Bezafibrate prevents hepatic stellate cell activation and fibrogenesis in a murine steatohepatitis model, and suppresses fibrogenic response induced by transforming growth factor-beta1 in a cultured stellate cell line

Current Clinical Trial Status and Future Prospects of PPAR-Targeted Drugs for Treating Nonalcoholic Fatty Liver Disease

The number of patients with nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) is increasing globally and is raising serious concerns regarding the increasing medical and economic burden incurred for their treatment. The progression of NASH to more severe conditions such as cirrhosis and hepatocellular carcinoma requires liver transplantation to avoid death. Therefore, therapeutic intervention is required in the NASH stage, although no therapeutic drugs are currently available for this. Several anti-NASH candidate drugs have been developed that enable treatment via the modulation of distinct signaling cascades and include a series of drugs targeting peroxisome proliferator-activated receptor (PPAR) subtypes (PPARα/δ/γ) that are considered to be attractive because they can regulate both systemic lipid metabolism and inflammation. Multiple PPAR dual/pan agonists have been developed but only a few of them have been evaluated in clinical trials for NAFLD/NASH. Herein, we review the current clinical trial status and future prospects of PPAR-targeted drugs for treating NAFLD/NASH. In addition, we summarize our recent findings on the binding modes and the potencies/efficacies of several candidate PPAR dual/pan agonists to estimate their therapeutic potentials against NASH. Considering that the development of numerous PPAR dual/pan agonists has been abandoned because of their serious side effects, we also propose a repositioning of the already approved, safety-proven PPAR-targeted drugs against NAFLD/NASH.

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.

Is there a role of lipid-lowering therapies in the management of fatty liver disease?

Atherogenic dyslipidemia is characterized by increased triglyceride-rich lipoproteins and low high-density lipoprotein cholesterol concentrations. It is highly prevalent in non-alcoholic fatty liver disease (NAFLD) and contributes to the increased cardiovascular risk associated with this condition. Alongside insulin resistance it plays an important pathogenetic role in NAFLD/non-alcoholic steatohepatitis (NASH) development and progression. It has been shown that cholesterol-lowering reduces cardiovascular risk more in NAFLD vs non-NAFLD high-risk individuals. This evidence highlights the importance of effective lipid modulation in NAFLD. In this narrative review the effects of the most commonly used lipid-lowering therapies on liver outcomes alongside their therapeutic implications in NAFLD/NASH are critically discussed. Preclinical and clinical evidence suggests that statins reduce hepatic steatosis, inflammation and fibrosis in patients with NAFLD/NASH. Most data are derived from observational and small prospective clinical studies using changes in liver enzyme activities, steatosis/fibrosis scores, and imaging evidence of steatosis as surrogates. Also, relevant histologic benefits were noted in small biopsy studies. Atorvastatin and rosuvastatin showed greater benefits, whereas data for other statins are scarce and sometimes conflicting. Similar studies to those of statins showed efficacy of ezetimibe against hepatic steatosis. However, no significant anti-inflammatory and anti-fibrotic actions of ezetimibe have been shown. Preclinical studies showed that fibrates through peroxisome proliferator-activated receptor (PPAR)α activation may have a role in NAFLD prevention and management. Nevertheless, no relevant benefits have been noted in human studies. Species-related differences in PPARα expression and its activation responsiveness may help explain this discrepancy. Omega-3 fatty acids reduced hepatic steatosis in numerous heterogeneous studies, but their benefits on hepatic inflammation and fibrosis have not been established. Promising preliminary data for the highly purified eicosapentaenoic acid require further confirmation. Observational studies suggest that proprotein convertase subtilisin/kexin9 inhibitors may also have a role in the management of NAFLD, though this needs to be established by future prospective studies.

Placental extract ameliorates liver fibrosis in a methionine- and choline-deficient diet-induced mouse model of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a severe form of fatty liver disease that is defined by the presence of inflammation and fibrosis, which ultimately leads to cirrhosis and hepatocellular carcinoma. We previously showed that human placental extract (hPE) was intramuscularly injected to ameliorates liver injury in a methionine- and choline-deficient (MCD) diet-induced NASH model. In the present study, we investigated the effects of hPE using dB/dB mice which exhibit obesity and insulin resistance and are thought to reproduce the pathological background of NASH. The MCD-diet induced liver atrophy accompanied by fibrosis around the liver sinusoids. hPE dose-dependently reduced the perivascular fibrosis. Moreover, αSMA-positive activated hepatic stellate cells increased in number in mice on the MCD diet, with this effect reversed by hPE treatment. hPE significantly decreased expression of Acta2, Col1a1, and Tgfb1 genes in hepatic stellate cells, and inhibited Smad phosphorylation. Moreover, hPE treatment increased the expression of the anti-oxidative genes Hmox1, Nqo1, Cat, and Sod1, and significantly enhanced nuclear factor erythroid 2-related factor 2 activity. Furthermore, hPE decreased the expression of Nox4 and attenuated the levels of intracellular reactive oxygen species. These results, along with our previous study, suggest that hPE effectively ameliorates liver fibrosis in NASH. This beneficial effect may, in part, be due to suppression of hepatic stellate cell activation.

