Deletion of nuclear factor-E2-related factor-2 leads to rapid onset and progression of nutritional steatohepatitis in mice

Department of Gastroenterology,Graduate School of Comprehensive Human Sciences, The University of Tsukuba, Tsukuba-shi, Ibaraki, Japan.
AJP Gastrointestinal and Liver Physiology (Impact Factor: 3.8). 11/2009; 298(2):G283-94. DOI: 10.1152/ajpgi.00296.2009
Source: PubMed

ABSTRACT Oxidative stress is a critical mediator in liver injury of steatohepatitis. The transcription factor Nrf2 serves as a cellular stress sensor and is a key regulator for induction of hepatic detoxification and antioxidative stress systems. The involvement of Nrf2 in defense against the development of steatohepatitis remains unknown. We aimed to investigate the protective roles of Nrf2 in nutritional steatohepatitis using wild-type (WT) and Nrf2 gene-null (Nrf2-null) mice. WT and Nrf2-null mice were fed a methionine- and choline-deficient (MCD) diet for 3 and 6 wk, and the liver tissues were analyzed for pathology and for expression levels of detoxifying enzymes and antioxidative stress genes via the Nrf2 transcriptional pathway. In WT mice fed an MCD diet, Nrf2 was potently activated in the livers, and steatohepatitis did not develop over the observation periods. However, in Nrf2-null mice fed an MCD diet, the pathological state of the steatohepatitis was aggravated in terms of fatty changes, inflammation, fibrosis, and iron accumulation. In the livers of the Nrf2-null mice, oxidative stress was significantly increased compared with that of WT mice based on the increased levels of 4-hydroxy-2-nonenal and malondialdehyde. This change was associated with the decreased levels of glutathione, detoxifying enzymes, catalase, and superoxide dismutase activity. Correlating well with the liver pathology, the mRNA levels of factors involved in fatty acid metabolism, inflammatory cytokines, and fibrogenesis-related genes were significantly increased in the livers of the Nrf2-null mice. These findings demonstrate that Nrf2 deletion in mice leads to rapid onset and progression of nutritional steatohepatitis induced by an MCD diet. Activation of Nrf2 could be a promising target toward developing new options for prevention and treatment of steatohepatitis.

