Oral amino acid load mimicking hemoglobin results in reduced regional cerebral perfusion and deterioration in memory tests in patients with cirrhosis of the liver

L-Isoleucine reverses hyperammonemia-induced myotube mitochondrial dysfunction and post-mitotic senescence

Perturbations in the metabolism of ammonia, a cytotoxic endogenous metabolite, occur in a number of chronic diseases, with consequent hyperammonemia. Increased skeletal muscle ammonia uptake causes metabolic, molecular, and phenotype alterations including cataplerosis of (loss of tricarboxylic acid cycle (TCA) cycle intermediate) α-ketoglutarate (αKG), mitochondrial oxidative dysfunction, and senescence-associated molecular phenotype (SAMP). L-Isoleucine (Ile) is an essential, branched-chain amino acid (BCAA) that simultaneously provides acetyl-CoA as an oxidative substrate and succinyl-CoA for anaplerosis (providing TCA cycle intermediates). Our multiomics analyses in myotubes and skeletal muscle from hyperammonemic mice and human patients with cirrhosis showed perturbations in BCAA transporters and catabolism. We, therefore, determined if Ile reverses hyperammonemia-induced impaired mitochondrial oxidative function and SAMP. Studies were performed in differentiated murine C2C12 myotubes that were early passage, late passage (senescent), or those depleted of LAT1/SLC7A5 and human induced pluripotent stem cell-derived myotubes (hiPSCM). Ile reverses hyperammonemia-induced reduction in the maximum respiratory capacity, complex I, II, and III functions in early passage murine myotubes and hiPSCM. Consistently, low ATP content and impaired global protein synthesis (high energy requiring cellular process) during hyperammonemia are reversed by Ile in murine myotubes and hiPSCM. Lower abundance of critical regulators of protein synthesis in mTORC1 signaling, and increased phosphorylation of eukaryotic initiation factor 2α are also reversed by Ile. Genetic depletion studies showed that Ile responses are independent of the amino acid transporter LAT1/SLC7A5. Our studies show that Ile reverses the hyperammonemia-induced impaired mitochondrial oxidative function, cataplerosis, and SAMP in a LAT1/SLC7A5 transporter-independent manner.

Prediction and prevention of the first episode of overt hepatic encephalopathy in patients with cirrhosis

Hepatic encephalopathy (HE) is one of the most important complications of patients with liver cirrhosis. In addition, HE is associated with a dismal prognosis and has detrimental effects on patients' quality of life. Thus, it is of pivotal importance to identify patients at high risk for overt HE (OHE) in whom primary prophylaxis may be justified. In this narrative review, we aim to provide insight into predictors and prediction tools for a first-time episode of OHE and to scrutinize the current level of evidence of primary prophylaxis. In recent decades, several cognitive tests, composite scores, and blood-based biomarkers have been demonstrated to be predictive of a first-time episode of OHE. Among the best validated are the established tests for minimal HE, such as the Psychometric Hepatic Encephalopathy Score, determination of the critical flicker frequency, Stroop EncephalApp, or the Animal Naming Test. Individualized risk stratification using blood-based biomarkers and cross-sectional imaging (sarcopenia and spontaneous portosystemic shunts) is coming to the fore, but validation in larger multicenter cohorts is often lacking. On the basis of current evidence, a recommendation for primary prophylaxis of a first episode of OHE cannot be made in general. Only 2 studies have investigated the prevention of a first-time OHE episode as the primary endpoint. In this narrative review, we provide a concise overview of the current evidence levels on prediction tools and pharmacological prevention of a first episode of OHE. In addition, we give an outlook on future research targets to improve knowledge on this important topic.

EASL Clinical Practice Guidelines on the management of hepatic encephalopathy

The EASL Clinical Practice Guidelines (CPGs) on the management of hepatic encephalopathy (HE) present evidence-based answers to a set of relevant questions (where possible, formulated in PICO [patient/population, intervention, comparison and outcomes] format) on the definition, diagnosis, differential diagnosis and treatment of HE. The document does not cover the pathophysiology of HE and does not cover all available treatment options. The methods through which it was developed and any information relevant to its interpretation are also provided.

