Gut ammonia production and its modulation

Implication of Hypotension in the Pathogenesis of Cognitive Impairment and Brain Injury in Chronic Liver Disease

The incidence of chronic liver disease is on the rise. One of the primary causes of hospital admissions for patients with cirrhosis is hepatic encephalopathy (HE), a debilitating neurological complication. HE is defined as a reversible syndrome, yet there is growing evidence stating that, under certain conditions, HE is associated with permanent neuronal injury and irreversibility. The pathophysiology of HE primarily implicates a strong role for hyperammonemia, but it is believed other pathogenic factors are involved. The fibrotic scarring of the liver during the progression of chronic liver disease (cirrhosis) consequently leads to increased hepatic resistance and circulatory anomalies characterized by portal hypertension, hyperdynamic circulatory state and systemic hypotension. The possible repercussions of these circulatory anomalies on brain perfusion, including impaired cerebral blood flow (CBF) autoregulation, could be implicated in the development of HE and/or permanent brain injury. Furthermore, hypotensive insults incurring during gastrointestinal bleed, infection, or liver transplantation may also trigger or exacerbate brain dysfunction and cell damage. This review will focus on the role of hypotension in the onset of HE as well as in the occurrence of neuronal cell loss in cirrhosis.

Paper-based colorimetric hyperammonemia sensing by controlled oxidation of plasmonic silver nanoparticles

High concentrations of ammonia in the human body can occur due to a wide variety of underlying causes such as liver cirrhosis and the symptoms of high ammonia concentrations are diffuse and hard to diagnose. The measurement of blood ammonia levels is an important diagnostic tool but is challenging to perform at the patient's bedside. Here, we present a plasmonic Ag nanoparticle-based ammonia sensor which provides a colorimetric optical readout and does not require specialised equipment. This is achieved using plasmonic Ag/SiO2 nanoparticles with the sensing mechanism that in the presence of OCl- they rapidly degrade reducing their plasmonic extinction and losing their characteristic colour. However, if ammonia is also present in the system, it neutralises the OCl- and thus the silver nanoparticles retain their plasmonic colour as can be measured by the naked eye or using a spectrometer. This sensing was further developed to enable measurements with animal serum as well as a implementing a facile "dip-stick" style paper-based sensor.

Impaired Enzymatic Antioxidant Defense in Erythrocytes of Rats with Ammonia-Induced Encephalopathy: Role of NMDA Receptors

Hepatic encephalopathy (HE), a neuropsychiatric disorder developing in patients with severe hepatic dysfunction, has been known for more than a century. However, pathogenetic mechanisms of cerebral dysfunction associated with liver disease are still poorly understood. There is a consensus that the primary cause of HE is accumulation of ammonia in the brain as a result of impaired liver detoxification capacity or the portosystemic shunt. Current evidence suggests that ammonia toxicity is mediated by hyperactivation of glutamate receptors, mainly N-methyl-D-aspartate receptors (NMDARs), and affects brain aerobic metabolism, which provides energy for multiple specific functions and neuronal viability. Recent reports on the presence of functional NMDARs in erythrocytes and the data on the deviations of blood parameters from their normal ranges indicate impaired hemodynamics and reduced oxygen-carrying capacity of erythrocytes in most patients with HE, thus suggesting a relationship between erythrocyte damage and cerebral dysfunction. In order to understand how hyperammonemia (HA)-induced disturbances in the energy metabolism in the brain (which needs a constant supply of large amounts of oxygen in the blood) lead to encephalopathy, it is necessary to reveal ammonia-induced impairments in the energy metabolism and antioxidant defense system of erythrocytes and to explore a potential role of ammonia in reduced brain oxygenation. To identify the said missing link, the activities of antioxidant enzymes and concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), and H2O2 were measured in the erythrocytes of rats with HA that were injected with the noncompetitive NMDAR antagonist MK-801. We found that in rats with HA, ammonia was accumulated in erythrocytes (cells lacking ammonia removal enzymes), which made them more susceptible to the prooxidant environment created during oxidative stress. This effect was completely or partially inhibited by MK-801. The data obtained might help to identify the risk factors in cognitive disorders and facilitate prediction of unfavorable outcomes of hypoperfusion in patients with a blood elevated ammonia concentration.

The pathogenesis of gut microbiota in hepatic encephalopathy by the gut-liver-brain axis

Hepatic encephalopathy (HE) is a neurological disease occurring in patients with hepatic insufficiency and/or portal-systemic blood shunting based on cirrhosis. The pathogenesis is not completely clear till now, but it is believed that hyperammonemia is the core of HE. Hyperammonemia caused by increased sources of ammonia and decreased metabolism further causes mental problems through the gut-liver-brain axis. The vagal pathway also plays a bidirectional role in the axis. Intestinal microorganisms play an important role in the pathogenesis of HE through the gut-liver-brain axis. With the progression of cirrhosis to HE, intestinal microbial composition changes gradually. It shows the decrease of potential beneficial taxa and the overgrowth of potential pathogenic taxa. Changes in gut microbiota may lead to a variety of effects, such as reduced production of short-chain fatty acids (SCFAs), reduced production of bile acids, increased intestinal barrier permeability, and bacterial translocation. The treatment aim of HE is to decrease intestinal ammonia production and intestinal absorption of ammonia. Prebiotics, probiotics, antibiotics, and fecal microbiota transplantation (FMT) can be used to manipulate the gut microbiome to improve hyperammonemia and endotoxemia. Especially the application of FMT, it has become a new treated approach to target microbial composition and function. Therefore, restoring intestinal microbial homeostasis can improve the cognitive impairment of HE, which is a potential treatment method.

Impact of L-ornithine L-aspartate on non-alcoholic steatohepatitis-associated hyperammonemia and muscle alterations

BACKGROUND

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common chronic liver disease in the world. Progression toward non-alcoholic steatohepatitis (NASH) is associated with alterations of skeletal muscle. One plausible mechanism for altered muscle compartment in liver disease is changes in ammonia metabolism. In the present study, we explored the hypothesis that NASH-associated hyperammonemia drives muscle changes as well as liver disease progression.

MATERIALS AND METHODS

In Alms1-mutant mice (foz/foz) fed a 60% fat diet (HFD) for 12 weeks; we investigated hepatic and muscular ammonia detoxification efficiency. We then tested the effect of an 8 week-long supplementation with L-ornithine L-aspartate (LOLA), a known ammonia-lowering treatment, given after either 4 or 12 weeks of HFD for a preventive or a curative intervention, respectively. We monitored body composition, liver and muscle state by micro computed tomography (micro-CT) as well as muscle strength by four-limb grip test.

RESULTS

According to previous studies, 12 weeks of HFD induced NASH in all foz/foz mice. Increase of hepatic ammonia production and alterations of urea cycle efficiency were observed, leading to hyperammonemia. Concomitantly mice developed marked myosteatosis. First signs of myopenia occurred after 20 weeks of diet. Early LOLA treatment given during NASH development, but not its administration in a curative regimen, efficiently prevented myosteatosis and muscle quality, but barely impacted liver disease or, surprisingly, ammonia detoxification.

CONCLUSION

Our study confirms the perturbation of hepatic ammonia detoxification pathways in NASH. Results from the interventional experiments suggest a direct beneficial impact of LOLA on skeletal muscle during NASH development, though it does not improve ammonia metabolism or liver disease.

