Kanji Yamaguchi

Inhibiting triglyceride synthesis improves hepatic steatosis but exacerbates liver damage and fibrosis in obese mice with nonalcoholic steatohepatitis

In the early stages of nonalcoholic fatty liver disease (NAFLD), triglycerides accumulate in hepatocytes. Diacylglycerol acyltransferase 2 (DGAT2) catalyzes the final step in hepatocyte triglyceride biosynthesis. DGAT2 antisense oligonucleotide (ASO) treatment improved hepatic steatosis dramatically in a previous study of obese mice. According to the 2‐hit hypothesis for progression of NAFLD, hepatic steatosis is a risk factor for nonalcoholic steatohepatitis (NASH) and fibrosis. To evaluate this hypothesis, we inhibited DGAT2 in a mouse model of NASH induced by a diet deficient in methionine and choline (MCD). Six‐week‐old genetically obese and diabetic male db/db mice were fed either the control or the MCD diet for 4 or 8 weeks. The MCD diet group was treated with either 25 mg/kg DGAT2 ASO or saline intraperitoneally twice weekly. Hepatic steatosis, injury, fibrosis, markers of lipid peroxidation/oxidant stress, and systemic insulin sensitivity were evaluated. Hepatic steatosis, necroinflammation, and fibrosis were increased in saline‐treated MCD diet–fed mice compared to controls. Treating MCD diet–fed mice with DGAT2 ASO for 4 and 8 weeks decreased hepatic steatosis, but increased hepatic free fatty acids, cytochrome P4502E1, markers of lipid peroxidation/oxidant stress, lobular necroinflammation, and fibrosis. Progression of liver damage occurred despite reduced hepatic expression of tumor necrosis factor alpha, increased serum adiponectin, and striking improvement in systemic insulin sensitivity. Conclusion: Results from this mouse model would suggest accumulation of triglycerides may be a protective mechanism to prevent progressive liver damage in NAFLD. (HEPATOLOGY 2007.)

p62, Upregulated during Preneoplasia, Induces Hepatocellular Carcinogenesis by Maintaining Survival of Stressed HCC-Initiating Cells

p62 is a ubiquitin-binding autophagy receptor and signaling protein that accumulates in premalignant liver diseases and most hepatocellular carcinomas (HCCs). Although p62 was proposed to participate in the formation of benign adenomas in autophagy-deficient livers, its role in HCC initiation was not explored. Here we show that p62 is necessary and sufficient for HCC induction in mice and that its high expression in non-tumor human liver predicts rapid HCC recurrence after curative ablation. High p62 expression is needed for activation of NRF2 and mTORC1, induction of c-Myc, and protection of HCC-initiating cells from oxidative stress-induced death.

Diacylglycerol acyltranferase 1 anti‐sense oligonucleotides reduce hepatic fibrosis in mice with nonalcoholic steatohepatitis

Retinyl ester (RE) stores decrease during hepatic stellate cell (HSC) activation and liver fibrosis. Although retinol esterification is mostly catalyzed by lecithin:retinol acyltransferase (LRAT), diacylglycerol acyltransferase (DGAT)1 also does this. In previous reports, LRAT−/− mice had reduced hepatic RE but neither excessive HSC activation nor liver fibrosis, and DGAT1−/− mice had increased liver levels of RE and retinol. We sought to clarify the role of DGAT1 in liver fibrosis. Expression of DGAT1/2 was compared by real time PCR in freshly isolated, primary mouse HSCs and hepatocytes. To induce nonalcoholic steatohepatitis (NASH) and liver fibrosis, adult male db/db mice were fed methionine choline–deficient (MCD) diets. Half were treated with DGAT1 antisense oligonucleotide (ASO); the rest were injected with saline. Results were compared with chow‐fed controls. Inhibition of DGAT1 in liver had no effect on hepatic triglyceride content or liver necroinflammation but reduced HSC activation and liver fibrosis in mice with NASH. To evaluate the role of DGAT1 in HSC activation, HSC were isolated from healthy rats treated with DGAT1 ASO or saline. DGAT1 was expressed at relatively high levels in HSCs. HSC isolated from DGAT1 ASO‐treated rats had reduced DGAT1 expression and increased messenger RNA (mRNA) levels of LRAT and cellular retinol binding protein‐1. During culture, they retained more vitamin A, had repressed collagen a2 (I) transcriptional activity, and expressed less collagen a1 (I) and a2 (I) mRNA. Conclusion: DGAT1 may be a therapeutic target in NASH because inhibiting DGAT1 favorably altered. HSC retinoid homeostasis and inhibited hepatic fibrosis in mice with NASH. (HEPATOLOGY 2007.)

