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Home , Citrulline, Ornithine, Ornithine translocase

S42 Gut 1994; supplement 1: S42-S45 Can and omithine support gut functions? Gut: first published as 10.1136/gut.35.1_Suppl.S42 on 1 January 1994. Downloaded from L Cynober

Abstract of arginine and related Arginine and are precursors of compounds in the gut and polyamines, respectively. Arginine synthesis and catabolism in specific These metabolites intimately participate in tissues is conditioned by the presence of permeability and adaptive responses ofthe arginosuccinase and respectively, but gut. The liver possesses high arginase only periportal hepatocytes and, to some activity as an intrinsic part of synthe- extent, certain brain areas, possess all the sis and would consume most of the portal required for arginine recycling and supply ofdietary arginine. The gut reduces urea synthesis.' The gut acts as a user of this possibility by converting dietary arginine because it possesses arginase (isoen- arginine to , which effectively zyme II) and ornithine carbamoyltransferase.4 bypass the liver and is resynthesised to The gut thus releases urea and citrulline.5 arginine in the kidney. Dietary ornithine In addition, enterocytes express omithine supplementation, in the form of ornithine decarboxylase6 and an NADPH2 dependent a-ketoglutarate (OKG) can be considered arginine deiminase78 which respectively lead to as an arginine precursor. Several supple- local production of aliphatic polyamines and ment studies have shown both amino acids nitric oxide. to promote and insulin Despite the high omithine decarboxylase secretion with anabolic effects in post- activity in enterocytes, however, most of the operative patients. Their intermediary omithine produced from arginine is released metabolites (for example, glutamine, pro- into the portal blood stream, and polyamine line) may also be of benefit in trauma formation accounts for a small part of arginine metabolism. Specific effects of either consumption.8 on the gut are poorly reported. After 14C-ornithine is given by the enteral One recent animal study showed improved route, 14C-, '4C-glutamate, and 14C- morphology after OKG administration, polyamines are detected,9 as expected, but, in perhaps through increased polyamine contrast with arginine administration, no secretion. Generation of nitric oxide from citrulline is produced. This could suggest a arginine has two facets. Excess production degree of metabolic compartmentalisation, from high dose arginine potentiated the arginine flux being directed preferentially http://gut.bmj.com/ effects of experimentally induced sepsis, towards ornithine and citrulline production. whereas low doses improved survival. Indeed, omithine , omithine These considerations suggest that the role carbamoyltransferase, and citrulline trans- of enteral diet supplementation with locase function as a multienzyme complex' arginine or OKG should be urgendy exam- (Fig 1). Figure 2 summarises arginine and ined for any benefits it may have on omithine pathways in the gut.

mucosal barrier function. on September 27, 2021 by guest. Protected copyright. (Gut 1994; supplement 1: S42-S45) Arginine and related compounds in artificial nutrition For many years, arginine and related com- Arginine has multiple biological properties, pounds (omithine and citrulline) have been including the ability to stimulate anabolic considered solely as intermediate metabolites hormone secretion: intravenous and enteral in the process of detoxification - that arginine administration increases both insulin is, in the context of ureagenesis. There is and human growth hormone secretion.'2 renewed interest, however, in these amino Several studies (reviewed in references 2 and Laboratoire de acids because ureagenesis may have an 13) show that arginine given to patients as well Biochimie, Groupe de role in homeostasis' Recherche en important pH and also as in various experimental stress models, acts Nutrition because arginine becomes an essential amino by improving nitrogen balance, accelerating Exp6rimentale et acid during growth and catabolic states.2 wound healing, and restoring depressed Metabolisme Hepatique, H6pital Ornithine is not a constituent of proteins, but immunity (Table). These effects are seen 15 Saint - Antoine, Paris, is clearly important in the regulation of nutri- whether arginine is given orally'4 or paren- France, and Centre de tional state as a precursor of aliphatic terally. 16 Recherche en In in the form of the a Nutrition Humaine, polyamines. addition, Omithine shares with arginine the ability to Clermont-Ferrand, ketoglutarate salt, omithine generates multiple stimulate human growth hormone secretion.3 France metabolic effects, which do not result solely In addition, omithine as its ao-ketoglutarate salt L Cynober to the additive action of the two moieties (OKG) generates various molecules (for Correspondence to: of this molecule.3 There is, however, a paucity example, glutamine) 17 which play a key part in Professor L Cynober, of data on the role of or its metabolites Laboratoire de Biochimie, arginine the control of protein metabolism.'8 OKG has Faculte de Pharmacie, 28 in the maintenance of gut function and been shown to improve nitrogen balance in Place H Dunant, BP38, this 63001 Clermont-Ferrand morphology; indicates possible future various acute and chronic malnutrition states Cedex, France. research directions. (see reference 3 for a review). OKG increases Can arginine and ornithine support gutfunctions? S43