Hyperammonemia in Inherited Metabolic Diseases

Ammonia is a neurotoxic compound which is detoxified through liver enzymes from urea cycle. Several inherited or acquired conditions can elevate ammonia concentrations in blood, causing severe damage to the central nervous system due to the toxic effects exerted by ammonia on the astrocytes. Therefore, hyperammonemic patients present potentially life-threatening neuropsychiatric symptoms, whose severity is related with the hyperammonemia magnitude and duration, as well as the brain maturation stage. Inherited metabolic diseases caused by enzymatic defects that compromise directly or indirectly the urea cycle activity are the main cause of hyperammonemia in the neonatal period. These diseases are mainly represented by the congenital defects of urea cycle, classical organic acidurias, and the defects of mitochondrial fatty acids oxidation, with hyperammonemia being more severe and frequent in the first two groups mentioned. An effective and rapid treatment of hyperammonemia is crucial to prevent irreversible neurological damage and it depends on the understanding of the pathophysiology of the diseases, as well as of the available therapeutic approaches. In this review, the mechanisms underlying the hyperammonemia and neurological dysfunction in urea cycle disorders, organic acidurias, and fatty acids oxidation defects, as well as the therapeutic strategies for the ammonia control will be discussed.

The digestive systems of carnivorous plants

To survive in the nutrient-poor habitats, carnivorous plants capture small organisms comprising complex substances not suitable for immediate reuse. The traps of carnivorous plants, which are analogous to the digestive systems of animals, are equipped with mechanisms for the breakdown and absorption of nutrients. Such capabilities have been acquired convergently over the past tens of millions of years in multiple angiosperm lineages by modifying plant-specific organs including leaves. The epidermis of carnivorous trap leaves bears groups of specialized cells called glands, which acquire substances from their prey via digestion and absorption. The digestive glands of carnivorous plants secrete mucilage, pitcher fluids, acids, and proteins, including digestive enzymes. The same (or morphologically distinct) glands then absorb the released compounds via various membrane transport proteins or endocytosis. Thus, these glands function in a manner similar to animal cells that are physiologically important in the digestive system, such as the parietal cells of the stomach and intestinal epithelial cells. Yet, carnivorous plants are equipped with strategies that deal with or incorporate plant-specific features, such as cell walls, epidermal cuticles, and phytohormones. In this review, we provide a systematic perspective on the digestive and absorptive capacity of convergently evolved carnivorous plants, with an emphasis on the forms and functions of glands.

Duodenal Microbiome and Serum Metabolites Predict Hepatocellular Carcinoma in a Multicenter Cohort of Patients with Cirrhosis

BACKGROUND

Hepatocellular carcinoma (HCC) is rapidly increasing in the U.S. and is a leading cause of mortality for patients with cirrhosis. Discovering novel biomarkers for risk stratification of HCC is paramount. We examined biomarkers of the gut-liver axis in a prospective multicenter cohort.

METHODS

Patients with cirrhosis without a history of HCC were recruited between May 2015 and March 2020 and prospectively followed at 3 tertiary care hospitals in Los Angeles. Microbiome analysis was performed on duodenal biopsies and metabolomic analysis was performed on serum samples, collected at the time of enrollment. Optimal microbiome-based survival analysis and Cox proportional hazards regression analysis were used to determine microbiota and metabolite associations with HCC development, respectively.

RESULTS

A total of 227 participants with liver cirrhosis contributed a total of 459.58 person-years of follow-up, with 14 incident HCC diagnoses. Male sex (HR = 7.06, 95% CI = 1.02-54.86) and baseline hepatic encephalopathy (HE, HR = 4.65, 95% CI = 1.60-13.52) were associated with developing HCC over follow-up. Adjusting for age, sex, baseline HE, and alkaline phosphatase, an increased risk of HCC were observed for participants with the highest versus lowest three quartiles for duodenal Alloprevotella (HR = 3.22, 95% CI = 1.06-9.73) and serum taurocholic acid (HR = 6.87, 95% CI = 2.32-20.27), methionine (HR = 9.97, 95% CI = 3.02-32.94), and methioninesulfoxide (HR = 5.60, 95% CI = 1.84-17.10). Being in the highest quartile for Alloprevotella or methionine had a sensitivity and specificity for developing HCC of 85.71% and 60.56%, respectively, with an odds ratio of 10.92 (95% CI = 2.23-53.48).

CONCLUSION

Alloprevotella and methionine, methioninesulfoxide, and taurocholic acid predicted future HCC development in a high-risk population of participants with liver cirrhosis.

The Modulation of Chaihu Shugan Formula on Microbiota Composition in the Simulator of the Human Intestinal Microbial Ecosystem Technology Platform and its Influence on Gut Barrier and Intestinal Immunity in Caco-2/THP1-Blue™ Cell Co-Culture Model

The traditional Chinese medicine (TCM)–Chaihu Shugan Formula (CSF), consisting of several Chinese botanical drugs like Bupleurum, is derived from the ancient Chinese pharmacopeia. It has been used for more than thousands of years in various suboptimal health statuses and diseases induced by chronic stress based on empirical therapy. Recent studies confirm the role of CSF in the development of many diseases, including depression, stress-induced hepatic injury and tumors. However, little has been known about the mechanisms behind the health effects of CSF. Here, we investigate the influence of CSF on the modulation of the simulated colonic microbiota of five healthy donors, gut barrier integrity, and intestinal immunity by combining the simulator of the human intestinal microbial ecosystem (SHIME^®) technology platform with co-culture of intestinal and immune cells. This approach revealed that CSF stimulated the production of SCFA (acetate, propionate and butyrate) across donors while significantly lowering the production of branched SCFA (bSCFA). In terms of community composition, CSF stimulated a broad spectrum of health-related Bifidobacterium species, which are potent acetate and lactate producers. At the same time, it lowered the abundance of opportunistic pathogenic Escherichia coli. Later, we explore the effect of colonic fermentation of CSF on the gut barrier and intestinal immunity in the Caco-2/THP1-blue™ cell co-culture model. Based on the study using SHIME technology platform, CSF showed protective effects on inflammation-induced intestinal epithelial barrier disruption in all donors. Also, the treatment of CSF showed pronounced anti-inflammatory properties by strongly inducing anti-inflammatory cytokines IL-6 and IL-10 and reducing pro-inflammatory cytokine TNF-α. These findings demonstrate a significant modulatory effect of CSF on intestinal gut microbiota. CSF-microbial fermentation products improved the gut barrier and controlled intestinal inflammation.

Tissue environment, not ontogeny, defines murine intestinal intraepithelial T lymphocytes

Tissue-resident intestinal intraepithelial T lymphocytes (T-IEL) patrol the gut and have important roles in regulating intestinal homeostasis. T-IEL include both induced T-IEL, derived from systemic antigen-experienced lymphocytes, and natural T-IEL, which are developmentally targeted to the intestine. While the processes driving T-IEL development have been elucidated, the precise roles of the different subsets and the processes driving activation and regulation of these cells remain unclear. To gain functional insights into these enigmatic cells, we used high-resolution, quantitative mass spectrometry to compare the proteomes of induced T-IEL and natural T-IEL subsets, with naive CD8+ T cells from lymph nodes. This data exposes the dominant effect of the gut environment over ontogeny on T-IEL phenotypes. Analyses of protein copy numbers of >7000 proteins in T-IEL reveal skewing of the cell surface repertoire towards epithelial interactions and checkpoint receptors; strong suppression of the metabolic machinery indicating a high energy barrier to functional activation; upregulated cholesterol and lipid metabolic pathways, leading to high cholesterol levels in T-IEL; suppression of T cell antigen receptor signalling and expression of the transcription factor TOX, reminiscent of chronically activated T cells. These novel findings illustrate how T-IEL integrate multiple tissue-specific signals to maintain their homeostasis and potentially function.

