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Wang WW, Feng QQ, Wang J, Wu SG, Qi GH, Zhang HJ. Cyst(e)ine fortification in low crude protein diet improves growth performance of broilers by modulating serum metabolite profile. J Proteomics 2021; 238:104154. [PMID: 33618029 DOI: 10.1016/j.jprot.2021.104154] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 01/23/2021] [Accepted: 02/11/2021] [Indexed: 10/22/2022]
Abstract
This study was aimed to explore the metabolomical mechanisms for the potentially ameliorative effect of cyst(e)ine (Cys) fortification on growth performance of broilers fed low crude protein (CP) diet. A total of 432 1-d-old broilers were randomly divided into 6 groups, each of which received one of the following diets: normal-CP diet (positive control, PC), low-CP diet (negative control, NC), NC diet fortified with 0.05%, 0.1%, 0.15% or 0.2% of Cys. Samples were collected on d 42. Results showed that increasing Cys fortification quadratically elevated (P < 0.05) the accumulative growth performance and leg muscle yield of broilers fed NC diet, with 0.1% being the optimal dose. Thus, samples from PC, NC and NC plus 0.1% Cys (NCC) groups were selected for further analysis. Both dietary CP reduction and fortification of 0.1% Cys in NC diet caused complex changes (P < 0.05) in serum amino acids and some other metabolites primarily involved in lipid metabolism. Multiple lipogenesis-related pathways were regulated (P < 0.05) following Cys fortification in NC diet, which could at least partially interpret the benefit of Cys fortification in NC diet on broiler performance. In conclusion, fortifying low-CP diet with 0.1% Cys promoted the growth performance of broilers probably through modulating serum metabolite profile.
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Affiliation(s)
- Wei-Wei Wang
- Risk Assessment Laboratory of Feed Derived Factors to Animal Product Quality Safety of Ministry of Agriculture & Rural Affairs, and National Engineering Research Center of Biological Feed, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Qian-Qian Feng
- Risk Assessment Laboratory of Feed Derived Factors to Animal Product Quality Safety of Ministry of Agriculture & Rural Affairs, and National Engineering Research Center of Biological Feed, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Jing Wang
- Risk Assessment Laboratory of Feed Derived Factors to Animal Product Quality Safety of Ministry of Agriculture & Rural Affairs, and National Engineering Research Center of Biological Feed, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Shu-Geng Wu
- Risk Assessment Laboratory of Feed Derived Factors to Animal Product Quality Safety of Ministry of Agriculture & Rural Affairs, and National Engineering Research Center of Biological Feed, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Guang-Hai Qi
- Risk Assessment Laboratory of Feed Derived Factors to Animal Product Quality Safety of Ministry of Agriculture & Rural Affairs, and National Engineering Research Center of Biological Feed, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Hai-Jun Zhang
- Risk Assessment Laboratory of Feed Derived Factors to Animal Product Quality Safety of Ministry of Agriculture & Rural Affairs, and National Engineering Research Center of Biological Feed, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
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Shivakumar N, Jackson AA, Courtney-Martin G, Elango R, Ghosh S, Hodgkinson S, Xipsiti M, Lee WTK, Kurpad AV, Tomé D. Protein Quality Assessment of Follow-up Formula for Young Children and Ready-to-Use Therapeutic Foods: Recommendations by the FAO Expert Working Group in 2017. J Nutr 2020; 150:195-201. [PMID: 31724705 DOI: 10.1093/jn/nxz250] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 05/20/2019] [Accepted: 09/18/2019] [Indexed: 12/18/2022] Open
Abstract
The FAO of the UN convened an Expert Working Group meeting to provide recommendations related to protein quality evaluation of Follow-up Formula for Young Children (FUF-YC) and Ready-to-Use Therapeutic Foods (RUTFs). The protein and amino acid (AA) scoring patterns for the target age groups were defined and recommendations provided on the use of currently available protein and indispensable AA digestibility data. For FUF-YC, an age category of 1-2.9 y was identified, and a matching protein requirement of 0.86 g · kg-1 · d-1 with corresponding AA requirements were recommended. For RUTF, the protein requirement recommended was 2.82 g · kg-1 · d-1, to achieve a catch-up weight gain of 10 g · kg-1 · d-1 in children recovering from severe acute malnutrition. The AA requirements were factorially derived based on the adult protein requirement for maintenance and tissue AA composition. A flowchart was proposed for the best available methods to estimate digestibility coefficients (of either protein or AAs), in the following order: human, growing pig, and rat true ileal AA digestibility values. Where this is not possible, fecal protein digestibility values should be used. The Expert Working Group recommends the use of the Protein Digestibility Corrected Amino Acid Score (PDCAAS), with existing protein digestibility values, or the Digestible Indispensable Amino Acid Score provided that individual AA digestibility values are available for protein quality evaluation using the latter score. The Group also recommends the use of ileal digestibility of protein or of AAs for plant-based protein sources, recognizing the possible effects of antinutritional factors and impaired gut function. A PDCAAS score of ≥90% can be considered adequate for these formulations, whereas with a score <90%, the quantity of protein should be increased to meet the requirements. Regardless of the protein quality score, the ability of formulations to support growth in the target population should be evaluated. Future research recommendations are also proposed based on the knowledge gaps identified.
