Induced hyperammonemia alters neuropsychology, brain MR spectroscopy and magnetization transfer in cirrhosis

The lipopolysaccharide-TLR4 axis regulates hepatic glutaminase 1 expression promoting liver ammonia build-up as steatotic liver disease progresses to steatohepatitis

INTRODUCTION

Ammonia is a pathogenic factor implicated in the progression of metabolic-associated steatotic liver disease (MASLD). The contribution of the glutaminase 1 (GLS) isoform, an enzyme converting glutamine to glutamate and ammonia, to hepatic ammonia build-up and the mechanisms underlying its upregulation in metabolic-associated steatohepatitis (MASH) remain elusive.

METHODS

Multiplex transcriptomics and targeted metabolomics analysis of liver biopsies in dietary mouse models representing the whole spectra of MASLD were carried out to characterize the relevance of hepatic GLS during disease pathological progression. In addition, the acute effect of liver-specific GLS inhibition in hepatic ammonia content was evaluated in cultured hepatocytes and in in vivo mouse models of diet-induced MASLD. Finally, the regulatory mechanisms of hepatic GLS overexpression related to the lipopolysaccharide (LPS)/Toll-like receptor 4 (TLR4) axis were explored in the context of MASH.

RESULTS

In mouse models of diet-induced MASLD, we found that augmented liver GLS expression is closely associated with the build-up of hepatic ammonia as the disease progresses from steatosis to steatohepatitis. Importantly, the acute silencing/pharmacological inhibition of GLS diminishes the ammonia burden in cultured primary mouse hepatocytes undergoing dedifferentiation, in steatotic hepatocytes, and in a mouse model of diet-induced steatohepatitis, irrespective of changes in ureagenesis and gut permeability. Under these conditions, GLS upregulation in the liver correlates positively with the hepatic expression of TLR4 that recognizes LPS. In agreement, the pharmacological inhibition of TLR4 reduces GLS and hepatic ammonia content in LPS-stimulated mouse hepatocytes and hyperammonemia animal models of endotoxemia.

CONCLUSIONS

Overall, our results suggest that the LPS/TLR4 axis regulates hepatic GLS expression promoting liver ammonia build-up as steatotic liver disease progresses to steatohepatitis.

The assessment and management of cirrhotic patients with encephalopathy

Hepatic encephalopathy (HE) is a debilitating complication associated with both acute and chronic liver injury. It is associated with a greater risk of death than any other significant hepatic decompensation event. It manifests as a wide spectrum of neuropsychological abnormalities ranging from subtle impairments in higher cognitive function, to confusion and coma. The pathophysiological role of ammonia in the development of HE is well known, but there is increasing recognition that the gut microbiome, gut-derived systemic inflammation and development of infection can serve as drivers of HE in patients with cirrhosis. The development of HE portents to the severity of cirrhosis and the prognosis is poor without liver transplantation. A referral for liver transplantation should therefore be considered early in those who are eligible. This review covers the pragmatic assessment of HE in patients with cirrhosis, as well as the current evidence base for the best practice management of HE in such patients.

[WITHDRAWN] Serum biomarkers of liver fibrosis identify changes in striatal metabolite levels

The full text of this preprint has been withdrawn by the authors due to author disagreement with the posting of the preprint. Therefore, the authors do not wish this work to be cited as a reference. Questions should be directed to the corresponding author.

New Insight in Hyperinsulinism/Hyperammonemia Syndrome by Magnetic Resonance Imaging and Spectroscopy

Hyperinsulinism/hyperammonemia syndrome (HI/HA) is an autosomal dominant disorder caused by monoallelic activating mutations in the glutamate dehydrogenase 1 (GLUD1) gene. While hyperinsulinism may be explained by a reduction in the allosteric inhibition of GLUD1, the pathogenesis of HA in HI/HA remains uncertain; interestingly, HA in the HI/HA syndrome is not associated with acute hyperammonemic intoxication events. We obtained a brain magnetic resonance (MR) in a woman with HI/HA syndrome with chronic asymptomatic HA. On MR spectroscopy, choline and myoinositol were decreased as in other HA disorders. In contrast, distinct from other HA disorders, combined glutamate and glutamine levels were normal (not increased). This observation suggests that brain biochemistry in HI/HA may differ from that of other HA disorders. In HI/HA, ammonia overproduction may come to the expense of glutamate levels, and this seems to prevent the condensation of ammonia with glutamate to produce glutamine that is typical of the other HA disorders. The absence of combined glutamate and glutamine elevation might be correlated to the absence of acute cerebral ammonia toxicity.

Hepatic encephalopathy and depression in chronic liver disease: is the common link systemic inflammation?

Hepatic encephalopathy and depression share a number of clinical features, such as cognitive impairment and psychomotor retardation, and are highly prevalent in patients with chronic liver disease. Both conditions signify a poor prognosis, carry an increased mortality and are major determinants of reduced health related quality of life. The pathophysiology of hepatic encephalopathy is complex. Whilst cerebral accumulation of ammonia is well-recognised as being central to the development of hepatic encephalopathy, systemic inflammation, which acts in synergy with hyperammonaemia, is emerging as a key driver in its development. The pro-inflammatory state is also widely documented in depression, and peripheral to brain communication occurs resulting in central inflammation, behavioural changes and depressive symptoms. Gut dysbiosis, with a similar reduction in beneficial bacteria, increase in pathogens and decreased bacterial diversity, has been observed in both hepatic encephalopathy and depression, and it may be that the resultant increased bacterial translocation causes their shared inflammatory pathophysiology. Whilst the literature on a positive association between hepatic encephalopathy and depression in cirrhosis remains to be substantiated, there is evolving evidence that treatment with psychobiotics may be of dual benefit, improving cognition and mood in cirrhosis.

SOFAMONIA: Comparison of the original SOFA score with the proposed new score including serum ammonia

Introduction:

Hyperammonemia can represent organic dysfunction of the brain, kidney, or liver. Evaluation of serum ammonia concentrations as a parameter for organ dysfunction may be justified.

Objective:

To evaluate the performance of serum ammonia as an additional or substitute variable for organ systems in the Sequential Organ Failure Assessment (SOFA) score.

Methods:

A prospective cohort study including 173 patients admitted to the intensive care unit between March 2015 and February 2016. SOFAMONIA scores were defined as follows: SOFAMONIA1 (Glasgow coma scale replaced by serum ammonia), SOFAMONIA2 (serum bilirubin replaced by serum ammonia), SOFAMONIA3 (renal system score replaced by serum ammonia), and SOFAMONIA4 (addition of serum ammonia to the original SOFA as the seventh variable, changing the maximum score from 24 to 28).

Results:

The original SOFA presented an area under the curve–receiver operating characteristic of 0.697 to predict hospital mortality. There was a positive correlation between SOFA and SOFAMONIA scores. SOFAMONIA1 presented a cut-off point of 5 for area under the curve 0.684 (0.610–0.753, 95% confidence interval), SOFAMONIA2 presented a cut-off point of 9 for area under the curve 0.701 (0.626–0.768, 95% confidence interval), SOFAMONIA3 presented a cut-off point of 8 for area under the curve 0.674 (0.598–0.743, 95% confidence interval), and SOFAMONIA4 presented a cut-off point of 8 for area under the curve 0.702 (0.628–0.769, 95% confidence interval).

Conclusions:

The addition of ammonia as the seventh parameter of the SOFA score showed the best performance to predict hospital mortality. The addition of ammonia as a representative of metabolic dysfunction may be useful in the follow-up of critically ill patients.

Laboratory Abnormalities of Hepatic Encephalopathy

Currently, there is no gold standard serologic or imaging modality to detect hepatic encephalopathy (HE). It is a clinical diagnosis gathered from the history and physical. Imaging is nonspecific; however, PET and MRI have shown areas of utility, but are not widely available, cost-efficient, or necessary for diagnosis. Electroencephalogram has shown promise as it can be used in conjunction with the Portal Systemic Hepatic Encephalopathy Score test to diagnose minimal HE. Further research on these techniques would need to be performed to identify strict criteria and cutoffs for diagnosing HE as well as associated sensitivities and specificities.

