanine oxidation occurred, above which plasma phenylalanine concentration and body balance rose exponentially. We regard this value of maximal disposal (oxidation) of an amino acid as one metabolic marker of the upper limit of intake. Recently, others have demonstrated a similar maximal oxidation rate for leucine in rats. Based on these experimental data and the paucity of published human data in controlled experiments, we think that a systematic approach needs to be undertaken to define the maximal oxidation rate for all dietary indispensable amino acids and other amino acids that may be ingested in excess by humans. We believe that this will provide a rational basis to begin to define the upper limits of tolerance for dietary amino acids. However, some amino acids, such as threonine and methionine, will be more difficult to study, because they have more than 1 route of disposal or very complex metabolic regulation, in which case defining their upper limits will be more multifaceted.
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Affiliation(s)
- Paul B Pencharz
- Research Institute, Hospital for Sick Children, M5G 1X8 Toronto, Ontario, Canada.
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Muramatsu T. Nutrition and Whole-Body Protein Turnover in the Chicken in Relation to Mammalian Species. Nutr Res Rev 2007; 3:211-28. [DOI: 10.1079/nrr19900013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Millward DJ. Vernon Young and the development of current knowledge in protein and amino acid nutritionVernon Young 1937–2004. Br J Nutr 2007; 92:189-97. [PMID: 15333147 DOI: 10.1079/bjn20041216] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- D Joe Millward
- Centre for Nutrition and Food Safety, School of Biomedical and Molecular Sciences, University of Surrey, Guildford, GU2 7XH, UK.
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Kurpad AV, Regan MM, Raj T, Gnanou JV. Branched-chain amino acid requirements in healthy adult human subjects. J Nutr 2006; 136:256S-63S. [PMID: 16365094 DOI: 10.1093/jn/136.1.256s] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
There is now an expanding body of evidence to recommend, in the case of adult humans, the use of revised indispensable amino acid requirement values; these are approximately 2 to 3 times higher than the current international recommendations. The earlier methodologies for determining amino acid requirements, based on nitrogen balance, were criticized because of their design and the associated high energy intakes. The 1985 World Health Organization/Food & Agriculture Organization/United Nations University requirement for leucine has been demonstrated to be too low by short- and long-term (24-h) tracer-derived estimates of leucine oxidation and balance. The best values for leucine requirements come from 24-h direct amino acid oxidation (DAAO) and direct amino acid balance (DAAB) studies. Finally, we also collated all available data from studies on fed-state leucine oxidation with an adequate dietary adaptation period to assess the inflection on the leucine oxidation-leucine intake curve. The mean requirements for leucine, valine, and isoleucine are likely to be 40, 17-25, and 19 mg . kg(-1) . d(-1), respectively. This adds up to a total of approximately 84 mg . kg(-1) . d(-1), which is much lower than the lowest estimate of the total BCAA requirement of approximately 110 mg . kg(-1) . d(-1) made by the short-term indicator amino acid oxidation (IAAO) method, which determined the BCAA requirement from the pattern of oxidation of an indicator amino acid (phenylyalanine) at different levels of BCAA intake. An additional estimate of the leucine requirement was also made by a meta-analysis of all available 24-h DAAO/DAAB data from different studies. This resulted in a higher value for the leucine requirement than that obtained by the specific studies that utilized the 24-h DAAO/DAAB approach; however, even adding this value to the total BCAA requirement does not account for the difference in the total BCAA requirement estimates and the summed individual BCAA estimates.
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Affiliation(s)
- Anura V Kurpad
- Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA.
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Kurpad AV, Regan MM, Raj TDS, Gnanou JV, Rao VN, Young VR. The daily valine requirement of healthy adult Indians determined by the 24-h indicator amino acid balance approach. Am J Clin Nutr 2005; 82:373-9. [PMID: 16087981 DOI: 10.1093/ajcn.82.2.373] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND The 1985 FAO/WHO/UNU requirement for valine was set at 10 mg x kg(-1) x d(-1) on the basis of nitrogen balance studies carried out in Western subjects. It is likely that the requirement is higher, however, because the requirement of another branched-chain amino acid, leucine, was found to be about 3 times as high (40 mg x kg(-1) x d(-1)) as the 1985 FAO/WHO/UNU value (14 mg x kg(-1) x d(-1)). OBJECTIVE We assessed the valine requirement in healthy, well-nourished Indians by using 7 test valine intakes (5, 10, 15, 20, 25, 30, and 35 mg x kg(-1) x d(-1)) and the 24-h indicator amino acid oxidation (24-h IAAO) and balance (24-h IAAB) method, with phenylalanine as the indicator amino acid, while maintaining leucine intake at 40 mg x kg(-1) x d(-1). DESIGN Eighteen healthy, well-nourished Indian men were studied during each of 3 randomly assigned 7-d diet periods supplying valine intakes that were equally placed on either side of a putative mean valine requirement of 20 mg x kg(-1) x d(-1). Twenty-four-hour IAAO and 24-h IAAB were measured on day 7 by use of a 24-h [13C]phenylalanine tracer infusion. The breakpoint in the relation between these values and the valine intake was determined. RESULTS Two-phase linear regression of daily phenylalanine oxidation or balance against valine intake estimated a breakpoint in the response curve at a valine intake of 17 mg x kg(-1) x d(-1) (95% Fieller's CI: 11, > 35 and 11, 28 mg x kg(-1) x d(-1), respectively). CONCLUSION From the 24-h IAAO/IAAB approach, a mean valine requirement of 17 mg x kg(-1) x d(-1) is proposed for healthy, well-nourished Indian adults.
