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.     

Rodent nutritional model of steatohepatitis: Effects of endotoxin (lipopolysaccharide) and tumor necrosis factor alpha deficiency

Background and Aims: Intestinal endotoxin (lipopolysaccharide) is thought to contribute to liver injury in both alcoholic and nonalcoholic steatohepatitis (NASH). Tumor necrosis factor alpha (TNFα) is an important mediator of this process and is considered central to the inflammatory response in NASH. This study aimed to investigate the effects of lipopolysaccharide on liver injury in the methionine choline deficient (MCD) nutritional model of NASH, and to determine if TNFα is required for the development of steatohepatitis in this model. Method: Male C57/BL6 mice received a MCD diet for 4 weeks, whilst a control group received an identical diet supplemented with 0.2% choline bitartrate and 0.3% methionine. At 4 weeks, mice received either an intraperitoneal injection of lipopolysaccharide (0.5 µg/g body mass) or sterile saline, and were killed 24 h thereafter. In a separate study, TNFα knockout and wild type C57BL/6 mice received either MCD or control diets for 4 weeks. Serum transaminase levels, liver histology (steatosis, inflammation and apoptosis), hepatic triglyceride concentration and hepatic lipid peroxidation products (conjugated dienes, lipid hydroperoxides and thiobarbituric reactive substances, free and total) were evaluated. Results: Intraperitoneal administration of lipopolysaccharide augmented serum alanine aminotransferase (ALT) levels (P < 0.02), hepatic inflammation (P < 0.025), apoptosis (P < 0.01) and free thiobarbituric acid reactive substances (P < 0.025) in MCD mice. TNFα knockout mice fed the MCD diet developed steatohepatitis with histological and biochemical changes similar to those seen in wild type counterparts. Conclusions: Lipopolysaccharide augments liver injury in MCD mice, and TNFα is not required for the development of steatohepatitis in MCD mice.     

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.     

改良蛋氨酸胆碱缺乏饮食喂养的非酒精性脂肪性肝炎大鼠模型的建立

目的:观察改良蛋氨酸胆碱缺乏饮食(MCD)建立的脂肪性肝炎大鼠模型肝脏的脂肪变性和炎症情况.方法:大鼠26只随机分为4组,分别喂养MCD饮食和胆碱添加饮食(CS).3-8wk后处死,肝脏标本在甲醛中固定和石蜡包埋.HE染色和Masson染色后对脂肪变性、炎症和纤维化进行评分.血清ALT,AST,CH,LDL等指标通过生化分析仪进行测定.结果:MCD喂养组3wk可以看见肝脂肪变性和炎症,肝指数显著增加,ALT和AST显著升高,8wk可见纤维形成.结论:可通过改良的蛋氨酸胆碱缺乏(MCD)饮食建立非酒精性脂肪肝动物模型.     

血红素加氧酶-1在非酒精性脂肪性肝炎进展中的作用

目的 探讨血红素加氧酶-1(HO-1)在非洒精性脂肪性肝炎进展中的作用及其机制.方法 选用健康雄性C57BL/6J小鼠,采用胆碱-蛋氨酸缺乏饮食(MCD)4周建立小鼠非酒精性脂肪性肝炎模型,以胆碱-蛋氨酸充足饮食设立对照组,并以MCD加HO-1激动剂血晶素或抑制剂锌原卟啉进行干预实验.小鼠血清ALT和AST采用全自动生化仪酶法测定.HE染色观察肝脂肪变、炎症活动及纤维化程度;逆转录聚合酶链反应和Western blot检测HO-1、肿瘤坏死因子(TNF)α和白细胞介素(IL)-6 mRNA及其蛋白的表达.结果 MCD喂养小鼠血清ALT及AST明显异常,出现中～重度肝细胞脂肪变性,伴有点状和灶状肝细胞坏死、炎性细胞浸润、轻度汇管区纤维组织增生及窦周纤维化;HO-1、TNF α和IL-6 mRNA及其蛋白的表达较对照组显著增强,相对表达量分别为1.13±0.11、1.74±0.05,0.20±0.01、1.92±0.10,0.58±0.02、2.06±0.05对比0.43±0.02、0.75±0.05,0.08±0.00、0.59±0.02,0.22±0.01、0.91±0.02(P＜0.01);应用血晶素小鼠随肝脏HO-1 mRNA及其蛋白表达的上调及TNF α和IL-6 mRNA及其蛋白表达的下调(P＜0.01),肝脂肪变及炎症活动度均显著减轻;而应用锌原卟啉小鼠,肝脏HO-1 mRNA及蛋白表达明显受抑制,TNF α和IL-6 mRNA及蛋白表达则明显增强(P＜0.01),肝脂肪变及炎症亦随之显著加重.结论 抗氧化基因HO-1靶向性激活可阻止非酒精性脂肪性肝炎的发生及进展.     

