Rie Irie

Hepatic AdipoR2 signaling plays a protective role against progression of nonalcoholic steatohepatitis in mice

It is unclear how hepatic adiponectin resistance and sensitivity mediated by the adiponectin receptor, AdipoR2, contributes to the progression of nonalcoholic steatohepatitis (NASH). The aim of this study was to examine the roles of hepatic AdipoR2 in NASH, using an animal model. We fed C57BL/6 mice a methionine‐deficient and choline‐deficient (MCD) diet for up to 8 weeks and analyzed changes in liver pathology caused by either an AdipoR2 short hairpin RNA–expressing adenovirus or an AdipoR2‐overexpressing adenovirus. Inhibition of hepatic AdipoR2 expression aggravated the pathological state of NASH at all stages: fatty changes, inflammation, and fibrosis. In contrast, enhancement of AdipoR2 expression in the liver improved NASH at every stage, from the early stage to the progression of fibrosis. Inhibition of AdipoR2 signaling in the liver diminished hepatic peroxisome proliferator activated receptor (PPAR)‐α signaling, with decreased expression of acyl‐CoA oxidase (ACO) and catalase, leading to an increase in lipid peroxidation. Hepatic AdipoR2 overexpression had the opposite effect. Reactive oxygen species (ROS) accumulation in liver increases hepatic production of transforming growth factor (TGF)‐β1 at all stages of NASH; adiponectin/AdipoR2 signaling ameliorated TGF‐β–induced ROS accumulation in primary cultured hepatocytes, by enhancing PPAR‐α activity and catalase expression. Conclusion: The adiponectin resistance and sensitivity mediated by AdipoR2 in hepatocytes regulated steatohepatitis progression by changing PPAR‐α activity and ROS accumulation, a process in which TGF‐β signaling is implicated. Thus, the liver AdipoR2 signaling pathway could be a promising target in treating NASH. (HEPATOLOGY 2008;48:458–473.)

Free cholesterol accumulation in hepatic stellate cells: Mechanism of liver fibrosis aggravation in nonalcoholic steatohepatitis in mice

Although nonalcoholic steatohepatitis (NASH) is associated with hypercholesterolemia, the underlying mechanisms of this association have not been clarified. We aimed to elucidate the precise role of cholesterol in the pathophysiology of NASH. C57BL/6 mice were fed a control, high‐cholesterol (HC), methionine‐choline‐deficient (MCD), or MCD+HC diet for 12 weeks or a control, HC, high‐fat (HF), or HF+HC diet for 24 weeks. Increased cholesterol intake accelerated liver fibrosis in both the mouse models without affecting the degree of hepatocellular injury or Kupffer cell activation. The major causes of the accelerated liver fibrosis involved free cholesterol (FC) accumulation in hepatic stellate cells (HSCs), which increased Toll‐like receptor 4 protein (TLR4) levels through suppression of the endosomal‐lysosomal degradation pathway of TLR4, and thereby sensitized the cells to transforming growth factor (TGF)β‐induced activation by down‐regulating the expression of bone morphogenetic protein and activin membrane‐bound inhibitor. Mammalian‐cell cholesterol levels are regulated by way of a feedback mechanism mediated by sterol regulatory element‐binding protein 2 (SREBP2), maintaining cellular cholesterol homeostasis. Nevertheless, HSCs were sensitive to FC accumulation because the high intracellular expression ratio of SREBP cleavage‐activating protein (Scap) to insulin‐induced gene (Insig) disrupted the SREBP2‐mediated feedback regulation of cholesterol homeostasis in these cells. HSC activation subsequently enhanced the disruption of the feedback system by Insig‐1 down‐regulation. In addition, the suppression of peroxisome proliferator‐activated receptor γ signaling accompanying HSC activation enhanced both SREBP2 and microRNA‐33a signaling. Consequently, FC accumulation in HSCs increased and further sensitized these cells to TGFβ‐induced activation in a vicious cycle, leading to exaggerated liver fibrosis in NASH. Conclusion: These characteristic mechanisms of FC accumulation in HSCs are potential targets to treat liver fibrosis in liver diseases including NASH. (Hepatology 2014;58:154–169)

A High-Cholesterol Diet Exacerbates Liver Fibrosis in Mice via Accumulation of Free Cholesterol in Hepatic Stellate Cells