Blockade of interleukin-6 signaling enhances hepatic steatosis but improves liver injury in methionine choline-deficient diet-fed mice.

Inflammatory processes have an important role in the development of hepatic steatosis and progression to nonalcoholic steatohepatitis (NASH). Interleukin-6 (IL-6) is known to be a proinflammatory cytokine, but also promotes liver regeneration and protects the liver against various forms of damage. The role of IL-6/Glycoprotein130 (GP130) in NASH remains unclear. In this study, we determined whether blocking IL-6/GP130 signaling prevents progression of steatohepatitis in a mouse NASH model. Six-week-old male C57/BL6 mice were fed either chow control or a methionine choline-deficient (MCD) diet for 8 weeks. Half of the MCD diet-fed mice were treated with 15 mg/kg rat anti-mouse IL-6 receptor antibody (MR16-1), intraperitoneally twice weekly, the remainder and chow-fed mice were injected with 15 mg/kg rat IgG as a control. Hepatic steatosis, injury, fibrosis, apoptosis, markers of lipid peroxidation/oxidant stress and IL-6-related gene expressions were evaluated. MR16-1 treatment decreased signal transducer and activator of transcription 3 activities and expression of suppressor of cytokine signaling 3 in MCD diet-treated mouse livers. Although this treatment enhanced intrahepatic lipid accumulation accompanied by increased sterol regulatory element-binding protein 1 and decreased peroxisome proliferator-activated receptor-α expression, elevated plasma alanine aminotransferase levels were improved with decreased plasma free fatty acid levels, lipid peroxidation/oxidant stress and hepatic apoptosis. Blocking IL-6/GP130 signaling by MR16-1 enhanced MCD diet-induced hepatic steatosis, but ameliorated liver injury. These findings suggest that hepatic IL-6 signaling has a protective role against the progression of hepatic steatosis but may enhance liver inflammation.

Association of gankyrin protein expression with early clinical stages and insulin-like growth factor-binding protein 5 expression in human hepatocellular carcinoma†

Gankyrin (also known as PSMD10) is a liver oncoprotein that interacts with multiple proteins including MDM2 and accelerates degradation of the tumor suppressors p53 and Rb. We produced a monoclonal anti‐gankyrin antibody and immunohistochemically assessed the clinicopathological significance of gankyrin overexpression in 43 specimens of human hepatocellular carcinoma (HCC). Specific cytoplasmic staining for gankyrin was observed in 62.8% (27/43) of HCCs, which was significantly associated with low TNM stage (P = 0.004), no capsular invasion (P = 0.018), no portal venous invasion (P = 0.008), and no intrahepatic metastasis (P = 0.012). The cumulative survival rate of patients with gankyrin‐positive HCC was significantly higher than that with gankyrin‐negative HCC (P = 0.037). p53 and MDM2 were positively stained by antibodies in 30.2% and 23.3%, respectively, of HCCs, but neither was inversely associated with gankyrin expression. In the Huh‐7 human HCC cell line, overexpression of gankyrin up‐regulated expression of insulin‐like growth factor binding protein 5 (IGFBP‐5), whereas suppression of gankyrin expression by siRNA down‐regulated it. Supression of IGFBP‐5 expression inhibited proliferation of Huh‐7 cells as well as U‐2 OS osteosarcoma cells. In HCC specimens, positive staining for IGFBP‐5 was observed by immunohistochemistry in 41.9% (18/43), and the level of expression was significantly correlated with that of gankyrin (rho = 0.629, P < 0.001). Conclusion: These results suggest that gankyrin plays an oncogenic role(s) mainly at the early stages of human hepatocarcinogenesis, and that IGFBP‐5 inducible by gankyrin overexpression may be involved in it. (HEPATOLOGY 2008.)

High expression of p300 in HCC predicts shortened overall survival in association with enhanced epithelial mesenchymal transition of HCC cells

P300 impacts the transcription of several genes involved in biological behavior of human malignancies including hepatocellular carcinomas (HCC). We found p300 is highly expressed in 47% of surgically resected HCC specimens by immunohistochemistry, which correlated with advanced TNM staging (P = 0.034), vascular invasion (P = 0.036), intrahepatic metastasis (P = 0.001) and shortened overall survival (P = 0.028). In vitro study, knocking down of p300 expression in hepatoma cells recovered E-cadherin expression, inhibited the translocation of beta (β)-catenin into the nuclei, decreased cyclin D1 activity and suppressed the migration/invasion of HCC cells. Furthermore, suppression of p300 led to down-regulation of epithelial-mesenchymal transition (EMT)-related molecules such as Snail, Twist and HIF-1 alpha. These observations suggest that p300 contributes to the EMT-related progression of HCCs.

