Histological Features of Cerebellar Neuropathology in Patients With Alcoholic and Nonalcoholic Steatohepatitis

Early stage of metabolic dysfunction associated steatotic liver disease disrupts circadian rhythm and induces neuroinflammation in rats

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) is a chronic liver disease affecting 25% of the European population, with rising global incidence. Liver damage includes ballooning, steatosis, inflammation and fibrosis. Associated brain disorders include sleep, cognitive issues, anxiety, and depression. While neurological complications in advanced MASLD are well documented, early cerebral manifestations remain largely unexplored. This study aimed at developing an MASLD rat model to assess the onset of early brain damage, focusing on impairments of the circadian cycle rhythm and associated neuroinflammation. Sprague Dawley rats were divided into two groups: one received a high-fat, high-cholesterol (HFHC) diet for 90 days, while the other received a standard diet. Histological analysis showed significant hepatic steatosis, ballooning, and inflammation in the HFHC group (p < 0.01). These lesions correlated with elevated hepatic triglycerides (p < 0.01), increased Alanine Aminotransferase, Aspartate Aminotransferase, total cholesterol, and low-density lipoprotein, alongside decreased plasma high-density lipoprotein. Behavioural analysis using activity wheels revealed that the HFHC rats steadily maintained their activity level during the rest periods when compared with controls (p < 0.05). This behavioural alteration occurred alongside neuroinflammation, demonstrated by changes in the expression of 36 and 17 inflammatory mediators in the cerebellum and frontal cortex respectively. These changes were associated with an increase in the expression of glial cell markers (Aif1 and Gfap genes) and an increase in the number of microglial cells, affecting the frontal cortex and cerebellum differently. This rat model of early MASLD shows circadian rhythm disturbances, which could reflect sleep disorders in humans. These early brain disturbances specific to MASLD, which occur before the symptoms of liver disease become clinically apparent, could therefore be used as an early diagnosis marker for MASLD patients.

The liver-brain axis in metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects around 30% of the global population. Studies suggest that MASLD is associated with compromised brain health and cognitive dysfunction, initiating a growing interest in exploring the liver-brain axis mechanistically within MASLD pathophysiology. With the prevalence of MASLD increasing at an alarming rate, leaving a large proportion of people potentially at risk, cognitive dysfunction in MASLD is a health challenge that requires careful consideration and awareness. This Review summarises the current literature on cognitive function in people with MASLD and discusses plausible causes for its impairment. It is likely that a multifaceted spectrum of factors works collectively to affect cognition in patients with MASLD. We describe the role of inflammation, vascular disease, and brain ageing and neurodegeneration as possible key players. This Review also highlights the need for future studies to identify the optimal test for diagnosing cognitive dysfunction in patients with MASLD, to examine the correlation between MASLD progression and the severity of cognitive dysfunction, and to evaluate whether new MASLD-targeted therapies also improve brain dysfunction.

A narrative review about cognitive impairment in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): Another matter to face through a holistic approach

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic hepatic disorder worldwide in both adults and children. It is well established that MASLD represents the hepatic manifestation of the metabolic syndrome whose definition includes the presence of obesity, type 2 diabetes (T2D), dyslipidemia, hypertension and hypercoagulability. All these conditions contribute to a chronic inflammatory status which may impact on blood brain barrier (BBB) integrity leading to an impaired function of central nervous system (CNS).

AIM OF REVIEW

Since the mechanisms underlying the brain-liver-gut axis derangement are still inconclusive, the present narrative review aims to make a roundup of the most recent studies regarding the cognitive decline in MASLD also highlighting possible therapeutic strategies to reach a holistic advantage for the patients.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Due to its ever-growing prevalence, the MASLD-related mental dysfunction represents an enormous socio-economic burden since it largely impacts on the quality of life of patients as well as on their working productivity. Indeed, cognitive decline in MASLD translates in low concentration and processing speed, reduced memory, sleepiness but also anxiety and depression. Chronic systemic inflammation, hyperammonemia, genetic background and intestinal dysbiosis possibly contribute to the cognitive decline in MASLD patients. However, its diagnosis is still underestimated since the leading mechanisms are multi-faceted and unexplained and do not exist standardized diagnostic tools or cognitive test strategies. In this scenario, nutritional and lifestyle interventions as well as intestinal microbiota manipulation (probiotics, fecal transplantation) may represent new approaches to counteract mental impairment in these subjects. In sum, to face the "mental aspect" of this multifactorial disease which is almost unexplored, cognitive tools should be introduced in the management of MASLD patients.

Vitamin D Supplementation Is Associated with Inflammation Amelioration and Cognitive Improvement in Decompensated Patients with Cirrhosis

Background/Objectives: Decompensated cirrhosis is characterized by systemic inflammation and innate and adaptive immune dysfunction. Hepatic encephalopathy (HE) is a prevalent and debilitating condition characterized by cognitive disturbances in which ammonia and inflammation play a synergistic pathogenic role. Extraskeletal functions of vitamin D include immunomodulation, and its deficiency has been implicated in immune dysfunction and different forms of cognitive impairment. The aim was to assess changes in cognitive function and inflammation in decompensated patients with cirrhosis receiving vitamin D supplementation. Methods: Patients with cirrhosis discharged from decompensation in two tertiary hospitals in Spain (from September 2017 to January 2020) were assessed before, at 6 and 12 months after vitamin D supplementation. A comprehensive neuropsychological battery and neuroinflammatory markers were examined. In a subgroup of patients, peripheral immune blood cells were analyzed. Results: Thirty-nine patients were recruited. Of those, 27 completed the 6 months evaluation and were analyzed [age 62.4 ± 11.3 years; 22 men; Model for End-Stage Liver Disease (MELD) 11.7 ± 4.0; prior overt HE 33%; median 25-hydroxyvitamin D (25OHD) plasma level 12.7 µgr/L] and 22 achieved 12 months assessment. At baseline, learning and memory (R = 0.382; p = 0.049) and working memory (R = 0.503; p = 0.047) subtests correlated with plasma 25OHD levels. In addition, processing speed (R = -0.42; p = 0.04), attention (R = -0.48; p = 0.04), Tinnetti balance (R = -0.656; p < 0.001) and Tinnetti score (R = -0.659; p < 0.001) were linked to neuroinflammation marker IL-1β. Patients with lower 25OHD had a greater proportion of TH1cells at baseline and a larger amelioration of IL-1β and IL-6 following supplementation. An improvement in working memory was found after 25OHD replacement (46.7 ± 13 to 50 ± 11; p = 0.047). Conclusions: This study supports that vitamin D supplementation modulates low-grade inflammation in decompensated cirrhosis providing cognitive benefits, particularly in working memory.