Predictive value of induced hyperammonaemia and neuropsychiatric profiling in relation to the occurrence of post-TIPS hepatic encephalopathy

Hepatic encephalopathy (HE) occurs in 20-50% of patients after transjugular intrahepatic portosystemic shunt (TIPS) placement. Older age, HE history and severe liver failure have all been associated with post-TIPS HE but it remains difficult to identify patients at risk. The aim of the present pathophysiological, pilot study was to assess the role of induced hyperammonaemia and associated neuropsychological and neurophysiological changes as predictors of post-TIPS HE. Eighteen TIPS candidates with no overt HE history (56 ± 8 yrs., MELD 11 ± 3) underwent neurophysiological [Electroencephalography (EEG)], neuropsychological [Psychometric Hepatic Encephalopathy Score (PHES) and Scan tests], ammonia and sleepiness assessment at baseline and after the induction of hyperammonaemia by an oral amino acid challenge (AAC). Pre-AAC, 17% of patients had abnormal EEG, 5% abnormal PHES, and 33% abnormal Scan performance. Post-AAC, 17% had abnormal EEG, 0% abnormal PHES, and 17% abnormal Scan performance. Pre-AAC, ammonia concentrations were 201 ± 73 μg/dL and subjective sleepiness 2.5 ± 1.2 (1-9 scale). Post-AAC, patients exhibited the expected increase in ammonia/sleepiness. Six months post-TIPS, 3 patients developed an episode of HE requiring hospitalization; these showed significantly lower pre-AAC fasting ammonia concentrations compared to patients who did not develop HE (117 ± 63 vs. 227 ± 57 μg/dL p = 0.015). They also showed worse PHES/Scan performance pre-AAC, and worse Scan performance post-AAC. Findings at 12 months follow-up (n = 5 HE episodes) were comparable. In conclusion, baseline ammonia levels and both pre- and post-AAC neuropsychiatric indices hold promise in defining HE risk in TIPS candidates with no HE history.

Novel spheroid reservoir bioartificial liver improves survival of nonhuman primates in a toxin-induced model of acute liver failure

This study aims to evaluate the effectiveness and safety of the spheroid reservoir bioartificial liver (SRBAL) with porcine hepatocyte organoids in a preclinical nonhuman primate model of acute liver failure (ALF). Methods: Thirty healthy rhesus monkeys were infused with α-amanitin and lipopolysaccharide and randomized into five groups (ALF alone control group; sham no-cell SRBAL treatment group; groups A, B and C with SRBAL treatment started at 12 h, 24 h and 36 h after induction of ALF, respectively). Animals were continuously treated with the SRBAL device for 6 h and followed for up to 336 h. Results: Survival of ALF monkeys improved with hepatocyte SRBAL treatment compared to control groups. Blood ammonia and total bilirubin were lower, and albumin levels were higher in all hepatocyte SRBAL treatment groups. No evidence of porcine endogenous retrovirus was identified in monkey liver or blood after SRBAL treatment. Titers of monkey antibody (IgG, IgM) did not rise after SRBAL treatment. In survival cases, the proportion of necrotic and apoptotic hepatocytes was lower in SRBAL-treated groups, with earlier liver regeneration leading to recovery. Cytokines TNF-α, IL-6, IL-12, IL-1β, IL-8, IFN-γ and IL-2 were ameliorated by the SRBAL treatment, while levels of M-CSF; HGF, EGF and VEGF; IL-1RA and MIF rose on priming, proliferation and the late phase of liver regeneration. Conclusions: The benefit of SRBAL therapy included preventive effects and therapeutic effects. SRBAL improved survival rate and prolonged median survival time in a nonhuman primate model of drug-induced ALF, and these benefits declined with a delay in the initiation of therapy. Improved survival and recovery of ALF monkeys was associated with a reduction in blood ammonia levels, inhibition of the pro-inflammatory response of ALF, and provided a microenvironment more suitable for regeneration of the injured liver.

Association of proton pump inhibitors with the risk of hepatic encephalopathy during hospitalization for liver cirrhosis

BACKGROUND

Hepatic encephalopathy is associated with altered gut microbiota. Proton pump inhibitors increase the risk of small bowel bacterial overgrowth.

OBJECTIVES

This was a case-control study aimed at exploring the relationship of proton pump inhibitor use with the risk of hepatic encephalopathy during hospitalization in liver cirrhosis.

METHODS

Case and control groups were defined as cirrhotic patients who developed hepatic encephalopathy during hospitalization and those without hepatic encephalopathy at admission or during hospitalization, respectively. Age, gender, and Child-Pugh score were matched between the groups. Odds ratios with 95% confidence intervals were calculated to express the association of proton pump inhibitors with the risk of hepatic encephalopathy. Four subgroup analyses were performed after excluding patients with acute upper gastrointestinal bleeding, infections, and in-hospital death, and after matching model for end-stage liver disease score.

RESULTS

In the overall analysis, 128 patients were included in each group of cases and controls. The proportion of proton pump inhibitor use was significantly higher in the case group than the control group (79.7% vs 43%, p < 0.001). Proton pump inhibitor use (odds ratio = 3.481, 95% confidence interval: 1.651-7.340, p = 0.001) was independently associated with the development of hepatic encephalopathy in the multivariate analysis. In the four subgroup analyses, proton pump inhibitor use remained independently associated with the risk of hepatic encephalopathy.

CONCLUSION

Proton pump inhibitor use might increase the risk of hepatic encephalopathy during hospitalization.

Sleep disturbances in patients of liver cirrhosis with minimal hepatic encephalopathy before and after lactulose therapy

Sleep disturbances are common in patients of cirrhosis with minimal hepatic encephalopathy (MHE) and affect health related quality of life (HRQOL). No study has evaluated effect of lactulose on sleep disturbances and correlation with HRQOL in patients with MHE. We assessed sleep disturbances in cirrhosis with MHE and effect of lactulose on sleep disturbances and HRQOL. One hundred patients of cirrhosis [MHE; (n = 50, age 45.3 ± 11.2 years, 45 males) no-MHE (n = 50, age 46.3 ± 10.4 years, 44 males)] were included. MHE was diagnosed with psychometric hepatic encephalopathy score (PHES) ≤ -5. All patients underwent laboratory parameters including arterial ammonia and critical flicker frequency (CFF) Sleep disturbances were measured with Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS) and polysomnography. HRQOL was measured with SF-36(v2) questionnaire. Patients with MHE were given lactulose therapy for 3 months and all the parameters were repeated. Poor quality of sleep and excessive day time sleepiness were more common in patients with MHE, compared to without MHE. With lactulose therapy there was improvement in MHE in 21 patients and arterial ammonia levels (93.74 ± 14.8 vs. 71.44 ± 18.8 μmol/L: p < 0.001), CFF (34.83 ± 3.54 vs. 39.44 ± 4.95 Hz: p < 0.001), PHES (-7.64 ± 2.1 vs. -5.58 ± 2.09: p < 0.001), PSQI (8.6 ± 3.3 vs. 5.2 ± 1.5: p < 0.001), ESS (12.52 ± 3.01 vs. 9.24 ± 2.27: p < 0.001) and HRQOL (p = 0.01). Excessive day time sleepiness and impaired sleep quality are common in patients with MHE and correlate with neuropsychiatric impairment. Improvement in MHE with lactulose also leads to improvement in sleep disturbances and HRQOL.

Ammonia mediates cortical hemichannel dysfunction in rodent models of chronic liver disease

The pathogenesis of hepatic encephalopathy (HE) in cirrhosis is multifactorial and ammonia is thought to play a key role. Astroglial dysfunction is known to be present in HE. Astrocytes are extensively connected by gap junctions formed of connexins, which also exist as functional hemichannels allowing exchange of molecules between the cytoplasm and the extracellular milieu. The astrocyte-neuron lactate shuttle hypothesis suggests that neuronal activity is fueled (at least in part) by lactate provided by neighboring astrocytes. We hypothesized that in HE, astroglial dysfunction could impair metabolic communication between astrocytes and neurons. In this study, we determined whether hyperammonemia leads to hemichannel dysfunction and impairs lactate transport in the cerebral cortex using rat models of HE (bile duct ligation [BDL] and induced hyperammonemia) and also evaluated the effect of ammonia-lowering treatment (ornithine phenylacetate [OP]). Plasma ammonia concentration in BDL rats was significantly reduced by OP treatment. Biosensor recordings demonstrated that HE is associated with a significant reduction in both tonic and hypoxia-induced lactate release in the cerebral cortex, which was normalized by OP treatment. Cortical dye loading experiments revealed hemichannel dysfunction in HE with improvement following OP treatment, while the expression of key connexins was unaffected.

CONCLUSION

The results of the present study demonstrate that HE is associated with central nervous system hemichannel dysfunction, with ammonia playing a key role. The data provide evidence of a potential neuronal energy deficit due to impaired hemichannel-mediated lactate transport between astrocytes and neurons as a possible mechanism underlying pathogenesis of HE. (Hepatology 2017;65:1306-1318).