Rodent nutritional model of non-alcoholic steatohepatitis: species, strain and sex difference studies

BACKGROUND AND AIM: The methionine choline-deficient (MCD) diet leads to steatohepatitis in rodents. The aim of the present study was to investigate species, strain and sex differences in this nutritional model of non-alcoholic steatohepatitis (NASH). METHODS: Male and female Wistar, Long-Evans and Sprague-Dawley rats, and C57/BL6 mice (n = 6 per group) were fed a MCD diet for 4 weeks. Control groups received an identical diet supplemented with choline bitartrate (0.2% w/w) and methionine (0.3% w/w). Liver pathology (steatosis and inflammation) and ultrastructure, liver lipid profile (total lipids, triglycerides, lipid peroxidation products), liver : body mass ratios and serum alanine aminotransferase (ALT) levels were compared between these groups. RESULTS: The MCD diet-fed male rats developed greater steatosis (P < 0.001), had higher liver lipid content (P < 0.05) and had higher serum ALT levels (P < 0.005) than did female rats. Wistar rats (both sexes) had higher liver lipid levels (P < 0.05), serum ALT levels (P < 0.05), and liver mass : body mass ratios (P < 0.025) than did Long-Evans and Sprague-Dawley rats. In female groups, Wistar rats showed greater fatty change than did the other two strains (P < 0.05). All rats fed the MCD diet developed hepatic steatosis, but necrosis and inflammation were minor features and fibrosis was absent. Compared with Wistar rats, male C57/BL6 mice showed a marked increase in inflammatory foci (P < 0.001), end products of lipid peroxidation (free thiobarbituric acid reactive substances) (P < 0.005), and mitochondrial injury, while showing less steatosis (P < 0.005), lower hepatic triglyceride levels, (P < 0.005) and lower early lipid peroxidation products (conjugated dienes and lipid hydroperoxides; P < 0.005 and P < 0.01, respectively). CONCLUSIONS: The Wistar strain and the male sex are associated with the greatest degree of steatosis in rats subjected to the MCD diet. Of the groups studied, male C57/BL6 mice develop the most inflammation and necrosis, lipid peroxidation, and ultrastructural injury, and best approximate the histological features of NASH.     

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‐α, transforming growth factor‐β1 and procollagen α1(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.     

Tumour necrosis factor alpha signalling through activation of Kupffer cells plays an essential role in liver fibrosis of non-alcoholic steatohepatitis in mice

BACKGROUND: While tumour necrosis factor alpha (TNF-alpha) appears to be associated with the development of non-alcoholic steatohepatitis (NASH), its precise role in the pathogenesis of NASH is not well understood. METHODS: Male mice deficient in both TNF receptors 1 (TNFR1) and 2 (TNFR2) (TNFRDKO mice) and wild-type mice were fed a methionine and choline deficient (MCD) diet or a control diet for eight weeks, maintaining isoenergetic intake. RESULTS: MCD dietary feeding of TNFRDKO mice for eight weeks resulted in attenuated liver steatosis and fibrosis compared with control wild-type mice. In the liver, the number of activated hepatic Kupffer cells recruited was significantly decreased in TNFRDKO mice after MCD dietary feeding. In addition, hepatic induction of TNF-alpha, vascular cell adhesion molecule 1, and intracellular adhesion molecule 1 was significantly suppressed in TNFRDKO mice. While in control animals MCD dietary feeding dramatically increased mRNA expression of tissue inhibitor of metalloproteinase 1 (TIMP-1) in both whole liver and hepatic stellate cells, concomitant with enhanced activation of hepatic stellate cells, both factors were significantly lower in TNFRDKO mice. In primary cultures, TNF-alpha administration enhanced TIMP-1 mRNA expression in activated hepatic stellate cells and suppressed apoptotic induction in activated hepatic stellate cells. Inhibition of TNF induced TIMP-1 upregulation by TIMP-1 specific siRNA reversed the apoptotic suppression seen in hepatic stellate cells. CONCLUSIONS: Enhancement of the TNF-alpha/TNFR mediated signalling pathway via activation of Kupffer cells in an autocrine or paracrine manner may be critically involved in the pathogenesis of liver fibrosis in this NASH animal model.     