Effects of Metabolic Dysfunction-Associated Steatohepatitis in Alertness, Associative Learning, and Astrocyte Density

PURPOSE

Metabolic dysfunction-associated steatohepatitis (MASH) is a prevalent disease caused by high fat and high cholesterol intake, which leads to systemic deterioration. The aim of this research is to conduct a psychobiological exploration of MASH in adult male rats.

METHODS

Subjects who were administered a high-fat and high-cholesterol diet for 14 weeks. Then, we assessed the acoustic startle response and alertness through the prepulse inhibition paradigm as well as the associative learning by the use of the passive avoidance test. Also, we explored the astrocyte density in the prefrontal cortex and hippocampus.

RESULTS

Our results showed that, whereas the MASH group did not display an impaired associative learning, a lower exploration rate was found in this group. Moreover, a reduced prepulse inhibition was found in these subjects in the case of the weaker and closer-to-the-stimulus prepulse, which indicates a mild alteration in this process. No differences were found in astrocyte density in the MASH group in comparison with controls.

CONCLUSION

MASH seems to be linked with cognitive dysfunction. Further research is needed to elucidate the pathway involved in this disease and its underlying mechanism, as well as the potential implication in human health.

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.

Hepatic encephalopathy as a result of ammonia-induced increase in GABAergic tone with secondary reduced brain energy metabolism

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome caused by liver insufficiency and/or portosystemic shunting. HE is mostly episodic and as such reversible. Hyperammonemia clearly plays a key role in the pathophysiology, but the precise detrimental events in the brain leading to HE remain equivocal. Several pathogenic models have been proposed, but few have been linked to clinical studies and observations. Decreased oxygen metabolism is observed in both type A and C HE and in this review, we advocate that this reflects an actual reduced oxygen demand and not a primary cause of HE. As driving force, we propose that the hyperammonemia via astrocytic glutamine synthetase causes an increased γ-aminobutyric acid (GABA) mediated neuro-inhibition which subsequently leads to an overall decreased energy demand of the brain, something that can be enhanced by concomitant neuroinflammation. This also explains the reversibility of the condition.

Mechanism of Alzheimer type II astrocyte development in hepatic encephalopathy

Type C hepatic encephalopathy (Type C HE) is a major and complex neurological condition that occurs following chronic liver failure. The molecular basis of Type C HE remains elusive. Type C HE is characterized by mental confusion, cognitive and motor disturbances. The presence of Alzheimer type II astrocytes (AT2A) is the key histopathological finding observed in Type C HE. However, nothing is currently known regarding AT2A development and its involvement in cognitive, and motor deficits in Type C HE. We, therefore, examined in rats the mechanisms by which liver failure contributes to the progression of AT2A, and its role in the development of cognitive and motor deficits in thioacetamide (TAA) model of Type C HE. We and others earlier reported increased oxidative/nitrosative stress (ONS), JNK1/2, and cMyc activation in ammonia-treated astrocyte cultures, as well as in brains from chronic liver failure. We now found increased levels of astrocytic glia maturation factor (GMF, a factor strongly implicated in neuroinflammation), as well as various inflammatory factors (IL-1β, TNF-α, IL-6, MMP-3, COX2, CXCL1, and PGE2), and reduced levels of GFAP and increased levels of aggregated nuclear protein Lamin A/C in rat brain cortex post-chronic liver failure. We also found increased levels of GMF and inflammatory factors (MMP-3, COX2, CXCL1, and PGE2) in astrocytes post-ammonia treatment in vitro. Additionally, pharmacological inhibition of upstream signaling of GMF (ONS, JNK1/2, and cMyc) or GMF inhibitors W-7 and trifluoperazine significantly reduced the levels of inflammatory factors, the number of AT2A cells, as well as the cognitive and motor deficits in TAA-treated rats. Increased levels of GMF were also identified in human post-mortem brain sections. These findings strongly suggest that increased levels of astrocytic GMF due to elevated levels of ONS, JNK1/2, and cMyc and the subsequent inflammation contribute to the development of AT2A and the consequent cognitive, and motor deficits in chronic liver failure.

Extracellular vesicles from mesenchymal stem cells alter gut microbiota and improve neuroinflammation and motor impairment in rats with mild liver damage

Gut microbiota perturbation and motor dysfunction have been reported in steatosis patients. Rats with mild liver damage (MLD) show motor dysfunction mediated by neuroinflammation and altered GABAergic neurotransmission in the cerebellum. The extracellular vesicles (EV) from mesenchymal stem cells (MSC) have emerged as a promising therapeutic proxy whose molecular basis relies partly upon TGFβ action. This study aimed to assess if MSC-EVs improve motor dysfunction in rats with mild liver damage and analyze underlying mechanisms, including the role of TGFβ, cerebellar neuroinflammation and gut microbiota. MLD in rats was induced by carbon tetrachloride administration and EVs from normal (C-EVs) or TGFβ-siRNA treated MSCs (T-EV) were injected. Motor coordination, locomotor gait, neuroinflammation and TNF-α-activated pathways modulating GABAergic neurotransmission in the cerebellum, microbiota composition in feces and microbial-derived metabolites in plasma were analyzed. C-EVs reduced glial and TNFα-P2X4-BDNF-TrkB pathway activation restoring GABAergic neurotransmission in the cerebellum and improving motor coordination and all the altered gait parameters. T-EVs also improved motor coordination and some gait parameters, but the mechanisms involved differed from those of C-EVs. MLD rats showed increased content of some Bacteroides species in feces, correlating with decreased kynurenine aside from motor alterations. These alterations were all normalized by C-EVs, whereas T-EVs only restored kynurenine levels. Our results support the value of MSC-EVs on improving motor dysfunction in MLD and unveil a possible mechanism by which altered microbiota may contribute to neuroinflammation and motor impairment. Some of the underlying mechanisms are TGFβ-dependent.

