Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease.

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 +/- 3.35; RCR: 2.55 +/- 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 +/- 1.53, 17.04 +/- 2.03, RCR: 3.15 +/- 0.15, 3.68 +/- 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 ± 3.35; RCR: 2.55 ± 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 ± 1.53, 17.04 ± 2.03, RCR: 3.15 ± 0.15, 3.68 ± 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

[Antioxidative effect of N2-mercaptopropionylglycine (N2 MPG) in experimental acute pancreatitis]. / Efeito do antioxidante N2-mercaptopropionilglicina (N2-MPG) na pancreatite aguda experimental.

The N2-Mercaptopropionylglycine (N2-MPG) is a potent antioxidant by inhibiting the abnormal production of xantina-oxidase. The aim of this research is to analyze the antioxidant capacity of this tiol compound by offering some protection to pancreatic tissue in the acute pancreatitis (AP). The induction of AP was obtained through two methods: a) supramaximal dose of cerulein; b) infusion of 2.5% sodium taurocholate into the biliopancreatic duct of the rat. Thirty-six male Wistar rats (220-270 g) were divided into four groups. AP with cerulein (Two parenteral doses of 20 micrograms/kg; one hour interval): in two groups: GI: nineteen rats previously treated with N2-MPG (100 mg/kg) ten minutes before AP. GII (control): seventeen animals which received saline 0.9%. AP with taurocholate (0.5 ml into the main biliopancreatic duct): in other two groups: GIII: eleven rats previously treated with N2-MPG (100 mg/kg) ten minutes before AP. GIV (control): fifteen animals which received saline 0.9%. The albumin leakage into the cell interstice as an inflammatory parameter was measured through Evans-Blue (EB) colorimetry, that links totally with serum albumin after injection into the pancreatic tissue, immediately before induction of AP. The rats were sacrificed one hour after. Water tissue content was also measured. There was a relevant reduction of EB leakage in GI (344 +/- 27 micrograms/gtissue) when compared to GII (729 +/- 84 micrograms/gtissue), p < 0.01, and in GIII (386 +/- 52 micrograms/gtissue) when compared to GIV (543 +/- 53 micrograms/gtissue), p < 0.05. There was no difference in tissue water content between GI (88.2 +/- 0.6%) and GII (87.4 +/- 0.9%), but certainly between GIII (77.7 +/- 2.1%) and GIV (82.8 +/- 1.2%), p < 0.05. The amilase levels didn't show any difference among the four groups. These results suggest that the use of the antioxidant N2-MPG offers a protective action, at least in rats, reducing the severity of AP induced by supramaximal dose of cerulein, and even in a more severe AP such as produced by sodium taurocholate at 2.5%, although apparently not interfering with its pathogenesis. It also strengthens the actual participation of free radicals of oxygen in the physiopathology of acute pancreatitis.

[Hepatic lesion in experimental acute pancreatitis. Influence of pancreatic enzyme storage reduction]. / Lesão hepática na pancreatite aguda experimental. Influência da redução da reserva enzimatica do pâncreas.

Acute Pancreatitis (AP) is known to produce morphologic and functional changes in liver. Administration of low doses of caerulein significant decreases the content of pancreatic enzymes, leading to reduced mortality of animals submitted to AP. The present study was designed to assess the effect of acute reduction of pancreatic enzymatic content in the hepatic mitochondrial function. Wistar male rats, submitted to AP by injection of Na thaurocholate into the pancreatic duct, with and without previous i.v. injection of 0.133 microgram Kg-1h-1 of caerulein for three hours, were divided in four groups: Group I: No caerulein infusion and AP; Group II: Previous caerulein infusion and with AP; Group III: Caerulein infusion without AP; Group IV (control): No caerulein infusion and without AP. After 2 hours of induction of AP the livers were removed and prepared to the mitochondrial oxidative and phosphorylative activities, measured polarographically with determination of oxygen consumption without ADP (Basal respiration-State 4) and in the presence of ADP (Activated respiration-State 3). Ascitic fluid contents of amylase, trypsin and total protein were routinely determined. After 2 hours of AP there was a significant increase in state 4 respiration (41%) and a decrease in respiratory control ratio and in ADP/O ratio (p < 0.05) in animals of Group I (AP without caerulein) when compared to Group II (AP with caerulein) (Table 1). Ascitic fluids contents of amylase (A) and trypsin (T) showed decrease in animals of Group II with AP that received previous caerulein infusion (A = 80 +/- 10 U/ml, T = 9.75 +/- 1.25 U/ml), when compared to animals of Group I that did not receive caerulein (A = 231 +/- 24, T = 40.32 +/- 5.19) (p < 0.001). Caerulein infusion by itself (Group III) did not have any influence on mitochondrial liver dysfunction. Reduction of pancreatic enzyme content through caerulein infusion attenuates the damage of mitochondrial respiration, demonstrated by uncoupling phase on mitochondrial function in experimental AP. Further studies are needed to elucidate this phenomena, but it is probably related to the decreased of the pathogenic effects of pancreatic activated enzymes that reach the systemic circulation in reduced amounts.

[Physiopathology of lung injury in acute pancreatitis]. / Fisiopatologia da lesão pulmonar na pancreatite aguda.

