Arginine Metabolism: Enzymology, Nutrition, and Clinical Significance

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Arginine Metabolism: Enzymology, Nutrition, and Clinical Signiﬁcance

Clinical Consequences of Urea Cycle Enzyme Deﬁciencies and Potential Links to Arginine and Nitric Oxide Metabolism1,2 Fernando Scaglia,* Nicola Brunetti-Pierri,* Soledad Kleppe,* Juan Marini,‡ Susan Carter,* ** Peter Garlick,‡ Farook Jahoor,† William O’Brien,* and Brendan Lee* ** 3

*Department of Molecular and Human Genetics and †Pediatrics, Children’s Nutrition Research Center, Baylor Downloaded from https://academic.oup.com/jn/article/134/10/2775S/4688495 by guest on 30 September 2021 College of Medicine, and **Howard Hughes Medical Institute, Houston, TX 77030 and ‡Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801

ABSTRACT Urea cycle disorders (UCD) are human conditions caused by the dysregulation of nitrogen transfer from ammonia nitrogen into urea. The biochemistry and the genetics of these disorders were well elucidated. Earlier diagnosis and improved treatments led to an emerging, longer-lived cohort of patients. The natural history of some of these disorders began to point to pathophysiological processes that may be unrelated to the primary cause of acute morbidity and mortality, i.e., hyperammonemia. Carbamyl phosphate synthetase I single nucleotide polymorphisms may be associated with altered vascular resistance that becomes clinically relevant when specific environmental stressors are present. Patients with argininosuccinic aciduria due to a deficiency of argininosuccinic acid lyase are uniquely prone to chronic hepatitis, potentially leading to cirrhosis. Moreover, our recent observations suggest that there may be an increased prevalence of essential hypertension. In contrast, hyperargininemia found in patients with arginase 1 deficiency is associated with pyramidal tract findings and spasticity, without significant hyperammonemia. An intriguing potential pathophysiological link is the dysregulation of intracellular arginine availability and its potential effect on nitric oxide (NO) metabolism. By combining detailed natural history studies with the development of tissue-specific null mouse models for urea cycle enzymes and measurement of nitrogen flux through the cycle to urea and NO in UCD patients, we may begin to dissect the contribution of different sources of arginine to NO production and the consequences on both rare genetic and common multifactorial diseases. J. Nutr. 134: 2775S–2782S, 2004.

KEY WORDS: ● urea cycle ● arginine ● nitric oxide

The enzymes of the urea cycle (UC)4 serve 2 purposes: the into urea. Deficiencies of all of the enzymes of the cycle were detoxification of ammonia into urea and the de novo biosyn- identified, and, although each specific disorder results in the thesis of arginine (1). The UC disorders (UCD) are a group of accumulation of different precursors, hyperammonemia and inborn errors of metabolism that affect the transfer of nitrogen hyperglutaminemia are common biochemical hallmarks of these disorders (2,3). Most of these disorders [N-acetyl glutamate synthase (NAGS) deficiency, carbamyl phosphate syn- 1 Prepared for the “Symposium on Arginine” held April 5–6, 2004, in Ber- thetase I deficiency (CPSID), argininosuccinate synthetase muda. The conference was sponsored in part by an educational grant from (ASS) deficiency, argininosuccinic acid lyase (ASL) defi- Ajinomoto USA, Inc. Conference proceedings are published as a supplement to ciency, and arginase 1 (ARG1) deficiency] are inherited in an The Journal of Nutrition. Guest editors for the supplement were Sidney M. Morris, Jr., Joseph Loscalzo, Dennis Bier, and Wiley W. Souba. autosomal recessive fashion, whereas ornithine transcarbamy- 2 The work was supported in part by the Baylor College of Medicine General lase deficiency (OTCD) is X-linked (4). These conditions are Clinical Research Center (RR00188), Mental Retardation and Developmental Dis- abilities Research Center (HD024064), the Child Health Research Center estimated to have an overall prevalence of 1:8200 in the (HD041648), and the NIH (DK54450). United States (5). Infants with null activity of a UC enzyme, 3 To whom correspondence should be addressed. other than an ARG1 deficiency, usually present with hyper- E-mail: [email protected]. 4 Abbreviations used: ALI, acute lung injury; ARG, arginase; ASA, arginino- ammonemic encephalopathy in the neonatal period (6). Pa- succinate aciduria; ASL, argininosuccinate lyase; ASS, argininosuccinate syn- tients with partial activity show late-onset presentation at any thetase; BMT, bone marrow transplantation; CPS, carbamyl phosphate syn- age, with hyperammonemic crises that are precipitated by thetase; CPSID, carbamoylphosphate synthetase I deficiency; GABA, gamma- amino butyric acid; HA, homoarginine; HTN, hypertension; HVOD, hepatic veno- catabolic stress and that carry a significant risk of developmen- occlusive disease; NAA, N-acetylarginine; NAGS, N-acetylglutamate synthase; tal disabilities (7). These patients may manifest with cerebral NMDA, N-methyl-D-aspartate; nNOS, neuronal nitric oxide synthase; NO, nitric palsy, developmental delay, psychiatric illness, hyperammone- oxide; NO2, nitrite; NO3, nitrate; NOS, NO synthase; NOx, total NO metabolites; OLT, orthotopic liver transplantation; OTCD, ornithine transcarbamylase defi- mia associated with valproate therapy, seizure activity, and ciency; PVT, pulmonary vascular tone; UC, urea cycle; UCD, urea cycle disorder. neurodevelopmental disabilities (3,8). Variable expressivity is