Neuropathology of deaths due to acute alcohol toxicity in Australia, 2011-2022

BACKGROUND

A major alcohol-related harm is structural pathology affecting the brain. The study aimed to: 1. Determine the frequency and nature of neuropathology amongst cases of death due to acute alcohol toxicity; 2. Compare diagnoses of brain atrophy with pathology in other organs; 3. Determine the demographic, clinical and organ pathology correlates of brain atrophy.

METHODS

Retrospective study of 500 cases of death attributed to acute alcohol toxicity in Australia, 2011-2022. Data on clinical characteristics, toxicology, neuropathology and other organ pathology were retrieved from police reports, autopsies, toxicology and coronial findings.

RESULTS

Mean age was 49.5 years, 69.4 % were male, with alcohol use problems documented in 70.2 %. Brain atrophy was diagnosed in 60 cases (12.0 %), most commonly in the cerebellum (32 cases, 6.4 %). Atrophy at other sites was present in 37 (7.4 %). The presence of brain atrophy was lower than other major pathologies: cardiomegaly (32.6 %, p<.001), nephro/arteriosclerosis (30.2 %, p<.001), and chronic obstructive pulmonary disease (21.8 %, p<.001) but not hepatic cirrhosis (11.9 % p=1.0). Those diagnosed with atrophy were older (53.4v 49.0 years, p<.001), more likely to have documented alcohol problems (85.0v 68.2 %, Odds ratio: OR 2.53) and seizure history (10.0v 3.0 %, OR 2.92), to have cardiomegaly (43.3v 31.0 %, OR 1.90, COPD (48.3v 18.2 %, 3.57) and nephro/arteriosclerosis (50.0 v 27.4 %, OR 2.27).

CONCLUSIONS

Despite the majority of cases having a history of alcohol problems, the level of neuropathology amongst cases of death due to acute alcohol toxicity was comparatively low.

Non-alcoholic Fatty Liver Disease: Also a Disease of the Brain? A Systematic Review of the Preclinical Evidence

Non-alcoholic fatty liver disease (NAFLD) currently affects 25% of the global adult population. Cognitive impairment is a recently recognised comorbidity impeding memory, attention, and concentration, affecting the patients' activities of daily living and reducing their quality of life. This systematic review provides an overview of the evidence for, and potential pathophysiological mechanisms behind brain dysfunction at a neurobiological level, in preclinical NAFLD. We performed a systematic literature search for animal models of NAFLD studying intracerebral conditions using PubMed, Embase and Scopus. We included studies that reported data on neurobiology in rodent and pig models with evidence of steatosis or steatohepatitis assessed by liver histology. 534 unique studies were identified, and 30 studies met the selection criteria, and were included. Findings of neurobiological changes were divided into five key areas: (1) neuroinflammation, (2) neurodegeneration, (3) neurotransmitter alterations, (4) oxidative stress, and (5) changes in proteins and synaptic density. Despite significant heterogeneity in the study designs, all but one study of preclinical NAFLD reported changes in one or more of the above key areas when compared to control animals. In conclusion, this systematic review supports an association between all stages of NAFLD (from simple steatosis to non-alcoholic steatohepatitis (NASH)) and neurobiological changes in preclinical models.

Increased levels and activation of the IL-17 receptor in microglia contribute to enhanced neuroinflammation in cerebellum of hyperammonemic rats

BACKGROUND

Patients with liver cirrhosis may show minimal hepatic encephalopathy (MHE) with mild cognitive impairment and motor incoordination. Rats with chronic hyperammonemia reproduce these alterations. Motor incoordination in hyperammonemic rats is due to increased GABAergic neurotransmission in cerebellum, induced by neuroinflammation, which enhances TNFα-TNFR1-S1PR2-CCL2-BDNF-TrkB pathway activation. The initial events by which hyperammonemia triggers activation of this pathway remain unclear. MHE in cirrhotic patients is triggered by a shift in inflammation with increased IL-17. The aims of this work were: (1) assess if hyperammonemia increases IL-17 content and membrane expression of its receptor in cerebellum of hyperammonemic rats; (2) identify the cell types in which IL-17 receptor is expressed and IL-17 increases in hyperammonemia; (3) assess if blocking IL-17 signaling with anti-IL-17 ex-vivo reverses activation of glia and of the TNFα-TNFR1-S1PR2-CCL2-BDNF-TrkB pathway.

RESULTS

IL-17 levels and membrane expression of the IL-17 receptor are increased in cerebellum of rats with hyperammonemia and MHE, leading to increased activation of IL-17 receptor in microglia, which triggers activation of STAT3 and NF-kB, increasing IL-17 and TNFα levels, respectively. TNFα released from microglia activates TNFR1 in Purkinje neurons, leading to activation of NF-kB and increased IL-17 and TNFα also in these cells. Enhanced TNFR1 activation also enhances activation of the TNFR1-S1PR2-CCL2-BDNF-TrkB pathway which mediates microglia and astrocytes activation.

CONCLUSIONS

All these steps are triggered by enhanced activation of IL-17 receptor in microglia and are prevented by ex-vivo treatment with anti-IL-17. IL-17 and IL-17 receptor in microglia would be therapeutic targets to treat neurological impairment in patients with MHE.

