Diabetes causes marked changes in function and metabolism of rat neutrophils.

Several studies have shown impairment of neutrophil function, a disorder that contributes to the high incidence of infections in diabetes. Since glucose and glutamine play a key role in neutrophil function, we investigated their metabolism in neutrophils obtained from the peritoneal cavity of streptozotocin-induced diabetic rats. The activities of hexokinase, glucose-6-phosphate dehydrogenase (G6PDH), phosphofructokinase (PFK), citrate synthase, phosphate-dependent glutaminase, NAD+-linked and NADP+-linked isocitrate dehydrogenase were assayed. Glucose, glutamine, lactate, glutamate and aspartate, and the decarboxylation of [U-14C], [1-14C] and [6-14C]glucose; [U-14C]palmitic acid; and [U-14C]glutamine were measured in 1-h incubated neutrophils. Phagocytosis capacity and hydrogen peroxide (H2O2) production were also determined. All measurements were carried out in neutrophils from control, diabetic and insulin-treated (2-4 IU/day) diabetic rats. Phagocytosis and phorbol myristate acetate (PMA)-stimulated H2O2 production were decreased in neutrophils from diabetic rats. The activities of G6PDH and glutaminase were decreased, whereas that of PFK was raised by the diabetic state. The activities of the remaining enzymes were not changed. Diabetes decreased the decarboxylation of [1-14C]glucose and [U-14C]glutamine; however, [6-14C]glucose and [U-14C]palmitic acid decarboxylation was increased. These observations indicate that changes in metabolism may play an important role in the impaired neutrophil function observed in diabetes. The treatment with insulin abolished the changes induced by the diabetic state even with no marked change in glycemia. Therefore, insulin may have a direct effect on neutrophil metabolism and function.

Evidence that macrophages transfer arachidonic acid and cholesterol to tissues in vivo.

Our previous studies have shown that [(14)C]-labelled cholesterol (CHOL) and arachidonic acid (AA) are transferred from macrophages (Mphi) to lymphocytes (LY) when these cells are co-cultured. In this study, we investigated whether these lipids can be transferred from control and thioglycollate-elicited Mphi (THIO-elicited Mphi) to various tissues and organs in vivo. For this purpose, control and THIO-elicited Mphi were pre-treated with [(14)C]-AA and [(3)H]-CHOL and then injected into the jugular vein of adult rats. More than 75% of the radioactivity injected was found in the liver of rats treated with [(14)C]-AA labelled-Mphi either control and THIO-stimulated. The radioactivity of [(3)H]-CHOL labelled Mphi was transferred mainly to the liver (51% in the control Mphi and 23% in the thioglycollate Mphi7) but it was also found in the kidney, lung and spleen. These results support the proposition that the transfer of lipids between cells also occurs in vivo. The full significance of this phenomenon however remains to be elucidated.

Effect of arginine, ornithine and citrulline supplementation upon performance and metabolism of trained rats.

During intense exercise there is an augmented production of ammonia and IMP in the exercised muscle that could be related to the establishment of peripheral fatigue. In order to prevent this accumulation, the urea cycle in the liver eliminates ammonia in the form of urea and the skeletal muscle buffers the increase of ammonia via transamination reactions. In the present study we evaluated the effect of arginine, citrulline and ornithine supplementation, intermediates of the urea cycle, on the performance of sedentary and swimming-trained rats submitted to a single bout of exhaustive exercise. We also measured the glycogen content of the soleus and gastrocnemius muscles and of the liver, as well as the plasma concentrations of ammonia, urea, glutamine, glucose and lactate. The results indicate that arginine, citrulline and ornithine supplementation increased the flux of substrate through the reaction catalysed by glutamine synthetase, leading to increased glutamine production after an exhaustive bout of exercise, and of the mechanism involved in ammonia buffering.

Diabetes causes marked changes in lymphocyte metabolism.

