Glucagonlike peptide-2 analogue: a possible new approach in the management of inflammatory bowel disease

Mechanisms of mucosal healing: treating inflammatory bowel disease without immunosuppression?

Almost all currently available treatments for inflammatory bowel disease (IBD) act by inhibiting inflammation, often blocking specific inflammatory molecules. However, given the infectious and neoplastic disease burden associated with chronic immunosuppressive therapy, the goal of attaining mucosal healing without immunosuppression is attractive. The absence of treatments that directly promote mucosal healing and regeneration in IBD could be linked to the lack of understanding of the underlying pathways. The range of potential strategies to achieve mucosal healing is diverse. However, the targeting of regenerative mechanisms has not yet been achieved for IBD. Stem cells provide hope as a regenerative treatment and are used in limited clinical situations. Growth factors are available for the treatment of short bowel syndrome but have not yet been applied in IBD. The therapeutic application of organoid culture and stem cell therapy to generate new intestinal tissue could provide a novel mechanism to restore barrier function in IBD. Furthermore, blocking key effectors of barrier dysfunction (such as MLCK or damage-associated molecular pattern molecules) has shown promise in experimental IBD. Here, we review the diversity of molecular targets available to directly promote mucosal healing, experimental models to identify new potential pathways and some of the anticipated potential therapies for IBD.

Mechanisms of mucosal healing: treating inflammatory bowel disease without immunosuppression?

Almost all currently available treatments for inflammatory bowel disease (IBD) act by inhibiting inflammation, often blocking specific inflammatory molecules. However, given the infectious and neoplastic disease burden associated with chronic immunosuppressive therapy, the goal of attaining mucosal healing without immunosuppression is attractive. The absence of treatments that directly promote mucosal healing and regeneration in IBD could be linked to the lack of understanding of the underlying pathways. The range of potential strategies to achieve mucosal healing is diverse. However, the targeting of regenerative mechanisms has not yet been achieved for IBD. Stem cells provide hope as a regenerative treatment and are used in limited clinical situations. Growth factors are available for the treatment of short bowel syndrome but have not yet been applied in IBD. The therapeutic application of organoid culture and stem cell therapy to generate new intestinal tissue could provide a novel mechanism to restore barrier function in IBD. Furthermore, blocking key effectors of barrier dysfunction (such as MLCK or damage-associated molecular pattern molecules) has shown promise in experimental IBD. Here, we review the diversity of molecular targets available to directly promote mucosal healing, experimental models to identify new potential pathways and some of the anticipated potential therapies for IBD.

Roles of gastrointestinal polypeptides in intestinal barrier regulation

The intestinal barrier is a dynamic entity that is organized as a multilayer system and includes various intracellular and extracellular elements. The gut barrier functions in a coordinated manner to impede the passage of antigens, toxins, and microbiome components and simultaneously preserves the balanced development of the epithelial barrier and the immune system and the acquisition of tolerance to dietary antigens and intestinal pathogens.Numerous scientific studies have shown a significant association between gut barrier damage and gastrointestinal and extraintestinal diseases such as inflammatory bowel disease, celiac disease and hepatic fibrosis. Various internal and external factors regulate the intestinal barrier. Gastrointestinal peptides originate from enteroendocrine cells in the luminal digestive tract and are critical gut barrier regulators. Recent studies have demonstrated that gastrointestinal peptides have a therapeutic effect on digestive tract diseases, enhancing epithelial barrier activity and restoring the gut barrier. This review demonstrates the roles and mechanisms of gastrointestinal polypeptides, especially somatostatin (SST) and vasoactive intestinal peptide (VIP), in intestinal barrier regulation.

The Role of Dipeptidyl Peptidase 4 as a Therapeutic Target and Serum Biomarker in Inflammatory Bowel Disease: A Systematic Review

BACKGROUND

The roles dipeptidyl peptidase 4 (DPP4), aminopeptidase N (APN), and their substrates in autoimmune diseases are being increasingly recognized. However, their significance in inflammatory bowel diseases (IBD) is not entirely understood. This systematic review aims to discuss the pathophysiological processes related to these ectopeptidases while comparing findings from preclinical and clinical settings.