Drugs for Non-alcoholic Steatohepatitis (NASH): Quest for the Holy Grail

Nonalcoholic fatty liver disease (NAFLD) is a global epidemic that is likely to become the most common cause of chronic liver disease in the next decade, worldwide. Though numerous drugs have been evaluated in clinical trials, most of them have returned inconclusive results and shown poorly-tolerated adverse effects. None of the drugs have been approved by the Food and Drug Administration for treating biopsy-proven non-alcoholic steatohepatitis (NASH). Vitamin E and pioglitazone have been extensively used in treatment of biopsy-proven nondiabetic NASH patients. Although some amelioration of inflammation has been seen, these drugs did not improve the fibrosis component of NASH. Therefore, dietary modification and weight reduction have remained the cornerstone of treatment of NASH; moreover, they have shown to improve histological activity as well as fibrosis. The search for an ideal drug or 'Holy Grail' within this landscape of possible agents continues, as weight reduction is achieved only in less than 10% of patients. In this current review, we summarize the drugs for NASH which are under investigation, and we provide a critical analysis of their up-to-date results and outcomes.

Antifibrotic effects of bezafibrate and pioglitazone against thioacetamide-induced liver fibrosis in albino rats

Activation of hepatic stellate cells is a central event in hepatic fibrogenesis that offers multiple potential sites for therapeutic interventions. Peroxisome proliferator-activated receptors are implicated in liver fibrosis. We aimed to evaluate the effect of bezafibrate and pioglitazone on a thioacetamide (TAA) rat model of liver fibrosis and to clarify the possible underlying mechanisms. Rats received intraperitoneal injections of TAA for 6 weeks. Daily oral treatments with bezafibrate or pioglitazone were started with the first day of TAA intoxication. Serum liver function tests, hepatic malondialdehyde (MDA), total nitrite and nitrate (NOx), superoxide dismutase, and hepatic histopathology were assessed to evaluate hepatic damage. Alpha smooth muscle actin (α-SMA) and tissue inhibitor metalloproteinase-1 (TIMP-1) and caspase-3 were also assessed. The TAA group experienced significant deterioration of liver functions, increased oxidative stress, and increased liver tissue NOx. Administration of bezafibrate or pioglitazone resulted in significant improvement of all liver functions and reduced oxidative stress in hepatic tissues. Only administration of bezafibrate significantly reduced NOx levels. Liver tissues from the TAA-treated group showed disrupted normal architecture. Administration of bezafibrate or pioglitazone attenuated this picture. Stronger α-SMA expression was detected in the TAA group. Treatment with bezafibrate or pioglitazone decreased the α-SMA expression.

Pirfenidone prevents and reverses hepatic insulin resistance and steatohepatitis by polarizing M2 macrophages

Nonalcoholic steatohepatitis (NASH) is associated with lipotoxic liver injury, leading to insulin resistance, inflammation, and fibrosis. Despite its increased global incidence, very few promising treatments for NASH are available. Pirfenidone is an antifibrotic agent used to treat pulmonary fibrosis; it suppresses the pulmonary influx of T cells and macrophages. Here, we investigated the effect of pirfenidone in a mouse model of lipotoxicity-induced NASH via a high-cholesterol and high-fat diet. After 12 weeks of feeding, pirfenidone administration attenuated excessive hepatic lipid accumulation and peroxidation by reducing the expression of genes related to lipogenesis and fatty acid synthesis and enhancing the expression of those related to fatty acid oxidation. Flow cytometry indicated that pirfenidone reduced the number of total hepatic macrophages, particularly CD11c⁺CD206^-(M1)-type macrophages, increased the number of CD11c^-CD206⁺(M2)-type macrophages, and subsequently reduced T-cell numbers, which helped improve insulin resistance and steatohepatitis. Moreover, pirfenidone downregulated the lipopolysaccharide (LPS)-induced mRNA expression of M1 marker genes and upregulated IL-4-induced M2 marker genes in a dose-dependent manner in RAW264.7 macrophages. Importantly, pirfenidone reversed insulin resistance, hepatic inflammation, and fibrosis in mice with pre-existing NASH. These findings suggest that pirfenidone is a potential candidate for the treatment of NASH.

Multiphoton dynamic imaging of the effect of chronic hepatic diseases on hepatobiliary metabolism in vivo

In this study, intravital multiphoton microscopy was used to quantitatively investigate hepatobiliary metabolism in chronic pathologies of the liver. Specifically, through the use of the probe molecule 6-carboxyfluorescein diacetate, the effects of liver fibrosis, fatty liver, and hepatocellular carcinoma on the metabolic capabilities of mouse liver were investigated. After the acquisition of time-lapse images, a first order kinetic model was used to calculate rate constant resolved images of various pathologies. It was found that the ability of the liver to metabolically process the probe molecules varies among different pathologies, with liver fibrosis and fatty liver disease negatively impacted the uptake, processing, and excretion of molecules. The approach demonstrated in this work allows the study of the response of hepatic functions to different pathologies in real time and is useful for studying processes such as pharmacokinetics through direct optical imaging.

