Hepatic endothelin-1 and endocannabinoids-dependent effects of hyperleptinemia in nonalcoholic steatohepatitis-cirrhotic rats

Intercellular communication among liver cells in the perisinusoidal space of the injured liver: Pathophysiology and therapeutic directions

Hepatic stellate cells (HSCs) in the perisinusoidal space are surrounded by hepatocytes, liver sinusoidal endothelial cells, Kupffer cells, and other resident immune cells. In the normal liver, HSCs communicate with these cells to maintain normal liver functions. However, after chronic liver injury, injured hepatocytes release several proinflammatory mediators, reactive oxygen species, and damage-associated molecular patterns into the perisinusoidal space. Consequently, such alteration activates quiescent HSCs to acquire a myofibroblast-like phenotype and express high amounts of transforming growth factor-β1, angiopoietins, vascular endothelial growth factors, interleukins 6 and 8, fibril forming collagens, laminin, and E-cadherin. These phenotypic and functional transdifferentiation lead to hepatic fibrosis with a typical abnormal extracellular matrix synthesis and disorganization of the perisinusoidal space of the injured liver. Those changes provide a favorable environment that regulates tumor cell proliferation, migration, adhesion, and survival in the perisinusoidal space. Such tumor cells by releasing transforming growth factor-β1 and other cytokines, will, in turn, activate and deeply interact with HSCs via a bidirectional loop. Furthermore, hepatocellular carcinoma-derived mediators convert HSCs and macrophages into protumorigenic cell populations. Thus, the perisinusoidal space serves as a critical hub for activating HSCs and their interactions with other cell types, which cause a variety of liver diseases such as hepatic inflammation, fibrosis, cirrhosis, and their complications, such as portal hypertension and hepatocellular carcinoma. Therefore, targeting the crosstalk between activated HSCs and tumor cells/immune cells in the tumor microenvironment may also support a promising therapeutic strategy.

Pathogenesis and treatment of non-alcoholic steatohepatitis and its fibrosis

The initial presentation of non-alcoholic steatohepatitis (NASH) is hepatic steatosis. The dysfunction of lipid metabolism within hepatocytes caused by genetic factors, diet, and insulin resistance causes lipid accumulation. Lipotoxicity, oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum stress would further contribute to hepatocyte injury and death, leading to inflammation and immune dysfunction in the liver. During the healing process, the accumulation of an excessive amount of fibrosis might occur while healing. During the development of NASH and liver fibrosis, the gut-liver axis, adipose-liver axis, and renin-angiotensin system (RAS) may be dysregulated and impaired. Translocation of bacteria or its end-products entering the liver could activate hepatocytes, Kupffer cells, and hepatic stellate cells, exacerbating hepatic steatosis, inflammation, and fibrosis. Bile acids regulate glucose and lipid metabolism through Farnesoid X receptors in the liver and intestine. Increased adipose tissue-derived non-esterified fatty acids would aggravate hepatic steatosis. Increased leptin also plays a role in hepatic fibrogenesis, and decreased adiponectin may contribute to hepatic insulin resistance. Moreover, dysregulation of peroxisome proliferator-activated receptors in the liver, adipose, and muscle tissues may impair lipid metabolism. In addition, the RAS may contribute to hepatic fatty acid metabolism, inflammation, and fibrosis. The treatment includes lifestyle modification, pharmacological therapy, and non-pharmacological therapy. Currently, weight reduction by lifestyle modification or surgery is the most effective therapy. However, vitamin E, pioglitazone, and obeticholic acid have also been suggested. In this review, we will introduce some new clinical trials and experimental therapies for the treatment of NASH and related fibrosis.

Obeticholic acid treatment ameliorates the cardiac dysfunction in NASH mice

BACKGROUND

Suppression of cardiac iinflammasome, which can be inhibited by Farnesoid X receptor (FXR) agonist, can ameliorate cardiac inflammation and fibrosis. Increased cardiac inflammasome decrease the abundance of regulatory T (Treg) cells and exacerbate cardiac dysfunction. Interaction between cardiomyocytes and Treg cells is involved in the development of nonalcoholic steatohepatitis (NASH)-related cardiac dysfunction.

AIMS

This study evaluates whether the FXR agonist obeticholic acid (OCA) treatment improves NASH-associated cardiac dysfunction.

METHODS

The in vivo and in vitro mechanisms and effects of two weeks of OCA treatment on inflammasome and Treg dysregulation-related cardiac dysfunction in NASH mice (NASH-OCA) at systemic, tissue and cellular levels were investigated.

RESULTS

The OCA treatment suppressed the serum and cardiac inflammasome levels, reduced the cardiac infiltrated CD3+ T cells, increased the cardiac Treg-represented anti-inflammatory cytokines (IL-10/IL-10R) and improved cardiac inflammation, fibrosis and function [decreased left ventricle (LV) mass and increased fractional shortening (FS)] in NASH-OCA mice. The percentages of OCA-decreased cardiac fibrosis and OCA-increased FS were positively correlated with the percentage of OCA-increased levels of cardiac FXR and IL-10/IL-10R. In the Treg cells from NASH-OCA mice spleen, in comparison with the Treg cells of the NASH group, higher intracellular FXR but lower inflammasome levels, and more proliferative/active and less apoptotic cells were observed. Incubation of H9c2 cardiomyoblasts with Treg-NASHcm [supernatant of Treg from NASH mice as condition medium (cm)], increased inflammasome levels, decreased the proliferative/active cells, suppressed the intracellular FXR, and downregulated differentiation/contraction marker. The Treg-NASHcm-induced hypocontractility of H9c2 can be attenuated by co-incubation with OCA, and the OCA-related effects were abolished by siIL-10R pretreatment.

