151
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Harada E, Nishiyori A, Tokunaga Y, Watanabe Y, Kuriya N, Kumashiro R, Kuno T, Kuromaru R, Hirose S, Ichikawa K, Yoshino M. Late-onset ornithine transcarbamylase deficiency in male patients: prognostic factors and characteristics of plasma amino acid profile. Pediatr Int 2006; 48:105-11. [PMID: 16635166 DOI: 10.1111/j.1442-200x.2006.02181.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND The occurrence of male patients with ornithine transcarbamylase (OTC) deficiency during adolescence or in adulthood has now been recognized. The aim of this study was to determine the prognostic factors that affect the prognosis of life, to explore a basis for therapeutic strategy. METHODS In 10 patients, nine of whom carried the R40H mutation and the other one carrying the Y55D mutation in the OTC gene, 32 demographic and laboratory data were first compared between survivors and non-survivors, using the unpaired t-test. The factors with significant difference were then subjected to multiple regression analysis. RESULTS The factors that exhibited significant difference were: age at onset, concentration of plasma ammonium, blood pH, and concentrations of six amino acids in plasma. The multiple regression analysis then revealed concentrations of ammonium, leucine, lysine, isoleucine, phenylalanine, glutamine and proline to be significant prognostic factors. The amino acid profile in the 10 patients showed increases in glutamine, proline, lysine, valine and methionine, and decreases in serine, ornithine and arginine. There was an inverse correlation between the age at onset and the level of the residual hepatic OTC activity. CONCLUSION The results implied that: (i) the plasma amino acid profile was unique, in comparison to other liver diseases; (ii) the plasma concentration of each of the (mentioned above) six amino acids was a significant predictor of prognosis; and (iii) suppression of protein catabolism, as suggested by the higher concentrations in isoleucine and leucine in the non-survivors, prevention of glutamine-induced brain edema, correction of alkalosis, and supplementation with ornithine or arginine may improve the prognosis of life.
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Affiliation(s)
- Eimei Harada
- Department of Pediatrics and Child Health, Kurume University School of Medicine, Asahi-machi, Kurume, Japan
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152
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Abstract
Over the last two decades, gene transfer experiments for the treatment of inherited or acquired diseases have mainly been performed in mice. While mice provide proof of principle and allow testing of a variety of therapeutic modalities, mouse models have some limitations, as only short-term experiments can be performed, their homogenous genetic background is unlike humans, and the knockout models do not always faithfully represent the human disease. Naturally occurring large animal models of human genetic diseases have become increasingly important despite the costs and the extensive clinical attention they require because of their similarities to human patients. Large animals are reasonably outbred, long lived allowing for longitudinal studies, are more similar in size to a neonate or small child providing an opportunity to address issues related to scaling up therapy, and many physiological parameters including the immune system are more similar to those in humans versus those in mice.
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Affiliation(s)
- Margret Casal
- School of Veterinary Medicine, University of Pennsylvania, Philadelphia, 19104-6051, USA
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153
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Monfort P, Muñoz MD, Felipo V. Chronic hyperammonemia in vivo impairs long-term potentiation in hippocampus by altering activation of cyclic GMP-dependent-protein kinase and of phosphodiesterase 5. J Neurochem 2005; 94:934-42. [PMID: 16092938 DOI: 10.1111/j.1471-4159.2005.03236.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Long-term potentiation (LTP) is impaired in the CA1 area of hippocampal slices from rats with chronic moderate hyperammonemia. We studied the mechanisms by which hyperammonemia in vivo impairs LTP. This process requires sequential activation of soluble guanylate cyclase, cyclic GMP-dependent protein kinase (PKG) and cyclic GMP-degrading phosphodiesterase. Application of the tetanus induced a rapid increase of cyclic GMP in slices from control or hyperammonemic rats, which is followed in control slices by a sustained decrease in cyclic GMP due to sustained activation of cyclic GMP-degrading phosphodiesterase, which in turn is due to sustained activation of PKG. In slices from rats with chronic hyperammonemia tetanus-induced decrease in cyclic GMP was delayed and transient due to lower and transient activation of PKG and of the phosphodiesterase. Hyperammonemia-induced impairment of LTP may be involved in the alterations of cognitive function in patients with hepatic encephalopathy.
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Affiliation(s)
- Pilar Monfort
- Laboratory of Neurobiology, Fundación Valenciana de Investigaciones Biomédicas, Valencia, Spain
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154
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de Boo HA, van Zijl PL, Smith DEC, Kulik W, Lafeber HN, Harding JE. Arginine and mixed amino acids increase protein accretion in the growth-restricted and normal ovine fetus by different mechanisms. Pediatr Res 2005; 58:270-7. [PMID: 16006429 DOI: 10.1203/01.pdr.0000169977.48609.55] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Protein metabolism may be perturbed in intrauterine growth restriction (IUGR). Arginine is indispensable for growth and nitrogen balance in young mammals. Fetuses with IUGR therefore may benefit from arginine supplementation. The purpose of this study was to determine 1) the effects of IUGR on protein metabolism in the ovine fetus and 2) the effects of arginine or mixed amino acid (AA) infusion on protein metabolism in these fetuses. Pregnant ewes and their fetuses were catheterized at 110 d gestation and randomly assigned to control or IUGR groups. IUGR was induced by repetitive placental embolization. Parameters of fetal protein metabolism were determined from [ring-(2)H(5)]phenylalanine kinetics at baseline and in response to a 4-h infusion of either arginine or an isonitrogenous AA mixture. There were no differences in protein metabolism between control and IUGR groups either at baseline or in response to arginine or AA treatment. Both arginine and AA infusion increased fetal protein accretion in both groups. Arginine did this by decreasing protein turnover, synthesis, and breakdown. AAs increased protein turnover and synthesis while decreasing protein breakdown. AA infusion resulted in a significantly higher increase in protein accretion than arginine infusion. Thus, in the ovine fetus, placental embolization has no clear effect on protein metabolism. Arginine and AAs both stimulate protein accretion but do so in distinctly different ways. Mixed AA infusion has a greater effect on protein accretion than arginine alone and therefore may be a better strategy for stimulating fetal growth.
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Affiliation(s)
- Hendrina A de Boo
- The Liggins Institute, Faculty of Medicine and Health Science, University of Auckland, Auckland, New Zealand
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155
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de Boo HA, Cranendonk A, Kulik W, Harding JE, Lafeber HN. Whole body protein turnover and urea production of preterm small for gestational age infants fed fortified human milk or preterm formula. J Pediatr Gastroenterol Nutr 2005; 41:81-7. [PMID: 15990635 DOI: 10.1097/01.mpg.0000161795.15127.2f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES To investigate protein metabolism and urea production in preterm small for gestational age neonates fed a preterm formula or fortified human milk. METHODS Ten preterm small for gestational age neonates were fed either their own mother's milk fortified with a powdered protein mineral supplement or a special preterm formula. Protein metabolism was determined using constant steady-state infusion of L-[ring-2H5]phenylalanine and L-[1-13C]valine. Urea production was determined from steady-state [13C]urea kinetics. RESULTS Mean protein intake was 24% higher in the preterm formula group than in the fortified human milk group. No differences in protein turnover, synthesis and breakdown were observed between the two groups, but protein accretion was 71% to 79% higher in the preterm formula group than the fortified human milk group. Urea production rates were not different in the two groups. There was a strong negative correlation between urea production and protein accretion calculated from phenylalanine kinetics but not when calculated from valine kinetics. CONCLUSIONS Preterm formula and fortified human milk appear equally well tolerated by preterm small for gestational age neonates, but protein accretion was higher in the preterm formula group. In preterm small for gestational age infants, both phenylalanine and valine kinetic methods can be used to accurately determine protein metabolism.
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Affiliation(s)
- Hendrina A de Boo
- Department of Pediatrics, Subdivision of Neonatology, Vrije Universiteit Medisch Centrum, Amsterdam, The Netherlands
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156
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Haller M, Henzler-Le Boulanger A, Sass JO, Brandis M, Zimmerhackl LB. Successful extracorporeal treatment of a male with hyperammonaemic coma. Nephrol Dial Transplant 2005; 20:453-5. [PMID: 15673699 DOI: 10.1093/ndt/gfh495] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Maria Haller
- Zentrum für Kinderheilkunde und Jugendmedizin, Albert-Ludwigs-Universität, Freiburg, Germany
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157
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Ensenauer R, Tuchman M, El-Youssef M, Kotagal S, Ishitani MB, Matern D, Babovic-Vuksanovic D. Management and outcome of neonatal-onset ornithine transcarbamylase deficiency following liver transplantation at 60 days of life. Mol Genet Metab 2005; 84:363-6. [PMID: 15781198 DOI: 10.1016/j.ymgme.2004.12.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2004] [Revised: 12/23/2004] [Accepted: 12/28/2004] [Indexed: 10/25/2022]
Abstract
Neonatal hyperammonemia secondary to X-linked ornithine transcarbamylase (OTC) deficiency carries a high risk of morbidity and mortality. Results of medical therapy are less than satisfactory. Experience with liver transplantation in very young affected infants is limited. We report a male newborn with severe OTC deficiency who underwent successful orthotopic, cadaveric liver transplantation at the age of 60 days. Although technically challenging in the neonatal period, liver transplantation should be considered early as the most promising treatment approach currently available.