The Role of Signal Transducer and Activator of Transcription 5 and Transforming Growth Factor-β1 in Hepatic Fibrosis Induced by Chronic Hepatitis C Virus Infection in Egyptian Patients

OBJECTIVE

To investigate the possible role of signal transducer and activator of transcription 5 (STAT5) in the pathogenesis of liver fibrosis in Egyptian patients with chronic hepatitis C (CHC) virus infection and its relation to hepatic stellate cells (HSC).

SUBJECTS AND METHODS

Sixty-five patients (46 males and 19 females) were divided into 4 groups based on the severity of fibrosis as detected by Fibroscan as follows: F1, n = 15; F2, n = 21; F3, n = 13; and F4, n = 16. Twenty age- and gender-matched healthy persons volunteered as controls. The serum levels of STAT5, TGF-β1, α-smooth muscle actin (α-SMA), fasting blood sugar, and fasting insulin, as well as homeostasis model assessment of insulin resistance (HOMA-IR), were determined and compared for all groups. The usefulness of the studied serum biomarkers for predicting liver fibrosis was evaluated using a receiver operating characteristic curve.

RESULTS

Serum levels of STAT5 were significantly lower in patients compared to controls (9.69 ± 5.62 vs. 14.73 ± 6.52, p ≤ 0.001); on the contrary, TGF-β1, α-SMA, and HOMA-IR were significantly higher in patients compared to controls (mean: 1,796.04 vs. 1,636.94; 14.94 vs. 8.1; and 7.91 vs. 4.18; p ≤ 0.01 and 0.001, respectively). TGF-β1 and α-SMA showed a progressive increase with advancing severity of hepatic fibrosis (mean TGF-β1: 2,058.4 in F1-F2 and 1,583.8 in F3-F4, p ≤ 0.04; mean α-SMA: 13.59 in F1-F2 and 16.62 in F3-F4, p ≤ 0.05). STAT5 had a significant negative correlation with TGF-β1 (p ≤ 0.001), while no correlation was detected with α-SMA (p ≤ 0.8).

CONCLUSIONS

STAT5 may play a significant role in hepatic fibrogenesis through the induction of TGF-β1 but not through the activation of hepatic stellate cells.

PPARs and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) encompasses a range of liver pathology ranging from simple steatosis to varying degrees of inflammation, hepatocyte injury and fibrosis. Without intervention it can progress to end-stage liver disease and hepatocellular carcinoma. Given its close association with obesity, the prevalence of NAFLD has increased dramatically worldwide. Currently, there are no FDA-approved medications for the treatment of NAFLD and although lifestyle modifications with appropriate diet and exercise have been shown to be beneficial, this has been difficult to achieve and sustain for the majority of patients. As such, the search for effective therapeutic agents is an active area of research. Peroxisome proliferator-activated receptors (PPARs) belong to a class of nuclear receptors. Because of their key role in the transcriptional regulation of mediators of glucose and lipid metabolism, PPAR ligands have been investigated as possible therapeutic agents. Here we review the current evidence from preclinical and clinical studies investigating the therapeutic potential of PPAR ligands for the treatment of NAFLD.

Non-alcoholic steatohepatitis-associated hepatic fibrosis and hepatocellular carcinoma in a combined mouse model of genetic modification and dietary challenge

AIM

Experimental models of non-alcoholic steatohepatitis (NASH) are still required for understanding the pathophysiology of this disease. This study aimed to examine whether disease progression is accelerated by combining dyslipidemic genetic modification and dietary challenges and develop NASH-associated hepatic fibrosis, cirrhosis, and carcinoma in a short period.

METHODS

Low-density lipoprotein receptor knockout mice were fed a modified choline-deficient amino acid-defined diet, including 1 w/w% cholesterol and 41 kcal% fat, and was comprehensively profiled over 1 year.

RESULTS

Microvesicular and macrovesicular steatosis in the liver was observed from the first week after starting the modified choline-deficient amino acid-defined diet. Macrovesicular steatosis was exacerbated with time and was observed in almost all hepatocytes at week 8, but slightly decreased at week 16. Infiltration of macrophages and neutrophils, and upregulation of hepatic inflammatory cytokines such as tumor necrosis factor-α and interleukin-1β were also observed from week 1. Plasma hepatic transaminase activities were increased at week 1, reached a peak at week 4, and gradually decreased thereafter. In parallel with increases in hepatic gene expression of collagen-I, the hepatic fibrosis area expanded after week 4 and massively spread all over the liver by week 8. Hepatocellular hyperplasia was observed from week 24. Hepatocellular adenoma and carcinoma were observed from week 31 and 39, respectively.

CONCLUSION

These results suggest that, in a rodent NASH model with the combination of genetic modification and dietary challenges, hepatic steatosis, inflammatory cell infiltration and hepatic injury, hepatic fibrosis, hepatocellular hyperplasia, adenoma, and carcinoma can be developed in a relatively short period.