The Gut Microbiota-Derived Immune Response in Chronic Liver Disease

In chronic liver disease, the causative factor is important; however, recently, the intestinal microbiome has been associated with the progression of chronic liver disease and the occurrence of side effects. The immune system is affected by the metabolites of the microbiome, and diet is the primary regulator of the microbiota composition and function in the gut–liver axis. These metabolites can be used as therapeutic material, and postbiotics, in the future, can increase or decrease human immunity by modulating inflammation and immune reactions. Therefore, the excessive intake of nutrients and the lack of nutrition have important effects on immunity and inflammation. Evidence has been published indicating that microbiome-induced chronic inflammation and the consequent immune dysregulation affect the development of chronic liver disease. In this research paper, we discuss the overall trend of microbiome-derived substances related to immunity and the future research directions.

Comprehensive Analysis of Fecal Microbiome and Metabolomics in Hepatic Fibrosis Rats Reveal Hepatoprotective Effects of Yinchen Wuling Powder From the Host-Microbial Metabolic Axis

Hepatic fibrosis (HF) is a typical consequence in the development of multiple chronic liver diseases, which is intimately related to the composition and metabolic status of gut microbiota. A myriad of evidence has indicated that traditional Chinese medicine can treat HF by regulating gut microbiota. Yinchen Wuling powder (YCWLP) is a famous traditional Chinese medicine prescription, which has been used to relieve liver diseases for thousands of years. YCWLP has demonstrated protective function on HF, but its effect on the alterations of gut microbiota is still unclear, and its explicit therapeutic mechanism also needs to be further elucidated. In this study, 16S rRNA gene sequencing and fecal metabolomics analysis were combined to investigate the influence of YCWLP on gut microbiota in HF rats and the interactions between gut microbiota and host metabolism. The results showed that YCWLP treatment significantly improved the disorder of multiple organ indices, HF-related cytokines and plasma LPS induced by HF. Masson's trichrome stainings also showed that YCWLP treatment could significantly alleviate the severity of HF in rats. Additionally, YCWLP could reverse the significant changes in the abundance of certain genera closely related to HF phenotype, including Barnesiella [Ruminococcus] and Christensenella. Meanwhile, YCWLP significantly increased the abundance of Bifidobacterium, Coprococcus and Anaerostipes, which are closely related to butyrate production. Metabolomics and Spearman's correlation analysis showed that YCWLP could regulate the disorder of arginine biosynthesis, sphingolipid metabolism and alanine, aspartate and glutamate metabolism in HF rats, and these regulations were intimately related to Barnesiella, [Ruminococcus], Christensenella, Coprococcus and Anaerostipes. By explaining the biological significance of the above results, we concluded that YCWLP might ameliorate HF by regulating the imbalance of gut microbiota, increasing the abundance of butyrate-producing bacteria to reduce ammonia production, promote ammonia degradation, and regulate pro-inflammatory cytokines and immune function.

Black Tea Theaflavin Detoxifies Metabolic Toxins in the Intestinal Tract of Mice

SCOPE

This study is to determine the in vivo efficacy of black tea theaflavin (TF) to detoxify two metabolic toxins, ammonia and methylglyoxal (MGO), in mice METHODS AND RESULTS: Under in vitro conditions, TF is able to react with ammonia, MGO, and hydrogen peroxide to produce its aminated, MGO conjugated, and oxidized products, respectively. In TF-treated mice, the aminated TF, the MGO conjugates of TF and aminated TF, and the oxidized TF are searched using LC-MS/MS. The results provide the first in vivo evidence that the unabsorbed TF is able to trap ammonia to form the aminated TF; furthermore, both TF and the aminated TF have the capacity to trap MGO to generate the corresponding mono-MGO conjugates. Moreover, TF is oxidized to dehydrotheaflavin, which underwent further amination in the gut. By exposing TF to germ-free (GF) mice and conventionalized mice (GF mice colonized with specific-pathogen-free microbiota), the gut microbiota is demonstrated to facilitate the amination and MGO conjugation of TF.

CONCLUSION

TF has the capacity to remove the endogenous metabolic toxins through oxidation, amination, and MGO conjugation in the intestinal tract, which can potentially explain why TF still generates in vivo efficacy while showing a poor systematic bioavailability.

Probiotics improve the neurometabolic profile of rats with chronic cholestatic liver disease

Chronic liver disease leads to neuropsychiatric complications called hepatic encephalopathy (HE). Current treatments have some limitations in their efficacy and tolerability, emphasizing the need for alternative therapies. Modulation of gut bacterial flora using probiotics is emerging as a therapeutic alternative. However, knowledge about how probiotics influence brain metabolite changes during HE is missing. In the present study, we combined the advantages of ultra-high field in vivo 1H MRS with behavioural tests to analyse whether a long-term treatment with a multistrain probiotic mixture (VIVOMIXX) in a rat model of type C HE had a positive effect on behaviour and neurometabolic changes. We showed that the prophylactic administration of this probiotic formulation led to an increase in gut Bifidobacteria and attenuated changes in locomotor activity and neurometabolic profile in a rat model of type C HE. Both the performance in behavioural tests and the neurometabolic profile of BDL + probiotic rats were improved compared to the BDL group at week 8 post-BDL. They displayed a significantly lesser increase in brain Gln, a milder decrease in brain mIns and a smaller decrease in neurotransmitter Glu than untreated animals. The clinical implications of these findings are potentially far-reaching given that probiotics are generally safe and well-tolerated by patients.

Non-Lactulose Medication Therapies for the Management of Hepatic Encephalopathy: A Literature Review

OBJECTIVE

The most appropriate medication regimen to mitigate the consequences hepatic encephalopathy remains inconclusive. This review seeks to serve as a reference for clinicians to help guide therapy decisions with regard to hepatic encephalopathy.

METHODS

A comprehensive literature review between August 2018 and April 2019 was accomplished with the assistance of a medical librarian. Sources of literature review include PubMed, MEDLINE, SCOPUS, ProQuest Central, CINAHL, and ProQuest Dissertations. The authors selected randomized clinical and double-blind cross-over trials evaluating probiotics, zinc, polyethylene glycol, rifaximin, and flumazenil. Sixteen clinical trials are discussed in this review. Pertinent safety, efficacy, and statistical and clinical outcomes are summarized by the authors.

CONCLUSIONS

The most appropriate regimen to mitigate the consequences of hepatic encephalopathy remains elusive; however, the agents discussed within this review offer alternative options for patients unresponsive to or intolerant of traditional lactulose therapy. This review seeks to serve as a repository for relevant clinical trials, and as a reference for clinicians to help guide therapy decisions.

