Pentoxifylline attenuates steatohepatitis induced by the methionine choline deficient diet

Pentoxifylline improves nonalcoholic steatohepatitis: a randomized placebo-controlled trial

The primary aim of this study was to compare the effects of pentoxifylline (PTX) versus placebo on the histological features of nonalcoholic steatohepatitis (NASH). In all, 55 adults with biopsy-confirmed NASH were randomized to receive PTX at a dose of 400 mg three times a day (n = 26) or placebo (n = 29) over 1 year. The primary efficacy endpoint was defined as improvement in histological features of NASH through reduction in steatosis, lobular inflammation, and/or hepatocellular ballooning as reflected by a decrease of ≥ 2 points in the nonalcoholic fatty liver disease (NAFLD) activity score (NAS). After 1 year, intention-to-treat analysis showed a decrease of ≥ 2 points in the NAS in 38.5% of patients on PTX versus 13.8% of those on placebo (P = 0.036). Per protocol analysis, a decrease of ≥ 2 points in the NAS from baseline was observed in 50% of the patients on PTX versus 15.4% of those on placebo (P = 0.01). The mean change in NAS score from baseline was -1.6 in the PTX group, versus -0.1 in the placebo group (P < 0.001). PTX significantly improved steatosis (mean change in score -0.9 versus -0.04 with placebo, P < 0.001) and lobular inflammation (median change -1 versus 0 with placebo, P = 0.02). No significant effects in hepatocellular ballooning were observed. PTX also improved liver fibrosis (mean change in fibrosis score was -0.2 among those on PTX versus +0.4 among those on placebo, P = 0.038). Although not statistically significant (P = 0.17), improvement in fibrosis was observed in a greater proportion (35%) of patients in the PTX group compared to placebo (15%). Adverse effects were similar in both groups.

CONCLUSION

PTX improved histological features of NASH compared to placebo. PTX was well tolerated in patients with NASH.

Decreased accumulation of ultrasound contrast in the liver of nonalcoholic steatohepatitis rat model

AIM: To investigate the diagnosis of nonalcoholic steatohepatitis (NASH) using contrast ultrasonography in the NASH rat model.

METHODS: The liver in methionine choline-deficient diet (MCDD) rats, a NASH model constructed by feeding an MCDD, was examined by contrast ultrasonography at weeks 2, 4, 8, 12 and 16, with late phase images of contrast ultrasonography (Kupffer imaging) in which contrast enhancement was achieved by incorporation of a contrast agent by Kupffer cells (KCs), and images were compared to those in rats taking a regular chow.

RESULTS: Decrease in contrast enhancement was observed first in MCDD rats at week 2. KCs were counted based on immunohistochemistry, but their numbers were not reduced and it was assumed that attenuation of contrast enhancement was attributable to reduced phagocytic activity of the KCs.

CONCLUSION: It is suggested that clinical application of contrast ultrasonography may be valuable for non-invasive diagnosis of NASH.

Mitochondria and redox signaling in steatohepatitis

Alcoholic and nonalcoholic fatty liver diseases are potentially pathological conditions that can progress to steatohepatitis, fibrosis, and cirrhosis. These conditions affect millions of people throughout the world in part through poor lifestyle choices of excess alcohol consumption, overnutrition, and lack of regular physical activity. Abnormal mitochondrial and cellular redox homeostasis has been documented in steatohepatitis and results in alterations of multiple redox-sensitive signaling cascades. Ultimately, these changes in signaling lead to altered enzyme function and transcriptional activities of proteins critical to mitochondrial and cellular function. In this article, we review the current hypotheses linking mitochondrial redox state to the overall pathophysiology of alcoholic and nonalcoholic steatohepatitis and briefly discuss the current therapeutic options under investigation.

The use of pentoxifylline as adjuvant therapy with praziquantel downregulates profibrogenic cytokines, collagen deposition and oxidative stress in experimental schistosomiasis mansoni

This study investigates the possible use of pentoxifylline (PTX), with antifibrotic and anti-inflammatory properties, as adjuvant in treatment of schistosomal liver fibrosis through determination of some profibrogenic cytokines, oxidative stress and collagen deposition. Animals were classified into seven groups: normal control (i), Schistosoma mansoni-infected untreated (ii), infected treated with praziquantel (PZQ) curative, 1000mg/kg (iii) or sub curative, 200mg/kg dose (iv), infected treated with PTX alone (10mg/kg/day; 5days/wk) for 8weeks starting from the 2nd to the 10th week post infection (v), or in addition to curative (vi) or sub curative dose of PZQ (vii). Serum transforming growth factor-β1 (TGF-β1), tumor necrosis factor-α (TNF-α), matrix metalloproteinases-2 (MMP-2) and hepatic hydroxyproline (Hyp) content, glutathione related antioxidant enzymes and malondialdehyde (MDA) were determined. Results showed that S. mansoni infection produced remarkable elevations in the serum levels of TGF-β1, TNF-α, MMP-2 and the hepatic contents of Hyp, glutathione reductase (GR), MDA with significant reduction in reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and superoxide dismutase (SOD) when compared with their corresponding normal controls. Treatment of infected mice with PTX in addition to PZQ curative rather than its sub curative dose produced the best results evidenced by complete normalization in the previously mentioned serum and hepatic parameters.

CONCLUSION

PTX could attenuate liver fibrosis in early stages of S. mansoni infection through downregulation of profibrogenic cytokines, oxidative stress and collagen deposition.

Ursodeoxycholic acid dose-dependently improves liver injury in rats fed a methionine- and choline-deficient diet

AIM

  The data on the beneficial effect of ursodeoxycholic acid (UDCA) in non-alcoholic steatohepatitis (NASH) are controversial. The difference of opinion is connected with UDCA dosage to be used. Therefore, we evaluated the dose-dependent efficacy of UDCA in experimental NASH.

METHODS

  Male Wistar rats were fed the methionine- and choline-deficient (MCD) diet for 10 weeks. Rats were administrated UDCA (10, 20, 40 and 80 mg/kg bodyweight intragastrically) after 6 weeks of the MCD diet.

RESULTS

  Animals fed the MCD diet developed severe steatohepatitis. Treatment with UDCA dose-dependently decreased liver damage, but only high-dose UDCA (80 mg/kg) significantly diminished ultrastructural changes in addition to preventing steatosis, ballooning and inflammatory changes in the liver. The activities of serum marker enzymes and the content of liver triglyceride and blood glucose were increased in MCD diet-fed rats, but decreased in all the UDCA-treated groups. Serum insulin concentration was decreased whereas the quantitative insulin sensitivity check index did not changed in MCD diet-fed groups. Serum tumor necrosis factor-α content was strongly increased after MCD diet and normalized in the UDCA-treated rats, with the most pronounced effect in the highest dose groups, 40 and 80 mg/kg. The contents of endogenous ethanol in blood and intestinal mucus were increased in MCD diet-fed rats which were significantly lowered by UDCA (40 and 80 mg/kg per day).