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Affiliation(s)
- Nirupama Shivakumar
- Department of Physiology, St. John's Medical College, St. John's National Academy of Health Sciences, Bangalore, India
| | - Alan Anthony Jackson
- University Hospitals Southampton, University of Southampton, Southampton, United Kingdom
| | - Glenda Courtney-Martin
- Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Rajavel Elango
- BC Children's Hospital Research Institute, BC Children's Hospital, Vancouver, British Columbia, Canada.,Department of Pediatrics, School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Shibani Ghosh
- Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA, USA
| | | | - Maria Xipsiti
- Nutrition and Food Systems Division, Food and Agriculture Organization of the United Nations, Rome, Italy
| | - Warren T K Lee
- Regional Office for Asia and the Pacific, Food and Agriculture Organization of the United Nations, Bangkok, Thailand
| | - Anura V Kurpad
- Department of Physiology, St. John's Medical College, St. John's National Academy of Health Sciences, Bangalore, India
| | - Daniel Tomé
- UMR PNCA (Research Unit for Nutrition Physiology and Ingestive Behavior), AgroParisTech, INRA (National Institute for Agricultural Research), Université Paris-Saclay, Paris, France
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Shivakumar N, Minocha S, Kurpad AV. Protein quality & amino acid requirements in relation to needs in India. Indian J Med Res 2018; 148:557-568. [PMID: 30666983 PMCID: PMC6366268 DOI: 10.4103/ijmr.ijmr_1688_18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Indexed: 11/04/2022] Open
Abstract
The relevance of protein and its constituent amino acids (AAs) in the structure and function of the human body is well known. Accumulating evidence has conferred specific functional and regulatory roles for individual AAs, adding relevance to their requirements across different age groups. The methods for measuring AA requirements have progressed from the classical nitrogen balance to the current stable isotope-based AA balance methods. Requirements of most of the indispensable AA (IAA) have been estimated in healthy Indian population by the best available balance method and has shown to be higher than earlier 1985 WHO/FAO/UNU (World Health Organization/Food and Agriculture Organization/United Nations University) recommendations. In addition, potential changes in the requirement, through adaptation to chronic undernutrition or to infection, have also been evaluated. In 2007, the WHO/FAO/UNU released a recommendation that increased the daily IAA requirement, based on primary evidence from Indian balance studies. This meant that to ensure that the new IAA requirements were met, individual foods or mixed diets needed to be assessed for their protein quality, or their ability to deliver the required amount of IAA. The recent FAO report on protein quality evaluation recommends the use of a new chemical AA score, the digestible IAA score (DIAAS), to replace the earlier protein digestibility corrected AA score. The DIAAS requires the determination of individual AA digestibility at the ileal level. A minimally invasive dual stable isotope tracer-based approach has been developed in India and has been used to determine digestibility of various foods in Indian adults and children. The increase in IAA requirements and subsequent protein quality requirements have implications for national regulatory frameworks, growth and development, and in turn, for economic and agricultural policy.
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Affiliation(s)
| | - Sumedha Minocha
- Division of Nutrition, St. John's Research Institute, Bengaluru, India
| | - Anura V. Kurpad
- Department of Physiology, St. John's Medical College, Bengaluru, India
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Abstract
Hydrogen sulfide (H₂S) has emerged as an important signaling molecule with beneficial effects on various cellular processes affecting, for example, cardiovascular and neurological functions. The physiological importance of H₂S is motivating efforts to develop strategies for modulating its levels. However, advancement in the field of H₂S-based therapeutics is hampered by fundamental gaps in our knowledge of how H₂S is regulated, its mechanism of action, and its molecular targets. This review provides an overview of sulfur metabolism; describes recent progress that has shed light on the mechanism of H₂S as a signaling molecule; and examines nutritional regulation of sulfur metabolism, which pertains to health and disease.
