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

Mollicutes-related infections in thoracic surgery including lung and heart transplantation: A systematic review

BACKGROUND

Urogenital Mollicutes, that is, Mycoplasma hominis and Ureaplasma spp., can colonize the urogenital tract. While urogenital colonization is frequent, infections are rare but should not be missed. Furthermore, extragenital infections are even rarer. Over the past years, they have been increasingly documented as a cause of hyperammonemia syndrome (HS) and post-surgical infections. We review the literature on studies focused on post-surgical infections and HS involving urogenital Mollicutes after thoracic surgery including lung (LTR) and heart (HTR) transplantation.

METHODS

A systematic review was performed by searching PubMed/Medline case reports, case series, cohort studies, and clinical trials. Cases of infections and HS by urogenital Mollicutes after HTR and LTR transplantations were reported.

RESULTS

Overall, urogenital Mollicutes were associated with 15 HS, 31 infections in HTR and LTR, and 18 post-thoracic surgical infections in another context. Post-surgical infections were reported in all contexts. They were mainly due to M hominis, the only species that could cultivate on standard enriched agar forming pinpoint colonies after 3-5 days of incubation. Microbiologists should be prompted to pinpoint colonies even if the examination of Gram-staining is negative. The patients' management required surgical treatment and antimicrobials, almost always tetracyclines and/or fluoroquinolones. Conversely, HS occurred almost exclusively in bilateral LTR and is more likely due to Ureaplasma spp. As Ureaplasma spp. do not cultivate on standard media, the microbiological diagnosis was performed using molecular methods.

CONCLUSIONS

Infections involving urogenital Mollicute should be considered in LTR with HS. The overall rate of mortality is high and might be due in part to delay in etiologic diagnosis. Post-surgical infections were reported in all contexts. The route of contamination with Mollicutes remains unknown in HTR and non-transplant surgery, but evidence of transmission from donors has been documented for LTR.

The Reciprocal Interplay between Infections and Inherited Metabolic Disorders

Infections represent the main cause of acute metabolic derangements and/or the worsening of the clinical course of many inherited metabolic disorders (IMDs). The basic molecular mechanisms behind the role of infections in these conditions have not been completely clarified. This review points out the different mechanisms behind the relationship between IMDs and infections, providing an overview of this still-under-investigated area. Classically, infections have been considered as the consequence of a compromised immune system due to a biochemical defect of energy production. An adjunctive pathogenetic mechanism is related to a genetically altered protein-attached glycans composition, due to congenital glycosilation defects. In addition, a dietary regimen with a reduced intake of both micro- and macronutrients can potentially compromise the ability of the immune system to deal with an infection. There is recent pre-clinical evidence showing that during infections there may be a disruption of substrates of various metabolic pathways, leading to further cellular metabolic alteration. Therefore, infective agents may affect cellular metabolic pathways, by mediation or not of an altered immune system. The data reviewed here strongly suggest that the role of infections in many types of IMDs deserves greater attention for a better management of these disorders and a more focused therapeutic approach.

Drug-induced hyperammonaemia

Hyperammonaemia (HA) as a consequence of numerous primary or secondary causes, gives rise to clinical manifestations due to its toxic effects on the brain. The neurological consequences broadly reflect the ammonia level, duration and age, with paediatric patients being more susceptible. Drug-induced HA may arise due to either decreased ammonia elimination or increased production. This is associated most frequently with use of valproate and presents a dilemma between ongoing therapeutic need, toxicity and the possibility of an alternative cause. As there is no specific test for drug-induced HA, prompt discussion with a metabolic physician is recommended, as the neurotoxic effects are time-dependent. Specific guidelines for managing drug-induced HA have yet to be published and hence the treatment approach outlined in this review reflects that outlined in relevant urea cycle disorder guidelines.

S100B Protein but Not 3-Nitrotyrosine Positively Correlates with Plasma Ammonia in Patients with Inherited Hyperammonemias: A New Promising Diagnostic Tool?

Individuals with inherited hyperammonemias often present developmental and intellectual deficiencies which are likely to be exaggerated by hyperammonemia episodes in long-term outcomes. In order to find a new, systemic marker common to the course of congenital hyperammonemias, we decided to measure the plasma level of S100 calcium-binding protein B (S100B), which is associated with cerebral impairment. Further, we analyzed three mechanistically diverged but linked with oxidative-nitrosative stress biochemical parameters: 3-nitrotyrosine (3-NT), a measure of plasma proteins' nitration; advanced oxidation protein products (AOPP), a measure of protein oxidation; and glutathione peroxidase (GPx) activity, a measure of anti-oxidative enzymatic capacity. The plasma biomarkers listed above were determined for the first time in congenital hyperammonemia. Also, the level of pro- and anti-inflammatory mediators (i.e., IL-12, IL-6, IL-8, TNF-α, IL-1β, and IL-10) and chemokines (IP-10, MCP-1, MIG, and RANTES) were quantified. S100B was positively correlated with plasma ammonia level, while noticeable levels of circulating 3-NT in some of the patients' plasma did not correlate with ammonia concentration. Overall, the linear correlation between ammonia and S100B but not standard oxidative stress-related markers offers a unique perspective for the future identification and monitoring of neurological deficits risk-linked with hyperammonemia episodes in patients with inherited hyperammonemias. The S100B measure may support the development of therapeutic targets and clinical monitoring in these disorders.

UK National audit of the measurement of ammonia

BACKGROUND

Severe hyperammonaemia is associated with significant morbidity and mortality. Rapid analysis and reporting of ammonia results is essential to prevent patient harm. The aim was to investigate the laboratory sample acceptance criteria, ammonia analysis and the reporting of ammonia results.

METHODS

A questionnaire was distributed to clinical biochemistry laboratories in the United Kingdom. The results were collated and compared to updated best practice guidelines on hyperammonaemia issued by the Metabolic Biochemistry Network (MetBio.net).

RESULTS

Seventy-six laboratories responded to the audit questionnaire. Although 83% laboratories are aware of the updated MetBio.net hyperammonaemia guidelines, most laboratories continue to reject samples for ammonia that are 'too old' for analysis (64%), haemolysed (72%) or not sent on ice (24%). Rapid ammonia analysis is available in 96% laboratories and all laboratories offer ammonia analysis on a 24/7 basis. Nearly all laboratories had implemented critical phoning limits for ammonia.

CONCLUSIONS

Laboratories are rejecting samples for ammonia analysis that have not been collected/transported in an optimal manner. Laboratories should review their sample acceptance criteria for ammonia and accept all samples in order to avoid delaying the diagnosis and management of hyperammonaemia.

