Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0015695 (fatty liver)
 13,941 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alcohol-induced fatty liver (steatosis) was believed to result from excessive generation of reducing equivalents from ethanol metabolism, thereby enhancing fat accumulation. Recent findings have revealed a more complex picture in which ethanol oxidation is still required, but specific transcription as well as humoral factors also have important roles. Transcription factors involved include the sterol regulatory element binding protein 1 (SREBP-1) which is activated to induce genes that regulate lipid biosynthesis. Conversely, ethanol consumption causes a general down-regulation of lipid (fatty acid) oxidation, a reflection of inactivation of the peroxisome proliferator-activated receptor-alpha (PPAR-alpha) that regulates genes involved in fatty acid oxidation. A third transcription factor is the early growth response-1 (Egr-1), which is strongly induced prior to the onset of steatosis. The activities of all these factors are governed by that of the principal regulatory enzyme, AMP kinase. Important humoral factors, including adiponectin, and tumor necrosis factor-alpha (TNF-alpha), also regulate alcohol-induced steatosis. Their levels are affected by alcohol consumption and by each other. This review will summarize the actions of these proteins in ethanol-elicited fatty liver. Because steatosis is now regarded as a significant risk factor for advanced liver pathology, an understanding of the molecular mechanisms in its etiology is essential for development of effective therapies.
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PMID:Alcohol-induced steatosis in liver cells. 1785 40

Conjugated linoleic acid (CLA) induces insulin resistance preceded by rapid depletion of the adipokines leptin and adiponectin, increased inflammation, and hepatic steatosis in mice. To determine the role of leptin in CLA-mediated insulin resistance and hepatic steatosis, recombinant leptin was coadministered with dietary CLA in ob/ob mice to control leptin levels and to, in effect, negate the leptin depletion effect of CLA. In a 2 x 2 factorial design, 6 week old male ob/ob mice were fed either a control diet or a diet supplemented with CLA and received daily intraperitoneal injections of either leptin or vehicle for 4 weeks. In the absence of leptin, CLA significantly depleted adiponectin and induced insulin resistance, but it did not increase hepatic triglyceride concentrations or adipose inflammation, marked by interleukin-6 and tumor necrosis factor-alpha mRNA expression. Insulin resistance, however, was accompanied by increased macrophage infiltration (F4/80 mRNA) in adipose tissue. In the presence of leptin, CLA depleted adiponectin but did not induce insulin resistance or macrophage infiltration. Despite this, CLA induced hepatic steatosis. In summary, CLA worsened insulin resistance without evidence of inflammation or hepatic steatosis in mice after 4 weeks. In the presence of leptin, CLA failed to worsen insulin resistance but induced hepatic steatosis in ob/ob mice.
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PMID:Conjugated linoleic acid fails to worsen insulin resistance but induces hepatic steatosis in the presence of leptin in ob/ob mice. 1790 21

Insulin resistance (IR) plays a key role in the pathophysiology of obesity-related diseases such as type 2 diabetes and nonalcoholic fatty liver disease. It has been demonstrated that IR is associated with a state of chronic low-grade inflammation, and several mediators released from various cell types, including immune cells and adipocytes, have been identified as being involved in the development of IR. Among those are several pro-inflammatory cytokines such as tumor necrosis factor-alpha(TNF-alpha), interleukin (IL)-1, IL-6, and various adipocytokines. Furthermore, several transcription factors and kinases such as c-Jun N-terminal kinase (JNK) and inhibitor of kappa B kinase-beta (IKKbeta), a kinase located proximal of nuclear factor-kappaB (NF-kappaB), participate in this process. Hepatocyte-specific overexpression of NF-kappaB is associated with IR and can mimic all features of fatty liver disease. Whereas the evidence for an important role of many pro-inflammatory pathways in IR in in vitro and animal studies is overwhelming, data from interventional studies in humans to prove this concept are still minor. As a complex network of inflammatory cytokines, adipocytokines, transcription factors, receptor molecules, and acute-phase reactants are involved in the development of IR, new therapeutic approaches in IR-related diseases will be based on a better understanding of their complex interactions.
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PMID:Inflammatory mechanisms in the regulation of insulin resistance. 1823 42

