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Urschel KL, Wilkinson CW, Pencharz PB, Ball RO. Coadministration of ornithine and alpha-ketoglutarate is no more effective than ornithine alone as an arginine precursor in piglets enterally fed an arginine-deficient diet. J Nutr 2007; 137:55-62. [PMID: 17182801 DOI: 10.1093/jn/137.1.55] [Citation(s) in RCA: 5] [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
Simultaneous administration of alpha-ketoglutarate and ornithine, in a 1:2 molar ratio, may improve the effectiveness of ornithine as an arginine precursor in neonatal piglets by shifting ornithine metabolism away from oxidation and toward the synthesis of arginine and other metabolically important compounds. To study this proposed mechanism, enterally fed piglets were allocated to receive 1 of 4 diets for 5 d: an arginine-deficient [1.2 mmol/(kg . d) arginine] diet (basal), or the basal diet supplemented with either alpha-ketoglutarate [4.6 mmol/(kg x d)] (+alpha-KG), ornithine [9.2 mmol/(kg x d)] (+Orn), or both ornithine and alpha-ketoglutarate (+alpha-KG/+Orn, molar ratio 1:2). Primed, constant infusions of [1-(14)C]ornithine given both intragastrically and intraportally were used to measure ornithine kinetics and determine the role of first-pass intestinal metabolism in ornithine metabolism. Whole body arginine and glutamate kinetics were measured using a primed, constant intragastric infusion of [guanido-(14)C]arginine and [3,4-(3)H]glutamate. The diets did not affect plasma arginine or ammonia concentrations, arginine flux, or arginine synthesis from ornithine. Therefore, arginine synthesis was not increased by the simultaneous infusion of ornithine and alpha-ketoglutarate. Piglets that received dietary ornithine had a 2-fold greater rate of proline synthesis from ornithine (P < 0.05) and oxidized a greater (P < 0.05) portion of the infused ornithine than piglets in the basal and +alpha-KG groups. Overall, ornithine addition to an arginine deficient diet had a greater effect on ornithine and arginine metabolism than the addition of alpha-ketoglutarate. First-pass intestinal metabolism was critical for ornithine synthesis and conversion to other metabolites but not for ornithine oxidation.
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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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Leslie MA, Coleman RA, Moehn S, Ball RO, Korver DR. Relationship Between Bicarbonate Retention and Bone Characteristics in Broiler Chickens. Poult Sci 2006; 85:1917-22. [PMID: 17032824 DOI: 10.1093/ps/85.11.1917] [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: 11/12/2022] Open
Abstract
Determination of the bicarbonate retention factor (BRF) is an important step during development of the indicator amino acid oxidation technique for use in a new model. A series of 4-h oxidation experiments were performed to determine the BRF of broilers aged 7, 14, 21, 28, 35, and 42 d using 4 birds per age group. A priming dose of 1.2 microCi of NaH(14)CO(3), followed by eight half-hourly doses of 1 microCi of NaH(14)CO(3) were given orally to each of 4 birds per age. The percentage of (14)C dose expired by the bird at a steady state was measured. These birds, as well as 12 additional birds matched for age and BW, were killed, and femur bone mineral density was measured by quantitative computed tomography to determine the relationship between bone development and bicarbonate retention at each age. There was a correlation (r = 0.50; P < 0.05) between total cross-sectional femur bone mineral density and bicarbonate retention at each age. A prediction equation (Y = 6.95 x 10(-2)X - 3.51 x 10(-5)X(2) + 27.58; P < 0.0001, R(2) = 0.79) where Y = bicarbonate retention and X = BW was generated to predict Y as a function of X. Bicarbonate retention values peaked at 28 d, during the stage of the most rapid bone deposition and the highest growth rate. A constant BRF was found from 1,900 to 2,700 g of BW of 35.15 +/- 1.095% (mean +/- SEM). This retention factor will allow the accurate correction of oxidation of (14)C-labeled substrates in broilers of different ages and BW in future indicator amino acid oxidation studies.