2775S 2776S SUPPLEMENT the rule in OTCD females because of a random X-inactivation Neurotoxicity in UCDs pattern in the liver (9). Morbidity and mortality in these disorders correlate with the duration and severity of hyperam- The mechanism of neurotoxicity in UCDs was not com- monemic episodes (2). pletely elucidated. The neurotoxic effect of ammonia was well While the neonatal presentation of UCD is relatively uni- recognized, although the manner by which it exerts its effects form, late-onset presentations are due to hypomorphic muta- upon the central nervous system is not very well known (18). tions whose clinical presentation can be quite varied. The Its acute effects include increased blood–brain barrier perme- different UCDs have unique clinical features that are only now ability, depletion of intermediates of cell energy metabolism, becoming recognized as the natural history of each disease and disaggregation of microtubules (18). The effects of becomes apparent with a longer-lived patient population. chronic, mildly elevated ammonia may include alterations of Moreover, the clinical and biochemical consequences of our axonal development and alterations in brain amino acid and therapeutic interventions themselves lent insight into unique neurotransmitter levels (19,20). In models of brain edema, gene–nutrient–environment interactions related to nitrogen where lethal doses of ammonia are administered, glial fibrillary acidic protein is reduced (21) and glutamine is increased (22), transfer. Much of these emerging data, however, are retrospec- Downloaded from https://academic.oup.com/jn/article/134/10/2775S/4688495 by guest on 30 September 2021 tive and/or anecdotal, and there is a dire need for coordinated preceded by an increase in blood flow (23). It is not known natural history studies. In spite of this, the clinical and labo- whether NO production plays a role in such an increase. The ratory observations provide important clues that led to emerg- arginine recycling enzymes are induced in astrocytes by am- ing hypotheses that can be tested in appropriate animal models monium, possibly originating NO via inducible NO synthase or neuronal NO synthesis (nNOS) (24). The stimulated and in the human subjects themselves. Similar observations – were derived from our diagnostic and therapeutic approaches nNOS might mainly produce O2 , which combines with NO to these patients. to form the highly toxic peroxynitrites (25). Clinical and laboratory diagnoses of UCDs may be difficult. Although chronic hyperammonemia impairs the activation Metabolic parameters such as hyperammonemia, plasma of N-methyl-D-aspartate (NMDA) receptors and leads to re- amino acid profile, or orotic aciduria are late indicators of duced re-uptake of extracellular glutamate (26), acute hyper- metabolic derangement and may be inadequate for predicting ammonemia leads to excessive activation of NMDA receptors clinical severity (10). It is not known whether circulating and increased intracellular calcium, which bounds to calmod- glutamine correlates well with brain glutamine (11). Although ulin and stimulates NOS. The difference between acute and the molecular basis for each of the UCDs was determined, a chronic hyperammonemia might be explained by the neuro- particular genotype and/or in vitro enzyme activity does not modulation of glutamate receptors by glutathione (27). There necessarily predict clinical severity (10). Moreover, the detec- is substantial evidence that creatine is essential for axonal tion of OTCD carriers can represent a diagnostic dilemma. elongation (20,23). The exposure of brain cells to ammonia Although DNA testing is recommended, in ϳ20% of the may alter the recycling of arginine, which plays a key role in cases, no mutations can be found (12), and the allopurinol the central nervous system, not only as a NO precursor but loading test is not completely specific or sensitive (13). also as a substrate for creatine synthesis. Exposure of brain-cell We previously developed stable isotope approaches to de- aggregates to NH4Cl leads to a decrease of intracellular crea- termine in vivo rates of total body urea synthesis and UC- tine and phosphocreatine concentrations (20). When creatine specific nitrogen transfer to evaluate phenotypic severity in is added to the aggregate cultures during NH4Cl exposure, it patients with a variety of UCDs (14). The ratio of isotopic seems to protect the axons from growth impairment (20). enrichments of 15N-urea/15N-glutamine allowed us to distin- guish normal control subjects from patients with neonatal and Management of UCDs late presentations. As expected, patients demonstrated a relatively greater glutamine flux in association with decreased The management in UCDs is achieved by restricting di- urea synthesis. This study demonstrated that the 15N-urea/ etary protein, providing supportive management of catabolic 15N-glutamine ratio, i.e., fractional transfer to urea, is a sen- stress, and the use of compounds that remove excess nitrogen sitive index of in vivo UC activity and correlates with clinical compounds by alternative pathways (28,29). Alternative path- severity (14). Moreover, we used this approach in an inte- way therapy includes the use of sodium phenylbutyrate or grated manner to aid in the diagnosis and the prospective sodium benzoate to stimulate the excretion of nitrogen in the treatment of an OTCD female (15). Potentially, this stable form of phenylacetylglutamine and hippuric acid (30). Argi- isotope protocol could provide a sensitive tool to aid in the nine becomes an essential amino acid in UCDs (29), except in diagnosis and the management of UCD patients and, more arginase deficiency, where arginine degradation is defective, specifically, OTCD females. These same studies may also lend resulting in its accumulation. Citrulline or arginine are pro- insight into the transfer of 15N via the UC into arginine and vided to fulfill the requirement for arginine and to provide ultimately nitric oxide (NO) as explored in a previous study (16). precursors for enzymatic steps upstream of the metabolic block. Using a stable isotope approach and by comparing the Oral citrulline, in combination with ammonia scavengers, 15 15 transfer of N from intravenous vs. oral NH4Cl into urea, is recommended for OTCD and CPSID (31). It was our we investigated whether OTCD females rely on alternative experience that use of the recommended dose of citrulline pathways to compensate for the reduced urea synthetic activity (170 mg kgϪ1 dϪ1) in several patients with OTCD resulted observed in this disorder to maintain good dietary protein in a low serum arginine level, prompting us to use additional tolerance (17). OTCD females seemed to retain good dietary supplementation with arginine to ensure optimal metabolic protein tolerance by maintaining higher ammonia appearance control. Other groups (11) had a similar experience. Further rates, expanding the plasma ammonia pool, and clearing ex- evaluations need to be performed to determine whether there cess ammonia via glutamine synthesis in the perivenous hepa- is any advantage in giving arginine for some OTCD patients. tocytes (17). The conclusions of the study showed the impor- Furthermore, there is evidence suggesting branched chain tance of preventing sudden changes in nitrogen metabolism in amino acid depletion with the use of sodium phenylbutyrate in UCD patients by minimizing their exposure to conditions that UCD patients (32). increase peripheral protein catabolism. In the longer term, advances in liver transplantation and UREA CYCLE ENZYME DEFICIENCIES 2777S

hepatocyte gene therapy offer the best hope for UCD patients as well as the production of citrulline, arginine, and urea. (33,34). The outcome for orthotopic liver transplantation Classic CPSID with null activity usually presents in the neo- (OLT) in children continues to improve. The metabolic effect natal period with hyperammonemia, with little effect from the of OLT was consistent; however, the disorder is not com- environment. A delayed onset form also was described pletely corrected. Most patients with OTCD or carbamyl (40,41). Diagnosis is based on the plasma amino acid profile phosphate synthetase I deficiency (CPSID) deficiency have with elevated glutamine and low or absent citrulline and urine low plasma citrulline concentrations, because the deficiency is orotic acid. These findings cannot discriminate this disorder not corrected in the gut by OLT (35,36). We also observed from a NAGS deficiency (MIM 237310). To establish a correct that besides low plasma citrulline concentrations, arginine diagnosis, enzymatic analysis of the liver tissue or identification of concentrations are significantly low (P Ͻ 0.05) in patients mutations in the CPS1 gene is required. Prenatal diagnosis in with OTCD and CPS deficiency who were transplanted and affected families is feasible, based on mutation analysis or identi- who were not receiving L-arginine supplementation when fication of disease-related CPS1 haplotypes (42). compared with the pre-OLT levels observed in the same NO was identified as the active factor in the endothelial-