Multiple Asparaginase Infusions Cause Increasingly Severe Acute Hyperammonemia

Adverse reactions during and shortly after infusing asparaginase for the treatment of acute lymphoblastic leukemia can increase in severity with later doses, limiting further use and increasing relapse risk. Although asparaginase is associated with hyperammonemia, the magnitude of the increase in serum ammonia immediately after the infusion and in response to multiple infusions has not been examined. The concurrence of hyperammonemia and infusion reactions was studied using weaned juvenile pigs that received 12 infusions of Erwinia asparaginase (Erwinase; 1250 U/kg) over 28 days, with two 5-day recovery periods without asparaginase after the eighth and eleventh doses. Infusion reactions and prolonged hyperammonemia (>50 µM ammonia 48 h after the infusion) began after the fourth dose and increased with later doses. Dense sampling for 60 min revealed an acute phase of hyperammonemia that peaked within 20 min after starting the first infusion (298 + 62 µM) and lasted less than 1 h, without apparent symptoms. A pronounced acute hyperammonemia after the final infusion (1260 + 250 µM) coincided with severe symptoms and one mortality during the infusion. The previously unrecognized acute phase of hyperammonemia associated with asparaginase infusion coincides with infusion reactions. The juvenile pig is a translational animal model for understanding the causes of acute and chronic hyperammonemia, differentiating from hypersensitivity reactions, and for improving infusion protocols to reduce acute hyperammonemia and to allow the continued use of asparaginase.

A 36-year-old Man with Repeated Short-term Transient Hyperammonemia and Impaired Consciousness with a Confirmed Carbamoyl Phosphate Synthase 1 Gene Monoallelic Mutation

A 36-year-old man experienced severely impaired consciousness twice after drinking because of hyperammonemia. No abnormal blood tests were found other than ammonia levels. However, magnetic resonance imaging (MRI) showed atrophy of the brain parenchyma. One the second occasion, the patient suffered severe impairment of consciousness, and because of seizures and glossoptosis, mechanical ventilation was started. Urea cycle disorders (UCDs) were assumed to be involved. Genetic testing revealed a monoallelic mutation of the carbamoyl phosphate synthase 1 (CPS1) gene. When transient hyperammonemia of unknown cause occurs repeatedly in adults, an active investigation for UCDs should be conducted.

Hepatic Encephalopathy and Melatonin

Hepatic encephalopathy (HE) is a severe metabolic syndrome linked with acute/chronic hepatic disorders. HE is also a pernicious neuropsychiatric complication associated with cognitive decline, coma, and death. Limited therapies are available to treat HE, which is formidable to oversee in the clinic. Thus, determining a novel therapeutic approach is essential. The pathogenesis of HE has not been well established. According to various scientific reports, neuropathological symptoms arise due to excessive accumulation of ammonia, which is transported to the brain via the blood–brain barrier (BBB), triggering oxidative stress and inflammation, and disturbing neuronal-glial functions. The treatment of HE involves eliminating hyperammonemia by enhancing the ammonia scavenging mechanism in systemic blood circulation. Melatonin is the sole endogenous hormone linked with HE. Melatonin as a neurohormone is a potent antioxidant that is primarily synthesized and released by the brain’s pineal gland. Several HE and liver cirrhosis clinical studies have demonstrated impaired synthesis, secretion of melatonin, and circadian patterns. Melatonin can cross the BBB and is involved in various neuroprotective actions on the HE brain. Hence, we aim to elucidate how HE impairs brain functions, and elucidate the precise molecular mechanism of melatonin that reverses the HE effects on the central nervous system.

Undifferentiated non-hepatic hyperammonemia in the ICU: Diagnosis and management

Hyperammonemia occurs frequently in the critically ill but is largely confined to patients with hepatic dysfunction or failure. Non-hepatic hyperammonemia (NHHA) is far less common but can be a harbinger of life-threatening diagnoses that warrant timely identification and, sometimes, empiric therapy to prevent seizures, status epilepticus, cerebral edema, coma and death; in children, permanent cognitive impairment can result. Subsets of patients are at particular risk for developing NHHA, including the organ transplant recipient. Unique etiologies include rare infections, such as with Ureaplasma species, and unmasked inborn errors of metabolism, like urea cycle disorders, must be considered in the critically ill. Early recognition and empiric therapy, including directed therapies towards these rare etiologies, is crucial to prevent catastrophic demise. We review the etiologies of NHHA and highlight the first presentation of it associated with a concurrent Ureaplasma urealyticum and Mycoplasma hominis infection in a previously healthy individual with polytrauma. Based on this clinical review, a diagnostic and treatment algorithm to identify and manage NHHA is proposed.

Hyperammonemia of unknown cause in a young postpartum woman: a case report

Background

Hyperammonemia is a medical condition described as increased or elevated serum ammonia levels. High serum levels of ammonia can cause neurotoxicity. Sudden onset severe hyperammonemia may cause severe encephalopathy with brain damage. It can result in cerebral edema, emesis, seizures, hypotonia, and death. We report a young postpartum woman who had a sudden rise in serum ammonia levels after vaginal delivery.

Case presentation

A 24-year-old, married, postpartum Pakistani woman was admitted to the intensive care unit through the emergency department, with complaints of fever, severe abdominal pain with distension, and altered levels of consciousness. The patient had a medical history of spontaneous vaginal delivery 2 weeks before this hospital admission, after which she gradually developed the above symptoms. However, the patient’s past medical history was unremarkable with no hepatic disease, but her investigations revealed a progressive rise in serum ammonia levels. In the intensive care unit, she developed generalized tonic–clonic seizures. This was followed by a coma, tonsillar herniation, and death.

Conclusion

Postpartum hyperammonemia is a rare entity. It is a critical illness and must be evaluated for underlying metabolic disorders. Early diagnosis and treatment may result in better outcomes and reduced mortality among postpartum women with hyperammonemia.

Treatment of Hyperammonemia by Transplanting a Symbiotic Pair of Intestinal Microbes

Hyperammonemia is a deleterious and inevitable consequence of liver failure. However, no adequate therapeutic agent is available for hyperammonemia. Although recent studies showed that the pharmabiotic approach could be a therapeutic option for hyperammonemia, its development is clogged with poor identification of etiological microbes and low transplantation efficiency of candidate microbes. In this study, we developed a pharmabiotic treatment for hyperammonemia that employs a symbiotic pair of intestinal microbes that are both able to remove ammonia from the surrounding environment. By a radioactive tracing experiment in mice, we elucidated how the removal of ammonia by probiotics in the intestinal lumen leads to lower blood ammonia levels. After determination of the therapeutic mechanism, ammonia-removing probiotic strains were identified by high-throughput screening of gut microbes. The symbiotic partners of ammonia-removing probiotic strains were identified by screening intestinal microbes of a human gut, and the pairs were administrated to hyperammonemic mice to evaluate therapeutic efficacy. Blood ammonia was in a chemical equilibrium relationship with intestinal ammonia. Lactobacillus reuteri JBD400 removed intestinal ammonia to shift the chemical equilibrium to lower the blood ammonia level. L. reuteri JBD400 was successfully transplanted with a symbiotic partner, Streptococcus rubneri JBD420, improving transplantation efficiency 2.3×10³ times more compared to the sole transplantation while lowering blood ammonia levels significantly. This work provides new pharmabiotics for the treatment of hyperammonemia as well as explains its therapeutic mechanism. Also, this approach provides a concept of symbiotic pairs approach in the emerging field of pharmabiotics.

