Apoptosis and Bcl-2 expression in the livers of patients with steatohepatitis

Protective Effects of Berberine on Nonalcoholic Fatty Liver Disease in db/db Mice via AMPK/SIRT1 Pathway Activation

OBJECTIVE

Berberine (BBR) has emerged as a promising therapeutic agent for nonalcoholic fatty liver disease (NAFLD). This study aims to elucidate the underlying molecular mechanisms.

METHODS

In this study, db/db mice were chosen as an animal model for NAFLD. A total of 10 healthy C57BL/6J mice and 30 db/db mice were randomly allocated to one of 4 groups: the normal control (NC) group, the diabetic control (DC) group, the Metformin (MET) therapy group, and the BBR therapy group. The total cholesterol (TC), triacylglycerol (TG), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels in the serum were measured. The glutathione peroxidase (GSH-Px), glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), interleukin (IL)-1β, tumor necrosis factor (TNF)-α and monocyte chemotactic protein 1 (MCP-1) levels in liver tissue were measured. Hematoxylin and eosin (H&E), acid-Schiff (PAS) and TUNEL stanning was performed for histopathological analysis. Western blotting and immunohistochemistry were conducted to detect the expression levels of key proteins in the AMPK/SIRT1 pathway.

RESULTS

BBR could improve lipid metabolism, attenuate hepatic steatosis and alleviate liver injury significantly. The excessive oxidative stress, high levels of inflammation and abnormal apoptosis in db/db mice were reversed after BBR intervention. BBR clearly changed the expression of AMP-activated protein kinase (AMPK)/Sirtuin 1 (SIRT1), and their downstream proteins.

CONCLUSION

BBR could reverse NAFLD-related liver injury, likely by activating the AMPK/SIRT1 signaling pathway to inhibit oxidative stress, inflammation and apoptosis in hepatic tissue.

Association between nonalcoholic fatty liver disease and increased glucose-to-albumin ratio in adults without diabetes

Background

Nonalcoholic fatty liver disease (NAFLD) affects approximately 30% of individuals globally. Both serum glucose and albumin were demonstrated to be potential markers for the development of NAFLD. We hypothesized that the risk of NAFLD may be proportional to the glucose-to-albumin ratio (GAR).

Methods

Based on information from the National Health and Nutrition Examination Survey (NHANES) 1999-2018, it was determined that GAR was associated with an increased risk of NAFLD and liver fibrosis utilizing weighted multivariable logistic regression. Participants with a fatty liver index (FLI) over 60 were identified with NAFLD, and those with an NAFLD fibrosis score (NFS) >0.676 with evidence of NAFLD were labeled with advanced hepatic fibrosis (AHF). The liver biopsy was utilized to verify the relationship between GAR and FLD in our center cohort. Mendelian randomization analysis investigated the genetic relationship between GAR and NAFLD.

Results

Of 15,534 eligible participants, 36.4% of participants were identified as NAFLD without AHF. GAR was positively correlated with the probability of NAFLD following full adjustment for possible variables (OR = 1.53, 95% CI: 1.39-1.67). It was confirmed that patients with NAFLD and AHF had an inferior prognosis. The relationship between GAR and NFS was favorable (R = 0.46, P< 0.0001), and NAFLD patients with a higher GAR tended to develop poor survival. In our center cohort, the association between GAR and NAFLD was verified.

Conclusion

Among participants without diabetes, greater GAR was linked to higher risks of NAFLD. In addition, NAFLD patients with higher GAR tended to develop liver fibrosis and adverse outcomes.

Rhamnetin ameliorates non-alcoholic steatosis and hepatocellular carcinoma in vitro

Non-alcoholic fatty liver (NAFLD) is a widespread disease with various complications including Non-alcoholic steatohepatitis (NASH) that could lead to cirrhosis and ultimately hepatocellular carcinoma (HCC). Up till now there is no FDA approved drug for treatment of NAFLD. Flavonoids such as Rhamnetin (Rhm) have been ascribed effective anti-inflammatory and anti-oxidative properties. Thus, Rhm as a potent flavonoid could target multiple pathological cascades causing NAFLD to prevent its progression into HCC. NAFLD is a multifactorial disease and its pathophysiology is complex and is currently challenged by the 'Multiple-hit hypothesis' that includes wider range of comorbidities rather than previously established theory of 'Two-hit hypothesis'. Herein, we aimed at establishing reliable in vitro NASH models using different mixtures of variable ratios and concentrations of oleic acid (OA) and palmitic acid (PA) combinations using HepG2 cell lines. Moreover, we compared those models in the context of oil red staining, triglyceride levels and their altered downstream molecular signatures for genes involved in de novo lipogenesis, inflammation, oxidative stress and apoptotic machineries as well. Lastly, the effect of Rhm on NASH and HCC models was deeply investigated. Over the 10 NASH models tested, PA 500 µM concentration was the best model to mimic the molecular events of steatosis induced NAFLD. Rhm successfully ameliorated the dysregulated molecular events caused by the PA-induced NASH. Additionally, Rhm regulated inflammatory and oxidative machinery in the HepG2 cancerous cell lines. In conclusion, PA 500 µM concentration is considered an effective in vitro model to mimic NASH. Rhm could be used as a promising therapeutic modality against both NASH and HCC pathogenesis.

Targeted therapeutics and novel signaling pathways in non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH)

Non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH) has become the leading cause of liver disease worldwide. NASH, an advanced form of NAFL, can be progressive and more susceptible to developing cirrhosis and hepatocellular carcinoma. Currently, lifestyle interventions are the most essential and effective strategies for preventing and controlling NAFL without the development of fibrosis. While there are still limited appropriate drugs specifically to treat NAFL/NASH, growing progress is being seen in elucidating the pathogenesis and identifying therapeutic targets. In this review, we discussed recent developments in etiology and prospective therapeutic targets, as well as pharmacological candidates in pre/clinical trials and patents, with a focus on diabetes, hepatic lipid metabolism, inflammation, and fibrosis. Importantly, growing evidence elucidates that the disruption of the gut-liver axis and microbe-derived metabolites drive the pathogenesis of NAFL/NASH. Extracellular vesicles (EVs) act as a signaling mediator, resulting in lipid accumulation, macrophage and hepatic stellate cell activation, further promoting inflammation and liver fibrosis progression during the development of NAFL/NASH. Targeting gut microbiota or EVs may serve as new strategies for the treatment of NAFL/NASH. Finally, other mechanisms, such as cell therapy and genetic approaches, also have enormous therapeutic potential. Incorporating drugs with different mechanisms and personalized medicine may improve the efficacy to better benefit patients with NAFL/NASH.

Free fatty acid-induced miR-181a-5p stimulates apoptosis by targeting XIAP and Bcl2 in hepatic cells

AIMS

Non-alcoholic fatty liver disease is one of the major health concerns in the World. The dietary free fatty acids (FFAs) affect the metabolic status of the hepatocytes by modulating cellular pathways. In this study, we showed that free fatty acids stimulate apoptosis by upregulating miR-181a-5p expression, which in turn targets XIAP and Bcl2.

METHODS

Huh7 cells were incubated with FFAs for 72 h and the expression of XIAP, Bcl2, bax, pAkt, Akt, PTEN and β-actin were determined by Western blots, and miR-181a-5p expression was determined using real-time RT-PCR. The Huh7 cells were transfected with either miR-181a-5p pre-miRs or anti-miR-181a-5p and the regulation of apoptosis and proliferation was studied. Three groups of C57BL/6 mice (n = 6 per group) were fed with standard diet, CSAA or CDAA diet for 6, 18, 32 and 54 weeks. Total protein and RNA were isolated from the liver tissues and used for Western blots and real-time RT-PCR respectively.

