Pauline Hall

Rodent nutritional model of non‐alcoholic steatohepatitis: Species, strain and sex difference studies

Background and Aim:  The methionine choline‐deficient (MCD) diet leads to steatohepatitis in rodents. The aim of the present study was to investigate species, strain and sex differences in this nutritional model of non‐alcoholic steatohepatitis (NASH).

Role of non-alcoholic steatohepatitis in methotrexate-induced liver injury

Background and Aims: Hepatotoxicity, especially liver fibrosis, is the major concern with long‐term, ‘low‐dose’ oral methotrexate (MTX) therapy for psoriasis. The histological features are non‐specific and resemble those of non‐alcoholic steatohepatitis (NASH). Moreover, most of the risk factors of MTX‐induced liver injury are also associated with NASH. In this study, we investigate whether NASH contributes to the prevalence and progression of MTX‐induced liver injury in patients receiving MTX for psoriasis.

PREVALENCE OF GENETIC HAEMOCHROMATOSIS AMONG DIABETIC PATIENTS

Since diabetes mellitus is a frequent manifestation of haemochromatosis the prevalence of the disease was investigated in 418 patients attending a diabetic clinic. 21 (5%) patients had a persistently high serum ferritin (men, over 400 micrograms/l; women, over 300 micrograms/l) and 5 of these had transferrin saturations consistently over 55%. Idiopathic haemochromatosis was confirmed by liver biopsy in 4 patients, all of whom had a hepatic iron index greater than 2.0. The prevalence rate of previously unrecognised idiopathic haemochromatosis was thus 9.6 per 1000 (general population prevalence 1 in 250), suggesting that screening of diabetic patients for this genetic disease may be more cost-effective than screening in the general population.

Transient diabetes insipidus and acute fatty liver of pregnancy

Objective To review the association of transient diabetes insipidus and acute fatty liver of pregnancy.

Free radical formation in vivo and hepatotoxicity due to anesthesia with halothane

&NA; In vivo studies were undertaken to determine whether free radical formation in the liver during administration of various halogenated anesthetics is associated with hepatotoxicity of these agents in an animal model. In addition to the anesthetics halothane, enflurane, and isoflurane, carbon tetrachloride was studied as an example of a hepatotoxic halogenated compound acting by a free radical mechanism. Free radicals were trapped in vivo during anesthesia as stable adducts using the spin trap, &agr;‐phenyl‐t‐butyl nitrone. These adducts were extracted from the liver and studied by electron spin resonance spectrometry. Free radicals were detected after administration of halothane or carbon tetrachloride, compounds which were hepatotoxic under the conditions of the experiment, but were not found after anesthesia induced with enflurane or isoflurane, anesthetics which were not hepatotoxic under identical conditions. The free radical trapped after &agr;‐phenyl‐t‐butyl nitrone treatment of halothane‐anesthetized rats appeared to be a metabolic intermediate of halothane.

Ethanol feeding enhances inflammatory cytokine expression in lipopolysaccharide-induced hepatitis

Elevated concentrations of plasma tumour necrosis factor (TNF)‐α, interleukin (IL)‐1 and IL‐6 have been detected in patients with alcoholic hepatitis and have been implicated in the pathogenesis of hepatocyte necrosis. The present study used a rat model to conduct a detailed histological and biochemical examination of the expression of various pro‐inflammatory cytokines and associated liver pathology in ethanol‐potentiated lipopolysaccharide (LPS)‐induced liver injury. Male Wistar rats were pair‐fed either the control or ethanol‐containing (36% of caloric intake as ethanol) form of the Lieber‐DeCarli liquid diet for 6 weeks. Liver injury was induced by the i.v. injection of LPS (1 μg/g bodyweight), with animals being killed at 0, 1, 3, 6, 12 and 24 h after injection. At the later time points, plasma transaminase and transpeptidase activities were significantly elevated in ethanol‐fed LPS‐treated rats compared with control‐fed LPS‐treated animals. At these times after LPS treatment, hepatocytes in ethanol‐fed animals displayed fatty change and necrosis with an associated neutrophil polymorph infiltrate. Time course analysis revealed that plasma TNF‐μ (1–3 h post‐LPS) and IL‐6 (3 h post‐LPS) bioactivity was significantly elevated in ethanol‐fed compared with control‐fed animals. No difference was seen in plasma IL‐1μ concentration (maximal in both groups 6 h post‐LPS). The expression of TNF‐μ, IL‐1μ, IL‐1β and IL‐6 mRNA were elevated between 1 and 6 h post‐LPS in the livers of both control and ethanol‐fed rats. However, ethanol‐fed LPS‐treated animals exhibited significantly higher maximal expression of IL‐1 and IL‐6 mRNA. Comparison of the appearance of cytokine mRNA and plasma bioactivity indicated an effect of ethanol feeding on post‐transcriptional processing and/or the kinetics of the circulating cytokines. Elevated levels of both hepatic cytokine mRNA expression and the preceding plasma cytokines are presumably a necessary prerequisite for hepatic injury seen in this model and, therefore, possibly for the damage seen in human alcoholics. Further studies using this model may lead to significant advances in our understanding of the pathogenic mechanisms of alcoholic liver disease in humans.

