Exogenous glucagon-like peptide-2 (GLP-2) prevents chemotherapy-induced mucositis in rat small intestine

Evolution and therapeutic potential of glucagon-like peptide 2 analogs

Glucagon-like peptide 2 (GLP-2) is a proglucagon-derived peptide released by intestinal endocrine cells. However, its therapeutic potential is limited by rapid inactivation via dipeptidyl peptidase-IV. The elucidation of three-dimensional structures of G-protein-coupled receptors, including GLP-2 receptor, has facilitated the rational design of novel peptide therapeutics. Recent studies have explored various structural modifications based on the structure of GLP-2, such as amino acid substitution, lipidation, and fusion with proteins, to extend the half-life of GLP-2 and enhance its biological activity. One promising avenue involves the development of multifunctional molecules targeting multiple pharmacological systems to boost therapeutic efficacy. This paper reviews the recent advancements in understanding GLP-2, including its physiological roles and structure-activity relationships, and evaluates the development prospects of GLP-2 analogs.

An unmet need for pharmacology: Treatments for radiation-induced gastrointestinal mucositis

Gastrointestinal mucositis (GIM) continues to be a significant issue in the management of abdominal cancer radiation treatments and chemotherapy, causing significant patient discomfort and therapy interruption or even cessation. This review will first focus on radiotherapy induced GIM, providing an understanding of its clinical landscape. Subsequently, the aetiology of GIM will be reviewed, highlighting diverse contributing factors. The cellular and tissue damage and associated molecular responses in GIM will be summarised in the context of the underlying complex biological processes. Finally, available drugs and pharmaceutical therapies will be evaluated, underscoring their insufficiency, and highlighting the need for further research and innovation. This review will emphasize the urgent need for improved pharmacologic therapeutics for GIM, which is a key research priority in oncology.

Post-prandial secretion of glucagon-like peptide-2 (GLP-2) after carbohydrate-, fat- or protein enriched meals in healthy subjects

Glucagon-like peptide 2 (GLP-2) is an important regulator of intestinal growth and function. In adherable mixed meals the macronutrient composition with the best potential for stimulating GLP-2 secretion is not known. We compared the effect of 3 iso-energetic meals, where approximately 60 % of the energy ratio was provided as either carbohydrate, fat, or protein, respectively, on the post-prandial endogenous GLP-2 secretion. The responses were compared to secretion profiles of peptide YY (PYY), and glucose-dependent insulinotropic peptide (GIP). Ten healthy subjects were admitted on three occasions, at least a week apart, after a night of fasting. In an open-label, crossover design, they were randomized to receive a high carbohydrate (HC), high fat (HF) or high protein (HP) meal. The meals were approximately ∼3.9 MJ. Venous blood was collected for 240 min, and plasma concentrations of GLP-2, GIP and PYY were measured with specific radioimmunoassays. Mean GLP-2 levels peaked already at 30 min for the HC meal, however the HP meal induced the highest mean GLP-2 peaking levels, resulting in significantly higher mean GLP-2 area under the curve (AUC) from baseline of 7279 pmol*min/L, 95 %-CI [6081;8477] compared to the HC meal: 4764 pmol*min/L, 95 %-CI [3498;6029], p = 0.020 and the HF meal: 4796 pmol*min/L, [3385;6207], p = 0.011. Findings were similar for the PYY. The HC meal provided a greater AUC for GIP compared to the HP- and HF meals. The HP meal was most effective with respect to stimulation of the postprandial GLP-2 and PYY secretion, whereas the HC meal was more effective for GIP.

Chemotherapy-induced gastrointestinal toxicity: Pathogenesis and current management

Chemotherapy is the most common treatment for malignant tumors. However, chemotherapy-induced gastrointestinal toxicity (CIGT) has been a major concern for cancer patients, which reduces their quality of life and leads to treatment intolerance and even cessation. Nevertheless, prevention and treatment for CIGT are challenging, due to the prevalence and complexity of the condition. Chemotherapeutic drugs directly damage gastrointestinal mucosa to induce CIGT, including nausea, vomiting, anorexia, gastrointestinal mucositis, and diarrhea, etc. The pathogenesis of CIGT involves multiple factors, such as gut microbiota disorders, inflammatory responses and abnormal neurotransmitter levels, that synergistically contribute to its occurrence and development. In particular, the dysbiosis of gut microbiota is usually linked to abnormal immune responses that increases inflammatory cytokines' expression, which is a common characteristic of many types of CIGT. Chemotherapy-induced intestinal neurotoxicity is also a vital concern in CIGT. Currently, modern medicine is the dominant treatment of CIGT, however, traditional Chinese medicine (TCM) has attracted interest as a complementary and alternative therapy that can greatly alleviate CIGT. Accordingly, this review aimed to comprehensively summarize the pathogenesis and current management of CIGT using PubMed and Google Scholar databases, and proposed that future research for CIGT should focus on the gut microbiota, intestinal neurotoxicity, and promising TCM therapies, which may help to develop more effective interventions and optimize managements of CIGT.

