Metabolic fluxes in the liver of rats bearing the Walker-256 tumour: influence of the circulating levels of substrates and fatty acids

Infusion of high concentration of lactate in perfused liver, simulating in vivo hyperlactatemia, prevents the reduction of gluconeogenesis in Walker-256 tumor-bearing rats

Gluconeogenesis (GN) is increased in patients with cancer cachexia, but is reduced in liver perfusion of Walker-256 tumor-bearing cachectic rats (TB rats). The causes of these differences are unknown. We investigated the influence of circulating concentrations of lactate (NADH generator) and NADH on GN in perfused livers of TB rats. Lactate, at concentrations similar to those found on days 5 (3.0 mM), 8 (5.5 mM), and 12 (8.0 mM) of the tumor, prevented the reduction of GN from 2.0 mM lactate (lactatemia of healthy rat) in TB rats. NADH, 50 or 75 μM, but not 25 μM, increased GN from 2.0 mM lactate in TB rats to higher values than healthy rats. High concentrations of pyruvate (no NADH generator, 5.0 and 8.0 mM) did not prevent the reduction of GN from 2.0 mM pyruvate in TB rats. However, 50 or 75 μM NADH, but not 25 μM, increased GN from 2.0 mM pyruvate in TB rats to similar or higher values than healthy rats. High concentration of glutamine (NADH generator, 2.5 mM) or 50 μM NADH prevented the reduction of GN from 1 mM glutamine in TB rats. Intraperitoneal administration of pyruvate (1.0 mg/kg) or glutamine (0.5 mg/kg) similarly increased the glycemia of healthy and TB rats. In conclusion, high lactate concentration, similar to hyperlactatemia, prevented the reduction of GN in perfused livers of TB rats, an effect probably caused by the increased redox potential (NADH/NAD⁺ ). Thus, the decreased GN in livers from TB rats is due, at least in part, to the absence of simulation of in vivo hyperlactatemia in liver perfusion studies.

Diet Supplemented with Chia Flour did not Modified the Inflammatory Process and Tumor Development in Wistar Rats Inoculated with Walker 256 Cells

Chia seed (Salvia hispanica L.) contains high amounts of n-3 α-linolenic acid (ALA) and has been associated with many health benefits. The aim of the present study was to evaluate the AIN-93 diet supplemented by chia flour on cancer-cachexia development and tissues inflammatory response. Wistar rats at 30 days old were treated with control diet or diet supplemented with chia flour for eight weeks. After this period, half of the animals in each diet group were inoculated with Walker 256 tumor cells. On the 14th day after tumor inoculation, the animals were euthanized and white adipose tissue depots, liver, gastrocnemius muscle, and tumor were removed. The tumor weight was higher and IL-10 content was lower in chia flour group. The tumor bearing did not modify the cytokines content in gastrocnemius muscle, retroperitoneal and epididymal adipose tissue, however, it decreased IL-1β and TNF-α content in liver, and IL6R and IL-10R protein content in mesenteric adipose tissue. In conclusion, our results demonstrated that supplementation with chia flour did not prevent the tumor bearing effects in Walker 256 model.

Changes in liver gluconeogenesis during the development of Walker-256 tumour in rats

Few studies have investigated liver gluconeogenesis in cancer and there is no agreement as to whether the activity of this pathway is increased or decreased in this disease. The aim of this study was to evaluate gluconeogenesis from alanine, pyruvate and glycerol, and related metabolic parameters in perfused liver from Walker-256 tumour-bearing rats on days 5 (WK5 group), 8 (WK8 group) and 12 (WK12 group) of tumour development. There was reduction (P < 0.05) of liver glucose production from alanine and pyruvate in WK5, WK8 and WK12 groups, which was accompanied by a decrease (P < 0.05) in oxygen consumption. Moreover, there was higher (P < 0.05) pyruvate and lactate production from alanine in the WK5 group and a marked reduction (P < 0.05) of pyruvate and urea production from alanine in the WK12 group. In addition, liver glucose production and oxygen consumption from glycerol were not reduced in WK5, WK8 and WK12 groups. Thus the, the results show inhibition of hepatic gluconeogenesis from alanine and pyruvate, but not from glycerol, on days 5, 8 and 12 of Walker-256 tumour development, which can be attributed to the metabolic step in which the substrate enters the gluconeogenic pathway.

Purinergic effects of a hydroalcoholic Agaricus brasiliensis (A. blazei) extract on liver functions

The effects of a hydroalcoholic extract of Agaricus brasiliensis (A. blazei) on functional parameters in the perfused rat liver were examined with emphasis on its content of nucleotides and nucleosides. Several nucleosides and nucleotides were identified in the A. brasiliensis extract, which was active on several liver functions. A significant part of the effects is the result of the purinergic action of nucleosides and nucleotides: pressure increment, glycogenolysis stimulation, transient inhibition of oxygen consumption, and redox state changes. Other phenomena such as the stimulation of gluconeogenesis, ureogenesis, and oxygen consumption are more likely consequences of the metabolic transformation of substrates contained within the extract, especially amino acids. It seems apparent that consumption of A. brasiliensis represents not only the ingestion of metabolic precursors but also the ingestion of substances that, even at low concentrations, can exert important signaling functions in the liver as well as in the organism as a whole.

The action of extracellular NAD+ in the liver of healthy and tumor-bearing rats: model analysis of the tumor-induced modified response

The chronic inflammatory state induced by cancer is expected to affect the actions of extracellular NAD(+) in the liver because these are largely mediated by eicosanoids. Under this assumption the present work was planned to investigate the influence of the Walker-256 tumor on the action of extracellular NAD(+) on metabolism and hemodynamics in the perfused rat liver. The experiments were done with livers from healthy and tumor-bearing rats with measurements of gluconeogenesis from lactate, pyruvate production, oxygen consumption and portal pressure. A model describing the biphasic effects of NAD(+) was proposed as an auxiliary worktool for interpretation. The Walker-256 tumor modified the responses of metabolism to extracellular NAD(+) by delaying the peak of maximal responses and by prolonging the inhibitory effects. The transient increase in portal perfusion pressure caused by NAD(+) was enhanced and delayed. The model was constructed assuming the mediation of a down-regulator (inhibition), an up-regulator (stimulation) and receptor dessensitization. Analysis suggested that the productions of both the down- and up-regulators were substantially increased and delayed in time in the tumor-bearing condition. Since the regulators are probably eicosanoids, this analysis is consistent with the increased capacity of producing these agents in the chronic inflammatory state induced by cancer.