Primary biliary cirrhosis: safety and benefits of established and emerging therapies

INTRODUCTION

Primary biliary cirrhosis (PBC) is a chronic, cholestatic liver disease characterized histologically by lymphocytic cholangitis and intralobular bile duct destruction. It is a progressive disorder associated with increased mortality and decreased quality of life related to hepatic fibrosis, troublesome symptoms such as fatigue and pruritus, and ultimately endstage cirrhosis. PBC affects adults around the world, and therefore effective treatment of PBC and its associated symptoms constitute significant issues for patients and providers as well as on a public health level. The only approved pharmacotherapy for PBC to date is ursodeoxycholic acid (UDCA), a choleretic, hydrophilic bile acid which has been in clinical use for decades. UDCA is effective in a majority of patients with PBC, but nearly a third of patients are UDCA non-responders. Non-response to UDCA is associated with an increased risk of death or need for liver transplantation (LT). Whereas LT is an effective treatment, it engenders substantial cost and a risk of PBC recurrence, among other complications. Patients who are non-responders to UDCA or have highly symptomatic disease (e.g., intractable pruritus) are thus in critical need of novel therapeutic approaches, which are both safe and effective.

AREAS COVERED

In this review, we provide a synopsis regarding the safety and benefits of established and emerging pharmacotherapies for PBC and present viewpoints on how they may evolve over the next several years.

EXPERT OPINION

It is our belief that the pharmacoscope of PBC, as with other cholestatic liver diseases, is likely to see important advancements in the near future.

Progression of diet induced nonalcoholic steatohepatitis is accompanied by increased expression of Kruppel-like-factor 10 in mice

Background

Kruppel-like-factor (KLF) 10 is identified as transforming growth factor (TGF) β inducible early gene and is reported to suppress lipogenic genes. Although previous studies report that TGFβ plays an important role in progression of nonalcoholic steatohepatitis (NASH) by regulating liver fibrosis, the association of KLF10 and NASH has never been explored. Thus we evaluated expressions and changes of KLF10 in diet induced NASH and in NASH which was alleviated by ursodeoxycholic acid (UDCA). We also assessed KLF10 in quiescent and activated hepatic stellate cells (HSCs).

Methods

C57BL/6 mice were given high fat, sucrose diet (HFSD) at least for 12 weeks up to 48 weeks and sacrificed at 12, 24 and 48 weeks thereafter. In other groups, either standard diet (SD) or HFSD was given for 24 weeks at which point mice fed with HFSD were divided into two groups, and were given either UDCA in combination with HFSD or vehicle with HFSD. Mice under SD were given vehicle. HSCs were isolated from C57BL/6 mice in order to evaluated KLF10 expression in activated HSCs.

Results

The mice were found to acquire liver steatosis and inflammation starting from week 12 of HFSD feeding, although significant liver fibrosis was noticed by week 24. Increased TGFβ and collagen α1(I) (Col1α(I)) expression was also apparent from week 24. However, expression of KLF10 mRNA started to increase from week 12, earlier than TGFβ gene. Up-regulation of KLF10 was accompanied by suppressed carbohydrate response element-binding protein (ChREBP) that is known to be protective against insulin resistance. The mice fed with HFSD and UDCA had decreased Colα(I) mRNA that was coincided with reduced TGFβ and KLF10 expression. Expression of ChREBP was also recovered by UDCA administration. Enhanced KLF10 was noticed in activated HSCs when quiescent cell showed minimal expression.

Conclusions

Our study demonstrated that KLF10 expression was significantly increased in diet induced NASH and collagen producing activated HSCs. We also noticed that this up-regulation of KLF10 was accompanied by increased TGFβ signaling genes and suppressed ChREBP expression. These observations suggest possible association of KLF10 and NASH progression.

Roles of the lipid metabolism in hepatic stellate cells activation △

The lipids present in hepatic stellate cells (HSCs) lipid droplets include retinyl ester, triglyceride, cholesteryl ester, cholesterol, phospholipids and free fatty acids. Activation of HSCs is crucial to the development of fibrosis in liver disease. During activation, HSCs transform into myofibroblasts with concomitant loss of their lipid droplets and production of excessive extracellular matrix. Release of lipid droplets containing retinyl esters and triglyceride is a defining feature of activated HSCs. Accumulating evidence supports the proposal that recovering the accumulation of lipids would inhibit the activation of HSCs. In healthy liver, quiescent HSCs store 80% of total liver retinols and release them depending on the extracellular retinol status. However, in injured liver activated HSCs lose their retinols and produce a considerable amount of extracellular matrix, subsequently leading to liver fibrosis. Further findings prove that lipid metabolism of HSCs is closely associated with its activation, yet relationship between activated HSCs and the lipid metabolism has remained mysterious.

Simvastatin ameliorates liver fibrosis via mediating nitric oxide synthase in rats with non-alcoholic steatohepatitis-related liver fibrosis

Background

Simvastatin exerts pleiotropic effects on cardiovascular system. However, its effect on non-alcoholic fatty liver disease, especially the liver fibrosis, remains obscure. We aimed to clarify the relationship between simvastatin and liver fibrosis both in vivo and in vitro.

