Károly Mészáros

Superoxide anion generation in the liver during the early stage of endotoxemia in rats.

Infiltration of polymorphonuclear neutrophils (PMN) in the rat liver 3 hr after an intravenous (IV) injection of a sublethal dose of Escherichia coli lipopolysaccharide (LPS) was observed without any significant alteration in the total number of Kupffer and endothelial cells. Since previous studies have demonstrated that phagocytic cells in the liver were in a state of metabolic activation under similar experimental conditions, we investigated the in vitro generation of superoxide anion (O2 ‐) by this cell type following the administration of LPS. Kupffer cells from normal rats did not release O2 ‐, in contrast to those obtained from LPS‐treated rats. The generation of O2 ‐ by Kupffer cells from endotoxic rats was elevated from 3.0 ± 1.9 nmol/106 cells/60 min (mean ± SD) in the absence of macrophage (Mφ) activators, to 5.0 ± 2.36, 11.33 ± 5.40, and 4.33 ± 0.90 in the presence of opsonized zymosan, phorbol myristate acetate (PMA), and the calcium ionophore A23187, respectively. Hepatocytes from normal or endotoxic rats did not produce detectable O2 ‐. Endothelial cells from LPS‐treated rats generated < 0.8 nmol/106 cells in the presence of zymosan. PMN that accumulated in the livers of endotoxic rats released O2 ‐ only in the presence of zymosan (8.12 ± 5.40), PMA (15.43 ± 5.84), or A23187 (1.70 ± 0.12). The O2 ‐ generation by blood monocytes and PMN increased significantly after endotoxin administration and in the presence of activators. These results suggest that the hypermetabolic state of phagocytic cells in the liver shortly after LPS treatment may be correlated with the increased generation of O2 ‐. The latter may subsequently contribute to the induction of hepatic injury in endotoxemia.

Tumor necrosis factor increases in vivo glucose utilization of macrophage-rich tissues

Glucose utilization of different tissues was investigated in vivo by the 2-deoxyglucose tracer technique. After infusion of a non-lethal dose of recombinant human TNF-alpha (150 micrograms/kg) to rats, glucose utilization was increased by 80-100% in spleen, liver, kidney, by 60% in skin and by 30-40% in lung and ileum. The largest increase (150%) was observed in the diaphragm. There was no significant change in glucose utilization by skeletal muscles, testis and brain. These data show that TNF exerts metabolic effects on macrophage-rich tissues, and suggest that enhanced secretion of TNF may be one of the important factors in eliciting the metabolic changes in sepsis and endotoxicosis.

Insulin-mediated glucose uptake by individual tissues during sepsis

Gram-negative hypermetabolic sepsis has been previously reported to produce whole body insulin resistance. The present study was performed to determine in vivo which tissues are responsible for the sepsis-induced decrease in insulin-mediated glucose uptake (IMGU), and whether that decrease was related to a change in regional blood flow. Vascular catheters were placed in rats and sepsis was induced by subcutaneous injections of Escherichia coli. Insulin action was assessed 20 hours after the first injection of bacteria by the combined use of the euglycemic hyperinsulinemic clamp and the tracer 2-deoxyglucose (dGlc) technique. Insulin was infused at various rates in separate groups of septic and nonseptic rats for 3 hours to produce steady-state insulin levels between 70 and 20,000 microU/mL. Rats were injected with [U-14C]-dGlc 140 minutes after the start of the euglycemic hyperinsulinemic clamp for the determination of the glucose metabolic rate (Rg) in selected tissues. The maximal response to insulin was decreased 30% to 40% in the gastrocnemius, and in the red and white quadriceps. The former two muscles also showed a decrease in insulin sensitivity. However, the insulin resistance seen in hindlimb muscles was not evident in all muscles of the body, since IMGU by abdominal muscle, diaphragm, and heart was not impaired by sepsis. The basal Rg by skin, spleen, ileum, and lung was increased by sepsis, and was higher than the insulin-stimulated increases in Rg by these tissues in nonseptic animals. Cardiac output was similar in septic and nonseptic rats and did not change during the infusion of insulin. Under basal conditions, sepsis appeared to redistribute blood flow away from the red quadriceps and skin, and increased flow to the liver (arterial), lung, and small intestine. When plasma insulin levels were elevated, hepatic arterial blood flow was increased, and flow to the red quadriceps and skin was decreased in nonseptic animals. Hyperinsulinemia did not produce any consistent change in regional blood flow in septic animals. The results of this study indicate that a decrease rate of IMGU in muscle is primarily responsible for the whole body insulin resistance seen during hypermetabolic sepsis, and that the impairment of insulin action in skeletal muscle is not dependent on fiber type or to changes in blood flow.