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Urschel KL, Shoveller AK, Uwiera RRE, Pencharz PB, Ball RO. Citrulline is an effective arginine precursor in enterally fed neonatal piglets. J Nutr 2006; 136:1806-13. [PMID: 16772441 DOI: 10.1093/jn/136.7.1806] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Although neonatal piglets can synthesize some arginine from proline, there is a limit to this synthesis, and piglets fed an arginine-deficient diet have diminished whole-body arginine status. To help elucidate where the limitation in arginine synthesis may occur, our objective was to determine the most effective arginine precursor in 1-wk-old enterally fed piglets. Piglets were administered either an arginine-deficient (basal) diet [1.15 mmol arginine/(kg.d)] or the basal diet supplemented with equimolar [9.18 mmol/(kg.d)] amounts of proline (+Pro), ornithine (+Orn), citrulline (+Cit) or arginine (+Arg) for 5 d (n = 5/diet). Daily blood samples were taken and indicators of whole-body arginine status including plasma amino acid, ammonia, and urea concentrations were measured. A primed, constant intragastric (i.g.) infusion of l-[U-(14)C]proline was given to measure the proline to arginine conversion, and intravenous (i.v.) and i.g. infusions of l-[guanido-(14)C]arginine were given to determine arginine flux and to quantify the splanchnic extraction of dietary arginine. Piglets fed the +Cit and +Arg diets had lower plasma ammonia and urea concentrations (P < 0.05) and higher plasma arginine concentrations (P < 0.0001) and arginine fluxes (P < 0.05) than piglets fed the other 3 diets. Piglets fed +Cit and +Arg had a lower proline to arginine conversion (P < 0.05). During first-pass splanchnic metabolism, 52% of the dietary arginine was extracted, and this extraction was not affected by whole-body arginine status (P > 0.05). These data indicate that citrulline, but not ornithine or proline, is an effective arginine precursor, and that either citrulline formation or availability appears to limit arginine synthesis in neonatal piglets.
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Mager DR, Wykes LJ, Roberts EA, Ball RO, Pencharz PB. Effect of orthotopic liver transplantation (OLT) on branched-chain amino acid requirement. Pediatr Res 2006; 59:829-34. [PMID: 16641206 DOI: 10.1203/01.pdr.0000219302.21321.87] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Little is known regarding the impact of liver transplantation on amino acid requirements in children. Since plasma levels of the branched-chain amino acids (BCAA) are decreased in the presence of normal levels of the aromatic amino acids after liver transplantation, normalization of hepatic function may not fully correct changes in BCAA metabolism that occur in the pretransplant period. The goal of the present study was to determine total BCAA requirements of children following liver transplantation. The requirement of total BCAA was determined using indicator amino acid oxidation (IAAO) in five clinically stable children (5.7 +/- 3.5 y, mean +/- SD) 1-8 y post liver transplantation. Children received in random order 6 graded intakes of total BCAA. Individual BCAA in the test diet were provided in the same proportions as 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/h], after a primed, continuous infusion of the tracer and using a two-phase linear regression crossover regression analysis. The estimated average requirement and the upper limit of the 95% CI for total BCAA in children who have undergone liver transplantation were 172 and 206 mg/kg/d), respectively. Total BCAA requirement in children who have undergone orthotopic liver transplantation (OLT) remain increased in the post-liver transplant period when compared with healthy school aged children, but is decreased when compared with children with mild-moderate chronic cholestatic (MCC) liver disease.
