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Eriksen PL, Djernes L, Vilstrup H, Ott P. Clearance and production of ammonia quantified in humans by constant ammonia infusion - the effects of cirrhosis and ammonia targeting treatments. J Hepatol 2023:S0168-8278(23)00220-9. [PMID: 37061198 DOI: 10.1016/j.jhep.2023.03.042] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 03/17/2023] [Accepted: 03/26/2023] [Indexed: 04/17/2023]
Abstract
BACKGROUND & AIMS Hyperammonaemia is a key pathological feature of liver disease and the primary driver of hepatic encephalopathy (HE). However, the relative roles of increased ammonia production and reduced clearance are poorly understood as is the action of ammonia-targeting HE drugs. We aimed to quantify whole-body ammonia metabolism in healthy persons and patients with cirrhosis and to validate our method by examining the effects of glycerol phenylbutyrate and lactulose + rifaximin treatment. METHODS Ten healthy men and ten male patients with cirrhosis were investigated by 90-minute constant ammonia infusion to achieve steady-state plasma ammonia. Whole-body ammonia clearance was calculated as infusion rate divided by steady-state concentration increase and ammonia production as clearance times baseline ammonia concentration. Participants were re-investigated after the ammonia targeting interventions. RESULTS In healthy persons, ammonia clearance was 3.5 (3.1-3.9) L/min and production 49 (35-63) μmol/min. Phenylbutyrate increased clearance by 11% (4-19%, p=0.009). Patients with cirrhosis had a 20% decreased ammonia clearance of 2.7 (2.1-3.3) L/min (p = 0.02) and a nearly tripled production to 131 (102-159) μmol/min (p<0.0001). Lactulose + rifaximin reduced production by 20% (2-37%, p=0.03). The infusion was generally well-tolerated save one hyperammonaemic patient with cirrhosis with possible bleeding unrelated to the infusion who developed clinical HE that reverted when infusion was discontinued. CONCLUSIONS Whole-body ammonia clearance and production may be measured separately by the technique used. The method identified a lower clearance and a higher production in patients with cirrhosis, and showed that phenylbutyrate increases clearance, whereas lactulose + rifaximin reduces production. The method may be used to examine a range of questions related to normo-/pathophysiology and ammonia-targeting treatment mechanisms. IMPACT AND IMPLICATIONS High blood ammonia plays a key role in liver cirrhosis related brain dysfunction. However, the relative roles of increased ammonia production and reduced ammonia clearance are poorly understood as is the action of ammonia-targeting treatments. This study presents a relatively simple test to measure ammonia metabolism. By use of this test, it was possible to show that patients with liver cirrhosis have decreased ammonia clearance and increased ammonia production compared with healthy persons and to quantify distinctively different ammonia-targeting treatment effects. The test presented holds several perspectives for future studies of normal physiology and pathophysiology, not least in regard to elucidating effects of ammonia-targeting therapies. CLINICAL TRIAL NUMBER ClinicalTrials.gov (1-16-02-297-20).
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Affiliation(s)
- Peter Lykke Eriksen
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Denmark.