CONCLUSIONS

Chronic FXR activation with OCA is a potential strategy for activating IL-10/IL-10R signalling, reversing cardiac regulatory T cell dysfunction, and improving inflammasome-mediated NASH-related cardiac dysfunction.

Increased CHCHD2 expression promotes liver fibrosis in nonalcoholic steatohepatitis via Notch/osteopontin signaling

Nonalcoholic steatohepatitis (NASH) is closely related to liver fibrosis. The role of coiled-coil-helix-coiled-coil-helix domain-containing 2 (CHCHD2) in NASH remains unknown. CHCHD2's functions as a transcription factor have received much less attention than those in mitochondria. Herein, we systematically characterized the role of CHCHD2 as a transcription factor by chromatin immunoprecipitation sequencing and found its target genes were enriched in nonalcoholic fatty liver disease (NAFLD). Overall, CHCHD2 expression was found to be increased in the livers of patients with NAFLD and those of NASH mice. In line with these findings, CHCHD2 deficiency ameliorated NASH- and thioacetamide-induced liver fibrosis, whereas hepatocyte-specific CHCHD2 overexpression promoted liver fibrosis in NASH mice via Notch signaling. Specifically, CHCHD2-overexpressing hepatocytes activated hepatic stellate cells by upregulating osteopontin levels, a downstream mediator of Notch signals. Moreover, Notch inhibition attenuated CHCHD2 overexpression-induced liver fibrosis in vivo and in vitro. Then we found lipopolysaccharide-induced CHCHD2 expression in hepatocytes was reverted by verteporfin, an inhibitor that disrupts the interaction between Yes-associated protein (YAP) and transcriptional enhanced associate domains (TEADs). In addition, CHCHD2 levels were positively correlated with those of TEAD1 in human samples. In conclusion, CHCHD2 is upregulated via YAP/TAZ-TEAD in NASH livers and consequently promotes liver fibrosis by activating the Notch pathway and enhancing osteopontin production.

Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD)-A Condition Associated with Heightened Sympathetic Activation

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common liver disease affecting a quarter of the global population and is often associated with adverse health outcomes. The increasing prevalence of MAFLD occurs in parallel to that of metabolic syndrome (MetS), which in fact plays a major role in driving the perturbations of cardiometabolic homeostasis. However, the mechanisms underpinning the pathogenesis of MAFLD are incompletely understood. Compelling evidence from animal and human studies suggest that heightened activation of the sympathetic nervous system is a key contributor to the development of MAFLD. Indeed, common treatment strategies for metabolic diseases such as diet and exercise to induce weight loss have been shown to exert their beneficial effects at least in part through the associated sympathetic inhibition. Furthermore, pharmacological and device-based approaches to reduce sympathetic activation have been demonstrated to improve the metabolic alterations frequently present in patients with obesity, MetSand diabetes. Currently available evidence, while still limited, suggests that sympathetic activation is of specific relevance in the pathogenesis of MAFLD and consequentially may offer an attractive therapeutic target to attenuate the adverse outcomes associated with MAFLD.

Role of the sympathetic nervous system in cardiometabolic control: implications for targeted multiorgan neuromodulation approaches

Sympathetic overdrive plays a key role in the perturbation of cardiometabolic homeostasis. Diet-induced and exercise-induced weight loss remains a key strategy to combat metabolic disorders, but is often difficult to achieve. Current pharmacological approaches result in variable responses in different patient cohorts and long-term efficacy may be limited by medication intolerance and nonadherence. A clinical need exists for complementary therapies to curb the burden of cardiometabolic diseases. One such approach may include interventional sympathetic neuromodulation of organs relevant to cardiometabolic control. The experience from catheter-based renal denervation studies clearly demonstrates the feasibility, safety and efficacy of such an approach. In analogy, denervation of the common hepatic artery is now feasible in humans and may prove to be similarly useful in modulating sympathetic overdrive directed towards the liver, pancreas and duodenum. Such a targeted multiorgan neuromodulation strategy may beneficially influence multiple aspects of the cardiometabolic disease continuum offering a holistic approach.

Non-alcoholic fatty liver disease: An overview of risk factors, pathophysiological mechanisms, diagnostic procedures, and therapeutic interventions

Non-alcoholic fatty liver disease (NAFLD) is a disorder of excessive fat accumulation in the liver, known as steatosis, without alcohol overconsumption. NAFLD can either manifest as simple steatosis or steatohepatitis, known as non-alcoholic steatohepatitis (NASH), which is accompanied by inflammation and possibly fibrosis. Furthermore, NASH might progress to hepatocellular carcinoma. NAFLD and NASH prevalence is in a continuous state of growth, and by 2018, NAFLD became a devastating metabolic disease with a global pandemic prevalence. The pathophysiology of NAFLD and NASH is not fully elucidated, but is known to involve the complex interplay between different metabolic, environmental, and genetic factors. In addition, unhealthy dietary habits and pre-existing metabolic disturbances together with other risk factors predispose NAFLD development and progression from simple steatosis to steatohepatitis, and eventually to fibrosis. Despite their growing worldwide prevalence, to date, there is no FDA-approved treatment for NAFLD and NASH. Several off-label medications are used to target disease risk factors such as obesity and insulin resistance, and some medications are used for their hepatoprotective effects. Unfortunately, currently used medications are not sufficiently effective, and research is ongoing to investigate the beneficial effects of different drugs and phytochemicals in NASH. In this review article, we outline the different risk factors and pathophysiological mechanisms involved in NAFLD, diagnostic procedures, and currently used management techniques.