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Affiliation(s)
- Omer Kabil
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600;
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Abstract
The gastrointestinal tract (GIT) is a metabolically significant site of sulfur amino acid (SAA) metabolism in the body and metabolises about 20 % of the dietary methionine intake which is mainly transmethylated to homocysteine and trans-sulfurated to cysteine. The GIT accounts for about 25 % of the whole-body transmethylation and trans-sulfuration. In addition, in vivo studies in young pigs indicate that the GIT is a site of net homocysteine release and thus may contribute to the homocysteinaemia. The gut also utilises 25 % of the dietary cysteine intake and the cysteine uptake by the gut represents about 65 % of the splanchnic first-pass uptake. Moreover, we recently showed that SAA deficiency significantly suppresses intestinal mucosal growth and reduces intestinal epithelial cell proliferation, and increases intestinal oxidant stress in piglets. These recent findings indicate that intestinal metabolism of dietary methionine and cysteine is nutritionally important for intestinal mucosal growth. Besides their role in protein synthesis, methionine and cysteine are precursors of important molecules. S-adenosylmethionine, a metabolite of methionine, is the principal biological methyl donor in mammalian cells and a precursor for polyamine synthesis. Cysteine is the rate-limiting amino acid for glutathione synthesis, the major cellular antioxidant in mammals. Further studies are warranted to establish how SAA metabolism regulates gut growth and intestinal function, and contributes to the development of gastrointestinal diseases. The present review discusses the evidence of SAA metabolism in the GIT and its functional and nutritional importance in gut function and diseases.
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Tang B, Mustafa A, Gupta S, Melnyk S, James SJ, Kruger WD. Methionine-deficient diet induces post-transcriptional downregulation of cystathionine β-synthase. Nutrition 2009; 26:1170-5. [PMID: 20036517 DOI: 10.1016/j.nut.2009.10.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 10/02/2009] [Accepted: 10/19/2009] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Elevated plasma total homocysteine (tHcy) is a risk factor for a variety of human diseases. Homocysteine is formed from methionine and has two primary metabolic fates: remethylation to form methionine or commitment to the transsulfuration pathway by the action of cystathionine β-synthase (CBS). We have examined the metabolic response in mice of a shift from a methionine-replete to a methionine-free diet. METHODS AND RESULTS We found that shifting 3-mo-old C57BL6 mice to a methionine-free diet caused a transient increase in tHcy and an increase in the tHcy/methionine ratio. Because CBS is a key regulator of tHcy, we examined CBS protein levels and found that within 3 d on the methionine-deficient diet, animals had a 50% reduction in the levels of liver CBS protein and enzyme activity. Examination of CBS mRNA and studies of transgenic animals that express CBS from a heterologous promoter indicated that this reduction is occurring post-transcriptionally. Loss of CBS protein was unrelated to intracellular levels of S-adenosylmethionine, a known regulator of CBS activity and stability. CONCLUSION Our results imply that methionine deprivation induces a metabolic state in which methionine is effectively conserved in tissue by shutdown of the transsulfuration pathway by an S-adenosylmethionine-independent mechanism that signals a rapid downregulation of CBS protein.