A longitudinal study of patients with cirrhosis treated with L-ornithine L-aspartate, examined with magnetization transfer, diffusion-weighted imaging and magnetic resonance spectroscopy

The presence of overt hepatic encephalopathy (HE) is associated with structural, metabolic and functional changes in the brain discernible by use of a variety of magnetic resonance (MR) techniques. The changes in patients with minimal HE are less well documented. Twenty-two patients with well-compensated cirrhosis, seven of whom had minimal HE, were examined with cerebral 3 Tesla MR techniques, including T₁- and T₂-weighted, magnetization transfer and diffusion-weighted imaging and proton magnetic resonance spectroscopy sequences. Studies were repeated after a 4-week course of oral L-ornithine L-aspartate (LOLA). Results were compared with data obtained from 22 aged-matched healthy controls. There was no difference in mean total brain volume between patients and controls at baseline. Mean cerebral magnetization transfer ratios were significantly reduced in the globus pallidus and thalamus in the patients with cirrhosis irrespective of neuropsychiatric status; the mean ratio was significantly reduced in the frontal white matter in patients with minimal HE compared with healthy controls but not when compared with their unimpaired counterparts. There were no significant differences in either the median apparent diffusion coefficients or the mean fractional anisotropy, calculated from the diffusion-weighted imaging, or in the mean basal ganglia metabolite ratios between patients and controls. Psychometric performance improved in 50 % of patients with minimal HE following LOLA, but no significant changes were observed in brain volumes, cerebral magnetization transfer ratios, the diffusion weighted imaging variables or the cerebral metabolite ratios. MR variables, as applied in this study, do not identify patients with minimal HE, nor do they reflect changes in psychometric performance following LOLA.

Quantitative magnetic resonance imaging in patients with cirrhosis: a cross-sectional study

Cerebral magnetic resonance imaging was undertaken, at 3 Tesla field strength, employing magnetization transfer (MT) and diffusion-weighted imaging (DWI) sequences, in 26 patients with well-compensated cirrhosis, free of overt hepatic encephalopathy. Results were compared to those from 18 aged-matched healthy volunteers. Cerebral magnetization transfer ratios (MTR) were reduced in the frontal white matter, caudate, putamen and globus pallidus in patients with cirrhosis, compared to healthy controls, while the apparent diffusion coefficients (ADC) on DWI were significantly increased in the genu and body of the corpus callosum. An association between previous excessive alcohol consumption and both MTR and ADCs was noted, but this association was lost when controls were exercised for the severity of liver disease and psychometric impairment on multivariate analysis. Eight (31 %) of the 26 patients had impaired psychometric performance consistent with a diagnosis of minimal hepatic encephalopathy. No statistically significant difference in regional cerebral MTRs or ADCs was found in relation to neuropsychiatric status, although there was a trend towards lower MTRs in patients with impaired psychometric performance. The alterations in MTR and ADC in the patients with functionally compensated cirrhosis are compatible with theories governing the genesis of hepatic encephalopathy, including changes in astrocyte membrane permeability, with subsequent redistribution of macromolecules.

The role of antioxidants and zinc in minimal hepatic encephalopathy: a randomized trial

BACKGROUND

Minimal hepatic encephalopathy (MHE) has a far-reaching impact on quality and function ability in daily life and may progress to overt hepatic encephalopathy. There is a synergistic effect between systemic oxidative stress and ammonia that is implicated in the pathogenesis of hepatic encephalopathy. The aim of this study is to investigate the effectiveness of oral supplementation of antioxidants and zinc gluconate on MHE versus lactulose.

METHODS

Our study included 58 patients with cirrhosis diagnosed as having MHE by neuropsychometric tests, including number connection test part A (NCT-A), digit symbol test (DST) and block design tests (BDTs). Patients were randomized to receive 175 mg zinc gluconate, 50,000 IU vitamin A, 500 mg vitamin C and 100 mg vitamin E once daily plus lactulose, dose 30-60 ml/day for 3 months [group A (n = 31)] or initiated and maintained on lactulose dose 30-60 ml/day for 3 months [group B (n = 27)]. Neuropsychometric tests and laboratory investigations were repeated after 3 months of therapy.

RESULTS

Compared with the baseline neuropsychometric tests, a significant improvement was reported in patients with MHE after 3 months of antioxidant and zinc therapy (group A) versus patients with lactulose therapy (group B) (NCT-A, p <0.001; DST, p = 0.006; BDT, p < 0.001). Antioxidant and zinc supplementation significantly decreased arterial ammonia level, alanine aminotransferase (ALT), aspartate aminotransferase (AST) (p < 0.001) and improved Child-Pugh score in MHE after 3 months of therapy (p= 0.024).

CONCLUSION

Antioxidant and zinc supplementation can improve MHE in patients with liver cirrhosis.

Computer-based tools for assessing micro-longitudinal patterns of cognitive function in older adults

Patterns of cognitive change over micro-longitudinal timescales (i.e., ranging from hours to days) are associated with a wide range of age-related health and functional outcomes. However, practical issues of conducting high-frequency assessments make investigations of micro-longitudinal cognition costly and burdensome to run. One way of addressing this is to develop cognitive assessments that can be performed by older adults, in their own homes, without a researcher being present. Here, we address the question of whether reliable and valid cognitive data can be collected over micro-longitudinal timescales using unsupervised cognitive tests.In study 1, 48 older adults completed two touchscreen cognitive tests, on three occasions, in controlled conditions, alongside a battery of standard tests of cognitive functions. In study 2, 40 older adults completed the same two computerized tasks on multiple occasions, over three separate week-long periods, in their own homes, without a researcher present. Here, the tasks were incorporated into a wider touchscreen system (Novel Assessment of Nutrition and Ageing (NANA)) developed to assess multiple domains of health and behavior. Standard tests of cognitive function were also administered prior to participants using the NANA system.Performance on the two "NANA" cognitive tasks showed convergent validity with, and similar levels of reliability to, the standard cognitive battery in both studies. Completion and accuracy rates were also very high. These results show that reliable and valid cognitive data can be collected from older adults using unsupervised computerized tests, thus affording new opportunities for the investigation of cognitive.

Spectral electroencephalogram in liver cirrhosis with minimal hepatic encephalopathy before and after lactulose therapy

BACKGROUND AND AIM

Minimal hepatic encephalopathy (MHE) represents the mildest form of hepatic encephalopathy. Spectral electroencephalogram (sEEG) analysis improves the recognition of MHE by decreasing inter-operator variability and providing quantitative parameters of brain dysfunction. We compared sEEG in patients with cirrhosis with and without MHE and the effects of lactulose on sEEG in patients with MHE.

METHODS

One hundred patients with cirrhosis (50 with and 50 without MHE) were enrolled. Diagnosis of MHE was based on psychometric hepatic encephalopathy score (PHES) of ≤ -5. Critical flicker frequency, model of end-stage liver disease score, and sEEG were performed at baseline in all patients. The spectral variables considered were the mean dominant frequency (MDF) and relative power in beta, alpha, theta, and delta bands. Patients with MHE were given 3 months of lactulose, and all parameters were repeated.

RESULTS

Spectral electroencephalogram analysis showed lower MDF (7.8 ± 1.7 vs 8.7 ± 1.3 Hz, P < 0.05) and higher theta relative power (34.29 ± 4.8 vs 24 ± 6.7%, P = 001) while lower alpha relative power (28.6 ± 4.0 vs 33.5 ± 5.3%, P = .001) in patients with MHE than in patients without MHE. With theta relative power, sensitivity 96%, specificity 84%, and accuracy of 90% were obtained for diagnosis of MHE. After lactulose treatment, MHE improved in 21 patients, and significant changes were seen in MDF (7.8 ± 0.5 vs 8.5 ± 0.6), theta (34.2 ± 4.8 vs 23.3 ± 4.1%), alpha (28.6 ± 4.0 vs 35.5 ± 4.5%), and delta relative power (13.7 ± 3.5 vs 17.0 ± 3.3%) after treatment (P ≤ 0.05).

CONCLUSIONS

Spectral EEG is a useful objective and quantitative tool for diagnosis and to assess the response to treatment in patients with cirrhosis with MHE.

The brain following transjugular intrahepatic portosystemic shunt: the perspective from neuroimaging

Hepatic encephalopathy (HE) is a common complication after implantation of a transjugular intrahepatic portosystemic shunt (TIPS). Neuroimaging offers a variety of techniques for non-invasive evaluation of alterations in metabolism, as well as structural and functional changes of the brain in patients after TIPS implantation. In this article, we review the epidemiology and pathophysiology of post-TIPS HE. The potential of neuroimaging including positron emission tomography and multimodality magnetic resonance imaging to investigate the pathophysiology of post-TIPS HE is presented. We also give a perspective on the role of neuroimaging in this field.