Nonhepatic Hyperammonemia With Septic Shock: Case and Review of Literature

Elevated ammonia levels lead to cerebral edema, encephalopathy, seizures, coma, and death. Hyperammonemia is primarily associated with liver disease; however, there are rare cases without liver disease. Noncirrhotic hyperammonemia is primarily due to increased production and/or decreased elimination of ammonia. We present a rare case of a 35-year-old female with severe acute noncirrhotic hyperammonemia associated with gram-negative septic shock and a suspected undiagnosed partial urea cycle enzyme deficiency. She had elevated blood and urine amino acid levels speculated to be due to an underlying urea cycle defect, which was unmasked in the setting of septic shock with urea splitting bacteria leading to severely elevated ammonia levels. Ammonia levels were rapidly corrected with hemodialysis, as other conventional treatments failed. We highlight the importance of considering noncirrhotic causes of hyperammonemia in patients with elevated ammonia levels and intact liver function. Prompt treatment should begin with reducing the catabolic state, nitrogen scavenging, replacing urea cycle substrates, decreasing intestinal absorption, and augmented removal of ammonia with renal replacement therapy.

Past Experiences for Future Applications of Metabolomics in Critically Ill Patients with Sepsis and Septic Shocks

A disruption of several metabolic pathways in critically ill patients with sepsis indicates that metabolomics might be used as a more precise tool for sepsis and septic shock when compared with the conventional biomarkers. This article provides information regarding metabolomics studies in sepsis and septic shock patients. It has been shown that a variety of metabolomic pathways are altered in sepsis and septic shock, including amino acid metabolism, fatty acid oxidation, phospholipid metabolism, glycolysis, and tricarboxylic acid cycle. Based upon this comprehensive review, here, we demonstrate that metabolomics is about to change the world of sepsis biomarkers, not only for its utilization in sepsis diagnosis, but also for prognosticating and monitoring the therapeutic response. Additionally, the future direction regarding the establishment of studies integrating metabolomics with other molecular modalities and studies identifying the relationships between metabolomic profiles and clinical characteristics to address clinical application are discussed in this article. All of the information from this review indicates the important impact of metabolomics as a tool for diagnosis, monitoring therapeutic response, and prognostic assessment of sepsis and septic shock. These findings also encourage further clinical investigations to warrant its use in routine clinical settings.

Influence of food on pharmacokinetics and pharmacodynamics of 4-phenylbutyrate in patients with urea cycle disorders

Urea cycle disorders (UCDs), inborn errors of hepatocyte metabolism, cause hyperammonemia and lead to neurocognitive deficits, coma, and even death. Sodium 4-phenylbutyrate (NaPB), a standard adjunctive therapy for UCDs, generates an alternative pathway of nitrogen deposition through glutamine consumption. Administration during or immediately after a meal is the approved usage of NaPB. However, we previously found that preprandial oral administration enhanced its potency in healthy adults and pediatric patients with intrahepatic cholestasis. The present study evaluated the effect of food on the pharmacokinetics and pharmacodynamics of NaPB in five patients with UCDs. Following an overnight fast, NaPB was administered orally at 75 mg/kg/dose (high dose, HD) or 25 mg/kg/dose (low dose, LD) either 15 min before or immediately after breakfast. Each patient was treated with these four treatment regimens with NaPB. With either dose, pre-breakfast administration rather than post-breakfast administration significantly increased plasma PB levels and decreased plasma glutamine availability. Pre-breakfast LD administration resulted in a greater attenuation in plasma glutamine availability than post-breakfast HD administration. Plasma levels of branched-chain amino acids decreased to the same extent in all tested regimens. No severe adverse events occurred during this study. In conclusion, preprandial oral administration of NaPB maximized systemic exposure of PB and thereby its efficacy on glutamine consumption in patients with UCDs.

Hyperammonemia in azotemic cats

OBJECTIVES

Hyperammonemia occurs in cats with hepatobiliary and nutritional (cobalamin and arginine deficiency) disorders, and has also been documented in four cats with renal azotemia. We hypothesized that in cats with renal azotemia, fasting hyperammonemia would correlate with indices of worsening kidney function, and would be independent of cobalamin, potassium, systemic inflammation or urinary tract infection (UTI) with urease-producing bacteria.

METHODS

A fasted blood sample was prospectively collected for ammonia and cobalamin analysis from 18 client-owned cats with renal azotemia (creatinine [Cr] ⩾1.6 mg/dl, urine specific gravity <1.030 or documentation of historical chronic kidney disease [CKD]). Correlations between blood ammonia and selected biochemical parameters were analyzed using Pearson's correlation coefficient.

RESULTS

Seven castrated males and 11 spayed females with a median age of 12 years (range 4-19 years) were enrolled. Ten of 18 (56%) cats presented for acute kidney injury (AKI) or acute on chronic kidney disease (AoCKD), and 8/18 (44%) presented for progressive CKD. The median Cr was 5.9 mg/dl (range 1.9-24.7 mg/dl). Hyperammonemia was documented in 4/18 (22%) cats, with a median of 95 µmol/dl (range 85-98 µmol/dl), and all four of these cats were classified as AKI/AoCKD. Blood ammonia concentrations had a significant moderate positive correlation between blood urea nitrogen (BUN) (r = 0.645, P = 0.003), Cr (r = 0.578, P = 0.012) and serum phosphorus (r = 0.714, P = 0.0009) but not with cobalamin, potassium or white blood cell count. No cats had UTIs with urease-producing bacteria.

CONCLUSIONS AND RELEVANCE

A correlation exists between blood ammonia and BUN, Cr and phosphorus in cats with renal azotemia. Future studies are warranted in a larger population of cats to determine the true prevalence, etiology and potential therapeutic effect of medical management of hyperammonemia on long-term prognosis in cats with kidney disease.