CONCLUSION

  The present data demonstrate a beneficial effect of UDCA that manifested by the decrease of liver steatosis, inflammatory signs and serum tumor necrosis factor-α content especially of the highest 40 and 80 mg/kg day doses.

Monocyte chemoattractant protein-1 deficiency does not affect steatosis or inflammation in livers of mice fed a methionine-choline-deficient diet

Monocyte chemoattractant protein-1 (MCP-1, Ccl2) expression is increased in livers of patients with nonalcoholic steatohepatitis and in murine models of steatohepatitis. Several studies in rodents indicate that MCP-1 contributes to liver steatosis induced by feeding a high-fat diet. However, the extent of MCP-1 involvement in the widely utilized methionine-choline-deficient (MCD) diet model of steatohepatitis has not been determined. We tested the hypothesis that MCP-1 contributes to steatohepatitis in mice fed the MCD diet. MCP-1-deficient mice on a C57Bl/6J background and age-matched C57Bl/6J mice were fed either MCD diet or control diet for 4 weeks. MCP-1 deficiency did not affect steatohepatitis, as indicated by liver histopathology, nor did it affect serum alanine aminotransferase activity, hepatic triglyceride levels, hepatic inflammatory gene induction, or macrophage accumulation in mice fed the MCD diet. MCP-1 deficiency reduced the expression of the profibrogenic genes, pro-collagen 1a1, connective tissue growth factor, and transforming growth factor-β, in mice fed the MCD diet. MCP-1 deficiency significantly reduced collagen deposition and α-smooth muscle actin protein levels in the livers of mice fed the MCD diet. The results indicate that MCP-1 does not contribute to liver steatosis or inflammation in the MCD diet model of steatohepatitis. Rather, the data suggest that MCP-1 contributes to fibrosis in mice fed the MCD diet, independent of effects on steatosis and inflammation.

Teucrium polium reversed the MCD diet-induced liver injury in rats

In the present study, we evaluated the ability of Teucrium polium ethyl acetate fraction, with high antioxidant activity, in the treatment of nonalcoholic steatohepatitis (NASH) in rats and its possible effect on factors involved in pathogenesis of the disease. To induce NASH, a methionine and choline deficient (MCD) diet was given to N-Mary rats for 8 weeks. After NASH development, MCD-fed rats were divided into 2 groups: NASH group that received MCD diet and NASH + T group which was fed MCD diet plus ethyl acetate fraction of T. polium orally for 3 weeks. Histopathological evaluations revealed that treatment with the extract has abated the severity of NASH among the MCD-fed rats. In addition, the fraction reduced the elevated levels of hepatic tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β) gene expression and also the elevated level of malondialdehyde (MDA). In addition, the extract increased the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and enhanced the level of hepatic glutathione (GSH). Moreover, the fraction treatments lowered caspase-3 level and the phosphorylated form of C-Jun N-terminal kinase (JNK) and augmented the phosphorylated level of extracellular regulated kinase1/2 (ERK1/2). These results indicate that the ethyl acetate fraction of T. poium effectively reversed NASH, mainly due to its strong antioxidant and anti-inflammatory properties.

Pentoxifylline alleviates high-fat diet-induced non-alcoholic steatohepatitis and early atherosclerosis in rats by inhibiting AGE and RAGE expression

AIM

To investigate the expression of advanced glycation end products (AGEs) and their receptor RAGE in the livers and blood vessels of rats with non-alcoholic steatohepatitis (NASH) and the effect of pentoxifylline (PTX) on liver and artery function in rats with NASH.

METHODS

Sprague-Dawley rats were fed a high-fat diet for 12 weeks and given PTX by gavage for 4 weeks. The effects of PTX on hepatic liver and vessel function as well as the expression of AGE and RAGE in rats with NASH were assessed. The intima-media thickness (IMT) of the aorta and carotid artery was evaluated using ultrasonography.

RESULTS

Serum aspartic aminotransferase (AST) and blood levels of glucose (GLU) were reduced in the PTX group relative to the NASH group. The IMT of the aorta and carotid artery was increased in the NASH group compared with the control group. The IMT was reduced in NASH rats after treatment with PTX. Rats with NASH demonstrated higher AGE and RAGE protein levels in the liver and arteries compared with those of control rats. PTX treatment in NASH rats resulted in a decrease in AGE and RAGE protein levels in the liver and arteries compared with those in the NASH group.

CONCLUSION

Early atherosclerosis was observed in rats with NASH induced by a 16-week high-fat diet. High expression of AGE and RAGE in the livers and arteries of rats with NASH may contribute to the pathogenesis of NASH and early atherosclerosis. PTX showed protective effects on hepatic and arterial function, partially through inhibition of AGE and RAGE expression.

Hepatic lipotoxicity and the pathogenesis of nonalcoholic steatohepatitis: the central role of nontriglyceride fatty acid metabolites

A significant body of evidence now forces us to rethink the causes of NASH. Once thought to be a disease caused by triglyceride accumulation in hepatocytes with subsequent oxidant stress and lipid peroxidation causing inflammation and fibrosis, new data from animal studies and a limited number of human studies now provide convincing evidence that triglyceride accumulation does not cause insulin resistance or cellular injury in the liver. The lipotoxic liver injury hypothesis for the pathogenesis of NASH suggests that we need to focus our therapeutic efforts on reducing the burden of fatty acids going to the liver or being synthesized in the liver. This can be accomplished by improving insulin sensitivity at the level of adipose tissue to prevent inappropriate peripheral lipolysis and by preventing unnecessary de novo lipogenesis in the liver. Excess carbohydrates are the major substrates for de novo lipogenesis, and thus, reducing carbohydrate consumption through dietary changes and increasing muscle glucose uptake through exercise remain important cornerstones of treatment and prevention of lipotoxic liver injury, a disease hitherto called NASH.

Contribution of gut bacteria to liver pathobiology

Emerging evidence suggests a strong interaction between the gut microbiota and health and disease. The interactions of the gut microbiota and the liver have only recently been investigated in detail. Receiving approximately 70% of its blood supply from the intestinal venous outflow, the liver represents the first line of defense against gut-derived antigens and is equipped with a broad array of immune cells (i.e., macrophages, lymphocytes, natural killer cells, and dendritic cells) to accomplish this function. In the setting of tissue injury, whereby the liver is otherwise damaged (e.g., viral infection, toxin exposure, ischemic tissue damage, etc.), these same immune cell populations and their interactions with the infiltrating gut bacteria likely contribute to and promote these pathologies. The following paper will highlight recent studies investigating the relationship between the gut microbiota, liver biology, and pathobiology. Defining these connections will likely provide new targets for therapy or prevention of a wide variety of acute and chronic liver pathologies.

Whole-blood-free choline and choline metabolites in infants who require chronic parenteral nutrition therapy

BACKGROUND AND AIM

Choline deficiency is associated with hepatic dysfunction. Parenteral nutrition (PN) and lipid emulsions contain phosphatidylcholine (PtdCho) but insignificant free choline (FCho). PtdCho is sequentially degraded to glycerolphosphocholine (GPCho), phosphocholine (PCho), and finally to FCho. Biosynthesis of FCho may be insufficient during PN therapy. The aim of the study was to examine the status of FCho and related metabolites in infants on prolonged (> or =4 weeks) PN.