壳脂胶囊对NASH小鼠肝组织血红素氧合酶-1表达的影响

目的观察壳脂胶囊对非酒精性脂肪性肝炎小鼠肝组织血红素氧合酶-1（HO-1）表达的影响。方法将C57 BL/6J小鼠20只随机分为对照组（采用蛋氨酸-胆碱充足饮食喂养）、模型组[给予高脂、蛋氨酸-胆碱缺乏（MCD）饮食喂养]、壳脂胶囊治疗组和自然恢复组。8周末检测血清转氨酶、瘦素水平,并观察肝组织脂肪变、炎症活动及纤维化程度;定量检测肝组织HO-1 mRNA的表达。结果治疗组动物肝脂肪变及炎症程度较模型组明显减轻,血清瘦素水平和肝组织HO-1表达较模型组明显降低（P〈0.05）。结论在高脂、胆碱-蛋氨酸缺乏饮食诱导的NASH小鼠,壳脂胶囊可降低肝组织HO-1表达,阻止NASH的发生发展。     

Fas基因突变在非酒精性脂肪性肝炎发病中的作用

目的 探讨Fas基因突变在非酒精性脂肪性肝炎发生、发展中的作用。方法 选用健康雄性野生型及Fas基因突变C57BL/6J小鼠,以高脂、胆碱-蛋氨酸缺乏饮食喂养3周建立小鼠非酒精性脂肪性肝炎模型,分别作为野生型小鼠模型组和Fas基因突变小鼠模型组,以胆碱-蛋氨酸充足饮食喂养两种小鼠分别设立野生型小鼠对照组和Fas基因突变小鼠对照组。检测血清ALT、AST、甘油三酯、总胆固醇水平;观察肝组织脂肪变、炎症活动及纤维化程度;用实时定量RT-PCR检测肝组织增殖细胞核抗原和转化生长因子β 1 mRNA的表达,免疫组织化学染色检测肝组织增殖细胞核抗原和转化生长因子β 1蛋白质表达情况。多组样本均数间差异比较用单因素方差分析,组间比较用LSD-t检验。结果 野生型小鼠模型组及Fas基因突变小鼠模型组血清ALT水平均较其对照组明显升高,分别为(126.33±10.50) U/L比(25.00±10.14) U/L、(160.33±48.29) U/L比(18.33±9.08) U/L,组间比较,t值分别为12.02、5.08,P值均＜0.01,差异均有统计学意义;两种模型组小鼠ALT水平比较,P＞0.05,差异无统计学意义;各组小鼠AST、甘油三酯、总胆固醇水平差异均无统计学意义（P值均＞0.05）。野生型小鼠模型组出现大泡性肝细胞脂肪变性,伴有点状和灶状肝细胞坏死、炎性细胞浸润、轻度汇管区纤维组织增生及窦周纤维化,肝组织增殖细胞核抗原、转化生长因子β 1 mRNA表达较对照组显著增强,相对表达量分别为2.84±0.73、2.77±0.54比1.31±0.18、0.89±0.18,组间比较,t值分别为4.99、8.08,P值均＜0.01,差异均有统计学意义;Fas基因突变小鼠模型组肝脂肪变及炎症、纤维化程度均较Fas基因突变小鼠对照组及野生型小鼠模型组明显加重,肝组织增殖细胞核抗原、转化生长因子p 1 mRNA表达较其对照组及野生型模型组显著增强,相对表达量分别为5.57±1.13比1.04±0.16、2.84±0.73和5.73±0.89比0.85±0.11、2.77±0.54,t值分别为10.15、5.33和13.19、6.91,P值均＜0.01 ;蛋白质表达变化趋势与mRNA变化一致。结论 Fas基因突变可诱导或加剧肝细胞损伤,促进非酒精性脂肪性肝炎的发生及进展。     

