Hisao Ezaki

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.

Estrogen deficiency worsens steatohepatitis in mice fed high-fat and high-cholesterol diet.

Recent studies indicate an accelerated progression of nonalcoholic steatohepatitis (NASH) in postmenopausal women. Hypercholesterolemia, an important risk factor for NASH progression, is often observed after menopause. This study examined the effects of estrogen on NASH in ovariectomized (OVX) mice fed a high-fat and high-cholesterol (HFHC) diet. To investigate the effects of estrogen deficiency, OVX mice and sham-operated (SO) mice were fed normal chow or HFHC diet for 6 wk. Next, to investigate the effects of exogenous estrogen replenishment, OVX mice fed with HFHC diet were treated with implanted hormone release pellets (containing 17β-estradiol or placebo vehicle) for 6 wk. OVX mice on the HFHC diet showed enhanced liver injury with increased liver macrophage infiltration and elevated serum cholesterol levels compared with SO-HFHC mice. Hepatocyte monocyte chemoattractant protein-1 (MCP1) protein expression in OVX-HFHC mice was also enhanced compared with SO-HFHC mice. In addition, hepatic inflammatory gene expressions, including monocytes chemokine (C-C motif) receptor 2 (CCR2), were significantly elevated in OVX-HFHC mice. Estrogen treatment improved serum cholesterol levels, liver injury, macrophage infiltration, and inflammatory gene expressions in OVX-HFHC mice. Moreover, the elevated expression of liver CCR2 and MCP1 were decreased by estrogen treatment in OVX-HFHC mice, whereas low-density lipoprotein dose dependently enhanced CCR2 expression in THP1 monocytes. Our study demonstrated that estrogen deficiency accelerated NASH progression in OVX mice fed HFHC diet and that this effect was improved by estrogen therapy. Hypercholesterolemia in postmenopausal women would be a potential risk factor for NASH progression.

Delayed liver regeneration after partial hepatectomy in adiponectin knockout mice.

We previously demonstrated that adiponectin has anti-fibrogenic and anti-inflammatory effects in the liver of mouse models of various liver diseases. However, its role in liver regeneration remains unclear. The aim of this study was to determine the role of adiponectin in liver regeneration. We assessed liver regeneration after partial hepatectomy in wild-type (WT) and adiponectin knockout (KO) mice. We analyzed DNA replication and various signaling pathways involved in cell proliferation and metabolism. Adiponectin KO mice exhibited delayed DNA replication and increased lipid accumulation in the regenerating liver. The expression levels of peroxisome proliferator-activated receptor (PPAR) alpha and carnitine palmitoyltransferase-1 (CPT-1), a key enzyme in mitochondrial fatty acid oxidation, were decreased in adiponectin KO mice, suggesting possible contribution of altered fat metabolism to these phenomena. Collectively, the present results highlight a new role for adiponectin in the process of liver regeneration.

Serum Mac‐2 binding protein levels as a novel diagnostic biomarker for prediction of disease severity and nonalcoholic steatohepatitis

Mac‐2 binding protein (Mac‐2bp) is one of the major fucosylated glycoproteins, which we identified with glycol‐proteomic analyses. We previously reported that fucosylated glycoproteins are secreted into bile, but scarcely secreted into sera in normal liver and hypothesized that the fucosylation‐based sorting machinery would be disrupted in ballooning hepatocytes due to the loss of cellular polarity. In the present study, we investigated the availability of Mac‐2bp for differential diagnosis of nonalcoholic steatohepatitis (NASH) from nonalcoholic fatty liver disease (NAFLD) as a biomarker.

Serum Fucosylated Haptoglobin as a Novel Diagnostic Biomarker for Predicting Hepatocyte Ballooning and Nonalcoholic Steatohepatitis.

