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Glutamine supplementation moderately affects growth, plasma metabolite and free amino acid patterns in neonatal low birth weight piglets. Br J Nutr 2022; 128:2330-2340. [PMID: 35144703 PMCID: PMC9723486 DOI: 10.1017/s0007114522000459] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Low birth weight (LBW) neonates show impaired growth compared with normal birth weight (NBW) neonates. Glutamine (Gln) supplementation benefits growth of weaning piglets, while the effect on neonates is not sufficiently clear. We examined the effect of neonatal Gln supplementation on piglet growth, milk intake and metabolic parameters. Sow-reared pairs of newborn LBW (0·8-1·2 kg) and NBW (1·4-1·8 kg) male piglets received Gln (1 g/kg body mass (BM)/d; Gln-LBW, Gln-NBW; n 24/group) or isonitrogenous alanine (1·22 g/kg BM/d; Ala-LBW; Ala-NBW; n 24/group) supplementation at 1-5 or 1-12 d of age (daily in three equal portions at 07:00, 12:00 and 17:00 by syringe feeding). We measured piglet BM, milk intake (1, 11-12 d), plasma metabolite, insulin, amino acid (AA) and liver TAG concentrations (5, 12 d). The Gln-LBW group had higher BM (+7·5%, 10 d, P = 0·066; 11-12 d, P < 0·05) and milk intake (+14·7%, P = 0·015) than Ala-LBW. At 5 d, Ala-LBW group had higher plasma TAG (+34·7%, P < 0·1) and lower carnosine (-22·5%, P < 0·05) than Ala-NBW and Gln-LBW, and higher liver TAG (+66·9%, P = 0·029) than Ala-NBW. At 12 d, plasma urea was higher (+37·5%, P < 0·05) with Gln than Ala supplementation. Several proteinogenic AA in plasma were lower (P < 0·05) in Ala-NBW v. Gln-NBW. Plasma arginine was higher (P < 0·05) in Gln-NBW v Ala-NBW piglets (5, 12 d). Supplemental Gln moderately improved growth and milk intake and affected lipid metabolism in LBW piglets and AA metabolism in NBW piglets, suggesting effects on intestinal and liver function.
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Citrulline, Biomarker of Enterocyte Functional Mass and Dietary Supplement. Metabolism, Transport, and Current Evidence for Clinical Use. Nutrients 2021; 13:nu13082794. [PMID: 34444954 PMCID: PMC8398474 DOI: 10.3390/nu13082794] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 07/28/2021] [Accepted: 07/28/2021] [Indexed: 12/25/2022] Open
Abstract
L-Citrulline is a non-essential but still important amino acid that is released from enterocytes. Because plasma levels are reduced in case of impaired intestinal function, it has become a biomarker to monitor intestinal integrity. Moreover, oxidative stress induces protein citrullination, and antibodies against anti-citrullinated proteins are useful to monitor rheumatoid diseases. Citrullinated histones, however, may even predict a worse outcome in cancer patients. Supplementation of citrulline is better tolerated compared to arginine and might be useful to slightly improve muscle strength or protein balance. The following article shall provide an overview of L-citrulline properties and functions, as well as the current evidence for its use as a biomarker or as a therapeutic supplement.