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Affiliation(s)
- Regina Ensenauer
- Department of Medical Genetics, Mayo Clinic College of Medicine, Rochester, MN, USA
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158
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Giordano G, Sanchez-Perez AM, Burgal M, Montoliu C, Costa LG, Felipo V. Chronic exposure to ammonia induces isoform-selective alterations in the intracellular distribution and NMDA receptor-mediated translocation of protein kinase C in cerebellar neurons in culture. J Neurochem 2005; 92:143-57. [PMID: 15606904 DOI: 10.1111/j.1471-4159.2004.02852.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hyperammonemia is responsible for most neurological alterations in patients with hepatic encephalopathy by mechanisms that remain unclear. Hyperammonemia alters phosphorylation of neuronal protein kinase C (PKC) substrates and impairs NMDA receptor-associated signal transduction. The aim of this work was to analyse the effects of hyperammonemia on the amount and intracellular distribution of PKC isoforms and on translocation of each isoform induced by NMDA receptor activation in cerebellar neurons. Chronic hyperammonemia alters differentially the intracellular distribution of PKC isoforms. The amount of all isoforms (except PKC zeta) was reduced (17-50%) in the particulate fraction. The contents of alpha, beta1, and epsilon isoforms decreased similarly in cytosol (65-78%) and membranes (66-83%), whereas gamma, delta, and theta; isoforms increased in cytosol but decreased in membranes, and zeta isoform increased in membranes and decreased in cytosol. Chronic hyperammonemia also affects differentially NMDA-induced translocation of PKC isoforms. NMDA-induced translocation of PKC alpha and beta is prevented by ammonia, whereas PKC gamma, delta, epsilon, or theta; translocation is not affected. Inhibition of phospholipase C did not affect PKC alpha translocation but reduced significantly PKC gamma translocation, indicating that NMDA-induced translocation of PKC alpha is mediated by Ca2+, whereas PKC gamma translocation is mediated by diacylglycerol. Chronic hyperammonemia reduces Ca+2-mediated but not diacylglycerol-mediated translocation of PKC isoforms induced by NMDA.
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Affiliation(s)
- Gennaro Giordano
- Laboratory of Neurobiology, Fundacion Valenciana de Investigaciones Biomédicas. Valencia, Spain
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159
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Colletti JE, Homme JL, Woodridge DP. Unsuspected neonatal killers in emergency medicine. Emerg Med Clin North Am 2004; 22:929-60. [PMID: 15474777 DOI: 10.1016/j.emc.2004.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A neonate presenting to the emergency department can present a challenge to even the most experienced clinician. This article has focused on four deceiving and potentially devastating neonatal diseases. 1. Neonatal herpes is a potentially devastating illness without pathognomonic signs or symptoms. Early recognition and therapy can reduce mortality markedly. Although no specific sign or symptom is diagnostic,the diagnosis should be strongly considered in the presence of HSV risk factors, atypical sepsis, unexplained acute hepatitis, or focal seizure activity. Acyclovir therapy should be initiated before viral dissemination or significant CNS replication occurs. 2. Pertussis is a disease in which infants are at greatest risk of death or severe complication. Neonatal pertussis often presents in an atypical manner, lacking the classic signs and symptoms such as the "whoop."More common signs and symptoms include cough, feeding difficulty,low-grade fever, emesis, increasing respiratory distress, apnea, cyanosis,and seizures. Management should include hospitalization, supportive care, and antibiotics. 3. Congenital heart defects, particularly ductal-dependent lesions, may have an initial asymptomatic period that culminates in a rapidly progressive and fatal course. A neonate with CHD presents with shock refractory to volume resuscitation or pressor support. Resuscitative efforts are ineffective unless PGE, is administered. 4. Inborn errors of metabolism often are unsuspected because of their protean and heterogeneous nature. Signs and symptoms are subtle,are nonspecific, and often mimic other, more common diseases.An elevated index of suspicion, along with application and correct interpretation of a select few laboratory tests, is the key to making a diagnosis. Therapy is relatively straightforward and focused on resuscitation followed by prevention of catabolism and correction of specifically identified abnormalities. Although these disorders are relatively uncommon, prompt diagnosis and therapy can lead to a decrease in morbidity and mortality. The key is to maintain a high index of suspicion.
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MESH Headings
- Diagnosis, Differential
- Electrocardiography
- Electroencephalography
- Emergency Medicine/methods
- Emergency Treatment/methods
- Fluorescent Antibody Technique, Direct
- Heart Defects, Congenital/diagnosis
- Heart Defects, Congenital/epidemiology
- Heart Defects, Congenital/etiology
- Heart Defects, Congenital/therapy
- Herpes Simplex/diagnosis
- Herpes Simplex/epidemiology
- Herpes Simplex/etiology
- Herpes Simplex/therapy
- Humans
- Infant Mortality
- Infant, Newborn
- Infant, Newborn, Diseases/diagnosis
- Infant, Newborn, Diseases/epidemiology
- Infant, Newborn, Diseases/etiology
- Infant, Newborn, Diseases/therapy
- Intensive Care, Neonatal/methods
- Metabolism, Inborn Errors/diagnosis
- Metabolism, Inborn Errors/epidemiology
- Metabolism, Inborn Errors/etiology
- Metabolism, Inborn Errors/therapy
- Morbidity
- Neonatal Screening
- Oximetry
- Polymerase Chain Reaction
- Resuscitation/methods
- Risk Factors
- Time Factors
- United States/epidemiology
- Whooping Cough/diagnosis
- Whooping Cough/epidemiology
- Whooping Cough/etiology
- Whooping Cough/therapy
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Affiliation(s)
- James E Colletti
- Department of Pediatric and Adolescent Medicine, Mayo Medical School, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
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160
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Monfort P, Muñoz MD, Kosenko E, Llansola M, Sánchez-Pérez A, Cauli O, Felipo V. Sequential activation of soluble guanylate cyclase, protein kinase G and cGMP-degrading phosphodiesterase is necessary for proper induction of long-term potentiation in CA1 of hippocampus. Alterations in hyperammonemia. Neurochem Int 2004; 45:895-901. [PMID: 15312984 DOI: 10.1016/j.neuint.2004.03.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Long-term potentiation (LTP) is a long-lasting enhancement of synaptic transmission efficacy and is considered the base for some forms of learning and memory. Nitric oxide (NO)-induced formation of cGMP is involved in hippocampal LTP. We have studied in hippocampal slices the effects of application of a tetanus to induce LTP on cGMP metabolism and the mechanisms by which cGMP modulates LTP. Tetanus application induced a transient rise in cGMP, reaching a maximum at 10s and decreasing below basal levels 5 min after the tetanus, remaining below basal levels after 60 min. Soluble guanylate cyclase (sGC) activity increased 5 min after tetanus and returned to basal levels at 60 min. The decrease in cGMP was due to sustained tetanus-induced increase in cGMP-degrading phosphodiesterase activity, which remained activated 60 min after tetanus. Tetanus-induced activation of PDE and decrease of cGMP were prevented by inhibiting protein kinase G (PKG). This indicates that the initial increase in cGMP activates PKG that phosphorylates (and activates) cGMP-degrading PDE, which, in turn, degrades cGMP. Inhibition of sGC, of PKG or of cGMP-degrading phosphodiesterase impairs LTP, indicating that proper induction of LTP involves transient activation of sGC and increase in cGMP, followed by activation of cGMP-dependent protein kinase, which, in turn, activates cGMP-degrading phosphodiesterase, resulting in long-lasting reduction of cGMP content. Hyperammonemia is the main responsible for the neurological alterations found in liver disease and hepatic encephalopathy, including impaired intellectual function. Hyperammonemia impairs LTP in hippocampus by altering the modulation of this sGC-PKG-cGMP-degrading PDE pathway. Exposure of hippocampal slices to 1 mM ammonia completely prevents tetanus-induced decrease of cGMP by impairing PKG-mediated activation of cGMP-degrading phosphodiesterase. This impairment is responsible for the loss of the maintenance of LTP in hyperammonemia, and may be also involved in the cognitive impairment in patients with hyperammonemia and hepatic encephalopathy.
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Affiliation(s)
- Pilar Monfort
- Laboratory of Neurobiology, Instituto de Investigaciones Citológicas, Fundación Valenciana de Investigaciones Biomédicas FVIB, Amadeo de Saboya 4, 46010 Valencia, Spain
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161
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Scaglia F, Brunetti-Pierri N, Kleppe S, Marini J, Carter S, Garlick P, Jahoor F, O'Brien W, Lee B. Clinical consequences of urea cycle enzyme deficiencies and potential links to arginine and nitric oxide metabolism. J Nutr 2004; 134:2775S-2782S; discussion 2796S-2797S. [PMID: 15465784 DOI: 10.1093/jn/134.10.2775s] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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.