Refining the ammonia hypothesis: a physiology-driven approach to the treatment of hepatic encephalopathy

Hepatic encephalopathy (HE) is one of the most important complications of cirrhosis and portal hypertension. Although the etiology is incompletely understood, it has been linked to ammonia directly and indirectly. Our goal is to review for the clinician the mechanisms behind hyperammonemia and the pathogenesis of HE to explain the rationale for its therapy. We reviewed articles collected through a search of MEDLINE/PubMed, Cochrane Database of Systematic Reviews, and Google Scholar between October 1, 1948, and December 8, 2014, and by a manual search of citations within retrieved articles. Search terms included hepatic encephalopathy, ammonia hypothesis, brain and ammonia, liver failure and ammonia, acute-on-chronic liver failure and ammonia, cirrhosis and ammonia, portosytemic shunt, ammonia and lactulose, rifaximin, zinc, and nutrition. Ammonia homeostatsis is a multiorgan process involving the liver, brain, kidneys, and muscle as well as the gastrointestinal tract. Indeed, hyperammonemia may be the first clue to poor functional reserves, malnutrition, and impending multiorgan dysfunction. Furthermore, the neuropathology of ammonia is critically linked to states of systemic inflammation and endotoxemia. Given the complex interplay among ammonia, inflammation, and other factors, ammonia levels have questionable utility in the staging of HE. The use of nonabsorbable disaccharides, antibiotics, and probiotics reduces gut ammoniagenesis and, in the case of antibiotics and probiotics, systemic inflammation. Nutritional support preserves urea cycle function and prevents wasting of skeletal muscle, a significant site of ammonia metabolism. Correction of hypokalemia, hypovolemia, and acidosis further assists in the reduction of ammonia production in the kidney. Finally, early and aggressive treatment of infection, avoidance of sedatives, and modification of portosystemic shunts are also helpful in reducing the neurocognitive effects of hyperammonemia. Refining the ammonia hypothesis to account for these other factors instructs a solid foundation for the effective treatment and prevention of hepatic encephalopathy.

Brain magnetic resonance in hepatic encephalopathy

The term hepatic encephalopathy (HE) covers a wide spectrum of neuropsychiatric abnormalities caused by portal-systemic shunting. The diagnosis requires demonstration of liver dysfunction or portal-systemic shunts and exclusion of other neurologic disorders. Most patients with this condition have liver dysfunction caused by cirrhosis, but it also occurs in patients with acute liver failure and less commonly, in patients with portal-systemic shunts that are not associated with hepatocellular disease. Various magnetic resonance (MR) techniques have improved our knowledge about the pathophysiology of HE. Proton MR spectroscopy and T1-weighted imaging can detect and quantify accumulations of brain products that are normally metabolized or eliminated such as glutamine and manganese. Other MR techniques such as T2-weighted and diffusion-weighted imaging can identify white matter abnormalities resulting from disturbances in cell volume homeostasis secondary to brain hyperammonemia. Partial or complete recovery of these abnormalities has been observed with normalization of liver function or after successful liver transplantation. MR studies have undoubtedly improved our understanding of the mechanisms involved in the pathogenesis of HE, and some findings can be considered biomarkers for monitoring the effects of therapeutic measures focused on correcting this condition.

Ammonia metabolism and hyperammonemic disorders

Human adults produce around 1000 mmol of ammonia daily. Some is reutilized in biosynthesis. The remainder is waste and neurotoxic. Eventually most is excreted in urine as urea, together with ammonia used as a buffer. In extrahepatic tissues, ammonia is incorporated into nontoxic glutamine and released into blood. Large amounts are metabolized by the kidneys and small intestine. In the intestine, this yields ammonia, which is sequestered in portal blood and transported to the liver for ureagenesis, and citrulline, which is converted to arginine by the kidneys. The amazing developments in NMR imaging and spectroscopy and molecular biology have confirmed concepts derived from early studies in animals and cell cultures. The processes involved are exquisitely tuned. When they are faulty, ammonia accumulates. Severe acute hyperammonemia causes a rapidly progressive, often fatal, encephalopathy with brain edema. Chronic milder hyperammonemia causes a neuropsychiatric illness. Survivors of severe neonatal hyperammonemia have structural brain damage. Proposed explanations for brain edema are an increase in astrocyte osmolality, generally attributed to glutamine accumulation, and cytotoxic oxidative/nitrosative damage. However, ammonia neurotoxicity is multifactorial, with disturbances also in neurotransmitters, energy production, anaplerosis, cerebral blood flow, potassium, and sodium. Around 90% of hyperammonemic patients have liver disease. Inherited defects are rare. They are being recognized increasingly in adults. Deficiencies of urea cycle enzymes, citrin, and pyruvate carboxylase demonstrate the roles of isolated pathways in ammonia metabolism. Phenylbutyrate is used routinely to treat inherited urea cycle disorders, and its use for hepatic encephalopathy is under investigation.

Chinese herbal medicine formula Jieduhuayu granules improves cognitive and neurophysiological functions in patients with cirrhosis who have minimal hepatic encephalopathy: a randomized controlled trial

BACKGROUND

Minimal hepatic encephalopathy (MHE) impairs patients' cognitive and neurophysiological functions. In this study, we investigated the effect of treatment-related improvement in cognitive and neurophysiological functions.

METHODS

We measured psychometric performance by number connection tests part A (NCT-A), digit symbol test (DST), mini-mental state examination (MMSE) and event related potential P300 wave of 80 patients with cirrhosis who have minimal hepatic encephalopathy on inclusion into the study and 15 days later. They were randomly assigned in a 1:1:1:1 ratio to four groups, to receive treatment of Chinese herbal medicine formula (HMG) or lactulose (LG) or Chinese herbal medicine formula combined with lactulose (HMCLG) for 15 days (n=20) or no treatment (CG) (n=20). This study was not blind.

RESULTS

The mean number of NCT-A and MMSE scores improved significantly in patients in the HMG (0 day, 102.00±24.49 for NCT-A, 18.55±2.89 for MMSE; 15 days, 78.30±22.55 for NCT-A, 24.20±2.78 for MMSE) compared with patients in the CG after 15 days of follow-up (0 day, 103.00±24.98 for NCT-A, 17.90±2.99 for MMSE; 15 days, 95.65±24.34 for NCT-A, 18.85±3.12 for MMSE), P<0.05; the mean number of P300 latency (ms) and wave amplitude (μV) improved significantly among patients in the HMG after 15 days of treatment (0 day, 341.90±14.04 for latency, 8.40±1.73 for wave amplitude; 15 days, 305.45±23.95 for latency, 13.00±3.80 for wave amplitude) compared with patients in the CG after 15 days of follow-up (0 day, 343.85±14.88 for latency, 8.29±1.77 for wave amplitude; 15 days, 340.40±13.06 for latency, 8.50±1.82 for wave amplitude), P<0.05. Similar improvement were also found among patients in the LG and HMCLG; improvements among patients in the HMG were significantly greater than they were in the LG (P<0.05). Synergistic action were shown among patients in the HMCLG (P<0.05).

CONCLUSION

Treatment with Chinese herbal medicine formula Jieduhuayu granules and lactulose may improve cognitive and neurophysiological functions in patients with cirrhosis who have MHE. Compared with lactulose alone, Chinese herbal medicine formula Jieduhuayu granules has higher efficacy of improving cognitive and neurophysiological functions in patients with cirrhosis who have MHE, and the two of them together show synergistic action.

TRIAL REGISTRATION NUMBER

ACTRN12614000193673.

Recent insights into the pathogenesis of hepatic encephalopathy and treatments

Hepatic encephalopathy (HE) encompasses a spectrum of neuropsychiatric disorders related to liver failure. The development of HE can have a profound impact on mortality as well as quality of life for patients and carers. Ammonia is central in the disease process contributing to alteration in neurotransmission, oxidative stress, and cerebral edema and astrocyte swelling in acute liver failure. Inflammation in the presence of ammonia coactively worsens HE. Inflammation can result from hyperammonemic responses, endotoxemia, innate immune dysfunction or concurrent infection. This review summarizes the current processes implicated in the pathogenesis of HE, as well as current and potential treatments. Treatments currently focus on reducing inflammation and/or blood ammonia levels and provide varying degrees of success. Optimization of current treatments and initial testing of novel therapies will provide the basis of improvement of care in the near future.

Serum endotoxin, inflammatory mediators, and magnetic resonance spectroscopy before and after treatment in patients with minimal hepatic encephalopathy

BACKGROUND

Minimal hepatic encephalopathy (MHE) represents the mildest form of hepatic encephalopathy (HE), with abnormal neuropsychologic findings. Inflammatory response may be important in the pathogenesis of MHE. On magnetic resonance spectroscopy (MRS), improvement of metabolic ratios after liver transplantation suggests an important role of myoinositol (mI) and choline (cho) in the development of MHE.