Ciliated hepatic foregut cyst: A report of one case and a review of the literature

We encountered a patient with a ciliated hepatic foregut cyst (CHFC), which is an uncommon cystic lesion of the liver and hard to distinguish from malignant tumor in imaging features. Cases of CHFC are very rare, five cases were reported in the 19th century and 53 cases in the 20th century. The histogenesis of CHFC is still unclear, but most authors consider that it could arise from the embryonic foregut. A few cases of CHFC mimicking neoplasm were reported. When the diagnosis of CHFC was obtained by fine needle aspiration, close follow-up is necessary in order to find early malignant change.

Fatty liver induced by free radicals and lipid peroxidation

Abstract An excessive accumulation of fat in the liver leads to chronic liver injury such as non-alcoholic fatty liver disease (NAFLD), which is an important medical problem affecting many populations worldwide. Oxidative stress has been implicated in the pathogenesis of NAFLD, but the exact nature of active species and the underlying mechanisms have not been elucidated. It was previously found that the administration of free radical-generating azo compound to mice induced accumulation of fat droplet in the liver. The present study was performed aiming at elucidating the changes of lipid classes and fatty acid composition and also measuring the levels of lipid peroxidation products in the liver induced by azo compound administration to mouse. The effects of azo compound on the liver were compared with those induced by high fat diet, a well-established cause of NAFLD. Azo compounds given to mice either by intraperitoneal administration or by dissolving to drinking water induced triacylglycerol (TG) increase and concomitant phospholipid decrease in the liver, whose pattern was quite similar to that induced by high fat diet. Lipid peroxidation products such as hydroxyoctadecadienoic acid and hydroxyeicosatetraenoic acid were increased in the liver in association with the increase in TG. These results show that free radicals as well as high fat diet induce fatty liver by similar mechanisms, in which lipid peroxidation may be involved.

Blockade of IL-6 signaling exacerbates liver injury and suppresses antiapoptotic gene expression in methionine choline-deficient diet-Fed db/db mice

Our previous study revealed that blockade of interleukin-6 (IL-6)–STAT3 signaling ameliorated liver injury, although hepatic STAT3−/− or GP130−/− mice have been reported to develop severe liver injury, in a murine methionine choline deficient (MCD) diet-induced model of non-alcoholic steatohepatitis (NASH). In this study, to determine whether profound blockade of IL-6–STAT3 signaling may still ameliorate liver injury, we studied db/db mice, which have impaired leptin-mediated STAT3 activation, using the MCD diet-induced NASH model. Male lean and db/db mice (6 weeks old) were fed either control chow or an MCD diet for 8 or 12 weeks. Half of the mice were treated with 15 mg/kg rat anti-mouse IL-6 receptor neutralizing antibody (MR16-1) intraperitoneally twice weekly, the remainder were injected with 15 mg/kg rat IgG as a control. Hepatic steatosis, injury, fibrosis, markers of lipid peroxidation/oxidant stress and antiapoptotic gene expression were evaluated. Plasma IL-6 levels were elevated in all groups of db/db mice. Although hepatic IL-6/ GP130 signaling was activated in chow-fed db/db mice, this was suppressed in MCD diet-fed db/db mice, accompanied by downregulation of hepatic IL-6 receptor and GP130 mRNA expression. MR16-1 treatment of MCD diet-fed db/db mice further repressed STAT3 activities and expression of STAT3-related antiapoptotic genes, such as Bcl-2 and Ref-1, but increased plasma-free fatty acid and hepatic markers of lipid peroxidation/oxidant stress, leading to increased liver injury, hepatocyte apoptosis and liver fibrosis. Although ‘moderate’ blockade of enhanced IL-6–STAT3 signaling may be beneficial in NASH, as we reported previously, these findings demonstrate that a profound defect in STAT3 activation is detrimental in terms of liver injury, hepatocyte apoptosis and liver fibrosis, indicating the hepato-protective role of IL-6 signaling in this severe NASH model.

Lower levels of insulin‐like growth factor‐1 standard deviation score are associated with histological severity of non‐alcoholic fatty liver disease

Growth hormone (GH) deficiency may be associated with histological progression of non‐alcoholic fatty liver disease (NAFLD) which includes non‐alcoholic fatty liver (NAFL) and non‐alcoholic steatohepatitis (NASH). Insulin‐like growth factor 1 (IGF‐1) is mainly produced by hepatocytes and its secretion is stimulated by GH. Our aim was to determine whether more histologically advanced NAFLD is associated with low circulating levels of IGF‐1 in Japanese patients.