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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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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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Mager DR, Wykes LJ, Roberts EA, Ball RO, Pencharz PB. Mild-to-moderate chronic cholestatic liver disease increases leucine oxidation in children. J Nutr 2006; 136:965-70. [PMID: 16549458 DOI: 10.1093/jn/136.4.965] [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: 11/12/2022] Open
Abstract
Malnutrition is prevalent in children with chronic cholestatic liver disease. Using the noninvasive indicator amino acid oxidation (IAAO) technique, we recently determined that mild-to-moderate chronic cholestatic (MCC) liver disease increases the need for branched-chain amino acids (BCAA) in children. To examine the underlying mechanisms responsible for this increased need for BCAA in liver disease, we measured L-[1-(13C)]-leucine oxidation in the postabsorptive and fed states in 10 children with MCC liver disease (8.8 +/- 3.5 y) and in 11 healthy children (9.4 +/- 2.2 y). The oxidation of L-[1-(13C)]-leucine to 13CO2 [F13CO2 in micromol/(kg.h)] was determined after a primed, continuous oral administration of the tracer. Total BCAA in diet was provided at 300 mg/(kg.d) to ensure that leucine oxidation was measured when leucine intake was in excess of requirements. In the postabsorptive state, the rate of release of 13CO2 from 13C-leucine oxidation (F13CO2) and whole-body leucine oxidation were significantly higher in children with MCC liver disease (P < 0.05). However, F13CO2 and whole-body leucine oxidation did not differ in the fed state. We conclude that the increased need for dietary BCAA in MCC liver disease is mediated in part by increased leucine oxidation in the postabsorptive state.
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Urschel KL, Pencharz PB, Ball RO. GLP‐2 infusion increases endogenous arginine synthesis in parenterally‐fed piglets receiving an arginine deficient diet. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a424-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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110
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Turner JM, Humayun MA, Elango R, Rafii M, Langos V, Ball RO, Pencharz PB. Total sulfur amino acid requirement of healthy school-age children as determined by indicator amino acid oxidation technique. Am J Clin Nutr 2006; 83:619-23. [PMID: 16522909 DOI: 10.1093/ajcn.83.3.619] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Current total sulfur amino acid (TSAA) requirements of children are based on a factorial estimate that involves several assumptions. OBJECTIVE The objective was to determine the TSAA requirement (methionine alone) of healthy school-age children by measuring the appearance of 13CO2 (F13CO2) in breath after the oxidation of l-[1-13C]phenylalanine in response to graded methionine intakes. DESIGN Six healthy school-age children randomly received each of 6 methionine intakes (0, 5, 10, 15, 25, and 35 mg.kg(-1).d(-1)) along with an amino acid mixture to give a final protein intake of 1.5 g.kg(-1).d(-1) and an energy intake of 1.7 x resting energy expenditure. The diet was devoid of cysteine. The mean TSAA requirement was determined by applying a biphase linear regression crossover analysis on F13CO2 data, which identified a breakpoint at minimal F13CO2 in response to graded methionine intakes. RESULTS The mean and population-safe (upper 95% CI) intakes of TSAA (as methionine) were determined to be 12.9 and 17.2 mg.kg(-1).d(-1), respectively. CONCLUSIONS The current study suggests that children of this age group have a mean TSAA requirement similar to that of adults (12.6 mg.kg(-1).d(-1)). Therefore, it is valid to use a factorial approach, which assumes that maintenance requirements in childhood are similar to adult requirements, to estimate TSAA requirements in school-age children.