L-Carnitine in the Treatment of Psychiatric and Neurological Manifestations: A Systematic Review

OBJECTIVE

L-carnitine (LC), a vital nutritional supplement, plays a crucial role in myocardial health and exhibits significant cardioprotective effects. LC, being the principal constituent of clinical-grade supplements, finds extensive application in the recovery and treatment of diverse cardiovascular and cerebrovascular disorders. However, controversies persist regarding the utilization of LC in nervous system diseases, with varying effects observed across numerous mental and neurological disorders. This article primarily aims to gather and analyze database information to comprehensively summarize the therapeutic potential of LC in patients suffering from nervous system diseases while providing valuable references for further research.

METHODS

A comprehensive search was conducted in PubMed, Web Of Science, Embase, Ovid Medline, Cochrane Library and Clinicaltrials.gov databases. The literature pertaining to the impact of LC supplementation on neurological or psychiatric disorders in patients was reviewed up until November 2023. No language or temporal restrictions were imposed on the search.

RESULTS

A total of 1479 articles were retrieved, and after the removal of duplicates through both automated and manual exclusion processes, 962 articles remained. Subsequently, a meticulous re-screening led to the identification of 60 relevant articles. Among these, there were 12 publications focusing on hepatic encephalopathy (HE), while neurodegenerative diseases (NDs) and peripheral nervous system diseases (PNSDs) were represented by 9 and 6 articles, respectively. Additionally, stroke was addressed in five publications, whereas Raynaud's syndrome (RS) and cognitive disorder (CD) each had three dedicated studies. Furthermore, migraine, depression, and amyotrophic lateral sclerosis (ALS) each accounted for two publications. Lastly, one article was found for other symptoms under investigation.

CONCLUSION

In summary, LC has demonstrated favorable therapeutic effects in the management of HE, Alzheimer's disease (AD), carpal tunnel syndrome (CTS), CD, migraine, neurofibromatosis (NF), PNSDs, RS, and stroke. However, its efficacy appears to be relatively limited in conditions such as ALS, ataxia, attention deficit hyperactivity disorder (ADHD), depression, chronic fatigue syndrome (CFS), Down syndrome (DS), and sciatica.

Impact of steatotic liver disease and non-alcoholic steatohepatitis on cognitive impairment in people living with HIV: A cross-sectional study

INTRODUCTION

The link between fatty liver diseases and cognitive impairment among people living with HIV (PLWH) remains unclear. We investigated the association of steatotic liver disease (SLD), advanced liver fibrosis and non-alcoholic steatohepatitis (NASH) with significant activity and liver fibrosis with cognitive impairment in PLWH.

METHODS

Cognitive performance was assessed for PLWH aged ≥50 years on stable antiretroviral therapy (ART) with the Thai-validated version of the Montreal Cognitive Assessment (MoCA), and a cut-off of <25/30 was used to define cognitive impairment. SLD and NASH with significant activity and liver fibrosis were defined as having a controlled attenuation parameter value ≥248 dB/m and a FibroScan-AST (FAST) score ≥0.67, respectively. Multivariable logistic regression was employed to investigate the association of cognitive impairment with SLD or NASH.

RESULTS

Of the 319 PLWH (63.3% male and 98% had HIV-1 RNA ≤50 copies/mL) included, 74 (38%) had SLD. NASH with significant activity and liver fibrosis was present in 66 (20.1%) participants. Some 192 (60.2%) participants had cognitive impairment. In a multivariable analysis, NASH with significant activity and liver fibrosis was significantly associated with cognitive impairment (adjusted odds ratio [aOR] 2.01, 95% CI 1.02-3.98, p = 0.04), after adjusting for HIV-related parameters, age, sex, body mass index, employment status, education, income level, smoking, alcohol use, diabetes mellitus, hypertension and HIV-related parameters. The association of a lone diagnosis of SLD and cognitive impairment was not statistically significant.

CONCLUSIONS

NASH with significant activity and liver fibrosis was associated with lower cognitive performance, even after controlling for demographics and HIV disease parameters. Additional research is needed to better understand the underlying mechanisms.

Patients who died with steatohepatitis or liver cirrhosis show neuroinflammation and neuronal loss in hippocampus

BACKGROUND

Neuroinflammation in the cerebral cortex of patients who died with liver cirrhosis and neuroinflammation, and neuronal death in the cerebellum of patients who died with steatohepatitis or cirrhosis, were reported. Hippocampal neuroinflammation could contribute to cognitive decline in patients with liver disease, but this has yet to be studied. The study aims were to assess if hippocampus from patients who died with steatohepatitis or cirrhosis showed: (i) glial activation, (ii) altered cytokine content, (iii) immune cell infiltration, (iv) neuronal apoptosis and (v) neuronal loss.

METHODS

Post-mortem hippocampus was obtained from 6 controls, 19 patients with steatohepatitis (SH) and 4 patients with liver cirrhosis. SH patients were divided into SH1 (n = 9), SH2 (n = 6) and SH3 (n = 4) groups depending on disease severity. Glial activation, IL-1β and TNFα content, CD4 lymphocyte and monocyte infiltration, neuronal apoptosis and neuronal loss were analyzed by immunohistochemistry.

RESULTS

Patients who died in SH1 showed astrocyte activation, whereas those who died in SH2 also showed microglial activation, CD4 lymphocyte and monocyte infiltration, neuronal apoptosis and neuronal loss. These changes remained in patients in SH3, who also showed increased IL-1β and TNFα. Patients who died of liver cirrhosis did not show CD4 lymphocyte infiltration, neuronal apoptosis or increase in TNFα, but still showed glial activation, increased IL-1β and neuronal loss.

CONCLUSIONS

Patients with steatohepatitis showed glial activation, immune cell infiltration, apoptosis and neuronal loss. Glial activation and neuronal loss remained in cirrhotic patients. This may explain the irreversibility of some cognitive alterations in hepatic encephalopathy. Cognitive reserve may contribute to different grades of cognitive impairment despite similar neuronal loss.

