Rifaximin for prevention and treatment of hepatic encephalopathy in people with cirrhosis

Role of astrocytes and microglia in hepatic encephalopathy associated with advanced chronic liver disease: lessons from animal studies

Hepatic encephalopathy, defined as neuropsychiatric dysfunction secondary to liver disease, is a frequent decompensating event in cirrhosis. Its clinical impact is highlighted by a notable increase in patient mortality rates and a concomitant reduction in overall quality of life. Systemically, liver disease, liver function failure, portosystemic shunting, and associated multi-organ dysfunction result in the increase of disease-causing neurotoxins in the circulation, which impairs cerebral homeostasis. Key circulating neurotoxins are ammonia and inflammatory mediators. In the brain, pathophysiology is less well understood, but is thought to be driven by glial cell dysfunction. Astrocytes are the only brain resident cells that have ammonia-metabolizing machinery and are therefore putatively most susceptible to ammonia elevation. Based on a large body of mostly in vitro evidence, ammonia-induced cellular and molecular disturbances include astrocyte swelling and oxidative stress. Microglia, the brain resident macrophages, have been linked to the translation of systemic inflammation to the brain microenvironment. Recent evidence from animal studies has provided novel insights into old and new downstream effects of astrocyte and microglial dysfunction such as toxin clearance disruption and myeloid cell attraction to the central nervous system parenchyma. Furthermore, state of the art research increasingly implicates neuronal dysfunction and possibly even irreversible neuronal cell death. Cell-type specific investigation in animal models highlights the need for critical revision of the contribution of astrocytes and microglia to well-established and novel cellular and molecular alterations in hepatic encephalopathy. In this review, we therefore give a current and comprehensive overview of causes, features, and consequences of astrocyte and microglial dysfunction in hepatic encephalopathy, including areas of interest for future investigation.

Incidence and efficacy of strategies for preventing hepatic encephalopathy following transjugular intrahepatic portosystemic shunt: A meta-analysis

BACKGROUND

Hepatic encephalopathy (HE) is a primary complication following transjugular intrahepatic portosystemic shunt (TIPS), but the utility of pharmacological prophylaxis for HE is unclear.

AIM

To assess the HE incidence post-TIPS across various groups and the prophylactic efficacies of various medications.

METHODS

A thorough literature search was performed in PubMed, Web of Science, EMBASE, and the Cochrane Library databases from their inception to November 24, 2024, to collect data regarding HE incidence. The main outcome was HE incidence post-TIPS. A meta-analysis using a random effects model was performed to obtain odds ratios (ORs) and 95% confidence intervals. Statistical analyses were conducted using Stata and RevMan software.

RESULTS

This meta-analysis included nine studies with 1140 patients; 647 received pharmacological agents including lactulose, rifaximin, albumin, and l-ornithin-l-aspartate, and 493 did not (controls). (1) In the single-group meta-analysis, the control group had higher short- and long-term HE rates than the drug intervention group. Among patients with and without prior HE, the non-intervention group's HE rates were also higher; (2) Pharmacological prevention post-TIPS significantly reduced HE incidence [OR = 0.59 (0.45, 0.77), P = 0.0001]. Compared with the no prophylaxis, rifaximin reduced the risk of HE after TIPS [OR = 0.52 (0.29, 0.95), P = 0.03], but lactulose did not; (3) In patients without prior HE, pharmacological prevention significantly reduced post-TIPS HE incidence [OR = 0.62 (0.41,0.95), P = 0.03]; and (4) Network meta-analysis showed no significant differences among five prevention strategies.

CONCLUSION

The HE incidence after TIPS was relatively high, and the use of drugs after TIPS may reduce the HE incidence. However, research, especially large-scale randomized controlled trials, is still lacking.

Hepatic encephalopathy treatment after transjugular intrahepatic portosystemic shunt: a new perspective on the gut microbiota

Transjugular intrahepatic portosystemic shunt (TIPS) placement alleviates portal hypertension symptoms. Hepatic encephalopathy (HE) is a common complication of TIPS, impacting patient quality of life and the healthcare burden. Post-TIPS HE is associated with portosystemic shunting, elevated blood ammonia levels, and inflammation. Increasing attention has been given to the liver and intestinal circulation in recent years. An imbalance in intestinal microecology plays a role in the occurrence of HE and may be a new target for treatment. This review discusses the causes, diagnosis, and treatment strategies for post-TIPS HE and focuses on exploring treatment strategies and their relationships with the gut microbiota, suggesting an innovative approach to address this complication.