The progression of doxorubicin-induced intestinal mucositis in rats

Chemotherapy-induced intestinal mucositis is a severe side effect contributing to reduced quality of life and premature death in cancer patients. Despite a high incidence, a thorough mechanistic understanding of its pathophysiology and effective supportive therapies are lacking. The main objective of this rat study was to determine how 10 mg/kg doxorubicin, a common chemotherapeutic, affected jejunal function and morphology over time (6, 24, 72, or 168 h). The secondary objective was to determine if the type of dosing administration (intraperitoneal or intravenous) affected the severity of mucositis or plasma exposure of the doxorubicin. Morphology, proliferation and apoptosis, and jejunal permeability of mannitol were examined using histology, immunohistochemistry, and single-pass intestinal perfusion, respectively. Villus height was reduced by 40% after 72 h, preceded at 24 h by a 75% decrease in proliferation and a sixfold increase in apoptosis. Villus height recovered completely after 168 h. Mucosal permeability of mannitol decreased after 6, 24, and 168 h. There were no differences in intestinal injury or plasma exposure after intraperitoneal or intravenous doxorubicin dosing. This study provides an insight into the progression of chemotherapy-induced intestinal mucositis and associated cellular mucosal processes. Knowledge from this in vivo rat model can facilitate development of preventive and supportive therapies for cancer patients.

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.

Chemotherapeutics-Induced Intestinal Mucositis: Pathophysiology and Potential Treatment Strategies

The gastrointestinal tract is particularly vulnerable to off-target effects of antineoplastic drugs because intestinal epithelial cells proliferate rapidly and have a complex immunological interaction with gut microbiota. As a result, up to 40-100% of all cancer patients dosed with chemotherapeutics experience gut toxicity, called chemotherapeutics-induced intestinal mucositis (CIM). The condition is associated with histological changes and inflammation in the mucosa arising from stem-cell apoptosis and disturbed cellular renewal and maturation processes. In turn, this results in various pathologies, including ulceration, pain, nausea, diarrhea, and bacterial translocation sepsis. In addition to reducing patient quality-of-life, CIM often leads to dose-reduction and subsequent decrease of anticancer effect. Despite decades of experimental and clinical investigations CIM remains an unsolved clinical issue, and there is a strong consensus that effective strategies are needed for preventing and treating CIM. Recent progress in the understanding of the molecular and functional pathology of CIM had provided many new potential targets and opportunities for treatment. This review presents an overview of the functions and physiology of the healthy intestinal barrier followed by a summary of the pathophysiological mechanisms involved in the development of CIM. Finally, we highlight some pharmacological and microbial interventions that have shown potential. Conclusively, one must accept that to date no single treatment has substantially transformed the clinical management of CIM. We therefore believe that the best chance for success is to use combination treatments. An optimal combination treatment will likely include prophylactics (e.g., antibiotics/probiotics) and drugs that impact the acute phase (e.g., anti-oxidants, apoptosis inhibitors, and anti-inflammatory agents) as well as the recovery phase (e.g., stimulation of proliferation and adaptation).

Dietary Fiber Is Essential to Maintain Intestinal Size, L-Cell Secretion, and Intestinal Integrity in Mice

Dietary fiber has been linked to improved gut health, yet the mechanisms behind this association remain poorly understood. One proposed mechanism is through its influence on the secretion of gut hormones, including glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2). We aimed to: 1) investigate the impact of a fiber deficient diet on the intestinal morphological homeostasis; 2) evaluate L-cell secretion; and 3) to ascertain the role of GLP-1, GLP-2 and Takeda G protein-receptor-5 (TGR5) signaling in the response using GLP-1 receptor, GLP-2 receptor and TGR5 knockout mice. Female C57BL/6JRj mice (n = 8) either received a standard chow diet or were switched to a crude fiber-deficient diet for a short (21 days) and long (112 days) study period. Subsequent identical experiments were performed in GLP-1 receptor, GLP-2 receptor and TGR5 knockout mice. The removal of fiber from the diet for 21 days resulted in a decrease in small intestinal weight (p < 0.01) and a corresponding decrease in intestinal crypt depth in the duodenum, jejunum and ileum (p < 0.001, p < 0.05, and p < 0.01, respectively). Additionally, colon weight was decreased (p < 0.01). These changes were associated with a decrease in extractable GLP-1, GLP-2 and PYY in the colon (p < 0.05, p < 0.01, and p < 0.01). However, we could not show that the fiber-dependent size decrease was dependent on GLP-1 receptor, GLP-2 receptor or TGR5 signaling. Intestinal permeability was increased following the removal of fiber for 112 days. In conclusion, our study highlights the importance of dietary fiber to maintain intestinal weight, colonic L-cell secretion and intestinal integrity.