Association between effective hepatic blood flow and the severity and prognosis of hepatitis B virus-related acute on chronic liver failure

BACKGROUND

Hepatic inflammation resulted in hepatocyte necrosis and microcirculatory dysfunction in acute on chronic liver failure (ACLF) with cirrhosis or not. The influence of effective hepatic blood flow (EHBF) on the severity of liver failure has not been fully elucidated.

AIM

The aim of this study was to assess the correlation between the EHBF and the severity and the prediction of 90-day mortality rate of hepatitis B virus-related ACLF (HBV-ACLF).

METHODS

In this retrospective study, patients hospitalized for HBV-ACLF or decompensated cirrhosis and who underwent an indocyanine green (ICG) clearance test between June 2016 and July 2018 were enrolled. EHBF was measured by the ICG clearance test and patients were categorized into the ACLF without cirrhosis (HBV-ACLF-no-Cir), ACLF with cirrhosis (HBV-ACLF-Cir) and decompensated cirrhosis (HBV-De-Cir).

RESULTS

A total of 522 patients (HBV-ACLF-no-Cir: 84, HBV-ACLF-Cir: 111 and HBV-De-Cir: 327) were enrolled. The mean EHBF in the HBV-De-Cir was significantly higher than that in the HBV-ACLF-no-Cir and HBV-ACLF-Cir (0.36 vs. 0.21 vs. 0.20 L/min, P < 0.001). EHBF was significantly correlated with the total bilirubin, prothrombin activity and model for end-stage liver disease (MELD) in the HBV-ACLF-no-Cir. The predicted 90-day mortality rate using the MELD, EHBF, ICG-retention rate at 15 min (R15%) and EHBF-R15% scores were similar. The sensitivity and specificity of the EHBF varied between 68.5-80.2% and 45.8-73.7%, respectively. The EHBF-MELD score had the highest specificity.

CONCLUSION

EHBF was significantly lower in the patients with ACLF compared to decompensated cirrhosis. The EHBF were closely related to the severity of HBV-ACLF and can be used for predicting the 90-day mortality rate of HBV-ACLF.

Nonalcoholic Fatty Liver Disease and Non-Alcoholic Steatohepatitis: Current Issues and Future Perspectives in Preclinical and Clinical Research

Nonalcoholic fatty liver disease (NAFLD) is a continuum of liver abnormalities often starting as simple steatosis and to potentially progress into nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis and hepatocellular carcinoma. Because of its increasing prevalence, NAFLD is becoming a major public health concern, in parallel with a worldwide increase in the recurrence rate of diabetes and metabolic syndrome. It has been estimated that NASH cirrhosis may surpass viral hepatitis C and become the leading indication for liver transplantation in the next decades. The broadening of the knowledge about NASH pathogenesis and progression is of pivotal importance for the discovery of new targeted and more effective therapies; aim of this review is to offer a comprehensive and updated overview on NAFLD and NASH pathogenesis, the most recommended treatments, drugs under development and new drug targets. The most relevant in vitro and in vivo models of NAFLD and NASH will be also reviewed, as well as the main molecular pathways involved in NAFLD and NASH development.

Unraveling the Role of Leptin in Liver Function and Its Relationship with Liver Diseases

Since its discovery twenty-five years ago, the fat-derived hormone leptin has provided a revolutionary framework for studying the physiological role of adipose tissue as an endocrine organ. Leptin exerts pleiotropic effects on many metabolic pathways and is tightly connected with the liver, the major player in systemic metabolism. As a consequence, understanding the metabolic and hormonal interplay between the liver and adipose tissue could provide us with new therapeutic targets for some chronic liver diseases, an increasing problem worldwide. In this review, we assess relevant literature regarding the main metabolic effects of leptin on the liver, by direct regulation or through the central nervous system (CNS). We draw special attention to the contribution of leptin to the non-alcoholic fatty liver disease (NAFLD) pathogenesis and its progression to more advanced stages of the disease as non-alcoholic steatohepatitis (NASH). Likewise, we describe the contribution of leptin to the liver regeneration process after partial hepatectomy, the mainstay of treatment for certain hepatic malignant tumors.