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Affiliation(s)
- Anura V Kurpad
- Division of Nutrition, Institute of Population Health and Clinical Research, St John's National Academy of Health Sciences, Bangalore, India.
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14
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Kurpad AV, Regan MM, Raj TDS, Gnanou JV, Rao VN, Young VR. The daily valine requirement of healthy adult Indians determined by the 24-h indicator amino acid balance approach. Am J Clin Nutr 2005. [DOI: 10.1093/ajcn/82.2.373] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Anura V Kurpad
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Meredith M Regan
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Tony DS Raj
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Justin V Gnanou
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Vidya N Rao
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Vernon R Young
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
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Bertolo R, Pencharz P, Ball R. Chapter 6 Role of intestinal first-pass metabolism on whole-body amino acid requirements. BIOLOGY OF GROWING ANIMALS 2005. [DOI: 10.1016/s1877-1823(09)70013-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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16
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Millward DJ. Vernon Young and the development of current knowledge in protein and amino acid nutrition. Vernon Young 1937–2004. Am J Clin Nutr 2004. [DOI: 10.1093/ajcn/80.5.1093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
A full review of the strengths and limitations of the various methods used to define amino acid requirements is provided. The focus is on the recent development of carbon oxidation techniques such as indicator amino acid oxidation and 24-h amino acid balance to determine dietary indispensable (essential) amino acid needs in adults. All approaches depend on the change in a metabolic parameter in response to graded intake of the test amino acid. In humans, the within-subject variance is less than the between-subject variance, which has led to an appreciation of the need to study each subject across a range of intakes, above and below the mean requirement level. The data can then be analyzed using two-phase linear regression crossover and a precise population mean requirement can be determined. Several approaches have been used to define the variance of the mean requirement. Finally, a minimally invasive indicator amino acid oxidation model has been developed which allows the determination of dietary essential amino acid requirements in children and other vulnerable populations.
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Affiliation(s)
- Paul B Pencharz
- Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada.
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Riazi R, Rafii M, Wykes LJ, Ball RO, Pencharz PB. Valine May Be the First Limiting Branched-Chain Amino Acid in Egg Protein in Men. J Nutr 2003; 133:3533-9. [PMID: 14608070 DOI: 10.1093/jn/133.11.3533] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Recently, we defined an estimate for total branched-chain amino acids (BCAA) using the indicator amino acid oxidation technique in men fed the three BCAA (leucine, isoleucine and valine) in the proportion present in egg protein. Although egg protein is regarded as a high quality dietary protein source, it is not known whether the proportions of the three BCAA are optimal. Five men with known total BCAA requirements were restudied. Each men was studied with isoleucine, leucine or valine held constant at that individual's requirement level while the intake of the other two BCAA was reduced; one BCAA was held constant and the intake of the other two was reduced by 10 and 20% in random order. The label appearance from the oxidation of L-[13C]-phenylalanine to 13CO2 (F13CO2) in breath was monitored in response to the change in amino acid intake. When either isoleucine or leucine was held constant, and the other two BCAA reduced by 20% (valine and leucine, or valine and isoleucine, respectively) F13CO2 increased (P = 0.007, P = 0.038, respectively). We conclude that valine may be the first limiting BCAA in egg protein.