AIMS

To investigate arterial ammonia, tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-18, serum endotoxin, and MRS before and after treatment in MHE.

PATIENTS AND METHODS

Sixty patients of cirrhosis with MHE were randomized to two groups, Gr. MHE-L (n = 30), treated with lactulose for 3 months, and Gr. MHE-NL (n = 30), who did not received lactulose. Arterial ammonia, TNF-α, IL-6, IL-18, serum endotoxin, and MRS were performed in all patients at baseline and at 3 months and 20 patients of cirrhosis without MHE and 20 healthy controls.

RESULTS

After 3 months, median arterial ammonia (69.4 vs 52.7 mcg/dL), TNF-α (26.6 vs 22 pg/mL), IL-6 (17.6 vs 12.4 pg/mL), IL-18 (42.5 vs 29 pg/mL), and serum endotoxin (0.68 vs 0.43 EU/mL) significantly decreased in Gr. MHE-L compared with baseline (P < 0.0001), while no change was seen in Gr. MHE-NL patients. On MRS, compared with patients of cirrhosis without MHE, mI and cho were significantly lower (P < 0.001) and glutamine (Glx) was significantly higher in both MHE groups (P < 0.001). After 3 months, mI and cho increased and Glx decreased significantly in Gr. MHE-L (P < 0.001), without changes in Gr. MHE-NL patients. Psychometric hepatic encephalopathic score (PHES) correlated well with arterial ammonia, TNF-α, IL-6, IL-18, serum endotoxin, and metabolic parameters on MRS.

CONCLUSIONS

Arterial ammonia, inflammatory mediators (TNF-α, IL-6, IL-18), and serum endotoxin reduce and MRS abnormalities improve after treatment with lactulose in patients with MHE.

Pathogenesis of hepatic encephalopathy: lessons from nitrogen challenges in man

Induction of hyperammonaemia with nitrogen challenge in man can be used to study the pathogenesis and treatment of hepatic encephalopathy complicating cirrhosis. Initially 20 g of glutamine was given orally as a flavored solution which resulted in doubling of blood ammonia concentration and this was associated with a deterioration in performance of the choice reaction time. The effect could have been due to a direct effect of glutamine rather than the ammonia generated so in subsequent experiments a glutamine free mixture of amino acids resembling the composition of haemoglobin was used (gastrointestinal bleeding is a known precipitant of hepatic encephalopathy). In Child grade B and C patients, 2-3 h after 54 g, slowing of the EEG was observed. The cerebral effects of induced hyperammonaemia were studied with diffusion weighted imaging and MR spectroscopy after giving 54 g of a mixture of threonine, serine and glycine when apparent diffusion coefficient increased. Also the change in ammonia levels correlated with the change in cerebral glutamine levels (r = 0.78, p = 0.002) suggesting intra cerebral formation of glutamine from ammonia and this may have accounted for the fall in cerebral myoinositol concentrations observed. Finally a colonic source for ammonia was confirmed by administering urea using colon coated capsules when ammonia concentrations slowly increased from 5 h after administration and rapidly after 10 h. In two patients the hyperammonaemia was ameliorated by pre treatment with Rifaximin 1200 mg per day for 1 week. Nitrogen challenge studies are thus a valuable model for studying new treatments for hepatic encephalopathy without the need to simultaneously treat precipitating factors.

Inflammation and hepatic encephalopathy

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome associated with both acute and chronic liver dysfunction, spanning a spectrum that ranges from mild neuropsychological disturbances to coma. The central role of ammonia in the pathogenesis of HE remains incontrovertible however, there is a robust evidence base indicating the important role of inflammation in exacerbating the neurological effects of HE. Inflammation can arise directly within the brain itself as a result of deranged nitrogen and energy homeostasis, with resultant neuronal, astrocyte and microglial dysfunction. Inflammation may also originate in the peripheral circulation and exert effects on the brain indirectly, via the release of pro-inflammatory mediators which directly signal to the brain via the vagus nerve. This review summarises the data that demonstrate the synergistic relationship of inflammation and ammonia that culminates in the manifestation of HE. Sterile inflammation arising from the inflamed or necrotic liver, circulating endotoxin arising from the gut (bacterial translocation) inducing immune dysfunction, and superimposed sepsis will be comprehensively discussed. Finally, this review will provide an overview of the existing and novel treatments on the horizon which can target the inflammatory response, and how they might translate into clinical practise as therapies in the prophylaxis and treatment of HE.

Serum endotoxin and inflammatory mediators in patients with cirrhosis and hepatic encephalopathy

BACKGROUND

Recent observations suggest that inflammatory response may be important in the pathogenesis of hepatic encephalopathy. The aim of the study was to measure arterial ammonia, tumour necrosis factor-alpha, Interleukin-6, Interleukin-18, and serum endotoxin levels and their correlation with different grades of hepatic encephalopathy.

METHODS

120 patients with cirrhosis were enrolled: 20 patients each of cirrhosis with grades I, II, III and IV hepatic encephalopathy, cirrhosis with and without minimal hepatic encephalopathy and healthy controls were tested for arterial ammonia, tumour necrosis factor-alpha, Interleukin-6, Interleukin-18 and serum endotoxin levels.

RESULTS

Median arterial ammonia, tumour necrosis factor-alpha, Interleukin-6, Interleukin-18 and serum endotoxin levels were significantly higher in patient with hepatic encephalopathy and minimal hepatic encephalopathy as compared to patients without minimal hepatic encephalopathy and healthy controls. Arterial ammonia (r = 0.72, p = 0.03), tumour necrosis factor alpha (r = 0.87, p = 0.02), Interleukin-6 (r = 0.50, p = 0.05), Interleukin-18 (r = 0.76, p = 0.02) and serum endotoxin (r = 0.91, p = 0.01) correlated with higher grades of hepatic encephalopathy.

CONCLUSION

In hepatic encephalopathy arterial ammonia, inflammatory mediators, and serum endotoxin are elevated and correlate with encephalopathy grade.

Overnight glucose infusion suppresses renal ammoniagenesis and reduces hyperammonaemia induced by a simulated bleed in cirrhotic patients

BACKGROUND

A simulated upper gastrointestinal (UGI) bleed in cirrhotic patients has been shown to induce hyperammonaemia. The kidney was the site of this exaggerated ammoniagenesis with alanine as substrate. Administration of alanine to decompensated cirrhotic patients did not change hepatic gluconeogenesis, but resulted in increased ammoniagenesis. We hypothesise that reduced hepatic glycogen stores result in hyperglucagonaemia which may drive increased renal gluconeogenesis and therefore alanine uptake and renal ammoniagenesis.

AIM

To determine whether an overnight glucose infusion lowers renal ammoniagenesis by reducing hyperglucagonaemia and renal ammoniagenesis.

METHODS

Patients with decompensated cirrhosis were studied in a cross-over design. An UGI bleed was simulated via intragastric administration of an amino acids mixture mimicking the haemoglobin molecule after a 12-h overnight fast (F-group) or after a 12-h treatment with 20% glucose solution (G-group).

RESULTS

Before the simulated bleed the glucagon levels were 21 (15-31) pmol/L in the F-group and 15 (9-21) pmol/L in the G-group (P < 0.01). After the simulated bleed, arterial ammonia levels increased in both groups [F-group: 73-118 μmol/L (P = 0.01); G-group 64-87 μmol/L (P = 0.01)]. The enhancement of hyperammonaemia was significantly higher in the F-group (45 [19-71] μmol/L) compared with the G-group (23 [13-39] μmol/L) (P = 0.01). The difference in renal ammoniagenesis during the simulated bleed in the F-group was 399 (260-655) nmol/kg/bwt/min and was significantly higher than in the G-group 313 (1-498) nmol/kg/bwt/min (P = 0.05).

CONCLUSIONS

Overnight glucose infusion results in reduced renal ammoniagenesis and attenuates ammonia levels. These observations have implications for the development of nutritional strategies in hyperammonaemic patients.

Reduction in hyperammonaemia by ornithine phenylacetate prevents lipopolysaccharide-induced brain edema and coma in cirrhotic rats

OBJECTIVE

In liver failure, inflammation synergistically exacerbates the deleterious cerebral effects of ammonia. The aims were to test whether treatment with the ammonia-lowering agent ornithine phenylacetate (OP) and/or anti-TNF-α (infliximab) prevent the deleterious brain consequences of lipopolysaccharide (LPS) in cirrhotic rats.

DESIGN

Rats 4 weeks following bile duct-ligation (BDL), sham-operation (sham) and/or 7 days hyperammonemic feed (HD), were randomized to receive LPS (1 mg/kg) or saline, and treatment with either 3 days intraperitoneal injections of OP (0.6 g/kg) and/or infliximab, 10 mg/kg. Animals were sacrificed at coma stages or at 3 h.

