Effect of glutamine on gut glutathione fractional release in the implanted tumor model

Immunosuppressive activity is attenuated by Astragalus polysaccharides through remodeling the gut microenvironment in melanoma mice

Astragalus polysaccharides (APS), the main effective component of Astragalus membranaceus, can inhibit tumor growth, but the underlying mechanisms remain unclear. Previous studies have suggested that APS can regulate the gut microenvironment, including the gut microbiota and fecal metabolites. In this work, our results showed that APS could control tumor growth in melanoma-bearing mice. It could reduce the number of myeloid-derived suppressor cells (MDSC), as well as the expression of MDSC-related molecule Arg-1 and cytokines IL-10 and TGF-β, so that CD8⁺ T cells could kill tumor cells more effectively. However, while APS were administered with an antibiotic cocktail (ABX), MDSC could not be reduced, and the growth rate of tumors was accelerated. Consistent with the changes in MDSC, the serum levels of IL-6 and IL-1β were lowest in the APS group. Meanwhile, we found that fecal suspension from mice in the APS group could also reduce the number of MDSC in tumor tissues. These results revealed that APS regulated the immune function in tumor-bearing mice through remodeling the gut microbiota. Next, we focused on the results of 16S rRNA, which showed that APS significantly regulated most microorganisms, such as Bifidobacterium pseudolongum, Lactobacillus johnsonii and Lactobacillus. According to the Spearman analysis, the changes in abundance of these microorganisms were related to the increase of metabolites like glutamate and creatine, which could control tumor growth. The present study demonstrates that APS attenuate the immunosuppressive activity of MDSC in melanoma-bearing mice by remodeling the gut microbiota and fecal metabolites. Our findings reveal the therapeutic potential of APS to control tumor growth.

Effects of glutamine for prevention of radiation-induced esophagitis: a double-blind placebo-controlled trial

Purpose Acute radiation-induced esophagitis (ARIE) leads to treatment delays, decreased quality of life (QOL), and secondary adverse events such as weight loss. Grade 3 ARIE occurs in 15%-30% of patients undergoing radiotherapy to the esophagus, leading to disruption or discontinuation of treatment. The purpose of this study was to assess the effects of glutamine, a common nutritional supplement, on ARIE in patients with thoracic malignancies. Patients and methods This double-blind, placebo-controlled trial enrolled patients with advanced thoracic malignancies receiving concurrent chemotherapy/radiotherapy or radiotherapy alone, with radiation doses to the esophagus ≥45 Gy. Patients were randomized (1:1) to receive 4 g of glutamine or glycine placebo twice daily. The primary objective was to determine whether glutamine decreases the severity of ARIE in these patients. Secondary objectives included assessment of the effects of glutamine on other measures of ARIE, weight, symptom burden measure assessed by the MD Anderson Symptom Inventory (MDASI-HN) questionnaire and the toxicity profile of glutamine. Results At the time of interim analysis, 53 patients were enrolled: 27 in the glutamine arm and 26 in the placebo arm. There was no difference in the incidence of esophagitis in the first 6 weeks of radiotherapy between the glutamine and placebo arms (74% versus 68%; P = 1.00). There were no significant differences between the two arms for time to onset of esophagitis. The duration of ARIE was shorter (6.3 versus 7.1 weeks; P = 0.54) and median weight loss was lower (0.9 kg versus 2.8 kg; p = 0.83) in the glutamine arm versus the placebo arm. The groups differ significantly in core symptom severity (2.1 vs 1.5, p < .03) but not in head and neck specific symptom severity (1.2 vs 1.1, p < .60) nor in symptom interference (2.1 vs 1.7, p < .22). There was no grade 3 or higher adverse event at least possibly related to glutamine. The study was terminated for futility following interim analysis. Conclusion Oral glutamine was not associated with significant improvement in severity of ARIE, weight loss, head and neck specific symptoms or symptom interference compared with placebo in patients with advanced thoracic malignancies receiving radiotherapy to the esophagus.Clinical trial information. NCT01952847, and date of registration is September 30, 2013.

Glutamine for Amelioration of Radiation and Chemotherapy Associated Mucositis during Cancer Therapy

Glutamine is a major dietary amino acid that is both a fuel and nitrogen donor for healing tissues damaged by chemotherapy and radiation. Evidence supports the benefit of oral (enteral) glutamine to reduce symptoms and improve and/or maintain quality of life of cancer patients. Benefits include not only better nutrition, but also decreased mucosal damage (mucositis, stomatitis, pharyngitis, esophagitis, and enteritis). Glutamine supplementation in a high protein diet (10 grams/day) + disaccharides, such as sucrose and/or trehalose, is a combination that increases glutamine uptake by mucosal cells. This increased topical effect can reduce painful mucosal symptoms and ulceration associated with chemotherapy and radiation in the head and neck region, esophagus, stomach and small intestine. Topical and oral glutamine seem to be the preferred routes for this amino acid to promote mucosal healing during and after cancer treatment.

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

PURPOSE OF REVIEW

Malignancy is characterized by a systemic deficiency of glutamine (GLN). The debate over whether GLN supplementation should be standard of cancer patients is still topical. This review focuses on recent findings on the effect of GLN administration on the incidence and severity of adverse effects in host due to radiotherapy or chemotherapy or both and on its putative adjuvant role on cytotoxicity of radiotherapy and chemotherapy on tumour.

RECENT FINDINGS

Animal and human studies have reported that high-dose GLN supplementation could prevent gastrointestinal tract injury after radiotherapy and chemotherapy. Animal studies are suggesting that GLN could actually decrease tumour growth by upregulating the immune system and through a regulation of the redox status associated to the metabolism of glutathione. GLN could enhance the selectivity of antitumour drugs by protecting normal tissues from chemotherapy and by sensitizing tumour cells to chemotherapy.

SUMMARY

Recent studies have shown that GLN could have dichotomic actions in host versus in tumour, probably in link with glutathione metabolism, suggesting that GLN could be used in clinical practice to increase the therapeutic index of oncological treatments.