53 Nitric oxide Cytoplasm Mitochondria arginine -..4citruiline Gut: first published as 10.1136/gut.35.1_Suppl.S42 on 1 January 1994. Downloaded from urea I AKU rT- Ia Polyamines ornithine carbamoyl P

CIT

. glutamate P5C proline

spermidine a ketoglutarate Polyamines GLU Co2 PRO Figure 2: Arginine and ornithine metabolic pathways in the enterocyte. Adaptedfrom Blachier et al.8, Seiler et al,'O Figure 1: Arginine (ARG) and ornithine (ORN) fluxes andJones. 1 1 (I Arginase (EC 3.5.3. 1); 2 ornithine compared. ASe=arginase; OT=; decarboxylase (EC 4.1.1.17); (a ornithine CT=citrulline translocase; OCT=ornithine carbamoyl- carbamoyltransferase (EC 2.1.3.3); (v) ; transferase; GLU=glutamate; PRO=proline. () ornithine aminotransferase (EC 2.6.1.13).

muscle protein anabolism in moderate cata- citrulline in the gut can also be seen as a means bolic states'9 and reduces protein catabolism of protecting this amino acid from excessive in hypercatabolic states.20 degradation in the liver. Finally, arginine and ornithine metabolism in enterocytes could par- ticipate in the support of gut morphology and Arginine and ornithine in the support of function by the synthesis of polyamines and gut functions nitric oxide, as will be discussed.

FUNCTIONS OF ARGININE AND ORNITHINE Arginine from dietary proteins is thus actively ACTIONS OF ARGININE AND ORNITHINE metabolised in the enterocyte and supports Surprisingly, published works contain few

several gut functions. Firstly, arginine metabo- studies dealing with the effects of arginine on http://gut.bmj.com/ lism in the enterocyte serves to remove excess gut function and morphology. With regard to arginine, although the liver also has a high ornithine, only one recent study is available capacity for arginine transport and metabol- (F Raul, personal communication). Rats were ism.21 It has been shown22 that portal arginine starved for three days and then fed for four concentrations rise with the percentage of pro- days by continuous enteral nutrition, with or tein in the diet, with a parallel increase in urea without supplementation with ornithine (032

synthesis. In fact, arginine acts in the hepato- g/kg/day) as the oa-ketoglutarate salt. Rats were on September 27, 2021 by guest. Protected copyright. cyte as a positive modulator of N-acetylgluta- then killed and intestinal morphology and mate synthesis, which is the allosteric content were studied. Ornithine led to obligatory activator of a significantly higher crypt height in the synthetase, the enzyme participating in the first jejunum and ileum and a higher total villous step of urea synthesis.1 Thus, arginine metabo- height in the ileum. In addition, sucrase and lism in the gut should be seen as a means of lactase contents were higher in the ileum of limiting arginine supply to the liver, thereby ornithine supplemented rats. limiting ureagenesis when protein intake is low. It is noteworthy that the intestine also contains significant concentrations ofN-acetylglutamate POSSIBLE MECHANISMS OF ACTION (IF ANY) (20% ofliver content),23 which must play a part As described, enterocytes are well equipped to in favouring citrulline formation from omithine convert arginine into ornithine and to after food intake. Interestingly, citrulline metabolise ornithine into putrescine and other uptake by the liver is low, and citrulline is aliphatic polyamines. Alternatively, arginine extensively converted into arginine in the kid- is the precursor of nitric oxide by arginine ney (Figure 3). Thus, arginine metabolism into desiminase.