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Affiliation(s)
- Fernando Scaglia
- Department of Molecular and Human Genetics, Children's Nutritional Research Center, Baylor College of Medicine, Houston, TX 77030, USA
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162
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McBride KL, Miller G, Carter S, Karpen S, Goss J, Lee B. Developmental outcomes with early orthotopic liver transplantation for infants with neonatal-onset urea cycle defects and a female patient with late-onset ornithine transcarbamylase deficiency. Pediatrics 2004; 114:e523-6. [PMID: 15466081 DOI: 10.1542/peds.2004-0198] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Urea cycle defects (UCDs) typically present with hyperammonemia, the duration and peak levels of which are directly related to the neurologic outcome. Liver transplantation can cure the underlying defect for some conditions, but the preexisting neurologic status is a major factor in the final outcome. Multicenter data indicate that most of the children who receive transplants remain significantly neurologically impaired. We wanted to determine whether aggressive metabolic management of ammonia levels after early referral/transfer to a metabolism center and early liver transplantation would result in better neurologic outcomes. We report on 5 children with UCDs, ie, 2 male patients with X-linked ornithine transcarbamylase deficiency and 2 male patients with carbamoyl phosphate synthase deficiency, all of whom had neonatal presentations and underwent orthotopic liver transplantation before 1 year of age, and 1 female patient with partial X-linked ornithine transcarbamylase deficiency that was intractable to medical therapy, who underwent transplantation at 35 months of age. Developmental testing with the Griffiths scale was performed on 3 occasions each, 12 months apart, up to 45 months after transplantation. Full-scale indices for 3 children who underwent early transplantation showed average developmental quotients of 67. All 5 children had metabolic cures. There were no deaths (30-month survival rate: 100%). One child is currently listed for repeat transplantation because of bile duct stenosis and cirrhosis. We conclude that early liver transplantation and aggressive metabolic management improve early neurologic outcomes for children with UCDs, but longer follow-up monitoring is needed.
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Affiliation(s)
- Kim L McBride
- Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
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163
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Mian A, McCormack WM, Mane V, Kleppe S, Ng P, Finegold M, O'Brien WE, Rodgers JR, Beaudet AL, Lee B. Long-Term Correction of Ornithine Transcarbamylase Deficiency by WPRE-Mediated Overexpression Using a Helper-Dependent Adenovirus. Mol Ther 2004; 10:492-9. [PMID: 15336649 DOI: 10.1016/j.ymthe.2004.05.036] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2003] [Accepted: 05/21/2004] [Indexed: 11/25/2022] Open
Abstract
The urea cycle disorders (UCDs) are important models for developing gene replacement therapy for liver diseases. Long-term correction of the most common UCD, ornithine transcarbamylase (OTC) deficiency, has yet to be achieved in clinical or preclinical settings. The single human clinical trial using early-generation adenovirus (Ad) failed to show any biochemical correction. In adult OTC-deficient mice, an E1/E2-deleted Ad vector expressing the mouse OTC gene, but not the human, was only transiently therapeutic. By using post-transcriptional overexpression in the context of the less immunogenic helper-dependent adenoviral vector, we achieved metabolic correction of adult OTC-deficient mice for >6 months. Demonstrating this result were normalized orotic aciduria, normal hepatic enzyme activity, and elevated OTC RNA and protein levels in the absence of chronic hepatotoxicity. Overexpressing the human protein may have overcome two potential mechanisms accounting for poor cross-species complementation: a kinetic block at the level of mitochondrial import or a dominant negative effect by the mutant polypeptide. These data represent an important approach for treating human inborn errors of hepatocyte metabolism like the UCDs that require high-level transduction and gene expression for clinical correction.
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Affiliation(s)
- Asad Mian
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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164
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Endo F, Matsuura T, Yanagita K, Matsuda I. Clinical manifestations of inborn errors of the urea cycle and related metabolic disorders during childhood. J Nutr 2004; 134:1605S-1609S; discussion 1630S-1632S, 1667S-1672S. [PMID: 15173438 DOI: 10.1093/jn/134.6.1605s] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Various disorders cause hyperammonemia during childhood. Among them are those caused by inherited defects in urea synthesis and related metabolic pathways. These disorders can be grouped into two types: disorders of the enzymes that comprise the urea cycle, and disorders of the transporters or metabolites of the amino acids related to the urea cycle. Principal clinical features of these disorders are caused by elevated levels of blood ammonium. Additional disease-specific symptoms are related to the particular metabolic defect. These specific clinical manifestations are often due to an excess or lack of specific amino acids. Treatment of urea cycle disorders and related metabolic diseases consists of nutritional restriction of proteins, administration of specific amino acids, and use of alternative pathways for discarding excess nitrogen. Although combinations of these treatments are extensively employed, the prognosis of severe cases remains unsatisfactory. Liver transplantation is one alternative for which a better prognosis is reported.
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Affiliation(s)
- Fumio Endo
- Department of Pediatrics, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860, Japan.
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165
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Monfort P, Muñoz MD, Felipo V. Hyperammonemia impairs long-term potentiation in hippocampus by altering the modulation of cGMP-degrading phosphodiesterase by protein kinase G. Neurobiol Dis 2004; 15:1-10. [PMID: 14751765 DOI: 10.1016/j.nbd.2003.09.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Hyperammonemia impairs long-term potentiation (LTP) in hippocampus, by an unknown mechanism. LTP in hippocampal slices requires activation of the soluble guanylate cyclase (sGC)-protein kinase G (PKG)-cGMP-degrading phosphodiesterase pathway. The aim of this work was to assess whether hyperammonemia impairs LTP by impairing the tetanus-induced activation of this pathway. The tetanus induced a rapid cGMP rise, reaching a maximum at 10 s, both in the absence or presence of ammonia. The increase in cGMP is followed in control slices by a sustained decrease in cGMP due to PKG-mediated activation of cGMP-degrading phosphodiesterase, which is required for maintenance of LTP. Hyperammonemia prevents completely tetanus-induced cGMP decrease by impairing PKG-mediated activation of cGMP-degrading phosphodiesterase. Addition of 8Br-cGMP to slices treated with ammonia restores both phosphodiesterase activation and maintenance of LTP. Impairment of LTP in hyperammonemia may be involved in the impairment of the cognitive function in patients with hepatic encephalopathy.
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Affiliation(s)
- Pilar Monfort
- Laboratory of Neurobiology, Fundación Valenciana de Investigaciones Biomédicas, 46010 Valencia, Spain
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166
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McBryde KD, Kudelka TL, Kershaw DB, Brophy PD, Gardner JJ, Smoyer WE. Clearance of amino acids by hemodialysis in argininosuccinate synthetase deficiency. J Pediatr 2004; 144:536-40. [PMID: 15069407 DOI: 10.1016/j.jpeds.2004.01.037] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We determined the dialytic clearance of amino acids involved in ammoniagenesis and nitrogen excretion in a neonate with argininosuccinate synthetase deficiency who underwent acute hemodialysis. Plasma ammonia and plasma and dialysate amino acid concentrations were obtained at baseline, 30-minute intervals during hemodialysis, and 30 minutes after the completion of hemodialysis. Plasma ammonia concentrations declined by 56% during the 90-minute hemodialysis treatment, whereas arginine, citrulline, glutamine, and glycine concentrations decreased by 65%, 55%, 40%, and 34%, respectively. Mean dialytic clearances for arginine, citrulline, glutamine, and glycine were 24, 282, 263, and 189 mL/min per 1.73 m(2), respectively. The high dialytic clearance of citrulline suggests a novel mechanism of hemodialysis removal of nitrogen. Dialytic clearances of glutamine and glycine may prevent further ammoniagenesis in hyperammonemic patients. However, our data suggest that hemodialysis affects the precursors of alternative pathway removal of ammonia. Further study is needed to optimize the intradialytic and interdialytic dosing of substrates.
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Affiliation(s)
- Kevin D McBryde
- Department of Nephrology, Children's National Medical Center, George Washington University, 111 Michigan Avenue NW, Washington, DC 20010, USA.
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167
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Gropman AL, Batshaw ML. Cognitive outcome in urea cycle disorders. Mol Genet Metab 2004; 81 Suppl 1:S58-62. [PMID: 15050975 DOI: 10.1016/j.ymgme.2003.11.016] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2003] [Revised: 08/03/2003] [Accepted: 11/17/2003] [Indexed: 11/30/2022]
Abstract
Despite treatment, cognitive and motor deficits are common in individuals with inherited urea cycle disorders. However, the extent to which the deficits involve specific cognitive or sensorimotor domains is unknown. Furthermore, little is known about the neurochemical basis of cognitive impairment in these disorders. This paper reviews studies of cognitive and motor dysfunction in urea cycle disorders, and discusses potential venues for investigation of the underlying neural basis that may elucidate these defects. Such methods of investigation may serve as a model for studying the relationship between genes, biochemical markers, brain function, and behavior in other metabolic diseases.