METHODS

This review was conducted according to the PRISMA guidelines. We performed a literature search in PubMed, SCOPUS, and Web of Science to identify all reports from inception until February 2020. The search included validated animal models of intestinal inflammation and studies in IBD patients. Quality assessment was performed using SYRCLE's risk of bias tool and CASP qualitative and cohort checklists.

RESULTS

From the 45 included studies, 36 were performed in animal models and 12 in humans (3 reports included both). Overall, the methodological quality of preclinical studies was acceptable. In animal models, DPP4 and APN inhibition significantly improved intestinal inflammation.Glucagon-like peptide (GLP)-1 and GLP-2 analogs and GLP-2-relase-inducing drugs also showed significant benefits in recovery from inflammatory damage. A nonsignificant trend toward disease remission with the GLP-2 analog teduglutide was observed in the sole interventional human study. All human studies reported an inverse correlation between soluble DPP4/CD26 levels and disease severity, in accordance with the proposal of DPP4 as a biomarker for IBD.

CONCLUSIONS

The use of DPP4 inhibitors and analogs of its substrates has clear benefits in the treatment of experimentally induced intestinal inflammation. Further research is warranted to validate their potential diagnostic and therapeutic applications in IBD patients.

Role of glucagon-like peptides in inflammatory bowel diseases-current knowledge and future perspectives

Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic, relapsing, intestinal inflammatory disorders with complex and yet unrevealed pathogenesis in which genetic, immunological, and environmental factors play a role. Nowadays, a higher proportion of elderly IBD patients with coexisting conditions, such as cardiovascular disease and/or diabetes is recorded, who require more complex treatment and became a great challenge for gastroenterologists. Furthermore, some patients do not respond to anti-IBD therapy. These facts, together with increasing comorbidities in patients with IBD, imply that urgent, more complex, novel therapeutic strategies in the treatment are needed. Glucagon-like peptides (GLPs) possess numerous functions in the human body such as lowering blood glucose level, controlling body weight, inhibiting gastric emptying, reducing food ingestion, increasing crypt cell proliferation, and improving intestinal growth and nutrient absorption. Thus, GLPs and dipeptidyl peptidase IV (DPP-IV) inhibitors have recently gained attention in IBD research. Several animal models showed that treatment with GLPs may lead to improvement of colitis. This review presents data on the multitude effects of GLPs in the inflammatory intestinal diseases and summarizes the current knowledge on GLPs, which have the potential to become a novel therapeutic option in IBD therapy.

Glucagon-like peptide-2-loaded microspheres as treatment for ulcerative colitis in the murine model

Glucagon-like peptide-2 (GLP-2) is an intestinal hormone that promotes intestinal growth, but the rapid degradation by dipeptidyl peptidase-IV limits its applications. PLGA microsphere is a well-developed drug delivery system, while seldom been studied as a solution for prolonging in vivo effects of GLP-2. In this study, we encapsulated porcine GLP-2 (pGLP-2) into microspheres and investigated its therapeutic effects in dextran sulfate sodium (DSS)-treated mice. pGLP-2 microspheres showed 20.36% in initial burst and constant release for at least 9 d. In the DSS-treated mice, a single injection of GLP-2 microspheres significantly increased the body weight, colonic length, small intestinal weight and mRNA expression of Occludin, decreased the colonic damage score, mRNA expression of IL-6, IL-10, TNF-α and IFN-γ. In conclusion, pGLP-2 microspheres were resistant to degradation and decreased the severity of DSS-induced ulcerative colitis which suggested that GLP-2-loaded microspheres could be a proper candidate for the treatment of ulcerative colitis.