Intestinal Adaptation upon Chemotherapy-Induced Intestinal Injury in Mice Depends on GLP-2 Receptor Activation

Intestinal adaptation is an important response and a natural repair mechanism in acute intestinal injury and is critical for recovery. Glucagon-like peptide 2 (GLP-2) has been demonstrated to enhance mucosal repair following intestinal damage. In this study, we aimed to investigate the role of GLP-2 receptor activation on intestinal protection and adaptation upon chemotherapy-induced intestinal injury. The injury was induced with a single injection of 5-fluorouracil in female GLP-2 receptor knockout (GLP-2R(-/-)) mice and their wild type (WT) littermates. The mice were euthanized in the acute or the recovery phase of the injury; the small intestines were analysed for weight changes, morphology, histology, inflammation, apoptosis and proliferation. In the acute phase, only inflammation was slightly increased in the GLP-2R(-/-) mice compared to WT. In the recovery phase, we observed the natural compensatory response with an increase in small intestinal weight, crypt depth and villus height in WT mice, and this was absent in the GLP-2R(-/-) mice. Both genotypes responded with hyperproliferation. From this, we concluded that GLP-2R signalling does not have a major impact on acute intestinal injury but is pivotal for the adaptive response in the small intestine.

GLP-2 Prevents Neuronal and Glial Changes in the Distal Colon of Mice Chronically Treated with Cisplatin

Cisplatin is a chemotherapeutic agent widely used for the treatment of solid cancers. Its administration is commonly associated with acute and chronic gastrointestinal dysfunctions, likely related to mucosal and enteric nervous system (ENS) injuries, respectively. Glucagon-like peptide-2 (GLP-2) is a pleiotropic hormone exerting trophic/reparative activities on the intestine, via antiapoptotic and pro-proliferating pathways, to guarantee mucosal integrity, energy absorption and motility. Further, it possesses anti-inflammatory properties. Presently, cisplatin acute and chronic damages and GLP-2 protective effects were investigated in the mouse distal colon using histological, immunohistochemical and biochemical techniques. The mice received cisplatin and the degradation-resistant GLP-2 analog ([Gly2]GLP-2) for 4 weeks. Cisplatin-treated mice showed mucosal damage, inflammation, IL-1β and IL-10 increase; decreased number of total neurons, ChAT- and nNOS-immunoreactive (IR) neurons; loss of SOX-10-IR cells and reduced expression of GFAP- and S100β-glial markers in the myenteric plexus. [Gly2]GLP-2 co-treatment partially prevented mucosal damage and counteracted the increase in cytokines and the loss of nNOS-IR and SOX-10-IR cells but not that of ChAT-IR neurons. Our data demonstrate that cisplatin causes mucosal injuries, neuropathy and gliopathy and that [Gly2]GLP-2 prevents these injuries, partially reducing mucosal inflammation and inducing ENS remodeling. Hence, this analog could represent an effective strategy to overcome colonic injures induced by cisplatin.

Pharmacological Characterization of Apraglutide, a Novel Long-Acting Peptidic Glucagon-Like Peptide-2 Agonist, for the Treatment of Short Bowel Syndrome

Glucagon-like peptide-2 (GLP-2) agonists have therapeutic potential in clinical indications in which the integrity or absorptive function of the intestinal mucosa is compromised, such as in short bowel syndrome (SBS). Native hGLP-2, a 33-amino acid peptide secreted from the small intestine, contributes to nutritional absorption but has a very short half-life because of enzymatic cleavage and renal clearance and thus is of limited therapeutic value. The GLP-2 analog teduglutide (Revestive/Gattex; Shire Inc.) has been approved for use in SBS since 2012 but has a once-daily injection regimen. Pharmacokinetic (PK) and pharmacodynamic studies confirm that apraglutide, a novel GLP-2 analog, has very low clearance, long elimination half-life, and high plasma protein binding compared with GLP-2 analogs teduglutide and glepaglutide. Apraglutide and teduglutide retain potency and selectivity at the GLP-2 receptor comparable to native hGLP-2, whereas glepaglutide was less potent and less selective. In rat intravenous PK studies, hGLP-2, teduglutide, glepaglutide, and apraglutide had clearances of 25, 9.9, 2.8, and 0.27 ml/kg per minute, respectively, and elimination half-lives of 6.4, 19, 16, and 159 minutes, respectively. The unique PK profile of apraglutide administered via intravenous and subcutaneous routes was confirmed in monkey and minipig and translated into significantly greater in vivo pharmacodynamic activity, measured as small intestinal growth in rats. Apraglutide showed greater intestinotrophic activity than the other peptides when administered at less-frequent dosing intervals because of its prolonged half-life. We postulate that apraglutide offers several advantages over existing GLP-2 analogs and is an excellent candidate for the treatment of gastrointestinal diseases, such as SBS. SIGNIFICANCE STATEMENT: Apraglutide is a potent and selective GLP-2 agonist with an extremely low clearance and prolonged elimination half-life, which differentiates it from teduglutide (the only approved GLP-2 agonist). The enhanced pharmacokinetics of apraglutide will benefit patients by enabling a reduced dosing frequency and removing the need for daily injections.