KEY FINDINGS

FFAs inhibited Akt phosphorylation, expression of XIAP and Bcl2, while upregulating the expression of PTEN, bax, and miR-181a-5p in Huh7 cells. Similar results were observed when the Huh7 cells were transfected with miR-181a-5p premiRs, while these changes were reversed in anti-miR-181a-5p-transfected, FFA-treated Huh7 cells. The CDAA-fed mice showed a significant inhibition of Akt phosphorylation, XIAP and Bcl2, whereas PTEN and bax expression were upregulated. The expression of miR-181a-5p was also significantly higher in CDAA-fed mice.

SIGNIFICANCE

These findings showed that free fatty acids induced apoptosis via upregulating miR-181a-5p in hepatic cells.

Independent of Calorie Intake, Short-term Alternate-day Fasting Alleviates NASH, With Modulation of Markers of Lipogenesis, Autophagy, Apoptosis, and Inflammation in Rats

Non-alcoholic steatohepatitis (NASH) is a worldwide health problem. Alternate-day fasting (ADF), although thought to be aggressive, has proven safety and efficacy. We aimed to evaluate the effect of short-term ADF against already established high-fat-fructose (HFF)-induced NASH, independent of the amount of calorie intake, and to study the effect of ADF on lipogenesis, apoptosis, and hepatic inflammation. Male Sprague Dawley rats were divided into two groups: (1) negative control and (2) NASH group fed on HFF for 9 weeks, and then randomized into two subgroups of either HFF alone or with ADF protocol for 3 weeks. The ADF could improve HFF-related elevation in serum lactate dehydrogenase and could decrease the mRNA expression of lipogenesis genes; acetyl CoA carboxylase, peroxisome proliferator-activated receptor γ, and peroxisome proliferator-activated receptor α; apoptotic genes caspase-3, p53, and inflammatory cyclo-oxygenase 2; and immunohistochemical staining for their proteins in liver with upregulation of LC3 and downregulation of P62 immunoexpression. Moreover, ADF ameliorated HFF-induced steatosis, inflammation, ballooning, and fibrosis through hematoxylin and eosin, Oil Red O, and Sirius Red staining, confirmed by morphometric analysis, without significant weight loss. Significant correlation of morphometric parameters with levels of gene expression was found. These findings suggest ADF to be a safe effective therapeutic agent in the management of NASH.

Oxidative stress in obesity-associated hepatocellular carcinoma: sources, signaling and therapeutic challenges

Obesity affects more than 650 million individuals worldwide and is a well-established risk factor for the development of hepatocellular carcinoma (HCC). Oxidative stress can be considered as a bona fide tumor promoter, contributing to the initiation and progression of liver cancer. Indeed, one of the key events involved in HCC progression is excessive levels of reactive oxygen species (ROS) resulting from the fatty acid influx and chronic inflammation. This review provides insights into the different intracellular sources of obesity-induced ROS and molecular mechanisms responsible for hepatic tumorigenesis. In addition, we highlight recent findings pointing to the role of the dysregulated activity of BCL-2 proteins and protein tyrosine phosphatases (PTPs) in the generation of hepatic oxidative stress and ROS-mediated dysfunctional signaling, respectively. Finally, we discuss the potential and challenges of novel nanotechnology strategies to prevent ROS formation in obesity-associated HCC.

An Experimental DUAL Model of Advanced Liver Damage

Individuals exhibiting an intermediate alcohol drinking pattern in conjunction with signs of metabolic risk present clinical features of both alcohol-associated and metabolic-associated fatty liver diseases. However, such combination remains an unexplored area of great interest, given the increasing number of patients affected. In the present study, we aimed to develop a preclinical DUAL (alcohol-associated liver disease plus metabolic-associated fatty liver disease) model in mice. C57BL/6 mice received 10% vol/vol alcohol in sweetened drinking water in combination with a Western diet for 10, 23, and 52 weeks (DUAL model). Animals fed with DUAL diet elicited a significant increase in body mass index accompanied by a pronounced hypertrophy of adipocytes, hypercholesterolemia, and hyperglycemia. Significant liver damage was characterized by elevated plasma alanine aminotransferase and lactate dehydrogenase levels, extensive hepatomegaly, hepatocyte enlargement, ballooning, steatosis, hepatic cell death, and compensatory proliferation. Notably, DUAL animals developed lobular inflammation and advanced hepatic fibrosis. Sequentially, bridging cirrhotic changes were frequently observed after 12 months. Bulk RNA-sequencing analysis indicated that dysregulated molecular pathways in DUAL mice were similar to those of patients with steatohepatitis. Conclusion: Our DUAL model is characterized by obesity, glucose intolerance, liver damage, prominent steatohepatitis and fibrosis, as well as inflammation and fibrosis in white adipose tissue. Altogether, the DUAL model mimics all histological, metabolic, and transcriptomic gene signatures of human advanced steatohepatitis, and therefore serves as a preclinical tool for the development of therapeutic targets.

The i-Motif as a Molecular Target: More Than a Complementary DNA Secondary Structure

Stretches of cytosine-rich DNA are capable of adopting a dynamic secondary structure, the i-motif. When within promoter regions, the i-motif has the potential to act as a molecular switch for controlling gene expression. However, i-motif structures in genomic areas of repetitive nucleotide sequences may play a role in facilitating or hindering expansion of these DNA elements. Despite research on the i-motif trailing behind the complementary G-quadruplex structure, recent discoveries including the identification of a specific i-motif antibody are pushing this field forward. This perspective reviews initial and current work characterizing the i-motif and providing insight into the biological function of this DNA structure, with a focus on how the i-motif can serve as a molecular target for developing new therapeutic approaches to modulate gene expression and extension of repetitive DNA.

Processes exacerbating apoptosis in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is a significant public health concern, owing to its high prevalence, progressive nature and lack of effective medical therapies. NAFLD is a complex and multifactorial disease involving the progressive and concerted action of factors that contribute to the development of liver inflammation and eventually fibrosis. Here, we summarize fundamental molecular mechanisms underlying the pathogenesis of non-alcoholic steatohepatitis (NASH), how they are interrelated and possible translation to clinical applications. We focus on processes triggering and exacerbating apoptotic signalling in the liver of NAFLD patients and their metabolic and pathological implications. Indeed, liver injury and inflammation are cardinal histopathological features of NASH, a duo in which derailment of apoptosis is of paramount importance. In turn, the liver houses a very high number of mitochondria, crucial metabolic unifiers of both extrinsic and intrinsic signals that converge in apoptosis activation. The role of lifestyle options is also dissected, highlighting the management of modifiable risk factors, such as obesity and harmful alcohol consumption, influencing apoptosis signalling in the liver and ultimately NAFLD progression. Integrating NAFLD-associated pathologic mechanisms in the cell death context could provide clues for a more profound understating of the disease and pave the way for novel rational therapies.

