Lívia Bracht

The urea cycle in the liver of arthritic rats.

The urea cycle in the liver of adjuvant-induced arthritic rats was investigated using the isolated perfused liver. Urea production in livers from arthritic rats was decreased during substrate-free perfusion and also in the presence of the following substrates: alanine, alanine + ornithine, ammonia, ammonia + lactate, ammonia + pyruvate and glutamine but increased when arginine and citrulline + aspartate were the substrates. No differences were found with ammonia + aspartate, ammonia + aspartate + glutamate, aspartate, aspartate + glutamate and citrulline. Ammonia consumption was smaller in the arthritic condition when the substance was infused together with lactate or pyruvate but higher when the substance was simultaneously infused with aspartate or aspartate + glutamate. Glucose production tended to correlate with the smaller or higher rates of urea synthesis. Blood urea was higher in arthritic rats (+25.6%), but blood ammonia was lower (−32.2%). Critical for the synthesis of urea from various substrates in arthritic rats seems to be the availability of aspartate, whose production in the liver is probably limited by both the reduced gluconeogenesis and aminotransferase activities. This is indicated by urea synthesis which was never inferior in the arthritic condition when aspartate was exogenously supplied, being even higher when both aspartate and citrulline were simultaneously present. Possibly, the liver of arthritic rats has a different substrate supply of nitrogenous compounds. This could be in the form of different concentrations of aspartate or other aminoacids such as citrulline or arginine (from the kidneys) which allow higher rates of hepatic ureogenesis.

Effects of simvastatin, atorvastatin, ezetimibe, and ezetimibe + simvastatin combination on the inflammatory process and on the liver metabolic changes of arthritic rats.

In this study, simvastatin, atorvastatin, ezetimibe, and ezetimibe + simvastatin combination were administered to arthritic rats, first to determine their effects on the inflammatory response, employing a low‐dose adjuvant‐induced arthritis model in rats. Arthritis was induced by the subcutaneous injection of a suspension of Mycobacterium tuberculosis (100 μg) in mineral oil [complete Freund’s adjuvant used (CFA)] into the plantar surface of the hind paws. Simvastatin40mg/kg, atorvastatin10mg/kg, ezetimibe10mg/kg, ezetimibe10mg/kg + simvastatin20mg/kg or 40mg/kg were given intragastrically and the treatment began on the day of CFA injection and continued daily up to the 28th day after arthritis induction. The ezetimibe + simvastatin combination was more effective in reducing the inflammatory response in arthritic rats than in atorvastatin, simvastatin, or ezetimibe monotherapy. The observed effect seems to be cholesterol‐independent as there were no changes in plasma cholesterol levels. In spite of the benefits on joint lesions, treatment with ezetimibe + simvastatin combination caused a marked increment in liver, kidneys, spleen size, and plasma transaminases activities. Therefore, animals treated with the ezetimibe10mg/kg + simvastatin40mg/kg combination were also submitted to liver perfusion experiments. In this regard, ezetimibe + simvastatin did not improve the liver metabolic alterations seen in control arthritic rats, on the contrary, a worsening was observed in liver production of glucose from alanine, as well as in oxygen uptake. All of these metabolic changes appear to be induced by treatment with ezetimibe + simvastatin combination, as the same metabolic effects were observed in normal and treated arthritic animals.

Topical anti-inflammatory effect of hypocholesterolaemic drugs.

Objectives  The topical anti‐inflammatory effect of simvastatin, atorvastatin, pravastatin, ezetimibe and combined ezetimibe + simvastatin was investigated, using the croton oil model of ear oedema in mice.

The Metabolic Responses to L-Glutamine of Livers from Rats with Diabetes Types 1 and 2.

There are several claims about the beneficial effects of supplementing L-glutamine to both type 1 and type 2 diabetes. The purpose of the present study was to provide detailed knowledge about the fate of this amino acid in the liver, the first organ that receives the compound when ingested orally. The study was done using the isolated perfused rat liver, an experimental system that preserves the microcirculation of the organ and that allows to measured several parameters during steady-state and pre steady-state conditions. L-Glutamine was infused in the portal vein (5 mM) and several parameters were monitored. Livers from type 1 diabetic rats showed an accelerated response to L-glutamine infusion. In consequence of this accelerated response livers from type 1 diabetic rats presented higher rates of ammonia, urea, glucose and lactate output during the first 25–30 minutes following L-glutamine infusion. As steady-state conditions approached, however, the difference between type 1 diabetes and control livers tended to disappear. Measurement of the glycogen content over a period of 100 minutes revealed that, excepting the initial phase of the L-glutamine infusion, the increased glucose output in livers from type 1 diabetic rats was mainly due to accelerated glycogenolysis. Livers from type 2 diabetic rats behaved similarly to control livers with no accelerated glucose output but with increased L-alanine production. L-Alanine is important for the pancreatic β-cells and from this point of view the oral intake of L-glutamine can be regarded as beneficial. Furthermore, the lack of increased glucose output in livers from type 2 diabetic rats is consistent with observations that even daily L-glutamine doses of 30 g do not increase the glycemic levels in well controlled type 2 diabetes patients.