Metabolic Interaction between Ammonia and Baicalein

Ammonia is treated as a primary waste product of cellular metabolism in vivo and can contribute to the alteration of neurotransmission, oxidative stress, and cerebral edema and astrocyte swelling when its concentration in the brain is high. The objective of this study was to determine whether bioactive polyphenol baicalein had the capacity to trap ammonia in vitro and in vivo. Under in vitro conditions, baicalein rapidly reacted with ammonia to generate two monoaminated products and one diaminated product under different reaction times. These three major aminated products were purified from the reaction mixture, and their structures were characterized as 5-NH₂-baicalein, 6-NH₂-baicalein, and 5,6-di-NH₂-baicalein based on the analysis of their HR-MS and 1D- and 2D-NMR data. In mice, both 5-NH₂-baicalein and 6-NH₂-baicalein were detected in 24 h fecal and urine samples collected from mice treated with baicalein (200 mg/kg) through oral gavage, and 6-NH₂-baicalein was also detected in mouse plasma and brain samples collected at 0.5 h after baicalein treatment. Significant amounts of 6-NH₂-baicalein were detected in all mouse samples including feces, urine, plasma, and brain. The levels of 6-NH₂-baicalein in feces and urine were significantly higher than those of 5-NH₂-baicalein. Furthermore, the average level of 6-NH₂-baicalein was very close to that of baicalein (3.62 vs 3.77 ng/g) in mouse brain, suggesting it is possible that baicalein has the capacity to be absorbed rapidly into the circulation system and then cross the blood-brain barrier into the brain to detoxify ammonia in the blood and brain. In conclusion, this study confirmed that baicalein, a flavonoid with a vic-trihydroxyl structure on the A-ring, has the potential to detoxify ammonia and treat ammonia-associated chronic diseases.

Lactulose improves cognition, quality of life, and gut microbiota in minimal hepatic encephalopathy: A multicenter, randomized controlled trial

OBJECTIVE

Lactulose is effective in the treatment and prevention of overt hepatic encephalopathy (OHE), but there are limited data on its use on microbiota in relations to minimal hepatic encephalopathy (MHE) recovery. The present study aimed to assess the efficacy of lactulose in recovery of MHE in aspects of cognitive function, quality of life, and impact on intestinal microbiota.

METHODS

This multicenter, open-label randomized controlled trial was conducted in 11 teaching hospitals in China. Participants were randomly allocated on a 2:1 basis to receive lactulose (Gp-L) or no therapy as control (Gp-NL) for 60 days. The primary endpoint was the MHE reversal rate. Gut microbiota were compared between MHE patients and healthy volunteers, as well as lactulose-responders and non-responders.

RESULTS

A total of 98 cirrhotic patients were included in the study, with 31 patients in the Gp-NL group and 67 patients in the Gp-L group. At day 60, the MHE reversal rate in Gp-L (64.18%) was significantly higher than that in Gp-NL (22.58%) (P = .0002) with a relative risk of 0.46 (95% confidence interval 0.32-0.67). Number needed to treat was 2.4. Further, there was significantly more improvement in physical functioning in Gp-L (4.62 ± 6.16) than in Gp-NL (1.50 ± 5.34) (P = .0212). Proteobacteria was significantly higher in MHE patients compared with healthy volunteers (12.27% vs 4.65%, P < .05). Significant differences were found between lactulose responders and non-responders in Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria.

CONCLUSIONS

Treatment with lactulose significantly improves MHE recovery rate, and gut microbiota change in MHE patients can modulate the effectiveness of this therapy. Chinese Clinical Trial Register (ChiCTR) (ID: ChiCTR-TRC-12002342).

A Narrative Review of Cancer-Related Fatigue (CRF) and Its Possible Pathogenesis

Many cancer patients suffer from severe fatigue when treated with chemotherapy or radiotherapy; however, the etiology and pathogenesis of this kind of fatigue remains unknown. Fatigue is associated with cancer itself, as well as adjuvant therapies and can persist for a long time. Cancer patients present a high degree of fatigue, which dramatically affects the quality of their everyday life. There are various clinical research studies and reviews that aimed to explore the mechanisms of cancer-related fatigue (CRF). However, there are certain limitations in these studies: For example, some studies have only blood biochemical texts without histopathological examination, and there has been insufficient systemic evaluation of the dynamic changes in relevant indexes. Thus, we present this narrative review to summarize previous studies on CRF and explore promising research directions. Plenty of evidence suggests a possible association between CRF and physiological dysfunction, including skeletal muscular and mitochondrial dysfunction, peripheral immune activation and inflammation dysfunction, as well as central nervous system (CNS) disorder. Mitochondrial DNA (mtDNA), mitochondrial structure, oxidative pressure, and some active factors such as ATP play significant roles that lead to the induction of CRF. Meanwhile, several pro-inflammatory and anti-inflammatory cytokines in the peripheral system, even in the CNS, significantly contribute to the occurrence of CRF. Moreover, CNS function disorders, such as neuropeptide, neurotransmitter, and hypothalamic-pituitary-adrenal (HPA) axis dysfunction, tend to amplify the sense of fatigue in cancer patients through various signaling pathways. There have been few accurate animal models established to further explore the molecular mechanisms of CRF due to different types of cancer, adjuvant therapy schedules, living environments, and physical status. It is imperative to develop appropriate animal models that can mimic human CRF and to explore additional mechanisms using histopathological and biochemical methods. Therefore, the main purpose of this review is to analyze the possible pathogenesis of CRF and recommend future research that will clarify CRF pathogenesis and facilitate the formulation of new treatment options.

"Dietary fibre": moving beyond the "soluble/insoluble" classification for monogastric nutrition, with an emphasis on humans and pigs

This review describes dietary fibres originating from a range of foods, particularly in relation to their plant cell walls. It explores the categorization of dietary fibres into “soluble” or “insoluble”. It also emphasizes dietary fibre fermentability, in terms of describing how the gastro-intestinal tract (GIT) microbiota respond to a selection of fibres from these categories. Food is categorized into cereals, legumes, fruits and vegetables. Mention is also made of example whole foods and why differences in physico-chemical characteristics between “purified” and “non-purified” food components are important in terms of health. Lastly, recommendations are made as to how dietary fibre could be classified differently, in relation to its functionality in terms of fermentability, rather than only its solubility.

Metabolic functions of the human gut microbiota: the role of metalloenzymes

Covering: up to the end of 2017 The human body is composed of an equal number of human and microbial cells. While the microbial community inhabiting the human gastrointestinal tract plays an essential role in host health, these organisms have also been connected to various diseases. Yet, the gut microbial functions that modulate host biology are not well established. In this review, we describe metabolic functions of the human gut microbiota that involve metalloenzymes. These activities enable gut microbial colonization, mediate interactions with the host, and impact human health and disease. We highlight cases in which enzyme characterization has advanced our understanding of the gut microbiota and examples that illustrate the diverse ways in which metalloenzymes facilitate both essential and unique functions of this community. Finally, we analyze Human Microbiome Project sequencing datasets to assess the distribution of a prominent family of metalloenzymes in human-associated microbial communities, guiding future enzyme characterization efforts.

Hepatic encephalopathy: Lessons from preclinical studies

Hepatic encephalopathy (HE) is a major complication that is closely related to the progression of end-stage liver disease. Metabolic changes in advanced liver failure can promote cognition impairment, attention deficits and motor dysfunction that may result in coma and death. HE can be subdivided according to the type of hepatic injury, namely, type A, which results from acute liver failure, type B, which is associated with a portosystemic shunting without intrinsic liver disease, and type C, which is due to chronic liver disease. Several studies have investigated the pathogenesis of the disease, and most of the mechanisms have been explored using animal models. This article aimed to review the use of preclinical models to investigate HE. The most used animal species are rats and mice. Experimental models of type A HE include surgical procedures and the administration of hepatotoxic medications, whereas models of types B and C HE are generally surgically induced lesions in liver tissue, which evolve to hepatic cirrhosis. Preclinical models have allowed the comprehension of the pathways related to HE.

Why and when to measure ammonemia in cirrhosis?