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Turner J, Humayun A, Elango R, Rafii M, Langos V, Geary D, Ball RO, Pencharz PB. Total sulphur amino acid requirement of children with end‐stage renal disease. FASEB J 2006. [DOI: 10.1096/fasebj.20.5.a1042-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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112
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Elango R, Humayun A, Ball RO, Pencharz PB. Indicator amino acid oxidation (1‐
13
C‐phenylalanine) is not affected by day of adaptation (1, 3 or 7d) to a wide range of lysine intake in young men. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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113
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Humayun A, Turner J, Elango R, Rafii M, Langos V, Ball RO, Pencharz PB. Dietary cysteine spares the methionine requirement in healthy school‐aged children. FASEB J 2006. [DOI: 10.1096/fasebj.20.5.a1043-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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114
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Hsu JWC, Goonewardene LA, Rafii M, Ball RO, Pencharz PB. Aromatic amino acid requirements in healthy men measured by indicator amino acid oxidation. Am J Clin Nutr 2006; 83:82-8. [PMID: 16400054 DOI: 10.1093/ajcn/83.1.82] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND In the current literature, no agreement exists on estimates for aromatic amino acid (phenylalanine plus tyrosine) requirements as measured by stable-isotope techniques. OBJECTIVE The goal of the present study was to determine the phenylalanine requirement in healthy men who were fed a diet without tyrosine by using the indicator amino acid oxidation method. DESIGN Five healthy men were assigned to receive in random order diets devoid of tyrosine and with 8 graded intakes of phenylalanine (5, 10, 15, 25, 35, 45, 60, and 70 mg x kg(-1) x d(-1)). The phenylalanine requirement was measured by the rate of 13CO2 release (F13CO2) from L-[1-(13)C]lysine oxidation. RESULTS The graded intakes of phenylalanine had no effect on lysine flux, as required for this method. The phenylalanine (ie, total aromatic amino acid) requirement, in the absence of tyrosine, was estimated to be 48 mg x kg(-1) x d(-1) by applying a two-phase linear regression crossover model to the F13CO2 data. CONCLUSIONS In the absence of tyrosine, the mean phenylalanine requirement is higher than the current FAO/WHO/UNU (1985) and Dietary Reference Intake (2002) recommendations.
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Pencharz PB, Ball RO. Amino acid requirements of infants and children. NESTLE NUTRITION WORKSHOP SERIES. PAEDIATRIC PROGRAMME 2006; 58:109-16; discussion 116-9. [PMID: 16902329 DOI: 10.1159/000095024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Nitrogen balances have been conducted in preterm infants, preschool children, and 6- to 10-year-old children to determine dietary indispensable amino acid. A recent review concluded that the data, being sufficiently uncertain, could not be used as the basis for defining amino acid requirements in infants and children. Therefore, it was decided to use a factorial approach (basal plus growth). This approach is based on the assumption that basal requirements are the same throughout the life cycle. Recently, using indicator oxidation, the requirements of the eight classical indispensable amino acids have been defined in adults. These values have been used as the basal component of requirement in childhood. The growth component was based on the changes in body protein with age. We have recently shown that the maintenance requirements for branched chain amino acids are similar in children and adults, thereby validating the factorial approach.
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Mager DR, Wykes LJ, Roberts EA, Ball RO, Pencharz PB. Branched-chain amino acid needs in children with mild-to-moderate chronic cholestatic liver disease. J Nutr 2006; 136:133-9. [PMID: 16365072 DOI: 10.1093/jn/136.1.133] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Protein-energy malnutrition is prevalent in children with chronic cholestatic liver disease. Supplementation of branched-chain amino acids (BCAA) in infants and children with chronic liver disease has been associated with significant improvement in growth and nitrogen balance, suggesting that BCAA requirements are increased in chronic liver disease. The goal of the present study was to determine the total BCAA requirement in children with mild-to-moderate chronic cholestatic (MCC) liver disease using indicator amino acid oxidation (IAAO). Total BCAA requirements were determined in 6 children (6.3 +/- 3.7 y, mean +/- SD) with MCC liver disease. Children were randomly assigned 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. The total BCAA requirement was determined by measuring the oxidation of l-[1-13C] Phe to 13CO2 [F13CO2 in micromol/(kg x h)], after a primed, continuous oral administration of the tracer and using a 2-phase linear regression crossover regression analysis. The estimated mean requirement and the upper limit of the 95% CI for total BCAA establishing using the IAAO in children with MCC liver disease were 209 and 272 mg/(kg x d), respectively. Total BCAA estimated average requirements using the IAAO were significantly higher than mean requirements established previously for healthy children (P < 0.05).
