Critical role of cytochrome P450 2E1 (CYP2E1) in the development of high fat-induced non-alcoholic steatohepatitis.
ABSTRACT Ethanol-inducible cytochrome P450 2E1 (CYP2E1) activity contributes to oxidative stress. However, CYP2E1 may have an important role in the pathogenesis of high-fat mediated non-alcoholic steatohepatitis (NASH). Thus, the role of CYP2E1 in high-fat mediated NASH development was evaluated.
Male wild type (WT) and Cyp2e1-null mice were fed a low-fat diet (LFD, 10% energy-derived) or a high-fat diet (HFD, 60% energy-derived) for 10weeks. Liver histology and tissue homogenates were examined for various parameters of oxidative stress and inflammation.
Liver histology showed that only WT mice fed a HFD developed NASH despite the presence of increased steatosis in both WT and Cyp2e1-null mice fed HFD. Markers of oxidative stress such as elevated CYP2E1 activity and protein amounts, lipid peroxidation, protein carbonylation, nitration, and glycation with increased phospho-JNK were all markedly elevated only in the livers of HFD-fed WT mice. Furthermore, while the levels of inflammation markers osteopontin and F4/80 were higher in HFD-fed WT mice, TNFα and MCP-1 levels were lower compared to the corresponding LFD-fed WT. Finally, only HFD-fed WT mice exhibited increased insulin resistance and impaired glucose tolerance.
These data suggest that CYP2E1 is critically important in NASH development by promoting oxidative/nitrosative stress, protein modifications, inflammation, and insulin resistance.
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ABSTRACT: Mitochondria are critically important in providing cellular energy ATP as well as their involvement in anti-oxidant defense, fat oxidation, intermediary metabolism and cell death processes. It is well-established that mitochondrial functions are suppressed when living cells or organisms are exposed to potentially toxic agents including alcohol, high fat diets, smoking and certain drugs or in many pathophysiological states through increased levels of oxidative/nitrative stress. Under elevated nitroxidative stress, cellular macromolecules proteins, DNA, and lipids can undergo different oxidative modifications, leading to disruption of their normal, sometimes critical, physiological functions. Recent reports also indicated that many mitochondrial proteins are modified via various post-translation modifications (PTMs) and primarily inactivated. Because of the recently-emerging information, in this review, we specifically focus on the mechanisms and roles of five major PTMs (namely oxidation, nitration, phosphorylation, acetylation, and adduct formation with lipid-peroxides, reactive metabolites, or advanced glycation end products) in experimental models of alcoholic and nonalcoholic fatty liver disease as well as acute hepatic injury caused by toxic compounds. We also highlight the role of the ethanol-inducible cytochrome P450-2E1 (CYP2E1) in some of these PTM changes. Finally, we discuss translational research opportunities with natural and/or synthetic anti-oxidants, which can prevent or delay the onset of mitochondrial dysfunction, fat accumulation and tissue injury. Published by Elsevier B.V.Redox biology. 10/2014; 3C:109-123.
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ABSTRACT: Abstract Green tea extract (GTE) protects against nonalcoholic steatohepatitis (NASH) by decreasing hepatic steatosis and nuclear factor kappa B (NFκB) activation. We hypothesized that hypolipidemic and anti-inflammatory activities of GTE would protect against NASH by reducing cyclooxygenase-2 (COX-2), an NFκB-dependent enzyme, and prostaglandin E2 (PGE2) in a dietary fat-induced obese model. Male Wistar rats were fed a low-fat diet containing no GTE or a high-fat (HF) diet containing GTE at 0%, 1%, or 2% for 8 weeks. Insulin resistance and total hepatic fatty acids increased following HF feeding (P<.05) and these were normalized by GTE at 1-2%. GTE (1-2%) normalized hepatic malondialdehyde without affecting cytochrome P450 2E1 mRNA expression, which was otherwise increased by HF feeding. HF-mediated increases in hepatic COX-2 protein and activity as well as PGE2 concentrations were normalized by GTE (1-2%). COX-2 activity and PGE2 were correlated to each other, and to serum alanine aminotransferase (ALT) and hepatic NFκB-binding activity (P<.05; r=0.28-0.49). GTE attenuated HF-mediated increases in total hepatic n-6 and n-3, without affecting the n-6/n-3 ratio. GTE did not affect HF-mediated increases in n-6 in nonesterified fatty acid (NEFA) and phospholipid pools, whereas n-3 and n-6/n-3 in both pools were unaffected by GTE and HF feeding. GTE decreased total hepatic arachidonic acid without affecting HF-mediated increases in arachidonic acid in NEFA or phospholipid pools. Thus, GTE attenuates lipid peroxidation and PGE2 accumulation by decreasing COX-2 activity independent of arachidonic acid availability and supports an additional mechanism by which GTE protects against liver injury during NASH in an HF-feeding model.Journal of Medicinal Food 12/2014; · 1.70 Impact Factor
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ABSTRACT: Nonalcoholic steatohepatitis (NASH), the advanced stage of nonalcoholic fatty liver disease that is characterized by both steatosis and severe injury in liver, still lacks efficient treatment. The traditional Chinese formula Salvia-Nelumbinis naturalis (SNN) is effectively applied to improve the symptoms of nonalcoholic simple fatty liver (NAFL) patients. Previous studies have confirmed that SNN could reduce the liver lipid deposition and serum transaminases of NAFL experimental models. This study aims to determine whether SNN is effective for murine NASH model and investigate the underlying pharmacological mechanisms. C57BL/6 J mice were fed with methionine- and choline-deficient (MCD) diet for six weeks to induce NASH. Simultaneously, SNN or saline was intragastrically administered daily to the mice in the SNN or model group, respectively. A standard diet was given to the control mice. Serum biochemical indices and tumor necrosis factor-α were measured. Liver histopathology was observed, and the contents of triglycerides and lipid peroxide malondialdehyde (MDA) in liver homogenates were evaluated. The hepatic expression and/or activation of genes associated with inflammation, apoptosis, and oxidative stress were determined by quantitative RT-PCR or Western blot analysis. The prominent liver steatosis displayed in the NASH model was prevented by SNN. The liver injury of NASH mice was obviously manifested by the increased levels of serum transaminases and bilirubin, as well as the lobular inflammation, elevated pro-inflammatory cytokines, and upregulated apoptosis in liver tissues. SNN administration improved the aforementioned pathological changes. The increased hepatic levels of MDA and cytochrome P450 2E1 of the model confirmed the unregulated balance of oxidative stress. The hepatic expression of nuclear factor erythroid 2-related factor 2 and its target genes decreased, whereas c-Jun N-terminal kinase activation in the model mice increased. Treating the mice with SNN significantly improved oxidative stress-related harmful factors. This study shows that SNN can protect the liver from severe steatosis and damage induced by MCD diet, which suggests the potential use of SNN on the treatment of NASH patient. The results also indicate that improving the hepatic antioxidant capability of the liver may contribute to the underlying hepatoprotective mechanism.Journal of Translational Medicine 12/2014; 12(1):315. · 3.99 Impact Factor