D-氨基半乳糖大鼠急性肝衰竭并发内毒素血症对糖代谢的影响及其机制

目的：探讨大鼠急性肝功能衰竭时内毒素血症对糖代谢的影响及其机制。方法：利用D-氨基半乳糖（D—GaLN）诱导建立大鼠肝衰竭模型,24只雄性Wistar大鼠随机分为对照组（等渗盐水）、低剂量组（100mg／kgD—GaLN）、中剂量组（200mg／kgD—GaLN）、高剂量组（300rag／kgD—GaLN）,收集各组血清和肝组织,检测内毒素、血糖、肝功能,采用半定量PCR方法检测大鼠肝组织中葡萄糖-6-磷酸酶（G6P）和磷酸烯醇丙酮酸羧激酶（PEPCK）的基因转录,6-磷酸葡萄糖法检测葡萄糖激酶（GCK）活性。结果：200mg／kg以上剂量D—GaIN可诱导大鼠急性肝衰竭,并出现低糖血症,内毒素水平随着D—GaIN浓度升高而升高;实验组大鼠GCK活性较对照组均升高,而G6P、PEPCK的mRNA表达随D—GaIN浓度升高而下调。结论：急性肝功能衰竭大鼠并发内毒素血症可能通过促进糖酵解、抑制糖异生导致低血糖的发生。     

Changes in cerebral oxidative metabolism in patients with acute liver failure

Acute liver failure patients with a persistence of hyperammonemia are at an increased risk of intracranial hypertension due to development of brain oedema. In vitro studies of brain tissue and cell cultures that indicates that exposure to ammonium inhibits enzymatic activity in the tricarboxylic acid cycle, induces substrate depletion through marked glutamate utilization for glutamine synthesis and leads to mitochondrial dysfunction. In patients with acute liver failure cerebral microdialysis studies show a linear correlation between the lactate to pyruvate ratio and the glutamine concentration, as well as to some of the adenosine triphosphate degradation products. However, clinical observations of cerebral exchange rates of oxygen, glucose, lactate and amino acids challenge the interpretation of these findings. In this review the conflicting data of cerebral metabolism during acute liver failure is discussed.     

Ammonia and related amino acids in the pathogenesis of brain edema in acute ischemic liver failure in rats.

The pathogenesis of brain edema in acute liver failure is poorly understood. We have previously shown that rats with ischemic acute liver failure (portacaval anastomosis followed by hepatic artery ligation) exhibit brain edema and intracranial hypertension, with swelling of cortical astrocytes as the most prominent neuropathological abnormality. Because ammonia has been shown to induce swelling of astrocytes in vivo and in vitro, we examined the relationship between brain ammonia, amino acids generated from ammonia metabolism and brain water content in this model. Four groups of animals were studied: rats subjected to two sham operations, rats subjected to portacaval anastomosis and a sham operation, rats subjected to a sham operation and hepatic artery ligation and rats subjected to portacaval anastomosis and hepatic artery ligation. The last group of animals was studied at three progressive stages of encephalopathy. Cortical gray matter water increased from 80.26% +/- 0.22% (sham + sham) to 82.46% +/- 0.06% (last stage of devascularization). In cerebral cortex, brain ammonia increased to a maximum of 5.4 mmol/L. Glutamine, generated in glial cells from ammonia and glutamate, increased sixfold to 24 mmol/L and remained at this level throughout all stages of encephalopathy. Alanine, which may be generated from the transamination of glutamine, increased in parallel to the increase in water (r = 0.80, n = 15). In this model of fulminant liver failure and associated brain edema, brain ammonia increases to levels associated with in vitro swelling of brain slices and glial cells. The accumulation of osmogenic aminoacids such as glutamine and alanine may contribute to the selective astrocyte swelling seen in this condition.(ABSTRACT TRUNCATED AT 250 WORDS)     