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Moehn S, Bertolo RFP, Pencharz PB, Ball RO. Development of the indicator amino acid oxidation technique to determine the availability of amino acids from dietary protein in pigs. J Nutr 2005; 135:2866-70. [PMID: 16317134 DOI: 10.1093/jn/135.12.2866] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Standardized ileal ("true") digestibility is currently the best estimate of amino acid digestibility, but it does not measure bioavailability. Growth assays to determine amino acid bioavailability are expensive and laborious; thus, a rapid method is needed. Applying the principle of slope-ratio assay to the indicator amino acid oxidation (IAAO) method, we hypothesized that the reduction in indicator oxidation per gram of lysine in feedstuffs relative to that per gram of free lysine represented the bioavailability of lysine, here termed "metabolic availability." Indicator oxidation in pigs was linear over increasing lysine intakes (r = 0.90, P = 0.001) when the dietary lysine contents were 2 SD below the mean lysine requirement of the pigs. Peas were treated (raw, heated to reduce lysine availability, or heated with added lysine) to test the responsiveness of the IAAO to differing lysine availability. Free lysine reduced indicator oxidation by 3.16% of dose oxidized per gram added lysine, whereas the addition of protein lysine as raw (-2.81%) and heated peas (-1.73%) reduced oxidation to a lesser degree. Adding free lysine to heated peas decreased indicator oxidation, evidence that heating had worsened the utilization of pea protein for protein synthesis by reducing the bioavailability of lysine alone. Pea diets differed only in the availability of lysine; therefore IAAO detected differences in lysine bioavailability. Because the IAAO technique responds to lysine available at the sites of protein synthesis, the metabolic availability covers all losses during digestion, absorption, and utilization of lysine. This method can determine the metabolic availability of amino acids of a feedstuff within 2 wk.
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Bertolo RF, Moehn S, Pencharz PB, Ball RO. Estimate of the variability of the lysine requirement of growing pigs using the indicator amino acid oxidation technique1. J Anim Sci 2005; 83:2535-42. [PMID: 16230650 DOI: 10.2527/2005.83112535x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Although AA requirements for the mean in a population of growing pigs are well established, there are no direct estimates of their variability within the population. The indicator AA oxidation method allows repeated measurements in a short period of time so that the AA requirement can be determined for individual pigs. The objective was to determine the Lys requirement in individual pigs to derive a first estimate of the population mean requirement and its variability. Nine individually housed barrows (15 to 18 kg) were surgically implanted with venous catheters for isotope infusion. Pigs were offered, in random order, isonitrogenous and isoenergetic diets with one of seven Lys concentrations (4.8 to 15.5 g of Lys/kg diet, as-fed basis). The pigs were fed twice daily, except for study days when they received one-half of the daily allowance in eight equal hourly meals. After a validated minimum adaptation period, indicator (Phe) oxidation was determined for each dietary Lys level during a 4-h primed, constant infusion of L-[1-(14C)]Phe at a rate of 464 kBq/h. The Lys requirement was calculated using a two-phase linear regression crossover analysis within individual pigs. For each pig, Phe oxidation decreased linearly (P < 0.02) as the dietary Lys concentration increased until the requirement was reached; thereafter, Phe oxidation was not different. The true ileal digestible Lys requirement ranged from 7.5 to 10.6 g/kg of diet (as-fed basis) for the nine animals. The mean requirement for all pigs was 9.1 g/d (CV, 11.6%) or 93.9% (CV, 9.8%) of the predicted (NRC, 1998) requirement based on each pig's mean BW and energy intake. The measured and predicted requirements did not differ. The indicator AA oxidation method gave values for Lys requirement similar to conventional methods. The short (< 3 wk) experimental period allows, for the first time, the estimate of population variability, which provides for more accurate calculation of the effect of altering Lys intake on herd performance and production economics. This method is suitable to use with all dietary indispensable AA.
