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)

We have previously reported that ingestion of mepanipyrim induces fatty liver in rats due to the inhibitory effect on the synthesis or secretion of hepatocytic very low density lipoproteins (VLDL). To clarify the mechanism by which mepanipyrim induces fatty liver, morphological and biochemical effects of mepanipyrim on the movement of VLDL in rat liver and in the primary culture of rat hepatocytes were investigated. In in vivo experiments, rats were fed for 4 days a diet containing mepanipyrim at 4,000 ppm. VLDL accumulation in the Golgi apparatus of the liver, especially in the secretory vacuoles, was observed in the treated rats and in the hepatocytes treated for 2 hr with 25 micrograms/ml mepanipyrim. Using 6-[N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)amino]caproyl-sphingosine (C6-NBD-ceramide), a selective staining agent for the Golgi apparatus, it was found that mepanipyrim inhibited C6-NBD-ceramide transport from the Golgi to the cell surface of cultured hepatocytes. The density of the VLDL-loaded secretory vacuoles isolated from the Golgi fractions was greater in mepanipyrim-treated rat livers compared with that in the control. Immunofluorescence micrograph of rat hepatocytes stained with anti-alpha-tubulin monoclonal antibody demonstrated that mepanipyrim neither affected microtubule network nor changed the intracellular ATP level. These results together suggested that fatty liver induced by mepanipyrim results mainly from the inhibition of the transport of hepatic VLDL from the Golgi to the cell surface. The inhibition of the transport of hepatic VLDL appears to result from qualitative changes in VLDL such as alteration of the apoprotein composition and/or insufficient lipidation of VLDL.
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PMID:Mepanipyrim, a new fungicide, inhibits intracellular transport of very low density lipoprotein in rat hepatocytes. 988 86

Current research on lipid metabolism in ruminants aims to improve the growth and health of the animals and the muscle characteristics associated with meat quality. This review, therefore, focuses on fatty acid (FA) metabolism from absorption to partitioning between tissues and metabolic pathways. In young calves, which were given high-fat milk diets, lipid absorption is delayed because the coagulation of milk caseins results in the retention of dietary fat as an insoluble clot in the abomasum. After weaning, the calves were fed forage- and cereal-based diets containing low levels of long-chain fatty acids (LCFA) but leading to high levels of volatile fatty acid (VFA) production by the rumen microflora. Such differences in dietary FA affect: i) the lipid transport system via the production of lipoproteins by the intestine and the liver, and (ii) the subsequent metabolism of lipids and FA by tissues. In preruminant calves, high-fat feed stimulates the secretion of triacylglycerols (TG)-rich lipoproteins (chylomicrons, very-low density lipoproteins (VLDL)). Diets rich in polyunsaturated FA (PUFA) stimulate the production of chylomicrons by the intestine (at peak lipid absorption) and of high density lipoproteins by the liver, leading to high blood concentrations of cholesterol. High levels of non-esterified FA (NEFA) uptake by the liver in high-yielding dairy cows in early lactation leads to TG infiltration of the hepatocytes (fatty liver). This is due to the low chronic capacity of the liver to synthesise and secrete VLDL particles. This abnormality in hepatic FA metabolism involves defects in apolipoprotein B synthesis and low availability of apolipoproteins and lipids for VLDL packaging. Fatty liver in calves is also caused by milk containing either soybean oil (rich in n-6 PUFA), or coconut oil (rich in C12:0 and C14:0). The ability of muscle tissue to use FA as an energy source depends on its mitochondrial content and, hence, on many physiological factors. The uptake and partitioning of LCFA between oxidation and storage in muscle is regulated by the activity of key intracellular enzymes and binding proteins. One such protein, carnitine palmitoyltransferase I (CPT I) controls the transport of LCFA into mitochondria. Metabolites derived from LCFA inhibit glucose oxidation, decrease the activity of CPT I and decrease the efficiency of ATP production by mitochondria. Most research on tissue lipid metabolism in ruminants is focused on: i) the partitioning of FA oxidation between intracellular peroxisomes and mitochondria in the liver and in muscles; (ii) the regulation of lipid metabolism by leptin, a recently discovered hormone secreted by mature adipocytes; and iii) the effects of activation of the nuclear receptors (PPARs and RXR) by LCFA or by phytol metabolites derived from chlorophyll.
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PMID:Intestinal absorption, blood transport and hepatic and muscle metabolism of fatty acids in preruminant and ruminant animals. 1022 98