Effects ofarginine supplementation in enteral nutrition The polyamine pathway _ protein catabolism in trauma (humans/rats) Ornithine is converted into putrescine by t immune response after trauma (humans/rats) Tthymic weight (EC 4.1.1.17), which tthymic lymphocyte content is the rate limiting enzyme in polyamine Tlymphocyte mitotic response to concanavalin A and PHA synthesis. Putrescine is converted into spermi- Improves wound healing (humans/rats) dine by the action of an aminopropyl- - Increases survival after burns (guinea pigs) transferase. A second, identical enzyme adds S44 Cynober

Urea Gut: first published as 10.1136/gut.35.1_Suppl.S42 on 1 January 1994. Downloaded from ARG

ARG ARG (proteins) I - lORN CIT CIT

Figure 3: Arginine (ARG) metabolism into citrulline (CIT) in the gut seen as a means ofprotecting arginine from excessive degradation in the liver. ORN=ornithine.

an additional propylamine moiety to spermi- and polyamines increase34 in parallel with the dine, thus forming spermidine. The source increase in mucosal proliferation indices.33 This of the propylamine groups is S-adenosyl is clear in the distal segment of the intestine .6 where polyamine content is lowest in the basal The functions of polyamines in mammalian state.35 With the administration of difluoro- cells are poorly understood, although the use methylomithine the increase in ornithine of omithine decarboxylase inhibitors such as decarboxylase and polyamines is suppressed difluoromethyl omithine has established that and intestinal adaptation is abrogated.33 polyamines are essential for cell growth6 and The real question is whether exogenous protein synthesis.24 In this way, it has been arginine can be a relevant precursor of poly- clearly shown that the action of ornithine on amines. It is noteworthy that food contains fibroblast growth in culture25 and on protein polyamines and that polyamines are produced

synthesis by the liver26 are both dependent by the flora of the gastrointestinal tract.36 http://gut.bmj.com/ upon polyamine synthesis. Thus, the direct uptake by enterocytes of pre- With regard to the intestine, there are con- formed polyamines could contribute to the sistent data supporting an important role of polyamine cellular pool. Indeed, putrescine37 polyamines in the control of hypo and hyper- and spermidine uptake38 have been shown in plasia ofthis tissue. Ornithine decarboxylase in isolated rat enterocytes. Interestingly, entero- the mucosa ofthe small intestine has high basal cytes from the distal quarter of the gut exhibit

activity compared with most tissues.6 the highest rate of uptake.37 The fact that a on September 27, 2021 by guest. Protected copyright. Ornithine decarboxylase is associated with large fraction of metabolised arginine is trans- mature cells of the villus tip as well as pro- ported out of the enterocyte as ornithine and liferating crypt cells, suggesting that citrulline may show that arginine metabolism is polyamines participate in both intestinal cell not responsible for relevant amounts of differentiation and proliferation.27 polyamines. Intestinal polyamine content falls after a fast28 and after an eight-day total parenteral nutrition programme in the rat,29 but increases The nitnic oxide pathway during refeeding.28 The fall in the concentra- The nitric oxide pathway is probably the most tions of polyamines during fasting results from important recent discovery in the field of a simultaneous decrease in polyamine syn- amino acid metabolism. Nitric oxide is pro- thesis (that is, a decrease in ornithine decarb- duced from arginine by arginine deiminase. oxylase content) and an increase in their Although this enzyme has been identified degradation (that is, an increase in diamine in various cell types, the pathway seems oxydase content). The reverse is true during to be located mainly in macrophages and refeeding.30 The trophic effect of nutrients endothelial cells,39 where nitric oxide triggers seems to be due in particular to glucose and to cytotoxic activity of phagocytic cells and amino acids such as and .31 32 vascular smooth muscle relaxation of endothe- This effect is strong in the jejunum and ileum, lial cells.40 Nitric oxide activates guanylate moderate in the duodenum, and small in the cyclase, thereby forming cyclic GMP, which is proximal colon.3' its second messenger.39 40 Experimental endo- In the same way, during intestinal adaptation toxemia (lipopolysaccharide from Escherichia in response to jejunectomy33 or to parasite colt) leads to accumulation of NO3- in urine. (Trichinella spiralis) induced ,34 Activation of the nitric oxide pathway is con- intestinal contents of ornithine decarboxylase trolled by cytokines.41 Taken together, the data Can arginine and ornithine support gutfunctions? S45