Mild Cognitive Impairment Is Associated with Enhanced Activation of Th17 Lymphocytes in Non-Alcoholic Fatty Liver Disease

Patients with nonalcoholic fatty liver disease (NAFLD) may show mild cognitive impairment (MCI). The mechanisms involved remain unclear. The plasma concentrations of several cytokines and chemokines were measured in 71 NAFLD patients (20 with and 51 without MCI) and 61 controls. Characterization and activation of leukocyte populations and CD4⁺ sub-populations were carried out and analyzed by flow cytometry. We analyzed the cytokines released from CD4⁺ cell cultures and the mRNA expression of transcription factors and receptors in peripheral blood mononuclear cells. The appearance of MCI in NAFLD patients was associated with increased activation of CD4⁺ T lymphocytes, mainly of the Th17 subtype, increased plasma levels of pro-inflammatory and anti-inflammatory cytokines such as IL-17A, IL-23, IL-21, IL-22, IL-6, INF-γ, and IL-13, and higher expression of the CCR2 receptor. Constitutive expression of IL-17 was found in cultures of CD4⁺ cells from MCI patients, reflecting Th17 activation. High IL-13 plasma levels were predictive of MCI and could reflect a compensatory anti-inflammatory response to the increased expression of pro-inflammatory cytokines. This study identified some specific alterations of the immune system associated with the appearance of neurological alterations in MCI patients with NAFLD that could be the basis to improve and restore cognitive functions and quality of life in these patients.

New Insight Into Mechanisms of Hepatic Encephalopathy: An Integrative Analysis Approach to Identify Molecular Markers and Therapeutic Targets

Hepatic encephalopathy (HE) is a set of complex neurological complications that arise from advanced liver disease. The precise molecular and cellular mechanism of HE is not fully understood. Differentially expressed genes (DEGs) from microarray technologies are powerful approaches to obtain new insight into the pathophysiology of HE. We analyzed microarray data sets of cirrhotic patients with HE from Gene Expression Omnibus to identify DEGs in postmortem cerebral tissues. Consequently, we uploaded significant DEGs into the STRING to specify protein-protein interactions. Cytoscape was used to reconstruct the genetic network and identify hub genes. Target genes were uploaded to different databases to perform comprehensive enrichment analysis and repurpose new therapeutic options for HE. A total of 457 DEGs were identified in 2 data sets totally from 12 cirrhotic patients with HE compared with 12 healthy subjects. We found that 274 genes were upregulated and 183 genes were downregulated. Network analyses on significant DEGs indicated 12 hub genes associated with HE. Enrichment analysis identified fatty acid beta-oxidation, cerebral organic acidurias, and regulation of actin cytoskeleton as main involved pathways associated with upregulated genes; serotonin receptor 2 and ELK-SRF/GATA4 signaling, GPCRs, class A rhodopsin-like, and p38 MAPK signaling pathway were related to downregulated genes. Finally, we predicted 39 probable effective drugs/agents for HE. This study not only confirms main important involved mechanisms of HE but also reveals some yet unknown activated molecular and cellular pathways in human HE. In addition, new targets were identified that could be of value in the future study of HE.

Sustained Hyperammonemia Activates NF-κB in Purkinje Neurons Through Activation of the TrkB-PI3K-AKT Pathway by Microglia-Derived BDNF in a Rat Model of Minimal Hepatic Encephalopathy

Chronic hyperammonemia is a main contributor to the cognitive and motor impairment in patients with hepatic encephalopathy. Sustained hyperammonemia induces the TNFα expression in Purkinje neurons, mediated by NF-κB activation. The aims were the following: (1) to assess if enhanced TrkB activation by BDNF is responsible for enhanced NF-κB activation in Purkinje neurons in hyperammonemic rats, (2) to assess if this is associated with increased content of NF-κB modulated proteins such as TNFα, HMGB1, or glutaminase I, (3) to assess if these changes are due to enhanced activation of the TNFR1-S1PR2-CCR2-BDNF-TrkB pathway, (4) to analyze if increased activation of NF-κB is mediated by the PI3K-AKT pathway. It is shown that, in the cerebellum of hyperammonemic rats, increased BDNF levels enhance TrkB activation in Purkinje neurons leading to activation of PI3K, which enhances phosphorylation of AKT and of IκB, leading to increased nuclear translocation of NF-κB which enhances TNFα, HMGB1, and glutaminase I content. To assess if the changes are due to enhanced activation of the TNFR1-S1PR2-CCR2 pathway, we blocked TNFR1 with R7050, S1PR2 with JTE-013, and CCR2 with RS504393. These changes are reversed by blocking TrkB, PI3K, or the TNFR1-SP1PR2-CCL2-CCR2-BDNF-TrkB pathway at any step. In hyperammonemic rats, increased levels of BDNF enhance TrkB activation in Purkinje neurons, leading to activation of the PI3K-AKT-IκB-NF-κB pathway which increased the content of glutaminase I, HMGB1, and TNFα. Enhanced activation of this TrkB-PI3K-AKT-NF-κB pathway would contribute to impairing the function of Purkinje neurons and motor function in hyperammonemic rats and likely in cirrhotic patients with minimal or clinical hepatic encephalopathy.

Emerging Links between Nonalcoholic Fatty Liver Disease and Neurodegeneration

The association between liver and brain health has gained attention as biomarkers of liver function have been revealed to predict neurodegeneration. The liver is a central regulator in metabolic homeostasis. However, in nonalcoholic fatty liver disease (NAFLD), homeostasis is disrupted which can result in extrahepatic organ pathologies. Emerging literature provides insight into the mechanisms behind the liver-brain health axis. These include the increased production of liver-derived factors that promote insulin resistance and loss of neuroprotective factors under conditions of NAFLD that increase insulin resistance in the central nervous system. In addition, elevated proinflammatory cytokines linked to NAFLD negatively impact the blood-brain barrier and increase neuroinflammation. Furthermore, exacerbated dyslipidemia associated with NAFLD and hepatic dysfunction can promote altered brain bioenergetics and oxidative stress. In this review, we summarize the current knowledge of the crosstalk between liver and brain as it relates to the pathophysiology between NAFLD and neurodegeneration, with an emphasis on Alzheimer's disease. We also highlight knowledge gaps and future areas for investigation to strengthen the potential link between NAFLD and neurodegeneration.