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Affiliation(s)
- Andrea L Gropman
- Children's Research Institute, Children's National Medical Center, Department of Pediatrics, George Washington University School of Medicine and Health Sciences, Washington, DC 20010-2916, USA
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168
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Gyato K, Wray J, Huang ZJ, Yudkoff M, Batshaw ML. Metabolic and neuropsychological phenotype in women heterozygous for ornithine transcarbamylase deficiency. Ann Neurol 2004; 55:80-6. [PMID: 14705115 DOI: 10.1002/ana.10794] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We compared neurocognitive indices with clinical status, mutation analysis, and urea synthetic capacity in 19 women heterozygous for ornithine transcarbamylase deficiency. Although as a group, these women had average IQ scores, they displayed a specific neuropsychological phenotype with significant strengths in verbal intelligence, verbal learning, verbal memory, and reading, and significant weaknesses in fine motor dexterity/speed and nonsignificant weaknesses in nonverbal intelligence, visual memory, attention/executive skills, and math. This suggests selective vulnerability of white matter and better preservation of gray matter. When the group was divided into symptomatic and asymptomatic subgroups, based on either clinical history or residual urea synthetic capacity, the asymptomatic subgroup outperformed the symptomatic subgroup on all tested domains of neuropsychological functioning. Furthermore, the amount of residual urea synthetic capacity was predictive of several end point cognitive measures. There was no correlation between neonatal versus late-onset mutation or between normal or abnormal allopurinol challenge and neuropsychological outcome. In sum, we identified a specific metabolic and neurocognitive phenotype in women heterozygous for ornithine transcarbamylase deficiency. The findings support the importance of maintaining meticulous metabolic control in children with urea cycle disorders, because even mildly symptomatic subjects demonstrate cognitive deficits.
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Affiliation(s)
- Kunsang Gyato
- North Shore-Long Island Jewish Health System, Schneider Children's Hospital, Division of Child and Adolescent Psychiatry, New Hyde Park, NY, USA
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169
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Banta-Wright SA, Steiner RD. Not so rare: errors of metabolism during the neonatal period. ACTA ACUST UNITED AC 2003. [DOI: 10.1053/s1527-3369(03)00116-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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170
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Bachmann C. Outcome and survival of 88 patients with urea cycle disorders: a retrospective evaluation. Eur J Pediatr 2003; 162:410-6. [PMID: 12684900 DOI: 10.1007/s00431-003-1188-9] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2002] [Revised: 01/27/2003] [Accepted: 01/27/2003] [Indexed: 10/25/2022]
Abstract
UNLABELLED This paper presents data obtained by questionnaires sent to local hospitals and metabolic centres in Germany, Austria, Italy and Switzerland concerning the survival and outcome of patients with urea cycle disorders treated between 1975 and 1986. A total of 130 questionnaires were sent out of which 88 questionnaires of patients were returned. This study compares results of conservative long-term management using protein restriction versus protein restriction combined with more extensive treatment (arginine/citrulline, essential amino acid supplements and sodium benzoate as alternate pathway therapy). While survival was improved in neonates receiving extensive therapy, there was an increased risk of mental retardation on long-term follow-up in this group. The time at which the first symptoms of hyperammonaemia appeared, the age at diagnosis, and the time of delay in diagnosis after the first symptom were not helpful in predicting outcome; however, when plasma ammonia concentrations exceeded 300 micromol/l initially or 480 micromol/l at its peak, none of the patients had a normal cognitive outcome. CONCLUSION there is a need to establish improved treatment approaches and a network of "rare disease" centres to assure the rapid diagnosis and effective treatment and follow-up of affected children. This should precede any consideration of neonatal screening for urea cycle disorders.
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Affiliation(s)
- Claude Bachmann
- Laboratoire Central de Chimie Clinique, Centre Hospitalier Universitaire Vaudois, Bugnon 46, 1011 Lausanne, Switzerland.
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171
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Keegan CE, Martin DM, Quint DJ, Gorski JL. Acute extrapyramidal syndrome in mild ornithine transcarbamylase deficiency: metabolic stroke involving the caudate and putamen without metabolic decompensation. Eur J Pediatr 2003; 162:259-63. [PMID: 12647200 DOI: 10.1007/s00431-002-1135-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2002] [Revised: 10/28/2002] [Accepted: 11/05/2002] [Indexed: 11/24/2022]
Abstract
UNLABELLED A 6-year-old male with partial ornithine transcarbamylase (OTC) deficiency had acute and rapidly progressive symmetrical swelling of the head of the caudate nuclei and putamina. Clinical presentation was ataxia and dysarthria progressing to seizures and coma; these symptoms gradually resolved with supportive management. Although he had been recently treated for mild hyperammonemia, there was no evidence of acute metabolic decompensation prior to presentation, and plasma ammonia and amino acids were consistent with good metabolic control. This case is novel in that the neurological insult affected the neostriatum of the basal ganglia and the episode occurred in the absence of an apparent metabolic abnormality, unique observations in a patient with OTC deficiency. CONCLUSION This case suggests that the pathophysiology of metabolic stroke is complicated. It also argues for an evaluation for metabolic stroke in patients with known inborn errors of metabolism who present with unusual neurological symptoms in the absence of biochemical abnormalities. Similarly, this case suggests that patients presenting with unexplained neurological insults might benefit from an evaluation for an inborn error of metabolism.
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Affiliation(s)
- C E Keegan
- Department of Pediatrics and Communicable Diseases, Division of Pediatric Genetics, University of Michigan School of Medicine, 3570 MSRB II, P.O. Box 0688, Ann Arbor, MI 48109-0688, USA
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172
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Kayler LK, Rasmussen CS, Dykstra DM, Punch JD, Rudich SM, Magee JC, Maraschio MA, Arenas JD, Campbell DA, Merion RM. Liver transplantation in children with metabolic disorders in the United States. Am J Transplant 2003; 3:334-9. [PMID: 12614291 DOI: 10.1034/j.1600-6143.2003.00058.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We studied pediatric liver transplantation for metabolic disease in a large national cohort to determine whether smaller studies suggesting a survival advantage for these recipients could be corroborated. We also hoped to determine whether higher survival rates in recipients with metabolic disease are associated with lack of structural liver disease, and to evaluate these recipients' risk factors for mortality. Data from the Scientific Registry of Transplant Recipients were used to analyze nationwide results (1990-99) of pediatric liver transplantation for patients with biliary atresia and metabolic disease. Adjusted patient survival rates for children with metabolic disease at 1 and 5 years were 94% and 92%, respectively, - significantly higher than for recipients with biliary atresia (90% and 86%) (p = 0.008). Cox regression models identified recipient black race [relative risk (RR) = 5.1] and simultaneous transplantation of other organs (RR = 3.2) as significant risk factors for mortality in the metabolic group. Adjusted survival rates for metabolic patients with structural and nonstructural liver diseases were similar to each other at both 1 and 5 years. Children with metabolic disease had significantly higher adjusted short- and long-term post-transplant survival rates than those with biliary atresia. Structural disease was not a risk factor for worse outcomes.
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Affiliation(s)
- Liise K Kayler
- Division of Transplantation, Department of Surgery, University of Michigan, Ann Arbor, MI, USA
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173
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Monfort P, Muñoz MD, ElAyadi A, Kosenko E, Felipo V. Effects of hyperammonemia and liver failure on glutamatergic neurotransmission. Metab Brain Dis 2002; 17:237-50. [PMID: 12602501 DOI: 10.1023/a:1021993431443] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Glutamate is the main excitatory neurotransmitter in mammals. Glutamatergic neurotransmission involves several steps, beginning with release of glutamate from the presynaptic neuron. Glutamate in the extracellular space activates glutamate receptors present in the synaptic membranes, leading to activation of signal transduction pathways associated with these receptors. To avoid continuous activation of glutamate receptors, glutamate is removed from the synaptic cleft by specific glutamate transporters located mainly on astrocytes. All these steps are tightly modulated under physiological conditions, and alterations of any of the above steps may result in impairment of glutamatergic neurotransmission, leading to neurological alterations. There are studies in the literature reporting alterations in all these steps in hyperammonemia and/or hepatic failure. Glutamatergic neurotransmission modulates important cerebral processes. Some of these processes are altered in patients with liver disease and hepatic encephalopathy, who show altered sleep-wake patterns, neuromuscular coordination, and decreased intellectual capacity. The alterations in glutamatergic neurotransmission may be responsible for some of these neurological alterations found in hepatic encephalopathy. The effects of hyperammonemia and liver failure on different steps of glutamatergic neurotransmission including alterations of glutamate concentration in the extracellular fluid in brain, transport and transporters of glutamate, the content and function of different types of glutamate receptors and signal transduction pathways. Alterations induced by hyperammonemia and liver failure on the glutamate-nitric oxide-cGMP pathway in brain may result in changes in long-term potetiation and learning ability.
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Affiliation(s)
- Pilar Monfort
- Department of Neurobiology, Instituto de Investigaciones Citológicas, FVIB, Valencia, Spain
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174
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Abstract
Hyperammonemia in neonates and infants affects brain development and causes mental retardation. We report that ammonium impaired cholinergic axonal growth and altered localization and phosphorylation of intermediate neurofilament protein in rat reaggregated brain cell primary cultures. This effect was restricted to the phase of early maturation but did not occur after synaptogenesis. Exposure to NH4Cl decreased intracellular creatine, phosphocreatine, and ADP. We demonstrate that creatine cotreatment protected axons from ammonium toxic effects, although this did not restore high-energy phosphates. The protection by creatine was glial cell-dependent. Our findings suggest that the means to efficiently sustain CNS creatine concentration in hyperammonemic neonates and infants should be assessed to prevent impairment of axonogenesis and irreversible brain damage.