Alterations in Lipid and Carbohydrate Metabolism in Sepsis

The effects of sepsis on lipid metabolism may be summarized as follows: The increased plasma catecholamine concentration stimulates adipose tissue FFA release. The increased FFA mobilization and plasma concentration results in an enhanced FFA uptake by the liver which promotes TGFA synthesis and output. Thus, triglyceride appearance rate also can be increased during hypermetabolic sepsis. In severe sepsis, the regulatory signals to increase FFA release from adipose tissue may be counterbalanced by blood flow limitations that inhibit FFA release, possibly due to the inadequate availability of the plasma carrier, albumin. Under such conditions, the arterial FFA concentration may be unchanged or decreased along with similar changes in the rate of peripheral FFA utilization. Triglyceride metabolism can also be altered during septic conditions in which plasma levels of cytokines are very high. Cytokines, notably TNF and IL-1, suppress synthesis of lipoprotein lipase which decreases the rate of TGFA clearance. Thus, hypertriglyceridemia can develop in the absence of elevated plasma FFA levels. The plasma concentration of cytokines necessary to inhibit LPL and how often this form of hypertriglyceridemia occurs in human sepsis are unknown at present. The sequence of events describing the influence of sepsis on carbohydrate metabolism is postulated to be the following: The presence of bacteria, or their products (eg, endotoxin) either directly or indirectly (via stimulating mononuclear phagocytes to release cytokines) activate the immune tissues. Glucose utilization by these tissues, which are predominantly glycolytic, is thereby stimulated resulting in increased lactate production. At the same time, glucose uptake by skeletal muscle and lactate release are also elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

A recombinant amino terminal fragment of bactericidal/permeability-increasing protein inhibits the induction of leukocyte responses by LPS

Bactericidal/permeability‐increasing protein (BPI) is a major component of the granules of polymorphonuclear neutrophils (PMNs) and is involved in the killing of gram‐negative bacteria. A 23‐kd recombinant protein, corresponding to the NH2‐terminal fragment of human BPI (rBPI23), has been shown to bind lipid A and antagonize some lipopolysaccharide (LPS)‐mediated effects. In this study the ability of rBPI23 to prevent a wide range of cellular responses to LPS was investigated. In vitro assays were carried out using human blood to more closely approximate in vivo conditions. The release of proinflammatory cytokines [tumor necrosis factor (TNF), interleukin‐1β (IL‐1β), IL‐6, IL‐8], induced by E. coli 0113 LPS, was markedly reduced by rBPl23 in a concentration‐dependent fashion. The production of the anti‐inflammatory protein IL‐lra (IL‐1 receptor antagonist) was triggered by lower LPS concentrations than those necessary for the other cytokines. Furthermore, prevention of IL‐lra release required higher rBPl23 concentrations than for other cytokines. The LPS‐induced production of oxygen‐derived free radicals by phagocytic cells (resulting in chemiluminescence) was also prevented by rBPl23· The inhibition was specific for LPS because the activation of leukocytes by phorbol myristate acetate, zymosan, or TNF was unaffected by BPI. The ability of rBPl23 to antagonize specifically the effects of endotoxin in the complex environment of human blood along with its bactericidal activity suggests that rBPI23 may be a novel therapeutic agent in the treatment of gram‐negative infections.

Effect of masoprocol on carbohydrate and lipid metabolism in a rat model of Type II diabetes

Summary Extracts of the creosote bush (Larrea tridentata, family Zygophyllaceae) have long been used as a folk remedy for Type II (non-insulin-dependent) diabetes by native Americans in southwestern North America. In this study we have evaluated the metabolic effects of masoprocol, a pure compound isolated from the creosote bush, in a rat model of Type II diabetes. Animals were fed a 20 % fat (by weight) diet for 2 weeks prior to intravenous injection with streptozotocin (STZ, 0.19 mmol/kg). Diabetic animals (glucose 16–33 mmol/l) were treated with vehicle, metformin (0.83 mmol/kg body weight) or masoprocol (0.83 mmol/kg body weight) twice a day for 4 days. Masoprocol treatment lowered glucose concentrations an average of 35 % compared with vehicle (14.2 ± 1.1 vs 21.7 ± 1.0 mmol/l, p < 0.001), a reduction similar to metformin treatment (12.8 ± 0.9 mmol/l), without any change in insulin concentration. Masoprocol treatment also lowered triglyceride concentrations 80 % compared with vehicle (1.0 ± 0.1 vs 4.8 ± 0.3 mmol/l, p < 0.001), a reduction far greater than following metformin treatment (3.6 ± 0.3 mmol/l). Non-esterified fatty acid and glycerol concentration were decreased by approximately 65 % by masoprocol compared with vehicle, a reduction approximately twice as great as seen with metformin (p < 0.001). The effect of masoprocol on in vivo insulin-mediated glucose disposal was evaluated by infusing fat-fed/STZ rats with glucose (0.22 mmol · kg · min–1) and insulin (30 pmol · kg · min–1) for 5 h. In response to the infusion, steady-state plasma glucose concentrations were reduced 30 % in masoprocol-treated animals compared with vehicle controls (p < 0.05) with no change noted in rats treated with metformin. The effect of masoprocol treatment was also tested in primary adipocytes isolated from normal animals. Adipocytes treated with masoprocol (30 μmol/l) had higher basal and insulin-stimulated glucose clearance than did adipocytes treated with vehicle (p < 0.05). These data show that masoprocol decreases both plasma glucose and triglyceride concentrations in fat-fed/STZ rats, presumably as a result of its ability to both increase glucose disposal and decrease lipolysis. [Diabetologia (1999) 42: 102–106]

