Munechika Enjoji

Liver X receptor in cooperation with SREBP-1c is a major lipid synthesis regulator in nonalcoholic fatty liver disease

Aim:  Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent causes of liver dysfunction and its incidence has increased markedly. However, the mechanisms involved in the pathogenesis of NAFLD in humans have not been thoroughly investigated. Sterol regulatory element binding protein (SREBP)‐1c and carbohydrate responsive element binding protein (ChREBP) are transcriptional factors that regulate the expression of lipogenic genes, including acetyl‐CoA carboxylases (ACCs) and fatty acid synthase (FAS). SREBP‐1c and ChREBP are transactivated by liver X receptor (LXR), a nuclear receptor that regulates the metabolism of cholesterol and fatty acids. To understand the mechanisms involved in the pathogenesis of NAFLD, we investigated the transcriptional factors and lipogenic genes activated in the liver with NAFLD.

Nutritional investigation of non-obese patients with non-alcoholic fatty liver disease: the significance of dietary cholesterol.

Objective. The onset and progression of non-alcoholic fatty liver disease (NAFLD) seem to be affected by nutritive intake; however, detailed examinations have not been performed in non-obese NAFLD patients. The purpose of this study was to identify potential nutritive factors that affect NAFLD and its related nutritional problems. Material and methods. We investigated the distribution of abdominal fat, dietary intake, and biochemical data in patients with NAFLD and compared non-obese with obese patients. Results. There was no significant difference in the percentage of patients with diabetes or dyslipidemia between the obese and non-obese groups. Waist circumference, total abdominal fat levels, and subcutaneous fat levels were significantly higher in the obese group, while visceral fat levels were not significantly different between the two groups. Immunoreactive insulin (IRI) and homeostasis model assessment-insulin resistance (HOMA-IR) were significantly lower in the non-obese group, suggesting that the non-obese patients were not overtly insulin resistant. Although serum adiponectin and TNF-α levels were similar in both groups, leptin levels were significantly higher in the obese group. Total energy and carbohydrate intake tended to be higher in the obese group. A characteristic feature was that dietary cholesterol intake was significantly higher, while the intake of polyunsaturated fatty acids (PUFAs) was significantly lower in the non-obese group. Conclusions. In non-obese NAFLD patients: 1) although visceral fat was increased, insulin resistance and/or dysregulated secretion of adipocytokines was not necessarily shown; 2) intakes of total energy and carbohydrates were not excessive, although dietary cholesterol was superabundant and dietary PUFAs were significantly lower compared with those in obese patients; and 3) characteristic fat intake may be associated with the formation of NAFLD.

A p160ROCK-specific inhibitor, Y-27632, attenuates rat hepatic stellate cell growth

BACKGROUND/AIMS p160ROCK, a serine/threonine protein kinase, is a direct RhoA target mediating RhoA-induced assembly of focal adhesions and stress fibers. Recently, Rho signaling pathways were reported to play an important role in the activation of rat hepatic stellate cells (HSC). The aim of this study was to investigate the mechanism of action of a p160ROCK-specific inhibitor, Y-27632, on cultured rat HSC. METHODS HSC were isolated from normal rat livers and cultured on fibronectin-coated dishes. The cell morphology and actin cytoskeleton were studied with phase contrast and fluorescence microscopy, respectively. Immunoblot analysis was used to examine phosphorylation of focal adhesion kinase and extracellular signal-regulated kinase, and the expression of cell cycle-associated proteins. HSC proliferation was measured by quantitating the percentage of cells that exhibited nuclear incorporation of 5-bromodeoxyuridine. Type I collagen gene expression and accumulation in HSC culture media were evaluated by Northern blot and enzyme-linked immunosorbent assay, respectively. RESULTS Y-27632 consistently blocked cell spreading and suppressed RhoA-induced formation of stress fibers in HSC. In addition, Y-27632 inhibited phosphorylation of focal adhesion kinase and extracellular signal-regulated kinase. Cells treated with Y-27632 failed to proliferate, in contrast to untreated spread cells. This shape-dependent block in cell proliferation correlated with a failure to increase cyclin D1 protein level and to down-regulate the cell cycle inhibitor p27. Y-27632 decreased type I collagen gene expression and accumulation in HSC culture media. CONCLUSIONS Our findings indicate that p160ROCK-mediated actin stress fiber assembly is involved in the pathophysiology of hepatic fibrogenesis and suggest that inhibitors of the RhoA-ROCK pathway might be useful therapeutically in liver fibrogenesis.