support a role for nitric oxide in the pathogen- 18 Rennie MJ, Babij P, Taylor PM, Hundal HS, Mac Lenan P, Watt PW, et al. Characteristics of a glutamine carrier in esis of septic shock syndrome. In this context, skeletal muscle have important consequences for nitrogen care must be taken with arginine supplementa- loss in injury, infection and chronic disease. Lancet 1986; ii: 1008-12. tion in severely ill patients at risk of developing 19 Wernerman J, Hammarqvist F, Ali MR, Vinnars E. Gut: first published as 10.1136/gut.35.1_Suppl.S42 on 1 January 1994. Downloaded from multiple organ failure. This dual effect ofnitric Glutamine and ornithine alpha-ketoglutarate but not branched-chain amino acids reduce the loss of muscle oxide (and therefore arginine) is illustrated by glutamine after surgical trauma. Metabolism 1989; 38 a recent study from Alexander's group.42 (suppl 1): 63-6. 20 Vaubourdolle M, Coudray-Lucas C, Jardel A, Ziegler F, Septic guinea pigs supplemented with low Ekindjian OG, Cynober L. Action of enterally-adminis- doses of arginine recovered better than con- tered ornithine alpha-ketoglutarate on protein breakdown in skeletal muscle and liver of the burned rat. JPEN 1991; trols, whereas supplementation with high 15: 517-20. doses led to catastrophic results. 21 De Bandt JP, Cynober L, Lim SK, Coudray-Lucas C, Poupon R, Giboudeau J. Metabolismes compares de In conclusion, enterocytes contain high con- l'ornithine et de l'arginine dans un systeme de foie isole centrations of polyamines, which play a crucial perfuse. Nutr Clin Metabol 1990; 4 (suppl): 46. 22 Morimoto BH, Brady JF, Atkinson DE. Effect of level of part in the control of cell multiplication and dietary protein on arginine-stimulated citrulline synthesis. differentiation, and are able to synthesise nitric Biochem 7 1990; 272: 671-5. 23 Tuchman M, Holznecht RA. N-acetylglutamate content in oxide, which emerges as a potent modulator of liver and gut of normal and fasted mice, normal human the response to inflammation. Despite these livers, and livers of individuals with carbamyl phosphate synthetase or ornithine transcarbamylase. Pediatr Res features, there is an extreme paucity of data on 1990; 27: 408-12. the action of arginine and omithine on gut 24 Grillo MA. Metabolism and function of polyamines. Int J Biochem 1985; 17: 943-8. function. Such studies are urgently required. 25 Vaubourdolle M, Salvucci M, Coudray-Lucas C, Agneray J, Cynober L, Ekindjian OG. Action of ornithine alpha- I am extremely grateful to Dr F Raul (INSERM U61, ketoglutarate on DNA synthesis by human fibroblasts. In Strasbourg) for providing exciting new results on the effects of Vitro Cell Dev Biol 1990; 26: 187-92. ornithine ox-ketoglutarate on gut morphology and function. The 26 Oratz M, Rothschild MA, Schreiber SS, Burks A, Mongelli secretarial assistance of Miss P Jue was greatly appreciated. J, Matarese B. The role of the and polyamines in albumine synthesis. Hepatology 1983; 3: 567-630. 1 Meijer AJ, Lamers WH, Chamuleau RAFM. Nitrogen 27 Johnson LR, Tseng CC, Wang P, Tipnis UR, Haddox MK. metabolism and omithine cycle function. Physiol Rev Mucosal ornithine decarboxylase in the small intestine: 1990; 70: 701-48. localization and stimulation. Am J Physiol 1989; 256: 2 Barbul A. Arginine: biochemistry, physiology and therapeu- G624-30. tic implications. JPEN 1986; 10: 227-38. 28 Alarcon P, Lin CH, Lebenthal E, Lee PC. Interaction of 3 Cynober L. Omithine alpha-ketoglutarate in nutritional malnutrition and difluoromethylornithine induced in- support. Nutrition 1991; 7: 313-22. testinal mucosal damage: degree of severity and sub- 4 Herzfeld A, Raper SM. The heterogeneity of arginases in rat sequent recovery. Digestion 1988; 41: 68-77. tissues. Biochem _J 1976; 153: 469-78. 29 Hosomi M, Stace NH, Lirussi F, Smith SM, Murphy GM, 5 Windmueller HG, Spaeth AE. Metabolism of absorbed Dowling RH. Role of polyamines in intestinal adaptation aspartate, asparagine, and arginine by rat small intestine in the rat. EurJClin Invest 1987; 17: 373-85. in vivo. Arch Biochem Biophys 1976; 175: 660-76. 30 D'Agostino L, Daniele B, Pignata S, Barone MV, 6 Pegg AE. Recent advances in the biochemistry of D'Argenio G, Mazzaca G. Modifications in ornithine polyamines in eukaryotes. Biochem J 1986; 234: 249-62. decarboxylase and diamine oxidase in small bowel mucosa 7 Blachier F, M'Rabet-Touil H, Darcy-Vrillon B, Posho L, of starved and refed rats. Gut 1987; 28 (suppl 1): 135-8. Duee PH. Stimulation by D-glucose of the direct conver- 31 Jain R, Eikenburg BE, Johnson LR. Stimulation ofornithine sion of arginine to citrulline in enterocytes isolated from decarboxylase activity in digestive tract mucosa. Am Jf pig jejunum. Biochem Biophys Res Commun 1991; 177: Physiol 1987; 253: G303-7. 1171-7. 32 Minami H, Mikamoto K, Fujii Y, Nakabou Y, Hagihira H. 8 Blachier F, Darcy-Vrillon B, Sener A, Duee PH, Malaisse Induction of intestinal ornithine decarboxylase by single WJ. Arginine metabolism in rat enterocytes. Biochim amino acid feeding. J Biochem 1985; 98: 133-9. http://gut.bmj.com/ BiophysActa 1991; 1092: 304-10. 33 Luk GD, Yang P. Polyamines intestinal and pancreatic 9 Vaubourdolle M, Jardel A, Coudray-Lucas C, Ekindjian adaptation. Gut 1987; 28 (suppl 1): 95-101. OG, Agneray J, Cynober L. Fate ofenterally administered 34 Wang JY, Johnson LR, Tsai YH, Castro GA. Mucosal omithine in healthy animals: interactions with alpha- ornithine decarboxylase, polyamines, and hyperplasia in ketoglutarate. Nutrition 1989; 5: 183-7. infected intestine. AmJPhysiol 1991; 23: G45-51. 10 Seiler N, Daune G, Bolkenius FN, Knodgen B. Ornithine 35 Hosomi MM, Smith SM, Murphy GM, Dowling RH. aminotransferase activity, tissue ornithine concentrations Polyamine distribution in the rat intestinal mucosa. and polyamines metabolism. Int J Biochem 1989; 21: JChromatogr 1986; 375: 267-75. 425-32. 36 McCormack SA, Johnson LR. Role of polyamines in gas-