| | - Lars Djernes
- Department of Anaesthesiology and Intensive Care, Viborg Regional Hospital, Denmark; Department of Anaesthesiology and Intensive Care, Aarhus University Hospital, Denmark
| | - Hendrik Vilstrup
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Denmark; Department of Clinical Medicine, Aarhus University, Denmark
| | - Peter Ott
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Denmark; Department of Clinical Medicine, Aarhus University, Denmark
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Involvement of ammonia metabolism in the improvement of endurance performance by tea catechins in mice. Sci Rep 2020; 10:6065. [PMID: 32269254 PMCID: PMC7142105 DOI: 10.1038/s41598-020-63139-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 03/21/2020] [Indexed: 02/07/2023] Open
Abstract
Blood ammonia increases during exercise, and it has been suggested that this increase is both a central and peripheral fatigue factor. Although green tea catechins (GTCs) are known to improve exercise endurance by enhancing lipid metabolism in skeletal muscle, little is known about the relationship between ammonia metabolism and the endurance-improving effect of GTCs. Here, we examined how ammonia affects endurance capacity and how GTCs affect ammonia metabolism in vivo in mice and how GTCs affect mouse skeletal muscle and liver in vitro. In mice, blood ammonia concentration was significantly negatively correlated with exercise endurance capacity, and hyperammonaemia was found to decrease whole-body fat expenditure and fatty acid oxidation–related gene expression in skeletal muscle. Repeated ingestion of GTCs combined with regular exercise training improved endurance capacity and the expression of urea cycle–related genes in liver. In C2C12 myotubes, hyperammonaemia suppressed mitochondrial respiration; however, pre-incubation with GTCs rescued this suppression. Together, our results demonstrate that hyperammonaemia decreases both mitochondrial respiration in myotubes and whole-body aerobic metabolism. Thus, GTC-mediated increases in ammonia metabolism in liver and resistance to ammonia-induced suppression of mitochondrial respiration in skeletal muscle may underlie the endurance-improving effect of GTCs.
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Sergeeva OA, Chepkova AN, Görg B, Rodrigues Almeida F, Bidmon HJ, Haas HL, Häussinger D. Histamine-induced plasticity and gene expression in corticostriatal pathway under hyperammonemia. CNS Neurosci Ther 2019; 26:355-366. [PMID: 31571389 PMCID: PMC7052803 DOI: 10.1111/cns.13223] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 08/10/2019] [Accepted: 09/04/2019] [Indexed: 01/13/2023] Open
Abstract
Aims Histamine H3 receptor (H3R) antagonists/inverse agonists increase vigilance. We studied brain histaminergic pathways under hyperammonemia and the transcriptome of receptors and their signaling cascades to provide a rationale for wake‐promoting therapies. Methods We analyzed histamine‐induced long‐lasting depression of corticostriatal synaptic transmission (LLDhist). As the expression of dopamine 1 receptors (D1R) is upregulated in LGS‐KO striatum where D1R‐H3R dimers may exist, we investigated actions of H3R and D1R agonists and antagonists. We analyzed transcription of selected genes in cortex and dorsal striatum in a mouse model of inborn hyperammonemia (liver‐specific glutamine synthetase knockout: LGS‐KO) and compared it with human hepatic encephalopathy. Results LGS‐KO mice showed significant reduction of the direct depression (DD) but not the long‐lasting depression (LLD) by histamine. Neither pharmacological activation nor inhibition of D1R significantly affected DDhist and LLDhist in WT striatum, while in LGS‐KO mice D1R activation suppressed LLDhist. Histaminergic signaling was found unchanged at the transcriptional level except for the H2R. A study of cAMP‐regulated genes indicated a significant reduction in the molecular signature of wakefulness in the diseased cortex. Conclusions Our findings provide a rationale for the development of aminergic wake‐promoting therapeutics in hyperammonemic disorders.