Short-term intensive treatment for donors with hepatic steatosis in living-donor liver transplantation.

Background. The use of steatotic livers is associated with increased primary nonfunction in liver transplantation. To reduce the risk of liver injury, we applied a short-term combination therapy of diet, exercise and drugs for 11 living-donor liver transplantation (LDLT) candidates with steatosis. Methods. Subjects were treated with a protein-rich (1000 kcal/day) diet, exercise (600 kcal/day), and bezafibrate (400 mg/day) for 2–8 weeks. Results. The treatment significantly improved macrovesicular steatosis (30±4% vs. 12±2% [mean±SEM], P= 0.0028). Body weight and BMI were significantly reduced (73.7±3.2 kg vs. 66.9±2.9 kg, P=0.0033, 26.4±0.7 kg/m2 vs. 24.1±0.8 kg/m2, P=0.0033). The treatment completely normalized liver function tests and lipid metabolism. Seven treated liver grafts (left lobe) were transplanted to the recipients. We compared transplanted graft function and resected liver function of donors using parameters such as peak total bilirubin, prothrombin time at postoperative day 3, and peak alanine aminotransferase between treated liver (n=7) and donor liver without hepatic steotosis (n=37). The transplanted grafts showed good liver functions, and there was no difference between them with respect to functional parameters. The treated donors also showed good liver functions, and no significant differences in functional parameters. Conclusions. The results of this study indicate that our short-term treatment effectively reduced steatosis and contributed to safer LDLT. Our findings also suggest that even severely steatotic livers can be used for LDLT grafting subsequent to our short-term treatment regimen.

Prevalence of hepatitis B or C virus infections in patients with non-Hodgkin's lymphoma.

Background: Hepatitis C virus (HCV) and hepatitis B virus (HBV) are not only hepatotropic, but also lymphotropic viruses. Recently, some reports suggested that these viruses may participate in the development of malignant lymphoproliferative disorders.

A selective ROCK inhibitor, Y27632, prevents dimethylnitrosamine-induced hepatic fibrosis in rats

BACKGROUND p160ROCK is a direct Rho target which mediates Rho-induced assembly of focal adhesions and stress fibers. We previously reported that Rho signaling pathways are involved in the activation of hepatic stellate cells (HSC) in vitro. The aim of the present study was to test the hypothesis that an inhibitor specific for p160ROCK (Y27632) could prevent experimental hepatic fibrosis induced by dimethylnitrosamine (DMN) in rats. METHODS Y27632 was given orally at 30 mg/kg daily for 4 weeks after the first injection of DMN. The degree of fibrosis was evaluated by image analysis and also by measurements of collagen and hydroxyproline content in the liver. The expression of alpha-smooth muscle actin (alpha-SMA) in the liver and in the primary cultured HSC was also evaluated. Semi-quantitative RT-PCR was performed to evaluate the expression of type I collagen mRNA in the liver. RESULTS Y27632 treatment significantly decreased the occurrence of DMN-induced hepatic fibrosis and reduced the collagen and hydroxyproline content and alpha-SMA expression in the liver. The expression of alpha-SMA in HSC was also suppressed in vitro. CONCLUSIONS These findings indicate that inhibitors of the Rho-ROCK pathway might be useful therapeutically in hepatic fibrosis.