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Affiliation(s)
- Roya Riazi
- Department of Nutritional Sciences, The University of Toronto, Toronto, Canada
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19
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Mager DR, Wykes LJ, Ball RO, Pencharz PB. Branched-Chain Amino Acid Requirements in School-Aged Children Determined by Indicator Amino Acid Oxidation (IAAO). J Nutr 2003; 133:3540-5. [PMID: 14608071 DOI: 10.1093/jn/133.11.3540] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The current WHO/FAO/UNU recommendations for BCAA requirements in school-aged children are based on nitrogen balance studies that have tended to produce lower estimates of amino acid requirements that those determined using stable isotope methodologies. The new dietary reference intake (DRI) recommendations for total BCAA requirements in children were determined using a factorial approach that included adult BCAA requirements plus the additional needs for growth. The purpose of this study was to determine directly total BCAA requirements in school children aged 6-10 y using indicator amino acid oxidation (IAAO). Five children (8.5 +/- 1.2 y) were assigned randomly to receive 7 graded intakes of total BCAA. Individual BCAA in the test diet were provided in the same proportions as those present in egg protein to minimize the potential interactive effects of individual BCAA on assessment of requirement. Total BCAA requirement was determined by measuring the oxidation of L-[1-13C] phenylalanine to 13CO2 [F13CO2 in micromol/(kg x h)], after a primed, continuous infusion of the labeled tracer and using a two-phase linear crossover regression analysis. The mean requirement and the population-safe intake level (upper limit of the 95% CI) of the total BCAA in healthy school aged children were 147 and 192 mg/(kg x d), respectively. The estimated mean requirements of the total BCAA as determined by IAAO is approximately 48% higher than the current DRI recommendations, suggesting that these recommendations may be too low to meet the needs of school-aged children.
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Affiliation(s)
- Diana R Mager
- Department of Nutritional Sciences, University of Toronto, Toronto, Canada
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20
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Riazi R, Wykes LJ, Ball RO, Pencharz PB. The total branched-chain amino acid requirement in young healthy adult men determined by indicator amino acid oxidation by use of L-[1-13C]phenylalanine. J Nutr 2003; 133:1383-9. [PMID: 12730426 DOI: 10.1093/jn/133.5.1383] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Previous recommendations for branched-chain amino acids (BCAA), based on nitrogen balance studies, were found to be low in a series of stable isotope-labeled amino acid studies. The BCAA requirement was increased in the new dietary reference intake (DRI) report on the basis of a series of stable isotope studies examining the requirement of leucine and valine individually, but not isoleucine. To reduce the possibility of interactions among these amino acids and imbalances in the mixture affecting the estimate of requirements, we decided to determine the requirement for the total BCAA of young healthy adult men, receiving a mixture of BCAA based on the proportion of these amino acids in egg protein, by use of indicator amino acid oxidation. Seven men were assigned to receive nine graded intakes of a BCAA mixture in random order: 34, 50, 66, 80, 100, 120, 140, 160 and 180 mg/(kg. d). The rate of release of (13)CO(2) from the oxidation of L-[1-(13)C]phenylalanine (F (13)CO(2)) was measured and a two-phase linear regression crossover model was applied to determine total BCAA requirement. The mean requirement and population-safe level (upper limit of 95% confidence interval) of the total BCAA were 144 and 210 mg/(kg. d), respectively. Based on the balance of BCAA in egg protein, our estimate for the mean leucine requirement is 55 mg/(kg. d), which is substantially higher than the 34 mg/(kg. d) recommended by the DRI.
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Affiliation(s)
- Roya Riazi
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada M5S 3E2
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21
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Tabiri HY, Bertolo RFP, Ball RO, Korver DR. Development of the indicator amino acid oxidation technique in chickens: L-[1-(14)C]phenylalanine infusion dose and phenylalanine oxidation. Poult Sci 2002; 81:1516-21. [PMID: 12412918 DOI: 10.1093/ps/81.10.1516] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Amino acid requirements of broiler breeder chickens are not well known. The indicator amino acid oxidation (IAAO) technique was adapted for use in broiler breeders as a rapid and sensitive method to determine amino acid requirements. During IAAO, phenylalanine oxidation decreases, inversely to the changes in protein synthesis, as the intake of the limiting test amino acid increases from deficient to adequate. Above the adequate level, phenylalanine oxidation remains constant. Before IAAO can be employed, the optimum priming and constant infusion doses of phenylalanine must be determined. Prelaying catheterized birds aged 20 to 24 wk were placed in closed oxidation chambers attached to a breath collection apparatus. A constant L-[1-(14)C]phenylalanine dose of 3.5 microCi/kg BW/h and priming doses of 4.5, 5.5, and 7.0 microCi/kg BW were used to determine optimal prime:constant dose ratios, minimum time taken for breath 14CO2 excretion to become constant (plateau), and adequate percentage of phenylalanine oxidized. At this constant infusion rate, the optimal priming dose of L-[1-(14)C]phenylalanine was 5.5 microCi/kg BW, resulting in a prime:constant dose ratio of 1.6:1. By using this ratio, the average time taken for breath 14CO2 to reach plateau was 60 min. Average phenylalanine oxidation at plateau, corrected for bicarbonate retention, was 5.5 +/- 1.4% (mean +/- SD), which is adequate for IAAO studies using deficient-to-excess levels of test amino acids. To the authors' knowledge, this study is the first in chickens to establish a primed, constant infusion technique using L-[1-(14)C]phenylalanine. The IAAO technique will be used in future studies to determine amino acid requirements in chickens.