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Tsonaka R, Signorelli M, Sabir E, Seyer A, Hettne K, Aartsma-Rus A, Spitali P. Longitudinal metabolomic analysis of plasma enables modeling disease progression in Duchenne muscular dystrophy mouse models. Hum Mol Genet 2021; 29:745-755. [PMID: 32025735 PMCID: PMC7104681 DOI: 10.1093/hmg/ddz309] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 11/26/2019] [Accepted: 12/16/2019] [Indexed: 12/12/2022] Open
Abstract
Duchenne muscular dystrophy is a severe pediatric neuromuscular disorder caused by the lack of dystrophin. Identification of biomarkers is needed to support and accelerate drug development. Alterations of metabolites levels in muscle and plasma have been reported in pre-clinical and clinical cross-sectional comparisons. We present here a 7-month longitudinal study comparing plasma metabolomic data in wild-type and mdx mice. A mass spectrometry approach was used to study metabolites in up to five time points per mouse at 6, 12, 18, 24 and 30 weeks of age, providing an unprecedented in depth view of disease trajectories. A total of 106 metabolites were studied. We report a signature of 31 metabolites able to discriminate between healthy and disease at various stages of the disease, covering the acute phase of muscle degeneration and regeneration up to the deteriorating phase. We show how metabolites related to energy production and chachexia (e.g. glutamine) are affected in mdx mice plasma over time. We further show how the signature is connected to molecular targets of nutraceuticals and pharmaceutical compounds currently in development as well as to the nitric oxide synthase pathway (e.g. arginine and citrulline). Finally, we evaluate the signature in a second longitudinal study in three independent mouse models carrying 0, 1 or 2 functional copies of the dystrophin paralog utrophin. In conclusion, we report an in-depth metabolomic signature covering previously identified associations and new associations, which enables drug developers to peripherally assess the effect of drugs on the metabolic status of dystrophic mice.
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Affiliation(s)
- Roula Tsonaka
- Biomedical Data Sciences, Leiden University Medical Center, Leiden 2333 ZC, The Netherlands
| | - Mirko Signorelli
- Biomedical Data Sciences, Leiden University Medical Center, Leiden 2333 ZC, The Netherlands.,Department of Human Genetics, Leiden University Medical Center, Leiden 2333 ZC, The Netherlands
| | - Ekrem Sabir
- Department of Human Genetics, Leiden University Medical Center, Leiden 2333 ZC, The Netherlands
| | | | - Kristina Hettne
- Department of Human Genetics, Leiden University Medical Center, Leiden 2333 ZC, The Netherlands
| | - Annemieke Aartsma-Rus
- Department of Human Genetics, Leiden University Medical Center, Leiden 2333 ZC, The Netherlands
| | - Pietro Spitali
- Department of Human Genetics, Leiden University Medical Center, Leiden 2333 ZC, The Netherlands
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Elke G, Hartl WH, Kreymann KG, Adolph M, Felbinger TW, Graf T, de Heer G, Heller AR, Kampa U, Mayer K, Muhl E, Niemann B, Rümelin A, Steiner S, Stoppe C, Weimann A, Bischoff SC. Clinical Nutrition in Critical Care Medicine - Guideline of the German Society for Nutritional Medicine (DGEM). Clin Nutr ESPEN 2019; 33:220-275. [PMID: 31451265 DOI: 10.1016/j.clnesp.2019.05.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 05/03/2019] [Indexed: 02/07/2023]
Abstract
PURPOSE Enteral and parenteral nutrition of adult critically ill patients varies in terms of the route of nutrient delivery, the amount and composition of macro- and micronutrients, and the choice of specific, immune-modulating substrates. Variations of clinical nutrition may affect clinical outcomes. The present guideline provides clinicians with updated consensus-based recommendations for clinical nutrition in adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function. METHODS The former guidelines of the German Society for Nutritional Medicine (DGEM) were updated according to the current instructions of the Association of the Scientific Medical Societies in Germany (AWMF) valid for a S2k-guideline. According to the S2k-guideline classification, no systematic review of the available evidence was required to make recommendations, which, therefore, do not state evidence- or recommendation grades. Nevertheless, we considered and commented the evidence from randomized-controlled trials, meta-analyses and observational studies with adequate sample size and high methodological quality (until May 2018) as well as from currently valid guidelines of other societies. The liability of each recommendation was described linguistically. Each recommendation was finally validated and consented through a Delphi process. RESULTS In the introduction the guideline describes a) the pathophysiological consequences of critical illness possibly affecting metabolism and nutrition of critically ill patients, b) potential definitions for different disease phases during the course of illness, and c) methodological shortcomings of clinical trials on nutrition. Then, we make 69 consented recommendations for essential, practice-relevant elements of clinical nutrition in critically ill patients. Among others, recommendations include the assessment of nutrition status, the indication for clinical nutrition, the timing and route of nutrient delivery, and the amount and composition of substrates (macro- and micronutrients); furthermore, we discuss distinctive aspects of nutrition therapy in obese critically ill patients and those treated with extracorporeal support devices. CONCLUSION The current guideline provides clinicians with up-to-date recommendations for enteral and parenteral nutrition of adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function. The period of validity of the guideline is approximately fixed at five years (2018-2023).