RESULTS

In sham rats, both HD and LPS increased brain water, with an increase in ammonia in the former and brain cytokines in the latter but with no effect on consciousness. BDL + HD rats caused significantly higher plasma ammonia, TNF-α and IL-6 levels compared to sham. LPS significantly worsened coma stage, increased brain water and plasma and brain TNF-α. OP significantly delayed LPS-induced progression to coma stages (P < 0.009), reduced arterial ammonia and brain water (P < 0.001 and P < 0.01 respectively), which was associated with a significant reduction in cytokines. Infliximab significantly reduced plasma and brain cytokines, but not brain water. OP + infliximab attenuated increase in brain water and delayed occurrence of coma, which was not different to OP alone. In BDL rats, OP reduced the expression of brain iNOS and NFκB.

CONCLUSION

Reduction in ammonia with OP in cirrhotic rats prevents LPS-induced brain edema and delays coma, suggesting that ammonia may prime the brain to the deleterious effect of LPS, possibly through effects on iNOS and NFκB related mechanisms.

Hepatic encephalopathy after transjugular intrahepatic portosystemic shunt

Transjugular intrahepatic portosystemic shunt (TIPS) has been used for more than 20 years to treat some of the complications of portal hypertension. When TIPS was initially proposed, it was claimed that the optimal calibration of the shunt could allow an adequate reduction of portal hypertension, avoiding, at the same time, the occurrence of hepatic encephalopathy (HE), a neurologic syndrome. However, several clinical observations have shown that HE occurred rather frequently after TIPS, and HE has become an important issue to be taken into consideration in TIPS candidates and a problem to be faced after the procedure.

Hepatic encephalopathy

Chronic liver disease and cirrhosis affect hundreds of millions of patients all over the world. The majority of patients with cirrhosis will eventually develop complications related to portal hypertension. One of these recurrent and difficult to treat complications is hepatic encephalopathy. Studies have indicated that overt hepatic encephalopathy affects 30 to 45% of patients with cirrhosis and a higher percentage may be affected by minimal degree of encephalopathy. All of these factors add to the impact of hepatic encephalopathy on the healthcare system and presents a major challenge to the gastroenterologist, hospitalist and primary care physician.

A capillary blood ammonia bedside test following glutamine load to improve the diagnosis of hepatic encephalopathy in cirrhosis

Background

Hepatic encephalopathy (HE) is a frequent and severe complication of cirrhosis. A single determination of ammonia in venous blood correlates poorly with neurological symptoms. Thus, a better biological marker is needed.

Aim

To make a diagnosis of HE, we explored the value of ammonia in capillary blood, an equivalent to arterial blood, measured at bedside following an oral glutamine challenge.

Methods

We included 57 patients (age 56 yrs; M/F: 37/20) with cirrhosis (alcoholic = 42; MELD score 13.8 [7-29], esophageal varices = 38) and previous episodes of HE (n = 19), but without neurological deficits at time of examination, and 13 healthy controls (age 54 yrs). After psychometric tests and capillary (ear lobe) blood ammonia measurements, 20 gr of glutamine was administered orally. Tests were repeated at 60 minutes (+ blood ammonia at 30'). Minimal HE was diagnosed if values were > 1.5 SD in at least 2 psychometric tests. Follow-up lasted 12 months.

Results

The test was well tolerated (nausea = 1; dizziness = 1). Patients showed higher values of capillary blood ammonia over time as compared to controls (0'-30'-60 minutes: 75, 117, 169 versus 52, 59, 78 umol/L, p < 0.05). At baseline, 25 patients (44%) had minimal HE, while 38 patients (67%) met the criteria for HE at 60 minutes (chi²: p < 0.01). For the diagnosis of minimal HE, using the ROC curve analysis, baseline capillary blood ammonia showed an AUC of 0.541 (CI: 0.38-0.7, p = 0.6), while at 60 minutes the AUC was 0.727 (CI: 0.58-0.87, p < 0.006). During follow-up, 18 patients (31%) developed clinical episodes of HE. At multivariate analysis, the MELD score (1.12 [1.018-1.236]), previous episodes of HE (3.2[1.069-9.58]), but not capillary blood ammonia, were independent predictors of event.

Conclusions

In patients with cirrhosis and normal neurological examination, bedside determination of ammonia in capillary blood following oral glutamine load is well tolerated and achieves a better diagnostic performance for minimal HE than basal capillary ammonia levels. However, capillary blood ammonia is a poor predictor of development of clinically overt HE.

Absence of neuropsychological impairment in hyperammonaemia in healthy young adults; possible synergism in development of hepatic encephalopathy (HE) symptoms?

The aetiology of minimal hepatic encephalopathy (mHE) remains unclear. It is generally accepted that hyperammonaemia plays a major role, however there are a multitude of metabolic perturbations present. To determine the contribution of hyperammonaemia to mHE symptom development, ten healthy males (Age:25 ± 5 yrs, BM:76.3 ± 7.1 kg, Height:178.6 ± 4.5 cm, mean ± SD) received two 4 h intravenous infusions of either a 2% ammonium chloride solution (AMM) or a placebo (PLA;0.9% sodium chloride) using a double blind cross-over design. Sensations of fatigue were measured at baseline, 2 and 4 h using the Multidimensional Fatigue Symptom Inventory-Short Form (MFSI-SF) questionnaire. Learning & memory, motor control and cognition were assessed using Rey's Auditory Verbal Learning Test (AVL), Continuous Compensatory Tracking (COMPTRACK) Task and Inhibitory Control Test (ICT) respectively. Arterialised venous blood samples were collected every hour, and analysed for ammonia concentration. There was a significantly higher plasma ammonia concentration in the AMM trial than the PLA trial at every time point during the infusion, peaking at 2 h (57 ± 4 μmol/L PLA, 225 ± 14 μmol/L AMM; p < 0.05). At 2 h there were significantly higher sensations of general fatigue (Z = -2.527, p = 0.008, 2 tailed) and physical fatigue (Z = -2.156, p = 0.027, 2 tailed), and lower sensations of vigour (Z = -2.456, p = 0.012, 2 tailed) for the AMM trial. There were no significant effects on the performance of the psychological tasks. These results demonstrate that hyperammonaemia in the absence of other complications induces significant sensations of fatigue but does not cause the typically observed performance impairment in individuals with mHE. Supporting the hypothesis for synergism between ammonia and other co-factors in mHE.

A randomized controlled trial comparing lactulose, probiotics, and L-ornithine L-aspartate in treatment of minimal hepatic encephalopathy

BACKGROUND

Minimal hepatic encephalopathy (MHE) impairs daily functioning and health-related quality of life (HRQoL). The modalities of treatment of MHE have not been adequately studied.

AIMS

To compare lactulose, probiotics, and L-ornithine L-aspartate (LOLA) in treatment of MHE and effect on HRQoL by Sickness Impact Profile questionnaire.

METHODS

Consecutive patients with cirrhosis were screened for MHE. MHE was diagnosed by two or more abnormal psychometric tests (number/figure connection tests A and B, block design test, picture completion test). Patients were randomized to no treatment (GpA), lactulose 30-60 ml/twice per day (GpB), probiotics 110 billion colony forming units twice in a day (GpC), LOLA 6 g three times per day (GpD) for 3 months. Arterial ammonia and HRQoL assessment using SIP questionnaire was done at baseline and at 3 months.

RESULTS

One hundred and sixty (49.69%) of 322 patients with cirrhosis had MHE. After 3 months, MHE recovered in GpA four (10%), GpB 19 (47.5%), GpC 14 (35%), and GpD 14 (35%). MHE improved significantly in all three treatment groups (GpB, GpC, GpD) compared with no treatment (GpA) (P=0.006). Overt hepatic encephalopathy developed in nine (5.6%) of 160 patients; GpA four (10%), GpB one (2.5%), GpC two (5%), and GpD two (5%), respectively. There was significant improvement in SIP score in GpB (6.98±4.1), GpC (6.24±3.4), and GpD (7.33±3.8) versus GpA (1.05±2.6), P value of less than 0.001. The decrease in SIP score correlated with an improvement in MHE on multivariate analysis but there was no correlation with the type of intervention offered. There was no significant change in arterial ammonia level after therapy in GpA (-0.52±7.8 μmol/l). Arterial ammonia level in GpB (-8.47±5.8 μmol/l), GpC (-7.31±7.9 μmol/l), and GpD (-9.61±9.3 μmol/l) were significantly more than GpA (P<0.0001).

CONCLUSION

Lactulose, probiotics, and LOLA significantly improve MHE and HRQoL in patients with chronic liver disease.