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Affiliation(s)
- Baiqing Tang
- Cancer Genetics and Signaling Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA
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Humayun MA, Elango R, Ball RO, Pencharz PB. Reevaluation of the protein requirement in young men with the indicator amino acid oxidation technique. Am J Clin Nutr 2007; 86:995-1002. [PMID: 17921376 DOI: 10.1093/ajcn/86.4.995] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The current estimated protein requirements are based on the nitrogen balance method, which has many limitations. An alternate approach is needed to permit a reevaluation of protein requirements. OBJECTIVE The objective was to determine protein requirements in men by using the indicator amino acid oxidation technique. DESIGN Eight healthy men randomly received graded protein intakes (0.10, 0.30, 0.60, 0.90, 1.2, 1.5 and 1.8 g kg(-1) d(-1)) as a crystalline amino acid mixture along with L-[1-(13)C]phenylalanine. The mean protein requirement was determined by applying a biphase linear regression crossover analysis on F(13)CO(2) data, which identified a breakpoint at the minimal rate of appearance of (13)CO(2) to graded protein intakes. RESULTS The mean and population-safe (recommended dietary allowance; RDA) protein requirements were found to be 0.93 and 1.2 g kg(-1) d(-1), respectively. These requirements are comparable with those estimated by the application of a biphase linear regression model to the data from nitrogen balance studies (0.91 and 1.0 g kg(-1) d(-1), respectively). These requirements are 41% and 50% higher than the current recommendations for the estimated average requirement (EAR) of 0.66 g kg(-1) d(-1) and the RDA of 0.80 g kg(-1) d(-1), as determined by applying a linear regression model where it intersects the zero balance line. CONCLUSION The indicator amino acid oxidation technique defined a protein requirement that is comparable with that estimated by the application of a biphase linear regression model to nitrogen balance data in the literature. Our data and the reanalysis of the preexisting nitrogen balance data suggest that the current recommended protein requirements are too low and require reassessment.
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Affiliation(s)
- Mohammad A Humayun
- Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
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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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Humayun MA, Turner JM, Elango R, Rafii M, Langos V, Ball RO, Pencharz PB. Minimum methionine requirement and cysteine sparing of methionine in healthy school-age children. Am J Clin Nutr 2006; 84:1080-5. [PMID: 17093160 DOI: 10.1093/ajcn/84.5.1080] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Cysteine can provide a portion of the sulfur amino acid requirement in adults. Whether this is true in children-and, if so, to what extent-is not known. OBJECTIVES The objectives were to determine minimum methionine requirements in healthy, school-age children when excess cysteine is provided and to subsequently determine the cysteine-sparing effect by comparing these methionine requirements with those determined previously in the same children when no cysteine was provided. DESIGN Six healthy, school-age children randomly received graded intakes of methionine (0, 2.5, 5, 7.5, 10, and 15 mg . kg(-1) . d(-1)) along with 21 mg cysteine . kg(-1) . d(-1) in the diet. The mean methionine requirement was determined by using a biphasic linear regression crossover analysis of measurements of the rate of appearance of (13)CO(2) in the breath (F(13)CO(2)), which identified a breakpoint at the minimal F(13)CO(2) in response to graded levels of methionine intake. RESULTS The mean and population-safe minimum methionine requirements, in the presence of excess dietary cysteine, were found to be 5.8 and 7.3 mg . kg(-1) . d(-1), respectively. The mean and population-safe (upper 95% CI) methionine requirements, in the absence of dietary cysteine, were previously determined to be 12.9 and 17.2 mg . kg(-1) . d(-1), respectively. These values represent a cysteine-sparing effect of 55% and 58% in comparison with mean and population-safe methionine requirements, respectively. CONCLUSION Excess intake of dietary cysteine results in the reduction in the requirements for methionine to a minimum obligatory requirement level.
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Ball RO, Courtney-Martin G, Pencharz PB. The in vivo sparing of methionine by cysteine in sulfur amino acid requirements in animal models and adult humans. J Nutr 2006; 136:1682S-1693S. [PMID: 16702340 DOI: 10.1093/jn/136.6.1682s] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Sulfur amino acid metabolism has been receiving increased attention because of the link to chronic diseases such as cardiovascular disease, Alzheimer's disease, and diabetes. In addition, the role of cysteine and optimal intakes for physiological substrates such as glutathione are currently of considerable interest in human health. Although the dietary indispensability of methionine is not in question, the ability of cysteine to substitute for a portion of its requirement has been the topic of much debate. Methionine is often the most limiting amino acid in the diets of the developing world's population because of its low concentration in cereal grains. Therefore, the ability of cysteine to substitute for methionine requirement is not just biologically interesting; it is also of considerable economic and social importance. The primary goal of this review is to discuss the available evidence on the effect of cysteine substitution for methionine to meet the total sulfur amino acid requirement in adult humans, including an assessment of the methodological features of experiments with conflicting results. Assessment of the requirement experiments for amino acids with complex metabolism such as methionine and cysteine must begin with a careful definition of requirements and what substitution means. As a result of these definitions, a set of criteria for the intakes of methionine that will allow demonstration of the substitution effect have been developed. Some recent publications are assessed using these definitions and criteria, and a possible reason for the conflicting results in the literature is proposed. An approach to estimating tolerable upper intakes is also proposed. Research on in vivo sulfur amino acid metabolism in humans is tremendously difficult, and therefore, we do not wish to be overly critical of the high-quality work of the ambitious and highly intelligent men and women who have conducted various studies. Our goal is to objectively review the data for the reader in a logical and comprehensive manner and propose methods that may avoid difficulties in future studies.