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Affiliation(s)
- Gunnar Elke
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Haus 12, 24105, Kiel, Germany.
| | - Wolfgang H Hartl
- Department of Surgery, University School of Medicine, Grosshadern Campus, Ludwig-Maximilian University, Marchioninistr. 15, 81377 Munich, Germany.
| | | | - Michael Adolph
- University Department of Anesthesiology and Intensive Care Medicine, University Hospital Tübingen, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany.
| | - Thomas W Felbinger
- Department of Anesthesiology, Critical Care and Pain Medicine, Neuperlach and Harlaching Medical Center, The Munich Municipal Hospitals Ltd, Oskar-Maria-Graf-Ring 51, 81737, Munich, Germany.
| | - Tobias Graf
- Medical Clinic II, University Heart Center Lübeck, University Medical Center Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany.
| | - Geraldine de Heer
- Center for Anesthesiology and Intensive Care Medicine, Clinic for Intensive Care Medicine, University Hospital Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Germany.
| | - Axel R Heller
- Clinic for Anesthesiology and Surgical Intensive Care Medicine, University of Augsburg, Stenglinstrasse 2, 86156, Augsburg, Germany.
| | - Ulrich Kampa
- Clinic for Anesthesiology, Lutheran Hospital Hattingen, Bredenscheider Strasse 54, 45525, Hattingen, Germany.
| | - Konstantin Mayer
- Department of Internal Medicine, Justus-Liebig University Giessen, University of Giessen and Marburg Lung Center, Klinikstr. 36, 35392, Gießen, Germany.
| | - Elke Muhl
- Eichhörnchenweg 7, 23627, Gross Grönau, Germany.
| | - Bernd Niemann
- Department of Adult and Pediatric Cardiovascular Surgery, Giessen University Hospital, Rudolf-Buchheim-Str. 7, 35392, Gießen, Germany.
| | - Andreas Rümelin
- Clinic for Anesthesia and Surgical Intensive Care Medicine, HELIOS St. Elisabeth Hospital Bad Kissingen, Kissinger Straße 150, 97688, Bad Kissingen, Germany.
| | - Stephan Steiner
- Department of Cardiology, Pneumology and Intensive Care Medicine, St Vincenz Hospital Limburg, Auf dem Schafsberg, 65549, Limburg, Germany.
| | - Christian Stoppe
- Department of Intensive Care Medicine and Intermediate Care, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany.
| | - Arved Weimann
- Department of General, Visceral and Oncological Surgery, Klinikum St. Georg, Delitzscher Straße 141, 04129, Leipzig, Germany.
| | - Stephan C Bischoff
- Department for Nutritional Medicine, University of Hohenheim, Fruwirthstr. 12, 70599, Stuttgart, Germany.