Rodent nutritional model of steatohepatitis: Effects of endotoxin (lipopolysaccharide) and tumor necrosis factor alpha deficiency

Background and Aims:  Intestinal endotoxin (lipopolysaccharide) is thought to contribute to liver injury in both alcoholic and nonalcoholic steatohepatitis (NASH). Tumor necrosis factor alpha (TNFα) is an important mediator of this process and is considered central to the inflammatory response in NASH. This study aimed to investigate the effects of lipopolysaccharide on liver injury in the methionine choline deficient (MCD) nutritional model of NASH, and to determine if TNFα is required for the development of steatohepatitis in this model.

Genetic Differences in Reductive Metabolism and Hepatotoxicity of Halothane in Three Rat Strains

The relationship between the reductive metabolism of halothane and hepatotoxicity was examined in three rat strains (Fischer 344, Sprague-Dawley, and black hooded Wistar) to determine if there were genetic differences in 1) the reductive metabolism of holthane under identical exposure conditions, and 2) the susceptibility to the hepatotoxic effects of halothane. Halothane hepatotoxicity was produced in all rat strains by exposing phenobarbital-pretreated rats to 1 per cent halothane under mild hypoxia (14 per cent oxygen, inspired) for 2 h. Generally the levels of both 2-chloro-1,1,1-trifluoroethane (CTF) and 2-chloro-1,1-difluoroethylene (CDF), two volatile metabolites of halothane, increased from the onset of anesthetic exposure and reached a plateau after approximately 60 min. The exception to this trend were phenobarbital-pretreated Wistar rats (exposed to 1 per cent halothane with 14 per cent oxygen) where the levels of either CDF or CTF were high initially (10-min sample) and decreased in subsequent samples to reach a plateau after 80 min. The plateau levels of both CDF (approximately 6 ppm) and CTF (approximately 20 ppm) were not significantly different among the three rat strains exposed to halothane (1 per cent) and hypoxia with prior enzyme induction. There were, however, significant differences in both biochemical and pathological changes among the three strains exposed under the above identical conditions when the rats were killed 24 h after anesthetic exposure. For example, serum alanine aminotransferase (ALT) was increased fourfold in the Fischer strain but only doubled for the other two strains. Moreover, while all three strains had various amounts of hepatocyte damage in the vicinity of the central veins when the rats were exposed to halothane, hypoxia, and enzyme induction, only the Fischer strain showed hepatocyte damage under the exposure conditions of halothane (1 per cent) and normoxia (21 per cent oxygen, inspired) with prior enzyme induction. The results support the role of reductive metabolism of halothane in the etiology of halothane hepatotoxicity. Furthermore, they suggest that genetic variations in the susceptibility of the liver to the reactive intermediates or metabolites formed during reductive metabolism of halothane may be a significant factor in halothane hepatotoxicity.

Effects of iron overload in a rat nutritional model of non‐alcoholic fatty liver disease

Abstract: Background/Aims: This study sought to determine whether excess hepatic iron potentiates liver injury in the methionine choline‐deficient (MCD) model of non‐alcoholic fatty liver disease (NAFLD).

The pathological spectrum of alcoholic liver disease

Alcoholic liver disease encompasses three main forms of liver injury: fatty change, alcoholic hepatitis and cirrhosis. However, there are many other types of injury, including perivenular fibrosis, venous occlusive lesions, microscopic cholangitis and chronic active hepatitis. The pathological spectrum is reviewed in this paper, and the contribution of other injurious agents to the pathological features is identified. Alcoholic liver disease can be mimicked by a variety of non-alcoholic liver diseases. However, features such as fatty liver with perivenular fibrosis, giant mitochondria, spotty hepatocyte necrosis, Mallory bodies, a micronodular pattern of cirrhosis, and iron deposition are strongly suggestive of an alcoholic aetiology. Correlation of clinical findings, and especially the alcohol history, and histopathological factors is necessary for the definitive diagnosis.