Nonalcoholic fatty liver disease (NAFLD) is a growing medical problem around the world. NAFLD patients with nonalcoholic steatohepatitis (NASH) can develop cirrhosis and hepatocellular carcinoma. The ability to distinguish NASH from simple steatosis would be of great clinical significance. Ballooning hepatocytes are characteristic of typical pathological NASH; here, the polarized secretion of proteins is disrupted due to destruction of the cytoskeleton. We previously reported that fucosylated glycoproteins are secreted into bile, but not into sera in normal liver. Therefore, we hypothesized that the fucosylation-based sorting machinery would be disrupted in ballooning hepatocytes, and serum fucosylated glycoproteins would increase in NASH patients. To confirm our hypothesis, we evaluated serum fucosylated haptoglobin (Fuc-Hpt) levels in biopsy-proven NAFLD patients (n = 126) using a lectin-antibody ELISA kit. Fuc-Hpt levels were significantly increased in NASH patients compared with non-NASH (NAFLD patients without NASH) patients. Interestingly, Fuc-Hpt levels showed a significant stepwise increase with increasing hepatocyte ballooning scores. Multiple logistic regression analysis showed that Fuc-Hpt levels were independent and significant determinants of the presence of ballooning hepatocytes. Moreover, Fuc-Hpt levels were useful in monitoring liver fibrosis staging. Next, to investigate the significance of serum Fuc-Hpt in a larger population, we measured Fuc-Hpt levels in ultrasound-diagnosed NAFLD subjects (n = 870) who received a medical health checkup. To evaluate NAFLD disease severity, we used the FIB-4 index (based on age, serum AST and ALT levels, and platelet counts). Fuc-Hpt levels increased stepwise with increasing FIB-4 index. Conclusion Measurement of serum Fuc-Hpt levels can distinguish NASH from non-NASH patients, and predict the presence of ballooning hepatocytes in NAFLD patients with sufficient accuracy. These results support the potential usefulness of measuring Fuc-Hpt levels in clinical practice.

Conditional loss of heparin-binding EGF-like growth factor results in enhanced liver fibrosis after bile duct ligation in mice.

Our aims were to evaluate the involvement of heparin-binding EGF-like growth factor (HB-EGF) in liver fibrogenesis of humans and mice and to elucidate the effect of HB-EGF deficiency on cholestatic liver fibrosis using conditional HB-EGF knockout (KO) mice. We first demonstrated that gene expression of HB-EGF had a positive significant correlation with that of collagen in human fibrotic livers, and was increased in bile duct ligation (BDL)-induced fibrotic livers in mouse. We then generated conditional HB-EGF knockout (KO) mice using the interferon inducible Mx-1 promoter driven Cre recombinase transgene and wild type (WT) and KO mice were subjected to BDL. After BDL, KO mice exhibited enhanced liver fibrosis with increased expression of collagen, compared with WT mice. Finally, we used mouse hepatic stellate cells (HSCs) to examine the role of HB-EGF in the activation of these cells and showed that HB-EGF antagonized TGF-β-induced gene expression of collagen in mouse primary HSCs. Interestingly, HB-EGF did not prevent the TGF-β-induced nuclear accumulation of Smad3, but did lead to stabilization of the Smad transcriptional co-repressor TG-interacting factor. In conclusion, our data suggest a possible protective role of HB-EGF in cholestatic liver fibrosis.

Secreted frizzled-related protein 5 (Sfrp5) decreases hepatic stellate cell activation and liver fibrosis

Obesity‐related adipocytokine dysregulation is known to accelerate liver fibrosis progression. Recently, a natural Wnt5a inhibitor, secreted frizzled‐related protein 5 (Sfrp5), was identified as a novel adipocytokine that has reduced expression in obese adipose tissue in both rodents and human. In addition, hepatic gene expression of Wnt5a and its receptor frizzled 2 (Fz2) is elevated during fibrosis progression. Therefore, Sfrp5 could have biological significance in liver fibrosis.

Adiponectin negatively correlates with alcoholic and non‐alcoholic liver dysfunction: Health check‐up study of Japanese men

Aim:  Central obesity, insulin resistance and alcohol consumption are thought to be major risk factors for fatty liver formation. Adiponectin (APN) prevents fatty liver formation, and its serum levels are lower in subjects with central obesity and/or insulin resistance. The aim of this study was to explore the association among serum APN levels, central obesity, insulin resistance and liver dysfunction with or without fatty liver classified by alcohol consumption in healthy subjects.

Pitavastatin ameliorated the progression of steatohepatitis in ovariectomized mice fed a high fat and high cholesterol diet

Many studies indicate an accelerated progression of non‐alcoholic steatohepatitis (NASH) in postmenopausal women. Very recently, we reported that estrogen deficiency enhanced the progression of steatohepatitis in mice fed a high fat and high cholesterol (HFHC) diet. Hypercholesterolemia is often observed in postmenopausal women, and recent studies indicate it to be an important risk factor for the progression of NASH. Statins can slow NASH progression in the estrogen‐deficient state but the precise mechanisms of their effects are still unclear.

Conditional knockout of heparin-binding epidermal growth factor-like growth factor in the liver accelerates carbon tetrachloride-induced liver injury in mice

Aim:  We previously demonstrated that heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) is induced in response to several liver injuries. Because the HB‐EGF knockout (KO) mice die in utero or immediately after birth due to cardiac defects, the loss of function study in vivo is limited. Here, we generated liver‐specific HB‐EGF conditional knockout mice using the interferon‐inducible Mx‐1 promoter driven cre recombinase transgene and investigated its role during acute liver injury.