Status epilepticus secondary to hyperammonaemia: a late presentation of an undiagnosed urea cycle defect

In this report, we describe the diagnosis, investigation and management of a patient presenting with refractory status epilepticus secondary to a previously unrecognised urea cycle defect, ornithine transcarbamylase deficiency, causing a hyperammonaemic encephalopathy. While metabolic disorders will be readily considered in a paediatric population presenting with difficult seizures, it is unusual for such cases to present in adulthood, and maintaining a broad differential in patients with status epilepticus is important. Early recognition and initiation of treatment are vital. Furthermore, the patient had been diagnosed with schizophrenia over a decade previously and more recently started on sodium valproate, a medication known to contribute to hyperammonaemia. This case also emphasises the importance of exclusion of underlying organic disease prior to diagnosis of psychiatric conditions.

Metabolic needs of the kidney graft undergoing normothermic machine perfusion

Normothermic machine perfusion (NMP) is emerging as a novel preservation strategy. During NMP, the organ is maintained in a metabolically active state that may not only provide superior organ preservation, but that also facilitates viability testing before transplantation, and ex situ resuscitation of marginal kidney grafts. Although the prevailing perfusion protocols for renal NMP are refined from initial pioneering studies concerning short periods of NMP, it could be argued that these protocols are not optimally tailored to address the putatively compromised metabolic plasticity of marginal donor grafts (i.e., in the context of viability testing and/or preservation), or to meet the metabolic prerequisites associated with prolonged perfusions and the required anabolic state in the context of organ regeneration. Herein, we provide a theoretical framework for the metabolic requirements for renal NMP. Aspects are discussed along the lines of carbohydrates, fatty acids, amino acids, and micronutrients required for optimal NMP of an isolated kidney. In addition, considerations for monitoring aspects of metabolic status during NMP are discussed.

A randomized trial to examine the impact of food on pharmacokinetics of 4-phenylbutyrate and change in amino acid availability after a single oral administration of sodium 4-phenylbutyrarte in healthy volunteers

Urea cycle disorders (UCDs), inborn errors of hepatocyte metabolism, result in the systemic accumulation of ammonia to toxic levels. Sodium 4-phenylbutyrate (NaPB), a standard therapy for UCDs for over 20 years, generates an alternative pathway of nitrogen deposition through glutamine consumption. Administration during or immediately after a meal is the accepted use of NaPB. However, this regimen is not based on clinical evidence. Here, an open-label, single-dose, five-period crossover study was conducted in healthy adults to investigate the effect of food on the pharmacokinetics of NaPB and determine any subsequent change in amino acid availability. Twenty subjects were randomized to one of four treatment groups. Following an overnight fast, NaPB was administered orally at 4.3 g/m² (high dose, HD) or 1.4 g/m² (low dose, LD) either 30 min before or just after breakfast. At both doses, compared with post-breakfast administration, pre-breakfast administration significantly increased systemic exposure of PB and decreased plasma glutamine availability. Pre-breakfast LD administration attenuated plasma glutamine availability to the same extent as post-breakfast HD administration. Regardless of the regimen, plasma levels of branched-chain amino acids (BCAA) were decreased below baseline in a dose-dependent manner. In conclusion, preprandial oral administration of NaPB maximized systemic exposure of the drug and thereby its potency to consume plasma glutamine. This finding may improve poor medication compliance because of the issues with odor, taste, and pill burden of NaPB and reduce the risk of BCAA deficiency in NaPB therapy.

Management of late onset urea cycle disorders-a remaining challenge for the intensivist?

Background

Hyperammonemia caused by a disorder of the urea cycle is a rare cause of metabolic encephalopathy that may be underdiagnosed by the adult intensivists because of its rarity. Urea cycle disorders are autosomal recessive diseases except for ornithine transcarbamylase deficiency (OTCD) that is X-linked. Optimal treatment is crucial to improve prognosis.

Main body

We systematically reviewed cases reported in the literature on hyperammonemia in adulthood. We used the US National Library of Medicine Pubmed search engine since 2009. The two main causes are ornithine transcarbamylase deficiency followed by type II citrullinemia. Diagnosis by the intensivist remains very challenging therefore delaying treatment and putting patients at risk of fatal cerebral edema. Treatment consists in adapted nutrition, scavenging agents and dialysis. As adults are more susceptible to hyperammonemia, emergent hemodialysis is mandatory before referral to a reference center if ammonia levels are above 200 µmol/l as the risk of cerebral edema is then above 55%. Definitive therapy in urea cycle abnormalities is liver transplantation.

Conclusion

Awareness of urea cycle disorders in adults intensive care units can optimize early management and accordingly dramatically improve prognosis. By preventing hyperammonemia to induce brain edema and herniation leading to death.

Hyperammonemia Post Lung Transplantation: A Review

Hyperammonemia is the pathological accumulation of ammonia in the blood, which can occur in many different clinical settings. Most commonly in adults, hyperammonemia occurs secondary to hepatic dysfunction; however, it is also known to be associated with other pathologies, surgeries, and medications. Although less common, hyperammonemia has been described as a rare, but consistent complication of solid organ transplantation. Lung transplantation is increasingly recognized as a unique risk factor for the development of this condition, which can pose grave health risks-including long-term neurological sequelae and even death. Recent clinical findings have suggested that patients receiving lung transplantations may experience postoperative hyperammonemia at rates as high as 4.1%. A wide array of etiologies has been attributed to this condition. A growing number of case studies and investigations suggest disseminated opportunistic infection with Ureaplasma or Mycoplasma species may drive this metabolic disturbance in lung transplant recipients. Regardless of the etiology, hyperammonemia presents a severe clinical problem with reported mortality rates as high as 75%. Typical treatment regimens are multimodal and focus on 3 main avenues of management: (1) the reduction of impact on the brain through the use of neuroprotective medications and decreasing cerebral edema, (2) augmentation of mechanisms for the elimination of ammonia from the blood via hemodialysis, and (3) the diminishment of processes producing predominantly using antibiotics. The aim of this review is to detail the pathophysiology of hyperammonemia in the setting of orthotopic lung transplantation and discuss methods of identifying and managing patients with this condition.

Irritability, Poor Feeding and Respiratory Alkalosis in Newborns: Think about Metabolic Emergencies. A Brief Summary of Hyperammonemia Management

The urea cycle is a series of metabolic reactions that convert ammonia into urea in order to eliminate it from the body. Urea cycle disorders are characterized by hyperammonemia, which can cause irreversible damages in central nervous system. We report a series of three newborns presenting irritability, poor feeding and tachypnea. Their first gas analysis revealed respiratory alkalosis. Hyperammonemia was confirmed, and three different enzymatic blocks in the urea cycle were diagnosed. Immediate treatment consisted in the removal of ammonia by reduction of the catabolic state, dietary adjustments, use of nitrogen scavenging agents and ultimately hemodiafiltration. Hyperammonemia is a medical emergency whose treatment should not be delayed. This report aims to highlight the importance of suspecting urea cycle disorders in newborns with aspecific signs of hyperammonemia and respiratory alkalosis, and to sum up the broad lines of hyperammonemia management.