Current management and future perspectives of covert hepatic encephalopathy in Japan: a nationwide survey

BACKGROUND

Covert hepatic encephalopathy (CHE) leads to devastating outcomes in patients with cirrhosis. This study aims to elucidate the current management and future perspectives of CHE in Japan.

METHODS

A questionnaire-based cross-sectional study was conducted among physicians involved in managing cirrhosis in Japan. The primary aim was to elucidate the real-world management of CHE, including testing and treatment. Factors influencing the implementation of CHE testing were analyzed using a logistic regression model. Limitations and future perspectives for improving the management of CHE were also evaluated.

RESULTS

Of 511 physicians surveyed, 93.9% recognized CHE as a significant problem, and 86.9% agreed that it should be tested. Overall, 62.8% of physicians tested for CHE, whereas 37.2% did not. Multivariable analysis identified institutional factors and certifying board as significant determinants of CHE test implementation. The Stroop (68.2%) and neuropsychiatric tests (57.5%) were the most commonly used methods of identifying CHE. Among those who tested for CHE, 87.7% treated CHE; the most common treatments were lactulose (81.5%), rifaximin (76.3%), and branched-chain amino acids (70.4%). Among non-testers, the primary barrier was the time requirement for testing. Proposals to encourage CHE testing included the development of simple tests and integration of multidisciplinary teams.

CONCLUSIONS

Most physicians involved in cirrhosis care in Japan recognize CHE as a significant problem that warrants testing. However, testing for CHE remains limited by institutional factors and physician specialties. Time requirements for CHE testing are the primary barrier, and simple tests and multidisciplinary teams are recommended to enhance CHE management.

Rifaximin prophylaxis in MASLD‑hepatocellular carcinoma: Lessons from a negative animal model

The incidence of hepatocellular carcinoma (HCC) has been rising, particularly among individuals diagnosed with metabolic dysfunction-associated steatotic liver disease. In the present study, the prophylactic effects of rifaximin (RIF) on HCC, inflammatory markers and cardiovascular risk (CVR) were investigated in an animal model. Adult Sprague-Dawley rats were randomly allocated into three groups (n=10, each): Control [standard diet/water plus gavage with vehicle (Veh)], HCC [high-fat choline deficient diet (HFCD)/diethylnitrosamine (DEN) in drinking water/Veh gavage] and RIF [HFCD/DEN/RIF (50 mg/kg/day) gavage] groups. After euthanasia at week 16, biochemical/inflammatory markers and the liver histology were assessed. The results demonstrated that the HCC and RIF animals had a significant increase in fresh liver weight, liver weight/body weight ratio, serum total cholesterol (TC), high-density lipoprotein-cholesterol, triglycerides, hepatic lipid accumulation and hepatic concentration of triglycerides and TC, relative to the controls (P<0.001, for all). Additionally, the HCC and RIF animals had higher plasminogen activator inhibitor, intercellular adhesion molecule-1, E-selectin and CVR scores than the controls (P<0.001, for all). The HCC animals had higher interleukin (IL)-1β (P=0.011), IL-10 (P<0.001), toll-like receptor-2 (P=0.012), lipopolysaccharide-binding protein (P=0.018) and metalloproteinase-2 (P=0.003) levels than the RIF animals. Furthermore, liver steatosis, inflammation and fibrosis, along with increased collagen fiber deposition occurred in the HCC and RIF groups. However, HCC occurred only in 2 RIF rats. In conclusion, although most animals did not develop HCC in the present study, RIF positively affected liver inflammation markers involved in steatohepatitis pathogenesis.

Infection, inflammation and hepatic encephalopathy from a clinical perspective

Hepatic encephalopathy (HE) is a syndrome that is associated with both acute and chronic liver injury. It manifests as a wide spectrum of neuropsychological abnormalities, ranging from subtle impairments in executive higher functions observed in cirrhosis, through to coma in acute liver failure. In acute liver failure, the central role of ammonia in the development of brain oedema has remained undisputed for 130 years. It latterly became apparent that infection and inflammation were profound determinants for the development of severe hepatic encephalopathy, associated with the development of cerebral oedema and intracranial hypertension. The relationship of the development of hepatic encephalopathy with blood ammonia levels in cirrhosis is less clear cut and the synergistic interplay of inflammation and infection with ammonia has been identified as being fundamental in the development and progression of hepatic encephalopathy. A perturbed gut microbiome and the presence of an impaired gut epithelial barrier that facilitates translocation of bacteria and bacterial degradation products into the systemic circulation, inducing systemic inflammation and innate and adaptive immune dysfunction, has now become the focus of therapies that treat hepatic encephalopathy in cirrhosis, and may explain why the prebiotic lactulose and rifaximin are efficacious. This review summarises the current clinical perspective on the roles of inflammation and infection in hepatic encephalopathy and presents the evidence base for existing therapies and those in development in the setting of acute and chronic liver failure.