Magnetic resonance quantification of water and metabolites in the brain of cirrhotics following induced hyperammonaemia

BACKGROUND & AIMS

Hepatic encephalopathy (HE) is now thought to be caused by cerebral oedema although the precise pathogenesis is uncertain. We hypothesised that if ammonia is a key factor, induced hyperammonaemia would lead to transient changes in brain water distribution and metabolite concentration, detectable by diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS).

METHODS

Thirteen cirrhotic patients being evaluated for liver transplantation were challenged with 54 g of equal parts of threonine, serine, and glycine. Conventional magnetic resonance imaging was performed to exclude structural lesions and localise regions of interest. DTI was used to generate white matter apparent diffusion coefficient (ADC) maps and proton MRS to measure brain metabolite concentrations before and after the challenge.

RESULTS

The challenge caused a mean (±SD) rise in blood ammonia of 58 (±41) μmol/L, which was accompanied by a significant 9% increase in ADC (p=0.004). Increased ADC significantly correlated with blood ammonia (r=0.58, p=0.04). The change in ammonia levels also correlated with the increase in glutamine levels (r=0.78, p=0.002). Myo-inositol concentration decreased significantly by 0.7 (±0.7)mMol/L between scans and this correlated with the mean difference in ADC (r=0.59, p<0.04).

CONCLUSIONS

These results show that ammonia can directly drive changes in brain water distribution as a mechanism for cerebral oedema development. Since cerebral astrocytes contain glutamine synthetase, our MRS data suggest intracerebral formation of glutamine from ammonia. The rapid decrease in myo-inositol indicates that this organic osmolyte plays a protective role in HE by release from astrocytes in order to maintain cell volume.

Infection and systemic inflammation, not ammonia, are associated with Grade 3/4 hepatic encephalopathy, but not mortality in cirrhosis

BACKGROUND & AIMS

Patients with cirrhosis are prone to infection which is a frequent precipitant of hepatic encephalopathy (HE). Clinical studies have examined the importance of inflammation and infection in modulating the manifestation of symptoms of HE in acute liver failure and patients with cirrhosis and minimal/low grade HE. It would be logical to presume that this relationship persists in patients who develop severe HE in cirrhosis although this has not been examined to date.

METHODS

We report the findings of a prospective audit of 100 consecutive patients with cirrhosis admitted between Jan 2000 and March 2008 to a liver Intensive Care Unit (ICU) where HE was the primary indication for admission (59% Grade 3; 41% Grade 4). Haematological and microbiological data were collected at ICU admission, and organ scores and outcomes were recorded.

RESULTS

46% of patients had positive cultures taken within ± 48h from admission to ICU [25% blood] and a further 22% were culture negative but had evidence of systemic inflammation (SIRS). SIRS score (p=0.03) and SOFA score (p=0.006) were significantly higher in those patients with Grade 4 HE, who were also less likely to survive (p<0.001). HE grade/coma score did not correlate with ammonia, biochemistry or MELD score. Fifty-two percent of patients survived their ICU stay while the remainder developed progressive multiorgan failure and died; 38% survived to discharge, and 16% were transplanted.

CONCLUSIONS

These data support an association between infection/SIRS and not ammonia, in patients with cirrhosis that develop severe HE. The presence or absence of infection/SIRS did not determine survival.

Changing face of hepatic encephalopathy: Role of inflammation and oxidative stress

The face of hepatic encephalopathy (HE) is changing. This review explores how this neurocognitive disorder, which is associated with both acute and chronic liver injury, has grown to become a dynamic syndrome that spans a spectrum of neuropsychological impairment, from normal performance to coma. The central role of ammonia in the pathogenesis of HE remains incontrovertible. However, over the past 10 years, the HE community has begun to characterise the key roles of inflammation, infection, and oxidative/nitrosative stress in modulating the pathophysiological effects of ammonia on the astrocyte. This review explores the current thoughts and evidence base in this area and discusses the potential role of existing and novel therapies that might abrogate the oxidative and nitrosative stresses inflicted on the brain in patients with, or at risk of developing, HE.

Role of aquaporin-4 in the development of brain oedema in liver failure

BACKGROUND & AIMS

Liver failure is associated with progressive cytotoxic brain oedema (astrocyte swelling), which underlies hepatic encephalopathy (HE). Ammonia and superimposed inflammation are key synergistic factors in HE, but the mechanism(s) involved remain unknown. We aimed to determine whether aquaporin-4 (AQP4), an astrocyte endfeet bi-directional water channel, is associated with the brain oedema of HE.

METHOD

Rats (n=60) received sham-operation (sham), 5 days hyperammonaemia-inducing diet (HD), galactosamine (GALN) induced acute liver failure (ALF), 4 weeks bile duct-ligation (BDL) induced cirrhosis, or caecal ligation and puncture (CLP), a 24h model of bacterial peritonitis. Rats from every group (except CLP) were randomised to receive intraperitoneal injections of lipopolysaccharide (LPS; 1mg/kg) or saline, prior to termination 3h later. Brain water, AQP4 protein expression (western blot) and AQP4 localisation by immunogold electron microscopy were investigated.

RESULTS

Significant hyperammonaemia was observed in saline-injected BDL (p<0.05), GALN (p<0.01), and HD (p<0.01), compared to sham rats. LPS injection did not affect arterial ammonia or plasma biochemistry in any of the treatment groups. Increased brain water was observed in saline-injected GALN (p<0.05), HD (p<0.01), and CLP (p<0.001) compared to sham rats. Brain water was numerically increased in BDL rats, but this failed to reach significance (p=0.09). LPS treatment further increased oedema significantly in all treatment groups (p<0.05, respectively). AQP4 expression was significantly increased in saline-injected BDL (p<0.05), but not other treatment groups, compared to sham rats. Membrane polarisation was maintained in BDL rats.

CONCLUSION

The results suggest that AQP4 is not directly associated with the development of brain oedema in liver failure, hyperammonaemia, or sepsis. In cirrhosis, there is increased AQP4 protein expression, but membrane polarisation, is maintained, possibly in a compensatory attempt to limit severe brain oedema.

Minimal hepatic encephalopathy: consensus statement of a working party of the Indian National Association for Study of the Liver

Hepatic encephalopathy (HE) is a major complication that develops in some form and at some stage in a majority of patients with liver cirrhosis. Overt HE occurs in approximately 30-45% of cirrhotic patients. Minimal HE (MHE), the mildest form of HE, is characterized by subtle motor and cognitive deficits and impairs health-related quality of life. The Indian National Association for Study of the Liver (INASL) set up a Working Party on MHE in 2008 with a mandate to develop consensus guidelines on various aspects of MHE relevant to clinical practice. Questions related to the definition of MHE, its prevalence, diagnosis, clinical characteristics, pathogenesis, natural history and treatment were addressed by the members of the Working Party.

Brain MR imaging and 1H-MR spectroscopy changes in patients with extrahepatic portal vein obstruction from early childhood to adulthood

BACKGROUND AND PURPOSE

MR imaging and (1)H-MR spectroscopy changes are well reported in cirrhotic patients, whereas they are inadequately reported in EHPVO. The aim of this study was to investigate age-related changes in brain MR imaging and metabolite profile in EHPVO with and without MHE and to explore any correlation of imaging and (1)H-MR spectroscopy parameters with blood ammonia.

MATERIALS AND METHODS

Sixty-three patients with EHPVO (children, 7-12 years [n = 22], adolescents, 13-18 years [n = 15] and adults, 19-41 years [n = 26]) and 47 healthy age/sex-matched volunteers were studied. Neuropsychological tests, MR imaging, (1)H-MR spectroscopy, and blood ammonia estimation were performed in all subjects.

RESULTS

Of 63 EHPVO patients, 25 (40%) who had MHE showed significantly increased MD, Glx, and blood ammonia in all 3 age groups; however, myo-inositol was significantly lower only in adults when compared with controls. MD positively correlated with blood ammonia and Glx in all age groups. Brain choline levels were normal in all patients with different age groups.

CONCLUSIONS

Increases in brain MD, Glx, and blood ammonia were associated with MHE in all age groups. Normal brain choline in EHPVO signifies healthy liver and may serve as a diagnostic marker for its differentiation from cirrhosis-induced encephalopathy. Significant decrease of myo-inositol in adults is probably due to cellular osmoregulation secondary to long-standing hyperammonemia.