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Affiliation(s)
- Olga A Sergeeva
- Molecular Neurophysiology, Medical Faculty, Institute of Neural and Sensory Physiology, Heinrich-Heine University, Duesseldorf, Germany.,Medical Faculty, Institute of Clinical Neurosciences and Medical Psychology, Heinrich-Heine University, Duesseldorf, Germany
| | - Aisa N Chepkova
- Molecular Neurophysiology, Medical Faculty, Institute of Neural and Sensory Physiology, Heinrich-Heine University, Duesseldorf, Germany.,Clinic of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich-Heine University, Duesseldorf, Germany
| | - Boris Görg
- Clinic of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich-Heine University, Duesseldorf, Germany
| | - Filipe Rodrigues Almeida
- Medical Faculty, Institute of Clinical Neurosciences and Medical Psychology, Heinrich-Heine University, Duesseldorf, Germany
| | - Hans-Jürgen Bidmon
- Medical Faculty, C.&O. Vogt Institute for Brain Research, Heinrich-Heine University, Duesseldorf, Germany
| | - Helmut L Haas
- Molecular Neurophysiology, Medical Faculty, Institute of Neural and Sensory Physiology, Heinrich-Heine University, Duesseldorf, Germany
| | - Dieter Häussinger
- Clinic of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty, Heinrich-Heine University, Duesseldorf, Germany
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Arias N, Méndez M, Alcalde I, Íñigo-Portugués A, Merayo-Lloves J, Arias J, Arias JL. Assessing the brain through the eye: New ways to explore hepatic encephalopathy. Physiol Behav 2017; 173:263-271. [PMID: 28238775 DOI: 10.1016/j.physbeh.2017.02.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 02/21/2017] [Accepted: 02/21/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS Minimal hepatic encephalopathy (mHE) has been shown to affect daily functioning, quality of life, driving and overall mortality. However, little is known about treating or diagnosing early impairments in mHE. We studied one of its precipitating factors, portal hypertension which is driving the inflammatory process behind mHE. The purpose was to describe an indirect diagnostic method able to detect the pathology at early stages based on the study of the vascularization and mast cells conjunctival hyperplasia as secondary inflammatory response associated to portal hypertension. Finally, we correlated the presence of histological changes in the eye in mHE with deficits in behavioral task acquisition. METHODS Rats were trained on a stimulus-response task and a spatial working memory task using the Morris water maze. Two groups of animals were used: a SHAM (sham-operated) group (n=10) and a portal hypertension (HT) group (n=10). The triple portal vein ligation method was used to create an animal model of mHE. Latencies to reach the platform, number of glial fibrillary acidic protein-immunoreactive astrocytes (GFAP-IR), mast cell expression and presence/absence of blood and lymphatic vessels were examined. RESULTS There were differences in stimulus-response behavioral performance, with a deficit in the acquisition in the HT group. However, no differences between groups were found on the spatial working memory task. At the same time, differences between groups were found in the GFAP-IR density, which was lower in the HT group, and in the number of mast cells and the presence of vessels, which were higher in the HT group. CONCLUSIONS In this study, we provide the first preliminary insight into the validity of exploring the eye as a possible tool to assess the diagnosis of mHE conditions.
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Affiliation(s)
- Natalia Arias
- Institute for Liver and Digestive Health, University College of London, Department of Medicine, Rowland Hill Street, London, UK; INEUROPA, Instituto de Neurociencias del Principado de Asturias, Spain.
| | - Marta Méndez
- INEUROPA, Instituto de Neurociencias del Principado de Asturias, Spain; Laboratorio de Neurociencias, Departamento de Psicología, Universidad de Oviedo, Plaza Feijoo s/n, 33003 Oviedo, Spain
| | - Ignacio Alcalde
- Fundación de Investigación Oftalmológica (FIO), Instituto Oftalmológico Fernández-Vega, Avda. Dres Fernández-Vega, 34, 33012 Oviedo, Spain
| | - Almudena Íñigo-Portugués
- Fundación de Investigación Oftalmológica (FIO), Instituto Oftalmológico Fernández-Vega, Avda. Dres Fernández-Vega, 34, 33012 Oviedo, Spain
| | - Jesús Merayo-Lloves
- Fundación de Investigación Oftalmológica (FIO), Instituto Oftalmológico Fernández-Vega, Avda. Dres Fernández-Vega, 34, 33012 Oviedo, Spain
| | - Jaime Arias
- Surgery Department, School of Medicine, Complutense University of Madrid, 28040 Madrid, Spain
| | - Jorge L Arias
- INEUROPA, Instituto de Neurociencias del Principado de Asturias, Spain; Laboratorio de Neurociencias, Departamento de Psicología, Universidad de Oviedo, Plaza Feijoo s/n, 33003 Oviedo, Spain