BACKGROUND & AIMS Some studies have indicated that dietary cholesterol has a role in the progression of liver fibrosis. We investigated the mechanisms by which dietary cholesterol might contribute to hepatic fibrogenesis. METHODS C57BL/6 mice were fed a high-cholesterol diet or a control diet for 4 weeks; liver fibrosis then was induced by bile-duct ligation or carbon tetrachloride administration. Hepatic stellate cells (HSCs) were isolated from mice fed high-cholesterol diets or from Niemann-Pick type C1-deficient mice, which accumulate intracellular free cholesterol. RESULTS After bile-duct ligation or carbon tetrachloride administration, mice fed high-cholesterol diets had significant increases in liver fibrosis and activation of HSCs compared with mice fed control diets. There were no significant differences in the degree of hepatocellular injury or liver inflammation, including hepatocyte apoptosis or Kupffer cell activation, between mice fed high-cholesterol or control diets. Levels of free cholesterol were much higher in HSCs from mice fed high-cholesterol diets than those fed control diets. In cultured HSCs, accumulation of free cholesterol in HSCs increased levels of Toll-like receptor 4 (TLR4), leading to down-regulation of bone morphogenetic protein and activin membrane-bound inhibitor (a pseudoreceptor for transforming growth factor [TGF]β); the HSCs became sensitized to TGFβ-induced activation. Liver fibrosis was not aggravated by the high-cholesterol diet in C3H/HeJ mice, which express a mutant form of TLR4; HSCs that express mutant TLR4 were not activated by accumulation of free cholesterol. CONCLUSIONS Dietary cholesterol aggravates liver fibrosis because free cholesterol accumulates in HSCs, leading to increased TLR4 signaling, down-regulation of bone morphogenetic protein and activin membrane-bound inhibitor, and sensitization of HSC to TGFβ. This pathway might be targeted by antifibrotic therapies.

p53/p66Shc-mediated signaling contributes to the progression of non-alcoholic steatohepatitis in humans and mice

BACKGROUND & AIMS The tumor suppressor p53 is a primary sensor of stressful stimuli, controlling a number of biologic processes. The aim of our study was to examine the roles of p53 in non-alcoholic steatohepatitis (NASH). METHODS Male wild type and p53-deficient mice were fed a methionine- and choline-deficient diet for 8 weeks to induce nutritional steatohepatitis. mRNA expression profiles in normal liver samples and liver samples from patients with non-alcoholic liver disease (NAFLD) were also evaluated. RESULTS Hepatic p53 and p66Shc signaling was enhanced in the mouse NASH model. p53 deficiency suppressed the enhanced p66Shc signaling, decreased hepatic lipid peroxidation and the number of apoptotic hepatocytes, and ameliorated progression of nutritional steatohepatitis. In primary cultured hepatocytes, transforming growth factor (TGF)-β treatment increased p53 and p66Shc signaling, leading to exaggerated reactive oxygen species (ROS) accumulation and apoptosis. Deficient p53 signaling inhibited TGF-β-induced p66Shc signaling, ROS accumulation, and hepatocyte apoptosis. Furthermore, expression levels of p53, p21, and p66Shc were significantly elevated in human NAFLD liver samples, compared with results obtained with normal liver samples. Among NAFLD patients, those with NASH had significantly higher hepatic expression levels of p53, p21, and p66Shc compared with the group with simple steatosis. A significant correlation between expression levels of p53 and p66Shc was observed. CONCLUSIONS p53 in hepatocytes regulates steatohepatitis progression by controlling p66Shc signaling, ROS levels, and apoptosis, all of which may be regulated by TGF-β. Moreover, p53/p66Shc signaling in the liver appears to be a promising target for the treatment of NASH.

Evaluating the severity of nonalcoholic steatohepatitis with superparamagnetic iron oxide-enhanced magnetic resonance imaging

To evaluate the utility of noninvasive assessment of human nonalcoholic fatty liver disease (NAFLD) patients using superparamagnetic iron oxide (SPIO)‐enhanced MRI.

Utility of quantitative 99mTc-phytate scintigraphy to diagnose early-stage non-alcoholic steatohepatitis

Objective. In patients with non-alcoholic fatty liver disease (NAFLD), liver biopsy remains the only reliable method to differentiate simple steatosis from non-alcoholic steatohepatitis (NASH). The objective of this study was to evaluate the efficacy of non-invasive 99mTc-phytate scintigraphy in the diagnosis of NASH. Material and methods. Thirty-seven patients with suspected NAFLD at the time of liver biopsy also underwent 99mTc-phytate scintigraphy. Signal intensities of regions of interest (ROI) in the liver, spleen, and heart were measured. We also examined scintigraphic features in a nutritional model of NASH in rats fed a methionine- and choline-deficient (MCD) diet. Results. The liver/spleen uptake ratio determined by scintigraphy was significantly decreased in patients with NASH in comparison with patients with simple steatosis. The liver/spleen ratio was an independent predictor distinguishing NASH from simple steatosis. The decrease was observed for all stages of NASH, including the early stage (stages 1 and 0). In animal studies, the liver/spleen uptake ratio was significantly decreased in rats after 8 weeks of MCD dietary feeding in comparison with control diet-fed rats. Conclusions. The non-invasive 99mTc-phytate scintigraphy test is a reliable tool to differentiate NASH from simple steatosis.