A novel Romani microdeletion variant in the promoter sequence of ASS1 causes citrullinemia type I

BACKGROUND

Citrullinemia type I (CTLN1, MIM #215700) is an autosomal recessive urea cycle disorder caused by deficiency of argininosuccinate synthase (ASS). CTLN1 is characterized by life-threatening hyperammonemia and risk for resulting neurocognitive impairments. The diagnosis of CTLN1 is confirmed by the identification of biallelic pathogenic variants in the ASS1 gene. However, there are a small percentage of CTLN1 patients with a characteristic biochemical phenotype without identifiable variants in ASS1. We describe the molecular characterization of two related Romani children with biochemically diagnosed CTLN1, whose clinical genetic testing failed to detect any pathogenic variant in ASS1.

METHODS

Genomic DNA was extracted from peripheral blood lymphocytes collected from both patients. Sanger sequencing was performed after PCR amplifications of 5'- and 3'-untranslated regions of the ASS1 gene. A luciferase reporter assay was performed using the human malignant melanoma A2058 cell line and the human liver cancer cell line HepG2.

RESULTS

We interrogated the non-coding regions of ASS1 by targeted PCR amplification and identified a homozygous 477-bp microdeletion in the promoter region of the ASS1 gene in both patients. Heterozygosity of the variant was confirmed in their parents. Sanger sequencing confirmed the microdeletion contained the entire sequence of the non-coding exon 1 of ASS1 that includes promoter elements of GC-box, E-box, AP2-binding site, and TATA-box. Luciferase reporter assay using an expression plasmid containing the wild-type or mutant ASS1 sequences showed robust reporter expression from the wild-type sequence and significantly reduced expression driven by the mutant insert (3.6% in A2058 cells and 3.3% in HepG2 cells). These findings were consistent with the hypothesis that the microdeletion identified in the patients disrupted an essential promoter element and resulted in deficiency of ASS1 mRNA expression.

CONCLUSIONS

This is the first report of CTLN1 patients caused by a Romani microdeletion variant affecting the non-coding upstream sequence of ASS1. Ablation of the promoter sequence can cause CTLN1 by the reduction of ASS1 expression. Currently available clinical sequencing methods usually do not cover the promoter sequence including the non-coding exon of ASS1, highlighting the importance of evaluating this region in genetic testing for CTLN1.

An Intriguing Case of Acute Encephalopathy: Lesson Learned from a Constipated Man

Hyperammonemia is a common cause of encephalopathy encountered in an intensive care unit (ICU). Absence of pre-existing liver disease may misguide a clinician and cases of non-cirrhotic hyperammonemia may be missed in ICU leading to life-threatening outcomes such as cerebral edema and herniation. A critical care physician must look beyond liver cirrhosis as a cause of hyperammonemia so that infrequent but potentially reversible causes of encephalopathy are not missed, and patient treatment is not jeopardized.

Characteristics and outcomes of critically ill patients with severe hyperammonemia

PURPOSE

To determine the etiology and outcomes of critically ill patients with severe hyperammonemia.

MATERIALS AND METHODS

Retrospective observational study of adults (18 years or older) admitted to a MICU from 2007 to 2016 who had a serum ammonia level >180 μmol/L (3 times the upper limit of normal).

RESULTS

The 78 patients (45 male, 32 female) had a median age of 52 (interquartile range [IQR] 46-58) years. Hyperammonemia occurred most often with acute-on-chronic liver failure (ACLF) (49 %) or decompensated cirrhosis (27 %) and less often as a consequence of prior gastric bypass (9%), acute hepatic failure (6%), or valproic acid (3%). Median serum ammonia level was 201 μmol/L (IQR 126-265, range 18-736) on admission, with peak value of 245 μmol/L (IQR 205-336, range 185-842). Fifty (64%) patients died during the hospitalization. Cerebral edema was documented in 8 (10%) patients, only one of whom survived. Six of the 8 patients with cerebral edema had hyperammonemia related to ACLF, giving an incidence of 14% in this subset of patients. Neither mortality nor cerebral edema was associated with peak ammonia level.

CONCLUSIONS

Critically ill patients with severe hyperammonemia have a high mortality rate and are at risk of developing cerebral edema.

Metabolic encephalopathy caused by nitrous oxide (‘laughing gas’) induced hyperammonaemia

A 26-year-old man presented at the emergency department with confusion and decreased consciousness after several days of vomiting. In the preceding 6 months, he had used a 2-litre tank of nitrous oxide (N2O) weekly. His metabolic encephalopathy was caused by hyperammonaemia which probably resulted from interference of N2O-induced vitamin B12 deficiency with ammonia degradation. A catabolic state might have contributed to the hyperammonaemia in this case. After treatment with vitamin B12 and lactulose, both his consciousness and hyperammonaemia improved. He reported no residual complaints after 3 months of follow-up. Since N2O is increasingly used as a recreational drug, we recommend considering hyperammonaemia as a cause of metabolic encephalopathy in cases of N2O use and altered mental status.

Amino and organic acid analysis: Essential tools in the diagnosis of inborn errors of metabolism

Inborn errors of metabolism (IEMs) are a large class of genetic disorders that result from defects in enzymes involved in energy production and metabolism of nutrients. For every metabolic pathway, there are defects that can occur and potentially result in an IEM. While some defects can go undetected in one's lifetime, some have moderate to severe clinical consequences. In the latter case, the biochemical defect leads to accumulation of metabolites and byproducts that are toxic or interfere with normal biological function. Disorders of amino acid metabolism, organic acid metabolism and the urea cycle comprise a large portion of IEMs. Two essential tools required for the diagnosis of these categories of disorders are amino acid and organic acid profiling. Most all clinical laboratories offering metabolic testing perform amino acid analysis, while organic acid profiling is restricted to more specialized pediatric hospitals and reference laboratories. In this chapter, we will provide an overview of various methodologies employed for amino acid and organic acid profiling as well as specific examples to demonstrate how these techniques are applied in clinical laboratories for the diagnosis of IEMs.

Inborn Errors of Metabolism in Children with Unexplained Developmental Delay in Misan, Iraq

Objectives

We sought to determine the prevalence of inborn errors of metabolism (IEM) in children with unexplained developmental delay and their types.

Methods

We conducted a cross-sectional study in Misan, Iraq, over a period of one year. A total of 112 infants with unexplained developmental delay were included in the study, and the required information was taken from their parents by direct interview. Tandem mass spectrometry (MS/MS) was done in collaboration with MedLabs’ Referral Laboratory in Amman, Jordan.