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Affiliation(s)
- H Y Tabiri
- Department of Agricultural, Food and Nutritional Science, University of Alberta Edmonton, Canada
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22
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Forslund AH, Hambraeus L, van Beurden H, Holmbäck U, El-Khoury AE, Hjorth G, Olsson R, Stridsberg M, Wide L, Akerfeldt T, Regan M, Young VR. Inverse relationship between protein intake and plasma free amino acids in healthy men at physical exercise. Am J Physiol Endocrinol Metab 2000; 278:E857-67. [PMID: 10780942 DOI: 10.1152/ajpendo.2000.278.5.e857] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of a "normal" (n = 8) and "high" (n = 6) protein intake (1 and 2.5 g x kg(-1) x day(-1), respectively) and of exercise on plasma amino acid (AA) concentrations, insulin, and glucagon concentrations was followed throughout a continuous 24-h period in adult male subjects at energy balance after six days on a standardized diet and exercise program. Subjects were fasting from 2100 on day 6 to 1200 on day 7 and then fed 10 identical meals hourly until 2100. Physical exercise was performed (46% maximal oxygen uptake) between 0830 and 1000 (fasting) and in a fed state (1600-1730) on each day. The normal-protein group showed fasting plasma AA concentrations that were higher (P < 0.05) than those for the high-protein group, except for leucine, methionine, and tyrosine. Glutamine, glycine, alanine, taurine, and threonine concentrations were distinctly higher ( approximately 30% or greater) throughout the 24-h period in subjects consuming the normal- vs. the high-protein diets. Exercise appeared to increase, although not profoundly, the plasma concentrations of amino acids except for glutamate, histidine, ornithine, and tryptophan. The profound diet-related differences in plasma AA concentrations are only partially explained by differences in the renal clearance of the amino acids. We speculate on the possible metabolic basis for these findings.
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Affiliation(s)
- A H Forslund
- Department of Medical Sciences, Nutrition and Clinical Chemistry, Uppsala University, SE-75237 Uppsala, Sweden
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23
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Millward DJ. Metabolic demands for amino acids and the human dietary requirement: Millward and rRvers (1988) revisited. J Nutr 1998; 128:2563S-2576S. [PMID: 9868206 DOI: 10.1093/jn/128.12.2563s] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In 1988, Millward and Rivers reappraised existing metabolic models for amino acid requirements. The metabolic demand for amino acids was reviewed in relation to both obligatory metabolic consumption and adaptive pathways of amino acid oxidation. The obligatory demand pattern was deemed unknowable from first principles except that the level of one amino acid would be similar to its concentration in an amount of tissue protein equivalent to the obligatory nitrogen loss. The adaptive demand pattern was predicted to vary in relation to the amount and the periodicity of food protein intake that influenced the amplitude of the diurnal cycle of gains and losses. A regulatory influence of protein intake on anabolism, the anabolic drive, was identified in animal studies; benefit appeared to derive from intakes in excess of the minimum for balance, which could facilitate definition of an optimal requirement. The inherent and design-related limitations of both nitrogen and stable isotope balance studies of requirement were recognized as a major problem in identifying secure values for indispensable amino acid requirements. A decade of research of increasing methodological sophistication has generated much new information, confirming the adaptive diurnal model of balance regulation and allowing development of the anabolic drive into a general protein-stat theory for coordinated control of growth and maintenance of the lean body mass. However, notwithstanding several new estimates of amino acid requirement values, definition of a widely accepted human amino acid requirement pattern remains unresolved. Although a case can be made for an adjusted 1985 FAO adult requirement pattern being a reasonable estimate of the obligatory indispensable amino acid requirements for human maintenance, the problems posed by adaptation, methodological inadequacies and lack of independent measures of adequacy mean that assessment of the adequacy of the human diet to satisfy amino acid needs remains inherently difficult.
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Affiliation(s)
- D J Millward
- Centre for Nutrition and Food Safety, School of Biological Sciences, University of Surrey, Guildford, Surrey GU2 5XH, UK
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24
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Brunton JA, Ball RO, Pencharz PB. Determination of amino acid requirements by indicator amino acid oxidation: applications in health and disease. Curr Opin Clin Nutr Metab Care 1998; 1:449-53. [PMID: 10565392 DOI: 10.1097/00075197-199809000-00014] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Indispensable amino acid requirements for children, patients and pregnant women are largely unknown. We describe a new, non-invasive technique that can estimate requirements in vulnerable populations. Future applications will lead to optimal nutritional care for populations in which an appropriate balance of amino acids is essential for metabolic health and growth.