Tumor necrosis factor α decreases glucagon-like peptide-2 expression by up-regulating G-protein-coupled receptor 120 in Crohn disease

Glucagon-like peptide (GLP)-2, secreted by L cells in the small intestine, has anti-inflammatory effects in the gastrointestinal tract. A GLP-2 analogue has been an effective treatment for Crohn disease (CD). G-protein-coupled receptor (GPR) 40 and GPR120 are probably involved in GLP-2 production, the mechanisms of which remain unclear. In our experiments, normal ileal mucosa expressed GPR40, but rarely expressed GPR120. However, both GPRs were overexpressed in the L cells of the inflamed ileal mucosa of CD patients. Mucosal inflammation induced the overexpression of GPR40, GPR120, and several inflammatory cytokines, with correlations between ileal concentrations of tumor necrosis factor (TNF)-α and GPR expression levels; however, inflammation did not induce the expression of proglucagon, a precursor of GLP-2 in CD patients. In rat L cells and GLUTag cells, TNF-α treatment increased GPR120 mRNA expression without affecting GPR40 mRNA expression. Dual agonists of GPR40 and GPR120, GW9508 and linoleic acid, respectively, increased GLP-2 production from L cells, but these agonists decreased it in the presence of TNF-α. The GPR40 antagonist, GW1100, inhibited the GW9508-induced increase in GLP-2 production, and silencing GPR120 resulted in further elevation of GLP-2 production. Thus, GPR120-dependent signaling inhibited the stimulatory effects of GPR40 on GLP-2 expression, and TNF-α treatment decreased GLP-2 expression by up-regulating GPR120 expression in L cells.

GLP-2 enhances barrier formation and attenuates TNFα-induced changes in a Caco-2 cell model of the intestinal barrier

INTRODUCTION

Tight junctions are intercellular permeability seals that regulate paracellular transport across epithelia. Tight junction function, expression and localisation of constituent proteins are significantly altered by cytokines such as TNFα. Glucagon-like peptide-2 (GLP-2) is an intestinotrophic enteroendocrine peptide. It is not known whether GLP-2 regulates the barrier or tight junctions. The aim of this study was to investigate whether GLP-2 has an effect on tight junction function or protein expression, alone or in response to TNFα exposure.

METHODS

Caco-2 cells were grown to confluence on filters in the presence or absence of GLP-2. The time course of transepithelial electrical resistance developing across the monolayer was measured; tight junction protein expression was quantified by immunoblotting. At day 20, TNFα in the presence or absence of GLP-2 was added. Changes in TEER and tight junction proteins expression were quantified. Both TNFα and GLP-2 were added on the basolateral side.

RESULTS

GLP-2 exposed Caco-2 cell monolayers showed a significant increase in transepithelial electrical resistance compared to that in untreated control cells. At the same time, expression of the tight junction proteins occludin and zona occludens-1 (ZO-1) was increased at day 17 post-seeding (1.6-fold; p=0.037 and 4.7 fold; p=0.039 respectively). Subsequent TNFα exposure induced a significant 9.3-fold (p<0.001) decrease in transepithelial electrical resistance and a corresponding reduction in the expression of ZO-1 (5.3 fold; p<0.01). However, the TNFα-induced reduction in transepithelial electrical resistance in GLP-2-exposed cells was highly attenuated to 1.8-fold (p<0.01). No change in tight junction protein expression was noted in GLP-2 exposed cells after cytokine exposure.

CONCLUSION

GLP-2 enhances formation of the epithelial barrier and its constituent proteins in Caco-2 cells, and diminishes the effects of TNFα. If these effects are replicated in vivo the GLP-2 receptor may present a therapeutic target in intestinal inflammation.