METHODS

Whole blood concentrations of FCho, PtdCho, GPCho, and PCho were measured and compared in infants on PN and infants on enteral feeds (controls).

RESULTS

Infants on PN (n = 14) had higher birth weight but same postnatal age as controls (n = 14) (mean +/- standard deviation) 8.3 +/- 3.9 versus 7.4 +/- 3.6 weeks. Parenteral nutrition was associated with increased PtdCho 1761 +/- 452 versus 1471 +/- 221 nmol/mL, P = 0.04. Mean whole blood FCho, GPCho, and PCho concentrations did not differ significantly in PN versus controls: 40.0 +/- 15.4 versus 50.8 +/- 49.7, 16.4 +/- 14.5 versus 25.2 +/- 29.3, and 15.3 +/- 13.5 versus 22.0 +/- 14.8 nmol/mL, respectively. However, PCho was positively correlated with GPCho in controls (r = 0.91, P < 0.01) but not PN (r = 0.24, P = NS), and infants receiving >90% of daily energy intake from PN (n = 6) had decreased PCho, 5.7 +/- 4.1 nmol/mL, compared with those receiving <90% of daily energy intake (n = 8) 22.5 +/- 13.7 nmol/mL, P < 0.05, and controls, 22.0 +/- 14.8 nmol/mL, P < 0.01.

CONCLUSIONS

Decreased whole-blood concentrations of choline suggest possible evidence of choline deficiency as illustrated by decreased whole-blood PCho. Choline supplementation should be investigated in infants who require prolonged PN, and whole-blood PCho can be used to monitor response.

Tissue factor-deficiency and protease activated receptor-1-deficiency reduce inflammation elicited by diet-induced steatohepatitis in mice

Altered hepatic lipid homeostasis, hepatocellular injury, and inflammation are features of nonalcoholic steatohepatitis, which contributes significantly to liver-related morbidity and mortality in the Western population. A collection of inflammatory mediators have been implicated in the pathogenesis of steatohepatitis in mouse models. However, the pathways essential for coordination and amplification of hepatic inflammation and injury caused by steatosis are not completely understood. We tested the hypothesis that tissue factor (TF)-dependent thrombin generation and the thrombin receptor protease activated receptor-1 (PAR-1) contribute to liver inflammation induced by steatosis in mice. Wild-type C57Bl/6J mice fed a diet deficient in methionine and choline for 2 weeks manifested steatohepatitis characterized by increased serum alanine aminotransferase activity, macrovesicular hepatic steatosis, hepatic inflammatory gene expression, and lobular inflammation. Steatohepatitis progression was associated with thrombin generation and hepatic fibrin deposition. Coagulation cascade activation was significantly reduced in low TF mice, which express 1% of normal TF levels. Hepatic triglyceride accumulation was not affected in low TF mice or PAR-1-deficient mice. In contrast, biomarkers of hepatocellular injury, inflammatory gene induction, and hepatic accumulation of macrophages and neutrophils were greatly reduced by TF-deficiency and PAR-1-deficiency. The results suggest that TF-dependent thrombin generation and activation of PAR-1 amplify hepatic inflammation and injury during the pathogenesis of steatohepatitis.

Pharmacologic therapy of non-alcoholic steatohepatitis

Specific therapy for non-alcoholic steatohepatitis (NASH) is needed because of the potential severity of this liver disease. NASH is a recognized cause of cryptogenic cirrhosis and, increasingly, of hepatocellular carcinoma. Therefore, there is an unmet medical need for the therapy of NASH. This article discusses this therapy, with particular emphasis on pharmacologic therapy.

Nutritional deficiencies in intestinal failure

Intestinal failure (IF) is the ultimate malabsorption state, with multiple causes, requiring long-term therapy with enteral or intravenous fluids and nutrient supplements. The primary goal during management of children with potentially reversible IF is to promote intestinal autonomy while supporting normal growth, nutrient status, and preventing complications from parenteral nutrition therapy. This article presents how an improved understanding of digestive pathophysiology is essential for diagnosis, successful management, and prevention of nutrient deficiencies in children with IF.

Genetic differences in oxidative stress and inflammatory responses to diet-induced obesity do not alter liver fibrosis in mice

OBJECTIVE

To determine how genetic factors might influence the progression of nonalcoholic fatty liver disease (NAFLD).

DESIGN/INTERVENTION

Beginning in adolescence, male C57BL6 (BL6) and 129/SVJ mice were fed control (n=15/group) or high-fat (HF) diets (n=30/group) for 6 months.

MAIN OUTCOME MEASURES

Assessed were body weight, insulin resistance, hepatic production of free radicals, expression of cytokines and fibrosis-related genes and severity of hepatic steatosis, injury and fibrosis.

RESULTS

High-fat diets induced comparable obesity, hepatic steatosis and insulin resistance in the two strains. Compared with BL6 mice, 129/SVJ mice had impaired induction of antioxidant genes, generated three- to four-fold more free radicals and exhibited two-fold greater induction of profibrogenic cytokines (interleukin-4 and transforming growth factor-beta1) and fibrosis-related genes (fibronectin and tissue inhibitor of metalloproteinase-1) (all P<0.05 for 129 vs BL6). Surprisingly, however, induction of collagen I alpha1 mRNA and accumulation of Sirius red-stained fibrils and hepatic hydroxyproline were similar in BL6 and 129/SVJ mice, and although patchy sinusoidal fibrosis emerged in both strains, neither developed bridging fibrosis.

CONCLUSIONS

Although BL6 and 129/SVJ mice with diet-induced obesity, insulin resistance and steatosis differed with respect to several factors that are thought to influence human NAFLD progression, they developed comparable liver fibrosis. Moreover, none of the risk factors for NAFLD-related cirrhosis in humans, including obesity, insulin resistance, chronic inflammatory and oxidant stress, steatohepatitis or activation of fibrogenic genes, proved to be sufficient to cause cirrhosis in these mice, even when exposure to one or more of these insults was very prolonged.

Adipocytokines and liver disease

Adipose tissue is a massive source of bioactive substances known as adipocytokines, including tumor necrosis factor (TNF)-alpha, resistin, leptin, and adiponectin. Recent advances in medical research view obesity as a chronic low-grade inflammatory state. Hypertrophied adipocytes in obesity release chemokines that induce macrophage accumulation in adipose tissue. Accumulated macrophages in obese adipose tissue produce proinflammatory cytokines and nitric oxide, and these inflammatory changes induce adipocytokine dysregulation. The latter is characterized by a decrease in insulinsensitizing and anti-inflammatory adipocytokines, and an increase in proinflammatory adipocytokines. Adipocytokine dysregulation induces obesity-related metabolic disorders, the so-called metabolic syndrome. Metabolic syndrome is a cluster of metabolic abnormalities, including diabetes mellitus, hypertension, hyperlipidemia, and nonalcoholic steatohepatitis (NASH). Recent studies have revealed that obesity is an independent risk factor for chronic liver diseases, such as NASH, alcoholic liver disease, chronic hepatitis C, and hepatocellular carcinoma. A common mechanism underlying these hepatic clinical states is thought to be adipocytokine dysregulation. In this review, we discuss the association of adipocytokines, especially leptin, adiponectin, TNF-alpha, and resistin, with liver diseases.