精氨酸对急性肝衰竭大鼠血清细胞因子水平的影响

目的探讨不同剂量精氨酸对急性肝衰竭大鼠血清细胞因子的影响。方法 60只大鼠被随机分为A组（正常对照组）、B组（肝衰竭组）、C组（精氨酸强化Ⅰ组）、D组（精氨酸强化Ⅱ组）、E组（精氨酸强化Ⅲ组）和F组（精氨酸强化Ⅳ组）。采用D-半乳糖胺诱导法复制大鼠急性肝衰竭模型。结果肝衰竭大鼠血清TNF-α含量升高,其中B、C组与A组比较差别有统计学意义（P〈0.05）;肝衰竭大鼠IL-2含量均低于正常组,其中B、C、D、F组与A组比较差别有统计学意义（P〈0.05）;肝衰竭动物IL-10含量均低于正常组,其中B、C组与A组比较差别有统计学意义（P〈0.05）;肝衰竭大鼠血清IGF-1含量降低,其中B、C组与A组比较差别有统计学意义（P〈0.05）。结论精氨酸可调节肝衰竭大鼠体内细胞因子水平,以0.8g.kg-1.d-1和1.6g.kg-1.d-1剂量比低剂量或高剂量效果更明显。     

Effects of vasodilatory antihypertensive agents on endothelial dysfunction in rats with ischemic acute renal failure.

Ischemic acute renal failure is associated with vascular endothelial dysfunction. We examined whether vasodilatory antihypertensive agents would improve endothelial function in rats with ischemia/reperfusion renal injury. Rat kidneys were isolated and perfused after clipping of the bilateral renal arteries for 45 min and reperfusion for 24 h, and renal perfusion pressure and nitric oxide concentration in the venous effluent (chemiluminescence assay) were monitored. Preischemic administration of celiprolol (a beta-blocker; 100 mg/kg p.o.), benidipine (a calcium channel blocker; 1 mg/kg p.o.), or imidapril (an angiotensin converting-enzyme inhibitor; 3 mg/kg p.o.) restored endothelial function in rats subjected to acute renal ischemia (deltarenal perfusion pressure [10(-8) M acetylcholine]: sham -42+/-3%, ischemia -31+/-1%, ischemia +celiprolol -39+/-1%*, ischemia+benidipine -38+/-2%*, ischemia+imidapril -42+/-2%*; *p<0.05 vs. ischemia). Serum urea nitrogen and creatinine levels were also lower in the treated groups. Furthermore, ischemia-induced decreases in the response to acetylcholine and renal excretory function were smaller in SHR than in deoxycorticosterone-salt hypertensive rats, in which endothelial damage was marked. These results suggest that preischemic endothelial function may influence the degree of ischemic renal injury. Calcium channel blockers, converting-enzyme inhibitors, and endothelial NO synthase-activating beta-blockers had beneficial effects on renovascular endothelial dysfunction due to ischemia.     

Electron microscopic study of the blood-brain barrier in rats with brain edema and encephalopathy due to acute hepatic failure

An electron microscopy study was conducted to investigate structural as well as functional changes of the blood-brain barrier in hepatic encephalopathy. Hepatic encephalopathy was induced in rats by two-stage hepatic devascularization producing ischemic liver damage. The permeability of the blood-brain barrier to lanthanum, horseradish peroxidase and [3H]inulin was determined, with electron microscopy performed on capillaries from different regions of rat brain. Marked swelling of the perivascular astroglial foot process and dilatation of extracellular spaces were observed in the cerebral cortex, pons, basal ganglia and cerebellar cortex in rats with acute hepatic failure. Diffusion of lanthanum and reaction products of horseradish peroxidase were completely restricted by intercellular tight junctions, but there was a significant increase in the amount of [3H]inulin leaking out of the capillaries in the cerebral cortex in rats with acute hepatic failure as compared with controls. [3H]inulin was found mainly in vesicles, vacuoles and endoplasmic reticulum. Our results indicate that brain edema in acute hepatic encephalopathy is mainly of the cytotoxic type and, to a lesser extent, of the vasogenic type, due to the increase of vascular permeability via the vesicle system.     

Flumazenil does not improve hepatic encephalopathy associated with acute ischemic liver failure in the rabbit

The effect of flumazenil, a benzodiazepine antagonist, on hepatic encephalopathy was studied in rabbits with acute hepatic failure induced by a two-stage liver devascularization procedure. The rabbits were randomized for treatment with 5 mg/kg of flumazenil or the placebo. The drug was administered at two easily recognizable time points in the course of the encephalopathy: first, when the righting reflex was disturbed, and second, when the animal could no longer achieve to the sitting position. The response after flumazenil did not differ from that after the placebo, as measured by clinical evaluation and automated EEG analysis. Furthermore, the progression of the encephalopathy, as measured by the survival time after the first injection, was not affected by flumazenil.     