The role of nitric oxide in small intestine differs between a single and a consecutive administration of methotrexate to rats

The role of nitric oxide (NO) on intestinal mucosal injury induced by single or consecutive administration of methotrexate was investigated in a rodent model. Rats received methotrexate intraperitoneally either as a single administration (50 mg/kg) or as a consecutive administration (12.5 mg/kg/day) for 4 days. N^G-nitro-l-arginine methyl ester (L-NAME) was given subcutaneously to inhibit NO synthase (NOS). Ninety-six hours after the first administration of methotrexate, ileal tissues were collected for analysis. Consecutive administration of methotrexate led to decreased body weight and reduced intake of food and water, which were further worsened by L-NAME. Although a slight mucosal injury resulted from single administration of methotrexate, L-NAME had almost no effect. Consecutive administration of methotrexate caused a significant mucosal injury, which was further worsened by L-NAME. Consecutive, but not single, administration of methotrexate induced mRNA expression of inflammatory cytokines in ileal tissue. Consecutive administration of methotrexate significantly induced constitutive NOS expression in ileal tissue. These results suggest that consecutive administration, rather than single administration, of methotrexate aggravates mucosal injury. Potentiation of constitutive NOS expression by consecutive administration might be one of the main reason to antagonize the intestinal mucosal injury as well as lead to a reduction in rat quality of life.

The GLP-2 analogue elsiglutide reduces diarrhoea caused by the tyrosine kinase inhibitor lapatinib in rats

PURPOSE

Lapatinib is a small molecule tyrosine kinase inhibitor used to treat breast cancer, often in combination with chemotherapy. Diarrhoea commonly occurs in up to 78% of patients undertaking lapatinib treatment. The mechanism of this diarrhoea is currently unknown. Elsiglutide is a GLP-2 analogue known to increase cell proliferation and reduce apoptosis in the intestine.

METHODS

We used a previously developed rat model of lapatinib-induced diarrhoea to determine if co-treatment with elsiglutide was able to reduce diarrhoea caused by lapatinib. Additionally, we analysed the caecal microbiome of these rats to assess changes in the microbiome due to lapatinib.

RESULTS

Rats treated with lapatinib and elsiglutide had less severe diarrhoea than rats treated with lapatinib alone. Serum lapatinib levels, blood biochemistry, myeloperoxidase levels and serum limulus amebocyte lysate levels were not significantly different between groups. Rats treated with lapatinib alone had significantly higher histopathological damage in the ileum than vehicle controls. This increase was not seen in rats also receiving elsiglutide. Rats receiving lapatinib alone had lower microbial diversity than rats who also received elsiglutide.

CONCLUSIONS

Elsiglutide was able to reduce diarrhoea from lapatinib treatment. This does not appear to be via reduction in inflammation or barrier permeability, and may be due to thickening of mucosa, leading to increased surface area for fluid absorption in the distal small intestine. Microbial changes seen in this study require further research to fully elucidate their role in the development of diarrhoea.

Glucagon-Like Peptide-1 Is a Marker of Systemic Inflammation in Patients Treated with High-Dose Chemotherapy and Autologous Stem Cell Transplantation

Autologous stem cell transplantation (ASCT) is challenged by side effects that may be propagated by chemotherapy-induced mucositis, resulting in bacterial translocation and systemic inflammation. Because gastrointestinal damage appears as an early event in this cascade of reactions, we hypothesized that markers reflecting damage to the intestinal barrier could serve as early predictive markers of toxicity. Glucagon-like peptide-1 (GLP-1), a well-known regulator of blood glucose, has been found to promote intestinal growth and repair in animal studies. We investigated fasting GLP-1 plasma levels in 66 adults undergoing ASCT for lymphoma and multiple myeloma. GLP-1 increased significantly after chemotherapy, reaching peak levels at day +7 post-transplant (median, 8 pmol/L [interquartile range, 4 to 12] before conditioning versus 10 pmol/L [interquartile range, 6 to 17] at day +7; P = .007). The magnitude of the GLP-1 increase was related to the intensity of conditioning. GLP-1 at the day of transplantation (day 0) was positively associated with peak C-reactive protein (CRP) levels (46 mg/L per GLP-1 doubling, P < .001) and increase in days with fever (32% per GLP-1 doubling, P = .0058). Patients with GLP-1 above the median at day 0 had higher CRP levels from days +3 to +10 post-transplant than patients with lower GLP-1 (P ≤ .041) with peak values of 238 versus 129 mg/L, respectively. This study, which represents the first clinical investigation of fasting GLP-1 in relation to high-dose chemotherapy, provides evidence that GLP-1 plays a role in regulation of mucosal defenses. Fasting GLP-1 levels may serve as an early predictor of systemic inflammation and fever in patients receiving high-dose chemotherapy.

The Intestinotrophic Effects of Glucagon-Like Peptide-2 in Relation to Intestinal Neoplasia

CONTEXT

Glucagon-like peptide-2 (GLP-2) is a gastrointestinal hormone with intestinotrophic and antiapoptotic effects. The hormone's therapeutic potential in intestinal diseases and relation to intestinal neoplasia has raised great interest among researchers. This article reviews and discusses published experimental and clinical studies concerning the growth-stimulating and antiapoptotic effects of GLP-2 in relation to intestinal neoplasia.