Role of peripheral inflammation in minimal hepatic encephalopathy

Many patients with liver cirrhosis show minimal hepatic encephalopathy (MHE) with mild cognitive impairment (MCI) and motor alterations that reduce their quality of life. Some patients with steatotic liver disease also suffer MCI. To design treatments to improve MHE/MCI it is necessary to understand the mechanisms by which liver disease induce them. This review summarizes studies showing that appearance of MHE/MCI is associated with a shift in the immunophenotype leading to an "autoimmune-like" form with increased pro-inflammatory monocytes, enhanced CD4 T and B lymphocytes activation and increased plasma levels of pro-inflammatory cytokines, including IL-17, IL-21, TNFα, IL-15 and CCL20. The contribution of peripheral inflammation to trigger MHE is supported by studies in animal models and by the fact that rifaximin treatment reverses MHE in around 60% of patients in parallel with reversal of the changes in peripheral inflammation. MHE does not improve in patients in which peripheral inflammation is not improved by rifaximin. The process by which peripheral inflammation induces MHE involves induction of neuroinflammation in brain, with activation of microglia and astrocytes and increased pro-inflammatory TNFα and IL-1β, which is observed in patients who died with steatotic liver disease (SLD) or liver cirrhosis and in animal models of MHE. Neuroinflammation alters glutamatergic and GABAergic neurotransmission, leading to cognitive and motor impairment. Transmission of peripheral alterations into the brain is mediated by infiltration in brain of extracellular vesicles from plasma and of cells from the peripheral immune system. Acting on any step of the process peripheral inflammation - neuroinflammation - altered neurotransmission may improve MHE.

Preventive and therapeutic effects of rifaximin on hepatic encephalopathy with differential application dosages and strategies: a network meta-analysis

BACKGROUND

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome that affects the prognosis of patients with liver disease and is considered an independent risk factor for hospitalization and death. Rifaximin has been approved for HE treatment. This review will analyze the effect of rifaximin on different stages of HE with differential application dosages and strategies by traditional and network meta-analyses.

METHODS

We performed a systematic search of PubMed, EmBase, and Cochrane Library databases up to February 26, 2023, to identify randomized controlled trials (RCTs) about rifaximin for the prevention and treatment of HE. The outcomes included incidence of HE and HE progression, HE reversal, mortality, and adverse effects.

RESULTS

A total of 21 studies were included. In the primary prevention of HE, rifaximin significantly reduced the incidence of HE (OR: 0.66; 95% CI: 0.45, 0.96; p = 0.032). In secondary prevention, rifaximin significantly reduced the risk of recurrence in patients who were in remission (OR: 0.38; 95% CI: 0.28, 0.52; p < 0.001). In the treatment of minimal HE, rifaximin significantly reduced the breakthrough of MHE to OHE (OR: 0.17; 95% CI: 0.04,0.63; p = 0.008). Rifaximin also significantly improved the clinical symptoms of MHE and OHE patients (OR: 3.76; 95% CI: 2.69, 5.25; p < 0.001). However, rifaximin did not reduce mortality at any stage in HE patients (OR: 0.79; 95% CI: 0.58, 1.08; p = 0.133). Additionally, rifaximin did not increase the risk of adverse effects (OR: 0.96; 95% CI: 0.74, 1.24; p = 0.749). In the network meta-analysis, the 400 mg T.I.D. intervention had a relative advantage for HE risks in primary and secondary prevention. In the treatment of MHE, 600 mg b.i.d. was superior in preventing the breakthrough from MHE to OHE.

CONCLUSION

Rifaximin prevented HE risks and progression and improved clinical symptoms in patients with MHE but did not reduce mortality. For primary and secondary prevention, 400 mg t.i.d. could be considered. 600 mg b.i.d. could be considered in patients with MHE.