Results

Twenty (17.9%) cases had abnormal MS/MS. Disorders of amino acid metabolism represented the majority of IEM (10 cases) in which phenylketonuria and maple syrup urine disease were the most common (found in five cases each). Organic and fatty acid metabolisms were found in five and two cases, respectively. Most cases of IEM had a positive family history and consanguinity, however, family history was the only significant factor (p < 0.001).

Conclusions

A high rate of IEM was detected in children with unexplained developmental delay in Misan. A high clinical suspicion with positive family history and consanguinity supported by the MS/MS results played an essential role in the diagnosis. However, implementation of newborn screening is essential for early diagnosis and to determine appropriate therapy in newborns with IEM in Iraq generally and in Misan in particular.

Acute Presentation and Management of the Encephalopathic Child With an Undiagnosed Inborn Error of Metabolism

BACKGROUND

Inborn errors of metabolism (IEM) commonly present in infancy and, less commonly, later in life.

CASE REPORT

This case describes an IEM, specifically, ornithine transcarbamylase deficiency, in a previously healthy 7-year-old boy who presented to an emergency department with vomiting for approximately 24 h prior to admission. The child became progressively encephalopathic while in the emergency department, but an ammonia level was not obtained until several hours after admission. Irreversible brain damage with cerebral edema was already present at time of diagnosis, leading to death. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case emphasizes that acute hyperammonemia can rapidly cause irreversible neurological damage and, in the case of a newly encephalopathic pediatric patient, ammonia levels should be evaluated early to facilitate proper diagnostic tests and treatment.

Measurement duration affects the calculation of whole body protein turnover kinetics but not between-day variability

BACKGROUND

Assessment of whole body protein turnover (WBPT) can provide fundamental information about protein kinetics which underpins the conservation of lean tissue. Reliability and methodology studies on the measurement of WBPT are scarce. This study aimed to assess the effects of urine collection duration (9 versus 12 h) and the reproducibility of WBPT with the end product method calculated from ammonia as the end product.

METHODS

WBPT was assessed in 21 healthy participants (11M, 10F) on 2 test days. WBPT was assessed using the end product method with a single dose of ¹⁵N glycine with ammonia as end product in a postprandial state with 9 and 12-h urine collections.

RESULTS

The CV for protein flux averaged 10% and 12% for 9 and 12-h urine collections respectively. Protein flux, synthesis and balance were significantly higher and protein breakdown significantly lower with 9-h urine collections compared to 12-h collections (P < 0.01) and there was a trend towards increasingly greater overestimation of 9-h calculated WBPT kinetics with greater overall rates of WBPT. Correlations between the 9 and 12-h values were strong (r > 0.962, P < 0.001 for all variables).

CONCLUSIONS

The reproducibility of WBPT with ammonia as the end product was similar to previously reported reproducibility of the gold standard precursor technique. The use of a 12-h urine collection is more effective to achieve full turnover of the ammonia free amino acid (AA) pool.

Features of Adult Hyperammonemia Not Due to Liver Failure in the ICU

OBJECTIVES

To evaluate the epidemiology of hyperammonemia unrelated to liver failure in the critical care setting.

DESIGN

Retrospective case series.

SETTING

Critically ill patients admitted to ICUs at Mayo Clinic, Rochester, MN (medical ICU, two mixed medical-surgical ICUs, coronary care unit, or the cardiosurgical ICU) between July 1, 2004, and October 31, 2015.

PATIENTS

Adult critically ill patients with hyperammonemia not related to acute or chronic liver failure. We excluded patients with diagnosis of moderate or severe liver disease, hyperbilirubinemia, and patients who denied the use of their medical records.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 3,908 ICU patients with hyperammonemia, 167 (4.5%) had no evidence of acute or chronic liver failure. One-hundred one patients (60.5%) were male with median age of 65.7 years (interquartile range, 50-74.5 yr) and median serum ammonia level of 68 µg/dL (interquartile range, 58-87 µg/dL). Acute encephalopathy was present in 119 patients (71%). Predisposing conditions included malnutrition 27 (16%), gastric bypass six (3.6%), total parenteral nutrition four (2.4%); exposure to valproic acid 17 (10%); status epilepticus 11 (6.6%), high tumour burden 19 (11.3%), and renal failure 82 (49.1%). Urea cycle defects were diagnosed in seven patients (4.1%). Hospital mortality was high (30%), and median ammonia level was higher among the nonsurvivors (74 vs 67 µg/dL; p = 0.05). Deaths were more likely in hyperammonemic patients who were older (p = 0.016), had greater illness severity (higher Acute Physiology and Chronic Health Evaluation III score, p < 0.01), malignancy (p < 0.01), and solid organ transplantation (p = 0.04), whereas seizure disorder was more common in survivors (p = 0.02). After adjustment, serum ammonia level was not associated with increased mortality.

CONCLUSIONS

Hyperammonemia occurs in a substantial minority of critically ill patients without liver failure. These patients have a poor prognosis, although ammonia level per se is not independently associated with mortality. Serum ammonia should be measured when risk factors are present, such as nutritional deficiencies and protein refeeding, treatment with valproic acid, high tumour burden, and known or suspected urea cycle abnormalities.

Urea cycle disorder presenting as bilateral mesial temporal sclerosis - an unusual cause of seizures: a case report and review of the literature

BACKGROUND

Urea cycle disorders are secondary to defects in the system converting ammonia into urea, causing accumulation of ammonia and other byproducts which are neurotoxic. Ornithine transcarbamylase deficiency is the most common of the urea cycle disorders and frequently presents with coma or seizures during hyperammonemia. However, seizures can also occur without metabolic decompensation.

CASE PRESENTATION

We describe a 23-year-old Chinese woman with urea cycle disorder who presented with confusion due to focal seizures arising from the left frontotemporal region. Interestingly, her ammonia levels remained normal during the seizures. Neuroimaging showed bilateral mesial temporal sclerosis. Her seizures were successfully controlled with two anti-epileptic medications.

CONCLUSIONS

This case adds evidence of the predisposition of the temporal lobe to injury in urea cycle disorder. Urea cycle disorder can lead to mesial temporal sclerosis which leads to increased susceptibility of patients to seizures regardless of their metabolic state.