罗格列酮阻止非酒精性脂肪性肝纤维化进展作用机制的研究

目的观察PPARγ靶向性激动剂罗格列酮对高脂、蛋氨酸-胆碱缺乏（MCD）饮食诱导的非酒精性脂肪性肝纤维化模型肝组织中转化生长因子（TGFβ1）及其下游效应因子结缔组织生长因子（CTGF）表达的影响，以明确其阻止脂肪性肝纤维化进展的作用及作用机制。方法采用MCD饮食8周建立C57BL6／J小鼠非酒精性脂肪性肝纤维化模型，以蛋氨酸-胆碱充足饮食设立对照组，干预组小鼠采用MCD饮食加罗格列酮（每日50mg／kg）喂养。血清丙氨酸氨基转移酶（ALT）采用全自动生化仪测定。HE染色、Masson染色观察肝脂肪变、炎症及纤维化程度。TGFβ1、CTGFmRNA及蛋白表达分别应用RT—PCR、免疫组织化学染色方法检测。结果模型组肝组织出现重度肝细胞脂肪变，伴有点、灶状肝细胞坏死及炎细胞浸润、汇管区纤维组织增生及窦周纤维化，ALT水平和TGFβ1、CTGFmRNA及蛋白表达均较对照组明显升高（P〈0．05和P值均〈0．01），罗格列酮干预组肝组织学改变较模型组明显减轻，ALT水平及TGFβ1、CTGF表达明显下降（P值均〈0．05）。结论在MCD饮食诱导的小鼠非酒精性脂肪性肝纤维化模型中，罗格列酮可通过靶向激活PPARγ下调TGFβ1及其下游效应因子CTGF表达，从而缓解或阻止疾病的进展。     

蛋氨酸-胆碱缺乏饮食诱导的非酒精性脂肪性肝炎小鼠模型的建立及动态监测

目的:研究蛋氨酸.胆碱缺乏(MCD)饮食诱导的非酒精性脂肪性肝炎(NASH)小鼠肝脏脂肪变性及炎症发生、发展的病理特点.方法:将40只C57/BL6小鼠随机分成2组,分别喂养MCD饮食(模型组)和对照蛋氨酸-胆碱充足(MCS)饮食(空白组),于造模的第1-5周动态连续取材,小鼠血清ALT、AST、TG及肝TG等生化指标...     

Hydrogen-rich water prevents progression of nonalcoholic steatohepatitis and accompanying hepatocarcinogenesis in mice

Oxidative stress is a strong contributor to the progression from simple fatty liver to nonalcoholic steatohepatitis (NASH). Molecular hydrogen is an effective antioxidant that reduces cytotoxic reactive oxygen species. In this study, we investigated the effects of hydrogen-rich water and the drug pioglitazone on the progression of NASH in mouse models. A methionine-choline-deficient (MCD) diet mouse model was prepared. Mice were divided into three experimental groups and fed for 8 weeks as follows: (1) MCD diet + control water (CW group); (2) MCD diet + hydrogen-rich water (HW group); and (3) MCD diet mixed with pioglitazone (PGZ group). Plasma alanine aminotransferase levels, hepatic expression of tumor necrosis factor-α, interleukin-6, fatty acid synthesis-related genes, oxidative stress biomarker 8-hydroxydeoxyguanosine (8-OHdG), and apoptosis marker terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL)-positive cells in the liver were decreased in the HW and PGZ groups. The HW group showed a smaller decrease in hepatic cholesterol; however, stronger antioxidative effects in serum and lower peroxisome proliferator-activated receptor-α expression in the liver were seen in comparison with the PGZ group. We then investigated the effects of hydrogen in the prevention of hepatocarcinogenesis in STAM mice, known as the NASH-related hepatocarcinogenesis model. Eight-week-old male STAM mice were divided into three experimental groups as follows: (1) control water (CW-STAM); (2) hydrogen-rich water (HW-STAM); and (3) pioglitazone (PGZ-STAM). After 8 weeks, hepatic tumors were evaluated. The number of tumors was significantly lower in the HW-STAM and PGZ-STAM groups than in the CW-STAM group. The maximum tumor size was smaller in the HW-STAM group than in the other groups. Conclusion: Consumption of hydrogen-rich water may be an effective treatment for NASH by reducing hepatic oxidative stress, apoptosis, inflammation, and hepatocarcinogenesis. (HEPATOLOGY 2012;56:912-921).     