Endothelin-1 in portal hypertension: The intricate role of hepatic stellate cells

IMPACT STATEMENT

Portal hypertension is pathologically defined as increase of portal venous pressure, mainly due to chronic liver diseases such as fibrosis and cirrhosis. In fibrotic liver, activated hepatic stellate cells increase their contraction in response to endothelin-1 (ET-1) via autocrine and paracrine stimulation from liver sinusoidal endothelial cells and injured hepatocytes. Clinical studies are limited with ET receptor antagonists in cirrhotic patients with portal hypertension. Hence, studies are needed to find molecules that block ET-1 synthesis. Accumulation of extracellular matrix proteins in the perisinusoidal space, tissue contraction, and alteration in blood flow are prominent during portal hypertension. Therefore, novel matrix modulators should be tested experimentally as well as in clinical studies. Specifically, tumor necrosis factor-α, transforming growth factor-β1, Wnt, Notch, rho-associated protein kinase 1 signaling antagonists, and peroxisome proliferator-activated receptor α and γ, interferon-γ and sirtuin 1 agonists should be tested elaborately against cirrhosis patients with portal hypertension.

SIRT1-dependent mechanisms and effects of resveratrol for amelioration of muscle wasting in NASH mice

Background

In non-alcoholic steatohepatitis (NASH), muscle wasting was an aggravating factor for the progression of hepatic steatosis. This study explores the potential benefits of chronic treatment with resveratrol, a strong activator of SIRT1 on the muscle wasting of NASH mice.

Methods

In vivo and in vitro study, we evaluate the SIRT1-dependent mechanisms and effects of resveratrol administration for 6 weeks with high-fat-methionine and choline deficient diet-induced NASH mice and palmitate-pretreated C2C12 myoblast cells.

Results

Resveratrol treatment improved grip strength and muscle mass of limbs, increased running distance and time on exercise wheels in NASH mice. There is a negative correlation between muscular SIRT1 activity and 3-nitrotyrosine levels of NASH and NASH-resv mice. The SIRT1-dependent effect of muscle wasting was associated with the suppression of oxidative stress, upregulation of antioxidants, inhibition of protein degradation, activation of autophagy, suppression of apoptotic activity, upregulation of lipolytic genes and the reduction of fatty infiltration in limb muscles of NASH mice. In vitro, resveratrol alleviated palmitate acid-induced oxidative stress, lipid deposition, autophagy dysfunction, apoptotic signals, and subsequently reduced fusion index and myotube formation of C2C12 cells. The beneficial effects of resveratrol were abolished by EX527.

Conclusions

Our study suggests that chronic resveratrol treatment is a potential strategy for amelioration of hepatic steatosis and muscle wasting in NASH mouse model.

Histopathological changes and onset of severe hepatic steatosis in rats fed a choline-free diet

Hepatic steatosis significantly increases morbidity and mortality associated with major liver surgery. Several rodent models of hepatic steatosis have been previously reported, which aimed to investigate the effect of various pharmaceutical agents and interventional procedures on the pathophysiology of steatotic liver. The aim of the present study was to investigate the time frame of severe hepatic steatosis in rats after they were fed a choline-free diet and any associated histopathological changes. The duration of feeding with a choline-free diet required to develop severe hepatic steatosis was investigated in Wistar rats. The severity of hepatic steatosis in liver specimens was evaluated at 8, 10, 12 and 14 weeks following the onset of the choline-free diet. Comparisons were made with rats receiving standardized laboratory food. Feeding rats for 12–13 weeks with a choline-free diet led to 66% fatty liver infiltration, which exceeded 68% after 14 weeks. Prior to 8 weeks, the fatty infiltration reached 43%, with a gradual increase revealing a stronger rate from 8–12 weeks and a gradual decline after 14 weeks. At 12–13 weeks the fatty infiltration was considered representative of severe hepatic steatosis. Macrovesicular fatty infiltration revealed a significant increase at a steady rate between 8 and 14 weeks, with evidence of the onset of lobular inflammation and steatohepatitis after 14 weeks of feeding with the choline-free diet. Microvesicular fatty infiltration demonstrated a lower growth rate between 8 and 12 weeks while maintaining a steady rate between 12 and 14 weeks. Mixed fatty infiltration maintained its steady rate of hepatic parenchyma from 8.8–9.5%. Rats fed with the standard laboratory diet did not demonstrate fatty infiltration >4.5%, so they did not develop hepatic steatosis. Developing an ideal model of hepatic steatosis is a particular challenge. The findings of the present study indicate that severe hepatic steatosis in rodents may lead to the development of steatohepatitis after feeding with a choline-free diet for at least 14 weeks. This model is of particular interest in experimental liver surgery and associated surgical maneuvers, and is easily reproducible.

Animal models of portal hypertension

Chronic liver diseases ultimately lead to cirrhosis and portal hypertension (PHT). Indeed, PHT is a major cause of severe complications, while medical treatment is limited to non-selective beta blockers. Sophisticated animal models are needed to investigate novel treatment options for different etiologies of liver disease, effective anti-fibrotic agents as well as vasoactive drugs against PHT. In this review, we present some of the most common animal models of liver disease and PHT - including pre-hepatic, intra-hepatic and post-hepatic PHT in rodents. Methodology for induction, considerations for disease etiology, advantages and limitations and practical issues of these animal models are discussed. The appropriate and sensible use of animal models in preclinical research supporting the 3R concept of replacement, reduction and refinement is highlighted.