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Affiliation(s)
- J A Brunton
- Department of Agricultural, Food and Nutritional Sciences, University of Alberta, Canada
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25
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House JD, Pencharz PB, Ball RO. Tyrosine kinetics and requirements during total parenteral nutrition in the neonatal piglet: the effect of glycyl-L-tyrosine supplementation. Pediatr Res 1997; 41:575-83. [PMID: 9098863 DOI: 10.1203/00006450-199704000-00020] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Tyrosine may be a conditionally indispensable amino acid in the neonate; however, the provision of aromatic amino acids to neonates receiving total parenteral nutrition (TPN) is complicated by the poor solubility of crystalline tyrosine. In the present study, we investigated tyrosine kinetics and requirements during TPN, when tyrosine was supplied as the soluble dipeptide, glycyl-L-tyrosine in a neonatal piglet model. Fifteen 3-d-old male Yorkshire piglets were fitted with external jugular and femoral catheters and randomized to one of five tyrosine intakes: 0.11, 0.31, 0.41, 0.51 and 0.71 g.kg-1.d-1. Total parenteral amino acid and energy intakes were 15.0 g.kg-1.d-1 and 1.1 MJ.kg-1.d-1, respectively. Piglets were maintained on TPN for 6 d, with nitrogen balance measured over the final 3 d of the study. On the final study day, tyrosine kinetics were measured during a 4-h primed-constant infusion of L-[l14C]tyrosine. Nitrogen retention was 67% at the lowest tyrosine intake and increased significantly (p < 0.05) at intakes of 0.31 g.kg-1.d-1 and above (84, 86, 87, and 88% for intakes of 0.31, 0.41, 0.51, and 0.71 g.kg-1.d-1, respectively). Plasma tyrosine concentrations and tyrosine oxidation (expressed as either a percentage of the dose oxidized or when corrected for flux) were low and similar at the two lowest intakes, but increased significantly at the higher intakes. Two-phase regression analysis of the data (plasma tyrosine, tyrosine oxidation) yielded estimates of a mean tyrosine requirement of 0.31 and 0.35, respectively, with estimated safe intakes (upper 95% confidence limit) of 0.44 and 0.42 g.kg-1.d-1. The present work also indicates that oxidation techniques may be suitable for the estimation of amino acid requirements during TPN in the neonate.
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Affiliation(s)
- J D House
- Department of Animal and Poultry Science, University of Guelph, Ontario, Canada
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26
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Tessari P, Barazzoni R, Zanetti M, Vettore M, Normand S, Bruttomesso D, Beaufrere B. Protein degradation and synthesis measured with multiple amino acid tracers in vivo. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 271:E733-41. [PMID: 8897862 DOI: 10.1152/ajpendo.1996.271.4.e733] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Whether tracers of different essential amino acids yield the same estimates of body protein turnover is still uncertain. Therefore, we have simultaneously determined leucine (Leu; using [14C]Leu), phenylalanine (Phe; using [13C]Phe), and tyrosine (Tyr; using [2H2]Tyr) rates of appearance (Ra) from proteolysis (PD), as well as Leu and Phe disposal, into protein synthesis (PS) both before and after an anabolic stimulus in healthy volunteers. Protein anabolism was stimulated by insulin plus a branched-chain amino acid-enriched aromatic amino acid-deficient amino acid solution, which increased Leu (from 145 +/- 9 to 266 +/- 10 mumol/l) but decreased Phe (from 57 +/- 2 to 46 +/- 3) and Tyr (from 58.7 +/- 5.5 to 21.0 +/- 2.2) concentrations. Postabsorptive endogenous Leu Ra (2.04 +/- 0.12 mumol.kg-1.min-1), Phe Ra (0.66 +/- 0.03), and Tyr Ra (0.45 +/- 0.06), as well as rates of PS determined with the leucine (1.65 +/- 0.10 mumol.kg-1.min-1) and the phenylalanine tracer (0.57 +/- 0.03), agreed well with the known abundance of these amino acids in body protein(s). After insulin and amino acids, PD was suppressed (P < 0.001) using all tracers. However, although percent suppression of endogenous Leu Ra (-->1.49 +/- 0.10 mumol.kg-1.min-1, 26 +/- 5%) and Phe Ra (-->0.53 +/- 0.02 mumol.kg-1.min-1, -20 +/- 2%) were comparable, endogenous Tyr Ra was suppressed to a larger extent (-->0.23 +/- 0.02 mumol.kg-1.min-1, -46 +/- 3% P = 0.038). PS was stimulated using the Leu (+24 +/- 7%, P < 0.02) but not the Phe (+6 +/- 4%, not significant) data. We conclude that isotopes of different essential amino acid: provide comparable estimates of PD and PS in the postabsorptive state. However, their responses to an anabolic stimulus may differ, possibly depending on exogenous amino acid availability and/or the resulting plasma levels.