Hyperammonemia plays a key role in the pathophysiology of hepatic encephalopathy (HE) and most HE treatments are ammonia-lowering drugs. However, the usefulness of measuring ammonemia in routine practice remains controversial and not recommended systematically even when neurological symptoms are present. First, ammonemia measurement should be carefully performed in order to avoid a falsely elevated result. When performed, a normal ammonemia in a cirrhotic patient with neurological symptoms should lead to reconsider the diagnosis of HE. Indeed, literature data show that most cirrhotic patients with HE have an elevated ammonemia, which is however individually poorly correlated with the severity of symptoms. Nevertheless, elevated ammonemia seems to be a factor of bad prognosis in cirrhosis. A decrease in ammonemia after treatments is well proven but it is not determined whether it is associated with clinical efficacy. Repeated measurements could be useful in this context, especially in non-responders, to help differentiating other causes of encephalopathy, such as drug induced. In acute liver failure, the prognostic value of hyperammonemia is well described and could help an early recognition the most severe forms of this disease. We will also discuss how integrating ammonemia into the diagnostic work-up of liver failure and/or encephalopathy. Ammonemia is also essential to diagnose urea cycle disorders or drug toxicity that both need specific interventions.

Metformin modifies glutamine metabolism in an in vitro and in vivo model of hepatic encephalopathy

AIM

to analyze the effect of metformin on ammonia production derived from glutamine metabolism in vitro and in vivo.

METHODS

twenty male Wistar rats were studied for 28 days after a porto-caval anastomosis (n = 16) or a sham operation (n = 4). Porto-caval shunted animals were randomized into two groups (n = 8) and either received 30 mg/kg/day of metformin for two weeks or were control animals. Plasma ammonia concentration, Gls gene expression and K-type glutaminase activity were measured in the small intestine, muscle and kidney. Furthermore, Caco2 were grown in different culture media containing glucose/glutamine as the main carbon source and exposed to different concentrations of the drug. The expression of genes implicated in glutamine metabolism were analyzed.

RESULTS

metformin was associated with a significant inhibition of glutaminase activity levels in the small intestine of porto-caval shunted rats (0.277 ± 0.07 IU/mg vs 0.142 ± 0.04 IU/mg) and a significant decrease in plasma ammonia (204.3 ± 24.4 µg/dl vs 129.6 ± 16.1 µg/dl). Glucose withdrawal induced the expression of the glutamine transporter SLC1A5 (2.54 ± 0.33 fold change; p < 0.05). Metformin use reduced MYC levels in Caco2 and consequently, SLC1A5 and GLS expression, with a greater effect in cells dependent on glutaminolytic metabolism.

CONCLUSION

metformin regulates ammonia homeostasis by modulating glutamine metabolism in the enterocyte, exerting an indirect control of both the uptake and degradation of glutamine. This entails a reduction in the production of metabolites and energy through this pathway and indirectly causes a decrease in ammonia production that could be related to a decreased risk of HE development.

Efficacy and safety of rifaximin in Japanese patients with hepatic encephalopathy: A phase II/III, multicenter, randomized, evaluator-blinded, active-controlled trial and a phase III, multicenter, open trial

AIM

The efficacy and safety of rifaximin in the treatment of hepatic encephalopathy (HE) are widely known, but they have not been confirmed in Japanese patients with HE. Thus, two prospective, randomized studies (a phase II/III study and a phase III study) were carried out.

METHODS

Subjects with grade I or II HE and hyperammonemia were enrolled. The phase II/III study, which was a randomized, evaluator-blinded, active-comparator, parallel-group study, was undertaken at 37 institutions in Japan. Treatment periods were 14 days. Eligible patients were randomized to the rifaximin group (1200 mg/day) or the lactitol group (18-36 g/day). The phase III study was carried out in the same patients previously enrolled in the phase II/III study, and they were all treated with rifaximin (1200 mg/day) for 10 weeks.

RESULTS

In the phase II/III study, 172 patients were enrolled. Blood ammonia (B-NH3 ) concentration was significantly improved in the rifaximin group, but the difference between the two groups was not significant. The portal systemic encephalopathy index (PSE index), including HE grade, was significantly improved in both groups. In the phase III study, 87.3% of enrolled patients completed the treatment. The improved B-NH3 concentration and PSE index were well maintained from the phase II/III study during the treatment period of the phase III study. Adverse drug reactions (ADRs) were seen in 13.4% of patients who received rifaximin, but there were no severe ADRs leading to death.

CONCLUSION

The efficacy of rifaximin is sufficient and treatment is well tolerated in Japanese patients with HE and hyperammonemia.

The Pharmabiotic Approach to Treat Hyperammonemia

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

Lactulose decreases neuronal activation and attenuates motor behavioral deficits in hyperammonemic rats

Lactulose is a nonabsorbable disaccharide commonly used in clinical practice to treat hepatic encephalopathy. However, its effects on neuropsychiatric disorders and motor behavior have not been fully elucidated. Male Wistar rats were bile-duct ligated, and 3 weeks after surgery, treated with lactulose administrated by gavage (1.43 or 3.57 g/kg), once a day for seven days. Plasma levels of ammonia, aspartate aminotransferase, total bilirubin, and creatinine were quantified and histopathological analysis of the livers was performed. Locomotor activity measurements were performed in an open field. The expression of water channel aquaporin-4 was investigated and the analysis of Fos protein immunoreactivity was used to evaluate the pattern of neural activation in brain areas related to motor behavior. Bile-duct ligated rats showed hyperammonemia, loss of liver integrity and function, impaired locomotor activity, reduced aquaporin-4 protein expression, and neuronal hyperactivity. Lactulose treatment was able to reduce ammonia plasma levels, despite not having an effect on biochemical parameters of liver function, such as aspartate aminotransferase activity and total bilirubin levels, or on the cirrhotic hepatic architecture. Lactulose was also able to reduce the locomotor activity impairments and to mitigate or reverse most changes in neuronal activation. Lactulose had no effect on reduced aquaporin-4 protein expression. Our findings confirm the effectiveness of lactulose in reducing hyperammonemia and neuronal hyperactivity in brain areas related to motor behavior, reinforcing the importance of its clinical use in the treatment of the symptoms of cirrhosis-associated encephalopathy.

Ammonia modifies enteric neuromuscular transmission through glial γ-aminobutyric acid signaling

Impaired gut motility may contribute, at least in part, to the development of systemic hyperammonemia and systemic neurological disorders in inherited metabolic disorders, or in severe liver and renal disease. It is not known whether enteric neurotransmission regulates intestinal luminal and hence systemic ammonia levels by induced changes in motility. Here, we propose and test the hypothesis that ammonia acts through specific enteric circuits to influence gut motility. We tested our hypothesis by recording the effects of ammonia on neuromuscular transmission in tissue samples from mice, pigs, and humans and investigated specific mechanisms using novel mutant mice, selective drugs, cellular imaging, and enzyme-linked immunosorbent assays. Exogenous ammonia increased neurogenic contractions and decreased neurogenic relaxations in segments of mouse, pig, and human intestine. Enteric glial cells responded to ammonia with intracellular Ca²⁺ responses. Inhibition of glutamine synthetase and the deletion of glial connexin-43 channels in hGFAP::CreER^T2+/-/connexin43^f/f mice potentiated the effects of ammonia on neuromuscular transmission. The effects of ammonia on neuromuscular transmission were blocked by GABA_A receptor antagonists, and ammonia drove substantive GABA release as did the selective pharmacological activation of enteric glia in GFAP::hM3Dq transgenic mice. We propose a novel mechanism whereby local ammonia is operational through GABAergic glial signaling to influence enteric neuromuscular circuits that regulate intestinal motility. Therapeutic manipulation of these mechanisms may benefit a number of neurological, hepatic, and renal disorders manifesting hyperammonemia.NEW & NOTEWORTHY We propose that local circuits in the enteric nervous system sense and regulate intestinal ammonia. We show that ammonia modifies enteric neuromuscular transmission to increase motility in human, pig, and mouse intestine model systems. The mechanisms underlying the effects of ammonia on enteric neurotransmission include GABAergic pathways that are regulated by enteric glial cells. Our new data suggest that myenteric glial cells sense local ammonia and directly modify neurotransmission by releasing GABA.