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175
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Joseph M, Hageman JR. Neonatal transport: a 3-day-old neonate with hypothermia, respiratory distress, lethargy and poor feeding. J Perinatol 2002; 22:506-9. [PMID: 12168133 DOI: 10.1038/sj.jp.7210755] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Monica Joseph
- Department of Pediatrics, Evanston Hospital, 2650 Ridge Avenue, Evanston, IL 60201-1493, USA
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176
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Kayler LK, Merion RM, Lee S, Sung RS, Punch JD, Rudich SM, Turcotte JG, Campbell DA, Holmes R, Magee JC. Long-term survival after liver transplantation in children with metabolic disorders. Pediatr Transplant 2002; 6:295-300. [PMID: 12234269 DOI: 10.1034/j.1399-3046.2002.02009.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Liver transplantation for inherited metabolic disorders aims to save the patient's life when the disorder is expected to progress to organ failure, and to cure the underlying metabolic defect. METHODS We retrospectively analyzed 146 pediatric liver transplants (28 metabolic; 118 non-metabolic) performed between 1986 and 2000. RESULTS Twenty-eight transplants were performed in 24 children with metabolic disease (8 females; 16 males; age range 3 months to 17 yr). Indications included alpha-1-antitrypsin deficiency (n = 8), two cases each of hyperoxaluria type 1, Wilson's disease, hereditary tyrosinemia type I, citrullinemia, methylmalonic acidemia, and one case each of propionic acidemia, Crigler-Najjar syndrome type I, neonatal hemachromatosis, hemophilia B, Niemann-Pick disease type B, and cystic fibrosis. Eighteen transplants were whole organ grafts and 10 were lobar or segmental. Auxiliary liver transplants were performed in two patients and three received combined liver-kidney transplants. There were three deaths from sepsis, two from chronic rejection, and one from fulminant hepatitis. Seven of 10 patients currently of school age are within 1 yr of expected grade and three who had pretransplant developmental delay have remained in special education. Actuarial survival rates at 5 and 10 yr are 78% and 68%, respectively, with mean follow-up in excess of 5 yr. These results compare favorably to 100 pediatric patients transplanted for non-metabolic etiologies (65% and 61%, respectively) (p= NS). CONCLUSIONS Pediatric liver transplantation for metabolic disorders results in excellent clinical and biochemical outcome with long survival and excellent quality of life for most recipients.
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Affiliation(s)
- Liise K Kayler
- Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan 48109, USA
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177
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Abstract
Hyperammonemia resulting from inherited urea cycle enzyme deficiencies or liver failure results in severe central nervous system dysfunction including brain edema, convulsions and coma. Neuropathologic evaluation in these disorders reveals characteristic alterations of astrocyte morphology ranging from cell swelling (acute hyperammonemia) to Alzheimer Type II astrocytosis (chronic hyperammonemia). Having no effective urea cycle, brain relies on glutamine synthesis for the removal of excess ammonia and the enzyme responsible, glutamine synthetase, has a predominantly astrocytic localization. Accumulation of ammonia in brain results in a redistribution of cerebral blood flow and metabolism from cortical to sub-cortical structures. In addition to changes in astrocyte morphology, increased brain ammonia concentrations result in alterations in expression of key astrocyte proteins including glial fibrillary acidic protein, glutamate and glycine transporters and "peripheral-type" (mitochondrial) benzodiazepine receptors. Such changes result in alterations of astrocytic volume and increased extracellular concentrations of excitatory and inhibitory substances. In addition, the ammonium ion has direct effects on excitatory-inhibitory transmission via distinct mechanisms involving cellular chloride extrusion and postsynaptic receptor function. Acute ammonia exposure leads to activation of NMDA receptors and their signal transduction pathways. Chronic hyperammonemia also results in increased concentrations of neuroactive L-tryptophan metabolites including serotonin and quinolinic acid. Therapy in hyperammonemic syndromes continues to rely on ammonia-lowering strategies via peripheral mechanisms (reduction of ammonia production in the gastrointestinal tract, increased ammonia removal by muscle).
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Affiliation(s)
- Vicente Felipo
- Department of Neurobiology, Laboratory of Neurobiology, Instituto de Investigaciones Citologicas, Amadeo de Saboya 4, Fundacion Valenciana de Investigaciones Biomedicas, 46010 Valencia, Spain
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178
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Abstract
Hyperammonemia is mainly found in hepatic encephalopathy and in genetic defects of the urea cycle or other pathways of the intermediary metabolism. Clinically a difference has to be made between chronic moderate hyperammonemia and acutely increased concentrations. Pathogenetic mechanisms of ammonia toxicity to the brain are partly unraveled. In some animal models confounding variables, such as the reduced intake of food and amino acid imbalance due to liver insufficiency, do not allow to establish unequivocal causal relationships between the ammonia concentration and measured effects. In chronic moderate hyperammonemia an increased flux through the serotonin pathway is a key factor. It is caused by an increased transport of large neutral amino acids (including tryptophan) through the blood-brain barrier, accentuated by the imbalance of plasma amino acids in hepatic insufficiency. It is stimulated by D- or L-glutamine. Evidence is presented showing that a functioning gamma-glutamyl cycle (glutathione formation) is a prerequisite. In acute hyperammonemia involvement of NMDA receptors, glutamate, NO and cGMP plays an additional role. In hyperammonemic crises the increased cerebral blood flow leads to brain edema; factors discussed here are increased osmolytes in astrocytes and serotoninergic activity. Recent data indicate that axonal development is affected by ammonia and can be normalized in vitro by creatine supplementation in developing mixed brain cell aggregate cultures, thus reviving the old hypothesis of the impact of hyperammonemia on energy metabolism in the developing brain that could cause mental retardation.
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Affiliation(s)
- Claude Bachmann
- Laboratoire Central de Chimie Clinique, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Switzerland.
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179
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Affiliation(s)
- Saul W Brusilow
- Department of Pediatrics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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180
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Holtsberg FW, Ensor CM, Steiner MR, Bomalaski JS, Clark MA. Poly(ethylene glycol) (PEG) conjugated arginine deiminase: effects of PEG formulations on its pharmacological properties. J Control Release 2002; 80:259-71. [PMID: 11943403 DOI: 10.1016/s0168-3659(02)00042-1] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Some tumors, such as melanomas and hepatocellular carcinomas, have a unique nutritional requirement for arginine. Thus, enzymatic degradation of extracellular arginine is one possible means for inhibiting these tumors. Arginine deiminase is an arginine degrading enzyme (ADI) that has been studied as an anti-cancer enzyme. However, ADI has a short serum half-life and, as a microbial enzyme, is highly immunogenic. Formulation of other therapeutic proteins with poly(ethylene glycol) (PEG) has overcome these problems. Here, ADI-PEGs were synthesized using PEGs of varying size, structure (linear or branched chain) and linker chemistries. All ADI-PEGs retained approximately 50% of enzyme activity when PEG was covalently attached to approximately 40% of the primary amines irrespective of the PEG molecular weight or attachment chemistry used. However, it was observed that, as the PEG size increases to 20 kDa, there was a corresponding increase in the pharmacokinetic (pK) and pharmacodynamic (pD) properties of the formulation. Variation in PEG linker or structure, or the use of PEGs >20,000 mw, did not affect the pK or pD. As has been shown with other therapeutic proteins, repeated injection of ADI-PEG into experimental animals resulted in significantly lower titers of antibodies against this protein than unmodified ADI. These data suggest that formulation of ADI with PEG of 20,000 mw results is the optimal method for formulating this promising therapeutic agent.
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Affiliation(s)
- Frederick W Holtsberg
- Department of Biology, T.H. Morgan Building, University of Kentucky, Lexington, KY 40506, USA
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181
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182
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Ogier de Baulny H. Management and emergency treatments of neonates with a suspicion of inborn errors of metabolism. SEMINARS IN NEONATOLOGY : SN 2002; 7:17-26. [PMID: 12069535 DOI: 10.1053/siny.2001.0084] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
During the neonatal period, inborn errors of metabolism mostly present with an overwhelming illness that requires prompt diagnosis and both supportive and specific treatments. The most frequent situations are due to branched-chain organic acidurias that present with ketoacidosis and urea cycle defects that are characterized by hyperammonaemia. During both situations, toxin removal procedures and nutritional support with a free-protein and high-energy diet are pivotal treatments. In patients presenting with hypoglycaemia blood glucose levels must be corrected. Progress following glucose provision is useful in recognizing the disorders that are mainly implicated. Hyperinsulinism requires high-glucose infusion. Glycogen storage diseases and gluconeogenesis defects are easily treated with a permanent glucose provision while hypoglycaemias quickly recur. In patients with galactosaemia, hereditary fructose intolerance or tyrosinaemia type I, the presentation is dominated by a liver failure requiring galactose and fructose exclusion associated with a low-protein diet. Many patients with beta-oxidation defects may present with hypoglycaemia that is usually easily corrected. The precise diagnosis can be easily missed in those patients that do well in the following weeks but may develop cardiac failure, arrhythmia and/or liver failure. Patients presenting with intractable convulsions, vitamin responsiveness to biotin, pyridoxine and folate must be considered.