Microarray analysis of apoptosis gene expression in liver injury induced by chronic exposure to arsenic and high-fat diet in male mice

Rapid growth in the incidence of liver disease is largely attributable to lifestyle and environmental contaminants, which are often overlooked as the leading causes of this problem. Thus, the possible contribution of arsenic (As) to high-fat diet (HFD)-induced liver damage was examined via microarray analysis. To perform this experiment, a total number of 40 healthy adult male NMRI mice (22-30 g) were used. To this end, these animals were randomly assigned to four groups of 10. Oxidative stress and histopathological parameters were also evaluated in the liver of the mice exposed to a minimally cytotoxic concentration of As (50 ppm) in drinking water while being fed with a HFD for 20 weeks. Subsequently, apoptosis gene expression profiling was utilized via real-time (RT) PCR array analysis. The results showed that As had increased the amount of HFD-induced liver damage and consequently amplified changes in oxidative stress factors, histopathological parameters, as well as apoptosis pathway genes. Investigating the expression profile of apoptosis pathway genes similarly revealed that caspase-8, as a main upstream contributor to the apoptosis pathway, might play an important role in the induction of apoptosis generated by As and HFD. Ultimately, this study highlighted that As in drinking water could increase sensitivity in mice to HFD-induced liver disease through strengthening apoptosis pathway.

S-allyl-l-cysteine (SAC) protects hepatocytes from alcohol-induced apoptosis

Hepatocyte apoptosis is frequently observed in alcohol‐related liver disease (ARLD), which ranks among the 30 leading causes of death worldwide. In the current study, we explored the impact of S‐allyl‐l‐cysteine (SAC), an organosulfur component of garlic, on hepatocyte apoptosis induced by alcohol. Rat liver (BRL‐3A) cells were challenged by ethanol with or without SAC treatment. Cell death/viability, reactive oxygen species (ROS) generation, mitochondrial Cytochrome C release, and caspase 3 activity were then examined. We found that ethanol remarkably induced apoptosis of hepatocytes, while SAC treatment rescued ethanol‐induced hepatocyte injury, as demonstrated by cell counting kit‐8 (CCK8) assay, TUNEL assay, and annexin V/PI staining assay. Ethanol evoked ROS generation in BRL‐3A cells, and this was abated by SAC pretreatment, as indicated by 2′,7′‐dichlorofluorescin diacetate (DCFDA) staining assay. Moreover, ethanol suppressed cellular anti‐apoptotic protein B‐cell lymphoma‐2 (Bcl‐2) expression, increased pro‐apoptotic protein Bcl‐2‐associated X protein (Bax) expression, induced mitochondrial Cytochrome C release, and activated the caspase 3‐dependent apoptosis pathway in BRL‐3A cells. SAC was sufficient to abolish all these changes induced by ethanol, thereby revealing the molecular mechanisms underlying its protective effects. In conclusion, SAC protects hepatocytes from ethanol‐induced apoptosis and may be suitable for use as a novel anti‐apoptotic agent for treating ARLD.

Biosafety evaluation of Janus Fe3O4-TiO2 nanoparticles in Sprague Dawley rats after intravenous injection

Introduction

Newly synthesized Janus-structured Fe₃O₄-TiO₂ nanoparticles (NPs) appear to be a promising candidate for the diagnosis and therapy of cancer. Although the toxicity of individual Fe₃O₄ or TiO₂ NPs has been studied extensively, the toxicity of Janus Fe₃O₄-TiO₂ NPs is not clear.

Methods

In this study, the biosafety of both Janus Fe₃O₄-TiO₂ NPs (20–25 nm) and the maternal material TiO₂ NPs (7–10 nm) were evaluated in Sprague Dawley rats after one intravenous injection into the tail vein. Healthy rats were randomly divided into one control group and six experimental groups. Thirty days after treatment, rats were killed, then blood and tissue samples were collected for hematological, biochemical, element-content, histopathological, and Western blot analysis.

Results

The results show that only a slight Ti element accumulation in the heart, spleen, and liver could be found in the Janus Fe₃O₄-TiO₂ NP groups (P>0.05 compared with control). However, significant Ti element accumulation in the spleen, lungs, and liver was found in the TiO₂ NP-treated rats. Both Fe₃O₄-TiO₂ NPs and TiO₂ NPs could induce certain histopathological abnormalities. Western blot analysis showed that both NPs could induce certain apoptotic or inflammatory-related molecular protein upregulation in rat livers. A certain degree of alterations in liver function and electrolyte and lipid parameters was also observed in rats treated with both materials. However, compared to Janus structure Fe₃O₄-TiO₂ NP-treated groups, TiO₂ NPs at 30 mg/kg showed more severe adverse effects.

Conclusion

Our results showed that under a low dose (5 mg/kg), both NP types had no significant toxicity in rats. Janus NPs certainly seem less toxic than TiO₂ NPs in rats at 30 mg/kg. To ensure safe use of these newly developed Janus NPs in cancer diagnosis and therapy, further animal studies are needed to evaluate long-term bioeffects.

Diet high in fructose promotes liver steatosis and hepatocyte apoptosis in C57BL/6J female mice: Role of disturbed lipid homeostasis and increased oxidative stress

The effects of high (H)-fructose (FR) diet (D) (HFRD) on hepatic lipid homeostasis, oxidative stress, inflammation and hepatocyte apoptosis were investigated in 6-week old female C57BL/6J mice fed a regular chow (ContD) or HFRD (35% fructose-derived calories) for 3 weeks. HFRD-fed mice exhibited increased levels of hepatic steatosis with a significant elevation of serum levels of triglyceride, cholesterol and TNFα compared to ContD-fed mice (P<0.05). HFRD-fed mice exhibited ∼2.7- fold higher levels FAS along with significantly decreased protein levels of adiponection-R2 (∼30%), P-AMPK (∼60%), P-ACC (∼70%) and RXR-α (∼55%), suggesting decreased hepatic fat oxidation compared to controls. Interestingly, hepatic fatty acid uptake into hepatocytes and lipolysis were significantly increased in HFRD-fed mice, as shown by decreased CD36 and fatty acid transporter protein-2, and increased adipose triglyceride lipase, respectively (P<0.05). Increased hepatic levels of iNOS and GSSG/GSH suggest elevated oxidative stress with a higher number of macrophages in the adipose tissue in HFRD-fed mice (P<0.05). Significantly elevated rates of hepatocyte apoptosis (∼2.4-fold), as determined by TUNEL analysis with increased Bax/Bcl2 ratio and PARP-1 levels (∼2- and 1.5-fold, respectively), were observed in HFRD-fed mice. Thus, HFRD exposure increased hepatic steatosis accompanied by oxidative stress and inflammation, leading to hepatocyte apoptosis.

Synergistic Effects of Jerusalem Artichoke in Combination with Pegylated Interferon Alfa-2a and Ribavirin Against Hepatic Fibrosis in Rats

BACKGROUND

Complementary and alternative medicine has been highly appreciated as a supportive regimen for classical treatment strategies. Here we offer a nutrition-based adjuvant therapy for liver fibrosis, a major risk factor for cirrhosis and hepatocellular carcinoma.

AIM OF THE STUDY

To evaluate the possible hepatoprotective effects of Jerusalem artichoke tubers (JAT) in combination with interferon and ribavirin.

MATERIALS AND METHODS

Twelve groups of rats were administered JAT, interferon and ribavirin either separately or in combination from day one of CCL4 administration until the end of the study. Animals were killed after 8 weeks of CCL4- induced hepatotoxicity.

RESULTS

Hepatocytes from rats treated with triple combination of interferon, ribavirin, and JAT showed more less normal architecture compared to CCL4- treated rats. We also detected significantly higher hepatic protein expression levels of p53, BAX and transforming growth factor-β (TGF-β) in the CCl4- intoxicated group compared to normal controls, as evidenced by immunohistochemical staining and western blotting analyses. Addition of JAT as a supportive regimen improved response to ribavirin and interferon and effectively participated in retaining normal histopathological and biochemical criteria and significantly lowered protein expression of p53, BAX, and TGF-β.