patients (Table 1). Here, correction of the hepatic deficiency derived relaxing factor in the 1980s (43,44), and it was the Downloaded from https://academic.oup.com/jn/article/134/10/2775S/4688495 by guest on 30 September 2021 does not relieve the net arginine requirement, because de novo focus of hundreds of investigations regarding its role in the arginine synthesis is initiated in the gut with the synthesis of regulation of systemic and pulmonary vascular resistance. citrulline and is completed in the kidney with the conversion There are increasing data showing that NOS may play a role of citrulline into arginine. However, most patients do not have in oxidative injury and that NOS may generate free radicals problems with a deficiency as long as they maintain their that can result in cellular damage. Therefore, the relationship dietary intake of arginine. Gene therapy trials in OTCD with between NO and L-arginine, an intermediate of the UC and a an adenoviral vector did not result in a useful increase in the precursor of NO, raised the question as to whether polymor- enzyme activity (37), and the studies now were discontinued phisms in the UC genes may play a role in the pathophysiology because of severe complications resulting in the death of a of neonatal pulmonary hypertension, postcardiac surgery pul- patient (38). Hepatocytes transplantation may provide an monary hypertension, and bone marrow transplantation alternative therapeutic approach (39). (BMT) complications, and whether patients with a classic In clinical practice, the first goal when treating hyperam- UCD may have abnormal blood pressure regulation. It was monemic crises is to abate the nitrogen load and subsequent hypothesized (45,46) that CPSI polymorphisms may affect the hyperammonemia. For the outpatient management of UCD function of the enzyme in conjunction with certain environ- patients, a depletion of arginine and other essential amino mental stressors such that the availability of the NO substrates acids can be prevented using a special mixture of essential may become clinically relevant. Summar et al. (47) evaluated amino acids to improve the quality of the limited natural a known CPS1 polymorphism to determine if it influences NO protein ingested. In summary, several of the findings described metabolite concentrations or NO dependent vasodilatation in above argue in favor of L-arginine supplementation in suffi- adults. A C Ͼ A (cytosine Ͼ adenosine) transversion at base cient amounts to provide for adequate brain creatine, protein, 4340 in exon 36 of the CPS1 gene results in the substitution and NO synthesis in UCD patients. of asparagine for threonine in the critical region for N-acetylglutamate binding (T1405N). The Thr1405 variant is known Observations on arginine metabolism from the study and to be associated with lower enzymatic activity (30–40% lower from the natural history of UCDs activity), when compared with the Asn1405 variant (45). This CPS1 polymorphism was shown to significantly influence ve- CPSID. CPSID (MIM 237300) is a rare UCD that results nous NO concentrations as well as NOS dependent and in- from the deficiency of CPSI (EC 6.3.4.16). CPSI is thought to dependent vasodilatation (47). These results support the hy- be the rate-limiting enzyme catalyzing the first step of the UC. pothesis that the CPS1 genotype affects the L-citrulline/L- Expression of CPSI is limited to high levels in the liver and arginine cycle and subsequent NO production. Also, this smaller amounts in the intestinal mucosa. This enzymatic step hypothesis was compatible with the fact that CPS1 genotype is part of the intramitochondrial component of the UC. CP- did not affect the response to the NO-independent tissue-type SID directly affects the removal of waste nitrogen compounds, plasminogen activator response to bradykinin (47). It was hypothesized that this functional polymorphism in the CPS1 gene might limit the availability of precursors for TABLE 1 NO synthesis and consequently might influence pulmonary vascular resistance, resulting in persistent pulmonary hyper- Amino acid levels pre- and post-OLT in UCD subjects tension of the newborn (48). When compared with the general population, the infants in the study (65 near-term neo- Pre-OLT Post-OLT Post-OLT nates with respiratory distress) had a significantly skewed Subject1 Diagnosis2 arginine3 arginine3 citrulline4 distribution of the genotypes for the CPS variants at the amino acid position 1405 (P Ͻ 0.005). None of the infants with ␮ M pulmonary hypertension were homozygous for the T1405N 1 CPSID 63 Ϯ 933Ϯ 68Ϯ 1 polymorphism. When compared with infants without pulmo- 2 OTCD 49 Ϯ 620Ϯ 34Ϯ 1 nary hypertension, infants with pulmonary hypertension had 3 CPSID 101 Ϯ 19 32 Ϯ 78Ϯ 4 lower mean plasma concentrations of arginine (P Ͻ 0.001) and NO metabolites (P ϭ 0.05). These data, when combined 1 Pre-OLT subjects were supplemented with citrulline (200 mg/kg/ with previous observations (49), suggest that arginine defi- d). Posttransplantation subjects were not supplemented. ciency might precede and lead to impaired NO synthesis in 2 ϭ Means with standard deviations are shown. N for each mean 5. infants with persistent pulmonary hypertension. 3 Pre- and post-OLT arginine levels are significantly different (P Ͻ 0.03), normal range for arginine (0–1 y range): 42–132 ␮M. Regarding postcardiac-surgery–related pulmonary hyper- 4 Citrulline levels are low normal, even post-transplantation; normal tension, arginine levels in patients with evidence of increased range for citrulline (0–1 y range): 2–41 ␮M. pulmonary vascular tone (PVTϩ) were compared with all 2778S SUPPLEMENT other patients (PVT–) to determine if the development of Genetics, Baylor College of Medicine, and B. Lee, Howard PVTϩ was associated with a decrease in substrate for NO Hughes Medical Institute, personal observation, unpublished production (45,50). Arginine levels were significantly lower in results). We currently follow 2 patients, of 19 and9yofage, the PVTϩ patients (P Ͻ 0.05). Patients with the AA geno- affected with ASA and high blood pressure in which second- type were less likely to develop increased postoperative PVT. ary causes of hypertension were excluded. In one case, systolic The overrepresentation of CCs and underrepresentation of blood pressure values range from 114 to 165 mm Hg and AAs in the PVTϩ patients made this group significantly diastolic blood pressure from 72 to 134 mm Hg. In the second different from the general population (P Ͻ 0.022). Similar case, the