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Affiliation(s)
- Ronald O Ball
- Department of Nutritional Science and Pediatrics, the University of Toronto, Toronto, Canada.
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Fukagawa NK. Sparing of methionine requirements: evaluation of human data takes sulfur amino acids beyond protein. J Nutr 2006; 136:1676S-1681S. [PMID: 16702339 DOI: 10.1093/jn/136.6.1676s] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The intimate relation between amino acids and protein and nitrogen requirements is well recognized. Nutrition research has focused on the capacity of food to meet the need for nitrogen and indispensable amino acids (IAA) and led to the conclusion that the quality, not just the quantity, of protein is critical. This is especially relevant in regard to the sulfur amino acids (SAA) methionine and cysteine because of the increased understanding of their relation to chronic diseases (e.g., cardiovascular disease, dementia, cirrhosis), immunomodulation, DNA transcription, and RNA translation. Considerable effort has been expended to determine whether and to what extent cysteine can spare the requirement for the IAA methionine. In vivo studies in humans generally concur that the dietary requirement of the SAA ranges between 13 and 16 mg.kg(-1).d(-1), but how much can be met by cysteine relative to methionine remains controversial. This review examines the current status of in vivo estimates of methionine and cysteine requirements in human adults and considers needs beyond what is necessary for protein synthesis. Factors influencing the utilization of methionine and cysteine, especially those conditions that lead to toxicity on the one hand or beneficial effects on the other, are discussed. Data on alternative dietary sources of methyl groups (e.g., betaine, choline, phosphatidylcholine, S-adenosylmethionine, S-methylmethionine) or sulfur (e.g., N-acetylcysteine or L-2-oxothiazolidine-4-carboxylic acid) support a role for the SAA "beyond protein." Other pathways may influence the specific requirement for methionine and/or cysteine, especially when the person is challenged by disease, inadequate availability of food, or environmental stress.
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Affiliation(s)
- Naomi K Fukagawa
- Department of Medicine and General Clinical Research Center, University of Vermont College of Medicine, Burlington, Vermont 05405, USA.
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Hsu JWC, Kriengsinyos W, Wykes LJ, Rafii M, Goonewardene LA, Ball RO, Pencharz PB. Leucine is not a good choice as an indicator amino acid for determining amino acid requirements in men. J Nutr 2006; 136:958-64. [PMID: 16549457 DOI: 10.1093/jn/136.4.958] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Leucine tracer has been widely used for examining whole-body protein turnover in humans, but has not been evaluated as an indicator to be used in the indicator amino acid oxidation (IAAO) method. The goal of this study was to determine whether the L-[1-(13C)]leucine isotope is an acceptable indicator by comparing it with an established tracer, L-[1-(13C)]lysine. Healthy men (n = 7; 29.9 +/- 4.8 y old) were fed in random order a diet with 7 graded intakes of phenylalanine without tyrosine. In the first study (n = 5), subjects were administered an excess leucine intake of 65 mg/(kg.d), and in the second study (n = 5), they were given the mean requirement of 45 mg/(kg.d) to determine whether leucine intake affected the pattern of response. Previous IAAO studies using lysine and phenylalanine demonstrated a clear pattern in 13CO2 production, i.e., increasing test amino acid intake resulted in a linear decrease to plateau, with a readily discernable breakpoint indicating the requirement. This pattern of production of 13CO2, indicates clear partitioning of the indicator amino acid between oxidation and protein synthesis. This was not observed with leucine at an intake of 65 mg/(kg.d). Conversely, at the lower leucine intake of 45 mg/(kg.d), a breakpoint was seen and a total aromatic amino acid requirement estimate that did not differ from that obtain using lysine as the indicator was obtained. In conclusion, leucine may be used as the indicator in the IAAO technique only when the daily intake leucine is given at its mean requirement level and the potential metabolic effects of other variables are taken into consideration.
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Affiliation(s)
- Jean W-C Hsu
- Department of Nutritional Sciences, University of Toronto, Toronto, ON, M5S 3E2, Canada
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