Polaprezinc attenuates liver fibrosis in a mouse model of non-alcoholic steatohepatitis

BACKGROUND AND AIM

The effect of polaprezinc, a zinc-carnosine chelate compound, on the development of non-alcoholic steatohepatitis (NASH) was investigated in dietary methionine and choline deficient (MCD) mice.

METHODS

Mice were fed the MCD diet with or without polaprezinc (2.2 g/kg diet) for 10 weeks. Liver histopathology, triglyceride and lipid peroxide levels, and the expression of genes linked to fibrosis were then assessed.

RESULTS

MCD mice developed steatohepatitis accompanied by mild fibrosis with an increase in lipid peroxidation, hepatic stellate cell (HSC) activation, and the augmented mRNA expression of tumor necrosis factor-alpha, transforming growth factor-beta1 and procollagen alpha1(I). The mRNA expression levels of matrix metalloproteinase (MMP)-2 and tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2 were also enhanced. Histopathologically, polaprezinc supplementation did not influence the development of steatosis but it apparently attenuated fibrosis. Polaprezinc slightly reduced lipid peroxidation and suppressed HSC activation as well as the mRNA expression of pro-inflammatory cytokines. Polaprezinc affected the MCD diet-enhanced expression of TIMP-1 even when administered relatively late.

CONCLUSION

These results suggest that polaprezinc attenuates fibrosis in NASH by reducing inflammation and lipid peroxidation and, during a later phase, promoting fibrolysis via the inhibition of TIMP expression in the liver. Further investigation is required to clarify the clinical efficacy of polaprezinc in patients with NASH.

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.

N-acetylcysteine attenuates progression of liver pathology in a rat model of nonalcoholic steatohepatitis

A "2-hit" model for nonalcoholic steatohepatitis (NASH) has been proposed in which steatosis constitutes the "first hit" and sensitizes the liver to potential "second hits" resulting in NASH. Oxidative stress is considered a candidate for the second hit. N-acetylcysteine (NAC), an antioxidant, has been suggested as a dietary therapy for NASH. We examined the effects of NAC in a rat total enteral nutrition (TEN) model where NASH develops as the result of overfeeding dietary polyunsaturated fat. Male Sprague-Dawley rats consumed pelleted AIN-93G diets ad libitum or were overfed a 9200 kJ.kg(-0.75).d(-1) liquid diet containing 70% corn oil with or without 2 g.kg(-1).d(-1) NAC i.g. for 65 d. Hepatic steatosis was not influenced by dietary supplementation with NAC; however, the liver pathology score was lower (P Collapse

Key Words

• steatosis
• oxidative stress
• lipid peroxidation
• tnf-α
• fibrosis

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MESH Headings

• Acetylcysteine/pharmacology
• Animals
• Autoantibodies/blood
• Disease Models, Animal
• Energy Intake
• Fatty Liver/immunology
• Fatty Liver/pathology
• Fatty Liver/physiopathology
• Fatty Liver/prevention & control
• Glutathione/metabolism
• Inflammation
• Liver/drug effects
• Liver/metabolism
• Liver/pathology
• Liver Function Tests
• Male
• Oxidative Stress
• Rats
• Rats, Sprague-Dawley
• Reverse Transcriptase Polymerase Chain Reaction
• Triglycerides/blood

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Grants

• R01 AA012819 NIAAA NIH HHS
• R01 AA012819-05 NIAAA NIH HHS
• R01 AA018282 NIAAA NIH HHS
• R01 AA 12819 NIAAA NIH HHS

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Affiliation(s)

January N. Baumgardner Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA Arkansas Children’s Nutrition Center, Little Rock, AR, 72202, USA
Kartik Shankar Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA Arkansas Children’s Nutrition Center, Little Rock, AR, 72202, USA
Leah Hennings Department of Pathology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
Emanuele Albano Department of Medical Sciences, University "Amedeo Avogadro" of East Piedmont, Via Solaroli, Novara, Italy
Thomas M. Badger Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA Arkansas Children’s Nutrition Center, Little Rock, AR, 72202, USA
Martin J. J. Ronis Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA Arkansas Children’s Nutrition Center, Little Rock, AR, 72202, USA

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Beyond insulin resistance: Innate immunity in nonalcoholic steatohepatitis

Obesity is an inflammatory disorder characterized by heightened activity of the innate immune system. Innate immune activation is central to the development of obesity-related insulin resistance; it also plays an important role in obesity-related tissue damage, such as that seen in atherosclerosis. Recent research has implicated the innate immune system in the pathophysiology of obesity-related liver disease. This review summarizes how innate immune processes, occurring both within and outside the liver, cause not only insulin resistance but also end-organ damage in the form of nonalcoholic fatty liver disease.

Weight loss, dietary advice and statin therapy in non-alcoholic fatty liver disease: a retrospective study

BACKGROUND

Studies have shown that weight loss can have a favourable effect upon non-alcoholic fatty liver disease (NAFLD). However, the most effective means of achieving weight loss and safety profile of lipid-lowering drugs in the presence of NAFLD is unknown.

AIM

To investigate the effect of dietary advice and lipid-lowering drugs, particularly statins, on patients with NAFLD and dyslipidaemia.

DESIGN

Observational records based study.

METHODS

We studied 71 patients with NAFLD and dyslipidaemia diagnosed and treated between 1996 and 2002 at University Hospital Lewisham. Some were referred to a dietician for weight loss advice as part of their management. After treatment all patients were assessed for changes in weight, serum alanine transaminase (ALT) and serum lipids including serum cholesterol, serum high density lipoprotein (HDL) and serum triglycerides.

RESULTS

Thirty-seven male and 34 female patients with NAFLD and dyslipidaemia were followed up for a mean period of 440 +/- 374 days (median 335). Regression analysis revealed a significant association between changes in weight and changes in serum ALT (p < 0.039). Dietary advice failed to reduce body weight but significantly lowered the serum cholesterol to HDL ratio (p = 0.05). Only 15.4% of patients taking statins experienced a rise in serum ALT > or = 40 U/l, and in each case the rise was transient, returning near baseline or below without discontinuation of statin treatment.

CONCLUSIONS

Weight loss appears to improve NAFLD, and dietary advice and lipid-lowering drugs may be beneficial for patients with NAFLD and dyslipidaemia even if weight loss is not achieved. Statins appear to be safe and efficacious in this group.