Is there a link between bacteriuria and a reversible encephalopathy in dogs and cats?

Bacteriuria has been associated with abnormal neurological status in humans, especially geriatric patients. In this report, we review 11 cases (seven dogs and four cats) that suggest an association between bacteriuria and abnormal neurological status in veterinary medicine. These cases showed diffuse forebrain signs with or without brainstem signs, but primary brain disease was excluded by MRI and cerebrospinal fluid analysis. Bacteriological culture of urine was positive in each animal and neurological deficits improved or resolved with initiation of antibiosis ± fluid therapy and levetiracetam. While further studies are needed to definitively confirm or refute the link between bacteriuria and a reversible encephalopathy, urine bacteriological culture should be considered in veterinary patients presented with acute onset forebrain neuro-anatomical localisation, even in the absence of clinical signs of lower urinary tract inflammation.

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.

Neuromodulation and Palliative Medicine

The palliative care population is generally vulnerable to experiencing medication-induced adverse effects and drug–drug interactions. Neuromodulation may offer particular advantages over systemic medications in this population. Spinal cord stimulation and peripheral nerve stimulation have long been utilized in efforts to provide analgesia for various painful conditions. More recently, deep brain stimulation/motor cortex stimulation has anecdotally been utilized for certain intractable pain states. Although brain electrical stimulation has not been adequately trialed or in some cases even tried at all for management of a variety of symptoms, it is conceivable that in the future it may be a potential therapeutic option in efforts to palliate various severe refractory symptoms (eg, intractable pain, nausea, dyspnea, delirium).

Association of pre-operative brain pathology with post-operative delirium in a cohort of non-small cell lung cancer patients undergoing surgical resection

OBJECTIVE

Post-operative delirium is associated with pre-operative cognitive difficulties and diminished functional independence, both of which suggest that brain pathology may be present in affected individuals prior to surgery. Currently, there are few studies that have examined imaging correlates of post-operative delirium. To our knowledge, none have examined the association of delirium with existing structural pathology in pre-operative cancer patients. Here, we present a novel, retrospective strategy to assess pre-operative structural brain pathology and its association with post-operative delirium. Standard of care structural magnetic resonance imaging (MRIs) from a cohort of surgical candidates prior to surgery were analyzed for white matter hyperintensities and cerebral atrophy.

METHODS

We identified 23 non-small cell lung cancer patients with no evidence of metastases in the brain pre-operatively, through retrospective chart review, who met criteria for post-operative delirium within 4 days of surgery. 24 age- and gender-matched control subjects were identified for comparison to the delirium sample. T1 and fluid-attenuated inversion recovery sequences were collected from standard of care pre-operative MRI screening and assessed for white matter pathology and atrophy.

RESULTS

We found significant differences in white matter pathology between groups with the delirium group exhibiting significantly greater white matter pathology than the non-delirium group. Measure of cerebral atrophy demonstrated no significant difference between the delirium and non-delirium group.

CONCLUSIONS

In this preliminary study utilizing standard of care pre-operative brain MRIs for assessment of structural risk factors to delirium, we found white matter pathology to be a significant risk factor in post-operative delirium. Limitations and implications for further investigation are discussed.

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.

Ammonia reduction with ornithine phenylacetate restores brain eNOS activity via the DDAH-ADMA pathway in bile duct-ligated cirrhotic rats