Morphological changes in the brain in liver cirrhosis of alcoholic and viral etiology

Background. Hepatic encephalopathy is an actual problem of modern medicine. However, its pathogenesis and histological picture are currently insufficiently studied. Less is known about the impact of the nature of primary liver disease on pathogenesis and histological picture of hepatic encephalopathy. This determines the relevance of further morphological studies of the brain in the late stages of liver cirrhosis of various etiologies.The aim. To establish and compare the morphological changes in the brain in alcoholic liver cirrhosis and viral (hepatitis C virus (HCV)) cirrhosis.Materials and methods. The morphological study of the brain of 40 deceased in outcome of HCV-associated cirrhosis and 23 patients died in outcome of chronic alcoholism was carried out. Histological changes in various parts of the brain were studied using survey and elective stains. The immunohistochemical study of HCV NS3 and CD68 expression in different brain regions was performed in cases of HCV-infection.Results. The changes of neurons, glial cells and cerebral microvessels underlie in the basis of morphological picture of brain damage in both studied groups underlie that corresponds to the “classical” model of hepatic encephalopathy pathogenesis. At the same time, a number of morphological features were observed. The most prominent differences concerned the manifestations of the glial reaction. The productive changes of macroglial cells with the appearance of multiple Alzheimer’s astrocytes type 2 as well as spongious changes in subcortical white matter dominated in the observations of alcoholic cirrhosis. In contrast, microglia cells reaction (microgliosis) in white matter was noticed in HCV-associated cirrhosis.Conclusions. The differences in histological signs of brain in the terminal stages of liver disease of viral and alcoholic etiology are shown. They broaden current idea of morphological picture of hepatic encephalopathy, and may be used to study its pathogenesis.

The role of brain inflammation and abnormal brain oxygen homeostasis in the development of hepatic encephalopathy

Hepatic encephalopathy (HE) is a frequent complication of chronic liver disease (CLD) and has a complex pathogenesis. Several preclinical and clinical studies have reported the presence of both peripheral and brain inflammation in CLD and their potential impact in the development of HE. Altered brain vascular density and tone, as well as compromised cerebral and systemic blood flow contributing to the development of brain hypoxia, have also been reported in animal models of HE, while a decrease in cerebral metabolic rate of oxygen and cerebral blood flow has consistently been observed in patients with HE. Whilst significant strides in our understanding have been made over the years, evaluating all these mechanistic elements in vivo and showing causal association with development of HE, have been limited through the practical constraints of experimentation. Nonetheless, improvements in non-invasive assessments of different neurophysiological parameters, coupled with techniques to assess changes in inflammatory and metabolic pathways, will help provide more granular insights on these mechanisms. In this special issue we discuss some of the emerging evidence supporting the hypothesis that brain inflammation and abnormal oxygen homeostasis occur interdependently during CLD and comprise important contributors to the development of HE. This review aims at furnishing evidence for further research in brain inflammation and oxygen homeostasis as additional therapeutic targets and potentially diagnostic markers for HE.

EASL Clinical Practice Guidelines on the management of hepatic encephalopathy

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

Diabetes mellitus - risk factor and potential future target for hepatic encephalopathy in patients with liver cirrhosis?

Hepatic encephalopathy (HE) is one of the major complications of cirrhosis, and its presence is associated with poor survival. Several risk factors for HE are well established, including age, history of HE, portosystemic shunts, or poorer liver function. In recent years, diabetes mellitus (DM) has emerged as another potential risk factor for the development of HE. This may be important for many patients, as the incidence of type 2 DM (T2DM) is increasing worldwide and, consequently, the incidence of NAFLD-related cirrhosis is rising simultaneously. In addition, DM is a critical factor in the progression of other liver diseases, such as alcohol-related liver disease. Thus, the number of patients with cirrhosis and comorbid T2DM will also increase. To date, the prevalence of DM already ranges between 22 - 40% in patients with cirrhosis. DM-associated factors that may influence the risk of HE include systemic inflammation, insulin resistance with increased muscle protein breakdown as well as autonomic dysfunction with prolonged intestinal transit time and small intestinal bacterial overgrowth. Currently, the evidence for an association between DM and both minimal and overt HE is weak and it seems likely that only poor glycemic control has an impact on HE risk. In addition, there are some early signs indicating that DM may impair the response of patients with HE to pharmacological therapies such as rifaximin. Thus, improvements in the management of glycemic control may be a candidate future target to reduce the risk of HE. In this concise review, we summarize the current evidence on the association between DM and HE and its potential future implications.

Management of Hepatic Encephalopathy Associated with Advanced Liver Disease

Hepatic encephalopathy (HE) is a very prevalent condition in patients with advanced liver disease and has a high recurrence rate. The pathophysiology has a multifactorial origin where hyperammonaemia and inflammation become particularly relevant. There are no HE-specific diagnostic tests, and diagnosis is usually made by taking into account the presence of suggestive and compatible clinical symptoms, the existence of a predisposing liver condition and ruling out other causes with similar clinical manifestations. Once the diagnosis of HE is established, it is essential to carry out an adequate classification based on the underlying liver disease, the intensity of clinical manifestations, the temporal course of the disease and the presence or absence of precipitating factors. Treatment should be aimed at decreasing the duration, intensity and consequences of episodes, preventing recurrence and limiting the impact of the disease in patients and their relatives.