Inhibition of α-Amylases by Condensed and Hydrolysable Tannins: Focus on Kinetics and Hypoglycemic Actions

The aim of the present study was to compare the in vitro inhibitory effects on the salivary and pancreatic α-amylases and the in vivo hypoglycemic actions of the hydrolysable tannin from Chinese natural gall and the condensed tannin from Acacia mearnsii. The human salivary α-amylase was more strongly inhibited by the hydrolysable than by the condensed tannin, with the concentrations for 50% inhibition (IC50) being 47.0 and 285.4 μM, respectively. The inhibitory capacities of both tannins on the pancreatic α-amylase were also different, with IC50 values being 141.1 μM for the hydrolysable tannin and 248.1 μM for the condensed tannin. The kinetics of the inhibition presented complex patterns in that for both inhibitors more than one molecule can bind simultaneously to either the free enzyme of the substrate-complexed enzyme (parabolic mixed inhibition). Both tannins were able to inhibit the intestinal starch absorption. Inhibition by the hydrolysable tannin was concentration-dependent, with 53% inhibition at the dose of 58.8 μmol/kg and 88% inhibition at the dose of 294 μmol/kg. For the condensed tannin, inhibition was not substantially different for doses between 124.4 μmol/kg (49%) and 620 μmol/kg (57%). It can be concluded that both tannins, but especially the hydrolysable one, could be useful in controlling the postprandial glycemic levels in diabetes.

The metabolic effects of diuron in the rat liver

A systematic study on the effects of diuron on the hepatic metabolism was conducted with emphasis on parameters linked to energy metabolism. The experimental system was the isolated perfused rat liver. The results demonstrate that diuron inhibited biosynthesis (gluconeogenesis) and ammonia detoxification, which are dependent of ATP generated within the mitochondria. Conversely, it stimulated glycolysis and fructolysis, which are compensatory phenomena for an inhibited mitochondrial ATP generation. Furthermore, diuron diminished the cellular ATP content under conditions where the mitochondrial respiratory chain was the only source of this compound. Besides the lack of circulating glucose due to gluconeogenesis inhibition, one can expect metabolic acidosis due to excess lactate production, impairment of ammonia detoxification and cell damage due to a deficient maintenance of its homeostasis. Some of the general signs of toxicity that were observed in diuron-treated rats can be attributed, partly at least, to the effects of the herbicide on energy metabolism.

Acetaminophen-induced hepatotoxicity: Preventive effect of trans anethole.

The hepatotoxicity induced by APAP is caused by the excessive production of N-acetyl-para-benzoquinone imine (NAPQI), which, when reacting with hepatic proteins proved to cause irreversible lesions. Associated with this process, an intense inflammatory process is also evidenced, characterized by the increased cell influx and production/release of inflammatory mediators. Trans anethole, an aromatic compounds has been showed anti-inflammatory efficacy by inhibit the cellular recruitment and synthesis/releases of many proinflammatory mediators such as prostaglandin (PGE2), cytokines (TNF, IL-1) and nitrico oxide (NO). The aim of this study is to investigate the effect of trans anethole on some inflammatory parameters that are involved in hepatotoxicity induced by high doses of acetaminophen. Our results demonstrate that treatment with AN at doses 125 and 250mg/kg once a day for seven days prevented the changes caused by the APAP overdose, showing less intensity in the histological changes (necrosis, size of hepatocyte area and inflammatory infiltration), and corroborating the findings of serum activities of transaminases and phosphatases and the activity of the enzyme myeloperoxidase. In addition, the treatment prevented the up-regulation of proinflammatory mediators such as NO, TNF, IL-1α, MIP-1α and MCP-1 and induced the up-regulation of anti-inflammatory cytokines (IL-4 and IL-10). Thus, our results demonstrate a possible protective effect of trans anethole on the hepatotoxicity induced by APAP.

