Down-regulation of rat hepatic microsomal cytochromes P-450 in microvesicular steatosis induced by orotic acid.
(17/3223)
Microvesicular steatosis is an important component of the overall pathogenesis of drug-mediated liver injury. Although mitochondrial damage has a role in the development of microvesicular steatosis, the consequences of fatty change for hepatic gene function are unclear. The present study was undertaken to evaluate hepatic cytochrome P-450 (CYP) function in a rat model of microvesicular steatosis produced by the intake of diets containing 1% orotic acid (OA) that were administered for 5, 10, or 21 days. Hepatic triglyceride levels were increased to 3-fold of control after 5 days and were elevated further at 10 and 21 days. Cholesterol and phospholipid contents were increased after 10 and 21 days but not by 5 days of feeding. Microsomal androst-4-ene-3,17-dione hydroxylation activities mediated by CYP2C11 (16alpha-hydroxylation) and CYP3A2 (6beta-hydroxylation) were decreased in liver from OA-fed rats for only 5 days, whereas CYP2A1/2-mediated steroid 7alpha-hydroxylation was decreased after 10 days; these observations were complemented by immunoblot analysis that demonstrated the impaired expression of the corresponding CYP proteins. CYP2C11 mRNA, the major CYP in male rat liver, was down-regulated in steatotic liver to 52 +/- 4% of control. Thus, microvesicular steatosis induced by short-term intake of OA-containing diets is histologically similar to that produced by hepatotoxic drugs and produces the rapid down-regulation of constitutive CYPs in rat liver. Analogous processes of lipid deposition in human liver after drug- or disease-related injury could precipitate adverse effects during subsequent drug therapy. (+info)
Cytogenetic studies in a patient with acute granulocytic leukemia of seven and one-half years duration.
(18/3223)
During a 7 1/2-yr period we monitored a chromosomally aberrant cell line in a woman with acute granulocytic leukemia (AGL) whose disease followed a rather unusual course. Her initial remission induced with 6-mercaptopurine (6-MP) and prednisone was maintained for 52 mo with biweekly doses of methotrexate (MTX) given orally. Because signs of liver dysfunction occurred, maintenance therapy was stopped. After 15 mo without chemotherapy, she suffered her first relapse (5 yr 7 mo after the initial diagnosis). A second remission, again induced with 6-MP and prednisone, was maintained for 1 yr, after which a second relapse occurred. Another remission lasting for only 4 mo was followed by a relapse of the leukemic process which led to her death. Cytogenetic studies of marrow cells and peripheral blood at the time of her initial diagnosis showed abnormal stem lines with characteristic chromosome markers. A small percentage of malignant cells bearing these markers persisted in her marrow during the years of her prolonged remission. At the time of her first relapse, 75% of her marrow cells had the marker karyotype, and at the time of her death (7 1/2 yr after the leukemia was diagnosed) all analyzable marrow metaphases had the characteristic chromosome changes. (+info)
Transgenic mice overexpressing insulin-like growth factor-II in beta cells develop type 2 diabetes.
(19/3223)
During embryonic development, insulin-like growth factor-II (IGF-II) participates in the regulation of islet growth and differentiation. We generated transgenic mice (C57BL6/SJL) expressing IGF-II in beta cells under control of the rat Insulin I promoter in order to study the role of islet hyperplasia and hyperinsulinemia in the development of type 2 diabetes. In contrast to islets from control mice, islets from transgenic mice displayed high levels of IGF-II mRNA and protein. Pancreases from transgenic mice showed an increase in beta-cell mass (about 3-fold) and in insulin mRNA levels. However, the organization of cells within transgenic islets was disrupted, with glucagon-producing cells randomly distributed throughout the core. We also observed enhanced glucose-stimulated insulin secretion and glucose utilization in islets from transgenic mice. These mice displayed hyperinsulinemia, mild hyperglycemia, and altered glucose and insulin tolerance tests, and about 30% of these animals developed overt diabetes when fed a high-fat diet. Furthermore, transgenic mice obtained from the N1 backcross to C57KsJ mice showed high islet hyperplasia and insulin resistance, but they also developed fatty liver and obesity. These results indicate that local overexpression of IGF-II in islets might lead to type 2 diabetes and that islet hyperplasia and hypersecretion of insulin might occur early in the pathogenesis of this disease. (+info)
CYP2E1 and CYP4A as microsomal catalysts of lipid peroxides in murine nonalcoholic steatohepatitis.