Butein protects the nonalcoholic fatty liver through mitochondrial reactive oxygen species attenuation in rats

One of the worldwide metabolic health dilemma is nonalcoholic fatty liver diseases (NAFLD). Researchers are searching effective drug to manage NAFLD patients. One of the best way to manage the metabolic imperfection is through natural principal isolated from different sources. Butein, a natural compound known to have numerous pharmacological application. In the current study we assessed the therapeutic effect of butein administration on liver function tests, oxidative stress, antioxidants, lipid abnormalities, serum inflammatory cytokines, and mitochondrial reactive oxygen species levels, in rats with methionine-choline deficient (MCD) diet induced NAFLD. Male Wistar rats were treated with MCD diet with/without butein (200 mg/kg body wt. orally) for 6 weeks. The protective effect of butein, were evident from decreased transaminase activities, restoration of albumin, globulin, albumin/globulin ratio, and oxidants in serum (P < 0.01), further it improved liver antioxidant status (P < 0.01). Butein significantly lowered lipid profile parameters (P < 0.01), suppressed inflammatory cytokines (P < 0.01), and improved liver histology. Further to understand the possible mechanism behind the hepatoprotective and lipid lowering effect of butein, the activities of heme oxygenase (HO1), myeloperoxidase (MPO), and mitochondrial reactive oxygen species (ROS) were measured. We found that butein supplementation significantly decreased the activity of HO1 (P < 0.001), and increased the activity of MPO (P < 0.001). Furthermore butein attenuated mitochondrial ROS produced in NAFLD condition. Present study shows that butein supplementation restore liver function by altering liver oxidative stress, inflammatory markers, vital defensive enzyme activities, and mitochondrial ROS. In summary, butein has remarkable potential to develop effective hepato-protective drug. © 2018 BioFactors, 44(3):289-298, 2018.

Correlations of Hepatic Hemodynamics, Liver Function, and Fibrosis Markers in Nonalcoholic Fatty Liver Disease: Comparison with Chronic Hepatitis Related to Hepatitis C Virus

The progression of chronic liver disease differs by etiology. The aim of this study was to elucidate the difference in disease progression between chronic hepatitis C (CHC) and nonalcoholic fatty liver disease (NAFLD) by means of fibrosis markers, liver function, and hepatic tissue blood flow (TBF). Xenon computed tomography (Xe-CT) was performed in 139 patients with NAFLD and 152 patients with CHC (including liver cirrhosis (LC)). The cutoff values for fibrosis markers were compared between NAFLD and CHC, and correlations between hepatic TBF and liver function tests were examined at each fibrosis stage. The cutoff values for detection of the advanced fibrosis stage were lower in NAFLD than in CHC. Although portal venous TBF (PVTBF) correlated with liver function tests, PVTBF in initial LC caused by nonalcoholic steatohepatitis (NASH-LC) was significantly lower than that in hepatitis C virus (C-LC) (p = 0.014). Conversely, the liver function tests in NASH-LC were higher than those in C-LC (p < 0.05). It is important to recognize the difference between NAFLD and CHC. We concluded that changes in hepatic blood flow occurred during the earliest stage of hepatic fibrosis in patients with NAFLD; therefore, patients with NAFLD need to be followed carefully.

Antifibrotic effects of ambrisentan, an endothelin-A receptor antagonist, in a non-alcoholic steatohepatitis mouse model

AIM: To examine the effects of the endothelin type A receptor antagonist ambrisentan on hepatic steatosis and fibrosis in a steatohepatitis mouse model.

METHODS: Fatty liver shionogi (FLS) FLS-ob/ob mice (male, 12 wk old) received ambrisentan (2.5 mg/kg orally per day; n = 8) or water as a control (n = 5) for 4 wk. Factors were compared between the two groups, including steatosis, fibrosis, inflammation, and endothelin-related gene expression in the liver.

RESULTS: In the ambrisentan group, hepatic hydroxyproline content was significantly lower than in the control group (18.0 μg/g ± 6.1 μg/g vs 33.9 μg/g ± 13.5 μg/g liver, respectively, P = 0.014). Hepatic fibrosis estimated by Sirius red staining and areas positive for α-smooth muscle actin, indicative of activated hepatic stellate cells, were also significantly lower in the ambrisentan group (0.46% ± 0.18% vs 1.11% ± 0.28%, respectively, P = 0.0003; and 0.12% ± 0.08% vs 0.25% ± 0.11%, respectively, P = 0.047). Moreover, hepatic RNA expression levels of procollagen-1 and tissue inhibitor of metalloproteinase-1 (TIMP-1) were significantly lower by 60% and 45%, respectively, in the ambrisentan group. Inflammation, steatosis, and endothelin-related mRNA expression in the liver were not significantly different between the groups.

CONCLUSION: Ambrisentan attenuated the progression of hepatic fibrosis by inhibiting hepatic stellate cell activation and reducing procollagen-1 and TIMP-1 gene expression. Ambrisentan did not affect inflammation or steatosis.

The multiple-hit pathogenesis of non-alcoholic fatty liver disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is increasingly prevalent and represents a growing challenge in terms of prevention and treatment. Despite its high prevalence, only a small minority of affected patients develops inflammation and subsequently fibrosis and chronic liver disease, while most of them only exhibit simple steatosis. In this context, the full understanding of the mechanisms underlying the development of NAFLD and non-alcoholic steatohepatitis (NASH) is of extreme importance; despite advances in this field, knowledge on the pathogenesis of NAFLD is still incomplete. The 'two-hit' hypothesis is now obsolete, as it is inadequate to explain the several molecular and metabolic changes that take place in NAFLD. The "multiple hit" hypothesis considers multiple insults acting together on genetically predisposed subjects to induce NAFLD and provides a more accurate explanation of NAFLD pathogenesis. Such hits include insulin resistance, hormones secreted from the adipose tissue, nutritional factors, gut microbiota and genetic and epigenetic factors. In this article, we review the factors that form this hypothesis.