The treatment with antibody of TNF-alpha reduces the inflammation, necrosis and fibrosis in the non-alcoholic steatohepatitis induced by methionine- and choline-deficient diet

To assess the effects of anti-TNF-alpha antibody (infliximab) in experimental steatohepatitis induced by methionine- and choline-deficient (MCD) diet. The study included thirty rats. One group received normal rat food, and two groups received MCD diet. The treatment group received a single dose intra-peritoneal infliximab (4 mg/kg), at week 8. MCD diet increased levels of AST, ALT, TNF-alpha, TGF-beta(1), tissue and plasma MDA (p < 0.05 for each). Moreover, it led to steatosis, ballooning degeneration, inflammation, fibrosis and increased actin expression, histopathologically (p < 0.05 for each). In this experimental steatohepatitis anti-TNF-alpha antibody decreased the levels of AST, ALT, TGF-beta(1) and plasma and tissue MDA (p < 0.05 for each). Moreover, inflammation, necrosis, actin expression and fibrosis decreased in anti-TNF-alpha group compared to placebo group (p < 0.05 for each). This study indicates that anti-TNF-alpha antibody is effective on necrosis, inflammation and fibrosis in the experimental model of non-alcoholic steatohepatitis, induced by MCD diet.

Hypoadiponectinemia accelerates hepatic tumor formation in a nonalcoholic steatohepatitis mouse model

BACKGROUND/AIMS

Adipose tissue produces a number of adipocytokines, including adiponectin, leptin, and tumor necrosis factor-alpha. Obesity, which is associated with low plasma adiponectin levels, is an independent risk factor for various liver diseases including nonalcoholic steatohepatitis (NASH). The aim of this study was to examine the effects of adiponectin on the progression of NASH to cirrhosis and tumor formation using adiponectin-knockout (KO) mice.

METHODS

Using a choline-deficient L-amino acid-defined (CDAA) diet-induced mouse NASH model, liver histology and oxidative stress markers were investigated in KO and wild-type (WT) mice.

RESULTS

Hepatic steatosis was enhanced to a greater extent in KO mice, compared to WT mice after a 1-week CDAA diet. After 24 weeks, 6 out of 14 KO mice developed liver cirrhosis and hepatic tumors, whereas the 15 WT mice showed only simple steatosis. In KO mice, hepatic cytochrome P450 2E1 levels were upregulated, and markers of oxidative stress (thiobarbituric acid reactive substances, 8-hydroxydeoxyguanosine-positive cells) were significantly increased compared with WT mice.

CONCLUSIONS

Our results indicate that lack of adiponectin enhances the progression of hepatic steatosis, fibrosis, and hepatic tumor formation in an animal model of NASH. Hypoadiponectinemia in obesity could be a risk factor for NASH-related hepatic tumor formation.

Importance of cytokines, oxidative stress and expression of BCL-2 in the pathogenesis of non-alcoholic steatohepatitis

OBJECTIVE

Non-alcoholic steatohepatitis (NASH) is a form of chronic hepatitis. The pathogenesis of NASH has been dealt with in only a few studies and so it has not been clearly identified yet. The purpose of this study was to investigate the roles of TNF-alpha, TGF-beta, IL-6, IL-8, malondialdehyde (MDA), nitric oxide (NO) and the expression of Bcl-2 and Bax in the pathogenesis of NASH.

MATERIAL AND METHODS

The study included 92 patients, 57 of whom were diagnosed with biopsy-proven NASH, 13 with biopsy-proven hepatosteatosis and 22 with ultrasonography-diagnosed hepatosteatosis. Serum levels of TNF-alpha, TGF-beta, IL-6 and IL-8 were measured using the ELISA method. The plasma levels of NO were studied using the Griess method. Expressions of Bcl-2 and Bax were examined in paraffin blocks of liver biopsy materials by means of immunohistochemical-staining. MDA levels were measured using the thiobarbituric acid method.

RESULTS

No significant difference was found in the levels of TNF-alpha, TGF-beta, IL-6 or NO between the three groups (p>0.05). No difference was found in expression of Bcl-2 and expression of Bax between the biopsy-proven NASH and biopsy-proven hepatosteatosis groups (p>0.05). In the NASH group, the levels of IL-8 and MDA were found to be higher than those in the hepatosteatosis groups (p<0.05).

CONCLUSIONS

The elevated levels of MDA may indicate the relationship between oxidative stress and NASH. Furthermore, IL-8 was found to be higher in the NASH group than in the hepatosteatosis group, demonstrating the importance of inflammation in the pathogenesis of NASH.

Amelioration of steatohepatitis with pentoxifylline in a novel nonalcoholic steatohepatitis model induced by high-fat diet

We sought to evaluate the effects of pentoxifylline (PTX) on steatohepatitis in a novel experimental nonalcoholic steatohepatitis (NASH) model induced by a high-fat diet (HFD). Thirty-three male Sprague-Dawley rats were randomly divided into 3 groups. The first group received only standard rat diet (control group); groups 2 (placebo group) and 3 were given HFD, ad libitum. After week 4, 0.5 mL of physiologic serum was injected subcutaneously to the placebo group and 50 mg/kg/d PTX was given intraperitoneally to the third group (group PTX). After 6 weeks all rats were humanely killed. Serum biochemistry, tumor necrosis factor-alpha (TNF-alpha), plasma, and liver tissue malondialdehyde (MDA) were analyzed. Histopathologically, steatosis, ballooning degeneration, inflammation, and fibrosis were determined. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, plasma and liver tissue MDA, and plasma TNF-alpha levels were significantly higher in placebo group than in the control group. Tumor growth factor-beta levels, however, were comparable in the placebo and control groups. On histopathologic examination, steatosis, inflammatory cells per square millimeter, and ballooning degeneration were significantly higher in the placebo group than in the control group. No fibrosis or Mallory bodies were found in the placebo group. AST, ALT, plasma and liver tissue MDA, and plasma TNF-alpha levels were significantly lower in PTX group compared to the placebo group. Histopathologically, steatosis, mean number of inflammatory cells/mm(2) and ballooning degeneration in PTX group were also significantly lower than in the placebo group. In conclusion, PTX strikingly ameliorates steatohepatitis in this novel NASH model not only by inhibiting the TNF-alpha but also suppressing the oxidative stress markers.

Angiotensin II type 1 receptor blocker inhibits fibrosis in rat nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is now the most frequent cause of chronic liver impairment in developed countries and is a suggested causative factor in the development of cryptogenic cirrhosis and hepatocellular carcinoma. At present there is no effective and accepted therapy for NASH. The renin-angiotensin system is involved in hepatic fibrosis through activation of hepatic stellate cells, major fibrogenic cells in the liver. Hepatic stellate cells are activated by liver injury to express excessive matrix proteins and profibrogenic cytokines such as transforming growth factor-beta 1. Medicines that inhibit this pathway may be of therapeutic potential in NASH. Using a methionine-choline-deficient rat model of NASH, we studied the potential utility of an angiotensin II type 1 receptor blocker (ARB), olmesartan, on biochemical, histologic, and antioxidant measures of disease activity. ARB significantly attenuated increases in aspartate aminotransferase, activation of hepatic stellate cells, oxidative stress, expression of transforming growth factor-beta 1, expression of collagen genes, and liver fibrosis.

CONCLUSION

Our observations strongly suggest a potential preventive role for ARB in the progression of nonalcoholic steatohepatitis.