Perfluorodecanoic acid (PFDA) is a potent peroxisome proliferator that causes hepatotoxicity but lacks tumor-promoting activity in rats. We previously showed that a single dose of PFDA at 50 mg/kg (approximately LD50) causes an elevation in liver phosphocholine (PCho) and other effects related to phospholipid metabolism. In this study, we examined metabolic effects in the dose range 2-50 mg/kg in rats. At doses < or =20 mg/kg, PFDA is significantly less hepatotoxic than the LD50 as manifested by electron microscopy and measurements of daily food consumption and body weight. At 50 mg/kg rat serum tumor necrosis factor (TNF)-alpha concentration was increased 8-fold, while at 15 mg/kg there was no apparent increase in this cytokine. This lower dose, however, induces metabolic effects similar to those seen at the LD50. Liver fatty acyl-CoA oxidase activity showed a dose-dependent increase from 5-25 mg/kg PFDA. Treatments at 15 and 50 mg/kg caused a significant increase in liver phosphatidylcholine (28 and 66%) and phosphatidylethanolamine (31 and 74%). Both doses caused a significant increase in liver PCho but did not affect liver ATP levels, as manifested in 31P nuclear magnetic resonance (NMR) spectra from rat livers in vivo. These data suggest that the increase in liver [PCho] observed following PFDA exposure in rats represents a specific metabolic response, rather than a broad-range hepatotoxic effect.
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PMID:Dose-response hapatotoxicity of the peroxisome proliferator, perfluorodecanoic acid and the relationship to phospholipid metabolism in rats. 1040 36

It is not known why viable hepatocytes in fatty livers are vulnerable to necrosis, but associated mitochondrial alterations suggest that reactive oxygen species (ROS) production may be increased. Although the mechanisms for ROS-mediated lethality are not well understood, increased mitochondrial ROS generation often precedes cell death, and hence, might promote hepatocyte necrosis. The aim of this study is to determine if liver mitochondria from obese mice with fatty hepatocytes actually produce increased ROS. Secondary objectives are to identify potential mechanisms for ROS increases and to evaluate whether ROS increase uncoupling protein (UCP)-2, a mitochondrial protein that promotes ATP depletion and necrosis. Compared to mitochondria from normal livers, fatty liver mitochondria have a 50% reduction in cytochrome c content and produce superoxide anion at a greater rate. They also contain 25% more GSH and demonstrate 70% greater manganese superoxide dismutase activity and a 35% reduction in glutathione peroxidase activity. Mitochondrial generation of H(2)O(2) is increased by 200% and the activities of enzymes that detoxify H(2)O(2) in other cellular compartments are abnormal. Cytosolic glutathione peroxidase and catalase activities are 42 and 153% of control values, respectively. These changes in the production and detoxification of mitochondrial ROS are associated with a 300% increase in the mitochondrial content of UCP-2, although the content of beta-1 ATP synthase, a constitutive mitochondrial membrane protein, is unaffected. Supporting the possibility that mitochondrial ROS induce UCP-2 in fatty hepatocytes, a mitochondrial redox cycling agent that increases mitochondrial ROS production upregulates UCP-2 mRNAs in primary cultures of normal rat hepatocytes by 300%. Thus, ROS production is increased in fatty liver mitochondria. This may result from chronic apoptotic stress and provoke adaptations, including increases in UCP-2, that potentiate necrosis.
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PMID:Mitochondrial adaptations to obesity-related oxidant stress. 1086 May 43

There is no known treatment for fatty liver, a ubiquitous cause of chronic liver disease. However, because it is associated with hyperinsulinemia and insulin-resistance, insulin-sensitizing agents might be beneficial. To evaluate this possibility, insulin-resistant ob/ob mice with fatty livers were treated with metformin, an agent that improves hepatic insulin-resistance. Metformin improved fatty liver disease, reversing hepatomegaly, steatosis and aminotransferase abnormalities. The therapeutic mechanism likely involves inhibited hepatic expression of tumor necrosis factor (TNF) alpha and TNF-inducible factors that promote hepatic lipid accumulation and ATP depletion. These findings suggest a mechanism of action for metformin and identify novel therapeutic targets in insulin-resistant states.
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PMID:Metformin reverses fatty liver disease in obese, leptin-deficient mice. 1113 85