Ammonia is central in the pathogenesis of hepatic encephalopathy, which is associated with dysfunction of the nitric oxide (NO) signaling pathway. Ornithine phenylacetate (OP) reduces hyperammonemia and brain water in cirrhotic animals. This study aimed to determine whether endothelial NO synthase activity is altered in the brain of cirrhotic animals, whether this is associated with changes in the endogenous inhibitor, asymmetric-dimethylarginine (ADMA) and its regulating enzyme, dimethylarginine-dimethylaminohydrolase (DDAH-1), and whether these abnormalities are restored by ammonia reduction using OP. Sprague-Dawley rats were studied 4-wk after bile duct ligation (BDL) (n = 16) or sham operation (n = 8) and treated with placebo or OP (0.6 g/kg). Arterial ammonia, brain water, TNF-α, plasma, and brain ADMA were measured using standard techniques. NOS activity was measured radiometrically, and protein expression for NOS enzymes, ADMA, DDAH-1, 4-hydroxynonenol ((4)HNE), and NADPH oxidase (NOX)-1 were measured by Western blotting. BDL significantly increased arterial ammonia (P < 0.0001), brain water (P < 0.05), and brain TNF-α (P < 0.01). These were reduced significantly by OP treatment. The estimated eNOS component of constitutive NOS activity was significantly lower (P < 0.05) in BDL rat, and this was significantly attenuated in OP-treated animals. Brain ADMA levels were significantly higher and brain DDAH-1 significantly lower in BDL compared with sham (P < 0.01) and restored toward normal following treatment with OP. Brain (4)HNE and NOX-1 protein expression were significantly increased in BDL rat brain, which were significantly decreased following OP administration. We show a marked abnormality of NO regulation in cirrhotic rat brains, which can be restored by reduction in ammonia concentration using OP.

Dynamic susceptibility contrast-enhanced first-pass perfusion MR imaging in patients with subclinical hepatic encephalopathy

BACKGROUND AND PURPOSE

Subclinical hepatic encephalopathy (SHE) is frequently reported on single-photon emission computed tomography (SPECT), but is rarely described with magnetic resonance (MR) techniques. This study aimed to investigate hemodynamic changes in brain basal ganglia in patients with SHE using dynamic susceptibility contrast (DSC)-enhanced MR perfusion imaging.

METHODS

Twelve patients with SHE and ten age- and education-matched volunteers agreed to undergo MR examination. The scanning protocol included conventional anatomical images and DSC-enhanced perfusion MR imaging. Using MGH perfusion software, parameter maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were created. The bilateral caudate nucleus head, globus pallidus, putamen and thalamus were selected as regions of interest (ROI), with ipsilateral white matter of the frontal lobe used as reference. Ratios (ROI versus ipsilateral white matter in frontal lobe) for CBF, CBV and MTT in the patient group were compared with those in the control group.

RESULTS

The CBF ratios for every ROI were higher in SHE patients versus the controls. Statistically, significant increases were detected in the left globus pallidus, putamen and thalamus (P<0.05). For MTT, the reduction in values reached statistical significance in the right head of the caudate nucleus and bilateral thalamus (P<0.05). CBV values were not significantly different compared with those of the control group (P>0.05).

CONCLUSION

Increased CBF and decreased MTT values in the basal ganglia and thalamus were identified in patients with SHE. The CBF increase was compatible with the idea that the CBF is redistributed from cortical areas to the basal ganglia structures.

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.

Hepatic encephalopathy: pathophysiology and emerging therapies

Hepatic encephalopathy is characterized by neuropsychiatric abnormalities in patients with liver failure. Severe hepatic encephalopathy is an indication for liver transplantation as it portends poor outcome. Treatment of hepatic encephalopathy involves correction of precipitating factors such as sepsis, gastrointestinal bleeding, medications, and electrolyte imbalance. Effective therapies include lactulose and antibiotics such as neomycin, metronidazole, and rifaximin.

Delirium in elderly adults: diagnosis, prevention and treatment

Delirium is a common and serious acute neuropsychiatric syndrome with core features of inattention and global cognitive dysfunction. The etiologies of delirium are diverse and multifactorial and often reflect the pathophysiological consequences of an acute medical illness, medical complication or drug intoxication. Delirium can have a widely variable presentation, and is often missed and underdiagnosed as a result. At present, the diagnosis of delirium is clinically based and depends on the presence or absence of certain features. Management strategies for delirium are focused on prevention and symptom management. This article reviews current clinical practice in delirium in elderly individuals, including the diagnosis, treatment, outcomes and economic impact of this syndrome. Areas of future research are also discussed.