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Affiliation(s)
- P Tessari
- Department of Metabolism, University of Padua, Italy
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27
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De Feo P, Volpi E, Lucidi P, Cruciani G, Monacchia F, Reboldi G, Santeusanio F, Bolli GB, Brunetti P. Ethanol impairs post-prandial hepatic protein metabolism. J Clin Invest 1995; 95:1472-9. [PMID: 7706451 PMCID: PMC295629 DOI: 10.1172/jci117818] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The effects of acute ethanol ingestion on whole body and hepatic protein metabolism in humans are not known. To simulate social drinking, we compared the effects of the association of a mixed meal (632 kcal, 17% amino acids, 50% glucose, 33% lipids) with a bottle of either table wine (ethanol content 71 g) or water on the estimates ([1-14C]-leucine infusion) of whole body protein breakdown, oxidation, and synthesis, and on the intravascular fractional secretory rates (FSR) of hepatically (albumin, fibrinogen) and extrahepatically (IgG) synthesized plasma proteins in two randomized groups (ethanol n = 7, water n = 7) of healthy nonalcoholic volunteers. Each study was carried out for 8 h. Protein kinetics were measured in the overnight post-absorptive state, over the first 4 h, and during a meal infusion (via a nasogastric feeding tube at constant rate) combined with the oral ingestion of wine or water, over the last 4 h. When compared with water, wine ingestion during the meal reduced (P < 0.03) by 24% the rate of leucine oxidation, did not modify the estimates of whole body protein breakdown and synthesis, reduced (P < 0.01) by approximately 30% the FSR of albumin and fibrinogen, but did not affect IgG FSR. In conclusion, 70 g of ethanol, an amount usual among social drinkers, impairs hepatic protein metabolism. The habitual consumption of such amounts by reducing the synthesis and/or secretion of hepatic proteins might lead to the progressive development of liver injury and to hypoalbuminemia also in the absence of protein malnutrition.
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Affiliation(s)
- P De Feo
- Department of Internal Medicine, Endocrine and Metabolic Sciences, University of Perugia, Italy
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29
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Zello GA, Pencharz PB, Ball RO. Dietary lysine requirement of young adult males determined by oxidation of L-[1-13C]phenylalanine. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 264:E677-85. [PMID: 8476044 DOI: 10.1152/ajpendo.1993.264.4.e677] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Lysine requirement was determined in seven adult males by examining the effect of varying dietary lysine intake on phenylalanine flux and oxidation under dietary conditions of adequate energy and phenylalanine (14 mg.kg-1 x day-1) and excess tyrosine (40 mg.kg-1 x day-1). Phenylalanine flux was determined from primed, constant intravenous infusions of L-[1-13C]phenylalanine (1.2 mg.kg-1 x day-1) and L-[ring-2H5]phenylalanine (0.5 mg.kg-1 x day-1) and measurement of isotopic enrichments of phenylalanine in plasma. Phenylalanine flux was not affected by graded increases in dietary lysine intake or by the isotope infused. Mean phenylalanine conversion to tyrosine was low (3.4%) and not significantly affected by lysine intake. Phenylalanine oxidation, estimated from the rate of 13CO2 released in expired air during the infusion of L-[1-13C]phenylalanine, decreased linearly as lysine intake increased to a break point that was interpreted as the mean dietary lysine requirement (37 mg.kg-1 x day-1). At lysine intakes of > 37 mg.kg-1 x day-1 phenylalanine oxidation was low and constant. Plasma lysine concentrations supported this estimate of requirement. These data show that: 1) indicator amino acid oxidation can be used as a new method to determine amino acid requirements of humans and 2) the lysine requirement of adult males is three times greater than the World Health Organization recommendation of 12 mg.kg-1 x day-1.
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Affiliation(s)
- G A Zello
- Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
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30
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De Feo P, Horber FF, Haymond MW. Meal stimulation of albumin synthesis: a significant contributor to whole body protein synthesis in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1992; 263:E794-9. [PMID: 1415702 DOI: 10.1152/ajpendo.1992.263.4.e794] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The present studies were performed to test the hypothesis that the liver, by increasing the synthesis of specific plasma proteins during the absorption of an amino acid meal, may play an important role in the temporary "storage" of ingested essential amino acids and to explore the effects of glucocorticosteroids and recombinant human growth hormone (rhGH) on these processes. The fractional synthetic rates of albumin and fibrinogen were determined using simultaneous infusions of intravenous [1-14C]leucine and intraduodenal [4,5-3H]leucine after 22 h fasting and during absorption of glucose and amino acids in four groups of normal subjects treated for 1 wk with placebo, prednisone (0.8 mg.kg-1.day-1), rhGH (0.1 mg.kg-1.day-1), or combined treatment. When compared with the fasted state and independent of the route of tracer delivery and hormonal treatment, albumin, but not fibrinogen, synthesis increased (P < 0.0001) during absorption of a mixed glucose amino acid meal in all groups. This increase in albumin synthesis accounted for 28% of the increase in whole body protein synthesis associated with feeding and for 24, 22, and 14% in the prednisone, rhGH, and combined treatment groups, respectively. These data suggest that the stimulation of albumin synthesis observed during feeding prevents irreversible oxidative losses of a significant fraction of ingested essential amino acids and may serve as a vehicle to capture excess dietary amino acids and transport them to peripheral tissues to sustain local protein synthesis.