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Marini JC, Agarwal U, Didelija IC, Azamian M, Stoll B, Nagamani SCS. Plasma Glutamine Is a Minor Precursor for the Synthesis of Citrulline: A Multispecies Study. J Nutr 2017; 147:549-555. [PMID: 28275102 PMCID: PMC5368584 DOI: 10.3945/jn.116.243592] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 01/10/2017] [Accepted: 02/10/2017] [Indexed: 01/21/2023] Open
Abstract
Background: Glutamine is considered the main precursor for citrulline synthesis in many species, including humans. The transfer of 15N from 2-[15N]-glutamine to citrulline has been used as evidence for this precursor-product relation. However, work in mice has shown that nitrogen and carbon tracers follow different moieties of glutamine and that glutamine contribution to the synthesis of citrulline is minor. It is unclear whether this small contribution of glutamine is also true in other species.Objective: The objective of the present work was to determine the contribution of glutamine to citrulline production by using nitrogen and carbon skeleton tracers in multiple species.Methods: Humans (n = 4), pigs (n = 5), rats (n = 6), and mice (n = 5) were infused with l-2-[15N]- and l-[2H5]-glutamine and l-5,5-[2H2]-citrulline. The contribution of glutamine to citrulline synthesis was calculated by using different ions and fragments: glutamine M+1 to citrulline M+1, 2-[15N]-glutamine to 2-[15N]-citrulline, and [2H5]-glutamine to [2H5]-citrulline.Results: Species-specific differences in glutamine and citrulline fluxes were found (P < 0.001), with rats having the largest fluxes, followed by mice, pigs, and humans (all P < 0.05). The contribution of glutamine to citrulline as estimated by using glutamine M+1 to citrulline M+1 ranged from 88% in humans to 46% in pigs. However, the use of 2-[15N]-glutamine and 2-[15N]-citrulline as precursor and product yielded values of 48% in humans and 28% in pigs. Furthermore, the use of [2H5]-glutamine to [2H5]-citrulline yielded lower values (P < 0.001), resulting in a contribution of glutamine to the synthesis of citrulline of ∼10% in humans and 3% in pigs.Conclusions: The recycling of the [15N]-glutamine label overestimates the contribution of glutamine to citrulline synthesis compared with a tracer that follows the carbon skeleton of glutamine. Glutamine is a minor precursor for the synthesis of citrulline in humans, pigs, rats, and mice.
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Affiliation(s)
- Juan C Marini
- Section of Critical Care Medicine, .,USDA/Agricultural Research Service, Children's Nutrition Research Center, and
| | - Umang Agarwal
- USDA/Agricultural Research Service, Children’s Nutrition Research Center, and
| | - Inka C Didelija
- USDA/Agricultural Research Service, Children’s Nutrition Research Center, and
| | - Mahshid Azamian
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX
| | - Barbara Stoll
- USDA/Agricultural Research Service, Children’s Nutrition Research Center, and
| | - Sandesh CS Nagamani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX
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Liu G, Cao W, Fang T, Jia G, Zhao H, Chen X, Wu C, Wang J. Urinary Metabolomic Approach Provides New Insights into Distinct Metabolic Profiles of Glutamine and N-Carbamylglutamate Supplementation in Rats. Nutrients 2016; 8:nu8080478. [PMID: 27527211 PMCID: PMC4997391 DOI: 10.3390/nu8080478] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 07/13/2016] [Accepted: 07/28/2016] [Indexed: 01/15/2023] Open
Abstract
Glutamine and N-carbamylglutamate can enhance growth performance and health in animals, but the underlying mechanisms are not yet elucidated. This study aimed to investigate the effect of glutamine and N-carbamylglutamate supplementation in rat metabolism. Thirty rats were fed a control, glutamine, or N-carbamylglutamate diet for four weeks. Urine samples were analyzed by nuclear magnetic resonance (NMR)-based metabolomics, specifically high-resolution 1H NMR metabolic profiling combined with multivariate data analysis. Glutamine significantly increased the urine levels of acetamide, acetate, citrulline, creatinine, and methymalonate, and decreased the urine levels of ethanol and formate (p < 0.05). Moreover, N-carbamylglutamate significantly increased the urine levels of creatinine, ethanol, indoxyl sulfate, lactate, methymalonate, acetoacetate, m-hydroxyphenylacetate, and sarcosine, and decreased the urine levels of acetamide, acetate, citrulline, creatine, glycine, hippurate, homogentisate, N-acetylglutamate, phenylacetyglycine, acetone, and p-hydroxyphenylacetate (p < 0.05). Results suggested that glutamine and N-carbamylglutamate could modify urinary metabolome related to nitrogen metabolism and gut microbiota metabolism. Moreover, N-carbamylglutamate could alter energy and lipid metabolism. These findings indicate that different arginine precursors may lead to differences in the biofluid profile in rats.