CONCLUSIONS

We suggest that addition of JAT as a supportive regimen to interferon and ribavirin effectively potentiates their anti-fibrotic effects.

Bcl-2 and Fas expression in peripheral blood leukocytes of patients with alcoholic and autoimmune liver disorders

BACKGROUND

This article is devoted to the inquiry of three diseases of the liver: alcoholic liver disease (ALD), primary biliary cirrhosis (PBC), and autoimmune hepatitis (AIH). The aim of the study was to assess the changes in populations of circulating lymphocytes expressing antiapoptotic bcl-2 molecule and proapoptotic Fas (cluster of differentiation 95(CD95)) receptor in patients with ALD, AIH, and PBC.

MATERIALS AND METHODS

The study population consisted of 110 patients with ALD (n = 50), PBC (n = 30), and AIH (n = 30) and age-matched healthy volunteers (n = 25). Peripheral blood lymphocytes were isolated, stained with monoclonal antibodies against CD4, CD8, and CD19 antigen; intracellular bcl-2; and surface Fas receptor (CD95) antigens, and estimated using the flow cytometric method.

RESULTS

Bcl-2 expression was the highest in CD4+ and CD19+ T lymphocytes in ALD; however, only the differences in median/mean fluorescence intensity values of CD4+bcl-2+ lymphocytes between ALD and PBC group and CD19+bcl-2+ between ALD and PBC groups were statistically significant, indicating the different role of B cells in pathology of ALD and PBC. In contrast to that, statistically significant higher percentage of CD4+, CD8+, and CD19+ bearing Fas receptor in all groups of patients with liver diseases in comparison with the control subjects were estimated. The highest expression of Fas in CD4+ lymphocytes in ALD and in CD8+ cells of PBC and AIH groups were detected.

CONCLUSION

Low expression of bcl-2 molecule and high expression of Fas in peripheral blood lymphocytes indicate significant dysregulation of apoptotic mechanisms not only in the liver but also in peripheral blood lymphocytes in all examined groups, especially in ALD group.

Nonalcoholic Steatohepatitis: A Search for Factual Animal Models

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis, which occurs in the absence of alcohol abuse. NAFLD can evolve into progressive liver injury and fibrosis in the form of nonalcoholic steatohepatitis (NASH). Several animal models have been developed to attempt to represent the morphological, biochemical, and clinical features of human NASH. The actual review presents a critical analysis of the most commonly used experimental models of NAFLD/NASH development. These models can be classified into genetic, nutritional, and a combination of genetic and nutritional factors. The main genetic models are ob/ob and db/db mutant mice and Zucker rats. The principal nutritional models employ methionine- and choline-deficient, high-fat, high-cholesterol and high-cholate, cafeteria, and high-fructose diets. Currently, associations between high-fructose and various compositions of high-fat diets have been widely studied. Previous studies have encountered significant difficulties in developing animal models capable of reproducing human NASH. Some models produce consistent morphological findings, but the induction method differs significantly compared with the pathophysiology of human NASH. Other models precisely represent the clinical and etiological contexts of this disease but fail to provide accurate histopathological representations mainly in the progression from steatosis to liver fibrosis.

microRNA-122 regulates hypoxia-inducible factor-1 and vimentin in hepatocytes and correlates with fibrosis in diet-induced steatohepatitis

BACKGROUND & AIMS

miR-122 is the most abundant miRNA in the liver particularly in hepatocytes where it targets cholesterol metabolism. Steatosis, a key component of non-alcoholic fatty liver disease, is regulated by hypoxia-inducible factor-1α (HIF-1α). Here, we hypothesized that reduced miR-122 has a pathogenic role in steatohepatitis.

METHODS

miR-122 and its target genes were evaluated in mouse livers and/or isolated hepatocytes after methionine-choline-deficient (MCD) or methionine-choline-supplemented (MCS) diet.

RESULTS

Liver and hepatocyte miR-122 expression was significantly decreased in steatohepatitis. A maximum reduction in miR-122 occurred at the fibrosis stage (8 weeks of MCD diet). MAP3K3, a miR-122 target gene, was induced at all stages of non-alcoholic steatohepatitis (NASH; 3-8 weeks) only at the mRNA level. Increased NF-κB activation was found in MCD diet-fed mice and MAP3K3 regulated the NF-κB DNA binding in naive hepatocytes. HIF-1α mRNA and DNA binding and expression of the HIF-1α target gene, profibrotic lysyl oxidase, was increased in advanced steatohepatitis (8 weeks). In addition, increase in vimentin and Sirius red staining (liver fibrosis) was found at 8 weeks of MCD diet. Using miR-122 overexpression and inhibition approaches, we confirmed that HIF-1α, vimentin and MAP3K3 are novel miR-122 targets in hepatocytes. We report transcriptional repression of miR-122 in NASH. Decreased liver miR-122 was associated with elevated circulating miR-122 in both exosome-rich and protein-rich serum fractions.

CONCLUSIONS

Our novel data suggest that decreased liver miR-122 contributes to upregulation of modulators of tissue remodelling (HIF-1α, vimentin and MAP3K3) and might play a role in NASH-induced liver fibrosis.

Non-alcoholic fatty liver disease: what the clinician needs to know

Non-alcoholic fatty liver disease (NAFLD) is the most frequent cause of liver disease in the Western world. Furthermore, it is increasing worldwide, paralleling the obesity pandemic. Though highly frequent, only about one fifth of affected subjects are at risk of developing the progressive form of the disease, non-alcoholic steatohepatitis with fibrosis. Even in the latter, liver disease is slowly progressive, though, since it is so prevalent, it is already the third cause of liver transplantation in the United States, and it is predicted to get to the top of the ranking in few years. Of relevance, fatty liver is also associated with increased overall mortality and particularly increased cardiovascular mortality. The literature and amount of published papers on NAFLD is increasing as fast as its prevalence, which makes it difficult to keep updated in this topic. This review aims to summarize the latest knowledge on NAFLD, in order to help clinicians understanding its pathogenesis and advances on diagnosis and treatment.

Revisiting the metabolic syndrome and paving the way for microRNAs in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) comprises a spectrum of stages from simple steatosis to non-alcoholic steatohepatitis, which can progress to fibrosis, cirrhosis and, ultimately, hepatocellular carcinoma. Despite being one of the most common chronic liver diseases, NAFLD pathogenesis remains largely unknown. In this review, we discuss the key molecular mechanisms involved in NAFLD development and progression, focusing on the emerging role of microRNAs. NAFLD is intrinsically related to obesity and the metabolic syndrome. Changes in lipid metabolism increase free fatty acids in blood, which in turn induces peripheral insulin resistance and increases oxidative and endoplasmic reticulum stress. Although not yet considered in the diagnosis of NAFLD, recent reports also reinforce the crucial role of apoptosis in disease progression via activation of either death receptor or mitochondrial pathways and p53. In addition, the role of gut microbiota and the gut-liver axis has been recently associated with NAFLD. Finally, there is an accumulating and growing body of evidence supporting the role of microRNAs in NAFLD pathogenesis and progression, as well as hinting at their use as biomarkers or therapeutic tools. The ultimate goal is to review different molecular pathways that may underlie NAFLD pathogenesis in the hope of finding targets for new and efficient therapeutic interventions.