Primary malignant hepatic pheochromocytoma with negative adrenal scintigraphy

A 60-year-old male patient with hypertension was referred to our hospital because of insufficient blood pressure control (190/98 mmHg) and to rule out secondary hypertension. A computed tomography scan revealed no adrenal tumor but a large liver mass (5 × 5 cm), and magnetic resonance imaging showed a high signal intensity lesion on the T2-weighted image. Twenty-four hour urinary excretion of catecholamine metabolites was markedly increased, although a 123I-metaiodobenzyl guanidine (MIBG) scintigram failed to show accumulation in the hepatic mass, and no difference was noted between the catecholamine concentration in the tumor-drainage vein and that obtained from the vein draining from the non-tumor area. Liver biopsy did show features compatible with pheochromocytoma (i.e., chromogranin A–positive cells). Transcatheter arterial embolization of the liver tumor was conducted and resulted in a marked (50%) decrease in the 24-h urine normetanephrine excretion. Several metastatic foci were noted in the spinal bone and transcatheter arterial embolization (TAE) was also conducted with successful results. Thus, we experienced a case of primary malignant hepatic pheochromocytoma with negative 123I-MIBG scanning.

Discontinuation of Living Donor Liver Transplantation for PSC Due to Histological Abnormalities in Intraoperative Donor Liver Biopsy

Liver transplantation is the only curative treatment known to date for end‐stage liver disease occurring as a result of primary sclerosing cholangitis (PSC). Here, we report a case in which living donor liver transplantation (LDLT) for PSC was cancelled because of histological abnormalities in intraoperative biopsy of the donor liver. The donor was the mother of the recipient, and her preoperative evaluation revealed no abnormalities. In the donor operation, the donor liver biopsy revealed expansion of the portal zone with lymphocytic infiltration and dense concentric fibrosis developed around a bile duct. These histological findings were identical to those of early‐stage PSC; therefore, the LDLT was called off. The experience in this case suggests that preoperative liver biopsy may be useful to exclude first‐degree relative donors with potential PSC prior to LDLT for PSC.

A case of severe cholestatic jaundice with hyperthyroidism successfully treated with methimazole

Liver dysfunction is a common complication observed in patients with hyperthyroidism, however the dysfunction is always mild and obvious jaundice is rarely observed. We present the case of a 43-year-old man who suffered from hyperthyroidism complicated by severe jaundice. The jaundice likely occurred as a secondary consequence of cholestasis due to hyperthyroidism, since other causes such as drug-induced or autoimmune liver dysfunction were ruled out. Treatment with methimazole improved severe cholestatic jaundice in parallel with normalization of thyroid function. The mechanism of cholestasis as a secondary complication of hyperthyroidism has not been uncovered and there is no specific biochemical marker for cholestasis due to this hormonal disease at present. This case serves as a reminder that severe jaundice can be a manifestation of simple hyperthyroidism, and that administration of antithyroid drugs is an effective treatment for severe cholestatic jaundice in such cases.

Mediastinal Schwannoma Diagnosed Preoperatively as a Cyst

Mediastinal schwannomas are sometimes diagnosed as pericardial or bronchogenic cysts, if cystic degeneration is extensive. When mediastinal schwannomas are not diagnosed as primary cardiac tumors, the use of cardiopulmonary bypass in their resection appears to be infrequent. We report the case of a 48-year-old woman who presented with symptoms from a suspected intrapericardial cyst. Multiple diagnostic images revealed a large mass, potentially a proteinaceous or hemorrhagic cyst, in the transverse sinus behind the ascending aorta and against the left main trunk. After complete resection with the use of cardiopulmonary bypass, the mass was identified as a benign extracardiac schwannoma. More than 3 years postoperatively, the patient had no relevant symptoms. We discuss the preoperative diagnosis, the method of resection, and our broad strategy for dealing with such a case.