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Affiliation(s)
- Guangmang Liu
- Institute of Animal Nutrition, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Chengdu 611130, Sichuan, China.
| | - Wei Cao
- Institute of Animal Nutrition, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Chengdu 611130, Sichuan, China.
| | - Tingting Fang
- Institute of Animal Nutrition, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Chengdu 611130, Sichuan, China.
| | - Gang Jia
- Institute of Animal Nutrition, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Chengdu 611130, Sichuan, China.
| | - Hua Zhao
- Institute of Animal Nutrition, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Chengdu 611130, Sichuan, China.
| | - Xiaoling Chen
- Institute of Animal Nutrition, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Chengdu 611130, Sichuan, China.
| | - Caimei Wu
- Institute of Animal Nutrition, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Chengdu 611130, Sichuan, China.
| | - Jing Wang
- Maize Research Institute, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
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Enteral Glutamine Administration in Critically Ill Nonseptic Patients Does Not Trigger Arginine Synthesis. J Nutr Metab 2016; 2016:1373060. [PMID: 27200186 PMCID: PMC4855021 DOI: 10.1155/2016/1373060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2015] [Revised: 02/10/2016] [Accepted: 02/21/2016] [Indexed: 12/19/2022] Open
Abstract
Glutamine supplementation in specific groups of critically ill patients results in favourable clinical outcome. Enhancement of citrulline and arginine synthesis by glutamine could serve as a potential mechanism. However, while receiving optimal enteral nutrition, uptake and enteral metabolism of glutamine in critically ill patients remain unknown. Therefore we investigated the effect of a therapeutically relevant dose of L-glutamine on synthesis of L-citrulline and subsequent L-arginine in this group. Ten versus ten critically ill patients receiving full enteral nutrition, or isocaloric isonitrogenous enteral nutrition including 0.5 g/kg L-alanyl-L-glutamine, were studied using stable isotopes. A cross-over design using intravenous and enteral tracers enabled splanchnic extraction (SE) calculations. Endogenous rate of appearance and SE of glutamine citrulline and arginine was not different (SE controls versus alanyl-glutamine: glutamine 48 and 48%, citrulline 33 versus 45%, and arginine 45 versus 42%). Turnover from glutamine to citrulline and arginine was not higher in glutamine-administered patients. In critically ill nonseptic patients receiving adequate nutrition and a relevant dose of glutamine there was no extra citrulline or arginine synthesis and glutamine SE was not increased. This suggests that for arginine synthesis enhancement there is no need for an additional dose of glutamine when this population is adequately fed. This trial is registered with NTR2285.
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Abstract
PURPOSE OF REVIEW This article analyzes the contribution of glutamine to the synthesis of citrulline and reviews the evidence that glutamine supplementation increases citrulline production. RECENT FINDINGS Glutamine supplementation has been proposed in the treatment of critically ill patients; however, a recent large multicenter randomized controlled trial resulted in increased mortality in the glutamine-supplemented group. Within this context, defining the contribution of glutamine to the production of citrulline, and thus to de-novo arginine synthesis, has become a pressing issue. SUMMARY The beneficial effects of glutamine supplementation may be partially mediated by the effects of glutamine on citrulline synthesis by the gut and the de-novo synthesis of arginine by the kidney and other tissues. Although there is no strong evidence to support that glutamine is a major precursor for citrulline synthesis in humans, glutamine has the potential to increase overall gut function and in this way increase citrulline production.