Delirium in elderly adults: diagnosis, prevention and treatment

Delirium is a common and serious acute neuropsychiatric syndrome with core features of inattention and global cognitive dysfunction. The etiologies of delirium are diverse and multifactorial and often reflect the pathophysiological consequences of an acute medical illness, medical complication or drug intoxication. Delirium can have a widely variable presentation, and is often missed and underdiagnosed as a result. At present, the diagnosis of delirium is clinically based and depends on the presence or absence of certain features. Management strategies for delirium are focused on prevention and symptom management. This article reviews current clinical practice in delirium in elderly individuals, including the diagnosis, treatment, outcomes and economic impact of this syndrome. Areas of future research are also discussed.

Enzymatic suppression of the membrane conductance associated with the glutamine transporter SNAT3 expressed in Xenopus oocytes by carbonic anhydrase II

The transport activity of the glutamine/neutral amino acid transporter SNAT3 (former SN1, SLC38A3), expressed in oocytes of the frog Xenopus laevis is associated with a non-stoichiometrical membrane conductance selective for Na⁺ and/or H⁺ (Schneider, H.P., S. Bröer, A. Bröer, and J.W. Deitmer. 2007. J. Biol. Chem. 282:3788–3798). When we expressed SNAT3 in frog oocytes, the glutamine-induced membrane conductance was suppressed, when carbonic anhydrase isoform II (CAII) had been injected into the oocytes. Transport of substrate, however, was not affected by CAII. The reduction of the membrane conductance by CAII was dependent on the presence of CO₂/HCO₃⁻, and could be reversed by blocking the catalytic activity of CAII by ethoxyzolamide (10 μM). Coexpression of wild-type CAII or a N-terminal CAII mutant with SNAT3 also reduced the SNAT3- associated membrane conductance. The catalytically inactive CAII mutant V143Y coexpressed in oocytes did not affect SNAT3-associated membrane conductance. Our results reveal a new type of interaction between CAII and a transporter-associated cation conductance, and support the hypothesis that the transport of substrate and the non-stoichiometrical ion conductance are independent of each other. This study also emphasizes the importance of carbonic anhydrase activity and the presence of CO₂-bicarbonate buffers for membrane transport processes.

The role of neuroimaging in elucidating delirium pathophysiology

Understanding of delirium pathogenesis remains limited despite improved diagnosis, and elucidation of risk factors and prognosis. Major advances in neuroimaging offer the possibility of probing the mechanisms and networks involved in delirium and hence improving understanding of this often devastating syndrome. This review describes the current literature of imaging studies in delirium and related conditions, introduces some of the newer capabilities of neuroimaging with magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography, and discusses how these techniques may be applied to the study of delirium. Despite considerable challenges in patient recruitment, study design, intersubject variability, and scanner and contrast agent availability, imaging offers great potential for the identification and clarification of pathogenic mechanisms of delirium and its long-term sequelae.

Role of ammonia and inflammation in minimal hepatic encephalopathy

BACKGROUND

Minimal hepatic encephalopathy (MHE) is common in cirrhosis but its pathophysiologic basis remains undefined. We evaluated whether the presence of MHE was associated with severity of liver disease, ammonia levels or the presence of inflammation and assessed factors determining neuropsychological deterioration accompanying induction of hyperammonemia.

METHODS

Eighty four cirrhotics were studied. A neuropsychological test battery was performed and blood taken for ammonia, WCC, CRP, nitrate/nitrite, IL-6 and amino acids, before and after, induction of hyperammonemia by administration of a solution mimicking the amino acid composition of haemoglobin (60) or placebo (24).