(20/3223)
Nonalcoholic steatohepatitis (NASH) and alcoholic liver disease have similar pathological features. Because CYP2E1 plays a key role in alcoholic liver disease with its ability to stimulate lipid peroxidation, we tested the proposal that CYP2E1 could also be a factor in the development of NASH. In a dietary model - mice fed a methionine- and choline-deficient (MCD) diet - liver injury was associated with both induction of CYP2E1 and a 100-fold increase in hepatic content of lipid peroxides. Microsomal NADPH-dependent lipid oxidases contributed to the formation of these lipid peroxides, and in vitro inhibition studies demonstrated that CYP2E1 was the major catalyst. To further define the role of CYP2E1 as an initiator of oxidative stress in NASH, Cyp2e1(-/-)mice were administered the MCD diet. CYP2E1 deficiency neither prevented the development of NASH nor abrogated the increased microsomal NADPH-dependent lipid peroxidation, indicating the operation of a non-CYP2E1 peroxidase pathway. In Cyp2e1(-/-) mice with NASH (but not in wild-type mice), CYP4A10 and CYP4A14 were upregulated. Furthermore, hepatic microsomal lipid peroxidation was substantially inhibited by anti-mouse CYP4A10 antibody in vitro. These results show that experimental NASH is strongly associated with hepatic microsomal lipid peroxidation. CYP2E1, the main enzyme associated with that process in wild-type mice, is not unique among P450 proteins in catalyzing peroxidation of endogenous lipids. We have now identified CYP4A enzymes as alternative initiators of oxidative stress in the liver. (+info)
Dietary oligofructose lessens hepatic steatosis, but does not prevent hypertriglyceridemia in obese zucker rats.
(21/3223)
We studied the influence of oligofructose (OFS), a nondigestible fructan, on lipid metabolism in obese fa/fa Zucker rats. The addition of 10 g/100 g OFS to the diet slowed the increase in body weight without modifying serum triglycerides or glucose concentrations after 7 wk of treatment. However, an oral load of 2 g glucose and 5 g corn oil/kg body weight increased triglyceridemia more in OFS-fed rats than in control rats. After 10 wk, OFS decreased the hepatic concentration of triglycerides 57% relative to controls. The less severe steatosis was confirmed by histologic analysis. Among the key enzymes involved in fatty acid synthesis and esterification, only malic enzyme activity was significantly lower in OFS-fed rats than in controls. The epididymal fat mass was significantly lower in OFS-fed rats. In conclusion, dietary enrichment with OFS can counteract both the fat mass development and the hepatic steatosis that occur in obese Zucker rats. Future studies will be designed to clarify in obese animals the influence of dietary OFS on postprandial triglyceridemia, which is an important variable associated with the development of atherosclerosis in humans, and to analyze the biochemical mechanism underlying the "hepatoprotective" effect of OFS. (+info)
Non-alcoholic steatohepatitis: association with obesity and insulin resistance, and influence of weight loss.
(22/3223)
Non-alcoholic steatohepatitis (NASH) is a disease of emerging identity and importance, and is now considered as one of the commonest liver diseases in western countries. It is frequently associated with severe obesity, especially abdominal adiposity, and is intimately related to various clinical and biological markers of the insulin resistance syndrome. Especially, both the prevalence and the severity of liver steatosis are related to male sex, body mass index, waist circumference, hyperinsulinaemia, hypertriglyceridaemia and impaired glucose tolerance or type 2 diabetes. A substantial weight loss following gastroplasty is accompanied by a marked reduction in the prevalence and the severity of the various biological abnormalities of the metabolic syndrome and, concomitantly, by an important regression of liver steatosis in most obese patients. However, in some patients, this rapid and drastic weight loss may result in a mild increase in inflammatory lesions (hepatitis), despite the regression of steatosis, which might result from the rapid mobilization of fatty acids or cytokines from adipose tissue, especially visceral fat. The intimate relationship between NASH and obesity leads to the concept that NASH may be considered as another disease of affluence, as is the insulin resistance syndrome and perhaps being part of it. (+info)
Reduction of carbon tetrachloride-induced hepatotoxic effects by oral administration of betaine in male Han-Wistar rats: a morphometric histological study.