range for systolic blood pressure was 106 to 160 mm observations were noted in hepatic veno-occlusive disease Hg, and the range for diastolic blood pressure was 69 to 115 (HVOD) after BMT (45). The presence of post-BMT compli- mm Hg. Hypertension was not reported as a long-term com- cations [acute lung injury (ALI), and HVOD] was correlated plication so far, although few follow-up studies of patients with with the T1405N genotypes. All patients with the CPSI ASA are available (51,54). Hypertension thus far was reported T1405N genotype, even those who developed ALI, had longer in one patient with ASA who developed high blood pressure Ͻ survival and did not develop HVOD (P 0.05). In this study, during the newborn period (55). The pathogenesis of hyper- Downloaded from https://academic.oup.com/jn/article/134/10/2775S/4688495 by guest on 30 September 2021 suboptimal production of arginine and NO correlated with tension in this condition is open to speculation, but the increased morbidity and mortality after BMT (45). potential downregulation of endothelial NO production sec- The data from CPSI polymorphisms suggest that subtle ondary to intracellular deficiency of L-arginine is intriguing. functional polymorphisms could play a major role in common The more mundane explanation is that ASA may be toxic to diseases, with availability of intracellular arginine derived from hepatocytes. Interestingly, NO was associated with the patho- nitrogen transfer via CPSI being the common pathogenetic genesis of liver cirrhosis (56), and this may potentially con- link. These studies could better determine the risk of outcomes tribute to liver dysfunction. Specifically, it was proposed that for patients undergoing cardiac surgery or chemotherapy trials. reduced NO production may lead to impaired blood pressure In the future, the application of stable isotope tracers could regulation in the liver, resulting in hepatic fibrosis (56). A low confirm the in vivo effects of these polymorphisms. Controlled intracellular arginine flux may contribute to alternative gen- trials, however, are needed to determine whether the supple- eration of free radicals, leading to cellular damage. These mentation of the precursor metabolites for NO could modify mechanisms may contribute to the significant liver dysfunc- the incidence of toxicity in BMT and cardiac surgery patients. tion observed in ASA. However, the contribution of plasma Argininosuccinic acid lyase deficiency. Argininosuccinic arginine to the intracellular arginine pool leading to NO aciduria (ASA) deficiency (MIM 207900) results from ASL production may confound this mechanism. On the other hand, (EC 4.3.2.1) deficiency. The reported incidence of this disease the contribution of de novo, intracellular arginine production is about 1 in 70,000 live births in the United States, and thus via ASL to NO production in different cell types is unknown. it is the second most common heritable disorder of the UC. In all cases, these patients offer a unique opportunity to study Patients with this disorder typically present in the neonatal the in vivo human consequences when intracellular contribu- period or during infancy with vomiting, lethargy, developmen- tion of de novo arginine production via ASL is clearly abol- tal delay, and hyperammonemia. A characteristic finding in ished due to the underlying genetic defect. these patients is trichorrexis nodosa, which consists of very Using our cohort of UCD and control subjects studied via friable hairs. The biochemical hallmarks of this disease consist our 15N glutamine/18O 13C urea primed constant infusion of the elevations of argininosuccinic acid and citrulline, and protocol (14), we further measured the 15N enrichment in low levels of plasma L-arginine (1). Patients identified through total NO metabolites or NOx [nitrite (NO2) plus nitrate a newborn screening program and who were initiated on a (NO3)] and steady-state NOx levels. Interestingly, no remark- protein restriction diet and arginine supplementation before able differences were noted in the plasma concentrations of the onset of symptoms developed normally (51). However, NOx,NO2,NO3, arginine, and ASA in 2 ASL deficient despite treatment and metabolic control, some patients may subjects, one of whom had essential hypertension (Table 2). exhibit intellectual impairment and delayed motor skills (B. However, both were being treated with arginine (500 Lee, Howard Hughes Medical Institute, personal observation). mg kgϪ1 dϪ1) at the time. In an unrelated male subject These sequelae are mainly thought to arise from initial hyper- with ASA, we were able to perform a stable isotopic infusion ammonemia, although the degree of impairment appears out of before and after OLT. As expected, the subject had a markedly proportion to the degree of recorded hyperammonemia. increased urea flux (140 ␮mol kgϪ1 hϪ1 pre-OLT vs. 294 Hence, it is possible that morbidity may also be associated with a cell autonomous deficiency of ASL, perhaps contributing to a compartmentalized UC intermediate deficiency. However, if TABLE 2 this is the case, it is still not clear why similar anecdotal observations were not reported for upstream deficiencies such Plasma amino acid, NO2, and NO3 levels in ASL deficiency as ASS deficiency, especially because ASS and ASL are thought to be coexpressed. Alternative possibilities include 1) Subject1 NOx2,3 NO22 NO32 Arginine4 ASA5 differential regulation of ASS and ASL, 2) differential in vivo ␮ expression of ASS and ASL, or 3) the existence of as yet mol/L undescribed functions for ASL outside of the UC. 1 (w/HTN) 48 13 35 81 127 The most compelling clinical evidence is the more complex 2 (w/o HTN) 41 10 31 78 106 clinical phenotype in ASA. Patients with ASA can suffer from progressive hepatic disease (36,52,53), which may ultimately 1 Subject 1 is a 9-y-old male with ASA and essential hypertension, evolve to cirrhosis. Importantly, this is independent of the risk and subject 2 is a 32-year-old female with ASA, who is normotensive. 2 and control of hyperammonemia. In addition, our experience NO2,NO3, and NOx values are shown. Comparable levels can be seen for all metabolites. suggests that these patients may be at risk for the development 3 NOx was measured as previously described (16). of previously unrecognized systemic hypertension (N. Bru- 4 Normal range for arginine (2–18 y range) is 18–127 ␮mol/L. netti-Pierri, F. Scaglia, Department of Molecular and Human 5 Normal range for ASA: 0 ␮mol/L. UREA CYCLE ENZYME DEFICIENCIES 2779S