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Ott P, Vilstrup H. Cerebral effects of ammonia in liver disease: current hypotheses. Metab Brain Dis 2014; 29:901-11. [PMID: 24488230 DOI: 10.1007/s11011-014-9494-7] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Accepted: 01/21/2014] [Indexed: 12/15/2022]
Abstract
Hyperammonemia is necessary for development of the cerebral complications to liver disease including hepatic encephalopathy and cerebral edema but the mechanisms are unclear. Ammonia is taken up by the brain in proportion to its arterial concentration. The flux into the brain is most likely by both diffusion of NH3 and mediated transport of NH4 (+) . Astrocytic detoxification of ammonia involves formation of glutamine at concentrations high enough to produce cellular edema, but compensatory mechanisms reduce this effect. Glutamine can be taken up by astrocytic mitochondria and initiate the mitochondrial permeability transition but the clinical relevance is uncertain. Elevated astrocytic glutamine interferes with neurotransmission. Thus, animal studies show enhanced glutamatergic neurotransmission via the NMDA receptor which may be related to the acute cerebral complications to liver failure, while impairment of the NMDA activated glutamate-NO-cGMP pathway could relate to the behavioural changes seen in hepatic encephalopathy. Elevated glutamine also increases GABA-ergic tone, an effect which is aggravated by mitochondrial production of neurosteroids; this may relate to decreased neurotransmission and precipitation of encephalopathy by GABA targeting drugs. Hyperammonemia may compromise cerebral energy metabolism as elevated cerebral lactate is generally reported. Hypoxia is unlikely since cerebral oxygen:glucose utilisation and lactate:pyruvate ratio are both normal in clinical studies. Ammonia inhibits α-ketoglutaratedehydrogenase in isolated mitochondria, but the clinical relevance is dubious due to the observed normal cerebral oxygen:glucose utilization. Recent studies suggest that ammonia stimulates glycolysis in excess of TCA cycle activity, a hypothesis that may warrant further testing, in being in accordance with the limited clinical observations.
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Affiliation(s)
- Peter Ott
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, 8000C, Aarhus, Denmark,
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Systematic review of the Multidimensional Fatigue Symptom Inventory-Short Form. Support Care Cancer 2014; 23:191-212. [DOI: 10.1007/s00520-014-2389-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 08/05/2014] [Indexed: 12/18/2022]
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Tivers MS, Handel I, Gow AG, Lipscomb VJ, Jalan R, Mellanby RJ. Hyperammonemia and systemic inflammatory response syndrome predicts presence of hepatic encephalopathy in dogs with congenital portosystemic shunts. PLoS One 2014; 9:e82303. [PMID: 24392080 PMCID: PMC3879253 DOI: 10.1371/journal.pone.0082303] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 10/22/2013] [Indexed: 12/29/2022] Open
Abstract
Hepatic encephalopathy (HE) is an important cause of morbidity and mortality in patients with liver disease. The pathogenesis of he is incompletely understood although ammonia and inflammatory cytokines have been implicated as key mediators. To facilitate further mechanistic understanding of the pathogenesis of HE, a large number of animal models have been developed which often involve the surgical creation of an anastomosis between the hepatic portal vein and the caudal vena cava. One of the most common congenital abnormalities in dogs is a congenital portosystemic shunt (cpss), which closely mimics these surgical experimental models of HE. Dogs with a cPSS often have clinical signs which mimic clinical signs observed in humans with HE. Our hypothesis is that the pathogenesis of HE in dogs with a cPSS is similar to humans with HE. The aim of the study was to measure a range of clinical, haematological and biochemical parameters, which have been linked to the development of HE in humans, in dogs with a cPSS and a known HE grade. One hundred and twenty dogs with a cPSS were included in the study and multiple regression analysis of clinical, haematological and biochemical variables revealed that plasma ammonia concentrations and systemic inflammatory response syndrome scores predicted the presence of HE. Our findings further support the notion that the pathogenesis of canine and human HE share many similarities and indicate that dogs with cPSS may be an informative spontaneous model of human HE. Further investigations on dogs with cPSS may allow studies on HE to be undertaken without creating surgical models of HE thereby allowing the number of large animals used in animal experimentation to be reduced.