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Affiliation(s)
- P De Feo
- Nemours Children's Clinic, Jacksonville, Florida 32247
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31
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Lecavalier L, De Feo P, Haymond MW. Isolated hypoisoleucinemia impairs whole body but not hepatic protein synthesis in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1991; 261:E578-86. [PMID: 1951682 DOI: 10.1152/ajpendo.1991.261.5.e578] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
It is not known whether an acute decrease in the plasma concentration of any essential amino acid, as occurs during insulin infusion, impairs protein synthesis. To test this hypothesis in humans, selective hypoisoleucinemia or hypothreoninemia was induced by insulin infusion while maintaining normal or elevated plasma concentrations of the other amino acids via their selective infusion. The effects on protein synthesis were assessed using leucine kinetics and fractional synthetic rates of the two hepatic proteins albumin and fibrinogen. Results were compared with those of a combined insulin and complete amino acid infusion. Hypoisoleucinemia increased leucine oxidation (P less than 0.03) and decreased nonoxidative leucine disposal (P less than 0.04) and net leucine balance (P less than 0.03), whereas hypothreoninemia had no effect on any of these parameters. Neither hypoisoleucinemia or hypothreoninemia altered albumin and fibrinogen fractional synthetic rates when compared with the control study. Because of the known relationships between intra- and extracellular amino acid concentrations, the hypoisoleucinemia was most likely associated with a decreased intracellular concentration of isoleucine; such would not be the case for hypothreoninemia. Thus acute limited availability of a single essential amino acid can adversely affect nonhepatic protein synthesis.
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Affiliation(s)
- L Lecavalier
- Istituto di Patologia Medica, University of Perugia, Italy
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32
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Berthold HK, Hachey DL, Reeds PJ, Thomas OP, Hoeksema S, Klein PD. Uniformly 13C-labeled algal protein used to determine amino acid essentiality in vivo. Proc Natl Acad Sci U S A 1991; 88:8091-5. [PMID: 11607211 PMCID: PMC52452 DOI: 10.1073/pnas.88.18.8091] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The edible alga Spirulina platensis was uniformly labeled with 13C by growth in an atmosphere of pure 13CO2. The labeled biomass was then incorporated into the diet of a laying hen for 27 days. The isotopic enrichment of individual amino acids in egg white and yolk proteins, as well as in various tissues of the hen at the end of the feeding period, was analyzed by negative chemical ionization gas chromatography/mass spectrometry. The amino acids of successive eggs showed one of two exclusive enrichment patterns: complete preservation of the intact carbon skeleton or extensive degradation and resynthesis. The same observation was made in tissue proteins. These patterns were cleanly divided according to known nutritional amino acid essentiality/nonessentiality but revealed differences in labeling among the nonessential amino acids: most notable was that proline accretion was derived entirely from the diet. Feeding uniformly 13C-labeled algal protein and recovering and analyzing de novo-synthesized protein provides a useful method to examine amino acid metabolism and determine conditional amino acid essentially in vivo.
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Affiliation(s)
- H K Berthold
- United States Department of Agriculture/Agricultural Research Service, Houston, TX 77030, USA
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33
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34
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Zello GA, Pencharz PB, Ball RO. Phenylalanine flux, oxidation, and conversion to tyrosine in humans studied with L-[1-13C]phenylalanine. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 259:E835-43. [PMID: 2260651 DOI: 10.1152/ajpendo.1990.259.6.e835] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Phenylalanine metabolism was determined in 41 studies of adult males (n = 10) consuming an energy-sufficient diet and receiving graded levels of dietary phenylalanine and excess tyrosine (40 mg.kg-1.day-1). After a dietary adaptation period to either 4.2 or 14.0 mg.kg-1.day-1 of phenylalanine; flux, plasma concentration, oxidation, and conversion to tyrosine were measured at test phenylalanine intakes of 5, 7, 10, 14, 21, 28, or 60 mg.kg-1.day-1. Oxidation was low and constant (1.3 mumol.kg-1.h-1) at intakes at or below 10 mg.kg-1.day-1 and increased linearly above this level. Conversion to tyrosine was minimal (2.1%) at these intakes. Breakpoint analysis showed the phenylalanine requirement with excess tyrosine to be 9.1 mg.kg-1.day-1. Plasma phenylalanine concentrations confirmed this estimate of requirement. Prior adaptation did not significantly affect overall flux, plasma concentration, or oxidation nor did it affect the requirement estimate. With the assumption that tyrosine can supply two-thirds of the aromatic amino acid requirement, these data suggest that the aromatic amino acid requirement should be 30 mg.kg-1.day-1 and the World Health Organization recommendation of 14 mg.kg-1.day-1 is an underestimate.
