Glutamine protects the small intestinal mucosa in anticancer drug-induced rat enteritis model

Experimental Chemotherapy-Induced Mucositis: A Scoping Review Guiding the Design of Suitable Preclinical Models

Mucositis is a common and most debilitating complication associated with the cytotoxicity of chemotherapy. The condition affects the entire alimentary canal from the mouth to the anus and has a significant clinical and economic impact. Although oral and intestinal mucositis can occur concurrently in the same individual, these conditions are often studied independently using organ-specific models that do not mimic human disease. Hence, the purpose of this scoping review was to provide a comprehensive yet systematic overview of the animal models that are utilised in the study of chemotherapy-induced mucositis. A search of PubMed/MEDLINE and Scopus databases was conducted to identify all relevant studies. Multiple phases of filtering were conducted, including deduplication, title/abstract screening, full-text screening, and data extraction. Studies were reported according to the updated Preferred Reporting Items for Systematic reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) guidelines. An inter-rater reliability test was conducted using Cohen's Kappa score. After title, abstract, and full-text screening, 251 articles met the inclusion criteria. Seven articles investigated both chemotherapy-induced intestinal and oral mucositis, 198 articles investigated chemotherapy-induced intestinal mucositis, and 46 studies investigated chemotherapy-induced oral mucositis. Among a total of 205 articles on chemotherapy-induced intestinal mucositis, 103 utilised 5-fluorouracil, 34 irinotecan, 16 platinum-based drugs, 33 methotrexate, and 32 other chemotherapeutic agents. Thirteen articles reported the use of a combination of 5-fluorouracil, irinotecan, platinum-based drugs, or methotrexate to induce intestinal mucositis. Among a total of 53 articles on chemotherapy-induced oral mucositis, 50 utilised 5-fluorouracil, 2 irinotecan, 2 methotrexate, 1 topotecan and 1 with other chemotherapeutic drugs. Three articles used a combination of these drugs to induce oral mucositis. Various animal models such as mice, rats, hamsters, piglets, rabbits, and zebrafish were used. The chemotherapeutic agents were introduced at various dosages via three routes of administration. Animals were mainly mice and rats. Unlike intestinal mucositis, most oral mucositis models combined mechanical or chemical irritation with chemotherapy. In conclusion, this extensive assessment of the literature revealed that there was a large variation among studies that reproduce oral and intestinal mucositis in animals. To assist with the design of a suitable preclinical model of chemotherapy-induced alimentary tract mucositis, animal types, routes of administration, dosages, and types of drugs were reported in this study. Further research is required to define an optimal protocol that improves the translatability of findings to humans.

A critical role of AMP-activated protein kinase in regulating intestinal nutrient absorption, barrier function, and intestinal diseases

As one of the most important organs in animals, the intestine is responsible for nutrient absorption and acts as a barrier between the body and the environment. Intestinal physiology and function require the participation of energy. 5'-adenosine monophosphate-activated protein kinase (AMPK), a classical and highly expressed energy regulator in intestinal cells, regulates the process of nutrient absorption and barrier function and is also involved in the therapy of intestinal diseases. Studies have yielded findings that AMPK regulates the absorption of glucose, amino acids, and fatty acids in the intestine primarily by regulating transportation systems, as we detailed here. Moreover, AMPK is involved in the regulation of the intestinal mechanical barrier and immune barrier through manipulating the expression of tight junctions, antimicrobial peptides, and secretory immunoglobulins. In addition, AMPK also participates in the regulation of intestinal diseases, which indicates that AMPK is a promising therapeutic target for intestinal diseases and cancer. In this review, we summarized the current understanding regarding how AMPK regulates intestinal nutrient absorption, barrier function, and intestinal diseases.

Ca2+-Permeable Channels/Ca2+ Signaling in the Regulation of Ileal Na+/Gln Co-Transport in Mice

Oral glutamine (Gln) has been widely used in gastrointestinal (GI) clinical practice, but it is unclear if Ca²⁺ regulates intestinal Gln transport, although both of them are essential nutrients for mammals. Chambers were used to determine Gln (25 mM)-induced I_sc through Na⁺/Gln co-transporters in the small intestine in the absence or the presence of selective activators or blockers of ion channels and transporters. Luminal but not serosal application of Gln induced marked intestinal I_sc, especially in the distal ileum. Lowering luminal Na⁺ almost abolished the Gln-induced ileal I_sc, in which the calcium-sensitive receptor (CaSR) activation were not involved. Ca²⁺ removal from both luminal and serosal sides of the ileum significantly reduced Gln- I_sc. Blocking either luminal Ca²⁺ entry via the voltage-gated calcium channels (VGCC) or endoplasmic reticulum (ER) release via inositol 1,4,5-triphosphate receptor (IP₃R) and ryanodine receptor (RyR) attenuated the Gln-induced ileal I_sc, Likewise, blocking serosal Ca²⁺ entry via the store-operated Ca²⁺ entry (SOCE), TRPV1/2 channels, and Na⁺/Ca²⁺ exchangers (NCX) attenuated the Gln-induced ileal I_sc. In contrast, activating TRPV1/2 channels enhanced the Gln-induced ileal I_sc. We concluded that Ca²⁺ signaling is critical for intestinal Gln transport, and multiple plasma membrane Ca²⁺-permeable channels and transporters play roles in this process. The Ca²⁺ regulation of ileal Na⁺/Gln transport expands our understanding of intestinal nutrient uptake and may be significant in GI health and disease.

