[Urea cycle disorders in adult patients]

[Vomiting associated with weight stagnation and convulsions: urea cycle disorder should be suspected]

Dans certaines maladies métaboliques héréditaires, les vomissements peuvent apparaître comme un symptôme étant au premier plan, en particulier les anomalies du cycle de l'urée, qui sont habituellement diagnostiqués en période néonatale ou dans l'enfance. Nous en rapportons un cas de révélation tardive par un état de mal convulsif. Nous rapportons le cas d'une patiente âgée de 13 ans, qui a été hospitalisé pour prise en charge d'un état de mal convulsif et un retard staturo-pondéral. L'interrogatoire a révélé la notion de vomissements chroniques avec des troubles du comportement, ralentissement idéomoteur et céphalées. L'examen a trouvé une ataxie. La ponction lombaire et le scanner cérébral sont normaux. Une ammoniémie nettement augmentée est mise en évidence 75 micromoles/l (11-50). La chromatographie des acides aminés dans le sang a montré une augmentation de la glutamine et de l'alanine, La chromatographie des acides aminés dans les urines a montré une augmentation des acides aminés basiques évoquant un déficit du cycle de l'urée par déficit de l'enzyme Argininosuccinate lyase. La patiente a été traité en urgence par une alimentation exclusivement glucidolipidique, et par benzoate de sodium permettant une amélioration de l'état clinique, et une reprise de poids. Les crises convulsives ont été maîtrisées par le phénobarbital. L'enquête familiale a trouvé une sœur âgée de 20 ans suivie depuis l'âge de 3 ans pour crises convulsives traité par le phénobarbital dont le bilan métabolique réalisé dans notre service a objectivé la même anomalie du cycle de l'urée que sa sœur. A tout âge, devant une encéphalopathie avec épilepsie, vomissement, stagnation pondérale et hyperammoniémie, il faut penser à un déficit du cycle de l'urée. Le diagnostic est très souvent posé lors d'un accès neuro-digestif aigue associant vomissements, troubles de conscience et/ou crises convulsives.

Ex Vivo Enteroids Recapitulate In Vivo Citrulline Production in Mice

Background

The endogenous production of arginine relies on the synthesis of citrulline by enteral ornithine transcarbamylase (OTC). Mutations in the gene coding for this enzyme are the most frequent cause of urea cycle disorders. There is a lack of correlation between in vivo metabolic function and DNA sequence, transcript abundance, or in vitro enzyme activity.

Objective

The goal of the present work was to test the hypothesis that enteroids, a novel ex vivo model, are able to recapitulate the in vivo citrulline production of wild-type (WT) and mutant mice.

Methods

Six-week-old male WT and OTC-deficient mice [sparse fur and abnormal skin (spf-ash) mutation] were studied. Urea and citrulline fluxes were determined in vivo, and OTC abundance was measured in liver and gut tissue. Intestinal crypts were isolated and cultured to develop enteroids. Ex vivo citrulline production and OTC abundance were determined in these enteroids.

Results

Liver OTC abundance was lower (mean ± SE: 0.16 ± 0.01 compared with 1.85 ± 0.18 arbitrary units; P < 0.001) in spf-ash mice than in WT mice, but there was no difference in urea production. In gut tissue, OTC was barely detectable in mutant mice; despite this, a lower but substantial citrulline production (67 ± 3 compared with 167 ± 8 µmol · kg-1 · h-1; P < 0.001) was shown in the mutant mice. Enteroids recapitulated the in vivo findings of a very low OTC content accompanied by a reduced citrulline production (1.07 ± 0.20 compared with 4.64 ± 0.44 nmol · µg DNA-1 · d-1; P < 0.001).

Conclusions

Enteroids recapitulate in vivo citrulline production and offer the opportunity to study the regulation of citrulline production in a highly manipulable system.

Ethane-Bridged Bisporphyrin Conformational Changes As an Effective Analytical Tool for Nonenzymatic Detection of Urea in the Physiological Range

Conformational switching induced in ethane-bridged bisporphyrins was used as a sensitive transduction method for revealing the presence of urea dissolved in water via nonenzymatic approach. Bisporphyrins were deposited on solid quartz slides by means of the spin-coating method. Molecular conformations of Zn and Ni monometalated bis-porphyrins were influenced by water solvated urea molecules and their fluorescence emission was modulated by the urea concentration. Absorption, fluorescence and Raman spectroscopies allowed the identification of supramolecular processes, which are responsible for host-guest interaction between the active layers and urea molecules. A high selectivity of the sensing mechanism was highlighted upon testing the spectroscopic responses of bis-porphyrin films to citrulline and glutamine used as interfering agents. Additionally, potential applicability was demonstrated by quantifying the urea concentration in real physiological samples proposing this new approach as a valuable alternative analytical procedure to the traditionally used enzymatic methods.

Psychiatric adult-onset of urea cycle disorders: A case-series

Adult onset urea cycle disorders (UCD) may present with psychiatric symptoms, occasionally as the initial presentation. We aimed to describe the characteristics of patients presenting with a psychiatric adult-onset of UCDs, to discuss which signs could suggest this diagnosis in such a situation, and to determine which tests should be conducted. A survey of psychiatric symptoms occurring in teenagers or adults with UCD was conducted in 2010 among clinicians involved in the French society for the study of inborn errors of metabolism (SFEIM). Fourteen patients from 14 to 57 years old were reported. Agitation was reported in 10 cases, perseveration in 5, delirium in 4, and disinhibition in 3 cases. Three patients had pre-existing psychiatric symptoms. All patients had neurological symptoms associated with psychiatric symptoms, such as ataxia or dysmetria, psychomotor slowing, seizures, or hallucinations. Fluctuations of consciousness and coma were reported in 9 cases. Digestive symptoms were reported in 7 cases. 9 patients had a personal history suggestive of UCD. The differential diagnoses most frequently considered were exogenous intoxication, non-convulsive status epilepticus, and meningoencephalitis. Hyperammonemia (180-600 μmol/L) was found in all patients. The outcome was severe: mechanical ventilation was required in 10 patients, 5 patients died, and only 4 patients survived without sequelae. Adult onset UCDs can present with predominant psychiatric symptoms, associated with neurological involvement. These patients, as well as patients presenting with a suspicion of intoxication, must have UCD considered and ammonia measured without delay.