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    • "Nrf2-null mice showed the dysregulation of β-oxidation and the increase in hepatic triglycerides.(18,19) In Nrf2-null mice, the methionine- and choline-deficient diet caused rapid onset and progression of nutritional steatohepatits.(20) Furthermore, Nrf2 activator prevented a high-fat diet induced hepatic lipid accumulation in wild type mice but not in Nrf2-null mice.(21) "
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    ABSTRACT: Nuclear factor-E2-related factor 2 (Nrf2) is a regulator of lipid metabolism as well as various cytoprotective enzymes and may be involved in the pathogenesis of non-alcoholic fatty liver disease. Although, bile acids affect lipid metabolism, the role of Nrf2 in bile acid metabolism remains unclear. In this study, it was tested how Nrf2 modulates lipid and bile acid homeostasis in liver in response to changes of cholesterol absorption under high-fat diet using Nrf2-null mice. Eight-week-old male wild-type and Nrf2-null mice (n = 6/group) were divided into three groups fed the following diets: 1) control diet containing 4% soybean oil and 16% lard, 2) control diet plus ezetimibe, 3) control diet plus cholesterol. Blood and livers were removed after 4 weeks feeding. High cholesterol diet increased hepatic expression of liver X receptor α target genes related to fatty acid metabolism (FAS, ACC1, SREBP-1c, SCD-1c and CD36), cholesterol transport (Abcg5/abcg8) and bile acid synthesis (Cyp7a1) in wild type mice. However, these genes were not induced in Nrf2-null mice. These findings suggest that Nrf2 has a relation to liver X receptor α and controls the regulation of gene expressions related to lipid and bile acid metabolism.
    Journal of Clinical Biochemistry and Nutrition 03/2014; 54(2):90-4. DOI:10.3164/jcbn.13-92 · 2.19 Impact Factor
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    • "Nuclear erythroid 2-related factor 2 (Nrf2) is a significant transcription factor for the induction of a variety of detoxification enzymes, biotransformation enzymes, and xenobiotic efflux transporters, which can regulate up or down inflammatory cytokine genes, fibrogenesis-related genes, and fatty acid metabolism via the Nrf2 transcriptional pathway. It has been proposed that the Nrf2 gene plays a role in NASH because deleting it from mice results in rapid onset and progression of the disease [6]. "
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    ABSTRACT: Nonalcoholic fatty liver disease begins with the aberrant accumulation of triglyceride in the liver. Its spectrum includes the earliest stage of hepatic simple steatosis (SS), nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. Generally, hepatic SS is often self-limited; however 10%-30% of patients with hepatic SS progress to NASH. The cause(s) of the transition from SS to NASH are unclear. We aimed to test the contribution of nuclear erythroid 2-related factor 2 (Nrf2) on the progression of "benign" SS to NASH in mice fed a high fat diet. In doing so, we discovered the influence of fatty acid in that progression. The involvement of Nrf2 in defending against the development of NASH was studied in an experimental model induced by a high-fat diet. Wild-type and Nrf2-null mice were fed the diet. Their specimens were analyzed for pathology as well as for fatty acid content and ratios.Result: In feeding the high-fat diet to the Wild-type and the Nrf2-null mice, the Wild-type mice increased hepatic fat deposition without inflammation or fibrosis (i.e., simple steatosis), while the Nrf2-null mice had significantly more hepatic steatosis and substantial inflammation, (i.e., nonalcoholic steatohepatitis). In addition, as a result of the high-fat diet, SFA (C20: 0, C22: 0) and MUFA (C18: 1, C20: 1) content in Nrf2-null mice were significantly higher than in Wild-type mice. In the Nrf2-null mice the PUFA/TFA ratio decreased; conversely, the MUFA/TFA ratio increased. The deletion of Nrf2 causes "benign" SS to develop into NASH in mice fed with a high-fat diet, through prompt fatty acid accumulation and disruption of hepatic fatty acid composition in the liver.
    Lipids in Health and Disease 11/2013; 12(1):165. DOI:10.1186/1476-511X-12-165 · 2.22 Impact Factor
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    • "For immunostainings of α-smooth muscle actin (α-SMA), 4-hydroxy-2-nonenal (4-HNE), and glutathione S-transferase placental form (GST-P), 5-µm-thick tissue sections were stained by the indirect immunoperoxidase method with anti-α-SMA (Sigma), anti-4-HNE (JaiCA, Shizuoka, Japan), and anti-GST-P (MBL, Nagoya, Japan) antibodies as described previously [26], [27]. "
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    ABSTRACT: Nonalcoholic fatty liver disease (NAFLD) includes simple steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. The gut-derived endotoxin plays an essential role in the pathophysiological development and progression of NAFLD. By using rat models of choline-deficient/L-amino acid-defined (CDAA)-diet-induced NAFLD, we examined whether MIYAIRI 588-a butyrate-producing probiotic - prevents the progression of pathophysiological changes from steatosis to hepatocarcinogenesis. In vivo experiments showed that treatment with MIYAIRI 588 reduced CDAA-diet-induced hepatic lipid deposition and significantly improved the triglyceride content, insulin resistance, serum endotoxin levels, and hepatic inflammatory indexes. We also found that MIYAIRI 588 substantially increased the activation of hepatic adenosine 5'-monophosphate-activated protein kinase (AMPK) and AKT and the expression of lipogenesis- or lipolysis-related proteins. MIYAIRI 588 also improved CDAA-diet-induced delocalization and substantially decreased the expression of the tight-junction proteins intestinal zonula occluden-1 and occludin in CDAA-diet-fed rats. Further, the MIYAIRI 588-treated rats also showed remarkable induction of nuclear factor erythoid 2-related factor 2 (Nrf2) and its targeted antioxidative enzymes, which suppressed hepatic oxidative stress. In vitro studies revealed that treatment with sodium butyrate (NaB) also activated AMPK and AKT and enhanced Nrf2 expression by precluding ubiquitination, thereby increasing the half-life of the Nrf2 protein. Pharmacological studies and siRNA knockdown experiments showed that NaB-mediated AMPK activation induced the phosphorylation and nuclear translocation of Sirtuin 1, leading to the increased assembly of mammalian TOR complex 2 and phosphorylation of AKT at Ser473 and subsequent induction of Nrf2 expression and activation. These favorable changes caused an obvious decrease in hepatic fibrous deposition, GST-P-positive foci development, and hepatocarcinogenesis. Our data clearly established that the probiotic MIYAIRI 588 has beneficial effects in the prevention of NAFLD progression.
    PLoS ONE 05/2013; 8(5):e63388. DOI:10.1371/journal.pone.0063388 · 3.23 Impact Factor
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