Alcohol is a well-known risk factor for liver damage and is one of the major causes of liver disease worldwide. Chronic intake of alcohol, over a certain limit, inevitably leads to hepatic steatosis. If the injury persists, steatosis with concomitant tumor necrosis factor-alpha and other cytokines, progresses to steatohepatitis, fibrosis and finally cirrhosis. Among the multiple factors involved in the process of alcohol-induced liver injury, a crucial role is played by oxidative stress. Several mechanisms during ethanol metabolism result in reactive oxygen species (ROS) production. Although the main site of ethanol metabolism is hepatocytes, other mechanisms are involved in alcohol-induced liver injury. Specifically, in the ROS production activity, an important role is played by the NADPH oxidase complex. NADPH oxidase is expressed in hepatocytes, hepatic stellate cells and Kupffer cells in the liver. Studying NADPH oxidase gives new insights into alcohol-induced liver damage and provides new direction for future therapeutic strategies.
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PMID:Oxidative stress in alcoholic liver disease: role of NADPH oxidase complex. 1833 75

Chronic consumption of ethanol induces hepatic steatosis and inflammation, which can eventually lead to more severe liver injury, characterized by fibrosis and cirrhosis. Recruitment of neutrophils to the liver, as well as activation of Kupffer cells, mediates the inflammatory responses observed after chronic ethanol exposure. Kupffer cells, the resident macrophages of the liver, are critical to the onset of ethanol-induced liver injury. Activation of Kupffer cells leads to an increased production of proinflammatory cytokines, such as tumor necrosis factor-alpha and also reactive oxygen species, a process mediated in part by changes in lipopolysaccharide-induced TLR4-dependent signal transduction. The isolation and culture of Kupffer cells is an important technique with which one can elucidate the mechanisms that contribute to alcoholic liver injury.
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PMID:Isolation of Kupffer cells from rats fed chronic ethanol. 1836 21

Whereas most individuals with nonalcoholic fatty liver disease (NAFLD) will have steatosis, only a minority will ever develop progressive disease. Family studies and interethnic variations in susceptibility suggest that genetic factors may be important in determining disease risk. Although no genetic associations with advanced NAFLD have been replicated in large studies, preliminary data suggest that polymorphisms in the genes encoding microsomal triglyceride transfer protein, superoxide dismutase 2, the CD14 endotoxin receptor, tumor necrosis factor-alpha, transforming growth factor-beta, and angiotensinogen may be associated with steatohepatitis and/or fibrosis. With the advent of high-throughput gene analyses and the reduced cost of whole genome-wide scans, it seems likely that genes contributing to inherited susceptibility to this common disease will be identified in the near future.
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PMID:Genes and nonalcoholic fatty liver disease. 1844 59

Ethanol induces the development of hepatic steatosis, increasingly recognized as causing vulnerability to subsequent liver injury. Ethanol has been shown to activate SREBP-1 (sterol regulatory element-binding protein) processing through the conventional cholesterol-sensitive pathway (1). The present study demonstrates that ethanol can also bring about SREBP-1 cleavage and activation through a novel pathway dependent on the endoplasmic reticulum-localized caspases-4 and -12. Evidence is presented that tumor necrosis factor can stimulate caspase-4 and -12 activation in ethanol-exposed cells, which cleaves SREBP-1 to a transcriptionally active form to induce the synthesis of lipogenic enzymes and triglycerides. Moreover, the caspase-4 and -12-dependent activation of SREBP-1 is insensitive to the normal negative feedback exerted by cholesterol and is mediated by the translocation of the scaffolding protein, TRAF-2, to the endoplasmic reticulum.
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PMID:Tumor necrosis factor-alpha can provoke cleavage and activation of sterol regulatory element-binding protein in ethanol-exposed cells via a caspase-dependent pathway that is cholesterol insensitive. 1863 49