Fatty liver and cerebrovascular disease: plausible association and possible mechanisms

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is a common comorbidity and has wide ranging extrahepatic manifestations, including through cardiometabolic pathways. As such, there is growing interest in the impact of NAFLD on cerebrovascular disease and brain health more broadly. In this review, we assess recent research into understanding the association between NAFLD and brain health while highlighting potential clinical implications.

RECENT FINDINGS

Mechanistically, NAFLD is characterized by both a proinflammatory and proatherogenic state, which results in vascular inflammation and neurodegeneration, potentially leading to clinical and subclinical cerebrovascular disease. Mounting epidemiological evidence suggests an association between NAFLD and an increased risk and severity of stroke, independent of other vascular risk factors. Studies also implicate NAFLD in subclinical cerebrovascular disease, such as carotid atherosclerosis and microvascular disease. In contrast, there does not appear to be an independent association between NAFLD and cognitive impairment.

SUMMARY

The current literature supports the formulation of NAFLD as a multisystem disease that may also have implications for cerebrovascular disease and brain health. Further prospective studies are needed to better assess a temporal relationship between the two diseases, confirm these early findings, and decipher mechanistic links.

Fiber scaffold bioartificial liver therapy relieves acute liver failure and extrahepatic organ injury in pigs

Rationale: Acute liver failure (ALF) causes severe liver injury and a systemic inflammatory response, leading to multiorgan failure with a high short-term mortality. Bioartificial liver (BAL) therapy is a promising approach that is hampered by the lack of appropriate bioreactors and carriers to retain hepatic cell function and poor understanding of BAL treatment mechanisms in ALF and extrahepatic organ injury. Recently, we used a fiber scaffold bioreactor (FSB) for the high-density, three-dimensional (3D) culture of primary porcine hepatocytes (PPHs) combined with an absorption component to construct a BAL and verified its function in a D-galactosamine (D-gal)-induced ALF porcine model to evaluate its protective effects on the liver and extrahepatic organs. Methods: Male pigs were randomized into standard/supportive therapy (ST), ST+no-cell BAL (ST+Sham BAL) and ST+BAL groups and received treatment 48 h after receiving a D-gal injection. Changes in blood chemistry and clinical symptoms were monitored for 120 h. Tissues and plasma were collected for analysis by pathological examination, immunoblotting, quantitative PCR and immunoassays. Results: PPHs cultured in the FSB obtained sufficient aeration and nutrition for high-density, 3D culture and maintained superior viability and functionality (biosynthesis and detoxification) compared with those cultured in flasks. All the animals developed ALF, acute kidney injury (AKI) and hepatic encephalopathy (HE) 48 h after D-gal infusion and received corresponding therapies. Animals in the BAL group showed markedly improved survival (4/5; 80%) compared with those in the ST+Sham BAL (0/5; p < 0.001) and ST (0/5; p < 0.001) groups. The levels of blood ammonia and biochemical and inflammatory indices were alleviated after BAL treatment. Increased liver regeneration and attenuations in the occurrence and severity of ALF, AKI and HE were observed in the ST+BAL group compared with the ST (p = 0.0009; p = 0.038) and ST+Sham BAL (p = 0.011; p = 0.031) groups. Gut leakage, the plasma endotoxin level, bacterial translocation, and peripheral and neuroinflammation were alleviated in the ST+BAL group compared with those in the other groups. Conclusions: BAL treatment enhanced liver regeneration and alleviated the systemic inflammatory response and extrahepatic organ injury to prolong survival in the ALF model and has potential as a therapeutic approach for ALF patients.

Cognitive Dysfunction in Non-Alcoholic Fatty Liver Disease-Current Knowledge, Mechanisms and Perspectives

Non-alcoholic fatty liver disease (NAFLD) has emerged as the hepatic component of the metabolic syndrome and now seemingly affects one-fourth of the world population. Features associated with NAFLD and the metabolic syndrome have frequently been linked to cognitive dysfunction, i.e. systemic inflammation, vascular dysfunction, and sleep apnoea. However, emerging evidence suggests that NAFLD may be a cause of cognitive dysfunction independent of these factors. NAFLD in addition exhibits dysbiosis of the gut microbiota and impaired urea cycle function, favouring systemic ammonia accumulation and further promotes systemic inflammation. Such disruption of the gut–liver–brain axis is essential in the pathogenesis of hepatic encephalopathy, the neuropsychiatric syndrome associated with progressive liver disease. Considering the growing burden of NAFLD, the morbidity from cognitive impairment is expected to have huge societal and economic impact. The present paper provides a review of the available evidence for cognitive dysfunction in NAFLD and outlines its possible mechanisms. Moreover, the clinical challenges of characterizing and diagnosing cognitive dysfunction in NAFLD are discussed.

A multi-omic study for uncovering molecular mechanisms associated with hyperammonemia-induced cerebellar function impairment in rats

Patients with liver cirrhosis may develop covert or minimal hepatic encephalopathy (MHE). Hyperammonemia (HA) and peripheral inflammation play synergistic roles in inducing the cognitive and motor alterations in MHE. The cerebellum is one of the main cerebral regions affected in MHE. Rats with chronic HA show some motor and cognitive alterations reproducing neurological impairment in cirrhotic patients with MHE. Neuroinflammation and altered neurotransmission and signal transduction in the cerebellum from hyperammonemic (HA) rats are associated with motor and cognitive dysfunction, but underlying mechanisms are not completely known. The aim of this work was to use a multi-omic approach to study molecular alterations in the cerebellum from hyperammonemic rats to uncover new molecular mechanisms associated with hyperammonemia-induced cerebellar function impairment. We analyzed metabolomic, transcriptomic, and proteomic data from the same cerebellums from control and HA rats and performed a multi-omic integrative analysis of signaling pathway enrichment with the PaintOmics tool. The histaminergic system, corticotropin-releasing hormone, cyclic GMP-protein kinase G pathway, and intercellular communication in the cerebellar immune system were some of the most relevant enriched pathways in HA rats. In summary, this is a good approach to find altered pathways, which helps to describe the molecular mechanisms involved in the alteration of brain function in rats with chronic HA and to propose possible therapeutic targets to improve MHE symptoms.