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Shoveller AK, Stoll B, Ball RO, Burrin DG. Nutritional and functional importance of intestinal sulfur amino acid metabolism. J Nutr 2005; 135:1609-12. [PMID: 15987836 DOI: 10.1093/jn/135.7.1609] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The metabolism of sulfur amino acids, methionine and cysteine, has been linked to several key aspects of human health and cellular function. In addition, the metabolism of dietary amino acids by the gastrointestinal tract is nutritionally important for normal function. In the case of sulfur amino acids (SAAs), in vivo, stable isotope studies in adults suggest that the splanchnic tissues utilize as much as 30-44% of the dietary methionine and cysteine. Similarly, the dietary methionine requirement is 30% lower in total parenteral nutrition (TPN)-fed piglets, a condition in which dietary nutrients largely bypass intestinal metabolism. These data suggest that intestinal metabolism of methionine is substantial, yet the intestinal metabolic fate of dietary methionine is largely unknown. Dietary cysteine likely plays a key role in intestinal epithelial antioxidant function as a precursor for glutathione. Moreover, cysteine and glutathione may also regulate epithelial cell proliferation via modulation of redox status. Recent evidence indicates that transformed colonic epithelial cells are capable of methionine transmethylation and transsulfuration. This review discusses the evidence of intestinal SAA metabolism and how this affects nutrient requirements and epithelial function.
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Urschel KL, Shoveller AK, Pencharz PB, Ball RO. Arginine synthesis does not occur during first-pass hepatic metabolism in the neonatal piglet. Am J Physiol Endocrinol Metab 2005; 288:E1244-51. [PMID: 15657089 DOI: 10.1152/ajpendo.00530.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have shown that first-pass intestinal metabolism is necessary for approximately 50% of whole body arginine synthesis from its major precursor proline in neonatal piglets. Furthermore, the intestine is not the site of increased arginine synthesis observed during dietary arginine deficiency. Primed constant intravenous (iv) and intraportal (ip) infusions of L-[U-14C]proline, and iv infusion of either L-[guanido-14C]arginine or L-[4,5-3H]arginine were used to measure first-pass hepatic arginine synthesis in piglets enterally fed either deficient (0.20 g.kg(-1).day(-1)) or generous (1.80 g.kg(-1).day(-1)) quantities of arginine for 5 days. Conversion of arginine to other urea cycle intermediates and arginine recycling were also calculated for both dietary treatments. Arginine synthesis (g.kg(-1).day(-1)) from proline was greater in piglets (P < 0.05) fed the deficient arginine diet in both the presence (generous: 0.07; deficient: 0.17; pooled SE = 0.01) and absence (generous: 0.06; deficient: 0.20; pooled SE = 0.01) of first-pass hepatic metabolism. There was no net arginine synthesis from proline during first-pass hepatic metabolism regardless of arginine intake. Arginine conversion to urea, citrulline, and ornithine was significantly greater (P < 0.05) in piglets fed the generous arginine diet. Calculated arginine fluxes were significantly lower (P = 0.01) for [4,5-3H]arginine than for [guanido-14C]arginine, and the discrepancy between the values was greater in piglets fed the deficient arginine diet (35% vs. 20%). Collectively, these findings show that first-pass hepatic metabolism is not a site of net arginine synthesis and that piglets conserve dietary arginine in times of deficiency by decreasing hydrolysis and increasing recycling.
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Darling PB, Dunn M, Gilani GS, Ball RO, Pencharz PB. Phenylalanine kinetics differ between formula-fed and human milk-fed preterm infants. J Nutr 2004; 134:2540-5. [PMID: 15465744 DOI: 10.1093/jn/134.10.2540] [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: 11/12/2022] Open
Abstract
Infants fed casein-dominant formulas have higher plasma phenylalanine and tyrosine concentrations than those fed mother's milk. Conversely, elevated plasma threonine concentrations are observed in infants fed whey-dominant formulas. We recently showed that formula-fed preterm infants have a lower capacity to degrade threonine than do preterm infants fed mother's milk. We hypothesized that these same infants (n = 18) would differ in their catabolism of phenylalanine in response to phenylalanine loads provided by formulas with increasing casein content of formulas (whey:casein 60:40, 40:60, and 20:80) compared with preterm infants fed mother's milk. Plasma phenylalanine concentrations significantly rose (49, 46, 79 micromol . L(-1) for whey:casein 60:40, 40:60, and 20:80, respectively, pooled SD 8, P < 0.05); and plasma phenylalanine concentrations in infants fed mother's milk were low (40 +/- 4 micromol . L(-1)). Using [1-(13)C]phenylalanine tracer and (13)CO(2) production in breath we found that although there was a significant positive relation between phenylalanine oxidation and phenylalanine intake in formula-fed infants (r(2) = 0.43, P = 0.03), these infants were not able to increase their oxidation of phenylalanine enough to prevent a significant rise in plasma phenylalanine when fed the 20:80 formula. Compared to infants fed mother's milk, formula-fed infants had significantly lower phenylalanine oxidation (39.1 vs. 30.7% of phenylalanine intake, respectively, P < 0.05). We conclude that one of the mechanisms for the differences in plasma amino acid concentration between formula-fed and mother's milk-fed preterm infants may be in vivo down-regulated catabolism of 2 important essential amino acids (phenylalanine in addition to threonine) in formula-fed preterm infants.
