Dichotomic actions of glutamine in host versus tumour: an emerging concept

Oral glutamine inhibits tumor growth of gastric cancer bearing mice by improving immune function and activating apoptosis pathway

Gastric cancer is one of the most common cancers in the world. It has been shown that exogenous glutamine (GLN) can inhibit the growth of tumor in vivo, but the relationship between GLN and gastric cancer has not been studied. The gastric cancer bearing mouse model was constructed and taken GLN orally at the same time, and the results found that oral GLN (1 or 2 g/kg/d) significantly inhibited the growth rate of tumor and reduce the weight of tumor tissues. Immunohistochemistry showed that oral GLN significantly reduced the PCNA index, which further proved that GLN could inhibit the growth of tumor cells. At the same time, TUNEL assay showed that oral GLN significantly enhanced the apoptosis levels of tumor cells. In addition, GLN reduced GSH levels in tumor tissues, but increased the levels of GSH in plasma, improved the T-lymphocyte transformation rate and NK cell activity, significantly inhibited the secretion of TNF-α and promoted the secretion of IL-2, thus regulating the immune function in vivo. Further detection of apoptosis pathway showed that oral GLN significantly enhanced the expression of pro-apoptotic factor Bad and inhibited the expression of Bcl-2. Meanwhile, GLN significantly increased the activities of Caspase-3, Caspase-8, caspase-9 and PARP. GSH activator NAC had a similar effect to GLN, which could improve the immune function and activate apoptosis pathway, while GSH inhibitor BSO significantly blocked the regulation of GLN, destroyed the immune balance and inhibited apoptosis, but IL-2 significantly blocked the anti-apoptotic effect of BSO. Therefore, oral GLN can improve immune function and activate apoptosis pathway through GSH, and then inhibit the growth of tumor in vivo.

Influence of enteral glutamine on inflammatory and hormonal response in patients with rectal cancer during preoperative radiochemotherapy

We conducted a randomized double-blind placebo-controlled study evaluating the influence of 5 weeks' duration of 30 g enteral glutamine supplementation on inflammatory and hormonal responses in 73 patients with rectal cancer undergoing preoperative radiochemotherapy. Plasma levels of inflammatory and hormonal parameters were controlled at the beginning and at the end of supplementation. Enteral glutamine resulted in modulation of inflammatory and hormonal responses as shown by a decreased plasma interleukin 6 and cortisol levels in glutamine compared with placebo group: 5.5±3.8 versus 11.1±19.9 ng/l (P=0.02) for IL-6 and 386±168.4 to 312.7±111.7 nmol/l (P=0.03) for cortisol. We conclude that enteral glutamine exhibits some anti-inflammatory activity and, consequently, leads to a lower hormonal stress response during radiochemotherapy in patients with rectal cancer.

Clinical application of immune-enhanced enteral nutrition in patients with advanced gastric cancer after total gastrectomy

OBJECTIVE

To determine whether immune-enhanced enteral nutrition (EN) was effective on nutritional status, immune function, surgical outcomes and days of hospitalization after total gastrectomy for patients with advanced gastric cancer (AGC).

METHODS

From August 2005 to May 2011, 78 patients with AGC who underwent a total gastrectomy were enrolled and divided randomly into three groups: immune-enhanced EN (EN + glutamine [Gln]) group, standard EN group and control group. Serum parameters including total protein, albumin, proalbumin and transferrin were examined on preoperative day 1, postoperative day 2 and day 12. Levels of immunoglobulin M (IgM), immunoglobulin G (IgG), natural killer (NK) cells, CD4⁺ and CD8⁺ T cells were also compared.

RESULTS

The formulas were tolerated well in all the patients except 5 with mild complications. The EN + Gln and EN groups showed a faster onset of flatus and shorter hospitalization duration than the control group. On postoperative day 12, serum total protein, albumin, proalbumin and transferrin levels of the EN + Gln and EN groups were significantly higher than those of the control group (P < 0.05). CD4⁺ T cells, NK cells, IgM and IgG levels of the EN + Gln group increased prominently, and were significantly higher than those before the operation as well as those in the EN and control groups.

CONCLUSION

Immune-enhanced EN can improve nutritional status and immune function for the patients with AGC after total gastrectomy.

Amino acid regulation of mammalian gene expression in the intestine

Some amino acids exert a wide range of regulatory effects on gene expression via the activation of different signalling pathways and transcription factors, and a number of cis elements were shown to respond to changes in amino acid concentration. Particular attention has been paid to the effects of glutamine and arginine, which modulate a number of cell functions through the activation of various pathways in different tissues. In the intestine, appropriate concentrations of both arginine and/or glutamine contribute to facilitate cell proliferation, to limit the inflammatory response and apoptosis, and to modulate intermediary metabolism through specific transcription factors. Particularly, besides its role as a major fuel for enterocytes, the regulatory effects of glutamine have been extensively studied and the molecular mechanisms involved appear diversified and complex. Indeed, in addition to a major role of NF-kappaB in its anti-inflammatory action and a stimulatory role of AP-1 in its growth-promoting action and cell survival, the involvement of some other transcription factors, such as PPAR-gamma or HSF-1, was shown to maintain intestinal cell integrity. The signalling pathways leading to the activation of transcription factors imply several kinases, particularly MAP kinases in the effect of glutamine and p70 S6 kinase for those of arginine, but in most cases the precise pathways from the entrance of the aminoacid into the cell to the activation of gene transcription has remained elusive.