Adipocytokines and hepatic fibrosis

Obesity and metabolic syndrome pose significant risk for the progression of many types of chronic illness, including liver disease. Hormones released from adipocytes, adipocytokines, associated with obesity and metabolic syndrome, have been shown to control hepatic inflammation and fibrosis. Hepatic fibrosis is the final common pathway that can result in cirrhosis, and can ultimately require liver transplantation. Initially, two key adipocytokines, leptin and adiponectin, appeared to control many fundamental aspects of the cell and molecular biology related to hepatic fibrosis and its resolution. Leptin appears to act as a profibrogenic molecule, while adiponectin has strong-antifibrotic properties. In this review, we emphasize pertinent data associated with these and other recently discovered adipocytokines that may drive or halt the fibrogenic response in the liver.

Experimental models of non-alcoholic fatty liver disease in rats

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the Western world, and it persists at a high prevalence. NAFLD is characterised by the accumulation of triglycerides in the liver and includes a spectrum of histopathological findings, ranging from simple fatty liver through non-alcoholic steatohepatitis (NASH) to fibrosis and ultimately cirrhosis, which may progress to hepatocellular carcinoma. The pathogenesis of NAFLD is closely related to the metabolic syndrome and insulin resistance. Understanding the pathophysiology and treatment of NAFLD in humans has currently been limited by the lack of satisfactory animal models. The ideal animal model for NAFLD should reflect all aspects of the intricate etiopathogenesis of human NAFLD and the typical histological findings of its different stages. Within the past several years, great emphasis has been placed on the development of an appropriate model for human NASH. This paper reviews the widely used experimental models of NAFLD in rats. We discuss nutritional, genetic and combined models of NAFLD and their pros and cons. The choice of a suitable animal model for this disease while respecting its limitations may help to improve the understanding of its complex pathogenesis and to discover appropriate therapeutic strategies. Considering the legislative, ethical, economical and health factors of NAFLD, animal models are essential tools for the research of this disease.

Effects of chitosan on plasma lipids and lipoproteins: a 4-month prospective pilot study

Chitosan can favorably modulate plasma lipids, but the available data are not conclusive. We evaluated the effect of chitosan on plasma lipids and lipoproteins in 28 patients with plasma triglyceride levels >150 mg/dL (mean age: 63 ± 12 years), not taking other lipid-lowering agents. All patients received a chitosan derived from fungal mycelium (Xantonet, Bromatech, Italy) at a fixed dose of 125 mg/d in addition to their current medications for 4 months. Polyacrylamide gel electrophoresis was used to measure low-density lipoprotein (LDL) subclasses. After treatment, total cholesterol reduced by 8%, LDL cholesterol by 2%, and triglycerides by 19%, with a concomitant 14% increase in high-density lipoprotein cholesterol. We also found a beneficial effect of chitosan on LDL subclasses, with a significant increase in LDL-2 particles (from 37 ± 8% to 47 ± 8%, P = .0001) and a decrease (although not significant) in atherogenic small, dense LDL. Whether these findings may affect cardiovascular risk remains to be established in future studies.

Beneficial effects of dual vascular endothelial growth factor receptor/fibroblast growth factor receptor inhibitor brivanib alaninate in cirrhotic portal hypertensive rats

BACKGROUND AND AIM

Vascular endothelial (VEGF) and fibroblast growth factor (FGF)-induced hepatic stellate (HSCs) and liver endothelial cells (LECs) activation accelerates hepatic fibrogenesis and angiogenesis, and hemodynamic dysarrangements in cirrhosis. VEGF targeting agents had been reported as potential drugs for cirrhosis. However, the evaluation of effects of dual VEGF/FGF targeting agent in cirrhosis is still limited.

METHODS

Using hemodynamic parameters, blood chemistry, primary isolated HSCs and LECs, histology, and digital imaging, we assess the effects of 2-week brivanib alaninate, a dual VEGFR/FGFR inhibitor, treatment in the pathophysiology of bile duct-ligated-cirrhotic rats.

RESULTS

Fibrogenic and angiogenic markers in the serum and liver of bile duct-ligated-cirrhotic rats, including hydroxyproline, transforming growth factor-β1, angiopoietin-1, VEGF, FGF-2, endocan and phosphorylated-VEGFR2/VEGFR2, and phosphorylated-FGFR/FGFR together with hepatic CD31/angiopoietin-1 expressions (immunohistochemistry staining), angiogenesis (micro-computed tomography scan), microcirculatory dysfunction (in vivo miscroscopy and in situ liver perfusion study), portal hypertension, and hyperdynamic circulations (colored microsphere methods) were markedly suppressed and ameliorated by brivanib alaninate treatment. In in vitro study, acute brivanib alaninate incubation inhibited the transforming growth factor-β1-induced HSCs contraction/migration and VEGF-induced LECs angiogenesis. Concomitantly, the overexpression of various fibrogenic and angiogenic markers in HSCs and LECs, and in their culture media, was increased in parallel and these changes were suppressed by acute brivanib alaninate incubation.