␮mol kgϪ1 hϪ1 post-OLT) after liver transplantation, in spite (59), whose pathogenesis is not very well understood. Those of being on the same protein intake (1.1 g/kg/d). However, the patients who were ascertained and treated at birth with pro- glutamine flux was not markedly different (388 ␮mol kgϪ1 tein restriction and essential amino acid supplementation hϪ1 vs. 410 ␮mol kgϪ1 hϪ1). Interestingly, the fractional trans- seem to remain asymptomatic, with the oldest patients being 15 Ͼ fer of N from arginine into NOx at 7.5 h of infusion was not 35 y of age (60). This suggests that chronically elevated dramatically affected by liver transplantation (Table 3). In levels of arginine directly contribute to the neuropathology. In 15 both experiments, N content of NOx and arginine was lower symptomatic patients whose treatment was begun at diagnosis, in the ASL deficiency subject compared with control subjects, there is ample evidence that effective therapy stops the pro- even though the controls were on the lower protein intake gressive neurological degeneration. While the lower-extremity (0.4 g kgϪ1 dϪ1), indicating impaired transfer of glutamine- spasticity may progress slightly, it can be effectively treated amide nitrogen to NO. This suggests that hepatic arginine via with botox or tendon-release procedures. nitrogen transfer through ASL and the UC is not a major It is unlikely that elevated plasma ammonia is the main contributor to total body NO production. In fact, the fractional neuropathogenic agent in argininemia, because hyperam- 15 transfer of N from arginine into NOx was identical pre- vs. monemia seldom occurs in this condition, and the severe Downloaded from https://academic.oup.com/jn/article/134/10/2775S/4688495 by guest on 30 September 2021 post-OLT. As expected, citrulline and ASA levels were still spasticity observed in this disease does not commonly occur in elevated after liver transplantation (Table 3). These data support other UC defects (61). Guanidino compounds accumulate in the hypothesis that de novo hepatic sources of arginine synthesis other conditions, such as uremia and epilepsy, and there is do not contribute significantly to NOx production. These data are evidence suggesting that these compounds might contribute to limited by the fact that citrulline flux or NO3 flux were not the neurological dysfunction observed in these disorders independently measured in these studies. Hence, the actual (62,63). It was postulated that these compounds might be flux of the NO pathway could not be derived. In the future, the involved as well in the neuropathology of argininemia (64– measurement of citrulline and/or NO3 flux, in conjunction 66). The guanidino compounds that accumulate in hyper- with an independent measure of total plasma arginine flux, argininemic patients [N-acetylarginine (NAA), homoarginine would be informative in dissecting the contributions of de (HA), and arginic acid] were found to have epileptogenic prop- novo production of arginine from the UC vs. exogenous con- erties (67–69). These guanidino compounds may affect neuro- tribution of arginine into total body NO flux. transmission or membrane fluidity (70,71). Certain guanidino Unfortunately, the mouse mutant for ASL was not helpful compounds accumulating in argininemia might affect (GABA)- with these studies. Asl null mice die in the perinatal period ergic neurotransmission, by inhibiting gamma-amino butyric acid secondary to hyperammonemia. There do not appear to be (GABA) and glycine responses in cultured neurons (67). Regard- differences in NO2 level, muscle and liver creatine, and uri- ing the potential for guanidino compounds to modulate mem- nary cyclic guanosine monophosphate (cGMP) levels (57). brane fluidity, it was shown that methylguanidine inhibits brain Ultimately, the generation of tissue-specific null mutants that Na, K, ATP-ase (72), an enzyme embedded in the cell mem- can bypass the neonatal lethality attributable to hyperam- brane. NAA, HA, and AA significantly inhibit Na, K, ATP-ase monemia may enable better physiological studies of nitrogen activity in the cerebral cortex of rats (73). transfer into arginine in different tissues. Arginine is known to modulate neuronal survival through ARG1 deficiency. Argininemia (MIM 207800) is a rare its ability to serve as a substrate for NOS (74). Subsequent autosomal recessive UCD caused by a defect in the final step studies showed that the protective effects of arginase were of the UC, the hydrolysis of arginine to urea and ornithine by related to depletion of arginine. In one study, it was demon- the enzyme ARG1 (EC 3.5.3.1). This is a rare disorder, for strated that arginine, HA, NAA, and AA induced free-radical example, with an estimated incidence of 1 in 1,000,000 live production and decreased cellular antioxidant defenses in vitro births in Quebec (58). This condition results in elevated (75). The guanidino compounds were found to inhibit the plasma arginine and ammonia levels, with elevated tissue activities of catalase, superoxide dismutase, and glutathione levels of arginine and other guanidino compounds (1). Pa- peroxidase, which are considered to be the main enzymatic tients affected with this condition usually present with a defenses in the brain against free radicals. Although the con- neurological syndrome that consists of a variable degree of centration of guanidino compounds used in the previously cognitive deficits, epilepsy, and progressive spastic diplegia described animal experiments were similar to those observed