1H NMR-based metabolomics reveals interactive effects between the carrier solvent methanol and a pharmaceutical mixture in an amphibian developmental bioassay with Limnodynastes peronii

Organic carrier solvents are used in aquatic toxicity testing to improve chemical solubility and facilitate the exploration of dose-response relationships. Both water- and solvent-control groups are normally included in these scenarios to ensure that the solvent itself has no effect on the test organism, but this fails to consider possible interactive effects between carrier solvents and contaminants of interest. We explored this topic by exposing Limnodynastes peronii tadpoles to a mixture of common water-soluble pharmaceuticals (diclofenac, metformin and valproic acid) in the presence and absence of the carrier solvent methanol, according to standard developmental bioassay methodology. Nuclear Magnetic Resonance (NMR) spectroscopy was applied as a platform for untargeted metabolomics, to compare broad sub-lethal hepatotoxicity in solvent- and solvent-free exposure scenarios. Considerable interactive effects were identified between the pharmaceutical mixture and a typical dose of methanol (0.003%). Specifically, pronounced differences were observed between the solvent- and solvent-free exposure groups for leucine, acetate, glutamine, citrate, glycogen, tyrosine, arginine, purine nucleotides and an unidentified metabolite at 6.53 ppm. Various other metabolites exhibited similar disparity related to the use of carrier solvent, but the interactions were non-significant. These results raise important questions about the use of carrier solvents for chemical exposures in aquatic ecotoxicology, and particularly for studies interested in sub-lethal mechanistic information and/or biomarker discovery.

Umbelliferone prevents oxidative stress, inflammation and hematological alterations, and modulates glutamate-nitric oxide-cGMP signaling in hyperammonemic rats

Hepatic encephalopathy (HE) is a serious neuropsychiatric complication that occurs as a result of liver failure. Umbelliferone (UMB; 7-hydroxycoumarin) is a natural product with proven hepatoprotective activity; however, nothing has yet been reported on its protective effect against hyperammonemia, the main culprit behind the symptoms of HE. Here, we evaluated the effect of UMB against ammonium chloride (NH₄Cl)-induced hyperammonemia, oxidative stress, inflammation and hematological alterations in rats. We demonstrated the modulatory role of UMB on the glutamate-nitric oxide (NO)-cGMP pathways in the cerebrum of rats. Rats received intraperitoneal injections of NH₄Cl (3 times/week) for 8 weeks and concomitantly received 50 mg/kg UMB. NH₄Cl-induced rats showed significantly elevated blood ammonia and liver function markers. Lipid peroxidation and NO were increased in the liver and cerebrum of rats while the antioxidant defenses were declined. UMB significantly reduced blood ammonia, liver function markers, lipid peroxidation and NO, and enhanced the antioxidant defenses in NH₄Cl-induced rats. UMB significantly prevented anemia, leukocytosis, thrombocytopenia and prolongation of PT and aPTT. Hyperammonemic rats showed elevated levels of cerebral TNF-α, IL-1β and glutamine as well as increased activity and expression of Na⁺/K⁺-ATPase, effects that were significantly reversed by UMB. In addition, UMB down-regulated nitric oxide synthase and soluble guanylate cyclase in the cerebrum of hyperammonemic rats. In conclusion, this study provides evidence that UMB protects against hyperammonemia via attenuation of oxidative stress and inflammation. UMB prevents hyperammonemia associated hematological alterations and therefore represents a promising protective agent against the deleterious effects of excess ammonia.

Colloidal solution of silver nanoparticles for label-free colorimetric sensing of ammonia in aqueous solutions

Silver nanoparticles were synthesized in the presence of saccharides and ammonia (NH3) in the concentration range from 10-2 to 103 ppm to develop an optical sensor for NH3 in aqueous solutions. Ammonia affects the features of the nanoparticles obtained in a concentration-dependent manner as determined by UV-vis absorption analysis and TEM observations. Structural and morphological analysis provides the basis for the production of a colorimetric label-free sensor for ammonia. Overall, surface plasmon resonance increases when ammonia concentration rises, although the functional trend is not the same over the entire investigated ammonia concentration range. Three different ranges have been identified: very low ammonia concentrations from 0.01 to 0.2 ppm, high ammonia concentrations from 20 to 350 ppm and, most importantly, the intermediate or physiological range of ammonia from 0.5 to 10 ppm.

The Pharmabiotic Approach to Treat Hyperammonemia

Ammonia is constantly produced as a metabolic waste from amino acid catabolism in mammals. Ammonia, the toxic waste metabolite, is resolved in the liver where the urea cycle converts free ammonia to urea. Liver malfunctions cause hyperammonemia that leads to central nervous system (CNS) dysfunctions, such as brain edema, convulsions, and coma. The current treatments for hyperammonemia, such as antibiotics or lactulose, are designed to decrease the intestinal production of ammonia and/or its absorption into the body and are not effective, besides being often accompanied by side effects. In recent years, increasing evidence has shown that modifications of the gut microbiota could be used to treat hyperammonemia. Considering the role of the gut microbiota and the physiological characteristics of the intestine, the removal of ammonia from the intestine by modulating the gut microbiota would be an ideal approach to treat hyperammonemia. In this review, we discuss the significance of hyperammonemia and its related diseases and the efficacy of the current management methods for hyperammonemia to understand the mechanism of ammonia transport in the human body. The possibility to use the gut microbiota as pharmabiotics to treat hyperammonemia and its related diseases is also explored.

Hyperammonemia Presenting as Refractory Status Epilepticus after Lung Transplant in a Patient Positive for Ureaplasma parvum

Hyperammonemia is a rare complication of lung transplant with a high mortality rate. It presents as encephalopathy and progresses to seizures, status epilepticus, coma, cerebral edema, and brain death. Multiple treatments have been documented including administration of medications, gut decontamination, and dialysis. However, no definitive treatments exist and mortality remains between 67% and 75%. We present the case of a 65-year-old male with idiopathic pulmonary fibrosis who developed refractory status epilepticus secondary to hyperammonemia following lung transplant. The patient presented on postoperative day 7 with super-refractory status epilepticus and normal computed tomography scan of the head. Hyperammonemia was suspected due to refractory seizures and confirmed with peak ammonia level >1000 μmol/L. Despite aggressive treatment, the patient developed global cerebral edema and died. Postmortem investigations revealed that the patient was positive for Ureaplasma parvum. Additional studies are needed to elucidate the exact mechanism of disease and investigate successful treatment options.

Hyperammonaemic encephalopathy following an uncomplicated surgery

A 59-year-old woman who underwent an uncomplicated exploratory laparotomy, adhesiolysis, small bowel resection and anterolateral thigh flap had a complicated postoperative period characterised by wound dehiscence and poor nutritional intake. 29 days postoperatively, a tremor developed in her upper limbs associated with weakness. Her Glasgow Coma Scale (GCS) fell to 4 and she was transferred to the intensive care unit. The patient was reviewed by multiple specialists and multiple differentials were considered and eliminated. Eventually, investigations revealed hyperammonaemic encephalopathy, being a result of low arginine and potentially small intestinal bacterial overgrowth. Following treatment with sodium benzoate, sodium phenylbutyrate and arginine along with haemodialysis and rifaximin, GCS and hyperammonaemia rapidly improved. She was stepped down to surgical high-dependency unit, continued arginine therapy with total parenteral nutrition and percutaneous endoscopic gastrostomy feeds. She was discharged with regular follow-up from surgeons and biochemistry and continues oral arginine therapy.