Free Amino Acids in Human Milk: A Potential Role for Glutamine and Glutamate in the Protection Against Neonatal Allergies and Infections

Breastfeeding is indicated to support neonatal immune development and to protect against neonatal infections and allergies. Human milk composition is widely studied in relation to these unique abilities, which has led to the identification of various immunomodulating components in human milk, including various bioactive proteins. In addition to proteins, human milk contains free amino acids (FAAs), which have not been well-studied. Of those, the FAAs glutamate and glutamine are by far the most abundant. Levels of these FAAs in human milk sharply increase during the first months of lactation, in contrast to most other FAAs. These unique dynamics are globally consistent, suggesting that their levels in human milk are tightly regulated throughout lactation and, consequently, that they might have specific roles in the developing neonate. Interestingly, free glutamine and glutamate are reported to exhibit immunomodulating capacities, indicating that these FAAs could contribute to neonatal immune development and to the unique protective effects of breastfeeding. This review describes the current understanding of the FAA composition in human milk. Moreover, it provides an overview of the effects of free glutamine and glutamate on immune parameters relevant for allergic sensitization and infections in early life. The data reviewed provide rationale to study the role of free glutamine and glutamate in human milk in the protection against neonatal allergies and infections.

Perioperative enteral supplementation with glutamine, fiber, and oligosaccharide reduces early postoperative surgical stress following esophagectomy for esophageal cancer

BACKGROUND

We clarified the effects of perioperative enteral supplementation with glutamine, fiber, and oligosaccharide (GFO) after an esophagectomy on preventing surgical stress.

METHODS

Of 326 patients with esophageal cancer, 189 received GFO administration (GFO group) and 137 did not (control group). The propensity score matching method was used to identify 89 well-balanced pairs of patients to compare postoperative laboratory parameters and clinical and postoperative outcomes.

RESULTS

The duration of the systemic inflammatory response syndrome (SIRS) was significantly shorter in the GFO group compared to the control group (p = 0.002). Moreover, the lymphocyte/neutrophil ratio (L/N ratio) had significantly recovered in the GFO group on postoperative day-3, and the CRP value was significantly lower in the GFO group than that in the control group on postoperative day-2.

CONCLUSIONS

Perioperative use of enteral supplementation with glutamine, fiber, and oligosaccharide likely contributes to a reduction in early surgical stress after an esophagectomy. These beneficial effects can bring about early recovery from postoperative immunosuppressive conditions after radical esophagectomy.

Glutamine-Induced Secretion of Intestinal Secretory Immunoglobulin A: A Mechanistic Perspective

Secretory immunoglobulin A (SIgA) is one important line of defense in the intestinal mucosal surface to protect the intestinal epithelium from enteric toxins and pathogenic microorganisms. Multiple factors, such as intestinal microbiota, intestinal cytokines, and nutrients are highly involved in production of SIgA in the intestine. Recently, glutamine has been shown to affect intestinal SIgA production; however, the underlying mechanism by which glutamine stimulates secretion of intestinal SIgA is unknown. Here, we review current knowledge regarding glutamine in intestinal immunity and show that glutamine-enhanced secretion of SIgA in the intestine may involve intestinal microbiota, intestinal antigen sampling and presentation, induction pathways for SIgA production by plasma cells (both T-dependent and T-independent pathway), and even transport of SIgA. Altogether, the glutamine-intestinal SIgA axis has broad therapeutic implications for intestinal SIgA-associated diseases, such as celiac disease, allergies, and inflammatory bowel disease.

Impact of intra-operative intraperitoneal chemotherapy on organ/space surgical site infection in patients with gastric cancer

BACKGROUND

Various risk factors for surgical site infection (SSI) have been identified such as age, overweight, duration of surgery, blood loss, etc. Intraperitoneal chemotherapy during surgery is a common procedure in patients with gastric cancer, yet its impact on SSI has not been evaluated.

AIM

To evaluate whether intra-operative intraperitoneal chemotherapy is a key risk factor for organ/space SSI in patients with gastric cancer.

METHODS

All patients with gastric cancer who underwent surgery at the Department of Gastrointestinal Surgery between January 2008 and December 2013 were studied. The organ/space SSI rates were compared between patients who received intra-operative intraperitoneal chemotherapy and patients who did not receive intra-operative intraperitoneal chemotherapy, and the risk factors for organ/space SSI were analysed by univariate and multi-variate regression analyses. The microbial causes of organ/space SSI were also identified.

FINDINGS

Of the eligible 845 patients, 356 received intra-operative intraperitoneal chemotherapy, and the organ/space SSI rate was higher in these patients compared with patients who did not receive intra-operative intraperitoneal chemotherapy (9.01% vs 3.88%; P = 0.002). Univariate analysis confirmed the significance of this finding (odds ratio 2.443; P = 0.003). As a result, hospital stay was increased in patients who received intra-operative intraperitoneal chemotherapy {mean 20.91 days [95% confidence interval (CI) 19.76-22.06] vs 29.72 days (95% CI 25.46-33.99); P = 0.000}. The results also suggested that intra-operative intraperitoneal chemotherapy may be associated with more Gram-negative bacterial infections.

CONCLUSION

Intra-operative intraperitoneal chemotherapy is a significant risk factor for organ/space SSI in patients with gastric cancer.