TABLE 3

15N transfer from glutamine to arginine and NOx in ASL deﬁciency

NOx2 Arg2 (m ϩ 1) Subject1 (m ϩ 1) ϩ (m ϩ 2) 15NOx/15NArg NOx NO2 NO3 Arg3 ASA3 NH33

MPE % ␮mol/L

ASA pre-OLT w/Arg 0.073 0.155 47.1 72 16 57 22 Ϯ 54 231 Ϯ 43 44 Ϯ 10 post-OLT 0.036 0.076 47.4 64 6 58 63 Ϯ 488Ϯ 63 17 Ϯ 2 Control 0.13 0.85 15.3 57 8 49 84 Ϯ 4022Ϯ 6 Control 0.16 0.50 32 53 20 33 88 Ϯ 34 0 18 Ϯ 4

TABLE 4 Nitrogen transfer in ARGI deﬁciency

15Nurea/ Subject1 Gln Ra2 Urea Ra215NOx NOx NO2 NO3 Arg 15Ngln

␮mol kgϪ1 hϪ1 MPE ␮mol/L

ARGI 145 female 291 11 0.121 52 11 40 91 Ϯ 153 0.02 146 female 274 29 0.221 48 13 35 277 Ϯ 17 0.06

1 Subjects were admitted and stabilized on a restricted protein intake (0.4 g kgϪ1 d Ϫ1). On d 3, primed coinfusions of 15N-glutamine and 18O 13C urea were performed for8haspreviously described (14). Blood sampling was performed at 0, 4, 6, and 7.5 h. 15N enrichment, shown as mole percent excess, is shown at the 7.5-h time point. 15N arginine and 15NOx was measured as previously described (16). For multiple samples, means Downloaded from https://academic.oup.com/jn/article/134/10/2775S/4688495 by guest on 30 September 2021 with standard deviations are shown. Control values for Gln Ra and Urea Ra are as previously reported (14). 2 Gln Ra, glutamine appearance rate; Urea Ra, urea appearance rate. 3 For multiple samples (n ϭ 3), means with standard deviations are shown. in patients with argininemia (67), it would be difficult to tions and hypotheses about the contribution of dysregulated extrapolate these findings to an in vivo condition. However, it NO metabolism to the pathogenesis of these conditions. At is tempting to think that these mechanisms may contribute to the same time, UCD patients constitute a unique resource for the pathogenesis of the neurological dysfunction found in answering these same questions. ARG1 deficiency. The transfer of nitrogen through the UC Specifically, human and animal models of UCDs are unique into NO was studied in 2 siblings with ARG1 deficiency using examples of gene–nutrient interactions centered on nitrogen our standard nitrogen flux protocol (Table 4). Both exhibited transfer between dietary vs. peripheral sources. They offer comparable glutamine fluxes and urea fluxes, but the latter was potentially important tools for dissecting extracellular vs. in- markedly low compared with control values (14). As expected, tracellular contributions of arginine to the production of NO, the fractional transfer of 15N from glutamine to urea was near free radicals, polyamines, and creatine. Genetic polymor- zero. However, one of the siblings (subject 145) exhibited phisms in CPSI, the gene encoding the rate-limiting enzyme of better metabolic control when on the protein-restricted study the UC, may correlate with altered arginine availability and diet (0.4 g kgϪ1 dϪ1), with a normal steady-state arginine endothelial dysfunction during specific times of environmental level, while the other sibling (subject 146) had a significantly stress. ASL deficiency is a window into the consequences of higher steady-state arginine level. Interestingly, the enrich- deficient de novo production of intracellular arginine. In con- 15 ment of NinNOx was substantially higher in subject 146 trast, ARG1 deficiency will provide insight into the conse- with higher serum arginine levels vs. in the subject with quences of chronic elevations of extracellular arginine as well normal serum arginine, supporting a direct correlation be- as the role of ARG1 as a direct intracellular regulator of NO tween plasma arginine levels and the fractional transfer of 15N flux. The therapeutic approaches to UCD patients may further arginine–imidino nitrogen into NOx in the cell. However, as offer models for understanding the effects of exogenous argi- in the ASL-deficient patients, further studies focused on mea- nine supplementation, the contribution of liver to nitrogen suring the actual flux of NO metabolites will be required to transfer in patients who have undergone liver transplantation, elucidate the effect of arginine levels in regulating NO pro- and the effects of diverting flux away from UC nitrogen duction. Clearly, the respective contributions of chronic ele- transfer using alternative route therapy, i.e., sodium phenyl- vation of plasma arginine vs. the intracellular deficiency of butyrate. ARG1 on the regulation of intracellular NO production can be addressed by studying this unique patient population. This has direct relevance to understanding the neuropathology ACKNOWLEDGMENTS associated with chronic arginine elevations. The authors thank Olivia Hernandez for administrative assistance, Similar to the animal model in ASL deficiency, both Arg1 and the excellent nursing staff at the Texas Children’s Hospital and Arg2 null mice were generated (76,77). The Arg1 null General Clinical Research Center. This review is dedicated to the mice succumb later than the Asl null mice, at about 10–12 d, memory of Peter Reeds. secondary to hyperammonemia. The mice have mild liver disease and elevated arginine, with low proline and ornithine LITERATURE CITED levels. Again, the generation of tissue-specific nulls will be important in performing steady-state studies in an adult ani- 1. Brusilow, S. W. & Horwich, A. L. (1995) Urea cycle enzymes. In: The mal. Molecular and Metabolic Basis of Inherited Disease (Scriver, C. R., Beaudet, A. L., Sly, W. S. & Valle, D., eds.), pp. 1187–1232. McGraw-Hill, New York, NY. 2. Batshaw, M. L., Roan, Y., Jung, A. L., Rosenberg, L. A. & Brusilow, S. W. Conclusions (1980) Cerebral dysfunction in asymptomatic carriers of ornithine transcarbamylase deficiency. N. Engl. J. Med. 302: 482–485. Human deficiencies of UC enzymes offer unique clinical 3. Msall, M., Batshaw, M. L., Suss, R., Brusilow, S. W. & Mellits, E. D. and experimental opportunities to study and to understand the (1984) Neurologic outcome in children with inborn errors of urea synthesis. Outcome of urea cycle enzymopathies. N. Engl. J. Med. 310: 1500–1505. effects of intracellular dysregulation of arginine production, as 4. Maestri, N. E., Lord, C., Glynn, M., Bale, A. & Brusilow, S. W. (1998) well as consequences of exogenous elevations of arginine. The phenotype of ostensibly healthy women who are carriers for ornithine tran- Unique genotype–phenotype correlations are emerging in scarbamylase deficiency. Medicine (Baltimore) 77: 389–397. 5. Brusilow, S. W. & Maestri, N. E. (1996) Urea cycle disorders: diagno- both these rare diseases and in more common pathophysio- sis, pathophysiology, and therapy. Adv. Pediatr. 43: 127–170. logic processes. The clinical observations raise important ques- 6. Maestri, N. E., Clissold, D. & Brusilow, S. W. (1999) Neonatal onset UREA CYCLE ENZYME DEFICIENCIES 2781S ornithine transcarbamylase deficiency: a retrospective analysis. J. Pediatr. 134: for carbamylphosphate synthetase deficiency [letter]. N. Engl. J. Med. 320: 1498– 268–272. 1499. 7. Batshaw, M. L., Msall, M., Beaudet, A. L. & Trojak, J. (1986) Risk of 36. Saudubray, J. M., Touati, G., Delonlay, P., Jouvet, P., Narcy, C., Laurent, serious illness in heterozygotes for ornithine transcarbamylase deficiency. J. Pe- J., Rabier, D., Kamoun, P., Jan, D. & Revillon, Y. (1999) Liver transplantation diatr. 108: 236–241. in urea cycle disorders. Eur. J. Pediatr. 158 (Suppl. 2): S55–S59. 8. Msall, M., Monahan, P. S., Chapanis, N. & Batshaw, M. L. (1988) 37. Raper, S. E., Yudkoff, M., Chirmule, N., Gao, G. P., Nunes, F., Haskal, Cognitive development in children with inborn errors of urea synthesis. Acta Z. J., Furth, E. E., Propert, K. J., Robinson, M. B., et al. (2002) A pilot study of Paediatr. Jpn. 30: 435–441. in vivo liver-directed gene transfer with an adenoviral vector in partial ornithine 9. Ahrens, M. J., Berry, S. A., Whitley, C. B., Markowitz, D. J., Plante, R. J. transcarbamylase deficiency. Hum. Gene Ther. 13: 163–175. & Tuchman, M. (1996) Clinical and biochemical heterogeneity in females of a 38. Raper, S. E., Chirmule, N., Lee, F. S., Wivel, N. A., Bagg, A., Gao, G. P., large pedigree with ornithine transcarbamylase deficiency due to the R141Q Wilson, J. M. & Batshaw, M. L. (2003) Fatal systemic inflammatory response mutation [published erratum appears in Am. J. Med. Genet. 71:125]. Am. J. Med. syndrome in a ornithine transcarbamylase deficient patient following adenoviral Genet. 66: 311–315. gene transfer. Mol. Genet. Metab. 80: 148–158. 10. DiMagno, E. P., Lowe, J. E., Snodgrass, P. J. & Jones, J. D. (1986) 39. Horslen, S. P., McCowan, T. C., Goertzen, T. C., Warkentin, P. I., Cai, Ornithine transcarbamylase deficiency—a cause of bizarre behavior in a man. H. B., Strom, S. C. & Fox, I. J. (2003) Isolated hepatocyte transplantation in an N. Engl. J. Med. 315: 744–747. infant with a severe urea cycle disorder. Pediatrics 111: 1262–1267. 11. Wilcken, B. (2004) Problems in the management of urea cycle disor- 40. Granot, E., Matoth, I., Lotan, C., Shvil, Y., Lijovetzky, G. & Yatziv, S. ders. Mol. Genet. Metab. 81 (Suppl.): 86–91.