Selective control of type I IFN induction by the Rac activator DOCK2 during TLR-mediated plasmacytoid dendritic cell activation

Plasmacytoid dendritic cells (pDCs) play a key role in antiviral immunity, but also contribute to the pathogenesis of certain autoimmune diseases, by producing large amounts of type I IFNs. Although activation of pDCs is triggered by engagement of nucleotide-sensing toll-like receptors (TLR) 7 and 9, type I IFN induction additionally requires IκB kinase (IKK) α–dependent activation of IFN regulatory factor (IRF) 7. However, the signaling pathway mediating IKK-α activation is poorly defined. We show that DOCK2, an atypical Rac activator, is essential for TLR7- and TLR9-mediated IFN-α induction in pDCs. We found that the exposure of pDCs to nucleic acid ligands induces Rac activation through a TLR-independent and DOCK2-dependent mechanism. Although this Rac activation was dispensable for induction of inflammatory cytokines, phosphorylation of IKK-α and nuclear translocation of IRF-7 were impaired in Dock2-deficient pDCs, resulting in selective loss of IFN-α induction. Similar results were obtained when a dominant-negative Rac mutant was expressed in wild-type pDCs. Thus, the DOCK2–Rac signaling pathway acts in parallel with TLR engagement to control IKK-α activation for type I IFN induction. Owing to its hematopoietic cell-specific expression, DOCK2 may serve as a therapeutic target for type I IFN–related autoimmune diseases.

High glucose stimulates hepatic stellate cells to proliferate and to produce collagen through free radical production and activation of mitogen-activated protein kinase.

Abstract: Background: Nonalcoholic steatohepatitis is a clinicopathologic condition that may progress to liver fibrosis. Hyperglycemia is supposed to be one of the factors inducing hepatic fibrogenesis, but the mechanism has not been fully clarified. Oxidative stress is increasingly found in patients with diabetes/hyperglycemia in which conditions reactive oxygen species (ROS) are produced.

Pirfenidone inhibits dimethylnitrosamine-induced hepatic fibrosis in rats

1. In the present study, we investigated the preventive effects of pirfenidone (PFD), an antifibrotic agent, on experimental hepatic fibrosis induced by dimethylnitrosamine (DMN) in rats.

NPC1L1 inhibitor ezetimibe is a reliable therapeutic agent for non-obese patients with nonalcoholic fatty liver disease

BackgroundWe recently examined the distribution of abdominal fat, dietary intake and biochemical data in patients with nonalcoholic fatty liver disease (NAFLD) and found that non-obese NAFLD patients did not necessarily exhibit insulin resistance and/or dysregulated secretion of adipocytokines. However, dietary cholesterol intake was superabundant in non-obese patients compared with obese patients, although total energy and carbohydrate intake was not excessive. Therefore, excess cholesterol intake appears to be one of the main factors associated with NAFLD development and liver injury.MethodsWe reviewed a year of follow-up data of non-obese NAFLD patients treated with Niemann-Pick C1 like 1 inhibitor ezetimibe to evaluate its therapeutic effect on clinical parameters related to NAFLD. Without any dietary or exercise modification, 10 mg/day of ezetimibe was given to 8 patients. In 4 of 8 patients, ezetimibe was administered initially. In the remaining 4 patients, medication was switched from ursodeoxycholic acid to ezetimibe.ResultsIn each patient, body mass index was maintained under 25 kg/m2 during the observation period. Serum ALT levels significantly decreased within 6 months and in 4 patients levels reached the normal range (<30 U/L), which was accompanied with at least a 10% decrease in serum total cholesterol and LDL-cholesterol. However, ultrasonographic findings of fatty liver did not show obvious improvement for a year.ConclusionWe conclude that the cholesterol absorption inhibitor ezetimibe can suppress hepatic injury in non-obese patients with NAFLD and that ezetimibe may offer a novel treatment for NAFLD.