Ammonia and the neutrophil in the pathogenesis of hepatic encephalopathy in cirrhosis

Hepatic encephalopathy (HE) constitutes a neuropsychiatric syndrome which remains a major clinical problem in patients with cirrhosis. In the severest form of HE, cirrhotic patients may develop varying degrees of confusion and coma. Ammonia has been regarded as the key precipitating factor in HE, and astrocytes have been the most commonly affected cells neuropathologically. Although the evidence base supporting a pivotal role of ammonia is robust, in everyday clinical practice a consistent correlation between the concentration of ammonia in the blood and the manifest symptoms of HE is not observed. More recently the synergistic role of inflammation and infection in modulating the cerebral effects of ammonia has been shown to be important. Furthermore, it has been recognized that infection impairs brain function both in the presence and absence of liver disease. Thus it could be postulated that in the presence of ammonia, the brain is sensitized to a systemic inflammatory stimulus and is able to elicit an inflammatory response involving both proinflammatory and neurotransmitter pathways. Ammonia is not only directly toxic to astrocytes but induces neutrophil dysfunction with the release of reactive oxygen species, which contribute to oxidative stress and systemic inflammation. This may further exacerbate the cerebral effects of ammonia and potentially reduce the capacity of the neutrophil to fight microbial attack, thus inducing a vicious circle. This evidence supports the neutrophil in addition to ammonia as being culpable in the pathogenesis of HE, making the neutrophil a target for future anti-inflammatory therapeutic strategies in addition to ammonia lowering therapies.

Encephalopathy assessment in children with extra-hepatic portal vein obstruction with MR, psychometry and critical flicker frequency

BACKGROUND & AIMS

Mild cognitive and psychomotor deficit has been reported in patients with extra-hepatic portal vein obstruction. This prospective study was done to ascertain the presence of minimal hepatic encephalopathy by neuropsychological testing and its correlation with diffusion tensor imaging derived metrics, T1 signal intensity, brain metabolites in (1)H magnetic resonance spectroscopy, blood ammonia and critical flicker frequency in patients with extra-hepatic portal vein obstruction.

METHODS

Neuropsychological tests, critical flicker frequency, blood ammonia, diffusion tensor imaging, T1 signal intensity and (1)H magnetic resonance spectroscopy were determined in 22 extra-hepatic portal vein obstruction and 17 healthy children. Bonferroni multiple comparison post hoc analysis was done to compare controls with patient groups.

RESULTS

Based on neuropsychological tests, 7/22 patients had minimal hepatic encephalopathy, and significantly increased Glx/Cr ratio, blood ammonia, mean diffusivity and globus pallidus T1 signal intensity with decreased critical flicker frequency in comparison to controls and in those without minimal hepatic encephalopathy. Cho/Cr, mI/Cr ratio and fractional anisotropy were unchanged in patient groups compared to controls. A significant inverse correlation of neuropsychological test with mean diffusivity, Glx/Cr ratio and blood ammonia and a positive correlation among mean diffusivity, blood ammonia and Glx/Cr ratio was seen.

CONCLUSIONS

Extra-hepatic portal vein obstruction is a true hyperammonia model with porto-systemic shunting and normal liver functions that results in minimal hepatic encephalopathy in one-third of these children. Hyperammonia results in generalized low grade cerebral edema and cognitive decline as evidenced by increased Glx/Cr ratio, mean diffusivity values and abnormal neuropsychological tests.

Ammonia metabolism, the brain and fatigue; revisiting the link

This review addresses the ammonia fatigue theory in light of new evidence from exercise and disease studies and aims to provide a view of the role of ammonia during exercise. Hyperammonemia is a condition common to pathological liver disorders and intense or exhausting exercise. In pathology, hyperammonemia is linked to impairment of normal brain function and the onset of the neurological condition, hepatic encephalopathy. Elevated blood ammonia concentrations arise due to a diminished capacity for removal via the liver and lead to increased exposure of organs, such as the brain, to the toxic effects of ammonia. High levels of brain ammonia can lead to deleterious alterations in astrocyte morphology, cerebral energy metabolism and neurotransmission, which may in turn impact on the functioning of important signalling pathways within the neuron. Such changes are believed to contribute to the disturbances in neuropsychological function, in particular the learning, memory, and motor control deficits observed in animal models of liver disease and also patients with cirrhosis. Hyperammonemia in exercise occurs as a result of an increased production by contracting muscle, through adenosine monophosphate (AMP) deamination (the purine nucleotide cycle) and branched chain amino acid (BCAA) deamination prior to oxidation. Plasma concentrations of ammonia during exercise often achieve or exceed those measured in liver disease patients, resulting in increased cerebral uptake. In this article we propose that exercise-induced hyperammonemia may lead to concomitant disturbances in brain function, potentially through similar mechanisms underpinning pathology, which may impact on performance as fatigue or reduced function, especially during extreme exercise.

Voxel-based analyses of magnetization transfer imaging of the brain in hepatic encephalopathy

AIM: To evaluate the spatial distribution of cerebral abnormalities in cirrhotic subjects with and without hepatic encephalopathy (HE) found with magnetization transfer imaging (MTI).

METHODS: Nineteen cirrhotic patients graded from neurologically normal to HE grade 2 and 18 healthy control subjects underwent magnetic resonance imaging. They gave institutional-review-board-approved written consent. Magnetization transfer ratio (MTR) maps were generated from MTI. We tested for significant differences compared to the control group using statistical non-parametric mapping (SnPM) for a voxel-based evaluation.

RESULTS: The MTR of grey and white matter was lower in subjects with more severe HE. Changes were found in patients with cirrhosis without neurological deficits in the basal ganglia and bilateral white matter. The loss in magnetization transfer increased in severity and spatial extent in patients with overt HE. Patients with HE grade 2 showed an MTR decrease in white and grey matter: the maximum loss of magnetization transfer effect was located in the basal ganglia [SnPM (pseudo-)t = 17.98, P = 0.0001].

CONCLUSION: The distribution of MTR changes in HE points to an early involvement of basal ganglia and white matter in HE.

Minimal hepatic encephalopathy

Minimal hepatic encephalopathy (MHE) is the mildest form of spectrum of hepatic encephalopathy (HE). Patients with MHE have no recognizable clinical symptoms of HE but have mild cognitive and psychomotor deficits. The prevalence of MHE is high in patients with cirrhosis of liver and varies between 30% and 84%; it is higher in patients with poor liver function. The diagnostic criteria for MHE have not been standardized but rest on careful patient history and physical examination, normal mental status examination, demonstration of abnormalities in cognition and/or neurophysiological function, and exclusion of concomitant neurological disorders. MHE is associated with impaired health-related quality of life, predicts the development of overt HE and is associated with poor survival. Hence, screening all patients with cirrhosis for MHE using psychometric tests, and treatment of those patients diagnosed to have MHE has been recommended. Ammonia plays a key role in the pathogenesis of MHE, which is thought to be similar to that of overt HE. Thus, ammonia-lowering agents such as lactulose and probiotics have been tried. These agents have been shown to improve cognitive and psychometric deficits, and have good safety profile. Future studies will better define the role of other drugs, such as rifaximin, acetyl L-carnitine and L-ornithine L-aspartate.

L-ornithine and phenylacetate synergistically produce sustained reduction in ammonia and brain water in cirrhotic rats

Treatment of hyperammonemia and hepatic encephalopathy in cirrhosis is an unmet clinical need. The aims of this study were to determine whether L-ornithine and phenylacetate/phenylbutyrate (administered as the pro-drug phenylbutyrate) (OP) combined are synergistic and produce sustained reduction in ammonia by L-ornithine acting as a substrate for glutamine synthesis, thereby detoxifying ammonia, and the phenylacetate excreting the ornithine-derived glutamine as phenylacetylglutamine in the urine. Sprague-Dawley rats were studied 4 weeks after bile duct ligation (BDL) or sham operation. Study 1: Three hours before termination, an internal carotid sampling catheter was inserted, and intraperitoneal saline (placebo), OP, phenylbutyrate, or L-ornithine were administered after randomization. BDL was associated with significantly higher arterial ammonia and brain water and lower brain myoinositol (P < 0.01, respectively), compared with sham-operated controls, which was significantly improved in the OP-treated animals; arterial ammonia (P < 0.001), brain water (P < 0.05), brain myoinositol (P < 0.001), and urinary phenylacetylglutamine (P < 0.01). Individually, L-ornithine or phenylbutyrate were similar to the BDL group. In study 2, BDL rats were randomized to saline or OP administered intraperitoneally for 6 hours or 3, 5, or 10 days and were sacrificed between 4.5 and 5 weeks. The results showed that the administration of OP was associated with sustained reduction in arterial ammonia (P < 0.01) and brain water (P < 0.01) and markedly increased arterial glutamine (P < 0.01) and urinary excretion of phenylacetylglutamine (P < 0.01) in each of the OP treated groups.

CONCLUSION

The results of this study provide proof of the concept that L-ornithine and phenylbutyrate/phenylacetate act synergistically to produce sustained improvement in arterial ammonia, its brain metabolism, and brain water in cirrhotic rats.