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183
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Raper SE, Yudkoff M, Chirmule N, Gao GP, Nunes F, Haskal ZJ, Furth EE, Propert KJ, Robinson MB, Magosin S, Simoes H, Speicher L, Hughes J, Tazelaar J, Wivel NA, Wilson JM, Batshaw ML. A pilot study of in vivo liver-directed gene transfer with an adenoviral vector in partial ornithine transcarbamylase deficiency. Hum Gene Ther 2002; 13:163-75. [PMID: 11779420 DOI: 10.1089/10430340152712719] [Citation(s) in RCA: 282] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Ornithine transcarbamylase deficiency (OTCD) is an inborn error of urea synthesis that has been considered as a model for liver-directed gene therapy. Current treatment has failed to avert a high mortality or morbidity from hyperammonemic coma. Restoration of enzyme activity in the liver should suffice to normalize metabolism. An E1- and E4-deleted vector based on adenovirus type 5 and containing human OTC cDNA was infused into the right hepatic artery in adults with partial OTCD. Six cohorts of three or four subjects received 1/2 log-increasing doses of vector from 2 x 10(9) to 6 x 10(11) particles/kg. This paper describes the experience in all but the last subject, who experienced lethal complications. Adverse effects included a flu-like episode and a transient rise in temperature, hepatic transaminases, thrombocytopenia, and hypophosphatemia. Humoral responses to the vector were seen in all research subjects and a proliferative cellular response to the vector developed in apparently naive subjects. In situ hybridization studies showed transgene expression in hepatocytes of 7 of 17 subjects. Three of 11 subjects with symptoms related to OTCD showed modest increases in urea cycle metabolic activity that were not statistically significant. The low levels of gene transfer detected in this trial suggest that at the doses tested, significant metabolic correction did not occur.
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Affiliation(s)
- Steven E Raper
- Institute for Human Gene Therapy and Department of Surgery, University of Pennsylvania, Philadelphia, PA 19104, USA
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184
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Daschner M, Schaefer F. Emergency dialysis in neonatal metabolic crises. ADVANCES IN RENAL REPLACEMENT THERAPY 2002; 9:63-9. [PMID: 11927909 DOI: 10.1053/jarr.2002.31433] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Metabolic crises in children with inborn errors of metabolism are caused by the accumulation of neurotoxic metabolites. Rapid elimination of these metabolites is apparently crucial to prevent irreversible neuronal damage; long-term outcome is correlated with the rate of toxin removal during the crisis. The usefulness of different blood purification techniques for removing accumulated neurotoxins is reviewed in this manuscript.
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Affiliation(s)
- Markus Daschner
- Division of Pediatric Nephrology, Children's Hospital, University of Heidelberg, Im Neuenheimer Feld 150, 69120 Heidelberg, Germany
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185
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Nicolaides P, Liebsch D, Dale N, Leonard J, Surtees R. Neurological outcome of patients with ornithine carbamoyltransferase deficiency. Arch Dis Child 2002; 86:54-6. [PMID: 11806886 PMCID: PMC1719070 DOI: 10.1136/adc.86.1.54] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Ornithine carbamoyltransferase (OCT) deficiency is the commonest of the inherited urea cycle disorders. AIMS To determine the long term neurological and cognitive outcome of continuously treated surviving patients. METHODS Twenty eight surviving children (five boys) with OCT deficiency who had been treated continuously with a low protein diet and alternative pathway therapy were identified. Those aged 5-16 years had a detailed neurological examination and psychometric testing. RESULTS Four presented in the neonatal period and four were treated prospectively following antenatal diagnosis. Median (range) age at diagnosis for the later onset group was 19 (2-144) months; median time between onset of symptoms and diagnosis was 10 (2-48) months. Nine children had had less than three episodes of hyperammonaemic encephalopathy, the others more. Seven had focal abnormalities on neurological examination; 14 had global cognitive impairment; four had a normal IQ but specific learning difficulties. Sixteen underwent neuroimaging which was normal in three, showed focal abnormalities of the cerebral hemispheres in six, and global cerebral atrophy in seven. CONCLUSION Eighteen of 28 surviving children with OCT deficiency had disabling neurological complications. Plasma ammonia at diagnosis was the only factor that predicted this outcome. While most neurological complications could be attributed to hyperammonaemic encephalopathy, other mechanisms may also contribute to the neurological abnormalities.
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Affiliation(s)
- P Nicolaides
- Neurodisability Service, Great Ormond Street Hospital for Children NHS Trust, The Wolfson Centre, Mecklenburgh Square, London WC1N 2AP, UK
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186
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Abstract
An infant aged 3 days presented with hyperammonaemic coma and seizures, which were found to be a result of a urea-cycle defect. Haemofiltration, alternative pathway metabolites, and glucose and insulin failed to lower the plasma ammonia concentration below 2000 micromol/L. The infant was then cooled to a rectal temperature of 34 degrees C for 48 h and put on haemofiltration for 12 h. Plasma ammonia fell to around 100 micromol/L and remained at this concentration after haemofiltration. He roused from his coma, breathed spontaneously, and resumed bottle feeding. Hypothermia may be therapeutic in such instances of metabolic coma because it lowers the enzymatic rate of production of the toxin while non-enzymatic methods remove the toxin.
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187
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Stadler S, Gempel K, Bieger I, Pontz BF, Gerbitz KD, Bauer MF, Hofmann S. Detection of neonatal argininosuccinate lyase deficiency by serum tandem mass spectrometry. J Inherit Metab Dis 2001; 24:370-8. [PMID: 11486903 DOI: 10.1023/a:1010560704092] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Argininosuccinate lyase (ASL) deficiency (McKusick 207900) is an inborn error of the urea cycle. The leading symptom is progressive hyperammonaemia, which is a life-threatening condition, particularly in patients with a neonatal onset. Early diagnosis and treatment of the hyperammonaemia are necessary to improve survival and the long-term outcome of ASL-deficient patients. Currently, the diagnosis of ASL deficiency is based on the measurement of urea cycle intermediates and amino acids by automated quantitative ion exchange chromatography in plasma and urine. Here, we report a newborn presenting with coma and severe hyperammonaemia. ASL deficiency was suspected on the basis of an adapted tandem mass spectrometric (MS-MS) procedure which allows determination of argininosuccinate in addition to the amino acids in serum samples. MS-MS measurements revealed a characteristic increase of argininosuccinate, a moderate increase of citrulline, and lowered levels of arginine and ornithine in the serum of the patient. The diagnosis was confirmed by the detection of a novel homozygous frameshift mutation in exon 14 of the argininosuccinate lyase gene. We propose MS-MS as a diagnostic tool suitable for the rapid detection of specific alterations in the amino acid spectra caused by ASL deficiency.
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Affiliation(s)
- S Stadler
- Institut für Klinische Chemie, Molekulare Diagnostik und Mitochondriale Genetik, Krankenhaus München-Schwabing, Germany
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188
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Abstract
Hyperammonemia associated with inherited disorders of amino acid and organic acid metabolism is usually manifested by irritability, somnolence, vomiting, seizures, and coma. Although the majority of these patients present in the newborn period, they may also present in childhood, adolescence, and adulthood with failure to thrive, persistent vomiting, developmental delay, or behavioral changes. Persistent hyperammonemia, if not treated rapidly, may cause irreversible neuronal damage. After the diagnosis of hyperammonemia is established in an acutely ill patient, certain diagnostic tests should be performed to differentiate between urea cycle defects and other causes of hyperammonemic encephalopathy. In a patient with a presumed inherited metabolic disorder, the aim of therapy should be to normalize blood ammonia levels. Recent experience has provided treatment guidelines that include minimizing endogenous ammonia production and protein catabolism, restricting nitrogen intake, administering substrates of the urea cycle, administering compounds that facilitate the removal of ammonia through alternative pathways, and, in severe cases, dialysis therapy. Initiation of dialysis in the encephalopathic patient with hyperammonemia is indicated if the ammonia blood level is greater than three to four times the upper limit of normal. Hemodialysis is the most effective treatment for rapidly reducing blood ammonia levels. Continuous hemofiltration and peritoneal dialysis are also effective modalities for reducing blood ammonia levels. An improved understanding of the metabolism of ammonia and neurological consequences of hyperammonemia will assist the nephrologist in providing optimal care for this high-risk patient population.
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Affiliation(s)
- R S Mathias
- Children's Renal Center and Department of Pediatrics, Division of Medical Genetics, University of California Medical Center, San Francisco, CA 94143-0748, USA.
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189
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Nagasaka H, Yorifuji T, Egawa H, Kikuta H, Tanaka K, Kobayashi K. Successful living-donor liver transplantation from an asymptomatic carrier mother in ornithine transcarbamylase deficiency. J Pediatr 2001; 138:432-4. [PMID: 11241058 DOI: 10.1067/mpd.2001.111318] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A liver transplantation from an asymptomatic mother, who was a carrier of ornithine transcarbamylase deficiency, to her daughter, who had severe manifestation, was successfully performed. One-year monitoring of plasma amino acid and urinary orotate/orotidine levels revealed no abnormality in the urea cycle in either subject.