Intestinotrophic glucagon-like peptide-2 (GLP-2) activates intestinal gene expression and growth factor-dependent pathways independent of the vasoactive intestinal peptide gene in mice

The enteroendocrine and enteric nervous systems convey signals through an overlapping network of regulatory peptides that act either as circulating hormones or as localized neurotransmitters within the gastrointestinal tract. Because recent studies invoke an important role for vasoactive intestinal peptide (VIP) as a downstream mediator of glucagon-like peptide-2 (GLP-2) action in the gut, we examined the importance of the VIP-GLP-2 interaction through analysis of Vip(-/-) mice. Unexpectedly, we detected abnormal villous architecture, expansion of the crypt compartment, increased crypt cell proliferation, enhanced Igf1 and Kgf gene expression, and reduced expression of Paneth cell products in the Vip(-/-) small bowel. These abnormalities were not reproduced by antagonizing VIP action in wild-type mice, and VIP administration did not reverse the intestinal phenotype of Vip(-/-) mice. Exogenous administration of GLP-2 induced the expression of ErbB ligands and immediate-early genes to similar levels in Vip(+/+) vs. Vip(-/-) mice. Moreover, GLP-2 significantly increased crypt cell proliferation and small bowel growth to comparable levels in Vip(+/+) vs. Vip(-/-) mice. Unexpectedly, exogenous GLP-2 administration had no therapeutic effect in mice with dextran sulfate-induced colitis; the severity of colonic injury and weight loss was modestly reduced in female but not male Vip(-/-) mice. Taken together, these findings extend our understanding of the complex intestinal phenotype arising from loss of the Vip gene. Furthermore, although VIP action may be important for the antiinflammatory actions of GLP-2, the Vip gene is not required for induction of a gene expression program linked to small bowel growth after enhancement of GLP-2 receptor signaling.

Dipeptidyl peptidase-4 expression is reduced in Crohn's disease

BACKGROUND

Dipeptidyl peptidase 4 (DP4) is a serine protease that preferentially cleaves N-terminal dipeptides from polypeptides containing proline or alanine as the penultimate amino acid. DP4 inactivates glucagon like peptide-2 (GLP-2), a trophic peptide with cytoprotective and reparative properties in the injured gut; therefore DP4 potentially inhibits repair processes. DP4 also modulates the activity of GLP-1 and polypeptide YY (PYY) which regulate appetite and motility. No data are yet available on the tissue and plasma expression of DP4 in inflammatory bowel disease (IBD).

METHODS

Tissue and plasma were studied from active CD and healthy controls for DP4 quantification. Experiments were also carried out in a reductionist Caco-2 cell line model of intestinal inflammation with TNFα incubation. DP4 expression was studied by tissue Western blotting and plasma enzymelinked immunosorbent assay (ELISA), in addition to quantitative polymerase chain reaction (qPCR).

RESULTS

There was a ~2.7-fold decrease in DP4 protein in CD tissue (p=0.05). Plasma DP4 in CD was also significantly lower than the control group. A negative correlation between plasma DP4 levels and inflammatory activity as measured by C-reactive protein was observed. In Caco-2 cells an ~18-fold increase (p<0.0001) in DP4 protein expression was seen after incubation with TNFα at a concentration of 25 ng/μl for 48 hours paralleled by a 2-fold increase in DP4 mRNA.

DISCUSSION

DP4 is reduced in tissue and plasma in active Crohn's disease. This is unlikely to represent simple downregulation induced by inflammation since the key proinflammatory cytokine strongly upregulated DP4 expression in Caco-2 cells. Clearly a more complex situation exists in vivo. We propose that reduced DP4 activity limits the cleavage of regulatory peptides, for example potentiating the trophic signal from GLP-2. Pharmacological DP4 inhibition may present an additional therapeutic target in IBD.

Induction of intestinal multidrug resistance-associated protein 2 by glucagon-like Peptide 2 in the rat