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Affiliation(s)
- J.C. Marini
- Section of Critical Care Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, United States of America
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, United States of America
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Citrulline and nitrogen homeostasis: an overview. Amino Acids 2015; 47:685-91. [PMID: 25676932 DOI: 10.1007/s00726-015-1932-2] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 01/28/2015] [Indexed: 12/15/2022]
Abstract
Citrulline (Cit) is a non-essential amino acid whose metabolic properties were largely ignored until the last decade when it began to emerge as a highly promising nutrient with many regulatory properties, with a key role in nitrogen homeostasis. Because Cit is not taken up by the liver, its synthesis from arginine, glutamine, ornithine and proline in the intestine prevents the hepatic uptake of the two first amino acids which activate the urea cycle and so prevents amino acid catabolism. This sparing effect may have positive spin-off for muscle via increased protein synthesis, protein content and functionality. However, the mechanisms of action of Cit are not fully known, even if preliminary data suggest an implication of mTOR pathway. Further exploration is needed to gain a complete overview of the role of Cit in the control of nitrogen homeostasis.
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Marini JC, Stoll B, Didelija IC, Burrin DG. De novo synthesis is the main source of ornithine for citrulline production in neonatal pigs. Am J Physiol Endocrinol Metab 2012; 303:E1348-53. [PMID: 23074237 PMCID: PMC3774079 DOI: 10.1152/ajpendo.00399.2012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Citrulline is an amino acid synthesized in the gut and utilized for the synthesis of the conditionally essential amino acid arginine. Recently, the origin of the ornithine utilized for citrulline synthesis has become a matter of discussion. Multiple physiological factors may have contributed to the differences found among different researchers; one of these is the developmental stage of the subjects studied. To test the hypothesis that during the neonatal period de novo synthesis is the main source of ornithine for citrulline synthesis, neonatal piglets were infused intravenously or intragastrically with [U-(13)C(6)]arginine, [U-(13)C(5)]glutamine, or [U-(13)C(5)]proline during the fasted and fed periods. [ureido-(15)N]citrulline and [(2)H(2)]ornithine were infused intravenously for the entire infusion protocol. During fasting, plasma proline (13%) and ornithine (19%) were the main precursors for citrulline synthesis, whereas plasma arginine (62%) was the main precursor for plasma ornithine. During feeding, enteral (27%) and plasma (12%) proline were the main precursors for the ornithine utilized in the synthesis of citrulline, together with plasma ornithine (27%). Enteral proline and glutamine were utilized directly by the gut to produce ornithine utilized for citrulline synthesis. Arginine was not utilized by the gut, which is consistent with the lack of arginase activity in the neonate. Arginine, however, was the main source (47%) of plasma ornithine and in this way contributed to citrulline synthesis. In conclusion, during the neonatal period, the de novo pathway is the predominant source for the ornithine utilized in the synthesis of citrulline, and proline is the preferred precursor.
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Affiliation(s)
- Juan C Marini
- United States Department of Agriculture/Agricultural Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
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Marini JC. Arginine and ornithine are the main precursors for citrulline synthesis in mice. J Nutr 2012; 142:572-80. [PMID: 22323761 PMCID: PMC3278269 DOI: 10.3945/jn.111.153825] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Recent isotopic tracer studies in mice, piglets, and humans have produced conflicting results as to the main carbon skeleton precursor for citrulline and arginine synthesis. This may be due in part to the different tracers infused and models used to interpret the stable isotope data. Furthermore, previous studies usually investigated a single precursor, which prevented the direct comparison among multiple precursors. To further elucidate the contribution of different precursors to citrulline synthesis, all possible enteral and plasma precursors of citrulline were studied in a mouse model during the postabsorptive and postprandial period using multitracer protocols. In addition, three different models were used to interpret the stable isotope data. The utilization of the classic precursor-product equation, developed for i.v. infused tracers but also used to include i.g. tracers, grossly overestimated the contribution of enteral precursors. Regardless of the model employed, dietary and plasma arginine were the main precursors for citrulline synthesis during feeding and plasma arginine during feed deprivation. The contribution of arginine was directly at the site of citrulline synthesis and through plasma ornithine. The predominant role of arginine and ornithine seen in this study supports the observations in mice, piglets, and humans suggesting that ornithine amino transferase is a pivotal enzyme in this pathway.
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