Possible pathogenetic role of ammonia in liver cirrhosis without hyperammonemia of venous blood: The so-called latency period of abnormal ammonia metabolism

Ammonia plays a crucial role in the pathogenesis of hepatic encephalopathy. Ammonia is also involved in many other pathological conditions seen in cirrhosis, such as sarcopenia, liver fibrosis, hepatocellular injury, immune dysfunction, and hyperammonemia. Furthermore, the ammonia level of the veins is a useful prognostic factor for cirrhosis. In cirrhosis without hyperammonemia of the vein, however, covert hepatic encephalopathy has been reported. This discrepancy is because of the anatomical features of ammonia metabolism. There are two systems in the body for detoxifying ammonia: one is the urea cycle in the liver, and the other is the glutamine synthesis pathway in skeletal muscle and other tissues. The blood processed in the liver's urea cycle is then transported via arteries to various organs. Further processing occurs in the brain and skeletal muscle's glutamine synthesis pathway before entering the veins. When the urea cycle function decreases in cirrhosis, the ammonia levels in the artery increase. In response, the glutamine synthesis pathway compensates by increasing the capacity to process ammonia. Therefore, the ammonia concentration in the veins downstream of skeletal muscles does not increase immediately. However, the brain and skeletal muscles, which receive arterial blood, might be exposed to high ammonia concentrations. In addition, branched-chain amino acids in venous blood decrease. This period is the transition phase from early- to late-phase cirrhosis, and understanding the pathophysiology during this stage is extremely important for preventing the progression of cirrhosis.

Improved cognition after rifaximin treatment is associated with changes in intra- and inter-brain network functional connectivity

BACKGROUND

Rifaximin is a non-reabsorbable antibiotic which acts at gut level, and improves cognition and inflammatory parameters in minimal hepatic encephalopathy (MHE) patients, but not all patients show the same level of response. This study aims to assess brain activity, both within and between brain networks, following rifaximin treatment, considering the differences between response groups as well.

METHODS

Twenty-two healthy controls and 53 patients with cirrhosis (22 without and 31 with MHE, diagnosed by Psychometric Hepatic Encephalopathy Score, PHES) performed psychometric, attention and coordination tests, and blood inflammatory parameters were measured. Resting-state functional magnetic resonance imaging (fMRI) acquisitions were performed on controls and MHE patients. Eighteen MHE patients underwent a rifaximin treatment for 6 months, after which all measures were repeated. fMRI images were analysed and changes after treatment were assessed.

RESULTS

After rifaximin treatment, 13 patients improved their PHES score (Responder patients) while 5 did not (Non-responder patients). No significant decrease in blood ammonia was observed after rifaximin treatment, but there was a decrease in plasma inflammatory cytokines in responder patients. A global effect of rifaximin was detected on the sensorimotor and fronto-parietal networks. Responder patients showed a relative increase of thalamic network connectivity in comparison to non-responder patients. Before treatment, responder and non-responder patients showed connectivity differences in basal ganglia network. The connection of the sensorimotor and thalamic networks between them and with other networks suffered changes after treatment. These connections between networks mostly decreased after treatment. All changes and differences showed a significant level of correlation with the performance of psychometric tests and the blood levels of inflammatory biomarkers.

CONCLUSIONS

There was an improvement of the communication between executive, motor and attention-related brain areas, and their functional independence following rifaximin treatment. Patients who respond also show a less deteriorated connection involved in these functions before treatment. Results suggest that the improved inflammatory state of MHE patients, following rifaximin treatment would favour the observed changes in brain function and enhanced cognitive performance.

Hepatic encephalopathy: investigational drugs in preclinical and early phase development

INTRODUCTION

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome, in patients with liver disease, which affects life quality and span. Current treatments are lactulose or rifaximin, acting on gut microbiota. Treatments aiming ammonia levels reduction have been tested with little success.

AREAS COVERED

Pre-clinical research shows that the process inducing HE involves sequentially: liver failure, altered microbiome, hyperammonemia, peripheral inflammation, changes in immunophenotype and extracellular vesicles and neuroinflammation, which alters neurotransmission impairing cognitive and motor function. HE may be reversed using drugs acting at any step: modulating microbiota with probiotics or fecal transplantation; reducing peripheral inflammation with anti-TNFα, autotaxin inhibitors or silymarin; reducing neuroinflammation with sulforaphane, p38 MAP kinase or phosphodiesteras 5 inhibitors, antagonists of sphingosine-1-phosphate receptor 2, enhancing meningeal lymphatic drainage or with extracellular vesicles from mesenchymal stem cells; reducing GABAergic neurotransmission with indomethacin or golexanolone.

EXPERT OPINION

A factor limiting the progress of HE treatment is the lack of translation of research advances into clinical trials. Only drugs acting on microbiota or ammonia reduction have been tested in patients. It is urgent to change the mentality on how to approach HE treatment to develop clinical trials to assess drugs acting on the immune system/peripheral inflammation, neuroinflammation or neurotransmission to improve HE.