The effects of glucagon-like peptide 2 (GLP-2) on expression and activity of jejunal multidrug resistance-associated protein 2 (Mrp2; Abcc2) and glutathione transferase (GST) were evaluated. After GLP-2 treatment (12 μg/100 g b.wt. s.c., every 12 h, for 5 consecutive days), Mrp2 and the α class of GST proteins and their corresponding mRNAs were increased, suggesting a transcriptional regulation. Mrp2 was localized at the apical membrane of the enterocyte in control and GLP-2 groups, as detected by confocal immunofluorescence microscopy. As a functional assay, everted intestinal sacs were incubated in the presence of 1-chloro-2,4-dinitrobenzene in the mucosal compartment, and the glutathione-conjugated derivative, dinitrophenyl-S-glutathione (DNP-SG; model Mrp2 substrate), was detected in the same compartment by high-performance liquid chromatography. A significant increase in apical secretion of DNP-SG was detected in the GLP-2 group, consistent with simultaneous up-regulation of Mrp2 and GST. GLP-2 also promoted an increase in cAMP levels as detected in homogenates of intestinal mucosa. Treatment of rats with 2',3'-dideoxyadenosine (DDA), a specific inhibitor of adenylyl cyclase, abolished the increase in cAMP levels and Mrp2 protein promoted by GLP-2, suggesting cAMP as a mediator of Mrp2 modulation. Increased expression of Mrp2 and cAMP levels in response to GLP-2 occurred not only at the tip but also at the middle region of the villus, where constitutive expression of Mrp2 is normally low. In conclusion, our study suggests a role for GLP-2 in the prevention of cell toxicity of the intestinal mucosa by increasing Mrp2 chemical barrier function.

Teduglutide, a novel mucosally active analog of glucagon-like peptide-2 (GLP-2) for the treatment of moderate to severe Crohn's disease

BACKGROUND

Teduglutide, an analog of glucagon-like peptide-2 (GLP-2), is associated with trophic effects on gut mucosa. Its role in the treatment of active Crohn's disease (CD) was assessed in a pilot, randomized, placebo-controlled, double-blinded, dose-ranging study.

METHODS

Subjects with moderate-to-severe CD were randomized 1:1:1:1 to placebo or 1 of 3 doses of teduglutide (0.05, 0.10, or 0.20 mg/kg daily) delivered as a daily subcutaneous injection for 8 weeks. The primary outcome measure was the percentage of subjects in each group that responded to treatment, defined as a decrease in Crohn's Disease Activity Index (CDAI) score to <150 or a decrease of > 100 points. At week 8 there was an optional 12-week open-label period of treatment with teduglutide 0.10 mg/kg/d.

RESULTS

One hundred subjects were enrolled and 71 completed the study. The mean baseline CDAI score was 290.8 +/- 57.6 and was similar across groups. There were numerically higher response and remission rates in all teduglutide-treated groups as compared with placebo, although the percentage of subjects who achieved a clinical response or remission was more substantial, and seen as early as week 2 of treatment in the highest dose (0.2 mg/kg/d) group (44% response and 32% remission versus 32% response and 20% remission in the placebo group). Of subjects who had not achieved remission during the 8-week placebo-controlled phase in the higher-dose group, 50% achieved remission during the more prolonged, open-label treatment phase. Plasma citrulline was similar across groups at baseline, but increased substantially over time in all teduglutide groups when compared with placebo at week 8. Adverse events were not different between placebo and active treatment groups.

CONCLUSIONS

Teduglutide is a novel and potentially effective therapy for inducing remission and mucosal healing in patients with active moderate-to-severe CD. Further clinical investigation of this growth factor is warranted.

GLP-2 receptor agonism ameliorates inflammation and gastrointestinal stasis in murine postoperative ileus