Increased expression of c-Jun in nonalcoholic fatty liver disease

Overnutrition is the major cause of nonalcoholic fatty liver disease (NAFLD) and its advanced form nonalcoholic steatohepatitis (NASH). We aimed to develop and characterize a murine model, which resembles both the pathology and nutritional situation, of NASH patients in Western societies. Mice were fed with a NASH-inducing diet (ND) containing sucrose, cholesterol and fats rich in saturated fatty acids in a composition, which mimics Western food. After 12 weeks, ND-fed mice revealed obesity and impaired glucose tolerance. In the liver, ND-feeding led to marked steatosis, hepatocellular damage, inflammation and beginning fibrosis. Transcriptome-wide gene expression analysis and search for over-represented transcription factor target sites among the differentially expressed genes identified activator protein-1 (AP-1) as the most likely factor to cause the transcriptional changes in ND livers. Combining differentially expressed gene and protein-protein interaction network analysis identified c-Jun as hub in the largest connected deregulated sub-network in ND livers. Accordingly, ND livers revealed c-Jun-phosphorylation and nuclear translocation. Moreover, hepatic c-Jun expression was enhanced in ND-fed mice. Combined tissue microarray technology and immunohistochemical analysis confirmed enhanced hepatic c-Jun levels in NAFLD patients, which correlated with inflammation, and notably, with the degree of hepatic steatosis. In summary, our new mouse model shows important pathological changes also found in human NASH and indicates c-Jun/AP-1 activation as critical regulator of hepatic alterations. Abundance of c-Jun in NAFLD likely facilitates development and progression of NASH.

Exercise as a therapeutic tool to prevent mitochondrial degeneration in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease, encompassing hepatic steatosis, nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis, is a significant health problem associated with modern lifestyle, based on caloric overconsumption and physical inactivity. Although the mechanisms associated with progression from the 'benign' steatosis to NASH are still elusive, mitochondrial dysfunction seems to play an important role in this degenerative process. Degeneration of mitochondrial function during NASH has been associated with impaired β-oxidation, oxidative phosphorylation and increased reactive oxygen species production, contributing to hepatocyte death and inflammatory response. Despite the fact that several therapeutic approaches can be used in the context of NASH, including insulin-sensitizing agents, anti-obesity drugs, lipid-lowering drugs or mitochondrial-targeted drugs, dietary and physical activity are still the most effective strategies. In fact, active lifestyles decrease insulin resistance and body weight and result in decreased histological signs of liver injury. In fatty liver, physical activity prevents the disease progression through mitochondrial adaptations, namely by increasing cytochrome c content, enzyme activities and fatty acid oxidation, which are lost after some days of physical inactivity. However, less is known about the effect of physical activity on NASH-associated mitochondrial dysfunction. After a brief characterization of NASH and its association with liver mitochondrial (dys)function, the present review addresses the impact of physical (in)activity on NASH and, particularly, the possible contribution of active lifestyles to the modulation of liver mitochondrial dysfunction.

Genetics of nonalcoholic Fatty liver disease: an overview

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the world today. Its incidence in adults and children is rising rapidly due to the ongoing epidemics of obesity and type 2 diabetes. Hence, it has become a global public health issue. Environmental factors have been found to play a major role in the etiology of NAFLD, especially for genetically susceptible populations. Among these, one of the most important factors is junk food, especially the typical "Western-style" diet rich in simple carbohydrates, saturated fat, and highly processed food materials. Genetic predisposition to NAFLD does occur; however, a precise definition of genetic factors responsible for NAFLD is still lacking. Specific variants of different genes have been shown to present a risk for NAFLD. Genetic studies might be helpful in the management of the disease by developing novel treatment strategies based on individual's genotype.

The protective effects of carnosine in alcohol-induced hepatic injury in rats

Consumption of alcohol leads to oxidative stress in liver by inducing lipid peroxidation. The aim of this study was to investigate the effects of carnosine (CAR) in alcohol-induced liver injury by biochemical and histomorphological evaluations. The rats were divided into four groups, namely, control group, alcohol (AL) group, CAR group and AL + CAR group. Three doses of ethanol (5 g/kg, 25% (v/v) in distilled water) were given by nasogastric catheter for twice-a-day. CAR (100 mg/kg) was given 1 h before the administration of ethanol using the same method. Levels of alanine aminotransferase, aspartate aminotransferase, myeloperoxidase and malondialdehyde were significantly increased in the AL group compared with control, CAR and AL + CAR groups. Glutathione level was significantly decreased in the AL group, while it was increased in the AL + CAR group. Immunoreactivity of caspase-3 and bax increased in the hepatocytes of AL group when compared with control and AL + CAR groups. Expression of bcl-2 was decreased in AL group than AL + CAR group. Under electron microscopy, dense mitochondria, accumulation of lipid, sinusoidal dilatation, vacuolization and decrease in the number of microvilli were observed in AL group, while these findings were markedly less in the AL + CAR group. In conclusion, pretreatment of CAR is effective for recovering biochemical alterations and morphologic damage in the liver of rats treated with ethanol.

Liver and muscle in morbid obesity: the interplay of fatty liver and insulin resistance

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) can be seen as a manifestation of overnutrition. The muscle is a central player in the adaptation to energy overload, and there is an association between fatty-muscle and -liver. We aimed to correlate muscle morphology, mitochondrial function and insulin signaling with NAFLD severity in morbid obese patients.

METHODS

Liver and deltoid muscle biopsies were collected during bariatric surgery in NAFLD patients. NAFLD Activity Score and Younossi's classification for nonalcoholic steatohepatitis (NASH) were applied to liver histology. Muscle evaluation included morphology studies, respiratory chain complex I to IV enzyme assays, and analysis of the insulin signaling cascade. A healthy lean control group was included for muscle morphology and mitochondrial function analyses.

RESULTS

Fifty one NAFLD patients were included of whom 43% had NASH. Intramyocellular lipids (IMCL) were associated with the presence of NASH (OR 12.5, p<0.001), progressive hepatic inflammation (p = 0.029) and fibrosis severity (p = 0.010). There was a trend to an association between IMCL and decreased Akt phosphorylation (p = 0.059), despite no association with insulin resistance. In turn, hepatic steatosis (p = 0.015) and inflammation (p = 0.013) were associated with decreased Akt phosphoryation. Citrate synthase activity was lower in obese patients (p = 0.047) whereas complex I (p = 0.040) and III (p = 0.036) activities were higher, compared with controls. Finally, in obese patients, complex I activity increased with progressive steatosis (p = 0.049) and with a trend with fibrosis severity (p = 0.056).

CONCLUSIONS

In morbid obese patients, presence of IMCL associates with NASH and advanced fibrosis. Muscle mitochondrial dysfunction does not appear to be a major driving force contributing to muscle fat accumulation, insulin resistance or liver disease. Importantly, insulin resistance in muscle might occur at a late point in the insulin signaling cascade and be associated with IMCL and NAFLD severity.

Etiopathogenesis of nonalcoholic steatohepatitis: role of obesity, insulin resistance and mechanisms of hepatotoxicity

Incidence of nonalcoholic fatty liver disease is increasing with an estimated prevalence of 20-30% in developed nations. This is leading to increased incidence of chronic liver disease, cirrhosis, and hepatocellular cancer. It is critical to understand the etiology and pathogenesis of any disease to create therapeutic targets and develop new treatments. In this paper we discuss the etiology and pathogenesis of nonalcoholic steatohepatitis with special focus on obesity, role of insulin resistance, and molecular mechanisms of hepatotoxicity.