Gut Fermentation of Dietary Fibres: Physico-Chemistry of Plant Cell Walls and Implications for Health

The majority of dietary fibre (DF) originates from plant cell walls. Chemically, DF mostly comprise carbohydrate polymers, which resist hydrolysis by digestive enzymes in the mammalian small intestine, but can be fermented by large intestinal bacteria. One of the main benefits of DF relate to its fermentability, which affects microbial diversity and function within the gastro-intestinal tract (GIT), as well as the by-products of the fermentation process. Much work examining DF tends to focus on various purified ingredients, which have been extracted from plants. Increasingly, the validity of this is being questioned in terms of human nutrition, as there is evidence to suggest that it is the actual complexity of DF which affects the complexity of the GIT microbiota. Here, we review the literature comparing results of fermentation of purified DF substrates, with whole plant foods. There are strong indications that the more complex and varied the diet (and its ingredients), the more complex and varied the GIT microbiota is likely to be. Therefore, it is proposed that as the DF fermentability resulting from this complex microbial population has such profound effects on human health in relation to diet, it would be appropriate to include DF fermentability in its characterization-a functional approach of immediate relevance to nutrition.

Validation study associating glutaminase promoter variations with hepatic encephalopathy in East Asian populations

BACKGROUND AND AIM

In a recent study, microsatellite variations (GCA tandem repeats) in the promoter region of the (kidney-type) glutaminase gene were associated with the development of hepatic encephalopathy (HE) in Spanish patients with cirrhosis. The objective of this study was to validate the relation between microsatellite variations in the glutaminase promoter region and the development of overt HE in Korean patients with liver cirrhosis.

METHODS

We performed a prospective cohort study of 154 cirrhotic patients who underwent a glutaminase microsatellite study without previous overt HE history at baseline. The primary end point was the first episode of overt HE. The microsatellite length was categorized into three groups based on its repeated number, with a cutoff value of 14; 65 (42.2%), 70 (45.5%), and 19 (12.3%) patients had the short-short, short-long, and long-long alleles, respectively.

RESULTS

Over a median 3.5 years of follow-up (range = 0.1-4.4), overt HE developed in 28 patients (18.2%). The 3-year cumulative incidence of overt HE was 18.4%. Multivariate Cox model indicated that past hepatocellular carcinoma history, alcoholic etiology for cirrhosis, higher Model for End-Stage Liver Disease scores and their deterioration, and serum ammonium levels were independently associated with HE development. However, microsatellite length was not associated with the development of overt HE.

CONCLUSIONS

In Korean patients with cirrhosis, microsatellite variations in the glutaminase promoter region were not associated with development of overt HE. Thus, additional studies are needed to identify other genetic factors related to glutaminase activity in Asians with overt HE.

Gut microbiome and liver diseases

The gut microbiota has recently evolved as a new important player in the pathophysiology of many intestinal and extraintestinal diseases. The liver is the organ which is in closest contact with the intestinal tract, and is exposed to a substantial amount of bacterial components and metabolites. Various liver disorders such as alcoholic liver disease, non-alcoholic liver disease and primary sclerosing cholangitis have been associated with an altered microbiome. This dysbiosis may influence the degree of hepatic steatosis, inflammation and fibrosis through multiple interactions with the host's immune system and other cell types. Whereas few results from clinical metagenomic studies in liver disease are available, evidence is accumulating that in liver cirrhosis an oral microbiome is overrepresented in the lower intestinal tract, potentially contributing to disease process and severity. A major role for the gut microbiota in liver disorders is also supported by the accumulating evidence that several complications of severe liver disease such as hepatic encephalopathy are efficiently treated by various prebiotics, probiotics and antibiotics. A better understanding of the gut microbiota and its components in liver diseases might provide a more complete picture of these complex disorders and also form the basis for novel therapies.

Gut microbiota drive the development of neuroinflammatory response in cirrhosis in mice

The mechanisms behind the development of hepatic encephalopathy (HE) are unclear, although hyperammonemia and systemic inflammation through gut dysbiosis have been proposed. The aim of this work was to define the individual contribution of hyperammonemia and systemic inflammation on neuroinflammation in cirrhosis using germ-free (GF) and conventional mice. GF and conventional C57BL/6 mice were made cirrhotic using CCl4 gavage. These were compared to their noncirrhotic counterparts. Intestinal microbiota, systemic and neuroinflammation (including microglial and glial activation), serum ammonia, intestinal glutaminase activity, and cecal glutamine content were compared between groups. GF cirrhotic mice developed similar cirrhotic changes to conventional mice after 4 extra weeks (16 vs. 12 weeks) of CCl4 gavage. GF cirrhotic mice exhibited higher ammonia, compared to GF controls, but this was not associated with systemic or neuroinflammation. Ammonia was generated through increased small intestinal glutaminase activity with concomitantly reduced intestinal glutamine levels. However, conventional cirrhotic mice had intestinal dysbiosis as well as systemic inflammation, associated with increased serum ammonia, compared to conventional controls. This was associated with neuroinflammation and glial/microglial activation. Correlation network analysis in conventional mice showed significant linkages between systemic/neuroinflammation, intestinal microbiota, and ammonia. Specifically beneficial, autochthonous taxa were negatively linked with brain and systemic inflammation, ammonia, and with Staphylococcaceae, Lactobacillaceae, and Streptococcaceae. Enterobacteriaceae were positively linked with serum inflammatory cytokines.

CONCLUSION

Gut microbiota changes drive development of neuroinflammatory and systemic inflammatory responses in cirrhotic animals. (Hepatology 2016;64:1232-1248).

Rifaximin Exerts Beneficial Effects Independent of its Ability to Alter Microbiota Composition

OBJECTIVES

Rifaximin has clinical benefits in minimal hepatic encephalopathy (MHE) but the mechanism of action is unclear. The antibiotic-dependent and -independent effects of rifaximin need to be elucidated in the setting of MHE-associated microbiota. To assess the action of rifaximin on intestinal barrier, inflammatory milieu and ammonia generation independent of microbiota using rifaximin.

METHODS

Four germ-free (GF) mice groups were used (1) GF, (2) GF+rifaximin, (3) Humanized with stools from an MHE patient, and (4) Humanized+rifaximin. Mice were followed for 30 days while rifaximin was administered in chow at 100 mg/kg from days 16-30. We tested for ammonia generation (small-intestinal glutaminase, serum ammonia, and cecal glutamine/amino-acid moieties), systemic inflammation (serum IL-1β, IL-6), intestinal barrier (FITC-dextran, large-/small-intestinal expression of IL-1β, IL-6, MCP-1, e-cadherin and zonulin) along with microbiota composition (colonic and fecal multi-tagged sequencing) and function (endotoxemia, fecal bile acid deconjugation and de-hydroxylation).