CONCLUSIONS

This study demonstrated that brivanib alaninate targeting multiple mechanisms and working in the different pathogenic steps of the complications of cirrhotic rats with portal hypertension.

Therapeutic potential of microRNA: a new target to treat intrahepatic portal hypertension?

Intrahepatic portal hypertension accounts for most of the morbidity and mortality encountered in patients with liver cirrhosis, due to increased portal inflow and intrahepatic vascular resistance. Most treatments have focused only on portal inflow or vascular resistance. However, miRNA multitarget regulation therapy may potentially intervene in these two processes for therapeutic benefit in cirrhosis and portal hypertension. This review presents an overview of the most recent knowledge of and future possibilities for the use of miRNA therapy. The benefits of this therapeutic modality--which is poorly applied in the clinical setting--are still uncertain. Increasing the knowledge and current understanding of the roles of miRNAs in the development of intrahepatic portal hypertension and hepatic stellate cells (HSCs) functions, as well as their potential as novel drug targets, is critical.

Anti-VEGFR agents ameliorate hepatic venous dysregulation/microcirculatory dysfunction, splanchnic venous pooling and ascites of NASH-cirrhotic rat

BACKGROUND & AIMS

Antivascular endothelial growth factor receptor (VEGFR) agents improve hepatic fibrosis and portal hypertension in cirrhosis. Detail interactions among recruited/activated leucocytes, hepatic angiogenesis and fibrogenesis, splanchnic blood pooling, decreased hepatic veins to fluctuated splanchnic blood volume (hepatic venous dysregulation), portal hypertensive syndrome and ascites have never explored in cirrhosis. Our study used two anti-VEGFR agents - brivanib and sorafenib - to elucidate the relationship between above abnormalities of nonalcoholic steatohepatitis (NASH)-cirrhotic rats.

MATERIALS AND METHODS

NASH-cirrhotic rats received 2-week brivanib, sorafenib or vehicle (NASH-cirrhotic+briv, NASH-cirrhotic+soraf and NASH-cirrhotic rats) were included for various measurements.

RESULTS

In comparison with NASH-cirrhotic rats, significant decreased plasma VEGF, fibroblast growth factor, platelet-derived growth factor, hepatic tumour necrosis factor (TNFα), IL-1β, IL-6, IL-17 were accompanied by decreased leucocyte mass/activity ((99 m) Tc-phytate and (18) F-FDG SPECT/PET/CT scans), hepatic leucocytes recruitment/microvascular density (fluorescence-enhanced intravital microscopy) and hydroxyproline content, and increased hepatic blood flow in NASH-cirrhotic+briv and NASH-cirrhotic+soraf rats. In addition, increased hepatic microvasculatures compliance-related improved buffering effect of portal vein to acute mannitol infusion was associated with decreased circulating nitric oxide and aldosterone, plasma volume expansion (dye dilution method), splanchnic blood pooling ((99 m) Tc-RBC SPECT/PET/CT scans), peripheral hypotension, portal hypertension and ascites in brivanib and sorafenib-treated NASH-cirrhotic rats.

CONCLUSION

Besides antifibrotic, antiangiogenic and portal hypertensive effects, chronic antagonism of anti-VEGFR with brivanib and sorafenib improves hepatic blood flow, hepatic venous dysregulation, inhibits leucocytes recruitment/activation, splanchnic blood pooling and ascites formation in NASH-cirrhotic rats. Thus, brivanib and sorafenib might be ideal therapeutic agents in cirrhotic patients suffering from severe haemodynamic disarrangement and ascites.

Pathophysiology of NASH: perspectives for a targeted treatment

Non alcoholic steatohepatitis (NASH) is the more severe form of nonalcoholic fatty liver disease. In NASH, fatty liver, hepatic inflammation, hepatocyte injury and fibrogenesis are associated, and this condition may eventually lead to cirrhosis. Current treatment of NASH relies on the reduction of body weight and increase in physical activity, but there is no pharmacologic treatment approved as yet. Emerging data indicate that NASH progression results from parallel events originating from the liver as well as from the adipose tissue, the gut and the gastrointestinal tract. Thus, dysfunction of the adipose tissue through enhanced flow of free fatty acids and release of adipocytokines, and alterations in the gut microbiome generate proinflammatory signals that underlie NASH progression. Additional 'extrahepatic hits' include dietary factors and gastrointestinal hormones. Within the liver, hepatocyte apoptosis, ER stress and oxidative stress are key contributors to hepatocellular injury. In addition, lipotoxic mediators and danger signals activate Kupffer cells which initiate and perpetuate the inflammatory response by releasing inflammatory mediators that contribute to inflammatory cell recruitment and development of fibrosis. Inflammatory and fibrogenic mediators include chemokines, the cannabinoid system, the inflammasome and activation of pattern-recognition receptors. Here we review the major mechanisms leading to appearance and progression of NASH, focusing on both extrahepatic signals and local inflammatory mechanisms, in an effort to identify the most promising molecular targets for the treatment of this condition.