[Diagnosis and treatment of urea cycle disorders in adult patients]

Urea cycle disorders (UCDs) are inborn errors of metabolism in which the clinical picture is mostly due to ammonia intoxication. UCD onset may be observed at any age. Acute decompensations of UCDs include neuro-psychiatric symptoms such as headache, confusion, convulsions, ataxia, agitation or delirium, as well as digestive symptoms, namely nausea and vomiting along with abdominal pain. Acute decompensations may lead to an irreversible coma in the absence of specific therapy. The first step is to measure promptly ammonemia in such patients, and start appropriate therapy on an emergency basis.

Hyperammonemia due to urea cycle disorders: a potentially fatal condition in the intensive care setting

Disorders of the urea cycle are secondary to a defect in the system that converts ammonia into urea, resulting in accumulation of ammonia and other products. This results in encephalopathy, coma, and death if not recognized and treated rapidly. Late-onset urea cycle disorders may be precipitated by acute disease and can be difficult to recognize because patients are already ill. Diagnosis of urea cycle disorders is based on clinical suspicion and determination of blood ammonia in suspected patients with neurological symptoms in the intensive care setting. Treatment is based on the removal of ammonia by dialysis or hemofiltration, reduction of the catabolic state, abolishment of nitrogen administration, and use of pharmacological nitrogen scavenging agents.

Late-onset ornithine carbamoyltransferase deficiency accompanying acute pancreatitis and hyperammonemia

Hyperammonemia related to urea cycle disorders is a rare cause of potentially fatal encephalopathy that is encountered in intensive care units (ICUs). Left undiagnosed, this condition may manifest irreversible neuronal damage. However, timely diagnosis and treatment initiation can be facilitated simply by increased awareness of the ICU staff. Here, we describe a patient with acute severe pancreatitis who developed hyperammonemia and encephalopathy without liver disease. Urea cycle disorder was suspected and hemodialysis was initiated. Following reduction of ammonia levels, subsequent treatment included protein restriction and administration of arginine and sodium benzoate. The patient was discharged to home after 47 days with plasma ammonia within normal range and without neurological symptoms. In clinical care settings, patients with neurological symptoms unexplained by the present illness should be assessed for serum ammonia levels to disclose any urea cycle disorders to initiate timely treatment and improve outcome.

Current pathogenetic aspects of hepatic encephalopathy and noncirrhotic hyperammonemic encephalopathy

Hepatic encephalopathy is a medical phenomenon that is described as a neuropsychiatric manifestation of chronic or acute liver disease that is characterized by psychomotor, intellectual and cognitive abnormalities with emotional/affective and behavioral disturbances. This article focuses on the underlying mechanisms of the condition and the differences between hepatic encephalopathy and noncirrhotic hyperammonemic encephalopathy. Hepatic encephalopathy is a serious condition that can cause neurological death with brain edema and intracranial hypertension. It is assumed that approximately 60%-80% of patients with liver cirrhosis develop hepatic encephalopathy. This review explores the complex mechanisms that lead to hepatic encephalopathy. However, noncirrhotic hyperammonemic encephalopathy is not associated with hepatic diseases and has a completely different etiology. Noncirrhotic hyperammonemic encephalopathy is a severe occurrence that is connected with multiple pathogeneses.

[Treatable hereditary neuro-metabolic diseases]

Hereditary metabolic diseases may appear during adolescence or young adulthood, revealed by an apparently unexplained neurological or psychiatric disorder. Certain metabolic diseases respond to specific treatments and should be identified early, particularly in emergency situations where rapid introduction of a treatment can avoid fatal outcome or irreversible neurological damage. The main diseases leading to an acute neurological syndrome in the adult are urea cycle disorders, homocysteine metabolisms disorders and porphyria. More rarely, Wilson's disease, aminoacid diseases, organic aciduria, or pyruvate dehydrogenase deficiency, beta-oxidation disordes or biotin metabolism may be involved. Most emergency situations can be screen correctly with simple tests (serum ammonia, homocysteine, lactate, urinary prophyrines, acylcarnitine pattern, amino acid and organic acid chromatography). For chronic situations, the main treatable diseases are Wilson's disease, homocysteine, cerebrotendinous xanthomatosis, Refsum's disease, vitamin E deficiency, Gaucher's disease, Fabry's disease, and neurotransmitter metabolism disorders. We present treatable metabolic disorders as a function of the different clinical situations observed in adults.

[Dietary advice for treatment of inborn errors of metabolism in adult neurology: principes and limitations]

Special diets can be an efficient treatment for certain inborn errors of metabolism. Regimens applicable in adult neurology include low protein diet (phenylketonuria, homocystinuria, urea cycle disorders, organic acidurias), low fatty acid diets (fatty acid B oxidation defects, adrenomyeloneuropathy, Refsum's disease) and ketogenic diet (pyruvate dehydrogenase deficiency, glucose transporter (GLUT1) deficiency, refractory epilepsy). Although, these regimens can be very efficient in some instances, withdrawal and nutrient deficiencies are major problems encountered.