RESULTS

The presence and severity of MHE were independent of severity of liver disease and ammonia concentration but markers of inflammation were significantly higher in those with MHE compared with those without. Induction of hyperammonemia produced deterioration in one or more neuropsychological tests by > or =1 SD in 73.3%. This was independent of the magnitude of change in plasma ammonia and severity of liver disease but was significantly greater in those with more marked inflammation.

CONCLUSION

Our data show that inflammation is an important determinant of the presence and severity of MHE. The change in neuropsychological function following induced hyperammonemia is greater in those with more severe inflammation.

Review article: bacterial flora and pathogenesis in hepatic encephalopathy

The aetiology of hepatic encephalopathy has not been conclusively established, but it is widely agreed that ammonia derived primarily from enteric bacterial flora plays a central role. Recent research on the pathogenesis of hepatic encephalopathy reinforces previous findings, supporting an integral role of bacteria-derived ammonia and reveals other potential mechanisms by which bacterial flora and pathogens may be pathophysiologically important. This review discusses this research and considers its implications for the therapeutic management of hepatic encephalopathy. Besides producing ammonia, the enteric flora generates other neurotoxic products, such as phenols and mercaptans, that may potentiate the effects of ammonia. Bacteria may also constitute a primary source of the benzodiazepine-like compounds implicated in neuropsychiatric symptoms in patients with liver disease. New evidence suggests that acute bacterial infections, long recognized as important precipitants of hepatic encephalopathy, may mediate clinical worsening through effects on systemic inflammatory responses. Considered together, these data suggest wide-ranging pathophysiological contributions of bacteria to hepatic encephalopathy and underline the potential for an integral role of antibiotics and other bactericidal agents in its management.

Amino acid challenge in patients with cirrhosis and control subjects: ammonia, plasma amino acid and EEG changes

BACKGROUND/AIMS

The pathogenesis of hepatic encephalopathy (HE) is controversial. We have therefore studied the effect of induced hyperammonaemia in man.

PATIENTS AND METHODS

108 g of an amino acid mixture was given orally to 18 cirrhotics and 11 control subjects and changes in blood ammonia, EEG and plasma amino acids were observed.

RESULTS

Basal (39+/-6 versus 14+/-2 micromol/l) and 120-min post amino acid (77+/-10 versus 27+/-4) blood ammonia concentrations in cirrhotics were significantly increased compared to healthy controls (p < 0.001). Associated with these changes there was a significant increase in the ratio of slow-to-fast wave activity indicating EEG slowing (+0.41+/-0.16; N=13 versus -0.05+/-0.08; N=8; p=0.036). As expected in cirrhotics, basal valine and leucine concentrations were decreased while phenylalanine, tyrosine and methionine were significantly increased. Although the basal molar ratio of branched chain amino acids to the aromatic amino acids phenylalanine and tyrosine was significantly decreased in cirrhotics (1.5+/-0.2 versus 3.2+/-0.2; p < 0.0001), after the challenge when EEG changes were apparent in cirrhotics, the ratio significantly increased (p < 0.005) in both groups to 2.7+/-0.3 versus 4.1+/-0.3 (p=0.002). In the combined groups, there were significant correlations between EEG ratio change and the 120-min blood ammonia concentration (r=0.498; p=0.022).

CONCLUSION

The alterations in plasma amino acid patterns do not support a specific role for any of the amino acid groups in the pathogenesis of hepatic encephalopathy. They are however more in keeping with the direct or indirect role of ammonia.

Low myo-inositol and high glutamine levels in brain are associated with neuropsychological deterioration after induced hyperammonemia