An enhanced susceptibility to infections is well known to occur in a poorly controlled diabetic state. Since glucose and glutamine are essential for lymphocyte function, we investigated whether their metabolism is changed in lymphocytes obtained from mesenteric lymph nodes of alloxan-induced diabetic rats (40 mg/kg body weight). The activities of hexokinase, phosphofructokinase, glucose-6-phosphate dehydrogenase (G6PDH), citrate synthase and phosphate-dependent glutaminase were determined. Decarboxylation of metabolites [U-14C]-, [1-14C]- and [6-14C]-glucose, [1-14C]- and [2-14C]-pyruvic acid, [U-14C]-palmitic acid and [U-14C]-glutamine was evaluated in incubated lymphocytes isolated from mesenteric lymph nodes. The measurements were carried out in cells following three experimental protocols: (1) lymphocytes freshly obtained from control and alloxan-induced diabetic rats, (2) lymphocytes from insulin-treated (2 U/rat per day) diabetic rats and (3) lymphocytes obtained from control and diabetic rats and cultured in the presence of insulin (1 mU/ml) for 6 h. The activities of hexokinase, G6PDH and citrate synthase were decreased by the diabetic state, whereas that of phosphofructokinase was raised. Decarboxylation of [U-14C]- and [6-14C]-glucose, [1-14C]- and [2-14C]-pyruvate and [U-14C]-glutamine were also decreased in lymphocytes from diabetic rats, whereas [U-14C]-palmitic acid decarboxylation was increased. Insulin administration in vivo or added to the culture medium reversed the changes observed in freshly obtained lymphocytes. Alloxan-induced diabetes did change lymphocyte metabolism and this may be an important mechanism leading to impairment of lymphocyte function.

Comparative effects of fish oil given by gavage and fish oil-enriched diet on leukocytes.

The comparative effects of fish oil given by gavage and fish oil enriched diet on metabolism and function of lymphocytes and macrophages were investigated. For this purpose, the following parameters were examined: 1) phagocytosis capacity, production of superoxide (O2*-) and hydrogen peroxide (H2O2) by macrophages, 2) lymphocytes proliferation capacity, 3) antioxidant enzyme activities in the mesenteric lymph nodes (MEN) and liver, 4) Thiobarbituric Acid Reactive Substances (TBARS) content in MLN, liver, and plasma, 5) total antioxidant capacity of the plasma, and 6) fatty acid composition of macrophages, MLN, liver and plasma. Both FO treatments did not affect phagocytosis capacity but increased hydrogen peroxide production by macrophages in the presence of PMA. FO given by gavage markedly increased lymphocytes proliferation both in the absence (5.8-fold) and in the presence (16.7-fold) of Con A, whereas FO-rich diet showed an increase in the presence of Con A only (53.3%). FO given by gavage raised the proliferation index by 2.9-fold and FO-rich diet increased by 29% only as compared to controls. Concomitantly, FO given by gavage was more effective to increase TBARS content in plasma. The proportion of some fatty acids in the tissues and cells was also differently changed depending on the way FO was administered to rats: in particular: myristic, arachidonic, and eicosapentaenoic acids. This fact may partially explain the differences between both FO treatments.

Modulation of hypersensitivity reaction by lipids given orally.

The effect of lipids administration by gavage (0.4% body weight) given daily during four weeks on the hypersensitivity reaction in trachea, upper and lower bronchi, liver, kidney, mesentery, and pancreas was investigated in male rats. The plasma exudation was assessed by using Evans blue (EB) dye extravasation method. There was a significant difference in the permeability of the organs in nonimmunized rats. The immunization increased the vascular permeability and the response with the organs varied greatly. The effect of lipids on anaphylactic reaction was compared to those of untreated rats (control group). The EB extravasation was significantly increased in the trachea obtained from rats treated with cocoa butter and soybean oil. In the upper bronchi of rats treated with soybean oil, the EB extravasation was increased. However, in the lower bronchi, none of the treatments with lipids changed the extravasation of EB. The same was observed in the liver and kidney. The animals treated with lipids by gavage did not present differences in EB extravasation in the mesentery. However, in the pancreas and duodenum, the treatment with fish and soybean oils and cocoa butter markedly lowered EB extravasation.