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Affiliation(s)
- Mickey S. Tivers
- Department of Veterinary Clinical Sciences, Royal Veterinary College, Hatfield, Hertfordshire, United Kingdom
| | - Ian Handel
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, The University of Edinburgh, Roslin, Midlothian, United Kingdom
| | - Adam G. Gow
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, The University of Edinburgh, Roslin, Midlothian, United Kingdom
| | - Vicky J. Lipscomb
- Department of Veterinary Clinical Sciences, Royal Veterinary College, Hatfield, Hertfordshire, United Kingdom
| | - Rajiv Jalan
- UCL Institute for Liver and Digestive Health, UCL Medical School, London, United Kingdom
| | - Richard J. Mellanby
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, The University of Edinburgh, Roslin, Midlothian, United Kingdom
- MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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Ameringer S, Elswick RK, Smith W. Fatigue in adolescents and young adults with sickle cell disease: biological and behavioral correlates and health-related quality of life. J Pediatr Oncol Nurs 2014; 31:6-17. [PMID: 24378816 PMCID: PMC3982311 DOI: 10.1177/1043454213514632] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
This descriptive, correlational study examined fatigue and potential biological and behavioral correlates in adolescents and young adults with sickle cell disease. Sixty adolescents and young adults with sickle cell disease completed the Brief Fatigue Inventory, Multidimensional Fatigue Symptom Inventory-Short Form, Patient Reported Outcomes Measurement Information System (PROMIS) fatigue short form and measures of pain, sleep quality, anxiety, depressive mood, stress, disease severity, and quality of life. Blood samples were obtained for hemoglobin and cytokines. Fatigue scores were mostly moderate in severity. Fatigue interfered to a moderate degree with daily activities and correlated significantly with pain, sleep quality, state and trait anxiety, depressive mood, stress, and quality of life. Fatigue was correlated with hemoglobin on the PROMIS measure. Fatigue was not correlated with cytokines or age, nor differed by disease severity. Fatigue was common in these adolescents and young adults, interfered with daily activities such as school, work and exercise, and significantly correlated with several potentially modifiable factors. As life expectancy increases in sickle cell disease, research is needed to test interventions to reduce fatigue.
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Affiliation(s)
| | - R. K. Elswick
- School of Nursing 1100 East Leigh Street, Richmond, VA, 23219 Virginia Commonwealth University
| | - Wally Smith
- Department of Internal Medicine PO Box 980306, Richmond, VA 23298 Virginia Commonwealth University
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Adeva MM, Souto G, Blanco N, Donapetry C. Ammonium metabolism in humans. Metabolism 2012; 61:1495-511. [PMID: 22921946 DOI: 10.1016/j.metabol.2012.07.007] [Citation(s) in RCA: 166] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 06/27/2012] [Accepted: 07/16/2012] [Indexed: 12/13/2022]
Abstract
Free ammonium ions are produced and consumed during cell metabolism. Glutamine synthetase utilizes free ammonium ions to produce glutamine in the cytosol whereas glutaminase and glutamate dehydrogenase generate free ammonium ions in the mitochondria from glutamine and glutamate, respectively. Ammonia and bicarbonate are condensed in the liver mitochondria to yield carbamoylphosphate initiating the urea cycle, the major mechanism of ammonium removal in humans. Healthy kidney produces ammonium which may be released into the systemic circulation or excreted into the urine depending predominantly on acid-base status, so that metabolic acidosis increases urinary ammonium excretion while metabolic alkalosis induces the opposite effect. Brain and skeletal muscle neither remove nor produce ammonium in normal conditions, but they are able to seize ammonium during hyperammonemia, releasing glutamine. Ammonia in gas phase has been detected in exhaled breath and skin, denoting that these organs may participate in nitrogen elimination. Ammonium homeostasis is profoundly altered in liver failure resulting in hyperammonemia due to the deficient ammonium clearance by the diseased liver and to the development of portal collateral circulation that diverts portal blood with high ammonium content to the systemic blood stream. Although blood ammonium concentration is usually elevated in liver disease, a substantial role of ammonium causing hepatic encephalopathy has not been demonstrated in human clinical studies. Hyperammonemia is also produced in urea cycle disorders and other situations leading to either defective ammonium removal or overproduction of ammonium that overcomes liver clearance capacity. Most diseases resulting in hyperammonemia and cerebral edema are preceded by hyperventilation and respiratory alkalosis of unclear origin that may be caused by the intracellular acidosis occurring in these conditions.