(1986) Partial carbamyl phosphate synthetase deficiency, simulating Reye’s Downloaded from https://academic.oup.com/jn/article/134/10/2775S/4688495 by guest on 30 September 2021 12. Tuchman, M., Jaleel, N., Morizono, H., Sheehy, L. & Lynch, M. G. (2002) syndrome, in a 9-year-old girl. Isr. J. Med. Sci. 22: 463–465. Mutations and polymorphisms in the human ornithine transcarbamylase gene. 41. Verbiest, H. B., Straver, J. S., Colombo, J. P., van der Vijver, J. C. & van Hum. Mutat. 19: 93–107. Woerkom, T. C. (1992) Carbamyl phosphate synthetase-1 deficiency discov- 13. Hauser, E. R., Finkelstein, J. E., Valle, D. & Brusilow, S. W. (1990) ered after valproic acid-induced coma. Acta Neurol. Scand. 86: 275–279. Allopurinol-induced orotidinuria. A test for mutations at the ornithine carbamoyl- 42. Summar, M. L. (1998) Molecular genetic research into carbamoyl- transferase locus in women. N. Engl. J. Med. 322: 1641–1645. phosphate synthase I: molecular defects and linkage markers. J. Inherit. Metab. 14. Lee, B., Yu, H., Jahoor, F., O’Brien, W., Beaudet, A. L. & Reeds, P. Dis. 21 (Suppl. 1): 30–39. (2000) In vivo urea cycle flux distinguishes and correlates with phenotypic 43. Furchgott, R. F. & Vanhoutte, P. M. (1989) Endothelium-derived re- severity in disorders of the urea cycle. Proc. Natl. Acad. Sci. U.S.A. 97: 8021– laxing and contracting factors. J. FASEB 3: 2007–2018. 8026. 44. Palmer, R. M., Ferrige, A. G. & Moncada, S. (1987) Nitric oxide release 15. Scaglia, F., Zheng, Q., O’Brien, W. E., Henry, J., Rosenberger, J., Reeds, accounts for the biological activity of endothelium-derived relaxing factor. Nature P. & Lee, B. (2002) An integrated approach to the diagnosis and prospective 327: 524–526. management of partial ornithine transcarbamylase deficiency. Pediatrics 109: 45. Summar, M. L., Hall, L., Christman, B., Barr, F., Smith, H., Kallianpur, A., 150–152. Brown, N., Yadav, M., Willis, A., et al. (2004) Environmentally determined 16. Goodrum, L. A., Saade, G. R., Belfort, M. A., Moise, K. J., Jr. & Jahoor, F. genetic expression: clinical correlates with molecular variants of carbamyl phos- (2003) Arginine flux and nitric oxide production during human pregnancy and phate synthetase I. Mol. Genet. Metab. 81 (Suppl.): 12–19. postpartum. J. Soc. Gynecol. Investig. 10: 400–405. 46. Summar, M. L., Hall, L. D., Eeds, A. M., Hutcheson, H. B., Kuo, A. N., 17. Scaglia, F., Marini, J., Rosenberger, J., Henry, J., Garlick, P., Lee, B. & Willis, A. S., Rubio, V., Arvin, M. K., Schofield, J. P. & Dawson, E. P. (2003) Reeds, P. (2003) Differential utilization of systemic and enteral ammonia for Characterization of genomic structure and polymorphisms in the human carbamyl urea synthesis in control subjects and ornithine transcarbamylase deficiency phosphate synthetase I gene. Gene 311: 51–57. carriers. Am. J. Clin. Nutr. 78: 749–755. 47. Summar, M. L., Gainer, J. V., Pretorius, M., Malave, H., Harris, S., Hall, 18. Butterworth, R. F. (1998) Effects of hyperammonaemia on brain func- L. D., Weisberg, A., Vaughan, D. E., Christman, B. W. & Brown, N. J. (2004) tion. J. Inherit. Metab. Dis. 21 (Suppl. 1): 6–20. Relationship between carbamoyl-phosphate synthetase genotype and systemic 19. Bachmann, C. (2002) Mechanisms of hyperammonemia. Clin. Chem. vascular function. Hypertension 43: 186–191. Lab. Med. 40: 653–662. 48. Pearson, D. L., Dawling, S., Walsh, W. F., Haines, J. L., Christman, B. W., 20. Braissant, O., Henry, H., Villard, A. M., Zurich, M. G., Loup, M., Eilers, B., Bazyk, A., Scott, N. & Summar, M. L. (2001) Neonatal pulmonary hyperten- Parlascino, G., Matter, E., Boulat, O., et al. (2002) Ammonium-induced impair- sion–urea-cycle intermediates, nitric oxide production, and carbamoyl-phos- ment of axonal growth is prevented through glial creatine. J. Neurosci. 22: phate synthetase function. N. Engl. J. Med. 344: 1832–1838. 9810–9820. 49. Christou, H., Adatia, I., Van Marter, L. J., Kane, J. W., Thompson, J. E., 21. Belanger, M., Desjardins, P., Chatauret, N. & Butterworth, R. F. (2002) Stark, A. R., Wessel, D. L. & Kourembanas, S. (1997) Effect of inhaled nitric Loss of expression of glial fibrillary acidic protein in acute hyperammonemia. oxide on endothelin-1 and cyclic guanosine 5Ј-monophosphate plasma concen- Neurochem. Int. 41: 155–160. 22. Cooper, A. J. (2001) Role of glutamine in cerebral nitrogen metabolism trations in newborn infants with persistent pulmonary hypertension. J. Pediatr. and ammonia neurotoxicity. Ment. Retard. Dev. Disabil. Res. Rev. 7: 280–286. 130: 603–611. 23. Larsen, F. S., Gottstein, J. & Blei, A. T. (2001) Cerebral hyperemia and 50. Barr, F. E., Beverley, H., VanHook, K., Cermak, E., Christian, K., Drink- nitric oxide synthase in rats with ammonia-induced brain edema. J. Hepatol. 34: water, D., Dyer, K., Raggio, N. T., Moore, J. H., et al. (2003) Effect of cardio- 548–554. pulmonary bypass on urea cycle intermediates and nitric oxide levels after con- 24. Braissant, O., Gotoh, T., Loup, M., Mori, M. & Bachmann, C. (1999) genital heart surgery. J. Pediatr. 142: 26–30. L-arginine uptake, the citrulline-NO cycle and arginase II in the rat brain: an in situ 51. Widhalm, K., Koch, S., Scheibenreiter, S., Knoll, E., Colombo, J. P., hybridization study. Brain Res. Mol. Brain Res. 70: 231–241. Bachmann, C. & Thalhammer, O. (1992) Long-term follow-up of 12 patients 25. Demchenko, I. T., Atochin, D. N., Boso, A. E., Astern, J., Huang, P. L. & with the late-onset variant of argininosuccinic acid lyase deficiency: no impair- Piantadosi, C. A. (2003) Oxygen seizure latency and peroxynitrite formation in ment of intellectual and psychomotor development during therapy. Pediatrics 89: mice lacking neuronal or endothelial nitric oxide synthesis. Neurosci. Lett. 344: 1182–1184. 53–56. 52. Zimmermann, A., Bachmann, C. & Baumgartner, R. (1986) Severe liver 26. Hermenegildo, C., Montoliu, C., Llansola, M., Munoz, M. D., Gaztelu, fibrosis in argininosuccinic aciduria. Arch. Pathol. Lab. Med. 110: 136–140. J. M., Minana, M. D. & Felipo, V. (1998) Chronic hyperammonemia impairs the 53. Mori, T., Nagai, K., Mori, M., Nagao, M., Imamura, M., Iijima, M. & glutamate-nitric oxide-cyclic GMP pathway in cerebellar neurons in culture and in Kobayashi, K. (2002) Progressive liver fibrosis in late-onset argininosuccinate the rat in vivo. Eur. J. Neurosci. 10: 3201–3209. lyase deficiency. Pediatr. Dev. Pathol. 5: 597–601. 27. Oja, S. S., Janaky, R., Varga, V. & Saransaari, P. (2000) Modulation of 54. Parsons, H. G., Scott, R. B., Pinto, A., Carter, R. J. & Snyder, F. F. (1987) glutamate receptor functions by glutathione. Neurochem. Int. 37: 299–306. Argininosuccinic aciduria: long-term treatment with arginine. J. Inherit. Metab. 28. Kleppe, S., Mian, A. & Lee, B. (2003) Urea cycle disorders. Curr. Treat. Dis. 10: 152–161. Options Neurol. 5: 309–319. 55. Fakler, C. R., Kaftan, H. A. & Nelin, L. D. (1995) Two cases suggesting 29. Brusilow, S., Tinker, J. & Batshaw, M. L. (1980) Amino acid acylation: a role for the L-arginine nitric oxide pathway in neonatal blood pressure regula- a mechanism of nitrogen excretion in inborn errors of urea synthesis. Science tion. Acta Paediatr. 84: 460–462. 207: 659–661. 56. Farzaneh-Far, R. & Moore, K. (2001) Nitric oxide and the liver. Liver 21: 30. Batshaw, M. L., MacArthur, R. B. & Tuchman, M. (2001) Alternative 161–174. pathway therapy for urea cycle disorders: twenty years later. J. Pediatr. 138: 57. Sutton, V. R., Pan, Y., Davis, E. C. & Craigen, W. J. (2003) A mouse S46–S54; discussion S54–S55. model of argininosuccinic aciduria: biochemical characterization. Mol. Genet. 31. Berry, G. T. & Steiner, R. D. (2001) Long-term management of patients Metab. 78: 11–16. with urea cycle disorders. J Pediatr 138: S56–S60; discussion S60–S61. 58. Lemieux, B., Auray-Blais, C., Giguere, R., Shapcott, D. & Scriver, C. R. 32. Scaglia, F., Carter, S., O’Brien, W. E. & Lee, B. (2004) Effect of (1988) Newborn urine screening experience with over one million infants in the alternative pathway therapy on branched chain amino acid metabolism in urea Quebec Network of Genetic Medicine. J. Inherit. Metab. Dis. 11: 45–55. cycle disorder patients. Mol. Genet. Metab. 81 (Suppl.): 79–85. 59. Iyer, R., Jenkinson, C. P., Vockley, J. G., Kern, R. M., Grody, W. W. & 33. Lee, B. & Goss, J. (2001) Long-term correction of urea cycle disorders. Cederbaum, S. (1998) The human arginases and arginase deficiency. J. In- J. Pediatr. 138: S62–S71. herit. Metab. Dis. 21 (Suppl. 1): 86–100. 34. Leonard, J. V. & McKiernan, P. J. (2004) The role of liver transplanta- 60. Cederbaum, S. D., Yu, H., Grody, W. W., Kern, R. M., Yoo, P. & Iyer, R. K. tion in urea cycle disorders. Mol. Genet. Metab. 81 (Suppl.): 74–78. (2004) Arginases I and II: do their functions overlap? Mol. Genet. Metab. 81 35. Tuchman, M. (1989) Persistent acitrullinemia after liver transplantation (Suppl.): 38–44. 2782S SUPPLEMENT