Pathophysiology of NASH: perspectives for a targeted treatment

Non alcoholic steatohepatitis (NASH) is the more severe form of nonalcoholic fatty liver disease. In NASH, fatty liver, hepatic inflammation, hepatocyte injury and fibrogenesis are associated, and this condition may eventually lead to cirrhosis. Current treatment of NASH relies on the reduction of body weight and increase in physical activity, but there is no pharmacologic treatment approved as yet. Emerging data indicate that NASH progression results from parallel events originating from the liver as well as from the adipose tissue, the gut and the gastrointestinal tract. Thus, dysfunction of the adipose tissue through enhanced flow of free fatty acids and release of adipocytokines, and alterations in the gut microbiome generate proinflammatory signals that underlie NASH progression. Additional 'extrahepatic hits' include dietary factors and gastrointestinal hormones. Within the liver, hepatocyte apoptosis, ER stress and oxidative stress are key contributors to hepatocellular injury. In addition, lipotoxic mediators and danger signals activate Kupffer cells which initiate and perpetuate the inflammatory response by releasing inflammatory mediators that contribute to inflammatory cell recruitment and development of fibrosis. Inflammatory and fibrogenic mediators include chemokines, the cannabinoid system, the inflammasome and activation of pattern-recognition receptors. Here we review the major mechanisms leading to appearance and progression of NASH, focusing on both extrahepatic signals and local inflammatory mechanisms, in an effort to identify the most promising molecular targets for the treatment of this condition.

The heme oxygenase system rescues hepatic deterioration in the condition of obesity co-morbid with type-2 diabetes

The prevalence of non-alcoholic fatty-liver disease (NAFLD) is increasing globally. NAFLD is a spectrum of related liver diseases that progressive from simple steatosis to serious complications like cirrhosis. The major pathophysiological driving of NAFLD includes elevated hepatic adiposity, increased hepatic triglycerides/cholesterol, excessive hepatic inflammation, and hepatocyte ballooning injury is a common histo-pathological denominator. Although heme-oxygenase (HO) is cytoprotective, its effects on hepatocyte ballooning injury have not been reported. We investigated the effects of upregulating HO with hemin or inhibiting it with stannous-mesoporphyrin (SnMP) on hepatocyte ballooning injury, hepatic adiposity and inflammation in Zucker-diabetic-fatty rats (ZDFs), an obese type-2-diabetic model. Hemin administration to ZDFs abated hepatic/plasma triglycerides and cholesterol, and suppressed several pro-inflammatory cytokines and chemokines including, TNF-α, IL-6, IL-1β, macrophage-inflammatory-protein-1α (MIP-1α) and macrophage-chemoattractant-protein-1 (MCP-1), with corresponding reduction of the pro-inflammatory M1-phenotype marker, ED1 and hepatic macrophage infiltration. Correspondingly, hemin concomitantly potentiated the protein expression of several markers of the anti-inflammatory macrophage-M2-phenotype including ED2, IL-10 and CD-206, alongside components of the HO-system including HO-1, HO-activity and cGMP, whereas the HO-inhibitor, SnMP abolished the effects. Furthermore, hemin attenuated liver histo-pathological lesions like hepatocyte ballooning injury and fibrosis, and reduced extracellular-matrix/profibrotic proteins implicated in liver injury such as osteopontin, TGF-β1, fibronectin and collagen-IV. We conclude that hemin restore hepatic morphology by abating hepatic adiposity, suppressing macrophage infiltration, inflammation and fibrosis. The selective enhancement of anti-inflammatory macrophage-M2-phenotype with parallel reduction of pro-inflammatory macrophage-M1-phenotype and related chemokines/cytokines like TNF-α, IL-6, IL-1β, MIP-1α and MCP-1 are among the multifaceted mechanisms by which hemin restore hepatic morphology.

Adipose tissue promotes a serum cytokine profile related to lower insulin sensitivity after chronic central leptin infusion

Obesity is an inflammatory state characterized by an augment in circulating inflammatory factors. Leptin may modulate the synthesis of these factors by white adipose tissue decreasing insulin sensitivity. We have examined the effect of chronic central administration of leptin on circulating levels of cytokines and the possible relationship with cytokine expression and protein content as well as with leptin and insulin signaling in subcutaneous and visceral adipose tissues. In addition, we analyzed the possible correlation between circulating levels of cytokines and peripheral insulin resistance. We studied 18 male Wistar rats divided into controls (C), those treated icv for 14 days with a daily dose of 12 μg of leptin (L) and a pair-fed group (PF) that received the same food amount consumed by the leptin group. Serum leptin and insulin were measured by ELISA, mRNA levels of interferon-γ (IFN-γ), interleukin-2 (IL-2), IL-4, IL-6, IL-10 and tumor necrosis factor-α (TNF-α) by real time PCR and serum and adipose tissue levels of these cytokines by multiplexed bead immunoassay. Serum leptin, IL-2, IL-4, IFN-γ and HOMA-IR were increased in L and TNF-α was decreased in PF and L. Serum leptin and IL-2 levels correlate positively with HOMA-IR index and negatively with serum glucose levels during an ip insulin tolerance test. In L, an increase in mRNA levels of IL-2 was found in both adipose depots and IFN-γ only in visceral tissue. Activation of leptin signaling was increased and insulin signaling decreased in subcutaneous fat of L. In conclusion, leptin mediates the production of inflammatory cytokines by adipose tissue independent of its effects on food intake, decreasing insulin sensitivity.