Sitagliptin attenuates methionine/choline-deficient diet-induced steatohepatitis

Aims

Accumulating evidence suggests that inhibitors of dipeptidyl peptidase-4 (DPP-4), such as sitagliptin, may play an important role in the prevention of non-alcoholic steatohepatitis (NASH). This study was conducted to elucidate whether sitagliptin could prevent steatohepatitis by inhibiting pathways involved in hepatic steatosis, inflammation, and fibrosis.

Methods

C57BL/6 mice were fed a methionine/choline-deficient (MCD) diet with or without supplement with sitagliptin for 5 weeks. Liver and adipose tissue from mice were examined histologically and immunohistochemically to estimate the effect of sitagliptin on the development of NASH.

Results

Supplementation with sitagliptin resulted in significant improvement of MCD diet-induced fat accumulation in the liver. In addition, sitagliptin treatment lowered fatty acid uptake, expression of VLDL receptor and hepatic triglyceride content. Sitagliptin also effectively attenuated MCD diet-induced hepatic inflammation, endoplasmic reticulum (ER) stress, and liver injury, as evidenced by reduced proinflammatory cytokine levels, ER stress markers, and TUNEL staining. Expression of CYP2E1 and 4NHE were strongly increased by the MCD diet, but this effect was successfully prevented by sitagliptin treatment. Furthermore, sitagliptin significantly decreased levels of MCD diet-induced fibrosis-associated proteins such as fibronectin and α-SMA in the liver. Inflammatory and atrophic changes of adipose tissue by MCD diet were restored by sitagliptin treatment.

Conclusions

Sitagliptin attenuated MCD diet-induced hepatic steatosis, inflammation, and fibrosis in mice through amelioration of mechanisms responsible for the development of NASH, including CD36 expression, NF-κB activation, ER stress, CYP2E1 expression, and lipid peroxidation. Treatment with sitagliptin may represent an effective approach for the prevention and treatment of NASH.     

Hepatic gene expression profile associated with non-alcoholic steatohepatitis protection by S-nitroso-N-acetylcysteine in ob/ob mice

BACKGROUND/AIMS: To understand the molecular mechanisms underlying non-alcoholic steatohepatitis (NASH) prevention by S-nitroso-N-acetylcysteine (SNAC), an NO donor that inhibits lipid peroxidation, we examined hepatic differentially expressed genes between ob/ob mice receiving or not SNAC treatment concomitantly with a methionine-choline deficient (MCD) diet. METHODS: Ob/ob mice were assigned to receive oral SNAC fed solution (MCD+SNAC group) or vehicle (MCD group) by gavage. After four weeks, histopathological analysis and microarray hybridizations were conducted in liver tissues from groups. GeneSifter system was used to identify differentially expressed genes and pathways according to Gene Ontology. RESULTS: NASH was absent in the MCD+SNAC group and no significant changes in food intake or body weight were observed in comparison to MCD group. After SNAC treatment, several genes belonging to oxidative phosphorylation, fatty acid biosynthesis, fatty acid metabolism and glutathione metabolism pathways were down-regulated in comparison to the MCD group. CONCLUSIONS: SNAC treatment promotes down regulation of several genes from fatty acid (FA) metabolism related pathways, possibly through abrogation of the cytotoxic effects of reactive oxygen species and lipid peroxides with consequent prevention of mitochondrial overload. Further studies are required to investigate the clinical implications of these findings, in attempt to develop novel therapeutic strategies for NAFLD treatment.     

