Glutamine and arginine metabolism in tumor-bearing rats receiving total parenteral nutrition

Effect of tumor weight and tube feeding on TNF-alpha and IL-1beta mRNA expression in the brain of mice

BACKGROUND

Previous studies have shown that cytokine mRNA expression is elevated in the brains of anorectic, tumor-bearing rats. The objectives of the current study were as follows: (1) to determine whether a small tumor would result in up-regulation of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta mRNA expression in the brain and other tissues of tumor-bearing mice; and (2) to determine whether hyperalimentation by tube feeding would prevent up-regulation of cytokine mRNA expression in the brain and other tissues of tumor-bearing mice.

METHODS

Male C57BL/6 mice were divided into 4 groups: (1) control mice fed ad libitum (Control); (2) tumor-bearing mice fed ad libitum (TB); (3) control mice receiving tube feeding (CTF); and (4) tumor-bearing mice receiving tube feeding (TBTF).

RESULTS

TNF-alpha and IL-1beta mRNA expression was elevated in the brains of mice with a 1% body weight tumor, relative to the control and CTF groups, without any detectable changes in the other organs. On the other hand, TNF-alpha and IL-1beta mRNA expression was elevated in all organs of mice with an 8% body weight tumor, relative to the control and CTF groups. Tube feeding did not change TNF-alpha and IL-1beta mRNA expression in mice burdened with either a 1% or 8% body weight tumor.

CONCLUSIONS

Up-regulation of cytokine mRNA synthesis occurs earlier in the brain than in other organs, and hyperalimentation does not change cytokine mRNA expression in tumor-bearing mice.

Influence of L-methionine-deprived total parenteral nutrition with 5-fluorouracil on gastric cancer and host metabolism

AIM: To investigate the influence of L-methionine-deprived total parenteral nutrition with 5-FU on gastric cancer and host metabolism.

METHODS: N-methyl-N’-nitro-nitrosoguanidine (MNNG) induced gastric cancer rats were randomly divided into four groups: Met-containing TPN group (n = 11), Met-deprived TPN group (n = 12), Met-containing TPN+5-FU group (n = 11) and Met-deprived TPN+5-FU group (n = 12). Five rats in each group were sacrificed after 7 d of treatment and the samples were taken for examination. The remaining rats in each group were then fed separately with normal diet after the treatment until death, the life span was noted.

RESULTS: The tumors were enlarged in Met-containing group and shrank in Met-deprived group markedly after the treatment. The DNA index (DI) of tumor cells and the body weight (BW) of rats had no significant change in the two groups, however, the ratio of tumor cells’ S phase was increased. The ratio of G2M phase went up in Met-containing group, but down in Met-deprived group. In the other two groups that 5-FU was added, the BW of rats, and the diameter of tumors, the DI of tumor cells, the S and G2M phase ratio of tumor cells were all decreased, particularly in Met-deprived plus 5-FU group. Pathological examination revealed that the necrotic foci of the tumor tissue increased after Met-deprived TPN treatment, and the nucleoli of tumor cells enlarged. In -MetTPN+5-FU group, severe nuclear damage was also found by karyopyknosis and karyorrhexis, meanwhile there was slight degeneration in some liver and kidney cells. The serum free Met and Cysteine decreased markedly (P ＜ 0.001), while other amino acids, such as serum free serine and glutamine increased significantly (P ＜ 0.005). All the rats died of multiple organ failure caused by cancer metastasis. The average survival time was 18.6 d in Met-containing TPN group, 31 d in Met-deprived TPN group, 27.5 d in Met-containing TPN+5-FU group, and 43 d in Met-deprived TPN+5-FU group (P ＜ 0.05).

CONCLUSION: Met-deprived TPN causes methionine starvation of tumor cells, and can enhance the anti-tumor effect of 5-FU and prolong the life span of gastric cancer-bearing rats.

Glutamine supplementation in cancer patients

OBJECTIVES

Three series of studies investigated whether 1) glutamine deficiency occurs in tumor-bearing rats, 2) glutamine supplementation improves protein metabolism during chemotherapy in tumor-bearing rats, and 3) oral glutamine supplement improves systemic immune and gut-barrier function in patients with esophageal cancer receiving radiochemotherapy.

METHODS

In the animal studies, AH109A hepatoma cells or Yoshida sarcoma cells were inoculated into male Donryu rats to induce tumors. Glutamine production was measured by U-14C-glutamine infusion and the conversion of arginine to glutamine was measured by infusion of U-14C-arginine. The effect of glutamine on protein metabolism was investigated by 1-14C-leucine infusion. In the clinical study, 13 patients with esophageal cancer were randomized into two groups, control and glutamine supplemented (30 g/d), for 4 wk.