Hepatic steatosis is associated with mitochondrial oxidative alterations. This study aimed to characterize in a choline-deficient model of rat fatty liver whether this oxidative imbalance is related to an impairment of the capacity of ATP synthesis both under fed conditions and after starvation, which may sensitize mitochondria to oxidative injury. Mitochondria were isolated from normal and fatty livers of fed or 18-hour fasted rats. Oxidative injury was evaluated by measuring the mitochondrial content of thiobarbituric reactive substances, protein carbonyls, glutathione, and protein sulfhydryls. The mitochondrial F(0)F(1)-ATP synthase content, tissue ATP concentration, and liver histology were also determined. Compared with normal liver, under fed conditions, fatty livers showed a greater mitochondrial content of oxidized lipids and proteins together with a low concentration of sulfhydryls and glutathione. The mitochondrial catalytic beta-F(1) subunit of the F(0)F(1)-ATP synthase was about 35% lower in fatty livers. Hepatic ATP was also significantly reduced in fatty liver. Starvation exacerbated mitochondrial oxidative injury in both groups but to a greater extent in fatty livers. In the steatotic group, fasting induced a significant decrease of the ATP levels, which was accompanied by a 70% fall of the catalytic beta-F(1) subunit. These data indicate that the mitochondrial oxidative alterations in fatty livers are associated with an important reduction of the F(0)F(1)-ATP synthase. These changes, which are greatly exacerbated after starvation, may account for the reduced synthesis of the hepatic ATP observed in the presence of fatty infiltration.
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PMID:Mitochondrial oxidative injury and energy metabolism alteration in rat fatty liver: effect of the nutritional status. 1128 43

Steatosis of the liver is common in Western countries, affecting about 25% of donors for liver transplantation and 20% of patients undergoing liver resection. Transplantation of livers with severe steatosis (> 60%) is associated with a high risk of primary nonfunction, and these livers should not be used for organ donation. In contrast, transplantation with livers containing mild steatosis (< 30%) yields results similar to those of transplantation performed with nonfatty livers. The outcome of livers with moderate steatosis (30 to 60%) are varying, and the use of these organs depends on the existence of additional risk factors. Similarly, liver resection in patients with steatosis is associated with a risk of postoperative mortality when compared with patients with nonfatty livers (14% versus 2%). Although hepatic steatosis is an important risk factor for surgery, little is known about the mechanisms of injury. In animal experiments, steatosis is associated with decreased ATP production and a disturbance of sinusoidal flow. Further contributing factors may include Kupffer cell dysfunction and leukocyte adhesion. Fatty hepatocytes have reduced tolerance against ischemic injury with a predominant necrotic form of cell death. In addition, the ability of hepatocytes to regenerate after major tissue loss is impaired in the steatotic liver. Very few protective strategies are known. Ischemic preconditioning and intermittent clamping protect the human liver against prolonged periods of ischemia. These techniques appear to be particularly protective in the steatotic liver. New insights into the mechanisms of liver failure in steatotic organs are needed to decrease the risk of surgery and increase the pool of organ donors.
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PMID:Fatty liver in liver transplantation and surgery. 1129 90