Superoxide dismutase, catalase and glutathione peroxidase activities in the lymphoid organs and skeletal muscles of rats treated with dexamethasone.

The effect of dexamethasone (a synthetic glucocorticoid) on the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase and glutathione peroxidase) of the lymphoid organs (mesenteric lymph nodes (MLN), spleen and thymus) was investigated. For comparison with non-immune tissues, skeletal muscles (soleus and gastrocnemius (GC) were also studied. As an indication of the occurrence of lipid peroxidation, the content of thiobarbituric acid reactant substances (TBARs) was also determined. Dexamethasone treatment decreased the TBARs content of the lymphoid organs and raised it in the GC and soleus muscles. The activity of Cu/Zn-SOD was reduced in all tissues. However, the activity of Mn-SOD was decreased in the MLN and soleus muscle only. The activity of catalase was reduced in the MLN and thymus and raised in the spleen and GC and soleus muscles. The imposed treatment raised the activity of GPX in the MLN, thymus and spleen and reduced it in GC and soleus muscles. These data led us to postulate that the mechanism for the therapeutic effect of glucocorticoids as antiinflammatory and immunosuppressive agents might include modification of antioxidant enzyme activities.

Roughening transition of a restricted solid-on-solid model in the directed percolation universality class.

We carried out a finite-size scaling analysis of the restricted solid-on-solid version of a recently introduced growth model that exhibits a roughening transition accompanied by spontaneous symmetry breaking. The dynamic critical exponent of the model was calculated and found to be consistent with the universality class of the directed percolation process in a symmetry-broken phase with a crossover to Kardar-Parisi-Zhang behavior in a rough phase. The order parameter of the roughening transition together with the string order parameter was calculated, and we found that the flat, gapped phase is disordered with an antiferromagnetic spin-fluid structure of kinks, although strongly dominated by the completely flat configuration without kinks. A possible interesting extension of the model is mentioned.

Effect of the i.v. administration of non-activated lymphocytes on rat plasma insulin and glucose levels.

Although several studies have shown the effect of cytokines on islet B cell function, the role of circulating cells in the control of insulin secretion has not been investigated. The effect of lymphocyte administration on plasma glucose and insulin levels was examined in male Wistar albino rats weighing 180-200 g. The animals were anesthetized and the jugular vein was cannulated for saline or lymphocyte injection (10(6) cells in 1 ml) and blood collection after 5, 10, 15, 20, 30, 45 and 60 min. A marked increase in plasma insulin levels (180 microU/ml as compared to 56 microU/ml in the control group, at 20 min) and an unexpected increase (P < 0.05) in blood glucose levels (at 60 min only) were observed after lymphocyte administration. Similar experiments undertaken with simultaneous administration of inhibitors of arachidonic acid metabolism, indomethacin and nordihydroguairetic acid at 1 mg/kg body weight, suggest that this effect of lymphocytes is not mediated by prostaglandins or leukotrienes.

Effect of the IV administration of non-activated lynphocytes on rat plasma insulin and glucose levels

Althugh several studies have shown the effect of cytokines on islet B cell function, the role of circulating cells in the control of insulin secretion has not been investigated. The effect of lymphocyte administration on plasma glucose and insulin levels was examined in male Wistar albino rats weighing 180-200g. The animals were anesthetized and the jugular vein was cannulated for saline or lymphocyte injection (10**6 cells in 1 ml) and blood collection after 5, 10, 15, 20, 30, 45, and 60 min. A marked increase in plasma insulin levels (180*U/ml as compared to 56*U/ml in the control group, at 20 min) and an unexpected increase (P<0.05) in blood glucose levels (at 60 min only) were observed after lymphocyte administration. Similar experiments undertaken with simultaneous administration of inhibitors of arachidonic acid metabolism, indomethacin and nordihydroguairetic acid at 1 mg/Kg body weight, suggest that this effect of lymphocytes is not mediated by prostaglandins or leukotrienes