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Affiliation(s)
- G A Zello
- Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
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Thompson GN, Walter JH, Bresson JL, Ford GC, Lyonnet SL, Chalmers RA, Saudubray JM, Leonard JV, Halliday D. Sources of propionate in inborn errors of propionate metabolism. Metabolism 1990; 39:1133-7. [PMID: 2233273 DOI: 10.1016/0026-0495(90)90084-p] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Amino acids are widely regarded as the most important sources of propionate in disorders of propionate metabolism. Propionate production was measured in the fasting state by continuous infusion of sodium [1-13C]propionate in three children with methylmalonic acidemia (MMA) and three with propionic acidemia (PA). The contribution of isoleucine, valine, threonine, and methionine catabolism to total propionate production was estimated by extrapolation from the hydroxylation of phenylalanine determined by a continuous-infusion [2H5]phenylalanine technique. The contribution of gut bacterial propionate production was determined by measuring total propionate production before and after treatment with oral metronidazole (10 to 20 mg/kg/d for 1 week). Amino acid catabolism accounted for a mean of 51.7% (range, 24.5% to 66.4%) of total propionate production. The mean decrease in propionate production after metronidazole was 22.2% +/- 8.5 (P less than .02); this percentage is likely to represent the minimum propionate production attributable to gut bacteria. Approximately 30% of total propionate production was unaccounted for, and is likely to arise primarily from odd-chain fatty acid catabolism in the fasting state. These results indicate that sources of propionate other than from protein catabolism are important in disorders of propionate metabolism, and explain the generally disappointing response to dietary protein restriction.
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Affiliation(s)
- G N Thompson
- Section of Perinatal and Child Health, Clinical Research Centre, Harrow, UK
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Walter JH, Leonard JV, Thompson GN, Halliday D. Parenteral nutrition in propionic acidemia and methylmalonic acidemia. J Pediatr 1990; 117:338-9. [PMID: 2116511 DOI: 10.1016/s0022-3476(05)80562-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Bier DM. Intrinsically difficult problems: the kinetics of body proteins and amino acids in man. DIABETES/METABOLISM REVIEWS 1989; 5:111-32. [PMID: 2647431 DOI: 10.1002/dmr.5610050203] [Citation(s) in RCA: 131] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- D M Bier
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110
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Millward DJ, Rivers JP. The need for indispensable amino acids: the concept of the anabolic drive. DIABETES/METABOLISM REVIEWS 1989; 5:191-211. [PMID: 2647435 DOI: 10.1002/dmr.5610050207] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- D J Millward
- Nutrition Research Unit, London School of Hygiene & Tropical Medicine, St Pancras Hospital, United Kingdom
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Bier DM. The use of stable isotopes in metabolic investigation. BAILLIERE'S CLINICAL ENDOCRINOLOGY AND METABOLISM 1987; 1:817-36. [PMID: 3330431 DOI: 10.1016/s0950-351x(87)80007-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The use of tracers to define substrate dynamics has been the sine qua non of metabolic investigation in vivo, because static measurements of substrate content alone are inadequate. The judicious use of radioactively labelled compounds remains the principal tracer approach in some adult subjects. However, in certain young adults, in pregnant women and in children, stable isotope tracers offer a practical alternative for answering important metabolic questions. In the last decade, the developmental problems previously associated with employing stable isotope tracers for this purpose have largely disappeared. Furthermore, the use of stable isotopically labelled materials offers certain additional advantages which are either difficult or impossible to achieve using radiotracers. These include the ability to measure simultaneously substrate content and isotopic enrichment with very high specificity and precision, the ability to determine the intramolecular location of the label, the ability to use the mass of the stable isotope substrate as a probe of the metabolite system response to perturbation, and the ability to study simultaneously and repeatedly the same subject with multiple substrate tracers. The practical application of these principles has been amply demonstrated by the expanding use of non-radioactive tracers to study body composition, energy balance, and the inter-organ transport and oxidation of the three major metabolic fuels--glucose, fat and amino acids. Continued development in the organic synthesis of new, stable isotopically labelled biochemicals will allow investigation of additional areas of biomedical importance which have been hitherto inaccessible to this approach, particularly in the pathophysiology of metabolic events in the growing child.
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Bier DM, Young VR. A kinetic approach to assessment of amino acid and protein replacement needs of individual sick patients. JPEN J Parenter Enteral Nutr 1987; 11:95S-97S. [PMID: 3669267 DOI: 10.1177/014860718701100514] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- D M Bier
- Metabolism Division, Washington University School of Medicine, St. Louis, Missouri 63110
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Young VR, Fukagawa N, Bier DM, Matthews D. Some aspects of in vivo human protein and amino acid metabolism, with particular reference to nutritional modulation. VERHANDLUNGEN DER DEUTSCHEN GESELLSCHAFT FUR INNERE MEDIZIN 1986; 92:640-65. [PMID: 3811566 DOI: 10.1007/978-3-642-85459-0_115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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