(23/3223)
Eighty-five male Han-Wistar rats were arranged into three groups: CCl4-exposed rats, CCl4 + betaine-exposed rats, and control rats. To see the effect of betaine alone, five rats of the control and of the CCl4 + betaine groups were sacrificed after 7 days, before exposure to CCl4. After that, two of the groups (the CCl4 and CCl4 + betaine groups) were exposed to CCl4 (1 ml/kg per day subcutaneously [SC] for 4 consecutive days), and one of the groups (control group) was given olive oil (1 ml/kg per day SC for 4 consecutive days). At the start of the study (day 0), day 1, day 2, day 3, day 4, and 3 days after the last CCl4 and olive oil injections (day 7), samples of five rats per group were sacrificed, and the livers were taken for chemical analyses and histological examination. Oral betaine, after the acclimation period of a week, increased the number of mitochondria but not mitochondria size (day 0), compared with the case in control rats. Exposure to CCl4 resulted in centrilobular hepatic steatosis, and the administration of betaine significantly reduced this. Morphometric analyses also revealed that the addition of betaine increased the volume density of rough endoplasmic reticulum (RER) in the perinuclear areas of liver cell cytoplasm (day 7). Additionally, the administration of betaine prevented the reduction of Golgi complexes and mitochondrial figures in the cytoplasm observed after the exposures to CCl4. Also, the volume density of mitochondria was smallest in the CCl4-group, but the difference was not statistically significant. The results indicate that oral betaine either improves recovery or reduces the toxic effects of CCl4 on cell organelles in liver cells of male Han-Wistar rats. (+info)
Defect in peroxisome proliferator-activated receptor alpha-inducible fatty acid oxidation determines the severity of hepatic steatosis in response to fasting.
(24/3223)
Fasting causes lipolysis in adipose tissue leading to the release of large quantities of free fatty acids into circulation that reach the liver where they are metabolized to generate ketone bodies to serve as fuels for other tissues. Since fatty acid-metabolizing enzymes in the liver are transcriptionally regulated by peroxisome proliferator-activated receptor alpha (PPARalpha), we investigated the role of PPARalpha in the induction of these enzymes in response to fasting and their relationship to the development of hepatic steatosis in mice deficient in PPARalpha (PPARalpha(-/-)), peroxisomal fatty acyl-CoA oxidase (AOX(-/-)), and in both PPARalpha and AOX (double knock-out (DKO)). Fasting for 48-72 h caused profound impairment of fatty acid oxidation in both PPARalpha(-/-) and DKO mice, and DKO mice revealed a greater degree of hepatic steatosis when compared with PPARalpha(-/-) mice. The absence of PPARalpha in both PPARalpha(-/-) and DKO mice impairs the induction of mitochondrial beta-oxidation in liver following fasting which contributes to hypoketonemia and hepatic steatosis. Pronounced steatosis in DKO mouse livers is due to the added deficiency of peroxisomal beta-oxidation system in these animals due to the absence of AOX. In mice deficient in AOX alone, the sustained hyperactivation of PPARalpha and up-regulation of mitochondrial beta-oxidation and microsomal omega-oxidation systems as well as the regenerative nature of a majority of hepatocytes containing numerous spontaneously proliferated peroxisomes, which appear refractory to store triglycerides, blunt the steatotic response to fasting. Starvation for 72 h caused a decrease in PPARalpha hepatic mRNA levels in wild type mice, with no perceptible compensatory increases in PPARgamma and PPARdelta mRNA levels. PPARgamma and PPARdelta hepatic mRNA levels were lower in fed PPARalpha(-/-) and DKO mice when compared with wild type mice, and fasting caused a slight increase only in PPARgamma levels and a decrease in PPARdelta levels. Fasting did not change the PPAR isoform levels in AOX(-/-) mouse liver. These observations point to the critical importance of PPARalpha in the transcriptional regulatory responses to fasting and in determining the severity of hepatic steatosis. (+info)