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Affiliation(s)
- H Nagasaka
- Department of Pediatrics, Hokkaido University School of Medicine, Sapporo, Japan
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190
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Abstract
The long-term treatment of patients with urea cycle disorders (UCDs) includes diet treatment and use of specific medications. Guidelines are provided for patients with a severe phenotype. However, treatment must be tailored for each individual, especially with regard to residual enzyme function and in vivo metabolic capacity. This will be reflected in tests used for monitoring therapy that should be performed on a periodic basis. The goal of therapy is to eliminate chronic complications, a laudable but rarely attainable goal. Sick-day rules are discussed. Chronic management also includes diverse services that are essential to the success of the metabolic program. These include neurologic and developmental evaluations, feeding team evaluation and therapy, physical and occupational therapies, speech therapy, school and educational services, social service intervention, psychologic services, and genetic counseling.
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Affiliation(s)
- G T Berry
- Division of Human Genetics and Molecular Biology, Department of Pediatrics, University of Pennsylvania School of Medicine, The Children's Hospital of Philadelphia, Pennsylvania 19104-4399, USA
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191
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Batshaw ML, MacArthur RB, Tuchman M. Alternative pathway therapy for urea cycle disorders: twenty years later. J Pediatr 2001; 138:S46-54; discussion S54-5. [PMID: 11148549 DOI: 10.1067/mpd.2001.111836] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Alternative pathway therapy is currently an accepted treatment approach for inborn errors of the urea cycle. This involves the long-term use of oral sodium phenylbutyrate, arginine supplements, or both, depending on the specific enzyme deficiency, and treatment of acute hyperammonemic crises with intravenous sodium benzoate/sodium phenylacetate plus arginine. A review of 20 years of experience with this approach illustrates the strengths and limitations of this treatment. It has clearly decreased the mortality and morbidity from these disorders, but they remain unacceptably high. The medications are generally well tolerated, but severe accidental overdosage has been reported because of the infrequent use of the medication. There is also a difference in their metabolism between newborns and older children that must be addressed in determining dosage. To avoid these complications it is recommended that drug levels in blood be monitored routinely and that very specific treatment protocols and oversight be followed to avoid overdoses. Finally, it must be acknowledged that alternative pathway therapy has limited effectiveness in preventing hyperammonemia and must be combined with effective dietary management. Therefore in children with neonatal-onset disease or in those with very poor metabolic control, liver transplantation should be considered. There should also be the continued search for innovative therapies that may offer a more permanent and complete correction, such as gene therapy.
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Affiliation(s)
- M L Batshaw
- Children's National Medical Center, Washington, DC 20010, USA
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192
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Abstract
Deficiency of any of the five enzymes in the urea cycle results in the accumulation of ammonia and leads to encephalopathy. Episodes of encephalopathy and associated symptoms are unpredictable and, if untreated, are lethal or produce devastating neurologic sequelae in long-term survivors. Although these disorders do not produce liver disease, the consequences of hyperammonemia resemble those seen in patients with hepatic failure or in a transient interference with the urea cycle, as seen in some forms of organic acidemias. Therefore, investigation for hyperammonemia in any infant or child with altered mental status (in the absence of obvious causes, such as trauma, infection, or poisoning) is essential for prompt diagnosis of urea cycle disorders and institution of treatment to avoid brain damage and death. This article addresses the function of the urea cycle and the diagnosis and management of urea cycle disorders.
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Affiliation(s)
- B K Burton
- Division of Genetics, Department of Pediatrics, Northwestern University Medical School, Chicago, Illinois, USA
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193
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Abstract
Successful liver transplantation in a child is often a hard-won victory, requiring all the combined expertise of a dedicated pediatric transplant team. This article outlines the considerable challenges still facing pediatric liver transplant physicians and surgeons. In looking to the future, where should priorities lie to enhance the success already achieved? First, solutions to the donor shortage must be sought aggressively by increasing the use of from split-liver transplants, judicious application of living-donor programs, and increasing the donation rate, perhaps by innovative means. The major immunologic barriers, to successful xenotransplantation make it unlikely that this option will be tenable in the near future. Second, current immunosuppression is nonspecific, toxic, and unable to be individually adjusted to the patient's immune response. The goal of achieving donor-specific tolerance will require new consideration of induction protocols. Developing a clinically applicable method to measure the recipient's immunoreactivity is of paramount importance, for future studies of new immunosuppressive strategies and to address the immediate concern of long-term over-immunosuppression. The inclusion of pediatric patients in new protocols will require the ongoing insistence of pediatric transplant investigators. Third, the current immunosuppressive drugs have a long-term morbidity and mortality of their own. These long-term effects are particularly important in children who may well have decades of exposure to these therapies. There is now some understanding of their long-term renal toxicity and the risk of malignancy. New drugs may obviate renal toxicity, whereas the risk of malignancy is inherent in any nonspecific immunosuppressive regimen. Although progress is being made in preventing and recognizing PTLD, this entity remains an important ongoing concern. The global effect of long-term immunosuppression on the child's growth, development, and intellectual potential is unknown. Of particular concern is the potential for neurotoxicity from the calcineurin inhibitors. Fourth, recurrent disease and new diseases, perhaps potentiated by immunosuppressive drugs, must be considered. Already the recurrence of autoimmune disease and cryptogenic cirrhosis have been documented in pediatric patients. Now, a new lesion, a nonspecific hepatitis, sometimes with positive autoimmune markers, that may progress to cirrhosis has been recognized. It is not known whether this entity is an unusual form of rejection, an unrecognized viral infection, or a response to immunosuppressive drugs themselves. Finally, pediatric transplant recipients, like any other children, must be protected and nourished physically and mentally if they are to fulfill their potential. After liver transplantation the child's growth, intellectual functioning, and psychologic adaptation may all require special attention from parents, teachers, and physicians alike. There is limited understanding of how the enormous physical intervention of a liver transplantation affects a child's cognitive and psychologic function as the child progresses through life. The persons caring for these children have the difficult responsibility of providing services to evaluate these essential measures of children's health over the long term and to intervene if necessary. Part of the transplant physician's our duty to protect and advocate for children is to fight for equal access to health care. In most of the developing world, economic pressures make it impossible to consider liver transplantation a health care priority. In the United States and in other countries with the medical infrastructure to support liver transplantation, however, health care professionals must strive to be sure that the policies governing candidacy for transplantation and allocation of organs are applied justly and uniformly to all children whose lives are threatened by liver disease. In the current regulatory climate that increasingly takes medical decisions out of the hands of physicians, pediatricians must be even more prepared to protect the unique and often complicated needs of children both before and after transplantation. Only in this way can the challenges of the present and the future be met.
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Affiliation(s)
- S V McDiarmid
- Pediatric Liver Transplant Program, University of California Los Angeles Medical Center, Los Angeles, California, USA
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194
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Ye X, Whiteman B, Jerebtsova M, Batshaw ML. Correction of argininosuccinate synthetase (AS) deficiency in a murine model of citrullinemia with recombinant adenovirus carrying human AS cDNA. Gene Ther 2000; 7:1777-82. [PMID: 11083500 DOI: 10.1038/sj.gt.3301303] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Citrullinemia is an autosomal recessive disorder caused by the deficiency of argininosuccinate synthetase (AS). It is characterized by elevated levels of blood citrulline and ammonia, which often results in hyperammonemic coma and early neonatal death in affected children. We have explored the use of adenoviral vectors as a treatment modality in a murine model of citrullinemia, the Ass mouse. The Ass mouse has no endogenous AS activity due to a targeted interruption of the AS gene. Homozygous mutant animals develop high levels of blood citrulline, become hyperammonemic, and die within 24-48 h after birth. We demonstrated that the neonatal crisis in Ass mice can be ameliorated by the injection of a recombinant adenovirus carrying human AS cDNA (Ad.CMVhAS) within hours after birth. The average life span of the virus-treated animals was extended from 30 +/- 9.5 h to 16.1 +/- 1.6 days. A second viral infusion 14 days after the first dose further prolonged the life span to an average of 36.2 +/- 7.0 days, and to 40.7 +/- 3.3 days with a concurrent daily injection of arginine and sodium benzoate. Significantly increased liver AS activity (47.3 +/- 7.9% of normal) was detected 24 h after viral infusion, which reached peak levels (80-90% of normal) at day 7 and decreased to about 20% of normal within 2-3 weeks after viral infusion. Southern blot analysis of liver DNA revealed a transduction efficiency of about one viral genome per hepatocyte 7 days after viral infusion and a gradual decrease of viral genome per cell parallel to the loss of liver AS activity. Plasma glutamine levels were partially normalized in virus-treated animals and were completely normalized in animals receiving Ad.CMVhAS concurrently with alternative pathway therapy. Plasma arginine levels were also partially normalized. Together, these results demonstrated that the recombinant adenovirus was capable of conferring AS activity in the liver of the recipient animals within 24 h, and the neonatal crisis of hyperammonemia could be averted by acute treatment with the AS containing adenovirus.