EVIDENCE ACQUISITION

The data used in this narrative review were collected through literature research in PubMed using English keywords. All studies to date examining GLP-2's relation to intestinal neoplasms have been reviewed in this article, as the studies on the matter are sparse.

EVIDENCE SYNTHESIS

GLP-2 has been found to stimulate intestinal growth through secondary mediators and through the involvement of Akt phosphorylation. Studies on rodents have shown that exogenously administered GLP-2 increases the growth and incidence of adenomas in the colon, suggesting that GLP-2 may play an important role in the progression of intestinal tumors. Clinical studies have found that exogenous GLP-2 treatment is well tolerated for up to 30 months, but the tolerability for even longer periods of treatment has not been examined.

CONCLUSION

Exogenous GLP-2 is currently available as teduglutide for the treatment of short bowel syndrome. However, the association between exogenous GLP-2 treatment and intestinal neoplasia in humans has not been fully identified. This leads to a cause for concern regarding the later risk of the development or progression of intestinal tumors with long-term GLP-2 treatment. Therefore, further research regarding GLP-2's potential relation to intestinal cancers is needed.

Endogenous glucagon-like peptide- 1 and 2 are essential for regeneration after acute intestinal injury in mice

Objective

Mucositis is a side effect of chemotherapy seen in the digestive tract, with symptoms including pain, diarrhoea, inflammation and ulcerations. Our aim was to investigate whether endogenous glucagon-like peptide -1 and -2 (GLP-1 and GLP-2) are implicated in intestinal healing after chemotherapy-induced mucositis.

Design

We used a transgenic mouse model Tg(GCG.DTR)(Tg) expressing the human diphtheria toxin receptor in the proglucagon-producing cells. Injections with diphtheria toxin ablated the GLP-1 and GLP-2 producing L-cells in Tg mice with no effect in wild-type (WT) mice. Mice were injected with 5-fluorouracil or saline and received vehicle, exendin-4, teduglutide (gly2-GLP-2), or exendin-4/teduglutide in combination. The endpoints were body weight change, small intestinal weight, morphology, histological scoring of mucositis and myeloperoxidase levels.

Results

Ablation of L-cells led to impaired GLP-2 secretion; increased loss of body weight; lower small intestinal weight; lower crypt depth, villus height and mucosal area; and increased the mucositis severity score in mice given 5-fluorouracil. WT mice showed compensatory hyperproliferation as a sign of regeneration in the recovery phase. Co-treatment with exendin-4 and teduglutide rescued the body weight of the Tg mice and led to a hyperproliferation in the small intestine, whereas single treatment was less effective.

Conclusion

The ablation of L-cells leads to severe mucositis and insufficient intestinal healing, shown by severe body weight loss and lack of compensatory hyperproliferation in the recovery phase. Co-treatment with exendin-4 and teduglutide could prevent this. Because both peptides were needed, we can conclude that both GLP-1 and GLP-2 are essential for intestinal healing in mice.

Stapled, Long-Acting Glucagon-like Peptide 2 Analog with Efficacy in Dextran Sodium Sulfate Induced Mouse Colitis Models

Glucagon-like peptide 2 (GLP-2) is a hormone that has been shown to stimulate intestinal growth and attenuate intestinal inflammation. Despite being efficacious in a variety of animal models of disease, its therapeutic potential is hampered by the short half-life in vivo. We now describe a highly potent, stapled long-acting GLP-2 analog, peptide 10, that has a more than 10-fold longer half-life than teduglutide and improved intestinotrophic and anti-inflammatory effects in mouse models of DSS-induced colitis.

Animal models of chemotherapy-induced mucositis: translational relevance and challenges

Chemotherapy for cancer patients induces damaging tissue reactions along the epithelium of the gastrointestinal tract (GIT). This chemotherapy-induced mucositis (CIM) is a serious side effect of cytotoxic drugs, and several animal models of CIM have been developed, mainly in rodents and piglets, to help understand the progression of CIM and how to prevent it. Animal models allow highly controlled experimental conditions, detailed organ (e.g., GIT) insights, standardized, clinically relevant treatment regimens, and discovery of new biomarkers. Still, surprisingly few results from animal models have been translated into clinical CIM management and treatments. The results obtained from specific animal models can be difficult to translate to the diverse range of CIM manifestations in patients, which vary according to the antineoplastic drugs, dose, underlying (cancer) disease, and patient characteristics (e.g., age, genetics, and body constitution). Another factor that hinders the direct use of results from animals is inadequate collaboration between basic science and clinical science in relation to CIM. Here, we briefly describe CIM pathophysiology, particularly the basic knowledge that has been obtained from CIM animal models. These model studies have indicated potential new preventive and ameliorating interventions, including supplementation with natural bioactive diets (e.g., milk fractions, colostrum, and plant extracts), nutrients (e.g., polyunsaturated fatty acids, short-chain fatty acids, and glutamine), and growth factor peptides (e.g., transforming growth factor and glucagon-like peptide-2), as well as manipulations of the gut microbiota (e.g., prebiotics, probiotics, and antibiotics). Rodent CIM models allow well-controlled, in-depth studies of animals with or without tumors while pig models more easily make clinically relevant treatment regimens possible. In synergy, animal models of CIM provide the basic physiological understanding and the new ideas for treatment that are required to make competent decisions in clinical practice.