11 Jones ME. Conversion of glutamate to ornithine and pro- trointestinal mucosal growth. Am J Physiol 1991; 260: on September 27, 2021 by guest. Protected copyright. line: pyrroline 5-carboxylate, a possible modulator of argi- G795-806. nine requirement.JNutr 1985; 115: 509-15. 37 Kumagai J, Johnson LR. Characteristics of putrescine 12 Merimee TJ, Lillicrap DA, Rabinowitz D. Effect of arginine uptake in isolated rat enterocytes. Am J Physiol 1988; 254: on serum-levels of human growth hormone. Lancet 1965; G81-6. ii: 668-70. 38 Kumagai J, Jain R, Johnson LR. Characteristics of spermi- 13 Barbul A. Arginine and immune function. Nutrition 1990; 6: dine uptake by isolated rat enterocytes. AmJPhysiol 1989; 53-8. 256: G905-10. 14 Seifter E, Rettura G, Barbul A, Levenson SM. Arginine: an 39 Marletta MA. Nitric oxide: and biological for injured rats. Surgery 1978; 84: significance. Trends in Biological Sciences 1989; 14: 224-30. 488-92. 15 Barbul A, Lazarou SA, Efron BA, Wasserkrug HL, Efron G. 40 Moncada S, Palmer RMJ, Higgs EA. Biosynthesis of nitric Arginine enhances wound healing and lymphocyte oxide from L-arginine. A pathway for the regulation of cell immune responses in humans. Surgery 1990; 108: 331-7. function and communication. Biochem Pharmacol 1989; 16 Leon P, Redmond P, Stein TP, Shou J, Schulter MD, Kelly 38: 1709-15. C, et al. Arginine supplementation improves and 41 Kilbourn RG, Gross SS, Jubran A, Adams J, Griffith OW, acute-phase protein synthesis during gram-negative sepsis Levi R, et al. N-methyl-L-arginine inhibits tumor necrosis in the rat. JPEN 1991; 15: 503-8. factor-induced hypotension: implications for the involve- 17 Cynober L, Coudray-Lucas C, De Bandt JP, Guechot J, ment of nitric oxide. Proc Nad Acad Sci USA 1990; 87: Aussel C, Salvucci M, et al. Action of ornithine alpha- 3629-32. ketoglutarate, omithine hydrochloride and calcium alpha- 42 Gonce SJ, Peck MD, Alexander JW, Miskell PW. Arginine ketoglutarate on plasma amino acid and hormonal supplementation and its effect on established peritonitis in patterns in healthy subjects. JAm Coil Nutr 1990; 9: 2-12. guinea pigs. JPEN 1990; 14: 237-44.