Glucagon-like peptide 2 (GLP-2) is a pleiotropic intestinotrophic hormone that we hypothesized could lessen gastrointestinal inflammation associated with postoperative ileus (POI). To test this idea, the prophylactic timing and dose of a long-acting variant of human GLP-2 linked to the Fc portion of murine immunoglobulin G (IgG) (GLP-2/IgG) was optimized in a murine model of POI. Surgically treated mice received a single dose of GLP-2/IgG, IgG isotype control, or phosphate-buffered saline 1 to 48 h before small bowel surgical manipulation. The distribution of orally fed fluorescein isothiocyanate-dextran and histological analyses of myeloperoxidase-positive immune cells were determined 24 and 48 h postoperatively. TaqMan quantitative polymerase chain reaction was used to determine early changes in mRNA expression in the muscularis or mucosa. In normal mice, prolonged exposure to GLP-2 increased upper gastrointestinal (GI) transit and mucosal weight. When administered 1 or 3 h before surgery, GLP-2/IgG reduced the leukocyte infiltrate 24 and 48 h postoperatively and improved GI transit 48 h postoperatively. Surgical manipulation rapidly increased gene expression of proinflammatory cytokines and enzymes for kinetically active mediators in the mucosa and muscularis. GLP-2/IgG2a affected the expression of genes associated with mucosal inflammation and barrier function. We conclude that prophylactic treatment with a long-acting GLP-2 agonist ameliorates inflammation and improves intestinal dysmotility associated with surgical manipulation of the bowel. The action of GLP-2 is consistent with a lessening of inflammation, leading to a more rapid recovery.

Growth factor based therapies and intestinal disease: is glucagon-like peptide-2 the new way forward?

Inflammatory bowel disease (IBD) is a chronic, debilitating disease associated with severe damage to the intestinal mucosa. Glucagon-like peptide-2 (GLP-2) is a potent and specific gastrointestinal growth factor that is demonstrating therapeutic potential for the prevention or treatment of an expanding number of intestinal diseases, including short bowel syndrome (SBS), small bowel enteritis and IBD. The biological activity of GLP-2 is limited due to proteolytic inactivation by the protease dipeptidyl peptidase (DP)IV. Inhibitors of DPIV activity may represent a novel strategy to prolong the growth promoting actions of GLP-2. This review outlines evidence for the clinical application of GLP-2, its degradation resistant analogue, Teduglutide, and novel DPIV inhibitors in efficacy studies utilizing pre-clinical models of intestinal damage, in particular IBD.

Interleukin-10-independent anti-inflammatory actions of glucagon-like peptide 2

Glucagon-like peptide 2 (GLP-2) is an important intestinal growth factor with anti-inflammatory activity. We hypothesized that GLP-2 decreases mucosal inflammation and the associated increased epithelial proliferation by downregulation of Th1 cytokines attributable to reprogramming of lamina propria immune regulatory cells via an interleukin-10 (IL-10)-independent pathway. The effects of GLP-2 treatment were studied using the IL-10-deficient (IL-10(-/-)) mouse model of colitis. Wild-type and IL-10(-/-) mice received saline or GLP-2 (50 microg/kg sc) treatment for 5 days. GLP-2 treatment resulted in significant amelioration of animal weight loss and reduced intestinal inflammation as assessed by histopathology and myeloperoxidase levels compared with saline-treated animals. In colitis animals, GLP-2 treatment also reduced crypt cell proliferation and crypt cell apoptosis. Proinflammatory (IL-1beta, TNF-alpha, IFN-gamma,) cytokine protein levels were significantly reduced after GLP-2 treatment, whereas IL-4 was significantly increased and IL-6 production was unchanged. Fluorescence-activated cell sorting analysis of lamina propria cells demonstrated a decrease in the CD4(+) T cell population following GLP-2 treatment in colitic mice and an increase in CD11b(+)/F4/80(+) macrophages but no change in CD25(+)FoxP3 T cells or CD11c(+) dendritic cells. In colitis animals, intracellular cytokine analysis demonstrated that GLP-2 decreased lamina propria macrophage TNF-alpha production but increased IGF-1 production, whereas transforming growth factor-beta was unchanged. GLP-2-mediated reduction of crypt cell proliferation was associated with an increase in intestinal epithelial cell suppressor of cytokine signaling (SOCS)-3 expression and reduced STAT-3 signaling. This study shows that the anti-inflammatory effects of GLP-2 are IL-10 independent and that GLP-2 alters the mucosal response of inflamed intestinal epithelial cells and macrophages. In addition, the suggested mechanism of the reduction in inflammation-induced proliferation is attributable to GLP-2 activation of the SOCS-3 pathway, which antagonizes the IL-6-mediated increase in STAT-3 signaling.