Alcoholic liver disease: pathogenesis and new targets for therapy

Alcoholic liver disease (ALD) is a major cause of morbidity and mortality worldwide. The spectrum of disease ranges from fatty liver to hepatic inflammation, necrosis, progressive fibrosis and hepatocellular carcinoma. In developed countries, ALD is a major cause of end-stage liver disease that requires transplantation. The most effective therapy for ALD is alcohol abstinence. However, for patients with severe forms of ALD (that is, alcoholic hepatitis) and for those who do not achieve abstinence from alcohol, targeted therapies are urgently needed. The development of new drugs for ALD is hampered by the scarcity of studies and the drawbacks of existing animal models, which do not reflect all the features of the human disease. However, translational research using liver samples from patients with ALD has identified new potential therapeutic targets, such as CXC chemokines, osteopontin and tumor necrosis factor receptor superfamily member 12A. The pathogenetic roles of these targets, however, remain to be confirmed in animal models. This Review summarizes the epidemiology, natural history, risk factors and current knowledge of the pathogenetic mechanisms of ALD. In addition, this article provides a detailed description of the findings of these translational studies and of the animal models used to study ALD.

Interleukin-22 protects against acute alcohol-induced hepatotoxicity in mice

The protective effects of interleukin-22 (IL-22) on acute alcohol-induced liver injury were investigated. Mice were gavaged with 7 doses of alcohol (56% wt/vol, 15.2 mL/kg of body weight for each dose) over the 24 h, and IL-22 (0.5 mg/kg BW) was given to the mice by injection into the tail vein 1 h after alcohol administration. The results indicated that acute alcohol administration caused prominent hepatic microvesicular steatosis and an elevation of serum transaminase activities, induced a significant decrease in hepatic glutathione in conjunction with enhanced lipid peroxidation, and increased hepatocyte apoptosis as well as hepatic TNF-alpha production. IL-22 treatment attenuated these adverse changes induced by acute alcohol administration. The protective effects of IL-22 on alcohol-induced hepatotoxicity were due mainly to its anti-inflammatory, anti-oxidant, and anti-apoptotic features.

Apoptosis and insulin resistance in liver and peripheral tissues of morbidly obese patients is associated with different stages of non-alcoholic fatty liver disease

AIMS/HYPOTHESIS

Non-alcoholic fatty liver disease (NAFLD) is associated with insulin resistance and characterised by different degrees of hepatic lesion. Its pathogenesis and correlation with apoptosis and insulin resistance in insulin target tissues remains incompletely understood. We investigated how insulin signalling, caspase activation and apoptosis correlate with different NAFLD stages in liver, muscle and visceral adipose tissues.

METHODS

Liver, muscle and adipose tissue biopsies from 26 morbidly obese patients undergoing bariatric surgery were grouped according to the Kleiner-Brunt scoring system into simple steatosis, and less severe and more severe non-alcoholic steatohepatitis (NASH). Apoptosis was assessed by DNA fragmentation, and caspase-2 and -3 activation. Insulin signalling and c-Jun NH(2)-terminal kinase (JNK) proteins were evaluated by western blot.

RESULTS

Caspase-3 and -2 activation, and DNA fragmentation were markedly increased in the liver of patients with severe NASH vs in that of those with simple steatosis (p < 0.01). Muscle tissue, and to a lesser extent the liver, had decreased tyrosine phosphorylated insulin receptor and insulin receptor substrate in patients with severe NASH, compared with those with simple steatosis (p < 0.01 muscle; p < 0.05 liver). Concomitantly, Akt phosphorylation decreased in muscle, liver and visceral adipose tissues in patients with severe NASH (at least p < 0.05). Finally, JNK phosphorylation was significantly increased in muscle (p < 0.01) and liver (p < 0.05) from NASH patients, compared with tissue from those with simple steatosis.

CONCLUSIONS/INTERPRETATION

Our results demonstrate a link between apoptosis, insulin resistance and different NAFLD stages, where JNK and caspase-2 may play a key regulatory role.

Cell death and nonalcoholic steatohepatitis: where is ballooning relevant?

Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver disease in the Western world. Progression to more aggressive forms of liver injury, such as nonalcoholic steatohepatitis (NASH) and cirrhosis, occurs in less than a third of affected subjects. Human data and both in vivo and in vitro models demonstrate that cell death, particularly apoptosis, is increased in NAFLD and NASH patients, suggesting that it is crucial in disease progression. Indeed, fatty acids - more specifically, saturated fatty acids - strongly induce hepatocyte apoptosis. In addition, hepatic steatosis renders hepatocytes more susceptible to apoptotic injury. Ballooned hepatocytes and Mallory-Denk bodies are important hallmarks of NASH and correlate with disease progression. There are complex correlations between ballooning, Mallory-Denk bodies and apoptosis through keratin metabolism and depletion, as well as through the endoplasmic reticulum stress response. Whether apoptosis may promote hepatocellular ballooning, or vice versa, will be discussed in this article.

Impact of pan-caspase inhibition in animal models of established steatosis and non-alcoholic steatohepatitis

BACKGROUND & AIMS

Non-alcoholic fatty liver disease is a progressive condition comprising steatosis, steatohepatitis, and cirrhosis. Caspase activation mediates apoptosis and the inflammatory response. Studies demonstrate increased apoptotic activity in NASH although its pathophysiological importance is uncertain. We sought to determine the effects of irreversible pan-caspase inhibition in murine models of established steatosis (high fat diet, HFD) and steatohepatitis (methionine-choline deficient diet, MCD).

METHODS

In one study arm, male C3H/HeN mice were fed HFD; in the other, Db/Db mice were fed MCD. Once disease was established, animals were randomised to receive caspase inhibitor (VX-166), TPGS/PEG vehicle or no additional therapy until the end of the study. Biochemical and histological indices were examined to determine NASH activity and tissue oxidative stress. Apoptotic activity and cell turnover were assessed immunohistochemically by staining for caspase-cleaved CK-18 and PCNA.

RESULTS

MCD and HFD significantly increased apoptosis, which was reduced by VX-166 treatment. VX-166 did not reduce steatosis but reduced histological inflammation, serum ALT levels, and oxidative stress, particularly in the MCD model. TPGS/PEG vehicle also exhibited some anti-inflammatory activity.

CONCLUSIONS

In both models, VX-166 inhibited apoptosis and reduced histological inflammatory infiltrate although there was a more modest impact on other indices of liver injury. In addition, TPGS/PEG vehicle also exhibited some anti-inflammatory activity, likely through the antioxidant effects of vitamin E and changes in gut flora/mucosal interactions. These data suggest that caspase inhibition may represent a valid therapeutic approach; however, further studies to assess the long-term value of more selective caspase inhibition are merited.

Nonalcoholic fatty liver disease: pathology and pathogenesis

Nonalcoholic fatty liver disease (NAFLD) is recognized as the leading cause of chronic liver disease in adults and children. NAFLD encompasses a spectrum of liver injuries ranging from steatosis to steatohepatitis with or without fibrosis. Fibrosis may progress to cirrhosis and complications including hepatocellular carcinoma. Histologic findings represent the complexity of pathophysiology. NAFLD is closely associated with obesity and is most closely linked with insulin resistance; the current Western diet, high in saturated fats and fructose, plays a significant role. There are several mechanisms by which excess triglycerides are acquired and accumulate in hepatocytes. Formation of steatotic droplets may be disordered in NAFLD. Visceral adipose tissue dysfunction in obesity and insulin resistance results in aberrant cytokine expression; many cytokines have a role in liver injury in NAFLD. Cellular stress and immune reactions, as well as the endocannabinoid system, have been implicated in animal models and in some human studies.