Anti‐Inflammatory and Antioxidant Actions of Copaiba Oil Are Related to Liver Cell Modifications in Arthritic Rats

The present study investigated the action of copaiba oil (Copaifera reticulata) on the systemic inflammation, oxidative status, and liver cell metabolism of rats with adjuvant‐induced arthritis. The later is an experimental autoimmune pathology that shares many features with the human rheumatoid arthritis. Holtzman rats were distributed into the following groups: control (healthy) rats; control rats treated with copaiba oil at the doses of 0.58 and 1.15 g · kg−1, arthritic rats, and arthritic rats treated with copaiba oil (0.58 and 1.15 g · kg−1). The oil was administrated orally once a day during 18 days after arthritis induction. Both doses of copaiba oil improved the paw edema and the dose of 0.58 mg · kg−1 improved the swollen adrenals and lymph nodes besides decreasing the plasmatic myeloperoxidase activity (−30%) of arthritic rats. Copaiba oil (1.15 g · kg−1) abolished the increases of protein carbonyl groups and reactive oxygen species in the liver and both doses increased the liver GSH content and the catalase activity in arthritic rats. Copaiba oil (1.15 g · kg−1) decreased glycolysis (−65%), glycogenolysis (−58%), and gluconeogenesis (−30%) in the liver of arthritic animals. However, gluconeogenesis was also diminished by the treatment of control rats, which presented lower body weight gain (−45%) and diminished number of hepatocytes per liver area (−20%) associated to higher liver weight (+29%) and increased hepatocyte area (+13%). The results reveal that copaiba oil presented systemic anti‐inflammatory and antioxidant actions in arthritic rats. These beneficial effects, however, were counterbalanced by harmful modifications in the liver cell metabolism and morphology of healthy control rats. J. Cell. Biochem. 118: 3409–3423, 2017.

Distribution, lipid-bilayer affinity and kinetics of the metabolic effects of dinoseb in the liver

&NA; Dinoseb is a highly toxic pesticide of the dinitrophenol group. Its use has been restricted, but it can still be found in soils and waters in addition to being a component of related pesticides that, after ingestion by humans or animals, can originate the compound by enzymatic hydrolysis. As most dinitrophenols, dinoseb uncouples oxidative phosphorylation. In this study, distribution, lipid bilayer affinity and kinetics of the metabolic effects of dinoseb were investigated, using mainly the isolated perfused rat liver, but also isolated mitochondria and molecular dynamics simulations. Dinoseb presented high affinity for the hydrophobic region of the lipid bilayers, with a partition coefficient of 3.75 × 104 between the hydrophobic and hydrophilic phases. Due to this high affinity for the cellular membranes dinoseb underwent flow‐limited distribution in the liver. Transformation was slow but uptake into the liver space was very pronounced. For an extracellular concentration of 10 &mgr;M, the equilibrium intracellular concentration was equal to 438.7 &mgr;M. In general dinoseb stimulated catabolism and inhibited anabolism. Half‐maximal stimulation of oxygen uptake in the whole liver occurred at concentrations (2.8–5.8 &mgr;M) at least ten times above those in isolated mitochondria (0.28 &mgr;M). Gluconeogenesis and ureagenesis were half‐maximally inhibited at concentrations between 3.04 and 5.97 &mgr;M. The ATP levels were diminished, but differently in livers from fed and fasted rats. Dinoseb disrupts metabolism in a complex way at concentrations well above its uncoupling action in isolated mitochondria, but still at concentrations that are low enough to be dangerous to animals and humans even at sub‐lethal doses. Graphical abstract Figure. No caption available. HighlightsDinoseb presents high affinity for the hydrophobic region of the lipid bilayers.Its cellular concentration may exceed the extracellular one by a factor of 43.9.One order of magnitude separates the active concentrations in mitochondria and liver.Hepatic metabolism is disrupted in the concentration range up to 10 &mgr;M.

The action of zymosan on octanoate transport and metabolism in the isolated perfused rat liver

The effects of zymosan on transport, distribution, and metabolism of octanoate in the perfused rat liver were investigated using the multiple‐indicator dilution technique. Livers were perfused with 300 µM octanoate in the absence or in the presence of 100 µg/mL zymosan. Tracer amounts of [1‐14C]octanoate, [3H] water, and [131I]albumin were injected into the portal vein, and the effluent perfusate was fractionated. The normalized dilution curves were analyzed by means of a space‐distributed variable transit time model. Zymosan decreased the space into which octanoate undergoes flow‐limited distribution, possibly the first cellular exchanging pool represented by plasma membranes and their adjacencies. However, the rate of transfer of octanoate from the plasma membrane into the rest of the cell was not modified as indicated by the similar values of the influx rates and also the net uptake of octanoate per unit of accessible cellular volume. However, when referred to the wet weight of the liver, the net uptake of octanoate was 37.5% reduced, a value corresponding to the diminution of the cellular accessible space. It can be concluded that an exclusion of a fraction of the liver parenchyma from the microcirculation is the main mechanism by which zymosan reduces the metabolism of exogenous octanoate.