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Affiliation(s)
- X Ye
- Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA
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195
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D'Hooge R, Marescau B, Qureshi IA, De Deyn PP. Impaired cognitive performance in ornithine transcarbamylase-deficient mice on arginine-free diet. Brain Res 2000; 876:1-9. [PMID: 10973586 DOI: 10.1016/s0006-8993(00)02589-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Sparse-fur (spf) mice are a model for the congenital deficiency of ornithine transcarbamylase (OTC), the most common inborn error of urea synthesis in man. In this study, performance of clinically stable spf and control mice (8-10-weeks-old) on two learning tests was assessed under normal Arg(+) or arginine-free Arg(-) diet conditions. Used as an indicator of the metabolic status of the animals, plasma ammonia concentrations were significantly higher in spf than in controls on normal diet, and increased even more during the Arg(-) diet episode. Behaviourally, we found no difference in passive avoidance learning between control and spf mice on Arg(+) diet, whereas in spf mice receiving Arg(-) diet during training, retention performance was significantly reduced. In the hidden-platform water maze, spf mice on Arg(+) diet only showed decreased swimming velocity compared to controls. In mice on Arg(-) diet during the first week of acquisition training, performance on acquisition and retention (probe) trials showed that spf mice experienced more difficulties in actually locating the platform. Visible-platform control experiments only showed a reduction in swimming velocity in spf mice on either diet. We conclude that cognitive performance is impaired in spf mice as a consequence of Arg(-) diet-induced neurochemical alterations.
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Affiliation(s)
- R D'Hooge
- Laboratory of Neurochemistry and Behaviour, Born-Bunge Foundation, Antwerp University, Universiteitsplein 1, B-2610, Wilrijk, Belgium.
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196
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Lee B, Yu H, Jahoor F, O'Brien W, Beaudet AL, Reeds P. In vivo urea cycle flux distinguishes and correlates with phenotypic severity in disorders of the urea cycle. Proc Natl Acad Sci U S A 2000; 97:8021-6. [PMID: 10869432 PMCID: PMC16663 DOI: 10.1073/pnas.140082197] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Urea cycle disorders are a group of inborn errors of hepatic metabolism that result in often life-threatening hyperammonemia and hyperglutaminemia. Clinical and laboratory diagnosis of partial deficiencies during asymptomatic periods is difficult, and correlation of phenotypic severity with either genotype and/or in vitro enzyme activity is often imprecise. We hypothesized that stable isotopically determined in vivo rates of total body urea synthesis and urea cycle-specific nitrogen flux would correlate with both phenotypic severity and carrier status in patients with a variety of different enzymatic deficiencies of the urea cycle. We studied control subjects, patients, and their relatives with different enzymatic deficiencies affecting the urea cycle while consuming a low protein diet. On a separate occasion the subjects either received a higher protein intake or were treated with an alternative route medication sodium phenylacetate/benzoate (Ucephan), or oral arginine supplementation. Total urea synthesis from all nitrogen sources was determined from [(18)O]urea labeling, and the utilization of peripheral nitrogen was estimated from the relative isotopic enrichments of [(15)N]urea and [(15)N]glutamine during i.v. co-infusions of [5-(amide)(15)N]glutamine and [(18)O]urea. The ratio of the isotopic enrichments of (15)N-urea/(15)N-glutamine distinguished normal control subjects (ratio = 0.42 +/- 0.06) from urea cycle patients with late (0.17 +/- 0.03) and neonatal (0.003 +/- 0.007) presentations irrespective of enzymatic deficiency. This index of urea cycle activity also distinguished asymptomatic heterozygous carriers of argininosuccinate synthetase deficiency (0. 22 +/- 0.03), argininosuccinate lyase deficiency (0.35 +/- 0.11), and partial ornithine transcarbamylase deficiency (0.26 +/- 0.06) from normal controls. Administration of Ucephan lowered, and arginine increased, urea synthesis to the degree predicted from their respective rates of metabolism. The (15)N-urea/(15)N-glutamine ratio is a sensitive index of in vivo urea cycle activity and correlates with clinical severity. Urea synthesis is altered by alternative route medications and arginine supplementation to the degree that is to be expected from theory. This stable isotope protocol provides a sensitive tool for evaluating the efficacy of therapeutic modalities and acts as an aid to the diagnosis and management of urea cycle patients.
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Affiliation(s)
- B Lee
- Departments of Molecular and Human Genetics and Pediatrics and Children's Nutrition Research Center, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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197
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Muñoz MD, Monfort P, Gaztelu JM, Felipo V. Hyperammonemia impairs NMDA receptor-dependent long-term potentiation in the CA1 of rat hippocampus in vitro. Neurochem Res 2000; 25:437-41. [PMID: 10823575 DOI: 10.1023/a:1007547622844] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Hyperammonemia is considered the main factor responsible for the neurological and cognitive alterations found in hepatic encephalopathy and in patients with congenital deficiencies of the urea cycle enzymes. The underlying mechanisms remain unclear. Chronic moderate hyperammonemia reduces nitric oxide-induced activation of soluble guanylate cyclase and glutamate-induced formation of cGMP. NMDA receptor-associated transduction pathways, including activation of soluble guanylate cyclase, are involved in the induction of long-term potentiation (LTP), a phenomenon that is considered to be the molecular basis for some forms of memory and learning. Using an animal model we show that chronic hyperammonemia significantly reduces the degree of long-term potentiation induced in the CA1 of hippocampus slices (200% increase in control and 50% increase in slices of hyperammonemic animals). Also, addition of 1 mM ammonia impaired the maintenance of non-decremental LTP. The LTP impairment could be involved in the intellectual impairment present in chronic hepatocerebral disorders associated with hyperammonemia.
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Affiliation(s)
- M D Muñoz
- Neurología Experimental (Unidad Asociada al CSIC), Departamento de Investigación, Hospital Ramón y Cajal, Madrid, Spain.
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198
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Butterworth RF. Evidence for forebrain cholinergic neuronal loss in congenital ornithine transcarbamylase deficiency. Metab Brain Dis 2000; 15:83-91. [PMID: 10885542 DOI: 10.1007/bf02680015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Congenital ornithine transcarbamylase (OTC) deficiency in humans results in failure to thrive, hypotonia, seizures and mental retardation. Neuropathologic evaluation reveals significant cerebral cortical atrophy, delayed myelination and Alzheimer type II astrocytosis. Using an animal model of congenital OTC deficiency, the sparse fur (spf) mouse, studies reveal convincing evidence of a loss of forebrain cholinergic neurons in this condition. Evidence includes (i) reduced activities of the cholinergic nerve terminal enzyme choline acetyltransferase (ChAT), (ii) a 25% loss of ChAT immunostaining, (iii) reduced high affinity transport of [3H]choline by cortical synaptosomes and (iv) a selective reduction in densities of presynaptic muscarinic M2 binding sites, in spf mouse brain compared to controls. A partial correction of the cholinergic deficit was observed following treatment with acetyl-L-carnitine. Possible mechanisms responsible for cholinergic neuronal loss in congenital OTC deficiency include decreased synthesis of the ChAT substrate acetyl CoA, impaired cerebral energy metabolism and NMDA receptor-mediated excitotoxicity. Loss of forebrain cholinergic neurons is consistent with the severe cognitive impairment characteristic of congenital OTC deficiency.
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Affiliation(s)
- R F Butterworth
- Neuroscience Research Unit, CHUM/Hôpital Saint-Luc, Montreal, Quebec, Canada.
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199
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Aguilar MA, Miñarro J, Felipo V. Chronic moderate hyperammonemia impairs active and passive avoidance behavior and conditional discrimination learning in rats. Exp Neurol 2000; 161:704-13. [PMID: 10686089 DOI: 10.1006/exnr.1999.7299] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The cerebral dysfunction associated with hepatic encephalopathy is generally considered to have hyperammonemia as one of its main causes. Hyperammonemia impairs the neuronal glutamate-nitric oxide-cyclic GMP pathway and the induction of NMDA receptor-dependent long-term potentiation in the hippocampus. We studied the performance of pre/neonatally and postnatally exposed rats to hyperammonemia on active avoidance, passive avoidance, and conditional discrimination tasks. Pre/neonatal hyperammonemia slowed learning of active avoidance behaviors and impaired memory for the passive avoidance task while postnatal hyperammonemia impaired learning on the conditional discrimination task. Hyperammonemia thus may produce cognitive disturbances that relate to the effects of ammonia on the neuronal glutamate-nitric oxide-cyclic GMP pathway.
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Affiliation(s)
- M A Aguilar
- Area de Psicobiología, Facultad de Psicología, Universitat de Valencia., Aptdo. 22109, Valencia, 46071, Spain
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200
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Batshaw ML, Robinson MB, Ye X, Pabin C, Daikhin Y, Burton BK, Wilson JM, Yudkoff M. Correction of ureagenesis after gene transfer in an animal model and after liver transplantation in humans with ornithine transcarbamylase deficiency. Pediatr Res 1999; 46:588-93. [PMID: 10541323 DOI: 10.1203/00006450-199911000-00016] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We report effects of gene transfer and liver transplantation on urea synthesis in ornithine transcarbamylase deficiency (OTCD). We measured the formation of [15N] urea after oral administration of 15NH4Cl in two girls with partial OTCD before and after liver transplantation. Ureagenesis was less than 20% of that observed in controls before transplantation, and was normalized afterward. Studies performed on the OTCD sparse fur (spf/Y) mouse showed discordance between OTC enzyme activity and ureagenesis with modest increases in OTC enzyme activity after gene transfer resulting in significant improvement in ureagenesis. This study suggests that both liver transplantation and gene therapy may be effective in improving ureagenesis in OTCD.
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Affiliation(s)
- M L Batshaw
- Children's National Medical Center, Washington, DC 20010, USA
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