Effect of losartan on early liver fibrosis development in a rat model of nonalcoholic steatohepatitis

BACKGROUND AND AIM

Nonalcoholic steatohepatitis (NASH) is a metabolic disorder of the liver that may evolve into fibrosis or cirrhosis. Recent studies have shown reduction of experimental liver fibrosis with the use of angiotensin-converting-enzyme inhibitors or angiotensin-receptor antagonists. The aim of this study was to determine whether losartan can influence the early phase of fibrogenesis in an animal model of NASH.

METHODS

To induce NASH, a choline-deficient diet (CDD) was given to Sprague-Dawley rats for 12 weeks. These animals were then compared with a control group receiving choline-supplemented diet (CSD) and a group fed a CDD plus losartan (10 mg/kg/day). Biochemical (serum levels of alanine aminotransferase and aspartate aminotransferase) and histological evaluation of fatty liver was performed by conventional techniques. Hydroxyproline content in liver tissue was assayed by spectrophotometry. In addition, mRNA levels of procollagen I and transforming growth factor (TGF)-beta were assessed by semiquantitative RT-PCR and stellate cell activation by alpha-actin immunofluorescence stain.

RESULTS

After 12 weeks CDD induced a marked elevation of serum aminotranferases, a severe fatty liver infiltration with mild histological inflammation and fibrosis. These findings correlated with a significant increase in mRNA levels of both procollagen I and TGF-beta and significant increased liver hydroxyproline content. No differences were seen between rats receiving CDD alone and rats receiving CDD plus losartan with regard to the biochemical, morphological or molecular alterations induced by the CDD.

CONCLUSION

Losartan does not seem to influence liver injury and fibrogenic events in the CDD model of NASH.

A growing burden: the pathogenesis, investigation and management of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common hepatic disorder in western countries, and its incidence is increasing. This review outlines the significant health burden posed by NAFLD and discusses what is presently known about its pathogenesis, including the roles of the metabolic syndrome, obesity, insulin resistance, hepatic steatosis, reactive oxygen species, inflammatory cytokines and adipocytokines. The way in which NAFLD is clinically diagnosed is described, and areas of uncertainty surrounding its investigation are identified, before discussing the relative merits of the limited treatment options available and looking ahead to potential therapeutic strategies for the future.

Beneficial effects of pentoxifylline on hepatic steatosis, fibrosis and necroinflammation in patients with non-alcoholic steatohepatitis

BACKGROUND AND AIM

Inhibition of tumor necrosis factor (TNF)-alpha is a logical approach to manage patients with non-alcoholic steatohepatitis (NASH). Pentoxifylline reduces TNF-alpha and alanine aminotransferase (ALT) levels in patients with NASH. The aim of the present paper was to study if pentoxifylline can improve histological injury in patients with NASH.

METHODS

Nine patients (mean age 31.6 +/- 7.2 years) with histologically proven NASH and with persistently elevated ALT (>1.5 times) were given pentoxyfylline at a dosage of 400 mg t.i.d. for 12 months. Besides biochemical assessment, a repeat liver biopsy was performed and the degree of inflammation and fibrosis was compared.

RESULTS

After 12 months of therapy a significant reduction in ALT (111 +/- 53 IU/L vs 45 +/- 19 IU/L, P = 0.003) and aspartate aminotransferase (AST) (61 +/- 27 IU/L vs 33 +/- 12 IU/L, P = 0.005) levels was observed. Steatosis and lobular inflammation each reduced in 55% and six (67%) patients down-staged on Brunt's staging (P = 0.009). Four out of six patients with baseline fibrosis had reduction in their fibrosis stage.

CONCLUSIONS

Long-term pentoxyfylline therapy effectively achieves sustained biochemical improvement. This correlates well with histological resolution of the disease.

Pharmacodynamics of pentoxifylline and/or praziquantel in murine schistosomiasis mansoni

Pentoxifylline (PTX) was proved to exert both anti-inflammatory and anti-fibrotic effects, and was used therapeutically in this experimental model to investigate its role alone or with praziquantel (PZQ) in Schistosoma mansoni-infected mice, and to explore its impact on the tissue expression of transforming growth factor-beta1 (TGF-beta1). S. mansoni-infected mice were divided into seven groups: Control untreated (I), treated with curative dose of PZQ, 500 mg/kg/day for 2 consecutive days (II), or subcurative dose, 100 mg/kg/day for 2 consecutive days (III), treated with PTX (10 mg/kg/day for 5 days/wk) alone for 4 weeks (IV) or in addition to subcurative dose of PZQ (V), and treated with PTX alone for 8 weeks (VI) or in addition to subcurative dose of PZQ (VII). All animals were killed 10 weeks post infection. Parasitological assessment of worm burden, tissue egg load and oogram pattern was carried out. The degree of granulomatous fibrosis and eosinophilic cell population was quantified in Sirius-red-stained sections and tissue transforming growth factor beta-1 expression was estimated immunohistochemically. Serum ALAT and GGT, as well as hepatic content of reduced GSH, were measured. The results revealed the highest percent of worm reduction and dead ova in groups (II) and (VII) accompanied by significant diminution in granulomatous parameters, collagen content and TGF-beta1 tissue expression. Moreover, treatments with PTX and/or PZQ ameliorated the liver functions. In conclusion, prolonged treatment with PTX has a potent anti-fibrogenic role especially when used in the early stages of infection, with limited toxic effects on schistosome worms and eggs. Thus, PTX can be used as an adjuvant therapeutic tool with anti-helminthic drugs in the treatment of human schistosomiasis.

Lipoprotein lipase activator ameliorates the severity of dietary steatohepatitis

Dietary model of steatohepatitis was established by feeding mice a methionine choline deficient (MCD) diet. Mice on MCD or control diet for 3 weeks were treated with or without NO-1886, a newly synthetic lipoprotein lipase (LPL) activator. In a separate experiment, NO-1886 was given after pre-treatment with 3 weeks of MCD diet. NO-1886 significantly reduced MCD-induced inflammation by repressing levels of hepatic lipid peroxides and pro-inflammatory tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and cyclooxygenase-2 (COX-2). In addition, NO-1886 dampened hepatic steatosis via accelerating fatty acid oxidation caused by enhanced expression of PPARalpha, cytochrome P450-10 (Cyp4a10), and Acyl-CoA oxidase (ACO). It failed to regulate genes of fatty acid uptake and synthesis pathways. In conclusion, NO-1886 ameliorated and induced regression of experimental steatohepatitis via increasing endogenous LPL activation resulting in suppression on pro-inflammatory factors and reduction of hepatic fatty acids. These findings indicate that NO-1886 is a potential therapeutic agent for steatohepatitis.

Severe steatosis increases hepatocellular injury and impairs liver regeneration in a rat model of partial hepatectomy

OBJECTIVE

The aim of this study was to assess the influence of severe steatosis with inflammation on hepatocellular recovery after 70% hepatectomy in a rat model of diet-induced steatosis.

BACKGROUND

Patients with steatosis have an increased risk of inflammatory complications after liver resection. This might be attributable to Kupffer cell-mediated inflammation in steatotic livers causing progressive injury.