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Wilkinson DL, Bertolo RFP, Brunton JA, Shoveller AK, Pencharz PB, Ball RO. Arginine synthesis is regulated by dietary arginine intake in the enterally fed neonatal piglet. Am J Physiol Endocrinol Metab 2004; 287:E454-62. [PMID: 15149954 DOI: 10.1152/ajpendo.00342.2003] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Arginine is conditionally indispensable in the neonate, and its synthesis in the intestine is not sufficient to meet requirements. It is not known how neonatal endogenous arginine synthesis is regulated and the degree to which proline and glutamate are used as precursors. Primed, constant intraportal and intragastric infusions of L-[U-14C]proline and L-[3,4-3H]glutamate, and intragastric L-[guanido-14C]arginine were used to measure whole body and first-pass intestinal arginine synthesis in 10 neonatal piglets fed generous (1.80 g.kg(-1).day(-1)) or deficient (0.20 g.kg(-1).day(-1)) quantities of arginine for 5 days. Glutamate tracer was not detected in arginine, indicating a biologically insignificant conversion of <1% of arginine flux. Endogenous arginine synthesis from proline had obligatory (0.36 g.kg(-1).day(-1)) and maximal (0.68 g.kg(-1).day(-1)) levels (P < 0.05, pooled SE 0.05). Although first-pass gut metabolism is responsible for 42-63% of whole body arginine synthesis, the gut is incapable of upregulating proline to arginine conversion during arginine deficiency, compared with a more than threefold increase without first-pass gut metabolism. These data suggest that upregulation of proline-to-arginine conversion occurs via increased arterial extraction of proline by the gut or in nonintestinal tissues. This study demonstrates that dietary arginine is an important regulator of endogenous arginine synthesis in the neonatal piglet and that proline, but not glutamate, is an important precursor for arginine synthesis in the neonate.
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Moehn S, Ball RO, Fuller MF, Gillis AM, de Lange CFM. Growth potential, but not body weight or moderate limitation of lysine intake, affects inevitable lysine catabolism in growing pigs. J Nutr 2004; 134:2287-92. [PMID: 15333718 DOI: 10.1093/jn/134.9.2287] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Inevitable catabolism contributes to the inefficiency of using dietary lysine intake for body protein deposition (PD). This study was conducted to determine the effects of true ileal digestible (TID) lysine intake, body weight (BW), and growth potential on lysine catabolism in growing pigs. Starting at 15 kg BW, 16 female Yorkshire pigs were offered a purified diet providing all nutrients in excess of requirements for maximum protein deposition (PDmax). At approximately 25 kg BW, the pigs' PDmax was determined using the N-balance method. Thereafter, 4 pigs were allocated to each of 4 diets, first-limiting in lysine, providing lysine intakes corresponding to 60, 70, 80, and 90% of estimated requirements for PDmax. The pigs were surgically fitted with catheters in the jugular and femoral veins. Lysine catabolism was determined at 2 BW (40-45 kg, low; 70-75 kg, high) either directly (oxidation) using a primed, constant infusion of l-[1-(14)C]-lysine or indirectly (disappearance) using the N-balance method. There was no effect of BW on the rate (g/d) or fraction of TID lysine intake catabolized. Lysine catabolism decreased with increasing growth potential. Lysine disappearance and lysine oxidation (% of TID lysine intake) were independent of lysine intake, except for the lowest lysine intake level, where they were lower. When lysine catabolism was independent of intake, lysine oxidation based on plasma free lysine specific radioactivity (SRA) was lower (9.9% of TID intake) than lysine disappearance (17.4% of TID intake) or lysine oxidation based on liver free lysine SRA (13.4% of TID intake).