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Yang HY, Chen DH, Gong HT, Zheng PY. Advances in diagnosis and treatment of minimal hepatic encephalopathy. Shijie Huaren Xiaohua Zazhi 2012; 20:2058-2062. [DOI: 10.11569/wcjd.v20.i22.2058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Minimal hepatic encephalopathy (MHE), also known as subclinical hepatic encephalopathy (SHE), is a common complex and potentially reversible neuropsychiatric syndrome secondary to chronic liver disease or cirrhosis. Although a clear pathogenesis is yet to be determined, elevated ammonia in serum and the central nervous system is the mainstay for pathogenesis and treatment of MHE. Patients with MHE, regardless of its cause, show a number of quantifiable neuropsychological defects, yet have a normal mental and neurological status on global clinical examination. Although ammonia is the main toxic substance involved in the pathogenesis of hepatic encephalopathy, other mechanisms, such as modifications of the blood-brain barrier, disruptions in neurotransmission and abnormalities in GABAergic and benzodiazepine pathways, may also play a role. Current treatments are based on reducing intestinal ammonia load by agents such as antibiotics, disaccharides and probiotics whose efficacy is yet to be clearly established. This paper summarizes the latest advances in the diagnosis and treatment of MHE.
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Bosoi CR, Yang X, Huynh J, Parent-Robitaille C, Jiang W, Tremblay M, Rose CF. Systemic oxidative stress is implicated in the pathogenesis of brain edema in rats with chronic liver failure. Free Radic Biol Med 2012; 52:1228-35. [PMID: 22300646 DOI: 10.1016/j.freeradbiomed.2012.01.006] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 01/05/2012] [Accepted: 01/12/2012] [Indexed: 12/16/2022]
Abstract
Chronic liver failure leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE); however, a correlation between blood ammonia levels and HE severity remains controversial. It is believed oxidative stress plays a role in modulating the effects of hyperammonemia. This study aimed to determine the relationship between chronic hyperammonemia, oxidative stress, and brain edema (BE) in two rat models of HE: portacaval anastomosis (PCA) and bile-duct ligation (BDL). Ammonia and reactive oxygen species (ROS) levels, BE, oxidant and antioxidant enzyme activities, as well as lipid peroxidation were assessed both systemically and centrally in these two different animal models. Then, the effects of allopurinol (xanthine oxidase inhibitor, 100mg/kg for 10days) on ROS and BE and the temporal resolution of ammonia, ROS, and BE were evaluated only in BDL rats. Similar arterial and cerebrospinal fluid ammonia levels were found in PCA and BDL rats, both significantly higher compared to their respective sham-operated controls (p<0.05). BE was detected in BDL rats (p < 0.05) but not in PCA rats. Evidence of oxidative stress was found systemically but not centrally in BDL rats: increased levels of ROS, increased activity of xanthine oxidase (oxidant enzyme), enhanced oxidative modifications on lipids, as well as decreased antioxidant defense. In PCA rats, a preserved oxidant/antioxidant balance was demonstrated. Treatment with allopurinol in BDL rats attenuated both ROS and BE, suggesting systemic oxidative stress is implicated in the pathogenesis of BE. Analysis of ROS and ammonia temporal resolution in the plasma of BDL rats suggests systemic oxidative stress might be an important "first hit", which, followed by increases in ammonia, leads to BE in chronic liver failure. In conclusion, chronic hyperammonemia and oxidative stress in combination lead to the onset of BE in rats with chronic liver failure.
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Affiliation(s)
- Cristina R Bosoi
- Neuroscience Research Unit, Hôpital Saint-Luc (CRCHUM), Université de Montréal, Montréal, QC H2X 1P1, Canada
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