Methods

A High-fat diet was given to establish rat models with non-alcoholic steatohepatitis (NASH)-related liver fibrosis and simvastatin (4mg·kg^-1·d^-1) was administrated intragastrically until hepatic histological findings confirmed the appearance of fibrosis. Human hepatic stellate cell (HSC) line lx-2 cells were cultured in an adipogenic differentiating mixture (ADM) and then were treated with transforming growth factorβ1 (TGF-β1), served as a positive control, simvastatin, TGF-β1 plus simvastatin, N_ω-nitro-L-arginine methyl ester hydrochloride (L-NAME, a inhibitor of nitric oxide synthase), and L-NAME plus simvastatin, respectively. The expressions of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and Collagen І as well as cellular α-smooth muscle actin (α-SMA) were measured by real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) and Western blot in liver tissue and HSC.

Results

With the progress of NASH-related fibrosis, hepatic mRNA and protein expressions of iNOS, α-SMA, and Collagen І were increased while those of eNOS were decreased. Compared with model rats in 24^th week group, rats in simvastatin group had less expressions of iNOS, α-SMA, and Collagen І and more expressions of eNOS. In vitro, LX-2 cells acquired quiescent phenotype when cultured in ADM, and TGF-β1 could activate the quiescent HSC. Simvastatin inhibited LX-2 cells activation due to TGF-β1 or L-NAME by increasing the expression of eNOS and decreasing the expression of iNOS.

Conclusions

Simvastatin improves the prognosis of NASH-related fibrosis by increasing the expression of eNOS, decreasing the expression of iNOS, and inhibiting the activation of HSC.

Paraoxonase-1 deficiency is associated with severe liver steatosis in mice fed a high-fat high-cholesterol diet: a metabolomic approach

Oxidative stress is a determinant of liver steatosis and the progression to more severe forms of disease. The present study investigated the effect of paraoxonase-1 (PON1) deficiency on histological alterations and hepatic metabolism in mice fed a high-fat high-cholesterol diet. We performed nontargeted metabolomics on liver tissues from 8 male PON1-deficient mice and 8 wild-type animals fed a high-fat, high-cholesterol diet for 22 weeks. We also measured 8-oxo-20-deoxyguanosine, reduced and oxidized glutathione, malondialdehyde, 8-isoprostanes and protein carbonyl concentrations. Results indicated lipid droplets in 14.5% of the hepatocytes of wild-type mice and in 83.3% of the PON1-deficient animals (P < 0.001). The metabolomic assay included 322 biochemical compounds, 169 of which were significantly decreased and 16 increased in PON1-deficient mice. There were significant increases in lipid peroxide concentrations and oxidative stress markers. We also found decreased glycolysis and the Krebs cycle. The urea cycle was decreased, and the pyrimidine cycle had a significant increase in orotate. The pathways of triglyceride and phospholipid synthesis were significantly increased. We conclude that PON1 deficiency is associated with oxidative stress and metabolic alterations leading to steatosis in the livers of mice receiving a high-fat high-cholesterol diet.

A Disintegrin and Metalloprotease with Thrombospondin Motif 2 May Contribute to Cirrhosis in Humans through the Transforming Growth Factor-β/SMAD Pathway

Background/Aims

We aimed to investigate the correlation between a disintegrin and metalloprotease with thrombospondin motif 2 (ADAMTS-2) and transforming growth factor-β1 (TGF-β1) in clinical human cirrhotic tissues.

Methods

The liver tissues of 24 patients (16 cases with cirrhotic portal hypertension as the cirrhosis group and eight cases with healthy livers as the normal group) were collected. Immunohistochemistry and Western blots were performed to evaluate the protein expression levels of ADAMTS-2 and TGF-β1. Western blots for other key mediators of cirrhotic progression, including SMAD2, SMAD3, TGF-β receptor II (TGFβRII), matrix metalloproteinases 2 (MMP2), and tissue inhibitor of matrix metalloproteinases 2 (TIMP2), were also performed.

Results

Cirrhotic tissues showed higher percentages of collagen. The protein expression levels of ADAMTS-2 and TGF-β1 were significantly higher in the cirrhotic group as compared to the matched normal group (p<0.05), and there was a positive correlation between these two proteins (r=0.862, p<0.01). The protein expressions of MMP2, TIMP2, and TGFβRII, as well as the phosphorylated forms of SMAD2 and SMAD3, were significant higher in the cirrhotic group (p<0.01 or p<0.05).

Conclusions

These findings suggested that ADAMTS-2 and TGF-β1 may play important roles in the pathogenesis of human cirrhosis; specifically, TGF-β1 may induce the expression of ADAMTS-2 through the TGFβ/SMAD pathway.