Clinically detectable signs of lung injury develop in up to 50-70 percent of patients with acute pancreatitis. Despite that, the physiopathology of the lung injury associated with acute pancreatitis is unclear so far. Pulmonary edema is the main respiratory complication in acute pancreatitis. Increased permeabilities of the pulmonary endothelial and alveolar epithelial barriers are the causes of the pulmonary edema. Several factors have been regarded as the cause to pulmonary edema: release of pancreatic-derived proteolytic enzymes, oxygen-free radicals, phospholipase A2, free fat acids, tumor necrosis factor, platelet activating factor, arachidonic acid metabolites and pulmonary embolization. Understanding lung injury physiopathology enables physicians to a better therapeutic approach of the patients with acute pancreatitis. The aim of this paper is to expose the theories that explain the pancreatic-derived lung injury.

[Lung injury in acute pancreatitis. Influence of pancreatic enzymes reduction]. / Lesão pulmonar na pancreatite aguda. Influência da redução do conteúdo enzimático do pâncreas.

UNLABELLED: A previous report has show that cerulein in physiological doses reduces the rate mortality of pancreatitis by decreasing the enzyme content of the pancreas. Clinically detectable signs of lung injury develop in up to 50-70 percent of patients with acute pancreatitis. The aim of the present study was to assess the effect of acute reduction of pancreatic enzyme content on the pancreatitis pulmonary injury. Experimental haemorrhagic pancreatitis was induced by intraductal injection of 5 per cent sodium taurocholate in two groups of Wistar rats: group I (pancreatitis) and group II (pancreatitis after decreasing pancreatic enzyme content). Dye Evans blue was used to evaluate the lung injury. The degree of histologically observed lesions were similar in both groups, but the pulmonary lesion was smaller in group II than group I (p < 0.05). IN CONCLUSION: 1) pancreatitis' pulmonary lesion may be related with pancreatic enzymes that reach the blood stream and 2) the reduction of the pancreatic enzyme content has a beneficial effect on acute pancreatitis and reduces its pulmonary injury.

[Lung lesion in acute pancreatitis]. / Lesão pulmonar na pancreatite aguda.

Clinically detectable signs of lung injury develop in up to 70 percent of patients with acute pancreatitis. In order to study the pulmonary injury, experimental haemorrhagic pancreatitis was induced in 63 Wistar rats by intraductal injection of 5 per cent sodium taurocholate. Investigations were carried out 2, 4, 6, 12, 24 and 48 hours after the end of pancreatitis induction. Lung injury was maximal at 12 hours after pancreatitis induction, pancreatic enzymes (amylase and trypsin) in peritonial fluid were maximal early (2-4h) and serum levels were maximal at about 4 hours after induction. In conclusion, in experimental acute pancreatitis pulmonary injury occurs 12 h after the start of infusion with increase in vascular permeability of the lung. This lesion may be related to pancreatic enzymes in peritonial fluid and blood.

[Effect of omeprazole administration on pancreatic content of enzymes in rats]. / Efeito da administração de omeprazol sobre o conteúdo pancreático de enzimas em ratos.

Gastric chloride acid plays an important role in pancreatic enzyme synthesis and secretion, mediated by cholecystokinin released in the duodenum. This study was designed to evaluate the influence of gastric acid suppression by omeprazole on pancreatic enzyme content. Eighteen male Wistar rats (180-220 g) were divided in two groups: I--control and II--omeprazole. Animals received by intraduodenal catheter 3 doses of 0.5 ml saline solution (NaCl 0.9%)--Group I or 5 mumol/Kg of omeprazole solution--Group II at 24 h intervals. All animals, after an overnight fasting period, were killed 3 h after the last dose. Serum amylase and pancreatic tissue content of protein, trypsinogen, elastase, lipase and phospholipase A2 were determinated. Omeprazole treated animals (group II) showed statistically significant lower levels of serum amylase and pancreatic trypsinogen content (P < 0.05). We believe that this effect is related with acid secretion suppression by omeprazole and that it may be mediated by cholecystokinin.

[Simplified model of induction of experimental acute pancreatitis with a supra-maximal dose of cerulein]. / Modelo simplificado de indução de pancreatite aguda experimental com uso de dose supramáxima de ceruleína.

The study was performed to compare an usual method of induction of acute experimental pancreatitis with a simplified, easier and faster induction through a subcutaneous and intravenous injection of cerulein, with good reproducibility as compared to the literature. Four groups were studied. In the group I, continuous three hour intravenous injection of 15 micrograms/Kg of cerulein, was given. Group II was a control group with saline infusion. Group III received a subcutaneous injection of 20 micrograms/Kg and an intravenous injection of 20 micrograms/Kg of cerulein one hour later. Group IV was the control group with saline. The results of biochemical measurements, such as tecidual trypsinogen, chimotrypsinogen, proelastase, cathepsin and serum amylase, showed no difference between the two methods. Histologic study revealed edematous pancreatitis in group I and III, with moderate acinar necrose in group III. These results suggest that the proposed simplified method induces enough acute and edematous pancreatitis to allow studies in physiopathology and therapeutics.