Irinotecan-induced mucositis: the interactions and potential role of GLP-2 analogues

PURPOSE

A common side effect of irinotecan administration is gastrointestinal mucositis, often manifesting as severe diarrhoea. The damage to the structure and function of the gastrointestinal tract caused by this cytotoxic agent is debilitating and often leads to alterations in patients' regimens, hospitalisation or stoppage of treatment. The purpose of this review is to identify mechanisms of irinotecan-induced intestinal damage and a potential role for GLP-2 analogues for intervention.

METHODS

This is a review of current literature on irinotecan-induced mucositis and GLP-2 analogues mechanisms of action.

RESULTS

Recent studies have found alterations that appear to be crucial in the development of severe intestinal mucositis, including early apoptosis, alterations in proliferation and cell survival pathways, as well as induction of inflammatory cascades. Several studies have indicated a possible role for glucagon-like peptide-2 analogues in treating this toxicity, due to its proven intestinotrophic, anti-apoptotic and anti-inflammatory effects in other models of gastrointestinal disease.

CONCLUSION

This review provides evidence as to why and how this treatment may improve mucositis through the possible molecular crosstalk that may be occurring in models of severe intestinal mucositis.

GLP-1 Induces Barrier Protective Expression in Brunner's Glands and Regulates Colonic Inflammation

BACKGROUND

Beneficial roles for glucagon-like peptide 1 (GLP-1)/GLP-1R signaling have recently been described in diseases, where low-grade inflammation is a common phenomenon. We investigated the effects of GLP-1 in Brunner's glands and duodenum with abundant expression of GLP-1 receptors, as well as GLP-1 effect on colonic inflammation.

METHODS

RNA from Brunner's glands of GLP-1R knockout and wild-type mice were subjected to full transcriptome profiling. Array results were validated by quantitative reverse transcription polymerase chain reaction in wild-type mice and compared with samples from inflammatory bowel disease (IBD) patients and controls. In addition, we performed a detailed investigation of the effects of exogenous liraglutide dosing in a T-cell driven adoptive transfer (AdTr) colitis mouse model.

RESULTS

Analyses of the Brunner's gland transcriptomes of GLP-1R knockout and wild-type mice identified 722 differentially expressed genes. Upregulated transcripts after GLP-1 dosing included IL-33, chemokine ligand 20 (CCL20), and mucin 5b. Biopsies from IBD patients and controls, as well as data from the AdTr model, showed deregulated expression of GLP-1R, CCL20, and IL-33 in colon. Circulating levels of GLP-1 were found to be increased in mice with colitis. Finally, the colonic cytokine levels and disease scores of the AdTr model indicated reduced levels of colonic inflammation in liraglutide-dosed animals.

CONCLUSIONS

We demonstrate that IL-33, GLP-1R, and CCL20 are deregulated in human IBD, and that prophylactic treatment with 0.6 mg/kg liraglutide improves disease in AdTr colitis. In addition, GLP-1 receptor agonists upregulate IL-33, mucin 5b, and CCL20 in murine Brunner's glands. Taken together, our data indicate that GLP-1 receptor agonists affect gut homeostasis in both proximal and distal parts of the gut.

Endocrine regulation of gut maturation in early life in pigs

After birth, the newborn must adapt to the acute challenges of circulatory changes, active respiration, thermoregulation, microbial colonization, and enteral nutrition. Whereas these processes normally occur without clinical complications in neonates born at term, birth at a preterm state of gestation is associated with high morbidity and mortality. In commercial pig production, perinatal mortality is higher than in any other mammalian species. Asphyxia, hypothermia, hypoglycemia, sepsis, and gut dysmotility, represent some of the most common findings. The intestine is a particularly sensitive organ after birth, as it must adapt acutely to enteral nutrition and microbial colonization. Likewise, during the weaning phase, the intestine must adapt to new diet types. Both critical phases are associated with high morbidity. This review focuses on the endocrine changes occurring around birth and weaning. There are a number of endocrine adaptations in late gestation and early postnatal life that are under influence of development stage and environmental factors such as diet. The review discusses general endocrine changes in perinatal life but specifically focuses on the role of glucagon-like peptide-2. This gut-derived hormone plays a key role in development and function of the intestine in early life.

Glucagon-like peptide 2 counteracts the mucosal damage and the neuropathy induced by chronic treatment with cisplatin in the mouse gastric fundus

BACKGROUND

Glucagon-like peptide-2 (GLP-2) is a pleiotropic hormone synthesized and secreted by the enteroendocrine 'L' cells able to exert intestine-trophic and anti-inflammatory effects. The antineoplastic drug cisplatin causes gastrointestinal alterations with clinical symptoms (nausea and vomiting) that greatly affect the therapy compliance. Experimentally, it has been reported that chronic cisplatin treatment caused mucosal damage and enteric neuropathy in the rat colon.