A critical analysis of three quantitative methods of assessment of hepatic steatosis in liver biopsies

The issue of adequately quantitatively evaluating hepatic steatosis is still unresolved. Therefore, we compared three methods of quantitative assessment. Two groups of mice (n = 10 each) were fed standard chow (10% fat, SC group) or a high-fat diet (60% fat, HF group) for 16 weeks, and hepatic triglyceride (HT) and liver tissue were then studied. Paraplast-embedded tissues stained by hematoxylin and eosin (H-E) were compared to frozen sections stained by Oil Red-O (ORO). In addition, the volume density of steatosis (Vv[steatosis, liver]) was measured by point counting (P-C, sections H-E or ORO) or by image analysis (I-A, sections ORO). HT was significantly higher in the HF group (104% greater, P = 0.0004) than in the SC group. With P-C and H-E, Vv[steatosis, liver] was 4.80 ± 0.90% in the SC group and 33.50 ± 3.17% in the HF group (600% greater, P < 0.0001). With P-C and ORO, Vv[steatosis, liver] was 4.86 ± 0.89% in the SC group and 25.21 ± 1.27% in the HF group (420% greater, P < 0.0001). With I-A and ORO, Vv[steatosis, liver] was 4.17 ± 0.85% in the SC group and 23.35 ± 1.58% in the HF group (460% greater, P < 0.0001). Correlations between Vv[steatosis, liver] and HT were strong and significant in all methods. In conclusion, all methods were appropriate and reproducible. In P-C and H-E, there is a slight overestimation of steatosis in the HF animals in comparison to frozen sections and ORO; in frozen sections, differences between P-C and I-A are insignificant.

Redox balance in the pathogenesis of nonalcoholic fatty liver disease: mechanisms and therapeutic opportunities

Nonalcoholic fatty liver disease (NAFLD) is currently the most common liver disease in the world. It encompasses a histological spectrum, ranging from simple, nonprogressive steatosis to nonalcoholic steatohepatitis (NASH), which may progress to cirrhosis and hepatocellular carcinoma. While liver-related complications are confined to NASH, emerging evidence suggests both simple steatosis and NASH predispose to type 2 diabetes and cardiovascular disease. The pathogenesis of NAFLD is currently unknown, but accumulating data suggest that oxidative stress and altered redox balance play a crucial role in the pathogenesis of steatosis, steatohepatitis, and fibrosis. We will examine intracellular mechanisms, including mitochondrial dysfunction and impaired oxidative free fatty acid metabolism, leading to reactive oxygen species generation; additionally, the potential pathogenetic role of extracellular sources of reactive oxygen species in NAFLD, including increased myeloperoxidase activity and oxidized low density lipoprotein accumulation, will be reviewed. We will discuss how these mechanisms converge to determine the whole pathophysiological spectrum of NAFLD, including hepatocyte triglyceride accumulation, hepatocyte apoptosis, hepatic inflammation, hepatic stellate cell activation, and fibrogenesis. Finally, available animal and human data on treatment opportunities with older and newer antioxidant will be presented.

Management of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a rare cholestatic liver disease with major morbidity and mortality. Therapeutic management is difficult, due to lack of conclusive data and individual disease progression. High-dose UDCA was used for years as a pharmacotherapeutic agent to prevent disease progression, based on a positive trend in pilot studies, but has recently been proven to have a negative effect in advanced disease. Immunosuppressants might be useful in patients with overlap syndromes. Dominant bile duct stenoses should be treated endoscopically, and cholangiocellular carcinoma (CCC) still remains a therapeutic challenge in PSC patients. Early diagnosis of CCC must be improved and new strategies such as neoadjuvant radiochemotherapy with subsequent liver transplantation in selected patients are further options to be considered.

Activation of the nuclear receptor PPARα regulates lipid metabolism in foetal liver from diabetic rats: implications in diabetes-induced foetal overgrowth

BACKGROUND

peroxisome proliferator-activated receptor α (PPARα) is a crucial regulator of liver lipid metabolism. As maternal diabetes impairs foetal lipid metabolism and growth, we aimed to determine whether PPARα activation regulates lipid metabolism in the foetal liver from diabetic rats as well as foetal weight and foetal liver weight.

METHODS

diabetes was induced by neonatal streptozotocin administration (90 mg/kg). For ex vivo studies, livers from 21-day-old foetuses from control and diabetic rats were explanted and incubated in the presence of PPARα agonists (clofibrate and leukotriene B(4) ) for further evaluation of lipid levels (by thin layer chromatography and densitometry), de novo lipid synthesis (by (14) C-acetate incorporation) and lipid peroxidation (by thiobarbituric reactive substances evaluation). For in vivo studies, foetuses were injected through the uterine wall with leukotriene B(4) on days 19, 20 and 21 of gestation. On day 21 of gestation, foetal liver concentrations of lipids and lipoperoxides were evaluated.

RESULTS

foetuses from diabetic rats showed increased body weight and liver weight, as well as accumulation of triglycerides and cholesteryl esters, increased de novo lipid synthesis and lipid peroxidation in the liver when compared to controls. Ex vivo studies showed that PPARα ligands reduced both the concentrations and synthesis of the lipid species studied and lipid peroxidation in the foetal liver from diabetic rats. In vivo experiments showed that leukotriene B(4) reduced the concentrations of triglycerides, cholesteryl esters and phospholipids, as well as lipid peroxidation, foetal weight and foetal liver weight in diabetic rats.

CONCLUSIONS

PPARα activation regulates the impaired foetal liver lipid metabolism, prevents hepatomegaly and reduces foetal overgrowth induced by maternal diabetes.