The neuropsychological effect of hyperammonemia is variable. This study tests the hypothesis that the effect of ammonia on the neuropsychological function in patients with cirrhosis is determined by the ability of the brain to buffer ammonia-induced increase in glutamine within the astrocyte by losing osmolytes like myo-inositol (mI) and not by the magnitude of the induced hyperammonemia. Fourteen cirrhotic patients with no evidence of overt hepatic encephalopathy were given a 75-g amino acid (aa) solution mimicking the hemoglobin molecule to induce hyperammonemia. Measurement of a battery of neuropsychological function tests including immediate memory, ammonia, aa, and short-echo time proton magnetic resonance spectroscopy were performed before and 4 h after administration of the aa solution. Eight patients showed deterioration in the Immediate Memory Test at 4 h. Demographic factors, severity of liver disease, change in plasma ammonia, and aa profiles after the aa solution were similar in those that showed a deterioration compared with those who did not. In patients who showed deterioration in the memory test, the mI-to-creatine ratio (mI/Cr) was significantly lower at baseline than those that did not deteriorate. In contrast, the glutamate/glutamine-to-Cr ratio was significantly greater in the patients that deteriorated. The observation that deterioration in the memory test scores was greater in those with lower mI/Cr supports the hypothesis that the neuropsychological effects of induced hyperammonemia is determined by the capacity of the brain to handle ammonia-induced increase in glutamine.

Systemic inflammatory response exacerbates the neuropsychological effects of induced hyperammonemia in cirrhosis

BACKGROUND/AIMS

Studies in acute liver failure show correlation between evidence of a systemic inflammatory response syndrome (SIRS) and progression of hepatic encephalopathy (HE). We tested the hypothesis that SIRS mediators, such as nitric oxide and proinflammatory cytokines, may exacerbate the neuropsychological effects of hyperammonemia in cirrhosis.

METHODS

Ten patients with cirrhosis were studied, 24-36 h after admission with clinical evidence of infection, and following its resolution. Hyperammonemia was induced by oral administration of an amino-acid (aa) solution mimicking hemoglobin composition. Inflammatory mediators, nitrate/nitrite, ammonia, aa profiles and a battery of neuropsychological tests were measured.

RESULTS

The hyperammonemia generated in response to the aa solution was similar prior to, and after resolution, of the inflammation (P=0.77). With treatment of the infection there were significant reductions in white blood cell count (WBC), C-reactive protein (CRP), nitrate/nitrite, interleukin-6, interleukin-1beta and tumour necrosis factor alpha. Induced hyperammonemia resulted in significant worsening of the neuropsychological scores when patients showed evidence of SIRS but not after its resolution.

CONCLUSIONS

The significant deterioration of neuropsychological test scores following induced hyperammonemia during the inflammatory state, but not after its resolution, suggests that the inflammation and its mediators may be important in modulating the cerebral effect of ammonia in liver disease.

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

Hyperammonemia is a universal finding after gastrointestinal hemorrhage in cirrhosis. We administered an oral amino acid solution mimicking the hemoglobin molecule to examine neuropsychological changes, brain glutamine levels, and brain magnetization transfer ratio (MTR). Forty-eight metabolically stable patients with cirrhosis and no evidence of "overt" hepatic encephalopathy (HE) were randomized to receive 75 g of amino acid solution or placebo; measurements were performed before and 4 hours after administration. Neuropsychological tests included the Trails B Test, Digit Symbol Substitution Test, memory subtest of the Randt battery, and reaction time. Plasma was collected for ammonia and amino acid measurements, and brain metabolism was studied using proton magnetic resonance (MR) spectroscopy in the first 16 randomized patients. In 7 other patients, MTR was measured. A significant increase in ammonia levels was observed in the amino acid group (amino acid group, 76 +/- 7.3 to 121 +/- 6.4 micromol/L; placebo, 83 +/- 3.3 to 78 +/- 2.9 micromol/L; P <.001). Neuropsychological function improved significantly in the placebo group, but no significant change in neuropsychological function was observed in the amino acid group. Brain glutamate/glutamine (Glx)/creatine (Cr) ratio increased significantly in the amino acid group. MTR decreased significantly from 30 +/-2.9 to 23 +/- 4 (P <.01) after administration of the amino acid solution. In conclusion, an improvement in neuropsychological test results followed placebo, which was not observed in patients administered the amino acid solution. Induced hyperammonemia resulted in an increase in brain Glx/Cr ratio and a decrease in MTR, which may indicate an increase in brain water as the operative mechanism.