RESULTS

Glutamine levels in plasma and skeletal muscle were decreased in tumor-bearing rats, although glutamine production and the conversion of arginine to glutamine were increased. Glutamine-supplemented total parenteral nutrition reduced whole-body protein breakdown rate during chemotherapy in tumor-bearing rats. Oral supplementation of glutamine to the patients with esophageal cancer enhanced lymphocyte mitogenic function and reduced permeability of the gut during radiochemotherapy.

CONCLUSIONS

Glutamine depletion in host tissues occurs in tumor-bearing rats. Glutamine supplementation can attenuate loss of protein in the muscle in tumor-bearing animals and protect immune and gut-barrier function during radiochemotherapy in patients with advanced cancer.

Dietary glutamine suppresses endogenous glutamine turnover in the rat

Plasma glutamine turnover was determined using 1-14C-labeled glutamine in rats that consumed crystalline amino acid diets containing the equivalent of 16% protein with 25% of the amino acids as glutamine or a control diet containing no glutamine (or glutamate) for 10 days. Glutamine turnover in glutamine-fed animals was 66% of the rate in the control group. Glutamine feeding caused 20% higher levels of arterial plasma glutamine. Arterial-portal differences across the portal-drained viscera showed net glutamine uptake in control animals but no net uptake or release in the glutamine-fed group. Skeletal muscle glutamine synthetase activity was similar in both groups. The results indicate that long-term consumption of relatively large amounts of dietary glutamine decreases the turnover of plasma glutamine and thus reduces the need for endogenous glutamine synthesis.

Sepsis increases lung glutamine synthetase expression in the tumor-bearing host

Acute stresses such as trauma or endotoxemia augment GLN demand and are associated with increased release of this amino acid from skeletal muscle and lung as well as increased expression of glutamine synthetase (GS, the principal enzyme of GLN synthesis) in these tissues. Muscle GLN release is also increased during chronic catabolic states which are associated with depletion of lean body mass, such as starvation or malignancy. We hypothesized that the expression of GS in response to an acute stress would be altered in tumor-bearing rats (TBR) experiencing severe cachexia and therefore a previously heightened GLN demand. Male Fischer 344 rats were implanted with methylcholanthrene-induced fibrosarcoma tumors or underwent sham operations and pair-feeding (sham) with TBR partners. When tumor burden reached approximately 15% of carcass weight, animals received injections of either Escherichia coli lipopolysaccharide (LPS, 1 mg/kg body wt) or saline vehicle. Rats were sacrificed 8 h after injection and lung and muscle tissue were analyzed for GS mRNA and protein via Northern and Western blot techniques, respectively. LPS injection caused an equivalent 4- to 6-fold increase in lung and muscle GS mRNA in both TBR and sham rats (P < 0.01). LPS did not produce a significant increase in GS protein level in muscle tissue of either group or in lung tissue of sham rats. In contrast, endotoxin did lead to a 3.5-fold increase in GS protein levels in lung tissue of TBRs (P < 0.05). This increase in lung GS protein may signify the importance of the lung in maintaining GLN homeostasis during chronic catabolic states where muscle mass is diminished.

Effects of glutamine supplements and radiochemotherapy on systemic immune and gut barrier function in patients with advanced esophageal cancer

OBJECTIVE

The objective of this study was to determine whether oral glutamine supplements can protect lymphocyte and gut barrier function in patients with advanced esophageal cancer undergoing radiochemotherapy.

SUMMARY BACKGROUND DATA

Glutamine supplements improved protein metabolism in tumor bearing rats who underwent chemotherapy and reduced the toxicity of chemotherapy through an enhancement of glutathione production in rats.

METHODS

Thirteen patients with esophageal cancer were randomly placed in either a control or a glutamine group. Glutamine was administered orally (30 g/day) at the start of radiochemotherapy and for the subsequent 28 days. All patients underwent mediastinal irradiation and chemotherapy consisting of 5-fluorouracil and cisplatin. The lymphocyte count was determined, and blast formation was assessed after stimulation with phytohemagglutinin and concanavalin A. Gut barrier function was assessed by measuring the total amount of phenolsulfonphthalein excreted in the urine after the oral administration of phenolsulfonphthalein.

RESULTS

Glutamine supplements prevented a reduction in the lymphocyte count (control: 567 +/- 96/mm3 vs. glutamine: 1007 +/- 151, p < 0.05), and blast formation of lymphocyte (phytohemagglutinin, control: 19478 +/- 2121 dpm vs. glutamine: 33860 +/- 1433, p < 0.01, concanavalin A, control: 19177 +/- 1897 dpm vs. glutamine: 29473 +/- 2302, p < 0.01), and amount of phenolsulfonphthalein excretion in the urine was greater with control than with glutamine group (control: 15.4 +/- 2.4% vs. glutamine: 7.4 +/- 1.2, p < 0.05) 7 days after the initiation of radiochemotherapy.

CONCLUSIONS

Oral glutamine supplementation protects lymphocytes and attenuates gut permeability in patients with esophageal cancer during radiochemotherapy.