Transforming Growth Factor-β1 as a Common Target Molecule for Development of Cardiovascular Diseases, Renal Insufficiency and Metabolic Syndrome

Transforming growth factor-β1 (TGF-β1) is a polypeptide member of the transforming growth factor β superfamily of cytokines. It is a secreted protein that performs many cellular functions including control of cell growth, cell proliferation, cell differentiation and apoptosis. In the cardiovascular system, TGF-β1 plays pivotal roles in the pathogenesis of hypertension, restenosis after percutaneous coronary intervention, atherosclerosis, cardiac hypertrophy and heart failure. In addition, TGF-β1 has been shown to be increased in adipose tissue of obese subjects with insulin resistance. Furthermore, TGF-β1 is a potent initiator of proliferation of renal mesangial cells leading to chronic kidney disease. Some currently available agents can manipulate TGF-β1 expression leading to amelioration of cardiovascular diseases. Thus, an understanding of interactions between chronic kidney disease and metabolic syndrome and the development of cardiovascular diseases is an important issue, and attention should be given to TGF-β1 as a crucial factor for regulation and modulation of those pathological conditions.

Effect of bezafibrate on hepatic oxidative stress: comparison between conventional experimental doses and clinically-relevant doses in mice

Several rodent studies have demonstrated that fibrate drugs can activate peroxisome proliferator-activated receptor alpha (PPARalpha) and increase reactive oxygen species (ROS) production. The persistence of strong PPARalpha activation is considered to be a possible mechanism related to the adverse effects of these agents in humans. We recently found that bezafibrate-treated mice at clinically-relevant doses (10 mg/kg/day) exhibited similar pharmacokinetics to humans, but were different from previous rodent data (> 50 mg/kg/day). To examine whether clinical doses of bezafibrate do in fact activate PPARalpha and increase hepatic oxidative stress in mice, we administered bezafibrate to wild-type and Ppara-null mice at high (100 mg/kg/day) or low (10 mg/kg/day) doses and assessed ROS-related pathways in the liver. High-dose bezafibrate increased hepatic lipid peroxides in a PPARalpha-dependent manner, likely from discordant induction of PPARalpha-regulated ROS-generating enzymes (acyl-CoA oxidase, cytochrome P450 4A, and NADPH oxidase) and enhancement of mitochondrial beta-oxidation. The treatment also activated protein kinase C and phosphatidylinositol-3-kinase in wild-type mice only, suggesting an association between strong PPARalpha activation and an altered cell signaling cascade. Meanwhile, low-dose bezafibrate reduced serum/liver triglycerides in both genotypes without activating PPARalpha or enhancing hepatic oxidative stress. These results may support the safety of bezafibrate treatment at clinically-relevant doses.

Adiponectin deficiency enhanced the severity of cerulein-induced chronic pancreatitis in mice

BACKGROUND

Adiponectin is recognized as an antiinflammatory and antifibrotic protein derived from adipocytes, and low serum adiponectin levels are present in obesity. Recent studies have highlighted the relationship between obesity and pancreatic diseases. However, the role of adiponectin in chronic pancreatitis remains uncertain. The aim of this study was to determine the effects of adiponectin in chronic pancreatitis.

METHODS

We investigated the effects of adiponectin in experimental chronic pancreatitis by using adiponectin-knockout (APN-KO) mice. Chronic pancreatitis was induced by repeated hourly (6 times) intraperitoneal injections of 50 microg/kg cerulein three times per week for 4 weeks in wild-type (WT) and APN-KO mice. We evaluated the severity of chronic pancreatitis biochemically and morphologically.

RESULTS

In cerulein-treated mice, macroscopically and histologically, severe pancreatic damage was observed in APN-KO mice compared with findings in WT mice. The histological scores for chronic pancreatitis, including glandular atrophy, pseudotubular complex, fibrosis, and total scores, were significantly higher in APN-KO mice than in WT mice. Activated pancreatic stellate cells and F4/80-positive pancreatic macrophages accumulated in the pancreas of APN-KO mice but not in WT mice. Overexpression of the mRNAs of transforming growth factor-beta1, CD68, and monocyte chemoattractant protein-1 was noted in APN-KO mice but not in WT mice. The gene expression level of collagen1 (alpha1) tended to be higher in APN-KO mice than in WT mice, albeit insignificantly.

CONCLUSIONS

Adiponectin deficiency enhanced the severity of cerulein-induced chronic pancreatitis in mice. Hypoadiponectinemia could enhance the severity of chronic pancreatitis.

Highly purified eicosapentaenoic acid ethyl ester prevents development of steatosis and hepatic fibrosis in rats

BACKGROUND AND AIMS

Pathogenesis of nonalcoholic steatohepatitis (NASH) is considered to be involved in fat accumulation, oxidative stress, inflammation, and fibrosis in liver, but no drug therapy has been established as yet. Eicosapentaenoic acid (EPA) is an agent used clinically to treat hypertriglyceridemia, and has been reported to suppress reactive oxygen species and inflammation. Here, we aimed to assess the effect of EPA on progression of hepatic fibrosis in an animal model of NASH.

METHODS

Wistar rats were fed a methionine- and choline-deficient (MCD) diet and given EPA ethyl ester (EPA-E) (1,000 mg/kg/day) or vehicle by gavage for 8 or 20 weeks.