Emerging attention has been paid to metabolic syndrome, which comprises several metabolic disorders including visceral obesity, diabetes mellitus, dyslipidemia, and hypertension. Whether the severity of each disease is mild to moderate, the comorbidity of these metabolic disorders has a serious impact on the development of atherosclerosis. Nonalcoholic fatty liver disease (NAFLD) is the major hepatic disorder in patients with metabolic syndrome, and indeed it is the most common cause of abnormal liver function tests in the working population in industrialized countries. In recent years, it has become recognized that NAFLD is no longer just a trivial disease, and a rather considerable proportion of the patients develop liver cirrhosis. Furthermore, chronic infection of hepatitis C virus also develops a pathological feature of steatohepatitis, and extended hepatic steatosis has a serious impact not only on the progression of hepatic fibrosis but also on the antiviral efficacy of interferon therapy. Emerging lines of studies indicated that insulin resistance, abnormal lipid metabolism, and dysregulation of cytokines/adipokines (e.g., tumor necrosis factor-alpha, adiponectin, and leptin) are profoundly involved in the pathogenesis of NAFLD. This review aims to integrate the reported evidence and to provide the current point of view for comprehensive understanding of the pathophysiology of steatohepatitis.
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PMID:Liver diseases and metabolic syndrome. 1864 37

Accumulation of fat in the liver, also known as steatosis, may lead to inflammation and tissue damage. Kupffer cells (KCs) are the resident macrophages of the liver and have an important role in inflammatory reactions. The inflammatory response of isolated rat KCs to endotoxin in the presence of lipids was investigated in this study. KCs were treated with lipopolysaccharide (LPS) and triglycerides (TGs) alone or in combination. TGs had no effect on the expression of pro-inflammatory mediators, but adding TGs to LPS enhanced the induction of inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and granulocyte colony-stimulating factor (G-CSF), compared with LPS treatment alone. Increased DNA binding of NF-kappaB transcription factor was seen on simultaneous exposure of the cells to TGs and LPS, which was accompanied by decreased intracellular ROS production and increased GSH levels. The inflammation-potentiating effect of TGs on iNOS expression was abolished on NF-kappaB inhibition. This enhanced inflammatory response might indicate a contribution of lipids to the inflammatory conditions in the fatty liver by increased activation of KCs.
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PMID:Triglycerides potentiate the inflammatory response in rat Kupffer cells. 1871 Mar 23

A "2-hit" model for nonalcoholic steatohepatitis (NASH) has been proposed in which steatosis constitutes the "first hit" and sensitizes the liver to potential "second hits" resulting in NASH. Oxidative stress is considered a candidate for the second hit. N-acetylcysteine (NAC), an antioxidant, has been suggested as a dietary therapy for NASH. We examined the effects of NAC in a rat total enteral nutrition (TEN) model where NASH develops as the result of overfeeding dietary polyunsaturated fat. Male Sprague-Dawley rats consumed pelleted AIN-93G diets ad libitum or were overfed a 9200 kJ.kg(-0.75).d(-1) liquid diet containing 70% corn oil with or without 2 g.kg(-1).d(-1) NAC i.g. for 65 d. Hepatic steatosis was not influenced by dietary supplementation with NAC; however, the liver pathology score was lower (P </= 0.05) and NAC provided partial protection against alanine aminotransferase release (P </= 0.05). NAC attenuated increased hepatic oxidative stress (TBARS; P </= 0.05) and prevented increases in cytochrome P450 2E1 apoprotein and mRNA and in tumor necrosis factor-alpha (TNFalpha) mRNA. Titers of auto-antibodies against proteins adducted to lipid peroxidation products were lower in serum of the NAC group than in the 70% corn oil group (P </= 0.05). NAC also decreased Picosirius red staining of collagen, a marker of fibrosis. However, markers of hepatic stellate cell activation were unaffected. Using NAC in a TEN model of NASH, we have demonstrated that NAC prevents many aspects of NASH progression by decreasing development of oxidative stress and subsequent increases in TNFalpha but does not block development of steatosis.
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PMID:N-acetylcysteine attenuates progression of liver pathology in a rat model of nonalcoholic steatohepatitis. 1880 95


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