Hepatic encephalopathy: Novel insights into classification, pathophysiology and therapy

Hepatic encephalopathy (HE) is a frequent and serious complication of both chronic liver disease and acute liver failure. HE manifests as a wide spectrum of neuropsychiatric abnormalities, from subclinical changes (mild cognitive impairment) to marked disorientation, confusion and coma. The clinical and economic burden of HE is considerable, and it contributes greatly to impaired quality of life, morbidity and mortality. This review will critically discuss the latest classification of HE, as well as the pathogenesis and pathophysiological pathways underlying the neurological decline in patients with end-stage liver disease. In addition, management strategies, diagnostic approaches, currently available therapeutic options and novel treatment strategies are discussed.

Depression and Cognitive Impairment-Extrahepatic Manifestations of NAFLD and NASH

Non-alcoholic fatty liver disease (NAFLD) and its complication non-alcoholic steatohepatitis (NASH) are important causes of liver disease worldwide. Recently, a significant association between these hepatic diseases and different central nervous system (CNS) disorders has been observed in an increasing number of patients. NAFLD-related CNS dysfunctions include cognitive impairment, hippocampal-dependent memory impairment, and mood imbalances (in particular, depression and anxiety). This review aims at summarizing the main correlations observed between NAFLD development and these CNS dysfunctions, focusing on the studies investigating the mechanism(s) involved in this association. Growing evidences point at cerebrovascular alteration, neuroinflammation, and brain insulin resistance as NAFLD/NASH-related CNS manifestations. Since the pharmacological options available for the management of these conditions are still limited, further studies are needed to unravel the mechanism(s) of NAFLD/NASH and their central manifestations and identify effective pharmacological targets.

Sustained hyperammonemia induces TNF-a IN Purkinje neurons by activating the TNFR1-NF-κB pathway

BACKGROUND

Patients with liver cirrhosis may develop hepatic encephalopathy. Rats with chronic hyperammonemia exhibit neurological alterations mediated by peripheral inflammation and neuroinflammation. Motor incoordination is due to increased TNF-a levels and activation of its receptor TNFR1 in the cerebellum. The aims were to assess (a) whether peripheral inflammation is responsible for TNF-a induction in hyperammonemic rats, (b) the cell type(s) in which TNF-a is increased, (c) whether this increase is associated with increased nuclear NF-κB and TNFR1 activation, (d) the time course of TNF-a induction, and (e) if TNF-a is induced in the Purkinje neurons of patients who die with liver cirrhosis.

METHODS

We analyzed the level of TNF-a mRNA and NF-κB in microglia, astrocytes, and Purkinje neurons in the cerebellum after 1, 2, and 4 weeks of hyperammonemia. We assessed whether preventing peripheral inflammation by administering an anti-TNF-a antibody prevents TNF-a induction. We tested whether TNF-a induction is reversed by R7050, which inhibits the TNFR1-NF-κB pathway, in ex vivo cerebellar slices.

RESULTS

Hyperammonemia induced microglial and astrocyte activation at 1 week. This was followed by TNF-a induction in both glial cell types at 2 weeks and in Purkinje neurons at 4 weeks. The level of TNF-a mRNA increased in parallel with the TNF-a protein level, indicating that TNF-a was synthesized in Purkinje cells. This increase was associated with increased NF-κB nuclear translocation. The nuclear translocation of NF-κB and the increase in TNF-a were reversed by R7050, indicating that they were mediated by the activation of TNFR1. Preventing peripheral inflammation with an anti-TNF-a antibody prevents TNF-a induction.

CONCLUSION

Sustained (4 weeks) but not short-term hyperammonemia induces TNF-a in Purkinje neurons in rats. This is mediated by peripheral inflammation. TNF-a is also increased in the Purkinje neurons of patients who die with liver cirrhosis. The results suggest that hyperammonemia induces TNF-a in glial cells and that TNF-a released by glial cells activates TNFR1 in Purkinje neurons, leading to NF-κB nuclear translocation and the induction of TNF-a expression, which may contribute to the neurological alterations observed in hyperammonemia and hepatic encephalopathy.

Peripheral inflammation induces neuroinflammation that alters neurotransmission and cognitive and motor function in hepatic encephalopathy: Underlying mechanisms and therapeutic implications

Several million patients with liver cirrhosis suffer minimal hepatic encephalopathy (MHE), with mild cognitive and coordination impairments that reduce their quality of life and life span. Hyperammonaemia and peripheral inflammation act synergistically to induce these neurological alterations. We propose that MHE appearance is because of the changes in peripheral immune system, which are transmitted to brain, leading to neuroinflammation that alters neurotransmission leading to cognitive and motor alterations. We summarize studies showing that MHE in cirrhotic patients is associated with alterations in the immune system and that patients died with HE show neuroinflammation in cerebellum, with microglial and astrocytic activation and Purkinje cell loss. We also summarize studies in animal models of MHE on the role of peripheral inflammation in neuroinflammation induction, how neuroinflammation alters neurotransmission and how this leads to cognitive and motor alterations. These studies identify therapeutic targets and treatments that improve cognitive and motor function. Rats with MHE show neuroinflammation in hippocampus and altered NMDA and AMPA receptor membrane expression, which impairs spatial learning and memory. Neuroinflammation in cerebellum is associated with altered GABA transporters and extracellular GABA, which impair motor coordination and learning in a Y maze. These alterations are reversed by treatments that reduce peripheral inflammation (anti-TNFα, ibuprofen), neuroinflammation (sulphoraphane, p38 inhibitors), GABAergic tone (bicuculline, pregnenolone sulphate) or increase extracellular cGMP (sildenafil or cGMP). The mechanisms identified would also occur in other chronic diseases associated with inflammation, aging and some mental and neurodegenerative diseases. Treatments that improve MHE may also be beneficial to treat these pathologies.