Nonalcoholic fatty liver disease: a review and update

The spectrum of nonalcoholic fatty liver disease (NAFLD) ranges from asymptomatic steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis. Hepatic steatosis occurs when free fatty acids, released in the setting of insulin resistance and the metabolic syndrome, are taken up by the liver. Additional biochemical insults, including oxidative stress, upregulation of inflammatory mediators, and dysregulated apoptosis, can result in inflammation (producing NASH) and fibrosis. Noninvasive methods (e.g., abdominal ultrasonography) are safe ways to support a diagnosis of hepatic steatosis, but advanced liver histopathologic findings including NASH and fibrosis cannot be identified without pursuing liver biopsy. Recent advances in serologic and imaging methods aim to determine severity of inflammation and fibrosis noninvasively. Currently, therapeutic options for NAFLD are limited to medications that reduce risk factors, but the future holds promise for therapies that might slow the progression of this increasingly prevalent disorder.

Antioxidants vitamin E and 1-aminobenzotriazole prevent experimental non-alcoholic steatohepatitis in mice

OBJECTIVE

Hepatic oxidative stress plays a key role in the development of non-alcoholic steatohepatitis (NASH). However, the protective effects of antioxidants on NASH are largely unknown. The aim of this study was to elucidate the effect and mechanism of antioxidants on NASH in mice.

MATERIAL AND METHODS

C57BL6/J mice were fed a methionine-choline-deficient (MCD) diet for 10 days or 3 weeks to induce steatohepatitis. Antioxidants (vitamin E, ABT, or vitamin E plus ABT) were supplemented in mice fed a MCD diet, respectively. The effect of antioxidants on oxidative stress and apoptosis was assessed, and activation of adiponectin and expressions of inflammatory factors, apoptosis-related genes, and fibrosis-related genes were assayed.

RESULTS

MCD feeding in mice showed increasing serum alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) levels, and progressive hepatic injury including hepatic steatosis and inflammatory infiltration. Administration of antioxidants vitamin E and/or ABT significantly lowered serum ALAT and ASAT levels (p<0.001) and ameliorated hepatic steatosis and necroinflammation. These effects were associated with repressed hepatic lipid peroxides through reducing hepatic MDA content and enhancing hepatic superoxide dismutase (SOD) activity; down-regulated inflammatory factor COX-2, lowered activity of NF-kappaB, up-regulated anti-apoptotic gene Bcl-2, and down-regulated pro-apoptotic gene Bax suppressed expression of the fibrotic genes TGF-beta1 and MMP2. Moreover, expression of the anti-inflammatory factor adiponectin was also induced by vitamin E or ABT. A combination of vitamin E and ABT showed an additive effect on preventing liver injury.

CONCLUSIONS

The present study provides morphological and molecular biological evidence for the protective role of the antioxidant vitamins E and ABT in ameliorating oxidative stress, hepatic apoptosis, and necroinflammation in experimental nutritional steatohepatitis.

Recent advances in understanding the pathogenesis of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a pathological condition characterized by macrovesicular steatosis, necroinflammation, loss of hepatocytes and fibrosis. NASH is often associated with type 2 diabetes mellitus, hypertension, hyperlipoproteinemia and obesity. Recent studies emphasize the role of insulin resistance, oxidative stress and subsequent lipid peroxidation, proinflammatory cytokines, adipokines and mitochondrial dysfunction in the development and progression of NASH. In this article, we will review the role of insulin resistance, oxidative stress and subsequent lipid peroxidation, mitochondrial dysfunction, proinflammatory cytokines, adipokines such as resistin, leptin, adiponectin and PPAR-α, apoptosis, NF kappa B, SREBP-1c, endotoxaemia, and iron overload in the pathogenesis of NASH. The pathogenesis of NASH is thought to be related mainly with insulin resistance and oxidative stress and subsequent lipid peroxidation. Adipocytokines also play an important role in the pathogenesis of NASH through complex and interactive paracrine and endocrine mechanisms. Understanding of the mechanisms responsible for the pathogenesis of NASH has important implications for the treatment of NASH.

Liver biopsy in alcoholic and non-alcoholic steatohepatitis patients

Alcoholic liver disease and non-alcoholic liver disease share a similar histological spectrum that starts with 'simple' steatosis, and may be accompanied by inflammation. Alcoholic steatohepatitis and non-alcoholic steatohepatitis (NASH) are progressive forms of alcoholic liver disease and non-alcoholic liver disease, respectively, and can evolve into cirrhosis. The currently accepted minimum diagnostic criteria for steatohepatitis include steatosis, lobular inflammation and hepatocellular injury, but not fibrosis. Steatosis involving more than 5% of hepatocytes is required for the diagnosis of non-alcoholic fatty liver disease, but is not necessary for the diagnosis of alcoholic liver disease. Lobular inflammation is usually mild and frequently consists of a mixed, acute and chronic, inflammatory cell infiltrate composed of neutrophils and mononuclear cells. The presence of large numbers of neutrophils favors an alcoholic etiology. Hepatocellular injury in fatty liver disease usually occurs in the form of ballooning, but it can also present as apoptotic (acidophilic) bodies and lytic necrosis. The characteristic pattern of fibrosis in non-cirrhotic steatohepatitis is pericellular/perisinusoidal and is the result of deposition of collagen in the space of Disse. In both alcoholic steatohepatitis and NASH, sinusoidal collagen formation is the result of hepatic stellate cell activation that, in NASH, has been correlated with the grade of steatosis and fibrosis.

Intramitochondrial crystalline inclusions in nonalcoholic steatohepatitis

Mitochondrial dysfunction is an important element in the pathogenesis of nonalcoholic steatohepatitis (NASH). Intramitochondrial crystals (IMCs) are a well-documented morphological abnormality seen on transmission electron microscopy in this disease. It has been suggested that IMCs consist of phospholipids, but their exact composition remain uncertain many years after their discovery. Micellar phase transitions of phospholipid bilayers is a well-known but little-studied phenomenon in living systems. Its presence in the mitochondria of NASH would offer significant insight into the disease with possible therapeutic implications. We postulated that intramitochondrial disturbances in NASH are sufficient to produce such transitions and that their detection in fresh biopsies would therefore be a dynamic process. To test this, we performed a blinded, prospective analysis of fresh liver biopsy samples immediately fixed under different conditions. Quantitative transmission electron microscopy morphometry, performed by systematically counting total mitochondria and IMCs within areas of uniform dimension, showed a stepwise decline in IMCs with cooler fixation temperature in each subject studied. Randomization testing (Monte Carlo resampling) confirmed that the detection of IMCs was strongly dependent on fixation temperature (P < 0.0001).

CONCLUSION

These results indicate that the intramitochondrial crystals characteristic of NASH are highly dynamic and unstable structures. The findings offer the strongest support yet for their origin in micellar phase transitions. We speculate that such transitions result from microenvironmental changes within the mitochondria and carry therapeutic implications, especially in regard to dietary manipulations of mitochondrial lipid composition.