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Kriengsinyos W, Wykes LJ, Goonewardene LA, Ball RO, Pencharz PB. Phase of menstrual cycle affects lysine requirement in healthy women. Am J Physiol Endocrinol Metab 2004; 287:E489-96. [PMID: 15308475 DOI: 10.1152/ajpendo.00262.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to investigate whether the phases of the menstrual cycle affect lysine requirement in healthy adult females, as determined by the indicator amino acid oxidation (IAAO) method. Five healthy females with regular menstrual cycles were studied at seven graded levels of lysine intake, in random order, with an oral [13C]phenylalanine tracer protocol in both the follicular and luteal phases. A total of 14 studies were conducted for each subject. Breath and plasma samples were collected according to the standard IAAO protocol. Serum 17beta-estradiol and progesterone concentrations were measured on each IAAO study day. The rate of release of 13CO2 from [13C]phenylalanine oxidation (F13CO2) was measured, and a two-phase linear regression crossover model was applied to determine lysine requirement. F13CO2 was higher during the luteal phase (P < 0.001) and was positively associated with serum concentrations of 17beta-estradiol and progesterone. The F13CO2 data were adjusted for subjects and sex hormones and used to define breakpoints for lysine requirements. The lysine requirement of healthy females in the luteal phase was 37.7 mg.kg(-1).day(-1) and higher (P = 0.025) than that of females in the follicular phase (35.0 mg.kg(-1).day(-1)). At all lysine intake levels, plasma amino acids were lower and phenylalanine oxidation was higher in the luteal relative to the follicular phase. Therefore, we reason that the higher lysine requirement observed in the luteal phase is probably due to higher amino acid catabolism.
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Moehn S, Bertolo RFP, Pencharz PB, Ball RO. Pattern of carbon dioxide production and retention is similar in adult pigs when fed hourly, but not when fed a single meal. BMC PHYSIOLOGY 2004; 4:11. [PMID: 15242516 PMCID: PMC476741 DOI: 10.1186/1472-6793-4-11] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2004] [Accepted: 07/08/2004] [Indexed: 11/10/2022]
Abstract
BACKGROUND The understanding of bicarbonate kinetics and CO2 retention in the body is necessary to conduct amino acid tracer oxidation studies in both humans and laboratory animals. Significant metabolic activity is associated with eating which can affect bicarbonate steady state kinetics. A study was conducted to assess the impact of feeding regimen on the recovery of labelled bicarbonate and energy expenditure in adult female pigs (sows). Five catheterized sows (235 +/- 5 kg) were fed semi-synthetic diets as: a single meal 2 h into the infusion after an overnight fast, or in eight hourly meals starting 2 h before the infusion. Oxygen consumption, CO2 production and 14CO2 recovery (ie fraction not retained) were determined during primed, constant intravenous infusions of NaH14CO3. RESULTS The 14CO2 recovery (%) after fasting (58.1 +/- 4.8) was lower than that after single meal feeding (78.8 +/- 5.9) or hourly meal feeding (81.0 +/- 2.6, P = 0.03). CO2 production correlated with 14CO2 recovery during hourly feeding (r = 0.40, P = 0.01); this relationship was not significant after single meal feeding (P = 0.30), probably due to physical activity-associated CO2 production. CONCLUSIONS The correlation of CO2 retention factors with CO2 production during hourly feeding suggests that this regimen should be preferred for future amino acid kinetics studies.
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