RESULTS

All mice survived until day 30. In the GF setting, rifaximin decreased intestinal ammonia generation (lower serum ammonia, increased small-intestinal glutaminase, and cecal glutamine content) without changing inflammation or intestinal barrier function. Humanized microbiota increased systemic/intestinal inflammation and endotoxemia without hyperammonemia. Rifaximin therapy significantly ameliorated these inflammatory cytokines. Rifaximin also favorably impacted microbiota function (reduced endotoxin and decreased deconjugation and formation of potentially toxic secondary bile acids), but not microbial composition in humanized mice.

CONCLUSIONS

Rifaximin beneficially alters intestinal ammonia generation by regulating intestinal glutaminase expression independent of gut microbiota. MHE-associated fecal colonization results in intestinal and systemic inflammation in GF mice, which is also ameliorated with rifaximin.

Impaired Gut-Liver-Brain Axis in Patients with Cirrhosis

Cirrhosis is associated with brain dysfunction known as hepatic encephalopathy (HE). The mechanisms behind HE are unclear although hyperammonemia and systemic inflammation through gut dysbiosis have been proposed. We aimed to define the individual contribution of specific gut bacterial taxa towards astrocytic and neuronal changes in brain function using multi-modal MRI in patients with cirrhosis. 187 subjects (40 controls, 147 cirrhotic; 87 with HE) underwent systemic inflammatory assessment, cognitive testing, stool microbiota analysis and brain MRI analysis. MR spectroscopy (MRS) changes of increased Glutamate/glutamine, reduced myo-inositol and choline are hyperammonemia-associated astrocytic changes, while diffusion tensor imaging (DTI) demonstrates changes in neuronal integrity and edema. Linkages between cognition, MRI parameters and gut microbiota were compared between groups. We found that HE patients had a significantly worse cognitive performance, systemic inflammation, dysbiosis and hyperammonemia compared to controls and cirrhotics without HE. Specific microbial families (autochthonous taxa negatively and Enterobacteriaceae positively) correlated with MR spectroscopy and hyperammonemia-associated astrocytic changes. On the other hand Porphyromonadaceae, were only correlated with neuronal changes on DTI without linkages with ammonia. We conclude that specific gut microbial taxa are related to neuronal and astrocytic consequences of cirrhosis-associated brain dysfunction.

Guidelines for acute management of hyperammonemia in the Middle East region

Background

Hyperammonemia is a life-threatening event that can occur at any age. If treated, the early symptoms in all age groups could be reversible. If untreated, hyperammonemia could be toxic and cause irreversible brain damage to the developing brain.

Objective

There are major challenges that worsen the outcome of hyperammonemic individuals in the Middle East. These include: lack of awareness among emergency department physicians about proper management of hyperammonemia, strained communication between physicians at primary, secondary, and tertiary hospitals, and shortage of the medications used in the acute management of hyperammonemia. Therefore, the urge to develop regional guidelines is extremely obvious.

Method

We searched PubMed and Embase databases to include published materials from 2011 to 2014 that were not covered by the European guidelines, which was published in 2012. We followed the process of a Delphi conference and involved one preliminary meeting and two follow-up meetings with email exchanges between the Middle East Hyperammonemia and Urea Cycle Disorders Scientific Group regarding each draft of the manuscript.

Results and discussion

We have developed consensus guidelines based on the highest available level of evidence. The aim of these guidelines is to homogenize and harmonize the treatment protocols used for patients with acute hyperammonemia, and to provide a resource to not only metabolic physicians, but also physicians who may come in contact with individuals with acute hyperammonemia.

Conclusion

These suggested guidelines aim to ease the challenges faced by physicians dealing with acute hyperammonemia in the region. In addition, guidelines have demonstrated useful collaboration between experts in the region, and provides information that will hopefully improve the outcomes of patients with acute hyperammonemia.

Intestinal microbiota in liver disease

The intestinal microbiota have emerged as a topic of intense interest in gastroenterology and hepatology. The liver is on the front line as the first filter of nutrients, toxins and bacterial metabolites from the intestines and we are becoming increasingly aware of interactions among the gut, liver and immune system as important mediators of liver health and disease. Manipulating the microbiota with therapeutic intent is a rapidly expanding field. In this review, we will describe what is known about the contribution of intestinal microbiota to liver homeostasis; the role of dysbiosis in the pathogenesis of liver disease including alcoholic and non-alcoholic fatty liver disease, cirrhosis and hepatocellular carcinoma; and the therapeutic manifestations of altering intestinal microbiota via antibiotics, prebiotics, probiotics and fecal microbiota transplantation.

Central and Peripheral Fatigue During Resistance Exercise - A Critical Review

Resistance exercise is a popular form of conditioning for numerous sport disciplines, and recently different modes of strength training are being evaluated for health benefits. Resistance exercise differs significantly in nature, and several variables determine the direction and range of adaptive changes that occur in the muscular and skeletal system of the body. Some modes of resistance training can also be effective in stimulating the cardiovascular system. These variables include exercise selection (general, specific, single or multi joint, dynamic, explosive), type of resistance (free weights, variable resistance, isokinetics), order of exercise (upper and lower body or push and pull exercises), and most of all the training load which includes intensity expressed as % of 1RM, number of repetitions, number of sets and the rest interval between sets. Manipulating these variables allows for specific adaptive changes which may include gains in muscle mass, muscle strength or muscle endurance. It has been well established that during resistance exercise fatigue occurs, regardless of the volume and intensity of work applied. The peripheral mechanisms of fatigue have been studied and explained in more detail than those related to the CNS. This review is an attempt to bring together the latest knowledge regarding fatigue, both peripheral and central, during resistance exercise. The authors of this review concentrated on physiological and biochemical mechanisms underlying fatigue in exercises performed with maximal intensity, as well as those performed to exhaustion with numerous repetitions and submaximal load.

Recent advances in the treatment of hyperammonemia

Ammonia is a neurotoxic agent that is primarily generated in the intestine and detoxified in the liver. Toxic increases in systemic ammonia levels predominantly result from an inherited or acquired impairment in hepatic detoxification and lead to potentially life-threatening neuropsychiatric symptoms. Inborn deficiencies in ammonia detoxification mainly affect the urea cycle, an endogenous metabolic removal system in the liver. Hepatic encephalopathy, on the other hand, is a hyperammonemia-related complication secondary to acquired liver function impairment. A range of therapeutic options is available to target either ammonia generation and absorption or ammonia removal. Therapies for hepatic encephalopathy decrease intestinal ammonia production and uptake. Treatments for urea cycle disorders eliminate ammoniagenic amino acids through metabolic transformation, preventing ammonia generation. Therapeutic approaches removing ammonia activate the urea cycle or the second essential endogenous ammonia detoxification system, glutamine synthesis. Recent advances in treating hyperammonemia include using synergistic combination treatments, broadening the indication of orphan drugs, and developing novel approaches to regenerate functional liver tissue. This manuscript reviews the various pharmacological treatments of hyperammonemia and focuses on biopharmaceutical and drug delivery issues.