Mechanisms of non-alcoholic steatohepatitis: pathophysiology and molecular biology

Non-alcoholic steatohepatitis (NASH), characterized by liver fatty infiltration, inflammation, hepatocellular injury and fibrosis, may easily develop into liver cirrhosis and hepatocellular carcinoma. The increased flow of FFAs (free fatty acids) to the liver and the de novo lipogenesis in the liver lead to fat overload. Lipotoxicity can induce oxidative stress, inflammatory reaction and apoptosis. Subsequently chronic liver injury activates a fibrogenic response that accelerates the evolution of NASH towards end-stage liver disease. Further research on pathophysiology and molecular biology is beneficial to clinical diagnosis and management of NASH.

Increased hepatic expression is a major determinant of serum alanine aminotransferase elevation in mice with nonalcoholic steatohepatitis

BACKGROUND

Serum alanine aminotransferase (ALT) is a biomarker for hepatitis of various aetiologies including fatty liver disease. Increased serum ALT is thought to be related to its increased release from dying hepatocytes.

AIM

We sought to understand the mechanisms by which serum ALT is elevated in a mouse model of experimental fatty liver disease where hepatocyte death is minimal.

METHODS

To induce fatty liver disease, female A/J mice were fed a methionine-choline deficient (MCD) diet for up to 12 weeks. Serum and liver ALT expression and hepatic inflammation, necrosis and apoptosis were assessed and expressed relative to their expressions in control-diet-fed mice.

RESULTS

Feeding mice the MCD diet produced hepatic steatosis with minimal hepatic inflammation or necrosis. Liver cell apoptosis was not significantly increased by MCD diet treatment. Conversely, serum ALT activity was approximately four-fold increased at 12 weeks of diet treatment, and ALT protein expressions in serum were correspondingly increased: ALT1 1.7-fold and ALT2 1.9-fold at 12 weeks. The expressions of ALT1 and ALT2 protein in liver increased over 2-12 weeks of MCD treatment. At 12 weeks, liver ALT1 protein was 2.27+/-0.31-fold increased and ALT2 protein 4.72+/-0.48-fold increased relative to their expressions in the mice fed a diet replete with methionine and choline. Liver ALT mRNA expressions were correspondingly increased: ALT1 mRNA 2.58-fold and ALT2 mRNA 4.97-fold at 12 weeks. Linear regression analysis showed a strong correlation between serum and liver tissue expressions for both ALT1 and ALT2.

CONCLUSIONS

These findings suggest that induction of hepatic expression significantly contributes to increased serum ALT in this model of experimental fatty liver disease, whereas cell death appears not to.

Disease-specific mechanisms of fibrosis: hepatitis C virus and nonalcoholic steatohepatitis

Our mechanistic understanding of liver fibrosis has increased dramatically in recent years for all liver diseases and for hepatitis C and nonalcoholic steatohepatitis (NASH) in particular. Hepatitis C causes liver injury and fibrosis through direct cytopathic means, direct and indirect interactions with hepatic stellate cells, and activation of the immune system. Steatosis and insulin resistance, which are intrinsic deficits in NASH, are also of great importance in hepatitis C and may be induced by viral or host metabolic factors. For NASH, the key mediators of damage include oxidative stress, fat compartmentalization, visceral fat, apoptosis, and adipokine derangement. This article explores in depth the disease-specific mechanisms of fibrosis in hepatitis C and NASH, with a focus on recent developments.

Molecular determinants of insulin resistance, cell apoptosis and lipid accumulation in non-alcoholic steatohepatitis

BACKGROUNDS AND AIMS

Non-alcoholic-steatohepatitis (NASH) is closely related to insulin resistance, but it is unknown whether insulin resistance may be localized in hepatocytes. This study investigates insulin signalling in liver tissue from NASH, and the molecular mechanisms by which insulin-resistance could lead to liver damage (apoptosis). Moreover, to investigate the mechanisms of lipid overload we studied key enzymes in hepatocytes lipid metabolism.

METHODS AND RESULTS

In liver specimens from 11 patients with NASH and 7 histological normal livers, we measured total and phosphorylated Akt (active form), Bax and Bcl-2 by Western-blot analysis. In addition, we studied AMP-activated protein Kinase and Carnitine-Palmitoyl-Transferase-1 gene expression, key regulators of non-esterified fatty acid synthesis and oxidation, by reverse transcription polymerase chain reaction. In NASH, phosphorylated Akt was impaired (104.3+/-10.6 vs 152.6+/-22.4 AU, p<0.002) and correlated with necroinflammatory score (r=-0.62; p<0.05). Bax/Bcl-2 ratio was increased in NASH. Moreover, we observed a decrease of AMP-activated protein Kinase (10.74+/-6 vs 144.7+/-41.6 AU, p<0.0001) and Carnitine-Palmitoyl-Transferase-1 gene expression (38.7+/-14.6 vs 192.1+/-26.2 AU, p<0.0001), and both were correlated with steatosis score (r=-0.56, p<0.05, r=-0.87, p<0.05 respectively).

CONCLUSIONS

Akt, a key molecule of insulin signalling and cell apoptosis is impaired in NASH, suggesting an important role of hepatic insulin resistance in liver failure. Moreover, decreased non-esterified fatty acid oxidation may cause hepatic lipid overload.

Inhibition of STAT3 expression and signaling in resveratrol-differentiated medulloblastoma cells

In this study, the potential influence of resveratrol (3,5,4'-trihydroxy-trans-stilbene) in signal transducer and activator of transcription 3 (STAT3) signaling of medulloblastoma cells was evaluated by checking the status of STAT3 signaling and its downstream gene expression in two medulloblastoma cell lines (UW228-2 and UW228-3) with and without resveratrol treatment. The results revealed that resveratrol induced neuronal differentiation of medulloblastoma cells. Signal transducer and activator of transcription 3 expression and phosphorylation were detected in normally cultured UW228-2 and UW228-3 cells that were apparently attenuated after resveratrol treatment. The expression of STAT3 downstream genes, survivin, cyclin D1, Cox-2, and c-Myc, was suppressed but Bcl-2 was enhanced by resveratrol. Meanwhile, the production and secretion of leukemia inhibitory factor, a STAT3 activator, became active in resveratrol-treated cells. To further ascertain the significance of STAT3 signaling for medulloblastoma cells, AG490, a selective inhibitor of STAT3 phosphorylation, was used to treat UW228-3 cells. Phosphorylation of STAT3 was inhibited by AG490 accompanied with growth suppression, differentiation-like changes, and down-regulation of survivin, cyclin D1, Cox-2, and c-Myc. Our data thus suggest the importance of STAT3 signaling in maintenance and survival of medulloblastoma cells. This signaling may be the major target of resveratrol. Enhanced leukemia inhibitory factor and Bcl-2 expressions in resveratrol-treated cells might reflect a compensatory response to the loss of STAT3 function.

Role of hepatocyte apoptosis in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) represents a clinicopathologic syndrome, characterized mainly by macrovesicular hepatic steatosis in the absence of significant alcohol ingestion and excluding other liver diseases. With the improvement of lifestyle, living habit and dietary choices, obesity and diabetes are becoming epidemic, subsequently increasing the risk for developing NAFLD. But the pathogenesis of NAFLD remains poorly understood yet. Recent research indicate that hepatocyte apoptosis and related factor such as Fas/FasL system, tumor necrosis factor (TNF) family, Bc1-2 family, Caspases, nuclear factorκB (NF-κB), cytochrome C, and cathepsin B are abnormally over-expressed in NAFLD. Apoptosis is one of the most important mechanisms leading to hepatocyte elimination, liver injury, inflammation and fibrosis in NAFLD. In this article, we reviewed the progress in the role of hepatocyte apoptosis in NAFLD.