METHODS

Male Wistar rats were fed a standard methionine- and choline-deficient diet for 1 or 5 weeks. A 70% partial hepatectomy (PH) was performed, after which rats were killed at 24, 48, or 72 hours. The extent of steatosis and inflammation was determined by assessment of hepatic triglycerides, cytokine content, and histopathology. Outcome parameters were: liver regeneration (MIB-5 proliferation rate, mitotic index, and regenerating liver mass), hepatocellular injury (plasma aminotransferases, lipid peroxidation, histopathology, and apoptosis), Kupffer cell-mediated proinflammatory response (TNF-alpha, IL-1beta, IL-6, IL-10 in plasma and liver) and antioxidant content (total glutathione).

RESULTS

Methionine- and choline-deficient diet induced uncomplicated steatosis after 1 week (<30% hepatocytes affected without inflammation) and severe steatosis after 5 weeks (>60% hepatocytes affected, including prominent inflammation) as confirmed by histopathology. After PH, liver regeneration was impaired at all time points in the severe steatosis group as compared with the mild and control groups (P < 0.05). Hepatocellular injury was significantly increased in the severe steatosis group at all time points (P < 0.05). Kupffer cell-mediated inflammatory responses were aggravated in the severe steatosis group along with decreased antioxidant content (P < 0.05). Necrosis was the main type of cell death in severe steatotic livers compared with mainly apoptotic cell death in mild steatotic and normal livers.

CONCLUSION

Steatosis with prominent inflammation impaired liver regeneration probably because of increased hepatocellular lipid peroxidation and damage in concert with Kupffer cell-mediated proinflammatory responses. These results suggest an increased risk of performing extensive liver resection in the presence of severe steatosis.

Pathogenesis of NASH: animal models

The incidence of non-alcoholic steatohepatitis, a disorder linked to visceral adiposity, insulin resistance, dyslipidemia, and type 2 diabetes mellitus, is increasing with the rise in the prevalence of the metabolic syndrome. This review focuses on animal models of steatohepatitis currently used to study (1) the mechanisms regulating hepatic lipid, glucose, and cholesterol homeostasis and (2) inflammatory recruitment and fibrogenesis in the steatotic liver. The ultimate aim of this research is to gain insights into the role of hepatic lipid, inflammation, and fibrosis in human non-alcoholic fatty liver disease.

Quantitative trait loci analysis of mice administered the methionine-choline deficient dietary model of experimental steatohepatitis

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is a common disease with a poorly understood etiology, and the methionine-choline-deficient (MCD) diet is a nutritional model of NASH. Quantitative trait loci (QTL) analysis is a standard method for chromosomal mapping of polygenic disease traits. The purpose of this study is to administer mice an MCD diet in order to determine the strain-specific susceptibility for developing steatohepatitis, and to apply a computational methodology of QTL analysis to identify associated chromosomal susceptibility loci.

METHODS

Inbred mice were fed an MCD diet and alanine aminotransferase (ALT), hepatic triglycerides, liver weight, and weight loss were measured as phenotypic markers of steatohepatitis.

RESULTS

A/J mice developed the highest ALT and hepatic triglyceride levels. Using linear regression analysis, gene loci affecting serum ALT levels were identified on four chromosomes, and four loci that affect liver weight were also identified. In contrast, no QTLs for hepatic triglycerides or body weight were identified. Of note, loci for ALT and liver weight co-localized to proximal segments of chromosomes 2 and 15, in regions previously identified as QTLs for liver fibrosis.

CONCLUSIONS

These data indicate that experimental steatohepatitis is a polygenic disease with genes determining ALT, liver weight, and liver fibrosis.

New treatments for nonalcoholic fatty liver disease

The majority of patients with nonalcoholic fatty liver disease are overweight and obese, lead relatively sedentary lifestyles, and have underlying insulin resistance. Treatment aimed at improving body weight and activity should be the cornerstone of our therapeutic armamentarium in combating this disease. Evidence suggests that diets low in processed carbohydrates and saturated fats with a goal to achieve a 500- to 1000-calorie/day deficit improve insulin sensitivity, reduce serum aminotransferases, and decrease hepatic steatosis. Encouragingly, improvements are seen with as little as a 5% reduction in body weight. Histopathologic parameters of steatohepatitis also appear to improve with weight loss. Antioxidant supplementation, specifically with vitamin E, may be considered as adjunctive therapy. Other antioxidants and the thiazolidinediones (pioglitazone and rosiglitazone) appear to be efficacious, but larger confirmatory studies are needed to ensure they are safe and beneficial in patients with nonalcoholic steatohepatitis. Novel agents such as renin-angiotensin system inhibitors may eventually prove to be efficacious as well. Future treatment for patients failing to achieve weight loss goals is likely to consist of combination therapy targeting insulin resistance, oxidative stress, and fibrogenesis.

Effect of pentoxifylline on levels of pro-inflammatory cytokines during chronic hepatitis C

The cellular and humoral natural immune response induced by hepatitis C virus (HCV) is commonly unable to eradicate the virus. HCV is a highly mutable, hepatotropic RNA virus that causes acute and chronic hepatitis, an infection that involves the production of various cytokines. The aim of the study is to analyse the expression of pro-inflammatory cytokines IL-1beta, TNF-alpha, IFN-gamma and the chemokine CXCL8 (IL-8) in liver tissue and their expression and secretion in PBMC of patients with chronic hepatitis C (CHC), in response to pentoxyfilline (PTX). We studied six CHC patients, naive to treatment. Patients received PTX 400 mg twice a day/8 weeks. Pentoxyfilline resulted in decreased expression of mRNA of liver IL-1beta, TNF-alpha and IFN-gamma: 144.2 versus 83.5 molecules of IL-1beta (P < 0.05), TNF-alpha 194.3 versus 17.6 molecules (P = 0.03) and IFN-gamma 26.1 versus 0.5 molecules (P = 0.04). Following PTX, PBMC exhibited a decrease in IFN-gamma mRNA 12.2 versus 1.5 molecules (P = 0.028) and CXCL8 4.2 versus 2.5 molecules (P = 0.027). In PBMC, only the secretion of TNF-alpha was decreased 1109 versus 933.5 pg/ml, P = 0.046. Production of cytokines both locally (within the liver) and systemically (PBMC) may serve as biomarkers of the infection with hepatitis C. PTX inhibits the expression of several pro-inflammatory cytokines in the liver. These results indicate that it is worth exploring PTX in hepatitis in future clinical trials in nonresponders to antiviral treatment.