Gut microbiota: its role in hepatic encephalopathy

Ammonia, a key factor in the pathogenesis of hepatic encephalopathy (HE), is predominantly derived from urea breakdown by urease producing large intestinal bacteria and from small intestine and kidneys, where the enzyme glutaminases releases ammonia from circulating glutamine. Non-culture techniques like pyrosequencing of bacterial 16S ribosomal ribonucleic acid are used to characterize fecal microbiota. Fecal microbiota in patients with cirrhosis have been shown to alter with increasing Child-Turcotte-Pugh (CTP) and Model for End stage Liver Disease (MELD) scores, and with development of covert or overt HE. Cirrhosis dysbiosis ratio (CDR), the ratio of autochthonous/good bacteria (e.g. Lachnospiraceae, Ruminococcaceae and Clostridiales) to non-autochthonous/pathogenic bacteria (e.g. Enterobacteriaceae and Streptococcaceae), is significantly higher in controls and patients with compensated cirrhosis than patients with decompensated cirrhosis. Although their stool microbiota do not differ, sigmoid colonic mucosal microbiota in liver cirrhosis patients with and without HE, are different. Linkage of pathogenic colonic mucosal bacteria with poor cognition and inflammation suggests that important processes at the mucosal interface, such as bacterial translocation and immune dysfunction, are involved in the pathogenesis of HE. Fecal microbiome composition does not change significantly when HE is treated with lactulose or when HE recurs after lactulose withdrawal. Despite improving cognition and endotoxemia as well as shifting positive correlation of pathogenic bacteria with metabolites, linked to ammonia, aromatic amino acids and oxidative stress, to a negative correlation, rifaximin changes gut microbiome composition only modestly. These observations suggest that the beneficial effects of lactulose and rifaximin could be associated with a change in microbial metabolic function as well as an improvement in dysbiosis.

Morphological changes of cortical pyramidal neurons in hepatic encephalopathy

Background

Hepatic encephalopathy (HE) is a reversible neuropsychiatric syndrome associated with acute and chronic liver diseases. It includes a number of neuropsychiatric disturbances including impaired motor activity and coordination, intellectual and cognitive function.

Results

In the present study, we used a chronic rat HE model by ligation of the bile duct (BDL) for 4 weeks. These rats showed increased plasma ammonia level, bile duct hyperplasia and impaired spatial learning memory and motor coordination when tested with Rota-rod and Morris water maze tests, respectively. By immunohistochemistry, the cerebral cortex showed swelling of astrocytes and microglia activation. To gain a better understanding of the effect of HE on the brain, the dendritic arbors of layer V cortical pyramidal neurons and hippocampal CA1 pyramidal neurons were revealed by an intracellular dye injection combined with a 3-dimensional reconstruction. Although the dendritic arbors remained unaltered, the dendritic spine density on these neurons was significantly reduced. It was suggested that the reduction of dendritic spines may be the underlying cause for increased motor evoked potential threshold and prolonged central motor conduction time in clinical finding in cirrhosis.

Conclusions

We found that HE perturbs CNS functions by altering the dendritic morphology of cortical and hippocampal pyramidal neurons, which may be the underlying cause for the motor and intellectual impairments associated with HE patients.

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.

Update on management of patients with overt hepatic encephalopathy

Hepatic encephalopathy (HE) is a multifactorial neuropsychiatric disease that affects patients with cirrhosis. We review the clinical impact, pathogenesis, evaluation, management, and prevention of overt HE in patients with cirrhosis. Articles published between January 1960 and November 2012 were acquired through a MEDLINE search of different combinations of the terms hepatic encephalopathy, pathophysiology, treatment, prophylaxis, prevention, prognosis, and recurrence. The Healthcare Cost and Utilization Project database was used to obtain prevalence and cost information related to hospitalizations of patients with HE. The literature describes significant morbidity and mortality of HE in patients with cirrhosis. Overt HE develops in 30% to 45% of patients with cirrhosis and is associated with a substantial pharmacoeconomic burden, particularly HE-related hospitalizations. The development of HE in patients with cirrhosis portends a worsened prognosis and is incorporated into the Child-Pugh classification of the severity of liver disease. In the hospitalized patient, the development of HE is associated with precipitating events (eg, gastrointestinal bleeding, dehydration, infection), and in some patients, its course is characterized by frequent and severe relapses. In addition, hospitalized patients with overt HE have a 3.9-fold increased mortality risk. Patient management employs nonabsorbable disaccharides, the nonsystemic antibiotic rifaximin, or both, to treat acute HE episodes and prevent HE relapse. In open-label trials, use of the nonabsorbable disaccharide lactulose reduced the risk of overt HE recurrence in patients compared with no-lactulose control groups for ≤ a median of 14 months. In a randomized, placebo-controlled trial, rifaximin 550 mg twice daily was more effective in maintaining HE remission compared with placebo and was associated with a reduction in HE-related hospitalizations. Recent advances in treatment and preventative therapies may reduce the personal, societal, and economic impact of this disorder.

Re-print of "Intestinal luminal nitrogen metabolism: role of the gut microbiota and consequences for the host"

Alimentary and endogenous proteins are mixed in the small intestinal lumen with the microbiota. Although experimental evidences suggest that the intestinal microbiota is able to incorporate and degrade some of the available amino acids, it appears that the microbiota is also able to synthesize amino acids raising the view that amino acid exchange between the microbiota and host can proceed in both directions. Although the net result of such exchanges remains to be determined, it is likely that a significant part of the amino acids recovered from the alimentary proteins are used by the microbiota. In the large intestine, where the density of bacteria is much higher than in the small intestine and the transit time much longer, the residual undigested luminal proteins and peptides can be degraded in amino acids by the microbiota. These amino acids cannot be absorbed to a significant extent by the colonic epithelium, but are precursors for the synthesis of numerous metabolic end products in reactions made by the microbiota. Among these products, some like short-chain fatty acids and organic acids are energy substrates for the colonic mucosa and several peripheral tissues while others like sulfide and ammonia can affect the energy metabolism of colonic epithelial cells. More work is needed to clarify the overall effects of the intestinal microbiota on nitrogenous compound metabolism and consequences on gut and more generally host health.

Analysis of breath by proton transfer reaction time of flight mass spectrometry in rats with steatohepatitis induced by high-fat diet

Breath testing has been largely used as a diagnostic tool, but the difficulties in data interpretation and sample collection have limited its application. We developed a fast (< 20 s), on-line, non-invasive method for the collection and analysis of exhaled breath in awake rats based on proton transfer reaction time of flight mass spectrometry (PTR-ToF-MS) and applied it to investigate possible relationships between pathologies induced by dietary regime and breath composition. As a case study, we investigated rats with dietary induced non-alcoholic steatohepatitis (NASH) and modifications induced by coffee addition to the diet. We considered two different diets (standard and high fat) complemented with two different drinking possibilities (water or decaffeinated coffee) for a total of four groups with four rats each. Several spectrometric peaks were reliable markers for both dietary fat content and coffee supplementation. The high resolution and accuracy of PTR-ToF-MS allowed the identification of related compounds such as methanol, dimethyl sulphide, dimethyl sulphone and ammonia. In conclusion, the rapid and minimally invasive breath analysis of awake rats permitted the identification of markers related to diet and specific pathologic conditions and provided a useful tool for broader metabolic investigations.

Ammonia-lowering strategies for the treatment of hepatic encephalopathy

Hyperammonemia leads to neurotoxic levels of brain ammonia and is a major factor involved in the pathogenesis of hepatic encephalopathy (HE). Ammonia-lowering treatments primarily involve two strategies: inhibiting ammonia production and/or increasing ammonia removal. Targeting the gut has been the primary focus for many years, with the goal of inhibiting the generation of ammonia. However, in the context of liver failure, extrahepatic organs containing ammonia metabolic pathways have become new potential ammonia-lowering targets. Skeletal muscle has the capacity to remove ammonia by producing glutamine through the enzyme glutamine synthetase (amidation of glutamate) and, given its large mass, has the potential to be an important ammonia-removing organ. On the other hand, glutamine can be deaminated to glutamate by phosphate-activated glutaminase, thus releasing ammonia (ammonia rebound). Therefore, new treatment strategies are being focused on stimulating the removal of both ammonia and glutamine.