For the first time in history, populations in affluent countries may concomitantly indulge in rich food and physical idleness. Various combinations of obesity, diabetes, and hypertriglyceridemia, with insulin resistance as the common feature, cause hepatic steatosis, which can trigger necroinflammation and fibrosis. Patients with "primary" steatohepatitis exhibit ultrastructural mitochondrial lesions, decreased activity of respiratory chain complexes, and have impaired ability to resynthesize ATP after a fructose challenge. Mitochondria play a major role in fat oxidation and energy production but also leak reactive oxygen species (ROS) and are the main cellular source of ROS. In patients with steatosis, mitochondrial ROS may oxidize hepatic fat deposits, as suggested in animal models. Lipid peroxidation products impair the flow of electrons along the respiratory chain, which may cause overreduction of respiratory chain components, further increasing mitochondrial ROS formation and lipid peroxidation. Another vicious circle could involve ROS-induced depletion of antioxidants, impairing ROS inactivation. Blood vitamin E is decreased in some obese children with steatohepatitis, and serum transaminases improve after vitamin E supplementation. Steatohepatitis is also caused by alcohol abuse, drugs, and other causes. In "secondary" steatohepatitis, mitochondrial ROS formation is further increased as the causative disease itself directly increases ROS or first impairs respiration, which secondarily increases mitochondrial ROS formation. This "second hit" could cause more lipid peroxidation, cytokine induction, Fas ligand induction, and fibrogenesis than in primary steatohepatitis.
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PMID:Mitochondria in steatohepatitis. 1129 97

Fatty livers are sensitive to lipopolysaccharide (LPS) damage. This study tests the hypothesis that this vulnerability occurs because protective, antiapoptotic mechanisms are not upregulated appropriately. Genetically obese, leptin-deficient ob/ob mice, a model for nonalcoholic fatty liver disease, and their lean litter mates were treated with a small dose of LPS. General measures of liver injury, early (i.e., cytochrome c release) and late (i.e., activation of caspase 3) events that occur during hepatocyte apoptosis, and various aspects of the signal transduction pathways that induce nuclear factor-kappaB (NF-kappaB) and several of its antiapoptotic transcriptional targets (e.g., inducible nitric oxide synthase, bfl-1, and bcl-xL) were compared. Within 0.5-6 h after LPS exposure, cytochrome c begins to accumulate in the cytosol of normal livers, and procaspase 3 cleavage increases. Coincident with these events, kinases (e.g., AKT and Erk-1 and -2) that result in the degradation of inhibitor kappa-B are activated; NF-kappaB activity is induced, and NF-kappaB-regulated gene products accumulate. Throughout this period, there is negligible histological evidence of liver damage, and serum alanine aminotransferase values barely increase over baseline values. Although ob/ob livers have significant histological liver injury and 11-fold greater serum alanine aminotransferase values than those of lean mice by 6 h post-LPS, they exhibit greater activation of AKT and Erk, more profound reductions in inhibitor kappa-B, enhanced activation of NF-kappaB, and greater induction of NF-kappaB-regulated genes. Consistent with this heightened antiapoptotic response, increases in cytochrome c and procaspase 3 cleavage products are inhibited. Together with evidence that ob/ob hepatocytes have a reduced ATP content and undergo increased lysis after in vitro exposure to tumor necrosis factor-alpha, these findings suggest that fatty livers are sensitive to LPS damage because of vulnerability to necrosis, rather than because of apoptosis.
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PMID:Fatty liver vulnerability to endotoxin-induced damage despite NF-kappaB induction and inhibited caspase 3 activation. 1144 19

Insulin receptor substrate (IRS)-2(-/-) mice develop diabetes because of insulin resistance in the liver and failure to undergo beta-cell hyperplasia. Here we show by DNA chip microarray analysis that expression of the sterol regulatory element-binding protein (SREBP)-1 gene, a downstream target of insulin, was paradoxically increased in 16-week-old IRS-2(-/-) mouse liver, where insulin-mediated intracellular signaling events were substantially attenuated. The expression of SREBP-1 downstream genes, such as the spot 14, ATP citrate-lyase, and fatty acid synthase genes, was also increased. Increased liver triglyceride content in IRS-2(-/-) mice assures the physiological importance of SREBP-1 gene induction. IRS-2(-/-) mice showed leptin resistance; low dose leptin administration, enough to reduce food intake and body weight in wild-type mice, failed to do so in IRS-2(-/-) mice. Interestingly, high dose leptin administration reduced SREBP-1 expression in IRS-2(-/-) mouse liver. Thus, IRS-2 gene disruption results in leptin resistance, causing an SREBP-1 gene induction, obesity, fatty liver, and diabetes.
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PMID:Increased expression of the sterol regulatory element-binding protein-1 gene in insulin receptor substrate-2(-/-) mouse liver. 1154 55


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