Mouse models in non-alcoholic fatty liver disease and steatohepatitis research

Non-alcoholic fatty liver disease (NAFLD) represents a histological spectrum of liver disease associated with obesity, diabetes and insulin resistance that extends from isolated steatosis to steatohepatitis and cirrhosis. As well as being a potential cause of progressive liver disease in its own right, steatosis has been shown to be an important cofactor in the pathogenesis of many other liver diseases. Animal models of NAFLD may be divided into two broad categories: those caused by genetic mutation and those with an acquired phenotype produced by dietary or pharmacological manipulation. The literature contains numerous different mouse models that exhibit histological evidence of hepatic steatosis or, more variably, steatohepatitis; however, few replicate the entire human phenotype. The genetic leptin-deficient (ob/ob) or leptin-resistant (db/db) mouse and the dietary methionine/choline-deficient model are used in the majority of published research. More recently, targeted gene disruption and the use of supra-nutritional diets to induce NAFLD have gained greater prominence as researchers have attempted to bridge the phenotype gap between the available models and the human disease. Using the physiological processes that underlie the pathogenesis and progression of NAFLD as a framework, we review the literature describing currently available mouse models of NAFLD, highlight the strengths and weaknesses of established models and describe the key findings that have furthered the understanding of disease pathogenesis.

Mice heterozygous for the Mdr2 gene demonstrate decreased PEMT activity and diminished steatohepatitis on the MCD diet

BACKGROUND/AIMS

The administration of a methionine and choline deficient (MCD) diet to mice serves as an animal model of NASH. The multidrug resistant 2 (Mdr2) P-glycoprotein encodes for the canalicular phospholipid transporter, and Mdr2 (+/-) mice secrete 40% less phosphatidylcholine than wild-type mice. We have hypothesized that phosphatidylethanolamine-N-methyl transferase (PEMT) up-regulation is a consequence of MCD diet administration, and is important for the pathogenesis of steatohepatitis in this model. However, the effect of decreased phosphatidylcholine secretion and modulation of PEMT on the development of diet-induced steatohepatitis in Mdr2 (+/-) mice has not been explored. Thus, the purpose of the study is to examine the effects of the MCD diet on Mdr2 (+/-) mice.

METHODS

Mdr2 (+/-) and Mdr2 (+/+) mice were treated with an MCD or control diet for up to 30 days, and the severity of steatohepatitis, PEMT activity and hepatic S-adenosylmethionine (SAM), and S-adenosylhomocysteine (SAH) levels were measured.

RESULTS

Serum ALT levels, hepatic inflammation, and PEMT activity were significantly lower, and hepatic SAM:SAH ratios were significantly higher in Mdr2 (+/-) mice at 7 and 30 days on the MCD diet.

CONCLUSIONS

Mdr2 (+/-) mice have diminished susceptibility to MCD diet-induced NASH, which is associated with a relative decrease in PEMT activity and increased SAM:SAH ratios.

Pathophysiological basis for antioxidant therapy in chronic liver disease

Oxidative stress is a common pathogenetic mechanism contributing to initiation and progression of hepatic damage in a variety of liver disorders. Cell damage occurs when there is an excess of reactive species derived from oxygen and nitrogen, or a defect of antioxidant molecules. Experimental research on the delicately regulated molecular strategies whereby cells control the balance between oxidant and antioxidant molecules has progressed in recent years. On the basis of this evidence, antioxidants represent a logical therapeutic strategy for the treatment of chronic liver disease. Clinical studies with large numbers of patients have not yet been performed. However, results from several pilot trials support this concept and indicate that it may be worth performing multicentre studies, particularly combining antioxidants with anti-inflammatory and/or antiviral therapy. Oxidative stress plays a pathogenetic role in liver diseases such as alcoholic liver disease, chronic viral hepatitis, autoimmune liver diseases and non-alcoholic steatohepatitis. The use of antioxidants (e.g. S-adenosylmethionine [SAMe; ademetionine], tocopherol [vitamin E], polyenylphosphatidylcholine or silymarin) has already shown promising results in some of these pathologies.

Mitochondrial dysfunction in NASH: causes, consequences and possible means to prevent it

Calorie-enriched diet and lack of exercise are causing a worldwide surge of obesity, insulin resistance and lipid accretion in liver (i.e. hepatic steatosis), which can lead to steatohepatitis. Steatosis and nonalcoholic steatohepatitis (NASH) can also be induced by drugs such as amiodarone, tamoxifen and some antiretroviral drugs, including stavudine and zidovudine. There is accumulating evidence that mitochondrial dysfunction (more particularly respiratory chain deficiency) plays a key role in the physiopathology of NASH whatever its initial cause. In contrast, the mitochondrial beta-oxidation of fatty acids can be either increased (as in insulin resistance-associated NASH) or decreased (as in drug-induced NASH). However, in both circumstances, generation of reactive oxygen species (ROS) by the damaged respiratory chain can be augmented. ROS generation in an environment enriched in lipids in turn induces lipid peroxidation which releases highly reactive aldehydic derivatives (e.g. malondialdehyde) that have diverse detrimental effects on hepatocytes and other hepatic cells. In hepatocytes, ROS, reactive nitrogen species and lipid peroxidation products further impair the respiratory chain, either directly or indirectly through oxidative damage to the mitochondrial genome. This consequently leads to the generation of more ROS and a vicious cycle occurs. Mitochondrial dysfunction can also lead to apoptosis or necrosis depending on the energy status of the cell. ROS and lipid peroxidation products also increase the generation of several cytokines (TNF-alpha, TGF-beta, Fas ligand) playing a key role in cell death, inflammation and fibrosis. Recent investigations have shown that some genetic polymorphisms can significantly increase the risk of steatohepatitis and that several drugs can prevent or even reverse NASH. Interestingly, most of these drugs could exert their beneficial effects by improving directly or indirectly mitochondrial function in liver. Finding a drug, which could fully prevent oxidative stress and mitochondrial dysfunction in NASH is a major challenge for the next decade.

Steatohepatitis develops rapidly in transgenic mice overexpressing Abcb11 and fed a methionine-choline-deficient diet

Nonalcoholic fatty liver disease is the most common reason for abnormal liver chemistries in the United States. The factors that lead from benign steatosis to nonalcoholic steatohepatitis are poorly understood. Transthyretin-Abcb11 (TTR-Abcb11) transgenic mice overexpress the bile salt transporter Abcb11 and hypersecrete biliary lipids. Thus the aim of this study is to employ feeding of the methionine-choline-deficient (MCD) diet to TTR-Abcb11 transgenic mice to further determine the mechanisms responsible for the development of steatohepatitis. FVB/NJ and TTR-Abcb11 mice were fed control or MCD diets for up to 30 days. Serum aminotransferase levels, serum and hepatic triglyceride content, cytokines, markers of oxidative stress, and expression of selective genes were examined. MCD diet-fed TTR-Abcb11, but not wild-type, mice have elevated serum aminotransferase levels when compared after 7 days. They also have significantly lower hepatic triglyceride levels at all time points studied. After 14 days on the MCD diet, TTR-Abcb11 mice have 3-fold increases in TNF-alpha mRNA and 3.9-fold increases in IL-6 mRNA compared with FVB/NJ mice. TTR-Abcb11 mice also had a greater increase in cytochrome P-450 2E1 expression. A greater decrease in sterol regulatory element binding protein-1c and fatty acid synthase mRNA expression was also seen in TTR-Abcb11 compared with wild-type mice fed an MCD diet. They also have enhanced TNF-alpha, IL-6, and cytochrome P-450 2E1 expression. We conclude that TTR-Abcb11 mice develop a more rapid hepatitis with less steatosis.