Impaired hepatic energy metabolism during taurocholate-induced acute pancreatitis in rats

The effect of acute pancreatitis on hepatic functions was evaluated. At 6 h after the induction of acute pancreatitis by injecting 5% sodium taurocholate into the rat pancreatico-biliary duct, malate dehydrogenase leakage from hepatic mitochondria was significantly increased in in-vitro incubation as compared with the control group. Hepatic ATP levels were significantly decreased and hepatic AMP levels were, on the contrary, significantly increased as compared with the control group. Reflecting these data, Hepatic adenylate energy charge levels were also significantly decreased as compared with the control group. These results indicate the impaired hepatic energy metabolism in the early stage of acute pancreatitis, and also indicate the intimate relationship between liver and exocrine pancreas in the pathological condition, such as in acute pancreatitis.     

Effects of mycophenolate mofetil in ischemic acute renal failure in rats

Mycophenolate mofetil (MMF) is a purine synthesis inhibitor commonly used as immunosupresive agent in transplantation. Kidney grafts undergo more or less prolonged cold ischemia after harvesting which results in variable degrees of ischemia reperfusion injury. To determine whether the inhibition of early events of cellular infiltration may influence the severity of damage induced by ischemic acute renal failure, 45 Sprague Dawley rats were given MMF at a dose of 20mg/kg/day (MMF-rats) by gavage 2 days before (pre-MMF group, n=15) or after (post-MMF group, n=15) clamping the left renal artery for 40 minutes followed by rigt-sided nephrectomy. (control group, n=15) received vehicle. Serum Creatinine (Screat) was measured daily in all groups. On the 2nd post-ischemic day Screat was significantly lower (p=0.001) in pre-MMF group compared with post-MMF group and control group (4 +/- 2mg/dl post-MMF group vs 1.7 +/- 1.2 mg/dl pre-MMF group, control group 5+/-2, p< 0.05). Kidney biopsies shown that the histologic damage was 54 +/- 28% in post-MMF group vs 34+/- 22% in pre-MMF group and 61 +/- 25% in control group (pre-MMF vs post-MMF, p NS). On the 5th day post-ischemic, MMF-rats showed more severe tubulointerstitial necrosis (pre-MMF group: 17 +/- 20 %, post-MMF group: 33 +/- 27%) than controls (4 +/- 5%). The severity of ATN was significantly higher in post-MMF group compared with controls (p=0.01). Tubulointersticial T-lymphocyte (T CD 5) and monocyte (ED 1) infiltration evaluated on the 2nd post-ischemic day was less intense in group I (T CD5: 3 +/- 3, ED 1: 10 +/- 9, cel/mm2) compared to post-MMF group (T CD 5: 10 +/- 4, ED 1: 55 +/- 40) and to control group (T CD 5: 10+/- 4, ED 1: 64 +/- 46). However, on the 5th post-ischemia day, ED 1 infiltration was significantly higher in post-MMF group (24 +/- 18%) compared to pre-MMF group (5 +/- 5, p NS) and also in pre-MMF group vs control group (31 +/- 33, p< 0.05). Our results suggest that MMF given before a renal ischemic insult may reduce the severity of histologic damage resulting from ischemia reperfusion injury.     

Changes of hepatic fatty acid metabolism produced by chronic thioacetamide administration in rats.

Hepatic mitochondrial functions related to fatty acid metabolism, including the respiratory control ratio, fatty acid oxidative capacity and carnitine palmitoyltransferase I activity, were studied in vitro with mitochondria isolated from rats treated with thioacetamide for up to 12 wk. The levels of ketone bodies, carnitine, carnitine esters and malonyl-coenzyme A were also determined in liver extracts. Polarography of mitochondrial respiration from succinate or glutamate plus malate showed a lower respiratory control ratio in thioacetamide-treated rats, whereas uncoupled oxygen consumption was not altered. This suggests that the mitochondrial respiratory chain capacity remained intact in the thioacetamide-treated rats. The oxygen consumption associated with palmitoyl-coenzyme A and palmitoyl-L-carnitine oxidation by isolated liver mitochondria was increased by thioacetamide treatment on both a per-mitochondrial protein and a per-total liver basis. The carnitine palmitoyl-transferase I activity; the tissue levels of ketone bodies, carnitine and carnitine esters; and the beta-hydroxybutyrate/acetoacetate ratio were all higher in the livers of thioacetamide-treated animals than in control livers, whereas the hepatic malonyl-coenzyme A level was decreased by thioacetamide. These results indicate the increased diversion of cytosolic long-chain acyl-coenzyme As into the mitochondria for beta-oxidation rather than their esterification and use in lipogenesis. These intrahepatic metabolic changes induced by chronic thioacetamide administration may reflect the whole-body catabolic state and can be seen as adaptive for maintaining energy homeostasis under conditions of impaired glucose tolerance.     