In vivo glucose utilization by individual tissues during nonlethal hypermetabolic sepsis.

Febrile sepsis was induced in rats by repeated s.c. injections of live Escherichia coli bacteria. Glucose utilization of different tissues was investigated in vivo by using the 2‐deoxyglucose tracer technique. In septic rats the rate of glucose utilization was increased in macrophage‐rich tissues, including the liver (2.7‐fold), spleen (2.4‐fold), and ileum (1.6‐fold), compared with tissues from time‐matched nonseptic animals. A smaller increase in glucose utilization was evident in the abdominal muscle (1.3‐fold) and in the white portion of the quadriceps muscle (1.3‐fold). Changes were not significant in nine other tissues, including the brain. We postulate that in sepsis the mononuclear phagocyte system may be responsible for most of the increment of glucose utilization, and the latter provides metabolic support for the increased antibacterial activity of these cells.—Meszaros, K.; Lang, C. H.; Bagby, G. J.; Spitzer, J. J. In vivo glucose utilization by individual tissues during nonlethal hypermetabolic sepsis. FASEB J. 2: 3083‐3086; 1988.

Epinephrine and glucagon counteract inhibition of protein synthesis induced by D-galactosamine in isolated mouse hepatocytes.

10 mM D-galactosamine enhibited protein synthesis (1 h incubation time) by 67% in isolated mouse liver cells. Counteracting uridylate deficiency induced by D-galactosamine by preventive administration of 20 mM uridine did not decrease the extent of protein synthesis inhibition. 20 mM D-galactose reverted the inhibition of protein synthesis by D-galactosamine. 10(-5) M epinephrine and 10(-7) M glucagon decreased the incorporation of D-galactosamine into glycogen to 38% and 26% of the control value, respectively, after a 35 min incubation and reduced the inhibition of protein synthesis by D-galactosamine effectively. Experimental evidence supports the view that aminoglycogen formed after D-galactosamine treatment is responsible for the inhibition of protein synthesis.

Reversible inhibition of RNA synthesis and irreversible inhibition of protein synthesis by D-galactosamine in isolated mouse hepatocytes

SummaryThe inhibition of RNA synthesis of isolated mouse liver parenchymal cells caused by 10 mM D-galactosamine was reversible, while the inhibition of protein synthesis remained unaltered after the removal of galactosamine. 10−5 M epinephrine and 10−7 M glucagon have been shown to decrease aminoglycogen formation and thus to reduce the inhibitory effect of galactosamine on protein synthesis (11). However, these hormones did not decrease the inhibition of RNA synthesis. 10 mM D-galactosamine did not effect the nucleoside and amino acid incorporation of isolated non-parenchymal mouse liver cells. The predominant role of aminoglycogen in the inhibition of protein synthesis in galactosamine induced liver injury is discussed.

Tumor necrosis factor increases in vivo glucose uptake in hepatic nonparenchymal cells.

This study aims to elucidate the in vivo metabolic response of different liver cells following a short‐term (30 min) infusion of a nonlethal dose of human recombinant tumor necrosis factor (TNF). In vivo glucose uptake of different tissues and isolated liver cells was determined by a sequential double‐labeling version of the tracer 2‐deoxyglucose technique. Following TNF administration glucose uptake was increased in the liver, lung, spleen, and skin while it was not changed in muscle and testis. In response to TNF infusion neutropenia developed which was sustained for 40 min. The number of lymphocytes in the blood was also decreased after the termination of TNF infusion. This short‐term infusion of TNF, however, was not accompanied by marked sequestration of leukocytes into the liver. In vivo glucose uptake in response to TNF was doubled in the Kupffer cells and increased by 56% in hepatic endothelial cells. Glucose uptake of parenchymal cells was not significantly affected. The prompt increase of glucose uptake in the reticuloendothelial cells of the liver, primarily in the Kupffer cells, following TNF administration suggests that a similar metabolic response of these cells to sepsis may be mediated at least in part by TNF. It is suggested that the increased glucose uptake by the hepatic nonparenchymal cells is a reflection of the immunmodulatory effect of TNF.