METHODS

We investigated, through a combined immunohistochemical and functional approach, whether [Gly(2) ]GLP-2, a GLP-2 analog, was able to counteract the detrimental effects of long-term cisplatin administration in the mucosa and myenteric neurons of mouse gastric fundus.

KEY RESULTS

Morphological experiments showed a reduction in the epithelium thickness in cisplatin-treated mice, which was prevented by [Gly(2) ]GLP-2 co-treatment. Immunohistochemistry demonstrated that cisplatin caused a significant decrease in myenteric neurons, mainly those expressing neuronal nitric oxide synthase (nNOS), that was prevented by [Gly(2) ]GLP-2 co-treatment. In the functional experiments, [Gly(2) ]GLP-2 co-treatment counteracted the increase in amplitude of the neurally induced contractions observed in strips from cisplatin-treated animals. The NO synthesis inhibitor L-N(G) -nitro arginine caused an increase in amplitude of the contractile responses that was greater in preparations from cisplatin+[Gly(2) ]GLP-2 treated mice compared to the cisplatin-treated ones.

CONCLUSIONS & INFERENCES

The results demonstrate that in cisplatin long-term treated mice [Gly(2) ]GLP-2 is able to counteract both the mucosal gastric fundus damage, by preventing the epithelium thickness decrease, and the neuropathy, by protecting the nNOS neurons. Taken together, the present data suggest that [Gly(2) ]GLP-2 could represent an effective strategy to overcome the distressing gastrointestinal symptoms present during the anti-neoplastic therapy.

Glucagon-like peptides 1 and 2: intestinal hormones implicated in the pathophysiology of mucositis

PURPOSE OF REVIEW

Chemotherapy often causes adverse effects, including pain, bloating, diarrhea, and inflammation and ulceration of the mucous membranes lining the digestive tract, which are collectively referred to as mucositis. Unfortunately, no remedy has been found yet to manage these side-effects.

RECENT FINDINGS

The intestinal glucagon-like peptide-2 (GLP-2) is secreted from the intestinal endocrine L cells after nutrient intake, but recent findings show that the peptide concentration in the plasma also rises after intestinal injury and that GLP-2 receptor activation is crucial for intestinal healing. The antidiabetic hormone GLP-1, cosecreted with GLP-2, diminished mucositis in an animal model of the condition. Therefore, both peptides could be involved in the pathophysiology of mucositis.

SUMMARY

The intestinal GLPs have shown beneficial effects in experimental trials and have potential for therapeutic use. In type 2 diabetic and obese patients, GLP secretion is impaired. Elucidating the role of these endogenous hormones could lead to the identification of mucositis risk factors and an alternative preventive therapy for these patients.

The glucagon-like peptide 2 receptor is expressed in enteric neurons and not in the epithelium of the intestine

Glucagon-like peptide 2 (GLP-2) is a potent intestinotrophic growth factor with therapeutic potential in the treatment of intestinal deficiencies. It has recently been approved for the treatment of short bowel syndrome. The effects of GLP-2 are mediated by specific binding of the hormone to the GLP-2 receptor (GLP-2R) which was cloned in 1999. However, consensus about the exact receptor localization in the intestine has never been established. By physical, chemical and enzymatic tissue fragmentation, we were able to divide rat jejunum into different compartments consisting of: (1) epithelium alone, (2) mucosa with lamina propria and epithelium, (3) the external muscle coat including myenteric plexus, (4) a compartment enriched for the myenteric plexus and (5) intestine without epithelium. Expression of Glp2r; chromogranin A; tubulin, beta 3; actin, gamma 2, smooth muscle, enteric and glial fibrillary acidic protein in these isolated tissue fractions was quantified with qRT-PCR. Expression of the Glp2r was confined to compartments containing enteric neurons and receptor expression was absent in the epithelium. Our findings provide evidence for the expression of the GLP-2R in intestinal compartments rich in enteric neurons and, importantly they exclude significant expression in the epithelium of rat jejunal mucosa.

Gastro-intestinal toxicity of chemotherapeutics in colorectal cancer: The role of inflammation

Chemotherapy-induced diarrhea (CID) is a common and often severe side effect experienced by colorectal cancer (CRC) patients during their treatment. As chemotherapy regimens evolve to include more efficacious agents, CID is increasingly becoming a major cause of dose limiting toxicity and merits further investigation. Inflammation is a key factor behind gastrointestinal (GI) toxicity of chemotherapy. Different chemotherapeutic agents activate a diverse range of pro-inflammatory pathways culminating in distinct histopathological changes in the small intestine and colonic mucosa. Here we review the current understanding of the mechanisms behind GI toxicity and the mucositis associated with systemic treatment of CRC. Insights into the inflammatory response activated during this process gained from various models of GI toxicity are discussed. The inflammatory processes contributing to the GI toxicity of chemotherapeutic agents are increasingly being recognised as having an important role in the development of anti-tumor immunity, thus conferring added benefit against tumor recurrence and improving patient survival. We review the basic mechanisms involved in the promotion of immunogenic cell death and its relevance in the treatment of colorectal cancer. Finally, the impact of CID on patient outcomes and therapeutic strategies to prevent or minimise the effect of GI toxicity and mucositis are discussed.