急性肝衰竭大鼠全营养液应用的实验研究

目的 探讨含30.6%支链氨基酸(BCAA)的复方氨基酸、中长链脂肪乳、葡萄糖、多种维生素和多种尢机盐联合应用的全营养液对急性肝衰竭大鼠的治疗效果. 方法 将30只大鼠随机分为正常对照组(A组)、肝衰竭对照组(B组)、无脂肪营养液组(C组)和全营养液组(D组),应用D-半乳糖胺制备急性肝衰竭模型.观察其肝功能、肾功能,氮平衡、血浆蛋白、氨基酸谱、肿瘤坏死因子、血糖、血脂的改变及淋巴细胞转化率.结果 数据比较采用单因素方差分析、SNK-q检验或重复测量资料的方差分析. 结果 肝、肾功能各项指标以D组恢复较好.ALT、碱性磷酸酶、总胆红素、血尿素氮指标D组优于C组(F值分别为1.280、1.878、2.439和1.473,P值均<0.05).D组总蛋白、白蛋白、前白蛋白、氮平衡恢复较好,前白蛋白D组优于C组.D组血浆氨基酸谱恢复接近正常.D组血中肿瘤坏死因子含量高于C组(F=1.609,P<0.05),D组刺激指数高于B组和C组(F值分别为2.648和1.432,P值均<0.05).D组与C组血糖差异有统计学意义(F=2.325,P<0.05),B组与A、C、D组甘油三酯差异有统计学意义(F值分别为1.180、2.578和2.432,P值均<0.05);D组与B组胆固醇差异有统计学意义(F=2.125,P<0.05);脂质过氧化物各组间差异无统计学意义(F=3.507,P>0.05).结论 大鼠急性肝衰竭后需要营养支持治疗的调整及营养底物的供给,结构比例合理的全营养液能使损伤的肝细胞得以再生,并促进合成代谢,有利于大鼠急性肝衰竭的逆转.     

Intensive liver care and management of acute hepatic failure

In describing acute liver failure, the term fulminant hepatic failure (FHF) is used to denote patients with the most rapid progression, normally defined as the onset of encephalopathy within eight weeks of the onset of symptoms. For patients with a slower onset of encephalopathy, ranging from eight weeks to six months after the onset of symptoms, late-onset hepatic failure is the term used to reflect the overlap in clinical features with some patients with FHF. The importance of accurately determining the type of acute liver failure results from increasing evidence of an inverse relationship between the tempo of disease progression and the chances of recovery. Prognosis is also dependent on the underlying etiology. Principles of management are as follows: (1) an accurate recognition of the tempo of the hepatic failure—fulminant, late onset, acute on chronic—and the establishment of a likely etiology; (2) early detection and treatment of complications, particularly metabolic acidosis (early), renal failure, cerebral edema, and infection (late); (3) optimization of conditions for regeneration by maintenance of a near normal metabolic milieu (with removal of toxins by various methods of artificial liver support if necessary); and (4) early consideration of an orthotopic liver transplant for those patients in the poor prognosis group. Variations in the natural history and clinical features of acute liver failure (ALF) have led to a number of different classifications and subgroupings. Knowledge of these is important in relation to the assessment of prognosis and is even more important now that transplantation is a therapeutic option. Fulminant hepatic failure (FHF) is the term used to denote the subgroup where the tempo is greatest and is variously defined as the onset of encephalopathy within four weeks (1), six weeks (EASL, 1979) and eight weeks [as described by Trey and Davidson (2)] of the onset of symptoms, or within two weeks of the onset of jaundice (3). The patients with a more protracted course are designated by the terms subacute or late-onset hepatic failure (LOHF) (4) or subfulminant hepatic failure (3). The etiology of the hepatic failure also has a major influence on the likely prognosis.Presented at the Proceedings of International Meeting on Normal and Neoplastic Growth in Hepatology, Bari, Italy, June 1989.     

Experimental studies of blood brain barrier permeability in acute hepatic failure

Permeability of the blood brain barrier in relation to the development of hepatic encephalopathy was investigated in two animal models of acute hepatic failure, in one of which there was the potential for recovery (D-galactosamine-induced hepatitis). In both this and the hepatic devascularization model, there was an approximate 3-fold increase in the passive permeability of the blood brain barrier to inulin and sucrose. Transport of amino acids was also significantly affected, with approximate 30% increases in the brain uptake of phenylalanine, tyrosine and arginine and a 65% increase in uptake of leucine. These changes are attributed to the action of circulating toxic substances, some of which increase blood brain barrier permeability in normal animals.     