Enteric neural pathways mediate the anti-inflammatory actions of glucagon-like peptide 2

Glucagon-like peptide-2 (GLP-2) is an important regulator of nutritional absorptive capacity with anti-inflammatory actions. We hypothesized that GLP-2 reduces intestinal mucosal inflammation by activation of vasoactive intestinal polypeptide (VIP) neurons of the submucosal plexus. Ileitis or colitis was induced in rats by injection of trinitrobenzene sulfonic acid (TNBS), or colitis was induced by administration of dextran sodium sulfate (DSS) in drinking water. Subsets of animals received (1-33)-GLP-2 (50 mug/kg sc bid) either immediately or 2 days after the establishment of inflammation and were followed for 3-5 days. The involvement of VIP neurons was assessed by concomitant administration of GLP-2 and the VIP antagonist [Lys(1)-Pro(2,5)-Arg(3,4)-Tyr(6)]VIP and by immunohistochemical labeling of GLP-2-activated neurons. In all models, GLP-2 treatment, whether given immediately or delayed until inflammation was established, resulted in significant improvements in animal weights, mucosal inflammation indices (myeloperoxidase levels, histological mucosal scores), and reduced levels of inflammatory cytokines (IFN-gamma, TNF-alpha, IL-1beta) and inducible nitric oxide synthase, with increased levels of IL-10 in TNBS ileitis and DSS colitis. Reduced rates of crypt cell proliferation and of apoptosis within crypts in inflamed tissues were also noted with GLP-2 treatment. These effects were abolished with coadministration of GLP-2 and the VIP antagonist. GLP-2 was shown to activate neurons and to increase the number of cells expressing VIP in the submucosal plexus of the ileum. These findings suggest that GLP-2 acts as an anti-inflammatory agent through activation of enteric VIP neurons, independent of proliferative effects. They support further studies to examine the role of neural signaling in the regulation of intestinal inflammation.

Review article: glucagon-like peptide 2--current applications and future directions

BACKGROUND

Glucagon-like peptide 2 (GLP-2) is an important peptide growth factor secreted from the human intestine. The trophic properties of GLP-2 are very specific to the gut where it is pivotal in the regulation of mucosal morphology, function and integrity.

AIMS

This review details the current understanding of the molecular biology of GLP-2, its mechanisms of action and physiological properties. A major focus is the discussion of recent clinical data evaluating the use of GLP-2 as a therapeutic agent.

METHODS

Relevant articles were identified using Medline searches and from the reference lists of key papers.

RESULTS AND CONCLUSIONS

In the treatment of short bowel syndrome, GLP-2 has been shown to be highly effective in improving fluid absorption. In Crohn's disease, GLP-2 is superior to placebo in the induction of remission. Early data also suggest that the effects of GLP-2 on bone metabolism can provide a new treatment approach for patients with osteoporosis. In the future, the positive effects of GLP-2 on intestinal barrier function, splanchnic perfusion and mucosal healing could be utilized to expand its therapeutic application to other causes of intestinal injury. However, important safety aspects need to be considered when using this potent growth-promoting agent for a long term.

Glucagon-like Peptide-2

Multiple peptide hormones produced within the gastrointestinal system aid in the regulation of energy homeostasis and metabolism. Among these is the intestinotrophic peptide glucagon-like peptide-2 (GLP-2), which is released following food intake and plays a significant role in the adaptive regulation of bowel mass and mucosal integrity. The discovery of GLP-2's potent growth-promoting and cytoprotective effects in the gastrointestinal (GI) tract stimulated interest in its use as a therapeutic agent for the treatment of GI diseases involving malabsorption, inflammation, and/or mucosal damage. Current research has focused on determining the physiological mechanisms contributing to the effects of GLP-2 and factors regulating its biological mechanisms of action. This chapter provides an overview of the biology of GLP-2 with a focus on the most recent findings on the role of this peptide hormone in the normal and diseased GI tract.