61. Terheggen, H. G., Lowenthal, A. & Colombo, J. P. (1982) Clinical and 70. Hiramatsu, M., Edamatsu, R. & Mori, A. (1992) Free radicals, lipid biochemical findings in argininemia. Adv. Exp. Med. Biol. 153: 111–119. peroxidation, SOD activity, neurotransmitters and choline acetyltransferase ac- 62. De Deyn, P., Marescau, B., Lornoy, W., Becaus, I. & Lowenthal, A. tivity in the aged rat brain. EXS 62: 213–218. (1986) Guanidino compounds in uraemic dialysed patients. Clin. Chim. Acta 71. Shiraga, H., Hiramatsu, M. & Mori, A. (1986) Convulsive activity of 157: 143–150. alpha-guanidinoglutaric acid and the possible involvement of 5-hydroxytrypta- 63. Hirayasu, Y., Morimoto, K., Okamoto, M., Otsuki, S. & Mori, A. (1990) mine in the alpha-guanidinoglutaric acid-induced seizure mechanism. J. Neuro- The changes in guanidino compounds in the brain of amygdala kindled seizure– chem. 47: 1832–1836. comparisons with electric convulsive shock seizure. Jpn. J. Psychiatry Neurol. 44: 72. Matsumoto, M. & Mori, A. (1976) Effects of guanidino compounds on 448–450. rabbit brain microsomal Naϩ-Kϩ ATPase activity. J. Neurochem. 27: 635–636. 64. De Deyn, P. P. & Macdonald, R. L. (1990) Guanidino compounds that 73. da Silva, C. G., Parolo, E., Streck, E. L., Wajner, M., Wannmacher, C. M. are increased in cerebrospinal fluid and brain of uremic patients inhibit GABA and & Wyse, A. T. (1999) In vitro inhibition of Naϩ,K(ϩ)-ATPase activity from rat glycine responses on mouse neurons in cell culture. Ann. Neurol. 28: 627–633. cerebral cortex by guanidino compounds accumulating in hyperargininemia. 65. D’Hooge, R., Manil, J., Colin, F. & De Deyn, P. P. (1991) Guanidino- Brain Res. 838: 78–84. succinic acid inhibits excitatory synaptic transmission in CA1 region of rat hip- 74. Esch, F., Lin, K. I., Hills, A., Zaman, K., Baraban, J. M., Chatterjee, S., pocampal slices. Ann. Neurol. 30: 622–623. Rubin, L., Ash, D. E. & Ratan, R. R. (1998) Purification of a multipotent 66. Marescau, B., De Deyn, P. P., Qureshi, I. A., De Broe, M. E., Antonozzi, I., Cederbaum, S. D., Cerone, R., Chamoles, N., Gatti, R., et al. (1992) The antideath activity from bovine liver and its identification as arginase: nitric oxide- pathobiochemistry of uremia and hyperargininemia further demonstrates a met- independent inhibition of neuronal apoptosis. J. Neurosci. 18: 4083–4095. abolic relationship between urea and guanidinosuccinic acid. Metabolism 41: 75. Wyse, A. T., Bavaresco, C. S., Hagen, M. E., Delwing, D., Wannmacher, Downloaded from https://academic.oup.com/jn/article/134/10/2775S/4688495 by guest on 30 September 2021 1021–1024. C. M., Severo Dutra-Filho, C. & Wajner, M. (2001) In vitro stimulation of 67. De Deyn, P. P., Marescau, B. & Macdonald, R. L. (1991) Guanidino oxidative stress in cerebral cortex of rats by the guanidino compounds accumu- compounds that are increased in hyperargininemia inhibit GABA and glycine lating in hyperargininemia. Brain Res. 923: 50–57. responses on mouse neurons in cell culture. Epilepsy Res. 8: 134–141. 76. Shi, O., Morris, S. M., Jr., Zoghbi, H., Porter, C. W. & O’Brien, W. E. 68. Mori, A. & Okusu, H. (1971) Isolation and identification of alpha-N- (2001) Generation of a mouse model for arginase II deficiency by targeted acetyk-L-arginine and its effect on convulsive seizure. Shinkei Kenkyu No Shimpo disruption of the arginase II gene. Mol. Cell. Biol. 21: 811–813. 15: 304–306. 77. Iyer, R. K., Yoo, P. K., Kern, R. M., Rozengurt, N., Tsoa, R., O’Brien, W. E., 69. Mori, A. (1987) Biochemistry and neurotoxicology of guanidino com- Yu, H., Grody, W. W. & Cederbaum, S. D. (2002) Mouse model for human pounds. History and recent advances. Pavlov J. Biol. Sci. 22: 85–94. arginase deficiency. Mol. Cell. Biol. 22: 4491–4498.