Changes of gut flora and endotoxin in rats with D-galactosamine-induced acute liver failure

AIM: To investigate the changes of gut microflora and endotoxin levels in rats with acute liver failure (ALF) induced by D-galactosamine (GaiN).METHODS: Flora and endotoxin levels in the jejunum, ileum and colon in normal rats (group A) and rats with GaIN-induced ALF were determined at 24 h (group B) or 48 h (group C) after GaIN injection, as well as the endotoxin level in portal venous blood (PVB) and right ventricle blood (RVB) were determined by chromogenic limulus amoebocyte assay.RESULTS: Intestinal(jejunum, ileum, colon) lactobacillus count was statistically reduced in group B compared with those in group A (3.4&#177;0.3 vs 4.9&#177;0.3, 6.1&#177;0.4 vs 8.0&#177;0.3,8.1&#177;0.2 vs 9.3&#177;0.2, P＜0.001, P＜0.001 and P＜0.001 respectively) and recovered partially in the group C compared with those in the group B, whereas the count of Enterobacteriaceae in the jejunum, ileum and colon in group B was increased markedly compared with those in the group A (5.1&#177;20.3 vs 3.6&#177;0.2, 6.9&#177;0.5 vs 5.3&#177;0.3,8.7&#177;0.2 vs 7.6&#177;0.1,P＜0.001, P＜0.05 and P＜0.05 respectively)and restored partially in the group C compared with those in the group B. The endotoxin level in ileum was increased in the group B compared with those in the group A (111.3&#177;22.8 vs 51.5&#177;8.9, P＜0.05). In addition, the endotoxin level in PVB was obviously increased in group B compared with that in the group A (76.8&#177;9.1 vs 40.6&#177;7.3,P＜0.01) and reduced to the baseline at 48 h (group C).CONCLUSION: Severely disturbed gut flora in rats with GaiN-induced acute liver failure plays an important role in the elevation of endotoxin level in PVB.     

Protective effects of mild hypothermia against hepatic injury in rats with acute liver failure

Introduction and ObjectivesAcute liver failure (ALF) is a severe disease which is associated with a high mortality rate. As mild hypothermia has been shown to have protective effects on the brain, this study aimed to determine whether it also provides protection to the liver in rats with ALF and to explore its underlying mechanism.Materials and methodsIn total, 72 rats were divided into 3 groups: control group (CG, treated with normal saline), normothermia group (NG, treated with d-galactosamine and lipopolysaccharide; d-GalN/LPS), and mild hypothermia group (MHG, treated with d-GalN/LPS and kept in a state of mild hypothermia, defined as an anal temperature of 32–35 °C). The rats were examined at 4, 8, and 12 h after treatment.ResultsMild hypothermia treatment significantly reduced serum alanine transaminase and aspartate transaminase levels and improved the liver condition of rats with d-GalN/LPS-induced ALF at 12 h. Serum tumor necrosis factor-alpha levels were significantly lower in the MHG than in the NG at 4 h, but no significant differences were observed in the interleukin-10 levels between the NG and MHG at any time. The serum and hepatic levels of high mobility group box 1 were significantly lower in the MHG than in the NG at 8 and 12 h. The protein expression levels of cytochrome C and cleaved-caspase 3 in hepatic tissues were significantly lower in the MHG than in the NG at 8 h.ConclusionMild hypothermia improved the liver conditions of rats with ALF via its anti-inflammatory and anti-apoptotic effects.     

Acute pancreatitis in patients with acute hepatic failure

The incidence of acute pancreatitis has been studied in 42 patients with acute liver failure, the majority due to short-incubation hepatitis. The diagnosis of pancreatitis was based on autopsy findings, and classified as severe, moderate, or mild. Fourteen patients (33%) had evidence of pancreatitis-severe in 4, moderate in 5, and mild in 5. It is suggested that this pancreatitis was due either to the virus causing infectious hepatitis or to the blood coagulation changes accompanying acute liver failure. Acute pancreatitis should be considered as one of the possible causes of sudden clinical deterioration in patients with acute liver failure.This work was supported in part by the Clinical Liver Research Fund of The Prince Henry Hospital.