Targeting the intestinal L-cell for obesity and type 2 diabetes treatment

Degradation-resistant glucagon-like peptide-1 (GLP-1) mimetics and GLP-1 enhancers (inhibitors of dipeptidyl peptidase-4, the enzyme which degrades and inactivates GLP-1) have been used for treatment of type 2 diabetes mellitus since 2005-2006. Cutting-edge research is now focusing on uncovering the secretory mechanisms of the GLP-1-producing cells (L-cells) with the purpose of developing agonists that enhance endogenous hormone secretion. Since GLP-1 co-localizes with other anorectic peptides, cholecystokinin, oxyntomodulin/glicentin and peptide YY, L-cell targeting might cause release of several hormones at the same time, providing additive effects on appetite and glucose regulation. In this review, we explore the role of proglucagon-derived peptides and other L-cell co-localizing hormones, in appetite regulation and the mechanism regulating their secretion.

Intestinal response to myeloablative chemotherapy in piglets

Chemotherapy-induced myeloablation prior to allogeneic hematopoietic stem cell transplantation (HSCT) may be associated with severe toxicity. The current understanding of the pathophysiology of oral and gastrointestinal (GI) toxicity is largely derived from studies in rodents and very little is known from humans, especially children. We hypothesized that milk-fed piglets can be used as a clinically relevant model of GI-toxicity related to a standard conditioning chemotherapy (intravenous busulfan, Bu plus cyclophosphamide, Cy) used prior to HSCT. In study 1, dose-response relationships were investigated in three-day-old pigs (Landrace × Yorkshire × Duroc, n = 6). Pigs were given one of three different dose combinations of Bu and Cy (A: 4 days Bu, 2 × 1.6 mg/kg plus 2 days Cy, 60 mg/kg; B: 4 days Bu, 2 × 0.8 mg/kg plus 2 days Cy, 30 mg/kg; C: 2 days Bu at 2 × 1.6 mg/kg plus 1 day Cy, 60 mg/kg) and bone marrow was collected on day 11. Histology of bone marrow samples showed total aplasia after treatment A. Using this treatment in study 2, Bu-Cy pigs showed lowered spleen and intestinal weights and variable clinical signs of dehydration, sepsis, and pneumonia at tissue collection. Oral mucositis was evident as ulcers in the soft palate in 4/9 Bu-Cy pigs and villus height and brush-border enzyme activities were reduced, especially in the proximal intestine. There were no consistent effects on tissue cytokine levels (IL-8, IL-6, IL-1β, TNF-α) or blood chemistry values (electrolytes, liver transaminases, bilirubin, alkaline phosphatase), except that blood iron levels were higher in Bu-Cy pigs. We conclude that a myeloablative Bu-Cy regimen to piglets results in clinical signs comparable to those seen in pediatric patients subjected to myeloablative treatment prior to HSCT. Piglets may be used as a model for investigating chemotherapy-induced toxicity and dietary and medical interventions.

Glucagon-like peptide-1 as a treatment for chemotherapy-induced mucositis

BACKGROUND

Glucagon-like peptide-2 (GLP-2) has been suggested for the treatment of mucositis, but the peptide has also been shown to accentuate colonic dysplasia in carcinogen-treated mice. Recently, an effect on intestinal growth was discovered for glucagon-like peptide-1 (GLP-1), OBJECTIVE: To determine whether endogenous GLP-1 contributes to the healing processes and if exogenous GLP-1 has a potential role in treating mucositis.

METHODS

Mice were injected with 5-fluorouracil (5-FU) or saline to induce mucositis and were then treated with GLP-1, GLP-2, GLP-2 (3-33), exendin (9-39) or vehicle. The mice were sacrificed 48 or 96 h after the 5-FU injections. The end points were intestinal weight, villus height, proliferation and histological scoring of mucositis severity. Rats were injected with 5-FU or saline, and after 48 h, blood was drawn and analysed for GLP-1 and GLP-2 concentration.

RESULTS

GLP-1 and GLP-2 significantly prevented the loss of mucosal mass and villus height and significantly decreased the mucositis severity score in the duodenum and jejunum 48 h after chemotherapy. The effect was equivalent. Exendin (9-39) reduced the intestinal weight 96 h after chemotherapy. The GLP-1 levels in blood were increased more than 10-fold, and GLP-2 levels were increased sevenfold.

CONCLUSIONS

GLP-1 and GLP-2 were secreted after intestinal injury, and recovery was delayed after treatment with exendin (9-39), indicating an important role for the peptides in the protection of the intestine from injury. GLP-1 treatment ameliorated mucositis, which suggests that mucositis and other acute intestinal disorders might benefit from treatment with GLP-1 analogues.