Adiponectin prevents progression of steatohepatitis in mice by regulating oxidative stress and Kupffer cell phenotype polarization

Aim:  We reported previously that hypoadiponectinemia enhances hepatic oxidative stress and accelerates progression of nonalcoholic steatohepatitis (NASH) in mice. However, the precise mechanism and preventive effects of adiponectin on NASH remain unclear. The aim of this study was to examine the effects of adiponectin on steatohepatitis using adiponectin-knockout (KO) mice and adenovirus-mediated adiponectin expression system.
Methods:  We used male KO mice and C57BL6/J (WT) mice fed methionine choline-deficient (MCD)-diet as a steatohepatitis model. Liver histology, hepatic oxidative stress markers, and hepatic gene expression levels were investigated. In addition, Hepa 1–6 cells, a mouse liver cell line, were cultured with or without recombinant adiponectin, and gene expressions were investigated by real-time RT-PCR.
Results:  After 2-week feeding of MCD diet, hepatic steatosis was enhanced and plasma alanine aminotransferase elevated in KO mice than in WT mice. In KO mice liver, thiobarbituric acid reactive substances increased, glutathione levels decreased, and mRNA expression levels of antioxidant enzymes (catalase, superoxide dismutase-1) downregulated. Adenovirus-mediated adiponectin expression prevented these changes in KO mice. Moreover, Kupffer cell infiltration was enhanced and mRNA levels of anti-inflammatory M2 macrophage markers (interleukin-10, arginase-1) were decreased in KO mice liver. In the in vitro study, adiponectin significantly increased catalase gene expression in Hepa 1–6 cells.
Conclusions:  Lack of adiponectin enhanced, and adiponectin administration prevented steatohepatitis progression in mice. These changes were due to the anti-oxidative effects of adiponectin, and its effects on Kupffer cells recruitment and phenotype polarization. Augmentation of adiponectin effects could be a useful preventive approach for NASH progression.     

MCD-induced steatohepatitis is associated with hepatic adiponectin resistance and adipogenic transformation of hepatocytes

BACKGROUND/AIMS: In these studies, we tested the hypothesis that increased lipid intake would exacerbate the severity of nutritional steatohepatitis. METHODS: C57Bl/6J mice were fed methionine-and-choline deficient (MCD) diets containing 20% (high) or 5% (low) fat by weight for 3 weeks and compared to lipid-matched controls. RESULTS: MCD feeding increased serum ALT levels and induced hepatic steatosis, lobular inflammation and ballooning degeneration of hepatocytes, irrespective of dietary fat content. Hepatic triglyceride accumulation was similar between high and low-fat MCD-fed mice, but lipoperoxide levels were approximately 3-fold higher in the high-fat MCD-fed animals. Serum adiponectin levels increased in MCD-fed mice, although to a lesser extent in high-fat fed animals. AMPK phosphorylation was correspondingly increased in muscle of MCD-fed mice, but hepatic AMPK phosphorylation decreased, and there was little evidence of PPARalpha activation, suggesting impaired adiponectin action in the livers of MCD-fed animals. Hepatocyte PPARgamma mRNA levels increased in MCD-fed mice, and were associated with increased aP2 expression, indicating adipogenic transformation of hepatocytes. CONCLUSIONS: Increased dietary lipid intake did not alter steatohepatitis severity in MCD-fed mice despite increased lipoperoxide accumulation. Instead, steatohepatitis was associated with impaired hepatic adiponectin action, and adipogenic transformation of hepatocytes in both low and high-fat MCD-fed mice.     

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-α (TNF-α), 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-α levels were significantly higher in placebo group than in the control group. Tumor growth factor-β 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-α levels were significantly lower in PTX group compared to the placebo group. Histopathologically, steatosis, mean number of inflammatory cells/mm² 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-α but also suppressing the oxidative stress markers.