RESULTS

The MCD diet caused development of hepatic fibrosis and nodule formation at 20 weeks. EPA-E treatment significantly suppressed MCD-induced increase in fibrosis and hepatic hydroxyproline, and inhibited nodule formation. EPA-E treatment also decreased hepatic transforming growth factor (TGF)-beta1, and messenger RNA (mRNA) levels of connective tissue growth factor. EPA-E suppressed MCD-induced elevation of serum levels of ferritin, 8-isoprostane, soluble tumor necrosis factor receptor 1 (sTNFR1), and sTNFR2 at 20 weeks, and hepatic triglyceride accumulation at 8 weeks.

CONCLUSIONS

EPA-E prevents progression of hepatic fibrosis in an MCD-induced NASH model with reduction of oxidative stress, inflammation, and initial hepatic steatosis. Thus, EPA-E treatment may be a potential therapy to treat NASH.

Deletion of nuclear factor-E2-related factor-2 leads to rapid onset and progression of nutritional steatohepatitis in mice

Oxidative stress is a critical mediator in liver injury of steatohepatitis. The transcription factor Nrf2 serves as a cellular stress sensor and is a key regulator for induction of hepatic detoxification and antioxidative stress systems. The involvement of Nrf2 in defense against the development of steatohepatitis remains unknown. We aimed to investigate the protective roles of Nrf2 in nutritional steatohepatitis using wild-type (WT) and Nrf2 gene-null (Nrf2-null) mice. WT and Nrf2-null mice were fed a methionine- and choline-deficient (MCD) diet for 3 and 6 wk, and the liver tissues were analyzed for pathology and for expression levels of detoxifying enzymes and antioxidative stress genes via the Nrf2 transcriptional pathway. In WT mice fed an MCD diet, Nrf2 was potently activated in the livers, and steatohepatitis did not develop over the observation periods. However, in Nrf2-null mice fed an MCD diet, the pathological state of the steatohepatitis was aggravated in terms of fatty changes, inflammation, fibrosis, and iron accumulation. In the livers of the Nrf2-null mice, oxidative stress was significantly increased compared with that of WT mice based on the increased levels of 4-hydroxy-2-nonenal and malondialdehyde. This change was associated with the decreased levels of glutathione, detoxifying enzymes, catalase, and superoxide dismutase activity. Correlating well with the liver pathology, the mRNA levels of factors involved in fatty acid metabolism, inflammatory cytokines, and fibrogenesis-related genes were significantly increased in the livers of the Nrf2-null mice. These findings demonstrate that Nrf2 deletion in mice leads to rapid onset and progression of nutritional steatohepatitis induced by an MCD diet. Activation of Nrf2 could be a promising target toward developing new options for prevention and treatment of steatohepatitis.

Nrf2 counteracts cholestatic liver injury via stimulation of hepatic defense systems

The transcription factor Nrf2 is a key regulator for hepatic induction of detoxifying enzymes, antioxidative stress genes and Mrp efflux transporters. We aimed to investigate whether Nrf2 activation counteracts liver injury associated with cholestasis. The role of Nrf2 activation in counteracting cholestatic liver injury was studied using a bile duct-ligation (BDL) model of Keap1 gene-knockdown (Keap1-kd) mice that represent the sustained activation of Nrf2 in the liver. Upon Nrf2 activation, Keap1-kd mice showed large increases in Mrp efflux transporters, detoxifying enzymes and antioxidative stress genes in the livers. After BDL, the number of hepatic parenchymal necrosis and the reactive oxygen species content were significantly smaller in the livers of the Keap1-kd mice than in those of the WT mice. Moreover, the increase in serum bilirubin levels was attenuated in the Keap1-kd mice. In conclusion, the results suggest a hepatoprotective role of sustained Nrf2 activation against liver injury associated with cholestasis.

Similarities and differences in the pathogenesis of alcoholic and nonalcoholic steatohepatitis

Subpopulations of individuals with alcohol-induced fatty livers and nonalcoholic steatosis develop steatohepatitis. Steatohepatitis is defined histologically: increased numbers of injured and dying hepatocytes distinguish this condition from simple steatosis. The increased hepatocyte death is generally accompanied by hepatic accumulation of inflammatory cells and sometimes increases in myofibroblastic cells, leading to hepatic fibrosis and eventually, cirrhosis. The purpose of this review is to summarize similarities and differences in the pathogenesis of steatohepatitis in alcoholic fatty liver disease and nonalcoholic fatty liver disease.

Treatment options for nonalcoholic Fatty liver disease

Nonalcoholic fatty liver disease comprises a range of disorders from steatosis and steatohepatitis through to cirrhosis. Nonalcoholic steatohepatitis can progress to cirrhosis and liver-related death. Therefore, managing this common disorder is becoming an important public health issue. Lifestyle measures are commonly suggested but robust data are lacking. Trials with antioxidants (vitamin E, betaine) as well as cytoprotectants (ursodeoxycholic acid) have been disappointing. While data for insulin sensitizers such as metformin are less conclusive, thiazolidinediones appear promising. However, not all patients respond to thiazolidinediones. Moreover, issues related to weight gain, cardiovascular risk need to be addressed. The use of endocannabinoid antagonists and insulin secretagogues are novel strategies to combat this disorder.