Commiphora molmol Modulates Glutamate-Nitric Oxide-cGMP and Nrf2/ARE/HO-1 Pathways and Attenuates Oxidative Stress and Hematological Alterations in Hyperammonemic Rats

Hyperammonemia is a serious complication of liver disease and may lead to encephalopathy and death. This study investigated the effects of Commiphora molmol resin on oxidative stress, inflammation, and hematological alterations in ammonium chloride- (NH₄Cl-) induced hyperammonemic rats, with an emphasis on the glutamate-NO-cGMP and Nrf2/ARE/HO-1 signaling pathways. Rats received NH₄Cl and C. molmol for 8 weeks. NH₄Cl-induced rats showed significant increase in blood ammonia, liver function markers, and tumor necrosis factor-alpha (TNF-α). Concurrent supplementation of C. molmol significantly decreased circulating ammonia, liver function markers, and TNF-α in hyperammonemic rats. C. molmol suppressed lipid peroxidation and nitric oxide and enhanced the antioxidant defenses in the liver, kidney, and cerebrum of hyperammonemic rats. C. molmol significantly upregulated Nrf2 and HO-1 and decreased glutamine and nitric oxide synthase, soluble guanylate cyclase, and Na⁺/K⁺-ATPase expression in the cerebrum of NH₄Cl-induced hyperammonemic rats. Hyperammonemia was also associated with hematological and coagulation system alterations. These alterations were reversed by C. molmol. Our findings demonstrated that C. molmol attenuates ammonia-induced liver injury, oxidative stress, inflammation, and hematological alterations. This study points to the modulatory effect of C. molmol on glutamate-NO-cGMP and Nrf2/ARE/HO-1 pathways in hyperammonemia. Therefore, C. molmol might be a promising protective agent against hyperammonemia.

Urea cycle disorder misdiagnosed as multiple sclerosis: a case report and review of the literature

Urea cycle disorders are a group of inborn errors of metabolism caused by dysfunction of any of the six enzymes or two transport proteins involved in urea biosynthesis. In this paper, we report a patient who presented with neurological dysfunction and coma in the immediate postpartum period. She was misdiagnosed for many years as a case of multiple sclerosis. The importance of reporting this case is to illustrate that the wrong diagnosis of patients as being affected with multiple sclerosis for many years due to magnetic resonance imaging abnormalities rather than the classic relapsing-remitting nature of the disease may lead to catastrophic consequences. The patient was treated with intravenous steroids several times, which is contraindicated in patients with urea cycle disorders as it may precipitate acute hyperammonemic attacks. In addition, the management of urea cycle disorder could have started earlier and avoided multiple admissions to the intensive care unit. We believe that the presence of symmetric hyperintense insular cortical changes are seen in multiple hyperammonemic processes, and in the context of the clinical presentation and high ammonia levels can be suggestive of a urea cycle disorder. For any patient presenting with atypical clinical features, images should be reviewed and discussed in detail with an experienced neuroradiologist. In addition, the ammonia levels should be checked if a urea cycle disorder is suspected.

Citrulline for urea cycle disorders in Japan

BACKGROUND

The amino acid l-citrulline is used as a therapeutic agent for urea cycle disorders (UCD) including ornithine transcarbamylase deficiency (OTCD), carbamoyl phosphate synthetase I deficiency (CPSD), and N-acetylglutamate synthase deficiency. There are few reports, however, on the use of l-citrulline in Japan and little consensus regarding the effects of l-citrulline.

METHODS

We conducted a questionnaire survey of patients undergoing l-citrulline treatment for a UCD to evaluate the current status of this therapy. The survey included patient background, details of l-citrulline treatment, clinical examination data, treatment, frequency of vomiting, and liver transplantation.

RESULTS

We retrospectively investigated 43 questionnaire respondents (OTCD, n = 33; CPSD, n = 10). The weight of male OTCD patients improved by +0.79 SD, and the ammonia level decreased by a mean of 44.3 μmol/L in all patients. The protein intake of all patients and of male OTCD patients increased by 0.14 g/kg/day and 0.17 g/kg/day, respectively.

CONCLUSIONS

l-Citrulline effectively reduced ammonia level, increased protein intake, and improved weight gain in UCD patients. l-Citrulline should be considered a standard therapy in OTCD and CPSD patients.

A Proposed Physiopathological Pathway to Hyperammonemic Encephalopathy in a Non-Cirrhotic Patient with Fibrolamellar Hepatocellular Carcinoma without Ornithine Transcarbamylase (OTC) Mutation

Patient: Male, 31

Final Diagnosis: Fibrolamellar hepatocellular carcinoma

Symptoms: Encephalopathy

Medication:—

Clinical Procedure: —

Specialty: Gastroenterology and Hepatology

Naringin regulates glutamate-nitric oxide cGMP pathway in ammonium chloride induced neurotoxicity

Naringin, plant bioflavonoid extracted mainly from grapefruit and other related citrus species. This study was designed to assess the neuroprotective effect of naringin on ammonium chloride (NH₄Cl) induced hyperammonemic rats. Experimental hyperammonemia was induced by intraperitonial injection (i.p) of NH₄Cl (100mg/kg body weight (b.w.)) thrice a week for 8 consecutive weeks. Hyperammonemic rats were treated with naringin (80mg/kg b.w.) via oral gavage. Naringin administration drastically restored the levels of blood ammonia, plasma urea, nitric oxide (NO), glutamate, glutamine, lipid peroxidation, lipid profile, activities of liver marker enzymes, antioxidant status and sodium/potassium-ATPase (Na⁺/K⁺-ATPase). In addition, naringin supplementation reverted back the pathological changes of liver, brain and kidney tissues, the expressions of Glutamine synthetase (GS), Na⁺/K⁺-ATPase, neuronal nitric oxide (nNOS) and soluble guanylate cyclase (sGC) in hyperammonemic rats. Hence, this study suggested that nargingin exhibited their protective effect against NH₄Cl induced toxicity via enhancing the activities of antioxidant enzymes and inhibiting the lipid peroxidation process. Take together, this study provides data that naingin effectively reduced neurotoxicity by attenuating hyperammonemia, suggesting that naringin act as a potential therapeutic agent to treat hyperammonemic rats.